000
FXUS65 KRIW 230906
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
306 AM MDT THU MAY 23 2013
.SHORT TERM...THURSDAY THROUGH SATURDAY NIGHT
SHOWERS AND THUNDERSTORMS HAVE BEEN ONGOING MUCH OF THE NIGHT AS AN
EASTERLY UPSLOPE FLOW...UPPER LEVEL DISTURBANCE AND JET STREAK HAVE
PROVIDED SOME DIVERGENCE AND LIFT THROUGH MAINLY WESTERN PORTIONS OF
THE COUNTY WARNING AREA...ESPECIALLY ON THE EAST SLOPES OF THE
ABSAROKAS. SATELLITE IMAGERY ACTUALLY SHOWS A JET STREAK PUSHING
ENERGY INTO ONGOING SHOWERS ACROSS WESTERN WYOMING AND THESE SHOULD
CONTINUE FOR THE REST OF THE NIGHT. MOST OF THIS ACTIVITY SHOULD END
SHORTLY AFTER SUNRISE AS THE BEST LIFT MOVES AWAY.
MODELS SHOW A WEAK AREA OF LOW PRESSURE DEVELOPING OVER SOUTHWESTERN
WYOMING THIS MORNING. THIS SHOULD TURN LOW LEVEL WINDS TO MORE OF A
SOUTH AND EVENTUALLY SOUTHWESTERLY DIRECTION THAT WILL BRING IN
WARMER AND DRIER AIR. MODELS STILL SHOW SOME PRECIPITABLE WATER
VALUES OVER 0.5 INCHES THIS AFTERNOON ACROSS THE BIG HORN BASIN AND
FROM THE BIG HORN RANGE AND EAST SO WE INCLUDED A SLIGHT CHANCE
OF AFTERNOON THUNDERSTORMS ACROSS THE LOWER ELEVATIONS IN THOSE
AREAS ALTHOUGH MOST AREAS WILL BE RAIN FREE. THE BEST CHANCE WILL
BE ACROSS NORTHWESTERN WYOMING WHERE SOUTHWEST FLOW WILL BRING
SOME UPSLOPE FLOW. THE OTHER ISSUE TODAY WILL BE THE WIND AS IT
WILL DEFINITELY BE A TOUPEE ALERT DAY TODAY...ESPECIALLY IN THE
SOUTHERN HALF OF THE COUNTY WARNING AREA. MODELS SHOW 700 MILLIBAR
WINDS UP TO 40 KNOTS IN MOST AREAS ALONG WITH A TIGHTENING
PRESSURE GRADIENT BETWEEN THE DEVELOPING LOW PRESSURE IN THE
NORTHERN PLAINS. IT DOES NOT LOOK WE WILL QUITE REACH HIGH WIND
BUT GUSTS TO 50 MPH ARE CERTAINLY POSSIBLE.
BY FRIDAY DRY WEST TO SOUTHWESTERLY FLOW WILL TAKE HOLD ACROSS THE
ENTIRE AREA SO A DRY DAY IS EXPECTED FOR GETAWAY DAY FOR THE
MEMORIAL DAY WEEKEND. EXPECT ABOVE NORMAL TEMPERATURES ACROSS THE
ENTIRE COUNTY WARNING AREA. ALTHOUGH IT WILL STILL BE BREEZY AT
TIMES EXPECT LESS WIND THAN ON ON THURSDAY. SATURDAY ALSO LOOKS TO
BE A DRY DAY FOR MOST AREAS ACROSS THE STATE. THE EXCEPTION WILL BE
ACROSS NORTHWESTERN WYOMING WHERE A WEAK SHORTWAVE MAY GET CLOSE
ENOUGH TO BRING SOME ISOLATED CONVECTION.
.LONG TERM...SUNDAY THROUGH THURSDAY
THE OVERALL SYNOPTIC PATTERN AT THE BEGINNING OF THIS PERIOD
FEATURES A TROUGH ALONG THE WEST COAST AND A RIDGE OVER THE
CENTRAL U.S. THIS PATTERN WILL PROGRESS SLOWLY EAST THROUGH THE
PERIOD RESULTING IN AN OVERALL COOLING TREND WITH CHANCES OF
SHOWERS AND THUNDERSTORMS INCREASING THROUGH NEXT WEEK AS THE
UPPER TROUGH MAKES ITS WAY INTO THE ROCKIES.
THE GFS REMAINS ON THE FASTER END OF GUIDANCE...BRINGING A
SIGNIFICANT PORTION OF WEST COAST TROUGH ACROSS THE AREA SUNDAY
NIGHT AND MONDAY...INTO THE BACKSIDE OF DOWNSTREAM RIDGE. THE ECMWF
AND TO A CERTAIN EXTENT...THE CANADIAN...KEEP THE DOWNSTREAM RIDGE
INTACT WITH ECMWF BRINGING A SHORTWAVE ACROSS THE GREAT BASIN LATE
SUNDAY AND UP THE BACKSIDE OF THE RIDGE ACROSS WESTERN
WYOMING/MONTANA MONDAY MORNING...OR NOT A WHOLE LOT OF CHANGE FROM
STORM TRACK TODAY. FORECAST REFLECTS THE ECMWF SCENARIO WITH BEST
CHANCES OF SHOWERS AND THUNDERSTORMS ACROSS THE WEST AND NORTH ON
SUNDAY AND MEMORIAL DAY WHILE A DRIER SOUTHERLY FLOW REMAINS OVER
THE SOUTH.
UPPER TROUGH EXPECTED TO DIG ACROSS THE SOUTHWEST U.S. TUESDAY AND
WEDNESDAY WITH MOIST DIFLUENT FLOW TAKING SHAPE DOWNSTREAM OVER
WYOMING. THIS WILL LEAD TO BETTER CHANCES OF SHOWERS AND
THUNDERSTORMS ACROSS THE AREA WITH THE POTENTIAL FOR LOCALLY HEAVY
RAINS AS DEEP EASTERLY FLOW ADVECTS LOW LEVEL MOISTURE INTO THE
REGION. NO SIGNIFICANT CHANGES ARE EXPECTED TO THIS OVERALL PATTERN
THROUGH THE END OF THE MONTH WITH UPPER TROUGH EXPECTED TO RELOAD
ACROSS THE WEST WHILE UPPER RIDGE HOLDS OVER THE CENTRAL U.S.
&&
.AVIATION.../12Z ISSUANCE/
AREAS OF LOW CLOUDS WITH MVFR TO IFR CONDITIONS WILL OCCUR UNTIL 17Z
FROM BUFFALO TO CASPER AND FROM CASPER TO RIVERTON. ISOLATED SHOWERS
ARE POSSIBLE OVER THE NW WY MOUNTAINS UNTIL 18Z. AFTER 18Z SHOWERS
AND THUNDERSTORMS WILL FORM OVER NW WY AS WELL AS AROUND THE BIGHORN
MOUNTAINS. THIS ACTIVITY WILL PERSIST THROUGH 06Z FRIDAY. SMALL HAIL
AND GUSTY WIND TO 40 KNOTS WILL OCCUR WITH SOME STORMS. LOCAL MVFR
CONDITIONS WILL OCCUR IN STORMS. VFR CONDITIONS WILL OCCUR AFTER 06Z
FRIDAY WITH ONLY ISOLATED MOUNTAIN SHOWERS IN NW WY.
&&
.FIRE WEATHER...
THE THREAT OF THUNDERSTORMS...ALTHOUGH LESS THAN ON WEDNESDAY WILL
REMAIN OVER THE NORTHERN AND FAR EASTERN FORE ZONES ON THURSDAY.
MEANWHILE...ACROSS THE SOUTHERN HALF OF THE AREA IT WILL BE A WINDY
AND WARMER DAY AS WINDS TURN FROM THE EAST TO A SOUTH OR
SOUTHWESTERLY DIRECTION. EXPECT DRY AND WARM WEATHER ON FRIDAY WITH
A GUSTY BREEZY AT TIMES.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HATTINGS
LONG TERM...AEM
AVIATION...AR
FIRE WEATHER...HATTINGS
000
FXUS65 KRIW 230527
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1127 PM MDT WED MAY 22 2013
.SHORT TERM...TONIGHT THROUGH THURSDAY (ISSUED AT 306 PM MDT)
TODAY...STILL CAUGHT BETWEEN DUELING UPPER LOWS WITH RIDGE IN
BETWEEN TRYING TO REACH BIG BROTHER OFF TO THE NORTH IN CENTRAL
CANADA. SFC LOW POSITION MORE ELONGATED AND STRENGTH AND
PROGRESSION LOOKS TO BE JUST SLIGHTLY BEHIND AND LESS VIGOROUS THAN
THE PAST COUPLE OF DAYS. STILL...WE SHOULD STILL BECOME SOMEWHAT
ACTIVE BY LATE THIS AFTERNOON...THUNDERSTORM-WISE...FROM THE SALT
AND GREEN MOUNTAINS...WESTERN WIND RIVER MOUNTAINS TO THE NORTHWEST
EDGE EDGE OF THE WIND RIVER BASIN AND ON UP TO THE WEST AND NORTH
BORDERS...WITH THE BIG HORN BASIN POSSIBLY MAKING OUT AS WELL.
SOUTHEASTERLY FLOW HAS FINALLY SET UP TODAY...WITH DEW POINTS THAT
STARTED OUT THIS MORNING WITH 30S AT LOWER ELEVATIONS AND 20S
MOUNTAINS...ONLY MAINTAINING OR INCREASING A POINT OR TWO THIS
AFTERNOON. THE REGION SOUTH OF THE WIND RIVER MOUNTAINS AND BASIN HAS
SOME DRYING OCCURRING AS SOUTHERN WARM/DRY PUSH WHICH HAS DEVELOPED
AHEAD OF SFC INVERTED TROF TRYING TO MAKE ITS WAY INTO WESTERN WY
AND IN RESPONSE TO UPPER LEVEL FORCING. A MINI WEAK DRY LINE PUSH.
BIG HORN MOUNTAINS AND ADJACENT EASTERN AREAS WILL BE PRIVY TO MORE
BOUNDARY LAYER MOISTURE...BUT WILL ALSO BE QUITE CAPPED THROUGH MOST
OF THE DAYTIME AND EARLY EVENING PERIOD...SO WILL NOT PRODUCE MUCH
IN THE WAY OF SHOWERS OR THUNDER DURING THE FIRST HALF OF THE FIRST
PERIOD OF THE FORECAST...EXCEPT PERHAPS RIGHT OVER CLOUD PEAK.
HOWEVER...THAT SAID...UPPER LEVEL DIVERGENCE AND SUPPORT WILL ARRIVE
OVER THE BIGHORNS LATER OVERNIGHT AND POSSIBLY SPARK A ROUND OF
SHOWERS THAT COULD LINGER THROUGH TOMORROW`S MORNING PERIOD.
FOR NORTHERN CWA TODAY...FORECAST SHEAR AND HODOGRAPHS CONTINUE TO
SHOW A MEAN VALUE OF 35 KTS AND MODERATE CLOCKWISE TURNING
RESPECTIVELY...WHICH SHOULD HELP TILT ROTATE AND SUSTAIN STORMS A
BIT LONGER WITH STORM MOTION RIGHT OF THE MEAN FLOW. A CATEGORY FOR
SOME STRONG STORMS...AND HARD TO GET TO VERY OCCASIONAL AND
MARGINAL SEVERE. STORMS SHOULD BE LOW TOPPED AND TOP OUT AT AROUND
35K FT MSL FOR THE STRONGER STORMS. FOR HAIL...FIRST LOOK FOR SEVERE
VIL OF THE DAY WILL BE BETWEEN 45 AND 50 TO CALCULATE VIL DENSITY
FROM. WILL HARD TO GET SEVERE HAIL IF WE DON`T JUICE UP A BIT.
MOSTLY WE CAN LOOK FOR PEA SIZE HAIL 80% OF TIME. FCST DCAPE RUNNING
BETWEEN 700 AND 800 J/KG OVER EASTERN FREMONT...HOT SPRINGS AND
WASHAKIE COUNTIES...AND SOMEWHAT LESS TO THE NORTH THROUGH THE REST
OF THE BIG HORN BASIN...THE USUAL CONVECTIVE WIND PRODUCING
SUSPECTS. SO WILL WATCH FOR SOME MODERATE BOWING SIGNATURES THIS
AFTERNOON/EVENING. EXPECT FIRST CONVECTION OVER THE SALT
RIVER/WYOMING AND ABSAROKA RANGES.
TONIGHT AND THURSDAY...OVERNIGHT SHOWERS WILL LINGER ACROSS NORTHERN
COUNTIES...AND AS MENTIONED ABOVE...START OVER AND NEAR THE BIG HORN
MOUNTAINS. THURSDAY DAYTIME...LESSER CHANCES FOR PRECIP AND THUNDER
WITH SCATTERED SHOWERS AND ISOLATED THUNDER NORTHWEST AND ISOLATED
SHOWERS AND THUNDER FROM BIGHORN BASIN AND MOUNTAINS SOUTH THROUGH
NATRONA COUNTY. MUCH OF THE SOUTHWEST PORTION OF THE CWA WILL BE
FREE FROM THUNDER ACTIVITY AND UNDER RATHER DRY SOUTHWEST FLOW. ONE
NOTE FOR TOMORROW...NATRONA COUNTY MAY FALL AT THE CROSS ROADS OF
JUST ENOUGH INSTABILITY TO GET A COUPLE OF STORMS OVER AND NEAR THE
MOUNTAINS...BUT THE STORMS SHOULD BE QUITE ELEVATED AND RELATIVELY
DRY...AND CAPABLE OF PRODUCING STRONG TO SEVERE WINDS. WILL HAVE TO
MONITOR AND WATCH THIS CONDITION OVER THE NEXT 36 HRS.
.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY NIGHT
AN UPPER LEVEL LOW PRESSURE TROUGH WILL EXTEND FROM THE PACIFIC NORTHWEST
SOUTH SOUTHEAST INTO THE GREAT BASIN WITH DRYING SOUTHWEST FLOW
ALOFT OVER WESTERN AND CENTRAL WYOMING THURSDAY EVENING. MOISTURE
AND INSTABILITY WILL BE LIMITED TO THE NORTH AND WESTERN MOUNTAINS
WHERE SOME EVENING SHOWERS AND THUNDERSTORMS ARE POSSIBLE. SOME
LIGHT SHOWERS WILL BE OVER THE FAR NORTH OVER NIGHT. OVERALL
TEMPERATURES WILL BE MILD. THE DRY SOUTHWEST FLOW WILL INCREASE ON
FRIDAY WITH BREEZY TO WINDY CONDITIONS AND WARMING. THE DRY AND
BREEZY CONDITIONS WILL CONTINUE FRIDAY NIGHT. THE PACIFIC TROUGH
WILL INCH CLOSER TO WESTERN WYOMING ON SUNDAY WITH SOME MOISTURE
INCREASING OVER THE NORTH AND WEST WITH SPOTTY AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS OVER THE NORTHERN AND WESTERN MOUNTAINS.
THE SOUTH...CENTRAL AND EAST WILL REMAIN DRY AND BREEZY TO WINDY
WITH TEMPERATURES REMAINING WARM. SOME CLOUDS WILL MOVE INTO THE
WEST SATURDAY NIGHT AND SUNDAY WITH THE RATHER STRONG SOUTHWEST
FLOW ALOFT CONTINUING. SUNDAY AFTERNOON AND EVENING SPOTTY SHOWERS
AND THUNDERSTORMS WILL RETURN TO THE NORTHERN AND WESTERN MOUNTAINS.
CLOUDS WILL INCREASE ACROSS THE SOUTH...CENTRAL AND EAST THROUGH
SUNDAY WITH A SLIGHT COOLING OF TEMPERATURES. A PORTION OF THE
PACIFIC TROUGH WILL SEPARATE FROM THE MAIN TROUGH AND MOVE EAST
SUNDAY NIGHT WITH CLOUDS AND SHOWERS INCREASING ACROSS THE NORTH AND
WESTERN MOUNTAINS WITH A SURFACE COLD FRONT MOVING SOUTH FROM
MONTANA COOLING TEMPERATURES. MONDAY WILL BE COOLER WITH INCREASED
CLOUDS AND SHOWERS OVER THE AREA AND ISOLATED AFTERNOON AND EVENING
THUNDERSTORMS. MONDAY NIGHT THE COLD FRONT WILL PASS SOUTH WITH
NORTH TO NORTHEAST WINDS AND COOLER TEMPERATURES. CLOUD COVER AND
SHOWERS WILL CONTINUE TO INCREASE OVER THE AREA. THE TROUGH WILL
REMAIN OVER THE AREA ON TUESDAY WITH CLOUDS AND SHOWERS...AND
ISOLATED AFTERNOON AND EVENING THUNDERSTORMS MAINLY OVER THE
MOUNTAINS. TEMPERATURES WILL CONTINUE COOLER. THE TROUGH WILL WEAKEN
AND EJECT NORTHEAST OF THE AREA TUESDAY NIGHT AND WEDNESDAY WITH
DRYING AND INCREASING SOUTHWEST FLOW ALOFT WITH DECREASING CLOUDS
AND SHOWERS THROUGH TUESDAY NIGHT AND WEDNESDAY MORNING. ANOTHER
PORTION OF THE PACIFIC TROUGH WILL MOVE EAST WEDNESDAY AFTERNOON
WITH CLOUDS...SHOWERS AND ISOLATED THUNDERSTORMS INCREASING
WEDNESDAY AFTERNOON AND EVENING. SLIGHT WARMING WILL OCCUR WITH THE
INCREASING SOUTHWEST FLOW...ESPECIALLY OVER AREAS EAST OF THE
CONTINENTAL DIVIDE. CLOUDS AND SHOWERS WILL LINGER THROUGH THE NIGHT
WEDNESDAY NIGHT.
