Damaging Winds in Nebraska, July 20, 2006

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
255 PM CDT THU JUL 20 2006

.DISCUSSION...

POTENTIAL FOR SVR AND HEAVY RAIN TONIGHT A MAIN CONCERN. CLOUD COVER
IS LIMITING INSOLATION SOME THIS AFTERNOON IN SRN PORTION OF THE
STATE. HOWEVER...IN NORTHERN KS SUNSHINE HAS REALIZED STRONG
INSTABILITY AND HIGH CAPE AS PER LAPS DATA. FURTHER NORTH...STRONG
SWRLY FLOW IN SERN MT AS INDICATED BY THE CLOUD STREAKS ALONG
THE HIGHER TERRAIN. SO LARGE SCALE SHEAR SHOULD BE AVAILABLE BY
LATE AFTERNOON FURTHER S IN THE PANHANDLE BASED ON THIS...COUPLED
WITH STRONG LOW LEVEL SERLY FLOW. GOES SOUNDER DPI INDICATING 1.4
TO POSSIBLY AS MUCH AS 1.6 PW NORTH OF THE FRONT IN SRN NEBR AND
FEEDING INTO THE PANHANDLE. INDIVIDUAL CELLS EARLY IN THE
INITIATION PROCESS SHOULD EASILY BE SUPERCELLULAR IN NATURE, BUT
AS THEY CONGEAL...DAMAGING WINDS AND VERY HEAVY RAINFALL WILL BE
THE MAIN THREAT LATER THIS EVENING INTO TONIGHT. SEEMS POTENTIAL
FOR LARGE HAIL MAY BE LIMITED TO THE PANHANDLE SINCE WBZ HEIGHTS
IS AROUND 12.4 KFT FROM LBF MORNING SOUNDING. RELATIVELY LOW LCL
HEIGHTS...FOR THE PANHANDLE ANYWAY...MAY ALLOW POTENTIAL FOR
A TORNADO POTENTIAL EARLY ON...BUT LOW LEVEL LAPSE RATES HAVE NOT BEEN
MAXIMIZED DUE TO CLOUD COVER...SO THREAT SEEMS LIMITED. FURTHER
EAST...PREIVOUSLY MENTIONED DPI...FAIRLY DEEP ERLY FLOW IN THE
BL...AND INCREASING K INDEX VALUES POINT TO HEAVY RAIN POTENTIAL.
IN ADDITION...NAM12 SUGGESTS PW VALUES APPROACHING 1.9 BY 06Z
OVER SWRN CWA...WELL OVER 2 STD ABOVE AVE FOR THIS TIME OF YEAR
AND A DEFINITE CONCERN. ONE NEGATIVE FACTOR FOR FLOODING THOUGH
WILL LIKELY BE QUICK MOVEMENT TO THE MCS THAT WILL LIKELY DEVELOP.
SOMEWHAT OF A DRY LAYER INDICATED ALOFT THIS MORNING IN LBF
SOUNDING WHICH MAY SUGGEST POTENTIAL FOR STRONG AND ORGANIZED COLD
POOL. CORFIDI AND FORWARD PROP CORFIDI VECTORS POINT TWD A SPEED
OF 40-50KTS WITH A MATURE SYSTEM...LIKELY INDICATING THE POTENTIAL
FOR WIND DAMAGE AS WELL...SIMILAR TO BUT NOT AS WIDESPREAD AS
IA/MO/IL LAST NIGHT. SYSTEM SHOULD TRACK ALONG AND SOUTH OF I-80
LATE THIS EVENING AND OVERNIGHT...AND HAVE TRENDED GRIDS TO
REFLECT THIS LINE OF THINKING.

