Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 021808
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
108 PM CDT THU JUL 2 2015

.SHORT TERM...(THIS AFTERNOON THROUGH FRIDAY AFTERNOON)
ISSUED AT 651 AM CDT THU JUL 2 2015

MOST IMPORTANT PLAYER TO THE SHORT TERM WEATHER IS COMPACT UPPER
WAVE MOVING SLOWLY SOUTHEAST ACROSS NORTH DAKOTA AND NORTHERN SOUTH
DAKOTA IN THE WEE HOURS THIS MORNING. LARGE MCS ACROSS WESTERN
NEBRASKA WORKING SOUTHWARD...AND IF LOWER LEVEL FLOW WAS CRITICAL TO
DEVELOPMENT WOULD EXPECT THIS TO HAVE A SIGNIFICANT IMPACT.
HOWEVER...LIFT FORCING PRIMARILY A RESULT OF THE STRONG UPPER WAVE
PUSHING SOUTHEAST...AND HAVE A FAIRLY DISTINCT INSTABILITY GRADIENT
IN PLACE ACROSS THE WESTERN HALF OF THE CWA...SOMEWHAT WEST OF
EARLIER MODEL GUIDANCE...AS WELL AS A MODEST LOWER TO MID LEVEL
CONVERGENCE AXIS ACROSS CENTRAL SD.  HAVE SEEN A RAPID INCREASE IN
SCATTERED CONVECTION COVERAGE BACK ALONG THESE BOUNDARIES IN CENTRAL
SD IN THE LAST HOUR OR TWO...WHICH LEADS TO A BIT HIGHER CONFIDENCE
IN THE HIGH RESOLUTION SOLUTIONS OF ENCROACHMENT IN THE WESTERN CWA
BETWEEN 09Z AND 12Z...AND A MUCH SLOWER AND LESS SIGNIFICANT
PROGRESSION INTO AREAS EAST OF I29 DURING THE MORNING. TRENDS IN
BOTH HIGH RESOLUTION AND OTHER SHORT RANGE OPERATIONAL SOLUTIONS IS
TO KEEP A FAIRLY STRONG BUFFER OF STABILITY OVER THE EASTERN
CWA...AND EITHER STOP OR AT LEAST LIMIT THE POTENTIAL PRECIPITATION
INTRUSION INTO FAR EASTERN PORTIONS OF THE CWA THROUGH THE DAY. WILL
FOCUS HIGHER POPS THROUGH THE JAMES VALLEY THIS MORNING...AND
GRADUALLY SETTLE TOWARD THE LOWER MISSOURI VALLEY AND NORTHEAST
NEBRASKA LATER MORNING AND AFTERNOON. LINGERING MOISTURE/CONVERGENCE
AXIS WILL KEEP A LOWER COVERAGE THREAT FOR PRECIPITATION LATER DAY
AND INTO THE EVENING ACROSS THE WEST AND SOUTH AS SUBTLE SECONDARY
WAVE SWINGS SOUTHWARD THROUGH THE WESTERN PLAINS...BEFORE FADING
WITH LOSS OF DIABATIC SUPPORT AND MEAGER UPPER FORCING.

AGAIN...NOT LOOKING AT A TREMENDOUS AMOUNT OF INSTABILITY TO START
THE DAY AS THE GREATER DYNAMIC LIFT SLIPS ACROSS THE AREA...WITH
ELEVATED CAPE PERHAPS 1000 J/KG OR A BIT MORE FAR WEST...AND
TAPERING OFF TO A COUPLE HUNDRED J/KG EAST OF INTERSTATE 29. WITH 40
KNOTS OF EFFECTIVE SHEAR ACROSS THE SOUTHWESTERN CWA CORRESPONDING
TO GREATER INSTABILITY...A COUPLE OF STORMS IN THE EARLY MORNING
WEST OF THE JAMES COULD BE CAPABLE OF MARGINALLY LARGE HAIL...BUT
NEITHER DEEP LAYER SHEAR OR INSTABILITY SUGGESTS ANY GREATER THREAT.

