Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Caribou ME
937 PM EDT Wednesday Jul 30 2014
upper level low pressure will remain to our northwest tonight. A
disturbance moving around the upper low will cross northern and
northwestern areas Thursday afternoon and evening. High pressure
will move east of the region Friday.
Near term /through Thursday/...
937 PM update...a weak middle level shortwave combined with low
level convergence has allowed the showers to continue past sunset
to the north of katahdin. Have massaged the probability of precipitation a bit across far
northern Maine based on the latest radar trends. Think that at
least isolated showers are possible in parts of the St John valley
until around 2 am. Elsewhere...low stratus and fog has developed
along much of the downeast coast and it may continue to spread
inland across the coastal zones. Patchy fog is likely in many of
the inland river valleys overnight. Otherwise the forecast is in
good shape with only slight adjustments to sky...wind...and temperatures
for current conditions and trends.
we will remain along the southeastern edge of a large and deep
upper low to our northwest tonight. Skies will become clear to
partly cloudy overnight although some fog could persist along the
immediate coast. A small but vigorous shortwave rounding the
bottom of the trough will lift into the area during the midday and
afternoon on Thursday. Convective available potential energy are averaging around 500 j/kg across
the north which is weak to moderate. However, the shortwave has
strong upper dynamics and lapse rates are steep so there will be a
good chance for thundershowers, especially in northwestern areas,
Thursday afternoon. Winds aloft are strong so any downdraft can
contain strong gusty winds. The potential for hail exists because
of steep lapse rates and the potential for strong gusty winds
exists because of the strong winds aloft so will keep mention of
hail and gusty winds in any thunderstorms on Thursday.
Short term /Thursday night through Saturday/...
showers and possible thunderstorms...most numerous across northern
areas with lesser chances downeast...will occur across much of the
forecast area early Thursday evening with the upper disturbance.
With the loss of diurnal heating and the upper disturbance lifting
north of the region...shower/thunderstorm coverage will then
decrease through the evening. Partly cloudy skies are expected
across the forecast area overnight. Could have an isolated
afternoon shower across the north and mountains Friday.
Otherwise...partly sunny skies are expected Friday. Cloud cover
will begin to increase later Friday night in advance of an upper
disturbance lifting northeast toward the region. The disturbance
will lift across the region Saturday...though the track and
strength of the disturbance are still uncertain. Expect a chance
of showers across the region Saturday...with an afternoon
thunderstorm also possible. Temperatures will be at near normal
Long term /Saturday night through Wednesday/...
high pressure will remain off the East Coast at the beginning of
this period. At the same time weak surface low pressure is
expected to produce showers Saturday night into the day Sunday.
Expect some instability so will also include mention of scattered
thunderstorms Sunday afternoon. Surface and upper level low
pressure will approach from the west Monday...so will also include
showers with thunder in the afternoon. Will keep chance probability of precipitation for
showers Tuesday into Wednesday as the upper level system moves
across the state. Will initialize all grids with superblend. Have
made some manual adjustments to pop and weather grids.
Aviation /01z Thursday through Monday/...
near term: IFR conditions have developed at kbhb in low stratus
and fog this evening...and IFR to at times vlifr will continue
into early Thursday morning. The IFR conditions may move into kbgr
overnight. At the northern terminals predominately VFR...but
patchy late night fog may intermittently lower conditions to IFR.
VFR conditions are expected Thursday, possibly lowering to IFR in
thundershowers over the north during the afternoon.
Short term: variable conditions will occur with any
showers/thunderstorms Thursday evening. Otherwise...expect
generally VFR conditions across the forecast area Thursday night
into early Friday night. Occasional MVFR conditions are possible
later Friday night through Saturday. Expect MVFR/IFR conditions
Saturday night into Sunday.
near term: winds and seas are expected to remain below Small Craft Advisory tonight
and Thursday. Fog will likely continue to limit visibilities.
Short term: winds/seas are expected to be below Small Craft
Advisory levels Thursday night through Saturday. Visibilities
could be reduced in showers and patchy fog Saturday. For Sunday
and Sunday night expect light winds with wave combined seas
dominated south to southeasterly long period wave systems around 2