Area Forecast Discussion
Issued by NWS Albany, NY

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000
FXUS61 KALY 290806
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
406 AM EDT Sun Mar 29 2020

.SYNOPSIS...
Periods of rain will continue today as a warm front works
through the region. A lingering upper level low pressure system will
result in showers continuing Monday into Monday night, with some
light snow over the high terrain. Clouds remain, but with drier
conditions on Tuesday. Temperatures will be near seasonal normals.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 340 am, steadier showers have exited along with initial
area of isentropic lift. In its wake, patchy fog and drizzle or
light showers will continue for the remainder of the night.

Today into tonight, the powerful closed low over the Upper Midwest
will gradually weaken as it drifts into southeastern Ontario. As it
translates eastward, a renewed low level jet surge into the local
area is expected to bring in an area of rain 12-18Z. The best
isentropic lift and most widespread rainfall coverage is expected to
be along and north of I-90 where categorical PoPs will exist. Deep
moisture will increase in concert with the LLJ with PWATs increasing
to 1-1.25 inches, which is 2 to 4 standard deviations above normal.
The combination of the LLJ forcing and orographic lift could result
in QPF in excess of an inch in portions of the southern Adirondacks
from 12-18Z. After 18Z, the precipitation should become more showery
as the best isentropic lift shifts north and east of the area.
However, there will still be forcing for ascent due to midlevel
height falls and the exit region of an upper jet punching into the
area. Models continue to show some elevated instability as midlevel
lapse rates steepen, so will add a slight chance of thunder from 18-
24Z. At the surface, the warm sector does not look to reach our
area, and low level flow will remain with an easterly component
thanks to a secondary coastal low developing south of Long Island.
This will keep high temperatures mainly in the 40s to near 50, which
is near seasonal normals. Easterly 925 mb flow increases to 30-40 kt
today, so despite the showers and inversion, the typically windy
spots within and to the lee of the high terrain in western New
England could see some gusts up to 30 kt.

Tonight, a midlevel dry slot will work in, resulting in a decrease
in shower coverage, especially after 06Z. A light wintry mix is
possible over the high terrain of the southern Greens and southern
Adirondacks late, but it should be of little consequence with lows
mainly AOA freezing. Lows will remain elevated in the mid-30s to mid-
40s as the parent system is occluded and cold advection will lag
well to the west. Some patchy fog cannot be ruled out, especially if
any clearing can develop.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Monday, the cutoff upper low will drift over the local area.
Midlevel moisture will increase as this happens, and numerous to
widespread showers will expand south and east through the day.
GFS/MAV guidance appears too warm given the upper low and cloud
cover, so sided toward the cooler NAM/MET MOS, which yields
highs near normal. Showers continue Monday night but taper off
late as the center of the low begins to shift east of the area.
Snow levels will likely fall to 1-1.5kft AGL with minor
accumulations possible over the high terrain, generally less
than an inch.

Tuesday into Tuesday night, the center of the upper low
continues to drift into the North Atlantic, but lower heights
will linger over the local area. Likely still generous cloud
coverage around, but moisture depth and forcing does not look to
be enough for any more than a few isolated showers over the
higher terrain. Temperatures generally near normal again.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Looks to be a fairly quiet.

U.S. and international models are in good agreement on weather
features.

A check of GEFS 500mb height and 850mb temperature anomalies shows
both remaining within +/- 1 standard deviation through the period.

Upper level troughing hangs over the area for Wednesday and
Thursday. As reflected in the anomalies above, troughing fairly
weak.

By Friday, the troughing is replaced by ridging. Again, nothing too
dramatic.

Temperatures through the extended will be near normal, with
precipitation on the light side.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
Conditions range from LIFR to MVFR now.

A break in the precipitation as best forcing has moved off to
the northeast.

Low level southeast jet increases through the morning daylight
hours into the afternoon promoting a steadier period of rain
with IFR conditions in VSBY and CIGS. Some improvement toward
MVFR conditions later in the TAF period.

Two items not in the TAFs worth mentioning.

First as noted above low level southeast jet gets going roughly
09z-18z with strongest winds forecast 15-18z. For now did not
include LLWS in TAF. Jet is strongest for KALB, KPSF, KGFL. Have
surface winds picking up at KALB and KPSF in response to
strengthening jet. Some potential for LLWS at these terminals
depending on how strong surface winds get. Will assess through
the night.

Second, CAMs - 3km NAM and HRRR - suggest potential for some
convective elements late this afternoon into the evening.
Surface instability is nil. There is elevated instability with
negative Showalters evident. Given uncertainty on whether
convection develops or not, no mention in TAFs for now.

Outlook...

Monday Night: Moderate Operational Impact. Chance of SHRA.
Tuesday: Low Operational Impact. Slight Chance of SHRA.
Tuesday Night: Low Operational Impact. Slight Chance of SHRA.
Wednesday: Low Operational Impact. Slight Chance of SHRA.
Wednesday Night: Low Operational Impact. Slight Chance of SHRA...SHSN.
Thursday: Moderate Operational Impact. Chance of SHRA.
Thursday Night: Moderate Operational Impact. Chance of SHRA.
Friday: Moderate Operational Impact. Chance of SHRA.

&&

.FIRE WEATHER...
Periods of rain will continue today half an inch up to an inch
and a half of rain expected. An upper level low pressure system
will linger Monday, with additional clouds and numerous light
showers for much of the day. Most of the showers will be gone by
Tuesday, but a good deal of clouds will remain along with
seasonable temperatures and fairly moist conditions.

&&

.HYDROLOGY...
Periods of rain will continue today as a warm front approaches
the area. The rain could be briefly heavy at times this morning,
especially north and west of the Capital District, where amounts
in excess of an inch are possible from 8 am to 2 pm. The
precipitation will become more showery in the afternoon and
evening, with an isolated thunderstorm possible.

Total QPF from yesterday through today is expected to be around
half an inch to an inch across much of the area with higher
amounts of 1 to 2 inches across the southern Adirondacks and
higher terrain of the eastern Catskills and southern Green
Mountains. NOHRSC estimates 1 to 3 inches SWE over portions of
the southern Adirondacks and southern Green Mountains with as
high as 6 inches over the high terrain in Hamilton County. Basin
average SWE is likely lower, as there are bare areas in the
lower elevations. The combination of rain and snowmelt will lead
to river rises, although there remains uncertainty with respect
to the magnitude of both factors. The cool temperatures may
limit snowmelt somewhat. At this time, the Sacandaga River at
Hope is expected to touch flood stage Sunday evening with minor
flooding forecast. Some slower responding points, such as the
Schroon at Riverbank and the West Canada at Hinckley will
continue to rise and possibly reach minor flood stage around
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
website.

&&

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

&&

$$
SYNOPSIS...Thompson
NEAR TERM...Thompson
SHORT TERM...Thompson
LONG TERM...OKeefe
AVIATION...IAA/OKeefe
FIRE WEATHER...Thompson
HYDROLOGY...Thompson


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