Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 291035
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
435 AM MDT FRI AUG 29 2014

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 430 AM MDT FRI AUG 29 2014

UPPER TROUGH RESPONSIBLE FOR THE COOL AND UNSETTLED WEATHER THE PAST
FEW DAYS WAS LOCATED OVER THE GREAT PLAINS SLOWLY PROGRESSING EAST.
A TRANSITORY SHORTWAVE RIDGE ON ITS HEELS WAS PROVIDING A DRIER
NORTHWEST FLOW ALOFT ACROSS THE CWA. THE NEXT WEATHER MAKER WAS A
SHORTWAVE TROUGH MOVING THROUGH CENTRAL MT AND NORTHWEST WY ACCOMPANIED
BY SCATTERED SHOWERS AND ISOLATED TSTORMS. A WEAK SURFACE RIDGE DOMINATED
THE CWA... WITH A COLD FRONT LOCATED FROM NORTHWEST ND TO WEST CENTRAL
MT. WINDS WERE LIGHT WITH TEMP/DEW POINT SPREADS OF A FEW DEGREES OVER
WESTERN NE. COULD SEE SOME PATCHY FOG DEVELOP BY SUNRISE IN THESE AREAS.

GREAT PLAINS TROUGH CONTINUES ITS EASTWARD TREK TOWARD THE MS VALLEY
THROUGH SATURDAY. MEANWHILE...THE SHORTWAVE TO THE NORTH MAKES A
BEELINE FOR THE NORTHERN GREAT PLAINS AND UPPER MIDWEST. A UPPER RIDGE
WEST OF THE CONTINENTAL DIVIDE SLIDES QUICKLY EAST INTO THE NORTHERN
AND CENTRAL GREAT PLAINS SATURDAY AS THE NEXT PACIFIC TROUGH BROADENS
WITH ITS AXIS OVER THE FRONT RANGE BY MIDDAY SUNDAY.

TODAY WILL BE DRIER AND WARMER. ISOLATED AFTERNOON CONVECTION WILL DEVELOP
OVER AND EAST OF THE MOUNTAINS WHERE SBCAPES RANGE FROM 400-800 J/KG.
MAIN THREATS WITH THE TSTORMS WILL BE LIGHTNING AND GUSTY WINDS. MODEL
QPFS GENERALLY AVERAGE FROM 0.10-0.25 INCH. 700MB TEMPERATURES WILL
BE ABOUT 5 DEGREES WARMER THIS AFTERNOON WITH HIGHS IN THE UPPER 70S
TO MIDDLE 80S FOR THE PLAINS. CONVECTION MAY LINGER THROUGH THE EARLY
EVENING FOR THE SOUTHEAST WY MOUNTAINS.

SATURDAY MORNING WILL BE DRY TO START WITH WARMER AND BREEZY CONDITIONS
THROUGHOUT THE DAY IN ADVANCE OF THE PACIFIC COLD FRONT AND TROUGH.
HIGH TEMPERATURES WILL RISE INTO THE 80S TO LOWER 90S FOR THE PLAINS.
PACIFIC MOISTURE WILL SPREAD EAST ACROSS WY SATURDAY AFTERNOON AND
WESTERN NE SATURDAY EVENING. INSTABILITY INCREASES EAST OF THE LARAMIE
RANGE WITH SBCAPES OF 800-1200 J/KG. EXPECT ISOLATED TO SCATTERED
TSTORM COVERAGE. BESIDE THE WIND AND LIGHTNING THREATS...LOCALLY HEAVY
RAINFALL WILL BE A POSSIBILITY. CONVECTION WILL LIKELY CONTINUE INTO
THE LATE NIGHT HOURS AS SHORTWAVE ENERGY PRECEDING THE TROUGH PASSES
THROUGH.

