high risk Posted November 15, 2020 Share Posted November 15, 2020 4 hours ago, CAPE said: From Mount Holly AFD regarding convection/wind potential tomorrow- As the aforementioned shortwave trough passes quickly to our north into the afternoon, heights will be falling rapidly (as will surface pressure) and widespread rain showers are expected to develop. These convective showers could help mix down some of the stronger winds from the developing low level jet. However the main feature of interest from a convective standpoint is the potential for power showers, or a power squall, to develop along the cold front as it passes quickly across the region from west to east. The primary timing of this appears to be the 4 PM to 8 PM time frame. Dewpoints will be surging quickly to near 60 degrees ahead of the cold front allowing for a brief window of MLCAPE in the 200-300 J/kg range. Guidance is notorious for under forecasting dewpoints/low- level moisture profiles in these regimes, so I tend to think dewpoints and CAPE values will be at least slightly higher than guidance currently suggests. This combined with ample forcing aloft, boundary parallel effective shear of about 45 kts, and strong low- level kinematic fields will support a line or broken line of convection along or just ahead of the cold front. This line may be capable of mixing down wind gusts on the order of 50 kts, which may prompt the issuance of a few Severe Thunderstorm Warnings. And yes, a few rumbles of thunder are possible as well. This setup remains quite marginal from a severe convective potential, but we will continue to evaluate. CAMs are very emphatic about a forced line of convection sweeping across the area later Sunday. Mixing down some strong winds to the surface and/or getting some lightning are both on the table although not particularly likely due to very weak instability. 1 Link to comment Share on other sites More sharing options...
high risk Posted November 15, 2020 Share Posted November 15, 2020 2 hours ago, losetoa6 said: 3k inspires some confidence. Looks like a decent squall line for November around 23z 0z There is no argument that there will be a strongline of convection later Sunday moving across the area - the radar will look nice. My questions are whether it will have lightning and whether it can produce strong wind gusts. The forecast soundings just don't have enough instability for lightning - stronger wind gusts are a better possibility, although they should stay below severe limits. if instability is greater than progged, some lightning and gusts near the severe threshold would be on the table. 1 Link to comment Share on other sites More sharing options...
yoda Posted November 15, 2020 Share Posted November 15, 2020 4 hours ago, high risk said: There is no argument that there will be a strongline of convection later Sunday moving across the area - the radar will look nice. My questions are whether it will have lightning and whether it can produce strong wind gusts. The forecast soundings just don't have enough instability for lightning - stronger wind gusts are a better possibility, although they should stay below severe limits. if instability is greater than progged, some lightning and gusts near the severe threshold would be on the table. MRGL risk from SPC today for isolated damaging wind gusts Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1158 PM CST Sat Nov 14 2020 Valid 151200Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL APPALACHIANS AND MID-ATLANTIC... ...SUMMARY... Thunderstorms associated with strong wind gusts will be possible this afternoon and evening across parts of the central Appalachians and Mid-Atlantic. ...Central Appalachians/Mid-Atlantic... An upper-level trough will move quickly east-northeastward across the southern Great Lakes region today. The system will become negatively tilted as a band of strong large-scale ascent moves into the central Appalachians. At the surface, a cold front will advance eastward into the central Appalachians with a pre-frontal trough developing ahead of the front. Thunderstorms will likely be ongoing along the pre-frontal trough at the start of the period across the Ohio and Tennessee Valleys. This line will move quickly eastward into the central Appalachians by midday. Ahead of the line, a corridor of maximized low-level moisture will exist with surface dewpoints mainly in the 50s F. This will be enough for weak destabilization ahead of the line. By afternoon, RAP forecast soundings have peak instability reaching the 200 to 400 J/kg range. This combined with extreme deep-layer shear of 100 to 110 kt and 40 to 50 kt winds just above the surface, should enable a fine line to develop. The fine line is expected to quickly move across the Appalachian crest eastward into the foothills and coastal areas during the late afternoon and early evening. Isolated damaging wind gusts will be possible with this line of storms. A marginal risk has been introduced in this outlook for much of Pennsylvania, Maryland and northern Virginia extending eastward to the Mid-Atlantic coast. ..Broyles/Squitieri.. 11/15/2020 Link to comment Share on other sites More sharing options...
