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fxus63 kpah 262353 
afdpah

Area forecast discussion
National Weather Service Paducah Kentucky
653 PM CDT Fri may 26 2017

Update...
issued at 653 PM CDT Fri may 26 2017

Updated aviation discussion for 00z tafs.

&&

Short term...(tonight through Sunday night)
issued at 334 PM CDT Fri may 26 2017

Will keep current Wind Advisory in place through expiration as
winds remain strong enough to hamper some outdoor activities on
area lakes and rivers.

Very complicated and conditional severe weather scenarios in place
for the Memorial Day weekend. A similar signal was noted in the
ECMWF, Canadian, NAM-WRF (including the nmm version), and the esrl
hrrr and was used in the background for the timing and coverage of
the convective activity tonight through Sunday.

GOES 16 visible satellite imagery and surface observations
pointing to broad lift and mixing under the low level inversion
with a Flat Ridge. Stable layer cloud cover is showing up near the
maximum moisture plume over southeast Missouri and southern
Illinois at this time. There is uncertainty whether there will be
enough lift for showers (or drizzle) this evening over southeast
Missouri. The convection allowing models (cam) suggest that there
may be some isolated shower or thunderstorm activity along the
differential heating boundary east of the cloud cover. This will
need to be monitored for tonight.

The mesoscale convective system/mesoscale convective vortex over northern Illinois at this time should provide
some further lift as it moves southeast into Indiana this evening.
This will likely generate a focused boundary along and north of
the Interstate 64 corridor in southern Illinois and southwest
Indiana. This will provide some potential isolated convective
activity along Interstate 64 tonight into early Saturday.

A rich source of moisture will continue to advect from Arkansas
overnight tonight into Saturday morning with an impressed warm
frontal boundary setting up across southeast Missouri, loosely
connected to the left over boundary along the Interstate 64
corridor in southern Illinois and southwest Indiana. With
precipitable water expected near two inches, decent rainfall rates
will be possible near the frontal boundary in southeast Missouri
during the early morning hours Saturday. Low to middle level flow
will be well into a faster zonal flow with decent shear available
for robust updrafts by midday Saturday. Given the increasing
shear, ample cape, and the proximity to boundaries, there will
significant severe weather potential, especially during the
afternoon and evening. Very large hail and damaging winds, and the
potential of a tornado near an outflow boundary will be expected,
especially in the Storm Prediction Center moderate risk area.

There may be a reduction in severe weather coverage and intensity
by mid-evening, but will pick up again around the midnight hour
when a well-organized linear mesoscale convective system is expected to move southeast
through Missouri, reaching into southeast Missouri and southwest
Illinois. There may be more widespread, enhanced wind damage
potential with this mesoscale convective system overnight.

The big question will be what happens to the mesoscale convective system once it moves
into the weather forecast office pah forecast area after midnight. Should the mesoscale convective system move
beyond its mature stage shortly after midnight into early Sunday
morning, there will be a rapid slow down/stalling of the outflow
and fixation of a impressed boundary over the weather forecast office pah forecast
area between 3 am and 8 am Sunday. If the thunderstorms stall and
train, excessive rainfall will be the primary weather hazard
through daybreak Sunday. This would set the stage for renewed
strong to severe convection on Sunday afternoon, as the upper
low/trough move into and through the weather forecast office pah forecast area.

Should thunderstorms move further south into west Kentucky late
Saturday night/early Sunday morning, the Storm Prediction Center day 3 slight risk of
severe thunderstorms may need to be adjusted further to the
southeast of the area.

Regardless, it will be Dicey for anyone attending/participating in
outdoor activities this weekend.

Long term...(monday through friday)
issued at 334 PM CDT Fri may 26 2017

This period will start out with high pressure moving through behind
sunday's frontal passage. For those with outdoor activities on
Memorial Day, the weather looks fantastic with dry weather and lower
humidity levels.

A weak cold front will sink south toward the area by Monday evening
as an upper level low churns over the Great Lakes region. Cyclonic
flow around this upper feature will continue to cause disturbances
to rotate around it. The influence of these waves will largely stay
north of our region, but there looks to be some minor ripples move
up from the southwest U.S. That may interact with the weak front
nearby and produce some minor precipitation for Tuesday and
Wednesday. Individual models aren't in great agreement so the
blended guidance seems to be a good approach at this time range.

Rain chances will ramp up later in the week as the upper low over
the Great Lakes finally pushes east on Thursday. Eventually our area
looks to become entrenched in southwest flow with increasing
moisture later in the week. This will lead to increased shower and
thunderstorm chances Wednesday night through Friday.

Temperatures will remain right around normal for late may. Highs
will generally be in the upper 70s to lower 80s with night time
temps dipping into the upper 50s to lower 60s.

&&

Aviation...
issued at 653 PM CDT Fri may 26 2017

VFR ceilings will persist across much of the area through the
evening, while MVFR conditions prevail over portions of southeast
Missouri and southern Illinois. Patchy drizzle is even possible
beneath the MVFR ceilings this evening. Ceilings are expected to
lower into the MVFR range across most of the area late tonight into
early Saturday morning. They should return to VFR category by the
late morning and afternoon hours Saturday. A little MVFR fog
development is possible late tonight--particularly over southeast
Missouri which may impact kcgi. While isolated storms cannot be
completely ruled out through noon Saturday, we believe the greatest
risk for thunderstorm development should hold off until late
Saturday afternoon and evening. Southerly winds at or below 10 knots will
prevail.

&&

Pah watches/warnings/advisories...
Illinois...none.
MO...none.
In...none.
Kentucky...none.

&&

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