000
FXUS63 KUNR 082204
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
304 PM MST SUN DEC 8 2013

.SHORT TERM...THIS EVENING THROUGH MONDAY NIGHT
ISSUED AT 212 PM MST SUN DEC 8 2013

CURRENT SURFACE ANALYSIS PLACES LOW OVER HUDSON BAY WITH
TROF/FRONTAL BOUNDARY DROPPING DOWN THROUGH MANITOBA TOWARDS
SOUTHEAST MONTANA. UPPER LEVEL ANALYSIS PLACES BROAD TROF COVERING
MUCH OF THE CONUS.

FOR TONIGHT...WINDS WILL CONTINUE TO SWITCH TO THE NW AS
AFOREMENTIONED TROF/BOUNDARY CONTINUES TO PUSH THROUGH THE AREA.
WINDS WILL INCREASE WHICH...COMBINED WITH THE COLD CONDITIONS AND
SECONDARY SHOT OF COLD AIR BEHIND THE SYSTEM...WILL BRING FRIGID
WIND CHILLS TO ALL THE CWA. THEREFORE...WILL KEEP CURRENT WIND
CHILL HEADLINES GOING. ALTHOUGH MOST AREAS WILL REMAIN DRY WITH
THIS SYSTEM...FROUDE AND MOISTURE ANALYSIS INDICATE THAT SOME
LIGHT SNOW MAY DEVELOP PRIMARILY OVER THE UPSLOPE REGIONS OF THE
NRN BLKHLS. ANY SNOW THAT DOES DEVELOP SHOULD TAPER BY LATE EVENING.

ON TUESDAY...LOW LEVEL FLOW SHIFTS MORE WEST/SOUTHWESTERLY
BRINGING SOME RELIEF IN TEMPERATURES AS HIGHS SHOULD PUSH INTO THE
TEENS OVER MOST LOCATIONS. VARIETY OF SHORT WAVES ROTATE THROUGH
BROAD CYCLONIC FLOW WITH THE STRONGEST ONE MAINLY AFFECTING THE
NRN CWA LATE AFTERNOON/EVENING BRINGING CHANCES FOR SNOW. SFC
PRESSURE GRADIENT ALSO TIGHTENS UP WITH THIS SYSTEM BRINGING
BREEZY CONDITIONS AS WINDS SHIFT TO THE NORTHWEST.

&&

.LONG TERM...TUESDAY THROUGH SUNDAY
ISSUED AT 212 PM MST SUN DEC 8 2013

MEAN MID LEVEL FLOW WILL TRANSITION TO ACTIVE NW FLOW
WITH THE BULK OF ARCTIC AIR SHIFTING EAST ACROSS SOUTHERN CANADA.
LOW AMPLITUDE SHORTWAVE TROUGHS WILL TRAVERSE THE SOUTHERN EDGE OF
THE CANADIAN NEGATIVE HEIGHT ANOMALY...SUPPORTING PERIODIC SFC
TROUGHS INTO THE REGION. MEAN LL BAROCLINIC ZONE WILL WAVER ACROSS
THE DAKOTAS...WITH THE LOCAL AREA SEEING A MEAN WARMUP THROUGH THE
PERIOD. ANOTHER CLIPPER SYSTEM WILL TRACK ACROSS THE REGION TUES
WITH A GLANCING SURGE OF ARCTIC AIR INTO THE REGION TUE. THIS WILL
SUPPORT CHANCES FOR SNOW TO THE NW HALF TUE...WITH SNOW CHANCES
SHIFTING SE THROUGH TUE NIGHT. SOME UPSLOPE ENHANCEMENT IS EXPECTED
OVER THE NORTHERN BLACK HILLS. THE MEAN LL BAROCLINIC ZONE AND
ASSOCIATED STORM TRACK WILL SHIFT NORTH...AND IS EXPECTED TO KEEP
THE REGION IN A DRY PATTERN THE REMAINDER OF THE PERIOD.

TUE...RETAINED LOW TO MID CHANCE POPS ACROSS THE NW ZONES TUES INTO
TUES NIGHT FOR A PASSING CLIPPER AND ASSOCIATED LINGERING LL
BAROCLINIC ZONE. THE BAROCLINIC ZONE WILL DIVED EXTREMELY COLD ARCTIC
AIR TO THE NE OF THE FA...FROM CP MODIFIED AIR TO THE WEST.
LINGERING CONVERGENCE ZONE MAY SUPPORT LIGHT SNOW AND CLOUDS THROUGH
MUCH OF THE NIGHT WESTERN HALF...SUPPORTING SLIGHTLY WARMER
OVERNIGHT LOWS THERE TOO AS WELL. LOWERED TEMPS CONSIDERABLY TUE
NIGHT...WITH FAIRLY HIGH CONFIDENCE FOR ANOTHER ARCTIC HIGH
SHIFTING EAST OF THE REGION...WITH CLEARING OVER THE NE ZONES. THIS
IS MORE IN LINE WITH THE ECMWF. IF PROGS HOLD...TEMPS MAY HAVE TO BE
LOWERED EVEN MORE EASTERN THIRD.

WED-SUN...DRY CONDITIONS EXPECTED THROUGH THIS PERIOD. MODERATE WAA
EXPECTED WED NIGHT INTO THUR WITH SCOURING OF LL ARCTIC AIRMASS
EXPECTED OVER THE HIGH TERRAIN. HAVE CONTINUED TO REMAIN CAUTIOUS
WITH TOO SIG OF A WARMUP OVER THE SD PLAINS...KEEPING WARMER TEMPS
CONFINED TO THE HIGHER TERRAIN OVER THE AREA GIVEN A RETREATING
ARCTIC HIGH. FRI-SUN TEMPS REMAIN IN QUESTION WITH A WAVERING DEGREE OF
CAA IN MODEL SOLUTIONS...INCLUDING THE POTENTIAL FOR EASTERLY
UPSLOPE WINDS OVER THE SD PLAINS WITH A PASSING CLIPPER SYSTEM.
HENCE...BIASED EASTERN AREAS COLDER...RETAINED WARMER NUMBERS OVER
THE WEST. A FAIRLY DECENT WARMUP MAY BE IN STORE FOR THE FOLLOWING
WEEK AS FLAT PROGRESSIVE FLOW SPREADS EAST...WITH THE NEGATIVE
HEIGHT ANOMALY TRENDING NE INTO CANADA. MATERIALIZATION WOULD ALLOW
SIG DOWNSLOPE WARMING TO SPREAD OVER MUCH OF THE NORTHERN HIGH
PLAINS.

&&

.AVIATION...FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING
ISSUED AT 212 PM MST SUN DEC 8 2013

MAINLY VFR CONDITIONS EXPECTED ACROSS THE FA TODAY
BEHIND A DEPARTING UPPER WAVE. SOME MVFR CIGS MAY REDEVELOP TONIGHT
AS COLDER AIR MOVES BACK INTO THE REGION...MAINLY OVER PORTIONS OF
NE WY AND THE NORTHERN BLACK HILLS. VFR CONDITIONS EXPECTED OVER THE
REMAINDER OF THE FA.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND CHILL ADVISORY UNTIL 11 AM MST /NOON CST/ MONDAY FOR SDZ001-
     002-012>014-024>032-041>044-046-047-049-072>074.

WY...WIND CHILL ADVISORY UNTIL 11 AM MST MONDAY FOR WYZ054>058-071.

&&

$$

SHORT TERM...77
LONG TERM...JC
AVIATION...JC