Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 211743 AAA
AFDCYS

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHEYENNE WY
1143 AM MDT TUE OCT 21 2014

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 215 AM MDT TUE OCT 21 2014

CURRENT IR SATELLITE LOOP SHOWS MAINLY CLEAR SKIES ACROSS
SOUTHEAST WYOMING AND WESTERN NEBRASKA...ALTHOUGH CLOUDS ARE
DEVELOPING AND PUSHING NORTHWARD OVER COLORADO. A VIGOROUS UPPER
LEVEL SHORTWAVE TROUGH IS CURRENTLY PUSHING ACROSS THE NORTHERN
GREAT BASIN REGION EARLY THIS MORNING WITH SOME LIGHT RAIN BEING
REPORTED ACROSS NAN NEVADA AND IDAHO. SKIES WILL BECOME PARTLY
CLOUDY THIS MORNING ALONG AND WEST OF THE LARAMIE RANGE AS THIS
TROUGH WILL QUICKLY MOVE INTO WESTERN WYOMING BY THIS AFTERNOON.
WINDS WILL INCREASE OUT OF THE SOUTH OR SOUTHWEST TODAY AHEAD OF
THE COLD FRONT...WHICH WILL GRADUALLY PUSH ACROSS THE AREA
SOMETIME LATER TODAY AND INTO TONIGHT. THERE IS NOT MUCH THAT IS
REALLY IMPRESSIVE ABOUT THIS SYSTEM AS IT EJECTS NORTHEAST ACROSS
WYOMING AND MONTANA THROUGH TONIGHT. ALL MODELS INDICATE A WEAKENING
JET ALOFT...WHICH WILL RESULT IN WEAK UPPER LEVEL DYNAMICS. THIS
WEAKENING APPEARS TO BE INFLUENCED BY THE STRENGTH OF THE HIGH
AMPLITUDE RIDGE ACROSS THE CENTRAL UNITED STATES. THERE IS SOME
MARGINAL INSTABILITY PRESENT AND SOME WEAK LARGE SCALE LIFT...SO
INCREASED POP BETWEEN 25 TO 35 PERCENT ALONG THE I80 CORRIDOR
THROUGH EARLY WEDNESDAY...MAINLY ACROSS SOUTHEAST WYOMING.  CAN
NOT RULE OUT A FEW THUNDER SHOWERS THIS AFTERNOON AND THIS EVENING
AS WELL AS LI/S LOWER BETWEEN ZERO AND -2. MOST OF THE ACTIVITY WILL
PRIMARILY BE RAIN SHOWERS WITH SOME SNOW IN THE HIGHER MOUNTAINS.
PRECIS WILL BE LIGHT WITH PF VALUES BELOW 0.25...AND MOST
LOCATIONS ONLY SEEING A TRACE UP TO A TENTH OF AN INCH OF LIQUID.
TEMPERATURES WILL BE WARM TODAY WITH HIGHS IN THE MID TO UPPER 60S
WEST OF THE LARAMIE RANGE...AND BETWEEN 70 TO 80 DEGREES ALONG AND
EAST OF I25 INCLUDING WESTERN NEBRASKA.

TEMPERATURES WILL BE 5 TO 10 DEGREES COOLER ON WEDNESDAY BEHIND
THE FRONT...BUT WILL STILL BE SEASONABLE FOR THIS TIME OF THE YEAR
AND GENERALLY IN THE UPPER 50S TO UPPER 60S. KEPT POP BELOW 15
PERCENT ON WEDNESDAY...BUT WILL HAVE TO WATCH THE I80 CORRIDOR
NEAR THE COLORADO BORDER FOR SOME ISOLATED SHOWERS AND PERHAPS A
FEW LIGHTNING STRIKES DUE TO LLVL INSTABILITY AND SOME LINGERING
MOISTURE. OTHERWISE...ANOTHER WARMING TREND IS EXPECTED TO BEGIN
ON THURSDAY AS AN UPPER LEVEL RIDGE BEGINS TO EXTEND NORTHWARD
ACROSS THE ROCKY MOUNTAINS.

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 215 AM MDT TUE OCT 21 2014

CONTINUED DRY AND BREEZY/WINDY CONDITIONS FOR MOST OF THE LONG
TERM. BUT THERE ARE CHANGES COMING UP.

