Area Forecast Discussion
Issued by NWS Cleveland, OH
Issued by NWS Cleveland, OH
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982 FXUS61 KCLE 021015 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 615 AM EDT Tue Jul 2 2024 .SYNOPSIS... A ridge continues to affect our region today as the parent high pressure center moves from the eastern Great Lakes to southern New England. This ridge exits eastward tonight as a warm front sweeps northward through northern Ohio and northwest Pennsylvania. A weak cold front is poised to sweep southeastward through our region Wednesday evening through the predawn hours of Thursday morning. Behind the cold front, a weak ridge builds from the western Great Lakes through the balance of Thursday. && .NEAR TERM /THROUGH WEDNESDAY/... 6:05 AM EDT Update... Forecast remains valid per latest trends in obs and model guidance. No changes appeared necessary. Previous Discussion... Fair weather is expected in northern OH and NW PA through tonight. Aloft, a ridge builds from the western Great Lakes today and then begins to exit E`ward tonight as a shortwave trough moves from the northern Rockies to the Upper Midwest. Simultaneously, the surface portion of the ridge exits slowly E`ward from our region today and is followed by the N`ward passage of a warm front tonight. This warm front will usher-in a much warmer and very humid air mass originating over the Gulf of Mexico and southern Gulf Stream. Forecast models continue to indicate the strongest frontogenesis and moist isentropic ascent along the upper-reaches of the warm front will occur north of our CWA, over/near Lake Huron. That is where any elevated convection is expected to be focused overnight tonight. The synoptic MSLP gradient is expected to strengthen gradually through tonight as the departing surface ridge interacts with a deepening surface trough approaching from the northern/central Great Plains. Nevertheless, the synoptic MSLP gradient and sufficient daytime heating of land surrounding ~72F Lake Erie will allow a lake breeze to form late this morning. This lake breeze is expected to penetrate up to two miles or so inland this afternoon before dissipating late this evening. Late afternoon highs are expected to reach the upper 70`s to lower 80`s within the lake breeze. Elsewhere, late afternoon highs are expected to reach mainly the lower to mid 80`s as daytime heating is complemented by strengthening WAA along the western flank of the low-level ridge. Tonight`s lows are expected to reach mainly the 60`s to lower 70`s around daybreak Wednesday as strengthening warm/moist air advection along the western flank of the departing low-level ridge and especially behind the aforementioned warm front contributes to limited nocturnal cooling. W`erly flow aloft and embedded shortwave disturbances affect the eastern Great Lakes and Upper OH Valley on Wednesday as the aforementioned surface trough overspreads our CWA from the west. A cold front will approach from the west and should reach far-western Lake Erie and far-northwestern portions of our CWA by nightfall. Continued low-level warm/moist air advection from the Gulf of Mexico and southern Gulf Stream combined with daytime heating amidst peeks of sunshine will result in a warmer and much more humid day (late afternoon highs in the mid 80`s to lower 90`s), weak to moderate destabilization of the warm/moist sector boundary layer, and PWAT values rising to near 2.0". These projected PWAT values are near the record-high values for 00Z/July 4th at the four upper-air stations closest to our CWA. Daytime heating will also allow convective mixing of the boundary layer to yield steep low-level lapse rates and about 500 to 1000 J/kg of DCAPE amidst moderate effective bulk shear. Given the aforementioned thermodynamic/kinematic environment, multicell showers/thunderstorms with periods of torrential rainfall, strong to damaging convective wind gusts, and frequent lightning are expected to develop via low-level convergence and ascent along the cold front, pre-front surface trough axes accompanying the aforementioned shortwave disturbances, and downshear outflow boundaries. Showers/storms may develop during the late morning, but the likeliest window for showers/storms spans midday through sunset. Since W`erly mean mid-level flow is expected to have a significant component perpendicular to the cold front and pre-front surface trough axes, the potential for training convection appears limited. However, isolated flash flooding is possible in low-lying and/or poor drainage areas impacted by multiple rounds of showers/storms. Severe hail is not expected since melting levels will easily exceed 10.5 kft AGL in the warm/moist sector. Tornadoes are not expected due to a lack of significant strengthening/veering of low-level winds with height. