Severe Thunderstorm Warning 2, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
305 PM CDT TUE APR 16 2002

MAIN PROBLEM IS SEVERE POTENTIAL BEFORE 06Z TNGT.  LATEST SURFACE
ANALYSIS EARLY THIS AFTN SHOWED CDFNT AND DRYLINE ADVANCING EWD.
HIGH BASED CONVECTION IN SWLY FLOW ALOFT DID CAUSE SOME SPRINKLES
AND A FEW LTG STRIKES...BUT SO FAR WAS INSIGNIFICANT.  MAIN ACTION
STARTING TO DEVELOP ALONG CDFNT.  PARAMETERS LOCALLY DO NOT APPEAR
TO BE JUXTAPOSITIONED FOR WIDESPREAD SEVERE...BUT THE 12Z MODELS
STILL INDICATED POTENTIAL FOR A SQUALL LINE IN NERN NE.  THE
QUESTION IS...WILL STORMS CONT TO DEVELOP ALONG THE FNT.  DECIDED
TO LOWER POPS JUST A BIT IN SWRN IA...FROM THE LATE MORNING ZFP
UPDATE.   THE CHANCE OF PCPN SHOULD DECREASE AFTER MIDNIGHT.  HIGH
PRES SHOULD BUILD OVER THE AREA LATE TNGT WITH WINDS BECOMING
VARIABLE LESS THAN 10 MPH.  WILL KEEP WIND ADVISORY GOING ERN
ZONES THIS EVENING.

RETURN FLOW STRENGTHENS DURING THE DAY WED...WITH A WARM FRONT
LIFTING BACK TO THE N.  HAVE INCLUDED A SLGT CHANCE OF LATE DAY
TSTMS IN SWRN IA...THEN CONT THAT CHANCE WED NGT MOST AREAS.
SOUTH WINDS SHOULD HELP KEEP TEMPS UP INTO THE 50S.  ON THU...
FNT WILL ADVANCE INTO OUR AREA.  NERN NE WILL SEE THE BULK OF
THE COOLING WITH THIS FNT ON THU...BUT SERN HALF OF THE AREA
SHOULD STILL REACH NEAR 80.  WEATHER LATER IN THE WEEK WILL BE
QUITE A BIT COOLER THAN THE LAST FEW DAYS.  HAVE GONE WITH A
CHANCE OF SHOWERS FRI...THEN AGAIN ON SUN AND MON.

MILLER
...

1040 AM CDT TUE APR 16 2002

UPDATED ZFP TO ADD WIND ADVISORY MOST AREAS.  WIND ALREADY THERE AND
MESOETA SHOWS BOUNDARY LAYER WINDS CRANKING UP TO 35-40 KTS THIS
AFTN.  LIGHT PCPN OVER KS THAT DEVELOPED ABOVE THE CAP WILL CONT TO
LIFT NEWD AND MAY THROW A WRENCH INTO LATEST THINKING.  OTHERWISE
MODELS CONT TO KEY ON CDFNT AND SEVERE POTENTIAL IN CENTRAL AND
NERN NE LATER TODAY.  MORE DISCUSSION LATER.

MILLER
...

205 AM CDT TUE APR 16 2002

FORECAST CHALLENGES -- SEVERE WEATHER POTENTIAL THIS
AFTERNOON/EVENING.

SYNOPSIS -- EARLY MORNING MOISTURE CHANNEL IMAGERY SHOWED A BROAD
MID LEVEL TROUGH OVER THE WRN U.S. WITH A WEAK SHORTWAVE CURRENTLY
TRANSLATING ACROSS WRN NEB.  AT THE SURFACE, A LOW WAS CENTERED OVER
THE NEB PNHDL AS OF 06Z WITH A WARM FRONT EXTENDING NEWD INTO CNTRL
SD, AND AN ATTENDANT DRYLINE FROM THE LOW SWD INTO THE ERN TX
PNHDL.  INSPECTION OF 00Z/16 PLAINS SOUNDINGS INDICATED THAT
SUFFICIENTLY DEEP LOW-LEVEL MOISTURE HAD MADE IT AS FAR N AS TOP.
CURRENT PLAN VIEW PROFILER DATA IS SHOWING A LOW-LEVEL JET OF 50-70
KTS OVER THE CNTRL PLAINS, SO BELIEVE THAT THE 60 DEGREE SURFACE
DEWPOINTS/DEVELOPING STRATUS PROBABLY MARK THE NRN EXTENT OF THIS
DEEPER MOISTURE.

