Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 170341
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1041 PM CDT SAT AUG 16 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 401 PM CDT SAT AUG 16 2014

SEEING SOME SCATTERED THUNDERSTORM DEVELOPMENT THROUGH OUR FAR
NORTHWEST THIS AFTERNOON AS AN UPPER LEVEL SHORTWAVE OVER NORTH
CENTRAL SOUTH DAKOTA BEGINS TO EXERT SOME INFLUENCE ON A WEAK
FRONTAL CIRCULATION/CONVERGENCE ZONE LOCATED THROUGH THE WESTERN
JAMES RIVER VALLEY AT THIS TIME. THIS SHORTWAVE WILL BE THE FOCUS
FOR ANY CONVECTIVE ACTIVITY FOR TONIGHT AND SUNDAY AS IT TRACKS FROM
CENTRAL SOUTH DAKOTA INTO WESTERN MINNESOTA BY LATE SUNDAY
AFTERNOON. WITH THAT...KEPT THE GREATER POPS GENERALLY NORTH OF
INTERSTATE 90 CLOSER TO THE WAVE...TAPERING DOWN LATER TONIGHT AND
EARLY ON SUNDAY...THEN POSSIBLY REGENERATING IN OUR EAST SUNDAY
AFTERNOON AS THE WAVE TRACKS EASTWARD AND A BACKDOOR FRONTAL
BOUNDARY SLIDES INTO OUR NORTHEAST. NOT EXPECTING ANY SEVERE STORMS
THROUGH THE PERIOD WITH RELATIVELY THIN CAPE PROFILES AND WEAK
SHEAR. WITH THE WEAK MIDLEVEL FLOW AND FAIRLY HIGH PRECIPITABLE
WATER VALUES...COULD HOWEVER SEE HEAVY RAIN WITH ANY STORMS THAT
DEVELOP.

TONIGHT WILL BE ANOTHER MILD NIGHT WITH LOWS IN THE MID 60S...AND WITH
LIGHT WINDS OVERNIGHT AND LOW LEVEL MOISTURE...CANNOT RULE OUT THAT
FOG WILL DEVELOP ONCE AGAIN ACROSS THE AREA LATE. THERMAL PROFILES
WARM A COUPLE OF DEGREES ON SUNDAY...WITH HIGHS RUNNING LOWER TO MID
80S...TO SOME UPPER 80S THROUGH SOUTH CENTRAL SOUTH DAKOTA.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 401 PM CDT SAT AUG 16 2014

PRETTY STRONG SHORT WAVE MOVES SOUTHEASTWARD THROUGH OUR FORECAST
AREA SUNDAY NIGHT...WITH DEEPER MOISTURE RESIDING GENERALLY IN OUR
NORTHERN AND WESTERN ZONES. DECENT CHANCE POPS ARE WARRANTED IN
EVERY ZONE...BUT DECIDED TO ELIMINATE THE LIKELY CHANCES AS THE
UPPER TROUGH FOLLOWING THE SHORT WAVE IS FARTHER REMOVED FROM THE
SHORT WAVE ITSELF. THEREFORE THIS MAY LEND TO A BIT LESS
WIDESPREAD COVERAGE. STILL THOUGH...NOT MUCH OF A DIFFERENCE
BETWEEN HIGH END SCATTERED POPS AND LOW END LIKELY POPS. AND THERE
COULD BE SOME LOCALIZED HEAVY RAINFALL UNDER THE STRONGER
INDIVIDUAL CELLS. NOT REAL EXCITED ABOUT SEVERE CHANCES AS
PROFILES CONTINUE TO SHOW A RATHER UNIDIRECTIONAL ENVIRONMENT. MID
LEVEL WIND SPEEDS FROM 700-400MB FINALLY INCREASE THOUGH INTO THE
25 TO 30 KNOT RANGE...SO WOULD NOT BE SURPRISED TO SEE SOME SMALL
HAIL.

