Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 192350
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
650 PM CDT SUN APR 19 2015

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 312 PM CDT SUN APR 19 2015

UPPER TROUGHING CONTINUES TO SLIDE EASTWARD THROUGH THE REGION THIS
AFTERNOON. STRONGER EMBEDDED VORTICITY MAXIMUM ROTATING NE THROUGH
IOWA WILL PRODUCE FAIRLY WIDESPREAD RAIN SHOWERS INTO THE EARLY
EVENING HOURS.  FURTHER WEST...CLOUDS WILL SLOWLY CLEAR THIS
EVENING...BUT STRATO-CU MAY LINGER WELL INTO THE OVERNIGHT HOURS.
WIND WINDS REMAINING RATHER BREEZY OVERNIGHT...LOW TEMPERATURES WILL
ONLY FALL INTO THE MID-UPR 30S.

MONDAY CONTAINS A FEW WEATHER CONCERNS...PRIMARILY WINDS AND FIRE
WEATHER.  UPPER TROUGH MOVING EASTWARD TODAY...WILL BEGIN TO STALL
AND DEEPENING ACROSS THE WESTERN GREAT LAKES ON MONDAY. THE DEEPENING
NATURE OF THIS WAVE WILL LEAD TO ENHANCED WIND FLOW ON THE BACKSIDE
OF THE UPPER TROUGH BY MONDAY AFTERNOON. SOUNDINGS INDICATE DEEP
MIXING...AOA 750 MB BY MID-DAY. DOWNWARD MOMENTUM TRANSFER WOULD
SUGGEST SUSTAINED WINDS APPROACHING 25 KNOTS WITH OCCASIONAL GUSTS
GREATER THAN 35 KNOTS. LATER SHIFTS WILL NEED TO MONITOR AND TAKE A
SECOND LOOK AT MONDAYS WINDS IN CASE A WIND ADVISORY IS
NEEDED...ESPECIALLY OVER THE BUFFALO RIDGE AREA.

SOUNDINGS ALSO SUGGEST A NARROW CORRIDOR OF INSTABILITY ACROSS THE
EASTERN HALF OF THE CWA BY THE AFTERNOON HOURS...ALONG A WEAK
SURFACE TROUGH EXPECTED TO DEVELOP NEAR THE MINNESOTA RIVER VALLEY.
AM EXPECTING SCATTERED CONVECTIVE SHOWERS PRIMARILY OVER SOUTHWEST
MN AND ADJACENT AREAS OF IA/SD. A FEW OF THESE SHOWERS COULD PULL
DOWN STRONGER WINDS ALOFT AS WELL.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 312 PM CDT SUN APR 19 2015

FIRE WEATHER AND FROST CONCERN IN THE MEDIUM RANGE AS PREVAILING
NORTHWEST FLOW LEADS TO COOLER THAN AVERAGE TEMPERATURES.  WITH THE
RELATIVELY MILD SPRING...PLANTS AROUND THE AREA HAVE GOTTEN A HEAD
START.  HOWEVER...VERY DRY AIRMASS ACROSS THE REGION EXPECTED THE
FIRST HALF OF THE WEEK WILL PROMOTE GREAT MIXING CONDITIONS.  WITH
MOMENTUM AND DRY AIR MIXING DOWN FROM ALOFT...AM CONCERNED ABOUT
RED FLAG POTENTIAL ON TUESDAY ESPECIALLY I-29 AND EAST. FURTHER TO
THE WEST...THE LIMITING FACTOR WILL BE THE DECREASING WINDS THAT
WILL NOT REACH RED FLAG CRITERIA. RH VALUES WILL STILL BE QUITE
LOW ON TUESDAY AFTERNOON...GENERALLY IN THE 15 TO 20 PERCENT
RANGE.

