Severe Thunderstorm Warning 147, NWS Hastings, NE

CENTRAL NEBRASKA/NORTH CENTRAL KANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
255 PM CDT MON SEP 8 1997

THUNDERSTORMS TONIGHT OF GREATEST CONCERN...THEN TEMPS BEYOND.

AT 18Z MDT SFC CDFNT WE'RE ANTICIPATING WAS LOCD FM CNTRL WY-VCNTY CDR
TO NR PIR AND NEWD TO WRN MN. 19Z OBS NOW SHOW GUSTY N WINDS AT CDR/VTN
SO WRN EDGE OF FNT WORKING SWD AT A GUD CLIP. ADAP HAS 2 AREAS MOIST
CONVG...ONE ASSOC WITH TSRA IN ERN SD...ANOTHER OVER WRN HI PLNS.
ALFT...FLOW PTTRN CHANGING OVR NRN PLAINS AS HTS RISE IN SW CAN AND
FALL OVR MO VLY AHD OF MIDLVL S/WV DIGGING TWD GTLKS. FLOW SHUD CHNG TO
MORE NLY COMPONENT THRU PD. 250 MB 80 KT JETSTREAK ALSO NOTED OVER NRN
MT.

AS THE PTTRN CHANGES...MDLS AGREE AND ARE RSBL WITH REAL WORLD THAT
CDFNT WL BE DRIVEN SWD THRU CWA TONIGHT AND THERE'S LTL DOUBT THAT SCT
TSRA WL OCCUR IN CWA AS IT INTERACTS WITH LLVL MOISTURE. QN IS WHERE WL
SVR BE?  AS HGHTS FALL...H7-H5 DPVA FM TAIL END OF S/WV AND RRQ OF H25
JETSTREAK RIDE OVER FNTL BNDRY TONITE TO PROVIDE QUITE A HELPING OF
VVELS PER ETA...NGM HAS SAME IDEA BUT WKR. AMT OF CAA SPILLING INTO
TROF AT 12Z ANLYS AND H20 VAP LOOP DKNG W/TIME TAFTN...TEND TO LEAN A
LTL CLOSER TO STRONGER SYS DEPICTED BY ETA. OAX SNDG WAS ALRDY MDTLY
UNSTABLE THIS AM...WHILE LBF HAS SHOWN SOME DESTABILIZATION THRU THE AM
AT 17Z SNDG...BUT INCRSD CAP. GTST INSTAB FM SC NEB EWD WITH WKNG CAP.
WL XPCT CONTD SWWD DVLPMT ALONG CDFNT FM SD INTO CNTRL NEB LATE
TAFTN...THEN INTO RMNDR SC NE/NC KS LATER THIS EVENING. BEST MOIST
CONVG...FRONTOGENETICAL FORCING AND THETE RIDGE IS PICKED UP MOSTLY TO
WEST OF AREA WHERE SPC HAS SVR OTLK...BUT WITH SYN LIFT FM TAIL END OF
S/WV AND JETLVL DVRG OVR AREA TONITE...CONFIDENCE THAT SOME
THUNDERSTORMS WL BECOME SVR HAILERS THIS EVE IS BCMG BETTER WITH POSN
SHIFTING FURTHER NE INCLDG MORE OF SC NEB. INSTAB AND WBZ WERE ALRDY
FVRBL AT 12Z.

ALL IN ALL...THE PRES FCST LUKS QUITE GOOD WITH SCT TSRA ALRDY IN THE
FCST TONITE. AM A LTL CONCERNED THAT SYS MAY SLOW UP A BIT AS IT
ENCOUNTERS WELL ENTRENCHED WARM/HUMID AMS (SIMILAR TO LAST WEEKS FROPA)
AND SRN ZONES MAY BE A BIT TOO COOL FOR MINS. WUD LEAN CLOSER TO FWC
AROUND 60 THERE...BUT NRN/WRN ZONES SHUD COOL OFF. BYND TON...CNSDBL
MIDLVL MOISTURE/CLDS NOTED UPSTRM ASSOC WITH ADVANCING SYS AND ALSO
POOL OF H8 MOISTURE BHND FNT...BUT NO CLDS. BLV LIFT WL DVLP PLENTY OF
POST FNTL CLDS FOR MORNING HRS B4 SUBS/MIXG MELTS AWAY FOR AFTN AS
DRIER AMS WORKS IN...AND LUKS LIKE SOME LINGERING LIFT MAY SQUEEZE OUT
A FEW SHRA IN NC KS...THUS WL INCLDD IN ERLY AM. CAA SC SHUD CONTU
UNTIL SUNDOWN OVER MOST AREAS ON TUES SO P/C AFTN LUKS GOOD.

WATCHES COMING OUT ATTM FOR PART OF CWA THAT NEED TO BE ADDRESSED...SO
3RD-4TH PDS LUK CLEAR...DRY AND COOLER WITH CHG OF AMS. CCF SHUD COVER
DETAILS OF OUTPDS.

GRI BS 063/075/048/078 4-00
HEB BS 062/074/049/080 4100
ODX BS 058/073/048/077 4000
LXN BS 060/073/047/079 4-00
BEL BS 067/078/052/081 3200

BREWSTER

KSZ005>007-017>019-NEZ039>041-046>049-060>064-072>077-082>087-090500-

SEVERE WEATHER OUTLOOK...UPDATE
NATIONAL WEATHER SERVICE HASTINGS NE
310 PM CDT MON SEP 8 1997

...SEVERE WEATHER OUTLOOK FOR SOUTH CENTRAL NEBRASKA AND PART OF
NORTH CENTRAL KANSAS...

SPOTTER ACTION...SPOTTER ACTIVATION MAY NOW BE NEEDED IN SOUTH CENTRAL
NEBRASKA OR NORTH CENTRAL KANSAS THIS EVENING AND TONIGHT.

DISCUSSION...

A COLD FRONT CONTINUES TO ADVANCE ON THE AREA AND WILL PUSH THROUGH
SOUTH CENTRAL NEBRASKA DURING THE LATE EVENING AND OVERNIGHT HOURS.
IT APPEARS NOW...THAT AN UPPER LEVEL SYSTEM ALONG THE JETSREAM IS ALSO
EXPECTED TO DIP FURTHER SOUTH AND PROVIDE ENHANCED LIFT ALONG THE COLD
FRONT AND IS FORECAST TO BE A BIT STRONGER THAN PREVIOUSLY THOUGHT.

THIS SYSTEM WILL BRING SOME COLDER AIR INTO THE UPPER LEVELS OF THE
ATMOSPHERE AND CONTINUE TO PROVIDE INSTABILITY THROUGH THE NIGHTTIME
HOURS. THEREFORE...SCATTERED THUNDERSTORMS SHOULD ERUPT OVER NORTHEAST
AND NORTH CENTRAL NEBRASKA THROUGH THE REST OF THE AFTERNOON AND
PROPAGATE INTO SOUTH CENTRAL NEBRASKA MAINLY AFTER 7 PM. SOME
THUNDERSTORMS ARE NOW EXPECTED TO REACH SEVERE LEVELS WITH THE PRIMARY
THREAT TO BE LARGE HAIL. SOME DAMAGING WIND GUSTS UP TO 60 MPH ARE A
LESSER POSSIBILITY.

BREWSTER