Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 260014
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
614 PM MDT SAT OCT 25 2014

.UPDATE...
ISSUED AT 545 PM MDT SAT OCT 25 2014

LATEST WATER VAPOR LOOP WAS SHOWING THE UPPER LEVEL TROF MOVING
INTO THE PACIFIC NORTHWEST WITH THE SURFACE FRONT EXTENDING FROM
NORTHERN WYOMING INTO CENTRAL MONTANA. AHEAD OF THIS
BOUNDARY...THE LOW LEVEL FLOW IS EXPECTED TO INCREASE AS THE NIGHT
WEARS ON. IN FACT...LATEST AIRCRAFT DATA WAS SHOWING 40 TO 45KT
SOUTHWEST WINDS ALREADY MOVING OUT OF UTAH. THIS APPEARS TO BE
SETTING THE STAGE FOR HIGH WINDS 50 TO 60 MPH ACROSS ARLINGTON
LATE TONIGHT AND POSSIBLY VEDAUWOO AND THE FOOTHILLS. AS A
RESULT...WE ARE PLANNING ON ISSUING A HIGH WIND WARNING FOR AT
LEAST THE ARLINGTON AREA AT THIS TIME WITH THE THREAT BEGINNING
AROUND 08Z OR SO. NOT CONFIDENT ENOUGH ABOUT VEDAUWOO...DUE TO THE
POTENTIAL FOR SOME CLOUD COVER FROM THE UPSLOPE FLOW WHICH MAY
LIMIT MIXING. HOWEVER...WE WILL EVALUATE LATER THIS EVENING.

&&

.SHORT TERM...(TONIGHT THROUGH MONDAY NIGHT)
ISSUED AT 300 PM MDT SAT OCT 25 2014

AFTERNOON WATER VAPOR IMAGERY LOOP SHOWED A HIGH AMPLITUDE RIDGE
ENCOMPASSING MOST OF THE GREAT PLAINS AND FRONT RANGE. THE 20Z
REGIONAL SURFACE ANALYSIS DEPICTED HIGH PRESSURE FROM THE DAKOTAS
TO NEBRASKA. A WARM FRONT EXTENDED SOUTHEAST FROM A LOW NEAR SHERIDAN
WYOMING THROUGH THE SOUTHWEST CORNER OF THE NEBRASKA PANHANDLE. SUNNY
SKIES PREVAILED WITH ABOVE NORMAL TEMPERATURES...RANGING FROM THE
MID 60S TO LOWER 80S. WINDS WERE LIGHT SOUTHEASTERLY ACROSS WESTERN
NEBRASKA...WHILE GUSTY SOUTHWESTERLY WINDS WERE OBSERVED THROUGHOUT
SOUTHEAST WYOMING.

THE LATEST NUMERICAL MODEL GUIDANCE CONTINUES THE PROGRESSIVE LARGE
SCALE PATTERN. THE GREAT PLAINS UPPER RIDGE SLIDES EAST THROUGH
THE MIDWEST AND EASTERN CONUS THROUGH MONDAY. MEANWHILE...A EASTERN
PACIFIC UPPER TROUGH MOVES THROUGH THE PACIFIC NORTHWEST AND NORTHERN
ROCKIES SUNDAY...THEN DIGS SOUTH AND EAST ACROSS WYOMING AND THE
NORTHERN GREAT PLAINS MONDAY. A STRONG PACIFIC COLD FRONT WILL PRECEDE
THE TROUGH...PASSING THROUGH THE CWA SUNDAY. AHEAD OF THE FRONT...THE
SURFACE PRESSURE GRADIENT TIGHTENS WITH 700MB WINDS PEAKING AROUND
50 KT JUST BELOW THE INVERSION EARLY SUNDAY MORNING OVER CARBON
AND ALBANY COUNTIES. THE CRAIG-CASPER GRADIENT PEAKS AROUND 50M DURING
THIS TIME. SUSTAINED WESTERLY WINDS OF 35 TO 45 MPH WITH GUSTS TO
AROUND 55 MPH WILL DEVELOP BETWEEN LARAMIE AND RAWLINS. THE GRADIENT
AND WINDS DECREASE AFTER THE FRONTAL PASSAGE SUNDAY AFTERNOON. IT
WILL BE ANOTHER UNSEASONABLY MILD AFTERNOON EAST OF THE LARAMIE
RANGE SUNDAY...WITH COOLER TEMPERATURES SPREADING INTO THE WEST
BEHIND THE COLD FRONT.

PRECIPITATION-WIDE...SHOWERS DEVELOP SUNDAY MORNING AND AFTERNOON OVER
THE SNOWY/SIERRA MADRE RANGES. THE PRECIPITATION PATTERN SPLITS
SUNDAY NIGHT INTO TWO AREAS...ONE ACROSS FAR SOUTHERN/SOUTHEAST
WYOMING AND SOUTHERN NEBRASKA PANHANDLE ASSOCIATED WITH A SURFACE
LOW...AND THE OTHER ACROSS NORTHEAST AND EAST CENTRAL WYOMING.
SNOW LEVELS WILL DROP TO AROUND 7000 FT BY MONDAY MORNING.
PRECIPITATION AMOUNTS WILL GENERALLY BE ON THE LIGHT SIDE...WITH
A FEW INCHES OF SNOW POSSIBLE OVER THE SNOWY/SIERRA MADRE RANGES.

