Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tallahassee Florida
636 am EST sun Dec 4 2016
Aviation [through 12z monday]...
Rain chances will increase throughout the day from west to east
across our area, with rainfall likely starting at dhn and ecp by
the early afternoon, at aby and tlh during the late afternoon or early
evening, and at vld late in the evening. Cigs and visibility will
gradually deteriorate through the afternoon and tonight with MVFR
conditions likely, along with a good chance of IFR/LIFR at all
sites except vld late tonight.
Previous discussion [350 am est]...
Near term [through today]...
An upper level ridge will continue to build over the eastern conus,
while at the surface a broad area of high pressure will continue to
drift north and east of our area. The current easterly flow pattern
will become more southeasterly during the morning and afternoon
hours, bringing increasing deep layer moisture into our area. As a
result, precipitable water values will increase above 1.5" by the afternoon hours,
especially north and west of Tallahassee. A weak area of low
pressure is also expected to drift eastward near the central Gulf
Coast region from the morning into the afternoon, with a warm front
to its east moving northward across our area. This will enhance
precipitation chances, mainly across western and northern parts of
our County Warning Area where moisture content is highest.
Little to no instability is expected throughout this period across
most of our area, but a few hundred j/kg of surface-based cape could
develop across the Florida Panhandle during the afternoon and early
evening. Combined with 50 knots or more of effective bulk shear, at
least 20 knots of 0-1 km shear, and ample values of low-level
helicity near the warm front, this will result in a marginal risk of
severe weather across the Panhandle throughout the day. While the
lack of instability will inhibit thunderstorm chances, isolated
tornadoes or damaging straight-line winds cannot be ruled out. High
temperatures will rise into the low-mid 70s across most of our area
as the warm front moves through, with upper 60s expected to the
north of the front in parts of southeast Alabama and SW Georgia.
Short term [tonight through tuesday]...
Closed upper level low situated near the western Mexico coast this
morning will lift northeast into southern Texas tonight with a
surface low along the western Gulf Coast beginning to deepen. As
this system continues to move northeast, a warm front lifts into
the County Warning Area today and will move pushed northward through much of the
area by tonight. This warm front brings warm, moist Gulf air to
the County Warning Area with dewpoints climbing into the upper 60s tonight and
lower 70s tomorrow. Any strong storms tonight would likely be more
limited to the coast where higher cape values are expected.
May see a brief lull, although still some activity tomorrow
morning, before an increase in shower and thunderstorm coverage
Monday afternoon. By this time, precipitable water values will begin increasing to
around 2 inches. These a very high values for this time of year
and thus the potential for localized flash flooding will increase
Monday afternoon and persist through the night.
While severe weather parameters will begin increasing Monday
afternoon low level shear is still on the lower side and thus Monday
night into Tuesday remains the most likely time frame for severe
weather. Cape values are around 600 j/kg in the GFS Monday night
with near 1000 j/kg in the NAM. Clouds and rain may limit some of
the destabilization and thus NAM instability may be a bit over
done. Overall though, enough instability for thunderstorms.
Although instability may be the limiting factor, have enough deep
layer shear (around 50 kts) and low level shear (30-40 kts) to
allow for severe storms Monday night into Tuesday. Both damaging
winds and a few tornadoes remain a threat. Storm Prediction Center has expanded the
slight risk further eastward for Monday night and now includes
The threat for strong to severe storms continues into Tuesday but
this will quickly diminish later in the day as the front pushes
Diurnal temperature differences will be limited through much of
the short term by the clouds and rain. Both high and low
temperatures will be above average with lows well above average.
At tlh, current low temperature forecast tonight and tomorrow
night is to break the high minimum temperature record.
Long term [tuesday night through sunday]...
Cold front will have cleared the County Warning Area by the beginning of the long
term. Differences still exist between the GFS and European model (ecmwf) late in
the week. The European model (ecmwf) drives a short wave further south than the
GFS, pushing a cold front through the County Warning Area and bringing the change
of rain back to the area Thursday and Thursday night. The GFS
doesn't develop the defined front as the European model (ecmwf) and thus is drier
for the same time period. Pops remain on the lower end of the
chance category for now.
Cold temperatures behind the front are the main story for the
long term with the current forecast for highs in the 40s and 50s
on Friday and lows that night in the 20s across much of the area.
Strong southeast winds will continue across the marine area this
morning with Small Craft Advisory conditions across much of the
area into the afternoon. Winds will strengthen again for Monday
night into Tuesday ahead of a cold with exercise caution levels
and at this time it appears any Small Craft Advisory conditions
would be brief. The aforementioned front will be showers and
thunderstorms to the marine area mainly tonight through Tuesday.
Another front is expected late in the week and will once again
No fire weather concerns are expected as a moist airmass and
periods of rain will move into our area through the next few days.
Expect widespread 2 to 4 inches of rain Sunday through Tuesday
with isolated higher amounts. While overall the area can handle
these amounts, it is the isolated higher amounts that will need to
be monitored closely as they have the potential to create
localized flash flooding, particularly in urban areas.
Preliminary point temps/pops...
Tallahassee 75 66 75 70 76 / 20 60 70 70 60
Panama City 73 68 75 69 73 / 50 70 70 70 40
Dothan 69 60 71 64 73 / 80 70 80 80 40
Albany 68 60 70 64 77 / 60 70 80 90 60
Valdosta 76 64 75 69 77 / 10 50 70 80 80
Cross City 78 64 77 70 78 / 10 30 50 60 70
Apalachicola 73 68 75 70 74 / 30 50 60 60 40
Florida...high rip current risk through this evening for coastal Bay-
coastal Franklin-coastal Gulf-south Walton.
GM...Small Craft Advisory until 2 PM EST this afternoon for coastal
waters from Ochlockonee River to Apalachicola FL out to 20
nm-coastal waters from Apalachicola to Destin Florida out 20 nm-
waters from Suwannee River to Apalachicola Florida from 20 to 60
nm-waters from Apalachicola to Destin Florida from 20 to 60 nm.