Marine Weather and Tide Forecast for South Hooksett, NH

KEY MESSAGES
1. Expect some widely scattered rain/snow showers this afternoon with gusty winds, diminishing in the evening.

2. A potent low pressure system will bring some locally heavy rain and gusty winds to most of the forecast area early Monday morning through Tuesday morning. Some localized flooding is possible as ice jams loosen and the remaining snow melts.

3. Gusty winds remain behind the departing system Tuesday, with otherwise little to no impactful weather through mid-week. Some guidance suggests the next chance for widespread precipitation around the Saturday timeframe, but there remains a wide envelop of outcomes.

DISCUSSION
KEY MESSAGE 1 DESCRIPTION...

Early this afternoon, an upper low continues to lift out of the forecast area towards the Canadian Maritimes. In it's wake, another weak shortwave embedded in near zonal flow will cross the area this afternoon and into the evening. This disturbance will lead to some widely scattered rain and show showers; likely rain over the Interior/Midcoast and snow in the mountains. By the evening, this activity should start to diminish but a few snow showers may linger in the mountains.

Significant surface pressure rises and strong low-level cold air advection will also lead to some gusty west winds through the afternoon. The strongest gusts outside of the mountains will likely be around 40 mph. Lows tonight will be on the chilly side, ranging from the mid teens north to the low/mid 20s south.

KEY MESSAGE 2 DESCRIPTION...

Attention then turns to the next strong system poised to impact the area early Monday morning through Tuesday morning. Not much has changed regarding our general thinking for the early week event as highly anomalous moisture is still forecast by virtually all guidance. The latest NBM probabilities for an inch or greater have now bumped up into the 80 to 90+ percent chance range for almost the entire forecast area. The one exception may be across the far north (NH and western ME). Another small trend is that probablilites for two inches or greater have increased in the Penobscot Bay/Midcoast region (30 to 60 percent). Thus, storm total values are still expected to generally be in the one to two inch range but some locally higher amounts around the Midcoast and up in the mountains will be possible. Now that we are in the range of some of the CAMs, it also appears that precipitation will generally come in two waves, one associated with the warm air advection early Monday morning and then the main wave and cold front arrive by the evening hours for the second round. Many locations could see a lull in activity sometime in the afternoon. Additionally, the NAM Nest is suggesting the potential for instability so some thunder is possible during the day on Monday as well as the evening. Finally, precipitation may start briefly as snow or a wintry mix, but should change to all rain quickly. Some more light snow also may mix in towards the end of the event across the mountains.

In general, the concern for ice jam flooding has decreased a bit as local partner observations from yesterday suggest that more ice has flushed out of the major rivers than originally thought.
The exception may be across the mountains where ice is still holding on a bit stronger. Long story short, the threat for flooding is not zero but the overall risk appears to be limited and localized. The expectation is that remaining ice should flush out fairly quickly once the heavy rainfall starts but it will still need to be watched closely.

Regarding the winds: Low-level winds will be highly anamolous with a 90+ knot 850 mb jet in the forecast. The question will be how much momentum can mix down as the surface pressure couplet and cold air advection moves in Monday night into Tuesday morning. A strong low level inversion will likely keep the more extreme values from mixing down but some gusts in the 40 to 50 mph range seem reasonable which could be enhanced under any convection that moves overhead. Thus wind headlines certainly look possible in the future but we will hold off for now. The wind threat will continue into the day on Tuesday but widespread precipitation will likely move out of the area in the morning.

KEY MESSAGE 3 DESCRIPTION...

Upper trough will move towards the East Coast Tuesday with remaining low level westerly CAA around 30-40 kts. On the heels of the exiting low, the mixing height should deepen with unstable air in the low levels. This means a blustery Tuesday with westerly gusts 30 to 35 mph. Can't rule out a few stronger gusts to 40 mph based on some model profiles at this range. The low levels could remain mixed into the evening and overnight hours, but overall intensity should be decreasing.

The forecast area then takes a step out of the active pattern with stronger jets placed north of the region and surface high pressure to the south. This should lead to a quieter period Wednesday and Thursday with high and low temperatures within a couple degrees of normal for mid March. During this period, there may be enough moisture against the mountains for errant snow showers, but notable QPF at this time appears doubtful.

The next chance for more widespread precip comes later this week in the Fri/Sat timeframe, although there is plenty of model spread here. ECMWF/Canadian seem to depict a low cutting from the Great Lakes into New England, while the GFS is void of this disturbance. Even incorporating cluster analysis there is a wide spread amid 500mb height patterns. Thus will continue to monitor how this potential system progresses through early to mid week.

AVIATION /18Z SATURDAY THROUGH THURSDAY/
Through 18Z Sunday: VFR conditions are generally expected through Sunday afternoon. A few widely scattered rain/snow showers are possible this afternoon, potentially bringing brief restrictions. A few snow showers may linger in the mountains this evening. Westerly winds will prevail with gusts up to 30 kts, relaxing a bit late tonight and into Sunday morning. VFR should prevail through Sunday afternoon.

Outlook...

Monday and Monday Night: High confidence in widespread IFR cigs as a storm arrives with RA and FG. LLWS is likely, with strong SE to S surface gusts along at least coastal terminals.

Tuesday: Cigs should be improving to VFR from MVFR through the morning. W gusts 30-35 kts through the day.

Tuesday Night: VFR with W gusts to 25 kts.

Wednesday and Wednesday Night: VFR, no sig wx.

MARINE
Gale force westerly winds are expected late this afternoon through the first half of tonight outside of the bays with SCA winds over the bays. Seas will build to 4-7 ft outside of the bays with 1-4 ft in the bays themselves. Winds and seas will relax on Sunday.

Large storm system will enter the Great Lakes Sunday night and lift into Quebec through Monday. Southerly gusts to at least Gale are expected Monday as the region enters a warm sector behind departing high pressure. Wave heights rise 8 to 15 ft.
Cold front will pass over the waters Monday night, with winds shifting W. Some gusts to Gale may remain, but generally will be not as strong as Monday. Quieter conditions arrive mid-week as high pressure nears the Northeast.

GYX WATCHES/WARNINGS/ADVISORIES
ME...None.
NH...None.
MARINE...Gale Warning from 6 PM this evening to 2 AM EDT Sunday for ANZ150-152-154.
Small Craft Advisory until 2 AM EDT Sunday for ANZ151-153.