Aug 8, 2016 11:31 PM
NH1 First Alert Weather: Plenty of weather changes coming for NH
NH1 Chief Meteorologist
The surface high sitting over us will be slowly tracking eastward across the region today and shifts offshore tonight. Tuesday should be mainly sunny with light winds, allowing a seabreeze to develop fairly early and make some headway inland. Highs will be in the mid-upper 80s inland, with a few areas approaching 90 during the afternoon. The coastal zones should top out around 80 with the early onset of the sea breeze. Some of the beaches may be limited to the mid 70s. The mountains will see highs in Lwr 80's. Tuesday night will see increased SW flow. This will prevent much radiational cooling and lows will be milder than Monday night, but not overly warm yet, running from the mid to upper 50s north to the low to mid 60s in the south.
A weak wave, or remnant convective system will approach from the SW by Wednesday morning. This weak wave moving through southern New England could bring some showers or thunderstorms to southern New Hampshire before moving offshore Wednesday night. Otherwise, high pressure offshore will bring a south to southwesterly low level flow to New England through much of the week, allowing the heat and humidity to build. By Thursday it should reach into the 90's degrees across most of the forecast area, with heat index values creeping into the upper 90s in southern New Hampshire.
A cold front will begin to push through Thursday and Friday. To the south of the front, the heat and humidity will continue, with southern New Hampshire likely to remain in this hot and humid airmass at least through the first part of the weekend. Temperatures in the low 90s with heat index values approaching 100 possible because of the oppressive humidity in place.
With the heat and humidity and the potential frontal boundary in the area, there will also be the chance for showers and thunderstorms beginning Friday afternoon. The chance of showers and storms will continue as long as the front remains in the area. Our GFS would like to move this front southward, keeping the threat of scattered showers and storms through Saturday. Once the front is through, an easterly surface flow and much cooler temperatures especially for the second half of the weekend. The Euro model keeps this boundary to the north, with the heat and humidity continuing through the weekend. A close call. With the ample moisture in place, any shower will have the potential for heavy rain.
A trough axis shifts into New England Monday and Tuesday, bringing a cold front with it as it does so. Cooler onshore winds will lock in low clouds along with the chance of a few more showers, before a shift to a little cooler and drier weather begins returns farther into next week.