000
FXUS65 KRIW 220537
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1137 PM MDT MON MAY 21 2012

.SHORT TERM...TONIGHT THROUGH THURSDAY
WARM...DRY DAY ACROSS THE AREA TODAY BUT THE MILD...BENIGN WEATHER
IS ABOUT TO COME TO AN END. A STRONG COLD FRONT WILL MOVE QUICKLY
FROM THE PACNW COAST INTO WESTERN WYOMING TUESDAY MORNING AND
SWEEP QUICKLY THROUGH THE AREA BY AFTERNOON. IT WILL BE DRY AND
WINDY ACROSS MOST OF THE SOUTH HALF WITH MORE WIDESPREAD SHOWERS
ACROSS THE NORTH...ESPECIALLY IN THE MOUNTAINS. SNOW LEVELS WILL
LOWER TUESDAY AND TUESDAY NIGHT...REACHING THE FOOTHILLS IN THE NW
AND POSSIBLY BRIEFLY ON THE VALLEY FLOOR LATE TUESDAY NIGHT. THE COLD
FRONT WILL STALL OUT IN NRN COLORADO OR FAR SRN WYOMING TUESDAY
NIGHT INTO WEDNESDAY WITH JET STREAK DYNAMICS OVERRUNNING THE
BOUNDARY PRODUCING SHOWERS ACROSS THE FAR SOUTH. CONTINUED THE
TREND OF INCREASING POPS IN THIS AREA BUT SOON WE MAY NEED LIKELY
POPS. THE NW WILL REMAIN QUITE UNSETTLED WEDNESDAY INTO THURSDAY
AS A SERIES OF SHORTWAVES CROSS THE AREA IN A MOIST...CYCLONIC SW
FLOW. LATER WEDNESDAY NIGHT INTO THURSDAY...THE BEGINNINGS OF OUR
GREAT BASIN LOW MAY START TO TAKE SHAPE AND BRING SOME UPSLOPE
INTO THE CODY FOOTHILLS. THE H7 TEMPERATURES ARE FORECAST TO BE AS
COLD AS -5C AT H7 AND IF THERE IS ENOUGH PRECIPITATION FALLING...
WE COULD SEE A BRIEF RAIN SNOW MIXTURE THURSDAY MORNING. THE NW
MOUNTAINS WILL CONTINUE TO SEE PERIODS OF COLD VALLEY RAIN AND AT
LEAST LIGHT MOUNTAIN SNOW.

.LONG TERM...THURSDAY NIGHT THROUGH MEMORIAL DAY

THE GFS AND THE ECMWF ARE MORE IN AGREEMENT NOW WITH AMPLIFYING THE
CUT OFF LOW OVER THE GREAT BASIN THURSDAY NIGHT AND FRIDAY ALONG
WITH BUILDING HEIGHTS ACROSS THE EAST HALF OF THE AREA AS WELL AS
BUILDING A SURFACE HIGH TO THE NORTH OF THE CWA. THIS WILL RESULT IN
A SIGNIFICANT UPSLOPE STRATIFORM PRECIPITATION EVENT...ESPECIALLY
FOR CENTRAL WYOMING EAST OF THE DIVIDE WITH SIGNIFICANT SNOW
ACCUMULATION EXPECTED IN THE SURROUNDING MOUNTAINS. SIGNIFICANT
SNOWFALL IS ALSO EXPECTED ACROSS THE NORTHERN AND WESTERN MOUNTAINS.
SOME WET SNOWFALL MAY ACTUALLY REACH THE VALLEY AND BASIN FLOORS IN
WESTERN AND NORTHERN WYOMING DURING THIS TIME FRAME. BY FRIDAY
EVENING THE WARM FRONT AND ACCOMPANYING DRY SLOT WILL PUSH MUCH OF
THE PRECIP NORTH OF THE AREA. HOWEVER...THE LOW OVER THE GREAT BASIN
WILL TRACK NORTHEAST TO NORTHWEST WYOMING SO COOL SHOWERY WEATHER
WITH SNOW SHOWERS IN THE MOUNTAINS WILL CONTINUE THROUGH THE WEEKEND
IN THE NORTH AND WEST...ESPECIALLY IN YELLOWSTONE PARK. A TRANSITORY
RIDGE WILL PROVIDE WARMER AND DRIER CONDITIONS FOR MEMORIAL DAY OVER
THE CWA.

.AVIATION.../06Z ISSUANCE/

ISOLATED SHOWERS WILL OCCUR IN THE NORTHWEST WY MOUNTAINS THROUGH
12Z. OTHERWISE DRY WITH VFR CONDITIONS THROUGH 12Z. EXPECT A WINDY
TUESDAY AT MOST TERMINAL SITES...INTO THIS EVENING...AS A COLD FRONT
AND WEATHER SYSTEM MOVES THROUGH WESTERN AND CENTRAL WY TUESDAY. THE
COLD FRONT WILL PUSH INTO WESTERN WY AROUND 15Z AND INTO NORTHERN WY
AFTER 21Z. THE FRONT WILL PUSH SOUTH THROUGH CENTRAL WY AFTER 00Z
WED. THE BEST CHANCE OF RAIN AND SNOW SHOWERS AND A FEW
THUNDERSTORMS WILL BE ACROSS THE WEST AND NORTH TUESDAY. ISOLATED
SHOWERS OR STORMS MAY OCCUR ALONG THE COLD FRONT AS IT MOVES THROUGH
CENTRAL WY AFTER 03Z WED. VFR CONDITIONS WILL PREVAIL OVER THE AREA
FROM 12Z TUE THROUGH 06Z WED. HOWEVER LOCAL MVFR CONDITIONS WILL
OCCUR OVER AND NEAR THE MOUNTAINS WITH SOME MOUNTAIN OBSCURATION AT
TIMES.

.FIRE WEATHER...

SLIGHT CHANCE OF A LIGHT SHOWER THROUGH THE EVENING IN THE
NORTHWEST WITH A STRAY LIGHTNING STRIKE POSSIBLE BUT NOT LIKELY.
STRONG COLD FRONT WILL MOVE WEST TO EAST ACROSS THE AREA STARTING
IN THE FAR WEST IN THE MORNING AND HITTING THE EASTERN ZONES IN
THE AFTERNOON WITH STRONG WEST WINDS. IT WILL BE VERY DRY ACROSS
THE SOUTH HALF WITH LOW MIN RH`S IN THE TEENS. SHOWERS WILL BE
MORE NUMEROUS ACROSS THE NORTH HALF WITH SOME SNOW ON THE HIGHER
PEAKS. ISOLATED THUNDERSTORMS ARE EXPECTED...MAINLY IN THE NORTHERN
ZONES. WEDNESDAY WILL BE MUCH COOLER EAST OF THE DIVIDE WITH SOME
SHOWERS ACROSS THE MOUNTAINS AND FAR SOUTH ALONG WITH A SLIGHT
CHANCE OF THUNDERSTORMS. HIGHER ELEVATION SNOW WILL CONTINUE IN
THE NORTHERN MOUNTAINS...ESPECIALLY IN THE NORTHWEST.

&&

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

&&

$$

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

000
FXUS65 KCYS 220455
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1055 PM MDT MON MAY 21 2012

.AVIATION...06Z TAF ISSUANCE...
VFR CONDITIONS CAN BE EXPECTED THROUGH THE PERIOD. HIGH CLOUDS
WILL BE ON THE INCREASE FROM WEST TO EAST AT AREA TERMINALS ON
TUESDAY. WEST/SOUTHWEST WINDS WILL BE ON THE INCREASE LATE TUESDAY
MORNING AND WILL CONTINUE THROUGH THE AFTERNOON. WIND GUSTS OF 25
TO 40 KNOTS CAN BE EXPECTED DURING THIS TIME. A COLD FRONT WILL
BEGIN TO PUSH SOUTH TUESDAY EVENING TURNING WINDS NORTHERLY AT
KCYS...KBFF...KCDR...KAIA AND KSNY. HAHN

&&

.PREV DISCUSSION... /ISSUED 446 PM MDT MON MAY 21 2012/

UPDATE...

AFTER COORDINATING WITH THE FUELS FOLKS IN THE PANHANDLE AND
CONVERSE/NIOBRARA COUNTIES THIS AFTERNOON...WENT AHEAD AND ADDED
THEM TO THE RED FLAG WARNINGS FOR TOMORROW...11 AM TO 7 PM.
UPDATES HAVE BEEN SENT.

PREV DISCUSSION... /ISSUED 332 PM MDT MON MAY 21 2012/

SHORT TERM...TONIGHT THROUGH WEDNESDAY...

CONVECTION EARLY THIS AFTERNOON WAS LOCATED MAINLY OVER THE SOUTHERN
PANHANDLE.  THE ACTIVITY WAS IN A SURFACE CONVERGENT AREA WITH
SURFACE DEW POINTS STILL NEAR 50F TO THE EAST OF THE BOUNDARY.
POTENTIAL FOR SOME STORMS TO BECOME STRONG YET THIS AFTERNOON OVER
THE SOUTHEAST CORNER OF THE CWA.  THOSE STORMS MAY PRODUCE SMALL
HAIL...MODERATE RAINFALL AND GUSTY WINDS THROUGH THE EARLY EVENING.
THE REST OF TONIGHT WILL BE QUIET AND MILD OVER THE CWA WITH SOME
CIRRUS APPROACHING FROM THE WEST.

THE RIDGE AXIS ALOFT MOVES EAST OF THE CWA BY 12Z TUESDAY WITH
INCREASING SOUTHWEST TO WEST WIND FLOW ALOFT OVER THE REGION.
SURFACE WINDS WILL GUST AS HIGH AS 50 MPH MAINLY IN AREAS ALONG
AND WEST OF THE LARAMIE RANGE ON TUESDAY. ALSO...THE 700 MB
THERMAL RIDGE WILL BE OVER THE CWA ON TUESDAY AND WILL PRODUCE
WELL ABOVE NORMAL TEMPERATURES. SOME CIRRUS WILL ALSO SPREAD OVER
MAINLY THE WEST AND NORTH PARTS OF THE CWA. FIRE WEATHER CONCERNS
WILL BE HEIGHTENED ON TUESDAY AFTERNOON DUE TO THE WARM...DRY AND
WINDY WEATHER.

A COLD FRONT MOVES ACROSS THE CWA TUESDAY EVENING AND WILL USHER IN
COOLER TEMPERATURES AND A BETTER CHANCE OF PRECIPITATION. BY
WEDNESDAY...HIGH TEMPERATURES WILL BE IN THE 50S AND 60S OVER THE
LOWER ELEVATIONS. THE BOUNDARY LAYER UPSLOPE WILL COMBINE WITH THE
300 MB JET OVER THE CWA TO PRODUCE A GOOD CHANCE OF SHOWERS AND
THUNDERSTORMS BY WEDNESDAY AFTERNOON. BUFKIT RAOBS SUGGEST UP TO A
THIRD OF AN INCH OF RAINFALL OVER PARTS OF THE CWA WEDNESDAY
AFTERNOON. LIGHT ACCUMULATIONS OF SNOW WILL ALSO BE POSSIBLE LATE
TUESDAY NIGHT AND WEDNESDAY ABOVE 9000 FEET MSL. FOR THE AFTERNOON
FORECAST HAVE INCREASED POPS AND CLOUD COVER FOR WEDNESDAY ACROSS
THE CWA.

LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...

GOOD CHANCE OF WIDESPREAD SHOWERS OVER THE SOUTHEASTERN PART OF
THE CWA ON WEDNESDAY NIGHT AS A MIDLEVEL TROUGH PASSES OVER THE
AREA. THE MODELS SHOW UPPER LEVEL JET SUPPORT ALONG WITH A LAYER
OF GOOD MIDLEVEL FRONTOGENESIS OVER MAINLY THE PANHANDLE THAT
WOULD ENHANCE PRECIP. A BROAD MIDLEVEL TROUGH WILL REMAIN DRAPED
OVER THE INTERMOUNTAIN WEST ON THURS WITH COOL 700MB TEMPS AROUND
-2C TO 0C. THE CWA WILL BE LOCATED IN THE LEFT EXIT REGION OF THE
WESTERLY UPPER LEVEL JET ACROSS NV-UT THROUGH THURS AFTN. THIS
SHOULD CONTINUE SCATTERED SHOWERS THROUGH THE DAY...HOWEVER NOT
EXPECTING ANY THUNDERSTORMS WITH LIMITED INSTABILITY IN A COOL
BOUNDARY LAYER. THE MODELS AGREE ON SHOWING A DEEP CLOSED LOW
DEVELOPING OVER NV ON FRI WITH INCREASING SOUTH-TO-SOUTHWESTERLY
MIDLEVEL FLOW OVER THE AREA. WITH SFC PRESSURE FALLS OVER THE
GREAT BASIN AND PRESSURE RISES OVER THE NORTHERN PLAINS...SE LLVL
FLOW WILL INCREASE ON FRI ALONG WITH MOISTURE ADVECTION. ALTHOUGH
THERE IS A FAVORABLE SHEAR PROFILE ON FRI AFTN WITH OVER 70 KTS OF
DEEP LAYER SHEAR...THE PLAINS LOOK RATHER STABLE WITH LIMITED CAPE
AND LOW CLOUD COVER TO CONTEND WITH. LLVLS ARE VERY MOIST TO THE
EAST OF THE LARAMIE RANGE ON FRI NIGHT WITH WIDESPREAD STRATUS.
MIDLEVEL LOW BEGINS TO MOVE NORTHEASTWARD ON SAT. APPEARS THAT SAT
WILL HAVE THE HIGHEST POTENTIAL OF STRONG TO SEVERE STORMS OVER
THE PLAINS...HOWEVER LOCATION WILL BE DEPENDENT ON SFC LOW
POSITION DURING THE AFTN. THE 12Z GFS WOULD KEEP MOST OF THE SVR
POTENTIAL INTO THE FAR EASTERN ZONES WITH A SFC LOW OVER THE
SOUTHERN PANHANDLE. A COLD FRONT IS PROGGED TO PASS OVER SOUTHEAST
WY AND THE PANHANDLE ON SUN MORNING WITH DRIER AIR AND DECREASING
TSTM CHANCES. MIDLEVEL FLOW BECOMES MORE ZONAL BY EARLY NEXT WEEK
WITH SEASONAL TEMPS.

FIRE WEATHER...
VERY WARM...DRY AND WINDY CONDITIONS ARE STILL EXPECTED OVER MUCH
OF THE CWA ON TUESDAY...ESPECIALLY THE WYOMING PORTIONS.  AS OF
THIS MORNING ONLY THE LOWER ELEVATIONS OF THE SNOWY AND SOUTHERN
LARAMIE RANGE HAVE FUELS THAT WOULD SUPPORT LARGE FIRE GROWTH.  SO
HAVE UPGRADED THE PREVIOUSLY ISSUED FIRE WEATHER WATCH TO A RED
FLAG WARNING FOR THOSE AREAS FROM LATE TUESDAY MORNING THROUGH THE
EARLY EVENING.  WETTER AND COOLER WEATHER WILL BEGIN OVER THE CWA
WEDNESDAY WITH THE PASSAGE OF A COLD FRONT EARLY TUESDAY NIGHT.
THE WETTER AND COOLER CONDITIONS WILL PERSIST THROUGH THE
WEEKEND AND WILL EASE THE FIRE WEATHER CONCERNS.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING FROM 11 AM TUESDAY TO 7 PM TUESDAY FOR WYZ101-
     WYZ102-WYZ103-WYZ106-WYZ114-WYZ116-WYZ117.
NE...RED FLAG WARNING FROM 11 AM TUESDAY TO 7 PM TUESDAY FOR NEZ002-
     NEZ003-NEZ019-NEZ020-NEZ021-NEZ054-NEZ055-NEZ095-NEZ096.

&&

$$

SHORT TERM/FIRE WEATHER...WEILAND
LONG TERM...FINCH

000
FXUS63 KUNR 220450
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1050 PM MDT MON MAY 21 2012

.AVIATION...06Z TAFS
GUSTY SOUTH TO SOUTHWEST WINDS WILL DEVELOP ACROSS THE AREA
TUESDAY MORNING. A COLD FRONT WILL THEN MOVE THROUGH NORTHEAST
WYOMING AND NORTHWEST SOUTH DAKOTA TUESDAY AFTERNOON...AND
THROUGH THE REST OF WESTERN SOUTH DAKOTA TUESDAY EVENING. STRONG
NORTHWEST WINDS WILL SPREAD ACROSS THE AREA BEHIND THE COLD FRONT.
SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS THE AREA TUESDAY
AFTERNOON AND EVENING...WITH THE BEST CHANCE FROM NORTHWEST SOUTH
DAKOTA INTO CENTRAL SOUTH DAKOTA.

&&

.PREV DISCUSSION... /ISSUED 303 PM MDT MON MAY 21 2012/

DISCUSSION...20Z SFC ANALYSIS SHOWS A N/S ORIENTED TROUGH OVER
WESTERN SOUTH DAKOTA WITH A LINE OF CU DEVELOPING ALONG THE TROUGH
LINE. DEWPOINTS ARE IN THE LOWER 50S TO THE EAST OF THE TROUGH AND
IN THE LOWER TO MID 30S TO THE WEST OF THE TROUGH.

LATEST MESO ANALYSIS SHOWS SBCAPE OF 500-1000J/KG EAST OF THE
TROUGH WITH DIMINISHING CIN. EXPECT TO SEE AN ISOLATED
THUNDERSTORM OR TWO DEVELOP LATE THIS AFTERNOON/EARLY
EVENING...AS A WEAK UPPER SHORTWAVE CROSSES THE AREA.

TUESDAY...UPPER TROUGH MOVES INTO THE NORTHERN ROCKIES WITH LEAD
SHORTWAVE ENERGY CREATING A NEW LOW OVER SOUTHEAST MT. TROUGH/DRY-
LINE WILL PUSH INTO SOUTHWEST SD DURING THE DAY WITH GUSTY
SOUTHWEST WINDS BEHIND IT AND VERY DRY RELATIVE HUMIDITIES. AHEAD
OF TROUGH...DEW POINTS IN THE LOWER 50S WILL POOL BRINGING ABOUT
1-2KJ/KG SBCAPE OVER THE FAR EASTERN REACHES OF THE CWA. CAP WILL
BE RATHER STRONG...SO VIGOROUS CONVECTION WILL LIKELY HAVE TO WAIT
UNTIL COLD FRONT THAT FORMS SOUTHWEST OF LOW MOVES INTO WESTERN SD.
SHEAR WILL BE SUFFICIENT FOR SURFACE/ELEVATED SUPERCELLS AND A
COUPLE OF SEVERE THUNDERSTORMS. TEMPERATURES WILL SOAR INTO THE
80S TO LOWER 90S TUESDAY AFTERNOON.

TUESDAY NIGHT/WEDNESDAY...BEHIND THE COLD FRONT COOLER AIR WILL
FILTER INTO THE REGION WITH UPPER TROUGH CLOSING OFF INTO AN UPPER LOW
OVER SOUTHERN SK. CYCLONIC FLOW EXPECTED OVER THE CWA WITH LIMITED
INSTABILITY. RESULT WILL BE GENERIC SHOWERS AND ISOLATED
THUNDERSTORMS OVER MUCH OF THE FORECAST AREA. TEMPERATURES NEAR
GUIDANCE APPEAR REASONABLE GIVEN MODEL FORECAST SOUNDINGS.

EXTENDED...A COUPLE OF UPPER LEVEL LOW PRESSURE SYSTEMS ARE PROGGED
TO PASS WEST AND NORTH OF THE AREA DURING THE LATTER PART OF THE
WEEK AND OVER THE WEEKEND. SOUTHWESTERLY FLOW ALOFT WILL DEVELOP TO
THE SOUTH OF THESE SYSTEMS OVER THE CENTRAL ROCKIES AND INTO THE
CENTRAL AND NORTHERN PLAINS. THIS PATTERN WILL BRING A SERIES OF
UPPER LEVEL DISTURBANCES THROUGH THE AREA...WITH DAILY CHANCES FOR
SHOWERS AND A FEW THUNDERSTORMS THROUGH THE WEEKEND. THE BEST CHANCE
FOR THUNDERSTORMS WILL BE THURSDAY INTO THURSDAY NIGHT AND FRIDAY
NIGHT THROUGH SATURDAY NIGHT. TEMPERATURES WILL GENERALLY BE NEAR OR
SLIGHTLY BELOW AVERAGE LATE THIS WEEK...WITH A WARMUP TO NEAR OR
SLIGHTLY ABOVE AVERAGE TEMPERATURES OVER THE HOLIDAY WEEKEND.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...FIRE WEATHER WATCH FROM 6 AM MDT TUESDAY THROUGH TUESDAY EVENING
     FOR SOUTHERN BLACK HILLS-SOUTHWESTERN SOUTH DAKOTA.

     WIND ADVISORY FROM 10 AM TO 8 PM CDT TUESDAY FOR TODD-TRIPP.

WY...FIRE WEATHER WATCH FROM 6 AM MDT TUESDAY THROUGH TUESDAY EVENING
     FOR LOWER ELEVATIONS OF CROOK AND WESTON COUNTIES-NORTHERN
     CAMPBELL-SOUTHERN CAMPBELL.

&&

$$

SHORT TERM...WFO UNR
LONG TERM....WFO UNR
AVIATION...07

000
FXUS65 KRIW 220235
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
835 PM MDT MON MAY 21 2012

.UPDATE...

UPDATED TO ADD RED FLAG WARNING FOR FWZ280 TUESDAY AFTERNOON. DRY
CONDITIONS ALONG WITH STRONG WIND AND CRITICAL FUELS WILL BRING
ENHANCED FIRE BEHAVIOR TO THE LOWER ELEVATIONS OF NATRONA COUNTY.

&&


.PREV DISCUSSION... /ISSUED 303 PM MDT MON MAY 21 2012/

SHORT TERM...TONIGHT THROUGH THURSDAY
WARM...DRY DAY ACROSS THE AREA TODAY BUT THE MILD...BENIGN WEATHER
IS ABOUT TO COME TO AN END. A STRONG COLD FRONT WILL MOVE QUICKLY
FROM THE PACNW COAST INTO WESTERN WYOMING TUESDAY MORNING AND
SWEEP QUICKLY THROUGH THE AREA BY AFTERNOON. IT WILL BE DRY AND
WINDY ACROSS MOST OF THE SOUTH HALF WITH MORE WIDESPREAD SHOWERS
ACROSS THE NORTH...ESPECIALLY IN THE MOUNTAINS. SNOW LEVELS WILL
LOWER TUESDAY AND TUESDAY NIGHT...REACHING THE FOOTHILLS IN THE NW
AND POSSIBLY BRIEFLY ON THE VALLEY FLOOR LATE TUESDAY NIGHT. THE COLD
FRONT WILL STALL OUT IN NRN COLORADO OR FAR SRN WYOMING TUESDAY
NIGHT INTO WEDNESDAY WITH JET STREAK DYNAMICS OVERRUNNING THE
BOUNDARY PRODUCING SHOWERS ACROSS THE FAR SOUTH. CONTINUED THE
TREND OF INCREASING POPS IN THIS AREA BUT SOON WE MAY NEED LIKELY
POPS. THE NW WILL REMAIN QUITE UNSETTLED WEDNESDAY INTO THURSDAY
AS A SERIES OF SHORTWAVES CROSS THE AREA IN A MOIST...CYCLONIC SW
FLOW. LATER WEDNESDAY NIGHT INTO THURSDAY...THE BEGINNINGS OF OUR
GREAT BASIN LOW MAY START TO TAKE SHAPE AND BRING SOME UPSLOPE
INTO THE CODY FOOTHILLS. THE H7 TEMPERATURES ARE FORECAST TO BE AS
COLD AS -5C AT H7 AND IF THERE IS ENOUGH PRECIPITATION FALLING...
WE COULD SEE A BRIEF RAIN SNOW MIXTURE THURSDAY MORNING. THE NW
MOUNTAINS WILL CONTINUE TO SEE PERIODS OF COLD VALLEY RAIN AND AT
LEAST LIGHT MOUNTAIN SNOW.

LONG TERM...THURSDAY NIGHT THROUGH MEMORIAL DAY

THE GFS AND THE ECMWF ARE MORE IN AGREEMENT NOW WITH AMPLIFYING THE
CUT OFF LOW OVER THE GREAT BASIN THURSDAY NIGHT AND FRIDAY ALONG
WITH BUILDING HEIGHTS ACROSS THE EAST HALF OF THE AREA AS WELL AS
BUILDING A SURFACE HIGH TO THE NORTH OF THE CWA. THIS WILL RESULT IN
A SIGNIFICANT UPSLOPE STRATIFORM PRECIPITATION EVENT...ESPECIALLY
FOR CENTRAL WYOMING EAST OF THE DIVIDE WITH SIGNIFICANT SNOW
ACCUMULATION EXPECTED IN THE SURROUNDING MOUNTAINS. SIGNIFICANT
SNOWFALL IS ALSO EXPECTED ACROSS THE NORTHERN AND WESTERN MOUNTAINS.
SOME WET SNOWFALL MAY ACTUALLY REACH THE VALLEY AND BASIN FLOORS IN
WESTERN AND NORTHERN WYOMING DURING THIS TIME FRAME. BY FRIDAY
EVENING THE WARM FRONT AND ACCOMPANYING DRY SLOT WILL PUSH MUCH OF
THE PRECIP NORTH OF THE AREA. HOWEVER...THE LOW OVER THE GREAT BASIN
WILL TRACK NORTHEAST TO NORTHWEST WYOMING SO COOL SHOWERY WEATHER
WITH SNOW SHOWERS IN THE MOUNTAINS WILL CONTINUE THROUGH THE WEEKEND
IN THE NORTH AND WEST...ESPECIALLY IN YELLOWSTONE PARK. A TRANSITORY
RIDGE WILL PROVIDE WARMER AND DRIER CONDITIONS FOR MEMORIAL DAY OVER
THE CWA.

AVIATION.../00Z ISSUANCE/
VFR CONDITIONS WILL OCCUR THROUGH 12Z TUESDAY. ISOLATED SHOWERS OR A
THUNDERSTORM ARE POSSIBLE OVER THE NORTHWEST WY MOUNTAINS FROM 20Z
UNTIL 02Z TUE. THEN CLOUDS WILL INCREASE AFTER 06Z TUE IN NW WYOMING
WITH SOME SHOWERS DEVELOPING OVER THE MOUNTAINS BY 12Z TUE. SHOWERS
AND THUNDERSTORMS WILL BECOME MORE NUMEROUS AFTER 18Z TUESDAY
SPREADING INTO THE REST OF WESTERN AND NORTHERN WYOMING RESULTING IN
MVFR AND LOCAL IFR CONDITIONS. SOUTHWEST WINDS WILL INCREASE TO 30
TO 40 MPH IN MANY AREAS WESTERN...SOUTHERN AND CENTRAL WYOMING AFTER
18Z. RAIN COULD TURN TO SNOW AT ELEVATIONS ABOVE 8500 FEET IN
NORTHWEST WYOMING BY 00Z WEDNESDAY WITH SOME MOUNTAIN OBSCURATIONS.

FIRE WEATHER...
SLIGHT CHANCE OF A LIGHT SHOWER THROUGH THE EVENING IN THE
NORTHWEST WITH A STRAY LIGHTNING STRIKE POSSIBLE BUT NOT LIKELY.
STRONG COLD FRONT WILL MOVE WEST TO EAST ACROSS THE AREA STARTING
IN THE FAR WEST IN THE MORNING AND HITTING THE EASTERN ZONES IN
THE AFTERNOON WITH STRONG WEST WINDS. IT WILL BE VERY DRY ACROSS
THE SOUTH HALF WITH LOW MIN RH`S IN THE TEENS. SHOWERS WILL BE
MORE NUMEROUS ACROSS THE NORTH HALF WITH SOME SNOW ON THE HIGHER
PEAKS. ISOLATED THUNDERSTORMS ARE EXPECTED...MAINLY IN THE NORTHERN
ZONES. WEDNESDAY WILL BE MUCH COOLER EAST OF THE DIVIDE WITH SOME
SHOWERS ACROSS THE MOUNTAINS AND FAR SOUTH ALONG WITH A SLIGHT
CHANCE OF THUNDERSTORMS. HIGHER ELEVATION SNOW WILL CONTINUE IN
THE NORTHERN MOUNTAINS...ESPECIALLY IN THE NORTHWEST.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING FROM 11 AM TO 8 PM MDT TUESDAY WYZ280.

&&

$$

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

000
FXUS63 KUNR 212346
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
546 PM MDT MON MAY 21 2012


.AVIATION...00Z TAFS
ISOLATED THUNDERSTORMS POSSIBLE OVER SOUTH CENTRAL SOUTH DAKOTA
THIS EVENING...OTHERWISE VFR CONDITIONS ARE EXPECTED THROUGH
TUESDAY AFTERNOON.

&&

.PREV DISCUSSION... /ISSUED 303 PM MDT MON MAY 21 2012/

DISCUSSION...20Z SFC ANALYSIS SHOWS A N/S ORIENTED TROUGH OVER
WESTERN SOUTH DAKOTA WITH A LINE OF CU DEVELOPING ALONG THE TROUGH
LINE. DEWPOINTS ARE IN THE LOWER 50S TO THE EAST OF THE TROUGH AND
IN THE LOWER TO MID 30S TO THE WEST OF THE TROUGH.

LATEST MESO ANALYSIS SHOWS SBCAPE OF 500-1000J/KG EAST OF THE
TROUGH WITH DIMINISHING CIN. EXPECT TO SEE AN ISOLATED
THUNDERSTORM OR TWO DEVELOP LATE THIS AFTERNOON/EARLY
EVENING...AS A WEAK UPPER SHORTWAVE CROSSES THE AREA.

TUESDAY...UPPER TROUGH MOVES INTO THE NORTHERN ROCKIES WITH LEAD
SHORTWAVE ENERGY CREATING A NEW LOW OVER SOUTHEAST MT. TROUGH/DRY-
LINE WILL PUSH INTO SOUTHWEST SD DURING THE DAY WITH GUSTY
SOUTHWEST WINDS BEHIND IT AND VERY DRY RELATIVE HUMIDITIES. AHEAD
OF TROUGH...DEW POINTS IN THE LOWER 50S WILL POOL BRINGING ABOUT
1-2KJ/KG SBCAPE OVER THE FAR EASTERN REACHES OF THE CWA. CAP WILL
BE RATHER STRONG...SO VIGOROUS CONVECTION WILL LIKELY HAVE TO WAIT
UNTIL COLD FRONT THAT FORMS SOUTHWEST OF LOW MOVES INTO WESTERN SD.
SHEAR WILL BE SUFFICIENT FOR SURFACE/ELEVATED SUPERCELLS AND A
COUPLE OF SEVERE THUNDERSTORMS. TEMPERATURES WILL SOAR INTO THE
80S TO LOWER 90S TUESDAY AFTERNOON.

