Possible Severe Weather Outbreak Update Three

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FXUS61 KCAR 281356

AFDCAR

Area Forecast Discussion

National Weather Service Caribou ME

956 AM EDT Fri Jul 28 2023

.SYNOPSIS...

A cold front will cross the region Friday night, then exit

across the Gulf of Maine Saturday while low pressure moves along

the front. High pressure will build toward the region Sunday.

Another cold front could cross the region Monday into Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...

945 a.m. update...High-res models are indicating an earlier

start for thunderstorms this afternoon as a few storms develop

along a pre-frontal trough. Have updated the forecast to reflect

this. Otherwise, fog has lifted into mostly cloudy skies that

are expected to clear later this morning. Temps/dewpoints/winds

updated to reflect current conditions.

Previous Discussion:

Areas of fog have developed over the western half of the

forecast area, as well as over much of the Downeast region, with

patchy fog filling in river valleys in between these two swaths

of fog. This fog will linger through the early morning hours and

begin to erode past sunrise, and is expected to fully dissipate

by mid morning.

A cold front will push into the area this afternoon, bringing

another round of thunderstorms to the forecast area, although

this time to the north. CAPE values ahead of the front will be

elevated, with the NAMNEST, RAP, and HRRR all hinting at values

reaching around 1500 J/kg. Additionally, the tight pressure

gradient aloft between systems in this zonal pattern remains

tight, and a lingering LLJ will keep shear values elevated with

forecast 0 to 6 km bulk shear around 40 to 60 kts. The CAPE

profile is expected to reach well above 400 mb across the north,

which puts the CAPE area within the hail growth zone. This fact

in addition to the increased shear leads to the threat for small

hail in any stronger thunderstorms that develop. Additionally,

relatively dry lower levels with a short but prominent inverted

V profile in forecast soundings, and combined with the lingering

LLJ of 30 to 40 kts aloft, leads to a gusty wind threat,

especially with any stronger thunderstorms that develop. With

drier air moving in with the cold front, PWs will only be

slightly above one inch at most, with forecast PWs sitting

around 1.3 inches. This does not challenge the 90th percentile

for PWs this time of year, and heavy rainfall is therefore not

as significant of a threat.

The cold front will quickly cross through the forecast area

through the afternoon, exiting Downeast through the Canadian

Maritimes this evening. A brief pause in the threat for rain is

expected behind this line, though a second boundary will

approach later tonight with another chance for rain showers

through the night tonight. Behind the cold front, temperatures

will begin to drop as drier air fills in behind, and low

temperatures across the north will fall into the 50s.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...

The cold front will move into the Gulf of Maine and stall out

there on Saturday. At the same time, a wave of low pressure will

ride along the front. Most guidance keeps rainfall with this

wave south of the area, with some light rain brushing the Bangor

region and Downeast for Saturday afternoon into the early

evening. The GFS is a northern outlier, brining steadier rain to

the aforementioned areas with lighter rain up to the Katahdin

region. As such, decided to trim back PoPs from previous

forecast. Confined likely PoPs south of Bangor and chance PoPs

south of Millinocket. Went completely dry in the Crown of Maine

as no guidance shows precipitation reaching there on Saturday.

Any rain will come to an end Saturday evening as the wave moves

off to the east. Regardless of any rainfall, Saturday will be a

much cooler and less humid day, with high temperatures generally

in the 70s. Dew points during the day will be in the 50s North

and in the 60s near Bangor and Downeast closer to the front.

Even drier air will filter into the entire region Saturday night

with northwest flow behind the front. This will result allow low

temperatures to fall to the upper 40s to lower 50s in the North,

and the mid to upper 50s further south. These will be the

coolest low temperatures seen across the region in several

weeks. High pressure will provide continued dry weather Sunday

and Sunday night. Highs will once again be in the 70s, with lows

ranging from the upper 40s to the upper 50s from northwest to

southeast.,,,,,,,

Hazardous Weather Outlook

National Weather Service Caribou ME

324 AM EDT Fri Jul 28 2023

MEZ001>006-010-290730-

Northwest Aroostook-Northeast Aroostook-Northern Somerset-

Northern Piscataquis-Northern Penobscot-Southeast Aroostook-

Central Piscataquis-

324 AM EDT Fri Jul 28 2023

This Hazardous Weather Outlook is for Central Highlands Maine, Far

Eastern Maine, Far Northern Maine and North Woods Maine.

.DAY ONE...Today and tonight.

A cold front will produce thunderstorms this afternoon into this

evening, some of which may be strong to severe. Strong thunderstorms

will have the potential for gusty winds and small hail.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather

conditions according to Standard Operating Procedures.

$$