textproduct: Cleveland

WHAT HAS CHANGED

A Freeze Warning remains in effect for most of our CWA from 8 PM this evening to 10 AM Tuesday morning, except for Lucas, Ottawa, Sandusky, Wood, and Hancock Counties.

KEY MESSAGES

1) One more unseasonably cold night tonight with below freezing temperatures, especially in NE Ohio and NW PA.

2) Much warmer air will arrive Tuesday and persist through early next week, but the pattern will turn active with numerous chances for rain starting this weekend.

DISCUSSION

KEY MESSAGE 1... Water vapor loops show an amplified mid/upper pattern that remains in place this afternoon characterized by a deep trough over the eastern CONUS, closed low offshore of the west coast, and broad ridge in between across the Intermountain West and Plains. The eastern trough continues to keep our region in a NW flow pattern, with temperatures running a solid 25 degrees below normal this afternoon. Despite the cold, a large area of surface high pressure sliding into the southern Great Lakes this afternoon has allowed most of the lake-effect clouds to dissipate, and this is supporting plenty of sunshine with afternoon cumulus.

The cold airmass in place and influence of the surface high will set up another cold night tonight. Much of NE Ohio and NW PA should end up colder than last night given the mostly clear skies and light winds, so expect widespread lows in the 25-30 F range in NE Ohio and NW PA, with some low 20s in interior NW PA. However, as the high drifts into the Appalachians tonight, low- level southerly return flow will quickly begin in NW Ohio. These S winds should increase to 5-15 knots by 09Z, and this combined with increasing high level cirrus ahead of a warm front should allow NW Ohio to be quite a bit milder. Lows will likely stay in the low/mid 30s in much of NW Ohio. Kept Lucas, Ottawa, Sandusky, Wood, and Hancock Counties out of the Freeze Warning, and it is possible that the rest of NW Ohio and parts of north central Ohio do not reach freezing either, but it will be close either way. Even if some of the NW and north central counties in the Freeze Warning do not reach freezing, they will still have patchy frost. Temperatures will quickly warm after sunrise Tuesday morning in the developing warm air advection pattern.

KEY MESSAGE 2... Much warmer, more pleasant temperatures remain on track to begin Tuesday as the surface high continues to drift into the Mid Atlantic states allowing for southerly return flow and resultant warm air advection. A warm front will lift across the region in the late morning and early afternoon. The main impact should only be some high and mid-level clouds given a significant amount of low-level dry air, but the latest HREF hints at some light showers or sprinkles possible in NW PA where isentropic ascent is maximized in the early afternoon. NBM slight chance POPS look reasonable for this. Otherwise, the better chance for rain will hold off until Tuesday night and early Wednesday morning as a cold front sags across the region in response to a mid/upper shortwave dropping through the continued longwave trough over the Northeast CONUS. Low-level moisture return will be very limited ahead of the front, so this will keep instability weak, but synoptic support from a modest 60-75 knot upper jet streak nosing into the central Great Lakes will generate an area of showers and a few rumbles of thunder that will slowly sink southeastward across the region Tuesday night into Wednesday morning. Most rainfall should only be 0.25 inch or less, with the greatest amounts likely in NW Ohio. Canadian high pressure at the surface building into the central Great Lakes behind the front will gradually dry out all areas Wednesday as the boundary slowly pushes south and washes out, with dry and mild conditions through Thursday. Daily lake breeze development will keep lakeshore areas cooler Wednesday and Thursday.

A more active but also lower confidence pattern will start to develop Friday and persist through early next week. The closed mid/upper low off the west coast will gradually move into the northern Plains by Friday and evolve into a broader and larger closed low while the old eastern CONUS mid/upper trough closes off into a closed low offshore of New England. This will pinch mid/upper ridging in between across the Ohio Valley Thursday and Friday. The ridge will gradually shift as the northern Plains closed low tries to come farther east, and that will slowly draw moisture into our region late Friday and Friday night ahead of a cold front. However, like all blocking patterns, timing of this front is uncertain, and it will likely remain near or just west of our region through next weekend keeping unsettled conditions in place. Deeper moisture may arrive by Monday as the block attempts to weaken and draw in a stronger SW flow from the Mississippi Valley, but evolution is very uncertain Friday through Monday. Chances for rain and occasional thunder are very broad Friday night through Monday, and timing will be fine tuned as we get closer since it certainly will not rain all the time.

AVIATION /18Z Monday THROUGH Saturday/

High pressure overhead will gradually move east through this evening. Remaining lake enhanced cloud cover will continue to fade over the next few hours giving way to widespread clear conditions. A warm front will lift across terminals bringing some high level cloud cover Tuesday morning and afternoon. Northerly to northwesterly winds have occasionally gusted to 15-20 knots this afternoon. Gusts will diminish this evening with light and variable winds returning tonight. Winds favor a southerly component by Tuesday morning with afternoon gusts 20-25 knots possible.

Outlook...Non-VFR possible Tuesday night and Wednesday in rain showers, some isolated thunderstorms are also possible. Non-VFR possible in scattered showers and thunderstorms Friday and Saturday.

MARINE

Mainly quiet conditions with light northwest flow continue across the lake under high pressure. The high will move east as a warm front lifts across the lake on Tuesday which will increase offshore southerly to southwesterly winds to 12-18 knots Tuesday afternoon. A cold front will cross south overnight Tuesday into Wednesday morning bringing a brief period of onshore northwesterly flow. High pressure re-enters behind the cold front bringing a window of light easterly flow. A system will enter the region towards the end of the week bringing increased southerly flow on Friday. Low pressure is expected to move across the lake on Saturday. No marine headlines are expected at this time.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Freeze Warning from 8 PM this evening to 10 AM EDT Tuesday for OHZ009>014-018>023-027>033-036>038-047-089. PA...Freeze Warning from 8 PM this evening to 10 AM EDT Tuesday for PAZ001>003. MARINE...None.