CLE issues Area Forecast Discussion (AFD) at Nov 20, 1:03 PM EST632
FXUS61 KCLE 201803
AFDCLE
Area Forecast Discussion
National Weather Service Cleveland OH
103 PM EST Wed Nov 20 2024
.SYNOPSIS...
Low pressure will move into the Great Lakes and intensify
this afternoon, driving a strong cold front across the region.
This low will continue to meander around the Great Lakes
Thursday before gradually moving east and getting absorbed into
another low near the east coast Friday into Saturday. High
pressure will build in from the west Sunday.
&&
.NEAR TERM /THROUGH THURSDAY/...
1230 PM Update...
Showers associated with a cold front moving east have begun to
impact the western tier of counties this afternoon. These
showers are being associated with wind gusts of 25 to 35 mph,
which will continue to spread east this afternoon. The highest
gusts are still anticipated along the lakeshore in NE OH and NW
PA with stronger winds expected off the lake. Have opted to
remove the chance of thunder for this afternoon as instability
does not look to be sufficient enough to sustained updrafts but
rather maintain low-top showers. If there were a rumble or two
of thunder, the best chance remains east of I77 this afternoon.
930 AM Update...
Patchy fog continues to linger across the central portion of the
area, especially along and west of I71. Conditions should
continue to improve over the next hour or two as warming
temperatures and increasing winds help to mix out the fog. There
is no longer a Dense Fog Advisory in effect given the patchy
nature, however motorists should still use caution as
visibilities may quickly drop to 1/4 to 1/2 SM in areas that
are still impacted. In terms of forecast update, slight
adjustments were made to temperatures, especially across eastern
counties where clear skies has allowed temperatures to warm a
bit quicker than previously forecast. The remainder of the
forecast is on track.
Previous Discussion...
A weakening cold front has departed to the east with
yesterday's rainfall contributing to a moist boundary layer
across much of the area. In combination with light winds and
subsidence aloft, radiation fog has developed across a good
chunk of the area, approximately along and west of I-77. A
dense fog advisory is in effect for this through 10 AM. Fog is a
little more patchy along and in the vicinity of the I-75
corridor where dew points were able to drop a bit before sunset.
There is also less fog in parts of Northeast Ohio and Northwest
Pennsylvania where some stratus streaming off of Lake Erie has
insulated the boundary layer and prevented radiational cooling.
If fog continues to expand, it's possible we may need to expand
the dense fog advisory to other counties.
Looking at the large scale pattern for the rest of the near
term forecast, we have a large upper-level trough located
across the Midwest region, entering the western Great Lakes this
morning with an upper-level jet stream of around 110-130 kts
rounding the base of the trough and extending eastward to the
mid-Atlantic region. An occluded low is located far northwest
back towards the Canadian Prairies, though a new low is in the
process of developing over the Great Lakes. A cold front
currently located over eastern Illinois will be accompanied by a
band of rain (can currently see it on radar over Illinois) and
will make eastward progress over Indiana this morning. A compact
and strong shortwave trough rounding the base of the broader
trough will cause this cold front to surge forward. Meanwhile,
an upper-level jet streak begins to take form and strengthen
over southern Appalachia, causing rapid cyclogenesis to occur
over Northwest Pennsylvania and eastern Lake Erie later this
afternoon. Together, this will result in rain expanding with
the cold front as it moves across the area this afternoon into
the evening, and as it does so, the strengthening surface low
will greatly increase the pressure gradient across the area.
Because of all of this, we should see quickly increasing winds
along and just behind the cold front as it moves across the area
(despite not seeing much wind with it now over in Illinois - it
will be a rapidly developing situation). Should see a somewhat
brief period of 3-5 hours of 35-45 mph wind gusts areawide. Wind
gusts will likely be stronger (to 50 mph) in parts of Northeast
Ohio and Northwest Pennsylvania near Lake Erie owing to the
lower friction on Lake Erie and proximity to the developing low.
A wind advisory will be in effect from 3 PM through 12 AM to
account for these stronger wind gusts.
A handful of hi-res models do actually have a strip of very weak
instability (around 100-200 J/kg MUCAPE) that develops ahead of
the cold front and post-frontal rain. Low-level convergence
ahead of the cold front will likely lead to additional
convection before the frontal passage, along and east of I-77.
