Area Forecast Discussion
Issued by NWS Cleveland, OH

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000
FXUS61 KCLE 181033
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
633 AM EDT Mon Mar 18 2024

.SYNOPSIS...
A trough lingers over and near the eastern Great Lakes today,
including northern Ohio and northwest Pennsylvania, before a
weak ridge moves eastward across our region tonight. Another
trough should overspread our region from the Upper Midwest on
Tuesday through Wednesday and a cold front should sweep eastward
through our region Tuesday evening through Tuesday night. A
ridge should then build from the Canadian Prairies during
Wednesday night through Thursday.

&&

.NEAR TERM /THROUGH TUESDAY/...

6:33 AM EDT Update...

Most of our forecast remains valid per latest trends in obs and
model guidance. Increased POP`s to at least 15% CWA-wide through
the rest of this morning given latest trends in surface obs and
radar data. Sensible WX grids were also updated accordingly.
Please see discussion below for further details.

Previous Discussion...

W`erly to NW`erly mid/upper-level flow impacts our region
through tonight. Multiple shortwave troughs embedded in this
flow aloft will move SE`ward over our CWA through this evening
before a subtle shortwave ridge moves quickly SE`ward across
our region overnight tonight. At the surface, a trough lingers
over/near the eastern Great Lakes, including our CWA, before a
weak ridge moves generally E`ward through our region tonight.
The pattern will allow a cold air mass to remain entrenched across
the eastern Great Lakes and Upper OH Valley. This afternoon`s highs
should be near 35F in NW PA and the mid to upper 30`s in northern
OH. Tonight`s lows should reach mainly the mid to upper 20`s around
daybreak Tuesday. Surface wet-bulb temperatures are expected to be
no greater than 33F with colder wet-bulb temperatures farther aloft.
Thus, snow is expected to be the only precip type through tonight.

Scattered to numerous lake-effect snow showers will continue to
impact the NE OH/NW PA snowbelt and vicinity through tonight
amidst lake surface to 850 mb temperature differences of ~14C to
~19C over ~6C Lake Erie, abundant synoptic low-level moisture,
lake-induced EL`s near 7kft to 10kft above lake level, and a
W`erly to WNW`erly mean low-level flow. Outside the LES, at
least isolated snow showers are expected through this evening as
potential instability in the lowest 1 km AGL is released by
ascent accompanying low-level convergence along surface trough
axes attendant to the aforementioned shortwave troughs aloft.
However, limited daytime warming of the boundary layer combined
with colder air farther aloft should yield weak SBCAPE/minimal
SBCIN late this morning through early evening, allowing snow
showers to become scattered to numerous along/near the surface
trough axes. Snow showers, including the LES, are expected to
be steady to heavy with visibility of 1/2 mile or less at times
since hi-res model soundings indicate low-level convergence
will allow strong ascent to become maximized in a cloudy DGZ
about 50 mb to 100 mb deep at times. Snow accumulations through
daybreak Tuesday should mainly be less than one inch, but 1-4"
of snow accumulation are expected in the heaviest/most-persistent
LES, especially in the colder higher terrain of the NE OH/NW PA
snowbelt. These forecast snow accumulations preclude the need
for a Winter WX Advisory. Of note: Given the relatively-high
March sun angle, snow should struggle to accumulate along low-
albedo surfaces (e.g. pavement and concrete) during daylight
hours, especially when snow falls at a light rate.

