Albany, NY WFO Forecast Discussion

Forecast Discussion for ALY NWS Office
000
FXUS61 KALY 281715
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
115 PM EDT Mon Sep 28 2020

.SYNOPSIS...
An upper level disturbance will bring some isolated to
scattered showers and patchy fog this morning to the region. A mild
air mass for late September will impact the region into Tuesday, as
a cold front will slowly approach during the day.  The cold front
and a low pressure system will bring a widespread rainfall late
Tuesday afternoon into Wednesday.  Another low pressure system could
bring additional rainfall late Wednesday night through Thursday
before cooler air moves back into eastern New York and western New
England.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A few showers left north of the Capital Region that will affect
those areas through the afternoon. Clouds are slowly breaking up
over eastern NY and western New England and the greater
frequency of breaks in the clouds will help temperatures reach
the mid 70s in many areas around 70 to lower 70s north and near
80 south. South to southeast winds will be steady and
occasionally breezy as well. Many areas may trend to mostly
clear by this evening and the showers north of the Capital
Region should shift mainly to northern NY and northern VT by
this evening..

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
Tonight...Partly cloudy conditions begin the period, but with
abundant low-level moisture we are expecting some low stratus to
reform ahead of the cold front slowly approaching from the west.
Some patchy fog is also possible, but with a persistent
southerly breeze this may prevent widespread fog formation in
many areas. We tried to keep it patchy. It will be a muggy
night. Mid and upper level heights will continue to fall
upstream over the Great Lakes Region, and OH Valley, as a deep
mid and upper level trough approaches. A fetch of moisture will
commence out of the Gulf of Mexico. A strong upper level jet
will set up along the east side of the mid and upper level
trough. We should seem some showers start to move into locations
in the western Adirondacks and western Mohawk Valley shortly
before sunrise from a prefrontal disturbance. Also, the moist
southerly flow may allow for some isolated showers or patchy
drizzle further east. However, the front with better dynamics
does not look to arrive until late TUE pm into WED. It will be
a muggy night with lows in the upper 50s to mid 60s.

Tuesday...It has been a few weeks, but the forecast area looks
to finally get a widespread rainfall over the next 12 to 24+
hours. Deep meridional flow continues over the region with water
vapor transport out of the Gulf of Mexico. Multiple short-waves
in the southwest flow ahead of the front will impact the region.
PWATS increase to +1 to +3 STDEVs above normal based on the
latest 00Z GEFS. A south to southwest H850 LLJ increases to
30-40+ kts. The u-wind anomalies will also be +2 to +3 STDEVs
above normal. The moist air mass will be tapped into for periods
of moderate to locally heavy showers to break out from west to
east across the region on TUE. There are still some timing
differences with the guidance. Locations from the
Berkshires/Capital Region and eastern Catskills have the
greatest chance for showers prior to nightfall. A few
thunderstorms are also possible with pockets of elevated
instability especially over the eastern Catskills/Schoharie
Valley. Temps will be mainly in the 60s to lower 70s west of the
Hudson River Valley, and lower to mid/upper 70s from the Hudson
River Valley eastward, except some upper 60s over the western
New England higher terrain.

Tuesday Night into Wednesday...A fairly widespread soaking
rainfall should encompass the region Tuesday night with the
front slowly moving eastward Tuesday night and potentially
reaching the eastern New England Coast WED morning. The mid and
upper level flow will run parallel to the sfc front. PWATS will
continue to run above normal by +1 to +3 STDEVs TUE night in the
1.25"-1.75". Good moisture convergence will occur ahead of the
front and with a weak wave moving along it. There are small
pockets of instability (mainly elevated) with Showalter indices
0 to -2C in the NAM/GFS for parts of the region. A slight chance
of thunderstorms was kept in the forecast TUE night across the
region. Some locally heavier bursts of rain will be possible.
The dry antecedent conditions should preclude any hydro issues.
WPC Day 2 ERO continues a Marginal Risk. Gridded FFG values
remain very high. The question will be where the front will be
located by WED morning. Our current thinking is that it should
be moving east of the region by late WED morning and we should
see a reduction of the showers from the Hudson River Valley
westward by the late pm.

Total rainfall from the initial front and wave will generally be
in the 1 to 2 inch range, but there continues to be variability
in the guidance on the placement of the axis of rainfall. A few
locations across the Litchfield Hills, as well as the eastern
Catskills and southern Adirondacks could have amounts closer to
3" due to the south/southeast flow orographically enhancing the
rainfall. Expect lows to fall back to the 50s to lower 60s with
a few upper 40s over the southern Adirondacks. Highs on WED will
be in the mid 50s to lower/mid 60s over the higher terrain, and
generally mid 60s to around 70F in the lower elevations.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
One final area of low pressure will track along a nearly stationary
front Wednesday night. This low is projected to be located in the
eastern NC/VA area Wednesday evening and then track northeastward
across New England through Thursday morning. There remain slight
model differences regarding the track of this low and how large the
precipitation shield will be. Have placed the greatest pops across
western New England (closer to the projected front and track of the
low) with lower pops farther west into Herkimer County. This system
could contain some much-needed moderate to heavy rainfall with the
greatest amounts across western New England. Will continue to
monitor trends over the coming days.

