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000
FXUS65 KCYS 071748
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1048 AM MST SAT DEC 7 2013

.UPDATE...ISSUED AT 1039 AM MST SAT DEC 7 2013

LOWERED HIGH TEMPERATURES A FEW DEGREES MORE AS TEMPERATURES ARE
REALLY STRUGGLING TO WARM. CLOUD COVER...SNOW COVER AND LIGHT
WINDS ARE INHIBITING MIXING AND EAST OF THE LARAMIE RANGE LIGHT
UPSLOPE FLOW IS FURTHER REDUCING MIXING POTENTIAL. IT APPEARS THE
ARCTIC INVERSION IS GOING TO HOLD THROUGH THIS AFTERNOON OVER A
MAJORITY OF THE AREA. IRONICALLY THE WARMEST TEMPERATURES COULD
ACTUALLY OCCUR THIS EVENING AS SNOW DEVELOPS. NOT EXPECTING
ANYTHING SUBSTANTIAL BUT TEMPERATURES COULD RISE A FEW DEGREES
THIS EVENING IN PLACES LIKE CHEYENNE.

UPDATE ISSUED AT 932 AM MST SAT DEC 7 2013

TWEAKED POP GRIDS FOR TODAY. BASED ON LATEST SATELLITE AND RADAR
DATA IT LOOKS LIKE SNOW WILL BE SLOWER ARRIVING THAN ANTICIPATED.
OBSERVATIONS SHOWING MOST SNOW STILL OVER COLORADO...AND THE
MODELS ARE ALSO SLOWER WITH SNOW DEVELOPING. THAT BEING THE CASE
SLOWED THE TIMING OF SNOW DEVELOPMENT MAINLY EAST OF THE LARAMIE
RANGE. WILL HAVE TO WAIT UNTIL LATE THIS AFTERNOON OR EVENING FOR
THE MAIN SNOW POTENTIAL. VISIBLE SATELLITE IS SHOWING A WHAT
APPEARS TO BE A SLUG OF MOISTURE WITH CONVECTIVE LIKE CLOUDS
STREAMING NORTHEAST. THIS AREA OF BETTER MOISTURE WILL IMPACT THE
SNOWY AND SIERRA MADRE RANGES WITHIN THE NEXT FEW HOURS.

UPDATE ISSUED AT 902 AM MST SAT DEC 7 2013

WIND CHILL ADVISORY EXPIRED AT 9 AM MDT AS WIND CHILL VALUES HAVE
STARTED TO RISE. COULD SEE A FEW OBSERVATION SITES RIGHT AROUND
MINUS 20 THE NEXT FEW HOURS BUT NOT NOT ENOUGH TO WARRANT KEEPING
THE ADVISORY GOING OVER THE PANHANDLE. WIND CHILL WARNING FOR THE
LARAMIE VALLEY HAS ALSO EXPIRED AT 9 AM.

FORECAST LOOKS TO BE IN GOOD SHAPE BUT DID SHAVE A FEW DEGREES OFF
OF THE HIGHS ON THE UPSLOPE SLIDE OVER THE LARAMIE RANGE WHERE
SOUTH WINDS SHOULD CONTINUE THROUGH THE AFTERNOON...HOLDING
TEMPERATURES DOWN SOMEWHAT. REGARDLESS IT WILL BE ANOTHER COLD DAY
WITH LOW WIND CHILL VALUES.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 449 AM MST SAT DEC 7 2013

SEVERAL CONCERNS FORESEEN THIS FORECAST CYCLE BEGINNING WITH
ONGOING FRIGID WIND CHILL TEMPERATURES. EARLY MORNING OBSERVATIONS
HAVE BEEN PRETTY CONSISTENT WITH -15 TO -30 DEGREE WIND CHILL
TEMPERATURES ACROSS AREAS EAST OF THE LARAMIE RANGE. DO NOT SEE
ANY REASON TO MAKE ANY CHANGES TO THE INHERITED WIND CHILL
ADVISORY/WARNINGS THIS MORNING. THESE WILL RISE ABOVE CRITICAL
THRESHOLDS BY MID-MORNING.

