River Flood Warning 81, NWS Tallahassee, FL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
932 PM EDT Sat Aug 17 2013

...Flash Flood Watch cancelled...

.DISCUSSION...
This evening's surface weather pattern was rather difficult to
analyze as mesoscale features have dominated the synoptic scale
for the past several hours. Earlier this afternoon an outflow
boundary (associated with "cold pools" from numerous showers and
thunderstorms) passed southeast across much of our forecast area,
covering the region with east-northeast winds, slightly lower
surface dewpoints, and a shallow, stable layer near the surface.
Just before this happened there was a quasi- stationary synoptic
scale front from near LA through central GA. At some point the
weather pattern will "return" toward the initial synoptic scale,
but this may take longer than normal over land due to the
nocturnal cooling limiting vertical mixing. However, over the Gulf
waters, this stable layer should be quickly over-turned. This
complex weather pattern casts at least some skepticism on the
12 UTC run of the Convection Allowing Models (CAM).

Vapor imagery and upper air appear to verify what the 12 UTC
global & regional models were showing, that the rain across our
forecast area overnight will diminish as a tongue of drier air
aloft essentially cuts off our deep tropical plume from the
tropics. Additionally, the deep convection in the Central Gulf of
Mexico has diminished compared to 12 hours ago, though it's
possible that is a diurnal trend. Even with a favorable large
scale weather pattern during the day Saturday, significant
flooding was limited primarily to the Panama City area. With less
favorable conditions setting up for tonight and Sunday, we
cancelled the Flash Flood Watch. However, isolated heavy rainfall
amounts remain possible, but the probability of flash flooding
appears low enough so that a watch is no longer needed.

&&

.AVIATION [Through 00Z Monday]...
MVFR to IFR conditions are expected to develop overnight.
Scattered showers and possibly a thunderstorm may also briefly
impact the terminals through daybreak becoming likely by Sunday
afternoon. Winds will be light from the southeast to south Sunday.

&&

.HYDROLOGY...
The highest threat for widespread heavy rain appears to have
ended, as any high rainfall amounts tonight through Sunday will be
isolated. Our QPF total from tonight through Sunday night is 0.50
to one inch for most areas.

Several local river systems have had (or will soon have) notable rises
and increased flows, except for perhaps the far southeast part of
our area in Taylor, Lafayette, and Dixie counties. The rivers, as
of a week ago, were running at lower levels than what we had seen
for most of July, so it has taken a considerable amount of rain to
move some to even a bankfull status. The next few river model runs
should be able to focus on the main threat areas, since these
models will have a more complete picture of the area rainfall the
past few days. A few rivers that may be particularly at risk include:
Choctawhatchee, Shoal, Apalachicola.

The most up to date, specific river forecast information can be
found on the AHPS web page at:

http:/water.weather.gov/ahps2/index.php?wfo=tae.

&&

.PRELIMINARY POINT TEMPS/POPS...
Tallahassee   73  90  73  91 /  50  60  30  50
Panama City   75  87  76  88 /  60  60  40  50
Dothan        70  86  72  89 /  60  70  30  50
Albany        71  88  72  90 /  50  60  30  50
Valdosta      72  90  72  91 /  60  50  30  50
Cross City    73  90  72  91 /  70  50  40  40
Apalachicola  77  87  77  86 /  50  50  40  50

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
GA...NONE.
FL...NONE.
GM...NONE.

&&

AVIATION...Barry
HYDROLOGY...Fournier/Lamers
REST OF DISCUSSION...Fournier