Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 291800
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1200 PM MDT FRI AUG 29 2014

.UPDATE...
ISSUED AT 922 AM MDT FRI AUG 29 2014

OVERALL FCST IS IN GOOD SHAPE TODAY. BROAD UPPER-LEVEL RIDGING
WILL DOMINATE THE FLOW PATTERN THROUGH THE AFTN WITH ISOLATED TO
WIDELY SCATTERED SHOWERS AND TSTMS EXPECTED WITH A WEAK MIDLVL
SHORTWAVE MOVING ACROSS NORTH CENTRAL WY ATTM. ADDED SOME LOW END
POPS TO OUR EAST CENTRAL WY AND NORTHERN PANHANDLE ZONES THROUGH
18Z AS SOME WEAK ECHOS HAVE ALREADY SHOWN UP ON RADAR BETWEEN LUSK
AND GLENDO. LATEST VISIBLE SATELLITE SHOWS A CONSIDERABLE AMOUNT
OF SMOKE HEADING IN OUR DIRECTION FROM WILDFIRES NEAR THE OREGON
AND CALIFORNIA BORDER. MAIN QUESTION IS WHETHER THIS WILL BE DENSE
ENOUGH TO HAVE A SIGNIFICANT IMPACT ON TEMPS TODAY...SO WILL NEED
TO WATCH AS THE SMOKE SPREADS FROM WEST TO EAST ACROSS THE CWA.
DID NOT MAKE ANY CHANGES FOR THE TIME BEING ...THINKING IT WOULD
ONLY BE A COUPLE OF DEGREES IF SO.

&&

.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 18Z TAFS THROUGH 18Z SATURDAY MORNING)
ISSUED AT 1200 AM MDT FRI AUG 29 2014

CONVECTIVE TIMING AND STRENGTH AGAIN THE MAIN FOCUS FOR THIS SET
OF TAFS. RADAR SHOWS LINE OF CONVECTIVE DEVELOPMENT EXTENDING FROM
AROUND KCDR SW TO NR KLAR AS OF NOON. THIS WILL BE THE AREA TO
WATCH THIS AFTERNOON AS THIS DISTURBANCE AND BOUNDARY SHIFTS
SOUTEHAST ACROSS THE AREA. FOR NOW HAVE KEPT AND ADDED VCTS TO ALL
LOCATIONS THIS AFTERNOON WITH THE EXCEPTION OF KRWL...WHICH ARE
ALREADY WEST OF THE DISTURBANCE. ANY SHOWERS OR THUNDERSTORMS THAT
DO DEVELOP SHOULD SLIDE EAST OF THE AREA BY BETWEEN 22-24Z...
LEAVING VFR CONDITIONS AS SKIES CLEAR.

&&

.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.
&&

$$

UPDATE...HAMMER
SHORT TERM...JAMSKI
LONG TERM...TJT
AVIATION...HAHN
FIRE WEATHER...JAMSKI





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