|Dew Point:||40.0°F (4.4°C)|
|Wind:||From the SE at 3.0 MPH|
|Sea Level Pressure:||30.19" (1022.1 mb)|
Partly CloudyLow: 35
SunnyHigh: 55 Low: 34
SunnyHigh: 59 Low: 49
Rain Showers LikelyHigh: 57 Low: 34
SunnyHigh: 46 Low: 32
Partly cloudy. Low around 35, with temperatures rising to around 41 overnight. Northwest wind around 12 mph.
Sunny, with a high near 55. Northwest wind 5 to 9 mph.
Mostly clear, with a low around 34. Southwest wind 0 to 5 mph.
Sunny, with a high near 59. Southwest wind 0 to 7 mph.
Rain showers likely after 8pm. Mostly cloudy, with a low around 49. Southwest wind 5 to 13 mph. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch possible.
Rain showers likely. Mostly cloudy, with a high near 57. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch possible.
A chance of rain showers before 8pm. Partly cloudy, with a low around 34. Chance of precipitation is 30%.
Sunny, with a high near 46.
Patchy frost after 3am. Mostly clear, with a low around 32.
... A dry cold front associated with a colder air mass will progress across the region early tonight. High pressure is expected to settle over the area tomorrow into Friday. Another cold front will bring a return of wet weather into Saturday. Temperatures will be below normal through the next five days.
NEAR TERM /THROUGH THURSDAY/... As of 710 PM EDT Wednesday...
Winds are diminishing in the piedmont, but forecast takes dewpoints to the mid 30s by dawn with temps in the upper 30s, and at the moment confidence is low on enough frost for advisory criteria, but would not be surprised if some outlying rural areas will see patchy frost at dawn Thursday. At the same time cirrus will be moving in, but should not inhibit any frost formation in the western valleys where winds should fall off late.
Previous discussion from early afternoon...
The central/southern Appalachians and Piedmont is entrenched in post-frontal dry conditions this afternoon. Air mass has dried out significantly with dewpoints commonly in the 30s to lower 40s. It remains blustery at times in the western half of the forecast area and particularly at elevation, as strong insolation has boosted temps in the 60s to near 70. Steepening of low-level lapse rates has allowed to tap into a robust 35-40 kt northwesterly jet. Thus far, wind gusts between 25 to 35 mph has been common tending higher at elevation. A secondary and dry cold front aloft is expected to cross the region late the afternoon, which will allow for the best cold advection into the early-evening hours, offset from peak heating. Look for northwesterly wind gusts to increase another 5 mph or so through sunset. Effects of cold advection and pressure rises will keep breezy conditions going well into the first part of the evening, though wind gust speeds will tend to decrease.
We expect tonight to be the first frost since the Spring across the western third of counties. We do have freeze warnings posted for Bath and western Greenbrier County, and frost advisories for all of southeastern WV, the rest of the Alleghany Highlands and into Bland and Tazewell Counties. These frost/freeze headlines take effect at midnight and continue until 9 AM Thursday. Based on today's forecast guidance, didn't see enough compelling reason to expand frost or freeze headlines further east. Combination of high pressure ridging into the region with clear skies, the very dry air mass in place and decoupling and easing surface winds should allow for good to near-ideal radiational cooling. 850 mb temperatures are forecast to be at or below freezing (0 to -2C) across the Alleghany Highlands and southern Shenandoah Valley hilltops, which supports freeze conditions mainly at elevation in the counties under the Freeze Warning into the pre-dawn hours. While forecast lows look warm enough to permit frost in the Piedmont/foothills into the Roanoke Valley, do expect at least patchy areas of frost in the Mountain Empire, Greenbrier Valley and in the deeper mountain valleys in southeast WV. Patchy frost could be observed in the New River Valley, Smyth/Wythe County and into the mountains of northern NC but expected frost coverage wasn't great enough to support expansion of headlines. May see some shallow moisture bank itself against the Alleghany Mtns which could support some scattered stratocu through the eastern WV mountains but this looks more likely to occur after peak nighttime cooling. Lows in the upper 20s to near 30 in the mountains of Bath and western Greenbrier County, low to mid 30s in the areas in the Frost Advisory, mid/upper 30s from the southern Blue Ridge into the New River Valley, and low 40s east of the Blue Ridge.
High pressure will continue to build southeastward from the upper Midwest/Ohio Valley, its center settling into the Alleghany Mtns toward early Thursday evening. Plentiful sunshine expected again Thursday but 850 mb temperatures around +1 to +5C will support cooler temperatures than today by some 5-10 degrees (mainly in the 50s to near 60, with mid/upper 40s in the higher elevations in the Blue Ridge and western Greenbrier County).
Forecast confidence is high, but some question on how quickly winds slacken lends moderate forecast confidence on frost potential.
SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... As of 339 PM EDT Wednesday...
Weak upper ridging on Friday then 500MB heights fall as trough deepens over the eastern United States. Piece of energy from the upper low over the southwest United States tracks east Friday and Saturday. Meanwhile deep troughing develops over the northeast United States. Friday morning surface high pressure will be centered over Virgina. This high moves offshore Friday night while a cold front will extend from the Great Lakes into the Central Plains. The cold front will cross the Mid Atlantic region on Saturday.
Models have slowed the return of deeper moisture over the central Appalachains from the southwest. Even the faster GFS does not have the high clouds reaching the mountains until Friday afternoon and low levels do not saturate until Friday evening. Will have a majority of the precipitation crossing through southwest Virginia, northwest North Carolina and southeast West Virginia between 03Z-15Z Saturday/11PM Friday to 11AM Saturday.
Residual low level moisture and upslope wind on Saturday night. Will have light rain or snow showers from southeast West Virginia into Tazwell County Virginia. Strongest cold air advection behind the front is Saturday afternoon into early Sunday morning. Strongest pressure rises also forecast for late Saturday night into Sunday morning, which will lead to gusty winds. Will keep below wind advisory criteria for now.
Confidence is below average for lows Thursday night and average for all other elements.
LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 338 PM EDT Wednesday...
Axis of long wave trough moves off the east coast Sunday morning followed by broad northwest flow. A short wave tracks through this flow reaching the Mid Atlantic region on Tuesday although there is some difference in timing with the different models and limited moisture. The ECMWF is still more amplified by late Wednesday then the other long range guidance, closing off a 500MB low off the northeast coast.
850MB temperatures bottom out in the -1 to -5 range Sunday afternoon. Operational GFS was warmer than most of the GEFS members for lows Sunday night. Will be leaning below climatology and MAV guidance. The air mass warms ahead of the Tuesday short wave then cools again for Wednesday behind a cold front.
Confidence is average for all elements.