Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 161738
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1238 PM CDT TUE SEP 16 2014

.UPDATE...
ISSUED AT 1048 AM CDT TUE SEP 16 2014

PROBABLY THE MAIN CONCERN IN THE NEAR TERM THIS AFTERNOON AND
EVENING WAS THE POTENTIAL FOR STRATUS NOSING INTO OUR FORECAST
AREA...SINCE IT IS CURRENTLY ABUNDANT IN THE CENTRAL PLAINS.
HOWEVER THE VARIOUS MODELS INCLUDING THE NAM12...NAM40...GFS...
ECMWF NEVER DO QUITE BRING IT UP INTO FORECAST AREA...EVEN LATER
TONIGHT. THEY TRY TO REDEVELOP STRATUS IN THE NEB SANDHILLS
OVERNIGHT TONIGHT...AND JUST WHEN IT MAY SNEAK INTO OUR SOUTH
CENTRAL SD ZONES...THE LOW LEVEL WINDS SHIFT IN THAT AREA TO THE
NORTH AND THUS KEEPS IT OUT. MOISTURE A LITTLE HIGHER MAXIMIZED
NEAR 850-800MB IS A DIFFERENT STORY. ALL MODELS SHOW A NORTH TO
SOUTH STRIPE OF THAT LEVEL OF MOISTURE MOVING INTO OUR WESTERN
ZONES BY MIDDAY TODAY...THEN MOVING IT IN BETWEEN THE JAMES AND I
29 BY EARLY EVENING. SO WOULD NOT BE SURPRISED TO SEE SOME FAIR
WEATHER CUMULUS POP THIS AFTERNOON WEST OF I 29. THE MOISTURE
STRIPE THEN MOVES EASTWARD TONIGHT INTO OUR EASTERN ZONES BY 12Z
WED. THEREFORE HIGHER BASED STRATUS MAY FORM ALONG AND EAST OF I
29 TONIGHT.

RIGHT NOW...THERE DOES NOT APPEAR TO BE ANYTHING NOTABLY WRONG
WITH GOING HIGH TEMPERATURES THIS AFTERNOON GIVEN CURRENT
READINGS...AS WELL AS WINDS AND DEW POINTS. ANY FUTURE
MODIFICATIONS TO THE FORECAST TODAY WOULD BE MINOR.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 312 AM CDT TUE SEP 16 2014

SOUTHERLY RETURN FLOW IN PLACE TODAY AS A SURFACE RIDGE OF HIGH
PRESSURE SHIFTS EAST. THIS WILL BRING WARMER AND GRADUALLY MORE
HUMID AIR INTO THE REGION. SOUTHERLY WINDS WILL LIKELY AVERAGE ABOUT
10 TO 20 MPH THIS AFTERNOON AS DEW POINTS CLIMB BACK INTO THE LOWER
50S BY AFTERNOON. TEMPERATURES LIKELY ABOUT 5 TO 10 DEGREES WARMER
THAN MONDAY...RANGING FROM THE UPPER 60S IN PARTS OF SOUTHWEST
MINNESOTA AND NORTHWEST IOWA TO THE MID 70S WEST OF THE JAMES RIVER
VALLEY. ALONG WITH THIS INCREASE IN MOISTURE WILL LIKELY COME AN
INCREASE IN CLOUD COVER...ALBEIT IN A MARGINALLY THIN LAYER. HOWEVER
LIKELY ENOUGH TO INCLUDE MOSTLY CLOUDY SKIES FOR A PERIOD TONIGHT
WHICH WILL ALSO KEEP TEMPERATURES ON THE MILDER SIDE. LOWS IN THE
UPPER 40S TO LOWER 50S IN MOST SPOTS...WHICH IS QUITE A BIT WARMER
THAN THE UPPER 30S TO LOWER 40S THE PAST COUPLE OF MORNINGS.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 312 AM CDT TUE SEP 16 2014

