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000
FXUS63 KUNR 231227
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
627 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 12Z TAFS THROUGH 12Z FRIDAY MORNING
ISSUED AT 626 AM MDT THU MAY 23 2013

MVFR/IFR CONDITIONS WILL PERSIST ACROSS MUCH OF NORTHEASTERN WY AND
FAR SOUTHWESTERN SD THIS MORNING. PATCHY FOG WILL ALSO LINGER ACROSS
PORTIONS OF THE FORECAST AREA EARLY THIS MORNING...ESPECIALLY IN
VALLEY LOCATIONS AND OVER THE HIGHER TERRAIN. STRONG SOUTHEASTERLY
WINDS WILL CONTINUE ACROSS NORTHEASTERN WY TODAY AND SPREAD ACROSS
MUCH OF FAR WESTERN SD BY 18Z. THE STRONGEST WINDS WILL BE ACROSS
NORTHEASTERN WY...WHERE GUSTS TO 45-50 HTS ARE EXPECTED TODAY.
GUSTS TO AROUND 45 KTS ARE ALSO EXPECTED ACROSS FAR NORTHWESTERN
SD THIS AFTERNOON INTO THIS EVENING.

&&
.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...26