Drought in Alabama, September 26 to 30, 2023

Area Forecast Discussion
National Weather Service Tallahassee FL
1000 PM EDT Mon Sep 25 2023

...New UPDATE, MARINE...

.UPDATE...
Issued at 1000 PM EDT Mon Sep 25 2023

Convection will start to blossom over the Gulf waters during the
next few hours, deep moisture over the Big Bend region slowly
advances northwest. Heavy rain is expected by sunrise over the
Forgotten Coast, but recent runs of the HRRR and other CAMS
guidance point to the heavy rain potential further west along the
Emerald Coast.

&&

.NEAR TERM...
(Through Tuesday)
Issued at 356 PM EDT Mon Sep 25 2023

A PV streamer coming off the far northern periphery of the tropical
wave, currently moving westward across the Gulf, will move northward
across our region tonight into tomorrow. This will overlap with a PV
streamer coming in from the NW associated with a trough moving
across the Great Lakes region. Both of these will provide enhanced
forcing for ascent, which when coupled with PWATs near or above two
inches will lead to the possibility for heavy downpours. There
doesn't appear to be much shear and lapse rates appear to be more on
the moist side, which makes sense given the environment. Thus,
primary concerns would be gusty winds and torrential rainfall. Areas
along the FL Big Bend and SW Georgia are currently the areas to
watch as higher PWATs lie in this region with lower PWATs to the NW.

Expect daytime highs generally in the mid to upper 80s with
overnight lows in the upper 60s to low 70s.

&&

.SHORT TERM...
(Tuesday night through Wednesday night)
Issued at 356 PM EDT Mon Sep 25 2023

An unseasonably moist airmass coupled with modest height falls aloft
and an approaching frontal boundary from the north maintains high
rain chances across the region through the short-term period.
Widespread cloud cover with areas of precipitation are expected.
Heavy rainfall leading to instances of isolated flash flooding
will continue to be the primary concern, though a few robust
thunderstorms capable of strong/gusty winds or even isolated
water- loading microbursts would not be surprising. Modeled
soundings depict long-skinny CAPE profiles, modest deep-layer
shear around 20- 25 kts, and very high Precipitable Waters of >2"
- supportive of the aforementioned threats. The latter flirts with
daily record values, per SPC sounding climo for KTLH. Greatest
potential for the wettest weather is across the FL counties,
especially in the Big Bend and near the coast. A Marginal Risk
(level 1 of 4) for excessive rainfall by the WPC remains in place
across much of the Tri-State area. Forecast temperatures have
highs in the low-mid 80s and lows ranging from the upper 60s to
low 70s.

&&

.LONG TERM...
(Thursday through Sunday)
Issued at 356 PM EDT Mon Sep 25 2023

Frontal boundary continues to sag southward late this week with
surface high pressure building in its wake. Meanwhile, large-scale
troughing scoots eastward toward the Mid-Atlantic region in response
to a building ridge across the middle of the US. This synoptic setup
supports continued elevated rain chances in the forecast, but more
focused along the Interstate corridors (especially I-10, southward)
into the weekend thanks to a likely meridional moisture gradient.

Looking ahead, details in the large-scale pattern become a bit
murky. In general, the building ridge noses into the Great Lakes
while the departing upper trough attempts to cut off over the
West/NW Atlantic. However, global models differ on the placement of
this feature. Further complicating matters is the potential for a
wave of low pressure to develop along the sagging front over the
Gulf. The deterministic 12Z GFS is a drier solution compared to the
12Z ECMWF given that the developing low tracks SW towards the GA/FL
coast and ushers reinforcing dry northeasterly flow into our area on
its left flank.

Forecast high temperatures are in the 80s with Thursday being the
coolest of the period given the expected cloud coverage and
precipitation. Overnight lows drop to the 60s. Locations north of I-
10 look to see readings down to the low 60s by Monday morning.

&&

.AVIATION...
(00Z TAFS)
Issued at 726 PM EDT Mon Sep 25 2023

Overnight, expect sub-MVFR cigs to set in 08Z-10Z at TLH and VLD,
with a period of LIFR cigs and fog at VLD around 12Z. At ECP, MVFR
cigs are forecast to begin around 12Z. There is some uncertainty
in the timing of cigs lowering, especially at ECP which is closer
to the fringe of the low clouds. Precip will overspread previously
mentioned terminals on Tuesday, with SHRA and thunder in the vcty
most of the day. Greatest coverage will be at TLH and VLD, with
lower confidence on north and west extent, especially into ABY and
DHN. For both of those terminals, we kept activity in the vcty
for now. It's also questionable how quickly precip exits portions
of the region, especially ECP and TLH, where we end it by 21Z attm.
Another challenge is how quickly cigs rise during the morning/aftn.
While confidence in timing category transitions is low (e.g.,
MVFR to VFR), we are confident that cigs will be slow to rise
during the day. Winds generally out of an easterly direction.

&&

.MARINE...
Issued at 1000 PM EDT Mon Sep 25 2023

An inverted trough of low pressure will slowly track westward to
the south of the Panhandle waters through Tuesday, followed by
southeast breezes. Numerous thunderstorms through about Thursday
will pose the risk of gusty winds, lightning strikes, and
potential waterspouts. Around Wednesday and Wednesday night, a
cold front will back in from the northeast. Northeast winds will
freshen, possibly becoming strong at times from Thursday night
through Saturday.

&&

.FIRE WEATHER...
Issued at 356 PM EDT Mon Sep 25 2023

Moisture is on the rise over the next few days as we transition to a
wet pattern through Thursday. There are currently no fire weather
concerns.

&&

.HYDROLOGY...
Issued at 356 PM EDT Mon Sep 25 2023

Wet weather is expected for at least the next 3 days thanks to a
rapidly moistening airmass and approaching front through mid-week.
Much of the Tri-State area is under a Marginal Risk for excessive
rainfall from Tuesday AM to Thursday AM. Isolated flash flooding
is a distinct possibility in response to torrential rain rates
and/or slow-moving, backbuilding storms. The most vulnerable
locations are in the Eastern FL Big Bend (including the coast) and
South- Central GA.

Guidance has painted much of our FL counties as focal points for the
heaviest rain. Local CAMS depict 2-day high probabilities for 3"
across much of the region and 6" along the coast. There are even
some non-zero probs for 9+" south of the Apalachicola Nat'l Forest!
The 48-hr worst case scenario shows values in excess of 4" roughly
along and south of Tallahassee. Meanwhile, the current HREF places
the greatest probabilities across the Forgotten Coast for amounts of
3-5+" over the next 24 hrs. Forecast amounts through late Thursday
are 1-3" (isolated higher).

In terms of rivers, only Aucilla - Lamont (US 27) is in action
stage, but forecast to fall below 51 ft by Wednesday afternoon. The
heaviest rainfall should be spotty enough to preclude river
flooding, especially given recent dry conditions.

&&

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur by calling the office or tweeting us @NWSTallahassee.

&&

.PRELIMINARY POINT TEMPS/POPS...
Tallahassee   72  85  72  82 /  40  70  60  80
Panama City   72  85  73  84 /  40  70  70  70
Dothan        67  86  70  83 /   0  50  40  70
Albany        67  87  71  82 /  10  50  50  70
Valdosta      70  85  71  81 /  30  80  60  80
Cross City    71  88  72  86 /  40  90  60  80
Apalachicola  74  84  74  83 /  70  80  70  80

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...None.
&&

NEAR TERM...Oliver
SHORT TERM...IG3
LONG TERM....IG3
AVIATION...LF
MARINE...IG3
FIRE WEATHER...Oliver
HYDROLOGY...IG3