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Area Forecast Discussion (AFD)

Issued by Albany, NY (ALY)

                            
000
FXUS61 KALY 232015
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
415 PM EDT Mon Sep 23 2019

.SYNOPSIS...
A cold front and an upper level disturbance will bring 
scattered showers and thunderstorms to the region tonight.  An upper 
level low will continue the threat for isolated to scattered showers 
from the Capital Region northward on Tuesday, and it will be much 
cooler and less humid. High pressure builds in from the Ohio 
Valley Tuesday night into Wednesday with fair and dry weather. 
Another cold front will bring isolated to scattered light rain 
showers on Thursday. 

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
As of 415 PM EDT...A prefrontal band of isolated showers has 
reached the Capital Region, northern Catskills, and Mohawk
Valley. The strong sfc to boundary layer southwest flow has
allowed dewpoints to fall into the upper 50s to lower 60s in
portions of the Hudson River Valley due to downsloping.

The latest SPC Mesoanalysis RAP data shows MLCAPE values 
generally less than 500 J/kg, despite dewpoints in the upper 
50s to mid 60s. The stronger synoptic forcing with the cold 
front will not arrive until 21Z to 00Z /5-8 pm/ west of the 
Hudson River Valley, and then 00Z to about 03Z /8-11 pm/ from 
roughly the Hudson River Valley eastward. The strong upper level
dynamics, favorable deep shear and height falls with limited 
instability still may promote a few strong thunderstorms, and 
may be a rogue severe in the very late pm and early evening 
especially from the I-90 corridor northward. A Marginal Risk 
continues for the northern two thirds of the forecast area. 
DCAPE values may peak in the 500-800 J/kg range due to steep 
low-level lapse rates and cooling from aloft. Some locations in 
the mid Hudson Valley have reached record highs in the lower 
90s, such as Poughkeepsie (the high hit 92F at 244 pm EDT), 
where the record was 90F sent in 1959 (the period of record goes
back to 1931)

The cold front will shift eastward across New England around
midnight with some lingering isolated to scattered showers, but
then the upper low takes over. The core of the coldest air with
the closed H500 low moves over southwest Quebec and northern NY.
some showers will pop up tapping lake moisture with cyclonic
vorticity advection around the low. Temps will fall back into
the 50s to around 60F in the low to mid level cold advection. 
It will be breezy with west to northwest winds of 5 to 15 mph. 
Humidity levels will drop considerably. 

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
Tuesday...The closed upper low will continue the threat for
diurnally driven instability isolated to scattered showers from
the Capital Region, northern Catskills, and Berkshires
northward. H500 temps fall close to -20C over northern NY and 
VT. In the cyclonic flow it will be much cooler with H850 temps 
close to early Fall values. More clouds than sun is expected 
over the majority of the forecast area. High temps will be in 
the mid 60s to around 70F in most of the valley locations with 
mid 50s to lower 60s over the higher terrain and in the western 
Mohawk Valley.

Tue night...The upper low and associated cyclonic vorticity 
advection moves downstream over northern New England and the 
Gulf of Maine. Mid and upper level ridging builds from the Great
Lakes Region and southeast Ontario over the forecast area. The 
showers over the northern zones will shrivel with the loss of 
the daytime heating. The skies will clear and the winds will go 
light to calm. Lows will fall into the 40s to around 50F in a 
few spots. Some patchy radiational fog will be possible in the 
Upper Hudson River Valley, the Mohawk Valley, and east of the 
southern Green Mountains. 

Wednesday...A nice mid week day is expected with a sfc
anticyclone ridging in from the Mid Atlantic States. The strong
subsidence with the ridge should yield mostly sunny/sunny skies
with temps trending to normal to slightly above normal readings
for late Sept with highs in the lower to mid 70s in the valleys,
and upper 50s to 60s over the higher terrain.

Wed night to Thu...A weak warm front moves through Wed night
with an increase of clouds and perhaps a few showers over the
Adirondack Park. H850 temps go above normal briefly based on the
the latest GEFS. Mins will be milder than the previous day with
upper 40s to mid 50s with the low to mid level thermal advection.
A cold front with limited moisture convergence swings across 
the region on THU with an isolated to scattered threat for a 
shower especially from the Capital Region north and west. Temps 
will be a little above normal from the Tri Cities south and 
east, and near or slightly below normal north and west due to 
the placement and timing of the cold front. Highs will be in the
60s to lower/mid 70s. 

