George BM

Verbatim... an elevated supercell/multicellular cluster w/ hail. Surface temps in the upper 40s locally at that time.

That line approaching Charleston, WV means business. It has a tornado warning box the size of some of the STW boxes we get here. Lots of kinks in the line.

Starting wet and possibly thundery.

Forecast Discussion Sunday, April 28, 2024 3:13PM EDT Much of the forecast area remains in a moderate (level 4 of 5) risk of severe weather from the Storm Prediction Center. The west to east frontal boundary remains draped over the region w/ the shortwave and associated area of low-pressure approaching from the west. Temperatures have risen into the mid-80s in most areas w/ unseasonably high low-level moisture (dewpoints into the lower 70sF). This combined with steep mid-level lapse rates (7.5-8C/km) has led to mlcape values exceeding 3,000 J/kg. There’s also a strong westerly flow aloft (700-400mb westerly winds of 60-70kts) contributing to the 65-80 kt effective bulk shear in place when combined with the easterly surface wind component. The unusually strong instability in place will allow storms to be able to take full advantage of this shear without getting ripped apart. Storms are expected to form within the next hour in the mountains west of 1-81 and move eastwards into the region as we go through the afternoon and evening. A few storms may also develop in the region in the general vicinity of the frontal boundary east of the mountains. With the shear in place supercells will be the primary storm-mode. Low-level shear will be high with effective SRH of 200-350m2/s2 commonplace. As a result, supercells could drop a couple of tornadoes, a tornado or two may become significant/long-track especially if it tracks right along the boundary. The strong instability in place combined with at least moderately strong downdraft CAPE (DCAPE: 900-1200J/kg) will also allow for severe downburst wind gusts. A few gusts may approach hurricane-force. With “fat-CAPE” particularly between the -10C and -30C level of the atmosphere, very large to giant hail may be common with these storms leading to extensive roof damage. Over time supercells may congeal into multicellular storm clusters, especially with additional storms that move in from the west allowing for areas to receive multiple rounds of severe storms through the evening. These storms will contain all hazards (tornadoes, severe wind, severe hail). This looks likely to be one of if not this region’s biggest severe weather event in more than a decade. Make sure you have a way to keep updated and get alerted with the severe weather going on, especially considering that storms will likely continue until after most peoples bedtime. Tornado Watch in effect until midnight EDT Monday, April 29, 2024 Hazards: A few tornadoes likely w/ a couple intense tornadoes possible Scattered large hail events w/ isolated very large hail events up to 3.5” diameter likely Widespread damaging winds w/ isolated significant gusts to 80 mph possible Watch Probs: Tor: 70/50 Wind: 80/50 Hail: 80/80 Average storm motion: 270/40

Woah. Kind of surprised to see us into the 15% risk for Tuesday and more surprised to see how far north the risk area extends (into southern PA) given how spring CAD setups usually play out. At a quick glance of the varsity models both the 0z CMC and 0z ECMWF had the warm front well to our south for Tuesday with only the GFS getting the warm front over us. I guess we'll see how this plays out. Now elevated convection/storms, on the other hand, I can see occurring to the north of the front. So, at the least, thunder/lightning is looking fairly likely for a good number of us on Tuesday. The SPC has better tools than we have at our disposal so it's definitely possible that they show something that the varsity models don't for Tuesday. As has been said, we'll see how this plays out and it's at least something severe-wise to track more locally.

A vibrant sunset will commence shortly.

SPC has that area in a 15% risk for that day. Slowly starting to warm up.

A number of birthdays in here today. Happy carrot cake/IPA day to those of you celebrating.

In the mountains to the west.

Starting to notice the smell of smoke and a slight "oranging" of the sun from the fires that have developed this afternoon in the mountains.

+17 at IAD.

IAD at 70/29.

I'd personally go with a completely cloudy totality. To see it go pitch black night in the middle of the afternoon is certainly quite the experience regardless of the weather... IMO at least.

IAD has hit 75F this afternoon.

