At early afternoon, temperatures were nearing 90 degrees as dew points hold in the lower to mid-seventies. It is making for a very humid and uncomfortable afternoon. There is a weak upper-level low west of the area that will continue to close in on our area which may provide enough lift to produce some scattered thunderstorms. CAPE is impressive and the composite indicies are showing the potential for any thunderstorm to contain damaging winds and large hail. Any thunderstorms that do develop should diminish with time after the loss of daytime heating. Tonight will be sticky and areas that see rain may once again see some patchy fog develop.
Tuesday looks to be another day where we hit or exceed 90 degrees in the city with another round of scattered afternoon and evening thunderstorms, some of which may feature gusty winds and hail. On Wednesday, it may end up being hot and humid with highs in the urbanized corridor possibly approaching the mid-nineties…although a backdoor front has to be monitored carefully and could really take down temperature expectations in the city. There was some spread between the GFS and NAM MOS with the 12z Guidance and it is possible that there is a large difference in temperature from NE to SW with Philly falling somewhere in-between for Wednesday. Right now, I went with 93 in the city with the thinking that the backdoor front falls short of Philly.
On Thursday and Friday, a cold front moves closer to the region from the Great Lakes area bringing a better opportunity for more organized showers and thunderstorms. Meanwhile, the backdoor cold front may sink south on Thursday before rising back to the north. This leads to another tricky temperature forecast for Thursday.
The pattern is favorable for frontal boundaries to crawl through and the latest model guidance indicates that the cold front arriving from the Great Lakes region will in fact slow down substantially, so thunderstorm chances will likely linger into the weekend.
With the wet month of June continuing, the flash flood guidance remains on the low side. Any locally heavy rainfall during the week may lead to flash flooding especially if the same areas are impacted this week. The movement in the atmosphere may allow for storms to sit or move slowly too.
More on the end of the week rain chances will be posted later on the site.