926 
FXUS63 KUNR 260948
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
348 AM MDT MON MAR 26 2012

.DISCUSSION...

TODAY THROUGH WEDNESDAY NIGHT

VIGOROUS UPPER LEVEL TROUGH WILL CONTINUE TO EJECT NE TOWARD THE 
NORTHERN PLAINS...SUPPORTING RAPID DEEPENING OF A SFC CYCLONE OVER 
THE CENTRAL ROCKIES. THIS SYSTEM WILL BRING A VARIETY OF WEATHER TO 
THE REGION DURING THE PERIOD...FROM THUNDERSTORM CHANCES TO FIRE 
WEATHER CONCERNS TO WIND. STRONG THETA-E ADV CONTINUES INTO THE FA 
PER 35 TO 50 KNOT LLJ UNDER STEEPENING MID LEVEL LAPSE 
RATES...SUPPORTING A STAUNCH EML INVERSION. TRAPPED MOISTURE UNDER 
THE INVERSION HAS ALLOWED THE DEVELOPMENT OF A LARGE AREA OF LL 
STRATUS...WHICH WILL BECOME KEY TO HIGH TEMPS TODAY AS WAA CONTINUES 
AT THE BASE OF THE INVERSION...LIMITING MIXING POTENTIAL IN ADDITION 
TO CONVECTION CHANCES AHEAD OF THE SFC TROUGH. LIMITED MIXING THROUGH 
MUCH OF THE DAY WITH CONTINUED ESE FLOW WILL LIMIT T RISES..ESP 
ACROSS THE NORTH WHERE STRATUS MAY LINGER. DAYTIME HIGHS WILL LIKELY 
BE REACHED ALONG AND JUST BEHIND THE SFC TROUGH GIVEN WIND SHIFT 
AND A PERIOD OF STRONG DEEP MIXING. HAVE INCORPORATED THESE CONCERNS 
INTO THE GRIDS. MID LEVEL IMPULSE WILL EJECT INTO WY BY THIS 
AFTERNOON FORCING THE REFLECTED SFC LOW EAST...WITH IMPRESSIVE LL 
PRESSURE RISES BEHIND THE SFC COLD FRONT. NAM GUIDANCE ALONE SUGGEST 
6-8 MB PER HOUR PRESSURE RISES BEHIND THE SFC COLD FRONT...WITH A 
VERY STRONG ISALLOBARIC WIND VECTOR INDICATED. EXPECTED DEEP 
MIXING/IMPRESSIVE PRESSURE RISES/AND LINKED LL FLOW PARALLEL TO THE 
ISALLOBARIC WIND WITH 70 KNOTS OF GEOSTROPHIC FLOW AT H9 WILL 
SUPPORT VERY STRONG WINDS OVER NE WY THIS AFTERNOON AND 
EVENING...WITH SUSTAINED WINDS OF 30 TO 50 MPH WITH HIGHER GUSTS. 
WILL ISSUE A HIGH WIND WARNING. MASSIVE PRESSER ADJUSTMENT WINDS 
WILL SPREAD INTO SW SD CLIPPING FALL RIVER COUNTY. THERE IS ALSO  
THE POTENTIAL FOR WINDS TO INTERACT WITH BLACK HILLS...SUPPORTING A 
PERIOD OF DOWNSLOPE WINDS OVER THE NORTHERN AND POSSIBLE CENTRAL 
FOOTHILLS...AS SUGGESTED IN HIRES ARW OUTPUT...ESP GIVEN A FROUDE 
NUMBER WELL IN EXCESS OF 1. HAVE UPGRADED TO A HW WARNING IN FALL 
RIVER COUNTY...WITH CONTINUATION OF THE WATCH OVER THE BLACK HILLS 
AND FOOTHILLS REGION GIVEN A STILL UNCLEAR PICTURE OF THE DEGREE OF 
DOWNWARD TRANSPORT INTO THIS REGION. SFC COLD FRONT WITH INCREASING 
BROAD LARGE SCALE ASCENT INTO THE REGION WILL SUPPORT A CONVECTIVE 
RESPONSE GIVEN SUFFICIENT LL MOISTURE IN PLACE. CAPPING INVERSION 
WILL LIKELY LIMIT CONVECTION UNTIL THE SFC COLD FRONT AND UPPER WAVE 
ADVECT INTO THE REGION. HENCE LIMITED POPS TO THE LATE AFTERNOON 
WESTERN SD...SAVE WY WHERE AN EARLIER FROPA AND DEEP MIXING MAY KICK 
OFF A TS. HAVE TRENDED TOWARD THE 00Z NAM PER MID LEVEL WAVE 
SPEED...SUGGESTING THE BEST FORCING FOR ASCENT WILL ARRIVE AROUND 
00Z. FORECAST MODELS HAVE TRENDED FARTHER NORTH WITH THE BEST AREA 
OF ASCENT...LIKELY LIMITING WIDER CONVECTIVE COVERAGE CLOSER TO 
ND...WITH MORE ISOLATED ACTIVITY TO THE SOUTH. PLACEMENT OF THE 
80-90 KNOT MID LEVEL SPEED MAX SUGGEST AMPLE SHEAR AND LIFT WILL BE 
PRESENT AT THE NOSE OF THE JETLET...SUPPORTING A SEVERE THREAT WITH 
CELLS GIVEN 1000+ J/KG OF ML CAPE IN PLACE. EXPECT DAMAGING WINDS TO 
BE THE MAIN THREAT GIVEN JET AXIS ORIENTATED TO THE LL FRONT AND 
FAST STORM PROPAGATION SPEEDS IN EXCESS OF 50 KNOTS...WITH LARGE 
HAIL CERTAINLY POSSIBLE GIVEN NEARLY 50 KNOTS OF 0-6KM BULK SHEAR ON 
THE NOSE OF THE MID LEVEL SPEED MAX. HAVE CONTINUED THE SEVERE 
MENTION IN THE EVENING ACROSS NORTHERN SD ZONES. 

