Area Forecast Discussion

FXUS64 KHUN 201730
Area Forecast Discussion
National Weather Service Huntsville AL
1230 PM CDT Tue Mar 20 2018
For 18Z TAFS.
.NEAR TERM...(Rest of Today)
Issued at 948 AM CDT Tue Mar 20 2018
A cloudy, dreary day is taking shape across the TN Valley, behind a
strong cold front that moved through earlier this morning. This cold
front is now well to the south and east of the forecast area, leaving
a northwesterly flow and CAA in its wake. Meanwhile, a strong upper
trough was moving east toward the TN Valley, with area radars over
the Mid South region showing light rain within the enhanced lift 
associated with the trough. As this trough shifts eastward through 
the day, this light rain will push into the TN Valley, beginning 
within the next couple of hours and continuing through the 
afternoon. Not expecting much QPF with this activity, with most areas
seeing less than one-tenth of an inch. The combination of mostly 
cloudy skies and increasing northerly flow will keep temperatures 
from rising this afternoon. In fact, most areas have already 
experienced their daytime highs, with temps expected to fall into the
40s by the afternoon. Add to this gusty winds thanks to the 
tightening pressure gradient, and an unseasonably cool day is 
expected. No major changes were made to the previous forecast. 
.SHORT TERM...(Tonight through Wednesday night) 
Issued at 323 AM CDT Tue Mar 20 2018
As we move into the evening hours today, temperatures will fall into
the mid to upper 30s primarily. This could cause lingering scattered 
precipitation to become a mix of light rain and snow in Southern
middle Tennessee and in northern Jackson county in Alabama. However,
this looks to move northeast of the area just after 10 PM. So not
expecting any accumulation of snowfall at this time. Could see some
flakes of snow in those areas, but not many other locations. Skies
should clear around and after midnight from west to east. This along
with strong cold air advection should allow low temperatures to drop 
just to or below freezing for a few hours before daybreak on
The colder air really moves southeast into the area behind the
departed front by Wednesday, as highs only climb into the mid 40s to
lower 50s despite abundant sunshine. A return to more widespread
freezing conditions look to shape up on Wednesday morning, as winds
lighten as high pressure builds into the area and good radiational
cooling occurs. Could see some locations dip into the upper 20s in
Southern Middle Tennessee. 
.LONG TERM...(Thursday through Monday) 
Issued at 323 AM CDT Tue Mar 20 2018
A sprawling surface high pressure remains in control of the local 
weather on Thursday. Aloft, we will be under northwesterly flow on 
the back side of a trough departing the northeast. However, a mid 
level ridge will be centered over LA and help push up heights and 
therefore, a warming trend. Thursday should be sunny and highs will 
warm into the upper 50s to around 60 degrees.
Clouds will increase slightly Thursday night as a shortwave dives
southeast along the upper trough. Lows will also be able to warm 
above freezing and into the mid 30s to lower 40s. There will be a 
slight chance of rain showers with that shortwave. 
A weak upper low will develop over the midwest Friday evening with
surface cyclogensis in the KS/MO area. Looks like a warm front will
be extending southeast with guidance showing QPF along it down
through most of the forecast area. There is quite a bit of
uncertainty with the system this weekend especially moving into 
Saturday. The surface low shifts east-southeast over SE MO with the
frontal boundary ahead of it. This boundary eventually dissipates
before another frontal boundary moves in Sunday ahead of an upper
trough digging into the desert southwest. Really tough to tell at 
this point where the rainfall gradient will be and when the highest 
rain chances will be. At this point, just left the blended chance 
pops in the forecast from Friday through Tuesday with the highest 
chances int the Monday/Tuesday range. Although thunderstorm 
parameters aren't impressive, with the area in the vicinity of 
multiple fronts, kept isolated thunder in for Sat through Monday. 
In terms of temps, southwest winds and rising heights push highs
Friday to the upper 50s/lower 60s and upper 60s/lower 70s for 
Sat/Sun/Mon. Lows will also slowly warm and be back into the mid 50s 
by Sat night. 
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1230 PM CDT Tue Mar 20 2018
MVFR conditions will prevail through at least 02Z at the KMSL and
KHSV terminals. An upper low will swing through the region this
afternoon, bringing isolated to scattered light rain across the
region. Confidence is low on if this activity will reach the area,
however if it does, visibilities may be reduced as low as 4SM. Given
the lower confidence, have not included these lower visibilities in
the TAF. Otherwise, cigs around 1500 feet will persist through 02Z
and then lift to around 2500 feet between 02Z and 06Z. By 06Z, cigs
will lift and VFR conditions will return. Winds will generally remain
from the northwest and gust up to 18 to 20 kts this afternoon before
diminishing after 02Z.
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