Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 260308
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
808 PM MST TUE NOV 25 2014

.UPDATE...
ISSUED AT 805 PM MST TUE NOV 25 2014

SEEING RAPIDLY COOLING CLOUD TOPS ON IR IMAGERY ACROSS NORTH
CENTRAL WYOMING THIS EVENING JUST NORTH OF CONVERSE COUNTY.
WEBCAMS NEAR NATURAL BRIDGE SHOWING I-25 SNOW COVERED WITH REDUCED
VISIBILITIES. GOT A REPORT OUT OF DOUGLAS OF 3 INCHES OF SNOW...SO
WENT AHEAD AND ADDED CONVERSE COUNTY TO THE WINTER WEATHER
ADVISORY. LOOKING AT WIND REPORTS FURTHER SOUTH...FRONT ALREADY
HAS MADE IT THROUGH BORDEAUX AND WINDS OUT WEST IN CARBON AND
NORTHERN ALBANY COUNTIES CONTINUE TO DECREASE. WENT AHEAD AND
CANCELLED THE HIGH WIND WARNING FOR THESE AREAS EARLY. UPDATES
HAVE BEEN SENT.

UPDATE ISSUED AT 700 PM MST TUE NOV 25 2014

LOOKING AT AREA WYDOT AND METAR OBSERVATIONS...DECIDED TO LET THE
HIGH WIND WARNINGS FOR MOST OF LARAMIE COUNTY...THE LARAMIE VALLEY
AND THE SARATOGA AREA EXPIRE ON TIME AT 7 PM THIS EVENING.
PROBABLY COULD HAVE TAKEN BORDEAUX OUT OF THE WARNING AS
WELL...BUT WILL WAIT ANOTHER HOUR OR SO TO SEE WHAT THEIR WINDS DO
UP THERE.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 342 PM MST TUE NOV 25 2014

FORECAST REMAINS ON TRACK FOR THE MOST PART REGARDING STRONG WINDS
AND SNOW PER UPDATED DISCUSSION ISSUED EARLIER THIS AFTERNOON. THE
COLD FRONT HAS MOVED SOUTH ABOUT HALFWAY-THREE QUARTERS THROUGH
THE CWA AT THIS HOUR...WITH SNOW AND LIGHT SHOWERS INCREASING IN
COVERAGE AS IT PASSES THROUGH. RAIN SHOULD QUICKLY CHANGE TO SNOW
AS COOLER AIR FILTERS IN BEHIND THE FRONT. STRONG WINDS CONTINUE
THIS AFTERNOON MAINLY ALONG AND WEST OF THE LARAMIE RANGE WITH
WINDS A BIT CALMER ACROSS THE WYO PLAINS AT THIS HOUR. WILL LEAVE
WIND HIGHLIGHTS AS IS AT LEAST UNTIL FRONTAL PASSAGE.

MADE A FEW CHANGES TO THE WINTER WEATHER ADVISORY TO INCLUDE THE
SUMMIT AND EXTEND THE TIMING OF THE HIGHLIGHT TO THE AFTERNOON TO
ACCOUNT FOR BLOWING SNOW CONCERNS. AFTER A FURTHER LOOK AT THE
WIND PROGS FOR TOMORROW MORNING...AND DISCUSSION WITH OUR
PARTNERS ABOUT POTENTIAL TRAVEL IMPACTS UP AT THE SUMMIT WITH THE
COMBO OF SNOW AND WIND...FELT IT NECESSARY TO ADJUST THE ADVISORY
FOR THESE TWO CHANGES. 2 TO 5 INCHES STILL LOOKS TO BE ON TRACK
FOR SNOW TOTALS ACROSS THE AREA...BUT WINDS OF 15 TO 20 MPH
INCREASING TO 25 TO 35 MPH WITH HIGHER GUSTS BY SUNRISE UP NEAR
THE SUMMIT AS THE SNOW ENDS WILL LIKELY CAUSE SOME TRAVEL PROBLEMS
THROUGH THE MORNING DUE TO BLOWING AND DRIFTING OF SNOW. WINDS
WILL INCREASE ACROSS THE EASTERN FOOTHILLS AND ADJACENT PLAINS IN
THE MORNING AS WELL WHERE THE HEAVIER SNOW IS EXPECTED TO
FALL...SO COULD SEE SOME HAZARDOUS TRAVEL ALONG I-25 AND I-80
APPROACHING CHEYENNE DUE TO BLOWING AND DRIFTING OF SNOW.
EXTENDING THE TIMING THROUGH 2 PM AS BLOWING SNOW SHOULD BE LESS
OF A CONCERN IN THE AFTERNOON AS WINDS AND SOME HEATING THROUGH
THE DAY WORK OVER THE SNOWPACK. BREEZY TO WINDY CONDITIONS WILL
CONTINUE THROUGH WEDNESDAY NIGHT AS THE LLVL GRADIENT REMAINS
TIGHT IN THE WAKE OF THE DEPARTING FRONT.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 342 PM MST TUE NOV 25 2014

