000
FXUS63 KUNR 181637
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1037 AM MDT TUE JUN 18 2013

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT
ISSUED AT 320 AM MDT TUE JUN 18 2013

CURRENT SURFACE ANALYSIS SHOWS WEAK HIGH PRESSURE CENTERED OVER
ND...WITH NEARLY STATIONARY FRONTAL BOUNDARY SOUTH AND WEST OF THE
CWA. UPPER LEVEL ANALYSIS SHOWS RIDGE CENTERED OVER THE NORTHERN
HIGH PLAINS...WITH UPPER LOW STILL ALONG THE PACIFIC NW COAST.
REGIONAL RADARS SHOW A COMPLEX OF STORMS OVER SOUTH CENTRAL NEB.
RELATIVELY QUIET WX ACROSS OUR AREA FOR A CHANGE EARLY THIS
MORNING. SKIES ARE CLEAR TO PARTLY CLOUDY WITH TEMPS IN THE UPPER
40S AND 50S AND LIGHT WINDS.

AN UNSETTLED WEATHER PATTERN WILL CONTINUE IN THE SHORT TERM PERIOD
AS THE NEXT UPPER LEVEL DISTURBANCE PASSES THROUGH THE WEAK RIDGE TO
THE WEST AND BRINGS A GOOD CHANCES FOR SHOWERS AND STORMS LATER THIS
AFTERNOON INTO TONIGHT. IN THE MEANTIME...THE DAY WILL START OFF
RATHER PLEASANT...WITH MOSTLY SUNNY SKIES INTO THE AFTERNOON HOURS.
SOME WARMER AIR ALOFT WILL BUILD INTO THE AREA AS THE RIDGE SLIDES A
BIT FURTHER EAST ACROSS THE HIGH PLAINS. HIGH TEMPERATURES WILL BE
IN THE UPPER 70S TO MID 80S ACROSS THE PLAINS...WITH 70S ACROSS THE
BLACK HILLS. SOUTHEASTERLY WINDS WILL INCREASE THROUGH THE
DAY...BECOMING BREEZY AT TIMES IN THE AFTERNOON ACROSS PORTIONS OF
THE PLAINS...ESPECIALLY NORTHWESTERN SD.

SHOWERS AND STORMS WILL BEGIN TO DEVELOP TOWARD MID AFTERNOON ACROSS
WESTERN PORTIONS OF THE CWA AS CAP WEAKENS SUFFICIENTLY BY THAT TIME
AND SHORTWAVE ENERGY APPROACHES. STRONG INSTABILITY IS PROGGED FOR
THE AFTERNOON INTO EARLY EVENING AS SOUTHEASTERLY WINDS BRING IN LOW
LEVEL MOISTURE. CAPE VALUES OF 1500 TO 2500 J/KG ARE ANTICIPATED
OVER MOST OF THE CWA DURING THIS TIME...WITH THE HIGHEST VALUES
GENERALLY OVER WESTERN SD. SHEAR WILL BE RELATIVELY WEAK EARLY IN
THE AFTERNOON...BUT STRENGTHEN AS THE DAY GOES ON. SHORT RANGE
MODELS ARE TIMING AND TRACKING THE WAVE PRETTY WELL...WITH THE BEST
CHANCES FOR STORMS FROM AFTER 21Z TO AROUND 06Z FROM WEST TO EAST.
THE BEST THREAT FOR SEVERE STORMS WILL BE FROM THE BLACK HILLS
AREA...SOUTH AND EASTWARD ACROSS THE CWA...WHERE THERE IS A SLIGHT
RISK FOR SEVERE STORMS. LARGE HAIL WILL BE THE MAIN THREAT...
ESPECIALLY EARLY ON...WITH STRONG WIND GUSTS ALSO BECOMING A BIGGER
THREAT INTO THE EVENING. ACTIVITY WILL BE AIDED BY DEVELOPING LOW
LEVEL JET OVER THE SD PLAINS IN THE EVENING. STORMS SHOULD BECOME
ELEVATED LATE IN THE EVENING AND THEREFORE DECREASE THE SEVERE
THREAT OVERNIGHT TOWARD CENTRAL SD. HOWEVER...WITH THE LOW LEVEL JET
IN PLACE AND FAIRLY STRONG THETA-E ADVECTION OVER EASTERN PORTIONS
OF THE CWA...WILL KEEP LINGERING CHANCES FOR CONVECTION FROM
PORTIONS OF NORTHWESTERN INTO CENTRAL SD INTO WEDNESDAY MORNING.

