... High pressure covering our area today will give way to a potent storm system that will sweep across our region Monday sparking showers and thunderstorms. In its wake will be cooler temperatures and brisk winds. Another complex storm system ejecting out of the southern plains will bring a good chance for widespread showers late in the week
NEAR TERM /THROUGH TONIGHT/... As of 230 AM EDT Sunday...
Warmer temperatures anticipated today.
At 06Z (2 AM EDT), water vapor satellite imagery shows a fast moving upper level shortwave skirting across the forecast area. This feature brought some light rain to southeast WV and some areas in VA north of highway 460. Drying/subsidence behind this feature is already reaching eastern KY, so expect precip to exit the forecast area by 12Z (8 am EDT).
Few changes were made to today's forecast, as shortwave ridging in advance of an upper level system seen across the Gulf Coast this morning, will lead to clearing skies and warmer temperatures . With a small spread in the NBM ensemble members, confidence is high that highs today east of the Blue Ridge reach into the middle 70s.
For tonight, our attention turns to the aforementioned approaching Gulf Coast wave, along with a northern stream potent closed low reaching the western Great Lakes by early Monday morning. With the approach of the Gulf Coast system, low level southerly winds increase which helps low level moisture push north into our area, especially east of the Blue Ridge late tonight/early Monday morning. With modest isentropic lift forming, would not be surprised to see some light rain develop or at least low clouds form east of the Blue Ridge. There are differences, however, in the timing of the arrival of the potential low clouds/light rain, so kept the forecast dry.
These southerly winds and increased low level moisture will keep lows on the warmer side of the guidance spread and temperatures may actually remain steady or slowly rise east of the Blue Ridge late Sunday night.
SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... As of 245 AM EDT Sunday...
Threat of severe thunderstorms Monday afternoon and evening.
Closed upper low crosses the Ohio Valley on Monday and trough continues to deepen over the East as the low over southeast Canada drops in behind the Ohio Valley system. By Tuesday night the low is deepening well off the Mid Atlantic coast. Wednesday and Wednesday night upper ridging and higher heights between the departing 500MB low and the large system over the central United States move across the region.
Good synoptic lift expected with cooler mid level temperatures coming in aloft which will enhance the instability, given any kind of surface heating, and strong upper diffluence in the left-front quadrant of the approaching upper jet by Monday afternoon. SPC SREF continued to show a high shear/low CAPE environment ahead of the front on Monday. Some alignment of the better shear with CAPES in the 500-1000J/kg range mainly between 21Z/5pm and 03Z/11PM in the piedmont of Virginia and North Carolina.
Moderate cold air advection behind the front Monday night will lead in 850MB temperatures in the +2 to +6 range by Tuesday morning. NAM was colder than the ECMWF and GFS Tuesday and Tuesday night. But even the 10th percentile of the GEFS only has Lewisburg with a low around 40 Wednesday morning. Will stay close to the temperatures currently forecast for lows Tuesday night. Northwest low level jet increases to around 45 knots by Tuesday morning. Combined with the cold air advection, winds will be gusty Monday night and Tuesday morning.
Surface and low level winds turn to the north on Tuesday night weakening the upslope into the west side of the central Appalachians. Downsloping and drier air will clear out clouds on the east side of the Blue Ridge on Tuesday, but it will not be until Wednesday morning that the clouds erode in southeast West Virginia. Mid and high clouds will spread into the area from the southwest ahead of the next low pressure system on Wednesday night.
LONG TERM /THURSDAY THROUGH SATURDAY/... As of 245 AM EDT Sunday..
Keeping Thursday wet.
Long range models were coming into better agreement with the timing and track of the large upper low on Thursday through Saturday. WPC and consensus now have this feature over the Tennessee Valley on Friday and over the Mid Atlantic region on Saturday.
Already well into southeast winds and deep upslope flow on the east side of the mountains Thursday. Low level jet increases which will result in higher rainfall amounts, especially Thursday night. Clouds and periods of showers remain in the forecast through Saturday. Will be keeping maximum temperatures on the cool side of guidance due to expected clouds and precipitation. Lows will remain roughly 5 to 10 degrees above normal for this of year.