... Seasonable temperature with increasingly humid conditions are expected to promote increased shower and thunderstorm activity for much of the work week.
NEAR TERM /THROUGH TUESDAY/... The forecast through this period remains quite tricky and uncertain. Convection is currently firing in the vicinity of the western Great Lakes - more or less in line with the expectation of convection- allowing models (CAMs). The general trend of the 12Z CAMs, as well as 18Z runs of the HRRR and NAM Nest, has been to push this convection across Michigan/the lower Great Lakes overnight, and then ESE following the established ridge/mid-level thicknesses, ahead of an advancing warm front. Timing of a line of showers and some scattered thunderstorms crossing the CWA generally between 12Z and 18Z has been consistent for a few runs as well. Elected to raise PoPs into the likely category during this period for most of the area, given this slightly increased confidence. Presumably, much, if not most of this activity would be elevated in nature, which is also supported by model soundings showing most CAPE aloft. This would reduce chances of severe weather during this period, and with the speed of the line, nothing more than brief, relatively fast-moving downpours would be associated with this morning activity.
Then, the hi-res models continue to show a relative dearth of activity between 18Z Tuesday and at least midnight in the warm sector of the surface low crossing southern Ontario into New York State, as low level stabilization and some mid-level capping prevent any redevelopment initially. Confidence continues to be low with this scenario, so will maintain the original chance PoPs already in place. However, if current trends continue, the afternoon and evening hours may end up being mostly dry.
No major changes were made to temperatures and dew points tonight and Tuesday. Both will increase notably behind the warm front, leading to a much stickier environment.
SHORT TERM /TUESDAY NIGHT/... Uncertainty continues through this period, as a cold front associated with the northeast low sinks into the heart of the CWA by 12Z Wednesday. The arrival of another shortwave trough in the continued northwest flow, plus the possible assistance of a low- level jet, could fire another round of convection overnight along the front. A severe weather threat, mainly in the form of wind gusts, could materialize if convection becomes surface-based. Also, the continued presence of 2 inch plus PWAT air, especially in the southwestern CWA, could lead to a heavy rainfall/isolated flash flood threat, especially in urbanized areas, despite the recent dry weather. However, some CAMs show this process occurring further to the west in what could be richer instability. With confidence still shaky in the overall scenario, elected to not raise PoPs at this time, but the situation will need to be monitored.
LONG TERM /WEDNESDAY THROUGH MONDAY/... The upper ridge over the Central Plains and the broad upper trough over the northeast U.S. will remain fairly parked through the work week, resulting in continued northwest flow over the Upper Ohio River Valley. Periodic shortwaves are expected to cross the region within the northwest flow through the week and promote shower and thunderstorm chances. Similar to Tuesday, the location for most likely storm development and the potential for storms to become severe will be predicated on evolution of prior day's convection and positioning of residual surface boundaries. Temperature will remain near seasonal averages during this period while enough moisture advection should maintain a humid airmass.
A more pronounced shortwave will likely cross the region Friday and deepen the upper trough over the area heading into the weekend. This should shunt precipitation south of the region as high pressure builds in from the north, returning dry and less humid conditions for the weekend.