textproduct: Cleveland

WHAT HAS CHANGED

The chance for showers and thunderstorms with locally gusty winds has increased near the lakeshore from about Toledo to Lake, Geauga, and Ashtabula Counties in the pre-dawn hours Wednesday.

KEY MESSAGES

1) Showers and isolated thunderstorms expected late tonight and Wednesday as a cold front slowly settles southward. These could produce locally gusty winds in the pre-dawn hours Wednesday.

2) Strong low pressure moving through the area Thursday night and Friday will bring rain, strong winds, and falling temperatures followed by the coldest air of the season Friday night and Saturday. Widespread frost/freeze headlines are likely Saturday night/Sunday morning.

DISCUSSION

KEY MESSAGE 1... Record high temperatures are occurring this afternoon in the warm sector of a low pressure system moving through the central Great Lakes. Warm air advection with 850 mb temps of 18-19 C, sunny skies, and gusty SW winds have led to surface temperatures in the mid 80s, with even isolated upper 80s in NW Ohio! This will set up a very warm and breezy evening.

The surface low will move into the eastern Great Lakes tonight, dragging a cold front to the vicinity of Lake Erie this evening. The front will become quasi-stationary near the south shore of the lake for several hours tonight as a secondary mid-level shortwave emanating out of a cut off low over the Four Corners region crosses the southern and central Great Lakes. This will result in a weak surface wave riding along the front tonight. The combination of this surface wave and 130+ knot H3 and 60-70 knot H5 jets associated with the mid/upper wave crossing the Great Lakes will enhance large scale forcing to generate showers and thunderstorms along the front late tonight and early Wednesday morning as it sags southward. The 12Z suite of HREF CAMS have become more aggressive with a cluster of convective showers and even some thunder developing in SE Lower Michigan and NW Ohio overnight then progressing across Lake Erie and the adjacent lakeshore counties of northern and NE Ohio in the 08-11Z timeframe. This is not shown nearly as much by the RRFS, but the aforementioned forcing tied to the surface and mid/upper waves traversing the sagging boundary support some convection, especially with lingering warmth overnight from today's record highs (lows in the mid 60s). The key will be Lake Erie. HREF and RRFS instability parameters suggest little to no surface or MUCAPE overnight, but the warm Lake Erie waters averaging 18C will likely generate some over-lake instability. This could help the convective cluster to become more organized over the lake as it moves east, and if so, the presence of 50 knots of westerly 0-6 Km bulk shear could cause strong to sub severe winds near the lakeshore. This probability is low overall and conditional on if the cluster can get a boost over the lake, but if any convective winds occur, the most likely area would be from roughly just east of Toledo through the Islands to Lake, Geauga, and Ashtabula Counties where the weak instability over and near the lake will aid in momentum transfer to the surface.

Additional showers and pockets of embedded thunder with heavier downpours will continue Wednesday as the cold frontal boundary continues pushing southward, but widespread cloud cover and the best jet support progressing east of the region will prevent anything organized, with mainly low-impact rain expected. The best potential for heavier rain and thunder will be along and south of the US-30 corridor in the afternoon. Overall QPF Wednesday will average a few hundredths to up to 0.20 in most areas, but some 0.25 to 0.50 inch amounts could occur along and south of US 30 if any isolated convective showers/thunder can redevelop in the afternoon. Any rain will trend farther south as the day wears on, with slow drying from north to south expected. All areas will be dry by Wednesday night as Canadian high pressure building into the Upper Great Lakes pushes the front into the Ohio River Valley.

KEY MESSAGE 2... The break in the weather will be brief as the Canadian high across the Great Lakes already retreats Thursday afternoon to allow the frontal boundary to lift back north as a warm front Thursday evening and night. This is in response to the old Four Corners cut off low phasing with an amplifying mid/upper trough through the northern Plains/Upper Midwest. The result will be a deep, negatively tilted trough digging through the Great Lakes and eastern U.S. Friday and Saturday. In response to this dynamic trough, strong surface cyclogenesis will take place over the southern Great Lakes Friday morning, with the deepening low lifting across upstate NY during the day.

