Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 291137
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
637 AM CDT WED OCT 29 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 338 AM CDT WED OCT 29 2014

HIGH PRESSURE WILL CONTINUE TO SHIFT OFF TO THE EAST
TODAY...WITH SOUTHERLY RETURN FLOW DEVELOPING. STRATUS IS SLOW TO
CLEAR EARLY THIS MORNING AS WE REMAIN MORE MIXED THAN MOST MODELS
SHOW. THE RAP SEEMS TO HAVE THE BEST HANDLE ON THINGS...AND THUS
FOLLOWED CLOSEST TO IT AND SLOWED DOWN EXIT OF CLOUD COVER THIS
MORNING. THE BACK EDGE OF THE STRATUS WILL CONTINUE TO SLOWLY PUSH
EAST AND BY LATE MORNING MOST LOCATIONS SHOULD BE MOSTLY SUNNY. WILL
BE ANOTHER COOL DAY WITH HIGHS RANGING FROM THE UPPER 40S OVER
SOUTHWEST MINNESOTA TO THE MID AND UPPER 50S WEST OF THE JAMES
RIVER.

AN UPPER WAVE WILL QUICKLY PUSH ACROSS THE REGION TONIGHT IN THE
NORTHWEST FLOW ALOFT. THUS EXPECTING INCREASING CLOUDS THROUGH THE
EVENING HOURS. BEST QG FORCING DOES GO OVER OUR CWA...HOWEVER BEST
MOISTURE STAYS TO THE NORTH. THUS THINKING WE MAINLY JUST SEE CLOUDS
AND VIRGA...WITH MOST OF THE PRECIPITATION NOT ABLE TO PUSH THROUGH
THE DRY LOWER LEVELS. HOWEVER FORCING IS STRONG ENOUGH THAT CAN NOT
RULE OUT A FEW LIGHT SHOWERS REACHING THE GROUND...AND THUS EXPANDED
THE SLIGHT CHANCE POPS TO INCLUDE MOST LOCATIONS NORTH OF THE
MISSOURI RIVER. GIVEN THE CLOUD COVER TEMPERATURES WILL PROBABLY
STAY IN THE 40S MOST OF THE NIGHT...HOWEVER WITH LIGHT
WINDS...READINGS IN ANY CLEAR POCKETS WILL DROP INTO THE 30S. AND
WITH MORE WIDESPREAD CLEARING EXPECTED LATE THINK MOST AREAS WILL
SEE LOWS IN THE 30S. COLD FRONT WILL MAKE IT TO ABOUT INTERSTATE 29
BY 12Z...AND WITH INCREASED MIXING BEHIND THE FRONT...PROBABLY WILL
SEE A SLIGHT WARMING AND A BIT OF A NORTHWESTERLY BREEZE DEVELOP
LATE TONIGHT ACROSS THE WEST.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 338 AM CDT WED OCT 29 2014

THURSDAY IS HIGHLIGHTED BY A HASTENING OF THE PACE OF THE NEXT
SURGE OF COLD AIR ADVECTION. THE AFOREMENTIONED UPPER WAVE RAPIDLY
DEPARTS BUT IN ITS WAKE...IS A STRONG SHORT WAVE MOVING DOWN FROM
WESTERN ONTARIO TO NORTHERN MN. COLD HIGH PRESSURE...CURRENTLY
FORECAST TO BE BETWEEN 1035 AND 1040MB FILLS IN ACROSS SOUTH
CENTRAL CANADA AND THE NORTHERN PLAINS. THEREFORE THURSDAY LOOKS
LIKE A DAY SIMILAR TO WHAT WE HAD YESTERDAY...BLUSTERY...COOL...
AND WHAT COULD BE PLENTY OF COLD AIR ADVECTION STRATUS FOR MANY
AREAS OTHER THAN POSSIBLY OUR MO RIVER VALLEY AREAS. THEREFORE
NOTCHED UP THE NORTHERLY WINDS AND FOR TEMPERATURES...THE VARIOUS
GUIDANCE VALUES HAVE MARKEDLY COOLED THE HIGHS OFF. NOTICED THAT
THE AFTERNOON 900-850MB TEMPERATURES ARE FORECAST TO BE NOT A
WHOLE LOT DIFFERENT THAN WHAT THEY WERE YESTERDAY. SO BLENDED THE
VERY CHILLY BIAS CORRECTED GEM GLOBAL AND BIAS CORRECTED MAV INTO
THE CONSENSUS GUIDANCE. THIS COOLED HIGHS OFF INTO THE UPPER 40S
NORTH TO MID 50S SOUTH. BUT IF THE STRATUS GETS AS INTRUSIVE AS IT
WAS ON TUESDAY...THEN EVEN THESE HIGHS ARE PROBABLY A CATEGORY
TOO WARM.

