Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 212044
AFDFSD

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

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 342 PM CDT TUE APR 21 2015

BROAD UPPER LEVEL LOW CENTERED OVER THE GREAT LAKES REGION WILL
WOBBLE EASTWARD OVERNIGHT...AS SURFACE HIGH PRESSURE BUILDS
SOUTHWARD INTO THE NORTHERN PLAINS. THIS WILL RESULT IN DECREASING
CLOUDS FOR OUR AREA...WITH WINDS DYING OFF AS THE ATMOSPHERE
DECOUPLES AND THE GRADIENT WEAKENS. THIS WILL ALLOW FOR GOOD
RADIATIONAL COOLING TONIGHT...AND STILL LOOKING LIKE MID AN UPPER
20S ARE APPROPRIATE FOR LOWS. IN LIGHT OF THAT...REMAINED WITH A
FREEZE WARNING FOR MUCH OF OUR NORTH AND WESTERN AREAS...AND
EXPANDED IT INTO TWO OF OUR SOUTHWESTERN MINNESOTA COUNTIES WHERE IT
ALSO APPEARS THAT TEMPERATURES WILL DIP DOWN INTO THE MID 20S FOR
THREE OR FOUR HOURS LATER TONIGHT.

ON WEDNESDAY THE SURFACE RIDGE AXIS SLIDES JUST TO THE WEST OF OUR
CWA...PROVIDING FOR LIGHT WINDS OVER MOST OF THE AREA. THE EXCEPTION
WILL BE OVER PORTIONS OF SOUTHWESTERN MINNESOTA INTO THE IOWA GREAT
LAKES AREA WITH SLIGHTLY HIGHER WINDS AS THE GRADIENT WILL BE
TIGHTER AND MIXED LAYER WINDS WILL BE STRONGER. WITH WARMING THERMAL
PROFILES HIGHS WILL BE A FEW DEGREES WARMER...IN THE LOWER 50S EAST
TO UPPER 50S WEST. WITH A DRY AIRMASS REMAINING ACROSS THE
AREA...STAYED ON THE LOW SIDE OF GUIDANCE WITH RESPECT TO
DEWPOINTS...WHICH YIELDS AFTERNOON RELATIVE HUMIDITY VALUES OF
AROUND 20 PERCENT. THIS WILL LEAD TO AN ENHANCED FIRE DANGER AS
EXPLAINED BELOW.


.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 342 PM CDT TUE APR 21 2015

LOW LEVEL JET IS EXPECTED TO FORM ACROSS THE PLAINS THURSDAY NIGHT
LEADING TO INCREASED MOISTURE TRANSPORT ACROSS THE AREA.  INITIALLY
THE PROFILE IS FAIRLY DRY...SO DESPITE ISENTROPIC LIFT...DO NOT
EXPECT MUCH TO FORM.  LATER IN THE NIGHT HOWEVER...ATMOSPHERE
BECOMES WEAKLY UNSTABLE. THE REAL QUESTION WILL BE TEMPERATURES FROM
650-500 MB...WHICH MAY SERVE AS A WEAK CAP FOR ANY POTENTIAL SHOWER
ACTIVITY THAT DEVELOPS.  HAVE SOME LOW POPS ACROSS THE SOUTH AFTER
09Z FRIDAY MORNING...EXPANDING NORTH THROUGH THE MORNING BEFORE THE
LOW LEVEL JET WEAKENS.  COULD CONTINUE TO SEE SHOWERS DURING THE DAY
ON FRIDAY AS WARM FRONT LIFTS NORTH THROUGH THE AREA.  BEST CHANCES
FOR PRECIPITATION WILL BE ACROSS THE SOUTHERN HALF OF THE FORECAST
AREA WHERE LOW LEVEL MOISTURE WILL BE MORE ABUNDANT.  NOT EXPECTING
MUCH IN THE WAY OF QPF...MAINLY A FEW HUNDREDTHS OF AN INCH OR LESS.

UPPER LEVEL LOW MOVING FROM THE SOUTHWEST INTO THE CENTRAL PLAINS
JUST SCRAPES BY JUST TO THE SOUTH OF THE FORECAST AREA ON SATURDAY.
HAVE SLIGHT CHANCE POPS ACROSS THE SOUTHERN FRINGE OF THE FORECAST
AREA...BUT WITH DYNAMICS BEING CONCENTRATED TO THE SOUTH...AM NOT
EXPECTING MUCH IN ACCUMULATION IF ANYTHING.  OF BIGGER CONCERN FOR
OUR AREA WILL BE THE EASTERLY WINDS AND INCREASED CLOUD COVER THAT
WILL MAKE IT DIFFICULT TO WARM UP.  HAVE NOTCHED FORECAST HIGHS
DOWN...BUT NOT AS MUCH AS THE ECMWF WOULD SUGGEST.

THEREAFTER...ENTER AN UNSETTLED PATTERN AS AN ELONGATED TROUGH
TRANSLATES FROM WEST TO EAST ACROSS THE FORECAST AREA.  NOT OVERLY
UNSTABLE AHEAD OF THE TROUGH...BUT THIS IS OUR BEST POTENTIAL FOR
WETTING RAINS ACROSS THE AREA OVER THE NEXT SEVEN DAYS ON SUNDAY
INTO SUNDAY NIGHT.

MONDAY LOOKS TO BE A RETURN TO BREEZY NORTHWEST WINDS BEHIND THE
COLD FRONT ASSOCIATED WITH THE TROUGH WITH MORE TRANQUIL CONDITIONS
EXPECTED ON TUESDAY.  WITH DRY NATURE OF AIRMASS BEHIND THE
FRONT...HAVE DROPPED MENTION OF GUIDANCE POPS MONDAY NIGHT INTO
TUESDAY.

&&

.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...

WITH A DRY AIR MASS REMAINING ACROSS THE REGION RELATIVE HUMIDITY
VALUES LOOK TO DROP TO AROUND 20 PERCENT ACROSS THE AREA ON
WEDNESDAY AFTERNOON. THIS WILL RESULT IN AN ENHANCED FIRE
DANGER...HOWEVER WINDS ARE EXPECTED TO BE RELATIVELY LIGHT SO FIRE
WEATHER HEADLINES ARE NOT EXPECTED AT THIS TIME. THE STRONGEST
WINDS WILL BE OVER SOUTHWESTERN MINNESOTA INTO THE IOWA GREAT
LAKES AREA...WHERE FIRE DANGER WILL BE THE GREATEST...THOUGH
SUSTAINED WINDS SPEEDS ARE EXPECTED TO REMAIN BELOW 20 MPH.

&&

.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...FREEZE WARNING FROM 3 AM TO 8 AM CDT WEDNESDAY FOR MNZ071-097.

     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...JM
LONG TERM...
AVIATION...JM
FIRE WEATHER...JM



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