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000
FXUS65 KCYS 071802
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1057 AM MST FRI MAR 7 2014

.SHORT TERM...(TODAY THROUGH SATURDAY NIGHT)
ISSUED AT 551 AM MST FRI MAR 7 2014

RADAR RETURNS CONTINUE TO EXPAND IN COVERAGE OVER THE CWA EARLY THIS
MORNING...WITH A FEW SITES REPORTING MAINLY RAIN OFF AND ON THROUGH
THE NIGHT. THE MAIN SURGE OF COLD AIR IS STILL UP IN NORTHERN
WYOMING BUT IS STEADILY MOVING SOUTH. THE SFC PRESSURE PATTERN
INDICATES AN INVERTED TROUGH FEATURE DEVELOPING OVER THE ROCKIES AS
AN UPPER LEVEL LOW APPROACHES WESTERN COLORADO...AND AS THE SFC COLD
FRONT THAT MOVED ACROSS THE HIGH PLAINS OVERNIGHT HAS SLOWED ITS
PROGRESS ALONG THE LARAMIE RANGE. MODELS SHOW THIS FEATURE
PERSISTING THROUGH THE AFTERNOON...AND WILL INDUCE NORTH-
NORTHEASTERLY UPSLOPE FLOW ACROSS THE EASTERN HALF OF THE FORECAST
AREA. WINDS DO NOT LOOK TO BECOME THAT STRONG THOUGH AS THE FRONT
WILL EVENTUALLY MOVE THROUGH THE REMAINDER OF WYOMING AND WEAKEN
THE INVERTED TROUGH. STILL...SHOULD SEE A PERIOD OF UPSLOPE
FORCING AIDED BY MODERATE CAA THROUGH EARLY AFTERNOON. THIS SFC
FORCING WILL COMBINE WITH WEAK MIDLEVEL ENERGY AND THE DIFFLUENT
RIGHT ENTRANCE REGION OF THE UPPER JET TO BRING A GOOD CHANCE FOR
RAIN/SNOW TO THE FORECAST AREA TODAY. WITH MANY AREAS STILL IN THE
MID 30S TO 40S...RAIN WILL LIKELY BEGIN THE EVENT BUT PRECIP WILL
EVENTUALLY CHANGE OVER TO SNOW AS THE MORNING PROGRESSES AND
COLDER AIR FILTERS IN FROM THE NORTH. LI VALUES OVER THE
MOUNTAINS ARE PROGGED TO BE SLIGHTLY NEGATIVE THIS AFTERNOON AS
WELL...SO WILL LIKELY SEE SOME ENHANCEMENT TO THE SNOW OUT IN THIS
AREA. LACK OF SIGNIFICANT FRONTOGENESIS ANALYZED WILL KEEP LOCAL
ENHANCEMENTS DUE TO BANDING AT A MINIMUM FOR THIS EVENT. ALL IN
ALL...STILL EXPECTING 1 TO 3 INCHES OF ACCUMULATION ACROSS THE
EASTERN PLAINS AND HIGH VALLEYS OUT WEST...WITH 5 TO 9 INCHES IN
THE SNOWY AND SIERRA MADRES AND 3 TO 6 IN THE LARAMIE RANGE BY
MIDNIGHT TONIGHT. THE UPPER TROUGH AXIS WILL MOVE OVERHEAD TONIGHT
WITH DRIER AIR AND SUBSIDENCE MOVING IN FROM THE NORTHWEST SO
SHOULD END THE SNOW CHANCES FROM NORTH TO SOUTH THIS EVENING.
THEREFORE...CUT THE SNOW ADVISORY ABOUT 6HRS SHORT AS SNOW SHOULD
BE ENDING EARLIER THAN PREVIOUSLY THOUGHT.

AFTER A COOLER DAY TODAY IN THE POST-FRONTAL ENVIRONMENT...SATURDAY
WILL MODERATE BACK INTO THE 40S AND 50S AS AN UPPER LEVEL RIDGE
BUILDS OVERHEAD FROM THE WEST. IN ADDITION...A STRONG WAVE MOVING
INTO THE PAC NW WILL BEGIN TO DEEPEN THE LEESIDE PRESSURE TROUGH
LATE IN THE DAY...SO WESTERLY WINDS SHOULD BE ON THE INCREASE LATE
SATURDAY AND SATURDAY NIGHT.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 312 AM MST FRI MAR 7 2014

UPPER LEVEL RIDGE AXIS WILL SHIFT OVER SOUTHEAST WYOMING SUNDAY
WHILE AT THE SOME TIME BEGINS TO FLATTEN. SHOULD SEE LOTS OF
SUNSHINE TO START SUNDAY WITH SOME HIGH CLOUDS SPILLING INTO THE
AREA DURING THE AFTERNOON. SOME OF THE WARMEST TEMPERATURES THUS
FAR THIS YEAR WILL OCCUR SUNDAY AFTERNOON WITH WIDESPREAD 50S WEST
AND 60S EAST AND COULD SEE A FEW 70S INTO THE NEBRASKA PANHANDLE.