TUESDAY NIGHT/WEDNESDAY...BEHIND THE COLD FRONT COOLER AIR WILL
FILTER INTO THE REGION WITH UPPER TROUGH CLOSING OFF INTO AN UPPER LOW
OVER SOUTHERN SK. CYCLONIC FLOW EXPECTED OVER THE CWA WITH LIMITED
INSTABILITY. RESULT WILL BE GENERIC SHOWERS AND ISOLATED
THUNDERSTORMS OVER MUCH OF THE FORECAST AREA. TEMPERATURES NEAR
GUIDANCE APPEAR REASONABLE GIVEN MODEL FORECAST SOUNDINGS.

EXTENDED...A COUPLE OF UPPER LEVEL LOW PRESSURE SYSTEMS ARE PROGGED
TO PASS WEST AND NORTH OF THE AREA DURING THE LATTER PART OF THE
WEEK AND OVER THE WEEKEND. SOUTHWESTERLY FLOW ALOFT WILL DEVELOP TO
THE SOUTH OF THESE SYSTEMS OVER THE CENTRAL ROCKIES AND INTO THE
CENTRAL AND NORTHERN PLAINS. THIS PATTERN WILL BRING A SERIES OF
UPPER LEVEL DISTURBANCES THROUGH THE AREA...WITH DAILY CHANCES FOR
SHOWERS AND A FEW THUNDERSTORMS THROUGH THE WEEKEND. THE BEST CHANCE
FOR THUNDERSTORMS WILL BE THURSDAY INTO THURSDAY NIGHT AND FRIDAY
NIGHT THROUGH SATURDAY NIGHT. TEMPERATURES WILL GENERALLY BE NEAR OR
SLIGHTLY BELOW AVERAGE LATE THIS WEEK...WITH A WARMUP TO NEAR OR
SLIGHTLY ABOVE AVERAGE TEMPERATURES OVER THE HOLIDAY WEEKEND.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...FIRE WEATHER WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING
     FOR SOUTHERN BLACK HILLS-SOUTHWESTERN SOUTH DAKOTA.

     WIND ADVISORY FROM 10 AM TO 8 PM CDT TUESDAY FOR TODD-TRIPP.

WY...FIRE WEATHER WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING
     FOR LOWER ELEVATIONS OF CROOK AND WESTON COUNTIES-NORTHERN
     CAMPBELL-SOUTHERN CAMPBELL.

&&

$$

SHORT TERM...WFO UNR
LONG TERM....WFO UNR
AVIATION...07

000
FXUS65 KCYS 212246
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
446 PM MDT MON MAY 21 2012

.UPDATE...

AFTER COORDINATING WITH THE FUELS FOLKS IN THE PANHANDLE AND
CONVERSE/NIOBRARA COUNTIES THIS AFTERNOON...WENT AHEAD AND ADDED
THEM TO THE RED FLAG WARNINGS FOR TOMORROW...11 AM TO 7 PM.
UPDATES HAVE BEEN SENT.

&&

AVIATION...00Z TAFS

VFR CONDITIONS THE NEXT 24 HOURS WITH STRONG WINDS DEVELOPING
TUESDAY. WIND GUSTS IN THE 35 TO 40KT RANGE EXPECTED AFTER
13-14Z...PERSISTING THROUGH THE EVENING HOURS. AFTERNOON SHOWERS AND
STORMS WILL AGAIN AFFECT THE CWA WEDNESDAY AND CONTINUE INTO THE
EARLY EVENING. CLOUD BASES WILL LOWER WEDNESDAY EVENING...WITH
WIDESPREAD IFR CONDITIONS AFFECTING MUCH OF THE CWA BY LATE
WEDNESDAY EVENING AND CONTINUING THROUGH FRIDAY. MVFR VISIBILITIES
IN RAIN AND FOG WILL ALSO BE WIDESPREAD OVER THE CWA DURING THAT
TIME.

CLAYCOMB

&&

.PREV DISCUSSION... /ISSUED 332 PM MDT MON MAY 21 2012/

SHORT TERM...TONIGHT THROUGH WEDNESDAY...

CONVECTION EARLY THIS AFTERNOON WAS LOCATED MAINLY OVER THE SOUTHERN
PANHANDLE.  THE ACTIVITY WAS IN A SURFACE CONVERGENT AREA WITH
SURFACE DEW POINTS STILL NEAR 50F TO THE EAST OF THE BOUNDARY.
POTENTIAL FOR SOME STORMS TO BECOME STRONG YET THIS AFTERNOON OVER
THE SOUTHEAST CORNER OF THE CWA.  THOSE STORMS MAY PRODUCE SMALL
HAIL...MODERATE RAINFALL AND GUSTY WINDS THROUGH THE EARLY EVENING.
THE REST OF TONIGHT WILL BE QUIET AND MILD OVER THE CWA WITH SOME
CIRRUS APPROACHING FROM THE WEST.

THE RIDGE AXIS ALOFT MOVES EAST OF THE CWA BY 12Z TUESDAY WITH
INCREASING SOUTHWEST TO WEST WIND FLOW ALOFT OVER THE REGION.
SURFACE WINDS WILL GUST AS HIGH AS 50 MPH MAINLY IN AREAS ALONG
AND WEST OF THE LARAMIE RANGE ON TUESDAY. ALSO...THE 700 MB
THERMAL RIDGE WILL BE OVER THE CWA ON TUESDAY AND WILL PRODUCE
WELL ABOVE NORMAL TEMPERATURES. SOME CIRRUS WILL ALSO SPREAD OVER
MAINLY THE WEST AND NORTH PARTS OF THE CWA. FIRE WEATHER CONCERNS
WILL BE HEIGHTENED ON TUESDAY AFTERNOON DUE TO THE WARM...DRY AND
WINDY WEATHER.

A COLD FRONT MOVES ACROSS THE CWA TUESDAY EVENING AND WILL USHER IN
COOLER TEMPERATURES AND A BETTER CHANCE OF PRECIPITATION. BY
WEDNESDAY...HIGH TEMPERATURES WILL BE IN THE 50S AND 60S OVER THE
LOWER ELEVATIONS. THE BOUNDARY LAYER UPSLOPE WILL COMBINE WITH THE
300 MB JET OVER THE CWA TO PRODUCE A GOOD CHANCE OF SHOWERS AND
THUNDERSTORMS BY WEDNESDAY AFTERNOON. BUFKIT RAOBS SUGGEST UP TO A
THIRD OF AN INCH OF RAINFALL OVER PARTS OF THE CWA WEDNESDAY
AFTERNOON. LIGHT ACCUMULATIONS OF SNOW WILL ALSO BE POSSIBLE LATE
TUESDAY NIGHT AND WEDNESDAY ABOVE 9000 FEET MSL. FOR THE AFTERNOON
FORECAST HAVE INCREASED POPS AND CLOUD COVER FOR WEDNESDAY ACROSS
THE CWA.

LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...

GOOD CHANCE OF WIDESPREAD SHOWERS OVER THE SOUTHEASTERN PART OF
THE CWA ON WEDNESDAY NIGHT AS A MIDLEVEL TROUGH PASSES OVER THE
AREA. THE MODELS SHOW UPPER LEVEL JET SUPPORT ALONG WITH A LAYER
OF GOOD MIDLEVEL FRONTOGENESIS OVER MAINLY THE PANHANDLE THAT
WOULD ENHANCE PRECIP. A BROAD MIDLEVEL TROUGH WILL REMAIN DRAPED
OVER THE INTERMOUNTAIN WEST ON THURS WITH COOL 700MB TEMPS AROUND
-2C TO 0C. THE CWA WILL BE LOCATED IN THE LEFT EXIT REGION OF THE
WESTERLY UPPER LEVEL JET ACROSS NV-UT THROUGH THURS AFTN. THIS
SHOULD CONTINUE SCATTERED SHOWERS THROUGH THE DAY...HOWEVER NOT
EXPECTING ANY THUNDERSTORMS WITH LIMITED INSTABILITY IN A COOL
BOUNDARY LAYER. THE MODELS AGREE ON SHOWING A DEEP CLOSED LOW
DEVELOPING OVER NV ON FRI WITH INCREASING SOUTH-TO-SOUTHWESTERLY
MIDLEVEL FLOW OVER THE AREA. WITH SFC PRESSURE FALLS OVER THE
GREAT BASIN AND PRESSURE RISES OVER THE NORTHERN PLAINS...SE LLVL
FLOW WILL INCREASE ON FRI ALONG WITH MOISTURE ADVECTION. ALTHOUGH
THERE IS A FAVORABLE SHEAR PROFILE ON FRI AFTN WITH OVER 70 KTS OF
DEEP LAYER SHEAR...THE PLAINS LOOK RATHER STABLE WITH LIMITED CAPE
AND LOW CLOUD COVER TO CONTEND WITH. LLVLS ARE VERY MOIST TO THE
EAST OF THE LARAMIE RANGE ON FRI NIGHT WITH WIDESPREAD STRATUS.
MIDLEVEL LOW BEGINS TO MOVE NORTHEASTWARD ON SAT. APPEARS THAT SAT
WILL HAVE THE HIGHEST POTENTIAL OF STRONG TO SEVERE STORMS OVER
THE PLAINS...HOWEVER LOCATION WILL BE DEPENDENT ON SFC LOW
POSITION DURING THE AFTN. THE 12Z GFS WOULD KEEP MOST OF THE SVR
POTENTIAL INTO THE FAR EASTERN ZONES WITH A SFC LOW OVER THE
SOUTHERN PANHANDLE. A COLD FRONT IS PROGGED TO PASS OVER SOUTHEAST
WY AND THE PANHANDLE ON SUN MORNING WITH DRIER AIR AND DECREASING
TSTM CHANCES. MIDLEVEL FLOW BECOMES MORE ZONAL BY EARLY NEXT WEEK
WITH SEASONAL TEMPS.

&&

FIRE WEATHER...
VERY WARM...DRY AND WINDY CONDITIONS ARE STILL EXPECTED OVER MUCH
OF THE CWA ON TUESDAY...ESPECIALLY THE WYOMING PORTIONS.  AS OF
THIS MORNING ONLY THE LOWER ELEVATIONS OF THE SNOWY AND SOUTHERN
LARAMIE RANGE HAVE FUELS THAT WOULD SUPPORT LARGE FIRE GROWTH.  SO
HAVE UPGRADED THE PREVIOUSLY ISSUED FIRE WEATHER WATCH TO A RED
FLAG WARNING FOR THOSE AREAS FROM LATE TUESDAY MORNING THROUGH THE
EARLY EVENING.  WETTER AND COOLER WEATHER WILL BEGIN OVER THE CWA
WEDNESDAY WITH THE PASSAGE OF A COLD FRONT EARLY TUESDAY NIGHT.
THE WETTER AND COOLER CONDITIONS WILL PERSIST THROUGH THE
WEEKEND AND WILL EASE THE FIRE WEATHER CONCERNS.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING FROM 11 AM TUESDAY TO 7 PM TUESDAY FOR WYZ101-
     WYZ102-WYZ103-WYZ106-WYZ114-WYZ116-WYZ117.
NE...RED FLAG WARNING FROM 11 AM TUESDAY TO 7 PM TUESDAY FOR NEZ002-
     NEZ003-NEZ019-NEZ020-NEZ021-NEZ054-NEZ055-NEZ095-NEZ096.

&&

$$

SHORT TERM/FIRE WEATHER...WEILAND
LONG TERM/AVIATION...FINCH

000
FXUS65 KCYS 212132
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
332 PM MDT MON MAY 21 2012

.SHORT TERM...TONIGHT THROUGH WEDNESDAY...

CONVECTION EARLY THIS AFTERNOON WAS LOCATED MAINLY OVER THE SOUTHERN
PANHANDLE.  THE ACTIVITY WAS IN A SURFACE CONVERGENT AREA WITH
SURFACE DEW POINTS STILL NEAR 50F TO THE EAST OF THE BOUNDARY.
POTENTIAL FOR SOME STORMS TO BECOME STRONG YET THIS AFTERNOON OVER
THE SOUTHEAST CORNER OF THE CWA.  THOSE STORMS MAY PRODUCE SMALL
HAIL...MODERATE RAINFALL AND GUSTY WINDS THROUGH THE EARLY EVENING.
THE REST OF TONIGHT WILL BE QUIET AND MILD OVER THE CWA WITH SOME
CIRRUS APPROACHING FROM THE WEST.

THE RIDGE AXIS ALOFT MOVES EAST OF THE CWA BY 12Z TUESDAY WITH
INCREASING SOUTHWEST TO WEST WIND FLOW ALOFT OVER THE REGION.
SURFACE WINDS WILL GUST AS HIGH AS 50 MPH MAINLY IN AREAS ALONG
AND WEST OF THE LARAMIE RANGE ON TUESDAY. ALSO...THE 700 MB
THERMAL RIDGE WILL BE OVER THE CWA ON TUESDAY AND WILL PRODUCE
WELL ABOVE NORMAL TEMPERATURES. SOME CIRRUS WILL ALSO SPREAD OVER
MAINLY THE WEST AND NORTH PARTS OF THE CWA. FIRE WEATHER CONCERNS
WILL BE HEIGHTENED ON TUESDAY AFTERNOON DUE TO THE WARM...DRY AND
WINDY WEATHER.

A COLD FRONT MOVES ACROSS THE CWA TUESDAY EVENING AND WILL USHER IN
COOLER TEMPERATURES AND A BETTER CHANCE OF PRECIPITATION. BY
WEDNESDAY...HIGH TEMPERATURES WILL BE IN THE 50S AND 60S OVER THE
LOWER ELEVATIONS. THE BOUNDARY LAYER UPSLOPE WILL COMBINE WITH THE
300 MB JET OVER THE CWA TO PRODUCE A GOOD CHANCE OF SHOWERS AND
THUNDERSTORMS BY WEDNESDAY AFTERNOON. BUFKIT RAOBS SUGGEST UP TO A
THIRD OF AN INCH OF RAINFALL OVER PARTS OF THE CWA WEDNESDAY
AFTERNOON. LIGHT ACCUMULATIONS OF SNOW WILL ALSO BE POSSIBLE LATE
TUESDAY NIGHT AND WEDNESDAY ABOVE 9000 FEET MSL. FOR THE AFTERNOON
FORECAST HAVE INCREASED POPS AND CLOUD COVER FOR WEDNESDAY ACROSS
THE CWA.

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...

GOOD CHANCE OF WIDESPREAD SHOWERS OVER THE SOUTHEASTERN PART OF
THE CWA ON WEDNESDAY NIGHT AS A MIDLEVEL TROUGH PASSES OVER THE
AREA. THE MODELS SHOW UPPER LEVEL JET SUPPORT ALONG WITH A LAYER
OF GOOD MIDLEVEL FRONTOGENESIS OVER MAINLY THE PANHANDLE THAT
WOULD ENHANCE PRECIP. A BROAD MIDLEVEL TROUGH WILL REMAIN DRAPED
OVER THE INTERMOUNTAIN WEST ON THURS WITH COOL 700MB TEMPS AROUND
-2C TO 0C. THE CWA WILL BE LOCATED IN THE LEFT EXIT REGION OF THE
WESTERLY UPPER LEVEL JET ACROSS NV-UT THROUGH THURS AFTN. THIS
SHOULD CONTINUE SCATTERED SHOWERS THROUGH THE DAY...HOWEVER NOT
EXPECTING ANY THUNDERSTORMS WITH LIMITED INSTABILITY IN A COOL
BOUNDARY LAYER. THE MODELS AGREE ON SHOWING A DEEP CLOSED LOW
DEVELOPING OVER NV ON FRI WITH INCREASING SOUTH-TO-SOUTHWESTERLY
MIDLEVEL FLOW OVER THE AREA. WITH SFC PRESSURE FALLS OVER THE
GREAT BASIN AND PRESSURE RISES OVER THE NORTHERN PLAINS...SE LLVL
FLOW WILL INCREASE ON FRI ALONG WITH MOISTURE ADVECTION. ALTHOUGH
THERE IS A FAVORABLE SHEAR PROFILE ON FRI AFTN WITH OVER 70 KTS OF
DEEP LAYER SHEAR...THE PLAINS LOOK RATHER STABLE WITH LIMITED CAPE
AND LOW CLOUD COVER TO CONTEND WITH. LLVLS ARE VERY MOIST TO THE
EAST OF THE LARAMIE RANGE ON FRI NIGHT WITH WIDESPREAD STRATUS.
MIDLEVEL LOW BEGINS TO MOVE NORTHEASTWARD ON SAT. APPEARS THAT SAT
WILL HAVE THE HIGHEST POTENTIAL OF STRONG TO SEVERE STORMS OVER
THE PLAINS...HOWEVER LOCATION WILL BE DEPENDENT ON SFC LOW
POSITION DURING THE AFTN. THE 12Z GFS WOULD KEEP MOST OF THE SVR
POTENTIAL INTO THE FAR EASTERN ZONES WITH A SFC LOW OVER THE
SOUTHERN PANHANDLE. A COLD FRONT IS PROGGED TO PASS OVER SOUTHEAST
WY AND THE PANHANDLE ON SUN MORNING WITH DRIER AIR AND DECREASING
TSTM CHANCES. MIDLEVEL FLOW BECOMES MORE ZONAL BY EARLY NEXT WEEK
WITH SEASONAL TEMPS.

&&

.AVIATION...18Z TAF ISSUANCE...
VFR CONDITIONS WILL CONTINUE OVER THE CWA THROUGH WEDNESDAY.
SOME HIGH BASED SHOWERS AND THUNDERSTORMS WILL AFFECT THE EAST
PART OF THE CWA THIS AFTERNOON AND EARLY EVENING.  THE ACTIVITY
WILL PRODUCE BRIEF WIND GUSTS TO 35 KNOTS...WITH REDUCED
VISIBILITIES IN MODERATE RAINFALL AND SMALL HAIL IN THE SOUTHEAST
PART OF THE CWA...NEAR KSNY.  AFTERNOON SHOWERS AND STORMS WILL
AGAIN AFFECT THE CWA WEDNESDAY AND CONTINUE INTO THE EARLY
EVENING.  CLOUD BASES WILL LOWER WEDNESDAY EVENING...WITH IFR
CONDITIONS AFFECTING MUCH OF THE CWA BY LATE WEDNESDAY EVENING
AND CONTINUING THROUGH THURSDAY MORNING.  MVFR VISIBILITIES IN
RAIN AND FOG WILL ALSO BE WIDESPREAD OVER THE CWA DURING THAT
TIME.

SOUTHWEST TO SOUTH SURFACE WINDS WILL GUST AS HIGH AS 25 KNOTS
THROUGH THE EARLY EVENING.  THEN SOUTHWEST TO WEST WINDS WILL
INCREASE RAPIDLY TUESDAY MORNING WITH GUSTS AS HIGH AS 45 KNOTS
IN AREAS ALONG AND WEST OF THE LARAMIE RANGE.  THOSE STRONG WINDS
WILL CONTINUE INTO TUESDAY EVENING.

&&

.FIRE WEATHER...
VERY WARM...DRY AND WINDY CONDITIONS ARE STILL EXPECTED OVER MUCH
OF THE CWA ON TUESDAY...ESPECIALLY THE WYOMING PORTIONS.  AS OF
THIS MORNING ONLY THE LOWER ELEVATIONS OF THE SNOWY AND SOUTHERN
LARAMIE RANGE HAVE FUELS THAT WOULD SUPPORT LARGE FIRE GROWTH.  SO
HAVE UPGRADED THE PREVIOUSLY ISSUED FIRE WEATHER WATCH TO A RED
FLAG WARNING FOR THOSE AREAS FROM LATE TUESDAY MORNING THROUGH THE
EARLY EVENING.  WETTER AND COOLER WEATHER WILL BEGIN OVER THE CWA
WEDNESDAY WITH THE PASSAGE OF A COLD FRONT EARLY TUESDAY NIGHT.
THE WETTER AND COOLER CONDITIONS WILL PERSIST THROUGH THE
WEEKEND AND WILL EASE THE FIRE WEATHER CONCERNS.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING FROM 11 AM TUESDAY TO 7 PM TUESDAY FOR WYZ106-
     WYZ114-WYZ116-WYZ117.
NE...NONE.

&&

$$

SHORT TERM/FIRE WEATHER...WEILAND
LONG TERM/AVIATION...FINCH

000
FXUS65 KRIW 212103
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
303 PM MDT MON MAY 21 2012

.SHORT TERM...TONIGHT THROUGH THURSDAY
WARM...DRY DAY ACROSS THE AREA TODAY BUT THE MILD...BENIGN WEATHER
IS ABOUT TO COME TO AN END. A STRONG COLD FRONT WILL MOVE QUICKLY
FROM THE PACNW COAST INTO WESTERN WYOMING TUESDAY MORNING AND
SWEEP QUICKLY THROUGH THE AREA BY AFTERNOON. IT WILL BE DRY AND
WINDY ACROSS MOST OF THE SOUTH HALF WITH MORE WIDESPREAD SHOWERS
ACROSS THE NORTH...ESPECIALLY IN THE MOUNTAINS. SNOW LEVELS WILL
LOWER TUESDAY AND TUESDAY NIGHT...REACHING THE FOOTHILLS IN THE NW
AND POSSIBLY BRIEFLY ON THE VALLEY FLOOR LATE TUESDAY NIGHT. THE COLD
FRONT WILL STALL OUT IN NRN COLORADO OR FAR SRN WYOMING TUESDAY
NIGHT INTO WEDNESDAY WITH JET STREAK DYNAMICS OVERRUNNING THE
BOUNDARY PRODUCING SHOWERS ACROSS THE FAR SOUTH. CONTINUED THE
TREND OF INCREASING POPS IN THIS AREA BUT SOON WE MAY NEED LIKELY
POPS. THE NW WILL REMAIN QUITE UNSETTLED WEDNESDAY INTO THURSDAY
AS A SERIES OF SHORTWAVES CROSS THE AREA IN A MOIST...CYCLONIC SW
FLOW. LATER WEDNESDAY NIGHT INTO THURSDAY...THE BEGINNINGS OF OUR
GREAT BASIN LOW MAY START TO TAKE SHAPE AND BRING SOME UPSLOPE
INTO THE CODY FOOTHILLS. THE H7 TEMPERATURES ARE FORECAST TO BE AS
COLD AS -5C AT H7 AND IF THERE IS ENOUGH PRECIPITATION FALLING...
WE COULD SEE A BRIEF RAIN SNOW MIXTURE THURSDAY MORNING. THE NW
MOUNTAINS WILL CONTINUE TO SEE PERIODS OF COLD VALLEY RAIN AND AT
LEAST LIGHT MOUNTAIN SNOW.

LONG TERM...THURSDAY NIGHT THROUGH MEMORIAL DAY

THE GFS AND THE ECMWF ARE MORE IN AGREEMENT NOW WITH AMPLIFYING THE
CUT OFF LOW OVER THE GREAT BASIN THURSDAY NIGHT AND FRIDAY ALONG
WITH BUILDING HEIGHTS ACROSS THE EAST HALF OF THE AREA AS WELL AS
BUILDING A SURFACE HIGH TO THE NORTH OF THE CWA. THIS WILL RESULT IN
A SIGNIFICANT UPSLOPE STRATIFORM PRECIPITATION EVENT...ESPECIALLY
FOR CENTRAL WYOMING EAST OF THE DIVIDE WITH SIGNIFICANT SNOW
ACCUMULATION EXPECTED IN THE SURROUNDING MOUNTAINS. SIGNIFICANT
SNOWFALL IS ALSO EXPECTED ACROSS THE NORTHERN AND WESTERN MOUNTAINS.
SOME WET SNOWFALL MAY ACTUALLY REACH THE VALLEY AND BASIN FLOORS IN
WESTERN AND NORTHERN WYOMING DURING THIS TIME FRAME. BY FRIDAY
EVENING THE WARM FRONT AND ACCOMPANYING DRY SLOT WILL PUSH MUCH OF
THE PRECIP NORTH OF THE AREA. HOWEVER...THE LOW OVER THE GREAT BASIN
WILL TRACK NORTHEAST TO NORTHWEST WYOMING SO COOL SHOWERY WEATHER
WITH SNOW SHOWERS IN THE MOUNTAINS WILL CONTINUE THROUGH THE WEEKEND
IN THE NORTH AND WEST...ESPECIALLY IN YELLOWSTONE PARK. A TRANSITORY
RIDGE WILL PROVIDE WARMER AND DRIER CONDITIONS FOR MEMORIAL DAY OVER
THE CWA.

AVIATION.../00Z ISSUANCE/
VFR CONDITIONS WILL OCCUR THROUGH 12Z TUESDAY. ISOLATED SHOWERS OR A
THUNDERSTORM ARE POSSIBLE OVER THE NORTHWEST WY MOUNTAINS FROM 20Z
UNTIL 02Z TUE. THEN CLOUDS WILL INCREASE AFTER 06Z TUE IN NW WYOMING
WITH SOME SHOWERS DEVELOPING OVER THE MOUNTAINS BY 12Z TUE. SHOWERS
AND THUNDERSTORMS WILL BECOME MORE NUMEROUS AFTER 18Z TUESDAY
SPREADING INTO THE REST OF WESTERN AND NORTHERN WYOMING RESULTING IN
MVFR AND LOCAL IFR CONDITIONS. SOUTHWEST WINDS WILL INCREASE TO 30
TO 40 MPH IN MANY AREAS WESTERN...SOUTHERN AND CENTRAL WYOMING AFTER
18Z. RAIN COULD TURN TO SNOW AT ELEVATIONS ABOVE 8500 FEET IN
NORTHWEST WYOMING BY 00Z WEDNESDAY WITH SOME MOUNTAIN OBSCURATIONS.

FIRE WEATHER...
SLIGHT CHANCE OF A LIGHT SHOWER THROUGH THE EVENING IN THE
NORTHWEST WITH A STRAY LIGHTNING STRIKE POSSIBLE BUT NOT LIKELY.
STRONG COLD FRONT WILL MOVE WEST TO EAST ACROSS THE AREA STARTING
IN THE FAR WEST IN THE MORNING AND HITTING THE EASTERN ZONES IN
THE AFTERNOON WITH STRONG WEST WINDS. IT WILL BE VERY DRY ACROSS
THE SOUTH HALF WITH LOW MIN RH`S IN THE TEENS. SHOWERS WILL BE
MORE NUMEROUS ACROSS THE NORTH HALF WITH SOME SNOW ON THE HIGHER
PEAKS. ISOLATED THUNDERSTORMS ARE EXPECTED...MAINLY IN THE NORTHERN
ZONES. WEDNESDAY WILL BE MUCH COOLER EAST OF THE DIVIDE WITH SOME
SHOWERS ACROSS THE MOUNTAINS AND FAR SOUTH ALONG WITH A SLIGHT
CHANCE OF THUNDERSTORMS. HIGHER ELEVATION SNOW WILL CONTINUE IN
THE NORTHERN MOUNTAINS...ESPECIALLY IN THE NORTHWEST.

&&

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

&&

$$

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

000
FXUS63 KUNR 212103
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
303 PM MDT MON MAY 21 2012

.DISCUSSION...20Z SFC ANALYSIS SHOWS A N/S ORIENTED TROUGH OVER
WESTERN SOUTH DAKOTA WITH A LINE OF CU DEVELOPING ALONG THE TROUGH
LINE. DEWPOINTS ARE IN THE LOWER 50S TO THE EAST OF THE TROUGHAND
IN THE LOWER TO MID 30S TO THE WEST OF THE TROUGH.

LATEST MESO ANALYSIS SHOWS SBCAPE OF 500-1000J/KG EAST OF THE
TROUGH WITH DIMINISHING CIN. EXPECT TO SEE AN ISOLATED
THUNDERSTORM OR TWO DEVELOP LATE THIS AFTERNOON/EARLY
EVENING...AS A WEAK UPPER SHORTWAVE CROSSES THE AREA.

TUESDAY...UPPER TROUGH MOVES INTO THE NORTHERN ROCKIES WITH LEAD
SHORTWAVE ENERGY CREATING A NEW LOW OVER SOUTHEAST MT. TROUGH/DRY-
LINE WILL PUSH INTO SOUTHWEST SD DURING THE DAY WITH GUSTY
SOUTHWEST WINDS BEHIND IT AND VERY DRY RELATIVE HUMIDITIES. AHEAD
OF TROUGH...DEW POINTS IN THE LOWER 50S WILL POOL BRINGING ABOUT
1-2KJ/KG SBCAPE OVER THE FAR EASTERN REACHES OF THE CWA. CAP WILL
BE RATHER STRONG...SO VIGOROUS CONVECTION WILL LIKELY HAVE TO WAIT
UNTIL COLD FRONT THAT FORMS SOUTHWEST OF LOW MOVES INTO WESTERN SD.
SHEAR WILL BE SUFFICIENT FOR SURFACE/ELEVATED SUPERCELLS AND A
COUPLE OF SEVERE THUNDERSTORMS. TEMPERATURES WILL SOAR INTO THE
80S TO LOWER 90S TUESDAY AFTERNOON.

TUESDAY NIGHT/WEDNESDAY...BEHIND THE COLD FRONT COOLER AIR WILL
FILTER INTO THE REGION WITH UPPER TROUGH CLOSING OFF INTO AN UPPER LOW
OVER SOUTHERN SK. CYCLONIC FLOW EXPECTED OVER THE CWA WITH LIMITED
INSTABILITY. RESULT WILL BE GENERIC SHOWERS AND ISOLATED
THUNDERSTORMS OVER MUCH OF THE FORECAST AREA. TEMPERATURES NEAR
GUIDANCE APPEAR REASONABLE GIVEN MODEL FORECAST SOUNDINGS.

EXTENDED...A COUPLE OF UPPER LEVEL LOW PRESSURE SYSTEMS ARE PROGGED
TO PASS WEST AND NORTH OF THE AREA DURING THE LATTER PART OF THE
WEEK AND OVER THE WEEKEND. SOUTHWESTERLY FLOW ALOFT WILL DEVELOP TO
THE SOUTH OF THESE SYSTEMS OVER THE CENTRAL ROCKIES AND INTO THE
CENTRAL AND NORTHERN PLAINS. THIS PATTERN WILL BRING A SERIES OF
UPPER LEVEL DISTURBANCES THROUGH THE AREA...WITH DAILY CHANCES FOR
SHOWERS AND A FEW THUNDERSTORMS THROUGH THE WEEKEND. THE BEST CHANCE
FOR THUNDERSTORMS WILL BE THURSDAY INTO THURSDAY NIGHT AND FRIDAY
NIGHT THROUGH SATURDAY NIGHT. TEMPERATURES WILL GENERALLY BE NEAR OR
SLIGHTLY BELOW AVERAGE LATE THIS WEEK...WITH A WARMUP TO NEAR OR
SLIGHTLY ABOVE AVERAGE TEMPERATURES OVER THE HOLIDAY WEEKEND.

