Flash Flood Warning 17, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
416 AM CDT TUE AUG 6 2013

.DISCUSSION...
SHORT TERM CONCERNS WILL BE MORNING CONVECTION AND THEN AFTERNOON
AND EVENING CONVECTION/SEVERE WEATHER POTENTIAL.

DUE TO MORNING CONVECTION...WILL LIKELY NEED TO RE-VISIT THE
FORECAST EARLY THIS MORNING.

WATER VAPOR SATELLITE IMAGERY AND LIGHTNING DATA CONTINUED TO SHOW
TROPICAL MOISTURE STREAMING NORTHWARD ACROSS MEXICO INTO THE FOUR
CORNERS REGION AND INTO THE PLAINS AND THEN SOUTHEAST TOWARD THE
LOWER MISSISSIPPI VALLEY AROUND THE LARGE H5 HIGH PRESSURE AREA
CENTERED IN WEST TEXAS.  THE H5 CANADIAN LOW WAS STILL CENTERED NEAR
CHURCHILL BY HUDSON/S BAY WITH A TROF TRAILING BACK TOWARD
WASHINGTON STATE. SHORTWAVES WERE OVER MONTANA/WYOMING AND KANSAS
WITH CONVECTION ASSOCIATED WITH THESE FEATURES. CHANGES FROM A DAY
AGO...SHOWED THAT THE H7 TEMPERATURES HAVE WARMED.  OMA WAS AT +12C
WITH +14C WIDESPREAD ACROSS KANSAS.  PER THE SPC MESOANALYSIS...THE
LARGE H7 +10C DEWPOINTS HAD SHIFT FROM EASTERN KS TO CENTRAL AND
PARTS OF WESTERN KS. H85 DEWPOINTS HAD WERE STILL QUITE HIGH WITH
WIDESPREAD +14 TO +18 FOR PARTS OF THE ROCKIES AND A LARGE AREA FROM
THE GULF NORTH THROUGH OK/KS INTO NEB.

EARLY THIS MORNING...THE MAIN FOCUS FOR THE LOW LEVEL JET WAS FROM
THE DAKOTAS INTO MINNESOTA AND FROM KANSAS INTO MISSOURI AND BY
4AM...THERE WAS GOOD DEVELOPMENT SOUTHWARD INTO NORTH CENTRAL
NEBRASKA...ALONG THE INSTABILITY GRADIENT AND WHERE MID LEVEL
LAPSE RATES WERE QUITE STEEP. THE GFS DID A GOOD JOB WITH THE
CONVECTION COMPARED TO THE OTHER MODELS AND HAS MOST OF IT THRU
BY 12Z...HOWEVER THE NAM HOLDS ON TO SHOWERS AND THUNDERSTORMS
THROUGH 15Z. THE CONVECTION HAS BEEN MAKING IT FARTHER NORTH OR
SOUTH THAN THE MODELS HAVE BEEN PROJECTING THE LAST COUPLE OF
DAYS. THE SHORT RANGE MODELS HAVE A TOUGH TIME WITH THESE
COMPLEXES...AND THE EXTENT IS ALWAYS DIFFICULT TO PIN DOWN. DID
INCREASE POPS ACROSS NORTHEAST AND EAST CENTRAL NEBRASKA INTO WEST
CENTRAL IOWA THIS MORNING. WILL CONTINUE TO MONITOR SHORT TERM
RADAR TRENDS FOR MORNING UPDATES. NAM/GFS/4KM WRF PROGS ARE
CONSISTENT IN BRINGING LIKELY POPS INTO NORTHEAST NEBRASKA THROUGH
00Z ESPECIALLY NORTH OF A LINE FROM OLU-SUX WITH THE COLD
FRONT...HOWEVER ARE A LITTLE SLOWER TO BRING IT SOUTH AND TO END
AND NOT AS ROBUST WITH THE PRECIPITATION. FEEL THERE ARE GOOD
PARAMETERS IN PLACE THERMALLY/DYNAMICALLY AND MOISTURE-WISE AND
WILL INCLUDE HIGH POPS IN THE NORTH AND TAPER TO CHANCE IN
SOUTHEAST NEBRASKA THROUGH 00Z...THEN SHIFT LIKELY POPS SOUTHWARD
WITH THE FRONT AFTER 00Z...DECREASING FROM NORTH TO SOUTH AFTER
06Z. DEPENDING ON HOW THE ONGOING CLUSTER OF THUNDERSTORMS
DEVELOPS CLOUDS WILL AGAIN AFFECT TEMPERATURES AND INSTABILITY. AHEAD
OF THE FRONT...DESTABILIZATION WITH CAPES OF 2500-3500J/KG AND
DEEP LAYER SHEAR INCREASING TO 40-50KTS AND ABUNDANT MOISTURE
SHOULD PROVIDE SUPPORT FOR MULTIPLE TSTORM MODES. A 50KT SPEED MAX
FROM FROM SD INTO IA COULD ENHANCE THE WIND THREAT.
HAIL...DAMAGING WINDS AND HEAVY RAIN WILL BE THE PRIMARY
HAZARDS...HOWEVER AN ISOLD TORNADO IS ALSO POSSIBLE.

