Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 091135
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
635 AM CDT WED JUL 9 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 257 AM CDT WED JUL 9 2014

IN GENERAL TODAY...LOTS OF SUNSHINE AND LIGHT WINDS AS HIGH PRESSURE
MOVES OVER THE AREA. SOME LINGERING LOW LEVEL MOISTURE AND
INSTABILITY MAY GIVE RISE TO A FEW CLOUDS FROM HEATING IN SOUTHWEST
MN...BUT EVEN THERE THINK SUNSHINE WILL BE THE RULE. MODELS ALSO
INDICATE SOME MILD LEVEL MOISTURE INCREASE OVER THE MISSOURI RIVER
AREA IN OUR SOUTHWESTERN FORECAST AREA BY AFTERNOON. FOR THE MOST
PART THE DAY SHOULD BE SEMI BRIGHT AND PLEASANT. THE SEMI PART
REFERS TO THE POSSIBILITY OF MORE SMOKINESS FROM  UPSTREAM FIRES.
SUCH SMOKE IF IT IS STILL CONING DOWN WILL STILL BE APPARENT ALOFT
EVEN AS SURFACE AND LOW LEVEL FLOW GOES LIGHT THEN STARTS TO GO
SOUTHEASTERLY. HIGH TEMPERATURES ARE EXPECTED TO BE AT OR WITHIN
SHOUTING DISTANCE OF 80.

SOME MID LEVEL MOISTURE WILL CONTINUE TO SPREAD INTO THE AREA
TONIGHT. SOME INCREASE IN MOISTURE AND INSTABILITY AND A WEAK SHORT
WAVE TO HELP PROVIDE SOME LIFT COULD LEAD TO ISOLATED STORMS NEAR
THE MISSOURI RIVER AS THE NIGHT GOES ON. A LOW LEVEL JET APPROACHING
FROM THE SOUTHWEST SEEMS WEAKER THAN IT DID A DAY OR TWO AGO. THAT
AND THE WEAKNESS OF OTHER FACTORS WILL KEEP THE POPS TO ISOLATED.
LOW TEMPERATURES SHOULD BE IN THE 58 TO 63 RANGE...OR A BIT WARMER
THAN THE CURRENT NIGHT.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 257 AM CDT WED JUL 9 2014