SUNDAY WILL BEGIN UNSETTLED WITH SCATTERED SHOWERS/TSTORMS ACCOMPANYING
THE TROUGH...AND TAPERING OFF FROM WEST TO EAST DURING THE AFTERNOON
WITH PASSAGE OF THE COLD FRONT. IT WILL TURN BREEZY AND MUCH COOLER
/10-15 DEGREES/ IN THE AFTERNOON WITH HIGHS IN THE 50S AND 60S WEST...
70S EAST.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 325 AM MDT FRI AUG 29 2014

MEDIUM AND LONG RANGE MODELS ARE IN FAIR AGREEMENT THROUGH NEXT WEEK.
EXPECT A DRIER AND WARMER PATTERN COMPARED TO THE LAST FEW WEEKS AS
THE SOUTHWEST MONSOON IS SHOWING SIGNS OF COMING TO AN END. OUTSIDE
OF A FEW SHOWERS AND TSTORMS ON MONDAY AS A WEAK DISTURBANCE QUICKLY
MOVES EASTWARD OVER THE AREA...TUESDAY THROUGH THURSDAY WILL LIKELY
BE DRY WITH TEMPERATURES ABOVE NORMAL. HIGHS IN THE 80S TO AROUND
90 WILL BE COMMON ACROSS THE HIGH PLAINS...WITH THE HIGHER VALLEYS
REMAINING IN THE UPPER 70S TO AROUND 80. MODELS INDICATE A PERIOD
OF TRANSITION IN THE OVERALL LONG WAVE PATTERN AS THE POLAR JET
STREAM BECOMES MORE DEFINED AND MORE ACTIVE BY THE MIDDLE OF THE
WEEK NEAR THE CANADIAN BORDER.

BY LATE NEXT WEEK...MODELS SHOW AN UPPER LEVEL TROUGH STALLING OVER
THE PACIFIC NORTHWEST. HIGH PRESSURE ALOFT WILL BUILD OVER THE SOUTH
CENTRAL UNITED STATES AS SOME SUBTROPICAL MOISTURE BEGINS TO ADVECT
NORTHWARD OVER THE CENTRAL ROCKY MOUNTAINS. ADDED A SLIGHT CHANCE OF
SHOWERS AND TSTORMS TO THE FORECAST BY LATE THURSDAY NIGHT AND INTO
FRIDAY WITH THE GFS AND ECMWF SHOWING SOME ORGANIZED CONVECTION OVER
THE FORECAST AREA.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY NIGHT)
ISSUED AT 207 AM MDT FRI AUG 29 2014

VFR CONDITIONS WILL PREVAIL TODAY AS SURFACE WINDS WILL SHIFT INTO THE
NORTH...BUT WILL BE RATHER LIGHT THROUGH THE DAY. ISOLATED SHOWERS AND
TSTORMS ARE EXPECTED BY THIS AFTERNOON...MAINLY EAST OF THE LARAMIE
RANGE.

&&

.FIRE WEATHER...
ISSUED AT 317 AM MDT FRI AUG 29 2014

TODAY WILL BE DRIER AND WARMER THAN THE PAST FEW DAYS. A UPPER LEVEL
DISTURBANCE WILL ADVANCE EAST FROM MONTANA AND NORTHERN WYOMING TO THE
DAKOTAS BY THIS EVENING. A COLD FRONT WILL MOVE SOUTH THROUGH EAST
CENTRAL WYOMING THIS EVENING THEN EAST AS A WARM FRONT SATURDAY. THERE
WILL BE A SLIGHT CHANCE OF AFTERNOON THUNDERSTORMS TODAY...MAINLY ALONG
AND EAST OF THE LARAMIE RANGE. GUSTY WEST TO SOUTHWEST WINDS WILL DEVELOP
SATURDAY IN ADVANCE OF A PACIFIC FRONT AND TROUGH. CHANCES FOR THUNDERSTORMS
WILL INCREASE SATURDAY AFTERNOON AND CONTINUE SUNDAY FOLLOWING THE PASSAGE
OF THE FRONT. AFTER A WARM SATURDAY...SUNDAY WILL BE MUCH COOLER. ANOTHER
DISTURBANCE WILL MOVE THROUGH THE DISTRICTS LABOR DAY BRINGING A SLIGHT
CHANCE OF AFTERNOON THUNDERSTORMS ALONG AND EAST OF THE MOUNTAINS. IT
WILL TREND DRIER AND WARMER FOR THE MIDDLE OF NEXT WEEK.

&&

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

$$

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





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