Forecast Discussion
Summary
SYNOPSIS
... Expect widespread showers and well-below normal temperatures this weekend as an upper low interacts with a coastal low that will move inland over the Carolinas through Monday. The coastal low will linger over our area into early next week and keep our weather wet and breezy. The low is expected to eventually dissipate over the Atlantic Coast toward mid-week with temperatures warming to near normal.
NEAR TERM /THROUGH TONIGHT/... As of 650 AM: Guidance shows showers continuing through the day as the low level flow turns to a more easterly upslope flow as a low pressure system moves north into the NC Coastal Plain. Weak isentropic lift remains over the area as well. Upper divergence increases as a jet streak rotates through the area. All this to say widespread showers expected for much of the area this morning. Precip chances taper off from the southwest through the afternoon as the better forcing moves north and the low level flow turns more westerly. There will be some elevated instability this afternoon, but the depth of the wedge will limit thunder chances. Still, can't rule out a rumble of thunder or two. Isolated heavy rainfall will be possible, especially along and near the NC Blue Ridge Escarpment where forcing and upslope flow will be maximized creating the potential for 1 to 2 inches, locally as high as 3 inches, of additional rainfall. Isolated excessive rainfall may lead to ponding of water in low lying areas of minor flooding. Low end gusty winds will continue this morning then taper off through the afternoon. Highs will be around 20 degrees below normal most locations. The exception is the Upper Savannah River valley and Little TN valley where highs will "only" be 10 to 15 degrees below normal.
Better precip chances will continue to move north following the better forcing. Precip will end after midnight for all but the Northern NC Mountains and I-40 corridor where only scattered showers are expected by daybreak. Low clouds will linger through the night even as precip ends. Winds taper off as well. Lows will be around 5 degrees below normal.
SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 215 AM EDT Sunday: Center of the closed upper low should be centered over the Carolinas at the start of the forecast period. The surface low riding underneath will gradual dissipate during the day Monday as it meanders over the eastern Carolinas. With lingering available moisture from this system and good upper dynamics, expect for scattered showers and a few thunderstorms to be possible on Monday. The best chance for precip will be along and north of the I- 40 corridor. The Rex Block will remain in place over the eastern CONUS, which will hold the upper low situated over the region through most of the period before it practically becomes undone by the middle part of the week. In this case, support for daily showers and thunderstorms will remain in the forecast through the end of the short-term. Outside of some localized heavy rainfall in thunderstorms, excessive QPF amounts are not expected. Temperatures will be 5-10 degrees below-normal for highs Monday and Tuesday, with a warming trend each day.
LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 300 AM EDT Sunday: The Rex blocking pattern will breakdown during the extended as whatever is left of the upper low will get absorbed by a digging upper trough that will swing into Atlantic Canada and New England by the end of the work week. Model guidance keep the overall pattern unsettled throughout most of the extended period. Once the pesky closed upper low fizzles, another weak upper low traverses across the Deep South and Gulf Coast, towards the Southeast by Friday or so. Weak area of high pressure to the northeast will continue to provide a wedge-like configuration through Wednesday before conditions gradually improve. With this overall pattern, expect temperatures to moderate and rebound back to near-normal values or even slightly higher Thursday through Saturday. Diurnal showers and thunderstorms will be possible each day during the extended, but finer details are too far out at this point in time.