MAIN STORY THROUGH LATE WEEK WILL BE HIGH WIND POTENTIAL IN THE MAIN
WIND CORRIDORS ACROSS SOUTHEAST WY. MEDIUM RANGE MODELS ARE STILL IN
GOOD AGREEMENT WITH A FAVORABLE PATTERN FOR STRONG GUSTS WITH AN H25
JET CORE REMAINING ANCHORED OVER THE NORTHERN ROCKIES WITH WEAK SFC
LOW PRESSURE SPREADING ACROSS MT INTO THE DAKOTAS. THIS PRETTY MUCH
KEEPS THE LLVL CAG-CPR GRADIENTS BETWEEN 60 AND 70 METERS THROUGH AT
LEAST FRIDAY. WITH THE GFS SHOWING A WIDESPREAD AREA OF 50 KT 700 MB
FLOW...INCREASED WINDS AND KEPT GUSTS RIGHT AROUND WARNING CRITERIA
THROUGH THE END OF THE WEEK FOR ARLINGTON/BORDEAUX AND I80 BETWEEN
LARAMIE AND CHEYENNE. ASIDE FROM THE WIND...CONFIDENCE IS HIGH IN A
RATHER WARM THANKSGIVING. BOTH THE GFS AND ECMWF SUGGEST H7 TEMPS IN
THE 2-3 DEG C RANGE. WESTERLY DOWNSLOPE WINDS WOULD FAVOR THE WARMER
MOS WITH HIGHS AROUND 60-65 F OVER THE PLAINS ON THU/FRI. A CANADIAN
SFC HIGH WILL BEGIN TO SINK SOUTH INTO THE NORTHERN HIGH PLAINS INTO
SAT...PUSHING THE BEST SFC PRESSURE GRADIENTS SOUTH OF THE CWA AND
PROVIDING A BREAK FROM HIGH WINDS BY LATE IN THE WEEKEND. A POTENT
SHORTWAVE WILL SWING ACROSS THE DAKOTAS ON SUN...SENDING A BACKDOOR
FRONT SOUTHWESTWARD. SOME DIFFERENCES IN THE GFS/ECM WITH THE DEPTH
OF COLD AIR. THE COLDER ECMWF SHOWS TEMPS AROUND -9C AT 700 MB IN
THE NORTHERN PANHANDLE AT 18Z SUN...WHEREAS THE GFS ONLY SHOWS -3C
AT THE SAME TIME. STILL LEANED MORE TOWARD THE ECMWF AND MADE FEW
CHANGES TO THE PREVIOUS FCST. GENERALLY A DRY PERIOD WITH A LACK OF
ANY SUBSTANTIAL DYNAMICS. PRECIP CHANCES LOOK TO INCREASE ALONG AND
WEST OF THE LARAMIE RANGE ON TUE AND WED WITH THE RETURN OF MOIST
SOUTHWEST FLOW ALOFT PER MEDIUM RANGE GUIDANCE.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 342 PM MST TUE NOV 25 2014

WINDS REMAIN VERY STRONG ACROSS SOUTHEAST WYOMING WITH AN OCCASIONAL
GUST TO 45 KTS POSSIBLE THROUGH 01Z. A COLD FRONT WILL MOVE THROUGH
THE AREA THIS EVENING...PROVIDING SOME TEMPORARY RELIEF TO HIGH WIND
FOR MOST AREAS. RAIN AND SNOW SHOWERS ARE ALREADY STARTING TO BECOME
MORE WIDESPREAD LATE THIS AFTERNOON. A BAND OF MODERATE SNOW SHOULD
TAKE SHAPE BETWEEN 03-09Z ALONG AND SOUTHWEST OF A LINE FROM DGW TO
SNY WITH SEVERAL INCHES OF ACCUMULATION POSSIBLE. VSBYS WILL LIKELY
BE IFR TO LIFR BENEATH THIS BAND. SNOW SHOWERS MAY SPREAD FURTHER
INTO THE NEBRASKA PANHANDLE ON WED MORNING. WINDS ARE EXPECTED TO
INCREASE AGAIN OVER THE WYOMING TERMINALS ON WED AFTERNOON ALONG
WITH THE POSSIBILITY OF MOUNTAIN WAVE TURBULENCE.


&&

.FIRE WEATHER...
ISSUED AT 342 PM MST TUE NOV 25 2014

WINDY CONDITIONS WILL DIMINISH TONIGHT AS A COLD FRONT MOVES
THROUGH THE AREA. A PERIOD OF SNOW WILL FALL TONIGHT WITH
ACCUMULATIONS OF 2 TO 5 INCHES EXPECTED ACROSS LOWER ELEVATIONS
IN SOUTHEAST WYOMING. THE SNOWY AND SIERRA MADRE RANGES WILL SEE
UP TO ANOTHER FOOT OF SNOW THROUGH TONIGHT.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER STORM WARNING UNTIL 7 AM MST WEDNESDAY FOR WYZ112-114.

     HIGH WIND WARNING UNTIL 2 PM MST WEDNESDAY FOR WYZ110.

     WINTER WEATHER ADVISORY UNTIL 2 PM MST WEDNESDAY FOR WYZ101-103-
     106-107-116>119.

     HIGH WIND WARNING UNTIL 11 PM MST THIS EVENING FOR WYZ116-117.

NE...NONE.
&&

$$

UPDATE...GCC
SHORT TERM...RJM
LONG TERM...CLH
AVIATION...CLH
FIRE WEATHER...RJM


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