Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 211702
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1202 PM CDT TUE APR 21 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 351 AM CDT TUE APR 21 2015

ANOTHER WINDY DAY TODAY ESPECIALLY NORTHEAST. THE IDEAL MIXING
STRONG WIND DAY WE HAD YESTERDAY STANDS OUT AGAINST THE LESS WINDY
CONDITIONS WE WILL HAVE TODAY...AND YET WINDS STILL LOOK STRONG
ENOUGH FOR AN ADVISORY FAR EAST/NORTHEAST SO WILL GO WITH ONE THERE.

THE FIRST PROBLEM IS THE WEAK SHORT WAVE APPROACHING FROM THE
NORTHWEST. THE FIRST THOUGHT WAS THAT PRECIPITATION WOULD HAVE
TROUBLE REACHING THE SURFACE FOR THE DRYNESS BELOW IT...BUT THAT
APPEARS TO BE HAPPENING TO THE NORTHWEST. WILL GO WITH A SMALL
MENTION OF LIGHT RAIN/SNOW SHOWERS NORTHWEST EARLY THIS MORNING THEN
CUT OUT THE MENTION BY LATE MORNING AS SOME WARMING AND DRYING OF
THE LOWER AIR IS EXPECTED...AND THERE DOES APPEAR TO BE DRIER AIR
READY TO BE ENTRAINED AS THE SYSTEM MOVES SOUTHEAST.

THIS WAVE SHOULD PASS TO THE SOUTHEAST OR SOUTH-SOUTHEAST DURING
THE DAY. WINDS WILL BE PICKING UP AND CAUSE FIRE WEATHER ISSUES AS
WELL...SEE FIRE WEATHER DISCUSSION. HIGH TEMPERATURES TODAY SHOULD
BE IN THE 50S EXCEPT UPPER 40S NORTHEAST CORNER.

COOLER AIR WILL FLOW IN BEHIND THE SHORT WAVE TONIGHT. SKIES WILL
CLEAR OR BE MOSTLY CLEAR AND WINDS WILL STEADILY DROP OFF. EXPECTING
FREEZING TEMPERATURES LATE TONIGHT AND THERE APPEARS TO BE A LONG
ENOUGH DURATION OF FREEZING TEMPERATURES EXPECTED WHERE READINGS DIP
INTO THE LOW TO MID 20S TO GO WITH A FREEZE WARNING...AS WE HAVE
REPORTS OF SOME ALREADY SUSCEPTIBLE VEGETATION...EVEN THOUGH WE ARE
NOT TO THE NORMAL LATEST FREEZE DATE YET. THE WARNING WILL BE FOR
OUR SOUTHEAST SOUTH DAKOTA ZONES EXCEPT FOR THE SOUTHEAST CORNER.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 351 AM CDT TUE APR 21 2015

DRY BUT LESS WINDY CONDITIONS ARE EXPECTED FOR WEDNESDAY AND
THURSDAY...AS COOL UPPER TROUGH BEGINS TO PULL AWAY AND SURFACE
RIDGE DRIFTS SLOWLY EAST ACROSS THE NORTHERN PLAINS. SHOULD BE LESS
MIXY AS THE RIDGE PASSES THROUGH...BUT WITH FAIRLY DRY AIR MASS
STILL IN PLACE...WILL CONTINUE TO HEDGE TOWARD DRIER DEW POINT
VALUES THROUGH THIS PERIOD. THIS WILL MEAN A FEW MORE DAYS WITH
MINIMUM RH VALUES IN THE 15-25 PERCENT RANGE...BUT FORTUNATELY THE
FIRE DANGER WILL BE MITIGATED DUE TO THE LIGHTER WINDS. DAYTIME
TEMPERATURES WILL SEE SOME RECOVERY FROM EARLY IN THE WEEK...AND THE
LIGHTER WINDS WILL HELP MAKE IT FEEL FAIRLY CLOSE TO NORMAL. GREATER
TEMPERATURE CONCERN WILL BE THE OVERNIGHTS...WITH LIGHT WINDS AND
DRY AIR MASS WEDNESDAY NIGHT PROVIDING OPTIMAL RADIATIVE CONDITIONS
FOR ANOTHER POTENTIAL FREEZE IN PARTS OF THE AREA. WILL HOLD ON ANY
HEADLINES FOR THAT PERIOD JUST YET...BUT WILL HIGHLIGHT POTENTIAL
FOR AREAS ALONG/NORTHEAST OF HURON-SIOUX FALLS-SPENCER IOWA LINE IN
THE HWO.

