100
FXUS63 KFSD 130345
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1045 PM CDT MON AUG 12 2013
.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 413 PM CDT MON AUG 12 2013
ANOTHER PLEASANT EVENING AND NIGHT IS EXPECTED ACROSS MUCH OF THE
REGION. WITH BROAD SURFACE HIGH PRESSURE EXPANDING FROM THE
NORTH...WINDS REMAIN LIGHT AT LESS THAN 5 KT. ASIDE FROM SOME THIN
CIRRUS...SCATTERED CUMULUS HAS DEVELOPED WITH AFTERNOON HEATING.
STARTING TO SEE SOME GROWTH ACROSS SOUTH CENTRAL SOUTH DAKOTA NEAR A
VERY SUBTLE MID LEVEL BOUNDARY EXISTS. MUCAPE VALUES ARE AROUND 1500
J/KG WITH PRETTY WEAK SHEAR AND MODEST LAPSE RATES IN THIS AREA.
GIVEN THE LIMITED DYNAMICAL SUPPORT...DO NOT EXPECT ANY ORGANIZED
THUNDERSTORM ACTIVITY TO HOLD TOGETHER. WITH UPSLOPE FLOW IN WESTERN
SOUTH DAKOTA BRINGING A BETTER CHANCE OF CONVECTION THIS AFTERNOON
AND EVENING...MAY ALSO SEE THE REMNANTS OF SOME OF THIS ACTIVITY
CLIP OUR EXTREME WESTERN FORECAST AREA LATE THIS EVENING AS WELL.
DRIER AIR IS SLOWLY FILTERING INTO THE REGION...SO FOG POTENTIAL
LOOKS LESS FAVORABLE TONIGHT DESPITE LIGHT WINDS OVERNIGHT. LOWS
TONIGHT WILL BE IN THE MID 50S TO LOWER 60S.
TUESDAY WILL BE QUITE SIMILAR TO TODAY WITH A CONTINUATION OF THE
UPPER LEVEL NORTHWEST FLOW AND SURFACE HIGH PRESSURE OVER THE
NORTHERN PLAINS GRADUALLY EXPANDING SOUTHEASTWARD. WITH THE UPSLOPE
FLOW PATTERN ACROSS THE HIGH PLAINS...WILL CONTINUE MENTION OF
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS IN OUR EXTREME
SOUTHWESTERN CORNER...MAINLY IN THE AFTERNOON. STILL NOT SEEING ANY
DYNAMIC SUPPORT TO POINT TOWARDS ANYTHING HIGHER THAN A 30 POP IN
THIS AREA. OTHERWISE...PARTLY CLOUDY SKIES AND PLEASANT TEMPERATURES
IN THE MID 70S TO NEAR 80.
.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 413 PM CDT MON AUG 12 2013
OUR AREA WILL REMAIN BETWEEN A DIGGING TROUGH ALONG THE EAST COAST
AND BUILDING RIDGE WEST OF THE ROCKIES AS WE HEAD INTO MID WEEK.
SOUTHEASTERLY UPSLOPE AND CONVERGENT FLOW SHOULD ALLOW FOR STORMS TO
FIRE IN THE WESTERN PLAINS ON TUESDAY. SOME SIGNS THAT A SUBTLE WAVE
MAY TURN THE LOW LEVEL FLOW ENOUGH TO INCREASE 850 MB CONVERGENCE ON
THE NOSE OF THE JET TUESDAY NIGHT INTO WEDNESDAY MORNING CLOSE TO
THE MISSOURI RIVER. ALTHOUGH EASTWARD EXTENT OF THIS ACTIVITY WILL
BE LIMITED BY DRYER AND STABLE AIR TO THE EAST...SO WILL NOT CARRY
POPS MUCH FURTHER EAST THAN THE JAMES RIVER AT THIS TIME. LOWS WILL
BE COOL EAST OF THE JAMES TUESDAY NIGHT...ESPECIALLY IF SKIES STAY
CLEAR...WITH LOW AND MID 50S LIKELY. WEDNESDAY WILL BE ANOTHER DAY
FEATURING BELOW NORMAL HIGHS...WITH MID 70S TO NEAR 80.
A BETTER MID LEVEL WAVE SHOULD TRAVERSE THE AREA WEDNESDAY NIGHT
THROUGH THURSDAY NIGHT. THIS SHOULD BRING A BETTER CHANCE OF
SCATTERED SHOWER AND THUNDERSTORM ACTIVITY. 18Z NAM IS AN OUTLIER
WITH ITS LOW LEVEL WIND FIELDS AND ALSO QPF OUTPUT...AND THUS A
SOLUTION CLOSER TO THE 12Z GFS AND 12Z ECMWF WAS USED. INSTABILITY
OF 1000 J/KG OR LESS IS GENERALLY EXPECTED...AND WITH DEEP LAYER
SHEAR ALSO BELOW 30 KTS...THINK SEVERE THREAT WILL REMAIN ON THE LOW
SIDE WITH ANY CONVECTION WEDNESDAY NIGHT INTO THURSDAY NIGHT. COULD
SEE SOME LINGERING ACTIVITY IN OUR EAST FRIDAY MORNING...OTHERWISE
EXPECTING A MOSTLY SUNNY AND DRY WEEKEND...AS RIDGING BUILDS INTO
THE AREA. THIS RIDGING AND WARMING ALOFT IS TRENDING A BIT
SLOWER...BUT STILL SHOULD SEE WARMING TEMPERATURES EACH
DAY...APPROACHING NORMAL LEVELS BY THE WEEKEND. MID 70S TO LOW 80S
ON FRIDAY...THEN FROM AROUND 80 TO THE MID 80S OVER THE WEEKEND.
TIMING OF THE NEXT NORTHERN STREAM WAVE CURRENTLY LOOKS LIKE SUNDAY
NIGHT INTO MONDAY...THUS THAT MAY END UP BEING THE NEXT CHANCE OF
STORMS...BUT ONE CAN PROBABLY EXPECT THE TIMING OF THIS TO CHANGE
SOME AS IT GETS CLOSER. CONFIDENCE INCREASING IN THE LONGER RANGE
ENSEMBLES THAT THE NEAR TO ABOVE NORMAL TEMPERATURES CONTINUE INTO
NEXT WEEK.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1045 PM CDT MON AUG 12 2013
VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE TAF PERIOD. THE
EXCEPTION WILL BE SOME PATCHY RADIATIONAL FOG WITH MVFR VSBYS EARLY
TUESDAY MORNING AGAIN...WITH THE BEST CHANCE AT KSUX. WIDESPREAD
FOG IS NOT EXPECTED HOWEVER SINCE THERE WILL STILL BE HIGH LEVEL
WILDFIRE SMOKE COVER OVERHEAD TONIGHT.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
SHORT TERM...
LONG TERM...CHENARD
AVIATION...