CLE issues Area Forecast Discussion (AFD) at Jul 24, 9:40 PM EDT754
FXUS61 KCLE 250145
AFDCLE
Area Forecast Discussion
National Weather Service Cleveland OH
940 PM EDT Wed Jul 24 2024
.SYNOPSIS...
A cold front exits southeast tonight. A trailing surface trough
moves through Thursday morning. High pressure builds in Thursday
night and persists through much of the weekend.
&&
.NEAR TERM /THROUGH THURSDAY NIGHT/...
9:31 PM EDT Update...
Forecast remains valid per latest trends in obs and model
guidance. Broken line of multicell showers and thunderstorms
from near Mount Vernon, OH to near Aliquippa, PA at time of
writing denotes the approximate location of the surface cold
front. This front and associated multicellular convection will
continue moving SE'ward and exit the rest of our CWA by ~10 PM
EDT this evening. Behind the front, primarily fair weather is
expected through the balance of the near-term period as a
surface ridge builds from the western Great Lakes and vicinity.
However, as noted in the previous discussion below, subtle
surface trough axes associated with shortwave troughs aloft are
expected to sweep SSE'ward through our region this evening
through Thursday afternoon. Isolated showers near Erie as well
as Flint and Port Huron in MI are accompanying some of these
surface trough axes. Hi-res models continue to indicate these
surface trough axes will encounter sufficient low-level moisture
and primarily weak boundary layer CAPE as the magnitude of deep
layer bulk shear remains at least moderate. Thus, isolated
multicell showers/thunderstorms are forecast to accompany these
trough axes, especially over ~77F Lake Erie, which will continue
to become the primary source of warmth, moisture, and instability
through daybreak Thursday morning as greater nocturnal cooling
occurs over surrounding land relative to nocturnal cooling over the
lake. Please see discussion below for further details.
Previous Discussion...
A cold front is currently working out of northwest OH and will
continue southeast through tonight. Multiple pre-frontal
boundaries (lake breeze and outflow) exist across northeast OH
and northwest PA. Scattered storms, including some severe storms
capable of producing damaging winds, continue from east-central
and interior northeast OH into Crawford Co PA late this
afternoon. Activity will exit to the southeast this evening.
A shortwave will zip across the region late tonight into early
Thursday. A few showers may graze our southwestern counties
pre-dawn Thursday. More robust potential for showers and perhaps
thunder with this feature will likely drop into parts of north
central OH, northeast OH, and northwest PA Thursday morning as
a surface trough moves across the relatively warm and unstable
bubble of air that will linger over Lake Erie overnight. Added
slight chance POPs pre-dawn Thursday from Findlay to Mount
Vernon, and added chance POPs and a thunder mention Thursday
morning-midday south of the lake, focused on the Cleveland metro
area. High pressure builds in late Thursday into Thursday night
ushering in dry weather.
Lows will settle into the mid to upper 60s tonight, possible a
bit cooler out towards TOL and east of I-79 in northwest PA.
Most of us will stay in the 70s for highs on Thursday. Lows
Thursday night will be refreshing for late July, in the 60s
along the immediate lakeshore and in Cleveland but settling into
the 50s for much of the rest of the forecast area.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
It will be a quiet end to the week and start to the weekend with dry
conditions and pleasant humidity levels, although temperatures will
be warming.
A pseudo Omega Block will be in place Friday and Saturday with
mid/upper troughs across the northern Rockies and eastern Great
Lakes and a narrow mid/upper ridge in between across the
central/northern Plains, while a weak cutoff low/trough is stuck
underneath over the southern Plains. The southern Great Lakes region
will be under the favorable portion of this block favoring upper
level confluence, which will allow strong surface high pressure to
remain in control. This high will be centered over Lower Michigan
and southern Ontario Friday and Friday night but will then drift
into the eastern Great Lakes Saturday and Saturday night. Highs in
the upper 70s/low 80s are expected Friday, warming into the
mid/upper 80s Saturday as return flow and resultant warm air
advection develops behind the departing high, but dew points will
remain comfortable through Saturday as the Gulf moisture is pinched
off by the southern Plains closed low/trough. Lows Friday night will
fall into the mid 50s to around 60, with upper 50s to mid 60s
Saturday night.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
The pattern will start to change to a more active one Sunday which
will carry into midweek as the Omega Block finally breaks down
allowing the mid/upper flow to turn more zonal by midweek.
