CLE issues Area Forecast Discussion (AFD) at Sep 6, 1:51 PM EDT304
FXUS61 KCLE 061751
AFDCLE
Area Forecast Discussion
National Weather Service Cleveland OH
151 PM EDT Fri Sep 6 2024
.SYNOPSIS...
A cold front will move southeast across the area this evening and
overnight. A surface trough will linger through the Great Lakes
through the weekend. A large area of high pressure will then build
across much of the central and eastern United States through the
middle of the week.
&&
.NEAR TERM /THROUGH SATURDAY/...
1:35 PM EDT Update...
Forecast remains valid per latest trends in obs and model
guidance. Based on latest surface obs, radar data, and satellite
imagery, a pre-front surface trough axis was located near an
Ashtabula to KCAK to Mount Vernon line and is expected to exit
the rest of our CWA to the east by ~5 PM EDT. Another pre-front
surface trough axis extended from central Lake Erie to near
Findlay and is expected to exit our CWA to the east by ~6 PM
EDT. The surface cold front was located near a Detroit to
northwest corner of Lucas County to Indianapolis line. This
front will continue sweeping SE'ward and is expected to traverse
our CWA through ~8 PM EDT this evening. Isolated to scattered
showers/thunderstorms are ongoing in association with low-level
convergence/ascent along the pre-front trough axes and enhanced
low-level isentropic ascent aloft preceding a cyclonic MCV
moving ENE'ward over eastern Lake Erie and toward western NY.
These lifting mechanisms are coinciding with sufficient moisture
and releasing weak to moderate CAPE, including elevated CAPE.
Expect isolated to scattered showers/thunderstorms to persist
along/ahead of the front for the same reasons. Still expect
coverage/intensity of showers/thunderstorms to be greatest
roughly along and east of I-71. Most of these areas will
continue to experience greater cloud breaks, peeks of sunshine,
and warm/moist sector boundary layer destabilization via daytime
heating, respectively, as moderate effective bulk shear
persists in our CWA. Stronger/deeper diurnal convective mixing
of the warm/moist sector boundary layer is expected to yield
steeper low-level lapse rates and greater DCAPE near 500-1000
J/kg from roughly Erie County, PA to Knox County, OH and areas
to the east through this early evening. Therefore, the marginal
risk of severe thunderstorms with damaging convective gusts
appears to be greatest in these areas. Please see discussion
below for further details.
Previous Discussion...
An active near term period is in store with multiple rounds of
showers and thunderstorms expected through Saturday. The first round
will be showers and thunderstorms, some strong, later this afternoon
and evening (3 to 7 PM) ahead of a cold front. The second round will
coincide with lake-effect showers and embedded thunder behind the
front late Friday night through Saturday.
This morning, a few isolated showers and thunderstorms have
developed, likely in response to weak isentropic lift ahead of an
approaching cold front. Just to the west of this activity, a pre-
frontal trough is resulting in more widespread showers and
thunderstorms, coinciding with a narrow ribbon of upper-level
moisture depicted on the ALPW. This pre-frontal trough is expected
to be the lifting mechanism for showers and thunderstorms today.
Believe the actual cold front is located across eastern IA/southern
WI, behind this narrow ribbon of atmospheric moisture.
A decent environment is already in place just ahead of this pre-
frontal trough, with around 1000 MUCAPE present across SE IN,
stretching into NW OH per SPC mesoanalysis. Afternoon instability
remains uncertain, with the HREF suggesting anywhere between 1000
and 2000 J/kg of MUCAPE this afternoon. The environment does become
more favorable for organized storms by mid to late afternoon (3-7
PM) as southwesterly shear increases to 35 to 40 knots at the base
of the approaching upper trough. The threat for strong to severe
storms is most concerning along and east of the I-71 corridor where
the past several HREF runs have been most consistent and clustered.
The primary threats with any stronger storms today will be damaging
wind gusts and large hail, given favorable mid-level flow (0-3 km
SRH ~150 m2/s2). The tornado threat appears low given straight and
long hodographs and weak 0-1 km SRH generally less than 50 m2/s2.
Heavy downpours will accompany any stronger showers and storms,
though not anticipating any flooding concerns.