&&

.AVIATION...18Z TAFS
VFR CONDITIONS ARE EXPECTED TONIGHT...WITH SOUTHERLY WINDS
CONTINUING OVER MUCH OF THE AREA. THERE IS A SLIGHT CHANCE FOR
SHOWERS AND THUNDERSTORMS LATE THIS AFTERNOON AND EARLY IN THE
EVENING ACROSS SOME AREAS EAST OF THE BLACK HILLS...ESPECIALLY OVER
SOUTH CENTRAL SD.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY FROM 10 AM TO 8 PM CDT TUESDAY FOR TODD-TRIPP.
WY...NONE.

&&

$$

000
FXUS65 KRIW 211718
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1118 AM MDT MON MAY 21 2012

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

HIGH PRESSURE CONTINUES TO BUILD IN TODAY ACROSS THE AREA BRINGING
MUCH WARMER TEMPERATURES THAN ON SUNDAY.  WHILE HOTTER TEMPERATURES
ARE EXPECTED...HAVE BACKED OFF A LITTLE ON HIGHS TODAY AS MODELS ARE
A BIT LESS BULLISH ON THE WARMEST H7 TEMPS.  HIGHS SHOULD STILL BE
IN THE MID 80S EAST OF THE CONTINENTAL DIVIDE WITH SOME UPPER 80S IN
THE BIG HORN BASIN.  WITH WARM ADVECTION AT LOW LEVELS AND COOLER
AIR REMAINING ALOFT...STEEP LAPSE RATES OF 8.5 TO 9.5 C/KM WILL
DEVELOP OVER WESTERN WYOMING.  HOWEVER...MOISTURE WILL BE A LIMITING
FACTOR AND WIDESPREAD CONVECTION IS NOT ANTICIPATED.  ISOLATED
AFTERNOON SHOWERS AND PERHAPS A RUMBLE OR TWO OF THUNDER ARE
POSSIBLE OVER YELLOWSTONE NATIONAL PARK.  WIND WILL INCREASE TUESDAY
AHEAD OF AN APPROACHING TROUGH AND ASSOCIATED COLD FRONT.  WESTERLY
WIND OF 25 TO 35 MPH WIND WITH HIGHER GUSTS WILL BE COMMON IN THE
MOUNTAINS AND ALONG THE WIND CORRIDOR FROM ROCK SPRINGS TO CASPER
DURING THE AFTERNOON HOURS.  HIGH WIND WILL BE APPROACHED IN SOME
AREAS.  INVOF AND BEHIND THE FRONT SHOWERS AND A FEW THUNDERSTORMS
WILL DEVELOP...MAINLY ACROSS WESTERN AND NORTHERN WYOMING.  SHOWERS
WILL TURN TO SNOW TUESDAY NIGHT OVER THE WESTERN MOUNTAINS.
SCATTERED SHOWER ACTIVITY AND COOLER TEMPERATURES WILL PERSIST
WEDNESDAY OVER MUCH OF THE AREA.  LIMITED INSTABILITY AND MARGINAL
LAPSE RATES WILL KEEP THUNDERSTORM COVERAGE LOW BUT ISOLATED
THUNDERSTORMS ARE POSSIBLE MAINLY OVER NORTHERN WYOMING.  BREEZY TO
WINDY CONDITIONS WILL PERSIST ALONG THE SOUTHERN WIND CORRIDOR BUT
HIGH WIND IS NOT EXPECTED BEHIND THE FRONT WEDNESDAY.


.LONG TERM...THURSDAY THROUGH MEMORIAL DAY

WET AND COLD START TO MEMORIAL DAY WEEKEND...THEN DRIER AND
WARMER WEATHER TO PREVAIL ON MEMORIAL DAY.

MEDIUM-RANGE GLOBAL MODELS HAVE TRENDED TOWARD MUCH
BROADER AND DEEPER FULL LATITUDE TROUGH STRETCHING FROM 140W-100W
BY THURSDAY...FLANKED BY UPPER RIDGES NEAR 145-150W AND ALONG THE
EAST COAST. GOOD AGREEMENT EXISTS WITH SYNOPTIC FEATURES AND
FORECAST CONTINUES TO TREND WETTER AND COOLER THURSDAY THROUGH
SATURDAY. WYOMING LARGELY BETWEEN SYSTEMS ROTATING THROUGH BROADER
UPPER TROUGH ON THURSDAY WITH DOWNSTREAM ENERGY SHEARING NE ACROSS
THE NORTHERN PLAINS AND NEXT UPPER LOW DIGGING DOWN NW COAST.
PREVIOUS RUNS HAD KEPT THIS UPSTREAM LOW ALONG OR SLIGHTLY OFF THE
WEST COAST...CLUSTERED NEAR SFO AT 00Z SATURDAY. THE LATEST RUNS
HAVE THIS UPPER LOW STACKED NEAR LAS VEGAS BY THIS TIME. SURFACE
HIGH PRESSURE OVER THE NORTHERN PLAINS AND DEEPENING LOW PRESSURE
OVER THE GREAT BASIN WILL RESULT IN UPSLOPE FLOW STRENGTHENING
EAST OF THE DIVIDE ON FRIDAY WITH ALL MODELS SHOWING LARGE SWATH
OF WCB PRECIPITATION DEVELOPING FROM NE COLORADO ACROSS NORTHERN
AND EASTERN WYOMING. THIS SWATH OF PRECIPITATION IS FORECAST TO
PUSH NORTH ALONG THE WARM FRONT FRIDAY NIGHT...MOSTLY INTO MONTANA
ON SATURDAY...AS UPPER LOW SHEARS NNE OUT OF THE GREAT BASIN...TO
NEAR GGW BY 00Z MONDAY. SLIGHTLY UNSTABLE...MOIST CYCLONIC FLOW ON
SUNDAY WILL GIVE WAY TO A DRIER AND MILDER WESTERLY FLOW ON
MONDAY.

&&

.AVIATION.../18Z ISSUANCE/

VFR CONDITIONS WILL OCCUR THROUGH 12Z TUESDAY. ISOLATED SHOWERS OR A
THUNDERSTORM ARE POSSIBLE OVER THE NORTHWEST WY MOUNTAINS FROM 20Z
UNTIL 02Z TUE. THEN CLOUDS WILL INCREASE AFTER 06Z TUE IN NW WYOMING
WITH SOME SHOWERS DEVELOPING OVER THE MOUNTAINS BY 12Z TUE. SHOWERS
AND THUNDERSTORMS WILL BECOME MORE NUMEROUS AFTER 18Z TUESDAY
SPREADING INTO THE REST OF WESTERN AND NORTHERN WYOMING RESULTING IN
MVFR AND LOCAL IFR CONDITIONS. SOUTHWEST WINDS WILL INCREASE TO 30
TO 40 MPH IN MANY AREAS WESTERN...SOUTHERN AND CENTRAL WYOMING AFTER
18Z. RAIN COULD TURN TO SNOW AT ELEVATIONS ABOVE 8500 FEET IN
NORTHWEST WYOMING BY 00Z WEDNESDAY WITH SOME MOUNTAIN OBSCURATIONS.

&&


.FIRE WEATHER...

MAINLY DRY AND WARMER CONDITIONS ARE EXPECTED TODAY UNDER HIGH
PRESSURE.  THERE IS A SLIGHT CHANCE FOR AN AFTERNOON SHOWER OR
THUNDERSTORM OVER YELLOWSTONE NATIONAL PARK.  AN APPROACHING COLD
FRONT WILL BRING SHOWERS AND A FEW THUNDERSTORMS TO THE WEST AND
NORTH ON TUESDAY.  AREAS EAST OF THE CONTINENTAL DIVIDE AND
MOUNTAINOUS AREAS WILL EXPERIENCE STRONG WIND WITH AREAS OF HIGH
WIND POSSIBLE.  LOW RH COUPLED WITH THE STRONG WIND WILL CAUSE
HAZARDOUS FIRE WEATHER CONDITIONS...PARTICULARLY ALONG THE ROCK
SPRINGS TO CASPER CORRIDOR.


&&

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

$$

SHORT TERM...BERC
LONG TERM...AEM
AVIATION...AR
FIRE WEATHER...BERC

000
FXUS65 KCYS 211709
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1110 AM MDT MON MAY 21 2012

.AVIATION...18Z TAF ISSUANCE...
VFR CONDITIONS WILL CONTINUE OVER THE CWA THROUGH WEDNESDAY.
SOME HIGH BASED SHOWERS AND THUNDERSTORMS WILL AFFECT THE EAST
PART OF THE CWA THIS AFTERNONO AND EARLY EVENING.  THE ACTIVITY
WILL PRODUCE BRIEG WIND GUSTS TO 35 KNOTS...WITH REDUCED
VISIBILITIES IN MODERATE RAINFALL AND SMALL HAIL IN THE SOUTHEAST
PART OF THE CWA...NEAR KSNY.  AFTERNOON SHOWERS AND STORMS WILL
AGAIN AFFECT THE CWA WEDNESDAY AND CONTINUE INTO THE EARLY
EVENING.  CLOUD BASES WILL LOWER WEDNESDAY EVENING...WITH IFR
CONDITIONS AFFECTING MUCH OF THE CWA BY LATE WEDNESDAY EVENING
AND CONTINUING THROUGH THURSDAY MORNING.  MVFR VISIBILITIES IN
RAIN AND FOG WILL ALSO BE WIDESPREAD OVER THE CWA DURING THAT
TIME.

SOUTHWEST TO SOUTH SURFACE WINDS WILL GUST AS HIGH AS 25 KNOTS
THROUGH THE EAELY EVENING.  THEN SOUTHWEST TO WEST WINDS WILL
INCREASE RAPIDLY TUESDAY MORNING WITH GUSTS AS HIGH AS 45 KNOTS
IN AREAS ALONG AND WEST OF THE LARAMIE RANGE.  THOSE STRONG WINDS
WILL CONTINUE INTO TUESDAY EVENING.

&&

.PREVIOUS DISCUSSION.../ISSUED AT 956 AM MDT MON MAY 21 2012/...

.DISCUSSION...
HEIGHTS ALOFT AND 700 MB TEMPERATURES WILL CONTINUE TO INCREASE
TODAY OVER THE CWA.  THAT WILL RESULT IN WARMER SURFACE READINGS
THAN THOSE OF SUNDAY AND AT 15Z...OBSERVED TEMPERATURES WERE
RUNNING WELL AHEAD OF SUNDAY IN MOST PLACES. CURRENT FORECAST HAS
TEMPERATURES FOR TODAY HANDELED WELL.  MAIN QUESTION FOR THE
AFTERNOON AND EARLY EVENING WILL BE THE LOCATION AND COVERAGE OF
THUNDERSTORMS.  IN A RECENT UPDATE HAVE INCREASED POPS MAINLY
EAST OF A KLAR TO KCDR LINE STARTING AROUND 20Z.  SOME MID LEVEL
MOISTURE IS PRESENT ON 12Z AREA RAOBS AND SURFACE HEATING WILL
BE GREATER THAN ON SUNDAY.  IN ADDITION...THERE APPEARS TO BE
AN AREA OF ASCENT MOVING OVER THE REGION THIS AFTERNOON AND EARLY
EVENING...CENTERED BETWEEN 700 MB AND 600 MB.  WEAK INSTABILITY
WILL ALSO BE PRESENT OVER THE EAST PART OF THE CWA DESPITE THE
RISING HEIGHTS ALOFT AND WARMING TEMPERATURES ALOFT.  MOST OF
THE ACTIVITY WILL BE WEAK AND PRODUCE GUSTY WINDS...WITH SOME
STRONGER STORMS POSSIBLE OVER THE SOUTHEAST PANHANDLE.  WILL
CONTINUE THE FIRE WEATHER WATCH AND WILL LIKELY UPGRADE TO A RED
FLAG WARNING IN THE AFTERNOON FORECAST.

&&

.PREVIOUS DISCUSSION.../ISSUED AT 540 AM MDT MON MAY 21 2012/...

.AVIATION...12Z TAF ISSUANCE...
UPPER LEVEL RIDGE TO BUILD ACROSS THE AREA TODAY THEN A TROUGH
MOVING IN TOMORROW. VFR TODAY AND TONIGHT UNDER CLEAR TO PARTLY
CLOUDY SKIES. MAINLY MID CLOUDS TODAY THEN CLEAR TONIGHT. VFR
TODAY AND TONIGHT WITH THE ONLY EXCEPTION BEING WITH ANY
THUNDERSTORMS THAT DEVELOP OF THE NEBRASKA PANHANDLE THIS
AFTERNOON. WINDS TODAY MAINLY 10 TO 15 MPH TODAY WITH GUST TO 25
MPH IN THE AFTERNOON.

&&

.PREV DISCUSSION... /ISSUED 346 AM MDT MON MAY 21 2012/

SHORT TERM...TODAY THROUGH WEDNESDAY...QUIET WEATHER IS EXPECTED
TODAY AND TUESDAY AS AN UPPER LEVEL RIDGE MOVES OVER THE FORECAST
AREA. MUCH DRIER CONDITIONS AND WARMER TEMPERATURES ARE FORECAST
WITH HIGHS INCREASING INTO THE UPPER 70S TO UPPER 80S TODAY...AND
EVEN WARMER ON TUESDAY...WITH HIGHS IN THE 80S TO MIDDLE 90S. THE
WARMEST TEMPERATURES WILL BE ACROSS THE LOWER ELEVATIONS OF THE
PLATTE RIVER VALLEY AND MOST OF THE WESTERN NEBRASKA PANHANDLE.
WITH SOME INSTABILITY AND CAPE VALUES AROUND 1000 J/KG TODAY
ACROSS THE HIGH PLAINS NEAR THE COLORADO BORDER...MAY SEE AN
ISOLATED TSTORM OR TWO SOUTH OF A LINE FROM CHEYENNE WYOMING TO
ALLIANCE NEBRASKA INTO THIS EVENING. ANY TSTORMS THAT DO FORM WILL
BE SHORT LIVED AND WEAK. A COLD FRONT WILL APPROACH THE AREA ON
TUESDAY RESULTING IN WINDY CONDITIONS TUESDAY AFTERNOON AND
TUESDAY EVENING...MAINLY ACROSS SOUTHEAST WYOMING WITH GUSTS OVER
50 MPH POSSIBLE.

A STRONG SURFACE COLD FRONT FOR THIS TIME OF THE YEAR AND
ASSOCIATED DEEP UPPER LEVEL TROUGH WILL PUSH EASTWARD INTO
SOUTHEAST WYOMING TUESDAY NIGHT. MUCH COOLER AIR WILL ARRIVE AFTER
MIDNIGHT WITH WINDS SHIFTING INTO THE WEST AND NORTHWEST. A STRONG
JET ALOFT...SOME INSTABILITY...AND LLVL CONVERGENCE WILL RESULT IN
SOME LIGHT PRECIP MAINLY ALONG AND WEST OF I25 THROUGH WEDNESDAY
MORNING...BUT WITH MODEL SOUNDINGS SHOWING AN INVERTED V PROFILE
AND VERY DRY LLVL BOUNDARY LAYER...BELIEVE IT WILL TAKE TIME FOR
THE LLVLS TO SATURATE ENOUGH FOR PRECIPITATION. KEPT LOW POP
BETWEEN 20 TO 30 PERCENT THROUGH EARLY WEDNESDAY MORNING. EXPECT A
MUCH HIGHER CHANCE OF RAINFALL WEDNESDAY AFTERNOON WITH ALL
MODELS SHOWING THE FRONT STALLING NEAR THE COLORADO BORDER.
INSTABILITY WILL COMBINE WITH OVERRUNNING ALOFT AND EASTERLY MOIST
UPSLOPE FLOW...PRODUCING WIDESPREAD RAINFALL AND SOME MOUNTAIN
SNOWFALL. ALL MODELS AROUND A QUARTER OF AN INCH OF QPF BY
WEDNESDAY AFTERNOON AS A BAND OF MODERATE TO LOCALLY HEAVY
RAINFALL DEVELOPS AND PUSHES NORTHEAST INTO WESTERN NEBRASKA. CAN
NOT RULE OUT SOME EMBEDDED TSTORMS DUE TO ADDITIONAL DYNAMIC LIFT
AND AFTERNOON INSTABILITY. INCREASED POP UP TO 50 PERCENT ACROSS
THE HIGH PLAINS WITH 70 PERCENT IN THE MOUNTAINS. TEMPERATURES
WILL LOWER INTO THE 50S AND 60S ACROSS MOST OF THE AREA WITH 30S
IN THE MOUNTAINS. MANY AREAS WILL LIKELY RECEIVE SOME MUCH NEEDED
MODERATE TO HEAVY RAINFALL THROUGH WEDNESDAY NIGHT.

LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...
CLOUDY AND COOL WITH INCREASED CHANCES FOR PRECIPITATION WEDNESDAY
NIGHT. SHORT WAVE ENERGY AND UPPER LEVEL JET ARE FORECAST TO SHIFT
ACROSS THE FORECAST AREA WEDNESDAY NIGHT. DYNAMIC FORCING AND
COOLING ALOFT WILL COUPLE WITH A STRONG MIDLEVEL BOUNDARY WHICH
WILL BE HUNG UP OVER SOUTHEAST WYOMING AND THE NEBRASKA PANHANDLE.
THIS AREA WILL BE THE FOCUS FOR PRECIPITATION. VERY WELL COULD SEE
WIDESPREAD HALF TO ONE INCH RAINFALL AMOUNTS ACROSS THE
AFOREMENTIONED AREA. LESS PRECIPITATION EXPECTED IN WESTERN
PORTIONS OF THE FORECAST AREA...BUT COULD SEE SEVERAL INCHES OF
SNOW IN THE MOUNTAINS. INCREASED POPS WEDNESDAY NIGHT...BUT WILL
NEED TO BE RAISED FURTHER SHOULD NEXT ROUND OF NUMERICAL MODELS
DEPICT SIMILAR SOLUTIONS.

CHANCES FOR PRECIPITATION WILL REMAIN THURSDAY WITH AN UPPER LEVEL
TROUGH OVER THE AREA AND SHORTWAVE ENERGY MOVING THROUGH THE UPPER
FLOW. TOUGH TO PINPOINT PLACEMENT AND TIMING OF SHORTWAVE FEATURES
BUT EXPECTING SCATTERED SHOWERS ACROSS THE FORECAST AREA THURSDAY.

THINGS SHOULD DRY OUT SOMEWHAT FRIDAY WITH SHORTWAVE RIDGING
TAKING PLACE. GFS AND EC DIVERGE SUBSTANTIALLY FRIDAY AND SATURDAY
TO THE EXTENT OF RIDGING ACROSS THE AREA. EC BUILDS THE RIDGE
FARTHER NORTH AND THUS MUCH LESS CHANCES FOR PRECIPITATION AND MUCH
WARMER. GFS ENSEMBLE WAS NOT MUCH HELP DECIDING WHICH SOLUTION TO
GO WITH AS THE GFS MEAN WAS CLOSE THE OPERATIONAL RUN BUT SEVERAL
PERTURBATIONS BUILT THE RIDGE FARTHER NORTH. LEANED TOWARD THE EC
SOLUTION TRENDING THE FORECAST THAT WAY. REGARDLESS...BOTH MODELS
BRING ANOTHER FRONT THROUGH SATURDAY NIGHT...PRODUCING A CHANCE
OF SHOWERS AND THUNDERSTORMS WITH MUCH COOLER TEMPERATURES FOR
SUNDAY.

AVIATION...06Z TAF ISSUANCE...
VFR TODAY WITH AN UPPER LEVEL RIDGE BUILDING OVER THE AREA. ONLY
POSSIBLE EXCEPTION WOULD BE AN ISOLATED THUNDERSTORMS INTO THE
NEBRASKA PANHANDLE THIS AFTERNOON. WINDS MAINLY 10 TO 15 MPH TODAY
WITH GUST TO 25 MPH IN THE AFTERNOON.

FIRE WEATHER...A STRONG COLD FRONT WILL APPROACH THE AREA FROM
THE WEST EARLY THIS WEEK. AHEAD OF THIS FRONT...DRY CONDITIONS ARE
EXPECTED WITH SOUTHWEST WINDS INCREASING EACH DAY. HUMIDITIES ARE
EXPECTED TO LOWER INTO THE SINGLE DIGITS AND TEENS MONDAY AND
TUESDAY AFTERNOON. HOWEVER...WITH MARGINAL DRY FUELS AND THE
FORECAST AREA IN GREEN UP...CRITICAL FIRE WEATHER CONDITIONS ARE
UNLIKELY. MUCH COOLER TEMPERATURES AND A WIDESPREAD CHANCE OF
RAINFALL IS EXPECTED LATE TUESDAY THROUGH THE END OF THE WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...FIRE WEATHER WATCH FROM 11 AM TUESDAY TO 7 PM TUESDAY FOR WYZ106-
     WYZ114-WYZ116-WYZ117.
NE...NONE.

&&

$$

SHORT TERM/FIRE WEATHER...TJT
LONG TERM/AVIATION...LIEBL
UPDATE...WEILAND

000
FXUS63 KUNR 211639
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1039 AM MDT MON MAY 21 2012

.UPDATE...16Z SFC ANALYSIS SHOWS HIGH PRESSURE OVER EASTERN
KANSAS WITH LOW PRESSURE CENTERED OVER SOUTHERN ALBERTA AND A
TROUGH EXTENDING SOUTHWARD FROM THE LOW INTO EASTERN WYOMING. THE
RESULTING PRESSURE GRADIENT WAS PRODUCING BREEZY TO WINDY
CONDITIONS OVER WESTERN SOUTH DAKOTA AND LIGHT WINDS NEAR THE
TROUGH IN EASTERN WYOMING. THE SFC TROUGH WILL CONTINUE TO SLIDE
SLOWLY EASTWARD TODAY. THERE MAY BE ENOUGH INSTABILITY AHEAD OF
THE TROUGH FOR A FEW THUNDERSTORMS TO DEVELOP EAST OF THE TROUGH
LINE OVER SOUTH CENTRAL SOUTH DAKOTA LATE THIS AFTERNOON OR EARLY
THIS EVENING.

&&

.AVIATION...18Z TAF FORECASTS
VFR CONDITIONS ARE EXPECTED TODAY AND
TONIGHT...WITH SOUTHERLY WINDS CONTINUING OVER MUCH OF THE AREA.
THERE IS A SLIGHT CHANCE FOR SHOWERS AND THUNDERSTORMS LATE THIS
AFTERNOON AND EARLY IN THE EVENING ACROSS SOME AREAS EAST OF THE
BLACK HILLS...ESPECIALLY OVER SOUTH CENTRAL SD.

&&

.PREV DISCUSSION... /ISSUED 239 AM MDT MON MAY 21 2012/

DISCUSSION...08Z SURFACE ANALYSIS HAD WEAK LOW OVER SOUTHEAST MT
WITH TROUGH INTO INTO SOUTH CENTRAL WY. LOW LEVEL JET CREATING
SOME ACCAS OVER CENTRAL SD/NE...BUT ACTIVITY SHOULD BE ON THE
WANE/OUT OF THE CWA BY 12Z. WATER VAPOUR SHOWED UPPER RIDGE
CONTINUED TO BUILD OVER THE NORTHERN PLAINS.

TODAY/TONIGHT...UPPER RIDGE BUILDS INTO THE REGION WITH THERMAL
RIDGE AMPLIFYING. TEMPERATURES WELL INTO THE 80S EXPECTED TODAY.
WEAK TROUGH WILL SHIFT ONTO THE SD PLAINS LATE TODAY/TONIGHT AND
MAY BE THE FOCUS FOR ISOLATED -TSRA ACTIVITY WITH ABOUT 1KJ/KG
SBCAPE AVAILABLE. CAP WILL BE INCREASING...SO THREAT WILL BE LOW.

TUESDAY...UPPER TROUGH MOVES INTO THE NORTHERN ROCKIES WITH LEAD
SHORTWAVE ENERGY CREATING A NEW LOW OVER SOUTHEAST MT. TROUGH/DRY-
LINE WILL PUSH INTO SOUTHWEST SD DURING THE DAY WITH GUSTY
SOUTHWEST WINDS BEHIND IT AND VERY DRY RELATIVE HUMIDITIES. AHEAD
OF TROUGH...DEW POINTS IN THE LOWER 50S WILL POOL BRINGING ABOUT
1-2KJ/KG SBCAPE OVER THE FAR EASTERN REACHES OF THE CWA. CAP WILL
BE RATHER STRONG...SO VIGOROUS CONVECTION WILL LIKELY HAVE TO WAIT
UNTIL COLD FRONT THAT FORMS SOUTHWEST OF LOW MOVES THROUGH ONTO
THE SD PLAINS. SHEAR WILL BE SUFFICIENT FOR SURFACE/ELEVATED
SUPERCELLS AND THUS EXPECTED A COUPLE OF SEVERE THUNDERSTORMS.
TEMPERATURES WILL SOAR INTO THE 80S TO LOWER 90S TUESDAY AFTERNOON.

TUESDAY NIGHT/WEDNESDAY...BEHIND COLD FRONT COOLER AIR WILL FILTER
INTO THE CWA WITH UPPER TROUGH CLOSING OFF INTO AN UPPER LOW OVER
SOUTHERN SK. CYCLONIC FLOW EXPECTED OVER THE CWA WITH LIMITED
INSTABILITY. RESULT WILL BE GENERIC POPS OVER MUCH OF THE CWA.
TEMPERATURES NEAR GUIDANCE APPEAR REASONABLE GIVEN FORECAST
SOUNDINGS.

EXTENDED...A COUPLE OF UPPER LEVEL LOW PRESSURE SYSTEMS ARE PROGGED
TO PASS WEST AND NORTH OF THE AREA DURING THE LATTER PART OF THE
WEEK AND OVER THE WEEKEND. SOUTHWESTERLY FLOW ALOFT WILL DEVELOP TO
THE SOUTH OF THESE SYSTEMS OVER THE CENTRAL ROCKIES AND INTO THE
CENTRAL AND NORTHERN PLAINS. THIS PATTERN WILL BRING A SERIES OF
UPPER LEVEL DISTURBANCES ACROSS THE AREA...WITH DAILY CHANCES FOR
SHOWERS AND A FEW THUNDERSTORMS FROM THURSDAY THROUGH THE WEEKEND.
THE BETTER CHANCES FOR THUNDERSTORMS WILL BE OVER THE WEEKEND AS
MOISTURE AND INSTABILITY INCREASE OVER THE AREA. TIMING OF THESE
WAVES ARE UNCERTAIN...BUT THE BETTER CHANCES FOR PCPN AT THIS TIME
LOOK TO BE THURSDAY INTO THURSDAY NIGHT AND FRIDAY NIGHT THROUGH
SATURDAY NIGHT. TEMPERATURES WILL GENERALLY BE NEAR OR SLIGHTLY
BELOW AVERAGE LATE THIS WEEK...WITH A WARMUP TO NEAR OR SLIGHTLY
ABOVE AVERAGE TEMPERATURES OVER THE WEEKEND.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

000
FXUS65 KCYS 211556
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
956 AM MDT MON MAY 21 2012

.DISCUSSION...
HEIGHTS ALOFT AND 700 MB TEMPERATURES WILL CONTINUE TO INCREASE
TODAY OVER THE CWA.  THAT WILL RESULT IN WARMER SURFACE READINGS
THAN THOSE OF SUNDAY AND AT 15Z...OBSERVED TEMPERATURES WERE
RUNNING WELL AHEAD OF SUNDAY IN MOST PLACES. CURRENT FORECAST HAS
TEMPERATURES FOR TODAY HANDELED WELL.  MAIN QUESTION FOR THE
AFTERNOON AND EARLY EVENING WILL BE THE LOCATION AND COVERAGE OF
THUNDERSTORMS.  IN A RECENT UPDATE HAVE INCREASED POPS MAINLY
EAST OF A KLAR TO KCDR LINE STARTING AROUND 20Z.  SOME MID LEVEL
MOISTURE IS PRESENT ON 12Z AREA RAOBS AND SURFACE HEATING WILL
BE GREATER THAN ON SUNDAY.  IN ADDITION...THERE APPEARS TO BE
AN AREA OF ASCENT MOVING OVER THE REGION THIS AFTERNOON AND EARLY
EVENING...CENTERED BETWEEN 700 MB AND 600 MB.  WEAK INSTABILITY
WILL ALSO BE PRESENT OVER THE EAST PART OF THE CWA DESPITE THE
RISING HEIGHTS ALOFT AND WARMING TEMPERATURES ALOFT.  MOST OF
THE ACTIVITY WILL BE WEAK AND PRODUCE GUSTY WINDS...WITH SOME
STRONGER STORMS POSSIBLE OVER THE SOUTHEAST PANHANDLE.  WILL
CONTINUE THE FIRE WEATHER WATCH AND WILL LIKELY UPGRADE TO A RED
FLAG WARNING IN THE AFTERNOON FORECAST.

&&

.PREVIOUS DISCUSSION.../ISSUED AT 540 AM MDT MON MAY 21 2012/...

.AVIATION...12Z TAF ISSUANCE...
UPPER LEVEL RIDGE TO BUILD ACROSS THE AREA TODAY THEN A TROUGH
MOVING IN TOMORROW. VFR TODAY AND TONIGHT UNDER CLEAR TO PARTLY
CLOUDY SKIES. MAINLY MID CLOUDS TODAY THEN CLEAR TONIGHT. VFR
TODAY AND TONIGHT WITH THE ONLY EXCEPTION BEING WITH ANY
THUNDERSTORMS THAT DEVELOP OF THE NEBRASKA PANHANDLE THIS
AFTERNOON. WINDS TODAY MAINLY 10 TO 15 MPH TODAY WITH GUST TO 25
MPH IN THE AFTERNOON.

&&

.PREV DISCUSSION... /ISSUED 346 AM MDT MON MAY 21 2012/

SHORT TERM...TODAY THROUGH WEDNESDAY...QUIET WEATHER IS EXPECTED
TODAY AND TUESDAY AS AN UPPER LEVEL RIDGE MOVES OVER THE FORECAST
AREA. MUCH DRIER CONDITIONS AND WARMER TEMPERATURES ARE FORECAST
WITH HIGHS INCREASING INTO THE UPPER 70S TO UPPER 80S TODAY...AND
EVEN WARMER ON TUESDAY...WITH HIGHS IN THE 80S TO MIDDLE 90S. THE
WARMEST TEMPERATURES WILL BE ACROSS THE LOWER ELEVATIONS OF THE
PLATTE RIVER VALLEY AND MOST OF THE WESTERN NEBRASKA PANHANDLE.
WITH SOME INSTABILITY AND CAPE VALUES AROUND 1000 J/KG TODAY
ACROSS THE HIGH PLAINS NEAR THE COLORADO BORDER...MAY SEE AN
ISOLATED TSTORM OR TWO SOUTH OF A LINE FROM CHEYENNE WYOMING TO
ALLIANCE NEBRASKA INTO THIS EVENING. ANY TSTORMS THAT DO FORM WILL
BE SHORT LIVED AND WEAK. A COLD FRONT WILL APPROACH THE AREA ON
TUESDAY RESULTING IN WINDY CONDITIONS TUESDAY AFTERNOON AND
TUESDAY EVENING...MAINLY ACROSS SOUTHEAST WYOMING WITH GUSTS OVER
50 MPH POSSIBLE.

