CLE issues Area Forecast Discussion (AFD) at Jul 5, 2:34 AM EDT196
FXUS61 KCLE 050634
AFDCLE
Area Forecast Discussion
National Weather Service Cleveland OH
234 AM EDT Fri Jul 5 2024
.SYNOPSIS...
A front currently stalled near the route 30 corridor will lift
north across the area tonight ahead of low pressure drifting
into the western Great Lakes. This low pressure will pass by to
our north Friday evening while pushing a cold front through.
Weak troughing will linger for Saturday before high pressure
builds in Saturday night through Monday.
&&
.NEAR TERM /THROUGH TONIGHT/...
9:30 PM Update...
Convection has developed across a good portion of the area.
moderate deep layer shear of around 40 knots has resulted in
some of these showers developing rotation, mainly towards the
southern portion of our forecast area. These low-topped
supercells have been weak though, with the lack of instability
really inhibiting their ability to strengthen and become a real
threat. Mesoanalysis suggests weak low-level shear, though low-
level mesocyclones have been observed on radar and there have
been a few pictures of wall clouds and funnel clouds to our
southwest in the supercells in ILN's area, so there must be
greater low-level shear/SRH than mesoanalysis is suggesting.
Either way, it's enough activity for us to keep our eyes glued
to radar, in case of a quick spin-up. Coverage of showers has
been greater than expected, so did increase PoPs through the
next few hours, but decreased PoPs for tonight as confidence
increases in precipitation end time.
Previous Discussion...
Unsettled and humid conditions are expected for the near term.
Weak low pressure will push into the Great Lakes from the west
tonight into Friday ahead of an upper-level trough. A front
currently draped across central OH will lift north as a warm
front this evening into tonight. The low pressure will pass to
our north late Friday into Friday night while pushing a cold
front across the region. Along with the fronts, lift from
convective-enhanced shortwaves and MCVs will move through at
times, encouraging occasional shower and thunder potential.
As of 3:30 PM the front is draped from roughly Marion to
Mansfield to Chardon to Meadville with several low-topped
convective cells ongoing along it. At the same time, an MCV is
moving across central OH. The combination of the two features
will keep shower and thunder chances going through early this
evening along and south of the front, with some lighter
stratiform rain possible north of the front. In the immediate
term, the combination of enhanced flow aloft with the MCV and
the boundary itself may encourage rotating updrafts from
Mansfield to Canton points south. However, skinny and modest
instability profiles and a lack of DCAPE argue against severe
weather. Still, any more persistent rotating updrafts will need
to be watched for a brief/isolated severe threat through about 5
PM in our far south, with any slower-moving or training storms
dropping locally heavy rain in this humid environment. The next
convectively-enhanced shortwave is currently moving east out of
central IL and will move through tonight. Modest lift ahead of
this feature along with weak instability and a humid airmass
will support another uptick in showers and thunder from west to
east this evening into tonight. The frontal boundary will begin
lifting ahead of this feature and may be a focus for more
numerous cells this evening. The wave will exit to the east
after midnight, allowing for a drying trend overnight. With
such a humid airmass and light winds a bit of patchy fog may
develop pre-dawn Friday if a period of partial clearing occurs.
Otherwise, look for muggy lows on either side of 70.
We should see a general lull in activity through much of Friday
morning due to weak subsidence and perhaps a bit of dry air
advection behind the shortwave that will move through tonight.
By Friday afternoon and evening, modest height falls and upper-
level divergence ahead of the upper trough moving into the Great
Lakes along with the approach of the cold front should encourage
at least some shower and thunderstorm development across our
area. Guidance disagrees on how quickly subsidence behind
tonight's wave will exit and on if convection will fire over
the Ohio Valley on Friday. Both could be limiting factors for
destabilization and subsequent convection local. However, still
have a mix of chance and likely POPs along and ahead of the
cold frontal passage from west to east Friday afternoon and
evening as the combination of a front, some forcing, a humid
airmass and timing near peak heating should yield at least some
convection. There is room for POPs to be adjusted higher or
lower depending on how much subsidence lingers over our area and
how robust the return of greater moisture/instability is from
the south/southwest through the day. Either way, expect muggy
conditions with highs generally in the low to mid 80s Friday.
