George BM

What was the relative humidity?

Just got back inside from a jog and there was heavy frost in clearings between trees that looked like a coating of snow.

Predawn run 4 days ago was a warmer than ideal 68F w/ moderate humidity. This mornings run featured temps into the 20s... just a wee bit of a difference. IAD snagged 25F.

First freeze for many likely by Thursday morning.

Forecast Discussion Monday, December 11, 2023 4:26AM EST A high to extreme impact overrunning winter event will affect the region over the next couple of days. Early this morning temps have fallen into the upper teens in the suburbs w/ low/mid 20s in town on NE winds. Snow has already moved into far southwestern areas including Charlottsville, Culpeper and Fredericksburg. This snow will overspread the rest of the area as dawn occurs. Temps could initially fall a few degrees, to 15-20F, as this occurs with the dry airmass in place. Snow will become heavy at times by mid-morning as the shortwave approaches from the west strengthening the WAA. Around that time, a changeover to sleet will occur over those southwestern areas towards central VA as warmer air aloft begins to overspread the region. This changeover to sleet will probably occur within the DC metro by midday or so as the aforementioned southwestern areas changeover to freezing rain. By the mid/late afternoon hours everyone south of I-70 in northern MD and the Baltimore metro region should have changed over to freezing rain. The precipitation throughout the day will be heavy at times. Temperature-wise most of the region will start the day in the mid/upper teens before rising into the lower 20s towards northern MD by late afternoon, mid/upper 20s in the Greater Washington metro region and perhaps to near freezing in our southern zones towards Fredericksburg and Culpeper. Despite the fairly heavy freezing rain rates through the afternoon the temperatures greater than 5F below freezing may allow for significant ice accretion on trees and powerlines leading to numerous to potentially widespread power outages by evening. Freezing rain will lighten up and become showery as we get into the mid to late evening hours but with temperatures remaining in the 20s ice accretion (especially given the lighter rates) will be efficient. By midnight, when round one should be out of the region, snow/sleet totals will range from 6-10”+ north of DC and across northern MD to 5-8” in the Greater DC metro region to 2-5” towards central VA and southern MD zones. Concerning ice accretion, areas near I-70 will most likely see around 0.25-0.4” of ice accretion with the Greater DC metro experiencing ½ to ¾ of an inch of accretion and southern areas receiving around half an inch as slightly warmer temps in those areas as well as the heaviest precip shifting north through the afternoon will limit ice accretion somewhat. As the first shortwave moves to our east during the overnight/ pre-dawn Tuesday hours colder air aloft will start moving back southwards over the region. As a larger slug of moisture moves into the region towards dawn with the main system approaching from the WSW precip in the form of snow and sleet will overspread the region with freezing rain most likely in southern zones. At the same time, a reinforcing shot of arctic cold air will push in from the very strong ~1060mb surface high to our north. As a result, as the air aloft warms during the day on Tuesday with heavy precip overspreading the region the surface temps will remain deep in the 20s and may even fall a few degrees F as we go into the midday/afternoon hours. Precip will take the form of heavy snow towards I-70 and Baltimore with heavy sleet across the Greater DMV. A significant to potentially catastrophic ice storm from freezing rain will be taking place mainly south of I-66 & US-50 at least through the midday hours. By Tuesday afternoon strong WAA aloft will allow all areas with the exception of far northern MD towards the MD/PA line (where a wintry mix will continue) to change over to freezing rain. Once again, the precip rates will be heavy at times w/ even some elevated convection possible during the afternoon and into the evening. While the air aloft will warm through Tuesday surface temperatures, thanks to the strong arctic high to the north, will likely remain steady ranging from the upper teens to the north to the mid/upper 20s in the southern reaches of the forecast area with the 20-25F range in between. It’s the PM hours of Tuesday that could prove to be truly historic with the chance of 1 to 2 inches of ice accretion on top of upwards of a foot or more of hardened snow and sleet. This may lead to catastrophic tree damage with structural damage to numerous buildings as well as nearly universal power outages. By Tuesday night the main area of low pressure will pass by just south of the region. As that happens freezing rain and a wintry mix will change back over to snow from northwest to southeast before all precip eventually tapers off by just before dawn on Wednesday. Once all of this is over snow and sleet totals of 10 to 15 inches will be commonplace in the region with upwards of 18+ inches in some locations in northern MD and 5 to 10 inches to the south. But on top of and embedded within that snow/sleet will likely be 1.5 to 2.5 inches of ice accretion potentially making roadways impassable for several days if not weeks given that temperatures will remain well below normal over at least the next 7-10 days with some sub-zero lows possible. Forecaster Wannabe: George BM

I can see the dark shelf-like clouds approaching with it in Herndon.

