Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 032050
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
250 PM MDT MON AUG 3 2015

.SHORT TERM...(TONIGHT THROUGH WEDNESDAY NIGHT)
ISSUED AT 256 PM MDT MON AUG 3 2015

CURRENT WATER VAPOR SATELLITE LOOP SHOWS THE POTENT UPPER LEVEL
SHORTWAVE TROUGH SHOWING SIGNS OF CLOSING OFF FROM THE MEAN FLOW
ALOFT...NEAR THE UTAH/WYOMING BORDER. THIS WILL BE THE PRIMARY
CONCERN TO IMPACT THE FORECAST AREA IN THE SHORT TERM WITH THE
POTENTIAL FOR TSTORMS...LOCALLY HEAVY RAINFALL...AND GUSTY WINDS
POSSIBLE THROUGH TUESDAY. MODELS HAVE BEEN TRENDING TOWARDS A
SIMILAR SOLUTION...BUT STILL SHOW DISCREPANCIES EVEN THOUGH IT
WILL BE MOVING ACROSS THE STATE IN THE NEXT 24 HOURS. THE GFS
CONTINUES TO BE QUITE DRY AND WINDY...SHOWING THE SHORTWAVE TROUGH
ACCELERATING NORTHEAST ONCE IT ENTERS WYOMING TONIGHT.
HOWEVER...DID NOTE THAT THE GFS HAS NOT INITIALIZED THE POSITION
OF THE TROUGH TOO WELL THIS AFTERNOON. THE GEM AND ECMWF ARE
FURTHER SOUTH AND SHOW THE DISTURBANCE BECOMING A CLOSED LOW
TONIGHT AND SLOWLY MOVING ACROSS THE CENTRAL TO SOUTHERN PART OF
THE STATE. THESE SOLUTIONS SHOW MORE MOISTURE AND A BETTER CHANCE
OF TSTORMS AND SHOWERS ACROSS THE ENTIRE AREA. THE 12Z AND 18Z ARE
IN BETWEEN THESE TWO EXTREMES...WITH DRY CONDITIONS FURTHER SOUTH
BY TUESDAY AFTERNOON BUT MORE MOIST WITH A BETTER CHANCE OF
THUNDERSTORMS NORTH OF I80. KEPT HIGH POP ALONG AND WEST OF THE
LARAMIE RANGE THROUGH TONIGHT FOR NUMEROUS SHOWERS AND SCATTERED
TSTORMS. THIS AREA WILL SHIFT INTO FAR EASTERN WYOMING AND THE
NEBRASKA PANHANDLE TOMORROW WHERE A FEW STRONG TSTORMS ARE
EXPECTED. FLASH FLOODING IS NOT A BIG CONCERN SO FAR TODAY DUE TO
THE EXTENT OF THE MID TO HIGH LEVEL CLOUDS FROM THIS MORNING.
HOWEVER...FLASH FLOOD CONCERNS WILL INCREASE ACROSS EAST CENTRAL
WYOMING AND INTO THE NEBRASKA PANHANDLE FOR TUESDAY. TEMPERATURES
WILL BE SLIGHTLY COOLER ON TUESDAY...WITH HIGHS IN THE LOW TO MID
80S OVER THE HIGH PLAINS AND CLOSER TO 75 WEST OF THE LARAMIE
RANGE.

FOR WEDNESDAY...MODELS SHOW THE UPPER LEVEL RIDGE AXIS REBUILDING
OVER THE ROCKY MOUNTAIN REGION BEHIND THE UPPER LEVEL TROUGH/LOW
AS IT EXITS THE REGION TO THE EAST. THE RIDGE AXIS IS RELATIVELY
WEAK...SO CAN NOT RULE OUT ISOLATED TO WIDELY SCATTERED SHOWERS
AND TSTORMS IN THE AFTERNOON AND EVENING HOURS ACROSS MUCH OF THE
AREA. HOWEVER...EXPECT TSTORM ACTIVITY TO BE RELATIVELY WEAK DUE
TO SOME SUBSIDENCE ALOFT. TEMPERATURES WILL INCREASE BACK INTO THE
MID 80S TO LOW 90S.

