Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 110104
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
704 PM MDT THU JUL 10 2014

.UPDATE...
ISSUED AT 702 PM MDT THU JUL 10 2014

CHEYENNE WSR-88D SHOWING SCATTERED TO NUMEROUS SHOWERS...AND
ISOLATED THUNDERSTORMS EAST OF A DOUGLAS TO SIDNEY LINE...WITH
ISOLATED SHOWERS FURTHER WEST...THUS HAVE UPDATED THE GRIDDED
FORECASTS TO ADJUST POPS FOR AREAL COVERAGE OF SHOWERS AND
THUNDERSTORMS THE REST OF THIS EVENING.   64/RUBIN

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 420 PM MDT THU JUL 10 2014

A WEAK SFC COLD FRONT WILL CONTINUE TO MOVE SOUTH ACROSS THE
FORECAST AREA THROUGH THIS AFTERNOON AND EVENING AS A SFC LOW
DEVELOPS WITHIN THE LEESIDE TROUGH OVER SE WYO/NEB/CO. THE MONSOONAL
PLUME CONTINUES TO MOVE OVERHEAD THIS AFTERNOON AS WELL BASED OFF
THE AMSU-SSM/I DERIVED TPW. EMBEDDED SHORTWAVE ENERGY EVIDENT ON
WATER VAPOR IMAGERY MOVING OVER THE ROCKIES/HIGH PLAINS IN ADDITION
TO THE COMBINATION SFC LOW/FRONT HAVE SPARKED OFF NUMEROUS SHOWERS
WITH SCATTERED TSTORMS THIS AFTERNOON. SO FAR MOST OF THIS ACTIVITY
HAS REMAINED VERTICALLY STACKED LIKELY A RESULT OF LACK OF SHEAR.
HOWEVER...MESOANALYSIS SHOWS 30 TO 40 KTS OF DEEP LAYER SHEAR OVER
NORTHERN PORTIONS OF THE CWA SO ONCE CONVECTION DEVELOPS UP IN
THAT VICINITY...COULD SEE MORE ORGANIZATION TO THIS ACTIVITY AND
THUS STRONGER TO SEVERE STORMS. EXPECT CONVECTION TO CONTINUE
THRU THE EVENING WITH A STEADY DECREASE IN COVERAGE IN THE EARLY
OVERNIGHT PERIOD. A FEW STORMS COULD REDEVELOP OVER THE NORTHERN
TIER OF COUNTIES UNDER A MORE OVERRUNNING SITUATION...AS GFS SHOWS
700 MB WINDS BACKING TO THE SOUTH TONIGHT AS THE UPPER LEVEL JET
CURRENTLY OVER MONTANA DIPS SOUTH INTO NORTHERN WYOMING AND
PROVIDES SOME UPPER LEVEL SUPPORT FOR CONTINUED SHOWER/TSTORM
ACTIVITY. FOR NOW...WILL KEEP IT MORE ISOLATED COVERAGE BUT WILL
HAVE TO WATCH FOR THE NEED TO INCREASE POPS AS THE SITUATION
UNFOLDS.

FRIDAY CONTINUES TO LOOK EVEN MORE ACTIVE THAN TODAY WITH INCREASING
UPWARD OMEGA OVER THE CWA AS THE RIGHT ENTRANCE REGION OF THE JET
MOVES OVERHEAD. THE SFC FRONT WILL FINALLY SHIFT SOUTH AND WEST
OVER REMAINING PORTIONS OF THE CWA BY THE AFTERNOON...AND EAST-
NORTHEAST SFC WINDS IN PLACE BEHIND THE FRONT WILL MAINTAIN A
STRONG LLVL UPSLOPE COMPONENT. IN ADDITION...700 MB WINDS WILL
RESPOND TO THE UPPER LEVEL JET AND WILL BECOME SOUTH-SOUTHEAST
OVER THE CWA...FURTHER ADDING TO OVERALL LIFT. WITH MULTIPLE
SOURCES OF UPWARD LIFT...THERE WILL BE PLENTY OF SUPPORT FOR NUMEROUS
SHOWERS WITH SCATTERED STORMS BEGINNING IN THE MOUNTAINS AFTER
SUNRISE AND SPREADING EAST THRU THE DAY. WITH PWATS INCREASING TO
AS HIGH AS 1.5 INCHES BY THE LATE AFTERNOON...RAINFALL FROM THE
ACTIVITY WILL BE MODERATE TO HEAVY AT TIMES. SOME
LOCATIONS...ESPECIALLY OVER THE MOUNTAINS AND ALONG THE LARAMIE
RANGE...COULD SEE ONE HALF INCH OR MORE OF QPF BY FRIDAY EVENING.
WORRIED A LITTLE ABOUT TRAINING OF STORMS DUE TO EASTERLY SFC
WINDS PERSISTING THROUGH THE DAY...BUT CONFIDENCE IS NOT HIGH
ENOUGH REGARDING EXACTLY WHERE THE HIGHEST THREAT FOR FLASH
FLOODING IS GOING TO BE TO ISSUE A WATCH JUST YET. WILL REVISIT
THIS POSSIBILITY THIS EVENING AND OVERNIGHT ONCE TODAYS STORMS
DIMINISH AND WE GET A BETTER HANDLE WHERE THE GROUND MAY HAVE
BECOME SATURATED. LIKELY TO SEE SOME ACTIVITY CONTINUE OVERNIGHT
ESPECIALLY ACROSS EASTERN ZONES AS THE POTENT SHORTWAVE MOVES
THROUGH.