A much cooler air mass will arrive behind the cold front later this
evening and overnight, characterized by 850 mb temperatures dropping
to around 1C by 8 AM Saturday and dropping to as low as 0C by
Saturday evening. Uniform north to northwest flow across Lake Erie
in addition to a lobe of more favorable mid-level moisture should
result in scattered lake-effect rain showers across much of North
and Northeast Ohio Saturday morning. The threat for lake-effect rain
showers will gradually shift further east into far NE OH and NW PA
by Saturday afternoon as the lobe of mid-level moisture pivots east
along the base of the trough. A few embedded thunderstorms are
possible Saturday afternoon with the lake-effect rain showers. Much
of the eastern half of the area will remain cloudy on Saturday, with
highs in some areas struggling to even reach 60.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
A large and deep upper level trough will continue to be over the
Great Lakes region through the end of this weekend before lifts out
by Sunday night. The lake effect clouds and rain showers will taper
off and clear out of the Snowbelt area of NEOH and NWPA late
Saturday evening. High pressure will build in from the Midwest into
the Ohio Valley Saturday night. The coolest temperatures so far this
Fall Season will arrive late Saturday night with skies becoming
mostly clear and lighter winds. Overnight temps will drop into the
low to mid 40s away from the lakeshore. There could be a few
locations in those usual colder spots that dip down into the upper
30s and a touch of patchy frost can't be ruled out as well. High
pressure will very slow slide eastward across the Ohio Valley and
into the Mid-Atlantic Region Sunday and Monday. Mostly sunny skies
and very nice weather will be around Sunday into Monday with a
gradual warming trend. High temps on Sunday will range from the mid
60s over NWPA and far NEOH. North central Ohio and NWOH will
temperatures in the lower 70s Sunday afternoon. Monday's temps will
be warmer from the low 70s NWPA to near 80 degrees for NWOH.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
The extended forecast will be very quiet and warmer. A large upper
level ridge of high pressure will develop right over our region and
basically not much for most of next week. We will have mostly clear
skies and no chances for rain. Temperatures will continue to climb
into the 80s areawide with some areas in NWOH possibly reach the 90
degree mark for the middle and end of next week.
&&
.AVIATION /18Z Friday THROUGH Wednesday/...
Aloft, a trough axis moves ESE'ward from the Upper Great Lakes
and Upper MS Valley to eastern Lake Erie and far-western PA
between 18Z/Fri and 18Z/Sat. This will cause cyclonic SW'erly
flow to veer to W'erly to NW'erly. At the surface, a pre-cold
front trough axis near KHZY, KCAK, and K4I3 continues moving
E'ward and is expected to exit the rest of our region by
21Z/Fri. In addition, a cold front is poised to sweep generally
SE'ward through our region between ~18Z/Fri and ~00Z/Sat.
Behind the front, a ridge builds very slowly from the north-
central U.S. and vicinity. Scattered to widespread low clouds
with bases ranging from 1kft to 5kft AGL are expected through
the TAF period.
Regional surface winds around 5 to 10 knots veer from SW'erly
to WNW'erly with the passage of the pre-front trough axis. The
cold front passage will cause our regional surface winds to veer
further from WNW'erly toward N'erly and increase to about 5 to
15 knots. Isolated to scattered showers/thunderstorms are
expected along/ahead of the pre-front surface trough axis and
surface cold front. These thunderstorms may produce
brief/erratic surface wind gusts as strong as 25 to 50 knots.
Behind the cold front, scattered lake-effect showers and
isolated thunderstorms are expected to stream generally SE'ward
from Lake Erie late this evening through 18Z/Sat. Brief MVFR to
IFR visibility is possible with any shower or storm.
Outlook...Non-VFR likely with isolated to scattered lake-effect
rain showers and thunderstorms over and generally southeast of
Lake Erie Saturday afternoon through the wee hours of Sunday
morning, especially in NE OH and NW PA.
&&
.MARINE...
Southwesterly winds 8 to 15 knots this morning will shift from the
northwest later today behind a cold front. Northwest winds will
increase 15 to 20 knots by late this afternoon or evening behind the
frontal passage and waves will increase as well with the onshore
flow. Generally Northwest winds 15 to 20 knots will continue for
most of this weekend as well as higher waves and the risk for rip
currents along our lakeshore. Small Craft Advisories and Beach
Hazard Statements have been issued starting this evening and lasting
through Sunday afternoon. Some of the western Lake Erie zones will
drop off either Saturday evening or Sunday morning. In addition to
the gusty winds, the cooler air mass over the warm lake will result
in the potential for waterspouts over the weekend, best chance with
the passage of the cold front today and with the strongest cold air
advection on Saturday.
Winds become southwesterly and diminish to about 10 to 15 knots by
Monday before diminishing to 10 knots or less by Tuesday through the
end of next week with very nice late season boating conditions
expected next week.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Beach Hazards Statement from 5 PM EDT this afternoon through
Saturday evening for OHZ003-007.
Beach Hazards Statement from 5 PM EDT this afternoon through
Sunday morning for OHZ009-010.
Beach Hazards Statement from 5 PM EDT this afternoon through
Sunday evening for OHZ011-012-089.
PA...Beach Hazards Statement from 5 PM EDT this afternoon through
Sunday evening for PAZ001.
NY...None.
MARINE...Small Craft Advisory from 5 PM this afternoon to 8 PM EDT
Saturday for LEZ142-143.
Small Craft Advisory from 5 PM this afternoon to 8 AM EDT
Sunday for LEZ144-145.
Small Craft Advisory from 5 PM this afternoon to 8 PM EDT
Sunday for LEZ146>149.
&&
$$
SYNOPSIS...Kahn
NEAR TERM...Jaszka/Kahn
SHORT TERM...Griffin
LONG TERM...Griffin
AVIATION...Jaszka
MARINE...Griffin
Source:
CLE issues Area Forecast Discussion (AFD) at Sep 6, 1:51 PM EDT---------------
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