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000
FXUS65 KCYS 210953
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
353 AM MDT TUE MAY 21 2013

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 352 AM MDT TUE MAY 21 2013

THE MAIN CONCERN WITH THIS PORTION OF THE FORECAST PACKAGE WILL BE
THE WIND ADVISORY POTENTIAL IN THE PANHANDLE THIS MORNING.

TODAY:
LATEST WATER VAPOR LOOP WAS SHOWING ANOTHER SHORTWAVE
ROTATING THROUGH WESTERN SOUTH DAKOTA IN ASSOCIATION WITH THE
CLOSED UPPER LEVEL LOW. AHEAD OF THIS SHORTWAVE...RADAR IMAGERY
WAS SHOWING THE SHOWERS CONTINUING TO MOVE THROUGH WESTERN SOUTH
DAKOTA WITH LIGHT RAIN ALSO BEING REPORTED IN THE NORTHERN
PANHANDLE. SCATTERED TO NUMEROUS SHOWERS SHOULD PERSIST ACROSS
THIS REGION THROUGH MID MORNING...BEFORE GRADUALLY SHIFTING EAST
DURING THE AFTERNOON. LATEST VWP FROM UDX IS SHOWING 50KTS JUST
ABOVE THE SFC WITH THE VWP AT CYS SHOWING AROUND 40KTS. THESE WIND
SPEEDS MAY BE ABLE TO MIX DOWN ESPECIALLY ACROSS THE SOUTHERN
PANHANDLE THIS MORNING WHERE THE CLOUD COVERAGE MAY BE LESS.
HOWEVER...THE RIDGE TOPS MAY EXPERIENCE SOME OF THESE HIGHER WIND
SPEEDS REGARDLESS OF WHETHER THEY MIX OUT OR NOT. THE ONLY FLY IN
THE OINTMENT IS WHETHER THE THE THICKER CLOUD COVER IN THE
NORTHERN PANHANDLE WILL MOVE SOUTH THIS MORNING. IF THESE CLOUDS
DO STAY IN THE NORTH...WE MAY END UP ISSUING A WIND ADVISORY FOR
AT LEAST THE SOUTHERN PANHANDLE. HOWEVER...WE MAY END UP PULLING
THE TRIGGER FURTHER NORTH AS WELL...WHERE THE HIGHER ELEVATIONS
MAY EXPERIENCE STRONGER WINDS. FOR NOW...WE HAVE COLLABORATED WITH
NORTH PLATTE AND RAPID CITY TO HOLD OFF ON AN ADVISORY AND WE WILL
CONTINUE TO MONITOR THE CLOUD TRENDS.

THE REMAINDER OF THE FORECAST AREA...SHOULD SEE PARTLY CLOUDY SKIES
THIS AFTERNOON WITH WIND SPEEDS GRADUALLY WEAKENING DURING THE
COURSE OF THE DAY AS THE UPPER LEVEL RIDGE BUILDS OVER THE AREA. MAY
SEE A FEW MOUNTAIN SHOWERS...BUT THE BULK OF THE PRECIPITATION
SHOULD END SHORTLY AFTER MIDDAY.

TONIGHT:
SURFACE HIGH PRESSURE IS PROGGED TO MOVE INTO THE AREA WHICH WILL
ALLOW FOR CLEARING SKIES AND GOOD RADIATIONAL COOLING. CURRENT
FORECASTED LOW TEMPERATURES LOOK TO BE IN GOOD SHAPE...BUT WE DID
TWEAK TEMPERATURES DOWN IN THE MOUNTAINS A BIT SINCE THERE CURRENT
READINGS ARE MOSTLY IN THE LOWER 30S.

WEDNESDAY:
THE MODELS ARE CONTINUING TO SHOW THE UPPER LEVEL RIDGE IN PLACE
WHICH SHOULD CONTINUE TO KEEP MILD TEMPERATURES WITH DEWPOINTS ON
THE LOW SIDE. HOWEVER...THERE WILL ALSO BE SOME GOOD UPPER LEVEL
DIFFLUENCE WHICH MAY HELP INITIATE SHOWERS AND THUNDERSTORMS IN THE
MOUNTAINS DURING THE EARLY AFTERNOON. AT THIS TIME...IT APPEARS LIKE
THE SHOWERS AND STORMS WILL BE SLOW MOVERS WITH FORWARD SPEEDS OF 10
TO 15KTS. DUE TO LIMITED INSTABILITY AROUND 500J/KG I WOULD NOT
EXPECT MUCH IN THE WAY OF STRONG TO SEVERE STORMS.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 352 AM MDT TUE MAY 21 2013

