FXUS63 KUNR 020407
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
907 PM MST TUE DEC 1 2009

.DISCUSSION...COLD ADVECTION TO CONTINUE OVERNIGHT ACRS OUR CWFA WITH
HIGH PRESSURE BUILDING INTO MT. MOISTURE QUITE LIMITED BUT THERE
IS JUST ENOUGH IN PLACE COMBINED WITH THE COLD ADVECTION FOR ISOLD
-SHSN TO CONTINUE OVERNIGHT...MAINLY FROM THE BLKHLS WESTWARD.

HAVE UPDATED FCST MAINLY TO RAISE OVERNIGHT LOWS ACRS SCNTRL SD
WHERE INCREASED CLOUD COVER SHOULD KEEP TEMPS FROM FALLING AS MUCH
AS PREVIOUSLY ANTICIPATED. REST OF FCST IN GOOD SHAPE.

&&

.PREV DISCUSSION... /ISSUED 527 PM MST TUE DEC 1 2009/ 

DISCUSSION...WINDS CONTINUE TO DIMINISH SO WIND ADVISORY HAS
EXPIRED.

PREV DISCUSSION... /ISSUED 135 PM MST TUE DEC 1 2009/ 

DISCUSSION...CURRENT WATER VAPOR IMAGERY SHOWS UPPER TROUGH
MOVING INTO SOUTHERN MONTANA. SNOW SHOWERS CONTINUE ACROSS
NORTHEAST WYOMING AND THE BLACK HILLS THIS AFTERNOON. EXPECT THIS
ACTIVITY TO CONTINUE INTO TONIGHT AS UPPER TROUGH SWINGS THROUGH THE
CWA. GUSTY NORTHWEST WINDS CONTINUE THIS AFTERNOON ACROSS THE
SOUTH DAKOTA PLAINS SO WILL LEAVE WIND ADVISORY IN PLACE UNTIL
00Z.

ON WEDNESDAY...COLD AIR WILL FILTER INTO THE REGION AS TROUGH DIGS
OUT OF SOUTHERN CANADA AND MOVES ACROSS THE AREA WEDNESDAY THROUGH
WEDNESDAY NIGHT. EXPECT SNOW SHOWERS TO DEVELOP ACROSS MUCH OF THE
AREA. THE BEST CHANCE FOR ACCUMULATION WILL BE ACROSS THE NORTHERN
BLACK HILLS WHERE UPSLOPE ENHANCEMENT COULD BRING 1 TO 2 INCHES OF
SNOW BY LATE WEDNESDAY NIGHT. MOISTURE IS LIMITED WITH THIS SYSTEM
SO EXPECT ACCUMULATIONS TO STAY BELOW ADVISORY CRITERIA.
LOW TEMPERATURES WILL BE ON THE COLD SIDE WEDNESDAY NIGHT WITH
LOWS DIPPING INTO THE SINGLE DIGITS ACROSS MUCH OF THE CWA. SOME
LOCATIONS IN THE HIGHER ELEVATIONS OF THE BLACK HILLS COULD DIP
BELOW ZERO.

ON THURSDAY...MAIN TROUGH WILL MEANDER EAST OF THE CWA. SHORTWAVE
WILL MOVE ACROSS THE REGION AND COULD BRING A FEW LIGHT SNOW SHOWERS
OR FLURRIES TO NORTHEAST WYOMING AND WESTERN SOUTH DAKOTA. THIS
ACTIVITY SHOULD END LATE THURSDAY AFTERNOON AS SURFACE HIGH
PRESSURE BUILDS INTO THE AREA.

EXTENDED...GFS/ECMWF/GEM IN BETTER AGREEMENT OVER THE WEEKEND INTO 
EARLY NEXT WEEK WITH UPPER TROF DIGGING ACROSS THE NRN ROCKIES/PAC 
NW. EVEN WITH SOME SPREAD IN 850/700MB TEMPS...AROUND 5C...ALL THREE 
MODELS ARE SHOWING A 1030+MB HIGH DROPPING INTO THE NRN PLAINS. THAT 
COMBINED WITH CLOUD COVER...WILL TREND TOWARDS LOWER END OF GUIDANCE 
TEMPERATURES. WITH UPPER TROF DIGGING TO THE WEST OF THE 
AREA...THERE WILL BE A PERIOD OF WEST-SOUTHWEST FLOW FROM 700-500MB 
WHICH SHOULD RESULT IN SOME ISENTROPIC LIFT OVER ARCTIC AIR. WILL 
CONTINUE WITH LOW POPS FOR NOW AS MOISTURE APPEARS TO BE LACKING. 

&&

AVIATION...LCL MVFR CONDS OVERNIGHT MAINLY ACRS NERN WY AND THE
BLKHLS...ALONG WITH ISOLD -SHSN. VFR CIGS EXPECTED EAST OF THE
BLKHLS.

&&

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

$$
JOHNSON