THE UPPER TROUGH THEN MOVES IN ON MONDAY RIGHT ON THE HEELS OF THE
LEADING SHORT WAVE...WHICH WILL KEEP THE ATMOSPHERE STIRRED UP
PRIMARILY EAST OF THE JAMES RIVER VALLEY. IN FACT LIKELY POPS ARE
STILL WARRANTED EAST OF I 29. HIGHS SHOULD BE IN THE 80S ON MONDAY
AND DESPITE A WESTERLY WIND DIRECTION...IT WILL STILL BE QUITE
HUMID EAST OF THE JAMES RIVER VALLEY...WITH DRIER AIR APPROACHING
OUR CENTRAL SD ZONES.

MONDAY NIGHT AND TUESDAY LOOK LIKE A COUPLE OF QUIET PERIODS FOR A
CHANGE. TUESDAY SHOULD BE A PLEASANT DAY WITH MODERATE LEVELS OF
HUMIDITY...LIGHT WINDS AND HIGHS IN THE 80S.

FURTHER OUT IN THE FORECAST...THE MAIN MODEL DISCREPANCIES LIE
WITH THE FACT THAT THE ECMWF ADVERTISES A MUCH MORE HIGHLY
AMPLIFIED PATTERN BY THURSDAY...WITH SHARP RIDGING NOSING UP INTO
THE EASTERN PLAINS FROM THE LOUISIANA AREA. CORRESPONDING TO THE
WEST...THERE IS A SHARP UPPER TROUGH DIGGING DOWN THE WESTERN
UNITED STATES. THE GFS AND GEM GLOBAL ARE EXTREMELY CLOSE IN THEIR
RESPECTIVE SOLUTIONS IN SHOWING MORE OF A FLAT RIDGE...WITH A
CLOSED LOW PINCHED OFF FROM THE FLOW OFF OF SOUTHERN CALIFORNIA
AND A BROAD UPPER TROUGH IN THE PACIFIC NORTHWEST. HAVE A TENDENCY
TO BELIEVE IN THE LATTER SOLUTION...AND WARMED UP HIGHS DUE TO IT.
EVEN THE 850MB TEMPERATURES OFF OF THE ECMWF SUGGEST WARMER HIGHS
THAN WHAT THE ALL BLEND IS SUGGESTING...SO BLENDED IN WARMER
CONSENSUS RAW READINGS WITH THE ALL BLEND TO PUSH TEMPERATURES A
FULL CATEGORY OR TWO WARMER. ONE THING FOR SURE IS IT WILL ALSO BE
HUMID...AND BY LATE WEEK HEAT INDEX READINGS SHOULD BE WELL INTO
THE 90S. HAVE NOT SEEN THAT IN A WHILE...BUT IT SEEMS LIKE WE
ALWAYS GET WARM AND HUMID JUST IN TIME FOR SCHOOLS STARTING AROUND
THE AREA. PRECIP CHANCES ARE PROBLEMATIC TO PREDICT. JUST WENT
WITH A GENERAL ALL BLEND FEEL FOR THOSE. THE ECMWF SHOWS A STRONG
SHORT WAVE MOVING NORTHEASTWARD OVER OUR AREA WEDNESDAY NIGHT. BUT
AGAIN THAT MAY NOT MATERIAL SO KEPT POPS ONLY IN THE CHANCE
CATEGORY WITH THAT FEATURE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1038 PM CDT SAT AUG 16 2014

HI RES MODELS CONTINUE TO DEVELOP FOG OVERNIGHT...LIKELY A RESULT
OF THE CONVECTION THAT THE MODEL IS DEVELOPING THAT ISN/T THERE.
WITH DECENT MIXING TODAY..HAVE CONTINUED TO CUT BACK ON FOG
MENTION FOR SUNDAY MORNING. OTHERWISE...MAINLY VFR CONDITION WITH
WEAK BOUNDARY IN THE JAMES VALLEY POTENTIALLY BECOMING THE FOCUS
FOR ADDITIONAL SHOWER AND THUNDERSTORM DEVELOPMENT SUNDAY
AFTERNOON. TIMING IS LOW...SO HAVE LEFT MENTION OUT OF TAFS FOR
NOW.


&&

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

$$

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





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