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000 
FXUS61 KALY 232059
AFDALY

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

.SYNOPSIS...
An unseasonably warm and humid air mass will be over the 
region tonight ahead of a slow moving cold front, as scattered 
showers will increase well in advance of the front with windy 
conditions towards daybreak.  The cold front will bring some heavy 
rain and a chance of thunderstorms with gusty winds Tuesday 
afternoon into the early evening period.  Some scattered showers may 
linger north and east of the Capital Region on Wednesday with 
slightly cooler and drier weather north and west until an upper 
level disturbance arrives Wednesday night with isolated to scattered 
showers.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
A Multi-Hazard Event will impact portions of the region tonight
through Tuesday with gusty winds, heavy rain, and strong to
possibly severe thunderstorms. 

As of 455 PM EDT...A high amplitude ridge continues to move 
downstream of NY and New England tonight as strong upper level 
trough is forming as a northern stream short-wave is phasing 
with a southern stream shortwave over the Midwest/lower Great 
Lakes Region early this evening. A strong sfc cyclone deepens 
and intensifies, as it lifts north/northeast in the northern 
Great Lakes Region by tomorrow morning. A full-latitude mid and 
upper level trough sets up east of the MS River Valley. 

The low-level south to southeast flow strengthens over the 
forecast area. As the 12Z GEFS continues to show a +v-component 
meridional /southerlies/ wind anomaly of +3 to nearly +5 
standard deviations /STD DEVS/ above normal. The H925 winds 
increase to 40-50+ kts by daybreak on the NAM/GFS/EC. The latest
NAM12 30AGL winds are increasing to 40-55 kts over the higher 
terrain, especially the eastern Catskills/southern 
Adirondacks/and western New England higher terrain including the
Taconics between 06Z-12Z. We are concerned some of these winds 
may translate to the sfc and have issued a Wind Advisory in all 
locations except southern Litchfield County, the mid Hudson 
Valley of western Dutchess and eastern Ulster Counties, and the
northern reaches of the Lake George Region including Warren and
northern Washington Counties, as well as eastern Windham Co in 
southern VT. Funneling/Channeling of the south to southeast 
winds may allow for stronger gusts in the Capital Region and 
narrow valleys leading into the Mohawk Valley. We are expecting 
winds gusts possibly in the 46-57 mph knocking down some leafed 
tree limbs/trees/power lines. The greatest threat definitely 
looks like the higher terrain. The winds increase towards 
daybreak. The BUFKIT profiles show lack of a strong inversion so
mixing down momentum/strong winds from 1-3 kft AGL is possible 
especially towards daybreak.

Meanwhile the low-level theta-e and moisture advection increases
on the nose of the low-level jet and with a weak impulse in the
south to southwest low to mid level flow. Scattered showers 
will become more numerous south and west of the Capital Region 
towards daybreak. Locations north and east will have some patchy
fog and light rain. Some downsloping off the western New 
England higher terrain may curtail the QPF and pcpn. The strong 
lift with the front looks like it will begin to reach our
western most zones close to daybreak based on the timing of the
consensus from the NAM/GFS/ECMWF/CAN GGEM.

It will be a warm and humid night with lows above the normal
highs for this time of year! Lows will only be in the mid 50s to
lower to mid 60s. South to southeast winds will be 15 to 25 mph
with some gusts in the 30-50 mph range. Sfc dewpts rising into
the mid 50s to lower 60s.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
A Multi-Hazard Event will impact portions of the region through
Tuesday with gusty winds, heavy rain, and strong to possibly 
severe thunderstorms. 

The cold front slowly moves west to east across the forecast
area in the morning, and there are some indications from the
guidance that strong to severe thunderstorms may materialize
with a narrow cold frontal rainband. The H850 winds increase to
50-75 kts. The H925 winds continue at 40-50 kts especially from
the Capital Region east into the afternoon. The 0-6 km bulk
shear values are 50-75 kts and the 0-1 km bulk shear is 40-50 
kts. Both the NAM/GFS have SBCAPES of 200-500+ J/kg with the 
highest values from the eastern Catskills and the Hudson River 
Valley eastward. A classic high shear and low CAPE environment 
for strong to possibly severe thunderstorms sets up. The SPC 
Slight Risk is maintained across the majority of the forecast
area. We agree with it, and many of the CAMS show some discrete
convective cells forming into a line/lines in the late morning 
to early to mid afternoon. Damaging winds would be the main 
concern, but we can not rule out an isolated spin-up tornado 
with impressive 0-1 km bulk shear/helicity, low LCLs and the 
impressive wind fields overall.

