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000
FXUS63 KUNR 030409
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
909 PM MST MON MAR 2 2015

.UPDATE...
ISSUED AT 901 PM MST MON MAR 2 2015

BAND OF SNOW IS SPREADING INTO SOUTHWESTERN SOUTH DAKOTA THIS
EVENING. 00Z MODELS AGREE IN SHOWING AND EXTENDED PERIOD OF LOW-
MID LEVEL FRONTOGENESIS OVER THE SRN BLKHLS AND FAR SOUTHWESTERN
SOUTH DAKOTA TONIGHT AND TUESDAY MORNING. HAVE RAISED THE STORM
TOTAL SNOWFALL IN THOSE AREAS BY AN INCH OR A BIT MORE AND SO HAVE
UPGRADED THE WINTER WEATHER ADVISORY OVER THOSE AREAS TO A WINTER
STORM WARNING DUE TO THE EXPECTED INCREASE IN SNOW TOTALS.

&&

.SHORT TERM...THIS EVENING THROUGH TUESDAY NIGHT
ISSUED AT 223 PM MST MON MAR 2 2015

21Z SURFACE ANALYSIS HAD LOW PRESSURE OVER CENTRAL CO WITH TROUGH
INTO EASTERN ND. ARCTIC BOUNDARY NOSING INTO CENTRAL MT. WATER
VAPOUR HAD TWO SHORTWAVES OF INTEREST...ONE OVER SOUTHERN AB AND
ANOTHER OVER SOUTHWEST UT. MODELS ARE IN DECENT AGREEMENT WITH
EVOLUTION OF THESE FEATURES.

TONIGHT/TUESDAY...UT SHORTWAVE EJECTS INTO CENTRAL NE BY 12Z TUESDAY
AND THEN SCOOTS EAST. AB SHORTWAVE WILL DROP INTO MT. PREVIOUS
GUIDANCE SUGGESTED THESE WAVES MIGHT MERGE...BUT LATEST GUIDANCE AND
SATELLITE LOOPS INDICATE THIS WON/T HAPPEN. AS A RESULT...UT
SHORTWAVE WILL ROCKET TO THE NORTHEAST ON 150KT JET STREAK. LIFT IN
LEFT EXIT REGION OF JET WILL BE QUITE VIGOROUS CAUSING
CYCLOGENESIS OVER CO AS SURFACE LOW MOVES INTO EASTERN NE 12Z
TUESDAY AND THEN INTO THE GREAT LAKES BY 00Z WEDNESDAY. LOW WILL
GRAB ARCTIC AIR. NARROW BAND OF WELL-DEFINED FRONTOGENESIS
DEVELOPS AT LEADING EDGE OF ARCTIC AIR...LINKING UP WITH SYNOPTIC
LIFT. BAND OF LIGHT-MODERATE SNOW WILL OCCUR FROM SOUTHWEST INTO
CENTRAL SD WITH 3-5 INCHES LIKELY BY MIDDAY TUESDAY. ADDITIONAL
LIFT FROM SECONDARY SHORTWAVE WILL KEEP -SN GOING OVER NORTHEAST
WY/BLACK HILLS THROUGH TUESDAY AFTERNOON WHERE SLIGHTLY HIGHER
AMOUNTS EXPECTED. SOME UPSLOPE ENHANCEMENT OVER THE NORTHERN BLACK
HILLS PER FROUDE NUMBERS/BOUNDARY LAYER MOISTURE PROFILE.

MAIN ISSUE WILL BE GRADIENT BETWEEN 1035MB ARCTIC HIGH AND 1002MB
SURFACE LOW RESULTING IN GUSTY NORTHERLY WINDS. BLSN WILL BECOME A
PROBLEM OVER MUCH OF THE PLAINS WITH WORST WINDS/SNOW FROM KIEN TO
KPHP TO KICR...AND THUS HAVE UPGRADED TO WINTER STORM WARNING FOR
THOSE AREAS. REST OF CWA LOOKS OK WITH ADVISORY FOR NOW...BUT LATER
SHIFTS WILL NEED TO MONITOR FINAL POSITION OF SNOW BAND.