CAPE Posted November 15, 2020 Share Posted November 15, 2020 Low of 36 here. Currently 39 as the sun comes up. Link to comment Share on other sites More sharing options...
high risk Posted November 15, 2020 Share Posted November 15, 2020 With the 1630 upgrade to SLGT, it's time to move discussion of the convective line over to the severe thread. Link to comment Share on other sites More sharing options...
WxUSAF Posted November 16, 2020 Share Posted November 16, 2020 Yay, we’re number 1! 1 Link to comment Share on other sites More sharing options...
JakkelWx Posted November 16, 2020 Share Posted November 16, 2020 Only thing noteworthy weather wise for the next 5 days are the temperature drops as soon as the sun goes down. For example it's already gone from the low 60s to the low 50s in less than an hour. 6:52 PM edit: 44/35 Link to comment Share on other sites More sharing options...
CAPE Posted November 16, 2020 Share Posted November 16, 2020 48 here after a high of 59. Link to comment Share on other sites More sharing options...
WEATHER53 Posted November 17, 2020 Share Posted November 17, 2020 So 27-32 around DC Tuesday and Wed night? Link to comment Share on other sites More sharing options...
CAPE Posted November 17, 2020 Share Posted November 17, 2020 Low of 34 here. Link to comment Share on other sites More sharing options...
mappy Posted November 17, 2020 Share Posted November 17, 2020 32 currently Link to comment Share on other sites More sharing options...
midatlanticweather Posted November 17, 2020 Share Posted November 17, 2020 Down to 31.6 degrees for the low. Gonna be a Chilly day! Link to comment Share on other sites More sharing options...
frd Posted November 17, 2020 Share Posted November 17, 2020 Coldest reading so far this Fall at 34 degrees. Link to comment Share on other sites More sharing options...
dailylurker Posted November 17, 2020 Share Posted November 17, 2020 43 wtf lol. I don't think I've hit 38 yet this flaming turd season so far. Link to comment Share on other sites More sharing options...
mappy Posted November 17, 2020 Share Posted November 17, 2020 1 hour ago, mappy said: 32 currently dipped to 29.8 before heading back up again Link to comment Share on other sites More sharing options...
WxUSAF Posted November 17, 2020 Share Posted November 17, 2020 A bit under 35 for a low, which might be coldest yet this fall. Pretty sad for mid November. First freeze should be tomorrow morning. Link to comment Share on other sites More sharing options...
EastCoast NPZ Posted November 17, 2020 Share Posted November 17, 2020 According to the nearest PWS, I got down to 27F around 3AM and then rose to 43F by 430, then fell back down to 33 before sunrise. WTF. And now up to 47F an hour later. ?? The wind is cranking here - again. Link to comment Share on other sites More sharing options...
Potvinsux Posted November 17, 2020 Share Posted November 17, 2020 Front just came through Snowshoe with some very gusty winds. Light snow now falling. Last chance for them to make snow in order to open Thanksgiving. Link to comment Share on other sites More sharing options...
George BM Posted November 17, 2020 Author Share Posted November 17, 2020 7 minutes ago, EastCoast NPZ said: According to the nearest PWS, I got down to 27F around 3AM and then rose to 43F by 430, then fell back down to 33 before sunrise. WTF. And now up to 47F an hour later. ?? The wind is cranking here - again. Between 3am and 4:30am is when cloud cover moved over YBY. You had probably decoupled allowing the temperature to fall to 27F. But when the clouds moved over you the added insulation allowed the warmer air just above the surface to mix down to the surface ( it probably got a bit breezy during that time there). Then those clouds moved away from you after 4:30am allowing radiational cooling to start doing it's work again. Link to comment Share on other sites More sharing options...
