Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 191717
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1117 AM CST WED NOV 19 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 340 AM CST WED NOV 19 2014

A COLD FRONT CONTINUES TO BARREL THROUGH THE REGION VERY EARLY
THIS MORNING...AND WHILE SEVERAL LOCALES ROSE INTO THE 30S EARLIER
IN THE NIGHT OUT AHEAD OF THE SYSTEM...STRONG COLD AIR ADVECTION
BEHIND THE FRONT HAS PRESENTLY DROPPED TEMPERATURES INTO THE TEENS
AND LOWER 20S. WILL MOST LIKELY SEE TEMPERATURES CONTINUE TO DROP
THROUGH MID MORNING...THEN WILL HAVE A MINOR RECOVERY DURING THE
AFTERNOON WHEN READINGS CLIMB BACK INTO THE UPPER TEENS TO MID 20S.
AS IS TYPICAL FOR COLD FRONTS THIS TIME OF YEAR...NORTHWESTERLY
WINDS HAVE RAMPED UP BEHIND THE FRONT WITH RAPID PRESSURE RISES AND
STEEP LOW LEVEL LAPSE RATES...AND WILL SEE THESE STRONG WINDS
PERSIST THROUGH THE DAY. THINK THE MAIN CHALLENGE FOR TODAY WILL BE
THE AMOUNT OF CLOUD COVER...WITH AN ABUNDANT STRATUS FIELD UPSTREAM
THROUGH MUCH OF THE DAKOTAS/EASTERN MONTANA/AND NORTH OF THE BORDER
BACK INTO CANADA...SO THINKING THAT MOSTLY CLOUDY SKIES WILL BE THE
RULE THROUGH AT LEAST THIS EVENING. HAVE SEEN SOME ISOLATED REPORTS
OF FLURRIES WITH THE STRATUS RESIDING IN THE DENDRITIC ZONE...SO DID
INCLUDE THIS IN THE FORECAST FOR MUCH OF THE AREA INTO AFTERNOON.
DID CUT BACK ON THE PATCHY BLOWING SNOW IN THE FORECAST DUE TO THE
FACT THAT EVEN WITH THE GUSTY CONDITIONS ACROSS THE REGION THERE
HAVE BEEN ONLY MINOR ISOLATED REDUCTIONS TO VISIBILITY...AND ONLY IN
LOCALES ACTUALLY RECEIVING LIGHT SNOW AT THE TIME.

BY TONIGHT A SURFACE RIDGE BEGINS TO CREEP EASTWARD INTO OUR
AREA...AND WITH DECOUPLING AND A LESSENING GRADIENT WILL SEE WINDS
DROP OFF FAIRLY QUICKLY IN THE EVENING. AGAIN THE CONFIDENCE IN
CLOUD COVER IS RATHER LOW WITH SOME MODELS HOLDING ONTO THE LOWER
LEVEL MOISTURE THROUGH MUCH OF THE NIGHT...AND NOT SURE IF THIS IS
REAL OR JUST A MODEL ARTIFACT OF THE COLD AIR SETTLING IN ACROSS THE
REGION. THIS MAKES TEMPERATURES TRICKY FOR TONIGHT...BECAUSE WITH
LIGHT WINDS IF THERE TURNS OUT TO BE LESS CLOUD COVER THAN CURRENTLY
FORECASTED IT WILL PROBABLY BE COLDER THAN FORECASTED. AT THIS
POINT GOING FOR LOWS JUST EITHER SIDE OF ZERO.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 340 AM CST WED NOV 19 2014

WELL BELOW NORMAL TEMPERATURES PERSIST INTO THURSDAY AS SURFACE
RIDGE MOVES ACROSS THE REGION. MODELS SHOW ABUNDANT LOW LEVEL
MOISTURE/POSSIBLE STRATUS LINGERING INTO THE MORNING...ESPECIALLY
WEST OF THE JAMES VALLEY...BUT MOISTURE GRADUALLY THINS OVER THE
REMAINDER OF THE CWA AND SHOULD ALLOW FOR FAIR AMOUNT OF SUNSHINE BY
AFTERNOON. TIMING OF SURFACE RIDGE MOVING EAST APPEARS TO HAVE
SLOWED A BIT OVER PREVIOUS FORECAST...KEEPING LIGHT WINDS ACROSS
MUCH OF THE CWA THROUGHOUT THE DAY. LIMITED MIXING WILL HOLD BACK
TEMPERATURES...WITH HIGHS ONLY EXPECTED TO RANGE FROM MID TEENS IN
SOUTHWEST MN TO LOWER 20S THROUGH THE MISSOURI VALLEY. EASTERN PARTS
OF THE AREA SHOULD SEE A QUICK DROP IN THE EVENING AS RIDGE AXIS
MOVES THROUGH...WHILE WESTERN AREAS SEE ONLY A MINIMAL FALL BEFORE
READINGS BEGIN TO RECOVER WITH AN INCREASE IN CLOUDS AND SOUTHERLY
LOW LEVEL FLOW.

