Area Forecast Discussion
Issued by NWS Cleveland, OH

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591 FXUS61 KCLE 150531 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 1231 AM EST Sun Dec 15 2019 ...06z Aviation Forecast Update... .SYNOPSIS... Low pressure currently over southern New York will continue to move north tonight and deepen rapidly with a secondary cold front moving southeast across the area early tonight. High pressure will build southeast across the Midwest and Ohio Valley on Sunday night. Another low pressure system will move northeast across the Ohio Valley late Monday and Monday night and off the New England coast by Tuesday. A ridge of high pressure will build east across the eastern CONUS Wednesday through Friday. && .NEAR TERM /THROUGH TODAY/... Update...Have made significant changes to the evening and overnight forecast. Forecast soundings show a loss of ice in the clouds overnight with only supercooled liquid clouds remaining across the region. Overnight forcing is weak which would favor a larger chance that any precip through the late evening and overnight would be drizzle vs snow. As temps drop this would become freezing drizzle. Have already seen pilot reports of icing and and few obs of light rain. Will continue with current advisory headlines across northwest PA and reword text to include more zl and less snow. Will also keep the warning. Although overnight snow will be limited, there is still a window Sunday morning to redevelop snow off the lake with dendrites again favored as colder air deepens. At this time, elsewhere will wait for development and not issue any additional advisories. Original...A negatively tilted trough will continue to lift north along the northeast CONUS. This trough is responsible for forcing a deep low, currently located over southern New York. This low is expected to continue almost due north (with a slight east component) while undergoing significant cyclogenesis. This has resulted in widespread precipitation, with a rain/snow mix currently across northeast Ohio and northwest Pennsylvania. Inland areas of northwest Pennsylvania and parts of inland northeast Ohio have completely transitioned to all snow where surface temperatures are a bit cooler. Precipitation associated with this low pressure will end from west to east early this evening into tonight. Beyond this, lake effect snow will develop tonight as northwest flow aloft continues and temperatures at 850 mb decreases to a minimum of 12 deg Celsius by 15 UTC Sunday. In addition lake effect, brief redevelopment of scattered snow showers may occur across northern Ohio tonight, adding to snow totals. Through 18 UTC Sunday, snow totals across the Ohio lake effect snow belt are expected to be 1 to 4 inches, with highest amounts in hills. Snow totals in northwest Pennsylvania are expected to be 5 to 9 inches with a very sharp gradient along the lakeshore. Gusty winds of 30 to 40 mph may introduce blowing snow and reduced visibility, especially closer to the lakeshore. Because of snow totals, a Winter Storm Warning has been issued for inland Erie County and a Winter Weather Advisory for lakeshore Erie and Crawford Counties, both of which are valid through 18 UTC Sunday. Light lake effect snow showers may continue into the afternoon but should be over by early Sunday night. High temperatures are expected to be on the cool side, staying right around freezing. Are next system comes in the form of low pressure developing over the lower Mississippi Valley Sunday night. Precipitation associated with this system will approach from the south late Sunday night, likely staying as all snow through Sunday night. There some uncertainty with the onset of snow on Sunday night and the model trend right now is for most of the precipitation to stay to our south. For that reason have stuck with a max 50 PoP through 12 UTC Monday. && .