... Tropical Storm Fay will move north and cross the New York City area to start this weekend then become weaker as it heads toward eastern Canada. A weak cold front moves into our region as well to start the weekend. A hot, humid air mass remains over the area through the upcoming week with only limited chances of afternoon and evening showers and thunderstorms.
NEAR TERM /THROUGH SATURDAY/... As of 830 pm EDT Friday: As anticipated, isolated showers and thunderstorms have managed to make its way into the mountains this evening with a secondary maxima across the I-77 corridor. Without strong forcing in place, this activity will continue to wane and press east out of the forecast area which closely matches the ongoing forecast. Winds may become light enough overnight for isolated fog development, especially where we saw recent rainfall and across sheltered mountain valleys. Any fog that does manage to form will burn off quickly after sunrise as light west to northwest winds pick up with daytime heating.
Otherwise, more definite northwesterly surface winds tonight will begin to dry-out thermodynamic profiles. Drying should continue through the day Saturday, with greatly reduced chances for precipitation.
Though dewpoints on Saturday will be about 5 degrees lower than Friday due to noted dry advection, temperatures will only be a degree or 2 cooler. Still, reduction in humidity on Saturday will be felt as something of a relief.
SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... As of 115 PM EDT Friday: The short term begins Saturday night as a sharp H5 shortwave dives towards the southeast and general upper troughing remains across the eastern CONUS. A very weak surface boundary may move through the area late Saturday night as the SW crosses the area, but guidance suggests drier air and a warm nose aloft could limit convective activity across most of the area. The more interesting day will be Sunday, when another, sharper shortwave will move through the area and deep-layer shear may increase enough during the day to allow for some organization of convection. Above- average temperatures will allow plenty of instability to develop by the afternoon hours as well, so if these can line up time-wise and coincide with the best forcing from the shortwave, there may be a slightly increased risk of severe weather Sunday afternoon. The current SPC marginal risk seems well-placed considering these factors, though the finer-scale details will come into better focus over the next 48 hours.
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 200 PM EDT Friday: The upper trough that's settled over the eastern CONUS for quite sometime will finally shear out and break at the beginning of the forecast period. Before that occurs, a shortwave trough will stagger through the deeper trough and could spark some convective development over the area during the afternoon and evening hours Monday and Tuesday. POPs begin to decrease Wednesday as higher heights and more subsidence aloft works into our atmospheric column. This is all part of an incoming upper ridge that will slowly propagate towards the Midwest and Mississippi Valley Tuesday and Wednesday. Wednesday and Thursday is when the upper ridge is expected to set up shop over much of the southern CONUS, including our region. With the expansive anti-cyclone settled overhead by the middle part of the week, expect typical midsummer heat to be in full force as temperatures are expected to be around 5 degrees above climo during this time frame. The atmosphere will be mostly capped Wednesday and should allow the area to remain mostly dry. A few wavy isobars in the upper high will help introduce some shortwave energy on Thursday and give the area an increase in afternoon POPs as moisture begins to work back in. The GFS and ECWMF diverge a bit on Friday as the GFS has a slightly weaker upper high with a sfc frontal boundary making its way through the CWA Friday evening. On the other hand, the ECWMF keep a stronger anti-cyclone over the central CONUS and not a clearly defined frontal boundary during that same time period. Either way, an increase in moisture is evident and with thickness levels greater than or equal to 594 dm, expect heat index values to flirt with the triple digits during the second half of the work week.