5.23 Midday Zones Update: Close Call with Rain Tonight & Wednesday AM, More Rain Likely Thursday

Good afternoon! Plenty of high clouds will continue to be around for rest of this afternoon. But sunshine will filter or break through these clouds and temperatures rise into the lower to middle 70s, over the much of region this afternoon. These clouds are from a broad area of low pressure developing along tale end of frontal boundary over the Southeast US. This low will organize and consolidate over the Carolinas this evening, as it will be more sandwiched in between upper-level jet streaks. This will cause clouds will thicken more this evening. But weak high pressure should keep most of the region dry, during the evening hours.

Then low pressure will move northeast off the Delmarva and New Jersey coast later tonight and Wednesday morning. Shortwave energy associated with this low is expected remain weak and disorganized. So this will likely keep the low tracking far enough southeast to spare most of the region any heavy rainfall. But some light showers or steadier periods of light to moderate rain can’t be ruled out, across the region, especially over parts of Southeast NJ and Eastern Long Island. We will continue to monitor this system for any significant throughout overnight and morning hours tomorrow.

GFS model still a northern outlier, with more moderate rainfall along coastal late tonight and tomorrow morning.

GFS model still a northern outlier, with more moderate rainfall along coastal late tonight and tomorrow morning.

Otherwise, mostly cloudy skies are expected later tonight and tomorrow morning, for entire region. Clouds will keep temperatures from dropping out the 50s, over most of the region late tonight. These clouds may break for some sunshine, as low pressure moves further tomorrow afternoon. More sunshine will support to rise into lower to middle 70s again over some inland areas. But a stronger northeasterly flow, as this storm moves more offshore,  may keep areas closer to the coast, areas rising out the mid-upper 60s tomorrow, especially if more clouds hang on longer into the afternoon hours.

Clouds will increase again tomorrow night, large upper-level low moves into the Ohio and Tennessee Valley. Residual high-latitude blocking and some ridging out west, will cause shortwave energy rotating around the base of upper-level low to amplify over Mid-Atlantic region Thursday. This will result in surface low pressure over the Ohio Valley transferring to secondary low somewhere along Delmarva coast. However, this storm system will remain rather large and disjointed while moving over the region, as the pattern becomes more progressive with another large trough moving the West Coast, around the same time. This is resulting is some uncertainty with rainfall totals over the region.

But with that being said, some strong lift from mid-level warm advection and positive voriticy advection will likely lead periods of rain on during day and evening hours on Thursday, over the local region. A deep southerly flow with plume of subtropical moisture, streaming northward, could lead to some heavy rainfall at times. At this time, more cloud cover and marine influence will likely mitigate any severe weather threat. But with some elevated instability, some thunderstorms are possible, with very heavy rainfall and frequent lightning.

NAM model showing more rainfall with next storm system on Thursday

NAM model showing more rainfall with next storm system on Thursday

On Friday, the low pressure will be tracking into New England with clouds breaking for some sunshine during the day. However, a cold pool aloft with the upper-level low and daytime surface heating will support the airmass to be more unstable, during the day. So this could result in some scattered showers and thunderstorms developing over the region again. Some thunderstorms may also be capable of producing some gusty winds and small hail.

After this storm system exits out Northeast, some more pleasant, drier weather looks likely for at least Saturday. But another storm system passing northwest region may bring more showers sometime during Sunday into Memorial Day. Stay tuned for more zone forecast updates this evening, on the weather for rest of the week and on Memorial Day weekend.