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000
FXUS61 KALY 031104
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
704 AM EDT Wed Jun 3 2020

.SYNOPSIS...
A warm front will initially bring some spotty showers
this morning, then a low pressure system and a cold front will bring
showers and some thunderstorms especially south of the Capital
District in the afternoon.  High pressure will briefly build in
tonight into Thursday, as temperatures will trend above normal.  A
warmer and more humid air mass will be over the region on Friday
with a threat of afternoon scattered showers or isolated
thunderstorms late in the day into the overnight period ahead of
another cold front.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 638 AM EDT...A warm front continues to be south and west
of most of the forecast area early this morning. Isolated
showers are across the Schoharie Valley and eastern Catskills.
The KENX radar is fairly quiet. The mid and upper level flow
continues to be nearly zonal. As a low pressure system will
approach from southeast Ontario for the early afternoon with a
cold front.

The question will be if the warm front makes it through the
entire forecast area. The low level forcing with the boundary
looks weak, but with the low-level moisture in place with dewpts
rising into the 50s and lower 60s will allow some spotty light
showers to be possible especially from the Capital Region
north. This is supported by the latest NAM/GFS/ECMWF/CMC and we
kept slight and low chance PoPs in these areas. The 09Z 3-km
HRRR is drier with some light showers northeast of Albany.
Plenty of low stratus and clouds will be over the region,
though some intermittent breaks with some sunshine are possible
from Albany south and east in the late morning into the
afternoon, where a mini warm sector sets up.

A strong short-wave in the west/northwest aloft and the cold
front will focus a mesoscale convective system /MCS/ in the late
morning moving southeast from Lake Erie/western NY and
northwest PA. This potential MCS or complex of showers and
thunderstorms may graze or impact the southern most zones of the
forecast area or roughly the I-84 corridor south. The majority
of the guidance keeps it barely south, though the latest GFS and
the 3-km NAM, last few runs of the 3-km HRRR are a little
further north into Ulster/Dutchess and Litchfield Counties. The
better instability, steeper mid-level lapse rates and strongest
model updraft helicity values are further south across PA and
NJ with the majority of the guidance. The 00Z HREFS have has
some mean SBCAPE values of 750-1000+ J/kg near the I-84 corridor
with 0-6 km shear values of 40-45 kts. The Day 1 Marginal Risk
for this small area looks good, and we will keep mention in the
HWO with our forecast area on the northern end of this MCS. We
did mention a period of gusty winds/small hail and heavy
rainfall especially 16Z-22Z /noon-6 pm/ in those areas. Damaging
winds and large hail would be the severe threats It looks like
these areas may get briefly in a stratiform region of the MCS
prior to the late pm. The last few runs of the 3-km HRRR show
some discrete convective cells popping north of the MCS we
widened the potential for isolated severe cell there.

Further north, a few thunderstorms may occur up to the Capital
Region, Berkshires, northern Catskills and southern VT, but
limited SBCAPE of 200-500 J/kg should limit updrafts from
getting taller, and we did not even include thunderstorms in the
northern most zones due to the lack of sfc heating and
instability.

The cold front tracks eastward during the afternoon with some
isolated to scattered showers and limited forcing. The initial
wind shift will likely be with the prefrontal trough, as the
wave moves across northern New England. We had to lower temps
slightly due to clouds possibly limiting sfc heating, despite
H850 temps getting to +10C to +14C. Highs were favored with a
blend of the GFS/NAM MOS guidance with mid 60s to lower 70s over
the higher terrain, and mid and upper 70s in the valleys and
over the southern Berkshires and NW CT.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
Tonight...The cold front moves across the region with very weak
low-level cold advection. The isolated to scattered showers
should end around midnight over the northern zones. Some patchy
fog may form, if the skies clear. We did not add it to the
forecast yet. Lows will be mainly in the 50s to around 60,
though some upper 40s are possible in the Adirondack Park.

Thursday...The mid and upper level flow remains quasi-zonal. A
piece of northern stream energy may increase the clouds a bit
over the northern zones and across the higher terrain. The 06Z
NAM tries to develop a few showers near the southern
Adirondacks. We kept it dry with a weak sfc high building in
from the Great Lakes Region. Partly to mostly sunny skies with
good mixing will allow temps rise about 5 to 7 degrees above
normal with upper 70s to lower 80s in the valleys (a few mid 80s
in the mid Hudson Valley), and upper 60s to mid 70s over mtns.

Thu night...A weak sfc wave and a warm front will move across
eastern Pa and NJ. Low-level moisture will increase from the
south and west. Weak thermal advection occurs which will allow a
few showers to move into the southeast Catskills, mid Hudson
Valley and NW CT. We kept some slight and low chance PoPs in the
forecast. Otherwise, it should be dry with an increase of some
clouds from the south and west. Lows will be in the 50s to lower
60s.

