textproduct: Caribou

WHAT HAS CHANGED

- 7 AM Update: Minor changes made to the Aviation section below to discuss LLWS with the 12z TAFs

KEY MESSAGES

1) Unseasonably warm today with afternoon highs climbing into the low to mid 70s away from the coast.

2) Dry and breezy conditions this weekend into Monday may lead to some fire weather concerns.

3) Thunderstorms and very warm temperatures possible Tuesday and Wednesday.

DISCUSSION

KEY MESSAGE 1...Unseasonably warm today with afternoon highs climbing into the low to mid 70s away from the coast.

KEY MESSAGE 1 DESCRIPTION... An unseasonably warm southwest flow is expected across the region today. Afternoon high temperatures are expected to climb into the low to mid 70s inland away from the coast.

Although air temperatures will be unseasonably warm this afternoon, water temperatures on areas rivers and lakes are only in the mid 40s, and in the lower 40s on the ocean waters. Anyone deciding to venture into the colder waters should be aware that hypothermia is a threat. Those venturing on the water are encouraged to refer to our Special Weather Statement, as well as our Beach Hazard Statement highlighting the cold water danger.

KEY MESSAGE 2...Dry and breezy conditions this weekend into Monday may lead to some fire weather concerns.

KEY MESSAGE 2 DESCRIPTION... Early Sunday, a cold front moves through with very little precipitation, gusty NW winds with gusts up to around 30 mph, coupled with RHs down to around 30 percent over the whole area will lead to increased fire risk.

Heading into the day on Monday, a deep mid level dry layer will begin the day between around 850 to 700 mb. Diurnal heating through Monday morning will create steep lapse rates and an inverted V signature that can be seen on forecast soundings. With a pattern like this, it is often seen that dewpoints will rapidly drop, and fall further than guidance is able to capture ahead of time. With that in mind, forecast dewpoints on Monday were lowered as compared to the NBM, with some tenth percentile blended in to pull these down. The resulting relative humidity may very well fall to between 20 and 30 percent during the day, with very dry weather persisting through the afternoon and continued increased fire risk. Winds will be less than was seen on Sunday, with generally light winds, though some breezier gusts up around 20 mph are possible in the Bangor and Downeast regions Monday afternoon under peak diurnal heating.

KEY MESSAGE 3...Thunderstorms and very warm temperatures possible Tuesday and Wednesday.

KEY MESSAGE 3 DESCRIPTION... The broad synoptic pattern through the middle of this week is a broad upper level ridge crested over the eastern CONUS. Despite this pattern, however, a potent 500 mb shortwave is forecast to cross Maine during the day on Tuesday, generating instability over the area that could translate into convective development by Tuesday afternoon.

For the finer convective details, around 500 J/kg of CAPE combined with around 30 kts of bulk shear could not only support thunderstorm development, but even potential for some isolated stronger storms that may become severe. There remains some uncertainty in the mesoscale features that any convective development will rely on in order to organize into storms, however. The main uncertainty is where a warm front will settle in the area. If the warm front sits across the Saint John Valley, the majority of the state will remain in the warm sector of the surface low pressure, with SW winds advecting warm, moist air into the region. Temperatures could reach into the 80s over most of the area, surface temperatures soar over the convective temperature, and plenty of ingredients will be available for storm development. Meanwhile, if the warm front settles further south, such as the 00z ECMWF or 18z GFS depiction with the front across central Aroostook county, more overcast skies and cooler temperatures will plague the state, minimizing how much the atmosphere can charge through the afternoon. Currently, the main hazard from any severe storms would be small hail and strong winds, based on the forecast shear and "inverted V" signature on forecast soundings. The current trend across 00z guidance is for the front to take the northern position, and we continue to monitor this day for the threat for strong to severe thunderstorms.

On Wednesday, the cold front associated with the shortwave/surface low may cross the forecast area, providing another source of lift for convective development. Though ingredients do not look quite as favorable, there remains the chance for thunderstorms, and with 40 kts bulk shear and a few hundred J/kg of CAPE, some of these storms may be strong as well. This cold front will clear the abnormally warm air mass from our CWA, with cooler temperatures into the second half of the week and maybe even a returned threat for frost in the North Woods.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

Today....VFR. Light S wind early, becoming SW 10 to 15 kt with gusts up to 20 kt.

Tonight...Generally VFR. Low chance MVFR in scattered showers. SW wind 10 t0 15 kt, becoming NW late. Brief LLWS possible at southern terminals late.

Sunday...VFR. NW wind 10 to 20 kt with gusts to 25 kt.

Sunday Night to Monday Night...VFR. NW wind around 5 kts, shifting to the S.

Tuesday and Wednesday...Potential exists for thunderstorms each afternoon, with greater chance for thunderstorms at northern terminals on Tuesday and across all terminals on Wednesday. Generally VFR conditions until precipitation moves in, when conditions may fall to MVFR/IFR. W winds 5 to 10 kts, becoming SW on Wednesday. Gusts 20 to 25 kts each afternoon, with higher gusts possible with any thunderstorms.

MARINE

Small Craft advisory remains in effect for the coastal waters through early Sunday morning.

Conditions will be generally under small craft advisory levels Sunday night through the middle of the upcoming week, with winds less than 25 kts on all but the outer waters through this time and seas generally 3 to 5 ft. Seas may approach 5 ft on the coastal waters Tuesday night into Wednesday with the next low pressure system. Stable air over the waters will limit any thunder threat, but some rain showers are possible on Wednesday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Beach Hazards Statement through this evening for MEZ029-030. MARINE...Small Craft Advisory until 8 AM EDT Sunday for ANZ050-051.