&&
.AVIATION.../06Z ISSUANCE/
AREAS OF LOW CLOUDS WITH MVFR TO IFR CONDITIONS WILL OCCUR UNTIL 17Z
FROM BUFFALO TO CASPER AND FROM CASPER TO RIVERTON. ISOLATED SHOWERS
ARE POSSIBLE OVER THE NW WY MOUNTAINS UNTIL 18Z. AFTER 18Z SHOWERS
AND THUNDERSTORMS WILL FORM OVER NW WY AS WELL AS AROUND THE BIGHORN
MOUNTAINS. THIS ACTIVITY WILL PERSIST THROUGH 06Z FRIDAY. SMALL HAIL
AND GUSTY WIND TO 40 KNOTS WILL OCCUR WITH SOME STORMS. LOCAL MVFR
CONDITIONS WILL OCCUR IN STORMS.
&&
.FIRE WEATHER...
RELATIVELY ACTIVE WEATHER PATTERN RETURNS TO THE AREA TODAY AFTER
A BRIEF RESPITE. A LARGE UPPER LEVEL DISTURBANCE BRINGS A GOOD
CHANCE FOR THUNDERSTORMS...ESPECIALLY IN THE NORTHWEST FIRE ZONES.
THESE STORMS WILL BE CAPABLE OF VERY GUSTY AND ERRATIC WINDS AND
SMALL HAIL. WINDS WILL LARGELY BE FROM THE SOUTH TO EAST ACROSS
THE AREA. THE THREAT OF THUNDERSTORMS WILL REMAIN ACROSS NORTHERN
ZONES ON THURSDAY WITH WARMER...WINDY AND MAINLY DRY WEATHER
ACROSS THE SOUTHERN HALF OF THE STATE.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...BRAUN
LONG TERM...C.BAKER
AVIATION...AR
FIRE WEATHER...BRAUN
000
FXUS65 KRIW 222106
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
306 PM MDT WED MAY 22 2013
.SHORT TERM...TONIGHT THROUGH THURSDAY
TODAY...STILL CAUGHT BETWEEN DUELING UPPER LOWS WITH RIDGE IN
BETWEEN TRYING TO REACH BIG BROTHER OFF TO THE NORTH IN CENTRAL
CANADA. SFC LOW POSITION MORE ELONGATED AND STRENGTH AND
PROGRESSION LOOKS TO BE JUST SLIGHTLY BEHIND AND LESS VIGOROUS THAN
THE PAST COUPLE OF DAYS. STILL...WE SHOULD STILL BECOME SOMEWHAT
ACTIVE BY LATE THIS AFTERNOON...THUNDERSTORM-WISE...FROM THE SALT
AND GREEN MOUNTAINS...WESTERN WIND RIVER MOUNTAINS TO THE NORTHWEST
EDGE EDGE OF THE WIND RIVER BASIN AND ON UP TO THE WEST AND NORTH
BORDERS...WITH THE BIG HORN BASIN POSSIBLEY MAKING OUT AS WELL.
SOUTHEASTERLY FLOW HAS FINALLY SET UP TODAY...WITH DEW POINTS THAT
STARTED OUT THIS MORNING WITH 30S AT LOWER ELEVATIONS AND 20S
MOUNTAINS...ONLY MAINTAINING OR INCREASING A POINT OR TWO THIS
AFTERNOON. THE REGION SOUTH OF THE WIND RIVER MOUNTAINS AND BASIN HAS
SOME DRYING OCCURING AS SOUTHERN WARM/DRY PUSH WHICH HAS DEVELOPED
AHEAD OF SFC INVERTED TROF TRYING TO MAKE ITS WAY INTO WESTERN WY
AND IN REPONSE TO UPPER LEVEL FORCING. A MINI WEAK DRY LINE PUSH.
BIG HORN MOUNTAINS AND ADJACENT EASTERN AREAS WILL BE PRIVY TO MORE
BOUNDARY LAYER MOISTURE...BUT WILL ALSO BE QUITE CAPPED THROUGH MOST
OF THE DAYTIME AND EARLY EVENING PERIOD...SO WILL NOT PRODUCE MUCH
IN THE WAY OF SHOWERS OR THUNDER DURING THE FIRST HALF OF THE FIRST
PERIOD OF THE FORECAST...EXCEPT PERHAPS RIGHT OVER CLOUD PEAK.
HOWEVER...THAT SAID...UPPER LEVEL DIVERGENCE AND SUPPORT WILL ARRIVE
OVER THE BIGHORNS LATER OVERNIGHT AND POSSIBLY SPARK A ROUND OF
SHOWERS THAT COULD LINGER THROUGH TOMORROW`S MORNING PERIOD.
FOR NORTHERN CWA TODAY...FORECAST SHEAR AND HODOGRAPHS CONTINUE TO
SHOW A MEAN VALUE OF 35 KTS AND MODERATE CLOCKWISE TURNING
RESPECTIVELY...WHICH SHOULD HELP TILT ROTATE AND SUSTAIN STORMS A
BIT LONGER WITH STORM MOTION RIGHT OF THE MEAN FLOW. A CATEGORY FOR
SOME STRONG STORMS...AND HARD TO GET TO VERY OCCASIONAL AND
MARGINAL SEVERE. STORMS SHOULD BE LOW TOPPED AND TOP OUT AT AROUND
35K FT MSL FOR THE STRONGER STORMS. FOR HAIL...FIRST LOOK FOR SEVERE
VIL OF THE DAY WILL BE BETWEEN 45 AND 50 TO CALCULATE VIL DENSITY
FROM. WILL HARD TO GET SEVERE HAIL IF WE DON`T JUICE UP A BIT.
MOSTLY WE CAN LOOK FOR PEA SIZE HAIL 80% OF TIME. FCST DCAPE RUNNING
BETWEEN 700 AND 800 J/KG OVER EASTERN FREMONT...HOT SPRINGS AND
WASHAKIE COUNTIES...AND SOMEWHAT LESS TO THE NORTH THROUGH THE REST
OF THE BIG HORN BASIN...THE USUAL CONVECTIVE WIND PRODUCING
SUSPECTS. SO WILL WATCH FOR SOME MODERATE BOWING SIGNATURES THIS
AFTERNOON/EVENING. EXPECT FIRST CONVECTION OVER THE SALT
RIVER/WYOMING AND ABSOROKA RANGES.
TONIGHT AND THURSDAY...OVERNIGHT SHOWERS WILL LINGER ACROSS NORTHERN
COUNTIES...AND AS MENTIONED ABOVE...START OVER AND NEAR THE BIG HORN
MOUNTAINS. THURSDAY DAYTIME...LESSER CHANCES FOR PRECIP AND THUNDER
WITH SCATTERED SHOWERS AND ISOLATED THUNDER NORTHWEST AND ISOLATED
SHOWERS AND THUNDER FROM BIGHORN BASIN AND MOUNTAINS SOUTH THROUGH
NATRONA COUNTY. MUCH OF THE SOUTHWEST PORTION OF THE CWA WILL BE
FREE FROM THUNDER ACTIVITY AND UNDER RATHER DRY SOUTHWEST FLOW. ONE
NOTE FOR TOMORROW...NATRONA COUNTY MAY FALL AT THE CROSS ROADS OF
JUST ENOUGH INSTABILITY TO GET A COUPLE OF STORMS OVER AND NEAR THE
MOUNTAINS...BUT THE STORMS SHOULD BE QUITE ELEVATED AND RELATIVELY
DRY...AND CAPABLE OF PRODUCING STRONG TO SEVERE WINDS. WILL HAVE TO
MONITOR AND WATCH THIS CONDITION OVER THE NEXT 36 HRS.
.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY NIGHT
AN UPPER LEVEL LOW PRESSURE TROUGH WILL EXTEND FROM THE PACIFIC NORTHWEST
SOUTH SOUTHEAST INTO THE GREAT BASIN WITH DRYING SOUTHWEST FLOW
ALOFT OVER WESTERN AND CENTRAL WYOMING THURSDAY EVENING. MOISTURE
AND INSTABILITY WILL BE LIMITED TO THE NORTH AND WESTERN MOUNTAINS
WHERE SOME EVENING SHOWERS AND THUNDERSTORMS ARE POSSIBLE. SOME
LIGHT SHOWERS WILL BE OVER THE FAR NORTH OVER NIGHT. OVERALL
TEMPERATURES WILL BE MILD. THE DRY SOUTHWEST FLOW WILL INCREASE ON
FRIDAY WITH BREEZY TO WINDY CONDITIONS AND WARMING. THE DRY AND
BREEZY CONDITIONS WILL CONTINUE FRIDAY NIGHT. THE PACIFIC TROUGH
WILL INCH CLOSER TO WESTERN WYOMING ON SUNDAY WITH SOME MOISTURE
INCREASING OVER THE NORTH AND WEST WITH SPOTTY AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS OVER THE NORTHERN AND WESTERN MOUNTAINS.
THE SOUTH...CENTRAL AND EAST WILL REMAIN DRY AND BREEZY TO WINDY
WITH TEMPERATURES REMAINING WARM. SOME CLOUDS WILL MOVE INTO THE
WEST SATURDAY NIGHT AND SUNDAY WITH THE RATHER STRONG SOUTHWEST
FLOW ALOFT CONTINUING. SUNDAY AFTERNOON AND EVENING SPOTTY SHOWERS
AND THUNDERSTORMS WILL RETURN TO THE NORTHERN AND WESTERN MOUNTAINS.
CLOUDS WILL INCREASE ACROSS THE SOUTH...CENTRAL AND EAST THROUGH
SUNDAY WITH A SLIGHT COOLING OF TEMPERATURES. A PORTION OF THE
PACIFIC TROUGH WILL SEPARATE FROM THE MAIN TROUGH AND MOVE EAST
SUNDAY NIGHT WITH CLOUDS AND SHOWERS INCREASING ACROSS THE NORTH AND
WESTERN MOUNTAINS WITH A SURFACE COLD FRONT MOVING SOUTH FROM
MONTANA COOLING TEMPERATURES. MONDAY WILL BE COOLER WITH INCREASED
CLOUDS AND SHOWERS OVER THE AREA AND ISOLATED AFTERNOON AND EVENING
THUNDERSTORMS. MONDAY NIGHT THE COLD FRONT WILL PASS SOUTH WITH
NORTH TO NORTHEAST WINDS AND COOLER TEMPERATURES. CLOUD COVER AND
SHOWERS WILL CONTINUE TO INCREASE OVER THE AREA. THE TROUGH WILL
REMAIN OVER THE AREA ON TUESDAY WITH CLOUDS AND SHOWERS...AND
ISOLATED AFTERNOON AND EVENING THUNDERSTORMS MAINLY OVER THE
MOUNTAINS. TEMPERATURES WILL CONTINUE COOLER. THE TROUGH WILL WEAKEN
AND EJECT NORTHEAST OF THE AREA TUESDAY NIGHT AND WEDNESDAY WITH
DRYING AND INCREASING SOUTHWEST FLOW ALOFT WITH DECREASING CLOUDS
AND SHOWERS THROUGH TUESDAY NIGHT AND WEDNESDAY MORNING. ANOTHER
PORTION OF THE PACIFIC TROUGH WILL MOVE EAST WEDNESDAY AFTERNOON
WITH CLOUDS...SHOWERS AND ISOLATED THUNDERSTORMS INCREASING
WEDNESDAY AFTERNOON AND EVENING. SLIGHT WARMING WILL OCCUR WITH THE
INCREASING SOUTHWEST FLOW...ESPECIALLY OVER AREAS EAST OF THE
CONTINENTAL DIVIDE. CLOUDS AND SHOWERS WILL LINGER THROUGH THE NIGHT
WEDNESDAY NIGHT.
&&
.AVIATION.../00Z ISSUANCE/
VFR CONDITIONS AROUND THE FORECAST AREA TODAY AND TONIGHT...WITH THE
EXCEPTION OF TERMINALS NEAR OR UNDER THUNDERSTORMS THIS EVENING...
WHEN GUSTY WINDS...SMALL HAIL AND REDUCED VISIBILITY CAN BE EXPECTED
FOR BRIEF PERIODS AND TERMINALS GO TO MVFR. AREAS TO WATCH INCLUDE
TERMINALS NEAR THE SALT AND GREEN MOUNTAINS...WESTERN WIND RIVER
MOUNTAINS TO THE NORTHWEST EDGE EDGE OF THE WIND RIVER BASIN
INCLUDING THE BIG HORN BASIN. LATER CHANCES IMPROVE FOR KCPR AND
AREA NEAR SOUTHERN BIG HORN MOUNTAINS. TOMORROW...KCPR COULD BE
SUBJECT TO DRY THUNDERSTORMS AND STRONG GUSTY STRAIGHT-LINE WINDS.
KRKS WILL BE THE LONE TERMINAL WITHOUT THUNDERSTORM CHANCES TODAY.
&&
.FIRE WEATHER...
RELATIVELY ACTIVE WEATHER PATTERN RETURNS TO THE AREA TODAY AFTER
A BRIEF RESPITE. A LARGE UPPER LEVEL DISTURBANCE BRINGS A GOOD
CHANCE FOR THUNDERSTORMS...ESPECIALLY IN THE NORTHWEST FIRE ZONES.
THESE STORMS WILL BE CAPABLE OF VERY GUSTY AND ERRATIC WINDS AND
SMALL HAIL. WINDS WILL LARGELY BE FROM THE SOUTH TO EAST ACROSS
THE AREA. THE THREAT OF THUNDERSTORMS WILL REMAIN ACROSS NORTHERN
ZONES ON THURSDAY WITH WARMER...WINDY AND MAINLY DRY WEATHER
ACROSS THE SOUTHERN HALF OF THE STATE.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...BRAUN
LONG TERM...C.BAKER
AVIATION...BRAUN
FIRE WEATHER...BRAUN
000
FXUS65 KRIW 221734
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1134 AM MDT WED MAY 22 2013
.SHORT TERM...WEDNESDAY THROUGH FRIDAY NIGHT
AFTER A FAIRLY QUIET WEATHER DAY ON TUESDAY IT LOOKS LIKE THE
WEATHER WILL TURN ACTIVE ONCE AGAIN. SATELLITE IMAGERY SHOWS A THIN
BAND OF CLOUDS WORKING ACROSS CENTRAL WYOMING AT THIS TIME WITH A
FEW SPRINKLES BUT THIS SHOULD BE OUT OF THE COUNTY WARNING AREA BY
DAYLIGHT. AFTER THE PASSAGE OF THESE CLOUDS PRECIPITABLE WATERS
SHOULD STAY RELATIVELY LOW. HOWEVER...700 MILLIBAR FLOW WILL SLOWLY
TURN FROM SOUTH TO SOUTHEAST AND EAST THROUGH THE DAY AND INCREASE
PRECIPITABLE WATER VALUES UP TO 0.6 TO 0.7 INCHES ACROSS MANY AREAS
EAST OF THE DIVIDE WITH THE HIGHEST VALUES IN NORTHERN AND EASTERN
PORTIONS OF THE AREA. CAPE VALUES WILL ALSO BE ON THE RISE WITH
VALUES OVER 300 J/KG FROM THE ABSAROKAS THROUGH THE WIND RIVER BASIN
AND IN AREAS FROM THE BIG HORN RANGE AND EAST. IN ADDITION...LIFTED
INDICES WILL FALL TO MINUS 3 IN MANY AREAS AND THERE IS SOME
DIRECTIONAL SHEAR WITH SOUTHWEST FLOW AT 500 MILLIBARS. WITH LOW
PRESSURE PROVIDING SOME LIFT LOOK FOR ISOLATED TO SCATTERED
THUNDERSTORMS IN THE FOREMENTIONED AREAS...SOME POSSIBLY STRONG...TO
DEVELOP THIS AFTERNOON AND EVENING WITH GUSTY WINDS AND HAIL THE
MAIN THREATS. THE THREAT OF THESE STORMS SHOULD END LATE TONIGHT
WITH THE LOSS OF DAYTIME HEATING.
STILL SOME UNCERTAINTY TOMORROW AS A LOT DEPENDS ON IF A DRY SLOT
SETS UP ACROSS PORTIONS OF THE COUNTY WARNING AREA...WITH THE BEST
CHANCE OF THAT ACROSS THE SOUTHERN PORTIONS OF THE COUNTY WARNING
AREA. WITH THE UNCERTAINTY WE HAVE LEFT CONTINUITY ALONE FOR THE
MOST PART WITH THE CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS
NORTHERN AND EASTERN AREAS WHERE MOISTURE WILL BE A BIT DEEPER. WITH
INCREASED SOUTH TO SOUTHWESTERLY FLOW TEMPERATURES WILL CONTINUE AN
UPWARD TREND TO ABOVE NORMAL LEVELS. IT WILL BECOME WINDY AS WELL
ACROSS SOUTHERN PORTIONS OF THE STATE WITH THE INCREASED SOUTH FLOW
AND GOOD MIXING FROM MORE SUNSHINE. AS FOR FRIDAY...MODELS NOW
INDICATE THAT MUCH DRIER AIR WILL MOVE AS THE BEST MOISTURE GETS
SHUNTED TO THE NORTH AND EAST OF WYOMING. STILL SOME UNCERTAINTY SO
WE MAINLY NUDGED DOWN THE POPS RATHER THAN REMOVE THEM AT THIS TIME.
.LONG TERM...SATURDAY THROUGH WEDNESDAY
UPPER LOW OVER THE NW U.S. TO FILL AND LIFT INTO SOUTHERN B.C. OVER
THE WEEKEND. THIS WILL LEAVE WYOMING IN SW FLOW BETWEEN PERSISTENT
WEST COAST TROUGH AND EXPANDING RIDGE OVER THE PLAINS. MEDIUM RANGE
GLOBAL MODELS SHOW A SLOW PROGRESSION OF THIS OVERALL PATTERN
THROUGH THE EXTENDED PERIOD...THE GFS IS ON THE FAST END OF THIS
PROGRESSION AND THE ECMWF IS ON THE SLOW END. FORECAST IS WEIGHTED
TOWARD THE SLOWER PROGRESSION.