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
After a brief lowering of mid/upper level heights across northeast 
CONUS, heights are expected to build once again during the extended 
period. Despite the rising heights, weak disturbances passing 
northwest of the region may be close enough to bring periods of 
clouds, and perhaps some showers, especially for northern areas on 
Saturday.

Temperatures will be relatively cool despite the building heights, 
with the potential for shallow cool air masses to settle south from 
southeast Canada into the region, depending on where a frontal 
boundary ultimately sets up. Coolest temperatures appear to be 
Friday, then possibly again Sunday into Monday, when max temps may 
only reach the upper 60s to lower 70s in valley areas, and upper 50s 
to mid 60s northern and higher terrain areas. Possible warming for 
Saturday, especially if a southwest flow develops ahead of an 
incoming frontal system, with highs in the 70s for most valley 
areas, and 60s to around 70 higher elevations.

Overnight lows should be coolest Friday morning, with the potential 
for widespread 40s, with some 30s possible across portions of the 
Catskills and southern Adirondacks. Lows warming slightly into the 
mid 40s to lower/mid 50s for Saturday-Monday mornings.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
A cold front will cross the TAF sites this evening. Scattered
showers will develop ahead of, and along the front and continue
through early tonight. An upper level disturbance will bring
clouds and isolated showers to some TAF sites through Tuesday
morning.

Through this afternoon, an initial band of light
showers/sprinkles will slowly move southeast across the TAF
sites through around 20Z/Mon. Despite these showers, VFR
conditions should prevail.

Somewhat heavier showers, and perhaps isolated thunderstorms, 
will approach the TAF sites with the cold front from northwest 
to southeast between roughly 23Z/Mon-03Z/Tue. A brief period of 
MVFR/IFR Vsbys will be possible within the heaviest showers, 
along with possible wind gusts of 25+ KT. Greatest chances for
these heavier showers will be at KGFL, KALB and KPSF.

Behind the front, mainly VFR conditions are expected until after
08Z/Tue, when a period of MVFR Cigs may develop through 14Z/Tue
at KGFL, KALB and KPSF. MVFR Cigs could linger even longer at
KPSF. Some light showers or sprinkles may also occur during 
this time at these TAF sites. Mainly VFR conditions are expected
at KPOU.

Although not mentioned in the TAFs, should winds and clouds
decrease for a period after the showers move through this
evening, there could be a period of ground fog at some TAF 
sites before higher based stratus/stratocumulus clouds 
develop.

Winds will be south to southwest at 8-12 KT this afternoon with
some gusts up to 25 KT possible. Winds will shift into the west
tonight at 5-10 KT, then west to northwest Tuesday at 8-12 KT
with some gusts up to 25 KT possible.

Winds will be stronger and variable in direction in and near any
thunderstorms, as well as heavy showers associated with the cold
frontal passage.

Outlook...

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

&&

.FIRE WEATHER...
A cold front will bring scattered showers and thunderstorms to 
the region tonight. An upper level low will continue the threat 
for isolated to scattered showers from the Capital Region 
northward on Tuesday, and it will be much cooler. High pressure 
builds in from the Ohio Valley Tuesday night into Wednesday with
fair and dry weather. 

The RH values will increase to 85 to 100 percent Tuesday and
Wednesday morning, and they will lower to 50 to 80 percent
tomorrow afternoon. 

The winds will veer from the south to southwest at 5 to 15 mph
early this evening to west to northwest at 10 to 20 mph. The
west to northwest winds of 10 to 20 mph with some gusts 25 to 30
mph will continue Tuesday afternoon, and become light to calm
Wednesday morning. 

&&

.HYDROLOGY...
No hydrologic problems are anticipated across the region over
the next 7 days. 

A cold front and an upper level disturbance will bring scattered
showers and isolated to scattered showers tonight. Most
locations will see between one tenth and one third of an inch 
of rain but isolated half an inch or greater amounts are
possible over the northern basins. Flows may rise briefly a few
inches, but then will quickly recede. According to USGS 
streamflow, most area rivers are seeing near normal or below 
normal flows for mid to late September.

Additional isolated to scattered showers tomorrow (especially 
for northern areas) may yield additional rainfall amounts of a 
few hundredths to a tenth of an inch with little impact on the
waterways. 

More dry weather is expected for Tuesday night into the mid
week period before another cold front bring spotty light showers
Wednesday night into Thursday. 

Overall, the HSA will remain very dry and portions continue to
be abnormally based on the latest US Drought Monitor. 

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...Wasula
NEAR TERM...Wasula
SHORT TERM...Wasula
LONG TERM...KL
AVIATION...KL
FIRE WEATHER...Wasula
HYDROLOGY...Wasula