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000 
FXUS61 KALY 201056
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
656 AM EDT Sun Aug 20 2017

.SYNOPSIS...
High pressure building into the mid Atlantic region will bring 
fair weather and seasonable temperatures on Sunday. A 
southwesterly return flow around the high will bring mostly 
sunny and warm weather Monday into Tuesday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
There are some clouds and isolated showers off Lake Ontario
into the western Mohawk Valley and southern Adirondacks that 
are in the process of diminishing. Other scattered to broken 
clouds spreading east from the eastern Catskills through much of
eastern NY, southern VT and the Berkshires that will tend to 
mix out through the morning.

Some afternoon fair weather clouds should form but there should
be plenty of sun and a west wind will be breezy at times. Some
weak cold advection will be occurring but the sun and west winds
should help temperatures reach highs in the mid 70s to lower
80s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...
Warm advection begins late tonight and through Monday. West
southwest boundary layer flow and warming boundary layer
temperatures will support lots of sun and mixing. The eclipse
will be seen quite well. We will see if limiting the sun during
the peak time of heating will keep high temperatures in the mid
to upper 80s or if there will be little effect on temperatures 
and some areas approach 90. Highs around 80 to lower 80s higher
terrain.

Good run to run consistency in guidance the last couple of days
showing strong upper energy dropping out of Canada Tuesday to
just north of the Great Lakes by Wednesday. An upper impulse 
tracking around the southern periphery of the primary upper 
system will track through our region later Tuesday night and 
Wednesday.

The initial approach of the upper energy combined with the
increased low level moisture and daytime heating will support a
pre frontal trough that will track east through our region
Tuesday afternoon and night. There are some discrepancies in
guidance as to how much instability will be over the region, 
ranging from near 1000 J/kg to potentially over 2000 J/kg in 
some southern areas Tuesday afternoon. There will be a strong
low level jet of 40+ Kt and approaching strong upper jet core. 
However, midlevel lapse rates will not be very steep and it 
will be quite warm aloft. Most of the instability will be 
surface based, so daytime heating and dewpoints will be 
important in evaluating whether our region sees the greater 
instability or less instability. 

Strong boundary layer winds and decent deep layer shear will
make up for any limitations in instability if there are any.
There should be enough instability, shear and upper dynamics for  
the potential for severe thunderstorms Tuesday afternoon and 
evening. Highs Tuesday in the upper 80s but maybe near 90
southern areas and lower to mid 80s northern areas.

Organized convection exits through the evening but the main
upper trough axis remains well west of our region and the
boundary layer thermal gradient leading edge of cooler and dryer
air does not track through our region until very late Tuesday 
night or early Wednesday. So, there could be some scattered 
showers and thunderstorms as the leading edge of the cooler air 
approaches late Tuesday night. Since the low level temperatures
and dew points are not expected to fall too much behind the pre
frontal trough, lows Tuesday night will not be too cool, in the
mid to upper 60s but around 60 to lower 60s northern areas.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
The extended portion of the forecast will feature cool and mainly 
dry late August weather as we head into next weekend.

A strong cold front will be progressing across portions of southern 
NY and New England Wednesday morning.  The latest GFS/ECMWF/Canadian 
GGEM and several Global Ensemble members all show some residual 
showers ahead of the front over portions of the mid Hudson Valley 
and western New England in the morning.  A secondary cold front 
associated with the upper trough may also focus some scattered 
showers over the rest of the forecast area.  We kept a slight chance 
of thunderstorms in over southeast portion of the forecast area 
including the mid Hudson Valley/southern Taconics/NW CT with small 
amounts of instability and dewpoints still in the lower to possibly 
mid 60s.  Low and mid level cold advection will be going on during 
the day, and H850 temps may start the day at +11C to to +16C from 
northwest to southeast across the region,  but will lower to +9C to 
+13C by the afternoon based on the 00Z GFS. It will become breezy 
and less humid by the late afternoon. Highs will be mainly in the 
upper 70s to lower 80s in the valleys with upper 60s to mid 70s over 
the hills and mtns. 

