Area Forecast Discussion
Issued by NWS Albany, NY

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466
FXUS61 KALY 231735
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
135 PM EDT Mon Oct 23 2017

.SYNOPSIS...
Another warm day is expected today with above normal
temperatures, despite increasing amounts of cloud cover. It will
continue to mild and muggy tonight, with showers becoming more
numerous towards daybreak Tuesday.  An approaching frontal boundary
will bring some heavy rain showers and thunderstorms to the region
tomorrow into tomorrow night, some of which may produce gusty winds.
Although some rain showers may linger into Wednesday, drier
conditions are expected later in the week, along with somewhat
cooler temperatures.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 130 PM EDT, a combination of lower clouds expanding north,
and high/mid level clouds above has led to mostly cloudy skies,
outside of more pronounced breaks in the clouds across portions
of the Adirondacks, and the greater Capital Region, where H925
winds still have just enough of a southwest component to produce
some downsloping.

Clouds should continue to expand through this afternoon. Temps
are already 65-70 in valley areas, despite the increasing
clouds. Expect temps to rise at least another 2-4 degrees
through mid afternoon from current levels.

South to southeast winds have increase to 10-20 mph, strongest
in north/south oriented valleys. Some gusts up to 25 mph will be
possible.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
     Multi-hazard storm to impact the region Tuesday with heavy
rainfall, gusty winds and thunderstorms...

As the upper level ridge shifts eastward, a large and deepening
trough over the Midwest and Ohio Valley will be heading towards
our area. The result will be a deep meridional flow across our
area, with a strengthening southerly low-level jet. 850 hpa
winds will be reaching 50-70 kts by late tonight into Tuesday
morning, and ensemble guidance suggest 850 v-wind anomalies of
about 3-4 STD above normal. This deep southerly flow will help
advect plenty of moisture into the region, and the 850/925
moisture transport is off the charts, according to the 00z GEFS.

Although some showers are possible overnight, the best chance
will be late in the night and especially for Tuesday. With the
strong southerly flow, upslope areas of the Catskills will be
favored late tonight into Tuesday morning for heavy rainfall.
Winds will be increasing through the night, especially for the
higher terrain, with some gusts over 45 MPH by late in the
night. It`s still tough to say if valley areas will see strong
winds overnight. Although there certainly will be stronger winds
due to funneling up the Hudson Valley, a low-level inversion
could help prevent the strongest winds from mixing down for
valley areas. There may be a window for gusty winds in valley
areas on Tuesday morning, as the mixing depth increases before
more widespread showers into the region. With the
clouds/increasing wind, temps overnight will be held steady in
the upper 50s to mid 60s, which is very mild for late October.

During the day Tuesday, the occluded/cold front to the west
will slowly be heading towards the area. However, this boundary
will be slowing down even further, as the surface boundary and
upper level flow become parallel to each other. As a result,
periods of showers and possible thunderstorms will be occurring
through the day, as moisture streams up the surface boundary.
With PWAT values exceeding 1.50 inches, locally heavy rainfall
will be possible. Some training of showers/thunderstorms looks
to occur, so poor drainage and flash flooding will be a concern
(see hydro discussion below). WPC has much of the area in a
slight risk for flash flooding.

In addition, surface CAPE values look to be around 500 J/kg.
Despite the limited instability, the strong wind-field just
above the surface will be available for any low-topped
convection to mix down gusty winds. SPC has a slight risk for
severe t-storms over the entire area. Any discrete storms could
also provide the risk of a brief spinup tornado thanks to the
low LCL heights and moisture-rich environment, so will have to
watch for that too. 3km NAM suggests that broken lines of
showers/t-storms will be occurring throughout the day, but the
main threat may be just along/ahead of the boundary late in the
afternoon and into the early evening hours.

Showers and thunderstorms will gradually end on Tuesday night
from west to east as the boundary slowly moves across the area.
By late Tuesday night, the heaviest precip will be east of the
region over central and eastern New England. If a wave of low
pressure develops along the boundary, it could try to linger
some showers into the day on Wednesday for our eastern zones,
although this is still uncertain. Even without this, there still
could be a passing shower in spots, as the cyclonic flow around
the deep upper level trough will be in place. However, this
rainfall won`t be as heavy as Tuesday.  Otherwise, clouds will
break for some sun during the Wednesday with temps in the mid
50s to mid 60s.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
An active period of weather remains in the forecast as we watch the
departure of the frontal boundary to our east Wednesday night to be
followed by a cold upper low/trough that crosses the region.  H500
temperatures are expected to drop close to -25C overnight Wednesday
as this chilly upper low transverses the region through Thursday
morning.  This will be sure to keep the chance for showers in the
forecast and per the thermal profiles, some graupal will be possible
with any deeper convective elements through Thursday morning and
early afternoon.

