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000
FXUS65 KCYS 050128
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
628 PM MST TUE MAR 4 2014

.UPDATE...
ISSUED AT 628 PM MST TUE MAR 4 2014

SATURATION AND THE TRANSITION TO RAIN HAS BEEN STRUGGLING MIGHTILY
BELOW ABOUT 7000 FEET SO FAR THIS AFTERNOON AND EVENING. RECENT
TRENDS ALONG WITH 18Z OUTPUT HAS PROMPTED THE CANCELLATIONS OF A
PORTION OF THE WINTER WEATHER ADVISORY IN ARLINGTON...THE CENTRAL
LARAMIE RANGE...AS WELL AS PLATTE AND KIMBALL COUNTIES. HAVE EVEN
DECREASED AMOUNTS WITHIN THE ADVISORY AS WELL. THESE MAY EVEN BE
TOO HIGH WITH THE BULK OF THE BEST BANDED PRECIP SHIFTING SOUTH
INTO NORTHERN COLORADO. HAVE ALSO PULLED THE END TIME UP TO
MIDNIGHT ON THE ADVISORY AS WELL. WILL RE- EVALUATE TRENDS AT 8
OR 9P TO MAKE THE FINAL DECISION WHETHER AN ADVISORY IS EVEN
NECESSARY OR NOT.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 300 PM MST TUE MAR 4 2014

AFTERNOON WATER VAPOR IMAGERY ANIMATION SHOWED THE UPPER LEVEL
SHORTWAVE TROUGH MOVING ACROSS THE CENTRAL ROCKIES. REGIONAL
RADARS HAVE BECOME QUITE ACTIVE AS SHOWERS HAVE BEEN DEVELOPING
AHEAD OF THIS FEATURE AND MOVING EAST-SOUTHEAST. TEMPERATURES
HAVE BEEN WARM ENOUGH FOR LIQUID PRECIPITATION EAST OF THE LARAMIE
RANGE. TO THE WEST...SNOW LEVELS WERE DROPPING AS COLDER AIR BEGINS
TO FILTER WITH THE PASSAGE OF THE UPPER TROUGH AND COLD FRONT. AT
3 PM...LIGHT SNOW WAS REPORTED AT SARATOGA WITH 32 DEGREES. RAIN
AND SNOW SHOWERS WILL CONTINUE TO DEVELOP THROUGH LATE AFTERNOON
AND SPREAD INTO MUCH OF WESTERN NEBRASKA PANHANDLE.

MAIN FORECAST CONCERNS DURING THE NEXT 12 HOURS WILL BE SNOWFALL
ACCUMULATIONS WITH THE UPPER TROUGH MOVING THE CWA. IT WILL BE
A QUICK MOVING SYSTEM...WITH THE PERIOD OF POTENTIALLY HEAVIEST
SNOWFALL FROM LATE THIS AFTERNOON THROUGH TONIGHT. WPC GUIDANCE
AND NAM/GFS HANDLE THIS SYSTEM SIMILARLY...DEPICTING A BAND OF
ADVISORY SNOWFALL...MAINLY ALONG AND SOUTH OF THE INTERSTATE 80
CORRIDOR FROM ARLINGTON TO CHEYENNE TO KIMBALL. THIS AREA IS
UNDER THE BEST MID LEVEL FRONTOGENETICAL LIFT AND MOISTURE
CONVERGENCE. GENERALLY 3 TO 5 INCHES FOR LOWER ELEVATIONS WITH 6
TO 8 INCHES ABOVE 7000 FT. NORTH TO NORTHEAST WINDS OF 15 TO 25
MPH AND FALLING SNOW WILL PRODUCE POOR VISIBILITIES IN THE
ADVISORY AREA. SNOW WILL TAPER OFF WEST OF THE LARAMIE RANGE LATER
THIS EVENING...AND EAST OF THE LARAMIE RANGE LATER TONIGHT. IT
WILL BE DRIER WITH SEASONAL TEMPERATURES WEDNESDAY WITH THE
INFLUENCE OF A UPPER RIDGE BUILDING TOWARD THE CONTINENTAL DIVIDE.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 315 PM MST TUE MAR 4 2014

WEDNESDAY NIGHT...CHALLENGE WILL BE WINDS. FAST MOVING SHORTWAVE
TROUGH ALOFT SWEEPS ACROSS THE NORTHERN PLAINS STATES WITH A 40 TO
50 KNOT 700 MB JETLET STREAKING ACROSS CARBON AND ALBANY COUNTIES
...WHILE CRAIG TO CASPER 700 MB HEIGHT GRADIENT DIFFERENCES PEAK AT
58 METERS LATE WEDNESDAY NIGHT. MITIGATING FACTORS FOR HIGH WINDS
WILL BE THE LACK OF DOWNWARD FORCING AS SEEN ON THE 500-300 MB AND
700-500 MB LAYERS QUASIGEOSTROPHIC FORCING...AND THE DISCONNECT OF
THE 300 MB JET MOVING TO OUR NORTH ACROSS MONTANA AND THE DAKOTAS.

