Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 190756

Area Forecast Discussion
National Weather Service Paducah KY
256 AM CDT Thu Oct 19 2017

.SHORT TERM...(Today through Saturday night)
Issued at 247 AM CDT Thu Oct 19 2017

This morning, we`ll monitor for Fog, which should be confined to
water bodies/nearby, similar to past couple mornings with waning
expanse each day. This is reflected in the ongoing grids and we
anticipate little change in that potential hazard. Other than
that, we still expect relative humidity values this afternoon will
drop thru the 30s in the SEMO Ozarks again, and these may garner
short term mention in the HWO.

A look at Wednesday Highs shows the entire area in the 70-75
range, running a degree or two above much of the guidance. This
trend has been picked up each night shift, and should continue as
we head thru the next 48 hours as well, with the same
positive/warming factors in play. Those being, H5 heights rising
another 50 meters plus as the upper ridge peaks across the Tn
valley Friday...850 mb temps bumping up another couple degrees C
thru Friday...and a very dry column esp below 400 mb, with
increasingly southerly return fetch in the lower trop. One note
today is, it does look like the blend has picked up on the warming
trend, and whereas the past couple mid shifts we had to bump
temps up 2-3 degrees or more for Thu-Fri time frame, now it looks
like just a minor massage of a degree, maybe 2, upwards for most
will work out nicely.

Time/height cross sections do show moisture increasing Friday, but
staying above 400 mb. Moisture works down below 500 mb beginning
Saturday, and surface dew points nudge upwards, thru the 50s,
during the pm hours. This is all prep for a developing cold front
to the west, that will introduce the next chance of
showers/storms, as it comes within striking range of the FA by
late Saturday night.

.LONG TERM...(Sunday through Wednesday)
Issued at 247 AM CDT Thu Oct 19 2017

Right at the get-go in the extended period, we will be dealing with
a system that will impact our Sunday and early next week. An upper
level enlongated trough will be bisecting the country at 12Z Sunday.
Precipitation will be ongoing from the period before (Saturday
night). As this trough moves east during the day on Sunday, a
surface cold front will be traversing the area as well. The main
problem right now with POPs for Sunday into early next week is
timing, as models have diverged on solutions.

All extended models develop an upper level closed low Sunday evening
but all differ on where exactly this occurs. The latest GFS is the
farthest east with this upper system and indicates a fairly
progressive system and has the rain from this system out of the
area by 12Z Tuesday. The newest run of the ECMWF indicates a
slower progression of the QPF due to a developing sfc low to our
south on the AR/LA border, which moves northeast on Monday,
prolonging the chances for precipitation through the day on
Tuesday. The mean GFS ensembles for MSLP and precip are pretty
much in line with the operational run and show a more progressive
system. The Canadian model starts off similar to the GFS but then
shows a much more northward upper low position. Needless to say,
the Sunday through Tuesday time period will go through some fine
tune details over the course of the next few days with placement
of best POPs/timing.

In addition, with wind fields being impressive, despite meager
instability, we will need to be watching. Sfc dewpoints will rise
well into the 60s beginning Saturday night and into Sunday. The
juxtaposition of the best instability and shear will be located over
southeast MO and far western KY Sunday morning into the afternoon.
However, given the scenarios mentioned in the previous paragraph,
agree with SPC`s reasoning that predictability of any organized
convection will be difficult due to the model differences at this

After this system moves out, we will be transitioning into a period
of much cooler weather as a deep upper trough builds in. In fact,
highs on Wed/Thu will be in the upper 50s to lower 60s, and lows
at night may be cool enough to induce some frost development, if
conditions pan out. On the flip side, we could also be dealing
with a few showers with the embedded moisture, but still too
early to tell right now.


Issued at 247 AM CDT Thu Oct 19 2017

We`ll watch patchy fog development closely this morning for
potential flight restrictions, but otherwise anticipate visual
flight rules prevailing again thru the period as high pressure
throughout the column retains its strong grip across the Ohio and
Tennessee river valleys. Time/height cross sections show a very
dry flight trop with scattered high cloud about the only
possibility. Surface flow will be diurnal southerlies diminishing
to light/variable or nearly calm at night.




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