Ridge both at the surface and aloft are expected to influence our
weather toward a more tranquil side Thursday night into Friday.  In
fact, warm advection through Friday as a strengthening low level jet
thanks to approaching deepening trough upstream will result in
temperatures moderating back into the 60s for valley locations.

The weekend looks rather unsettled as a few meteorological players
to watch closely.  First, the aforementioned nearly full
longitudinal trough across the eastern third of NOAM slowly
approaches with its associated frontal boundary(ies).  Second,
moisture transport from the Gulf and deep Atlantic will advect in
higher PWATS yet placement of this plume remains in question. Third,
what if anything develops in the tropics that could become entrained
into the large scale synoptic flow regime and impact the region. Per
the National Hurricane Center, the area being monitored in
southwestern Caribbean Sea has a 40% chance to develop in the next 5
days.  Global models and ensembles suggest the potential for this
entity to influence our weather through the second half of the
weekend.  For now, we will place chance PoPs for rain
showers/periods-of-rain.

Temperatures through the period will likely average near normal and
precipitation near to potentially above normal.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
A strong cold front will approach from the west Tuesday, and
pass across the TAF sites Tuesday afternoon.

Clouds have expanded across the region, and are mainly in the
MVFR/low VFR range. Expect this to continue through early this
evening, trending lower into MVFR tonight. There could be some
embedded IFR Cigs after 08Z/Mon, esp at KPSF. Also, patchy
drizzle may develop.

On Tuesday, as the cold front approaches from the west, showers
should increase in areal coverage from W to E. A narrow line of
heavier showers should develop along the actual front, but is
not expected to pass across the TAF sites until after 18Z/Tue.
Expect mainly MVFR conditions Tuesday morning.

Winds will increase from the southeast to south at 10-15 KT this
afternoon into tonight, with some gusts of 20-25 KT possible,
esp at KALB.

On Tuesday, south winds will increase to 10-20 KT, with some
gusts of 30 KT or higher possible, esp at KALB.

Low level wind shear is likely tonight at KGFL and KPOU, as
surface winds remain from the south at less than 10 KT, while
winds around 2000 FT AGL increase from the south to 35-45 KT.

Outlook...

Tuesday Night: High Operational Impact. Breezy Definite SHRA...TSRA.
Wednesday: Low Operational Impact. Slight Chance of SHRA.
Wednesday Night: Moderate Operational Impact. Chance of SHRA.
Thursday: Moderate Operational Impact. Chance of SHRA.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: No Operational Impact. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.

&&

.FIRE WEATHER...
Although much of today will be dry, wet weather is expected for
tonight into Tuesday, with periods of showers and thunderstorms
expected. RH values will only to fall to 60 percent today and 70
to 80 percent on Tuesday. Southerly winds of 10 to 15 mph today
will increase to 15 to 25 mph on Tuesday, with higher gusts
possible.

&&

.HYDROLOGY...
Although recent dry weather has allowed for low river flows, a
period of excessive rainfall may still allow for some hydrologic
impacts this week.

A deep and persistent southerly flow will allow a very moist
air mass to move into the region for Tuesday, with PWAT values
reaching 1.50 to 1.80 inches. These values are 2-3 STD above
normal for late October. As a slow moving frontal boundary
approaches the region, bands of heavy rain showers and
thunderstorms will train over the region.

In areas that see repeated bursts of heavy rainfall, flooding of
poor drainage and low lying areas looks to occur. This will
especially be true in urbanized areas and flash flooding is
possible as well. A Flash Flood Watch may be needed for parts of
the area, as high rainfall rates (over 1" per hour) may cause
flooding to occur, despite the initially low flows.

Main stem rivers will have large rises and some will come close
to bankfull. Overall, basin average QPF will be 1 to 3 inches,
although localized point totals that see repeated heavy rainfall may
be close to 5 inches. While widespread river flooding is not
expected, some flashier river points could see a brief period of
minor flooding for Tuesday into Tuesday night.

Although there could be some lingering rain showers Wednesday
into Thursday, any additional rainfall looks rather light. Dry
weather will then return for Friday into Saturday, which should
allow flows to recede somewhat. However, additional rainfall
will be possible to end the weekend and into early next week.

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...Frugis
NEAR TERM...Frugis/KL
SHORT TERM...Frugis
LONG TERM...BGM
AVIATION...KL/BGM
FIRE WEATHER...Frugis
HYDROLOGY...Frugis



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