textproduct: Cleveland

WHAT HAS CHANGED

A late season lake-effect snow event is still expected tonight over the snowbelt of NE Ohio and NW PA. Snow amounts remain consistent, with a coating to up to 0.5 inches across much of the primary and secondary snowbelts, but 1-2 inches are likely across the highest elevations of northern Geauga County, and 2-3 inches are likely in southern and eastern Erie County, PA.

KEY MESSAGES

1) Unseasonably cold through Tuesday night, with lake-effect snow showers tonight through Tuesday morning. This will lead to light accumulations in the snowbelts of NE Ohio and NW PA, with the greatest amounts in the highest elevations inland from the lakeshore. This could cause localized slippery roads.

2) Dry conditions and warming temperatures midweek, with chances for showers and thunderstorms returning Friday.

3) Periodic chances for showers and thunderstorms late in the weekend through early next week as temps warm well above normal.

DISCUSSION

KEY MESSAGE 1... The weather pattern over the next day and a half will be more typical of mid winter, characterized by a broad mid/upper trough across the central and eastern CONUS downstream of broad western CONUS mid/upper ridging. This will bring a late season surge of arctic air across the Great Lakes region, and given the broad, cyclonic NW flow pattern, this spells the typical lake-effect snow showers.

Diurnally driven rain showers are ongoing this afternoon as a result of the strong April sunshine that has steepened the low- level lapse rates beneath the cold pool aloft. This activity will not be very impactful through early evening, with just occasional light rain mixed with some graupel at times. The attention this evening will turn to a potent mid-level shortwave and associated surface low that is expected to cross the central Great Lakes before passing over Lake Ontario late tonight. This feature can be seen on water vapor loops over northern Lower Michigan this afternoon. As the associated surface trough approaches Lake Erie this evening, the combination of increasing synoptic moisture, low-level convergence, and deepening cold air will allow lake enhanced rain and snow showers to blossom in coverage. Most HREF members, the RAP, and RGEM have widespread rain/snow moving into far NE Ohio and NW PA after 23Z where the combination of synoptic moisture and forcing will be best, and this will transition to pure snow after sunset due to both wet bulbing and the cold air deepening. This should lead to a quick coating to few tenths of an inch of snow in the highest terrain of southern and eastern Erie County, PA.

Behind the trough overnight, well aligned NW boundary layer flow and 850 mb temps dropping to -13 to -15 C will set up a multi- banded lake-effect snow/upslope regime. Boosted POPS overnight across both the primary and secondary snowbelts given pattern recognition and the fact that lake induced instability will be moderate to strong (several hundred joules) now that lake temps have warmed to an average of over 7 C. The one thing that will help to keep accumulations in-check is that the widow of greatest boundary layer moisture only goes through about 09Z before drier air starts to work in thanks to Canadian high pressure building down from the Upper Midwest. With this all being said, most of the primary and secondary snowbelts inland from the lakeshore should see a coating to as much as 0.5 inches, with up to 2 inches over the Chardon/Hambden/Thompson areas of northern Geauga County. A favorable fetch off Lake Huron when combined with the snow from the shortwave this evening should boost totals in southern and eastern Erie County, PA, so kept some 2-3 inch amounts there.

Snow showers will quickly end by 15Z Tuesday morning as the high builds overhead, and this should lead to plenty of sunshine for the afternoon. However, the impressive airmass will keep temperatures 20-25 degrees below normal. Expect highs only to reach the mid 30s in most areas, with low 40s in far NW Ohio. Lows Tuesday night will be very cold under strong radiational cooling, with widespread low to mid 20s. Some teens are likely in sheltered valley areas of eastern Ohio and interior NW PA

KEY MESSAGE 2... After the cold snap, a welcomed warming trend will take place Wednesday through Thursday as the surface high departs across New England and mid/upper heights rise ahead of another shortwave trough tracking from the northern Plains into northern Ontario. This shortwave and attendant surface low will slowly push a cold front into the region from the NW Thursday night and Friday, bringing the next chance for showers and thunderstorms. We may need to watch for pockets of heavy rainfall with repeated rounds of convection as this front looks to become quasi-stationary near the region through Friday in response to another possible wave tracking along the boundary.

KEY MESSAGE 3... Another Canadian high will push the front south to the Ohio River Valley Saturday allowing for dry and cooler conditions, but the front will quickly return north as a warm front Sunday in response to a series of shortwaves ejecting out of a trough/closed low moving into the western CONUS. This will set up a very warm and potentially active pattern through early next week depending on where the front eventually stalls out. Confidence is high that temperatures will warm to much above normal levels through early next week, but confidence on the timing and placement of convection is low given the uncertainty on the placement of the boundary.

AVIATION /18Z Monday THROUGH Saturday/

Predominately VFR conditions are expected through this period with the exception of periodic MVFR ceilings associated with lower lake enhanced clouds downstream of Lake Erie. At these terminals, ceilings gradually range from 2-3kft. As a secondary cold front pushes south across the area this evening, colder temperatures will result in the potential for lake enhanced rain/snow showers, primarily impacting KERI. There may be other impacts to KCLE and KYNG, although confidence is lower there. Visibilities within snow showers may drop to 4SM at times, but overall impact should remain minimal. By 15Z Tuesday, high pressure should limit moisture available for snow showers and conditions across all terminals should improve to VFR.

West-northwest of 10-15 knots will persist through this afternoon with gusts up to 20-25 knots. The strongest winds are expected near the lakeshore and across western terminals. These winds will quickly weaken on Tuesday as high pressure pushes in and allows winds to gain a more northerly component at 5-10 knots.

Outlook...Non-VFR likely Monday night into Tuesday morning in rain and/or snow showers, particularly across the snowbelt. Non-VFR may return in scattered rain showers Thursday night into Friday.

MARINE

As a secondary cold front pushes south across Lake Erie today, west-northwest winds will increase to 15-25 knots allowing waves to build to 4-6 feet. These winds will persist into mid Tuesday morning. A Small Craft Advisory is in effect for the Islands to the east into Tuesday morning. On Tuesday, high pressure will become dominant across the region, allowing for northerly winds to weaken to 55-12 knots, gradually veering throughout the day to become southeasterly by Wednesday morning. On Thursday, a warm front will shift north of the area, shifting winds to south-southwesterly and once again increasing them to 15-20 knots. Will have to monitor conditions Thursday for any need for a small craft, but given off shore flow, it should be really marginal. The associated cold front will push east on Friday, shifting winds to northwesterly at 5-10 knots which will persist into Saturday.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...Small Craft Advisory from 10 PM this evening to 10 AM EDT Tuesday for LEZ144>149.