Severe Thunderstorm Warning 186, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
253 PM CDT TUE JUL 11 2000

THE MAIN FORECAST CHALLENGE IS FIRST PERIOD CONVECTION...FOLLOWED BY
TEMPS.

SHORT TERM...VERY MOIST AIR AT LOW LEVELS IS BEGINNING TO
DESTABILIZE ALONG WEAK SFC CONVERGENCE ZONE BETWEEN LNK AND OMA.
WHILE SCT TSTMS ARE LIKELY TO INCREASE IN ERN NE INTO THE
EVENING...I THINK THE MAIN CONVECTIVE THREAT WILL COME FROM SFC
CONVERGENCE ALONG THE FRONT HEADED SEWD OUT OF SD.  THIS MAY BE
ENOUGH TO FORCE DEEPER LIFT OF THE AIR ADVECTING INTO THE FRONTAL
ZONE.  IN ADDITION...ALL MODELS AGREE ON MID LEVEL DRYING BEHIND THE
FRONT...WHICH WILL ALLOW IT TO GENERATE STRONGER OUTFLOW.  SO WILL
THE NW COMPONENT OF MID LEVEL WINDS.  BECAUSE OF THIS...BELIEVE THAT
THE MODELS WEAKEN THE NW FLOW BEHIND THE SYSTEM TOO MUCH OVERNIGHT.
WILL GO FOR MUCH HIGHER POPS THAN GUIDANCE...AND BOOST PREVIOUS
FORECAST BY ABOUT 20 PCT.

AFTER SOME EARLY MORNING LEFTOVERS IN THE SOUTHEAST ZONES WED
MORNING...A DRY FORECAST SETS UP FOR A COUPLE OF PERIODS AS STRONG
MID LEVEL DRYING SHOULD PRECLUDE ANY THUNDERSTORMS FOR A WHILE.
STRONG INSOLATION SHOULD ALLOW TEMPS TO RISE TO AROUND 90 OR LOWER
90S WEDNESDAY...ESPECIALLY SINCE THE COOL ADVECTION BEHIND THE FRONT
IS UNIMPRESSIVE.  DROPPING THE SFC DEW POINTS INTO THE 60S WOULD BE
IMPRESSIVE...BUT EVAPOTRANSPIRATION HAS BEEN SO INTENSE THAT THIS IS
NOT LIKELY IN THE SOUTHEAST ZONES UNTIL PERHAPS WEDNESDAY NIGHT.

AVN MOS IS QUITE A BIT COOLER THAN NGM ON THURSDAY.  WITH RETURN
FLOW SETTING UP AND RISING TEMPS AT ALL LEVELS...I WILL BE LEANING
CLOSE TO THE NGM.  I WILL KEEP TEMPS IN THE LOWER TO MID 90S FOR
NOW...ALTHOUGH IF ETA IS RIGHT ABOUT STRONG SFC TROUGH DEVELOPING
ACROSS SD WITH SW FLOW AT LOW LEVELS GETTING INTO ERN
NEBRASKA...SOME UPPER 90S COULD RESULT.  IN ADDITION...MOISTURE
RETURNING INTO THE HOT AIR IN THE NORTHWEST ZONES ALONG WITH A
POSSIBLE MID LEVEL TROUGH ROTATING AROUND THE RIDGE COULD RESULT IN
A FEW LATE AFTN TSTMS IN THE NORTHWEST ZONES.  THIS IS WORTH A
SLIGHT CHANCE ONLY FOR NOW.

IN THE EXTENDED...POSITION ON THE EAST SIDE OF STRONG UPPER RIDGE I
MAY KEEP US IN THE RING OF FIRE...BUT WARM TEMPS ALOFT SUGGEST
ACTIVITY WILL NOT BE WIDESPREAD.  HOT WITH A SLIGHT CHC OF TSTMS
LOOKS RIGHT WITH LITTLE DAY TO DAY VARIATION.

.OMA...NONE
POLLACK

NEZ011-012-015>018-030>034-042>045-050>053-065>068-078-088>093-
IAZ043-055-056-069-079-080-090-091-121200-

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
505 PM CDT TUE JUL 11 2000

...SEVERE WEATHER OUTLOOK FOR EASTERN NEBRASKA AND SOUTHWEST IOWA...

STORM SPOTTER ACTIVATION MAY BE REQUIRED THIS EVENING INTO EARLY
TONIGHT.  THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER ALL
OF THE AREA.

THE AIRMASS IS VERY MOIST AND UNSTABLE.  A THUNDERSTORM COMPLEX OVER
SOUTH DAKOTA ASSOCIATED WITH AN UPPER LEVEL DISTURBANCE MAY CONTINUE
TO DEVELOP SOUTHEASTWARD.  OTHER STORMS MAY FORM OVER THE LOCAL AREA
IN THE WARM AND HUMID CONDITIONS.  MID LEVEL TEMPERATURES ARE NOT AS
QUITE AS WARM AS THEY HAVE BEEN THE PAST FEW DAYS...SO THE CAP IS
WEAKER.

ANY STORMS THAT DEVELOP WILL BE CAPABLE OF PRODUCING VERY HEAVY RAIN
AND GUSTY WINDS.  SOME HAIL COULD ALSO OCCUR.

MILLER