In terms of impacts, rain will lift back into the region late Thursday afternoon and evening as warm air advection and isentropic ascent generate a rain shield along and north of the lifting warm front. There will likely be a lull in the warm sector Thursday night with gusty SW winds developing (gusting up to 30 knots) beneath a 50+ knot low-level jet, but showers will fill back in ahead of the strong cold front that will cross the region Friday morning. Will need to watch for a low-topped squall line along the front if at least weak instability can be realized since the strong wind fields could produce damaging winds. Nevertheless, strong cold air advection in the wake of the front, the tight pressure gradient, and strong post-frontal pressure rises will lead to strong winds Friday morning into Friday night. The probability of wind gusts over 40 knots (50 mph) is increasing Friday, so Wind Advisories will likely be needed, especially in NW Ohio and along the lakeshore. Additionally, the strong cold air advection and NW flow will lead to lake-effect showers in NE Ohio and NW PA Friday afternoon and evening.

Winds will gradually subside Friday night and Saturday morning, but lake-effect showers will continue in NE Ohio and NW PA, and with 850 mb temps dipping below -5C (some guidance continues to be colder), graupel is possible, and the first snow flakes of the season could also occur in southern Erie and Crawford Counties of NW PA. High pressure building in Saturday afternoon and Saturday night will dry out all areas, but the coldest night of the season so far is likely, with widespread lows in the low/mid 30s. Some upper 20s are possible in interior NE Ohio and NW PA. This will lead to a widespread frost and freeze that should end the growing season in many areas. Moderating temperatures are expected Sunday and Monday as the arctic high drifts east.

AVIATION /18Z Tuesday THROUGH Sunday/

Mainly VFR conditions are expected for this TAF update. Clouds will increase tonight ahead of slow moving cold front. Scattered showers and isolated thunder will be possible along the front between 09z and 15z Wednesday morning. We will maintain -SHRA in the TAF but future forecast updates may have to include VCTS or some reduction in visibility/ceilings. MVFR ceilings are expected to move in late Wednesday morning at CLE, YNG, and ERI. Winds will be gusty this afternoon from the southwest 12 to 15 knots with gusts up to 25 knots. Winds will relax after 23z from the west around 5 knots. Winds will shift from the northwest or north around 5 knots Wednesday morning.

Outlook...Intermittent non-VFR is likely Wednesday with widespread showers and perhaps a few thunderstorms. Additional non-VFR in rain is likely Thursday afternoon through Friday night with wind gusts exceeding 30 knots on Friday.

MARINE

SW winds will be near 20 knots at times through early this evening before decreasing to 5-10 knots and veering to NW tonight behind a cold front sagging across the lake. NNW winds will continue at 5-10 knots most of Wednesday, turning NE and increasing to 15-20 knots Wednesday night and Thursday as high pressure builds into the Upper Great Lakes. Another Small Craft Advisory may be needed Wednesday night into Thursday, especially in the western and central basins.

After a lull late Thursday, SW winds will increase to 20-30 knots late Thursday night as a warm front lifts across the lake ahead of a potent low pressure system. These winds will turn NW Friday morning behind the system's cold front, increasing to 25-35 knot gales. Gale force winds, potentially up to 40 knots, will likely continue into Friday night. This will build wave heights to 8-12 feet at times Friday and Friday night, so the first gale headlines of the season are expected late Thursday night into Saturday. Winds will gradually diminish Saturday, becoming SW at 15-20 knots by Sunday.

CLIMATE

Temperatures are forecast to be near record high values across Northwest and North Central Ohio this afternoon. Records for October 13 are listed below for the official climate locations.

Date Toledo Mansfield Cleveland Akron Youngstown Erie

10-13 83(1975) 84(1969) 82(1969) 82(1969) 83(1969) 83(1983)

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...Small Craft Advisory until 2 AM EDT Wednesday for LEZ147>149.