Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 031122

Area Forecast Discussion
National Weather Service Paducah KY
622 AM CDT Wed Jun 3 2020

.SHORT TERM...(Today through Friday night)
Issued at 312 AM CDT Wed Jun 3 2020

Convective potential this afternoon and tonight will somewhat
complex due to the lifting mechanisms and moisture
availability/advection across the WFO PAH forecast area, as well a
mesoscale MCS maintenance and propagation.

To the south, in the lower Mississippi Valley, including AR/TN, a
pre-existing weak low/middle level circulation and moisture will
be in the vicinity of the WFO PAH forecast area. Given the weak
shear aloft, insolation will be the key to initiate surface
parcels to generate diurnal convection in the peak heating part of
the day, when the greatest CAPE availability can be tapped. This
will likely provide the best chance for showers and a few
thunderstorms across the southern part of the WFO PAH forecast
area mainly this afternoon and early this evening.

The main focus will then shift to the north through midnight, as
remnants of an expected MCS over northern MO/central IL propagate
southward with time. The loss of daytime heating and decent
environmental shear will slow the southward progress and intensity
with time, making the system more outflow dominated with time. The
NAM-WRF guidance is most aggressive with MCS probabilities working
into the northern third of the WFO PAH forecast area after
midnight, but am more inclined to lean toward the RAP/ECMWF
solutions for convective potential overnight. This would place the
best chances for rain in the southeast Illinois and southwest
Indiana areas (closer to the 06z HRRRv4 guidance). At this time,
feel that SPC`s outlook area for mainly Marginal Severe weather in
the WFO PAH forecast area is quite optimistic. Cannot rule out
some wind potential, especially along the Interstate 64 corridor
this evening, but it should remain rather isolated. We will see.

On Thursday, the remnant cold pool boundary from the overnight MCS
from the north, will the differential thermal/moisture boundary
for renewed convection daytime convection, mainly across west
Kentucky and the southeast Missouri Delta region. Adjusted the
highest PoP/Weather toward this area. Severe potential will be
quite limited, focused toward favored mesoscale/microscale
thunderstorm environments aided by convective outflows and
differential heating. Am a little troubled by the aggressive 06z
HRRRv4 model interaction with Central Plains/western MO MCS
scenario and MCS remnants over the WFO PAH forecast area early
Thursday. This may bear watching for run to run consistency.

A series of intermittent shortwaves will arc down the eastern side
of an approaching Central Plains ridge late Thursday into Friday.
This will set the stage for small, intermittent, and mainly
diurnal chances for showers and thunderstorms during the day on
Friday. By Friday night, ridging will move in from the west. This
ridge and capping, along with the loss of insolation, should
markedly drop any chances for rain Friday night.

.LONG TERM...(Saturday through Tuesday)
Issued at 312 AM CDT Wed Jun 3 2020

Models show a frontal boundary just south of the PAH forecast area
on Saturday.  We could see a few showers or storms mainly across the
eastern half of our counties Saturday afternoon, so just included
slight chances for these areas.  Loss of heating Saturday night will
prevent any additional convection, and the front should sink just
far enough south by Sunday to keep us dry.

Models do not take the front as far south as previous runs,
primarily due to the approaching remnants of the Gulf tropical
system Cristobal, so we will not see the drop in dew points over the
weekend as previously expected. Sunday afternoon dew points will
bottom out in the lower to middle 60s, and this will be our least
humid conditions of the extended forecast.

Latest runs of the ECMWF and GFS have similar timing and track of
the remnants of Cristobal through 00z Tuesday, centering it over
northern Louisiana.  Beyond 00z Tuesday, GFS takes it into eastern
Kansas, while the ECMWF takes it right up the lower Mississippi
valley into the PAH forecast area.  These diverging solutions make
it difficult to have high confidence in timing of shower and
thunderstorm chances early next week.  Models blends continue
indicate a gradual increase in precipitation chances from southwest
to northeast Monday afternoon into Tuesday, and this seems like a
good compromise at this point.

Highs on Saturday will be in the 89 to 93 degree range, and with dew
points around 70 degrees, heat indices will reach the middle to
possibly upper 90s.  Highs will remain around 8 degrees above
seasonal normals on Sunday, but as mentioned earlier, it will be a
little less humid.  Humidity will be increasing Monday and
especially Tuesday, and temperatures will remain above normal.


Issued at 621 AM CDT Wed Jun 3 2020

Generally VFR conditions will dominate the 12z Wednesday WFO PAH
TAF issuance. The greatest uncertainty will be the impact of late
evening/early overnight thunderstorm activity on the KMVN, KEVV,
and KOWB TAF locations. Due to the small temporal window for the
development of thunderstorm activity in the aforementioned TAF
locations, did not address any change in wind direction/speed or
ceilings for thunderstorm development.




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