Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 040017
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
617 PM MDT THU SEP 3 2015

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 246 PM MDT THU SEP 3 2015

CURRENT RADAR IMAGERY SHOWS SHOWERS AND THUNDERSTORMS MOVING INTO
SOUTHERN WYOMING AND NEBRASKA PANHANDLE. THESE SHOWERS WILL
CONTINUE TO MOVE NORTHWARD THROUGH THIS EVENING DUE TO A WEAK
SHORTWAVE MOVING THROUGH THE CWA. THUNDERSTORMS ARE NOT EXPECTED
TO BE SEVERE...WITH THE MAIN CONCERNS BEING LOCALLY HEAVY
RAINFALL FROM A FEW THUNDERSTORMS. TONIGHT CHANCE OF POPS WILL
START TO DECREASE WITH THE SHORTWAVE DISTURBANCE PUSHING OFF TO
THE NORTHEAST. ON FRIDAY THERE IS DIFFLUENCE ALOFT ASSOCIATED WITH
THE UPPER LEVEL JET. EXPECT TO SEE SOME SHOWERS AND THUNDERSTORMS
DEVELOPING INTO THE AFTERNOON AND EVENING HOURS...THE BEST CHANCES
WEST OF THE LARAMIE RANGE. SATURDAY THERE IS AN UPPER LEVEL
TROUGH...CURRENTLY OVER THE PACIFIC NORTHWEST...THAT WILL BEGIN
TO MOVE OVER THE CWA. A FEW SHOWERS AND THUNDERSTORMS WILL ONCE
AGAIN BE POSSIBLE BUT OVERALL POP CHANCES WILL BE ON THE LOW SIDE.
TEMPERATURES WILL BEGIN TO TREND COOLER AS THE TROUGH SHIFTS INTO
THE AREA.

.LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 246 PM MDT THU SEP 3 2015

THE MEDIUM RANGE MODEL GUIDANCE PROGS THE UPPER TROUGH TO TRACK
NORTHEAST ACROSS MT AND NORTHERN WY SATURDAY NIGHT AND SUNDAY
MORNING WITH A PACIFIC FRONTAL PASSAGE. POST-FRONTAL SURFACE WINDS
WILL INCREASE SUNDAY MORNING WITH 700MB WINDS OF 35 TO 50 KT OVER
EAST CENTRAL AND SOUTHEAST WY. THE GRADIENT RELAXES SUNDAY AFTERNOON
WITH DIMINISHING WINDS. THE MUCH DRIER AIR MASS COMBINED WITH THE
GUSTY WINDS WILL RAISE THE FIRE DANGER DESPITE COOLER TEMPERATURES.
THE DRY ZONAL FLOW ALOFT WILL PREVAIL THROUGH EARLY NEXT WEEK WITH
PRECIPITABLE WATER VALUES OF 0.25-0.5 INCH. TEMPERATURES WILL AVERAGE
NEAR SEASONAL NORMALS. THERE ARE MODEL DIFFERENCES BY THE MIDDLE OF
NEXT WEEK AS THE GFS AND ECMWF DIFFER IN THE LOCATION AND STRENGTH
OFA SHORTWAVE TROUGH MOVING ACROSS THE NORTHERN ROCKIES AND PLAINS.
NONETHELESS...IT SHOULD BE A DRY PERIOD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 617 PM MDT THU SEP 3 2015

LIGHT RAIN SHOWERS CONTINUE TO MOVE NORTH-NORTHEAST ACROSS THE
FORECAST AREA THIS EVENING AS AN UPPER LEVEL DISTURBANCE
MOVES OVERHEAD. A FEW EMBEDDED T-STORMS ARE LOCATED NEAR KDGW AS
WELL. GUSTY WINDS ARE FAIRLY WIDESPREAD WITH THIS SHOWER
ACTIVITY...WITH GUSTS AVERAGING 25-35 MPH...AND AS HIGH AS 50-55
MPH. RAIN WILL END AND WINDS WILL CALM LATER THIS EVENING AS THE
DISTURBANCE MOVES NORTHEAST OF THE FORECAST AREA. TSTMS WILL
REDEVELOP FRIDAY AFTERNOON OVER THE HIGH COUNTRY AS ANOTHER
DISTURBANCE APPROACHES FROM THE SOUTHWEST. GUSTY WINDS ARE
EXPECTED NEAR KRWL FRIDAY AFTERNOON AS WELL...WITH SPEEDS OF 20 TO
25 KTS EXPECTED.

&&

.FIRE WEATHER...
ISSUED AT 246 PM MDT THU SEP 3 2015

SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL BE COMMON THROUGH
SATURDAY...ESPECIALLY DURING THE AFTERNOON HOURS. WINDS WILL GENERALLY
BE ON THE LIGHTER SIDES ALONG WITH HIGHER DEW POINTS. THEREFORE NO
FIRE WEATHER CONCERNS THROUGH SATURDAY.

A STRONG DISTURBANCE WILL MOVE ACROSS THE NORTHERN ROCKIES SATURDAY
NIGHT. GUSTY WEST WINDS WILL DEVELOP BEHIND THIS DISTURBANCE
ON SUNDAY ALONG WITH MUCH DRIER AIR. WEST WINDS GUSTING 30 TO 40 MPH
WILL BE COMMON SUNDAY. CRITICAL TO NEAR CRITICAL FIRE WEATHER
CONDITIONS CAN BE EXPECTED WITH RELATIVE HUMIDITY VALUES DIPPING INTO
THE 10 TO 20 PERCENT RANGE.

&&

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

$$

SHORT TERM...SML/KC
LONG TERM...MAJ
AVIATION...RJM
FIRE WEATHER...SML



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