Weather

Flooding rain and damaging winds possible in storms in D.C. area

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* Severe thunderstorm watch till 9 p.m. | Flood watch till 11 p.m. *

3:50 p.m. — Storms northwest of Washington pushing south into western suburbs

Heavy storms that originated in Pennsylvania have pushed southward and stretch from roughly Martinsburg to Germantown. This exercise is aimed toward Loudoun and western Fairfax County over subsequent 30 to 60 minutes. It will include heavy rain, frequent lightning and some robust wind gusts. To the east, storms are extra extensively scattered and not as intense however may move contained in the Beltway a while after 4:15 p.m. or so.

Our subsequent replace will probably be arond 4:50 p.m. or sooner if extreme climate is threatening the fast area.

3:10 p.m. — Strong to extreme storms racing into D.C.’s northern suburbs

A bowing line of storms is sweeping southward from Pennsylvania into northern Maryland, prompting a extreme thunderstorm warning from northern Montgomery County north to the Mason Dixon line. It consists of Thurmont and Frederick. The storms — which stretch from roughly Hagerstown to Westminster — might produce wind gusts to 60 mph in addition to torrential rain and lightning.

This line of storms, reserving south at 50 mph, may attain the Beltway and D.C.’s western suburbs earlier than 4 p.m.

2:10 p.m. — Severe thunderstorm watch issued till 9 p.m.

As intense storms have already erupted in the area, the National Weather Service has issued a extreme thunderstorm watch till 9 p.m. Additional storms — a few of which may very well be extreme — are anticipated to comb by way of the area into the night. Many storms will unleash torrential rain and harmful lightning whereas some may produce damaging wind gusts and hail.

The watch spans from central Virginia by way of central Pennsylvania, the place the storms are growing and sweeping southward. It doesn’t embody counties alongside the Chesapeake Bay the place storms are projected to be considerably much less quite a few and intense.

Remember {that a} extreme thunderstorm watch means situations are favorable for intense storms, however not a assure. Stay climate conscious. If a extreme thunderstorm warning is issued on your location, it means a extreme storm is imminent and that it is best to search shelter.

The preliminary spherical of showers and storms that has already handed will make means for one more wave growing in southern Pennsylvania arriving in the course of the late afternoon. It could also be extra intense.

Original article from noon

The blissfully dry climate of the previous a number of days has departed; a really heat, humid sample is taking its place. But cooler air lurks to our northeast and northwest. We’re caught in the transition zone the place these contrasting air plenty meet, a ripe setting for intense thunderstorms.

Storms are most possible between about 3 and 11 p.m., and some could also be extreme — containing damaging winds and hail in addition to heavy downpours and harmful lightning. Some areas may very well be hit by heavy storms repeatedly — growing the chance of flooding.

The National Weather Service has issued a flood look ahead to a lot of the area, apart from Southern Maryland and counties subsequent to the Chesapeake Bay, the place showers and storms will most likely be much less quite a few.

The heaviest rain and biggest flood risk will probably focus between Interstates 95 and 81. “Rainfall amounts of 1 to 3 inches are possible within the span of a couple of hours, with locally higher amounts possible,” the Weather Service cautions.

Rain totals will probably be extremely variable all through the area, relying on the place the heaviest storm cells monitor — which may’t be predicted earlier than they begin to kind. Some areas may see lower than a tenth of an inch whereas some fashions present most totals over 5 inches, which is a severe quantity of rain. This quantity of rain would require heavy storms forming and reforming whereas monitoring over the identical area repeatedly — a phenomenon referred to as coaching. The biggest risk of coaching storm cells is west of Route 15, working from Frederick to Warrenton.

The Weather Service has positioned the western half of our area in a Level 2 out of 4 threat zone for extreme rain; our japanese areas are underneath a Level 1 threat.

The flooding risk could also be mitigated considerably by the actual fact June has been dry thus far — however if 2 or more inches falls in short amount of time, that would rapidly trigger streams to overflow and for poor drainage areas to be overwhelmed.

“Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations,” the Weather Service writes.

Remember to by no means try to drive throughout a flooded street because the water stage is troublesome to evaluate. Turn round, don’t drown.

In addition to the heavy rain risk, the Weather Service’s Storm Prediction Center has positioned the area in a Level 2 out 5 threat for extreme storms that would produce “damaging winds and isolated large hail.” An remoted twister additionally can’t be dominated out.

The most possible timing for extreme storms can be in the late afternoon and early night earlier than the risk wanes towards darkish. However, the chance of heavy rainfall may proceed till 10 or 11 p.m. in elements of the area.

An uncommon sample is coming collectively for the following 12 to 18 hours.

As proven in the forecast floor chart (legitimate 8 p.m.) beneath, we have now an approaching chilly entrance from the west. Over the Bay and I-95 hall, one other slow-moving frontal boundary is approaching from the east: an odd route, in reality, a course of that’s known as retrograding. Along this boundary, a weak area of low stress is predicted to develop.

So the area will probably be positioned in a zone in which the humid, unstable air mass in between the fronts is getting squeezed from each instructions. This is named convergence of air, and the end result will probably be a big mass of air compelled to ascend.

Adding to the efficiency is a really excessive humidity content material of the air. The morning climate balloon at Dulles revealed aggressive moistening of the deep ambiance is underway, to the purpose the place the “precipitable water” (complete liquid equal depth of water vapor) will probably be between 2 to 2.5 inches — a price that’s fairly extreme for our area in late June — close to report ranges. These anomalously excessive values at 8 this night are proven by the ribbon of pink colours in the map beneath.

So we have now very excessive moisture content material, getting squeezed upward over the area between two fronts, in an environment unstable sufficient to generate thunderstorms. These elements will intensify late this afternoon and probably be sustained till about midnight.

The deep airflow aloft can also be anomalous for this time of year, from due north — so storm cells will develop in Pennsylvania and drift south into the Baltimore-Washington area.

We suppose the retrograding entrance draped alongside I-95 will act as a conduit alongside which storm cells will repeatedly hearth and monitor from north to south. It’s troublesome to say a priori the precise counties/locales impacted, however this “training” impact may result in spectacular rain totals for some, upward of two to three inches. One of the high-resolution forecast mannequin simulations of radar protection for by way of tonight is proven beneath — you’ll be able to select the improved hall of storm cells alongside and west of I-95.

Another area of targeted, heavy rain could also be close to or simply west of the I-81 hall, the place enhanced lifting of humid air by the mountains and the approaching chilly entrance might wring out additional atmospheric moisture. Note, nevertheless, the above radar simulation is simply a tough information as to how storms might evolve; the precise timing and placement of storms may find yourself being fairly totally different.

Locally extreme storm cells may additionally generate damaging wind gusts, intense lightning and, maybe, even a weak twister. We don’t count on the extreme climate protection to be as widespread because the flood risk. But the wind shear (or enhance in wind pace and change in route with altitude) is ample, together with native “spin” generated alongside the retrograding entrance, for the specter of an remoted twister.

Damaging straight-line winds are extra probably, in the type of downbursts, in which the heavy mass of descending water in cell downdrafts drags the air all the way down to the floor in a high-velocity influence.

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