Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 301541
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
1141 AM EDT THU JUL 30 2015
.Near Term [Through Today]...
A mixture of low and mid level cloud layers this morning across
the area have affected surface temperature trends through 15Z.
Most notably, it has kept many of our southwest Georgia counties
in the lower 80s. However, we expect that with further daytime
mixing that the low-level clouds will eventually scatter out
sufficiently to yield mid-90s highs over the interior northwest
half of our forecast area, with highs around 90 into the low 90s
over the remainder of the area. Dewpoints are quite high again,
and the 12Z Tallahassee sounding reveals much higher mixing ratios
in the 1000-3000 ft AGL layer this morning compared to 24 hours
ago. This should allow surface dewpoints to generally persist in
the mid 70s through the day across much of the area, and the upper
70s to around 80 near the coast. This will generate a fairly broad
area of maximum heat indices around 107-110 degrees - which is
near the criteria for a Heat Advisory. Given the abundance of
cloud cover, some convection already initiating, and coordination
with WFOs MOB and BMX, we will hold off on an advisory although a
few scattered locations in the western half of the area could
briefly hit advisory criteria. Overall heat indices of 105-110
are expected in much of the area.
Pivoting to convective expectations, some isolated convection was
already initiating over land areas in the 14-15Z timeframe. We
expect convective activity to gradually become more widespread by
19Z (3 PM EDT) over our Florida zones. Through propagation of
outflow boundaries, other locations reaching their convective
temperature, and a surface trough over the forecast area, these
showers and storms are likely to expand to the rest of the area in
the afternoon hours. Therefore, we expanded "likely" PoPs (60-70%)
into the entire forecast area during the afternoon hours. The 12Z
Tallahassee sounding measured a precipitable water value of 2.12"
and model forecasts suggest 2.1" to 2.2" PWATs across the area
today with high freezing levels. This suggests very efficient
rainfall producers and locally heavy rain. As was the case
yesterday, frequent lightning will be likely in many storms, and a
few storms could also produce strong-severe winds.
.Prev Discussion [350 AM EDT]...
.Short Term [Tonight Through Saturday]...
East-west oriented mid-level ridge axis will remain just north of
the forecast area on Friday, with the surface trough stretching
across the Florida Panhandle into southern Georgia. Deep layer
moisture will remain plentiful across the region, with scattered
to numerous showers and thunderstorms expected to develop during
the afternoon and evening hours. Best rain chances will be along
and south of the surface trough (far southern Georgia into the
Florida Big Bend). A few severe storms cannot be ruled out, with
mid-level northwesterly flow still around 20 knots.
By Saturday, the mid-level ridge axis will shift slightly south.
However, the surface trough will remain generally stationary.
The southward shift of the ridge axis should help to reduce
coverage for the northwestern third of the area. However, the
remainder of the region will see another active afternoon of
.Long Term [Saturday Night Through Thursday]...
Late in the weekend into early next week, the upper ridge will
weaken as a trough deepens over the eastern half of the country.
At the surface, the weak trough of low pressure is expected to
remain relatively stationary along the northern Gulf Coast. Best
rain chances into next week will be along and south of the
surface trough, with slightly drier air filtering in north of the
[Through 06Z Friday] Scattered to numerous TSRA are expected this
afternoon across the area, some of which will likely contain gusty
winds. The highest coverage is expected to be near KTLH and KECP
with slightly lower coverage around KDHN and KABY this afternoon.
Outside of convection, VFR conditions are expected.
A lingering trough of low pressure along the northeastern Gulf
Coast will keep light southwesterly to westerly winds in place
over the coastal waters through the weekend. Scattered to numerous
showers and thunderstorms each day will generate locally higher
winds and seas.
Red flag conditions will not occur for the next several days.
Rain chances will remain elevated through the rest of the week
with 5 day estimated rain totals around 3-4" along the coast,
especially in the southeastern Big Bend. Elsewhere, 1.5-2.5" is
likely. Area rivers are still below action stage. With the
heaviest rainfall expected near the coast, river flooding is not
expected. However, localized flooding will be possible with the
.Preliminary Point Temps/PoPs...
Tallahassee 94 76 90 75 91 / 60 30 60 40 60
Panama City 91 79 87 78 87 / 60 40 60 40 50
Dothan 96 76 92 74 91 / 60 40 50 40 50
Albany 96 76 91 74 91 / 60 30 50 40 50
Valdosta 92 75 90 74 90 / 60 30 60 40 60
Cross City 91 75 88 75 88 / 60 30 60 40 60
Apalachicola 91 78 88 78 88 / 60 40 60 40 40