The long wave pattern remains substantially unchanged from what we have seen over the past few days. The highly anamolous blocky
pattern over the CONUS features a ridge over the Southwest, a
trough axis from the Upper Mississippi Valley to the Southern
Plains, and a ridge off the Mid Atlantic coast. The forecast area
remains stuck in between the latter two with deep layer onshore flow
through the entire troposphere. Satellite derived Total Precipitable
water values remain around 2 inches with higher values offshore.
Model consensus brings these 2+ values ashore into our western zones again today. Unfortunately the various CAMs, particularly the 00Z run of the local WRF indicate we will see yet another round of
potentially torrential downpours.
If things evolve as expected, this will be the third consecutive day of flooding rains for parts of the Florida Panhandle. Parts of Bay, Washington, Holmes and Walton Counties could easily see another 3-5 inches of rain. Flash flood guidance is down to around 0.5-1 inch per hour in some of these areas, so the flooding could be subtantial.
Needless to say, the flash flood watch will be maintained and extended out in time. Our confidence in the flash flood threat is lower for the northern and eastern portions of the watch area, but we will defer to the day shift any decision about further reduction in the area. We did extend the watch out in time through 12z Saturday and would not be surprised if a further extension into Saturday eventually becomes necessary, at least for our Panhandle zones.
With all of the clouds and persistent showers, the MOS guidance has
been of little use lately with daytime temps. We undercut it
considerably across the western zones and by a few degrees to the
Finally, along the coast, we will see surf heights gradually subside
and the advisory will be allowed to expire for Bay and Walton
Counties later this morning. The high risk for rip currents has been
trimmed back to include only Walton County. That said, it should be
understood that dangerous rip currents will still be possible
further east where a moderate risk is in effect.
SHORT TERM [Tonight Through Sunday]...
The large scale longwave blocking pattern remains highly amplified into tonight. This is highlighted by ridge over Wrn states, trough across Cntrl states Ewd to Ern states with axis vcnty of Mid MS River Valley and with a low over MO, and a strong ridge Ewd over Ern seaboard into Wrn Atlc. At surface, N-S weak and dissipating front from Great Lakes to LA. High east of Carolinas with axis Ewd to Ern seaboard. All this continues a fetch of deep layer moisture nwd across gulf region with PWATs hovering around 2 inches. TAE GFS sounding with strong unidirectional SWLY flow from sfc-H3 so high POPs flooding concerns continue especially SE AL and adjacent Panhandle.
During the rest of the weekend, the trough and assocd low will
continue to lift newd with Atlc ridge building further west as reflected in slow warming of H5 temps and rising heights.
Area of highest rainfall shift slowly Wwd and W of our CWA. By Sun eve, base of trough axis has lifted to Nrn TN Valley with stacked ridge and drier air further encroaching SWWD on CWA. Also by that time,
low moves wwd to reach Bahamas. At surface, absent lifting upper
support, front loses its identity but assocd low lifts Newd.
Still, deep and moist and nearly uni-directional sly sounding
profiles with PWATs AOA 1.8 inches remain wrn sites down to ely
flow and AOB 1.5 inches east at 00z Mon.
Thus rain will slowly decrease from E-W thru the period POPs but remain AOA climo, especially Wrn counties and each aftn. Localized and river flooding issues continue thru weekend.
Will go with 40-70% E-W POP gradient on Sat and 20-60% SE-NW on Sun, 40-60% NW-SE tonight and 30-40% E-W Sat night. Based on persistence used a blend of HPC/GFS/ECMWF/CAM max/min and simple QPF for my QPF totals. This yields sharp NW-SW QPF totals thru rest of the period from around 0.6 inches Ern most GA counties to about 5.00 inches Walton county. E-W cloud/rain gradient will also impact temps. Temp forecast tricky as normal guidance keeps coming in way too warm daytime especially for Wrn counties. Based on recent tends went with a blend of CMC/ECMWF/GFS and NAM which showed sharp W-E gradient on Sat with upper 70s west to mid-upper 80s east. Mid 80s to low 90s East.
LONG TERM [Sunday Night Through Wednesday]...
The upper level trough extending down from the Midwest continues
to deamplify and lift to the northeast allowing the west and east
coast ridge to merge by Monday.
