Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 310843
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
443 AM EDT Fri Oct 31 2014
.Near Term [Through Today]...
Although it will be significantly cooler and drier across the region
today with highs limited to the lower to middle 70s under plenty of
sunshine, (which is 3-5 degrees below climo for this time of year)
the real blast of cold air is still on the way for the upcoming
weekend. This unseasonably cold air mass (which will be described in
detail in the Short Term discussion) will be preceded by a dry cold
front which will approach the region from the NW this aftn. Outside
of some patchy Cirrus and slowly increasing N-NW winds, not much in
the way of weather will be indicative that such a cold blast of air
will be on its way.
.Short Term [Tonight Through Sunday]...
As has been well advertised for the past few days, a big cold snap
is coming this weekend. A rather anomalously large upper low will
drop into the Southern US by Saturday morning pushing a dry cold
front across the forecast area by daybreak. The surface pressure
gradient between a developing low pressure area off the Carolina
coast and an arctic high pressure area moving down the Mississippi
River Valley will generate strong northerly winds quickly
ushering in this much colder airmass. The cold advection behind
this front will be sufficiently strong that high temperatures on
Saturday will likely struggle to warm out of the 50s, which is
rather incredible for the first day of November. The current
forecast highs for Saturday are very near record low maximum
levels for the date.
By Saturday night, the core of the high pressure area will be
building over the Tennessee River Valley with the ridge axis
extending southward to the Central Gulf Coast. The models differ
here in whether the position of the ridge is close enough to
result in light to calm winds across the region by sunrise.
The NAM and Euro MOS for 31/00z are surprisingly similar in
temperatures in the lower 30s across the region with winds very
near or precisely calm by 12z Sunday. Only the GFS shows winds in
the 4 to 6 kt range throughout the night and accordingly has
warmer min temperatures.
The MOS (excluding the MAV) would seem to indicate a borderline
freeze across some of our interior counties - mainly from TLH-ABY
and westward. However, the surface pressure fields in the model
would suggest that it would be unlikely that surface winds become
calm by sunrise.
While the incoming airmass will be very cold, I`m just not
confident we`ll effectively radiate in this pattern or that we
can advect temperatures much cooler than the mid 30s into the
region by daybreak on Sunday. As a result, will utilize a forecast
blend heavily weighted toward the previous forecast - which was
warmer than the 00z guidance set - and the 00z GFS. This results
in lows generally in the mid 30s in western areas and in the upper
30s in the east. Should future forecasts suggest the ridge center
will be located further south, downward adjustments to the min
temp forecast may be needed. In areas with the mid 30s, frost is
unlikely since the airmass will be especially dry.
The moderating trend for afternoon temperatures begins on Sunday
as high pressure builds just north of the region. Highs are
expected to be in the low to mid 60s, which is still around 10
degrees below normal for early November.
.Long Term [Sunday Night Through Friday]...
The extended forecast will be marked by gradually moderating
temperatures and mostly dry weather as a mid-upper level ridge
builds across the eastern US and we transition into more of a
+NAO/+AO regime. Highs should be closer to 80 degrees by the
middle of next week. The next chance of rain is expected to hold
off until Wednesday at the earliest.
[Through 12Z Saturday] Nearly unlimited VFR conditions are
expected to prevail through the period at all of the Taf sites,
but the initially light winds will be on the increase out of the
NW both this aftn and tonight at most of the terminals.
Winds will be on the increase this afternoon in the wake of a cold
frontal passage from Thursday evening. Winds will sharply increase
around midnight as a reinforcing cold front surges across the
marine area. Frequent gusts to gale force are expected behind this
front with sustained winds possibly nearing gale force as well.
Saturday afternoon, high pressure will build near enough to the
marine area to eliminate the threat for gale force gusts, though
advisory conditions will continue into Sunday. High pressure will
then build to the northeast of the marine area starting a period
of moderate easterly flow.
A much colder and drier air mass will rush into the region this
weekend behind a very strong but dry cold front. This unseasonably
cold airmass will generate quite strong and gusty transport winds
and very high dispersions. Red flag conditions may still be possible
over parts of the region on Sunday, but the chilly afternoon temps
appear likely to keep relative humidities just above Red Flag levels
at this time.
Dry conditions are expected over the next several days, with no
impacts expected along area rivers and streams.
.Preliminary Point Temps/PoPs...
Tallahassee 73 41 58 38 64 / 0 10 0 0 0
Panama City 74 42 59 41 63 / 0 10 0 0 0
Dothan 72 38 57 35 62 / 0 10 0 0 0
Albany 72 39 57 37 62 / 0 10 0 0 0
Valdosta 73 41 57 37 62 / 0 10 0 0 0
Cross City 75 45 58 39 65 / 0 10 0 0 0
Apalachicola 74 44 59 42 63 / 0 10 0 0 0
GM...Gale Warning from 11 PM Friday evening to 2 PM EDT Saturday
from Destin to the Suwannee River Entrance out to 60 NM.
Small Craft Advisory from 2 PM EDT Saturday to 10 AM EST Sunday
from Destin to the Suwannee River Entrance out to 60 NM.