NEAR TERM [Until 6 AM Monday Morning]...
An unseasonably deep upper level low is traversing the Upper
Mississippi Valley this afternoon. The associated surface cold front
stretches from the Great Lakes southwest across the Tennessee Valley to the central Gulf Coast.
The remnant low that was Karen is about to be absorbed by this front. The front will make its way about half way across the area by 12 UTC Monday. Out ahead of it, we continue to call for likely to categorical PoPs will periods of heavy rain as deep layer moisture moves into the region raising precipitable water values to about 2 standard deviations above normal. We have seen bands of convection streaming in off the Gulf all day and these have already produced radar perceived local areas of 3-4 inch rainfall.
Most other areas along the coast have seen roughly 1-2 inches.
We plan to maintain the flash flood watch through the night, mainly for the possibility of training echoes. We did lower the maximum totals though to 4-8 inches, while maintaining that most locations in the watch area will see 2-3 inches. We have also seen a lone supercell offshore that likely spawned a waterspout. Shear profiles indicate that this will remain a possibility through this evening.
One thing we will not have to worry about tonight is dense fog as winds should stay up and keep the boundary layer mixed.
Min temps will remain well above early October norms across most of the forecast area with upper 60s to lower 70s common. Only Southeast AL will get into the cooler air by sunrise and drop into the lower 60s.
SHORT TERM [Monday through Tuesday night]...
There will be significant changes in the weather across the area
during this period as a strong cold front moves from west to east
overnight and early tomorrow. Higher precipitable water values
are being advected north along and east of the front with readings
up to 2.4 inches, or near the 99th percentile of PWs for this time
of year. The front will be progressive, moving east of the FL Big
Bend Monday afternoon.
Much drier and cooler air will work its way into SE Alabama and the
western FL panhandle Monday evening and slowly spread across GA and the FL Big Bend Tuesday. Scattered showers will linger in
southwest GA and the FL Big Bend tomorrow and tomorrow night with
dry conditions Tuesday.
Temperatures will cool in the wake of the front Monday with upper
70s to lower 80s and mid to upper 80s ahead of the front.
Temperatures on Tuesday will range from the upper 70s to lower 80s.
Monday night will be the coldest for the period with a tight northwest
to southeast gradient across the forecast area. Overnight lows will drop into the upper 40s in SE Alabama with mid 60s in the FL Big Bend.
LONG TERM [Wednesday through Sunday]...
In general there is good model agreement for this period with quiet weather and temperatures near or slightly below climatology.
Expect dry conditions with highs in the low to mid 80s and overnight lows in the mid 50s to mid 60s.
AVIATION [Through 18 UTC Monday]...
Showers and isolated thunderstorms will impact all of the terminals this period, although it will take until evening for them to arrive at ABY and VLD. Ceilings will occasionally be MVFR in the convection with brief periods of IFR visibility in the heavier showers.
A wind shift to the northwest will occur with a cold frontal passage Monday morning. The front will not quite make it to VLD by 18 UTC.
A cold front will move across the region this evening through Monday
with southerly flow ahead of the front. There will be widespread
showers and isolated thunderstorms along and ahead of the front,
with moderate onshore winds west of Apalachicola tonight.
The front will produce a pronounced wind shift from south winds to
northwest winds tonight from Apalachicola westward, with the wind
shift occuring from Apalachicola eastward to the FL Big Bend
Seas will be in the 2-4 foot range increasing to 5 feet offshore Monday and Monday night before diminishing Tuesday through the end of the week.
A wetting rain will occur ahead of an approaching cold front that will cross the area on Monday. Much drier air will arrive behind the front for the remainder of the week. However, relative humidity will remain above critical values.
Locally heavy rain is possible overnight as precipitable water values increase ahead of the advancing cold front. Radar estimated rainfall totals through this afternoon have ranged from 3-5 inches in eastern Gulf county to 1-2 inches across Franklin and Liberty counties. Would expect to see similar amounts overnight with isolated heavier amounts of up to 4-8 inches doubtful but not out of the question.
The factor that is in our favor to diminish the chances of flash flooding is the progressive nature of the synoptic pattern.
A flash flood watch remains in effect overnight for the FL counties
west of the Apalachicola river.
PRELIMINARY POINT TEMPS/POPS...
Tallahassee 72 87 61 85 66 / 70 40 10 10 10
Panama City 71 84 60 82 65 / 80 10 0 0 10
Dothan 65 81 53 80 60 / 80 10 0 0 10
Albany 69 83 57 80 61 / 70 30 10 10 10
Valdosta 71 85 63 83 64 / 50 60 20 20 10
Cross City 71 87 65 86 66 / 50 60 20 10 20
Apalachicola 72 84 62 80 67 / 70 30 10 0 10
FLASH FLOOD WATCH through Monday morning for Calhoun-Central
Walton-Coastal Bay-Coastal Franklin-Coastal Gulf-Holmes-Inland Bay-Inland Franklin-Inland Gulf-Inland Walton-Jackson-Liberty-South Walton-Washington.