Scientific Forecaster Discussion
fxus64 kohx 250855
Area forecast discussion
National Weather Service Nashville Tennessee
255 am CST sun Feb 25 2018
Looks as though the fireworks are over for the night. The heaviest
showers have pushed off the Cumberland Plateau as of forecast time
and we're left with some light to moderate showers across a good
portion of the mid-state. Rains will continue to push eastward and
I would expect everybody to be rainfree by mid-morning at the
latest. The downside is, we aren't done with the rain, by any
means. Two more systems this week will bring precip to middle Tennessee
and the first one starts tonight. As the frontal system pulls off
to the east today, it can't get far enough away before another
shortwave develops across the Gulf states this evening and spreads
this additional rainfall into the southeastern half of middle Tennessee.
Two good pieces of news with this: first, it looks like all rain
as the surface low remain well south of US. The second, it should
only affect areas of the mid-state that have seen the least amount
of rain in the last week. Because of this, we're going to lift the
Flood Watch as the forecast package is released this morning.
Again, this doesn't mean we're out of the Woods regarding all of the
water. Several area rivers are on the rise due to tonight's
rainfall, however, they should only reach action stage later today.
No flooding is expected.
We'll finally get a respite after tonight's rainfall. Monday and
Tuesday will be dry, allowing for much of the recent rains to begin
to recede. This will be very helpful, but by Tuesday evening, our
second system of the week will begin to move into the region and as
quick as we began to see some relief, we might be right back into
the mix for flooding once again. This mid-week system will be a
double hitter: first with a shortwave that will bring light to
moderate rain Tuesday night and Wednesday, and by Wednesday
afternoon, the coup-de-gras will develop to our west and move into
the mid-state Wednesday evening. A couple of things stand out in
the models for Wednesday evening: we'll already be in a weak warm
sector. Dew points should already be in the upper 50s to around 60,
especially near the Alabama state line. Then, both the GFS and the
Euro develop a secondary low pressure system and drag an additional
warm frontal boundary across our southern counties. Now granted,
this is day 4 in the forecast, so things can (and probably will)
change, however, wind shear sky rockets as that warm front and
surface low drag across our southern counties and while surface
instability isn't great, I never like to see a boundary like this
develop in an already moist environment. It can spike a severe
weather threat quickly. We'll monitor that potential over the next
couple of days, but even if we don't see severe weather, flooding
may become an issue. Precipitable water values jump back to 2 South Dakota above normal, a
60 kt nocturnal low level jet develops and we could be looking at 2-3 inches
of additional rain across the southern half of the mid-state
Wednesday night into Thursday. That could lead to some localized
flooding, but would definitely have an adverse affect on area
rivers and streams. So, while we'll see a couple days of quiet
weather to start the week, we will all need to remain weather
aware, especially as that second system ramps up mid-week.
Things should get much better after Thursday. An extended period of
dry weather is expected to return to middle Tennessee and temperatures
look hang out right around normal.
06z taf discussion.
Ckv/bna/mqy/csv...have tailored terminal forecasts to match
current regional radar conditions as main line of shwrs/tstms
continues to progress eastward across the mid state region.
Expect several amendments at least thru 25/12z as ceilings
fluctuations from at least MVFR to VFR thresholds expected. Look
for clearing skies after 25/12z with possible influx of additional
moisture from the south after 26/06z
Preliminary point temps/pops...
Nashville 59 40 64 39 68 / 30 20 10 0 0
Clarksville 56 35 62 37 67 / 10 10 10 0 0
Crossville 57 41 59 38 62 / 80 40 20 0 0
Columbia 58 41 63 38 67 / 30 30 10 0 0
Lawrenceburg 58 42 64 38 67 / 40 50 10 0 0
Waverly 57 38 63 39 67 / 10 10 10 0 0