Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 302051
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
251 PM MDT THU JUL 30 2015

.SHORT TERM...(TODAY THROUGH SATURDAY NIGHT)

A COMPARISON BETWEEN SFC OBS AND VIS IMAGERY SHOWS A CONVERGENCE
BOUNDARY SPANNING SOUTHWEST-NORTHEAST FROM NORTHEAST COLORADO UP
INTO NORTH-CENTRAL NEBRASKA EARLY THIS AFTERNOON. SFC DEW POINTS
EAST OF THIS BOUNDARY ARE IN THE MID 50S WITH SOME UPPER LEVEL
MOISTURE EVIDENT ON WATER VAPOR OVER THIS AREA AS WELL. RESULTANT
CAPES RANGE FROM 1000-2000 J/KG...SO FEEL LIKE A FEW
SHOWERS/THUNDERSTORMS ARE A POSSIBILITY THRU THE AFTERNOON AND
EVENING. ADDED IN ISOLATED THUNDER CHANCES TO ACCOUNT FOR THE GOOD
LLVL CONVERGENCE AND MODEST INSTABILITY...MAINLY FOR AREAS EAST OF A
KIMBALL TO ALLIANCE LINE. LACK OF WAA AND LLVL JET DEVELOPMENT
TONIGHT LENDS TO THE IDEA THAT THE OVERNIGHT TIMEFRAME WILL REMAIN
DRY...SO LEFT POPS OUT FOR NOW EVEN THO SOME ELEVATED INSTABILITY
LOOKS TO PERSIST OVER THIS AREA.

A WEAK MIDLEVEL WAVE WILL APPROACH FROM THE NORTHWEST EARLY TOMORROW
AFTERNOON WITH INCREASING SOUTHEAST SFC FLOW AND MOISTURE ADVECTION.
THUS...STILL EXPECTING CONVECTION TO DEVELOP OVER THE HIGH COUNTRY
AND ALONG THE LARAMIE RANGE AND PINE RIDGE IN THE AFTERNOON WITH
ISOLATED STORMS TO TREK EASTWARD INTO THE PLAINS. STILL CONCERNED
ABOUT A WEAK CAP THAT LOOKS TO BE OVER THE PLAINS BUT THINK AT LEAST
A FEW STORMS COULD MAINTAIN WITH HELP FROM THE UPPER WAVE THROUGH
THE EVENING.

A WEAK SFC BOUNDARY WILL SLIDE SLOWLY SOUTH ACROSS MUCH OF THE CWA
ON SATURDAY. A FEW SHOWERS AND T-STORMS LOOK TO DEVELOP ALONG THE
FRONT...ESPECIALLY WHERE THE FRONT INTERSECTS TERRAIN FEATURES SUCH
AS THE LARAMIE RANGE...PINE RIDGE...AND CHEYENNE RIDGE. SO
MAINTAINED AT LEAST ISOLATED T-STORMS FOR SATURDAY AFTERNOON IN
THESE FAVORED LOCALES. WILL DRY OUT QUICKLY IN THE EARLY EVENING AS
CONDITIONS STABILIZE BEHIND THE FRONT.

TEMPERATURES WILL STEADILY INCREASE A BIT EACH DAY AS THE UPPER
LEVEL HIGH SLIDES WESTWARD FROM THE SOUTHERN PLAINS.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 315 PM MDT THU JUL 30 2015

MEDIUM TO LONG RANGE MODELS IN POOR AGREEMENT FOR MOST OF NEXT
WEEK. THE ECMWF AND GEM SOLUTIONS ARE SIMILAR EARLY IN THE
WEEK...BUT BOTH ARE INCONSISTENT WITH THE GFS WHICH SHOWS A
COMPLETELY DIFFERENT PATTERN. FOR SUNDAY...MODELS ARE THE BEST
AGREEMENT SHOWING A RIDGE AXIS EXTENDING FROM NORTHERN TEXAS
NORTHWEST TOWARDS WYOMING AND IDAHO. THIS RIDGE APPEARS TO BREAK
DOWN AS SOME MONSOON MOISTURE MOVES NORTHWARD FROM NEW MEXICO AND
COLORADO. CAN NOT RULE OUT SOME ISOLATED TSTORMS OVER THE HIGH
PLAINS SUNDAY AFTERNOON AS THE UPPER LEVEL RIDGE AXIS BEGINS TO
BREAK DOWN. REGARDLESS...SUNDAY SHOULD BE A PLEASANT DAY ACROSS
MOST OF THE REGION WITH HIGHS IN THE MID 80S TO MID 90S.

LOTS OF UNCERTAINTY FOR NEXT WEEKS FORECAST. THE ECMWF SHOWS A
VIGOROUS UPPER LEVEL TROUGH LIFTING NORTHEAST ACROSS WYOMING AND
THEN STALLING OVER MONTANA AND THE DAKOTAS FOR MOST OF THE
WEEK...RESULTING IN A BACK DOOR COOL FRONT MOVING SOUTHWARD AND
KEEPING THE HIGH PLAINS RELATIVELY COOL WITH A DAILY THREAT OF
SHOWERS AND TSTORMS. THE GFS ON THE OTHER HAND SHOWS THE UPPER
LEVEL RIDGE REBUILDING QUICKLY EARLY NEXT WEEK WITH NO INDICATION
OF THE TROUGH SHOWN BY THE ECMWF. THEREFORE...THE GFS CONTINUES TO
AMPLIFY THE RIDGE AXIS NORTHWARD AS THE CENTER OF THE ASSOCIATED
HIGH STALLS JUST EAST OF THE FOUR CORNERS REGION. THE GFS ALSO
INDICATES A DRIER SOLUTION IN TERMS OF PRECIP COVERAGE AND MUCH
WARMER COMPARED TO THE ECMWF. DUE TO THE LEVEL OF
UNCERTAINTY...PREFER TO STICK CLOSE TO CLIMATOLOGY THIS TIME OF
THE YEAR. KEPT POP BETWEEN 15 TO 25 PERCENT ACROSS PORTIONS OF THE
AREA. KEPT HIGH TEMPERATURES NEAR NORMAL AND IN THE 80S TO LOW
90S...WARMEST ACROSS WESTERN NEBRASKA...WHICH IS CLOSE TO THE
GFS/ECMWF CONSENSUS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH FRIDAY MORNING)

VFR CONDITIONS ARE EXPECTED OVER THE NEXT 24 HOURS WITH RELATIVELY
LIGHT WINDS. OUTSIDE OF AN ISOLATED THUNDERSTORM NEAR KSNY AND
POSSIBLY KAIA THIS AFTERNOON...DRY WEATHER IS EXPECTED WITH MINIMAL
IMPACTS.


&&

.FIRE WEATHER...
ISSUED AT 220 PM MDT THU JUL 30 2015

VERY WARM AND DRY CONDITIONS WILL CONTINUE IN THE HIGH COUNTRY
THROUGH THE WEEKEND...BUT WINDS WILL REMAIN RELATIVELY LIGHT. A FEW
SHOWERS AND T-STORMS ARE POSSIBLE ALONG AND EAST OF THE LARAMIE
RANGE ON FRIDAY...WITH A BROADER COVERAGE OF SHOWERS AND STORMS
POSSIBLE ACROSS THE DISTRICT EARLY NEXT WEEK.

&&

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

$$

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



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