Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 180847

Area Forecast Discussion
National Weather Service Huntsville AL
347 AM CDT Wed Oct 18 2017

.NEAR TERM...(Today)
Issued at 347 AM CDT Wed Oct 18 2017

A few mid/high clouds embedded within a WNW flow regime over the mid
TN Valley moved across portions of the local area earlier tonight,
although these clouds have just about cleared the area to the E.
Otherwise, quiet/seasonably cool wx conditions prevailed over the
cntrl TN Valley this early Wed morning, with temp trends predom in
the 40s. Some very light fog has formed over some portions of the TN
River, and this trend may certainly continue nearing daybreak in more
of the river/valley locations. Given the depth of the dry air though
coupled with some mixing just off the sfc, am not xpcting anything
more than just some continued patchy light fog. Temps look to bottom
out this morning mainly in the lower/mid 40s range, and several
locations may be at their forecasted lows right now.

The sfc high remains located ENE of the cntrl TN Valley across the
mid Atlantic states. This should allow more of a veering wind out of
the E/SE later today, and perhaps aid afternoon temps in climbing a
couple of degrees more compared to Tue`s high temps. Afternoon highs
look to climb into the lower/mid 70s, under predom sunny skies, as
the upper flow regime across the region remains out of the WNW.

.SHORT TERM...(Tonight through Friday)
Issued at 347 AM CDT Wed Oct 18 2017

Little change in the sfc pattern is xpcted thru the end of the work
week, with the high pressure xpcted to remain entrenched across the
mid Atlantic Coast. With another clr night xpcted with light winds,
optimal radiational cooling conditions should again allow morning
lows Thu to fall mainly into the lower/mid 40s range. Upper ridging
building across the SE states Thu/Fri will then allow for a slight
warming trend, as afternoon highs climb more into the mid to perhaps
upper 70s, while lows Thu night trend well into the mid 40s. All of
this will continue to occur under a predom mostly clr/sunny sky given
the presence of a building ridge pattern.

.LONG TERM...(Friday night through Tuesday)
Issued at 347 AM CDT Wed Oct 18 2017

At the present, a powerful cyclone moving across the Gulf of
Alaska/far northern Pacific continued heading to the east. It will
induce upper troughing along the west coast, and further amplify the
ridge controlling our sensible weather. This upper ridge at the
start of the extended forecast should be situated along the
southeast coast. At the same time, strong surface high pressure
sprawled from the eastern Great Lakes to the Mid Atlantic will result
in a SE flow across the Tennessee Valley, bringing deeper moisture
towards this region. The high during Saturday should shift further to
the east, with a more southerly flow becoming established. This
southerly flow will continue to bring warm temperatures for mid
October on Saturday, with highs warming into the upper 70s (~73F are
normal highs). An increase in clouds, moisture, and rain chances -
then a frontal passage will bring gradually cooler temperatures
during the course of early next week.

This morning`s forecast model output in contrast to last nights good
agreement - were not in good agreement from Sunday onward. Before
then, with the models in sync, long wave troughing advances eastward
from the west coast to east of the Rockies before daybreak Sunday.
The trough axis takes on a neutral to slight negative tilt during
Sat/Sun. This could bring strong to severe thunderstorms well west
of here. However, sufficient moisture and lift will bring rain
chances to the Tennessee Valley beginning Sunday. Convective
parameters from the models remained on the weak side regarding storm
strength, so will stay with "general" storm intensity. In-congruent
model output from Sunday onward also leads to a low confidence
forecast for the early work week. The Canadian first early Sunday,
then the GFS late that day both develop separate southern lows on
the south side of the trough, while the EC stays with troughing.
Cannot totally disregard the first two solutions, as the EC about 3
runs ago indicated a southern cutoff low. Given those differences,
leaned closer to the EC early next week, with the best rain chances
mainly from Sunday night into Monday night. The more consistent EC
as of late suggests a Monday frontal passage, with showers ending by
Tuesday. It should become notably colder by the middle of next week,
with lows nearing 40 in a few locations.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1230 AM CDT Wed Oct 18 2017

With a strong area of high pressure in place ENE of the local area,
VFR conds are xpcted thru the TAF period.





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