Tornado watch issued until 3 o'clock in the morning: strong storms striking the west and northwestern Mexico region

Several tornado warnings are in effect southwest of Charlottesville. All this activity is heading north-east and could affect the Washington area between 7 pm and 10 pm

5:50 pm – First wave of storms in Loudoun County

A strong line of storms is developing in western Loudoun County between Middleburg and Lovettsville, which could worsen as it moves northeast to west of Leesburg and southern Frederick County during the next hour. Heavy rain and wind gusts of at least 40 to 50 mph are likely with this area of ​​storms.

These storms could affect mainly our far western and northwestern regions over the next two hours.

But there are storms near Charlottesville, some of which have triggered tornado warnings, which could affect the immediate metropolitan area between 7pm and 9pm. They may weaken some but it is not a given and we will follow closely.

The main concern is at night, between 1 and 4 hours, as shown below. "In the face of the threat of severe weather at night, it is extremely important to ensure that you and your family have several ways to receive warnings and react when they are issued for your area," he said. warned the National Meteorological Service.

Original message from 15h

A powerful storm system that caused a strong storm in the south Saturday moves to the center of the Atlantic coastline. Showers and storms, some of which may be intense, probably occur in at least two turns.

We expect a first rain and a few thunderstorms tonight, as warm, moist air rushes north, to the front of a cold front. Some of these storms have the potential to be severe or severe.

The second round, which will arrive after midnight, is more of a serious and widespread risk. This band will be located just on the cold front itself and will take advantage of exceptionally strong winds at altitude. Destructive winds are the main threat, but extreme wind shear (change in wind speed and direction depending on altitude) can generate enough rotation for one or more tornadoes.

The HRRR model predicts an intense line of storms crossing the Washington area around 3am.

This article will be updated as storms approach and / or alerts or warnings are issued.

Storm dashboard

Approximate arrival time for storms:

• Round 1: 17h-22h from west to east (18h to 20h, most likely immediate area)
• Tour 2: From midnight to 4 am (Monday) from west to east (1 am to 3 pm, most likely immediate area)

Duration of the storm: about 30 to 45 minutes for each turn

Chance of precipitation measurable anywhere: 80%

Storm movement: from south-west to north-east

Probable storm effects: heavy rain, lightning, gusty winds

Possible storm effects: damaging wind gusts, flash flood, short or isolated tornado, hail

Very low chance of: multiple tornadoes, possibly strong, significant hail

Precipitation potential: average 0.5 inches, but very variable. Localized amounts of 2 to 3 inches are possible.

Discussion

The National Meteorological Service's Storm Prediction Center is keeping a close eye on this large spring cyclone, which has been fairly vigorous on the Gulf Coast and in the Southeast. As a result, a very large area east of the Mississippi is exposed to at least a slight risk of severe thunderstorms.

By early afternoon, the risk for the Washington, DC area has increased one more step. This level three on the center scale 1 to 5 for thunderstorm risk.

This afternoon, a warm front rises northward across the region. Our region remains under thick layers of low and medium clouds, but it can thin a few hours later in the afternoon, under a surge of strong winds. South. In the middle or late afternoon, we will enter the most powerful "hot sector" of the hurricane. Moisture values ​​will reach very high levels for this time of year.

The upper atmosphere is quite volatile, with a pronounced dip in the jet that takes a configuration called "negative tilt", which means that the rising of the air will intensify as this region moves further. above us tonight. In addition, the winds in the middle atmosphere will increase, which will further enhance wind shear. This will include winds that turn (turning clockwise) with height, as well as speed, which creates some concerns about the potential for rotation of a storm.

Our only limiting factor for severe weather – and that's a good thing – is the lack of a very unstable air mass. The clouds of this afternoon are destabilizing at bay. But it is a type of meteorological configuration that has other ways of generating some instability – namely the expected rise of warm, moist air at low altitude coming from the south, which will actually trigger at sunset .

For the first series of storms tonight, we expect a less volatile atmosphere. In addition, the trigger of the first turn is somewhat diffuse, because the cold front still remains far to the west. However, judging by the satellite loops, it is possible that some clouds will clear or even that breaks will occur in the late afternoon or evening, before sunset. Air pockets could destabilize, so that some places could face a strong or violent storm, including an isolated supercell (rotating storm) or two, especially in our western regions.

Around 1 or 2 o'clock in the morning, the cold front begins to move from west to east in our region. It is at this point that all high resolution forecast models develop a grain line, with showers and thunderstorms, and move it rapidly into the region.

With a strong uplift along the front, a dynamic uplift triggered aloft by the jet stream, a powerful wind shear and perhaps just unstable enough air (from these southerly winds) … l & rsquo; Installation favors some integrated violent storms. This is not the classic moment of the day that can be expected, it is an intense storm line. And if this same configuration were played hours earlier, with hours of heating by the afternoon sun, we would face a major epidemic of severe weather in the central Atlantic.

The storm line will probably be wavy in appearance, with arcuate segments, a type we call a quasi-linear convective system (QLCS). In the hollows between the arches and the arches, small whirlpools (mesocyclones) can draw on the rotational energy contained in the rich shear of the wind. One or more of these mesocyclones could generate a couple of transient tornadoes. These are not the strongest types of tornadoes that were unleashed on Saturday in Texas and Mississippi.

However, after midnight, the most serious and serious threat will be scattered pockets of violent, linear winds. In addition, due to the high humidity, some cells could be heavy rain producers, locally. Spot flash floods are possible, but the rapid movement of these storms should limit the more widespread flooding problems.

Stay tuned for updates on this situation, which we publish at the top of this article. A severe thunderstorm is possible in our region and we can not totally exclude a night watch against tornadoes. A watch would indicate that conditions are favorable for severe thunderstorms and / or tornadoes.

Forecast for Monday

Rain and thunderstorms are expected to be in the eastern part of the area at Monday's sunrise, but we can not rule out the possibility of a prolonged downpour at any time of the day. The sky is usually partly sunny with cooler temperatures and wind gusts. Highs will peak in the 50s to 60s, with a strong west / northwest wind at 15-20 mph and gusts of up to 35+ mph. Clear, cool and windy tomorrow night with minimums in the top 30 and low 40s and northwesterlies at 10-20 mph.