FAIR AMOUNT OF LOW LEVEL MOISTURE INDICATED ACROSS THE REGION BY
LATER THURSDAY NIGHT THROUGH FRIDAY NIGHT AS MOISTURE BECOMES
TRAPPED BENEATH STRENGTHENING INVERSION ABOVE 900MB. SOME MODELS
CONTINUE TO POINT TOWARD POSSIBLE FREEZING DRIZZLE SCENARIO ACROSS
WESTERN PORTIONS OF THE AREA LATER THURSDAY NIGHT INTO FRIDAY...THEN
DEVELOPING EASTWARD THROUGH THE DAY WITH PERSISTENT WARM ADVECTION
ABOVE/WEAK LIFT WITHIN THE STRATUS LAYER. STILL SOME UNCERTAINTY
REGARDING DEPTH OF LOW LEVEL MOISTURE AND TIMING OF WEAK LIFT IN THE
AREA...SO OPTED TO LEAVE MENTION OUT FOR NOW. WILL BE SOMETHING TO
MONITOR IN LATER FORECASTS HOWEVER.

WITH THE INCREASE IN MOISTURE WILL COME LONG-AWAITED WARMING TO NEAR
NORMAL TEMPERATURES. LOCATIONS NEAR/WEST OF THE JAMES RIVER MOST
LIKELY TO WARM ABOVE FREEZING ON FRIDAY...WITH PERSISTENT SOUTHERLY
FLOW AND MOISTURE ADVECTION HELPING TO PUSH MOST OF THE FORECAST
AREA ABOVE FREEZING ON SATURDAY. ALAS THE WARMTH WILL BE SHORT-LIVED
AS ANOTHER COLD FRONT PUSHES ACROSS THE REGION ON SUNDAY. SHOULD SEE
A MILD START TO THE DAY AHEAD OF THE FRONT...AND WITH DEEPER MIXING
BEHIND STILL ANTICIPATE NEAR NORMAL TEMPERATURES IN THE MID 30S TO
AROUND 40 FOR HIGHS ON SUNDAY. ASIDE FROM AFOREMENTIONED DRIZZLE
POTENTIAL WHICH COULD LINGER INTO FRIDAY NIGHT...LOOKS LIKE OUR AREA
SHOULD ESCAPE ANY PRECIPITATION CHANCES THROUGH THE WEEKEND AS WE
REMAIN IN SPLIT FLOW BETWEEN SOUTHERN STREAM WAVE SWINGING INTO THE
MID-MISSISSIPPI VALLEY AND NORTHERN STREAM WAVE MOVING INTO NORTH
DAKOTA. THE LATTER MAY DIG FAR ENOUGH SOUTH SUNDAY NIGHT/MONDAY TO
BRING A CHANCE OF LIGHT SNOW TO THE AREA...THOUGH MODELS DISAGREE ON
JUST HOW FAR SOUTH THE WAVE WILL DIG AND THUS WILL KEEP POPS ON THE
LOWER END OF CHANCE RANGE FOR NOW. BELOW NORMAL TEMPS WILL RETURN TO
THE REGION FOR THE EARLY PART OF THE HOLIDAY WEEK WITH HIGHS MAINLY
IN THE 20S EXPECTED BOTH MONDAY AND TUESDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1112 AM CST WED NOV 19 2014
GUSTY WIND WILL BE AT OR BELOW 10 KTS AFTER 6 PM LOCAL TIME.
BROKEN CLOUD LAYER WILL REMAIN TRAPPED UNDER AN INVERSION UNTIL
SOMETIME AFTER SUNSET. VFR CONDITIONS EXPECTED THROUGH THE DAY ON
THURSDAY.

&&

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

$$

SHORT TERM...JM
LONG TERM...JH
AVIATION...SALLY



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