Boone

Summary

SYNOPSIS

... An upper level trough of low pressure is slowly moving across the Mid-Atlantic region, resulting in mostly cloudy skies, areas of rain and rain showers, and a few thunderstorms. Rainfall amounts will be highly variable, with the heaviest occuring along and east of the Blue Ridge. Daily afternoon showers and thunderstorms are possible through much of the upcoming week.

NEAR TERM /THROUGH MONDAY/... As of 1045 PM EDT Sunday...

Latest radar imagery indicates only isolated showers remain this evening, located across the mountains from southeast West Virginia into northwest North Carolina. Can't rule out localized redevelopment through the night, but believe this activity will be light and short-lived, if at all. Adjusted temperatures and cloud cover based on latest observations, though these adjustments were minor.

As of 700 PM EDT Sunday...

Scattering cloud cover across the mountains this afternoon allowed temperatures to spike some 5 to 8 degrees over the span of a couple hours, and triggered spotty showers with an isolated rumble of thunder or two. These lingering showers will persist through around 10 pm and will gradually fade heading into late evening with the loss of heating. Still looking for clouds to redevelop overnight, with patchy fog forming more so after midnight.

As of 145 PM EDT Sunday...

Key Messages:

1. Scattered showers and thunderstorms this afternoon and again Monday afternoon. 2. Warmer temperatures Monday.

The wedge of high pressure will finally erode by later today, and the warm front lifts northward, putting the area in the broad warm sector behind the front. So, through this afternoon and evening, scattered showers and isolated thunderstorms can be expected, with the highest probabilities along and west of the Blue Ridge. Thunderstorm coverage will depend on how much the atmosphere can destabilize through diurnal heating from any breaks in the clouds. Right now, some pockets of sunshine and thinner cloud cover is observed west of the Blue Ridge, in far southwest VA and northwest NC mainly. Most of the showers and storms will diminish by tonight, but plenty of residual moisture will lead to overcast skies and patchy fog, especially over the higher terrain, through the overnight and into tomorrow morning.

A cold front is currently situated from the upper Ohio Valley into the Tennessee Valley, with the surface low in the ArkLaTex region. By tomorrow, this low will track northeastward along the front and closer to the Mid Atlantic, moving just west of the forecast area by Monday afternoon. Monday will start off dry as mid level ridging builds in overhead, and generally low level southwesterly flow brings warmer and more moist air into the area. However, heating throughout the day will help to increase instability, with SBCAPE forecast to reach around 1000 J/kg by the afternoon, highest along and east of the Blue Ridge. However, the better upper level dynamics will be closer to the surface low, mainly over the western mountains, and closer to the frontal boundary, which will be draped across the upper Mid Atlantic region. That all being said, thinking for Monday afternoon is showers beginning first in the west and expanding eastward into the Foothills and Piedmont, but with a higher potential for some thunderstorms in the east where the greater instability will be.

Temperatures overnight will be mild, with overcast skies preventing much radiational cooling. Highs Monday will be warmer than today, as south and southwesterly flow ahead of the cold front increases and mid level ridging builds overhead.

Forecast confidence is moderate, but lower on specific locations of thunderstorms this afternoon and tomorrow.

SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 200 PM EDT Sunday...

Key Messages:

1. Showers and thunderstorm possible each day, especially in the afternoons and evenings.

2. Moderate rainfall possible as well as damaging winds and marginally severe hail.

3. Warm temperatures continue.

Monday night into Tuesday, a short wave will cross the forecast area, helping to steer an elongated baroclinic zone towards us from the north. This will keep scattered to numerous showers and thunderstorms in the area. Another short wave moves through Tuesday afternoon and evening, and this will trigger some stronger thunderstorms, mainly over the western mountains. However, antecedent cloud cover and rain as well as weak ridging aloft and westerly winds should keep a lid on the severe potential, but an isolated damaging wind gust or marginally severe hail will be possible, along with moderate rainfall.

On Wednesday, we remain in the warm sector, and a surface trough crossing the area should help organize convection. Expect showers and storms to develop during the afternoon and evening, with MLCAPE increasing to between 500 and 1000 J/kg over the southern Shenandoah Valley and the Piedmont based on GEFS probabilities. Dew points will be in the 50s to low 60s for the mountains, so prolonged thunderstorm activity there looks less likely. Forecast soundings indicate tall, skinny CAPE each day, along with unidirectional westerly flow, which would indicate more linear bowing structures could develop with damaging winds. Very slow storm motion as well as PWATs approaching our recorded maximum for these dates indicate urban, small stream, and flash flooding may be a concern.

Temperatures during this time will be on the warm side, with 70s and 80s each day, reaching the mid to upper 80s for areas east of the Blue Ridge Wednesday.

Confidence in the short term is moderate.

LONG TERM /THURSDAY THROUGH SUNDAY/... As of 200 PM EDT Sunday...

Key Messages:

1. Warming trend to start the work week, cooler and dry next weekend.

2. Showers and thunderstorm chances each day.

Thursday into Thursday night we will see more chances for showers and thunderstorms. A slowly filling surface low will move west to east across the OH Valley, putting us just south of the triple point and well under dense cloud cover for most of the area. Instability looks best for our northern NC counties, which may see some strong thunderstorms. The initial short wave trough associated with the upper level system will be positively tilted and crosses the Appalachians Friday and Saturday, pushing a cold front ahead of it. This will mean more widespread rain and thunderstorms. While there are mixed signals as far as severe thunderstorm chances, the chances for moderate to heavy widespread rainfall leading to flooding increases each day during this wet period, and at the moment looks like the bigger threat.

High temperatures gradually decrease each day Thursday through Saturday with overcast skies and the passage of the front. We may finally see the sun either late Friday or Saturday. The weekend looks cooler and drier with dew points dropping into the 30s and 40s, and this is supported by NAEFS situational awareness projections.

Confidence in the long term is moderate for most parameters, but lower for timing of showers and storms.