George BM

URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 393 NWS Storm Prediction Center Norman OK 1200 PM EDT Wed Jul 22 2020 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of District Of Columbia Western and Central Maryland South Central Pennsylvania Northern and Central Virginia Eastern Panhandle of West Virginia Coastal Waters * Effective this Wednesday afternoon and evening from NOON until 700 PM EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph likely Isolated large hail events to 1.5 inches in diameter possible SUMMARY...Thunderstorms will intensify and over the mountains of northern Virginia and southwest Pennsylvania and spread eastward this afternoon and early evening. Damaging winds and perhaps hail are expected with the more intense storms today.

Yeah... It sure seems like we've not seen too many of those events this year.

Just had a thunderstorm pop up over me this hour in Herndon. Safe to say that I've seen my high for today here.

Now up to 99F at IAD.

IAD up to 98F now. 98/72/106.

IAD has hit 97F so far per one-min obs.

When you get back from the trip feel free to let me know whether you experienced any lightning/thunder and what the snowfall rates were.

Morning lows at local airports: DCA: 83F BWI: 79F IAD: 75F

Ditto. It was the awesome running weather for my run this morning. /s IAD at 83/72 now after a surprisingly cool low of 75F.

9pm Local Airport Obs: BWI: 88/77/100 IAD: 90/70/96 DCA: 93/69/98

91F at IAD after sunset. Warm.

An Excessive Heat Watch is up for tomorrow. URGENT - WEATHER MESSAGE National Weather Service Baltimore MD/Washington DC 247 PM EDT Sun Jul 19 2020 DCZ001-MDZ011-013-014-016>018-504-506-508-VAZ052>057-200300- /O.NEW.KLWX.EH.A.0001.200720T1600Z-200721T0000Z/ /O.CON.KLWX.HT.Y.0001.000000T0000Z-200720T0000Z/ District of Columbia-Southern Baltimore-Prince Georges- Anne Arundel-Charles-St. Marys-Calvert- Central and Southeast Montgomery-Central and Southeast Howard- Southeast Harford-Prince William/Manassas/Manassas Park-Fairfax- Arlington/Falls Church/Alexandria-Stafford-Spotsylvania- King George- Including the cities of Washington, Baltimore, Bowie, Suitland-Silver Hill, Clinton, College Park, Greenbelt, Laurel, Camp Springs, Glen Burnie, Annapolis, Severn, South Gate, Severna Park, Arnold, Odenton, St. Charles, Waldorf, Lexington Park, California, Chesapeake Beach, Huntingtown, Dunkirk, North Beach, Lusby, Prince Frederick, Bethesda, Rockville, Gaithersburg, Silver Spring, Columbia, Ellicott City, Aberdeen, Dale City, Manassas, Woodbridge, Lake Ridge, Montclair, Reston, Herndon, Annandale, Centreville, Chantilly, McLean, Franconia, Arlington, Alexandria, Falls Church, Falmouth, Fredericksburg, and Dahlgren 247 PM EDT Sun Jul 19 2020 ...HEAT ADVISORY REMAINS IN EFFECT UNTIL 8 PM EDT THIS EVENING... ...EXCESSIVE HEAT WATCH IN EFFECT FROM MONDAY AFTERNOON THROUGH MONDAY EVENING... The National Weather Service in Baltimore MD/Washington has issued an Excessive Heat Watch, which is in effect from Monday afternoon through Monday evening. * WHAT...Heat index values between 105 and 109 through 8 PM EDT this evening. Heat index values between 110 and 115 possible Monday from Noon to 8 PM EDT. * WHERE...The District of Columbia, and portions of central, northern Maryland, northern and northwest Virginia. * WHEN...The Heat Advisory is in effect through 8 PM EDT this evening. The Excessive Heat Watch is in effect from noon to 8 PM EDT Monday. * Impacts...Hot temperatures and high humidity may cause heat illnesses to occur. PRECAUTIONARY/PREPAREDNESS ACTIONS... Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. Young children and pets should never be left unattended in vehicles under any circumstances. Take extra precautions if you work or spend time outside. When possible reschedule strenuous activities to early morning or evening. Know the signs and symptoms of heat exhaustion and heat stroke. Wear lightweight and loose fitting clothing when possible. To reduce risk during outdoor work, the Occupational Safety and Health Administration recommends scheduling frequent rest breaks in shaded or air conditioned environments. Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency! Call 9 1 1. CDC recommends that if you need to go to a cooling center, wear a cloth face covering. While you are there, wash your hands with soap, or use hand sanitizer, often. Face covers should not be used by children under the age of 2. They also should not be used by people having trouble breathing, or who are unconscious, injured, or can`t remove the mask themselves. An Excessive Heat Watch means that a prolonged period of dangerously high temperatures is possible. Prepare for extreme temperatures and high humidity which would create a situation in which heat illnesses are expected. Take extra precautions if you work or spend time outside. When possible, reschedule strenuous activities to early morning or evening. Know the signs and symptoms of heat exhaustion and heat stroke. Wear light weight and loose fitting clothing when possible and drink plenty of water. To reduce risk during outdoor work, the Occupational Safety and Health Administration recommends scheduling frequent rest breaks in shaded or air conditioned environments. Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency - call 911. && $$

