Damaging Winds in Nebraska, July 22, 2001

SOUTH CENTRAL NEBRASKA/NORTH CENTRAL KANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE...CORRECTED FOR HEAT ADVISORY
KS
255 PM CDT SUN JUL 22 2001

...PRCIP CHANCES TONIGHT WILL BE PRIMARY CONCERN THIS FORECAST
PACKAGE...

12Z MORNING UPPER AIR ANALYSIS SHOWED SUBTLE CHANGES FROM PREVIOUS
24 HOURS. 5910M UPPER RIDGE NOW CENTERED OVER NE OK/SW MO. EASTERN
PROGRESSION OF WRN TROUGH AND ASSOCIATED VORT ENERGY WILL BEGIN TO
FLATTEN OUT RIDGE WITH MORE OF A W-E ORIENTATION. MOST SIGNIFICANT
CHANGES SEEN IN STRENGTH OF SHORTWAVES ROTATING THROUGH WRN TROUGH
ENERGY.  TODAY THE MOST NOTABLE WAVE IS OVER NE CO AT H5 IN DEEP
MOISTURE PLUME THAT EXTENDS BORDER TO BORDER THROUGH CONUS. TEMPS IN
MID LEVELS HAVE NOT CHANGED DURING PAST 24 HOURS...AND EXPECT THIS
S/W TO HAVE MINIMAL IMPACT IN REDUCING CAP STRENGTH AT H7 SINCE WARM
TEMPS STILL IN PLACE BEHIND WAVE OVR WRN WY.  ANOTHER SPOT TO WATCH
WILL BE OVER ERN NEB/NE KS WHERE CAP IS ALREADY RELATIVELY WEAK AT
11C. THIS IS SLIGHTLY WEAKER THAN LAST NIGHT WHERE CONVECTION FIRED
OFF IN OUR ERN KS ZONES...AND CONTINUED THIS MORNING BEFORE SUNRISE.
18Z VIS SAT PIX INDICATING CU FORMATION QUITE A BIT EARLIER THAN
YESTERDAY. ALSO...MOISTURE CONVERGENCE LOOKS BEST IN THIS AREA THIS
EVENING PER THE AVN PROG...IN SPITE OF HPC THINKING IT TO BE TOO FAR
NORTH.

SPEAKING OF MODEL SOLUTIONS...ACCORDING TO THE ETA...IT LOOKS LIKE
ANOTHER THING WELL HAVE GOING FOR US TONIGHT WILL BE AN H85 THETA E
RIDGE. ADDED KICK FROM S/W JUST MAY BE ENOUGH TO GET THINGS GOING IN
WEST EARLY...ALTHOUGH EXACT PLACEMENT WILL BE DIFFICULT CONSIDERING
DEPENDENCE ON BOUNDARY INTERACTIONS. LEE TROUGH EMANATING FROM LOW
OVER WRN NEB SEEING BETTER ORGANIZATION FROM 16Z THROUGH WRN KS.
FURTHER EAST...POSITION OF LINGERING SFC BOUNDARY INTO IA FROM LAST
NIGHTS NOCTURNAL CONVECTION WILL BE KEY FACTOR OVERNIGHT. AS H85 LLJ
STIRS THE MIX BY 06Z...THINK THE AREA TO WATCH WILL BE IN NRN AND
ERN CWFA AND WILL RECONFIGURE ZONE GROUPING TO REFLECT THIS. ANY
DEVELOPMENT THERE AFTER 06Z IS PROGGED BY ETA TO BACKBUILD AS SFC
LOW MIGRATES EAST. CORFIDI VECTORS PROPAGATE ANY MCS S-SWWARD .

AS FOR THE ADVANCEMENT OF THE ADVERTISED SURFACE FRONT...HEIGHT
RISES OVER NE WY WERE 4MB/3HR BEHIND SFC LOW OVER WRN NEB AT 12Z.
TSRA HAD ALREADY FIRED IN THIS AREA BY NOON AND GIVES SOME
INDICATION OF STRENGTH OF LOW. ALTHOUGH SIGNIFICANTLY COOLER AIR
STILL LAGS BEHIND OVER NRN MT...HEAT ADVISORY CRITERIA WILL BE
NON-ISSUE IN NEBRASKA ZONES BEYOND THIS EVENING AND INCLINED TO LET
IT GO. HOWEVER...AFTER COORDINATION WITH TOP WILL BE EXTENDING HEAT
ADVISORY THROUGH TOMORROW FOR KS ZONES BASED ON EXPECTATION OF SFC
FRONT PLACEMENT CONFINED TO NEB AND POOLING MOISTURE AHEAD OF IT.

TSRA CHANCES MON NIGHT PERIOD WILL AGAIN BE CONCERN AS BOUNDARY WILL
BE CLOSER TO HOME IN UNSTABLE ENVIRONMENT.  LOOKS TO BE BETTER SHOT
OVERALL WITH KS ZONES ALSO INCLUDED THIS TIME AROUND.

NEXT CONCERN IS FOR TEMPS REST OF THE WEEK. SKEPTICISM ABOUNDS WITH
NUMERICAL GUIDANCE OF 10 DEGREE DROP IN TEMPS TOMORROW...FOLLOWED BY
20 DEGREE DROP ON TUES. BELIEVE THIS CAN BE ATTRIBUTED TO AVN COLD
BIAS AS SEEN DURING SIMILAR REGIMES. AS SFC LOW SKIRTS EAST
MONDAY...TEMPORARY WIND SHIFT IS WITHIN REALM OF POSSIBILITY AND
WILL HOLD WITH LOWER 90S.

IN THE EXTENDED PERIOD...LONG TERM MODELS IN AGREEMENT AND FAIRLY
CONSISTENT. LOOKS LIKE GOING FORECAST IS ODD MAN OUT WITH ADJACENT
WFOS GOING 80S FROM TUES ON.  MRF/ECMWF THICKNESS TRENDS DO SUGGEST
COOLER VALUES THRU WEEK WITH GOOD CHANCE FOR PRECIP EVENT WED OR
THUR. BEYOND THAT...WILL LEAVE FRI-WEEKEND DRY WITH TEMPS REBOUNDING
INTO LOWER 90S.

.GID...HEAT ADVISORY TONIGHT AND MONDAY KSZ005>007-017>019.

33