Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 170923
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
423 AM CDT THU APR 17 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 421 AM CDT THU APR 17 2014

A FAIRLY BENIGN SHORT TERM PERIOD ACROSS THE AREA...AT LEAST
COMPARED TO LATE. MAIN CHALLENGE TODAY WILL BE DEALING WITH
TEMPERATURES. TRENDS LIKELY TO BE IMPACTED MUCH MORE SEVERELY IN THE
IMMEDIATE TERM BY SNOW COVER NORTH AND STUBBORN LOWER CLOUDS ACROSS
THE SOUTHEAST...AND HAVE ADJUSTED THE TREND TO SLOW WARMING IN THESE
TWO AREAS INTO MIDDAY. EXPECT THE SNOW TO BE GONE BY SOMETIME THIS
AFTERNOON...BUT MAY HOLD ON LONG ENOUGH IN THE FAR NORTH WHERE FLOW
WILL WEAKEN BENEATH THE RIDGE AXIS TO KEEP MAXES IN THE UPPER 30S IN
A COUPLE SPOTS...WHILE THE FAR SOUTH AND WEST WILL REACH NEAR 50...
EVEN WITH THE GREATER SUNSHINE THROUGH MIDDAY GIVING WAY TO MORE MID
LEVEL CLOUDS FROM THE WEST DURING THE AFTERNOON.

LIFT FORCING LATER TONIGHT IS EXCLUSIVELY A RESULT OF LOWER TO MID
LEVEL WARM AIR ADVECTION...WITH STRONGER RIDGING ALOFT ACTING TO
SUPPRESS DEEPER LIFT. HARD TO JUSTIFY ANY MORE THAN THE LOWEST OF A
CHANCE POPS...AND WILL CONCENTRATE JUST AHEAD OF THE SUPPORT FROM
WEAK MID LEVEL TROUGH PUSHING ACROSS SD LATER IN THE NIGHT. WILL
ALSO HAVE IMPACT OF LOWER LEVEL SOMEWHAT DRIER LAYER TO OVERCOME.
LIKELY THAT EVENTUAL CLIMB IN SURFACE TEMPS IN THE STRENGTHENING
SOUTHEAST TO SOUTH FLOW IS UNDERESTIMATED IN MODEL GUIDANCE AS IS
THE CASE IN ALMOST ANY SIMILAR EVENT...AND FOR THE MOST PART THIS
SHOULD PRECLUDE MOST THREAT FOR ANY MIXED TYPE OF THE INSIGNIFICANT
PRECIPITATION. SHOULD BE MUCH GREATER THREAT FOR VERY LIGHT RAINFALL
OR SPRINKLES THAN ANYTHING ELSE...WITH JUST A SMALL THREAT FOR
SURFACE TEMPS TO BE HOVERING NEAR FREEZING IN THE FAR NORTH AND
NORTHEAST...AND ABOUT THE SAME THREAT THAT THE MEAGER WET BULB
PROCESSES IN LIGHT RATES WOULD BE ENOUGH FOR A BRIEF MIX TO SNOW
BY LATER IN THE NIGHT.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 421 AM CDT THU APR 17 2014

LIGHT PRECIPITATION ASSOCIATED WITH WEAK WARM AIR ADVECTION AND MID
LEVEL MOISTURE WILL QUICKLY SWITCH ENTIRELY TO LIGHT RAINFALL OR
SPRINKLES AT DAYBREAK FRIDAY BEFORE IT LIFTS AWAY FROM THE AREA LATE
MORNING. DRY LOW LEVELS AND MEAGER SUPPORT WILL KEEP SOME ISOLATED
COVERAGE IN PLACE ACROSS OUR NORTHEASTERN THIRD OF THE FORECAST
AREA. CLOUDS WILL THIN FROM WEST TO EAST INTO THE AFTERNOON...
HOWEVER WINDS WILL BE ON THE INCREASE THROUGH THE DAY...AVERAGING 25
TO 35 MPH IN OUR WEST IN THE AFTERNOON. THIS WILL ALLOW FOR MUCH
WARMER TEMPERATURES TO RETURN TO REGION...PARTICULARLY IN THE WEST
WHERE SUNSHINE WILL BE MORE ABUNDANT AND SOUTHERLY WINDS STRONGEST.
HIGHS REACH THE LOW 70S IN SOUTH CENTRAL SD...BUT WILL BE DECIDEDLY
COOLER IN THE MID AND UPPER 50S IN SOUTHWEST MINNESOTA.