ANY THUNDERSTORMS THAT DEVELOP NEAR THE NEBRASKA AND SOUTH DAKOTA
BORDER ON WEDNESDAY NIGHT WILL LIKELY CONTINUE MOVING TO THE
SOUTHEAST AND SLOWLY WEAKEN AS THE AIR MASS IS MORE STABLE OVER
NORTHEAST NEBRASKA. THEN A FAIRLY STRONG SHORT WAVE IS EXPECTED TO
PROGRESS FROM NORTH DAKOTA INTO MINNESOTA BY THURSDAY EVENING. AT
THE SAME TIME THERE WILL BE A STRONG INFLUX OF MOISTURE DUE TO
INCREASING 850 MB FLOW INTO AREA. THIS RESULTS IN A FAIRLY STRONG
850 MB THETA-E GRADIENT DEVELOPING IN THE VICINITY OF THE UPPER
WAVE DURING THE AFTERNOON AND EVENING. WHILE LAPSE RATES WILL
STRUGGLE TO REACH 7 C/KM AND CAPES ARE LIKELY TO BE 1000 J/KG OR
LESS...THE COMBINATION OF WEAK INSTABILITY...A FAIRLY STRONG
SYNOPTIC SCALE WAVE AND A FRONTAL BOUNDARY IS EXPECTED TO RESULT
IN DEVELOPMENT OF THUNDERSTORMS DURING THE AFTERNOON IN CENTRAL
SOUTH DAKOTA AND SPREADING TOWARD SOUTHWEST MINNESOTA DURING THE
EVENING. THE QUESTION IS HOW FAR SOUTH CONVECTION WILL DEVELOP.
THE NAM FAVORS ALMOST ALL OF THE PRECIPITATION NEAR THE UPPER
LEVEL WAVE CLOSER TO HWY 14 IN SD AND THEN INTO SW MN...WHILE THE
ECMWF AND GFS HAVE MORE WIDESPREAD PRECIPITATION. THE BEST
DYNAMICS ARE DEFINITELY FROM NORTHEAST SOUTH DAKOTA INTO SOUTHWEST
MINNESOTA. BUT WITH THE STRONG MOISTURE FLUX AND WEAK INSTABILITY
...EXPECT THAT CONVECTION WILL GRADUALLY SPREAD SOUTHWEST FROM THE
MAIN COMPLEX OF STORMS THROUGH THE EVENING. ALSO EXPECT THAT
CONVECTION WILL HOLD OFF UNTIL LATER IN THE AFTERNOON FOR MOST
AREAS SO HAVE THE HIGHEST POPS IN LATE THU AFTERNOON...THEN
INCREASING TO 50 TO 70 PERCENT EAST OF THE JAMES RIVER AFTER 00Z
AND CONTINUING ABOVE 50 PERCENT EAST OF I29 THROUGH 12Z. SOME OF
THE INITIAL CONVECTION COULD PRODUCE SMALL HAIL IN THE LATE
AFTERNOON AND EVENING BUT INSTABILITY IS SO LIMITED...SEVERE
WEATHER IS NOT ANTICIPATED. GENERALLY HAVE FROM A THIRD TO HALF AN
INCH RAIN IN THIS AREA BUT THAT SHOULD REALLY BE SEEN AS A BROAD
AREAL AVERAGE. WITH PRECIPITABLE WATER AROUND 1.5"...AND A
RELATIVELY SLOW PROPAGATION SPEED...LOCAL AMOUNTS COULD BE DOUBLE
OR MORE OF THIS AVERAGE. HOWEVER...THERE IS SO MUCH UNCERTAINTY
ON THE EXACT AREA WHERE PRECIPITATION WILL BE HEAVIEST HAVE KEPT
FORECAST RAINFALL AMOUNTS DOWN. WHILE MUCH OF THE DAY WILL BE
DRY...THERE ARE GOING TO BE A LOT OF CLOUDS AROUND...ESPECIALLY
DURING THE AFTERNOON...SO ONLY EXPECT HIGHS TO REACH THE LOWER
80S. BUT THE CLOUDS AND MOISTURE WILL KEEP LOWS IN THE MID TO
UPPER 60S THU NIGHT.

FRIDAY IS MUCH MORE UNCERTAIN AT THIS TIME. DURING THE
MORNING...THE WAVE THAT IS EXPECTED TO BRING RAINFALL THURSDAY
NIGHT WILL MOVE EAST BRINGING AN END TO RAIN IN NW IOWA BY EARLY
AFTERNOON. AFTER THAT...THE AREA WILL BE BETWEEN TWO
BOUNDARIES...ONE NEAR I-80 THAT WILL LIKELY DEVELOP DUE TO ALL THE
PRECIPITATION AND CLOUDS FARTHER NORTH...AND A STRONGER SYNOPTIC
BOUNDARY ACROSS NRN SD. IN BETWEEN...EXPECT THE SUN TO BREAK
THROUGH AND THE ATMOSPHERE TO BECOME FAIRLY UNSTABLE...WITH
MLCAPES APPROACHING 2000 J/KG. THERE IS A WEAK CAP IN PLACE AND NO
REAL MESOSCALE BOUNDARY TO FOCUS LIFT. SO ALTHOUGH THERE IS A WEAK
UPPER LEVEL WAVE MOVING ACROSS THE AREA DURING THE LATE
AFTERNOON...ONLY INTRODUCED A SLIGHT CHANCE OF THUNDERSTORMS NEAR
HIGHWAY 14 WITH THAT LOW CHANCE SPREADING SOUTHEAST THROUGH
FRIDAY NIGHT. CERTAINLY IF A STRONGER BOUNDARY SETS UP OVER THE
AREA...THE DEGREE OF INSTABILITY ALONG WITH THE WEAK WAVE WOULD
RESULT IN THUNDERSTORMS...A FEW WHICH COULD PRODUCE MARGINALLY
SEVERE HAIL. BUT WITH NO EVIDENCE OF A BOUNDARY...THE EXPECTATION
IS THAT STORMS WILL BE ISOLATED AT BEST. WITH MORE SUN HIGHS ON
FRIDAY WILL RANGE FROM THE LOWER 80S WEST OF I-29 TO AROUND 90 IN
SOUTH CENTRAL SD. FRIDAY NIGHT WILL AGAIN BE WARM WITH LOWS IN THE
MID TO UPPER 60S.

