Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 240222
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
822 PM MDT THU APR 23 2015

.UPDATE...
ISSUED AT 820 PM MDT THU APR 23 2015

BASED ON RADAR TRENDS AND THE 00Z MODEL PROGS...LOOKS LIKE SHOWER
CHANCES HAVE SIGNIFICANTLY DWINDLED FOR THE REST OF THE NIGHT...
THUS HAVE REMOVED MENTION OF SHOWERS. ONLY A FEW OTHER MINOR
CHANGES MADE TO THE GRIDDED FORECASTS FOR THE REST OF THE NIGHT.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 259 PM MDT THU APR 23 2015

THE MAIN CONCERN WITH THIS PORTION OF THE FORECAST IS THE TIMING
OF WHEN THE STORMS WILL MOVE OUT OF THE PICTURE THIS EVENING.

TONIGHT:
LATEST RADAR LOOP WAS SHOWING THE CLUSTER OF SHOWERS AND
THUNDERSTORMS CONTINUING PUSH EAST AND MAY EXIT THE AREA BY 5 PM
OR SO. NOT SEEING A LOT OF CONVECTION DEVELOPING BEHIND THIS
CLUSTER. IN ADDITION...THERE IS A LOT OF CLOUD COVER IN PLACE
WHICH MAY REDUCE THE INSTABILITY THIS EVENING. HOWEVER...WITH DECENT
CONVERGENCE IN PLACE WE MAY END UP WITH MORE SCATTERED
THUNDERSTORMS DEVELOPING AFTER 6 PM NEAR THE JUXTAPOSITION OF THE
LEE TROF. AS A RESULT...WE WILL KEEP THE CHANCE OF THUNDERSTORMS
ON THE HIGH SIDE IN THE SOUTHERN NEBRASKA PANHANDLE EARLY THIS
EVENING. THE REST OF THE FORECAST AREA SHOULD SEE ISOLATED TO
SCATTERED SHOWERS THIS EVENING BEFORE DISSIPATING AFTER SUNSET.
THE REST OF THE NIGHT WILL BE VERY SIMILAR TO LAST NIGHT WITH
QUITE A BIT OF CLOUD COVER IN PLACE WHICH SHOULD TEND TO KEEP
TEMPERATURES A BIT WARMER.

FRIDAY-FRIDAY NIGHT:
LATEST WATER VAPOR LOOP WAS SHOWING A WEAK SHORTWAVE MOVING
THROUGH THE CENTRAL SECTIONS OF MONTANA AND IDAHO. THIS FEATURE
WILL BEGIN PUSHING INTO NORTHERN WYOMING BY DAYBREAK AND SHIFT
SOUTHEAST INTO THE NEBRASKA PANHANDLE BY THE END OF THE DAY. THIS
SHORTWAVE WILL ALSO DRAG A WEAK FRONTAL BOUNDARY SOUTHEAST THROUGH
THE NEBRASKA PANHANDLE AND SOUTHEAST WYOMING THROUGH THE COURSE OF
THE DAY. AS THIS BOUNDARY INTERACTS WITH THE 40 DEGREE DEWPOINTS
IT SHOULD TRIGGER A FEW SHOWERS AND THUNDERSTORMS IN THE
PANHANDLE TOMORROW AFTERNOON ALONG WITH PORTIONS OF SOUTHEAST
WYOMING. NOT EXPECTING ANYTHING SEVERE AT THIS TIME...DUE TO
LIMITED SHEAR...BUT CERTAINLY ENOUGH INSTABILITY TO PRODUCE SOME
THUNDERSTORMS. THESE THUNDERSTORMS SHOULD DISSIPATE TOWARDS
SUNSET.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 259 PM MDT THU APR 23 2015

|NO BIG CHANGES ON THE AFTERNOON PACKAGE IN THE EXTENDED RANGE.  GFS
AND ECMWF STILL IN FAIR AGREEMENT SLOWLY MIGRATING A BROAD UPPER
TROUGH CROSSING THE FRONT RANGE SUNDAY INTO MONDAY...AND AN EVENTUAL
UPPER LOW THAT DEEPENS ACROSS COLORADO PASSING TO OUR SOUTH LATE IN
THE WEEKEND.  MAIN DIFFERENCES THIS PACKAGE ARE WITH THE ECMWF
WANTING TO HANG ON TO A LITTLE MORE DEEP MOISTURE ON THE BACKSIDE OF
THE SYSTEM AS IT EJECTS OUT TO THE EAST ON MONDAY...HOLDING SOME
SMALL POPS IN ACROSS THE SOUTHEASTERN ZONES.  FOR NOW...WE MAINTAIN
HIGH POPS SATURDAY THROUGH EARLY MONDAY WITH SNOW SHOWERS IN THE
WESTERN FORECAST AREA ABOVE 7500 FT AND MOSTLY RAIN OUT TO THE EAST
WITH A PERIODIC MIX DURING THE OVERNIGHT PERIODS IN BETWEEN.  WE
KEPT A MENTION OF THUNDER IN THE FORECAST SATURDAY MOST AREAS AND
THEN ACROSS THE SOUTHERN COUNTIES ON SUNDAY AFTERNOON WHERE THE
MODELS ARE DEPICTING SOME INSTABILITY.  MOST SNOW TOTALS ALONG AND
WEST OF THE LARAMIE RANGE FOR THE EVENT WILL BE FAIRLY LIGHT BELOW
GIVEN THE OVERALL WARM NATURE OF THE SETUP.  THE HIGHER ELEVATIONS
ABOVE 9000 FT MAY GET SEVERAL INCHES OF NEW SNOW...POSSIBLY UP TO A
FOOT.  WITH THE UPPER SYSTEM EXITING TO THE EAST ON MONDAY...A
RATHER LARGE UPPER RIDGE BUILDS ACROSS WYOMING AND WESTERN NEBRASKA
RESULTING IN A WARM AND DRY TREND SETTING UP MID TO LATE NEXT
WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 607 PM MDT THU APR 23 2015

VFR PREVAILS. ISOLATED SHOWERS AND THUNDERSTORMS THROUGH EARLY
THIS EVENING PRODUCING LOCALIZED MVFR AND GUSTY WINDS...PRIMARILY
AT CHADRON WITH LESSER CHANCES AT THE OTHER TAF SITES. ISOLATED
TO SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ON FRIDAY THOUGH
NOT ENOUGH CONFIDENCE NOW TO INCLUDE IN THE TAFS.


&&

.FIRE WEATHER...
ISSUED AT 259 PM MDT THU APR 23 2015

VERY LIMITED FIRE WEATHER CONCERNS ARE ANTICIPATED THROUGH THE
WEEKEND DUE TO ANOTHER SHORTWAVE MOVING INTO THE REGION WHICH WILL
BRING GOOD CHANCES OF PRECIPITATION TO THE MAJORITY OF THE AREA.
THIS PRECIPITATION SHOULD HELP PROLONG THE GREENUP IN MOST AREAS.

&&

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

$$

UPDATE...RUBIN
SHORT TERM...REC
LONG TERM...JG
AVIATION...RUBIN
FIRE WEATHER...REC



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