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000
FXUS65 KRIW 012046
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
246 PM MDT TUE SEP 1 2015

.SHORT TERM...TONIGHT THROUGH WEDNESDAY

SHOWERS AND THUNDERSTORMS WILL CONTINUE ACROSS THE SOUTH INTO THE
EVENING ALONG THE EDGE OF A MOISTURE PLUME AND WEAK THETA E RIDGE.
THE GFS TRIES TO BRING THIS AREA OF MID LEVEL MOISTURE AS FAR
NORTH AS THE ABSAROKAS EARLY IN THE PERIOD...WHICH COULD KICK OFF
A FEW MOUNTAIN THUNDERSTORMS WITH GUSTY OUTFLOW WINDS AND LITTLE
RAIN...ESPECIALLY INTO THE FOOTHILLS AND BASINS. THE NAM HAS A
DIFFERENT STORY FOR TONIGHT WITH MUCH LESS MOISTURE AVAILABLE. AS
OF LATE THIS AFTERNOON IT APPEARS AS THOUGH THE MORE MODEST NAM
IS VERIFYING A LITTLE BETTER BUT NEITHER MODEL RAMPS UP THE
ACTIVITY FURTHER NORTH UNTIL ABOUT 00Z THROUGH 06Z. WENT WITH A
BLEND OF THE TWO INTO THE EVENING THOUGH GIVEN THE CRITICAL NATURE
OF ANY LIGHTNING ACTIVITY THIS LATE IN THE FIRE SEASON.

ALSO ADDED THE OTHER REGIONS OF THE FORECAST AREA WITH CRITICALLY
DRY VEGETATION INTO THE RED FLAG WARNING TO COVER THE POTENTIAL
FOR DRY STORMS WITH GUSTY OUTFLOW WINDS...HIGH HAINES INDEX AND
VERY LOW HUMIDITY...WHICH HAS ALSO BEEN LOWER THAN GUIDANCE THE
PAST TWO DAYS. LOOKS LIKE WINDS ARE STARTING TO PICK UP THIS
AFTERNOON WITH WIDESPREAD WIND GUSTS OVER 25 MPH SHOWING UP IN THE
OBSERVATIONS. NOT BAD FOR A DAY THAT LOOKED VERY MARGINAL IN THE
MODELS A COUPLE OF DAYS AGO.

GOING INTO WEDNESDAY...THIS HAS CONSISTENTLY BEEN THE DAY
ADVERTISED WITH THE MOST WIDESPREAD LOW HUMIDITY AND STRONG WIND
AND IT IS STILL LOOKING THAT WAY TODAY. EXPECT SOUTHWEST FLOW TO
PICK UP AHEAD OF A TROUGH APPROACHING FROM THE NORTHWEST. THERE IS
STILL SOME INCONSISTENCY BETWEEN THE MODELS AS TO HOW MUCH
MOISTURE COMES UP INTO THE SOUTHWEST FLOW AHEAD OF THIS TROUGH.
SOME MID LEVEL MOISTURE COULD MAKE IT UP AS SOON AS WEDNESDAY
AFTERNOON...WHICH COULD KEEP RELATIVE HUMIDITY FROM BOTTOMING OUT
ACROSS THE WEST.

.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY

SOUTHWEST FLOW WILL CONTINUE WEDNESDAY NIGHT INTO THURSDAY AHEAD OF
THE COLD TROUGH OVER THE PAC NW.  SOME MID-LEVEL MOISTURE MAY
PRODUCE WEAK SHOWERS AND ISOLATED THUNDERSTORMS OVER SW AND WESTERN
WY WED EVENING.  BETTER CHANCE APPEARS TO BE FRIDAY AFTERNOON ACROSS
WESTERN AND NW WY AS THE INFLUENCE OF THE TROUGH MOVES SLIGHTLY TO
THE SE AND STARTS TO DESTABILIZE THE MID LEVELS A BIT.  SOUTHWEST
FLOW ACROSS SOUTHERN AND CENTRAL WY EXPECTED TO CONTINUE WITH MORE
MOISTURE BEING DRAWN UP FROM UTAH AND COLORADO AS WELL.  GFS STILL
GOES GANGBUSTERS WITH THE PRECIPITATION COMPARED TO THE NAM...ECMWF
AND GEM NH DURING THIS TIME.  THE CORE OF THE TROUGH IS MORE IN
PHASE TODAY COMPARED TO 24 HOURS AGO BETWEEN THE GFS AND ECMWF...YET
SOME DETAILS ARE STILL DIFFERENT TO CREATE ENOUGH UNCERTAINTY
SATURDAY AND SUNDAY.  SATURDAY LOOKS TO BE FAIRLY CLOUDY ACROSS THE
AREA...WITH MORE OF A CHANCE OF PRECIPITATION ESPECIALLY ACROSS NW
WY.  THE COLDEST MID LEVEL TEMPS SWEEP FROM WEST TO NORTHEAST ACROSS
NW WY FROM SATURDAY NIGHT INTO SUNDAY.  LIKELY TO SEE SOME SNOW AT
THE LOWER ELEVATIONS OF YNP...WITH A FEW INCHES OF SNOW AT LEAST IN
THE HIGHER TERRAIN.  DURING THIS TIME ALSO...SOUTHERN AND CENTRAL WY
WIND WILL SWITCH TO WEST TO NORTHWEST WITH LIGHT AMOUNTS OF
PRECIPITATION.  A SURFACE BOUNDARY WILL DRAPE ACROSS NORTHERN WY
FROM SATURDAY INTO SUNDAY...POSSIBLY BRINGING MORE RAIN TO THE
NORTHERN BIG HORN BASIN LATE SATURDAY INTO SUNDAY.  THE CLOSED LOW
THEN MOVES RAPIDLY INTO THE NORTHERN PLAINS CREATING BRISK
CONDITIONS SUNDAY EVENING AND A FAIRLY COLD MORNING ON MONDAY.
MONDAY LOOKS TO BE MOSTLY CLEAR AND COOL...WITH TUESDAY WARMING A
BIT AND SEEING SOME CLOUDINESS SNEAKING UP FROM THE SOUTH. AS
ANOTHER TROUGH MOVES INTO THE PAC NW MONDAY INTO TUESDAY...SW BREEZY
FLOW IS LIKELY TO SET UP TUESDAY INTO WEDNESDAY.

&&

.AVIATION.../00Z ISSUANCE/

ISOLATED HIGH BASED SHOWERS AND STORMS POSSIBLE ACROSS THE SOUTH
AND WEST. OUTFLOW WIND GUSTS TO 30 KNOTS WILL BE EASILY ACHIEVED
NEAR ANY SHOWERS OR STORMS. THE SHOWER AND STORM ACTIVITY WILL END
IN THE WEST BY 04Z WED AND IN THE EAST AROUND 09Z WED. WINDS WILL
BE BREEZY FROM THE SOUTHWEST ONCE FULL MIXING OCCURS IN ALL AREAS
THROUGH THE TAF PERIOD.

&&

.FIRE WEATHER...

.ELEVATED FIRE DANGER FOR MUCH OF THE WEEK...

THERE WILL BE DRY AND BREEZY PERIODS FOR THE NEXT SEVERAL DAYS WITH
OCCASIONAL LIGHTNING AND COLD FRONTS LATER IN THE WEEK AS ANOTHER
LARGE UPPER TROUGH APPROACHES...INCREASING FLOW FROM THE SOUTHWEST
FOR WEDNESDAY AND THURSDAY WITH WIDESPREAD LOW HUMIDITY AND GUSTY
WINDS. A PUSH OF MID LEVEL MOISTURE AND INSTABILITY WILL ARRIVE
THIS AFTERNOON WHICH WILL INCREASE THUNDERSTORM COVERAGE...
ESPECIALLY ACROSS THE SOUTH WITH PERHAPS A SECONDARY FOCUS IN THE
WESTERN MOUNTAINS THIS EVENING. SOME OF THESE STORMS COULD
VENTURE INTO THE FOOTHILLS AND SEND OUTFLOW WINDS DEEP INTO THE
BASINS. THESE STORMS WILL BE MAINLY DRY WITH OCCASIONAL WET
THUNDERSTORMS POSSIBLE...MAINLY ABOVE 8000 FEET.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THURSDAY FOR WYZ275>277-279>283-
285-287-289-300-414>416.

&&

$$

SHORT TERM...ALLEN
LONG TERM...MCDONALD
AVIATION...ALLEN
FIRE WEATHER...ALLEN





000
FXUS65 KRIW 012046
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
246 PM MDT TUE SEP 1 2015

.SHORT TERM...TONIGHT THROUGH WEDNESDAY

SHOWERS AND THUNDERSTORMS WILL CONTINUE ACROSS THE SOUTH INTO THE
EVENING ALONG THE EDGE OF A MOISTURE PLUME AND WEAK THETA E RIDGE.
THE GFS TRIES TO BRING THIS AREA OF MID LEVEL MOISTURE AS FAR
NORTH AS THE ABSAROKAS EARLY IN THE PERIOD...WHICH COULD KICK OFF
A FEW MOUNTAIN THUNDERSTORMS WITH GUSTY OUTFLOW WINDS AND LITTLE
RAIN...ESPECIALLY INTO THE FOOTHILLS AND BASINS. THE NAM HAS A
DIFFERENT STORY FOR TONIGHT WITH MUCH LESS MOISTURE AVAILABLE. AS
OF LATE THIS AFTERNOON IT APPEARS AS THOUGH THE MORE MODEST NAM
IS VERIFYING A LITTLE BETTER BUT NEITHER MODEL RAMPS UP THE
ACTIVITY FURTHER NORTH UNTIL ABOUT 00Z THROUGH 06Z. WENT WITH A
BLEND OF THE TWO INTO THE EVENING THOUGH GIVEN THE CRITICAL NATURE
OF ANY LIGHTNING ACTIVITY THIS LATE IN THE FIRE SEASON.

ALSO ADDED THE OTHER REGIONS OF THE FORECAST AREA WITH CRITICALLY
DRY VEGETATION INTO THE RED FLAG WARNING TO COVER THE POTENTIAL
FOR DRY STORMS WITH GUSTY OUTFLOW WINDS...HIGH HAINES INDEX AND
VERY LOW HUMIDITY...WHICH HAS ALSO BEEN LOWER THAN GUIDANCE THE
PAST TWO DAYS. LOOKS LIKE WINDS ARE STARTING TO PICK UP THIS
AFTERNOON WITH WIDESPREAD WIND GUSTS OVER 25 MPH SHOWING UP IN THE
OBSERVATIONS. NOT BAD FOR A DAY THAT LOOKED VERY MARGINAL IN THE
MODELS A COUPLE OF DAYS AGO.

GOING INTO WEDNESDAY...THIS HAS CONSISTENTLY BEEN THE DAY
ADVERTISED WITH THE MOST WIDESPREAD LOW HUMIDITY AND STRONG WIND
AND IT IS STILL LOOKING THAT WAY TODAY. EXPECT SOUTHWEST FLOW TO
PICK UP AHEAD OF A TROUGH APPROACHING FROM THE NORTHWEST. THERE IS
STILL SOME INCONSISTENCY BETWEEN THE MODELS AS TO HOW MUCH
MOISTURE COMES UP INTO THE SOUTHWEST FLOW AHEAD OF THIS TROUGH.
SOME MID LEVEL MOISTURE COULD MAKE IT UP AS SOON AS WEDNESDAY
AFTERNOON...WHICH COULD KEEP RELATIVE HUMIDITY FROM BOTTOMING OUT
ACROSS THE WEST.

.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY

SOUTHWEST FLOW WILL CONTINUE WEDNESDAY NIGHT INTO THURSDAY AHEAD OF
THE COLD TROUGH OVER THE PAC NW.  SOME MID-LEVEL MOISTURE MAY
PRODUCE WEAK SHOWERS AND ISOLATED THUNDERSTORMS OVER SW AND WESTERN
WY WED EVENING.  BETTER CHANCE APPEARS TO BE FRIDAY AFTERNOON ACROSS
WESTERN AND NW WY AS THE INFLUENCE OF THE TROUGH MOVES SLIGHTLY TO
THE SE AND STARTS TO DESTABILIZE THE MID LEVELS A BIT.  SOUTHWEST
FLOW ACROSS SOUTHERN AND CENTRAL WY EXPECTED TO CONTINUE WITH MORE
MOISTURE BEING DRAWN UP FROM UTAH AND COLORADO AS WELL.  GFS STILL
GOES GANGBUSTERS WITH THE PRECIPITATION COMPARED TO THE NAM...ECMWF
AND GEM NH DURING THIS TIME.  THE CORE OF THE TROUGH IS MORE IN
PHASE TODAY COMPARED TO 24 HOURS AGO BETWEEN THE GFS AND ECMWF...YET
SOME DETAILS ARE STILL DIFFERENT TO CREATE ENOUGH UNCERTAINTY
SATURDAY AND SUNDAY.  SATURDAY LOOKS TO BE FAIRLY CLOUDY ACROSS THE
AREA...WITH MORE OF A CHANCE OF PRECIPITATION ESPECIALLY ACROSS NW
WY.  THE COLDEST MID LEVEL TEMPS SWEEP FROM WEST TO NORTHEAST ACROSS
NW WY FROM SATURDAY NIGHT INTO SUNDAY.  LIKELY TO SEE SOME SNOW AT
THE LOWER ELEVATIONS OF YNP...WITH A FEW INCHES OF SNOW AT LEAST IN
THE HIGHER TERRAIN.  DURING THIS TIME ALSO...SOUTHERN AND CENTRAL WY
WIND WILL SWITCH TO WEST TO NORTHWEST WITH LIGHT AMOUNTS OF
PRECIPITATION.  A SURFACE BOUNDARY WILL DRAPE ACROSS NORTHERN WY
FROM SATURDAY INTO SUNDAY...POSSIBLY BRINGING MORE RAIN TO THE
NORTHERN BIG HORN BASIN LATE SATURDAY INTO SUNDAY.  THE CLOSED LOW
THEN MOVES RAPIDLY INTO THE NORTHERN PLAINS CREATING BRISK
CONDITIONS SUNDAY EVENING AND A FAIRLY COLD MORNING ON MONDAY.
MONDAY LOOKS TO BE MOSTLY CLEAR AND COOL...WITH TUESDAY WARMING A
BIT AND SEEING SOME CLOUDINESS SNEAKING UP FROM THE SOUTH. AS
ANOTHER TROUGH MOVES INTO THE PAC NW MONDAY INTO TUESDAY...SW BREEZY
FLOW IS LIKELY TO SET UP TUESDAY INTO WEDNESDAY.

&&

.AVIATION.../00Z ISSUANCE/

ISOLATED HIGH BASED SHOWERS AND STORMS POSSIBLE ACROSS THE SOUTH
AND WEST. OUTFLOW WIND GUSTS TO 30 KNOTS WILL BE EASILY ACHIEVED
NEAR ANY SHOWERS OR STORMS. THE SHOWER AND STORM ACTIVITY WILL END
IN THE WEST BY 04Z WED AND IN THE EAST AROUND 09Z WED. WINDS WILL
BE BREEZY FROM THE SOUTHWEST ONCE FULL MIXING OCCURS IN ALL AREAS
THROUGH THE TAF PERIOD.

&&

.FIRE WEATHER...

.ELEVATED FIRE DANGER FOR MUCH OF THE WEEK...

THERE WILL BE DRY AND BREEZY PERIODS FOR THE NEXT SEVERAL DAYS WITH
OCCASIONAL LIGHTNING AND COLD FRONTS LATER IN THE WEEK AS ANOTHER
LARGE UPPER TROUGH APPROACHES...INCREASING FLOW FROM THE SOUTHWEST
FOR WEDNESDAY AND THURSDAY WITH WIDESPREAD LOW HUMIDITY AND GUSTY
WINDS. A PUSH OF MID LEVEL MOISTURE AND INSTABILITY WILL ARRIVE
THIS AFTERNOON WHICH WILL INCREASE THUNDERSTORM COVERAGE...
ESPECIALLY ACROSS THE SOUTH WITH PERHAPS A SECONDARY FOCUS IN THE
WESTERN MOUNTAINS THIS EVENING. SOME OF THESE STORMS COULD
VENTURE INTO THE FOOTHILLS AND SEND OUTFLOW WINDS DEEP INTO THE
BASINS. THESE STORMS WILL BE MAINLY DRY WITH OCCASIONAL WET
THUNDERSTORMS POSSIBLE...MAINLY ABOVE 8000 FEET.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THURSDAY FOR WYZ275>277-279>283-
285-287-289-300-414>416.

&&

$$

SHORT TERM...ALLEN
LONG TERM...MCDONALD
AVIATION...ALLEN
FIRE WEATHER...ALLEN




000
FXUS65 KRIW 011738 AAA
AFDRIW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RIVERTON WY
1138 AM MDT TUE SEP 1 2015

UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS AS WELL AS THE RED
FLAG WARNINGS TO EXTEND THE WARNINGS TO ALL ZONES WITH CRITICALLY
DRY FUELS TODAY THROUGH THURSDAY

.PREV DISCUSSION... /ISSUED 311 AM MDT TUE SEP 1 2015/

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT

PRESENTLY...A MONSOON PLUME IS DRAWING UP MOISTURE FROM THE
SOUTHWEST AND JUST BARELY SKIRTING FAR EASTERN SWEETWATER COUNTY AND
THE SOUTHEAST HALF OF NATRONA COUNTY. ANY LIGHTNING ACTIVITY IS IN
THE DEEPER MOISTURE OVER THE CENTRAL PLAINS TO THE DESERT SOUTHWEST.
MOST OF THIS HIGH AND MID LEVEL MOISTURE WILL CONTINUE TO SLIDE OFF
TO THE SOUTH AND EAST AS WE BECOME MORE INFLUENCED BY THE EASTERN
PACIFIC TROUGH AND THE PACIFIC MOISTURE. WE ARE LOOKING AT SCT T
STORMS MAINLY IN THE NW MTNS THIS AFTERNOON AS THE PROMINENT
EASTERN PACIFIC TROUGH EJECTS A WEAK VORT TRACKING EAST NORTHEAST
ACROSS THE NORTHERN ROCKIES WITH LIMITED PACIFIC MOISTURE.
EVENTUALLY ONLY VERY ISOLD CONVECTION CAN BE EXPECTED ELSEWHERE.
OTHERWISE...WARM DRY SOUTHWEST FLOW WILL CONTINUE THROUGH
THURSDAY...INCREASING AND BACKING SLIGHTLY DURING THE WEEK AS THE
CLOSED LOW WITHIN THE STRONG PACIFIC TROUGH ALONG THE BC COAST
SLOWLY SLIDES SOUTHEAST TO THE PAC NW THROUGH
THURSDAY...TIGHTENING THE GRADIENT. THE SOUTHWEST WINDS WILL
INCREASE NOTICEABLY BY WEDNESDAY...THUS INCREASING THE CRITICAL
FIRE WEATHER ACTIVITY UP ANOTHER NOTCH. BY THURSDAY...AS THE
PACIFIC TROUGH NEARS...QG FORCING ON THE FRONT SIDE OF THE PACIFIC
TROUGH WILL BE IN PLACE WELL TO OUR NORTHWEST OVER NORTHERN IDAHO
AND WESTERN MT...BUT ENOUGH PACIFIC MOISTURE AND JUST ENOUGH
INSTABILITY SHOULD GET SOME SCT THUNDERSTORMS GOING IN YNP LATE
THURSDAY. TEMPS SHOULD REMAIN ABOVE AVERAGE TODAY THROUGH
THURSDAY.

.LONG TERM...FRIDAY THROUGH TUESDAY

COLD TROUGH CURRENTLY OVER ERN GULF OVER INTO NRN B.C. WILL CONTINUE
TO DIG SEWD IN AMPLIFYING FLOW UPSTREAM. END RESULT IS A MAJOR
TROUGH OVER THE WEST THE SECOND HALF OF THE WEEK WHICH LOOKS TO EVEN
GET CUT-OFF FROM THE FLOW SLOWING ITS EWD PROGRESS. THE GFS HAS
SLOWED CONSIDERABLY SINCE LAST NIGHT AS SUSPECTED AND IS NOW IN MUCH
BETTER AGREEMENT WITH THE ECMWF. NOT FULLY YET BUT MUCH BETTER.
BOTTOM LINE IS STILL FOR A SIGNIFICANT COLD TROUGH/UPPER LOW TO DIG
INTO THE OREGON/IDAHO/NRN NEVADA REGION ON SATURDAY BEFORE MOVING E
AND NE SATURDAY NIGHT INTO SUNDAY MORNING INTO OUR AREA. SYSTEM THEN
STARTS TO EXIT THE REGION SUNDAY NIGHT WITH A VERY DRY WLY FLOW ON
MONDAY. ANOTHER TROUGH MAY DIG INTO THE PACNW NEXT TUESDAY WITH THE
POTENTIAL FOR INCREASING SW WIND ACROSS THE AREA ALONG WITH WARMER
AND CONTINUED DRY CONDS. AHEAD OF THE TROUGH FRIDAY...WE SHOULD SEE
SOME MONSOONAL MOISTURE CLIPPING OUR SERN ZONES WITH THE LEADING
EDGE OF THE TROUGH ASSISTING WITH STORMS IN THE NWRN ZONES. FRONTAL
BOUNDARY WILL BE HOVERING NEAR THE NRN ZONES WITH COOLER CONDS
BEHIND IT. ON SATURDAY...DIGGING TROUGH INTO THE NRN GREAT BASIN MAY
ALLOW THIS COLD FRONT TO SAG FURTHER SWD INTO CENTRAL WYO INCREASING
THE CHANCES OF SHOWERS/TSTMS THERE AND OF COURSE IN THE WEST. COOL
IF NOT COLD UPPER LOW THEN LIFTS NEWD ACROSS OUR NWRN ZONES SATURDAY
NIGHT INTO SUNDAY MORNING WITH WIDESPREAD SHOWERS AND SOME TSTMS
ALONG ITS PATH WITH LOWERING SNOW LEVELS. CAMPERS/HIKERS AND OTHER
OUTDOOR ENTHUSIASTS SHOULD BE PREPARED FOR THIS DRAMATIC CHANGE TO
COLD AND WET WEATHER WITH LOWERING SNOW LEVELS. CURRENT MODELS ARE
SHOWING -2C TO -3C IN YNP EARLY SUNDAY. SNOW LEVELS MAY DROP ALL THE
WAY DOWN TO THE LOW SPOTS IN THE PART WITH SEVERAL INCHES OF SNOW IN
THE MOUNTAINS OF THE NW. STRONG SW WIND AHEAD OF THIS SYSTEM WILL
LIKELY BLOW ACROSS THE MTNS AND SRN PARTS. A CHILL DAY SUNDAY IN THE
WEST AND COOL TO MILD AT BEST IN THE EAST. A GRADUAL WARMING TREND
MONDAY INTO TUESDAY WITH DRY LOW LEVELS. INCREASING WIND AGAIN
TUESDAY AHEAD OF THE NEXT TROUGH.

.AVIATION.../18Z ISSUANCE/

ISOLATED HIGH BASED SHOWERS AND STORMS WILL DEVELOP OVER THE WEST
AFTER 19Z. THIS ACTIVITY WILL DEVELOP EAST OF THE CONTINENTAL
DIVIDE AFTER 22Z. OUTFLOW WIND GUSTS TO 30 KNOTS WILL BE EASILY
ACHIEVED NEAR ANY SHOWERS OR STORMS. THE SHOWER AND STORM
ACTIVITY WILL END IN THE WEST BY 04Z WED AND IN THE EAST AROUND
09Z WED. WINDS WILL BE BREEZY FROM THE SOUTHWEST ONCE FULL MIXING
OCCURS IN ALL AREAS THRUOGH THE TAF PERIOD.

.FIRE WEATHER...

..ELEVATED FIRE DANGER FOR MUCH OF THE WEEK...

THERE WILL BE DRY AND BREEZY PERIODS FOR THE NEXT SEVERAL DAYS WITH
OCCASIONAL LIGHTNING AND COLD FRONTS LATER IN THE WEEK AS ANOTHER
LARGE UPPER TROUGH APPROACHES...INCREASING FLOW FROM THE SOUTHWEST
FOR WEDNESDAY AND THURSDAY WITH WIDESPREAD LOW HUMIDITY AND GUSTY
WINDS. A PUSH OF MID LEVEL MOISTURE AND INSTABILITY WILL ARRIVE
THIS AFTERNOON WHICH WILL INCREASE THUNDERSTORM
COVERAGE...ESPECIALLY IN THE WESTERN MOUNTAINS THIS AFTERNOON AND
EVENING. SOME OF THESE STORMS COULD VENTURE INTO THE FOOTHILLS AND
SEND OUTFLOW WINDS DEEP INTO THE BASINS. THESE STORMS WILL BE
MAINLY DRY WITH OCCASIONAL WET THUNDERSTORMS POSSIBLE...MAINLY
ABOVE 8000 FEET.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THURSDAY FOR WYZ275>277-279>283-
285-287-289-300-414>416.

&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...ALLEN
FIRE WEATHER...ALLEN




000
FXUS65 KRIW 011738 AAA
AFDRIW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RIVERTON WY
1138 AM MDT TUE SEP 1 2015

UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS AS WELL AS THE RED
FLAG WARNINGS TO EXTEND THE WARNINGS TO ALL ZONES WITH CRITICALLY
DRY FUELS TODAY THROUGH THURSDAY

.PREV DISCUSSION... /ISSUED 311 AM MDT TUE SEP 1 2015/

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT

PRESENTLY...A MONSOON PLUME IS DRAWING UP MOISTURE FROM THE
SOUTHWEST AND JUST BARELY SKIRTING FAR EASTERN SWEETWATER COUNTY AND
THE SOUTHEAST HALF OF NATRONA COUNTY. ANY LIGHTNING ACTIVITY IS IN
THE DEEPER MOISTURE OVER THE CENTRAL PLAINS TO THE DESERT SOUTHWEST.
MOST OF THIS HIGH AND MID LEVEL MOISTURE WILL CONTINUE TO SLIDE OFF
TO THE SOUTH AND EAST AS WE BECOME MORE INFLUENCED BY THE EASTERN
PACIFIC TROUGH AND THE PACIFIC MOISTURE. WE ARE LOOKING AT SCT T
STORMS MAINLY IN THE NW MTNS THIS AFTERNOON AS THE PROMINENT
EASTERN PACIFIC TROUGH EJECTS A WEAK VORT TRACKING EAST NORTHEAST
ACROSS THE NORTHERN ROCKIES WITH LIMITED PACIFIC MOISTURE.
EVENTUALLY ONLY VERY ISOLD CONVECTION CAN BE EXPECTED ELSEWHERE.
OTHERWISE...WARM DRY SOUTHWEST FLOW WILL CONTINUE THROUGH
THURSDAY...INCREASING AND BACKING SLIGHTLY DURING THE WEEK AS THE
CLOSED LOW WITHIN THE STRONG PACIFIC TROUGH ALONG THE BC COAST
SLOWLY SLIDES SOUTHEAST TO THE PAC NW THROUGH
THURSDAY...TIGHTENING THE GRADIENT. THE SOUTHWEST WINDS WILL
INCREASE NOTICEABLY BY WEDNESDAY...THUS INCREASING THE CRITICAL
FIRE WEATHER ACTIVITY UP ANOTHER NOTCH. BY THURSDAY...AS THE
PACIFIC TROUGH NEARS...QG FORCING ON THE FRONT SIDE OF THE PACIFIC
TROUGH WILL BE IN PLACE WELL TO OUR NORTHWEST OVER NORTHERN IDAHO
AND WESTERN MT...BUT ENOUGH PACIFIC MOISTURE AND JUST ENOUGH
INSTABILITY SHOULD GET SOME SCT THUNDERSTORMS GOING IN YNP LATE
THURSDAY. TEMPS SHOULD REMAIN ABOVE AVERAGE TODAY THROUGH
THURSDAY.

.LONG TERM...FRIDAY THROUGH TUESDAY

COLD TROUGH CURRENTLY OVER ERN GULF OVER INTO NRN B.C. WILL CONTINUE
TO DIG SEWD IN AMPLIFYING FLOW UPSTREAM. END RESULT IS A MAJOR
TROUGH OVER THE WEST THE SECOND HALF OF THE WEEK WHICH LOOKS TO EVEN
GET CUT-OFF FROM THE FLOW SLOWING ITS EWD PROGRESS. THE GFS HAS
SLOWED CONSIDERABLY SINCE LAST NIGHT AS SUSPECTED AND IS NOW IN MUCH
BETTER AGREEMENT WITH THE ECMWF. NOT FULLY YET BUT MUCH BETTER.
BOTTOM LINE IS STILL FOR A SIGNIFICANT COLD TROUGH/UPPER LOW TO DIG
INTO THE OREGON/IDAHO/NRN NEVADA REGION ON SATURDAY BEFORE MOVING E
AND NE SATURDAY NIGHT INTO SUNDAY MORNING INTO OUR AREA. SYSTEM THEN
STARTS TO EXIT THE REGION SUNDAY NIGHT WITH A VERY DRY WLY FLOW ON
MONDAY. ANOTHER TROUGH MAY DIG INTO THE PACNW NEXT TUESDAY WITH THE
POTENTIAL FOR INCREASING SW WIND ACROSS THE AREA ALONG WITH WARMER
AND CONTINUED DRY CONDS. AHEAD OF THE TROUGH FRIDAY...WE SHOULD SEE
SOME MONSOONAL MOISTURE CLIPPING OUR SERN ZONES WITH THE LEADING
EDGE OF THE TROUGH ASSISTING WITH STORMS IN THE NWRN ZONES. FRONTAL
BOUNDARY WILL BE HOVERING NEAR THE NRN ZONES WITH COOLER CONDS
BEHIND IT. ON SATURDAY...DIGGING TROUGH INTO THE NRN GREAT BASIN MAY
ALLOW THIS COLD FRONT TO SAG FURTHER SWD INTO CENTRAL WYO INCREASING
THE CHANCES OF SHOWERS/TSTMS THERE AND OF COURSE IN THE WEST. COOL
IF NOT COLD UPPER LOW THEN LIFTS NEWD ACROSS OUR NWRN ZONES SATURDAY
NIGHT INTO SUNDAY MORNING WITH WIDESPREAD SHOWERS AND SOME TSTMS
ALONG ITS PATH WITH LOWERING SNOW LEVELS. CAMPERS/HIKERS AND OTHER
OUTDOOR ENTHUSIASTS SHOULD BE PREPARED FOR THIS DRAMATIC CHANGE TO
COLD AND WET WEATHER WITH LOWERING SNOW LEVELS. CURRENT MODELS ARE
SHOWING -2C TO -3C IN YNP EARLY SUNDAY. SNOW LEVELS MAY DROP ALL THE
WAY DOWN TO THE LOW SPOTS IN THE PART WITH SEVERAL INCHES OF SNOW IN
THE MOUNTAINS OF THE NW. STRONG SW WIND AHEAD OF THIS SYSTEM WILL
LIKELY BLOW ACROSS THE MTNS AND SRN PARTS. A CHILL DAY SUNDAY IN THE
WEST AND COOL TO MILD AT BEST IN THE EAST. A GRADUAL WARMING TREND
MONDAY INTO TUESDAY WITH DRY LOW LEVELS. INCREASING WIND AGAIN
TUESDAY AHEAD OF THE NEXT TROUGH.

.AVIATION.../18Z ISSUANCE/

ISOLATED HIGH BASED SHOWERS AND STORMS WILL DEVELOP OVER THE WEST
AFTER 19Z. THIS ACTIVITY WILL DEVELOP EAST OF THE CONTINENTAL
DIVIDE AFTER 22Z. OUTFLOW WIND GUSTS TO 30 KNOTS WILL BE EASILY
ACHIEVED NEAR ANY SHOWERS OR STORMS. THE SHOWER AND STORM
ACTIVITY WILL END IN THE WEST BY 04Z WED AND IN THE EAST AROUND
09Z WED. WINDS WILL BE BREEZY FROM THE SOUTHWEST ONCE FULL MIXING
OCCURS IN ALL AREAS THRUOGH THE TAF PERIOD.

.FIRE WEATHER...

..ELEVATED FIRE DANGER FOR MUCH OF THE WEEK...

THERE WILL BE DRY AND BREEZY PERIODS FOR THE NEXT SEVERAL DAYS WITH
OCCASIONAL LIGHTNING AND COLD FRONTS LATER IN THE WEEK AS ANOTHER
LARGE UPPER TROUGH APPROACHES...INCREASING FLOW FROM THE SOUTHWEST
FOR WEDNESDAY AND THURSDAY WITH WIDESPREAD LOW HUMIDITY AND GUSTY
WINDS. A PUSH OF MID LEVEL MOISTURE AND INSTABILITY WILL ARRIVE
THIS AFTERNOON WHICH WILL INCREASE THUNDERSTORM
COVERAGE...ESPECIALLY IN THE WESTERN MOUNTAINS THIS AFTERNOON AND
EVENING. SOME OF THESE STORMS COULD VENTURE INTO THE FOOTHILLS AND
SEND OUTFLOW WINDS DEEP INTO THE BASINS. THESE STORMS WILL BE
MAINLY DRY WITH OCCASIONAL WET THUNDERSTORMS POSSIBLE...MAINLY
ABOVE 8000 FEET.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THURSDAY FOR WYZ275>277-279>283-
285-287-289-300-414>416.

&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...ALLEN
FIRE WEATHER...ALLEN





000
FXUS65 KRIW 011738 AAA
AFDRIW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RIVERTON WY
1138 AM MDT TUE SEP 1 2015

UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS AS WELL AS THE RED
FLAG WARNINGS TO EXTEND THE WARNINGS TO ALL ZONES WITH CRITICALLY
DRY FUELS TODAY THROUGH THURSDAY

.PREV DISCUSSION... /ISSUED 311 AM MDT TUE SEP 1 2015/

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT

PRESENTLY...A MONSOON PLUME IS DRAWING UP MOISTURE FROM THE
SOUTHWEST AND JUST BARELY SKIRTING FAR EASTERN SWEETWATER COUNTY AND
THE SOUTHEAST HALF OF NATRONA COUNTY. ANY LIGHTNING ACTIVITY IS IN
THE DEEPER MOISTURE OVER THE CENTRAL PLAINS TO THE DESERT SOUTHWEST.
MOST OF THIS HIGH AND MID LEVEL MOISTURE WILL CONTINUE TO SLIDE OFF
TO THE SOUTH AND EAST AS WE BECOME MORE INFLUENCED BY THE EASTERN
PACIFIC TROUGH AND THE PACIFIC MOISTURE. WE ARE LOOKING AT SCT T
STORMS MAINLY IN THE NW MTNS THIS AFTERNOON AS THE PROMINENT
EASTERN PACIFIC TROUGH EJECTS A WEAK VORT TRACKING EAST NORTHEAST
ACROSS THE NORTHERN ROCKIES WITH LIMITED PACIFIC MOISTURE.
EVENTUALLY ONLY VERY ISOLD CONVECTION CAN BE EXPECTED ELSEWHERE.
OTHERWISE...WARM DRY SOUTHWEST FLOW WILL CONTINUE THROUGH
THURSDAY...INCREASING AND BACKING SLIGHTLY DURING THE WEEK AS THE
CLOSED LOW WITHIN THE STRONG PACIFIC TROUGH ALONG THE BC COAST
SLOWLY SLIDES SOUTHEAST TO THE PAC NW THROUGH
THURSDAY...TIGHTENING THE GRADIENT. THE SOUTHWEST WINDS WILL
INCREASE NOTICEABLY BY WEDNESDAY...THUS INCREASING THE CRITICAL
FIRE WEATHER ACTIVITY UP ANOTHER NOTCH. BY THURSDAY...AS THE
PACIFIC TROUGH NEARS...QG FORCING ON THE FRONT SIDE OF THE PACIFIC
TROUGH WILL BE IN PLACE WELL TO OUR NORTHWEST OVER NORTHERN IDAHO
AND WESTERN MT...BUT ENOUGH PACIFIC MOISTURE AND JUST ENOUGH
INSTABILITY SHOULD GET SOME SCT THUNDERSTORMS GOING IN YNP LATE
THURSDAY. TEMPS SHOULD REMAIN ABOVE AVERAGE TODAY THROUGH
THURSDAY.

