textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes with this evening forecast update. Storms have not been able to sustain themselves so far this evening and with the liner convection currently over New York still hours away the concern for severe weather in our area is decreasing, but can't rule out a thunderstorm or two making the journey. Otherwise, we can just expect rain (some pockets of heavier rain) overnight.

The aviation discussion has been updated to reflect the 00Z TAF package.

KEY MESSAGES

1. Showers and thunderstorms overspread the area this evening. Strong to severe storms are possible along the CT River Valley and across south-central New Hampshire with damaging winds the primary threat.

2. Above normal temperatures and scattered showers will remain possible on Friday, especially across southern locations.

3. Cooler temperatures will arrive on Saturday and persist through much of next week with numerous chances for showers along with dry periods mixed in between. A steadier period of rain is possible Sunday into Sunday night.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Latest surface analysis shows an area of low pressure lifting northeast through the St Lawrence Valley. South to southwest winds across interior New England are advecting warm and moist air into interior New Hampshire while ESE winds are holding the marine layer in place across Maine and far eastern New Hampshire. Latest satellite imagery shows partly to mostly clear skies across much of SW New Hampshire where the atmosphere has started to destabilize. Instability is expected to increase across western and southern NH through late afternoon providing fuel for thunderstorms this evening.

The 12Z HREF continues to highlight the 5 PM to 10 PM time range for strong to severe storms with the greatest threat across central and southern New Hampshire. Storms that track to the NH/ME border will likely encounter marine air and pose less of a severe threat into Maine. CAMs have been suggesting a few discrete cells will possibly develop over Upstate NY and VT and track into western NH between 6-8 PM. If these discrete cells are able to materialize they will encounter an environment supportive of super cell structures that will pose both a damaging wind and hail threat. Low level wind fields also suggest that a tornado cannot be ruled out. From 8 PM onward CAMs bring additional storms across the NH with storm mode favoring multi cell clusters and small line segments. These storms will primary bring a damaging wind threat, although the later arrival of storms past sunset will work against this threat. Storms will continue to track across southwest Maine to the coast but will be weakening as they do so. Any thunderstorm activity should diminish by 11 PM with showers and fog lingering overnight.

KEY MESSAGE 2 DESCRIPTION...

Friday will feature one more warm day as a weak area of low pressure tracks along a stationary boundary to our south, ahead of a cold front which will cross later in the day. Increasing sunshine is expected from north to south with high temperatures into the 60s and lower 70s. A few showers are possible across southern locations, especially during the morning. Partly cloudy skies will prevail Friday night with lows into 40s.

KEY MESSAGE 3 DESCRIPTION...

Mid-lvl ridging will move across the forecast area on Saturday, allowing for a dry day with with partly sunny skies. High temperatures will be cooler with readings mainly into the 50s across western ME with lower 60s in NH. Cloudy skies will prevail on Saturday night with scattered showers becoming likely as overnight lows fall once again into the 40s. A surface cold front and accompanying weak area of low pressure will cross on Sunday and Sunday night, bringing widespread rainfall. Drier weather then is likely Monday into Tuesday before a cutoff low pressure system arrives towards the middle to end of the week, potentially resulting in several days of unsettled weather and cooler than average temperatures.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Through 00Z Saturday... A marine airmass will continue IFR/LIFR at KRKD and KAUG overnight. Farther west, KPWM and KPSM will see MVFR lower to IFR/LIFR overnight and a TS cannot be ruled out between 00Z and 03Z. VFR likely continues into this evening at KCON and KMHT and a TS cannot be ruled out from 00Z to 03Z. VFR at KHIE and KLEB will give way to chances for MVFR in showers past 00Z. Scattered showers will persist overnight and lowering cigs and fog will likely bring IFR to LIFR everywhere overnight. Cigs will remain around IFR thresholds Friday morning and will gradually lift through Friday afternoon north to south with many terminals VFR by 20Z.

Outlook:

Friday Night: Mainly VFR conditions outside of any lingering morning showers and lower ceilings. NE winds at 10-15 kts.

Saturday-Saturday Night: VFR conditions expected. E-SE winds at 10-20 kts.

Sunday/Sunday Night: Mainly VFR conditions through 00Z Monday before RA develops Sunday evening through Sunday night, bringing MVFR-IFR restrictions. S-SE winds becoming NW.

Monday/Monday Night: VFR conditions expected with W-NW winds.

Tuesday/Tuesday Night: Mainly VFR conditions but scattered showers are possible.

MARINE

Winds and seas remain below SCA thresholds through Saturday. A stalled front over the waters will continue areas of fog into Friday. Showers and possibly a few thunderstorms will track into the waters late this evening through the first half of tonight.

W-NW wind gusts up to 25-30 kts are possible on Sunday night into Monday morning across the coastal waters with seas of 4-6 ft. Otherwise, wind and seas are expected to mostly remain below SCA criteria through the period.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...None.