textproduct: Cleveland

WHAT HAS CHANGED

Forecast remains largely unchanged this afternoon. Only slight adjustment was adding a fog potential over Lake Erie and the immediate lakeshore tonight, but this should quickly dissipate as showers and storms push east.

KEY MESSAGES

1) There is a Slight Risk (Level 2 of 5) across portions of the area as a strong cold front moves east on Saturday. Primary concern is damaging winds, although large hail and a tornado or two are all possible.

2) Colder airmass returns on Sunday and Monday, bringing near normal temperatures and an isolated chance of light snow showers late Sunday.

DISCUSSION

KEY MESSAGE 1... As a strong low pressure system moves east through the region, an associated warm front and cold front will accompany on Saturday. These two boundaries will quickly follow one another with the warm front pushing north Saturday morning, followed quickly by the cold front late Saturday morning through the afternoon/evening hours. Initial showers will approach the far western counties late tonight, slowly pushing east into Saturday morning. These showers/storms will primarily be along and ahead of the robust cold front. The severe threat increases further east in the CWA (closer to the I-71 corridor and east) as diurnal instability increases to 1000-1500 J/kg. This CAPE will be the final piece to the puzzle as strong frontogenetic forcing, a strong LLJ, ample moisture, and additional dynamic support for mid-level energy will all accompany this system. Strong winds are the primary hazard associated with these storms. Given the positioning of the shear to the boundary, cannot rule out some isolated convection, which may pose additional hail concerns. Finally, as the LLJ nudges north and increases the low level shear, cannot rule out a tornado or two across the area, especially in the most organized convection. To highlight this severe threat, SPC has issued a Day 2 Slight Risk (2 of 5) for I-71 and east and a Marginal Risk (1 of 5) elsewhere.

Even will such a robust set-up, the timing of the precipitation and increasing cloud coverage will play a vital role in enhancing or inhibiting severe potential later in the day. If showers move in much earlier than currently forecast, instability will likely remain marginal at best, leading to a more isolated severe event. On the contrary, if the showers slow their arrival, instability values will have more time to increase, likely resulting in more widespread severe storms. Will have to continue to monitor the severe threat over the Midwest today to get the best timing for the CWAs timing tomorrow.

KEY MESSAGE 2... Behind the robust cold front that pushes east on Saturday, a much cooler airmass will build in, ushering in below average temperatures for Sunday and Monday. A surface trough lingering over the area Sunday may allow for some scatter, light snow showers, but no accumulation is expected, especially given how warm it has been the last week. This warmth has allowed for the growing season to officially begin as vegetation comes to life. Unfortunately, with this push of cold, there is a possibility of a widespread frost and/or freeze to occur both Sunday and Monday nights. Temperatures are expected to fall into the low to mid 30s with light winds near the surface. Will continue to monitor trends in model guidance, but worth giving a heads up this far out. Temperatures will begin to rebound back towards average by Tuesday.

AVIATION /18Z Friday THROUGH Wednesday/

Conditions have improved to VFR this afternoon and are largely expected to remain VFR through the overnight hours. High level cloud cover will enter from the west overnight tonight. Patchy dense marine fog will be possible over Lake Erie again tonight. Some patchy fog may impact KERI and have included a line from 00Z/Sat to 03Z/Sat where IFR to LIFR impacts may occur.

There will be two main periods of showers and thunderstorms moving across terminals. The first will be showers with embedded thunderstorms along a warm front early tomorrow morning. For now, have impacts timed out in TEMPO groups for western terminals and PROB30 lines for central terminals based on level of confidence of impacts. The warm front will be followed by a cold front tomorrow afternoon and evening bringing another period of showers and thunderstorms to terminals. anticipate a higher coverage of thunderstorms along and ahead of the cold front. There remains the potential for strong to severe thunderstorms tomorrow afternoon and evening, particulary along and east of I-77. Most convection will occur after 18Z/Sat but have included a mention of TSRA in a PROB30 group at all TAF eastern TAF sites.

Light and variable winds this afternoon and evening will eventually become southerly at 8-12 knots tonight. Southerly winds will increase to 12-15 knots tomorrow morning with gusts to 20-25 knots. Peak southwesterly winds and gusts will occur tomorrow afternoon where gusts to 25-30 knots are possible. Locally higher wind gusts will be possible in any strong to severe thunderstorm that develops in the afternoon.

Outlook...Periods of rain with non-VFR should occur overnight Saturday night through Sunday evening. Rain may mix with or change to scattered wet snow at times Sunday morning and again Sunday evening.

MARINE

Light and variable winds expected across Lake Erie tonight which coupled with a moist airmass will give way to another period of marine dense fog this evening and overnight. Southerly winds will increase to 15-20 knots early Saturday morning ahead of a cold front. Given the offshore flow, highest wave heights will remain across the open waters. Behind the cold front, winds shift westerly while remaining between 15-20 knots. By Saturday evening winds turn northwesterly while remaining elevated which will allow for wave heights across the nearshore waters of the western basin to build to 3 to 4 feet Saturday night into Sunday morning. A Small Craft Advisory will likely be needed. Winds will oscillate between westerly to northwesterly while dissipating to 10-15 knots by Sunday night as high pressure builds overhead.

CLE WATCHES/WARNINGS/ADVISORIES

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