AS IS TYPICAL IN WARM SEASON SW FLOW...THE MAIN SURFACE FEATURE WILL
BE A QUASI-STATIONARY SURFACE TROUGH ACROSS NORTHERN AND EASTERN
WYOMING WITH AN E-SE FLOW BRINGING IN MORE MOISTURE AND INSTABILITY
TO THE NORTH AND EAST OF THIS BOUNDARY...A DRIER SW FLOW TO THE
SOUTH. ON SATURDAY...THIS BOUNDARY WILL BE NEAR A THERMOPOLIS TO
MIDWEST LINE...WITH SLIGHT CHANCES OF AFTN/EVE THUNDERSTORMS TO THE
NORTH. SOME STRONGER STORMS ARE POSSIBLE IN NE JOHNSON COUNTY.
ON SUNDAY AND MEMORIAL DAY...MORE CONVECTION IS EXPECTED FROM
EASTERN IDAHO INTO FAR WEST WYOMING AHEAD OF A SLOW-MOVING COLD
FRONT. A STRONGER SW FLOW AHEAD OF THE FRONT MAY PUSH THE SURFACE
TROUGH EAST OF THE DIVIDE FURTHER TO THE N AND E...THUNDERSTORM
INITIATION PRIMARILY FROM MEETEETSE TO BUFFALO AND NORTH.
UPPER TROUGH IS EXPECTED TO SLOWLY PROGRESS ACROSS THE GREAT
BASIN/ROCKIES TUESDAY AND WEDNESDAY WHICH WILL BRING AN INCREASING
CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS MOST OF THE AREA ALONG
WITH A COOLING TREND.
&&
.AVIATION.../18Z ISSUANCE/
VFR CONDITIONS WILL PREVAIL ACROSS THE FORECAST AREA TODAY AND
TONIGHT...WITH THE EXCEPTION OF AREAS IN AND AROUND THUNDERSTORMS
THIS AFTERNOON AND EVENING WHEN GUSTY WINDS...SMALL HAIL AND REDUCED
VISIBILITY CAN BE EXPECTED FOR BRIEF PERIODS AND TERMINALS GO TO
MVFR. AREAS TO WATCH INCLUDE TERMINALS NEAR THE SALT AND GREEN
MOUNTAINS...WESTERN WIND RIVER MOUNTAINS TO THE NORTHWEST EDGE EDGE
OF THE WIND RIVER BASIN INCLUDING THE BIG HORN BASIN. LATER CHANCES
INPROVE FOR KCPR AND AREA NEAR SOUTHERN BIG HORN MOUNTAINS.
TOMORROW...KCPR COULD BE SUBJECT TO DRY THUNDERSTORMS AND STRONG
GUSTY STRAIGHTLINE WINDS. KRKS WILL BE THE LONE TERMINAL WITHOUT
THUNDERSTORM CHANCES TODAY.
&&
.FIRE WEATHER...
MORE ACTIVE WEATHER WILL RETURN TO THE AREA TODAY AS ANOTHER STORM
SYSTEM BRINGS A BETTER CHANCE FOR THUNDERSTORMS IN THE NORTHWEST
FIRE ZONES ON WEDNESDAY. THESE STORMS WILL BE CAPABLE OF VERY GUSTY
AND ERRATIC WINDS. WINDS WILL LARGELY BE FROM THE SOUTH TO SOUTHEAST
ACROSS THE AREA. THE THREAT OF THUNDERSTORMS WILL REMAIN ACROSS
NORTHERN ZONES ON THURSDAY WITH WARMER...WINDY AND MAINLY DRY
WEATHER ACROSS THE SOUTHERN HALF OF THE STATE.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HATTINGS
LONG TERM...AEM
AVIATION...BRAUN
FIRE WEATHER...HATTINGS
000
FXUS65 KRIW 220943
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
343 AM MDT WED MAY 22 2013
.SHORT TERM...WEDNESDAY THROUGH FRIDAY NIGHT
AFTER A FAIRLY QUIET WEATHER DAY ON TUESDAY IT LOOKS LIKE THE
WEATHER WILL TURN ACTIVE ONCE AGAIN. SATELLITE IMAGERY SHOWS A THIN
BAND OF CLOUDS WORKING ACROSS CENTRAL WYOMING AT THIS TIME WITH A
FEW SPRINKLES BUT THIS SHOULD BE OUT OF THE COUNTY WARNING AREA BY
DAYLIGHT. AFTER THE PASSAGE OF THESE CLOUDS PRECIPITABLE WATERS
SHOULD STAY RELATIVELY LOW. HOWEVER...700 MILLIBAR FLOW WILL SLOWLY
TURN FROM SOUTH TO SOUTHEAST AND EAST THROUGH THE DAY AND INCREASE
PRECIPITABLE WATER VALUES UP TO 0.6 TO 0.7 INCHES ACROSS MANY AREAS
EAST OF THE DIVIDE WITH THE HIGHEST VALUES IN NORTHERN AND EASTERN
PORTIONS OF THE AREA. CAPE VALUES WILL ALSO BE ON THE RISE WITH
VALUES OVER 300 J/KG FROM THE ABSAROKAS THROUGH THE WIND RIVER BASIN
AND IN AREAS FROM THE BIG HORN RANGE AND EAST. IN ADDITION...LIFTED
INDICES WILL FALL TO MINUS 3 IN MANY AREAS AND THERE IS SOME
DIRECTIONAL SHEAR WITH SOUTHWEST FLOW AT 500 MILLIBARS. WITH LOW
PRESSURE PROVIDING SOME LIFT LOOK FOR ISOLATED TO SCATTERED
THUNDERSTORMS IN THE FOREMENTIONED AREAS...SOME POSSIBLY STRONG...TO
DEVELOP THIS AFTERNOON AND EVENING WITH GUSTY WINDS AND HAIL THE
MAIN THREATS. THE THREAT OF THESE STORMS SHOULD END LATE TONIGHT
WITH THE LOSS OF DAYTIME HEATING.
STILL SOME UNCERTAINTY TOMORROW AS A LOT DEPENDS ON IF A DRY SLOT
SETS UP ACROSS PORTIONS OF THE COUNTY WARNING AREA...WITH THE BEST
CHANCE OF THAT ACROSS THE SOUTHERN PORTIONS OF THE COUNTY WARNING
AREA. WITH THE UNCERTAINTY WE HAVE LEFT CONTINUITY ALONE FOR THE
MOST PART WITH THE CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS
NORTHERN AND EASTERN AREAS WHERE MOISTURE WILL BE A BIT DEEPER. WITH
INCREASED SOUTH TO SOUTHWESTERLY FLOW TEMPERATURES WILL CONTINUE AN
UPWARD TREND TO ABOVE NORMAL LEVELS. IT WILL BECOME WINDY AS WELL
ACROSS SOUTHERN PORTIONS OF THE STATE WITH THE INCREASED SOUTH FLOW
AND GOOD MIXING FROM MORE SUNSHINE. AS FOR FRIDAY...MODELS NOW
INDICATE THAT MUCH DRIER AIR WILL MOVE AS THE BEST MOISTURE GETS
SHUNTED TO THE NORTH AND EAST OF WYOMING. STILL SOME UNCERTAINTY SO
WE MAINLY NUDGED DOWN THE POPS RATHER THAN REMOVE THEM AT THIS TIME.
.LONG TERM...SATURDAY THROUGH WEDNESDAY
UPPER LOW OVER THE NW U.S. TO FILL AND LIFT INTO SOUTHERN B.C. OVER
THE WEEKEND. THIS WILL LEAVE WYOMING IN SW FLOW BETWEEN PERSISTENT
WEST COAST TROUGH AND EXPANDING RIDGE OVER THE PLAINS. MEDIUM RANGE
GLOBAL MODELS SHOW A SLOW PROGRESSION OF THIS OVERALL PATTERN
THROUGH THE EXTENDED PERIOD...THE GFS IS ON THE FAST END OF THIS
PROGRESSION AND THE ECMWF IS ON THE SLOW END. FORECAST IS WEIGHTED
TOWARD THE SLOWER PROGRESSION.
AS IS TYPICAL IN WARM SEASON SW FLOW...THE MAIN SURFACE FEATURE WILL
BE A QUASI-STATIONARY SURFACE TROUGH ACROSS NORTHERN AND EASTERN
WYOMING WITH AN E-SE FLOW BRINGING IN MORE MOISTURE AND INSTABILITY
TO THE NORTH AND EAST OF THIS BOUNDARY...A DRIER SW FLOW TO THE
SOUTH. ON SATURDAY...THIS BOUNDARY WILL BE NEAR A THERMOPOLIS TO
MIDWEST LINE...WITH SLIGHT CHANCES OF AFTN/EVE THUNDERSTORMS TO THE
NORTH. SOME STRONGER STORMS ARE POSSIBLE IN NE JOHNSON COUNTY.
ON SUNDAY AND MEMORIAL DAY...MORE CONVECTION IS EXPECTED FROM EASTERN
IDAHO INTO FAR WEST WYOMING AHEAD OF A SLOW-MOVING COLD FRONT. A
STRONGER SW FLOW AHEAD OF THE FRONT MAY PUSH THE SURFACE TROUGH EAST
OF THE DIVIDE FURTHER TO THE N AND E...THUNDERSTORM INITIATION
PRIMARILY FROM MEETEETSE TO BUFFALO AND NORTH.
UPPER TROUGH IS EXPECTED TO SLOWLY PROGRESS ACROSS THE GREAT
BASIN/ROCKIES TUESDAY AND WEDNESDAY WHICH WILL BRING AN INCREASING
CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS MOST OF THE AREA ALONG
WITH A COOLING TREND.
&&
.AVIATION.../12Z ISSUANCE/
VFR CONDITIONS WILL PREVAIL OVER THE REGION THROUGH 12Z THURSDAY.
ISOLATED SHOWERS AND THUNDERSTORMS WILL OCCUR EAST OF THE
CONTINENTAL DIVIDE FROM 20Z UNTIL 03Z WITH LOCAL MVFR CONDITIONS.
WEST OF THE DIVIDE...SHOWERS AND THUNDERSTORMS WILL BE MORE NUMEROUS
FROM 20Z THROUGH 06Z WITH AREAS OF MVFR CONDITIONS. A FEW SHOWERS
MAY LINGER IN NW WY THROUGH 12Z THURSDAY. WINDY CONDITIONS WILL
OCCUR ACROSS SOUTHERN AND SOUTHWEST WY THIS AFTERNOON WITH GUSTS TO
30 KNOTS.
&&
.FIRE WEATHER...
MORE ACTIVE WEATHER WILL RETURN TO THE AREA TODAY AS ANOTHER STORM
SYSTEM BRINGS A BETTER CHANCE FOR THUNDERSTORMS IN THE NORTHWEST
FIRE ZONES ON WEDNESDAY. THESE STORMS WILL BE CAPABLE OF VERY GUSTY
AND ERRATIC WINDS. WINDS WILL LARGELY BE FROM THE SOUTH TO SOUTHEAST
ACROSS THE AREA. THE THREAT OF THUNDERSTORMS WILL REMAIN ACROSS
NORTHERN ZONES ON THURSDAY WITH WARMER...WINDY AND MAINLY DRY
WEATHER ACROSS THE SOUTHERN HALF OF THE STATE.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HATTINGS
LONG TERM...AEM
AVIATION...AR
FIRE WEATHER...HATTINGS
000
FXUS65 KRIW 220525
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1125 PM MDT TUE MAY 21 2013
.SHORT TERM...TONIGHT THROUGH WEDNESDAY (ISSUED AT 329 PM MDT)
TODAY...CAUGHT BETWEEN TWO UPPER LOWS TODAY WITH MODERATE RIDGING
BEGINNING TO SLOWLY INCH ITS WAY INTO THE STATE FROM LEFT TO RIGHT.
WARMER TODAY WITH HIGH TEMPS RISING SOME 6 TO 8 DEG OVER YESTERDAY
GIVING US WIDESPREAD 60S ACROSS THE CWA...WITH NEAR 70S BIG HORN
BASIN...AND 50S MOUNTAINS. OVERALL...LOW INSTABILITY TODAY...BUT A
FEW SHOWERS OR ISOLATED THUNDER WILL BE POSSIBLE OVER THE HIGHER
MOUNTAINOUS TERRAIN...PARTICULARLY THE WIND RIVER AND ABSAROKA
MOUNTAINS PLUS NEARBY ADJACENT AREAS.
TONIGHT AND WEDNESDAY...OVERNIGHT LOWS FALLING INTO THE 40S MOST
AREAS WITH 30S HIGH MOUNTAINS. PERHAPS SOME LOCALIZED LIGHT PATCHY
FOG IN THE SOAP HILL BASIN AREA...AS SOME LIGHT E TO SE FLOW WORKS
ITS WAY IN OVERNIGHT AND INTO WED MORNING. DURING THE DAY
TOMORROW...WE RETURN TO SOME STORMINESS ONCE AGAIN AS SFC LOW
PRESSURE DEVELOPS OVER SW WY WITH LL FLOW TURNING SOUTH TO SOUTHEAST
ACROSS MUCH OF CWA AND LOW TO MID LVL MOISTURE
INCREASES...PARTICULARLY IN THE NWRN PORTION THE CWA. WARMER DAYTIME
TEMPS...INCREASED MOISTURE AND SOME GOOD UPPER LVL DIVERGENCE WITH
ASSOCIATED SHEAR VALUES IN THIS AREA INCREASING THROUGH THE
AFTERNOON...GIVING EFFECTIVE SHEAR OF 35 TO 40 KTS. THIS WILL ALL
COME TOGETHER TO YIELD TERRAIN BASED CAPE FROM 400 TO 800 J/KG...AND
ML CAPE FROM 300 TO 700 OVER THE HIGHER TERRAIN. FORECAST CLOCKWISE
TURNING HODOGRAPHS FROM OVER THE NORTHERN HALF OF THE CWA GIVE STORM
MOTION FROM THE SSW TO SW WITH THE POSSIBILITY OF THE STRONGER
STORMS BEING RIGHT TURNERS. STRONGEST CONVECTION SHOULD OCCUR
NORTHWEST OF RIVERTON TOWARDS YELLOWSTONE.
.LONG TERM...WEDNESDAY NIGHT THROUGH FRIDAY
A COUPLE FEATURES WILL KEEP THE THREAT OF THUNDERSTORMS INTO THE
EVENING WEDNESDAY. THE MOIST E TO SE FLOW ACROSS NRN
FREMONT...NATRONA AND NWD WILL AID IN THUNDERSTORMS ALONG AND IN THE
MOUNTAINS AND ALSO ALONG THE DRIER PUNCH OF AIR MOVING NWD OUT OF
THE RED DESERT. GENERAL NEWD STEERING FLOW WILL LIKELY ALLOW SOME OF
THESE TO MOVE OFF THE MOUNTAINS INTO THE EVENING...ESPECIALLY IN THE
BIG HORN BASIN AND ALONG THE CONVERGENCE BOUNDARY BETWEEN THE DRY
AND MOIST AIR OVER NERN FREMONT AND NATRONA. ALL THESE AREAS WILL
HAVE A CHANCE OF THUNDERSTORMS THROUGH WEDNESDAY EVENING. OUT WEST...
THE SHORTWAVE MOVING UP FROM THE SW MAY PROVIDE ENOUGH FORCING TO
KEEP SHOWERS AND A FEW THUNDERSTORMS GOING WELL INTO THE NIGHT. A
FEW OF THESE ARE EVEN POSSIBLE IN THE CENTRAL AREAS. ON THURSDAY...A
DRIER PUSH WILL ADVANCE NWD INTO THE BIG HORN BASIN AND AT LEAST WRN
NATRONA COUNTIES WHILE A MOIST SELY FLOW CONTINUES IN ERN NATRONA
AND MOST OF JOHNSON COUNTY AND ACROSS THE NRN BIG HORN BASIN. OUT
WEST...THE NEXT SHORTWAVE AND ASSOCIATED COLD FRONT WILL MOVE INTO
THE WEST. THE AIRMASS IS NOT AS UNSTABLE AS WEDNESDAY BUT STILL
ENOUGH TO FIRE SHOWERS AND SOME THUNDERSTORMS OVER THE
NW...ESPECIALLY DURING THE AFTERNOON AND EVENING. A DRIER SW FLOW IS
STILL EXPECTED TO OVERTAKE THE AREA ON FRIDAY WITH LITTLE OR NO
CONVECTION EXPECTED. LIMITED THE ISOLATED STORMS TO THE NW THIRD.
WARMER THURSDAY AND THEN A LITTLE COOLER MOST AREAS FRIDAY BEHIND
THE WEAK COLD FRONT...ESPECIALLY WEST HALF.
FRIDAY NIGHT THROUGH TUESDAY
LARGE UPPER LOW BETWEEN THE PACNW AND NRN GREAT BASIN WILL BE THE
MAIN WEATHER FEATURE THROUGH THE MEDIUM RANGE PERIOD. THE WEEKEND
WILL GENERALLY BE WARM AND DRY EXCEPT FOR POTENTIAL STORMS IN THE
NRN MTNS...FAR NORTH AND FAR EAST WHERE THE DRIER SW WINDS MEET THE
MORE MOIST SE FLOW. ON MEMORIAL DAY...A STRONGER SHORTWAVE IN THE SW
FLOW MAY PROVIDE AN INCREASED CHANCE OF THUNDERSTORMS. ON
TUESDAY...ANOTHER SHORTWAVE IN THE SW FLOW WILL LIKELY KEEP AN
INCREASED CHANCE OF CONVECTION WITH THE PEAK IN THE AFTERNOON AND
EARLY EVENING BUT THERE WILL LIKELY BE SOME SHOWERS AND POTENTIALLY
ISOLATED THUNDERSTORMS MONDAY NIGHT.
