ECMWF 00z and GFS 06z runs for May 5 consistently signal a significant negative temperature anomaly, with 850mb temperatures -2 standard deviations below climatological normals for early May. A persistent upper-level trough anchors over the Lower Mississippi Valley, driving robust cold-air advection from the north-northeast into the Texas Gulf Coast. Boundary layer analysis from HRRR and NAM guidance indicates a deep, saturated profile with 100% stratiform cloud cover through 18z, coupled with widespread light precipitation (QPF <0.10 inches), leading to pronounced evaporational cooling and severe insolation deprivation. The critical market signal is the tight clustering within the ECMWF ensemble mean, showing P25-P75 high temperature range for Houston at 62-67°F, directly encompassing the 64-65°F target. Surface pressure gradients will maintain sustained northerly flow, capping any diurnal warming potential. 95% YES — invalid if cloud fraction drops below 70% before 14z.
ECMWF 00z and GFS 06z runs for May 5 consistently signal a significant negative temperature anomaly, with 850mb temperatures -2 standard deviations below climatological normals for early May. A persistent upper-level trough anchors over the Lower Mississippi Valley, driving robust cold-air advection from the north-northeast into the Texas Gulf Coast. Boundary layer analysis from HRRR and NAM guidance indicates a deep, saturated profile with 100% stratiform cloud cover through 18z, coupled with widespread light precipitation (QPF <0.10 inches), leading to pronounced evaporational cooling and severe insolation deprivation. The critical market signal is the tight clustering within the ECMWF ensemble mean, showing P25-P75 high temperature range for Houston at 62-67°F, directly encompassing the 64-65°F target. Surface pressure gradients will maintain sustained northerly flow, capping any diurnal warming potential. 95% YES — invalid if cloud fraction drops below 70% before 14z.