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... Southwesterly flow aloft persists Monday morning through daybreak Tuesday as a trough aloft approaches from the west. Simultaneously, a surface low should track from near AR to near south-central PA, allowing our CWA to remain within the surface low`s cold sector. Periods of widespread precipitation associated with warm air advection and isentropic lift are expected on Monday and Monday night. Temperatures at the surface and aloft will be critical in determining precip type(s) at the surface. In general, a rain/snow mix on Monday should change to all snow Monday night. However, periods of sleet and/or freezing rain may also occur and this potential will be watched closely. High temperatures should reach the low to mid 30`s on Monday, while low temperatures should reach the mid 20`s to lower 30`s Monday night. On Tuesday and Tuesday night, the surface low should continue moving northeastward from near south-central PA to near the Canadian Maritimes, allowing cold air advection to overtake our CWA. Simultaneously, the trough aloft should settle eastward over our CWA and merge with a potent mid- to upper-level low settling southeastward over northern ON. Widespread wraparound snow should end from west to east on Wednesday and transition to multiple bands of lake effect snow across the snowbelt Tuesday night as a westerly flow of progressively colder air crosses Lake Erie. High temperatures in the low to mid 30`s on Tuesday should be followed by lows reaching the upper teens or lower 20`s Tuesday night. On Wednesday, northwesterly flow aloft is expected as the mid- to upper-low moves from near Georgian Bay to northern New England and high pressure at the surface and aloft builds from the west. Lake effect snow should continue in the snowbelt as the low-level flow veers from westerly to northwesterly and becomes even colder. Fair weather is expected outside the lake snow. Wednesday will likely be the coldest day of the week, with highs only reaching the 20`s. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... High pressure aloft builds eastward over our CWA Wednesday night through Thursday night, causing northwesterly flow aloft to eventually become westerly. Simultaneously, surface high pressure crests over our region. Lingering lake effect snow in the snowbelt should end by daybreak Thursday as the stabilizing high pressure ridge allows lake-induced CAPE to diminish. Otherwise, fair weather is expected across our CWA. Low temperatures in the teens to lower 20`s are expected overnight Wednesday night. On Thursday, afternoon highs should reach the upper 20`s to mid 30`s. Lows should reach the 20`s Thursday night. At this point, odds favor fair weather Friday through Saturday as high pressure ridging at the surface and especially aloft should remain in control over northern OH and northwest PA. Temperatures should moderate during this period, including high temperatures reaching the 30`s to lower 40`s. && .AVIATION /06Z Sunday THROUGH Thursday/... Widespread MVFR and IFR is expected through the rest of the night into Sunday. MVFR is expected for the western TAF locations and IFR is expected for the I-71 corridor eastward into northeastern Ohio and NW Pennsylvania. Low ceilings between 700 feet to 1500 feet is expected along with areas of drizzle/light snow with visibilities dropping between 2sm and 5sm at most locations across the northeastern Ohio. A band of lake effect snow may develop late morning into the afternoon and impact ERI later today. MVFR ceilings are expected through the afternoon with ceiling lifting to around 5K feet by this evening. .OUTLOOK...Non-VFR possible Monday and Tuesday with periods of rain and/or snow. Freezing rain may also be possible on Monday. Non-VFR possible with lake effect snow on Tuesday and Wednesday. && .MARINE... Small Craft Advisories are in effect for Lake Erie today into Sunday. Westerly winds as strong as 20 to 25 knots are expected through tonight, resulting in waves as large as 4 to 8 feet, especially east of The Islands. Westerly to southwesterly winds will diminish gradually on Sunday and waves will lower gradually as a northeastward-moving low pressure system pulls away from Lake Erie and high pressure builds from the west. Quieter conditions should affect the lake on Monday, while Small Craft Conditions may return Tuesday into Wednesday as low pressure moves northeastward from the Ohio Valley to Canadian Maritimes Tuesday and then extends a trough over the lake into Wednesday. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...Winter Weather Advisory until 1 PM EST this afternoon for PAZ001-003. Winter Storm Warning until 1 PM EST this afternoon for PAZ002. MARINE...Small Craft Advisory until 10 PM EST this evening for LEZ147>149. Small Craft Advisory until 10 AM EST this morning for LEZ143- 144. Small Craft Advisory until 4 PM EST this afternoon for LEZ145- 146. && $$ SYNOPSIS...Saunders NEAR TERM...Griffin/TK SHORT TERM...Jaszka LONG TERM...Jaszka AVIATION...Griffin MARINE...Jaszka

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