IAD casually up to 86F breaking the daily record by 3F.

IAD got down to 34F. I saw patchy frost on the roofs this morning.

Notice how no one here even talks about them anymore lately.

Sixty-nine years ago today a truly historic thing occurred in the region. Hurricane Hazel blasted the region with 70-100+ mph wind gusts! A truly phenomenal thing experiencing limbs dashing across the street with shingles flying like bats everywhere. DC gusted up to 98mph that afternoon. Truly incredible.

That was crazy. Snow covering fully leafed trees that were still well before peak fall foliage. Would be very intriguing to experience again.

IAD got down to 40F.

Almost had a 2018 snowfall contest moment. ... DCA: 11/07 IAD: 10/27 BWI: 10/27 RIC: 11/08 BWI Oct departure: +0.2F

IAD down to 42F this morning.

IAD has fallen to 59F behind the front. Light rain.

I don't recommend getting an ulcer.

Currently 68/67 at IAD. Hoomid.

Nah. It's not out just yet.

JAS ONI: +1.3C (rounded to nearest tenth) JAS RONI: +0.81C

DCA: 2/01/24 IAD: 12/25 BWI: 2/01/24 RIC: 12/25 BWI Oct departure: +2.2F

Winter approaches. Happy October!

Forecast Discussion Tuesday, October 31, 2023 3:45AM EDT The strong arctic front is currently in eastern WV about to enter into western VA. A line of heavy gusty downpours and embedded thunderstorms stretches from NNE to SSW along this front. Temperatures have risen into the lower/mid 70s on strong south to SSE winds ahead of the front. These synoptic winds will continue to gust into the 35-45+ mph range w/ up to 50 mph gusts along the Potomac and Chesapeake shores and mountains to the west gusting into the 50 to 60 mph range with the 70+ kt LL jet overhead. A High Wind Warning for the highest elevations of the Blue Ridge and a Wind Advisory in the metro areas and near the Chesapeake Bay accounts for the wind threat ahead of the front. The main line will affect far western areas (between the VA/WV border and the Blue Ridge) between 8z and 10z, the Greater Metropolitan region in the 9-12z timeframe and eastern and southern MD eastwards through the rest of the Delmarva in the 11z-15z timeframe. Dewpoints ahead of this line are in the upper 60s to around 70F leading to around 500-1000 J/kg of CAPE. The main threat from the line of storms will be strong winds and perhaps a brief qlcs tornado given the low-level shear. With Pwats in excess of 1.75” there is a slight risk of flash flooding of some streams and low-lying areas, though the progressive nature of the line will prevent a bigger flood threat. Behind the front temperatures will fall rapidly on strong NNW winds as light/moderate anafrontal rain continues. In fact, temperatures in the metros will fall into the lower 40s by the early afternoon hours w/ upper 30s in the far NW suburbs. At the same time, a potent shortwave trough will have rounded the base of the longwave trough taking on a negative-tilt allowing another wave of low pressure to rapidly deepen along the front in the eastern Carolinas into the Virginia Beach area. This area of low-pressure will travel northeast along the front which will be situated along the Atlantic coastline through the afternoon and evening. As this occurs, more moisture will be thrown northwest into the cold airmass courtesy of the strongly negatively tilted trough increasing precip intensity. By mid-afternoon rain will change over to snow in the mountains with this changeover moving eastwards into the metros by 21-22z as temperatures fall to near freezing. Snowfall rates will be heavy with 1-2”+/hr rates commonplace, perhaps nearing 3”/hr at times in the heaviest bands that form. At the same time, courtesy of the increasing surface pressure gradient, NNW winds may gust over 50 mph at times from late afternoon through the evening. This will lead to low visibilities of under a quarter mile at times. A Winter Storm Warning is currently in place from the mid-afternoon hours into the early overnight hours for the metros with Blizzard warnings along the Blue Ridge and higher elevations. An upgrade to a Blizzard Warning for the majority of the region may very well be needed if current model and realtime trends continue this morning. Snow should taper off by midnight or 1am at latest with many areas receiving 6-10”+ of snow (locally up to a foot where the heaviest bands set up) with 10”-15”+ amounts in the mountains to the west. Temperatures will bottom out in record territory and hover in the lower/mid 20s through the overnight hours but the strong gusty NW winds will put wind chills in the single digits making for a mid-winter like start to November. Forecaster Wannabe: George BM

By December of 2018 if MBY got even as little as several hundredths of an inch of rain puddles would form in the low points of the lawn and walkways and remain all day. Bizarre.

When's the last time that you got at least three 1"+ rain days in a single month out there?