Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Gray ME
900 am EDT sun Apr 19 2015
high pressure will build east and crest across the area late today
before sliding offshore tonight. An increasing easterly onshore
flow will provide cool and damp weather Monday with rain chances
increasing ahead of an approaching low pressure system. Significant
rainfall and flooding...along with coastal flooding from astronomical
high tides...are possible with this system Monday night and Tuesday.
Unsettled weather then looks to dominate middle to late week.
Near term /until 6 PM this evening/...
9am... just a quick update for current temperatures. Today will be
a beautiful day as the high crests across the region.
633 am...minor estf update to reflect the current satellite
trends and to ingest the 10z mesonet into near term grids.
at 06z...a 1030 millibar high ws centered along the Ontario-Quebec
border. A weak surface trough extended from the Gulf of Maine
into eastern Maine. Clouds with this trough...as well as a few
upslope clouds across the higher terrain...should exit the region
this morning as the surface high builds eastward. Highs today
should range from around 60 southern and interior sections...as
well as the Connecticut valley...with 50s elsewhere. As surface
gradient relaxes with building high expect winds to shift
onshore...with falling afternoon temperatures near the coast.
Short term /6 PM this evening through 6 PM Monday/...
clouds will gradually spread north and east into the forecast area
tonight as the surface high retreats into the Maritimes. The
onshore flow may also introduce some low marine stratus into
coastal sections towards dawn. Some light overrunning
rain could reach far southwestern sections of New Hampshire by
dawn Monday...otherwise a dry forecast for tonight. On
Monday...overrunning precipitation spreads north and east and
becomes steady and heavier towards evening in advance of a potent
50 knot low level jet. While it'll be warm enough in the column
for rain...elevations above 2000 feet in northern New Hampshire
and the western Maine mountains could see several inches of wet
Long term /Monday night through Saturday/...
not much has changed in the last 24 hours as far as the model
consensus GOES with the setup for potentially heavy rainfall
Monday night into Tuesday.
Low pressure will develop to our south...and a developing coastal
front looks to act as a focus for heavy rain as strong easterly
inflow overruns the boundary. In addition...this deep
southeasterly inflow in the lowest 4 kft will upslope into the
White Mountains and the Maine foothills and will help to wring out
the moisture. Therefore...the thinking is that there should be two
rainfall maxes...one in those upslope regions and another on the
coastal plain of Maine to the west of the coastal front. These
areas should see 2 to 2.5 inches of rain while basin averages
elsewhere should be 1 to 2 inches.
This combined with continued snowmelt...soggy ground...and
already rising rivers and streams should push several near or over
bankfull. Urban and poor drainage flooding is possible as well.
Therefore...a Flood Watch has been issued for most of the County Warning Area from
Monday evening through Tuesday night.
The column may be cold enough across the western Maine
mountains...especially the higher elevations...for a few inches of
wet snow Monday night.
East/southeast winds should become quite gusty on the immediate coast Monday
night...with gusts 30-40 miles per hour possible there. Therefore a wind-
swept rain looks to be in the cards.
Most models show elevated instability developing late Monday
night into early Tuesday across southernmost zones...so we have a
chance for thunder in the forecast during that time as well.
The heaviest rainfall should move out after midday
Tuesday...earlier across SW zones. We/ll dry out a bit Tuesday
night into Wednesday before the next system brings lighter
precipitation to the region on Thursday.
Overall...with upper level low pressure looking to hang around
through the weekend...the forecast calls for continued cooler and
occasional wet weather. Not very pleasant...considering some
models say that we may not have seen the last Snowflake of the
Aviation /13z Sunday through Thursday/...
short term...VFR expected through Sunday night...with MVFR ceilings
possible vicinity of the coast in marine stratus after 10z Monday. Conds
deteriorate to IFR by Monday afternoon in rain and fog with southeast surface
winds near the coast gusting up to 30 knots during the afternoon.
Long term...IFR or lower conditions in heavy rain is likely
Monday night into Tuesday. Some improvement is foreseen Tuesday
afternoon...especially across southern New Hampshire and southern ME. Occasional
MVFR conditions will be possible Thursday with the next low pressure
short term...quiet through tonight as surface high builds across
the waters. Increasing onshore flow Monday with steadily building
seas and winds gusting to strong small craft by afternoon.
Long term...easterly gales are expected Monday night into Tuesday
with coastal low pressure. These should bring seas up to at least
15 feet on the offshore waters. Subsiding conditions are expected
later Tuesday into midweek.
drier air will move in through today. A sea breeze develops in
the afternoon today... keeping humidity levels higher over the
coastal plain. But to the west of the mountains the humidity will
fall below 30 percent in the afternoon...but light winds should
prevent any elevated fire weather conditions. Onshore flow on
Monday brings more moisture and eventually rain to the area. A
soaking rain is expected late Monday and Tuesday.
a widespread 1 to 2 inches of rain is expected from Monday
afternoon through Tuesday. However...given strong moisture
inflow...localized amounts of up to 3 inches could occur. This
would lead to flooding problems...especially in areas where snow
melt is still occurring. A Flood Watch has been issued.
highest tide of the month occurs tonight at 11.6 feet MLLW in
Portland. Light wind flow at the time should prevent any
significant flooding problems. However... the tide Monday night
reaches 11.4 feet with a stronger easterly flow over the Gulf of
Maine. Onshore flow and building seas will increase the threat of
coastal flooding for the high tide Monday night and a coastal
Flood Watch has been issued to highlight this threat.
ME...Flood Watch from Monday evening through Wednesday morning for
Coastal Flood Watch from Monday evening through late Monday
night for mez023>028.
New Hampshire...Flood Watch from Monday evening through Wednesday morning for
Coastal Flood Watch from Monday evening through late Monday
night for nhz014.
Marine...gale watch from Monday afternoon through Tuesday afternoon for