A STRONG SURFACE COLD FRONT FOR THIS TIME OF THE YEAR AND
ASSOCIATED DEEP UPPER LEVEL TROUGH WILL PUSH EASTWARD INTO
SOUTHEAST WYOMING TUESDAY NIGHT. MUCH COOLER AIR WILL ARRIVE AFTER
MIDNIGHT WITH WINDS SHIFTING INTO THE WEST AND NORTHWEST. A STRONG
JET ALOFT...SOME INSTABILITY...AND LLVL CONVERGENCE WILL RESULT IN
SOME LIGHT PRECIP MAINLY ALONG AND WEST OF I25 THROUGH WEDNESDAY
MORNING...BUT WITH MODEL SOUNDINGS SHOWING AN INVERTED V PROFILE
AND VERY DRY LLVL BOUNDARY LAYER...BELIEVE IT WILL TAKE TIME FOR
THE LLVLS TO SATURATE ENOUGH FOR PRECIPITATION. KEPT LOW POP
BETWEEN 20 TO 30 PERCENT THROUGH EARLY WEDNESDAY MORNING. EXPECT A
MUCH HIGHER CHANCE OF RAINFALL WEDNESDAY AFTERNOON WITH ALL
MODELS SHOWING THE FRONT STALLING NEAR THE COLORADO BORDER.
INSTABILITY WILL COMBINE WITH OVERRUNNING ALOFT AND EASTERLY MOIST
UPSLOPE FLOW...PRODUCING WIDESPREAD RAINFALL AND SOME MOUNTAIN
SNOWFALL. ALL MODELS AROUND A QUARTER OF AN INCH OF QPF BY
WEDNESDAY AFTERNOON AS A BAND OF MODERATE TO LOCALLY HEAVY
RAINFALL DEVELOPS AND PUSHES NORTHEAST INTO WESTERN NEBRASKA. CAN
NOT RULE OUT SOME EMBEDDED TSTORMS DUE TO ADDITIONAL DYNAMIC LIFT
AND AFTERNOON INSTABILITY. INCREASED POP UP TO 50 PERCENT ACROSS
THE HIGH PLAINS WITH 70 PERCENT IN THE MOUNTAINS. TEMPERATURES
WILL LOWER INTO THE 50S AND 60S ACROSS MOST OF THE AREA WITH 30S
IN THE MOUNTAINS. MANY AREAS WILL LIKELY RECEIVE SOME MUCH NEEDED
MODERATE TO HEAVY RAINFALL THROUGH WEDNESDAY NIGHT.

LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...
CLOUDY AND COOL WITH INCREASED CHANCES FOR PRECIPITATION WEDNESDAY
NIGHT. SHORT WAVE ENERGY AND UPPER LEVEL JET ARE FORECAST TO SHIFT
ACROSS THE FORECAST AREA WEDNESDAY NIGHT. DYNAMIC FORCING AND
COOLING ALOFT WILL COUPLE WITH A STRONG MIDLEVEL BOUNDARY WHICH
WILL BE HUNG UP OVER SOUTHEAST WYOMING AND THE NEBRASKA PANHANDLE.
THIS AREA WILL BE THE FOCUS FOR PRECIPITATION. VERY WELL COULD SEE
WIDESPREAD HALF TO ONE INCH RAINFALL AMOUNTS ACROSS THE
AFOREMENTIONED AREA. LESS PRECIPITATION EXPECTED IN WESTERN
PORTIONS OF THE FORECAST AREA...BUT COULD SEE SEVERAL INCHES OF
SNOW IN THE MOUNTAINS. INCREASED POPS WEDNESDAY NIGHT...BUT WILL
NEED TO BE RAISED FURTHER SHOULD NEXT ROUND OF NUMERICAL MODELS
DEPICT SIMILAR SOLUTIONS.

CHANCES FOR PRECIPITATION WILL REMAIN THURSDAY WITH AN UPPER LEVEL
TROUGH OVER THE AREA AND SHORTWAVE ENERGY MOVING THROUGH THE UPPER
FLOW. TOUGH TO PINPOINT PLACEMENT AND TIMING OF SHORTWAVE FEATURES
BUT EXPECTING SCATTERED SHOWERS ACROSS THE FORECAST AREA THURSDAY.

THINGS SHOULD DRY OUT SOMEWHAT FRIDAY WITH SHORTWAVE RIDGING
TAKING PLACE. GFS AND EC DIVERGE SUBSTANTIALLY FRIDAY AND SATURDAY
TO THE EXTENT OF RIDGING ACROSS THE AREA. EC BUILDS THE RIDGE
FARTHER NORTH AND THUS MUCH LESS CHANCES FOR PRECIPITATION AND MUCH
WARMER. GFS ENSEMBLE WAS NOT MUCH HELP DECIDING WHICH SOLUTION TO
GO WITH AS THE GFS MEAN WAS CLOSE THE OPERATIONAL RUN BUT SEVERAL
PERTURBATIONS BUILT THE RIDGE FARTHER NORTH. LEANED TOWARD THE EC
SOLUTION TRENDING THE FORECAST THAT WAY. REGARDLESS...BOTH MODELS
BRING ANOTHER FRONT THROUGH SATURDAY NIGHT...PRODUCING A CHANCE
OF SHOWERS AND THUNDERSTORMS WITH MUCH COOLER TEMPERATURES FOR
SUNDAY.

AVIATION...06Z TAF ISSUANCE...
VFR TODAY WITH AN UPPER LEVEL RIDGE BUILDING OVER THE AREA. ONLY
POSSIBLE EXCEPTION WOULD BE AN ISOLATED THUNDERSTORMS INTO THE
NEBRASKA PANHANDLE THIS AFTERNOON. WINDS MAINLY 10 TO 15 MPH TODAY
WITH GUST TO 25 MPH IN THE AFTERNOON.

FIRE WEATHER...A STRONG COLD FRONT WILL APPROACH THE AREA FROM
THE WEST EARLY THIS WEEK. AHEAD OF THIS FRONT...DRY CONDITIONS ARE
EXPECTED WITH SOUTHWEST WINDS INCREASING EACH DAY. HUMIDITIES ARE
EXPECTED TO LOWER INTO THE SINGLE DIGITS AND TEENS MONDAY AND
TUESDAY AFTERNOON. HOWEVER...WITH MARGINAL DRY FUELS AND THE
FORECAST AREA IN GREEN UP...CRITICAL FIRE WEATHER CONDITIONS ARE
UNLIKELY. MUCH COOLER TEMPERATURES AND A WIDESPREAD CHANCE OF
RAINFALL IS EXPECTED LATE TUESDAY THROUGH THE END OF THE WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...FIRE WEATHER WATCH FROM 11 AM TUESDAY TO 7 PM TUESDAY FOR WYZ106-
     WYZ114-WYZ116-WYZ117.
NE...NONE.

&&

$$

SHORT TERM/FIRE WEATHER...TJT
LONG TERM/AVIATION...LIEBL
UPDATE...WEILAND

000
FXUS65 KCYS 211140
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
540 AM MDT MON MAY 21 2012

.AVIATION...12Z TAF ISSUANCE...
UPPER LEVEL RIDGE TO BUILD ACROSS THE AREA TODAY THEN A TROUGH
MOVING IN TOMORROW. VFR TODAY AND TONIGHT UNDER CLEAR TO PARTLY
CLOUDY SKIES. MAINLY MID CLOUDS TODAY THEN CLEAR TONIGHT. VFR
TODAY AND TONIGHT WITH THE ONLY EXCEPTION BEING WITH ANY
THUNDERSTORMS THAT DEVELOP OF THE NEBRASKA PANHANDLE THIS
AFTERNOON. WINDS TODAY MAINLY 10 TO 15 MPH TODAY WITH GUST TO 25
MPH IN THE AFTERNOON.


&&


.PREV DISCUSSION... /ISSUED 346 AM MDT MON MAY 21 2012/

SHORT TERM...TODAY THROUGH WEDNESDAY...QUIET WEATHER IS EXPECTED
TODAY AND TUESDAY AS AN UPPER LEVEL RIDGE MOVES OVER THE FORECAST
AREA. MUCH DRIER CONDITIONS AND WARMER TEMPERATURES ARE FORECAST
WITH HIGHS INCREASING INTO THE UPPER 70S TO UPPER 80S TODAY...AND
EVEN WARMER ON TUESDAY...WITH HIGHS IN THE 80S TO MIDDLE 90S. THE
WARMEST TEMPERATURES WILL BE ACROSS THE LOWER ELEVATIONS OF THE
PLATTE RIVER VALLEY AND MOST OF THE WESTERN NEBRASKA PANHANDLE.
WITH SOME INSTABILITY AND CAPE VALUES AROUND 1000 J/KG TODAY
ACROSS THE HIGH PLAINS NEAR THE COLORADO BORDER...MAY SEE AN
ISOLATED TSTORM OR TWO SOUTH OF A LINE FROM CHEYENNE WYOMING TO
ALLIANCE NEBRASKA INTO THIS EVENING. ANY TSTORMS THAT DO FORM WILL
BE SHORT LIVED AND WEAK. A COLD FRONT WILL APPROACH THE AREA ON
TUESDAY RESULTING IN WINDY CONDITIONS TUESDAY AFTERNOON AND
TUESDAY EVENING...MAINLY ACROSS SOUTHEAST WYOMING WITH GUSTS OVER
50 MPH POSSIBLE.

A STRONG SURFACE COLD FRONT FOR THIS TIME OF THE YEAR AND
ASSOCIATED DEEP UPPER LEVEL TROUGH WILL PUSH EASTWARD INTO
SOUTHEAST WYOMING TUESDAY NIGHT. MUCH COOLER AIR WILL ARRIVE AFTER
MIDNIGHT WITH WINDS SHIFTING INTO THE WEST AND NORTHWEST. A STRONG
JET ALOFT...SOME INSTABILITY...AND LLVL CONVERGENCE WILL RESULT IN
SOME LIGHT PRECIP MAINLY ALONG AND WEST OF I25 THROUGH WEDNESDAY
MORNING...BUT WITH MODEL SOUNDINGS SHOWING AN INVERTED V PROFILE
AND VERY DRY LLVL BOUNDARY LAYER...BELIEVE IT WILL TAKE TIME FOR
THE LLVLS TO SATURATE ENOUGH FOR PRECIPITATION. KEPT LOW POP
BETWEEN 20 TO 30 PERCENT THROUGH EARLY WEDNESDAY MORNING. EXPECT A
MUCH HIGHER CHANCE OF RAINFALL WEDNESDAY AFTERNOON WITH ALL
MODELS SHOWING THE FRONT STALLING NEAR THE COLORADO BORDER.
INSTABILITY WILL COMBINE WITH OVERRUNNING ALOFT AND EASTERLY MOIST
UPSLOPE FLOW...PRODUCING WIDESPREAD RAINFALL AND SOME MOUNTAIN
SNOWFALL. ALL MODELS AROUND A QUARTER OF AN INCH OF QPF BY
WEDNESDAY AFTERNOON AS A BAND OF MODERATE TO LOCALLY HEAVY
RAINFALL DEVELOPS AND PUSHES NORTHEAST INTO WESTERN NEBRASKA. CAN
NOT RULE OUT SOME EMBEDDED TSTORMS DUE TO ADDITIONAL DYNAMIC LIFT
AND AFTERNOON INSTABILITY. INCREASED POP UP TO 50 PERCENT ACROSS
THE HIGH PLAINS WITH 70 PERCENT IN THE MOUNTAINS. TEMPERATURES
WILL LOWER INTO THE 50S AND 60S ACROSS MOST OF THE AREA WITH 30S
IN THE MOUNTAINS. MANY AREAS WILL LIKELY RECEIVE SOME MUCH NEEDED
MODERATE TO HEAVY RAINFALL THROUGH WEDNESDAY NIGHT.

LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...
CLOUDY AND COOL WITH INCREASED CHANCES FOR PRECIPITATION WEDNESDAY
NIGHT. SHORT WAVE ENERGY AND UPPER LEVEL JET ARE FORECAST TO SHIFT
ACROSS THE FORECAST AREA WEDNESDAY NIGHT. DYNAMIC FORCING AND
COOLING ALOFT WILL COUPLE WITH A STRONG MIDLEVEL BOUNDARY WHICH
WILL BE HUNG UP OVER SOUTHEAST WYOMING AND THE NEBRASKA PANHANDLE.
THIS AREA WILL BE THE FOCUS FOR PRECIPITATION. VERY WELL COULD SEE
WIDESPREAD HALF TO ONE INCH RAINFALL AMOUNTS ACROSS THE
AFOREMENTIONED AREA. LESS PRECIPITATION EXPECTED IN WESTERN
PORTIONS OF THE FORECAST AREA...BUT COULD SEE SEVERAL INCHES OF
SNOW IN THE MOUNTAINS. INCREASED POPS WEDNESDAY NIGHT...BUT WILL
NEED TO BE RAISED FURTHER SHOULD NEXT ROUND OF NUMERICAL MODELS
DEPICT SIMILAR SOLUTIONS.

CHANCES FOR PRECIPITATION WILL REMAIN THURSDAY WITH AN UPPER LEVEL
TROUGH OVER THE AREA AND SHORTWAVE ENERGY MOVING THROUGH THE UPPER
FLOW. TOUGH TO PINPOINT PLACEMENT AND TIMING OF SHORTWAVE FEATURES
BUT EXPECTING SCATTERED SHOWERS ACROSS THE FORECAST AREA THURSDAY.

THINGS SHOULD DRY OUT SOMEWHAT FRIDAY WITH SHORTWAVE RIDGING
TAKING PLACE. GFS AND EC DIVERGE SUBSTANTIALLY FRIDAY AND SATURDAY
TO THE EXTENT OF RIDGING ACROSS THE AREA. EC BUILDS THE RIDGE
FARTHER NORTH AND THUS MUCH LESS CHANCES FOR PRECIPITATION AND MUCH
WARMER. GFS ENSEMBLE WAS NOT MUCH HELP DECIDING WHICH SOLUTION TO
GO WITH AS THE GFS MEAN WAS CLOSE THE OPERATIONAL RUN BUT SEVERAL
PERTURBATIONS BUILT THE RIDGE FARTHER NORTH. LEANED TOWARD THE EC
SOLUTION TRENDING THE FORECAST THAT WAY. REGARDLESS...BOTH MODELS
BRING ANOTHER FRONT THROUGH SATURDAY NIGHT...PRODUCING A CHANCE
OF SHOWERS AND THUNDERSTORMS WITH MUCH COOLER TEMPERATURES FOR
SUNDAY.

AVIATION...06Z TAF ISSUANCE...
VFR TODAY WITH AN UPPER LEVEL RIDGE BUILDING OVER THE AREA. ONLY
POSSIBLE EXCEPTION WOULD BE AN ISOLATED THUNDERSTORMS INTO THE
NEBRASKA PANHANDLE THIS AFTERNOON. WINDS MAINLY 10 TO 15 MPH TODAY
WITH GUST TO 25 MPH IN THE AFTERNOON.

FIRE WEATHER...A STRONG COLD FRONT WILL APPROACH THE AREA FROM
THE WEST EARLY THIS WEEK. AHEAD OF THIS FRONT...DRY CONDITIONS ARE
EXPECTED WITH SOUTHWEST WINDS INCREASING EACH DAY. HUMIDITIES ARE
EXPECTED TO LOWER INTO THE SINGLE DIGITS AND TEENS MONDAY AND
TUESDAY AFTERNOON. HOWEVER...WITH MARGINAL DRY FUELS AND THE
FORECAST AREA IN GREEN UP...CRITICAL FIRE WEATHER CONDITIONS ARE
UNLIKELY. MUCH COOLER TEMPERATURES AND A WIDESPREAD CHANCE OF
RAINFALL IS EXPECTED LATE TUESDAY THROUGH THE END OF THE WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...FIRE WEATHER WATCH FROM 11 AM TUESDAY TO 7 PM TUESDAY FOR WYZ106-
     WYZ114-WYZ116-WYZ117.
NE...NONE.

&&

$$

SHORT TERM/FIRE WEATHER...TJT
LONG TERM/AVIATION...LIEBL

000
FXUS65 KCYS 210946
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
346 AM MDT MON MAY 21 2012

.SHORT TERM...TODAY THROUGH WEDNESDAY...QUIET WEATHER IS EXPECTED
TODAY AND TUESDAY AS AN UPPER LEVEL RIDGE MOVES OVER THE FORECAST
AREA. MUCH DRIER CONDITIONS AND WARMER TEMPERATURES ARE FORECAST
WITH HIGHS INCREASING INTO THE UPPER 70S TO UPPER 80S TODAY...AND
EVEN WARMER ON TUESDAY...WITH HIGHS IN THE 80S TO MIDDLE 90S. THE
WARMEST TEMPERATURES WILL BE ACROSS THE LOWER ELEVATIONS OF THE
PLATTE RIVER VALLEY AND MOST OF THE WESTERN NEBRASKA PANHANDLE.
WITH SOME INSTABILITY AND CAPE VALUES AROUND 1000 J/KG TODAY
ACROSS THE HIGH PLAINS NEAR THE COLORADO BORDER...MAY SEE AN
ISOLATED TSTORM OR TWO SOUTH OF A LINE FROM CHEYENNE WYOMING TO
ALLIANCE NEBRASKA INTO THIS EVENING. ANY TSTORMS THAT DO FORM WILL
BE SHORT LIVED AND WEAK. A COLD FRONT WILL APPROACH THE AREA ON
TUESDAY RESULTING IN WINDY CONDITIONS TUESDAY AFTERNOON AND
TUESDAY EVENING...MAINLY ACROSS SOUTHEAST WYOMING WITH GUSTS OVER
50 MPH POSSIBLE.

A STRONG SURFACE COLD FRONT FOR THIS TIME OF THE YEAR AND
ASSOCIATED DEEP UPPER LEVEL TROUGH WILL PUSH EASTWARD INTO
SOUTHEAST WYOMING TUESDAY NIGHT. MUCH COOLER AIR WILL ARRIVE AFTER
MIDNIGHT WITH WINDS SHIFTING INTO THE WEST AND NORTHWEST. A STRONG
JET ALOFT...SOME INSTABILITY...AND LLVL CONVERGENCE WILL RESULT IN
SOME LIGHT PRECIP MAINLY ALONG AND WEST OF I25 THROUGH WEDNESDAY
MORNING...BUT WITH MODEL SOUNDINGS SHOWING AN INVERTED V PROFILE
AND VERY DRY LLVL BOUNDARY LAYER...BELIEVE IT WILL TAKE TIME FOR
THE LLVLS TO SATURATE ENOUGH FOR PRECIPITATION. KEPT LOW POP
BETWEEN 20 TO 30 PERCENT THROUGH EARLY WEDNESDAY MORNING. EXPECT A
MUCH HIGHER CHANCE OF RAINFALL WEDNESDAY AFTERNOON WITH ALL
MODELS SHOWING THE FRONT STALLING NEAR THE COLORADO BORDER.
INSTABILITY WILL COMBINE WITH OVERRUNNING ALOFT AND EASTERLY MOIST
UPSLOPE FLOW...PRODUCING WIDESPREAD RAINFALL AND SOME MOUNTAIN
SNOWFALL. ALL MODELS AROUND A QUARTER OF AN INCH OF QPF BY
WEDNESDAY AFTERNOON AS A BAND OF MODERATE TO LOCALLY HEAVY
RAINFALL DEVELOPS AND PUSHES NORTHEAST INTO WESTERN NEBRASKA. CAN
NOT RULE OUT SOME EMBEDDED TSTORMS DUE TO ADDITIONAL DYNAMIC LIFT
AND AFTERNOON INSTABILITY. INCREASED POP UP TO 50 PERCENT ACROSS
THE HIGH PLAINS WITH 70 PERCENT IN THE MOUNTAINS. TEMPERATURES
WILL LOWER INTO THE 50S AND 60S ACROSS MOST OF THE AREA WITH 30S
IN THE MOUNTAINS. MANY AREAS WILL LIKELY RECEIVE SOME MUCH NEEDED
MODERATE TO HEAVY RAINFALL THROUGH WEDNESDAY NIGHT.

.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...
CLOUDY AND COOL WITH INCREASED CHANCES FOR PRECIPITATION WEDNESDAY
NIGHT. SHORT WAVE ENERGY AND UPPER LEVEL JET ARE FORECAST TO SHIFT
ACROSS THE FORECAST AREA WEDNESDAY NIGHT. DYNAMIC FORCING AND
COOLING ALOFT WILL COUPLE WITH A STRONG MIDLEVEL BOUNDARY WHICH
WILL BE HUNG UP OVER SOUTHEAST WYOMING AND THE NEBRASKA PANHANDLE.
THIS AREA WILL BE THE FOCUS FOR PRECIPITATION. VERY WELL COULD SEE
WIDESPREAD HALF TO ONE INCH RAINFALL AMOUNTS ACROSS THE
AFOREMENTIONED AREA. LESS PRECIPITATION EXPECTED IN WESTERN
PORTIONS OF THE FORECAST AREA...BUT COULD SEE SEVERAL INCHES OF
SNOW IN THE MOUNTAINS. INCREASED POPS WEDNESDAY NIGHT...BUT WILL
NEED TO BE RAISED FURTHER SHOULD NEXT ROUND OF NUMERICAL MODELS
DEPICT SIMILAR SOLUTIONS.

CHANCES FOR PRECIPITATION WILL REMAIN THURSDAY WITH AN UPPER LEVEL
TROUGH OVER THE AREA AND SHORTWAVE ENERGY MOVING THROUGH THE UPPER
FLOW. TOUGH TO PINPOINT PLACEMENT AND TIMING OF SHORTWAVE FEATURES
BUT EXPECTING SCATTERED SHOWERS ACROSS THE FORECAST AREA THURSDAY.

THINGS SHOULD DRY OUT SOMEWHAT FRIDAY WITH SHORTWAVE RIDGING
TAKING PLACE. GFS AND EC DIVERGE SUBSTANTIALLY FRIDAY AND SATURDAY
TO THE EXTENT OF RIDGING ACROSS THE AREA. EC BUILDS THE RIDGE
FARTHER NORTH AND THUS MUCH LESS CHANCES FOR PRECIPITATION AND MUCH
WARMER. GFS ENSEMBLE WAS NOT MUCH HELP DECIDING WHICH SOLUTION TO
GO WITH AS THE GFS MEAN WAS CLOSE THE OPERATIONAL RUN BUT SEVERAL
PERTURBATIONS BUILT THE RIDGE FARTHER NORTH. LEANED TOWARD THE EC
SOLUTION TRENDING THE FORECAST THAT WAY. REGARDLESS...BOTH MODELS
BRING ANOTHER FRONT THROUGH SATURDAY NIGHT...PRODUCING A CHANCE
OF SHOWERS AND THUNDERSTORMS WITH MUCH COOLER TEMPERATURES FOR
SUNDAY.


&&

.AVIATION...06Z TAF ISSUANCE...
VFR TODAY WITH AN UPPER LEVEL RIDGE BUILDING OVER THE AREA. ONLY
POSSIBLE EXCEPTION WOULD BE AN ISOLATED THUNDERSTORMS INTO THE
NEBRASKA PANHANDLE THIS AFTERNOON. WINDS MAINLY 10 TO 15 MPH TODAY
WITH GUST TO 25 MPH IN THE AFTERNOON.


&&

.FIRE WEATHER...A STRONG COLD FRONT WILL APPROACH THE AREA FROM
THE WEST EARLY THIS WEEK. AHEAD OF THIS FRONT...DRY CONDITIONS ARE
EXPECTED WITH SOUTHWEST WINDS INCREASING EACH DAY. HUMIDITIES ARE
EXPECTED TO LOWER INTO THE SINGLE DIGITS AND TEENS MONDAY AND
TUESDAY AFTERNOON. HOWEVER...WITH MARGINAL DRY FUELS AND THE
FORECAST AREA IN GREEN UP...CRITICAL FIRE WEATHER CONDITIONS ARE
UNLIKELY. MUCH COOLER TEMPERATURES AND A WIDESPREAD CHANCE OF
RAINFALL IS EXPECTED LATE TUESDAY THROUGH THE END OF THE WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...

WY...FIRE WEATHER WATCH FROM 11 AM TUESDAY TO 7 PM TUESDAY FOR WYZ106-
     WYZ114-WYZ116-WYZ117.
NE...NONE.

&&

$$

SHORT TERM/FIRE WEATHER...TJT
LONG TERM/AVIATION...LIEBL

000
FXUS65 KRIW 210933
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
333 AM MDT MON MAY 21 2012

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

HIGH PRESSURE CONTINUES TO BUILD IN TODAY ACROSS THE AREA BRINGING
MUCH WARMER TEMPERATURES THAN ON SUNDAY.  WHILE HOTTER TEMPERATURES
ARE EXPECTED...HAVE BACKED OFF A LITTLE ON HIGHS TODAY AS MODELS ARE
A BIT LESS BULLISH ON THE WARMEST H7 TEMPS.  HIGHS SHOULD STILL BE
IN THE MID 80S EAST OF THE CONTINENTAL DIVIDE WITH SOME UPPER 80S IN
THE BIG HORN BASIN.  WITH WARM ADVECTION AT LOW LEVELS AND COOLER
AIR REMAINING ALOFT...STEEP LAPSE RATES OF 8.5 TO 9.5 C/KM WILL
DEVELOP OVER WESTERN WYOMING.  HOWEVER...MOISTURE WILL BE A LIMITING
FACTOR AND WIDESPREAD CONVECTION IS NOT ANTICIPATED.  ISOLATED
AFTERNOON SHOWERS AND PERHAPS A RUMBLE OR TWO OF THUNDER ARE
POSSIBLE OVER YELLOWSTONE NATIONAL PARK.  WIND WILL INCREASE TUESDAY
AHEAD OF AN APPROACHING TROUGH AND ASSOCIATED COLD FRONT.  WESTERLY
WIND OF 25 TO 35 MPH WIND WITH HIGHER GUSTS WILL BE COMMON IN THE
MOUNTAINS AND ALONG THE WIND CORRIDOR FROM ROCK SPRINGS TO CASPER
DURING THE AFTERNOON HOURS.  HIGH WIND WILL BE APPROACHED IN SOME
AREAS.  INVOF AND BEHIND THE FRONT SHOWERS AND A FEW THUNDERSTORMS
WILL DEVELOP...MAINLY ACROSS WESTERN AND NORTHERN WYOMING.  SHOWERS
WILL TURN TO SNOW TUESDAY NIGHT OVER THE WESTERN MOUNTAINS.
SCATTERED SHOWER ACTIVITY AND COOLER TEMPERATURES WILL PERSIST
WEDNESDAY OVER MUCH OF THE AREA.  LIMITED INSTABILITY AND MARGINAL
LAPSE RATES WILL KEEP THUNDERSTORM COVERAGE LOW BUT ISOLATED
THUNDERSTORMS ARE POSSIBLE MAINLY OVER NORTHERN WYOMING.  BREEZY TO
WINDY CONDITIONS WILL PERSIST ALONG THE SOUTHERN WIND CORRIDOR BUT
HIGH WIND IS NOT EXPECTED BEHIND THE FRONT WEDNESDAY.


.LONG TERM...THURSDAY THROUGH MEMORIAL DAY

WET AND COLD START TO MEMORIAL DAY WEEKEND...THEN DRIER AND
WARMER WEATHER TO PREVAIL ON MEMORIAL DAY.

MEDIUM-RANGE GLOBAL MODELS HAVE TRENDED TOWARD MUCH
BROADER AND DEEPER FULL LATITUDE TROUGH STRETCHING FROM 140W-100W
BY THURSDAY...FLANKED BY UPPER RIDGES NEAR 145-150W AND ALONG THE
EAST COAST. GOOD AGREEMENT EXISTS WITH SYNOPTIC FEATURES AND
FORECAST CONTINUES TO TREND WETTER AND COOLER THURSDAY THROUGH
SATURDAY. WYOMING LARGELY BETWEEN SYSTEMS ROTATING THROUGH BROADER
UPPER TROUGH ON THURSDAY WITH DOWNSTREAM ENERGY SHEARING NE ACROSS
THE NORTHERN PLAINS AND NEXT UPPER LOW DIGGING DOWN NW COAST.
PREVIOUS RUNS HAD KEPT THIS UPSTREAM LOW ALONG OR SLIGHTLY OFF THE
WEST COAST...CLUSTERED NEAR SFO AT 00Z SATURDAY. THE LATEST RUNS
HAVE THIS UPPER LOW STACKED NEAR LAS VEGAS BY THIS TIME. SURFACE
HIGH PRESSURE OVER THE NORTHERN PLAINS AND DEEPENING LOW PRESSURE
OVER THE GREAT BASIN WILL RESULT IN UPSLOPE FLOW STRENGTHENING
EAST OF THE DIVIDE ON FRIDAY WITH ALL MODELS SHOWING LARGE SWATH
OF WCB PRECIPITATION DEVELOPING FROM NE COLORADO ACROSS NORTHERN
AND EASTERN WYOMING. THIS SWATH OF PRECIPITATION IS FORECAST TO
PUSH NORTH ALONG THE WARM FRONT FRIDAY NIGHT...MOSTLY INTO MONTANA
ON SATURDAY...AS UPPER LOW SHEARS NNE OUT OF THE GREAT BASIN...TO
NEAR GGW BY 00Z MONDAY. SLIGHTLY UNSTABLE...MOIST CYCLONIC FLOW ON
SUNDAY WILL GIVE WAY TO A DRIER AND MILDER WESTERLY FLOW ON
MONDAY.

&&


.AVIATION.../12Z ISSUANCE/

VFR CONDITIONS WILL OCCUR THROUGH 12Z TUESDAY. ISOLATED SHOWERS OR A
THUNDERSTORM ARE POSSIBLE OVER THE NORTHWEST WY MOUNTAINS FROM 20Z
UNTIL 02Z TUE. THEN CLOUDS WILL INCREASE AFTER 06Z TUE IN NW WYOMING
WITH SOME SHOWERS DEVELOPING OVER THE MOUNTAINS BY 12Z TUE.

&&


.FIRE WEATHER...

MAINLY DRY AND WARMER CONDITIONS ARE EXPECTED TODAY UNDER HIGH
PRESSURE.  THERE IS A SLIGHT CHANCE FOR AN AFTERNOON SHOWER OR
THUNDERSTORM OVER YELLOWSTONE NATIONAL PARK.  AN APPROACHING COLD
FRONT WILL BRING SHOWERS AND A FEW THUNDERSTORMS TO THE WEST AND
NORTH ON TUESDAY.  AREAS EAST OF THE CONTINENTAL DIVIDE AND
MOUNTAINOUS AREAS WILL EXPERIENCE STRONG WIND WITH AREAS OF HIGH
WIND POSSIBLE.  LOW RH COUPLED WITH THE STRONG WIND WILL CAUSE
HAZARDOUS FIRE WEATHER CONDITIONS...PARTICULARLY ALONG THE ROCK
SPRINGS TO CASPER CORRIDOR.


