Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 011728
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1028 AM MST SUN MAR 1 2015

.UPDATE...
ISSUED AT 836 AM MST SUN MAR 1 2015

UPPER WAVE PASSING THROUGH EASTERN MT/WESTERN DAKOTAS IS PRODUCING
SOME SNOW SHOWERS ACROSS THE WYOMING BLACK HILLS AND AREAS
NORTHWEST OF THE CWA. HULETT IS REPORTING REDUCED
VISIBILITIES...SO ADDED SOME ISOLATED SNOW SHOWERS TO THE NORTHERN
HILLS. ALSO ADDED SOME SCATTERED FLURRIES ACROSS NORTHWEST SD
TODAY. UPDATED SKY GRIDS TO MATCH POPS/WX...BUT REST OF FORECAST
LOOKS ON TRACK FOR NOW.

&&

.SHORT TERM...TODAY THROUGH MONDAY NIGHT
ISSUED AT 237 AM MST SUN MAR 1 2015

NW FLOW WILL PREVAIL IN THE PERIOD WITH A STRONG
PHASING SYSTEM ON TRACK MONDAY INTO TUES. A STRONG NW FLOW UPPER
LEVEL TROUGH WILL MERGE WITH THE EJECTING SW CONUS UPPER LEVEL
TROUGH...HELPING TO FORCE OF PERIOD OF LONG TRAJECTORY NORTHERLY
FLOW. THIS WILL SUPPORT ANOTHER ROUND OF ARCTIC AIR INTO THE
CONUS...ALONG WITH SOME SNOW AND WIND LOCALLY. A WEAKER SHORTWAVE
WILL TRAVERSE THE NORTHERN PLAINS TODAY...SUPPORTING REINFORCING
COLD THERMAL FIELDS. LACK OF MOISTURE WITH LARGE SCALE SINK
LOCALLY...EXPECTED TO SUPPORT DRY CONDS IN THE FA. INCREASING RETURN
FLOW FORCED BY SHORTWAVE RIDGING AHEAD OF THE APPROACHING STRONGER
NW FLOW IMPULSE...WILL SUPPORT A WARMER DAY MONDAY WITH CONTINUED
DRY CONDS...BEFORE SNOW AND WIND RETURN TO THE REGION MONDAY NIGHT.

TODAY...ANOTHER NW FLOW IMPULSE EXPECTED INTO THE REGION. ALTHOUGH
MOST IF NOT ALL OF THE LSA/UVM WILL PASS NORTH OF THE FA...CANNOT
RULE OUT A FEW HIGH BASED SNOW SHOWERS OVER THE NORTH HALF OF THE FA
AND OVER THE BLACK HILLS GIVEN FAIRLY STEEP LL LAPSE RATES.
HOWEVER...GIVEN DRY PROFILES...VIRGA WOULD BE ANTICIPATED THUS NO
POPS WARRANTED. STEEP LL LAPSE RATES PER INSOLATION AND MIXING WILL
FORCE FASTER FLOW DOWN SUPPORTING BREEZY CONDS...ESP ON THE SD
PLAINS WITH 15 TO 25 MPH WINDS EXPECTED. THERMAL FIELDS WILL
BASICALLY SEE NEAR NEUTRAL TEMP ADV...WITH TEMPS SIMILAR TO SAT/S
NUMBERS...SLIGHTLY WARMER. ASSOCIATED SFC HIGH WILL SHIFT SE OF THE
REGION TONIGHT...WITH GUSTY SOUTHERLY RETURN FLOW DEVELOPING OVER NE
WY AND PORTIONS OF THE SD PLAINS.

