Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 190345
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
945 PM MDT SAT APR 18 2015

.UPDATE...
ISSUED AT 945 PM MDT SAT APR 18 2015

THE BAND OF MODERATE TO LOCALLY HEAVY SNOW CONTINUES TO SLOWLY
SHIFT EAST THIS EVENING...BUT PERHAPS SLIGHTLY SLOWER THAN
PREVIOUS THINKING. EARLIER ANALYSIS SUGGESTED A FEW STRONGER SNOW
SHOWERS WERE PERSISTING FROM THE NORTHERN LARAMIE RANGE SOUTHWEST
THROUGH THE ARLINGTON AREA AND ON UP INTO THE SNOWY RANGE AND
SOUTHERNMOST AREAS OF THE SIERRA MADRE MOUNTAINS. SHORT TERM
MODELS ALSO SUGGESTED THAT THE BAND WOULD MOVE SLOW TO THE EAST
THIS EVENING... SO FELT IT PRUDENT TO EXTEND THE WINTER STORM
WARNING AND ADVISORY FOR A FEW MORE HOURS AS SNOW WOULD CONTINUE
TO IMPACT THESE LOCATIONS. ENDED THE HEADLINES AT 11PM AS IR
IMAGERY IS SHOWING A RAPID WARMING OF CLOUD TOPS...AND MODELS
SUGGEST THE BAND WILL HAVE WEAKENED AND SHIFTED ENOUGH TO THE EAST
TO CANCEL ALL WINTER HEADLINES AT THIS TIME.

ALSO...ADDED AREAS OF FOG TO THE SUMMIT THROUGH MIDNIGHT AS
WEBCAMS SHOWED THE DEVELOPMENT OF FOG EARLIER...AND HRRR KEEPS
THE FOG AROUND THROUGH 11PM-12AM.

.UPDATE ISSUED AT 546 PM MDT SAT APR 18 2015

TORNADO WATCH HAS BEEN CANCELLED. CONDITIONS ARE NO LONGER
FAVORABLE FOR TORNADO DEVELOPMENT IN THE SOUTHERN NEBRASKA
PANHANDLE WITH THE BOUNDARY LAYER STABILIZING. A FEW
THUNDERSTORMS AREA STILL POSSIBLE OVER THE NEXT FEW HOURS INTO
SOUTHEAST WYOMING AND PANHANDLE BUT SEVERE WEATHER IS VERY
UNLIKELY. A ROUGE FUNNEL CLOUD AND SMALL HAIL STILL POSSIBLE FOR
THE NEXT HOUR OR SO.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 440 PM MDT SAT APR 18 2015

LOTS OF WEATHER CONCERNS OVER THE NEXT 12 HOURS. HEAVY SNOW
CONTINUES IN A NARROW BAND...MAINLY ACROSS EASTERN/CENTRAL CARBON
COUNTY...STRETCHING NORTHEAST INTO THE NORTHERN LARAMIE RANGE. ON
EITHER SIDE OF THE HEAVY BAND...MAINLY LOOKING AT LIGHT NON
ACCUMULATING SNOW OR RAIN. THIS WILL CONTINUE TO BE THE CASE UNTIL
LATE THIS EVENING WHEN THE DEFORMATION AXIS BEGINS TO SHIFT EAST
AS THE NORTHWEST FLOW KICKER PUSHES THE UPPER LOW INTO THE PLAINS.
THE BAND WILL SHIFT EAST LATE THIS EVENING INTO THE OVERNIGHT
HOURS BUT IT WILL ALSO WEAKEN SUBSTANTIAL WILL LITTLE IN THE WAY
OF ADDITION MEASURABLE PRECIPITATION AFTER MIDNIGHT ANYWHERE IN
THE FORECAST AREA.