FORECAST --  THE LATEST RUNS OF BOTH THE ETA AND AVN HAVE TRENDED TO
A SLIGHTLY MORE PROGRESSIVE AND MORE AMPLIFIED SOLUTION WITH RESPECT
TO THE SHORTWAVE THAT WILL EJECT ACROSS THE NRN/CNTRL PLAINS THIS
AFTERNOON.  OVERALL PATTERN RECOGNITION INDICATES A FAVORABLE SEVERE
WEATHER SETUP, BUT INCREASING CIRRUS FROM THE S AND WEAK MID-LEVEL
WIND FIELDS CURRENTLY OVER THE PLAINS (REF. 500 MB PROFILER WINDS)
MUDDY THE WATERS.  BY THIS AFTERNOON, SURFACE DEWPOINTS IN THE LOWER
TO MID 60S OVER ERN NEB LOOK REASONABLE, AND THIS SHOULD YIELD CAPES
OF 2000-3000 J/KG.  ETA PROGGED KINEMATIC AND THERMODYNAMIC DATA
SUGGEST THAT THE BEST COMBINATION OF INSTABILITY AND DEEP-LAYERED
SHEAR WILL RESIDE OVER NERN NEB THIS AFTERNOON AND EVENING,  WHICH
IS CONSISTENT WITH THE LATEST SPC DAY 1 CONVECTIVE OUTLOOK.
ALTHOUGH ETA FORECAST SOUNDINGS SUGGEST RELATIVELY HIGH LCL HEIGHTS
IN THE WARM SECTOR AND SLIGHTLY VEERED NEAR-SURFACE WINDS, A
LOCATION TO WATCH WILL BE TO THE IMMEDIATE N AND NE OF A SECONDARY
LOW THAT IS FORECAST TO MOVE FROM CNTRL INTO NERN NEB BY 00Z.  LOCAL
HODOGRAPHS SHOULD IMPROVE IN THIS AREA OWING TO THE BACKED SURFACE
WINDS.

FARTHER S, WEAKER SYNOPTIC ASCENT AND ITS AFFECTS ON THE CONVECTIVE
INHIBITION MAKE CONVECTIVE DEVELOPMENT MUCH MORE CONDITIONAL.
BELIEVE THINGS MAY NOT GET GOING UNTIL WE SEE THE COLD FRONT/DRYLINE
OCCLUSION AFTER 00Z.

THE COLD FRONT PUSHES THROUGH THE AREA TONIGHT, WITH A WEAK
ANTICYCLONE PROGRESSING TO THE E ON WEDNESDAY.  BY WEDNESDAY
AFTERNOON, CYCLOGENESIS IS ALREADY FORECAST TO OCCUR OVER SERN WY
WITH A WARM FRONT DEVELOPING ACROSS NRN KS.  THIS WARM FRONT WILL
RAPIDLY MOVE NWD WEDNESDAY EVENING AS THE ASSOCIATED SURFACE LOW
MOVES INTO SD.  THE ETA AND AVN SHOW DIFFERENCES ON THE TIMING AND
LOCATION OF THIS LOW AND THE ASSOCIATED MID LEVEL SHORTWAVE.
NONETHELESS, WARM ADVECTION (SEEN IN THE 850-700MB Q-VECTOR FIELDS)
INCREASES SIGNIFICANTLY ACROSS OUR NRN ZONES, ALONG WITH A RAPID
MOISTURE RETURN.  WE WILL CARRY A CHANCE OF THUNDER ACROSS THE FAR N
AND KEEP THE REMAINDER OF THE FORECAST DRY.