THE MONSOONAL PLUME WILL REMAIN OVERHEAD FOR SATURDAY...HOWEVER THE
HIGHEST PWATS WILL HAVE SHIFTED TO THE SOUTH AND EAST WITH THE UPPER
WAVE. WILL MAINTAIN CHANCE POPS FOR ISO-SCAT STORMS THROUGH THE
DAY...WITH MODERATE RAIN EXPECTED OUT OF THIS ACTIVITY.

.LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 420 PM MDT THU JUL 10 2014

NWLY UPPER FLOW WILL BE OVER THE CWA SUNDAY THROUGH TUESDAY ON THE
SW SIDE OF AN UNUSUALLY STRONG UPPER VORTEX THAT WILL MOVE FROM
CENTRAL CANADA SOUTH INTO THE GREAT LAKES REGION BY TUESDAY.
MONSOONAL MOISTURE WILL CONTINUE TO MOVE ACROSS THE REGION SUNDAY
THEN IT LOOKS TO GET SHUNTED TO THE SOUTH BY MONDAY AS THE
STRONGER NWLY FLOW TAKES OVER. THIS PATTERN WILL ALSO ALLOW FOR A
COUPLE SURGES OF COOLER AIR TO DROP OUT OF THE CANADIAN PRAIRIES
INTO THE REGION EARLY NEXT WEEK BRINGING A PERIOD OF BELOW AVERAGE
TEMPERATURES. BEST CHANCES FOR CONVECTION WILL BE SUNDAY THEN THEY
WILL TAPER OFF EARLY NEXT WEEK WITH THE DRYING OF THE AIR.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY AFTERNOON)
ISSUED AT 513 PM MDT THU JUL 10 2014

SHOWERS AND THUNDERSTORMS COULD IMPACT AREA AIRPORTS LATE THIS
AFTERNOON THROUGH EARLY EVENING. MOST PROBABLE AREA IS THE
NORTHERN NEBRASKA PANHANDLE. HAVE TEMPO CONDITIONS FOR
THUNDERSTORMS. GOT A SPOTTER REPORT OF HEAVY RAIN JUST WEST OF
KAIA. GOOD THING...NO HAIL REPORTED. IT WILL ARRIVE AT THE KCDR
AIRPORT A LITTLE LATER...SAY 01Z AND LAST FOR AN HOUR.


&&

.FIRE WEATHER...
ISSUED AT 420 PM MDT THU JUL 10 2014

A MONSOONAL MOISTURE PLUME WILL REMAIN OVER THE DISTRICT THROUGH
SATURDAY AND WILL BRING A GOOD CHANCE FOR SHOWERS AND
THUNDERSTORMS THROUGH THIS TIME. THE BEST CHANCE WILL OCCUR ON
FRIDAY...AND SOME STORMS MAY PRODUCE ONE QUARTER TO ONE HALF INCH
OF RAINFALL IN THE AFTERNOON. MINIMUM AFTERNOON HUMIDITY VALUES
WILL GENERALLY STAY ABOVE 25 PERCENT EACH AFTERNOON THROUGH THE
WEEKEND DUE TO THE ELEVATED MOISTURE LEVELS.

&&

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

$$

UPDATE...RUBIN
SHORT TERM...RJM
LONG TERM...RE
AVIATION...CLAYCOMB
FIRE WEATHER...RJM





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