Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 241750
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1250 PM CDT THU APR 24 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 313 AM CDT THU APR 24 2014

SPLIT FLOW IS CURRENTLY TAKING PLACE ACROSS THE PLAINS...WITH A
NORTHERN STREAM UPPER TROUGH MOVING THROUGH THE WESTERN AND CENTRAL
DAKOTAS...AND THE SOUTHERN STREAM EXTENDING FROM WESTERN KS TO WEST
TX. PRETTY DECENT HOOKUP OF THE TWO STREAMS IS PHASING TOGETHER IN
THE SIOUX FALLS FORECAST AREA AT THIS TIME...AND LIGHT TO MODERATE
RAINFALL IS BECOMING INCREASINGLY WIDESPREAD EAST OF THE JAMES RIVER
VALLEY. THE ACTIVITY WILL PERSIST INTO EARLY THURSDAY EAST OF THE
JAMES...THEN WILL BECOME INCREASINGLY MORE ISOLATED TO SCATTERED
EAST OF I 29 AS THE MORNING PROGRESSES. FIRE WEATHER CONCERNS
CONTINUE FOR AREAS WEST OF I 29 HIGHLIGHTED BELOW...WITH AREAS RIGHT
ALONG I 29 ALSO CLOSE TO A RED FLAG WARNING AND WILL NEED TO BE
WATCHED. HIGHS TODAY ARE A LITTLE PROBLEMATIC EAST OF I 29...AS THE
DEPTH OF MIXING IS NOT NEAR AS HIGH AS IT IS TO THE WEST. MIXING TO
850MB OR A BIT HIGHER...LOCATIONS FROM MARSHALL TO STORM LAKE SHOULD
TOP OUT IN THE 60 TO 65 DEGREE RANGE. HOWEVER ALONG AND WEST OF I
29...WENT ONCE AGAIN WITH THE WARMER BIAS CORRECTED VALUES AND EVEN
ADDED A COUPLE OF DEGREES TO THEM IN OUR FAR WESTERN ZONES...WITH
LOWER 70S WIDESPREAD IN SOUTH CENTRAL SD.

TONIGHT LOOKS QUIET BUT THERE WILL BE AN INCREASE IN MID AND HIGH
LEVEL CLOUDINESS. SURFACE RIDGING BEGINS TO SLIDE TO THE EAST WHICH
WILL SHIFT THE WINDS TO A SOUTHERLY DIRECTION IN OUR WESTERN ZONES.
BUT WINDS WILL BEGIN TO RAPIDLY DROP OFF EVERYWHERE AFTER SUNSET.
LOWS WILL BE ON THE CHILLY SIDE WITH A LOT OF 35 TO 40.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 313 AM CDT THU APR 24 2014

FRIDAY SHOULD BE A FAIRLY WARM DAY WITH GOOD HEATING POTENTIAL.
INITIAL BAND OF MIDDLE CLOUDS SHOULD PASS OFF TO THE NORTHEAST.
SPOTTY MORNING CONVECTION NOT OUT OF THE QUESTION BUT THE STILL WEAK
INSTABILITY AND LIMITED MOISTURE SUGGESTS KEEPING MENTION OUT OF THE
FORECAST. FOR THE AFTERNOON...REAL GOOD HEATING OUT CONDITIONS WILL
EXIST WITH MODEL SOUNDINGS INDICATING MAXIMUM HEATING POTENTIAL IN
WEAK SOUTHERLY LOW LEVEL FLOW. FAIRLY LIGHT WINDS WILL ADD A TOUGH
OF EFFECTIVE WARMTH.

FRIDAY NIGHT AND SATURDAY WILL BRING THE DEVELOPMENT OF AN
INCREASING LOW TO MID LEVEL EASTERLY FLOW...AND TEMPERATURES HOLDING
STEADY OR EVEN COOLING BELOW THE MID LEVELS...AS INDICATED ON ALL
MODEL SOUNDINGS. MOISTURE INCREASE LOOK MODEST THOUGH THAT SHOULD
PICK UP SOME SATURDAY AFTERNOON. THE RESULT WILL LIKELY BE AT LEAST
SIGHTLY COOLER HIGH TEMPERATURES SATURDAY THAN FRIDAY...WITH THE
EFFECTIVE COOLING GREATER BECAUSE OF THE DEVELOPING STRONGER WINDS.
THE COOLING BELOW THE MID LEVELS SHOULD PUT THE LID ON ANY THOUGHTS
OF CONVECTION THROUGH DAYTIME SATURDAY...SO THE FORECAST WILL STAY
DRY. THINK HIGHS FRIDAY IN THE MID 60S TO MID 70S SHOULD BE ROUGHLY
5 DEGREES COOLER FOR SATURDAY.

