CASILIST : Severe Weather Update - HIGH RISK Still in effect overnight

J (j{at}weatherwatchers.org)
Wed, 08 Apr 1998 22:30:31 -0400

At 9:45 PM there were approximately 50 counties were under Severe
Thunderstorm Warnings in the SE US along with 10 counties under Tornado
Warnings. Over 50 individual Warnings have been issued for *each* of
the following states since noon today (I can't find summary records for
before that time, I'll have to go through the text of the warnings
later): GA, AL, MS, TN. At 8pm Tornado Warnings were being issued at an
average of 1 every 3 minutes.

During the hours 9pm and 10pm, a total of 13,138 cloud to ground
lightning strikes were detected in the US by the National Lightning
Detection Network.

I even got a small storm here in Central PA this evening. Wasn't much
but it's all I've had so far this season.

Despite the loss of daytime heating... Severe Weather will continue over
the Southern CASI region tonight and tomorrow morning due to a low-level
jet stream which will keep warm air (read: dewpoints in the 70's on the
Gulf Coast) pumping through the SE US overnight. You can see this flow
from the gulf on the 850mb Chart at
http://asp1.sbs.ohio-state.edu/gifs/upperair/up850ws.gif

MESOETA CAPES over NE NC this evening were over 3200 while estimated
LI's (Lifted Index) values were under -6. For those of you unfamiliar,
both CAPES and LI's are meteorological indicators of the possibility of
severe thunderstorms. For more explanation, please see this URL:
http://wxp.atms.purdue.edu/upper_air/details.html
For the graphics that I mentioned see:
http://hail.met.psu.edu/comet/automet2/surface/current/li.gif
http://hail.met.psu.edu/comet/automet2/surface/current/cape.gif

A HIGH RISK is still in effect through 8am for N. GA and AL. A MODERATE
RISK is still in effect for the Western Carolinas and Central GA through
8am. A SLIGHT RISK is still in effect for the rest of the Southern CASI
region (excluding southern FL).

Currently (10pm), for the CASI area, Tornado Watches are in effect for
N. GA and Western Carolinas.

These severe storms are very dangerous, especially at night. Please be
careful if you are outside and keep your choice of Media near in case
of a Warning.

I have *got* to go to bed now or I will not be able to get up in the
morning. I will rejoin the effort of tracking these storms at that
time.

Specifics from the SPC:

THERE IS A HIGH RISK OF SVR TSTMS THIS EVENING OVER PARTS OF
NORTHERN AND CENTRAL AL...NORTHERN GA...AND SOUTHEAST TN...

SURROUNDING THE HIGH RISK...THERE IS A MDT RISK OF SVR TSTMS OVER
PARTS OF EASTERN MS...SOUTHERN AL...CENTRAL GA...MUCH OF SC...
CENTRAL AND WESTERN NC...AND NORTHEAST TN...

...GULF COAST STATES/TN VALLEY/WESTERN ...
NUMEROUS SUPERCELL THUNDERSTORMS...SOME TORNADIC...ARE CURRENTLY
AFFECTING MUCH OF NORTHERN AL/NORTHERN GA/MIDDLE AND EASTERN TN.
00Z SOUNDINGS IN THIS REGION ALONG WITH VAD PROFILES SHOW EXTREMELY
STRONG LOW AND DEEP LAYER SHEAR PROFILES....WITH HELICITY VALUES
NEAR 500 M2/S2 AND SFC-6KM SHEAR OF 60-70 KNOTS. SHEAR IS ACTUALLY
FORECAST TO INCREASE DURING THE LATE EVENING HOURS AS 100 KNOT
500MB JET OVERSPREADS AREA. GIVEN AMPLE LOW LEVEL MOISTURE...
MODERATE INSTABILITY...STEEP LAPSE RATES...AND DRY MID LEVEL
AIRMASS...BELIEVE THREAT FOR MAJOR TORNADOES REMAINS QUITE
SIGNIFICANT FOR THE NEXT SEVERAL HOURS OVER THE HIGH RISK AREA.

STORMS ARE EXPECTED TO SPREAD EASTWARD ACROSS EASTERN TN AND
NORTHERN GA INTO PARTS OF SC/NC OVERNIGHT. ALTHOUGH INSTABILITY
WILL BE SLIGHTLY WEAKER IN THIS AREA...EXTREMELY STRONG SHEAR MAY
ALLOW SUPERCELL STRUCTURES TO PERSIST WITH CONTINUED POTENTIAL FOR
ISOLATED TORNADOES AND DAMAGING WINDS.

--
==============================================================
Jesse Ferrell - Meteorologist - j{at}weatherwatchers.org
Central Atlantic Storm Investigators - www.weatherwatchers.org
"A tornado?  Why wasn't it dissipated by the weather
modification net?"  --Jean-Luc Picard     || ICQ No. 136862 ||