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000
FXUS65 KCYS 250409
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1009 PM MDT FRI MAY 24 2013

.UPDATE...
ISSUED AT 1008 PM MDT FRI MAY 24 2013

THE LAST OF THE STRONG STORMS HAS WEAKENED OVER SCOTTS BLUFF
COUNTY. IN A RECENT UPDATE CANCELLED THE SEVERE THUNDERSTORM
WATCH FOR THE SOUTHERN PANHANDLE AND LOWERED POPS QUITE A BIT
THROUGH EARLY SATURDAY MORNING. MAIN QUESTION FOR THE REST OF
TONIGHT WILL BE THE DEVELOPMENT OF LOW CLOUDS AND FOG. THE
MOIST BOUNDARY LAYER HAS SPREAD WEST WITH DEW POINTS INCREASING
SOME 20 DEGREES IN A SHORT TIMES AT KBFF AND KTOR. WITH THE
LIGHT EASTERLY SURFACE WIND FLOW EXPECT THAT LOW CLOUDS WILL
BECOME COMMON AT ELEVATIONS BELOW 5500 FEET MSL ALONG WITH AREAS
OF FOG. INCREASED CLOUDS AND ADDED FOG FOR LATER TONIGHT IN A
RECENT UPDATE TO THOSE AREAS.

UPDATE ISSUED AT 600 PM MDT FRI MAY 24 2013

THUNDERSTORMS HAVE FINALLY GOT GOING OVER PARTS OF THE SOUTHERN
PANHANDLE AT OF 2330Z. THE MORE INTENSE ACTIVITY IS TO THE
SOUTH AND EAST OF THE CWA...BUT THE STORMS IN EASTERN BANNER
COUNTRY PRODUCE SMALL HAIL AND HEAVY RAIN. THE POTENTIAL EXISTS
FOR THAT STORM AND OTHERS DEVELOPING IN THE AREA TO BECOME EVEN
STRONGER AND POSSIBLY SEVERE. FURTHER WEST...SOME BANDS OF
SHOWERS HAVE RECENTLY FORMED TO THE NORTHWEST OF CHEYENNE.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 250 PM MDT FRI MAY 24 2013

QUIET SO FAR THIS AFTERNOON BUT SOME CONVECTION MAY STILL DEVELOP
MAINLY OVER THE SOUTHERN NEBRASKA PANHANDLE INTO EARLY THIS
EVENING NEAR A WEAK SFC BOUNDARY. OTHERWISE A RATHER PERSISTENT
PATTERN WILL BE OVER THE AREA THROUGH THE WEEKEND WITH SW FLOW
ALOFT AHEAD OF UPPER TROFFING OVER THE WESTERN PART OF THE
COUNTRY. WEAK IMPULSES MOVING NORTHEAST SHOULD COMBINE WITH SOME
INSTABILITY TO PRODUCE WIDELY SCATTERED SHOWERS AND TSTRMS OVER
MAINLY THE PANHANDLE AGAIN SATURDAY AND SUNDAY WHERE SFC BOUNDARY
SHOULD MEANDER. CURRENTLY IT APPEARS THE STRONGER STORMS WILL BE
JUST EAST OF THE CWA BUT WILL HAVE TO WATCH. TEMPERATURES
REMAINING WARM BOTH DAYS.

