Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 030523
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1123 PM MDT SAT MAY 2 2015

.SHORT TERM...THIS EVENING THROUGH SUNDAY NIGHT
ISSUED AT 222 PM MDT SAT MAY 2 2015

UPPER LEVEL SHORTWAVE TROUGH NOW TRAVERSING THE NORTHERN PLAINS
WITH AN ASSOCIATED SFC TROUGH EXTENDING SOUTH ACROSS THE EASTERN
FA. DIURNAL HEATING COUPLED WITH SUFFICIENT LL MOISTURE WILL
CONTINUE TO SUPPORT ML CAPES IN EXCESS OF 1000 J/KG ALONG AND
AHEAD OF THE TROUGH...WITH ISOLD SHRA/TS EXPECTED THROUGH EVENING
THERE. A FEW STRONG STORMS WITH SMALL HAIL AND GUSTY WINDS WILL BE
POSSIBLE IN THIS PULSE ENV WITH NEGLIGIBLE DEEP LAYER SHEAR. UPPER
LEVEL JET STREAM WILL SLIDE SE ACROSS ND WITH A HIGH CENTERED WEAK
FGEN RESPONSE DEVELOPING LATE TONIGHT ACROSS THE FAR NW. HAVE
INCLUDED A LOW POP FOR THIS. OTHERWISE...DRY WX EXPECTED ACROSS
THE MAJORITY OF THE FA TONIGHT.

SUNDAY...LL FLOW WILL VEER N-E THROUGH THE DAY WITH UPSLOPE
CONVERGENT FLOW DEVELOPING OVER NE WY AND THE WESTERN BH BY
AFTERNOON. DIURNAL HEATING WILL SUPPORT WEAK INSTABILITY OVER THIS
AREA...ALLOWING ISOLD/SCT SHRA/TS WITH THE BEST CHANCES OVER THE
HIGHER TERRAIN OF THE WESTERN BH. BETTER CHANCES FOR PRECIP WILL
DEVELOP OVER THE WESTERN HALF OF THE FA SUNDAY NIGHT AS DEEPER
MOISTURE TRANSPORT ENSUES PER THE EJECTING SW CONUS UPPER LOW.
LINGERING LL BAROCLINIC ZONE IN PLACE OVER THE REGION WITH A GRAZING
NORTHERN STREAM IMPULSE WILL PROVIDE SUFFICIENT LIFT AND FORCING.
HENCE...HAVE INCREASED POPS TO HIGHER CHANCE FOR THIS AREA...WITH
THE BEST CHANCE BEING LATE SUNDAY NIGHT WITH POTENTIAL ADDED LIFT
FROM A PASSING UPPER JET STREAK. OTHERWISE..COOLER CONDS CAN BE
EXPECTED WITH HIGHS IN THE 60S NW HALF...WITH 70S SCENTRAL SD.

.LONG TERM...MONDAY THROUGH SATURDAY
ISSUED AT 222 PM MDT SAT MAY 2 2015

NEARLY ZONAL UPPER FLOW WILL CONTINUE INTO TUESDAY WITH
NEAR TO SLIGHTLY ABOVE AVERAGE TEMPERATURES IN THE 60S AND LOWER
70S. SEVERAL DISTURBANCES EMBEDDED IN THE FLOW WILL BRING DAILY
CHANCES FOR SHOWERS AND THUNDERSTORMS...ESPECIALLY DURING THE
AFTERNOON/EVENING HOURS. BREEZY SOUTHEASTERLY RETURN FLOW IS ALSO
THROUGH TUESDAY AS HIGH PRESSURE SLIDES OVER MN.

UPPER FLOW THEN BECOMES SOUTHWESTERLY BY MID WEEK AS A DEEP
TROUGH DEVELOPS OVER THE WESTERN CONUS. BOTH GFS/ECMWF CONTINUE TO
SHOW A STRONG DISTURBANCE EJECTING INTO THE CENTRAL/NORTHERN
PLAINS WHICH WOULD BRING INCREASING CHANCES FOR
PRECIPITATION...BUT THE TIMING HAS BECOME A LITTLE FASTER INTO THE
TUE NIGHT TO WED NIGHT TIME FRAME. GFS AND ECM ARE SHOWING AROUND
AN INCH OF QPF FOR MANY LOCATIONS ACROSS WRN SD. NOW BOTH MODELS
ARE SHOWING THE MAIN UPPER LOW BECOMING NEGATIVELY TILTED NEXT
SATURDAY JUST W/SW OF THE CWA. IF THIS PANS OUT...THIS MAIN SYSTEM
COULD BRING ANOTHER INCH OR MORE OF QPF.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1121 PM MDT SAT MAY 2 2015

VFR CONDITIONS WILL PERSIST THROUGH EARLY SUNDAY AFTERNOON.
-SHRA/-TSRA WILL DEVELOP LATER SUNDAY AFTERNOON OVER THE HIGHER
TERRAIN AND THEN OVER NORTHEAST WY/SOUTHWEST SD SUNDAY NIGHT WITH
LOCAL MVFR CONDITIONS.

&&

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

$$

SHORT TERM...JC
LONG TERM...13
AVIATION...HELGESON


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