Sunday Briefing: More Rain Today, Then Progressive Pattern for the Northeast

Happy Sunday! A frontal boundary remains stalled over the Northeast and Mid-Atlantic regions. Waves of low pressure will continue to run, along this front today, with more periods of rain, that may be moderate to heavy at times, this afternoon and early this evening. Temperatures will remain mild in the upper 40s to middle 50s throughout the region, with a southwest flow. Some spots could reach the upper 50s to lower 60s, especially over Southern NJ and Southeast PA. Some areas of patchy fog with reduced visibilites will also be around in some areas, especially when rain intensity decreases.

Rainfall totals along the I-95 corridor from PHL to  NYC are around 1″ as of late this morning. An additional 1″ to 2″ rainfall is possible, with more lift and elevated instability, from 850mb southerly jet streak, that may enhance some embedded convection with very heavy downpours. This will result in some localized flooding in poor drainage and low-lying areas during the day. Also some minor flooding along small streams and rivers may still occur.  Thus flood watches remain in effect for much of New Jersey and Southeast PA. Rainfall totals over parts of southern NJ already exceeded 2”, where flood advisories are in effect.

The HRRR suggest a rain with an embedded line of convection or thunderstorms may move across the parts of Eastern PA, New Jersey and Southeast New York later today.

The HRRR suggests a rain with an embedded line of convection or thunderstorms may move across the parts of Eastern PA, New Jersey and Southeast New York later today.

Rain will gradually taper off later this evening and during the overnight hours tonight, as the frontal boundary with waves of low pressure, all finally begins moving offshore. Some areas of patchy fog and some light showers or drizzle may still be around into late tonight or early Monday morning. Then high pressure begins building into the Northeast with clearing skies for rest of Monday. Some cooler air will begin to return. But temperatures will remain above normal, with daytime highs likely in the middle to upper 40s.

Then it will turn even colder Monday night and Tuesday. High pressure will provide plenty of sunshine on Tuesday. But highs will be in the upper 30s to lower 40s. Which is slightly below normal for this time of year. But again the temperatures will begin moderating back to above normal on Wednesday and Thursday, as high pressure moves offshore with a return southwest flow developing. It may also be somewhat unsettled with more clouds and showers with a few passing couple disturbances. But no heavy precipitation appears likely giving the progressive nature the pattern.

ECMWF model showing temperatures 20 degrees above normal by Friday monring

Latest ECMWF model showing temperatures 20 degrees above normal early  Friday morning

Thursday night or Friday, a stronger cold front associated  upper-level trough will move through with possibly more rain showers. Then a colder airmass arrives, bringing temperatures down to slightly below normal again by at least the beginning of next weekend. We will be watching northern and southern stream disturbances  passing through the Northeast US. But a progressive pattern, doesn’t support phasing between these disturbances. So we aren’t anticipating a large or significant storm, at this time.

In fact, latest model and ensemble data suggest temperatures may moderate again for following week. Despite the NAO becoming negative, the PNA may remain negative with larger trough positioned more over the Western and Central US. This may support more ridging along the East Coast of the United States with some warmer than normal persisting into late in the month. Stay tuned for more updates on pattern going forward, during this upcoming week.