National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KFSD 051808
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1208 PM CST WED MAR 5 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 356 AM CST WED MAR 5 2014

THE SNOW IS DONE...AND DO NOT EXPECT ANY PRECIPITATION TODAY OR
TONIGHT AS THE SURFACE RIDGE MOVES OUT AND A SOUTHERLY SURFACE/LOW
LEVEL FLOW INCREASES. LOW LEVEL MOISTURE IS CERTAINLY A PROBLEM BUT
DO NOT SEE THAN BECOMING PREDOMINANT OR DEEP ENOUGH FOR THE
DEVELOPMENT OF FREEZING DRIZZLE.

WHILE THE HIGHER LEVEL/H850 AREA/ CLOUD DECK APPEARS TO DRY UP
SLOWLY FROM THE WEST TODAY AND TONIGHT...MOIST AIR AT LOWER LEVELS
PRESENTS A PROBLEM. THIS MOISTURE CAN EASILY BECOME STRATIFIED IN
THIS TYPE OF PATTERN...BOTH IN THE LIGHT FLOW TODAY AND AS THE
GRADIENT INCREASES TONIGHT. FIRST...SUBSIDENCE ASSOCIATED WITH THE
SURFACE AND LOW LEVEL RIDGE SEEMS FOR THE TIME BEING TO LIMIT ANY
LOW STRATUS DEVELOPMENT. THEREFORE...STILL EXPECT SOME PARTIAL
BREAKING UP OF CLOUD COVER OVER THE WESTERN PART OF THE AREA TODAY.
FURTHER EAST...THE HIGHER H850 CLOUD DECK MENTIONED ABOVE WILL
LINGER. THEN...LATER TODAY...AS SUBSIDENCE DECREASES...EXPECT LOWER
CLOUDS TO INCREASE...KEEPING THE EASTERN PART OF OUR AREA CLOUDY.
THIS TREND SHOULD CONTINUE THROUGH TONIGHT IN THE EAST. FOR THE TIME
BEING...INCREASING SOUTHERLY FLOW SEEMS TO BRING ENOUGH DRYING TO
THE WESTERN PART OF OUR AREA TO COUNTER MOISTURE STRATIFICATION
POTENTIAL AND PREVENT LOW STRATUS FROM RETURNING. IT APPEARS THE
MAIN FORECAST PROBLEMS ARE THE SPEED/SLOWNESS OF DECREASING CLOUDS
WEST TODAY...AND FIGURING HOW FAR EAST THE PARTIAL BREAKING UP WILL
GET BEFORE IT RUNS INTO THE LOW LEVEL MOISTURE EAST. RIGHT NOW IT
SEEMS THE AREA BETWEEN THE JAMES AND BIG SIOUX RIVERS WILL BE THE
TRANSITION AREA.

TEMPERATURES WILL BE A LITTLE MORE LIMITED TODAY THAN WE HAD
BEFORE...BUT IT WILL STILL BE A LITTLE WARMER WITH HIGHS IN THE 20S.
LOW TEMPERATURES TONIGHT WILL BE ON THE MILD SIDE WITH THE WARMING
AND THE CLOUD COVER IN THE EAST...WITH TEMPERATURES BECOMING STEADY
THEN RISING A BIT DURING THE NIGHT...AND LOWS FOR THE PERIOD IN THE
MID TEENS TO LOWER 20S.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 356 AM CST WED MAR 5 2014

WITH WARM AIR ADVECTION AND A BRISK SOUTHERLY FLOW CONTINUING INTO
THURSDAY...HIGHS WILL FINALLY BE NEAR NORMAL...AND EVEN ABOVE
NORMAL IN OUR WESTERN ZONES. THIS IS JUST MIXING 925MB TEMPERATURES
ROUGHLY ISOTHERMAL...BUT WITH THE AMOUNT OF SNOW COVER AROUND THIS
SEEMS REASONABLE. CLOUDS ARE PROJECTED TO CLEAR OUT OF OUR MANY OF
OUR WESTERN ZONES THUS HELPING TO GIVE THE MILD READINGS. BUT IN
THE EAST...HOW LONG ANY LOW CLOUDS HANG ON IS A WILD CARD.

