Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 220938
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
438 AM CDT TUE APR 22 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 438 AM CDT TUE APR 22 2014

SURFACE RIDGE AXIS SITUATED OVER THE CWA EARLY THIS MORNING WILL
PUSH OFF TO THE EAST TODAY...WITH A STRONG SOUTHERLY LOW LEVEL FLOW
DEVELOPING ACROSS OUR WEST ON THE BACKSIDE OF THE HIGH. IN A
TIGHTENING GRADIENT AND WINDS AT THE TOP OF THE MIXED LAYER
INCREASING TO AROUND 30 TO 35 KTS BY AFTERNOON...IT WILL BECOME
WINDY THROUGH SOUTH CENTRAL SOUTH DAKOTA AND THE JAMES RIVER
VALLEY...CONTRIBUTING AGAIN TO AN ENHANCED FIRE DANGER ACROSS THAT
AREA...WHICH WILL BE ADDRESSED IN THE DISCUSSION BELOW. 850 MB
TEMPERATURES WILL WARM OVER YESTERDAY...MOST NOTABLY ACROSS OUR
WEST...AND LOOKING AT HIGHS IN THE LOWER TO MID 70S THROUGH THE
JAMES RIVER VALLEY INTO THE LOWER MISSOURI RIVER CORRIDOR...TO MID
60S OVER EAST CENTRAL SOUTH DAKOTA AND SOUTHWESTERN MINNESOTA WHERE
THERMAL PROFILES ARE A LITTLE COOLER AND AFTERNOON MID CLOUDS MAY
HOLD TEMPS DOWN A BIT.

FOR TONIGHT...A STRONG LOW LEVEL JET WILL DEVELOP ACROSS CENTRAL AND
EASTERN SOUTH DAKOTA...AND WITH INCREASING MID LEVEL THETA E
ADVECTION AND INSTABILITY MAY SEE SHOWERS AND ISOLATED THUNDERSTORMS
DEVELOP ACROSS THE AREA LATER IN THE NIGHT. MOISTURE LOOKS TO BE
RATHER LIMITED AND INSTABILITY IS WEAK...SO WOULD NOT EXPECT
WIDESPREAD CONVECTION. IT WILL BE A WINDY NIGHT AS THE GRADIENT
CONTINUES TO TIGHTEN...AND WITH THAT IT WILL BE MILD WITH LOWS ONLY
DROPPING INTO THE UPPER 40S TO LOWER 50S.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 438 AM CDT TUE APR 22 2014

WILL CARRY CHANCE OF SHOWERS AND ISOLATED STORMS ACROSS OUR EAST
INTO WEDNESDAY MORNING...FOR LINGERING ACTIVITY AS LOW LEVEL JET
SHIFTS A BIT FARTHER EAST THROUGH THE MORNING. PRIMARY FOCUS FOR
THUNDERSTORMS WILL BE LATE WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT
THOUGH...AS UPPER TROUGH AND ASSOCIATED COLD FRONT MOVE ACROSS THE
REGION. MODELS CONTINUE TO SHOW STRONG DEEP LAYER SHEAR ALONG AND
BEHIND THE BOUNDARY IN THE LATE AFTERNOON AND EVENING. INSTABILITY
STILL ON THE WEAKER SIDE DUE TO LIMITED MOISTURE...THOUGH MAY BE
LOCALLY HIGHER WITH LOW LEVEL MOISTURE POOLING NEAR THE BOUNDARY.
WITH THE STRONG SHEAR CANNOT RULE OUT A MARGINALLY SEVERE STORM...
BUT THREAT APPEARS ISOLATED AND HARD TO ARGUE WITH SUB-SLIGHT RISK
IN SPC OUTLOOK FOR WEDNESDAY ACROSS OUR FORECAST AREA. WITH MOST
AREAS EXPECTED TO SEE LIMITED PRECIP THREAT MUCH OF THE DAY WITH
SOME AFTERNOON SUNSHINE...WILL CONTINUE WITH HIGHS RANGING FROM THE
UPPER 50S IN OUR FAR NORTHEAST...TO SOME UPPER 70S WEST OF THE JAMES
VALLEY.

