5.28 PM Zones Update: Memorial Day Rain, Unsettled Weather Pattern Continues

Good evening! We hope you’ve been enjoying you’re the weekend so far. Despite some cloudiness at times, the weather overall has been decent. A complete washout is still not expected for Memorial Day. However, more inclement weather appears to be in store, as frontal  system impacts the region. Especially during the morning hours. Overall an unsettled weather pattern will continue this week, with more chances of rain. We break down some details on the forecast for Memorial Day and the rest of the week. Also discuss a little bit about any pattern changes coming in the couple weeks!

First for tonight, clouds will increase and thicken tonight, as warm front approaches the region. Some rain is already pushing into Southern NJ and Southeast PA this evening. But elsewhere much of the evening will be dry. More rain is likely to move in from southwest later tonight. Overnight low temperatures will be in the low to middle 50s over the region. More periods of rain are likely tomorrow morning, as isentropic lift increases. Some elevated instability could also result in few embedded thunderstorms with heavy rainfall.  These showers and thunderstorms will move east of the region during early afternoon hours.

Despite high precipitable water values over 1.25″, best dynamics with a southeasterly low-level jet and moisture convergence, will be farther northwest of the region. So overall rainfall totals are likely to be under 1″ over much of the region. This rainfall is not expected to cause much more than some ponding on roadways. However, some locally higher rainfall totals are possible with any thunderstorms that cause some localized minor flooding over poor drainage or low-lying areas.

NAM model showing rain with frontal system and offshore low

NAM model forecast for showing rain with frontal system over the region late Memorial Day morning

The warm front will likely stall southwest of region tomorrow, as a wave of low pressure developing off the Mid-Atlantic coast will likely keep onshore winds. There may be enough low-level moisture for some fog and drizzle over the region for the rest of the afternoon. Temperatures will likely remain mostly in the 50s. There is chance the clouds could begin clear later in the day. But the best chance for clouds to break for more sunshine, with further south over Central and Southern New Jersey and Southeast Pennsylvania. If this happens, sunshine will help temperatures rise into the 60s or 70s.

On Tuesday, a cold front will be moving through the region during the afternoon and evening. Some scattered showers and thunderstorms are possible during the afternoon and evening. There is some uncertainty with how much the region will be in warmer, unstable airmass and timing of more mid-upper level shear and forcing arriving. So organized severe weather is not anticipated in the local region at this time. However, the Storm Prediction Center has a marginal risk for some isolated strong-severe t-storms northwest of NYC with

For the rest of the week, an unsettled weather pattern will continue. A ridge over Western Canada and residual blocking over the Davis Strait the upper-level trough will be over Great Lakes to the Southeast Canada. Multiple disturbances rounding this the upper-level trough will move through Northeast. There is some uncertainty with timing of these disturbances. But there will be likely another threat or two for showers and thunderstorms, later in the week. Temperatures will depend on amount of clouds and rainfall each day. But will likely run near or below normal in this pattern. There will tendency for the coolest anomalies to be closer to more troughiness over the Great Lakes.

GFS ensembles showing ridge over Western Canada for mid-late week period

GFS ensembles showing a ridge over Western Canada for the mid-late part of this week

In the longer range, there doesn’t appear to be whole lot changing, especially sensible weather wise.. There is a trend in the ensemble guidance towards less high-latitude blocking and more positive AO/NAO after about 10 days. This may allow for the Southeast ridge to build back a stronger into Northeast during the second week of June. However a ridge still persists over Western parts of the United States and Canada, which will support more troughs to move into at least the Great Lakes and Northeast regions. So while there some periods of warmer, drier weather are possible. Some cooler, wetter weather will likely return at times over next two weeks. Stay tuned for more zone forecast updates this week!