Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 120255
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
855 PM CST Mon Dec 11 2017

.NEAR TERM...(Tonight)
Issued at 855 PM CST Mon Dec 11 2017

Predom clr skies and quiet wx conditions prevail across the cntrl TN
Valley this Mon evening, although some mid/high cloud cover is
approaching from the NW. A fairly strong cold front is also beginning
to move out of the Midwest states and into W TN, with sfc winds
turning toward the NW around 15-20 MPH with higher gusts in the wake
of the frontal passage. Closer to home, a fairly large temp gradient
is in place over the TN Valley, with Muscle Shoals checking in at 50F
while Fort Payne has dropped all the way to 34F. With the cold front
not xpcted to cross into the wrn half of the area until early Tue
morning, temps across most of the area should begin to fall below 40F
after midnight, even with some mid/high clouds moving into the area.
Morning lows Tue were adjusted a couple of degrees based on the
latest trends, but overall no major changes were needed to the
ongoing forecast at this point.

.SHORT TERM...(Tuesday through Wednesday Night)
Issued at 222 PM CST Mon Dec 11 2017

The final piece of upper lift associated with the wave will be
through the area by 18z Tuesday but right before that, there could
be enough moisture to squeeze out some flurries or sprinkles in the
southern middle TN counties. However, guidance keeps coming in drier
so removed the mention for now but don`t be surprised to see a flake
or two tomorrow morning up there. Clouds will clear out quickly for
Tue afternoon but that won`t mitigate the effects of the front as
highs will only reach the middle 40s. With strong afternoon mixing,
we will be able to mix down some slightly higher wind around 900mb.
This should translate to sustained winds of 15-20mph with gusts of
20-25mph. No need for a wind advisory right now but the midnight
shift may change that based on new model guidance.

Another bitterly cold night expected Tuesday night with clear skies
and light winds. Current forecast lows are in the lower 20s but dew
points have been trending lower than model guidance so we could see
isolated locations have lows in the upper teens. Surface high
pressure builds in from the south on Wednesday with sunny skies and
southerly return flow warming highs into the upper 40s to lower 50s.
Lows will also warm into the lower 30s.

.LONG TERM...(Thursday through Sunday)
Issued at 222 PM CST Mon Dec 11 2017

Thursday starts off with zonal flow aloft behind the passage of the
weak shortwave and ahead of another clipper system/shortwave digging
into the upper midwest. Surface winds turn slightly SW as a low
passes to the north, helping to warm highs into the lower 50s. Even
with cloud cover, the weak shortwave that moved through Wed night
will slowly push in cooler air. Thurs highs won`t be impacted but the
lows will drop to the upper 20s/lower 30s.

The next clipper system digs into the deep south Friday morning
sweeping a cold front through by Friday afternoon. Upper lift and jet
dynamics are strong with this system but moisture is of course
lacking. The ECMWF is dry with the system but the GFS is trying to
hint at some light QPF. There will be a saturated layer aloft
overnight Thursday with a brief saturation around 18z at the mid
levels Friday. Wouldn`t be overly surprised with the strength of the
system to get a few flurries/sprinkles. Will match the neighbors for
now and add some light rain/snow to the southern middle TN counties.
Very dry air quickly returns as strong surface high pressure builds
from the west. Friday highs/lows will be cooler because of the front
with highs in the 40s and lows in the upper 20s.

Southerly flow quickly returns Saturday with warmer and dry weather
and temps in the 50s. The next upper system dives into western states
Saturday night with model differences on the placement of the surface
low. GFS is farther south and moves it over the area and therefore
much wetter with the ECMWF farther north and drier. Will stick with
the blends at this time. Sunday and Monday should be warmer with the
southerly flow, in the mid to upper 50s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 532 PM CST Mon Dec 11 2017

VFR conds will continue at the two main terminals into the evening
hrs, although mid/high clouds will begin to stream into the area from
the NW later this evening. A cold front will also move ewd thru the
area later tonight, with sfc winds turning toward the NW near 10-15KT
with higher gusts by Tue morning. A strong low level jet may briefly
accompany the front and translate into some strong LLWS into the
overnight hrs. Cigs will fall into the 4-5K ft range in the wake of
the frontal passage, as sfc flow increases to 15KT with higher gusts.


&&

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

$$

NEAR TERM...09
SHORT TERM...LN
LONG TERM...LN
AVIATION...09


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