Area Forecast Discussion
Issued by NWS Cleveland, OH

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000 FXUS61 KCLE 150502 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 102 AM EDT Tue Oct 15 2019 .SYNOPSIS... High pressure will move east across the area tonight and off the New Jersey coast Tuesday. Low pressure will move east across the central Great Lakes and deepen rapidly by Wednesday evening. A strong cold front will move east across the area Tuesday night. Another low pressure will develop off the Carolina coast Wednesday and rapidly intensify as it absorbs the Great Lakes low pressure system. The combined low center will move northeast along the coast High pressure will move slowly east to the local area by Friday. && .NEAR TERM /THROUGH TODAY/... As expected, the lake-effect cloud band is shifting northward over/near the Lake Erie shore from Lake County to Erie County, PA. Expect these clouds to be totally offshore by daybreak Tuesday as the mean steering flow continues backing from west- southwesterly to southwesterly. Elsewhere in our CWA, mainly clear skies, very light or calm winds, and limited humidity will promote efficient radiational cooling through daybreak Tuesday. Decreased forecast low temperatures for Tuesday morning for inland portions of the CWA. The 10th percentile low temperatures from all available model guidance were used for this adjustment. Accordingly, the Frost Advisory was expanded to include the following counties: Geauga, inland Ashtabula, Crawford County, PA, and southern Erie County, PA. The Frost Advisory remains in effect from 2 AM to 9 AM EDT Tuesday. Lastly, patchy fog may affect interior portions of far-northeast OH and northwest PA between 2 AM and 9 AM EDT Tuesday. The remainder of our near-term forecast remains valid. PREVIOUS DISCUSSION...A weak broad upper level ridge will move east across the area during this forecast period. This will result in surface high pressure that will move east across the local area tonight. As the high pressure moves in, the lake effect rain showers and clouds will continue to wane this afternoon and even further tonight. The rest of the northeast Ohio continues to see rapidly diminishing clouds as drier air pushes into the region. Winds are expected to become very light and variable overnight as air mass decouples. Dewpoint temperatures upstream are in the upper 20s to lower 30s and expecting this cooler air to move east toward the region overnight. Therefore, expecting a widespread frost to develop across the forecast area tonight and will hoist a frost advisory late tonight through sunrise. Exception will be the northeast snowbelt where the blanketing cloud cover should hang on long enough to keep frost from forming. If they clear out much faster, then we could see frost up there as well. Looking at lows tonight in the middle 30s most areas and in the 40s in the northeast. High pressure moves east allowing moisture to advance east ahead of the next storm system. The low pressure system will move east through the central Great Lakes Tuesday and force a strong cold front east across the local area Tuesday night. Precipitation will move into the western portions of the forecast area by late tomorrow afternoon. Can`t rule out a possible rumble of thunder or two with the front tomorrow night. Highs in the quick warm air advection will recover back into the 60s tomorrow and then drop back to the middle 40s west and lower 50s east in the cold air advection. && .SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/... We begin the short term period with an upper level closed low over southern Ontario and the associated surface pressure very close to vertically stacked with this upper low. The cold front will be slowly exiting to the east during the day on Wednesday, with the associated widespread rain exiting the forecast area as well. Cold temperatures aloft move over the lake immediately following the cold front, with temperatures at 850mb at or slightly below freezing and near or just above -10 Celsius at 700mb. With lake surface temperatures around 17 to 18 degrees Celsius, that will be near 20 degrees lake sfc to 850 temperature difference. Combined with unidirectional northwest flow and good moisture from the upper level low, and we have ourselves a solid setup for lake effect precipitation over Northern Ohio and Northwestern Pennsylvania. Lake induced CAPE will be upwards of 700 J/kg, which should be enough instability to support isolated thunderstorms as well. Moisture lingers for quite a long time, persisting through Wednesday night and most of Thursday. Most model guidance have low level moisture finally pushing off to the east Thursday night, with it completely dry by at least Friday afternoon. With high pressure building in from the west on Friday, clouds should be clearing out most of the day Friday. With high temperatures around 60, which will be higher than the previous two days, it should be nice fall day. && .LONG TERM /FRIDAY THROUGH MONDAY/... With surface high pressure and the upper level ridge building in from the west, skies should continue to become clear through the night, with radiational cooling producing fairly cool overnight temperatures. High pressure will have moved off to the Mid-Atlantic by Saturday morning, allowing southerly winds to advect warmer air into the region, bringing high temperatures back into the upper 60s on Saturday. The pattern becomes more amplified on Sunday with a deep upper level trough building over the plains on Sunday. This trough will introduce the chance for widespread precipitation across the area on Sunday night into Monday. && .AVIATION /06Z Tuesday THROUGH Saturday/... High pressure is currently over Ohio and western PA and was drifting slowly east. Flow off Lake Erie still holding clouds into KERI however conditions were VFR. Elsewhere, skies were clear. Expecting low level winds to back towards morning taking clouds offshore from KERI. Otherwise expect clear skies to persist through afternoon before clouds begin to thicken and lower from the west ahead of an approaching cold front. Rain should move in from the west after 00Z with conditions lowering to MVFR after about 04z in the west. Isolated thunder not out of the question. MVFR conditions reach KCLE by 10Z Wed. .OUTLOOK...Non-VFR likely overnight Tuesday night. Non-VFR possible in lake effect rain showers at/near KERI late Wednesday morning through Thursday and perhaps Friday morning. && .MARINE... The Small Craft Advisory will continue through this evening. Most observations along the lakeshore are showing waves of around 4 feet with west winds as high as 25 knots. Winds are expected to slowly diminish this evening into tonight as high pressure builds in from the west. As this high pressure moves east of Lake Erie and low pressure develops over the western lakes, southerly winds increase up to 10 to 20 knots 18Z Tuesday through 06Z Wednesday. The aforementioned area of low pressure progresses eastward Tuesday evening and Wednesday overnight, deepening to 998mb over Lake Huron by 12Z Wednesday. The associated cold front will move east across the lake on Wednesday, with fairly strong westerly winds of 20 to 25 knots immediately behind the front. A fairly strong pressure gradient is expected to persist over the lake through at least 00Z Friday, through which at least Small Craft Advisory conditions will be present. Gale force winds may be possible over the open waters of Lake Erie briefly late Wednesday night, which will largely be dependent on how strong the low pressure will deepen to. A couple models have the low getting to as low as 994 mb on Wednesday afternoon. Waves of up to 10 feet may be possible late Wednesday night over the open waters of Lake Erie. Winds will diminish through the day on Friday as high pressure builds in from the west. Southerly winds of 10 to 15 knots develops on Saturday as this high pressure pushes off to the east coast. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...Frost Advisory until 9 AM EDT this morning for OHZ003-006>010- 013-014-017>023-027>033-036>038-047. PA...Frost Advisory until 9 AM EDT this morning for PAZ002-003. MARINE...None. && $$ SYNOPSIS...Lombardy NEAR TERM...Jaszka/Lombardy SHORT TERM...Saunders LONG TERM...Saunders AVIATION...TK MARINE...Saunders is the U.S. government's official web portal to all federal, state and local government web resources and services.