THURSDAY...FLOW BECOMES ZONAL...WEST TO EAST...WITH NEXT SLUG OF
MOISTURE ADVECTING ACROSS SOUTHERN WYOMING...PRODUCING SCATTERED
OROGRAPHIC SNOW SHOWERS ACROSS THE SNOWY AND SIERRA MADRE RANGES...
AND DRY ELSEWHERE. RELATIVELY MILD PER THICKNESS AND 700 MB
TEMPERATURES PROGS.

FRIDAY...NEXT PROGRESSIVE POSITIVELY TILTED SHORTWAVE TROUGH MOVES
ACROSS THE ROCKIES...SENDING THE NEXT COLD FRONT ACROSS OUR
COUNTIES...AND PRODUCING MEASURABLE SNOW FOR MOST OF OUR
COUNTIES...THOUGH PREFER THE WETTER GFS SOLUTION OVER THE DRIER NAM
BASED ON THE SHORTWAVE TROUGH TRACK. HIGHEST POPS OVER OUR SOUTHERN
TIER CLOSER TO THE DEEPER MOISTURE AND DYNAMICS.

SATURDAY...DRIER DAY AS RIDGING ALOFT DEVELOPS...THOUGH WITH
TEMPERATURES LIMITED BY NORTH FLOW IN THE LOW AND MID LEVELS.

SUNDAY...WILL BE A BALMY DAY FOR MILD WEATHER OUTDOOR ENTHUSIASTS AS
FLOW ALOFT BECOMES ZONAL...AIDING A DECENT SURFACE LEE TROUGH TO
DEVELOP ALONG THE SPINE OF THE ROCKIES...AND PRODUCING MAXIMUM
TEMPERATURES IN THE 50S AND 60S WITH DOWNSLOPE KATABATIC WARMING IN
THE LOW LEVELS AND PLENTY OF SUNSHINE.

MONDAY...WILL BE SLIGHTLY COOLER WITH LOWERING HEIGHTS ALOFT AND
LOWERING MID LEVEL TEMPERATURES. STILL RELATIVELY MILD UNDER ZONAL
FLOW WITH MAXIMUM TEMPERATURES IN THE 40S.

TUESDAY...NEXT SHORTWAVE TROUGH ALOFT AFFECTS OUR REGION...PRODUCING
AT LEAST ISOLATED TO SCATTERED SNOW SHOWERS. WITH DIFFERENCES IN QPF
PLACEMENT BETWEEN THE ECMWF AND GFS...WILL BROAD-BRUSH POPS BEING A
WEEK OUT AND BLEND OUR GRIDS WITH OUR NEIGHBORING OFFICES.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY AFTERNOON)
ISSUED AT 530 PM MST TUE MAR 4 2014

EXPECT A PERIOD OF POOR AVIATION CONDITIONS MAINLY AT KLAR...
KCYS...AND KSNY YET THIS EVENING. -SN HAS BEEN FALLING ACROSS THE
SOUTHEAST WYOMING MOUNTAINS AS WELL AS ALONG THE I-80 CORRIDOR.
MVFR/IFR CIGS/VSBYS CAN BE EXPECTED IN THESE AREAS WITH LIGHT
ACCUMULATIONS EXPECTED. THERE IS SOME CONCERN THAT SNOW
ACCUMULATIONS WILL BE LIGHTER THAN EARLIER ANTICIPATED. WILL ALSO
SEE A PERIOD OF LOWER CIGS AT KCDR...KAIA AND KBFF LATER TONIGHT
BEHIND THE FRONT. SNOW WILL END BY AROUND 06Z...WITH VFR
CONDITIONS RETURNING TO MOST PLACES BETWEEN 12-15Z.


&&

.FIRE WEATHER...
ISSUED AT 215 PM MST TUE MAR 4 2014

NO FIRE WEATHER CONCERNS THIS WEEK AS PACIFIC STORMS MOVE THROUGH
THE DISTRICT THIS AFTERNOON AND TONIGHT...AND AGAIN FRIDAY.
ACCUMULATING SNOW WILL ADD TO THE EXISTING SNOW PACK. COOL
TEMPERATURES WEDNESDAY WILL BE REPLACED BY ABOVE AVERAGE WARMTH
AND WINDY CONDITIONS THURSDAY...FOLLOWED BY COLDER TEMPERATURES
FOR FRIDAY.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR WYZ112-
     114>119.

NE...NONE.
&&

$$

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