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Area forecast discussion 
National Weather Service Tallahassee Florida
657 am EDT sun Aug 30 2015

[through 12z monday]...

IFR ceilings prevail across the region with some MVFR mixed in.
Additionally LIFR visibilities are mainly confined to dhn and ecp.
Expect restrictions to clear within the next couple of hours.
Scattered showers are expected this morning at aby and vld, with
thunderstorms more likely at vld later this afternoon.


Prev discussion [406 am edt]...

Near term [through today]...

As seen vividly on WV imagery this morning, a +pv anomaly/upper
low spins over the far western Panhandle of Florida. This
feature and its associated surface trough will be the primary
forcing mechanisms for convection across the region today. As of
07z, some showers can be found across southwest GA, along the
surface trough. As the upper low moves northeast through the
region today, the surface trough will shift east as well. This
will result in the bulk of our convective initiation this
afternoon occurring east of a line from Albany through
Tallahassee. Some heavy rain will be possible across the southeast
Big Bend and south-central Georgia where steering flow will run
parallel to the surface trough. Expect average rainfall amounts in
this area to be around an inch, with isolated totals between 2-4
inches. Late in the afternoon and early evening, some of the
storms may begin to drift back west as the influence of the upper
low diminishes and broad troughing across the Florida Peninsula
moves north, turning steering flow more easterly. Highs today will
be in the upper 80s to low 90s area-wide.

Short term [tonight through tuesday]...

The main forecast challenge in the Monday-Tuesday timeframe is how
the remnants of Erika evolve across the region. The aforementioned
+pv anomaly should have quickly exited northeast of the area by
tonight, with the western edge of a broad subtropical ridge
settling over the region into the early part of the upcoming week.
Therefore, the bubble of higher precipitable water values (2.2 to
2.5 inches), sampled by the evening Miami and Key West soundings
as well as GOES satellite, and any lingering vorticity maxima
should drift north toward our forecast area over the next couple
days. Complicating matters will be the eastward advection of drier
mid-level air over the north-central Gulf of Mexico as the +pv
anomaly lifts out and mid-upper level westerlies become better
established. Most available model guidance creates a very sharp
precipitable water gradient across our forecast area in this time frame. East of
wherever the gradient sets up, locally heavy rain is possible.

This entire scenario could leave the western sections of our area
relatively dry and sunny, with eastern sections mostly cloudy with
fairly widespread showers. For now we have stayed fairly close to
a consensus approach on the location of this sharp moisture
gradient with the highest pops roughly east of a Tallahassee, to
Moultrie, to Fitzgerald line. It should be noted, though, that
small details could shift things enough to bring rainy conditions
into most of the forecast area, or to largely push it off to the
east. Confidence is also diminished given poor 00z model
performance in the vicinity of the Keys and South Florida, where
6-hour model forecast mslp errors are around +2mb over a fairly
large area. Therefore, it's questionable whether models are
showing a strong enough wave drifting north into the eastern Gulf
of Mexico, which affects the rest of the forecast.

Long term [tuesday night through sunday]...

Models generally show more abundant low-mid level moisture
expanding westward to encompass the remainder of the forecast area
later in the week. Rain chances were kept around 40-50% during the
daytime hours for much of the extended forecast as a result. With
the possibility of precipitable water values exceeding 2 inches,
this could have probably been higher, but given lower than normal
confidence in model solutions we have stayed closer to the multi-
model consensus for now. Temperatures should be near normal.


An area of lower pressure should persist over the southern half of
the Gulf during the next couple days, which should lead to winds
generally from an easterly direction. Right now, winds are
expected to remain below scec levels, but there is a chance for
some periods of stronger winds that can't be discounted. This will
be especially true if a low pressure wave moving into the eastern
Gulf ends up being more vigorous than models are expecting.

Fire weather...

Hazardous fire weather conditions are not expected over the next
several days.


Through Tuesday, the best rain chances will exist over the eastern
part of the area, generally to the east of a Tallahassee to Albany
line. Some locally heavy rain will be possible in these areas,
with average rain totals on the order of 1-2 inches expected
(possibly closer to 2-3 inches around Dixie, Taylor, and Lafayette
counties in the eastern Florida big bend). Lower amounts are
expected to the west. Later in the week, rain chances will
increase over the western parts of the area with locally heavy
rainfall becoming possible over much of the area. Although
localized flooding will be possible as a result, flooding on main
rivers seems unlikely right now.


Preliminary point temps/pops...

Tallahassee 91 74 91 73 89 / 30 20 30 20 40
Panama City 87 75 88 76 87 / 20 10 10 10 20
Dothan 88 70 91 71 91 / 20 10 10 10 10
Albany 88 72 90 70 88 / 50 20 30 10 30
Valdosta 89 72 88 72 87 / 60 40 50 30 60
Cross City 90 74 87 74 87 / 50 50 60 30 60
Apalachicola 87 76 89 76 88 / 20 20 20 20 20


Tae watches/warnings/advisories...


Near term...Harrigan
short term...lamers
long term...lamers
fire weather...Harrigan

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