Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 030356

Area Forecast Discussion
National Weather Service Huntsville AL
1056 PM CDT Thu Apr 2 2020

For 06Z TAFS.


.NEAR TERM...(Rest of tonight)
Issued at 1003 PM CDT Thu Apr 2 2020

IR satellite data confirms that a gradual increase in mid/high-level
cloudiness can be expected across the TN Valley overnight, as
convective debris moves through the apex of an amplified 500-mb ridge
extending from the lower-MS Valley into Ontario. Although any cloud
ceilings will be above 25 kft, the broken-overcast nature of the
incoming cirrostratus may have a minor impact on radiational cooling,
and we have increased temperatures by a degree or so to reflect
this. Regardless, most locations will still fall into the l-m 40s by
sunrise. Some patchy fog may also tend to briefly develop in wind-
protected valleys and near large bodies of water between 6-14Z, but
due to uncertainties regarding the impact of the increasing cloud
cover, we have not included any fog in the grids at this point.
Finally, we have made a minor change to the POP grids to reflect a
non-mentionable but non-zero probability of precip between 09-15Z.
This was done to reflect an increasing coverage of virga and the
possibility for a few sprinkles of rain (mainly across the western
half of the CWFA), as a weakening mid-level disturbance tracks
southeastward from the Ozarks region.

.SHORT TERM...(Friday through Saturday night)
Issued at 229 PM CDT Thu Apr 2 2020

The above noted storm system east of New England would normally head
out to the N-E, closer to the Canadian maritimes or over the north
Atlantic. But not this time, as an upper level block situated from
the Arctic to the north Atlantic hinders the usual NE movement of
this system. In fact, the low will pushed towards the SW tonight,
moving closer to NY/NJ shore on Friday. The low by this time should
be somewhat weaker (980s mb central pressure). Friday evening into
Saturday, the influence of blocking should relax over the Atlantic,
allowing the low to finally exit to east during the weekend. The low
leaving will help lessen a NE-E flow over region, and help daily
high/low temperatures moderate even more this weekend. High
temperatures on Saturday should warm into the lower 70s; close to
normal levels. A tad warm is expected on Saturday, with high
temperatures rising into the mid 70s.

A weak system slowly forming to our west will finally head this
direction during the course of the weekend. It will bring an increase
in clouds. Despite the clouds, a tad warmer is expected to start a
new week, with high temperatures warming into the mid 70s. The system
continued to hint as signs of weakening as it moves eastward. Enough
moisture should remain to bring lower end rain chances, especially in
the overnight hours of Saturday night. Kept the forecast thunder free
in the short term, as there is not enough instability nor shear to
support convection. Low temperatures Friday night near 50, should be
in the lows/mid 50s on Saturday night.

.LONG TERM...(Sunday through Wednesday)
Issued at 229 PM CDT Thu Apr 2 2020

An unstable zonal flow pattern sets up over the Southeast early next
week. Shortwaves traveling along the flat flow will lead to several
periods of showers and thunderstorms. Under this type of regime,
there is a lot of uncertainty in the timing of these shortwaves,
which leads to a lot of uncertainty in exactly when these showers and
thunderstorms will develop and move through. Good news is that this
is also not a good pattern for strong or severe thunderstorms.

We start to see a bit of weak ridging build up along the Gulf Coast
midweek next week, which may lead to increased moisture and warm air
advection into the Tennessee Valley. This may lead to heavier
rainfall with showers and storms that develop Tuesday and Wednesday.
In general temperatures early next week should stay in the mid-to-
upper 70s until Wednesday, when stronger warm air advection should
bring high temperatures up into the low 80s.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1056 PM CDT Thu Apr 2 2020

A minor increase in mid/high-level cloud cover is anticipated
overnight, as convective debris clouds originating from the southern
Plains/mid-MS Valley spill around the apex of a mid-level ridge to
our west. However, a slightly stronger disturbance in the WNW flow
aloft will likely result in a greater coverage of As/Cs clouds Friday
aftn/evening. Low-lvl flow will remain lgt/vrbl for much of the TAF
period, given the persistent influence of a broad sfc ridge across
the region.






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