textproduct: Cleveland

WHAT HAS CHANGED

No major changes to the forecast.

KEY MESSAGES

1.) Heat and humidity build to start the week, but fairly widespread showers and thunderstorms Tuesday will produce locally heavy rainfall.

2.) The warmest temperatures of the summer so far are likely Wednesday and Thursday, and heat indices could approach 100 F.

3.) Scattered afternoon and evening thunderstorms will continue Wednesday and Thursday, but a more organized round of strong to severe thunderstorms is possible Friday.

DISCUSSION

KEY MESSAGE 1... A strong mid/upper ridge axis will slide over the Ohio Valley and Great Lakes Monday as the downstream mid/upper trough currently over the eastern Great Lakes slides off the East Coast. This will allow the surface high to drift across New England and the Mid Atlantic through the day, setting up southerly return flow. This warm air advection combined with 850 mb temps warming above 17 C will yield highs in the upper 80s to low 90s Monday, but luckily, dew points will remain fairly comfortable (a drier heat).

By Monday night and Tuesday, the first piece of broad overall western CONUS mid/upper troughing ejecting across south central Canada will help to pick up a southern stream mid-level shortwave and eject it through the Ohio Valley/Great Lakes. This will temporarily weaken the mid/upper ridge overhead, and as the associated surface low lifts through the western and central Great Lakes Tuesday, a warm front will lift through the region. This will usher in a much more moist low-level airmass. A few showers are possible in the isentropic ascent ahead of the warm front Monday night, but surface heating of the increasingly rich low-level moisture Tuesday (dew points rising into the low 70s) will yield moderate to strong destabilization. This will lead to widespread convection Tuesday afternoon and evening. Boundary layer flow will be weak, and PWATs look to climb to near 2 inches, which is near the maximum climatology for June 9, so slow moving convection with torrential/efficient rainfall will be a concern. Luckily, most of the CWA has had a bone dry past 2 weeks, but training convection will need to be monitored for localized flooding of low-lying and poor drainage areas, especially where locally heavy rain occurred yesterday. The bulk of the area has been placed in a day 3 marginal risk for excessive rainfall by WPC. Temperatures will be a few degrees lower Tuesday due to the clouds and convection, but the much higher humidity will probably make it feel worse than Monday.

KEY MESSAGE 2... The mid/upper ridge will become reestablished across the Great Lakes and Ohio Valley Wednesday and Thursday while also expanding across the eastern CONUS ahead of the main piece of the western CONUS mid/upper trough progressing into the northern Plains. Deep west-southwest flow and 850 mb temps of 20-22 C advecting into the region beneath the thermal ridge will allow for the warmest temperatures of the young summer season. Ensemble guidance points to highs between 88 and 93 F across most of the area Wednesday and Thursday, and this combined with dew points in the low 70s will yield heat indices approaching or exceeding 100 F in some areas. The NWS HeatRisk map depicts an increasing area of major (level 3 of 4) heat impacts Wednesday and Thursday, and with this being the first extended period of heat and humidity of the season, extra precautions will need to be taken to stay cool and hydrated. Overnight low temperatures will remain elevated in the upper 60s to low 70s.

KEY MESSAGE 3... The hot and humid airmass will allow for scattered diurnal convection Wednesday and Thursday, but fairly strong mid-level capping beneath an Elevated Mixed Layer (EML) plume will keep coverage much lower than Tuesday. Nevertheless, if coverage ends up higher than expected, temperatures and resultant heat indices could end up a little lower Wednesday and Thursday. This will be monitored, but as of now, hot and humid is the main message.

The aforementioned mid/upper trough progressing through the northern Plains is trending faster and looks to reach the Great Lakes Friday. This will break down the ridge and allow for a cold frontal passage Friday. The trough will bring mid/upper synoptic support and dynamics, so depending on the timing of the front, strong to severe thunderstorms are possible Friday. Lower temperatures and humidity are expected Friday through the weekend, but still on the somewhat sticky side as the front becomes quasi-stationary nearby.

AVIATION /18Z Sunday THROUGH Friday/

VFR conditions are expected under high pressure through the TAF window. North winds less than 10 knots become light and variable and then southeast during the day tomorrow.

Outlook...Periods of non-VFR likely in occasional showers and thunderstorms early Tuesday through Thursday.

MARINE

High pressure will depart to the east by tomorrow. Winds turn easterly while increasing to 10-15 knots on Monday, resulting in some nearshore choppiness, especially in the western basin. A warm front approaches the lake on Tuesday allowing for winds to shift southerly while remaining between 10-15 knots. Southerly to southwesterly flow will continue through the remainder of the week.

CLE WATCHES/WARNINGS/ADVISORIES

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