NATIONAL WEATHER SERVICE TALLAHASSEE FL
620 AM EST Sat Feb 22 2014
Near Term [Through Today]...
The large scale pattern will deamplify becoming generally zonal with dry WNW steering flow locally thru today as a shortwave lifts rapidly to the northeast.
Sct to Bkn high clouds will stream Ewd across mainly zonal flow.
At the surface...a front was slowly drifting Swd during pre-dawn hours located along a line from between JAX and St Augustine thru Dixie County and into the NE Gulf of Mex.
Front was easily detected by comparing dew points, ranging from
the mid 30s across SE AL to low 60s Dixie county.
There may be just enough lift across SE most Big Bend and adjacent waters to sustain some drizzle or sprinkles plus low clouds and patchy fog until around sunrise. Otherwise...front will continue to slowly make its way SWD then stall across N/Cntrl Peninsula later today.
In wake of front...surface ridge slides Ewd to east coast rest of today scouring our remaining low level moisture bringing much drier air to the local region. i.e RAP13 sounding for Tallahassee shows
PWATS dropping to around 0.5 inch by sunrise.
24 HR temp/dew point comparison upstream from front indicates that local airmass 10 to 17 degrees cooler and 15 to 25 degrees drier than same time yesterday.
Winds veer to NE this morning then very light SE late.
Expect highs to reach the upper 60s to lower 70s by afternoon.
Short Term [Tonight Through Monday]...
Tonight a weak southern stream impulse will lift north out of the
northern Gulf and merge in with the base of the northern stream
As the two regions of WAA aloft combine, an area of increased moist ascent will develop within the 400-600mb layer.
At the same time, a surface warm front will be lifting north into north Florida increasing low level moist isentropic ascent.
By morning, the mid/upper features and surface features will link up
resulting in robust deep layer ascent.
Expected precipitable water values around 1.5 in. are around 2 standard deviations above the norm for this time of year and would support the potential for heavy rain.
At this time, average rainfall amounts of an inch to an inch and a half are expected, though isolated spots could see rainfall amounts between 2 to 4 inches.
The best shot at these higher amounts will be around the time the low and mid level features link up and as the warm front is just moving ashore (through the first half of the day Sunday).
At this time, deep layer boundary parallel flow and low level convergence will be maximized.
This will essentially promote training cells right along the warm front, with individual storms capable of dropping over an inch in a short amount of time.
Another mid/upper disturbance will nose into the area through the late afternoon and evening Sunday, though the warm front will be well to our north at this time.
This disturbance will primarily provide continued upper level support
for showers through the evening, though rain is expected to be
By morning Monday, a cold front will slowly push through the area and provide a somewhat short-lived uptick in convection as it moves south to a position along the panhandle coast and grinds to a halt in a deep layer zonal flow regime.
Through the period, instability will remain very limited and low layer shear will remain rather light.
Thus, severe thunderstorms are not expected though there may be a rumble of thunder from time-to-time.
Long Term [Monday Night Through Saturday]...
A stationary boundary will stall over north Florida bringing cloud cover and keep the weather unsettle until a cold front moves through Wednesday.
Behind the front high pressure will build in bringing drier air and colder temperatures.
As the low levels continue to dry out, expect the 4K cigs to erode with VFR conditions at all sites during rest of the pre-dawn hours.
VFR conditions will prevail through rest of the period as increasing upper level cloudiness streams overhead.
After 07z...calm winds and increasing dew points will generate low
stratus and vsby reductions.
Expect MVFR cigs and/or vsbys all sites with IFR possible at TLH and VLD before sunrise.
Winds will decrease to mainly light from the NE today to calm tonight.
Winds and seas will remain low for the next several days, with rain chances likely Sunday through mid-week.
In the wake of yesterday`s cold front...a drier airmass will plunge
humidity values today into the low to mid 20s across southern AL/GA
and the low to mid 30s across N FL.
With light wind and low ERC values...no red flag conditions are expected.
These light winds and ample low clouds will yield low mixing heights and dispersions today and especially on Sunday.
Beginning Sunday into Monday...low level moisture will be on the increase.
No fire weather concerns are expected through at least Wednesday.
As mentioned above, there is a potential for heavy rainfall during
the first part of the day on Sunday, though the heaviest rain will
likely be confined to north Florida and especially along and west
of the Apalachicola River.
Flash flooding will likely not be a concern as these basins should be able to accommodate the expected rainfall amounts.
However, nuisance urban flooding will certainly be a possibility.
As far as area rivers are concerned, ensemble guidance fed with the expected average rainfall totals show the potential for river systems (primarily across north Florida) to reach at least minor flood stage by Monday or Tuesday.
More sensitive rivers (i.e. the Choctawhatchee), or rivers receiving
the isolated higher amounts could reach moderate flood stage.
Preliminary Point Temps/PoPs...
Tallahassee 72 51 72 60 73 / 0 10 70 40 40
Panama City 69 56 66 61 70 / 0 20 70 40 40
Dothan 70 49 67 57 72 / 0 20 60 30 30
Albany 70 47 70 56 69 / 0 0 60 30 30
Valdosta 73 50 73 59 73 / 0 0 70 40 40
Cross City 72 55 73 60 74 / 10 10 70 40 40
Apalachicola 66 58 66 61 69 / 0 20 70 40 40