Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 261748
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1248 PM CDT THU MAR 26 2015

.UPDATE...
ISSUED AT 1249 PM CDT THU MAR 26 2015

THE COMBINATION OF THE NEARING NORTHWESTERLY UPPER WAVE AND
FRONTOGENETIC BAND IS PRODUCING PRECIPITATION WHICH WILL BE AN
ASSORTMENT OF RAIN AND SNOW OVER THE SOUTHWEST CORNER OF THE
AREA FROM A LITTLE NORTH OF CHAMBERLAIN TO NEAR YANKTON AND
SOUTHWEST. PRECIPITATION WILL BE SNOW THROUGH EARLY AFTERNOON FAR
SOUTHWEST CORNER FROM CHAMBERLAIN TO GREGORY AND HAVE UPDATED FOR
HIGHER POPS AND SNOW ACCUMULATIONS WHICH SHOULD BE LESS THAN ONE
INCH...BUT COULD LOCALLY GET CLOSE TO THAT MARK. PRECIPITATION
SHOULD MOVE OUT TO THE SOUTHEAST AND WEAKEN LATE THIS AFTERNOON TO
PERHAPS THE START OF THE EVENING.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 442 AM CDT THU MAR 26 2015

CLIPPER WAVE CURRENTLY NEAR THE MONTANA AND NORTH DAKOTA BORDER WILL
DIVE SOUTHEAST TODAY...MOVING INTO SOUTH CENTRAL SOUTH DAKOTA AROUND
MIDDAY. MODELS ARE IN GOOD AGREEMENT THAT THIS WAVE WILL INTERACT
WITH A BAND OF MID LEVEL FRONTOGENESIS STRETCHING ACROSS CENTRAL SD
INTO EAST CENTRAL NEBRASKA...PRODUCING SOME SHOWER ACTIVITY ACROSS
OUR FAR SOUTHWEST COUNTIES. LIGHT PRECIPITATION WILL BE LIKELY MID
MORNING THROUGH EARLY AFTERNOON IN GREGORY COUNTY WITH CHANCE POPS
IN BRULE AND CHARLES MIX. TEMPERATURE PROFILES SUGGEST THAT RAIN
WILL BE MOST LIKELY WITH SURFACE TEMPERATURES RISING INTO THE UPPER
30S TO NEAR 40 BY MIDDAY. CANNOT RULE OUT A FEW SLUSHY SNOW SHOWERS
MIXED WITH THE RAIN IF PRECIPITATION RATES PICK UP A BIT AND
TEMPERATURE PROFILES MANAGE TO WET BULB. DO NOT EXPECT MORE THAN A
TENTH OR SO OF QPF IN GREGORY WITH A FEW TENTHS OF QUICKLY MELTING
SNOW ACCUMULATION.

ELSEWHERE...MID AND HIGH CLOUDS WILL INCREASE FROM WEST TO EAST THIS
MORNING AND LINGER INTO THE AFTERNOON. TEMPERATURES WILL BE SLIGHTLY
COOLER THAN NORMAL WITH NORTHWEST WINDS GENERALLY 15 MPH OR LESS.
WENT WITH THE MIDDLE GROUND CONSENSUS GUIDANCE - HIGHS WILL RANGE
FROM THE UPPER 30S TO MID 40S. SKIES CLEAR THIS EVENING EAST OF THE
JAMES RIVER...HOWEVER WITH THE APPROACH OF YET ANOTHER SHORTWAVE
TRACKING ALONG THE NORTHERLY UPPER FLOW...CLOUDS WILL INCREASE AGAIN
IN THE WEST LATE TONIGHT. LOWS WILL DROP INTO THE MID TEENS IN EAST
CENTRAL SOUTH DAKOTA AND SOUTHWEST MINNESOTA...BUT WITH CLOUDS IN
THE FAR WEST...LOWS WILL BE MILDER IN THE MID TO UPPER 20S.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 442 AM CDT THU MAR 26 2015

