Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 262324
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
524 PM MDT TUE MAY 26 2015

.SHORT TERM...THIS EVENING THROUGH WEDNESDAY NIGHT
ISSUED AT 223 PM MDT TUE MAY 26 2015

SCATTERED INSTABILITY SHOWERS ONGOING OVER THE BLACK HILLS THIS
AFTERNOON WITH MORE ISOLATED ACTIVITY OVER NE WY. CONVECTION WILL
CONTINUE IN THESE LOCATIONS INTO THE EVENING. OTHERWISE...WEAK
SUBSIDENCE OVER MUCH OF THE SD PLAINS HAS ALLOWED FOR PARTLY TO
MOSTLY SUNNY SKIES THERE. UPPER LEVEL TROUGH OVER THE PAC NW WILL
REMAIN NEARLY STATIONARY IN THE PERIOD WITH AN ASSOCIATED FRONT
SIDE JET STREAK EXPECTED TO LIFT NE INTO THE REGION TONIGHT INTO
WEDNESDAY. THIS SYSTEM WILL INDUCE A FRONT SIDE LLJ WITH POS
THETA-E ADV ENSUING TONIGHT INTO WED. CONCENTRATED FORCING ALONG
THE WAA/POS THETA-E ADV ZONE WILL SUPPORT SCATTERED TO ISOLATED
SHRA/TS ACTIVITY OVER NE WY INTO NW SD INTO WED MORNING. DIURNAL
INSTABILITY AHEAD OF THE MID LEVEL JET STREAK WILL SUPPORT
INCREASING CHANCES FOR SHRA/TS OVER MUCH OF THE AREA
WEDNESDAY...ESP THE NORTHERN BLACK HILLS WHERE EDDY CONVERGE WILL
BE IN PLACE. EDDY CONVERGENCE COUPLED WITH AN ADVANCING SFC TROUGH
WILL BE THE PRIMARY FORCING MECHANISMS FOR SHRA/TS ACTIVITY WED
AFTERNOON. MEAN FORECAST SOUNDINGS SUGGEST A DEVELOPING AXIS OF
HIGHER CAPE FROM THE BH SE INTO SCENTRAL SD WITH 1000-1500 J/KG
POSSIBLE IN THIS AREA. BULK DEEP LAYER SHEAR REMAINS QUITE
MARGINAL WITH 25 TO 30 KNOTS FORECAST. OVERALL NOT THE BEST SETUP
FOR STRONG TO SEVERE STORMS. HOWEVER...CAN NOT RULE OUT A STRONGER
STORM OR TWO ESP IN THE NORTHERN BLACK HILLS AND THEN ACROSS
SCENTRAL SD ESP AFTER CIN BREAKS DOWN. LOCALIZED HEAVY RAINFALL
WILL ALSO BE POSSIBLE WITH ANY HEAVY CELLS GIVEN HIGH PW/S OVER AN
INCH AT MANY LOCATIONS ACROSS WESTERN SD. ADDED A HEAVY RAIN
MENTION TO MAINLY NW SD. UPPER IMPULSE AND MAIN LOBE OF ASCENT
WILL PUSH EAST WED EVENING WITH SHRA/TS CHANCES DIMINISHING. A
SECONDARY IMPULSE MAY BRING A FEW SHRA TO NE WY LATER WED NIGHT.
HOWEVER...CONFIDENCE IN SYSTEM STRENGTH AND RESULTING PRECIP
REMAINS LOW. DRIED MOST PLACES OUT WED NIGHT SAVE SOME LOW POPS
OVER NE WY.

.LONG TERM...THURSDAY THROUGH TUESDAY
ISSUED AT 223 PM MDT TUE MAY 26 2015

UPPER LEVEL LOW ACROSS THE NORTHERN ROCKIES WILL WEAKEN AND
SLOWLY CROSS THE NORTHERN PLAINS ON THURSDAY AND FRIDAY. SCATTERED
SHOWERS AND THUNDERSTORMS ARE EXPECTED THURSDAY AND THURSDAY
NIGHT...THEN GRADUALLY DISSIPATING FRIDAY AS DRIER AIR MOVES IN.
BY THE WEEKEND...BROAD RIDGING DEVELOPS WITH DRY WEATHER EXPECTED
AS HIGH PRESSURE BUILDS SOUTHWARD FROM CANADA. COOLER TEMPERATURES
ARE EXPECTED FOR THE WEEKEND. A WARM UP IS EXPECTED THE FOLLOWING
WEEK ALONG WITH A RETURN OF THUNDERSTORMS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 523 PM MDT TUE MAY 26 2015

ISOLATED/SCATTERED -SHRA/-TSRA OVER NORTHEAST WY/BLACK HILLS WILL
PERSIST TONIGHT AND THEN EXPAND OVER WESTERN SD WEDNESDAY. VFR
CONDITIONS EXPECTED OUTSIDE OF PRECIPITATION...WITH MVFR
CIGS/VSBYS NEAR ANY STORMS.

&&

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

$$

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



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