&&

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

$$

SHORT TERM...BERC
LONG TERM...AEM
AVIATION...AR
FIRE WEATHER...BERC

000
FXUS63 KUNR 210839
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
239 AM MDT MON MAY 21 2012

.DISCUSSION...08Z SURFACE ANALYSIS HAD WEAK LOW OVER SOUTHEAST MT
WITH TROUGH INTO INTO SOUTH CENTRAL WY. LOW LEVEL JET CREATING
SOME ACCAS OVER CENTRAL SD/NE...BUT ACTIVITY SHOULD BE ON THE
WANE/OUT OF THE CWA BY 12Z. WATER VAPOUR SHOWED UPPER RIDGE
CONTINUED TO BUILD OVER THE NORTHERN PLAINS.

TODAY/TONIGHT...UPPER RIDGE BUILDS INTO THE REGION WITH THERMAL
RIDGE AMPLIFYING. TEMPERATURES WELL INTO THE 80S EXPECTED TODAY.
WEAK TROUGH WILL SHIFT ONTO THE SD PLAINS LATE TODAY/TONIGHT AND
MAY BE THE FOCUS FOR ISOLATED -TSRA ACTIVITY WITH ABOUT 1KJ/KG
SBCAPE AVAILABLE. CAP WILL BE INCREASING...SO THREAT WILL BE LOW.

TUESDAY...UPPER TROUGH MOVES INTO THE NORTHERN ROCKIES WITH LEAD
SHORTWAVE ENERGY CREATING A NEW LOW OVER SOUTHEAST MT. TROUGH/DRY-
LINE WILL PUSH INTO SOUTHWEST SD DURING THE DAY WITH GUSTY
SOUTHWEST WINDS BEHIND IT AND VERY DRY RELATIVE HUMIDITIES. AHEAD
OF TROUGH...DEW POINTS IN THE LOWER 50S WILL POOL BRINGING ABOUT
1-2KJ/KG SBCAPE OVER THE FAR EASTERN REACHES OF THE CWA. CAP WILL
BE RATHER STRONG...SO VIGOROUS CONVECTION WILL LIKELY HAVE TO WAIT
UNTIL COLD FRONT THAT FORMS SOUTHWEST OF LOW MOVES THROUGH ONTO
THE SD PLAINS. SHEAR WILL BE SUFFICIENT FOR SURFACE/ELEVATED
SUPERCELLS AND THUS EXPECTED A COUPLE OF SEVERE THUNDERSTORMS.
TEMPERATURES WILL SOAR INTO THE 80S TO LOWER 90S TUESDAY AFTERNOON.

TUESDAY NIGHT/WEDNESDAY...BEHIND COLD FRONT COOLER AIR WILL FILTER
INTO THE CWA WITH UPPER TROUGH CLOSING OFF INTO AN UPPER LOW OVER
SOUTHERN SK. CYCLONIC FLOW EXPECTED OVER THE CWA WITH LIMITED
INSTABILITY. RESULT WILL BE GENERIC POPS OVER MUCH OF THE CWA.
TEMPERATURES NEAR GUIDANCE APPEAR REASONABLE GIVEN FORECAST
SOUNDINGS.

EXTENDED...A COUPLE OF UPPER LEVEL LOW PRESSURE SYSTEMS ARE PROGGED
TO PASS WEST AND NORTH OF THE AREA DURING THE LATTER PART OF THE
WEEK AND OVER THE WEEKEND. SOUTHWESTERLY FLOW ALOFT WILL DEVELOP TO
THE SOUTH OF THESE SYSTEMS OVER THE CENTRAL ROCKIES AND INTO THE
CENTRAL AND NORTHERN PLAINS. THIS PATTERN WILL BRING A SERIES OF
UPPER LEVEL DISTURBANCES ACROSS THE AREA...WITH DAILY CHANCES FOR
SHOWERS AND A FEW THUNDERSTORMS FROM THURSDAY THROUGH THE WEEKEND.
THE BETTER CHANCES FOR THUNDERSTORMS WILL BE OVER THE WEEKEND AS
MOISTURE AND INSTABILITY INCREASE OVER THE AREA. TIMING OF THESE
WAVES ARE UNCERTAIN...BUT THE BETTER CHANCES FOR PCPN AT THIS TIME
LOOK TO BE THURSDAY INTO THURSDAY NIGHT AND FRIDAY NIGHT THROUGH
SATURDAY NIGHT. TEMPERATURES WILL GENERALLY BE NEAR OR SLIGHTLY
BELOW AVERAGE LATE THIS WEEK...WITH A WARMUP TO NEAR OR SLIGHTLY
ABOVE AVERAGE TEMPERATURES OVER THE WEEKEND.

&&

.AVIATION...12Z TAFS
VFR CONDITIONS ARE EXPECTED THROUGH THIS EVENING...WITH SOUTH TO
SOUTHWEST WINDS CONTINUING OVER MUCH OF THE AREA. THERE IS A SLIGHT
CHANCE FOR SHOWERS AND THUNDERSTORMS LATE THIS AFTERNOON AND EVENING
ACROSS SOME AREAS EAST OF THE BLACK HILLS...ESPECIALLY OVER SOUTH
CENTRAL SD.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

SHORT TERM...HELGESON
LONG TERM....26
AVIATION...26

000
FXUS65 KRIW 210524
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1124 PM MDT SUN MAY 20 2012

.SHORT TERM...TONIGHT THROUGH WEDNESDAY
WEAK ISENTROPIC UPGLIDE CLOUDS ACROSS IDAHO THIS MORNING HAVE
MOVED INTO WESTERN IDAHO WITH SOME VERY WEAK SHOWERS OVER THE
HIGHER NORTHWEST MOUNTAINS. WEAK INSTABILITY IN THE NE ZONES HAS
RESULTED IN SOME SMALL CU BUT NO SHOWERS. WILL LEAVE THE ISOLATED
SHOWERS IN THE FORECAST INTO THE EVENING ACROSS MAINLY THE
NORTHERN MOUNTAINS. FLAT RIDGE MOVES OVERHEAD ON MONDAY WITH A
JUST A WEAK WAVE POSSIBLY BRUSHING THE FAR NW. NEGATIVELY TILTED
TROUGH AND COLD FRONT THEN MOVE IN TUESDAY WITH WIDESPREAD SHOWERS
EXPECTED IN THE NORTHWEST AND FAR NORTH WITH A STRONG COLD FRONT
BLASTING EAST ACROSS THE AREA. WINDS WILL LIKELY BE QUITE STRONG
WITH THE POSSIBILITY OF SOME HIGH WINDS FOR A FEW HOURS ACROSS THE
CENTRAL AND SRN ZONES WITH AND FOR A FEW HOURS AFTER FROPA. WILL
NEED TO WATCH THIS CLOSELY FOR POTENTIAL HIGH WIND WATCHES. SHOWER AND
THUNDERSTORM POSSIBILITIES EXIST FURTHER SOUTH BUT THE HIGHEST
PROBABILITY WILL BE IN THE NW AND FAR NORTH. FRONTAL BOUNDARY MAY
STALL OUT ACROSS THE FAR SOUTH OR INTO NRN COLORADO KEEPING SOME
SHOWER POSSIBILITIES ACROSS SWEETWATER COUNTY LATER TUESDAY NIGHT
INTO WEDNESDAY. DEFINITELY COLD ENOUGH FOR SOME HIGHER ELEVATION
SNOW BEHIND THE FRONT IN THE NW MOUNTAINS TUESDAY INTO TUESDAY
EVENING. SOUNDINGS AREN`T SHOWING MUCH CAPE AHEAD OF THE FRONT
WITH DRY LOW LEVELS AND EARLY FRONTAL PASSAGE EXCEPT IN THE EAST
BUT WE WILL STILL NEED TO KEEP AN EYE ON THIS. COOLER AND
UNSETTLED THEN INTO WEDNESDAY WITH SEVERAL SHORTWAVES MOVING
THROUGH THE SW FLOW. BEST SHOT OF SHOWERS WILL BE IN THE MOUNTAINS
BUT ALL AREAS WILL SEE A FEW SHOWERS AROUND AT LEAST TUESDAY NIGHT
AND WEDNESDAY.

.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY

A TURN TO COOLER AND SHOWERY CONDITIONS EXPECTED.

A CLOSED LOW WILL ESTABLISH ITSELF OVER MONTANA PER ECMWF BY
WEDNESDAY NIGHT WITH THE GFS ALREADY MOVING NORTHEAST INTO THE
NORTHERN PLAINS BY THEN AS THE GFS WILL BE THE FASTER OF THE TWO
MODELS AS WELL AS SWINGING A COLDER TROUGH ACROSS THE AREA THURSDAY
WHEREAS THE ECMWF KEEPS THE TROUGHINESS NORTHWEST OVER THE PACIFIC
NORTHWEST. WILL CONTINUE TO SIDE WITH THE ECMWF ALONG WITH A LITTLE
BIT OF A COMPROMISE IN THE FORECAST. BY FRIDAY THE GFS HAS A COL
REGION OVER US WITH THE ECMWF SCOOTING THE TROUGH TO THE NORTHEAST
INTO CANADA ALLOWING SOUTHWEST FLOW TO INFILTRATE THE AREA. HOWEVER
THE ECMWF ALSO INDICATES A SURFACE HIGH TO THE NORTH AND A SURFACE
LOW OVER THE GREAT BASIN ALLOWING FOR COOL UPSLOPE CONDITIONS IN
MAINLY IN CENTRAL WYOMING EAST OF THE DIVIDE AS THE SOUTHWEST WINDS
ALOFT OVERRUN THE MOIST SURFACE UPSLOPE CONDITIONS. WITH THIS
POSSIBILITY...COOLED THINGS DOWN FRIDAY WITH STRATIFORM PRECIP IN
UPSLOPE FAVORED AREAS IN CENTRAL WYOMING FOR NOW. ONLY COOLED TEMPS
A FEW DEGREES FRIDAY BUT LATER SHIFTS CAN LOOK INTO THIS. SOME SNOW
IS EXPECTED IN THE MOUNTAINS ESPECIALLY ON THURSDAY AND DRY WITH H7
TEMPS DIPPING TO -6C IN NORTHERN WY THURSDAY. ON SATURDAY...WITH THE
UPSTREAM LOW ASSOCIATED WITH THE RELOADING TROUGH TO THE WEST...WILL
BECOME INCREASINGLY CUT OFF OVER CALIFORNIA...A SOUTHWEST FLOW AND
RESULTING WARMING AND DRYING TREND WILL ENSUE SATURDAY OVER WYOMING.
BY SUNDAY THIS LOW WILL TRACK NORTHEAST TO THE VICINITY OF WYOMING
SO HAVE INCREASED PRECIP FOR SUNDAY.

&&

.AVIATION.../06Z ISSUANCE/

VFR CONDITIONS WILL OCCUR THROUGH 12Z TUESDAY. ISOLATED SHOWERS OR A
THUNDERSTORM ARE POSSIBLE OVER THE NORTHWEST WY MOUNTAINS FROM 20Z
UNTIL 02Z TUE. THEN CLOUDS WILL INCREASE AFTER 06Z TUE IN NW WYOMING
WITH SOME SHOWERS DEVELOPING OVER THE MOUNTAINS BY 12Z TUE.

&&

.FIRE WEATHER...
FLAT RIDGE OF HIGH PRESSURE WILL MOVE OVER THE AREA TONIGHT INTO
MONDAY. A FEW LIGHT SHOWERS WILL REMAIN A POSSIBILITY THROUGH
EARLY THIS EVENING IN THE NORTHERN MOUNTAINS. THE RIDGE OF HIGH
PRESSURE WILL MOVE OVERHEAD ON MONDAY FOR A DRY AND WARM DAY WITH
ONLY A SLIGHT CHANCE OF SHOWERS AND ISOLATED THUNDERSTORMS IN THE
FAR NORTHWEST MOUNTAINS. A STRONG COLD FRONT WILL BLAST EAST
ACROSS THE AREA ON TUESDAY WITH WIDESPREAD SHOWERS AND SOME
THUNDERSTORMS IN THE NORTHWEST AND FAR NORTH WITH A CHANCE OF
SHOWERS AND ISOLATED THUNDERSTORMS ELSEWHERE. STRONG WEST TO
NORTHWEST WINDS WILL ACCOMPANY THIS COLD FRONT WITH FAIRLY LOW MIN
RH`S OF 15 TO 20 PERCENT IN THE LOWER ELEVATIONS OF THE SOUTH.

&&

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

&&

$$

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

000
FXUS63 KUNR 210228
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
828 PM MDT SUN MAY 20 2012

.DISCUSSION...CURRENT SURFACE MAP SHOWS HIGH PRESSURE ACROSS THE
EASTERN DAKOTAS. A FEW CU/ACCAS ACROSS NORTHEAST WYOMING AND THE BLACK
HILLS IN AREA OF WEAK INSTABILITY/THETA-E ADVECTION. THREAT OF
THUNDERSTORMS DIMINISHING. FORECAST UPDATED TO REMOVE
THUNDERSTORMS FOR THE REMAINDER OF THE NIGHT.

&&

.AVIATION...00Z TAFS
VFR CONDITIONS EXPECTED THROUGH MONDAY EVENING.
ISOLATED THUNDERSTORMS ARE POSSIBLE ACROSS SOUTH CENTRAL SOUTH
DAKOTA LATE MONDAY AFTERNOON AND EVENING.

&&

.PREV DISCUSSION... /ISSUED 242 PM MDT SUN MAY 20 2012/

DISCUSSION...20Z SURFACE ANALYSIS SHOWED HIGH PRESSURE OVER THE
GREAT PLAINS. SOUTHERLY WINDS HAVE DEVELOPED TO THE WEST OF THE
HIGH...OVER NORTHEASTERN WYOMING AND WESTERN SOUTH DAKOTA. CUMULUS
WERE NOTED DEVELOPING OVER NORTHEASTERN WYOMING AND THE BLACK
HILLS THIS AFTERNOON WHERE SBCAPE HAS RISEN TO 250-500J/KG.

TONIGHT...THE UPPER RIDGE BUILDING OVER MONTANA AND WYOMING WILL
PROVIDE LARGE SCALE DESCENT OVER THE REGION SO ANY THUNDERSTORMS
WILL HAVE TO OVERCOME THAT AND SHOULD THEREFORE BE ISOLATED AND SHORT-LIVED.
LOW LEVEL JET DEVELOPS OVER CENTRAL SOUTH DAKOTA LATE
TONIGHT...WHICH MAY PROVIDE ENOUGH MID LEVEL INSTABILITY FOR
ISOLATED THUNDERSTORMS TO DEVELOP OVER SOUTH CENTRAL SOUTH DAKOTA
LATE TONIGHT/EARLY MONDAY.

MONDAY/MONDAY NIGHT...UPPER/THERMAL RIDGE BUILDS OVER THE FORECAST
AREA. SOUTHERLY LOW LEVEL JET UP TO 40KTS WILL SHIFT FROM WESTERN
SD INTO EASTERN SD...AND THEN REDEVELOP OVER NORTHEAST WY/WESTERN
SD MONDAY NIGHT. CAPPING BECOMES MORE PRONOUNCED...BUT NARROW AXIS
OF 1KJ/KG SBCAPE MAY BE ENOUGH FOR A FEW -TSRA OVER SOUTH CENTRAL
SD DURING PEAK HEATING LATE MONDAY AFTERNOON/EARLY EVENING.
TEMPERATURES WILL BE NOTICEABLY WARMER.

TUESDAY/TUESDAY NIGHT...UPPER RIDGE SHIFTS EAST AS UPPER TROUGH
SHIFTS INTO THE NORTHERN PLAINS WITH UPPER LOW OVER SOUTHERN SK.
SEVERAL SHORTWAVES WILL CROSS THE NORTHERN PLAINS. COOL FRONT MOVES
THROUGH LATE. INSTABILITY/SHEAR ALONG FRONT WILL LIKELY BE
SUFFICIENT FOR A FEW SEVERE STORMS...MAINLY OVER EASTERN PORTIONS
OF THE CWA. BEHIND FRONT...MODERATE BAND OF 850-700MB
FRONTOGENESIS WILL BRING BETTER CHANCES FOR POST FRONTAL
PRECIPITATION. TUESDAY SHOULD BE THE WARMEST DAY WITH 700MB
THERMAL RIDGE PEAKING AROUND 12C.

EXTENDED...AN UPPER LEVEL SYSTEM WILL PASS NORTH OF THE AREA DURING
THE MIDDLE AND LATTER PART OF THE WEEK. SOUTHWESTERLY FLOW ALOFT
WILL DEVELOP TO THE SOUTH OF THE SYSTEM OVER THE ROCKIES AND INTO
THE PLAINS. THIS PATTERN WILL LIKELY BRING A SERIES OF UPPER LEVEL
DISTURBANCES ACROSS THE AREA...WITH DAILY CHANCES FOR SHOWERS AND A
FEW STORMS FROM WEDNESDAY THROUGH THE END OF THE WEEK. TEMPERATURES
WILL GENERALLY BE NEAR OR SLIGHTLY BELOW AVERAGE LATE THIS WEEK...
WITH A WARMUP LIKELY OVER THE WEEKEND.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

SHORT TERM...07
LONG TERM....WFO UNR
AVIATION...07

000
FXUS65 KCYS 210045
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
645 PM MDT SUN MAY 20 2012

.UPDATE...SHOWERS DECREASING ON REFLECTIVITY LOOPS FROM DOPPLER
RADARS...THUS HAVE REMOVED SHOWERS AND THUNDERSTORMS THE REST OF
THE NIGHT.  RUBIN

&&

.PREV DISCUSSION... /ISSUED 553 PM MDT SUN MAY 20 2012/

AVIATION...00Z TAF ISSUANCE...
LATEST RADAR LOOP WAS SHOWING A FEW SHOWERS AND THUNDERSTORMS
MOVING THROUGH CHEYENNE COUNTY NEAR THE SNY TAF SITE. AFTER THESE
SHOWERS AND STORMS PASS...THINGS CLEAR OUT FAIRLY QUICKLY. RADAR
WAS ALSO INDICATING A CLUSTER OF SHOWERS AND THUNDERSTORMS
DEVELOPING AROUND DAWES AND SIOUX COUNTIES. A COUPLE OF THESE
SHOWERS AND THUNDERSTORMS MAY CLIP CHADRON...BUT MOST OF THE
ACTIVITY SHOULD REMAIN SOUTH OF THAT TAF SITE.

THE REMAINDER OF THE AREA...SHOULD HAVE VFR CONDITIONS THROUGH THE
PERIOD AS THE UPPER LEVEL RIDGE BUILDS OVER THE REGION.

COX

PREV DISCUSSION... /ISSUED 321 PM MDT SUN MAY 20 2012/

SHORT TERM...TONIGHT THROUGH WEDNESDAY

FIRE WEATHER IS THE MAIN CONCERN WITH THIS FORECAST PACKAGE AS
HIGH WINDS AND VERY WARM TEMPERATURES DEVELOP.

CURRENTLY...AS EXPECTED...ISOLATED TO WIDELY SCATTERED SHOWERS
HAS DEVELOPED OVER THE LARAMIE RANGE ALONG A WELL DEFINED
CONVERGENCE ZONE. EAST OF THE LARAMIE RANGE...SOUTHEAST WINDS
PREVAIL...TO THE WEST...SOUTHWESTERLY WINDS ARE BEING OBSERVED.
LATEST SPC MESOANALYSIS PAGE SHOWING AROUND 500 J/KG CAPE ALONG
THE EASTERN SLOPES OF THE LARAMIE RANGE...WITH SHORT RANGE
FORECAST OF THIS CAPES SPREADING EAST INTO THE PANHANDLE. THESE
SHOWERS ARE EXPECTED TO QUICKLY DISSIPATE AFTER SUNSET. FURTHER
WEST...THE NEXT LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT ARE
APPROACHING THE PACNW.

UPPER RIDGE CONTINUES TO BUILD OVER THE CWA TONIGHT INTO MONDAY
WITH HEIGHTS RISING FROM 576DM TODAY TO 582 DM MONDAY AFTERNOON.
RIDGE AXIS PASSES OVER THE CWA MONDAY NIGHT AND WINDS WILL SHIFT
MORE TO THE WEST. BY TUESDAY MORNING...700MB WINDS INCREASE TO
30KTS AT 12Z AND THEN UP TO 40KTS BY TUESDAY AFTERNOON. 700MB
TEMPERATURES QUITE WARM TUESDAY AFTERNOON...INCREASING FROM +10C
MONDAY AFTERNOON TO +15C OVER EXTREME SOUTHEAST WYOMING AND
SOUTHERN NEBRASKA PANHANDLE TUESDAY AFTERNOON. TUESDAY LOOKS TO BE
DOWNRIGHT HOT OUT OVER THE PANHANDLE WITH MID 90S EXPECTED.
FURTHER WEST...MID 80S LIKELY FOR SOUTHEAST WYOMING. WENT AHEAD
AND WILL ISSUE A FIRE WEATHER WATCH AS AFTERNOON HUMIDITIES WILL
GET QUITE LOW...SINGLE DIGIT HUMIDITIES EXPECTED DURING THE
AFTERNOON HOURS.

BY WEDNESDAY MORNING...COLD FRONT LOOKS TO HANG UP NEAR THE
WYOMING/COLORADO STATE LINE ON THE GFS. ECMWF SUPPORTS THIS
SOLUTION AND IS QUITE BULLISH ON QPFS...MORE SO THAN THE GFS. WENT
AHEAD AND UPPED POPS A LITTLE MORE AND LATER SHIFTS WILL LIKELY
NEED TO UP EVEN FURTHER IF THIS CURRENT SOLUTION HOLDS TRUE. SURE
IS LOOKING LIKE WE ARE GOING TO GET ANOTHER GOOD ROUND OF MUCH
NEEDED RAINFALL DURING MOST OF THE DAY WEDNESDAY.

LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...
MEDIUM RANGE GUIDANCE OFFERS SIMILAR SOLUTIONS ON THE BROAD
SYNOPTIC PATTERN THROUGH THE PERIOD. BROAD TROUGHING ACROSS THE
PACIFIC NORTHWEST EARLY IN THE PERIOD WILL AMPLIFY BY THE UPCOMING
WEEKEND AS SHORTWAVE ENERGY CARVES A CLOSED LOW OVER THE GREAT
BASIN.

SFC COLD FRONT WILL BE SOUTH OF THE CWA BY WEDNESDAY NIGHT.
HOWEVER...WILL STILL SEE GOOD MOISTURE CHANCES PERSIST AT LEAST
ACROSS THE SOUTHEAST THIRD OF THE CWA WEDNESDAY NIGHT. A
REINFORCING SURFACE FRONT WILL SURGE SOUTH DURING THE DAY ON
THURSDAY. THIS FRONT WILL COMBINE WITH A 100+ KNOT JET STREAK TO
PROVIDE A CONTINUATION OF PRECIPITATION CHANCES DURING THE DAY.
TEMPERATURES WILL REMAIN FAIRLY SEASONABLE ON THURSDAY WITH HIGHS
CLIMBING INTO THE 60S ACROSS MOST OF THE CWA WITH LOW 70S IN THE
LOWEST ELEVATIONS OF THE WRN NEBRASKA PANHANDLE. BY FRIDAY...THE
MID/UPPER-LEVEL FLOW WILL AMPLIFY AS THE CLOSED LOW FORMS OVER
THE GREAT BASIN. THIS SHOULD BOOST TEMPERATURES AND PRODUCE A FEW
ISOLATED SHOWERS/THUNDERSTORMS ON FRIDAY...THOUGH COVERAGE SHOULD
BE LESS THAN THURSDAY. THE UPPER-LOW WILL BEGIN TO LIFT NORTHEAST
TOWARDS THE NORTHERN ROCKIES DURING THE DAY ON SATURDAY. BY MIDDAY
SATURDAY...THE GFS PUTS THE H5 LOW CENTER OVR SW UTAH...WHILE THE
ECMWF TRACKS IT ACROSS NORTHEAST NEVADA. PACIFIC COLD FRONT IS
PROGD TO PUSH ACROSS THE CWA SATURDAY AFTERNOON/EVENING. THE
COMBINATION OF FRONTAL FORCING AND INSTABILITY APPROACHING 1000
J/KG SUGGESTS THAT AT LEAST SOME STRONG THUNDERSTORMS MIGHT BE A
POSSIBILITY. STILL TOO FAR TO BE TOO CONFIDENT...BUT WILL NEED TO
KEEP AN EYE ON OVER THE COMING DAYS. THE ENTIRE SYSTEM WILL FILL
AS IT LIFTS NORTHEAST ON SUNDAY. DRIER WEST FLOW BEHIND LATE
SATURDAYS FRONTAL PASSAGE SHOULD LIMIT PRECIPITATION CHANCES ON
SUNDAY.

AVIATION...18Z TAF ISSUANCE...
VFR CONDITIONS EXPECTED THROUGH THE PERIOD. MAIN AVIATION CONCERN
WILL BE DURING THE AFTERNOON AND EARLY EVENING HOURS AS A FEW
ISOLATED SHOWERS AND PERHAPS EVEN A THUNDERSTORM OR TWO DEVELOP
ACROSS AREA TERMINALS. NOT EXPECTING ALL THAT GREAT OF COVERAGE
NOR IMPACT AT TAF SITES...SO HAVE JUST KEPT VCTS MENTION FOR NOW.
THESE SHOWERS/THUNDERSTORMS WILL DISSIPATE BY EARLY EVENING...
GIVING WAY TO CLEARING SKIES TONIGHT. BREEZY SOUTH/SOUTHEAST WINDS
WILL PERSIST AT KCYS...KBFF...KSNY...KAIA AND KCDR...WHILE
SOUTHWEST WINDS PREVAIL AT KLAR AND KCYS TODAY. THESE WINDS WILL
RELAX SOME TONIGHT AS WELL.

FIRE WEATHER...

ISOLATED TO WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WILL COME
TO AN END AFTER SUNSET TODAY. EXPECT WARMING CONDITIONS MONDAY AS
WINDS SHIFT SOUTHWEST AND BEGIN TO INCREASE IN STRENGTH. BY
TUESDAY...A COLD FRONT APPROACHING WESTERN WYOMING WILL CAUSE
STRONG WEST TO SOUTHWEST WINDS TO DEVELOP AND BECOME WIDESPREAD
OVER SOUTHEAST WYOMING. CRITICAL FIRE WEATHER CONDITIONS EXPECTED
AHEAD OF THIS FRONT AS AFTERNOON HUMIDITIES DROP INTO THE UPPER
SINGLE DIGITS AND LOW TEENS...WITH TEMPERATURES IN THE MID 80S
ACROSS SOUTHEAST WYOMING AND LOW TO MID 90S IN THE PANHANDLE.
FRONT EXPECTED TO MOVE INTO SOUTHERN WYOMING NEAR THE STATE LINE
WITH COLORADO WEDNESDAY AFTERNOON...BRINGING COOLER
TEMPERATURES...HIGHER HUMIDITIES AND INCREASING CHANCES FOR
SHOWERS TO END THE WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...FIRE WEATHER WATCH FROM 11 AM TUESDAY TO 7 PM TUESDAY FOR WYZ106-
     WYZ114-WYZ116-WYZ117.
NE...NONE.

&&

$$

SHORT TERM/FIRE WEATHER...CLAYCOMB
LONG TERM/AVIATION...HAHN

000
FXUS65 KCYS 202353
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
553 PM MDT SUN MAY 20 2012

.AVIATION...00Z TAF ISSUANCE...
LATEST RADAR LOOP WAS SHOWING A FEW SHOWERS AND THUNDERSTORMS
MOVING THROUGH CHEYENNE COUNTY NEAR THE SNY TAF SITE. AFTER THESE
SHOWERS AND STORMS PASS...THINGS CLEAR OUT FAIRLY QUICKLY. RADAR
WAS ALSO INDICATING A CLUSTER OF SHOWERS AND THUNDERSTORMS
DEVELOPING AROUND DAWES AND SIOUX COUNTIES. A COUPLE OF THESE
SHOWERS AND THUNDERSTORMS MAY CLIP CHADRON...BUT MOST OF THE
ACTIVITY SHOULD REMAIN SOUTH OF THAT TAF SITE.

THE REMAINDER OF THE AREA...SHOULD HAVE VFR CONDITIONS THROUGH THE
PERIOD AS THE UPPER LEVEL RIDGE BUILDS OVER THE REGION.

COX
&&

.PREV DISCUSSION... /ISSUED 321 PM MDT SUN MAY 20 2012/

SHORT TERM...TONIGHT THROUGH WEDNESDAY

FIRE WEATHER IS THE MAIN CONCERN WITH THIS FORECAST PACKAGE AS
HIGH WINDS AND VERY WARM TEMPERATURES DEVELOP.

CURRENTLY...AS EXPECTED...ISOLATED TO WIDELY SCATTERED SHOWERS
HAS DEVELOPED OVER THE LARAMIE RANGE ALONG A WELL DEFINED
CONVERGENCE ZONE. EAST OF THE LARAMIE RANGE...SOUTHEAST WINDS
PREVAIL...TO THE WEST...SOUTHWESTERLY WINDS ARE BEING OBSERVED.
LATEST SPC MESOANALYSIS PAGE SHOWING AROUND 500 J/KG CAPE ALONG
THE EASTERN SLOPES OF THE LARAMIE RANGE...WITH SHORT RANGE
FORECAST OF THIS CAPES SPREADING EAST INTO THE PANHANDLE. THESE
SHOWERS ARE EXPECTED TO QUICKLY DISSIPATE AFTER SUNSET. FURTHER
WEST...THE NEXT LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT ARE
APPROACHING THE PACNW.

UPPER RIDGE CONTINUES TO BUILD OVER THE CWA TONIGHT INTO MONDAY
WITH HEIGHTS RISING FROM 576DM TODAY TO 582 DM MONDAY AFTERNOON.
RIDGE AXIS PASSES OVER THE CWA MONDAY NIGHT AND WINDS WILL SHIFT
MORE TO THE WEST. BY TUESDAY MORNING...700MB WINDS INCREASE TO
30KTS AT 12Z AND THEN UP TO 40KTS BY TUESDAY AFTERNOON. 700MB
TEMPERATURES QUITE WARM TUESDAY AFTERNOON...INCREASING FROM +10C
MONDAY AFTERNOON TO +15C OVER EXTREME SOUTHEAST WYOMING AND
SOUTHERN NEBRASKA PANHANDLE TUESDAY AFTERNOON. TUESDAY LOOKS TO BE
DOWNRIGHT HOT OUT OVER THE PANHANDLE WITH MID 90S EXPECTED.
FURTHER WEST...MID 80S LIKELY FOR SOUTHEAST WYOMING. WENT AHEAD
AND WILL ISSUE A FIRE WEATHER WATCH AS AFTERNOON HUMIDITIES WILL
GET QUITE LOW...SINGLE DIGIT HUMIDITIES EXPECTED DURING THE
AFTERNOON HOURS.