&&
.AVIATION.../06Z ISSUANCE/
VFR CONDITIONS WILL PREVAIL OVER THE REGION THROUGH 06Z THURSDAY.
ISOLATED SHOWERS AND THUNDERSTORMS WILL OCCUR EAST OF THE
CONTINENTAL DIVIDE FROM 20Z UNTIL 03Z WITH LOCAL MVFR CONDITIONS.
WEST OF THE DIVIDE...SHOWERS AND THUNDERSTORMS WILL BE MORE NUMEROUS
FROM 20Z THROUGH 06Z WITH AREAS OF MVFR CONDITIONS. WINDY CONDITIONS
WILL OCCUR ACROSS SOUTHERN AND SOUTHWEST WY WEDNESDAY AFTERNOON WITH
GUSTS TO 30 KNOTS POSSIBLE.
&&
.FIRE WEATHER...
UPPER LEVEL RIDGING HAS DRIED OUT AND WARMED UP THE FORECAST AREA
TODAY. THERE COULD STILL BE AN ISOLATED SHOWERS OR A THUNDERSTORM
OVER THE WESTERN HIGHER MOUNTAINS. THIS CONDITION WILL BE SHORT
LIVED HOWEVER AS ANOTHER STORM SYSTEM BRINGS A BETTER CHANCE FOR
THUNDERSTORMS IN THE NORTHWEST FIRE ZONES ON WEDNESDAY. THESE STORMS
WILL MOVE FROM SOUTH TO NORTH AND BE CAPABLE OF VERY GUSTY AND
ERRATIC WINDS. AMBIENT WINDS WILL LARGELY BE FROM THE SOUTH TO
SOUTHEAST ACROSS THE AREA.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...BRAUN
LONG TERM...SKRBAC
AVIATION...AR
FIRE WEATHER...BRAUN
000
FXUS65 KRIW 212129
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
329 PM MDT TUE MAY 21 2013
.SHORT TERM...TONIGHT THROUGH WEDNESDAY
TODAY...CAUGHT BETWEEN TWO UPPER LOWS TODAY WITH MODERATE RIDGING
BEGINNING TO SLOWLY INCH ITS WAY INTO THE STATE FROM LEFT TO RIGHT.
WARMER TODAY WITH HIGH TEMPS RISING SOME 6 TO 8 DEG OVER YESTERDAY
GIVING US WIDESPREAD 60S ACROSS THE CWA...WITH NEAR 70S BIG HORN
BASIN...AND 50S MOUNTAINS. OVERALL...LOW INSTABILITY TODAY...BUT A
FEW SHOWERS OR ISOLATED THUNDER WILL BE POSSIBLE OVER THE HIGHER
MOUNTAINOUS TERRAIN...PARTICULARLY THE WIND RIVER AND ABSOROKA
MOUNTAINS PLUS NEARBY ADJACENT AREAS.
TONIGHT AND WEDNESDAY...OVERNIGHT LOWS FALLING INTO THE 40S MOST
AREAS WITH 30S HIGH MOUNTAINS. PERHAPS SOME LOCALIZED LIGHT PATCHY
FOG IN THE SOAP HILL BASIN AREA...AS SOME LIGHT E TO SE FLOW WORKS
ITS WAY IN OVERNIGHT AND INTO WED MORNING. DURING THE DAY
TOMORROW...WE RETURN TO SOME STORMINESS ONCE AGAIN AS SFC LOW
PRESSURE DEVELOPS OVER SW WY WITH LL FLOW TURNING SOUTH TO SOUTHEAST
ACROSS MUCH OF CWA AND LOW TO MID LVL MOISTURE
INCREASES...PARTICULARLY IN THE NWRN PORTION THE CWA. WARMER DAYTIME
TEMPS...INCREASED MOISTURE AND SOME GOOD UPPER LVL DIVERGENCE WITH
ASSOCIATED SHEAR VALUES IN THIS AREA INCREASING THROUGH THE
AFTERNOON...GIVING EFFECTIVE SHEAR OF 35 TO 40 KTS. THIS WILL ALL
COME TOGETHER TO YIELD TERRAIN BASED CAPE FROM 400 TO 800 J/KG...AND
ML CAPE FROM 300 TO 700 OVER THE HIGHER TERRAIN. FORECAST CLOCKWISE
TURNING HODOGRAPHS FROM OVER THE NORTHERN HALF OF THE CWA GIVE STORM
MOTION FROM THE SSW TO SW WITH THE POSSIBILITY OF THE STRONGER
STORMS BEING RIGHT TURNERS. STRONGEST CONVECTION SHOULD OCCUR
NORTHWEST OF RIVERTON TOWARDS YELLOWSTONE.
.LONG TERM...WEDNESDAY NIGHT THROUGH FRIDAY
A COUPLE FEATURES WILL KEEP THE THREAT OF THUNDERSTORMS INTO THE
EVENING WEDNESDAY. THE MOIST E TO SE FLOW ACROSS NRN
FREMONT...NATRONA AND NWD WILL AID IN THUNDERSTORMS ALONG AND IN THE
MOUNTAINS AND ALSO ALONG THE DRIER PUNCH OF AIR MOVING NWD OUT OF
THE RED DESERT. GENERAL NEWD STEERING FLOW WILL LIKELY ALLOW SOME OF
THESE TO MOVE OFF THE MOUNTAINS INTO THE EVENING...ESPECIALLY IN THE
BIG HORN BASIN AND ALONG THE CONVERGENCE BOUNDARY BETWEEN THE DRY
AND MOIST AIR OVER NERN FREMONT AND NATRONA. ALL THESE AREAS WILL
HAVE A CHANCE OF THUNDERSTORMS THROUGH WEDNESDAY EVENING. OUT WEST...
THE SHORTWAVE MOVING UP FROM THE SW MAY PROVIDE ENOUGH FORCING TO
KEEP SHOWERS AND A FEW THUNDERSTORMS GOING WELL INTO THE NIGHT. A
FEW OF THESE ARE EVEN POSSIBLE IN THE CENTRAL AREAS. ON THURSDAY...A
DRIER PUSH WILL ADVANCE NWD INTO THE BIG HORN BASIN AND AT LEAST WRN
NATRONA COUNTIES WHILE A MOIST SELY FLOW CONTINUES IN ERN NATRONA
AND MOST OF JOHNSON COUNTY AND ACROSS THE NRN BIG HORN BASIN. OUT
WEST...THE NEXT SHORTWAVE AND ASSOCIATED COLD FRONT WILL MOVE INTO
THE WEST. THE AIRMASS IS NOT AS UNSTABLE AS WEDNESDAY BUT STILL
ENOUGH TO FIRE SHOWERS AND SOME THUNDERSTORMS OVER THE
NW...ESPECIALLY DURING THE AFTERNOON AND EVENING. A DRIER SW FLOW IS
STILL EXPECTED TO OVERTAKE THE AREA ON FRIDAY WITH LITTLE OR NO
CONVECTION EXPECTED. LIMITED THE ISOLATED STORMS TO THE NW THIRD.
WARMER THURSDAY AND THEN A LITTLE COOLER MOST AREAS FRIDAY BEHIND
THE WEAK COLD FRONT...ESPECIALLY WEST HALF.
FRIDAY NIGHT THROUGH TUESDAY
LARGE UPPER LOW BETWEEN THE PACNW AND NRN GREAT BASIN WILL BE THE
MAIN WEATHER FEATURE THROUGH THE MEDIUM RANGE PERIOD. THE WEEKEND
WILL GENERALLY BE WARM AND DRY EXCEPT FOR POTENTIAL STORMS IN THE
NRN MTNS...FAR NORTH AND FAR EAST WHERE THE DRIER SW WINDS MEET THE
MORE MOIST SE FLOW. ON MEMORIAL DAY...A STRONGER SHORTWAVE IN THE SW
FLOW MAY PROVIDE AN INCREASED CHANCE OF THUNDERSTORMS. ON
TUESDAY...ANOTHER SHORTWAVE IN THE SW FLOW WILL LIKELY KEEP AN
INCREASED CHANCE OF CONVECTION WITH THE PEAK IN THE AFTERNOON AND
EARLY EVENING BUT THERE WILL LIKELY BE SOME SHOWERS AND POTENTIALLY
ISOLATED THUNDERSTORMS MONDAY NIGHT.
&&
.AVIATION.../00Z ISSUANCE/
VFR CONDITIONS WILL PREVAIL ACROSS THE
FORECAST AREA TONIGHT. ONE AREA TO WATCH COULD BE IN THE SOAP HOLE
BASIN AFTER 09Z...INCLUDING EITHER KBPI OR KPNA...AS THERE ARE
INDICATIONS THAT PATCHY FOG COULD FOR NEAR SUNRISE.
OTHERWISE...ISOLATED SHOWERS OR THUNDERSTORMS ARE POSSIBLE THIS
AFTERNOON FROM THE SOUTHERN BIG HORNS TO NEAR CASPER MOUNTAIN AND
ALSO ALONG AND NEAR THE GREEN...SALT...WIND RIVER AND ABSOROKA
MOUNTAINS TIL AROUND 03Z. LOCAL MVFR CONDITIONS WILL BE POSSIBLE
WITH THESE STORMS ALONG WITH GUSTY WINDS TO 25 KNOTS.
&&
.FIRE WEATHER...
UPPER LEVEL RIDGING HAS DRIED OUT AND WARMED UP THE FORECAST AREA
TODAY. THERE COULD STILL BE AN ISOLATED SHOWERS OR A THUNDERSTORM
OVER THE WESTERN HIGHER MOUNTAINS. THIS CONDITION WILL BE SHORT
LIVED HOWEVER AS ANOTHER STORM SYSTEM BRINGS A BETTER CHANCE FOR
THUNDERSTORMS IN THE NORTHWEST FIRE ZONES ON WEDNESDAY. THESE STORMS
WILL MOVE FROM SOUTH TO NORTH AND BE CAPABLE OF VERY GUSTY AND
ERRATIC WINDS. AMBIENT WINDS WILL LARGELY BE FROM THE SOUTH TO
SOUTHEAST ACROSS THE AREA.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...BRAUN
LONG TERM...SKRBAC
AVIATION...BRAUN
FIRE WEATHER...BRAUN
000
FXUS65 KRIW 211726
AFDRIW
AREA FORECAST DISCUSSION...RESENT
NATIONAL WEATHER SERVICE RIVERTON WY
1126 AM MDT TUE MAY 21 2013
.SHORT TERM...TUESDAY THROUGH THURSDAY NIGHT
RADAR IS STILL SHOWING A COUPLE OF AREAS OF SHOWERS ACROSS EASTERN
AND SOUTHERN PORTIONS OF THE COUNTY WARNING AREA ON THE OUTER EDGE
OF THE UPPER LEVEL LOW NOW SPINNING OVER SOUTH DAKOTA. A FEW SHOWERS
WILL LINGER ACROSS EASTERN AREAS EARLY THIS MORNING BUT A VAST
MAJORITY OF THE DAY LOOKS TO BE RAIN FREE WITH WARMER TEMPERATURES
THAN RECENT DAYS. THE DRIER WEATHER IS DUE TO A SHORTWAVE RIDGE THAT
WILL BE MOVING OVER THE AREA. THE AREA WILL NOT BE COMPLETELY DRY AS
THERE IS JUST ENOUGH INSTABILITY IN THE AIR FOR A COUPLE OF
AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS TO FIRE OVER THE
HIGHER ELEVATIONS OF THE MOUNTAINS WITH THE HIGH ELEVATION HEAT
SOURCE. ALMOST ALL AREAS SHOULD BE DRY FROM LATER TONIGHT INTO
WEDNESDAY MORNING.
THE WEATHER MAY GET A BIT MORE INTERESTING ON WEDNESDAY AFTERNOON
AND EVENING...ESPECIALLY EAST OF THE DIVIDE. FLOW LOOKS TO TURN MORE
SOUTHERLY BRINGING IN WARMER TEMPERATURES. AT THE SAME TIME...AN
APPROACHING SHORTWAVE WILL HELP TO DECREASE HEIGHTS AND DECREASE
INSTABILITY A BIT. EAST OF THE DIVIDE...LOW LEVEL FLOW LOOKS TO TURN
MORE SOUTHEASTERLY WHICH WILL DRIVE PRECIPITABLE WATER VALUES UP
FROM AROUND 0.35 TO AROUND 0.5 TO 0.6 INCHES ON WEDNESDAY AFTERNOON.
MODELS ALSO SHOW LIFTED INDICES TO AROUND MINUS 3 ACROSS MUCH OF
THE AREA WITH CAPE VALUES OVER 300 J/KG WITH THE HIGHEST VALUES IN
THE ABSAROKAS WITH THE UPSLOPE SOUTHEASTERLY FLOW. WITH SOME DECENT
DIRECTIONAL SHEAR AS WELL WITH SOUTHWEST WINDS AT 500
MILLIBARS...ANY THUNDERSTORMS THAT FIRE COULD BECOME STRONG WITH
GUSTY WINDS OR HAIL. THESE STORMS LOOK TO END WEDNESDAY EVENING WITH
LEFTOVER SHOWERS IN NORTHWESTERN WYOMING FOR LATER WEDNESDAY NIGHT.
COVERAGE OF SHOWERS AND THUNDERSTORMS WILL LIKELY BE LESS ON
THURSDAY AS MUCH OF THE COUNTY WARNING AREA WILL BE IN A DRY SLOT
WITH LOW PRESSURE OVER NORTHWESTERN WYOMING. ANY CONVECTION THAT DAY
WILL LIKELY BE CONFINED TO AREAS NORTH OF THE OWL CREEK RANGE AND
EAST OF THE BIG HORN RANGE. SOUTH TO SOUTHWEST FLOW WILL KEEP ABOVE
NORMAL TEMPERATURES ACROSS MOST OF THE STATE.
.LONG TERM...FRIDAY THROUGH TUESDAY
A SOUTHWEST FLOW WILL PREVAIL THROUGH THIS PERIOD THAT WILL BRING
CHANCES OF AFTERNOON AND EVENING THUNDERSTORMS TO PRIMARILY THE FAR
WEST AND NORTH WHILE A DRIER AIRMASS PREVAILS ACROSS SOUTHERN AND
CENTRAL WYOMING.
A SHORTWAVE WILL ROTATE NORTH ACROSS THE AREA EARLY FRIDAY
DOWNSTREAM OF UPPER LOW OVER THE NW U.S. THE GFS IS FASTER AND
FURTHER WEST WITH THIS SHORTWAVE...PUTTING IT OVER SW MONTANA 12Z
FRIDAY AND LIFTING IT INTO SOUTHERN CANADA BY 00Z SATURDAY. THE
ECMWF AND CANADIAN ARE SLOWER AND HAVE TRENDED FURTHER EAST WITH
THIS FEATURE...LIFTING IT ACROSS THE NW HALF OF WYOMING 12Z-18Z
FRIDAY. FORECAST WEIGHTED TOWARD THIS LATTER...SLOWER SCENARIO AND
MAINTAINS CHANCES OF THUNDERSTORMS ACROSS THE NORTH AND FAR WEST.
THE ASSOCIATED COLD FRONT WILL RESULT IN TEMPERATURES 5 TO 10
DEGREES COOLER THAN ON THURSDAY...ALONG WITH BREEZY TO WINDY
CONDITIONS BEHIND THE FRONT.
UPPER RIDGE STRENGTHENS OVER THE SOUTHERN AND CENTRAL PLAINS THROUGH
THE WEEKEND WITH REMNANTS OF UPPER LOW OVER THE NW U.S. LIFTING INTO
SW CANADA. SW FLOW WITH EMBEDDED WEAK SHORTWAVES WILL INTERACT WITH
MEAN SURFACE TROUGH ACROSS NORTHERN AND EASTERN WYOMING WITH HIGHER
DEWPOINTS TO THE NORTH AND EAST OF THIS BOUNDARY...PRIMARILY ALONG
AND NORTH OF A JACKSON-MEETEETSE-BUFFALO LINE. ISOLATED TO
SCATTERED AFTERNOON AND EVENING THUNDERSTORMS WILL FIRE OFF NEAR
THIS SURFACE BOUNDARY AND MOVE OFF TO THE NE WITH SHORTWAVES MOVING
THROUGH DURING MAX HEATING RESULTING IN BETTER ORGANIZATION...THOUGH
WE DO NOT HAVE MUCH CONFIDENCE IN ANY ONE MODEL`S TIMING WITH THESE
IMPULSES.
A WARMING TREND WILL OCCUR OVER THE WEEKEND WITH CENTRAL
BASINS SEEING MOSTLY 80S. A SLIGHT COOLING TREND WILL FOLLOW EARLY
NEXT WEEK THOUGH WE WILL REMAIN IN ABOVE NORMAL TERRITORY FOR THE
MOST PART.
&&
.AVIATION.../18Z ISSUANCE/
VFR CONDITIONS WILL PREVAIL OVER MOST OF THE AREA TODAY WITHT THE
EXCEPTION OF KBPI AND KPNA WHCICH WILL HAVE BOUTS WITH MVFR CIGS
OVER THE NEXT HOUR OR SO. OTHERWISE...ISOLATED SHOWERS OR A POSSIBLE
THUNDERSTORM ARE POSSIBLE THIS AFTERNOON FROM THE SOUTHERN BIG HORNS
TO NEAR CASPER MOUNTAIN AND ALSO ALONG AND NEAR THE
GREEN...SALT...WIND RIVER AND ABSOROKA MOUNTAINS FROM 20Z UNTIL 03Z.
LOCAL MVFR CONDITIONS WILL BE POSSIBLE IN STORMS ALONG WITH GUSTY
WINDS TO 25 KNOTS.
&&
.FIRE WEATHER...
