Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 021734
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1134 AM MDT WED SEP 2 2015

.UPDATE...

ISSUED AT 1015 AM MDT WED SEP 2 2015

ONLY MINOR CHANGES TO TODAY FORECAST. DECREASED CLOUD COVER FOR
CLEAR SKIES THIS MORNING FOR WESTERN PORTIONS OF THE FORECAST
AREA. SHOULD SEE SOME CUMULUS DEVELOP THIS AFTERNOON ESPECIALLY
OFF THE HIGHER ELEVATIONS. WATER VAPOR IMAGERY IS SHOWING
INCREASING MOISTURE ACROSS NORTHERN COLORADO BEGINNING TO MOVE
INTO SOUTHEAST WYOMING. CHANCES FOR SHOWERS AND THUNDERSTORMS IS
ON THE LOW SIDE BUT MAY SEE A FEW DEVELOP OVER THE MOUNTAINS THIS
AFTERNOON. ANYTHING THAT DOES DEVELOP SHOULD DIE OFF AS IT MOVES
OFF THE MOUNTAINS.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)

TODAY...SOUTHWEST FLOW ALOFT. SURFACE TROUGH SETS UP THIS AFTERNOON
ALONG INTERSTATE 25. THOUGH WITH LIMITED LOW AND MID LEVEL
MOISTURE...OTHER THAN AN ISOLATED LATE DAY THUNDERSTORM OVER THE
SOUTHERN LARAMIE RANGE...IT WILL BE DRY.

TONIGHT...INCREASING CLOUDS FROM OUR SOUTHWEST IN ADVANCE OF THE
NEXT STORM SYSTEM APPROACHING FROM THE FOUR CORNERS AREA.

THURSDAY...NEXT SHORTWAVE TROUGH ALOFT MOVES INTO COLORADO AND OUR
SOUTHERN COUNTIES...WITH THE LOWER AND MID LEVEL SATURATING EVEN
FURTHER. FEEL COMFORTABLE WITH POPS OVER OUR SOUTHERN MOUNTAIN
RANGES NEAR THE COLORADO BORDERS.

.LONG TERM...(SATURDAY THROUGH TUESDAY)
ISSUED AT 300 AM MDT WED SEP 2 2015

ALL MEDIUM RANGE MODELS INDICATE SOUTHWEST FLOW ALOFT OVER THE
CENTRAL AND SOUTHERN ROCKY MOUNTAINS INTO THE WEEKEND AS A STRONG
STORM SYSTEM GRADUALLY MOVES EASTWARD ACROSS THE PACIFIC NW AND
THE NORTHERN GREAT BASIN REGION. THERE WILL BE A PRETTY STRONG JET
STREAM FOR THIS TIME OF THE YEAR OVER THE AREA...WHICH MAY
INFLUENCE THE POTENTIAL FOR DAYTIME CONVECTION ON SATURDAY EVEN
THOUGH INSTABILITY APPEARS MARGINAL. SOME COOLER AIR ALOFT WILL
MOVE INTO THE AREA...BUT DO NOT SEE A CLEARLY DEFINED COLD FRONT
UNTIL LATER IN THE WEEKEND AS THE UPPER LEVEL TROUGH MOVES ACROSS
WYOMING. KEPT HIGH TEMPERATURES IN THE MID 70S TO UPPER 80S ON
SATURDAY.

MODELS ARE NOW IN BETTER AGREEMENT FOR SUNDAY...AND ALL ARE
SHOWING A NEGATIVELY TILTED OPEN WAVE THROUGH LIFTING NORTHEASTWARD
ACROSS MONTANA THROUGH THE DAY. THE GEM IS THE LEAST PROGRESSIVE
COMPARED TO THE GFS AND ECMWF...BUT STILL PRETTY SIMILAR. IF THIS
SOLUTION VERIFIES...MOST OF THE FORECAST AREA WILL BE DRY BUT VERY
WINDY ON SUNDAY DUE TO THE NORTHWARD STORM TRACK. LOWER POP BELOW
10 PERCENT ON SUNDAY...BUT INCREASED WINDS ACROSS THE AREA WITH
GUSTS OVER 50 MPH POSSIBLE DUE TO A 110 KT JET MAX MOVING ACROSS
WYOMING AND MONTANA.

MODELS THEN INDICATE NEAR ZONAL FLOW AND COOLER TEMPERATURES
BEHIND THE COLD FRONT BY EARLY TO MID NEXT WEEK. HIGHS WILL BE
NEAR OR SLIGHTLY BELOW NORMAL AND IN THE 70S TO AROUND 80 WITH
GENERALLY DRY CONDITIONS THROUGH TUESDAY. THE ECMWF IS HINTING
TOWARDS A MAJOR COLD FRONT DIGGING SOUTHWARD OUT OF CANADA BY THE
MIDDLE OF THE WEEK...BRINGING MUCH COOLER TEMPERATURES AND A
CHANCE OF WIDESPREAD RAINFALL.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1127 AM MDT WED SEP 2 2015

VFR CONDITIONS WILL PREVAIL THROUGH THE NEXT 24 HOURS. IT WILL
BE BREEZY AT THE SOUTHEAST WY TERMINALS THIS AFTERNOON WITH
WESTERLY SURFACE WINDS GUSTING TO 25 KT OR HIGHER AT TIMES. THE
WINDS WILL DIMINISH THIS EVENING. CONVECTIVE DEVELOPMENT WILL
BE RATHER ISOLATED AND CONFINED TO THE HIGHER TERRAIN THIS
AFTERNOON.

&&

.FIRE WEATHER...
ISSUED AT 233 AM MDT WED SEP 2 2015

NEAR CRITICAL TO CRITICAL FIRE WEATHER CONDITIONS TODAY
ESPECIALLY OVER OUR NORTHERN AND WESTERN DISTRICT WHERE LOW
HUMIDITIES WILL OCCUR ALONG WITH GUSTY WINDS IN EXCESS OF 25 MPH
AT TIMES. LOW HUMIDITIES AGAIN THURSDAY AFTERNOON NORTH OF A
RAWLINS TO LUSK LINE WITH GUSTY WINDS OVER 25 MPH...THUS WE MAY
NEED ANOTHER FIRE WEATHER WATCH.

&&

.CLIMATE...NEAR RECORD HIGH TEMPERATURES TODAY AT SEVERAL
LOCATIONS. RECORD MAXIMUM TEMPERATURES/YEAR FOR SEP 2...

RAWLINS 89/1995
LARAMIE 87/2013
CHEYENNE 92/1947
CHADRON 101/1960
ALLIANCE 97/2001
SCOTTSBLUFF 98/1983
SIDNEY 99/1983

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING UNTIL 7 PM MDT THIS EVENING FOR WYZ301>304-306-
     308.

NE...NONE.
&&

$$

UPDATE...SML
SHORT TERM...RUBIN
LONG TERM...TJT
AVIATION...MAJ
FIRE WEATHER...RUBIN
CLIMATE...RUBIN



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