1/21 All Zones AM Update on Significant Storm for Monday & Tuesday

As we discussed, previous article significant storm will impact region early next week. This storm will could turn into major Nor’easter with heavy rainfall, strong gusty winds, and some coastal flooding during the high tides. Even some snow and sleet is also possible for some of the Interior locations. More discussion on some details on each potential impacts below for the all the zones.

Rainfall: Some rain could arrive by Sunday night. But the steadiest and heaviest rainfall will be late morning/early afternoon on Monday through early Monday night, with strong low-level jet moving northward through the region. Then low pressure transfer from inland too off the coast, weakens and occludes, rain will be somewhat lighter and more intermittent late Monday night and Tuesday.

Some models vary somewhat rainfall totals over the region. Some places with less rainfall than others.  But precipitable water values continue to be around 3 or 4 Standard Deviations above normal with strong easterly low-level jet off the Atlantic. We have pretty high confidence in rainfall totals between 1” to 3 ” across most of the zones. Some locally higher amounts are possible. Particularly, if there is enough instability for any convection.

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The 0z/21 GFS showing standard deviations around between 2 and 4 above normal

Winds: A tight pressure between deepening low pressure over the Mid-Atlantic region and high pressure over Eastern Quebec, will cause increasing easterly winds with strong low-level jet over the region on Monday. Models show a stout inversion near 900mb, that would keep prevent most of the winds at or above that level, from mixing down to surface. However, models have been showing plenty winds between 40-60kts between 950mb and 975mb. Model soundings also indicate much of these winds, mixing down from on top of a dry-adiabatic mixed-layer.

Frequent wind gusts between 30-50mph are likely for much of the region, including some areas further inland. Especially Monday afternoon and evening. Some occasional wind gusts between 50-60mph are also likely, especially for coastal areas. There is somewhat lower risk for some wind gusts between 60-70mph along the coast, especially over Eastern Long Island and the Central New Jersey shore, where the 0z EPS has been consistent shows 50kt+ potential wind gusts. This potential damaging winds, are more possible if stronger winds closer to 950mb can mix down tomorrow.

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The 6z/21 NAM showing 950mb winds over 60kt-65kt+ near the coast on Monday

Coastal Flooding: A strong persistent easterly flow combined with astronomically high tide cycle with new moon later in the week, will likely lead at least some minor to moderate coastal flooding. Especially along New Jersey shore and around the back bays along the south shore of Long Island. High tides during Monday morning and evening are at most of risk of seeing the most flooding from. The extend of coastal flooding is still somewhat uncertain and will depend on the timing and strength of maximum winds from the low-level jet over the region.

Winter Weather: At this time, we aren’t anticipating significant frozen precipitation for much of the region, due to a warm antecedent airmass. However, some wet snow or sleet can’t be entirely ruled out, hills over Northwest New Jersey, the Hudson Valley and Northern CT. Winds may be east-northeasterly enough to allow for cold air to remain in these locations. If this, becomes more likely then some snow/sleet accumulations may have to considered in the future.

Stay tuned more updates, as new model and ensemble guidance comes in today. We will likely have more individual zone forecast updates with more focus on certain impacts  beginning on Sunday.