Area Forecast Discussion
Issued by NWS Nashville, TN

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FXUS64 KOHX 272324
AFDOHX

Area Forecast Discussion
National Weather Service Nashville TN
624 PM CDT WED JUL 27 2016

.UPDATE...
FOR 00Z AVIATION DISCUSSION.

&&

.DISCUSSION...

For several days we have mentioned the developing threat for
locally heavy downpours and flash flooding. The latest information
continues to support this concern, so we have issued a Flash Flood
Watch for much of Mid Tn for late tonight through all of Thursday.
The Flash Flood Watch covers areas generally along and north of a
line from Waynesboro to Columbia, Murfreesboro, Cookeville and
Jamestown.

This afternoon, scattered thunderstorms had once again developed
over the area, mostly across the north half. A moisture rich
environment was contributing to heavy downpours. Precipitable
water values were near 2 inches. We will also have the potential
for strong storms with wind gusts over 40 mph through the rest of
the afternoon and evening. Cape values are around 2000, plenty of
energy for some strong storms and perhaps a few brief severe
cells.

For late tonight through Thursday night, a trough with deep
tropical moisture over the lower Ms Valley region will lift north
northeastward as a disturbance comes down from our northwest.
These systems will bring together rich tropical moisture and
seasonally strong vertical motion across Mid Tn. Forecast
soundings also show good instability through the column, with
1000-2000 capes on Thursday. Thunderstorms will become widespread
and vigorous with some very heavy downpours. Precipitable water
will climb over 2.25 inches, perhaps reaching a record setting
(for the date) 2.5 inches by Thursday afternoon. Our northern
counties are expected to have the greatest rainfall and greatest
flash flood potential. Relatively lower amounts are expected
across our southeast counties, so areas including Pulaski,
Shelbyville, Manchester, and McMinnville will not be included in
the Flash Flood Watch at this time, although some hefty downpours
will occur there as well.

Areal average qpf values for this event through Thursday night
will be in the 1 to 3 inch range, but any given thunderstorm could
produce that much in a short period of time. So, it is the
localized downpours we are most concerned about. If several storms
affect a single location, significant flash flooding could occur,
and that is the reason for issuance of the watch. The widespread
rain will keep temperature down on Thursday, with highs only in
the upper 70s to lower 80s.

Looking ahead to this weekend and beyond, the big system for
Thursday will help carve out a longwave trough over the MS/OH/TN
Valley regions. A series of waves will come down into the trough,
keeping our wx unsettled with a chance for showers and
thunderstorms each day. Some of the storms could be strong with
gusty winds and downpours each day. Temperatures will creep upward
around 90 for highs this weekend. Then as the upper trough
gradually lifts, highs will climb into the low to mid 90s through
next week as thunderstorm chances gradually drop back to 20-30
percent.

&&

.AVIATION...
00Z TAF DISCUSSION.

Expect a lull in showers and storms this evening then more
widespread showers/storms with MVFR/IFR vis/cigs developing late
early Thursday morning as an area of low pressure moves across
the region. Light south to southwest winds anticipated through the
TAF period.

&&

.OHX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from 1 AM CDT Thursday through late Thursday
night FOR Cannon-Cheatham-Clay-Davidson-De Kalb-Dickson-Fentress-
Hickman-Houston-Humphreys-Jackson-Lewis-Macon-Maury-Montgomery-
Overton-Perry-Pickett-Putnam-Robertson-Rutherford-Smith-Stewart-
Sumner-Trousdale-Wayne-Williamson-Wilson.

&&

$$

DISCUSSION......13
AVIATION........Unger


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