SHOWERS AND THUNDERSTORMS HAVE DEVELOPED OVER THE PLAINS. A
TORNADO WATCH IS IN EFFECT FOR MORRILL AND CHEYENNE COUNTY IN THE
SOUTHERN NEBRASKA PANHANDLE UNTIL 8 PM MDT. BASED ON RADAR TRENDS
AND CURRENT ATMOSPHERIC ENVIRONMENT...ANY TORNADO THREAT IS
RAPIDLY DECREASING. CURRENT SHOWER ACTIVITY WILL RAPIDLY
STABILIZE THE BOUNDARY LAYER. ALSO...LIMITED SHEAR IS ONLY
SUPPORTIVE OFF VERY SHORT LIVED AND WEAK TORNADIC ACTIVITY. WOULD
NOT BE SURPRISED TO SEE A FEW FUNNEL CLOUD REPORTS WITH
DEVELOPING SHOWERS AND THUNDERSTORMS AS THE OVERALL ENVIRONMENT IS
MORE SUPPORTIVE OF FUNNEL CLOUDS BUT THAT TOO WILL QUICKLY WANE
OVER THE NEXT FEW HOURS.

ANOTHER CONCERN FOR TONIGHT IS NORTHERN WINDS WHICH WILL RAMP UP
THIS EVENING INTO THE OVERNIGHT AS A COLD FRONT MOVES ACROSS THE
AREA. COULD SEE A SHORT PERIOD OF NASTY WINTER CONDITIONS...MAINLY
INTO THE SOUTHERN LARAMIE RANGE AND CHEYENNE AS THE SNOW BAND
SHIFTS EAST AND INTERACTS WITH STRONG GUSTY NORTHERN WINDS. NAM
AND GFS BUFKIT SOUNDINGS AROUND MIDNIGHT SHOWING 45 TO 50 KT
WINDS AT CHEYENNE NOT TOO FAR OFF THE SURFACE. VERY WELL COULD SEE
A 3 TO 4 HOUR PERIOD WITH LOW VISIBILITIES DUE TO FALLING SNOW AND
GUSTY WINDS. FORTUNATELY THIS WILL BE SHORT LIVED IF IT THIS
COMBINATIONS DOES INDEED OCCUR. ALSO WINDS SPEEDS WILL APPROACH
WIND ADVISORY LEVELS INTO THE NEBRASKA PANHANDLE LATER TONIGHT
AND INTO SUNDAY AFTERNOON. DID NOT ISSUE ANY WIND HEADLINES GIVEN
WINTER WEATHER AND CONVECTIVE HEADLINES...BUT A WIND ADVISORY MAY
BE NEEDED EVENTUALLY.

QUIETER WEATHER ACROSS THE AREA SUNDAY WITH THE UPPER LOW OUT OF
THE PICTURE. KEPT SOME LOW POPS GOING ACROSS THE WEST DURING THE
DAY SUNDAY...BUT IT IS LOOKING LESS AND LESS LIKELY FOR ANY
MEASURABLE PRECIPITATION FOR MOST OF SUNDAY. MAIN CHANCES WILL BE
WITH NORTHERN STREAM SHORTWAVE AND UPPER LEVEL JET ENERGY WHICH
SHOULD IMPACT THE SNOWY AND SIERRA MADRES SUNDAY NIGHT.
ACCUMULATIONS WILL BE MINIMAL.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 250 PM MDT SAT APR 18 2015

MEDIUM TO LONG RANGE MODELS IN FAIR AGREEMENT THROUGH THE MIDDLE
OF NEXT WEEK...WITH SOME DISAGREEMENT REGARDING THE TRACK AND
EVOLUTION OF A DEVELOPING LOW PRESSURE SYSTEM LIFTING NORTHEAST
ACROSS THE CENTRAL AND SOUTHERN ROCKY MOUNTAINS BY THURSDAY AND
FRIDAY. FOR EARLY NEXT WEEK...ALL MODELS SHOW NORTHWEST FLOW
INITIALLY WITH RELATIVELY DRY CONDITIONS LASTING INTO EARLY
WEDNESDAY. A WEAK SHORTWAVE TROUGH WILL PUSH ACROSS THE REGION
EMBEDDED IN THE NORTHWEST FLOW...BUT OUTSIDE OF SOME MOUNTAIN/HIGH
VALLEY RAIN AND SNOW SHOWERS...DO NOT EXPECT ANYTHING SIGNIFICANT
WITH HIGH TEMPERATURES ABOUT 10 TO 15 DEGREES COOLER THAN SEASONAL
AVERAGES. TEMPERATURES WILL FINALLY MODERATE SOME BY TUES AND
ESPECIALLY INTO WED...BACK INTO THE UPPER 50S TO UPPER 60S TO THE
EAST OF THE LARAMIE RANGE. A SURFACE HIGH WILL BUILD OVER THE
GREAT PLAINS LATE WEDNESDAY AND ON THURSDAY...RESULTING IN WINDS
VEERING INTO THE EAST AND SOUTHEAST. KEPT TSTORMS IN THE FORECAST
FOR THURSDAY WEST OF THE LARAMIE RANGE...BUT KEPT SHOWERS FURTHER
EAST DUE TO A PERSISTENT LLVL STRATUS DECK.