VERY STRONG BAROCLINIC BOUNDARY WILL PUSH SLOWLY EASTWARD ON
FRIDAY INTO THE CWA. INITIALLY...FAIRLY DRY AT LOWER LEVELS WITH
CHILLY RIDGE ALONG AND EAST OF INTERSTATE 29...WHICH IS STUBBORN
BUT DOES SLIP EASTWARD THROUGH THE DAY. BOUNDARY ALOFT WILL MAKE
PROGRESSION EASTWARD...BUT FORCING IS LARGELY LIMITED EARLY IN THE
DAY TO WARM ADVECTION AND PROCESS OF SATURATION. THEREFORE...NOT
INCLINED TO START THE FIRST HALF OF THE DAY WITH MUCH MORE THAN A
SLIGHT CHANCE. HOWEVER...MOVING THROUGH THE AFTERNOON...THERE IS A
DRASTIC INCREASE IN LOW TO MID LEVEL FRONTOGENESIS NOTED...WITH
THIS FRONTAL TIGHTENING MORE THAN IN PART DUE TO WAVE SLIDING
SOUTHEAST THROUGH THE EASTERN HALF OF THE REGION. SATURATION
DEEPENS...AND ALLOWS ICE PROCESSES TO BECOME MORE LIKELY THROUGH
THE DAY. WHILE MAY SEE THE VERY LIGHT PRECIP AND PROXIMITY TO
WARMER PUSH ALOFT ALLOWING A RAIN/SNOW MIX TO START IN THE WEST...
THE TENDENCY FOR COLD AIR TO REMAIN ALOFT IN THE EAST WILL CREATE
A FEW TYPE ISSUES AS FORCING SPREADS EAST DURING THE AFTERNOON AND
EVENING. WOULD LIKELY HAVE GONE WITH A SHARPER SURFACE THERMAL
DROP WITHIN FRONTAL PRECIP BAND IF HIGHER POPS WERE IN THE
FORECAST...AND WITH ANY WARMER PARTS OF THE PROFILE NEAR
SURFACE...DIABATIC COOLING PROVIDES SUPPORT TO RETAIN SNOW ALONG
AND EAST OF I 29. BAND MAXIMIZES EARLY TO MID EVENING ACROSS
SOUTHWEST MINNESOTA AND NORTHWEST IOWA...WHERE HAVE THE AMOUNTS OF
MAINLY HALF INCH TO INCH...LESSER AMOUNTS TO THE WEST. CONCERN FOR
GREATER AMOUNTS IS ABSENT WITH THE OVERALL STABLE PROFILE.
HOWEVER...ONE ELEMENT TO WATCH WILL BE LOSS OF DEEPER SATURATION
LATER INTO THE NIGHT...WHICH MAY YIELD A FREEZING DRIZZLE THREAT.

AS WAVE PASSES BY ON FRIDAY EVENING...THE BUILDING PRESSURES TO
THE EAST WILL INHIBIT FURTHER EASTWARD PUSH OF THE LOWEST PORTIONS
OF THE FRONTAL BOUNDARY...LEAVING A MOIST SOUTHEAST FLOW AT LOWER
LEVELS AND LIKELY BACKING THE LOWER CLOUDS WESTWARD AGAIN THROUGH
MUCH OF THE CWA BY SATURDAY MORNING. THESE CLOUDS WILL BATTLE
WARMING AS THE SOUTHERLY GRADIENT IS EXPECTED TO INCREASE ON
SATURDAY. WOULD EXPECT THAT LOWER CLOUDS WILL ERODE/ADVECT TO A
POINT WHICH THERE IS FAIRLY MINIMAL COVERAGE REMAINING BY MID
AFTERNOON ALONG AND EAST OF I29. HOWEVER...THE DAMAGE WILL BE DONE
BY THE STABLE THERMAL PROFILE AND EAST OF SOUTH SURFACE WINDS...
WITH ENOUGH SIGNAL TO CUT BACK HIGHS EASTERN CWA A FEW DEGREES
INTO THE MID 40S...WHILE 70 WILL BE POSSIBLE IN THE EXTREME WEST
ON THE WARM SIDE OF THE LOW LEVEL THERMAL BOUNDARY.

WARMEST TEMPS ALOFT WILL OCCUR SATURDAY NIGHT...WITH STRONG LOW
LEVEL JET AHEAD OF NEXT WAVE DIGGING INTO THE NORTHERN PLAINS.
VARIATIONS ON HOW SPLITTY THE WAVE WILL BE...WITH ECMWF TAKING A
GOOD CHUNK OF ENERGY SOUTHWARD TOWARD THE CENTRAL PLAINS...AND GFS
MORE CONSOLIDATED IN NORTHERN STREAM WITH QUICKER PROGRESSION.
EACH SOLUTION DOES PUSH A STRONG COLD FRONT SOUTHWARD LATER
SATURDAY NIGHT THROUGH SUNDAY MORNING...BUT MOST OF THE STRONG
MID TO UPPER LEVEL LIFT FORCING HOLDS OFF UNTIL AFTER MIDNIGHT.
WENT WITH A SHOWERY TYPE RAIN CHANCE...AND WOULD NOT BE SURPRISED
TO FIND A ROGUE RUMBLE OF THUNDER GIVEN THE 8-9C/KM LAPSE RATES IN
PLACE WHEN STRONGER PV ADVECTION REACHES THE AREA LATE NIGHT.

