... Upper level disturbances brings a chance of storms to portions of the area tonight and Tuesday. Cold front arrives Tuesday night, becoming stationary to provide shower/thunderstorm through the end of the week.
NEAR TERM /THROUGH TUESDAY/... As of 451 PM Monday...
Made some significant changes part of the Near Term forecast period. Reduced POPs significantly for the remainder of this afternoon and into the evening hours. A very dry atmospheric profile exists across all but the far western CWA this afternoon. Thus, any convection that tries to develop through sunset should be very isolated, and mainly across NE KY (and possibly far SW VA).
Focus for later tonight then turns to ongoing large bow echo currently moving east across Illinois. This complex is prog to move into Indiana over the next hour and begin to shift move southeasterly. During the evening, this complex should gradually weaken as it begins to encounter a drier and increasingly stable airmass. At this time, severe weather is not expected across our CWA tonight, and the majority of the expected remnant convection is likely to be confined to the far western CWA. As such, I have lowered inherited POPs for tonight and Tuesday morning across the board by about 20%. Will likely make further significant changes to POPs for tonight with the evening update...once better convective trends and 00z surface and upper air analysis takes place.
As of 215 PM Monday...
The surface high pressure, responsible for dry weather during the last couple of days, will weaken even further by Tuesday. This will allow for upper level disturbances to initiate convection from abundant low level moisture in the boundary layer. Models show differences in their solutions especially tonight. The RUC and NAM suggest a possible MCV dropping from the northwest overnight tonight. In other hand NMB and GFS/ECMWF models brings a dry quiet night. Decided to introduce some PoPs across the area to account for this possibility. Any precipitation activity should wane down before sunrise Tuesday morning, but showers and storms are expected during the afternoon and evening hours as additional upper shortwaves cross the area.
Temperatures will remain above average through the period.
SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 209 PM Monday...
Surface high pressure will build into the Great Lakes Tuesday night into Wednesday, bringing drier air across much of the northern Ohio Valley, particularly areas north of Interstate-70 where dewpoints mainly in the 50s to near 60 will exist. However, our area will remain too far south of this feature to benefit from this drier air as dewpoints are expected to be in the upper 60s to low 70s across the region. In addition, a stalled frontal boundary across our area will combine with shortwave energy aloft to produce a risk of scattered showers and storms Wednesday afternoon and evening. The frontal boundary will then remained stalled across the middle Ohio Valley into Thursday, with additional chances for scattered showers and storms continuing across the region.
With models showing PWAT values as high as 2 inches Wednesday and Thursday, locally heavy rainfall is possible with any of the convection that develops. While dry antecedent conditions will limit a threat for widespread flooding concerns, can't completely rule out localized high water issues as these storms will be very slow moving. Otherwise, weak shear and poor mid level lapse rates should generally keep severe weather threat on the lower side through mid week. In addition, high temperatures for Wednesday and Thursday will be in the upper 80s to low 90s across the lowlands and 70s for the higher elevations.
LONG TERM /FRIDAY THROUGH MONDAY/... As of 209 PM Monday...
The aforementioned frontal boundary will continue to linger in the vicinity of the middle Ohio Valley late week and to start the weekend. This feature will continue to support daily chances for showers and storms Friday and Saturday amid the warm and humid airmass and mid level impulses aloft. By Sunday an upper level trough is expected to drop into the Great Lakes region, which should help the frontal boundary finally lift out of the area.
By early next week, models show a strong upper ridge amplifying across the western US and broad troughing across the Great Lakes and Ohio Valley. This should result in slightly cooler air with temperatures slowly trending towards more normal values by the end of the long term period. This feature should also help maintain some chances of showers and storms across the region with conditions remaining unsettled at times through early next week.