MODELS STRUGGLING WITH A SHORTWAVE DISTURBANCE LIFTING NORTHEAST
OUT OF ARIZONA THURSDAY NIGHT. 12Z GFS ATTEMPTS TO FORM A CLOSED
LOW ACROSS THE NORTH CENTRAL PLAINS OF COLORADO BY EARLY
FRIDAY...WITH PRECIP EXTENDING INTO THE I80 CORRIDOR OF SOUTHEAST
WYOMING AND WESTERN NEBRASKA. THE ECMWF ON THE OTHER HAND IS MUCH
FURTHER SOUTH...MAINLY SHOWING THE FEATURE ACROSS NORTHERN NEW
MEXICO LIFTING NORTHEAST INTO KANSAS BY FRIDAY. KEPT A 20 TO 30
PERCENT CHANCE OF RAIN AND HIGH ELEVATION SNOW FOR FRIDAY AND EARLY
SATURDAY MORNING.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH SUNDAY AFTERNOON)

A BAND OF SNOW AND RAIN WILL REMAIN OVER CONVERSE...CARBON...AND
ALBANY COUNTIES THIS EVENING...AND THEN WILL RAPIDLY PUSH
SOUTHEAST NEAR A COLD FRONT...WHICH WILL PUSH SOUTHWARD TONIGHT. SCATTERED
TSTORMS HAVE DEVELOPED NEAR KSNY AND JUST EAST OF KCYS THIS
AFTERNOON. THESE TSTORMS WILL GRADUALLY MOVE NORTHWEST THIS
AFTERNOON AND THIS EVENING. SMALL HAIL AND BRIEF HEAVY RAINFALL IS
EXPECTED. A MORE STABLE AIRMASS WILL PUSH INTO THE REGION ON
SUNDAY BEHIND A WEAK COLD FRONT...RESULTING IN LOW PRECIPITATION
CHANCES ACROSS MOST OF THE FORECAST AREA. HOWEVER...IT WILL BE
WINDY BEHIND THIS FRONT WITH NORTH WINDS BETWEEN 20 TO 30 KNOTS
EAST OF THE LARAMIE RANGE.


&&

.FIRE WEATHER...
ISSUED AT 250 PM MDT SAT APR 18 2015

SHOWERS AND THUNDERSTORMS WILL END ACROSS ACROSS THE PLAINS
TONIGHT WITH SNOW ENDING OVER HIGHER ELEVATIONS OF WYOMING AS THE
UPPER LEVEL DISTURBANCE SHIFTS EAST INTO THE CENTRAL PLAINS.
WARMING TREND THROUGH MID WEEK BUT GENERALLY ON THE COOLER SIDE
AND DRY. NEXT CHANCE FOR WIDESPREAD PRECIPITATION IS LATE NEXT
WEEK...MAYBE.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER STORM WARNING UNTIL 11 PM MDT THIS EVENING FOR WYZ110-114.

     WINTER WEATHER ADVISORY UNTIL 11 PM MDT THIS EVENING FOR WYZ103-
     105-112-113.

NE...NONE.
&&

$$

UPDATE...RJM
SHORT TERM...SML
LONG TERM...TJT
AVIATION...TJT
FIRE WEATHER...SML


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