TUESDAY NIGHT...BITTERLY COLD WIND CHILLS EXPECTED WITH WIND CHILL
ADVISORIES LIKELY OVER PARTS OF THE AREA.

.LONG TERM...WEDNESDAY THROUGH MONDAY
ISSUED AT 223 PM MST MON MAR 2 2015

ARCTIC HIGH SLIDES SOUTHEAST ACROSS THE DAKOTAS ON
WEDNESDAY...WITH BITTER COLD AIR REMAINING ACROSS THE AREA. WARMER
AIR WILL BEGIN TO BUILD INTO THE REGION LATER WEDNESDAY NIGHT AND
ESPECIALLY ON THURSDAY. MEDIUM RANGE MODELS GENERALLY IN GOOD
AGREEMENT FOR THE REST OF THE WEEK AND THE WEEKEND AS MAINLY DRY
NORTHWEST FLOW ALOFT REMAINS THROUGH THE PERIOD. A RIDGE OVER THE
WESTERN CONUS WILL SLOWLY MOVE EAST INTO THE ROCKIES OVER THE
WEEKEND. TEMPERATURES WILL BE ABOVE AVERAGE FRIDAY THROUGH
MONDAY...WITH HIGHS IN THE 40S AND 50S.

&&

.AVIATION...FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING
ISSUED AT 425 PM MST MON MAR 2 2015

A STRONG WEATHER DISTURBANCE WILL MOVE INTO NORTHEASTERN WYOMING AND
SOUTHWESTERN SOUTH DAKOTA AROUND OR SHORTLY AFTER 00Z...WITH FLIGHT
CONDITIONS DETERIORATING QUICKLY TO IFR/LIFR IN SNOW BY MID TO LATE
EVENING ACROSS THESE AREAS. SNOW AND IFR/LIFR CONDITIONS WILL SPREAD
QUICKLY NORTH AND EAST ACROSS MOST OF THE CWA OVERNIGHT...WITH THE
HEAVIEST SNOWFALL GENERALLY EXPECTED ACROSS PORTIONS OF THE BLACK
HILLS AND FAR SOUTHWEST SD...EASTWARD INTO SOUTH CENTRAL SD. SNOW
SHOULD TAPER OFF QUICKLY IN MOST AREAS TUESDAY MORNING.

A STRONG ARCTIC FRONT WILL ALSO DROP SOUTH THROUGH THE FORECAST AREA
THIS EVENING...INCREASING NORTH WINDS TO 20 TO 35 MPH WITH HIGHER
GUSTS THROUGH TUESDAY AFTERNOON. THIS WILL PRODUCE BLOWING SNOW AND
GREATLY REDUCED VISIBILITIES AT TIMES.


&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY UNTIL 5 PM MST TUESDAY FOR SDZ024-025-
     028-072.

     WINTER STORM WARNING UNTIL NOON MST /1 PM CST/ TUESDAY FOR
     SDZ032-043-044-046-047-049.

     WINTER STORM WARNING UNTIL 5 PM MST TUESDAY FOR SDZ027-029-041-
     074.

     WINTER STORM WARNING UNTIL NOON MST TUESDAY FOR SDZ030-031-042.

     WINTER WEATHER ADVISORY UNTIL NOON MST TUESDAY FOR SDZ001-002-
     012>014.

     WINTER WEATHER ADVISORY UNTIL NOON MST TUESDAY FOR SDZ026-073.

WY...WINTER WEATHER ADVISORY UNTIL 5 PM MST TUESDAY FOR WYZ054>058-
     071.

&&

$$

UPDATE...10
SHORT TERM...HELGESON
LONG TERM...26
AVIATION...10