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Area Forecast Discussion (AFD)

Issued by Gray - Portland, ME (GYX)

                            
000
FXUS61 KGYX 172230
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
630 PM EDT Fri Aug 17 2018

.SYNOPSIS...
A warm front will cross the region tonight as low pressure 
moves through northern Maine. The low will shift east into the 
maritimes Saturday with a trailing cold front pushing offshore 
by evening. High pressure will build in from the northeast 
Saturday night through Sunday and then hold over the region 
Monday and Tuesday. Low pressure will move in from the west 
Tuesday night and Wednesday. High pressure will build in from 
the west Wednesday night and Thursday.

&&

.NEAR TERM /THROUGH SATURDAY/...
6pm update... Have trended the Pops downward through tonight.
Still expecting convection to impact the area with some risk for
stronger thunderstorms to contain damaging winds however the
coverage looking to the west isn't quite high enough to justify
definite pops, so have dropped to likely across the area.
Showers that are forming are producing very heavy rainfall so
expect QPF amounts to vary widely with the scattered nature of
the convection. 

Prev disc...Warm front currently pushing northeast through the 
Connecticut Valley early this afternoon. A band of light to 
moderate showers are accompanying this boundary across west 
central and northern New Hampshire with some thunderstorms 
pushing into southwest New Hampshire. Moderate onshore flow in 
southeast New Hampshire will likely inhibit this convection as 
it continues east through mid afternoon.

Clearing in the warm sector noted in sat pics over eastern New 
York and southwest Vermont and this area of clearing will shift 
into southern and central New Hampshire towards evening. Big
question will be how much CAPE can be generated with this
clearing coming so late in the day but latest radar loop showing
convection quickly firing in areas which cleared first in east
central New York and this activity should push into western New
Hampshire during the evening hours. Main threat with any severe
storms will be mostly wind damage. With freezing levels above
15KFT will probably only see small hail if any.

Later this evening expect shower and scattered thunderstorms to
continue as low pressure shifts into northern zones along a slow
moving frontal boundary. With PWAT's at 1.5 to 2 inches would
expect heavy rainfall in any convection and any training cells
may cause flash flooding issues. Low temperatures overnight 
will remain mild with readings generally ranging through the 60s
to near 70 in the far south.

&&

.SHORT TERM /SATURDAY NIGHT/...
Frontal boundary will gradually sag south through the region
Saturday as weak low pressure moves east along it. This will
keep rain in the forecast for much of the day...especially in
southern zones. May develop enough CAPE in the afternoon in
southern New Hampshire to pop off a few thunderstorms but most 
of the region should just see rain. The front will gradually 
shift offshore Saturday afternoon with showers ending in 
northern and central portions of the forecast area. Showers and 
clouds will likely linger in southern and coastal zones into the
evening hours. Highs on Saturday will range from the mid 60s 
north to near 80 in the far south.

Clouds will gradually clear Saturday night as high pressure
begins to build south from Canada. Would expect areas of fog in
the usual locations after midnight. Lows will range from the
lower 50s north to the lower 60s south.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
The extended forecast will feature some battling between the 500
MB sub-tropical ridging over the wrn Atlantic, and some cooler
troughing extending off Arctic near nrn Hudson Bay. Overall,
thru the period, the ridge should enough to keep the energetic
part of the trough well to our N, but it should allow some more
moderate 850 MB temps to settle over the region, pretty close to
normal anyway, based on sounding climatology. Initially, though
will see more NE flow, and some of that cold-air damming 
signature we saw a little of last week, then some warming around
the middle of the week, followed by another could down to 
normal toward the end of the week. No major systems in our 
areas, but will see several chance for showers/convection. 

Sunday should be a decent day with partly to mostly sunny skies
/sunniest in the N/, but cool with NE flow, with highs mainly in
the 70s. There a slight chance for a shower in srn NH and the ME
coast as the front remains stalled to the south, but there
should be enough dry flow from the NE to prevent anything more
than a quick shower or sprinkle in this area.  

Models continue to struggle with weak wave passing to our south
for Sunday night an Monday, and therefore will keep some chc to
slt chc pops going in the srn zones in this time frame, but
again it looks best activity would remain S of the CWA. Sunday
mins should be in the mid 50s to low 60s, with highs on Monday 
in then 70s again.

After a brief break Mon night into Tue night, will see another
chc for showers ans t-storms Wednesday, as low pressure passes
to our N and drags a cold front across the region. This should
bring a decent day Thu with temps coming in around normal 
again. Could see things warm up gain toward the end of next 
week.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Short Term...Areas of MVFR/IFR ceilings/vsby developing
overnight and persisting through Saturday. Becoming VFR with
areas of IFR/LIFR ceilings/vsby in valley fog Saturday night.

Long Term...For the most part, should see VFR Sunday through Tue
night, with vly fog possible each night. Sct SHRA/TSRA possible
on Wed.

&&

.MARINE...
Short Term...SCA's may be needed Saturday night.

Long Term...Border SCA conds possible in NE flow on Sunday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.

