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WHAT HAS CHANGED

The Winter Weather Advisory has been upgraded to a Lake Effect Snow Warning for southern Erie County PA for snow accumulations between 6 and 10 inches with locally higher amounts possible where heavy snow bands persist. The lake effect setup for tonight through Thursday evening continues to trend slightly more favorable for snow in the region and additional headline changes may need to be considered today.

KEY MESSAGES

1) Rain will change to snow today, and a quick 1 to 2 inches of snow is expected during the late afternoon hours, which may cause hazardous travel conditions during the evening commute.

2) Lake effect snow will continue tonight through Thursday evening, bringing several inches of snow and more hazardous travel conditions in NE OH and NW PA.

3) Temperatures will rapidly fall below into the teens tonight into Thursday with near to below zero wind chills, posing a minor cold exposure risk.

4) A cold weather outbreak is expected for this weekend into next week with several systems bringing additional rounds of snow, single digit low temperatures, and wind chills below zero.

DISCUSSION

KEY MESSAGE 1... The local area will be between a system moving through the Ohio Valley and an approaching cold front to start the day. Therefore, with forcing surrounding but not over the area, it may take a while for some rain showers to spread into the region and have a slightly drier start to the forecast. The main cold front feature should reach the Toledo Metro area by Noon and spread east this afternoon, changing any rain over to snow with a more organized band of snow expected with the front. This band of snow should allow for a half inch to inch for most locations outside of the snow belt and there could be some low travel impacts just due to the evening commute timing. However, for the snow belt region of NE OH and NW PA, there will be the potential for both some lake enhancement and upslope with this snow band there could be a quick 1-2" of snow for the Cleveland metro up along I-90 into NW PA. This may allow for the evening commute to be a bit more messy for travel impacts. Some Special Weather Statements, or even a Snow Squall Warning, are likely for later today, especially if there can be an organized band with visibility drops, increased winds, and quick road impacts.

KEY MESSAGE 2... With the cold frontal passage today, temperatures will plummet with 850 mb temperatures of -16 to -19 C settling over Lake Erie, which is back to being mostly ice-free. While snow will start more synoptically-driven with the cold front, snow showers should sustain and transition to a more traditional lake enhanced snow event for NE OH and NW PA. The main question for the forecast will be - Where will the closed mid-level low track tonight into Thursday? Overall, the trend in many of the models is for this low to be stronger and more helpful in pulling some of the moisture from a low pressure system moving up the Appalachians back toward Lake Erie. That is worthy of about another inch of snow in NE OH/NW PA from the previous forecast. However, despite being 20-30 hours away from this low moving across Lake Erie, there is still some spread and this will be key to the location for the heaviest snow through Thursday evening. The closed low track on some guidance, including the RGEM and ECMWF, show a low further southwest over Cleveland/NE OH by 12z Thursday. This would offer more synoptic support for snow tonight and allow for snow totals to increase quite a bit. Whereas, other guidance, including the GFS and NAM, have this low tracking more from London, Ontario to Jamestown, NY tonight and suggesting more efficient snowfall east of the forecast area into NY and less QPF/snow over NE OH and NW PA tonight. In the end, opted to go in the middle of the two scenarios for QPF and snow, but will need to watch trends today. Additionally, the track of this low will also be key in the direction of the Lake Huron lake effect bands that will impact the area on Thursday with winds going from northwest to west-northwest. Overall, the consensus is that some portion of Erie County PA will be the main target but the spread may be Albion/Cranesville/Edinboro vs. Colt Station/Little Hope/Lowville/Wattsburg. Therefore, have totals in southern Erie County PA as 6 to 10 inches through 1 AM Friday with the potential for higher amounts where the snow bands end up setting up.

With all of this considered, have upgraded southern Erie County, PA to a Lake Effect Snow Warning from 11 AM today to 1 AM Friday. Have left all of the other Winter Weather Advisories alone with the timing but amounts are up an inch on average or so. If a more wet and snowy pattern emerges tonight, there is potential for more snow in NE OH and NW PA and advisories may need to be expanded and some advisories may need to be upgraded to Lake Effect Snow Warnings.