HAVE LEFT WEDNESDAY DRY...WITH PRECIPITATION CHANCES MOVING
NORTHWARD FOR THURSDAY. THE GFS/EC ARE MORE AGGRESSIVE WITH A
SHORTWAVE TROF AND RETURN OF MOISTURE AND A FRONT IN THE AREA. TIME
SECTIONS/FORECAST SOUNDING ARE PRETTY ROBUST HOWEVER LOW LEVEL DRY
AIR WILL NEED TO BE OVERCOME. ONCE THE SYSTEM MOVES OUT OF THE
AREA FRIDAY IT SHOULD BE DRY FRIDAY NIGHT.

TEMPERATURES STILL LOOK AT OR BELOW NORMAL FRIDAY THROUGH MONDAY.
A DEEPENING LONGWAVE TROF FROM CANADA INTO THE PLAINS SHOULD BRING
CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE FORECAST AREA SATURDAY
NIGHT THROUGH SUNDAY NIGHT.

&&

.AVIATION...
06Z TAFS FOR KOMA...KLNK...KOFK.

HIGH LEVEL CLOUDS SHOULD THIN DURING THE OVERNIGHT HOURS. STILL
EXPECT SOME DECREASE IN CEILINGS...EXPECIALLY AT KOFK. WIDESPREAD
IFR CONDITIONS DO NOT LOOK QUITE AS LIKELY AS THEY DID 6 HOURS
AGO FOR KOMA AND KLNK. IF THEY DEVELOP...IFR CONDITIONS COULD
LAST UNTIL 8 OR 9 AM.

TSRA COULD AFFECT KOFK BY EARLY AFTERNOON...WITH TSRA POSSIBLE AT
BOTH KOMA AND KLNK IN THE LATE AFTERNOON AND EVENING TUESDAY. JUST
WENT WITH MVFR CONDITIONS WITH PROB30 GROUPS TUESDAY FOR NOW.

MILLER

&&

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

ZAPOTOCNY

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
630 AM CDT TUE AUG 6 2013

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-070130-
MONONA-HARRISON-SHELBY-POTTAWATTAMIE-MILLS-MONTGOMERY-FREMONT-
PAGE-KNOX-CEDAR-THURSTON-ANTELOPE-PIERCE-WAYNE-BOONE-MADISON-
STANTON-CUMING-BURT-PLATTE-COLFAX-DODGE-WASHINGTON-BUTLER-
SAUNDERS-DOUGLAS-SARPY-SEWARD-LANCASTER-CASS-OTOE-SALINE-
JEFFERSON-GAGE-JOHNSON-NEMAHA-PAWNEE-RICHARDSON-
630 AM CDT TUE AUG 6 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
IOWA...WEST CENTRAL IOWA...EAST CENTRAL NEBRASKA...NORTHEAST
NEBRASKA AND SOUTHEAST NEBRASKA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS WILL PUSH ACROSS NORTHEAST AND PARTS OF EAST CENTRAL
NEBRASKA INTO WEST CENTRAL IOWA THIS MORNING. THE ISOLATED STORMS
MAY BE SEVERE WITH DAMAGING WINDS AND LARGE HAIL ALONG WITH
PERIODS OF HEAVY RAIN POSSIBLE WITH THE STORMS. THIS AFTERNOON
AND TONIGHT SEVERE THUNDERSTORMS WILL AGAIN BE POSSIBLE WITH
DAMAGING WINDS...LARGE HAIL AND HEAVY RAINFALL THE PRIMARY
HAZARDS...HOWEVER AN ISOLATED TORNADO CANNOT BE RULED OUT.

