Issued: 8pm on Sunday, December 8th 2024
Technical Forecast Discussion
Short-term Forecast (Sunday 12/08/2024 through Tuesday 12/10/2024):
A series of low-pressure systems will dominate the short-term period, with warm and moist air advection driving widespread precipitation. Tonight, a robust low-level jet (~40-50 knots at 850mb) will enhance moisture transport from the Gulf, with precipitable water values climbing above 1.0 inch—well above climatological norms for December. This will support moderate to heavy rain, particularly overnight as isentropic lift and frontogenesis strengthen. Expect rainfall rates to decrease into Monday morning as the first system moves eastward. On Monday night into Tuesday, a secondary shortwave trough and surface low will approach from the west. Height falls aloft and a deepening surface cyclone will bring renewed rain, with possible convective elements due to modest elevated instability. By late Tuesday, a trailing cold front will sweep through, bringing an end to precipitation while cooler air begins to filter into the region. Cloud cover will remain persistent, with post-frontal winds shifting to the northwest.
Long-term Forecast (Wednesday 12/11/2024 through Saturday 12/14/2024):
A pronounced shift to colder conditions is anticipated midweek as a broad trough amplifies over the eastern U.S. On Wednesday, strong cold air advection (CAA) will lower thickness values, bringing a transition from rain to snow showers, especially in higher terrain. Steep low-level lapse rates combined with lingering moisture in the dendritic growth zone will favor scattered snow showers into Wednesday night, with minor accumulations possible. By Thursday, high pressure will begin building from the west, leading to drier conditions but maintaining below-average temperatures. The synoptic pattern will favor mostly cloudy skies early, gradually clearing by Friday as subsidence strengthens. Overnight lows will plunge under radiational cooling conditions, especially Friday and Saturday nights. Expect a return to sunny skies by the weekend as the high pressure axis moves directly overhead. Temperature recovery will remain slow, limited by continued CAA and a shallow boundary layer.
