Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Albany New York
700 am EDT Sat Aug 1 2015
a weak cold front and an upper level disturbance will
bring isolated to scattered showers and isolated thunderstorms to
eastern New York and western New England today. High pressure will
briefly build in from the Tennessee Valley and the Middle Atlantic
States tonight into Sunday with fair and dry weather. A stronger
cold front will bring more scattered showers and thunderstorms for
Near term /until 6 PM this evening/...
as of 650 am EDT...New York and New England will be under the influence
of cyclonic flow aloft today. A surface trough or weak cold front
continues to move east across west-central New York and western PA. Scattered showers
and isolated thunderstorms continue to move across central-eastern New York...and
southern Quebec this morning. Very little cloud-to-ground lightning is occurring over
upstate New York with a more stable air mass in place. A middle/upper
level short-wave will pivot through the long-wave trough late
this morning into the afternoon continuing isolated-scattered
showers...and some isolated thunderstorms.
The steepest middle level lapse rates will generally be north of the
Mohawk Valley/capital region in the 6.5-6.8c/km range. H500 temperatures
will fall close to -14c to -16c from the capital district north.
The instability continues to be the biggest question today for any
sustained convection...with the NAM still painting SBCAPE values
of 500-1000 j/kg with some greater pockets...while the GFS is in
the 100-500 j/kg range with the greater sbcapes north. 0-6 km
bulk shear values are in the 30-45 knots range...but the better shear
is out of phase with the better instability. The better shear is
south of the capital region. Surface dewpoints will generally be in the
50s with spotty 60f readings. It appears a few multi-
cells/cellular convection is possible...but for any strong taller
updrafts more instability would need to be utilized. Can not rule
out a rogue/isolated severe cell to the north...but any convection
with the cold pool/steeper lapse rates may yield pea to perhaps
dime/penny size hail. The marginal risk further downstream
outside of the aly forecast area across northern New England looks on track
from Storm Prediction Center.
The isolated thunderstorms will increase towards noon and into the
afternoon...but will diminish towards sunset. The winds will
increase from the west/southwest at 10 to 20 miles per hour...with high
temperatures getting into the u70s to l80s in the valley areas...except
for the middle Hudson Valley/southern Litchfield city where some middle/u80s
are possible. U60s to u70s will be common over the hills and mountains
Short term /6 PM this evening through Monday night/...
tonight...any leftover cellular showers/thunderstorms should
quickly diminish between 6-9 PM with the loss of the diurnal
heating. The atmosphere should stabilize...and the clouds will
thin. There maybe be patchy fog where any rain occurs...and across
portions of the Lake George region...southern Vermont...Berkshires...near
the CT River Valley...and down the Hudson River valley. The
decoupling winds and clearing skies will also promote shallow
radiational mist or fog. Lows were favored with a blend of the
mav/met guidance with m50s to around 60f in most
locations...except some u40s to l50s in the sheltered valley
locations...and across parts of the southern dacks...Berks...nrn
Taconics...and southern Vermont.
Sunday...the short-range guidance is in agreement for a dry close
to the weekend with surface high pressure building in from the
virginias. The middle and upper level flow shifts from zonal to
southwesterly...as the next upper level trough will be
approaching. The weak low and middle level ridging will allow h850
temperatures to rise back to +15c to +17c. Partly to mostly sunny
conditions with decent boundary layer mixing due to the SW flow
should allow temperatures to rise into the lower to m80s in the valley
areas...and middle 70s to around 80f over the hills and mountains
Sunday night...low pressure will be moving towards SW Quebec. A
cold front will be moving through the central-eastern Great Lakes
region. Some short-wave energy will be rounding the base of the
upper level trough. Clouds will be increasing from west to east.
Slight to low chance probability of precipitation were placed in overnight...especially northwest/west
of the capital district/Hudson Valley. Lows will be milder than
the previous night with u50s to m60s over the region.
Monday-Monday night...inclement weather returns with the cold
front moving across the region potentially during the peak diurnal
heating. Some stronger storms may be possible with increasing surface
dewpoints into the 60s. Sbcapes may be in the 500-1500 j/kg range with
increasing bulk vertical shear ahead of the front and short-wave.
