Area Forecast Discussion
Issued by NWS Cleveland, OH
Issued by NWS Cleveland, OH
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196 FXUS61 KCLE 050634 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 234 AM EDT Fri Jul 5 2024 .SYNOPSIS... A front currently stalled near the route 30 corridor will lift north across the area tonight ahead of low pressure drifting into the western Great Lakes. This low pressure will pass by to our north Friday evening while pushing a cold front through. Weak troughing will linger for Saturday before high pressure builds in Saturday night through Monday. && .NEAR TERM /THROUGH TONIGHT/... 9:30 PM Update... Convection has developed across a good portion of the area. moderate deep layer shear of around 40 knots has resulted in some of these showers developing rotation, mainly towards the southern portion of our forecast area. These low-topped supercells have been weak though, with the lack of instability really inhibiting their ability to strengthen and become a real threat. Mesoanalysis suggests weak low-level shear, though low- level mesocyclones have been observed on radar and there have been a few pictures of wall clouds and funnel clouds to our southwest in the supercells in ILN`s area, so there must be greater low-level shear/SRH than mesoanalysis is suggesting. Either way, it`s enough activity for us to keep our eyes glued to radar, in case of a quick spin-up. Coverage of showers has been greater than expected, so did increase PoPs through the next few hours, but decreased PoPs for tonight as confidence increases in precipitation end time. Previous Discussion... Unsettled and humid conditions are expected for the near term. Weak low pressure will push into the Great Lakes from the west tonight into Friday ahead of an upper-level trough. A front currently draped across central OH will lift north as a warm front this evening into tonight. The low pressure will pass to our north late Friday into Friday night while pushing a cold front across the region. Along with the fronts, lift from convective-enhanced shortwaves and MCVs will move through at times, encouraging occasional shower and thunder potential. As of 3:30 PM the front is draped from roughly Marion to Mansfield to Chardon to Meadville with several low-topped convective cells ongoing along it. At the same time, an MCV is moving across central OH. The combination of the two features will keep shower and thunder chances going through early this evening along and south of the front, with some lighter stratiform rain possible north of the front. In the immediate term, the combination of enhanced flow aloft with the MCV and the boundary itself may encourage rotating updrafts from Mansfield to Canton points south. However, skinny and modest instability profiles and a lack of DCAPE argue against severe weather. Still, any more persistent rotating updrafts will need to be watched for a brief/isolated severe threat through about 5 PM in our far south, with any slower-moving or training storms dropping locally heavy rain in this humid environment. The next convectively-enhanced shortwave is currently moving east out of central IL and will move through tonight. Modest lift ahead of this feature along with weak instability and a humid airmass will support another uptick in showers and thunder from west to east this evening into tonight. The frontal boundary will begin lifting ahead of this feature and may be a focus for more numerous cells this evening. The wave will exit to the east after midnight, allowing for a drying trend overnight. With such a humid airmass and light winds a bit of patchy fog may develop pre-dawn Friday if a period of partial clearing occurs. Otherwise, look for muggy lows on either side of 70. We should see a general lull in activity through much of Friday morning due to weak subsidence and perhaps a bit of dry air advection behind the shortwave that will move through tonight. By Friday afternoon and evening, modest height falls and upper- level divergence ahead of the upper trough moving into the Great Lakes along with the approach of the cold front should encourage at least some shower and thunderstorm development across our area. Guidance disagrees on how quickly subsidence behind tonight`s wave will exit and on if convection will fire over the Ohio Valley on Friday. Both could be limiting factors for destabilization and subsequent convection local. However, still have a mix of chance and likely POPs along and ahead of the cold frontal passage from west to east Friday afternoon and evening as the combination of a front, some forcing, a humid airmass and timing near peak heating should yield at least some convection. There is room for POPs to be adjusted higher or lower depending on how much subsidence lingers over our area and how robust the return of greater moisture/instability is from the south/southwest