Severe Thunderstorm Warning 48, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
314 AM CDT WED MAY 6 2009

.DISCUSSION...

WEAK IMPULSES MOVING THRU FAST WNWLY FLOW ALOFT WL CREATE SMALL
CHANCES FOR SHOWERS AND TSTMS THRU THE NEXT SEVERAL DAYS. REGIONAL
RADAR IMAGERY SHOWS SCATTERED SHOWERS AND ISOLATED TSTMS MOVING
ESE ACROSS NCNTRL NEB WHILE A FEW ISOLATED TSTMS MOVE
ACROSS NERN NEB. THIS IS ALL OCCURRING AHEAD OF WEAK MID LEVEL
SHORTWAVE ENERGY ACROSS NRN NEB PER LATEST WATER VAPOR IMAGERY.
LATEST SUBJECTIVE SFC ANALYSIS SHOWS A TROF EXTENDING FM CNTRL ND
INTO NCNTRL NEB. AHEAD OF THE TROF...SFC DEWPOINTS ARE IN THE
LOWER TO MID 50S. PLENTY OF LLVL MOISTURE HAS WORKED INTO THE
REGION WITH 850MB MOIST AXIS EXTENDING FM CNTRL NEB INTO NERN NEB.

EXPECT WEAKLY ORGANIZED SHOWERS AND TSTMS TO HOLD TOGETHER AS
THEY MOVE THRU THE CWA THIS MORNING DUE IN PART TO THE MID LEVEL
SHORTWAVE ENERGY MOVING ACROSS THE REGION. OTHER ISSUE FOR THE
MORNING IS STRATUS DECK CURRENTLY IN PLACE AS RICH LLVL MOIST AXIS
REMAINS OVER THE AREA. AREAS SHOULD BEGIN TO SCOUR OUT FROM WEST
TO EAST AS PREVIOUS MENTIONED SFC TROF WL PUSH ACROSS THE CWA AND
TURNS WINDS TO THE NORTH. THIS SHOULD ALLOW TEMPS TO MIX OUT INTO
THE MID TO UPPER 70S ACROSS MOST AREAS. AHEAD OF THE TROF ACROSS
WRN IA...WEAK INSTABILITY...MODERATE 0-6KM SHEAR VALUES AND MID
LEVEL LAPSE RATES NEAR 7.0-7.5C/KM SHOULD HELP PROMOTE SOME
ISOLATED TSTMS LATE THIS MORNING/EARLY THIS AFTERNOON AND COULD
SUPPORT MARGINAL SEVERE HAIL. SWODY1 HAS VERY FAR SERN COUNTIES IN
SLIGHT RISK FOR THIS AFTERNOON.

AFTER THE TROF PASSAGE...DRY CONDITIONS ARE EXPECTED FOR THE
EVENING HOURS WITH THE NEXT CHANCE OF SHOWERS AND TSTMS COMING
EARLY THURSDAY MORNING. STRONG ISENTROPIC UPGLIDE IN WAA REGIME
ACROSS CNTRL AND ERN NEB SHOULD SPARK WIDESPREAD SHOWERS AND
TSTMS THURSDAY MORNING WITH ADDED UPPER LEVEL SUPPORT FROM
PASSING SHORTWAVE ENERGY INTO THE AFTERNOON HOURS. A SFC WMFNT IS
EXPECTED TO EXTEND ACROSS NRN KS AND NRN MO BY AFTERNOON AND WL
LIKELY BE THE FOCUS FOR AFTERNOON TSTMS...SOME OF WHICH COULD BE
SEVERE. MOST ACTIVITY WL REMAIN NEAR THE FRONTAL BOUNDARY WHICH
SHOULD REMAIN JUST TO THE SOUTH OF OUR CWA.

STRENGTHENING UPPER LEVEL LOW WL MOVE SE INTO THE NRN PLAINS BY
FRIDAY AND STRENGTH AND TIMING OF THIS FEATURE HAVE YET TO BE
WORKED OUT. IN ANY CASE...THIS FEATURE SHOULD PUSH A CDFNT INTO
THE CNTRL PLAINS AT SOME POINT EARLY THIS WEEKEND. PREVIOUS
FORECAST HAD PCPN MENTIONED WITH THIS FEATURE AND DO NOT SEE ANY
REASON TO CHANGE THAT AT THIS POINT.

&&

.AVIATION...

FOR TAF SITES KOFK/KOMA/KLNK FORECAST VALID THROUGH 07/06Z.

STRATUS AND THUNDERSTORMS COULD BOTH IMPACT TAF SITES...SPCLY EARLY
IN THE FORECAST PD.  STATUS CIGS MOSTLY IN 14K-24K FT RANGE HAD
SPREAD AS FAR N AS A YORK TO FREMONT TO BLAIR LINE AS OF
06/07Z...ALTHOUGH SOME LOCATIONS SE OF THAT LINE HAD EXPERIENCED A
TEMPORARY LOSS OF LOW CLOUD CIGS.  CIGS ON WRN END OF THE STATUS
WERE A BIT LOWER...GENERALLY AROUND 8 OR 9 HUNDRED FT.  CIGS AT KOMA
AND KLNK COULD PERSIST AND WERE FCST IN TAF TO LAST INTO THIS
AFTN...ALTHOUGH THEY COULD BEGIN TO SCATTER OUT BFR 18Z.  A PD OF
CIGS FM 8 HUNDRED TO 12 HUNDRED FEET COULD MOVE INTO THE KOFK AREA
THRU 06/15Z...BUT A MORE SWRLY WIND IS EXPECTED TO KEEP THE BULK OF
THE LOW CLOUDS S OF THAT SITE.  SCT THUNDERSTORMS MOVING ACROSS
CNTRL NEBR COULD MOVE ACROSS TAF SITES THROUGH 06/16Z...ALTHOUGH DUE
TO A MORE ISOLD NATURE OF LTG/THUNDER EXPECTED...ONLY SHRA WITH A CB
REMARK WAS INCLUDED WITH 06/06Z TAF ISSUANCE.  IF TRENDS CHANGE AND
TSTM CHCS BECOME MORE APPARENT TAFS WL BE AMENDED AS NEEDED.  A WIND
SHIFT TO NW WINDS SHOULD REACH KOFK BY 06/17Z AND KOMA AND KLNK BY
06/19-20Z.

&&

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

GRIFFIS/CHERMOK

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