Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 241756

Area Forecast Discussion
National Weather Service Albany NY
156 PM EDT Sat Jun 24 2017

Breezy, cooler and more comfortable airmass through the evening
hours as a narrow surface high builds across the region. However,
isolated to scattered showers and perhaps a few thunderstorms are
expected Sunday afternoon as another cold front approaches. An even
cooler airmass will be ushered in with the passage this front with
below normal temperatures for the start of next week.


A brisk, cooler and less humid airmass continues to filter into
the region as dewpoints have dropped back into the 50s for most
areas with diurnally driven cumulus clouds across the terrain
has developed per the GOES 16 experimental satellite imagery.
Lake breeze convergence along the Thruway from ROC-BUF has
resulted in an area of convection, however, this too should
dissipate with the combination of outrunning this low level
convergence and loss of daytime heating before it were to
arrive to our western areas. So a partly sunny remainder of day
with dry conditions as highs should achieve the previous
excellent forecast.

Tonight a narrow ridge settles into the region with a mostly
clear sky expected. This too should allow for winds to decouple
for a diminishing trend as temperatures should settle back to
rather comfortable values for this time of the year with mostly
50s region-wide.


H2O vapor loop shows a distinct short wave across the State of
Minnesota that will track eastward through Sunday and be in the
vicinity of the Great Lakes in the morning. Meanwhile, mid and
upper level jet core of 70-115kts, respectfully, will be
approaching from the Ohio Valley. The combination of exit region
dynamics along with the approach of the upstream wave and
increasing lapse rates and instability, convection should
quickly develop once the convective temperature is achieved
(around 70F). Previous forecast has an excellent grid forecast
with little changes at this time. Convective parameters are
rather meager with CAPES averaging 300-500 J/KG and Showalter
Index values near 0C. With wet-bulb zero heights less than 10k
feet, would not be surprised to see some hail with the deeper
convective elements.

Convection should diminish with the loss of daytime heating
Sunday evening with a party cloudy to mostly clear skies. Short
wave quickly transverses across the St Lawrence Valley through
the evening hours leaving behind small height rises overnight
which will extend through Monday morning.

The next short wave, currently near Lake Winnipeg, will begin
to sharpen the trough Monday into Monday night. Again scattered
convection is expected to develop with help of instability from
diurnal heating as lapse rates increase between 6.5-7C/km.
However, greater coverage is expected as height falls will
be more dramatic to maintain threat for convection into Monday
night. The chances for thunderstorms should be be tied to
daytime heating once again. With more cloud cover expected
Monday temperatures will be cooler with highs in the mid 60s to
upper 70s.


On Tuesday, models are in generally good agreement that the
sharpening longwave trough axis will swing across the forecast area.
This will be an anomalously deep trough with H500 heights around -2
SD per the GEFS. The thermal profiles are also anomalously cool,
with H500/H850 temps around -22C/+7C per the ECMWF. With the dynamic
forcing from the upper trough, as well as the midlevel cold pocket,
expect diurnally enhanced scattered convection to occur. The best
coverage would appear to be across the north. High temperatures
appear to come up well short of seasonal normals.

Northwesterly upper flow quickly builds in on the back side of the
trough, leading to subsidence and tranquil weather Tuesday night
into Wednesday. Temperatures still somewhat on the cooler side.

Thursday and Friday, quasi-zonal, fast midlevel flow sets up. At
lower levels, return southwesterly flow around the high will result
in a warm and moist advection pattern. A stalled low-level frontal
boundary may provide the focus for rounds of showers and
thunderstorms toward the end of the week within this warm and humid
environment, with lift possibly augmented by shortwave troughs
embedded within the midlevel flow. Low confidence with respect to
the timing and location of the lifting mechanisms, so a broad-brush
approach with chance PoPs was used until things become clearer.


The sky has cleared and should remain mostly clear through tonight.
There could be some patchy fog around KGFL and KPSF after 09Z so
including BCFG through about 13Z.  A scattered variable broken cloud
layer at 5000 feet or higher should develop mid morning Sunday and
some isolated to scattered showers are possible with a weak
reinforcing cold front and some upper energy Sunday afternoon.

Winds will be west to northwest at around 15 Kt this afternoon,
gusting to around 25 Kt.  Winds diminish to 5 Kt or less this
evening and tonight.  Winds become west to southwest at less than 10
Kt Sunday morning.


Sunday Night: Low Operational Impact. Slight Chance of SHRA.
Monday: Moderate Operational Impact. Chance of SHRA...TSRA.
Monday Night: Moderate Operational Impact. Chance of SHRA.
Tuesday: Moderate Operational Impact. Chance of SHRA...TSRA.
Tuesday Night: No Operational Impact. NO SIG WX.
Wednesday: No Operational Impact. NO SIG WX.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: Moderate Operational Impact. Chance of SHRA...TSRA.


Wind gusts of 25 to 30 mph expected this afternoon...

A brisk, cooler and less humid air mass continues to filter into
the region. Westerly winds of 10 to 18 mph today with gusts of
25 to 30 mph. Relative humidity value minimums of 35 to 45
percent this afternoon.

Winds will diminish this evening. Winds will be westerly again
Sunday but not as strong at around 10 mph with gusts into the
teens. Isolated to scattered showers and perhaps a few thunderstorms
are expected Sunday afternoon as another cold front approaches.
Minimum relative humidity values of 45 to 55 percent are expected
Sunday afternoon.


Hydrological problems are not anticipated through over the next
several days. A drier, more comfortable airmass continues to
settle into the region. Isolated to scattered showers and
perhaps a few thunderstorms are expected Sunday afternoon as
another cold front approaches. The weather will remain unsettled
early next week as another low pressure system approaches and
moves across the region with chances for convection Monday
afternoon into Tuesday.

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


KGFL airport observations are coming in and we will continue to
monitor this trend.




LONG TERM...Thompson
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