Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 171146
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
646 AM CDT Sat Jun 17 2017

.UPDATE...
Issued at 646 AM CDT Sat Jun 17 2017

Updated to add high chance/likely PoPs to western portions of SEMO
due to recent development there as the outflow boundary passed.
The cells are trying to move east behind the southeastward moving
outflow boundary, but will struggle to reach the MS River this
morning before dissipating. Figure all precipitation will be gone
by 11 AM.

The AVIATION section has been updated for the 12Z TAF issuance.

&&

.SHORT TERM...(Today through Monday night)
Issued at 314 AM CDT Sat Jun 17 2017

This morning`s MCS is propagating southward through Missouri, but
is dissipating on its eastward end. Most of the available guidance
this morning kills off the precipitation right as it approaches
our northwest and west territories around 12Z. Will have some
small chance PoPs there for a few hours later this morning, but
even if some remnant rainfall reaches the area, it will not last
long. The entire area should be dry this afternoon.

The main concern for this forecast is the convective evolution
for tonight into Sunday. An upper-level trough will pivot
southward through the Upper Midwest this evening, and that will
increase the zonal flow over our region a bit, but not a
tremendous amount.

Thunderstorms are expected to develop near the cold front late
this afternoon generally from eastern Kansas northeast into
northern Illinois. Of course these storms are likely to form into
one or more complexes which will then attempt to push southeast
through our region. With the increased flow expected, they just
might make it, but the 00Z ARW and NMM WRF runs both really wipe
it out as it moves into our area.

The non-convection allowing models have no trouble pushing a band
of decent QPF southward into and through our area, but they do
not all agree on the timing. The 00Z GFS is the fast outlier,
bringing the system through 03Z to 09Z, while the ECMWF, GEM and
NAM wait until 06Z to bring it into our region. The slower models
also do not necessarily push it all the way through the region
until Sunday morning.

We will have increasing PoPs from the north through the evening,
but hold the likely PoPs for the overnight period for much of the
region. Figure that the complex will be weakening as it attempts
to move through our region, but if it is well developed enough
there may still be some damaging wind threat initially, however,
would not expect that to persist for long. The best chance of
severe late tonight will be across northern portions of southeast
Missouri into the southern Illinois along the I-64 corridor. Of
more concern will be heavy rainfall potential and lightning.

Sunday`s weather will be highly dependent on what happens tonight.
The 00Z guidance seems to be a bit more bullish for convection
developing near the cold front in the afternoon roughly over the
southeast half of the region. However, if tonight`s MCS is still
raining out over the region into Sunday morning, redevelopment is
not a great bet. If storms can develop, a few may become strong
and produce strong to severe winds. The shear expected will not
support rotating storms, so any stronger storms will be short-
lived. Once again locally heavy rainfall and lightning are likely
to be the bigger concerns Sunday.

With the base of a developing larger-scale upper-level trough
swinging through the region Sunday night, the 00Z models keep
plenty of convection/QPF over west Kentucky through the night and
even into Monday morning in the far southeast. This has been a
fairly persistent signal, so will have likely to categorical PoPs.
Storm total QPF has trended upward a bit with 1" to 1.3" now
forecast from Fulton county eastward through Muhlenberg and Todd
counties tonight through Sunday night.

Temperatures today will climb up to near 90 in most places. Am
somewhat concerned that convective debris cloudiness will hold
temperatures down over portions of southeast Missouri and southern
Illinois. Lower 70 dewpoints will return to most of the region by
midday, so heat indices will generally be in the middle to upper
90s, with a few isolated areas topping out near 100. Will continue
to mention this in the HWO.

Guidance continues to advertise a very mild night tonight with
lows in the middle to upper 70s, but with significant rainfall
expected over most of the region, lower 70s seem like a better
bet. Sunday will be dependent on clouds and precipitation and most
locations will be much cooler with highs in the lower 80s. The
sun will show up Monday along with decent northwest winds, so
temperatures will likely hang in the lower to middle 80s again.
Monday night will be coolish with lows in the lower 60s.

.LONG TERM...(Tuesday through Friday)
Issued at 314 AM CDT Sat Jun 17 2017

It is looking like a relatively quiet but warm week ahead. Sfc high
pressure will be overhead to start out the period. A weak frontal
boundary will sag south into the area Tuesday night but due to its
weakness and lack of decent moisture, convection will be limited.
Best moisture will be over the Evansville Tri state and that is
where we have inserted some small chances for rain for Tuesday
evening/overnight. The latest GFS ensembles agree with this
thinking. Highs will remain in the upper 80s but dew points will be
rather tame in the lower 60s so not too bad for mid June.

Weak high pressure will move into the area early on Wednesday but
will be rather transient and keep moving eastward during the day.
This will mean another dry but warm day. Dry weather will continue
on Thursday with those warm temperatures continuing. However, with
the steady southerly flow across the area, we will see moisture
levels start to increase, therefore dew points will begin rising. In
fact, by Friday, we will likely see dew points back around 70
degrees with temperatures remaining in the upper 80s to around 90
degrees. That increase in moisture will give us a small chance for
some afternoon type showers and storms with the best chances over
our eastern sections (east of the Mississippi River).

Right now, our best chances for widespread showers and thunderstorms
appears to be with a frontal boundary that is progged to come
through Friday night into Saturday. Models are in pretty good
agreement on timing right now. This idea also jives with the GFS
ensembles as well.

&&

.AVIATION...
Issued at 646 AM CDT Sat Jun 17 2017

An outflow boundary from this morning`s Missouri MCS will bring a
brief northwest wind to KCGI near the beginning of the period.
The active convection is to the west of KCGI in SEMO, but it is
not likely to reach KCGI before it dissipates or slips farther
south. Inserted a VCSH at KCGI just to be safe. The outflow may
effect KPAH, but the convection should not. Diurnal development
is not expected this afternoon, and winds should recover to the
south and become gusty.

Another MCS is expected to move southeast through the region late
tonight. Threw in a prevailing north or northwest gust, TS and a
PROB30 for IFR conditions in TS at all sites at 09Z or 10Z through
the end of the period. The timing may fluctuate some, but the
outflow at the very least should impact all sites very late in the
period.


&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&

$$

UPDATE...DRS
SHORT TERM...DRS
LONG TERM...CW
AVIATION...DRS



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