Area Forecast Discussion
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407
FXUS62 KTAE 170123
AFDTAE

Area Forecast Discussion
National Weather Service Tallahassee FL
823 PM EST Sat Dec 16 2017

.UPDATE...

No significant changes were made to tonight`s forecast as high
clouds will gradually increase overnight; lows will be in the 40s
inland with lower 50s near the Gulf Coast. Chances of rain
showers have been slightly increased/expanded tomorrow throughout
the day as a warm front and increasing deep layer moisture move
northward into our area. PWAT values increasing to around 1.5" by
the afternoon and isentropic lift along with the warm front
should support the development of isolated/scattered showers
during this time; some recent runs of the HRRR have been more
aggressive with an initial wave of scattered showers near the Gulf
Coast during the late morning as well. As a result, increased
PoPs into the 20-30% range across much of our area tomorrow. A
slight downward adjustment was made to forecast highs on Sunday as
well due to increased cloud cover and rain chances, although most
areas should still see highs around 70 as southerly flow
increases behind the warm front.


&&

.PREV DISCUSSION [626 PM EST]...

.NEAR TERM [Through Tonight]...
A shortwave near the Texas Big Bend this afternoon will lift
northeastward into the Central Plains overnight. At the surface, a
cold front will advance into the Lower Mississippi Valley with rain
preceding it. However, the rain will hold off for our area until
after daybreak. Look for increasing clouds through the period with
lows in the lower to mid 40s.


.SHORT TERM [Sunday Through Monday Night]...
Moist isentropic ascent will begin over the western portions of
the forecast area Sunday morning with increasing chances of rain
by midday along a frontal zone extending from coastal LA into West
Central Georgia. Model guidance suggests the lift will maximize
by 18z Sunday and then diminish into the evening.

By Sunday evening, another batch of forced ascent will lead to
more widespread shower activity across the Central Gulf Coast
States. With the best lift remaining focused just west of our
region, will maintain a tight W-E PoP gradient across the forecast
area. The big difference to the forecast by Sunday night will be
the much warmer than normal overnight lows in the upper 50s to low
60s.

On Monday, the frontal zone will continue lifting north of the
region in response to ridging building east of the Florida
Peninsula. Rain chances will be decreasing south to north
throughout the daytime hours with rain chances nearing zero by the
overnight hours. Temperatures will be noticeably warmer and the
airmass more humid when compared to the previous weeks.


.LONG TERM [Tuesday Through Saturday]...
The period begins with a large ridge aloft centered over the
Florida Straits and an approaching trough in the southern stream
moving through Texas. Though Tuesday is likely to be dry and warm
with moist southerly flow ahead of the approaching system, rain
chances will increase considerably by Wednesday as the upper
disturbance moves quickly into the Mid South. Though this wave
will weaken with time moving through the Tennessee Valley,
sufficient height falls (around 60m) across the western portion of
the forecast area along with other favorable severe parameters
(0-6 km shear of 40-45kt and non-zero surface based instability)
would suggest at least some threat for severe weather on
Wednesday. It should be noted, however, that with an extensive
period of offshore flow and cooler than normal temperatures, the
nearshore shelf waters are quite cool, especially from Apalachicola
eastward, and this could have a stabilizing effect on the severe
potential across Srn GA and into the Florida Big Bend.

After the system on Wednesday, the region will be between systems
heading into the weekend. With the pattern supporting above normal
temperatures and a humid airmass, there is potential, particularly
across the western portion of the region for scattered showers
beginning Friday and continuing through the end of the period.
Unseasonably warm temperatures in the mid 70s during the day and
mid to upper 50s at night will be common by the end of the long
term period.


.AVIATION [Through 00Z Monday]...

Cloud cover will gradually increase overnight through Sunday
morning and afternoon, but VFR conditions are likely to prevail
through the remainder of the period. Only high clouds are expected
overnight, with mid-level clouds expected to increase Sunday
morning and afternoon. There will also be slight chances of
showers on Sunday late morning and afternoon, but chances are too
low at this time to include in the TAFs.


.MARINE...
Winds will shift to a more southerly component by Sunday afternoon
and briefly increase to near 15 knots. A period of lighter winds
is expected by Monday night. A storm system will approach the
marine area on Wednesday, increasing winds to near advisory
levels. Winds will then decrease in the wake of a frontal system
by Thursday and remain low into the start of the weekend.


.FIRE WEATHER...
Increasing moisture will result in high RH values from tonight
through the next several days. As a result, no fire weather concerns
are anticipated.


.HYDROLOGY...
Decent rain chances are expected on Monday and then again on
Wednesday across the region, where totals after both events could
be in the 1-2 inch range. While flooding is not expected with
either event, this rainfall will help improve the ongoing dry
conditions across the region.


.SPOTTER INFORMATION STATEMENT...

Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur by calling the office or tweeting us @NWSTallahassee.

&&

.PRELIMINARY POINT TEMPS/POPS...

Tallahassee   45  70  61  75  61 /   0  20  30  20  10
Panama City   51  69  65  74  63 /   0  30  50  20  10
Dothan        44  68  62  73  60 /   0  30  50  50  30
Albany        42  68  59  73  59 /   0  20  40  50  30
Valdosta      42  71  59  76  60 /   0  10  20  30  10
Cross City    44  73  57  78  58 /   0  10  10  10   0
Apalachicola  52  69  63  74  62 /   0  30  40  10  10

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...None.
&&

$$

UPDATE...Lahr
NEAR TERM...Barry
SHORT TERM...Godsey
LONG TERM...Godsey
AVIATION...Lahr
MARINE...Godsey
FIRE WEATHER...Lahr
HYDROLOGY...Godsey



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