Starting off Sunday, the mid/upper trough over the Rockies looks to
quickly eject ENE across south central Canada while pulling the old
southern Plains cut off low northward through the Mid Mississippi
Valley as it opens up into more of a trough. This shortwave then
looks to drift through the western and central Great Lakes Sunday
night and Monday, breaking down the ridging, while the
aforementioned northern stream energy passes well north across
northern Ontario and Quebec. Increasing warm/moist advection ahead
of the shortwave drifting north/northeast from the Mississippi
Valley will bump dew points back into the mid 60s Sunday resulting
in weak to moderate diurnal instability, but feel the best coverage
of diurnal convection will still be to the west given plenty of dry
air over NE Ohio and NW PA, so confined slight chance to chance PoPs
to NW Ohio Sunday. Chances for widely scattered showers and
thunderstorms will gradually expand east across the region Sunday
night and Monday as the shortwave drifts into the Great Lakes,
especially with daytime heating Monday afternoon, so have chance
PoPs areawide. With that being said, still think coverage will be
scattered Monday due to limited synoptic forcing and the tendency to
underachieve on convective coverage this summer, so went lower than
NBM POP guidance. Seasonably high PWATs will support locally heavy
downpours where it does rain.
Monday night through Wednesday, mid/upper troughing looks to deepen
across the Great Lakes as a strong mid/upper ridge (heat dome)
strengthens across the southern and central Plains and tries to
nudge eastward late in the week. This will develop a NW flow aloft
with a frontal boundary/baroclinic zone setting up near the southern
Great Lakes and Ohio Valley on the eastern fringe of the heat. Such
a pattern will support potential MCS activity riding southeastward
from time to time as weak shortwave impulses crest the ridge, but it
is impossible to tell where the instability gradient will reside
this far out, so therefore, no way to tell where the convective
complexes will go at this point. For now, stayed with NBM chance
PoPs for scattered convection Tuesday through Wednesday with very
warm and humid temperatures, but the biggest heat stays to the west.
Highs in the mid 80s to near 90 will be common Sunday through
Tuesday, perhaps cooling slightly into the mid/upper 80s
Wednesday.
&&
.AVIATION /00Z Thursday THROUGH Monday/...
Mainly VFR expected through 00Z/Fri. Simultaneously, cyclonic
W'erly to NW'erly flow aloft and embedded disturbances affect
northern OH and NW PA. At the surface, a cold front near a KMNN
to KUCP line at 23:30Z/Wed continues moving SE'ward and is
expected to exit the rest of our region by 02Z/Thurs at the
latest. Behind the front, a ridge builds from the western Great
Lakes and vicinity through 00Z/Fri. However, several subtle
trough axes are expected to sweep SSE'ward through our region
this evening through mid-afternoon on Thurs.
W'erly surface winds around 5 to 10 knots veer to NW'erly with
the passage of the cold front. Our regional surface winds are
expected to become variable in direction and ease to around 5
knots by 02Z/Thurs. Light and variable winds are then expected
to persist through end of the TAF period as a weakening MSLP
gradient accompanies the ridge.
Isolated showers and thunderstorms are expected along/ahead of
the SE'ward-moving cold front. Additional showers/thunderstorms
are possible this evening through Thurs afternoon, along the
aforementioned surface trough axes. The best potential for these
additional showers/storms exists over/near Lake Erie, which is
expected to become the primary source of warmth, moisture,
and instability later this evening through about mid-morning on
Thurs. Brief MVFR to IFR are possible with showers/storms.
Isolated to broken lake-effect stratocumuli with bases near 3kft
AGL should develop and stream generally SE'ward from Lake Erie
late this evening through about mid-morning on Thurs. These low
clouds should affect KCLE, KERI, KYNG, KCAK, and KMFD. Lingering
low-level moisture from recent rainfall may allow patchy
radiation fog with MVFR or lower visibility to impact interior
NE OH and NW PA between ~06Z and ~13Z/Thurs. This includes KCAK
and KYNG.
Outlook...Patchy fog with non-VFR possible in interior NE OH and
NW PA on Friday morning. Isolated to scattered showers and
thunderstorms with non-VFR possible Sunday into Monday.
&&
.MARINE...
Quiet conditions are expected on Lake Erie through the period with
generally weak pressure gradients. Winds will turn NW behind a cold
front this evening, but speeds of 10-15 knots will keep waves in the
1 to 3 foot range. Generally N to NE winds of 5-15 knots are then
expected tonight through Thursday night, becoming more NE and
decreasing to 5-10 knots Friday. Winds then turn light E to SE this
weekend followed by SW at 10-15 knots Sunday night and Monday.
Locally higher winds and waves are possible in and near
thunderstorms this evening and then Sunday and Monday. There may
be a waterspout or two Thursday morning over the lake.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
NY...None.
MARINE...None.
&&
$$
SYNOPSIS...Sullivan
NEAR TERM...Jaszka/Sullivan
SHORT TERM...Garuckas
LONG TERM...Garuckas
AVIATION...Jaszka
MARINE...Garuckas
Source:
CLE issues Area Forecast Discussion (AFD) at Jul 24, 9:40 PM EDT---------------
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