ILN issues Area Forecast Discussion (AFD) at Aug 1, 6:54 AM EDT369
FXUS61 KILN 011054
AFDILN
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
654 AM EDT Thu Aug 1 2024
.SYNOPSIS...
Very warm and humid conditions are expected for today. An
embedded mid level disturbance will interact with an unstable
airmass to bring the threat for showers and thunderstorms.
Showers and thunderstorms this evening will become more
scattered in nature overnight as the disturbance moves east. For
Friday into Saturday, a mid level low pressure system will
rotate southeast across the Great Lakes and Ohio Valley,
continuing the threat for showers and thunderstorms. Dry weather
and seasonable conditions are then forecast for Sunday and
Monday as weak high pressure resides over the region.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Through sunrise, a weak mid level disturbance along with weak
moist ascent will keep a chance of showers and thunderstorms
across the lower Scioto Valley and northeast Kentucky. These
should shift and diminish in coverage toward morning.
For today, as has been the case for the last several days, the
timing, location, and coverage of convection will be difficult
to pinpoint. Ongoing convection stretching from Illinois into
Missouri is expected to weaken as it heads east into mid
morning. Associated MCVs and left over outflow boundaries will
have to be watched as they enter our region from the west this
afternoon. Instability will increase as the day wears on with
temperatures warming into the upper 80s to lower 90s and
dewpoints rising into the mid 70s. This will result in MLCAPEs
in the 2000 to 3000 J/kg range. With DCAPEs near 1000 J/kg, low
end moderate shear, the potential exists for an MCS or two to
form in this environment from aforementioned MCVs/outflow
boundaries. Thus, SPC has placed much of our forecast area in a
slight risk for severe thunderstorms. The main threat will be
damaging winds given bowing segment potential and the favorable
DCAPE environment. However, some isolated large hail will be
possible given mid level lapse rates approaching 7.0 C/km. In
addition, the threat for heavy rain and scattered instances for
flooding will exist as pwats continue to register around 2+
inches. Best chance for the greatest convective coverage will be
from mid afternoon into the evening hours. With the heat and
humidity, heat index values will range between 95 and 100
degrees. Will mention all these hazards in the HWO product.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
Convection should be ongoing this evening, but it should become
more scattered overnight as activity shifts east/southeast.
Lows will drop into the upper 60s to the lower 70s.
For Friday into Friday night, a synoptic scale mid level low
pressure system is forecast to dig southeast across the Great
Lakes and Ohio Valley. Lift associated with this feature will
interact with increasing instability to bring the likelihood of
showers and thunderstorms, most numerous from mid afternoon into
the evening. The potential exists for isolated strong to severe
wind gusts given pcpn loading. Also, slower moving storms in a
pwat environment of 2+ inches will continue the instances for
localized flooding. More clouds and the pcpn threat will result
in lower highs from today, ranging from the lower 80s west to
the upper 80s east. Lows Friday night will drop into the upper
60s.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
On Saturday morning, a well-defined mid-level trough will be in
place over the Ohio Valley, only very slowly moving eastward as
it dampens with time. The air mass will still be very moist,
with dewpoints in the 70s and precipitable water values of about
1.75". The air mass will modify slightly as the trough moves
away, with drier conditions advecting in behind it. However,
before this happens, another round of showers and thunderstorms
is expected on Saturday. The greatest chances will be in the
southeastern ILN CWA, which should remain ahead of the trough
axis for much of the day. With narrow CAPE profiles and weak
flow, the severe potential for Saturday looks like it will be
rather low, but some storms may produce heavy rainfall.
A brief period of high pressure will build into the region
behind the trough on Sunday. This high will provide dry
conditions, with dewpoints in the mid to upper 60s -- still
somewhat moist, but not to the degree of the previous week.
Forecast confidence becomes very low beyond Sunday. It is
expected that a northwest flow pattern will set back up over the
region, but with a wide spread of model solutions in terms of
two items -- the latitudinal position of the zone of ascent, and
the timing of any potential convection to develop within this
flow pattern. In addition, models are also marred by a
significant amount of spread regarding a potential tropical
system next week. This could have some impacts on the overall
pattern over the region as well, even if the system itself
remains nowhere near the Ohio Valley. Overall, this forecast
will keep Monday dry, with some slight chance / chance PoPs from
Tuesday onward. Temperatures through this period will peak out
in the mid 80s to around 90, with dewpoints generally in the
upper 60s. This will be warm and somewhat humid, but as of now
appears comfortably below criteria for eventual heat headlines.
&&
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
For today, as has been the case for the last several days,
chances for showers and thunderstorms developing in a moist and
unstable environment will be dependent on weak mid level
embedded disturbances (weakly forced environment) rippling
through the atmosphere from the west. This makes timing,
location, and coverage of showers and thunderstorms difficult to
pinpoint. Weak moist ascent through about mid to late morning
will result in isolated to scattered showers/storms. By mid/late
this afternoon and into this evening, one of those mid level
disturbances will arrive, which should provide for a greater
chance for showers and thunderstorms. Have placed some SHRA and
VCTS/CB in the terminals for this threat for now. Will have to
adjust and update as confidence in timing and coverage
increases. Given the moist airmass, MVFR ceilings and IFR or
less visibilities will be possible in thunderstorms.
Winds will generally be from the south and southwest between 5
and 10 knots.
For later this evening into the overnight, a chance of
showers/storms will linger, but coverage should not be as high.
Abundant low level moisture is expected to result in MVFR/IFR
ceilings and mainly MVFR visibilities.
OUTLOOK...Thunderstorms are possible Friday into Saturday.
MVFR/IFR ceilings and MVFR visibilities possible Friday morning
and again Friday night into Saturday morning.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...Hickman
NEAR TERM...Hickman
SHORT TERM...Hickman
LONG TERM...Hatzos
AVIATION...Hickman
Source:
ILN issues Area Forecast Discussion (AFD) at Aug 1, 6:54 AM EDT---------------
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