Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 220921
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
321 AM MDT WED APR 22 2015

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT
ISSUED AT 320 AM MDT WED APR 22 2015

CURRENT SURFACE ANALYSIS SHOWS CANADIAN HIGH PRESSURE SINKING
SOUTH INTO THE DAKOTAS...WITH FRONT SOUTH AND WEST OF THE FORECAST
AREA. UPPER LEVEL ANALYSIS SHOWS LARGE TROF OVER THE EASTERN
CONUS...WITH LOW OVER THE NORTHERN GREAT LAKES. RIDGING IN PLACE
TO THE WEST OF THE AREA...WITH AN UPPER LOW OVER SOUTHERN CA.
SKIES ARE MAINLY CLEAR ACROSS THE AREA WITH LIGHT WINDS AND TEMPS
RANGING FROM THE 30S OVER NORTHEAST WY TO THE UPPER TEENS AND 20S
OVER THE SD PLAINS.

MODELS ARE IN GOOD AGREEMENT ON GENERAL FEATURES OVER THE THE NEXT
COUPLE OF DAYS. AFTER A CHILLY START IN MANY AREAS...MILDER AIR WILL
CONTINUE TO BUILD IN FROM THE SOUTH AND WEST...WITH HIGHS INTO THE
60S IN MOST AREAS THIS AFTERNOON. SOME HIGHER CLOUDS WILL FILTER
INTO MOSTLY WESTERN PORTIONS OF THE CWA DURING THE DAY..BUT SKIES
SHOULD BE MOSTLY SUNNY. WINDS WILL BECOME EAST-SOUTHEAST LATER THIS
MORNING AS HIGH PRESSURE NOSES EAST OF THE AREA...REMAINING ON THE
LIGHTER SIDE THROUGH THE DAY...MOSTLY IN THE 10 TO 15 MPH RANGE THIS
AFTERNOON. LOWS WILL BE NEAR AVERAGE TONIGHT...IN THE 30S...UNDER
MOSTLY CLEAR TO PARTLY CLOUDY SKIES. SOUTHEASTERLY LOW LEVEL JET
WILL INCREASE OVERNIGHT OVER MOST OF THE CWA...BUT IS NOT EXPECTED
TO BE VERY STRONG. THIS WILL HELP TO KEEP WINDS UP AT TIMES OVER
NORTHEAST WY AND PORTIONS OF WESTERN SD...THOUGH NOTHING MORE THAN
OCCASIONALLY BREEZY.

THURSDAY WILL START OFF WITH SOME SUN IN MANY AREAS EARLY...BUT
CLOUDS WILL INCREASE THROUGH THE LATE MORNING AND AFTERNOON AS
WEAKENING RIDGE MOVES OVER THE AREA AND SHORTWAVE ENERGY APPROACHES.
HIGHS WILL AGAIN BE IN THE 60S...WITH SOUTHEASTERLY WINDS BECOMING
RATHER BREEZY ACROSS THE SD PLAINS AHEAD OF APPROACHING LOW
PRESSURE. CHANCES FOR SHOWERS WILL INCREASE IN THE AFTERNOON FROM
THE SOUTH AND WEST. A FEW THUNDERSTORMS ARE ALSO EXPECTED...
ESPECIALLY OVER NORTHEAST WY AND SOUTHWEST SD...AS LOW LEVEL
MOISTURE INCREASES. CAPE VALUES PROGGED AT 500 T0 1000 J/KG AND
DECENT SHEAR COULD SUPPORT A STRONGER STORM OR TWO LATER IN THE
AFTERNOON OVER NORTHEAST WY AND SOUTHWEST SD...WITH SMALL HAIL AND
GUSTY WINDS POSSIBLE, WIDESPREAD CHANCES FOR SHOWERS AND ISOLATED
THUNDERSTORMS CAN BE EXPECTED IN THE EVENING AS WEAKENING LOW
PRESSURE AND SHORTWAVE CROSS THE AREA. ACTIVITY WILL TAPER OFF
OVERNIGHT.

.LONG TERM...FRIDAY THROUGH TUESDAY
ISSUED AT 320 AM MDT WED APR 22 2015

UPPER LEVEL SHORTWAVE CROSSES THE NORTHERN PLAINS FRIDAY. WITH
WEAK FORCING AND STEEP MID LEVEL LAPSE RATES...SCATTERED SHOWERS
EXPECTED. ISOLATED THUNDERSTORMS POSSIBLE ACROSS NORTHEAST WYOMING
INTO SOUTHWEST SOUTH DAKOTA.

GFS/GEM/ECMWF TRENDING TOWARDS STRONG UPPER TROF DIGGING FROM THE
PACIFIC NORTHWEST THROUGH THE CENTRAL ROCKIES THIS WEEKEND. UPPER
FLOW SPLITS...WITH LOW CLOSING OFF OVER THE SOUTHERN PLAINS AND
WEAKER NORTHERN STREAM TROF SLIDING THROUGH THE NORTHERN PLAINS.
MODELS IN DECENT AGREEMENT WITH PRECIPITATION POTENTIAL FOR THE
WEEKEND INTO MONDAY. THERMAL PROFILES SUPPORT POTENTIAL FOR
RAIN/SNOW MIX IN HIGHER ELEVATION OF THE BLACK HILLS...MAINLY AT
NIGHT. UPPER LEVEL RIDGE BUILDS ACROSS THE ROCKIES EARLY NEXT
WEEK...WITH DRY WEATHER AND WARMER TEMPERATURES.

&&

.AVIATION...FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING
ISSUED AT 320 AM MDT WED APR 22 2015

VFR CONDITIONS WILL CONTINUE THROUGH TONIGHT.

&&

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

$$

SHORT TERM...26
LONG TERM...7
AVIATION...7



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