Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 282306
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
406 PM MST FRI NOV 28 2014

.SHORT TERM...THIS EVENING THROUGH SATURDAY NIGHT
ISSUED AT 213 PM MST FRI NOV 28 2014

21Z SURFACE ANALYSIS HAD LOW PRESSURE OVER CENTRAL MT WITH WARM
FRONT INTO EASTERN NE AND ARCTIC FRONT SNEAKING OVER THE
MT/CANADIAN BORDER. SPECTACULARLY WARM AIR OVER MUCH OF THE CWA
THIS AFTERNOON...SAVE FOR AREAS ALONG/EAST OF A LINE FROM LEMMON
TO PIERRE. WATER VAPOUR LOOP SHOWED UPPER TROUGH DIVING INTO
SOUTHWEST CANADA...AND THIS ALONG WITH THE ARCTIC FRONT WILL CAUSE
A MASSIVE TEMPERATURE DROP AND SOME SNOW FOR LATER SATURDAY INTO
SUNDAY.

TONIGHT...UPPER RIDGE SHIFTS EAST AS UPPER TROUGH DROPS INTO THE
NORTHERN ROCKIES. ARCTIC FRONT WILL OOZE INTO SOUTHERN MT AS LOW
PRESSURE MOVES ALONG IT INTO ND. BOUNDARY LAYER WINDS INCREASE FROM
THE WEST AS PRESSURE FALLS STRENGTHEN EAST OF THE CWA. BREEZY/GUSTY
WINDS EXPECTED OVER NORTHEAST WY/HIGHER BLACK HILLS LATER
TONIGHT...AND POSSIBLY THE NORTH THROUGH EAST FOOTHILLS
OVERNIGHT...BUT PRESSURE DIFFERENCE ACROSS THE HILLS ONLY 3-4MB...SO
THE HIGHER WINDS MIGHT NOT MAKE IT TO THE LOWER ELEVATIONS. PATCHY
FOG POSSIBLE OVER NORTHEAST FIFTH OF CWA LATER TONIGHT GIVEN T/TD
SPREADS.

SATURDAY...UPPER TROUGH MOVES INTO THE NORTHERN PLAINS AS 1038MB
ARCTIC HIGH MOVES IN BEHIND ARCTIC FRONT. ARCTIC FRONT WILL REACH
CWA BY 15Z AND THEN SHUFFLE SOUTHWARD INTO NE AROUND 00Z.
TEMPERATURES WILL BE IN THE 50S/60S AHEAD OF IT AND 30S BEHIND IT
FOR HIGHS...BUT GREAT UNCERTAINTY EXISTS FOR ACTUAL HIGHS GIVEN
TIGHT TEMPERATURE GRADIENT. MOISTURE WILL BE LIMITED AHEAD OF
FRONT...BUT AS T/TD SPREADS CONVERGE BEHIND FRONT...AN AREA OF -SN
WILL DEVELOP SATURDAY NIGHT. THIS WILL BE ESPECIALLY TRUE IN THE
WEST WHERE BEST SYNOPTIC FORCING COMBINED WITH STRONG LOW LEVEL
FRONTOGENESIS. 1-2 INCHES POSSIBLE BY SUNDAY MORNING. GUSTY
NORTHERLY WINDS EXPECTED BEHIND FRONT CAUSING PATCHY BLSN. WIND
CHILLS WILL DROP TO -20F BY SUNDAY MORNING. THE DIFFERENCE BETWEEN
SATURDAY/S HIGHS AND SATURDAY NIGHT/S LOWS WILL BE 30 TO 50 DEGREES.

&&

.LONG TERM...SUNDAY THROUGH FRIDAY
ISSUED AT 213 PM MST FRI NOV 28 2014

ARCTIC AIR SETTLES INTO THE NORTHERN PLAINS WITH LIGHT SNOW AND
FLURRIES LINGERING SUNDAY...MAINLY ACROSS NORTHEAST WYOMING AND
FAR WESTERN SOUTH DAKOTA. HIGHS WILL ONLY BE IN THE TEENS FOR MOST
AREAS ON SUNDAY...WITH WIND CHILLS NEAR OR BELOW ZERO. THE BRUNT
OF THE ARCTIC AIR STILL LOOKS TO BE SHORT-LIVED ACROSS THE AREA AS
RETURN FLOW AROUND THE DEPARTING SURFACE HIGH DEVELOPS ON MONDAY.
MAINLY DRY WEST-NORTHWEST FLOW IS EXPECTED FOR MUCH OF NEXT WEEK
WITH TEMPERATURES NEAR OR ABOVE AVERAGE...ESPECIALLY FROM TUESDAY
ONWARD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 401 PM MST FRI NOV 28 2014

VFR CONDITIONS ARE EXPECTED THROUGH SATURDAY MRNG. IFR CIGS
AND -SN WILL BUILD INTO NERN WY AND FAR NWRN SD SATURDAY AFTN
BEHIND A STRONG CDFNT.

&&

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

$$

SHORT TERM...HELGESON
LONG TERM...15
AVIATION...JOHNSON






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