textproduct: Cleveland

WHAT HAS CHANGED

No major changes. The timing of rain chances on Saturday is beginning to come into better focus.

KEY MESSAGES

1) Dry and milder conditions today and tonight.

2) Shower and thunderstorm chances with increasing temperatures and humidity this weekend as a warm front lifts through.

3) Summer-like warmth expected for Monday and Tuesday. Shower and storm chances increase for Tuesday and Wednesday as a cold front crosses, with a cooling trend behind the front.

DISCUSSION

KEY MESSAGE #1:

After a chilly (and in a few spots frosty) start to our Friday, high pressure exiting to the east will allow south-southwest winds to take hold. This will begin a significant warm-up process, with highs generally expected to range from the mid 60s to near 70 today. A weak lake breeze may impact the lakeshore northeast of Cleveland this afternoon. It will be dry today beneath passing higher-level clouds. Tonight will be dry until rain-chances spread into the I-75 corridor towards dawn Saturday. Lows will range from the mid 40s to mid 50s, coolest across interior eastern OH and PA.

KEY MESSAGE #2:

A warm front will lift across most of the area on Saturday, stalling near Lake Erie Saturday night into Sunday, before clearing well to the north to end the weekend and start next week. Weak shortwaves or vort maxes (likely aided by upstream convection) are generally agreed upon to move east across the region Saturday morning/early afternoon and again late Saturday into Saturday night. Mid to upper-level heights will be gradually rising on Sunday as ridging builds in, though some models suggest one more (weakening) shortwave may lift out of the Ohio Valley and across the area during the day Sunday.

There is decent agreement in an initial batch of elevated, gradually weakening convection moving east across the area Saturday morning and early afternoon. This convection will occur just ahead of the surface warm front, aided by lift from the first shortwave and elevated instability. Not expecting severe weather with this initial round, with the greatest potential for thunder across Northwest and Central/North Central Ohio Saturday morning in closer proximity to deeper instability. With that said, there's decent potential for lighter/decaying showers to work east across the rest of the area Saturday morning/early afternoon.

We should see a brief lull behind the initial round on Saturday, though a combination of the front across the area, boundaries left by the first round of showers/thunder, daytime heating, and another weak shortwave quickly approaching likely allows showers and storms to re-develop Saturday afternoon. How widespread and organized this next round is will depend on how quickly the first round exits and allows destabilization...guidance produces varying solutions, though confidence in destabilization and a later round of surface-based convection is higher farther south. Uncertainty increases farther north, though ultimately the whole area has at least a chance for showers/thunder mentioned later Saturday afternoon/evening. Moderate flow aloft may allow for organized convection with severe potential Saturday afternoon/evening if we see sufficient destabilization, especially across the southern half of the area. Confidence is low pending the earlier activity, and the SPC currently does not have any of our area "outlooked" for a severe risk in the Day 2 outlook...though that will be worth watching. Activity will generally diminish Saturday night, though with the lingering nearby front and a modest low-level jet we may not completely dry out. For those reasons some lower POPs linger through Saturday night.

Sunday will be the drier of the two weekend days in all likelihood. However, most of the area has a low (generally 20-30%) chance for showers and thunder mentioned, due to the nearby front and potential for one most subtle shortwave to move through during the afternoon.

Highs on Saturday are expected to range from the mid 70s to lower 80s as dew points warm into the 60s from the west. Leaned a bit cooler than blended guidance (NBM) for highs on Saturday given obvious cloud/convective potential. A moderate southwesterly low- level jet could contribute to gusty winds (30 MPH or so) on Saturday, especially if we end up a bit drier and warmer. Highs push into the 80s for much of the area on Sunday, with parts of PA perhaps lagging in the upper 70s still. By Sunday night lows will stay in the 60s.

KEY MESSAGE #3:

The main story to start next week will be summer-like warmth, with temperatures expected to surge roughly 15 degrees above average to near daily records for Monday and possibly Tuesday. 850mb temperatures rising to 17-19C generally support high temperatures ranging from the mid 80s to near 90 across the area. Monday should be the warmer of the two days given higher confidence in dry weather with plenty of sunshine, and appears to be the greatest chance for a few normally warmer locations to try touching 90. Tuesday will still be quite warm (mid-upper 80s) but may end up just a bit cooler as clouds and shower/storm chances increase from the west ahead of the approaching cold front. Dew points generally in the low-mid 60s on Monday and mid 60s to near 70 on Tuesday will add a bit of a heat index on top of the expected air temperatures. While temperature and heat index values should end up well-shy of headline criteria, the expected temperatures are especially noteworthy this early in the season, highlighted by the NWS Heat Risk product highlighting the entire area in "moderate" to nearly "major" risk for heat related impacts. This tool has locally shown utility in highlighting days with increased impacts (ER/hospital visits) due to heat, and those with outdoor plans or sensitivity to the heat will want to ensure heat precautions are in place for Monday and Tuesday. As a note, the NBM continues to run too warm on high temperatures both Monday and Tuesday due to known issues with bias correction during early-season heat events, and the official forecast continues to undercut it.

Troughing is expected to push into the Great Lakes late Tuesday into Wednesday, flattening ridging over the eastern U.S. and pushing a cold front across the local area late Tuesday night or Wednesday. Monday should be dry, though with some potential for storms that develop to our west to drift into Northwest OH Monday evening. Shower and storm potential ramps up more significantly Tuesday afternoon and evening as the front approaches from the west. Shower and storm chances continue into Wednesday until the front clears to the southeast. The exact timing of the front still has some uncertainty as is typical in this range, and will influence the timing and magnitude of shower and storm chances. There could be potential for severe weather on Tuesday, though overall this will be a more weakly- forced frontal passage with weaker to moderate shear, which should limit the potential for more organized severe weather potential.

Cooler and drier weather build for the second half of the week as high pressure presses into the Great Lakes and Northeast. Forecast temperatures for Wednesday and Thursday will likely need to trend a few or several degrees cooler than the current forecast as we get closer if the airmass is as cool as currently modeled.

AVIATION /18Z Friday THROUGH Wednesday/

VFR under high pressure with mid/upper level clouds and winds potentially gusting to 20kts at TOL/FDY through 03Z tonight. A warm front moving through tonight brings convective chances after 11Z Saturday, and then again sporadically through the day Saturday. Winds will become gusty for all terminals out of the southwest at 20-25kts, and may need to add TSRA to some of the sites for the 00Z issuance later today. MVFR ceilings possible FL020-030 in shower/storms Saturday, but keep visibility restrictions limited for now.

Outlook...Non-VFR possible in scattered showers and thunderstorms Sunday afternoon and evening, though chances are lower. Non-VFR to return on Tuesday in showers and thunderstorms.

MARINE

Winds become south 10-20kts tonight into Saturday with a warm front moving across the lake, then southwesterly 10-20kts through late Saturday. Wave heights less than 2ft nearshore, but 2-4ft in the open water zones. A stationary front over Lake Erie Sunday brings variable winds less than 10kts and waves continued less than 2ft, and then back to offshore early next week 15-20kts Monday and Tuesday, where wave heights once again will increase with distance from shore.

CLE WATCHES/WARNINGS/ADVISORIES

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