textproduct: Gray - Portland

WHAT HAS CHANGED

Remaining fog this morning should dissipate quickly once direct sunlight gets to it and west winds begin to mix. Otherwise, little change to the going forecast for the next few days as model continuity seems reasonable.

KEY MESSAGES

1. Humidity abates this weekend while temperatures run warm with highs in the 80s to low 90s today and Sunday.

2. A cold front will cross the region Sunday and bring a possibility for some strong thunderstorms.

3. Seasonable weather returns for much of the work week.

4. High astronomical tides into early next week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

A much drier day in terms of dewpoints is expected today with no precipitation forecasted. Highs will still be quite warm, with max temps today well into the the 80s to near 90. Since humidity levels will be much lower than yesterday, heat indices should be lower than the actually temperatures.

KEY MESSAGE 2 DESCRIPTION...

Sun is still looking like the last of the truly hot days until at least the end of the work week. NBM guidance has been relatively on target for temps this week, and so I do not see much need to go against it at this time. Seeing it with some low 90s and widespread upper 80s, but mixing will tap some drier air aloft still and dewpoints are not expected to be oppressive. Still could leave use flirting with heat advisory criteria in some locations, and we will have to monitor those trends.

Model guidance still hinting at a prefrontal trof setting up locally, but the main cold frontal convection holding off until late evening. That timing is certainly not ideal for severe weather, but CAMs continue to show some isolated storm coverage across northern zones and popping across western NH during the afternoon and early evening. These will be the storms we have to watch closely, as there will be enough low level instability and deep layer shear for storm organization and strong/severe storms. CSU machine learning still showing some severe weather probabilities for our forecast area, mainly tied to wind. This includes both straight-line and tornado. While I don't think tornadoes will be the most likely hazard, forecast soundings do show enough low level turning to produce some favorable hodographs for tornadoes. So I am not ruling out the threat completely. More likely the mid level dry air will be available to help evaporatively cool downdrafts and lead to gusty outflow. The forecast area has been placed in marginal/slight risk areas for severe weather on the latest Day 3 outlook from SPC. So will be continuing with the thunder mention, but hold off on enhanced wording until it is clear there will be convection during the daylight hours.

KEY MESSAGE 3 DESCRIPTION...

Little change in model guidance for a return to seasonable weather for much of the next week. Once the cold front clears the coast, which may delay until Mon morning we should see widespread high temps in the 75 to 85 degree range. Nighttime lows will be a comfortable 50s to low 60s, though a couple nights may sneak into the 40s for the northern valleys. Ahead of the next trof late in the week temps will start to creep back up along with humidity. This could bring back upper 80s to near 90 for parts of southern NH and coastal western Maine. Especially towards the mid to latter half of the week diurnal convection will become more likely, but certainly not organized. That will have to wait until that trof Fri or Sat, when a large upper low axis is forecast to cross the Northeast. Showers/thunderstorms along that cold front should be fairly numerous, and will represent our next chance for widespread rainfall.

KEY MESSAGE 4 DESCRIPTION...

High astronomical tides combined with storm surge up to around 1/2 foot may bring total water levels to near minor flood stage around the times of high tide this weekend into early next week.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

Through 12z Sunday...Dense fog along the ME coast this morning dissipates by 14z. VFR today with some west gusts to 15 kts. VFR continues tonight and into Sunday morning. A drier airmass should prevent overnight fog development tonight.

Outlook:

Sunday: VFR. Late afternoon/early evening showers or thunderstorms possible for western NH terminals.

Sunday Night: Showers/storms continue local MVFR or lower conditions, becoming VFR after midnight outside of the mountains.

Monday - Thursday: VFR conditions expected during the day. Some local valley fog possible in the vicinity of LEB and HIE at night.

MARINE

Some marginal SCA conditions are possible ahead of the cold front Sun night into Mon morning. Otherwise winds and seas are expected to remain below SCA thresholds. Areas of fog and low clouds are possible Sun into Sun night before cold front clears out. While thunderstorms are possible Sun night over the coastal waters, there does appear to be a diminishing threat for strong to severe convection.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Beach Hazards Statement through this evening for MEZ023>028. NH...Beach Hazards Statement through this evening for NHZ014. MARINE...None.