Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 250354
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
954 PM MDT TUE MAR 24 2015

.UPDATE...
ISSUED AT 946 PM MDT TUE MAR 24 2015
LATEST AIRCRAFT DATA WAS SHOWING SOUTHEAST WYOMING IN A FAVORABLE
ASCENT REGION IN THE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET.
THIS IS ALLOWING FOR GOOD UPPER LEVEL DIFFLUENCE ESPECIALLY OVER
THE I-80 SUMMIT. THIS AREA IS ALSO EXPERIENCING GOOD UPSLOPE FLOW
WHICH IS CAUSING MODERATE SNOWFALL. AS A RESULT...ROAD CONDITIONS
WERE BEGINNING TO DETEORIATE ACCORDING TO LATEST WEBCAMS. THIS IS
ALSO OCCURRING AHEAD OF A DEVELOPING WAVE MOVING INTO NORTHERN
WYOMING WHERE WE ARE SEEING AN ENHANCEMENT IN THE SNOW SHOWERS. WE
WILL CONTINUE TO MONITOR ROAD CONDITIONS FOR NOW...BUT WE MAY END
UP HAVING TO ISSUE A WINTER WEATHER ADVISORY FOR THE SUMMIT DURING
THE NEXT HOUR OR TWO. FOR NOW...WE WILL HANDLE THIS AREA WITH A
SPECIAL WEATHER STATEMENT.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 309 PM MDT TUE MAR 24 2015

GUSTY WINDS ACROSS MUCH OF THE CWA THIS AFTERNOON WILL EASE THIS
EVENING AS A SURFACE LOW OVER NORTH DAKOTA MOVES SLOWLY NORTHEAST
AND THE GRADIENT RELAXES. EXPECT TO SEE AN UPTICK IN SHOWER
ACTIVITY ACROSS THE CWA OVERNIGHT AS A SHORTWAVE DROPS SOUTH
ACROSS THE AREA LATER TONIGHT INTO EARLY WEDS MORNING WITH A FEW
INCHES OF SNOW POSSIBLE MAINLY OVER THE NORTH LARAMIE RANGE AS
WELL AS THE SNOWY AND SIERRA MADRES. SHORTWAVE WILL EXIT TO THE
SE OF THE CWA WEDS AFTERNOON BUT SOME SNOW SHOWERS SHOULD PERSIST
OVER THE MTNS WITH A FEW BANDS EXTENDING OVER PARTS OF THE PLAINS
IN FAVORABLE NORTHWEST FLOW. BREEZY AGAIN WEDS AFTERNOON BUT NOT
AS STRONG AS TODAY. A LITTLE COOLER WEDS WITH A SFC HIGH SETTLING
INTO THE NORTHERN PLAINS. WARMING AGAIN THURSDAY AS UPPER RIDGING
TO THE WEST EDGES CLOSER TO THE REGION AND HEIGHTS BEGIN RISING.
COULD SEE A FEW SHOWERS OVER NORTHEAST PARTS OF THE CWA THURSDAY
WHERE THE RETREATING SURFACE BOUNDARY MAY INTERACT WITH A BIT OF
INSTABILITY.