EastCoast NPZ Posted November 17, 2020 Share Posted November 17, 2020 7 minutes ago, George BM said: Between 3am and 4:30am is when cloud cover moved over YBY. You had probably decoupled allowing the temperature to fall to 27F. But when the clouds moved over you the added insulation allowed the warmer air just above the surface to mix down to the surface ( it probably got a bit breezy during that time there). Then those clouds moved away from you after 4:30am allowing radiational cooling to start doing it's work again. Must have because it was crystal clear when I went to bed and crystal clear again at dawn. Cloudy now here. Link to comment Share on other sites More sharing options...
George BM Posted November 17, 2020 Author Share Posted November 17, 2020 Just now, EastCoast NPZ said: Must have because it was crystal clear when I went to bed and crystal clear again at dawn. Yeap. Can confirm looking at this shortwave IR satellite loop. https://weather.cod.edu/satrad/?parms=subregional-Virginias-07-96-1-25-1&checked=map&colorbar=undefined Link to comment Share on other sites More sharing options...
Eskimo Joe Posted November 17, 2020 Share Posted November 17, 2020 1 hour ago, EastCoast NPZ said: According to the nearest PWS, I got down to 27F around 3AM and then rose to 43F by 430, then fell back down to 33 before sunrise. WTF. And now up to 47F an hour later. ?? The wind is cranking here - again. I thought you moved out of Stephens City? Link to comment Share on other sites More sharing options...
wxdude64 Posted November 17, 2020 Share Posted November 17, 2020 Roller coaster temp wise here, was 29.6 at 2am, rose to 37.7 at 5 am, fell again to 30.0 for the 7 am CoCoRaHS, when it was clear and calm with frost. An hour later it was cloudy with WSW winds 10 mph and the temp up to 41.2!! Crazy. Link to comment Share on other sites More sharing options...
WinterWxLuvr Posted November 17, 2020 Share Posted November 17, 2020 I’m no genius here, and I have not looked to know but I’d say you’ve got some southwesterly wind in front of a cold front. 1 Link to comment Share on other sites More sharing options...
Potvinsux Posted November 17, 2020 Share Posted November 17, 2020 Snowing heavily now! 9 1 Link to comment Share on other sites More sharing options...
EastCoast NPZ Posted November 17, 2020 Share Posted November 17, 2020 49 minutes ago, Eskimo Joe said: I thought you moved out of Stephens City? I did. But I dont think i updated my location, and I don't see it using mobile. I'm just NW of lake holiday in Frederick Co. 1 Link to comment Share on other sites More sharing options...
Eskimo Joe Posted November 17, 2020 Share Posted November 17, 2020 2 minutes ago, EastCoast NPZ said: I did. But I dont think i updated my location, and I don't see it using mobile. I'm just NW of lake holiday in Frederick Co. You're actually in a very good position for storms that run a bit inland. While DCA will be 40 and rain, you'll still stand a fighting chance of a mix or some frozen. 1 Link to comment Share on other sites More sharing options...
EastCoast NPZ Posted November 17, 2020 Share Posted November 17, 2020 1 hour ago, George BM said: Yeap. Can confirm looking at this shortwave IR satellite loop. https://weather.cod.edu/satrad/?parms=subregional-Virginias-07-96-1-25-1&checked=map&colorbar=undefined Awesome. Thanks for that link. Transient clouds really screwed up what could have been a really hard freeze. Link to comment Share on other sites More sharing options...
CAPE Posted November 17, 2020 Share Posted November 17, 2020 50 minutes ago, WinterWxLuvr said: I’m no genius here, and I have not looked to know but I’d say you’ve got some southwesterly wind in front of a cold front. Yup. Pretty standard stuff. Temp was 34 here at 430am, and by 6am it was 43. Link to comment Share on other sites More sharing options...
EastCoast NPZ Posted November 17, 2020 Share Posted November 17, 2020 2 minutes ago, Eskimo Joe said: You're actually in a very good position for storms that run a bit inland. While DCA will be 40 and rain, you'll still stand a fighting chance of a mix or some frozen. I sure hope so. Unfortunately, I'm also in a really good place for wind. Link to comment Share on other sites More sharing options...
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