Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 240915
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
315 AM MDT SUN APR 24 2016

.SHORT TERM...(TODAY THROUGH MONDAY NIGHT)
ISSUED AT 235 AM MDT SUN APR 24 2016

TODAY...UPPER LOW MOVES FROM EAST CENTRAL WYOMING THIS MORNING TO
NORTH CENTRAL NEBRASKA THIS AFTERNOON. LOOKS LIKE ENOUGH LOW AND MID
LEVEL MOISTURE...COMBINED WITH SYSTEM DYNAMICS AND 500-300 MB AND
700-500 MB QG LIFT TO PRODUCE WIDESPREAD SHOWERS NORTH OF A RAWLINS
TO LUSK LINE...WITH ISOLATED TO SCATTERED SHOWER COVERAGE FURTHER
SOUTH IN CYCLONIC FLOW ALOFT. LOW AND MID LEVEL GRADIENTS...AND THE
CRAIG TO CASPER HEIGHT DIFFERENCES OF 60 TO 80 METERS AT 850 MB AND
70 TO 80 METERS AT 700 MB LOOK MORE THAN SUFFICIENT TO PRODUCE WIND
GUSTS IN EXCESS OF 58 MPH ACROSS THE INHERITED HIGH WIND WARNING
LOCATION...ESPECIALLY WITH THE GFS SHOWING 700 MB WINDS OF 55 TO 60
KNOTS AND DOWNWARD QG THIS AFTERNOON HELPING TO BRING THE STRONGER
WINDS TO THE SURFACE. WIND ADVISORY FOR THE SOUTHERN PANHANDLE ALSO
LOOKING ON TRACK.

TONIGHT...RIDGING ALOFT AND DECREASING LOW AND MID LEVEL MOISTURE
WILL PUT AN END TO MOST OF THE SHOWERS.

MONDAY...PROGRESSIVE PATTERN CONTINUES WITH THE NEXT TROUGH ALOFT
MOVING INTO UTAH...AND WINDS ALOFT OVER WYOMING BACKING TO SOUTH
SOUTHWEST. IN RESPONSE...SURFACE LOW DEVELOPS ACROSS WESTERN
COLORADO INDUCING LOW LEVEL EASTERLY FLOW ACROSS OUR COUNTIES AND
ADVECTING LOW LEVEL MOISTURE WESTWARD. STILL LOOKS LIKE A DECENT BET
FOR SCATTERED TO NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS TO
DEVELOP IN THE AFTERNOON AND EVENING ALONG AND WEST OF I-25 IN
DIFFLUENT ZONE ALOFT AND WITH LOW LEVEL MECHANICAL LIFT FROM EAST
WINDS. COMPROMISED BETWEEN THE NAM AND GFS MOS FOR MAXIMUM
TEMPERATURES.

MONDAY NIGHT...QUITE AN INCREASE IN PRECIPITATION COVERAGE
ANTICIPATED AS THE UPPER LOW MOVES TO NORTHWEST COLORADO AND 500-300
MB AND 700-500 MB LAYER QG LIFT SPREAD ACROSS OUR COUNTIES WITH
MOIST LOW AND MID LEVELS. WILL NEED TO WATCH OUR NORTHERN LARAMIE
RANGE FOR POSSIBLE SNOWFALL ACCUMULATIONS IN THE 6 TO 12 INCH
RANGE...WINTER WEATHER ADVISORY CRITERIA.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 300 AM MDT SUN APR 24 2016

EXPECT A PROLONGED PERIOD OF ACTIVE AND UNSETTLED WEATHER ACROSS
SOUTHEAST WYOMING AND WESTERN NEBRASKA INTO NEXT WEEK AS A SERIES
OF STRONG STORM SYSTEMS IMPACT THE REGION. HOWEVER...UNCERTAINTY
REMAINS WITH PRECIP TYPE AS WELL AS TIMING AND SPECIFIC IMPACTS.

