Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Tallahassee Florida
923 PM EDT Wed Apr 23 2014
Near term [through tonight]...
the regional mid/upper pattern is marked by a large ridge of high
pressure with subsidence aloft. At surface...a weak frontal
boundary located invcnty of I-10 at 9 PM EDT will move swd into
the waters overnight leaving a rather weak pressure pattern in
place. This boundary marked on satellite by thinning cumulus. In its
wake...drier air clearly will slowly shift swd in tandem with
front. All this reflected in rap13 00z soundings which show light
northerly flow becoming calm after midnight at lowest levels and westerly
flow above. However with proximity of front...lowest level still
moist with precipitable waters near 1 inch over North Florida down to around 0.8 inches
across southeast Alabama and nrn tier Georgia counties decreasing to 0.8 to 0.6
inches S-north by sunrise.
Dew points ranging from mid 50s north to around 60f across coastal
counties plus near calm winds will favor the development of at least
patchy fog after midnight for al/GA....areas of fog inland North Florida and
areas of dense fog coastal Florida counties. Cam/sref/local confidence
fog products all show this trend. Would not be surprised of a dense
fog advisory is issued for portions of our County Warning Area...especially south of
I-10. Other than a stray shower or sprinkles along the coast or
adjacent waters before midnight...no rain is expected. Expect lows
from mid 50s nrn most counties to around 60 coastal counties.
Aviation...[through 00z friday] lingering cloud cover around 5000-7000
feet should quickly dissipate this evening, leaving mostly clear
skies. Model forecasts consistently Show Low ceilings and fog
advancing inland from near the Gulf Coast later tonight,
especially after 06z. Some of the fog could be dense. We included
1/2sm fog at tlh and ecp, with some IFR fog at vld and MVFR at dhn
and aby. By 14z, we are forecasting all terminals to be VFR for
the remainder of the period.
Prev discussion [307 PM edt]...
Short term [thursday through Friday night]...
surface high pressure and light southeast flow at the lower levels
over our area should force a sea-breeze over the Panhandle and Big
Bend tomorrow, but with a fairly dry airmass in place, this isn't
expected to cause a lot of rain so much as an increase in afternoon
cloud cover over the area, although an isolated shower cannot be
ruled out. With a mid-level shortwave over the western Florida
Peninsula and south-central Georgia, however, the chance for
thunderstorms and showers increases slightly (to around 30%) for the
eastern portions of our forecast area tomorrow afternoon. Highs
Thursday will be in the mid 80s with noticeably cooler temps along
the immediate coastline in the upper 70s to low 80s. Lows Thursday
night will stay around 60.
On Friday, an approaching cold front will begin to decay as it
approaches US with the upper level low supporting it begins to
de-amplify and lift northeastward. Rain chances will be around 20%
for our southeast Alabama and southwest Georgia counties on Friday
with highs in the mid-80s once again and lows in the low 60s.
Long term [saturday through wednesday]...
the period begins with upper level ridging in place with surface
high pressure off of the coast of South Carolina. To our northwest,
an upper level low will begin to deepen over the Central Plains as a
shortwave trough propagates through it, deepening a surface low
beneath it. As the shortwave trough swings through Monday, the low
will become cut off and move eastward, pushing the surface low
across the plains and into the Ohio Valley. The associated front
will bring thunderstorms to our area Monday through Tuesday. The GFS
is showing around 1000-1500 j/kg MLCAPE and 30-40 kts, so there is
the potential for some of these storms to be strong to severe. The
system may linger over the eastern portion of the forecast area
Tuesday night-Wednesday, but instability will be lower by mid-week,
reducing the chances of severe weather.
nocturnal surges in the Apalachee Bay and afternoon surges along
the coastline due to the sea-breeze will bump up winds to around
15 knots, with winds further offshore staying around 10 knots or
less and seas around 1 to 2 feet through the weekend. Ahead of our
next cold front, winds and seas will begin to pick up Monday, but
are expected to remain below headline criteria at this time.
relative humidity levels will remain above critical thresholds into
the weekend. Thus, hazardous fire weather conditions are not
most of our area rivers are above normal stage with many in flood
stage. The Choctawhatchee at Bruce is at major flood stage. Most
area rivers have already crested with the exception of the Suwannee
where river levels will rise slowly for the remainder of the week.
The next chance for any significant rainfall is next Tuesday.
The most up-to-date river forecast information can always be found
on our ahps Page (below).
Preliminary point temps/pops...
Tallahassee 60 84 60 85 63 / 0 10 10 10 10
Panama City 64 77 63 75 66 / 10 10 10 10 10
Dothan 57 84 60 85 62 / 0 10 10 20 10
Albany 56 84 60 86 62 / 0 10 10 20 10
Valdosta 59 85 59 85 61 / 0 20 20 10 10
Cross City 59 83 58 82 62 / 0 20 10 10 10
Apalachicola 62 75 61 74 65 / 10 10 10 10 10