Area Forecast Discussion

WHAT HAS CHANGED

A Freeze Warning has been issued for the entire area for tonight into Monday morning. Some brief snow is expected late tonight in NE OH and NW PA; any accumulations will be negligible.

KEY MESSAGES

1) A colder than normal air mass is entering the region, allowing for temperatures 10 to 20 degrees below normal for the third week of April. Frost and freeze headlines are in effect and will be needed through Monday night with the cold air.

2) Scattered rain chances will continue this morning and tonight with some changeover to snow overnight. Little snow accumulation is expected in NE OH and NW PA.

3) The pattern will return to warmer weather starting on Tuesday. There will be a window for showers and storms to return on Tuesday night and Wednesday; the severe potential for storms is low.

DISCUSSION

KEY MESSAGE 1... A deep upper trough is entering the Great Lakes region and bringing a colder than normal air mass into the area. 850 mb temperatures will dip to around -11 C and that will translate to high temperatures remaining steady in the 40s today with low temperatures tonight falling into the 20s for most with lower 30s near Lake Erie. The Freeze Watch has been upgraded to a Freeze Warning. High pressure entering from the northwest for Monday will dry out weather but keep temperatures cool in the 40s. Low temperatures will again be in the 20s and 30s and another Freeze Warning will likely be needed.

KEY MESSAGE 2... With the upper trough moving through the region, this feature will provide lift for additional rounds of showers this morning and tonight. For this morning, a strong southwesterly jet will move through aloft and support rain showers through daybreak. For this afternoon and tonight the main upper trough axis will approach with a secondary surface cold front and allow for another round of showers to develop. Tonight, showers will transition to lake enhanced showers with -8 to -11C at 850 mb moving over an 8 to 10 C lake. Given the lake instability, the rain could be convective and come with graupel/small hail with the falling freezing levels. Eventually, precipitation will transition to some snow. Snow ratios should be low with snow favoring a more graupel-style vs. large dendrites. Surface and pavement temperature remain well above freezing and will need time to allow for accumulations, which is unlikely given the brief window for precipitation. Therefore, will have just little accumulation in the forecast with no impacts expected at this time. High pressure entering from the northwest for Monday will dry out the atmosphere and back winds through the day, ending the rain/snow threat.

KEY MESSAGE 3... A large ridge will enter the central US on Tuesday and expand east into the Great Lakes region. Temperatures will moderate once again into the 70s and eventually 80s later in the week, bringing back a late Spring feeling. A weak trough will overtop this ridge and allow a weak cold front into the region on Tuesday night into Wednesday. This front will bring the potential for scattered showers and storms. Both timing and dynamics with this system appear unfavorable for severe weather at this time.

AVIATION /18Z Sunday THROUGH Friday/

Scattered showers are developing ahead of a trough that will swing across Lake Erie this evening. The showers will be light this afternoon, but they will be very difficult to time, so added a broad period of VCSH. A more concentrated period of rain showers even mixing with snow is expected across north central and NE Ohio this evening as the trough crosses the area, so added prevailing SHRA for this at KMFD, KCLE, KCAK, KYNG, and KERI. The rain and snow will be more scattered farther west. Periods of MVFR will occur in the heaviest precip, and cannot rule out brief IFR. The steadiest rain and snow showers will exit in the 03-06Z timeframe, but scattered lake-effect snow showers will continue at KCLE, KMFD, KCAK, KYNG, and KERI through tonight before ending Monday morning. Mainly VFR is expected at these sites overnight, but brief drops could occur in any heavier bursts of snow.

WNW winds of 15-20 knots will occasionally gust to 30 knots this afternoon before turning NW behind the trough this evening and gradually diminishing. NW winds will decrease to 5-10 knots tonight and Monday morning.

Outlook...Non-VFR possible Tuesday night and Wednesday in rain showers.

MARINE

Small Craft Advisories are in effect for the entire near shore water today. Winds will be from the west 15 to 20 knots with gusts up to 30 knots and waves up to 4 feet. Winds will become northwesterly around 10 knots tonight and Monday. Southerly winds will return late Monday night 10 to 15 knots. Winds will increase from the south on Tuesday 15 to 20 knots. We get close to SCA headlines again on Tuesday with the offshore flow.

CLE WATCHES / WARNINGS / ADVISORIES

OH...Freeze Warning from 11 PM this evening to 11 AM EDT Monday for OHZ003-006>014-017>023-027>033-036>038-047-089. PA...Freeze Warning from 11 PM this evening to 11 AM EDT Monday for PAZ001>003. MARINE...Small Craft Advisory until 8 PM EDT this evening for LEZ142- 147>149. Small Craft Advisory until 11 PM EDT this evening for LEZ143>146.