000 
FXUS63 KUNR 160925
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
225 AM MST WED JAN 16 2008

.DISCUSSION...09Z SURFACE ANALYSIS HAD INITIAL COLD FRONT WELL
SOUTH AND EAST OF THE CWA WITH SECONDARY ARCTIC BOUNDARY NOW
PUSHING SOUTH OF I-90...CAUSING WINDS TO BUBBLE UP FOR LAST GASP
EARLY THIS MORNING. ALTHOUGH THERE COULD BE A COUPLE MORE HOURS OF
MARGINAL WIND ADVISORY WINDS...FEEL WINDS WILL SLOWLY SUBSIDE THIS
MORNING AS SURFACE RIDGE BUILDS INTO THE CWA. REGIONAL RADARS SHOW
MAIN -SN ACTIVITY ABOUT DONE...WITH WARMING IR TOPS. COULD BE A
FEW UPSLOPE/INSTABILITY -SHSN OVER THE NORTHERN HILLS TODAY. HIGHS
NOT MUCH HIGHER THAN CURRENT TEMPERATURES. FOR TONIGHT...UPPER
TROUGH SETTLES INTO THE MIDWEST AS NEXT WAVE OF INTEREST OVER
CENTRAL AB WRAPS AROUND DEEP HUDSON BAY LOW.

THURSDAY/FRIDAY...CENTRAL AB WAVE DROPS INTO THE NORTHERN PLAINS
BRINGING WELL DEFINED FORCING. SHARP SFC-700MB BAROCLINIC ZONE
WILL BE PRESENT FROM EASTERN MT INTO WESTERN NE. LIFT OVER ZONE
WILL RAPIDLY INCREASE THURSDAY AFTERNOON AND CONTINUE THURSDAY
NIGHT. VERY STEEP LAPSE RATES WITH NICE BAND OF FRONTOGENESIS.
CONVECTIVE -SN PROBABLE AS SURFACE LOW MOVES FROM SOUTHERN SK 12Z
THURSDAY TO IA/MN BY 12Z FRIDAY. INVERTED TROUGH-TYPE FEATURE
HANGS BACK OVER THE CWA ALLOWING SNOW TO CONTINUE IN THE WEST MOST
OF THURSDAY NIGHT. GRADIENT INCREASES WITH COLD AIR ADVECTION
SUPPORTING WINDY CONDITIONS AND AREAS OF BLOWING SNOW THURSDAY
NIGHT AND FRIDAY MORNING. VERY WELL DEFINED UPSLOPE SIGNATURE PER
BUFKIT SOUNDINGS SUGGEST ENHANCED SNOW OVER THE USUAL
AREAS...PARTICULARLY FROM 00-18Z FRIDAY. WILL HOIST WINTER STORM
WATCH FOR LATE THURSDAY AFTERNOON UNTIL FRIDAY MORNING FOR
NORTHEASTERN WY...NORTHWESTERN SD...AND THE NORTHERN AND CENTRAL
BLACK HILLS. THE HILLS WILL LIKELY HAVE MORE THAN 6 INCHES...WITH
THE PLAINS IN THE 3-6 INCH RANGE ON AVERAGE...BUT WITH A LOT OF
BLOWING SNOW. PARTS OF THE HILLS COULD EASILY SEE IN EXCESS OF 1
FOOT WITH 00Z NAM PAINTING 1.2 INCHES LIQUID OVER THE NORTHERN
BLACK HILLS. 15 TO 1 RATIOS OR BETTER LIKELY.

FRIDAY NIGHT...CLIPPER SYSTEM EXITS LEAVING SOME LINGERING
ACTIVITY ALONG LEFTOVER SURFACE THOUGH IN THE WEST.

EXTENDED...UPPER LEVEL NORTH TO NORTHWEST FLOW WILL DOMINATE THE 
EXTENDED PORTION OF THE FORECAST ACROSS THE NORTHERN PLAINS. BRUNT 
OF COLD AIR WILL REMAIN EAST OF OUR AREA...BUT BELOW AVERAGE TEMPS 
IN GENERAL WILL CONTINUE THROUGH THE PERIOD...ESPECIALLY NORTH AND 
EAST OF THE BLACK HILLS. ANOTHER UPPER LEVEL DISTURBANCE WILL SLIDE 
SOUTH ACROSS THE REGION THIS COMING WEEKEND...BRINGING ADDITIONAL  
CHANCES FOR SNOW. THE BEST CHANCES FOR SNOW WITH SOME ACCUMULATION 
WILL CONTINUE TO BE OVER THE NORTHERN BLACK HILLS AREA AND PORTIONS 
OF NORTHEAST WYOMING. 

&&

.AVIATION...GUSTY NORTHWEST WINDS WILL CONTINUE ACROSS THE AREA FOR 
THE NEXT SEVERAL DAYS. OTHERWISE...VFR CONDITIONS WILL PERSIST 
THROUGH TONIGHT. ANOTHER STRONG CLIPPER SYSTEM WILL AFFECT THE BLACK 
HILLS AREA ON THURSDAY WITH AREAS OF IFR CIGS AND VISIBILITIES WITH 
SNOW.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER STORM WATCH FROM THURSDAY AFTERNOON THROUGH FRIDAY 
     MORNING FOR BUTTE-CENTRAL BLACK HILLS-HARDING-NORTHERN 
     BLACK HILLS-NORTHERN FOOT HILLS-NORTHERN MEADE CO PLAINS-
     PERKINS-SOUTHERN MEADE CO PLAINS-STURGIS/PIEDMONT FOOT 
     HILLS.

WY...WINTER STORM WATCH FROM THURSDAY AFTERNOON THROUGH FRIDAY 
     MORNING FOR NORTHEASTERN CROOK-NORTHERN CAMPBELL-SOUTHERN 
     CAMPBELL-WESTERN CROOK-WESTON-WYOMING BLACK HILLS.

&&

$$

HELGESON/RUDGE