BY WEDNESDAY MORNING...COLD FRONT LOOKS TO HANG UP NEAR THE
WYOMING/COLORADO STATE LINE ON THE GFS. ECMWF SUPPORTS THIS
SOLUTION AND IS QUITE BULLISH ON QPFS...MORE SO THAN THE GFS. WENT
AHEAD AND UPPED POPS A LITTLE MORE AND LATER SHIFTS WILL LIKELY
NEED TO UP EVEN FURTHER IF THIS CURRENT SOLUTION HOLDS TRUE. SURE
IS LOOKING LIKE WE ARE GOING TO GET ANOTHER GOOD ROUND OF MUCH
NEEDED RAINFALL DURING MOST OF THE DAY WEDNESDAY.

LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...
MEDIUM RANGE GUIDANCE OFFERS SIMILAR SOLUTIONS ON THE BROAD
SYNOPTIC PATTERN THROUGH THE PERIOD. BROAD TROUGHING ACROSS THE
PACIFIC NORTHWEST EARLY IN THE PERIOD WILL AMPLIFY BY THE UPCOMING
WEEKEND AS SHORTWAVE ENERGY CARVES A CLOSED LOW OVER THE GREAT
BASIN.

SFC COLD FRONT WILL BE SOUTH OF THE CWA BY WEDNESDAY NIGHT.
HOWEVER...WILL STILL SEE GOOD MOISTURE CHANCES PERSIST AT LEAST
ACROSS THE SOUTHEAST THIRD OF THE CWA WEDNESDAY NIGHT. A
REINFORCING SURFACE FRONT WILL SURGE SOUTH DURING THE DAY ON
THURSDAY. THIS FRONT WILL COMBINE WITH A 100+ KNOT JET STREAK TO
PROVIDE A CONTINUATION OF PRECIPITATION CHANCES DURING THE DAY.
TEMPERATURES WILL REMAIN FAIRLY SEASONABLE ON THURSDAY WITH HIGHS
CLIMBING INTO THE 60S ACROSS MOST OF THE CWA WITH LOW 70S IN THE
LOWEST ELEVATIONS OF THE WRN NEBRASKA PANHANDLE. BY FRIDAY...THE
MID/UPPER-LEVEL FLOW WILL AMPLIFY AS THE CLOSED LOW FORMS OVER
THE GREAT BASIN. THIS SHOULD BOOST TEMPERATURES AND PRODUCE A FEW
ISOLATED SHOWERS/THUNDERSTORMS ON FRIDAY...THOUGH COVERAGE SHOULD
BE LESS THAN THURSDAY. THE UPPER-LOW WILL BEGIN TO LIFT NORTHEAST
TOWARDS THE NORTHERN ROCKIES DURING THE DAY ON SATURDAY. BY MIDDAY
SATURDAY...THE GFS PUTS THE H5 LOW CENTER OVR SW UTAH...WHILE THE
ECMWF TRACKS IT ACROSS NORTHEAST NEVADA. PACIFIC COLD FRONT IS
PROGD TO PUSH ACROSS THE CWA SATURDAY AFTERNOON/EVENING. THE
COMBINATION OF FRONTAL FORCING AND INSTABILITY APPROACHING 1000
J/KG SUGGESTS THAT AT LEAST SOME STRONG THUNDERSTORMS MIGHT BE A
POSSIBILITY. STILL TOO FAR TO BE TOO CONFIDENT...BUT WILL NEED TO
KEEP AN EYE ON OVER THE COMING DAYS. THE ENTIRE SYSTEM WILL FILL
AS IT LIFTS NORTHEAST ON SUNDAY. DRIER WEST FLOW BEHIND LATE
SATURDAYS FRONTAL PASSAGE SHOULD LIMIT PRECIPITATION CHANCES ON
SUNDAY.

AVIATION...18Z TAF ISSUANCE...
VFR CONDITIONS EXPECTED THROUGH THE PERIOD. MAIN AVIATION CONCERN
WILL BE DURING THE AFTERNOON AND EARLY EVENING HOURS AS A FEW
ISOLATED SHOWERS AND PERHAPS EVEN A THUNDERSTORM OR TWO DEVELOP
ACROSS AREA TERMINALS. NOT EXPECTING ALL THAT GREAT OF COVERAGE
NOR IMPACT AT TAF SITES...SO HAVE JUST KEPT VCTS MENTION FOR NOW.
THESE SHOWERS/THUNDERSTORMS WILL DISSIPATE BY EARLY EVENING...
GIVING WAY TO CLEARING SKIES TONIGHT. BREEZY SOUTH/SOUTHEAST WINDS
WILL PERSIST AT KCYS...KBFF...KSNY...KAIA AND KCDR...WHILE
SOUTHWEST WINDS PREVAIL AT KLAR AND KCYS TODAY. THESE WINDS WILL
RELAX SOME TONIGHT AS WELL.

FIRE WEATHER...

ISOLATED TO WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WILL COME
TO AN END AFTER SUNSET TODAY. EXPECT WARMING CONDITIONS MONDAY AS
WINDS SHIFT SOUTHWEST AND BEGIN TO INCREASE IN STRENGTH. BY
TUESDAY...A COLD FRONT APPROACHING WESTERN WYOMING WILL CAUSE
STRONG WEST TO SOUTHWEST WINDS TO DEVELOP AND BECOME WIDESPREAD
OVER SOUTHEAST WYOMING. CRITICAL FIRE WEATHER CONDITIONS EXPECTED
AHEAD OF THIS FRONT AS AFTERNOON HUMIDITIES DROP INTO THE UPPER
SINGLE DIGITS AND LOW TEENS...WITH TEMPERATURES IN THE MID 80S
ACROSS SOUTHEAST WYOMING AND LOW TO MID 90S IN THE PANHANDLE.
FRONT EXPECTED TO MOVE INTO SOUTHERN WYOMING NEAR THE STATE LINE
WITH COLORADO WEDNESDAY AFTERNOON...BRINGING COOLER
TEMPERATURES...HIGHER HUMIDITIES AND INCREASING CHANCES FOR
SHOWERS TO END THE WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...FIRE WEATHER WATCH FROM 11 AM TUESDAY TO 7 PM TUESDAY FOR WYZ106-
     WYZ114-WYZ116-WYZ117.
NE...NONE.

&&

$$

SHORT TERM/FIRE WEATHER...CLAYCOMB
LONG TERM/AVIATION...HAHN

000
FXUS65 KCYS 202319
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
519 PM MDT SUN MAY 20 2012

.UPDATE...BASED ON WSR-88D REFLECTIVITY...BOOSTED SHOWER AND
THUNDERSTORM CHANCES THROUGH EARLY EVENING ACROSS MORRILL AND
CHEYENNE COUNTIES OF WESTERN NEBRASKA AND A LITTLE HIGHER OVER
THE NORTHERN NEBRASKA PANHANDLE...WHILE DECREASING CHANCES
ELSEWHERE.  RUBIN

&&

.PREV DISCUSSION... /ISSUED 321 PM MDT SUN MAY 20 2012/

SHORT TERM...TONIGHT THROUGH WEDNESDAY

FIRE WEATHER IS THE MAIN CONCERN WITH THIS FORECAST PACKAGE AS
HIGH WINDS AND VERY WARM TEMPERATURES DEVELOP.

CURRENTLY...AS EXPECTED...ISOLATED TO WIDELY SCATTERED SHOWERS
HAS DEVELOPED OVER THE LARAMIE RANGE ALONG A WELL DEFINED
CONVERGENCE ZONE. EAST OF THE LARAMIE RANGE...SOUTHEAST WINDS
PREVAIL...TO THE WEST...SOUTHWESTERLY WINDS ARE BEING OBSERVED.
LATEST SPC MESOANALYSIS PAGE SHOWING AROUND 500 J/KG CAPE ALONG
THE EASTERN SLOPES OF THE LARAMIE RANGE...WITH SHORT RANGE
FORECAST OF THIS CAPES SPREADING EAST INTO THE PANHANDLE. THESE
SHOWERS ARE EXPECTED TO QUICKLY DISSIPATE AFTER SUNSET. FURTHER
WEST...THE NEXT LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT ARE
APPROACHING THE PACNW.

UPPER RIDGE CONTINUES TO BUILD OVER THE CWA TONIGHT INTO MONDAY
WITH HEIGHTS RISING FROM 576DM TODAY TO 582 DM MONDAY AFTERNOON.
RIDGE AXIS PASSES OVER THE CWA MONDAY NIGHT AND WINDS WILL SHIFT
MORE TO THE WEST. BY TUESDAY MORNING...700MB WINDS INCREASE TO
30KTS AT 12Z AND THEN UP TO 40KTS BY TUESDAY AFTERNOON. 700MB
TEMPERATURES QUITE WARM TUESDAY AFTERNOON...INCREASING FROM +10C
MONDAY AFTERNOON TO +15C OVER EXTREME SOUTHEAST WYOMING AND
SOUTHERN NEBRASKA PANHANDLE TUESDAY AFTERNOON. TUESDAY LOOKS TO BE
DOWNRIGHT HOT OUT OVER THE PANHANDLE WITH MID 90S EXPECTED.
FURTHER WEST...MID 80S LIKELY FOR SOUTHEAST WYOMING. WENT AHEAD
AND WILL ISSUE A FIRE WEATHER WATCH AS AFTERNOON HUMIDITIES WILL
GET QUITE LOW...SINGLE DIGIT HUMIDITIES EXPECTED DURING THE
AFTERNOON HOURS.

BY WEDNESDAY MORNING...COLD FRONT LOOKS TO HANG UP NEAR THE
WYOMING/COLORADO STATE LINE ON THE GFS. ECMWF SUPPORTS THIS
SOLUTION AND IS QUITE BULLISH ON QPFS...MORE SO THAN THE GFS. WENT
AHEAD AND UPPED POPS A LITTLE MORE AND LATER SHIFTS WILL LIKELY
NEED TO UP EVEN FURTHER IF THIS CURRENT SOLUTION HOLDS TRUE. SURE
IS LOOKING LIKE WE ARE GOING TO GET ANOTHER GOOD ROUND OF MUCH
NEEDED RAINFALL DURING MOST OF THE DAY WEDNESDAY.

LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...
MEDIUM RANGE GUIDANCE OFFERS SIMILAR SOLUTIONS ON THE BROAD
SYNOPTIC PATTERN THROUGH THE PERIOD. BROAD TROUGHING ACROSS THE
PACIFIC NORTHWEST EARLY IN THE PERIOD WILL AMPLIFY BY THE UPCOMING
WEEKEND AS SHORTWAVE ENERGY CARVES A CLOSED LOW OVER THE GREAT
BASIN.

SFC COLD FRONT WILL BE SOUTH OF THE CWA BY WEDNESDAY NIGHT.
HOWEVER...WILL STILL SEE GOOD MOISTURE CHANCES PERSIST AT LEAST
ACROSS THE SOUTHEAST THIRD OF THE CWA WEDNESDAY NIGHT. A
REINFORCING SURFACE FRONT WILL SURGE SOUTH DURING THE DAY ON
THURSDAY. THIS FRONT WILL COMBINE WITH A 100+ KNOT JET STREAK TO
PROVIDE A CONTINUATION OF PRECIPITATION CHANCES DURING THE DAY.
TEMPERATURES WILL REMAIN FAIRLY SEASONABLE ON THURSDAY WITH HIGHS
CLIMBING INTO THE 60S ACROSS MOST OF THE CWA WITH LOW 70S IN THE
LOWEST ELEVATIONS OF THE WRN NEBRASKA PANHANDLE. BY FRIDAY...THE
MID/UPPER-LEVEL FLOW WILL AMPLIFY AS THE CLOSED LOW FORMS OVER
THE GREAT BASIN. THIS SHOULD BOOST TEMPERATURES AND PRODUCE A FEW
ISOLATED SHOWERS/THUNDERSTORMS ON FRIDAY...THOUGH COVERAGE SHOULD
BE LESS THAN THURSDAY. THE UPPER-LOW WILL BEGIN TO LIFT NORTHEAST
TOWARDS THE NORTHERN ROCKIES DURING THE DAY ON SATURDAY. BY MIDDAY
SATURDAY...THE GFS PUTS THE H5 LOW CENTER OVR SW UTAH...WHILE THE
ECMWF TRACKS IT ACROSS NORTHEAST NEVADA. PACIFIC COLD FRONT IS
PROGD TO PUSH ACROSS THE CWA SATURDAY AFTERNOON/EVENING. THE
COMBINATION OF FRONTAL FORCING AND INSTABILITY APPROACHING 1000
J/KG SUGGESTS THAT AT LEAST SOME STRONG THUNDERSTORMS MIGHT BE A
POSSIBILITY. STILL TOO FAR TO BE TOO CONFIDENT...BUT WILL NEED TO
KEEP AN EYE ON OVER THE COMING DAYS. THE ENTIRE SYSTEM WILL FILL
AS IT LIFTS NORTHEAST ON SUNDAY. DRIER WEST FLOW BEHIND LATE
SATURDAYS FRONTAL PASSAGE SHOULD LIMIT PRECIPITATION CHANCES ON
SUNDAY.

AVIATION...18Z TAF ISSUANCE...
VFR CONDITIONS EXPECTED THROUGH THE PERIOD. MAIN AVIATION CONCERN
WILL BE DURING THE AFTERNOON AND EARLY EVENING HOURS AS A FEW
ISOLATED SHOWERS AND PERHAPS EVEN A THUNDERSTORM OR TWO DEVELOP
ACROSS AREA TERMINALS. NOT EXPECTING ALL THAT GREAT OF COVERAGE
NOR IMPACT AT TAF SITES...SO HAVE JUST KEPT VCTS MENTION FOR NOW.
THESE SHOWERS/THUNDERSTORMS WILL DISSIPATE BY EARLY EVENING...
GIVING WAY TO CLEARING SKIES TONIGHT. BREEZY SOUTH/SOUTHEAST WINDS
WILL PERSIST AT KCYS...KBFF...KSNY...KAIA AND KCDR...WHILE
SOUTHWEST WINDS PREVAIL AT KLAR AND KCYS TODAY. THESE WINDS WILL
RELAX SOME TONIGHT AS WELL.

FIRE WEATHER...

ISOLATED TO WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WILL COME
TO AN END AFTER SUNSET TODAY. EXPECT WARMING CONDITIONS MONDAY AS
WINDS SHIFT SOUTHWEST AND BEGIN TO INCREASE IN STRENGTH. BY
TUESDAY...A COLD FRONT APPROACHING WESTERN WYOMING WILL CAUSE
STRONG WEST TO SOUTHWEST WINDS TO DEVELOP AND BECOME WIDESPREAD
OVER SOUTHEAST WYOMING. CRITICAL FIRE WEATHER CONDITIONS EXPECTED
AHEAD OF THIS FRONT AS AFTERNOON HUMIDITIES DROP INTO THE UPPER
SINGLE DIGITS AND LOW TEENS...WITH TEMPERATURES IN THE MID 80S
ACROSS SOUTHEAST WYOMING AND LOW TO MID 90S IN THE PANHANDLE.
FRONT EXPECTED TO MOVE INTO SOUTHERN WYOMING NEAR THE STATE LINE
WITH COLORADO WEDNESDAY AFTERNOON...BRINGING COOLER
TEMPERATURES...HIGHER HUMIDITIES AND INCREASING CHANCES FOR
SHOWERS TO END THE WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...FIRE WEATHER WATCH FROM 11 AM TUESDAY TO 7 PM TUESDAY FOR WYZ106-
     WYZ114-WYZ116-WYZ117.
NE...NONE.

&&

$$

SHORT TERM/FIRE WEATHER...CLAYCOMB
LONG TERM/AVIATION...HAHN

000
FXUS65 KRIW 202139
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
339 PM MDT SUN MAY 20 2012

.SHORT TERM...TONIGHT THROUGH WEDNESDAY
WEAK ISENTROPIC UPGLIDE CLOUDS ACROSS IDAHO THIS MORNING HAVE
MOVED INTO WESTERN IDAHO WITH SOME VERY WEAK SHOWERS OVER THE
HIGHER NORTHWEST MOUNTAINS. WEAK INSTABILITY IN THE NE ZONES HAS
RESULTED IN SOME SMALL CU BUT NO SHOWERS. WILL LEAVE THE ISOLATED
SHOWERS IN THE FORECAST INTO THE EVENING ACROSS MAINLY THE
NORTHERN MOUNTAINS. FLAT RIDGE MOVES OVERHEAD ON MONDAY WITH A
JUST A WEAK WAVE POSSIBLY BRUSHING THE FAR NW. NEGATIVELY TILTED
TROUGH AND COLD FRONT THEN MOVE IN TUESDAY WITH WIDESPREAD SHOWERS
EXPECTED IN THE NORTHWEST AND FAR NORTH WITH A STRONG COLD FRONT
BLASTING EAST ACROSS THE AREA. WINDS WILL LIKELY BE QUITE STRONG
WITH THE POSSIBILITY OF SOME HIGH WINDS FOR A FEW HOURS ACROSS THE
CENTRAL AND SRN ZONES WITH AND FOR A FEW HOURS AFTER FROPA. WILL
NEED TO WATCH THIS CLOSELY FOR POTENTIAL HIGH WIND WATCHES. SHOWER AND
THUNDERSTORM POSSIBILITIES EXIST FURTHER SOUTH BUT THE HIGHEST
PROBABILITY WILL BE IN THE NW AND FAR NORTH. FRONTAL BOUNDARY MAY
STALL OUT ACROSS THE FAR SOUTH OR INTO NRN COLORADO KEEPING SOME
SHOWER POSSIBILITIES ACROSS SWEETWATER COUNTY LATER TUESDAY NIGHT
INTO WEDNESDAY. DEFINITELY COLD ENOUGH FOR SOME HIGHER ELEVATION
SNOW BEHIND THE FRONT IN THE NW MOUNTAINS TUESDAY INTO TUESDAY
EVENING. SOUNDINGS AREN`T SHOWING MUCH CAPE AHEAD OF THE FRONT
WITH DRY LOW LEVELS AND EARLY FRONTAL PASSAGE EXCEPT IN THE EAST
BUT WE WILL STILL NEED TO KEEP AN EYE ON THIS. COOLER AND
UNSETTLED THEN INTO WEDNESDAY WITH SEVERAL SHORTWAVES MOVING
THROUGH THE SW FLOW. BEST SHOT OF SHOWERS WILL BE IN THE MOUNTAINS
BUT ALL AREAS WILL SEE A FEW SHOWERS AROUND AT LEAST TUESDAY NIGHT
AND WEDNESDAY.

.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY

A TURN TO COOLER AND SHOWERY CONDITIONS EXPECTED.

A CLOSED LOW WILL ESTABLISH ITSELF OVER MONTANA PER ECMWF BY
WEDNESDAY NIGHT WITH THE GFS ALREADY MOVING NORTHEAST INTO THE
NORTHERN PLAINS BY THEN AS THE GFS WILL BE THE FASTER OF THE TWO
MODELS AS WELL AS SWINGING A COLDER TROUGH ACROSS THE AREA THURSDAY
WHEREAS THE ECMWF KEEPS THE TROUGHINESS NORTHWEST OVER THE PACIFIC
NORTHWEST. WILL CONTINUE TO SIDE WITH THE ECMWF ALONG WITH A LITTLE
BIT OF A COMPROMISE IN THE FORECAST. BY FRIDAY THE GFS HAS A COL
REGION OVER US WITH THE ECMWF SCOOTING THE TROUGH TO THE NORTHEAST
INTO CANADA ALLOWING SOUTHWEST FLOW TO INFILTRATE THE AREA. HOWEVER
THE ECMWF ALSO INDICATES A SURFACE HIGH TO THE NORTH AND A SURFACE
LOW OVER THE GREAT BASIN ALLOWING FOR COOL UPSLOPE CONDITIONS IN
MAINLY IN CENTRAL WYOMING EAST OF THE DIVIDE AS THE SOUTHWEST WINDS
ALOFT OVERRUN THE MOIST SURFACE UPSLOPE CONDITIONS. WITH THIS
POSSIBILITY...COOLED THINGS DOWN FRIDAY WITH STRATIFORM PRECIP IN
UPSLOPE FAVORED AREAS IN CENTRAL WYOMING FOR NOW. ONLY COOLED TEMPS
A FEW DEGREES FRIDAY BUT LATER SHIFTS CAN LOOK INTO THIS. SOME SNOW
IS EXPECTED IN THE MOUNTAINS ESPECIALLY ON THURSDAY AND DRY WITH H7
TEMPS DIPPING TO -6C IN NORTHERN WY THURSDAY. ON SATURDAY...WITH THE
UPSTREAM LOW ASSOCIATED WITH THE RELOADING TROUGH TO THE WEST...WILL
BECOME INCREASINGLY CUT OFF OVER CALIFORNIA...A SOUTHWEST FLOW AND
RESULTING WARMING AND DRYING TREND WILL ENSUE SATURDAY OVER WYOMING.
BY SUNDAY THIS LOW WILL TRACK NORTHEAST TO THE VICINITY OF WYOMING
SO HAVE INCREASED PRECIP FOR SUNDAY.

.AVIATION.../00Z ISSUANCE/

MAINLY VFR CONDITIONS WILL OCCUR THROUGH 002Z TUESDAY. ISOLATED
SHOWERS ARE POSSIBLE OVER THE HIGHER PEAKS OF THE BIGHORN MOUNTAINS
AND IN THE NW WY MOUNTAINS FROM 20Z UNTIL 02Z MONDAY WITH ISOLATED
THUNDERSTORMS EXPECTED IN THESE AREAS ON MONDAY AFTERNOON. SOUTHWEST
WINDS INCREASE MONDAY AFTERNOON COINCIDENT WITH THE DEVELOPMENT OF A
WEAK LEE SIDE TROUGH.


.FIRE WEATHER...
FLAT RIDGE OF HIGH PRESSURE WILL MOVE OVER THE AREA TONIGHT INTO
MONDAY. A FEW LIGHT SHOWERS WILL REMAIN A POSSIBILITY THROUGH
EARLY THIS EVENING IN THE NORTHERN MOUNTAINS. THE RIDGE OF HIGH
PRESSURE WILL MOVE OVERHEAD ON MONDAY FOR A DRY AND WARM DAY WITH
ONLY A SLIGHT CHANCE OF SHOWERS AND ISOLATED THUNDERSTORMS IN THE
FAR NORTHWEST MOUNTAINS. A STRONG COLD FRONT WILL BLAST EAST
ACROSS THE AREA ON TUESDAY WITH WIDESPREAD SHOWERS AND SOME
THUNDERSTORMS IN THE NORTHWEST AND FAR NORTH WITH A CHANCE OF
SHOWERS AND ISOLATED THUNDERSTORMS ELSEWHERE. STRONG WEST TO
NORTHWEST WINDS WILL ACCOMPANY THIS COLD FRONT WITH FAIRLY LOW MIN
RH`S OF 15 TO 20 PERCENT IN THE LOWER ELEVATIONS OF THE SOUTH.

&&

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

&&

$$

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

000
FXUS65 KCYS 202121
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
321 PM MDT SUN MAY 20 2012

.SHORT TERM...TONIGHT THROUGH WEDNESDAY

FIRE WEATHER IS THE MAIN CONCERN WITH THIS FORECAST PACKAGE AS
HIGH WINDS AND VERY WARM TEMPERATURES DEVELOP.

CURRENTLY...AS EXPECTED...ISOLATED TO WIDELY SCATTERED SHOWERS
HAS DEVELOPED OVER THE LARAMIE RANGE ALONG A WELL DEFINED
CONVERGENCE ZONE. EAST OF THE LARAMIE RANGE...SOUTHEAST WINDS
PREVAIL...TO THE WEST...SOUTHWESTERLY WINDS ARE BEING OBSERVED.
LATEST SPC MESOANALYSIS PAGE SHOWING AROUND 500 J/KG CAPE ALONG
THE EASTERN SLOPES OF THE LARAMIE RANGE...WITH SHORT RANGE
FORECAST OF THIS CAPES SPREADING EAST INTO THE PANHANDLE. THESE
SHOWERS ARE EXPECTED TO QUICKLY DISSIPATE AFTER SUNSET. FURTHER
WEST...THE NEXT LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT ARE
APPROACHING THE PACNW.

UPPER RIDGE CONTINUES TO BUILD OVER THE CWA TONIGHT INTO MONDAY
WITH HEIGHTS RISING FROM 576DM TODAY TO 582 DM MONDAY AFTERNOON.
RIDGE AXIS PASSES OVER THE CWA MONDAY NIGHT AND WINDS WILL SHIFT
MORE TO THE WEST. BY TUESDAY MORNING...700MB WINDS INCREASE TO
30KTS AT 12Z AND THEN UP TO 40KTS BY TUESDAY AFTERNOON. 700MB
TEMPERATURES QUITE WARM TUESDAY AFTERNOON...INCREASING FROM +10C
MONDAY AFTERNOON TO +15C OVER EXTREME SOUTHEAST WYOMING AND
SOUTHERN NEBRASKA PANHANDLE TUESDAY AFTERNOON. TUESDAY LOOKS TO BE
DOWNRIGHT HOT OUT OVER THE PANHANDLE WITH MID 90S EXPECTED.
FURTHER WEST...MID 80S LIKELY FOR SOUTHEAST WYOMING. WENT AHEAD
AND WILL ISSUE A FIRE WEATHER WATCH AS AFTERNOON HUMIDITIES WILL
GET QUITE LOW...SINGLE DIGIT HUMIDITIES EXPECTED DURING THE
AFTERNOON HOURS.

BY WEDNESDAY MORNING...COLD FRONT LOOKS TO HANG UP NEAR THE
WYOMING/COLORADO STATE LINE ON THE GFS. ECMWF SUPPORTS THIS
SOLUTION AND IS QUITE BULLISH ON QPFS...MORE SO THAN THE GFS. WENT
AHEAD AND UPPED POPS A LITTLE MORE AND LATER SHIFTS WILL LIKELY
NEED TO UP EVEN FURTHER IF THIS CURRENT SOLUTION HOLDS TRUE. SURE
IS LOOKING LIKE WE ARE GOING TO GET ANOTHER GOOD ROUND OF MUCH
NEEDED RAINFALL DURING MOST OF THE DAY WEDNESDAY.

.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...
MEDIUM RANGE GUIDANCE OFFERS SIMILAR SOLUTIONS ON THE BROAD
SYNOPTIC PATTERN THROUGH THE PERIOD. BROAD TROUGHING ACROSS THE
PACIFIC NORTHWEST EARLY IN THE PERIOD WILL AMPLIFY BY THE UPCOMING
WEEKEND AS SHORTWAVE ENERGY CARVES A CLOSED LOW OVER THE GREAT
BASIN.

SFC COLD FRONT WILL BE SOUTH OF THE CWA BY WEDNESDAY NIGHT.
HOWEVER...WILL STILL SEE GOOD MOISTURE CHANCES PERSIST AT LEAST
ACROSS THE SOUTHEAST THIRD OF THE CWA WEDNESDAY NIGHT. A
REINFORCING SURFACE FRONT WILL SURGE SOUTH DURING THE DAY ON
THURSDAY. THIS FRONT WILL COMBINE WITH A 100+ KNOT JET STREAK TO
PROVIDE A CONTINUATION OF PRECIPITATION CHANCES DURING THE DAY.
TEMPERATURES WILL REMAIN FAIRLY SEASONABLE ON THURSDAY WITH HIGHS
CLIMBING INTO THE 60S ACROSS MOST OF THE CWA WITH LOW 70S IN THE
LOWEST ELEVATIONS OF THE WRN NEBRASKA PANHANDLE. BY FRIDAY...THE
MID/UPPER-LEVEL FLOW WILL AMPLIFY AS THE CLOSED LOW FORMS OVER
THE GREAT BASIN. THIS SHOULD BOOST TEMPERATURES AND PRODUCE A FEW
ISOLATED SHOWERS/THUNDERSTORMS ON FRIDAY...THOUGH COVERAGE SHOULD
BE LESS THAN THURSDAY. THE UPPER-LOW WILL BEGIN TO LIFT NORTHEAST
TOWARDS THE NORTHERN ROCKIES DURING THE DAY ON SATURDAY. BY MIDDAY
SATURDAY...THE GFS PUTS THE H5 LOW CENTER OVR SW UTAH...WHILE THE
ECMWF TRACKS IT ACROSS NORTHEAST NEVADA. PACIFIC COLD FRONT IS
PROGD TO PUSH ACROSS THE CWA SATURDAY AFTERNOON/EVENING. THE
COMBINATION OF FRONTAL FORCING AND INSTABILITY APPROACHING 1000
J/KG SUGGESTS THAT AT LEAST SOME STRONG THUNDERSTORMS MIGHT BE A
POSSIBILITY. STILL TOO FAR TO BE TOO CONFIDENT...BUT WILL NEED TO
KEEP AN EYE ON OVER THE COMING DAYS. THE ENTIRE SYSTEM WILL FILL
AS IT LIFTS NORTHEAST ON SUNDAY. DRIER WEST FLOW BEHIND LATE
SATURDAYS FRONTAL PASSAGE SHOULD LIMIT PRECIPITATION CHANCES ON
SUNDAY.

&&

.AVIATION...18Z TAF ISSUANCE...
VFR CONDITIONS EXPECTED THROUGH THE PERIOD. MAIN AVIATION CONCERN
WILL BE DURING THE AFTERNOON AND EARLY EVENING HOURS AS A FEW
ISOLATED SHOWERS AND PERHAPS EVEN A THUNDERSTORM OR TWO DEVELOP
ACROSS AREA TERMINALS. NOT EXPECTING ALL THAT GREAT OF COVERAGE
NOR IMPACT AT TAF SITES...SO HAVE JUST KEPT VCTS MENTION FOR NOW.
THESE SHOWERS/THUNDERSTORMS WILL DISSIPATE BY EARLY EVENING...
GIVING WAY TO CLEARING SKIES TONIGHT. BREEZY SOUTH/SOUTHEAST WINDS
WILL PERSIST AT KCYS...KBFF...KSNY...KAIA AND KCDR...WHILE
SOUTHWEST WINDS PREVAIL AT KLAR AND KCYS TODAY. THESE WINDS WILL
RELAX SOME TONIGHT AS WELL.

&&

.FIRE WEATHER...

