000
FXUS63 KFSD 262053
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
253 PM CST MON JAN 26 2015

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 253 PM CST MON JAN 26 2015

FRONTAL BOUNDARY SURGED THROUGH THE CWA EARLIER TODAY...LEAVING
BREEZY NORTHWESTERLY WINDS IN ITS WAKE. DEEPER MIXING THIS AFTERNOON
HAS ALLOWED TEMPERATURES TO MIX DOWN WELL INTO THE 40S AND EVEN 50S
IN PORTIONS OF SOUTH CENTRAL SOUTH DAKOTA.  THE PRIMARY FORECAST
CONCERNS THROUGH TUESDAY AFTERNOON ARE FOCUSED ON FOG POTENTIAL
OVERNIGHT.

THROUGH THE EVENING AND OVERNIGHT...SURFACE HIGH PRESSURE WILL DRIFT
SOUTHEAST AND ACROSS THE CWA OVERNIGHT. WINDS WILL QUICKLY TURN
LIGHT AND VARIABLE BY MIDNIGHT...WITH THE LIGHTEST SFC WINDS
REACHING THE TRI-STATE AREA BY DAYBREAK.  THE CONCERNS
OVERNIGHT...GIVEN INCREASED BOUNDARY LAYER MOISTURE AND LIGHT
WINDS...WILL BE WITH FOG POTENTIAL.  DEW POINTS THIS AFTERNOON AT
PEAK MIXING REMAIN IN THE LOWER TO MIDDLE 30S. SHOULD FOG FORM...IT
MAY LIKELY DO SO NEAR THE JAMES AND MISSOURI RIVER VALLEY AND THEN
GRADUALLY SPREAD SOUTH AND EAST THROUGH DAYBREAK.  A LIGHT EAST
CONVERGENT SFC WIND MAY HOLD FOG WEST OF I-29. DEPENDING ON HOW
QUICKLY THINGS EVOLVE THIS EVENING...COULD ENVISION A FOG ADVISORY
AT SOME POINT TONIGHT.

TUESDAY WILL BE ANOTHER WARM DAY OVER THE REGION. SOME UNCERTAINTY
PERSISTS ON POTENTIAL IMPACT OF FOG/STRATUS...BUT SOUNDINGS SUGGEST
CLEARING BY THE AFTERNOON AS SOUTHERLY WINDS INCREASE.  THE MISSOURI
RIVER VALLEY WILL BE THE WARMEST AREA OF THE CWA...AS A WEAK SFC
WARM FRONT FORMS IN OR NEAR THE AREA.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 253 PM CST MON JAN 26 2015

INCREASING SOUTHERLY FLOW IS EXPECTED TUESDAY NIGHT AHEAD OF A
TROUGH APPROACHING FROM THE NORTHWEST. WITH INCREASING SOUTHERLY
WINDS...WILL LIKELY SEE TEMPERATURES SLIGHTLY WARMER ON THE NORTH
SIDE OF THE BUFFALO RIDGE.

AS THE TROUGH APPROACHES...EXPECT LOW CLOUDS TO INCREASE LATE IN THE
NIGHT.  A COUPLE OF THE MODELS ARE PRODUCING PRECIPITATION AS THE
WAVE MOVES THROUGH...BUT DID NOT ADD PRECIP AS MUCH OF THE LIFT IS
CONCENTRATED IN DRY LAYER FROM 850-NEAR 500 MB.

NORTHWEST WINDS REALLY INCREASE DURING THE DAY ON WEDNESDAY BEHIND
THE EXITING WAVE.  925 HPA WINDS ARE AROUND 40 KNOTS...AND HAVE
RAISED WINDS SOME OVER GUIDANCE.  COOLER AIR MOVES INTO THE THE
REGION BEHIND THE TROUGH....THOUGH MODELS DEBATING ON HOW MUCH
COOLER AIR MOVES INTO THE REGION.  925 HPA TEMPS ARE CLOSER TO -6C
IN THE ECMWF...WHILE THE GFS IS 3 TO 5 DEGREES WARMER.  WITH LACK OF
CONSISTENCY...STAYED FAIRLY CLOSE TO GUIDANCE FOR NOW.

LOW CONFIDENCE FORECAST FOR THIS WEEKEND AS A SERIES OF WAVES MOVE
IN FROM THE SOUTHWEST AND COLD AIR MOVES IN FROM THE NORTH.  GFS IS
EXTREMELY PROGRESSIVE WITH THE COLD AIR...WHILE THE ECMWF LINGERS
THE COOLER AIR THROUGH THE EXTENDED.  CONCENTRATED POPS MAINLY
DURING THE DAY ON SATURDAY. FORCING APPEARS TO BE FAIRLY BROAD AND
WEAK...SO AT THIS TIME IT IS HARD TO PIN POINT A FAVORED AREA FOR
PRECIPITATION.  HAVE TRENDED GUIDANCE TEMPERATURES OVER THE WEEKEND
TOWARDS THE COOLER SIDE OF GUIDANCE...BUT WITH THE DISCREPANCIES DID
NOT ALTER MORE THAN A FEW DEGREES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1124 AM CST MON JAN 26 2015

VFR CONDITIONS LIKELY THROUGH THE EVENING HOURS. THE BIGGEST
QUESTION GOING INTO TUESDAY WILL BE FOR THE POTENTIAL OF FOG
TOWARDS AND AFTER MIDNIGHT AS SURFACE RIDGING MOVES ACROSS THE
AREA. DEW POINTS REMAIN RELATIVELY HIGH THIS AFTERNOON...AND WITH
TEMPERATURES FALLING INTO THE UPPER 20S...NEARLY ALL OPERATIONAL
GUIDANCE SUPPORT FOG FORMATION. WILL INTRODUCE AT ALL TAF SITES
AFTER 09Z TO GIVE A HINT AT THE POTENTIAL...BUT SHOULD FOG
FORM...IT WILL LIKELY BE EVEN LOWER THAN MVFR LVLS.

&&

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

$$

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