arlwx12

Tornado watches up to the west of the Blue Ridge from about Luray northward.

Looks like another bunch of shattered high temperatures today. So far, DCA hit 84, IAD and BWI 82. Records at all three airports for the date had been 79.

Might (or might NOT) be a bit stormy tomorrow. From LWX's latest AFD: (snip) KEY MESSAGE 1...Severe Thunderstorms are possible Wednesday afternoon and evening. Tomorrow`s forecast is an extremely challenging one. At this point, there`s a wide range of potential solutions on the table, with very low confidence in which solution will ultimately verify. Forecast details follow below...

Outside, my neighbor's tree has started shedding pollen all over my car. Another neighbor's daffodils may bloom soon. My shaded trees' buds still haven't burst, though.

Totally smashed today's records for the DC-area airports. So far, they have all hit 84. The old records were 79 DCA, 80 at IAD and BWI. Might tie or break records tomorrow (before we plunge back into the cooler).

Back up to a whole quarter-mile plus in South Arlington.

Foggy in south Arlington this morning. Can barely see some lights at 1/4 mile, none at 1/2 mile. Channel 5 in DC warned those about to drive to NOT put on their high-beams.

Some schools (Fairfax and some to the NW) are delayed two hours. Probably to ensure most leftover black ice gets melted/washed away or visible.

Visibility under 1/2 mile here in South Arlington. About 1/4 inch or more on tree branches and shrubs. My Hill of Doom and the sidewalks haven't surrendered yet, though.

Sticking now to shrubs and some grass, trying to do the same for car tops. Visibility probably under a mile now.

Snow flurries in south Arlington. Visibility about 1 mile.

DCA has hit 32. Frost has formed on cars and grass in Arlington.

Despite the NWS noting freezing fog potential for the DC suburbs, it was 35 at DCA with 3 mile visibility. Here in Arlington, the visibility is well over the half-mile to the nearby hilltop.

In Arlington, I think elevation had some impact. Far western Arlington (about 300-350 elevation): 3.5 West of Lake Barcroft (about 250-300 elevation): 2.5 Me (about 100 feet up from DCA): about an inch and a half DCA (just about on the river): 1.0 ((Of course, when I saw the predicted temperatures, I figured DCA didn't have much of a chance. I'm a bit surprised it managed to get an inch despite not hitting 32 for an extended period until shortly before 5 am.))

Thanks!

I Meant LWX. ((Is there some way to edit postings??))

I see LX took down the WWAs for Washington and immediate Baltimore metros.

Took a look out my window uphill from DCA. Looks like around an inch and a half stuck to tree branches and car tops. My Hill of Doom got covered, but it looks like Arlington came through and salted the center of the roadway into submission. Sidewalks vary. Some partially or fully resisted, others did not.

HOW did that car/grasstopper sneak up on me in South Arlington? At least the streets and sidewalks are still clear.

One listing of closings and delays: Closings

DCA finally went down to 34.

I'd guess a 50/50 mix near DCA. Still melting on cars, though.

meant mixing, Not maxing.

OOH! I think there are actual snowflakes maxing in near DCA!

