Starting out with the temperature map this morning we see there’s a very large heat dome over a majority of the country, from the Desert SW to the East coast as a large heat ridge is setting up over this Mississippi River Valley and intensifying because of … well itself. A heat ridge is a an area of upper level high pressure system which causes the upper troposphere to be warm and that in turn causes sinking air, sinking air warms so that causes that warm air aloft to become VERY hot at the surface and the hotter it gets t the surface the hotter it becomes at the upper levels so it’s just one big feedback process , a heat ridge just continues to intensify because of just its own presence. While the center of the heat ridge is well west of us, the intensification of it means expanding heat and its expanding towards and into the forecast area
The whole reason this heat ridge developed in the first place is that there’s a very cold stratosphere over the Mississippi River Valley. This is the set up I exect through the end of June and all of July with variations in placement and intensity of this heat ridge, which will cause the heat in our area to be somewhat transient in our area so we will have breaks and the worst heat will set up west and out of us from the SE US to the upper Midwest then SW to the Dessert SW
Above I drew out the current set up and the set up we will se through next Tuesday.
Today will be the hottest day, with full sun after morning thunderstorms, and highs in the upper 80s to low 90s over NE PA and along the coast to mid to upper 90s with even 100 possible in the Philadelphia metro. Delaware on south and especially MD on south will easily exceed 100 today with general highs in the DC area between 103-107!!
Heat advisories in effect for NYC metro and excessive heat warnings for Philadelphia metro through Southern NJ. Lows tonight will only fall into the 70s for most besides NE PA where mid to upper 60s are expected
Saturday will be a little cooler, still very hot with highs in the upper 80s over NE PA to low to mid 90s for the rest, upper 90s possible for urban areas , especially in the Philadelphia area. Theres a chance of thunderstorms in the afternoon and night as we are on the edge of the heat ridge so we have disturbances coming from the NW , something called a MCS or mesoscale convective system (like what we saw this AM) looks to develop and move through the area Saturday night through Sunday morning, It’s basically a big cluster of thunderstorms, I expect the focus to be over southern NJ and Philadelphia but scattered storms still possible for the NYC area
Above is Sunday morning and the potential MCS I expect.
Sunday again will be hot but slightly cooler with highs in the mid 80s over NE PA to generally low to mid 90s for the rest of the area, Sunday will make it a official heat wave for many, except for the areas that did reach 90 yesterday (Thursday)
We will continue to have disturbance coming from NW TO SE on the edge of the ridge with a chance of isolated storms everyday, I expect the general path of these disturbances to keep the best chance of storms south of the forecast area bt we will have to now cast each of these disturbances
Monday through Wednesday will be uniform with hot conditions continuing but the brutal heat stays S & W with mid 80s NE PA to mid 90s for urban locations , chance of isolated storms every afternoon and night but nothing too widespread.
4TH OF JULY PREVIEW
As of now I expect the 4th of July to be overall nice and sunny with temperatures near to slightly above average in the low to mid 80s over NE PA and mid 80s to around 90 for the rest of the area with a chance of a storm in the afternoon and night
Going through the 4th of July we will remain in a similar pattern with continuation of hot weather and highs generally ranging from the low to mid 80s over NE PA to mid 80s to low 90s for the rest of the area along with some humidity to make it feel a little hotter than it really is. I will go more into day-to-day details by early next week for the holiday weekend.