Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 051718
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1118 AM MDT SUN JUL 5 2015

.UPDATE...
ISSUED AT 937 AM MDT SUN JUL 5 2015

CURRENT SURFACE ANALYSIS SHOWS LOW PRESSURE OVER WESTERN SD...WITH
COLD FRONT STRETCHING FROM CENTRAL ND...THROUGH THE BLACK HILLS
AREA...AND INTO NORTHEAST AND CENTRAL WY. UPPER LEVEL ANALYSIS
SHOWS LOW PRESSURE OVER CENTRAL CANADA...WITH ZONAL FLOW ACROSS
THE NORTHERN PLAINS. ONE SHORTWAVE IS MOVING ACROSS ND AND
NORTHERN SD THIS MORNING...WHILE THE NEXT WAVE OVER WY WILL MOVE
EAST ACROSS OUR CWA THIS AFTERNOON AND EVENING. KUDX RADAR SHOWS
SCATTERED SHOWERS AND THUNDERSTORMS OVER NORTHWEST SD...WITH SOME
ACTIVITY STARTING TO DEVELOP FURTHER SOUTH AND WEST NEAR THE COLD
FRONT OVER THE BLACK HILLS AND NORTHEAST WY. SKIES RANGE FROM
MAINLY SUNNY OVER SOUTH CENTRAL SD TO MOSTLY CLOUDY OVER FAR
NORTHEAST WY AND NORTHWEST SD. WITH THE FRONT AND VARIABLE
CLOUDINESS ACROSS THE AREA...TEMPS RIGHT NOW RANGE FROM THE UPPER
60S ACROSS NORTHWEST SD TO THE LOWER 80S ACROSS FAR SOUTHERN SD.
WINDS ARE BREEZY FROM THE NORTHWEST BEHIND THE FRONT...WITH SOUTH
TO SOUTHEAST WINDS AHEAD OF THE FRONT.

MINOR UPDATE WAS ISSUED TO MAKE SOME ADJUSTMENTS TO TEMPS...
WIND,,,AND CLOUD COVER THROUGH THE AFTERNOON. HIGHS WILL BE TRICKY
ALONG AND BEHIND THE FRONT TODAY AS IT SLOWLY MOVES SOUTH AND
EAST...GENERALLY RANGING FROM THE 70S OVER MOST OF NORTHEAST WY
AND NORTHWEST SD TO THE LOWER 90S OVER SOUTH CENTRAL SD. THE RISK
OF SEVERE STORMS WILL STILL BE GREATEST NEAR AND AHEAD OF THE
FRONT...GENERALLY FROM THE BLACK HILLS SOUTH AND EASTWARD...THIS
AFTERNOON INTO THIS EVENING.

&&

.SHORT TERM...TODAY THROUGH MONDAY NIGHT
ISSUED AT 242 AM MDT SUN JUL 5 2015

08Z SURFACE ANALYSIS HAD COLD FRONT FROM NORTHEAST ND INTO
SOUTHWEST MT WITH LOW PRESSURE DEVELOPING OVER SOUTH CENTRAL MT
NEAR THE FRONT AND TROUGH FROM THE LOW INTO CENTRAL NE. NOCTURNAL
LOW LEVEL JET PUSHING EAST EARLY THIS MORNING WITH MAIN THETA-E
ADVECTION OVER EASTERN SD/CENTRAL NE ALLOWING TSRA TO END OVER THE
CWA. STILL MIGHT BE AN ELEVATED STORM THROUGH 12Z OVER CENTRAL SD.