through the day. Either way, expect muggy conditions with highs generally in the low to mid 80s Friday. Poor mid-level lapse rates will act against a greater severe threat Friday afternoon and evening. However, stronger heating could yield 1000-2000 J/KG of MLCAPE given such a moist airmass and deep-layer shear of 40-50 knots is expected. Enough surface heating and mid-level drying may play out to allow moderate DCAPE to develop as well. Given a number of conflicting factors, the current Day 2 Marginal Risk (level 1/5) for severe weather driven by isolated damaging wind potential is reasonable. However, there is a somewhat less-likely potential for greater destabilization and more robust convection. Given the amount of shear, a more robust evolution could support a mix of supercells and small lines with a more organized wind damage threat and potentially some marginally severe hail and tornado potential. This may come down to a "nowcast" situation on Friday. Activity should gradually exit to the east and diminish in intensity Friday evening and night as the cold front continues progressing with some clearing of the skies too. Lows will generally fall in the mid 60s to near 70 by early Saturday. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... While the model data is not completely supportive, have added slight chance POPs to the land portion of the CWA for Saturday given the cold pool aloft moving in and some instability off the boundary layer combined with peak daytime heating and perhaps a hint of PVA aloft. Layer moisture is definitely a concerning factor and a reason not to go above 20 percent, but could get an isolated shower to form in this setup. Vast majority of the area will be dry. High pressure will continue to build in the southern Great Lakes, paving the way for a dry remainder of the weekend. Slightly warmer Sunday with generally low to mid 80s for the most part. An upper level trough will be working its way into the western Great Lakes by the end of the short term forecast period, likely weakening as it does so. && .LONG TERM /MONDAY THROUGH THURSDAY/... Upper trough south of the axis in the Great Lakes mentioned at the end of the short term period will be the main driver for the next chances for showers and storms for the region. Until then, high pressure should still be in control for one more day on Monday, but will be on the exit to the east. Best bet for the surface low pressure/cold front to come through is Tuesday afternoon/evening. POPs linger in cyclonic flow aloft through mid week in the wake of the system. && .AVIATION /06Z Friday THROUGH Tuesday/... Overall, there is fairly low confidence in the TAFs early this morning. High amounts of low level moisture remain the region behind several rounds of rain on Thursday. This is allowing for a mixture of fog and stratus across the region. Unfortunately, there is quite a bit of variability with a range of VFR to IFR in conditions this morning. Suspect that conditions will trend down to MVFR to LIFR for most locations; however, some mid-level clouds continue to move through the region and may prevent more significant fog and stratus from developing. There should be some mixing with daybreak and a trend to VFR by late morning. A cold front will approach the region from the west today. The atmosphere could destabilize and allow for showers and storms to develop during the late afternoon hours. However, clouds in the region could mitigate the energy across the area to help sustain widespread storms. Therefore, have some VCSH and VCTS mentions at the TAFs for this afternoon into tonight. However, do not have the confidence to go with any non-VFR restrictions due to the wide range in possibilities for convection this afternoon and evening. The cold front will sweep through tonight and end the rain threat and allow for conditions to trend to VFR with drying conditions. Winds through the period will have variable direction this morning, ahead of the front this afternoon, and then behind the front tonight, but winds should be 10 kt or less. Outlook...Non-VFR possible in showers and thunderstorms Tuesday into Tuesday night. && .MARINE... Light and variable winds through early Friday morning with wave heights less than 1ft become southerly around 10kts Friday afternoon ahead of a cold front with chances for showers and storms, then southwesterly 10-20kts in the wake of the cold front Friday evening through Saturday. Wave heights east of Cleveland 1-3ft during that time, west of Cleveland 1-2ft away from shore in the nearshore zones. Winds ease out of the northwest Sunday with wave heights dropping below 1ft despite the more onshore flow at around 5kts. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. NY...None. MARINE...None. && $$ SYNOPSIS...Sullivan NEAR TERM...Saunders/Sullivan SHORT TERM...26 LONG TERM...26 AVIATION...Sefcovic MARINE...26