... A deep upper level low will continue to circulate in the Northeast through today before moving further offshore tonight. Low pressure system approaches the area next week.
NEAR TERM /THROUGH TONIGHT/... 1030 AM Update: Smoke thickness continues to decrease across most of the area with dramatic improvements compared to 24 hours ago. Mid-level clouds will continue to roll in late this morning as a disturbance associated with the upper level low will move through the area during the day today. Latest CAMs suggest showers and a few isolated thunderstorms early this afternoon, mainly east of the Blue Ridge. No significant impacts are expected with these thunderstorms. Highs will continue to climb into the low 70s for most with 60s for the higher elevations.
Previous Discussion Follows:
Heavy smoke exited the area yesterday evening as seen on last GeoColor images of the day and on the most recent NESDIS Fire and Smoke analysis. Visibility has also improved with no sites reporting any visibility restrictions less than 7SM due to haze or smoke. Another area of medium density smoke was analyzed yesterday evening by NESDIS extending from LK Superior southeastward through Chicago and into northern IN and OH. In that region, I've not seen any vsby restrictions in the past several hours. Will keep the haze in the forecast only during this morning as the nocturnal inversion strengthens, but have removed it for the rest of the day as deep mixing and NW flow should mix out any remaining haze/smoke. Light haze may make into the area this evening from the plume over the Midwest, but it isn't likely to cause any vsby restrictions.
Main concern today is the risk of showers and thunderstorms as one last shortwave-trough pivots through the area around the base of the upper low over northern New England. This s/w trough is expected to track early on the diurnal heating cycle keeping most storms below severe limits. Drying will take place quickly this evening with a nice comfortable evening.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... Shortwave-ridging will build over the region tonight through Sunday with a warming trend expected. Dry weather is expected Saturday with a small chance of t-storms Sun afternoon as heat and humidity return. Better chance for showers Sunday night as heights begin to fall in advance of next upper low diving across the western Great Lks.
LONG TERM /MONDAY THROUGH THURSDAY/... Model guidance is in very good agreement that a sprawling cutoff upper low will become situated over the Great Lakes on Monday. In response, an area of low pressure is expected to form at the surface in the Ohio Valley, and then lift northeastward into western NY, and then eventually into Ontario/Quebec. As this occurs, a plume of deep layer moisture will be drawn northward to the east of the cutoff upper low. Warm/moist advection and large scale ascent downstream of the upper low will lead to widespread precipitation across the area on Monday, in the form of showers and thunderstorms. Currently it appears as though this rainfall will be beneficial in nature considering the abnormally dry or drought conditions in place across the forecast area. The vast majority of both deterministic and ensemble solutions show less than an inch of rain, with just a few outliers amongst the ensemble members producing in excess of an inch. Shear should be sufficient for organized storms at around 30- 35 knots, but instability will be marginal at around 500-1000 J/kg, and model soundings show deep saturation through much of the troposphere. As a result, a few stronger storms can't be ruled out, but it doesn't appear to be a classic setup for severe thunderstorms.
As we progress through the remainder of the work week, models favor a slow eastward progression of the aforementioned upper low across the eastern Great Lakes, Upstate NY, and New England. At the surface, much of the low-level moisture will be cleared out by a cold frontal passage Monday night. However, a few showers can't be ruled out each afternoon as the upper low lingers to our north. Ensemble guidance shows a fair amount of spread with respect to temperatures from Tuesday through Thursday. This is likely due to some spread in the north/south positioning of the upper low. Using the ensemble means for temperatures would yield near to slightly below normal temperatures.