Poor mid-level lapse rates will act against a greater severe
threat Friday afternoon and evening. However, stronger heating
could yield 1000-2000 J/KG of MLCAPE given such a moist airmass
and deep-layer shear of 40-50 knots is expected. Enough surface
heating and mid-level drying may play out to allow moderate
DCAPE to develop as well. Given a number of conflicting factors,
the current Day 2 Marginal Risk (level 1/5) for severe weather
driven by isolated damaging wind potential is reasonable.
However, there is a somewhat less-likely potential for greater
destabilization and more robust convection. Given the amount of
shear, a more robust evolution could support a mix of supercells
and small lines with a more organized wind damage threat and
potentially some marginally severe hail and tornado potential.
This may come down to a "nowcast" situation on Friday.
Activity should gradually exit to the east and diminish in
intensity Friday evening and night as the cold front continues
progressing with some clearing of the skies too. Lows will
generally fall in the mid 60s to near 70 by early Saturday.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
While the model data is not completely supportive, have added slight
chance POPs to the land portion of the CWA for Saturday given the
cold pool aloft moving in and some instability off the boundary
layer combined with peak daytime heating and perhaps a hint of PVA
aloft. Layer moisture is definitely a concerning factor and a reason
not to go above 20 percent, but could get an isolated shower to form
in this setup. Vast majority of the area will be dry. High pressure
will continue to build in the southern Great Lakes, paving the way
for a dry remainder of the weekend. Slightly warmer Sunday with
generally low to mid 80s for the most part. An upper level trough
will be working its way into the western Great Lakes by the end of
the short term forecast period, likely weakening as it does so.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
Upper trough south of the axis in the Great Lakes mentioned at the
end of the short term period will be the main driver for the next
chances for showers and storms for the region. Until then, high
pressure should still be in control for one more day on Monday, but
will be on the exit to the east. Best bet for the surface low
pressure/cold front to come through is Tuesday afternoon/evening.
POPs linger in cyclonic flow aloft through mid week in the wake of
the system.
&&
.AVIATION /06Z Friday THROUGH Tuesday/...
Overall, there is fairly low confidence in the TAFs early this
morning. High amounts of low level moisture remain the region
behind several rounds of rain on Thursday. This is allowing for
a mixture of fog and stratus across the region. Unfortunately,
there is quite a bit of variability with a range of VFR to IFR
in conditions this morning. Suspect that conditions will trend
down to MVFR to LIFR for most locations; however, some mid-level
clouds continue to move through the region and may prevent more
significant fog and stratus from developing. There should be
some mixing with daybreak and a trend to VFR by late morning. A
cold front will approach the region from the west today. The
atmosphere could destabilize and allow for showers and storms
to develop during the late afternoon hours. However, clouds in
the region could mitigate the energy across the area to help
sustain widespread storms. Therefore, have some VCSH and VCTS
mentions at the TAFs for this afternoon into tonight. However,
do not have the confidence to go with any non-VFR restrictions
due to the wide range in possibilities for convection this
afternoon and evening. The cold front will sweep through tonight
and end the rain threat and allow for conditions to trend to VFR
with drying conditions. Winds through the period will have
variable direction this morning, ahead of the front this
afternoon, and then behind the front tonight, but winds should
be 10 kt or less.
Outlook...Non-VFR possible in showers and thunderstorms Tuesday
into Tuesday night.
&&
.MARINE...
Light and variable winds through early Friday morning with wave
heights less than 1ft become southerly around 10kts Friday afternoon
ahead of a cold front with chances for showers and storms, then
southwesterly 10-20kts in the wake of the cold front Friday evening
through Saturday. Wave heights east of Cleveland 1-3ft during that
time, west of Cleveland 1-2ft away from shore in the nearshore
zones. Winds ease out of the northwest Sunday with wave heights
dropping below 1ft despite the more onshore flow at around 5kts.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
NY...None.
MARINE...None.
&&
$$
SYNOPSIS...Sullivan
NEAR TERM...Saunders/Sullivan
SHORT TERM...26
LONG TERM...26
AVIATION...Sefcovic
MARINE...26
Source:
CLE issues Area Forecast Discussion (AFD) at Jul 5, 2:34 AM EDT---------------
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