TODAY/TONIGHT...ATTENTION TURNS TO COLD FRONT/LOW. LATEST WATER
VAPOUR LOOP HAD UPPER TROUGH MOVING SOUTHEAST OUT OF CENTRAL CANADA
AND THEN ACROSS THE US/CANADIAN BORDERS OF MT/ND. LIFT UNDER RIGHT
ENTRANCE REGION OF 120KT JET SUPPORTING ACTIVE CONVECTION ACROSS
NORTHEAST MT AT 0830Z...WHICH WILL HEAD INTO WESTERN ND THIS
MORNING...MAINLY NORTH OF THE CWA. CONVECTION WILL LIKELY PUT OUT AN
OUTFLOW BOUNDARY...WHICH WILL PUSH COLD FRONT INTO NORTHWEST REACHES
OF CWA THIS MORNING. UPPER LEVEL DIVERGENCE UNDER RIGHT ENTRANCE
REGION OF JET WILL ENHANCE SURFACE LOW ALONG COLD FRONT...WHICH WILL
SLIP TO I-90 EARLY THIS AFTERNOON WITH LOW NEAR KRAP. VERY
WARM/MOIST AIR AHEAD OF LOW WILL POOL ALONG BOUNDARY WITH 2-4KJ/KG
MLCAPE AND 25-50J/KG MLCIN. EFFECTIVE 0-6KM BULK SHEAR AROUND 20M/S
EXPECTED ALONG BOUNDARY. AS CAP BREAKS ALONG/AHEAD OF FRONT...EXPECT
SUPERCELLS TO DEVELOP EARLY THIS AFTERNOON. GIVEN STRENGTH OF
INSTABILITY...VERY LARGE HAIL POSSIBLE. TORNADO THREAT IS THERE
GIVEN NORTHEAST BOUNDARY LAYER FLOW BEHIND COLD FRONT...ELONGATING
HODOGRAPHS IF SUPERCELLS ARE POST FRONTAL...WHICH IS A DISTINCT
POSSIBILITY GIVEN SETUP...BUT MLLCL/S FAIRLY HIGH EXCEPT FOR
FAVORED AREA JUST EAST/NORTHEAST OF SURFACE LOW. ACTIVITY WILL
SLOWLY GROW UPSCALE LATE THIS AFTERNOON/EARLY THIS EVENING AND
MORPH INTO A POTENTIALLY STRONG FORWARD PROPAGATING MCS OVER
CENTRAL INTO EASTERN SD WITH ENHANCED WIND THREAT. GIVEN
PARAMETERS...ENHANCED RISK OF SEVERE WEATHER LOOKS ON TARGET EAST
OF RAPID CITY. COLD FRONT PUSHES SOUTHEAST OF CWA TONIGHT WITH A
PERIOD OF GUSTY NORTH/NORTHEAST WINDS BEHIND IT THIS
AFTERNOON/EARLY THIS EVENING. TEMPERATURES WILL BE TRICKY GIVEN
FRONTAL POSITION.

MONDAY...HIGH PRESSURE BUILDS INTO THE CWA WITH DRIER CONDITIONS ON
TAP.

.LONG TERM...TUESDAY THROUGH SATURDAY
ISSUED AT 242 AM MDT SUN JUL 5 2015

GENERALLY DRY WEATHER WILL CONTINUE INTO TUESDAY AS STRONG HIGH
PRESSURE SHIFTS EAST INTO THE UPPER MIDWEST. RETURN FLOW ACROSS NE
WY AND FAR WRN SD WILL BRING BACK SOME CHANCES OF STORMS TUE
AFTN/NGHT. BROAD CYCLONIC FLOW IS PROGGED TO DEVELOP ACROSS THE
REGION WED AND THU WITH DAILY CHANCES FOR STORMS. TEMPERATURES
WILL BE NEAR AVERAGE. MODELS ARE DIVERGING GREATLY FOR THE END OF
THE WEEK WITH HOW AN UPPER LOW OVER CA WILL PHASE BACK INTO THE
MAIN FLOW. THE WETTER SOLUTION IS THE GFS WHICH HAS MOST OF THE
ENERGY PUSHING WITHIN THE SW FLOW INTO THE NRN PLAINS. THE ECMWF
KEEP STRONG UPPER RIDGING CENTERED ACROSS THE SRN PLAINS WHICH
KEEPS THE REMNANT LOW PUSHING NE THRU THE NRN ROCKIES...ALONG WITH
THE BEST CHANCES FOR STORMS.

&&

.AVIATION...FOR THE 18Z TAFS THROUGH 18Z MONDAY
ISSUED AT 1116 AM MDT SUN JUL 5 2015

A STRONG COLD FRONT WILL CONTINUE TO CROSS THE AREA TODAY. WITH
THIS FRONT...NUMEROUS SHRA/TSRA WILL DEVELOP WITH SOME SEVERE
STORMS. MVFR/IFR CONDITIONS ARE EXPECTED WITH THE STRONG STORMS AS
WELL AS STRONG AND ERRATIC WIND GUSTS. STORM ACTIVITY WILL END
THROUGH THE NIGHT AS COOLER AND DRIER AIR MOVES IN FROM THE
NW...LEADING TO VFR CONDITIONS.


&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

UPDATE...26
SHORT TERM...HELGESON
LONG TERM...13
AVIATION...MLS



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