DEEPER MOISTURE FLOWS INTO THE AREA THROUGH THE EVENING/OVERNIGHT
AHEAD OF THE BOUNDARY...AND EXPECT TO SEE RAIN COVERAGE INCREASE
ACROSS OUR EASTERN CWA. EXPECT THUNDERSTORM COVERAGE TO REMAIN MORE
SCATTERED TO ISOLATED THOUGH WITH INSTABILITY WEAKENING FURTHER
THROUGH THE OVERNIGHT HOURS.

THURSDAY WILL PROBABLY SEE SOME LINGERING SHOWERS ACROSS OUR EAST IN
THE MORNING...BUT THEN SHOULD BE A STRONG MIXING DAY...ESPECIALLY
ACROSS THE SOUTHWEST HALF OF THE CWA WITH DEEP WEST-NORTHWEST FLOW
THROUGH A RELATIVELY DRY ATMOSPHERE. WITH THAT IN MIND...KEPT
AFTERNOON/EARLY EVENING DEW POINTS CLOSER TO BIAS-CORRECTED GRIDS
WITH VALUES MIXING DOWN INTO LOWER 20S ALONG/WEST OF THE JAMES RIVER
IN THE AFTERNOON. A WEAK TRAILING MID LEVEL WAVE KEEPS A BIT DEEPER
MID LEVEL MOISTURE ACROSS NORTHEAST PORTIONS OF THE AREA THROUGH THE
AFTERNOON...WITH MARGINALLY UNSTABLE MID LEVEL LAPSE RATES PROVIDING
POTENTIAL FOR SOME SPOTTY SHOWERS. GIVEN THE DRY SUB-CLOUD LAYER...
NOT SURE HOW MUCH OF THIS ACTIVITY WILL REACH THE SURFACE...BUT WILL
CARRY SOME LOW POPS FROM EAST CENTRAL SD INTO SOUTHWEST MN. STRONG
MIXING WILL ALLOW FOR DECENT HEATING ONCE AGAIN...WITH HIGHS IN THE
60S LIKELY FOR MOST AREAS.

BEGINNING OF THE LONGER RANGE LOOKS TO REMAIN ON THE DRY SIDE...
THOUGH STILL SOME MODEL DISCREPANCIES REGARDING HOW QUICKLY THE
CHANCE FOR RAIN WILL RETURN AHEAD OF THE NEXT APPROACHING TROUGH.
THINK UPPER LEVEL RIDGING ALONG WITH RELATIVELY DRY LOW LEVEL
EASTERLY FLOW WILL KEEP MOST OF THE AREA DRY THROUGH SATURDAY...WITH
CHANCES RAMPING UP SATURDAY NIGHT THROUGH SUNDAY NIGHT AS THE UPPER
RIDGE SHIFTS NORTHEAST AND UPPER TROUGH SWINGS OUT INTO THE PLAINS.
THERMAL PROFILES SUGGEST MOST AREAS SHOULD JUST SEE A COLD RAIN...
HOWEVER...NORTHERN AREAS DO COOL ENOUGH BY SUNDAY NIGHT THAT COULD
SEE A LITTLE SNOW MIX IN AND WILL CARRY THAT IN SOME OF OUR HIGHER
ELEVATIONS LATER SUNDAY NIGHT FOR NOW. ALSO CANNOT RULE OUT ISOLATED
THUNDER THREAT...MAINLY SOUTH WHERE SOME ELEVATED INSTABILITY WORKS
INTO THE AREA AHEAD OF THE WAVE. HOWEVER...DIFFICULT TO DETERMINE
FAVORED TIMING/LOCATION AT THIS POINT SO WILL STICK WITH JUST RAIN
SHOWERS FOR NOW.

