000
FXUS63 KUNR 161418
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
818 AM MDT THU MAY 16 2013

.UPDATE...
ISSUED AT 812 AM MDT THU MAY 16 2013

14Z SURFACE ANALYSIS HAD STATIONARY FRONTAL BOUNDARY ACROSS WY
INTO NE. COMPACT SHORTWAVE OVER NE PANHANDLE PER WATER VAPOUR WITH
CONVECTION DEVELOPING AHEAD OF IT ON NOSE OF 30KT LOW LEVEL JET.
12Z RAP/LAST NIGHT/S UNR WRF SHOW CURRENT CLUSTER OF SHRA/TSRA
MOVING NORTHEAST INTO CENTRAL SD THROUGH THE EARLY AFTERNOON HOURS
AND THUS HAVE ADJUSTED POPS TO MATCH.

FURTHER WEST...500-1000J/KG SBCAPE BECOMES AVAILABLE THIS
AFTERNOON AS A WEAK SHORTWAVE MOVES FROM WY INTO THE DAKOTAS.
EXPECT SCATTERED TSRA TO DEVELOP WITH THESE FEATURES AND THIS IS
HANDLED WITH CURRENT FORECAST.

0-6KM BULK SHEAR WILL BE MARGINAL FOR ORGANIZED ACTIVITY ACROSS
THE CWA TODAY/TONIGHT.

&&

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT
ISSUED AT 250 AM MDT THU MAY 16 2013

SATELLITE IMAGERY SHOWS A COMPACT UPPER LEVEL SHORT
WAVE CROSSING AN OLD STATIONARY FRONTAL BOUNDARY IN NORTHEASTERN
WYOMING THIS MORNING.  SCATTERED SHOWERS WITH A SMALL AMOUNT OF
LIGHTNING HAVE BEEN ONGOING FOR MOST OF THE OVERNIGHT HOURS ACROSS
THE WYOMING PART OF THE FORECAST AREA INCLUDING THE WESTERN BLKHLS
AS WELL AS ACROSS NORTHWEST SOUTH DAKOTA...BUT HAVE DECREASED IN
INTENSITY SINCE MIDNIGHT. CLOUD COVER HAS GENERALLY INCREASED ALSO.

TODAY...THE MODELS HAVE ALL JUMPED ON THE BAND WAGON FOR A
WIDESPREAD INCREASE IN MOISTURE AS THE SHORT WAVE CROSSES INTO SOUTH
DAKOTA. MODEL SOUNDINGS SHOW A MOSTLY SATURATED AIRMASS BY MIDDAY.
BY MIDDAY WHEN SOME HEATING CAN HELP DEVELOP UPDRAFTS, THE MODELS
ARE CONSISTENT IN DEVELOPING PRECIPITATION OVER MOST OF WESTERN
SOUTH DAKOTA. SEVERE STORMS ARE NOT EXPECTED DURING THE DAY DUE TO
HAVING ONLY MODERATE INSTABILITY AND MINIMAL BULK SHEAR.

TONIGHT AND FRIDAY...UNSETTLED CONDITIONS ARE FORECAST TO CONTINUE
THROUGH FRIDAY WITH THE CHARACTER OF THE ACTIVITY TURNING TO MORE
TYPICAL SPRING CONVECTION. CAPE VALUES WILL LIKELY TOP 1000 IN
MANY LOCATIONS LATE THIS EVENING...BUT WITHOUT HEATING...AND THEN
AGAIN FRIDAY AFTERNOON. ONCE AGAIN WIDESPREAD SEVERE THUNDERSTORMS
ARE NOT EXPECTED BUT THE CONVECTION IS EXPECTED TO BE SOMEWHAT MORE
INTENSE THAN TODAY.

&&

.LONG TERM...SATURDAY THROUGH WEDNESDAY
ISSUED AT 250 AM MDT THU MAY 16 2013

DEEP UPPER TROF ACROSS THE PACIFIC NORTHWEST WILL SLOWLY SHIFT
ACROSS THE NORTHERN ROCKIES THIS WEEKEND. THIS WILL RESULT IN A
SOUTHWEST FLOW PATTERN WITH SEVERAL SHORTWAVES EJECTING OUT OF THE
TROF. THIS WILL BRING GOOD CHANCES FOR SHOWERS AND THUNDERSTORMS ON
SATURDAY...WITH SOME SEVERE STORMS POSSIBLE ACROSS THE SOUTH DAKOTA
PLAINS. WIDESPREAD RAIN SHOWERS AND THUNDERSTORMS ARE EXPECTED FOR
SUNDAY AS THE UPPER LOW CUTS OFF OVER THE NORTHERN PLAINS. PRECIP
CHANCES WILL CONTINUE THROUGH MONDAY NIGHT AND TUESDAY AS THE UPPER
LOW SLOWLY SHIFTS EAST OF THE NORTHERN PLAINS. WEAK RIDGING MOVES IN
TUESDAY NIGHT INTO WEDNESDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 519 AM MDT THU MAY 16 2013

ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
RE-DEVELOP EARLY THIS MORNING ACROSS NORTHEAST WYOMING AND EXPAND
ACROSS SOUTH DAKOTA TODAY. GUSTY WINDS AND MVFR CONDITIONS CAN BE
EXPECTED AROUND SHOWERS AND STORMS.


&&

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

$$

UPDATE...HELGESON
SHORT TERM...CARPENTER
LONG TERM...15
AVIATION...15