.LONG TERM...(THURSDAY THROUGH MONDAY)

QUASI-ZONAL FLOW ALOFT CAN BE EXPECTED THROUGH MUCH OF THE EXTENDED
FORECAST PERIOD. A SERIES OF MID-LEVEL SHORTWAVE DISTURBANCES SHOULD
TRAVERSE THE FLOW DURING THIS TIME...ALONG WITH A FEW SHOTS OF H7-H3
MOISTURE. CONVECTIVE CHANCES WILL BE HEAVILY DEPENDENT ON THE EXACT
TIMING/PLACEMENT OF THESE WAVES...AND CONFIDENCE IS SIMPLY NOT HIGH
ENOUGH TO WARRANT ANYTHING HIGHER THAN ISO TO WIDELY SCT POPS ATTM.
THE BEST CHANCE FOR MORE WIDESPREAD PRECIPITATION SHOULD BE AROUND
SAT/EARLY SUN AS A SHARP/NEGATIVE TILT TROUGH LIFTS NORTHEAST OUT OF
THE GREAT BASIN EARLY IN THE WEEKEND. AT THIS TIME...GFS/ECMWF BOTH
SHOW THE BEST JET DYNAMICS TO THE NORTH OF THE CWA WHICH COULD LIMIT
CONVECTIVE COVERAGE. LEE TROUGHING WILL CONTRIBUTE TO PLENTY OF LLVL
CONVERGENCE OVER THE PLAINS THOUGH...SO WILL KEEP SCATTERED POPS FOR
THE WESTERN NE PANHANDLE BETWEEN 18Z SAT-12Z SUN. DAYTIME HIGH TEMPS
SHOULD BE RIGHT AROUND SEASONAL NORMS FOR EARLY TO MID AUGUST.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1159 AM MDT MON AUG 3 2015

SCATTERED SHOWERS AND THUNDERSTORMS WILL OCCUR ACROSS MUCH OF THE
AREA THROUGH THE AFTERNOON/EVENING. A FEW STORMS COULD BE STRONG
WITH GUSTY/ERRATIC WINDS AND SMALL HAIL POSSIBLE. BRIEF MVFR VSBYS
ARE POSSIBLE BENEATH HEAVIER STORMS...BUT VFR CONDITIONS SHOULD BE
A GENERAL RULE. A FEW SHOWERS MAY CONTINUE THROUGH THE NIGHT...BUT
THIS IS NOT EXPECTED TO HAVE A SIGNIFICANT AVIATION IMPACT. WINDS
WILL INCREASE EARLY TOMORROW MORNING...WITH GUSTS AROUND 30 TO 35
KTS POSSIBLE OVER WYOMING TERMINALS BY 15Z TUE.


&&

.FIRE WEATHER...
ISSUED AT 156 PM MDT MON AUG 3 2015

FIRE WEATHER CONCERNS WILL BE ELEVATED THIS EVENING AND TUESDAY AS
A VIGOROUS DISTURBANCE ALOFT MOVES ACROSS THE AREA.
HOWEVER...CONDITIONS APPEAR TO BE A LITTLE MORE MOIST ACROSS THE
AREA COMPARED TO 24 HOURS AGO...WITH RELATIVE HUMIDITIES BETWEEN
20 TO 35 PERCENT TUESDAY AFTERNOON. WITH WESTERLY WINDS GUSTING TO
35 TO 40 MPH AT TIMES...A FEW AREAS MAY HIT RED FLAG CONDITIONS
ACROSS SOUTHEAST WYOMING. KEPT DAYTIME MINIMUM HUMIDITIES ABOVE 20
PERCENT FOR NOW. DRY CONDITIONS ARE EXPECTED THROUGH THE REMAINDER
OF THE WEEK...ALTHOUGH WINDS WILL GRADUALLY SUBSIDE.

&&

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

$$

SHORT TERM...KC/TJT
LONG TERM...CLH
AVIATION...CLH
FIRE WEATHER...TJT


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