Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Caribou ME
808 PM EDT sun Aug 2 2015
high pressure will cross the area overnight into Monday. A cold
front will approach Monday night...then cross the region Tuesday
with showers and thunderstorms in advance of the front. Cooler
and drier weather is expected for the middle and end of the week.
Near term /through Monday/...
isolated showers have now largely exited or dissipated across the
region with an upper level disturbance moving to the east and the
loss of diurnal heating. High pressure will build across the
region overnight. Generally expect partly cloudy skies across
northwest portions of the forecast area tonight...with mostly
clear skies across the remainder of the region. Overnight low
temperatures will range from the middle to upper 50s across northern
areas...to the upper 50s to around 60 downeast. Have updated the
forecast to adjust for current conditions along with expected
overnight temperatures and cloud cover.
County Warning Area will be in wmsector on Monday with temperatures climbing above normal.
Latest BUFKIT soundings show northwest zones will likely be capped until close to
18z before temperatures aloft begin to drop with appch of 500 mb trough. Cin will
slowly erode from west to east and expect line of showers and scattered
thunderstorms to work west by the end of the near term. Airmass
destabilizes in wmsector with strong middle-level jet expected helping
to organize any cells that are able to develop tomorrow afternoon.
Question is what will be the focus for convection as cold front remains well
back to the west. 12z NAM and hires models indicate a trough of
lopres dvlpng along the international border by 00z Tuesday which may
serve as focus. Cyclonically-curved hodographs favor severe weather with
40-50kt of bulk shear values also supporting damaging winds and
storms capable of producing large hail. Have continued midnight shift
advertisement of gusty winds and small hail given question of how
likely cells will develop drg the afternoon and how quickly cap will erode.
Later shifts may have to introduce severe wording for late afternoon
Short term /Monday night through Wednesday/...
unsettled weather is expected for the short term forecast period as a
large upper level trough beings to move over Quebec and the
northeast. A couple of shortwaves moving the cyclonic flow around
the trough will tap moisture and warmth in the boundary layer and
bring two rounds of showers/storms to our County Warning Area. The round of precipitation
will arrive on Monday and last through Tuesday. A brief respite in
the rainfall is expected Tuesday night before the second round of
showers/storms arrives on Wednesday. There is a small chance that
some of the thunderstorms across our County Warning Area could be strong to
severe. The main threat for any severe storms will be across our
western zones on Tuesday...and then across our southeastern zones on
Wednesday. Temperatures will start cooling off...with highs
expected to range from the middle 70s to the lower 80s on Tuesday...and
range through the 70s on Wednesday.
Long term /Wednesday night through Sunday/...
the semi permanent upper trough over Quebec weakens later this week
with the upper low center lifting into Canadian Maritimes. A weak
coastal surface low moves across the base of the upper trough
Thursday into early Friday. It appears that this system will stay
south of eastern Maine. Temperatures will start below normal and
slowly warm into next weekend.
Weak disturbances in the upper level flow may bring a chance of
showers and thunderstorms to eastern Maine next weekend.
Aviation /00z Monday through Friday/...
near term: VFR conditions are expected across the region tonight
through early Monday afternoon. Variable conditions could then
begin to occur with any developing showers or thunderstorms later
Monday afternoon...particularly across northern and western
portions of the forecast area. Some of the stronger storms could
contain hail and gusty winds later Monday afternoon.
Short term: showers and storms will affect the forecast area most of
the short term period. There is a small risk that some of the
storms may be severe producing frequent lightning...damaging winds
and large hail. Ceilings/visibilities associated with the stronger showers
and storms will be reduced into the IFR/MVFR flight categories.
near term: winds/seas will generally remain below Small Craft
Advisory levels tonight through Monday. However...seas could begin
to approach marginal Small Craft Advisory levels late Monday.
Short term: a Small Craft Advisory may be needed Tuesday night
into Wednesday as southwesterly winds strengthen across the Gulf of Maine
ahead of the approaching front. The winds may induce wave heights
ranging from 4 to 6 feet.