5/8 AM Zones Update: Cool Weather Week, Potential Weekend Coastal Storm

Happy Monday! It’s been chilly with some sunshine has been this morning. But an large, anomalous cold upper-level low continues to linger over the northeast today. This will cause the atmosphere to become more unstable, with more daytime heating. So more clouds will likely increase again this afternoon, with some isolated or widely scattered showers around. These should be mostly on light side however, with very limited lift and moisture overall. Temperatures will be cooler than normal today with highs in mid-upper 50s to around 60 in most spots.

Any showers around will taper off during this evening. Then some clear to partly cloudy will likely remain overnight. Clouds may prevent more radiational cooling overnight. But temperatures with anomalous cold airmass, will get down into lower to middle 40s over urban and coastal areas. While some interior locations will get down at least into mid-upper 30s, where some pockets of patchy frost are possible.

High-latitude -NAO blocking retrograding from over Davis Strait will only allow the upper-level low to slowly lift of the Northeast this week. So temperatures are likely to remain below normal into at least Tuesday and Wednesday. Each day will start with some sunshine then more clouds arrive during the afternoon. Some isolated showers can’t be ruled out. But these showers will be shifting further north and east with after each day, as deeper, drier northwest flow develops over the region. High temperatures will be generally range upper 50s to lower 60s. Overnight lows will be in 30s over Interior and 40s near the coast.

Then the upper-level low will finally begin moving slow into the Northwest Atlantic late this week. A couple disturbance still rotating, around this low, could still produce some isolated-scattered showers around region. But rising mid-level heights and weak ridging will likely lead to moderation in temperatures with more sunshine mixing with clouds on Thursday and Friday. Perhaps only a few degrees below normal with highs in the mid-upper 60s.

Then attention will turn to a significant storm system likely develop along the East coast. This is the result on blocking retrograding and cause northern stream energy from the upper-level low split into Central Canada or the Great Lakes. Then this energy begins to phase with some pacific energy coming out Southwest US, as another ridge builds over the Rockies. This will lead to more an amplified trough and deepening area of low pressure near Mid-Atlantic coast.

This setup is what we often call an Archamault event, (name based on research from Heather Archamault) that occurs during weakening/retrograding -NAO blocking periods, during the winter. The pattern is so anomalous for spring this week, that tend to believe this storm with likely develop with some significant impacts, at least over much the Mid-Atlantic region. There is a little more skepticism with us however, in how far north storm will track. As the blocking with northern stream energy be little to strong over Southeast Canada or phase timing with the southern stream, may be too late to allow to this storm turn more northward along the coast.  Some various model run solutions and a sizeable spread on ensemble guidance, also leads to more caution on being more gun-ho now with more major impacts on the local region.

If this storm tracks more east-northeast off the Mid-Atlantic coast, this could keep more heavy rainfall and strong winds just south and east of NYC metro. But if this storm tracks further north and intensifies, this will turn into the Nor’easter for the region. Heavy rainfall could produce localized flooding in poor drainage and low-lying areas.. High wind gusts over 45 mph possible, depending any inversion to keep stronger winds aloft form mixing down. This storm will happen between the full moon and half moon phases, where astronomical tides are not typically not higher. But a persistent onshore flow out of the east or northeast could also lead to some minor to locally moderate coastal flooding, during high tides weekend.

We will continue to monitor this potential storm it throughout the week, with more zone forecast updates, and technical analysis through premium articles and videos if necessary.