Dust Storm in Nebraska, May 22, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
305 AM CDT WED MAY 22 2002

FORECAST CHALLENGES -- WINDS AND THUNDERSTORM CHANCES.

SYNOPSIS -- EARLY MORNING MOISTURE CHANNEL IMAGERY AND LAST
EVENINGS UPPER-AIR ANALYSIS SHOW A CLOSED, MID-LEVEL CIRCULATION
CENTERED OVER NWRN WY WITH DOWNSTREAM DIFFLUENCE OVER THE DAKOTAS
AND NEB.  IN THE LOW-LEVELS, RICHER MOISTURE RETURN AT 850MB WAS
SITUATED ALONG A OUN-LBF-UNR-GGW AXIS, JUXTAPOSITIONED UNDER STEEP
MID-LEVEL LAPSE RATES, PER 00Z/22 HIGH PLAINS SOUNDINGS.  AT THE
SURFACE, THE PRIMARY SURFACE LOW ASSOCIATED WITH THE WY CIRCULATION
WAS LOCATED OVER NERN MT WITH ATTENDANT COLD FRONT/DRY TROUGH THAT
EXTENDED SWD TO A SECONDARY LOW OVER ERN CO.  TO THE E OF THIS
FRONTAL SYSTEM, PLAN VIEW PROFILER DATA INDICATED A 60-70 KT
LOW-LEVEL JET FROM THE SRN PLAINS THROUGH NEB.

FORECAST -- ALL SHORT RANGE MODELS ARE IN FAIR AGREEMENT ON THE
LARGE SCALE FEATURES THROUGH 36 HRS, WITH DIFFERENCES ON THE
UPSTREAM 500 MB HEIGHT FIELD AND SURFACE FRONTAL POSITION
THEREAFTER.  IN THE SHORT TERM, OUR MAIN CONCERNS ARE WINDS AND
CONVECTIVE POTENTIAL.  00Z/22 ETA AND 06Z/22 RUCII BOTH INDICATE A
SLOW EWD SHIFT OF THE LOW-LEVEL JET AXIS ACROSS THE AREA THIS
MORNING.  BY THIS AFTERNOON, OUR NWRN ZONES WILL FALL IN CLOSER
PROXIMITY TO THE SURFACE/850 MB TROUGHS, EFFECTIVELY ALLOWING FOR
SOME DECREASE IN WINDS.  THUS, WE WILL ISSUE A WIND ADVISORY FOR
THIS MORNING ACROSS THE NW AND ALL DAY ACROSS THE REMAINDER OF THE
AREA.

THE OTHER CONCERN IS CONVECTIVE POTENTIAL.  WE WILL CONTINUE TO
MONITOR THE CONVECTIVE DEVELOPMENT OVER CNTRL SD, AS RECENT
RADAR/SATELLITE/LDS TRENDS INDICATE A CONTINUED SWD DEVELOPMENT INTO
THE LOW-LEVEL JET.  BY THIS AFTERNOON, WE AGREE WITH SPCS DAY 1
OUTLOOK IN THAT THE ETA IS TOO AGGRESSIVE IN THE SURFACE DEWPOINTS.
NONETHELESS, WE WILL STILL LIKELY SEE SBCAPES OF AROUND 1000 J/KG
AHEAD OF THE FRONT.  THIS COMBINED WITH DEEP-LAYER SHEAR VALUES OF
20-25 M/S, SUPPORTS THE POSSIBILITY OF A HIGH-BASED SUPERCELL OR
TWO, GIVEN THE LARGE BOUNDARY-LAYER T/TD SPREADS.  WE WILL CARRY
CHANCE POPS THIS AFTERNOON AREAWIDE WITH TEMPERATURES CLOSER TO THE
WARMER NGM NUMBERS.

TONIGHT, WE WILL CARRY THE HIGHEST POPS ACROSS OUR SRN ZONES, WITH
ONLY AN EVENING MENTION NW.  THERE WILL STILL BE A CHANCE OF SOME
SEVERE STORMS, MAINLY IN THE EVENING ACROSS THE CNTRL AND S.