LOWS THURSDAY NIGHT ARE TRICKY...IN THAT THE HIGH PRESSURE AREA
WILL CAUSE SOME LINGERING MIXING POTENTIAL EAST OF INTERSTATE 29.
IN ADDITION...THERE IS A QUESTION OF HOW QUICKLY THE FORECAST
STRATUS WILL EXIT...AT LEAST IN OUR EASTERN ZONES. WOULD NOT BE AT
ALL SURPRISED IF THE STRATUS LINGERS LONGER THAN ANTICIPATED...
THEREFORE DID NOT GO WITH THE COLDEST GUIDANCE VALUES ON THURSDAY
EXCEPT IN OUR FAR WEST. CONSENSUS VALUES LOOKED PRETTY GOOD FOR
OUR EASTERN ZONES...BUT HAVE CLOSE TO 20 DEGREES FOR CHAMBERLAIN
AND HURON.

FRIDAY AND SATURDAY EXHIBIT A HIGH AMPLITUDE UPPER FLOW WITH
STRONG RIDGING IN THE MIDDLE PART OF THE COUNTRY. FRIDAY WILL BE
COOL ONCE AGAIN BUT WITH MUCH LESS WIND AS THE SURFACE RIDGE MOVES
ACROSS THE FORECAST AREA. BUT THEN A TIGHT GRADIENT WILL RETURN
FRIDAY NIGHT AND SATURDAY WITH STOUT WINDS OFF THE SURFACE. WINDY
SOUTHERLY WINDS OF 20 TO 35 MPH SHOULD EASILY PREVAIL ON SATURDAY
WITH TEMPERATURES STILL BELOW NORMAL AS THE COOL HIGH PRESSURE
SYSTEM TO THE EAST INFLUENCES OUR WEATHER FOR ANOTHER DAY. THE
GRASSLAND FIRE DANGER INDEX WILL LIKELY REACH THE VERY HIGH
CATEGORY ACROSS THE ENTIRE FORECAST AREA...AND WILL BE CONVEYED IN
THE FORTHCOMING HWO. FOR SUNDAY...CONSENSUS TEMPERATURES LOOKED A
LITTLE COOL GIVEN THE ECMWF AND GFS 900MB TEMPERATURES...ESPECIALLY
ALONG AND WEST OF I 29. THEREFORE BLENDED THE MORE MILD BIAS
CORRECTED ECMWF VALUES INTO THE MIX TO BUMP THE READINGS UP A
CATEGORY OR TWO.

THE DETERMINISTIC MODELS BEGIN TO DIVERGE A BIT IN HOW THEY HANDLE
THE NEXT UPPER TROUGH MOVING EASTWARD INTO THE PLAINS SUNDAY NIGHT
AND MONDAY. AT THIS TIME...THE ECMWF LOOKS A LITTLE BETTER THAN
THE GFS. BUT AT ANY RATE...DECENT RAIN CHANCES LOOK MINIMAL AS THE
NORTHERN STREAM WAVE TAKES OVER AND CUTS OFF THE DEEP MOISTURE.
TEMPERATURES LOOK UNEVENTFUL AND CLOSE TO NORMAL ON MONDAY AND
TUESDAY...BUT MONDAY WILL LIKELY BE PRETTY BREEZY AGAIN WITH
NORTHWEST WINDS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 634 AM CDT WED OCT 29 2014

STRATUS CONTINUES TO DISSIPATE THIS MORNING...ALTHOUGH SEEING
SOME MVFR CIGS ACROSS PORTIONS OF SOUTHWEST MINNESOTA AND
NORTHWEST IOWA. EXPECT EVERYONE TO BECOME VFR BY LATER THIS
MORNING AND REMAIN THAT WAY THROUGH THE PERIOD. WILL SEE
INCREASING MID LEVEL CLOUDS TONIGHT AND POSSIBLY A BRIEF LIGHT
SHOWER...BUT NOTHING SIGNIFICANT EXPECTED.

&&

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

$$

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



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