Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 220915
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
315 AM MDT TUE APR 22 2014

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT
ISSUED AT 315 AM MDT TUE APR 22 2014

CURRENT SURFACE ANALYSIS SHOWS HIGH PREESURE OVER THE EASTERN
DAKOTAS...WITH LOW PRESSURE DEVELOPING OVER NORTHERN ID. A WARM
FRONT STRETCHES FROM THE LOW ACROSS MT INTO WESTERN SD. UPPER
LEVEL ANALYSIS SHOWS RIDGING OVER THE NORTHERN AND CENTRAL HIGH
PLAINS...WITH TROF AND AREA OF LOW PRESSURE ALONG THE PACIFIC NW
COAST. SKIES ARE MOSTLY CLEAR IN MOST AREAS...WITH SOME HIGH
CLOUDS NOW MOVING INTO NORTHERN AND WESTERN PORTIONS OF THE CWA.
TEMPS ARE MOSTLY IN THE 40S...WITH SOUTH TO SOUTHEAST WINDS AT
MOST LOCATIONS...BREEZY AT TIMES OVER NORTHEAST WY AND FAR
SOUTHWEST SD.

ANOTHER WARM DAY IS ON TAP BEFORE A COOLDOWN TO MORE SEASONABLE
TEMPS TAKES PLACE AGAIN FROM WEST TO EAST WEDNESDAY INTO WEDNESDAY
NIGHT. CHANCES FOR SHOWERS AND THUNDERSTORMS OVER THE NEXT COUPLE
OF DAYS WILL BE MINIMIZED IN MOST AREAS AS THE VARIOUS MODELS ARE
IN GOOD AGREEMENT NOW THAT THE UPPER LEVEL SYSTEM CROSSING THE
REGION WILL TAKE A MORE NORTHERLY TRACK AND KEEP US ON THE DRIER
AND WINDY SIDE OF THE SYSTEM.

FOR TODAY...SKIES WILL BE PARTLY CLOUDY IN GENERAL...WITH THE MOST
SUN IN THE MORNING. THE UPPER LEVEL RIDGE OVER THE AREA WILL SHIFT
EAST DURING THE DAY...WITH SOUTHWEST FLOW DEVELOPING OVER WESTERN
AREAS BY THE AFTERNOON. THIS WILL ALLOW WEAK SHORTWAVE ENERGY TO
MOVE NORTHEAST INTO THE AREA DURING THE AFTERNOON AND EVENING. AT
THE SURFACE...LOW PRESSURE WILL MOVE EAST ACROSS MT AND STRENGTHEN
SOME...ALLOWING THE PRESSURE GRADIENT TO CONTINUE TO TIGHTEN OVER
THE DAKOTAS. SOUTH TO SOUTHEAST WINDS WILL GRADUALLY INCREASE
THROUGH THE MORNING...WITH THE STRONGEST WINDS FROM NORTHWEST
INTO CENTRAL SD BY THE AFTERNOON. SUSTAINED 20 TO 30 MPH AND GUSTS
TO 40 MPH ARE EXPECTED FROM BUFFALO...SOUTHEAST TO THE WINNER AREA
IN THE AFTERNOON. WARM FRONT WILL SLOWLY LIFT INTO NORTHERN SD
DURING THE DAY...ALLOWING FOR HIGHS IN THE 70S AND LOWER 80S ACROSS
MUCH OF THE CWA....WARMEST TO THE SOUTHEAST OF THE BLACK HILLS.
SHOWER AND THUNDERSTORM ACTIVITY LATER THIS AFTERNOON AND EVENING
SHOULD MOSTLY BE ISOLATED IN NATURE...STARTING OFF ACROSS NORTHEAST
WY AND SOUTHWEST SD AND MOVING NORTHEAST THROUGH THE EVENING. THE
THREAT FOR SEVERE THUNDERSTORMS CONTINUES TO LOOK RATHER LOW...WITH
CAPE VALUES PROGGED NEAR OR BELOW 500 J/KG...BUT A STRONG STORM OR
TWO WITH GUSTY WINDS AND SMALL HAIL IS POSSIBLE...ESPECIALLY OVER
NORTHEASTERN WY AND WESTERN SD LATE TODAY/EARLY EVENING. SOUTHERLY
LOW LEVEL JET WILL STRENGTHEN OVER THE CENTRAL DAKOTAS OVERNIGHT AND
COULD HELP TO KEEP ACTIVITY GOING OVER FAR EASTERN PORTIONS OF THE
CWA INTO THE LATE NIGHT HOURS.