CONVECTION WILL QUICKLY ADVECT EAST OUT OF THE REGION...WITH THE 
SYSTEM DEFORMATION ZONE PUSHING INTO THE FAR NORTHERN SD ZONES. HAVE 
ADJUSTED POPS UP ACROSS THE FAR NORTH...WHERE BEST OVERALL ASCENT 
WILL BE FAVORED OVERNIGHT. SFC PRESSURE FALLS WILL CONTINUE OVER 
ND...WITH A STRONG PRESSURE GRADIENT EXPECTED ACROSS THE NORTHERN SD 
ZONES TUES. WIND ADV CRITERIA WILL LIKELY BE MET THERE...ALTHOUGH 
THE POTENTIAL FOR A HWW CRITERIA STILL LOOMS GIVEN CAA 
REGIME/LINKED STRONG FLOW/AND SUFFICIENT MIXING. IN 
ADDITION...SQUEEZING AFFECT FROM THE BLACK HILLS MAY ENHANCED WINDS 
IN THE NORTHERN FOOTHILLS. WILL CONTINUED THE HIGH WIND WATCH. 
LINGERING SHRA WILL BE POSSIBLE TUE MORNING...WITH BL DRYING IN THE 
AFTERNOON AND EVENING. 

MUCH QUIETER WEATHER EXPECTED WED AHEAD OF ANOTHER SW FLOW 
IMPULSE...WHICH WILL SUPPORT PRESSURE FALLS OVER WY/MT. EXPECTED SE 
FLOW WILL LIKELY LIMIT TEMPS ACROSS THE SD PLAINS GIVEN UPSLOPE 
COMPONENT...AND SO HAVE ADJUSTED TO THE COOLER SIDE OF MODEL 
GUIDANCE. LL THETA-E ADV IS EXPECTED TO DEVELOP LATE WED 
NIGHT...WITH A FEW SHRA POSSIBLE IN THE FAR EAST. GIVEN LOW 
CONFIDENCE IN PRECIP MATERIALIZATION ATTM...WILL LEAVE THE FORECAST 
DRY. 


EXTENDED...A MAINLY DRY AND WARM WEATHER PATTERN CAN BE EXPECTED 
LATE THIS WEEK THROUGH THE WEEKEND AS A WEAK UPPER LEVEL RIDGE 
BUILDS OVER THE REGION. A WEAK UPPER LEVEL DISTURBANCE AND COOL 
FRONT PASSING THROUGH THE RIDGE COULD BRING A FEW SHOWERS AND STORMS 
TO SOUTH CENTRAL SD THURSDAY. HIGHS EACH DAY WILL BE IN THE 60S AND 
70S...WITH THE WARMEST DAYS LIKELY BEING FRIDAY AND SATURDAY. SOME 
COOLER AIR IS LIKELY TO BEGIN BUILDING INTO THE WESTERN PORTIONS OF 
THE AREA ON SUNDAY AS RIDGE SHIFTS TO THE EAST OF THE REGION.   

&&

.AVIATION...06Z TAF UPDATE
PERSISTENT LOW LEVEL MOISTURE AND EASTERLY WINDS OVER THE WESTERN 
SOUTH DAKOTA PLAINS IS LEADING TO REDEVELOPMENT OF THE STRATUS DECK 
OVER PORTIONS OF THE AREA. AREAS OF IFR/LIFR CONDITIONS AND FOG CAN 
BE EXPECTED THROUGH THE MORNING HOURS...ESPECIALLY ALONG THE EASTERN 
SLOPES OF THE BLACK HILLS AND ADJACENT PLAINS....INCLUDING KRAP.  
SOME OF THESE LOW CLOUDS WILL PUSH INTO NORTHEASTERN WY AS WELL 
EARLY THIS MORNING.   