FRIDAY COULD STILL BE ON THE MILD SIDE...ESPECIALLY SOUTH WHERE LOW
LEVEL TEMPERATURES DO NOT COOL QUITE AS QUICKLY AS NORTHERN AREAS.
CURRENTLY HAVE HIGHS FROM THE MID 50S NORTH TO MID 60S FAR SOUTH...
THOUGH THIS PERIOD MOST LIKELY TO SEE SOME CHANGES AS WILL DEPEND ON
TIMING OF STRONGER COLD ADVECTION. WEEKEND INTO EARLY NEXT WEEK THEN
JUST LOOKS CHILLY...WITH HIGHS 10 TO 20 DEGREES BELOW LATE APRIL
NORMALS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1043 PM CDT MON APR 21 2014

WINDS WILL INCREASE DURING THE DAY TOMORROW OUT OF THE SOUTHEAST
WITH GUSTS OVER 20 KTS EXPECTED BY LATE AFTERNOON...ESPECIALLY
WEST OF I-29. THERE COULD BE A FEW HIGH BASED THUNDERSTORMS FROM
HURON TO BROOKINGS AND PIPESTONE BETWEEN 03Z AND 06Z. AT THIS
POINT...EXPECT COVERAGE TO BE ISOLATED AND PROBABILITY OF
AFFECTING HON TO BE VERY LOW SO DID NOT INCLUDE IN TAFS AT THIS
TIME. OTHERWISE...VFR CONDITIONS EXPECTED THROUGH 06Z WEDNESDAY.


&&

.FIRE WEATHER...
ISSUED AT 438 AM CDT TUE APR 22 2014

SOUTHEASTERLY WINDS WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30
TO 35 MPH THROUGH SOUTH CENTRAL SOUTH DAKOTA AND THE JAMES RIVER
VALLEY TODAY. THIS IN COMBINATION WITH AFTERNOON RELATIVE HUMIDITY
OF AROUND 25 PERCENT WILL RESULT IN A VERY HIGH FIRE DANGER ACROSS
THAT AREA. WITH RH VALUES BEING MARGINAL...HELD OFF ON ISSUING A RED
FLAG WARNING...HOWEVER...IF DEW POINTS DROP LOWER THAN EXPECTED OR
TEMPERATURES WARM MORE THAN EXPECTED...FUTURE SHIFT MAY HAVE TO RE
EVALUATE.

WINDY CONDITIONS WILL CONTINUE ACROSS THE REGION WEDNESDAY...THOUGH
INCREASING LOW LEVEL MOISTURE AHEAD OF AN APPROACHING FRONT SHOULD
KEEP HUMIDITY LEVELS IN CHECK...WITH MINIMUM AFTERNOON HUMIDITY
LEVELS RANGING FROM 30 TO 40 PERCENT IN THE LOWER BRULE AREA...TO 50
PERCENT OR HIGHER IN SOUTHWEST MINNESOTA AND THE IOWA GREAT LAKES.
DESPITE THE HIGHER HUMIDITY LEVELS...FIRE DANGER WILL STILL BE HIGH
TO VERY HIGH DUE TO THE STRONG WINDS.

FIRE DANGER CONCERNS INCREASE AGAIN ON THURSDAY HOWEVER...WITH LOW
LEVEL DRYING AND GUSTY WESTERLY WINDS DEVELOPING BEHIND THE DEPARTING
FRONT. THE AREA OF GREATEST CONCERN WOULD BE FROM THE LOWER BRULE
INTO THE JAMES RIVER VALLEY AND LOWER BIG SIOUX RIVER VALLEY. THESE
AREAS WILL SEE THE STRONGEST AFTERNOON WINDS IN THE 20 TO 30 MPH
RANGE...ALONG WITH THE POTENTIAL FOR MINIMUM HUMIDITY LEVELS OF 15 TO
25 PERCENT. WILL NOT ISSUE ANY FIRE WEATHER HEADLINES AT THIS TIME...
BUT THE FORECAST FOR THESE AREAS WILL HAVE TO BE MONITORED CLOSELY
OVER THE NEXT COUPLE OF DAYS.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...JM
LONG TERM...JH
AVIATION...SCHUMACHER
FIRE WEATHER...JM/JH





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