Area Forecast Discussion
Issued by NWS Cheyenne, WY

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156
FXUS65 KCYS 010108
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
708 PM MDT SAT APR 30 2016

.UPDATE...
ISSUED AT 704 PM MDT SAT APR 30 2016

CURRENT RADAR MOSAIC ACROSS WESTERN NEBRASKA SHOWS THE LAST BAND
OF MODERATE SNOW/RAIN PUSHING ACROSS THE SOUTHERN PANHANDLE AND
INTO EXTREME SOUTHEAST WYOMING...WITH SNOW CHANGING BACK TO RAIN
ACROSS THE LOWER ELEVATIONS OF THE PLATTE RIVER VALLEY AS THE
UPPER LEVEL LOW BEGINS TO MOVE OUT OF THE AREA. WILL LIKELY CANCEL
THE WINTER WEATHER HEADLINES OVER THE NEXT HOUR AS THIS LAST BAND
DISSIPATES AS IT MOVES SOUTHWEST. ANY ADDITIONAL ACCUMULATIONS
WILL BE LESS THAN ONE INCH TONIGHT...BUT THE SNOW WILL BE LIGHT
ENOUGH TO NOT HAVE MUCH IMPACT ON AREA ROADWAYS.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 330 PM MDT SAT APR 30 2016

FORECAST CHALLENGES DEAL WITH ENDING TIMES FOR HEADLINES AND SNOW
THIS AFTERNOON AND TONIGHT.

CURRENTLY...WATER VAPOR IMAGERY SHOWING UPPER LOW CURRENTLY OVER
THE KANSAS/NEBRASKA BORDER SOUTH SOUTHEAST OF NORTH PLATTE. MOSAIC
RADAR SHOWING WRAP AROUND MOISTURE FROM NORTH CENTRAL NEBRASKA
EXTENDING SOUTHWEST TO SCOTTSBLUFF AND EVENTUALLY HERE TO
CHEYENNE. NOT GETTING A WHOLE LOT OF ACCUMULATIONS THIS AFTERNOON
AS TEMPERATURES FROM AREA METARS ARE ABOVE FREEZING. INTERESTING
NOTE...CHADRON NEVER DID TURN OVER TO SNOW THROUGH THIS WHOLE
EVENT...WHILE IT SNOWED ALL DAY AT ALLIANCE. THERE IS AN ELEVATION
DIFFERENCE OF 600 FEET BETWEEN THESE TWO LOCATIONS. LATEST WYDOT
ROAD TEMPERATURES STILL WELL ABOVE FREEZING THIS
AFTERNOON...RANGING FROM AROUND 59 AT ELK MOUNTAIN ON I-80 TO 40
UP ON THE SUMMIT.

DECIDED TO CANCEL THE WINTER HEADLINES FOR SOUTHEAST WYOMING WITH
THE AFTERNOON PACKAGE. UPPER LOW CONTINUES TO MOVE NORTHEAST INTO
EASTERN NEBRASKA THIS AFTERNOON AND EVENING. AS THIS HAPPENS...THE
TROWAL FEATURE WILL SLOWLY MOVE OFF TO THE SOUTHEAST. DID KEEP THE
PANHANDLE IN CURRENT HEADLINES AND WILL LET THE EVENING SHIFT TAKE
ANOTHER LOOK AT THINGS WHEN WE APPROACH SUNSET TO SEE IF SNOW
ACCUMULATIONS RETURN.

NORTHEAST UPSLOPE FLOW TO CONTINUE FOR SUNDAY AS WE STAY IN
CYCLONIC FLOW ACROSS THE EASTERN HALF OF THE CWFA. KEPT INHERITED
POPS IN THE FORECAST FOR SUNDAY WITH BEST CHANCES ALONG THE
LARAMIE RANGE. ALL MODELS SHOWING VERY LIGHT QPF AMOUNTS DURING
THE DAY SUNDAY...SO THE LOW POP FORECAST LOOKS PRETTY GOOD.

