Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 050800
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
300 AM EST Thu Dec 5 2013
...Unseasonably warm weather to continue...
.NEAR TERM [Through Today]...
Northwest parts of our forecast area (roughly DTS-DHN) have been
experiencing a relatively persistent rain band through the evening
and into the early part of the overnight hours. Looking at surface
observations, there is a subtle boundary near the Florida
Panhandle coast. Southerly winds with higher thetae values over
the water stand in contrast to backed winds and lower thetae
values over the land areas. North of the boundary, there appears
to be a narrow band of stronger southwesterly winds in the 1-2km
AGL layer (around 30 knots or so). It is in this region of more
focused moisture transport and isentropic ascent that the rain
band has been focused. Rainfall rates have not been trivial - dual
pol estimates from EOX and EVX are around 0.5-1.0"/hr in narrow
bands of training echoes. QPF and PoPs were increased for the
06-12z period in these areas earlier this evening (around 05z).
The HRRR and other CAM output do show a continuation of rain
showers in the NW third of our area through the day today, but the
rain is of a more scattered nature. Thus, PoPs were pared back for
the 12-00z timeframe, but maintained due to continued isentropic
ascent in nearly saturated layers.
Highs were adjusted to be close to yesterday: mid 70s in cloudier
areas in our northwest, and around 80 elsewhere. The record high in
Tallahassee today is 81, which is what we are forecasting so we
should get close to record highs barring any unforseen cloud cover.
Finally, there is the issue of fog during the pre-dawn and early
morning hours. A Dense Fog Advisory was issued earlier as fog was
causing visibility to decrease at many observing sites, and when the
visibility in Tallahassee was around 1/8 mile. Since then, a
mid-level cloud deck has caused fog to dissipate and redevelop, with
substantial fluctuations in visibility. However, with each new set
of observations that comes in, there is usually at least one or two
sites that are down around 1/4 mile. Therefore, the advisory will be
maintained as is, but will be re-evalulated closer to sunrise.
.SHORT TERM [Tonight Through Saturday]...
Strong upper ridge will remain in place over Florida tonight into
Saturday, keeping temperatures well above normal and in sharp
contrast to the record cold temperatures in the plains states.
Boundary between the airmasses will stretch from far northeast
Alabama into central Louisiana tonight, and will slowly push
southeastward Friday into Saturday. Ahead of the front (away from
the center of the upper ridge), isolated showers will be possible
across SE Alabama tonight and Friday. Very warm temperatures are
expected through Friday night, with highs in the lower 80s and
lows generally in the 60s. The highs on Friday will be very close
to record temperatures for the date.
The cold front will edge into the forecast area on Saturday before
stalling and lifting back to the north Saturday night. This will
lead to a wide range of temperatures across the region, with
temperatures forecast to hold steady in the 50s in southeast
Alabama, while upper 70s are expected south and east of the
Fog will continue to be of concern over the next few nights.
However, the more southeasterly direction expected tonight is not
as favorable a trajectory for advecting the moist Gulf airmass
across the cool Apalachee Bay waters. By Friday night, the flow is
expected to be weaker, which will also limit the potential for
advection fog. So while widespread fog is expected, the potential
for widespread dense fog is much less certain.
.LONG TERM [Saturday Night through Wednesday]...
The cold front will push back north as a warm front Saturday night,
meaning that our area never gets into the deeper moisture or lift
behind the front. The drier return flow on Sunday is short-lived,
as a second much stronger cold front pushes through the area late
Monday night into early Tuesday. This front has the upper support
to push all the way south across the FL peninsula, putting AL, GA,
and northern FL well into the cold air. As a result, the very warm
temperatures of the past week could drop by 15 to 20 degrees
behind the front on Tuesday and Wednesday, with readings in the
50s in SE Alabama and SW Georgia to the 50s and lower 60s across
Precipitation will generally be scattered through the period with
a chance of thunderstorms along and ahead of the first front
Saturday and again with the much more vigorous front on Monday.
.AVIATION [Through 06Z Friday]...
Current conditions are varying widely early this morning due to a
scattered deck of mid-level clouds between 7000-10000 feet. This is
causing fog to dissipate and redevelop with flight categories at
some of the terminals varying between VFR and LIFR in the space of a
couple hours. The bottom line is that when mid-level cloud cover
thins a bit, there is a good chance of IFR/LIFR with fog through
14-15z this morning at TLH, ABY, and VLD, and perhaps also at ECP. A
band of rain showers near DHN should prevent much fog there although
CIGS should be in the IFR range. We expect VFR after 15z, with
another round of fog developing tomorrow evening.
Light to moderate southeasterly flow will continue over the
coastal waters through Friday night as high pressure remains
anchored off the east coast. A front will slide into the western
waters on Saturday before lifting back to the north Saturday
night, with southeasterly flow continuing into early next week.
Red flag conditions are not expected the next several days. Dense
fog is likely in spots over the next several nights with poor
mixing and light winds.
Isolated to scattered showers will be possible over the western
half of the forecast area through Saturday. Total rainfall amounts
should generally remain below 1 inch, which will lead to only
minimal impacts on area rivers and streams.
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 81 59 78 63 75 / 20 10 10 10 30
Panama City 75 65 76 65 70 / 30 10 10 30 30
Dothan 76 63 80 59 62 / 40 20 10 30 50
Albany 79 61 81 64 69 / 30 10 10 20 40
Valdosta 81 61 81 62 78 / 20 10 10 10 20
Cross City 81 59 81 59 79 / 10 10 10 10 10
Apalachicola 76 64 74 66 73 / 10 10 10 10 20
FL...DENSE FOG ADVISORY until 10 AM EST /9 AM CST/ this morning for
Coastal Dixie-Coastal Franklin-Coastal Gulf-Coastal
Jefferson-Coastal Taylor-Coastal Wakulla-Gadsden-Inland
Dixie-Inland Franklin-Inland Gulf-Inland Jefferson-Inland
GA...DENSE FOG ADVISORY until 10 AM EST this morning for Baker-Ben
GM...DENSE FOG ADVISORY until 10 AM EST this morning 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.