textproduct: Blacksburg
This forecast discussion was created in the public domain by the National Weather Service. It can be found in its original form here.
SYNOPSIS
High pressure will remain wedged down the east side of the Appalachians through Tuesday. The chance of rain increases across the area on Tuesday through Thursday as moisture advects into the areas between the high offshore and a low pressure system over the Ohio and Tennesse Valleys. Temperatures remain above normal for the rest of the week.
NEAR TERM /THROUGH MONDAY/
As of 1250 PM EST Sunday
Key message:
- More clouds on Monday
Pressure gradient tightens tonight and Monday increasing wind speeds. The center of the main surface high moves offshore of New England on Monday but wedge will still be in place over central Appalachians. As the southeast wind becomes stronger downslope component will add warming on the western side of the mountains. Clouds will fill in Monday over the foothills and piedmont, limiting the amount of heating. Will be increasing the maximum temperatures in the Mountain Empire area and wind gusts for Mercer and Tazewell Counties. Also plan to lower the maximum temperatures a couple degrees east of the Blue Ridge.
SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/
As of 220 PM EST Sunday...
Key Messages:
1). Classic wedge holds temperatures down somewhat Tuesday with northeast flow and more clouds. Some light rain or drizzle possible Monday night into Tuesday along the southern Blue Ridge.
2). Precipitation chances increase Wednesday as a frontal system approaches from the west and we see an increasing fetch of Gulf moisture develop across the region.
As the strong and high amplitude 591-594dm subtropical ridge that has provided us with mainly dry weather and above normal temperatures over the past week or so shifts east and a deep upper trough in the western U.S. slowly progresses eastward, our weather conditions will become increasingly unsettled, especially during the later half of the week.
During this period, the two above mentioned synoptic features will combine to help result in a classic wedge developing across the region as Canadian high pressure slides into a position across New England and the northern ATlantic. Northeast to east flow will gradually become more southeasterly going into Tuesday morning potentially resulting in light rain or drizzle and fog along the southern Blue Ridge until about mid-day on Tuesday.
As the period progresses, our attention will turn toward a frontal system approaching from the west and a conveyor belt of Gulf moisture tracking northeastward into the region sandwiched between the strong upper ridge to our east and the deep trough to our west. While the front will be weakening, the lingering boundary could serve as a focusing mechanism for showers, especially on Wednesday.
Temperatures will remain above normal through the period. Unseasonably high dewpoints streaming north from the Gulf of Mexico will result in very mild nights in the 50s, well above normal for early November. Clouds will not be solid during the daytime with periodic breaks in the clouds resulting in glimpses of sunshine and warming. High temperatures will be mostly in the 60s west to the 70s east, a good 10-15 degrees above normal.
/Confidence Levels in Forecast Parameters/ - Moderate Confidence in Temperatures, - Low to Moderate Confidence in Precipitation Probabilities, - Moderate Confidence in Wind Direction and Speed.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
As of 245 PM EST Sunday...
Key Messages:
1). Keeping a close eye on Potential Tropical Cyclone No. 18 (potentially named later in the week) moving north through the eastern Gulf of Mexico.
2) Stalled frontal system across the region likely an important component to "if" and "where" PTC #18 will track.
3) Temperatures to remain well above normal on the order of 20 degrees above normal for lows and 10-15 degrees above normal for highs.
Expectations are that the subtropical ridge to our southeast and the deep trough to our west will be in a favorable position during the later half of the week for a conveyor belt of deep Gulf moisture to track north toward the region. However, an increasingly split flow evolving aloft may allow a west-east oriented frontal boundary to sag southward through the region and stall across the Carolinas. Meanwhile, what is currently PTC #18 in the Caribbean will likely be in the eastern Gulf. Models have come into better agreement on the development of PTC #18, but not on its evolution and track once it reaches the Gulf. Nonetheless, even if the actual cyclone itself does not track toward/through our region, there does appear to be the potential for a Predecessor Rain Event as PTC #18 (potentially a named storm by then) is moving north through the eastern Gulf of Mexico. The stalled frontal boundary would be in a favorable position for such a rain event. We shall see, but there are some subtle signs that this is a possibility with most of the long range models. The best chance for rain from this type of scenario would be on Thursday.
Beyond Thursday, the forecast becomes increasingly uncertain and problematic focused on the movement of PTC #18. Will it head north and through our region or will it turn toward the west as a preponderance of the long range models suggest right now. If the front sags far enough to the south, drier air would work into the area and keep in heavier rain well to our south.
At any rate, temperatures will remain well above normal. With dewpoints hovering around 60, well above normal for November, nighttime temperatures will be very mild for early November holding mostly in the 50s and 60s, some 20+ degrees above normal. Clouds and precipitation will hold down daytime temperatures, but they will still average 10-15 degrees above normal in the 60s west to the 70s east.
/Confidence Levels in Forecast Parameters/ - Moderate to High Confidence in Temperatures, - Moderate Confidence in Precipitation Probabilities, - Moderate Confidence in Wind Direction and Speed.
AVIATION /20Z SUNDAY THROUGH FRIDAY/
As of 1255 PM EST Sunday...
Starting VFR across southwest Virginia, northwest North Carolina and southeast West Virginia this afternoon through early Monday morning.
Pressure gradient tightens tonight and Monday increasing wind speeds. The center of the main surface high moves offshore of New England on Monday but wedge will still be in place over central Appalachians. Southeast downslope wind gusts up to 20 knots are expected on the west side of the Appalachians, including at KBLF.
High clouds spread in from the west overnight. Then lower clouds will fill in Monday over the foothills and piedmont due to the upslope southeast wind. Bufkit forecast soundings have ceilings lowering to MVFR mainly after 09Z/5AM with little until after 14Z/9AM.
Average confidence for timing of lower clouds Monday morning. Above average confidence for wind and visibility.
EXTENDED AVIATION OUTLOOK...
More MVFR clouds in the foothills and piedmont are possible on Monday night, along with a low chance of light rain and MVFR fog.
Wednesday and Thursday, a frontal system approaches the region with showers possible. These will likely be confined to LWB/BLF, possibly lowering flight conditions to MVFR.
High pressure and dry weather are expected to build into the region with VFR flight conditions on Friday.
RNK WATCHES/WARNINGS/ADVISORIES
VA...None. NC...None. WV...None.
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