Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 060515
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1215 AM CDT WED MAY 6 2015

.UPDATE...
ISSUED AT 1213 AM CDT WED MAY 6 2015

SURFACE CONVERGENCE ALONG NORTHWARD LIFTING WARM FRONT HAS LED TO
DENSE FOR FORMATION ACROSS PORTIONS OF SOUTHERN MINNESOTA AND
IOWA. HRRR/RAP HANDLING THESE REDUCED VISIBILITIES VERY
WELL...GIVING CONFIDENCE TO THE NEED FOR A DENSE FOG ADVISORY FOR
EASTERN ZONES THROUGH DAYBREAK.


&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 358 PM CDT TUE MAY 5 2015

SUBTLE WARM FRONT CREEPING NORTHWARD ACROSS THE AREA.  WITH THE GULF
WIDE OPEN SEEING GOOD MOISTURE RETURN IN QUITE SOME TIME.  PWAT
VALUES CLIMBING TO OVER AN INCH ACROSS THE AREA...OR 90 PERCENT OF
THE MOVING AVERAGE.  MOIST ADIABATIC LAPSE RATES FROM THE SURFACE
TO 200 MB...SO AS THE MOISTURE CONTINUES TO INCREASE...WILL LIKELY
SEE SCATTERED SHOWERS DEVELOP ACROSS THE AREA. NOT A LOT TO GRASP ON
IN TERMS OF FORCING...BUT HAVE FOCUSED POPS ESPECIALLY ALONG AND
WEST OF THE JAMES RIVER VALLEY AS THE UPPER WAVE LIFTS TO THE
NORTHEAST.  WITH DIURNAL HEATING...SHOULD SEE GREATER INSTABILITY
THROUGH THE AFTERNOON HOURS. THEREFORE...HAVE SHOWERS WITH ISOLATED
THUNDER THROUGH THE NIGHT AND MORE BONAFIDE THUNDERSTORMS TOMORROW
AFTERNOON.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 358 PM CDT TUE MAY 5 2015

UPPER TROUGH SWINGS NORTHEAST THROUGH THE REGION WEDNESDAY NIGHT...
WITH GFS/GEM/ECMWF IN GOOD AGREEMENT SHOWING BAND OF SHOWERS AND
THUNDERSTORMS PROGRESS EAST ACROSS THE FORECAST...WITH WESTERN AREAS
DRYING OUT AS WINDS SHIFT TO THE SOUTHWEST AND WEST BEHIND THE
SURFACE FRONT. DEEP MOISTURE SHOULD SUPPORT FAIRLY EFFICIENT
RAINFALL WITH THE WEDNESDAY NIGHT ACTIVITY...WITH THIS PERIOD
SHOWING THE BEST POTENTIAL FOR RAINFALL AMOUNTS OF A HALF INCH OR
MORE IN SOME LOCATIONS.

STILL UNSETTLED WITH A CHANCE OF SCATTERED SHOWERS/THUNDERSTORMS
INTO THURSDAY AS A SECONDARY WAVE AND COLD FRONT SLIDE THROUGH THE
AREA...THEN LOOKS LIKE A DRIER PERIOD ON TRACK FOR FRIDAY/SATURDAY
AS WEAK UPPER RIDGE MOVES ACROSS THE REGION. THESE DAYS LOOK TO BE A
LITTLE COOLER THAN RECENT DAYS...BUT STILL SEASONABLY MILD WITH
HIGHS MOSTLY IN THE 60S THURSDAY THROUGH SATURDAY.

ANOTHER LARGE TROUGH DEVELOPS ACROSS THE ROCKIES THROUGH THE FIRST
PART OF THE WEEKEND...AND IS THEN PROGGED TO SHIFT INTO THE PLAINS
SATURDAY NIGHT THROUGH MONDAY. WHILE THERE ARE MODEL DIFFERENCES IN
THE TIMING/STRENGTH OF THE OF THE TROUGH...GENERALLY SEEING STRONG
AGREEMENT IN INCREASED PRECIP CHANCES SPREADING OVER THE AREA FOR
SATURDAY NIGHT/SUNDAY...THEN GRADUALLY DIMINISHING THROUGH SUNDAY
NIGHT/MONDAY. POTENTIAL RAIN WILL KEEP TEMPERATURES ON THE COOLER
SIDE TO START THE WEEK...WITH SOME AREAS LIKELY STRUGGLING TO REACH
LOWER-MID 50S FOR HIGHS SUNDAY AND/OR MONDAY. LOOKS LIKE POTENTIAL
FOR MORE MUCH NEEDED RAINFALL...BUT AT THIS TIME THE SEVERE THREAT
APPEARS LOW.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1106 PM CDT TUE MAY 5 2015

SCATTERED RAIN SHOWERS WITH ISOLATED THUNDER WILL BEGIN BUILDING
BACK INTO THE FORECAST AREA AFTER 08Z TONIGHT...BEGINNING
PRIMARILY WEST OF I29. AN AREA OF MVFR AND IFR CEILINGS AND
VISIBILITY AS LOW AS 1/2 MILE HAS DEVELOPED EAST OF 129...WITH
FLOW SUGGESTING THAT THIS LAYER WILL PERSIST OVERNIGHT AND
EVENTUALLY MERGE WITH THE INCREASING STRATUS TO OUR SOUTH.
WITH THE APPROACHING UPPER LOW...PRECIPITATION CHANCES SPREAD
EAST AND INCREASE INTO THE EVENING HOURS. MVFR CEILINGS WILL
ACCOMPANY THE INCREASING RAIN THREAT LATE TONIGHT AND LINGER
THROUGH THE DAY WEDNESDAY.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...DENSE FOG ADVISORY UNTIL 8 AM CDT THIS MORNING FOR MNZ080-081-
     089-090.

IA...DENSE FOG ADVISORY UNTIL 8 AM CDT THIS MORNING FOR IAZ002-003-
     013-014-022.

NE...NONE.
&&

$$

UPDATE...DUX
SHORT TERM...
LONG TERM...JH
AVIATION...


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