textproduct: Cleveland

WHAT HAS CHANGED

Temperatures and heat indices on Tuesday and Wednesday have trended a bit higher with this forecast package. Heat Advisories may need to be considered for parts of Northwest Ohio.

KEY MESSAGES

1)Hot conditions are expected this week. Heat indices will peak in the mid 90s to low 100s Tuesday and Wednesday, resulting in Major HeatRisk conditions (level 3 of 4).

2) Showers and thunderstorms return Friday night and continue at times through the weekend.

DISCUSSION

KEY MESSAGE 1... A closed off mid-level high with anomalous 500mb heights up to 600 dam is currently centered over the upper Midwest. This high will drift southeastward as it flattens out and dissipates with time through the week.

Relative to our forecast area, this will contribute to increasing low-level heat and humidity, though the hottest conditions will be displaced to our northwest. Temperatures will be in the upper 80s to around 90 today, but daytime heating resulting in the mixing of dry air aloft will yield lower dew points and reduced heat indices (to near the actual air temperature).

Tuesday and Wednesday is when the worst heat and humidity are expected with widespread temperatures in the 90s. Dew points in the mid to upper 60s on Tuesday and possibly 70 on Wednesday will contribute to heat indices in the mid 90s to low 100s and Major HeatRisk conditions (level 3 of 4) both days. A Heat Advisory may need to be considered for Toledo and adjacent areas on Tuesday, and then a broader region across portions of the area west of I-77 for Wednesday. An extreme heat watch was considered for the Toledo area Tuesday but there are risks of lower humidity (due to mixing of dry air aloft) and the 00Z HREF/REFS only have a 10-20% chance of reaching or exceeding 105.

A cold front will swing through the area Wednesday evening into Wednesday night. Relative to the hot conditions on Tuesday and Wednesday, temperatures will cool down to highs in the upper 80s to low 90s, though downwind of Lake Erie in far Northeast Ohio (Lake, Geauga, Ashtabula area) and in Northwest Pennsylvania, more reasonable temperatures are expected in the low to mid 80s, due to west to northwest flow off Lake Erie. Relief will mainly come in the form of much lower humidity as dew points potentially drop to below 60 on Thursday before building back up into the low 60s.

KEY MESSAGE 2... The upper level high/ridge retreats back westward this weekend, while an upper-level trough further entrenches itself over the northeast CONUS. We're caught in between these two synoptic- scale features, with a theta-e gradient expected across the upper Midwest, Great Lakes region, towards the mid-Atlantic. Overlap of cooler temperatures aloft from the trough towards the northeast and surface heat and humidity from the ridge to the west and southwest will contribute to a stormy pattern along this gradient this weekend. Locally, the latest model guidance is pointing to Friday night through Saturday evening being the most likely chance for storms; however, a weakly forced setup like this yields low predictability. Even so, wherever storms occur, they will likely present some amount of severe weather risk, so this weekend is worth keeping an eye on.

AVIATION /12Z Monday THROUGH Friday/

VFR conditions are prevalent across the region as only high level clouds move through. Probability is low, but a few pop up showers are possible this afternoon at KMFD, KCAK, and KYNG. If over station, this could bring visibility down to IFR. Otherwise, expected VFR conditions throughout the TAF period.

Winds will be light and variable across much of the region this morning, then shift to be predominantly out of the north to northeast at 5-10 knots over the next few hours. After 00Z, winds will shift around to be out of the south-southwest and light at less than 5 knots.

Outlook...VFR favored through Thursday. Non-VFR chances increase starting late Friday with showers and thunderstorms possible.

MARINE

Quiet marine conditions are expected over the next several days as high pressure builds into the region. Winds will be light at around 5 knots out of the north this morning before shifting to south- southwest by at 5-10 knots this afternoon. Throughout the day Tuesday, winds will increase to around 10-15 knots out of the southwest and persist through Wednesday morning. Waves will build to 1-3 feet, primarily in the central and eastern open waters during that time. A cold front will sweep across the lake on Wednesday and winds will shift to be out of the north and though should remain less than 10 knots. With the northerly winds, waves could build to around 2 feet in the near shore zones behind the cold front to end the week.

CLE WATCHES/WARNINGS/ADVISORIES

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