Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 060518
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1118 PM MDT SAT JUL 5 2014

.UPDATE...
ISSUED AT 806 PM MDT SAT JUL 5 2014

00Z KUNR SOUNDING SHOWED SIGNIFICANT CIN THIS EVENING. ISOLATED
TSRA WERE ABLE TO POP UP IN FAR NORTHWEST SD NEAR A WEEK COOL
FRONT...PLUS SHORTWAVE MOVING ACROSS ND. FORCING IS SHIFTING EAST
AND IT LOOKS LIKE PRECIPITATION CHANCES HAVE DROPPED TO THE
UNMENTIONABLE LEVEL...SO HAVE DROPPED FROM OVERNIGHT FORECAST.

&&

.SHORT TERM...THIS EVENING THROUGH SUNDAY NIGHT
ISSUED AT 154 PM MDT SAT JUL 5 2014

THE NORTHERN PLAINS WILL REMAIN ON THE NORTHERN PERIPHERY OF A
BROAD UPPER RIDGE THROUGH THE PERIOD...WITH MID LEVEL IMPULSES
TRAVERSING THE NORTHERN CONUS ON THE EQUATORIAL SIDE OF FASTER MID
LEVEL FLOW. ONCE SUCH IMPULSE IS IN THE PROCESS OF ADVANCING EAST
ACROSS THE REGION AND WILL SUPPORT ISOLD TS ACROSS NW SD INTO THE
BLACK HILLS THIS AFTERNOON AND EVENING...EVENTUALLY FORCING A SFC
TROUGH THROUGH THE AREA OVERNIGHT. MAINLY QUIET WEATHER EXPECTED
SUNDAY WITH LARGE SCALE SUBSIDENCE OVER THE REGION...ALTHOUGH
INSOLATION MIXED WITH RESIDUAL LL MOISTURE MAY PROVIDE ENOUGH
INSTABILITY FOR A SHRA/TS OVER THE BLACK HILLS LATE SUNDAY
AFTERNOON. ANOTHER SMALL SCALE IMPULSE WILL ADVECT THROUGH THE
REGION SUNDAY NIGHT...POSSIBLY SUPPORTING A FEW SHRA/TS IN A POS
THETA-E ADV REGIME AHEAD OF THE WAVE.

TONIGHT...ISOLD TS WILL BE POSSIBLE LATE THIS AFTERNOON AND EVENING
NW SD AND THE BLACK HILLS...WITH RAIN CHANCES QUICKLY TRENDING EAST
THIS EVENING. UPPER LEVEL IMPULSE ADVECTING THROUGH SOUTHERN CANADA
WITH A WEAK SOUTHWARD EXTENSION OVER SOUTH DAKOTA MAY PROVIDE ENOUGH
UPPER LEVEL SUPPORT FOR CONVECTION. SUFFICIENT ML CAPE WILL BE IN
PLACE OVER THIS AREA WITH 1500-3500 J/KG. IN ADDITION...INCREASED
MID LEVEL FLOW ASSOCIATED WITH THE PASSING IMPULSE WILL SUPPORT AN
UPTICK IN DEEP LAYER SHEAR...WITH 30 TO 35 KNOTS OF 0-6 KM BULK
SHEAR BY EARLY THIS EVENING. IF STORMS DO FIRE AND ARE ABLE TO ROOT
IN THE BL...A SEVERE STORM OR TWO WOULD BE POSSIBLE...ESP ACROSS FAR
NW SD. THIS IMPULSE WILL FORCE A SFC TROUGH/COOL FRONT INTO THE FA
OVERNIGHT...WITH WINDS VEERING NW AND INCREASING...ESP ACROSS NW SD.
DRIER AIR WILL PUSH INTO THE REGION...WITH THE LL THERMAL RIDGE
SHIFTING EAST OF THE FA.

SUNDAY...LARGE SCALE SUBSIDENCE WILL SPREAD OVER THE AREA...WITH
GENERALLY NORTHERLY FLOW ALL PLACES HELPING TO ADVECT DRIER AIR INTO
THE FA. DRY WEATHER EXPECTED NEARLY ALL OF THE FA. HOWEVER...DIURNAL
HEATING AND RESULTING MID-RIDGE CONVERGENCE...COUPLED WITH WEAK
SOUTHERN HILLS CONVERGENT FLOW MAY BE ENOUGH TO FORCE A SHRA OR TS
LATE IN THE AFTERNOON AT PEAK HEATING. GIVEN ONGOING MOIST
CONDITIONS...RETAINED A LOW POP MENTION CENTRAL/SOUTHERN BH. WARM
CONDITIONS EXPECTED AGAIN TOMORROW...ALTHOUGH QUELLED SOME FROM
TODAY/S NUMBERS PER TONIGHT/S SFC TROUGH. SLIGHTLY BETTER
CHANCES/COVERAGE FOR SHRA/TS SUNDAY NIGHT FROM NE WY INTO SCENTRAL
SD WITH THE NEXT IMPULSE. ELEVATED POS THETA-E ADV WITH ENHANCED
SOUTHERLY FLOW UNDER STEEP LL LAPSE RATES WILL BE SUFFICIENT FOR
ISOLD TO SCT SHRA/TS LATE SUNDAY NIGHT. ADDED A LOW POP FOR THIS.

&&

.LONG TERM...MONDAY THROUGH SATURDAY
ISSUED AT 154 PM MDT SAT JUL 5 2014

UNSETTLED WEATHER IS EXPECTED ON MONDAY AS NORTHWEST FLOW ALOFT
DEVELOPS ACROSS THE REGION AND A COOL FRONT EVENTUALLY SINKS SOUTH
OF THE AREA. NORTHWESTERLY FLOW WILL REMAIN PERSISTENT THROUGH MUCH
OF THE WEEK...WITH OCCASIONAL DISTURBANCES BRINGING CHANCES FOR
SHOWERS AND THUNDERSTORMS AT TIMES THROUGH MUCH OF THE WEEK.
TEMPERATURES WILL BE NEAR AVERAGE THROUGH AT LEAST MIDWEEK...WITH A
BIT OF A WARMING TREND LIKELY TOWARD THE END OF THE WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1117 PM MDT SAT JUL 5 2014

VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD. ISOLATED TSRA ARE
POSSIBLE OVER THE HIGHER TERRAIN LATER SUNDAY AFTERNOON.

&&

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

$$

UPDATE...HELGESON
SHORT TERM...JC
LONG TERM...26
AVIATION...HELGESON




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