A RIDGE BUILDING ACROSS THE AREA WILL BRING A WARMER AND DRIER DAY
TO THE AREA TODAY. THERE COULD STILL BE ISOLATED SHOWERS AND
THUNDERSTORMS BUT THESE SHOULD BE CONFINED TO THE HIGHER ELEVATIONS
OF THE MOUNTAINS. ANOTHER STORM SYSTEM WILL BRING A CHANCE OF
THUNDERSTORMS TO THE NORTHWEST FIRE ZONES ON WEDNESDAY WITH GUSTY
SOUTH TO SOUTHEAST WINDS ACROSS THE AREA.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HATTINGS
LONG TERM...AEM
AVIATION...BRAUN
FIRE WEATHER...HATTINGS
000
FXUS65 KRIW 211055
AFDRIW
AREA FORECAST DISCUSSION...RESENT
NATIONAL WEATHER SERVICE RIVERTON WY
328 AM MDT TUE MAY 21 2013
.SHORT TERM...TUESDAY THROUGH THURSDAY NIGHT
RADAR IS STILL SHOWING A COUPLE OF AREAS OF SHOWERS ACROSS EASTERN
AND SOUTHERN PORTIONS OF THE COUNTY WARNING AREA ON THE OUTER EDGE
OF THE UPPER LEVEL LOW NOW SPINNING OVER SOUTH DAKOTA. A FEW SHOWERS
WILL LINGER ACROSS EASTERN AREAS EARLY THIS MORNING BUT A VAST
MAJORITY OF THE DAY LOOKS TO BE RAIN FREE WITH WARMER TEMPERATURES
THAN RECENT DAYS. THE DRIER WEATHER IS DUE TO A SHORTWAVE RIDGE THAT
WILL BE MOVING OVER THE AREA. THE AREA WILL NOT BE COMPLETELY DRY AS
THERE IS JUST ENOUGH INSTABILITY IN THE AIR FOR A COUPLE OF
AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS TO FIRE OVER THE
HIGHER ELEVATIONS OF THE MOUNTAINS WITH THE HIGH ELEVATION HEAT
SOURCE. ALMOST ALL AREAS SHOULD BE DRY FROM LATER TONIGHT INTO
WEDNESDAY MORNING.
THE WEATHER MAY GET A BIT MORE INTERESTING ON WEDNESDAY AFTERNOON
AND EVENING...ESPECIALLY EAST OF THE DIVIDE. FLOW LOOKS TO TURN MORE
SOUTHERLY BRINGING IN WARMER TEMPERATURES. AT THE SAME TIME...AN
APPROACHING SHORTWAVE WILL HELP TO DECREASE HEIGHTS AND DECREASE
INSTABILITY A BIT. EAST OF THE DIVIDE...LOW LEVEL FLOW LOOKS TO TURN
MORE SOUTHEASTERLY WHICH WILL DRIVE PRECIPITABLE WATER VALUES UP
FROM AROUND 0.35 TO AROUND 0.5 TO 0.6 INCHES ON WEDNESDAY AFTERNOON.
MODELS ALSO SHOW LIFTED INDICES TO AROUND MINUS 3 ACROSS MUCH OF
THE AREA WITH CAPE VALUES OVER 300 J/KG WITH THE HIGHEST VALUES IN
THE ABSAROKAS WITH THE UPSLOPE SOUTHEASTERLY FLOW. WITH SOME DECENT
DIRECTIONAL SHEAR AS WELL WITH SOUTHWEST WINDS AT 500
MILLIBARS...ANY THUNDERSTORMS THAT FIRE COULD BECOME STRONG WITH
GUSTY WINDS OR HAIL. THESE STORMS LOOK TO END WEDNESDAY EVENING WITH
LEFTOVER SHOWERS IN NORTHWESTERN WYOMING FOR LATER WEDNESDAY NIGHT.
COVERAGE OF SHOWERS AND THUNDERSTORMS WILL LIKELY BE LESS ON
THURSDAY AS MUCH OF THE COUNTY WARNING AREA WILL BE IN A DRY SLOT
WITH LOW PRESSURE OVER NORTHWESTERN WYOMING. ANY CONVECTION THAT DAY
WILL LIKELY BE CONFINED TO AREAS NORTH OF THE OWL CREEK RANGE AND
EAST OF THE BIG HORN RANGE. SOUTH TO SOUTHWEST FLOW WILL KEEP ABOVE
NORMAL TEMPERATURES ACROSS MOST OF THE STATE.
.LONG TERM...FRIDAY THROUGH TUESDAY
A SOUTHWEST FLOW WILL PREVAIL THROUGH THIS PERIOD THAT WILL BRING
CHANCES OF AFTERNOON AND EVENING THUNDERSTORMS TO PRIMARILY THE FAR
WEST AND NORTH WHILE A DRIER AIRMASS PREVAILS ACROSS SOUTHERN AND
CENTRAL WYOMING.
A SHORTWAVE WILL ROTATE NORTH ACROSS THE AREA EARLY FRIDAY
DOWNSTREAM OF UPPER LOW OVER THE NW U.S. THE GFS IS FASTER AND
FURTHER WEST WITH THIS SHORTWAVE...PUTTING IT OVER SW MONTANA 12Z
FRIDAY AND LIFTING IT INTO SOUTHERN CANADA BY 00Z SATURDAY. THE
ECMWF AND CANADIAN ARE SLOWER AND HAVE TRENDED FURTHER EAST WITH
THIS FEATURE...LIFTING IT ACROSS THE NW HALF OF WYOMING 12Z-18Z
FRIDAY. FORECAST WEIGHTED TOWARD THIS LATTER...SLOWER SCENARIO AND
MAINTAINS CHANCES OF THUNDERSTORMS ACROSS THE NORTH AND FAR WEST.
THE ASSOCIATED COLD FRONT WILL RESULT IN TEMPERATURES 5 TO 10
DEGREES COOLER THAN ON THURSDAY...ALONG WITH BREEZY TO WINDY
CONDITIONS BEHIND THE FRONT.
UPPER RIDGE STRENGTHENS OVER THE SOUTHERN AND CENTRAL PLAINS THROUGH
THE WEEKEND WITH REMNANTS OF UPPER LOW OVER THE NW U.S. LIFTING INTO
SW CANADA. SW FLOW WITH EMBEDDED WEAK SHORTWAVES WILL INTERACT WITH
MEAN SURFACE TROUGH ACROSS NORTHERN AND EASTERN WYOMING WITH HIGHER
DEWPOINTS TO THE NORTH AND EAST OF THIS BOUNDARY...PRIMARILY ALONG
AND NORTH OF A JACKSON-MEETEETSE-BUFFALO LINE. ISOLATED TO
SCATTERED AFTERNOON AND EVENING THUNDERSTORMS WILL FIRE OFF NEAR
THIS SURFACE BOUNDARY AND MOVE OFF TO THE NE WITH SHORTWAVES MOVING
THROUGH DURING MAX HEATING RESULTING IN BETTER ORGANIZATION...THOUGH
WE DO NOT HAVE MUCH CONFIDENCE IN ANY ONE MODEL`S TIMING WITH THESE
IMPULSES.
A WARMING TREND WILL OCCUR OVER THE WEEKEND WITH CENTRAL
BASINS SEEING MOSTLY 80S. A SLIGHT COOLING TREND WILL FOLLOW EARLY
NEXT WEEK THOUGH WE WILL REMAIN IN ABOVE NORMAL TERRITORY FOR THE
MOST PART.
&&
.AVIATION.../12Z ISSUANCE/
VFR CONDITIONS WILL PREVAIL OVER THE AREA TODAY AND TONIGHT.
ISOLATED SHOWERS ARE POSSIBLE UNTIL 16Z FROM THE BIGHORN MOUNTAINS
SOUTH TO CASPER MOUNTAIN. ISOLATED SHOWERS AND THUNDERSTORMS WILL
OCCUR OVER AND NEAR THE WESTERN MOUNTAINS FROM 18Z UNTIL 03Z. LOCAL
MVFR CONDITIONS ARE POSSIBLE IN STORMS ALONG WITH GUSTY WIND TO 25
KNOTS.
&&
.FIRE WEATHER...
A RIDGE BUILDING ACROSS THE AREA WILL BRING A WARMER AND DRIER DAY
TO THE AREA TODAY. THERE COULD STILL BE ISOLATED SHOWERS AND
THUNDERSTORMS BUT THESE SHOULD BE CONFINED TO THE HIGHER ELEVATIONS
OF THE MOUNTAINS. ANOTHER STORM SYSTEM WILL BRING A CHANCE OF
THUNDERSTORMS TO THE NORTHWEST FIRE ZONES ON WEDNESDAY WITH GUSTY
SOUTH TO SOUTHEAST WINDS ACROSS THE AREA.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HATTINGS
LONG TERM...AEM
AVIATION...AR
FIRE WEATHER...HATTINGS
000
FXUS65 KRIW 211051 RRA
AFDRIW
AREA FORECAST DISCUSSION...RETRANSMITTED
NATIONAL WEATHER SERVICE RIVERTON WY
328 AM MDT TUE MAY 21 2013
.SHORT TERM...TUESDAY THROUGH THURSDAY NIGHT
RADAR IS STILL SHOWING A COUPLE OF AREAS OF SHOWERS ACROSS EASTERN
AND SOUTHERN PORTIONS OF THE COUNTY WARNING AREA ON THE OUTER EDGE
OF THE UPPER LEVEL LOW NOW SPINNING OVER SOUTH DAKOTA. A FEW SHOWERS
WILL LINGER ACROSS EASTERN AREAS EARLY THIS MORNING BUT A VAST
MAJORITY OF THE DAY LOOKS TO BE RAIN FREE WITH WARMER TEMPERATURES
THAN RECENT DAYS. THE DRIER WEATHER IS DUE TO A SHORTWAVE RIDGE THAT
WILL BE MOVING OVER THE AREA. THE AREA WILL NOT BE COMPLETELY DRY AS
THERE IS JUST ENOUGH INSTABILITY IN THE AIR FOR A COUPLE OF
AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS TO FIRE OVER THE
HIGHER ELEVATIONS OF THE MOUNTAINS WITH THE HIGH ELEVATION HEAT
SOURCE. ALMOST ALL AREAS SHOULD BE DRY FROM LATER TONIGHT INTO
WEDNESDAY MORNING.
THE WEATHER MAY GET A BIT MORE INTERESTING ON WEDNESDAY AFTERNOON
AND EVENING...ESPECIALLY EAST OF THE DIVIDE. FLOW LOOKS TO TURN MORE
SOUTHERLY BRINGING IN WARMER TEMPERATURES. AT THE SAME TIME...AN
APPROACHING SHORTWAVE WILL HELP TO DECREASE HEIGHTS AND DECREASE
INSTABILITY A BIT. EAST OF THE DIVIDE...LOW LEVEL FLOW LOOKS TO TURN
MORE SOUTHEASTERLY WHICH WILL DRIVE PRECIPITABLE WATER VALUES UP
FROM AROUND 0.35 TO AROUND 0.5 TO 0.6 INCHES ON WEDNESDAY AFTERNOON.
MODELS ALSO SHOW LIFTED INDICES TO AROUND MINUS 3 ACROSS MUCH OF
THE AREA WITH CAPE VALUES OVER 300 J/KG WITH THE HIGHEST VALUES IN
THE ABSAROKAS WITH THE UPSLOPE SOUTHEASTERLY FLOW. WITH SOME DECENT
DIRECTIONAL SHEAR AS WELL WITH SOUTHWEST WINDS AT 500
MILLIBARS...ANY THUNDERSTORMS THAT FIRE COULD BECOME STRONG WITH
GUSTY WINDS OR HAIL. THESE STORMS LOOK TO END WEDNESDAY EVENING WITH
LEFTOVER SHOWERS IN NORTHWESTERN WYOMING FOR LATER WEDNESDAY NIGHT.
COVERAGE OF SHOWERS AND THUNDERSTORMS WILL LIKELY BE LESS ON
THURSDAY AS MUCH OF THE COUNTY WARNING AREA WILL BE IN A DRY SLOT
WITH LOW PRESSURE OVER NORTHWESTERN WYOMING. ANY CONVECTION THAT DAY
WILL LIKELY BE CONFINED TO AREAS NORTH OF THE OWL CREEK RANGE AND
EAST OF THE BIG HORN RANGE. SOUTH TO SOUTHWEST FLOW WILL KEEP ABOVE
NORMAL TEMPERATURES ACROSS MOST OF THE STATE.
.LONG TERM...FRIDAY THROUGH TUESDAY
A SOUTHWEST FLOW WILL PREVAIL THROUGH THIS PERIOD THAT WILL BRING
CHANCES OF AFTERNOON AND EVENING THUNDERSTORMS TO PRIMARILY THE FAR
WEST AND NORTH WHILE A DRIER AIRMASS PREVAILS ACROSS SOUTHERN AND
CENTRAL WYOMING.
A SHORTWAVE WILL ROTATE NORTH ACROSS THE AREA EARLY FRIDAY
DOWNSTREAM OF UPPER LOW OVER THE NW U.S. THE GFS IS FASTER AND
FURTHER WEST WITH THIS SHORTWAVE...PUTTING IT OVER SW MONTANA 12Z
FRIDAY AND LIFTING IT INTO SOUTHERN CANADA BY 00Z SATURDAY. THE
ECMWF AND CANADIAN ARE SLOWER AND HAVE TRENDED FURTHER EAST WITH
THIS FEATURE...LIFTING IT ACROSS THE NW HALF OF WYOMING 12Z-18Z
FRIDAY. FORECAST WEIGHTED TOWARD THIS LATTER...SLOWER SCENARIO AND
MAINTAINS CHANCES OF THUNDERSTORMS ACROSS THE NORTH AND FAR WEST.
THE ASSOCIATED COLD FRONT WILL RESULT IN TEMPERATURES 5 TO 10
DEGREES COOLER THAN ON THURSDAY...ALONG WITH BREEZY TO WINDY
CONDITIONS BEHIND THE FRONT.
UPPER RIDGE STRENGTHENS OVER THE SOUTHERN AND CENTRAL PLAINS THROUGH
THE WEEKEND WITH REMNANTS OF UPPER LOW OVER THE NW U.S. LIFTING INTO
SW CANADA. SW FLOW WITH EMBEDDED WEAK SHORTWAVES WILL INTERACT WITH
MEAN SURFACE TROUGH ACROSS NORTHERN AND EASTERN WYOMING WITH HIGHER
DEWPOINTS TO THE NORTH AND EAST OF THIS BOUNDARY...PRIMARILY ALONG
AND NORTH OF A JACKSON-MEETEETSE-BUFFALO LINE. ISOLATED TO
SCATTERED AFTERNOON AND EVENING THUNDERSTORMS WILL FIRE OFF NEAR
THIS SURFACE BOUNDARY AND MOVE OFF TO THE NE WITH SHORTWAVES MOVING
THROUGH DURING MAX HEATING RESULTING IN BETTER ORGANIZATION...THOUGH
WE DO NOT HAVE MUCH CONFIDENCE IN ANY ONE MODEL`S TIMING WITH THESE
IMPULSES.
A WARMING TREND WILL OCCUR OVER THE WEEKEND WITH CENTRAL
BASINS SEEING MOSTLY 80S. A SLIGHT COOLING TREND WILL FOLLOW EARLY
NEXT WEEK THOUGH WE WILL REMAIN IN ABOVE NORMAL TERRITORY FOR THE
MOST PART.
&&
.AVIATION.../12Z ISSUANCE/
VFR CONDITIONS WILL PREVAIL OVER THE AREA TODAY AND TONIGHT.
ISOLATED SHOWERS ARE POSSIBLE UNTIL 16Z FROM THE BIGHORN MOUNTAINS
SOUTH TO CASPER MOUNTAIN. ISOLATED SHOWERS AND THUNDERSTORMS WILL
OCCUR OVER AND NEAR THE WESTERN MOUNTAINS FROM 18Z UNTIL 03Z. LOCAL
MVFR CONDITIONS ARE POSSIBLE IN STORMS ALONG WITH GUSTY WIND TO 25
KNOTS.
&&
.FIRE WEATHER...
A RIDGE BUILDING ACROSS THE AREA WILL BRING A WARMER AND DRIER DAY
TO THE AREA TODAY. THERE COULD STILL BE ISOLATED SHOWERS AND
THUNDERSTORMS BUT THESE SHOULD BE CONFINED TO THE HIGHER ELEVATIONS
OF THE MOUNTAINS. ANOTHER STORM SYSTEM WILL BRING A CHANCE OF
THUNDERSTORMS TO THE NORTHWEST FIRE ZONES ON WEDNESDAY WITH GUSTY
SOUTH TO SOUTHEAST WINDS ACROSS THE AREA.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HATTINGS
LONG TERM...AEM
AVIATION...AR
FIRE WEATHER...HATTINGS
000
FXUS65 KRIW 211028 RRA
AFDRIW
AREA FORECAST DISCUSSION...RETRANSMITTED
NATIONAL WEATHER SERVICE RIVERTON WY
328 AM MDT TUE MAY 21 2013
.SHORT TERM...TUESDAY THROUGH THURSDAY NIGHT
RADAR IS STILL SHOWING A COUPLE OF AREAS OF SHOWERS ACROSS EASTERN
AND SOUTHERN PORTIONS OF THE COUNTY WARNING AREA ON THE OUTER EDGE
OF THE UPPER LEVEL LOW NOW SPINNING OVER SOUTH DAKOTA. A FEW SHOWERS
WILL LINGER ACROSS EASTERN AREAS EARLY THIS MORNING BUT A VAST
MAJORITY OF THE DAY LOOKS TO BE RAIN FREE WITH WARMER TEMPERATURES
THAN RECENT DAYS. THE DRIER WEATHER IS DUE TO A SHORTWAVE RIDGE THAT
WILL BE MOVING OVER THE AREA. THE AREA WILL NOT BE COMPLETELY DRY AS
THERE IS JUST ENOUGH INSTABILITY IN THE AIR FOR A COUPLE OF
AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS TO FIRE OVER THE
HIGHER ELEVATIONS OF THE MOUNTAINS WITH THE HIGH ELEVATION HEAT
SOURCE. ALMOST ALL AREAS SHOULD BE DRY FROM LATER TONIGHT INTO
WEDNESDAY MORNING.
