Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 140910
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
410 AM CDT MON APR 14 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 410 AM CDT MON APR 14 2014

COLD HIGH PRESSURE WILL CONTINUE TO EXPAND SOUTH AND EAST INTO THE
FORECAST AREA TODAY. THE MAIN CONCERN WILL BE A WEAK 700 MB
SHORTWAVE TRAVERSING THE NORTHWEST FLOW ACROSS THE FORECAST AREA
THIS AFTERNOON. MID LEVEL MOISTURE WILL INCREASE ENOUGH FOR PARTLY
TO MOSTLY CLOUDY SKIES LATE MORNING THROUGH THE AFTERNOON. WITH ONLY
VERY WEAK SUPPORT AND VERY DRY LOW LEVELS...COULD SEE A FEW COLD AIR
INSTABILITY SPRINKLES OR FLURRIES...BUT NO MEASURABLE PRECIPITATION
IS EXPECTED. ADDED ISOLATED FLURRY AND SPRINKLE MENTION TO THE
FORECAST FOR A FEW HOURS THIS AFTERNOON. NORTH NORTHWEST WINDS
REMAIN BRISK TODAY AROUND 10 TO 20 MPH WITH SOME HIGHER GUSTS. HIGHS
TODAY WILL ONLY REACH THE MID 30S TO MID 40S. LOWERED HIGHS SLIGHTLY
IN THE AREAS THAT RECEIVED SNOWFALL YESTERDAY IN NORTHWEST IOWA.

WINDS QUICKLY DECREASE AFTER SUNSET AS THE SURFACE HIGH BUILDS
OVERHEAD. LIGHT AND VARIABLE WINDS IN THE EARLY MORNING HOURS TURN
SOUTHERLY ON THE BACK SIDE OF THE HIGH...ESPECIALLY ACROSS THE WEST.
LIGHT FLOW AND DECREASING CLOUDS WILL STILL ALLOW FOR A VERY CHILLY
NIGHT. LOWS ARE EXPECTED NEAR 20 INTO THE MID 20S.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 410 AM CDT MON APR 14 2014

STRONG WARM ADVECTIVE PATTERN WILL DEVELOP ON TUESDAY...AHEAD OF
STRONG NORTHERN STREAM WAVE DIGGING THROUGH THE NORTHERN ROCKIES.
MID LEVEL FRONTOGENETIC FORCING WILL START TO FOCUS A BIT MORE AS
FEATURES SHIFT EAST ACROSS THE CWA. HOWEVER...QUITE DRY LOWER LEVELS
WILL BE EXCRUCIATINGLY DIFFICULT TO BREACH WITH ANY PRECIPITATION
YET ON TUESDAY AFTERNOON...SO WILL SETTLE FOR THICKENING PERIOD OF
MID CLOUDS. THESE CLOUDS ALONG WITH A SOMEWHAT EAST OF SOUTH
SURFACE COMPONENT WILL CHALLENGE THE WARMING POTENTIAL...AND EVEN
MODEST MIXING DEPTHS SUGGEST COMING UP JUST A BIT SHY OF PREVIOUS
FORECAST.

SHARPENING TROUGH WILL PUSH INTO THE NORTHERN PLAINS OVERNIGHT
TUESDAY NIGHT. VERY DRY AIRMASS AHEAD OF THE POSITIVELY TILTED
SYSTEM. FAIRLY WARM AIR LOWER TO MID LEVELS WILL SPREAD NORTHWARD
THROUGH THE CWA AND SHOULD PRECLUDE ANY OTHER PRECIP TYPES ALL THE
WAY INTO WEDNESDAY MORNING...AS SURFACE TEMPS LOOK TO REMAIN IN
THE MID 30S TO LOWER 40S AT THEIR COLDEST TUESDAY NIGHT. MOST OF
THE AREA SHOULD REMAIN DRY OVERNIGHT...BUT AS MID LEVEL LAPSE
RATES APPROACH 8C/KM...ALONG WITH INCREASE IN MID LEVEL MOISTURE
AND CONTINUED BROAD ISENTROPIC LIFT...SHOULD SEE AN INCREASE IN
HIGH BASED RETURNS LATER AT NIGHT...AND HAVE VARIED MENTION FROM
A LOWER CHANCE OF SHOWERS FAR NORTHWEST...TO JUST A FEW SPRINKLES
EAST.

