000
FXUS65 KCYS 220459
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1059 PM MDT TUE MAY 21 2013

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 325 PM MDT TUE MAY 21 2013

EXTENDED THE WIND ADVISORY UNTIL 6 PM MDT FOR MOST OF THE NEBRASKA
PANHANDLE. AT 2 PM MDT WINDS WERE GUSTING TO 51 MPH AT SCOTTSBLUFF
AND 44 MPH AT ALLIANCE. WINDS SHOULD BEGIN A SLOW DECREASE THE
REST OF THIS AFTERNOON AND THEN DROP OFF MORE QUICKLY THIS
EVENING.

WINDS WILL SHIFT TO THE NORTHEAST OVER EASTERN AREAS TONIGHT AND
THEN TURN TO THE SOUTHEAST WEDNESDAY. THIS WILL BEGIN TO ALLOW LOW
LEVEL MOISTURE TO ADVECT WESTWARD WHICH MAY ALLOW FOR INCREASING
CHANCES OF THUNDERSTORMS THROUGH THE WEEK. KEPT A SLIGHT CHANCE
FOR SHOWERS AND THUNDERSTORMS OVER THE MOUNTAINS AND ADJACENT
PLAINS FOR WEDNESDAY AFTERNOON. MODEL SOUNDINGS SHOWING STEEP
LAPSE RATES WITH LITTLE TO NO CONVECTIVE INHIBITION. INSTABILITY
IS NOT ALL THAT GREAT SO MAINLY LOOKING AT SHOWERS WITH A FEW WEAK
THUNDERSTORMS. MODELS DO SHOW AN ELEVATED WARM FRONT MOVE EAST
ACROSS THE FORECAST AREA WEDNESDAY NIGHT. THERE MAY BE ENOUGH
INSTABILITY AND LIFT TO KEEP ISOLATED SHOWERS AND WEAK
THUNDERSTORMS PECULATING INTO THE NIGH-TIME WHILE SHIFTING EAST
INTO WESTERN NEBRASKA.

SOUTH TO SOUTHEAST WINDS SHOULD BEGIN TO RAMP UP WEDNESDAY NIGHT
AND THURSDAY. MODELS HAVE BEEN TRENDING STRONGER WITH LOW LEVEL
FLOW THURSDAY. NAM AND GFS BUFKIT SOUNDING AT LUSK SHOWING 50 KT
WINDS A FEW THOUSAND FEET ABOVE GROUND LEVEL THURSDAY AFTERNOON.
SOUNDINGS ALSO SHOWING A VERY STRONG LOW LEVEL INVERSION DUE IN
PART TO THE MOIST LOW LEVEL FLOW. KEPT A CHANCE FOR THUNDERSTORMS
MAINLY OVER THE MOUNTAINS THURSDAY. MOST LIKELY A FEW STORMS WILL
DEVELOP OVER THE LARAMIE RANGE...BUT WITH SUCH A STRONG CAP IN
PLACE...STORMS MAY HAVE A TOUGH TIME MOVING INTO LOWER ELEVATIONS.
ALONG WITH THE INVERSION EXPECTING A LOT OF STRATUS THURSDAY.
STRATUS SHOULD PUT A LID ON TEMPERATURES. FOLLOWED THE PREVIOUS
FORECAST SHIFT IN LOWERING DAYTIME HIGHS FOR THURSDAY. ALSO WARMED
THE LOW A BIT WEDNESDAY NIGHT AND THURSDAY NIGHT.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 325 PM MDT TUE MAY 21 2013

FIRST UPPER SHORTWAVE EJECTING FROM PAC NW UPPER LOW WILL MOVE
ACROSS THE AREA FRIDAY MORNING. TIMING SUCH THAT THERE MAY BE A BIT
OF CONVECTION OVER MAINLY THE PANHANDLE BUT IF SFC BOUNDARY MOVES
FAR ENOUGH EAST THE ACTIVITY WOULD BE EAST OF THE CWA. WILL KEEP
SOME LOW POPS IN PLACE UNTIL BETTER CERTAINTY. SW FLOW ALOFT
REMAIN IN PLACE OVER THE CWA OVER THE WEEKEND INTO EARLY NEXT WEEK
SO SOME AFTERNOON AND EVENING CONVECTION WILL CONTINUE TO BE A
POSSIBILITY...THOUGH TIMING WILL BE DIFFICULT. ECMWF DEPICTING IT
PRETTY MUCH DAILY WHILE GFS DRIER. WILL KEEP POPS WHERE IT LOOKS
MORE FAVORABLE SUCH AS SUNDAY AND MONDAY. TEMPERATURES WILL BE
ON THE WARM SIDE FOR MUCH OF THE PERIOD...GENERALLY A LITTLE ABOVE
SEASONAL AVERAGES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY EVENING)
ISSUED AT 1057 PM MDT TUE MAY 21 2013

LATEST SREF AND HRRR GUIDANCE SHOWING SOME WRAP AROUND LOW CLOUDS
MAKING IT INTO KCDR AND KAIA OVERNIGHT. UPSTREAM OBSERVATIONS IN
SOUTH DAKOTA REPORTING CEILINGS DOWN AROUND 1500 FEET...SO THEIR
FORECAST SEEMS REASONABLE. WENT AHEAD AND LOWERED CEILINGS AT KCDR
AND KAIA TONIGHT. VFR ELSEWHERE.

&&

.FIRE WEATHER...
ISSUED AT 325 PM MDT TUE MAY 21 2013
WINDS WILL DROP OFF QUICKLY THIS EVENING AND BECOME LIGHT. WINDS
WILL REMAIN ON THE LIGHT SIDE MAINLY IN THE 10 TO 15 MPH RANGE
WEDNESDAY BUT WILL BEGIN TO INCREASE WEDNESDAY NIGHT...WITH STRONG
SOUTHEAST WINDS ALONG AND EAST OF THE LARAMIE RANGE FOR THURSDAY.
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL MAINLY BE CONFINED TO
THE MOUNTAINS WEDNESDAY AND THURSDAY AFTERNOON.

WEATHER CONDITIONS WILL VARY GREATLY FROM WEST TO EAST OVER THE
FORECAST AREA LATE THIS WEEK AND WEEKEND. RELATIVELY MOIST
CONDITIONS WILL BE FOUND EAST OF THE LARAMIE RANGE UNDER SOUTH TO
SOUTHEAST LOW LEVEL FLOW...WHILE WEST OF THE LARAMIE RANGE DRY
SOUTHWEST FLOW WILL DOMINATE PRODUCING LOW HUMIDITY.

&&

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

$$

SHORT TERM...LIEBL
LONG TERM...RE
AVIATION...CLAYCOMB
FIRE WEATHER...LIEBL