THE WEATHER MAY GET A BIT MORE INTERESTING ON WEDNESDAY AFTERNOON
AND EVENING...ESPECIALLY EAST OF THE DIVIDE. FLOW LOOKS TO TURN MORE
SOUTHERLY BRINGING IN WARMER TEMPERATURES. AT THE SAME TIME...AN
APPROACHING SHORTWAVE WILL HELP TO DECREASE HEIGHTS AND DECREASE
INSTABILITY A BIT. EAST OF THE DIVIDE...LOW LEVEL FLOW LOOKS TO TURN
MORE SOUTHEASTERLY WHICH WILL DRIVE PRECIPITABLE WATER VALUES UP
FROM AROUND 0.35 TO AROUND 0.5 TO 0.6 INCHES ON WEDNESDAY AFTERNOON.
MODELS ALSO SHOW LIFTED INDICES TO AROUND MINUS 3 ACROSS MUCH OF
THE AREA WITH CAPE VALUES OVER 300 J/KG WITH THE HIGHEST VALUES IN
THE ABSAROKAS WITH THE UPSLOPE SOUTHEASTERLY FLOW. WITH SOME DECENT
DIRECTIONAL SHEAR AS WELL WITH SOUTHWEST WINDS AT 500
MILLIBARS...ANY THUNDERSTORMS THAT FIRE COULD BECOME STRONG WITH
GUSTY WINDS OR HAIL. THESE STORMS LOOK TO END WEDNESDAY EVENING WITH
LEFTOVER SHOWERS IN NORTHWESTERN WYOMING FOR LATER WEDNESDAY NIGHT.
COVERAGE OF SHOWERS AND THUNDERSTORMS WILL LIKELY BE LESS ON
THURSDAY AS MUCH OF THE COUNTY WARNING AREA WILL BE IN A DRY SLOT
WITH LOW PRESSURE OVER NORTHWESTERN WYOMING. ANY CONVECTION THAT DAY
WILL LIKELY BE CONFINED TO AREAS NORTH OF THE OWL CREEK RANGE AND
EAST OF THE BIG HORN RANGE. SOUTH TO SOUTHWEST FLOW WILL KEEP ABOVE
NORMAL TEMPERATURES ACROSS MOST OF THE STATE.
.LONG TERM...FRIDAY THROUGH TUESDAY
A SOUTHWEST FLOW WILL PREVAIL THROUGH THIS PERIOD THAT WILL BRING
CHANCES OF AFTERNOON AND EVENING THUNDERSTORMS TO PRIMARILY THE FAR
WEST AND NORTH WHILE A DRIER AIRMASS PREVAILS ACROSS SOUTHERN AND
CENTRAL WYOMING.
A SHORTWAVE WILL ROTATE NORTH ACROSS THE AREA EARLY FRIDAY
DOWNSTREAM OF UPPER LOW OVER THE NW U.S. THE GFS IS FASTER AND
FURTHER WEST WITH THIS SHORTWAVE...PUTTING IT OVER SW MONTANA 12Z
FRIDAY AND LIFTING IT INTO SOUTHERN CANADA BY 00Z SATURDAY. THE
ECMWF AND CANADIAN ARE SLOWER AND HAVE TRENDED FURTHER EAST WITH
THIS FEATURE...LIFTING IT ACROSS THE NW HALF OF WYOMING 12Z-18Z
FRIDAY. FORECAST WEIGHTED TOWARD THIS LATTER...SLOWER SCENARIO AND
MAINTAINS CHANCES OF THUNDERSTORMS ACROSS THE NORTH AND FAR WEST.
THE ASSOCIATED COLD FRONT WILL RESULT IN TEMPERATURES 5 TO 10
DEGREES COOLER THAN ON THURSDAY...ALONG WITH BREEZY TO WINDY
CONDITIONS BEHIND THE FRONT.
UPPER RIDGE STRENGTHENS OVER THE SOUTHERN AND CENTRAL PLAINS THROUGH
THE WEEKEND WITH REMNANTS OF UPPER LOW OVER THE NW U.S. LIFTING INTO
SW CANADA. SW FLOW WITH EMBEDDED WEAK SHORTWAVES WILL INTERACT WITH
MEAN SURFACE TROUGH ACROSS NORTHERN AND EASTERN WYOMING WITH HIGHER
DEWPOINTS TO THE NORTH AND EAST OF THIS BOUNDARY...PRIMARILY ALONG
AND NORTH OF A JACKSON-MEETEETSE-BUFFALO LINE. ISOLATED TO
SCATTERED AFTERNOON AND EVENING THUNDERSTORMS WILL FIRE OFF NEAR
THIS SURFACE BOUNDARY AND MOVE OFF TO THE NE WITH SHORTWAVES MOVING
THROUGH DURING MAX HEATING RESULTING IN BETTER ORGANIZATION...THOUGH
WE DO NOT HAVE MUCH CONFIDENCE IN ANY ONE MODEL`S TIMING WITH THESE
IMPULSES.
A WARMING TREND WILL OCCUR OVER THE WEEKEND WITH CENTRAL
BASINS SEEING MOSTLY 80S. A SLIGHT COOLING TREND WILL FOLLOW EARLY
NEXT WEEK THOUGH WE WILL REMAIN IN ABOVE NORMAL TERRITORY FOR THE
MOST PART.
&&
.AVIATION.../12Z ISSUANCE/
VFR CONDITIONS WILL PREVAIL OVER THE AREA TODAY AND TONIGHT.
ISOLATED SHOWERS ARE POSSIBLE UNTIL 16Z FROM THE BIGHORN MOUNTAINS
SOUTH TO CASPER MOUNTAIN. ISOLATED SHOWERS AND THUNDERSTORMS WILL
OCCUR OVER AND NEAR THE WESTERN MOUNTAINS FROM 18Z UNTIL 03Z. LOCAL
MVFR CONDITIONS ARE POSSIBLE IN STORMS ALONG WITH GUSTY WIND TO 25
KNOTS.
&&
.FIRE WEATHER...
A RIDGE BUILDING ACROSS THE AREA WILL BRING A WARMER AND DRIER DAY
TO THE AREA TODAY. THERE COULD STILL BE ISOLATED SHOWERS AND
THUNDERSTORMS BUT THESE SHOULD BE CONFINED TO THE HIGHER ELEVATIONS
OF THE MOUNTAINS. ANOTHER STORM SYSTEM WILL BRING A CHANCE OF
THUNDERSTORMS TO THE NORTHWEST FIRE ZONES ON WEDNESDAY WITH GUSTY
SOUTH TO SOUTHEAST WINDS ACROSS THE AREA.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HATTINGS
LONG TERM...AEM
AVIATION...AR
FIRE WEATHER...HATTINGS
000
FXUS65 KRIW 210930 CCA
AFDRIW
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE RIVERTON WY
328 AM MDT TUE MAY 21 2013
.SHORT TERM...TUESDAY THROUGH THURSDAY NIGHT
RADAR IS STILL SHOWING A COUPLE OF AREAS OF SHOWERS ACROSS EASTERN
AND SOUTHERN PORTIONS OF THE COUNTY WARNING AREA ON THE OUTER EDGE
OF THE UPPER LEVEL LOW NOW SPINNING OVER SOUTH DAKOTA. A FEW SHOWERS
WILL LINGER ACROSS EASTERN AREAS EARLY THIS MORNING BUT A VAST
MAJORITY OF THE DAY LOOKS TO BE RAIN FREE WITH WARMER TEMPERATURES
THAN RECENT DAYS. THE DRIER WEATHER IS DUE TO A SHORTWAVE RIDGE THAT
WILL BE MOVING OVER THE AREA. THE AREA WILL NOT BE COMPLETELY DRY AS
THERE IS JUST ENOUGH INSTABILITY IN THE AIR FOR A COUPLE OF
AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS TO FIRE OVER THE
HIGHER ELEVATIONS OF THE MOUNTAINS WITH THE HIGH ELEVATION HEAT
SOURCE. ALMOST ALL AREAS SHOULD BE DRY FROM LATER TONIGHT INTO
WEDNESDAY MORNING.
THE WEATHER MAY GET A BIT MORE INTERESTING ON WEDNESDAY AFTERNOON
AND EVENING...ESPECIALLY EAST OF THE DIVIDE. FLOW LOOKS TO TURN MORE
SOUTHERLY BRINGING IN WARMER TEMPERATURES. AT THE SAME TIME...AN
APPROACHING SHORTWAVE WILL HELP TO DECREASE HEIGHTS AND DECREASE
INSTABILITY A BIT. EAST OF THE DIVIDE...LOW LEVEL FLOW LOOKS TO TURN
MORE SOUTHEASTERLY WHICH WILL DRIVE PRECIPITABLE WATER VALUES UP
FROM AROUND 0.35 TO AROUND 0.5 TO 0.6 INCHES ON WEDNESDAY AFTERNOON.
MODELS ALSO SHOW LIFTED INDICES TO AROUND MINUS 3 ACROSS MUCH OF
THE AREA WITH CAPE VALUES OVER 300 J/KG WITH THE HIGHEST VALUES IN
THE ABSAROKAS WITH THE UPSLOPE SOUTHEASTERLY FLOW. WITH SOME DECENT
DIRECTIONAL SHEAR AS WELL WITH SOUTHWEST WINDS AT 500
MILLIBARS...ANY THUNDERSTORMS THAT FIRE COULD BECOME STRONG WITH
GUSTY WINDS OR HAIL. THESE STORMS LOOK TO END WEDNESDAY EVENING WITH
LEFTOVER SHOWERS IN NORTHWESTERN WYOMING FOR LATER WEDNESDAY NIGHT.
COVERAGE OF SHOWERS AND THUNDERSTORMS WILL LIKELY BE LESS ON
THURSDAY AS MUCH OF THE COUNTY WARNING AREA WILL BE IN A DRY SLOT
WITH LOW PRESSURE OVER NORTHWESTERN WYOMING. ANY CONVECTION THAT DAY
WILL LIKELY BE CONFINED TO AREAS NORTH OF THE OWL CREEK RANGE AND
EAST OF THE BIG HORN RANGE. SOUTH TO SOUTHWEST FLOW WILL KEEP ABOVE
NORMAL TEMPERATURES ACROSS MOST OF THE STATE.
.LONG TERM...FRIDAY THROUGH TUESDAY
A SOUTHWEST FLOW WILL PREVAIL THROUGH THIS PERIOD THAT WILL BRING
CHANCES OF AFTERNOON AND EVENING THUNDERSTORMS TO PRIMARILY THE FAR
WEST AND NORTH WHILE A DRIER AIRMASS PREVAILS ACROSS SOUTHERN AND
CENTRAL WYOMING.
A SHORTWAVE WILL ROTATE NORTH ACROSS THE AREA EARLY FRIDAY
DOWNSTREAM OF UPPER LOW OVER THE NW U.S. THE GFS IS FASTER AND
FURTHER WEST WITH THIS SHORTWAVE...PUTTING IT OVER SW MONTANA 12Z
FRIDAY AND LIFTING IT INTO SOUTHERN CANADA BY 00Z SATURDAY. THE
ECMWF AND CANADIAN ARE SLOWER AND HAVE TRENDED FURTHER EAST WITH
THIS FEATURE...LIFTING IT ACROSS THE NW HALF OF WYOMING 12Z-18Z
FRIDAY. FORECAST WEIGHTED TOWARD THIS LATTER...SLOWER SCENARIO AND
MAINTAINS CHANCES OF THUNDERSTORMS ACROSS THE NORTH AND FAR WEST.
THE ASSOCIATED COLD FRONT WILL RESULT IN TEMPERATURES 5 TO 10
DEGREES COOLER THAN ON THURSDAY...ALONG WITH BREEZY TO WINDY
CONDITIONS BEHIND THE FRONT.
UPPER RIDGE STRENGTHENS OVER THE SOUTHERN AND CENTRAL PLAINS THROUGH
THE WEEKEND WITH REMNANTS OF UPPER LOW OVER THE NW U.S. LIFTING INTO
SW CANADA. SW FLOW WITH EMBEDDED WEAK SHORTWAVES WILL INTERACT WITH
MEAN SURFACE TROUGH ACROSS NORTHERN AND EASTERN WYOMING WITH HIGHER
DEWPOINTS TO THE NORTH AND EAST OF THIS BOUNDARY...PRIMARILY ALONG
AND NORTH OF A JACKSON-MEETEETSE-BUFFALO LINE. ISOLATED TO
SCATTERED AFTERNOON AND EVENING THUNDERSTORMS WILL FIRE OFF NEAR
THIS SURFACE BOUNDARY AND MOVE OFF TO THE NE WITH SHORTWAVES MOVING
THROUGH DURING MAX HEATING RESULTING IN BETTER ORGANIZATION...THOUGH
WE DO NOT HAVE MUCH CONFIDENCE IN ANY ONE MODEL`S TIMING WITH THESE
IMPULSES.
A WARMING TREND WILL OCCUR OVER THE WEEKEND WITH CENTRAL
BASINS SEEING MOSTLY 80S. A SLIGHT COOLING TREND WILL FOLLOW EARLY
NEXT WEEK THOUGH WE WILL REMAIN IN ABOVE NORMAL TERRITORY FOR THE
MOST PART.
&&
.AVIATION.../12Z ISSUANCE/
VFR CONDITIONS WILL PREVAIL OVER THE AREA TODAY AND TONIGHT.
ISOLATED SHOWERS ARE POSSIBLE UNTIL 16Z FROM THE BIGHORN MOUNTAINS
SOUTH TO CASPER MOUNTAIN. ISOLATED SHOWERS AND THUNDERSTORMS WILL
OCCUR OVER AND NEAR THE WESTERN MOUNTAINS FROM 18Z UNTIL 03Z. LOCAL
MVFR CONDITIONS ARE POSSIBLE IN STORMS ALONG WITH GUSTY WIND TO 25
KNOTS.
&&
.FIRE WEATHER...
A RIDGE BUILDING ACROSS THE AREA WILL BRING A WARMER AND DRIER DAY
TO THE AREA TODAY. THERE COULD STILL BE ISOLATED SHOWERS AND
THUNDERSTORMS BUT THESE SHOULD BE CONFINED TO THE HIGHER ELEVATIONS
OF THE MOUNTAINS. ANOTHER STORM SYSTEM WILL BRING A CHANCE OF
THUNDERSTORMS TO THE NORTHWEST FIRE ZONES ON WEDNESDAY WITH GUSTY
SOUTH TO SOUTHEAST WINDS ACROSS THE AREA.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HATTINGS
LONG TERM...AEM
AVIATION...AR
FIRE WEATHER...HATTINGS
000
FXUS65 KRIW 210925
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
325 AM MDT TUE MAY 21 2013
.SHORT TERM...TUESDAY THROUGH THURSDAY NIGHT
RADAR IS STILL SHOWING A COUPLE OF AREAS OF SHOWERS ACROSS EASTERN
AND SOUTHERN PORTIONS OF THE COUNTY WARNING AREA ON THE OUTER EDGE
OF THE UPPER LEVEL LOW NOW SPINNING OVER SOUTH DAKOTA. A FEW SHOWERS
WILL LINGER ACROSS EASTERN AREAS EARLY THIS MORNING BUT A VAST
MAJORITY OF THE DAY LOOKS TO BE RAIN FREE WITH WARMER TEMPERATURES
THAN RECENT DAYS. THE DRIER WEATHER IS DUE TO A SHORTWAVE RIDGE THAT
WILL BE MOVING OVER THE AREA. THE AREA WILL NOT BE COMPLETELY DRY AS
THERE IS JUST ENOUGH INSTABILITY IN THE AIR FOR A COUPLE OF
AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS TO FIRE OVER THE
HIGHER ELEVATIONS OF THE MOUNTAINS WITH THE HIGH ELEVATION HEAT
SOURCE. ALMOST ALL AREAS SHOULD BE DRY FROM LATER TONIGHT INTO
WEDNESDAY MORNING.
THE WEATHER MAY GET A BIT MORE INTERESTING ON WEDNESDAY AFTERNOON
AND EVENING...ESPECIALLY EAST OF THE DIVIDE. FLOW LOOKS TO TURN MORE
SOUTHERLY BRINGING IN WARMER TEMPERATURES. AT THE SAME TIME...AN
APPROACHING SHORTWAVE WILL HELP TO DECREASE HEIGHTS AND DECREASE
INSTABILITY A BIT. EAST OF THE DIVIDE...LOW LEVEL LOW LOOKS TO TURN
MORE SOUTHEASTERLY WHICH WILL DRIVE PRECIPITABLE WATER VALUES UP
FROM AROUND 0.35 TO AROUND 0.5 TO 0.6 INCHES ON WEDNESDAY AFTERNOON.
MODELS ALSO SHOW LIFTED INDICES TO AROUND MINUS 3 ACROSS MUCH OF
THE AREA WITH CAPE VALUES OVER 300 J/KG WITH THE HIGHEST VALUES IN
THE ABSAROKAS WITH THE UPSLOPE SOUTHEASTERLY FLOW. WITH SOME DECENT
DIRECTIONAL SHEAR AS WELL WITH SOUTHWEST WINDS AT 500
MILLIBARS...ANY THUNDERSTORMS THAT FIRE COULD BECOME STRONG WITH
GUSTY WINDS OR HAIL. THESE STORMS LOOK TO END WEDNESDAY EVENING WITH
LEFTOVER SHOWERS IN NORTHWESTERN WYOMING FOR LATER WEDNESDAY NIGHT.
