Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 130554
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1054 PM MST FRI FEB 12 2016

.UPDATE...
ISSUED AT 807 PM MST FRI FEB 12 2016

THE WDSPRD FOG/FZDZ HAS DISSIPATED AROUND THE FOOTHILLS...AND
LATEST HI RES MODEL SOLUTIONS DO NOT SHOW IT REDEVELOPING
OVERNIGHT. THUS...HAVE CANCELLED THE WINTER WX ADVISORY THAT WAS
IN EFFECT. WILL KEEP PATCHY FOG/FZDZ WORDING IN THE GRIDS FOR MUCH
OF THE AREA. REST OF FCST LARGELY UNCHANGED...WITH BEST CHANCES
FOR LIGHT SNOW ACCUMS WITHIN THE BAROCLINIC ZONE FROM NWRN SD
THROUGH SCNTRL SD.

UPDATE ISSUED AT 404 PM MST FRI FEB 12 2016

FREEZING DRIZZLE AND DENSE FOG HAVE BECOME A BIT MORE WDSPRD
ACROSS THE FOOTHILLS AND ADJACENT PLAINS OF WRN SD AND FAR NERN
WY. THESE POOR CONDITIONS WILL CONTINUE INTO SATURDAY MRNG SO HAVE
ISSUED A WINTER WX ADVISORY. REST OF FCST UNCHANGED.

&&

.SHORT TERM...THIS EVENING THROUGH SATURDAY NIGHT
ISSUED AT 325 PM MST FRI FEB 12 2016

CURRENT SURFACE ANALYSIS SHOWS FRONTAL BOUNDARY NEARLY
STATIONARY FROM CENTRAL MT TO NORTHEAST WY TO FAR WESTERN NEB.
ARCTIC HIGH PRESSURE IS CENTERED OVER SOUTH CENTRAL CANADA. UPPER
LEVEL ANALYSIS SHOWS DEEP LOW OVER SOUTHERN HUDSON BAY...WITH LARGE
SCALE TROF COVERING EASTERN NORTH AMERICA. RIDGE AXIS TO THE WEST OF
THE AREA IS CENTERED OVER THE GREAT BASIN REGION. FAST AND ACTIVE
NORTHWEST FLOW IN PLACE ACROSS THE NORTHERN PLAINS TO THE MS RIVER
VALLEY.

CLOUDS COVER MUCH OF THE CWA...WITH LOW CLOUDS ACROSS MUCH OF THE
WESTERN SD IN UPSLOPE EAST-NORTHEAST FLOW. AREAS OF FOG AND PATCHY
FREEZING DRIZZLE MAINLY BANKED UP AGAINST THE NORTHERN AND EASTERN
SLOPES OF THE BLACK HILLS AND ADJACENT PLAINS AT THIS TIME. KUDX
RADAR SHOWS MOSTLY SOME LIGHT SNOW SHOWERS OVER FAR NORTHEAST WY AND
FAR WESTERN SD. TEMPS ARE MAINLY IN THE 20S OVER WESTERN SD...WITH
30S AND LOWER 40S OVER NORTHEAST WY.

ACTIVE PATTERN WILL CONTINUE THROUGH THE WEEKEND AS NORTHWEST FLOW
ALOFT CONTINUES TO BRING DISTURBANCES ACROSS THE AREA. THE BEST
CHANCE FOR PCPN WILL COME SATURDAY AFTERNOON AND EVENING AS A
STRONGER SHORTWAVE DISTURBANCE CROSSES THE AREA. THIS DISTURBANCE
WILL HELP TO PUSH THE FRONT EASTWARD ACROSS THE REGION AS A WARM
FRONT SATURDAY AND SATURDAY NIGHT. AS A RESULT...A MIX OF PCPN CAN
BE EXPECTED ACROSS THE AREA.

FOR TONIGHT...THE FRONT WILL REMAIN ACROSS NORTHEAST WY...BEGINNING
TO SLIDE EAST LATE TONIGHT. WEAK ENERGY ALOFT WILL INTERACT WITH THE
RELATIVELY TIGHT BAROCLINIC ZONE IN PLACE TO THE EAST OF THE FRONT
TO BRING SOME SNOW SHOWERS...AND POSSIBLY A BIT OF LIGHT FREEZING
RAIN IN A FEW SPOTS AROUND THE BLACK HILLS AREA AS WARMER AIR ALOFT
BEGINS TO SURGE EASTWARD. AREAS OF FOG WILL LIKELY PERSIST ACROSS
THE NORTHERN AND EASTERN SLOPES OF THE BLACK HILLS AND ADJACENT
PLAINS TONIGHT...WITH PATCHY FOG ELSEWHERE. SOME LIGHT FREEZING
DRIZZLE WILL ALSO CONTINUE...ESPECIALLY ACROSS WEST CENTRAL SD.