MONDAY WILL TURN OUT TO BE A COOL BREEZY DAY AS THE UPPER TROUGH
PASSES OVERHEAD. LINGERING RAIN/SNOW SHOWERS ACROSS THE NORTH AND
EAST PARTS OF THE CWA WILL END BY AFTERNOON WITH PARTIAL CLEARING.
THE PRESSURE GRADIENT INCREASES MONDAY WITH GUSTY NORTHWEST WINDS.
HIGH TEMPERATURES MONDAY WILL BE 20-25 DEGREES COOLER THAN
SUNDAY...MORE TYPICAL OF LATE OCTOBER. UNDER MOSTLY CLEAR SKIES
AND DIMINISHING WINDS...LOWS MONDAY NIGHT WILL PLUMMET INTO THE
UPPER TEENS TO UPPER 20S.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 200 PM MDT SAT OCT 25 2014

MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT THROUGH THE PERIOD. THE
BEST CHANCE FOR ANY PCPN WOULD BE TUE OR WED BENEATH QUASI-ZONAL FLOW
ALOFT AS A POSITIVE TILT SHORTWAVE MOVES OVER THE NORTHERN ROCKIES.
GFS AND ECMWF BOTH SHOW THE BEST FORCING TO THE NORTH OF THE CWA
THOUGH...SO HAVE MAINTAINED A DRY FORECAST FOR THIS TIME RANGE. IT
WILL REMAIN COOL THROUGH TUE WITH GFS H7 TEMPERATURES STILL IN THE
SINGLE DIGITS BELOW 0C. SUBSIDENCE AND WARMING TEMPERATURES ALOFT
BENEATH AN AMPLIFYING UPPER RIDGE SHOULD YIELD A WARMING TREND WITH
CONTINUED DRY CONDITIONS THROUGH THE END OF THE WORK WEEK. A WEAK
SURFACE COOL FRONT IS LIKELY TO INTERRUPT THIS TREND THU. LATE IN
THE PERIOD...THE MODELS AGREE ON A STRONG TROUGH DIGGING INTO THE
GREAT BASIN. AT THIS TIME...IT APPEARS ANY ASSOCIATED PCPN SHOULD
BE JUST BEYOND THE END OF THE EXTENDED FORECAST PERIOD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 545 PM MDT SAT OCT 25 2014

FRONTAL BOUNDARY IN WESTERN WYOMING IS PROGGED TO PUSH EAST
THROUGH CENTRAL AND NORTHERN WYOMING OVERNIGHT AND THROUGH THE
PANHANDLE IN THE MORNING. AHEAD OF THIS FRONT...IT WILL BE QUITE
BREEZY IN RWL OVERNIGHT WITH SPEEDS GENERALLY HANGING AROUND 15 TO
20KTS. HIGHER WIND SPEEDS WILL BEGIN MIXING DOWN DURING THE
LATE MORNING INTO THE EARLY AFTERNOON ACROSS THE RWL...LAR AND CYS
TAF SITES. SOME LOWER CLOUDS MAY DEVELOP OVER THE SUMMIT DURING
LATE MORNING INTO THE AFTERNOON...BUT LAR AND CYS SHOULD SEE GOOD
DOWNSLOPE FLOW WHICH WILL LIMIT THE POTENTIAL FOR CLOUD COVER AND
ALLOW FOR GUSTY WEST WINDS AT SPEEDS OVER 25KTS.

&&

.FIRE WEATHER...
ISSUED AT 200 PM MDT SAT OCT 25 2014

WARM...BREEZY AND DRY CONDITIONS WILL CONTINUE THIS AFTERNOON FOR
AREAS ALONG AND JUST EAST OF THE LARAMIE RANGE. LOWEST HUMIDITIES
WILL BOTTOM OUT BETWEEN 10 AND 15 PERCENT. FORTUNATELY...GUSTY WINDS
WILL REMAIN WEST OF THE LARAMIE RANGE WHERE FUELS ARE NOT SUPPORTIVE
OF RAPID FIRE GROWTH. STRONGER WINDS WILL DEVELOP SUNDAY AND MONDAY
AS A COLD FRONT AND UPPER LEVEL TROUGH MOVE FROM WEST TO EAST. MUCH
COOLER TEMPERATURES WILL INCREASE HUMIDITIES AND PROVIDE CHANCES FOR
RAIN AND SNOW SHOWERS. SEASONABLY COOL AND DRY WEATHER WILL PREVAIL
MID WEEK FOLLOWED BY A WARMING TREND FOR THE END OF THE WEEK.

&&

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

$$

UPDATE...REC
SHORT TERM...JAMSKI
LONG TERM...HAMMER
AVIATION...REC
FIRE WEATHER...JAMSKI



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