SUNDAY WILL EVOLVE INTO A VERY MIXY DAY...WITH UP TO 40 TO 50
KNOTS OF WIND AT 85O HPA EARLY IN THE DAY. VERY DRY AIR INDICATED
ON RAW MODEL SOUNDING AS WELL...WELL BELOW STATISTICAL NUMBERS...
WHICH DESPITE A COOLER TEMPERATURE RESULTS IN A FIRE DANGER
CONCERN DISCUSSED BELOW. HIGHS WILL BE MAINLY MID 50S TO LOWER
60S...WELL AGREED UPON BY VARIOUS MIXED OUT SOLUTIONS.

FOR MONDAY TO WEDNESDAY...MODEL SOLUTIONS SETTLING IN ON A MORE
PROGRESSIVE ZONAL PATTERN...WHICH SUGGESTS WARMER TEMPERATURES
ACROSS THE REGION. CONCERN WILL CONTINUE WITH FIRE DANGER AS
SEVERAL DAYS INDICATE A STRONGER WIND POTENTIAL TO COUPLE WITH
PERIODS OF LOWER AFTERNOON HUMIDITY. WITH ONE POTENTIAL WAVE ON
MONDAY PASSING NORTH...SETS UP A CLASSIC PRE FRONTAL MIXING DAY
ACROSS THE AREA LIKELY WARMER AND DRIER SOUTH OF I 90 THAN
SOLUTIONS INDICATE. TUESDAY A BIT MORE UP IN THE AIR TRANSITIONING
TOWARD A STRONGER SOUTHERLY FLOW LATER IN THE DAY. A STRONGER WAVE
MOVING INTO THE PLAINS ON WEDNESDAY WOULD REPRODUCE A DEEPER
WESTERLY COMPONENT AND PUSH OF WARMER AND DRIER AIR OVER MUCH OF
THE AREA. ANY PRECIPITATION THREAT WOULD BE MEAGER...AND IMPACT
MAINLY THE NORTHERN PORTIONS OF THE CWA TUESDAY NIGHT/WEDNESDAY...
IF EVEN THAT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1249 PM CDT THU MAR 26 2015

MVFR TO IFR VISIBILITIES AND CEILINGS IN RAIN AND SNOW THROUGH 23Z
WILL BE CONFINED TO THE SOUTHWEST CORNER OF THE AREA WEST AND
SOUTH OF MHE AND WEST OF YKN. CONDITIONS WILL IMPROVE TO VFR AFTER
23Z. OUTSIDE OF THIS AREA INCLUDING TAF SITES GENERALLY VFR WITH
SOME CEILINGS 3-5K FEET. CEILINGS MAY LOWER TO 1-3K FEET FAR
WESTERN PART OF THE AREA AFTER 27/15Z.

&&

.FIRE WEATHER...
ISSUED AT 442 AM CDT THU MAR 26 2015

INCREASING SOUTHERLY FLOW ON SATURDAY WILL BRING BACK POTENTIAL
FOR A VERY HIGH FIRE DANGER WEST OF THE JAMES RIVER ON SATURDAY.
HOWEVER...SUNDAY WOULD APPEAR TO BRING AT LEAST VERY HIGH FIRE
DANGER TO THE ENTIRE CWA...AS STRONG NORTHWEST WINDS GUSTING TO 35
TO 45 MPH COMBINE WITH VERY LOW HUMIDITY AS LOW AS AROUND 20
PERCENT WEST...AND 25 TO 35 PERCENT EAST OF THE JAMES RIVER.
MONDAY AND TUESDAY WILL LIKELY BRING A VERY HIGH FIRE DANGER TO
PARTS OF THE WESTERN AND SOUTHERN CWA...WITH WEDNESDAY ANOTHER DAY
OF ENHANCED CONCERN FOR ALL WITH STRONG WESTERLY WINDS AND
LOWERING HUMIDITY.

&&

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

$$

UPDATE...
SHORT TERM...
LONG TERM...CHAPMAN
AVIATION...
FIRE WEATHER...CHAPMAN


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