Severe Thunderstorm Warning 18, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
255 PM CDT SAT MAY 3 2003

FCST CHALLENGE WILL BE PCPN CHANCES SUNDAY/MONDAY ON BACKSIDE OF
UPPER LEVEL LOW...

A VERY ACTIVE WEATHER PATTERN THE NEXT 24 TO 48 HOURS ACROSS THE
CENTRAL U.S. WATER VAPOR IMAGERY CLEARLY SHOWS H25 JET MAX ACROSS
SRN CA INTO WRN CO. SOME CONVECTION FIRING FROM ERN ID INTO WRN
WYOMING IN AREA OF UPPER DIVERGENCE.

THE ETA MODEL IS VERY CONSISTENT WITH PREVIOUS RUN AT 12Z SUNDAY.
HEAVY PRECIP CONSISTENT AND EAST OF A VTN TO BBW LINE.

SEVERE POTENTIAL CERTAINLY A CONCERN TONIGHT. INITIATION WILL BE
MOST FAVORABLE IN PNHDLE NEAR DRYLINE AS H5 DISTURBANCE RIDES SWRLY
FLOW OUT OF CO-SE WY. STRONG VEERING OF WINDS WITH HEIGHT WITH
FAVORABLE 40-50KT 0-6KM SHEAR AS CONVECTION DEVELOPS INTO AN MCS BY
LATE EVENING FUELED BY 40-50KTS 850 LLVL JET.

ON SUNDAY H7 LOW CLOSES OFF AND MOVES SLOWLY FROM NERN CWFA AT 15Z
TO NWRN IA BY 00Z MON. MAIN SFC LOW TO MOVE FROM JUST EAST OF MCK AT
12Z INTO NWRN IA BY 00Z. OCCASIONAL SHOWERS ACROSS NERN CWFA WITH
CHC POPS BACK TO THE WEST. H85 TEMPS SUPPORT UPPER 70S SOUTHWEST BUT
STEEP H7 TO H5 LAPSE RATES WILL KEEP SKIES MOSTLY CLOUDY WITH A FEW
SHOWERS AROUND. WILL FAVOR THE COOLER MAV GUIDANCE.

SUNDAY NIGHT/MONDAY...H7 LOW MOVES SLOWLY NORTHEAST INTO SWRN MN.
WILL PLACE 30 POPS EVENING IN THE SW AND OVERNIGHT NORTHEAST. ON
MONDAY H7 TO H5 LAPSE RATES ARE ONLY 5-6 C/KM. MOIST SOUNDINGS IN
NORTHEAST WITH ANY WEAK WAVES ROTATING AROUND THE LOW WILL STILL
SUPPORT ISOLATED SHOWERS NORTHEAST. WILL KEEP SOUTHWEST CWFA DRY.
WILL AGAIN FAVOR THE COOLER MAV GUIDANCE FOR HIGHS.

MONDAY NIGHT/TUESDAY...SURFACE HIGH PRESSURE BUILDS IN AS UPPER LOW
MOVES INTO UPPER GREAT LAKES. THIS WILL ALLOW FOR SKIES TO CLEAR AND
FOR LOWS TO FALL TO AROUND 40 (UPPER 30S IN THE VALLEYS). DESPITE
ZONAL FLOW ALOFT...TEMPS TUESDAY WILL BE 5-10 DEGREES BELOW NORMAL AS
H85 TEMPS WARM TO ONLY ABOUT 8C IN AFTN. 60-65 DEGREES SHOULD COVER
TUESDAY HIGHS.

GFS INDICATES A DISTURBANCE TO MOVE FROM ERN CO INTO WRN KS TUESDAY
NIGHT BUT WILL LEAVE DRY ATTM.

EXTENDED...DISTURBANCE TIMED TO MOVE THROUGH WED NIGHT. H85 JET MAY
AGAIN BE STRONG WITH SFC LOW LIKELY INTO NERN CO. CHC CONTINUES THUR
AND INTO ERN CWFA THU NIGHT. DRY AGAIN TIL FRIDAY NIGHT/SATURDAY
WHEN ANOTHER SYSTEM ARRIVES. LATEST GFS RUN CAME IN WITH A CLOSED H5
LOW. H85 LOW IN NEBR PNHDL AT 12Z SAT.

.LBF...NONE.

KAR

NEZ004>010-022>029-035>038-056>059-069>071-094-032045-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORTH PLATTE NE
106 PM CDT SAT MAY 3 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND NORTH CENTRAL
NEBRASKA.

.DAY ONE...TODAY

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORM DEVELOPMENT LATE THIS
AFTERNOON AND TONIGHT OVER ALL OF THE OUTLOOK AREA. A LOW PRESSURE
SYSTEM OVER THE EASTERN PLAINS OF WYOMING WILL BECOME MORE ORGANIZED
THIS AFTERNOON AND MOVE OUT INTO WESTERN PORTIONS OF SOUTH DAKOTA
AND NEBRASKA THIS AFTERNOON AND SPREAD EAST TONIGHT. ABUNDANT
MOISTURE OVER THE AREA AND AN UNSTABLE ATMOSPHERE WILL COMBINE FOR
THUNDERSTORM DEVELOPMENT. THE GREATEST POTENTIAL FOR SEVERE
THUNDERSTORM DEVELOPMENT WILL BE WEST OF A VALENTINE TO NORTH PLATTE
LINE THROUGH MIDNIGHT CDT AND THEN SHIFT EAST OF A VALENTINE TO
NORTH PLATTE LINE AFTER MIDNIGHT.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

ON SUNDAY THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORM DEVELOPMENT
GENERALLY EAST OF A LINE FROM VALENTINE TO BROKEN BOW AS THE LOW
PRESSURE SYSTEM DEEPENS AND MOVES INTO EASTERN NEBRASKA THROUGH THE
DAY. NO HAZARDOUS WEATHER EXPECTED MONDAY THROUGH FRIDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NECESSARY IN PORTIONS OF WESTERN AND NORTH
CENTRAL NEBRASKA THIS AFTERNOON...INTO SUNDAY.

POWER