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FXUS61 KCAR 191919 AFDCAR

Area Forecast Discussion National Weather Service Caribou ME 319 PM EDT Sun May 19 2024

SYNOPSIS
High pressure will ridge across the region today through early week, then build south of the area through the middle of the week. A strong cold front will cross the area Thursday, followed by high pressure Friday into next weekend.

NEAR TERM /THROUGH MONDAY/
An upper level ridge will continue to influence the surface ridge sitting over the region tonight. High-res guidance indicates a coastal boundary developing with ENE winds over the waters and SE winds on the coast. This in addition with the 500mb vort max sitting over Downeast will bring in a low stratus deck into the region, starting in the south, then spreading north throughout the night with the S flow. In addition, patchy fog could develop at the surface. Temps will be in the low 50s in the north and upper 40s in the south with slightly cooler temps on the coast.

By Monday, as the axis of the upper level ridge begins to shift south, a weak surface trof develops. For the morning, RH models show the skies starting to clear with fair weather cumulus sticking around into the afternoon. Upper air model soundings show the instability increasing across the north with the higher values in the North Woods. CAPE values greater than 1000 J/kg, lapse rates greater than 7, and increasing upper level divergence are all good indicators for isolated thunderstorms in the afternoon and into the evening. Bulk shear is lower than general severe criteria, so the possibility of stronger storms is low, but cannot rule it out. Temps in the upper 70s in the north and low 70s in the south with coolers temps at the coast.

SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/
In general, a powerful upper ridge will dominate area weather through the period with subsidence and warming. The warmest temperatures of the year can be expected during the period with highs reaching the 80s and lows over 60F for large portions of the forecast area by Tuesday night.

A series of fronts riding the northern periphery of the ridge through the period represents the forecast challenge in terms of thunderstorms and exact hi/low temperatures through the period.

On Monday night, expect a weak northern stream cold front to sag southward into the area accompanied by an equally weak upper shortwave. The net result is expected to be an isolated evening thunderstorm in northern Aroostook County and no cold air advection. Lows in the northern half of the forecast area will be in the mid to upper 50s while an onshore flow of cool marine air will drop coastal lows towards 50F with the threat of fog.
The front will likely stall over the area for Tuesday.

The big question for Tuesday will be the progression of today's convective disturbance over Kansas over the upper ridge and towards northern Maine. Guidance is offering a wide variety of timing solutions from Tuesday to Tuesday night, possibly as an MCS. The former timing favors the risk of a fairly significant convective outbreak featuring robust shear and some of the unpleasant outcomes that can bring in late May. The latter solution brings the hottest day of the year to date on Tuesday without thunderstorms until Tuesday night, if any.

Onshore winds will ensure cooler temps and stability towards the coast on Tuesday.

The frontal boundary location remains the nexus between temperature and PoP forecasts into Wednesday. At this point, have played for slightly cooler highs in northern zones due to the boundary, but mid 80s or higher seems likely for the Bangor area. If the frontal boundary moves northward more rapidly, these mid 80s may extend northward across the entire forecast area. In terms of convection, expect the upper level ridge to build on Wednesday and cap convection. Did mention a slight chance of afternoon thunderstorms in case the cap breaks or there is a large timing error regarding the disturbance expected Tuesday and Tuesday night.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
Thunderstorms are again a threat for Wednesday night as a weakening warm occlusion moves through the area. Clouds, precip and warm advection will keep lows in the 60s and humidity will reach its zenith so far this year with dew points in the lower to mid 60s.

These dew points will continue ahead of a strong cold front on Thursday. The cold front will act a potent trigger for widespread convection. All of the ingredients for an active day seem to be in place: CAPE, strong shear and anomalous PWs. About the only issues to lessen severe potential will be unfavorable timing for the frontal passage or unexpected development of a strong/persistent low level inversion. It has been quite a few years since we have seen such a favorable setup for severe weather in late May. The hydro aspect will also have to be watched given the deep moisture.

The front will exit quite quickly Thursday night and bring a very welcome relief in terms of temperatures and dew points for Friday and throughout next weekend. There will still be the chance of light rainshowers with the upper trough on Friday, but expect the threat of thunderstorms to be over. Highs return to the 60s for the holiday weekend with lows in the 40s.

AVIATION /18Z SUNDAY THROUGH FRIDAY/
NEAR TERM: MVFR conditions will continue throughout tonight.
After midnight, all terminals will decrease to IFR with possible LIFR cigs in low stratus. By Monday morning, the cigs will begin to lift to MVFR, with VFR by the afternoon. Possible thunderstorms for north terminals in the afternoon and evening.
Light S winds tonight and Monday morning, then increase to 5-10 kts Monday afternoon.

SHORT TERM: Monday night...VFR except a slight chance of evening thunder near FVE and slight chance of fog at BHB. Light south winds.

Tuesday
VFR with a chance of thunderstorms
mostly in the afternoon north of BGR. Light south winds.

Tuesday night...VFR except a slight chance of fog at BHB. Light south winds.

Wednesday...VFR with a slight chance of afternoon thunderstorms.
Light south winds.

Wednesday night...VFR with a slight chance of fog at BHB. Light south winds.

Thursday...VFR tempo IFR in strong thunderstorms. Light south winds outside of thunderstorms.

Thursday night into Friday...VFR with tempo MVFR cigs possible north of HUL early Friday. Scattered showers possible north of HUL.

MARINE
NEAR TERM: Winds and seas will remain below SCA conditions tonight and Monday. Patchy fog is expected over the waters tonight.

SHORT TERM: Warm and relatively humid air moving over the cold waters is likely to cause fog at times Monday night into Thursday night. The stability will reduce winds and seas through next week. In general, southwest winds around 10 to 15 kt can be expected until Friday night when winds will become more westerly. Seas will mostly run 2 to 4 feet, but south swell may exceed 5 feet on Thursday and necessitate an SCA.

CAR WATCHES/WARNINGS/ADVISORIES
ME...None.
MARINE...None.

Bonsecours
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Sun -- 03:13 AM EDT     Moonset
Sun -- 03:39 AM EDT     4.14 meters High Tide
Sun -- 05:00 AM EDT     Sunrise
Sun -- 09:51 AM EDT     1.21 meters Low Tide
Sun -- 03:54 PM EDT     4.23 meters High Tide
Sun -- 04:21 PM EDT     Moonrise
Sun -- 08:16 PM EDT     Sunset
Sun -- 10:11 PM EDT     1.28 meters Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION

Bonsecours, Quebec, Tide feet

St-Jean-Port-Joli
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Sun -- 03:07 AM EDT     4.47 meters High Tide
Sun -- 03:13 AM EDT     Moonset
Sun -- 04:59 AM EDT     Sunrise
Sun -- 09:25 AM EDT     1.19 meters Low Tide
Sun -- 03:28 PM EDT     4.30 meters High Tide
Sun -- 04:20 PM EDT     Moonrise
Sun -- 08:16 PM EDT     Sunset
Sun -- 09:36 PM EDT     1.22 meters Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION

St-Jean-Port-Joli, Quebec, Tide feet

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