Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 161832
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1132 AM MST SUN NOV 16 2014

.UPDATE...
ISSUED AT 1125 AM MST SUN NOV 16 2014

A STRONG COLD FRONT IS CURRENTLY MOVING INTO SOUTH CENTRAL SOUTH
DAKOTA. VERY WINDY CONDITIONS EXIST OVER THE REST OF WESTERN SOUTH
DAKOTA AS COLDER AIR FLOW IN BEHIND THE FRONT. WINDS ARE A BIT
LIGHTER OVER NORTHEASTERN WYOMING BUT STILL WINDY. THE GUSTY
NORTHWEST WINDS ARE BLOWING THE SNOW THAT FELL OVER THE PAST
COUPLE OF DAYS AND CREATING HAZARDOUS TRAVEL CONDITIONS DUE TO
GREATLY REDUCED VISIBILITY IN BLOWING SNOW. CONDITIONS ARE EXPECTED
TO BE WORST ALONG AND SOUTH OF I-90 IN WESTERN SOUTH DAKOTA WHERE
THE MOST SNOW HAD OCCURRED. SCATTERED SNOW SHOWERS ARE ALSO
OCCURRING ACROSS THE AREA WHICH WILL ALSO REDUCE THE VISIBILITY AT
TIMES. THE WIND WILL DIMINISH SLIGHTLY THIS EVENING...HOWEVER
WINDY CONDITIONS AND AREAS OF BLOWING SNOW ARE STILL EXPECTED
THROUGH MUCH OF THE NIGHT OVER PARTS OF WESTERN SOUTH DAKOTA.

&&

.SHORT TERM...TODAY THROUGH MONDAY NIGHT
ISSUED AT 218 AM MST SUN NOV 16 2014

09Z SURFACE ANALYSIS HAD LOW PRESSURE OVER EAST CENTRAL MB WITH
TROUGH INTO NORTHWEST MT. VIGOROUS LOOKING SHORTWAVE LOCATED OVER
SOUTHERN SK PER WATER VAPOR. MAINLY CLEAR SKIES OVER THE CWA
EARLY THIS MORNING WITH SOME CHILLY TEMPERATURES OVER FRESH SNOW
COVER AND LOW-LYING AREAS. CONCERN THIS FORECAST IS AFOREMENTIONED
SHORTWAVE.

TODAY/TONIGHT...SHORTWAVE ROCKETS INTO THE NORTHERN GREAT LAKES AS
SHEAR AXIS PINWHEELS THROUGH THE CWA TODAY. SURFACE LOW WILL TRACK
OVER LAKE SUPERIOR BY 12Z MONDAY PUSHING TROUGH/COLD FRONT THROUGH
THE AREA. COMBINATION OF LOW PRESSURE AND 1043MB ARCTIC HIGH OVER
THE NORTHERN ROCKIES WILL RESULT IN A TIGHT PRESSURE GRADIENT
TODAY/TONIGHT. AHEAD OF COLD FRONT...WARM AIR ADVECTION
PRESENT...BUT QUICKLY TURNS TO MODEST LOW LEVEL COLD AIR ADVECTION.
850MB WINDS INCREASE TO 35-50KTS. WINDS WILL BEGIN TO MIX TO SURFACE
THIS MORNING AND ESPECIALLY THIS AFTERNOON LEADING TO VERY WINDY
CONDITIONS OVER MUCH OF THE CWA. SNOW COVER WILL BE DISLODGED AND
TURNED INTO WIDESPREAD AREAS OF BLSN WITH WHITEOUT CONDITIONS AT
TIMES THROUGH THIS EVENING. LOW LEVEL MOISTURE PROFILES AND LAPSE
RATES SUGGEST ISOLATED/SCATTERED -SHSN OVER MUCH OF THE CWA BY
AFTERNOON. FROUDE NUMBERS SHOW STRONG POTENTIAL FOR UPSLOPE
ENHANCEMENT OVER THE BLACK HILLS...PARTICULARLY FROM CHEYENNE
CROSSING TO ONEIL PASS. HAVE UPPED SNOW AMOUNTS FOR THESE AREAS INTO
THE 3-5 INCH RANGE. IF MOISTURE IS DEEPER/MORE PERSISTENT THAN
EXPECTED...A WINTER STORM WARNING MAY BE NECESSARY FOR HIGHER
AMOUNTS. CURRENT HEADLINES WILL REMAIN INTACT FOR TODAY/TONIGHT.

MONDAY...FEW BREEZY SPOTS/PATCHY BLSN EXPECTED WITH TEMPERATURES
NEAR GUIDANCE.

&&

.LONG TERM...TUESDAY THROUGH SATURDAY
ISSUED AT 218 AM MST SUN NOV 16 2014

NORTHWEST FLOW WILL CONTINUE OVER THE REGION THROUGH THE WEEK
WITH A FEW WEAK DISTURBANCES PASSING THROUGH. MODELS AGREE ON A
BRIEF WARMUP TUESDAY /HIGHS IN THE 30S/ BEFORE ANOTHER SHOT OF
ARCTIC AIR AS A COLD FRONT PASSES THROUGH IN THE EVENING. WINDS
WILL BE BREEZY ON TUESDAY...BUT WILL BECOME STRONGER IN THE
EVENING BEHIND THE FRONT. WEDNESDAY WILL BE COOLER...BUT STILL IN
THE 20S. MODELS BEGIN TO DIVERGE MIDWEEK...WITH THE ECMWF SWEEPING
ANOTHER ROUND OF COLD AIR THROUGH THE REGION THURSDAY...WHILE THE
GFS KEEPS THE COLD AIR FARTHER EAST AND HAS THE CWA WARMING. WHILE
DISAGREEING ON TEMPERATURES...MODELS AGREE TO KEEP THIS WEEK
MAINLY DRY...WITH THE NEXT CHANCE OF SNOW NEXT WEEKEND AS A LOW
PRESSURE SYSTEM STRENGTHENS OVER THE CENTRAL US.

&&

.AVIATION...FOR THE 18Z TAFS THROUGH 18Z MONDAY
ISSUED AT 1039 AM MST SUN NOV 16 2014

A PASSING COLD FRONT IS BRINGING STRONG NORTHWEST WINDS GUSTING
TO 40-50 MPH. THIS WILL RESULT IN WIDESPREAD BLOWING SNOW WITH
IFR/LIFR VSBY. AREAS OF MODERATE TO HEAVY SNOW SHOWERS ACROSS THE
NRN BLKHLS AREA WILL ALSO CONTRIBUE TO IFR/LIFR CONDITIONS.
WSTRONGEST WINDS WILL DECREASE THIS EVENING...BUT STILL REMAIN
GUSTY OVERNIGHT. CONDITIONS WILL IMPROVE TO VFR OVERNIGHT INTO
MONDAY MRNG.


&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY UNTIL 6 AM MST /7 AM CST/ MONDAY FOR
     SDZ001-002-012>014-024>032-041>044-046-047-049-072>074.

WY...WINTER WEATHER ADVISORY UNTIL 6 AM MST MONDAY FOR WYZ057.

     WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR
     WYZ054>056-058-071.

&&

$$

UPDATE...10
SHORT TERM...HELGESON
LONG TERM...POJORLIE
AVIATION...13






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