MAY SEE A LITTLE PATCHY FOG ACROSS MAINLY AREAS NEAR/WEST OF I29
LATE TONIGHT AS THE CLOUDS BREAK AND GRADIENT GOES LIGHT. EASTERN
AREAS SHOULD BE FREE OF FOG WITH A LITTLE MORE DRY TRAJECTORY.
OTHERWISE...A SEASONALLY COOL DAY WITH HIGHS IN THE 70S...COOLEST IN
THE PRECIP AXIS. FOR TONIGHT...SHOULD AGAIN RETURN MAINLY TO UPPER
50S TO AROUND 60.

.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 651 AM CDT THU JUL 2 2015

FRIDAY LOOKING LIKE A VERY NICE SLIGHTLY HUMID DAY WITH WINDS LESS
THAN 20 KNOTS UP TO ABOUT 200MB. WHILE THE MAJORITY OF THE AREA WILL
REMAIN DRY A WEAK BOUNDARY WILL LEAK INTO THE FAR EASTERN CWA BY
LATE AFTERNOON AND AT PEAK HEATING WITH A MINOR AMOUNT OF CAPE A FEW
THUNDERSTORMS COULD BE POSSIBLE. WILL ONLY CARRY A 20 POP FOR NOW.
HIGHS MAINLY UPPER 70S TO MID 80S.

FRIDAY NIGHT INTO SATURDAY WILL CONTINUE THE FAIRLY QUIET WEATHER AS
HIGH PRESSURE GRADUALLY WORKS THROUGH. RETURN FLOW WILL SET UP OVER
CENTRAL SOUTH DAKOTA BY SATURDAY AFTERNOON AND WILL NEED TO HAVE A
SMALL CHANCE FOR THUNDERSTORMS SATURDAY AFTERNOON AND SATURDAY NIGHT
BUT AT THIS TIME NOT ANTICIPATING ANY SEVERE WEATHER.

IN THE OUTER PERIODS(SUNDAY THROUGH WEDNESDAY)...A LARGE AREA OF LOW
PRESSURE OVER CENTRAL CANADA WILL KEEP WESTERLY FLOW IN PLACE ACROSS
THE NORTHERN PLAINS. IT ALSO KEEPS RIDGING FROM DEVELOPING ALOFT SO
NO MAJOR HEATING EXPECTED THROUGH THIS PERIOD. IN FACT TEMPERATURES
WILL MORE THAN LIKELY BE BELOW NORMAL DURING THIS TIME AS THIS FLOW
FAVORS LOCKING IN COOLER AIR FROM THE NORTH AND KEEPING HEAT TO THE
SOUTH AND WEST OF THE AREA. THE ONLY DECENT CHANCE FOR THUNDERSTORMS
DURING THIS TIME SHOULD BE ON SUNDAY/SUNDAY NIGHT AS A JET MAX MOVES
THROUGH NORTH DAKOTA AND SWINGS A COLD FRONT THROUGH. STILL LOOKING
LIKE A THREAT FOR SEVERE SO WILL NEED TO CONTINUE TO MONITOR
POTENTIAL. THE NEXT BETTER CHANCE WILL MORE THAN LIKELY BE
WEDNESDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 104 PM CDT THU JUL 2 2015

CONDITIONS SHOULD GRADUALLY IMPROVE THROUGHOUT THE DAY AS
SHORTWAVE EXITS THE AREA LEADING TO GRADUALLY CLEARING SKIES. AN
AREA OF SHOWERS NEAR KHON WILL SINK SOUTH SOUTH EAST THROUGH THE
AFTERNOON HOURS AND WILL WEAKEN WHILE DOING SO. THIS COULD PRODUCE
SOME SHOWERS ACTIVITY AROUND 20Z NEAR KFSD...BUT CONFIDENCE IS NOT
THERE AT THIS POINT TO INCLUDE MENTION IN THE FORECAST. WITH
HEAVIER RAIN FALLING IN THE JAMES RIVER VALLEY...COULD SEE SOME
PATCH FOG DEVELOP AS SKIES CLEAR. CONFIDENCE NOT ALL THAT
HIGH...SO ONLY LEFT A SMALL VISBY REDUCTION IN KHON.

&&

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

$$

SHORT TERM...CHAPMAN
LONG TERM...08
AVIATION...



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