THE UPPER RIDGING SHIFTS ACROSS THE REGION FRIDAY NIGHT AND
SATURDAY. STRONG SOUTHERLY WINDS CONTINUE FRIDAY NIGHT...RESULTING
IN A VERY MILD NIGHT. BUMPED LOWS UP INTO THE MID 40S TO MID 50S
GIVEN VERY MILD MID LEVEL TEMPERATURES AROUND +12C AT 850 MB AND
INCREASING CLOUDS EXPECTED OVERNIGHT. A DECENT FETCH OF LOW LEVEL
MOISTURE ALSO ADVECTS INTO THE AREA...BOOSTING DEWPOINTS WELL INTO
THE 40S. COLD FRONT DROPS INTO SOUTH CENTRAL SD SATURDAY MORNING AND
SAGS ACROSS THE NORTHERN FORECAST AREA INTO THE EVENING. WITH THE
MAIN ENERGY FROM THE WAVE MOVING WELL NORTH OF THE FORECAST
AREA...AND A SECOND WEAK SOUTHERN STREAM WAVE STAYING WELL TO OUR
SOUTH...PRECIPITATION CHANCES LOOK RATHER MINIMAL DURING THE DAY.
WILL LEAVE MENTION OF ISOLATED SHOWERS IN THE MORNING AND CHANCES OF
SHOWERS AND STORMS IN OUR EASTERN HALF IN THE AFTERNOON. SOME MODEST
ELEVATED CAPE VALUES DEVELOP MAINLY ACROSS OUR EASTERN HALF IN THE
AFTERNOON THROUGH SATURDAY NIGHT. THE BOUNDARY STALLS NEAR OUR
EASTERN CWA SATURDAY NIGHT AND NUDGES EAST ON SUNDAY...HOWEVER THE
LOCATION OF THIS FEATURE REMAINS UNCERTAIN AT THIS TIME. THE ECMWF
AND GEM CONTINUE TO HOLD THE BOUNDARY ACROSS OUR FORECAST AREA FOR
MUCH LONGER THAN THE GFS...SO ADJUSTED POPS SLIGHTLY FURTHER WEST
THAN THE ALLBLEND ON SUNDAY. NOT EXPECTING ANY SEVERE STORMS...BUT
SHOULD SEE SOME THUNDER AT LEAST IN NORTHWEST IOWA WITH THIS SYSTEM.

RIDGING QUICKLY REBOUNDS OVER THE WESTERN PLAINS SUNDAY NIGHT AND
GRADUALLY BUILDS EASTWARD ACROSS THE PLAINS INTO MID WEEK NEXT WEEK.
TEMPERATURES LOOK QUITE PLEASANT DURING THIS PERIOD...GENERALLY IN
THE 70S. CONTINUED THE TREND OF BUMPING HIGHS ABOVE GUIDANCE DURING
THIS PERIOD WITH ALL MODELS INDICATING VERY WARM LOW AND MID LEVEL
TEMPERATURES. WEDNESDAY LOOKS TO BE THE WARMEST DAY WITH STRONG
SOUTHERLY WINDS AND 850 MB TEMPS AS WARM AS +20C. BOTH THE GFS AND
ECMWF BRING A NICE SHORTWAVE INTO THE NORTHERN PLAINS TUESDAY NIGHT
INTO WEDNESDAY...WHICH COULD BRING SOME SCATTERED...LIKELY ELEVATED
STORMS TO THE FORECAST AREA.


&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1108 PM CDT WED APR 16 2014

THE 06Z TAFS WILL REFLECT A CLEARING TREND AS THE REST OF THE
NIGHT PROGRESSES. CURRENTLY THE CLEARING LINE IS PAST THE KHON TAF
SITE...WHILE THE REST OF THE FORECAST AREA IS IN THE MVFR
CATEGORY. THE CLEARING LINE WILL ENCROACH INTO THE KFSD TAF SITE
CLOSE TO 10Z/17 AND THE KSUX TAF SITE PROJECTED AROUND 13Z/17.
ONCE THE CLEARING TAKE HOLDS...THE FORECAST AREA SHOULD BE VFR ON
THURSDAY AND THURSDAY EVENING WITH LIGHT WINDS BY AFTERNOON...
ALTHOUGH VFR MID LEVEL CLOUDS WILL BE AROUND THURSDAY EVENING.


&&

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

$$

SHORT TERM...CHAPMAN
LONG TERM...
AVIATION...MJ








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