Severe Thunderstorm Warning 199, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
303 PM CDT FRI JUL 20 2001

...FORECAST CHALLENGE TO BE POPS TONIGHT...

CURRENT SFC ANALYSIS INDICATES MORE OF THE SAME SCENARIO OVER LBF
CWA. AS OF 18Z A COUPLE OF BOUNDARIES ARE NOTED. ONE EXTENDING FROM
CDR TO ONL AND ANOTHER FROM LBF TO OMA. THE FIRST BOUNDARY IS
OUTFLOW FROM THE MCS OVER SD LAST NIGHT. NORTH OF THE BOUNDARY PER
GOES SOUNDER DATA...AIRMASS SEEMS FAIRLY STABLE WITH COLD POOL
ALOFT. LOOK FOR INITIATION TO BE SOUTH OF THE FIRST BOUNDARY...AND
ALONG SECOND (ACCUS) BOUNDARY OVER SRN NEBR. ALOFT MORE OF THE SAME
WITH H5 HIGH CENTERED OVER SCENT KANSAS. RIDGE WILL PROGRESS WWD
THROUGH PERIOD AS PATTERN BECOMES MORE ZONAL.

TONIGHT...AVN AND ETA HANDLE PRECIP SOMEWHAT DIFFERENTLY. BOTH
MODELS FOCUS PRECIP LATE ON LOCATION OF H85 JET NOSE...BUT ETA KEEPS
PCPN SOUTH. LIKE THIS SOLN BETTER. THETA E RIDGE SETS UP ALONG I80
CORRIDOR BY 03Z. ADDITIONAL SUPPORT WILL ARISE FROM FAVORABLE LOW
LEVEL MOISTURE CONVERGENCE AND H85 FRONTO GENESIS OVER SRN NEBR NEAR
06Z. CAPE REMAINS HIGHEST OVER SRN AND SERN CWA WITH CAPES EXCEEDING
3000 J/KG OVER CUSTER COUNTY. CIN DURING THIS PERIOD REMAINS LOW
ALSO...SO INITIATION SHOULD BE QUICK.  WILL EVALUATE POSITIONING OF
OUTFLOW BOUNDARY NEAR ISSUANCE FOR DEGREE OF POPS OVER NERN CWA.
WILL PLACE EVENING WORDING FOR TSRAS OVER PANHANDLE AND FAR WESTERN
COUNTIES. LAPSE RATES AND CAPE REMAINS HIGH...WHILE CIN IS WEAK IN
THESE LOCATIONS. SHOULD SEE CONVECTION IN THESE AREAS DECAY QUICKLY
AFTER SUNSET GIVEN LACK OF DYNAMICS. WILL KEEP HIGH POPS IN SERN
CWA. WILL FEATHER THEM DOWN THROUGH TO THE NW WITH EVENING WORDING
THERE.

SATURDAY AND SATURDAY NIGHT...KEY ON SATURDAY WILL BE POSITIONING OF
SFC BOUNDARIES FROM EXPECTED MCS TONIGHT OVER S CENT NEBR. ETA SEEMS
A LITTLE AGGRESSIVE WITH PASSAGE OF SURFACE BOUNDARY ACROSS CWA
DURING THE DAY. AT H85 THIS MAKES IT AS FAR EAST AS LBF TO VTN.
MODEL IS NOTING A WEAK H5 SHORTWAVE OVER SWRN COUNTIES LATE AND SOME
DECENT H3 DIVERGENCE OVER CENTRAL CWA BY 00Z. DO THINK DRY LINE WILL
MAKE IT AS FAR EAST AS LBF SO FOCUS OF PCPN WILL BE EAST OF THIS
LINE. CAP REMAINS WEAK DURING PERIOD. WILL MENTION LATE AFTN TSRAS
OVER PANHANDLE AND WESTERN CWA. WILL USE ISOLATED WORDING HERE. WILL
GO WITH 20 POPS ELSEWHERE AS LOCATION OF BOUNDARIES WILL BE KEY.
SHOULD BE SUBSTANTIALLY WARMER THAN TODAYS READINGS AS H85 TEMPS
WARM AS HIGH AS 31C IN SW. AFTERNOON INITIATION OF STORMS WILL BE
KEY TO POSITIONING OF LATE TSRAS. FOCUS OF PCPN WILL CONTINUE TO BE
EAST OF LBF TO VTN AS LLJ WILL BE FOCUSED THERE.

