textproduct: Cleveland

WHAT HAS CHANGED

No significant changes to the forecast with the morning update.

KEY MESSAGES

1) A few rounds of showers and thunderstorms late tonight through Friday. Some of the storms could be strong Thursday afternoon.

2) Seasonably cool temperatures through Saturday followed by a major change to building heat and humidity Sunday through Tuesday.

DISCUSSION

KEY MESSAGE 1... Dry weather will continue today as the large Canadian high settles into the Ohio Valley before departing across the Mid Atlantic region tonight. This will support plenty of sunshine again and continued below normal temperatures as broad mid/upper troughing persists across the northern tier of the CONUS.

Attention tonight will turn to the next system as a low amplitude shortwave progresses through the broad longwave trough and moves from the upper Midwest tonight into the central Great Lakes by Thursday morning. The left exit of a 90-100 knot H3 jet streak will support a modest surface low tracking across northern Lower Michigan and Lake Huron Thursday, and this will pull a fairly strong cold front across the region.

Southerly return flow and resultant warm air advection behind the departing surface high and ahead of the approaching low will lead to some rain showers entering the region late tonight, especially where isentropic ascent can be maximized ahead of the lifting warm front. The latest CAMS are in some disagreement on how widespread this activity will be, but trends have been toward a stronger nocturnal low-level jet averaging 20-30 knots in response to the approaching upper jet streak mentioned above, and this will advect in enough elevated instability for thunder and will also boost the moisture advection to expand the coverage of rain near the warm frontal boundary. Consensus points toward the greatest coverage being near the lakeshore counties, so expanded likely and categorical POPS in that area late tonight into Thursday morning. Some locally heavy downpours could occur with any embedded convection, but this is expected to be low-impact rain.

Considerable uncertainty still exists with how convection will evolve ahead of the cold front Thursday afternoon. Guidance is starting to converge on an afternoon and early evening frontal passage, which is diurnally favorable for stronger storms. However, the morning showers and associated cloud cover lingering from the remnants of the overnight activity will dictate how much instability is able to build. The clouds and showers will probably linger over much of NE Ohio and NW PA through at least late morning, and that will disrupt surface heating of what is already not a very warm and moist airmass by summer standards. If enough heating can occur, MLCAPE should reach around 1000 J/kg, and this combined with deep layer effective shear likely over 40 knots will support organized updrafts and a few strong to severe storms. The latest SWODY2 places a marginal risk (level 1 of 5) in the southeastern CWA, and this is reasonable. The 90-100 knot upper jet streak rotating overhead and 45-50 knots of mid-level flow make things potentially interesting if enough instability can be reached. The 00Z HREF is starting to pick up on convection ahead of the front in the afternoon and evening, especially along and east of the I-71 corridor, so we will continue to monitor and would not be surprised to see this marginal risk expanded farther northwest into more of our CWA.

Brief drying is expected Thursday night as the cold front settles toward the Ohio Valley, but another mid/upper shortwave rotating through the base of the broad trough will support a surface low tracking along the front as it becomes quasi-stationary over central and southern Ohio Friday and Friday night. The NAM seems to have convective feedback issues the past few runs and blows up an unrealistically strong surface low, but plenty of mid/upper jet support will exist for widespread showers along the boundary Friday and Friday night. The best instability will be south of the region, so the bulk of the convection will stay to our south, but stratiform rain showers are likely to reach into our CWA at times Friday into Friday night, especially south of a Findlay to Warren line. This will elevate cloud cover as well.

KEY MESSAGE 2... If you have enjoyed the cool weather of late, enjoy it while it lasts because a prolonged period of heat and humidity is likely next week. The mid/upper longwave trough that has dominated the northern tier will remain in place through the end of the week and then start to retreat into New England this weekend as a subtropical ridge amplifies over the central CONUS in response to a deep mid/upper trough digging west of the Rockies. Near to below normal temperatures in the upper 70s to around 80 will continue today through Saturday (slightly cooler Friday behind the front), but that will be replaced by building heat and humidity Sunday through Tuesday as the central CONUS ridge further strengthens and drifts into the Mid Mississippi and Tennessee Valleys. Highs in the upper 80s Sunday will reach the low 90s Monday and Tuesday, and with dew points rising into the 70s, heat indices will likely near or exceed 100 F early next week. Early season heat is always more dangerous, and everyone will have to re-aclimate after the recent cool weather. Ensemble guidance suggests that this ridge and associated heat could persist all of next week, so heat headlines are possible if the pattern continues to evolve in this manner.

AVIATION /06Z Wednesday THROUGH Sunday/

High pressure, light winds, and clear skies will create the potential for patchy fog overnight. Confidence is highest in MVFR/IFR visibilites at YNG but could see brief restrictions at TOL/FDY/MFD/CAK as well. Otherwise, VFR through the period with increasing high cloud later today. Chances of precipitation arrive between 06-12Z Thurs and included a vicinity shower at CLE late in the period.

Winds will be light and variable overnight, then southwesterly after 15Z. The exception will be at CLE/ERI where lake breezes are expected with north/northwest flow of 5-9 knots.

Outlook...Non-VFR possible with a chance of showers and thunderstorms Wednesday night into Thursday and again on Friday night into Saturday.

MARINE

Lake breezes with onshore flow of 5-10 knots are expected today with high pressure and light winds over the region. Southerly winds will increase overnight becoming southwesterly at 10-20 knots on Thursday ahead of low pressure moving through the Central Great Lakes. Showers with scattered thunderstorms are possible on the lake Wednesday night through Thursday and could lead to erratic wind/wave conditions. Otherwise winds will shift to the north/northeast behind a cold front on Friday and remain out of the east/northeast through the weekend.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...None.