textproduct: Caribou

WHAT HAS CHANGED

Updated aviation section for 12z TAF issuance

Issued Gale Watch for Outer Waters.

The Storm Prediction Center introduced a marginal risk for severe thunderstorms Tuesday

High confidence in widespread soaking rain Tuesday night into Wednesday night.

Confidence decreasing in any meaningful rain later in the week.

KEY MESSAGES

1) A slight chance of thunderstorms Monday afternoon and Tuesday afternoon.

2) Significant rainfall expected Tuesday night through Wednesday night. The rain will provide continued improvement to drought conditions. While it is not expected to lead to flooding, it could cause the ponding of water in known poor drainage areas.

DISCUSSION

KEY MESSAGE 1... A slight chance of thunderstorms this afternoon and Tuesday afternoon.

KEY MESSAGE 1 DESCRIPTION... A shortwave trough moving in from the west today should provide ample lift for showers to develop late morning over the North Woods and spread eastward throughout the day. Steep low and mid- level lapse rates in combination with sufficient moisture should favor a weak instability profile supportive of a few rumbles of thunder, mainly in the Bangor and Downeast region. Model soundings show a modest inverted-V signature which could favor some gusty winds.

A cold front approaches from the west on Tuesday afternoon/evening and convective allowing models are showing some storms developing ahead of the boundary in an area over northern and western Maine characterized by around 500 J/kg of surface-based instability. Generally expecting storms to remain north of the line between Dover-Foxcroft and Houlton. A relatively dry surface should yield a modest inverted V sounding which again could lead to some gusty winds with any thunderstorms, especially given winds may already be gusting near 30 mph and strong winds near the top of the boundary layer could be mixed down to the surface. Not expecting widespread damage but loose objects may be blown around and a few weak tree limbs could come down. The Storm Prediction Center currently has northern Maine in a marginal risk for severe thunderstorms.

KEY MESSAGE 2... Significant rainfall expected Tuesday night through Wednesday night. The rain will provide continued improvement to drought conditions. While it is not expected to lead to flooding, it could cause the ponding of water in known poor drainage areas.

KEY MESSAGE 2 DESCRIPTION... A northern stream trough slowly approaches from the west Canada Tuesday night and Wednesday then weakens as it lifts to the northeast over Maine Wednesday night. At the surface, a cold front slowly sinks southeast into Maine Tuesday night, an elongated wave of low pressure riding along the front slowly crosses Maine from southwest to northeast Wednesday and Wednesday night, as the cold front continues to track southeastward, pushing offshore late Wednesday night.

With a few hundred J/kg of CAPE still progged to be around northeastern/central Maine at 00z Wed, it warrants a slight chance of thunder to go along with likely pops. The rain associated with the cold front/passing shortwave embedded in the northern stream trough/forcing from the right rear quadrant of a 140+ kt upper jet, then slowly pushes in from NW to SE after 00z into Wednesday afternoon; as indicated by most CAMs. Pops at 00z/03z were a blend of the NAMNest/HiResFV3/HREF/NBM - blending to NBM Pops at 06z to reflect the initial convective precipitation being focused more over central/northeastern Maine at 00z, with maybe some light rain just moving into far NW Maine, to rain mainly focused over Western Maine by 03z.

The rain should become moderate to possibly locally heavy at times from late Wednesday morning through Wednesday afternoon as the region is in the middle of a coupled jet structure, still in the right rear quadrant of a 130kt jet to the N/NW and also in the left front quadrant of a 130kt jet approaching from the SW. In addition, will have additional forcing from a strong low level located just offshore from Tuesday night into Wednesday evening. At this time do not quite have the confidence to place a mention of locally heavy rainfall in the forecast.

The rain should taper off from NW to SE from late Wednesday afternoon through Wednesday night, as the bulk of the supporting forcing exits to the northeast and east. At this time, expecting 1 to 1.5" of rain across the Central Highlands, eastern Aroostook, and the upper Penobscot Valley from Tuesday afternoon through Wednesday night, with from around 0.5" to 1" of rain expected elsewhere, except at elevations above 2000 ft, where around 1.5-2" of rain is forecast. Locally higher amounts are possible in areas experiencing stronger convection Tuesday afternoon/early Tuesday evening and moderate to locally heavy rainfall on Wednesday. Given the current soil and ground moistures, and the levels of area rivers and streams, do not expect any flooding as a result. However, there is the risk of the ponding of water in known poor drainage area, especially in areas receiving moderate to possibly locally heavy rainfall.

Even though the low level jet starts out at 70-75kt Tuesday night, diminishing to 50-55kt on Wednesday, a strong low level inversion should prevent the bulk of this from reaching the surface, so strong winds are not a concern with this system overland.

Currently tidal departures are forecast to be less than 1 ft, and with the region in the middle range of high tide levels, no coastal flooding or overwash is expected from this system.

AVIATION /09Z MONDAY THROUGH FRIDAY/

Today-Tonight...VFR early then brief periods of MVFR possible this afternoon with showers, especially at southern terminals. A few rumbles of thunder possible at BGR between 18z and 22z and thus introduced a PROB30 group for it. Showers end this evening with VFR conditions overnight. W winds at 10 to 15 kts becoming S at 5 to 10 kts overnight. LLWS expected tonight beginning at 5-6z for southern terminals and 8-9z for northern terminals.

Tuesday...Generally VFR, with local MVFR possible in the afternoon with any showers or storms, mainly in the north. S winds 15 to 20 kts with gusts up to 30 kts. LLWS possible, mainly at BHB.

Tuesday Night: IFR or lower likely. LLWS likely at southern terminals. SW winds G15-20KT possible at northern terminals Tuesday evening.

Wednesday-Wednesday Night...IFR or lower likely, with improvement to VFR possible late Wednesday night. LLWS likely at southern terminals Wednesday/Wednesday evening. S winds G15-20KT possible at northeastern terminals Wednesday. NW winds G15-20KT possible late Wednesday night.

Thursday...VFR with a low chance of MVFR.

Thursday Night and Friday...MVFR possible. Low chance of LLWS at southern terminals Thursday night. WNW winds G15-20KT possible Friday.

MARINE

Low end SCA seas today over the coastal waters with below SCA winds. SCA winds on the coastal waters tonight into Tuesday with seas building towards 10ft. Gale conditions on the outer waters possible beginning Tuesday afternoon.

For now it looks like SCA conditions on the coastal/intra-coastal waters Tuesday night-Wednesday night, with gales expected Tuesday night and likely Wednesday/Wednesday night on the outer waters. For now have a gale watch on the outer waters through Tuesday night, this quite likely will need to be extended if the forecast holds. Of some concern is that the models are suggesting the low level jet will not be transient in nature but could linger over the waters for 24-36 hours. If this occurs, not a frequent occurrence at all, then gales might need to be expanded to include the coastal ocean waters as well.

Conditions become sub-SCA on all waters by late Thursday and continue Thursday evening. Building seas could bring a return to SCA conditions to the coastal ocean waters for late Thursday night and Friday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Small Craft Advisory until 8 AM EDT Tuesday for ANZ050-051. Gale Watch from Tuesday afternoon through late Tuesday night for ANZ080-081.