Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 071625
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1125 AM CDT MON JUL 7 2014

.UPDATE...
ISSUED AT 1124 AM CDT MON JUL 7 2014

CHANGES TO GRIDS THIS MORNING GENERALLY SURROUND THE PROGRESS OF
SCATTERED CONVECTION...AND IMPACT ON TEMPERATURES. FAIRLY LARGE
COMPLEX ACROSS NORTHERN NEBRASKA HAS BEEN BRUSHING THROUGH LOWER
BRULE LOCATIONS THROUGH MID TO LATE MORNING...WITH FORMIDABLE COLD
POOL AND CLOUD SHIELD BEING SUSTAINED BY MORE INTENSE UPDRAFTS ON
THE SOUTHWEST FLANK OF THE AREA OF PRECIPITATION. CURRENT THOUGHTS
IS A COUPLE MORE HOURS OF THIS WILL GROSSLY IMPACT THE POTENTIAL
FOR DESTABILIZATION THROUGH THE LOWER MISSOURI VALLEY...BEFORE
ADVANCING COLD FRONT/WAVE MOVES THROUGH THE AREA. AREA PERHAPS SET
UP TO BE MORE DYNAMICALLY AND THERMODYNAMICALLY IMPACTED WILL THE
THE NORTHEAST THIRD TO HALF OF THE CWA...BUT EVEN THERE CLOUDS AND
SOUTHWEST TO WEST FLOW OUT OF THE COLD POOL AREA WILL IMPACT ANY
SURFACE BASED DESTABILIZATION. HI RES MODELS ARE FOCUSING
GENERALLY ON SOME DEVELOPMENT BY MID AFTERNOON ALONG THE ADVANCING
COLD FRONT ACROSS THE NORTHERN CWA...AND WHILE SHEAR IS DECENT...
INSTABILITY WILL BE A FRACTION OF WHAT MOST MODELS INDICATE /RUC
AND HRRR WITH SURFACE TEMPS IN UPPER 80S TO LOWER 90S MOST AREAS/.
RATHER HAVE TRENDED DOWNWARD ON THERMAL POTENTIAL QUITE A BIT
THROUGH THE SOUTHWEST HALF...AND NUDGED DOWN A BIT TOWARD THE
NORTHEAST AS WELL GOING INTO THE AFTERNOON. IF THERE IS ANY SEVERE
POTENTIAL... LOOKS TO BE PRIMARILY A KBKX/KSLB AND EASTWARD LINE AT
THIS TIME FOR MID AFTERNOON TO EARLY EVENING...ALONG FRONTAL ZONE
AND IN ZONE OF STRONGER LIFT FORCING ON SOUTHERN EDGE OF STRONG
WAVE CURRENTLY PUSHING INTO NORTHWEST SOUTH DAKOTA.

&&

.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 MT 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 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 628 AM CDT MON JUL 7 2014

WEAK HIGH TO THE SOUTH DRIVING LIGHT SOUTHWESTERLY WINDS THIS
MORNING. MAIN CONCERN IS POTENTIALLY TWO ROUNDS OF TSRA MIDDAY AND
THIS EVENING. COMPLEX IN SW SD WILL MOVE THROUGH BY LATE MORNING OR
EARLY AFTERNOON FOLLOWED BY LIKELY NEW DEVELOPMENT ASSOCIATED WITH
SHORT WAVE TRACKING THROUGH SD AROUND 18-20Z. CURRENT THINKING IS
THAT STORMS WILL FOCUS ALONG BOUNDARY SETTING UP NEAR THE NEBRASKA
STATE LINE. SO HAVE KEPT HON DRY BUT THAT IS NOT A GUARANTEE. AT
FSD AND SUX, HAVE TSRA CHANCES IN AND ASSOCIATED LOWER CIGS THROUGH
EARLY AFTERNOON FOLLOWED BY A BREAK AND THEN MORE RAIN AND
SLIGHTLY LOWER CIGS. CONVECTION SHOULD CLEAR AREA AROUND SUNSET
BUT HAVE KEPT SCT CLOUDS IN TO ACCOUNT FOR ANY CONVECTIVE DEBRIS
LEFT OVER. THAT SHOULD FINALLY CLEAR OUT AFTER 06Z BY WHICH TIME
WINDS TURN MORE NORTHWESTERLY IN ADVANCE OF AREA OF HIGH PRESSURE
MOVING IN FROM THE WEST.


&&

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

$$

UPDATE...CHAPMAN
SHORT TERM...SCHUMACHER
LONG TERM...
AVIATION...CONNELLY







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