MONDAY...RETURN FLOW WILL REV UP WITH SOUTHERLY WINDS INCREASING
THROUGH THE DAY. WAA WILL BE ONGOING WITH MOST LOCATIONS SEEING 40S
FOR HIGHS...POSSIBLY NEAR 50 IN THE LEE OF THE BLACK HILLS. STRONG
NW FLOW UPPER TROUGH AND THE EJECTING SW CONUS UPPER LOW WILL
SUPPORT INCREASING LARGE SCALE ASCENT ACROSS THE SOUTHERN HALF OF
THE FA MONDAY EVENING WITH INCREASING MOISTURE AND FORCING
SUPPORTING INCREASING CHANCES FOR SNOW. BETTER CHANCES WILL ARRIVE
LATER MONDAY NIGHT AS A STRONG COLD FRONT IS FORCED THROUGH THE
FA...SUPPORTING INCREASING FGEN ACROSS MOST OF THE FA...ESP THE
SOUTHERN THIRD. DECENT LL MOISTURE COUPLED WITH MODEST FORCING WILL
AT LEAST SUPPORT UP TO A COUPLE INCHES OF SNOW ACROSS SCENTRAL
SD...WITH LESSER AMOUNTS OUTSIDE OF THE NORTHERN BLACK HILLS.
INCREASING FLOW WITH SUFFICIENT LL MOISTURE AND FORCING IN THE DGZ
WILL SUPPORT A GOOD PERIOD OF UPSLOPE IN THE NORTHERN HILLS WITH A
FEW INCHES POSSIBLE THERE BY TUE MORNING. STRONG CAA COUPLED WITH
FAST LL MOMENTUM WILL SUPPORT STRONG GUSTY WINDS NW WINDS ON THE SD
PLAINS EARLY TUES MORNING. ALTHOUGH SNOW AMOUNTS LOOK MINIMAL ON
THE PLAINS...BLOWING SNOW AND HAZARDOUS TRAVEL IS A CONCERN AND
WILL CERTAINLY NEED TO BE MONITORED WITH FUTURE FORECAST PACKAGES.
VERY COLD AIR WILL BEGIN TO ADVECT INTO THE REGION EARLY TUE MORNING
OVER THE NW HALF...WITH WINDCHILLS FALLING BELOW ZERO BY DAWN MOST
PLACES THERE.

.LONG TERM...TUESDAY THROUGH SATURDAY
ISSUED AT 237 AM MST SUN MAR 1 2015

ARCTIC HIGH PRESSURE CONTINUES TO SURGE INTO THE NORTHERN PLAINS ON
TUESDAY...WITH STRONG NORTHWESTERLY WINDS PERSISTING THROUGH MUCH OF
THE DAY...AND TEMPERATURES STEADY OR CONTINUING TO FALL INTO THE
EVENING. LIGHT SNOW WILL BE LIKELY FROM NORTHEAST WYOMING THROUGH
SOUTHERN SOUTH DAKOTA...WITH SNOWFALL DIMINISHING FROM NORTH TO
SOUTH DURING THE DAY. TEMPERATURES WILL FALL BELOW ZERO ACROSS MUCH
OF THE AREA TUESDAY NIGHT.

THE BITTER COLD WILL LAST THROUGH WEDNESDAY BEFORE ANOTHER WARM UP
IS EXPECTED. THIS NEXT WARM UP...HOWEVER...LOOKS TO BE FAIRLY LONG
LIVED AND DRY. THE GFS AND ECMWF HAVE BEEN SHOWING A VERY STRONG
RIDGE BUILDING INTO THE WESTERN US BY MIDWEEK AND PERSISTING WELL
BEYOND THE END OF THE FORECAST PERIOD. EXPECT HIGHS DURING THAT
PERIOD TO BE ABOVE CLIMATOLOGY FOR THIS TIME OF YEAR.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY)
ISSUED AT 1025 AM MST SUN MAR 1 2015

ISOLATED SNOW SHOWERS POSSIBLE FAR NORTHWEST SOUTH DAKOTA AND OVER
BLACK HILLS THROUGH THIS AFTERNOON..WITH LCL MVFR CIGS/IFR VSBY.
OTHERWISE VFR CONDITIONS EXPECTED THROUGH MONDAY MORNING.


&&

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

$$

UPDATE...POJORLIE
SHORT TERM...JC
LONG TERM...15
AVIATION...7





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