The 850 hPa moisture flux convergence increase to +5 STD DEVS 
above normal with PWATS in the +3 to +4 STD DEVS above normal
based on the 12Z GEFS. The actual PWATS will be in the
1.25-1.75+ inch range which are uncanny for late OCT. The
anomalous moisture is being tapped from the Gulf and Caribbean
with an atmospheric river. The low-level wind anomaly gradually
shift east during the day, but it is concerning how the low to
mid and upper level flow becomes parallel. The GFS/NAM/EC 
shifted slightly further east with the axis of heaviest
rainfall. We believe 1-2+ inches is possible over eastern NY 
with some slightly higher amounts. East of the Hudson River 
Valley into western New England 2-4" are possible especially 
since a wave may get going along the front into the evening 
period. We believe 1"/hr rainfall rates are possible, and our 
greatest confidence for potential flash flooding is over western
New England, and we collaborated with our neighboring offices 
and have placed a Flash Flood Watch out from noon tomorrow until
6 am WED. It might be canceled sooner if the front shifts east 
far enough. Training of the showers is also a strong 
possibility. Some training of showers/thunderstorms looks to 
occur outside the watch area, and poor drainage flooding of low 
lying areas will also be a concern (see hydro discussion below).
WPC continued much of the area in slight risk for flash 
flooding. The Zonal FFG values remain high in the 3-hr range at 
2-3" due to the dry antecedent conditions across the forecast, 
but if the rain rates are too heavy, then the rain may just run 
off. We also kept the Wind Advisory running until 6 pm, but 
should be able to drop portions possibly earlier. 

Tuesday night the rain begins to diminish from west to east Tue
night especially after midnight from the Hudson River Valley 
eastward. There is still some uncertainty how quickly the front
moves east and where any weak ripples of low pressure track
along it. A dry slot to system begins to work in and we tapered
the showers westward. Highs will be in the mid 60s to lower 70s
on Tuesday with lows in the upper 40s to lower 50s west of the 
Hudson River Valley, and mid and upper 50s to the east.

Overall expecting 1-3" of rain across the region with the higher
amounts of 3-4" and possibly more over western New England and
possibly portions of the eastern Catskills/southern Adirondacks
with southeasterly upslope flow. 

Wed-Wed night...Some showers may linger across western New 
England in the morning. Low and mid level cold advection occurs 
in the wake of the boundary, as the mid and upper level trough 
lingers upstream. Some sunshine may mix with clouds during the
pm. Some lake effect/enhanced showers may move into the western
Adirondacks late in the day into the early evening. The winds 
will be much lighter from the south to southwest with highs in 
the mid 50s to lower 60s over the higher terrain, and mainly mid
and upper 60s in the valleys and over some of the hills. The 
upper level trough/secondary cold front moves through Wed night 
with limited moisture to work with. Some isolated to scattered 
showers are possible outside of the Hudson River Valley. Lows 
fall back into the mid 30s to mid 40s across the region.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
The pattern will be dominated by a long-wave trough over the eastern 
U.S. through this period with strong short-waves re-inforcing a turn 
to cooler and unsettled weather. The GFS/ECMWF and GEFS are in 
reasonably good agreement through this period with relatively minor 
differences developing over the weekend with a potential coastal 
system. Our early-to-mid week system will be lifting northeast away 
from the area on Thursday with low chance pops for showers ending 
from southwest to northeast. A weak ridge of high pressure will move 
east across New England on Friday then the flow will return to 
southwesterly on Saturday as the next cold front approaches from the 
west. This will allow temperatures to rebound to above normal again 
by Saturday, but this will be a short-lived occurrence as 
another significant trough is forecast to develop over the 
northeast over the weekend through early next week. 

