Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 012333
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
535 PM MDT WED APR 1 2015

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 330 PM MDT WED APR 1 2015

FORECAST CHALLENGES DEAL WITH PRECIP ONSET/LOCATIONS AS WELL AS
SNOW AMOUNTS THROUGH THURSDAY NIGHT.

CURRENTLY...COLD FRONT LOOKS TO HAVE MOVED SOUTH OF CHEYENNE EARLY
THIS AFTERNOON. STARTING TO GET SOME CONVECTION GOING SOUTH OF THE
FRONT WITH A PRETTY STRONG CELL JUST SOUTH OF THE WYOMING/COLORADO
STATELINE. WILL NEED TO WATCH THESE CELLS AS AFTERNOON HUMIDITIES
ARE QUITE LOW STILL AND WE COULD GET SOME FIRE STARTS.

CONVECTION EXPECTED TO COME TO AN END AT SUNSET WITH LOSS OF
SURFACE HEATING. SECONDARY UPPER SHORTWAVE LOOKS TO MOVE INTO THE
AREA THURSDAY MORNING. GUIDANCE PEGGING THE I-80 CORRIDOR SOUTH TO
THE COLORADO BORDER FOR THE HEAVIEST QPF. SNOW LEVELS LOOK TO FALL
DOWN TO 5500 TO 6000 FEET DURING THE DAY. SOME GUIDANCE SHOWING
PRETTY HEAVY SNOW AMOUNTS WITH THIS BAND. BUT GIVEN THE TIME OF
DAY THAT SNOW IS EXPECTED TO START...I DECIDED TO HOLD OFF ON ANY
HEADLINES AND LET THE EVENING/NIGHT CREWS TAKE ANOTHER LOOK.

COULD SEE ADVISORY LEVEL SNOW AMOUNTS IN THE SNOWY...SIERRA MADRE
AND SOUTH LARAMIE RANGES AS HPC FORECAST IS SHOWING 8-10 INCHES
FOR TOMORROW AFTERNOON/EVENING. GFS 300-315K ISENTROPIC LIFT STILL
STRONGEST OVER NORTHEAST COLORADO TOMORROW AFTERNOON/EVENING...SO
FEEL WE DO NOT HAVE TO RAISE THE ALARM JUST YET. WE WILL NEED TO
WATCH THIS CLOSELY THOUGH OVER THE NEXT 12-24 HOURS AS ANY FURTHER
NORTHWARD MOVEMENT OF THIS LIFT WILL PLACE SOME OF OUR LOWER SOUTHERN
ZONES INTO HEAVY SNOW.

SHORTWAVE AND ASSOCIATED COLD FRONT SHIFT SOUTHEAST THURSDAY
NIGHT WITH SNOW ENDING AFTER MIDNIGHT. LOOKS TO STAY FAIRLY COLD
FRIDAY AS 700MB TEMPERATURES REMAIN AROUND -6 TO -10C.
FOR SATURDAY...LOOK FOR ANOTHER WARM UP AS WESTERLY WINDS BEGIN
TO PICK UP. GFS 700MB WINDS BACK UP TO 40KTS ACROSS OUR NORTHERN
ZONES...SO WE COULD BE BACK INTO ELEVATED TO CRITICAL FIRE WEATHER
CONDITIONS SATURDAY AFTERNOON.

.LONG TERM...(SATURDAY THROUGH TUESDAY)
ISSUED AT 330 PM MDT WED APR 1 2015

AFTER A FEW DAYS OF COOLER CONDITIONS...TEMPS WILL BEGIN TO
MODERATE ON SAT AND SUN AS HEIGHTS RISE ACROSS THE REGION. SAT
WILL BE A PLEASANT DAY WITH HIGHS IN THE 50S AND 60S. THE MODELS
INDICATE AN UPPER TROUGH SWEEPING NORTHEASTWARD ACROSS THE
NORTHERN INTERMOUNTAIN WEST ON SUN WITH PRESSURE FALLS OCCURRING
OVER NORTHERN WYOMING. 700MB SOUTHWEST WINDS INCREASE TO 35-40
KTS TO THE WEST OF THE LARAMIE RANGE...SO IT WILL BE WINDY DAY OUT
THERE. MIN RH VALUES FALL INTO THE 15-20 PERCENT RANGE ON SUN...SO
COULD BE LOOKING AT AN ELEVATED TO CRITICAL FIRE WEATHER DAY. SOME
MODEL DIFFERENCES APPEAR ON MON AS THE GFS SHOWS A MORE PRONOUNCED
SHORTWAVE AND COLD FRONT MOVING ACROSS THE REGION...WHEREAS THE
ECMWF SHOWS LITTLE COOLING FROM SUN. REGARDLESS...IT APPEARS THAT
POPS WILL BE SLIM THROUGH MON. A COOLER AND POTENTIALLY WETTER
PATTERN COULD TAKE SHAPE BY LATE TUES INTO WED AS LLVL EAST TO
SOUTHEAST UPSLOPE COMBINES WITH INCREASING ASCENT AHEAD OF A
SYSTEM MOVING ACROSS UTAH. WILL KEEP THE POPS GENERALLY LESS THAN
30 PERCENT FOR NOW.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH NOON THURSDAY)

VFR CONDITIONS THROUGH TONIGHT. A PACIFIC UPPER LEVEL DISTURBANCE
WILL MOVE TOWARDS WYOMING AND COLORADO TONIGHT WITH LIGHT SNOW
DEVELOPING NEAR THE COLORADO BORDER AS EARLY AS 15Z. SNOW MAY MIX
WITH RAIN AT TIMES UP TO 6000 FEET...BUT MOSTLY SNOW IS EXPECTED
ABOVE 5500-6000 FEET THURSDAY AFTERNOON. LOW IFR CONDITIONS ARE
POSSIBLE BY 18Z FROM KLAR...EASTWARD TO KCYS AND KSNY. WINDS WILL BE
RELATIVELY LIGHT AND SHIFT INTO THE NORTHEAST BY NOON THURSDAY.

&&

.FIRE WEATHER...
ISSUED AT 330 PM MDT WED APR 1 2015

WE GET A BREAK IN FIRE WEATHER CONDITIONS OVER THE NEXT SEVERAL
DAYS AS A COLD FRONT MOVES THROUGH THIS AFTERNOON . ALL AREAS WILL
SEE COOLER TEMPERATURES AND HIGHER HUMIDITIES. SOME LOCATIONS
SUCH AS THE SNOWY...SIERRA MADRE AND LARAMIE RANGES AND THE
INTERSTATE 80 CORRIDOR FROM SIDNEY TO RAWLINS WILL SEE WETTING
RAINS AND ACCUMULATING SNOWS. UNFORTUNATELY...NOT MUCH RAINFALL IS
EXPECTED NORTH OF A LINE FROM WHEATLAND TO TORRINGTON TO
SCOTTSBLUFF WITH THIS SYSTEM AND MOST LOCATIONS NORTH OF THIS LINE
WILL STAY DRY. WARMER TEMPERATURES AND WINDY CONDITIONS LOOK TO
RETURN THIS WEEKEND AND WE COULD BE DEALING WITH ELEVATED TO
CRITICAL FIRE WEATHER CONDITIONS...ESPECIALLY ACROSS OUR NORTHERN
ZONES...WESTERN 301...NORTHERN 310 AND 311-312 FOR THIS WEEKEND AS
AFTERNOON HUMIDITIES ONCE AGAIN FALL TO NEAR 10 PERCENT.

&&

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

$$

SHORT TERM...GCC
LONG TERM...ZF
AVIATION...TJT
FIRE WEATHER...GCC



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