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Area Forecast Discussion (AFD)

Issued by Huntsville, AL (HUN)

                            
314 
FXUS64 KHUN 102308 AAA
AFDHUN

Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
608 PM CDT Thu Aug 10 2017

.UPDATE...
For 00Z TAFS.

&&

.NEAR TERM...(Tonight)
Issued at 228 PM CDT Thu Aug 10 2017

A couple features and concerns will linger through tonight given the 
continued progressive pattern. Heavy rainfall, which caused 
widespread flooding across portion of northern and southeastern 
Madison County, have primed the saturated grounds for potentially 
more flooding if rainfall from today's activity again trains over 
impacted areas. Flooded areas from early this morning will only need 
around 0.25" or less from a shower/storm to cause more flooding 
problems. 

At the moment, scattered showers are being observed, mainly south of 
the TN River from Colbert Co. through southern Marshall Co. With 
both 12z soundings from OHX and BMX showing favorable instability, 
expect shower and thunderstorm coverage to increase through the 
afternoon. However, with the BMX profile similar to yesterday (same 
with model profiles), not expecting enhanced coverage of 
thunderstorms so only mentioned a slight chance for this 
afternoon/tonight. Rain chances will again favor the southern and 
eastern zones through this evening with a better shot of seeing a 
thunderstorm east of I-65 and south of HWY 72. Regardless, any
scattered shower/storm could potentially have rain rates exceeding 
1"/hr.

We're also watching the progression of an complex of thunderstorms 
moving out of central MS. Hi-res guidance from HRRR, NMM, and ARW 
show a few showers/storms moving through portions of the TN Valley 
overnight tonight. As such, have kept chance PoPs in the forecast 
through the night.

.SHORT TERM...(Friday through Saturday)
Issued at 228 PM CDT Thu Aug 10 2017

While the pattern will remain fairly active and progressive, we will
get somewhat of a transition beginning tomorrow as the warm front 
shifts out of the area ahead of an approaching cold front swinging 
into the Mid MS Valley. Ahead of this frontal system, a couple short 
waves will continue to migrate around the southern fringe of the mid 
level trough tomorrow. With the added addition of some shear, this 
extra support will give us a better shot of seeing a stronger 
thunderstorm or two tomorrow afternoon. While not expecting 
widespread strong or severe storms, cannot rule out a few storms 
producing gusts to 40-50mph with small hail. Additionally, any extra 
rainfall with stress areas with previous flood impacts. 

By Saturday, we'll still be watching the progression of the cold 
front moving through the Ohio Valley. Current forecast slows, maybe 
stalls, the front north of the CWA. With this scenario, we'll 
continue to see much of the same with humid conditions and daily 
scattered shower/thunderstorm chances. 

With the lingering cloud cover and enhanced rain chances, expect
temps to continue to run a few degrees below normal during the
afternoon and range from the upper 60s to low 70s overnight. 

.LONG TERM...(Sunday through Wednesday)
Issued at 228 PM CDT Thu Aug 10 2017

Majority of the extended forecast sounds like a broken record at 
this rate and can probably be summed up in one sentence! 

A series of disturbances will track through the base of a broad 
upper-level trough and into the TN Valley through early next week. A 
sfc front will stall to just to our north on Sunday and southerly 
flow will bring additional moisture in. With PWATs hovering around 2 
inches and multiple rounds of showers and thunderstorms on top of 
soils receiving rainfall from the short term, will need to keep an 
eye on additional flooding potential. 

On Monday, an upper-level trough digs out of the Northern Plains and
a sfc front departing for the east coast will send a cold front into
the TN Valley on Tuesday. Will finally see a decrease in POP values 
on Tuesday and Wednesday behind the front as some drier air filters 
in and sfc high pressure tries to build southward into the region. 

As for temps, daytime highs for the forecast period will continue to
be a little below normal reaching the mid/upper 80s. Overnight lows 
will be near normal, around 70 degrees. 

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 615 PM CDT Thu Aug 10 2017

Scattered heavy showers and a few thunderstorms will persist this
evening into the overnight hours, especially for areas near and east
of the KHSV vicinity. At this time, have kept the forecast VFR
through 10Z, but if showers or thunderstorms affect the terminal,
conditions could easily deteriorate to IFR due to low visibility in
heavy rainfall. Mist and possibly fog are expected to develop by 10Z
along with at least scattered clouds less than 010agl. It is
conceivable that ceilings could also develop and will assess that
further this evening. On Friday, more showers and thunderstorms
should develop by midday into the afternoon, and have included VCTS
at KHSV where the probability is a bit higher than KMSL.

&&

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

$$

NEAR TERM...Barron
SHORT TERM...Barron
LONG TERM...JMS
AVIATION...17


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at weather.gov/huntsville.