Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 240511
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1011 PM MST MON FEB 23 2015

.SHORT TERM...THIS EVENING THROUGH TUESDAY NIGHT
ISSUED AT 201 PM MST MON FEB 23 2015

MILDER WEATHER CONTINUES TO ADVECT INTO THE NRN PLAINS AS A SHORT-
WAVE RIDGE WAS MOVING SOUTHEAST ACROSS ALBERTA AND SASKATCHEWAN.
24-HR TEMPERATURE RISES UPSTREAM OF THE CWA WERE 20-40F. THE
LARGE-SCALE PATTERN FEATURED TROUGHING OVER MOST OF THE CONUS WITH
A STRONG UPPER JET ACROSS THE SRN AND ERN CONUS. A SHARP AND
NARROW RIDGE WAS OFF THE WEST COAST AND EXTENDED NWD INTO BRITISH
COLUMBIA. THAT PATTERN WILL CONTINUE TO FAVOR SOUTHWARD SURGES OF
ARCTIC AIR INTO THE CWA...WITH THE NEXT ONE COMING TUESDAY NIGHT.

FOR TONIGHT...RELATIVELY QUIET/MILD WEATHER IS EXPECTED AS A LEE
TROUGH ADVANCES EAST OF THE CWA AND MILD NORTHWEST BL FLOW BRINGS
WARM ADVECTION. AN INCREASE IN MIDLEVEL CLOUDS WILL OCCUR LATER AS
THE WARM ADVECTION CONTINUES...WITH SOME LOW CLOUDS POSSIBLE IN FAR
NWRN SD LATE.

FOR TUESDAY...ANOTHER LEE TROUGH MOVES OVER THE CWA WHILE A SHARP
ARCTIC FRONT BACKS INTO THE NERN CWA. MOST OF THE AREA WILL BE QUITE
MILD...BUT LOW CLOUDS AND SOME LIGHT RAIN/SNOW WILL DEVELOP ALONG
THE ARCTIC FRONT WERE ISENTROPIC LIFT IS PRESENT. THIS WILL KEEP
TEMPS RELATIVELY LOWER IN PARTS OF NWRN SD.

ON TUESDAY NIGHT...THE ARCTIC FRONT BACKS SOUTHWEST ACROSS MOST OF
THE CWA...FOLLOWED BY BRISK NLY WINDS AND COLD ADVECTION. ISENTROPIC
LIFT AND AND SHORT-WAVE TROUGH WILL FOSTER RELATIVELY HIGH POPS NEAR
THE FRONT FROM NWRN-SCNTRL SD. ELSEWHERE...ANOTHER SHORT-WAVE TROUGH
WILL MOVE OVER WY WITH DECENT LIFT AND MOISTURE...BRINGING ANOTHER
AREA OF FAIRLY HIGH POPS ACROSS NERN WY INTO THE BLKHLS. WCNTRL SD
WILL SEE ONLY LIGHT ACCUMULATIONS IN-BETWEEN THE TWO WAVES. THE
BRUNT OF THE COLD AIR WILL NOT ARRIVE UNTIL AFTER 12Z WEDNESDAY.

.LONG TERM...WEDNESDAY THROUGH MONDAY
ISSUED AT 201 PM MST MON FEB 23 2015

DOMINANT NW FLOW WILL SUPPORT A COLD AND UNSETTLED EXTENDED
PERIOD. MAIN LOBE OF ARCTIC AIR WILL SETTLE INTO THE REGION WED-
THU BEHIND A STRONG NW FLOW UPPER TROUGH. THIS SYSTEM WILL BRING
SOME LIGHT SNOW THE AREA AS TEMPS DROP SIG WED. WESTERN NOAM RIDGE
THAT HAS BEEN POSITIONED JUST WEST OF THE REGION WILL BREAKDOWN
AND SHIFT WEST...WITH LARGE SCALE NORTHERLY FLOW REMAINING IN
PLACE INTO NEXT WEEK. MAINLY DRY WX EXPECTED THROUGH THE PERIOD
AFTER WED...AS DRY NORTHERLY FLOW PREVAILS. THE NEXT CHANCE FOR
PRECIP WILL BE IN THE SAT-SUN PERIOD AS MODELS EJECT THE SW CONUS
UPPER TROUGH EAST INTO THE CENTRAL PLAINS. THE FA REMAINS ON THE
NW EDGE OF THIS SYSTEM WITH LITTLE IMPACT EXPECTED ATTM...ESP
GIVEN STRONG TENDENCIES FOR A MORE PROGRESSIVE NW FLOW.
OVERALL...SIDED MORE TOWARD THE COLDER SIDE OF GUIDANCE WITH THE
FIRST ARCTIC INTRUSION WED-FRI...WITH A TREND TOWARD THE MIDDLE
INTO THE WEEKEND GIVEN FLOW MODERATION AND LACK OF SIG TEMP
ANOMALIES.

A DECENT CHANCE FOR SNOW REMAINS WED AS THE AFOREMENTIONED IMPULSE
DIVES SE ACROSS THE ROCKIES AND AN ARCTIC FRONT BACKS INTO THE
REGION. GENERALLY LIGHT ACCUMS /1-3 INCHES/ EXPECTED PER FGEN
PROCESSES...WITH THE BULK OF LSA PASSING SOUTH OF THE FA. COLD AIR
WILL SETTLE INTO THE REGION THUR...WITH TEMPS AVERAGING 20-30
DEGREES BELOW SEASONAL NORMS. SOME MODERATION IN TEMPS EXPECTED
FRI-SAT AND AGAIN MON WITH WEAK RIDGING AHEAD OF PROGGED NW FLOW
UPPER TROUGHS. RETAINED LOW CHANCES POPS SAT-SUN ACROSS THE SOUTH
GIVEN POTENTIAL GRAZING CENTRAL PLAINS SYSTEM. HOWEVER...FORECAST
MODELS ARE CERTAINLY OPTING FOR A MORE PROGRESSIVE NORTHERN
STREAM WAVE IN THIS PERIOD...WHICH WOULD SUPPORT A MORE DOMINATE SFC
RIDGE OVER THE REGION AND A SE BIAS TO THIS SYSTEM/S TRACK.
THIS WOULD SIG LIMIT PRECIP POTENTIAL IN MOST OF THE FA.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1009 PM MST MON FEB 23 2015

VFR CONDITIONS WILL PREVAIL THROUGH TUESDAY AFTERNOON...EXCEPT
FOR LOCAL MVFR CIGS EAST OF A LINE FROM K2WX TO KICR. AN
APPROACHING STORM SYSTEM WILL BRING LOWER CIGS TUESDAY EVENING
ACROSS NORTHERN PORTIONS OF THE AREA...WITH MVFR CIGS AT TIMES
LIKELY NORTH OF KRAP/KGCC/KPHP.

&&

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

$$

SHORT TERM...BUNKERS
LONG TERM...JC
AVIATION...HELGESON



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