Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 240841
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
341 AM CDT SUN AUG 24 2014

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 309 AM CDT SUN AUG 24 2014

...POTENTIAL FOR HEAVY RAIN MONDAY NIGHT THROUGH TUESDAY NIGHT...

SEVERAL FORECAST CHALLENGES IN THE SHORT TERM INCLUDING SHARP
TEMPERATURE CONTRASTS ACROSS THE FORECAST AREA AS A COOL FRONT
MOVES INTO THE AREA...THEN STALLS. THERE WILL ALSO BE SEVERAL
CHANCES OF THUNDERSTORMS...ESPECIALLY BY MONDAY NIGHT THROUGH
TUESDAY NIGHT...WITH HEAVY RAIN POSSIBLE NORTH OF THE STALLED
BOUNDARY OF SEVERAL INCHES IN THE NORTH HALF OF THE FORECAST AREA.

UPPER CLOSED LOW REMAINS ACROSS THE NORTHERN ROCKIES THIS MORNING
WITH ANOTHER LOBE MOVING THROUGH THE PLAINS TRIGGERING THUNDERSTORMS
ACROSS EASTERN NEBRASKA. ACCAS FIELD ACROSS SOUTHWEST IOWA COULD
ALSO BE GENERATING SPOTTY SHOWERS THERE...ALTHOUGH CLOUD BASES
WERE QUITE AROUND 17000 FEET. MEANWHILE...A COLD FRONT IS POISED
JUST WEST OF THE FORECAST AREA...WHICH WILL MOVE EASTWARD LATER
TODAY...BUT COULD BE A TRIGGER FOR ADDITIONAL STORM DEVELOPMENT
LATER TODAY AND TONIGHT.

FOR EARLY THIS MORNING...THE BULK OF THE PRECIP COULD BE NORTH OF
THE AREA BY 12Z...ALTHOUGH HRRR/NAM ARW/RAP INDICATE THERE COULD
BE SPOTTY LINGERING ACTIVITY THROUGH ABOUT 15Z. WILL LIKELY MAKE
SOME VERY LAST MINUTE POP ADJUSTMENTS BEFORE 4 AM TO ACCOUNT FOR
VERY SPOTTY ACTIVITY ACROSS PRIMARILY EASTERN NEBRASKA THIS
MORNING.

WITH FRONT PUSHING IN LATER TODAY...ATMOSPHERE COULD BE CAPPED
FOR MOST OF THE DAY...BUT COULD BEGIN TO SEE SPOTTY LATE AFTERNOON
DEVELOPMENT ALONG/EAST OF THE MISSOURI RIVER...THAT COULD EXPAND
THIS EVENING ACROSS WESTERN IOWA AS LOW LEVEL JET STRENGTHENS.
HIGHS TODAY WILL AGAIN BE HOT AHEAD OF THE FRONT...RANGING FROM
THE LOWER TO MID 90S...BUT COOLER LOWER 80S BEHIND IT. HEAT INDEX
VALUES AHEAD OF THE FRONT WILL RANGE AROUND 100 THIS AFTERNOON BUT
NOT WARM ENOUGH FOR A HEAT ADVISORY.

THE THE FRONT STALLS IN SOUTHEAST NEBRASKA AND SOUTHWEST IOWA
OVERNIGHT...AND COULD SEE ADDITIONAL SPOTTY ACTIVITY NEAR THE
FRONT OVERNIGHT...BUT LIKELY NOT MUCH IN NORTHEAST/EAST CENTRAL
NEBRASKA. THEN WE`LL BE WAITING FOR THE NEXT IMPULSE TO MOVE OFF
THE HIGH PLAINS MONDAY. MOST OF MONDAY MORNING COULD ACTUALLY BE
DRY...BUT CHANCES BEGIN TO INCREASE JUST SLIGHTLY MONDAY
AFTERNOON. TEMPS AGAIN MONDAY COULD BE TRICKY...WITH MID 70S NORTH
OF THE FRONT...BUT MID 90S FOR SOUTHEAST NEBRASKA.

PRECIP CHANCES SUBSTANTIALLY INCREASE MONDAY NIGHT FOR THE NORTHERN
FORECAST AREA NORTH OF THE STALLED SURFACE FRONT. PW VALUES INCREASE
TO THE 90-97 30-YEAR CLIMATOLOGICAL PERCENTILE BASED ON NAEFS
OUTPUT. LOCALLY HEAVY RAIN OF AN INCH OR TWO WILL BE POSSIBLE IN
NORTHEAST NEBRASKA THROUGH DAYBREAK TUESDAY...AND THE AREA IS IN
SLIGHT RISK FOR EXCESSIVE HEAVY RAINFALL. BELIEVE WE CAN HANDLE
THE RAIN MONDAY NIGHT WITHOUT TOO MUCH TROUBLE...AND HAVE POPS
RANGING FROM JUST SLIGHT CHANCE KS/NE BORDER INCREASING TO
CATEGORICAL NORTH OF I80.

