textproduct: Blacksburg

SYNOPSIS

A warm moist airmass will allow for daily shower and thunderstorm chances. An approaching front from the northwest stalls to the north today through the rest of the week, which will allow for an increased coverage of showers and thunderstorms. Hot conditions are expected today and Wednesday, with slightly cooler temperatures Wednesday.

NEAR TERM /THROUGH TONIGHT/

As of 130 AM EDT Tuesday...

Key Messages:

1) Hot, with a Heat Advisory in effect for part of Southside VA and the NC Piedmont.

2) Scattered showers and storms this afternoon. Heat will be the main concern today, with abnormally high temperatures over the area at the surface and aloft. With temperatures in the low to upper 80s for the mountains, and the low to mid 90s for the Piedmont, along with dew points in the low to mid 70s, heat index values of over 100 are expected over Southside VA and parts of the NC Piedmont. As such, a Heat Advisory has been issued for this area beginning at 10 AM and ending tonight.

We remain in southwest flow aloft today and tonight, with a trough from central Canada down to TX, and ridging over the desert SW and the western Atlantic. There will be only weak positive vorticity aloft moving through this afternoon, but with temperatures in the 80s and 90s (about 5 to 10 degrees above normal) and dew points in the 60s and 70s, resultant instability will trigger showers and storms this afternoon and evening. A pre-frontal/lee trough along the Blue Ridge will also encourage storm development. The best instability will be over the far SE NC/VA Piedmonts, with another smaller area over the WV/VA border area. Poor lapse rates, shear, and kinematic support will mean storms will be weak and garden variety. Still, if instability reaches 2500-3000 J/kg over Southside VA and the NC Piedmont, we could see some briefly severe storms with damaging winds, although forecast soundings show skinny CAPE through the column. Moderate to heavy rain will remain an issue, with storm motions around 15 to 20 mph.

Dense fog will be possible in the usual mountain and river valleys late tonight into Wednesday morning. Lows will be in the 60s to low 70s.

Confidence in the near term is high.

..As of 240 AM EDT TUESDAY

Key Messages:

1) Daily pulse convection

A classic summertime stalled front will take up residence just to the north of the forecast area. This will leave us on the southern warm and humid side of the boundary. As a series of short waves move along the boundary through the week, it will work in tandem with the already existent instability to force mainly pulse-type single cellular convection. Modest shear may allow a few storms to become more organized and sustained long enough to form a small multicell system. There is a marginal risk for severe thunderstorms on Wednesday, and given a similar atmospheric setup through the end of the week, it is entirely within the realm of possibility to be alert for severe thunderstorms each afternoon/evening in this forecast period.

In addition, the daily nature of convection brings concerns of localized flooding, as any particular area that receives heavy rain multiple days in a row could experience flooding due to saturated ground.

..As of 300 AM EDT TUESDAY

Key Messages:

1) Showers and storms continue

2) Frontal passage early next week changes pattern

The situation described in the short term discussion will last through most of the weekend, as no progressive system passes through to cause a change in pattern or air mass. There are signals pointing towards a cold front moving through the Midwest and into the OH River Valley late Sunday or early next week. This would pick up the stationary front and give us a change in airmass from the hot and humid. Another round of showers would be associated with the front, but then a period of quieter weather would likely follow. There is considerable uncertainty in this front's timing and impacts on the local weather at this juncture however.

EXTENDED AVIATION OUTLOOK

The forecast continues in a typical summertime weather pattern with daily chance of showers/storms during the peak heating hours each day through the end of the work week. Morning fog will also be possible each day, especially at LWB and BCB.

RNK WATCHES/WARNINGS/ADVISORIES

VA...Heat Advisory from 10 AM this morning to 8 PM EDT this evening for VAZ058-059. NC...Heat Advisory from 10 AM this morning to 8 PM EDT this evening for NCZ006. WV...None.