Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
201 am EDT Wednesday may 6 2015
a weak wave of low pressure sliding along a stalled out front over
northern Pennsylvania will bring showers to a significant portion of
western New York tonight while areas from Rochester north and east
remain dry. Shower activity should retreat from the Buffalo metropolitan
later tonight while lingering across the southern tier and Finger
Lakes through Wednesday. Following the passage of this wave...the
remainder of the work week will feature a return to dry weather
and above normal temperatures...before the next chance for
precipitation arrives this weekend.
Near term /through today/...
shower activity continues to retreat to the south and east overnight
with the passage of a weak upper level disturbance along a stalled
frontal boundary over northern OH/PA. Another round of heavier
showers will be likely early Wednesday morning closer to the New York/PA border
as another weak impulse makes its way along the boundary from the
Midwest. Given the continued abundance of low-level moisture from
Tuesday evening's rainfall and current observation trends indicating
shrinking dewpoint depressions will have areas of fog across wny and
the southern tier overnight.
On Wednesday...expect any lingering fog to mix out as we move
through the morning hours with increasing sunshine across the
northern half of the forecast area as high pressure builds across
the region from the northwest. Clouds ad showers will likely linger
across much of the southern tier and Finger Lakes...closer to the
weakening frontal boundary...through the morning hours...decreasing
to just a chance of showers near the New York/PA border in the afternoon
with dry conditions and increasing sunshine as high pressure takes
over...particularly north of the thruway corridor.
Regarding the temperature forecast...given the lingering moisture
and extensive cloud cover across the southern tier and Finger
Lakes...have bumped up overnight lows a few degrees. There will
likely be a decent north-south temperature gradient across the
forecast area overnight with lows in the 40s along and north of
the thruway and across the north country...where the greatest
clearing is expected overnight. Otherwise...look for 50s south of
Short term /tonight through Friday/...
no major changes to the short-term forecast this evening based on
current observations this evening.
The frontal zone will sink farther south Wednesday night and wash
out...with high pressure building over the lower lakes and New
England. Skies will clear as subsidence and drying take hold behind
the weakening frontal zone. The high pressure will drift off the
eastern Seaboard Thursday and gradually advect warmer air into the
region. Temperatures will rise into the upper 70s to around 80 in
most inland locations. With the light flow a Shallow Lake breeze
should develop during the afternoon hours. Upper level ridging
should suppress isolated showers to our south and west on Thursday
afternoon...so will stay with a dry forecast.
Expect more dry weather Thursday night with the crest of the upper
level ridge across the region. After this...model consensus slides
the 500 mb ridge axis into New England which will bring a slightly
more warm and moist airmass into our region. NAM/GFS/ggem/ECMWF all
forecast some quantitative precipitation forecast across portions of the County Warning Area Friday afternoon. This
is misleading since any precipitation will be convective and
scattered in nature. There does appear to be ample instability for a
few showers...but these should be confined to the southern tier
inland of the lake breeze. Elsewhere...the upper ridge departing
from the north country and the stabilizing lake breeze should
prevent any instability showers from forming. Otherwise the big
story is the above normal temperatures with daytime highs likely to
rise into the 80s in most locations off the immediate Lakeshore.
Long term /Friday night through Tuesday/...
overall it will be a very Summer-like pattern throughout the
period. On Friday night the upper level ridge axis will still be
near the region...but this ridge is forecast to very gradually break
down with a slow moving frontal boundary eventually forecast to
cross the region. Timing this slow moving front differs
significantly...and by significantly there is almost a two day
difference between the 12z GFS/ECMWF. The difference in position is
not that large...but weak forcing and slow moving boundary leads to
the huge difference in timing. This is similar to 00z runs of each
model...with the ggem generally supporting the European model (ecmwf) solution.
Forecast will use a weighted blend of guidance...which hedges closer
to the slow European model (ecmwf) timing.
This means a gradually increasing chance for showers and
thunderstorms. Initially this will be a small and diurnally driven
chance on Saturday...but as the boundary gets closer showers may
occur at night as well. Until this front passes...temperatures will
be above normal with forecast highs in the upper 70s to lower 80s
for the weekend. If the drier European model (ecmwf)/ggem verify...highs will be
several degrees warmer than that with more sun and less chance for
showers. However...if the GFS is correct these temperatures are
probably too warm. Whatever the case...the boundary should push
through by Tuesday with both the GFS/European model (ecmwf) forecasting a more
significant shortwave to push through. There is a good chance for
showers and thunderstorms Monday night into Tuesday when this wave
and front are most likely to cross the region. This also will usher
in cooler...but still fairly seasonable...air into the region for
Aviation /06z Wednesday through Sunday/...
will have lower MVFR to IFR conditions across western New York and
the southern tier overnight as areas of fog and stratus form in the
rain saturated air. While IFR conditions should improve rapidly
through the morning across the Niagara Frontier...they will be
slower to improve across the southern tier...again owing to the
nearby frontal boundary. Conditions there may not improve to MVFR
until the afternoon hours. Otherwise...expect VFR conditions to
persist through the rest of the period from kroc east and across the
north country where high pressure and drier air will build in from
Wednesday night through Thursday night...VFR.
Friday...mainly VFR with a chance of showers southeast of Lake Erie.
Saturday through Monday...mainly VFR...with a chance of showers/
thunderstorms and attendant MVFR.
with a weak pressure gradient remaining in place across the lower lakes
region through the end of the work week...expect relatively light winds
and minimal waves to continue through Friday.