SUNDAY WILL BRING A STILL DIFFERENT BALL GAME AS MOIST UNSTABLE AIR
IS FORCED NORTH INTO OUR AREA BY STRONG NEGATIVELY TILTED UPPER LOW.
THE STRONG UPPER WIND OUTLOOK SEEMS TO BRING A THREAT OF SEVERE
WEATHER FOR SUNDAY. THIS MAY BE ELEVATED WITH LIKELY LIMITED LOW
LEVEL HEATING AGAIN...BUT THE THREAT SEEMS STRONG ENOUGH TO MENTION
IN HAZARDOUS WEATHER OUTLOOK. HAVE GONE WITH THE EXTENDED GUIDANCE
ON HIGH TEMPERATURES ACCOUNTING FOR THE LIMITED NATURE OF ANY LOW
LEVEL/SURFACE WARMING. IN ANY EVENT THERE WILL LIKELY BE LOTS OF
CLOUD COVER.

THIS UPPER SYSTEM IS DESTINED TO HANG AROUND FOR A WHILE AT THE
START OF NEXT WEEK...AND WILL KEEP A SLOWLY DECREASING CHANCE OF
SHOWERS OR RAIN IN FOR MONDAY AND TUESDAY...THEN DRY FOR WEDNESDAY
AFTER THE SYSTEM MOVES SOUTHEAST OF THE AREA IN RESPONSE TO CANADIAN
RIDGING. TEMPERATURES WILL BE ON THE COOL SIDE...BUT FOR NOW DO NOT
SEE IT GETTING COOL ENOUGH FOR ANY SURPRISE END OF APRIL
SNOWFALL...WHICH WOULD NOT BE TOO MUCH OF A SURPRISE AFTER LAST
YEARS FIRST OF MAY EVENT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1245 PM CDT THU APR 24 2014

IFR CONDITIONS ACROSS SOUTHWEST MINNESOTA INTO NORTHWEST IOWA
SHOULD GRADUALLY IMPROVE TO VFR LATE THIS AFTERNOON AND EVENING AS
A SURFACE RIDGE BUILDS INTO THE AREA. BRISK NORTHWEST WINDS ACROSS
SOUTHEAST SOUTH DAKOTA ARE EXPECTED TO DECREASE THROUGH THE
EVENING HOURS WITH SUNSET. VFR CONDITIONS ARE EXPECTED TO REMAIN
THROUGH THE OVERNIGHT INTO FRIDAY MORNING WITH LIGHT WESTERLY
WINDS PREVAILING.

&&

.FIRE WEATHER...
ISSUED AT 313 AM CDT THU APR 24 2014

EXTREME MIXING WILL BE TAKING PLACE TODAY WEST OF INTERSTATE
29...WITH MANY AREAS EXHIBITING A MIXING DEPTH OF WELL OVER 5000
FEET AGL BY AFTERNOON. UNFORTUNATELY...THESE AREAS ARE ALSO
COINCIDING WHERE RAINFALL IS CURRENTLY SPOTTY. MIXED LAYER WINDS ARE
AVERAGING 25 TO 35 KNOTS FROM THE NORTHWEST THROUGH THE DAY...
COUPLED WITH MINIMUM HUMIDITY VALUES DROPPING TO 15 TO 20 PERCENT.
THEREFORE WILL CERTAINLY LEAVE THE RED FLAG WARNING IN PLACE FOR
WEST OF I 29. WINDS ARE EXPECTED TO DROP OFF HEADING EAST OF I 29 TO
BELOW RED FLAG CRITERIA. THE TRICKIEST ZONES ARE RIGHT ALONG I 29
FROM BROOKINGS...TO SIOUX FALLS TO SIOUX CITY. THESE ZONES WILL BE
DRY ENOUGH FOR A WARNING...BUT AT THIS TIME...IT APPEARS THAT THE
MIXING DEPTH IS NOT QUITE STRONG ENOUGH TO PRODUCE THE WINDS NEEDED
FOR A RED FLAG WARNING. BUT IT COULD BE CLOSE AND WILL MONITOR FOR
CHANGES. FOR NOW...HAVE THE ZONES ALONG I 29 IN THE VERY HIGH
CATEGORY IN THE GRASSLAND FIRE DANGER INDEX...DROPPING TO HIGH
HEADING EAST OF I 29.

LIGHTER WINDS SHOULD LIMIT THE FIRE DANGER FRIDAY DESPITE DECENT
MIXING...HEATING...AND STILL FAIRLY DRY AIR. SATURDAY COULD BE A
PROBLEM AGAIN DESPITE INCREASING HUMIDITY AS WINDS WILL BE MUCH
STRONGER.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...RED FLAG WARNING UNTIL 7 PM CDT THIS EVENING FOR SDZ255-256-258.

MN...NONE.
IA...NONE.
NE...RED FLAG WARNING UNTIL 7 PM CDT THIS EVENING FOR NEZ249.

&&

$$

SHORT TERM...MJ
LONG TERM...
AVIATION...
FIRE WEATHER...MJ






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