Fri-Fri night...The biggest change for Friday is the slower
progression of the cold front. The latest trends are for the
frontal passage to be more in the night time period for the
forecast area. Heat and humidity will increase with sfc dewpts
rising into the mid 50s to lower/mid 60s. H850 temps increase to
+1 to +2 STD DEVs above normal based on the 00Z GEFS. Some
scattered showers are possible during the morning south and east
of Albany with the wave passing to the south. Some clearing is
possible later with partly sunny skies and highs in the mid and
upper 80s in the valleys, and mid 70s to lower 80s over the
higher terrain. Some pop-up showers or isolated thunderstorms
are possible in the late afternoon ahead of the cold front. The
upper trough upstream begins to amplify which should help the
cold front move across the region Friday night with scattered
showers and isolated thunderstorms. We are not expecting these
to be severe at this time, as the latest SPC DAY 3 graphic has
general thunderstorms.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
After a muggy and very warm Friday, a positively tilted trough will
approach the Northeast from southern Canada on Saturday. Guidance
has waffled on its arrival time with the latest 00 UTC guidance
maintaining the delayed onset trend. Now, it looks like the
strongest height falls do indeed hold off until towards 12 UTC
Saturday which is when the main cold front looks to push through
eastern NY/western New England. This is a bit atypical since we
usually see cold frontal passages in the afternoon but the
global guidance shows the front pushing through in the morning
and early afternoon with northwest flow in place by the end of
the day. Given the ongoing timing uncertainties, we show chance
POPS for both Saturday morning and afternoon but placed slightly
higher POPs for areas near and south of I-90 where dew points
still near 60 combined with a few hours of daytime heating ahead
of the front could contribute to a region of enhanced
instability and thunderstorm activity. Otherwise, temperatures
should end up slightly above normal reaching into the upper 70s
to near 80 since we probably will not see an air mass change
just yet.

The positively tilted upper level trough swings into the region
Saturday night, clearing us of the humid air mass with cold air
advection ensuing in the northwest flow.  The trough is slow to exit
on Sunday and with guidance showing some mid-level moisture within
its upper level cold pool, we expect partly to mostly cloudy skies
with even potential for a few isolated showers in western New
England, which should be closer to the cold pool. While the 500mb
cold pool ranges between -15C to -18C, we did not include any
thunder mention at this time but it will be something to
monitor. Temperatures will be cooler and less humid Sunday given
this set-up and because of the potential for few on/off showers
and increased cloud coverage, we went slightly cooler than the
blended guidance and only show highs in the low to mid 70s. This
matched up well with the 50 percentile of the ensemble MOS
guidance output which was slightly cooler than the operational
run.

The ECMWF continues to suggest that the trough strengthens as it
digs into New England Sunday night and becomes neutrally tilted
which would enhance the cold air advection overnight. The GFS and
CMC do not show as sharp of a feature and keep it more broad. With
clearing skies and Canadian air infiltrating the region thanks to
breezy northwest winds, we show overnight lows falling into the 40s
to near 50 but if the ECWMF is correct, temperatures may trend
cooler.

Upper level ridging from the Central CONUS builds into the Northeast
Monday and Tuesday, keeping a mainly dry forecast with seasonable
temperatures. The next warm front looks to cross into our region mid-
week which could lead to another day or two of above normal
temperatures. While the ridge axis looks to move overhead mid-week,
it`s worth mentioning that some members of the global guidance show
a potent cut-off low exiting the Rockies and steering the remnants
of Cristobal towards the Great Lakes/Southern Canada mid to late
next week. Still much too early to know the details but it`s
something to keep an eye on. For the latest information on
Cristobal, visit www.hurricanes.gov.

&&

.AVIATION /11Z WEDNESDAY THROUGH SUNDAY/...
MVFR ceilings continue at ALB and PSF with VFR conditions at POU and
GFL. Expecting currently ceilings to persist through 15-16 UTC with
potential for a passing shower as a warm front remains stalled
nearby. A decaying MCS in western NY will progress eastward this
morning with a few leftover showers possible at PSF, POU and ALB. We
did not include thunder for this period but we will monitor
conditions. Once these showers exit, ceilings should improve to 4-
5kft and could even break for sun. Winds could also shift to the
southwest and become a bit breezy (sustained 5-10kts, gusts to
20mph).

A cold front sagging southward through the TAF sits this afternoon
could lead to a few scattered showers. Thunderstorms, some
potentially strong to severe, are possible at POU and we included a
TEMPO group to illustrate this potential. Any storm could produce
damaging winds and heavy downpours. PSF and ALB may also see
thunderstorms but we did not include at this time since confidence
is lower in these areas.

Once the front exits this evening, skies could partially clear and
any areas that had showers could see fog quickly develop. We
included MVFR visibilities developing after 03 UTC at POU, GFL and
PSF.

Outlook...

Thursday Night: No Operational Impact. NO SIG WX.
Friday: Moderate Operational Impact. Chance of SHRA...TSRA.
Friday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Saturday: Moderate Operational Impact. Chance of SHRA.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: High Operational Impact. NO SIG WX.

&&

.FIRE WEATHER...
A warm front will initially bring some spotty showers
this morning, then a low pressure system and a cold front will bring
showers and some thunderstorms especially south of the Capital
District in the afternoon.  High pressure will briefly build in
tonight into Thursday. A warmer and more humid air mass will be
over the region on Friday with a threat of afternoon scattered
showers or isolated thunderstorms late in the day.

The RH values will only lower to 55 to 70 percent this
afternoon, and then increase close to 100 percent Thursday
morning. The RH values will drop to 35 to 45 percent Thursday
afternoon.

The winds will begin south to southeast at 5 to 10 mph this
morning, and then shift to the southwest to west at 10 to 20
mph in the afternoon. The winds will become light tonight at
less than 10 mph from the west. Expect west winds of 5 to 15 mph
on Thursday.

&&

.HYDROLOGY...
Widespread hydrologic issues are not expected on the main stem
rivers the next several days.

A cold front and low pressure system will bring some scattered
showers and isolated to scattered thunderstorms. A complex of
thunderstorms may produce the heaviest rainfall in the
southeast Catskills, mid Hudson Valley and NW CT. Some brief
heavy downpours are possible, especially south of Albany. Basin
average QPF is expected to remain less than half an inch.

Dry weather returns Thursday, with a chance of showers and
isolated thunderstorms Friday afternoon into Friday night. Some
showers may linger on Saturday before drier weather returns for
the 2nd half of the weekend.

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...Speciale
AVIATION...Speciale
FIRE WEATHER...Wasula
HYDROLOGY...Thompson/Wasula