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... The expectation of widespread showers and thunderstorms with a strong to severe storm threat, as mentioned above, will continue into Wednesday night as the cold front will move southeast across the region. Have a larger area of categorical PoPs across the southeast half of the area to start the period and will trend the highest PoPs south with the timing of the cold front. For Thursday, the question all will lie with where does the cold front stall out. The last several forecast cycles have the front reaching the Ohio River and settling across southern Ohio. This could be a good omen for much of the area for the July 4th holiday as this front will be a focus area for shower and thunderstorm activity and will limit the amount of moisture can return north into the region. However, some mid-level energy will ripple through the region on Thursday afternoon and evening and with the peak heating of the diurnal cycle, there could be some scattered convection. In the end, have a forecast with the lowest PoPs north and highest PoPs south, closer to the front. The Lake Erie adjacent areas are more of a 20-30% range, whereas Central Ohio counties south of US 30 are more of a 50-60% range. An upper trough will enter the Upper Midwest on Friday and develop a low pressure system west of the Great Lakes. This low will lift the front near the Ohio River north, across the area, as a warm front. Higher shower and storm chances will expected on Friday afternoon and evening with the frontal passage. Rain chances will become more scattered Friday night with the low north of the forecast area and drier air entering ahead of the associated cold front. Temperatures through the period will be near normal in the 80s. && .LONG TERM /SATURDAY THROUGH MONDAY/... All in all, the forecast continues to trend toward a generally quiet weekend after several days of unsettled weather across the region. A low pressure system will be moving east across the Great Lakes on Saturday, north of the forecast area. This low should allow for a cold front to sweep through earlier in the day and there are some lower rain chances to start on Saturday with the highest chances east. Some upper ridging will build into the region for Saturday night into Sunday and support surface high pressure across the region. This will allow for a generally dry forecast through Sunday night. An upper trough and associated surface cold front will approach the forecast area on Monday and some scattered rain chances could return to the region. Temperatures through the period will be generally seasonable in the 80s. && .AVIATION /12Z Tuesday THROUGH Saturday/... VFR and fair weather expected through 12Z/Wed. Aloft, a ridge continues to build from the western Great Lakes and vicinity as multiple/subtle disturbances ripple E`ward through the ridge. Few to scattered mid/upper-level clouds will accompany these disturbances. At the surface, the ridge exits slowly E`ward and a warm front sweeps N`ward through northern OH and NW PA overnight tonight. Any showers/thunderstorms associated with this front are expected to develop over/near Lake Huron overnight tonight and remain north of our region. Our regional surface winds will be primarily SE`erly around 5 to 10 knots ahead of the warm front. Behind the front, winds veer to S`erly and increase to around 10 to 15 knots. Note: A Lake Erie lake breeze is expected to develop by midday and penetrate up to two miles or so inland this afternoon before dissipating by ~00Z/Wed. This lake breeze is expected to impact KERI. Outlook...Non-VFR expected with periodic/scattered showers/thunderstorms this late Wednesday morning through Saturday. && .MARINE... A warm front will lift north toward Lake Erie today. The front will struggle to clear the lake during the daytime hours and southeast flow will become brief northeast flow during the late afternoon and early evening hours. The front will fully cross the lake tonight and southerly flow will take over and increase into Wednesday as a cold front approaches the region. The offshore flow could get strong enough on Wednesday to merit a marginal Small Craft Advisory with wind touching 20 knots. The cold front will cross the lake by Wednesday night and light westerly flow will become favored across the basin. The front will stall over the Ohio River for Thursday and light generally offshore flow will be favored. This front will lift back north as a warm front on Friday and slightly stronger south to southeast flow will return to the lake. A low pressure system will move north of the lake on Friday night into Saturday and a stronger pressure gradient across the region will allow for increasing southwest flow and another Small Craft Advisory could be needed. Shower and storm chances are in place for Wednesday through Saturday with several fronts moving near and across the lake. Some storms may need a short fused marine warning headline, especially on Wednesday and Friday. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. NY...None. MARINE...None. && $$ SYNOPSIS...Jaszka NEAR TERM...Jaszka SHORT TERM...Sefcovic LONG TERM...Sefcovic AVIATION...Jaszka MARINE...Sefcovic