PCPN CHANCES WILL INCREASE ACROSS THE AREA SATURDAY...ESPECIALLY IN
THE AFTERNOON...AS SHORTWAVE MOVES ACROSS MT AND INTO THE DAKOTAS.
FRONT WILL SLOWLY MOVE EAST ACROSS THE BLACK HILLS AREA AND FAR
WESTERN SD DURING THE DAY. WARMEST TEMPS WILL BE ACROSS NORTHEAST WY
AND THE BLACK HILLS AREA DURING THE DAY...WITH COLDEST AIR TOWARD
CENTRAL SD. HIGHS WILL RANGE FROM AROUND 30 OVER CENTRAL SD TO THE
LOWER 50S OVER NORTHEAST WY AND FAR SOUTHWEST SD. PCPN TYPE WITH THE
SYSTEM WILL MAINLY BE RAIN ACROSS NORTHEAST WY AND FAR WESTERN
SD...WITH A MIXED BAG OF PCPN TO THE NORTH AND EAST. ACROSS
NORTHEASTERN PORTIONS OF THE CWA...FREEZING RAIN AND SNOW IS
LIKELY...ESPECIALLY ACROSS PERKINS AND ZIEBACH COUNTIES. NOT SURE AT
THIS POINT WHICH PCPN TYPE WILL BE DOMINANT...BUT SOME ICE AND SNOW
ACCUMULATION CAN BE EXPECTED IN THESE AREAS...SO WENT AHEAD AND PUT
OUT A WINTER WX ADVISORY FOR THOSE COUNTIES FOR TOMORROW. MAY NEED
TO EXPAND THE ADVISORY A BIT FURTHER SOUTH AND EAST DEPENDING ON THE
TRACK OF HEAVIER PCPN...BUT CONFIDENCE TOO LOW RIGHT NOW. BULK
OF PCPN WILL QUICKLY MOVE EAST OF THE AREA BY MIDNIGHT.

.LONG TERM...SUNDAY THROUGH FRIDAY
ISSUED AT 325 PM MST FRI FEB 12 2016

NORTHWESTERLY FLOW ALOFT WILL PERSIST ACROSS THE NORTHERN PLAINS
THROUGH THE EXTENDED PERIOD AS AN UPPER RIDGE REMAINS IN PLACE
OVER THE WESTERN CONUS. STRONGEST SHORTWAVE DEPARTS THE AREA EARLY
SUNDAY...WITH LEFT OVER -SHRA/-SHSN FOR PORTIONS OF NORTHEAST
WYOMING INTO THE BLACK HILLS. WEAK DISTURBANCES IN THE NORTHWEST
FLOW MONDAY/TUESDAY MAY BRING SOME LIGHT PRECIPITATION ACROSS THE
AREA...WITH BEST CHANCE IN UPSLOPE FLOW ACROSS NORTHERN BLACK
HILLS. DRY CONDITIONS WITH TEMPERATURES WELL ABOVE AVERAGE
EXPECTED FOR THE MIDDLE OF NEXT WEEK.

&&

.AVIATION...FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT
ISSUED AT 1050 PM MST FRI FEB 12 2016

WIDESPREAD MVFR/IFR CIGS WILL CONTINUE OVER WESTERN AND CENTRAL
SOUTH DAKOTA THROUGH TONIGHT... SOME PATCHY FZFG IS POSSIBLE
OVERNIGHT NEAR THE BLACK HILLS. CONFIDENCE INCREASES SAT MORNING
FOR FZFG/FZDZ WITH LOCAL LIFR CIGS OVER EASTERN FOOTHILLS AS WINDS
BECOME MORE EASTERLY AHEAD OF NEXT SYSTEM. MVFR/IFR CONDITIONS
WILL PERSIST THROUGH SAT ACROSS NORTHWEST INTO SOUTH CENTRAL SOUTH
DAKOTA WITH A WINTRY MIX OF SNOW AND FREEZING RAIN. CONDITIONS
WILL IMPROVE IN NORTHEAST WYOMING AND FAR SOUTHWEST SOUTH DAKOTA
THROUGH SATURDAY AFTERNOON.

CONDITIONS WILL DETERIORATE AGAIN FROM WEST TO EAST SATURDAY LATE
AFTERNOON THROUGH THE REST OF THE PERIOD AS FAIRLY STRONG FRONT
MOVES THROUGH WITH GUSTY NORTHWESTERLY WINDS AND RAIN SHOWERS. SOME
CONVECTION IS ALSO POSSIBLE ALONG FRONT AS MODELS ARE SHOWING SOME
LIMITED INSTABILITY OF 200-400 J/KG. THUNDER CANT BE RULED OUT.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY FROM 8 AM TO 8 PM MST SATURDAY FOR
     SDZ002-014.

WY...NONE.
&&

$$

UPDATE...JOHNSON
SHORT TERM...26
LONG TERM...7
AVIATION...WARD


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