Severe Thunderstorm Warning 129, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
218 AM CDT FRI JUN 19 2009

.DISCUSSION...
ONGOING CONVECTION THIS MORNING IS THE MAIN FORECAST
CONCERN...THEN WHEN TO REINTRODUCE STORMS INTO THE FORECAST WITH
LITTLE MODEL CONSENSUS IS THE SECONDARY CHALLENGE. SHORT
DISCUSSION DUE TO SEVERE OPERATIONS FOLLOWS.

STRONG STORMS IN CENTRAL NEBRASKA AROUND MIDNIGHT HAVE BEGUN TO ROLL
EAST INTO THE CWA. SPC MESO ANALYSIS RUC PROGS SHOW INCREASING
INSTABILITY AS THOSE STORMS MOVE EAST TOWARD THE MISSOURI
RIVER...AND LOW LEVEL JET WAS KICKING IN ACROSS KANSAS INTO
SOUTHEAST NEBRASKA. THIS ALL SUGGESTS STORMS WILL CONTINUE ACROSS
MUCH OF THE CENTRAL AND SOUTHERN CWA THROUGH AT LEAST SUNRISE AS
STORMS LINED UP ACROSS THE STATE FEED ON BETTER MOISTURE/INSTABILITY
AS THEY SPREAD EAST. EXPECT CLUSTER OF STORMS TO BE ONGOING AS OF 7
AM ACROSS THE INTERSTATE 80 CORRIDOR...THEN SPREAD EAST OF THE
MISSOURI RIVER EARLY THIS AFTERNOON BEFORE EXITING OUR EASTERN CWA.
HAVE HIT POPS FAIRLY HARD THIS MORNING...THEN TAPERED TO CHANCE POPS
THIS AFTERNOON IN THE EAST.

SHOULD HAVE A RELATIVELY QUIET PERIOD FOR A SHORT WHILE AFTER STORMS
EXIT THIS AFTERNOON. SURFACE HIGH PRESSURE BUILDS INTO THE CWA
BEHIND WEAK COLD FRONT NUDGED BY TODAYS CONVECTION. MODELS ARE
FAIRLY SIMILAR IN THIS REGARD...SO HAVE KEPT DRY FORECAST FOR
TONIGHT. HOWEVER MODELS DIVERGE ON HOW QUICKLY RETURN FLOW IGNITES
STORMS SATURDAY OR SATURDAY NIGHT. GFS IS THE MOST AGGRESSIVE IN
TRIGGERING STORMS SATURDAY MORNING. THINK THIS IS A BIT TOO
FAST...SO HAVE SIDED WITH ECMWF AND NAM IN THE SLIGHTLY SLOWER
SOLUTION BRINGING STORMS INTO OUR SOUTH SATURDAY AFTERNOON. SURFACE
BASED INSTABILITY IS SOMEWHAT LIMITED DESPITE UPPER 60S DEW
POINTS...BUT BETTER MID LEVEL FLOW/SHEAR SHOULD BE SUFFICIENT TO
MAINTAIN STORMS IN OUR WEST AND NORTH THROUGH SATURDAY NIGHT.

THE REST OF THE FORECAST WAS LEFT BASICALLY UNCHANGED. AS FAR AS
PRECIPITATION GOES...UPPER RIDGING REMAINS OVER THE CWA THROUGH MUCH
OF THE WEEK...BUT SEVERAL RIPPLES ROUNDING TOP OF RIDGE MAY BRING
STORMS TO OUR NORTHERN CWA FROM TIME TO TIME. TEMPERATURES SUNDAY
INTO MONDAY ARE ANOTHER PROBLEM AS GFS SUGGESTS LIGHT SOUTHEAST LOW
LEVEL FLOW WILL HOLD TEMPS IN THE 80S...BUT THE ECMWF HAS GUSTY
SOUTHWEST FLOW WHICH WOULD PUSH TEMPS WELL INTO THE 90S. HAVE SPLIT
THE DIFFERENCE FOR NOW...BUT EXPECT THE WARMER TEMPS WILL LIKELY WIN
OUT.

&&

.AVIATION...
FOR TAF SITES KOFK/KOMA/KLNK VALID THROUGH 20/06Z.

TSRA ONGOING AT KLNK AND EXPECTED TO EXPAND ACRS ECNTRL NEB AND INTO
WRN IA. SFC FNT WAS NOTED WITH AN AREA OF LOW PRES AROUND KLNK AND
KOMA WITH THE WRMFNT INTO NCNTRL IA. TSRA...SOME SEVERE (HAIL/WIND)
TO AFFECT THE OMAHA/LNK TAF SITES OR IN THE VICINITY OVERNIGHT AND
THROUGH AROUND 15Z AS MID LEVEL TROF ADVANCES AND SHIFTS CONVECTION
EAST OF THE TAF SITES.  REDUCED VSBYS AND CIGS WITH THE TSRA AND
HEAVY RAIN TO MVFR AND POSSIBLY IFR. MAINLY VFR CIGS...HOWEVER THERE
COULD BE SOME LINGERING SHOWERS DURING THE AFTERNOON...WITH
DECREASING CLDS AND AFT 00Z.

&&

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

DERGAN/ZAPOTOCNY

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