Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 230837

Area Forecast Discussion
National Weather Service Huntsville AL
337 AM CDT Wed Aug 23 2017

.NEAR TERM...(Today)
Issued at 337 AM CDT Wed Aug 23 2017

After a pre-frontal trough kicked up showers and a few thunderstorms
overnight, the KHTX radar is quiet right now. This leaves the focus
on low clouds and fog for this morning. The lingering pre-frontal
trough boundary has kept the majority of the low clouds at bay, but
as it shifts southward, those who saw rainfall overnight will have
the greatest potential for low clouds/fog. Case in point, ceilings at
Muscle Shoals have fallen to 400ft while Huntsville`s ceiling is
over 5kft as of 8Z. The cold front itself is still to our north and
will move into the TN Valley this morning. This will redevelop
showers and thunderstorms, especially along and south of the TN River
where the boundary will stall out and better moisture will be at.
Precip won`t last long, tapering off later this afternoon as drier
air filters in behind the front.

.SHORT TERM...(Tonight through Friday Night)
Issued at 337 AM CDT Wed Aug 23 2017

Sfc high pressure anchored across the Midwest will build into the
region tonight. Reinforcing our cooler and drier air, we will have
mostly clear skies that will let temps drop into the lower 60s.
Conditions will be dry and comfortable on Thursday and Friday! Look
for dewpoints in the upper 50s by Thursday with daytime highs in the
low/mid 80s and overnight lows in the lower 60s to upper 50s in
southern middle TN! A near rinse and repeat for Friday with temps
only a few degrees warmer.

.LONG TERM...(Saturday through Tuesday)
Issued at 337 AM CDT Wed Aug 23 2017

Saturday starts off with a broad upper trough encompassing much of
the northeast with surface high pressure building down from the
north. The remnants of TS Harvey will have just made landfall
somewhere along the SE Texas coast. The GFS at this point continues
to show a vort max ejecting eastward out of Harvey and interacting
with a moist southerly flow to bring showers/storms north into the
area. The ECMWF continues to be dry because the upper part of Harvey
is not yet enveloped into the upper trough. Due to uncertainty, will
keep slight chance pops for Saturday and Saturday night.

Going forward, the Superblend definitely favors more of a GFS
solution in regards to the remnants of Harvey. This is a quicker
solution where it gets picked up by the upper trough and quickly
moves across the Gulf coast by Tuesday evening with dry conditions
following. This favors a wetter and cooler Sunday-Tuesday. The ECMWF
is slower and sort of meanders the system in eastern Texas before
ejecting it into the Tennessee Valley Thursday night. This solution
keeps it wet across the area for the majority of the week with the
heaviest rain mid week and later. After discussion with neighboring
offices as well as glancing at the GEFS members and tropical models,
the operational GFS is a quick outlier. The other guidance is
favoring a slower solution similar to the ECMWF. Therefore, dropped
the SuperBlend pops early in the period and raised them later in the
period to account for this. Made similar adjustments to Dew
points/Temps: Raised dew points 2 ish deg through the long term and
adjusted the temps up Sun/Mon and down Tue/Wed.

High temps will generally be in the lower to mid 80s with lows in
the lower to mid 60s. Slight variations are possible depending on
the track of Harvey. Follow the National Hurricane Center`s website
on additional information about Harvey.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1031 PM CDT Tue Aug 22 2017

Storms have dissipated leaving just a lingering shower or two near
the terminals but they are not expected to have any impacts.
Lingering cloud cover from the storms could keep the development of
low clouds/fog at bay until close to 08-09z. These will most likely
impact the MSL terminal as a result of the earlier heavy rainfall and
cigs/vis could drop to IFR. However, still uncertain due to poor
performance from guidance this evening. Have kept the MVFR cigs/vis
starting at 08z but this may need to be updated.

The front that generated the storms should be south of the terminals
during the day Wednesday with VFR cigs and northerly winds between





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