Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 260200
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
900 PM CDT TUE AUG 25 2015

.UPDATE...
ISSUED AT 859 PM CDT TUE AUG 25 2015

HAVE ADDED SOME VERY LOW POPS TO WESTERN AREAS LATE TONIGHT INTO
EARLY WEDNESDAY. A LITTLE CONCERNED ABOUT POTENTIAL FOR ACCAS
SHRA/TSRA AS SOME ELEVATED INSTABILITY WORKS EASTWARD AHEAD OF
850MB WARM FRONT. AIR MASS IS MOISTENING SLIGHTLY IN THE LOWER
LEVELS WITH SURFACE DEW POINTS IN THE LOWER-MID 50S ACROSS OUR
WEST AS OF 02Z...AND COULD TAP INTO SOME UPPER 50S NOW SEEN IN
EASTERN NEBRASKA AS WINDS BECOME MORE SOUTHEASTERLY LATE TONIGHT.
WOULD NOT EXPECT ANYTHING TO SURVIVE TOO MUCH BEYOND DAYBREAK...SO
HAVE MINIMAL POPS TAPERING BACK TO NON-MEASURABLE BY 14Z.

OTHERWISE JUST MINOR ADJUSTMENTS TO HOURLY TEMPS THIS EVENING AS
EASTERN AREAS COOLING MORE QUICKLY THAN FORECAST. OVERALL LOWS
LOOK REASONABLE THOUGH.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 258 PM CDT TUE AUG 25 2015

SURFACE RIDGE WILL REMAIN ACROSS THE EASTERN HALF OF THE FORECAST
AREA THROUGH THE OVERNIGHT LEADING TO NEARLY IDEAL RADIATIVE
CONDITIONS.  ONLY POTENTIAL ISSUE WILL BE ELEVATED VEIL OF SMOKE
FROM FIRES ACROSS THE PACIFIC NORTHWEST.

SOUTHEASTERLY WINDS WILL INCREASE THROUGH THE DAY ON WEDNESDAY.
WITH WINDS INCREASING...MOISTURE WILL CREEP UPWARDS WITH DEW POINTS
CLIMBING INTO THE 50S. HIGH TEMPERATURES WILL BE A FEW DEGREES SHY
OF 850 HPA MIXOUT WITH ELEVATED INVERSION LAYER AND A LOWER SUN
ANGLE. EXPECT SEASONAL HIGHS IN THE UPPER 70S TO NEAR 80.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 258 PM CDT TUE AUG 25 2015

THE MAIN STORY IN THE MEDIUM AND EXTENDED PORTIONS OF THE FORECAST
CONTINUES TO REVOLVE AROUND RAIN CHANCES DURING THE SECOND HALF OF
THE WORK WEEK.   MODELS HAVE TRENDED A BIT CLOSER TOGETHER THIS
MORNING...WITH THE EXCEPTION OF THE NAM WHICH REMAINS A NORTHERN
OUTLIER WITH SFC AND LOW-LVL CIRCULATIONS. HAVE PUT PREFERENCES
TOWARDS THE GFS/ECMWF FOR FORECAST DETAILS. THAT SAID...WOULD NOT
BE SURPRISED TO SEE A FEW ACCAS SHOWERS LATE TOMORROW AFTN AND
EARLY EVENING. RAIN CHANCES WILL GRADUALLY BEGIN TO INCREASE INTO
THURSDAY MORNING...PRIMARILY ALONG A NEWRD LIFTING ELEVATED
BOUNDARY. SOUNDINGS SHOW A FAIRLY CAPPED SFC ENVIRONMENT THROUGH
THE AFTERNOON HOURS OF THURSDAY...BUT THAT DOES NOT RULE OUT THE
POTENTIAL FOR A FEW ELEVATED SHOWERS THROUGH THE DAY.

THE BEST CHANCE OF RAIN WILL FALL THURSDAY NIGHT INTO FRIDAY AS
STRONG UPPER FORCING MOVES ACROSS THE AREA...AND THE LLJ
INTENSIFIES. THIS SYSTEM WILL BRING A SLUG OF SUB-TROPICAL MOISTURE
ALONG WITH IT...BUMPING PWAT VALUES UPWARDS OF 1.8 INCHES BY 12AM
FRIDAY.  EVEN THOUGH THE POTENTIAL FOR THUNDER IS ON THE LOWER
SIDE...COULD SEE RATHER HEALTHY RAINFALL RATES WITH AN AREA OF MORE
FOCUSED HEAVIER RAINS OVER THE SOUTHERN AND SOUTHEASTERN CWA.

THIS SYSTEM WILL MOVE AWAY FROM THE AREA ON FRIDAY...WITH DRY
WEATHER INTO THE WEEKEND. TEMPERATURES WILL BEGIN TO WARM BACK TO
NORMAL LVLS INTO EARLY NEXT WEEK.  THE NEXT CHANCE OF RAIN WILL HOLD
OFF UNTIL NEXT TUESDAY OR WEDNESDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 556 PM CDT TUE AUG 25 2015

VFR CONDITIONS EXPECTED ACROSS THE AREA THROUGH THIS TAF PERIOD
WITH LIGHT/VARIABLE WINDS BECOMING PREDOMINANTLY SOUTHEAST 8-15KT
AFTER DAYBREAK WEDNESDAY. SOME MODELS POINTING TO POTENTIAL FOR
ISOLATED ELEVATED SHOWERS/STORMS WEST OF I-29 LATE TONIGHT/EARLY
WEDNESDAY MORNING...POSSIBLY CREEPING INTO I-29 CORRIDOR BY MID-
MORNING IF THEY DEVELOP AT ALL. CHANCE OF ANYTHING IMPACTING TAF
LOCATIONS IS QUITE LOW AND WILL NOT INCLUDE MENTION IN TAFS AT
THIS TIME.

OTHER ITEM OF NOTE WILL BE ELEVATED SMOKE LAYER MOVING BACK INTO
THE REGION FROM WILDFIRES IN PACIFIC NORTHWEST. DIFFICULT TO
DETERMINE HEIGHT OF THIS LAYER...THOUGH ISOLATED PIREP FROM THIS
AFTERNOON INDICATES NEAR/ABOVE 10KFT...SO NOT EXPECTED TO IMPACT
SURFACE VISIBILITY. HOWEVER...ADDITIONAL PIREPS DEFINING HEIGHT OF
THE ELEVATED SMOKE LAYER WOULD BE APPRECIATED.


&&

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

$$

UPDATE...JH
SHORT TERM...
LONG TERM...DUX
AVIATION...JH


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