textproduct: Caribou

WHAT HAS CHANGED

Update to 00z aviation discussion.

KEY MESSAGES

1) Showers this afternoon and early this evening, most numerous this afternoon. Thunderstorms are possible, mainly across the north, as well. Any storms could produce gusty winds and small hail.

2) Scattered showers Monday afternoon, mainly over Northern Maine.

3) Areas of frost possible across interior Downeast Maine and the Bangor region Monday and Tuesday night, which could impact sensitive plants.

4) Another soaking rainfall possible for central and southern areas Wednesday night through Thursday night which could further improve drought conditions.

DISCUSSION

KEY MESSAGE 1... Showers this afternoon and early this evening, most numerous this afternoon. Thunderstorms are possible, mainly across the north, as well. Any storms could produce gusty winds and small hail.

KEY MESSAGE 1 DESCRIPTION... A combination of the passage of multiple northern stream shortwaves and the approach of a surface to 850 mb cold front will trigger showers across the region into the early evening hours. Across the North, there should be sufficient low level CAPE of around 250-500 J/kg, along with mid-level lapse rates around 7.5-8C/km, to support some isolated to scattered thunderstorms as well. Any storms could produce wind gusts up to 35-45 mph and small hail. The risk for any thunderstorms should die out fairly quickly as the sunsets. Showers will tapper off from NW to SE from late this afternoon into early this evening.

Rainfall from these showers/thunderstorms should not have any significant hydrologic impact.

KEY MESSAGE 2... Scattered showers Monday afternoon, mainly over Northern Maine.

KEY MESSAGE 2 DESCRIPTION... The main axis of the mean northern stream trough approaches Monday, with the North in the left front quadrant of a 120+ kt 300 mb jet. So even though values of CAPE should only be at most 200 J/kg, low level lapse rates should run around 8.5-9C/km. This should be enough instability to support small hail in any stronger showers, but not quite enough mixing to support any thunder. However, because we are right on the margins for having thunder or not, will not completely rule it out at this time. Once again, no significant hydrologic issues are expected.

KEY MESSAGE 3... Areas of frost possible across interior Downeast Maine and the Bangor region Monday and Tuesday night, which could impact sensitive plants.

KEY MESSAGE 3 DESCRIPTION... The frost/freeze program begins on 5/11 for zones 15-17 (Bangor Region, Northern Hancock and Central Washington) and zones 29-30 (coastal Downeast Maine). So, while frost may occur further north, the climatological growing season has not begun yet there, so impacts there will not be discussed.

A combination of mainly clear to clear sky conditions and light winds should allow for lows to fall into the upper 30s Monday night across zones 15-17. This should allow for areas of frost to occur, especially outside of developed city/town centers.

At this time, there is still some uncertainty on exactly how much cloud cover there will be on Monday night, so no frost headlines will be issued at this time.

On Tuesday night, mostly clear skies and calm winds should allow temperatures to drop rapidly as a result of strong radiational cooling. Currently expecting temperatures to dip into the low to mid 30s across the interior Downeast and Bangor regions which should result in some areas of frost that could damage tender plants. A harder frost is possible in typically cool spots that radiate energy well such as valleys

KEY MESSAGE 4... Another soaking rainfall possible for central and southern areas Wednesday night Thursday night which could further improve drought conditions.

KEY MESSAGE 4 DESCRIPTION... Low pressure over the Great Lakes Wednesday will approach the area from the west. As it reaches coastal New England, a secondary low pressure system may develop just offshore. Rain begins Wednesday evening and eventually clears out early Friday although a few showers could linger. Expect the highest totals in the Bangor and Downeast regions where ensemble models show the probability of at least 0.5 of rain to be around 50%. This event should further contribute to drought relief by recharging soil moisture and helping groundwater deficits.

AVIATION /00Z MONDAY THROUGH FRIDAY/

Tonight...VFR at Aroostook terminals, though cannot rule out brief MVFR vsbys at HUL in -shra the first hour or two this evening. BGR potentially dropping to MVFR vsbys between 03-06z before cold front crosses. BHB experience IFR/LIFR tonight ahead of cold front before improving to VFR by 08z. Mainly SSW winds this evening, becoming lgt/vrb tonight and then NW winds 5-10kts by morning.

Monday...Mainly VFR. WNW winds 5-15kts.

Monday night...VFR. Light NW winds.

Tuesday - Tuesday night...VFR. NW winds 5-15kt, with gusts to 20kt possible during the afternoon. Winds shift W and relax overnight becoming light and variable.

Wednesday - Wednesday night...VFR during the day. MVFR overnight as showers begin to move in, south to north. W/SW winds 5-15kt. Shift S/SE overnight.

Thursday-Thursday night...MVFR with rain showers. IFR possible southern terminals. S/SE winds 10 to 15 kts today becoming E/NE around 5 kts overnight

Friday...MVFR/VFR with rain showers. NW wind 5 to 10 kts.

MARINE

Persistent S swells should keep seas at SCA levels on the coastal ocean waters through at least Monday, so have extended the SCA there through 22z Monday. There is some uncertainty as to how fast the swells dissipate, so did not feel comfortable pushing the SCA into Monday night on the coastal ocean waters at this time.

The intra-coastal waters should remain below SCA levels through Monday night. On the outer waters, winds should be 20 kt or less and seas in the 4-6 ft range, mainly due to southerly swells, through Monday night.

Below SCA conditions Tuesday through Wednesday. SCA conditions on the coastal waters possible Wednesday night early Thursday night and on the intracoastal waters Thursday. Seas not expected to get above 5 ft on the coastal and intracoastal waters and 6 ft on the outer waters Tuesday-Friday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Small Craft Advisory until 6 PM EDT Monday for ANZ050-051.