Area Forecast Discussion
Issued by NWS Cleveland, OH

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000 FXUS61 KCLE 210533 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 133 AM EDT Wed Aug 21 2019 ...06z Aviation Forecast Update... .SYNOPSIS... A cold front will move southeast across the local area Wednesday evening. A ridge of high pressure will build southeast across the area Thursday. High pressure will be centered over the local area Friday night. Below average temperatures are expected for the end of the week and weekend. && .NEAR TERM /THROUGH TODAY/... A line of showers and thunderstorms stretches from Mentor to Warren to Salem, moving east-northeast at about 25-30 mph. These storms will only last for about the next four hours or so and most of the area should be dry for tonight after being worked over by convection over the last several hours. Some showers may try to creep along the lakeshore overnight following a subtle boundary across southern Lower Michigan, but precipitation chances appear isolated at best. Winds are light and variable behind the convection but will likely settle into a westerly direction at some point overnight. Temperatures will remain warm overnight with lows in the upper 60s to near 70. Previous Discussion... Focus of the near term forecast is thunderstorm potential this afternoon evening, as thunderstorms begin to develop in west central Ohio ahead of a long lived but somewhat decaying MCS tracking through Indiana. Surface destabilization has continued through the afternoon across the local area, with 2-3k j/kg MLCAPE centered across western Ohio. Mid level lapse rates steepen ahead of the MCS, which will influence the area in the next several hours. Shear remains marginal, with effective bulk shear values of 20-25 kts across the area through early evening, which should limit overall organization of storm activity. However, dry air above 700mb and resultant DCAPE values of 1000-1300 j/kg across the area, coupled with steep low level lapse rates, will enhance the risk for damaging winds with the stronger thunderstorms across the area. SPC has expanded the Day 1 slight risk northward into the southwest part of the forecast area, with a marginal risk for the rest of the area. The best severe thunderstorm potential will be from 4 PM through 10 PM across the area. The associated MCV will slowly shear out/weaken across the area this evening and push east of the area by Wednesday morning. Precip chances will be on the downtrend after midnight, but held onto chance pops east/slight chance pops elsewhere with the disturbance across the area and ample boundary layer moisture and perhaps residual outflow boundaries as a focus of surface forcing. A synoptic cold front will slowly sink south towards the area Wednesday and into the area Wednesday night. Surface forcing is marginal with the boundary, and weak destabilization may limit widespread precipitation development across the area during the day, especially with the better mid level forcing displaced north and southwest of the area. Have kept pops in the chance range on Wednesday, with MLCAPE values up to 1000 j/kg as much drier air in the 850-700mb layer moves into the area from the north. High temperatures rise into the mid/upper 80s across the area. Forecast pops diminish to slight chance range Wednesday night as the front slides south across the area, with the loss of daytime heating inhibiting much fuel for precip development. Pops may linger across the south and southwest parts of the forecast area after midnight into early Thursday morning as upstream convectively induced disturbances propagate eastward along the front, although much of the guidance favors precip placement just south of the area. && .SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... Weak cold front will start off across our southern counties on Thursday. A deepening upper level trough will push south across Lake Michigan on Thursday, maintaining a southwest flow aloft. This may delay the southward movement of the front and will hold onto a low chance of showers and possibly a thunderstorm across the south on Thursday. A noticeable change in airmass will be felt with highs dropping below normal into the 70s where they will remain heading into the weekend. High pressure will strengthen across the Great Lakes Thursday night into Friday, finally pushing the front south of the area. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Upper level trough shifts east across New England allowing a ridge to build overhead. Some weak troughing will also be in place across the southeastern states with moisture focused across the Tennessee Valley and Mid-Atlantic. The 12Z GFS is the fastest in trying to pull moisture back north into the area on Sunday but given the strength of the surface high will continue with a dry forecast. Finally by Monday the next upper trough will approach from the northwest with low pops returning to our western counties Monday, increasing and expanding Monday night into Tuesday. && .AVIATION /06Z Wednesday THROUGH Sunday/... Mainly VFR conditions are expected through the next 24 to 30 hours with the exception for some brief drops in ceilings and visibilities possible between 10z and 14z this morning due to scattered showers. Have mentioned this possibility in TEMPO groups. Otherwise, outside of scattered showers, expect VFR conditions for the most part. Winds will be light and variable to a light southwest or west wind. All wind speeds will be 5 to 8 knots and not an aviation impact issue. There could be a few isolated storms Wednesday afternoon around the area but coverage and potential for impacts are too low to mention in TAFs at this time. OUTLOOK...Intervals of non-VFR possible primarily with thunderstorms on Wednesday. && .MARINE... Southerly flow of 10-15 knots will develop on Lake Erie tonight and increase into the 10-20 knot range on Wednesday ahead of an approaching cold front. Winds will shift to the north with the passage of the front Wednesday night and a Small Craft Advisory will likely be needed east of the Lake Erie Islands. Winds will drop off fairly quickly on Thursday as high pressure expands south over the Great Lakes Region. Northeast to east winds of 5-15 knots will maintain a little bit of a chop on Lake Erie on Friday and Saturday with flow becoming more east/southeast on Sunday. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...Greenawalt NEAR TERM...Greenawalt/Sefcovic SHORT TERM...KEC LONG TERM...KEC AVIATION...Griffin MARINE...

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