Though it's usually very little instability, the strong
forcing/dynamics will make use of every bit of it (supported by
a few stronger looking cells in modeled reflectivity of several
CAMs), so have added a couple hours of slight chance
thunderstorms for this this evening (~22-00Z timeframe east of
I-77). The instability that will be present will be wholly
confined to the low-levels, contributing to modest 0-3km CAPE
and low-level lapse rates. With abundant low-level shear, it
isn't out of the question that we see a very quick tornado
spin-up though probabilities of this occurring are very low and
weren't included in the SPC convective Outlook.
Rain and strong wind gusts should end within about 3-4 hours of
the frontal passage. Cold air will rush behind it, with
temperatures in the mid to upper 50s ahead of the front quickly
dropping to the low 40s and upper 30s within a couple hours of
the cold front. Temperatures continue to drop tonight to the low
to mid 30s, where they will generally stay through the day
Thursday (aside from a couple degree bump upward during the
afternoon). A clear slot will lead to several hours of partly
to mostly clear skies overnight before deeper pool of moisture
arrives from the northwest. This moisture overtop steep low-
level lapse rates will result in numerous snow showers across
the region throughout the day on Thursday. Broader QPF won't
amount to much and even so, daytime temperatures of around 35-38
will limit any potential snow accumulations. Brief coating of
snow is possible during the morning hours, especially the pre-
dawn hours when temperatures will be at their coolest.
With regard to snow potential on Thursday, there are a couple
things to note. The surface low we talked about earlier will
develop around eastern Lake Erie this evening and is expected
to rotate counter-clockwise around the cutoff low, northern to
Lake Huron, westward to Lake Michigan, and then back southward
across Indiana. The best synoptic-scale moisture/lift and snow
accumulation potential will occur with these features (we're
talking 2-4" of snow). The broader 00Z suite of model guidance
has accumulations from this just to the west of our forecast
area. However, the 06Z NAM did just shift it a bit eastward,
producing 1-2" of snow along the I-75 corridor. So, this is a
trend we will have to monitor (if it continues this shift, look
for a slight bump to snow accumulations for parts of Northwest
Ohio for Thursday). The other thing we want to mention is that
many CAMs develop a decent looking lake effect band over Lake
Erie during the day Thursday, moving it onshore to a few
counties somewhere in the snow belt (primary and/or secondary
snowbelt). This is best presented by the 00Z/06Z HRRR but the
latest ARW/FV3/RAP also show something similar happening. This
could produce a couple inches of snow somewhere locally in the
snowbelt that isn't necessarily present in the current forecast,
especially for higher terrain.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
A very complex weather system will be impacting the region Thursday
night. A large, slow-moving, fairly deep (500mb heights ~3 standard
deviations below normal) closed low aloft will be overhead. One
weakening surface low is expected to be dropping out of the Great
Lakes and into the Ohio Valley (just to our west) Thursday night,
while another low deepens along the eastern seaboard. The surface
low along the East Coast will become dominant into Friday and become
stacked beneath the larger closed low aloft as it continues drifting
east-southeast towards the Mid Atlantic. This interaction will lead
to the surface low becoming nearly stationary or even retrograding a
bit on Friday over the Northeast. The entire package, including the
closed low aloft and surface low, will begin slowly exiting to the
east-northeast Friday night into Saturday. However, broad surface
troughing and cyclonic flow will persist over the Great Lakes into
the weekend, with the surface ridge axis not expected to build into
the local area until Saturday night or Sunday.
From a sensible weather perspective, our "taste o' winter" with some
snow in the forecast continues through early Friday, at which time a
more maritime airmass from the Atlantic will make its way all the
way around the deep/closed-off system and begin wrapping in from the
north, leading to temperatures at the surface and aloft moderating a
bit across the local area. From Friday morning through Saturday
night all or nearly all precip will fall in the form of chilly rain
across the local area, with just a small potential for a few flakes
to mix back in across the higher elevations of Northwest PA Saturday
night as one last surge of chillier air grazes the region.
In terms of when, where, and how much it will precipitate this
period, it's fair to say that a similar system in December or
January would dump oodles of snow in the snowbelt. It will be quite
a wet forecast period downwind of Lake Erie. We'll be in a relative
lull in precipitation between the low pressure dropping out of
Michigan to our west and the developing east coast low Thursday
evening. Maintain a chance for snow in our western and southwestern
counties Thursday evening as some guidance still clips locations
from Toledo down to Mount Vernon points west with light snow,
despite a gradual but persistent westward trend with that piece of
energy. Given the continued western trend in that swath of snow and
marginal temperatures, have snow amounts of <0.5" in our western
counties Thursday evening. Some solutions that bring snow into our
western counties Thursday morning could still support a low
probability (~20% chance) for an inch or so of snow on non-paved
surfaces. Moisture is expected to wrap back in from the north and
northeast Thursday night into early Friday allowing precipitation to
fill back in from north-central and northeastern OH into PA. There
will be lake enhancement and upslope enhancement to this precip.
