Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 202026
Area Forecast Discussion
National Weather Service Tallahassee FL
326 PM EST Fri Jan 20 2017
...Multiple Rounds of Severe Weather Possible This Weekend...
.NEAR TERM [Through Tonight]...
In the upper levels a ridge is over most of Florida with a broad
trough to the west over the Mississippi River Valley. At the surface
southerly low level flow continues to bring warm moist air from the
Gulf. A batch of steady rain will move in from the west during the
overnight hours. POPs are 60 to 70 pecent in Southeast Alabama,
Southwest Georgia and the Florida Panhandle. POPs are 30 to 50
percent elsewhere. A few rumbles of thunder are possible. Lows will
be in the mid 60s.
.SHORT TERM [Saturday Through Sunday Night]...
A complicated pattern is setting up across the forecast area for the
weekend as an energetic system evolves across the Southern U.S. An
upper low is forecast to cut off over the southern High Plains
Saturday and move quickly eastward to Alabama by 00Z Monday. The
initial round of severe weather will develop in a warm air advection
regime along the Gulf Coast on Saturday under diffluent flow aloft
and with a broad and weakening low level jet. Unusually steep mid
level lapse rates will mean large hail is a possibility with this
system on Saturday. Deep layer bulk shear values of around 50 kt and
and decent low level shear will allow for both a damaging wind and
tornado threat, particularly if we can get some discrete cell
development. Shear will increase even further Saturday night into
Sunday as the low level jet over Alabama strengthens (deep layer
shear near 80 kt and 0-1km near 40 kt) with all three modes of
severe weather possible. Streaks of high updraft helicity from many
CAM members indicate the potential for one or two strong (EF2 or
higher), possibly long-track tornadoes. The Storm Prediction Center
has most of the forecast area under an enhanced risk for severe
storms from Saturday into Sunday. After sunrise Sunday, the severe
threat will be over for our western zones and end by roughly midday
across the central zones and the mid afternoon further east.
.LONG TERM [Monday Through Friday]...
As the big upper trough pulls east, we will dry out on Monday. While
it will be cooler, temperatures really only settle back down to
where they are supposed to be in late January for Tuesday. We`ll be
back in the 70s on Wednesday. Another cold front will then bring a
chance of showers to the region Wednesday evening through Friday
morning. A colder air mass will follow this second front with highs
Friday only in the 50s for most areas.
.AVIATION [Through 18Z Saturday]...
Showers are forming over the Florida Panhandle and Big Bend. They
will continue to develop and spread into Southeast Alabama and
Southwest Georgia this afternoon. A few thunderstorms cannot be
ruled out. After sunset showers will dissipate and ceilings and
visibilities will deteriorate rapidly. Overnight a steady rain will
move in from the west. LIFR conditions are likely in the early
morning hours. Conditions will be slow to improve in the morning.
Southerly winds will be gusty on Saturday.
Onshore winds will increase overnight and small craft advisory
conditions will overspread the region from west to east on Saturday.
After a cold frontal passage on Sunday, sustained winds will
approach gale force and we will certainly see frequent gusts at that
level. We therefore anticipate needing to issue a gale watch/warning
at some point. Significant wave heights will rise as high as 9 feet
or so ahead of the front and increase to 15 feet behind it.
Conditions will not drop below headline criteria until Tuesday.
Several rounds of thunderstorms this weekend will keep relative
humidity high through early next week and fuel moistures high
through the period. Transport and 20 foot winds will be elevated
with this series of approaching systems, which will cause high
dispersions on Sunday.
Widespread storm total rainfall of 3 to 4 inches is expected across
most of the forecast area. Rivers have been able to drop enough
since the most recent floods that we are not expecting any to reach
flood stage with this event. Likewise, coastal flooding is not
anticipated at this time, although tides will be running a foot or
two above normal.
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 65 76 65 76 51 / 50 80 90 80 30
Panama City 67 74 67 72 54 / 60 70 80 80 30
Dothan 64 74 62 72 49 / 70 90 100 60 30
Albany 64 74 62 74 50 / 60 90 100 80 30
Valdosta 64 76 64 76 50 / 40 80 90 80 30
Cross City 64 77 65 76 53 / 30 50 60 80 60
Apalachicola 67 74 67 73 55 / 50 60 70 80 50
FL...High Rip Current Risk through Monday morning for Coastal Bay-
Coastal Gulf-South Walton.
GM...Small Craft Advisory from 7 PM Saturday to 7 AM EST Tuesday for
Apalachee Bay or Coastal Waters From Keaton Beach to
Ochlockonee River Fl out to 20 Nm-Coastal Waters From
Ochlockonee River to Apalachicola Fl out to 20 Nm-Coastal
waters from Suwannee River to Keaton Beach out 20 NM-Waters
from Suwannee River to Apalachicola FL from 20 to 60 NM.
Small Craft Advisory from 7 AM Saturday to 7 AM EST Tuesday for
Coastal waters from Apalachicola to Destin FL out 20 NM-
Waters from Apalachicola to Destin FL from 20 to 60 NM.