Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 291138
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
638 AM CDT TUE JUL 29 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 334 AM CDT TUE JUL 29 2014

COOL HIGH PRESSURE IN CONTROL EARLY THIS MORNING...WITH A FEW RANDOM
PATCHES OF MID CLOUDS IN THE JAMES VALLEY...AND SOME RAGGED CIRRUS
ROTATING INTO THE REGION ON THE EDGE OF THE SUBTROPICAL PLUME
THROUGH THE ROCKIES. ALL BUT ASSURED TO SEE ADDITIONAL CUMULUS
DEVELOP WITH THE DIURNAL CYCLE TODAY...BUT LAYER IS QUITE THIN
COMPARED TO YESTERDAY...SO QUICK FORMATION AND A FASTER THAN
TYPICAL ENTRAINMENT AIDED DISSIPATION ARE PROBABLY IN ORDER.
TEMPS WILL BE 2-4 DEGREES WARMER THAN TUESDAY BASED ON TRENDS AT
850/925 HPA...MID 70S TO LOWER 80S EXPECTED.

THERE IS A VERY SUBTLE CONVERGENCE BOUNDARY IN SEVERAL SOLUTIONS
WHICH PUSHES SOUTHWARD FROM NORTH DAKOTA INTO SOUTH DAKOTA
TONIGHT...AND A ROGUE SOLUTION OR TWO THAT SUGGEST AN ISOLATED
SHOWER OR THUNDERSTORM COULD WANDER TOWARD THE NORTHWESTERN CWA
LATER IN THE NIGHT. WITH LARGER SCALE LESS THAN HELPFUL TO SUSTAINED
LIFT...HAVE CHOSEN TO IGNORE ANY THREAT FOR NOW...AND JUST PUT A FEW
MORE CLOUDS INTO THE WEST AFTER EVENING CLEARING. LOWS UNDER LOW
LEVEL RIDGE AXIS LIKELY AGAIN TOWARD THE LOWER SIDE OF GUIDANCE
ENVELOPE.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 334 AM CDT TUE JUL 29 2014

AN EXTENDED PERIOD OF DRY AND PLEASANT WEATHER IS EXPECTED AT LEAST
THROUGH THE END OF THE WEEK. A WELL AMPLIFIED BLOCKING PATTERN WILL
ALLOW VERY LITTLE CHANGE IN THE UPPER LEVEL PATTERN DURING THIS TIME
WITH COOL NORTHWEST UPPER FLOW REMAINING THE NORM. WEAK LOW LEVEL
FLOW WILL ALSO RESULT IN AN EXTENDED PERIOD OF UNUSUALLY LIGHT
WINDS...GENERALLY LESS THAN 10 MPH AND OFTEN LIGHT AND VARIABLE AT
THE SURFACE. DIURNALLY DRIVEN SCATTERED CUMULUS WILL POP UP WITH THE
HEAT OF THE DAY...HOWEVER AM NOT EXPECTING ANY MEASURABLE
PRECIPITATION WITH VERY WEAK FORCING AND DRY LOWER LEVELS. THE GFS
AND NAM ARE PICKING UP ON VERY SPOTTY SHOWERS OR SPRINKLES LATE
WEEK...BUT CONFIDENCE IN ANY MEASURABLE REACHING THE GROUND IS LOW
ENOUGH AT THIS TIME TO LEAVE OUT ANY MENTION.

WITH A DECENT AMOUNT OF SUNSHINE...MIXING SHOULD BE DECENT ENOUGH TO
CONTINUE FOLLOWING SOME OF THE WARMER GUIDANCE FOR DAYTIME
TEMPERATURES. A VERY SUBTLE WARMING TREND CAN BE EXPECTED...BUT NOT
MORE THAN A FEW DEGREES THROUGH THE ENTIRE PERIOD. HIGHS WILL BE IN
THE UPPER 70S TO MID 80S...PERHAPS APPROACHING 90 IN SOUTH CENTRAL
SD BY THE WEEKEND.

MODELS ARE NOW COMING INTO SLIGHTLY BETTER AGREEMENT IN FINALLY
BREAKING DOWN THE PATTERN EARLY NEXT WEEK. THE GFS IS QUITE A BIT
MORE BULLISH IN DRIVING A TROUGH INTO THE NORTHERN PLAINS SUNDAY
AFTERNOON THROUGH AND MONDAY WITH A TRAILING FRONT BECOMING STALLED
NEAR THE MISSOURI RIVER INTO AT LEAST MONDAY NIGHT. THE ECMWF IS
MUCH SLOWER IN PROGRESSION...THEREFORE PRECIPITATION CHANCES REMAIN
LOW END AT THIS TIME WITH LOW CONFIDENCE IN THE TIMING OF THIS
SYSTEM.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 638 AM CDT TUE JUL 29 2014

KFSD AND KHON TAF LOCATIONS WILL FIND SOME VERY SHALLOW FOG
DISSIPATING BY 13Z...BUT WEBCAMS INDICATE THIS WILL NOT LIMIT
VISIBILITY OVER THE NECESSARY PORTION OF THE HORIZON CIRCLE TO PUT
A REDUCED VISIBILITY IN THE TAFS. SHALLOW FOG MAY REPEAT FOR ALL
LOCATIONS TOWARD 12Z WED...BUT WILL NOT INTRODUCE ANY IN TAFS AT
THIS TIME.

&&

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

$$

SHORT TERM...CHAPMAN
LONG TERM...
AVIATION...CHAPMAN






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