101 FXUS61 KCLE 300152 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 952 PM EDT Tue Oct 29 2019 .SYNOPSIS... The weather pattern features ridging over the eastern seaboard with elongated troughing from the northern Plains and Rockies. At the surface a cold front will stall across Ohio tonight and linger over the area into Thursday. Meanwhile a storm system over the Mississippi Valley will track northeast along this boundary bringing heavy rain Wednesday into Thursday followed by windy conditions Thursday Night. && .NEAR TERM /THROUGH WEDNESDAY NIGHT/... The frontal boundary previously discussed continues to slowly move into the area bringing widespread overcast conditions across northern Ohio. A chance of drizzle still exists for the next several hours. However due to limited moisture, most upstream stations have not reported any precipitation, so coverage remains patchy at best. Cooler temperatures associated with the cold air advection along the boundary will allow NW Ohio to drop into the lower 40s overnight, but central and eastern Ohio, along with NW Pennsylvania will remain in the upper 40s. Previous Discussion... A low pressure system over Georgian Bay is dragging a weak cold front extending into Indiana this afternoon. The front will slowly drift east and into Ohio this evening where it will stall. Moisture is limited with this feature, however could see some drizzle or pockets of light rain pop up along the front. Reports from upstream have shown lowering clouds but little to no rain development. Gradient weak behind the front and cold air advection will be held mainly north in Michigan with a little drop in thicknesses over NW Ohio where temps could fall into the lower 40s tonight. Attention turns to the Gulf states where the next storm system will originate. This low will move north through the Ohio Valley along the stalled frontal boundary. Overrunning moisture ahead of this system will spread over the area on Wednesday. Rain will initialize in the south, and by the afternoon increasing frontogenesis will help the rain shield expand to the northeast counties. Rain will increase in intensity overnight as precipitable waters are expected to climb near 1.5" due to a nice moisture feed from the gulf on a strong low level jet. Areas could see up to an inch of rain by daybreak Thursday. Temperatures will be influenced by the increased humidity with highs around 60 during the day and mid 50s overnight for areas along and east of the frontal boundary. The far western counties could remain on the cold side of the boundary and may hold temperatures in the 40s to low 50s. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... The main weather story will be the spooky storm system impacting the region on Halloween. Being about 48 hours out from the main system, we still have some uncertainty with exact track of the surface low and evolution of deepening as it moves through the Ohio River Valley region into southern Ontario by Thursday night and Friday morning. A strong upper level storm system will be moving out of the central Plains region up into the Great Lakes region on Thursday. A surface low is forecast to rapidly develop and strengthen from the Tennessee River Valley and move up to southern Ontario by Thursday night. Northern Ohio and northwest Pennsylvania will be in the warm sector of the storm system on Thursday afternoon with a crash in temperatures by Thursday night and Friday. There looks to be just enough instability of a few hundred Jules of CAPE for a slight chance of thunderstorms. But as of right now, strong or severe convection are not expected. There are some slight differences in timing amongst the 12z suite of model data with the NAM quicker to bring in the dry slot into the area by Thursday evening. With this forecast update, we will maintain widespread moderate to locally heavy rainfall and isolated thunderstorms most of the daytime Thursday. We will maintain highest rain chances during Thursday evening and night for the eastern Ohio into northwest Pennsylvania with a dry slot coming into the area sometime late evening or overnight. Winds will also be the be a problem with gusty winds increasing to 20 to 30 mph with gusts up to 40 mph during Thursday evening through Friday morning with a decrease by Friday afternoon as the low pressure system pulls away. Wrap around moisture and lower thickness values on the back side of the system will bring scattered rain showers possible mix with snow showers early Friday morning. No impacts or accumulations are expected with temperatures above freezing. Lingering lake effect rain/snow showers may continue into the afternoon downwind of the lake in the primary snowbelt areas. High pressure builds in and clears out the skies for the most part Friday night into early Saturday. Southerly winds briefly return on Saturday ahead of the next fast moving storm system through the Great Lakes Region. A sharp upper level trough will move across the region going into Saturday evening. Temperatures will be below average for the end of the week. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Another reinforcing shot of colder air will move across the region Saturday through the rest of the weekend with a sharp upper level trough. With 850 mb temperatures dropping to around -8C by Sunday morning and lake induced CAPE increases up to 250-500 J/KG. There is a very good signal for lake effect bands of showers and/or snow showers. This setup looks favorable for efficient rain bands coming off the lake for the snowbelt areas changing to wet snow. There could be even some claps of thunder if local instability is high enough. We will have to monitor Saturday night through Sunday morning closely. The lake effect rain and snow showers will decrease by Sunday afternoon or evening. The flow changes to a southerly flow by early next week. Temperatures remain below average into early next week. && .AVIATION /00Z Wednesday THROUGH Sunday/... A cold front is approaching the airspace from the northwest this evening and will stall over the area overnight. With the front, ceilings are lowering to MVFR, if not some patchy IFR. These ceilings will spread east overnight and all areas should be MVFR by morning. Moisture will increase along the stalled front on Wednesday and allow for showers to enter the region. Have timed in showers across the area based on the best forcing with the front and will also lower ceilings to IFR in the TAFs as increased low-level moisture should bring ceilings below 1000 ft. Winds will be light through the TAF period and slowly pivot from the south to the west to the northeast over the next 24 hours. .OUTLOOK...Non-VFR conditions and gusty winds possible Thursday and Friday with a low pressure system moving through the region. && .MARINE... A weak frontal boundary will move across the lake this evening and shift the winds from southwesterly to northerly this evening 5 to 10 knots. An area of low pressure developing down in the Ohio River Valley region will increase northeasterly winds on the lake 10 to 20 knots by midday Wednesday. There is about a 6 hour window Wednesday afternoon that Small Craft Advisory criteria could be met, mainly west of the Islands. A deepening low pressure system tracks north across the lake on Thursday evening into Ontario. Winds will increase initially from the southeast to southwest 20 to 30 knots as the low moves across the lake and deepens. As the low slowly pulls away late Thursday night into Friday. Winds will become westerly 25 to 35 knots with gusts up to 50 knots possible, especially over the open portions of the lake. Gale Watches will be issued from Thursday evening through Friday afternoon. Significant waves are as high as 14 feet on the east end of the lake. There is still some uncertainty on the strength of the low pressure system and thus the strength of the winds. However, confidence is high that this will be a potent and impactful system for the lake. We will have to monitor the potential for some lakeshore flooding along the Erie PA lakeshore areas. At the same time, we will also be monitoring the potential for low water conditions on the western basin of the lake as the water will be pushed from west to east across the lake with strong west to southwest winds. West to southwest winds remain elevated through at least the weekend. A Small Craft Advisory may be needed for an extended period of time over the weekend. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...Gale Watch from Thursday afternoon through Friday afternoon for LEZ142>145-162>165. Gale Watch from Thursday evening through Friday evening for LEZ146>149-166>169. && $$ SYNOPSIS...Jamison NEAR TERM...Campbell/Jamison/Sefcovic SHORT TERM...Griffin LONG TERM...Griffin AVIATION...Sefcovic MARINE...Griffin