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Area Forecast Discussion (AFD)

Issued by Gray - Portland, ME (GYX)

                            
000
FXUS61 KGYX 222145 AAA
AFDGYX

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
545 PM EDT Mon Jul 22 2019

.SYNOPSIS...
Low pressure will track along a stationary front over southern
New England this evening, bringing potentially heavy rain to 
the area. A second area of low pressure will cross along this
front Tuesday morning, bringing additional precipitation to
southernmost portions of Maine and New Hampshire. High pressure
will build over New England Wednesday into the weekend with 
temperatures and humidity slowly increasing.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Update...I have bumped PoP up to 100 percent for areas currently
raining and expected to remain that way into the evening.
Otherwise the forecast remains largely unchanged. The 12z HREF
continues to highlight Srn NH as the most likely location to see
upwards of 2 inches of rain thru this evening. Will be keeping
an eye on flash flood potential...but soil moisture was quite
low headed into the event and as long as it all does not come
down in an hour or two the ground should be able to handle it. 

Previous discussion...Interesting and complex weather scenario 
expected over the next 18 to 24 hours.

Initial batch of rain with embedded heavier showers will 
continue across forecast area through this evening as a wave of 
low pressure rides northeast along a stationary front located 
along the southern New England coastline. While much of the 
heat, instability and surface moisture has shifted out of our 
forecast area, dynamics aloft will be the focus for 
precipitation above the surface. Warm air advection will 
continue along a narrow, but sharp H8 front located just off the
coastline of Maine and New Hampshire through this evening. 
Mesoscale models continue suggest a band of heavy rain will 
extend from southern New Hampshire to along or near the 
coastline of Maine. Thunderstorms should be confined to mainly
south of the New Hampshire/Massachusetts border.

There may be a lull in the precipitation late this evening
before an additional round of rainfall enters the region from a
second wave of low pressure after midnight tonight. Some of the
synoptic and mesoscale models keep this second area of rainfall
over southern New England, while others indicated the
precipitation crosses southern portions of the region. These
subtle differences play a role as to whether the second batch of
precipitation could produce localized flooding over southern
areas of New Hampshire, extending into far southwest Maine. 
Will continue to monitor for this second area. Antecedent 
conditions have become dry with the very hot weather conditions 
over the last few days, however localized heavy downpours in our
high precipitable water atmosphere, combined with modest 
atmosphere dynamics could produce poor drainage and low lying 
flooding in a few locations. Have highlighted the potential for
maximum rainfall in DSS products will be over southern New
Hampshire with the Euro indicating some locations with locally
just over 3 inches of rainfall. Some flooding may occur. This
axis of heavy rainfall will need to be monitored for potentially
extending into far southwest Maine. We remain in a slight risk 
in the excessive rainfall outlook.

Much cooler temperatures during the overnight hours can be 
expected. Lows in the mid 50s to lower 60s will give a relief 
from the recent heat. Rainfall and narrowing dew point 
depressions will allow for the development of fog as well.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Showers may briefly continue in southern portions of the 
forecast area early Tuesday, bringing more showers, some of them
heavy, to the region. The tendency thereafter will be for 
precipitation to shift gradually to the south and east off the 
coastline. With plenty of clouds in place, temperatures will be 
limited to the 70s for highs.

Clearing and seasonably cool conditions expected for Tuesday
night as low pressure heads into the Canadian Maritimes.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
The week starts with an upper level trough to our west which 
will slowly weaken and move east through the end of the week. 
With building high pressure expect little in the way of 
rainfall, and only a few days have a chance of showers. 
Temperatures will remain near average as the warmth has departed
to the east. 

Wednesday low pressure will pass south and east of us across the 
Gulf of Maine. This will keep the land area under a most westerly 
flow and limit the seabreeze to just the immediate coastline, 
allowing temperatures inland to reach 80s south to mid 70s north. 

Thursday and Friday will see high pressure building in with 
temperatures continuing to increase. Expect a seabreeze to limit 
temperatures through the immediate coastline. 

Saturday/Sunday - A cold front beings to approach from Quebec. 
This may be close enough to touch off a few thunderstorms in the
mountains on Saturday afternoon, but with lapse rates marginal 
do not expect any severe.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
Short Term...Expect IFR conditions in many areas tonight over
southern and central areas due to low clouds, as well as rain
and fog. Additional showers may cross the region over southern
areas Tuesday morning, followed by conditions returning to VFR.

Long Term...VFR conditions will continue from wednesday through the 
weekend as high pressure remains in control.

&&

.MARINE...
Short Term...Low pressure tracks along a stalled front to our south
tonight with a second system early Tuesday bringing rain and 
fog to the waters. Winds and seas should stay below advisory 
levels tonight.

Long Term... Low pressure will pass southeast of the Gulf of 
Maine on Wednesday. Afterwards high pressure will build in 
through the weekend with calm winds and seas.

&&

.EQUIPMENT...
The Sugarloaf NWR transmitter is off the air until further
notice. This will be an extended outage as the tower, which was 
severely damaged in a winter storm, is rebuilt.

&&

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

&&

$$

NEAR TERM...Legro