Scientific Forecaster Discussion
fxus61 kaly 272316
Area forecast discussion
National Weather Service Albany New York
716 PM EDT Thu Jul 27 2017
rain showers will come to an end this evening as a cold
front crosses the forecast area. Dry weather is expected for most
of the area Friday into the weekend; however, some rainfall is
possible across far southern areas as low pressure passes by to the
south. Temperatures will remain a bit cooler than normal.
Near term /until 6 am Friday morning/...
as of 716 PM, weak ascent ahead of a positively tilted upper
trough was resulting in widespread cloud cover and scattered
showers across much of the forecast area. Some breaks in the
clouds are occurring across parts of the southern Adirondacks,
Mohawk Valley, Lake George Saratoga region and into the capital
As a weak surface boundary continues to wash out over the
forecast area, showers are coming to an end. Aside from a few
light sprinkles, most have have seen the end of rainfall for
today. The exception is over the central Adirondacks, where a
few additional showers (and possibly a stray thunderstorm) will
be possible over the next few hours, as another weak boundary
approaches that area.
The main challenge will be cloud cover/fog potential. Guidance
and satellite trends suggest the midlevel clouds will diminish
or move south of the forecast area. This will leave US under a
weak cold air advection regime at low to mid levels of the
atmosphere, so there is potential for southward expansion of
lower stratus. Have made sky cover mostly cloudy for the higher
elevations of the Adirondacks and greens in collaboration with
neighboring offices. Still uncertainty to how far southward
these clouds will develop, if they do so. For areas that see
clearing skies, there is potential for fog as the surface winds
decouple and the boundary layer remains moist. So for the
majority of the area, have gone with partly cloudy skies with
patchy fog mention. Lows tonight near to slightly above normal
in the upper 50s to mid-60s.
Short term /6 am Friday morning through Sunday/...
the main player in the forecast for Friday into the weekend will
be a vigorous, compact upper low forecast to move from the
western Great Lakes to around the Delmarva. A surface low will
develop in the Lee of the mid-Atlantic Appalachians and slowly
expand northeastward into the Atlantic Ocean south of Cape Cod.
Models are in generally good agreement on the synoptic scale with
the progression of the upper low and area of lower surface
pressure, but still differ a bit on stronger mesoscale areas of
lower pressure developing over the waters on the weekend.
Guidance indicates potential for strong moisture advection in
association with these strong mesoscale lows, with deformation
precipitation to the north. Model consensus continues to keep
the majority of the forecast area dry during the period.
However, the northern extent of the deformation zone could
impact the Mid-Hudson valley and northwest Connecticut Friday
night into Saturday with some showers. As of now, aside from a
few ensemble member outliers, precipitation amounts appear to be
Friday appears to be a tranquil weather day for the entire
forecast area as the region remains situated between high
pressure to the northwest and the developing low to the south.
High temperatures are expected to be warmer than Thursday but
still slightly below normal. Saturday could become a bit breezy
as the low strengthens to our south, with seasonably strong
northeasterly winds developing. H850 cold air advection will also occur as the
low wraps cooler air in, with temps dropping to around 10c. As a
result, highs are expected to struggle to reach the mid-70s even
with good diurnal mixing outside of southern areas that see more
in the way of cloud cover and possibly some showers. Humidity
should be low for this time of year for most of the forecast
A bit cooler saturdaypressure gradient relaxes
somewhat, with lows mainly in the 50s (possibly some 40s up
north). Current indications are for another tranquil day Sunday
as the low becomes situated more to our south or east. Highs a
bit warmer than Saturday but still a bit below normal with low
Long term /Sunday night through Thursday/...
at the start of the extended period, a closed off low at 500 hpa
will be situated just south of the region over the mid-Atlantic
states. This upper level low will be associated with a surface
storm located just off the New Jersey shore and this storm will
slowly drift northeast through Tuesday.
Our region should be far enough north of these features to remain dry
for Sunday night through at least Monday night, as any precipitation
will likely only reach as far north as the New York City area and a
weak area of surface high pressure remains situated close enough to
the region. Overnight lows will mainly be in the 50s with highs
reaching into the upper 70s to low 80s for valley areas on Monday
under a partly to mostly sunny sky.
The upper level low will start to open up on Tuesday as it passes
over far eastern New England. In addition, a weak and subtle upper
level disturbance passing within the northern stream could help
allow a few showers and possibly a thunderstorm to develop on
Tuesday afternoon, mainly for northwestern parts of the area. Most
areas should continue to remain dry, with seasonable temps in the
low to mid 80s along with a partly sunny sky.
Another upper level shortwave trough will be diving towards the
Great Lakes and eventually the northeast for the middle to latter
part of the week. The models are still unclear on the exact
strength and timing of the trough, but we will allow for slight to
low chc pops for showers and possible thunderstorms for Wednesday
into Thursday, as this feature heads towards the area. With warmer
temps expected aloft, it should be seasonably warm with high temps
reaching into the mid 80s for most valley areas. The humidity also
looks to creep up as well, as the low-level southerly flow ahead of
the approaching shortwave trough will allow dewpoints to reach back
into the 60s.
Aviation /00z Friday through Tuesday/...
with a weakening frontal boundary moving across the area, the
threat for rain showers has ended for today. Clouds will start
to clear out through the evening hours. However, with plenty of
lingering low-level moisture in place and light to calm winds at
the surface, some radiational fog will form tonight. The best
chance will be at kgfl, kpsf and kpou, mainly after 06z,
although there could be some patches that develop as early as
03z-4z (mainly at kpsf). Fog will lower flying conditions down
to IFR for most sites, although not enough confidence for IFR
fog at kalb to have in the taf at this time, so have only
included a tempo there for MVFR br starting at 08z.
Any fog/mist should dissipate by 11z-12z, allowing for VFR
conditions to return for Friday, with light winds throughout the
day. It looks to be dry, with just some passing high cirrus
clouds through the day.
Friday night: no operational impact. No sig weather.
Saturday: no operational impact. No sig weather.
Saturday night: no operational impact. No sig weather.
Sunday: no operational impact. No sig weather.
Sunday night: no operational impact. No sig weather.
Monday: no operational impact. No sig weather.
Monday night: no operational impact. No sig weather.
Tuesday: low operational impact. Slight chance of rain showers...tsra.
drier weather is expected to take hold Friday into the weekend,
although isolated to scattered showers are possible over
portions of the Mid-Hudson valley and northwest Connecticut. Relative humidity
values will still remain somewhat elevated Friday, only falling
into the mid-50s to mid-60s. It will be progressively drier
into Sunday, with relative humidity values bottoming out near 40 percent by
Sunday. North-winds could become a bit breezy on
Saturday, gusting to around 25 mph at times.
rain showers will continue to diminish through this evening and
generally be on the light side.
Conditions will generally be dry Friday into the weekend, but
some periods of rainfall may impact areas around the Mid-Hudson
valley and northwest Connecticut Friday night into Saturday.
Models continue to keep the heavier rainfall south of the
forecast area, with generally light amounts of 0.25" or less
expected. Trends will continue to be monitored as there will be
a sharp cutoff in precipitation amounts, so a slight northward
shift in the storm track could result in increased quantitative precipitation forecast totals.
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 website.