Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tallahassee Florida
408 PM EDT Sat Apr 18 2015
Near term [through tonight]...
A warm front stretched across the northern Gulf Coast has initiated
some rather robust convection this morning/afternoon. The more
focused upslope flow has remained southwest of our Gulf waters, thus
only light to moderate rain has reached the Florida coast this
morning as the convection decays on its northeast trek. We're
starting to get some scattered convection in The Big Bend, most
likely associated with the southwesterly low-level flow intersecting
a differential heating boundary where scattering in cloud cover has
allowed temperatures to warm. It's possible there is also some
highly disturbed seabreeze influence as well. A few of these storms
may produce gusty winds.
Scattered convection will come to and end this evening and we'll
likely continue to see rounds of light rain associated with decay
convection along the front advecting inland overnight. As a
shortwave moves into the southeast near dawn, a surface low is
expected to develop, strengthening the low level wind field. This is
expected to organize a squall line at the door of our Alabama and
Panhandle counties early tomorrow morning.
Short term [sunday through Monday night]...
An upper level cut off low over the Southern Plains with an associated
+pv anomaly will swing east-neward, decaying into a SW trough as it
lifts towards the Great Lakes through the period. As this low heads
towards the East Coast, it will enhance the ul jet as well as the
low level jet. This +pv anomaly aloft will also help to develop a low pressure
system at the surface with a low in the Mississippi Valley by Sunday
morning lifting toward the northestern states by Monday, trailing a cold
front with it along the eastern states through the period. Locally, our
highest chances for showers and thunderstorms will be Sunday with
most of the storms clearing by Sunday evening.
With deep layer flow from the southwest, a rich plume of Gulf
moisture will feed this system and allow moderate to heavy
rainfall with these thunderstorms. Widespread rainfall totals are
expected to be around 1-2", but hi-res guidance is indicating the
possibility of isolated areas receiving 3-6" of rain, which could
cause some flash flooding. Additionally, the enhanced low level jet and ul
jet will mean the potential for some of the thunderstorms
associated with this system to produce strong to severe wind
gusts. Damaging wind gusts will be the main threat, although hail
around 1" in diameter and an isolated tornado or two can also not
be ruled out.
Long term [tuesday through saturday]...
Although the period will start out drier, with surface high pressure
over the southeastern states Tuesday through Wednesday night, the disturbed
pattern will quickly return with more short wave disturbances
ejecting through the upper level pattern. The area will see cloud
cover return with 20-30% chances for showers and thunderstorms
Thursday through next weekend. Temperatures will be near normal for
this time of year with highs in the upper 70s to middle 80s and lows in
the middle 50s to middle 60s.
[through 18z sunday] all sites should scatter to VFR this
afternoon, with scattered thunderstorms near tlh and vld.
Overnight, low ceilings mixed with fog and light winds will
prevail. A squall line will bring heavy rain and thunderstorms
early tomorrow morning, through the afternoon. Storms are expected
to impact all terminals, with isolated severe thunderstorms
possible as well.
Winds will approach cautionary levels tomorrow as a developing
low pressure system crosses the area. More cautionary periods will
be possible through the period as a disturbed weather pattern
continues, but at this time advisory levels are not anticipated
for the next several days.
Red flag conditions are not expected at least through the middle
of next week. Low ceilings will be possible again late tonight into
Sunday morning with a very moist air mass in place. Some patchy
fog cannot be ruled out.
Rainfall this week has resulted in a rise of area rivers with
many reaching action or bank full stage. The Choctawhatchee River
is forecast to reach minor flood stage at Caryville on Sunday
night and at Bruce on Monday. With an additional 1 to 2 inches of
rain expected through Tuesday, with isolated totals of 3-6"
possible, other rivers may approach minor flood stage by the end
of the week and flash flooding may be possible where the heaviest
Preliminary point temps/pops...
Tallahassee 70 81 67 84 64 / 50 70 30 30 10
Panama City 71 78 71 78 65 / 70 80 20 30 10
Dothan 68 79 66 81 59 / 80 90 20 30 10
Albany 69 79 66 82 59 / 50 80 20 30 10
Valdosta 70 83 67 86 62 / 30 80 20 30 10
Cross City 70 83 67 81 65 / 30 60 30 40 10
Apalachicola 73 79 71 80 67 / 40 70 30 30 10
Florida...Flash Flood Watch from late tonight through Sunday evening for
Calhoun-central Walton-coastal Bay-coastal Franklin-coastal
Gulf-coastal Wakulla-Gadsden-Holmes-inland Bay-inland
Franklin-inland Gulf-inland Wakulla-Jackson-Leon-Liberty-
north Walton-south Walton-Washington.
Georgia...Flash Flood Watch from late tonight through Sunday evening for
Alabama...Flash Flood Watch from late tonight through Sunday evening for