Area Forecast Discussion
Issued by NWS Nashville, TN

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FXUS64 KOHX 242252
AFDOHX

Area Forecast Discussion
National Weather Service Nashville TN
552 PM CDT Fri Mar 24 2017

.UPDATE...
FOR 00Z AVIATION DISCUSSION.

&&

.DISCUSSION...

As they say in Boston, we`re in for a wicked ride the next several
days.  Multiple days of showers and thunderstorms and multiple days
of strong to severe potential.  Spring is here, for sure.

Current GOES-16 visible satellite shows a fairly intense, wound-up
system over the Plains.  Its cold front, stretching from the central
Plains, southward through Arklatex is firing up showers and
thunderstorm west of the Mississippi River and giving them a good
severe potential.  This system will push eastward tonight and by
tomorrow afternoon, begin to affect Middle TN.  Some showers and
thunderstorms should be ongoing west of the TN River by daybreak and
start to creep into our far western counties prior to noon.  By
early afternoon, we should begin to get a solid push of dew points
into our western counties, pushing our sfc-based CAPE values higher.
Here`s the problem:  models are still not in very good agreement on
how high these values will be. The NAM (per usual) is very
aggressive, with steep mid-level lapse rates and CAPE values in
excess of 1300 J/Kg by mid-afternoon. The GFS, however, is half
of that, with very little dry air aloft. Bottom line, even if we
take a blend of the two and meet in the middle, we should still
have enough instability to meet up with the sufficient wind shear
both are showing. If you`re a weather watcher, keep an eye on dew
points in the west late tomorrow morning and early afternoon. If
they climb above 60, then this should set the stage for severe
weather development. As far as threats, I think damaging winds,
hail and heavy rain should be the main threats, but there is
enough low-level helicity to provide rotation in some of these
storms, so the tornado threat, while low, is not zero. Our best
window of opportunity for severe weather should be 2 pm to 10 pm,
however, showers and thunderstorms could persist on the Cumberland
Plateau later into the overnight hours.

Sunday should provide us with a lull in the activity however, clouds
will hang around for most of the day.  I`m above guidance for
afternoon highs, but we could get even warmer if the sun comes out.

Sunday night and first thing Monday morning, another warm front will
pull northward, bringing more moisture and instability to the
region (and a shot at scattered thunderstorms). This is ahead of
our second system of this crazy forecast. With the fact that the
first system never really offers us a cold frontal passage and we
stay ensconced in quasi-warm sector, this secondary warm frontal
passage Monday morning will only serve to further destabilize the
atmosphere. Surface-based CAPE values on Monday are even more
impressive than Saturday, however, the shear parameters aren`t
near as high. As you know, there needs to be a good balance
between shear and instability for severe weather. For now, I`m
going to add a potential for strong to severe storms to the
Hazardous Weather Outlook for Monday, but there are still some
details to be worked out.

Beyond Monday, the thunderstorm train rolls on. It looks like
we`ll have another system on Thursday/Thursday night and yet
another is being progged for next weekend. If this isn`t spring,
I don`t know what is. Either way, buckle in. We could be in for a
bumpy ride.

&&

.AVIATION...
00Z TAF DISCUSSION.

BNA/CKV/CSV...Surface map this evening shows the pressure gradient
really tightening up ahead of a strong cold front that is
currently situated over the southern Plains. Winds will remain
gusty overnight with VFR ceilings the next several hours. Look for
convection to develop across the mid state after 12Z while
propagating from west to east, possibly not reaching CSV until
after 00Z. Tomorrow`s convection will form well ahead of the
surface front, so we won`t be expecting an actual fropa until
several hours after the main line of convection.

&&

.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

DISCUSSION......Unger
AVIATION........08



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