ISOLATED TO WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WILL COME
TO AN END AFTER SUNSET TODAY. EXPECT WARMING CONDITIONS MONDAY AS
WINDS SHIFT SOUTHWEST AND BEGIN TO INCREASE IN STRENGTH. BY
TUESDAY...A COLD FRONT APPROACHING WESTERN WYOMING WILL CAUSE
STRONG WEST TO SOUTHWEST WINDS TO DEVELOP AND BECOME WIDESPREAD
OVER SOUTHEAST WYOMING. CRITICAL FIRE WEATHER CONDITIONS EXPECTED
AHEAD OF THIS FRONT AS AFTERNOON HUMIDITIES DROP INTO THE UPPER
SINGLE DIGITS AND LOW TEENS...WITH TEMPERATURES IN THE MID 80S
ACROSS SOUTHEAST WYOMING AND LOW TO MID 90S IN THE PANHANDLE.
FRONT EXPECTED TO MOVE INTO SOUTHERN WYOMING NEAR THE STATE LINE
WITH COLORADO WEDNESDAY AFTERNOON...BRINGING COOLER
TEMPERATURES...HIGHER HUMIDITIES AND INCREASING CHANCES FOR
SHOWERS TO END THE WEEK.


&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...FIRE WEATHER WATCH FROM 11 AM TUESDAY TO 7 PM TUESDAY FOR WYZ106-
     WYZ114-WYZ116-WYZ117.
NE...NONE.

&&

$$

SHORT TERM/FIRE WEATHER...CLAYCOMB
LONG TERM/AVIATION...HAHN

000
FXUS63 KUNR 202042
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
242 PM MDT SUN MAY 20 2012

.DISCUSSION...20Z SURFACE ANALYSIS SHOWED HIGH PRESSURE OVER THE
GREAT PLAINS. SOUTHERLY WINDS HAVE DEVELOPED TO THE WEST OF THE
HIGH...OVER NORTHEASTERN WYOMING AND WESTERN SOUTH DAKOTA. CUMULUS
WERE NOTED DEVELOPING OVER NORTHEASTERN WYOMING AND THE BLACK
HILLS THIS AFTERNOON WHERE SBCAPE HAS RISEN TO 250-500J/KG.

TONIGHT...THE UPPER RIDGE BUILDING OVER MONTANA AND WYOMING WILL
PROVIDE LARGE SCALE DESCENT OVER THE REGION SO ANY THUNDERSTORMS
WILL HAVE TO OVERCOME THAT AND SHOULD THEREFORE BE ISOLATED AND SHORT-LIVED.
LOW LEVEL JET DEVELOPS OVER CENTRAL SOUTH DAKOTA LATE
TONIGHT...WHICH MAY PROVIDE ENOUGH MID LEVEL INSTABILITY FOR
ISOLATED THUNDERSTORMS TO DEVELOP OVER SOUTH CENTRAL SOUTH DAKOTA
LATE TONIGHT/EARLY MONDAY.

MONDAY/MONDAY NIGHT...UPPER/THERMAL RIDGE BUILDS OVER THE FORECAST
AREA. SOUTHERLY LOW LEVEL JET UP TO 40KTS WILL SHIFT FROM WESTERN
SD INTO EASTERN SD...AND THEN REDEVELOP OVER NORTHEAST WY/WESTERN
SD MONDAY NIGHT. CAPPING BECOMES MORE PRONOUNCED...BUT NARROW AXIS
OF 1KJ/KG SBCAPE MAY BE ENOUGH FOR A FEW -TSRA OVER SOUTH CENTRAL
SD DURING PEAK HEATING LATE MONDAY AFTERNOON/EARLY EVENING.
TEMPERATURES WILL BE NOTICEABLY WARMER.

TUESDAY/TUESDAY NIGHT...UPPER RIDGE SHIFTS EAST AS UPPER TROUGH
SHIFTS INTO THE NORTHERN PLAINS WITH UPPER LOW OVER SOUTHERN SK.
SEVERAL SHORTWAVES WILL CROSS THE NORTHERN PLAINS. COOL FRONT MOVES
THROUGH LATE. INSTABILITY/SHEAR ALONG FRONT WILL LIKELY BE
SUFFICIENT FOR A FEW SEVERE STORMS...MAINLY OVER EASTERN PORTIONS
OF THE CWA. BEHIND FRONT...MODERATE BAND OF 850-700MB
FRONTOGENESIS WILL BRING BETTER CHANCES FOR POST FRONTAL
PRECIPITATION. TUESDAY SHOULD BE THE WARMEST DAY WITH 700MB
THERMAL RIDGE PEAKING AROUND 12C.

EXTENDED...AN UPPER LEVEL SYSTEM WILL PASS NORTH OF THE AREA DURING
THE MIDDLE AND LATTER PART OF THE WEEK. SOUTHWESTERLY FLOW ALOFT
WILL DEVELOP TO THE SOUTH OF THE SYSTEM OVER THE ROCKIES AND INTO
THE PLAINS. THIS PATTERN WILL LIKELY BRING A SERIES OF UPPER LEVEL
DISTURBANCES ACROSS THE AREA...WITH DAILY CHANCES FOR SHOWERS AND A
FEW STORMS FROM WEDNESDAY THROUGH THE END OF THE WEEK. TEMPERATURES
WILL GENERALLY BE NEAR OR SLIGHTLY BELOW AVERAGE LATE THIS WEEK...
WITH A WARMUP LIKELY OVER THE WEEKEND.

&&

.AVIATION...00Z TAFS
VFR CONDITIONS ARE EXPECTED THROUGH MONDAY...WITH SOUTHERLY WINDS
CONTINUING OVER THE AREA. AN ISOLATED THUNDERSTORM OR TWO WILL BE
POSSIBLE ACROSS NORTHEASTERN WY AND THE BLACK HILLS LATE THIS
AFTERNOON AND EARLY EVENING.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

000
FXUS65 KCYS 201817
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1217 PM MDT SUN MAY 20 2012

.AVIATION...18Z TAF ISSUANCE...
VFR CONDITIONS EXPECTED THROUGH THE PERIOD. MAIN AVIATION CONCERN
WILL BE DURING THE AFTERNOON AND EARLY EVENING HOURS AS A FEW
ISOLATED SHOWERS AND PERHAPS EVEN A THUNDERSTORM OR TWO DEVELOP
ACROSS AREA TERMINALS. NOT EXPECTING ALL THAT GREAT OF COVERAGE
NOR IMPACT AT TAF SITES...SO HAVE JUST KEPT VCTS MENTION FOR NOW.
THESE SHOWERS/THUNDERSTORMS WILL DISSIPATE BY EARLY EVENING...
GIVING WAY TO CLEARING SKIES TONIGHT. BREEZY SOUTH/SOUTHEAST WINDS
WILL PERSIST AT KCYS...KBFF...KSNY...KAIA AND KCDR...WHILE
SOUTHWEST WINDS PREVAIL AT KLAR AND KCYS TODAY. THESE WINDS WILL
RELAX SOME TONIGHT AS WELL.

&&

.PREV DISCUSSION... /ISSUED 600 AM MDT SUN MAY 20 2012/

SHORT TERM...
AXIS OF SURFACE HIGH PRESSURE OVER THE NEBRASKA PANHANDLE EARLY
THIS MORNING WILL SHIFT EAST AS THE MORNING CONTINUES. GENERALLY
WILL SEE CLEAR SKIES THROUGH THIS MORNING...BUT A SUBTLE DISTURBANCE
MOVING THROUGH WESTERLY FLOW ALOFT WILL PRODUCE SOME HIGH CLOUDS
AS IT SKIRTS ACROSS THE AREA. AS THE HIGH SHIFTS EAST WILL SEE
SOUTHEAST LOW LEVEL FLOW SET IN EAST OF THE LARAMIE RANGE WHILE
WESTERLY LOW LEVEL WINDS WILL DEVELOP WEST OF THE LARAMIE RANGE.
WEAK LOW CONVERGENCE ZONE...AND LEFT EXIT REGION OF AN UPPER JET
WILL CREATE AN ENVIRONMENT FOR ISOLATED THUNDERSTORM DEVELOPMENT
THIS AFTERNOON. BIGGEST INHIBITOR FOR THUNDERSTORM DEVELOP WILL
BE THE LACK OF LOW LEVEL MOISTURE BUT MODELS DO PRODUCE UPWARDS OF
500 JOULES/KG OF CAPE THIS AFTERNOON AND WITH VERY STEEP LAPSE
RATES SHOULD BE ABLE TO POP A FEW THUNDERSTORMS. MAIN THUNDERSTORM
POTENTIAL SHOULD BE OVER SOUTHEAST WYOMING EAST OF THE LARAMIE
RANGE BUT COULD SEE THUNDERSTORMS INTO THE NEBRASKA PANHANDLE TOO.
NOT EXPECTING SEVERE THUNDERSTORMS BUT GIVEN SOME CAPE...40-45 KTS
OF BULK SHEAR AND RELATIVELY LOW FREEZING LEVELS...CAN NOT
COMPLETELY RULE OUT MARGINALLY SEVERE SIZED HAIL. SEVERE STORMS
PREDICTION CENTER FORECASTING GENERAL THUNDER WITH 5 PERCENT
CHANCE SEVERE HAIL AND SEVERE WINDS. THIS LOOKS VERY REASONABLE
GIVEN CURRENT MODEL DATA.

ANY SHOWERS OR THUNDERSTORMS THAT DO DEVELOP WILL HAVE AN IMPACT
ON VIEWING THE PARTIAL SOLAR ECLIPSE THAT WILL OCCUR LATE TODAY.
THE ECLIPSE WILL OCCUR IN THE WESTERN SKY STARTING AROUND 620 PM
AND CONTINUE THROUGH SUNSET. SKIES WILL CLEAR FROM WEST TO EAST AS
THE NIGHT CONTINUES BUT MAY BE TOO LATE FOR ECLIPSE VIEWING
DEPENDING ON LOCATION.

TEMPERATURES WILL BE MILD TODAY AFTER STARTING THE MORNING OFF ON
THE CHILLY SIDE. HIGHS TODAY WILL BE IN THE UPPER 60S TO MID 70S
ACROSS THE AREA. A GOOD DEAL WARMER TOMORROW WITH HIGHS MAINLY IN
THE 80S AS AN UPPER RIDGE BUILDS ACROSS THE AREA. UPPER RIDGE
MEANS VIRTUALLY NO CHANCES FOR PRECIPITATION TOMORROW ALONG WITH
CLEAR SKIES. FOR MOST OF THE FORECAST AREA THE WARMEST DAY OF THE
WEEK WILL BE TUESDAY JUST AHEAD OF AN APPROACHING TROUGH. WESTERLY
DOWN SLOPE FLOW WILL PUSH TEMPERATURES INTO THE 90S INTO THE
NEBRASKA PANHANDLE.

LONG TERM...TUESDAY NIGHT THROUGH SATURDAY NIGHT...MODELS IN
GOOD AGREEMENT THROUGH NEXT WEEK...SHOWING PERIODS OF UNSETTLED
WEATHER ACROSS SOUTHEAST WYOMING AND WESTERN NEBRASKA AS AN UPPER
LEVEL LOW PUSHES INTO THE WEST COAST AND NORTHERN ROCKIES. THIS
WILL RESULT IN A GOOD CHANCE OF SOME MUCH NEEDED RAINFALL ACROSS
THE AREA TUESDAY THROUGH FRIDAY. AN UPPER LEVEL RIDGE AXIS
WILL PUSH EAST OF THE FORECAST AREA ON TUESDAY AS THE STRONG UPPER
LOW AND ASSOCIATED COLD FRONT MOVES INTO THE PACIFIC NW COASTLINE.
THIS COLD FRONT WILL BE RATHER STRONG FOR THIS TIME OF THE
YEAR...AND WILL PUSH EASTWARD INTO EASTERN WYOMING AND WESTERN
NEBRASKA TUESDAY NIGHT AND EARLY WEDNESDAY. STRONG GUSTY WINDS
ARE EXPECTED AHEAD OF THIS FRONT THROUGH TUESDAY EVENING WITH
GUSTS OVER 50 MPH POSSIBLE...ESPECIALLY ALONG AND WEST OF THE
LARAMIE RANGE. THERE IS MORE CONFIDENCE THAT WEDNESDAY WILL BE
MUCH COOLER ACROSS THE FORECAST AREA AS ALL MODELS ARE SHOWING A
FASTER FRONTAL PASSAGE. EXPECT HIGH TEMPERATURES TO LOWER INTO THE
UPPER 50S TO UPPER 60S WEDNESDAY AFTERNOON. ALONG WITH THE GUSTY
WINDS AND COOLER TEMPERATURES...THERE IS A GOOD CHANCE OF
PRECIPITATION ACROSS THE WHOLE FORECAST AREA TUESDAY NIGHT THROUGH
WEDNESDAY AS THE FRONT STALLS OR SLOWLY PUSHES SOUTHWARD. AS THE
UPPER LEVEL LOW PUSHES INLAND AND DIGS SOUTHWARD ACROSS THE WEST
COAST LATE IN THE WEEK...THE FRONT AND ASSOCIATED 140KT JET MAX IS
EXPECTED TO PUSH NORTHWARD...WITH ANOTHER GOOD CHANCE OF
WIDESPREAD MODERATE PRECIPITATION. CONTINUED TO INCREASE POP UP TO
50 PERCENT THROUGH THURSDAY NIGHT FOR NUMEROUS RAIN SHOWERS AND
ISOLATED TSTORMS.

BY EARLY NEXT WEEK...ALL MODELS INDICATE THE FRONT MOVING NORTH OF
THE FORECAST AREA AS A WARM FRONT WITH DRIER AIR ALOFT PUSHING
ACROSS THE FORECAST AREA. THE UPPER LEVEL LOW TO THE WEST WILL
SLOWLY MOVE EAST INTO THE GREAT BASIN REGION AND STALL. EXPECT
TEMPERATURES TO INCREASE BACK INTO THE 70S AND 80S WITH WARM
SOUTHWEST FLOW ALOFT. CAN NOT RULE OUT SOME PATCHY FOG OR LOW
STRATUS CLOUDS EAST OF THE LARAMIE RANGE DUE TO LLVL SOUTHEAST FLOW.

&&

.FIRE WEATHER...
NO FIRE WEATHER CONCERNS TODAY OR TOMORROW. MINIMUM HUMIDITY
TODAY WILL BE ABOVE 20 PERCENT FOR MOST OF THE AREA TODAY AND
WINDS WILL BE ON THE LIGHTER SIDE. WARMER WITH LOWER RELATIVE
HUMIDITY MONDAY BUT WINDS WILL REMAIN ON THE LIGHT SIDE. CRITICAL
FIRE THRESHOLDS COULD BE REACHED TUESDAY WITH HUMIDITY VALUES
DROPPING TO 10 TO 15 PERCENT OVER MUCH OF THE AREA ALONG WITH
WINDY CONDITIONS.

ISOLATE THUNDERSTORMS ARE EXPECTED FROM THE LARAMIE RANGE EAST
INTO THE NEBRASKA PANHANDLE THIS AFTERNOON. GUSTY WINDS AND SMALL
HAIL POSSIBLE WITH THESE STORMS. DRY MONDAY AND TUESDAY UNDER THE
INFLUENCE OF THE UPPER LEVEL RIDGE...THEN CHANCES FOR SHOWERS AND
THUNDERSTORMS THE REMAINDER OF THE WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.

&&

$$

SHORT TERM/FIRE WEATHER...LIEBL
LONG TERM...TJT

000
FXUS65 KRIW 201802
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1200 PM MDT SUN MAY 20 2012

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

MAINLY DRY AND WARMER CONDITIONS WILL PREVAIL TODAY AS AN UPPER
RIDGE BUILDS OVER THE WESTERN CONUS.  HAVE INTRODUCED SLIGHT POPS TO
THE BIGHORNS THIS AFTERNOON AS AN EXTREMELY WEAK WAVE TRANSITS THE
RIDGE.  SOME VERY LIGHT SHOWERS POSSIBLE BUT THUNDER UNLIKELY.  MUCH
WARMER CONDITIONS ARE ON TAP FOR MONDAY AS H7 TEMPS APPROACH +13C IN
THE AFTERNOON.  THIS WILL BRING MID 80S TO THE LOWER ELEVATIONS EAST
OF THE CONTINENTAL DIVIDE WITH TEMPERATURES NEAR 90 POSSIBLE IN
ISOLATED AREAS OF THE BIG HORN BASIN. FAVORABLE LAPSE RATE WILL
BRING SOME HIGH BASED CUMULUS CLOUDS MONDAY AFTERNOON BUT MOISTURE
WILL BE LACKING TO PRODUCE SHOWERS OVER MUCH OF THE AREA. ANY
SHOWERS THAT DO FORM SHOULD REMAIN CONFINED TO THE HIGHER TERRAIN
IN THE NORTH AND FAR WEST. TUESDAY WILL SEE THE APPROACH OF A
PACIFIC TROUGH AND VIGOROUS SHORTWAVE. THIS WILL BRING BREEZY TO
WINDY SOUTHWEST WIND TO MUCH OF THE AREA DURING THE AFTERNOON
HOURS. FIRE WEATHER CONCERNS WILL BE HEIGHTENED AS WIND GUSTING TO
NEAR 40 MPH IS EXPECTED WITH LOW HUMIDITY ACROSS A LARGE PORTION
OF SOUTHERN AND CENTRAL WYOMING. SLIGHTLY COOLER LL TEMPERATURES
WILL MAKE FOR MORE MARGINAL LAPSE RATES HOWEVER INCREASED PACIFIC
MOISTURE AND DYNAMIC FORCING WILL BRING MORE WIDESPREAD SHOWER
ACTIVITY WITH SOME ISOLATED THUNDER POSSIBLE...MAINLY IN THE NORTH
AND WEST. SHOWER ACTIVITY WILL CONTINUE INTO THE NIGHTTIME HOURS
BEHIND A COLD FRONT ASSOCIATED WITH THE LEADING EDGE OF THE
TROUGH. WITH SIGNIFICANT COOLING BEHIND THE FRONT...SHOWERS WILL
CHANGE OVER TO SNOW IN THE HIGH COUNTRY AFTER MIDNIGHT. AN INCH OR
TWO OF ACCUMULATION WILL BE POSSIBLE ABOVE 8500 FEET.


.LONG TERM...WEDNESDAY THROUGH SUNDAY

WEDNESDAY AND THURSDAY...COOLER. CHANCES OF SHOWERS/ISOLATED
THUNDERSTORMS NORTH.  MAINLY DRY SOUTH.  WINDY AREAS SOUTH AND
CENTRAL ON WEDNESDAY.

FRIDAY THROUGH SUNDAY...WARMER.  CONTINUING CHANCES OF SHOWERS AND
ISOLATED THUNDERSTORMS NORTH AND FAR WEST ON FRIDAY THEN MAINLY
ACROSS THE FAR WEST AND FAR NORTH OVER THE WEEKEND.  WINDY AREAS
SOUTH AND CENTRAL.

UPPER LOW JUST SOUTH OF THE ALEUTIAN CHAIN WITH SHORTWAVE TO THE
SOUTH ON NOSE OF 150 KNOT JET WILL BE PRIMARY WEATHER MAKERS IN THE
EXTENDED.  MEDIUM RANGE MODELS CONTINUE TO SHOW QUITE A BIT OF
SPREAD WITH THE SHORTWAVE EJECTING OUT AHEAD OF THE ALEUTIAN LOW
WITH THE ECMWF CONSISTENTLY PUSHING THIS ENERGY FURTHER NORTH INTO
ALBERTA/SASKATCHEWAN TUESDAY/WEDNESDAY WHILE GFS DIGS UPPER LOW
INTO EASTERN MONTANA ON WEDNESDAY. FORECAST CONTINUES TO BE
WEIGHTED TOWARD THE ECMWF FURTHER NORTH SOLUTION HERE...OR A
MILDER POST-FRONTAL AIRMASS WITH A DRIER WESTERLY FLOW ACROSS
SOUTHERN WYOMING. BETTER AGREEMENT EXISTS WITH THE TRAILING UPPER
LOW AS IT DIGS DOWN THE NORTHWEST COAST THURSDAY AND FRIDAY.
MODELS HAVE THE H5 LOW CLUSTERED NEAR SFO BY 00Z SATURDAY AS
RETROGRADING RIDGE UPSTREAM REACHES ITS WESTWARD EXTENT NEAR 150W.
FURTHER DOWNSTREAM...UPPER HIGH STRENGTHENS ACROSS THE SOUTHEAST
U.S.. ECMWF QUICKER TO SHEAR UPPER LOW NE ACROSS THE INTERMOUNTAIN
WEST OVER THE WEEKEND WHICH LOOKS MORE REALISTIC THAN GFS ATTEMPT
TO PLOW THIS TROUGH INTO BACKSIDE OF THIS HOT EXPANDING RIDGE
DOWNSTREAM. EITHER WAY...VERY WARM AIRMASS IS PULLED UP EAST OF
THE DIVIDE SATURDAY IN DEEP SOUTHERLY FLOW WITH MOISTURE AND
INSTABILITY ARCING ACROSS THE WESTERN AND NORTHERN BORDERS. ECMWF
SHIFTS THERMAL RIDGE INTO PLAINS ON SUNDAY AS UPPER LOW SHEARS
NORTH...WEST OF THE DIVIDE...WHILE GFS KEEPS HOT AIRMASS OVER
EASTERN WYOMING THROUGH SUNDAY.

&&

.AVIATION.../18Z ISSUANCE/

VFR CONDITIONS WILL OCCUR THROUGH 12Z MONDAY. ISOLATED SHOWERS ARE
POSSIBLE OVER THE HIGHER PEAKS OF THE BIGHORN MOUNTAINS AND IN THE
NW WY MOUNTAINS FROM 20Z UNTIL 02Z MONDAY AND AGAIN ON MONDAY AFTERNOON.
SOUTHWEST WINDS INCREASE MONDAY AFTERNOON COINCIDENT WITH THE
DEVELOPMENT OF A WEAK LEE SIDE TROUGH.

&&

.FIRE WEATHER...

A WARMING TREND IS IN STORE THROUGH MONDAY AS A RIDGE OF HIGH
PRESSURE BUILD OVER THE WESTERN U.S.  NO PRECIPITATION IS EXPECTED
OVER MUCH OF THE AREA TODAY WITH LIGHT WIND PREVAILING.  THERE IS A
SLIGHT CHANCE FOR A SHOWER OR TWO OVER THE BIGHORNS THIS AFTERNOON.
WARMER TEMPERATURES ARE EXPECTED FOR MONDAY WITH LOW HUMIDITY.  A
FEW SHOWERS ARE POSSIBLE IN THE HIGH COUNTRY BUT THUNDER IS
UNLIKELY.  TUESDAY WILL SEE AN APPROACHING COLD FRONT WITH DRY AND
WINDY CONDITIONS EAST OF THE CONTINENTAL DIVIDE.


&&

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

$$

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

000
FXUS63 KUNR 201730
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1130 AM MDT SUN MAY 20 2012

.AVIATION...18Z TAFS
VFR CONDITIONS ARE EXPECTED THROUGH MONDAY...WITH SOUTHEASTERLY
WINDS CONTINUING OVER THE AREA. AN ISOLATED THUNDERSTORM OR TWO
WILL BE POSSIBLE ACROSS NORTHEASTERN WY AND THE BLACK HILLS THIS
AFTERNOON AND EARLY EVENING.

&&

.PREV DISCUSSION... /ISSUED 1012 AM MDT SUN MAY 20 2012/

UPDATE...16Z SFC ANALYSIS SHOWS HIGH PRESSURE OVER THE WESTERN
DAKOTAS/NEBRASKA. SOUTHEASTERN WINDS WILL DEVELOP ACROSS MUCH OF
THE FORECAST AREA TODAY AS THE HIGH PRESSURE SYSTEM CONTINUES TO
GRADUALLY SLIDE SOUTHEASTWARD. PREVIOUS FORECAST REMAINS ON TRACK
SO NO UPDATES PLANNED ATTM.

PREV DISCUSSION... /ISSUED 219 AM MDT SUN MAY 20 2012/

DISCUSSION...08Z SURFACE ANALYSIS SHOWED WEAK HIGH PRESSURE OVER
THE CWA. SHORTWAVE ENERGY NOTED OVER EASTERN MT PER WATER VAPOR...WITH
A FEW MID CLOUDS ASSOCIATED WITH IT. UPPER RIDGE STARTING TO BUILD
OVER THE NORTHERN ROCKIES.

TODAY/TONIGHT...UPPER RIDGE BUILDS INTO MT/WY AS WEAK LEE TROUGH
DEVELOPS FROM CENTRAL MT INTO CENTRAL WY. SURFACE HIGH SHIFTS EAST
WITH WEAK RETURN FLOW ACROSS THE WEST. AROUND 250J/KG SBCAPE
DEVELOPS THIS AFTERNOON/EARLY EVENING AND MAY BE ENOUGH FOR
ISOLATED -TSRA NEAR TERRAIN/LEE TROUGH. SUBSIDENCE UNDER BUILDING
UPPER RIDGE WILL KEEP COVERAGE LIMITED. TEMPERATURES NEAR GUIDANCE.

MONDAY/MONDAY NIGHT...UPPER/THERMAL RIDGE CONTINUES TO BUILD OVER
CWA. SOUTHERLY LOW LEVEL JET UP TO 40KTS WILL SHIFT FROM WESTERN
SD INTO EASTERN SD...AND THEN REDEVELOP OVER NORTHEAST WY/WESTERN
SD MONDAY NIGHT. CAPPING BECOMES MORE PRONOUNCED...BUT NARROW AXIS
OF 0.5-1KJ/KG SBCAPE MAY BE ENOUGH FOR A FEW -TSRA OVER SOUTH
CENTRAL SD DURING PEAK HEATING LATE MONDAY AFTERNOON/EARLY
EVENING. TEMPERATURES WILL BE NOTICEABLY WARMER.

TUESDAY/TUESDAY NIGHT...UPPER RIDGE SHIFTS EAST AS UPPER TROUGH
SHIFTS INTO THE NORTHERN PLAINS WITH UPPER LOW OVER SOUTHERN SK.
SEVERAL SHORTWAVES WILL MOVE THROUGH THE CWA. COOL FRONT MOVES
THROUGH LATE. INSTABILITY/SHEAR ALONG FRONT WILL LIKELY BE
SUFFICIENT FOR A FEW SEVERE STORMS...MAINLY OVER EASTERN PORTIONS
OF THE CWA. BEHIND FRONT...MODERATE BAND OF 850-700MB
FRONTOGENESIS WILL BRING BETTER CHANCES FOR POST FRONTAL
PRECIPITATION. KEPT POPS IN THE CHANCE CATEGORY FOR NOW...BUT
LIKELIES MAY BE NEEDED. TUESDAY SHOULD BE THE WARMEST DAY WITH
700MB THERMAL RIDGE PEAKING AROUND 12C.

EXTENDED...AN UPPER LEVEL SYSTEM WILL PASS NORTH OF THE AREA DURING
THE MIDDLE AND LATTER PART OF THE WEEK. SOUTHWESTERLY FLOW ALOFT
WILL DEVELOP TO THE SOUTH OF THE SYSTEM OVER THE ROCKIES AND INTO
THE PLAINS. THIS PATTERN WILL LIKELY BRING A SERIES OF UPPER LEVEL
DISTURBANCES ACROSS THE AREA...WITH DAILY CHANCES FOR SHOWERS AND A
FEW STORMS FROM WEDNESDAY THROUGH THE END OF THE WEEK. TEMPERATURES
WILL GENERALLY BE NEAR OR SLIGHTLY BELOW AVERAGE LATE THIS WEEK...
WITH A WARMUP LIKELY OVER THE WEEKEND.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

SHORT TERM...10
LONG TERM....15
AVIATION...15

000
FXUS63 KUNR 201612
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1012 AM MDT SUN MAY 20 2012

.UPDATE...16Z SFC ANALYSIS SHOWS HIGH PRESSURE OVER THE WESTERN
DAKOTAS/NEBRASKA. SOUTHEASTERN WINDS WILL DEVELOP ACROSS MUCH OF
THE FORECAST AREA TODAY AS THE HIGH PRESSURE SYSTEM CONTINUES TO
GRADUALLY SLIDE SOUTHEASTWARD. PREVIOUS FORECAST REMAINS ON TRACK
SO NO UPDATES PLANNED ATTM.

&&

.AVIATION...12Z TAF UPDATE
VFR CONDITIONS ARE EXPECTED TODAY INTO TONIGHT...WITH
SOUTHEASTERLY WINDS DEVELOPING OVER THE AREA. AN ISOLATED
THUNDERSTORM OR TWO WILL BE POSSIBLE ACROSS NORTHEASTERN WY AND
THE BLACK HILLS THIS AFTERNOON AND EARLY EVENING...AND OVER PARTS
OF WESTERN AND CENTRAL SOUTH DAKOTA AFTER MIDNIGHT.

&&

.PREV DISCUSSION... /ISSUED 219 AM MDT SUN MAY 20 2012/

DISCUSSION...08Z SURFACE ANALYSIS SHOWED WEAK HIGH PRESSURE OVER
THE CWA. SHORTWAVE ENERGY NOTED OVER EASTERN MT PER WATER VAPOUR...WITH
A FEW MID CLOUDS ASSOCIATED WITH IT. UPPER RIDGE STARTING TO BUILD
OVER THE NORTHERN ROCKIES.

TODAY/TONIGHT...UPPER RIDGE BUILDS INTO MT/WY AS WEAK LEE TROUGH
DEVELOPS FROM CENTRAL MT INTO CENTRAL WY. SURFACE HIGH SHIFTS EAST
WITH WEAK RETURN FLOW ACROSS THE WEST. AROUND 250J/KG SBCAPE
DEVELOPS THIS AFTERNOON/EARLY EVENING AND MAY BE ENOUGH FOR
ISOLATED -TSRA NEAR TERRAIN/LEE TROUGH. SUBSIDENCE UNDER BUILDING
UPPER RIDGE WILL KEEP COVERAGE LIMITED. TEMPERATURES NEAR GUIDANCE.

MONDAY/MONDAY NIGHT...UPPER/THERMAL RIDGE CONTINUES TO BUILD OVER
CWA. SOUTHERLY LOW LEVEL JET UP TO 40KTS WILL SHIFT FROM WESTERN
SD INTO EASTERN SD...AND THEN REDEVELOP OVER NORTHEAST WY/WESTERN
SD MONDAY NIGHT. CAPPING BECOMES MORE PRONOUNCED...BUT NARROW AXIS
OF 0.5-1KJ/KG SBCAPE MAY BE ENOUGH FOR A FEW -TSRA OVER SOUTH
CENTRAL SD DURING PEAK HEATING LATE MONDAY AFTERNOON/EARLY
EVENING. TEMPERATURES WILL BE NOTICEABLY WARMER.

TUESDAY/TUESDAY NIGHT...UPPER RIDGE SHIFTS EAST AS UPPER TROUGH
SHIFTS INTO THE NORTHERN PLAINS WITH UPPER LOW OVER SOUTHERN SK.
SEVERAL SHORTWAVES WILL MOVE THROUGH THE CWA. COOL FRONT MOVES
THROUGH LATE. INSTABILITY/SHEAR ALONG FRONT WILL LIKELY BE
SUFFICIENT FOR A FEW SEVERE STORMS...MAINLY OVER EASTERN PORTIONS
OF THE CWA. BEHIND FRONT...MODERATE BAND OF 850-700MB
FRONTOGENESIS WILL BRING BETTER CHANCES FOR POST FRONTAL
PRECIPITATION. KEPT POPS IN THE CHANCE CATEGORY FOR NOW...BUT
LIKELIES MAY BE NEEDED. TUESDAY SHOULD BE THE WARMEST DAY WITH
700MB THERMAL RIDGE PEAKING AROUND 12C.

