Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 200146
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
746 PM CST Sun Jan 19 2020

.NEAR TERM...(Tonight)
Issued at 746 PM CST Sun Jan 19 2020

Few adjustments necessary at this time for the overnight hours.
However, imagery indicates a deck of lower clouds (015-025agl)
drifting steadily southward through central and western KY. For now,
will monitor these clouds trends, but may need to introduce these
clouds in our southern TN and far north AL counties after 06Z if
these hold together. Model soundings and 925 mb RH progs indicate
some potential for this to get into our area. Temperatures have
dipped into the u20s in southern middle TN to the l-m30s in north
AL. A brisk north wind continues with gusts of 15-20kt, and a bit
higher atop the higher elevations/plateaus. Wind chill values are
already down into the u10s to m20s.

.SHORT TERM...(Monday through Tuesday)
Issued at 222 PM CST Sun Jan 19 2020

A bitter cold start to the day is expected on Monday, with
temperatures in the mid/upper teens and wind chill values in the
single digits. Despite another day of sunshine and clear conditions,
northerly winds will continue to reinforce this chilly, arctic air
mass. As a result, highs will struggle to climb much above the
freezing mark -- peaking in the mid 30s in most locations.

High pressure will quickly shift east of the region by Monday
evening as a swift moving shortwave "clipper" system will dive
southeastward along the edge of a broad longwave trough over the
eastern CONUS. The shortwave will actually begin the day over the
Dakotas before shifting into the Mid-Mississippi Valley by Monday
evening and through the Tennessee Valley after midnight. This
shortwave trough is quite vigorous and will not only bring another
shot of cold air, but also some substantial lift has it dashes
across the region late Monday night. Models continue to show a good
bit of moistening in the mid to upper-levels of the atmosphere during
this window. However, it should also be noted that some fairly dry
air will exist near the surface, especially below 7-8 kft. All this
to say, think that it`s likely we will see a few snow flurries late
Monday night into Tuesday morning across the region. However, no
impacts or accumulations are expected as the very dry air near the
surface will prevent most of these snowflakes from reaching the
ground.

Clouds will quickly depart Tuesday morning as the shortwave races
south toward the Florida Panhandle. Expect another clear and cold
day, with northerly winds helping to keep highs well below normal in
the upper 30s to around 40 degrees.

.LONG TERM...(Tuesday night through Saturday)
Issued at 222 PM CST Sun Jan 19 2020

Most guidance continues to shift the center of the area of
high pressure east into West Virginia or western Pennsylvania
Tuesday night. This strong area of high pressure extends southwest
into the Tennessee Valley as well though in guidance. This should
setup a good radiational cooling environment over northern Alabama
and southern middle Tennessee once again. Therefore, trended toward
the lower end of guidance for lows, primarily keeping them in the
upper teens to lower 20s. This may not be low enough, given dewpoint
values progged by many models (they may drop into the mid teens).
Winds should be light in more sheltered valley locations, but
guidance is showing winds around 5 mph in our highest elevations
(above 1200 feet). This could keep these locations a tad warmer as
well.

As the high shifts further east on Wednesday, models continue to
show southeast winds increasing, as a storm system in the Midwest
begins to develop. This should help temperatures under clear skies
climb into the mid 40s.

As the storm system becomes stronger over the Midwest Wednesday
night through Thursday, winds continue to increase and become more
southerly/southeasterly. A low level jet around 30 knots develops
over the area. However, with a strong low level inversion remaining
in place most of this wind energy will stay aloft. We will likely see
and increase in winds to between 5 and 10 mph with some higher gusts
around 15 mph in the afternoon. This will continue to bring warmer
and more moist air into the region as well. Highs on Thursday will
likely climb into the 50s again.

GFS continues to develop a shortwave over northern Mississippi/Alabama
Thursday morning. However, it remains the only solution to do this.
If this solution pans out, then it would mean more cloud cover/rainfall
early on Thursday, keeping high temperatures lower. Again though, most
other guidance keeps the shortwave over eastern Texas/Louisiana towards
midday on Thursday. With such a strong upper ridge setting up ahead of
this system approaching from the Midwest, this makes me want to discount
the GFS solution even more. Thus, have kept with the slower solution
and a dry forecast for much of the day on Thursday. By Thursday
evening, as the approaching storm system strengthens and moves into
Arkansas, expect rainfall to push back into northwestern Alabama in
earnest with some scattered rainfall possible in northeastern
Alabama. Should see a bit more than light rain given PWATS. However,
the heaviest rainfall will likely occur on Friday, when deeper and
strong lift moves int the area ahead of an approaching frontal
boundary. However, the storm system will be detached from the main
jet stream. So it doesn`t look to be able to pull very cold air in
behind the front. It will turn slightly cooler again, but not much.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 454 PM CST Sun Jan 19 2020

VFR flight weather conditions are expected. North-northwest flow will
diminish to less than 10kt tonight. A few gusts around 14kt will
redevelop Monday morning.


&&

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

$$

NEAR TERM...17
SHORT TERM...AMP.24
LONG TERM...KTW
AVIATION...17


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