Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 070917
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
417 AM CDT MON JUL 7 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 413 AM CDT MON JUL 7 2014

A FAIRLY ACTIVE DAY EXPECTED ACROSS THE AREA AS TWO SHORT-WAVES MOVE
ACROSS THE NORTHERN PLAINS THROUGH 06Z TUESDAY. THE FIRST SHORTWAVE
WAS LOCATED OVER ND AT 08Z AND MOVING SOUTHEAST INTO MN. ISOLATED TO
SCATTERED THUNDERSTORMS HAVE DEVELOPED WITH THIS TROUGH. MID LEVEL
LAPSE RATES OVER MN ARE MARGINAL FOR CONVECTION BUT WITH THE MID
LEVELS BECOMING MORE UNSTABLE THE REMAINDER OF THE NIGHT AND INTO
EARLY THIS MORNING...EXPECT THAT A FEW SHOWERS AND THUNDERSTORMS MAY
MOVE INTO AREAS AROUND HWY 14 IN SD AND MN. A LARGE AREA OF MID
LEVEL CONVECTION HAS DEVELOPED IN SOUTHEAST MONTANA AND IS SPREADING
INTO WESTERN SD. THIS IS AHEAD OF A MUCH STRONGER WAVE MOVING INTO
EASTERN MT. BY 12Z...A FEW OF THESE STORMS MAY BE APPROACHING THE
MISSOURI RIVER IN CENTRAL SD ESPECIALLY WITH LAPSE RATES INCREASING
TO 7 C/KM OVER THIS AREA.

BOTH OF THESE WAVES ARE EXPECTED TO MOVE ACROSS THE AREA DURING THE
DAY. AS NOTED ABOVE...LAPSE RATES ARE EXPECTED TO INCREASE TO AROUND
7 C/KM THIS MORNING. MODEL SOUNDINGS SHOW VERY LITTLE CONVECTIVE
INHIBITION AND WITH STRONG SYNOPTIC SCALE FORCING FOR ASCENT...
EXPECT CONVECTION TO BEGIN DEVELOPING THIS MORNING AND RAPIDLY
INCREASE IN COVERAGE ACROSS SD AND MN. THESE STORMS WILL SPREAD INTO
IOWA DURING THE LATE MORNING AND AFTERNOON. REALLY EXPECT TWO AREAS
OF FOCUS. THE FIRST IS WITH THE BETTER INSTABILITY NEAR THE NEBRASKA
AND SOUTH DAKOTA BORDER. THIS WILL RESULT IN CONVECTION CLOSER TO
THE NEBRASKA AND SD BORDER LATER THIS MORNING AND THEN WILL SPREAD
INTO NW IOWA DURING THE AFTERNOON AND EVENING. THE SECOND AREA IS
WITH THE UPPER WAVE MOVING FROM NT INTO WRN MN BY LATER THIS
AFTERNOON. EXPECT MUCH OF SW MN TO SEE THUNDERSTORMS AT SOME POINT
TODAY WITH THE GREATEST COVERAGE DURING THE AFTERNOON AND EARLY
EVENING. THERE IS CERTAINLY A LOT OF SHEAR IN PLACE WITH 0-6 KM BULK
SHEAR BETWEEN 40 AND 50 KTS THROUGHOUT THE DAY. THE REAL QUESTION IS
INSTABILITY. WITH THUNDERSTORMS EXPECTED THIS MORNING...IT SEEMS
UNLIKELY ENOUGH CAPE WILL DEVELOP TO SUSTAIN STRONG UPDRAFTS OVER
MUCH OF SOUTHEAST SD. HOWEVER...WITH A LITTLE MORE SUN IN NW IA THIS
MORNING...ENOUGH INSTABILITY WITH CAPES AROUND 1000 J/KG...MAY
RESULT TO PRODUCE STRONG UPDRAFTS. THIS COMBINED WITH THE STRONG
SHEAR MAY ACTUALLY SUPPORT A FEW SUPERCELLS. THE 0 TO 1 KM SHEAR
REMAINS LOW SO THE MAIN THREAT WILL BE HAIL AND DAMAGING WINDS. WITH
THE LIMITED INSTABILITY...HAIL MAY GET AS LARGE AS GOLF BALLS WITH
GUSTS TO 60 OR 70 MPH POSSIBLE IN A FEW STORMS.  STORMS SHOULD
RAPIDLY MOVE EAST THIS EVENING MOVING TOWARD I35 BY 06Z.

