Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 311756
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1156 AM MDT SUN AUG 31 2014

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 345 AM MDT SUN AUG 31 2014

CURRENT KCYS RADAR LOOP SHOWS AN AREA OF RAIN SHOWERS AND EMBEDDED
THUNDERSTORMS QUICKLY MOVING EASTWARD ACROSS THE AREA EARLY THIS
MORNING. THIS ACTIVITY IS IN ADVANCE OF AN UPPER LEVEL TROUGH AXIS
MOVING INTO WESTERN WYOMING. 250 MB JET STREAM WINDS WILL CONTINUE
TO INCREASE THIS MORNING OVER 100 KNOTS AS THE SURFACE COLD FRONT
HAS JUST STARTED TO ACCELERATE SOUTHEAST ACROSS THE FORECAST AREA.
EXPECT A COOLER THAN AVERAGE DAY TODAY BEHIND THIS COLD FRONT AS
THE TROUGH AXIS MOVES ACROSS SOUTHEAST WYOMING...RESULTING IN
SURFACE TEMPERATURES IN THE UPPER 60S TO MID 70S ACROSS MOST OF
THE FORECAST AREA. IT WILL BE A LITTLE WARMER FURTHER SOUTH AND
EAST ACROSS THE SOUTHERN NEBRASKA PANHANDLE SINCE THE FRONT WILL
STALL LATER TODAY. SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED
THROUGH TODAY. THE GFS CONTINUES TO BE ON THE DRY SIDE EVEN THOUGH
THE RADAR IMAGERY THIS MORNING HAS BEEN ACTIVE. WITH A STRONG JET
OVERHEAD...BELIEVE MODELS CONTINUE TO DOWNPLAY THE CHANCES FOR
WIDESPREAD SHOWERS TODAY. KEPT POP BETWEEN 40 TO 60 PERCENT FOR
SCATTERED SHOWERS AND ISOLATED THUNDER INTO THIS EVENING. WINDY
CONDITIONS ARE EXPECTED THIS AFTERNOON AFTER FROPA...WITH GUSTS UP
TO 45 MPH POSSIBLE WEST OF THE LARAMIE RANGE. WINDS WILL STRUGGLE
TO REACH 30 MPH OVER THE NEBRASKA PANHANDLE THIS AFTERNOON. SHOWER
ACTIVITY WILL QUICKLY COME TO AND END EARLY THIS EVENING AS DRIER
AND MORE STABLE AIR MOVE INTO THE REGION. SKIES WILL QUICKLY CLEAR
TONIGHT WITH CHILLY OVERNIGHT LOWS IN THE 30S TO MID 40S EXPECTED.

ANOTHER COOL DAY EXPECTED ON MONDAY WITH HIGHS STRUGGLING TO
REACH THE LOW TO MID 70S ACROSS MOST OF THE AREA. MODELS SHOW A
SECONDARY SHORTWAVE QUICKLY PUSHING ACROSS THE AREA...RESULTING IN
SOME RAIN SHOWER ACTIVITY AND MAYBE A FEW LIGHTNING STRIKES.

UPPER LEVEL FLOW BECOMES MORE ZONAL FOR TUESDAY WITH INCREASING
TEMPERATURES INTO THE UPPER 70S TO MID 80S ACROSS THE AREA. DRIER
AIR WILL PUSH INTO THE REGION WITH PW/S LOWERING BELOW ONE HALF
INCH DURING THE DAY.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 300 AM MDT SUN AUG 31 2014

THE LONG TERM FORECAST WILL START OFF DRY AND BREEZY WEDNESDAY UNDER
ZONAL FLOW ACROSS THE CONUS. DOWNSLOPE FLOW WILL PUSH TEMPERATURES
INTO THE 80S ACROSS SOUTHEAST WYOMING AND 90S INTO THE PANHANDLE. BY
THURSDAY AN UPPER LEVEL TROUGH WILL DIG OVER THE PACIFIC NORTHWEST
WITH SOUTHWEST FLOW KICKING IN ACROSS THE CENTRAL AND NORTHERN
ROCKIES. WILL START TO SEE INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS LATE THURSDAY AND THEN INTO THURSDAY NIGHT. THURSDAY
SHOULD BE A BIT COOLER AS MID AND UPPER LEVEL CLOUD COVER LIMITS
DEEPER MIXING.

FORECAST MUCH MORE TRICKY FRIDAY AND SATURDAY AS MODEL SOLUTIONS
DIVERGE. GFS DEVELOPS A SLOW MOVING CLOSE LOW OVER THE WESTERN CONUS
WITH RELATIVELY DRY SOUTHWEST FLOW FOR THE FORECAST AREA. THE ECMWF
ON THE OTHER HAND SHOWS A MORE PROGRESSIVE WAVE SUPPRESSING THE RIDGE
OVER THE ROCKIES FRIDAY AND THEN DEVELOPING NORTHWEST FLOW BY
SATURDAY. IN OTHER WORDS THE ECMWF IS NOT ONLY COOLER BUT WOULD ALSO
SUGGESTS INCREASED PRECIPITATION CHANCES. NOT COMPLETELY CONFIDENT IN
EITHER MODEL BUT LEANING TOWARD THE ECMWF AS OVERALL WEATHER PATTERN
PERSISTENCE GOING ALL THE WAY BACK TO LAST WINTER FAVORS NORTHWEST
FLOW.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY MORNING)
ISSUED AT 1146 AM MDT SUN AUG 31 2014

SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL BE POSSIBLE
THROUGH THE AFTERNOON. MUCH OF THE ACTIVITY WILL SHIFT EASTWARD
OUT OF SOUTHEAST WY BY LATE AFTERNOON. MODERATE RAIN WILL
ACCOMPANY SOME OF THE STRONGER SHOWERS...WITH BRIEF MVFR VIS
POSSIBLE. WEST TO NORTHWEST WINDS WILL BE BREEZY THROUGH 00Z OVER
MUCH OF SOUTHEAST WY WITH GUSTS TO 30 KTS.

&&

.FIRE WEATHER...
ISSUED AT 244 AM MDT SUN AUG 31 2014

NO FIRE WEATHER CONCERNS THROUGH MONDAY...BUT THEN CONCERN OF NEAR
CRITICAL CONDITIONS INCREASE FOR TUESDAY AND WEDNESDAY. A STRONG
WEATHER DISTURBANCE AND ASSOCIATED COLD FRONT WILL MOVE ACROSS
THE AREA EARLY THIS MORNING. SHOWERS AND TSTORMS WILL CONTINUE
ACROSS SOUTHEAST WYOMING AND WESTERN NEBRASKA TODAY WITH GUSTY
WEST TO SOUTHWEST WINDS. DRIER CONDITIONS WILL DEVELOP BY MIDDLE
OF NEXT WEEK WHILE GUSTY WEST WINDS CONTINUE IN AREAS ALONG AND
WEST OF THE LARAMIE RANGE.

&&

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

$$

SHORT TERM...TJT
LONG TERM...SML
AVIATION...FINCH
FIRE WEATHER...TJT




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