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Area Forecast Discussion (AFD)

Issued by Huntsville, AL (HUN)

FXUS64 KHUN 182324

Area Forecast Discussion
National Weather Service Huntsville AL
624 PM CDT Tue Sep 18 2018

For 00Z TAFS.


.NEAR TERM...(Tonight)
Issued at 351 PM CDT Tue Sep 18 2018

For the latter half of September, it is undoubtedly very warm to hot
outdoors, with mid afternoon temperatures rising into the upper 80s
to mid 90s. "Normal" highs this time of year are around 84 - both in
Muscle Shoals and Huntsville. The remnants of TD Florence was finally
moving off of the northern Mid Atlantic coast, thanks to broad high
pressure extending southward from Ontario to the Ohio Valley. Despite
the former TD moving off of the coast, looks like it could try to 
make some sort of a comeback very late in the forecast period - more 
on that later.

At the moment, isolated showers were in progress across parts of the
Tennessee Valley, moving southward at 10-15 mph. This activity for 
the most part has been lightning free so far. Deeper moisture and 
higher instability values to our south has resulted in more organized
storms closer to the Gulf coast. Showers that form will provide a 
little relief from the heat, but will add additional moisture to
areas affected. This could come in to play later tonight, as more 
patchy fog is expected. Added areas of fog, with greater coverage of
fog in and close the river valleys. As was the case last night, a 
few spots could be affected by locally dense fog with visibilities 
reduced to 1/4 of a mile or less in spots. Warm conditions for late 
Sept tonight, with low temperatures cooling in the mid 60s to around 
70. Normal lows this time of year are in the lower 60s.

.SHORT TERM...(Wednesday through Thursday)
Issued at 351 PM CDT Tue Sep 18 2018

A foggy start is possible around daybreak Monday, otherwise a near
repeat performance temperature wise is expected. Drier air filtering
in from the west and more subsidence will make for a dry day across
the Tennessee Valley. High temperatures should rise into the lower
90s. Given recent trends with highs now nearing the mid 90s, they may
need to be boosted into the mid 90s. Previous record highs of 99 in 
Muscle Shoals and 101 in Huntsville should survive. Similar
conditions are expected on Thursday, with highs rising into the lower
90s once again. Light northeast to east winds on Wednesday, should
become southeasterly during Thursday, as the surface ridge exits the
New England/Mid Atlantic coast.

.LONG TERM...(Thursday night through Monday)
Issued at 351 PM CDT Tue Sep 18 2018

The return southerly flow will bring greater amounts of moisture from
a very warm Gulf of Mexico (average water temperatures in the mid
80s). This moisture, along with lift and instability will bring
isolated to scattered showers and thunderstorms to the forecast
beginning on Friday. Stayed on a diurnal trend into Sunday night,
with higher rain chances in the daytime and lower at night. 

An upper low currently near Bermuda will in part absorb a portion of
TD Florence as it moves out to sea. But it should begin returning to
the west as it rounds the eastern half of the Bermuda high and heads
westward during the weekend and early next week. However, it will
return only as an unorganized area of deeper moisture in the trade
flow, across the Bahamas and further SE CONUS early next week. 


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 624 PM CDT Tue Sep 18 2018

VFR conditions are expected at the KMSL and KHSV terminals through
the first 6 to 9 hours of the forecast period. Winds will be light
and variable through most of the night, and become calm by 09Z. 
Given the calm winds and moisture in place, MVFR fog may develop
after 09Z at each terminal. While confidence is very low, have 
maintained a reduction in visibility, though thinking visibilities 
will remain at or above 4SM. Any fog that does develop will lift by 
14Z, leaving VFR conditions through the remainder of the period. 





For more information please visit our website 
at weather.gov/huntsville.