![National Oceanic and Atmospheric Administration](/build/images/header/noaa.d87e0251.png)
![National Weather Service](/build/images/header/nws.4e6585d8.png)
![United States Department of Commerce](/build/images/header/doc.b38ba91a.png)
Area Forecast Discussion
Issued by NWS Blacksburg, VA
Issued by NWS Blacksburg, VA
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
169 FXUS61 KRNK 151457 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1057 AM EDT Thu Aug 15 2024 .SYNOPSIS... High pressure will keep our weather mainly dry through tonight. A front will bring a better opportunity for showers and storms Friday into the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 1045 AM EDT Thursday... No change to near term forecast. Regional soundings remain dry above 700 mb, so cu development will be hard pressed to get any depth. Exception will be along the Appalachian Divide, TNB- BLF, where increasing moisture from the southwest will begin to infiltrate aloft promoting weak CAPE, cloud build-ups and isolated showers. Key Message: Mainly dry/quiet weather through tonight. High pressure centered to our north will provide another dry day today, though a warm front lifts across the TN/OH Valleys this afternoon. Cannot rule out a few showers across the mountains, but most stay dry with mostly sunny skies. Temperatures through the near term will be close to normal. Patchy fog possible again early this morning favoring the rivers valleys. Tonight, a 500mb ridge will be over the area, while trough approaches from the upper Midwest. The ridge aloft and high pressure at the surface will keep conditions dry through early Friday morning, though looking at increasing clouds with warm front an potential for a few showers making it to our far southwest VA into southern WV counties around dawn. && .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/... As of 115 AM EDT Thursday... Key Points: 1. Showers/Storms expected each day. 2. Locally heavy rain possible Friday into Friday night, especially western sections. 3. Temperatures trending milder to slightly above normal values. A look at the 14 Aug 12Z NCEP Ensemble Mean 500 mb Geopotential heights shows a shortwave trough over the Upper Mississippi Valley that progresses slowly eastward. As it moves east, it gradually become more amplified with its axis over our region by late Sunday night. At the surface, on Friday, a ridge of high pressure will be situated along the US East Coast. Low pressure will be over the Upper Mississippi Valley. As we progress through the weekend, the low pressure is expected to progress eastward, reaching the area of PA/NY/NJ by late Sunday night. An associated cold front is expected to cross our region late Saturday night into early Sunday morning. Output from the 14 Aug 12Z Ensemble Situational Awareness Table shows 850mb temperatures ranging from +16C to +18C on Friday, +17C to +19C on Saturday, and +16C to +17C on Sunday. Precipitable Water values are expected to range from 1.25 to 1.50 inch on Friday, 1.50 to 1.75 inch on Saturday, and 1.25 to 1.50 inch on Sunday. The values on Friday into Friday night that reach or top 1.75 inch falls within the 90 to 97.5 percentile of the 30-year climatology. Mean Integrated Water Vapor Transport is expected to reach a maximum of 400 to 500 units Friday night into Saturday across the region. This range of values corresponds to the 90 to 97.5 percentile of the 30- year climatology for this parameter. The above weather scenario offers a forecast with good chances of showers and storms in advance of and coincident to the passage of a cold front. Precipitable Water values over 1.75 inch on Friday and well above normal moisture transport Friday night through Saturday point at this time period for the best opportunities for locally heavy rain, especially across western sections. While the cold front is expected to cross the region late Saturday night into early Sunday, the parent upper trough is not expected to reach our area until late Sunday night. With this feature still approaching, we will continue to have showers/storms in the forecast Sunday/Sunday night, just not the level of coverage prior to the frontal passage. Temperatures during this portion of the forecast will trend milder into the weekend. Confidence in this portion of the forecast is moderate to high. && .LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 115 AM EDT Thursday... Key Points: 1. Precipitation chances trending lower each day, with the best chances on Monday. 2. Temperatures trending cooler to near or slightly below normal values. A look at the 14 Aug 12Z NCEP Ensemble Mean 500 mb Geopotential heights shows an upper trough over our area Monday morning. Through Wednesday, this feature is expected to make little to no headway eastward. Rather, it loses its amplification as it experiences overall height rises and broadening of the trough. As the surface, a cold front will become stalled along the Southeast US Coast Monday into Tuesday as the center of high pressure moves from the Upper Mississippi Valley into the Ohio Valley. By Wednesday, the front still remains stalled along the Southeast US Coast while the high shifts east toward the mid-Atlantic region. Output from the 14 Aug 12z Ensemble Situational Awareness Table shows 850mb temperatures ranging from +15C to +17C on Monday through Wednesday. Precipitable Water values are expected to be around 1.25 inch on Monday, a little less than 1.00 to a little less than 1.25 inch on Tuesday, and 1.00 to 1.25 inch on Wednesday. An upper level trough parked over the region through Thursday. However, this feature will be weakening each day. Additionally, each day, surface high pressure makes more progress into at least western parts of the region. This combination offers a trend of decreasing potential of showers/storms each day, although with no day have a zero chance over at least some portion of the area. Coverage will be greatest on Monday. Temperatures will trend cooler during this portion of the forecast. Confidence in the above weather scenario is moderate. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... As of 1100 AM EDT Thursday... VFR conditions are expected at all terminals through most of the TAF period. SCT-BKN cumulus field expected this afternoon with cloud build- ups and isolated showers along the Appalachian Divide...BLF-TNB. Winds stay light and shift to the south. Thinking increasing clouds early Friday will limit fog so not adding it to LWB at this point. .EXTENDED AVIATION OUTLOOK... Clouds will increase from the west due to an approaching cold front Friday. This front should bring a good chance of showers and thunderstorms along with potential MVFR/IFR ceilings during Friday-Sunday, with less coverage by Monday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PM/WP NEAR TERM...PM/WP SHORT TERM...DS LONG TERM...DS AVIATION...PM