NATIONAL WEATHER SERVICE TALLAHASSEE FL
941 PM EST Sun Jan 26 2014
Near Term [Through Tonight]...
Rather quiet night in store across the region as weak southerly flow begins ahead of a strong arctic cold front.
Weak ascent overnight will lead to the possibility of some light
showers, particularly in the Florida Panhandle.
Further off to the east across Southern Georgia and the Florida Big Bend, areas of fog will be possible again tonight, especially after the cirrus canopy clears to the east.
Temperatures should fall through about 06z then either level off or slowly rise as the low level southerly flow becomes more established.
Short Term [Monday Through Wednesday]...
Some change in the 18z GFS/NAM and 21z SREF runs this evening,
with a little of a shift to the south with the cooler air and heavier precip by Wednesday morning, and thus these models are showing the potential for heavier ice accumulations nearing one quarter inch.
Given this possibility, went ahead and extended the winter storm watch a few counties to the east in Southern Georgia and in the Florida Panhandle.
The overall synoptic reasoning is unchanged from this afternoon.
The degree of uncertainty and difficulty with this forecast was well stated in this afternoon`s discussion and that text appears below.
Certainly going to be an interesting next couple of days watching this event unfold.
Monday will be the last day of a brief reprieve from our recent cold weather.
An arctic cold front will move through the region Monday Night, then stall across the southern Gulf of Mexico and South FL on Tuesday.
A weak frontal wave, perhaps more than one, will develop along this front and translate east-northeastward along the front, ahead of an approaching positive tilted long wave trough over the Central Plains.
Deep layer moisture (above the very dry and cold boundary layer) and large scale ascent will form a shield of precipitation along the Gulf Coast States Tuesday Night and Wednesday.
This is where the forecast becomes very challenging.
There are two main solutions.
1) The 12 UTC GFS and NAM forecast a prolonged period of precipitation that lasts from Tuesday Night through most of Wednesday.
This solution doesn`t bring the deepest, cold air as far south, which results in a non-liquid precipitation line that runs roughly along and north of a line from Tifton to Panama City.
Along and north of this line, this solution (especially the NAM) suggests widespread, significant ice accumulations, mixing in with sleet and snow on Wednesday as the column gradually cools.
During the day on Wednesday the freezing line moves farther south,
bringing the first snow storm in recent history to Tallahassee, but
not much measurable snow.
2) The 00 UTC ECMWF is colder and more progressive than the GFS, showing about a 6 to 12-hour period of mostly sleet and snow across much of our forecast area Tuesday Night and early Wednesday.
It seems that the main difference between the two solutions boils down to their handling of a cutoff low currently off the CA coast.
The GFS essentially "captures" this feature and partially phases it with the main long wave trough. This means a more shallow cold airmass and a much wetter storm system.
The ECMWF keeps the system cut off from the westerlies, resulting in a quick shot of wintry precipitation in our area.
Given these differences, we have no choice but to continue to forecast closer to the mean of these solutions.
This means a gradual changeover (from northwest to southeast Tuesday Night through Wednesday Morning) from cold rain, to freezing rain, to sleet, to finally snow.
Places north of a line from Panama City to Tifton stand the best chance of accumulating snow/sleet, though a dusting is still possible farther south and east.
The disconcerting part of the forecast is the potential for significant ice accumulations.
Much of our forecast area could get between 0.05 and 0.25", with
isolated higher amounts.
In a part of the country with very little infrastructure to handle extreme cold and freezing/frozen precipitation, this could have as much of an impact as a tropical cyclone...perhaps more.
Downed power lines & large tree limbs would undoubtedly result in widespread power outages and impassable roads.
Those who lack properly winterized shelter and true cold weather
clothing risk hypothermia (or even frostbite).
Long Term [Wednesday Night through Sunday]...
A hard freeze is possible Wednesday Night, though the differences
between the GFS and ECMWF make this a tough call.
The more progressive, colder ECMWF pattern (plus the fresh snow cover from that model run) has the arctic high centered over South Georgia, which would yield incredibly cold low temperatures (lower to mid teens?).
The GFS pattern has the ridge farther to our northeast, which could limit radiational cooling somewhat.
So far the MOS consensus is in the mid 20s, but this will be something to watch, especially if there are power outages from the wintry precipitation the day before.
A light freeze is possible Thursday Night after a cool day on Thursday.
A gradual warming trend will take place for the remainder of the
forecast period, as the GFS and ECMWF remain in good agreement in flipping the large scale 500 mb height pattern- with a trough in the
west and a ridge in the east.
Temperatures are likely to be above average next weekend. Generally fair weather is expected through the period.
VFR conditions will dominate the area rest of this evening with low cigs and visibilities forming in the late night/early morning hours.
IFR/LIFR conditions are expected for KABY, KDHN, KTLH, and
KVLD overnight with MVFR conditions at KECP.
VFR conditions will return Monday morning.
Winds will remain light and southwesterly increasing to west 5 to 10 mph in the afternoon.
Will go with VCSH 16-18Z and PROB30 for rain with marginal MVFR CIGS KDHN...KABY and KECP 18Z-24Z.
Generally light winds and low seas are expected through Monday
before conditions deteriorate from northwest to southeast Monday night as an Arctic front approaches.
Small craft advisory conditions may then continue well into Wednesday before conditions improve again at the end of the week.
Surface high pressure will create a light onshore flow generating
scattered rain on Monday before a cold front moves across Monday
night likely stalling over the northern Gulf of Mex overnight.
In its wake...a colder airmass plus an upper disturbance moving south across the local area Tuesday into Wednesday and the proximity of the stalled front and associated low will produce ample rain with a wintry mix expected Tuesday night into Wednesday... especially over Alabama and Georgia counties.
Red flag conditions are unlikely through the work week.
Some light precipitation is expected early this week, but local creeks and rivers will not be impacted.
Preliminary Point Temps/PoPs...
Tallahassee 46 70 40 45 33 / 10 30 40 60 70
Panama City 53 67 36 44 32 / 20 40 40 60 70
Dothan 45 64 31 39 26 / 10 40 40 70 70
Albany 43 65 35 42 27 / 10 30 40 60 70
Valdosta 43 68 38 45 31 / 10 20 40 60 70
Cross City 47 69 48 54 37 / 10 30 30 50 60
Apalachicola 52 68 42 48 35 / 20 30 40 60 70
Winter Storm Watch from Tuesday evening through Wednesday morning for Central Walton-Holmes-Inland Walton-Jackson- Washington.
Winter Storm Watch from Tuesday evening through Wednesday afternoon for Baker-Ben Hill-Calhoun-Clay-Colquitt-Decatur- Dougherty-Early-Irwin-Lee-Miller-Mitchell-Quitman-Randolph- Seminole-Terrell-Tift-Turner-Worth.
Winter Storm Watch from Tuesday evening through Wednesday morning for Coffee-Dale-Geneva-Henry-Houston.