Area Forecast Discussion Update

403 PM EST Tue Dec 25 2012

...A Tornado watch is in effect until 10 PM CST for all of SE AL,
the FL Panhandle and the adjacent waters...

...Significant severe weather outbreak expected across much of the
area tonight...

Latest meso-analysis shows that surface low was moving from NE LA
newd towards TN Valley. As a result, warm front has lifted into SE
AL placing all of local area in the warm sector (with dew points in
the 60s) as noted by large pressure falls just north of this front.
This has placed our area in a destabilizing and very favorable
environment with strengthening LLJ moving EWD to generate discrete
severe wx cells well moving NNE from the Gulf to over local land
area, well ahead of the squall line. Recent guidance show that deep
and low level shear have increased noticeably in last few hours. We
have already issued a special marine and tornado warning for Walton
County and surrounding waters. This trend is expected to increase
thru the eve especially as strong shortwave trough approaches
increasing tornado threat. Therefore a tornado watch was issued for
all of SE AL, the FL Panhandle and the adjacent waters
until 11 pm CST.

This is just leading edge of what will be a very active next 12-18
hrs. Latest WRF run has vigorous squall line moving across Dothan at
1AM EST (midnight CST) and 3 AM EST across Tallahassee. Rap13 and
model sounding for Dothan at 06z show the following indices:

a)ML cape 275, b) 0-1 km shear 45kts, c)0-6km shear 70 kts d)0-1km
helicity 520, e)0-3km helicity 600, f)BRN shear 175 m/s, g)700-500
mb lapse rate 6.7, h)500 mb wind 70kts, i)850mb wind 65 kts,
j)LCL 1455 feet and k)LFC 4018 feet. All these variable reflect a
high potential of severe wx and a good chance of at least a few
tornadoes. Much will depend on how linear squall line sets
up (damaging winds vs tornadoes). Indices are more stable downstream
but still reflect decent chance of severe wx. Good Luck!!!

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