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000
FXUS63 KUNR 231705
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1105 AM MDT THU MAY 23 2013

.UPDATE...
ISSUED AT 535 AM MDT THU MAY 23 2013

UPDATED FORECAST TO ISSUE HIGH WIND WARNING FOR PORTIONS OF NORTHEAST
WYOMING. A FEW LOCATIONS ALREADY GUSTING TO 50 MPH. 06Z NAM/10Z
RAP SHOW BOUNDARY LAYER WINDS INCREASING TO 45-50 KTS THIS
AFTERNOON. 900MB GEOSTROPHIC WIND AS HIGH AS 65 KTS. HIGH WIND
WARNING MAY NEED TO BE EXTENDED INTO THE BEAR LODGE MOUNTAINS AND
NORTHERN BLACK HILLS THIS EVENING/OVERNIGHT. LATEST FORECAST
SOUNDINGS FROM THE 06Z NAM SHOW POTENTIAL FOR STRONG DOWNSLOPE
WINDS AS LOW LEVEL JET INCREASES.

&&

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT
ISSUED AT 208 AM MDT THU MAY 23 2013

CURRENT SURFACE MAP PLACES HIGH PRESSURE RIDGE ACROSS THE EASTERN
DAKOTAS...WITH LEE SIDE TROF ACROSS MONTANA/WYOMING. LARGE UPPER
LOW SPINNING ACROSS THE PACIFIC NORTHWEST.

TIGHT PRESSURE GRADIENT ACROSS THE FORECAST AREA ALONG WITH
3-4MB/3HR PRESSURE FALLS ACROSS MONTANA WILL RESULT IN WINDY
CONDITIONS...ESPECIALLY ACROSS NORTHEAST WYOMING AND NORTHWEST
SOUTH DAKOTA. WIND GUSTS OF 45-50 MPH LIKELY. WITH UPPER LEVEL
SUBSIDENCE AND STRONG INVERSION...WILL BE DRY TODAY.

FOR TONIGHT...40-50KT LOW LEVEL JET IS LOCATED ACROSS WESTERN
SOUTH DAKOTA WHILE STRONG SHORTWAVE LIFTS THROUGH WESTERN WYOMING
INTO SOUTHERN MONTANA. 2-3C/HR 850-700MB THETA-E ADVECTION
DEVELOPS ACROSS CENTRAL SOUTH DAKOTA. WITH MUCAPE AROUND
250J/KG...A FEW THUNDERSTORMS POSSIBLE ACROSS SOUTH CENTRAL SOUTH
DAKOTA LATE TONIGHT. AS UPPER SHORTWAVE LIFTS INTO EASTERN MONTANA
EARLY FRIDAY MORNING...MODERATE Q-G FORCING PASSES THROUGH
WESTERN SOUTH DAKOTA. BEST CHANCE OF PRECIPITATION ON FRIDAY
SHIFTS EAST OF THE FORECAST EARLY IN THE DAY. HAVE TRIMMED BACK ON
POPS ACROSS WESTERN SOUTH DAKOTA DUE TO LACK OF INSTABILITY.

&&

.LONG TERM...SATURDAY THROUGH WEDNESDAY
ISSUED AT 208 AM MDT THU MAY 23 2013

UPPER LOW OVER THE PACIFIC NORTHWEST WILL GENERALLY REMAIN IN PLACE
OVER THE WEEKEND...WITH SOUTHWESTERLY FLOW ALOFT OVER OUR REGION. A
SERIES OF DISTURBANCES IN THIS FLOW WILL MOVE ACROSS THE NORTHERN
PLAINS OVER THE HOLIDAY WEEKEND...BRINGING DAILY CHANCES FOR SHOWERS
AND THUNDERSTORMS. LEE TROF/DRY LINE WILL GENERALLY REMAIN IN PLACE
ACROSS FAR EASTERN MT AND NORTHEASTERN WY DURING THE PERIOD...WITH
MOIST SOUTHEASTERLY FLOW AND INCREASING INSTABILITY TO THE EAST OF
THE TROF ACROSS THE DAKOTAS. THE THREAT FOR STRONG TO SEVERE
THUNDERSTORMS WILL BEGIN TO INCREASE ON SATURDAY OVER MOST OF THE
FORECAST AREA...WITH THE BETTER CHANCES STILL LOOKING TO BE ON
SUNDAY AND MONDAY. THE EXTENT OF THE SEVERE RISK WILL DEPEND ON THE
TIMING OF THESE DISTURBANCES...WHICH IS STILL UNCERTAIN AT THIS
POINT. CHANCES FOR THUNDERSTORMS WILL LIKELY CONTINUE INTO THE
MIDDLE OF NEXT WEEK AS GENERAL PATTERN CONTINUES. TEMPERATURES WILL
REMAIN ABOVE AVERAGE...WITH HIGHS IN THE 70S AND LOWER 80S ACROSS
THE AREA THROUGH EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1059 AM MDT THU MAY 23 2013

A SMALL AREA OF MVFR CIGS WILL PERSIST INTO EARLY THIS AFT ACROSS
NERN WY BEFORE DISSIPATING. VFR CONDITIONS THEN EXPECTED THROUGH
THIS EVENING BEFORE SOME ADDITIONAL MVFR CIGS DEVELOP OVERNIGHT
ACROSS PORTIONS OF NERN WY AND FAR WRN SD. STRONG SE WINDS GUSTING
TO AROUND 45KTS WILL CONTINUE ACROSS NERN WY THROUGH
TONIGHT...WITH GUSTS OF AROUND 40KTS EXPECTED ACROSS THE WRN SD
PLAINS THROUGH TONIGHT. GUSTS OVER 50KTS MAY DEVELOP LATE TONIGHT
ACROSS THE NRN BLKHLS/FOOTHILLS AREA. LO LEVEL WIND SHEAR WILL
LIKELY DEVELOP LATE TONIGHT AT THE KRAP TERMINAL AS SURFACE WINDS
DECOUPLE AND WINDS JUST OFF THE SURFACE CONTINUE AT AROUND 45KTS.
STRONG WINDS SHOULD DIMINISH FROM WEST TO EAST ON FRIDAY AS A
SURFACE TROF MOVES THROUGH.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY UNTIL 9 PM MDT THIS EVENING FOR SDZ001-002-012>014-
     025-026-031-072-073.

WY...HIGH WIND WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ054>056-058.

&&

$$

UPDATE...7
SHORT TERM...7
LONG TERM...26
AVIATION...JOHNSON