5.16 Midday Zones Update: Low 90s Possible by Thursday, More High Latitude Blocking

Happy Tuesday! Get ready for more summery weather over next several days! For today, sunshine will continue into the early afternoon hours. Then more mid-high clouds may filter sunshine this afternoon, as some convective debris from the Great Lakes moves southeast into region. But there should be enough sunshine with west-southwest winds to help temperatures rise into upper 70s and 80 over most of the region. Clear to partly cloudy skies are expected tonight. Low temperatures overnight will be in the upper 50s to lower 60s, over most of region with a light southwest flow.

Then a strong mid-level ridge will be over region on Wednesday and Thursday. 500mb heights between 582 to 585 dm will support more summer-like airmass over the region both days. Some sunshine with southwest winds will support highs at least mid-upper 80s, in many areas. A stronger gradient will likely lead to more afternoon sea-breezes that may keep, near the shore, cooler in the 70s or lower 80s. While not oppressive, humidity will also be higher with dewpoints in the 60s.

850mb temperatures between 16°C to 17°C on Wednesday may support some spots reach 90°F on Wednesday. But latest models suggest, deeper mixing with 850mb temperatures 17° C to 18°C and stronger southwest flow, on Thursday could support more lower 90s along the I-95 corridor from NE NJ/NYC to PHL Metro. However, a cavet may some convective debris from thunderstorm complexes coming out the Midwest and Great Lakes Wednesday night, may cause more clouds to mix with sunshine by Thursday.

 

NAM model forecast for temperatures, dewpoints Thursday afternoon

NAM model forecast for temperatures, dewpoints Thursday afternoon

A cold front will likely approaching the region by Thursday night or Friday morning. Only some isolated to widely scattered showers or thunderstorms are likely with this front, with lack of moisture and dynamics in the region. Some heavy rainfall and lightning are the main threats. Behind this front, more west-northwest downslope flow may help temperatures rise well into 80s again on Friday, with skies clear for more sunshine during the day.

Then a cooler, maritime airmass over the region is still expected for this weekend. High pressure to north and east, will support more onshore winds. But also dry conditions,  until the next frontal system approaches with possibly some showers and thunderstorms by Sunday night or  Monday. High temperatures with more sunshine on Saturday will likely be in the upper 60s to lower 70s. Sunday’s high temperatures will depend on quickly cloud cover increase ahead of warm front lift northward. Temperatures may also be a little cooler each day, near the shore, with more marine influence from onshore winds.

Model and ensemble guidance continues suggest more high-latitude blocking, over the next few weeks. This will support more below normal heights with no prolonged heat over Eastern US, for the rest of the month. In fact, some cooler, wetter or unsettled weather may return at times with a more active pacific jet or multiple disturbances, undercutting this blocking over the CONUS. But there enough intricacies with the pattern that may still result in some pleasant, drier weather at times as well. We may not start getting a clearer picture on the forecast for Memorial Day weekend until early next week.

GFS ensembles showing high-latitude blocking with more troughiness over the Eastern US going into next week

GFS ensembles showing high-latitude blocking with more troughiness or lower 500mb heights over the Eastern US going into next week

There some indications from climate indices and weekly guidance, that this pattern with high-latitude blocking may continue into at least first first couple weeks of June as well. Stay tuned for more zone forecast and other long range updates the pattern over next few weeks!