Area Forecast Discussion
Issued by NWS Huntsville, AL

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023
FXUS64 KHUN 251122
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
622 AM CDT Mon Sep 25 2017

.UPDATE...
For 12Z TAFS.

&&

.NEAR TERM...(Today)
Issued at 345 AM CDT Mon Sep 25 2017

A broad/weak upper low continues to drift wwd across the cntrl Gulf
region this early Mon morning, with bands of mid/high clouds
streaming nwd across W AL along the ern fringe of the upper low axis.
Elsewhere, mostly clr skies prevailed across the area thx in part to
a sfc ridge stretching from the mid Atlantic states swwd into the
mid TN Valley. Patchy fog has been slow to form this early morning,
even in some of the more fog prone areas. Given the very little
spread though in the temp/dew pt trend thus far, coupled with
little/if any wind, still expecting some patchy fog to develop prior
to daybreak, especially in the valley areas across srn mid TN into NE
AL where hardly any cloud cover is present.

Any lingering fog should then quickly diminish/lift within a couple
of hrs after daybreak. The upper low along the Gulf Coast should also
continue to gradually translate wwd, allowing some of the mid/high
clouds over the wrn counties to perhaps diminish a bit. This should
set the stage for another unseasonably warm/muggy day, as an upper
ridge axis becomes entrenched over the fairly stagnant sfc high in
place stretching from the NE/mid Atlantic into the region. As temps
once again warm into the mid/upper 80s across much of the area going
into the afternoon hrs, latest model runs are hinting at some weak
dynamic lift developing from srn mid TN leading into NW AL. This
could be the result of lingering energy stretching nwd from the
exiting upper low to the S. In any case, have introduced a slight chc
of showers/tstms in these zones this afternoon to account for any
weak convection that may result, especially with some decent moisture
in place below H7. Partly cloudy/mostly sunny skies should otherwise
prevail across N cntrl/NE AL thru the afternoon period, with the
warm/muggy pattern remaining in place.

.SHORT TERM...(Tonight through Wednesday)
Issued at 345 AM CDT Mon Sep 25 2017

The overall wx pattern definitely turns more quiet starting tonight,
with the only real concern some more patchy dense fog possible across
the sheltered/valley areas and near bodies of water. Overnight temps
will again be similar to the last couple of mornings, with lows well
in the mid 60s for most locations. Quiet and unseasonably warm wx
should then be the trend into mid week, with the sfc/upper ridge
remaining fairly stagnant from the NE/mid Atlantic states swwd into
much of the region. Afternoon highs will again climb well into the
mid/upper 80s both Tue/Wed while overnight lows remain predom in the
mid 60s. Latest model runs are still showing the well advertised cold
front dropping out of the Plains states and approaching the local
area from the NW late Wed. The sfc boundary though may not start to
cross thru the cntrl TN Valley until late Wed afternoon into Wed
evening, with the brunt of the cooler air displaced a bit wwd behind
the lead front.

.LONG TERM...(Wednesday night through Sunday)
Issued at 345 AM CDT Mon Sep 25 2017

At the start of the longer term, an upper level Rex-style block was
situated across Europe, helping to maintain a generalized troughing
west and ridging east setup across the greater North American
domain. This block will break down somewhat after the middle of the
week, allowing troughing across the North Atlantic to advance
somewhat further to the east. Another item of interest, a speed
max/upper level system currently moving ashore the Alaska
Panhandle, will induce upper level troughing near the Great Lakes;
with it amplifying southward to the Appalachians and Mid Atlantic
region. This trough will in part help weaken and begin a NE movement
of Hurricane Maria from the continent, forecast to be east of the
VA/NC border on Wednesday.

The above noted trough digging southward will help bring a cold
front across the Tennessee Valley during the Wednesday evening to
early Thursday time frame. With the lion`s share of atmospheric
moisture remaining well to our southwest, will stay with a dry
forecast with the front passage. Cooler air NW of the front, as
promised should start bringing a noticeable cooler trend for daily
high/low temperatures for the later half of the week into early next
week. A reinforcing dry front is forecast to move across the area
during late Friday. Highs on Thursday, in the low/mid 80s will be
the last 80s this week. Even cooler conditions on Friday, with highs
in the upper 70s, and in the mid 70s for the Sat/Sun/Mon timeframe.
Lows in the mid 60s Wednesday night, will cool into the mid 50s for
Friday night through Sunday night. Normal high/low temperatures on
Sunday, or October 1st are around 80/55 for reference.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 622 AM CDT Mon Sep 25 2017

Patchy br/fg has been limited thus far by mid/high cloud cover
streaming N/W into parts of the area. Even so, some -br/MVFR vis are
affecting the KMSL airport, and this trend will continue for another
hr or so before ending. VFR conds should then prevail at both main
terminals thru the afternoon period, with mainly just some sct cu
forming over much of the area. An iso shra/tsra is possible across NW
AL this afternoon, but the prob is too low to mention in the KMSL
TAF. Some -br is then again possible late tonight at both airports.

&&

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

$$

NEAR TERM...09
SHORT TERM...09
LONG TERM...RSB
AVIATION...09


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