.LONG TERM...FRIDAY THROUGH TUESDAY

COLD TROUGH CURRENTLY OVER ERN GULF OVER INTO NRN B.C. WILL CONTINUE
TO DIG SEWD IN AMPLIFYING FLOW UPSTREAM. END RESULT IS A MAJOR
TROUGH OVER THE WEST THE SECOND HALF OF THE WEEK WHICH LOOKS TO EVEN
GET CUT-OFF FROM THE FLOW SLOWING ITS EWD PROGRESS. THE GFS HAS
SLOWED CONSIDERABLY SINCE LAST NIGHT AS SUSPECTED AND IS NOW IN MUCH
BETTER AGREEMENT WITH THE ECMWF. NOT FULLY YET BUT MUCH BETTER.
BOTTOM LINE IS STILL FOR A SIGNIFICANT COLD TROUGH/UPPER LOW TO DIG
INTO THE OREGON/IDAHO/NRN NEVADA REGION ON SATURDAY BEFORE MOVING E
AND NE SATURDAY NIGHT INTO SUNDAY MORNING INTO OUR AREA. SYSTEM THEN
STARTS TO EXIT THE REGION SUNDAY NIGHT WITH A VERY DRY WLY FLOW ON
MONDAY. ANOTHER TROUGH MAY DIG INTO THE PACNW NEXT TUESDAY WITH THE
POTENTIAL FOR INCREASING SW WIND ACROSS THE AREA ALONG WITH WARMER
AND CONTINUED DRY CONDS. AHEAD OF THE TROUGH FRIDAY...WE SHOULD SEE
SOME MONSOONAL MOISTURE CLIPPING OUR SERN ZONES WITH THE LEADING
EDGE OF THE TROUGH ASSISTING WITH STORMS IN THE NWRN ZONES. FRONTAL
BOUNDARY WILL BE HOVERING NEAR THE NRN ZONES WITH COOLER CONDS
BEHIND IT. ON SATURDAY...DIGGING TROUGH INTO THE NRN GREAT BASIN MAY
ALLOW THIS COLD FRONT TO SAG FURTHER SWD INTO CENTRAL WYO INCREASING
THE CHANCES OF SHOWERS/TSTMS THERE AND OF COURSE IN THE WEST. COOL
IF NOT COLD UPPER LOW THEN LIFTS NEWD ACROSS OUR NWRN ZONES SATURDAY
NIGHT INTO SUNDAY MORNING WITH WIDESPREAD SHOWERS AND SOME TSTMS
ALONG ITS PATH WITH LOWERING SNOW LEVELS. CAMPERS/HIKERS AND OTHER
OUTDOOR ENTHUSIASTS SHOULD BE PREPARED FOR THIS DRAMATIC CHANGE TO
COLD AND WET WEATHER WITH LOWERING SNOW LEVELS. CURRENT MODELS ARE
SHOWING -2C TO -3C IN YNP EARLY SUNDAY. SNOW LEVELS MAY DROP ALL THE
WAY DOWN TO THE LOW SPOTS IN THE PART WITH SEVERAL INCHES OF SNOW IN
THE MOUNTAINS OF THE NW. STRONG SW WIND AHEAD OF THIS SYSTEM WILL
LIKELY BLOW ACROSS THE MTNS AND SRN PARTS. A CHILL DAY SUNDAY IN THE
WEST AND COOL TO MILD AT BEST IN THE EAST. A GRADUAL WARMING TREND
MONDAY INTO TUESDAY WITH DRY LOW LEVELS. INCREASING WIND AGAIN
TUESDAY AHEAD OF THE NEXT TROUGH.

.AVIATION.../18Z ISSUANCE/

ISOLATED HIGH BASED SHOWERS AND STORMS WILL DEVELOP OVER THE WEST
AFTER 19Z. THIS ACTIVITY WILL DEVELOP EAST OF THE CONTINENTAL
DIVIDE AFTER 22Z. OUTFLOW WIND GUSTS TO 30 KNOTS WILL BE EASILY
ACHIEVED NEAR ANY SHOWERS OR STORMS. THE SHOWER AND STORM
ACTIVITY WILL END IN THE WEST BY 04Z WED AND IN THE EAST AROUND
09Z WED. WINDS WILL BE BREEZY FROM THE SOUTHWEST ONCE FULL MIXING
OCCURS IN ALL AREAS THRUOGH THE TAF PERIOD.

.FIRE WEATHER...

..ELEVATED FIRE DANGER FOR MUCH OF THE WEEK...

THERE WILL BE DRY AND BREEZY PERIODS FOR THE NEXT SEVERAL DAYS WITH
OCCASIONAL LIGHTNING AND COLD FRONTS LATER IN THE WEEK AS ANOTHER
LARGE UPPER TROUGH APPROACHES...INCREASING FLOW FROM THE SOUTHWEST
FOR WEDNESDAY AND THURSDAY WITH WIDESPREAD LOW HUMIDITY AND GUSTY
WINDS. A PUSH OF MID LEVEL MOISTURE AND INSTABILITY WILL ARRIVE
THIS AFTERNOON WHICH WILL INCREASE THUNDERSTORM
COVERAGE...ESPECIALLY IN THE WESTERN MOUNTAINS THIS AFTERNOON AND
EVENING. SOME OF THESE STORMS COULD VENTURE INTO THE FOOTHILLS AND
SEND OUTFLOW WINDS DEEP INTO THE BASINS. THESE STORMS WILL BE
MAINLY DRY WITH OCCASIONAL WET THUNDERSTORMS POSSIBLE...MAINLY
ABOVE 8000 FEET.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THURSDAY FOR WYZ275>277-279>283-
285-287-289-300-414>416.

&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...ALLEN
FIRE WEATHER...ALLEN





000
FXUS65 KRIW 011738 AAA
AFDRIW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RIVERTON WY
1138 AM MDT TUE SEP 1 2015

UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS AS WELL AS THE RED
FLAG WARNINGS TO EXTEND THE WARNINGS TO ALL ZONES WITH CRITICALLY
DRY FUELS TODAY THROUGH THURSDAY

.PREV DISCUSSION... /ISSUED 311 AM MDT TUE SEP 1 2015/

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT

PRESENTLY...A MONSOON PLUME IS DRAWING UP MOISTURE FROM THE
SOUTHWEST AND JUST BARELY SKIRTING FAR EASTERN SWEETWATER COUNTY AND
THE SOUTHEAST HALF OF NATRONA COUNTY. ANY LIGHTNING ACTIVITY IS IN
THE DEEPER MOISTURE OVER THE CENTRAL PLAINS TO THE DESERT SOUTHWEST.
MOST OF THIS HIGH AND MID LEVEL MOISTURE WILL CONTINUE TO SLIDE OFF
TO THE SOUTH AND EAST AS WE BECOME MORE INFLUENCED BY THE EASTERN
PACIFIC TROUGH AND THE PACIFIC MOISTURE. WE ARE LOOKING AT SCT T
STORMS MAINLY IN THE NW MTNS THIS AFTERNOON AS THE PROMINENT
EASTERN PACIFIC TROUGH EJECTS A WEAK VORT TRACKING EAST NORTHEAST
ACROSS THE NORTHERN ROCKIES WITH LIMITED PACIFIC MOISTURE.
EVENTUALLY ONLY VERY ISOLD CONVECTION CAN BE EXPECTED ELSEWHERE.
OTHERWISE...WARM DRY SOUTHWEST FLOW WILL CONTINUE THROUGH
THURSDAY...INCREASING AND BACKING SLIGHTLY DURING THE WEEK AS THE
CLOSED LOW WITHIN THE STRONG PACIFIC TROUGH ALONG THE BC COAST
SLOWLY SLIDES SOUTHEAST TO THE PAC NW THROUGH
THURSDAY...TIGHTENING THE GRADIENT. THE SOUTHWEST WINDS WILL
INCREASE NOTICEABLY BY WEDNESDAY...THUS INCREASING THE CRITICAL
FIRE WEATHER ACTIVITY UP ANOTHER NOTCH. BY THURSDAY...AS THE
PACIFIC TROUGH NEARS...QG FORCING ON THE FRONT SIDE OF THE PACIFIC
TROUGH WILL BE IN PLACE WELL TO OUR NORTHWEST OVER NORTHERN IDAHO
AND WESTERN MT...BUT ENOUGH PACIFIC MOISTURE AND JUST ENOUGH
INSTABILITY SHOULD GET SOME SCT THUNDERSTORMS GOING IN YNP LATE
THURSDAY. TEMPS SHOULD REMAIN ABOVE AVERAGE TODAY THROUGH
THURSDAY.

.LONG TERM...FRIDAY THROUGH TUESDAY

COLD TROUGH CURRENTLY OVER ERN GULF OVER INTO NRN B.C. WILL CONTINUE
TO DIG SEWD IN AMPLIFYING FLOW UPSTREAM. END RESULT IS A MAJOR
TROUGH OVER THE WEST THE SECOND HALF OF THE WEEK WHICH LOOKS TO EVEN
GET CUT-OFF FROM THE FLOW SLOWING ITS EWD PROGRESS. THE GFS HAS
SLOWED CONSIDERABLY SINCE LAST NIGHT AS SUSPECTED AND IS NOW IN MUCH
BETTER AGREEMENT WITH THE ECMWF. NOT FULLY YET BUT MUCH BETTER.
BOTTOM LINE IS STILL FOR A SIGNIFICANT COLD TROUGH/UPPER LOW TO DIG
INTO THE OREGON/IDAHO/NRN NEVADA REGION ON SATURDAY BEFORE MOVING E
AND NE SATURDAY NIGHT INTO SUNDAY MORNING INTO OUR AREA. SYSTEM THEN
STARTS TO EXIT THE REGION SUNDAY NIGHT WITH A VERY DRY WLY FLOW ON
MONDAY. ANOTHER TROUGH MAY DIG INTO THE PACNW NEXT TUESDAY WITH THE
POTENTIAL FOR INCREASING SW WIND ACROSS THE AREA ALONG WITH WARMER
AND CONTINUED DRY CONDS. AHEAD OF THE TROUGH FRIDAY...WE SHOULD SEE
SOME MONSOONAL MOISTURE CLIPPING OUR SERN ZONES WITH THE LEADING
EDGE OF THE TROUGH ASSISTING WITH STORMS IN THE NWRN ZONES. FRONTAL
BOUNDARY WILL BE HOVERING NEAR THE NRN ZONES WITH COOLER CONDS
BEHIND IT. ON SATURDAY...DIGGING TROUGH INTO THE NRN GREAT BASIN MAY
ALLOW THIS COLD FRONT TO SAG FURTHER SWD INTO CENTRAL WYO INCREASING
THE CHANCES OF SHOWERS/TSTMS THERE AND OF COURSE IN THE WEST. COOL
IF NOT COLD UPPER LOW THEN LIFTS NEWD ACROSS OUR NWRN ZONES SATURDAY
NIGHT INTO SUNDAY MORNING WITH WIDESPREAD SHOWERS AND SOME TSTMS
ALONG ITS PATH WITH LOWERING SNOW LEVELS. CAMPERS/HIKERS AND OTHER
OUTDOOR ENTHUSIASTS SHOULD BE PREPARED FOR THIS DRAMATIC CHANGE TO
COLD AND WET WEATHER WITH LOWERING SNOW LEVELS. CURRENT MODELS ARE
SHOWING -2C TO -3C IN YNP EARLY SUNDAY. SNOW LEVELS MAY DROP ALL THE
WAY DOWN TO THE LOW SPOTS IN THE PART WITH SEVERAL INCHES OF SNOW IN
THE MOUNTAINS OF THE NW. STRONG SW WIND AHEAD OF THIS SYSTEM WILL
LIKELY BLOW ACROSS THE MTNS AND SRN PARTS. A CHILL DAY SUNDAY IN THE
WEST AND COOL TO MILD AT BEST IN THE EAST. A GRADUAL WARMING TREND
MONDAY INTO TUESDAY WITH DRY LOW LEVELS. INCREASING WIND AGAIN
TUESDAY AHEAD OF THE NEXT TROUGH.

.AVIATION.../18Z ISSUANCE/

ISOLATED HIGH BASED SHOWERS AND STORMS WILL DEVELOP OVER THE WEST
AFTER 19Z. THIS ACTIVITY WILL DEVELOP EAST OF THE CONTINENTAL
DIVIDE AFTER 22Z. OUTFLOW WIND GUSTS TO 30 KNOTS WILL BE EASILY
ACHIEVED NEAR ANY SHOWERS OR STORMS. THE SHOWER AND STORM
ACTIVITY WILL END IN THE WEST BY 04Z WED AND IN THE EAST AROUND
09Z WED. WINDS WILL BE BREEZY FROM THE SOUTHWEST ONCE FULL MIXING
OCCURS IN ALL AREAS THRUOGH THE TAF PERIOD.

.FIRE WEATHER...

..ELEVATED FIRE DANGER FOR MUCH OF THE WEEK...

THERE WILL BE DRY AND BREEZY PERIODS FOR THE NEXT SEVERAL DAYS WITH
OCCASIONAL LIGHTNING AND COLD FRONTS LATER IN THE WEEK AS ANOTHER
LARGE UPPER TROUGH APPROACHES...INCREASING FLOW FROM THE SOUTHWEST
FOR WEDNESDAY AND THURSDAY WITH WIDESPREAD LOW HUMIDITY AND GUSTY
WINDS. A PUSH OF MID LEVEL MOISTURE AND INSTABILITY WILL ARRIVE
THIS AFTERNOON WHICH WILL INCREASE THUNDERSTORM
COVERAGE...ESPECIALLY IN THE WESTERN MOUNTAINS THIS AFTERNOON AND
EVENING. SOME OF THESE STORMS COULD VENTURE INTO THE FOOTHILLS AND
SEND OUTFLOW WINDS DEEP INTO THE BASINS. THESE STORMS WILL BE
MAINLY DRY WITH OCCASIONAL WET THUNDERSTORMS POSSIBLE...MAINLY
ABOVE 8000 FEET.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THURSDAY FOR WYZ275>277-279>283-
285-287-289-300-414>416.

&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...ALLEN
FIRE WEATHER...ALLEN




000
FXUS65 KRIW 010911
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
311 AM MDT TUE SEP 1 2015

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT

PRESENTLY...A MONSOON PLUME IS DRAWING UP MOISTURE FROM THE
SOUTHWEST AND JUST BARELY SKIRTING FAR EASTERN SWEETWATER COUNTY AND
THE SOUTHEAST HALF OF NATRONA COUNTY. ANY LIGHTNING ACTIVITY IS IN
THE DEEPER MOISTURE OVER THE CENTRAL PLAINS TO THE DESERT SOUTHWEST.
MOST OF THIS HIGH AND MID LEVEL MOISTURE WILL CONTINUE TO SLIDE OFF
TO THE SOUTH AND EAST AS WE BECOME MORE INFLUENCED BY THE EASTERN
PACIFIC TROUGH AND THE PACIFIC MOISTURE. WE ARE LOOKING AT SCT T
STORMS MAINLY IN THE NW MTNS THIS AFTERNOON AS THE PROMINENT
EASTERN PACIFIC TROUGH EJECTS A WEAK VORT TRACKING EAST NORTHEAST
ACROSS THE NORTHERN ROCKIES WITH LIMITED PACIFIC MOISTURE.
EVENTUALLY ONLY VERY ISOLD CONVECTION CAN BE EXPECTED ELSEWHERE.
OTHERWISE...WARM DRY SOUTHWEST FLOW WILL CONTINUE THROUGH
THURSDAY...INCREASING AND BACKING SLIGHTLY DURING THE WEEK AS THE
CLOSED LOW WITHIN THE STRONG PACIFIC TROUGH ALONG THE BC COAST
SLOWLY SLIDES SOUTHEAST TO THE PAC NW THROUGH
THURSDAY...TIGHTENING THE GRADIENT. THE SOUTHWEST WINDS WILL
INCREASE NOTICEABLY BY WEDNESDAY...THUS INCREASING THE CRITICAL
FIRE WEATHER ACTIVITY UP ANOTHER NOTCH. BY THURSDAY...AS THE
PACIFIC TROUGH NEARS...QG FORCING ON THE FRONT SIDE OF THE PACIFIC
TROUGH WILL BE IN PLACE WELL TO OUR NORTHWEST OVER NORTHERN IDAHO
AND WESTERN MT...BUT ENOUGH PACIFIC MOISTURE AND JUST ENOUGH
INSTABILITY SHOULD GET SOME SCT THUNDERSTORMS GOING IN YNP LATE
THURSDAY. TEMPS SHOULD REMAIN ABOVE AVERAGE TODAY THROUGH
THURSDAY.

.LONG TERM...FRIDAY THROUGH TUESDAY

COLD TROUGH CURRENTLY OVER ERN GULF OVER INTO NRN B.C. WILL CONTINUE
TO DIG SEWD IN AMPLIFYING FLOW UPSTREAM. END RESULT IS A MAJOR
TROUGH OVER THE WEST THE SECOND HALF OF THE WEEK WHICH LOOKS TO EVEN
GET CUT-OFF FROM THE FLOW SLOWING ITS EWD PROGRESS. THE GFS HAS
SLOWED CONSIDERABLY SINCE LAST NIGHT AS SUSPECTED AND IS NOW IN MUCH
BETTER AGREEMENT WITH THE ECMWF. NOT FULLY YET BUT MUCH BETTER.
BOTTOM LINE IS STILL FOR A SIGNIFICANT COLD TROUGH/UPPER LOW TO DIG
INTO THE OREGON/IDAHO/NRN NEVADA REGION ON SATURDAY BEFORE MOVING E
AND NE SATURDAY NIGHT INTO SUNDAY MORNING INTO OUR AREA. SYSTEM THEN
STARTS TO EXIT THE REGION SUNDAY NIGHT WITH A VERY DRY WLY FLOW ON
MONDAY. ANOTHER TROUGH MAY DIG INTO THE PACNW NEXT TUESDAY WITH THE
POTENTIAL FOR INCREASING SW WIND ACROSS THE AREA ALONG WITH WARMER
AND CONTINUED DRY CONDS. AHEAD OF THE TROUGH FRIDAY...WE SHOULD SEE
SOME MONSOONAL MOISTURE CLIPPING OUR SERN ZONES WITH THE LEADING
EDGE OF THE TROUGH ASSISTING WITH STORMS IN THE NWRN ZONES. FRONTAL
BOUNDARY WILL BE HOVERING NEAR THE NRN ZONES WITH COOLER CONDS
BEHIND IT. ON SATURDAY...DIGGING TROUGH INTO THE NRN GREAT BASIN MAY
ALLOW THIS COLD FRONT TO SAG FURTHER SWD INTO CENTRAL WYO INCREASING
THE CHANCES OF SHOWERS/TSTMS THERE AND OF COURSE IN THE WEST. COOL
IF NOT COLD UPPER LOW THEN LIFTS NEWD ACROSS OUR NWRN ZONES SATURDAY
NIGHT INTO SUNDAY MORNING WITH WIDESPREAD SHOWERS AND SOME TSTMS
ALONG ITS PATH WITH LOWERING SNOW LEVELS. CAMPERS/HIKERS AND OTHER
OUTDOOR ENTHUSIASTS SHOULD BE PREPARED FOR THIS DRAMATIC CHANGE TO
COLD AND WET WEATHER WITH LOWERING SNOW LEVELS. CURRENT MODELS ARE
SHOWING -2C TO -3C IN YNP EARLY SUNDAY. SNOW LEVELS MAY DROP ALL THE
WAY DOWN TO THE LOW SPOTS IN THE PART WITH SEVERAL INCHES OF SNOW IN
THE MOUNTAINS OF THE NW. STRONG SW WIND AHEAD OF THIS SYSTEM WILL
LIKELY BLOW ACROSS THE MTNS AND SRN PARTS. A CHILL DAY SUNDAY IN THE
WEST AND COOL TO MILD AT BEST IN THE EAST. A GRADUAL WARMING TREND
MONDAY INTO TUESDAY WITH DRY LOW LEVELS. INCREASING WIND AGAIN
TUESDAY AHEAD OF THE NEXT TROUGH.

&&

.AVIATION.../12Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL THROUGH TUESDAY EVENING. ISOLATED
SHOWERS AND STORMS WILL DEVELOP OVER THE WEST AFTER 19Z. THIS
ACTIVITY WILL DEVELOP EAST OF THE CONTINENTAL DIVIDE AFTER 22Z.
OUTFLOW WIND GUSTS TO 30 KNOTS WILL BE POSSIBLE NEAR ANY SHOWERS
OR STORMS. THE SHOWER AND STORM ACTIVITY WILL END IN THE WEST BY
04Z WED AND IN THE EAST AROUND 09Z WED.

&&

.FIRE WEATHER...

...ELEVATED FIRE DANGER FOR MUCH OF THE WEEK...

THERE WILL BE DRY AND BREEZY PERIODS THROUGHOUT THE WEEK WITH
OCCASIONAL LIGHTNING AND COLD FRONTS LATER IN THE WEEK AS ANOTHER
LARGE UPPER TROUGH APPROACHES. WESTERLY BREEZES WILL CONTINUE
INTO THE EVENING WITH A FEW SPOTS EXCEEDING 30 MPH...ESPECIALLY
NEAR STORMS AND OVER HIGHER TERRAIN. RELATIVE HUMIDITY WILL
IMPROVE ON TUESDAY AFTERNOON BUT IT WILL STILL DIP INTO THE MID
TEENS IN MANY AREAS. A LARGE TROUGH WILL APPROACH ON
WEDNESDAY...INCREASING FLOW FROM THE SOUTHWEST FOR WEDNESDAY AND
THURSDAY WITH WIDESPREAD LOW HUMIDITY AND GUSTY WINDS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
FIRE WEATHER WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY
EVENING FOR WYZ275-277-279-414-415.

RED FLAG WARNING UNTIL 9 PM MDT WEDNESDAY FOR WYZ276-280>283-285-
287-289-300-416.

&&

$$

SHORT TERM...LIPSON
LONG TERM...PS
AVIATION...AR
FIRE WEATHER...LIPSON





000
FXUS65 KRIW 010445
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1045 PM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH TUESDAY (ISSUED AT 335 PM MDT)

A SUBSIDENCE INVERSION SURFACED...DRASTICALLY DROPPING RELATIVE
HUMIDITIES THIS AFTERNOON WITH WESTERLY WINDS INCREASING TO ABOVE
25 MPH IN MANY AREAS...

A FEW THUNDERSTORMS WILL LINGER ACROSS THE SOUTH THIS EVENING AS A
PLUME OF MOISTURE AND THETA E RIDGE TO OUR SOUTH AND EAST
MAINTAINS AN UNSTABLE ATMOSPHERE INTO THE EVENING HOURS. SOME OF
THE STORMS EAST OF NATRONA COUNTY COULD KICK SOME MOIST OUTFLOW
BOUNDARIES WESTWARD INTO NORTHERN AND CENTRAL NATRONA
COUNTY...THIS COULD KICK OFF A FEW STORMS IN THIS AREA TOO.
OTHERWISE...THE BEST CHANCE FOR A THUNDERSTORM IN NATRONA COUNTY
THIS EVENING WILL BE SOUTH OF CASPER WITH DRY AND BREEZY
CONDITIONS ELSEWHERE.

DRIER AIR FROM THE NORTHWEST ADVANCES TO THE SOUTHEAST FOR TUESDAY
MORNING BUT ANOTHER PUSH OF MID LEVEL MOISTURE ARRIVES INTO THE
WEST LATER TUESDAY AFTERNOON WHICH COULD HELP A FEW THUNDERSTORMS
DEVELOP OVER THE MOUNTAINS. THERE IS NOT A LOT OF PWAT WITH THIS
SYSTEM SO NOT A LOT OF RAIN IS EXPECTED WITH THESE
STORMS...HOWEVER THERE COULD BE WIND GUSTS OVER 40 MPH THAT TRAVEL
FAR FROM THE PARENT STORM. THERE IS SOME SLIGHTLY BETTER MOISTURE
ACROSS THE SOUTH SO EXPECT A FEW MORE STORMS TO HAVE SOME RAIN
WITH THEM IN SWEETWATER AND LINCOLN COUNTIES...BUT AT THE SAME
TIME...STORMS COULD BE MORE NUMEROUS.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY...

WITH A LONG WAVE TROUGH OVER THE PACIFIC NORTHWEST AND THE RIDGE
OVER THE CENTRAL US FROM TUESDAY THROUGH SATURDAY...WYOMING WILL BE
IN THE SOUTHWEST FLOW SECTOR THROUGH MUCH OF THE PERIOD.  WEDNESDAY
SHOULD SEE FAIRLY DRY FLOW OVER THE STATE AS THE MOISTURE REMAINS
EITHER OVER THE SOUTHERN ROCKIES OR FARTHER NORTHWEST.  THE PRESSURE
GRADIENT AND SURFACE LOW OVER EASTERN MONTANA WILL ALLOW WINDY
CONDITIONS TO DEVELOP DURING THE AFTERNOON AND EARLY EVENING HOURS
OVER MUCH OF THE AREA. COMBINED WITH LOW RELATIVE HUMIDITIES OF 15
PERCENT OR LOWER...FIRE WEATHER CONCERNS WILL CERTAINLY BE
HEIGHTENED.

AS THE TROUGH SLOWLY MIGRATES SLIGHTLY SOUTHEASTWARD THURSDAY...SOME
MOISTURE AND INSTABILITY WILL GIVE RISE TO ISOLATED SHOWERS AND
THUNDERSTORMS OVER YNP AND THE NW MOUNTAINS.  BREEZY CONDITIONS WILL
CONTINUE THROUGH SOUTHERN TO CENTRAL WYOMING WITH LOW HUMIDITIES AS
WELL...WITH A BIT OF SOME RELIEF ACROSS NORTHERN WYOMING.

THROUGH FRIDAY...THE GFS AND ECMWF ARE IN FAIRLY GOOD
AGREEMENT...ALTHOUGH THE GFS LOOKS TO BRING MORE MOISTURE INTO
SOUTHERN WY.  AS THE TROUGH MOVES MORE OVER THE NORTHERN ROCKIES
(PER GFS) OR SOLIDIFIES OVER OREGON (ECMWF AND GEM)...BOTH MODELS
INCREASE THE MOISTURE AND PRECIPITATION ALL DAY SATURDAY.  WITH THE
FASTER GFS TRACK...A COLD FRONT IS LIKELY TO MOVE INTO NORTHERN
WYOMING LATER ON SATURDAY TO ENHANCE PRECIPITATION ACROSS THAT AREA.

SO...FOCUS OF ACTIVITY REMAINS TO BE SEEN WITH THE OVERALL PATTERN
OF THE LOW PRESSURE SYSTEM...WITH SATURDAY HAVING THE HIGHEST CHANCE
OF PRECIPITATION THROUGH THE PERIOD.  700MB TEMPERATURES WILL DROP
CONSIDERABLY AS THE CORE OF THE LOW MOVES OVER THE AREA SATURDAY
NIGHT INTO SUNDAY...WITH LIGHT SNOW LIKELY IN THE HIGHEST ELEVATIONS
ACROSS NORTHWEST WYOMING.

SUNDAY LOOKS TO BE COOL REGARDLESS...WITH EITHER CLEARING BEHIND THE
SYSTEM...OR CONTINUED SHOWERS.  MONDAY LOOKS TO WARM UP SLIGHTLY
OVER SUNDAY WITH SOME SHOWERS AND THUNDERSTORMS ACROSS SOUTHERN
WYOMING.

&&

.AVIATION.../06Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL THROUGH TUESDAY EVENING. ISOLATED
SHOWERS AND STORMS WILL DEVELOP OVER THE WEST AFTER 19Z. THIS
ACTIVITY WILL DEVELOP EAST OF THE CONTINENTAL DIVIDE AFTER 22Z.
OUTFLOW WIND GUSTS TO 30 KNOTS WILL BE POSSIBLE NEAR ANY SHOWERS OR
STORMS. THE SHOWER AND STORM ACTIVITY WILL END IN THE WEST BY 04Z
WED AND IN THE EAST AROUND 09Z WED.

&&

.FIRE WEATHER...

...ELEVATED FIRE DANGER FOR MUCH OF THE WEEK...

THERE WILL BE DRY AND BREEZY PERIODS THROUGHOUT THE WEEK WITH
OCCASIONAL LIGHTNING AND COLD FRONTS LATER IN THE WEEK AS ANOTHER
LARGE UPPER TROUGH APPROACHES. WESTERLY BREEZES WILL CONTINUE
INTO THE EVENING WITH A FEW SPOTS EXCEEDING 30 MPH...ESPECIALLY
NEAR STORMS AND OVER HIGHER TERRAIN. RELATIVE HUMIDITY WILL
IMPROVE ON TUESDAY AFTERNOON BUT IT WILL STILL DIP INTO THE MID
TEENS IN MANY AREAS. A LARGE TROUGH WILL APPROACH ON
WEDNESDAY...INCREASING FLOW FROM THE SOUTHWEST FOR WEDNESDAY AND
THURSDAY WITH WIDESPREAD LOW HUMIDITY AND GUSTY WINDS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...

FIRE WEATHER WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY
EVENING FOR WYZ275-277-279-414-415.

RED FLAG WARNING UNTIL 9 PM MDT WEDNESDAY FOR WYZ276-280>283-285-
287-289-300-416.

&&

$$

SHORT TERM...ALLEN
LONG TERM...MCDONALD
AVIATION...AR
FIRE WEATHER...ALLEN




000
FXUS65 KRIW 312135
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
335 PM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH TUESDAY

A SUBSIDENCE INVERSION SURFACED...DRASTICALLY DROPPING RELATIVE
HUMIDITIES THIS AFTERNOON WITH WESTERLY WINDS INCREASING TO ABOVE
25 MPH IN MANY AREAS...

A FEW THUNDERSTORMS WILL LINGER ACROSS THE SOUTH THIS EVENING AS A
PLUME OF MOISTURE AND THETA E RIDGE TO OUR SOUTH AND EAST
MAINTAINS AN UNSTABLE ATMOSPHERE INTO THE EVENING HOURS. SOME OF
THE STORMS EAST OF NATRONA COUNTY COULD KICK SOME MOIST OUTFLOW
BOUNDARIES WESTWARD INTO NORTHERN AND CENTRAL NATRONA
COUNTY...THIS COULD KICK OFF A FEW STORMS IN THIS AREA TOO.
OTHERWISE...THE BEST CHANCE FOR A THUNDERSTORM IN NATRONA COUNTY
THIS EVENING WILL BE SOUTH OF CASPER WITH DRY AND BREEZY
CONDITIONS ELSEWHERE.

DRIER AIR FROM THE NORTHWEST ADVANCES TO THE SOUTHEAST FOR TUESDAY
MORNING BUT ANOTHER PUSH OF MID LEVEL MOISTURE ARRIVES INTO THE
WEST LATER TUESDAY AFTERNOON WHICH COULD HELP A FEW THUNDERSTORMS
DEVELOP OVER THE MOUNTAINS. THERE IS NOT A LOT OF PWAT WITH THIS
SYSTEM SO NOT A LOT OF RAIN IS EXPECTED WITH THESE
STORMS...HOWEVER THERE COULD BE WIND GUSTS OVER 40 MPH THAT TRAVEL
FAR FROM THE PARENT STORM. THERE IS SOME SLIGHTLY BETTER MOISTURE
ACROSS THE SOUTH SO EXPECT A FEW MORE STORMS TO HAVE SOME RAIN
WITH THEM IN SWEETWATER AND LINCOLN COUNTIES...BUT AT THE SAME
TIME...STORMS COULD BE MORE NUMEROUS.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY...

WITH A LONG WAVE TROUGH OVER THE PACIFIC NORTHWEST AND THE RIDGE
OVER THE CENTRAL US FROM TUESDAY THROUGH SATURDAY...WYOMING WILL BE
IN THE SOUTHWEST FLOW SECTOR THROUGH MUCH OF THE PERIOD.  WEDNESDAY
SHOULD SEE FAIRLY DRY FLOW OVER THE STATE AS THE MOISTURE REMAINS
EITHER OVER THE SOUTHERN ROCKIES OR FARTHER NORTHWEST.  THE PRESSURE
GRADIENT AND SURFACE LOW OVER EASTERN MONTANA WILL ALLOW WINDY
CONDITIONS TO DEVELOP DURING THE AFTERNOON AND EARLY EVENING HOURS
OVER MUCH OF THE AREA. COMBINED WITH LOW RELATIVE HUMIDITIES OF 15
PERCENT OR LOWER...FIRE WEATHER CONCERNS WILL CERTAINLY BE
HEIGHTENED.

AS THE TROUGH SLOWLY MIGRATES SLIGHTLY SOUTHEASTWARD THURSDAY...SOME
MOISTURE AND INSTABILITY WILL GIVE RISE TO ISOLATED SHOWERS AND
THUNDERSTORMS OVER YNP AND THE NW MOUNTAINS.  BREEZY CONDITIONS WILL
CONTINUE THROUGH SOUTHERN TO CENTRAL WYOMING WITH LOW HUMIDITIES AS
WELL...WITH A BIT OF SOME RELIEF ACROSS NORTHERN WYOMING.

THROUGH FRIDAY...THE GFS AND ECMWF ARE IN FAIRLY GOOD
AGREEMENT...ALTHOUGH THE GFS LOOKS TO BRING MORE MOISTURE INTO
SOUTHERN WY.  AS THE TROUGH MOVES MORE OVER THE NORTHERN ROCKIES
(PER GFS) OR SOLIDIFIES OVER OREGON (ECMWF AND GEM)...BOTH MODELS
INCREASE THE MOISTURE AND PRECIPITATION ALL DAY SATURDAY.  WITH THE
FASTER GFS TRACK...A COLD FRONT IS LIKELY TO MOVE INTO NORTHERN
WYOMING LATER ON SATURDAY TO ENHANCE PRECIPITATION ACROSS THAT AREA.

SO...FOCUS OF ACTIVITY REMAINS TO BE SEEN WITH THE OVERALL PATTERN
OF THE LOW PRESSURE SYSTEM...WITH SATURDAY HAVING THE HIGHEST CHANCE
OF PRECIPITATION THROUGH THE PERIOD.  700MB TEMPERATURES WILL DROP
CONSIDERABLY AS THE CORE OF THE LOW MOVES OVER THE AREA SATURDAY
NIGHT INTO SUNDAY...WITH LIGHT SNOW LIKELY IN THE HIGHEST ELEVATIONS
ACROSS NORTHWEST WYOMING.

SUNDAY LOOKS TO BE COOL REGARDLESS...WITH EITHER CLEARING BEHIND THE
SYSTEM...OR CONTINUED SHOWERS.  MONDAY LOOKS TO WARM UP SLIGHTLY
OVER SUNDAY WITH SOME SHOWERS AND THUNDERSTORMS ACROSS SOUTHERN
WYOMING.

&&

.AVIATION.../00Z ISSUANCE/

WESTERLY WIND WITH GUSTS TO 30 MPH POSSIBLE INTO THE EVENING WITH
OCCASIONAL LLWS TONIGHT AS WINDS GO ALOFT. ISOLATED TO WIDELY
SCATTERED THUNDERSTORMS WILL DEVELOP THIS AFTERNOON VCNTY OF A
KRKS-KCPR LINE. THUNDERSTORM ACTIVITY WILL MOSTLY END ACROSS THE
SOUTH BY 3Z TUESDAY. EXPECT THUNDERSTORMS TO RETURN AFTER 18Z TUE
OVER THE WESTERN MOUNTAINS AND ACROSS THE SOUTH WITH STRONG
OUTFLOW WINDS POSSIBLE.

&&

.FIRE WEATHER...

...ELEVATED FIRE DANGER FOR MUCH OF THE WEEK...

THERE WILL BE DRY AND BREEZY PERIODS THROUGHOUT THE WEEK WITH
OCCASIONAL LIGHTNING AND COLD FRONTS LATER IN THE WEEK AS ANOTHER
LARGE UPPER TROUGH APPROACHES. WESTERLY BREEZES WILL CONTINUE
INTO THE EVENING WITH A FEW SPOTS EXCEEDING 30 MPH...ESPECIALLY
NEAR STORMS AND OVER HIGHER TERRAIN. RELATIVE HUMIDITY WILL
IMPROVE ON TUESDAY AFTERNOON BUT IT WILL STILL DIP INTO THE MID
TEENS IN MANY AREAS. A LARGE TROUGH WILL APPROACH ON
WEDNESDAY...INCREASING FLOW FROM THE SOUTHWEST FOR WEDNESDAY AND
THURSDAY WITH WIDESPREAD LOW HUMIDITY AND GUSTY WINDS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
FIRE WEATHER WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY
EVENING FOR WYZ275-277-279-414-415.

RED FLAG WARNING UNTIL 9 PM MDT WEDNESDAY FOR WYZ276-280>283-285-
287-289-300-416.

&&

$$

SHORT TERM...ALLEN
LONG TERM...MCDONALD
AVIATION...ALLEN
FIRE WEATHER...ALLEN




000
FXUS65 KRIW 312135
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
335 PM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH TUESDAY

A SUBSIDENCE INVERSION SURFACED...DRASTICALLY DROPPING RELATIVE
HUMIDITIES THIS AFTERNOON WITH WESTERLY WINDS INCREASING TO ABOVE
25 MPH IN MANY AREAS...

A FEW THUNDERSTORMS WILL LINGER ACROSS THE SOUTH THIS EVENING AS A
PLUME OF MOISTURE AND THETA E RIDGE TO OUR SOUTH AND EAST
MAINTAINS AN UNSTABLE ATMOSPHERE INTO THE EVENING HOURS. SOME OF
THE STORMS EAST OF NATRONA COUNTY COULD KICK SOME MOIST OUTFLOW
BOUNDARIES WESTWARD INTO NORTHERN AND CENTRAL NATRONA
COUNTY...THIS COULD KICK OFF A FEW STORMS IN THIS AREA TOO.
OTHERWISE...THE BEST CHANCE FOR A THUNDERSTORM IN NATRONA COUNTY
THIS EVENING WILL BE SOUTH OF CASPER WITH DRY AND BREEZY
CONDITIONS ELSEWHERE.

DRIER AIR FROM THE NORTHWEST ADVANCES TO THE SOUTHEAST FOR TUESDAY
MORNING BUT ANOTHER PUSH OF MID LEVEL MOISTURE ARRIVES INTO THE
WEST LATER TUESDAY AFTERNOON WHICH COULD HELP A FEW THUNDERSTORMS
DEVELOP OVER THE MOUNTAINS. THERE IS NOT A LOT OF PWAT WITH THIS
SYSTEM SO NOT A LOT OF RAIN IS EXPECTED WITH THESE
STORMS...HOWEVER THERE COULD BE WIND GUSTS OVER 40 MPH THAT TRAVEL
FAR FROM THE PARENT STORM. THERE IS SOME SLIGHTLY BETTER MOISTURE
ACROSS THE SOUTH SO EXPECT A FEW MORE STORMS TO HAVE SOME RAIN
WITH THEM IN SWEETWATER AND LINCOLN COUNTIES...BUT AT THE SAME
TIME...STORMS COULD BE MORE NUMEROUS.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY...

