Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 131146
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
646 AM CDT SUN JUL 13 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 317 AM CDT SUN JUL 13 2014

IN THE NEAR TERM...WILL MONITOR SHALLOW FOG WHICH IS CURRENTLY
FORMING IN NORTHWEST IA...AND UPDATE THE FORECAST AS NEEDED IF IT
BECOMES MORE WIDESPREAD. BUT NO DOUBT THAT THE FOG WILL BURN OFF BY
MID MORNING.

MAJOR CHALLENGE FOR THE REST OF TODAY INCLUDES CONVECTIVE
POTENTIAL...WHEN AND WHERE. THE MAJOR FACTOR INHIBITING CONVECTION
TODAY IS A FAIRLY STOUT INVERSION BASED 500MB. THIS IS KEEPING CAPE
VALUES MODERATELY THIN UNTIL YOU GET INTO OUR SOUTHERN ZONES. THAT
SAID...IT APPEARS THE NAM IS AN OUTLIER IN DRYING OUT SURFACE DEW
POINT VALUES NORTH OF OUR MO RIVER VALLEY COUNTIES TOO QUICKLY. IN
ADDITION...THE NAM APPEARS TOO DRY NEAR 700MB WHEN COMPARED TO THE
OTHER HIRES MODELS. THEREFORE OPTED TO PUT IN LOW POPS FOR MANY OF
OUR CENTRAL AND SOUTHERN ZONES COINCIDENT WITH THE AFTERNOON AND
VERY EARLY EVENING HEATING. EVEN THE NAM HAS ML CAPES OVER 1000 J/KG
THIS AFTERNOON IN OUR SOUTHERN ZONES...NOSING UP TOWARD MITCHELL AND
SIOUX FALLS. SO THERE MAY BE A LITTLE CONVECTIVE ACTIVITY AROUND.
OTHERWISE THIS AFTERNOON WILL BE WELL MIXED...WITH TEMPERATURES IN
THE UPPER 70S TO MID 80S...AND WINDS WILL BE PRETTY BREEZY ALONG AND
NORTH OF I 90. FOR HIGHS TODAY...USED THE RAW GUIDANCE VALUES WHICH
WERE WARMER THAN OTHER CONSENSUS READINGS.

FOR TONIGHT...AFTER THE EARLY EVENING CONVECTIVE POTENTIAL IN THE
AFOREMENTIONED AREAS DIMINISHES...DECIDED TO EXTEND SLIGHT CHANCE
AND CHANCE POPS IN OUR MO RIVER VALLEY COUNTIES THROUGH THE NIGHT.
THESE AREAS HAVE STRONG 800-750MB FRONTOGENESIS SLOWLY OOZING
SOUTHWARD ALL NIGHT...AS WELL AS A GOOD AMOUNT OF 700-500MB MOISTURE
TO WORK WITH. DOES NOT LOOK OVERLY UNSTABLE...AND IN FACT DID NOT
EVEN INCLUDE THE MENTION OF THUNDER AFTER EVENING. BUT WOULD NOT BE
SURPRISED AT ALL TO SEE SHOWERS AROUND IN THOSE AREAS. AS ADVERTISED
LOWS TONIGHT WILL BE CHILLY FOR THIS TIME OF YEAR AS THE SURGE OF
COOL AIR RUSHES IN ON THE BACKSIDE OF A VERY STRONG...CHILLY UPPER
LOW IN SOUTHEAST CANADA AND THE GREAT LAKES REGION. BIAS CORRECTED
VALUES LOOKED TOO WARM DESPITE SOME WIND LINGERING THROUGH THE
NIGHT. THEREFOR BLENDED MOS AND RAW VALUES.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 317 AM CDT SUN JUL 13 2014

THE MAIN WEATHER STORY AS WE HEAD INTO EARLY NEXT WEEK WILL BE THE
COOL TEMPERATURES AS A STRONG CUTOFF UPPER LOW ROTATES SOUTH INTO
THE GREAT LAKES REGION. LOOKING AT HIGHS 10 TO 20 DEGREES BELOW
NORMAL...WITH MID 60S TO LOW 70S ON MONDAY. WITH THE COOL
TEMPERATURES ALOFT...LAPSE RATES MAY BE STEEP ENOUGH TO GENERATE A
FEW SHOWERS ON MONDAY...MAINLY ACROSS SOUTHWEST MINNESOTA. OTHERWISE
IT WILL BE A PARTLY CLOUD DAY...WITH DIURNAL CU LIKELY. ALSO WILL BE
BREEZY...WITH NORTHWESTERLY WINDS GUSTING TO AROUND 30 KTS. LOOKS
LIKE A COOL ONE MONDAY NIGHT WITH LOWS IN THE UPPER 40S TO AROUND
50. AROUND 20 KTS AT 900 MB...SO A LIGHT SURFACE BREEZE WILL
PROBABLY REMAIN. BUT IF WINDS WERE ABLE TO GO NEARLY CALM...SOME
SITES WOULD PROBABLY APPROACH RECORD LOWS OF MID 40S TUESDAY
MORNING.

