Mount Washington Valley Forecast

A lot to go over today, so one step at a time. Bermuda high pressure that has been dominating the weather this past week will be pushed a bit south today as a trough approaches from the west. Although the high is weakening, it will once again be hot, humid, and hazy today. Air quality conditions will be poor enough that the NH Dept of Environmental Services has declared an air quality action day for Rockingham and Hillsborough Counties and elevations above 3000 feet. As a result of the poor air quality, it is advised that sensitive individuals like children, the elderly, or those with heart or lung conditions limit activities requiring prolonged or heavy exertion; like hiking or biking. But even healthy individuals should take caution and may feel the ill effects of the poor air. In addition, the southern half of the state has a heat advisory in effect into this evening with heat indexes expected in the 100F range here. Skies in the south be sunny due to the high but the north will see some clouds along with showers or thunderstorms this afternoon as a cold front approaches from the northwest. This cold front will then stall out as a frontal boundary just north of the Presidentials and will act as a focus for clouds and possible shower or thunderstorm activity this afternoon into the overnight hours. Overnight into early Friday, this boundary will then lift north as a warm front as a low approaches from the west. The low lifting this front northward won’t affect the state until later this weekend but first we have to get through Hurricane Earl. As the warm front exits early Friday, a brief gap will occur in the weather allowing for a bit of clearing but this won’t last long as high clouds start in from the south from Earl. Clouds will thicken and lower during the day and showers and possible thunderstorms may approach for the afternoon but most of the activity will occur overnight Friday into Saturday morning. The heaviest rain will occur along the coast along with tidal surge and the highest winds. But even inland areas in the south will see some impact from the storm. The least impacted, as of now, will be Coos County. And the good news is that the overall consensus in the models this morning is to keep the center of the storm offshore enough to keep the heaviest rain and highest winds well to our east. But there are a few variables that may track this differently. The main factor will be the timing of the trough to the west but also the timing of the surface low with this trough expected on Sunday. If these slow and the storm shifts to the left of the track cone by as little as 2 degrees, this could be a direct hit. If the storm shifts to the right more, we could get almost nothing out of it. But so far, everything is tracking correctly and should, at least for NH and the summit, be a glancing blow. Beyond this, the low to the west will move northeast Sunday and merge with what remains of Earl then move towards Hudson Bay. High pressure will then build in from the south. This will set up a breezy but drying pattern going into Monday with cooler seasonable temperatures. But looking beyond, Earl may just be the first of a Daisy Chain of trouble brewing in the Atlantic. Next up is Fiona but so far this looks to steer out to sea with no impact but Gaston is TBD. Other storms forming with unknown futures are another cell forming off the coast of Africa and a cell over southern Chad and another near the Horn of Africa all with a strong potential to form the next three Hurricanes.

Today:

Partly sunny w/ a slight chance of afternoon showers or thunderstorms.

Highs: lower 90s, humid°F

Wind: W around 10 mph

Tonight:

Mostly cloudy w/ a chance of showers or thunderstorms. Patchy fog.

Lows: lower 60s, humid°F

Wind: Variable and light

Tomorrow:

Increasingly cloudy. Chance of day time showers. Overnight, rain w/ a chance of thunderstorms.

Highs: mid 80s, humid°F

Lows: lower 60s°F

Saturday

Mostly cloudy w/ a chance of showers.

Highs: mid 70s°F

Lows: upper 40s°F

Sunday

Partly cloudy w/ a chance of showers.

Highs: upper 60s°F

Lows: mid 40s°F

Monday

Sunny.

Highs: upper 60s°F

Lows: mid 40s°F