textproduct: Cleveland

WHAT HAS CHANGED

Our day shift issued A Frost Advisory and Freeze Warning, which is in effect from 11 PM this evening to 9 AM EDT Sunday for all of northern OH and NW PA. Based on latest trends in observations, including radar data, and NWP model guidance, periodic sprinkles and/or snow flurries are expected through about daybreak Sunday as a shortwave trough axis moves SE'ward across our region late this evening through about daybreak. This precip will primarily result from moist isentropic ascent aloft, ahead of the shortwave trough axis, releasing weak potential instability in and near the 850-700 mb layer. In addition, lake-effect sprinkles and/or snow flurries are possible through about daybreak Sunday in north-central OH and especially NE OH and NW PA as an unusually-cold mean low-level flow backs from NW'erly to W'erly over/downwind of ~11C Lake Erie, yet weak lake-induced CAPE wanes gradually via the following: low-level dry air advection on the synoptic-scale; a lowering subsidence inversion accompanying a ridge at the surface and aloft that will build behind the shortwave trough. However, the chance of measurable precipitation and measurable snowfall remains very low, so elected to maintain POP's of mainly less than 15% through daybreak Sunday.

KEY MESSAGES

1) Some improvements coming to the temperatures into Monday.

2) Strong frontal system midweek brings more rain to the area and temperatures back down into the 50s and likely not drying out until after Thursday.

DISCUSSION

KEY MESSAGE 1... Frost/Freeze expected tonight.

While the main upper trough bringing chilly and wet weather to the region the past couple of days exits, high pressure moving west to east south of the CWA will finally get east enough to bring a warm advective pattern. 850mb temperatures that have been below zero will creep above zero with low level warm air advection for Monday and Tuesday, and will see temperature improvements each day, accordingly. Some low end shower activity is possible Sunday night in some short lived isentropic lift mainly at 290K. An upper level wave brings shower/storm chances ahead of a strengthening frontal system late Monday into Tuesday. Could see temperatures in the 70s in places on Monday.

KEY MESSAGE 2... Ahead of the cold front, showers and storms to become more numerous. As the front moves into the southern Great Lakes, forward progress of the system will likely be slowed as waves of surface low pressure develop along the front. This will serve to lengthen the amount of time that the rain chances settle over the CWA as those waves of low pressure keep the front from pushing eastward. High POPs will linger with the front through Wednesday before finally exiting, only to be followed by a trailing upper trough axis Thursday as broad low pressure aloft reclaims the Great Lakes. Temperatures back below normal and into the 50s for the end of the week before finally showing slow improvement again into the weekend.

AVIATION /06Z Sunday THROUGH Thursday/

Clouds are clearing with high pressure located over the Ohio Valley. The high shifts south today which will allow winds to increase with gust of 22-28 knots developing after 15Z. Wind gusts will drop off towards 00Z for inland locations in the east like CAK/YNG while most other terminals maintain gusty winds tonight. If winds drop off in NW Ohio, may need to add some low level wind sheer as speeds increase to 45 knots near 2K feet.

Otherwise some cumulus cloud around 5-7K feet is expected this afternoon with coverage of VFR clouds increasing after 22Z. There is some potential for a few light rain showers tonight as a shortwave passes aloft but coverage is low with little to no impacts.

Outlook...Non-VFR possible in scattered showers and thunderstorms Monday afternoon/night followed by increasing coverage of precipitation Tuesday afternoon and night and again on Thursday.

MARINE

Some lingering 2 footers out there early this afternoon after a push of 10-15kt northerly winds this morning, but those are decreasing with tranquil marine conditions taking over. West- southwest winds increase modestly to 10-15kt overnight tonight, trending a bit stronger (15-20kt) on Sunday. Winds may exceed 20kt at times Sunday and especially Sunday night, building 3-5 foot waves in the open waters. South-southwest winds briefly slacken to 10-15kt during the day Monday, increasing to 15-25kt again Monday night into Tuesday ahead of an approaching cold front. Winds flip northerly behind the front late Tuesday into Tuesday night, diminishing into Wednesday. The impression is that Small Craft Advisories may be needed at times for stronger southwest winds late Sunday/Sunday night, and again Monday night and Tuesday through the frontal passage. Any advisories would be marginal and future shifts will evaluate the potential need.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Frost Advisory until 9 AM EDT this morning for OHZ003-006>009- 011-012-017-018-027-036-089. Freeze Warning until 9 AM EDT this morning for OHZ010-013-014- 019>023-028>033-037-038-047. PA...Frost Advisory until 9 AM EDT this morning for PAZ001. Freeze Warning until 9 AM EDT this morning for PAZ002-003. MARINE...None.