ATTENTION THEN SHIFTS TO THE UPSTREAM SHORTWAVE ENERGY WHICH THE
LATEST SATELLITE PIX INDICATES WAS SPINNING INTO NORTHERN
CALIFORNIA. 10Z SFC ANALYSIS HAD THE SFC LOW DEVELOPING ACROSS THE
GREAT BASIN. IR IMAGERY SHOWS AREA OF WAA OCCURRING AHEAD OF THIS
FEATURE WITH CLOUD TOPS COOLING ACROSS EASTERN UTAH INTO WESTERN
COLORADO. NEITHER REGIONAL RADAR NOR AREA WEBCAMS SHOWING ANY SNOW
FALLING ACROSS THE CWA JUST YET. HOWEVER...OBSERVATIONS SHOW -SN
DEVELOPING FROM RIFLE TO KREMMLING IN NW/W COLORADO EARLY THIS
MORNING. THIS AREA OF WAA/ISENTROPIC LIFT WILL SHIFT NORTH INTO
THE CWFA DURING THE MORNING HOURS. SNOW WILL BEGIN TO FALL FIRST
ACROSS THE SNOWY RANGE BEFORE SPREADING OUT ONTO OTHER LOWER
ELEVATIONS LATE THIS AFTERNOON AND MORE SO DURING THE OVERNIGHT
HOURS TONIGHT. SNOWY AND SIERRA MADRES SHOULD GET A FAIRLY LONG
DURATION LIGHT TO MODERATE SNOW THAT WILL LINGER THROUGH THE DAY
ON SUNDAY. HAVE GENERALLY INCREASED SNOW CHANCES TO CATEGORICAL
AND BOOSTED SNOWFALL AMOUNTS INTO ADVISORY CRITERIA OVER THE
MOUNTAINS. THINK THAT 6 TO 10 INCHES WILL BE FAIRLY SAFE BET FOR
THE SNOWY/SIERRA MADRES WITH GENERALLY 1 TO 3 INCHES ACROSS LOWER
ELEVATIONS (HIGHEST WEST OF THE LARAMIE RANGE). BY SATURDAY
NIGHT/SUNDAY MORNING WAA WILL WANE AS THE TROUGH AXIS MOVES
OVERHEAD AND ASSOCIATED SFC LOW PASSES SOUTH OF THE AREA ACROSS
COLORADO. THIS WILL TRANSITION SNOWFALL PRODUCTION FROM ISENTROPIC
LIFT TO OROGRAPHICS. SUBSIDENCE WILL WORK IN BEHIND TROFPA
BRINGING AND END TO SNOW CHANCES IN THE PLAINS DURING THE DAY ON
SUNDAY. ALTHOUGH OROGRAPHICALLY ENHANCED SNOW WILL CONTINUE IN THE
MOUNTAINS. HAVE ISSUED A WINTER WEATHER ADVISORY FOR THE MOUNTAINS
FROM 15Z TODAY THROUGH 06Z MONDAY.

TRAILING SHORTWAVE WILL DIVE THROUGH MONDAY MORNING. THIS FTR WILL
HAVE LITTLE MOISTURE TO WORK WITH...SO DO NOT ANTICIPATE MUCH FOR
PRECIPITATION CHANCES. WHAT IT WILL DO HOWEVER...IS INCREASE WINDS
ACROSS PORTIONS OF SOUTHEAST WYOMING ON MONDAY. PROGD H7 WINDS PEAK
OUT BETWEEN 40-45 KNOTS. SO FOR NOW HAVE LEFT WINDS SUB-WARNING WITH
GUSTS OF NEAR 50 MPH ON MONDAY.