THE REMAINDER OF THE WEEK WILL REMAIN COOL...BUT WILL
FEATURE A SLOW WARMING TREND EACH DAY. SHOULD SEE A RETURN TO 80S
WEST OF THE JAMES RIVER BY WEDNESDAY...BUT NOT ELSEWHERE UNTIL
FRIDAY OR SATURDAY. HUMIDITY WILL ALSO SLOWLY INCREASE...WITH
DEWPOINTS BACK INTO THE 60S BY THURSDAY INTO SATURDAY. LOWS IN THE
UPPER AND 40S AND LOW 50S AGAIN LIKELY WEDNESDAY MORNING...WITH LOWS
WARMING BACK TO NEAR NORMAL VALUES OF LOW 60S BY FRIDAY MORNING INTO
THE WEEKEND. SHOULD BE PARTLY CLOUDY THROUGH THE WEEK...WITH DIURNAL
CU LIKELY EACH AFTERNOON. WITH SURFACE HIGH PRESSURE IN CONTROL...NOT
EXPECTING ANY PRECIPITATION THROUGH FRIDAY NIGHT. WILL FINALLY SEE
ANOTHER WAVE AND COLD FRONT APPROACH THE REGION SATURDAY INTO
SATURDAY NIGHT. THINGS CAN CHANGE THAT FAR OUT...BUT GIVEN THE GOOD
FORCING AND EXPECTED INSTABILITY...SATURDAY AFTERNOON INTO THE
OVERNIGHT MAY SEE OUR NEXT CHANCE OF SOME THUNDERSTORMS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 645 AM CDT SUN JUL 13 2014

THE SIOUX CITY TAF LOCATION HAS TANKED TO A QUARTER MILE AND FOG.
IN FACT...THE ENTIRE CORRIDOR FROM SIOUX CITY...TO CHEROKEE...IDA
GROVE AND STORM LAKE IOWA SHOWS PATCHY VISIBILITIES AT OR LESS
THAN A QUARTER MILE. THESE AREAS ARE IN THE LOCATIONS WHERE THE
HEAVY RAIN FELL SATURDAY MORNING. WEBCAMS IN THOSE LOCATIONS
INCLUDING THE SIOUX CITY METRO SHOW THE FOG IS DEFINITELY
SHALLOW...AND WILL VERY LIKELY BURN OFF IN SHORT ORDER EARLY THIS
MORNING. THEREFORE ONLY MENTIONED FOG IN THE SIOUX CITY TAF
THROUGH 13Z. THERE IS ALSO A STRIPE OF FOG VISIBLE ON IR SATELLITE
IMAGERY ON THE EAST SIDE OF THE JAMES RIVER VALLEY EAST OF KHON.
THAT FOG PATCH APPEARS TO BE NEARLY STATIONARY...POSSIBLY OOZING
A LITTLE SOUTHWARD. SO AS LONG AS IT DOES NOT EXPAND TO THE
WEST...KHON WILL NOT RECEIVE FOG.

OTHERWISE THERE IS ENOUGH INSTABILITY TO PRODUCE A FEW SHOWERS OR
STORMS THIS AFTERNOON AND VERY EARLY EVENING IN SOUTHEAST SD...
NORTHWEST IA AND EXTREME NORTHEAST NEB. DID MENTION A SHOWER
POSSIBILITY LATE THIS AFTERNOON AT KSUX...BUT DO NOT WANT TO
INCLUDE TSRA AT THIS TIME AS THE ACTIVITY WILL LIKELY BE FAIRLY
ISOLATED. BUT WANTED TO GIVE A HEADS UP THAT IT IS A POSSIBILITY.
SHOWERS OR STORMS AROUND KFSD WILL LIKELY BE TOO ISOLATED TO
WARRANT ANY MENTION IN THE TAF AT THIS TIME.

&&

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

$$

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





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