OPEN NORTHERN STREAM PORTION TO WAVE SHOWN IN MODELS WITH VARIOUS
DEGREES OF PROGRESSION...AND LATEST ECMWF HAS REALLY TAKEN OVER
WITH ANOMALOUSLY QUICK PACE TO DEEPER LIFT FORCING...ACTUALLY
MOSTLY GONE FROM AREA BY 18Z WED. PREFER A MORE MODEST TRANSLATION
TO WAVE PER ENSEMBLE MEAN/GFS TIMING...WHICH WOULD BRING BEST
PRECIP CHANCES DURING LATER MORNING AND THROUGH THE AFTERNOON
ACROSS THE NORTHERN CWA. STILL LOOKING AT SITUATION WITH TEMPS
ALOFT COOLING APPRECIABLY THROUGH THE DAY...AND WOULD CERTAINLY
OPEN THE DOOR FOR A MIX/CHANGE TO SNOW ACROSS THE WEST/NORTH
DURING THE AFTERNOON...AND POTENTIAL FOR SOME LIGHTER SNOW
ACCUMULATIONS FOR KHON-KMML CORRIDOR...ESPECIALLY EASTERN PORTION
OF THIS ZONE. FURTHER SOUTHEAST...PRECIP MAY MIX WITH OR CHANGE TO
SNOW...BUT SHEARING PAST OF DEEPER LIFT FORCING BY EVENING SHOULD
KEEP ACCUMULATIONS EVEN MORE MINIMAL. PRECIP THREAT SHOULD BE
PRETTY MUCH OVER BY LATER EVENING FOR MOST OF THE CWA.

SOUTHERN PORTIONS OF ENERGY IN TROUGH IS TREATED SOMEWHAT
DIFFERENTLY BY MODELS ONCE AGAIN...BUT GENERAL IDEA OF HAVING WAVE
STARTING TO COLLAPSE IN SCALE AND WRAP UP TO THE SOUTHEAST OF THE
AREA LATER THURSDAY INTO EARLY FRIDAY A COMMON ELEMENT. WHILE A
MAJORITY OF IMPACT FROM THIS WAVE WILL LIKELY OCCUR SOUTHEAST OF
THE AREA...HAVE KEPT A MODEST CHANCE FOR PRECIPITATION ACROSS THE
FAR SOUTHEAST FROM THURSDAY AFTERNOON THROUGH THURSDAY NIGHT.
THERMAL PROFILES AGAIN ARE A BIT TOWARD THE WHITE VERSUS WET SIDE...
AND HAVE AGAIN MENTIONED SOME SNOW POTENTIAL FOR THE FAR SOUTHEAST...
ESPECIALLY BY LATER THURSDAY NIGHT AS ANOTHER PULSE OF COLD
ADVECTION WORKS IN BEHIND DEEPENING SYSTEM. WILL HAVE TO KEEP
A WATCHFUL EYE ON HOW RAPIDLY SYSTEM WRAPS UP AND HOW MUCH PHASING
OCCURS WITH NORTHERN STREAM...BECAUSE SUCH SYSTEMS WILL OFTEN
CREEP A BIT MORE NORTHWEST THAN PROGGED.

GOOD NEWS IS THAT BEHIND THE WAVE DEEPENING TO THE EAST ON
FRIDAY...APPEARS LARGER SCALE SHIFT TO RIDGING WILL START TO BRING
WARMING TREND BACK TO THE NORTHERN PLAINS HEADING THROUGH THE WEEKEND.
START OF WARM ADVECTION ALONG WITH SOUTHERN EDGE OF LIFT FORCING
WITH WAVE TO THE NORTH WILL LIKELY THICKEN UP CLOUDS A BIT ON
SATURDAY BUT WILL LEAVE PRECIP OUT OF THE FORECAST. WARMING MAY
NOT REACH POTENTIAL FROM INCREASING 925 HPA TEMPS WITH CLOUDS AND
SLIGHT EASTERLY WIND COMPONENT...BUT DRY CHARACTER TO AIRMASS
SHOULD BALANCE AT LEAST A SHARE OF THIS IMPEDANCE. SOMEWHAT MORE
VARIANCE IN SPECIFIC SOLUTIONS BY SUNDAY IN TERMS OF SURFACE
PATTERN...BUT GENERAL AGREEMENT IN PLACE OVERALL. WEAK FRONTAL
ZONE MAY LIMP INTO THE AREA ON SUNDAY...BUT SHOULD CONTINUE TO SEE
A MODERATION TO TEMPS WITH TREND TOWARD GREATER SUNSHINE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1120 PM CDT SUN APR 13 2014

VFR CONDITIONS EXPECTED TO PREVAIL THROUGH THE FORECAST PERIOD.
GUSTY NORTH WINDS WILL PERSIST THROUGH THE PERIOD...STRONGEST AT THE
START OF THE PERIOD...ESPECIALLY EAST OF INTERSTATE 29 WHERE GUSTS
IN EXCESS OF 30KT WILL CONTINUE THROUGH THE EARLY MORNING HOURS. BY
SUNRISE...EXPECT LOCATIONS EAST OF HIGHWAY 75 IN SWRN MN/NWRN IA TO
BE SEEING GUSTS IN 25-30KT RANGE...WITH GUSTS BELOW 25KT EXPECTED
ALONG AND WEST OF HIGHWAY 75...INCLUDING AT ALL TAF LOCATIONS. GUSTY
WINDS WILL QUICKLY DIMINISH TOWARD SUNSET MONDAY AS SURFACE RIDGE
MOVES INTO THE FORECAST AREA.


&&

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

$$

SHORT TERM...
LONG TERM...CHAPMAN
AVIATION...JH






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