WITH A LONG WAVE TROUGH OVER THE PACIFIC NORTHWEST AND THE RIDGE
OVER THE CENTRAL US FROM TUESDAY THROUGH SATURDAY...WYOMING WILL BE
IN THE SOUTHWEST FLOW SECTOR THROUGH MUCH OF THE PERIOD.  WEDNESDAY
SHOULD SEE FAIRLY DRY FLOW OVER THE STATE AS THE MOISTURE REMAINS
EITHER OVER THE SOUTHERN ROCKIES OR FARTHER NORTHWEST.  THE PRESSURE
GRADIENT AND SURFACE LOW OVER EASTERN MONTANA WILL ALLOW WINDY
CONDITIONS TO DEVELOP DURING THE AFTERNOON AND EARLY EVENING HOURS
OVER MUCH OF THE AREA. COMBINED WITH LOW RELATIVE HUMIDITIES OF 15
PERCENT OR LOWER...FIRE WEATHER CONCERNS WILL CERTAINLY BE
HEIGHTENED.

AS THE TROUGH SLOWLY MIGRATES SLIGHTLY SOUTHEASTWARD THURSDAY...SOME
MOISTURE AND INSTABILITY WILL GIVE RISE TO ISOLATED SHOWERS AND
THUNDERSTORMS OVER YNP AND THE NW MOUNTAINS.  BREEZY CONDITIONS WILL
CONTINUE THROUGH SOUTHERN TO CENTRAL WYOMING WITH LOW HUMIDITIES AS
WELL...WITH A BIT OF SOME RELIEF ACROSS NORTHERN WYOMING.

THROUGH FRIDAY...THE GFS AND ECMWF ARE IN FAIRLY GOOD
AGREEMENT...ALTHOUGH THE GFS LOOKS TO BRING MORE MOISTURE INTO
SOUTHERN WY.  AS THE TROUGH MOVES MORE OVER THE NORTHERN ROCKIES
(PER GFS) OR SOLIDIFIES OVER OREGON (ECMWF AND GEM)...BOTH MODELS
INCREASE THE MOISTURE AND PRECIPITATION ALL DAY SATURDAY.  WITH THE
FASTER GFS TRACK...A COLD FRONT IS LIKELY TO MOVE INTO NORTHERN
WYOMING LATER ON SATURDAY TO ENHANCE PRECIPITATION ACROSS THAT AREA.

SO...FOCUS OF ACTIVITY REMAINS TO BE SEEN WITH THE OVERALL PATTERN
OF THE LOW PRESSURE SYSTEM...WITH SATURDAY HAVING THE HIGHEST CHANCE
OF PRECIPITATION THROUGH THE PERIOD.  700MB TEMPERATURES WILL DROP
CONSIDERABLY AS THE CORE OF THE LOW MOVES OVER THE AREA SATURDAY
NIGHT INTO SUNDAY...WITH LIGHT SNOW LIKELY IN THE HIGHEST ELEVATIONS
ACROSS NORTHWEST WYOMING.

SUNDAY LOOKS TO BE COOL REGARDLESS...WITH EITHER CLEARING BEHIND THE
SYSTEM...OR CONTINUED SHOWERS.  MONDAY LOOKS TO WARM UP SLIGHTLY
OVER SUNDAY WITH SOME SHOWERS AND THUNDERSTORMS ACROSS SOUTHERN
WYOMING.

&&

.AVIATION.../00Z ISSUANCE/

WESTERLY WIND WITH GUSTS TO 30 MPH POSSIBLE INTO THE EVENING WITH
OCCASIONAL LLWS TONIGHT AS WINDS GO ALOFT. ISOLATED TO WIDELY
SCATTERED THUNDERSTORMS WILL DEVELOP THIS AFTERNOON VCNTY OF A
KRKS-KCPR LINE. THUNDERSTORM ACTIVITY WILL MOSTLY END ACROSS THE
SOUTH BY 3Z TUESDAY. EXPECT THUNDERSTORMS TO RETURN AFTER 18Z TUE
OVER THE WESTERN MOUNTAINS AND ACROSS THE SOUTH WITH STRONG
OUTFLOW WINDS POSSIBLE.

&&

.FIRE WEATHER...

...ELEVATED FIRE DANGER FOR MUCH OF THE WEEK...

THERE WILL BE DRY AND BREEZY PERIODS THROUGHOUT THE WEEK WITH
OCCASIONAL LIGHTNING AND COLD FRONTS LATER IN THE WEEK AS ANOTHER
LARGE UPPER TROUGH APPROACHES. WESTERLY BREEZES WILL CONTINUE
INTO THE EVENING WITH A FEW SPOTS EXCEEDING 30 MPH...ESPECIALLY
NEAR STORMS AND OVER HIGHER TERRAIN. RELATIVE HUMIDITY WILL
IMPROVE ON TUESDAY AFTERNOON BUT IT WILL STILL DIP INTO THE MID
TEENS IN MANY AREAS. A LARGE TROUGH WILL APPROACH ON
WEDNESDAY...INCREASING FLOW FROM THE SOUTHWEST FOR WEDNESDAY AND
THURSDAY WITH WIDESPREAD LOW HUMIDITY AND GUSTY WINDS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
FIRE WEATHER WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY
EVENING FOR WYZ275-277-279-414-415.

RED FLAG WARNING UNTIL 9 PM MDT WEDNESDAY FOR WYZ276-280>283-285-
287-289-300-416.

&&

$$

SHORT TERM...ALLEN
LONG TERM...MCDONALD
AVIATION...ALLEN
FIRE WEATHER...ALLEN





000
FXUS65 KRIW 312135
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
335 PM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH TUESDAY

A SUBSIDENCE INVERSION SURFACED...DRASTICALLY DROPPING RELATIVE
HUMIDITIES THIS AFTERNOON WITH WESTERLY WINDS INCREASING TO ABOVE
25 MPH IN MANY AREAS...

A FEW THUNDERSTORMS WILL LINGER ACROSS THE SOUTH THIS EVENING AS A
PLUME OF MOISTURE AND THETA E RIDGE TO OUR SOUTH AND EAST
MAINTAINS AN UNSTABLE ATMOSPHERE INTO THE EVENING HOURS. SOME OF
THE STORMS EAST OF NATRONA COUNTY COULD KICK SOME MOIST OUTFLOW
BOUNDARIES WESTWARD INTO NORTHERN AND CENTRAL NATRONA
COUNTY...THIS COULD KICK OFF A FEW STORMS IN THIS AREA TOO.
OTHERWISE...THE BEST CHANCE FOR A THUNDERSTORM IN NATRONA COUNTY
THIS EVENING WILL BE SOUTH OF CASPER WITH DRY AND BREEZY
CONDITIONS ELSEWHERE.

DRIER AIR FROM THE NORTHWEST ADVANCES TO THE SOUTHEAST FOR TUESDAY
MORNING BUT ANOTHER PUSH OF MID LEVEL MOISTURE ARRIVES INTO THE
WEST LATER TUESDAY AFTERNOON WHICH COULD HELP A FEW THUNDERSTORMS
DEVELOP OVER THE MOUNTAINS. THERE IS NOT A LOT OF PWAT WITH THIS
SYSTEM SO NOT A LOT OF RAIN IS EXPECTED WITH THESE
STORMS...HOWEVER THERE COULD BE WIND GUSTS OVER 40 MPH THAT TRAVEL
FAR FROM THE PARENT STORM. THERE IS SOME SLIGHTLY BETTER MOISTURE
ACROSS THE SOUTH SO EXPECT A FEW MORE STORMS TO HAVE SOME RAIN
WITH THEM IN SWEETWATER AND LINCOLN COUNTIES...BUT AT THE SAME
TIME...STORMS COULD BE MORE NUMEROUS.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY...

WITH A LONG WAVE TROUGH OVER THE PACIFIC NORTHWEST AND THE RIDGE
OVER THE CENTRAL US FROM TUESDAY THROUGH SATURDAY...WYOMING WILL BE
IN THE SOUTHWEST FLOW SECTOR THROUGH MUCH OF THE PERIOD.  WEDNESDAY
SHOULD SEE FAIRLY DRY FLOW OVER THE STATE AS THE MOISTURE REMAINS
EITHER OVER THE SOUTHERN ROCKIES OR FARTHER NORTHWEST.  THE PRESSURE
GRADIENT AND SURFACE LOW OVER EASTERN MONTANA WILL ALLOW WINDY
CONDITIONS TO DEVELOP DURING THE AFTERNOON AND EARLY EVENING HOURS
OVER MUCH OF THE AREA. COMBINED WITH LOW RELATIVE HUMIDITIES OF 15
PERCENT OR LOWER...FIRE WEATHER CONCERNS WILL CERTAINLY BE
HEIGHTENED.

AS THE TROUGH SLOWLY MIGRATES SLIGHTLY SOUTHEASTWARD THURSDAY...SOME
MOISTURE AND INSTABILITY WILL GIVE RISE TO ISOLATED SHOWERS AND
THUNDERSTORMS OVER YNP AND THE NW MOUNTAINS.  BREEZY CONDITIONS WILL
CONTINUE THROUGH SOUTHERN TO CENTRAL WYOMING WITH LOW HUMIDITIES AS
WELL...WITH A BIT OF SOME RELIEF ACROSS NORTHERN WYOMING.

THROUGH FRIDAY...THE GFS AND ECMWF ARE IN FAIRLY GOOD
AGREEMENT...ALTHOUGH THE GFS LOOKS TO BRING MORE MOISTURE INTO
SOUTHERN WY.  AS THE TROUGH MOVES MORE OVER THE NORTHERN ROCKIES
(PER GFS) OR SOLIDIFIES OVER OREGON (ECMWF AND GEM)...BOTH MODELS
INCREASE THE MOISTURE AND PRECIPITATION ALL DAY SATURDAY.  WITH THE
FASTER GFS TRACK...A COLD FRONT IS LIKELY TO MOVE INTO NORTHERN
WYOMING LATER ON SATURDAY TO ENHANCE PRECIPITATION ACROSS THAT AREA.

SO...FOCUS OF ACTIVITY REMAINS TO BE SEEN WITH THE OVERALL PATTERN
OF THE LOW PRESSURE SYSTEM...WITH SATURDAY HAVING THE HIGHEST CHANCE
OF PRECIPITATION THROUGH THE PERIOD.  700MB TEMPERATURES WILL DROP
CONSIDERABLY AS THE CORE OF THE LOW MOVES OVER THE AREA SATURDAY
NIGHT INTO SUNDAY...WITH LIGHT SNOW LIKELY IN THE HIGHEST ELEVATIONS
ACROSS NORTHWEST WYOMING.

SUNDAY LOOKS TO BE COOL REGARDLESS...WITH EITHER CLEARING BEHIND THE
SYSTEM...OR CONTINUED SHOWERS.  MONDAY LOOKS TO WARM UP SLIGHTLY
OVER SUNDAY WITH SOME SHOWERS AND THUNDERSTORMS ACROSS SOUTHERN
WYOMING.

&&

.AVIATION.../00Z ISSUANCE/

WESTERLY WIND WITH GUSTS TO 30 MPH POSSIBLE INTO THE EVENING WITH
OCCASIONAL LLWS TONIGHT AS WINDS GO ALOFT. ISOLATED TO WIDELY
SCATTERED THUNDERSTORMS WILL DEVELOP THIS AFTERNOON VCNTY OF A
KRKS-KCPR LINE. THUNDERSTORM ACTIVITY WILL MOSTLY END ACROSS THE
SOUTH BY 3Z TUESDAY. EXPECT THUNDERSTORMS TO RETURN AFTER 18Z TUE
OVER THE WESTERN MOUNTAINS AND ACROSS THE SOUTH WITH STRONG
OUTFLOW WINDS POSSIBLE.

&&

.FIRE WEATHER...

...ELEVATED FIRE DANGER FOR MUCH OF THE WEEK...

THERE WILL BE DRY AND BREEZY PERIODS THROUGHOUT THE WEEK WITH
OCCASIONAL LIGHTNING AND COLD FRONTS LATER IN THE WEEK AS ANOTHER
LARGE UPPER TROUGH APPROACHES. WESTERLY BREEZES WILL CONTINUE
INTO THE EVENING WITH A FEW SPOTS EXCEEDING 30 MPH...ESPECIALLY
NEAR STORMS AND OVER HIGHER TERRAIN. RELATIVE HUMIDITY WILL
IMPROVE ON TUESDAY AFTERNOON BUT IT WILL STILL DIP INTO THE MID
TEENS IN MANY AREAS. A LARGE TROUGH WILL APPROACH ON
WEDNESDAY...INCREASING FLOW FROM THE SOUTHWEST FOR WEDNESDAY AND
THURSDAY WITH WIDESPREAD LOW HUMIDITY AND GUSTY WINDS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
FIRE WEATHER WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY
EVENING FOR WYZ275-277-279-414-415.

RED FLAG WARNING UNTIL 9 PM MDT WEDNESDAY FOR WYZ276-280>283-285-
287-289-300-416.

&&

$$

SHORT TERM...ALLEN
LONG TERM...MCDONALD
AVIATION...ALLEN
FIRE WEATHER...ALLEN




000
FXUS65 KRIW 312135
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
335 PM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH TUESDAY

A SUBSIDENCE INVERSION SURFACED...DRASTICALLY DROPPING RELATIVE
HUMIDITIES THIS AFTERNOON WITH WESTERLY WINDS INCREASING TO ABOVE
25 MPH IN MANY AREAS...

A FEW THUNDERSTORMS WILL LINGER ACROSS THE SOUTH THIS EVENING AS A
PLUME OF MOISTURE AND THETA E RIDGE TO OUR SOUTH AND EAST
MAINTAINS AN UNSTABLE ATMOSPHERE INTO THE EVENING HOURS. SOME OF
THE STORMS EAST OF NATRONA COUNTY COULD KICK SOME MOIST OUTFLOW
BOUNDARIES WESTWARD INTO NORTHERN AND CENTRAL NATRONA
COUNTY...THIS COULD KICK OFF A FEW STORMS IN THIS AREA TOO.
OTHERWISE...THE BEST CHANCE FOR A THUNDERSTORM IN NATRONA COUNTY
THIS EVENING WILL BE SOUTH OF CASPER WITH DRY AND BREEZY
CONDITIONS ELSEWHERE.

DRIER AIR FROM THE NORTHWEST ADVANCES TO THE SOUTHEAST FOR TUESDAY
MORNING BUT ANOTHER PUSH OF MID LEVEL MOISTURE ARRIVES INTO THE
WEST LATER TUESDAY AFTERNOON WHICH COULD HELP A FEW THUNDERSTORMS
DEVELOP OVER THE MOUNTAINS. THERE IS NOT A LOT OF PWAT WITH THIS
SYSTEM SO NOT A LOT OF RAIN IS EXPECTED WITH THESE
STORMS...HOWEVER THERE COULD BE WIND GUSTS OVER 40 MPH THAT TRAVEL
FAR FROM THE PARENT STORM. THERE IS SOME SLIGHTLY BETTER MOISTURE
ACROSS THE SOUTH SO EXPECT A FEW MORE STORMS TO HAVE SOME RAIN
WITH THEM IN SWEETWATER AND LINCOLN COUNTIES...BUT AT THE SAME
TIME...STORMS COULD BE MORE NUMEROUS.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY...

WITH A LONG WAVE TROUGH OVER THE PACIFIC NORTHWEST AND THE RIDGE
OVER THE CENTRAL US FROM TUESDAY THROUGH SATURDAY...WYOMING WILL BE
IN THE SOUTHWEST FLOW SECTOR THROUGH MUCH OF THE PERIOD.  WEDNESDAY
SHOULD SEE FAIRLY DRY FLOW OVER THE STATE AS THE MOISTURE REMAINS
EITHER OVER THE SOUTHERN ROCKIES OR FARTHER NORTHWEST.  THE PRESSURE
GRADIENT AND SURFACE LOW OVER EASTERN MONTANA WILL ALLOW WINDY
CONDITIONS TO DEVELOP DURING THE AFTERNOON AND EARLY EVENING HOURS
OVER MUCH OF THE AREA. COMBINED WITH LOW RELATIVE HUMIDITIES OF 15
PERCENT OR LOWER...FIRE WEATHER CONCERNS WILL CERTAINLY BE
HEIGHTENED.

AS THE TROUGH SLOWLY MIGRATES SLIGHTLY SOUTHEASTWARD THURSDAY...SOME
MOISTURE AND INSTABILITY WILL GIVE RISE TO ISOLATED SHOWERS AND
THUNDERSTORMS OVER YNP AND THE NW MOUNTAINS.  BREEZY CONDITIONS WILL
CONTINUE THROUGH SOUTHERN TO CENTRAL WYOMING WITH LOW HUMIDITIES AS
WELL...WITH A BIT OF SOME RELIEF ACROSS NORTHERN WYOMING.

THROUGH FRIDAY...THE GFS AND ECMWF ARE IN FAIRLY GOOD
AGREEMENT...ALTHOUGH THE GFS LOOKS TO BRING MORE MOISTURE INTO
SOUTHERN WY.  AS THE TROUGH MOVES MORE OVER THE NORTHERN ROCKIES
(PER GFS) OR SOLIDIFIES OVER OREGON (ECMWF AND GEM)...BOTH MODELS
INCREASE THE MOISTURE AND PRECIPITATION ALL DAY SATURDAY.  WITH THE
FASTER GFS TRACK...A COLD FRONT IS LIKELY TO MOVE INTO NORTHERN
WYOMING LATER ON SATURDAY TO ENHANCE PRECIPITATION ACROSS THAT AREA.

SO...FOCUS OF ACTIVITY REMAINS TO BE SEEN WITH THE OVERALL PATTERN
OF THE LOW PRESSURE SYSTEM...WITH SATURDAY HAVING THE HIGHEST CHANCE
OF PRECIPITATION THROUGH THE PERIOD.  700MB TEMPERATURES WILL DROP
CONSIDERABLY AS THE CORE OF THE LOW MOVES OVER THE AREA SATURDAY
NIGHT INTO SUNDAY...WITH LIGHT SNOW LIKELY IN THE HIGHEST ELEVATIONS
ACROSS NORTHWEST WYOMING.

SUNDAY LOOKS TO BE COOL REGARDLESS...WITH EITHER CLEARING BEHIND THE
SYSTEM...OR CONTINUED SHOWERS.  MONDAY LOOKS TO WARM UP SLIGHTLY
OVER SUNDAY WITH SOME SHOWERS AND THUNDERSTORMS ACROSS SOUTHERN
WYOMING.

&&

.AVIATION.../00Z ISSUANCE/

WESTERLY WIND WITH GUSTS TO 30 MPH POSSIBLE INTO THE EVENING WITH
OCCASIONAL LLWS TONIGHT AS WINDS GO ALOFT. ISOLATED TO WIDELY
SCATTERED THUNDERSTORMS WILL DEVELOP THIS AFTERNOON VCNTY OF A
KRKS-KCPR LINE. THUNDERSTORM ACTIVITY WILL MOSTLY END ACROSS THE
SOUTH BY 3Z TUESDAY. EXPECT THUNDERSTORMS TO RETURN AFTER 18Z TUE
OVER THE WESTERN MOUNTAINS AND ACROSS THE SOUTH WITH STRONG
OUTFLOW WINDS POSSIBLE.

&&

.FIRE WEATHER...

...ELEVATED FIRE DANGER FOR MUCH OF THE WEEK...

THERE WILL BE DRY AND BREEZY PERIODS THROUGHOUT THE WEEK WITH
OCCASIONAL LIGHTNING AND COLD FRONTS LATER IN THE WEEK AS ANOTHER
LARGE UPPER TROUGH APPROACHES. WESTERLY BREEZES WILL CONTINUE
INTO THE EVENING WITH A FEW SPOTS EXCEEDING 30 MPH...ESPECIALLY
NEAR STORMS AND OVER HIGHER TERRAIN. RELATIVE HUMIDITY WILL
IMPROVE ON TUESDAY AFTERNOON BUT IT WILL STILL DIP INTO THE MID
TEENS IN MANY AREAS. A LARGE TROUGH WILL APPROACH ON
WEDNESDAY...INCREASING FLOW FROM THE SOUTHWEST FOR WEDNESDAY AND
THURSDAY WITH WIDESPREAD LOW HUMIDITY AND GUSTY WINDS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
FIRE WEATHER WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY
EVENING FOR WYZ275-277-279-414-415.

RED FLAG WARNING UNTIL 9 PM MDT WEDNESDAY FOR WYZ276-280>283-285-
287-289-300-416.

&&

$$

SHORT TERM...ALLEN
LONG TERM...MCDONALD
AVIATION...ALLEN
FIRE WEATHER...ALLEN





000
FXUS65 KRIW 311830
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1230 PM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

THE THUNDERSTORMS THAT OCCURRED EARLIER THIS EVENING WERE FAST MOVING
WITH HEAVY RAINFALL BUT WITH A SHORT RESIDENCE TIME AND FREQUENT
LIGHTNING ALONG WITH UP TO 40 MPH WIND GUSTS. THE FROPA AND
HAS OCCURRED AND THE SHOWERS HAVE EXITED OFF TO THE EAST AND
DISSIPATED. CONFLUENT FLOW HAS TAKEN OVER. TODAY SOME INSTABILITY
WILL LINGER IN THE FAR SOUTH AND UP INTO SOUTHWEST NATRONA COUNTY
WHERE ISOLATED T STORMS ARE EXPECTED WITH SOME CONVECTION
STREAMING OFF THE UINTAS INTO SOUTHERN SWEETWATER COUNTY. ON
TUESDAY EXPECT ISOLD T STORMS ONLY IN THE NW MTNS WHEN CAPES
INCREASE SLIGHTLY BUT ARE NOT EXPECTED TO MOVE OFF THE MTNS.
WEDNESDAY WILL FEATURE INCREASE SOUTHWEST WINDS AS A CLOSED LOW
MOVES INLAND INTO BC AND THE ASCT TROUGH MAKES LANDFALL ONTO THE
PAC NW COAST THUS INCREASING OUR SOUTHWEST GRADIENT. TEMPS WILL BE
SLIGHTLY COOLER TODAY AND THEN BEGIN A WARMING TREND TUESDAY WITH
WEDNESDAY BEING THE WARMEST DAY OF THE PERIOD.

.LONG TERM...THURSDAY THROUGH MONDAY

MAJOR MEDIUM RANGE DIFFERENCES TONIGHT AS TO THE EVOLUTION OF OUR
LATE WEEK TROUGH. THE MODELS DO AGREE THAT THERE WILL BE A COLD
TROUGH OVER THE PACNW/NRN ROCKIES TO START THE PERIOD BUT HOW THIS
TROUGH TRANSLATES EWD WITH TIME IS WHERE THEY DEPART SIGNIFICANTLY.
THE GFS IS THE FASTEST TO MOVE THIS TROUGH OUT OF THE WAY BY
SATURDAY NIGHT WHILE THE ECMWF/GEM DON`T SWING THE TROUGH THROUGH
UNTIL MONDAY MORNING. THE FIRST SHORTWAVE THAT GETS KICKED OUT BY
THE DEVELOPING COLD TROUGH SHOULD LIFT NE ACROSS THE NRN ROCKIES
THURSDAY INTO THURSDAY NIGHT LEADING TO THE FRONT SAGGING SWD INTO
OUR NRN ZONES BEHIND THIS WAVE. THE GFS THEN KEEPS THIS FRONT IN THE
FAR NORTH PRETTY MUCH THROUGH THE PERIOD WITH SHARPLY COOLER TEMPS
BEHIND IT. THE ECMWF WASHES IT OUT EXCEPT MAYBE NEAR THE NRN BORDER
AS IT DEVELOPS AN INTENSE UPPER LOW OVER IDAHO ON SATURDAY THAT
LIFTS ACROSS THE PARK SATURDAY NIGHT WITH -4C AIR AT H7. LEANING
TOWARDS A STRONGER...SLOWER TROUGH...MAYBE NOT ECMWF STRONG...BUT
MORE TOWARDS THAT TIMING. WILL HAVE TO LOOK AT THIS AGAIN TONIGHT
AND HIT THE POPS MUCH HARDER IF THESE TRENDS CONTINUE AND THE MODELS
COME INTO BETTER AGREEMENT. POTENTIAL FOR A COLD LABOR DAY WEEKEND
WITH COLD RAIN AND MOUNTAIN SNOW IS STILL QUITE POSSIBLE IN THE
NORTHWEST PART OF WYOMING INCLUDING YELLOWSTONE NATIONAL PARK.
OTHERWISE...STILL WARM AND BREEZY TO WINDY AHEAD OF THE FRONT
THURSDAY AND IN THE SOUTH THROUGH AT LEAST FRIDAY BEFORE COOLER TO
COLDER AIR FILTERS IN. THE  WEST AND NORTH WILL SEE THE LONGEST
PERIOD OF COOLER WEATHER AND POTENTIALLY DOWNRIGHT COLD IN YNP OVER
THE WEEKEND.

&&

.AVIATION.../18Z ISSUANCE/

ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL DEVELOP THIS
AFTERNOON VCNTY OF A KRKS-KCPR LINE. SURFACE HIGH PRESSURE WILL
KEEP NORTHERN WYOMING UNDER PREVAILING SKC-FEW FL150-200
CONDITIONS AND S-SE WINDS AROUND 10KTS. THUNDERSTORM ACTIVITY WILL
MOSTLY END ACROSS THE SOUTH BY 3Z TUESDAY.

&&

.FIRE WEATHER...

IT WILL BE DRY TODAY BEHIND THIS MORNINGS COOL FRONT BUT A BIT
COOLER. THERE WILL BE SOME 20 MPH BREEZES IN THE AFTERNOON BUT RED
FLAG CONDITIONS ARE NOT EXPECTED. FOR THE REST OF THE WEEK THE
MINIMUM RELATIVE HUMIDITY WILL BE MAINLY IN THE TEENS AT THE LOWER
ELEVATIONS EAST OF THE DIVIDE AND 20S WEST. SOUTHWEST WINDS WILL
INCREASE WEDNESDAY OUT AHEAD OF THE NEXT DEVELOPING PACIFIC
TROUGH.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...ALLEN
FIRE WEATHER...LIPSON




000
FXUS65 KRIW 311830
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1230 PM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

THE THUNDERSTORMS THAT OCCURRED EARLIER THIS EVENING WERE FAST MOVING
WITH HEAVY RAINFALL BUT WITH A SHORT RESIDENCE TIME AND FREQUENT
LIGHTNING ALONG WITH UP TO 40 MPH WIND GUSTS. THE FROPA AND
HAS OCCURRED AND THE SHOWERS HAVE EXITED OFF TO THE EAST AND
DISSIPATED. CONFLUENT FLOW HAS TAKEN OVER. TODAY SOME INSTABILITY
WILL LINGER IN THE FAR SOUTH AND UP INTO SOUTHWEST NATRONA COUNTY
WHERE ISOLATED T STORMS ARE EXPECTED WITH SOME CONVECTION
STREAMING OFF THE UINTAS INTO SOUTHERN SWEETWATER COUNTY. ON
TUESDAY EXPECT ISOLD T STORMS ONLY IN THE NW MTNS WHEN CAPES
INCREASE SLIGHTLY BUT ARE NOT EXPECTED TO MOVE OFF THE MTNS.
WEDNESDAY WILL FEATURE INCREASE SOUTHWEST WINDS AS A CLOSED LOW
MOVES INLAND INTO BC AND THE ASCT TROUGH MAKES LANDFALL ONTO THE
PAC NW COAST THUS INCREASING OUR SOUTHWEST GRADIENT. TEMPS WILL BE
SLIGHTLY COOLER TODAY AND THEN BEGIN A WARMING TREND TUESDAY WITH
WEDNESDAY BEING THE WARMEST DAY OF THE PERIOD.

.LONG TERM...THURSDAY THROUGH MONDAY

MAJOR MEDIUM RANGE DIFFERENCES TONIGHT AS TO THE EVOLUTION OF OUR
LATE WEEK TROUGH. THE MODELS DO AGREE THAT THERE WILL BE A COLD
TROUGH OVER THE PACNW/NRN ROCKIES TO START THE PERIOD BUT HOW THIS
TROUGH TRANSLATES EWD WITH TIME IS WHERE THEY DEPART SIGNIFICANTLY.
THE GFS IS THE FASTEST TO MOVE THIS TROUGH OUT OF THE WAY BY
SATURDAY NIGHT WHILE THE ECMWF/GEM DON`T SWING THE TROUGH THROUGH
UNTIL MONDAY MORNING. THE FIRST SHORTWAVE THAT GETS KICKED OUT BY
THE DEVELOPING COLD TROUGH SHOULD LIFT NE ACROSS THE NRN ROCKIES
THURSDAY INTO THURSDAY NIGHT LEADING TO THE FRONT SAGGING SWD INTO
OUR NRN ZONES BEHIND THIS WAVE. THE GFS THEN KEEPS THIS FRONT IN THE
FAR NORTH PRETTY MUCH THROUGH THE PERIOD WITH SHARPLY COOLER TEMPS
BEHIND IT. THE ECMWF WASHES IT OUT EXCEPT MAYBE NEAR THE NRN BORDER
AS IT DEVELOPS AN INTENSE UPPER LOW OVER IDAHO ON SATURDAY THAT
LIFTS ACROSS THE PARK SATURDAY NIGHT WITH -4C AIR AT H7. LEANING
TOWARDS A STRONGER...SLOWER TROUGH...MAYBE NOT ECMWF STRONG...BUT
MORE TOWARDS THAT TIMING. WILL HAVE TO LOOK AT THIS AGAIN TONIGHT
AND HIT THE POPS MUCH HARDER IF THESE TRENDS CONTINUE AND THE MODELS
COME INTO BETTER AGREEMENT. POTENTIAL FOR A COLD LABOR DAY WEEKEND
WITH COLD RAIN AND MOUNTAIN SNOW IS STILL QUITE POSSIBLE IN THE
NORTHWEST PART OF WYOMING INCLUDING YELLOWSTONE NATIONAL PARK.
OTHERWISE...STILL WARM AND BREEZY TO WINDY AHEAD OF THE FRONT
THURSDAY AND IN THE SOUTH THROUGH AT LEAST FRIDAY BEFORE COOLER TO
COLDER AIR FILTERS IN. THE  WEST AND NORTH WILL SEE THE LONGEST
PERIOD OF COOLER WEATHER AND POTENTIALLY DOWNRIGHT COLD IN YNP OVER
THE WEEKEND.

&&

.AVIATION.../18Z ISSUANCE/

ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL DEVELOP THIS
AFTERNOON VCNTY OF A KRKS-KCPR LINE. SURFACE HIGH PRESSURE WILL
KEEP NORTHERN WYOMING UNDER PREVAILING SKC-FEW FL150-200
CONDITIONS AND S-SE WINDS AROUND 10KTS. THUNDERSTORM ACTIVITY WILL
MOSTLY END ACROSS THE SOUTH BY 3Z TUESDAY.

&&

.FIRE WEATHER...

IT WILL BE DRY TODAY BEHIND THIS MORNINGS COOL FRONT BUT A BIT
COOLER. THERE WILL BE SOME 20 MPH BREEZES IN THE AFTERNOON BUT RED
FLAG CONDITIONS ARE NOT EXPECTED. FOR THE REST OF THE WEEK THE
MINIMUM RELATIVE HUMIDITY WILL BE MAINLY IN THE TEENS AT THE LOWER
ELEVATIONS EAST OF THE DIVIDE AND 20S WEST. SOUTHWEST WINDS WILL
INCREASE WEDNESDAY OUT AHEAD OF THE NEXT DEVELOPING PACIFIC
TROUGH.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...ALLEN
FIRE WEATHER...LIPSON





000
FXUS65 KRIW 311830
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1230 PM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

THE THUNDERSTORMS THAT OCCURRED EARLIER THIS EVENING WERE FAST MOVING
WITH HEAVY RAINFALL BUT WITH A SHORT RESIDENCE TIME AND FREQUENT
LIGHTNING ALONG WITH UP TO 40 MPH WIND GUSTS. THE FROPA AND
HAS OCCURRED AND THE SHOWERS HAVE EXITED OFF TO THE EAST AND
DISSIPATED. CONFLUENT FLOW HAS TAKEN OVER. TODAY SOME INSTABILITY
WILL LINGER IN THE FAR SOUTH AND UP INTO SOUTHWEST NATRONA COUNTY
WHERE ISOLATED T STORMS ARE EXPECTED WITH SOME CONVECTION
STREAMING OFF THE UINTAS INTO SOUTHERN SWEETWATER COUNTY. ON
TUESDAY EXPECT ISOLD T STORMS ONLY IN THE NW MTNS WHEN CAPES
INCREASE SLIGHTLY BUT ARE NOT EXPECTED TO MOVE OFF THE MTNS.
WEDNESDAY WILL FEATURE INCREASE SOUTHWEST WINDS AS A CLOSED LOW
MOVES INLAND INTO BC AND THE ASCT TROUGH MAKES LANDFALL ONTO THE
PAC NW COAST THUS INCREASING OUR SOUTHWEST GRADIENT. TEMPS WILL BE
SLIGHTLY COOLER TODAY AND THEN BEGIN A WARMING TREND TUESDAY WITH
WEDNESDAY BEING THE WARMEST DAY OF THE PERIOD.

.LONG TERM...THURSDAY THROUGH MONDAY

MAJOR MEDIUM RANGE DIFFERENCES TONIGHT AS TO THE EVOLUTION OF OUR
LATE WEEK TROUGH. THE MODELS DO AGREE THAT THERE WILL BE A COLD
TROUGH OVER THE PACNW/NRN ROCKIES TO START THE PERIOD BUT HOW THIS
TROUGH TRANSLATES EWD WITH TIME IS WHERE THEY DEPART SIGNIFICANTLY.
THE GFS IS THE FASTEST TO MOVE THIS TROUGH OUT OF THE WAY BY
SATURDAY NIGHT WHILE THE ECMWF/GEM DON`T SWING THE TROUGH THROUGH
UNTIL MONDAY MORNING. THE FIRST SHORTWAVE THAT GETS KICKED OUT BY
THE DEVELOPING COLD TROUGH SHOULD LIFT NE ACROSS THE NRN ROCKIES
THURSDAY INTO THURSDAY NIGHT LEADING TO THE FRONT SAGGING SWD INTO
OUR NRN ZONES BEHIND THIS WAVE. THE GFS THEN KEEPS THIS FRONT IN THE
FAR NORTH PRETTY MUCH THROUGH THE PERIOD WITH SHARPLY COOLER TEMPS
BEHIND IT. THE ECMWF WASHES IT OUT EXCEPT MAYBE NEAR THE NRN BORDER
AS IT DEVELOPS AN INTENSE UPPER LOW OVER IDAHO ON SATURDAY THAT
LIFTS ACROSS THE PARK SATURDAY NIGHT WITH -4C AIR AT H7. LEANING
TOWARDS A STRONGER...SLOWER TROUGH...MAYBE NOT ECMWF STRONG...BUT
MORE TOWARDS THAT TIMING. WILL HAVE TO LOOK AT THIS AGAIN TONIGHT
AND HIT THE POPS MUCH HARDER IF THESE TRENDS CONTINUE AND THE MODELS
COME INTO BETTER AGREEMENT. POTENTIAL FOR A COLD LABOR DAY WEEKEND
WITH COLD RAIN AND MOUNTAIN SNOW IS STILL QUITE POSSIBLE IN THE
NORTHWEST PART OF WYOMING INCLUDING YELLOWSTONE NATIONAL PARK.
OTHERWISE...STILL WARM AND BREEZY TO WINDY AHEAD OF THE FRONT
THURSDAY AND IN THE SOUTH THROUGH AT LEAST FRIDAY BEFORE COOLER TO
COLDER AIR FILTERS IN. THE  WEST AND NORTH WILL SEE THE LONGEST
PERIOD OF COOLER WEATHER AND POTENTIALLY DOWNRIGHT COLD IN YNP OVER
THE WEEKEND.

&&

.AVIATION.../18Z ISSUANCE/

ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL DEVELOP THIS
AFTERNOON VCNTY OF A KRKS-KCPR LINE. SURFACE HIGH PRESSURE WILL
KEEP NORTHERN WYOMING UNDER PREVAILING SKC-FEW FL150-200
CONDITIONS AND S-SE WINDS AROUND 10KTS. THUNDERSTORM ACTIVITY WILL
MOSTLY END ACROSS THE SOUTH BY 3Z TUESDAY.

&&

.FIRE WEATHER...

IT WILL BE DRY TODAY BEHIND THIS MORNINGS COOL FRONT BUT A BIT
COOLER. THERE WILL BE SOME 20 MPH BREEZES IN THE AFTERNOON BUT RED
FLAG CONDITIONS ARE NOT EXPECTED. FOR THE REST OF THE WEEK THE
MINIMUM RELATIVE HUMIDITY WILL BE MAINLY IN THE TEENS AT THE LOWER
ELEVATIONS EAST OF THE DIVIDE AND 20S WEST. SOUTHWEST WINDS WILL
INCREASE WEDNESDAY OUT AHEAD OF THE NEXT DEVELOPING PACIFIC
TROUGH.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...ALLEN
FIRE WEATHER...LIPSON




000
FXUS65 KRIW 311830
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1230 PM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

THE THUNDERSTORMS THAT OCCURRED EARLIER THIS EVENING WERE FAST MOVING
WITH HEAVY RAINFALL BUT WITH A SHORT RESIDENCE TIME AND FREQUENT
LIGHTNING ALONG WITH UP TO 40 MPH WIND GUSTS. THE FROPA AND
HAS OCCURRED AND THE SHOWERS HAVE EXITED OFF TO THE EAST AND
DISSIPATED. CONFLUENT FLOW HAS TAKEN OVER. TODAY SOME INSTABILITY
WILL LINGER IN THE FAR SOUTH AND UP INTO SOUTHWEST NATRONA COUNTY
WHERE ISOLATED T STORMS ARE EXPECTED WITH SOME CONVECTION
STREAMING OFF THE UINTAS INTO SOUTHERN SWEETWATER COUNTY. ON
TUESDAY EXPECT ISOLD T STORMS ONLY IN THE NW MTNS WHEN CAPES
INCREASE SLIGHTLY BUT ARE NOT EXPECTED TO MOVE OFF THE MTNS.
WEDNESDAY WILL FEATURE INCREASE SOUTHWEST WINDS AS A CLOSED LOW
MOVES INLAND INTO BC AND THE ASCT TROUGH MAKES LANDFALL ONTO THE
PAC NW COAST THUS INCREASING OUR SOUTHWEST GRADIENT. TEMPS WILL BE
SLIGHTLY COOLER TODAY AND THEN BEGIN A WARMING TREND TUESDAY WITH
WEDNESDAY BEING THE WARMEST DAY OF THE PERIOD.

