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fxus61 kaly 220820 
afdaly

Area forecast discussion
National Weather Service Albany New York
320 am EST Wed Feb 22 2017

Synopsis...
a weak disturbance approaching from the eastern Great Lakes will
move across the area tonight, bringing chances for light rain or
light freezing rain in some spots. Mild conditions with well above
normal temperatures are then expected to build in for the remainder
of the week.

&&

Near term /until 6 PM this evening/...
for today...expect morning clouds to give way to partly sunny
skies as a ridge of high pressure builds across the region. It
will be another mild day with highs in the mid 40s to mid 50s.

&&

Short term /6 PM this evening through Friday night/...
for tonight...clouds will gradually increase although it should
remain dry. Another warm front will be lifting north of the
region across southern Canada late at night. Lows will be in
the mid to upper 30s.

Thursday and Thursday night...will see an increase in clouds and
chances of rainfall mainly across the northern half of the
region as a cold front drops southeast through the region. It
will continue to be very mild ahead of the front with highs on
Thursday in the mid 50s to mid 60s and lows Thursday night in
the mid 30s to mid 40s.

Friday and Friday night...the frontal boundary will return
north as a warm front lifting into southern Canada by late
Friday night. There will be a chance of rain across the region
through the period although any rainfall is expected to be
light. Highs on Friday will be in the upper 40s to upper 50s
with lows Friday night in the 40s to around 50.

&&

Long term /Saturday through Tuesday/...
main focus in the long term will be on the strong cold front
crossing the local area Saturday. The system will feature strong
dynamics as a surface low deepens from around 990 to around 980 mb
within a coupled jet structure as it tracks from southern Ontario to
near Hudson Bay. Spread among the deterministic models and gefs
members continues to be small for a system as dynamic as this,
lending confidence to the forecast. A very warm airmass will be in
place within the ridging ahead of this system, with 925/850 mb temps
in the upper single digits over the local area resulting in high
temperatures some 20-25 degrees above normal. With the strong low-
level moisture advection, fog developing over the areas that still
have snow pack is a good bet. It appears the upper ridging will
allow for only limited shower activity until the main upper
wave/cold front swings through. Deterministic models have slowed
down the frontal passage slightly, favoring late on Saturday or
early Saturday evening. Have adjusted pop timing accordingly. Good
moisture pooling along the front with precipitable water values near 1 inch along
with convective potential as showalter values go slightly negative
should allow for some heavier rainfall, though the progressive
nature of this system will limit widespread heavy rain potential.
The potential for convection to mix the strong low-level wind field
to the surface is always a tough call with very little instability,
especially this far out, but with the strong front there is at least
the possibility of a narrow squall line that could produce gusty
winds.

The temperature contrast along the front looks impressive, with 850
mb temps forecast to fall 15-20c in 24 hours. This should allow
some lake-effect snow showers to develop late Saturday night into
Sunday. Winds will also increase and become quite gusty during this
time frame as deep mixing develops in the cold advection behind the
front. Temperatures will ease back toward normal, at least for
Sunday and Monday. Still high uncertainty for the beginning of next
week as we transition from cyclonic to fast zonal flow. A surface
anticyclone will expand into the region somewhat Monday, but there
is potential for a quick clipper system to develop somewhere across
the eastern US. Slight chance pops for now.

&&

Aviation /08z Wednesday through Sunday/...
forecast change for this taf issuance was to remove IFR mention.
Guidance has backed off on the low-level moisture, catching onto
the fact that the nearest IFR conditions are over southern
Ontario where a good snow pack exists. So, expect VFR conditions
to prevail, with the exception of a few light showers crossing
the terminals prior to 09z or so. Freezing rain potential at kpsf appears
to be quite low as well, so have removed that mention as well.

Looking ahead, fog development appears possible toward the end
of the taf period, but appears to be a better chance after 06z
Thursday so will omit for now and reassess with the 12z
package.

Winds will be light and variable throughout the taf period.

Outlook...

Wednesday night: low operational impact. Patchy fog.
Thursday: low operational impact. Slight chance of rain showers.
Thursday night: moderate operational impact. Chance of rain showers.
Friday: moderate operational impact. Chance of rain showers...dz.
Friday night: moderate operational impact. Slight chance of rain showers...dz...fg.
Saturday: high operational impact. Definite rain showers...tsra.
Saturday night: moderate operational impact. Chance of rain showers...shsn.
Sunday: no operational impact. No sig weather.

&&

Hydrology...
no widespread Hydro problems are expected through the rest of the
work week, with just light precipitation forecast and overnight
temperatures falling into the 30s to mid 40s the next few
nights.

However, mild temperatures that will be well above normal, are
expected for later this week. This will cause snowmelt and
subsequent runoff. Also, a strong storm system may bring a period of
moderate to heavy rainfall on Saturday. The meteorological model
ensemble river forecasts /mmefs/ continue to suggest significant
river rises will occur, with flooding possible Saturday into Sunday
due to the combination of snow melt and locally heavy rain.

At this time, at least minor flooding appears likely for a few to
several points along main Stem rivers. Depending on the degree
of snow melt, flooding could reach moderate levels in some
locations. We will have more specific information as the weekend
draws nearer.

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.
New York...none.
Massachusetts...none.
Vermont...none.

&&

$$
Synopsis...11/jpv
near term...11

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