... A stationary front will remain near the Chesapeake Bay through Monday before pushing offshore. High pressure will build across the area for much of the work week, with a cold front approaching by the end of the week.
NEAR TERM /THROUGH TONIGHT/... Quiet weather to start this Sunday...with diurnal cloud cover starting to blossom across the region. Dewpoints remain seasonably reasonable...mainly in the low to mid 60s. Temperatures at 10 AM are running warmer than this time yesterday...mainly in the lower 80s, except mid to upper 70s west of the Blue Ridge.
An upper level disturbance is currently over Ohio, along with the longwave trough axis. This will prograde toward our region, slowly, for the remainder of the day. The timing has slowed a bit, which means many locations east of the Blue Ridge will just see some diurnal cumulus until late in the day, while west of the Blue Ridge clouds will increase faster. It appears the more copious clouds over southern Ohio should arrive into the CWA a little after 18 UTC.
High-res models indicate scattered showers and thunderstorms developing, mainly after noon. A quick look at lift/instability parameters shows MUCAPE a little over 1000 J/kg and shear around 20 kts. Could see an isolated severe storm with damaging winds, but at the moment it seems like the shortwave timing is after the loss of daytime heating, so not everything totally comes together at the same time. Still have to keep an eye on everything as activity evolves.
I did lower PoPs tonight a bit -- for now -- and will reassess with the arrival of 12z guidance.
SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... We will likely be dealing with plenty of clouds and remnant showers Monday morning from the Sunday night disturbance, so temperatures Monday have been lowered to reflect this. The upper trough axis will still be aligned overhead on Monday, shifting east of the mountains during the afternoon, bringing additional showers and thunderstorms into the metro areas and to the Bay. Uncertainty remains in how much clouds will be able to break to allow sufficient heating and instability to build and bring a strong to severe thunderstorm threat Monday afternoon. If we do see clearing, that would allow instability to build and bring such a threat to fruition with the trough axis pushing through the area. The best coverage of showers/storms and ultimately a threat for strong to severe storms will be along and east of the I-95 corridor, where a Marginal Risk is highlighted once again by SPC.
The embedded shortwave shifts to our east Monday evening with diminishing activity. The primary upper trough axis will the finally swing to our east late Monday night into Tuesday as heights rise with high pressure building into the region. Dry conditions are expected during this timeframe with near normal temperatures for the middle of July.
LONG TERM /WEDNESDAY THROUGH SATURDAY/... On Wednesday, upper level ridging will be overhead with surface high pressure located to the northeast. This will allow for a slight warming trend, though a southeast/onshore component to the low level flow will prevent the really hot/humid air from arriving. A stray shower or storm in the mountains can't be ruled out due to orographic lift, but the ridging should suppress most activity.
The overall synoptic pattern for the remainder of the week is well- forecast with a hot summertime ridge across the southern US, and a closed low drifting east from Saskatchewan/Manitoba with low amplitude flow between it and the ridge. The main issue is that the local area will be on the periphery of these features, which means smaller scale variability will have the most impact on the weather. There has been a trend to slow down the progression of the hot low level air toward the area, with Thursday looking not quite as hot as it did a few days ago. There could even be some marine influence with continued SSE surface flow. Friday and Saturday still look hot, though the latest consensus blends have highs mainly in the lower to mid 90s. However, heat indices will become more of a factor as dew points increase. So bottom line is, yes it will be hot, though uncertainty remains if it will be excessively so.
Likewise, pegging which day will have the best chance of thunderstorms (if any) will likely depend on any embedded subtle shortwaves in the flow to our north. At this time, there isn't much model to model or run to run consistency with that. So will keep PoPs in the chance category (or lower) for Thursday-Saturday. Expect the terrain and lee trough to be the main players in initiation as the heat/humidity lead to larger instability, unless a prominent disturbance brings more widespread forcing.