COVERAGE OF SHOWERS AND THUNDERSTORMS WILL LIKELY BE LESS ON
THURSDAY AS MUCH OF THE COUNTY WARNING AREA WILL BE IN A DRY SLOT
WITH LOW PRESSURE OVER NORTHWESTERN WYOMING. ANY CONVECTION THAT DAY
WILL LIKELY BE CONFINED TO AREAS NORTH OF THE OWL CREEK RANGE AND
EAST OF THE BIG HORN RANGE. SOUTH TO SOUTHWEST FLOW WILL KEEP ABOVE
NORMAL TEMPERATURES ACROSS MOST OF THE STATE.
.LONG TERM...XXX THROUGH XXX
A SOUTHWEST FLOW WILL PREVAIL THROUGH THIS PERIOD THAT WILL BRING
CHANCES OF AFTERNOON AND EVENING THUNDERSTORMS TO PRIMARILY THE FAR
WEST AND NORTH WHILE A DRIER AIRMASS PREVAILS ACROSS SOUTHERN AND
CENTRAL WYOMING.
A SHORTWAVE WILL ROTATE NORTH ACROSS THE AREA EARLY FRIDAY
DOWNSTREAM OF UPPER LOW OVER THE NW U.S. THE GFS IS FASTER AND
FURTHER WEST WITH THIS SHORTWAVE...PUTTING IT OVER SW MONTANA 12Z
FRIDAY AND LIFTING IT INTO SOUTHERN CANADA BY 00Z SATURDAY. THE
ECMWF AND CANADIAN ARE SLOWER AND HAVE TRENDED FURTHER EAST WITH
THIS FEATURE...LIFTING IT ACROSS THE NW HALF OF WYOMING 12Z-18Z
FRIDAY. FORECAST WEIGHTED TOWARD THIS LATTER...SLOWER SCENARIO AND
MAINTAINS CHANCES OF THUNDERSTORMS ACROSS THE NORTH AND FAR WEST.
THE ASSOCIATED COLD FRONT WILL RESULT IN TEMPERATURES 5 TO 10
DEGREES COOLER THAN ON THURSDAY...ALONG WITH BREEZY TO WINDY
CONDITIONS BEHIND THE FRONT.
UPPER RIDGE STRENGTHENS OVER THE SOUTHERN AND CENTRAL PLAINS THROUGH
THE WEEKEND WITH REMNANTS OF UPPER LOW OVER THE NW U.S. LIFTING INTO
SW CANADA. SW FLOW WITH EMBEDDED WEAK SHORTWAVES WILL INTERACT WITH
MEAN SURFACE TROUGH ACROSS NORTHERN AND EASTERN WYOMING WITH HIGHER
DEWPOINTS TO THE NORTH AND EAST OF THIS BOUNDARY...PRIMARILY ALONG
AND NORTH OF A JACKSON-MEETEETSE-BUFFALO LINE. ISOLATED TO
SCATTERED AFTERNOON AND EVENING THUNDERSTORMS WILL FIRE OFF NEAR
THIS SURFACE BOUNDARY AND MOVE OFF TO THE NE WITH SHORTWAVES MOVING
THROUGH DURING MAX HEATING RESULTING IN BETTER ORGANIZATION...THOUGH
WE DO NOT HAVE MUCH CONFIDENCE IN ANY ONE MODEL`S TIMING WITH THESE
IMPULSES.
A WARMING TREND WILL OCCUR OVER THE WEEKEND WITH CENTRAL
BASINS SEEING MOSTLY 80S. A SLIGHT COOLING TREND WILL FOLLOW EARLY
NEXT WEEK THOUGH WE WILL REMAIN IN ABOVE NORMAL TERRITORY FOR THE
MOST PART.
&&
.AVIATION.../12Z ISSUANCE/
VFR CONDITIONS WILL PREVAIL OVER THE AREA TODAY AND TONIGHT.
ISOLATED SHOWERS ARE POSSIBLE UNTIL 16Z FROM THE BIGHORN MOUNTAINS
SOUTH TO CASPER MOUNTAIN. ISOLATED SHOWERS AND THUNDERSTORMS WILL
OCCUR OVER AND NEAR THE WESTERN MOUNTAINS FROM 18Z UNTIL 03Z. LOCAL
MVFR CONDITIONS ARE POSSIBLE IN STORMS ALONG WITH GUSTY WIND TO 25
KNOTS.
&&
.FIRE WEATHER...
A RIDGE BUILDING ACROSS THE AREA WILL BRING A WARMER AND DRIER DAY
TO THE AREA TODAY. THERE COULD STILL BE ISOLATED SHOWERS AND
THUNDERSTORMS BUT THESE SHOULD BE CONFINED TO THE HIGHER ELEVATIONS
OF THE MOUNTAINS. ANOTHER STORM SYSTEM WILL BRING A CHANCE OF
THUNDERSTORMS TO THE NORTHWEST FIRE ZONES ON WEDNESDAY WITH GUSTY
SOUTH TO SOUTHEAST WINDS ACROSS THE AREA.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HATTINGS
LONG TERM...AEM
AVIATION...AR
FIRE WEATHER...HATTINGS
000
FXUS65 KRIW 210525
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1125 PM MDT MON MAY 20 2013
.SHORT TERM...TONIGHT THROUGH TUESDAY (ISSUED AT 309 MDT)
TODAY...LARGE STUCK...STACKED...CLOSED LOW OVER THE DAKOTAS
TODAY...NOT GOING ANYWHERE IN A HURRY. THIS WAVE WILL BEGIN TO OPEN
AND MOVE TUESDAY AS ANOTHER LARGE ALASKAN SYSTEM PLUNGES INTO THE
PAC NW BY TUESDAY NIGHT. IN THE MEANTIME...LOW CLOUDS...SCATTERED
RAIN AND SNOW SHOWERS (ABOVE 8500 FT) WHILE SFC LOW DEVELOPS OVER
WRN CWA AND COLD AIR CONTINUES TO POUR IN ALOFT. MAIN THREAT TODAY
WILL BE STRONG WINDS AROUND MOST THE EASTERN CWA WITH NICE LOW LEVEL
PRESSURE GRADIENT SET UP THIS THIS MORNING...TOGETHER WITH VIGOROUS
NEARLY UNIDIRECTIONAL FLOW ALOFT...GIVING NEAR HIGH WIND CATEGORY FOR
ELEVATIONS ABOVE 7000 FT IN THE OWL CREEK...BRIDGER...AND BIG HORN
MOUNTAINS. SUSTAINED NORTHERLY WINDS OF 40 TO 45 MPH ARE COMMON WITH
OCCASIONAL GUSTS TO 60 MPH ACROSS ELEVATED AREAS. THESE WILL PERSIST
THROUGH AT LEAST LATE AFTERNOON BEFORE QUIETING DOWN EAST OF THE
DIVIDE WITH THE RELAXATION OF THE LL PRESSURE GRADIENT. ACROSS THE
SOUTHERN BIG HORN BASIN AND OWL CREEK/BRIDGER MOUNTAINS...THE STRONG
WIND WILL LIKELY PERSIST A LITTLE LONGER INTO THE EVENING.
SECONDARY THREAT WILL A MORE PERSISTENT PRECIPITATION SHIELD OVER
THE BIG HORN MOUNTAINS AND PORTIONS OF ADJACENT EASTERN COUNTIES
INCLUDING JOHNSON AND NATRONA...AND SECONDLY ALONG AND NEAR THE WIND
RIVER AND ABSAROKA MOUNTAINS...PARTICULARLY THE MOUNTAINS THAT HAVE
GOOD NORTHERN EXPOSURE AND WILL TAKE ADVANTAGE OF THE UPSLOPE ALONG
WITH THE REGION SOUTH OF THE WIND RIVER MOUNTAINS WHERE LL
CONVERGENCE AND MODERATE MID AND UPPER LAPSE RATES WILL BE MAXIMIZED.
TONIGHT AND TUESDAY...PRECIP CHANCES WILL BEGIN TO WANE COMPARED TO
THE LAST FEW DAYS AND THE STRONGER WINDS WILL SUBSIDE AS THE CLOSED
LOW TO OUT EAST STARTS TO OPEN AND SLOWLY MIGRATE EASTWARD AND
SURFACE HIGH PRESSURE ALSO BEGINS TO DEVELOP OVER OUR HEADS. WE
WILL THEN GET SOME NEEDED MILD RIDGING BUILDING IN AHEAD OF THE NEXT
BIG SYSTEM...CURRENTLY LOCATED IN THE ALASKAN/SRN YUKON AREA IN WV
IMAGERY. DRYING...WARMING OF 5 TO 8 DEG OVER TODAY...AND MORE IN THE
WAY OF SUNSHINE WILL BE THE NAME OF THE GAME TOMORROW. THERE WILL BE
SOME MILD THERMAL INSTABILITY WITH INCREASING LAPSE RATES BUT
WORKING POTENTIAL ENERGY THROUGH THE DAY WILL BE MISSING AS
COMBINATION OF OVERALL DRYING AND UPPER LEVEL SHEAR DYNAMICS ON THE
WEAK SIDE (SUBSTENANCE THE GENERAL RULE)...ONLY ISOLATED ELEVATED
CONVECTION OCCURRING OVER THE HIGHEST AREAS OF THE WIND
RIVER...ABSAROKAS AND BIG HORN MOUNTAINS WILL BE POSSIBLE.
.LONG TERM...TUESDAY NIGHT THROUGH THURSDAY
CONVECTION WILL LINGER OVER THE FAR WEST MOUNTAINS INTO TUESDAY
EVENING AS A WEAK SHORTWAVE RIPPLES NE ACROSS THE AREA. A
POTENTIALLY MORE INTERESTING SCENARIO SETS UP ON WEDNESDAY OVER
MAINLY THE NW THIRD OR SO. A SURFACE HIGH DEVELOPS BEHIND OUR UPPER
LOW AND PUSHES A GENTLE BOUNDARY SOUTH AND THEN WWD ACROSS AREAS
EAST OF THE DIVIDE TUESDAY NIGHT. A DRIER S TO SW FLOW OVER THE SRN
THIRD WILL PUSH NWD DURING THE DAY ALONG WITH A POTENTIAL WEAK
SHORTWAVE COMING UP FROM THE SSW. LOWERING PRESSURES OVER THE NRN
GREAT BASIN WILL ALSO HELP TO DRAW SOME OF THIS MOISTURE WWD. THE NW
MTNS WILL BE THE MOST FAVORED FOR STRONGER CONVECTION BUT WITH THE
SW STEERING FLOW ALOFT SOME STORMS MAY FORM OVER THE MTNS AND DRIFT
NE ACROSS THE FOOTHILLS AND POTENTIALLY PARTS OF THE CENTRAL BASINS
LATE IN THE DAY WEDNESDAY. INDICATED SOME HAIL AND GUSTY WIND
WORDING IN THE STORMS FOR THIS AREA FROM ABOUT LANDER AND RIVERTON
NORTH TO CODY AND THEN WWD THROUGH THE NW MTNS. ON THURSDAY...THE
DRIER AIR WILL LIKELY MIX OUT FURTHER NORTH WITH THE
BOUNDARY/CONVERGENCE RETREATING TO THE FAR NRN AND NERN SECTIONS
WHERE A FEW STRONGER STORMS MAY STILL FIRE. TEMPERATURES WILL BE
WARMING AS THIS WARMER...DRIER AIR MOVES NWD WEDNESDAY INTO THURSDAY.
THURSDAY NIGHT THROUGH MONDAY
A STRONGER SHORTWAVE IS EXPECTED TO ROTATE AROUND OUR LARGE PACNW
AND NRN GREAT BASIN UPPER LOW THURSDAY NIGHT WHICH WILL PUSH A COOL
FRONT MUCH OF THE AREA WITH THE BIGGEST COOL DOWN FRIDAY IN THE
CENTRAL AND WRN ZONES. STILL MILD BUT NOT AS WARM AS THURSDAY.
ISOLATED THUNDERSTORMS MAY STILL FIRE ACROSS THE FAR NORTH WHERE
TROUGH DYNAMICS AND DAYTIME HEATING CREATE ENOUGH INSTABILITY AND
LIFT. THURSDAY NIGHT WILL BE A MILD NIGHT AS THIS BOUNDARY LIFTS
NORTH AND A GUSTY SOUTH TO SOUTHWEST WIND BLOWS IN MANY AREAS
OVERNIGHT. MODELS ARE KEEPING A FAIRLY DRY AIRMASS OVER THE AREA ON
SATURDAY BUT WITH MOIST GROUND AND DAYTIME HEATING WILL KEEP
ISOLATED THUNDERSTORMS GOING ACROSS THE NORTH THIRD TO HALF. ON
SUNDAY...THE UPPER LOW REDEVELOPS FURTHER SOUTH INTO THE GREAT BASIN
AGAIN AS A STRONG SHORTWAVE DROPS SE BEHIND THE OLD LOW. STRONG
DYNAMICS WILL LIKELY ROTATE NW ACROSS THE AREA ON SUNDAY WITH AN
INCREASING CHANCE OF THUNDERSTORMS. A VERY MOIST AIRMASS WILL BE
JUST TO THE EAST OF US LATE IN THE WEEKEND AND IF SOME OF THIS GETS
DRAWN JUST A LITTLE FURTHER WWD...SOME STRONG STORMS MAY FIRE IN THE
ERN ZONES. OUT WEST...THERE WILL BE LESS MOISTURE BUT STRONGER
DYNAMICS FROM THE SHORTWAVE ROTATING NWD ACROSS THE WEST. WILL
INDICATE SCATTERED THUNDERSTORMS OVER THE ABSAROKAS WITH ISOLATED
STORMS ACROSS MOST OF THE NW AND NERN ZONES. PLENTY OF SHORTWAVES IN
THE SW FLOW ON MEMORIAL DAY WITH THE POTENTIAL FOR THUNDERSTORMS
CONTINUING ACROSS AT LEAST THE NRN MOUNTAINS AND POTENTIALLY
ELSEWHERE EVEN THOUGH THE MODELS ARE SHOWING STORMS MAINLY CONFINED
TO THE NRN MOUNTAINS. EACH DAY WILL HAVE TO BE WATCHED CLOSELY AS
WITH MOIST GROUND AND DAY TIME HEATING WILL LIKELY CREATE MORE
INSTABILITY THAN THE MODELS ARE SHOWING RIGHT NOW.
&&
.AVIATION.../06Z ISSUANCE/
ISOLATED SHOWERS WILL END BY 12Z IN MOST PLACES. HOWEVER...ISOLATED
SHOWERS ARE POSSIBLE UNTIL 16Z FROM THE BIGHORN MOUNTAINS SOUTH TO
CASPER MOUNTAIN. OTHERWISE VFR CONDITIONS WILL PREVAIL UNTIL 06Z
WED. ISOLATED SHOWERS AND THUNDERSTORMS WILL OCCUR OVER AND NEAR THE
WESTERN MOUNTAINS FROM 18Z UNTIL 03Z. LOCAL MVFR CONDITIONS ARE
POSSIBLE IN STORMS ALONG WITH GUSTY WIND TO 25 KNOTS.
&&
.FIRE WEATHER...
THE BACK END OF A COOL AND WET STORM SYSTEM WILL CONTINUE TO IMPACT
THE AREA THROUGH THIS EVENING BEFORE IMPROVING CONDITIONS RETURN
TONIGHT AND THROUGH TUESDAY. ISOLATED SHOWERS WEST OF THE DIVIDE
MOST AREAS WILL PRODUCE OFF AND ON LIGHT RAIN WITH HIGH ELEVATION
SNOW (ABOVE 8500 FT) THROUGH THIS EVENING ALONG WITH PERIODS OF
GUSTY NORTH TO NORTHWEST WINDS RUNNING 30 TO 40 MPH ABOVE 7000 FT.
ANOTHER STORM SYSTEM WILL BRING A CHANCE OF THUNDERSTORMS TO THE
NORTHWEST FIRE ZONES ON WEDNESDAY WITH GUSTY SOUTH TO SOUTHEAST
WINDS ACROSS THE AREA.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...BRAUN
LONG TERM...SKRBAC
AVIATION...AR
FIRE WEATHER...BRAUN
000
FXUS65 KRIW 202109
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
309 PM MDT MON MAY 20 2013
.SHORT TERM...TONIGHT THROUGH TUESDAY
TODAY...LARGE STUCK...STACKED...CLOSED LOW OVER THE DAKOTAS
TODAY...NOT GOING ANYWHERE IN A HURRY. THIS WAVE WILL BEGIN TO OPEN
AND MOVE TUESDAY AS ANOTHER LARGE ALASKAN SYSTEM PLUNGES INTO THE
PAC NW BY TUESDAY NIGHT. IN THE MEANTIME...LOW CLOUDS...SCATTERED
RAIN AND SNOW SHOWERS (ABOVE 8500 FT) WHILE SFC LOW DEVELOPS OVER
WRN CWA AND COLD AIR CONTINUES TO POUR IN ALOFT. MAIN THREAT TODAY
WILL BE STRONG WINDS AROUND MOST THE EASTERN CWA WITH NICE LOW LEVEL
PRESSURE GRADIENT SET UP THIS THIS MORNING...TOGETHER WITH VIGOROUS
NEARLY UNIDIRECTIONAL FLOW ALOFT...GIVING NEAR HIGH WIND CATEGORY FOR
ELEVATIONS ABOVE 7000 FT IN THE OWL CREEK...BRIDGER...AND BIG HORN
MOUNTAINS. SUSTAINED NORTHERLY WINDS OF 40 TO 45 MPH ARE COMMON WITH
OCCASIONAL GUSTS TO 60 MPH ACROSS ELEVATED AREAS. THESE WILL PERSIST
THROUGH AT LEAST LATE AFTERNOON BEFORE QUIETING DOWN EAST OF THE
DIVIDE WITH THE RELAXATION OF THE LL PRESSURE GRADIENT. ACROSS THE
SOUTHERN BIG HORN BASIN AND OWL CREEK/BRIDGER MOUNTAINS...THE STRONG
WIND WILL LIKELY PERSIST A LITTLE LONGER INTO THE EVENING.