EXTENDED...AN UPPER LEVEL SYSTEM WILL PASS NORTH OF THE AREA DURING
THE MIDDLE AND LATTER PART OF THE WEEK. SOUTHWESTERLY FLOW ALOFT
WILL DEVELOP TO THE SOUTH OF THE SYSTEM OVER THE ROCKIES AND INTO
THE PLAINS. THIS PATTERN WILL LIKELY BRING A SERIES OF UPPER LEVEL
DISTURBANCES ACROSS THE AREA...WITH DAILY CHANCES FOR SHOWERS AND A
FEW STORMS FROM WEDNESDAY THROUGH THE END OF THE WEEK. TEMPERATURES
WILL GENERALLY BE NEAR OR SLIGHTLY BELOW AVERAGE LATE THIS WEEK...
WITH A WARMUP LIKELY OVER THE WEEKEND.



&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

000
FXUS65 KCYS 201153
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
600 AM MDT SUN MAY 20 2012

.SHORT TERM...
AXIS OF SURFACE HIGH PRESSURE OVER THE NEBRASKA PANHANDLE EARLY
THIS MORNING WILL SHIFT EAST AS THE MORNING CONTINUES. GENERALLY
WILL SEE CLEAR SKIES THROUGH THIS MORNING...BUT A SUBTLE DISTURBANCE
MOVING THROUGH WESTERLY FLOW ALOFT WILL PRODUCE SOME HIGH CLOUDS
AS IT SKIRTS ACROSS THE AREA. AS THE HIGH SHIFTS EAST WILL SEE
SOUTHEAST LOW LEVEL FLOW SET IN EAST OF THE LARAMIE RANGE WHILE
WESTERLY LOW LEVEL WINDS WILL DEVELOP WEST OF THE LARAMIE RANGE.
WEAK LOW CONVERGENCE ZONE...AND LEFT EXIT REGION OF AN UPPER JET
WILL CREATE AN ENVIRONMENT FOR ISOLATED THUNDERSTORM DEVELOPMENT
THIS AFTERNOON. BIGGEST INHIBITOR FOR THUNDERSTORM DEVELOP WILL
BE THE LACK OF LOW LEVEL MOISTURE BUT MODELS DO PRODUCE UPWARDS OF
500 JOULES/KG OF CAPE THIS AFTERNOON AND WITH VERY STEEP LAPSE
RATES SHOULD BE ABLE TO POP A FEW THUNDERSTORMS. MAIN THUNDERSTORM
POTENTIAL SHOULD BE OVER SOUTHEAST WYOMING EAST OF THE LARAMIE
RANGE BUT COULD SEE THUNDERSTORMS INTO THE NEBRASKA PANHANDLE TOO.
NOT EXPECTING SEVERE THUNDERSTORMS BUT GIVEN SOME CAPE...40-45 KTS
OF BULK SHEAR AND RELATIVELY LOW FREEZING LEVELS...CAN NOT
COMPLETELY RULE OUT MARGINALLY SEVERE SIZED HAIL. SEVERE STORMS
PREDICTION CENTER FORECASTING GENERAL THUNDER WITH 5 PERCENT
CHANCE SEVERE HAIL AND SEVERE WINDS. THIS LOOKS VERY REASONABLE
GIVEN CURRENT MODEL DATA.

ANY SHOWERS OR THUNDERSTORMS THAT DO DEVELOP WILL HAVE AN IMPACT
ON VIEWING THE PARTIAL SOLAR ECLIPSE THAT WILL OCCUR LATE TODAY.
THE ECLIPSE WILL OCCUR IN THE WESTERN SKY STARTING AROUND 620 PM
AND CONTINUE THROUGH SUNSET. SKIES WILL CLEAR FROM WEST TO EAST AS
THE NIGHT CONTINUES BUT MAY BE TOO LATE FOR ECLIPSE VIEWING
DEPENDING ON LOCATION.

TEMPERATURES WILL BE MILD TODAY AFTER STARTING THE MORNING OFF ON
THE CHILLY SIDE. HIGHS TODAY WILL BE IN THE UPPER 60S TO MID 70S
ACROSS THE AREA. A GOOD DEAL WARMER TOMORROW WITH HIGHS MAINLY IN
THE 80S AS AN UPPER RIDGE BUILDS ACROSS THE AREA. UPPER RIDGE
MEANS VIRTUALLY NO CHANCES FOR PRECIPITATION TOMORROW ALONG WITH
CLEAR SKIES. FOR MOST OF THE FORECAST AREA THE WARMEST DAY OF THE
WEEK WILL BE TUESDAY JUST AHEAD OF AN APPROACHING TROUGH. WESTERLY
DOWN SLOPE FLOW WILL PUSH TEMPERATURES INTO THE 90S INTO THE
NEBRASKA PANHANDLE.


.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY NIGHT...MODELS IN
GOOD AGREEMENT THROUGH NEXT WEEK...SHOWING PERIODS OF UNSETTLED
WEATHER ACROSS SOUTHEAST WYOMING AND WESTERN NEBRASKA AS AN UPPER
LEVEL LOW PUSHES INTO THE WEST COAST AND NORTHERN ROCKIES. THIS
WILL RESULT IN A GOOD CHANCE OF SOME MUCH NEEDED RAINFALL ACROSS
THE AREA TUESDAY THROUGH FRIDAY. AN UPPER LEVEL RIDGE AXIS
WILL PUSH EAST OF THE FORECAST AREA ON TUESDAY AS THE STRONG UPPER
LOW AND ASSOCIATED COLD FRONT MOVES INTO THE PACIFIC NW COASTLINE.
THIS COLD FRONT WILL BE RATHER STRONG FOR THIS TIME OF THE
YEAR...AND WILL PUSH EASTWARD INTO EASTERN WYOMING AND WESTERN
NEBRASKA TUESDAY NIGHT AND EARLY WEDNESDAY. STRONG GUSTY WINDS
ARE EXPECTED AHEAD OF THIS FRONT THROUGH TUESDAY EVENING WITH
GUSTS OVER 50 MPH POSSIBLE...ESPECIALLY ALONG AND WEST OF THE
LARAMIE RANGE. THERE IS MORE CONFIDENCE THAT WEDNESDAY WILL BE
MUCH COOLER ACROSS THE FORECAST AREA AS ALL MODELS ARE SHOWING A
FASTER FRONTAL PASSAGE. EXPECT HIGH TEMPERATURES TO LOWER INTO THE
UPPER 50S TO UPPER 60S WEDNESDAY AFTERNOON. ALONG WITH THE GUSTY
WINDS AND COOLER TEMPERATURES...THERE IS A GOOD CHANCE OF
PRECIPITATION ACROSS THE WHOLE FORECAST AREA TUESDAY NIGHT THROUGH
WEDNESDAY AS THE FRONT STALLS OR SLOWLY PUSHES SOUTHWARD. AS THE
UPPER LEVEL LOW PUSHES INLAND AND DIGS SOUTHWARD ACROSS THE WEST
COAST LATE IN THE WEEK...THE FRONT AND ASSOCIATED 140KT JET MAX IS
EXPECTED TO PUSH NORTHWARD...WITH ANOTHER GOOD CHANCE OF
WIDESPREAD MODERATE PRECIPITATION. CONTINUED TO INCREASE POP UP TO
50 PERCENT THROUGH THURSDAY NIGHT FOR NUMEROUS RAIN SHOWERS AND
ISOLATED TSTORMS.

BY EARLY NEXT WEEK...ALL MODELS INDICATE THE FRONT MOVING NORTH OF
THE FORECAST AREA AS A WARM FRONT WITH DRIER AIR ALOFT PUSHING
ACROSS THE FORECAST AREA. THE UPPER LEVEL LOW TO THE WEST WILL
SLOWLY MOVE EAST INTO THE GREAT BASIN REGION AND STALL. EXPECT
TEMPERATURES TO INCREASE BACK INTO THE 70S AND 80S WITH WARM
SOUTHWEST FLOW ALOFT. CAN NOT RULE OUT SOME PATCHY FOG OR LOW
STRATUS CLOUDS EAST OF THE LARAMIE RANGE DUE TO LLVL SOUTHEAST FLOW.

&&

.AVIATION...12Z TAF ISSUANCE. VFR CONDITIONS WILL PREVIAL TODAY.
THERE IS A SMALL CHANCE (15 TO 20 PERCENT) OF TSTORMS THIS AFTERNOON
ACROSS THE HIGH PLAINS...INCLUDING KLAR AND KCYS AND MOST OF THE
WESTERN NEBRASKA PANHANDLE. OTHERWISE...LIGHT SOUTH WINDS ARE
FORECAST ACROSS THE HIGH PLAINS...WITH SOUTHWEST WINDS WEST OF THE
LARAMIE RANGE.

&&

.FIRE WEATHER...
NO FIRE WEATHER CONCERNS TODAY OR TOMORROW. MINIMUM HUMIDITY
TODAY WILL BE ABOVE 20 PERCENT FOR MOST OF THE AREA TODAY AND
WINDS WILL BE ON THE LIGHTER SIDE. WARMER WITH LOWER RELATIVE
HUMIDITY MONDAY BUT WINDS WILL REMAIN ON THE LIGHT SIDE. CRITICAL
FIRE THRESHOLDS COULD BE REACHED TUESDAY WITH HUMIDITY VALUES
DROPPING TO 10 TO 15 PERCENT OVER MUCH OF THE AREA ALONG WITH
WINDY CONDITIONS.

ISOLATE THUNDERSTORMS ARE EXPECTED FROM THE LARAMIE RANGE EAST
INTO THE NEBRASKA PANHANDLE THIS AFTERNOON. GUSTY WINDS AND SMALL
HAIL POSSIBLE WITH THESE STORMS. DRY MONDAY AND TUESDAY UNDER THE
INFLUENCE OF THE UPPER LEVEL RIDGE...THEN CHANCES FOR SHOWERS AND
THUNDERSTORMS THE REMAINDER OF THE WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.

&&

$$

SHORT TERM/FIRE WEATHER...LIEBL
LONG TERM/AVIATION...TJT

000
FXUS65 KCYS 200910
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
310 AM MDT SUN MAY 20 2012

.SHORT TERM...
AXIS OF SURFACE HIGH PRESSURE OVER THE NEBRASKA PANHANDLE EARLY
THIS MORNING WILL SHIFT EAST AS THE MORNING CONTINUES. GENERALLY
WILL SEE CLEAR SKIES THROUGH THIS MORNING...BUT A SUBTLE DISTURBANCE
MOVING THROUGH WESTERLY FLOW ALOFT WILL PRODUCE SOME HIGH CLOUDS
AS IT SKIRTS ACROSS THE AREA. AS THE HIGH SHIFTS EAST WILL SEE
SOUTHEAST LOW LEVEL FLOW SET IN EAST OF THE LARAMIE RANGE WHILE
WESTERLY LOW LEVEL WINDS WILL DEVELOP WEST OF THE LARAMIE RANGE.
WEAK LOW CONVERGENCE ZONE...AND LEFT EXIT REGION OF AN UPPER JET
WILL CREATE AN ENVIRONMENT FOR ISOLATED THUNDERSTORM DEVELOPMENT
THIS AFTERNOON. BIGGEST INHIBITOR FOR THUNDERSTORM DEVELOP WILL
BE THE LACK OF LOW LEVEL MOISTURE BUT MODELS DO PRODUCE UPWARDS OF
500 JOULES/KG OF CAPE THIS AFTERNOON AND WITH VERY STEEP LAPSE
RATES SHOULD BE ABLE TO POP A FEW THUNDERSTORMS. MAIN THUNDERSTORM
POTENTIAL SHOULD BE OVER SOUTHEAST WYOMING EAST OF THE LARAMIE
RANGE BUT COULD SEE THUNDERSTORMS INTO THE NEBRASKA PANHANDLE TOO.
NOT EXPECTING SEVERE THUNDERSTORMS BUT GIVEN SOME CAPE...40-45 KTS
OF BULK SHEAR AND RELATIVELY LOW FREEZING LEVELS...CAN NOT
COMPLETELY RULE OUT MARGINALLY SEVERE SIZED HAIL. SEVERE STORMS
PREDICTION CENTER FORECASTING GENERAL THUNDER WITH 5 PERCENT
CHANCE SEVERE HAIL AND SEVERE WINDS. THIS LOOKS VERY REASONABLE
GIVEN CURRENT MODEL DATA.

ANY SHOWERS OR THUNDERSTORMS THAT DO DEVELOP WILL HAVE AN IMPACT
ON VIEWING THE PARTIAL SOLAR ECLIPSE THAT WILL OCCUR LATE TODAY.
THE ECLIPSE WILL OCCUR IN THE WESTERN SKY STARTING AROUND 620 PM
AND CONTINUE THROUGH SUNSET. SKIES WILL CLEAR FROM WEST TO EAST AS
THE NIGHT CONTINUES BUT MAY BE TOO LATE FOR ECLIPSE VIEWING
DEPENDING ON LOCATION.

TEMPERATURES WILL BE MILD TODAY AFTER STARTING THE MORNING OFF ON
THE CHILLY SIDE. HIGHS TODAY WILL BE IN THE UPPER 60S TO MID 70S
ACROSS THE AREA. A GOOD DEAL WARMER TOMORROW WITH HIGHS MAINLY IN
THE 80S AS AN UPPER RIDGE BUILDS ACROSS THE AREA. UPPER RIDGE
MEANS VIRTUALLY NO CHANCES FOR PRECIPITATION TOMORROW ALONG WITH
CLEAR SKIES. FOR MOST OF THE FORECAST AREA THE WARMEST DAY OF THE
WEEK WILL BE TUESDAY JUST AHEAD OF AN APPROACHING TROUGH. WESTERLY
DOWN SLOPE FLOW WILL PUSH TEMPERATURES INTO THE 90S INTO THE
NEBRASKA PANHANDLE.


.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY NIGHT...MODELS IN
GOOD AGREEMENT THROUGH NEXT WEEK...SHOWING PERIODS OF UNSETTLED
WEATHER ACROSS SOUTHEAST WYOMING AND WESTERN NEBRASKA AS AN UPPER
LEVEL LOW PUSHES INTO THE WEST COAST AND NORTHERN ROCKIES. THIS
WILL RESULT IN A GOOD CHANCE OF SOME MUCH NEEDED RAINFALL ACROSS
THE AREA TUESDAY THROUGH FRIDAY. AN UPPER LEVEL RIDGE AXIS
WILL PUSH EAST OF THE FORECAST AREA ON TUESDAY AS THE STRONG UPPER
LOW AND ASSOCIATED COLD FRONT MOVES INTO THE PACIFIC NW COASTLINE.
THIS COLD FRONT WILL BE RATHER STRONG FOR THIS TIME OF THE
YEAR...AND WILL PUSH EASTWARD INTO EASTERN WYOMING AND WESTERN
NEBRASKA TUESDAY NIGHT AND EARLY WEDNESDAY. STRONG GUSTY WINDS
ARE EXPECTED AHEAD OF THIS FRONT THROUGH TUESDAY EVENING WITH
GUSTS OVER 50 MPH POSSIBLE...ESPECIALLY ALONG AND WEST OF THE
LARAMIE RANGE. THERE IS MORE CONFIDENCE THAT WEDNESDAY WILL BE
MUCH COOLER ACROSS THE FORECAST AREA AS ALL MODELS ARE SHOWING A
FASTER FRONTAL PASSAGE. EXPECT HIGH TEMPERATURES TO LOWER INTO THE
UPPER 50S TO UPPER 60S WEDNESDAY AFTERNOON. ALONG WITH THE GUSTY
WINDS AND COOLER TEMPERATURES...THERE IS A GOOD CHANCE OF
PRECIPITATION ACROSS THE WHOLE FORECAST AREA TUESDAY NIGHT THROUGH
WEDNESDAY AS THE FRONT STALLS OR SLOWLY PUSHES SOUTHWARD. AS THE
UPPER LEVEL LOW PUSHES INLAND AND DIGS SOUTHWARD ACROSS THE WEST
COAST LATE IN THE WEEK...THE FRONT AND ASSOCIATED 140KT JET MAX IS
EXPECTED TO PUSH NORTHWARD...WITH ANOTHER GOOD CHANCE OF
WIDESPREAD MODERATE PRECIPITATION. CONTINUED TO INCREASE POP UP TO
50 PERCENT THROUGH THURSDAY NIGHT FOR NUMEROUS RAIN SHOWERS AND
ISOLATED TSTORMS.

BY EARLY NEXT WEEK...ALL MODELS INDICATE THE FRONT MOVING NORTH OF
THE FORECAST AREA AS A WARM FRONT WITH DRIER AIR ALOFT PUSHING
ACROSS THE FORECAST AREA. THE UPPER LEVEL LOW TO THE WEST WILL
SLOWLY MOVE EAST INTO THE GREAT BASIN REGION AND STALL. EXPECT
TEMPERATURES TO INCREASE BACK INTO THE 70S AND 80S WITH WARM
SOUTHWEST FLOW ALOFT. CAN NOT RULE OUT SOME PATCHY FOG OR LOW
STRATUS CLOUDS EAST OF THE LARAMIE RANGE DUE TO LLVL SOUTHEAST FLOW.

&&

.AVIATION...06Z TAF ISSUANCE. VFR CONDITIONS ARE EXPECTED TONIGHT
WITH LIGHT WINDS. THERE IS A SMALL CHANCE (15 TO 20 PERCENT) OF
TSTORMS SUNDAY AFTERNOON ACROSS THE HIGH PLAINS...INCLUDING KLAR
AND KCYS. OTHERWISE...VFR CONDITIONS WILL PERSIST WITH LIGHT SOUTH
WINDS ACROSS THE HIGH PLAINS...AND SOUTHWEST WINDS WEST OF THE
LARAMIE RANGE.

&&

.FIRE WEATHER...
NO FIRE WEATHER CONCERNS TODAY OR TOMORROW. MINIMUM HUMIDITY
TODAY WILL BE ABOVE 20 PERCENT FOR MOST OF THE AREA TODAY AND
WINDS WILL BE ON THE LIGHTER SIDE. WARMER WITH LOWER RELATIVE
HUMIDITY MONDAY BUT WINDS WILL REMAIN ON THE LIGHT SIDE. CRITICAL
FIRE THRESHOLDS COULD BE REACHED TUESDAY WITH HUMIDITY VALUES
DROPPING TO 10 TO 15 PERCENT OVER MUCH OF THE AREA ALONG WITH
WINDY CONDITIONS.

ISOLATE THUNDERSTORMS ARE EXPECTED FROM THE LARAMIE RANGE EAST
INTO THE NEBRASKA PANHANDLE THIS AFTERNOON. GUSTY WINDS AND SMALL
HAIL POSSIBLE WITH THESE STORMS. DRY MONDAY AND TUESDAY UNDER THE
INFLUENCE OF THE UPPER LEVEL RIDGE...THEN CHANCES FOR SHOWERS AND
THUNDERSTORMS THE REMAINDER OF THE WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.

&&

$$

SHORT TERM/FIRE WEATHER...LIEBL
LONG TERM/AVIATION...TJT

000
FXUS65 KRIW 200846
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
246 AM MDT SUN MAY 20 2012

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

MAINLY DRY AND WARMER CONDITIONS WILL PREVAIL TODAY AS AN UPPER
RIDGE BUILDS OVER THE WESTERN CONUS.  HAVE INTRODUCED SLIGHT POPS TO
THE BIGHORNS THIS AFTERNOON AS AN EXTREMELY WEAK WAVE TRANSITS THE
RIDGE.  SOME VERY LIGHT SHOWERS POSSIBLE BUT THUNDER UNLIKELY.  MUCH
WARMER CONDITIONS ARE ON TAP FOR MONDAY AS H7 TEMPS APPROACH +13C IN
THE AFTERNOON.  THIS WILL BRING MID 80S TO THE LOWER ELEVATIONS EAST
OF THE CONTINENTAL DIVIDE WITH TEMPERATURES NEAR 90 POSSIBLE IN
ISOLATED AREAS OF THE BIG HORN BASIN. FAVORABLE LAPSE RATE WILL
BRING SOME HIGH BASED CUMULUS CLOUDS MONDAY AFTERNOON BUT MOISTURE
WILL BE LACKING TO PRODUCE SHOWERS OVER MUCH OF THE AREA. ANY
SHOWERS THAT DO FORM SHOULD REMAIN CONFINED TO THE HIGHER TERRAIN
IN THE NORTH AND FAR WEST. TUESDAY WILL SEE THE APPROACH OF A
PACIFIC TROUGH AND VIGOROUS SHORTWAVE. THIS WILL BRING BREEZY TO
WINDY SOUTHWEST WIND TO MUCH OF THE AREA DURING THE AFTERNOON
HOURS. FIRE WEATHER CONCERNS WILL BE HEIGHTENED AS WIND GUSTING TO
NEAR 40 MPH IS EXPECTED WITH LOW HUMIDITY ACROSS A LARGE PORTION
OF SOUTHERN AND CENTRAL WYOMING. SLIGHTLY COOLER LL TEMPERATURES
WILL MAKE FOR MORE MARGINAL LAPSE RATES HOWEVER INCREASED PACIFIC
MOISTURE AND DYNAMIC FORCING WILL BRING MORE WIDESPREAD SHOWER
ACTIVITY WITH SOME ISOLATED THUNDER POSSIBLE...MAINLY IN THE NORTH
AND WEST. SHOWER ACTIVITY WILL CONTINUE INTO THE NIGHTTIME HOURS
BEHIND A COLD FRONT ASSOCIATED WITH THE LEADING EDGE OF THE
TROUGH. WITH SIGNIFICANT COOLING BEHIND THE FRONT...SHOWERS WILL
CHANGE OVER TO SNOW IN THE HIGH COUNTRY AFTER MIDNIGHT. AN INCH OR
TWO OF ACCUMULATION WILL BE POSSIBLE ABOVE 8500 FEET.


.LONG TERM...WEDNESDAY THROUGH SUNDAY

WEDNESDAY AND THURSDAY...COOLER. CHANCES OF SHOWERS/ISOLATED
THUNDERSTORMS NORTH.  MAINLY DRY SOUTH.  WINDY AREAS SOUTH AND
CENTRAL ON WEDNESDAY.

FRIDAY THROUGH SUNDAY...WARMER.  CONTINUING CHANCES OF SHOWERS AND
ISOLATED THUNDERSTORMS NORTH AND FAR WEST ON FRIDAY THEN MAINLY
ACROSS THE FAR WEST AND FAR NORTH OVER THE WEEKEND.  WINDY AREAS
SOUTH AND CENTRAL.

UPPER LOW JUST SOUTH OF THE ALEUTIAN CHAIN WITH SHORTWAVE TO THE
SOUTH ON NOSE OF 150 KNOT JET WILL BE PRIMARY WEATHER MAKERS IN THE
EXTENDED.  MEDIUM RANGE MODELS CONTINUE TO SHOW QUITE A BIT OF
SPREAD WITH THE SHORTWAVE EJECTING OUT AHEAD OF THE ALEUTIAN LOW
WITH THE ECMWF CONSISTENTLY PUSHING THIS ENERGY FURTHER NORTH INTO
ALBERTA/SASKATCHEWAN TUESDAY/WEDNESDAY WHILE GFS DIGS UPPER LOW
INTO EASTERN MONTANA ON WEDNESDAY. FORECAST CONTINUES TO BE
WEIGHTED TOWARD THE ECMWF FURTHER NORTH SOLUTION HERE...OR A
MILDER POST-FRONTAL AIRMASS WITH A DRIER WESTERLY FLOW ACROSS
SOUTHERN WYOMING. BETTER AGREEMENT EXISTS WITH THE TRAILING UPPER
LOW AS IT DIGS DOWN THE NORTHWEST COAST THURSDAY AND FRIDAY.
MODELS HAVE THE H5 LOW CLUSTERED NEAR SFO BY 00Z SATURDAY AS
RETROGRADING RIDGE UPSTREAM REACHES ITS WESTWARD EXTENT NEAR 150W.
FURTHER DOWNSTREAM...UPPER HIGH STRENGTHENS ACROSS THE SOUTHEAST
U.S.. ECMWF QUICKER TO SHEAR UPPER LOW NE ACROSS THE INTERMOUNTAIN
WEST OVER THE WEEKEND WHICH LOOKS MORE REALISTIC THAN GFS ATTEMPT
TO PLOW THIS TROUGH INTO BACKSIDE OF THIS HOT EXPANDING RIDGE
DOWNSTREAM. EITHER WAY...VERY WARM AIRMASS IS PULLED UP EAST OF
THE DIVIDE SATURDAY IN DEEP SOUTHERLY FLOW WITH MOISTURE AND
INSTABILITY ARCING ACROSS THE WESTERN AND NORTHERN BORDERS. ECMWF
SHIFTS THERMAL RIDGE INTO PLAINS ON SUNDAY AS UPPER LOW SHEARS
NORTH...WEST OF THE DIVIDE...WHILE GFS KEEPS HOT AIRMASS OVER
EASTERN WYOMING THROUGH SUNDAY.

&&

.AVIATION.../12Z ISSUANCE/

VFR CONDITIONS WILL OCCUR THROUGH 12Z MONDAY. ISOLATED SHOWERS ARE
POSSIBLE OVER THE HIGHER PEAKS OF THE BIGHORN MOUNTAINS AND IN THE
NW WY MOUNTAINS FROM 20Z UNTIL 02Z MONDAY.

&&


.FIRE WEATHER...

A WARMING TREND IS IN STORE THROUGH MONDAY AS A RIDGE OF HIGH
PRESSURE BUILD OVER THE WESTERN U.S.  NO PRECIPITATION IS EXPECTED
OVER MUCH OF THE AREA TODAY WITH LIGHT WIND PREVAILING.  THERE IS A
SLIGHT CHANCE FOR A SHOWER OR TWO OVER THE BIGHORNS THIS AFTERNOON.
WARMER TEMPERATURES ARE EXPECTED FOR MONDAY WITH LOW HUMIDITY.  A
FEW SHOWERS ARE POSSIBLE IN THE HIGH COUNTRY BUT THUNDER IS
UNLIKELY.  TUESDAY WILL SEE AN APPROACHING COLD FRONT WITH DRY AND
WINDY CONDITIONS EAST OF THE CONTINENTAL DIVIDE.


&&

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

$$

SHORT TERM...BERC
LONG TERM...AEM
AVIATION...AR
FIRE WEATHER...BERC

000
FXUS63 KUNR 200819
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
219 AM MDT SUN MAY 20 2012

.DISCUSSION...08Z SURFACE ANALYSIS SHOWED WEAK HIGH PRESSURE OVER
THE CWA. SHORTWAVE ENERGY NOTED OVER EASTERN MT PER WATER VAPOUR...WITH
A FEW MID CLOUDS ASSOCIATED WITH IT. UPPER RIDGE STARTING TO BUILD
OVER THE NORTHERN ROCKIES.

TODAY/TONIGHT...UPPER RIDGE BUILDS INTO MT/WY AS WEAK LEE TROUGH
DEVELOPS FROM CENTRAL MT INTO CENTRAL WY. SURFACE HIGH SHIFTS EAST
WITH WEAK RETURN FLOW ACROSS THE WEST. AROUND 250J/KG SBCAPE
DEVELOPS THIS AFTERNOON/EARLY EVENING AND MAY BE ENOUGH FOR
ISOLATED -TSRA NEAR TERRAIN/LEE TROUGH. SUBSIDENCE UNDER BUILDING
UPPER RIDGE WILL KEEP COVERAGE LIMITED. TEMPERATURES NEAR GUIDANCE.

MONDAY/MONDAY NIGHT...UPPER/THERMAL RIDGE CONTINUES TO BUILD OVER
CWA. SOUTHERLY LOW LEVEL JET UP TO 40KTS WILL SHIFT FROM WESTERN
SD INTO EASTERN SD...AND THEN REDEVELOP OVER NORTHEAST WY/WESTERN
SD MONDAY NIGHT. CAPPING BECOMES MORE PRONOUNCED...BUT NARROW AXIS
OF 0.5-1KJ/KG SBCAPE MAY BE ENOUGH FOR A FEW -TSRA OVER SOUTH
CENTRAL SD DURING PEAK HEATING LATE MONDAY AFTERNOON/EARLY
EVENING. TEMPERATURES WILL BE NOTICEABLY WARMER.

TUESDAY/TUESDAY NIGHT...UPPER RIDGE SHIFTS EAST AS UPPER TROUGH
SHIFTS INTO THE NORTHERN PLAINS WITH UPPER LOW OVER SOUTHERN SK.
SEVERAL SHORTWAVES WILL MOVE THROUGH THE CWA. COOL FRONT MOVES
THROUGH LATE. INSTABILITY/SHEAR ALONG FRONT WILL LIKELY BE
SUFFICIENT FOR A FEW SEVERE STORMS...MAINLY OVER EASTERN PORTIONS
OF THE CWA. BEHIND FRONT...MODERATE BAND OF 850-700MB
FRONTOGENESIS WILL BRING BETTER CHANCES FOR POST FRONTAL
PRECIPITATION. KEPT POPS IN THE CHANCE CATEGORY FOR NOW...BUT
LIKELIES MAY BE NEEDED. TUESDAY SHOULD BE THE WARMEST DAY WITH
700MB THERMAL RIDGE PEAKING AROUND 12C.

EXTENDED...AN UPPER LEVEL SYSTEM WILL PASS NORTH OF THE AREA DURING
THE MIDDLE AND LATTER PART OF THE WEEK. SOUTHWESTERLY FLOW ALOFT
WILL DEVELOP TO THE SOUTH OF THE SYSTEM OVER THE ROCKIES AND INTO
THE PLAINS. THIS PATTERN WILL LIKELY BRING A SERIES OF UPPER LEVEL
DISTURBANCES ACROSS THE AREA...WITH DAILY CHANCES FOR SHOWERS AND A
FEW STORMS FROM WEDNESDAY THROUGH THE END OF THE WEEK. TEMPERATURES
WILL GENERALLY BE NEAR OR SLIGHTLY BELOW AVERAGE LATE THIS WEEK...
WITH A WARMUP LIKELY OVER THE WEEKEND.

&&

.AVIATION...12Z TAFS
VFR CONDITIONS ARE GENERALLY EXPECTED TODAY INTO TONIGHT...WITH
SOUTHEASTERLY WINDS DEVELOPING OVER THE AREA. AN ISOLATED
THUNDERSTORM OR TWO WILL BE POSSIBLE ACROSS NORTHEASTERN WY AND
THE BLACK HILLS THIS AFTERNOON AND EARLY EVENING.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

SHORT TERM...HELGESON
LONG TERM....26
AVIATION...26