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Area forecast discussion 
National Weather Service Binghamton New York
641 am EST Tuesday Mar 3 2015

Synopsis...
after a quiet start to the day...a complex storm system will spread
a quick coating of snow across the area this afternoon...followed
by an icy wintry mix tonight with light ice accumulations. Our
weather pattern will stay busy...with chances for precipitation
lasting through Thursday night.

&&

Near term /through Wednesday/...
630 am update...
of course main problem is the incoming snow-to-mix system /more on
that below/...but in the very near term our temperatures early this
morning needed some additional qc due to differences where
radiational cooling was strongest from clear sky...and where the
last of the lake clouds kept other locales slightly milder. Some
of the colder 6am temperatures include 7 below in Rome...0 in
Sidney and Norwich...1 above in Cortland and Syracuse...and 2 in
Elmira. Meanwhile Avoca is a relatively balmy 14...and Penn Yan
has a little wind stirring which is keeping the temperature there
at 10.

Previous discussion...
snow-to-icy-mix storm is the main concern of the period. Winter
Weather Advisory has been issued for entire area...however...for
Steuben-Yates-Schuyler-Tompkins-Chemung- Tioga-Bradford counties
the start time was moved up to 1pm. Remainder of advisory begins
at 3pm.

Water vapor imagery shows strong and moist southwesterly flow
streaming across the central U.S. Pumping clouds and precipitation into
the western Great Lakes...and thickening high clouds across
western New York through central PA...as incoming system takes shape.
Meanwhile...surface high is sitting directly over US but will slide
off the coast by late morning. Strong warm air advection will
occur on back side of departing high...including very impressive
isentropic lift. Models in great agreement on shield of snow
breaking out between 1pm-3pm for much of twin tiers to Finger
Lakes...and 3pm-5pm points farther east and north...thus the
earlier adjustment made to start time to a good chunk of the
advisory.

Model soundings tell the story...of a period of snow /shortest
duration south...longest duration in central New York/ this afternoon
into early evening. Given the abundant moisture with good lift
through and beyond the dendritic growth zone...this should be a
quite abrupt burst of snow once it gets going. However...significant
nose of above freezing air aloft will materialize within just
about 3 or so hours of the snow starting...which will yield sleet.
The below freezing air near the surface will be quite deep and
cold...which leads ME to believe that the next transition....from
sleet to freezing rain...will be a little more gradual /or maybe
even back-and-forth a bit/ than we are used to for this type of
system. Once it is primarily freezing rain...we will also lose
much of the deeper moisture so amounts overnight will be fairly
light.

Before the switch to icy mix...snow amounts will range from a
denser 1 to 2 inches from twin tiers- southern Catskills
southward...to 2 to 4 inches in central New York- upper Susquehanna
region. Then for the ice through tonight...generally tenth to
quarter inch with highest amounts twin tiers to northeast PA-
Sullivan County New York.

One additional thing to note...southerly winds especially at
higher elevations will gust to 30-35 miles per hour range. Snow followed by
sleet-freezing rain with gusty winds is a bad combination. The
weight of the dense precipitation plus winds could lead to isolated
power outages and minor tree damage such as broken branches.

Lower elevations will should start to get above freezing before dawn
especially central twin tiers...Finger Lakes...and Wyoming Valley.
Majority of the region will reach above freezing Wednesday
morning...some areas even getting upper 30s-near 40. Cold front GOES
through however...and cold air advection will cause lingering rain
showers to gradually mix to snow showers from northwest to southeast afternoon-
evening. Amounts Wednesday though will be nominal.

&&

Short term /Wednesday night through Thursday night/...
3 am update...

Front drops southeast to be from NYC to crw Wednesday night. Snow will move NE
along the front and be across the southern County Warning Area with accumulating snow.
Questions on how far north this snow will come. NE PA and the
Catskills could pick up another 1 to 3 inches. In central New York snow
amounts will be less but cold air advection and a northwest flow aided by a strong short
wave providing lift. Amounts up to 2 inches but localized higher.
An upper level trough and short wave GOES through late Thursday kicking
the cold front and steady snow off the coast. Scattered lake
effect will continue with more light amounts. Thursday night the les will
weaken as a large area of high pressure moves in from the SW
dropping the winds. As this happens the flow shifts to west and
the les will move north to the tug.

&&

Long term /Friday through Monday/...
3 am update...
little change to previous. As usual followed wpc guidance. Most
notable event will be more Arctic air Thursday into Friday. More
lows in the single digits Friday morning.

Previous discusssion...
Thursday night through Monday...
medium range models indicate the northeast will remain in a mean
upper level trough through the period although heights within this
trough are rising indicating airmass modification. Overall no
significant storms are anticipated just a few northern stream
systems moving through southern Canada.

Thursday night into Friday, lingering lake effect snow showers
over the northern County Warning Area will lift north through this period and weaken.
Rest of area will be dry with lows Thursday night around zero and
highs Friday in the lower to middle 20s. On Saturday and again on
Monday, overrunning may produce some snow showers across parts of
central New York which may mix with rain showers on Monday.
Rest of area will remain primarily dry. Temperatures may warm to seasonal
values by late next weekend into the early week.

&&

Aviation /12z Tuesday through Saturday/...
630 am update...

VFR to start with middle and high clouds moving in at this time. This will
last until at least 16z.

A storm system will spread snow across the terminals from
west to east between 17z and 20z. The snow will change over to
sleet 2 to 4 hours after the snow starts. After a few hours of
sleet, freezing rain in the evening. Snow and sleet amounts 1 to 3
inches before a tenth of an inch or less of freezing rain. Runways
will need treating as soon as it starts. With the snow visibilities
quickly drop to IFR and ceilings to low MVFR. With the sleet and
freezing rain ceilings will stay low but visibilities should improve to MVFR.
After 6z tonight mixed precipitation is very light. Possible some ceiling
improvement with the frontal passage.

Light and variable winds becoming S at 4 to 8 kts late morning
then south at 10 kts in the afternoon. This evening S winds at 10 kts with
gusts to 20 kts at bgm syr ith. Late tonight winds shift to SW and
west at 10 kts.

Outlook...

Wednesday...mostly MVFR restrictions due to ceilings.

Wednesday night...MVFR/IFR restrictions in snow at avp and probably ith
bgm Elm.

Thursday-Thursday night...restrictions possible from lake effect snow
showers...mainly cny terminals.

Friday through Saturday...primarily VFR.

&&

Bgm watches/warnings/advisories...
PA...Winter Weather Advisory from 3 PM this afternoon to 7 am EST
Wednesday for paz039-040-043-044-047-048-072.
Winter Weather Advisory from 1 PM this afternoon to 7 am EST
Wednesday for paz038.
New York...Winter Weather Advisory from 3 PM this afternoon to 7 am EST
Wednesday for nyz009-016>018-036-037-044>046-056-057-062.
Winter Weather Advisory from 1 PM this afternoon to 7 am EST
Wednesday for nyz015-022>025-055.

&&

$$
Synopsis...mdp
near term...mdp
short term...tac
long term...rrm/tac
aviation...tac

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