textproduct: Cleveland

WHAT HAS CHANGED

8:54 PM Jan 24th: As snow, related to moist isentropic ascent aloft, continues to overspread our region generally from southwest to northeast, it is reaching the surface via the wet- bulb effect a bit faster than expected previously. Based on 00Z/Sun consensus of short- term model guidance and the 00Z/Sun run of the HRRR, increased POP's and increased QPF slightly through daybreak Sunday. As a result, our storm-total snowfall forecast has increased by about one inch CWA-wide. Please see our Winter Storm Warning text for additional details.

KEY MESSAGES

1) A major winter storm remains on track to impact the region late tonight through early Monday morning with widespread snowfall impacting travel.

2) Temperatures will drop below zero Monday and Tuesday morning behind the low pressure system with wind chill values near -10F on Monday and below -20F on Tuesday.

3) Prolonged cold with occasional light snow is expected through the end of next week creating elevated risks for cold exposure and damage to infrastructure.

DISCUSSION

KEY MESSAGE 1... A low pressure system has began to take shape across the southern CONUS that will deepen as it moves northeast into the Tennessee and Ohio Valleys through Monday morning. Precipitation can be seen upstream over central Illinois, and though there may be some light returns moving into Ohio this afternoon, the dewpoints are far too low for any snow to reach the ground. There's quite a bit of dry air located in the low levels that will slowly erode away this evening as better moisture advection moves north into the region ahead of the low. This will create overrunning moisture that will move atop of the very cold air mass already in place of the region and the column will saturate efficiently. The onset of precipitation has continued to trend slower over the past few model runs due the aforementioned abundance of low level dry air. Currently, not expecting snowfall to reach the ground in the western counties until just before midnight if not after. The further east in the CWA, the onset will be pushed until the early morning hours of Sunday around 2-3AM with northwestern Pennsylvania being the last hold out. Once snow begins, there's not much that will stop it until the low moves off the east coast early Monday morning.

As for snowfall amounts, as mentioned above, the QPF for the event have been increasing with the past few model runs showing stronger moisture advection once the system gets going. QPF for the time period from tonight through Monday night has increased to around 0.50-0.75" with the largest increase seen in an area from Mt. Vernon up through Youngstown. Relating this to snowfall totals, those have increased close to an inch across the board with the same area mentioned above seeing close to a foot of snow when it's all said in done. Snowfall totals will decrease further north and west in the CWA, though much of the region from Findley to Sandusky eastward, will be seeing 9-11" and 6-9" for areas west of that to include Toledo. Probabilistic snowfall totals of over 12" have been increasing the past couple of days as well, up to 70-85% across the southeast portion of the CWA and above 60% for areas starting east of Findley. For areas northwest of Findley, to include Toledo and Bowling Green, probabilities of 12" or more are much less, if not zero. Though, for receiving over 8" they range from 60% near Toledo up to 85% just northwest of Findley.

After the low departs to the northeast, there will be some minimal snowfall accumulations across northeastern Ohio and northwestern Pennsylvania due to cold air moving across Lake Erie and upsloping. Though drier air will move in quickly as a high pressure builds just south of the region and will cut off any remaining snow showers. Another factor for these lake enhanced snow showers is that Lake Erie may be completely frozen over at that point which will limit the lake effect. Though, there still could be some cracks in the ice due to shifting with the winds that will allow for snow showers to form.

KEY MESSAGE 2... High pressure will move in behind the departing low pressure system and temperatures will begin to drop starting late Sunday night. With the new snow pack across the region and the strong arctic high pressure and eventual clearing skies, temperatures will be able to drop down to dangerous levels. For Monday morning, the high will still be moving in so temperatures will still be in the single digits across the region with wind chill values ranging from -10F out west to just below zero out east. Tuesday will be colder with the high completely built in and and approaching low pressure system from the north creating a stronger pressure gradient and increasing winds. Low temperatures for Tuesday morning will drop down below zero for the entire region with some interior areas seeing -10F. With the winds gusting upwards of 20mph, wind chills will be down to -15F to -20F with areas from US Route 30 southward seeing wind chills near -25F. A cold weather headline will be needed from late Monday night through mid-morning Tuesday.

KEY MESSAGE 3... Prolonged cold weather is expected through the end of the week as arctic air will stay situated over the region. Little air mass modifications are expected as well during this time frame, with only a couple of troughs moving through during the week. Another arctic high pressure will build in just west of the Great Lakes later in the week with north to northwesterly flow across the area reinforcing the frigid temperatures. With fairly high confidence, temperatures across the region are not expected to get above 20 degrees during this forecast period. High temperatures will be around 10-15 degrees with lows near or below zero. Winds chills will be down near -10F to -15F most mornings. This extended cold stretch will cause elevated risk of cold exposure for people and potential damage to infrastructure.

AVIATION /06Z Sunday THROUGH Thursday/

At the surface, a low strengthens gradually while wobbling NE'ward from the northwestern Gulf to near the Upper OH Valley through 00Z/Mon. Between 00Z and 06Z/Mon, the first low should dissipate in vicinity of PA as a new low forms south of Long Island and then wobbles NE'ward to near Nantucket. These lows will extend a trough over our region through the TAF period. Our regional surface winds, around 5 to 15 knots in magnitude, will back gradually from E'erly to NW'erly through the TAF period. Periodic gusts up to about 20 knots are expected between ~12Z/Sun and ~03Z/Mon, especially west of the longitude of KCLE.

Ceilings continue to lower slowly to the MVFR range and generally from southwest to northeast through ~10Z/Sun. Widespread MVFR ceilings then persist through 06Z/Mon. Widespread snow associated with the aforementioned low pressure system continues to overspread our region generally from southwest to northeast through ~09Z/Sun. Visibility will range between MVFR and LIFR in snow. Periods of heavy snow are expected and periodic IFR ceilings are possible, especially between 12Z/Sun and 00Z/Mon. Snow should begin to exit from west to east after ~04Z/Mon. The back edge of the widespread snow should near the longitude of KMFD by 06Z/Mon.

Outlook...Widespread snow with non-VFR should exit the rest of our region generally from west to east during the predawn hours of Monday morning. During the rest of Monday through Thursday, additional periods of snow with non-VFR are possible, especially in NE OH and NW PA, where periodic lake-effect snow may occur downwind of mainly ice-covered Lake Erie.

MARINE

Lake Erie is mostly ice-covered and the ice will continue to expand and thicken through next week as several bouts of cold air impact the region. Stronger southwest winds on Tuesday may break up and shift the ice northeastward away from the southwestern shoreline of Lake Erie.

East-northeast winds of 10-15kt are expected tonight into Sunday, increasing to 15-20kt and shifting more northerly Sunday afternoon and evening. Winds remain 15-20kt through Monday while gradually backing to a more westerly direction. Winds shift southwest and increase to 20-30kt Monday night and Tuesday. Winds shift west-southwest Tuesday night into Wednesday and gradually subside to 10-15kt.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Winter Storm Warning until 7 AM EST Monday for OHZ003-006>008- 017. Winter Storm Warning until 10 AM EST Monday for OHZ009>014- 018>023-027>033-036>038-047-089. PA...Winter Storm Warning until 1 PM EST Monday for PAZ001>003. MARINE...None.