Tornado Warning 54, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
259 PM CDT SAT AUG 5 2000

FORECAST CHALLENGES REMAIN POPS AND TEMPS.

IN THE SHORT TERM...THE PRIMARY CONCERN IS A SEVERE THREAT FOR
SOUTHEASTERN ZONES.  THIS APPEARS SIGNIFICANT ALONG AND SOUTH OF A
WEAK WAVY CDFNT WHICH SHOWS AS A NARROW BAND OF CU FROM S CNTRL
NEBRASKA TO LNK THEN TENDING TOWARD DSM ON 19Z VISIBLE IMAGERY.
DEW POINTS HAVE POOLED TO VERY UNCOMFORTABLE LEVELS NEAR THE FRONT
IN A SHALLOW LAYER OF POORLY MIXED AIR OVERLAIN BY HOT DRY CAP.
COOL ADVECTION AT MID LEVELS WILL BE WEAKENING THE CAP THIS EVE...
AND IF IT BREAKS DEVELOPMENT COULD BE EXPLOSIVE.  DO NOT EXPECT
DEVELOPMENT NORTH OF SFC FRONT WHERE DRY ADVN IS ALSO OCCURING AND
LOW LEVEL CONVERGENCE IS LACKING.  WILL LEAVE CHC POPS IN THE
SOUTH...UNLESS DEVELOPMENT OCCURS BEFORE ZONE ISSUANCE.  HIGH BASED
AC SEEMS TO BE HEADED SOUTH OF THE BORDER AND WILL PROBABLY ACT ONLY
TO KEEP SFC TEMPS DOWN A BIT IN FAR SRN NEBRASKA.

LATER TONIGHT...EXPECT DRY ADVECTION TO TAKE OVER AT LOW AND MID
LEVELS TO PUT AN END TO POPS THROUGH SUNDAY AFTN.  AVN SEEMS TOO
SLOW WITH THE FRONT...SO PREFER ETA/NGM SOLUTION OF STALLING FAR
ENOUGH INTO KS TO ALLOW LOWER DEW POINTS SUNDAY...MORESO NORTH THAN
SOUTH.  NGM HAS THE MOST COOL ADVECTION SUNDAY AND WILL GIVE IT A
BIT MORE WEIGHT THAN THE ETA...WHICH HAS TENDED TO BE ON THE WARM
SIDE LATELY.  IN EITHER CASE...FCST TEMPS TONIGHT SEEM
REASONABLE...AS DO MOST HIGHS SUNDAY.  LNK MAY HIT 90 THOUGH.

MY THINKING IS SIMILAR TO GID DISCUSSION FOR SUNDAY NIGHT AND MON.
ETA HAS THE MOST COHERENT PICTURE WITH WARM MOIST ADVECTION BRINGING
A POP BACK INTO THE FORECAST LATER SUNDAY NIGHT AND CONTINUING
MONDAY.  COHERENT DOES NOT MEAN RIGHT...SINCE ALL THE MODELS HAVE
HAD A TOUGH TIME WITH WEAK WAVES IN NW FLOW...BUT THE OVERALL
SEQUENCE SEEMS REASONABLE.  RETURN OF CLOUDS AND POPS WOULD KEEP
SUN NIGHT LOWS SIMILAR TO TONIGHT.  HIGHS MONDAY WILL BE HEAVILY
INFLUENCED BY EXTENT OF CONVECTIVE CLOUDS.  PERSISTENCE FROM SUNDAY
OK FOR A FIRST GUESS.  ASSUMING NORMAL DIURNAL TIMING WILL GENERALLY
GO CHC POPS SUNDAY NIGHT AND SLGT CHC MONDAY EXCEPT IN NORTHEAST
WHERE COOLER TEMPS ALOFT COULD ALLOW CONVECTION TO CONTINUE MORE
EASILY.

LONGER TERM...THE MDLS ARE FOLLOWING SIMILAR TRENDS.  AFTER ANOTHER
POSSIBLE WAVE FOR CHC THUNDER MONDAY NIGHT INTO TUESDAY...HOT AND
DRY SEEMS LIKELY.

POLLACK

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-060430-

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
455 PM CDT SAT AUG 5 2000

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

STORM SPOTTER MAY BE REQUIRED IN THE SOUTHERN PART OF SOUTHWEST IOWA
THROUGH MID EVENING.

A WEAK COOL FRONT ACROSS SOUTHERN SOUTHEAST NEBRASKA AND SOUTHERN
SOUTHWEST IOWA WILL MOVE SOUTH INTO KANSAS AND MISSOURI THIS EVENING.
 THERE IS STILL A POSSIBILITY OF THUNDERSTORMS NEAR THIS FRONT
THIS EVENING.  IT IS POSSIBLE THAT A FEW OF THESE THUNDERSTORMS
COULD PRODUCE LARGE HAIL OR DAMAGING WINDS. THE AIRMASS BEHIND THE
FRONT IS NOT AS MOIST OR UNSTABLE.   ANY THUNDERSTORMS NORTH OF A
LINE FROM BEATRICE NEBRASKA TO RED OAK IOWA ARE LIKELY TO BE ISOLATED
AND UNLIKELY TO PRODUCE SEVERE WEATHER.

THE THREAT IN SOUTHERN SOUTHEAST NEBRASKA AND SOUTHERN SO"UTHWEST
IOWA WILL END WITH MOVEMENT OF THE FRONT INTO KANSAS AND MISSOURI.

POWERS

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-060615-

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
711 PM CDT SAT AUG 5 2000

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

STORM SPOTTER WILL BE REQUIRED IN SOUTHWEST IOWA THIS EVENING.
STORMS SPOTTERS MAY BE REQUIRED IN EAST CENTRAL OR SOUTHEAST
NEBRASKA FROM AROUND WISNER AND TEKAMAH SOUTH.

A WAVE ALOFT IS INTERACTING WITH A BOUNDARY FROM NEAR COLUMBUS EAST
TO NEAR ONAWA IOWA AND ON EAST.  THUNDERSTORMS ARE MOST LIKELY TO
CONTINUE TO FORM ALONG THIS BOUNDARY BUT SCATTERED THUNDERSTORMS MAY
DEVELOP ANYWHERE FROM THERE SOUTH.  THESE STORMS WILL BE CAPABLE OF
PRODUCING SEVERE WEATHER...PARTICULARLY LARGE HAIL.  A FEW STORMS
COULD PRODUCE TORNADOES...PARTICULARLY IN SOUTHWEST IOWA.

POWERS