KEY MESSAGE 3... As mentioned above, the cold front moving through today will usher in colder air with 850 mb temperatures as low as -19 C into the region tonight. This will translate to surface low temperatures in the teens. With elevated northwest winds in the region of 15 to 25 mph and gusts to 35 mph, there will be a notable impact to wind chills. Wind chill values will fall to 5 to -5 F overnight and into the Thursday morning commute. This will pose a minor cold exposure risk to those outdoors.

KEY MESSAGE 4... As continually mentioned for several days now, there will be several systems starting this weekend that will allow for sustained cold air and chances for snow through the middle of next week. A series of upper level troughs with origins over the Arctic will dig into the Great Lakes region and allow for cold clipper systems to move through the area. Each clipper system will bring snow chances and flare up lake effect snow machine. However, each system will bring colder temperatures each time. High temperatures will fall into the teens or lower 20s starting on Sunday and low temperatures will be in the single digits as early as Saturday night. Synoptic winds will remain with 10 to 20 mph of flow and wind chills overnight will start near zero on Saturday night and trend to below zero for the morning commutes on Sunday through Wednesday. There continue to be signals that this colder air mass may trend colder and that could prompt Cold Weather Advisories some time next week.

AVIATION /12Z Wednesday THROUGH Sunday/

Big bag of MVFR/VFR ceilings will steadily diminish to low end MVFR and IFR into this afternoon as a low pressure system begins to spread precipitation across the area. Initial precipitation will fall as rain before a brief period of a rain/snow mix along the boundary transitions to all snow this afternoon. Periods of heavy snow are possible, especially along and east of I-71 where visibilities have the potential to drop below 1SM at times. Confidence was too low to place those visibilities in the TAFs at this point, but worth noting the potential of rapidly changing conditions through the afternoon. Late this evening, the front pushes east, leaving a surface trough across the area which will usher in lake effect snow. Terminals including KCLE, KYNG, and KERI will likely be the most impacted by these snow showers through the end of the period.

Winds this morning will quickly shift from westerly to northwesterly and increase to 12-15 knots behind the front across the western counties. East of I71, sustained winds will increase to 10-12 knots. Gusts across the area today will be in the 20-25 knots range. These winds will gradually weaken overnight tonight, although at least 20 knot gusts will remain possible.

Outlook...Non-VFR expected to continue on Thursday, most widespread east of the I-71 corridor in lake effect snow showers. Non-VFR likely in snow showers on Friday and Saturday. Non-VFR may linger across NE OH and NW PA on Sunday.

MARINE

Unsettled marine conditions are expected to persist into next week as multiple low pressure systems traverse the Great Lakes region. Given only very brief periods of weaker winds, the central and eastern Small Craft Advisories have been extended through Friday, although will likely need extended further. In the western basin, there is likely going to be a more notable lull in winds between systems so opted to issue a Small Craft this afternoon through Thursday and will reevaluate the need for extension with future forecast updates.

There is currently a brief lull in winds this morning from the southwest, but as a cold front pushes east late this morning into the afternoon, winds will back to become northwesterly and increase to 20-25 knots across the entire lake. Given onshore flow, expect waves of of 3-5 feet to with waves occasionally up to 10 feet across the central and eastern basins. There is a non-zero chance that a period of brief gales will occur across the central basin late tonight into Thursday, however confidence was not high enough to further upgrade any marine headlines.

A brief area of high pressure will nudge north on Thursday, allowing for winds to become southwesterly and once again increase to 2-25 knots ahead of another cold front Thursday night into Friday morning and persist through Friday night.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Winter Weather Advisory from 11 AM this morning to 7 PM EST Thursday for OHZ011>014-089. PA...Winter Weather Advisory from 11 AM this morning to 1 AM EST Friday for PAZ001-003. Lake Effect Snow Warning from 11 AM this morning to 1 AM EST Friday for PAZ002. MARINE...Small Craft Advisory from 1 PM this afternoon to 4 PM EST Thursday for LEZ142>144. Small Craft Advisory until 7 PM EST Friday for LEZ145>149.