Making progress now. I'm on my way.

IAD has hit 98F so far for the day.

Nope. See the post above yours.

Yeah. I couldn't access the site for a short while this afternoon.

Looks like we just got the watch! PDS Severe Thunderstorm Watch 379 in effect until 1AM EDT THIS IS A POTENTIALLY DEADLY SITUATION... Hazards: Numerous extreme and potentially deadly wind gusts up to 200mph Numerous giant and potentially deadly hail events of 12+ inches in diameter A few tornadoes likely with an intense tornado or two possible Discussion: With near 20,000 J/kg MLCAPE, 3,000+ J/kg DCAPE and high-end extreme effective bulk-shear (120-150+kts) storms will fire up over the higher terrain over the next few hours as the cap continues to erode. With the shear in place supercells will be the main storm-mode. These supercells will move eastward off of the higher terrain through the watch area through the evening. This is a potentially deadly situation. There may be wind gusts equivalent to that of a violent tornado and hail large enough to penetrate through roofs and multiple floors/ceilings of homes and structures in general. While there is definitely the possibility of a couple tornadoes given the extreme effective SRH (700-1200 m2/s2) the large difference between the temperature and dewpoint temperature (145/96 temperature and dewpoint respectively at KIAD) cloud bases will be very high so tornadoes will have a difficult time sustaining themselves, especially given the extreme downbursts that may undercut their inflow. Nevertheless, a few tornadoes may still become strong briefly given the intensity of the updrafts that are expected. Storms should move out into the ocean by 4z (Midnight EDT).

@WinterWxLuvr Do you have memory of the July 5th derecho that year (1980)? Currently 87/54 at IAD.

What would you guesstimate that the strength of the wind gusts were?

Correct. It was, however, only 5 degrees above the NNW horizon yesterday evening 80 minutes post-sunset (I did not see it). IIRC it will be 10 degrees above the horizon 80 minutes post-sunset by tomorrow evening (7/14) and up to 20 degrees above the NW horizon by 7/19 at the same time relative to sunset. All the while, however, it will probably ever so slowly be getting dimmer night by night as it moves away from the sun.

I was actually out for an early morning run (4am hour) this morning but never saw it despite clear skies. I was looking towards the northeastern horizon for it as I ran.

Yeap. Philippe Papin has a nice short thread about the feature from this morning.

@WxWatcher007 This is not going to develop into a tropical cyclone, obviously, but check out the convection associated with a vort-max feeding off of the 80F water temperatures of Lake Erie. Pretty neat.

IAD has also hit at least 90F for today.

The most exciting weather event of the year thus far locally.