Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 192118

Area Forecast Discussion
National Weather Service Huntsville AL
318 PM CST Thu Jan 19 2017

.NEAR TERM...(Tonight)
Issued at 317 PM CST Thu Jan 19 2017

Widespread showers were in progress across the greater Tennessee
Valley this afternoon, as a warm front returns northward. This
frontal boundary was from north of Lawrenceville and Huntsville to
near Ft Payne. Despite the front/clouds/showers, very warm
temperatures for mid January continued with mid/upper 50s over
southern middle Tennessee and far NE Alabama to the lower 60s near
and south of the Tennessee River. All in all with these showers,
lightning has been a rare occurrence around these parts so far. But
sporadic strikes were occurring across central Alabama west of I-65
and most of them south of I-20. Given radar trends with some of the
stronger cells nearing the region, this area could experience a
strike or two during the remainder of the afternoon.

An upper low across eastern Kansas has produced a diffluent flow
across much of the southeastern states, including the Tennessee
Valley. The water vapor view, along with forecast heights/vorticity/
omega fields indicate more upper level disturbances in a negatively
tilted orientation moving across the region tonight. So will keep
predominate showers with a few thunderstorms in the forecast. Given
brief strong shear, wind gusts to 50 mph and locally heavy rains are
the primary risks this evening. Shower activity should wind down from
west to east during the overnight. Given light winds, warm temps and
plenty of residual moisture, introduced patchy fog across the area
in the late night. Thinking that fog that forms will be mainly
in/near wind sheltered locations. Lows will be only in the mid 50s,
above normal highs this time of year around 51.

.SHORT TERM...(Friday through Saturday)
Issued at 317 PM CST Thu Jan 19 2017

For Friday, shower activity should continue waning from west to east
during the morning, with dry conditions expected from the late
morning into Friday evening. With the short dry spell, a few peeks of
sun are possible as the cloud deck thins; before the next system out
west nears.

Another, and stronger system in the meanwhile will be taking shape
over the southern plains and headed this direction. It will bring
another chance for more showers for the forecast area late Friday
night and during much of the weekend. The forecast models, especially
the GFS and ECMWF depict two systems moving across the region. The
NAM and its DGEX extended (especially the latter) went more with a
single surface low. Going with the double barrel effect, widespread
showers/thunderstorms look more likely during Saturday as the first
low traverses the region. While this low was not particularly strong,
a modest amount of shear in an already unstable environment could
produce marginally severe storms. The main threat with lower wet-bulb
zero heights ~7000 feet could be marginally severe hail and wind
gusts. The second low appears to be stronger with central pressures
at or below 1000mb (pretty good for this area). Along with
categorical rain chances, strong to marginally severe storms are also
possible with it during Sunday.

.LONG TERM...(Sunday night through Wednesday)
Issued at 317 PM CST Thu Jan 19 2017

The weekend will end on a soggy note with rain continuing
through Sunday Night. As the trough lifts NE Monday, precip chances
will decrease throughout the day but northerly winds will remain
breezy. With cooler and drier air filtering in, party cloudy skies
and colder overnight temps in the upper 30s are in store for Monday
night. The ECMWF is the faster solution compared to the GFS with
moving the trough up the East coast, however the trend remains the
same. Behind this system, dry conditions and unseasonable temps
around 60 degrees are expected on Tuesday as a ridge builds. The
warm temps stick around Tuesday night, lows mid/upper 40s, but the
ridge doesn`t as the next system swings across the Midwest. The next
best chance of rain will be on Wednesday as a weak cold front
associated with the Great Lakes sfc low moves through.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1140 AM CST Thu Jan 19 2017

As a developing storm system and cold front approach from the west,
extensive clouds and inclement flying weather is expected for the
period. As of issuance time, scattered to numerous showers and a few
embedded t-storms were affecting areas mostly west of the I-65
corridor and south of the Tennessee River towards northeast/central
Alabama. This activity should overspread the region this afternoon
and evening. Thus mainly MVFR CIG/VIS values are expected, with
reductions to IFR in and near the heavier showers and/or storms. The
main area of showers should be east of the region before daybreak
Friday. However lingering low clouds and light post system rain will
produce IFR (mainly low ceilings) through late Fri AM.





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