AM Zones Update: More Warmth Fri & Sat, Cooler Sunday, More Active Weather Next Week

Happy Thursday! An somewhat active or unsettled weather pattern through will continue overall over next couple weeks. There will be couple chances for isolated showers and thunderstorms, over next few days. But much warmer temperatures are still expected to end this week. No widespread rainfall is anticipated, until perhaps strong cold front and upper-level trough moves through early next week. We breakdown more forecast details below!

Today and Friday

Low cloud cover with areas of patchy fog and drizzle will continue for rest of this morning and perhaps into early this afternoon. Plenty of low-level moisture remains over the region, behind a decaying cut-off low just south of Cape Cod. But as the low continues to move away, more subsidence it’s wake will cause clouds to gradually break for some sunshine from southwest to northeast across the region as this afternoon goes on.

Overall with little more sunshine this afternoon, temperatures should rise in the upper 60s to lower 70s over Northeast NJ, NYC and nearby areas. Some parts of Western NJ and Southeast PA, may see temperatures rising into mid-upper 70s this afternoon with a little more clearing likely later this afternoon. But some areas along the coast and further northeast, including Long Island and Connecticut may see more clouds and southeast winds keep temperatures from rising out of the low to mid 60s.

3km NAM model forecast high temperatures today

3km NAM model forecast high temperatures for this afternoon.

More low clouds, patchy fog and drizzle may return tonight,  as low-level moisture becomes trapped underneath more inversion. Temperatures overnight will likely only fall into the 50s through the region. Some isolated showers or thunderstorms are possible, as weakening cold front passes through the region late tonight and Friday morning. But many areas will likely remain dry.

Then more sunshine and warmer weather is likely Friday afternoon, with drier westerly winds. High temperatures will be in upper 70s to lower 80s across most the region. Even coastal areas will be approaching and exceeding 70.

Saturday and Sunday

Overall more pleasant weather is in store for the weekend, as upper-level ridge builds over the region. Saturday continues to look like a very warm, summer-like day with partly sunny skies. West-southwest winds will help temperatures rise into the low to mid 80s, across the region. Some afternoon sea-breezes may keep coastal areas from rising out of the 70s. But just about every areas should be still be very warm and dry for most of the day.

Then a backdoor cold front will be sagging southward through the region during afternoon and evening hours. Latest trends show this front a little further south, with lower surface dewpoints with westerly winds, north of the front. But with more instability building south of this front, some isolated or widely-scattered  showers and thunderstorms could develop, over other parts of the region. Some strong shear, drier mid-levels and steep low-level lapse rates could support a few of these thunderstorms to become strong or severe with some gusty winds and hail. But lack of upper-level forcing and a stout mid-level cap with an EML (elevated mixed-layer) move through region will likely mitigate more organized or widespread convection.

GFS showing the instability axis juxtaposed with stronger shear further south over Mason-Dixon line.

GFS model late Saturday afternoon showing the instability axis juxtaposed with 40-50kts of bulk shear, ahead of backdoor cold front over the Northern Mid-Atlantic region

Much cooler weather will arrive later Saturday night and Sunday, as a maritime airmass moves into the region. But high pressure will build in, with more sunshine and dry conditions on Sunday. High temperatures will be in the lower to middle 60s across much of the region on Sunday. Onshore winds and could keep some coastal areas from rising out of the 50s. While areas further inland over New Jersey, could rise into upper 60s to near 70.

Monday and the rest of next week

The backdoor cold front will likely return north as warm front Sunday night or early Monday with more clouds and scattered showers possible. If the front lifts far enough north, temperatures could be very warm again, at least in the 70s with some clearing during the midday hours on Monday.

Then a large, closed deep area of low pressure will tracking across the Great Lakes on Monday. A strong cold front and upper-level trough from this system, will come through region sometime late Monday or early Tuesday.  There is still some uncertainty with timing. But model guidance suggests low instability and high shear environment with large scale forcing and a plume of sub-tropical moisture streaming northward. This will support more showers and thunderstorms with heavy rainfall this system.

GFS model showing plume of high precipitable water values with low SBCAPE (instability) and high shear

GFS model showing a plume of sub-tropical moisture with high precipitable water values, ahead of strong cold front with low SBCAPE (instability) and strong 500mb bulk shear by late Monday afternoon over Northeast and Mid-Atlantic regions

Behind this front,  a more fair and seasonable weather returns for the middle of next week. But model and ensemble guidance are another large, deep trough moving through the Great Lakes and Ohio Valley later in the week. More high-latitude blocking over Greenland/Davis Strait, may cause the trough to amplify and a large storm system to develop somewhere over the Eastern US late next week or next weekend. Stay tuned for zone forecast and other updates coming out later today.