Despite a warm airmass overhead, despite southerly winds aloft, and despite the presence of plenty of warmth back to our west...none of that mattered today. Fog and low clouds won out and temperatures struggled to approach 50 this afternoon in the city.
The presence of low clouds at the surface and clouds aloft helped trapped oceanic air close to the surface, preventing the air from mixing out as sunshine was nonexistent today thanks to mid level clouds on top of the marine stratus. The result was a foggy soup of low clouds that hung tight through the region today, not able to lift and mix out with limited January daylight.
Fog did manage to lift for a time across Central Jersey, allowing temperatures in the Pinelands to jump into the middle 50's for a couple of hours. However, the surface flow of air was weak and modest...not strong enough to help mix the atmosphere out. A surface warm front was down across Virginia and out west across Western Pennsylvania, locations where winds were a bit stronger and more southwesterly. Temperatures out to our west and southwest were much warmer once below or west of this boundary.
Instead, the weak southerly flow off of the Atlantic provided moisture to produce warm advection fog over the region. This fog didn't lift in many places today as the airmass was stable, mid level cloud cover overhead not able to provide any sunshine to help mix the atmosphere, and the result was a January thaw gone bust.
That said, we were still several degrees above average for this time of the year. Just not as warm as hyped and hoped.