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Area Forecast Discussion (AFD)

Issued by Huntsville, AL (HUN)

FXUS64 KHUN 150245

Area Forecast Discussion
National Weather Service Huntsville AL
945 PM CDT Sun Oct 14 2018

.NEAR TERM...(Rest of tonight)
Issued at 945 PM CDT Sun Oct 14 2018

Weak frontal boundary remains stalled N/W of the cntrl TN Valley 
from mid KY swwd into west TN/NW MS. Lingering shower activity has 
been ongoing along/just ahead of this boundary over portions of 
wrn/mid TN leading into north MS, but thus far most/if not all of the
precip has remained out of the local area. As this boundary though 
begins to drift further to the south later tonight, some of this 
light rainfall/showers will prob work their way into the area in a 
corridor from srn mid TN swwd into north cntrl/NW AL. Given the 
abundant cloud cover in place across most of the area, current temp 
trends are very mild ranging from the upper 60s/lower 70s for most 
spots. A light influx of slightly cooler air out of the NW with the 
drifting front should allow these temps to lower a few more degrees 
into mainly the lower/mid 60s by early Mon morning. Ongoing forecast 
represents this overall pattern well, and no major changes are needed
to the forecast package at this point.

.SHORT TERM...(Monday through Tuesday)
Issued at 317 PM CDT Sun Oct 14 2018

With a weak front just to the north and west of the region again on
Monday, opportunities for isolated to scattered showers will be 
possible. The region will be caught in a transition area between a 
building subtropical ridge over Florida and an amplifying upper-
trough over the Great Lakes. Some weak shortwaves and the 
aforementioned boundary to the north will serve as a focus for this 
activity from Monday through Tuesday, before the boundary drops 
through the area Tuesday night. For Monday, expect almost a mirror 
image of today, with high-end chance PoPs over northwest Alabama and
more isolated activity further to the south and east. With a few 
more breaks in the clouds and southerly winds, highs in the upper 70s
to lower 80s seem plausible. Big changes coming by Tuesday as an 
upper- wave over the Great Lakes should finally force the front 
south. This will result in more widespread showers, especially by the
afternoon and evening as a weak shortwave rotates across the region.
Think the window for highest PoPs may be 18z Tuesday through 06z 
Wednesday, before gradually tapering off by early Wednesday morning 
as the front moves south. Cooler air will filter in behind the 
boundary as winds shift to the north as highs in the 60s will be 
common on Tuesday. Much drier will filter into the region by 
Wednesday as discussed in the section below. 

.LONG TERM...(Wednesday through Saturday)
Issued at 317 PM CDT Sun Oct 14 2018

On Wednesday, post-frontal showers will be ending from NW-SE during
the day, as drier and slightly cooler air builds in across the area
from the NW. A surface high pressure situated over the central High
Plains in the midweek, will build eastward during the course of the 
latter half of week, reaching the Mid Atlantic coast during Friday. 
Northerly winds during the Wed/Thu timeframe, will become SE then 
southerly during Friday. This will bring slightly warmer conditions 
and higher amounts of moisture to the Tennessee Valley. Greater 
amounts of moisture pooling over the NW Gulf region will advect to 
the NE, returning rain chance to this area - just in time for the 
weekend. This next system appears to be taking on a baroclinic
"overrunning" appearance from the ECMWF; with the GFS indicating a
surface low forming over the lower Mississippi Valley region. This
would bring higher rain chances vs the EC more leaf appearance. 

Timing wise, did a slight delay in timing regarding the start of the
showers, not until Friday night. Scattered to numerous showers look 
to occur as this moisture builds and instability increases, with 
precip water amounts rising above 1.5 inches. Overall atmospheric 
instability and forcing this go around does not look sufficient for 
convection, so kept the forecast thunder free. Both the GFS/ECMWF 
indicate a front moving across the forecast area during the latter 
half of Saturday, with drier weather returning next Sunday. High 
temperatures on Friday around 70 should cool into the lower 60s by 
Sunday. Sunday night (a little further out than this forecast) could 
have lows nearing 40 to start out the next work week on Oct 22nd.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 640 PM CDT Sun Oct 14 2018

With a frontal boundary stalled north of the area, sct shra are
possible in a corridor from srn mid TN into NW AL later tonight. As
such, a prevailing VCSH group has been maintained at the KMSL 
airport from late tonight into the daytime hrs. VFR conds otherwise 
prevail at both main terminals, as mid/high clouds continue to spread
ENE across the region. The frontal boundary to the north is xpcted 
to move swd thru the area later in the day Mon, with shra perhaps 
tapering off some in the afternoon. Cloud bases may also begin to 
lower more into the MVFR range around 2-3K ft following the passage 
of the front. Light/var sfc winds will begin to shift more to the NW 
near 7-8kt Mon afternoon as well in the wake of the frontal passage.





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