.LONG TERM...THURSDAY THROUGH MONDAY

MAJOR MEDIUM RANGE DIFFERENCES TONIGHT AS TO THE EVOLUTION OF OUR
LATE WEEK TROUGH. THE MODELS DO AGREE THAT THERE WILL BE A COLD
TROUGH OVER THE PACNW/NRN ROCKIES TO START THE PERIOD BUT HOW THIS
TROUGH TRANSLATES EWD WITH TIME IS WHERE THEY DEPART SIGNIFICANTLY.
THE GFS IS THE FASTEST TO MOVE THIS TROUGH OUT OF THE WAY BY
SATURDAY NIGHT WHILE THE ECMWF/GEM DON`T SWING THE TROUGH THROUGH
UNTIL MONDAY MORNING. THE FIRST SHORTWAVE THAT GETS KICKED OUT BY
THE DEVELOPING COLD TROUGH SHOULD LIFT NE ACROSS THE NRN ROCKIES
THURSDAY INTO THURSDAY NIGHT LEADING TO THE FRONT SAGGING SWD INTO
OUR NRN ZONES BEHIND THIS WAVE. THE GFS THEN KEEPS THIS FRONT IN THE
FAR NORTH PRETTY MUCH THROUGH THE PERIOD WITH SHARPLY COOLER TEMPS
BEHIND IT. THE ECMWF WASHES IT OUT EXCEPT MAYBE NEAR THE NRN BORDER
AS IT DEVELOPS AN INTENSE UPPER LOW OVER IDAHO ON SATURDAY THAT
LIFTS ACROSS THE PARK SATURDAY NIGHT WITH -4C AIR AT H7. LEANING
TOWARDS A STRONGER...SLOWER TROUGH...MAYBE NOT ECMWF STRONG...BUT
MORE TOWARDS THAT TIMING. WILL HAVE TO LOOK AT THIS AGAIN TONIGHT
AND HIT THE POPS MUCH HARDER IF THESE TRENDS CONTINUE AND THE MODELS
COME INTO BETTER AGREEMENT. POTENTIAL FOR A COLD LABOR DAY WEEKEND
WITH COLD RAIN AND MOUNTAIN SNOW IS STILL QUITE POSSIBLE IN THE
NORTHWEST PART OF WYOMING INCLUDING YELLOWSTONE NATIONAL PARK.
OTHERWISE...STILL WARM AND BREEZY TO WINDY AHEAD OF THE FRONT
THURSDAY AND IN THE SOUTH THROUGH AT LEAST FRIDAY BEFORE COOLER TO
COLDER AIR FILTERS IN. THE  WEST AND NORTH WILL SEE THE LONGEST
PERIOD OF COOLER WEATHER AND POTENTIALLY DOWNRIGHT COLD IN YNP OVER
THE WEEKEND.

&&

.AVIATION.../18Z ISSUANCE/

ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL DEVELOP THIS
AFTERNOON VCNTY OF A KRKS-KCPR LINE. SURFACE HIGH PRESSURE WILL
KEEP NORTHERN WYOMING UNDER PREVAILING SKC-FEW FL150-200
CONDITIONS AND S-SE WINDS AROUND 10KTS. THUNDERSTORM ACTIVITY WILL
MOSTLY END ACROSS THE SOUTH BY 3Z TUESDAY.

&&

.FIRE WEATHER...

IT WILL BE DRY TODAY BEHIND THIS MORNINGS COOL FRONT BUT A BIT
COOLER. THERE WILL BE SOME 20 MPH BREEZES IN THE AFTERNOON BUT RED
FLAG CONDITIONS ARE NOT EXPECTED. FOR THE REST OF THE WEEK THE
MINIMUM RELATIVE HUMIDITY WILL BE MAINLY IN THE TEENS AT THE LOWER
ELEVATIONS EAST OF THE DIVIDE AND 20S WEST. SOUTHWEST WINDS WILL
INCREASE WEDNESDAY OUT AHEAD OF THE NEXT DEVELOPING PACIFIC
TROUGH.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...ALLEN
FIRE WEATHER...LIPSON





000
FXUS65 KRIW 310819 CCA
AFDRIW

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE RIVERTON WY
219 AM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

THE THUNDERSTORMS THAT OCCURRED EARLIER THIS EVENING WERE FAST MOVING
WITH HEAVY RAINFALL BUT WITH A SHORT RESIDENCE TIME AND FREQUENT
LIGHTNING ALONG WITH UP TO 40 MPH WIND GUSTS. THE FROPA AND
HAS OCCURRED AND THE SHOWERS HAVE EXITED OFF TO THE EAST AND
DISSIPATED. CONFLUENT FLOW HAS TAKEN OVER. TODAY SOME INSTABILITY
WILL LINGER IN THE FAR SOUTH AND UP INTO SOUTHWEST NATRONA COUNTY
WHERE ISOLATED T STORMS ARE EXPECTED WITH SOME CONVECTION
STREAMING OFF THE UINTAS INTO SOUTHERN SWEETWATER COUNTY. ON
TUESDAY EXPECT ISOLD T STORMS ONLY IN THE NW MTNS WHEN CAPES
INCREASE SLIGHTLY BUT ARE NOT EXPECTED TO MOVE OFF THE MTNS.
WEDNESDAY WILL FEATURE INCREASE SOUTHWEST WINDS AS A CLOSED LOW
MOVES INLAND INTO BC AND THE ASCT TROUGH MAKES LANDFALL ONTO THE
PAC NW COAST THUS INCREASING OUR SOUTHWEST GRADIENT. TEMPS WILL BE
SLIGHTLY COOLER TODAY AND THEN BEGIN A WARMING TREND TUESDAY WITH
WEDNESDAY BEING THE WARMEST DAY OF THE PERIOD.

.LONG TERM...THURSDAY THROUGH MONDAY

MAJOR MEDIUM RANGE DIFFERENCES TONIGHT AS TO THE EVOLUTION OF OUR
LATE WEEK TROUGH. THE MODELS DO AGREE THAT THERE WILL BE A COLD
TROUGH OVER THE PACNW/NRN ROCKIES TO START THE PERIOD BUT HOW THIS
TROUGH TRANSLATES EWD WITH TIME IS WHERE THEY DEPART SIGNIFICANTLY.
THE GFS IS THE FASTEST TO MOVE THIS TROUGH OUT OF THE WAY BY
SATURDAY NIGHT WHILE THE ECMWF/GEM DON`T SWING THE TROUGH THROUGH
UNTIL MONDAY MORNING. THE FIRST SHORTWAVE THAT GETS KICKED OUT BY
THE DEVELOPING COLD TROUGH SHOULD LIFT NE ACROSS THE NRN ROCKIES
THURSDAY INTO THURSDAY NIGHT LEADING TO THE FRONT SAGGING SWD INTO
OUR NRN ZONES BEHIND THIS WAVE. THE GFS THEN KEEPS THIS FRONT IN THE
FAR NORTH PRETTY MUCH THROUGH THE PERIOD WITH SHARPLY COOLER TEMPS
BEHIND IT. THE ECMWF WASHES IT OUT EXCEPT MAYBE NEAR THE NRN BORDER
AS IT DEVELOPS AN INTENSE UPPER LOW OVER IDAHO ON SATURDAY THAT
LIFTS ACROSS THE PARK SATURDAY NIGHT WITH -4C AIR AT H7. LEANING
TOWARDS A STRONGER...SLOWER TROUGH...MAYBE NOT ECMWF STRONG...BUT
MORE TOWARDS THAT TIMING. WILL HAVE TO LOOK AT THIS AGAIN TONIGHT
AND HIT THE POPS MUCH HARDER IF THESE TRENDS CONTINUE AND THE MODELS
COME INTO BETTER AGREEMENT. POTENTIAL FOR A COLD LABOR DAY WEEKEND
WITH COLD RAIN AND MOUNTAIN SNOW IS STILL QUITE POSSIBLE IN THE
NORTHWEST PART OF WYOMING INCLUDING YELLOWSTONE NATIONAL PARK.
OTHERWISE...STILL WARM AND BREEZY TO WINDY AHEAD OF THE FRONT
THURSDAY AND IN THE SOUTH THROUGH AT LEAST FRIDAY BEFORE COOLER TO
COLDER AIR FILTERS IN. THE  WEST AND NORTH WILL SEE THE LONGEST
PERIOD OF COOLER WEATHER AND POTENTIALLY DOWNRIGHT COLD IN YNP OVER
THE WEEKEND.

&&

.AVIATION.../12Z ISSUANCE/

A COLD FRONT WILL PLUNGE SOUTH ACROSS NORTH AND CENTRAL WYOMING THROUGH 09Z.
GUSTY NORTH WIND AT 15 TO 25 KT WILL FOLLOW THE FRONT VCNTY AND
NORTH OF A KGEY TO KBYG LINE WITH WINDS NOT QUITE AS STRONG
FURTHER SOUTH. A FEW THUNDERSTORMS WILL ALSO CONTINUE VCNTY AND
SOUTH OF INTERSTATE 80 THROUGH 9Z. WINDS WILL DIMINISH BY 12Z.

ON MONDAY...ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL DEVELOP MONDAY
AFTERNOON VCNTY OF A KRKS-KCPR LINE. SURFACE HIGH PRESSURE WILL
KEEP NORTHERN WYOMING UNDER PREVAILING SKC-FEW FL150-200
CONDITIONS AND S-SE WINDS AROUND 10KTS. THUNDERSTORM ACTIVITY WILL
MOSTLY END ACROSS THE SOUTH BY 3Z TUESDAY.

&&

.FIRE WEATHER...

IT WILL BE DRY TODAY BEHIND THIS MORNINGS COOL FRONT BUT A BIT
COOLER. THERE WILL BE SOME 20 MPH BREEZES IN THE AFTERNOON BUT RED
FLAG CONDITIONS ARE NOT EXPECTED. FOR THE REST OF THE WEEK THE
MINIMUM RELATIVE HUMIDITY WILL BE MAINLY IN THE TEENS AT THE LOWER
ELEVATIONS EAST OF THE DIVIDE AND 20S WEST. SOUTHWEST WINDS WILL
INCREASE WEDNESDAY OUT AHEAD OF THE NEXT DEVELOPING PACIFIC
TROUGH.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...LIPSON
LONG TERM...PS
AVIATION...AEM
FIRE WEATHER...LIPSON




000
FXUS65 KRIW 310819 CCA
AFDRIW

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE RIVERTON WY
219 AM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

THE THUNDERSTORMS THAT OCCURRED EARLIER THIS EVENING WERE FAST MOVING
WITH HEAVY RAINFALL BUT WITH A SHORT RESIDENCE TIME AND FREQUENT
LIGHTNING ALONG WITH UP TO 40 MPH WIND GUSTS. THE FROPA AND
HAS OCCURRED AND THE SHOWERS HAVE EXITED OFF TO THE EAST AND
DISSIPATED. CONFLUENT FLOW HAS TAKEN OVER. TODAY SOME INSTABILITY
WILL LINGER IN THE FAR SOUTH AND UP INTO SOUTHWEST NATRONA COUNTY
WHERE ISOLATED T STORMS ARE EXPECTED WITH SOME CONVECTION
STREAMING OFF THE UINTAS INTO SOUTHERN SWEETWATER COUNTY. ON
TUESDAY EXPECT ISOLD T STORMS ONLY IN THE NW MTNS WHEN CAPES
INCREASE SLIGHTLY BUT ARE NOT EXPECTED TO MOVE OFF THE MTNS.
WEDNESDAY WILL FEATURE INCREASE SOUTHWEST WINDS AS A CLOSED LOW
MOVES INLAND INTO BC AND THE ASCT TROUGH MAKES LANDFALL ONTO THE
PAC NW COAST THUS INCREASING OUR SOUTHWEST GRADIENT. TEMPS WILL BE
SLIGHTLY COOLER TODAY AND THEN BEGIN A WARMING TREND TUESDAY WITH
WEDNESDAY BEING THE WARMEST DAY OF THE PERIOD.

.LONG TERM...THURSDAY THROUGH MONDAY

MAJOR MEDIUM RANGE DIFFERENCES TONIGHT AS TO THE EVOLUTION OF OUR
LATE WEEK TROUGH. THE MODELS DO AGREE THAT THERE WILL BE A COLD
TROUGH OVER THE PACNW/NRN ROCKIES TO START THE PERIOD BUT HOW THIS
TROUGH TRANSLATES EWD WITH TIME IS WHERE THEY DEPART SIGNIFICANTLY.
THE GFS IS THE FASTEST TO MOVE THIS TROUGH OUT OF THE WAY BY
SATURDAY NIGHT WHILE THE ECMWF/GEM DON`T SWING THE TROUGH THROUGH
UNTIL MONDAY MORNING. THE FIRST SHORTWAVE THAT GETS KICKED OUT BY
THE DEVELOPING COLD TROUGH SHOULD LIFT NE ACROSS THE NRN ROCKIES
THURSDAY INTO THURSDAY NIGHT LEADING TO THE FRONT SAGGING SWD INTO
OUR NRN ZONES BEHIND THIS WAVE. THE GFS THEN KEEPS THIS FRONT IN THE
FAR NORTH PRETTY MUCH THROUGH THE PERIOD WITH SHARPLY COOLER TEMPS
BEHIND IT. THE ECMWF WASHES IT OUT EXCEPT MAYBE NEAR THE NRN BORDER
AS IT DEVELOPS AN INTENSE UPPER LOW OVER IDAHO ON SATURDAY THAT
LIFTS ACROSS THE PARK SATURDAY NIGHT WITH -4C AIR AT H7. LEANING
TOWARDS A STRONGER...SLOWER TROUGH...MAYBE NOT ECMWF STRONG...BUT
MORE TOWARDS THAT TIMING. WILL HAVE TO LOOK AT THIS AGAIN TONIGHT
AND HIT THE POPS MUCH HARDER IF THESE TRENDS CONTINUE AND THE MODELS
COME INTO BETTER AGREEMENT. POTENTIAL FOR A COLD LABOR DAY WEEKEND
WITH COLD RAIN AND MOUNTAIN SNOW IS STILL QUITE POSSIBLE IN THE
NORTHWEST PART OF WYOMING INCLUDING YELLOWSTONE NATIONAL PARK.
OTHERWISE...STILL WARM AND BREEZY TO WINDY AHEAD OF THE FRONT
THURSDAY AND IN THE SOUTH THROUGH AT LEAST FRIDAY BEFORE COOLER TO
COLDER AIR FILTERS IN. THE  WEST AND NORTH WILL SEE THE LONGEST
PERIOD OF COOLER WEATHER AND POTENTIALLY DOWNRIGHT COLD IN YNP OVER
THE WEEKEND.

&&

.AVIATION.../12Z ISSUANCE/

A COLD FRONT WILL PLUNGE SOUTH ACROSS NORTH AND CENTRAL WYOMING THROUGH 09Z.
GUSTY NORTH WIND AT 15 TO 25 KT WILL FOLLOW THE FRONT VCNTY AND
NORTH OF A KGEY TO KBYG LINE WITH WINDS NOT QUITE AS STRONG
FURTHER SOUTH. A FEW THUNDERSTORMS WILL ALSO CONTINUE VCNTY AND
SOUTH OF INTERSTATE 80 THROUGH 9Z. WINDS WILL DIMINISH BY 12Z.

ON MONDAY...ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL DEVELOP MONDAY
AFTERNOON VCNTY OF A KRKS-KCPR LINE. SURFACE HIGH PRESSURE WILL
KEEP NORTHERN WYOMING UNDER PREVAILING SKC-FEW FL150-200
CONDITIONS AND S-SE WINDS AROUND 10KTS. THUNDERSTORM ACTIVITY WILL
MOSTLY END ACROSS THE SOUTH BY 3Z TUESDAY.

&&

.FIRE WEATHER...

IT WILL BE DRY TODAY BEHIND THIS MORNINGS COOL FRONT BUT A BIT
COOLER. THERE WILL BE SOME 20 MPH BREEZES IN THE AFTERNOON BUT RED
FLAG CONDITIONS ARE NOT EXPECTED. FOR THE REST OF THE WEEK THE
MINIMUM RELATIVE HUMIDITY WILL BE MAINLY IN THE TEENS AT THE LOWER
ELEVATIONS EAST OF THE DIVIDE AND 20S WEST. SOUTHWEST WINDS WILL
INCREASE WEDNESDAY OUT AHEAD OF THE NEXT DEVELOPING PACIFIC
TROUGH.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...LIPSON
LONG TERM...PS
AVIATION...AEM
FIRE WEATHER...LIPSON





000
FXUS65 KRIW 310819 CCA
AFDRIW

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE RIVERTON WY
219 AM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

THE THUNDERSTORMS THAT OCCURRED EARLIER THIS EVENING WERE FAST MOVING
WITH HEAVY RAINFALL BUT WITH A SHORT RESIDENCE TIME AND FREQUENT
LIGHTNING ALONG WITH UP TO 40 MPH WIND GUSTS. THE FROPA AND
HAS OCCURRED AND THE SHOWERS HAVE EXITED OFF TO THE EAST AND
DISSIPATED. CONFLUENT FLOW HAS TAKEN OVER. TODAY SOME INSTABILITY
WILL LINGER IN THE FAR SOUTH AND UP INTO SOUTHWEST NATRONA COUNTY
WHERE ISOLATED T STORMS ARE EXPECTED WITH SOME CONVECTION
STREAMING OFF THE UINTAS INTO SOUTHERN SWEETWATER COUNTY. ON
TUESDAY EXPECT ISOLD T STORMS ONLY IN THE NW MTNS WHEN CAPES
INCREASE SLIGHTLY BUT ARE NOT EXPECTED TO MOVE OFF THE MTNS.
WEDNESDAY WILL FEATURE INCREASE SOUTHWEST WINDS AS A CLOSED LOW
MOVES INLAND INTO BC AND THE ASCT TROUGH MAKES LANDFALL ONTO THE
PAC NW COAST THUS INCREASING OUR SOUTHWEST GRADIENT. TEMPS WILL BE
SLIGHTLY COOLER TODAY AND THEN BEGIN A WARMING TREND TUESDAY WITH
WEDNESDAY BEING THE WARMEST DAY OF THE PERIOD.

.LONG TERM...THURSDAY THROUGH MONDAY

MAJOR MEDIUM RANGE DIFFERENCES TONIGHT AS TO THE EVOLUTION OF OUR
LATE WEEK TROUGH. THE MODELS DO AGREE THAT THERE WILL BE A COLD
TROUGH OVER THE PACNW/NRN ROCKIES TO START THE PERIOD BUT HOW THIS
TROUGH TRANSLATES EWD WITH TIME IS WHERE THEY DEPART SIGNIFICANTLY.
THE GFS IS THE FASTEST TO MOVE THIS TROUGH OUT OF THE WAY BY
SATURDAY NIGHT WHILE THE ECMWF/GEM DON`T SWING THE TROUGH THROUGH
UNTIL MONDAY MORNING. THE FIRST SHORTWAVE THAT GETS KICKED OUT BY
THE DEVELOPING COLD TROUGH SHOULD LIFT NE ACROSS THE NRN ROCKIES
THURSDAY INTO THURSDAY NIGHT LEADING TO THE FRONT SAGGING SWD INTO
OUR NRN ZONES BEHIND THIS WAVE. THE GFS THEN KEEPS THIS FRONT IN THE
FAR NORTH PRETTY MUCH THROUGH THE PERIOD WITH SHARPLY COOLER TEMPS
BEHIND IT. THE ECMWF WASHES IT OUT EXCEPT MAYBE NEAR THE NRN BORDER
AS IT DEVELOPS AN INTENSE UPPER LOW OVER IDAHO ON SATURDAY THAT
LIFTS ACROSS THE PARK SATURDAY NIGHT WITH -4C AIR AT H7. LEANING
TOWARDS A STRONGER...SLOWER TROUGH...MAYBE NOT ECMWF STRONG...BUT
MORE TOWARDS THAT TIMING. WILL HAVE TO LOOK AT THIS AGAIN TONIGHT
AND HIT THE POPS MUCH HARDER IF THESE TRENDS CONTINUE AND THE MODELS
COME INTO BETTER AGREEMENT. POTENTIAL FOR A COLD LABOR DAY WEEKEND
WITH COLD RAIN AND MOUNTAIN SNOW IS STILL QUITE POSSIBLE IN THE
NORTHWEST PART OF WYOMING INCLUDING YELLOWSTONE NATIONAL PARK.
OTHERWISE...STILL WARM AND BREEZY TO WINDY AHEAD OF THE FRONT
THURSDAY AND IN THE SOUTH THROUGH AT LEAST FRIDAY BEFORE COOLER TO
COLDER AIR FILTERS IN. THE  WEST AND NORTH WILL SEE THE LONGEST
PERIOD OF COOLER WEATHER AND POTENTIALLY DOWNRIGHT COLD IN YNP OVER
THE WEEKEND.

&&

.AVIATION.../12Z ISSUANCE/

A COLD FRONT WILL PLUNGE SOUTH ACROSS NORTH AND CENTRAL WYOMING THROUGH 09Z.
GUSTY NORTH WIND AT 15 TO 25 KT WILL FOLLOW THE FRONT VCNTY AND
NORTH OF A KGEY TO KBYG LINE WITH WINDS NOT QUITE AS STRONG
FURTHER SOUTH. A FEW THUNDERSTORMS WILL ALSO CONTINUE VCNTY AND
SOUTH OF INTERSTATE 80 THROUGH 9Z. WINDS WILL DIMINISH BY 12Z.

ON MONDAY...ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL DEVELOP MONDAY
AFTERNOON VCNTY OF A KRKS-KCPR LINE. SURFACE HIGH PRESSURE WILL
KEEP NORTHERN WYOMING UNDER PREVAILING SKC-FEW FL150-200
CONDITIONS AND S-SE WINDS AROUND 10KTS. THUNDERSTORM ACTIVITY WILL
MOSTLY END ACROSS THE SOUTH BY 3Z TUESDAY.

&&

.FIRE WEATHER...

IT WILL BE DRY TODAY BEHIND THIS MORNINGS COOL FRONT BUT A BIT
COOLER. THERE WILL BE SOME 20 MPH BREEZES IN THE AFTERNOON BUT RED
FLAG CONDITIONS ARE NOT EXPECTED. FOR THE REST OF THE WEEK THE
MINIMUM RELATIVE HUMIDITY WILL BE MAINLY IN THE TEENS AT THE LOWER
ELEVATIONS EAST OF THE DIVIDE AND 20S WEST. SOUTHWEST WINDS WILL
INCREASE WEDNESDAY OUT AHEAD OF THE NEXT DEVELOPING PACIFIC
TROUGH.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...LIPSON
LONG TERM...PS
AVIATION...AEM
FIRE WEATHER...LIPSON





000
FXUS65 KRIW 310819
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
219 AM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

THE THUNDERSTORMS THAT OCCURRED EARLIER THIS EVENING WERE FAST MOVING
WITH HEAVY RAINFALL BUT WITH A SHORT RESIDENCE TIME AND FREQUENT
LIGHTNING ALONG WITH UP TO 40 MPH WIND GUSTS. THE FROPA AND
 HAS OCCURRED AND THE SHOWERS HAVE EXITED OFF TO THE EAST AND
DISSIPATED. CONFLUENT FLOW HAS TAKEN OVER. TODAY SOME INSTABILITY
WILL LINGER IN THE FAR SOUTH AND UP INTO SOUTHEAST NEUTRINO COUNTY
WHERE ISOLATED T STORMS ARE EXPECTED WITH SOME CONVECTION
STREAMING OFF THE UINTAS INTO SOUTHERN SWEETWATER COUNTY. ON
TUESDAY EXPECT ISOLD T STORMS ONLY IN THE NW MTNS WHEN CAPES
INCREASE SLIGHTLY BUT ARE NOT EXPECTED TO MOVE OFF THE MTNS.
WEDNESDAY WILL FEATURE INCREASE SOUTHWEST WINDS AS A CLOSED LOW
MOVES INLAND INTO BC AND THE ASCT TROUGH MAKES LANDFALL ONTO THE
PAC NW COAST THUS INCREASING OUR SOUTHWEST GRADIENT. TEMPS WILL BE
SLIGHTLY COOLER TODAY AND THEN BEGIN A WARMING TREND TUESDAY WITH
WEDNESDAY BEING THE WARMEST DAY OF THE PERIOD.

.LONG TERM...THURSDAY THROUGH MONDAY

MAJOR MEDIUM RANGE DIFFERENCES TONIGHT AS TO THE EVOLUTION OF OUR
LATE WEEK TROUGH. THE MODELS DO AGREE THAT THERE WILL BE A COLD
TROUGH OVER THE PACNW/NRN ROCKIES TO START THE PERIOD BUT HOW THIS
TROUGH TRANSLATES EWD WITH TIME IS WHERE THEY DEPART SIGNIFICANTLY.
THE GFS IS THE FASTEST TO MOVE THIS TROUGH OUT OF THE WAY BY
SATURDAY NIGHT WHILE THE ECMWF/GEM DON`T SWING THE TROUGH THROUGH
UNTIL MONDAY MORNING. THE FIRST SHORTWAVE THAT GETS KICKED OUT BY
THE DEVELOPING COLD TROUGH SHOULD LIFT NE ACROSS THE NRN ROCKIES
THURSDAY INTO THURSDAY NIGHT LEADING TO THE FRONT SAGGING SWD INTO
OUR NRN ZONES BEHIND THIS WAVE. THE GFS THEN KEEPS THIS FRONT IN THE
FAR NORTH PRETTY MUCH THROUGH THE PERIOD WITH SHARPLY COOLER TEMPS
BEHIND IT. THE ECMWF WASHES IT OUT EXCEPT MAYBE NEAR THE NRN BORDER
AS IT DEVELOPS AN INTENSE UPPER LOW OVER IDAHO ON SATURDAY THAT
LIFTS ACROSS THE PARK SATURDAY NIGHT WITH -4C AIR AT H7. LEANING
TOWARDS A STRONGER...SLOWER TROUGH...MAYBE NOT ECMWF STRONG...BUT
MORE TOWARDS THAT TIMING. WILL HAVE TO LOOK AT THIS AGAIN TONIGHT
AND HIT THE POPS MUCH HARDER IF THESE TRENDS CONTINUE AND THE MODELS
COME INTO BETTER AGREEMENT. POTENTIAL FOR A COLD LABOR DAY WEEKEND
WITH COLD RAIN AND MOUNTAIN SNOW IS STILL QUITE POSSIBLE IN THE
NORTHWEST PART OF WYOMING INCLUDING YELLOWSTONE NATIONAL PARK.
OTHERWISE...STILL WARM AND BREEZY TO WINDY AHEAD OF THE FRONT
THURSDAY AND IN THE SOUTH THROUGH AT LEAST FRIDAY BEFORE COOLER TO
COLDER AIR FILTERS IN. THE  WEST AND NORTH WILL SEE THE LONGEST
PERIOD OF COOLER WEATHER AND POTENTIALLY DOWNRIGHT COLD IN YNP OVER
THE WEEKEND.

&&

.AVIATION.../12Z ISSUANCE/

A COLD FRONT WILL PLUNGE SOUTH ACROSS NORTH AND CENTRAL WYOMING THROUGH 09Z.
GUSTY NORTH WIND AT 15 TO 25 KT WILL FOLLOW THE FRONT VCNTY AND
NORTH OF A KGEY TO KBYG LINE WITH WINDS NOT QUITE AS STRONG
FURTHER SOUTH. A FEW THUNDERSTORMS WILL ALSO CONTINUE VCNTY AND
SOUTH OF INTERSTATE 80 THROUGH 9Z. WINDS WILL DIMINISH BY 12Z.

ON MONDAY...ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL DEVELOP MONDAY
AFTERNOON VCNTY OF A KRKS-KCPR LINE. SURFACE HIGH PRESSURE WILL
KEEP NORTHERN WYOMING UNDER PREVAILING SKC-FEW FL150-200
CONDITIONS AND S-SE WINDS AROUND 10KTS. THUNDERSTORM ACTIVITY WILL
MOSTLY END ACROSS THE SOUTH BY 3Z TUESDAY.

&&

.FIRE WEATHER...

IT WILL BE DRY TODAY BEHIND THIS MORNINGS COOL FRONT BUT A BIT
COOLER. THERE WILL BE SOME 20 MPH BREEZES IN THE AFTERNOON BUT RED
FLAG CONDITIONS ARE NOT EXPECTED. FOR THE REST OF THE WEEK THE
MINIMUM RELATIVE HUMIDITY WILL BE MAINLY IN THE TEENS AT THE LOWER
ELEVATIONS EAST OF THE DIVIDE AND 20S WEST. SOUTHWEST WINDS WILL
INCREASE WEDNESDAY OUT AHEAD OF THE NEXT DEVELOPING PACIFIC
TROUGH.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...LIPSON
LONG TERM...PS
AVIATION...AEM
FIRE WEATHER...LIPSON





000
FXUS65 KRIW 310819 CCA
AFDRIW

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE RIVERTON WY
219 AM MDT MON AUG 31 2015

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

THE THUNDERSTORMS THAT OCCURRED EARLIER THIS EVENING WERE FAST MOVING
WITH HEAVY RAINFALL BUT WITH A SHORT RESIDENCE TIME AND FREQUENT
LIGHTNING ALONG WITH UP TO 40 MPH WIND GUSTS. THE FROPA AND
HAS OCCURRED AND THE SHOWERS HAVE EXITED OFF TO THE EAST AND
DISSIPATED. CONFLUENT FLOW HAS TAKEN OVER. TODAY SOME INSTABILITY
WILL LINGER IN THE FAR SOUTH AND UP INTO SOUTHWEST NATRONA COUNTY
WHERE ISOLATED T STORMS ARE EXPECTED WITH SOME CONVECTION
STREAMING OFF THE UINTAS INTO SOUTHERN SWEETWATER COUNTY. ON
TUESDAY EXPECT ISOLD T STORMS ONLY IN THE NW MTNS WHEN CAPES
INCREASE SLIGHTLY BUT ARE NOT EXPECTED TO MOVE OFF THE MTNS.
WEDNESDAY WILL FEATURE INCREASE SOUTHWEST WINDS AS A CLOSED LOW
MOVES INLAND INTO BC AND THE ASCT TROUGH MAKES LANDFALL ONTO THE
PAC NW COAST THUS INCREASING OUR SOUTHWEST GRADIENT. TEMPS WILL BE
SLIGHTLY COOLER TODAY AND THEN BEGIN A WARMING TREND TUESDAY WITH
WEDNESDAY BEING THE WARMEST DAY OF THE PERIOD.

.LONG TERM...THURSDAY THROUGH MONDAY

MAJOR MEDIUM RANGE DIFFERENCES TONIGHT AS TO THE EVOLUTION OF OUR
LATE WEEK TROUGH. THE MODELS DO AGREE THAT THERE WILL BE A COLD
TROUGH OVER THE PACNW/NRN ROCKIES TO START THE PERIOD BUT HOW THIS
TROUGH TRANSLATES EWD WITH TIME IS WHERE THEY DEPART SIGNIFICANTLY.
THE GFS IS THE FASTEST TO MOVE THIS TROUGH OUT OF THE WAY BY
SATURDAY NIGHT WHILE THE ECMWF/GEM DON`T SWING THE TROUGH THROUGH
UNTIL MONDAY MORNING. THE FIRST SHORTWAVE THAT GETS KICKED OUT BY
THE DEVELOPING COLD TROUGH SHOULD LIFT NE ACROSS THE NRN ROCKIES
THURSDAY INTO THURSDAY NIGHT LEADING TO THE FRONT SAGGING SWD INTO
OUR NRN ZONES BEHIND THIS WAVE. THE GFS THEN KEEPS THIS FRONT IN THE
FAR NORTH PRETTY MUCH THROUGH THE PERIOD WITH SHARPLY COOLER TEMPS
BEHIND IT. THE ECMWF WASHES IT OUT EXCEPT MAYBE NEAR THE NRN BORDER
AS IT DEVELOPS AN INTENSE UPPER LOW OVER IDAHO ON SATURDAY THAT
LIFTS ACROSS THE PARK SATURDAY NIGHT WITH -4C AIR AT H7. LEANING
TOWARDS A STRONGER...SLOWER TROUGH...MAYBE NOT ECMWF STRONG...BUT
MORE TOWARDS THAT TIMING. WILL HAVE TO LOOK AT THIS AGAIN TONIGHT
AND HIT THE POPS MUCH HARDER IF THESE TRENDS CONTINUE AND THE MODELS
COME INTO BETTER AGREEMENT. POTENTIAL FOR A COLD LABOR DAY WEEKEND
WITH COLD RAIN AND MOUNTAIN SNOW IS STILL QUITE POSSIBLE IN THE
NORTHWEST PART OF WYOMING INCLUDING YELLOWSTONE NATIONAL PARK.
OTHERWISE...STILL WARM AND BREEZY TO WINDY AHEAD OF THE FRONT
THURSDAY AND IN THE SOUTH THROUGH AT LEAST FRIDAY BEFORE COOLER TO
COLDER AIR FILTERS IN. THE  WEST AND NORTH WILL SEE THE LONGEST
PERIOD OF COOLER WEATHER AND POTENTIALLY DOWNRIGHT COLD IN YNP OVER
THE WEEKEND.

&&

.AVIATION.../12Z ISSUANCE/

A COLD FRONT WILL PLUNGE SOUTH ACROSS NORTH AND CENTRAL WYOMING THROUGH 09Z.
GUSTY NORTH WIND AT 15 TO 25 KT WILL FOLLOW THE FRONT VCNTY AND
NORTH OF A KGEY TO KBYG LINE WITH WINDS NOT QUITE AS STRONG
FURTHER SOUTH. A FEW THUNDERSTORMS WILL ALSO CONTINUE VCNTY AND
SOUTH OF INTERSTATE 80 THROUGH 9Z. WINDS WILL DIMINISH BY 12Z.

ON MONDAY...ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL DEVELOP MONDAY
AFTERNOON VCNTY OF A KRKS-KCPR LINE. SURFACE HIGH PRESSURE WILL
KEEP NORTHERN WYOMING UNDER PREVAILING SKC-FEW FL150-200
CONDITIONS AND S-SE WINDS AROUND 10KTS. THUNDERSTORM ACTIVITY WILL
MOSTLY END ACROSS THE SOUTH BY 3Z TUESDAY.

&&

.FIRE WEATHER...

IT WILL BE DRY TODAY BEHIND THIS MORNINGS COOL FRONT BUT A BIT
COOLER. THERE WILL BE SOME 20 MPH BREEZES IN THE AFTERNOON BUT RED
FLAG CONDITIONS ARE NOT EXPECTED. FOR THE REST OF THE WEEK THE
MINIMUM RELATIVE HUMIDITY WILL BE MAINLY IN THE TEENS AT THE LOWER
ELEVATIONS EAST OF THE DIVIDE AND 20S WEST. SOUTHWEST WINDS WILL
INCREASE WEDNESDAY OUT AHEAD OF THE NEXT DEVELOPING PACIFIC
TROUGH.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...LIPSON
LONG TERM...PS
AVIATION...AEM
FIRE WEATHER...LIPSON




000
FXUS65 KRIW 310554
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1152 PM MDT SUN AUG 30 2015

.UPDATE...AVIATION.../06Z ISSUANCE/

A COLD FRONT WILL PLUNGE SOUTH ACROSS NORTH AND CENTRAL WYOMING
THROUGH 09Z.  GUSTY NORTH WIND AT 15 TO 25 KT WILL FOLLOW THE FRONT
VCNTY AND NORTH OF A KGEY TO KBYG LINE WITH WINDS NOT QUITE AS
STRONG FURTHER SOUTH.  A FEW THUNDERSTORMS WILL ALSO CONTINUE VCNTY
AND SOUTH OF INTERSTATE 80 THROUGH 9Z.  WINDS WILL DIMINISH BY 12Z.

ON MONDAY...ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL DEVELOP
MONDAY AFTERNOON VCNTY OF A KRKS-KCPR LINE.  SURFACE HIGH PRESSURE
WILL KEEP NORTHERN WYOMING UNDER PREVAILING SKC-FEW FL150-200
CONDITIONS AND S-SE WINDS AROUND 10KTS.  THUNDERSTORM ACTIVITY WILL
MOSTLY END ACROSS THE SOUTH BY 3Z TUESDAY.

 &&

.PREV DISCUSSION... /ISSUED 237 PM MDT SUN AUG 30 2015/

SHORT TERM...TONIGHT THROUGH MONDAY

A TROUGH AND COLD FRONT CONTINUE TO TRACK EASTWARD ACROSS THE
INTERMOUNTAIN WEST. THE COLD FRONT IS LYING NEAR THE MONTANA BORDER
AND IS EXPECTED TO SURGE SOUTHWARD AGAIN AROUND SUNSET WITH THE
MAIN PUSH ARRIVING TOWARD MIDNIGHT...THOUGH THE TIMING ON COLD
FRONTS CAN BE TRICKY AS THEY OFTEN MOVE FASTER THAN EXPECTED. WE
CAN CONTINUE TO EXPECT RED FLAG CONDITIONS SOUTH OF THE FRONT AND
MUCH COOLER AND MOIST CONDITIONS TO THE NORTH THROUGH THE EARLY
EVENING HOURS.

