Marine Weather and Tide Forecast for Portsmouth, NH

NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
1045 PM Update...Little change to the going forecast. Clear skies and chilly temps continue to be the forecast overnight.

715 PM Update...Little change to the going forecast. A mostly clear and cold night is expected with diminishing winds for the balance of the evening hours.

Previously...

Mostly clear skies tonight as high pressure passes to the south. Low dewpoints in the teens today foreshadow cooling temps overnight, but elevated locations may remain lightly mixed overnight. Decoupling looks more likely in lower spots like valleys. Here, overnight lows may fall into the lower 20s to the upper teens.

SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/
Friday begins dry and sunny. Expect quick diurnal temperature recovery after sunrise from overnight lows. Temps climb for warmer day in the upper 50s to mid 60s. It will be less gusty, but drier across more of the forecast area with RH values falling into the 20 to 30 percent range. Winds become SW in return flow from high pressure passing offshore to the south.

High clouds begin to invade during the afternoon, lowering through late afternoon. Isolated to scattered showers develop in the mid to late afternoon west to east. Due to low level dry air, measurable precip should be light for the initial wave.
High res guidance following through the evening and overnight shows additional periods of rain and showers possible. These could add up to a wetting rain for much of the central forecast area, but uncertainty remains on positioning. A lot of this will be part of upstream convection exiting the northern Great Lakes and moving across southern Ontario and Quebec. With elevated instability, can't rule out some thunder overnight.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/
1030 PM Evening update...01z NBM remains in line with the rest of the the latest guidance and therefore no significant changes have been made. Continued warm and cool interludes with no heavy precipitation events expected.

Previously...

Overview: The extended portion of the forecast will begin on a warm note with above average temperatures behind a warm frontal passage on Saturday. This will then be followed by a breezy and cooler day on Sunday behind a cold front. High pressure then builds in for Monday before shower chances from a weak disturbance increase on Tuesday. Mainly dry and seasonably warm conditions look to return for the middle of next week.

Impacts: No significant weather related impacts are expected through Saturday. West-northwesterly wind gusts could approach 35-45 mph on Sunday.

Forecast Details: Saturday will feature above average temperatures as we sit within the warm sector from closed low pressure that will be traveling across Quebec. Southwesterly WAA will help to boost h925 temperatures up to around +15C, which will allow highs to reach the lower to middle 70s in most locations with a few lower 80s possible in southern NH. The exception to the warmth will be along the Mid-Coast of ME where highs will likely only reach the 50s to near 60. Skies will be partly sunny but other than a few stray showers it should be a mostly dry day.

A strong cold front will cross on Saturday evening and night, bringing a few scattered showers and increasing westerly winds. Low temperatures will range from the 30s across the north/mtns to the 40s elsewhere. Deepening low pressure will track northeastward over southern Canada on Sunday as high pressure builds over the Great Lakes region. This will result in a strong pressure gradient over the forecast area, which combined with deep mixing will result in a breezy day. West-northwesterly wind gusts between 35-45 mph are likely with the potential for some stronger gusts. Blended in some NBM 75th percentile to account for this. Highs will also be about 20 degrees cooler, which combined with the winds will feel chilly compared to Saturday. Sunday night will be cold with lows falling into the 20s to lower 30s.

High pressure looks to build over the area on Monday, allowing for continued dry conditions and slightly warmer temperatures into the 50s and lower 60s. Shower chances then increase Monday night into Tuesday as a weak disturbance approaches from the west. High pressure then builds for the middle of next week.

AVIATION /03Z FRIDAY THROUGH TUESDAY/
Short Term...VFR with winds decreasing tonight. Winds increase again Friday morning, but not as gusty as today. SHRA chances increase late afternoon west to east, with additional showers overnight. LLWS is also possible overnight.

Long Term...VFR conditions will prevail through the period. A possible exception will be at KHIE where some restrictions are possible on Saturday and again on Sunday due to -SHRA and lower ceilings. West-northwesterly winds could approach 35 kts on Sunday.

MARINE
Short Term...High pressure passes south of the waters tonight and tomorrow. Return flow brings a S wind shift over the waters with increasing winds. A surface inversion may keep these winds below SCA criteria, but gusts 25 to 30 kt may be attainable once rain moves overhead.

Long Term...Southwesterly wind gusts between 25-30 kts are possible on Saturday with seas of 4-7 ft over the outer waters.
Winds will become west-northwesterly behind a cold front on Saturday night and Sunday with a few gusts up to 35 kts possible. High pressure will bring lighter winds and smaller seas early next week.

GYX WATCHES/WARNINGS/ADVISORIES
ME...None.
NH...None.
MARINE...None.