Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Binghamton New York
323 PM EST Friday Nov 21 2014
lake effect snow showers will transition to the north of central
New York tonight. On Saturday...a fast moving warm frontal system
will usher in warmer air...and also a chance for a light mix of
wintry precpitation during the afternoon and night. A mild and
breezy day on Sunday will be followed by much warmer weather and a
period of rain Sunday night into Monday.
Near term /through Saturday/...
1 PM update... multi-band les is becoming cellular in appearance early
this afternoon...as terrestrial instability at least temporarily detracts
from the overall organization. The les bands may briefly flare up
again later this afternoon into the evening hours (after 21-22z)...as they drift
northeastward...owing to backing low-level winds. However...the transitory
nature of the snow bands at that point should limit addtnl accums
(keeping them generally 1-2"...or less across portions of
Onondaga...Madison...and Oneida cntys).
Overnight into Sat morning...mainly dry weather is expected for cny/NE
PA...as any lingering les drifts well northward and weakens. A brief period of
clear to partly cloudy skies should give way to increasing clouds again towards
daybreak...out ahead of the next system.
Model consensus from the 12z run is developing light precipitation towards
midday/early afternoon Sat...especially over cny...due to strong low-level warm air advection...and
the approach of a low-amplitude shortwave from the west. At this
pt...thermal profiles support a brief period of frozen/freezing precipitation at the
onset. For this reason...we'll call for a mix of -sn/-pl/-fzra
initially...with a transition over to rain from west to east...as the
blyr gradually warms. Still a bit too early/uncertain for an advsy
at this time...so we'll retain mention of a possible wintry mix on Sat in the
severe weather potential statement.
Short term /Saturday night through Monday night/...
3 PM update...
The quick hitting weak wave on Saturday looks to have the biggest
chance for light precipitation during the late afternoon and evening
across cny. Have bumped up probability of precipitation for a high confidence event for
some light precipitation across the north central zones...but not much quantitative precipitation forecast.
The thermal profiles suggest any early onset mixed precipitation
changes over to light rain in The Finger lakes/Mohawk Valley...however...
colder air locking into our eastern areas could persist into
Saturday night. There is only a small chance of any precipitation
here at all...though. Will continue a mention of rain or freezing rain for
the western Catskills and northeast Pennsylvania where diurnal cooling
may win out in the evening before next system approaches with
overwhelming warm advection by Sunday morning.
Sunday looks to be a relative lull in the action...although
warm/moist advection continues and this could lead to areas of
light drizzle/sprinkles or passing showers.
From Sun night to Monday...model consensus is reasonable with
bringing a high amplitude trough and deep surface low through the Great
Lakes. This will be a good track for a significant warming trend
as the occluding frontal system sweeps from SW-NE across New York
and PA. Confidence in a brief rain event seems rather high and
will continue with categorical probability of precipitation. The rain amounts will be under
an inch...probably closer to one half inch in this area with
little to no Hydro problems expected.
Temperatures on Monday look to be significantly above normal which
will be a welcome change for US here...but not good news out to
our west. We are thinking 50s to near 60.
Long term /Tuesday through Friday/...
3 PM update...
medium range models suggest a high amplitude trough setting up over
the eastern half of the Continental U.S.. this will set the area back into
near...to below normal temperatures and somewhat unsettled
weather. The main focus will be on periods of Minor Lake effect
bands off Ontario...and then a coastal low (or two?) Flirting with
parts of our forecast area from Wednesday to Friday. The GFS
suggests development out to sea...while the European model (ecmwf) indicates a
closer to the coast track with a primary low. The 12z run has limited
it's westward extent of the precipitation shield from previous
runs...so the trend is going toward the GFS fish storm. At this
time...have left low chance precipitation probabilities across our southeast
zones from Wed-thurs. The European model (ecmwf) and GFS agree on a closed upper
low near the Delaware-Maryland-Virginia on Friday...however the surface solutions are in
complete disagreement. This later system may still be too far east
before significant development to affect cny/nepa takes place.
Lots of uncertainty in the Post Holiday travel forecast...so we
will be in wait and see Mode for now.
Aviation /20z Friday through Wednesday/...
18z Friday update... multi-band les will continue to produce occasional IFR
restrictions at kbgm/kith through 19-20z...with improvement
foreseen thereafter. At krme/ksyr...les may briefly swing through
again early this evening...so IFR vsby's were mentioned...roughly in the
23-03z Sat time frame. Othws...VFR should be the rule into Sat
Towards the end of the valid taf period (15-18z sat)...an area of light
precipitation is expected to develop over portions of cny. At this early
juncture...mixed precipitation looks quite possible...so we've included a
prob30 group for -fzra/-pl/-sn. Hopefully...as we draw
closer...we'll get a better handle on specific pytp and timing.
Gusty northwest surface winds this afternoon...will diminish tonight...then become
southeast Sat morning at 5-10 knots.
Sat night...restrictions possible in -ra/-fzra.
Sun into Sun night...VFR.
Later Sun night and Monday...restrictions possible in rain/lower cigs/fog.
Tuesday and Wednesday...possible restrictions in -shsn/flrys.