Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 212140
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
340 PM CST WED JAN 21 2015

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 339 PM CST WED JAN 21 2015

CURRENTLY...STILL HAVE SOME UPPER QG FORCING MOVING SLOWLY
SOUTHEASTWARD THROUGH THE FORECAST AREA. UNTIL THIS GETS TOTALLY
THROUGH...WE ARE RUNNING THE RISK OF AREAS OF LIGHT SNOW OR FLURRIES
LIKELY WINDING DOWN FROM NORTH TO SOUTH THROUGH THE EVENING HOURS.
DUE TO TEMPERATURES HOVERING ONLY A COUPLE OF DEGREES BELOW FREEZING
AT MOST LOCATIONS...SNOWFALL HAS BEEN HAVING TROUBLE STICKING DUE TO
THE LIGHT RATES. OTHERWISE ADDED A MENTION OF PATCHY FOG FOR SOME OF
OUR WESTERN ZONES LATE TONIGHT AND EARLY THURSDAY...MAINLY IN THE
JAMES RIVER VALLEY AND AROUND THE CHAMBERLAIN AREA. THIS IS BECAUSE
THE GFS 925MB RH FIELDS ARE SHOWING A DECREASE IN CLOUDS FOR THAT
AREA AFTER MIDNIGHT AS THE WINDS OFF THE SURFACE BECOME MORE
SOUTHWESTERLY. SOUTHWEST NEBRASKA DOES NOT HAVE A LOT OF STRATUS AT
THIS TIME. THEREFORE IF THEIR STRATUS DOES CLEAR OUT AT THAT TIME OF
DAY...SOME FOG COULD FORM. BUT THE STRATUS FIELD MAY STILL BE
ABUNDANT EAST OF THE JAMES LATE TONIGHT AND EARLY THURSDAY SO LEFT
THE MENTION OF FOG OUT OF THOSE AREAS. THAT SAID...THE 925MB RH DOES
DECREASE THROUGH THE MORNING ON THURSDAY EAST OF THE JAMES
SUGGESTING A DECREASE IN CLOUDS FROM WEST TO EAST. THE NAM LOW LEVEL
RH FIELDS KEEPS EVERYONE SOPPED IN THROUGH THE DAY THURSDAY...AND
THAT WAS NOT FOLLOWED NOTING THE AFOREMENTIONED WIND DIRECTION.

CONCERNING TEMPERATURES...TEMPERED THE FALL IN READINGS THIS EVENING
FROM MANY GUIDANCE VALUES DUE TO CLOUD COVER. OUR LOWS TONIGHT ARE
MOST CLOSELY CORRELATED WITH BIAS CORRECTED MOS VALUES WHICH KEEP
TEMPERATURES PRETTY MILD FOR THIS TIME OF YEAR. WITH A MILD AIR FLOW
ON THURSDAY...ALSO FOLLOWED THE WARMER MOS VALUES FOR THAT PERIOD...
ESPECIALLY THE BIAS CORRECTED VALUES WHICH PLACES HIGHS IN THE MID
30S TO LOWER 40S. THURSDAY SHOULD BE A NICE DAY FOR JANUARY
STANDARDS.


.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 339 PM CST WED JAN 21 2015

FRIDAY INTO THE WEEKEND WILL SEE RIDGING BUILD IN ACROSS THE WESTERN
PART OF THE COUNTRY...PUTTING OUR CWA BACK INTO A NORTHWEST FLOW
PATTERN. ONE WEAK WAVE MAY BRING A FEW SPRINKLES ON FRIDAY.
OTHERWISE WILL SEE LOW LEVEL TEMPERATURES WARM BACK UP...AND GIVEN
RECENT TEMPERATURES...SEE NO REASON NOT TO STAY WITH THE WARMER
GUIDANCE. SOME UNCERTAINTY ON DEGREE OF WARMING EARLY NEXT WEEK WITH
A DECENT SPREAD IN ENSEMBLE GUIDANCE. BUT THE OPERATIONAL ECMWF AND
GFS ARE BOTH WARM...AND GIVEN THE LACK OF SNOW COVER...STAYED WITH
THE WARMER GUIDANCE THROUGH THE PERIOD. THUS FOLLOWING THE WARMER
BIAS CORRECTED GUIDANCE YIELDS HIGHS IN THE 40S FRIDAY INTO EARLY
NEXT WEEK. LOWS WILL BE MILD AS WELL...GENERALLY 20S AND 30S.

MODELS CONTINUE TO BE PRETTY CONSISTENT WITH A WAVE IN THE NORTHWEST
FLOW IMPACTING THE AREA LATER SATURDAY INTO EARLY SUNDAY. MODELS
HAVE TRENDED A BIT FASTER WITH THE SYSTEM AND A BIT WEAKER THOUGH.
BEST FORCING AND MOISTURE END UP REMAINING TO OUR NORTH. THUS QPF
AMOUNTS SEEM TO BE TRENDING DOWN. WITH THE TRACK TO OUR NORTH...LOW
LEVELS SHOULD REMAIN QUITE WARM SATURDAY AFTERNOON AND NIGHT. THUS
THINKING MOST OF THE PRECIPITATION WILL PROBABLY BE LIGHT
RAIN...POSSIBLY MIXED WITH SOME SNOW. BEST CHANCE OF A LIGHT COATING
SEEMS TO BE IN SOUTHWEST MINNESOTA CLOSER TO THE COLDER AIR...BUT
EVEN THERE ANY ACCUMULATION MAY BE DIFFICULT. WILL NEED TO CONTINUE
TO MONITOR TRENDS THOUGH IN CASE THE STRENGTH OR TRACK OF THE SYSTEM
CHANGES. GIVEN THE WEAKER NATURE OF THE SYSTEM...WINDS SATURDAY
NIGHT INTO SUNDAY DO NOT LOOK QUITE AS STRONG...ALTHOUGH WILL STILL
BE BLUSTERY. STILL NOT SEEING ANY SIGNIFICANT PRECIPITATION THREATS
IN THE FORESEEABLE FUTURE.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1114 AM CST WED JAN 21 2015

THIS AFTERNOON AND EVENING WILL LIKELY SEE MOSTLY MVFR TO LOWER
END VFR CONDITIONS THROUGHOUT THE FORECAST AREA. REDUCTIONS IN
VISIBILITY DUE TO SNOWFALL SHOULD NOT BE A GREAT CONCERN...AS ONLY
FLURRIES ARE BEING NOTED UPSTREAM FROM THE FORECAST AREA. A BIGGER
QUESTION CONCERNING THE CEILINGS ARRIVES AFTER EVENING TONIGHT.
WINDS OFF THE SURFACE IN THE 925MB-850MB LAYER BEGIN TO TURN
WESTERLY AFTER MIDNIGHT TONIGHT...THEN GO SOUTHWESTERLY THURSDAY
MORNING. THE CURRENT OBSERVATIONS ARE MAINLY SHOWING VFR IN
WESTERN AND CENTRAL NEBRASKA...SO ITS POSSIBLE THAT SOME DRIER LOW
LEVEL AIR MAY ENTRAIN IN LATER TONIGHT. THE TAFS WERE PLAYED THIS
WAY...BUT IT NEEDS TO BE NOTED THAT THE NAM DOES KEEP A LOT OF LOW
LEVEL MOISTURE AROUND THROUGH THE ENTIRE NIGHT AND THURSDAY
MORNING...WHEREAS THE GFS DRIES OUT THE LOWER LEVELS. FOR NOW...
FAVORED THE GFS.


&&

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

$$

SHORT TERM...MJ
LONG TERM...CHENARD
AVIATION...MJ


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