000
FXUS63 KUNR 072205
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
305 PM MST SAT DEC 7 2013

.SHORT TERM...THIS EVENING THROUGH SUNDAY NIGHT
ISSUED AT 237 PM MST SAT DEC 7 2013

CURRENT SURFACE ANALYSIS PLACES BROAD HIGH STRETCHING FROM THE
MIDWEST INTO THE NORTHERN PLAINS...WHILE LOW REMAINS OVER THE
GREAT BASIN. UPPER LEVEL ANALYSIS PLACES BROAD TROF OVER THE WRN
CONUS WITH VARIETY OF WEAK WAVES MOVING THROUGH. FRIGID AIRMASS
REMAINS SITUATED OVER THE AREA...WITH ALMOST ALL READINGS ACROSS
THE CWA BELOW ZERO. WEAK WAA ALOFT CONTINUES TO PRODUCE SOME AREAS
OF LIGHT SNOW OVER PTNS OF THE CWA.

FOR TONIGHT...ISENTROPIC LIFT OVER SFC COLD AIRMASS WILL CONTINUE
TO BRING SOME LIGHT SNOW TO THE AREA OVERNIGHT...THOUGH ANY
ACCUMULATIONS WILL BE LIGHT. TEMPERATURES WILL AGAIN BE VERY
COLD...WITH LOWS WELL BELOW ZERO OVER MANY LOCATIONS. COLDEST
AREAS WILL BE OVER NWRN/W CTRL SD WHERE LIGHT SERLY WINDS BEHIND
SFC HIGH WILL COMBINE WITH THE COLD TEMPS TO BRING WIND CHILLS
INTO ADVISORY CRITERIA FOR ANOTHER NIGHT.

ON SUNDAY...PERIODS OF SNOW WILL CONTINUE INTO THE MORNING THOUGH
WILL DIMINISH IN THE AFTERNOON AS ISENTROPIC LIFT ENDS AS COLDER
AIR STARTS PUSHING INTO THE AREA. THIS WILL ALSO BRING A WIND
SHIFT TO THE NORTHWEST ALONG WITH AN INCREASE IN WIND SPEED
BRINGING ANOTHER NIGHT OF WIND CHILL CONCERNS.

&&

.LONG TERM...MONDAY THROUGH SATURDAY
ISSUED AT 237 PM MST SAT DEC 7 2013

MEAN MID LEVEL FLOW WILL TRANSITION TO ACTIVE NW FLOW.
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. CLIPPER TRACK WILL BE CLOSE ENOUGH TO THE REGION
MON-TUE...TO SUPPORT CHANCES FOR SNOW TO THE NW ZONES...INCLUDING
CONDITIONS FOR SOME UPSLOPE SNOWS ACROSS THE NORTHERN BLACK HILLS.
HOWEVER...THE MEAN LL BAROCLINIC ZONE AND ASSOCIATED STORM TRACK
WILL SHIFT NORTH...KEEPING MOST OF THE REGION IN A DRY PATTERN BY
WEEKS END. LITTLE CHANGE TO THE PREVIOUS FORECAST WITH ONLY SLIGHT
ADJUSTMENTS MADE.

MON-TUE...RETAINED LOW CHANCE POPS ACROSS THE NW ZONES MON AFTERNOON
THROUGH TUE NIGHT WITH A PASSING CLIPPER AND ASSOCIATED LINGERING LL
BAROCLINIC ZONE. MODELS HAVE BACKED OFF ON PRECIP CHANCES FOR WEAK
LL CONVERGENCE TUE NIGHT...BUT HAVE RETAINED POPS ATTM GIVEN
WAVERING SOLUTIONS.

WED-SAT...DRY CONDITIONS EXPECTED THROUGH THIS PERIOD. HOWEVER...NW
AREAS COULD POSSIBLY SEE SOME SNOW IN THE FRIDAY NIGHT SAT PERIOD
WITH A CLIPPER SYSTEM. GIVEN THE PERIOD...HAVE DECIDED TO HOLD ON
ANY POP MENTION ATTM. STRONG 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. FRI AND SAT TEMPS REMAIN IN QUESTION WITH A WAVERING
DEGREE OF CAA IN MODEL SOLUTIONS...INCLUDING THE POTENTIAL FOR
EASTERLY UPSLOPE WINDS OVER THE SD PLAINS. HAVE OPTED FOR THE MIDDLE
OF GUIDANCE NUMBERS ATTM.

&&

.AVIATION...FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING
ISSUED AT 237 PM MST SAT DEC 7 2013

AN UPPER LEVEL IMPULSE WILL SUPPORT AREAS OF MVFR CIGS
ACROSS THE FA...ESP THE SOUTHERN HALF...WITH AREAS OF FLURRIES. MORE
WIDE SPREAD MVFR/IFR FLIGHT RESTRICTIONS CAN BE EXPECTED TONIGHT INTO
SUNDAY AS AN UPPER LEVEL TROUGH PUSHES NE ACROSS THE FA...ESP ACROSS
SCENTRAL SD.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND CHILL ADVISORY UNTIL 11 AM MST SUNDAY FOR SDZ001-002-
     012>014-025-072-073.

WY...WIND CHILL ADVISORY UNTIL 11 AM MST SUNDAY FOR WYZ071.

&&

$$

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