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Area Forecast Discussion (AFD)

Issued by Huntsville, AL (HUN)

FXUS64 KHUN 162357

Area Forecast Discussion
National Weather Service Huntsville AL
657 PM CDT Mon Jul 16 2018

For 00Z TAFS.


.NEAR TERM...(Tonight)
Issued at 248 PM CDT Mon Jul 16 2018

Rainfall has just about cleared out of the area as the earlier swath
of showers/tstms continues to move into parts of east TN/north GA.
There may not be adequate time for the airmass to recover enough for
additional showers/tstms to develop thru the remaining afternoon hrs
although the prob cannot be completely ruled out. Additional upper
waves are forming upstream over AR, although whether these hold
together or the trajectory brings them closer to the cntrl TN Valley
area later tonight remains to be seen. For now, will maintain sct
showers/tstms in the forecast this evening pending what course these
disturbances actually take. If the wx across the area actually stays
more quiet, some light fog is then possible overnight given the
rainfall that occurred earlier today. The fog could certainly be more
locally dense in the sheltered/valley locations and near bodies of
water as is usually the case. This remains somewhat uncertain though
and is not in the forecast at this point, but may need to be added
later this evening. Temps should trend near seasonal heading into the
overnight hrs, with lows mainly in the lower 70s for most areas.

.SHORT TERM...(Tuesday through Wednesday night)
Issued at 248 PM CDT Mon Jul 16 2018

Latest model suites are still hinting at a cold front dropping into
the area out of the NW Tue and Tue night. This boundary should serve
as a focus for additional sct showers/tstms into the day Tue, and
continuing into the evening hrs Tue night. Little in the way of
cooler air though is xpcted with this oncoming front, as afternoon
temps Tue are still xpcted to climb toward the 90F mark. However,
overnight lows going into early Wed may at least be a few degrees 
cooler with the frontal passage, with temps falling into the upper 
60s/around 70F. Some slightly drier air may then filter into the area
from the north in the wake of the front on Wed, bringing perhaps a 
temporary break in showers/tstms. The exception may be the far SW 
corner of the local area where slightly better convergence will be in
place near the stalled frontal boundary. Unfortunately, no such 
break is xpcted with afternoon temps, with highs again around 90F for
most locations.

.LONG TERM...(Thursday through Sunday)
Issued at 248 PM CDT Mon Jul 16 2018

An unsettled pattern will continue late this week into the weekend as
a large, subtropical ridge deepens over the Southwest and a broad 
upper-trough develops over the Great Lakes and Northeast. This will 
place much of the Deep South, including the Tennessee Valley under 
prevailing northwest flow aloft. After a mostly dry day Thursday, the
through will amplify and a stronger piece of energy move from the 
Northern Plains into the Ohio Valley. This feature will force another
weak front into (or very near) the area on Friday, setting the stage
for an active day on Friday and Saturday -- as this feature will 
serve as a focus for scattered to numerous showers and thunderstorms.
With sufficient instability and at least some appreciable wind shear
in place, the potential for some organized convection will exist 
along and ahead of this boundary. Given the continued very moist 
environment in place across the region, heavy rainfall and localized 
flooding issues will continue to exist with any of the activity later
this week. 

Both the GFS, ECMWF, and Canadian model suites all generally show
this upper-trough sinking SE into the Southern Appalachians and
Carolinas Sunday into early next week -- taking the front with it. 
This would cut back on the precipitation chances late this weekend to
more isolated to scattered thunderstorm activity, and yield some 
partial clearing. However, northerly flow would also help to maintain
seasonable to slightly below temperatures in the upper 80s to lower 
90s during this time period as well. 


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 656 PM CDT Mon Jul 16 2018

A rogue storm or two cannot be ruled out thru 01-02Z, but odds are
too low to include. Otherwise, VFR conditions are expected thru 
07-08Z, before giving way to fog formation at both KHSV and KMSL. 
Confidence is high in MVFR visibility, and even high enough in IFR to
include a 3-4 hour TEMPO group at both KHSV and KMSL. Guidance hints
at LIFR conditions but confidence is NOT high enough to include at 
this time. Any fog will take an hour or two to dissipate with VFR 
conditions resuming by mid- morning at the latest. There is a low 
chance that thunderstorms could form along a cold front over MO/AR 
and push SE into the area around/shortly after daybreak, but 
confidence is far too low to include at this time.





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