Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 241131

Area Forecast Discussion
National Weather Service Huntsville AL
631 AM CDT Sun Sep 24 2017

For 12Z TAFS.


.NEAR TERM...(Today)
Issued at 350 AM CDT Sun Sep 24 2017

Quiet weather prevailed across the Tennessee Valley for the start of
a new week - controlled by broad surface high pressure situated
across the eastern Great Lakes, and an upper low over the Deep
South. The upper low, seen best via experimental GOES-16 high
altitude 6.19 micrometer band was over southern Alabama. On a wider
view, upper troughing extended southward to the Great Basin, with
general ridging north of the southern low. Hurricane Maria continued
spinning 350-400 miles east of Cape Canaveral, heading northward
around 9 mph.

With an exception of fog forming over the next few hours, no weather
of consequence is forecast this morning. Those favored areas, such
as valleys, near bodies of water, and places that had recent wetting
rains will be more apt to be affected by fog. GOES-16 night-time
Micro Physics view was doing a good job indicating fog within the
Paint Rock Valley, over the Tennessee River in eastern Jackson
county, and western half of Tims Ford lake in eastern Lincoln and
southern Moore counties.

Overall, weather systems including the hurricane will move slowly
over the next few days, thanks to a blocking pattern across Europe.
The upper low will slowly move westward and gradually weaken early
this week. The presence of the low west of the region, along with
strong early autumn heating, could result in isolated showers and
thunderstorms this afternoon. A lack of strong upper support should
keep convection mainly across our western areas, with storms
generally weaker than they were on Saturday. Along with isolated
shower chances, another very warm day is in the forecast, with highs
rising into the mid 80 to around 90. Went to and above suggested
guidance values.

.SHORT TERM...(Tonight through Tuesday)
Issued at 350 AM CDT Sun Sep 24 2017

The first part of the new work week should feature a continuation of
very warm high temperatures and dry weather. High pressure at the
surface and aloft should keep hurricane Maria well east of this
region. With more sun than clouds, high temperatures both on Monday
and Tuesday should warm into the mid and upper 80s. Normal highs by
Tuesday are around 81 degrees. Low temperatures should only cool
into the mid 60s for most spots.

.LONG TERM...(Tuesday night through Saturday)
Issued at 350 AM CDT Sun Sep 24 2017

A transitional wx pattern will be the main story for much of this
forecast period. The sfc/upper ridge pattern which had been in place
from the mid Atlantic swwd into the region will begin to weaken and
translate ewd going into mid week. The 00Z ECMWF/GFS are hinting at a
dry cold front being just to the NW by the start of Wed, before the
sfc boundary moves sewd thru the cntrl TN Valley during the day. The
brunt of the cooler/drier air though looks displaced about 12 hrs or
so behind the lead frontal passage, or more into Thu. This looks to
translate into unseasonably warm temps continuing thru Wed/early Thu.
Afternoon highs look to remain in the mid/upper 80s range on Wed,
with lows both Tue night/Wed night trending well into the mid 60s.
The only bit of fanfare with the initial frontal passage looks to be
a slight increase in cloud cover Wed/Thu.

Cooler/drier air though will be streaming into the area from the NNW
during the day Thu, with afternoon highs around 10F lower than the
previous days. As a strong dome of high pressure out of the nrn/mid
Plains builds sewd into the region, seasonably cooler/drier air will
continue to filter into the area, as lows Thu night fall below 60F. A
reinforcing cold front may then quickly move sewd thru the region on
Fri, as another dome of high pressure moves into the Midwest states
out of the nrn Plains. This should easily translate into tranquil and
seasonal wx conditions to end the work week, with highs predom in
the mid/upper 70s and lows in the mid 50s. Little change in these
overall conditions/temps look to continue into next weekend, under
mostly clr/partly cloudy skies, as the large dome of high pressure
slowly moves ewd into the TN/OH Valley states.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 631 AM CDT Sun Sep 24 2017

So far, VFR weather has prevailed over the TAF sites. That said,
patchy fog was evident via satellite, mainly across NE AL and very
isolated elsewhere. Given spotty wetting rain yesterday, cannot
totally rule out brief MVFR (3-5SM visibility) fog towards daybreak.
Otherwise, generally sunny skies are forecast today. A passing upper
level system could bring isolated convection across NW AL this
afternoon; but with such low precip chances did not include it in
the TAF this issuance. Late in the TAF, do have more confidence of
late night MVFR fog, so included a mention at the sites.





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