Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 250507

Area Forecast Discussion
National Weather Service Huntsville AL
1207 AM CDT Tue Oct 25 2016

For 06Z TAFS.


.NEAR TERM...(Tonight)
Issued at 840 PM CDT Mon Oct 24 2016

A weak cold front is draped across the area from west to east just
south of the AL/TN border. This frontal boundary will continue to
drop south this evening. While surface winds have decoupled, VAD wind
profiler from KHTX is showing 10-15kt winds out of the N/NE. These
winds will help to advect some drier and slightly cooler air into the
region. Dewpoints are about 5 to 10 degrees above yesterdays values
at this time but should wind up near what we had yesterday
evening/overnight. With clear skies forecast tonight, expecting
slightly better radiational cooling and nudged temps down a degree or
two in the cooler locations of the area.

Lows overnight will be in the low to mid 40s with a few locations in
our TN counties dipping below the 40 degree mark. Will monitor the
trends to see if another update is needed.

.SHORT TERM...(Tuesday through Wednesday)
Issued at 310 PM CDT Mon Oct 24 2016

Winds should veer quickly to the southeast on Tuesday. A rather large
diurnal rise in temps is expected again with 850 mb temps of 15-16C
equating to potential highs well into the 80s. We will go closer to
the warmer NAM values in the l-m80s. Southerly flow Tuesday Night
should allow warm advection to offset radiational cooling a bit more.
So going with lows slightly above guidance in the west, but going a
bit cooler than guidance in our typical drainage cooling valleys in
our east.

Wednesday should be another warm one, although MOS is dropping back
max temps a bit due to abundant ci/cs indicated in the models. I`m
the skeptic and will go on the warm side again given a combination of
several ongoing factors including increasing southwest flow, dry
soils, and persistence forecast.

.LONG TERM...(Wednesday night through Sunday)
Issued at 310 PM CDT Mon Oct 24 2016

An upper level disturbance will continue to move eastward from
Missouri and the central Great Lakes region towards the Tennessee
Valley on Wednesday morning. The southern extent of the energy with
this system will remain over Tennessee northward into Illinois
through Wednesday afternoon. However, low level (especially 925 mb
winds) will strengthen significantly Wednesday night into Thursday
morning, as the upper level disturbance pushes through northern
Alabama. At this point, although wet-bulb temperatures lower
significantly, surface based instability is too meager for more than
isolated showers/thunderstorms. Not expecting any stronger storms
Wednesday night given nominal shear and weak instability. The big
question is how much shower/thunderstorm activity we have on
Thursday. Synoptic models show that the surface front associated with
this disturbance hangs back a bit further west of the upper level
trough axis. These models continue to forecast around 1500 J/kg (NAM
even more) developing during the morning and early afternoon hours on
Thursday. The lagging of the surface front puts it somewhere over
northeastern Alabama. Given very low wet-bulb temperatures ~ 7500 ft,
if convection occurs some strong storms could develop if they can
overcome a developing CAP aloft just above 700 mb. The main threat
with these would be small hail. Winds may need to be raised on
future shifts for Wednesday night into Thursday due to the strength
of the 925 mb jet.

Although, some drier and cooler air will move into the area via
northwesterly flow, there is not strong colder air advection that
occurs over the area Friday into Saturday. Temperatures should drop
off behind the front back into the upper 70s to lower 80s as a
result. Models hint at another dry front approaching the area over
the weekend, but are in fairly large disagreement about the strength
of low level cold air advection with this feature. Thus went with
Superblend for Saturday night into Monday.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1207 AM CDT Tue Oct 25 2016

VFR conditions are forecast through the period. A weak frontal
boundary is pushing south through the area and winds will favor a
northerly direction with speeds remaining below 5kts. By late Tuesday
morning winds become more easterly.




NEAR TERM...Stumpf

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