PER PMDHMD REASONING, WE WILL FOLLOW THE MORE PROGRESSIVE ETA
SOLUTION ON THE HANDLING OF THE SURFACE FRONT ON THURSDAY.  THAT
SAID, WE WILL ONLY MAINTAIN CHANCE POPS ACROSS THE FAR SRN ZONES
INTO AFTERNOON.  GOOD SYNOPTIC-SCALE SUBSIDENCE OVER THE DAKOTAS,
SUGGESTS WINDY CONDITIONS ACROSS THE NRN ZONES WITH THE BUILDING
HIGH PRESSURE.

THE NEXT CHANCE FOR PRECIPITATION WILL OCCUR ON FRIDAY AS THE ETA
AND AVN BOTH ADVERTISE THE MOVEMENT OF A SHORTWAVE THROUGH THE
AREA.  THE CWFA WILL BE IN A STABILIZED, POST-FRONTAL AIRMASS, SO WE
WILL ONLY MENTION SHOWERS.

BOTH THE ECMWF AND THE NEW AVN EXTENSION SUGGEST THAT THE CWFA WILL
REMAIN IN A SURFACE RIDGE AXIS THROUGH THE REMAINDER OF THE
WEEKEND.  WE WILL BEGIN TO SEE LEE CYCLOGENESIS OVER THE HIGH PLAINS
EARLY NEXT WEEK, WITH THE TROUGH AXIS REMAINING OFF TO OUR W THROUGH
TUESDAY.  EXCEPT FOR A MENTION OF THUNDER ON TUESDAY, WE WILL KEEP
THE EXTENDED FORECAST DRY.

COORDINATED WITH DSM, LBF, GID, TOP AND EAX

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...WIND ADVISORY THIS MORNING WEST OF WAYNE TO COLUMBUS
       LINE...AND ALL DAY FOR REMAINDER OF CWFA.

MEAD

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-221700-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
545 AM CDT WED MAY 22 2002

STORM SPOTTER ACTIVATION MAY BE REQUIRED THIS AFTERNOON AND
TONIGHT IN EASTERN NEBRASKA AND SOUTHWEST IOWA.

SCATTERED THUNDERSTORMS OVER THE AREA THIS MORNING SHOULD END BY
AROUND 10 AM...WITH NO SEVERE WEATHER EXPECTED.

MORE THUNDERSTORMS WILL BE POSSIBLE THIS AFTERNOON AND
EVENING...WITH LARGE HAIL AND DAMAGING STRAIGHT LINE WINDS BEING
THE MAIN SEVERE WEATHER THREATS.

STRONG SOUTH WINDS WILL CONTINUE TO CHANNEL INCREASING AMOUNTS OF
MOISTURE INTO THE AREA TODAY...AHEAD OF A COLD FRONT THAT IS
MOVING ACROSS NEBRASKA.  THUNDERSTORMS ARE EXPECTED TO DEVELOP
ALONG THIS FRONT...MAINLY AFTER 3 PM...AS IT MOVES INTO EASTERN
NEBRASKA.  THE THUNDERSTORMS ARE EXPECTED TO INCREASE IN COVERAGE
THIS EVENING...AS THE FRONT MOVES SOUTHEAST THROUGH THE AREA.

BY THIS AFTERNOON...THE ATMOSPHERE IS FORECAST TO BECOME
MODERATELY UNSTABLE...AND WIND SHEAR PROFILES WILL BE FAVORABLE
FOR SEVERE THUNDERSTORM DEVELOPMENT.  AT THIS TIME...IT APPEARS
THAT SEVERE WEATHER WILL BE MOST LIKELY BETWEEN 3 PM AND 9
PM...WITH LARGE HAIL AND DAMAGING STRAIGHT LINE WINDS BEING THE
MAIN THREATS.

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).

MEAD