&&

$$
SYNOPSIS...
NEAR TERM...Curtis
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...

206 
FXUS61 KGYX 172230
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
630 PM EDT Fri Aug 17 2018

.SYNOPSIS...
A warm front will cross the region tonight as low pressure 
moves through northern Maine. The low will shift east into the 
maritimes Saturday with a trailing cold front pushing offshore 
by evening. High pressure will build in from the northeast 
Saturday night through Sunday and then hold over the region 
Monday and Tuesday. Low pressure will move in from the west 
Tuesday night and Wednesday. High pressure will build in from 
the west Wednesday night and Thursday.

&&

.NEAR TERM /THROUGH SATURDAY/...
6pm update... Have trended the Pops downward through tonight.
Still expecting convection to impact the area with some risk for
stronger thunderstorms to contain damaging winds however the
coverage looking to the west isn't quite high enough to justify
definite pops, so have dropped to likely across the area.
Showers that are forming are producing very heavy rainfall so
expect QPF amounts to vary widely with the scattered nature of
the convection. 

Prev disc...Warm front currently pushing northeast through the 
Connecticut Valley early this afternoon. A band of light to 
moderate showers are accompanying this boundary across west 
central and northern New Hampshire with some thunderstorms 
pushing into southwest New Hampshire. Moderate onshore flow in 
southeast New Hampshire will likely inhibit this convection as 
it continues east through mid afternoon.

Clearing in the warm sector noted in sat pics over eastern New 
York and southwest Vermont and this area of clearing will shift 
into southern and central New Hampshire towards evening. Big
question will be how much CAPE can be generated with this
clearing coming so late in the day but latest radar loop showing
convection quickly firing in areas which cleared first in east
central New York and this activity should push into western New
Hampshire during the evening hours. Main threat with any severe
storms will be mostly wind damage. With freezing levels above
15KFT will probably only see small hail if any.

Later this evening expect shower and scattered thunderstorms to
continue as low pressure shifts into northern zones along a slow
moving frontal boundary. With PWAT's at 1.5 to 2 inches would
expect heavy rainfall in any convection and any training cells
may cause flash flooding issues. Low temperatures overnight 
will remain mild with readings generally ranging through the 60s
to near 70 in the far south.

&&

.SHORT TERM /SATURDAY NIGHT/...
Frontal boundary will gradually sag south through the region
Saturday as weak low pressure moves east along it. This will
keep rain in the forecast for much of the day...especially in
southern zones. May develop enough CAPE in the afternoon in
southern New Hampshire to pop off a few thunderstorms but most 
of the region should just see rain. The front will gradually 
shift offshore Saturday afternoon with showers ending in 
northern and central portions of the forecast area. Showers and 
clouds will likely linger in southern and coastal zones into the
evening hours. Highs on Saturday will range from the mid 60s 
north to near 80 in the far south.

Clouds will gradually clear Saturday night as high pressure
begins to build south from Canada. Would expect areas of fog in
the usual locations after midnight. Lows will range from the
lower 50s north to the lower 60s south.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
The extended forecast will feature some battling between the 500
MB sub-tropical ridging over the wrn Atlantic, and some cooler
troughing extending off Arctic near nrn Hudson Bay. Overall,
thru the period, the ridge should enough to keep the energetic
part of the trough well to our N, but it should allow some more
moderate 850 MB temps to settle over the region, pretty close to
normal anyway, based on sounding climatology. Initially, though
will see more NE flow, and some of that cold-air damming 
signature we saw a little of last week, then some warming around
the middle of the week, followed by another could down to 
normal toward the end of the week. No major systems in our 
areas, but will see several chance for showers/convection. 

Sunday should be a decent day with partly to mostly sunny skies
/sunniest in the N/, but cool with NE flow, with highs mainly in
the 70s. There a slight chance for a shower in srn NH and the ME
coast as the front remains stalled to the south, but there
should be enough dry flow from the NE to prevent anything more
than a quick shower or sprinkle in this area.  

Models continue to struggle with weak wave passing to our south
for Sunday night an Monday, and therefore will keep some chc to
slt chc pops going in the srn zones in this time frame, but
again it looks best activity would remain S of the CWA. Sunday
mins should be in the mid 50s to low 60s, with highs on Monday 
in then 70s again.

After a brief break Mon night into Tue night, will see another
chc for showers ans t-storms Wednesday, as low pressure passes
to our N and drags a cold front across the region. This should
bring a decent day Thu with temps coming in around normal 
again. Could see things warm up gain toward the end of next 
week.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Short Term...Areas of MVFR/IFR ceilings/vsby developing
overnight and persisting through Saturday. Becoming VFR with
areas of IFR/LIFR ceilings/vsby in valley fog Saturday night.

Long Term...For the most part, should see VFR Sunday through Tue
night, with vly fog possible each night. Sct SHRA/TSRA possible
on Wed.

&&

.MARINE...
Short Term...SCA's may be needed Saturday night.

Long Term...Border SCA conds possible in NE flow on Sunday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.

&&

$$
SYNOPSIS...
NEAR TERM...Curtis
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...