239 
FXUS64 KHUN 291915
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
215 PM CDT Mon Oct 29 2018

.NEAR TERM...(Tonight through Tuesday Night)
Issued at 215 PM CDT Mon Oct 29 2018

The ridge of high pressure at the surface will shift east into the
central and lower Appalachians tonight. The 8h ridge will also shift
east of middle TN and AL as well. Isentropic lift may induce a band 
of high based stratus (040-060agl) late tonight but should exit 
rather quickly on Tuesday. Most areas tonight should be milder with 
lows in the m-u40s, although a few colder eastern valleys could dip 
into the l40s.

On Tuesday, another nice day is ahead with good low level warm air
advection and sunshine returning after the morning clouds exit to the
northeast. Highs should easily reach the middle 70s, and won't rule
out upper 70s for some areas. Model soundings do not show strong
indications of low cloud development Tuesday night. Overnight lows
should still be mild with steady south-southwest flow. Looking at
m50s-a60 at this time (coolest east, warmest west).

.SHORT TERM...(Wednesday through Thursday)
Issued at 215 PM CDT Mon Oct 29 2018

The short range guidance (i.e. NAM) seems to be leaning toward a
slower solution as has been advertised by the previous ECMWF and
Canadian. This is in regard to a possible QLCS that will develop on
Wednesday along a deep southwesterly flow in mid to upper levels
across TX northeast through the southeast Ozarks into the OH valley.
The warm sector looks to be largely capped due to limited deep
moisture return further east, including north AL and southern TN. So
have backed off on the PoP on Wednesday in this regard. The QLCS may
just get close to far northwest AL by 00Z/31. With a deepening of the
trough axis and low level flow backing, the progression of the
precipitation may be held up a bit. Instability magnitude is still a
question mark for our area, with CAPE values increasing to only 500
j/kg or less in advance of the line late Wednesday evening. However,
high shear will be sufficient for at least a marginal severe weather
concern. 2km bulk shear vectors do increase to 30-35kt and 1km SRH
values increase to above 300 m2/s2 in response to the LLJ 
acceleration late Wednesday night. The main period of concern west of
I-65 will be from 03-09Z, and areas further east from 09-15Z.
Have drawn a sharp gradient in the PoP forecast as such, with areas
along the I-59 corridor likely remaining dry until Thursday morning
after 12Z. Will continue to address the potential for strong to
severe wx possible in our HWO and graphics. The QLCS will exit to the
east with MCS stratiform precipitation or showers lasting into early
Thursday afternoon before ending.

.LONG TERM...(Thursday night through Sunday)
Issued at 215 PM CDT Mon Oct 29 2018

The extended portion of the forecast begins Thursday in the wake of
the line of storms that marched across the area overnight Wednesday
into Thursday. Compared to the overnight model runs, not a lot has
changed, with the exception of another model/two getting on board
with the slowing down of the upper system as it traverses the area.
Overall, the timing of the GFS was followed, albeit a bit slower than
it's advertising, but not as slow as the slowest solution/ECMWF (it's
a full 12+ hours slower than its counterparts). This should have the
bulk of the precip pushing out of NE AL by 18/21Z Thursday, with 
some light rainfall expected post-fropa through the late aftn/early 
evening hours.

With the CAA expected in the wake of the fropa, daytime temps Friday
will be about 10 degrees cooler than Thursday, topping out around 60
degrees (after starting out in the mid/upper 40s). Morning lows
Saturday will start off in the low 40s (with even a few upper 30s
possible in NE AL/Srn Middle TN). Concurrent with this timeframe,
models show a quick-moving shortwave rounding the base of the upper
trof, and this should bring us another brief round of light
rain/showers overnight Friday into Saturday. Am not expecting much
other than a few hundredths at most during this time, and PoPs are
relatively low (~20%).  

A general warming trend is expected through the weekend, with daytime
temps topping out in the lower 60s Saturday and the middle 60s
Sunday. Morning lows will once again start out cool on Sunday, but
with winds becoming more southerly overnight Sunday, morning lows
Monday will climb to 45-50 degrees across the area. 

It's at this point in the forecast that details become murky. While
the GFS keeps an upper level system well N of the area during
Monday/Tuesday, the ECMWF is far more progressive with this system,
sparking another round of showers/storms for us during this time.
PoPs have been retained at 20% coverage attm since this is the end of
the forecast period, and the uncertainty is so large. 

Beyond this timeframe though (and just outside the forecast window),
the ECMWF is highlighting another shot at strong storms possible for
midweek. The GFS has rain for our area, but the strength/placement 
of upper level features is quite different. Either way, we're heading
into our second severe weather season in the TN Valley, 
climatologically speaking, so folks should get safety plans in place 
anyway in the event that something come to fruition out of either
events in the forecast period. Stay tuned for further information
coming to light in the next few days!

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1143 AM CDT Mon Oct 29 2018

VFR flight weather conditions are expected during the next 24 hours.
A band of clouds based ~040agl will arrive around 09Z at KMSL and 12Z
at KHSV. These clouds will exit close to the end of the forecast
period.


&&

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

$$

NEAR TERM...17
SHORT TERM...17
LONG TERM...12
AVIATION...17


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