Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 172357
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
657 PM CDT Sat Jun 17 2017

.UPDATE...
Issued at 657 PM CDT Sat Jun 17 2017

Updated aviation discussion for 00Z TAFs.

&&

UPDATE Issued at 413 PM CDT Sat Jun 17 2017

Updated the gridded forecast and related products, for newly
developed convection across far West Kentucky (Graves, Marshall
counties). 1 minute GOES-16 data shows this activity should drift
ENE through the late day, early evening hours. Mid level lapse
rates are well below 6, and greatest instability is a bit west of
this activity. So it should remain general convection.

CN

&&

.SHORT TERM...(Tonight through Monday night)
Issued at 239 PM CDT Sat Jun 17 2017

Main concern for the short term will be incoming fropa with strong
to severe storm potential. Recent trends continue to depict the
overnight into tomorrow morning activity to be the main show for our
area. However, there is still some guidance, like the 12Z ECMWF that
holds off most precip until after 12z Sunday.

Clusters of thunderstorms are expected to develop from eastern
Kansas into northern Missouri and central Illinois late this
afternoon and evening. This activity will then merge into 1 or more
MCS`s and proceed southeastward. It appears the convective complex
should enter our far northwest counties sometime in the 05-07z
timeframe. Leaned toward the NAM 4km Nest and WRF-ARW for timing of
the storms through the area overnight into tomorrow morning. The
best wind fields/shear will remain off to our northwest, however the
flow should increase enough to warrant some strong storm potential
mainly in the form of damaging winds. SPC has continued to push the
slight risk further south, now encompassing much of the area except
closer to the TN border. The complex will more than likely be losing
steam as it progresses further southeast into the area, thus the
severe storm threat will be lower for southern and eastern counties.
Heavy rain will be a concern as well as PWATs increase to over 2
inches.

Expecting a lull in the activity by late morning into midday before
possible new development forms over the Pennyrile region of west KY.
This activity will be contingent on just how the overnight
convection plays out. If the overnight MCS lingers through the
morning hours, we likely won`t destabilize enough to get much in the
way of redevelopment. However, if storms can develop, the potential
exists for a few strong storms, although the greater potential looks
to be off to our south and east. Post frontal precipitation should
largely be winding down by midnight across our area, but could still
be some lingering rain across the southeast counties right into
early Monday morning.

Moisture levels will remain high until cool northwesterly flow works
in from the north tomorrow evening/overnight. Lows will be held up
in the 70s tonight. Highs tomorrow look to be cooler with the
precipitation and clouds around, holding in the low to mid 80s. More
comfortable temperatures will be seen by Monday morning with lows
down into the low to mid 60s.

.LONG TERM...(Tuesday through Saturday)
Issued at 239 PM CDT Sat Jun 17 2017

In the extended forecast period, the broad upper air pattern will
consist of a broad upper ridge centered over the Desert Southwest
U.S. and a broad low pressure center over eastern Canada. This will
keep the WFO PAH forecast area in northwesterly flow aloft through
at least late Wednesday or early Thursday.

The flow become more zonal Thursday and Friday with the WFO PAH
forecast area fixed along the base of the faster westerlies in the
northern half the the U.S. and broader ridging to the south and
southwest.

In early part of the extended period, the deep layer moisture for
robust convection is severely limited, with most of the greater
forcing focused closer the the Great Lakes region. Even with lower
moisture content, temperatures will likely rebound into the upper
80s to near 90 around the middle of next week.

By Friday, the regionally initialized blended model guidance chances
for precipitation seem loosely tied with the ECMWF 00z/12z Saturday
numerical model runs, as the baroclinic zone shift southward across
the WFO PAH forecast area and phases in with a deformation zone east
of the Southwest U.S. ridge.

At this point, the forecast confidence with the late week
precipitation chances are 40-60 percent, mainly due to location
issues associated with the precipitation across the WFO PAH forecast
area.

Otherwise, the blended guidance has a fairly good handle on
temperatures, dewpoints, and winds into next week.

&&

.AVIATION...
Issued at 657 PM CDT Sat Jun 17 2017

Main concern over the next 24 hours is with a thunderstorm complex
forecast to dive southeast into the region overnight into Sunday
morning. Gusty winds and lower cigs/vsbys can be expected with this
activity. Preliminary indications are that this complex may reach
far northwest counties around 05-07z and then progress southeast
through the area, exiting much of the region by 14-16z. Timing is
subject to change as some guidance is a bit faster or slower with
the convective complex. The potential for another round of storms
tomorrow afternoon across southeastern portions of the area is
largely contingent on how the first round evolves. Most of this
activity should be focused in western Kentucky. Otherwise, expect
VFR conditions through much of the period outside of thunderstorm
activity. Southerly winds tonight will tend to veer to the west as a
cold front moves through on Sunday.

&&

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

$$

SHORT TERM...SP
LONG TERM...Smith
AVIATION...RJP



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