MIDDLE RANGE OF THE FORECAST FOR FRIDAY AND SATURDAY SHOWING FAIR
AMOUNT OF DISAGREEMENT BETWEEN THE MODELS...WITH GEM/ECMWF SHOWING A
BROAD OPEN TROUGH SLIDING THROUGH THE REGION WHILE THE GFS HANGS ON
TO SOME MID LEVEL RIDGING WHICH SHUNTS THE CENTRAL PLAINS SYSTEM
FARTHER TO THE SOUTH. HARD TO COMPLETELY IGNORE THE WETTER MODELS...
BUT WILL LEAN MORE TOWARD PERSISTENCE OF THE DRIER PATTERN AND
CARRY ONLY SLIGHT CHANCE POPS FOR FRIDAY/FRIDAY NIGHT.
TEMPERATURES DURING THIS PERIOD BEGIN TO SHOW UPWARD
TREND...ESPECIALLY OVERNIGHTS AS A LITTLE MORE MOISTURE WORKS INTO
THE REGION AND HOLDS THE NIGHTTIME READINGS ABOVE FREEZING.

A LITTLE BETTER AGREEMENT IN BRINGING AN UPPER WAVE AND ASSOCIATED
SURFACE FRONT THROUGH THE REGION SUNDAY/SUNDAY NIGHT...AND WILL
STICK CLOSE TO BLENDED GUIDANCE POPS FOR THIS PERIOD. SHOULD SEE A
MORE SIGNIFICANT WARMING TOWARD THE END OF THE FORECAST PERIOD...
THROUGH LATEST OPERATIONAL ECMWF A LITTLE STRONGER/LESS PROGRESSIVE
WITH THE WAVE...WHICH RESULTS IN ANOTHER SHOT OF COOLER AIR WRAPPING
INTO THE NORTHERN PLAINS. THIS A PRETTY DRASTIC CHANGE FROM PREVIOUS
COUPLE OF RUNS...AND WITH GFS ALSO TRENDING WARMER WILL STICK WITH
MORE MILD HIGHS IN THE MID-UPPER 60S FOR MONDAY AT THIS POINT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1200 PM CDT TUE APR 21 2015

VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. GUSTY
NORTHWESTERLY WINDS THROUGH THE AFTERNOON WILL BECOME LIGHT AFTER
02Z THIS EVENING.

&&

.FIRE WEATHER...
ISSUED AT 351 AM CDT TUE APR 21 2015

VERY HIGH TO EXTREME FIRE WEATHER OVER MOST OF THE AREA TODAY GIVEN
THE WINDS AND STILL DRY AIR. RED FLAG WILL BE ISSUED FOR THE
SOUTH DAKOTA FIRE ZONES EXCEPT IN THE NORTHEAST...AND ALSO WILL BE
ISSUED FOR EXTREME NORTHEAST NEBRASKA. FURTHER EAST...THE HUMIDITY
WILL STAY A LITTLE ABOVE CRITERIA...OR A LITTLE MORE SO IN THE
EASTERN PART OF SOUTHWEST MN. THE SATURDAY RAIN IS NO LONGER A
FACTOR GIVEN THE STRONG DRYING YESTERDAY IN REMAINING DORMANT
VEGETATION. WHILE SOME GREENING OF GRASSES NEAR THE SURFACE MAY BE
CUTTING THE FIRE START THREAT...ANY FIRES THAT DO START WILL STILL
SPREAD RAPIDLY SINCE THE TALL AND STILL DORMANT GRASSES WILL THEN
CARRY THE FIRE.

VERY DRY AIR WILL PERSIST OVER MUCH OF THE AREA WEDNESDAY AND
THURSDAY...WITH AFTERNOON HUMIDITY LEVELS OF 15 TO 25 PERCENT...
EASING A BIT THROUGH THE MISSOURI RIVER VALLEY BY THURSDAY. WINDS
WILL BE MUCH LIGHTER THAN MONDAY OR TODAY THROUGH...WHICH SHOULD
LESSEN THE FIRE DANGER. ONLY EXCEPTION WILL BE A SMALL PART OF
SOUTHWEST MINNESOTA ON WEDNESDAY...WHERE LINGERING STRONGER WINDS
MAY STILL RESULT IN VERY HIGH FIRE DANGER.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...RED FLAG WARNING UNTIL 8 PM CDT THIS EVENING FOR SDZ255-256-258.

     FREEZE WARNING FROM 3 AM TO 8 AM CDT WEDNESDAY FOR SDZ038>040-
     050-052>065-068.

MN...WIND ADVISORY UNTIL 6 PM CDT THIS EVENING FOR MNZ071-072-080-081-
     089-090-097.

IA...WIND ADVISORY UNTIL 6 PM CDT THIS EVENING FOR IAZ002-003-013-014-
     022.

NE...RED FLAG WARNING UNTIL 8 PM CDT THIS EVENING FOR NEZ249.

&&

$$

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


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