Area Forecast Discussion
Issued by NWS Huntsville, AL

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783
FXUS64 KHUN 070428
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1028 PM CST Fri Dec 6 2019

.UPDATE...
For 06Z TAFS.

&&

.NEAR TERM...(Tonight)
Issued at 816 PM CST Fri Dec 6 2019

No major changes from last update. SFC low has pushed off to our
east, but low level moisture has resulted in wide spread stratus
across the Tennessee Valley. Drier air out over the Plains begins to
works its way into the area overnight, but likely will not reach the
CWA until tomorrow morning when a gradual lowering in cloud coverage
can be expected.

.SHORT TERM...(Saturday through Sunday night)
Issued at 303 PM CST Fri Dec 6 2019

High pressure centered over the Ohio Valley will try to nose into
the region on Saturday, resulting in dry weather to kick off the
weekend. Moisture trapped in the boundary layer will likely keep
some low stratus in place for the early morning hours. However,
models continue to show strong subsidence from the ridge having more
of an influence over Tennessee and North Alabama on Saturday. Per
the soundings, would expect dry air to mix down late Saturday
morning through the afternoon, helping to scatter out some of the
cloud cover, resulting in at least a partly sunny sky for the
afternoon. This added sunshine will help us overcome the light
northeast flow and push high temperatures close to the 60-degree mark.

As high pressure shifts into the Mid-Atlantic region Saturday night
into Sunday, a backdoor cold front will approach the region from the
NC/GA Piedmont region. This may bring some slightly cooler air into
the Northeast Alabama by Sunday morning. This, combined with the
increased cloud cover during the day, should mean slightly cooler
temperatures on Sunday, with a gradient existing from west to east
across the area. By late Sunday afternoon into Sunday evening,
expect southerly flow to kick in, resulting in some low-level
moisture advection. With weak lift increasing ahead of a deepening
low pressure system to the west, expect a few isolated to scattered
showers to develop Sunday evening into Sunday night.

.LONG TERM...(Monday through Thursday)
Issued at 303 PM CST Fri Dec 6 2019

As high pressure shifts off the Atlantic coast Sunday night into
Monday, deep southerly flow will develop ahead of a strong low
pressure system and its associated cold front. This will result in
strong warm air (and moisture) advection as temperatures surge into
the mid 60s along with good moisture return by Monday afternoon, with
dewpoints in the mid 50s. Additionally, we will see PWATs climb as
high as 1.5" by 00z Tuesday. With the cold front moving into the
region Monday night into Tuesday morning, lift and moisture flux
will become maximized over the area, resulting in a window for
widespread convection and locally heavy rainfall. With enough warm
air advection, we expect there to be some modest elevated CAPE,
sufficient to warrant a few isolated thunderstorms during the Monday
evening/night period. The latest model projections indicate that the
frontal boundary may be a little more progressive and have cut back
Storm Total QPF closer to the 1 to 1.5 inch range. This may result
in a couple tributaries of the Tennessee River briefly responding,
but the overall flooding threat appears to be low.

As the cold front moves through the region on Tuesday, expect
temperatures to drop through the afternoon in its wake as cold air
advection occurs. As is often the case with these winter frontal
systems, model resolution issues exist regarding the amount of
available moisture behind the front and the magnitude of the colder
air moving in. While we do think that there may be the potential for
a brief period of rain/snow mix and/or snow flurries late Tuesday
evening and Tuesday night, the drier, colder air mass should move in
quickly enough to usher the deeper moisture southeast of the area.
Thus, for now, do not expect much, if any, wintry precipitation or
impacts on the backside of this frontal system. As always, we will
continue to watch the model trends.

A strong Canadian high will build into the region Wednesday into
Thursday ushering in a much cooler and drier air mass. This will
result in highs in the 40s and lows back below the freezing mark once
again through the end of the period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1028 PM CST Fri Dec 6 2019

Some clearing in the stratus deck is being observed using the
nighttime microphysics RGB at TAF issuance. As a result expect low
end VFR CIGs to improve by sunrise. Some areas of patchy fog have
developed this evening in locations where some clearing has occurred.
However, left out mention of fog in the TAFs given the presence of
dry air advection overnight with the light northwest winds.

&&

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

$$

NEAR TERM...GH
SHORT TERM...AMP.24
LONG TERM...AMP.24
AVIATION...GH


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