THE LOW LEVEL CLOUD DECK IN THE MOISTURE FETCH WILL BE OVER THE
EASTERN PART OF THE FORECAST AREA WEDNESDAY MORNING. MIXING AND
MODEST HEATING SHOULD BREAK IT UP A BIT AND MORE GENERALIZE THE
CLOUD COVER WEDNESDAY...THOUGH THE LOW LEVEL MOISTURE SHOULD REMAIN.
THERE SEEMS TO BE LITTLE LIFT...MEAGER MOISTURE...AND SCANT
INSTABILITY HIGHER UP SO WILL KEEP OUT ANY MENTION OF CONVECTION. IT
WILL STAY OUT THROUGH THURSDAY AFTERNOON...AS WARMING SLOWLY PICKS
UP IN THE WAKE OF THE DISSIPATING BACK DOOR COLD FRONT WEDNESDAY.
MEANWHILE...LOW LEVEL MOISTURE WILL BE REINFORCED BY AN INFLOW
DEVELOPING FROM THE SOUTHWEST WEDNESDAY NIGHT...THOUGH WILL KEEP
WHAT COULD BE AN OPTIMISTIC PARTLY CLOUDY FORECAST FOR THURSDAY FOR
NOW.

BY THURSDAY NIGHT...A STRONGER MID LEVEL WARM ADVECTION PATTERN WILL
BEGIN TO DEVELOP...AND A FEW SHOWERS OR STORMS WILL BE POSSIBLE
THURSDAY NIGHT INTO WHAT SHOULD BE A FAIRLY WARM AND WINDY FRIDAY.
ON THOSE FRIDAY WINDS...SRLY TO SWRLY FLOW SHOULD BECOME FAIRLY
STRONG AND AIDED BY THE LOW LEVEL WARMING.

COLD FRONT ARRIVING FRIDAY NIGHT SHOULD HELP BRING A DECENT ROUND OF
SHOWERS AND STORMS..SINCE BY THEN THE MOISTURE INFLOW WILL HAVE TIME
TO WORK AT LOW AND MID LEVELS...AND A FOCUS WILL BE PRESENT. THE
WEEKEND SHOULD THEN BE TURNING DRY AND COOLER...THOUGH HOW LONG
INTO SATURDAY THIS PROCESS TAKES IS IN QUESTION THIS FAR AHEAD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1238 PM CDT TUE SEP 16 2014

THE VARIOUS MODELS ALL CONTINUE TO SHOW A SOUTH TO NORTH ELONGATED
BAND OF HIGHER LEVEL STRATUS POSSIBLY DEVELOPING NEAR I 29 THIS
EVENING...THEN SHIFTING TO EAST OF I 29 LATE TONIGHT AND EARLY
WEDNESDAY. CUMULUS IS INDEED FORMING RIGHT NOW BETWEEN I 29 AND
THE JAMES RIVER VALLEY...WHICH COULD BE THE BEGINNING OF THIS
TREND. SO FAR ALL INDICATIONS ARE THAT THE CLOUD DECK WILL REMAIN
IN THE LOWER END VFR CATEGORY TONIGHT FOR KFSD AND KSUX. IF THE
CLOUDS ARE LOWER THAN THE MODEL SOUNDINGS SUGGEST...THEN THE CLOUD
BASES WILL PROBABLY STILL BE UPPER END MVFR. THE OTHER THING THE
MODELS DO IS KEEP THE LOW STRATUS IN THE IFR CATEGORY TO THE SOUTH
OF OUR FORECAST AREA. THEY DO DEVELOP SOME OF THIS IN CENTRAL NEB
OVERNIGHT TONIGHT...BUT JUST WHEN IT BEGINS TO NUDGE INTO OUR
SOUTH CENTRAL SD ZONES...THE WIND SHIFTS IN THAT AREA TO THE NORTH
AND KEEP THE LOW STRATUS SOUTH OF OUR FORECAST AREA. AT ANY
RATE...IFR TO LIFR STRATUS DOES NOT LOOK TO BE A PROBLEM FOR OUR
TAF SITES AT LEAST AT THIS TIME. THE FINAL THING TO WATCH IS MORE
PATCHY FOG DEVELOPMENT AROUND SUNRISE FOR KSUX. THE MISSOURI RIVER
WITH LIGHT WINDS COULD ALLOW THIS TO OCCUR AGAIN. HEDGED WITH A
SHORT TERM IFR TEMPO GROUP FOR KSUX NEAR SUNRISE TO ALERT TO THIS
POSSIBILITY.

&&

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

$$

UPDATE...MJ
SHORT TERM...08
LONG TERM...
AVIATION...MJ


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