Mid/upper-level flow remains W`erly to NW`erly over our region
on Tuesday as multiple/subtle shortwave troughs traverse our
CWA. Closer to the surface, a shortwave trough at/near 850 mb
approaches from the western Great Lakes as the attendant
surface trough overspreads our CWA. Low-level WAA develops ahead
of the shortwave trough axis and is forecast to contribute to
afternoon highs reaching mainly the upper 30`s to lower 40`s in
NW PA, and the lower 40`s to lower 50`s in northern OH. Thus,
a W`erly gradient in high temperatures is forecast. Primarily
fair weather is expected. However, lingering LES in the primary
snowbelt of NE OH/NW PA is expected to shift N`ward and out of
the region by the afternoon as the mean low-level flow of
sufficiently-cold/moist air over/downwind of Lake Erie backs
from W`erly to SW`erly ahead of the aforementioned low-level
shortwave trough. However, low-level moist isentropic ascent
aloft may allow isolated snow showers mixed with rain to impact
far-NE OH and NW PA from roughly midday through sunset. Any
additional snow accumulations are expected to be one inch or
less.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
A persistent upper level trough and northwest flow across the region
will allow for continued cold temperatures and scattered snow shower
chances for the middle of the week. The best snow chances throughout
the period will be in the NE OH and NW PA snow belt where energy and
moisture from Lake Erie along with the higher terrain of the region
will help with snow chances and possible accumulations. The overall
best snow time within the forecast period will be during the daytime
on Wednesday with a vorticity maximum and upper level trough axis
moving through the Great Lakes region to be supportive lift for snow
while a push of colder air will help with instability to increase
snowfall intensity. However, all of this will occur during the
daytime hours and it is tough to see how of this snow will
accumulate given the relatively warm surface and higher sun angle.
High pressure will build into the region on Thursday and allow for a
largely dry forecast. Temperatures will be cool for the first days
of astronomical spring with 40s on Wednesday and 30s to near 40 on
Thursday for highs.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
The weekend forecast will have some element of a forecast pattern
change as the persistent upper trough will exit the region to the
east. Another wave of the northern stream jet will dip toward the
area, but it may pick up a shortwave moving through the southern
stream over the Gulf Coast states. This combination should allow for
a broader low pressure system to move through the eastern CONUS and
bring some rain chances on Friday with some warmer temperatures
toward the 50s. High pressure will build into the region with a more
zonal pattern aloft, and dry weather with stagnant seasonable
temperatures are expected for the weekend.

&&

.AVIATION /12Z Monday THROUGH Friday/...
W`erly to NW`erly flow aloft and embedded disturbances affect
our region through 12Z/Tues. The axis of the strongest
disturbance should move SE`ward across northern OH and NW PA
between ~12Z and ~21Z/Mon. At the surface, a trough lingers
before a weak ridge traverses our region generally from west to
east between ~00Z and 12Z/Tues. Our regional surface winds vary
between SW`erly and WNW`erly around 5-15 knots with gusts up to
20-25 knots at times, especially between ~14Z and ~22Z/Mon.

Scattered to widespread low clouds with bases near 3kft to 5kft
AGL persist through the TAF period, especially downwind of Lake
Erie. Scattered to widespread lake-effect snow showers are
expected generally east-southeast of Lake Erie through ~09Z/Tues
and then generally east of the lake thereafter. Periods of
isolated to scattered snow showers are expected elsewhere,
especially between ~14Z and ~21Z/Mon given the passage of the
aforementioned stronger disturbance and limited diurnal
destabilization of the boundary layer. Brief MVFR to LIFR
visibility is expected in steadier to heavy snow.

Outlook...Non-VFR expected with periods of snow and/or rain this
Tuesday through Friday.

&&

.MARINE...
Overall, the marine weather forecast for this week is rather poor
for small craft vessels with several waves of low pressure through
the region allowing for strong winds and increased waves. A trough
continues to sit over the region today and a cold front will enhance
westerly flow this afternoon and evening. Therefore, a Small Craft
Advisory remains for all of the nearshore waters but areas east of
Vermilion OH will have the advisory into Tuesday. Low pressure will
move through the region on Tuesday into Wednesday with another cold
front moving across the lake on Wednesday. Onshore flow will
increase once again with waves responding accordingly and expect
another Small Craft Advisory headline to be needed for Tuesday night
through the first part of Thursday. High pressure will build into
the region for Thursday to lighten winds and allow for one benign
weather day on the lake. Low pressure will move through the region
on Friday and promote northeast flow on the lake. Flow may not be
all that strong but the unfavorable long fetch over the lake may
present some choppy conditions for smaller watercraft.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
NY...None.
MARINE...Small Craft Advisory until 10 AM EDT this morning for
     LEZ142>144.
     Small Craft Advisory until 4 AM EDT Tuesday for LEZ145.
     Small Craft Advisory until 8 PM EDT Tuesday for LEZ146>149.

&&

$$

SYNOPSIS...Jaszka
NEAR TERM...Jaszka
SHORT TERM...Sefcovic
LONG TERM...Sefcovic
AVIATION...Jaszka
MARINE...Sefcovic


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