WE WILL SEE ANOTHER FRONTAL PASSAGE ON THURSDAY AND AT THIS TIME, IT
APPEARS THAT DEVELOPING SWLY SURFACE WINDS AHEAD OF THE FRONT MAY
SWEEP THE MOISTURE OUT PRIOR TO FROPA.  THUS, WE WILL TRIM BACK ON
THE POPS AND ONLY CARRY A CHANCE OF AFTERNOON THUNDER ACROSS THE S.

A BROAD AREA OF HIGH PRESSURE ESTABLISHES ITSELF OVER THE NRN PLAINS
THROUGH THE REMAINDER OF THE WORKWEEK AS THE MODELS DIVERGE ON THE
TIMING OF THE NEXT SIGNIFICANT SHORTWAVE INTO THE PLAINS.  WE WILL
LOOK AT THE NEW MRF WHEN IT ARRIVES AND MAKE CHANGES TO THE EXTENDED
IF NECESSARY.

MEAD

IF YOU HAVE COMMENTS ON THE NEW FORECAST DISCUSSION FORMAT...PLEASE
E-MAIL THEM TO W-OAX.WEBMASTER@NOAA.GOV OR CALL DAVE THEOPHILUS AT
402 359-5166.

.OMA...NONE.

MILLER

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-162300-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1135 AM CDT TUE APR 16 2002

STORM SPOTTER GROUPS ACROSS NORTHEAST NEBRASKA SHOULD BE ALERT
AND READY FOR ACTIVATION THIS AFTERNOON AND EVENING.  STORM
SPOTTER ACTIVATION MAY BE REQUIRED THIS AFTERNOON AND EVENING
OVER THE REST OF EASTERN NEBRASKA AND SOUTHWEST IOWA.

THERE IS A CHANCE OF SEVERE THUNDERSTORMS THIS AFTERNOON ACROSS
MOST OF F EASTERN NEBRASKA AND SOUTHWEST IOWA.	THE MAIN RISK IS
NORTH OF A LINE FROM DAVID CITY TO TEKAMAH.

A COLD FRONT...A DRY LINE AND AND STRONG UPPER AIR DISTURBANCE
WILL MOVE ACROSS THE AREA DURING THE AFTERNOON AND EVENING.
STRONG SOUTH WINDS HAVE BROUGHT WARM AND UNSTABLE AIR INTO THE
REGION.  SCATTERED SHOWERS AND THUNDERSTORMS MAY OCCUR ACROSS
PARTS OF SOUTHEAST NEBRASKA AND SOUTHWEST IOWA INTO MID
AFTERNOON...BUT WIDESPREAD SEVERE WEATHER IS NOT EXPECTED.
SEVERE STORMS ARE MORE LIKELY OVER CENTRAL AND NORTHEAST
NEBRASKA...ALONG THE ADVANCING
COLD FRONT.  THESE THUNDERSTORMS WILL RAPIDLY MOVE EAST INTO THE
AREA LATE THIS AFTERNOON AND EVENING.

FORECAST INSTABILITIES AND WIND SHEAR PROFILES INDICATE THAT A
THE MOST LIKELY STORM TYPE WOULD BE A SQUALL LINE...WITH DAMAGING
WINDS AND HAIL.  HOWEVER...SOME SUPERCELL STORMS COULD BE
EMBEDDED IN THE LINE...ESPECIALLY NEAR THE INTERSECTION OF THE
COLD FRONT AND DRY LINE.   ISOLATED TORNADOES ARE POSSIBLE.

A MORE STABLE AIRMASS WILL MOVE INTO THE AREA BEHIND THE COLD
FRONT LATE TONIGHT AND WEDNESDAY...WITH ANOTHER CHANCE OF SHOWERS
AND THUNDERSTORMS WEDNESDAY NIGHT AND THURSDAY.

THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC AND CLIMATIC
INFORMATION...IS AVAILABLE ON THE INTERNET AT
WWW.CRH.NOAA.GOV/OAX OR AT WEATHER.GOV (LOWER CASE).

MILLER