WEDNESDAY LOOKS TO BE THE WARMEST DAY OF THE WEEK FOR MOST AREAS AS
THERMAL RIDGE SLIDES OVER THE WESTERN DAKOTAS. HIGHS WILL BE IN THE
MID TO UPPER 80S ACROSS THE PLAINS...UPPER 70S AND LOWER 80S OVER
THE BLACK HILLS. THE WARM AIR ALOFT WILL HELP TO PROVIDE A PRETTY
STRONG CAP OVER MUCH OF THE AREA. AT THIS POINT...THE THREAT FOR
STORMS LOOKS PRETTY LOW...AT LEAST THROUGH THE AFTERNOON...UNLESS
ENOUGH UPPER LEVEL SUPPORT CAN HELP TO LOOSEN THE CAP. WILL KEEP LOW
CHANCES OVER THE BLACK HILLS AREA EASTWARD TO CENTRAL SD. BRISK
SOUTHEASTERLY WINDS WILL REDEVELOP OVER THE AREA...KEEPING
SIGNIFICANT LOW LEVEL MOISTURE IN PLACE. IF ANY STORMS DO DEVELOP
LATE WEDNESDAY INTO WEDNESDAY EVENING...SEVERE STORMS WOULD
CERTAINLY BE POSSIBLE.

&&

.LONG TERM...THURSDAY THROUGH MONDAY
ISSUED AT 320 AM MDT TUE JUN 18 2013

WEAK COOL FRONT WILL TRY TO MOVE THROUGH THE CWA THURSDAY AS
UPPER LEVEL RIDGE SHIFTS OVER THE EASTERN DAKOTAS AND UPPER LEVEL
TROUGH MOVE INTO THE NORTHERN ROCKIES. SIGNIFICANT CAP MAY IMPEDE
CONVECTION ALONG THE FRONT...BUT HAVE LEFT POPS IN GIVEN RATHER
LARGE DIFFERENCES IN TIMING/MOVEMENT OF FRONT AS WELL AS STABILITY
PARAMETERS. TEMPERATURES QUITE UNCERTAIN.

UPPER LEVEL TROUGH TO OUR WEST/UPPER RIDGE TO OUR EAST WILL REMAIN
IN PLACE THROUGH THE FIRST PART OF THE WEEKEND WITH A PARADE OF
SHORTWAVES MOVING ACROSS THE CWA UNDER SOUTHWEST FLOW ALOFT. LEE
TROUGH/LEFTOVER FRONTAL BOUNDARY WILL BE FOCUS FOR TSRA ACTIVITY.
FLOW THEN BECOMES INCREASINGLY ZONAL FOR THE END OF THE WEEKEND INTO
EARLY NEXT WEEK...WITH SMALLER CHANCES FOR TSRA. UPPER LEVEL RIDGE
MAY THEN BECOME QUITE ENTRENCHED THE MIDDLE OF NEXT WEEK WITH HOT
WEATHER.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1034 AM MDT TUE JUN 18 2013

VFR CONDITIONS EXPECTED MOST OF THE PERIOD. TSTMS WILL DEVELOP
IN NERN WY LATE THIS AFTN THEN SPREAD ACROSS WRN SD THIS
EVENING...WITH LOCAL IFR CONDITIONS IN HEAVIER STORMS.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

SHORT TERM...26
LONG TERM...HELGESON
AVIATION...JOHNSON