.LONG TERM...(FRIDAY THROUGH MONDAY)
ISSUED AT 309 PM MDT TUE MAR 24 2015

FLOW ALOFT BEGINS TO DECREASE ON FRI AS THE UPPER JET SHIFTS
EASTWARD INTO EASTERN NEBRASKA.  AS A RESULT...WINDS WILL BE WEAKER
DURING THE DAY ON FRI BUT STILL EXPECTING GUSTS TO 25-30 KTS.
HEIGHTS RISE ON FRI AND TEMPS WILL WARM INTO THE 60S TO THE EAST OF
THE LARAMIE RANGE.  SAT IS STILL LOOKING QUITE WARM AS PRESSURE
FALLS OCCUR TO THE EAST OF THE CWA AND SFC WINDS BECOME MORE
WESTERLY.  SOUNDINGS INDICATE A WARM AND VERY DRY AIRMASS WITH MIN
RH VALUES DROPPING TO AROUND 15 PERCENT TO THE EAST OF THE LARAMIE
RANGE.  SINCE WINDS WILL LIKELY BE GUSTING TO 25 KTS DURING THE AFTN
WITH DEEP MIXING...CRITICAL FIRE WEATHER CONDITIONS DEFINITELY LOOK
POSSIBLE.  WILL HAVE TO KEEP AN EYE ON THIS AS WE APPROACH THE
WEEKEND.  A WEAK DRY COLD FRONT IS FCSTED TO MOVE OVER THE PLAINS ON
SAT NIGHT AND THIS WILL MEAN SLIGHTLY COOLER TEMPS FOR SUN.  THE
ECMWF SHOWS A WEAK SHORTWAVE APPROACHING NW COLORADO ON SUN WHEREAS
THE GFS JUST SHOWS ZONAL FLOW ALOFT.  COULD BE SOME WEAK AFTN
CONVECTION DEVELOPING ON BOTH SUN AND MON AS THE GFS INDICATES CAPE
OF 100-300 J/KG.  GUSTY WINDS WOULD BE THE PRIMARY CONCERN WITH DEEP
BOUNDARY LAYERS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 532 PM MDT TUE MAR 24 2015

THE MAIN CONCERN WITH THIS TAF ISSUANCE IS THE POTENTIAL FOR MVFR/IFR
CONDITIONS DEVELOPING AFTER 12Z.

LATEST AIRCRAFT DATA WAS SHOWING ANOTHER JET STREAK MOVING THROUGH
THE PACIFIC NORTHWEST. THIS FEATURE WILL CONTINUE TO NOSE INTO THE
NORTHERN ROCKIES THIS EVENING AND CAUSE A WEAK MID LEVEL TROF TO
DEVELOP OVER NORTHWEST WYOMING TONIGHT WITH THIS TROF SHIFTING
SOUTHEAST THROUGH THE REMAINDER OF WYOMING WEDNESDAY MORNING. THIS
WILL ALSO CAUSE A FRONTAL BOUNDARY TO SHIFT THROUGH THE FORECAST
AREA. AS A RESULT...WE COULD SEE QUITE A BIT OF COVERAGE OF
SNOW SHOWERS LATE TONIGHT INTO TOMORROW MORNING. THE GREATEST
COVERAGE APPEARS TO BE AT RWL WHERE THEY MAY SEE MVFR CONDITIONS
AFTER 13Z WITH THE VISIBILITY POSSIBLY DROPPING BELOW 1 MILE AT
TIMES. MEANWHILE...THE REST OF THE WYOMING TAF SITES MAY SEE
SCATTERED SNOW SHOWERS WITH VISIBILITIES POSSIBLY DROPPING TO NEAR 1
MILE AT TIMES. MEANWHILE...THE NEBRASKA TAF SITES MAY ESCAPE THE
BULK OF THE SHOWERS WITH MAINLY VFR CONDITIONS.


&&

.FIRE WEATHER...
ISSUED AT 309 PM MDT TUE MAR 24 2015

HAVE STRUGGLED TO ATTAIN RED FLAG CONDITIONS THIS AFTERNOON BUT
CLOSE ENOUGH TO MAINTAIN RED FLAG WARNING...THOUGH HAVE OPTED TO
END IT AT 6PM. CONCERNS THEN BECOME LOW FOR THE NEXT FEW DAYS WITH
COOLER TEMPS AND LESS WIND WITH SCTD RAIN AND SNOW SHOWERS LATER
TONIGHT INTO WEDS AFFECTING MOST DISTRICTS.

&&

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

$$

UPDATE...REC
SHORT TERM...RE
LONG TERM...ZF
AVIATION...REC
FIRE WEATHER...RE



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