Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 212146
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
446 PM EST Fri Nov 21 2014
.Near Term [Through Tonight]...
Very uneventful near term period, with mostly clear skies and a
gradual warming trend. Low temps will range from the upper 30s well
to the NE to the upper 40s near the coast.
.Short Term [Saturday Through Sunday Night]...
Nearly zonal upper-level flow locally will begin to amplify on
Saturday afternoon in response to a strong shortwave forecast to
be passing through Texas. A southern stream PV anomaly will
energize convection in the western to central Gulf on Saturday,
spreading into the northeast Gulf late Saturday night. The
developing warm front will lift into the Tri-State region very
early on Sunday morning. Anomalously high PWAT values will combine
with a strong southerly low-level jet and boundary parallel upper-
layer flow to present a threat for very heavy rainfall. Widespread
average rainfall amounts of 2.5"-3.5" will be possible over a
relatively short period of time. Due to the progressive nature of
the system, any sort of significant flooding is not expected at
this time. For further information on the heavy rain threat
reference the hydrology section below. Impressive wind shear
profiles suggest a non-zero threat for an isolated severe
thunderstorm during the overnight hours, though pretty much all
thunderstorms should be elevated during this period.
On the heels of the aforementioned system, the previously
mentioned strong northern stream shortwave will be moving into the
Tri-State region. Once again, very impressive shear profiles will
overspread the region from west to east through the late morning
and afternoon hours on Sunday. The main question will be just how
much instability will be present in the wake of the morning
rainfall. Early indications from some of our high resolution
modeling suggests a quicker progression of the morning rainfall
and thus a better chance for destabilization during the day on
Sunday, while the global-scale models indicate very little surface
destabilization and lingering rain through the day on Sunday. With
the event just starting to fall within the range of the higher
resolution models, there is quite a bit of uncertainty but given
the fact that the global-scale models tend to be a bit slow with
isentropic rain development, it is certainly possible that the
hires models may be on to something. Should the severe threat pan
out, the primary threats would be damaging winds and tornadoes
within discrete supercells.
The more dynamic shortwave will move out of the region by Sunday
evening, stalling a weak front across the region. Continued
southern stream support will keep the potential for showers and
isolated thunderstorms through the night on Sunday, but the severe
threat will have come to an end.
.Long Term [Monday Through Friday]...
The primary northern stream longwave trough will gradually
approach through Tuesday. Increased diffluence between the
northern stream and southern stream anomalies will continue to
support primarily showers across the eastern half of the region
until a stronger cold front clears out all of the rain by
Wednesday morning. Arctic high pressure will fill in across the
Southeast on Wednesday, capping afternoon highs in the 50s to
finish out the week. Overnight lows starting on Wednesday night
will fall back into, at least, the lower 30s.
[Through 18Z Saturday]
VFR conditions are expected to prevail through the period, with
some increasing cloudiness during the afternoon hours. Also, winds
nay become a bit breezy out of the E and NE (greater than 10 kts)
from early in the afternoon onwards.
Advisory level winds and seas should be expected through Sunday
associated with a complex frontal system. A temporary dip below
headline levels is expected on Monday before another strong cold
front re-introduces headline conditions on Tuesday, possibly
through the end of the week.
With increasing low level moisture and rain chances, no Red Flag
concerns are expected through the weekend. In fact, Wet Flags are
expected on Sunday.
Storm total rainfall amounts Saturday through Tuesday will be on
the order of 2 to 4 inches, with most of the rainfall coming over
a 12 hour period late Saturday night through Sunday morning. Low
river levels will likely prevent any river flooding even with
these high totals. However, there is a concern for some localized
flooding in the more urbanized locations that receive the higher
totals over a short period of time. Any decisions about a Flash
Flood watch will likely come overnight tonight, or tomorrow
afternoon when more guidance becomes available.
.Preliminary Point Temps/PoPs...
Tallahassee 45 68 60 75 64 / 0 20 100 70 50
Panama City 49 67 63 75 66 / 0 30 100 80 50
Dothan 40 65 56 74 62 / 0 10 100 80 40
Albany 39 65 56 74 63 / 0 10 100 80 50
Valdosta 43 68 58 76 64 / 0 20 100 80 50
Cross City 49 72 63 77 64 / 0 20 100 60 40
Apalachicola 51 67 66 74 67 / 0 30 100 60 50
GM...Small Craft Advisory until 7 PM EST Sunday for Coastal waters
From Ochlockonee River to Apalachicola FL out to 20 NM-
Coastal waters from Apalachicola to Destin FL out 20 NM-
Waters from Suwannee River to Apalachicola FL from 20 to 60
NM-Waters from Apalachicola to Destin FL from 20 to 60 NM.