Gale Warning 20, NWS Gray, ME

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1030 AM EDT Fri May 4 2018

.SYNOPSIS...
Low pressure will develop over the eastern Great Lakes region
today before heading up the Saint Lawrence River Valley tonight.
This will allow a warm front to enter Maine and New Hampshire
today, followed by the passage of a cold front tonight. A cold
front will approach from the northwest Saturday, before crossing
the region late Sunday and Sunday night as low pressure passes
east of New England. High pressure will build over the region
from Canada on Monday and Tuesday followed by a passage of
another cold front Tuesday night with more high pressure
expected for Wednesday and Thursday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1015 am Update: Going forecast largely in good shape this
morning with primary changes being to match mid morning
temperature/dewpoint trends and also back off on PoPs for a few
hours based on regional radar composites.

As we move into this afternoon...attention turns to convective
potential as low pressure now over lower Michigan continues to
strengthen as it lifts north and east. At mid levels...height
falls will continue to spread into New England from the west.
Largest question...which it typically is for our area is the
amount of destabilization that will be realized. Mid morning
visible imagery doesn't offer a lot of hope with filtered sun at
the moment and only and increase in clouds from the west
expected. However...enough insolation has already been realized
to bring temps into the lower 70s across southern NH with
dewpoints above 60 in these spots. Feeling is that any
convection will wait until later...when the mid level jet streak
/100kt/ arrives from the west /after 4pm/. By this time...HREF
suggests some potential for 500-1000 J/KG of MUCAPE over the
southwestern half of NH. Thus...while I do expect convection to
be in a weakening mode when it arrives late this afternoon...
isolated severe is certainly possible with damaging winds being
the greatest threat. Inherited forecast has this potential
covered well and did not make any significant adjustments
through the afternoon.

Also watching a period around midnight tonight just after the
cold frontal passage when winds may near advisory levels for a
few hours before settling back down /but remaining gusty/
towards daybreak. Contemplating headlines in this area...as well
as a need for gales over the waters.

Finally...rivers continue to run high with some concern for
flooding on the Pemi at Woodstock tonight given sufficient
rainfall. Not enough widespread heavy rain or expected flooding
to warrant a watch...but something we will continue to watch.

630 am Update: Only minor tweaks to temps otherwise no changes
needed at this time.

Previous Discussion:
A developing low pres system over the eastern Great Lakes will
move east along the St. Lawrence Valley and push a frontal
boundary currently south of the area northward today. Dewpoints
will rise into the lower 60s across the area today while wind
fields and low level/deep layer vertical shear increase in the
afternoon. Heating will be hampered by cloud cover in the
morning but any breaks may be enough to help enhance some of the
storms in the afternoon. Expect numerous showers and scattered
tstorms to develop in the afternoon and into the evening hours.
Some of the storms may reach severe limits with hail and strong
damaging winds...especially over NH and extreme southwest ME.
Temps today will be warmest across NH reaching into the 70s to
lower 80s while cooler temps in the mid 60s to mid 70s expected
in Maine. Coolest readings today will be along the immediate
Maine coast from points east of Portland where temps will
struggle to climb out of the upper 50s to lower 60s due to the
developing onshore south to southeast flow.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Tonight the low pressure system rapidly exits northeast into the
maritimes and allows a trailing cold front to move across the
region later in the evening so the convection is expected to
continue into the evening ahead of the front. After midnight
behind the FROPA winds will shift to the west and allow clearing
to take place.

Saturday a gusty west wind will continue under mostly sunny
skies as high pres builds into the region. Temps will be at
seasonal levels.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
A cold front will approach from the northwest Saturday, before
crossing the region late Sunday and Sunday night as low pressure
passes east of New England. This will allow for scattered
showers in Maine and New Hampshire on Sunday. Scattered showers
will continue into Sunday night as an area of low pressure
develops and passes east of New England.

Cold air advection will allow H8 temperatures to drop to between
minus 2C and minus 4C by late at night, Sunday night. This will
allow some of the rain showers to change to snow showers over
the higher terrain.

On Monday, Canadian high pressure will build over the region.
This will bring dry conditions to the region with possibly a
late day sea breeze as the gradient relaxes over the region.
High will generally be in the lower 60s over Maine and New
Hampshire, however the coastline will struggle to warm greater
than the upper 50s due to the developing onshore winds.

A cold front will approach the region from Canada on Tuesday,
before crossing the region Tuesday night. This front will be
relatively moisture starved as well so no precipitation is
expected with this weak system. High pressure will then follow
with more dry conditions Wednesday and Thursday as low pressure
passes by to our south.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
Short Term...Mainly VFR conditions this morning except for
isolated areas of IFR cigs over eastern areas of Maine. During
the afternoon and into the evening showers and sct tstorms will
lower conditions to MVFR/IFR at times. Some of the storms may
contain hail and strong gusty winds. Conditions return to VFR
by Sat morning.

Long Term...Areas of MVFR conditions in lowering ceilings and
possibly lowering visibilities in any showers Sunday and Sunday
night. Otherwise, VFR conditions through the period.

&&

.MARINE...
Short Term...Winds/Seas will build to SCA conditions tonight and
continue through Sat. Some gusts will be briefly near Gale
force behind the cold frontal passage later tonight over the
outer waters.

Long Term...Seas and winds mainly below SCA thresholds through
the period.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory from 11 PM this evening to 8 PM EDT
     Saturday for ANZ150>154.

&&

NEAR TERM UPDATE...ARNOTT

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