RH WILL NOT BE MUCH BETTER ON WEDNESDAY...BUT WINDS WILL BE LIGHTER
PREVENTING ANY HEADLINES.  AS FOR HIGHS AND LOWS...HAVE SIDED WITH
WARM GUIDANCE HIGHS WITH MIXY AND DRY CONDITIONS...WHICH ARE NEAR MAX
POTENTIAL FOR MIX OUT.  FOR LOWS...HAVE SIDED WITH BLEND OF GUIDANCE
WHICH YIELDS LOW TEMPERATURES GENERALLY FROM 26 TO 31. AM NOT
SURE ON FROST POTENTIAL WITH DRY AIRMASS...BUT THESE TEMPERATURES
MAY LEAD TO HARD FREEZE ACROSS THE AREA. DON/T HAVE MENTION OF
FROST IN THE FORECAST AS UNCERTAINTY WITH DRY AIR...BUT HAVE ADDED
MENTION OF FROST/FREEZE INTO THE HWO.

LATER IN THE WEEK NORTHWEST FLOW BEGINS TO RELAX AS THE HUDSON BAY
LOW INCHES EASTWARD.  BOTH ECMWF AND GFS SHOW A SERIES OF WAVES
MOVING ACROSS THE COUNTRY FROM THE WEST TO THE EAST THIS
WEEKEND...THOUGH THE TRAJECTORY IS VERY DIFFERENT.  WITH THE GFS
MODEL KEEPING MUCH OF THE ACTIVITY TO THE SOUTH AND THE ECMWF
EVOLVING TOWARDS A BLOCKING PATTERN...HAVE SLOWED POPS SUBSTANTIALLY
 INTO THE WEEKEND.  OVERALL...A CONTINUATION OF WHAT WE HAVE SEEN AS
OF LATE...BREEZY/WINDY AND DRY CONDITIONS PREVAILING THROUGH THE
FORECAST PERIOD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 648 PM CDT SUN APR 19 2015

VFR WILL PREVAIL TONIGHT AND MONDAY. DECREASING WINDS WILL OCCUR
THIS EVENING...BUT IT WILL REMAIN BRISK ALL NIGHT. THEN ON
MONDAY...NORTHWEST WINDS WILL ONCE AGAIN FREQUENTLY GUST TO OVER
25 KNOTS.

&&

.FIRE WEATHER...
VERY HIGH TO EXTREME FIRE WEATHER EXPECTED ON MONDAY. HAVE LOWERED
DEW POINTS GIVEN DEEPER MIXING AND DRY CONDITIONS WEST OF THE JAMES
RIVER. RED FLAG CRITERIA SHOULD EASILY BE MET WEST OF I-29 ON
MONDAY...AND CRITERIA COULD BE REACHED FURTHER SOUTHEAST IN PORTIONS
OF NORTHWEST IOWA.  HOWEVER...STILL FEEL THAT THERE IS ENOUGH OF AN
IMPACT FROM SATURDAYS RAINFALL TO HOLD OFF ANY HEADLINES IN IA/MN.

STRONG NORTHWEST WINDS OF 20 -30 MPH ARE EXPECTED
TO DEVELOP TUESDAY AFTERNOON ALONG AND EAST OF I-29.  THESE STRONG
NORTHWEST WINDS COMBINED WITH RH VALUES OF 15 -20 PERCENT WILL
CREATE EXTREME FIRE WEATHER CONDITIONS. FURTHER TO THE WEST...WINDS
WILL BE IN THE 15 TO 25 MPH RANGE PROMOTING A VERY HIGH FIRE DANGER.

ELEVATED FIRE WEATHER CONDITIONS WILL CONTINUE INTO WEDNESDAY WITH
LOW RELATIVE HUMIDITY CONTINUING. THE WINDS ARE EXPECTED TO BE IN
THE 10-20 MPH RANGE...THUS LEADING TO A HIGH-VERY HIGH FIRE
DANGER.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...RED FLAG WARNING FROM NOON TO 8 PM CDT MONDAY FOR SDZ255>258.

MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...DUX
LONG TERM...
AVIATION...MJ


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