Area Forecast Discussion
Issued by NWS Nashville, TN

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FXUS64 KOHX 240829 AAA
AFDOHX

Area Forecast Discussion...UPDATED
National Weather Service Nashville TN
329 AM CDT Tue Oct 24 2017

.DISCUSSION...

.SHORT TERM...
(Today thru Thu)

Deep upper troughing is well entrenched across the eastern U.S. this
morning. Middle TN is well within the cooler sector as current temps
are generally in the upper 40s to lower 50s. Vort max upstream will
swing across the area this afternoon. Euro, gfs and hrrr solutions
all agreeing that light shower activity may move across the area.
Will go ahead and include a slight chance of afternoon showers with
sprinkles across the Plateau this evening.

It will be on the cool side as thermal troughing keep 850 mb temps
down below 1c. May see peaks of sunshine in the morning, but clouds
will win out by afternoon. Highs will be in the upper 50s to lower
60s.

Clouds to hang on into tonight although partial clearing expected
across western areas. The location of the sfc high on 12z wed will
be back over TX, so we will see a continuation of westerly winds of
5 mph or so. Coolest areas will be the southwest where more clearing
will occur. For lows, should see upper 30s west to near 40
elsewhere.

Skies are looking partly cloudy for Wed and Wed nt. The sfc high
will pass to our south as the aforementioned upper trough slides east
toward the Atlantic states. Another cold night, Wed nt, with lows
upper 30s to lower 40s. But then, look for a warming trend to
commence on Thu as heights rebound and delta T850 approaches 10c.
Highs Thu afternoon will approach 70 degrees, west of Plateau.

.LONG TERM...
(Fri thru Mon)

Some significant changes in the forecast for Fri thru Mon as
compared to yesterday`s afternoon forecast package. Even with
this significant change lean, played it on the conservative
side when it came to frost potential Sat and Sun nights.
Let me explain. In reasonable agreement with and leaned toward the
latest thinking per the WPC Extended Forecast Discussion with its
lean toward the 00Z ECMWF/GFS solution blend. With that in mind,
these models are showing a much more enhanced chance of rainfall Fri
night into Sat, making the jump from sct light shwrs previously
forecasted yesterday afternoon to cat light to mdt shwrs. This due
to more of a timing agreement between these two model solutions on
sfc frontal passage and associated moisture potential.

Now I am going to break out the quandary term, as it pertains to
frost potential Sat and Sun nights. Although both nights one could
argue that areas to widespread frost could develop across the mid
state region per strong CAA expected behind sfc frontal passage,
with overnight low temps forecasted generally in the low to mid 30s,
there is at least a couple of flies in the ointment here to
consider. First, for Sat night, these consensus model solutions
along with WPC sfc progs showing the development of a sfc pressure
gradient as 29/12Z approaches across the mid state region. Forecast
this morning depicting nwly sfc winds 5 to 7 mph with gusts to
potentially 10 mph, not ideal by any means for areas to widespread
frost development, i.e. very light to calm winds preferred. Also,
cloud coverage not ideal also, ptcldy skies are forecasted vs moclr
to clr skies preferred. As for Mon night, although temp wise it
looks much better for broader frost development across the mid state
region, there is a swly sfc wind component forecasted. Will that
usher in potentially warmer air to the mid state region than what is
currently being forecasted? Also, again a question about cloud
coverage, i.e. forecasting ptcldy skies at this time. With all of
this said, believe that there will be a potential for frost, and
will mention patchy, but do not have the confidence enough yet to
mention areas to widespread like our neighboring offices to our
north are currently doing.

After seasonable afternoon high temps on Fri, with pcpn chances
holding off until the afternoon hours, look for the CAA scenario to
come into play with lows in the upper 30s to lower 40s Fri night,
with highs on Sat and Sun generally around 15 degrees or so below
seasonal normal values, mainly in the lower 50s, upper 40s to around
50 Cumberland Plateau Region. As sfc ridging influences begin to
shift eastward, that southwesterly sfc flow will definitely begin to
kick in as the day on Mon progresses, with afternoon high temps
still expected to be seasonal cool, but rising into the mid to upper
50s, lower 50s Cumberland Plateau Region. As for some of those
rumors mentioned in yesterday afternoon`s forecast package
indicating a possible snowflake on the back side of the moisture,
looks like best potential of any convection associated with upper
level low moving into the mid state will be during the Sun afternoon
time period, with the mid state remaining dry Sun night and Mon.
Initial indications show that patchy frost may once again be
possible on Mon night across the eastern half of the mid state as
temps are expected to be in the mid 30s across this portion of the
mid state.

&&

.AVIATION...
06Z TAF DISCUSSION.

BNA/MQY/CKV/CSV...Occluded front is moving into Middle Tennessee
late this evening, with mainly mid-level moisture associated with
the front. Low levels have dried out considerably, and all
precipitation has exited the mid state. Winds will stay up a few
knots overnight, and with dew points falling along with
temperatures, radiation fog appears unlikely. So look for VFR wx
the next 24 hrs. Winds will increase during the day tomorrow.


&&

.PRELIMINARY POINT TEMPS/POPS...
Nashville      62  40  57  42  70 /  20  10   0   0   0
Clarksville    61  38  58  41  71 /  20  10   0   0   0
Crossville     59  37  49  38  62 /  10  10   0   0   0
Columbia       62  37  57  40  70 /  20  10   0   0   0
Lawrenceburg   62  37  57  39  69 /  20  10   0   0   0
Waverly        60  38  57  41  70 /  20  10   0   0   0

&&

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

&&

$$

DISCUSSION......21
AVIATION........31



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