Snip of the 320 LWX AFD... As of 315am, light snow has been observed over the Alleghenies with light to moderate pockets of shower/drizzle over the Shenandoah Valley. Elsewhere, cloud cover continues to increase with some virga as the atmospheric profile begins to moisten with large scale ascent ahead of the approaching upper level trough. Precipitation should begin as a mixture of light rain and snow for most, with all snow above around 1500 feet. Expect precipitation to remain relatively light through mid to late morning then turning steadier later this afternoon as the main lift from the trough/coastal low move overhead. Surface temperatures will initially be in the mid to upper 30s at lower elevations, and should hold in the mid 30s through mid-late afternoon (prior to 6pm). As a result, much of the region will experience several hours of mixed rain and snow "white rain" that won`t accumulate and will largely be unimpactful other than making for wet roads. However, snow will accumulate across the higher elevations (i.e Catoctins, Alleghenies, and crest of the Blue Ridge) above 1500 feet throughout the day. Temperatures will gradually fall later this afternoon and evening as dynamical cooling ensue from the approaching coastal low and upper level trough. The large scale ascent from these features will allow the atmospheric column to cool allowing for the rain/snow mix to transition over to all snow across the forecast region. Temperatures will fall from the mid 30s into the upper 20s and low 30s during this time as the heaviest precipitation moves in Ratios will also climb during this time with 1:1-5:1 ratios outside of the elevations above 1500 feet during the day climbing to 8:1 to 13:1 overnight into Monday morning. Either way expect a wet character to the snow given the high liquid equivalent. This will make it hard to pick up with a shovel (heart attack snow) compared to pushing with a plow or removing with a snow blower. The greatest impact from snow locally is expected later this evening through predawn Monday morning as the coastal low tracks off the Delmarva and the upper axis trough moves overhead. Expect two areas of enhanced snowfall: one with the coastal low that will encompass the western shore of the bay up into the northeast/central MD and another with the inverted trough (or norlun trough) across the Catoctin/Potomac Highlands. In addition to this expect heavy upslope snow/squalls over the Alleghenies given strong north/northwest flow. The first area of enhanced snowfall rates will be close to Chesapeake Bay, where mid- level frontogenetic forcing to northwest of the coastal low will be strongest. Uncertainty remains in how far west this area of heavier snow gets, but most solutions show it only impacting the counties immediately adjacent to Chesapeake Bay in our forecast area (St.Mary`s northward through Cecil). Snowfall rates could approach an 1-2 inches per hour at times in this area between roughly 7 PM and 3 AM. Near blizzard conditions are also possible with gales over the waters and gusts in excess of 30-40 mph. The second area of enhanced snowfall rates will be along an inverted trough axis (sometimes referred to as a Norlun trough) that will extend north to south through north-central portions of the forecast area. Dynamically, this will occur along a low-level trough axis (in the 900-700 hPa layer) where northeasterly winds in response to the developing coastal low offshore converge with northwesterly winds advancing beneath the upper trough. Model guidance remains in good agreement that such a feature will occur, but there is still some uncertainty with respect to the positioning. 00z CAMS have trended slightly west with this features extending from Washington/Frederick counties down through Jefferson/Loudoun/Fauquier counties. Such features typically are very, very narrow in width (likely only 10-20 miles from west to east), and are notorious for producing very heavy snowfall rates. Most guidance shows hourly QPF values of around 0.2- 0.4 inches, which would translate to 1-2 inches per hour of snow. This feature will likely be either stationary or very slow moving over several hours tomorrow evening into early tomorrow night. A narrow band of 6-12 inches could occur as a result. Due to position uncertainty, we spread this enhancement in precipitation out over a slightly wider location than will likely occur in reality. Our current forecast hedges the placement slightly more toward the eastern solution (Washington County to Loudoun County), but has an enhancement over that broader region. This is also why the Winter Storm Warning extends southward in Fauquier Co. and wraps around the DC Metro area. The immediate DC Metro will likely fall within a relative min between these two areas of precipitation enhancement, but will still experience several hours of accumulating snow this evening into tonight. Another localized minimum will be between the inverted trough and the Allegheny Front where downslope flow could diminish accumulations especially in eastern Mineral and eastern Grant counties. Very little in the way of snow may end up falling in the shadow of the mountains just to the east of the Allegheny Front and also in the Central Shenandoah Valley. Snow totals will be heavily elevation and snow rate dependent. With such marginal temperatures in place, a lot of the snow will be lost to melting at lower elevations with surface temperatures above freezing, while higher elevations have lower temperatures and accumulate more efficiently. Snowfall: 2-4 inches is expected in the DC Metro, although there could be locally lower totals at the lowest elevations if warmer temperatures and lighter precipitation rates verify. 4-7 inches is expected along the Bay shore from St. Mary`s northward through Baltimore City, with higher totals of 6-12" from Carroll eastward toward Cecil. Higher totals of 8-16 inches are expected in the Catoctins, where snow will accumulate more efficiently throughout the event. Snow will also accumulate efficiently southward along the Blue Ridge, where a general 6-12 inches of snow is expected. To the west of the Blue Ridge, snow totals will be heavily elevation dependent, with 3-6 inches expected at higher elevations between the Allegheny Front and Blue Ridge, while lower elevations in the Central Shenandoah Valley and Potomac Highlands see little in the way of accumulation. A general 1-3 inches is expected at lower elevations along the I-70 corridor to the west of the Blue Ridge, with the exception of near Hagerstown, where they could receive significantly more snow under the inverted trough. For now, that inverted trough area which extends southward from near Hagerstown into Frederick and Loudoun is forecast to receive around 3-6", but as mentioned before, the gradient will likely be tighter than depicted, and the max there will likely be between 6 and 12 inches. In the Alleghenies Winter Storm Warnings are in effect. Snow will linger much longer there throughout Monday within upslope flow behind the departing low. Snowfall accumulations there are expected to reach 6-12 inches by Monday evening. Elsewhere, snow should wind down by mid-morning Monday.