Area Forecast Discussion
Issued by NWS Paducah, KY
FXUS63 KPAH 261705
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
1205 PM CDT Sat Jul 26 2014
Issued at 1205 PM CDT SAT JUL 26 2014
A relatively shallow boundary layer will allow temperatures warm
into the lower 90s over most of the area as expected this
afternoon. However, it will also trap the low-level moisture, and
allow mid 70 dewpoints to overspread the region through the
afternoon. This will create heat indices in the 100 to 105 range
over most of the region. Will likely issue an SPS for the heat in
the next hour.
As for severe weather, SPC has just pushed the southern edge of
their moderate risk northward, right along our northern border in
southern Illinois. There is a whole lot of uncertainty in the
convective evolution to support a moderate risk into our area.
The latest HRRR runs have been developing convection near the STL
metro area around 00Z, presumably near the MCV that is currently
over northwest Missouri. The HRRR then pushes the convection east
southeast along our northern border areas in the 02Z-05Z timeframe.
It has not shown any signs of a larger-scale bowing MCS/derecho,
like the 00Z WRF runs were advertising.
If storms do push into our area this evening, damaging winds will
be the primary concern, with large hail and tornadoes lesser
concerns. Of course, there is a real possibility that this evening
activity could stay completely north of our forecast area. There
could be some convection firing over the Evansville Tri State into
the overnight hours, if an outflow boundary pushes into that area.
Damaging wind would be the primary concern overnight.
UPDATE Issued at 733 AM CDT SAT JUL 26 2014
For aviation section only.
.SHORT TERM...(Today through Sunday night)
Issued at 249 AM CDT SAT JUL 26 2014
Biggest forecast challenge this period is on how to deal with
MCS development this afternoon and possibly again early tonight.
Much of the meso-convective models this morning point to rapid
destabilization this afternoon as surface temperatures soar into
the 90s and dew points climb into the upper 60s to near 70. Thing
is, most of the region should remain under thermal capping until
later in the day. MCS development is likely to occur over se IA and
west central MO this afternoon, then propagate ese toward the I-70
and I-64 corridors late in the day as the capping weakens. There is
some question as to whether this initial convection will brush by
just to our north or actually clip the I-64 corridor of IL/sw IN.
Given the extreme instability expected and decent wind fields
aloft, what convection does form later today has a very good
chance of being severe at times, with damaging wind gusts, large
hail and even isolated tornadoes possible. Even if this initial
convection/MCS misses our forecast area, additional thunderstorm
development will be possible along its outflow boundary early this
evening and into the night.
Cold front enters the scene late tonight into Sun AM, and will
likely be located somewhere near the OH River by noon. Depending on
the degree of heating that can occur along ahead of this front,
more strong thunderstorm development could occur in areas along
and south of the OH River Sunday afternoon. Should finally clear
out Sunday night behind the sfc front as much cooler and drier air
flows back into the region.
.LONG TERM...(Monday through Friday)
Issued at 249 AM CDT SAT JUL 26 2014
A very tranquil week is coming up for the region next week. By 12Z
Monday, the upper level wave and associated sfc front will be in the
eastern Great Lakes region and will continue to move off the eastern
seaboard by 12Z Tuesday. During the week, our region will be under
the influence of a large trough across the eastern half of the
country, with amplified ridging taking place out west. Models bring
a weak lobe of energy southward across the area on Monday, but it
should only result in some passing clouds, as moisture is limited.
The 00Z NAM/GFS hints at a possible shower to two in parts of
southwest IN where moisture might be a little better, but will leave
dry for now. However, the bigger story to start out the week, will
be the below normal temperatures.
High pressure from central Canada will migrate south/southeastward
toward us early next week and bring a much cooler/drier airmass into our
region. While we will see much cooler temperatures on Monday as
compared to the projected weekend heat, the coolest air will likely
take until about Tuesday to arrive. This means that we should
experience another few degree drop in temperatures then, with some
places likely only reaching the upper 70s for highs. Guidance
numbers have been rather consistent for the past few days so no real
changes to temperatures needed right now.
With high pressure influencing the weather through at least
Thursday, we should expect a mainly rain free forecast with
temperatures moderating back into the low to mid 80s by mid to late
week. Northwest flow can be tricky with regards to figuring out if
there could be any decent chances for rain, but moisture will
definitely be limited to just the lower levels. By Thursday night
and into Friday though, the sfc high breaks down and deeper moisture
advects into the area. This increase in moisture, along with a lobe
of energy pivoting down in the northwest flow aloft, could mean some
chances convection by the end of the week.
Issued at 733 AM CDT SAT JUL 25 2014
Will be in warm sector during this TAF period. A complex of
thunderstorms is expected to develop over IA/IL and move east
southeast toward the I 64 region aft 21z. Could brush KEVV/KOWB
late in the day or during the evening, but confidence not high
enough at this time to mention explicitly in TAFS.