Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 180255 AAB
AFDHUN

Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
855 PM CST Wed Jan 17 2018

.NEAR TERM...(Tonight)
Issued at 855 PM CST Wed Jan 17 2018

High pressure at the surface is
settling into the Tennessee Valley
late this evening, reinforcing a cold, dry, stable air mass across
the region. Winds have slacked off a bit with the loss of the sun as
the nocturnal boundary layer develops, but a light 5 kt northerly
surface flow was noted in most obs as of 0230z. These light winds
(and some slightly higher dewpoints in the 8-12 degree range) may
help to keep temperatures from dropping as low as the yesterday.
Regardless, it will still be bitterly cold, with single digits likely
in Southern Middle Tennessee (where there is a greater snowpack) and
lower 10s elsewhere across Northern Alabama. A few spots in the
Bankhead National Forest may drop into the single digits once again
as well.

The lighter winds will keep wind chill values higher than last night
as well, though it will still feel brutally cold outside. Generally,
wind chill values in the 0 to 10 degree range will be common, but a
few localized spots along the Cumberland Plateau could drop below
zero. Given the isolated nature of these readings, will hold off on
an Advisory and keep a mention in the HWO. This very cold air has
also caused some refreezing of melted snow in some areas, creating
patchy icy/slick spots once again. Will issue a SPS to address this
as folks heading out on the roads tonight and the Thursday morning
commute should exercise caution.

Model soundings also hint at the possibility for some light, patchy
fog development along area lakes. Given the subfreezing air, some
freezing fog may occur late tonight into early Thursday morning. This
could cause some localized icing issues on river bridges and will
mention this in the HWO/SPS as well.

.SHORT TERM...(Thursday through Friday)
Issued at 220 PM CST Wed Jan 17 2018

Some good news for Thursday/Friday as we begin to see a slow
"warming" trend. The aforementioned surface ridge will begin to
weaken and drift southeast with time. We once again reach the
freezing mark by midday Thursday and by that time any remnant
snow/ice should be history. One more rather cold night is in store
Thursday night with temperatures well down in the teens areawide.
Have hedged toward the lower end of guidance as the last night of a
cold outbreak tends to be lower/colder than guidance predicts.

Weak southerly flow commences on Friday in advance of a developing
weak upper low in the vicinity of the northwest Gulf. Although we
won`t reach normal highs on Friday, temperatures in the mid to upper
40s will seem almost springlike compared to earlier in the week.
Some guidance has trended a bit more aggressive with the low
developing in the gulf and we will need to monitor its progress and
associated moisture return as we move toward the extended period.

.LONG TERM...(Friday night through Tuesday)
Issued at 220 PM CST Wed Jan 17 2018

If you are looking to catch a break from the cold stretch we have
been stuck in, the extended forecast has it for you. We could even
exceed normal temps, especially on Sunday. Normal temps for this
time frame is a high of 51 and low of 31 degrees.

Sfc high pressure that is currently sprawled across the southeast
will shift eastward this weekend, returning southerly flow and
moisture to the region. A shortwave will swing just to our south
Saturday. Soundings show an increase in shallow moisture with sfc
temps remaining just above freezing. The ECMWF brings it through
much later, so continued to keep precip out at this time. Saturday`s
highs warm up and return to normal, reaching the lower 50s across
the TN Valley! Overnight lows will be in the upper 30s/lower 40s. A
strong trough will sweep across the country this weekend and
strengthen as it lifts into the Great Lakes region by Monday. WWA
ramps up ahead of this system helping Sunday be the warmest day of
the forecast period. Sunday`s highs will be around 60 degrees with
lows in the mid 40s! As we head into the new work week, a sfc low
will lift up into the Great Lakes region. Showers and a few
thunderstorms will develop along the trailing cold front and push
into the forecast area Sunday night/Monday morning. The front will
move through quickly with precip exiting the area late Monday night.
Models differ in timing with the GFS still trending faster than the
ECMWF, but both increase PWATS over an inch Monday afternoon and
keep instability limited, therefore not expecting severe weather at
this time. Tuesday will see mostly sunny skies with near normal
temperatures.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 532 PM CST Wed Jan 17 2018

VFR conditions will be the predominant flight category at each
terminal through the period. Winds will drop off after 01-02z as the
nocturnal boundary layer sets up under a clear sky. Some light fog
may develop late tonight into early Thursday morning at KMSL.
Otherwise, clear conditions and light winds will continue into the
day on Thursday, gradually backing to the west to WSW late in the
day.


&&

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

$$

NEAR TERM...AMP.24
SHORT TERM...15
LONG TERM...JMS
AVIATION...AMP.24


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