Area Forecast Discussion
Issued by NWS Binghamton, NY

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FXUS61 KBGM 201405

Area Forecast Discussion
National Weather Service Binghamton NY
905 AM EST Mon Feb 20 2017

High pressure at the surface will result in mostly clear skies
over the region with above normal temperatures today. A front
will move into the region Tuesday evening and bring the
possibility for rain showers across the area. Above normal
temperatures will linger through the work week.


9 AM Update...
Made some tweaks for current post-frontal clouds over Central
Twin Tiers, those these will scatter out in the dry air mass
advecting over the region. Also adjusted expected highs up about
another couple degrees due to 06Z run model trends and also cold
bias of models the last couple days. This often happens in the
models as the gradual winter-to-spring transition begins; they
struggle particularly on mostly clear days as the increasing sun
angle produces super-adiabatic lapse rates near the surface. When
seeing the values obtained from dry adiabatically mixing down
model temperatures from 900-925 mb, it is apparent that the bias
should not be as dramatic as yesterday now that we have more cool
air advection out of the north, but there will still be some.

Previous discussion...
So far it has been very quiet this morning as a weak and dry
boundary sinks southward across central NY. Some low clouds are
attendant with the boundary, but for the most part the majority of
the area will see mostly clear skies this morning. High pressure
will build across the region from the north as a very broad ridge
aloft amplifies and shifts east today. This combination will
produce plenty of subsidence, thus we will see lots of sunshine
today. Temps this afternoon will vary, with temps reaching the
uppr 30s across the southern Tug Hill Plateau, Western Mohawk
Valley, portions of the Finger Lakes region and the Catskills.
Further south along the southern Tier and NEPA, temps will range
in the low to mid 40s. And locations along the Wyoming valley may
reach the uppr 40s to low 50s.

Late tonight a deep trough will start to propagate eastward across
the Great Lakes region and force the ridge over the eastern CONUS to
break down slightly. This shortwave will be our next storm system to
impact the region. This system still appears to be stacked and will
drag a frontal boundary over the region. Delayed the onset of the
showers moving into the area. Still appears that the GFS is slightly
too fast. Went more with a NAM/ECMWF/CAN-REG blend on the timing.
Expect showers to push into the Finger Lakes region between 21 TUES-
00Z Wed. ATTM do not expect showers to be heavy in nature and rain
to be the dominant precip type.

Temps during this period will continue to be well above the seasonal
average. Temps Tues morning will start off in the low 20s and rise
into the mid 40s to low 50s across much of the area.


145 AM Update...

Latest model runs show the frontal system boundary weakening and
slowing Tuesday night as it passes the area. I have extended the
time the showers may be over the area Tuesday night into early
Wednesday. Otherwise, just some weak cold advection briefly behind
the front before upper ridging returns later Wednesday into
Thursday. Previous discussion continues below.

330 PM Update...
Frontal system will bring a batch of rain showers late Tuesday
afternoon through evening during an otherwise uneventful period
with above normal temperatures.

Amplified wave is now over Four Corners region out west, after
wreaking havoc in Southern California. However, it will gradually
weaken while carrying across the lower 48. In fact, the main
surface low will eject across the Central to Northern Plains,
right into Canada. By the time the occluded front moves into our
region late Tuesday, the parent low will be distant in far
northern Ontario or perhaps even a piece of Hudson Bay. What is
more, is that the air mass behind the front will be of Pacific
origin. This will take already mild above normal temperatures of
40s-near 50 Tuesday, to mainly 50s-near 60 Wednesday.

Weakening occluding fronts marching all the way across the country
often end up delaying their arrival as the event approaches, so do
not be surprised if most or all of the rain waits until Tuesday
night itself. Chances will be best in Finger Lakes of Central New
York but there is at least some chance for a brief window of rain
showers areawide. Amounts are not looking that much however;
generally one to two tenths of an inch in the northern zones and
mainly less than a tenth of an inch from Twin Tiers-Catskills
southward. Wednesday looks dry and warm with increasing sunshine.


145 AM Update...

Very little change in the long term at this update. Did bump the
pops up for Saturday`s rather vigorous looking system and trailing
cold front. Also added isolated thunder for the NE PA counties as
the models bring some instability into the southern part of the
forecast area. Previous discussion continues below.

330 PM Update...
While more complicated than this, generally speaking a western
trough-eastern ridge pattern will be dominant during this period.
Southwest flow, with occasional embedded waves, will yield
temperatures well above normal. This is particularly the case for
Thursday through early in the weekend, when temperatures will run
15-20 degrees warmer than climatology.

With this pattern setting up, over time more moisture will be
drawn up from the Gulf of Mexico and thus rain chances will become
greater as will potential amounts. A smaller wave Thursday could
produce lighter showers, but sometime around Friday night-Saturday
the GFS-ECMWF-GEMglobal are in agreement on a deeper wetter
system moving through. Behind that, temperatures will probably be
knocked down back at least closer to normal into Sunday but this
is probably only temporary. The overall southwest flow pattern
does not appear likely to back down.


A MVFR stratus deck developed over central NY and NEPA this
morning. This deck is impacting KELM, KITH, KBGM and KAVP. This
deck should lift fairly quickly as strong mixing is expected to
occur this morning shortly after sunrise. High pressure will start
to build over the region this afternoon and strong subsidence will
settle over the region, thus mostly sunny skies will prevail this
afternoon and evening. A cirrus deck is expected to move into the
region from the SW after 00Z Tues.

Winds will be N/NW winds around 5-10 knots through the afternoon,
then become light and variable after sunset.


Tuesday night into Wednesday...Restrictions possible in lower
ceilings and light precipitation with cold front.

Wednesday night and Thursday...VFR.

Thursday night and Friday...possible restrictions with warm
front and rain.




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