Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 230503
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1003 PM MST SUN FEB 22 2015

.SHORT TERM...THIS EVENING THROUGH MONDAY NIGHT
ISSUED AT 135 PM MST SUN FEB 22 2015

UPPER LEVEL ANALYSIS HAS HIGH AMPLITUDE POSITIVELY TILTED TROF
ACROSS THE NORTHERN PLAINS INTO THE GREAT BASIN...WITH RIDGE JUST
OFF THE PACIFIC COAST. SKIES ARE SUNNY TO PARTLY CLOUDY ACROSS THE
NORTHERN PLAINS. AT THE SURFACE...ARCTIC HIGH RESIDES ACROSS THE
EASTERN DAKOTAS WITH WARMER AIR LOCATED JUST WEST OF THE ROCKIES.
TEMPERATURES AT 2PM ARE IN THE SINGLE DIGITS AND TEENS ACROSS THE
AREA WITH LIGHT WINDS.

TONIGHT...HIGH AMPLITUDE TROF SHEARS OUT WITH NORTHERN STREAM
SHIFTING EAST AND CUT-OFF LOW DEVELOPING ACROSS THE SW CONUS.
WESTERN RIDGE NOSES INTO SW CANADA AND THE PACIFIC NORTHWEST.
ARCTIC SURFACE HIGH SHIFTS INTO IOWA WITH LIGHT RETURN FLOW
DEVELOPING ACROSS THE AREA. UNDER MOSTLY CLEAR SKIES...TEMPS WILL
TUMBLE...INTO THE SINGLE DIGITS EITHER SIDE OF ZERO. SOME WARMER
AIR WILL BEGIN TO BUILD IN FROM THE WEST LATE TONIGHT...POSSIBLY
BRINGING SLOWLY RISING TEMPS OVER WESTERN PORTIONS OF THE CWA
TOWARD MORNING.

MONDAY...WESTERN UPPER RIDGE EXTENDS EAST INTO THE NORTHERN
ROCKIES WITH UPPER LOW SINKING INTO SOUTHERN CALIFORNIA. DECENT
PRESSURE GRADIENT BETWEEN DEPARTING ARCTIC SURFACE HIGH AND STRONG
SURFACE LOW IN CENTRAL CANADA WILL PRODUCE ROBUST WEST TO
SOUTHWEST BOUNDARY LAYER FLOW ACROSS THE NORTHERN PLAINS...AND
ADVECT MUCH WARMER AIR INTO THE AREA FROM THE WEST. UNDER
PLENTIFUL SUNSHINE...HIGHS WILL CLIMB INTO THE 30S TO LOWER 40S.
CLOUDS WILL INCREASE SOME FROM THE NORTH MONDAY NIGHT...WITH LOWS
NEAR SEASONAL AVERAGES...MOSTLY IN THE MID TEENS TO MID 20S.

.LONG TERM...TUESDAY THROUGH SUNDAY
ISSUED AT 135 PM MST SUN FEB 22 2015

PERSISTENT NW FLOW WILL REMAIN IN PLACE THROUGH THE PERIOD. A
MORE PRONOUNCED CP/MODIFIED ARCTIC INTRUSION STILL ON TRACK IN THE
MIDDLE OF THE WEEK. THE WESTERN NOAM RIDGE WILL SHIFT WEST AS A
STRONG RIDGE TOPPING TROUGH SHIFTS SE ACROSS THE ROCKIES...WITH
THE RIDGE THEN BUILDING NORTH INTO THE HIGH LATITUDES. THIS WILL
ALLOW A MUCH DEEPER COLD AIRMASS TO SHIFT WEST OVER THE
REGION...WITH A LONGER RESIDENCE TIME...AS SIG TROUGH LOADING
OCCURS INTO THE WEST SIDE OF THE RIDGE. SNOW WILL ACCOMPANY THIS
IMPULSE AND ASSOCIATED ARCTIC COLD FRONT...WITH GENERALLY AN INCH
OR TWO EXPECTED...POTENTIALLY MORE OVER THE NORTHERN BLACK HILLS.
THE WESTERN BIAS TO THE EASTERN PAC RIDGE STILL LOOKS TO LINGER
INTO NEXT WEEKEND...SUGGESTING THAT COLD CONDS WILL PREVAIL INTO
NEXT WEEK. SOME DETERMINISTIC SOLUTIONS ARE SUGGESTING THE
POTENTIAL FOR A MORE ORGANIZED SNOW TOWARD THE BEGINNING OF NEXT
WEEK AS THE SW CONUS UPPER TROUGH EJECTS INTO THE CENTRAL PLAINS.
HOWEVER...GIVEN THE PATTERN THE MAJORITY OF THIS SYSTEM/S
INFLUENCE SHOULD PASS SOUTH OF THE REGION...WITH ONLY THE SE THIRD
POTENTIALLY IMPACTED WITH SNOW ACCUMS.

A BRIEF WARM UP EXPECTED TUE AS A FAST MOVING CLIPPER SYSTEM SURGES
WAA INTO THE REGION BEFORE THE TRAILING STRONGER IMPULSE SHIFTS A
COLD FRONT SOUTH. MAINLY 40S WITH SOME 50S EXPECTED FOR HIGHS THEN.
A DECENT CHANCE FOR SNOW REMAINS TUE NIGHT-WED AS THE AFOREMENTIONED
IMPULSE DIVES SE ACROSS THE ROCKIES AND AN ARCTIC FRONT BACKS INTO
THE REGION. ATTM MOST OF THE LSA AND ASSOCIATED LIFT CONTINUES TO BE
PROGGED SW OF THE FA...WITH GENERALLY LIGHT ACCUMS /1-3 INCHES/
EXPECTED PER FGEN PROCESSES. COLD AIR WILL SETTLE INTO THE REGION
THUR...WITH TEMPS AVERAGING 10-25 DEGREES BELOW SEASONAL NORMS. SOME
MODERATION IN TEMPS EXPECTED FRI-SAT WITH WEAK RIDGING AHEAD OF
ANOTHER PROGGED STRONG NW FLOW UPPER TROUGH. TRENDED A LOW CHANCE
POP FURTHER NORTH ACROSS THE SOUTHERN HALF OF THE FA SAT-SUN IN
RESPONSE TO THE EXPECTED EJECTION OF THE SW CONUS UPPER TROUGH AND
POTENTIAL PHASING WITH THE NORTHERN STREAM. A PARTIAL TO FULL PHASE
WOULD SHIFT CHANCES FOR SNOW ACCUMS FURTHER NW. ATTM...THE BULK
OF SNOW LOOKS TO REMAIN SOUTH OF THE FA...HOWEVER THIS COULD
CERTAINLY CHANGE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 959 PM MST SUN FEB 22 2015

VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD.

&&

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

$$

SHORT TERM...15
LONG TERM...JC
AVIATION...HELGESON






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