Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
741 am EDT Monday may 25 2015
a weak warm front will push north across Lake Ontario today...and
this will usher in a warmer and noticeably more humid airmass that
will be with US for much of this week. Persistent high pressure
anchored off the East Coast will be the primary supporter of the
more summery airmass...as its clockwise circulation will keep a
moisture rich southerly flow in place. This airmass will also be
conducive for some needed showers and thunderstorms.
Near term /through tonight/...
after nearly a week of below normal temperatures...which included
an unusual middle may freeze...our region will finally return to more
A weak warm front will push northwards across the lower Great
Lakes today...and this will usher in a warmer and noticeably more
humid airmass. The front will also generate some showers and
possibly a thunderstorm or two for sites near and north of the
boundary. This would primarily be for the Eastern Lake Ontario and
Thousand Islands regions where a tenth or two of rain will be
possible. There will be a lesser opportunity for some needed
rainfall across the western southern tier in the vicinity of a lake
breeze boundary this afternoon. Will use slight to low chance probability of precipitation for
this area. For the bulk of the forecast area though...the day will
be rain free.
By this Memorial Day afternoon...the majority of western New York
will find itself squarely in the warm sector of a surface/mid-
level low found over the upper Mississippi Valley. Corresponding
850 mb temperatures in the vicinity of 14c should easily support maximum temperatures in
the lower 80s...with middle 80s likely in the normally warmer valleys
of the southern tier and Genesee Valley. The thicker cloud cover
and presence of shower activity should hold the Mercury a few
degrees lower across the north country.
Tonight...the axis of the anomalously strong...overlying 500 mb ridge
will shift just to our east. This will allow a weakened ribbon of
vorticity to cross our region...and with some diurnally induced
instability still in place...there will be the chance for a shower
of thunderstorm. Drier middle level air...seen early this morning in
WV imagery over the Southern Plains...will rotate across the top
of the aforementioned ridge by late tonight and sweep across the
lower Great Lakes in the wake of the sheared vorticity. This
should bring an end to any spotty convection from earlier in the
All in all though...the bulk of tonight will be rain free and
rather humid with overnight lows generally in the middle 60s. These
values will be a solid 10 degree f above normal late may normals.
Short term /Tuesday through Thursday night/...
after a relative minimum in convective activity early Tuesday
morning...increasing daytime heating and instability coupled with
the approach of a modest middle level shortwave from the Ohio Valley
should lead to a renewed opportunity for scattered showers and
thunderstorms Tuesday afternoon. Initially...the convection will
probably tend to fire inland from the lakes along lake breeze
boundaries and in areas of more favorable orographic
influences...before increasing synoptic-scale lift from the
aforementioned shortwave results in this activity spreading into
the remainder of the region as the afternoon progresses.
In terms of severe potential...the overall setup on Tuesday does
not look particularly favorable for an organized severe weather
threat. This stated...with some of the shorter-term model guidance
suggesting the potential for some pockets of decent instability
(sbcapes of 1000-1500 j/kg) and 0-6 km bulk shear values flirting
with 30 knots...a few isolated stronger storms cannot be
completely ruled out either. With this in mind...the current Storm Prediction Center
day 2 forecast of a marginal severe risk for our area looks fairly
reasonable at the present time.
Aside from the above...expect a very warm and humid day on
Tuesday with highs ranging in the middle to upper 80s away from any
lake influences...with slightly cooler temperatures found across the
Any convection that develops Tuesday afternoon should then tend
to fade with the loss of heating and the departure of the
supporting shortwave Tuesday evening...before convective potential
increases again later Tuesday night and Wednesday with the
approach of a modest middle level trough...and its attendant pre-
cold-frontal surface trough. Expect the best overall convective
chances to come during the day on Wednesday when renewed diurnal
heating will again lead to greater amounts of available
instability for the aforementioned features to work with...with
this in turn leading to another round of scattered to numerous
showers and thunderstorms. At this juncture... it currently
appears that these will be most likely from interior portions of
the Genesee Valley eastward across The Finger lakes and north
country during the afternoon...as these areas should experience
the passage of the prefrontal trough during peak daytime heating.