12/06/2023: T (brief light graupel (~2:25pm)) 12/11/2023: 0.9" ( Fairly heavy wet snow overnight... heaviest between 2:45 and 3:35am) 1/01/2024: T (Flurries w/ some graupel from late morning into the afternoon before changing to very light rain/drizzle) 1/06/2024: T (Morning sleet w/ few flakes before changing into a cold soaking afternoon rain) 1/14/2024: T (Moderate snow squall around 11am. Some ground whitening at the bottom of fences) 1/15-16/2024: 4.5" (Light snow started in the 2am hour (15th) continued mostly uninterrupted as flurries/light snow rimmed flakes through the day. Picked up to moderate at times between 7-11pm. Some light snow/freezing drizzle continued into the wee hours of the 16th. Freezing drizzle continues as of this morning.) 1/19/2024: 4.1" (Snow started in the 2am hour<-- (sound familiar?) and was moderate to maybe even modestly heavy at times (heaviest rates in the 5am hour (~1"/hr)). Flurries to light snow between 6am and 9am followed by light to occasionally moderate snow between 9am and 11am. Snow slowly tapered down to flurries through the early/mid afternoon before briefly mostly ceasing in the 3pm hour. Moderate snow squalls moved through during the 4pm hour.) 2/13/2024: 0.6" (Following a roughly 5-7am lull in the rain, precip changed over to snow between 7:10am and 7:20am w/ moderate to moderate/heavy snow until it was nearing 9am followed by light snow until around 9:30am. Temp bottomed out at 34F.) 2/17/2024: 1.5" (Snow started in the 12am hour (could've been a few raindrops mixed in). The snow became fairly heavy during the 1am hour (1-1.5"/hr rates), continued light/moderate during the 2am hour and mostly tapered off by 3am. 2/24/2024: T (Flurries between 5pm and 6:15pm. Briefly up to flurries/very light snow intensity around 6pm w/ slightly bigger flakes.) 3/10/2024: T (Occasional wet flurries between 4:25pm and 5:30pm. Briefly at flurry/very light snow intensity w/ few raindrops mixed in between 5:17pm and 5:25pm.) 2023-2024 winter total as of Mar 12, 2024: 11.6"

IAD w/ a gust to 47kts just now.

Wild wild west.

Happy Meteorological/Climatological Spring. A seasonal start it appears.

Forecast Discussion Saturday, March 16, 2024 3:28PM EDT Blizzard Warning in effect from 8AM EDT Sunday, March 17, 2024 until 3PM EDT Monday, March 18, 2024 High Wind Warning in effect from 9AM EDT Sunday, March 17, 2024 until 6PM EDT Monday, March 18, 2024 Hurricane-Force Wind Warning in effect from 2PM EDT Sunday, March 17, 2024 until 6AM EDT Monday, March 18, 2024 (for tidal-Potomac and Chesapeake Bay) Life-Threatening Late-Winter Storm to cripple the region. Temps are currently holding in the mid-50sF across the DC metro area but are already starting to fall in far northern Maryland as the cold front associated with the strong northern stream system drops south through the region. Temps will plummet out of the 50s and through the 40s and 30s through the evening and reach the lower 20s in many areas by morning as the unusually cold airmass pushes in. As this occurs through the late afternoon and evening hours skies will become overcast both from lift associated with the southward moving cold front and from the strong southern stream system to our south/southwest. There may be enough lift and moisture associated with the front for some light sprinkles and/or a few flurries/light snow showers to develop through the evening before precip slips to the southeast. Northerly winds will become quite gusty during this time with gusts of 25 to 40 mph. As the strong southern storm system moves toward the coastal Carolinas tonight it will begin to phase with a second powerful northern stream vort diving south from the eastern Great Lakes/ Toronto region leading to strong diffluence over the surface low leading to rapid deepening. The two will pinwheel around each other as they phase bringing the southern storm and associated surface low northwards as rapid deepening takes place allowing snow to overspread the region by morning from southeast to northwest. The snow will quickly become heavy as NE winds increase with gusts to over 50 mph across the region likely by midday. Temperatures during this time will be in the lower 20sF leading to windchills in the single digits. By the late afternoon/evening the surface low will slow down and eventually stall over the Virginia peninsula/ southern Chesapeake Bay area. The surface pressure could be as low as the mid-950s in millibars breaking monthly low-pressure records in that area. Meanwhile, the areas northwest of the surface low (the greater Washington DC and Baltimore metros) will be getting the worst of this storm with blinding snowfall and widespread 60-75+ mph wind gusts w/ 80-90+ mph gusts along the coast of the Bay. In fact, snowfall rates in the heaviest bands will likely be in the 4-6”+/hr range leading to visibilities as low as 50 feet (effectively zero visibility for the sake of argument) from the late afternoon hours through the night and into Monday morning. Temperatures will remain in the 20s throughout the duration of this event with upper teens possible in the higher elevations north and west and temperatures closer to 32F in far southern MD and along the bay where warmer air will be located near the surface low. Windchills during the duration of the event will stay in the single-digits for most w/ negative single-digits in the mountains and lower teens in southern MD and along the bay. Near-whiteout and conditions and severe wind gusts will still be ongoing by dawn Monday as the low-pressure system slowly pulls northeastwards. Heavy snow will continue through the late morning to midday hours before tapering off from west to east. When all is set and done with total liquid-equivalent precipitation of 4-7”+ across the region, snowfall totals of 4 to 6 FEET will likely be commonplace with snow drifts of as high as 30 feet possible. Areas in southern MD and near the Bay may end up with slightly less (roughly 2 to 4 feet) as the warmer air associated with the low-pressure center cuts down on totals in that area. This will be the worst blizzard, by far, to impact the region since weather records started in the later 1800s. It will essentially be a high-impact hurricane with snow instead of rain as the main precip-type. People who venture outside during this time may get disoriented and lost in the whiteout conditions and/or get seriously injured by flying debris. Emergency services may not be able to reach you for days should something happen to you outside. This is the DC and Baltimore urban corridor not Lake Tahoe or the Japanese Alps. We’re not equipped with the snow removal equipment that they have. So, if you absolutely must venture outside during the storm no caution that you use would be too extreme given the circumstances. Temperatures will only rebound to the lower 30s as skies start clearing by mid to late afternoon on Monday. Forecaster Wannabe: George BM

