Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 120204
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
804 PM MDT THU SEP 11 2014

.UPDATE...
ISSUED AT 757 PM MDT THU SEP 11 2014

THE FRONTAL ZONE AND UPPER LEVEL SYSTEM ARE MAKING SLOW PROGRESS
TO THE EAST THIS EVENING. PRECIPITATION ACROSS THE BLKHLS REGION
AND NORTHEAST WYOMING HAS DECREASED CONSIDERABLY THE LAST COUPLE
OF HOURS. AS DESCRIBED IN THE AFTERNOON DISCUSSION A SECONDARY
BAND OF -R/-S IS MOVING INTO THE SOUTH CENTRAL COUNTIES AND WILL
LIKELY LINGER FOR MUCH OF THE OVERNIGHT HOURS SUPPORTING THE
CHANCE CATEGORY POPS. MUCH DRIER/COOLER AIR IS MOVING THIS
DIRECTION... WITH UPPER 20S DEWPOINTS HAVING PUSHED INTO NORTHWEST
SOUTH DAKOTA ALREADY. THE FORECAST FOR MINIMUM TEMPS IN THE UPPER
20S LOOKS GOOD.

&&

.SHORT TERM...THIS EVENING THROUGH FRIDAY NIGHT
ISSUED AT 214 PM MDT THU SEP 11 2014

DEEP UPPER LEVEL TROUGH AND ASSOCIATED SOUTHERN
PERIPHERY IMPULSE WILL CONTINUE TO SHIFT SE OF THE AREA THROUGH
TONIGHT...WITH FGEN ASSOCIATED RAIN/SNOW ENDING. MASSIVE SFC HIGH
PRESSURE WILL BUILD INTO THE REGION TONIGHT...SUPPORTING LL DRYING
AND CLEARING SKIES WITH VERY COLD CONDITIONS FOR THE SEASON. UPPER
TROUGH AND ASSOCIATED COLD POCKET ALOFT WILL SLOWLY MIGRATE EAST
THROUGH FRIDAY...POSSIBLY SUPPORTING A FEW EARLY AFTERNOON SHOWERS
ACROSS FAR SE AREAS FRI AFTERNOON GIVEN DIURNAL DESTABILIZATION.

TONIGHT...ADJUSTED POPS UP ACROSS THE SW THIRD FOR THE PROPAGATING
FGEN BAND...WITH RAIN/SNOW EXPECTED THERE THROUGH EARLY EVENING.
UPPER IMPULSE/JET STREAK WILL PIVOT AND SHIFT NE ACROSS THE
REGION...POSSIBLY SUPPORTING LINGERING CHANCES FOR PRECIP ACROSS THE
FAR SE LATE TONIGHT. LL DRYING WILL CERTAINLY LIMIT THE CHANCE FOR
PRECIP AND ANY AMOUNTS...THUS KEPT POPS IN THE CHANCE RANGE OR LOWER
SCENTRAL LATE. SOME LIGHT SNOW ACCUMS /GENERALLY LESS THAN ONE INCH/
WILL BE POSSIBLE THIS EVENING ACROSS THE FAR SW...MAINLY ON GRASSY
SFC/S. MAIN CONCERN TONIGHT WILL BE THE COLD TEMPS. SFC RIDGE WILL
BUILD INTO THE REGION WITH SIG SINK AND LL DRYING. CLEAR SKIES WILL
RESULT BY LATER TONIGHT NW 2/3. STRONG RADIATIONAL COOLING/LIGHT
WINDS/COLD START/AND DRY LL PROFILES WILL SUPPORT SHARP T FALLS
WESTERN 2/3...WITH 20S EXPECTED MANY LOCATIONS. EASTERN 2/3 WILL SEE
SLIGHTLY WARMER TEMPS...WITH 30S FOR LOWS. HOWEVER...FROST WILL BE
OF CONCERN GIVEN EXPECTED LIGHT WINDS AND EVENTUAL CLEAR SKIES.
RETAINED FROST/FREEZE HEADLINES.

FRIDAY...MOSTLY SUNNY SKIES WILL SUPPORT WARMER TEMPS WITH 50S
EXPECTED MOST LOCATIONS. TEMPS MAY BE AFFECTED BY SNOW COVER IN THE
BLACK HILLS...LEAVING MANY PLACES IN THE UPPER 30S LOW 40S THERE.
AFOREMENTIONED COLD POCKET ALOFT WILL SUPPORT STEEP LL LAPSE RATES
AND DESTABILIZATION FAR SE. HAVE ADDED A SLIGHT CHANCE FOR RAIN
SHOWERS EARLY FRI AFTERNOON THERE. SFC HIGH WILL SHIFT SE OF THE
REGION...SUPPORTING RETURN SOUTHERLY FLOW. SIG PRESSURE FALLS WILL
SUPPORT A LEE SIDE LLJ...WITH FLOW MIXING DOWN FRIDAY NIGHT ACROSS
NE WY/THE NORTHERN BH FOOTHILLS/AND POSSIBLY EASTERN BH FOOTHILLS.
ANOTHER COLD NIGHT IS EXPECTED...WITH LOWS BEING REACHED EARLY ON
FRIDAY NIGHT GIVEN INCREASING FLOW AND MIXING PROCESS OVERNIGHT.
HAVE LEFT FROST MENTION OUT OF THE GRIDS FRIDAY NIGHT SE AREAS GIVEN
CONCERNS ON MIXING. OTHERWISE...DRY WEATHER EXPECTED.

&&

.LONG TERM...SATURDAY THROUGH THURSDAY
ISSUED AT 214 PM MDT THU SEP 11 2014

MAINLY DRY WEATHER AND A WARMING TREND WILL CONTINUE
THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK AS A RIDGE BUILDS
ACROSS THE WESTERN STATES AND EVENTUALLY MOVES INTO THE PLAINS.
TEMPERATURES WILL RISE BACK TO NEAR AVERAGE LEVELS EARLY NEXT WEEK.
AN EXCEPTION TO THE DRY WEATHER WILL BE ON SUNDAY AND SUNDAY NIGHT.
ISOLATED SHOWERS ARE POSSIBLE MAINLY OVER SOUTH CENTRAL SD AS A
DISTURBANCE CROSSES THE AREA.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 532 PM MDT THU SEP 11 2014

COLD FRONT AND UPPER LEVEL SYSTEM ARE MOVING SLOWLY OFF TO THE
EAST AND SOUTHEAST THROUGH EASTERN WYOMING AND WESTERN SOUTH DAKOTA.
WIDESPREAD MVFR/IFR CONDITIONS WILL IMPROVE TO VFR FROM NORTH TO
SOUTH AS PRECIP GRADUALLY ENDS THROUGH THE LATE EVENING HOURS. VFR
CONDITIONS ARE EXPECTED THROUGH THE DAY FRIDAY.


&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM MDT FRIDAY FOR
     SDZ014-032-043-044.

     FREEZE WARNING FROM MIDNIGHT TONIGHT TO 8 AM MDT FRIDAY FOR
     SDZ001-002-012-013-025>027-030-031-041-042-072>074.

WY...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 8 AM MDT FRIDAY FOR
     WYZ054>056-058-071.

&&

$$

UPDATE...CARPENTER
SHORT TERM...JC
LONG TERM...13
AVIATION...CARPENTER






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