A CLUSTER OF THUNDERSTORMS THAT ORIGINATED IN WESTERN SOUTH DAKOTA
HAVE CONTINUED DEVELOP EARLY THIS MORNING ALONG AN INSTABILITY
GRADIENT AND AN AREA OF DEEP MOISTURE. THESE SHOULD WEAKEN LATER
THIS MORNING. AN UPPER LEVEL WEATHER DISTURBANCE...COMBINED WITH A
COLD FRONT AND HOW MUCH HEATING WE GET THIS AFTERNOON WILL SET THE
STAGE FOR THUNDERSTORM REDEVELOPMENT THIS AFTERNOON AND
TONIGHT...SOME OF WHICH MAY BE SEVERE.

LOCALLY DENSE FOG CAN BE EXPECTED THIS MORNING FOR PARTS OF
SOUTHWEST IOWA...LIFTING AFTER 9AM.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THE CHANCE OF STORMS WILL RETURN TO SOUTHEAST NEBRASKA WEDNESDAY
NIGHT THROUGH FRIDAY AND FOR MUCH OF THE AREA SATURDAY NIGHT INTO
MONDAY.

.SPOTTER INFORMATION STATEMENT...

STORM SPOTTER ACTIVATION MAY BE REQUIRED TODAY AND TONIGHT.

ZAPOTOCNY

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
642 AM CDT TUE AUG 6 2013

NEZ031-032-042-061215-
STANTON NE-MADISON NE-PLATTE NE-
642 AM CDT TUE AUG 6 2013

...SIGNIFICANT WEATHER ADVISORY FOR STANTON...MADISON AND PLATTE
COUNTIES UNTIL 715 AM CDT...

AT 640 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
LINE OF STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM 6 MILES
SOUTHEAST OF NORFOLK TO ST. EDWARD...OR ALONG A LINE EXTENDING FROM
54 MILES SOUTHWEST OF PONCA TO 25 MILES NORTHWEST OF COLUMBUS...AND
MOVING SOUTHEAST AT 35 MPH.

HAIL UP TO THE SIZE OF DIMES AND WIND GUSTS UP TO 40 MPH WILL BE
POSSIBLE WITH THESE STORMS.

LOCATIONS IMPACTED INCLUDE...
MADISON...STANTON...NEWMAN GROVE...PLATTE CENTER...LINDSAY...
CRESTON...HUMPHREY...TARNOV AND CORNLEA.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TORRENTIAL RAINFALL IS ALSO OCCURRING WITH THESE STORMS...AND MAY
LEAD TO FLASH FLOODING. DO NOT DRIVE YOUR VEHICLE THROUGH FLOODED
ROADWAYS.

THESE STORMS MAY INTENSIFY...SO BE CERTAIN TO MONITOR LOCAL RADIO AND
TV STATIONS...AS WELL AS LOCAL CABLE TV OUTLETS...FOR ADDITIONAL
INFORMATION AND POSSIBLE WARNINGS FROM THE NATIONAL WEATHER SERVICE.

&&

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 1200 PM CDT
TUESDAY AFTERNOON.

LAT...LON 4178 9783 4203 9742 4193 9703 4174 9719
      4174 9725 4167 9725 4154 9736 4152 9781
      4154 9783
TIME...MOT...LOC 1140Z 303DEG 30KT 4195 9736 4162 9779

DEWALD

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