SUNDAY AND SUNDAY NIGHT...H85 TROF TRAVERSES CWA AND WINDS SWITCH TO
THE WEST EARLY. BULGE OF DRY LINE APPEARS OVER DONE AGAIN. THINK
FOCUS OF PCPN WILL BE FROM NERN COUNTIES EAST. SHOULD BE HOT AS H85
TEMPS ARE AT OR ABOVE 28C THROUGHOUT PERIOD. WILL KEEP DRY FOR
SUNDAY AS UNCERTAINTY OF BOUNDARY LOCATION STILL EXISTS. SUNDAY
NIGHT...INDICATIONS ARE FOR A DRY FORECAST AS ALL DYNAMICS ARE
DEFLECTED INTO THE DAKOTAS. FORCING STAYS OUT OF CWA UNTIL AFTR
PERIOD.

.EXTENDED...
MONDAY THROUGH WEDNESDAY...LATE AVN IS NOW SOMEWHAT FASTER WITH
FROPA AND PCPN ON MONDAY AM. ADDITIONALLY...UPPER AIR PATTERN
FLATTENS TO WEST SWRLY FLOW VS NW FLOW IN PVS RUNS. SURFACE HIGH
OVER NRN WYOMING COUPLED WITH A LOW OVER WRN KS WILL PLACE CWA IN
GOOD EAST UPSLOPE FLOW. H85 TEMPS INDICATE A FAIRLY SUBSTANTIAL COOL
DOWN DURING PERIOD WITH AMPLE PRECIPITATION.
THURSDAY AND FRIDAY...H5 HIGH WILL CONTINUE TO SLOWLY RETROGRADE
WEST DURING THE TWO PERIODS. FLOW WILL FLATTEN AND BULK OF HEAVY
PRECIP SHOULD STAY NORTH. LATE MRF SEEMS TO BASE QPF ON PARAMETERS
OTHER THAN H5 SHORTWAVES. HINT OF SFC BOUNDARY ON FRIDAY...BUT WITH
SUCH UNCERTAINTY IN OUT PERIODS GIVEN CURRENT WEATHER
SCENARIO...WILL KEEP PERIOD DRY. MRF IS INDICATING SLIGHT UPWARD
TREND IN TEMPS FOR FRIDAY...SO WILL ADJUST ACCORDINGLY.

.LBF...NONE.

CLB

NEZ004>010-022>029-035>038-056>059-069>071-202045-

SEVERE WEATHER OUTLOOK FOR WESTERN AND NORTH CENTRAL NEBRASKA
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1110 AM CDT FRI JUL 20 2001

...STORM SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND
EVENING AND INTO LATE TONIGHT...

THERE IS A RISK OF SEVERE THUNDERSTORMS OVER NEARLY ALL OF WESTERN
AND NORTH CENTRAL NEBRASKA THROUGH TONIGHT. THE GREATEST RISK OF
SEVERE WEATHER THIS AFTERNOON AND EVENING WILL BE NORTH AND WEST OF
A LINE FROM AINSWORTH THROUGH HYANNIS TO OGALLALA. HOT HUMID
CONDITIONS WILL ALLOW SCATTERED THUNDERSTORMS TO DEVELOP. WITH THE
EXTREME ATMOSPHERIC INSTABILITY...LARGE HAIL AND DAMAGING WIND ARE
THE PRIMARY RISK.

IN THE AREA SOUTH AND EAST OF A LINE FROM ONEILL THROUGH BROKEN BOW
TO IMPERIAL...THE GREATEST RISK WILL BE FROM LATE THIS EVENING INTO
THE LATE NIGHT. ONCE AGAIN THE PRIMARY SEVERE WEATHER THREATS ARE
DAMAGING WIND AND LARGE HAIL. THIS SYSTEM IS EXPECTED TO BE WELL
ORGANIZED...AND IT IS LIKELY TO DEVELOP IN SOUTHERN NEBRASKA AND
GRADUALLY WORK ITS WAY EASTWARD ACROSS THE STATE. DUE TO SLOW SYSTEM
MOVEMENT EXTREMELY HEAVY RAIN IS ALSO POSSIBLE...WITH ISOLATED
AMOUNTS EXCEEfDING THREE INCHES.

SPRINGER

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORTH PLATTE, NE
1133 AM CDT FRI JUL 20 2001

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

1005 PM    4 NE MAXWELL              NE   WIND DAMAGE
07/19/01   LINCOLN                        NUMEROUS LIMBS 8 INCHES IN
                                          DIAMETER OR LARGER DOWN.

RLB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORTH PLATTE, NE
242 PM CDT FRI JUL 20 2001

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0950 PM    MAXWELL                   NE   WIND DAMAGE
07/19/01   LINCOLN                        ROOF DAMAGE TO GARAGE

RS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORTH PLATTE, NE
502 PM CDT FRI JUL 20 2001

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0500 PM    7 ESE HAYES CENTER        NE   .75 INCH HAIL
07/20/01   HAYES

DP