3/30 All Zones AM Update: Significant Storm with Heavy Rainfall Likely on Friday

Happy Thursday! High pressure will support another beautiful day for the region with more sunshine and dry condtions. Some high clouds will arrive by the afternoon hours, ahead of the next storm system approaching from the west. High temperatures today will be a little cooler than on Wednesday– in the lower to middle 50s. But with the center of high pressure near the region, winds will be much calmer this afternoon.

Then clouds will increase and thicken tonight, as the next storm system approaches and high pressure moves offshore. Increasing isentropic lift and from mid-level warm-air advection, well ahead could some areas of precipitation to breakout over the region later tonight and tomorrow morning. Much of this precipitation will be on the lighter side and most areas will be warm enough for rain with increasing east-southeast winds. But some pockets of sleet or freezing rain are possible over Lower Hudson Valley and Connecticut north of I-84. Temperatures tonight will drop into the middle-upper 30s to lower 40s over the region. Except in the lower 30s in some of the higher elevations.

Stronger confluence over the Northeast, will cause a primary low to weaken as it track to into Ohio Valley later tonight and tomorrow. Then a secondary low will develop over the Mid-Atlantic coast and begin intensifying tomorrow night. How far north this secondary low tracks will determine how much wintry precipitation falls over Interior zones, mainly north of I-84 in the Lower Hudson Valley and Connecticut. If the low tracks farther south of Long Island, this will allow for more colder air in the low-levels to remain or filter in as this storm consolidates off the coast by tomorrow night. But with 700mb and 850mb lows tracking further northwest, mid-level warming is likely and will support more wintry mix sleet and freezing rain, as shown in the ECMWF thermal crossections for areas such as Hartford, CT. So while some slippery travel is possible at times, in some of the far northern interior areas. No significant impacts are currently anticipated from any wintry precipitation in the entire region.

ECMWF model showing rainfall most zones in the region. A wintry mix of snow, sleet and freezing confined north of I-84 in Lower Hudson Valley and Northern CT

ECMWF model  Saturday night showing rainfall most zones in the region. Some areas of sleet and freezing rain confined north of I-84 in Lower Hudson Valley and Northern CT. More significant snow and ice  remains further north over Northern NY and Interior New England

Our much bigger concern, is the potential for flooding from heavy rainfall over much more of the region. Model guidance indicates a firehouse-type low-level jet with plume of moisture from the Atlantic to move over the region by tomorrow afternoon and evening.  This will result in rain becoming heavy at times over much of the region during afternoon and evening hours on Friday. Precipitable water values will be at 2 to 3 standard deviations above normal over the region. Rainfall totals between 1 to 2 inches are likely for much of the region, by late tomorrow night. Some locally heavier rainfall totals are possible with any training elevated convection, especially closer to the low track over Central and Southern parts of New Jersey and perhaps into Long Island and Coastal CT. This amount of rainfall could result localized flash flooding in poor drainage and low-lying areas. Some flooding around small streams and rivers is also, possible. Especially over New Jersey where flood guidance suggests only around a inch of rain is need to cause flooding.

 

High winds and some flooding during high tides along the coast. Models are also currently showing low-level jet with 850mb winds around 50kt-65kt moving across parts of the region.  However, model soundings show a strong inversion, that will likely keep much of these winds from mixing down to surface. Still onshore winds between 20mph to 35mph with gusts up 45 mph are possible, especially over Long Island and New Jersey shore and especially with heavier rainfall. Also with new moon earlier this week. These strong onshore winds may lead to widespread minor coastal flooding during high tides Friday evening, along New Jersey, New York and Connecticut shores. Latest guidance suggests some locally moderate coastal flooding is even possible along south shore back bays of Long Island.

3km NAM 850mb wind charts showing firehose-type low-level over the region.

3km NAM model showing a strong 850mb southerly jet moving over Long Island by tomorrow night

A wide range temperatures from north to south possible through Friday night, depending on the track of the secondary low. Then rain will begin tapering off to lighter showers and drizzle, from  later tomorrow night and early Saturday morning, best forcing low-level jet moves northeast region. Some rain could linger into morning hours over parts of Long Island and Connecticut, as low pressure continues to intensify and wrap around moisture. Then skies will begin clearing for more sunshine Saturday afternoon with drier northwest winds behind this system. Highs will be in the upper 40s to lower 50s on Saturday.

High pressure will build over the region on Sunday with mostly sunny skies and highs in the lower to middle 50s. On Monday, high pressure will be moving offshore late in the day. This will allow for some clouds to increase during the afternoon. But it should remain dry for the Mets Home Opener at Citifield. High temperatures will once again be in the lower to middle 50s.

Then next storm system will be arriving from the southwest with more significant rainfall possible again late Monday night and Tuesday. The pattern will remain active and somewhat volitale pattern continuing for the rest of next week. More temperatures swings every a couple days, between below and above normal are possible. But any prolonged warmth doesn’t appear likely to start April. Stay tuned for more zone forecast updates on this storm system for Friday and the weather through next week.