Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
1046 PM EDT Wednesday Oct 22 2014
slow moving low pressure just off the coast of New England will
keep the area in a cloudy, damp and cool weather pattern into
Friday, though showers are still possible over the weekend. Warmer
and drier weather will return early next week.
Near term /until 8 am Thursday morning/...
as of 1035 PM EDT Wednesday...little overall change to previous
forecast. Deep, slow-moving low pressure off the southern New Jersey
coast will continue northeastward to near the 40n 70w benchmark by
23/12 UTC. Cloud canopy associated with offshore low and
associated cyclonic circulation encompasses the north
country...but generally looking at middle-upper level clouds west of
the Champlain Valley. Low-level moisture/cloud cover is more
extensive with upslope component east of the Green Mountain spine
this evening. Composite radar reflectivity at 0240 UTC shows
increasing coverage of rain across the Gulf of Maine...which will
continue to translate from east to west from New Hampshire into Vermont
toward daybreak. Pop fields depict this increase from east to
west across the area. The St Lawrence Valley should remain dry
for a good chunk of the overnight.
Temperatures will not deviate much across the region, nor will
they drop much given near saturation and overcast conditions. Lows
will generally be in the middle 40s. Some patchy fog is expected to
develop east of/along The Greens...especially as rain increases
Rainfall amounts through dawn Thursday will range from 0.20-0.40"
across central/southeastern Vermont...0.10-0.20" across Rutland County and much
of the Champlain Valley...and generally <0.10" across the
remainder of northern New York.
Short term /8 am Thursday morning through Friday night/...
as of 400 PM EDT Wednesday...still looking wet, especially
Thursday. The precipitation shield is expected to be covering all
of Vermont and much of northern New York by first thing Thursday. As the
surface and upper low slowly start moving northeast, we should see
an area of rainfall move into northern Vermont and then begin to
pivot and slowly move east. Some of this rain will be moderate to
perhaps briefly heavy. Anticipate upwards of 1" of rain in areas
tomorrow. By the time most of the rain winds down Thursday night
and early Friday, we are looking for about 1.5" (much less in the
St Lawrence valley) totals, however we are not anticipating any
Highs tomorrow should be very similar to today as the clouds and
rain hold temperatures down. In fact, I tried to indicate diurnal
swings of 5 degrees or less.
Thursday night through Friday will feature slow improvement as the
slow moving low slowly pushes northeast away from the area.
Cyclonic flow will continue, and with lots of low level moisture
around, have continued the idea for 30-45% probability of precipitation and a ton of
clouds. Still little temperature variation.
Long term /Saturday through Wednesday/...
as of 320 PM EDT Wednesday...northwest flow developing at 500 mb
from 12z Saturday Onward. Weak shortwave ridging over the forecast
area starting at 12z for a dry start to the weekend...but low
pressure in northwest flow moving across Ottawa will begin to make its
presence felt late Saturday. Area still in relatively warm air and
precipitation type to be all rain. From Sunday night Onward surface and
upper ridge settles over the area with dry and seasonal
conditions. Toward middle week the ridge breaks down with the next
low tracking along the US Canadian border and surface low/cold
front combo. GFS and European model (ecmwf) in good agreement with track of surface
low moving north of forecast area...and trailing cold front
bringing new chance of rain for Wednesday.
Temperatures start off near normal with highs in the 50s...then as ridge
builds in Tuesday temperatures rise into the upper 50s and lower 60s in
the warmer valleys.
Aviation /03z Thursday through Monday/...
low pressure off the middle-Atlantic coast is really developing fast
now and will bring deteriorating flight conditions to the area
with prevailinig MVFR/IFR ceilings and visibilities in low clouds and rain from
east to west especially overnight and toward 12z Thursday. Higher
confidence on this scenario than last evening. Bands of rain on
radar will become gradually more numerous and have indicated with
tempo groups of rain showers then just prevailing rain by morning.
Winds will mainly northerly 8-15 knots through the period could be a
little higher at times.
Outlook 00z Friday through Monday...
00z Thursday - 12z Friday...MVFR/IFR in rain MVFR/IFR as low pressure
lifts slowly northeast along the New England coast.
Friday...IFR becoming MVFR/VFR with -shra and north winds.
Sat...VFR/MVFR with PM showers with approaching cold front.
Sun/Mon...MVFR/LCL IFR with clouds and -shra valleys and -shsn
mountains under cyclonic northwest flow.
as of 400 PM EDT Wednesday...appears that the bulk of the rainfall
will occur late tonight through Thursday. With less rain falling
today than earlier expected, overall rainfall totals by Friday
morning are less than we thought as of a few days ago. Generally
looking at about 1.5" for much of Vermont (lower values in the
Northeast Kingdom due to rain shadowing from the white mountains)
and perhaps spot 2" amounts along the eastern slopes of the
central Green Mountains. Out in the St Lawrence Valley, amounts
will be much less 1/2" or less. Given the relative long duration
of rainfall and the base level river flows, we certainly expect
river levels to rise, but not looking for anything to go out of
their banks. Perhaps the worst we'll see is some ponding on roads
where drainages have been blocked by leaves.
as of 400 PM EDT Wednesday...northerly winds are expected to
continue all night, all day Thursday and even into Thursday
evening over Lake Champlain, with speeds in the 15-25kt range.
Strongest of these northerly winds will be found in the southern
half of the lake. These winds should generate choppy 2-3 foot
waves. As a result, a lake Wind Advisory will be in effect.