THE NEXT SHORT WAVE AND ATTENDANT COLD FRONT MOVES SOUTHWARD
ACROSS THE NORTHERN PLAINS THURSDAY NIGHT AND EARLY FRIDAY. EXCEPT
FOR WHAT IS LIKELY TO BE SOME POST FRONTAL STRATUS AROUND 925MB
FOR ROUGHLY 6 HOURS...THE LAYER BETWEEN 925MB AND 700MB IS RATHER
MOISTURE STARVED. THIS MAKES THE POP FORECAST DIFFICULT. FURTHERMORE...
THE OVERALL TREND OF THE MODELS IS FOR WARMER TEMPERATURES ALOFT
CENTERED AROUND 850MB MAKING PRECIPITATION TYPE DIFFICULT TO
FORECAST IF MEASURABLE PRECIP DOES DEVELOP. TOOK THE GFS AVERAGED
TEMPERATURE ALOFT IN TWO 6 HOUR PERIODS...FROM 06Z TO 12Z FRIDAY...
AND 12Z TO 18Z FRIDAY TO COME UP WITH THE PRECIP TYPE FORECAST. IT
DOES INDEED PRODUCE SOME LIGHT FREEZING RAIN...AND AM ALSO WORRIED
ABOUT SOME LIGHT SLEET POTENTIAL AS THE SOUNDINGS WET BULB COOL
DOWNWARD CLOSER TO SATURATION. BY FRIDAY AFTERNOON...THE COLD AIR
LOOKS DEEP ENOUGH TO GIVE OUR SOUTHERN ZONES A CHANCE FOR ALL LIGHT
SNOW. AGAIN...ANY PRECIP WHICH FALLS WILL LIKELY BE EXTREMELY
LIGHT. BUT OF COURSE...IT DOES NOT TAKE MUCH WINTRY MIX TO MAKE
UNTREATED SURFACES SLICK SO WILL MENTION THIS POSSIBILITY IN THE
FORTHCOMING HWO. EVEN FREEZING SPRINKLES COULD POSE SOME WEATHER
PROBLEMS. CONCERNING TEMPERATURES...WITH A SOUTHWEST WIND AHEAD OF
THE FRONT THURSDAY NIGHT...TEMPERATURES WILL LIKELY HOVER JUST
BELOW FREEZING FOR MANY LOCATIONS...SOMEWHAT ELEVATION DEPENDENT
AS LOCATIONS NEAR MARSHALL COULD ACTUALLY STAY SLIGHTLY ABOVE
FREEZING FOR MUCH OF THE NIGHT. THEN ON FRIDAY...TEMPERATURES WILL
LIKELY BE STEADY TO SLOWLY FALLING FOR MOST LOCATIONS.

THE THURSDAY NIGHT/FRIDAY MORNING COLD FRONT WILL DEFINITELY SET
OUR TEMPERATURES BACK TO BELOW NORMAL FRIDAY NIGHT AND SATURDAY.
BY SATURDAY 925MB TEMPERATURES STRONG SUGGEST 20S EAST...TO 30S IN
OUR WEST.

THE EXTENDED STILL SHOWS UPPER RIDGING OVER THE WESTERN HALF OF
THE U.S. ON SUNDAY...FLATTENING SOMEWHAT ON MONDAY AND TUESDAY. A
STRONG SOUTH TO SOUTHWEST FLOW BEGINS TO USHER IN VERY STRONG WARM
AIR ADVECTION SATURDAY NIGHT WHICH WILL LIKELY PRODUCE SLOWLY
RISING TEMPERATURES. THEN ON SUNDAY...TEMPERATURES LOOK WELL ABOVE
NORMAL FINALLY. IN FACT THE ALL BLEND LOOKED TOO COLD GIVEN THE
CURRENT 925MB TO 850MB THERMAL FORECAST. SO BLENDED SOME OF THE
VERY MILD ECMWF INTO THE ALL BLEND READINGS. TOOK INTO ACCOUNT THE
FRESH...DEEP SNOW COVER IN OUR NORTHEAST ZONES. BUT EVEN SO IN
THOSE LOCATIONS...FEEL THAT LOWER 40S ARE CERTAINLY POSSIBLE THIS
TIME OF YEAR WITH THE HIGHER SUN ANGLE. THE MO RIVER VALLEY SHOULD
WARM NICELY WELL INTO THE 50S. HIGHS WILL BE SIMILAR ON MONDAY...
THEN SOME WEAK LOW LEVEL COOLING BEGINS TO TAKE HOLD ON TUESDAY
COOLING OFF TEMPERATURES 5 TO 10 DEGREES. AFTER THE EXTENDED...IT
IS QUITE POSSIBLE BY MID AND LATE WEEK THAT WE WILL HAVE ANOTHER
COOL DOWN. BUT AT THIS TIME...TEMPERATURES DURING THAT TIME FRAME
DO NOT LOOK TOO COLD...AT LEAST COMPARED TO WHAT WE HAVE BEEN HAVING.
CONCERNING PRECIPITATION IN THE EXTENDED...THERE IS REALLY NO
CONCRETE SHORT WAVES TO KEY ON...SO WENT DRY FOR NOW.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1159 AM CST WED MAR 5 2014

MVFR TO LOW END VFR STRATUS RAPIDLY BECOMING SCATTERED OR DISSIPATING
ACROSS THE FORECAST AREA. MODELS SUGGEST THE POTENTIAL FOR THIS
STRATUS TO REDEVELOP THIS EVENING AND TONIGHT...MAINLY ALONG AND EAST
OF INTERSTATE 29. IF STRATUS DOES MANAGE TO REDEVELOP TONIGHT...EXPECT
DRYING SOUTHWEST MIXING LEVEL WINDS TO BEGIN SCATTERING OUT THE
STRATUS FROM WEST TO EAST IN THE MORNING.

&&

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

$$

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