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Area Forecast Discussion (AFD)

Issued by Huntsville, AL (HUN)

                            
458 
FXUS64 KHUN 171741
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1241 PM CDT Tue Jul 17 2018

.UPDATE...
For 18Z TAFS.

&&

.NEAR TERM...(Rest of Today)
Issued at 939 AM CDT Tue Jul 17 2018

Low stratus clouds and fog are finally beginning to lift/dissipate
across the area this morning, with visibilities slowly improving
attm. An SPS remains in effect through 10am for the low
ceilings/patchy fog (especially in the terrain locations of NE AL/Srn
Middle TN). Otherwise, a look at regional radars shows some shower
activity bubbling up/dissipating upstream over Srn TN and SEwrd into
NW AL. This activity is in response to a sfc cold front sprawled NE
to SW across portions of Central/Wrn TN. This boundary will slowly
meander Swrd through the day, increasing the coverage of showers and
storms this afternoon. As in days past, locally heavy rainfall and
gusty winds will be the primary hazards, and the forecast handles
this well.

The only changes made to the current forecast were to adjust current
temps downward a bit thanks to the lower clouds hanging around a
little longer than anticipated this morning. Once they break up, 
temps are expected to rebound nicely to the current temp trend to top
out in the upper 80s. 

.SHORT TERM...(Tonight through Thursday)
Issued at 447 AM CDT Tue Jul 17 2018

As this front pushes further south this evening, can not rule out
some lingering scattered showers or storms into the early evening 
hours before ending. As this front stalls to our south, drier and
cooler air should push into the area. Lows should drop into the mid
60s to around 70 degrees on Wednesday morning, before warming into
the 85 to 90 degree range in most areas (with abundant sunshine). 
An even cooler night looks to be in store on Wednesday night into 
Thursday morning. Clear skies and light winds should allow lows to 
dip into the lower to mid 60s. 

A bit warmer temperatures are expected on Thursday, as highs climb 
into the upper 80s to lower 90s, with lows rising back to around 70 
degrees. 

.LONG TERM...(Thursday night through Monday)
Issued at 447 AM CDT Tue Jul 17 2018

Upper blocking over the eastern Europe/western Asia region will be a
player regarding the extended forecast. This Rex-type block should
transition to an Omega style into early next week. Output from the 
GFS/ECMWF (in comparison to each other) become notably different in 
the northern stream, regarding positions of systems further east and 
in the future. Over the North American domain, the main feature noted
include a strong and warm upper ridge over the SW CONUS and troughing
over the Great Lakes (with the trough amplifying to the SE along the
Appalachians next week). A slow transition of the eastern trough to 
the east will bring unsettled weather across the Tennessee Valley for
the weekend. 

On Friday, chances for convection will continue as the boundary that
moved south of the area today, returns northward as a warm front. 
This will place the area back into the warmer, more unstable sector 
for Sat/Sun time frame. The ECMWF in comparison to the last nights 
run, has become aggressive and depicted a sharper trough in the 
westerlies, similar with the GFS ensemble. This trough amplifying 
across the Ohio Valley will bring a another cold front across the 
area during Sunday. Given lift with this front, have raised PoPs to 
the likely range to end the week. Drier air filtering in behind the 
front will bring drier weather to start the new work week. 

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1227 PM CDT Tue Jul 17 2018

Convection in the vicinity of the terminals will increase through the
afternoon as a cold front approaches from the N. Vsby reductions and
an increase in winds is expected if storms directly affect the
terminals, and has been handled with a TEMPO group for a few hours
this aftn. Otherwise, convection will end and skies will clear from 
N to S shortly after sunset. This will set the stage for fog
development across the area by midnight, with MVFR vsbys expected by
this time. Further reductions are likely by sunrise, with at least
IFR (1-2SM) conds by sunrise. As mixing ensues after sunrise,
conditions will improve to VFR by 18/13-14Z, lingering through the
end of the TAF period Wednesday. 

&&

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

$$

NEAR TERM...12
SHORT TERM...KTW
LONG TERM...RSB
AVIATION...12


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