THE SURFACE BOUNDARY REMAINS STALLED ON TUESDAY. WILL LIKELY SEE
NUMEROUS SHOWERS NORTH OF THE FRONT ACROSS NORTHEAST NEBRASKA...
TAPERING TO NOT MUCH OR ANY PRECIP SOUTH OF THE BOUNDARY. TEMPS
AGAIN WILL VARY WIDELY NORTH TO SOUTH ACROSS THE FRONT...FROM THE
MID 70S NEAR NE/SD BORDER TO MID 90S NEAR KS/NE BORDER REGION.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 309 AM CDT SUN AUG 24 2014

ANOTHER STRONG IMPULSE MOVES OFF THE HIGH PLAINS TUESDAY NIGHT.
AGAIN...A RATHER LARGE AREA OF 90-97 PERCENT 30-YEAR CLIMATOLOGICAL
PERCENTILE FOR PW REMAINS ACROSS THE MID MISSOURI RIVER VALLEY...
RESULTING IN ANOTHER NIGHT OF CONVECTIVE RAINS...WITH HIGHEST
AMOUNTS EXPECTED NORTH OF THE BOUNDARY ALONG/NORTH OF I80. THIS
SECOND NIGHT OF HEAVY RAIN MAY BE COLOCATED WITH MANY AREAS THAT
RECEIVED THE HEAVY RAIN MONDAY NIGHT...AND AGAIN THE AREA IS
WITHIN A SLIGHT RISK OF EXCESSIVE HEAVY RAINFALL. TOO FAR OUT TO
GO WITH ANY TYPE OF FLOOD WATCH...BUT WILL MONITOR CLOSELY IN
LATER FORECASTS FOR POTENTIAL FLOODING BASED ON A COUPLE OF
NIGHTS OF EXPECTED HEAVY RAIN.

MODEL DIFFERENCES BEGIN TO DEVELOP BY THURSDAY AND BEYOND. THE GFS
IS A BIT MORE PROGRESSIVE IN EJECTING THE FILLING MEAN TROUGH AND
THE ECMWF IS SIGNIFICANTLY SLOWER. WILL STILL SEE NUMEROUS SHOWERS
AND THUNDERSTORMS WEDNESDAY THROUGH WEDNESDAY NIGHT...AND THEN
DIMINISHING BY THURSDAY/THURSDAY NIGHT. WILL MAINTAIN A DRY FORECAST
FOR FRIDAY AND SATURDAY BASED ON PROGRESSIVE GFS MODEL...BUT TEMPS
ALSO RETURN TO NORMAL BY THEN REBOUNDING TO THE MID 80S. WILL HAVE
TO MONITOR THE ECMWF MODEL TO SEE IF SLOWER TRENDS CONTINUE.

OVERALL SEVERE WEATHER THREAT THROUGH THE PERIOD SEEMS LOW...WITH
MORE FOCUS ON HEAVY CONVECTIVE RAINS INSTEAD.

&&

.AVIATION...(06Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1130 PM CDT SAT AUG 23 2014

CONVECTION HAD INCREASED FROM CENTRAL INTO NERN NEBR BY 04Z AND
ALTHOUGH THERE REMAINS A CHANCE OF TSTMS AT ALL SITES THE REST OF
TONIGHT...KOFK STILL APPEARED MOST LIKELY TO BE IMPACTED AND A
TEMPO GROUP WAS MAINTAINED THERE. ALSO WITH A MODERATELY STRONG
LOW SSW LOW LEVEL JET AND SSE SFC WINDS...A WIND SHEAR RISK
REMAINED AT MAINLY KOMA AND KLNK TONIGHT WHICH WAS ALSO CARRIED
FORWARD. A COOL FRONT IN WESTERN NEBR IS EXPECTED TO MOVE INTO ERN
NEBR SUNDAY AND WEAKEN AS IT MOVES TOWARD MO RIVER BY LATE AFTN. A
FEW ELEVATED SHOWERS/TSTMS COULD OCCUR ALONG/BHND FRONT EARLY IN
THE DAY WITH REDEVELOPMENT POSSIBLE TOWARD EVENING. THUS PROB30
GROUPS WERE MENTIONED AT KOFK FOR THE MIDDAY SHOWER CHANCE AND AT
KOMA/KLNK FOR LATE DAY CONVECTION.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&

$$

SHORT TERM...DEWALD
LONG TERM...DEWALD
AVIATION...CHERMOK



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