THERE IS ALSO SOME DECENT LIFT ON THE FRONT SIDE OF THIS TROUGH
WITH JET SUPPORT ALOFT...A THETA E RIDGE LYING APPROXIMATELY FROM
FLAMING GORGE TO KAYCEE...AND QG FORCING ARRIVING LATER IN THE
EVENING. AREAS WITH DECENT LOW LEVEL MOISTURE IN PLACE...ACROSS
THE WEST AND THE SOUTH...AND ON THE OTHER SIDE OF THE FRONT WILL
SEE WET THUNDERSTORMS AND AREAS LIKE THE SOUTHERN BIGHORN
BASIN...NATRONA COUNTY AND FREMONT COUNTY WILL SEE MAINLY DRY
THUNDERSTORMS THROUGH SUNSET...SHOWERS AND STORMS HAVE A BETTER
CHANCE OF PRODUCING A WETTING RAIN THEREAFTER.

MONDAY WILL BE DRY AGAIN BUT LESS WINDY AS WE LOSE THE GRADIENT AT
THE SURFACE AND ALOFT. TEMPERATURES WILL BE CLOSER TO SEASONAL
NORMS WITH HIGHS IN THE LOW TO MID 80S EAST...MID TO UPPER 70S
WEST AND SOUTH. A PLUME OF MOISTURE ACROSS COLORADO COULD BEGIN TO
POKE NORTH INTO SOUTHERN SWEETWATER COUNTY WITH A FEW STRAY
AFTERNOON STORMS POSSIBLE OTHERWISE IT WILL BE DRY AND RAIN FREE.

LONG TERM...MONDAY NIGHT THROUGH SUNDAY

MEDIUM-RANGE FORECAST MODELS ARE CONSISTENT AND AGAIN IN FAIRLY GOOD
AGREEMENT THROUGH THE FORECAST PERIOD. WEST-SOUTHWEST FLOW ALOFT ON
TUESDAY WILL BACK TO THE SOUTHWEST WEDNESDAY AND THURSDAY AS A
TROUGH DEEPENS OVER THE PACIFIC NORTHWEST. LIMITED MOISTURE IN
SOUTHWEST FLOW FOR TUESDAY...BUT SOME PRECIPITABLE WATER VALUES
AROUND 0.70 INCHES COULD LEAD TO WEAK CONVECTION IN JOHNSON AND
NATRONA COUNTIES. HOWEVER...WITH DEW POINTS IN THE 30S HAVE
CONTINUED A GENERALLY DRY FORECAST FOR NOW. SOUTHWEST FLOW ADVECTS
IN DRIER AIR FROM THE GREAT BASIN WEDNESDAY AND THURSDAY AND DO NOT
SEE MUCH IN THE WAY OF AVAILABLE MOISTURE FOR ANY CONVECTION.
SURFACE DEW POINTS WILL GENERALLY RANGE FROM 25-35F. ALSO...
WEDNESDAY LOOKS TO BE THE WARMEST DAY OF THE WEEK WITH TEMPERATURES
RUNNING ABOUT 5-10F ABOVE NORMAL AND THE NORTHERN BASINS PUSHING
INTO THE 90S AGAIN. THE COMBINATION OF THE UNSEASONABLY HOT
TEMPERATURES...LOW HUMIDITY...AND INCREASING SOUTHWEST WIND OF 15-30
MPH WILL VERY LIKELY LEAD TO CRITICAL FIRE WEATHER CONDITIONS FOR
WEDNESDAY AND MOST PROBABLY THURSDAY. MOST INTENSE WINDS WILL BE IN
THE CORRIDOR FROM ROCK SPRINGS TO CASPER. THOSE WITH FIRE WEATHER
INTERESTS SHOULD BE AWARE OF THE LIKELIHOOD OF THESE CONDITIONS FOR
WEDNESDAY AND THURSDAY AND BE ON THE ALERT FOR POSSIBLE HIGHLIGHTS ISSUED
EARLY THIS WEEK. FIRST UPPER LOW IN THE PACIFIC NORTHWEST TROUGH
WILL EJECT INTO ALBERTA THURSDAY. THIS UPPER LOW WILL QUICKLY BE
REPLACED BY ANOTHER SHORTWAVE THAT WILL DROP INTO THE BASE OF THE
TROUGH OVER THE INTERMOUNTAIN WEST FOR FRIDAY. UPPER FLOW WILL
PARALLEL SURFACE FRONT THAT WILL BE ORIENTED NORTHEAST-SOUTHWEST
JUST TO THE WEST OF WYOMING FOR FRIDAY. HAVE NUDGED TEMPERATURES
UP A TAD FOR FRIDAY AS IT DOES LOOK LIKE THE COOLER AIR WILL HANG
BACK ONE MORE DAY. AM STILL CONCERNED THAT FRIDAY MAY INDEED BE
WARMER THAN CURRENTLY FORECAST WITH COMPRESSIONAL WARMING AHEAD OF
THE APPROACHING FRONT/TROUGH. MOISTURE WILL RIDE ALONG OUR
NORTHWESTERN ZONES FOR FRIDAY AFTERNOON AND SATURDAY.
THEREFORE...HAVE INCREASED PRECIP CHANCES OVER YELLOWSTONE AND THE
SURROUNDING MOUNTAINS. ENERGY IN THE BASE OF THE TROUGH WILL BEGIN
TO EJECT SATURDAY WHILE AT THE SAME TIME A SURFACE LOW TAKES SHAPE
TO OUR SOUTHEAST. THIS WILL BRING THE COLD FRONT ACROSS THE
FORECAST AREA SATURDAY. BOTH THE ECMWF AND GFS HAVE THE FORECAST
AREA DRY SLOTTED SATURDAY AS THE UPPER LOW TRACKS TO OUR NORTH.
BEST CHANCE FOR MEASURABLE PRECIP OVER THE WEEKEND WILL BE ACROSS
THE NORTHERN THIRD OF THE FORECAST AREA CLOSEST TO THE UPPER LOW.
SURFACE HIGH PUSHES INTO WYOMING SUNDAY AND 700MB TEMPERATURES
FALL INTO THE ZERO TO +4C RANGE ACROSS THE NORTH. THIS WILL LEAD
TO COOLER THAN AVERAGE TEMPERATURES FOR SUNDAY IN ALL BUT
SOUTHWEST AND FAR WEST WYOMING.

AVIATION.../00Z ISSUANCE/

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST WITH SFC WINDS GENERALLY FROM THE SOUTHWEST TO WEST ACROSS MUCH
OF THE STATE AHEAD OF THE COLD FRONT...WINDS WILL BRIEFLY SWITCH TO
THE NW BEHIND THE FRONT WITH SOME AREAS OF 30-40KT GUSTS BEHIND THE
FRONT VCNTY KBYG KPOY KU68. THE MAIN AREA OF ISOLD-SCT -TSRA VCNTY
AND SOUTH OF A KEVW- KLND- KCPR LINE WITH HIGH BASED WINDY STORMS
EXPECTED INTO THE EARLY EVENING. THE COLD FRONT WILL BRING DRIER AIR
AND GUSTY WEST WIND INTO NW WYOMING MID TO LATE THIS
AFTERNOON...PUSHING ACROSS NORTH AND CENTRAL WYOMING LATE THIS
EVENING. CLEAR SKIES AND DIMINISHING WIND WILL PREVAIL ACROSS THE
AREA BEHIND THE FRONT EARLY MONDAY MORNING.

FIRE WEATHER...

..RED FLAG WARNING FOR PORTIONS OF CENTRAL AND NORTHERN WYOMING
THROUGH THE EVENING HOURS...

A COLD FRONT ASSOCIATED WITH THE TROUGH DIGGING TO THE WEST REMAINS
IN THE AREA NEAR THE MONTANA BORDER THIS AFTERNOON WITH COOLER
TEMPERATURES AND MODERATE HUMIDITY TO THE NORTH OF IT AND RED FLAG
TO NEAR RED FLAG CONDITIONS JUST TO THE SOUTH OF IT. MODELS ARE
CALLING FOR SOUTHWEST FLOW TO OVERTAKE THE FRONT AND CAUSE IT TO
RETREAT BACK NORTH FOR THE LATE AFTERNOON HOURS. THE MAIN FRONTAL
SURGE WILL COME LATER TONIGHT WITH STEADY 25 TO 35 MPH WINDS IN
JOHNSON COUNTY AND NORTHERN BIGHORN COUNTY BEHIND THE
FRONT...EXTENDED THE NORTHERN RED FLAG WARNINGS TO 3AM TO COVER THE
FRONTAL PASSAGE THOUGH IT MAY HAPPEN SOONER.

IN ADDITION...ISOLATED TO WIDELY SCATTERED MIXED WET AND DRY
THUNDERSTORMS ARE EXPECTED TO CONTINUE TO DEVELOP INTO THE EVENING
HOURS...WITH A FEW PERSISTING INTO THE NIGHT...ESPECIALLY EAST OF
THE DIVIDE.

IT WILL BE DRY BEHIND THE FRONT FOR MONDAY BUT A BIT COOLER. THERE
WILL BE SOME 20MPH BREEZES IN THE AFTERNOON BUT RED FLAG CONDITIONS
ARE NOT EXPECTED.

IT SILL LOOKS LIKE THERE COULD BE WIDESPREAD RED FLAG CONDITIONS MID
WEEK...STAY TUNED FOR UPDATES ON THE NEXT SYSTEM.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 3 AM MDT MONDAY FOR WYZ275-276-281-282-
287.

&&

$$

UPDATE...AEM
SHORT TERM...ALLEN
LONG TERM...CNJ
AVIATION...AEM
FIRE WEATHER...ALLEN





000
FXUS65 KRIW 310554
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1152 PM MDT SUN AUG 30 2015

.UPDATE...AVIATION.../06Z ISSUANCE/

A COLD FRONT WILL PLUNGE SOUTH ACROSS NORTH AND CENTRAL WYOMING
THROUGH 09Z.  GUSTY NORTH WIND AT 15 TO 25 KT WILL FOLLOW THE FRONT
VCNTY AND NORTH OF A KGEY TO KBYG LINE WITH WINDS NOT QUITE AS
STRONG FURTHER SOUTH.  A FEW THUNDERSTORMS WILL ALSO CONTINUE VCNTY
AND SOUTH OF INTERSTATE 80 THROUGH 9Z.  WINDS WILL DIMINISH BY 12Z.

ON MONDAY...ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL DEVELOP
MONDAY AFTERNOON VCNTY OF A KRKS-KCPR LINE.  SURFACE HIGH PRESSURE
WILL KEEP NORTHERN WYOMING UNDER PREVAILING SKC-FEW FL150-200
CONDITIONS AND S-SE WINDS AROUND 10KTS.  THUNDERSTORM ACTIVITY WILL
MOSTLY END ACROSS THE SOUTH BY 3Z TUESDAY.

 &&

.PREV DISCUSSION... /ISSUED 237 PM MDT SUN AUG 30 2015/

SHORT TERM...TONIGHT THROUGH MONDAY

A TROUGH AND COLD FRONT CONTINUE TO TRACK EASTWARD ACROSS THE
INTERMOUNTAIN WEST. THE COLD FRONT IS LYING NEAR THE MONTANA BORDER
AND IS EXPECTED TO SURGE SOUTHWARD AGAIN AROUND SUNSET WITH THE
MAIN PUSH ARRIVING TOWARD MIDNIGHT...THOUGH THE TIMING ON COLD
FRONTS CAN BE TRICKY AS THEY OFTEN MOVE FASTER THAN EXPECTED. WE
CAN CONTINUE TO EXPECT RED FLAG CONDITIONS SOUTH OF THE FRONT AND
MUCH COOLER AND MOIST CONDITIONS TO THE NORTH THROUGH THE EARLY
EVENING HOURS.

THERE IS ALSO SOME DECENT LIFT ON THE FRONT SIDE OF THIS TROUGH
WITH JET SUPPORT ALOFT...A THETA E RIDGE LYING APPROXIMATELY FROM
FLAMING GORGE TO KAYCEE...AND QG FORCING ARRIVING LATER IN THE
EVENING. AREAS WITH DECENT LOW LEVEL MOISTURE IN PLACE...ACROSS
THE WEST AND THE SOUTH...AND ON THE OTHER SIDE OF THE FRONT WILL
SEE WET THUNDERSTORMS AND AREAS LIKE THE SOUTHERN BIGHORN
BASIN...NATRONA COUNTY AND FREMONT COUNTY WILL SEE MAINLY DRY
THUNDERSTORMS THROUGH SUNSET...SHOWERS AND STORMS HAVE A BETTER
CHANCE OF PRODUCING A WETTING RAIN THEREAFTER.

MONDAY WILL BE DRY AGAIN BUT LESS WINDY AS WE LOSE THE GRADIENT AT
THE SURFACE AND ALOFT. TEMPERATURES WILL BE CLOSER TO SEASONAL
NORMS WITH HIGHS IN THE LOW TO MID 80S EAST...MID TO UPPER 70S
WEST AND SOUTH. A PLUME OF MOISTURE ACROSS COLORADO COULD BEGIN TO
POKE NORTH INTO SOUTHERN SWEETWATER COUNTY WITH A FEW STRAY
AFTERNOON STORMS POSSIBLE OTHERWISE IT WILL BE DRY AND RAIN FREE.

LONG TERM...MONDAY NIGHT THROUGH SUNDAY

MEDIUM-RANGE FORECAST MODELS ARE CONSISTENT AND AGAIN IN FAIRLY GOOD
AGREEMENT THROUGH THE FORECAST PERIOD. WEST-SOUTHWEST FLOW ALOFT ON
TUESDAY WILL BACK TO THE SOUTHWEST WEDNESDAY AND THURSDAY AS A
TROUGH DEEPENS OVER THE PACIFIC NORTHWEST. LIMITED MOISTURE IN
SOUTHWEST FLOW FOR TUESDAY...BUT SOME PRECIPITABLE WATER VALUES
AROUND 0.70 INCHES COULD LEAD TO WEAK CONVECTION IN JOHNSON AND
NATRONA COUNTIES. HOWEVER...WITH DEW POINTS IN THE 30S HAVE
CONTINUED A GENERALLY DRY FORECAST FOR NOW. SOUTHWEST FLOW ADVECTS
IN DRIER AIR FROM THE GREAT BASIN WEDNESDAY AND THURSDAY AND DO NOT
SEE MUCH IN THE WAY OF AVAILABLE MOISTURE FOR ANY CONVECTION.
SURFACE DEW POINTS WILL GENERALLY RANGE FROM 25-35F. ALSO...
WEDNESDAY LOOKS TO BE THE WARMEST DAY OF THE WEEK WITH TEMPERATURES
RUNNING ABOUT 5-10F ABOVE NORMAL AND THE NORTHERN BASINS PUSHING
INTO THE 90S AGAIN. THE COMBINATION OF THE UNSEASONABLY HOT
TEMPERATURES...LOW HUMIDITY...AND INCREASING SOUTHWEST WIND OF 15-30
MPH WILL VERY LIKELY LEAD TO CRITICAL FIRE WEATHER CONDITIONS FOR
WEDNESDAY AND MOST PROBABLY THURSDAY. MOST INTENSE WINDS WILL BE IN
THE CORRIDOR FROM ROCK SPRINGS TO CASPER. THOSE WITH FIRE WEATHER
INTERESTS SHOULD BE AWARE OF THE LIKELIHOOD OF THESE CONDITIONS FOR
WEDNESDAY AND THURSDAY AND BE ON THE ALERT FOR POSSIBLE HIGHLIGHTS ISSUED
EARLY THIS WEEK. FIRST UPPER LOW IN THE PACIFIC NORTHWEST TROUGH
WILL EJECT INTO ALBERTA THURSDAY. THIS UPPER LOW WILL QUICKLY BE
REPLACED BY ANOTHER SHORTWAVE THAT WILL DROP INTO THE BASE OF THE
TROUGH OVER THE INTERMOUNTAIN WEST FOR FRIDAY. UPPER FLOW WILL
PARALLEL SURFACE FRONT THAT WILL BE ORIENTED NORTHEAST-SOUTHWEST
JUST TO THE WEST OF WYOMING FOR FRIDAY. HAVE NUDGED TEMPERATURES
UP A TAD FOR FRIDAY AS IT DOES LOOK LIKE THE COOLER AIR WILL HANG
BACK ONE MORE DAY. AM STILL CONCERNED THAT FRIDAY MAY INDEED BE
WARMER THAN CURRENTLY FORECAST WITH COMPRESSIONAL WARMING AHEAD OF
THE APPROACHING FRONT/TROUGH. MOISTURE WILL RIDE ALONG OUR
NORTHWESTERN ZONES FOR FRIDAY AFTERNOON AND SATURDAY.
THEREFORE...HAVE INCREASED PRECIP CHANCES OVER YELLOWSTONE AND THE
SURROUNDING MOUNTAINS. ENERGY IN THE BASE OF THE TROUGH WILL BEGIN
TO EJECT SATURDAY WHILE AT THE SAME TIME A SURFACE LOW TAKES SHAPE
TO OUR SOUTHEAST. THIS WILL BRING THE COLD FRONT ACROSS THE
FORECAST AREA SATURDAY. BOTH THE ECMWF AND GFS HAVE THE FORECAST
AREA DRY SLOTTED SATURDAY AS THE UPPER LOW TRACKS TO OUR NORTH.
BEST CHANCE FOR MEASURABLE PRECIP OVER THE WEEKEND WILL BE ACROSS
THE NORTHERN THIRD OF THE FORECAST AREA CLOSEST TO THE UPPER LOW.
SURFACE HIGH PUSHES INTO WYOMING SUNDAY AND 700MB TEMPERATURES
FALL INTO THE ZERO TO +4C RANGE ACROSS THE NORTH. THIS WILL LEAD
TO COOLER THAN AVERAGE TEMPERATURES FOR SUNDAY IN ALL BUT
SOUTHWEST AND FAR WEST WYOMING.

AVIATION.../00Z ISSUANCE/

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST WITH SFC WINDS GENERALLY FROM THE SOUTHWEST TO WEST ACROSS MUCH
OF THE STATE AHEAD OF THE COLD FRONT...WINDS WILL BRIEFLY SWITCH TO
THE NW BEHIND THE FRONT WITH SOME AREAS OF 30-40KT GUSTS BEHIND THE
FRONT VCNTY KBYG KPOY KU68. THE MAIN AREA OF ISOLD-SCT -TSRA VCNTY
AND SOUTH OF A KEVW- KLND- KCPR LINE WITH HIGH BASED WINDY STORMS
EXPECTED INTO THE EARLY EVENING. THE COLD FRONT WILL BRING DRIER AIR
AND GUSTY WEST WIND INTO NW WYOMING MID TO LATE THIS
AFTERNOON...PUSHING ACROSS NORTH AND CENTRAL WYOMING LATE THIS
EVENING. CLEAR SKIES AND DIMINISHING WIND WILL PREVAIL ACROSS THE
AREA BEHIND THE FRONT EARLY MONDAY MORNING.

FIRE WEATHER...

..RED FLAG WARNING FOR PORTIONS OF CENTRAL AND NORTHERN WYOMING
THROUGH THE EVENING HOURS...

A COLD FRONT ASSOCIATED WITH THE TROUGH DIGGING TO THE WEST REMAINS
IN THE AREA NEAR THE MONTANA BORDER THIS AFTERNOON WITH COOLER
TEMPERATURES AND MODERATE HUMIDITY TO THE NORTH OF IT AND RED FLAG
TO NEAR RED FLAG CONDITIONS JUST TO THE SOUTH OF IT. MODELS ARE
CALLING FOR SOUTHWEST FLOW TO OVERTAKE THE FRONT AND CAUSE IT TO
RETREAT BACK NORTH FOR THE LATE AFTERNOON HOURS. THE MAIN FRONTAL
SURGE WILL COME LATER TONIGHT WITH STEADY 25 TO 35 MPH WINDS IN
JOHNSON COUNTY AND NORTHERN BIGHORN COUNTY BEHIND THE
FRONT...EXTENDED THE NORTHERN RED FLAG WARNINGS TO 3AM TO COVER THE
FRONTAL PASSAGE THOUGH IT MAY HAPPEN SOONER.

IN ADDITION...ISOLATED TO WIDELY SCATTERED MIXED WET AND DRY
THUNDERSTORMS ARE EXPECTED TO CONTINUE TO DEVELOP INTO THE EVENING
HOURS...WITH A FEW PERSISTING INTO THE NIGHT...ESPECIALLY EAST OF
THE DIVIDE.

IT WILL BE DRY BEHIND THE FRONT FOR MONDAY BUT A BIT COOLER. THERE
WILL BE SOME 20MPH BREEZES IN THE AFTERNOON BUT RED FLAG CONDITIONS
ARE NOT EXPECTED.

IT SILL LOOKS LIKE THERE COULD BE WIDESPREAD RED FLAG CONDITIONS MID
WEEK...STAY TUNED FOR UPDATES ON THE NEXT SYSTEM.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 3 AM MDT MONDAY FOR WYZ275-276-281-282-
287.

&&

$$

UPDATE...AEM
SHORT TERM...ALLEN
LONG TERM...CNJ
AVIATION...AEM
FIRE WEATHER...ALLEN




000
FXUS65 KRIW 310346
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
946 PM MDT SUN AUG 30 2015

.UPDATE...CANADIAN COLD FRONT WAS JUST NORTH AND WEST OF BILLINGS
AT 3Z...AND STILL ON TRACK TO PLOW ACROSS THE NORTHERN BORDER
AROUND 06Z...UP TO THE OWL CREEK MOUNTAINS 2Z-3Z. DRY AIR HAS
PUNCHED IN ACROSS WESTERN AND CENTRAL WYOMING WITH A FEW STORMS
CONTINUING TO TRACK MAINLY ALONG AND SOUTH OF INTERSTATE 80 AND
AHEAD OF THE FRONT ACROSS THE NORTHERN BIGHORN RANGE AND EASTERN
MONTANA. MAIN CONCERN CONTINUES TO BE RAPID SPREAD OF ANY FIRES
ACROSS NORTH CENTRAL AREAS WITH GUSTY NORTH WIND BEHIND THE
FRONT. RED FLAG WARNINGS REMAIN IN EFFECT FOR THESE AREAS UNTIL 3
AM. ALL OTHER RED FLAG WARNINGS HAVE BEEN ALLOWED TO EXPIRE.

&&

.PREV DISCUSSION... /ISSUED 237 PM MDT SUN AUG 30 2015/

SHORT TERM...TONIGHT THROUGH MONDAY

A TROUGH AND COLD FRONT CONTINUE TO TRACK EASTWARD ACROSS THE
INTERMOUNTAIN WEST. THE COLD FRONT IS LYING NEAR THE MONTANA BORDER
AND IS EXPECTED TO SURGE SOUTHWARD AGAIN AROUND SUNSET WITH THE
MAIN PUSH ARRIVING TOWARD MIDNIGHT...THOUGH THE TIMING ON COLD
FRONTS CAN BE TRICKY AS THEY OFTEN MOVE FASTER THAN EXPECTED. WE
CAN CONTINUE TO EXPECT RED FLAG CONDITIONS SOUTH OF THE FRONT AND
MUCH COOLER AND MOIST CONDITIONS TO THE NORTH THROUGH THE EARLY
EVENING HOURS.

THERE IS ALSO SOME DECENT LIFT ON THE FRONT SIDE OF THIS TROUGH
WITH JET SUPPORT ALOFT...A THETA E RIDGE LYING APPROXIMATELY FROM
FLAMING GORGE TO KAYCEE...AND QG FORCING ARRIVING LATER IN THE
EVENING. AREAS WITH DECENT LOW LEVEL MOISTURE IN PLACE...ACROSS
THE WEST AND THE SOUTH...AND ON THE OTHER SIDE OF THE FRONT WILL
SEE WET THUNDERSTORMS AND AREAS LIKE THE SOUTHERN BIGHORN
BASIN...NATRONA COUNTY AND FREMONT COUNTY WILL SEE MAINLY DRY
THUNDERSTORMS THROUGH SUNSET...SHOWERS AND STORMS HAVE A BETTER
CHANCE OF PRODUCING A WETTING RAIN THEREAFTER.

MONDAY WILL BE DRY AGAIN BUT LESS WINDY AS WE LOSE THE GRADIENT AT
THE SURFACE AND ALOFT. TEMPERATURES WILL BE CLOSER TO SEASONAL
NORMS WITH HIGHS IN THE LOW TO MID 80S EAST...MID TO UPPER 70S
WEST AND SOUTH. A PLUME OF MOISTURE ACROSS COLORADO COULD BEGIN TO
POKE NORTH INTO SOUTHERN SWEETWATER COUNTY WITH A FEW STRAY
AFTERNOON STORMS POSSIBLE OTHERWISE IT WILL BE DRY AND RAIN FREE.

LONG TERM...MONDAY NIGHT THROUGH SUNDAY

MEDIUM-RANGE FORECAST MODELS ARE CONSISTENT AND AGAIN IN FAIRLY GOOD
AGREEMENT THROUGH THE FORECAST PERIOD. WEST-SOUTHWEST FLOW ALOFT ON
TUESDAY WILL BACK TO THE SOUTHWEST WEDNESDAY AND THURSDAY AS A
TROUGH DEEPENS OVER THE PACIFIC NORTHWEST. LIMITED MOISTURE IN
SOUTHWEST FLOW FOR TUESDAY...BUT SOME PRECIPITABLE WATER VALUES
AROUND 0.70 INCHES COULD LEAD TO WEAK CONVECTION IN JOHNSON AND
NATRONA COUNTIES. HOWEVER...WITH DEW POINTS IN THE 30S HAVE
CONTINUED A GENERALLY DRY FORECAST FOR NOW. SOUTHWEST FLOW ADVECTS
IN DRIER AIR FROM THE GREAT BASIN WEDNESDAY AND THURSDAY AND DO NOT
SEE MUCH IN THE WAY OF AVAILABLE MOISTURE FOR ANY CONVECTION.
SURFACE DEW POINTS WILL GENERALLY RANGE FROM 25-35F. ALSO...
WEDNESDAY LOOKS TO BE THE WARMEST DAY OF THE WEEK WITH TEMPERATURES
RUNNING ABOUT 5-10F ABOVE NORMAL AND THE NORTHERN BASINS PUSHING
INTO THE 90S AGAIN. THE COMBINATION OF THE UNSEASONABLY HOT
TEMPERATURES...LOW HUMIDITY...AND INCREASING SOUTHWEST WIND OF 15-30
MPH WILL VERY LIKELY LEAD TO CRITICAL FIRE WEATHER CONDITIONS FOR
WEDNESDAY AND MOST PROBABLY THURSDAY. MOST INTENSE WINDS WILL BE IN
THE CORRIDOR FROM ROCK SPRINGS TO CASPER. THOSE WITH FIRE WEATHER
INTERESTS SHOULD BE AWARE OF THE LIKELIHOOD OF THESE CONDITIONS FOR
WEDNESDAY AND THURSDAY AND BE ON THE ALERT FOR POSSIBLE HIGHLIGHTS ISSUED
EARLY THIS WEEK. FIRST UPPER LOW IN THE PACIFIC NORTHWEST TROUGH
WILL EJECT INTO ALBERTA THURSDAY. THIS UPPER LOW WILL QUICKLY BE
REPLACED BY ANOTHER SHORTWAVE THAT WILL DROP INTO THE BASE OF THE
TROUGH OVER THE INTERMOUNTAIN WEST FOR FRIDAY. UPPER FLOW WILL
PARALLEL SURFACE FRONT THAT WILL BE ORIENTED NORTHEAST-SOUTHWEST
JUST TO THE WEST OF WYOMING FOR FRIDAY. HAVE NUDGED TEMPERATURES
UP A TAD FOR FRIDAY AS IT DOES LOOK LIKE THE COOLER AIR WILL HANG
BACK ONE MORE DAY. AM STILL CONCERNED THAT FRIDAY MAY INDEED BE
WARMER THAN CURRENTLY FORECAST WITH COMPRESSIONAL WARMING AHEAD OF
THE APPROACHING FRONT/TROUGH. MOISTURE WILL RIDE ALONG OUR
NORTHWESTERN ZONES FOR FRIDAY AFTERNOON AND SATURDAY.
THEREFORE...HAVE INCREASED PRECIP CHANCES OVER YELLOWSTONE AND THE
SURROUNDING MOUNTAINS. ENERGY IN THE BASE OF THE TROUGH WILL BEGIN
TO EJECT SATURDAY WHILE AT THE SAME TIME A SURFACE LOW TAKES SHAPE
TO OUR SOUTHEAST. THIS WILL BRING THE COLD FRONT ACROSS THE
FORECAST AREA SATURDAY. BOTH THE ECMWF AND GFS HAVE THE FORECAST
AREA DRY SLOTTED SATURDAY AS THE UPPER LOW TRACKS TO OUR NORTH.
BEST CHANCE FOR MEASURABLE PRECIP OVER THE WEEKEND WILL BE ACROSS
THE NORTHERN THIRD OF THE FORECAST AREA CLOSEST TO THE UPPER LOW.
SURFACE HIGH PUSHES INTO WYOMING SUNDAY AND 700MB TEMPERATURES
FALL INTO THE ZERO TO +4C RANGE ACROSS THE NORTH. THIS WILL LEAD
TO COOLER THAN AVERAGE TEMPERATURES FOR SUNDAY IN ALL BUT
SOUTHWEST AND FAR WEST WYOMING.

AVIATION.../00Z ISSUANCE/

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST WITH SFC WINDS GENERALLY FROM THE SOUTHWEST TO WEST ACROSS MUCH
OF THE STATE AHEAD OF THE COLD FRONT...WINDS WILL BRIEFLY SWITCH TO
THE NW BEHIND THE FRONT WITH SOME AREAS OF 30-40KT GUSTS BEHIND THE
FRONT VCNTY KBYG KPOY KU68. THE MAIN AREA OF ISOLD-SCT -TSRA VCNTY
AND SOUTH OF A KEVW- KLND- KCPR LINE WITH HIGH BASED WINDY STORMS
EXPECTED INTO THE EARLY EVENING. THE COLD FRONT WILL BRING DRIER AIR
AND GUSTY WEST WIND INTO NW WYOMING MID TO LATE THIS
AFTERNOON...PUSHING ACROSS NORTH AND CENTRAL WYOMING LATE THIS
EVENING. CLEAR SKIES AND DIMINISHING WIND WILL PREVAIL ACROSS THE
AREA BEHIND THE FRONT EARLY MONDAY MORNING.

FIRE WEATHER...

..RED FLAG WARNING FOR PORTIONS OF CENTRAL AND NORTHERN WYOMING
THROUGH THE EVENING HOURS...

A COLD FRONT ASSOCIATED WITH THE TROUGH DIGGING TO THE WEST REMAINS
IN THE AREA NEAR THE MONTANA BORDER THIS AFTERNOON WITH COOLER
TEMPERATURES AND MODERATE HUMIDITY TO THE NORTH OF IT AND RED FLAG
TO NEAR RED FLAG CONDITIONS JUST TO THE SOUTH OF IT. MODELS ARE
CALLING FOR SOUTHWEST FLOW TO OVERTAKE THE FRONT AND CAUSE IT TO
RETREAT BACK NORTH FOR THE LATE AFTERNOON HOURS. THE MAIN FRONTAL
SURGE WILL COME LATER TONIGHT WITH STEADY 25 TO 35 MPH WINDS IN
JOHNSON COUNTY AND NORTHERN BIGHORN COUNTY BEHIND THE
FRONT...EXTENDED THE NORTHERN RED FLAG WARNINGS TO 3AM TO COVER THE
FRONTAL PASSAGE THOUGH IT MAY HAPPEN SOONER.

IN ADDITION...ISOLATED TO WIDELY SCATTERED MIXED WET AND DRY
THUNDERSTORMS ARE EXPECTED TO CONTINUE TO DEVELOP INTO THE EVENING
HOURS...WITH A FEW PERSISTING INTO THE NIGHT...ESPECIALLY EAST OF
THE DIVIDE.

IT WILL BE DRY BEHIND THE FRONT FOR MONDAY BUT A BIT COOLER. THERE
WILL BE SOME 20MPH BREEZES IN THE AFTERNOON BUT RED FLAG CONDITIONS
ARE NOT EXPECTED.

IT SILL LOOKS LIKE THERE COULD BE WIDESPREAD RED FLAG CONDITIONS MID
WEEK...STAY TUNED FOR UPDATES ON THE NEXT SYSTEM.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 3 AM MDT MONDAY FOR WYZ275-276-281-282-
287.

&&

$$

UPDATE...AEM
SHORT TERM...ALLEN
LONG TERM...CNJ
AVIATION...ALLEN
FIRE WEATHER...ALLEN




000
FXUS65 KRIW 302037
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
237 PM MDT SUN AUG 30 2015

.SHORT TERM...TONIGHT THROUGH MONDAY

A TROUGH AND COLD FRONT CONTINUE TO TRACK EASTWARD ACROSS THE
INTERMOUNTAIN WEST. THE COLD FRONT IS LYING NEAR THE MONTANA BORDER
AND IS EXPECTED TO SURGE SOUTHWARD AGAIN AROUND SUNSET WITH THE
MAIN PUSH ARRIVING TOWARD MIDNIGHT...THOUGH THE TIMING ON COLD
FRONTS CAN BE TRICKY AS THEY OFTEN MOVE FASTER THAN EXPECTED. WE
CAN CONTINUE TO EXPECT RED FLAG CONDITIONS SOUTH OF THE FRONT AND
MUCH COOLER AND MOIST CONDITIONS TO THE NORTH THROUGH THE EARLY
EVENING HOURS.

THERE IS ALSO SOME DECENT LIFT ON THE FRONT SIDE OF THIS TROUGH
WITH JET SUPPORT ALOFT...A THETA E RIDGE LYING APPROXIMATELY FROM
FLAMING GORGE TO KAYCEE...AND QG FORCING ARRIVING LATER IN THE
EVENING. AREAS WITH DECENT LOW LEVEL MOISTURE IN PLACE...ACROSS
THE WEST AND THE SOUTH...AND ON THE OTHER SIDE OF THE FRONT WILL
SEE WET THUNDERSTORMS AND AREAS LIKE THE SOUTHERN BIGHORN
BASIN...NATRONA COUNTY AND FREMONT COUNTY WILL SEE MAINLY DRY
THUNDERSTORMS THROUGH SUNSET...SHOWERS AND STORMS HAVE A BETTER
CHANCE OF PRODUCING A WETTING RAIN THEREAFTER.

MONDAY WILL BE DRY AGAIN BUT LESS WINDY AS WE LOSE THE GRADIENT AT
THE SURFACE AND ALOFT. TEMPERATURES WILL BE CLOSER TO SEASONAL
NORMS WITH HIGHS IN THE LOW TO MID 80S EAST...MID TO UPPER 70S
WEST AND SOUTH. A PLUME OF MOISTURE ACROSS COLORADO COULD BEGIN TO
POKE NORTH INTO SOUTHERN SWEETWATER COUNTY WITH A FEW STRAY
AFTERNOON STORMS POSSIBLE OTHERIWSE IT WILL BE DRY AND RAIN FREE.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY

MEDIUM-RANGE FORECAST MODELS ARE CONSISTENT AND AGAIN IN FAIRLY GOOD
AGREEMENT THROUGH THE FORECAST PERIOD. WEST-SOUTHWEST FLOW ALOFT ON
TUESDAY WILL BACK TO THE SOUTHWEST WEDNESDAY AND THURSDAY AS A
TROUGH DEEPENS OVER THE PACIFIC NORTHWEST. LIMITED MOISTURE IN
SOUTHWEST FLOW FOR TUESDAY...BUT SOME PRECIPITABLE WATER VALUES
AROUND 0.70 INCHES COULD LEAD TO WEAK CONVECTION IN JOHNSON AND
NATRONA COUNTIES. HOWEVER...WITH DEW POINTS IN THE 30S HAVE
CONTINUED A GENERALLY DRY FORECAST FOR NOW. SOUTHWEST FLOW ADVECTS
IN DRIER AIR FROM THE GREAT BASIN WEDNESDAY AND THURSDAY AND DO NOT
SEE MUCH IN THE WAY OF AVAILABLE MOISTURE FOR ANY CONVECTION.
SURFACE DEW POINTS WILL GENERALLY RANGE FROM 25-35F. ALSO...
WEDNESDAY LOOKS TO BE THE WARMEST DAY OF THE WEEK WITH TEMPERATURES
RUNNING ABOUT 5-10F ABOVE NORMAL AND THE NORTHERN BASINS PUSHING
INTO THE 90S AGAIN. THE COMBINATION OF THE UNSEASONABLY HOT
TEMPERATURES...LOW HUMIDITY...AND INCREASING SOUTHWEST WIND OF 15-30
MPH WILL VERY LIKELY LEAD TO CRITICAL FIRE WEATHER CONDITIONS FOR
WEDNESDAY AND MOST PROBABLY THURSDAY. MOST INTENSE WINDS WILL BE IN
THE CORRIDOR FROM ROCK SPRINGS TO CASPER. THOSE WITH FIRE WEATHER
INTERESTS SHOULD BE AWARE OF THE LIKELIHOOD OF THESE CONDITIONS FOR
WEDNESDAY AND THURSDAY AND BE ON THE ALERT FOR POSSIBLE HIHGLIGHTS
ISSUED EARLY THIS WEEK. FIRST UPPER LOW IN THE PACIFIC NORTHWEST
TROUGH WILL EJECT INTO ALBERTA THURSDAY. THIS UPPER LOW WILL QUICKLY
BE REPLACED BY ANOTHER SHORTWAVE THAT WILL DROP INTO THE BASE OF THE
TROUGH OVER THE INTERMOUNTAIN WEST FOR FRIDAY. UPPER FLOW WILL
PARALLEL SURFACE FRONT THAT WILL BE ORIENTED NORTHEAST-SOUTHWEST
JUST TO THE WEST OF WYOMING FOR FRIDAY. HAVE NUDGED TEMPERATURES UP
A TAD FOR FRIDAY AS IT DOES LOOK LIKE THE COOLER AIR WILL HANG BACK
ONE MORE DAY. AM STILL CONCERNED THAT FRIDAY MAY INDEED BE WARMER
THAN CURRENTLY FORECAST WITH COMPRESSIONAL WARMING AHEAD OF THE
APPROACHING FRONT/TROUGH. MOISTURE WILL RIDE ALONG OUR NORTHWESTERN
ZONES FOR FRIDAY AFTERNOON AND SATURDAY. THEREFORE...HAVE INCREASED
PRECIP CHANCES OVER YELLOWSTONE AND THE SURROUNDING MOUNTAINS.
ENERGY IN THE BASE OF THE TROUGH WILL BEGIN TO EJECT SATURDAY WHILE
AT THE SAME TIME A SURFACE LOW TAKES SHAPE TO OUR SOUTHEAST. THIS
WILL BRING THE COLD FRONT ACROSS THE FORECAST AREA SATURDAY. BOTH
THE ECMWF AND GFS HAVE THE FORECAST AREA DRY SLOTTED SATURDAY AS THE
UPPER LOW TRACKS TO OUR NORTH. BEST CHANCE FOR MEASURABLE PRECIP
OVER THE WEEKEND WILL BE ACROSS THE NORTHERN THIRD OF THE FORECAST
AREA CLOSEST TO THE UPPER LOW. SURFACE HIGH PUSHES INTO WYOMING
SUNDAY AND 700MB TEMPERATURES FALL INTO THE ZERO TO +4C RANGE ACROSS
THE NORTH. THIS WILL LEAD TO COOLER THAN AVERAGE TEMPERATURES FOR
SUNDAY IN ALL BUT SOUTHWEST AND FAR WEST WYOMING.

