DANGEROUS WEEKEND HEAT EXPECTED; severe weather a growing concern for sunday

The past several days have been hot with temps at or above 90 degrees, but it hasn't been too terrible especially with the lower humidity. But that is about to change especially once we get to Friday and into the weekend when DANGEROUSLY HOT temperatures are expected. I would strongly advise avoiding outdoor activities over the weekend and use extreme caution if you must spend time outdoors. Heat safety tips can be found here. 

THURSDAY: Expect partly to mainly sunny skies with temperatures near or above 90 degrees (mainly low 90s). Dew points will be in the mid 60s so while it will be a bit humid, its certainly tolerable considering how bad it could be this time of year. There is no chance of rain, only worsening drought conditions. 

FRIDAY: Mainly sunny on Friday with very hot temperatures peaking in the mid to upper 90s. Dew points this time will be in the upper 60s to around 70, which will lead to heat index values around 100 degrees. We cant totally rule out a stray storm across northern/western Maryland, but the chance is less than 10%. Almost everyone will stay bone dry again on Friday.

SATURDAY: This is when the dangerous heat begins. High temperatures in the upper 90s to low 100s are expected (most between 96 and 99 but a few around 100 possible). With dew points around 70, this will lead to heat index values of 100-105 which will likely prompt a heat advisory. Isolated strong to severe thunderstorms are possible, primarily NW of I-95 and especially north of the Mason Dixon line. Little to no relief is expected overnight with temps in the upper 70s to around 80.

SUNDAY: This is when the heat is expected to peak with many areas along the I-95 corridor reaching or surpassing 100 degrees. Elsewhere, highs will range from 97-99 degrees. Combined yet again with dew points around 70, expect heat index values to range between 105 and 107 degrees. This will require a heat advisory. Scattered severe thunderstorms are possible as well which may provide some relief late afternoon and evening. Little to no relief is expected overnight with temps in the upper 70s to around 80.

MONDAY: While still hot, it wont be extreme with highs in the low-mid 90s and less humidity with dew points in the mid 60s so not as high of a heat index. Scattered thunderstorms remain possible on Monday. Depending on how soon the thunderstorms form, we may need to raise temperatures into the upper 90s to near 100 once again. Some of these storms may also be severe. 

TUESDAY: Once again in the 90s but drastically lower humidity with dew points only in the 50s and low 60s so no heat index. Skies will be mostly sunny with no chance of rain and light winds. Overall not a horrible day even with temps in the low-mid 90s.

​WEDNESDAY: Temps increase slightly to between 92 and 96 degrees but the humidity still wont be too bad, only topping out in the low-mid 60s as far as dew points go. Skies should be mostly sunny with no chance of precipitation. 

SEVERE WEATHER CHANCES SATURDAY-MONDAY:

With all this heat and humidity, there comes the obvious risk of severe weather. Its typical for us to end large heat waves with severe storms in our area. While any storm that forms between Saturday and Monday, the most significant threat will exist on Sunday. The graphic above shows that there will be an increased risk of scattered severe storms across the east coast on Sunday.

Sunday will feature the hottest temperatures as well as the most favorable amount of moisture leading to the highest instability. Currently, we expect CAPE to reach the 1500-2000 j/kg range with 800-1100 j/kg of DCAPE due to a bit of dry air aloft and steep lapse rates. With an upper trough approaching from the west, this should trigger scattered thunderstorms and any that form in this kind of environment will pose a risk of damaging wind gusts. In fact depending on just how unstable we get, significant damaging winds may occur (gusts possibly over 70mph) in microbursts. Frequent lightning and small hail will also be possible in the strongest storms. 

That being said, this wont happen everywhere, and overall coverage in even just regular thunderstorms should remain isolated to scattered. But some of them definitely could be on the intense side. 

On Monday, lower dew points and westerly winds could limit the threat for storms, but a cold front leading to better forcing and remnant hot temperatures could still spark a few strong to severe storms.