The persistent plume of deep layer moisture will linger over our region through Sunday. At the surface, high pressure will be centered just east of the mid- Atlantic states with the axis extending westward through the Lower Mississippi Valley and north of our CWA. Although a moist southeast flow will continue in the lower levels, we should see an intrusion of drier air in the mid- levels Monday through Tuesday.
Deep layer moisture is forecast to return on Wednesday as a
tropical wave moves into the eastern Gulf of Mexico. PoPs will be
tapered from likely (60-70%) west to mid range chance (40%) east
on Sunday. Mid Range chance (40%) on Monday. Below climo PoPs
(20-40%) for Tuesday with seasonal PoPs returning on Wednesday
(40-50%). Max temps will be around 90 degrees with min temps in
the lower 70s.
We could see a brief period of IFR/MVFR ceilings in the pre-dawn hours this morning. The rest of this forecast was based largely on persistence and the 00z local WRF. Unfortunately, this means a substantial portion of the forecast period will feature more heavy rains at ECP and DHN with persistent MVFR and periods of IFR conditions along with gusty winds. Further east at TLH, we expect two rounds of rain, one in the morning and another in the afternoon. While the prevailing conditions will be showers, we cannot rule out thunderstorms. In any heavy showers or thunderstorms, conditions will be MVFR with brief IFR possible. At ABY and VLD, we are limiting convection to the afternoon and evening hours with periods of MVFR possible.
Weak Gulf low pressure has moved onshore allowing the formerly
tight pressure gradient to weaken. As a result winds and seas continue to decrease. The small craft advisory has been dropped for the waters east of Apalachicola and is expected to drop below advisory levels for the western waters this afternoon.
Conditions will improve FURTHER through the weekend.
Red Flag conditions are not expected in the foreseeable future.
The flash flood threat continues across the western half of our
forecast area through at least Saturday morning, with the greatest
threat across the Florida Panhandle.
Additional rainfall amounts of 2 to 3 inches are likely in the watch area, but 3 to 5 inches are expected in the Panhandle. In fact, localized amounts of 5 to 10 inches are still possible in the areas that have already seen excessive rainfall during each of the past two days. Outside the watch area, 1 to 2 inches of additional rain is possible.
On area rivers, the St. Marks near Newport has risen to moderate
flood stage, but appears to have crested.
The Apalachicola River at Blountstown is also forecast to rise to minor flood stage this evening.
The Aucilla River near Lamont is expected to reach minor flood stage Saturday morning with a crest Sunday afternoon.
The Choctawhatchee River has crested just above minor flood stage at Newton.
At Caryville, the river should crest about a foot below moderate flood stage Saturday night.
Downstream at Bruce, the river will rise to moderate flood stage this evening and get very close to major flood stage early next work week.
We are keeping a close eye on the Shoal River at Mossy Head additional possible heavy rain could potentially push that river into flood stage as well.
PRELIMINARY POINT TEMPS/POPS...
Tallahassee 83 72 84 72 89 / 80 40 60 30 40
Panama City 78 75 86 75 85 /100 50 60 40 50
Dothan 76 72 77 72 86 /100 40 60 40 60
Albany 84 72 83 72 90 / 90 40 50 30 50
Valdosta 87 71 87 71 91 / 70 40 40 30 40
Cross City 86 72 86 71 90 / 70 40 50 30 20
Apalachicola 81 77 86 76 85 / 90 50 60 40 40
FLASH FLOOD WATCH through Saturday morning for Calhoun-Central Walton-Coastal Bay-Coastal Franklin-Coastal Gulf-Gadsden-
Holmes-Inland Bay-Inland Franklin-Inland Gulf-Inland Walton-Jackson-Liberty-South Walton-Washington.
HIGH RIP CURRENT RISK WALTON COUNTY.
HIGH SURF ADVISORY WALTON AND BAY until 7 AM CDT.
FLASH FLOOD WATCH through Saturday morning for Baker-Calhoun-
FLASH FLOOD WATCH through Saturday morning for Coffee-Dale-
SMALL CRAFT ADVISORY until 2 PM EDT this afternoon for Coastal
waters from Apalachicola to Destin FL out 20 NM-Waters from Apalachicola to Destin FL from 20 to 60 NM.