NATIONAL WEATHER SERVICE TALLAHASSEE FL
559 AM EST Sat Nov 23 2013
NEAR TERM [Today]...
Locally, a nearly zonal pattern aloft between a trough to our north
and ridging to our south, will gradually (and only slightly) amplify
today as the main energy with the trough moves southeast into the
At the surface, as of 09z, a strong cold front is positioned northeast to southwest along the spine of the Appalachians, to the AL/FL line, and into the northwest Gulf.
Ahead of this front, the remnants of a pre-frontal trough can still be found across southern Georgia (though weakening fast). A thermal trough has been noted moving east to west across the Big
Bend and Apalachee Bay.
Showers continue along the weakening pre- frontal trough and will likely become a little more numerous near the Tri-State intersection as the thermal trough interacts in the next hour or so.
Then the cold front will finally catch up to all of this mess and clear it out from west to east.
The front should enter the southeast Big Bend a little after noon, with little to no rain remaining behind it.
There is the slight possibility that a few light showers may move into our Alabama and Florida panhandle counties late this afternoon, into the early evening associated with a weakening low-level PV anomaly.
However, we`d probably only be able to squeeze out a few sprinkles at best.
All shower activity should come to an end by early evening. With a
front passing through the Tri- State region, expect about a 10 deg
temperature gradient this afternoon. Highs should reach 80 degrees
in Cross City, while capping out around 70 degrees at Dothan.
SHORT TERM [Tonight Through Monday]...
The large scale regional pattern commences tonight highlighted by
tight quasi-zonal flow across SE.
At surface, lack of upper forcing and limited low-level convergence leads to weak cold front exiting I-75 with chance of light mainly eve post-frontal rain across SE quarter of CWFA. QPF should max out at only 0.01 inches.
Rapid clearing behind the front means that local temperatures will drop as low as the mid to upper 30s for portions of SE AL by sunrise Sunday and to low 50s across SE Big Bend.
On Sunday, in the wake of this front, cutoff low aloft over SW states advances slowly EWD.
At surface, a strong 1045MB anticyclone over Cntrl plains will build EWD into Sunday night allowing strong and gusty NW winds (especially into Sun aftn) and a much colder airmass will overspread the SE and into NE Gulf region.
So despite full sun, strong cold air advection means that high temperatures will struggle to reach the upper 50s to lower 60s.
By Sunday night surface high centered over OH Valley ridging Swd
into Gulf region.
With the pressure gradient relaxing, Sunday night into Monday morning should be even colder. Much of the guidance is suggesting a light freeze across the northern half of the forecast area at this time and only to the mid 30s elsewhere.
Working against a freeze is that the high is not in a favorable location for a freeze along the Gulf Coast (centered in North Carolina sunrise
In addition, high clouds may be on the increase ahead of next
weather maker, further limiting radiational cooling.
With these factors in mind, have generally gone above guidance for low temperatures Monday morning, keeping freezing temperatures confined to the northern border of the forecast area.
During Monday, high pressure over local region will slide east towards the coast as an upper low advances into S/Cntrl states while surface low develops over NE Gulf and begins to track NEWD.
Both will contribute to the next weather maker on Tuesday.
Main short term impact will be to weaken gradients, veer winds and raise high temps back to upper 50s SE AL to upper 60s Big Bend.
Clouds will noticeably increase from W-E thru the day but the rain will likely hold off until eve except possibly over Panhandle waters and
LONG TERM [Monday Night through Friday]...
As the upper low ejects from the Desert Southwest and moves east on Monday, surface low pressure will develop in the Western Gulf and
move east northeast through Tuesday and Tuesday night.
It looks fairly certain that this system will tap into enough deep moisture to generate a solid rain event across the region.
Widespread rainfall amounts of 1 to 2 inches appear likely, given the upper support and deep moisture.
Primary concern is any potential for severe weather. With the expected slow retreat of the cold dome of high pressure, low-level return flow will be very limited ahead of the approaching system.
Surface dewpoints are only progged to recover to around 60 degrees by Tuesday afternoon (and even then, confined close to the coast).
This will likely limit the available instability for the system to tap, despite the strong shear profiles. In addition, the track of the surface low remains in question, with the latest GFS (22/12z) keeping the low offshore until moving inland in the eastern Big Bend. Such a low track would inhibit any severe storms for the region.
All of the guidance shows the surface low and associated front
exiting to the east Tuesday night. However, there may be some
lingering shower activity into early Wednesday as the potent upper
low crosses the Northern Gulf Coast.
Cold air will move in to the region on Wednesday, keeping temperatures well below average through Thanksgiving.
AVIATION [Beginning 12Z Saturday]...
Although there are patchy spots of IFR visibilities around, category restrictions are primarily a function of low ceilings this morning as mid-level cloudiness as kept the fog from becoming more widespread. Where the mid-clouds are not, higher winds are eliminating the fog threat.
MVFR/IFR ceilings this morning will become a rather widespread MVFR deck through the entire day.
VFR conditions will return to all sites by late evening with middle clouds lingering through the night.
After a brief period of light winds and lowering seas over the coastal waters through this morning, strong offshore flow will develop later today into tonight in the wake of a strong cold front.
Another even stronger cold front will move across on Tuesday.
Exercise caution level winds are expected offshore this afternoon.
Then, Small Craft Advisory winds and seas are forecast for all the
waters from tonight thru at least Wed eve.
Although very dry conditions are anticipated behind the strong cold
front tomorrow, afternoon highs will remain well below average.
This will keep relative humidity values just above critical levels.
Beginning Monday, moisture will gradually return to the region and
hazardous fire weather conditions are not anticipated through
Rainfall through the weekend is expected to be less than a quarter
of an inch and should not have an impact on the river stages.
The next chance for significant rain will be Tuesday with widespread 1
to 2 inch rainfall totals expected.
Isolated heavier totals are possible which could result in some increase in river stages.
PRELIMINARY POINT TEMPS/POPS...
Tallahassee 77 47 60 34 64 / 50 20 0 0 20
Panama City 75 47 60 41 62 / 20 10 0 0 30
Dothan 71 39 56 33 58 / 20 10 0 0 20
Albany 74 41 57 31 58 / 70 10 0 0 20
Valdosta 75 48 58 34 62 / 50 30 0 0 10
Cross City 80 52 65 36 68 / 30 30 10 0 10
Apalachicola 77 50 62 43 63 / 20 10 0 0 20