Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 182058
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
258 PM CST Sun Feb 18 2018

.NEAR TERM...(Tonight)
Issued at 258 PM CST Sun Feb 18 2018

A stratus deck covering locations south of the greater Huntsville
forecast/warning area area, as promised earlier continued to advect
to the northeast. The northern edge of these clouds were roughly
noted in a line from near Corinth MS to south of Huntsville and Ft
Payne. Isolated light showers were occurring under these clouds, even
close to the leading edge.

Rather warm temperatures reigned across the greater Tennessee Valley,
ranging in the the upper 50s to lower 60s. The showers per high
resolution models should continue off/on the remainder of this
afternoon and evening, then taper off from SW to NE after midnight.
Compared to last night, warmer nighttime lows are expected with lows
in the mid 50s. "Normal" lows are in the mid 30s this time of year.

.SHORT TERM...(Monday through Tuesday night)
Issued at 258 PM CST Sun Feb 18 2018

Earlier analysis of 12Z upper air data revealed an upper low moving
southward along the Pacific NW coast. This low will help carve out
a deep trough over the western CONUS, kept from moving eastward in
part by a strong upper high situated north of the Bahamas and east of
Florida. This more amplified pattern will result in slower eastward
movement of the systems to our west eastward. It will also bring more
warmer air northward across the region. Thus lower to mid 70s for
highs are expected for Washingtons Birthday/Monday. Normals this time
of year are in the mid to upper 50s.

Even warmer temperatures expected tomorrow night and Tuesday.
Nighttime lows will fall only into the mid 50s to lower 60s. Highs on
Tuesday will rise into the mid/upper 70s. Record high temperatures
tomorrow and Tuesday could be given a run for the money (especially
on Tuesday). Respective standing records then are 79/1917 and
79/1986, in Muscle Shoals and Huntsville respectively.

Another change from the recent wet trend, decided to keep Mon-Tue
dry, but brought scattered showers back into the picture Tuesday
night, as deeper moisture and better lift is realized across the
Tennessee Valley.

.LONG TERM...(Wednesday through Saturday)
Issued at 258 PM CST Sun Feb 18 2018

The forecast area will be situated between an upper trough extending
through the Intermountain West and a fairly strong subtropical ridge
over the southeastern CONUS and eastern seaboard at the start of the
long term period. A cold front will be meandering over the central
CONUS and approach the TN Valley on Wednesday. Ahead of this front,
moisture will continue to advect northward as southerly flow
persists at the surface and southwesterly flow persists aloft. The
upper trough over the west will weaken quite a bit as it progresses
eastward, while the upper ridge maintains a strong hold to our
southeast. This will make it hard for the cold front to make much
progression, which is evident in the models forecasts, as they
continue to struggle with the evolution of this system. At this
point, it does seem clear that the front will make it at least into
the Mississippi Valley, with rain chances increasing across the TN
Valley during the day on Wednesday. The GFS continues to be the more
progressive model, swinging the front through on Wednesday, before it
stalls to our south. Meanwhile, the ECWMF hangs it up just to our
north, leaving the potential for outflow boundaries to move into the
region and generate precip. Still too far to go into much detail
about mesoscale features, but for these reasons, have maintained the
blended guidance of likely pops on Wednesday, with higher chances on
Wednesday night given the possibility of the front sagging through
the area.

The front looks to be within the vicinity of the TN Valley from
Thursday through Saturday. Meanwhile, southerly flow through the
vertical column will keep a rather moist profile across the area.
This will mean a continued wet pattern for the TN Valley at the end
of the week. It`s difficult to pinpoint which days will have the
higher potential for rain, so have kept chance pops in the forecast
for Thursday night and onward. The front looks to finally move
through the area on Saturday, bringing a higher chance for showers
Saturday and Saturday night, along with isolated thunderstorms.
Still a lot of uncertainty, so undercut the guidance a little due
the discrepancies noted in the midweek front.

Temperatures through much of the extended period will be well above
normal for late February given the strength of the ridge and upper
level heights. Rain and cloud cover may help, but the slow movement
of the cold front and continued WAA will likely overcome any precip
to help temps warm into the upper 60s to upper 70s during the period.
The warmest day will likely be on Wednesday, as the front remains to
our north at this time. Overnight lows will be on the warm and muggy
side, with temps remain in the upper 50s to lower 60s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1140 AM CST Sun Feb 18 2018

VFR flying weather across the Tennessee Valley, will deteriorate in
the mid/late afternoon and evening, as lower level stratus returns
from the south. The northern edge of those clouds extended west-east
from north of Columbus AFB MS to north of BHM and near I20 and the
AL/GA border. MVFR CIGs under this deck were 10-20 nmi south of
leading edge of the stratus. The northward movement of these clouds
should result in MVFR ~2000-3000 ft AGL over KMSL and KHSV by the
late afternoon. Along with the clouds, VCSH are also possible, mainly
in the late afternoon and evening. Lower MVFR CIGS ~1000-2000` AGL
are forecast for late tonight and Mon AM. SE winds should also
increase into the 5-15 kt range by late Mon AM.


&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&

$$

NEAR TERM...RSB
SHORT TERM...RSB
LONG TERM...73
AVIATION...RSB


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