SECONDARY THREAT WILL A MORE PERSISTENT PRECIPITATION SHIELD OVER
THE BIG HORN MOUNTAINS AND PORTIONS OF ADJACENT EASTERN COUNTIES
INCLUDING JOHNSON AND NATRONA...AND SECONDLY ALONG AND NEAR THE WIND
RIVER AND ABSORKA MOUNTAINS...PARTICULARLY THE MOUNTAINS THAT HAVE
GOOD NORTHERN EXPOSURE AND WILL TAKE ADVANTAGE OF THE UPSLOPE ALONG
WITH THE REGION SOUTH OF THE WIND RIVER MOUNTAINS WHERE LL
CONVERGENCE AND MODERATE MID AND UPPER LAPSE RATES WILL BE MAXIMIZED.
TONIGHT AND TUESDAY...PRECIP CHANCES WILL BEGIN TO WANE COMPARED TO
THE LAST FEW DAYS AND THE STRONGER WINDS WILL SUBSIDE AS THE CLOSED
LOW TO OUT EAST STARTS TO OPEN AND SLOWLY MIGRATE EASTWARD AND
SURFACE HIGH PRESSURE ALSO BEGINS TO DEVELOP OVER OUR HEADS. WE
WILL THEN GET SOME NEEDED MILD RIDGING BUILDING IN AHEAD OF THE NEXT
BIG SYSTEM...CURRENTLY LOCATED IN THE ALASKAN/SRN YUKON AREA IN WV
IMAGERY. DRYING...WARMING OF 5 TO 8 DEG OVER TODAY...AND MORE IN THE
WAY OF SUNSHINE WILL BE THE NAME OF THE GAME TOMORROW. THERE WILL BE
SOME MILD THERMAL INSTABILITY WITH INCREASING LAPSE RATES BUT
WORKING POTENTIAL ENERGY THROUGH THE DAY WILL BE MISSING AS
COMBINATION OF OVERALL DRYING AND UPPER LEVEL SHEAR DYNAMICS ON THE
WEAK SIDE (SUBSTENANCE THE GENERAL RULE)...ONLY ISOLATED ELEVATED
CONVECTION OCCURRING OVER THE HIGHEST AREAS OF THE WIND
RIVER...ABSOROKAS AND BIG HORN MOUNTAINS WILL BE POSSIBLE.
.LONG TERM...TUESDAY NIGHT THROUGH THURSDAY
CONVECTION WILL LINGER OVER THE FAR WEST MOUNTAINS INTO TUESDAY
EVENING AS A WEAK SHORTWAVE RIPPLES NE ACROSS THE AREA. A
POTENTIALLY MORE INTERESTING SCENARIO SETS UP ON WEDNESDAY OVER
MAINLY THE NW THIRD OR SO. A SURFACE HIGH DEVELOPS BEHIND OUR UPPER
LOW AND PUSHES A GENTLE BOUNDARY SOUTH AND THEN WWD ACROSS AREAS
EAST OF THE DIVIDE TUESDAY NIGHT. A DRIER S TO SW FLOW OVER THE SRN
THIRD WILL PUSH NWD DURING THE DAY ALONG WITH A POTENTIAL WEAK
SHORTWAVE COMING UP FROM THE SSW. LOWERING PRESSURES OVER THE NRN
GREAT BASIN WILL ALSO HELP TO DRAW SOME OF THIS MOISTURE WWD. THE NW
MTNS WILL BE THE MOST FAVORED FOR STRONGER CONVECTION BUT WITH THE
SW STEERING FLOW ALOFT SOME STORMS MAY FORM OVER THE MTNS AND DRIFT
NE ACROSS THE FOOTHILLS AND POTENTIALLY PARTS OF THE CENTRAL BASINS
LATE IN THE DAY WEDNESDAY. INDICATED SOME HAIL AND GUSTY WIND
WORDING IN THE STORMS FOR THIS AREA FROM ABOUT LANDER AND RIVERTON
NORTH TO CODY AND THEN WWD THROUGH THE NW MTNS. ON THURSDAY...THE
DRIER AIR WILL LIKELY MIX OUT FURTHER NORTH WITH THE
BOUNDARY/CONVERGENCE RETREATING TO THE FAR NRN AND NERN SECTIONS
WHERE A FEW STRONGER STORMS MAY STILL FIRE. TEMPERATURES WILL BE
WARMING AS THIS WARMER...DRIER AIR MOVES NWD WEDNESDAY INTO THURSDAY.
THURSDAY NIGHT THROUGH MONDAY
A STRONGER SHORTWAVE IS EXPECTED TO ROTATE AROUND OUR LARGE PACNW
AND NRN GREAT BASIN UPPER LOW THURSDAY NIGHT WHICH WILL PUSH A COOL
FRONT MUCH OF THE AREA WITH THE BIGGEST COOL DOWN FRIDAY IN THE
CENTRAL AND WRN ZONES. STILL MILD BUT NOT AS WARM AS THURSDAY.
ISOLATED THUNDERSTORMS MAY STILL FIRE ACROSS THE FAR NORTH WHERE
TROUGH DYNAMICS AND DAYTIME HEATING CREATE ENOUGH INSTABILITY AND
LIFT. THURSDAY NIGHT WILL BE A MILD NIGHT AS THIS BOUNDARY LIFTS
NORTH AND A GUSTY SOUTH TO SOUTHWEST WIND BLOWS IN MANY AREAS
OVERNIGHT. MODELS ARE KEEPING A FAIRLY DRY AIRMASS OVER THE AREA ON
SATURDAY BUT WITH MOIST GROUND AND DAYTIME HEATING WILL KEEP
ISOLATED THUNDERSTORMS GOING ACROSS THE NORTH THIRD TO HALF. ON
SUNDAY...THE UPPER LOW REDEVELOPS FURTHER SOUTH INTO THE GREAT BASIN
AGAIN AS A STRONG SHORTWAVE DROPS SE BEHIND THE OLD LOW. STRONG
DYNAMICS WILL LIKELY ROTATE NW ACROSS THE AREA ON SUNDAY WITH AN
INCREASING CHANCE OF THUNDERSTORMS. A VERY MOIST AIRMASS WILL BE
JUST TO THE EAST OF US LATE IN THE WEEKEND AND IF SOME OF THIS GETS
DRAWN JUST A LITTLE FURTHER WWD...SOME STRONG STORMS MAY FIRE IN THE
ERN ZONES. OUT WEST...THERE WILL BE LESS MOISTURE BUT STRONGER
DYNAMICS FROM THE SHORTWAVE ROTATING NWD ACROSS THE WEST. WILL
INDICATE SCATTERED THUNDERSTORMS OVER THE ABSAROKAS WITH ISOLATED
STORMS ACROSS MOST OF THE NW AND NERN ZONES. PLENTY OF SHORTWAVES IN
THE SW FLOW ON MEMORIAL DAY WITH THE POTENTIAL FOR THUNDERSTORMS
CONTINUING ACROSS AT LEAST THE NRN MOUNTAINS AND POTENTIALLY
ELSEWHERE EVEN THOUGH THE MODELS ARE SHOWING STORMS MAINLY CONFINED
TO THE NRN MOUNTAINS. EACH DAY WILL HAVE TO BE WATCHED CLOSELY AS
WITH MOIST GROUND AND DAY TIME HEATING WILL LIKELY CREATE MORE
INSTABILITY THAN THE MODELS ARE SHOWING RIGHT NOW.
&&
.AVIATION.../00Z ISSUANCE/
ISOLATED TO SCATTERED LIGHT RAIN SHOWERS CONTINUES TODAY ACROSS MUCH
OF THE REGION THROUGH THE MID EVENING PERIODS...AND PERHAPS A TIL
AROUND 06Z NEAR KRKS. SHOWER CONDITIONS WILL KEEP MVFR CONDITIONS
AROUND AS WELL. GUSTY WIND WILL OCCUR AT MANY TERMINAL SITES
THROUGH THIS EVENING WITH THE WIND DECREASING MOST TERMINALS AFTER
03Z THIS EVENING. BEST AREA FOR WIND TODAY WILL OCCUR IN THE
CORRIDOR BETWEEN KRIV AND KWRL WITH GUSTS TO 60 KT POSSIBLE ABOVE
7000 FT MSL. VFR CONDITIONS WILL THEN PREVAIL AFTER 06Z TUE
ALTHOUGH ISOLATED SHOWERS BE A VERY SLIGHT POSSIBILITY OVER THE
HIGHEST ELEVATIONS ON TUESDAY.
&&
.FIRE WEATHER...
THE BACK END OF A COOL AND WET STORM SYSTEM WILL CONTINUE TO IMPACT
THE AREA THROUGH THIS EVENING BEFORE IMPROVING CONDITIONS RETURN
TONIGHT AND THROUGH TUESDAY. ISOLATED SHOWERS WEST OF THE DIVIDE
MOST AREAS WILL PRODUCE OFF AND ON LIGHT RAIN WITH HIGH ELEVATION
SNOW (ABOVE 8500 FT) THROUGH THIS EVENING ALONG WITH PERIODS OF
GUSTY NORTH TO NORTHWEST WINDS RUNNING 30 TO 40 MPH ABOVE 7000 FT.
ANOTHER STORM SYSTEM WILL BRING A CHANCE OF THUNDERSTORMS TO THE
NORTHWEST FIRE ZONES ON WEDNESDAY WITH GUSTY SOUTH TO SOUTHEAST
WINDS ACROSS THE AREA.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...BRAUN
LONG TERM...SKRBAC
AVIATION...BRAUN
FIRE WEATHER...BRAUN
000
FXUS65 KRIW 201727
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1127 AM MDT MON MAY 20 2013
.SHORT TERM...MONDAY THROUGH WEDNESDAY NIGHT
THE SOGGY PATTERN CONTINUES AT THIS TIME WITH AREAS OF RAIN MOVING
NORTH TO SOUTH ACROSS THE STATE WITH AN UPPER LEVEL LOW CONTINUING
TO SPIN OVER NEBRASKA AND HINTS OF AN UPPER LEVEL LOW DEVELOPING
OVER WESTERN SOUTH DAKOTA. AS FOR RAIN TODAY...SATELLITE IMAGERY
SHOWS SOME COOLING CLOUD TOPS OVER EASTERN MONTANA AND BILLINGS
RADAR SHOWING SOME MORE RAIN MOVING SOUTHWARD INTO SOUTHERN MONTANA.
AS A RESULT WE EXPECT ANOTHER DAY OF SHOWERS AND ISOLATED
THUNDERSTORMS. MODELS ARE SHOWING LESS QPF THAN YESTERDAY SO
RAINFALL AMOUNTS FOR THE MOST PART SHOULD BE LESS THAN YESTERDAY.
SOME CREEKS HAVE RISEN QUITE A BIT AND HAVE TO BE WATCHED BUT AT
THIS POINT SINCE THE RAIN HAS BEEN MORE STRATIFORM RATHER THAN
CONVECTIVE AT THE MOST I COULD SEE SMALL STREAM FLOOD ADVISORIES FOR
A FEW SPOTS. THERE WILL ALSO BE SOME SNOW OVER THE HIGHER ELEVATIONS
BUT SIMILAR TO YESTERDAY NO WINTER WEATHER HIGHLIGHTS SHOULD BE
NEEDED SINCE ROADS WILL BE MAINLY WET TO ONLY SLUSHY IN PLACES.
THERE IS ANOTHER DILEMMA WITH POSSIBLE STRONG WINDS. MODELS ARE
SHOWING STRONG 700 MILLIBAR WINDS WITH THE NAM HAVING 50 TO 55 KNOTS
ALOFT OVER NORTHERN JOHNSON COUNTY WITH FAVORED NORTHWEST FLOW. THE
GFS MOS IS SHOWING 40 KNOTS SUSTAINED AT BUFFALO ALTHOUGH THIS IS
NOTORIOUS FOR OVERDOING WIND. HOWEVER...THE BEST CONDITIONS ARE
USUALLY WITH A COLD FRONTAL PASSAGE AND THERE IS NONE. ALSO...THE
PRESSURE GRADIENT IS NOT THAT GREAT WITHOUT MUCH COLD ADVECTION. IF
IT OCCURRED IT WOULD BE WITH A HEAVIER SHOWER THAT COULD MIX THE
WINDS ALOFT DOWN TO THE SURFACE. AT THIS TIME...WE WILL GO WITH AN
SPS BUT THE DAY SHIFT WILL HAVE TO MONITOR IT CLOSELY.
PRECIPITATION SHOULD TAPER ON TONIGHT AS THE LOW MOVES AWAY TO THE
EAST. BY TUESDAY RIDGING WILL BUILD OVER THE AREA AND BRING A DRIER
AND WARMER DAY MOST OF THE AREA. THERE WILL STILL BE A FEW SHOWERS
AND THUNDERSTORMS AROUND IN THE AFTERNOON AND EVENING...MAINLY IN
THE MOUNTAINS WITH THE HIGH ELEVATION HEAT SOURCE.
THE WEATHER MAY TURN ACTIVE ONCE AGAIN WEDNESDAY AFTERNOON AND
EVENING AS THE RIDGE MOVES A BIT FURTHER TO THE EAST AND A SHORTWAVE
APPROACHES WESTERN WYOMING. WITH PLENTY OF RESIDUAL MOISTURE AROUND
WITH THE STILL MOIST GROUND WE HAVE KEPT AT LEAST SLIGHT POPS FOR
THE ENTIRE AREA WITH THE HIGHEST CHANCE ACROSS NORTHWESTERN WYOMING
FOR THAT DAY.
.LONG TERM...THURSDAY THROUGH MONDAY
A LARGE AND COMPLEX UPPER LOW CENTERED ACROSS THE PACIFIC NORTHWEST
FOR MUCH OF THE EXTENDED...WILL SEND MULTIPLE SHORTWAVE TROUGHS
ACROSS THE NORTHERN ROCKIES IN THE SOUTHWEST FLOW. PERIODIC COLD
FRONTS WITH THESE SYSTEMS WILL PUSH INTO WEST/NORTHWEST WYOMING
BEFORE QUICKLY RETREATING...MAKING A TOUGH CALL ON TEMPS ESPECIALLY
ACROSS THE EXTREME WEST AND NORTHWEST. GLOBAL MODELS STILL SHOW A
DRY AIR MASS ACROSS THE GREAT BASIN ADVECTING NORTHEAST INTO THE
AREA THURSDAY. THIS SHOULD REDUCE THE COVERAGE OF CONVECTION
TO...MAINLY ACROSS THE NORTH AND EXTREME EAST. INSTABILITY DOES NOT
LOOKS AS GOOD AS YESTERDAY...BUT COULD STILL SEE SOME VIGOROUS
STORMS THURSDAY. THE SAME SCENARIO REPEATS ITSELF THROUGH THE REST
OF THE EXTENDED...WITH PROBABLY SOME INTRUSIONS OF MOISTURE
ASSOCIATED WITH INDIVIDUAL SHORTWAVES ROTATING AROUND THE LARGE
COMPLEX UPPER LOW ACROSS THE NORTHWEST. HARD TO PINPOINT BEST TIMING
FOR POPS THIS FAR OUT WITH THESE QUICK MOVING SYSTEMS...AND HAVE
KEPT MAINLY SLIGHT POPS ONGOING MAINLY IN THE AFTERNOON AND EVENING
FOR THE NORTHWEST AND NORTH. LATER SHIFTS CAN ADJUST AS NEEDED AS
TIMING OF INDIVIDUAL SYSTEMS AND EXTENT OF THE DRY AIR MASS IN THE
SOUTHWEST FLOW BECOMES CLEARER.
&&
.AVIATION.../18Z ISSUANCE/
ISOLATED TO SCATTERED LIGHT RAIN SHOWERS CONTINUES TODAY ACROSS MUCH
OF THE REGION THROUGH THE MID EVEING PERIOS...AND PERHAPS A TIL
AROUND 06Z NEAR KRKS. SHOWER CONDITIONS WILL KEEP MVFR CONDITIONS
AROUND AS WELL. GUSTY WIND WILL OCCUR AT MANY TERMINAL
SITES THROUGH THIS EVENING WITH THE WIND DECREASING MOST TERMINALS
AFTER 03Z THIS EVENING. BEST AREA FOR WIND TODAY WILL OCCUR IN THE
CORRIDOR BETWEEN KRIV AND KWRL WITH GUSTS TO 60 KT POSSIBLE ABOVE
7000 FT MSL. VFR CONDITIONS WILL THEN PREVAIL AFTER 06Z TUE ALTHOUGH
ISOLATED SHOWERS BE A VERY SLIGHT POSSIBILITY OVER THE HIGHEST
ELEVATIONS ON TUESDAY.
&&
.FIRE WEATHER...
A COOL AND WET STORM SYSTEM WILL CONTINUE TO IMPACT THE AREA THROUGH
TODAY BEFORE IMPROVING CONDITIONS RETURN ON LATE TONIGHT AND
TUESDAY. MOST AREAS WILL SEE OFF AND ON RAIN WITH HIGHER ELEVATION
SNOW THROUGH MONDAY EVENING ALONG WITH PERIODS OF GUSTY NORTH TO
NORTHWEST WIND. ANOTHER STORM SYSTEM WILL BRING A CHANCE OF
THUNDERSTORMS TO THE NORTHWEST ON WEDNESDAY WITH GUSTY SOUTH TO
SOUTHEAST WINDS ACROSS THE AREA.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...HATTINGS
LONG TERM...WM
AVIATION...BRAUN
FIRE WEATHER...HATTINGS
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