BY WEDNESDAY MORNING...UPPER LOW IS FORECAST TO BE OVER NORTHWEST
MT...WITH TROF COVERING THE NORTHERN ROCKIES. THE LOW WILL MOVE EAST
ALONG THE CANADIAN/MT BORDER WEDNESDAY AND WEDNESDAY NIGHT...
REACHING SOUTHEAST SK/NORTHWEST ND AREA BY THURSDAY MORNING. PACIFIC
COLD FRONT WILL BE OVER EASTERN MT INTO NORTHEAST WY EARLY WEDNESDAY...
THEN TRACK EAST ACROSS THE CWA DURING THE DAY. WEST TO NORTHWEST
WINDS WILL INCREASE FROM WEST TO EAST...WITH THE STRONGEST WINDS
GENERALLY EXPECTED OVER THE WESTERN SD PLAINS DURING THE LATE
MORNING AND AFTERNOON HOURS. A WIND ADVISORY MAY BE NEEDED FOR
SOME AREAS OF WESTERN SD...BUT STILL PLENTY OF UNCERTAINTY WITH
THAT AT THIS POINT. HIGHS WILL RANGE FROM THE UPPER 50S OVER
NORTHEAST WY TO THE UPPER 70S OVER FAR SOUTH CENTRAL SD. THE BEST
CHANCES FOR PCPN ON WEDNESDAY WILL BE OVER NORTHEAST WY EARLY IN
THE DAY AND TOWARD CENTRAL SD LATER IN THE DAY AS THR FRONT
ARRIVES. LOOKS LIKE THE REST OF THE AREA WILL BE IN THE DRY
SLOT...WITH DRIER AIR PUSHING IN QUICKLY BEHIND THE FRONT. A
THUNDERSTORM OR TWO IS POSSIBLE ACROSS SOUTH CENTRAL SD AS THE
FRONT MOVES THROUGH...WITH THE MAIN THREAT FOR STRONGER STORMS
STAYING SOUTHEAST OF THE CWA. MAINLY DRY CONDITIONS ARE EXPECTED
WEDNESDAY NIGHT...WITH MORE SEASONABLE TEMPS EXPECTED.

&&

.LONG TERM...THURSDAY THROUGH MONDAY
ISSUED AT 315 AM MDT TUE APR 22 2014

GENERALLY MILD CONDITIONS WILL PREVAIL ON THU AND FRI AS UPPER
LOW SHIFTS EWD ALONG THE CNDN BORDER AND TRANSITORY UPPER RIDGE
CROSSES THROUGH THE ROCKIES INTO THE PLAINS. COULD BE SOME -SHRA
ACRS THE WRN CWFA THU BEFORE DRIER AIR WORKS IN. WINDY CONDITIONS
EXPECTED THU AS UPPER LOW PASSES TO OUR NORTH.

FOCUS THEN TURNS TO A STRONG TROF WORKING THROUGH THE WEST EARLY IN
THE WEEKEND...AND INTO THE PLAINS LATER IN THE WEEKEND AND EARLY
NEXT WEEK. THE ECMWF/GFS/GEM ALL SHOW AN UPPER LOW TRACKING THROUGH
THE CNTRL ROCKIES SAT/EARLY SUN AND INTO THE CNTRL/NRN PLAINS
SUN/MON. WDSPRD PCPN LOOKING QUITE LIKELY BY LATE IN THE
WEEKEND...WITH LATEST THERMAL PROFILES BOOSTING CONFIDENCE THAT
TEMPS SHOULD BECOME QUITE COLD...20 DEGREES OR MORE BELOW AVERAGE
FOR HIGH TEMPS. THIS COULD LEAD TO SOME ACCUMULATING SNOW...BUT IT
REMAINS MUCH TOO EARLY TO KNOW HOW MUCH AND WILL BE DEPENDENT ON THE
EXACT TRACK OF THE UPPER LOW. STAY TUNED.

&&

.AVIATION...FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING
ISSUED AT 315 AM MDT TUE APR 22 2014

AN UPPER LEVEL DISTURBANCE WILL ROTATE THROUGH THE REGION LATE
THIS AFTN AND TONIGHT...BRINGING A CHANCE OF SOME HIGH BASED
SHOWERS/TSTMS CONTAINING BRIEF MVFR VSBYS. OTHERWISE...VFR
CONDITIONS WILL PREVAIL NEXT 24 HOURS.

&&

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

$$

SHORT TERM...26
LONG TERM...JOHNSON
AVIATION...JOHNSON





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