TEMPERATURES TODAY ARE REALLY DEPENDENT UPON SUNSHINE. WITH MORE
CLOUDS EXPECTED IN SW MN...KEPT HIGHS AROUND 80 WITH LOW TO MID 80S
ELSEWHERE. HOWEVER...IF CLOUDS AND RAIN ARE MORE WIDESPREAD THAN
ANTICIPATED IN SE SD...HIGHS MAY ALSO STRUGGLE TO REACH 80 IN THESE
AREAS AS WELL. WITH DRIER AIR MOVING IN...LOWS OVERNIGHT WILL BE IN
THE 50S TO LOWER 60S.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 413 AM CDT MON JUL 7 2014

DRY WEATHER AND MODESTLY COOL MIDSUMMER TEMPERATURES WILL CONTINUE
TUESDAY THROUGH MOST OF WEDNESDAY WITH SURFACE HIGH PRESSURE MOVING
OVER THE AREA THEN BEGINNING TO MOVE EAST. WARM ADVECTION PATTERN
AND DEVELOPING LOW LEVEL JET SHOULD BRING SCATTERED STORMS
DEVELOPING FROM WEST TO EAST WEDNESDAY NIGHT INTO THURSDAY. THE
CHANCE OF STORMS SHOULD PEAK THURSDAY NIGHT WITH DECENT SHORT WAVE
PROVIDING A LARGE SCALE LIFT BOOSTER. THEREAFTER STORM CHANCES
BECOME MARGINAL AND HAZY WITH CANADIAN SHORT WAVES BATTLING ROCKIES
RIDGING TO PRODUCE A PATTERN WHICH COULD BE WARM OR COOL DEPENDING
ON WHICH OPERATIONAL MODEL IS SELECTED...WITH JUST AS MUCH DOUBT ON
ANY THUNDERSTORM THREAT. FOR NOW WILL GO WITH A MOSTLY MARGINAL
MENTION EACH DAY AS PER EXTENDED GUIDANCE WITH AN INDICATION OF A
CONSISTENT NORTHWESTERLY UPPER FLOW AND A DRY PATTERN DEVELOPING
ABOUT THE END OF THE PERIOD...OR AT THE START OF NEXT WEEK. BOTH THE
GFS AND EC SHOW THIS...BUT THE EC LOOKS SUSPICIOUSLY COOL AS IT
DROPS A CANADIAN UPPER LOW SOUTHEAST TO THE UPPER GREAT LAKES. WILL
NOT DISCOUNT THIS YET GIVEN THAT FOR A FEW DAYS THE EC WAS NOT
SHOWING THE MONSTER UPPER RIDGING AND HOT SPELL THAT THE GFS WAS
TRYING TO BUILD...AND FROM WHICH THE GFS HAS NOW RETREATED...BUT
SAID UPPER LOW DOES LOOK TOO STRONG TOO FAR SOUTH FOR MIDSUMMER ON
THE EC AT THE END OF THE FORECAST PERIOD.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY EVENING)
ISSUED AT 1100 PM CDT SUN JUL 6 2014

VFR CONDITIONS EXPECTED THROUGH MUCH OF THE OVERNIGHT. FORECAST
TURNS MORE COMPLICATED AS WE HEAD INTO TOMORROW. ONE WEAK WAVE AND
WIND SHIFT SHOULD CROSS THE AREA IN THE MORNING INTO EARLY
AFTERNOON...AND SHOULD BE ACCOMPANIED WITH SOME CONVECTION.
IF WE CAN HEAT UP ENOUGH DURING THE DAY...COULD SEE ANOTHER ROUND OF
THUNDERSTORMS MID AFTERNOON INTO THE EVENING HOURS ASSOCIATED WITH
THE MAIN WAVE AND FRONTAL PASSAGE. GIVEN THE UNCERTAINTY WITH
RESPECT TO TIMING AND COVERAGE OF STORMS...WILL LEAVE OUT OF THE
TAFS FOR NOW. BUT AM EXPECTING AT LEAST ISOLATED TO SCATTERED
COVERAGE IN THE MORNING AND POSSIBLY AGAIN LATER IN THE DAY. A FEW
OF THE STRONGER STORMS COULD BE ACCOMPANIED BY STRONG WIND
GUSTS OF 40 TO 50 KTS AND HAIL. IF WE GET ENOUGH SUN AND ARE THUS
ABLE TO MIX...WESTERLY WINDS WILL LIKELY BECOME BLUSTERY BY
AFTERNOON...ESPECIALLY AT KHON AND KFSD...WHERE GUSTS AROUND 25 KTS
SEEM POSSIBLE.


&&

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

$$

SHORT TERM...SCHUMACHER
LONG TERM...
AVIATION...CHENARD





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