Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Caribou ME
1004 PM EDT Tuesday Jul 7 2015
a cold front will approach the region from the west tonight and
cross the region on Wednesday. High pressure will then build
toward the region from the Great Lakes Wednesday night and
Near term /through Wednesday/...
10 PM update...
have dropped probability of precipitation across downeast sections as showers have dwindled with
loss of daytime htg, though still present to a lesser extent, on 35kt
low level jet. Lgtng affected Waterville ME but has since weakened. Have gone
with scattered -shra and perhaps an isolated thunderstorm tonight but not too
gung-Ho on potential at this time. Fog has mvd onshore as far
north as downeast areas with stratus hvg spread as far north as
Houlton. Areas of fog prevalent in offshore and coastal zones with
patchy fog expected to reach as far north as a Dover-Foxcroft to
Danforth line. No major changes needed with this update.
Previous discussion below...
Not may changes from the last forecast update...xcpt we lowered cloud cover
over the NE third of the forecast area going into the Erly evening portion of period 1.
Otherwise...latest radar only indicating widely scattered showers entering
northwest ME from eastern qb...with somewhat stronger activity further west
moving NE along the St Lawrence seaway. We expect more activity later
tonight...initially over the far northwest this evening...than potentially over
downeast areas overnight with whats left of the southern stream shortwave vorticity
maximum from the northern aplchns. Otherwise...more general showers with
embedded thunderstorms associated with a cold front and supporting northern br
shortwave will move northwest to southeast across the forecast area beginning during the pre-
dawn hours Wednesday over far northwest ME reaching southeast portions of the forecast area by late Wednesday
morning. Although there is good precipitable waters ranging from 1.50 to 1.75
inches with the middle level srly moisture stream ahead of the cold
front...meager middle/upper level dynamics and instability and fast
flow will result in msly showers with embedded elevated cape cnvctv
elements perhaps enough to cause a few rumbles of thunder and
brief heavy downpours along a broken line of showers.
For this reason...we maximum probability of precipitation out around 80 percent north and 70
percent S with all of these features prior to the frontal
passage...with total rainfall that will likely range from as little as
tenth of an inch or less for lctns that fall between showers to as
much as a half inch+ for lctns that experience heavier cnvctv
elements. Most lctns will receive between 0.15 to 0.35 inches.
Given the speed of the cold frontal shower band msly exiting the forecast area
by 18z Wednesday...we do not see much opportunity of stronger thunderstorms to
fire ahead of the front over southeast ME Wednesday afternoon.
Overnight lows will be quite warm...likely the warmest of the season
so far due to high dewpoints...breezy south-southwest winds and cloud cover. High
temperatures Wednesday afternoon will resume a more typical north to S coherency toward
hi temperatures...with the northwest about 10 degree cooler than this afternoon...
despite the return of sunshine behind the cold front.
Short term /Wednesday night through Friday/...
progressive zonal flow at 500mb for this period...with pleasant
Summer weather expected. Wednesday night the surface cold front
pushes off the coast of Maine with dry northwest flow developing
behind the front. This will lead to a mostly clear night and a bit
cooler then the last few nights. Thursday looks to be a fantastic
Summer day under mostly clear skies and light northwesterly flow.
Highs will reach into the middle to upper 70s and less muggy. Another
nice night on Thursday with a weak 500mb shortwave pushing
through...but no moisture to work with. On Friday a slightly
stronger 500mb shortwave pushes into northern Maine...this will
increase cloud cover with a stray shower possible during maximum
daytime heating over the western Highlands...but overall another
nice day. Overall great July weather...get out and enjoy if you
Long term /Friday night through Tuesday/...
we will be on the northeastern edge of a warm ridge of high pressure
as we go into the weekend. Friday night will turn out partly cloudy
and seasonably mild. A small weather disturbance sliding over the
ridge on Saturday will bring variable cloudiness with a chance for
some scattered showers or thunderstorms. Most of the day Saturday,
however, should be rain free. The ridge will build over the area
Sunday bringing partial sunshine. A small shortwave approaching from
the west may then give US a chance for showers and thunderstorms in
the afternoon. Cloud and showers will be possible Sunday night into
Monday as the shortwave moves through. High pressure building down
from Canada then has a chance of bringing drier weather in for
Aviation /02z Wednesday through Sunday/...
near term: VFR will give way to IFR conditions across northern
terminals after 07z tonight as low level moisture pools along cold
front. -Shra expected to move into fve by 07z, spreading south
from there. At bhb and bgr, expect IFR restrictions through most
of the day until frontal passage occurs around 16z Wednesday.
Short term: VFR conditions expected at all taf terminals with
high pressure firmly in control and dry northwest flow.
near term: winds and waves will be just below Small Craft Advisory criteria tonight into
Wednesday morning with a srly fetch...with winds and seas then diminishing
behind a cold front Wednesday afternoon Onward as winds become offshore. Went
with about 90 percent of ww3 guidance for forecast WV heights for the
outer mzs050-051 and about 65 to 75 percent for the inner