.LONG TERM...(MONDAY THROUGH FRIDAY)
ISSUED AT 247 PM MDT FRI MAY 24 2013

MODELS IN GOOD AGREEMENT EARLY NEXT WEEK...ALTHOUGH THEY DIVERGE
BY THE MIDDLE AND END OF THE WEEK REGARDING A PACIFIC STORM
SYSTEM MOVING ONSHORE MONDAY. AS THIS SYSTEM MOVES ONSHORE ON
MONDAY...UPPER LEVEL SOUTHWEST FLOW WILL CONTINUE WITH WARMER THAN
NORMAL TEMPERATURES IN THE 70S AND 80S EXPECTED ON MEMORIAL DAY. A
DRYLINE WILL BE LOCATED OVER THE HIGH PLAINS...MOVING EASTWARD
INTO WESTERN NEBRASKA EARLY MONDAY MORNING AND THEN RETREATING
WESTWARD TOWARDS THE LARAMIE RANGE DURING THE DAY. ALONG AND EAST
OF THIS BOUNDARY WILL BE THE LIKELY LOCATION OF THUNDERSTORM
DEVELOPMENT ON MEMORIAL DAY...WITH THE BEST CHANCE FOR STORMS
ACROSS WESTERN NEBRASKA. KEPT POP BETWEEN 20 TO 30 PERCENT IN
THESE AREAS...AND BELOW 15 PERCENT WEST OF A LINE FROM CHEYENNE TO
DOUGLAS. A FEW OF THESE THUNDERSTORMS MAY BECOME SEVERE MONDAY
EVENING WITH PLENTY OF INSTABILITY AND SOME LLVL SHEAR AS A WEAK
SHORTWAVE TROUGH MOVES ACROSS CENTRAL WYOMING.

AS WITH THE 00Z MODEL RUNS FROM LAST NIGHT...THE ECMWF CONTINUES
TO SHOW THE UPPER LEVEL PACIFIC TROUGH BECOMING A CLOSED LOW
ACROSS THE GREAT BASIN REGION ON TUESDAY...AND THEN EVENTUALLY
TRACKING THIS LOW EASTWARD AND NORTHEASTWARD BY THURSDAY. ALL THE
OTHER MODELS SHOW AN OPEN WAVE NEGATIVELY TILTED TROUGH QUICKLY
PUSHING ACROSS THE FORECAST AREA ON WEDNESDAY. ENSEMBLES FORECASTS
ARE NOT TRENDING IN ANY PARTICULAR DIRECTION...SO ONLY SLIGHTLY
INCREASED POP WITH A CHANCE OF SHOWERS AND THUNDERSTORMS LATE
TUESDAY THROUGH THURSDAY WITH THE HIGHEST POP ON WEDNESDAY BETWEEN
30 TO 50 PERCENT. THE ECMWF IS THE WETTER SOLUTION...AS THE LLVL
FRONT/DRYLINE REMAINS NEARLY STATIONARY OVER THE HIGH PLAINS WHILE
THE GFS/GEM SOLUTION SHOWS THE BOUNDARY PUSHING NORTHWARD AS THE
TROUGH AXIS QUICKLY MOVES NORTHEAST ON WEDNESDAY. TEMPERATURES
WILL LOWER SLIGHTLY NEXT WEEK AS THE TROUGH AXIS MOVES OVER
WYOMING...INTO THE 60S AND 70S FOR HIGHS BY THURSDAY AND FRIDAY.
LOWS WILL REMAIN NEAR NORMAL OR A FEW DEGREES ABOVE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY EVENING)
ISSUED AT 1008 PM MDT FRI MAY 24 2013

LOWER CLOUDS WILL REDEVELOP OVER THE PANHANDLE LATER TONIGHT
AFTER THE STORMS END. EXPECT IFR CEILINGS AND VISIBILITIES IN FOG
OVER MUCH OF THE PANHANDLE BY 09Z AND LASTING THROUGH 16Z
SATURDAY. OTHERWISE...VFR CONDITIONS WILL CONTINUE OVER THE CWA
THROUGH EARLY SATURDAY NIGHT.

&&

.FIRE WEATHER...
ISSUED AT 250 PM MDT FRI MAY 24 2013

GUSTY WINDS AND LOW AFTERNOON RELATIVE HUMIDITIES WILL OCCUR IN
THE AFTERNOONS OVER WESTERN PARTS OF THE CWA BUT CONCERNS WILL BE
MITIGATED BY NON-FAVORABLE FUELS. OTHERWISE WARM CONDITIONS WILL
CONTINUE INTO EARLY NEXT WEEK. BEST CHANCES FOR SHOWERS AND TSTMS
WILL BE IN THE AFTERNOONS AND EVENING MAINLY OVER THE NEB
PANHANDLE.

&&

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

$$

UPDATE...WEILAND
SHORT TERM...RE
LONG TERM...TJT
AVIATION...WEILAND
FIRE WEATHER...RE