&&

.AVIATION.../00Z ISSUANCE/

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST WITH SFC WINDS GENERALLY FROM THE SOUTHWEST TO WEST ACROSS MUCH
OF THE STATE AHEAD OF THE COLD FRONT...WINDS WILL BRIEFLY SWITCH TO
THE NW BEHIND THE FRONT WITH SOME AREAS OF 30-40KT GUSTS BEHIND THE
FRONT VCNTY KBYG KPOY KU68. THE MAIN AREA OF ISOLD-SCT -TSRA VCNTY
AND SOUTH OF A KEVW- KLND- KCPR LINE WITH HIGH BASED WINDY STORMS
EXPECTED INTO THE EARLY EVENING. THE COLD FRONT WILL BRING DRIER AIR
AND GUSTY WEST WIND INTO NW WYOMING MID TO LATE THIS
AFTERNOON...PUSHING ACROSS NORTH AND CENTRAL WYOMING LATE THIS
EVENING. CLEAR SKIES AND DIMINISHING WIND WILL PREVAIL ACROSS THE
AREA BEHIND THE FRONT EARLY MONDAY MORNING.

&&

.FIRE WEATHER...

...RED FLAG WARNING FOR PORTIONS OF CENTRAL AND NORTHERN WYOMING
THROUGH THE EVENING HOURS...

A COLD FRONT ASSOCIATED WITH THE TROUGH DIGGING TO THE WEST REMAINS
IN THE AREA NEAR THE MONTANA BORDER THIS AFTERNOON WITH COOLER
TEMPERATURES AND MODERATE HUMIDITY TO THE NORTH OF IT AND RED FLAG
TO NEAR RED FLAG CONDITIONS JUST TO THE SOUTH OF IT. MODELS ARE
CALLING FOR SOUTHWEST FLOW TO OVERTAKE THE FRONT AND CAUSE IT TO
RETREAT BACK NORTH FOR THE LATE AFTERNOON HOURS. THE MAIN FRONTAL
SURGE WILL COME LATER TONIGHT WITH STEADY 25 TO 35 MPH WINDS IN
JOHNSON COUNTY AND NORTHERN BIGHORN COUNTY BEHIND THE
FRONT...EXTENDED THE NORTHERN RED FLAG WARNINGS TO 3AM TO COVER THE
FRONTAL PASSAGE THOUGH IT MAY HAPPEN SOONER.

IN ADDITION...ISOLATED TO WIDELY SCATTERED MIXED WET AND DRY
THUNDERSTORMS ARE EXPECTED TO CONTINUE TO DEVELOP INTO THE EVENING
HOURS...WITH A FEW PERSISTING INTO THE NIGHT...ESPECIALLY EAST OF
THE DIVIDE.

IT WILL BE DRY BEHIND THE FRONT FOR MONDAY BUT A BIT COOLER. THERE
WILL BE SOME 20MPH BREEZES IN THE AFTERNOON BUT RED FLAG CONDITIONS
ARE NOT EXPECTED.

IT SILL LOOKS LIKE THERE COULD BE WIDESPREAD RED FLAG CONDITIONS MID
WEEK...STAY TUNED FOR UPDATES ON THE NEXT SYSTEM.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ280-283-285-
289-300.

RED FLAG WARNING UNTIL 3 AM MDT MONDAY FOR WYZ275-276-281-282-
287.

&&

$$

SHORT TERM...ALLEN
LONG TERM...CNJ
AVIATION...ALLEN
FIRE WEATHER...ALLEN





000
FXUS65 KRIW 302037
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
237 PM MDT SUN AUG 30 2015

.SHORT TERM...TONIGHT THROUGH MONDAY

A TROUGH AND COLD FRONT CONTINUE TO TRACK EASTWARD ACROSS THE
INTERMOUNTAIN WEST. THE COLD FRONT IS LYING NEAR THE MONTANA BORDER
AND IS EXPECTED TO SURGE SOUTHWARD AGAIN AROUND SUNSET WITH THE
MAIN PUSH ARRIVING TOWARD MIDNIGHT...THOUGH THE TIMING ON COLD
FRONTS CAN BE TRICKY AS THEY OFTEN MOVE FASTER THAN EXPECTED. WE
CAN CONTINUE TO EXPECT RED FLAG CONDITIONS SOUTH OF THE FRONT AND
MUCH COOLER AND MOIST CONDITIONS TO THE NORTH THROUGH THE EARLY
EVENING HOURS.

THERE IS ALSO SOME DECENT LIFT ON THE FRONT SIDE OF THIS TROUGH
WITH JET SUPPORT ALOFT...A THETA E RIDGE LYING APPROXIMATELY FROM
FLAMING GORGE TO KAYCEE...AND QG FORCING ARRIVING LATER IN THE
EVENING. AREAS WITH DECENT LOW LEVEL MOISTURE IN PLACE...ACROSS
THE WEST AND THE SOUTH...AND ON THE OTHER SIDE OF THE FRONT WILL
SEE WET THUNDERSTORMS AND AREAS LIKE THE SOUTHERN BIGHORN
BASIN...NATRONA COUNTY AND FREMONT COUNTY WILL SEE MAINLY DRY
THUNDERSTORMS THROUGH SUNSET...SHOWERS AND STORMS HAVE A BETTER
CHANCE OF PRODUCING A WETTING RAIN THEREAFTER.

MONDAY WILL BE DRY AGAIN BUT LESS WINDY AS WE LOSE THE GRADIENT AT
THE SURFACE AND ALOFT. TEMPERATURES WILL BE CLOSER TO SEASONAL
NORMS WITH HIGHS IN THE LOW TO MID 80S EAST...MID TO UPPER 70S
WEST AND SOUTH. A PLUME OF MOISTURE ACROSS COLORADO COULD BEGIN TO
POKE NORTH INTO SOUTHERN SWEETWATER COUNTY WITH A FEW STRAY
AFTERNOON STORMS POSSIBLE OTHERIWSE IT WILL BE DRY AND RAIN FREE.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY

MEDIUM-RANGE FORECAST MODELS ARE CONSISTENT AND AGAIN IN FAIRLY GOOD
AGREEMENT THROUGH THE FORECAST PERIOD. WEST-SOUTHWEST FLOW ALOFT ON
TUESDAY WILL BACK TO THE SOUTHWEST WEDNESDAY AND THURSDAY AS A
TROUGH DEEPENS OVER THE PACIFIC NORTHWEST. LIMITED MOISTURE IN
SOUTHWEST FLOW FOR TUESDAY...BUT SOME PRECIPITABLE WATER VALUES
AROUND 0.70 INCHES COULD LEAD TO WEAK CONVECTION IN JOHNSON AND
NATRONA COUNTIES. HOWEVER...WITH DEW POINTS IN THE 30S HAVE
CONTINUED A GENERALLY DRY FORECAST FOR NOW. SOUTHWEST FLOW ADVECTS
IN DRIER AIR FROM THE GREAT BASIN WEDNESDAY AND THURSDAY AND DO NOT
SEE MUCH IN THE WAY OF AVAILABLE MOISTURE FOR ANY CONVECTION.
SURFACE DEW POINTS WILL GENERALLY RANGE FROM 25-35F. ALSO...
WEDNESDAY LOOKS TO BE THE WARMEST DAY OF THE WEEK WITH TEMPERATURES
RUNNING ABOUT 5-10F ABOVE NORMAL AND THE NORTHERN BASINS PUSHING
INTO THE 90S AGAIN. THE COMBINATION OF THE UNSEASONABLY HOT
TEMPERATURES...LOW HUMIDITY...AND INCREASING SOUTHWEST WIND OF 15-30
MPH WILL VERY LIKELY LEAD TO CRITICAL FIRE WEATHER CONDITIONS FOR
WEDNESDAY AND MOST PROBABLY THURSDAY. MOST INTENSE WINDS WILL BE IN
THE CORRIDOR FROM ROCK SPRINGS TO CASPER. THOSE WITH FIRE WEATHER
INTERESTS SHOULD BE AWARE OF THE LIKELIHOOD OF THESE CONDITIONS FOR
WEDNESDAY AND THURSDAY AND BE ON THE ALERT FOR POSSIBLE HIHGLIGHTS
ISSUED EARLY THIS WEEK. FIRST UPPER LOW IN THE PACIFIC NORTHWEST
TROUGH WILL EJECT INTO ALBERTA THURSDAY. THIS UPPER LOW WILL QUICKLY
BE REPLACED BY ANOTHER SHORTWAVE THAT WILL DROP INTO THE BASE OF THE
TROUGH OVER THE INTERMOUNTAIN WEST FOR FRIDAY. UPPER FLOW WILL
PARALLEL SURFACE FRONT THAT WILL BE ORIENTED NORTHEAST-SOUTHWEST
JUST TO THE WEST OF WYOMING FOR FRIDAY. HAVE NUDGED TEMPERATURES UP
A TAD FOR FRIDAY AS IT DOES LOOK LIKE THE COOLER AIR WILL HANG BACK
ONE MORE DAY. AM STILL CONCERNED THAT FRIDAY MAY INDEED BE WARMER
THAN CURRENTLY FORECAST WITH COMPRESSIONAL WARMING AHEAD OF THE
APPROACHING FRONT/TROUGH. MOISTURE WILL RIDE ALONG OUR NORTHWESTERN
ZONES FOR FRIDAY AFTERNOON AND SATURDAY. THEREFORE...HAVE INCREASED
PRECIP CHANCES OVER YELLOWSTONE AND THE SURROUNDING MOUNTAINS.
ENERGY IN THE BASE OF THE TROUGH WILL BEGIN TO EJECT SATURDAY WHILE
AT THE SAME TIME A SURFACE LOW TAKES SHAPE TO OUR SOUTHEAST. THIS
WILL BRING THE COLD FRONT ACROSS THE FORECAST AREA SATURDAY. BOTH
THE ECMWF AND GFS HAVE THE FORECAST AREA DRY SLOTTED SATURDAY AS THE
UPPER LOW TRACKS TO OUR NORTH. BEST CHANCE FOR MEASURABLE PRECIP
OVER THE WEEKEND WILL BE ACROSS THE NORTHERN THIRD OF THE FORECAST
AREA CLOSEST TO THE UPPER LOW. SURFACE HIGH PUSHES INTO WYOMING
SUNDAY AND 700MB TEMPERATURES FALL INTO THE ZERO TO +4C RANGE ACROSS
THE NORTH. THIS WILL LEAD TO COOLER THAN AVERAGE TEMPERATURES FOR
SUNDAY IN ALL BUT SOUTHWEST AND FAR WEST WYOMING.

&&

.AVIATION.../00Z ISSUANCE/

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST WITH SFC WINDS GENERALLY FROM THE SOUTHWEST TO WEST ACROSS MUCH
OF THE STATE AHEAD OF THE COLD FRONT...WINDS WILL BRIEFLY SWITCH TO
THE NW BEHIND THE FRONT WITH SOME AREAS OF 30-40KT GUSTS BEHIND THE
FRONT VCNTY KBYG KPOY KU68. THE MAIN AREA OF ISOLD-SCT -TSRA VCNTY
AND SOUTH OF A KEVW- KLND- KCPR LINE WITH HIGH BASED WINDY STORMS
EXPECTED INTO THE EARLY EVENING. THE COLD FRONT WILL BRING DRIER AIR
AND GUSTY WEST WIND INTO NW WYOMING MID TO LATE THIS
AFTERNOON...PUSHING ACROSS NORTH AND CENTRAL WYOMING LATE THIS
EVENING. CLEAR SKIES AND DIMINISHING WIND WILL PREVAIL ACROSS THE
AREA BEHIND THE FRONT EARLY MONDAY MORNING.

&&

.FIRE WEATHER...

...RED FLAG WARNING FOR PORTIONS OF CENTRAL AND NORTHERN WYOMING
THROUGH THE EVENING HOURS...

A COLD FRONT ASSOCIATED WITH THE TROUGH DIGGING TO THE WEST REMAINS
IN THE AREA NEAR THE MONTANA BORDER THIS AFTERNOON WITH COOLER
TEMPERATURES AND MODERATE HUMIDITY TO THE NORTH OF IT AND RED FLAG
TO NEAR RED FLAG CONDITIONS JUST TO THE SOUTH OF IT. MODELS ARE
CALLING FOR SOUTHWEST FLOW TO OVERTAKE THE FRONT AND CAUSE IT TO
RETREAT BACK NORTH FOR THE LATE AFTERNOON HOURS. THE MAIN FRONTAL
SURGE WILL COME LATER TONIGHT WITH STEADY 25 TO 35 MPH WINDS IN
JOHNSON COUNTY AND NORTHERN BIGHORN COUNTY BEHIND THE
FRONT...EXTENDED THE NORTHERN RED FLAG WARNINGS TO 3AM TO COVER THE
FRONTAL PASSAGE THOUGH IT MAY HAPPEN SOONER.

IN ADDITION...ISOLATED TO WIDELY SCATTERED MIXED WET AND DRY
THUNDERSTORMS ARE EXPECTED TO CONTINUE TO DEVELOP INTO THE EVENING
HOURS...WITH A FEW PERSISTING INTO THE NIGHT...ESPECIALLY EAST OF
THE DIVIDE.

IT WILL BE DRY BEHIND THE FRONT FOR MONDAY BUT A BIT COOLER. THERE
WILL BE SOME 20MPH BREEZES IN THE AFTERNOON BUT RED FLAG CONDITIONS
ARE NOT EXPECTED.

IT SILL LOOKS LIKE THERE COULD BE WIDESPREAD RED FLAG CONDITIONS MID
WEEK...STAY TUNED FOR UPDATES ON THE NEXT SYSTEM.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ280-283-285-
289-300.

RED FLAG WARNING UNTIL 3 AM MDT MONDAY FOR WYZ275-276-281-282-
287.

&&

$$

SHORT TERM...ALLEN
LONG TERM...CNJ
AVIATION...ALLEN
FIRE WEATHER...ALLEN




000
FXUS65 KRIW 301747 AAA
AFDRIW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RIVERTON WY
1147 AM MDT SUN AUG 30 2015

.PREV DISCUSSION... /ISSUED 250 AM MDT SUN AUG 30 2015/

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

A STRONG TROUGH OF LOW PRESSURE JUST OFF THE PACIFIC NORTHWEST COAST
HAS EJECTED A SHEARED UPPER LEVEL SHORTWAVE EASTWARD THAT APPEARS TO
BE LOCATED OVER NORTHERN IDAHO AND WESTERN MT. ACTIVE CONVECTION
CONTINUES OUT AHEAD OF THIS FEATURE ACROSS EASTERN IDAHO NEAR THE
WYOMING BORDER AND INTO YNP AT THE TIME OF THIS WRITING. IT WILL BE
AN EARLY SHOW FOR CONVECTION IN WESTERN WY TODAY WITH THESE STORMS
ABOUT TO SWEEP ACROSS FAR WEST WYOMING DURING THE REMAINDER OF THE
NIGHT. THEN THE MAIN TROUGH WILL APPROACH THE NORTHERN ROCKIES TODAY
FOR ANOTHER ROUND OF CONVECTION FIRING UP IN FAR WESTERN WY BY MID
DAY AHEAD OF THE MAIN TROUGH AND ASCT COLD FRONT. IN THE
MEANTIME...EAST OF THE DIVIDE...SOUTHWEST WINDS WILL INCREASE OVER
WHAT THEY WERE SATURDAY AS THEY DRAW IN SLIGHTLY HIGHER LOWER LEVEL
MOISTURE. INSTABILITY WILL BE IN PLACE OVER THE ENTIRE CWA BUT ONLY
SCANT MOISTURE TO WORK WITH TO PRODUCE THUNDERSTORMS EAST OF THE
DIVIDE...AT LEAST INITIALLY IN THE EARLY TO MID AFTERNOON. THERE
WILL BE A SEPARATE FINGER OF WEAK HIGH AND MID LEVEL MONSOON
MOISTURE THAT WILL STREAM IN ACROSS RKS AND CPR. HOWEVER THE BEST
INSTABILITY WILL BE IN PLACE ACROSS NORTHERN WY WHERE THE BEST CAPES
WILL BE. IT APPEARS THE BEST CHANCE OF ANY DRY LIGHTNING WILL OCCUR
ON THE PERIPHERY OF ANY HIGH BASED THUNDERSTORMS ALONG THE
AFOREMENTIONED WEAK MONSOON MOISTURE PLUME AS WELL AS ACROSS
NORTHERN WY EAST OF THE DIVIDE WHERE RELATIVELY HIGH BASED STORMS
WILL CORRELATE WITH THE BEST CAPES. DRY THUNDERSTORMS WILL MORPH
INTO MORE WET STORMS AS THE FRONT DRAWS NEAR. THE TROUGHPA WILL
SWEEP ACROSS THE CWA TONIGHT. THEN ON MONDAY...ANOTHER SURGE OF WEAK
MID/UPPER LEVEL MOISTURE WILL OVERLAP SOME LINGERING INSTABILITY
OVER EXTREME SOUTHERN WY WHERE SOME ISOLD T STORMS ARE EXPECTED.
THEN BY TUESDAY...ANOTHER CLOSED LOW WILL ESTABLISH ITSELF ALONG THE
SOUTHERN BC COAST. THIS LOW WILL EJECT A WEAK VORT LOBE EAST
NORTHEAST ACROSS THE NORTHERN ROCKIES THAT WILL RESULT IN ISOLD
CONVECTION...MAINLY OVER THE NW MTNS TUE AFTERNOON. TODAY WILL BE A
COUPLE OF DEGREES COOLER THAN SATURDAY AS CLOUDS AND SHOWER ACTIVITY
DECREASE THE SOLAR INSULATION. AFTERWARD...TEMPS WILL COOL A FEW
DEGREES MONDAY BEFORE WARMING BACK UP TUESDAY.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

HIGH LATITUDE ENERGY CURRENTLY OVER AK AND THE BERING SEA AREA WILL
DIVE SWD INTO OUR PACNW TROUGH AS UPSTREAM ENERGY...TYPHOON
REMNANTS...PUMPS UP THE UPSTREAM RIDGE OVER THE ERN PACIFIC. THE
END RESULT IS A DEEPENING COLD EARLY SEPTEMBER TROUGH OVER THE
PACNW AND INTERMOUNTAIN WEST THE SECOND HALF OF NEXT WEEK THAT
GRADUALLY TRANSLATES EWD AS THE FLOW DEAMPLIFYS TOWARDS THE END OF
THE PERIOD AND POSSIBLE SPLIT DEVELOPS OVER THE WEST EARLY NEXT
WEEK. THE MIDWEEK PERIOD WILL GENERALLY BE DRY AND QUITE WARM WITH
BREEZY TO LOCALLY WINDY PERIODS AND VERY LIMITED MAINLY MTN TSTMS
CHANCES AT BEST. BY FRIDAY...THE FIRST SIGNIFICANT SHORTWAVE OUT
AHEAD OF THE TROUGH IS ALREADY IMPACTING THE WEST AND NORTH AS A
COLD FRONT TRIES TO SAG SWD INTO THE NRN ZONES. THIS FRONTAL
BOUNDARY WILL BE A SIGNIFICANT PLAYER THROUGH THE WEEKEND WITH
CONSIDERABLY COOLER IF NOT COLDER WEATHER BEHIND IT AS THE MAIN
TROUGH OPENS UP AND PASSES ACROSS NRN WYO AND MONTANA OVER THE
LABOR DAY WEEKEND. A GOOD CHANCE OF SHOWERS AND TSTMS SHOULD OCCUR
IN AT LEAST THE NWRN SECTIONS WITH THIS FIRST SHORTWAVE AND THEN
MORE OF THE WEST AND NORTH AS THE DYNAMICS INTERACT/OVERRUN THE
FRONTAL BOUNDARY OVER THE WEEKEND. DETAILS ARE STILL UNCERTAIN BUT
THE GFS AND ECMWF ARE IN PRETTY GOOD AGREEMENT WITH THE BIG
PICTURE. THE SOURCE REGION OF THIS TROUGH IS QUITE COLD AND MODEL
GUIDANCE IS DROPPING H7 TEMPS DOWN TO AROUND ZERO TO EVEN BELOW
WITH THE FIRST SHORTWAVE FRIDAY NIGHT AND THEN WITH THE MAIN
TROUGH SATURDAY NIGHT SO MOUNTAINS WOULD GET A DECENT SHOT OF SOME
SNOW WITH EACH OF THESE. IT IS LABOR DAY WEEKEND AFTER ALL.

.AVIATION.../18Z ISSUANCE/

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST TODAY WITH SFC SW FLOW INCREASING ACROSS WEST AND CENTRAL
WYOMING AHEAD OF THE FRONT...ALONG WITH AREAS OF LLWS.  SFC SW WINDS
AT 20-30KTS WILL PREVAIL ACROSS THE AREA INTO THIS AFTERNOON. THE
MAIN AREA ISOLD-SCT -TSRA ARE DEVELOPING VCNTY AND SOUTH OF A
KEVW- KLND- KCPR LINE WITH HIGH BASED WINDY STORMS EXPECTED INTO
THE EARLY EVENING. THE COLD FRONT WILL BRING DRIER AIR AND GUSTY
WEST WIND INTO NW WYOMING MID TO LATE THIS AFTERNOON...PUSHING
ACROSS NORTH AND CENTRAL WYOMING THIS EVENING. CLEAR SKIES AND
DIMINISHING WIND WILL PREVAIL ACROSS THE AREA BEHIND THE FRONT
EARLY MONDAY MORNING.

.FIRE WEATHER...

...RED FLAG WARNING FOR PORTIONS OF CENTRAL AND NORTHERN WYOMING...

OVERALL IT WILL BE WINDIER THAN IT WAS SATURDAY BUT WITH SLIGHTLY
HIGHER RELATIVE HUMIDITY. AS THE COLD FRONT ASSOCIATED WITH THE
TROUGH DIGGING TO THE WEST ADVANCES...IT WILL LIKELY SETTLE INTO
WESTERN...NORTHERN AND SOUTHERN WYOMING FAIRLY EARLY IN THE
DAY...WHICH WOULD END THE FIRE WEATHER THREAT IN THOSE LOCATIONS
ALONG WITH INCREASING CLOUDS AS WELL AS A SLIGHT CHANCE FOR A
WETTING RAIN. STRONG SOUTHWEST FLOW BUT STILL LOW HUMIDITY ACROSS
FREMONT...JOHNSON AND NATRONA COUNTIES WILL OCCUR SO THESE AREAS
WILL CONTINUE TO BE UNDER THE RED FLAG WARNING FOR TODAY. IN
ADDITION...A SWATH OF MID LEVEL MOISTURE AND CONTINUED INSTABILITY
WILL KICK OF A FEW MIXED WET AND DRY THUNDERSTORMS...SOME OF WHICH
COULD CONTRIBUTE TO NEW FIRE STARTS WITH THE MOST ACTIVITY
EXPECTED ACROSS NORTHERN AND WESTERN WYOMING...WITH A SECONDARY
SWATH EXPECTED OVER NATRONA AND EASTERN FREMONT COUNTIES LATE
SUNDAY AFTERNOON...THE CHANCE OF A WETTING RAIN OUT OF THESE
STORMS IS NEXT TO ZERO. THE BEST CHANCE OF ANY DRY LIGHTNING
STARTS WILL LIKELY BE ON THE PERIPHERY OF ANY THUNDERSTORMS THAT
FORM ACROSS NORTHERN WYOMING EAST OF THE DIVIDE THROUGH MID DAY
WHERE THE BEST INSTABILITY WILL BE...THEN FROM EASTERN SWEETWATER
COUNTY TO CASPER AND THE REST OF NATRONA COUNTY LATER IN THE
AFTERNOON WHERE THE COMBINATION OF DRIEST BOUNDARY LEVEL MOISTURE
AND WIDEST TEMP/DEW POINT SPREADS WILL LIE.

A REPEAT OF THESE CONDITIONS WILL BE POSSIBLE MID WEEK.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ280-283-285-
289-300.

RED FLAG WARNING UNTIL 3 AM MDT MONDAY FOR WYZ275-276-281-282-
287.

&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...ALLEN
FIRE WEATHER...LIPSON




000
FXUS65 KRIW 301747 AAA
AFDRIW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RIVERTON WY
1147 AM MDT SUN AUG 30 2015

.PREV DISCUSSION... /ISSUED 250 AM MDT SUN AUG 30 2015/

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

A STRONG TROUGH OF LOW PRESSURE JUST OFF THE PACIFIC NORTHWEST COAST
HAS EJECTED A SHEARED UPPER LEVEL SHORTWAVE EASTWARD THAT APPEARS TO
BE LOCATED OVER NORTHERN IDAHO AND WESTERN MT. ACTIVE CONVECTION
CONTINUES OUT AHEAD OF THIS FEATURE ACROSS EASTERN IDAHO NEAR THE
WYOMING BORDER AND INTO YNP AT THE TIME OF THIS WRITING. IT WILL BE
AN EARLY SHOW FOR CONVECTION IN WESTERN WY TODAY WITH THESE STORMS
ABOUT TO SWEEP ACROSS FAR WEST WYOMING DURING THE REMAINDER OF THE
NIGHT. THEN THE MAIN TROUGH WILL APPROACH THE NORTHERN ROCKIES TODAY
FOR ANOTHER ROUND OF CONVECTION FIRING UP IN FAR WESTERN WY BY MID
DAY AHEAD OF THE MAIN TROUGH AND ASCT COLD FRONT. IN THE
MEANTIME...EAST OF THE DIVIDE...SOUTHWEST WINDS WILL INCREASE OVER
WHAT THEY WERE SATURDAY AS THEY DRAW IN SLIGHTLY HIGHER LOWER LEVEL
MOISTURE. INSTABILITY WILL BE IN PLACE OVER THE ENTIRE CWA BUT ONLY
SCANT MOISTURE TO WORK WITH TO PRODUCE THUNDERSTORMS EAST OF THE
DIVIDE...AT LEAST INITIALLY IN THE EARLY TO MID AFTERNOON. THERE
WILL BE A SEPARATE FINGER OF WEAK HIGH AND MID LEVEL MONSOON
MOISTURE THAT WILL STREAM IN ACROSS RKS AND CPR. HOWEVER THE BEST
INSTABILITY WILL BE IN PLACE ACROSS NORTHERN WY WHERE THE BEST CAPES
WILL BE. IT APPEARS THE BEST CHANCE OF ANY DRY LIGHTNING WILL OCCUR
ON THE PERIPHERY OF ANY HIGH BASED THUNDERSTORMS ALONG THE
AFOREMENTIONED WEAK MONSOON MOISTURE PLUME AS WELL AS ACROSS
NORTHERN WY EAST OF THE DIVIDE WHERE RELATIVELY HIGH BASED STORMS
WILL CORRELATE WITH THE BEST CAPES. DRY THUNDERSTORMS WILL MORPH
INTO MORE WET STORMS AS THE FRONT DRAWS NEAR. THE TROUGHPA WILL
SWEEP ACROSS THE CWA TONIGHT. THEN ON MONDAY...ANOTHER SURGE OF WEAK
MID/UPPER LEVEL MOISTURE WILL OVERLAP SOME LINGERING INSTABILITY
OVER EXTREME SOUTHERN WY WHERE SOME ISOLD T STORMS ARE EXPECTED.
THEN BY TUESDAY...ANOTHER CLOSED LOW WILL ESTABLISH ITSELF ALONG THE
SOUTHERN BC COAST. THIS LOW WILL EJECT A WEAK VORT LOBE EAST
NORTHEAST ACROSS THE NORTHERN ROCKIES THAT WILL RESULT IN ISOLD
CONVECTION...MAINLY OVER THE NW MTNS TUE AFTERNOON. TODAY WILL BE A
COUPLE OF DEGREES COOLER THAN SATURDAY AS CLOUDS AND SHOWER ACTIVITY
DECREASE THE SOLAR INSULATION. AFTERWARD...TEMPS WILL COOL A FEW
DEGREES MONDAY BEFORE WARMING BACK UP TUESDAY.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

HIGH LATITUDE ENERGY CURRENTLY OVER AK AND THE BERING SEA AREA WILL
DIVE SWD INTO OUR PACNW TROUGH AS UPSTREAM ENERGY...TYPHOON
REMNANTS...PUMPS UP THE UPSTREAM RIDGE OVER THE ERN PACIFIC. THE
END RESULT IS A DEEPENING COLD EARLY SEPTEMBER TROUGH OVER THE
PACNW AND INTERMOUNTAIN WEST THE SECOND HALF OF NEXT WEEK THAT
GRADUALLY TRANSLATES EWD AS THE FLOW DEAMPLIFYS TOWARDS THE END OF
THE PERIOD AND POSSIBLE SPLIT DEVELOPS OVER THE WEST EARLY NEXT
WEEK. THE MIDWEEK PERIOD WILL GENERALLY BE DRY AND QUITE WARM WITH
BREEZY TO LOCALLY WINDY PERIODS AND VERY LIMITED MAINLY MTN TSTMS
CHANCES AT BEST. BY FRIDAY...THE FIRST SIGNIFICANT SHORTWAVE OUT
AHEAD OF THE TROUGH IS ALREADY IMPACTING THE WEST AND NORTH AS A
COLD FRONT TRIES TO SAG SWD INTO THE NRN ZONES. THIS FRONTAL
BOUNDARY WILL BE A SIGNIFICANT PLAYER THROUGH THE WEEKEND WITH
CONSIDERABLY COOLER IF NOT COLDER WEATHER BEHIND IT AS THE MAIN
TROUGH OPENS UP AND PASSES ACROSS NRN WYO AND MONTANA OVER THE
LABOR DAY WEEKEND. A GOOD CHANCE OF SHOWERS AND TSTMS SHOULD OCCUR
IN AT LEAST THE NWRN SECTIONS WITH THIS FIRST SHORTWAVE AND THEN
MORE OF THE WEST AND NORTH AS THE DYNAMICS INTERACT/OVERRUN THE
FRONTAL BOUNDARY OVER THE WEEKEND. DETAILS ARE STILL UNCERTAIN BUT
THE GFS AND ECMWF ARE IN PRETTY GOOD AGREEMENT WITH THE BIG
PICTURE. THE SOURCE REGION OF THIS TROUGH IS QUITE COLD AND MODEL
GUIDANCE IS DROPPING H7 TEMPS DOWN TO AROUND ZERO TO EVEN BELOW
WITH THE FIRST SHORTWAVE FRIDAY NIGHT AND THEN WITH THE MAIN
TROUGH SATURDAY NIGHT SO MOUNTAINS WOULD GET A DECENT SHOT OF SOME
SNOW WITH EACH OF THESE. IT IS LABOR DAY WEEKEND AFTER ALL.

.AVIATION.../18Z ISSUANCE/

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST TODAY WITH SFC SW FLOW INCREASING ACROSS WEST AND CENTRAL
WYOMING AHEAD OF THE FRONT...ALONG WITH AREAS OF LLWS.  SFC SW WINDS
AT 20-30KTS WILL PREVAIL ACROSS THE AREA INTO THIS AFTERNOON. THE
MAIN AREA ISOLD-SCT -TSRA ARE DEVELOPING VCNTY AND SOUTH OF A
KEVW- KLND- KCPR LINE WITH HIGH BASED WINDY STORMS EXPECTED INTO
THE EARLY EVENING. THE COLD FRONT WILL BRING DRIER AIR AND GUSTY
WEST WIND INTO NW WYOMING MID TO LATE THIS AFTERNOON...PUSHING
ACROSS NORTH AND CENTRAL WYOMING THIS EVENING. CLEAR SKIES AND
DIMINISHING WIND WILL PREVAIL ACROSS THE AREA BEHIND THE FRONT
EARLY MONDAY MORNING.

.FIRE WEATHER...

...RED FLAG WARNING FOR PORTIONS OF CENTRAL AND NORTHERN WYOMING...

OVERALL IT WILL BE WINDIER THAN IT WAS SATURDAY BUT WITH SLIGHTLY
HIGHER RELATIVE HUMIDITY. AS THE COLD FRONT ASSOCIATED WITH THE
TROUGH DIGGING TO THE WEST ADVANCES...IT WILL LIKELY SETTLE INTO
WESTERN...NORTHERN AND SOUTHERN WYOMING FAIRLY EARLY IN THE
DAY...WHICH WOULD END THE FIRE WEATHER THREAT IN THOSE LOCATIONS
ALONG WITH INCREASING CLOUDS AS WELL AS A SLIGHT CHANCE FOR A
WETTING RAIN. STRONG SOUTHWEST FLOW BUT STILL LOW HUMIDITY ACROSS
FREMONT...JOHNSON AND NATRONA COUNTIES WILL OCCUR SO THESE AREAS
WILL CONTINUE TO BE UNDER THE RED FLAG WARNING FOR TODAY. IN
ADDITION...A SWATH OF MID LEVEL MOISTURE AND CONTINUED INSTABILITY
WILL KICK OF A FEW MIXED WET AND DRY THUNDERSTORMS...SOME OF WHICH
COULD CONTRIBUTE TO NEW FIRE STARTS WITH THE MOST ACTIVITY
EXPECTED ACROSS NORTHERN AND WESTERN WYOMING...WITH A SECONDARY
SWATH EXPECTED OVER NATRONA AND EASTERN FREMONT COUNTIES LATE
SUNDAY AFTERNOON...THE CHANCE OF A WETTING RAIN OUT OF THESE
STORMS IS NEXT TO ZERO. THE BEST CHANCE OF ANY DRY LIGHTNING
STARTS WILL LIKELY BE ON THE PERIPHERY OF ANY THUNDERSTORMS THAT
FORM ACROSS NORTHERN WYOMING EAST OF THE DIVIDE THROUGH MID DAY
WHERE THE BEST INSTABILITY WILL BE...THEN FROM EASTERN SWEETWATER
COUNTY TO CASPER AND THE REST OF NATRONA COUNTY LATER IN THE
AFTERNOON WHERE THE COMBINATION OF DRIEST BOUNDARY LEVEL MOISTURE
AND WIDEST TEMP/DEW POINT SPREADS WILL LIE.

A REPEAT OF THESE CONDITIONS WILL BE POSSIBLE MID WEEK.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ280-283-285-
289-300.

RED FLAG WARNING UNTIL 3 AM MDT MONDAY FOR WYZ275-276-281-282-
287.

