textproduct: Blacksburg

SYNOPSIS

A quasi-stationary front will remain draped across the area today into the weekend, with widespread showers and storms expected. Flash flooding will be possible each day, as storms may train from west to east. Damaging winds are also possible today, particularly in the Piedmont. The pattern continues through the weekend before a cold front clears things out Tuesday into the middle of next week.

NEAR TERM /THROUGH SATURDAY/

AS OF 215 PM EDT Friday...

Key Messages:

1) Flood Watch in effect for the entire area through midnight tonight.

2) Widespread showers and storms will continue to form today along and south of a stationary front.

3) Severe storms are possible, with damaging winds as the threat.

A quasi-stationary front has now sagged south into the RNK CWA today, and will continue to be the trigger for widespread to numerous showers and storms across the area. Storms have already formed across WV/KY and are moving into the western CWA. Scattered showers/storms across the rest of the area will continue to develop and fill in as daytime heating increases over the next few hours. Flash flooding will be a concern, due to a very moist airmass with seasonably high PW values near 2.0". Rainfall rates will continue to be efficient, which could cause flooding in urban and low-lying areas, especially with recent heavy rainfall in parts of the area. Mid-level flow will keep storms moving eastward at a decent rate, which will help limit flooding potential, but due to the east to west orientation of the front, training storms could become an issue. Clear skies across the Piedmont has allowed CAPE to rise, overcoming the early day CIN. This will support strong to severe storms this afternoon. The entire area is in a Marginal Risk, with a Slight Risk from Roanoke eastward. Damaging winds will again be the threat, but the risk is more elevated than the last few days, thanks to the front providing more shear across the area. Storms progress eastward through the rest of the afternoon and into the evening hours before dissipating overnight with the loss of daytime heating.

Saturday will see a similar setup, with the front remaining stalled over the area, which will again instigate widespread showers and storms during the afternoon and evening hours. Moisture will further increase in the mid-levels, as the low along the Gulf Coast will ride around the high pressure ridge over the Southeastern US and work into our area late Saturday. Flash flooding will remain a concern as heavy rainfall will be expected with the potential for training storms to occur. Severe weather does not look likely tomorrow, due to heavier cloud cover, which will limit instability. However, isolated damaging winds cannot be ruled out in the strongest convection.

Temperatures remain slightly above average, with highs today in the low 80s for the mountains, and low 90s for the Piedmont. Overnight lows will fall into the mid 60s to low 70s. Tomorrow will be a degree or two cooler, with upper 70s in the highest elevations to around 90 in the Piedmont, due to more cloud cover anticipated.

SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/

As of 1230 PM EDT Friday...

Key Messages:

1) Mostly dry Sunday then storms likely Monday.

2) Any stronger storms Monday pose a risk of localized flash flooding, damaging winds, and frequent lightning.

A trough of low pressure will move east across the region Saturday night. This trough will push convection east of the VA/NC piedmont Saturday evening. Only notable change behind the trough will be a west wind, which will help limit showers to the western slopes Sunday. A backdoor cold front will track across the area Sunday night into Monday. Behind this front will be a noticeable change in the weather with cooler temperatures and drier air. As this front travels south across the area Monday, scattered showers and thunderstorms are possible with the stronger storms developing along and south of the VA/NC border during the late afternoon and evening hours. Any of the stronger storms Monday may cause heavy rainfall leading to localized flash flooding, damaging winds from wet microbursts that could blow down trees and power lines, and frequent lightning.

High temperatures Sunday will range from 80s across the mountains to lower 90s in the foothills and Piedmont. Slightly cooler temperatures are expected Monday as the front slowly moves over the area. Highs Monday will range in the 80s with the cooler temperatures to the north.

LONG TERM /TUESDAY THROUGH FRIDAY/

As of 1245 PM EDT Friday...

Key Messages:

1) Dry weather for most through the period.

2) Cooler than normal temperatures Tuesday moderating warmer each day through next weekend.

Dry surface high pressure with a cool east wind will make for a nice day across the region Tuesday. High temperatures will run from the upper 70s to lower 80s. An upper level ridge will track east from the Midwest Tuesday to the Mid Atlantic states on Thursday. This heat dome will have temperatures warming above normal by the weekend. The chance for afternoon and evening thunderstorms will also return next weekend.

EXTENDED AVIATION OUTLOOK

The stagnant weather pattern remains in place through the weekend and into early next week, with daily chances for afternoon showers and storms that would bring sub-VFR conditions when they impact terminals. Nightly patchy fog will remain a possibility, limiting VSBY during the early morning hours to sub-VFR and lowering cigs. Otherwise, VFR conditions will remain in place when not impacted by convection or fog. By Tuesday, a cold front moves through the area, with quieter weather and prevailing VFR conditions expected at all terminals into midweek.

HYDROLOGY

As of 230 PM EDT Friday...

A Flood Watch continues for the entire forecast area through midnight tonight, as there is a slight risk (level 2 of 4) for excessive rainfall.

Streams across the hydrologic service area are generally running above normal. Parts of the Dan River and upper James River basins are near the 90th percentile. Most other basins are between the 50th and 90th percentile...not your typical July.

Showers and storms will be very "efficient", meaning that with high moisture content in the air, with PW values near 2.0", that even a small storm can produce very heavy rainfall in a short amount of time. Rainfall rates of 2-4" per hour are possible this afternoon into this evening. Modest westerly flow will keep storms moving east at a decent rate, but storms could train over the same areas, and possibly backbuild along the stalled front draped across the area.

WPC has highlighted an area just north of our county warning area (the Shenandoah Valley) with a moderate risk, level 3 of 4, for excessive rainfall. Those counties which border this moderate risk will have the greatest chance for receiving excessive rainfall this afternoon...Bath, Alleghany, Rockbridge, Botetourt, Amherst, Bedford, City of Lynchburg, Buckingham, Appomattox, and Charlotte. 1 hour flash flood guidance (FFG) in these areas is 1.5 inches in an hour. 3 hour FFG and 2.5 inches. 6 hour FFG is around 3 inches. Rain rates expected with these storms may eclipse 4 inches an hour. Emergency Managers within our bordering counties should take note because there is always some margin of error in the models with respect to geographic placement of these outlooks.

As for the remainder of our service area, we are still looking at airmass (peak heating of the day) driven storms that will be rain efficient...with potential for localized flash flooding in low-lying or flood prone areas, along with urban flooding also possible. Storms will drift into the foothills and piedmont through the afternoon and into this evening before dissipating overnight with the loss of daytime heating.

RNK WATCHES/WARNINGS/ADVISORIES

VA...Flood Watch until midnight EDT tonight for VAZ007-009>020- 022>024-032>035-043>047-058-059. NC...Flood Watch until midnight EDT tonight for NCZ001>006-018>020. WV...Flood Watch until midnight EDT tonight for WVZ042>044-507-508.