FXUS64 KHUN 152358

Area Forecast Discussion
National Weather Service Huntsville AL
658 PM CDT Mon Oct 15 2018

For 00Z TAFS.


.NEAR TERM...(Tonight)
Issued at 307 PM CDT Mon Oct 15 2018

Quite the temperature gradient across the Southern/Central United
States, thanks to a strong cold front that is slowly creeping toward
the Tennessee Valley. As of 20z, temperatures range from 83 degrees at
Huntsville to 56 degrees at Nashville, and 52 degrees at Memphis.
This frontal boundary will continue to drop into the region late
this afternoon and evening, prompting a wind shift to the northwest
and bringing in this cooler air. By 00z, the boundary should make it
close to the HSV Metro and through the area by 03-06z. Temperatures
will fall into the 60s in its wake, and eventually the 50s by early
Tuesday morning. Enough forcing is taking place along and ahead of
the boundary to generate some isolated to widely scattered light
showers. This will continue this evening and into the overnight
hours, though QPF amounts will be very light. In fact, most areas
will remain dry. The more synoptic scale forcing that help generate
the heavier precipitation over West and Middle Tennessee earlier
today has since lifted into the Ohio Valley, so rainfall totals will
be much lower across North Alabama. Overall a quiet night, with a
persistent northerly wind, helping to usher in a new, cooler air

.SHORT TERM...(Tuesday through Wednesday)
Issued at 307 PM CDT Mon Oct 15 2018

Changes coming to the forecast as the aformentioned boundary sags
south into the Tennessee Valley, bringing cooler air, and serving as
a focus for scattered to perhaps numerous showers Tuesday and Tuesday
night. A mostly cloudy sky and a cooler air mass will keep highs in
the low to mid 60s, reinforced by northerly winds. Some upper 50s
highs are not totally out of the question across far Northwest

Speaking of precipitation, another feature will assist in
providing the necessary lift for this activity. A shortwave trough
that will rotate along the southern edge of a broad upper-trough over
the Great Lakes/Ohio Valley, helping to regenerate rain showers
Tuesday afternoon and evening, and providing some periods of light to
moderate showers across the region. The greatest coverage will be
closest to the boundary which is progged to stall south of the
Tennessee River. The front will continue to move into Central Alabama
by Wednesday morning, sharply tapering off rain chances after 12-15z
Wednesday. A strong push of dry air will move into the region by 18z
Wednesday, scouring out any lingering cloud cover and resulting in
mostly sunny conditions later in the day. A stout northerly flow will
keep temperatures around 10 degrees below normal however, with
readings in the mid to upper 60s.

.LONG TERM...(Wednesday night through Sunday)
Issued at 307 PM CDT Mon Oct 15 2018

Large dome of high pressure out of the Plains states will continue
to build sewd into the Midwest/OH Valley regions with the start of
the latter portion of the forecast package. This should translate
into some quiet/tranquil wx conditions for the cntrl TN Valley going
into the end of the work week. Afternoon temps look to trend
seasonably cool for both Thu/Fri, with highs mainly in the upper
60s/near 70F. Overnight temps will also trend near/perhaps slightly
below normal, with lows ranging predom from the mid 40s/around 50F
into early Fri. The latter half of the global models then remain
consistent with the sfc high translating to the east heading into the
weekend period, as the influx of moisture increases into the region
out of the south. The latest model runs are also hinting at a weak
sfc/tropical wave forming over the extreme wrn Gulf in the Thu/Fri
time frame. This energy/moisture looks to be diverted to the NE this
weekend as it becomes embedded within a WSW flow regime ahead of an
oncoming upper trough axis out of the Plains states. Much of the
associated shower activity also looks to be picked up by the approach
of another cold front out of the NW, as rainfall begins to spread
ewd into the area around the first half of the weekend period. The
rainfall though quickly moves east of the region by Sun with the
passage of the cold front. This should allow for some additional
cooler air to filter into the area heading into the new week, with
highs both Sat/Sun struggling to get past the lower/mid 60s, while
overnight lows this weekend fall well into the lower 40s/around 40F
in most spots.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 657 PM CDT Mon Oct 15 2018

Regional sfc observations indicate that a cold front has now pushed
through the majority of northern AL, with moderate NNE flow on the
order of 10 knots forecast to persist throughout the night at both
terminals. An overcast deck of low stratus clouds will continue to
build swd into the region in the wake of the front, with cigs arnd
1500 ft expected to descend into the IFR category btwn 06-14Z. Some
light rain will also be possible, especially during the period from
06-10Z, but should be of no impact to airport operations at either
terminal. Sfc flow will gradually back to N and subside tomorrow
morning, with cigs expected to slowly improve into the MVFR range
beginning arnd 14Z. However, a disturbance approaching the region in
SW flow aloft should result in another round of fairly widespread but
lgt-mod rainfall beginning arnd 19Z and continuing well beyond the
end of the valid TAF period. Due to uncertainty at the longer time
range, we will maintain MVFR cigs during this portion of the
forecast, although IFR cigs will certainly be possible.





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