In this particular region...developing sbcapes of 1000-1500 j/kg
coupled with somewhat stronger wind fields aloft /and consequent
greater amounts of bulk shear/ than seen on Tuesday could
potentially allow for a somewhat better risk for strong to severe
Otherwise...warm and humid conditions will persist through both
Tuesday night and Wednesday...with lows Tuesday night struggling
to fall below the middle to upper 60s...and highs on Wednesday
reaching into the upper 70s to lower 80s...with the warmest
overall readings located from the Genesee Valley eastward across
The Finger lakes.
Wednesday night and Thursday...lingering scattered showers and
storms should generally tend to diminish from west to east as the
middle level trough axis and its attendant weak surface cold front
pushes eastward across our region...and as a small bubble of high
pressure and slightly drier and cooler air builds into our region
in its wake...with this ridge then settling directly overhead and
providing our region with mainly dry and quiet weather Thursday
With the arrival of the slightly drier and cooler airmass...temperatures
and humidity levels should also both pull back a little for
Thursday and Thursday night. Expect dewpoints to drop to more
comfortable levels in the upper 50s...while daytime highs retreat
to the middle 70s to lower 80s on Thursday...and nighttime lows fall
back into the upper 50s and lower 60s Thursday night.
Long term /Friday through Sunday/...
as the surface ridge axis slides off to our east on Friday...a
southwesterly return flow of warmer and more humid air will then
redevelop across our region...which will help boost temperatures
back up some 3-5 degrees or so from Thursday/S readings...while
surface dewpoints climb back up a couple notches into the lower
60s. Coupled with daytime heating...the increasing warmth and
humidity will probably be enough to result in the redevelopment of
very scattered convection during Friday...for which some
broadbrush low chance probability of precipitation will again be in play.
As we head into next weekend...the GFS/European model (ecmwf) remain in general
agreement on a much more significant and wave-laden cold frontal
boundary sinking into our area from Ontario and Quebec...though
these packages still also exhibit quite a bit of disagreement on
its timing...with the GFS remaining considerably faster and more
aggressive than its European counterpart. Given the very wavy and
elongated nature of the boundary...tend to believe the wpc-backed
slower European model (ecmwf) solution at this particular juncture...which would
suggest the boundary easing its way across our region between
Saturday and Saturday night...before settling just a little to our
south during Sunday. This scenario would allow for warm and humid
weather to persist into Saturday along with another general risk
for convection Saturday and Saturday evening...followed by a
return to cooler weather and lingering shower chances on Sunday.
Aviation /12z Monday through Friday/...
despite the presence of a warm front over our region today...VFR
conditions can be expected.
The warm front will lift north across the lower Great Lakes
during the course of the day. This feature will generate a wealth
of Alto-cumulus across the bulk of the region this morning...with
lowering VFR ceilings expected in the afternoon. This cloud cover
will accompanied by showers and possibly an afternoon across the
north country (kart/kgtb). The only other area of concern will be
the western southern tier where an isolated thunderstorm could be
found this afternoon.
Tonight...VFR conditions should remain in place across the region
although there will be the chance of a shower or thunderstorm
during the first half of the night. The exception to the VFR
conditons could be over the western southern tier where ceilings may
lower to IFR/MVFR levels after 06z.
Tuesday through Friday...mainly VFR with isolate/scattered -shra/tsra.
a weak warm front will push north across the lower Great Lakes
today. While this feature will generate some showers and possible
thunderstorms north of Lake Ontario...no flags are expected over
the lower Great Lakes as a weak surface pressure gradient will remain
The relative close proximity of sprawling high pressure anchored
off the East Coast will keep a weak surface pressure gradient over
lakes Erie and Ontario tonight and Tuesday...which will be
supportive of gentle to moderate winds and negligible waves.
Southwest winds will freshen somewhat on Lake Erie on Wednesday
though...and this may promote waves to approach Small Craft Advisory levels.
While winds and waves will likely remain below Small Craft
Advisory levels on Tuesday and Wednesday...there will be the risk
for some thunderstorms.