SFC HIGH PRESSURE OVER THE PLAINS COMBINED WITH PRESSURE FALLS
ACROSS THE NORTHERN INTERMOUNTAIN WEST WILL CAUSE SOUTHEAST WINDS TO
TRANSPORT LLVL MOISTURE ALONG AND EAST OF THE LARAMIE RANGE ON WED
NIGHT.  SOUNDINGS AND LLVL RH PROGS SHOW STRATUS DEVELOPMENT DURING
THE NIGHT AND THESE LOW CLOUDS MAY BE RATHER PERSISTENT ON THURS
ESPECIALLY ALONG THE CHEYENNE RIDGE AND SOUTHERN LARAMIE RANGE.
LOWERED MAX TEMPS ON THURS A FEW DEGREES WITH THE LLVL CLOUD COVER.
WHILE THE GFS AND NAM BOTH SHOW WEAK INSTABILITY (LI VALUES TO -2C)
ALONG AND JUST EAST OF THE LARAMIE RANGE ON THURS AFTN...THERE IS A
CAPPING LAYER THAT SHOULD KEEP CONVECTION LIMITED.  SE WINDS WILL BE
QUITE GUSTY ON THURS AFTN THROUGH THE EARLY NIGHT.  SHORTWAVE
RESPONSIBLE FOR THE ENHANCED PRESSURE GRADIENT WILL MOVE NORTHWARD
FROM WYOMING INTO MONTANA ON THURS NIGHT.

GENERAL SOUTHWESTERLY FLOW ALOFT WILL PREVAIL ACROSS THE CWA FROM
FRIDAY THROUGH THE WEEKEND AS A TROUGH REMAINS ANCHORED ALONG THE
WEST COAST.  THE GFS AND ECMWF...SIMILAR TO ONE NIGHT AGO...DIFFER
ON THE AMOUNT OF LLVL MOISTURE OVER THE PLAINS ESPECIALLY OVER THE
WEEKEND.  THE DRIER GFS WOULD TEND TO KEEP THE BEST TSTM CHANCES
OVER THE FAR EASTERN ZONES...WHEREAS THE ECMWF PUSHES 45-50F
DEWPOINTS TO THE LARAMIE RANGE.  TEND TO BELIEVE THAT WITH THE UPPER
TROUGH THAT FAR WEST ALONG THE WEST COAST...THAT THE GFS IS TOO
AGGRESSIVE WITH ITS LEE SIDE PRESSURE TROUGH AND IS PUSHING THE
MOISTURE TOO FAR EAST.  THUS...HAVE SLIGHT CHANCE POPS OVER MUCH OF
THE PLAINS THROUGH THE WEEKEND.  THE DEEP LAYER SHEAR WOULD BE
SUFFICIENT (AROUND 35-40 KTS) FOR A FEW STRONG TO SEVERE
STORMS...BUT IT REMAINS TO BE SEEN HOW MUCH LLVL MOISTURE AND
INSTABILITY WILL BE PRESENT.


&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY EVENING)
ISSUED AT 1118 PM MDT MON MAY 20 2013

LATEST RADAR LOOP WAS SHOWING LIGHT SHOWERS CONTINUING TO AFFECT
THE CDR TAF SITE. CEILINGS IN WESTERN SD WERE MAINLY IN THE MVFR
CATEGORY IN THE RAIN BANDS. WOULD NOT SURPRISED IF THE CEILINGS
DROP INTO THE MVFR CATEGORY DURING THE NEXT HOUR OR TWO...BUT THEY
MAY FLUCTUATE BETWEEN VFR AND MVFR DURING THE COURSE OF THE NIGHT.
AFTER DAYBREAK...THE CEILINGS SHOULD CLIMB TO THE VFR
CATEGORY. ELSEWHERE...CEILINGS SHOULD REMAIN VFR THROUGH THE NEXT
24 HOURS. GUSTY NORTHWEST WINDS CAN BE EXPECTED ONCE AGAIN 15Z-00Z
ESPECIALLY ACROSS THE PANHANDLE TAF SITES...DUE TO GOOD MIXING.

COX


&&

.FIRE WEATHER...
ISSUED AT 352 AM MDT TUE MAY 21 2013

ANOTHER WINDY DAY IS ON TAP FOR THE NEBRASKA PANHANDLE.
HOWEVER...EXTENSIVE CLOUD COVER ALONG WITH HIGH RELATIVE HUMIDITY
VALUES OF 40 TO 60 PERCENT WILL TEND TO SUPPRESS FIRE ACTIVITY. THE
REST OF THE WEEK...WE WILL SEE AN INCREASE IN LOW LEVEL MOISTURE.
THIS COMBINED WITH GREEN-UP CONDITIONS WILL LIMIT THE FIRE RISK
POTENTIAL.

&&

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

$$

SHORT TERM...REC
LONG TERM...FINCH
AVIATION...COX
FIRE WEATHER...REC