&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...ALLEN
FIRE WEATHER...LIPSON





000
FXUS65 KRIW 301747 AAA
AFDRIW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RIVERTON WY
1147 AM MDT SUN AUG 30 2015

.PREV DISCUSSION... /ISSUED 250 AM MDT SUN AUG 30 2015/

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

A STRONG TROUGH OF LOW PRESSURE JUST OFF THE PACIFIC NORTHWEST COAST
HAS EJECTED A SHEARED UPPER LEVEL SHORTWAVE EASTWARD THAT APPEARS TO
BE LOCATED OVER NORTHERN IDAHO AND WESTERN MT. ACTIVE CONVECTION
CONTINUES OUT AHEAD OF THIS FEATURE ACROSS EASTERN IDAHO NEAR THE
WYOMING BORDER AND INTO YNP AT THE TIME OF THIS WRITING. IT WILL BE
AN EARLY SHOW FOR CONVECTION IN WESTERN WY TODAY WITH THESE STORMS
ABOUT TO SWEEP ACROSS FAR WEST WYOMING DURING THE REMAINDER OF THE
NIGHT. THEN THE MAIN TROUGH WILL APPROACH THE NORTHERN ROCKIES TODAY
FOR ANOTHER ROUND OF CONVECTION FIRING UP IN FAR WESTERN WY BY MID
DAY AHEAD OF THE MAIN TROUGH AND ASCT COLD FRONT. IN THE
MEANTIME...EAST OF THE DIVIDE...SOUTHWEST WINDS WILL INCREASE OVER
WHAT THEY WERE SATURDAY AS THEY DRAW IN SLIGHTLY HIGHER LOWER LEVEL
MOISTURE. INSTABILITY WILL BE IN PLACE OVER THE ENTIRE CWA BUT ONLY
SCANT MOISTURE TO WORK WITH TO PRODUCE THUNDERSTORMS EAST OF THE
DIVIDE...AT LEAST INITIALLY IN THE EARLY TO MID AFTERNOON. THERE
WILL BE A SEPARATE FINGER OF WEAK HIGH AND MID LEVEL MONSOON
MOISTURE THAT WILL STREAM IN ACROSS RKS AND CPR. HOWEVER THE BEST
INSTABILITY WILL BE IN PLACE ACROSS NORTHERN WY WHERE THE BEST CAPES
WILL BE. IT APPEARS THE BEST CHANCE OF ANY DRY LIGHTNING WILL OCCUR
ON THE PERIPHERY OF ANY HIGH BASED THUNDERSTORMS ALONG THE
AFOREMENTIONED WEAK MONSOON MOISTURE PLUME AS WELL AS ACROSS
NORTHERN WY EAST OF THE DIVIDE WHERE RELATIVELY HIGH BASED STORMS
WILL CORRELATE WITH THE BEST CAPES. DRY THUNDERSTORMS WILL MORPH
INTO MORE WET STORMS AS THE FRONT DRAWS NEAR. THE TROUGHPA WILL
SWEEP ACROSS THE CWA TONIGHT. THEN ON MONDAY...ANOTHER SURGE OF WEAK
MID/UPPER LEVEL MOISTURE WILL OVERLAP SOME LINGERING INSTABILITY
OVER EXTREME SOUTHERN WY WHERE SOME ISOLD T STORMS ARE EXPECTED.
THEN BY TUESDAY...ANOTHER CLOSED LOW WILL ESTABLISH ITSELF ALONG THE
SOUTHERN BC COAST. THIS LOW WILL EJECT A WEAK VORT LOBE EAST
NORTHEAST ACROSS THE NORTHERN ROCKIES THAT WILL RESULT IN ISOLD
CONVECTION...MAINLY OVER THE NW MTNS TUE AFTERNOON. TODAY WILL BE A
COUPLE OF DEGREES COOLER THAN SATURDAY AS CLOUDS AND SHOWER ACTIVITY
DECREASE THE SOLAR INSULATION. AFTERWARD...TEMPS WILL COOL A FEW
DEGREES MONDAY BEFORE WARMING BACK UP TUESDAY.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

HIGH LATITUDE ENERGY CURRENTLY OVER AK AND THE BERING SEA AREA WILL
DIVE SWD INTO OUR PACNW TROUGH AS UPSTREAM ENERGY...TYPHOON
REMNANTS...PUMPS UP THE UPSTREAM RIDGE OVER THE ERN PACIFIC. THE
END RESULT IS A DEEPENING COLD EARLY SEPTEMBER TROUGH OVER THE
PACNW AND INTERMOUNTAIN WEST THE SECOND HALF OF NEXT WEEK THAT
GRADUALLY TRANSLATES EWD AS THE FLOW DEAMPLIFYS TOWARDS THE END OF
THE PERIOD AND POSSIBLE SPLIT DEVELOPS OVER THE WEST EARLY NEXT
WEEK. THE MIDWEEK PERIOD WILL GENERALLY BE DRY AND QUITE WARM WITH
BREEZY TO LOCALLY WINDY PERIODS AND VERY LIMITED MAINLY MTN TSTMS
CHANCES AT BEST. BY FRIDAY...THE FIRST SIGNIFICANT SHORTWAVE OUT
AHEAD OF THE TROUGH IS ALREADY IMPACTING THE WEST AND NORTH AS A
COLD FRONT TRIES TO SAG SWD INTO THE NRN ZONES. THIS FRONTAL
BOUNDARY WILL BE A SIGNIFICANT PLAYER THROUGH THE WEEKEND WITH
CONSIDERABLY COOLER IF NOT COLDER WEATHER BEHIND IT AS THE MAIN
TROUGH OPENS UP AND PASSES ACROSS NRN WYO AND MONTANA OVER THE
LABOR DAY WEEKEND. A GOOD CHANCE OF SHOWERS AND TSTMS SHOULD OCCUR
IN AT LEAST THE NWRN SECTIONS WITH THIS FIRST SHORTWAVE AND THEN
MORE OF THE WEST AND NORTH AS THE DYNAMICS INTERACT/OVERRUN THE
FRONTAL BOUNDARY OVER THE WEEKEND. DETAILS ARE STILL UNCERTAIN BUT
THE GFS AND ECMWF ARE IN PRETTY GOOD AGREEMENT WITH THE BIG
PICTURE. THE SOURCE REGION OF THIS TROUGH IS QUITE COLD AND MODEL
GUIDANCE IS DROPPING H7 TEMPS DOWN TO AROUND ZERO TO EVEN BELOW
WITH THE FIRST SHORTWAVE FRIDAY NIGHT AND THEN WITH THE MAIN
TROUGH SATURDAY NIGHT SO MOUNTAINS WOULD GET A DECENT SHOT OF SOME
SNOW WITH EACH OF THESE. IT IS LABOR DAY WEEKEND AFTER ALL.

.AVIATION.../18Z ISSUANCE/

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST TODAY WITH SFC SW FLOW INCREASING ACROSS WEST AND CENTRAL
WYOMING AHEAD OF THE FRONT...ALONG WITH AREAS OF LLWS.  SFC SW WINDS
AT 20-30KTS WILL PREVAIL ACROSS THE AREA INTO THIS AFTERNOON. THE
MAIN AREA ISOLD-SCT -TSRA ARE DEVELOPING VCNTY AND SOUTH OF A
KEVW- KLND- KCPR LINE WITH HIGH BASED WINDY STORMS EXPECTED INTO
THE EARLY EVENING. THE COLD FRONT WILL BRING DRIER AIR AND GUSTY
WEST WIND INTO NW WYOMING MID TO LATE THIS AFTERNOON...PUSHING
ACROSS NORTH AND CENTRAL WYOMING THIS EVENING. CLEAR SKIES AND
DIMINISHING WIND WILL PREVAIL ACROSS THE AREA BEHIND THE FRONT
EARLY MONDAY MORNING.

.FIRE WEATHER...

...RED FLAG WARNING FOR PORTIONS OF CENTRAL AND NORTHERN WYOMING...

OVERALL IT WILL BE WINDIER THAN IT WAS SATURDAY BUT WITH SLIGHTLY
HIGHER RELATIVE HUMIDITY. AS THE COLD FRONT ASSOCIATED WITH THE
TROUGH DIGGING TO THE WEST ADVANCES...IT WILL LIKELY SETTLE INTO
WESTERN...NORTHERN AND SOUTHERN WYOMING FAIRLY EARLY IN THE
DAY...WHICH WOULD END THE FIRE WEATHER THREAT IN THOSE LOCATIONS
ALONG WITH INCREASING CLOUDS AS WELL AS A SLIGHT CHANCE FOR A
WETTING RAIN. STRONG SOUTHWEST FLOW BUT STILL LOW HUMIDITY ACROSS
FREMONT...JOHNSON AND NATRONA COUNTIES WILL OCCUR SO THESE AREAS
WILL CONTINUE TO BE UNDER THE RED FLAG WARNING FOR TODAY. IN
ADDITION...A SWATH OF MID LEVEL MOISTURE AND CONTINUED INSTABILITY
WILL KICK OF A FEW MIXED WET AND DRY THUNDERSTORMS...SOME OF WHICH
COULD CONTRIBUTE TO NEW FIRE STARTS WITH THE MOST ACTIVITY
EXPECTED ACROSS NORTHERN AND WESTERN WYOMING...WITH A SECONDARY
SWATH EXPECTED OVER NATRONA AND EASTERN FREMONT COUNTIES LATE
SUNDAY AFTERNOON...THE CHANCE OF A WETTING RAIN OUT OF THESE
STORMS IS NEXT TO ZERO. THE BEST CHANCE OF ANY DRY LIGHTNING
STARTS WILL LIKELY BE ON THE PERIPHERY OF ANY THUNDERSTORMS THAT
FORM ACROSS NORTHERN WYOMING EAST OF THE DIVIDE THROUGH MID DAY
WHERE THE BEST INSTABILITY WILL BE...THEN FROM EASTERN SWEETWATER
COUNTY TO CASPER AND THE REST OF NATRONA COUNTY LATER IN THE
AFTERNOON WHERE THE COMBINATION OF DRIEST BOUNDARY LEVEL MOISTURE
AND WIDEST TEMP/DEW POINT SPREADS WILL LIE.

A REPEAT OF THESE CONDITIONS WILL BE POSSIBLE MID WEEK.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ280-283-285-
289-300.

RED FLAG WARNING UNTIL 3 AM MDT MONDAY FOR WYZ275-276-281-282-
287.

&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...ALLEN
FIRE WEATHER...LIPSON





000
FXUS65 KRIW 301747 AAA
AFDRIW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RIVERTON WY
1147 AM MDT SUN AUG 30 2015

.PREV DISCUSSION... /ISSUED 250 AM MDT SUN AUG 30 2015/

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

A STRONG TROUGH OF LOW PRESSURE JUST OFF THE PACIFIC NORTHWEST COAST
HAS EJECTED A SHEARED UPPER LEVEL SHORTWAVE EASTWARD THAT APPEARS TO
BE LOCATED OVER NORTHERN IDAHO AND WESTERN MT. ACTIVE CONVECTION
CONTINUES OUT AHEAD OF THIS FEATURE ACROSS EASTERN IDAHO NEAR THE
WYOMING BORDER AND INTO YNP AT THE TIME OF THIS WRITING. IT WILL BE
AN EARLY SHOW FOR CONVECTION IN WESTERN WY TODAY WITH THESE STORMS
ABOUT TO SWEEP ACROSS FAR WEST WYOMING DURING THE REMAINDER OF THE
NIGHT. THEN THE MAIN TROUGH WILL APPROACH THE NORTHERN ROCKIES TODAY
FOR ANOTHER ROUND OF CONVECTION FIRING UP IN FAR WESTERN WY BY MID
DAY AHEAD OF THE MAIN TROUGH AND ASCT COLD FRONT. IN THE
MEANTIME...EAST OF THE DIVIDE...SOUTHWEST WINDS WILL INCREASE OVER
WHAT THEY WERE SATURDAY AS THEY DRAW IN SLIGHTLY HIGHER LOWER LEVEL
MOISTURE. INSTABILITY WILL BE IN PLACE OVER THE ENTIRE CWA BUT ONLY
SCANT MOISTURE TO WORK WITH TO PRODUCE THUNDERSTORMS EAST OF THE
DIVIDE...AT LEAST INITIALLY IN THE EARLY TO MID AFTERNOON. THERE
WILL BE A SEPARATE FINGER OF WEAK HIGH AND MID LEVEL MONSOON
MOISTURE THAT WILL STREAM IN ACROSS RKS AND CPR. HOWEVER THE BEST
INSTABILITY WILL BE IN PLACE ACROSS NORTHERN WY WHERE THE BEST CAPES
WILL BE. IT APPEARS THE BEST CHANCE OF ANY DRY LIGHTNING WILL OCCUR
ON THE PERIPHERY OF ANY HIGH BASED THUNDERSTORMS ALONG THE
AFOREMENTIONED WEAK MONSOON MOISTURE PLUME AS WELL AS ACROSS
NORTHERN WY EAST OF THE DIVIDE WHERE RELATIVELY HIGH BASED STORMS
WILL CORRELATE WITH THE BEST CAPES. DRY THUNDERSTORMS WILL MORPH
INTO MORE WET STORMS AS THE FRONT DRAWS NEAR. THE TROUGHPA WILL
SWEEP ACROSS THE CWA TONIGHT. THEN ON MONDAY...ANOTHER SURGE OF WEAK
MID/UPPER LEVEL MOISTURE WILL OVERLAP SOME LINGERING INSTABILITY
OVER EXTREME SOUTHERN WY WHERE SOME ISOLD T STORMS ARE EXPECTED.
THEN BY TUESDAY...ANOTHER CLOSED LOW WILL ESTABLISH ITSELF ALONG THE
SOUTHERN BC COAST. THIS LOW WILL EJECT A WEAK VORT LOBE EAST
NORTHEAST ACROSS THE NORTHERN ROCKIES THAT WILL RESULT IN ISOLD
CONVECTION...MAINLY OVER THE NW MTNS TUE AFTERNOON. TODAY WILL BE A
COUPLE OF DEGREES COOLER THAN SATURDAY AS CLOUDS AND SHOWER ACTIVITY
DECREASE THE SOLAR INSULATION. AFTERWARD...TEMPS WILL COOL A FEW
DEGREES MONDAY BEFORE WARMING BACK UP TUESDAY.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

HIGH LATITUDE ENERGY CURRENTLY OVER AK AND THE BERING SEA AREA WILL
DIVE SWD INTO OUR PACNW TROUGH AS UPSTREAM ENERGY...TYPHOON
REMNANTS...PUMPS UP THE UPSTREAM RIDGE OVER THE ERN PACIFIC. THE
END RESULT IS A DEEPENING COLD EARLY SEPTEMBER TROUGH OVER THE
PACNW AND INTERMOUNTAIN WEST THE SECOND HALF OF NEXT WEEK THAT
GRADUALLY TRANSLATES EWD AS THE FLOW DEAMPLIFYS TOWARDS THE END OF
THE PERIOD AND POSSIBLE SPLIT DEVELOPS OVER THE WEST EARLY NEXT
WEEK. THE MIDWEEK PERIOD WILL GENERALLY BE DRY AND QUITE WARM WITH
BREEZY TO LOCALLY WINDY PERIODS AND VERY LIMITED MAINLY MTN TSTMS
CHANCES AT BEST. BY FRIDAY...THE FIRST SIGNIFICANT SHORTWAVE OUT
AHEAD OF THE TROUGH IS ALREADY IMPACTING THE WEST AND NORTH AS A
COLD FRONT TRIES TO SAG SWD INTO THE NRN ZONES. THIS FRONTAL
BOUNDARY WILL BE A SIGNIFICANT PLAYER THROUGH THE WEEKEND WITH
CONSIDERABLY COOLER IF NOT COLDER WEATHER BEHIND IT AS THE MAIN
TROUGH OPENS UP AND PASSES ACROSS NRN WYO AND MONTANA OVER THE
LABOR DAY WEEKEND. A GOOD CHANCE OF SHOWERS AND TSTMS SHOULD OCCUR
IN AT LEAST THE NWRN SECTIONS WITH THIS FIRST SHORTWAVE AND THEN
MORE OF THE WEST AND NORTH AS THE DYNAMICS INTERACT/OVERRUN THE
FRONTAL BOUNDARY OVER THE WEEKEND. DETAILS ARE STILL UNCERTAIN BUT
THE GFS AND ECMWF ARE IN PRETTY GOOD AGREEMENT WITH THE BIG
PICTURE. THE SOURCE REGION OF THIS TROUGH IS QUITE COLD AND MODEL
GUIDANCE IS DROPPING H7 TEMPS DOWN TO AROUND ZERO TO EVEN BELOW
WITH THE FIRST SHORTWAVE FRIDAY NIGHT AND THEN WITH THE MAIN
TROUGH SATURDAY NIGHT SO MOUNTAINS WOULD GET A DECENT SHOT OF SOME
SNOW WITH EACH OF THESE. IT IS LABOR DAY WEEKEND AFTER ALL.

.AVIATION.../18Z ISSUANCE/

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST TODAY WITH SFC SW FLOW INCREASING ACROSS WEST AND CENTRAL
WYOMING AHEAD OF THE FRONT...ALONG WITH AREAS OF LLWS.  SFC SW WINDS
AT 20-30KTS WILL PREVAIL ACROSS THE AREA INTO THIS AFTERNOON. THE
MAIN AREA ISOLD-SCT -TSRA ARE DEVELOPING VCNTY AND SOUTH OF A
KEVW- KLND- KCPR LINE WITH HIGH BASED WINDY STORMS EXPECTED INTO
THE EARLY EVENING. THE COLD FRONT WILL BRING DRIER AIR AND GUSTY
WEST WIND INTO NW WYOMING MID TO LATE THIS AFTERNOON...PUSHING
ACROSS NORTH AND CENTRAL WYOMING THIS EVENING. CLEAR SKIES AND
DIMINISHING WIND WILL PREVAIL ACROSS THE AREA BEHIND THE FRONT
EARLY MONDAY MORNING.

.FIRE WEATHER...

...RED FLAG WARNING FOR PORTIONS OF CENTRAL AND NORTHERN WYOMING...

OVERALL IT WILL BE WINDIER THAN IT WAS SATURDAY BUT WITH SLIGHTLY
HIGHER RELATIVE HUMIDITY. AS THE COLD FRONT ASSOCIATED WITH THE
TROUGH DIGGING TO THE WEST ADVANCES...IT WILL LIKELY SETTLE INTO
WESTERN...NORTHERN AND SOUTHERN WYOMING FAIRLY EARLY IN THE
DAY...WHICH WOULD END THE FIRE WEATHER THREAT IN THOSE LOCATIONS
ALONG WITH INCREASING CLOUDS AS WELL AS A SLIGHT CHANCE FOR A
WETTING RAIN. STRONG SOUTHWEST FLOW BUT STILL LOW HUMIDITY ACROSS
FREMONT...JOHNSON AND NATRONA COUNTIES WILL OCCUR SO THESE AREAS
WILL CONTINUE TO BE UNDER THE RED FLAG WARNING FOR TODAY. IN
ADDITION...A SWATH OF MID LEVEL MOISTURE AND CONTINUED INSTABILITY
WILL KICK OF A FEW MIXED WET AND DRY THUNDERSTORMS...SOME OF WHICH
COULD CONTRIBUTE TO NEW FIRE STARTS WITH THE MOST ACTIVITY
EXPECTED ACROSS NORTHERN AND WESTERN WYOMING...WITH A SECONDARY
SWATH EXPECTED OVER NATRONA AND EASTERN FREMONT COUNTIES LATE
SUNDAY AFTERNOON...THE CHANCE OF A WETTING RAIN OUT OF THESE
STORMS IS NEXT TO ZERO. THE BEST CHANCE OF ANY DRY LIGHTNING
STARTS WILL LIKELY BE ON THE PERIPHERY OF ANY THUNDERSTORMS THAT
FORM ACROSS NORTHERN WYOMING EAST OF THE DIVIDE THROUGH MID DAY
WHERE THE BEST INSTABILITY WILL BE...THEN FROM EASTERN SWEETWATER
COUNTY TO CASPER AND THE REST OF NATRONA COUNTY LATER IN THE
AFTERNOON WHERE THE COMBINATION OF DRIEST BOUNDARY LEVEL MOISTURE
AND WIDEST TEMP/DEW POINT SPREADS WILL LIE.

A REPEAT OF THESE CONDITIONS WILL BE POSSIBLE MID WEEK.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ280-283-285-
289-300.

RED FLAG WARNING UNTIL 3 AM MDT MONDAY FOR WYZ275-276-281-282-
287.

&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...ALLEN
FIRE WEATHER...LIPSON




000
FXUS65 KRIW 300850
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
250 AM MDT SUN AUG 30 2015

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

A STRONG TROUGH OF LOW PRESSURE JUST OFF THE PACIFIC NORTHWEST COAST
HAS EJECTED A SHEARED UPPER LEVEL SHORTWAVE EASTWARD THAT APPEARS TO
BE LOCATED OVER NORTHERN IDAHO AND WESTERN MT. ACTIVE CONVECTION
CONTINUES OUT AHEAD OF THIS FEATURE ACROSS EASTERN IDAHO NEAR THE
WYOMING BORDER AND INTO YNP AT THE TIME OF THIS WRITING. IT WILL BE
AN EARLY SHOW FOR CONVECTION IN WESTERN WY TODAY WITH THESE STORMS
ABOUT TO SWEEP ACROSS FAR WEST WYOMING DURING THE REMAINDER OF THE
NIGHT. THEN THE MAIN TROUGH WILL APPROACH THE NORTHERN ROCKIES TODAY
FOR ANOTHER ROUND OF CONVECTION FIRING UP IN FAR WESTERN WY BY MID
DAY AHEAD OF THE MAIN TROUGH AND ASCT COLD FRONT. IN THE
MEANTIME...EAST OF THE DIVIDE...SOUTHWEST WINDS WILL INCREASE OVER
WHAT THEY WERE SATURDAY AS THEY DRAW IN SLIGHTLY HIGHER LOWER LEVEL
MOISTURE. INSTABILITY WILL BE IN PLACE OVER THE ENTIRE CWA BUT ONLY
SCANT MOISTURE TO WORK WITH TO PRODUCE THUNDERSTORMS EAST OF THE
DIVIDE...AT LEAST INITIALLY IN THE EARLY TO MID AFTERNOON. THERE
WILL BE A SEPARATE FINGER OF WEAK HIGH AND MID LEVEL MONSOON
MOISTURE THAT WILL STREAM IN ACROSS RKS AND CPR. HOWEVER THE BEST
INSTABILITY WILL BE IN PLACE ACROSS NORTHERN WY WHERE THE BEST CAPES
WILL BE. IT APPEARS THE BEST CHANCE OF ANY DRY LIGHTNING WILL OCCUR
ON THE PERIPHERY OF ANY HIGH BASED THUNDERSTORMS ALONG THE
AFOREMENTIONED WEAK MONSOON MOISTURE PLUME AS WELL AS ACROSS
NORTHERN WY EAST OF THE DIVIDE WHERE RELATIVELY HIGH BASED STORMS
WILL CORRELATE WITH THE BEST CAPES. DRY THUNDERSTORMS WILL MORPH
INTO MORE WET STORMS AS THE FRONT DRAWS NEAR. THE TROUGHPA WILL
SWEEP ACROSS THE CWA TONIGHT. THEN ON MONDAY...ANOTHER SURGE OF WEAK
MID/UPPER LEVEL MOISTURE WILL OVERLAP SOME LINGERING INSTABILITY
OVER EXTREME SOUTHERN WY WHERE SOME ISOLD T STORMS ARE EXPECTED.
THEN BY TUESDAY...ANOTHER CLOSED LOW WILL ESTABLISH ITSELF ALONG THE
SOUTHERN BC COAST. THIS LOW WILL EJECT A WEAK VORT LOBE EAST
NORTHEAST ACROSS THE NORTHERN ROCKIES THAT WILL RESULT IN ISOLD
CONVECTION...MAINLY OVER THE NW MTNS TUE AFTERNOON. TODAY WILL BE A
COUPLE OF DEGREES COOLER THAN SATURDAY AS CLOUDS AND SHOWER ACTIVITY
DECREASE THE SOLAR INSULATION. AFTERWARD...TEMPS WILL COOL A FEW
DEGREES MONDAY BEFORE WARMING BACK UP TUESDAY.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

HIGH LATITUDE ENERGY CURRENTLY OVER AK AND THE BERING SEA AREA WILL
DIVE SWD INTO OUR PACNW TROUGH AS UPSTREAM ENERGY...TYPHOON
REMNANTS...PUMPS UP THE UPSTREAM RIDGE OVER THE ERN PACIFIC. THE
END RESULT IS A DEEPENING COLD EARLY SEPTEMBER TROUGH OVER THE
PACNW AND INTERMOUNTAIN WEST THE SECOND HALF OF NEXT WEEK THAT
GRADUALLY TRANSLATES EWD AS THE FLOW DEAMPLIFYS TOWARDS THE END OF
THE PERIOD AND POSSIBLE SPLIT DEVELOPS OVER THE WEST EARLY NEXT
WEEK. THE MIDWEEK PERIOD WILL GENERALLY BE DRY AND QUITE WARM WITH
BREEZY TO LOCALLY WINDY PERIODS AND VERY LIMITED MAINLY MTN TSTMS
CHANCES AT BEST. BY FRIDAY...THE FIRST SIGNIFICANT SHORTWAVE OUT
AHEAD OF THE TROUGH IS ALREADY IMPACTING THE WEST AND NORTH AS A
COLD FRONT TRIES TO SAG SWD INTO THE NRN ZONES. THIS FRONTAL
BOUNDARY WILL BE A SIGNIFICANT PLAYER THROUGH THE WEEKEND WITH
CONSIDERABLY COOLER IF NOT COLDER WEATHER BEHIND IT AS THE MAIN
TROUGH OPENS UP AND PASSES ACROSS NRN WYO AND MONTANA OVER THE
LABOR DAY WEEKEND. A GOOD CHANCE OF SHOWERS AND TSTMS SHOULD OCCUR
IN AT LEAST THE NWRN SECTIONS WITH THIS FIRST SHORTWAVE AND THEN
MORE OF THE WEST AND NORTH AS THE DYNAMICS INTERACT/OVERRUN THE
FRONTAL BOUNDARY OVER THE WEEKEND. DETAILS ARE STILL UNCERTAIN BUT
THE GFS AND ECMWF ARE IN PRETTY GOOD AGREEMENT WITH THE BIG
PICTURE. THE SOURCE REGION OF THIS TROUGH IS QUITE COLD AND MODEL
GUIDANCE IS DROPPING H7 TEMPS DOWN TO AROUND ZERO TO EVEN BELOW
WITH THE FIRST SHORTWAVE FRIDAY NIGHT AND THEN WITH THE MAIN
TROUGH SATURDAY NIGHT SO MOUNTAINS WOULD GET A DECENT SHOT OF SOME
SNOW WITH EACH OF THESE. IT IS LABOR DAY WEEKEND AFTER ALL.

&&

.AVIATION.../12Z ISSUANCE/

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST TODAY WITH SFC SW FLOW INCREASING ACROSS WEST AND CENTRAL
WYOMING AHEAD OF THE FRONT...ALONG WITH AREAS OF LLWS.  SFC SW WINDS
AT 20-30KTS WILL PREVAIL ACROSS THE AREA LATE THIS MORNING INTO
THIS AFTERNOON. THE MAIN AREA ISOLD-SCT -TSRA WILL DEVELOP VCNTY
AND SOUTH OF A KEVW-KLND-KCPR LINE AROUND 18Z TODAY WITH THIS
AREA SLOWLY PROPAGATING SOUTH AND EAST THROUGH THE AFTERNOON AND
EARLY EVENING. THE COLD FRONT WILL BRING DRIER AIR AND GUSTY WEST
WIND INTO NW WYOMING MID TO LATE THIS AFTERNOON...PUSHING ACROSS
NORTH AND CENTRAL WYOMING THIS EVENING. CLEAR SKIES AND
DIMINISHING WIND WILL PREVAIL ACROSS THE AREA BEHIND THE FRONT
EARLY MONDAY MORNING.

&&

.FIRE WEATHER...

RED FLAG WARNING THROUGH SUNDAY FOR PORTIONS OF
CENTRAL WYOMING...

ON SUNDAY...OVERALL IT WILL BE WINDIER THAN IT WAS SATURDAY BUT WITH
SLIGHTLY HIGHER RELATIVE HUMIDITY. AS THE COLD FRONT ASSOCIATED WITH
THE TROUGH DIGGING TO THE WEST ADVANCES...IT WILL LIKELY SETTLE INTO
WESTERN...NORTHERN AND SOUTHERN WYOMING FAIRLY EARLY IN THE
DAY...WHICH WOULD END THE FIRE WEATHER THREAT IN THOSE LOCATIONS
ALONG WITH INCREASING CLOUDS AS WELL AS A SLIGHT CHANCE FOR A
WETTING RAIN. STRONG SOUTHWEST FLOW BUT STILL LOW HUMIDITY ACROSS
FREMONT...JOHNSON AND NATRONA COUNTIES WILL OCCUR SO THESE AREAS
WILL CONTINUE TO BE UNDER THE RED FLAG WARNING FOR TODAY. IN
ADDITION...A SWATH OF MID LEVEL MOISTURE AND CONTINUED INSTABILITY
WILL KICK OF A FEW MIXED WET AND DRY THUNDERSTORMS...SOME OF WHICH
COULD CONTRIBUTE TO NEW FIRE STARTS WITH THE MOST ACTIVITY EXPECTED
ACROSS NORTHERN AND WESTERN WYOMING...WITH A SECONDARY SWATH
EXPECTED OVER NATRONA AND EASTERN FREMONT COUNTIES LATE SUNDAY
AFTERNOON...THE CHANCE OF A WETTING RAIN OUT OF THESE STORMS IS NEXT
TO ZERO. THE BEST CHANCE OF ANY DRY LIGHTNING STARTS WILL LIKELY BE
ON THE PERIPHERY OF ANY THUNDERSTORMS THAT FORM ACROSS NORTHERN
WYOMING EAST OF THE DIVIDE THROUGH MID DAY WHERE THE BEST
INSTABILITY WILL BE...THEN FROM EASTERN SWEETWATER COUNTY TO CASPER
AND THE REST OF NATRONA COUNTY LATER IN THE AFTERNOON WHERE THE
COMBINATION OF DRIEST BOUNDARY LEVEL MOISTURE AND WIDEST TEMP/DEW
POINT SPREADS WILL LIE.

A REPEAT OF THESE CONDITIONS WILL BE POSSIBLE MID WEEK.



&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ280-281-283-
285-289-300.

&&

$$

SHORT TERM...LIPSON
LONG TERM...PS
AVIATION...AEM
FIRE WEATHER...LIPSON





000
FXUS65 KRIW 300850
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
250 AM MDT SUN AUG 30 2015

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

A STRONG TROUGH OF LOW PRESSURE JUST OFF THE PACIFIC NORTHWEST COAST
HAS EJECTED A SHEARED UPPER LEVEL SHORTWAVE EASTWARD THAT APPEARS TO
BE LOCATED OVER NORTHERN IDAHO AND WESTERN MT. ACTIVE CONVECTION
CONTINUES OUT AHEAD OF THIS FEATURE ACROSS EASTERN IDAHO NEAR THE
WYOMING BORDER AND INTO YNP AT THE TIME OF THIS WRITING. IT WILL BE
AN EARLY SHOW FOR CONVECTION IN WESTERN WY TODAY WITH THESE STORMS
ABOUT TO SWEEP ACROSS FAR WEST WYOMING DURING THE REMAINDER OF THE
NIGHT. THEN THE MAIN TROUGH WILL APPROACH THE NORTHERN ROCKIES TODAY
FOR ANOTHER ROUND OF CONVECTION FIRING UP IN FAR WESTERN WY BY MID
DAY AHEAD OF THE MAIN TROUGH AND ASCT COLD FRONT. IN THE
MEANTIME...EAST OF THE DIVIDE...SOUTHWEST WINDS WILL INCREASE OVER
WHAT THEY WERE SATURDAY AS THEY DRAW IN SLIGHTLY HIGHER LOWER LEVEL
MOISTURE. INSTABILITY WILL BE IN PLACE OVER THE ENTIRE CWA BUT ONLY
SCANT MOISTURE TO WORK WITH TO PRODUCE THUNDERSTORMS EAST OF THE
DIVIDE...AT LEAST INITIALLY IN THE EARLY TO MID AFTERNOON. THERE
WILL BE A SEPARATE FINGER OF WEAK HIGH AND MID LEVEL MONSOON
MOISTURE THAT WILL STREAM IN ACROSS RKS AND CPR. HOWEVER THE BEST
INSTABILITY WILL BE IN PLACE ACROSS NORTHERN WY WHERE THE BEST CAPES
WILL BE. IT APPEARS THE BEST CHANCE OF ANY DRY LIGHTNING WILL OCCUR
ON THE PERIPHERY OF ANY HIGH BASED THUNDERSTORMS ALONG THE
AFOREMENTIONED WEAK MONSOON MOISTURE PLUME AS WELL AS ACROSS
NORTHERN WY EAST OF THE DIVIDE WHERE RELATIVELY HIGH BASED STORMS
WILL CORRELATE WITH THE BEST CAPES. DRY THUNDERSTORMS WILL MORPH
INTO MORE WET STORMS AS THE FRONT DRAWS NEAR. THE TROUGHPA WILL
SWEEP ACROSS THE CWA TONIGHT. THEN ON MONDAY...ANOTHER SURGE OF WEAK
MID/UPPER LEVEL MOISTURE WILL OVERLAP SOME LINGERING INSTABILITY
OVER EXTREME SOUTHERN WY WHERE SOME ISOLD T STORMS ARE EXPECTED.
THEN BY TUESDAY...ANOTHER CLOSED LOW WILL ESTABLISH ITSELF ALONG THE
SOUTHERN BC COAST. THIS LOW WILL EJECT A WEAK VORT LOBE EAST
NORTHEAST ACROSS THE NORTHERN ROCKIES THAT WILL RESULT IN ISOLD
CONVECTION...MAINLY OVER THE NW MTNS TUE AFTERNOON. TODAY WILL BE A
COUPLE OF DEGREES COOLER THAN SATURDAY AS CLOUDS AND SHOWER ACTIVITY
DECREASE THE SOLAR INSULATION. AFTERWARD...TEMPS WILL COOL A FEW
DEGREES MONDAY BEFORE WARMING BACK UP TUESDAY.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

HIGH LATITUDE ENERGY CURRENTLY OVER AK AND THE BERING SEA AREA WILL
DIVE SWD INTO OUR PACNW TROUGH AS UPSTREAM ENERGY...TYPHOON
REMNANTS...PUMPS UP THE UPSTREAM RIDGE OVER THE ERN PACIFIC. THE
END RESULT IS A DEEPENING COLD EARLY SEPTEMBER TROUGH OVER THE
PACNW AND INTERMOUNTAIN WEST THE SECOND HALF OF NEXT WEEK THAT
GRADUALLY TRANSLATES EWD AS THE FLOW DEAMPLIFYS TOWARDS THE END OF
THE PERIOD AND POSSIBLE SPLIT DEVELOPS OVER THE WEST EARLY NEXT
WEEK. THE MIDWEEK PERIOD WILL GENERALLY BE DRY AND QUITE WARM WITH
BREEZY TO LOCALLY WINDY PERIODS AND VERY LIMITED MAINLY MTN TSTMS
CHANCES AT BEST. BY FRIDAY...THE FIRST SIGNIFICANT SHORTWAVE OUT
AHEAD OF THE TROUGH IS ALREADY IMPACTING THE WEST AND NORTH AS A
COLD FRONT TRIES TO SAG SWD INTO THE NRN ZONES. THIS FRONTAL
BOUNDARY WILL BE A SIGNIFICANT PLAYER THROUGH THE WEEKEND WITH
CONSIDERABLY COOLER IF NOT COLDER WEATHER BEHIND IT AS THE MAIN
TROUGH OPENS UP AND PASSES ACROSS NRN WYO AND MONTANA OVER THE
LABOR DAY WEEKEND. A GOOD CHANCE OF SHOWERS AND TSTMS SHOULD OCCUR
IN AT LEAST THE NWRN SECTIONS WITH THIS FIRST SHORTWAVE AND THEN
MORE OF THE WEST AND NORTH AS THE DYNAMICS INTERACT/OVERRUN THE
FRONTAL BOUNDARY OVER THE WEEKEND. DETAILS ARE STILL UNCERTAIN BUT
THE GFS AND ECMWF ARE IN PRETTY GOOD AGREEMENT WITH THE BIG
PICTURE. THE SOURCE REGION OF THIS TROUGH IS QUITE COLD AND MODEL
GUIDANCE IS DROPPING H7 TEMPS DOWN TO AROUND ZERO TO EVEN BELOW
WITH THE FIRST SHORTWAVE FRIDAY NIGHT AND THEN WITH THE MAIN
TROUGH SATURDAY NIGHT SO MOUNTAINS WOULD GET A DECENT SHOT OF SOME
SNOW WITH EACH OF THESE. IT IS LABOR DAY WEEKEND AFTER ALL.

&&

.AVIATION.../12Z ISSUANCE/

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST TODAY WITH SFC SW FLOW INCREASING ACROSS WEST AND CENTRAL
WYOMING AHEAD OF THE FRONT...ALONG WITH AREAS OF LLWS.  SFC SW WINDS
AT 20-30KTS WILL PREVAIL ACROSS THE AREA LATE THIS MORNING INTO
THIS AFTERNOON. THE MAIN AREA ISOLD-SCT -TSRA WILL DEVELOP VCNTY
AND SOUTH OF A KEVW-KLND-KCPR LINE AROUND 18Z TODAY WITH THIS
AREA SLOWLY PROPAGATING SOUTH AND EAST THROUGH THE AFTERNOON AND
EARLY EVENING. THE COLD FRONT WILL BRING DRIER AIR AND GUSTY WEST
WIND INTO NW WYOMING MID TO LATE THIS AFTERNOON...PUSHING ACROSS
NORTH AND CENTRAL WYOMING THIS EVENING. CLEAR SKIES AND
DIMINISHING WIND WILL PREVAIL ACROSS THE AREA BEHIND THE FRONT
EARLY MONDAY MORNING.

&&

.FIRE WEATHER...

RED FLAG WARNING THROUGH SUNDAY FOR PORTIONS OF
CENTRAL WYOMING...

