Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 200524

Area Forecast Discussion
National Weather Service Huntsville AL
1124 PM CST Thu Jan 19 2017

For 06Z TAFS.


.NEAR TERM...(Tonight)
Issued at 832 PM CST Thu Jan 19 2017

Currently, an upper low is spinning in NE Kansas with a weak surface
low extending through southern MO. A warm front moved north across
the area earlier today with a weakening stationary front in central
MS. This front will wash out before it gets to the area. The upper
low will continue to swing to the northeast which will help push the
precip out of the local area. The back edge is almost to NW AL as of
8:30PM and hires guidance has been good tracking the timing of this
line. We should be clear of rain in NW AL by 10PM, probably earlier,
through Huntsville by midnight and out of NE AL by 2AM. There`s a
very thin band of moderate showers moving east of Muscle Shoals now
but no lightning has been reported. I am not confident yet in pulling
the thunder from the forecast given the strong dynamics. There`s
also some lingering instability and weak low level wind shear,
especially east of Huntsville. So will leave isolated thunder in
through the overnight.

Next issue is going to be what happens behind it. Although higher
level clouds will clear out, low level moisture isn`t going anywhere
fast, coupled with continued weak isentropic lift. It becomes a
question if we will see dense fog or just very low clouds and right
now it`s looking like a mix of both. Could see areas of patchy dense
fog with visibilities less than 1/2 mile but also clouds around
600ft which could obscure parts of the higher terrain.

Temps have been nearly steady, maybe fluctuating up/down a deg or
two. They should still fall into the middle 50s just with the loss of
daytime heating and the rain coming to an end.

.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 06Z TAFS through 06Z Friday night)
Issued at 1124 PM CST Thu Jan 19 2017

Ceilings will continue to be a challenge tonight with IFR/LIFR
conditions earlier and now bouncing back to VFR behind the rain. The
IFR ceilings and low visibilities are in central MS and we are still
expecting them to make it to the terminals tonight. Guidance has
backed off slightly on the very low visibilities so raised the TEMPO
groups to 1SM and kept it at OVC005. These will have to be watched
closely and amendments will be likely.

Looks like we should get CIGS to lift tomorrow and even scatter out
by 22-23z. A few showers may be around tomorrow but not widespread
enough to include in the TAFs.





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