Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 232350
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
650 PM CDT MON MAR 23 2015

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 243 PM CDT MON MAR 23 2015

EARLY THIS AFTERNOON...STRATUS WAS FINALLY BEGINNING TO CLEAR THE
CWA.  TEMPERATURES WILL MAKE A LATE DAY RUN INTO THE 40S...BUT MANY
AREAS WILL REMAIN IN THE 30S. LOOKING INTO THE FORECAST FOR THE
SHORT TERM...THE PRIMARY CONCERNS WILL BE WITH PRECIPITATION CHANCES
TUESDAY AND THE POTENTIAL FOR RAIN TO RAPIDLY CHANGE TO SNOW TUESDAY
AFTERNOON AND EVENING.

LATEST HIGH-RES GUIDANCE SHOWS WARM ADVECTION SHOWERS BEGINNING TO
DEVELOP ALONG AN ADVANCING THETA-E GRADIENT LATE TONIGHT OVER THE
WESTERN PLAINS. PRECIPITATION WILL BE LIGHT IN NATURE WITHIN THE
INITIAL BAND OF PRECIP...BUT SHOULD BE ENOUGH TO SATURATE THE INITIAL
DRY LAYER OF AIR RESIDING WITHIN THE 900:700 MB LAYER. PRECIPITATION
SHOULD BEGIN TO BLOSSOM BY THE LATE MORNING AND EARLY AFTERNOON
HOURS AS PRIMARY UPPER TROUGH AXIS APPROACHES. SOUNDINGS SHOW STEADY
DYNAMIC COOLING ALOFT AS THIS WAVE DEEPENS AS IT CROSSES THE AREA.
AT THE SURFACE...TEMPERATURES...ONCE PRECIPITATION FORMS WILL LIKELY
REMAIN STEADY OR EVEN COOL A FEW DEGREES INTO THE LOWER 30S GIVEN
THE COLDER AIR MOVING IN ALOFT.

THE BIGGEST QUESTION IS IF RAIN WILL BRIEFLY TRANSITION TO SNOW AS
THE WAVE DEEPENS.  LATEST NAM/GFS HAVE TRENDED COOLER ALOFT WITH
THIS SYSTEM...BUT SOUNDINGS CONTINUE TO SHOW A THERMAL PROFILE THAT
WOULD SUGGEST EITHER PRECIPITATION TYPE IS POSSIBLE. ANY CHANGE OVER
TO SNOW MAY BE INTENSITY DRIVEN...BUT DO BELIEVE WE WILL TRANSITION
TO A RAIN/SNOW OR EVEN MODERATE SNOW BRIEFLY IN AREAS EAST OF I-29
BY MID-LATE TUESDAY AFTERNOON.  OBVIOUSLY ACCUMULATIONS WILL BE
DIFFICULT TO PINPOINT GIVEN POTENTIAL WET GROUND...TEMPERATURES
HOVERING BETWEEN 32 AND 35...AND WILL BE SOLELY RATE DRIVEN. IF A
HEAVIER BAND OF SNOW WERE TO DEVELOP...A QUICK 1 TO 3 INCHES OF SNOW
COULD BE POSSIBLE. THIS FALLS IN LINE WITH SREF AND WPC GUIDANCE.

THE OTHER TREND IN GUIDANCE FOR TUESDAY IS A SLIGHTLY FASTER
PROGRESSION OF THE WAVE MOVING THROUGH...WITH ISENTROPIC DOWNGLIDE
MOVING IN QUICKLY TUESDAY AFTERNOON.  HAVE PUSHED PRECIPITATION
EASTWARD SLIGHTLY QUICKER AND EVEN WARMED TEMPERATURES IN THE WESTERN
ZONES UP A COUPLE CATEGORIES.

ONE FINAL CONCERN FOR TUESDAY NIGHT INTO WEDNESDAY...GIVEN HIGH
PRESSURE MOVING INTO THE AREA AND ABUNDANT SURFACE MOISTURE...WILL
BE THE POTENTIAL FOR FOG TO DEVELOP ALONG WESTERN FLANK OF STRATUS
DECK. WILL INCLUDE PATCHY FOG WORDING ATTM.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 243 PM CDT MON MAR 23 2015

MAIN STORY WEDNESDAY INTO FRIDAY WILL BE THE COOLER TEMPERATURES
WITH UPPER TROUGHING OVERHEAD. HIGHS OF 40S AND 50S ON
WEDNESDAY...AND ONLY 30S AND 40S THURSDAY AND FRIDAY. LOWS WILL BE
IN THE TEENS AND 20S...WITH THE COLDEST TEMPERATURES LOOKING TO BE
FRIDAY MORNING WITH HIGH PRESSURE NEARBY. CAN NOT COMPLETELY RULE
OUT A BIT OF LIGHT PRECIPITATION THURSDAY NIGHT OR FRIDAY NIGHT AS
WEAK WAVES DIVE SOUTHEAST IN THE QUICK NORTHWEST FLOW. NOTHING
SIGNIFICANT EXPECTED THOUGH...AND GIVEN INCONSISTENCY ON TIMING AND
LOCATION WILL KEEP THE FORECAST DRY. OTHER ISSUE WILL BE STRONG
NORTHWEST WINDS ON WEDNESDAY. SPEEDS OF 25 TO 40 MPH SEEM LIKELY.
GFS IS A BIT STRONGER WITH THE CORE OF WINDS ALOFT...AND IF IT
VERIFIES MAY END UP NEEDING AN ADVISORY AS WOULD SEE GUSTS AROUND 40
TO 50 MPH.

UPPER RIDGING BEGINS TO BUILD IN ON SATURDAY...ALTHOUGH MODELS
CONTINUE TO TREND TOWARDS A SLOWER EXIT OF THE COOLER AIR OFF TO THE
EAST. SO AT THIS TIME LOOKS LIKE IT WILL BE AROUND 50 IN OUR FAR
EAST...WHILE SOUTH CENTRAL SD APPROACHES 70. COLD FRONT MOVES
THROUGH SATURDAY NIGHT...AND AGAIN CAN NOT COMPLETELY RULE OUT A FEW
SHOWERS...BUT MODEL CONSENSUS IS TO KEEP IT DRY FOR NOW. NOT A
LOT OF COLD AIR BEHIND THIS FRONT AS UPPER RIDGING QUICKLY BUILDS
BACK IN. THUS AS OF NOW ABOVE AVERAGE TEMPERATURES OF 50S AND 60S
SEEM MOST LIKELY SUNDAY INTO MONDAY...WITH THE DRY CONDITIONS
CONTINUING.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 650 PM CDT MON MAR 23 2015

MAINLY MID LEVEL CLOUDS WILL OVERSPREAD THE AREA THIS EVENING...
WITH CONDITIONS EXPECTED TO DETERIORATE INTO MVFR-IFR RANGE FROM
10Z-16Z AS WIDESPREAD RAIN DEVELOPS ACROSS THE REGION. AS SYSTEM
STRENGTHENS AND COOLS TEMPERATURES ALOFT...WILL LIKELY SEE RAIN
MIX WITH/CHANGE TO SNOW AS IT LIFTS TOWARD SOUTHWEST MN. COULD SEE
BRIEF PERIOD OF RAIN/SNOW MIX AT KFSD LATE IN THIS TAF PERIOD...
BUT MORE LIKELY TO SEE SNOW FROM SOUTHWEST MN INTO THE IOWA GREAT
LAKES.

&&

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

$$

SHORT TERM...DUX
LONG TERM...CHENARD
AVIATION...JH


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