Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 030459
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1059 PM MDT TUE SEP 2 2014

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 420 PM MDT TUE SEP 2 2014

MAIN FORECAST CONCERN OVER THE NEXT FEW DAYS WILL BE THE
CRITICAL FIRE WEATHER CONDITIONS ACROSS THE CWA. IT TOOK A LITTLE
WHILE FOR RH VALUES TO DROP TO CRITICAL LEVELS THIS
AFTERNOON...BUT WE ARE CURRENTLY SEEING A RH OF AROUND 15 PERCENT
IN THE FOOTHILLS OF THE LARAMIE RANGE (FIRE WEATHER ZONES 309 AND
301). RH VALUES ARE GENERALLY 15-20 PERCENT TO THE WEST OF THE
LARAMIE RANGE. WITH GUSTS TO 25-30 MPH THROUGH EARLY
EVENING...THIS CONTINUES TO LOOK LIKE A MARGINAL RED FLAG EVENT
AND WILL KEEP THE WARNINGS GOING. CLOUD COVER THIS AFTERNOON IS
QUITE LIMITED WITH ONLY ISOLATED CUMULUS. SFC MOISTURE IS BETTER
IN SOUTHERLY WINDS JUST TO THE EAST OF THE CWA (DEUEL AND GARDEN
COUNTIES) BUT IT WILL BE TOUGH TO ADVECT THIS MOISTURE WESTWARD.
THE HRRR MODEL ALONG WITH THE OTHER MODELS DO NOT SHOW ANY QPF
OVER THE PANHANDLE TONIGHT SO WILL KEEP SLIGHT CHANE POPS OUT OF
THE FCST.

WEDNESDAY CONTINUES TO LOOK LIKE A MORE CRITICAL FIRE WEATHER DAY
OVER THE REGION. A SHORTWAVE MOVING FROM WASHINGTON INTO MONTANA
WILL INDUCE PRESSURE FALLS OVER WESTERN SOUTH DAKOTA WHICH
STRENGTHENS THE PRESSURE GRADIENT OVER ESPECIALLY SOUTHEAST WY.
MOS GUIDANCE SHOWS WINDS ABOUT 5 KTS HIGHER THAN THIS AFTN ALONG
WITH AN ADDITIONAL 5 DEGREES OF WARMING. THE FIRE WEATHER WATCH
FOR TOMORROW AFTN INCLUDES TWO ZONES (310 AND 306) THAT ARE NOT
INCLUDED IN TODAYS RED FLAG WARNING. THIS LOOKS GOOD SINCE BOTH
THESE ZONES WERE CLOSE TO HITTING THE CRITERIA TODAY AND
CONDITIONS WILL BE DRIER AND MORE BREEZY TOMORROW. THE DEEP
SOUTHWESTERLY FLOW WILL RESULT IN A VERY WARM DAY WITH HIGHS
RISING INTO THE UPPER 80S TO MID 90S ACROSS THE PLAINS. THIS COULD
BE ONE OF THE WARMEST DAYS FOR THE REST OF THE YEAR SINCE A COLD
FRONTAL PASSAGE IS STILL PROGGED FOR THURS MORNING. TEMPS WILL
DROP CLOSE TO 20 DEGREES ON THURS. STILL NO GOOD CHANCE OF PRECIP
THROUGH AT LEAST THURS EVENING. COULD BE ISOLATED SHOWERS
DEVELOPING BY THURS NIGHT ALTHOUGH THE MODEL TREND HAS BEEN TO
SHIFT THE MORE WIDESPREAD RAIN WELL TO THE SOUTH OVER NORTHWEST KS.

.LONG TERM...(FRIDAY THROUGH MONDAY NIGHT)
ISSUED AT 420 PM MDT TUE SEP 2 2014

MODELS ARE IN FAIR AGREEMENT WITH THE MEDIUM RANGE PERIOD SHOWING A
PERSISTENT QUASI-ZONAL PATTERN OVER THE CENTRAL CONUS. TEMPERATURES
WILL START OFF BELOW AVERAGE ON FRIDAY IN THE POST FRONTAL
AIRMASS...WITH THE SFC HIGH SLIDING TO THE SOUTHEAST ACROSS THE
CENTRAL PLAINS. SFC WINDS ACROSS THE HIGH PLAINS WILL BE OUT OF THE
SOUTHEAST AS THE SFC HIGH SLIDES SOUTHEAST...WITH CONVECTION
DEVELOPING OVER THE MOUNTAINS IN THE LATE AFTERNOON IN THIS LLVL
UPSLOPE REGIME. SHOULD STAY FAIRLY CAPPED ACROSS THE PLAINS WITHIN
THE COOLER AIRMASS...BUT CANT RULE OUT SHOWERS/WEAK TSTORMS
MAINTAINING AS THEY MOVE OFF THE MOUNTAINS AS A 70 KT JET AND
SHORTWAVE ENERGY WILL BE MOVING OVERHEAD AT THIS TIME. SATURDAY
LOOKS VERY SIMILAR ALBEIT WITH WEAKER UPSLOPE FLOW AND SLIGHTLY
WARMER TEMPS/HIGH INSTABILITY. SUNDAY AND MONDAY COULD SEE A BIT
MORE SUBTROPICAL MOISTURE ADVECT UP FROM THE SOUTHWEST AS A TROUGH
DIGS ALONG THE WEST COAST AND MOVES ACROSS THE GREAT BASIN. THE
DEEPEST MOISTURE LOOKS TO REMAIN TO OUR SOUTH...BUT CAN SEE SOME OF
THIS MOISTURE MAKING IT UP TO SOUTHERN PORTIONS OF THE CWA SO WILL
MAINTAIN AT LEAST SLIGHT CHANCE POPS FOR MUCH OF THE CWA. TEMPS WILL
INCREASE BACK TO MORE NORMAL VALUES FOR THIS TIME OF YEAR BY MONDAY
AS THE UPPER TROUGH DEEPENS AND A WARM AIR ADVECTION PATTERN
DEVELOPS OVER THE ROCKIES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY EVENING)
ISSUED AT 1058 PM MDT TUE SEP 2 2014

VFR CONDITIONS TO PREVAIL THRU THE PERIOD. WINDS WILL BE GENERALLY
LIGHT AT LESS THAN 10 KNOTS OVERNIGHT...BUT BECOME GUSTY AFTER 16Z
WEDNESDAY.

&&

.FIRE WEATHER...
ISSUED AT 649 PM MDT TUE SEP 2 2014

PER OUR FIRE WEATHER BRIEFING AND MODEL GUIDANCE...RED FLAG
CONDITIONS LOOKING EVEN MORE LIKELY FOR PORTIONS OF SOUTHEAST
WYOMING ON WEDNESDAY...THUS WE HAVE UPGRADED THE FIRE WEATHER
WATCH TO A RED FLAG WARNING...AND HAVE ALSO CANCELLED THE RED
FLAG WARNING THAT WAS IN EFFECT FOR THIS AFTERNOON.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING FROM NOON TO 7 PM MDT WEDNESDAY FOR WYZ301-302-
     304-306-309-310.

NE...NONE.
&&

$$

SHORT TERM...FINCH
LONG TERM...RJM
AVIATION...HAHN
FIRE WEATHER...RUBIN




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