TWO POTENTIALLY SIGNIFICANT STORM SYSTEMS ARE EXPECTED TO BRING
COOLER AIR...WIDESPREAD PRECIPITATION...THUNDERSTORMS...AND HIGH
ELEVATION SNOW TO THE REGION. THE FIRST ONE WILL IMPACT THE REGION
AS EARLY AS LATE MONDAY...BUT WILL LIKELY LINGER INTO WEDNESDAY AS
IT WILL BE SLOW MOVING. MODELS NOW SHOW ONE MAIN UPPER LEVEL LOW
AS OPPOSED TO TWO DISTINCT AREAS OF LOW PRESSURE 24 HOURS AGO.
THIS SYSTEM NEEDS TO BE MONITORED CLOSELY AS THERE IS SOME
POTENTIAL FOR ACCUMULATING SNOWFALL ACROSS SOUTHEAST WYOMING. THE
GFS IS THE FURTHEREST NORTH WITH THE CENTER OF LOW...BASICALLY
OVER THE FORECAST AREA BY TUESDAY AFTERNOON AND THEN INDICATES
RAPID CYCLOGENESIS OVER FAR EASTERN COLORADO AND KANSAS. THE 12Z
AND 00Z ECMWF ARE 3C TO 4C COLDER AND LESS PROGRESSIVE COMPARED TO
THE GFS. BOTH THE GEM AND ECMWF INDICATE RAIN CHANGING TO SNOW
DOWN TO 5500 FEET...WHILE THE GFS SHOWS SNOWLEVELS ABOVE 7000
FEET. QUITE A SIGNIFICANT DIFFERENCE WITH THIS STORM...SO STARTED
TRENDING TEMPERATURES LOWER. THE LATEST SREF FORECASTS INDICATE A
LARGE SPREAD...BUT ARE ALSO GRADUALLY TRENDING TOWARDS THE ECMWF
AND GEM SOLUTIONS. INCLUDED SOME ACCUMULATING SNOW WITH A
RAIN/SNOW LEVEL BETWEEN 5500 TO 6500 FEET THROUGH TUESDAY NIGHT.
CONTINUED TO INCREASE POP BETWEEN 60 TO 80 PERCENT ACROSS THE HIGH
VALLEYS AND HIGH PLAINS WITH SOME RESPECTABLE QPF AMOUNTS BETWEEN
0.50 TO 1.50 INCHES. THANKFULLY EVEN IF IT DOES SNOW DOWN TO 5500
FEET...MOST OF THE SNOW WILL OCCUR DURING THE DAY AND WILL LIKELY
MELT QUICK ON AREA ROADWAYS THIS TIME OF THE YEAR. ONLY THE GEM
INDICATES MODERATE TO HEAVY SNOW FROM TUESDAY EVENING THROUGH
MIDNIGHT WEDNESDAY. RAIN...WITH SOME SNOW MIXING IN AT
TIMES...WILL LINGER ACROSS WESTERN NEBRASKA INTO EARLY WEDNESDAY
AS THE STORM SYSTEM SLOWLY DRIFTS EASTWARD INTO THE NORTH-CENTRAL
PLAINS. DAYTIME HIGHS WILL STRUGGLE TO REACH THE MID TO UPPER 40S
BOTH TUESDAY AND WEDNESDAY WITH LOWS NEAR FREEZING.

MODELS SHOW A BRIEF BREAK ON THURSDAY BEFORE THE NEXT STORM SYSTEM
DIGS SOUTHWARD INTO SOUTHERN NEVADA/CALIFORNIA. SOLUTIONS THEN
DIVERGE SIGNIFICANTLY BY FRIDAY AND SATURDAY...WITH LOW CONFIDENCE
ON THE STORMS MOVEMENT AND EVOLUTION. ANOTHER ROUND OF HEAVY
RAINFALL IS POSSIBLE...ESPECIALLY ALONG AND SOUTH OF INTERSTATE
80. THIS STORM APPEARS SOMEWHAT WARMER THAN THE ONE ON
TUESDAY...SO SNOWFALL MAY NOT BE MUCH OF AN ISSUE LATE NEXT WEEK.
COOLER THAN NORMAL TEMPERATURES WILL LIKELY CONTINUE INTO NEXT
WEEKEND.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH SUNDAY NIGHT)
ISSUED AT 235 AM MDT SUN APR 24 2016

WINDS HAVE STRUGGLED TO INCREASE EARLY THIS MORNING AS THE UPPER
LEVEL LOW IS CURRENTLY MOVING ACROSS THE CENTRAL WYOMING.
HOWEVER...STILL EXPECT WINDS TO INCREASE OVER THE NEXT 3 TO 6
HOURS AS THE PRESSURE GRADIENT INCREASES JUST OFF THE SURFACE.
WRAP AROUND PRECIPITATION WILL INCREASE IN COVERAGE NEAR
KRWL...AND EVENTUALLY FURTHER EAST NEAR KLAR AND KCYS LATER TODAY.
CAN NOT RULE OUT IFR VIS EARLY THIS MORNING DUE TO SOME SNOWFALL
MIXED WITH RAIN. EVENTUALLY...PRECIPITATION TYPE WILL MAINLY BE
RAIN SINCE THERE IS A LACK OF COLD AIR WITH THIS SYSTEM...SO MVFR
CIGS AND VIS EXPECTED ALONG AND EAST OF INTERSTATE 25 INTO THE
WESTERN NEBRASKA PANHANDLE THIS AFTERNOON.

&&

.FIRE WEATHER...
ISSUED AT 222 AM MDT SUN APR 24 2016

NO CONCERNS BASED ON EXPECTED HUMIDITIES AND WINDS.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...

WY...HIGH WIND WARNING UNTIL 6 PM MDT THIS EVENING FOR WYZ106-110-116-
     117.

     HIGH WIND WARNING FROM 6 AM THIS MORNING TO 6 PM MDT THIS
     EVENING FOR WYZ115-118.

NE...WIND ADVISORY FROM 10 AM THIS MORNING TO 6 PM MDT THIS EVENING
     FOR NEZ019>021-054-055.

&&

$$

SHORT TERM...RUBIN
LONG TERM...TJT
AVIATION...TJT
FIRE WEATHER...RUBIN



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