MODELS HAVE SLOWED UP THE PROGRESSION OF A WEST COAST TROUGH ON
MONDAY. MODELS NOW SHOWING THE UPPER LEVEL TROUGH AXIS OVER THE
INTERMOUNTAIN WEST MONDAY AFTERNOON WITH SHORTWAVE RIDGING OVER
SOUTHEAST WYOMING. THIS WILL LEAD TO ONE MORE WARM DAY BEFORE A
COLD FRONT MOVES THROUGH MONDAY NIGHT. TEMPERATURES MONDAY SHOULD
BE AS WARM AS SUNDAY IF NOT A BIT WARMER. TEMPERATURES ALOFT WILL
WILL BE WARMER BUT INCREASING MID AND HIGH CLOUDS MAY INHIBIT FULL
MIXING.

COOL AND WET TUESDAY AS THE UPPER TROUGH AXIS MOVES INTO THE
ROCKIES AND A COLD FRONT MOVES ACROSS THE FORECAST AREA. LOOKS
LIKE ANOTHER ROUND OF SNOW FOR MOST OF THE AREA TUESDAY INTO
TUESDAY NIGHT. AT THIS TIME NOT EXPECTING ANYTHING SIGNIFICANT FOR
SNOW AMOUNTS BUT THERE IS POTENTIAL DEPENDING ON THE SPEED AND EXACT
TRACK OF THE UPPER LOW.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH SATURDAY MORNING)
ISSUED AT 1050 AM MST FRI MAR 7 2014

A STORM SYSTEM MOVING ACROSS THE ROCKIES TODAY WILL BRING POOR
AVIATION CONDITIONS AND IFR OR LIFR TO THE FORECAST AREA. EXPECTING
RAIN TO CHANGE TO SNOW THROUGH THE MORNING WITH IFR/LIFR CONDITIONS
ANTICIPATED THROUGH MIDDLE AFTERNOON. NORTH-NORTHEAST SFC WINDS WILL SHIFT
TO THE WEST-NORTHWEST TONIGHT WHICH SHOULD HELP TO END THE SNOW AND
LIFT CIGS/VSBYS. BUT A MOIST BOUNDARY LAYER WITH FRESH SNOWPACK
COULD KEEP MVFR/IFR THROUGH TONIGHT FOR MOST AREAS.

&&

.FIRE WEATHER...
ISSUED AT 312 AM MST FRI MAR 7 2014

NO FIRE WEATHER ISSUES THROUGH NEXT WEEK. A SHOT OF RAIN AND SNOW
TODAY THEN DRY THROUGH THE WEEKEND WITH MILD TEMPERATURES AND
WINDY CONDITIONS. ONE MORE WARM DAY MONDAY THEN ANOTHER CHANCE FOR
RAIN AND SNOW TUESDAY.

&&

.HYDROLOGY...
ISSUED AT 312 AM MST FRI MAR 7 2014
MELTING SNOW CAUSING SOME FLOODING PROBLEMS OVER PORTIONS OF THE
FORECAST AREA. SEVERAL STREETS CURRENTLY UNDER WATER IN LUSK WY AS
THE NIOBRARA RIVER OVERFLOWS ITS BANKS. INTO KIMBALL COUNTY NE
MANY ROADS UNDERWATER DUE LARGELY TO OVERLAND FLOODING. THE
FLOODING IS OCCURRING EVEN THOUGH THERE IS NOT ALL THAT MUCH SNOW
TO MELT. THE BIGGEST FACTOR IS LIKELY THE FROZEN GROUND. VERY
COLD TEMPERATURES OVER THE LAST FEW MONTHS HAVE FROZE THE GROUND
AND IS LIKELY NOT LETTING SNOW MELT SOAK INTO THE GROUND. ALSO LAST
FALL WAS VERY WET WHICH PROBABLY IS NOT HELPING ANY. THE FROST
DEPTH A FEW DAYS AGO WAS 4 INCHES IN CHEYENNE BUT WITH MILD
TEMPERATURES IS NOW COMPLETELY THAWED. THESE FLOODING AREAS SHOULD
NOT BE FAR BEHIND IN LOSING THERE FROZEN GROUND LAYER. SHOULD
START TO SEE RELIEF OVER THE NEXT DAY OR TWO AS RUNOFF PUSHES OUT
OF THE AREA AND WATER STARTS TO SOAK INTO THE GROUND.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER WEATHER ADVISORY UNTIL 6 AM MST SATURDAY FOR WYZ112-114.

NE...NONE.
&&

$$

SHORT TERM...RJM
LONG TERM...SML
AVIATION...RJM
FIRE WEATHER...SML
HYDROLOGY...SML