Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 232021
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
221 PM CST Mon Jan 23 2017

.NEAR TERM...(Tonight)
Issued at 220 PM CST Mon Jan 23 2017

A potent upper trough that brought tornadic severe weather across the
portions of the Southeast yesterday and Sat night continues to push
off to the east with lingering cloud cover and windy conditions the
only vestiges of its presence over the TN Valley. Speaking of winds,
have cancelled the wind advisory as wind speeds have dropped below
criteria. However, it still breezy this afternoon with 10-15 MPH
sustained northwest winds gusting up to 20-25 MPH. Cloud cover also
continues to recede to the east leaving mostly sunny to partly cloudy
conditions.

However, cloud cover should return later tonight from the northeast
as low clouds on the windward side of the appalachians of TN/NE
GA/Carolinas move SW underneath the nighttime inversion in
conjunction with decoupling. Winds should continue to diminish
further tonight with much cooler air (since Jan 9th) advecting
southeast across the TN Valley as temperatures drop into the mid to
upper 30s. This is still above normal for this time of year, but
definitely closer to what winter is supposed to feel like.

.SHORT TERM...(Tuesday through Wednesday night)
Issued at 220 PM CST Mon Jan 23 2017

Broad ridging will follow the exiting trough with any lingering cloud
cover dissipating from southwest to northeast. As this occurs,
expecting mostly sunny conditions (combined with light surface
winds) to warm the already modified airmass resulting in daytime
highs near 60 degrees. As this occurs an elongated positively tilted
broad trough will be moving across the western half of the CONUS
bringing snowfall to the Rockies but likely bringing rainfall to the
Southern Plains and Southeast. The progression of this trough and
subsequent sfc cyclogenesis over western KS looks to be handled
fairly well by the med range models with embedded shortwave troughs
within the longwave trough moving along the northwest flank of the
ridge. As of result, the surface low moves fairly quickly to the
northeast over the Midwest on Tuesday night into Wednesday while a
cold cP airmass front accompanies the surface low.

As the front encounters lower dewpoint depressions at the surface
/low-levels, expecting rainfall to develop over E TX/LA/AR/Lower MS
River Valley along the front on Wednesday morning. As it shifts east,
not expecting much precip due to forecast sounding showing dry mid-
high levels. Did include a slightly higher POP late on Wednesday
morning into Wednesday afternoon mainly due to the fairly similar
front timing. The QPF seems to be coming in lighter on the precip,
but the models may not be resolving the moisture advection and
resulting weaker lift along the front as it is largely removed from
the upper forcing. Behind this front, a cP airmass will advect over
the Southeast bringing cooler overnight lows in the upper 30s.

.LONG TERM...(Thursday through Sunday)
Issued at 220 PM CST Mon Jan 23 2017

A transition in the overall synoptic pattern will kick off the long
term period as a cold front shifts south of the state and cold air
advection commences.  Global models are in good agreement early on
with the temp change showing anywhere between a 10-15 deg C change
at 850MB between Wednesday and late Thursday. This will translate to
highs only reaching the mid to upper 40s on Thursday (may touch the
low 50s south) with a potential for a freeze on Friday morning.

Not much change in the overall pattern Friday through the weekend
given a relatively dry air mass settling in place. Global models do
hint at a couple mid level shortwaves breaking up the zonal
mid/upper level flow Saturday night and into Sunday, but not
expecting much at all in the way of precip given the dry air mass.
Temps through the weekend will persist in the mid/upper 40s during
the afternoon and mid/upper 20s overnight.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1120 AM CST Mon Jan 23 2017

The MVFR cigs that had been in place across N AL/S Middle TN have
begun to move off/dissipate to the northeast. This has resulted in
VFR conditions gradually returning and have incorporated that into
the TAFs through 24/05Z-24/06Z. There is an area of MVFR cigs moving
slowly east across the MS River (near KMEM), and may make
adjustments to TAFs if these clouds maintain their structure as they
slowly move towards N MS. Later on tonight MVFR cloud cover may
return from the northeast between 24/05Z-24/06Z. This may affect
both terminals and it may drop further to IFR before dissipating
after 24/12Z-24/15Z. The clouds are forecast to move off to the
northeast meaning KMSL should return more quickly to VFR that KHSV
and NE AL/S Middle TN.

&&

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

$$

NEAR TERM...SL.77
SHORT TERM...SL.77
LONG TERM...Barron
AVIATION...SL.77


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