Spring Wx

Potential for 70 Degree Warmth 4/11 – 4/14

Miguel Pierre Spring Wx

A weakening cold front move through the day tomorrow. It will be accompanied by some some clouds and scattered showers. If there’s enough sunshine between the clouds tomorrow temperatures, may soar to near 70 degrees with westerly down slope winds tomorrow. A weak wave of low pressure will form along this cold tomorrow, with a period of steady rain tomorrow night. At this time, dynamics don’t appear to be supportive for heavy rainfall totals greater than .50″. This wave should move out the area by Saturday morning. Leading to skies to mostly sunny skies on Saturday afternoon, with light west or northwest winds causing temperatures to rise into the upper 60s to around 70 degrees over NE NJ and NYC. Sea-breezes developing tomorrow afternoon will keep the south shore of LI and the NJ shore in middle to upper 60s for highs tomorrow.

On Sunday, a warm front will attempt move across the area. However, most of guidance shows high pressure develops over the Atlantic, causing more SSE winds ahead of the front. Which will bring a marine airmass of the ocean. This may force the warm front to slow down or stall just southwest of NYC on Sunday afternoon. The south shore of NYC and Long Island may be stuck 40s or 50s with some low clouds and drizzle on Sunday. While inland areas sees more sunshine and temperatures rising into 60s or 70s.

18z NAM showing 70+ temps over Western NJ and 50s with drizzle over NYC, LI and the NJ and CT coasts.
18z NAM showing 70+ temps over Western NJ and 50s with drizzle over NYC, LI and the NJ and CT coasts.

On Monday,  the warm front is more likely to push northward over NE NJ and NYC. As stronger flow out the south-southwest develops, ahead a deep trough and strong cold front, approaching from the west. Temperatures in the 70s, should be more widespread across the Northeast NJ and NYC than on Sunday. Although sea-breeze developing along the coast, may push inland during middle and late afternoon hours. Dropping temperatures back into 60s or 50s.

On Tuesday, the cold front moves closer to the area. Precipitable water values increase to over 1.00″, with strong LLJ ahead of this front. Some heavy rainfall from showers and possible thunderstorms may occur.. This should keep high temperatures in the 60s, for most of the area. Behind this is cold front, are much colder temperatures. Highs may not get out 40s for Wednesday or Thursday. With possibility for record low temperatures in 30s or 20s. So while you maybe wearing shorts on Monday. You might not want to pack away the winter coats yet.

 

Suprise Snows after Heavy Weekend Rains

Miguel Pierre Spring Wx, Winter Wx ,

A narrow, band, behind a a cut-off low brought surprise snowfall 2″ – 6″ for parts of Central Long Island and Central Connecticut, this morning. Even thundersnow was reported over at Islip, NY, with snowfall rates up 3″ per hour and visibility down to 1/8th  of a mile. The rest of the area saw rain mix or change to some wet snow and sleet, when more intense rates of precipitation  at times. This was due to colder air aloft, being dragged down to the surface. But little or no accumulation occurred.

OKX radar showing narrow frontogentic band over Central LI and CT
OKX radar from wunderground.com showing narrow frontogentic band over Central LI and CT

So what caused this heavy snow band? One cause for this some frontogenetic forcing occurring behind the cut-off low.  Another cause was instability.  The OKX sounding was unstable with mid-lapse rates over 7.0 C/km. This produced convective banding with thunder over Central LI and CT :

OKX sounding at 12 UTC time. Showing steep mid-level lapes rates
OKX sounding at 7am time, showing 3-6km agl and 700-500mb lapse rates 7.0 C/km and higher

Models showed this the last 3 days, showed that this band would form. But they were less consistent, on the timing, and placement. As well amount of dynamic cooling that would need to occur for snow to accumulate. Add on that it’s end of March, when it’s typically more difficult to get boundary temperatures to support snow. Especially along the coast. So considering those factors, it just wasn’t a likelyhood and a good move beforehand to forecast 2″-6″ for any specific area. Despite the outcome. However, we can use what we  learned from it, to improve forecasts in the future.

This cut-off low also gave us heavy rains and thunderstorms, this past weekend. Many received between 1.50″ to 3.00″ of rain.  As discussed in the previous blog post, a 50-60kt low-level jet move through area with pwats over 1.00″. This enhanced deep moist convergence, along a warm front over eastern parts of LI and CT most early Sunday morning. Causing elevated convection to train over these areas and increase rainfall totals to 3.50″ – 5.50″

dlcp_14033004

Heavy Rainfall Likely Saturday Night

Miguel Pierre Spring Wx ,

As I discussed previous post heavy rainfall is likely weekend. Particularity during Saturday night. Latest guidance is showing rainfall totals between 2″ – 3″ for much of the area. With locally heaver amounts between 3″-4″. Especially N&W of NYC.

The 12z NAM today has area of very heavy rainfall moving through NJ, SE NY and CT between 7pm – 1am Saturday night. Bukfit sounding for LGA shows a 50-60kt LLJ, pwat near 1.35″ and a large of strong omega.  There is also an area 600-800mb frontogenesis moving through the area tomorrow night. All this translates into strong lift and high moisture content over the area. Strong winds aloft are being prevent from reaching the due to strong inversion near the surface. However, downpours could bring down some portion of these winds down to the surface.

Bukfit sounding for LGA 12z NAM shows a 50-60kt LLJ, pwat near 1.35" and a large of omega
12z NAM Bukfit sounding for LGA  shows a 50-60kt LLJ, pwat near 1.35″ and a large of omega
12z NAM showing 600mb-800mb frontogenesis Saturday night
12z NAM showing 600mb-800mb frontogenesis Saturday night

The 12z ECMWF is also showing a 50kt+ LLJ and moving pwats over 1.25″ – 1.50″ through tomorrow night. Another aspect of this storm that needs to be watch frontogentic forcing  and elevated instability, behind the upper-level low Sunday afternoon and night.The 12z NAM shows enough dynamic cooling and cold air advection, for rain to change wet snow. Especially for inland areas. At this time, I am skeptical of this solution. But it’s not impossible to happen.