869
FXUS65 KCYS 120845
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
244 AM MDT MON MAY 12 2008
SHORT TERM
SW FLOW WILL CONT OVER THE AREA TODAY AS AN UPPER
TROUGH DEEPENS OVER THE INTER-MOUNTAIN WEST. A COLD FRONT MOVING
INTO THE WESTERN PORTION OF THE CWA ATM...WILL MOVE EAST ACROSS THE
REST OF THE CWA BY EARLY THIS AFTERNOON. SCATTERED SHOWERS WILL
DEVELOP WEST OF THE LARAMIE RANGE THIS MORNING WITH SNOW SHOWERS IN
THE MOUNTAINS. THE SHOWERS WILL SPREAD EAST THIS AFTERNOON...WITH
ISOLATED THUNDERSTORMS OCCURRING IN THE NEBRASKA PANHANDLE THIS
AFTERNOON...WHICH WILL CHANGE TO RAIN SHOWERS AS THE COLD FRONT
MOVES EAST OF THE AREA. LIS WILL BE AROUND -1 WITH LOW CAPES BEFORE
THE FRONTAL PASSAGE...SO THE CHANCE OF SEVERE STORMS IS VERY
MINIMAL. THE SHOWERS WILL CONTINUE OVERNIGHT WITH THE RAIN CHANGING
TO SNOW FROM WEST TO EAST BY MIDNIGHT. THE PANHANDLE MAY JUST SEE A
MIX OF RAIN AND SNOW AT BEST. SNOW ACCUMULATIONS WILL BE NEGLIGIBLE
AT THE LOWER ELEVATIONS...MAINLY IN GRASSY AREAS...HOWEVER THE LOWER
ELEVATIONS OF CARBON AND ALBANY COUNTIES COULD PICK UP A FEW
INCHES. THE MOUNTAINS WILL LIKELY SEE 3 TO 6 INCHES BY
MORNING...WHICH IS BELOW THE CRITERIA OF 5 TO 8 INCHES REQUIRED FOR
A SNOW ADVISORY. DAY SHIFT CAN TAKE A LOOK AND SEE IF THEY SEE
ANYTHING DIFFERENT AND ISSUE HIGHLIGHT IF NEEDED FOR LATE TONIGHT
AND TUESDAY MORNING. HIGH TEMPERATURES WILL BE AROUND 3 TO 5
DEGREES BELOW NORMAL TODAY.
LONG TERM...TUESDAY THROUGH SUNDAY
THE CWA WILL CONTINUE TO BE AFFECTED BY THE STORM SYSTEM THROUGH
TUESDAY MORNING. THE 1000 TO 500 MB THICKNESS VALUES AND 700 MB
TEMPERATURES ARE COLD ENOUGH DURING THAT TIME FOR THE PRECIPITATION
TYPE TO BE SNOW...EXCEPT FOR PERHAPS THE SOUTHERN PANHANDLE. THE
MODELS MOVE THE NORTHERN STREAM TROUGH AXIS EAST OF THE CWA EARLY
TUESDAY AFTERNOON AND THE SURFACE LOW AT THAT TIME IS WELL SOUTH AND
EAST OF THE CWA. THE RESULT SHOULD BE WEATHER CONDITIONS IMPROVING
FROM NORTH TO SOUTH STARTING LATE MORNING TUESDAY WITH TEMPERATURES
BELOW NORMAL. THE UPPER LEVEL RIDGE ALONG THE WEST COAST STARTS TO
REALLY INCREASE IN AMPLITUDE ON WEDNESDAY WITH NORTHERLY FLOW ALOFT
OVER THE ROCKIES THROUGH FRIDAY MORNING. A SHORTWAVE TROUGH WITHIN
THAT FLOW WILL MOVE ACROSS THE CWA WEDNESDAY NIGHT AND THURSDAY
MORNING WITH CHANNELED VORTICITY LINGERING THROUGH EARLY THURSDAY
NIGHT. THE GFS IS TRENDING DEEPER AND SLIGHTLY SLOWER WITH THE
FEATURE BUT IS STILL SIMILAR TO THE 00Z ECMWF. THE CWA WILL ALSO BE
ON THE CYCLONIC SIDE OF THE STRONG 300 MB JET DURING THAT TIME.
WITH THE MOISTURE AND LIFT THAT WILL BE PRESENT OVER THE CWA IT
WOULD APPEAR THAT SHOWERS WILL BE LIKELY WEDNESDAY NIGHT AND
THURSDAY. WILL TREND POPS UP FOR THOSE PERIODS AT THIS TIME. SOME
SHOWERS MAY LINGER INTO FRIDAY MORNING. THE HEIGHTS ALOFT THEN RISE
OVER THE CWA THROUGH SATURDAY AS THE UPPER LEVEL RIDGE STARTS TO
SLOWLY MOVE EAST. THE 18Z DGEX IS THE FASTEST WITH THE EASTWARD
MOVEMENT AND THE 00Z CANADIAN IS THE SLOWEST. HPC PREFERS THE
SLOWER MOVEMENT EAST OF THE RIDGE AT THIS TIME. FOR MOST OF THE
FRIDAY THROUGH NEXT MONDAY TIME FRAME IT WILL BE WARM AND DRY OVER
THE CWA. IF THE CANADIAN...UKMET AND ECMWF VERIFY...A SHALLOW COLD
FRONT WILL BACK INTO THE EAST PARTS OF THE CWA SUNDAY FOR A BIT
COOLER TEMPERATURES SUNDAY AND MONDAY.
AVIATION
AREA OF MVFR CONDITIONS WILL DEVELOP WEST OF THE LARAMIE
RANGE THIS MORNING AS A STORM SYSTEM BEGINS TO MOVE ACROSS THE
AREA. THE AREAS OF MVFR CONDITIONS WILL SPREAD EAST OF THE LARAMIE
RANGE THIS AFTERNOON AS A COLD FRONT MOVES ACROSS THE AREA.
ISOLATED THUNDERSTORMS WILL OCCUR EARLY THIS AFTERNOON IN THE
NEBRASKA PANHANDLE AHEAD OF THE COLD FRONT.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
KMD/WEILAND
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