WE DRY OUT SUNDAY NIGHT INTO MONDAY AS WESTERLY WINDS RETURN IN
THE MID LEVELS. 700MB TEMPERATURES CLIMB TO AROUND FREEZING
MONDAY...SO WE SHOULD SEE AFTERNOON HIGHS BACK INTO THE UPPER 40S
AND LOW 50S BY THEN.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 330 PM MDT SAT APR 30 2016

THE GFS AND ECMWF ARE IN GOOD AGREEMENT WITH HIGH AMPLITUDE UPPER-
LEVEL RIDGING OVER THE CENTRAL ROCKIES EARLY IN THE PERIOD. MAINLY
DRY CONDITIONS SHOULD PREVAIL THROUGH AT LEAST THU...GIVEN LIMITED
MOISTURE AND LARGE SCALE SUBSIDENCE. H7 TEMPERATURES BETWEEN 6 AND
9 DEG C WILL BE COMMON BY MIDWEEK...LIKELY SUPPORTING DAYTIME HIGH
TEMPERATURES IN THE 60S AND 70S. THE MODELS BEGIN TO DIVERGE AFTER
THURSDAY WITH THE TIMING OF THE NEXT...AND POTENTIALLY SIGNIFICANT
WEATHER SYSTEM. THE ECMWF KEEPS UPPER-LEVEL RIDGING INTACT THROUGH
SATURDAY MORNING...WHILE THE GFS IS ABOUT 12-24 HOURS EARLIER WITH
THE BREAKDOWN OF THE RIDGE. REGARDLESS...CONSENSUS IS FOR A STORMY
WEATHER PATTERN TO RETURN FOR THE WEEKEND WITH A VIGOROUS...CLOSED
UPPER LOW ENCOMPASSING MUCH OF THE WESTERN CONUS. THE GFS SUGGESTS
SOME POTENTIAL FOR STRONG/SEVERE THUNDERSTORMS FOR THE HIGH PLAINS
ON FRI OR SAT AFTERNOON WITH CAPES OF 1500-2500 J/KG AND DECENT 0-
6 KM BULK SHEAR APPROACHING 30 KTS. THERE IS POTENTIAL FOR SNOW AS
EARLY AS SUN MORNING AS THERMAL PROFILES BEGIN TO COOL...BUT IT IS
MUCH TOO EARLY TO START TALKING ABOUT POTENTIAL ACCUMULATIONS. YET
AGAIN THOUGH...FOR THE THIRD YEAR IN A ROW...WE COULD VERY WELL BE
LOOKING AT A WINTRY MOTHERS DAY. STAY TUNED.

&&

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

IFR/LIFR CEILINGS AND VISIBILITIES WILL LIKELY PERSIST ACROSS MUCH
OF THE AREA THROUGH THE TAF PERIOD...WITH MVFR CONDITIONS LIKELY TO
PERSIST AT KRWL TONIGHT. WIDESPREAD RAIN/SNOW OVER THE HIGH PLAINS
THIS EVENING IS EXPECTED TO SLOWLY DIMINISH OVERNIGHT...WITH A SLOW
IMPROVEMENT IN CONDITIONS AFTER 12Z-18Z SUN.


&&

.FIRE WEATHER...
ISSUED AT 330 PM MDT SAT APR 30 2016

MINIMAL FIRE WEATHER CONCERNS OVER SOUTHEAST WYOMING AND NEBRASKA
PANHANDLE AS THE AREA HAS SEEN WIDESPREAD WETTING RAINS AND
ACCUMULATING SNOW. SNOW WILL COME TO AN END SUNDAY WITH A DRIER
PATTERN MOVING INTO THE AREA. MAINLY DRY CONDITIONS WITH SLOWLY
WARMING TEMPERATURES THROUGH THE WEEK. STILL NO FIRE CONCERNS AS
AFTERNOON HUMIDITIES ARE ONLY EXPECTED TO FALL INTO THE UPPER 20
TO LOW 30 PERCENT RANGE.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...

WY...NONE.
NE...NONE.

&&

$$

UPDATE...TJT
SHORT TERM...GCC
LONG TERM...CLH
AVIATION...TJT
FIRE WEATHER...GCC



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