Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 222333
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
433 PM MST MON DEC 22 2014

.SHORT TERM...THIS EVENING THROUGH TUESDAY NIGHT
ISSUED AT 230 PM MST MON DEC 22 2014

UPPER LOW IS CENTERED OVER SD...WITH SURFACE LOW OVER
NORTHEAST SD. RAIN/SNOW IS WRAPPING AROUND THE LOW INTO WESTERN SD.
A TIGHT PRESSURE GRADIENT IS KEEPING NORTHWEST WINDS STRONG THIS
AFTERNOON...ESPECIALLY JUST EAST OF THE HILLS. TEMPS ARE IN THE 30S
TO LOW 40S.

WINDS WILL BECOME MORE NORTHERLY TONIGHT AS THE LOW SLIDES
SOUTHEASTWARD. STRONG WINDS OF 25-35 KTS WITH HIGHER GUSTS ARE STILL
EXPECTED THROUGH THE NIGHT...WITH THE STRONGEST WINDS GRADUALLY
SHIFTING SOUTHWARD. TWEAKED THE ADVISORIES TO CONVERT RAPID CITY AND
CUSTER COUNTY PLAINS TO WINTER WEATHER ADVISORIES FOR BLOWING SNOW
THIS EVENING AFTER THOSE AREAS RECEIVE SNOW. EXTENDED THE WIND
ADVISORY FOR THE SOUTHEASTERN FOOTHILLS AND THE FALL RIVER PLAINS
THROUGH TUESDAY MORNING. WILL LET SOUTHERN FOOTHILLS WIND ADVISORY
EXPIRE THIS EVENING...AS DO NOT EXPECT AS STRONG WINDS THERE WITH
THE MORE NORTHERLY DIRECTION.

MOST OF THE SNOW WILL FALL OVERNIGHT...AND TOTAL AMOUNTS HAVE NOT
CHANGED MUCH FROM PREVIOUS FORECAST. LOOKS LIKE AN ADDITIONAL 6 TO 9
INCHES IS POSSIBLE IN THE NORTHERN HILLS...WITH ABOUT 3 TO 5 INCHES
ON THE SD PLAINS...POSSIBLY MORE AROUND THE SHANNON/JACKSON/BENNETT
COUNTY AREAS. FOR THE RAPID CITY AREA...1-3 INCHES STILL LOOKS ON
TRACK. THREAT OF MOST CONCERN WILL BE THE REDUCED VISIBILITIES DUE
TO BLOWING SNOW...WHICH COULD RESULT IN WHITE-OUT CONDITIONS AT
TIMES. CONSIDERED A WARNING FOR THE SHANNON/JACKSON/BENNETT
AREAS...BUT MAINLY FOR BLOWING SNOW. WINDS DO NOT LOOK INCREDIBLY
STRONG THERE...AND ALTHOUGH SNOW AMOUNTS MAY APPROACH WINTER STORM
WARNING CRITERIA...THINK THE WINTER WEATHER ADVISORY SHOULD COVER
THE THREAT FOR BLOWING SNOW.

BREEZY WINDS WILL CONTINUE ON TUESDAY...AND SNOW WILL LINGER LONGEST
OVER SOUTH CENTRAL SD. SKIES WILL GRADUALLY CLEAR FROM WEST TO
EAST...AND HIGHS WILL BE IN THE 30S. LOWS TUESDAY NIGHT WILL BE IN
THE TEENS.