DIFFERENCES EXIST IN HOW FAST THE SYSTEM MOVES OUT AND POTENTIAL
FOR LEFT OVER WEAK CONVECTION IN DECENT INSOLATION BEHIND EXITING
SYSTEM. HAVE TYPICALLY SEEN A FEW WEAK SHRA/-TSRA IN THE WAKE OF
THESE KINDS OF SYSTEMS WHERE CLOUDS CLEAR OUT EARLY ENOUGH...SO
HAVE INCLUDED SMALL POPS FOR FRIDAY. CLOUD COVER SHOULD LIMIT
TEMPS SIGNIFICANTLY IN THE ERN CWA...A NICE BREAK FROM THE LAST
FEW DAYS. UPPER FLOW TRANSITIONS TO NWRLY INTO THE WEEKEND AND
FIRST OF NEXT WEEK. AGREE WITH GID AFD THAT MODELS TEND TO NOT
PICK UP ON WEAK SHORT WAVES IN THIS TYPE OF PATTERN AND WITH RETURN
FLOW DEVELOPING...SHEAR WILL BE THERE AND ENOUGH MODERATE CAPE
WOULD PRODUCE SOME TSRA GIVEN A DECENT SFC CONVERGENT AXIS.
HOWEVER...TIMING IS DIFFICULT AND HAVE THEREFORE NOT GONE TOO
AGGRESSIVE ON POPS...AND WILL WAIT UNTIL AFTER TONIGHT TO BETTER
ASSESS POTENTIAL FOR LATER IN THE WEEKEND.

TEMPS WILL GRADUALLY WARM BY THE FIRST OF THE WEEK. UPPER RIDGE
QUITE STRONG OVER THE WEST INITIALLY...BUT GET KNOCKED DOWN
SOMEWHAT BY WEEKS END. GFS QUITE AGGRESSIVE IN DEVELOPING UPPER
TROUGH OVER THE NWRN US LATE IN THE WEEK WHICH WOULD REPRESENT A
MAJOR PATTERN SHIFT...WILL HAVE TO WATCH TO SEE IF IT EVOLVES THAT
QUICKLY. OTHERWISE TIMING OF PRECIP WOULD BE THE MAIN THING. MAY
APPROACH 100 AGAIN IN SRN ZONES BY MID WEEK IF CLR SKIES.

&&

.FIRE WEATHER...PRECIP POTENTIAL AND COOLER TMEPS WILL ALLEVIATE
FIRE WX CONCERNS OF THE PAST FEW DAYS. TEMPS WILL WARM BY THE
FIRST OF THE WEEK...BUT BETTER LOW LEVEL MOISTURE SHOULD KEEP
MINIMUM RH VALUES MANAGEABLE.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

69

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORTH PLATTE NE
953 PM CDT THU JUL 20 2006

NEZ004>010-022>029-035>038-056>059-069>071-094-211030-
SHERIDAN-EASTERN CHERRY-KEYA PAHA-BOYD-BROWN-ROCK-HOLT-GARDEN-
GRANT-HOOKER-THOMAS-BLAINE-LOUP-GARFIELD-WHEELER-ARTHUR-MCPHERSON-
LOGAN-CUSTER-DEUEL-KEITH-PERKINS-LINCOLN-CHASE-HAYES-FRONTIER-
WESTERN CHERRY-
953 PM CDT THU JUL 20 2006 /853 PM MDT THU JUL 20 2006/

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

.DAY ONE...REST OF TONIGHT.

A SLIGHT RISK OF SEVERE THUNDERSTORMS EXISTS OVERNIGHT SOUTH OF A
LINE FROM ANTIOCH...TO OCONTO. STRONG DAMAGING WINDS AND HEAVY
RAIN ARE THE MAIN SEVERE THREATS.

A STRONG UPPER LEVEL DISTURBANCE WILL LIFT FROM NORTHEASTERN
COLORADO OVERNIGHT...TOUCHING OFF NUMEROUS SHOWERS AND
THUNDERSTORMS. SOME OF THESE MAY BE HEAVY RAIN PRODUCERS...SO
FLASH FLOODING IS A CONCERN SOUTH OF THE BEFORE MENTIONED LINE. IT IS
POSSIBLE AN ISOLATED THUNDERSTORM MAY PRODUCE WINDS IN EXCESS OF
60 MPH. HOWEVER...THE THREAT FOR WINDS WILL DIMINISH THROUGH THE
OVERNIGHT HOURS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED TONIGHT...HOWEVER
COOPERATIVE OBSERVERS ARE ENCOURAGED TO PHONE IN PRECIPITATION
REPORTS TO THE NATIONAL WEATHER SERVICE IN NORTH PLATTE FRIDAY
MORNING.

&&

THIS PRODUCT IS NOW AVAILABLE...ALONG WITH OTHER WEATHER...
HYDROLOGICAL AND CLIMATOLOGICAL INFORMATION...AT
HTTP://WWW.WEATHER.GOV/NORTHPLATTE (ALL LOWERCASE)

CLB