... A large low pressure system will cover much of the northeast United States tonight and Monday. A series of low pressure systems will track across the southern United States Tuesday through Friday. By Saturday, a stronger system will be off the East Coast.
NEAR TERM /THROUGH MONDAY/... As of 156 PM EST Sunday...
Broad upper low drifts into southeast Canada tonight and Monday with several shorts waves tracking around the low. Period of vorticity advection and the associated jet streak reach the Tennessee Valley early Monday morning then crosses the central and southern Appalachians during the day.
Low level jet increases from the west tonight, then after the short wave goes by winds become northwest Monday afternoon. Deeper moisture arrives in North Carolina and southern Virginia after midnight but clouds now over the Tennessee Valley will reach the area this evening. Probability of precipitation will spill over into the foothills and piedmont as they short wave crosses on Monday but due to the deep westerly flow any precipitation amounts of more than 0.10 inch liquid will be confined to a small strip from western Smyth County to western Watauga County with the highest snow amounts at the highest elevations. Will keep maximum temperatures under the cloud cover on the cooler side of guidance.
SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 156 PM EST Sunday...
The upper trough axis will push off the East Coast Monday night. The upper disturbance rotating around the upper trough should move off in the Virginia coast around 06z Tuesday and further out to sea by 12z. Low temperatures Monday night into Tuesday morning will range from the mid 20s in the mountains to the lower 30s along the southern Blue Ridge.
High pressure from the Great Lake Region will build southeast into our region Tuesday into Tuesday night. High temperatures on Tuesday will vary from the upper 20s in the northwest mountains of Greenbrier county to around 50 degrees in the piedmont. Under partly to mostly cloudy conditions, it will be cold Tuesday night with readings from the lower 20s in the mountains to near 30 degrees in the piedmont.
Another shortwave will approach on Wednesday and moves across Wednesday evening into Thursday morning. Under plenty of clouds, high temperatures Wednesday looks to be cooler than Tuesday ranging from the lower 30s in the northwest to the mid 40s in the southeast.
With the system Wednesday night, there is a chance of snow for the higher elevations and rain in the lower elevations. Snow accumulations are expected to remain less than 1 inch and confined to elevations generally above 3000 ft. Low temperatures Wednesday will drop into the mid 20s to around 30 degrees.
Moderate to High confidence in the Short Term Period.
LONG TERM /THURSDAY THROUGH SATURDAY/... As of 156 PM EST Sunday...
Broad cyclonic flow will persist across the eastern U.S., with shortwave energy spilling over the western ridge and undergoing some potential for amplification farther east.
Low pressure in the lower Mississippi Valley Wednesday morning will weaken and move east across the Southeast Wednesday night into Thursday. Meanwhile, another shortwave will drop south east across the region Wednesday night into Thursday.
Longer range models continue to be plagued by differences in timing and track with respect to a southern stream shortwave and the potential for it to result in the development of an area of low pressure somewhere across the southeast or along the southeast U.S. coast late in the weekend.
The 12z ECMWF continues to show a very far southern track of this system, across the Gulf and south Florida, then out into the Atlantic ocean with little to no northeastward trajectory or interaction with the northern stream. Timing with the ECMWF is also much slower, namely early next week as opposed to Friday night into Saturday indicated by the GFS. The GFS on the other hand, attempts to phase the northern and southern streams together, but far enough inland that precipitation in our area would appear to be mostly rain as temperatures are a bit too warm it appears for a significant snow event, except perhaps in the mountains. To much uncertainty to mention any snow accumulations at this time. The details of this forecast will be revealed over time as we get closer to the event.
Confidence in the forecast for the extended periods remains low at this point.