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000
FXUS65 KCYS 131129
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
429 AM MST FRI DEC 13 2013

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 330 AM MST FRI DEC 13 2013

OVERNIGHT WATER VAPOR IMAGERY REVEALED A SHORTWAVE TROUGH APPROACHING
THE GREAT BASIN...WITH ANOTHER DOWNSTREAM TROUGH FROM COLORADO TO A
CLOSED LOW NEAR THE ARIZONA-NEW MEXICO BORDER. FASTER WEST-NORTHWEST
FLOW ALOFT WAS SITUATED FROM THE NORTHERN ROCKIES THROUGH THE UPPER
MIDWEST AND NORTHEAST CONUS...BOUNDED ON THE SOUTH BY A FRONTAL
BOUNDARY. MODERATE PRESSURE GRADIENT SUPPORTING GUSTY SOUTHWEST WINDS
WEST OF THE LARAMIE RANGE. GUSTS AS HIGH AS 50 MPH WERE OCCURRING
BETWEEN LARAMIE AND WALCOTT JUNCTION. SCATTERED HIGH CLOUDS WERE
OBSERVED PER INFRARED SATELLITE. TEMPERATURES WERE MILDER THAN RECENT
NIGHTS WITH READINGS IN THE 20S AND 30S.

00Z DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT SUPPORTING A
PROGRESSIVE UPPER LEVEL PATTERN. THE GREAT BASIN TROUGH WILL MOVE
SOUTHEAST ACROSS THE CWA TONIGHT. THE SREF AND TO A LESSER EXTEND THE
NAM DEPICT VERY LIGHT QPF OVER THE SNOWY AND SIERRA MADRES LATER THIS
AFTERNOON THROUGH SATURDAY. SNOW ACCUMULATIONS OF AN INCH OR TWO WILL
BE POSSIBLE. A LOW PRESSURE TROUGH WILL MOVE THROUGH THE REGION THIS
MORNING...WITH THE FRONT TO THE NORTH PUSHING SOUTH ACROSS THE HIGH
PLAINS THIS AFTERNOON. THIS WILL SHIFT THE SOUTHWEST WINDS TO NORTHWEST.
BREEZY TO WINDY CONDITIONS THIS MORNING WILL GRADUALLY DIMINISH THIS
AFTERNOON WITH THE WEAKENING GRADIENT. HIGH TEMPERATURES TODAY WILL
BE ABOUT 10 DEGREES COOLER TODAY WITH 700MB TEMPERATURES FALLING TO
-7C.

UPPER TROUGH PUSHES FURTHER SOUTHEAST THROUGH THE GREAT PLAINS AND
MIDWEST SATURDAY. DEEP LAYER RIDGE TO THE WEST OF THE CONTINENTAL
DIVIDE DRIFTS EASTWARD. A WEAK SHORTWAVE DROPPING SOUTHEAST ON THE
DOWNWIND SIDE OF THE RIDGE WILL KEEP SOME MOISTURE TO SQUEEZE OUT
LIGHT SNOW FOR THE SOUTHERN MOUNTAINS SATURDAY AFTERNOON AND EVENING.
HIGH TEMPERATURES SATURDAY WILL BE SLIGHTLY COOLER WEST OF THE LARAMIE
RANGE WITH LITTLE OR NO CHANGE FROM TODAY/S HIGHS EAST OF THE LARAMIE
RANGE. LOW LEVEL PRESSURE GRADIENT BEGINS TO INCREASE SATURDAY AFTERNOON
AND CONTINUE THROUGH SUNDAY. THE CRAIG TO CASPER 850MB GRADIENT
APPROACHES 60M BY SUNDAY MORNING. 700MB WINDS OF 40 TO 50 KT DEVELOP
LATE SATURDAY NIGHT AND LINGER THROUGH SUNDAY. DOWNWARD MOMENTUM OF
THESE WINDS MAY RESULT IN A PERIOD OF HIGH WINDS FOR THE WIND CORRIDORS
OF SOUTHEAST WYOMING...INCLUDING ARLINGTON...VEDAUWOO AND BORDEAUX.
700MB TEMPERATURES WARM TO -3C SUNDAY. DOWNSLOPE WIND COMPONENT
LEE OF THE LARAMIE RANGE WILL PUSH THE MERCURY WELL INTO THE 40S TO
NEAR 50. AREAS ALONG AND WEST OF THE LARAMIE RANGE CAN EXPECT 20S AND
30S.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 250 AM MST FRI DEC 13 2013

SUNDAY NIGHT...RELATIVELY MILD NIGHT DUE TO DECENT WINDS AND MIXING.

MONDAY...WINDY DAY DUE TO PROGGED SURFACE THROUGH 700 MB GRADIENTS...
AND MAY SEE NEAR HIGH WIND CRITERIA WINDS AT WIND PRONE LOCATIONS.
STILL RELATIVELY MILD PER PROGGED THICKNESSES AND 700 MB TEMPERATURES.

TUESDAY...WINDY AGAIN BASED ON PROJECTED SURFACE TO 700 MB GRADIENTS.
STILL MILD AND DRY WITH PROGGED THICKNESSES AND LIMITED LOW AND MID
LEVEL MOISTURE.

WEDNESDAY...WARMER AND LESS WINDY AS THE FLOW ALOFT BACKS AND HEIGHTS
AND THICKNESSES RISE.

THURSDAY...NEXT PROGRESSIVE SHORTWAVE TROUGH MOVES OVER THE NORTHERN
ROCKIES...SENDING THE NEXT POWERFUL ARCTIC COLD FRONT SOUTHWARD INTO
WYOMING. THE ECMWF IS FURTHER SOUTH THAN THE GFS...WHICH SEEMS MORE
PLAUSIBLE...WITH THE COLD FRONT...THUS OUR MAXIMUM TEMPERATURES MAY
NEED TO BE LOWERED BY FUTURE FORECASTS. CHANCES FOR SNOW WILL INCREASE
THROUGH THE DAY IN THE WAKE OF THE ARCTIC COLD FRONTAL PASSAGE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 427 AM MST FRI DEC 13 2013

SCATTERED TO BROKEN CLOUDS AT OR ABOVE 4000 FEET AGL. WIND GUSTS
20 TO 30 MPH LATE THIS MORNING AND THIS AFTERNOON.

&&

.FIRE WEATHER...
ISSUED AT 250 AM MST FRI DEC 13 2013

NO FIRE WEATHER CONCERNS ARE EXPECTED THROUGH THE WEEKEND. MINIMUM
RELATIVE HUMIDITIES WILL RANGE FROM 30 TO 40 PERCENT. WEST TO
SOUTHWEST WINDS GUSTING AS HIGH AS 35 MPH THIS MORNING WILL BECOME
WEST TO NORTHWEST 15 TO 25 MPH THIS AFTERNOON WITH THE PASSAGE OF
A SURFACE TROUGH. THERE WILL BE A SLIGHT CHANCE OF LIGHT SNOW OVER
THE SNOWY AND SIERRA MADRE MOUNTAINS THIS AFTERNOON AND TONIGHT.
IT WILL BE COOLER TODAY AND SATURDAY. STRONGER WESTERLY WINDS WILL
USHER IN WARMER TEMPERATURES SUNDAY AND MONDAY. MUCH COLDER
TEMPERATURES AND A CHANCE OF SNOW WILL RETURN TO THE DISTRICTS
LATER NEXT WEEK.

&&

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

$$

SHORT TERM...JAMSKI
LONG TERM...RUBIN
AVIATION...RUBIN
FIRE WEATHER...JAMSKI