textproduct: Caribou

WHAT HAS CHANGED

-Updated aviation discussion.

KEY MESSAGES

1) A light wintry mix will occur Monday morning producing a light glaze of ice. Snow accumulations of up to an inch are also possible across northern areas, with less than an inch Downeast. The snow and ice could create hazardous conditions for the Monday morning commute.

2) A strong storm Monday into Tuesday will bring high winds and heavy rain, creating potential for scattered power outages and flooding.

3) Strong winds will generate high seas which could lead to wave runup and coastal flooding impacts, particularly if timing lines up with tidal surges.

DISCUSSION

KEY MESSAGE 1... A light wintry mix will occur Monday morning producing a light glaze of ice. Snow accumulations of up to an inch are also possible across northern areas, with less than an inch Downeast. The snow and ice could create hazardous conditions for the Monday morning commute.

KEY MESSAGE 1 DESCRIPTION... A warm front will approach late tonight, then lift across the region Monday. Light overrunning precipitation will develop in advance of the front during the early morning hours of Monday in the form of a light wintry mix. The light wintry mix will then transition to rain, from south to north, through Monday morning. Before the transition to rain occurs, a glaze of ice is possible. Snow accumulations of up to an inch are also possible across northern areas, with less than an inch Downeast. Have issued Winter Weather Advisories for much of the region, with the exception of the Downeast coast, Monday morning. The snow and ice could create hazardous conditions for the Monday morning commute.

KEY MESSAGE 2...A strong storm Monday into Tuesday will bring high winds and heavy rain, creating potential for scattered power outages and flooding.

KEY MESSAGE 2 DESCRIPTION... Per the previous discussion: A strong occluding low pressure system will continue to approach from the west on Monday, with the forecast area in the warm sector Monday into Monday night prior to a strong frontal passage late Monday night into Tuesday morning.

Rain: - Deep moisture will advect into the forecast area on Monday with southerly flow and a strengthening LLJ. PWATs could surge towards well over 1 inch by Monday night with this event, which is 5 standard deviations above normal. To put this extreme moisture surge in perspective, the daily record 00z March 17 PWAT sample from KCAR is 0.83 inches, with forecast PWATs potentially being half an inch of additional moisture into a relatively cool air mass. With strong forcing spanning from the approaching low pressure system, this will likely result in moderate to heavy rainfall across the forecast area, with highest precip totals being across the Downeast region, where storm total rain amounts could exceed 2 inches.

Hydro: - Combined with warm temperatures lifting into the 50s through this time, the Downeast snow pack will quickly melt. All this water and snow melt could result urban and small stream flooding, especially Downeast. The snow pack in the north is better able to absorb the rain, and expected rain totals are less in the northern half of the forecast area. However, rain combined with what snow melt does occur in the north could also lead to localized ponding. Ice rot is likely in the north, while ice movement is quite possible Downeast, such as along the Penobscot.

Winds: - The strong LLJ projected with this system could reach 3 to 4 standard deviations above normal for 850 mb, and could see sustained winds as strong as 70 kts at this level. Rain Monday afternoon through Monday night will mix these higher winds towards the surface, with gusts reaching 35 to 45 mph. The strongest gusts could convectively occur along the FROPA early Tuesday morning, with an extra source of forcing and tightening of the pressure gradient. Strong southerly winds combined with the thawing ground could result in scattered power outages.

KEY MESSAGE 3...Strong winds will generate high seas which could lead to wave runup and coastal flooding impacts, particularly if timing lines up with tidal surges.

KEY MESSAGE 3 DESCRIPTION... Models continue to show the LLJ ramping up Monday afternoon and reaching its peak Monday night. As pressure gradient tightens, sfc winds range from 30-35 kts Monday afternoon with an increase in sustained speeds between 35-40kts on Monday night. These will gradually shift toward the southwest Tuesday morning and drop back down toward 30kts on Tuesday afternoon.

Storm Surge: The probabilistic storm surge shows the peak during Monday night towards the early morning hours of Tuesday. The range of the peak storm surge is between 1.0 to 1.7 ft with lower amounts during the ramp up and cool down.

Winds: Winds over the waters and long on coast will be from the SE on Monday during the increasing of the LLJ. The winds will shift from the S during Monday night during the peak periods.

Waves: During the peak period of Monday night, waves are expected to reach 12-16 feet along the shoreline with periods of 9-10 seconds.

Tides: High tide times will be around 9:30 am Monday morning, 10 pm Monday night and 10:30 am Tuesday morning. Though the peak of the storm should be after the 10 pm Monday night high tide, any shift in storm track will change the timing of the peak of the storm.

As of this update, the total water levels and wave runup levels only reach statement criteria. However, this could quickly change once the peak of the storm approaches high res model runs.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Today: Occasional MVFR ceilings across northern areas early this morning. Otherwise, VFR across the entire region. Northwest/west winds 10 to 15 knots, becoming east/southeast 5 to 10 knots.

Tonight: VFR early. VFR/MVFR, occasional LIFR, late with a light wintry mix developing. East/southeast winds around 10 knots, becoming south/southeast 10 to 20 knots with gusts up to 25 to 30 knots. Southerly low level wind shear develops overnight.

Monday: IFR/LIFR, occasional VLIFR. An early light wintry mix transitioning to rain, from south to north, through the morning. Rain during the afternoon. South/southeast winds 15 to 25 knots with gusts up to 30 to 35 knots. Stronger wind gusts possible along the Downeast coast. Low level wind shear.

Mon night-Tues morning: IFR/LIFR, with VLIFR at times, particularly at KBGR/KBHB. Locally heavy rain probable, -TSRA possible. LLWS likely. SE winds 15 to 20 kts gusting 25 to 30 kts, with brief gusts 40 to 45 kts possible in any stronger convection Tuesday morning.

Tue afternoon: Becoming VFR. WSW winds 10 to 15 kts gusting 25 to 30 kts.

Tue night-Wed: VFR. W winds 10 to 15 kts gusting to 20 kts.

Wed night-Thurs: VFR early, becoming MVFR particularly at northern terminals in -SN. Winds light and variable shifting S at around 10 kts.

MARINE

A Small Craft Advisory remains in effect for all the waters through noon today. Small craft advisory level conditions then re-develop again later tonight. Gale conditions then develop Monday along with building seas. Rain Monday.

Strong gale conditions are likely Monday night through Tuesday, with highest winds overnight Monday night that could approach storm strength. A Storm Watch has been issued for all waters Monday night. Seas 6 to 9 ft on Monday will increase into Monday night, becoming 13 to 20 ft by Tuesday morning. Winds and seas will then gradually improve through the middle of the week. Rain, heavy at times, Monday through Monday night, with lightning possible.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory from 4 AM to noon EDT Monday for MEZ001>006-010. Winter Weather Advisory from 6 AM to 10 AM EDT Monday for MEZ011-015>017-031-032. MARINE...Small Craft Advisory until noon EDT today for ANZ050>052. Storm Watch from Monday evening through Tuesday morning for ANZ050>052.