textproduct: Cleveland

WHAT HAS CHANGED

Increased fog potential in north central and NE Ohio and NW PA early this morning, especially inland from Lake Erie.

KEY MESSAGES

1) Mainly dry conditions with slowly warming temperatures expected through Thursday.

2) Widespread showers expected Thursday night into Friday with the passage of a cold front.

3) High pressure brings brief drying Saturday and much cooler temperatures before another cold front brings additional showers Sunday into Monday and even cooler temperatures.

DISCUSSION

KEY MESSAGE 1... The picture perfect stretch of Fall weather will continue for a few more days, but a changing mid/upper air pattern will result in warming temperatures. The persistent surface high over the Great Lakes will drift into the Mid Atlantic today as the big East Coast low finally weakens and ejects toward Nova Scotia. This will allow the mid/upper ridge over the center of the country to build east across the Ohio Valley and eastern Great Lakes today through Thursday, eventually resulting in a strong eastern CONUS mid/upper ridge and strong surface high over the Carolinas and western Atlantic by Thursday. At the same time, a closed mid/upper low over the Desert Southwest today will slowly lift into the central Plains by Thursday and begin to phase with a deepening northern stream mid/upper trough over the northern Rockies and northern Plains.

This set up will result in deepening southerly flow and resultant warm air advection. Highs will warm into the low/mid 70s areawide today, then mid/upper 70s Wednesday. Upper 70s/low 80s are expected by Thursday, and it will be noticeably more humid, with dew points in the low/mid 60s.

Much of this time period through Thursday should stay dry with just increasing clouds Wednesday and Thursday, but increasing moisture advection and isentropic ascent ahead of a cold front slowly sinking south through the central Great Lakes in response to the digging trough could lead to some rain showers in the far northern counties Wednesday night. The NAMNest and RRFS bring some showers across the area Wednesday night into Thursday morning, while other CAMS, the NAM12, ECMWF, and GFS remain mainly dry. At this time, stuck with dry NBM POPS Wednesday night into Thursday morning, but may need to eventually introduce some showers if the trend continues.

KEY MESSAGE 2... The aforementioned cold front will begin to sag south through the region Thursday night and Friday. The front will be very slow to progress through due to the aforementioned closed low phasing with the digging northern stream trough, resulting in a weak surface wave on the front Thursday night and Friday. This surface wave will have synoptic support from the right entrance region of a 100-120+ knot H3 jet streak over Lower Michigan, so expect enhanced moisture advection and isentropic ascent along the front to drive a band of widespread showers. Isolated thunder cannot be ruled out, but given the time of year and very little instability projected, this will mainly be a stratiform rain event. Early QPF estimates give 0.25 to 0.75 inches across the region, so no flooding is expected. The greatest probabilities to exceed 1 inch appear to be in NW Ohio and near the lakeshore areas. The clouds and precip will hold temperatures down Friday, so expect highs in the upper 60s/low 70s.

KEY MESSAGE 3... Canadian high pressure building down across the Great Lakes in the wake of the cold front will allow the area to dry out Friday night and Saturday, but it will be much cooler as the longwave mid/upper trough carves out across the northern Plains, Great Lakes, and Northeast. Highs Saturday will only reach the mid 60s. A strong, reinforcing shortwave trough dropping through the broader longwave trough Sunday will further deepen the broad trough and push another cold front through the region. Showers are expected with the frontal passage, but the shortwave and deepening trough may lead to cyclogenesis over the Appalachians/Mid Atlantic that would have a larger shield of rain. Confidence is low 5 days out, so NBM POPS look reasonable Sunday, with the highest chances in eastern Ohio and western PA. Nevertheless, it will dry out Sunday night and Monday, but some of the coolest temperatures of the season so far are expected as an impressive 1035 mb surface high drops into the Upper Midwest. Highs Monday will only be in the upper 50s/low 60s. This could set up frost potential early next week.

AVIATION /06Z Tuesday THROUGH Saturday/

A few clouds around 5kft linger across southern and eastern fringes of the forecast area, but otherwise clear skies are observed. Patchy BR/FG is possible through just after sunrise this morning, with the most likely place for fog development at KYNG. VFR is otherwise expected as mostly clear skies persist alongside light and variable winds through the rest of the TAF period.

Outlook...Non-VFR possible with rain showers Thursday night through the weekend.

MARINE

High pressure slowly drifting toward the Mid Atlantic today will bring one more day of light winds on Lake Erie before SSW winds increase to 10-15 knots late tonight into Wednesday in response to the gradient tightening between the high setting up along the East Coast and a cold front slowly sinking into the Great Lakes from the Northwest. After a brief lull Wednesday afternoon and evening, SSW winds will increase again to 10-20 knots Wednesday night and Thursday while turning more SW. The cold front will slowly sink across the lake Thursday night turning winds to the N, and expect N winds to increase to 15-20 knots Friday, then turn NE and further increase to 15-25 knots Friday night into Saturday. This will build at least 2-4 foot waves Friday night and Saturday in the central basin, and winds and waves will likely trend higher, so expect that Small Craft Advisories will be needed.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...None.