Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 190300

Area Forecast Discussion
National Weather Service Paducah KY
1000 PM CDT Thu May 18 2017

Issued at 959 PM CDT Thu May 18 2017

Short term modifications made to current forecast to reflect
trends through Friday night.

Most of the evening activity was focused along an impressed warm
frontal boundary and theta-e maximum along the I-64 corridor. The
late afternoon/early evening convection has generated an moisture
discontinuity which should be preserved through Friday morning.
There is at least a two degree celcius rise in mid-level
temperatures, which will likely suppress any meaningful convection
during the morning hours on Friday. There is a suggestion of a
weak surface wave working along the impressed warm front during
the afternoon. This wave should help sharpen lapse rates enough to
generate a more pronounced (and isentropically lifted) zone of
convection (and relatively higher PoPs) over southern Illinois,
the Purchase area of West Kentucky, and the Delta region of
southeast Missouri for the afternoon and evening hours on Friday.

Forecast confidence for any higher PoPs tonight into Friday is
less  50% based on some of the higher resolution model guidance.
The Canadian, 12km NAM-WRF, and ECWMF were preferred with this

UPDATE Issued at 726 PM CDT Thu May 18 2017

Updated aviation discussion.


.SHORT TERM...(Tonight through Saturday night)
Issued at 310 PM CDT Thu May 18 2017

Well, apparently the mid-level warm air is still effectively
capping convection this afternoon. We have had a few lightning
strikes, but nothing of any significant intensity has been able to
sustain itself for long. LAPS indicates that 2500-3000 J/kg of
CAPE is available over much of the region, so if deep convection
can develop, we could see a few strong cores. Shear still looks
too meager to expect much storm organization.

Whatever happens late this afternoon should dissipate with or
shortly after sunset this evening, and much of the night should be
dry. Some of the latest CAM data indicates that an MCS may push
eastward into the area overnight, but the timing on this varies
considerably. Did increase PoPs from the west around 09Z, and then
spread good chances eastward across the area through the morning.
Everything should lift back north in the afternoon, leaving much
of the region dry heading into Friday evening.

Similar to late tonight, there is a signal for another MCS to move
eastward into our region late Friday night into Saturday. This is
when the upper-level system begins to lift north out the Plains,
and the larger-scale models really push plentiful QPF into our
region. Given the time of day and weaker wind fields over
our region, figure that any such system will be weakening as it
arrives. However, with PWs over 1.5" and climbing up near 2"
later Saturday, heavy rainfall and flash flooding will be a
concern. There is far too much uncertainty in this convectively-
driven situation to consider a Flash Flood Watch at this time, but
the potential will have to be monitored closely over the next 24

As the storm system lifts north northeast into the Upper Midwest,
the trailing cold front will eventually push into our region
Saturday night. This should provide a decent focus for more
widespread convection and of course more heavy rain concerns.
Storm total QPF is currently 1-2" throughout the area tonight
through Sunday. Of course, some more isolated areas are likely to
see much more rain, but it is just too soon to determine where.

.LONG TERM...(Sunday through Thursday)
Issued at 310 PM CDT Thu May 18 2017

By Sunday, we will be dealing with departing precipitation through
the morning hours mainly, as a cold front continues shifting
eastward. Best chances for lingering precipitation will be across
our eastern counties, as models are in good agreement on timing
right now. A dry Sunday afternoon looks fairly reasonable at this
point for most locations except for maybe the far far southeastern
sections. Much cooler air will be filtering in behind this cold
front so highs on Sunday should only reach into the 70s.

Dry weather will continue Sunday night into Monday as sfc high
pressure settles over the region. Highs will remain in the mid/upper
70s on Monday.

Timing of our next front seems to handled fairly well by the latest
guidance, at least initially. Another frontal boundary will be
impacting our area late Monday night into Tuesday with another round
of scattered showers and storms possible. Some wrap around showers
will be likely on Tuesday night into Wednesday with the passage of
the upper system, though timing of the upper system is still in
question at this there will be a dry period in there.

Another cool blast will arrive on Wednesday with that upper system
and temperatures on Wednesday may not get out of the 60s for highs
in many locations. We should see some warmer and drier weather on
Thursday as the upper trough shifts eastward. Low temperatures
during the extended forecast period look to be in the 50s. A few
locales could dip down close to the upper 40s at some point early
next week, especially north, according to some of the latest data.


Issued at 726 PM CDT Thu May 18 2017

The lull in pcpn has begun this evening, but there is some potential
for a convective system to move into southeast Missouri and southern
Illinois late tonight into Fri morning. This would most likely
impact KCGI, but confidence is not great at this time. For now, a
vicinity shower was mentioned in the 00Z TAF. It now appears that
cigs across the region associated with the possible cluster of pcpn
Fri morning will probably be VFR. A light southerly wind will
continue through the 24 hr TAF period.




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