This precip will be mainly rain or rain mixed with wet snow near the
lake, but has a decent chance to arrive as mainly snow as it pushes
south into our area Thursday night. Precipitation will gradually
change to all rain from the north into Friday. While a narrow window
of time, marginal temperatures, and disagreement over how quickly
precipitation fills in from the north-northeast Thursday night into
early Friday makes it difficult to expect much snow to accumulate,
there could be a brief period of decent snow rates in the higher
terrain of the snowbelt Thursday night into very early Friday where
lake enhancement and upslope occur. This could allow for a 1 to 3
inch type accumulation in the higher elevations of the snowbelt,
namely parts of Geauga, inland Erie, and northern/eastern Crawford
Counties. Given favorable timing at night or in the early morning,
lower elevations well inland from the lake in NE Ohio could see a
slushy coating before precip changes to rain into Friday. Locations
near the immediate lakeshore will likely see little/no
accumulation.
Once precip changes to a cold rain on Friday, moist cyclonic flow
and lake/upslope enhancement will keep frequent showers (if not just
a steady rain) going from approximately Sandusky to Mansfield points
east, with the greatest precipitation amounts found in the higher
terrain south-southeast of the lake from Medina County points east-
northeast through the snowbelt. Locations farther west may see
intermittent showers, though as usual the I-75 corridor will be
much, much drier than nearly all of the rest of our forecast area
during this lake enhanced precip pattern Friday into Friday night.
Expect drying to begin inching east Friday night and Saturday as
precipitation gradually become more focused on Northeast OH and
Northwest PA, though the precipitation in the primary snowbelt will
not completely shut off through the forecast period. A long running
QPF forecast from Thursday evening through Saturday evening yields a
good 1-2" in the bulk of the snowbelt from Cleveland points east-
northeast, and it wouldn't be surprising to see a bit more on
northwest facing hills where upslope is maximized. This shouldn't
cause flooding, but demonstrates how wet it will be downwind of the
lake for a decent period of time Thursday night through Saturday.
Lows Thursday night generally range from the upper 20s to the lower
30s away from Lake Erie, with mid to upper 30s against the lake,
especially from Cleveland points northeast. Highs on Friday will be
several degrees milder than Thursday, generally in the low to mid
40s. Lows Friday night will generally be in the upper 30s and lower
40s, with highs on Saturday very similar to Friday or a bit warmer,
especially west. Lows Saturday night will generally be in the mid to
upper 30s, slightly milder along the lake, perhaps slightly chillier
if clearing occurs out west. Not expecting any sun on Friday, though
there may be a few peeks of it west Saturday.
Winds are expected to pick back up out of the west-northwest late
Thursday night or Friday, then continuing into Friday night before
starting to gradually relax Saturday. Gusts to around 40 MPH will be
possible near Lake Erie Friday into Friday night, with 25-35 MPH
more common elsewhere Friday into Friday evening.
&&
.LONG TERM /SUNDAY THROUGH TUESDAY/...
Lake effect rain showers may linger into far Northeast OH/Northwest
PA into Sunday but will be in the process of ending and shifting
back over the lake as a narrow ridge of high pressure slides through
the region. Low pressure develops over the Midwest on Sunday and
tracks into the Great Lakes Sunday night and Monday as the pattern
becomes much more zonal. A cold front sweeps through Monday night or
Tuesday behind this low pressure. Some rain showers are possible
early next week as the system moves through the Great Lakes, though
0z models and ensembles generally backed off on the amount of QPF
and have a wide array of actual outcomes in terms of the
track/strength of the low. Given this, capped POPs in the 30-50%
range early next week. Temperatures briefly moderate to milder than
average on Monday, but get knocked back a bit for Tuesday.
&&
.AVIATION /18Z Wednesday THROUGH Monday/...
A cold front moving east across the area marks the divide
between hazardous and non-hazardous aviation conditions this
afternoon. The frontal boundary currently extends from near
Sandusky to Marion OH. Along and ahead of this boundary, rain
showers have developed, reducing visibilities to around 3 to
6SM. The strong cold front is resulting in enhanced winds, with
sustained winds of 15-25 knots, gusting up to 35 knots possible.
