Lightning Strike in Florida, June 20, 2022

Area Forecast Discussion
National Weather Service Tallahassee FL
102 PM EDT Mon Jun 20 2022

.AVIATION...
[Through 18Z Tuesday]

Seabreeze thunderstorm(s) continue to be indicated with VCTS at
TLH and ECP for a few hours late this afternoon and early evening.
Otherwise, the remainder of the terminals will remain dry with
SCT cumulus. Winds East-Southeast 5-10 kts today will become West-
Northwest around 5 kts on Tuesday.

&&

.PREV DISCUSSION [1110 AM EDT]...

.UPDATE...

Hourly temperatures are outperforming a bit, so raised those just
a scoche, with no changes to the forecast high temperatures. Also
raised PoPs slightly, mainly in the FL Panhandle, where a higher
PWAT air mass resides. No additional changes were necessary from
the near term section below.

&&

.NEAR TERM [Through Tonight]...

A very strong upper high is centered over the Mid-South, and 500
mb heights today will approach the SPC sounding climatologys max
moving average for the date. However, low-level easterly flow
continue to bring in Atlantic-influenced air and hold high temps
merely in the mid 90s.

Northeast flow aloft will further dry out the mid-levels.
Except for the FL Panhandle, Precipitable Water (PW) values will
fall into the 0.9-1.3 inch range, which is generally not enough to
support summertime air mass thunderstorms. As mentioned, the FL
Panhandle will keep enough moistening seabreeze during the day for
a scattered storms along and south of I-10. The Nature Coast could
also see some seabreeze thunderstorms, but the prevailing
northeast flow should pin the seabreeze there fairly close to the
coast.

.SHORT TERM [Tuesday Through Thursday]...

The cooling easterly low-level flow will collapse after Tuesday
morning, and a hearty warming trend will get underway. Curiously,
models show a heat-induced surface low forming over the Atlantic
Coastal Plain of the Carolinas and Georgia on Tuesday afternoon as
an upper ridge axis pivots southeast across the Appalachians.
Such a heat low is more commonly associated with the Desert
Southwest, but it basically forms because of the lightness and
buoyancy of hot air. Rising upper heights and lowering surface
pressure will really boost low-level thickness values and heat.

On Wednesday, the heat low will still be off to our east.
Counterclockwise flow around this feature will support a northerly
breeze that day. This will pin the Gulf seabreeze right along the
coast and prevent the cooling seabreeze from penetrating more than
about 5 miles inland. Then on Thursday, the heat low will pass
directly across the forecast area. So Thursday is when temps will
top out.

On Wednesday and Thursday, deterministic runs of the GFS and EC
top our 850 mb temps in the 24C-26C range, which would shatter the
daily max values for 850 mb temps that are closer to 21C. GEFS
mean 850 temps of 23C still handily beat the record in the SPC
sounding climatology. The current official forecast for Thursday
shows inland high temps reaching 100-105 degrees, with daily
record highs already forecast to be tied or broken at ABY, VLD,
and TLH. This is conservatively based on the lower ensemble mean
values. However, the deterministic GFS-based MOS guidance for TLH
specifically forecasts 105 degrees on Wednesday, which would tie
the all-time record high. It is certainly in the realm of
possibility that we could break the all-time record, especially
given long days and intense sunshine during this summer solstice
week.

From a comfort standpoint, the only silver lining is that deep
mixing and northerly winds on Wed will support afternoon
dewpoints in the 60s, inland of the seabreeze. This will not
provide much boost to the heat index over the already sizzling air
temperatures. By Thursday, the seabreeze and its higher dewpoints
will penetrate further inland over our FL counties, providing a
dangerous boost to the heat index.

The air mass will be too dry for our common summer thunderstorms.
At most, a little nighttime convection over the 86-degree Gulf
waters is possible.

.LONG TERM [Thursday Night Through Monday]...

Late this week, the giant upper high over the Mid-South will
retrograde west across the Southern Plains and reach a more
climatologically favored position over the U.S. Southern Rockies
by this time next week. That surface heat low will move west in
tandem, exiting our area into western Alabama and Mississippi on
Friday. South and southeast low-level flow will bring a more
substantial return of maritime air. This will start to bring
daytime air temperatures down a few degrees each day from Friday
through this weekend (the cooling trend might wait til Saturday
over Alabama Wiregrass country). However, gross dewpoints in the
mid-upper 70s will return, contributing to heat index. The heat
index over our FL counties on Friday is currently forecast to
reach the 107-114 degree range.

The return of maritime air will boost PW values enough to support
more typical afternoon and evening thunderstorms again. The
initial return of scattered thunderstorms is now forecast for
Friday. Until the mid-level moisten up later in the weekend,
thunderstorms will have particularly high gusty potential.

.MARINE...

High pressure over the Carolinas will support easterly flow
through Tuesday morning, interrupted by nearshore afternoon
seabreezes. Winds over the northeast Gulf will become
southwesterly late Tuesday, as low pressure develops over eastern
Georgia and the eastern Carolinas. That low will slowly move
westward on Thursday, arriving over Mississippi around Friday.

.FIRE WEATHER...

A warming and drying trend early this week will culminate in
near-record high temperatures and unseasonably low relative
humidity on Wednesday and Thursday. By Wednesday, the mixing
height may exceed 10,000 feet! High dispersion values are expected
over Georgia districts on Tuesday, with very high dispersion on
Wednesday for all but the immediate coast. Given these factors,
fire weather concerns are high this week.

.HYDROLOGY...

No river or large-scale flooding is expected in the next 7 days.
Thunderstorms will be hard to come by through at least Thursday.
Thunderstorms will first re-emerge on Friday, and coverage will
ramp up through this weekend toward summertime normals. Of
course, thunderstorms come with heavy downpours which can bring
short- lived drainage issues.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur (while following all local, state, and CDC guidelines) by
calling the office or tweeting us @NWSTallahassee.

&&

.PRELIMINARY POINT TEMPS/POPS...

Tallahassee   96  71  98  73 102 /  20  20   0   0   0
Panama City   93  75  94  77  98 /  30  20  10  10   0
Dothan        96  71  97  73 100 /  10   0   0   0   0
Albany        97  70  99  72 103 /   0   0   0   0   0
Valdosta      95  67  97  70 102 /  10   0   0   0   0
Cross City    94  68  96  72  97 /  40  10   0   0   0
Apalachicola  90  77  91  77  95 /  40  20  10   0   0

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through this evening for Coastal Franklin.

GA...None.
AL...None.
GM...None.
&&

NEAR TERM...Haner
SHORT TERM...Haner
LONG TERM...Haner
AVIATION...LF
MARINE...Haner
FIRE WEATHER...Haner
HYDROLOGY...Haner