In the wake of this system, another weaker low across Quebec will
send a cold front across the region later Thursday into Friday,
bringing a cooler air mass for the remainder of the period. With 850
hPa temperatures falling below 5C, there will be enough low-level
moisture and a temperature difference with Lake Ontario for lake-
effect/enhanced showers Friday into Saturday. Locations north and
west of the Capital District will be most favored for this activity
given the projected west to southwesterly mid-level flow over the
lake. Additional instability-driven showers cannot be ruled out
either due to the strong upper-level support and cold air aloft.
Another weak area of low pressure may form just off the Northeast
coast later Friday into Saturday, but confidence on whether it
develops remains low. High pressure will work into the region on
Sunday, gradually bringing an end to any shower activity.

Temperatures will trend downward to below-normal values during the
long term period, with highs going from the mid-50s to upper 60s to
near 70 on Thursday to the upper 40s to lower 60s over the weekend.
Lows will start in the mid-40s to lower 50s Wednesday and trend
downward to the mid-30s to lower 40s by Friday and Saturday
night.

&&

.AVIATION /17Z MONDAY THROUGH FRIDAY/...
Through 12z/Tue...Isolated showers, patchy drizzle and low-level
stratus is causing mainly IFR/MVFR conditions early this morning.
These conditions will continue for a few more hours until a gradual
return to VFR is anticipated between 14z-18z. A tempo group was
included to show this transition. The afternoon hours will feature
generally sct stratocu coverage with still the chance for a brief
shower. Shower activity will come to an end later Monday afternoon
into early Monday evening as clouds partially clear. However, some
patchy fog/mist and/or low-level stratus is anticipated to develop
overnight. Highest confidence at this time is MVFR stratus, so will
only show that in the TAF`s.

Winds will be light out of the south to southeast early this
morning, increasing to 6-12 kt with gusts to around 20 kt this
afternoon. Winds will then decrease to 4-8 kt tonight.

Outlook...

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

&&

.FIRE WEATHER...
An upper level disturbance will bring some isolated to
scattered showers and patchy fog this morning to the region. A
warm and humid air mass for late September will impact the
region into Tuesday, as a cold front will slowly approach
during the day. The cold front and a low pressure system will
bring a widespread rainfall late Tuesday afternoon into
Wednesday. More unsettled weather is likely Wednesday night into
Thursday.

Minimum RH values are expected to only be 55 to 70 percent this
afternoon, as a warm and humid air mass remains in place. Max
RH values will be around 100 percent Tuesday morning, and will
only lower to 60 to 85 percent with rain moving in Tuesday
afternoon.

The winds will be southerly today at 10 to 20 mph, decreasing
to around 5 to 10 mph tonight. The winds will be south to
southwest at 10 to 15 mph on Tuesday.

A widespread rainfall is expected Tuesday into Wednesday.

&&

.HYDROLOGY...
Some isolated to scattered light showers will continue today
into tonight with amounts of a few hundredths to a tenth of an
inch a few spots.

A more appreciable and widespread rainfall is then expected
Tuesday into Wednesday, as a slow-moving cold front moves across
the region. There remains some uncertainty with regards to
placement or timing of maximum rainfall amounts, although it
does appear increasingly likely for a storm total of 1-2 inches
of rainfall with up to 3 inches in favored higher terrain
upslope locations /southern Adirondacks...eastern Catskills and
Litchfield Hills/ in southerly flow. Given extremely dry
antecedent conditions and low stream flows/river levels, this
rainfall is not forecast to result in flooding and will be
beneficial. Gridded FFG values remain high. If rainfall rates
approach an inch an hour some ponding of water may occur on some
roadways.

Another area of low pressure tracking northward along the east
coast may bring additional rainfall to at least parts of the
region Wednesday night into Thursday. An additional half an inch
to an inch of rainfall is possible.

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.

&&

.CLIMATE...
Here is a look at how much precipitation had occurred so far this
month at our climate sites and their annual precipitation and
departure.

Albany NY:
September: 0.50 inches
2020: 24.41 inches (-4.68 inches)

Glens Falls NY:
September: 0.28 inches
2020: 24.35 inches (-4.48 inches)

Poughkeepsie NY:
September: 0.77 inches
2020: 20.61 inches (-13.98 inches)

Bennington VT:
September: 2.08 inches
2020: 25.36 inches (-5.34 inches)

Pittsfield MA:
September: 0.97 inches
2020: 23.73 inches (-9.49nches)

&&

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

&&

$$
SYNOPSIS...Wasula
NEAR TERM...NAS
SHORT TERM...Wasula
LONG TERM...Rathbun
AVIATION...Speciale
FIRE WEATHER...Wasula
HYDROLOGY...JPV/Wasula
CLIMATE...

NWS ALY Office Area Forecast Discussion