SOUTH-SOUTHWEST WINDS WILL INCREASE ACROSS NORTHEASTERN WYOMING THIS 
MORNING AND BECOME GUSTY BY EARLY AFTERNOON. A STRONG LOW PRESSURE 
SYSTEM WILL THEN SWEEP ACROSS THE FORECAST AREA LATE THIS AFTERNOON 
AND EVENING...BRINGING STRONG WEST TO NORTHWEST WINDS ACROSS MUCH OF 
THE AREA...INCLUDING KGCC AND KRAP. SUSTAINED WINDS OF 25 TO 45 MPH 
AND GUSTS TO 60 MPH CAN BE EXPECTED IN MANY AREAS...ESPECIALLY FROM 
NORTHEASTERN WY INTO NORTHWESTERN SD. GUSTY WINDS WILL LINGER 
THROUGH TUESDAY MORNING ACROSS MUCH OF WESTERN SD. THERE IS A CHANCE 
FOR SHOWERS AND THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT AS 
THE SYSTEM MOVES THROUGH...WITH SEVERE THUNDERSTORMS POSSIBLE EARLY 
ON. THE BEST CHANCES FOR PCPN AND SEVERE STORMS WILL BE FROM THE 
NORTHERN BLACK HILLS AREA INTO NORTHWESTERN SD. 

&&

FIRE WEATHER...A STRONG UPPER LEVEL LOW PRESSURE SYSTEM WILL CROSS
THE NORTHERN AND CENTRAL ROCKIES TODAY AS A SURFACE LOW/TROF
SHIFTS EAST INTO THE PLAINS. VERY STRONG WEST TO SOUTHWEST WINDS
WILL DEVELOP THIS AFTERNOON AND EVENING EVENING. THESE VERY
STRONG WINDS ALONG WITH WELL ABOVE AVERAGE TEMPERATURES AND LOW
RELATIVE HUMIDITIES WILL PRODUCE CRITICAL FIRE WEATHER CONDITIONS
ACROSS MUCH OF THE AREA THIS AFTERNOON AND EARLY
EVENING...ESPECIALLY ACROSS NORTHEASTERN WYOMING AND SOUTHWESTERN
SOUTH DAKOTA.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...RED FLAG WARNING FROM NOON TODAY TO 9 PM MDT THIS EVENING FOR 
     BADLANDS AREA-NORTHERN BLACK HILLS-NORTHWESTERN SOUTH 
     DAKOTA PLAINS-SOUTHERN BLACK HILLS-SOUTHWESTERN SOUTH 
     DAKOTA.

     HIGH WIND WATCH FROM 3 PM MDT THIS AFTERNOON THROUGH LATE 
     TONIGHT FOR CENTRAL BLACK HILLS-CUSTER CO PLAINS-HERMOSA 
     FOOT HILLS-NORTHERN BLACK HILLS-RAPID CITY-SHANNON-SOUTHERN 
     BLACK HILLS-SOUTHERN FOOT HILLS.

     HIGH WIND WATCH FROM THIS EVENING THROUGH LATE TONIGHT FOR 
     BENNETT-JACKSON.

     HIGH WIND WARNING FROM 3 PM THIS AFTERNOON TO MIDNIGHT MDT 
     TONIGHT FOR FALL RIVER.

     HIGH WIND WATCH FROM TUESDAY MORNING THROUGH TUESDAY AFTERNOON 
     FOR BUTTE-HAAKON-HARDING-NORTHERN MEADE CO PLAINS-
     PENNINGTON CO PLAINS-PERKINS-SOUTHERN MEADE CO PLAINS-
     ZIEBACH.

     HIGH WIND WATCH FROM 3 PM MDT THIS AFTERNOON THROUGH TUESDAY 
     AFTERNOON FOR NORTHERN FOOT HILLS-STURGIS/PIEDMONT FOOT 
     HILLS.

WY...RED FLAG WARNING FROM NOON TODAY TO 9 PM MDT THIS EVENING FOR 
     LOWER ELEVATIONS OF CROOK AND WESTON COUNTIES-NORTHERN 
     CAMPBELL-SOUTHERN CAMPBELL-WYOMING BLACK HILLS.

     HIGH WIND WATCH FROM 3 PM MDT THIS AFTERNOON THROUGH LATE 
     TONIGHT FOR NORTHEASTERN CROOK-WYOMING BLACK HILLS.

     HIGH WIND WARNING FROM 3 PM THIS AFTERNOON TO MIDNIGHT MDT 
     TONIGHT FOR NORTHERN CAMPBELL-SOUTHERN CAMPBELL-WESTERN 
     CROOK-WESTON.

&&

$$

SHORT TERM...JC
LONG TERM...26
AVIATION...26