Area Forecast Discussion
Issued by NWS Rapid City, SD

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131
FXUS63 KUNR 070510
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1010 PM MST SAT FEB 6 2016

.UPDATE...
ISSUED AT 722 PM MST SAT FEB 6 2016

00Z KUNR SOUNDING MIXED TO ABOUT 500MB SAVE FOR A MODEST FRONTAL
INVERSION AROUND 750MB. INITIAL ISALLOBARIC FORCING BEHIND COLD
FRONT QUITE VIGOROUS WITH MANY REPORTS OF HIGH WINDS. WATER VAPOUR
LOOP SHOWED WELL DEFINED SHORTWAVE ZIPPING ACROSS THE EASTERN
DAKOTAS WITH EXCELLENT SUBSIDENCE/DRYING BEHIND IT. SURFACE LOW
WAS LOCATED OVER SOUTHERN MB AT 02Z...WHICH WILL MAINTAIN TIGHT
GRADIENT OVER THE CWA THROUGH SUNDAY...BUT PARTIAL DECOUPLING WILL
OCCUR REST OF THE NIGHT UNTIL SHORTWAVE CURRENTLY OVER SOUTHERN
AB/SK STIRS THINGS UP AGAIN FOR SUNDAY WITH HIGH WINDS LIKELY OVER
MOST OF WESTERN SD.

CURRENT HEADLINES IN GOOD SHAPE...BUT WILL TWEAK FORECAST FOR
LATEST WIND/CLOUD COVER TRENDS.

&&

.SHORT TERM...THIS EVENING THROUGH SUNDAY NIGHT
ISSUED AT 132 PM MST SAT FEB 6 2016

VERY POTENT BUT COMPACT SHORTWAVE CONTINUES TO TRAVERSE THE
NORTHERN PLAINS WITH A SFC COLD FRONT QUICKLY ADVECTING SE TOWARD
THE FA. THIS SYSTEM WILL BRING VERY STRONG WINDS TO THE REGION FOR
A PROLONGED PERIOD OF TIME /TONIGHT INTO SUN EVENING/. INITIAL
ROUND OF PRESSURE RISES AND CAA WILL ENSUE LATE THIS
AFTERNOON/EVENING...SUPPORTING A PERIOD OF STRONG WINDS. DIURNAL
BL COOLING WILL SUBDUE WINDS MOST PLACES OUTSIDE OF TERRAIN
ENHANCED AREAS THROUGH TONIGHT. A SECONDARY BACKSIDE IMPULSE WILL
DIRECT RE-NEWED PRESSURE RISES ACROSS THE REGION SUN
MORNING,...WITH DIURNAL HEATING ALLOWING MIXING OF STRONGER
MOMENTUM TO THE SFC. BUFR PROFILES SUGGEST VERY STRONG WINDS WITH
MIXING POTENTIALS SUPPORTING SUSTAINED WINDS OF 35 TO 45 MPH WITH
GUSTS IN THE 70S/S MPH. WOULD NOT BE SURPRISED TO SEE WINDS GUSTS
OVER 80 MPH IN FAR NW SD AND IN THE LEE OF THE BH GIVEN FLOW
ENHANCEMENT AROUND THE HILLS. STRONGEST WINDS ARE EXPECTED IN THE
LATE SUNDAY MORNING TO MID AFTERNOON PERIOD. LEFT ALL HEADLINES AS
IS.

AS FOR PRECIP WITH THIS SYSTEM...VERY DRY PROFILES PER RAOB
ANALYSIS CONFIRMS DISMAL QPF OUTPUT FROM MODELS. RETAIN A LOW
CHANCE MENTION IN THE HILLS WHERE UPSLOPE FORCING MAY SQUEEZE A
FEW SNOW SHOWERS. OTHERWISE...A FEW CONVECTIVE SHOWERS IN THE
SYSTEM COLD POOL MAY CLIP FAR EASTERN SCENTRAL SD SUN AFTERNOON.

.LONG TERM...MONDAY THROUGH SATURDAY
ISSUED AT 132 PM MST SAT FEB 6 2016

THE STRONG WINDS FROM SUNDAY WILL BEGIN TO DIE DOWN DURING THE
DAY MONDAY AS THE PRESSURE GRADIENT RELAXES AND HIGH PRESSURE
BUILDS INTO THE REGION. THE EXTENDED FORECAST LOOKS TO BE MAINLY
DRY AS A HIGHLY AMPLIFIED TROUGH AND RIDGE SET UP IN THE EAST AND
WEST CONUS...RESPECTIVELY. THIS WILL GIVE WAY TO NORTHWESTERLY
FLOW ALOFT AND LARGE SCALE SUBSIDENCE FOR THE CENTRAL CONUS.
TEMPERATURES WILL ALSO WARM UP CONSIDERABLY BY MID WEEK AS UPPER
LEVEL RIDGING BUILDS INTO THE AREA.

THE NEXT CHANCE FOR ANY PRECIPITATION MAY NOT OCCUR UNTIL LATE
THURSDAY AND FRIDAY...AS NWP GUIDANCE FORECASTS A WEAK SHORTWAVE
EMBEDDED WITHIN THE NORTHWESTERLY FLOW ALOFT TO CLIP NORTHERN AND
EASTERN PORTIONS OF THE CWA. AROUND THIS SAME TIME...AN ARCTIC FRONT
WILL BEGIN MOVING INTO THE REGION FROM THE NORTHEAST. GFS FORECAST
SOUNDINGS SUGGEST FREEZING DRIZZLE/RAIN AS THE LOWEST SEVERAL
THOUSAND FEET REMAIN SATURATED AND BELOW FREEZING...BUT THE
DENDRITIC SNOW GROWTH ZONE IS DRY. ECMWF SOUNDINGS ARE A BIT MORE
SATURATED IN THE DENDRITIC GROWTH ZONE AND WOULD SUGGEST SNOW AS THE
PREDOMINANT PRECIPITATION. AFTER COLLABORATING WITH NEIGHBORING
OFFICES...HAVE DECIDED TO KEEP THE FORECAST MAINLY DRY FOR THIS TIME
PERIOD...BUT WILL MONITOR THE POTENTIAL FOR SNOW/ICE IN THE COMING
DAYS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1008 PM MST SAT FEB 6 2016

GUSTY NORTHWEST WINDS WILL CONTINUE OVERNIGHT WITH GUSTS FROM
20-35KTS. STRONG WINDS WILL DEVELOP SUNDAY MORNING WITH GUSTS FROM
40-65KTS ACROSS MUCH OF THE AREA. MAINLY VFR CONDITIONS
EXPECTED...EXCEPT FOR LOCAL MVFR CIGS FROM K2WX TO KICR SUNDAY.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...HIGH WIND WARNING UNTIL 8 PM MST /9 PM CST/ SUNDAY FOR SDZ024-
     028-029-043-044-046-047-049.

     WIND ADVISORY UNTIL 8 PM MST SUNDAY FOR SDZ027-041-042.

     HIGH WIND WARNING UNTIL 8 PM MST SUNDAY FOR SDZ001-002-012>014-
     025-026-030>032-072>074.

WY...HIGH WIND WARNING UNTIL 8 PM MST SUNDAY FOR WYZ057.

     HIGH WIND WARNING UNTIL 8 PM MST SUNDAY FOR WYZ071.

&&

$$

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



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