Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 070808

Area Forecast Discussion
National Weather Service Huntsville AL
208 AM CST Wed Dec 7 2016

.NEAR TERM...(Today)
Issued at 206 AM CST Wed Dec 7 2016

The weather for today is mainly focused on the presence of low
clouds and the approaching Arctic front for tonight. The deep upper
low over Minnesota/Quebec along with the accompanying expansive polar
jet is responsible for pushing the Arctic front towards the Southeast
over the next 24 hours. This will plunge much of the Southeast into
well below normal temperatures over the coming days.

For the TN Valley, another mostly cloudy day is expected with that
aforementioned low cloud deck prevailing for most of the day. Some
breaking in the clouds is possible over northeast AL/N GA area before
the Arctic cold front approaches for tonight. However, the break in
the clouds over northeast AL will be tenuous as low to high level
clouds will accompany its arrival later this afternoon and evening.
This will make the forecast for daytime highs today challenging as
some areas over northeast AL may see brief sunshine and somewhat
higher daytime highs (mid 50s) as opposed to low 50s over northwest

.SHORT TERM...(Tonight through Friday night)
Issued at 206 AM CST Wed Dec 7 2016

Then, as the cold front approaches northeast to north winds will
increase and gradually back to the northwest with frontal passage
between 04Z-06Z (10PM-1AM) tonight. Not much saturation is present
for long in the low-levels, but may still see some light rain prior
to the frontal passage this evening. Have kept a generally low POP
for that possibility with generally liquid precip anticipated except
over southern Middle TN and far northern portions of AL where snow
may occur. In particular, a few areas could experience a drop to
between 30-32F over southern middle TN, and have incorporated a
rain/snow mix over those areas, especially early Thursday morning
between 09Z-14Z (3AM-9AM). Due to the lack of saturation in the
dendritic ("snow growth") zone of -10C to -20C, flurries would be the
main type of snow over those areas. Temperatures should steadily drop
throughout the evening into the overnight with surface temperatures
dropping into the mid 30s across most of the area.

Then, as significant geopotential height rises, dry/cold air
advection, and subsidence becomes entrenched across the TN Valley,
clouds will be quick to clear on Thursday afternoon. Northwest winds
will also increase especially over the higher elevations of northeast
AL where wind speeds to 15-20 MPH winds will be possible.
Temperatures will not rise much from Thursday morning with daytime
highs forecast to be in the low 40s.

After sunset, the already brisk conditions will diminish somewhat,
but temperatures will likely drop into the upper teens to low 20s due
to the clear sky and prevailing cold air advection. So by Friday
morning wind chills will be in the single digits over southern middle
TN. Little in the way of airmass modification should occur on Friday
due to continued cold air advection and despite the sunny conditions.
Daytime highs should be in the low to mid 30s with the lowest daytime
high temperatures over the Cumberland Plateau in Jackson/DeKalb and
Franklin TN counties. Then, temperatures nosedive again on Friday
night into the upper teens and low 20s.

.LONG TERM...(Saturday through Wednesday)
Issued at 206 AM CST Wed Dec 7 2016

High pressure will be centered over the region on Saturday providing
for dry conditions but cold temps. Afternoon highs on Saturday will
only be in the low to mid 40s. However the large sfc high will move
east by Saturday night allowing a sfc low and associated cdfnt to
approach the region. This will increase the chc of rain across the TN
valley on Sunday. By Sunday night the cdfnt is progged to push out of
the cwa by GFS. However the ECMWF keep the chc of rain lingering on
into Monday. The blended models also shows pcpn lingering on Monday
as well. Thus will keep the chc of rain thru Monday aftn before
ending it by Monday night. By Tuesday return flow setup across the TN
valley but not expecting any pcpn Tuesday mrng or aftn. However by
Tuesday night and into Wednesday, another cdfnt over the Ohio valley
will quickly be approaching the TN valley with yet another chance of

For the moment will keep all pcpn in the extended portion of the
fcst as rain (no thunder) due to low instabilities and stable


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1100 PM CST Tue Dec 6 2016

Reinforcing cold front is currently moving ewd through the area this
late Tue evening, with MVFR cigs well in place at the two main
terminals. These conds look to remain in place into the morning hrs
Wed, before cigs lift above VFR levels by the early afternoon period
as drier mid level air begins to mix swd toward the sfc. Sfc flow is
generally xpcted to turn toward the n around 5kt or less by the onset
of the morning hrs.





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