textproduct: Cleveland

WHAT HAS CHANGED

Slightly increased chances for lake-effect rain showers late tonight and Sunday morning in NW and north central Ohio.

KEY MESSAGES

1) Cooler and much less humid conditions will move in tonight, and a NE flow will bring lake-effect showers to NW and north central Ohio late tonight into Sunday morning.

2) Seasonable and dry weather is expected Sunday afternoon through the rest of the holiday weekend before a brief period of hot, humid, and unsettled weather returns mid week.

DISCUSSION

KEY MESSAGE 1... Mid/upper water vapor loops this afternoon show the broad ridge finally being shunted farther west into the Plains as a trough deepens across the Great Lakes and Northeast U.S. This will bring the much anticipated airmass change by this evening and tonight as Canadian high pressure at the surface builds down across the Great Lakes. A secondary cold front currently sinking south and west through the area is advecting in the lower dew points, with surface observations falling into the 50s in far NE Ohio and NW PA. These lower dew points will continue to spread south and west behind the front through the evening.

The drier air and high pressure will allow for a pleasantly cool night, with lows in the low/mid 50s away from the lake. This will set up a much different day Sunday, with skies becoming mostly sunny and highs only in the mid/upper 70s. The one caveat to the cooler, quieter weather is growing potential for lake-effect rain showers tonight through Sunday morning. NE boundary layer flow will lead to bands of showers impacting NW and north central Ohio, especially between the islands and Toledo, but areas immediately near the lakeshore from Lorain to Erie, PA could be clipped by brief showers as well. Increased POPS for this potential late tonight into Sunday morning. The long northeasterly fetch and 850 mb temps falling below 10 C will support a few hundred joules of lake induced CAPE, and low- level convergence will also aid in band development, so confidence is increasing for showers. Relatively shallow low- level moisture should at least keep the activity fairly light. Otherwise, the seasonably cool and dry weather will continue through Labor Day Monday.

KEY MESSAGE 2... The large Canadian high will drift into the Mid Atlantic Tuesday and Tuesday night as the central CONUS mid/upper ridge once again expands east into the Ohio and Tennessee Valleys. This will set up return southerly flow and advect the hot and humid air back into the area for midweek. Highs Tuesday will get back into the low/mid 80s with a noticeable increase in humidity, and some 90s are possible Wednesday as the heat and humidity becomes firmly reestablished. Shortwave energy topping the building ridge Tuesday night/Wednesday morning combined with a low-level jet impinging on the lifting warm front could spark some showers and thunderstorms in NE Ohio and NW PA, but left things dry at this time. Better potential for showers and thunderstorms will come late Wednesday and Wednesday night as a strong northern stream mid/upper shortwave trough digs into the Great Lakes with a deep associated surface low progressing through northern Ontario and Quebec. This will push a cold front through the region Wednesday night. Depending on timing of the frontal passage, strong to severe storms will be possible since jet dynamics look impressive. The front will be slow to push south, so expect showers to continue Thursday, especially south of a Findlay to Youngstown line before Canadian high pressure returns Friday and Saturday. So, after the brief midweek heat and storms, cooler, drier, and less humid air will return Thursday through Saturday.

AVIATION /18Z Saturday THROUGH Thursday/

Scattered clouds between 2-5kft continue to stream southeast across the area this afternoon, resulting in patchy MVFR conditions at terminals extending from near Toledo (TOL) toward Akron (CAK). In addition, isolated light showers have developed along this boundary but should not have any impact to terminals including VSBY or lightning. As the boundary continues to shift south, dry and widespread VFR conditions and will return and persist for the remainder of the weekend.

North to northwest winds of 5-10 knots will persist through the period with occasional gusts nearest the lakeshore on Sunday up to 20 knots.

Outlook...Non- VFR possible with isolated showers and thunderstorms on Wednesday.

MARINE

As a cold front moves south of the area today, north to northeast winds will gradually increase to 10-20 knots into Monday. This wind direction should result in waves building across the central basin to 2-4 feet. There may need to be a Small Craft Advisory, especially for Sunday afternoon, but given the overall weak flow and very marginal conditions opted to not issue one now. Calm conditions return Monday evening through Tuesday before a more robust low pressure system impacts the region on Wednesday. The increased gradient with this midweek system should increase southwest winds to 20-25 knots and will likely require additional marine headlines.

CLE WATCHES/WARNINGS/ADVISORIES

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