ON SUNDAY...OVERALL IT WILL BE WINDIER THAN IT WAS SATURDAY BUT WITH
SLIGHTLY HIGHER RELATIVE HUMIDITY. AS THE COLD FRONT ASSOCIATED WITH
THE TROUGH DIGGING TO THE WEST ADVANCES...IT WILL LIKELY SETTLE INTO
WESTERN...NORTHERN AND SOUTHERN WYOMING FAIRLY EARLY IN THE
DAY...WHICH WOULD END THE FIRE WEATHER THREAT IN THOSE LOCATIONS
ALONG WITH INCREASING CLOUDS AS WELL AS A SLIGHT CHANCE FOR A
WETTING RAIN. STRONG SOUTHWEST FLOW BUT STILL LOW HUMIDITY ACROSS
FREMONT...JOHNSON AND NATRONA COUNTIES WILL OCCUR SO THESE AREAS
WILL CONTINUE TO BE UNDER THE RED FLAG WARNING FOR TODAY. IN
ADDITION...A SWATH OF MID LEVEL MOISTURE AND CONTINUED INSTABILITY
WILL KICK OF A FEW MIXED WET AND DRY THUNDERSTORMS...SOME OF WHICH
COULD CONTRIBUTE TO NEW FIRE STARTS WITH THE MOST ACTIVITY EXPECTED
ACROSS NORTHERN AND WESTERN WYOMING...WITH A SECONDARY SWATH
EXPECTED OVER NATRONA AND EASTERN FREMONT COUNTIES LATE SUNDAY
AFTERNOON...THE CHANCE OF A WETTING RAIN OUT OF THESE STORMS IS NEXT
TO ZERO. THE BEST CHANCE OF ANY DRY LIGHTNING STARTS WILL LIKELY BE
ON THE PERIPHERY OF ANY THUNDERSTORMS THAT FORM ACROSS NORTHERN
WYOMING EAST OF THE DIVIDE THROUGH MID DAY WHERE THE BEST
INSTABILITY WILL BE...THEN FROM EASTERN SWEETWATER COUNTY TO CASPER
AND THE REST OF NATRONA COUNTY LATER IN THE AFTERNOON WHERE THE
COMBINATION OF DRIEST BOUNDARY LEVEL MOISTURE AND WIDEST TEMP/DEW
POINT SPREADS WILL LIE.

A REPEAT OF THESE CONDITIONS WILL BE POSSIBLE MID WEEK.



&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ280-281-283-
285-289-300.

&&

$$

SHORT TERM...LIPSON
LONG TERM...PS
AVIATION...AEM
FIRE WEATHER...LIPSON




000
FXUS65 KRIW 300558
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1155 PM MDT SAT AUG 29 2015

.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT

HEIGHTS CONTINUE TO LOWER AS AN UPPER LEVEL RIDGE CONTINUES TO
SHIFT SOUTHEAST INTO THE CENTRAL PLAINS AND A DYNAMIC TROUGH
CONTINUES TO APPROACH FROM THE WEST. SOUTHWEST FLOW WILL CONTINUE
TO INCREASE INTO THE EVENING AND WILL REMAIN SPEEDY THROUGH
SUNDAY. AT THE SURFACE...A LEE TROUGH WILL DIG THROUGH THE DAY ON
SUNDAY FURTHER INCREASING THE GRADIENT IN PORTIONS OF CENTRAL AND
EASTERN WYOMING. AT THE SAME TIME...THE COLD FRONT ASSOCIATED
WITH THE PREVIOUSLY MENTIONED TROUGH WILL ADVANCE INTO WESTERN
WYOMING EARLY...DECREASING FIRE DANGER OVER WESTERN ZONES...THEN
IT WILL STALL FOR MUCH OF THE DAY ALLOWING DRY SOUTHWEST FLOW TO
RETURN TO AREAS EAST OF THE DIVIDE...SO THE RED FLAG WARNINGS WERE
EXTENDED IN JOHNSON FREMONT AND NATRONA COUNTIES INTO SUNDAY
EVENING. ALOFT...THE RIGHT ENTRANCE REGION OF A JET STREAK WILL
ENTER THE AREA INCREASING FORCING FOR ASCENT ACROSS MUCH OF THE
STATE...THE LIMITING FACTOR FOR THUNDERSTORMS OF COURSE WILL BE
MOISTURE. THERE ARE INDICATIONS OF SOME MID LEVEL MOISTURE NOSING
NORTH INTO EASTERN SWEETWATER...EASTERN FREMONT...NATRONA AND
SOUTHERN JOHNSON COUNTIES THAT COULD PROVIDE ENOUGH FUEL FOR
SOME VERY DRY AND HIGH BASED STORMS IN THE AFTERNOON. ACROSS
CENTRAL WYOMING...THERE WILL BE A LITTLE LESS MOISTURE AVAILABLE
FOR THUNDERSTORMS BUT THERE COULD BE A STRAY COME OFF OF THE
HIGHER TERRAIN...SO EXPANDED POPS TO ALL AREAS IN THE LATE
AFTERNOON. IN THE WESTERN MOUNTAINS...THERE WILL BE PLENTY OF
MOISTURE AND FORCING ALONG THE STALLED FRONT FOR SCATTERED
THUNDERSTORMS...THOUGH PRECIPITABLE WATER IS A BIT LIMITED SO
EXPECTING A MIX OF WET AND DRY STORMS THERE. RELATIVE HUMIDITY
WILL BE QUITE A BIT HIGHER SO THAT WILL LIMIT FIRE POTENTIAL. THE
COLD FRONT WILL FINALLY GAIN TRACTION AGAIN SUNDAY EVENING AND
WILL FINISH ITS PROGRESSION EASTWARD BY SUNRISE ON MONDAY.

.LONG TERM...MONDAY THROUGH SATURDAY

AGREEMENT AMONG MEDIUM-RANGE FORECAST MODELS IS VERY GOOD THROUGH
THE MIDDLE OF NEXT WEEK. SMALL DIFFERENCES FOR FRIDAY AND SATURDAY
HAVE BECOME BETTER ALIGNED WITH MOST RECENT MODELS RUNS WITH REGARDS
TO THE TRACK AND EVOLUTION OF A PACIFIC NORTHWEST TROUGH THAT WILL
MOVE THROUGH THE INTERMOUNTAIN WEST AND ROCKIES NEXT FRIDAY AND
SATURDAY.

DRIER WESTERLY FLOW WILL COVER THE FORECAST AREA MONDAY IN THE WAKE
OF THE DEPARTING SHORTWAVE TROUGH. SOME WEAK INSTABILITY AND
LINGERING MID-LEVEL MOISTURE NEAR THE COLORADO BORDER IN SWEETWATER
COUNTY DURING THE AFTERNOON AND EVENING. CONVECTION WOULD BE SHORT-
LIVED AND WEAK IF IT CAN MAKE MUCH PROGRESS OFF THE HIGHER TERRAIN
OF NORTHEAST UTAH. OTHERWISE...A DRY MONDAY WITH SEASONAL
TEMPERATURES AND LESS WIND THAT WHAT WILL BE SEEN THIS WEEKEND.
UPPER LEVEL FLOW BEGINS TO BACK TO THE SOUTHWEST ON TUESDAY IN
RESPONSE TO DEEPENING UPPER LEVEL LOW DIGGING INTO THE PACIFIC
NORTHWEST. THERE COULD BE ENOUGH MID-LEVEL MOISTURE TO INITIATE WEAK
MOUNTAIN CONVECTION TUESDAY THROUGH THURSDAY. THEREFORE...HAVE LEFT
LOW PRECIP CHANCES OVER MAINLY THE NORTHWEST MOUNTAINS. BELIEVE THAT
VERY LITTLE RAIN WOULD FALL WITH ANY CONVECTION THAT DEVELOPS AS DEW
POINTS WILL BE LESS THAN 40F AND PRECIPITABLE WATER VALUES LESS THAN
IMPRESSIVE. 700MB TEMPERATURES TUESDAY AND WEDNESDAY WILL AGAIN
APPROACH +15C WHICH WILL HAVE US STARING AT 90F SURFACE
TEMPERATURES. WOULD NOT BE SURPRISED TO SEE MAXIMUM TEMPERATURES
EXCEED 90F...ESPECIALLY ON WEDNESDAY AND MAYBE THURSDAY...DUE TO
INCREASING SOUTHWEST WIND AT THE SURFACE. THE MIDWEEK PATTERN...
BETWEEN TUESDAY AND THURSDAY...IS SHAPING UP TO BE ONE THAT COULD
HAVE CRITICAL FIRE WEATHER IMPLICATIONS. UNSEASONABLY WARM
TEMPERATURES...RELATIVE HUMIDITY IN THE TEENS...AND INCREASING
SOUTHWEST WIND AHEAD OF THE PACIFIC NORTHWEST TROUGH ALL LOOK TO BE
PRESENT ON THESE DAYS. IN FACT...DRIER SURFACE AIR WILL BE ADVECTED
INTO THE STATE FROM THE GREAT BASIN WITH AFTERNOON DEW POINTS
POSSIBLE FALLING TO LESS THAN 30F. THOSE WITH FIRE WEATHER INTERESTS
SHOULD CONTINUE TO MONITOR THE FORECAST FOR POSSIBLE HIGHLIGHTS.
APPROACH OF THE TROUGH WILL LEAD TO A BETTER OPPORTUNITY FOR
CONVECTION ACROSS THE NORTHWEST FRIDAY AFTERNOON AND EVENING. STILL
SOME DISCREPANCIES REGARDING HOW FAR SOUTH THE PACIFIC NORTHWEST
TROUGH WILL DIG AND HOW FAST IT WILL MOVE ACROSS THE FORECAST AREA.
BOTH ISSUES WILL HAVE AN IMPACT ON TEMPERATURES AND SENSIBLE WEATHER
HEADING INTO NEXT WEEKEND. COOLER AIR WILL SLIP SOUTH BEHIND A COLD
FRONT AND COOL THINGS DOWN FOR SATURDAY. FRIDAY TEMPERATURES WILL BE
MORE TRICKY AND DEPENDENT UPON THE TIMING OF THE COLD FRONTAL
PASSAGE. FORECAST FRIDAY TEMPERATURES EAST OF THE CONTINENTAL DIVIDE
COULD END UP BEING TOO COOL...BUT AT THIS RANGE HAVE NOT STRAYED
FROM KEEPING CONSISTENT REGIONAL FORECAST.

&&

.AVIATION.../06Z ISSUANCE/

A LINE OF THUNDERSTORMS WILL PUSH TO NEAR A VCNTY KJAC-KCOD LINE
THROUGH AROUND 07Z BEFORE DISSIPATING.  ERRATIC WIND GUSTS 30-40KTS
WILL BE THE MAIN HAZARD WITH THESE STORMS.  OTHERWISE ISOLD -SHRA/-
TSRA WILL CONTINUE VCNTY AND WEST OF THE DIVIDE OVERNIGHT.

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST ON SUNDAY WITH SFC SW FLOW INCREASING ACROSS WEST AND CENTRAL
WYOMING AHEAD OF THE FRONT...ALONG WITH AREAS OF LLWS.  SFC SW WINDS
AT 20-30KTS WILL PREVAIL ACROSS THE AREA LATE SUNDAY MORNING INTO
SUNDAY AFTERNOON.  THE MAIN AREA ISOLD-SCT -TSRA WILL DEVELOP VCNTY
AND SOUTH OF A KEVW-KLND-KCPR LINE AROUND 18Z SUNDAY WITH THIS AREA
SLOWLY PROPAGATING SOUTH AND EAST THROUGH THE AFTERNOON AND EARLY
EVENING.  THE COLD FRONT WILL BRING DRIER AIR AND GUSTY WEST WIND
INTO NW WYOMING MID TO LATE SUNDAY AFTERNOON...PUSHING ACROSS NORTH
AND CENTRAL WYOMING SUNDAY EVENING.  CLEAR SKIES AND DIMINISHING
WIND WILL PREVAIL ACROSS THE AREA BEHIND THE FRONT EARLY MONDAY
MORNING.

FIRE WEATHER...

.RED FLAG WARNING THROUGH SUNDAY FOR PORTIONS OF CENTRAL
WYOMING...

ON SUNDAY...OVERALL IT WILL BE WINDIER THAN IT WAS TODAY BUT WITH
SLIGHTLY HIGHER RELATIVE HUMIDITY. THE COLD FRONT ASSOCIATED WITH
THE TROUGH DIGGING TO THE WEST ADVANCES...IT WILL LIKELY SETTLE
INTO WESTERN...NORTHERN AND SOUTHERN WYOMING FAIRLY EARLY IN THE
DAY...WHICH WOULD END THE FIRE WEATHER THREAT IN THOSE LOCATIONS
ALONG WITH INCREASING CLOUDS AS WELL AS A SLIGHT CHANCE FOR A
WETTING RAIN. LATEST GUIDANCE CONTINUES TO SUGGEST THAT THE FRONT
WILL RETREAT BACK INTO MONTANA DURING THE LATE MORNING...CLEARING
THE WAY FOR MORE STRONG SOUTHWEST FLOW AND LOW HUMIDITY ACROSS
FREMONT...JOHNSON AND NATRONA COUNTIES. SO...THESE AREAS WILL
CONTINUE TO BE UNDER THE RED FLAG WARNING FOR SUNDAY. IN
ADDITION...A SWATH OF MID LEVEL MOISTURE AND CONTINUED INSTABILITY
WILL KICK OF A FEW MIXED WET AND DRY THUNDERSTORMS...SOME OF WHICH
COULD CONTRIBUTE TO NEW FIRE STARTS WITH THE MOST ACTIVITY
EXPECTED ACROSS NORTHERN AND WESTERN WYOMING...WITH A SECONDARY
SWATH EXPECTED OVER NATRONA AND EASTERN FREMONT COUNTIES LATE
SUNDAY AFTERNOON...THE CHANCE OF A WETTING RAIN OUT OF THESE
STORMS IS NEXT TO ZERO. THE BEST CHANCE OF ANY DRY LIGHTNING
STARTS WILL LIKELY BE ON THE PERIPHERY OF ANY THUNDERSTORMS OVER
NATRONA AND JOHNSON COUNTY WHERE THE COMBINATION OF DRIEST
BOUNDARY LEVEL MOISTURE...WIDEST TEMP/DEW POINT SPREADS AND
INSTABILITY WILL LIE ON SUNDAY AFTERNOON.

A REPEAT OF THESE CONDITIONS WILL BE POSSIBLE MID WEEK.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ275>277-279-
282-287-414>416.

RED FLAG WARNING UNTIL 9 PM MDT SUNDAY FOR WYZ280-281-283-285-
289-300.

&&

$$

SHORT TERM...ALLEN
LONG TERM...CNJ
AVIATION...AEM
FIRE WEATHER...ALLEN




000
FXUS65 KRIW 300558
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1155 PM MDT SAT AUG 29 2015

.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT

HEIGHTS CONTINUE TO LOWER AS AN UPPER LEVEL RIDGE CONTINUES TO
SHIFT SOUTHEAST INTO THE CENTRAL PLAINS AND A DYNAMIC TROUGH
CONTINUES TO APPROACH FROM THE WEST. SOUTHWEST FLOW WILL CONTINUE
TO INCREASE INTO THE EVENING AND WILL REMAIN SPEEDY THROUGH
SUNDAY. AT THE SURFACE...A LEE TROUGH WILL DIG THROUGH THE DAY ON
SUNDAY FURTHER INCREASING THE GRADIENT IN PORTIONS OF CENTRAL AND
EASTERN WYOMING. AT THE SAME TIME...THE COLD FRONT ASSOCIATED
WITH THE PREVIOUSLY MENTIONED TROUGH WILL ADVANCE INTO WESTERN
WYOMING EARLY...DECREASING FIRE DANGER OVER WESTERN ZONES...THEN
IT WILL STALL FOR MUCH OF THE DAY ALLOWING DRY SOUTHWEST FLOW TO
RETURN TO AREAS EAST OF THE DIVIDE...SO THE RED FLAG WARNINGS WERE
EXTENDED IN JOHNSON FREMONT AND NATRONA COUNTIES INTO SUNDAY
EVENING. ALOFT...THE RIGHT ENTRANCE REGION OF A JET STREAK WILL
ENTER THE AREA INCREASING FORCING FOR ASCENT ACROSS MUCH OF THE
STATE...THE LIMITING FACTOR FOR THUNDERSTORMS OF COURSE WILL BE
MOISTURE. THERE ARE INDICATIONS OF SOME MID LEVEL MOISTURE NOSING
NORTH INTO EASTERN SWEETWATER...EASTERN FREMONT...NATRONA AND
SOUTHERN JOHNSON COUNTIES THAT COULD PROVIDE ENOUGH FUEL FOR
SOME VERY DRY AND HIGH BASED STORMS IN THE AFTERNOON. ACROSS
CENTRAL WYOMING...THERE WILL BE A LITTLE LESS MOISTURE AVAILABLE
FOR THUNDERSTORMS BUT THERE COULD BE A STRAY COME OFF OF THE
HIGHER TERRAIN...SO EXPANDED POPS TO ALL AREAS IN THE LATE
AFTERNOON. IN THE WESTERN MOUNTAINS...THERE WILL BE PLENTY OF
MOISTURE AND FORCING ALONG THE STALLED FRONT FOR SCATTERED
THUNDERSTORMS...THOUGH PRECIPITABLE WATER IS A BIT LIMITED SO
EXPECTING A MIX OF WET AND DRY STORMS THERE. RELATIVE HUMIDITY
WILL BE QUITE A BIT HIGHER SO THAT WILL LIMIT FIRE POTENTIAL. THE
COLD FRONT WILL FINALLY GAIN TRACTION AGAIN SUNDAY EVENING AND
WILL FINISH ITS PROGRESSION EASTWARD BY SUNRISE ON MONDAY.

.LONG TERM...MONDAY THROUGH SATURDAY

AGREEMENT AMONG MEDIUM-RANGE FORECAST MODELS IS VERY GOOD THROUGH
THE MIDDLE OF NEXT WEEK. SMALL DIFFERENCES FOR FRIDAY AND SATURDAY
HAVE BECOME BETTER ALIGNED WITH MOST RECENT MODELS RUNS WITH REGARDS
TO THE TRACK AND EVOLUTION OF A PACIFIC NORTHWEST TROUGH THAT WILL
MOVE THROUGH THE INTERMOUNTAIN WEST AND ROCKIES NEXT FRIDAY AND
SATURDAY.

DRIER WESTERLY FLOW WILL COVER THE FORECAST AREA MONDAY IN THE WAKE
OF THE DEPARTING SHORTWAVE TROUGH. SOME WEAK INSTABILITY AND
LINGERING MID-LEVEL MOISTURE NEAR THE COLORADO BORDER IN SWEETWATER
COUNTY DURING THE AFTERNOON AND EVENING. CONVECTION WOULD BE SHORT-
LIVED AND WEAK IF IT CAN MAKE MUCH PROGRESS OFF THE HIGHER TERRAIN
OF NORTHEAST UTAH. OTHERWISE...A DRY MONDAY WITH SEASONAL
TEMPERATURES AND LESS WIND THAT WHAT WILL BE SEEN THIS WEEKEND.
UPPER LEVEL FLOW BEGINS TO BACK TO THE SOUTHWEST ON TUESDAY IN
RESPONSE TO DEEPENING UPPER LEVEL LOW DIGGING INTO THE PACIFIC
NORTHWEST. THERE COULD BE ENOUGH MID-LEVEL MOISTURE TO INITIATE WEAK
MOUNTAIN CONVECTION TUESDAY THROUGH THURSDAY. THEREFORE...HAVE LEFT
LOW PRECIP CHANCES OVER MAINLY THE NORTHWEST MOUNTAINS. BELIEVE THAT
VERY LITTLE RAIN WOULD FALL WITH ANY CONVECTION THAT DEVELOPS AS DEW
POINTS WILL BE LESS THAN 40F AND PRECIPITABLE WATER VALUES LESS THAN
IMPRESSIVE. 700MB TEMPERATURES TUESDAY AND WEDNESDAY WILL AGAIN
APPROACH +15C WHICH WILL HAVE US STARING AT 90F SURFACE
TEMPERATURES. WOULD NOT BE SURPRISED TO SEE MAXIMUM TEMPERATURES
EXCEED 90F...ESPECIALLY ON WEDNESDAY AND MAYBE THURSDAY...DUE TO
INCREASING SOUTHWEST WIND AT THE SURFACE. THE MIDWEEK PATTERN...
BETWEEN TUESDAY AND THURSDAY...IS SHAPING UP TO BE ONE THAT COULD
HAVE CRITICAL FIRE WEATHER IMPLICATIONS. UNSEASONABLY WARM
TEMPERATURES...RELATIVE HUMIDITY IN THE TEENS...AND INCREASING
SOUTHWEST WIND AHEAD OF THE PACIFIC NORTHWEST TROUGH ALL LOOK TO BE
PRESENT ON THESE DAYS. IN FACT...DRIER SURFACE AIR WILL BE ADVECTED
INTO THE STATE FROM THE GREAT BASIN WITH AFTERNOON DEW POINTS
POSSIBLE FALLING TO LESS THAN 30F. THOSE WITH FIRE WEATHER INTERESTS
SHOULD CONTINUE TO MONITOR THE FORECAST FOR POSSIBLE HIGHLIGHTS.
APPROACH OF THE TROUGH WILL LEAD TO A BETTER OPPORTUNITY FOR
CONVECTION ACROSS THE NORTHWEST FRIDAY AFTERNOON AND EVENING. STILL
SOME DISCREPANCIES REGARDING HOW FAR SOUTH THE PACIFIC NORTHWEST
TROUGH WILL DIG AND HOW FAST IT WILL MOVE ACROSS THE FORECAST AREA.
BOTH ISSUES WILL HAVE AN IMPACT ON TEMPERATURES AND SENSIBLE WEATHER
HEADING INTO NEXT WEEKEND. COOLER AIR WILL SLIP SOUTH BEHIND A COLD
FRONT AND COOL THINGS DOWN FOR SATURDAY. FRIDAY TEMPERATURES WILL BE
MORE TRICKY AND DEPENDENT UPON THE TIMING OF THE COLD FRONTAL
PASSAGE. FORECAST FRIDAY TEMPERATURES EAST OF THE CONTINENTAL DIVIDE
COULD END UP BEING TOO COOL...BUT AT THIS RANGE HAVE NOT STRAYED
FROM KEEPING CONSISTENT REGIONAL FORECAST.

&&

.AVIATION.../06Z ISSUANCE/

A LINE OF THUNDERSTORMS WILL PUSH TO NEAR A VCNTY KJAC-KCOD LINE
THROUGH AROUND 07Z BEFORE DISSIPATING.  ERRATIC WIND GUSTS 30-40KTS
WILL BE THE MAIN HAZARD WITH THESE STORMS.  OTHERWISE ISOLD -SHRA/-
TSRA WILL CONTINUE VCNTY AND WEST OF THE DIVIDE OVERNIGHT.

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST ON SUNDAY WITH SFC SW FLOW INCREASING ACROSS WEST AND CENTRAL
WYOMING AHEAD OF THE FRONT...ALONG WITH AREAS OF LLWS.  SFC SW WINDS
AT 20-30KTS WILL PREVAIL ACROSS THE AREA LATE SUNDAY MORNING INTO
SUNDAY AFTERNOON.  THE MAIN AREA ISOLD-SCT -TSRA WILL DEVELOP VCNTY
AND SOUTH OF A KEVW-KLND-KCPR LINE AROUND 18Z SUNDAY WITH THIS AREA
SLOWLY PROPAGATING SOUTH AND EAST THROUGH THE AFTERNOON AND EARLY
EVENING.  THE COLD FRONT WILL BRING DRIER AIR AND GUSTY WEST WIND
INTO NW WYOMING MID TO LATE SUNDAY AFTERNOON...PUSHING ACROSS NORTH
AND CENTRAL WYOMING SUNDAY EVENING.  CLEAR SKIES AND DIMINISHING
WIND WILL PREVAIL ACROSS THE AREA BEHIND THE FRONT EARLY MONDAY
MORNING.

FIRE WEATHER...

.RED FLAG WARNING THROUGH SUNDAY FOR PORTIONS OF CENTRAL
WYOMING...

ON SUNDAY...OVERALL IT WILL BE WINDIER THAN IT WAS TODAY BUT WITH
SLIGHTLY HIGHER RELATIVE HUMIDITY. THE COLD FRONT ASSOCIATED WITH
THE TROUGH DIGGING TO THE WEST ADVANCES...IT WILL LIKELY SETTLE
INTO WESTERN...NORTHERN AND SOUTHERN WYOMING FAIRLY EARLY IN THE
DAY...WHICH WOULD END THE FIRE WEATHER THREAT IN THOSE LOCATIONS
ALONG WITH INCREASING CLOUDS AS WELL AS A SLIGHT CHANCE FOR A
WETTING RAIN. LATEST GUIDANCE CONTINUES TO SUGGEST THAT THE FRONT
WILL RETREAT BACK INTO MONTANA DURING THE LATE MORNING...CLEARING
THE WAY FOR MORE STRONG SOUTHWEST FLOW AND LOW HUMIDITY ACROSS
FREMONT...JOHNSON AND NATRONA COUNTIES. SO...THESE AREAS WILL
CONTINUE TO BE UNDER THE RED FLAG WARNING FOR SUNDAY. IN
ADDITION...A SWATH OF MID LEVEL MOISTURE AND CONTINUED INSTABILITY
WILL KICK OF A FEW MIXED WET AND DRY THUNDERSTORMS...SOME OF WHICH
COULD CONTRIBUTE TO NEW FIRE STARTS WITH THE MOST ACTIVITY
EXPECTED ACROSS NORTHERN AND WESTERN WYOMING...WITH A SECONDARY
SWATH EXPECTED OVER NATRONA AND EASTERN FREMONT COUNTIES LATE
SUNDAY AFTERNOON...THE CHANCE OF A WETTING RAIN OUT OF THESE
STORMS IS NEXT TO ZERO. THE BEST CHANCE OF ANY DRY LIGHTNING
STARTS WILL LIKELY BE ON THE PERIPHERY OF ANY THUNDERSTORMS OVER
NATRONA AND JOHNSON COUNTY WHERE THE COMBINATION OF DRIEST
BOUNDARY LEVEL MOISTURE...WIDEST TEMP/DEW POINT SPREADS AND
INSTABILITY WILL LIE ON SUNDAY AFTERNOON.

A REPEAT OF THESE CONDITIONS WILL BE POSSIBLE MID WEEK.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ275>277-279-
282-287-414>416.

RED FLAG WARNING UNTIL 9 PM MDT SUNDAY FOR WYZ280-281-283-285-
289-300.

&&

$$

SHORT TERM...ALLEN
LONG TERM...CNJ
AVIATION...AEM
FIRE WEATHER...ALLEN





000
FXUS65 KRIW 300558
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1155 PM MDT SAT AUG 29 2015

.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT

HEIGHTS CONTINUE TO LOWER AS AN UPPER LEVEL RIDGE CONTINUES TO
SHIFT SOUTHEAST INTO THE CENTRAL PLAINS AND A DYNAMIC TROUGH
CONTINUES TO APPROACH FROM THE WEST. SOUTHWEST FLOW WILL CONTINUE
TO INCREASE INTO THE EVENING AND WILL REMAIN SPEEDY THROUGH
SUNDAY. AT THE SURFACE...A LEE TROUGH WILL DIG THROUGH THE DAY ON
SUNDAY FURTHER INCREASING THE GRADIENT IN PORTIONS OF CENTRAL AND
EASTERN WYOMING. AT THE SAME TIME...THE COLD FRONT ASSOCIATED
WITH THE PREVIOUSLY MENTIONED TROUGH WILL ADVANCE INTO WESTERN
WYOMING EARLY...DECREASING FIRE DANGER OVER WESTERN ZONES...THEN
IT WILL STALL FOR MUCH OF THE DAY ALLOWING DRY SOUTHWEST FLOW TO
RETURN TO AREAS EAST OF THE DIVIDE...SO THE RED FLAG WARNINGS WERE
EXTENDED IN JOHNSON FREMONT AND NATRONA COUNTIES INTO SUNDAY
EVENING. ALOFT...THE RIGHT ENTRANCE REGION OF A JET STREAK WILL
ENTER THE AREA INCREASING FORCING FOR ASCENT ACROSS MUCH OF THE
STATE...THE LIMITING FACTOR FOR THUNDERSTORMS OF COURSE WILL BE
MOISTURE. THERE ARE INDICATIONS OF SOME MID LEVEL MOISTURE NOSING
NORTH INTO EASTERN SWEETWATER...EASTERN FREMONT...NATRONA AND
SOUTHERN JOHNSON COUNTIES THAT COULD PROVIDE ENOUGH FUEL FOR
SOME VERY DRY AND HIGH BASED STORMS IN THE AFTERNOON. ACROSS
CENTRAL WYOMING...THERE WILL BE A LITTLE LESS MOISTURE AVAILABLE
FOR THUNDERSTORMS BUT THERE COULD BE A STRAY COME OFF OF THE
HIGHER TERRAIN...SO EXPANDED POPS TO ALL AREAS IN THE LATE
AFTERNOON. IN THE WESTERN MOUNTAINS...THERE WILL BE PLENTY OF
MOISTURE AND FORCING ALONG THE STALLED FRONT FOR SCATTERED
THUNDERSTORMS...THOUGH PRECIPITABLE WATER IS A BIT LIMITED SO
EXPECTING A MIX OF WET AND DRY STORMS THERE. RELATIVE HUMIDITY
WILL BE QUITE A BIT HIGHER SO THAT WILL LIMIT FIRE POTENTIAL. THE
COLD FRONT WILL FINALLY GAIN TRACTION AGAIN SUNDAY EVENING AND
WILL FINISH ITS PROGRESSION EASTWARD BY SUNRISE ON MONDAY.

.LONG TERM...MONDAY THROUGH SATURDAY

AGREEMENT AMONG MEDIUM-RANGE FORECAST MODELS IS VERY GOOD THROUGH
THE MIDDLE OF NEXT WEEK. SMALL DIFFERENCES FOR FRIDAY AND SATURDAY
HAVE BECOME BETTER ALIGNED WITH MOST RECENT MODELS RUNS WITH REGARDS
TO THE TRACK AND EVOLUTION OF A PACIFIC NORTHWEST TROUGH THAT WILL
MOVE THROUGH THE INTERMOUNTAIN WEST AND ROCKIES NEXT FRIDAY AND
SATURDAY.

DRIER WESTERLY FLOW WILL COVER THE FORECAST AREA MONDAY IN THE WAKE
OF THE DEPARTING SHORTWAVE TROUGH. SOME WEAK INSTABILITY AND
LINGERING MID-LEVEL MOISTURE NEAR THE COLORADO BORDER IN SWEETWATER
COUNTY DURING THE AFTERNOON AND EVENING. CONVECTION WOULD BE SHORT-
LIVED AND WEAK IF IT CAN MAKE MUCH PROGRESS OFF THE HIGHER TERRAIN
OF NORTHEAST UTAH. OTHERWISE...A DRY MONDAY WITH SEASONAL
TEMPERATURES AND LESS WIND THAT WHAT WILL BE SEEN THIS WEEKEND.
UPPER LEVEL FLOW BEGINS TO BACK TO THE SOUTHWEST ON TUESDAY IN
RESPONSE TO DEEPENING UPPER LEVEL LOW DIGGING INTO THE PACIFIC
NORTHWEST. THERE COULD BE ENOUGH MID-LEVEL MOISTURE TO INITIATE WEAK
MOUNTAIN CONVECTION TUESDAY THROUGH THURSDAY. THEREFORE...HAVE LEFT
LOW PRECIP CHANCES OVER MAINLY THE NORTHWEST MOUNTAINS. BELIEVE THAT
VERY LITTLE RAIN WOULD FALL WITH ANY CONVECTION THAT DEVELOPS AS DEW
POINTS WILL BE LESS THAN 40F AND PRECIPITABLE WATER VALUES LESS THAN
IMPRESSIVE. 700MB TEMPERATURES TUESDAY AND WEDNESDAY WILL AGAIN
APPROACH +15C WHICH WILL HAVE US STARING AT 90F SURFACE
TEMPERATURES. WOULD NOT BE SURPRISED TO SEE MAXIMUM TEMPERATURES
EXCEED 90F...ESPECIALLY ON WEDNESDAY AND MAYBE THURSDAY...DUE TO
INCREASING SOUTHWEST WIND AT THE SURFACE. THE MIDWEEK PATTERN...
BETWEEN TUESDAY AND THURSDAY...IS SHAPING UP TO BE ONE THAT COULD
HAVE CRITICAL FIRE WEATHER IMPLICATIONS. UNSEASONABLY WARM
TEMPERATURES...RELATIVE HUMIDITY IN THE TEENS...AND INCREASING
SOUTHWEST WIND AHEAD OF THE PACIFIC NORTHWEST TROUGH ALL LOOK TO BE
PRESENT ON THESE DAYS. IN FACT...DRIER SURFACE AIR WILL BE ADVECTED
INTO THE STATE FROM THE GREAT BASIN WITH AFTERNOON DEW POINTS
POSSIBLE FALLING TO LESS THAN 30F. THOSE WITH FIRE WEATHER INTERESTS
SHOULD CONTINUE TO MONITOR THE FORECAST FOR POSSIBLE HIGHLIGHTS.
APPROACH OF THE TROUGH WILL LEAD TO A BETTER OPPORTUNITY FOR
CONVECTION ACROSS THE NORTHWEST FRIDAY AFTERNOON AND EVENING. STILL
SOME DISCREPANCIES REGARDING HOW FAR SOUTH THE PACIFIC NORTHWEST
TROUGH WILL DIG AND HOW FAST IT WILL MOVE ACROSS THE FORECAST AREA.
BOTH ISSUES WILL HAVE AN IMPACT ON TEMPERATURES AND SENSIBLE WEATHER
HEADING INTO NEXT WEEKEND. COOLER AIR WILL SLIP SOUTH BEHIND A COLD
FRONT AND COOL THINGS DOWN FOR SATURDAY. FRIDAY TEMPERATURES WILL BE
MORE TRICKY AND DEPENDENT UPON THE TIMING OF THE COLD FRONTAL
PASSAGE. FORECAST FRIDAY TEMPERATURES EAST OF THE CONTINENTAL DIVIDE
COULD END UP BEING TOO COOL...BUT AT THIS RANGE HAVE NOT STRAYED
FROM KEEPING CONSISTENT REGIONAL FORECAST.

&&

.AVIATION.../06Z ISSUANCE/

A LINE OF THUNDERSTORMS WILL PUSH TO NEAR A VCNTY KJAC-KCOD LINE
THROUGH AROUND 07Z BEFORE DISSIPATING.  ERRATIC WIND GUSTS 30-40KTS
WILL BE THE MAIN HAZARD WITH THESE STORMS.  OTHERWISE ISOLD -SHRA/-
TSRA WILL CONTINUE VCNTY AND WEST OF THE DIVIDE OVERNIGHT.

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST ON SUNDAY WITH SFC SW FLOW INCREASING ACROSS WEST AND CENTRAL
WYOMING AHEAD OF THE FRONT...ALONG WITH AREAS OF LLWS.  SFC SW WINDS
AT 20-30KTS WILL PREVAIL ACROSS THE AREA LATE SUNDAY MORNING INTO
SUNDAY AFTERNOON.  THE MAIN AREA ISOLD-SCT -TSRA WILL DEVELOP VCNTY
AND SOUTH OF A KEVW-KLND-KCPR LINE AROUND 18Z SUNDAY WITH THIS AREA
SLOWLY PROPAGATING SOUTH AND EAST THROUGH THE AFTERNOON AND EARLY
EVENING.  THE COLD FRONT WILL BRING DRIER AIR AND GUSTY WEST WIND
INTO NW WYOMING MID TO LATE SUNDAY AFTERNOON...PUSHING ACROSS NORTH
AND CENTRAL WYOMING SUNDAY EVENING.  CLEAR SKIES AND DIMINISHING
WIND WILL PREVAIL ACROSS THE AREA BEHIND THE FRONT EARLY MONDAY
MORNING.

FIRE WEATHER...

.RED FLAG WARNING THROUGH SUNDAY FOR PORTIONS OF CENTRAL
WYOMING...

ON SUNDAY...OVERALL IT WILL BE WINDIER THAN IT WAS TODAY BUT WITH
SLIGHTLY HIGHER RELATIVE HUMIDITY. THE COLD FRONT ASSOCIATED WITH
THE TROUGH DIGGING TO THE WEST ADVANCES...IT WILL LIKELY SETTLE
INTO WESTERN...NORTHERN AND SOUTHERN WYOMING FAIRLY EARLY IN THE
DAY...WHICH WOULD END THE FIRE WEATHER THREAT IN THOSE LOCATIONS
ALONG WITH INCREASING CLOUDS AS WELL AS A SLIGHT CHANCE FOR A
WETTING RAIN. LATEST GUIDANCE CONTINUES TO SUGGEST THAT THE FRONT
WILL RETREAT BACK INTO MONTANA DURING THE LATE MORNING...CLEARING
THE WAY FOR MORE STRONG SOUTHWEST FLOW AND LOW HUMIDITY ACROSS
FREMONT...JOHNSON AND NATRONA COUNTIES. SO...THESE AREAS WILL
CONTINUE TO BE UNDER THE RED FLAG WARNING FOR SUNDAY. IN
ADDITION...A SWATH OF MID LEVEL MOISTURE AND CONTINUED INSTABILITY
WILL KICK OF A FEW MIXED WET AND DRY THUNDERSTORMS...SOME OF WHICH
COULD CONTRIBUTE TO NEW FIRE STARTS WITH THE MOST ACTIVITY
EXPECTED ACROSS NORTHERN AND WESTERN WYOMING...WITH A SECONDARY
SWATH EXPECTED OVER NATRONA AND EASTERN FREMONT COUNTIES LATE
SUNDAY AFTERNOON...THE CHANCE OF A WETTING RAIN OUT OF THESE
STORMS IS NEXT TO ZERO. THE BEST CHANCE OF ANY DRY LIGHTNING
STARTS WILL LIKELY BE ON THE PERIPHERY OF ANY THUNDERSTORMS OVER
NATRONA AND JOHNSON COUNTY WHERE THE COMBINATION OF DRIEST
BOUNDARY LEVEL MOISTURE...WIDEST TEMP/DEW POINT SPREADS AND
INSTABILITY WILL LIE ON SUNDAY AFTERNOON.

A REPEAT OF THESE CONDITIONS WILL BE POSSIBLE MID WEEK.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ275>277-279-
282-287-414>416.

RED FLAG WARNING UNTIL 9 PM MDT SUNDAY FOR WYZ280-281-283-285-
289-300.

&&

$$

SHORT TERM...ALLEN
LONG TERM...CNJ
AVIATION...AEM
FIRE WEATHER...ALLEN





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