IAD with a gust to 51kts (59mph).

Yeap that's right around the time that the front should be moving through IAD give or take 15-30mins. What kind of plane are you flying in, btw? Boeing 757? 767?

That MRGL has since been expanded east across the region for the 13z update.

IAD at 69F tying its record high for the day from 2002.

12/06/2023: T (brief light graupel (~2:25pm)) 12/11/2023: 0.9" ( Fairly heavy wet snow overnight... heaviest between 2:45 and 3:35am) 1/01/2024: T (Flurries w/ some graupel from late morning into the afternoon before changing to very light rain/drizzle) 1/06/2024: T (Morning sleet w/ few flakes before changing into a cold soaking afternoon rain) 1/14/2024: T (Moderate snow squall around 11am. Some ground whitening at the bottom of fences) 1/15-16/2024: 4.5" (Light snow started in the 2am hour (15th) continued mostly uninterrupted as flurries/light snow rimmed flakes through the day. Picked up to moderate at times between 7-11pm. Some light snow/freezing drizzle continued into the wee hours of the 16th. Freezing drizzle continues as of this morning.) 1/19/2024: 4.1" (Snow started in the 2am hour<-- (sound familiar?) and was moderate to maybe even modestly heavy at times (heaviest rates in the 5am hour (~1"/hr)). Flurries to light snow between 6am and 9am followed by light to occasionally moderate snow between 9am and 11am. Snow slowly tapered down to flurries through the early/mid afternoon before briefly mostly ceasing in the 3pm hour. Moderate snow squalls moved through during the 4pm hour.) 2/13/2024: 0.6" (Following a roughly 5-7am lull in the rain, precip changed over to snow between 7:10am and 7:20am w/ moderate to moderate/heavy snow until it was nearing 9am followed by light snow until around 9:30am. Temp bottomed out at 34F.) 2/17/2024: 1.5" (Snow started in the 12am hour (could've been a few raindrops mixed in). The snow became fairly heavy during the 1am hour (1-1.5"/hr rates), continued light/moderate during the 2am hour and mostly tapered off by 3am. 2/24/2024: T (Flurries between 5pm and 6:15pm. Briefly up to flurries/very light snow intensity around 6pm w/ slightly bigger flakes.) 2023-2024 winter total as of Feb 25, 2024: 11.6"

Down to 21F at IAD.