Aggressive Canadian airmass advection post-frontal passage confirms a significant cooling event for NYC on May 10. Both ECMWF HRES and GFS 00z/06z runs are converging on a robust trough axis digging into the Northeast, pushing 850mb temperatures to an anomalously low -1°C to +1°C range by 12Z on May 10. This is a severe departure from the climatological mean of +6.5°C for that date. With a strong surface high building in from the Great Lakes, clear skies and light winds are forecasted, maximizing radiational cooling potential overnight. GEFS and EPS ensemble means show a 65% probability of surface lows dipping below 48°F. The 46-47°F band is critically supported by the 25th-percentile outcome across both key ensembles, indicating prime conditions for lows firmly in this range with optimal cooling efficiency. This setup is classic for below-average temperatures. 90% YES — invalid if cloud cover exceeds 30% by 06Z May 10.
Aggressive Canadian airmass advection post-frontal passage confirms a significant cooling event for NYC on May 10. Both ECMWF HRES and GFS 00z/06z runs are converging on a robust trough axis digging into the Northeast, pushing 850mb temperatures to an anomalously low -1°C to +1°C range by 12Z on May 10. This is a severe departure from the climatological mean of +6.5°C for that date. With a strong surface high building in from the Great Lakes, clear skies and light winds are forecasted, maximizing radiational cooling potential overnight. GEFS and EPS ensemble means show a 65% probability of surface lows dipping below 48°F. The 46-47°F band is critically supported by the 25th-percentile outcome across both key ensembles, indicating prime conditions for lows firmly in this range with optimal cooling efficiency. This setup is classic for below-average temperatures. 90% YES — invalid if cloud cover exceeds 30% by 06Z May 10.