Decent height falls should be occurring aloft with the front. The
GFS has middle-level lapse rates in the 6.5-7c/km range over the forecast
area by the PM. This will have to be monitored over the next few
days for the possibility of some severe thunderstorms. Storm Prediction Center has
placed the entire area in a marginal risk for day 3.
Some locally heavy downpours will be possible too as precipitable waters rise
back to the 1.25-1.50 inch range. Chance and likely probability of precipitation have been
used for Monday...and tapered to chance probability of precipitation at night. Highs will
range from the lower to u80s in the valley areas...and m70s to
l80s over the higher terrain. Lows Monday night will be in the m50s
Long term /Tuesday through Friday/...
a large closed off upper level low will be the dominate feature
next week. The low is expected move eastward across eastern Canada
as short waves rotate about it.Guidance is not in agreement with
the timing of the individual short waves and their influence on
the low. However there is general agreement the upper level flow
should become more zonal by late in the week.
Have favored guidance from the weather prediction center to maintain
forecast consistency with the timing of systems. Based on this...a cold
front is expected to move across the area Wednesday with the boundary
eventually stalling near the middle Atlantic region and off the East Coast
for late in the week. There are indications a wave of low pressure should
move along the boundary Thursday into Friday. In addition...with cool
temperatures aloft diurnally driven showers would be expected however
coverage should be fairly isolated. Have chance probability of precipitation into the southern
portion f the forecast area for Thursday otherwise have climatological
slight chance probability of precipitation in the forecast.
Overall expecting slightly below normal temperatures by around about
5 degrees. Highs mainly in the 70s (bit cooler across the higher terrain)
with lows mainly in the 50s.
Aviation /12z Saturday through Wednesday/...
a couple of pieces of energy will move through the longwave trough
over the region today. Some light rain showers are currently moving
across the area this morning. A lull is then expected. The next wave
will have the help of daytime heating. Isolated to scattered storms
are expected for the afternoon hours. Have addressed threat with
vcsh since do not have enough confidence in the placement and timing
of expected convection. Storms will dissipate with loss of heating
and passage of the wave.
Mainly VFR conditions are expected. The exceptions are for MVFR
conditions with convection this afternoon and for MVFR fog overnight
at kgfl and kpsf.
Light/variable to calm winds through the early morning with south to
southwest developing after sunrise. The winds will shift to the
southwest to west as a weak cold frontal boundary moves across the
region today. The westerly flow is expected to become gusty for a period
this afternoon into the early evening with gusts into the teens to
20 knots. Winds will weaken as the evening progresses and should
become light to calm overnight.
Sat night: low operational impact. Slight chance of rain showers...tsra.
Sun: no operational impact. No sig weather.
Sun night: low operational impact. Slight chance of rain showers.
Mon: moderate operational impact. Breezy. Chance of rain showers...tsra.
Monday night: moderate operational impact. Chance of rain showers...tsra.
Tue: low operational impact. Slight chance of rain showers...tsra.
Tuesday night-Wed: low operational impact. Slight chance of rain showers.
minimal fire weather concerns through the weekend as an upper
level disturbance will result in isolated to scattered showers
and isolated thunderstorms today...and then expect fair and dry
weather tonight into Sunday.
Relative humidity values are expected to lower to 35 to 50 percent
this afternoon...then increase to 85 to 100 percent tonight with
some patchy fog in some locations. Min relative humidity values Sunday will drop
to 35 to 45 percent during the afternoon.
The winds today will be southwest to west at 10 to 20 miles per hour and
will become light and variable in direction at 5 miles per hour or less
tonight. The winds will be from the south to southwest at 5 to 10
miles per hour on Sunday.
isolated to scattered showers and isolated thunderstorms are
forecast for today into early this evening. More showers and
thunderstorms are expected Monday into Monday night. Widespread
heavy rainfall isn/T expected...but any thunderstorm will be
capable of producing locally heavy downpours on Monday. These
downpours will cause ponding of water on roads...and perhaps some
poor drainage flooding of low-lying areas.
Scattered showers are expected into the middle week with an upper
level low...but little impact on the rivers is expected in the
aly Hydro service area.
For details on specific area rivers and lakes...including
observed and forecast river stages and lake elevations...please
visit the advanced hydrologic prediction service /ahps/ graphs on