.LONG TERM...WEDNESDAY THROUGH MONDAY
ISSUED AT 230 PM MST MON DEC 22 2014

ALTHOUGH EXTENDED PERIOD STARTS UNDER UPPER RIDGING...
LONG WAVE TROF DEEPENS OVER THE WESTERN US...INFLUENCING THE WEATHER
OVER THE PLAINS THROUGH THE WEEK BEFORE MOVING EASTWARD AND NEXT
SYSTEM MOVES ONSHORE. BROAD RIDGE WILL BE IN PLACE OVER THE ROCKIES
AND NORTHERN PLAINS WED WHILE SURFACE LOW TRACKS ACROSS SOUTHERN
CANADA WITH A WARM FRONT MOVING NORTH. FORECAST AREA WILL BE IN THE
WARM SECTOR WITH SOUTHWEST WINDS AND PARTLY CLOUDY SKIES...WHICH
WILL WARM TEMPERATURES INTO THE 40S OVER FAR SOUTHWESTERN SD AND THE
NORTHERN AND EASTERN SLOPES OF THE BLACK HILLS. WITH POTENTIAL
SNOWFALL FROM CURRENT STORM...TEMPERATURES PROBABLY WILL NOT GET
INTO THE 50S. COLD FRONT WILL DROP ACROSS THE AREA LATE ON CHRISTMAS
EVE. AS TROF MOVES OVER THE ROCKIES...PRECIPITATION WILL SPREAD
NORTHEASTWARD AHEAD OF IT...WITH MODELS CONVERGING ON THE SURFACE
LOW TRACK ACROSS THE CENTRAL PLAINS INTO THE MISSOURI RIVER
VALLEY...WHICH WOULD GIVE SOUTH CENTRAL SD THE MOST SNOW.
PRECIPITATION SHOULD BE JUST SNOW AS AIRMASS IS DRY WHEN FORECAST
SOUNDINGS SHOW TEMPERATURES ABOVE FREEZING...BUT COOLS QUICKLY
BEHIND COLD FRONT BEFORE BECOMING SATURATED AND BETTER DYNAMICS
REACH THE AREA. TROF CLEARS THE AREA FRIDAY MORNING. AN ALBERTA
CLIPPER SYSTEM DROPS ACROSS THE NORTHERN PLAINS LATE FRIDAY...GFS
SHOWS IT WEAK WITH VIRTUALLY NO QPF...BUT ECMWF HAS A STRONGER
SOLUTION...SO POPS MAY INCREASE IN SUBSEQUENT FORECASTS. ARCTIC HIGH
WILL PUSH SOUTHWARD...WITH MUCH COOLER TEMPERATURES FRIDAY. ANOTHER
ARCTIC HIGH WILL FORCE A BACKDOOR COLD FRONT WESTWARD OVER THE
AREA...WITH EVEN COOLER TEMPERATURES. NEXT SYSTEM DEEPENS AS IT
MOVES FROM THE PACIFIC NORTHWEST INTO THE GREAT BASIN...WITH MORE
SNOW POSSIBLE EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 430 PM MST MON DEC 22 2014

SNOW/BLOWING SNOW WILL CONTINUE OVER WESTERN SD THROUGH
TONIGHT...WITH LOBES OF IT PUSHING INTO NORTHEAST WY AT TIMES.
WIDESPREAD MVFR/IFR CIGS AND IFR VSBYS EXPECTED...WITH LIFR
CONDITIONS WITH THE HEAVIEST SNOW OVER THE HIGHER BLACK HILLS.
GUSTY NORTHWEST WINDS WILL CONTINUE WITH THE STRONGEST WINDS
AROUND 50KTS JUST EAST OF THE BLACK HILLS THROUGH MID-EVENING.
CONDITIONS WILL GRADUALLY IMPROVE TUESDAY...BUT MVFR CIGS WILL
LIKELY LINGER MUCH OF THE DAY.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER STORM WARNING UNTIL NOON MST TUESDAY FOR SDZ024-025.

     WINTER WEATHER ADVISORY UNTIL NOON MST TUESDAY FOR SDZ013-014-
     028-031-032-042>044-072-073.

     WINTER WEATHER ADVISORY UNTIL 6 PM CST TUESDAY FOR SDZ046-047-
     049.

     WIND ADVISORY UNTIL NOON MST TUESDAY FOR SDZ041-074.

     WINTER WEATHER ADVISORY UNTIL 5 AM MST TUESDAY FOR SDZ001-002-
     012.

     WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO NOON MST
     TUESDAY FOR SDZ026-030.

     WIND ADVISORY UNTIL 8 PM MST THIS EVENING FOR SDZ027-030.

     HIGH WIND WARNING UNTIL 8 PM MST THIS EVENING FOR SDZ026.

WY...WINTER STORM WARNING UNTIL NOON MST TUESDAY FOR WYZ057.

     WINTER WEATHER ADVISORY UNTIL 5 AM MST TUESDAY FOR WYZ056-071.

&&

$$

SHORT TERM...POJORLIE
LONG TERM...55
AVIATION...HELGESON




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