Wednesday night into Thursday...The cooler air mass continues to 
build in with a mean longwave trough setting up over southeast 
Canada, the Great Lakes Region, and the Northeast.  The 00Z GEFS 
indicates H500 heights on the order of 1 to 2 standard deviations 
below normal with H850 temps slightly below normal, especially west 
of the Hudson River Valley.  Some short-wave energy moving through 
the cyclonic flow in the upper trough will focus some lake effect 
isolated to scattered rain showers downwind of Lake Ontario that may 
impact the western Adirondacks, and west central Mohawk Valley. 
Diurnal cumulus will likely pop-up along or near the higher terrain 
too. Otherwise, humidity levels will be comfortable with partly to 
mostly sunny conditions during the afternoon with a large Canadian 
anticyclone ridging in from Upper Midwest and Western Great Lakes 
Region.  Lows Wed night will be mainly in the 50s with some upper 
40s over the southern Adirondacks, eastern Catskills and southern 
Greens,

Thu night into Sat...The air mass will feel a bit like early autumn 
with temps ranging from the mid 40s to mid 50s both Thu and Fri 
nights. There could be some patchy radiational mist or fog along or 
near the major river valleys.  H850 temps will only be in the +8C to 
+10C range over the region on Friday with limited mixing due to the 
strong subsidence from the sfc high with max temps in the 60s over 
the mountains and mainly lower to mid 70s over the hills and in the 
valleys with a few upper 70s in the mid-Hudson Valley and NW CT. Not 
much change with the sensible weather is expected heading into the 
weekend with the sfc anticylone shifting from the Great Lakes Region 
to over the Northeast.  High temps will be similar to Friday with 
highs running about 5 degrees or so below normal for late
August.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
An upper level trough continues to move east of the region this
morning. High pressure will ridge in from the Ohio Valley and 
Mid Atlantic Region today into tonight.

Mid-level cloudiness is mainly impacting KGFL/KALB this morning
with some high clouds near KPOU. Low MVFR stratus developed at 
KPSF this morning. The low stratus should dissipate between
13Z-14Z there with better mixing and the upper trough moving
further downstream. Some lingering cumulus/stratocumulus will
linger in the 4-5 kft AGL range there into the pm. 

By the late morning into the early afternoon expect sct-bkn 
diurnal fair weather cumulus in the 4-5 kft AGL range. The skies
will quickly clear in the late afternoon/early evening due to
the strong subsidence with the sfc high. Some radiational mist
or fog is possible in the tonight with the best chance in the 
climatological favor TAF sites of KGFL and KPSF where we have 
IFR/LIFR conditions forecasted mainly after 06Z/MON.

The winds will increase from the west to northwest at 8-12 kts 
in the late morning into the afternoon with some gusts in the 
15-20 kt range especially at KALB/KPSF. The winds will become
light to calm shortly before or just after 00Z/MON.

Outlook...

Monday Night: No Operational Impact. NO SIG WX.
Tuesday: Moderate Operational Impact. Breezy Chance of SHRA...TSRA.
Tuesday Night: High Operational Impact. Likely SHRA...TSRA.
Wednesday: Moderate Operational Impact. Chance of SHRA.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: No Operational Impact. NO SIG WX.

&&

.FIRE WEATHER...
High pressure building into the mid Atlantic region will bring 
fair weather and seasonable temperatures on Sunday. A 
southwesterly return flow around the high will bring mostly 
sunny and warm weather Monday into Tuesday.

RH values will be near 100 percent at night. RH values will be 
40 to 55 percent this afternoon and Monday afternoon.

Winds will be west at 5-15 mph today with a few gusts to 20 
mph this afternoon. Winds will switch to southwest and again 
diminish to 5-10 MPH or less tonight, increasing to around 15
mph Monday.

&&

.HYDROLOGY...
Widespread rainfall forecast during the next week is forecast to
be less than an inch. Some locally higher amounts are possible
in showers and thunderstorms later Tuesday into Tuesday night. 
Only minor changes in stage and flow are forecast for larger 
rivers and streams.

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.

&&

.EQUIPMENT...
While repairing the azimuthal gear box, radar technicians have
determined that the bull gear on KENX radar needs to be
replaced. This will require the radar to be out of service until
at least next Friday, August 25th.

&&

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.

&&

$$
SYNOPSIS...NAS
NEAR TERM...NAS
SHORT TERM...NAS
LONG TERM...Wasula

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