Medium to long-range models are in reasonably good agreement showing 
the significant deepening of the upper trough over the eastern U.S. 
from Saturday through Monday. Models all indicate that a mid-level 
trough will close off somewhere over the east by late Sunday with 
low pressure developing along the coast and moving north toward New 
England the Canadian maritimes. Details are somewhat uncertain at 
this time but this system will certainly bring the potential for a 
significant rain event somewhere over the eastern third of the  U.S. 
Sunday into Monday. Per previous discussion this trough may end  up 
entraining some tropical moisture depending on how much amplitude 
ultimately develops, and this of course would greatly enhance the 
heavy precipitation potential. Some high elevation snow can't be 
ruled out by early next week as the surface through mid-level system 
brings the coldest air mass of the season to the region by
Monday. 

&&

.AVIATION /20Z 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. Definite SHRA...TSRA.
Wednesday:  Slight Chance of SHRA.
Wednesday Night: No Operational Impact. NO SIG WX.
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: Low Operational Impact. Slight Chance of SHRA.


&&

.FIRE WEATHER...
An unseasonably warm and humid air mass will be over the 
region tonight ahead of a slow moving cold front, as scattered 
showers will increase well in advance of the front with windy 
conditions towards daybreak.  The cold front will bring some heavy 
rain and a chance of thunderstorms with gusty winds Tuesday 
afternoon into the early evening period.  Some scattered showers may 
linger north and east of the Capital Region on Wednesday with 
slightly cooler and drier weather.

The RH values increase to 85 to 100 percent tonight in the
showers, and only lower to 65 to 85 percent tomorrow afternoon.
They increase close to 100 percent Wednesday morning.

The winds will increase from the south to southeast at 15 to 25
mph overnight with some gusts in the 30 to 50 mph range towards
daybreak. These winds will linger into Tuesday. The winds will 
decrease to the west to southwest at 5 to 15 mph on Wednesday. 

A widespread rainfall is expected tonight into Tuesday evening. 

&&

.HYDROLOGY...
A Flash Flood Watch has been issued from noon tomorrow to 6 am
Wednesday for all of western New England including southern VT,
the Berkshires and Litchfield County CT.

Although recent dry weather has allowed for low river flows, a 
period of excessive rainfall may still allow for some hydrologic
impacts Tuesday through Wednesday.

A deep and persistent southerly flow will allow a very moist 
air mass to move into the region for tomorrow, with PWAT values
reaching 1.25 to 1.75+ inches. These values are 3-4 STD DEVs 
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 isolated flash 
flooding is possible as well. However, the high 3-hr FFG values
of 2-3" may lower the threat of flash flooding over eastern NY 
due to a slightly faster movement of the front. A Flash Flood 
Watch was issued for high rainfall rates (over 1" per hour) 
which may cause flooding to occur, despite the initially low 
flows in western New England. We may have to expand the Flash 
Flood Watch westward if the threat increases over eastern NY.

Main stem rivers will have large rises and some will come close
to bankfull. Overall, basin average QPF will be 1 to 2.5 
inches in eastern NY, although localized point totals that see 
repeated heavy rainfall may receive 2-4+ inches of rain,
especially over western New England. 

While widespread river flooding is not expected, some flashier 
river points could see a brief period of minor flooding for 
Tuesday into Tuesday night. At this point Hope in Hamilton 
County on the Schroon is only forecasted to reach minor
flooding.  We will continue to monitor this possibility. 

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

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...Wind Advisory from midnight tonight to 6 PM EDT Tuesday for 
     CTZ001.
     Flash Flood Watch from Tuesday afternoon through late Tuesday 
     night for CTZ001-013.
NY...Wind Advisory from midnight tonight to 6 PM EDT Tuesday for 
     NYZ032-033-038>041-047>054-058>061-063-066-082-084.
MA...Wind Advisory from midnight tonight to 6 PM EDT Tuesday for 
     MAZ001-025.
     Flash Flood Watch from Tuesday afternoon through late Tuesday 
     night for MAZ001-025.
VT...Wind Advisory from midnight tonight to 6 PM EDT Tuesday for 
     VTZ013-014.
     Flash Flood Watch from Tuesday afternoon through late Tuesday 
     night for VTZ013>015.

&&

$$
SYNOPSIS...Wasula
NEAR TERM...Wasula
SHORT TERM...Wasula

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