FOR THE EXTENDED...SATURDAY THROUGH TUESDAY...A BIG CHANGE IS
FORECAST BY ALL MODELS AS A UNSEASONABLY STRONG UPPER LOW IS
FORECAST TO DEVELOP OVER SOUTHWEST ONTARIO AND IMPACT WEATHER FROM
THE PLAINS INTO THE NORTHEAST. PRIOR TO THIS UPPER LOW
DEVELOPING...ALL MODELS SHOW ANOTHER WAVE MOVING ACROSS THE AREA
ON SATURDAY ACCOMPANIED BY A COLD FRONT. THEN A SECONDARY COLD
FRONT IS EXPECTED EARLY NEXT WEEK AHEAD OF THE UPPER LOW. THE 00Z
ECMWF AND 00Z CANADIAN GEM ARE VERY SIMILAR IN THEIR SCENARIO WITH
THE UPPER LOW AND BASICALLY MOVE THE FRONT RELATIVELY QUICKLY
SOUTHWARD ON SUNDAY NIGHT WITH COLDER AIR OVER THE AREA BY MONDAY.
THE GFS IS MUCH SLOWER WITH THE FRONT MOVING THROUGH MONDAY NIGHT.
WHICH SUCH A STRONG UPPER LOW DIGGING SOUTHWARD...THE MORE LIKELY
SOLUTION IS A FASTER FRONTAL PASSAGE AND MUCH COOLER AIR IN PLACE
BY MONDAY SO FOLLOWED THE ECMWF/GEM SOLUTION.

FOR THE PARTICULARS...THE PASSAGE OF THE SHORT-WAVE ON SATURDAY
WILL BRING A CHANCE FOR THUNDERSTORMS TO THE ENTIRE MUCH OF
SATURDAY AND INTO SATURDAY NIGHT. WITH CLOUDS EXPECTED...TEMPERATURES
WILL ONLY BE IN THE UPPER 70S TO MID 80S. THE THREAT FOR
THUNDERSTORMS WILL REMAIN ON SUNDAY ALTHOUGH WITH A MUCH LOWER
PROBABILITY. THERE SHOULD BE MORE SUN AND ALSO RELATIVELY
EFFICIENT MIXING WITHIN THE BOUNDARY TO SUPPORT TEMPERATURES IN
THE 80S. WITH A SUNDAY NIGHT FRONTAL PASSAGE AND ACTUALLY VERY
LITTLE CONVERGENCE...DO NOT EXPECT CONVECTION ALONG THE FRONT AS
IT MOVES THROUGH SUNDAY NIGHT WITH DRY WEATHER THEN EXPECTED
THROUGH TUESDAY. HIGHS MONDAY AND TUESDAY ARE EXPECTED TO
GENERALLY BE IN THE 70S WITH THE COOLEST DAY EXPECTED ON TUESDAY.
IN FACT...IF THE ECMWF IS CORRECT...MANY PLACES WILL STRUGGLE TO
REACH 70 DEGREES ON MONDAY AND TUESDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 634 AM CDT WED JUL 9 2014

PATCHY VISIBILITIES 3-5SM IN BR UNTIL 14Z. SMOKE ALOFT FROM
CANADIAN FIRES WILL REDUCE VISIBILITIES SLIGHTLY BUT VISBILITIES
ARE CURRENTLY EXPECTED TO REMAIN ABOVE 5SM. OTHERWISE VFR THROUGH
10/12Z.

&&

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

$$

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





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