328
FXUS63 KUNR 130926
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
326 AM MDT TUE AUG 13 2013
.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT
ISSUED AT 325 AM MDT TUE AUG 13 2013
CURRENT SURFACE ANALYSIS SHOWS NEARLY STATIONARY
FRONTAL BOUNDARY STRETCHING FROM CENTRAL MT TO SOUTHEASTERN WY AND
THEN EASTWARD ACROSS THE CENTRAL PLAINS. WEAK HIGH PRESSURE REMAINS
OVER SOUTH CENTRAL CANADA. UPPER LEVEL ANALYSIS CONTINUES TO SHOW
LARGE SCALE TROF OVER THE GREAT LAKES AND NORTHEASTERN CONUS...WITH
WEAKENING UPPER LOW ALONG THE PACIFIC NW COAST. A RIDGE REMAINS
ACROSS THE ROCKIES INTO THE SOUTHERN PLAINS. WEAK NORTHWEST FLOW
ALOFT IS IN PLACE OVER THE NORTHERN PLAINS. SHOWERS AND
THUNDERSTORMS HAVE DEVELOPED OVERNIGHT FROM SOUTHEASTERN MT INTO
WESTERN SD AND NORTH CENTRAL NEB...WHERE LOW LEVEL JET HAS SET UP.
THESE STORMS ARE GENERALLY SLOW MOVERS...WITH THE MOST CONCENTRATED
AND HEAVIEST RAINFALL ACROSS SOUTHERN JACKSON AND BENNETT COUNTIES
OVER THE LAST FEW HOURS. SKIES ARE VARIABLY CLOUDY...WITH PATCHY
AREAS OF LOW CLOUDS AND FOG OVER THE SD PLAINS. TEMPS ARE IN THE MID
50S TO MID 60S WITH LIGHT WINDS IN MOST AREAS.
DAILY CHANCES FOR SHOWERS AND STORMS WILL CONTINUE FOR A FEW MORE
DAYS AS BLOCKING PATTERN REMAINS IN PLACE. THE BEST OVERALL CHANCES
IN THE NEAR TERM LOOK TO BE THIS AFTERNOON AND EVENING...THEN AGAIN
DURING THE DAY ON WEDNESDAY. TEMPERATURES WILL REMAIN SLIGHTLY BELOW
AVERAGE THROUGH THE MIDDLE OF THE WEEK IN MOST AREAS...WITH HIGHS IN
THE 70S TO MID 80S.
FOR TODAY...SOME SHOWERS AND THUNDERSTORMS WILL LINGER ACROSS SOUTH
CENTRAL SD IN THE MORNING...AND POSSIBLY ACROSS NORTHWESTERN SD AS
WELL. THIS ACTIVITY SHOULD TAPER OFF THROUGH THE MORNING AS LOW
LEVEL JET DISSIPATES. THE CHANCES FOR STORMS WILL INCREASE AGAIN IN
THE AFTERNOON AS ATMOSPHERE DESTABILIZES AND WEAK UPPER LEVEL ENERGY
PASSES OVERHEAD. THE BEST CHANCES EARLY IN THE AFTERNOON LOOK TO BE
ACROSS THE BLACK HILLS AGAIN...WITH ISOLATED TO SCATTERED ACTIVITY
DEVELOPING ACROSS THE PLAINS BY THE LATE AFTERNOON AND EVENING.
SHEAR WILL AGAIN BE RATHER WEAK...WITH ANY POTENTIAL SUPERCELLS
LIKELY BEING SHORT-LIVED. HOWEVER...ABUNDANT MOISTURE AND STEEP
LAPSE RATES WILL HELP TO PRODUCE A LOT OF INSTABILITY IN THE
AFTERNOON AND EVENING...WITH CAPE VALUES OF 1000 TO OVER 2000 J/KG
EXPECTED ACROSS MUCH OF THE CWA. A FEW STRONG TO SEVERE STORMS CAN
BE EXPECTED AGAIN...MAINLY IN THE AFTERNOON AND EVENING. LARGE HAIL
AND STRONG WIND GUSTS WILL BE THE MAIN THREATS FROM ANY SEVERE
STORMS. STORMS WILL BE RELATIVELY SLOW MOVERS...SO LOCALLY HEAVY
RAINFALL IS POSSIBLE AS WELL. ACTIVITY WILL LIKELY LINGER INTO THE
OVERNIGHT HOURS...BUT BECOME MORE ISOLATED IN NATURE.
WEDNESDAY LOOKS TO BE A SIMILAR SETUP AGAIN...WITH CHANCES ACROSS
MUCH OF THE AREA WEDNESDAY INTO WEDNESDAY NIGHT. A BIT STRONGER
SUPPORT ALOFT COULD BRING A HIGHER COVERAGE OF STORMS...ESPECIALLY
IN THE AFTERNOON AND EARLY EVENING. ISOLATED STRONG TO SEVERE STORMS
LOOK LIKELY AGAIN...MAINLY FOR THE AFTERNOON AND EVENING HOURS.
&&
.LONG TERM...THURSDAY THROUGH MONDAY
ISSUED AT 325 AM MDT TUE AUG 13 2013
CHANCE FOR STORMS CONTINUES ON THURSDAY UNTIL THE UPPER HIGH OVER
THE DESERT SOUTHWEST BUILDS AND BECOMES POSITIVELY TILTED. THIS
WILL ALLOW FOR DRIER AIR AND WARMER TEMPERATURES ACROSS THE CWA ON
FRIDAY AND SATURDAY. ON SUNDAY...AN UPPER TROF FLATTENS THE RIDGE
AND TROF SLOWLY MOVES THROUGH THE NORTHERN PLAINS. THE MODELS
STILL HAVE SOME UNCERTAINTY IN THE STRENGTH/PATH/AND LOCAL EFFECTS
OF THIS TROF...HOWEVER IT WOULD BRING A CHANCE FOR THUNDERSTORMS
ESPECIALLY SINCE MOISTURE AXIS REMAINS OVER THE REGION.
&&
.AVIATION...FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING
ISSUED AT 325 AM MDT TUE AUG 13 2013
ISOLATED TSRA WILL CONTINUE THROUGH THIS MORNING WITH
ADDITIONAL ACTIVITY DEVELOPING THIS AFTERNOON. STORMS WILL HAVE
LOCAL MVFR CIGS/VSBYS. OTHERWISE...VFR CONDITIONS WILL PREVAIL
EXCEPT FOR SOME BR AND LOW STRATUS EARLY THIS MORNING ACROSS
PORTIONS OF THE SOUTH DAKOTA PLAINS.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
SHORT TERM...26
LONG TERM...MLS
AVIATION...MLS