TODAY WILL BE SLIGHTLY WARMER THAN THE PAST SEVERAL DAYS...A RESULT
OF THE WAA IN ADVANCE OF THE UPSTREAM SHORTWAVE. AFTERNOON HIGHS
WILL CLIMB INTO THE TEENS MOST PLACES WITH OVERNIGHT LOWS ONLY
FALLING INTO THE SINGLE DIGITS BELOW ZERO. HARD TO BELIEVE THATS
ACTUALLY CONSIDERED A WARM-UP. SO DONT ANTICIPATE ANY NEED FOR MORE
WIND CHILL HIGHLIGHTS TONIGHT. TEMPERATURES WILL DIP AGAIN ON SUNDAY
BEFORE WARMING AGAIN VERY SLIGHTLY ON MONDAY. SEE WIND CHILLS
POTENTIALLY DIPPING INTO HIGHLIGHT CRITERIA ONE MORE TIME ON SUNDAY
NIGHT SUBJECT TO WIND SPEEDS BEING HIGH ENOUGH.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 449 AM MST SAT DEC 7 2013

GENERAL WARMING TREND THROUGH THE EXTENDED PERIOD. STRONG
NORTHWESTERLY FLOW WILL IMPACT THE AREA ON TUESDAY WITH A WEAK
SHORTWAVE MOVING THROUGH. THE LLVL GRADIENT WILL BE STRONG ENOUGH
IN COMBINATION WITH 700MB WINDS AROUND 50 KTS ACROSS SOUTHEAST
WYOMING TO PRODUCE WINDY CONDITIONS...ESPECIALLY IN THE WIND PRONE
AREAS. PLACES LIKE ARLINGTON AND VEDAUWOO COULD APPROACH HIGH WIND
CRITERIA BY TUESDAY AFTN. TEMPS WILL STILL BE BELOW NORMAL WITH
LLVL WARM ADVECTION LIMITED. SFC HIGH SLIDES EASTWARD BEHIND THE
SHORTWAVE ON WEDNESDAY AND BECOMES SITUATED ACROSS THE PLAINS.
THIS WILL MEAN LESS WIND ON WEDNESDAY. HEIGHTS REALLY BEGIN TO
RISE ON THURSDAY AS A SHORTWAVE RIDGE MOVES OVERHEAD. 700MB TEMPS
RISE AROUND 10C FROM WEDNESDAY AND A LEE TROUGH DEVELOPS OVER THE
PLAINS. TEMPS WILL FINALLY RISE TO AROUND NORMAL OR EVEN SLIGHTLY
ABOVE NORMAL IN THIS PATTERN. LITTLE CHANGE FOR FRIDAY WITH TEMPS
A FEW DEGREES COOLER WITH A WEAK FROPA. POPS THROUGHOUT THE LONG
TERM WILL BE SLIM.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY MORNING)
ISSUED AT 1033 AM MST SAT DEC 7 2013

FAIRLY WIDESPREAD MVFR WITH PATCHY IFR CIGS EXPECTED INTO SUNDAY
MORNING BEFORE IMPROVING DURING THE DAY SUNDAY.  AREAS OF LIGHT SNOW
WILL ALSO OCCUR MAINLY TONIGHT LOWERING VISIBILITIES.


&&

.FIRE WEATHER...
ISSUED AT 449 AM MST SAT DEC 7 2013

NO FIRE WEATHER CONCERNS GIVEN THAT THE EXTREMELY COLD AIR MASS
WILL PERSIST INTO EARLY NEXT WEEK. ALSO WILL LIKELY SEE A PERIOD
OF LIGHT SNOW LATER TODAY ACROSS MOST OF THE REGION.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST SUNDAY NIGHT FOR
     WYZ112-114.

NE...NONE.
&&

$$

UPDATE...LIEBL
SHORT TERM...HAHN
LONG TERM...FINCH
AVIATION...RE
FIRE WEATHER...HAHN