Tornado Warning 12, NWS Nashville, TN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
150 PM CST SUN JAN 17 1999

INCREASING CAPES, MODERATELY HIGH 1000-700MB HELICITIES AND
STRENGTHENING UPPER LVL JET ALL SUGGEST A PSBLTY FOR ISOLATED
SVR TSTMS TONIGHT AND PSBLY A FEW TORNADOES. MID-LVL DRYING
ALSO WORKS INTO SRN MIDDLE TN BTWN 12HRS AND 18HRS, HELPING TO
MAKE THIS THE MOST FERTILE AREA FOR SVR TSTM DEVELOPMENT.
94O/SWODY1 APPEARS TO HAVE A GOOD HANDLE ON SVR WX POTENTIAL
AND WOULD PROBABLY MENTION PSBLTY OF SVR TSTMS IN FCST TEXT
TONIGHT (ESPECIALLY FOR SRN 1/2 OF OUR CWA). CONDITIONAL POPS
ARE PROBABLY WARRANTED OVER ENTIRE AREA, AND BLV FWC MOS POPS
SUGGESTED FOR SWRN PARTS OF OUR CWA ARE NOT USEFUL. POPS
APPEAR TO BE STILTED WAY TOO LOW IN AREAS WHERE MID-LVL DRYING
IS EXPECTED (IE, AREAS WHERE CHC FOR SVR TSTMS IS HIEST). THUS,
BLV FNT WILL DEPOSIT MEASUREABLE PRECIP AMOUNTS EVERYWHERE
OVERNIGHT.

FNT ZIPS THROUGH PRETTY QUICKLY BTWN 06Z AND 10Z, BUT WILL
STILL HAVE POTENTIAL TO DROP GREATER AMOUNTS OF WATER THAN
INDICATED BY MODELS (AND MORE IN LINE WITH 94Q). WITH PWAS
EXPECTED TO BE NEAR 0.8 BLV MOST AREAS WILL GET 1/2-3/4 INCH,
WITH LOCALLY HIER AMOUNTS QUITE PSBL.

HI RH IN 850-700MB LYR WILL LINGER BEHIND FNT OVER NRN MID-STATE
TONIGHT, WHICH MEANS ANY CLEARING WILL BE LATE. WOULD ALSO KEEP
AT LEAST A CHC FOR SHOWERS AFTER MIDNIGHT. BEST CHC FOR SOME
CLEARING AFTER MIDNIGHT WILL BE OVER SWRN AREAS, WHERE AMS WILL
BE DRIER.

MOS TEMPS LOOK PRETTY GOOD THRU TOMORROW, AND WOULD PROBABLY TRIM
CURRENT MID-STATE ZFP EXPECTATIONS BACK JUST A HAIR. CLIMO FOR
BNA IS 45, AND CANT SEE TEMPS GOING 10 ABV CLIMO TOMORROW WITH
SFC CAA, EVEN WITH DAY STARTING OUT IN THE LOWER 40S. THUS, BLV A
10 DEG RISE TOMORROW IS PROBABLY SUFFICIENT.

WOULD GO LOWER THAN GUIDANCE FOR 3RD PD, AS SFC DWPTS DROP TO
25 TO 30 DEGS AND HI PRES BUILDS IN FOR A MOSTLY CALM NIGHT.
ALSO, BLV CI WILL REMAIN OUT OF OUR AREA MON NIGHT AND NOT
RACE BACK IN UNTIL TUE.

SHOT OF SOME UPPER LVL MOISURE QUICKLY SPREADS BACK IN TUE WITH
RAPID ZONAL FLOW. THUS, WOULD PROBABLY GO PTSUNNY ON DAY2.
RETURN SLY FLOW WILL HELP TEMPS RECOVER A FEW DEGS ABV MON,
WITH MIDDLE 50S JUST ABOUT EVERYWHERE (EXCEPT UPPER 50S SW).

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