AM All Zones Update: Cut-off Low with Heavy Rain Today, Warmer Late Week

A cut-off low that we have been discussing here since last week, will finally bring some heavy rainfall to much of the region, this afternoon and early evening. Afterward, some unsettled weather will continue over the couple of days, as the cut-off low weakens and slowly moves away from the region. Then more pleasant weather with much warmer than normal temperatures return for the end of the week and start of the weekend. But a backdoor cold front may spoil the warm up later in the weekend! Get more details on the weather over next several days in a breakdown below.

Today and Tonight

Mostly cloudy skies with some showers will continue to be around this morning. But rain will become steadier, and then heavy at times this afternoon and into early this evening, as an easterly 40-60kt low-level jet, associated with the cut-off low further south, moves through the local region. Instability still appears to be very low, but some rumbles of thunder can’t be complete ruled out. Then rain will begin taper off showers later this evening, as the low-level jet moves north the region. Temperatures will likely hold lower to middle 50s around the region, through today and tonight.

Precipitable water values well above normal, with sub-tropical plume moisture coming off the Atlantic later today. Thus, rainfall totals between 1” to 2” are likely is parts of the region. However some heavier rain bands may result in higher totals up to around 3” in some spots. While other spots may see more subsidence that may lead some lower rainfall totals. Regardless, some ponding on area roadways is possible. Some very localized flash flooding in poor drainage or low-lying areas is also possible. But not enough rainfall is expected, for more significant flooding along rivers and streams.

As the low-level jet passes overhead, easterly winds will be increasing between 15 to 25 mph with some gust 30-40 mph likely, over parts of region this afternoon and early this evening. Some isolated up to near 45 mph are possible right along the shore. But a stout inversion will keep be the strongest winds at 850mb-925mb (several thousand feet up), from reaching the surface. These onshore winds will also likely lead to some minor to locally moderate coastal flooding during high tides early this evening. Winds will diminish later this evening, as the low-level jet moves north of the region.

Wednesday through Friday

The cut-off low will begin decaying later tonight and Wednesday, moves near the region. Mostly cloudy skies are expected with low-level moisture trapped underneath inversion. Some areas of patchy fog are also possible. However, no significant rainfall is expected as mid-level dry air will be entrained into this storm system. So only some scattered showers are possible, as some voriticy rotates around the cut-off low. It will be little brighter and warmer than today with high temperatures in upper 50s to lower 60s.Wednesday night will be partly cloudy with some areas patchy fog still possible. Temperatures will drop back into the 50s overnight.

Then weather conditions will likely improve more on Thursday, as the cut-off low moves further northeast into the Gulf of Maine. Some cloud cover in the morning, should gradually break for more sunshine by the afternoon hours. This should temperatures rise into mid-upper 60s to lower 70s, especially over inland areas. Onshore winds from the southeast direction, may keep temperatures a little cooler in the lower to middle 60s. along the coast.

On Friday, more southwesterly winds, ahead an approaching weak cold front, will help temperatures may rise well mid-upper 70s to lower 80s Friday. Areas near the shore, will have more sea-breezes keep high temperatures cooler the mid-upper 60s to lower 70s. The cold front will be lacking more lift and moisture. But it could still produce some scattered showers and isolated thunderstorms, as it passing through Friday afternoon and evening.

This weekend through early next week

High pressure building in behind the cold front with west/southwest winds winds will send temperatures into lower to middle 80s on Saturday. Areas along the shore still be little cooler with sea-breezes during the afternoon. Then uncertainty increases for the rest of the weekend, as models are wavering back and forth on backdoor cold front coming through the region. If the front, stay farther north temperatures will. If the cold front moves further south, more scattered showers are possible with some cooler temperatures Saturday night and Sunday.

A stronger cold front and large upper-level trough from the Great Lakes, will move into the region during Monday and Tuesday of the next week. Large synoptic forcing, strong wind fields and plume of subtropical moisture feeding this this system, may support more heavy rainfall with showers and thunderstorms with this front. If a warmer, unstable airmass returns, there might also be threat for some strong to severe thunderstorms. But there is plenty of time to watch this and for changes. Behind this front, will be a cooler, drier airmass for the middle of next week. Stay tuned for more zone forecast updates through the week, improving weather later this week!