NEAR TERM [Today]...
This is a tricky forecast due to a large amount of uncertainty with
the developing area of low pressure in the northeast Gulf.
The hi-res models, especially our local ARW runs, are aggressive with this feature and start moving it northward during the day today. The GFS also has a weak area of low pressure, but it never develops it to the extent that the hi-res guidance does. The NAM is somewhere in between.
This has large implications for rainfall amounts and the potential for flooding. Satellite and radar imagery does confirm that an area of low pressure appears to be developing in the northeast Gulf, but at this time we feel that the hi-res models are overdoing it a bit with respect to this low.
However, this will have to be watched very closely by the next shift, and if it appears that our local 00z ARW is going to be right after all, then the forecast rainfall amounts and flooding impacts would have to be increased considerably into tonight.
Regardless of which solution verifies, today is expected to be
another high PoP day across most of the area with plenty of deep
layer moisture lingering. Highs are expected to be below normal.
SHORT TERM [Tonight Through Tuesday]...
Models continue to show a highly unusual pattern for July over
much of the U.S. during this period.
The upper trough that is currently digging southward toward the Gulf Coast is forecast to cut off from the jet stream and form a closed low over the Ohio Valley. This upper low is expected to retrograde toward the west throughout the period, possibly reaching the southern Great Plains on Monday.
Another feature to watch for this period is a weak low in the NE Gulf that some models are developing from Saturday night into Sunday along the weak stationary front in this region.
Still uncertain how much this feature would develop due to
inconsistencies in the past few hi-res model runs, and where it
would come onshore if it does develop.
The main threat from this feature would be heavy rain, which, depending on its track, could aggravate flooding issues in areas that have received heavy rain recently.
Regardless of how much the surface low develops, above average
chances for precipitation will continue through most of the period
as the surface front should remain stalled near our area through
at least Monday. Also, moist southeasterly flow from the Gulf is
forecast to continue through this time and will keep PWAT values
around 2" over our area.
During Monday night, a tropical wave from the Atlantic is forecast to move through our region. Precipitation chances may diminish a bit by Monday night into Tuesday, as our pattern will likely be dominated by easterly flow and a broad area of high pressure at the surface during this time.
LONG TERM [Tuesday Night through Friday]...
By the start of this period, the upper low will have retrograded all the way to the Southern Plains with a large upper high centered over
Ohio ridging southward to the Northeast Gulf of Mexico.
The surface ridge will be displaced a bit to the east of the upper feature, but will still ridge into our area.
The deep layer ridging would normally suppress convection below typical summertime levels. However, a series of easterly waves will work their way across the FL Peninsula during this time and keep PoPs closer to normal.
Temps will be close to normal overnight and a couple of degrees below normal during the afternoons.
AVIATION [Through 06z Sunday]...
Unsettled conditions will continue through the period.
Occasional MVFR to IFR cigs are expected through mid-morning, followed by scattered to numerous showers and thunderstorms.
The greatest chance of showers and thunderstorms is expected to reside across KTLH and KVLD.
While winds and seas over the marine area will initially be light,
a weak surface low is developing about 150 miles south of Panama
This low is expected to slowly move northwestward and bring increasing winds and seas to the area late tonight and into Sunday.
After the low pressure area moves away from the region, moderate easterly flow will prevail into the middle of next week as the Bermuda ridge extends westward into the Mid Atlantic States.
Red flag conditions are not expected through the period.
Most rivers in the central and western half of the region continue
to trend downward this morning with only the Lower Choctawhatchee
and Aucilla Rivers in flood stage.
The Middle Suwannee continues to rise steadily as routed flows from the Withlacoochee and Alapaha Rivers move toward Ellaville. It looks like the Withlacoochee is in the process of cresting near Pinetta with the crest of the Alapaha not quite to Statenville yet. As these flows
progress downstream it is anticipated that the Middle Suwannee
points from Ellaville down through Branford will near action stage by the latter part of next week. It is possible minor flood stage could be reached, though this depends on future rainfall as current routed flows may not be enough to reach minor flood.
Now the next rainfall event.
The area of low pressure off the Florida Panhandle coast could lead to a very favorable setup for heavy rainfall across North Florida and perhaps into Southern Alabama/Georgia starting late Saturday evening and continuing into Sunday.
Our local WRF is quite active with a strong convective band persisting through the overnight hours with 2 in/hr rates. While the eventual amounts seem overdone, the potential for areal totals of 2 to 4 inches across North Florida with isolated maximum totals nearing 6 to 8 inches appears possible should this area of low pressure drift further northward and intensify.
Because there is significant uncertainty with regards to the placement of the heaviest rain, it is just a bit too early to issue a flash flood watch, though this may be needed by the next shift.
However, with soils essentially saturated across North Florida, an
additional 2 to 3 inches of rain within a short amount of time
would easily cause localized flood problems with heavier amounts
likely causing potentially significant flash flooding.
The fast responding river basins (Sopchoppy and Shoal Rivers) will
need to be watched closely as river model simulations easily
exceed flood stage with just a couple of inches accumulating in
PRELIMINARY POINT TEMPS/POPS...
Tallahassee 85 71 88 71 89 / 70 50 60 30 60
Panama City 85 73 86 75 88 / 60 60 60 30 50
Dothan 85 71 88 71 90 / 60 40 60 30 50
Albany 85 72 89 72 90 / 70 40 60 30 50
Valdosta 85 71 91 71 91 / 70 50 60 30 50
Cross City 88 71 89 70 90 / 80 50 60 30 60
Apalachicola 83 75 86 76 87 / 80 70 60 40 50