The exception to this is at KERI and KCLE which will be impacted
by enhanced flow off the lakeshore and gusts as high as 40 to 45
knots through 06Z tonight. These conditions will gradually
push east through the evening, impacting all terminals at some
point before departing to the east between 00-06Z. Although the
frontal boundary is quite strong, removed any chance of thunder
from the forecast as instability remains very limited across the
area. If any were to develop, the most likely impacted
terminals would be KCAK and KYNG this afternoon/early evening.
Behind the departing cold front, conditions will gradually
improve to VFR as a push of drier air moves southeast around
the occluded low pressure centered over the Great Lakes. Winds
are expected to weaken overnight to 5 to 15 knots from the
southwest. As this system continues to meander towards the
southeast, another round of showers is possible Thursday
morning, gradually transitioning to a primarily lake effect
pattern by the afternoon. Any showers Thursday morning will
likely be all snow, with the exception of terminals near the
lakeshore that will remain a rain/snow mix with slightly warmer
temperatures along the lake. These showers and lower clouds will
result in MVFR ceilings, possibly dipping down into high end
IFR, with visibilities varying based on shower intensity over
the terminals. The good news is that winds on Thursday will be
weaker at 5-10 knots from the southwest, with local gusts up to
20 knots for terminals along and west of I-71.
Outlook...A large area of low pressure is expected to impact
the region through Saturday, bringing breezy conditions and
periodic non-VFR conditions in rain showers, possibly mixed
with snow showers Thursday and Thursday night.
&&
.MARINE...
It will be rough on the lake for the next few days. It's relatively
tranquil this morning and will remain that way through early this
afternoon. A strong cold front will sweep across the lake between
about 2 PM and 9 PM from west to east, with low pressure developing
along the front over eastern OH or western PA this afternoon and
deepening into this evening while lifting towards the Buffalo/
Toronto area. There is now high-confidence in a period of strong,
gusty winds for a 3 to 6 hour window behind the front across the
lake, with overnight guidance trending a bit stronger with the
developing low pressure and overall wind fields over the lake. Have
issued a Gale Warning east of the islands due to the potential for
35-40 knot sustained winds with gusts of 45 to perhaps 50 knots. The
warnings kick in from west to east between 3 PM and 6 PM and expire
between 10 PM and 1 AM tonight. Locations west of The Islands are
expected to see sustained winds to 25 to 30 knots with gusts to 40
knots, which isn't quite enough for a Gale Warning but still
supports a high-end Small Craft Advisory beginning after 1 PM. With
the wind forecast trending a bit higher, concern for the water level
in the western basin to dip below the critical mark this evening
into tonight has increased enough to go with a Low Water Advisory
from 4 PM this afternoon through 7 AM Thursday. While it will
probably bounce around the critical mark for several hours and may
struggle to dip below, would prefer to get the headline out now to
allow any needed adjustments in shipping plans to be made.
We will likely see a relative lull in conditions on Thursday across
the lake, though winds/waves will still be at or near Small Craft
Criteria out of a west-southwest direction. Winds increase out of
the northwest later Thursday night through Friday night, with a
solid period of 20-30 knots expected across the lake with some lower-
confidence potential (20-40%) in a marginal gale, particularly
across the central basin Friday into Friday evening. Winds gradually
shift more west and then southwest over the weekend, persisting at
15-25 knots through Saturday before gradually subsiding to 20 knots
or less into Sunday. Policy precludes us from issuing Small Craft
Advisories following an active Gale Warning , but plan on prolonged
Small Craft Advisories to be needed east of the islands through at
least Saturday and perhaps into Sunday farther east once the Gale
Warning comes off the board.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Wind Advisory until midnight EST tonight for OHZ010>014-089.
PA...Wind Advisory until midnight EST tonight for PAZ001-002.
MARINE...Small Craft Advisory until 7 PM EST Thursday for LEZ142-143.
Low Water Advisory from 4 PM this afternoon to 7 AM EST
Thursday for LEZ142>144-162>164.
Gale Warning until 10 PM EST this evening for LEZ144>146-
164>166.
Gale Warning from 5 PM this afternoon to 1 AM EST Thursday for
LEZ147>149-167>169.
&&
$$
SYNOPSIS...Saunders
NEAR TERM...Campbell/Saunders
SHORT TERM...Sullivan
LONG TERM...Sullivan
AVIATION...Campbell
MARINE...Sullivan
Source:
CLE issues Area Forecast Discussion (AFD) at Nov 20, 1:03 PM EST---------------
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