FXUS63 KOAX 221943
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
243 PM CDT WED SEP 22 2010
.DISCUSSION...
SYNOPSIS...12Z UPPR AIR ANLYS INDCD BROAD UPPR LVL RIDGE OVR THE
HIGH PLAINS WITH AN UPSTREAM POTENT SHRTWV TROF OVR THE GREAT
BASIN. THE SYSTEM WAS ASSOCIATED WITH 50 M H5 HEIGHT FALLS AND A
100 KT H3 JET. QUALITY LO LVL MOISTURE WAS IN PLACE ACRS THE CNTRL
PLAINS WITH +15 C H85 DWPC POINTS ACRS NEB AND POINTS S. 19Z SFC
ANLYS INDCD LO PRES OVR ERN CO WITH A WRM FNT NEWD THRU CNTRL NEB
TO SUX.
FORECAST...MAIN FORECAST CHALLENGE OVR THE NEXT 30 HRS IS SVR WX
AND HEAVY RAINFALL. 12Z KOAX SOUNDING INDCD GOOD MID LVL LAPSE
RATES AND A NEARLY UNCAPPED SOUNDING TO A PARCEL LIFTED FROM NEAR
H85. THIS ATMOSPHERE HAS BEEN RESPONSIBLE FOR NUMEROUS ELEVATED
STORMS /SOME SVR/ OVR THE NRN FA THIS MRNG/AFTN. ELEVATED MIXED
LAYER HAS NOW STARTED TO SPREAD EWD /PER 18Z LBF SOUNDING/ AND
CONVECTION HAS ENDED FOR A TIME FOR OUR FA. MODIFYING OUR 12Z KOAX
SOUNDING FOR CURRENT CONDITIONS INDCS CAP THOUGH IS WEAKENING TO
SFC-BASED PARCELS OVR NE NEB NEAR THE WRM FNT. LITTLE UPSTRM
SYNOPTIC SCALE SUPPORT IS NOTED FOR ASCENT THOUGH BEFORE THE GREAT
BASIN TROF...AND THUS COVERAGE OF TSRA THIS EVNG IS IN QUESTION.
GIVEN THE RELATIVELY WEAKLY CAPPED ATMOSPHERE...CONVERGENCE ALNG
THE WRM FNT...AND FRONTOGENETICAL PROCESSES ASSOCIATED WITH THE
THERMAL GRADIENT ALNG THE BOUNDARY...IT APPEARS MESOSCALE FACTORS
MAY OVERCOME THIS AND LEAD TO ISO TO SCT TSRA DVLPMT NEAR THE
BOUNDARY THIS EVNG IN NE NEB. IF THIS DOES OCCUR...SUFFICIENT
SHEAR AND INSTABILITY DO EXISTS FOR SIG SVR WX INCLUDING VERY
LARGE HAIL AND ISOLATED TORNADOES. OTHERWISE...ELEVATED STORMS
WILL BECOME INCREASINGLY NUMEROUS OVERNIGHT TO THE N OF THE
BOUNDARY MAINLY IN SD AND WRN NEB. TO THE S OF THIS AREA...OVER
MOST OF EASTERN NEB AND WESTERN IOWA...A QUIET NIGHT IS IN STORE.
UPPR LVL TROF THEN DOES ADVANCE EWD ON THURS WITH AN ASSOCIATED
CDFNT MOVG INTO ERN NEB/WRN IA DURING THE AFTN. PLENTY OF LO LVL
MOISTURE WL REMAIN...BUT INSTABILITY IS IN QUESTION DUE TO PLENTY
OF CLDS AND PRECIP. WL HAVE CAT POPS NEAR THE FNT THRU THE DAY. IF
SOME SUN CAN BREAK OUT...WIND FIELDS ARE SUPPORTIVE OF ORGANIZED
SVR WX...BUT THIS IS HIGHLY DEPENDENT ON THE AMOUNT OF
SUN/INSTABILITY. NEVERTHELESS...SHLD SEE SOME GOOD RAIN TMRW WITH
THE FNT GIVEN THE SYNOPTIC SCALE FORCING. FNT MOVES S OF THE FA ON
THUR NIGHT...BUT SHLD SEE A GOOD DEAL OF CLDS AROUND INTO FRI
MRNG.
EXTENDED...MODELS HAVE COME INTO BETTER AGREEMENT IN DROPPING A
CLOSED LO SWD OVER THE WEEKEND THRU THE MO RIVER VALLEY. THUS WL
INCLUDE SOME CHC POPS FOR SHOWERS WITH THE Q-G FORCING ON SAT INTO
SAT NIGHT. HAVE ALSO COOLED TMPS THRU THE WEEKEND AND INTO EARLY
NEXT WEEK. MODELS STILL HAVE SOME DIFFERENCES AS TO THE TIMING OF
THE EJECTION OF THE UPPR LO INTO THE GREAT LAKES. CURRENTLY PREFER
THE EC WHICH IS THE FASTER AND THIS SHLD ALLOW FOR US TO START TO
WARM BACK UP TOWARD THE END OF THE PERIOD.
BOUSTEAD
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
VFR TO MVFR CONDITIONS ARE EXPECTED ACROSS THE TAF SITES THROUGH
THIS EVENING. A WARM FRONT EXTENDING ACROSS NORTHEASTERN NEBRASKA WL
LIKELY SPARK TSTMS OVERNIGHT WHICH MAY SPREAD INCREASING MID AND
HIGH CLOUDS INTO KOFK AND KOMA. WIDESPREAD THUNDERSTORMS WILL LIKELY
DEVELOP CLOSE TO OR BEFORE SUNRISE THURSDAY AND COULD BE STRONG IN
SOME AREAS. WL JUST COVER WITH -SHRA WITH CB FOR NOW UNTIL WE GET
CLOSER IN TIME TO NARROW DOWN WHERE STORMS ARE GOING TO BE. SOUTHERLY
WINDS WITH GUSTS TO NEAR 25 TO 30KTS ARE ALSO EXPECTED THURSDAY.
KERN
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$