Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Albany New York
930 am EDT Sat Jul 4 2015
low pressure tracking to the south of the region will coincide
with an upper level disturbance to bring clouds and a period of
wet weather for Independence day. Improving conditions are in the
forecast tonight with generally dry and warmer weather to return
for Sunday and Monday as high pressure once again builds across
Near term /through tonight/...
As of 930 am EDT...rain showers have worked into the Hudson Valley
including the capital region. For this update...will fine tune
probability of precipitation/temperatures/dewpoints/wind for this update.
The rain showers will be most numerous through midday...then taper
back to scattered showers during the middle afternoon.
With the clouds and showers...temperatures will hard pressed to get
out of the 60s today. It looks as if we should reach higher than on
all-time low maximum for Independence...64 degrees set back in 1932.
Water vapor loop continued to reveal an approaching long wave trough
for the eastern third of North America with embedded short waves
across the Great Lakes region and Ohio Valley. A closer examination
shows a strengthening middle to upper level jet per the GOES satellite
high density wind magnitudes from the Ohio Valley into western New York.
The divergence aloft has resulted in an expanding area of rain now
reaching our area.
Fgen forcing along with deformation dynamics and upper diffluence
all point toward raising probability of precipitation to likely across the southeastern
2/3rds of the forecast area. However...as the coastal low
intensifies...the upper dynamics quickly track to our north and east
with a decrease in coverage of the rainfall across the region around
21z. Yet the next short wave was forecast to approach from the Great
Lakes region. Here the rainfall from earlier in the day is not
expected to impact these areas too much and may allow for additional
insolation before this wave approaches. Hires models point toward a
region of increasing sbcapes close to 1k j/kg across portions of the
dacks to introduce isolated thunderstorms to the forecast. While no
severe weather is expected /limited shear profiles and instability
parameters and marginal lapse rates/...lightning will pose a hazard
for those across the dacks later this afternoon. Due to the cloud
coverage and precipitation...we will lower afternoon high temperatures a
couple of degrees and in closer ensemble approach of the MOS data.
For tonight...residual showers will be diminishing in coverage and
intensity as we will quickly dissipate the probability of precipitation/weather across the
region. Cloud coverage too should slowly dissipate for evening
activities and night view of the sky improving. Some patchy fog
will be possible overnight as low levels should remain moist with
a weak surface gradient/winds and not too much change of an
airmass in the wake of the trough. MOS numbers are very close /if
not identical/ as a blended approach was utilized.
Short term /Sunday through Monday/...
for the remainder of the Holiday weekend and into Monday...high
pressure will be building both at the surface and aloft through
the short term period per the NCEP model suite and ensemble
consensus. This will result in dry and increasingly warmer
temperatures /and humidity/ as h850 temperatures moderate into the middle
teens. This points toward high temperatures climbing well into the
70s and lower 80s on Sunday and well into the 80s /sub 90f/ on
Monday under a good deal of early July sunshine. Overnight lows
Sunday night into Monday morning will average mainly into the
55-60f general range.
Long term /Monday night through Friday/...
some uncertainty remains regarding the exact timing of a frontal
passage during the middle of the upcoming week. The 00z GFS is a
little faster than the 00z European model (ecmwf)/ggem regarding the speed of a cold
front approaching the area. Because of this...the GFS suggest
showers/thunderstorms develop both on Tuesday along a pre-frontal
trough and again on Wednesday ahead/along the actual
boundary...while the ggem/European model (ecmwf) are mainly dry for Tuesday with
showers and thunderstorms for Wednesday. For now...will go with low
chance probability of precipitation for Tuesday into Tuesday night...and high chance probability of precipitation for
Wednesday. Temperatures look fairly warm in the middle 80s for both Tuesday/Wednesday
ahead of the boundary...with muggy lows in the middle to upper 60s for
valley areas for both Monday and Tuesday nights.
The frontal boundary may winding up stalling just south/east of the
region for Thursday into Friday...so will keep slight to low chance
probability of precipitation in the forecast for Thursday/Friday. If the front is more
progressive...it could wind up just dry everywhere...as high
pressure attempts to build into the area from the Great Lakes. Temperatures
will be a little cooler and less humid behind the front...with highs
in the low 80s for thurs/Fri...and overnight lows in the upper 50s
to low 60s.
Another shortwave could approach the region for some point next
weekend with another chance of showers/thunderstorms. Temperatures look to
be near normal levels.
Aviation /13z Saturday through Wednesday/...
VFR conditions will deteriorate to MVFR during the morning dues
to lowering ceilings and a period of rain. As of 1245z...kpsf has
already gone to MVFR ceilings.
These mainly light rain showers look to arrive shortly.
Initially...this rainfall will be falling out of a middle level
deck...and VFR conditions will continue with rather light
rainfall. Eventually...the rainfall will pick up in intensity and
this may allow for some lower cigs/vsbys...with periods of MVFR
conditions possible for all sites for the late morning/early afternoon
through the middle afternoon hours. Cannot totally rule out some IFR
conditions but not confident enough in the timing/extent of this
to occur in the tafs at this time. The surface wind will variable
to south with speeds generally 5 kts or less.
Rain showers will taper off by about 20z-22z...although lingering
low level moisture may keep some lower ceilings around through the
evening hours. The clouds may start to decrease for late this
evening...and it is a good bet some br may develop for late
tonight into Sunday morning...especially kpsf/kgfl. There could even be
some IFR conditions for a period as well. Winds will become calm
for tonight at all sites.
Sunday night: no operational impact. No sig weather.
Monday: no operational impact. No sig weather.
Monday night: no operational impact. No sig weather.
Tuesday: moderate operational impact. Chance of rain showers...tsra.
Tuesday night: moderate operational impact. Chance of rain showers...tsra.
Wednesday: moderate operational impact. Chance of rain showers...tsra.
Wednesday night: low operational impact. Slight chance of rain showers.
Thursday: moderate operational impact. Chance of rain showers...tsra.
increasing wet weather probabilities through this morning into the
early-middle afternoon hours will keep relative humidity values rather elevated to
between 55-75 percent. Moist low levels and some patchy fog
tonight will keep relative humidity values at or above 90 percent. Then generally
dry weather will return for Sunday and Monday as high pressure
once again builds across the region.
increasing probabilities of a period with wet conditions this
morning into the early-middle afternoon hours with forecast quantitative precipitation forecast/S
ranging from one-tenth to one-third of an inch across the
region...isolated higher amounts are possible where convection
develops /mainly into the Adirondacks/. These rainfall amounts
will have little if any effect on flows on area streams and
Dry conditions are expected for Sunday and Monday.
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 our
Synopsis...bgm near term...bgm/