UPPER RIDGE AXIS LOOKS TO PASS OVERHEAD THURSDAY NIGHT. GFS
SHOWING 700MB WINDS INCREASING TO NEAR 40KTS BY FRIDAY MORNING AS
THE RIDGE AXIS CONTINUES TO MOVE OFF TO THE EAST. GOING TO BE
PRETTY WARM WITH THESE STRONGER...DOWNSLOPING WINDS FOR FRIDAY AND
SATURDAY. HAVE HIGHS BOTH DAYS APPROACHING 80 IN THE PANHANDLE.
GFS 700MB TEMPERATURES ARE +8 TO +10C OVER THE CWFA FRIDAY AND
SATURDAY AHEAD OF OUR NEXT COLD FRONT.

GFS AND ECMWF BOTH CONTINUE TO SHOW A CHANGE FOR SUNDAY NIGHT INTO
MONDAY. ECMWF STRONGER ON THE SHORTWAVE OVER THE GFS AND HAS THE
SHORTWAVE TRACKING A LITTLE FURTHER SOUTH. DID BUMP UP POPS FOR
THIS TIMEFRAME. WITH 700MB TEMPERATURES OF -4 TO -6C...A LOT OF
THIS PRECIP COULD FALL AS SNOW. SHOULD THE ECMWF SOLUTION HOLD
TRUE...WE COULD BE LOOKING AT WINTER HEADLINES AS TOTAL PF
FORECAST CLOSE TO .75 INCHES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY MORNING)
ISSUED AT 1143 AM MDT TUE OCT 21 2014

A WEAK COLD FRONT ASSOCIATED WITH A PASSING UPPER LEVEL TROUGH
WILL MOVE INTO THE RAWLINS AREA AROUND 6 PM THIS EVENING AND
PROGRESS EASTWARD ACROSS SOUTHEASTERN WYOMING AND THE WESTERN
NEBRASKA PANHANDLE DURING THE OVERNIGHT PERIOD. THERE IS JUST
ENOUGH INSTABILITY TO EXPECT ISOLATED THUNDERSTORMS TO POP UP
STARTING MID AFTERNOON IN THE RAWLINS AND LARAMIE AREAS. LATEST
HIGH RESOLUTION RAPID REFRESH MODEL SUGGESTS MOSTLY SHOWERS WITH A
FEW THUNDERSTORMS PROGRESSING EAST OF THE LARAMIE RANGE DURING THE
LATE AFTERNOON AND EARLY EVENING HOURS WITH MODEST UPPER LEVEL
FORCING ASSOCIATED WITH A PASSING WEAK UPPER LEVEL JET MAXIMUM.
NOT ENOUGH COVERAGE OF SHOWERS OR STORMS TO WARRANT A PREVAILING
PERIOD OF LOWERED VISIBILITIES/CEILINGS IN THE FORECAST, SO WE
CARRIED VFR CATEGORY PREVAILING ALL PERIODS WITH A VICINITY
MENTION OF SHOWERS OR THUNDERSTORMS MID AFTERNOON THROUGH MID
EVENING FOR MOST SITES. ANY LINGERING SHOWERS OR THUNDERSTORMS
WILL WEAKEN AS WE GO INTO THE LATE EVENING AS THE UPPER LEVEL
SUPPORT LIFTS OUT TO THE NORTHEAST.

&&

.FIRE WEATHER...
ISSUED AT 150 AM MDT TUE OCT 21 2014

MINIMAL FIRE WEATHER CONCERNS THIS WEEK WITH DAYTIME HUMIDITIES
MAINLY BETWEEN 20 TO 35 PERCENT. BREEZY OR WINDY CONDITIONS ARE
EXPECTED THIS AFTERNOON AS WELL AS WEDNESDAY AS A WEAK COLD FRONT
PUSHES ACROSS WYOMING. THERE IS A CHANCE OF RAIN SHOWERS AND
PERHAPS A FEW THUNDERSTORMS ALONG INTERSTATE 80 THIS AFTERNOON AND
INTO TONIGHT. OTHERWISE...DRY CONDITIONS ARE EXPECTED AFTER
WEDNESDAY AND INTO NEXT WEEKEND.

&&

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

$$

SHORT TERM...TJT
LONG TERM...CLAYCOMB
AVIATION...GARMON
FIRE WEATHER...TJT






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