Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 260936

Area Forecast Discussion
National Weather Service Buffalo NY
536 AM EDT Wed Apr 26 2017

An area of low pressure will track northward along the Atlantic
coastline today, with a deck of clouds across our region slowly
giving way to some sunshine this afternoon and evening. A narrow
ridge of high pressure will provide for dry and summer-like
conditions through Thursday afternoon before a line of showers and
gusty thunderstorms pass across the region Thursday afternoon and
evening. A few of these storms will could be strong across western
portions of New York State.


Regional radars this morning display scattered showers east of Lake
Ontario. IR satellite imagery, and surface observations indicate
that a deck of stratus clouds covers much of the forecast region,
with the westward extent of the stratus across Western PA and into

As convergence diminishes due to the low level jet weakening this
early morning these scattered rain showers will end shortly after
sunrise east of Lake Ontario. Forecast soundings of both the NAM and
GFS suggest that this thin deck of clouds will linger between 3 and
5k feet well into the afternoon hours before drier air from the
west, erodes the deck of strato-cumulus. With a light wind field
today will opt to side towards more of a cloudier day today.

Though a thin veil of moisture/clouds today we should be able to mix
close to the 850 hPa level, where temperatures of +12C east of Lake
Ontario and +16C across SW NYS will reside. This will bring
afternoon highs into the low to mid 70s. Where clouds linger the
longest, east of Lake Ontario, high temperatures may remain in the
upper 60s.

Tonight we should complete the clearing trend, with a narrow ridge
of high pressure between an Atlantic low, and midwest low providing
for continual light winds. As these light winds veer to southeast,
and later southerly overnight temperatures will dip into the mid to
upper 50s.


Near record warmth will be found across all of western and north
central New York to start this our forecast area be
deeply immersed within a warm sector ahead of an approaching cold
front. H85 temps will already be in the mid to upper teens C across
the region as day as the day progresses and full mixing
of the lower boundary layer takes place under sun filled skies...we
can fully anticipate afternoon max temperatures to reach into the mid
80s for most areas. Readings will likely reach into the upper 80s
across the Genesee Valley and portions of the Finger Lakes Region...
and with a south to southeast sfc-H925 flow in place...we can
confidently remove any of the cooling typically offered by the lakes
(specifically Lake Erie).

As mentioned...the warmth on Thursday should at least threaten the
current record highs for the date. These include...84 at Buffalo
(1984)...86 at Rochester (1990)...and 85 at Watertown (2009). This
will certainly make it feel more like July rather than the end of
April. For what its worth...many of the mainstream guidance packages
are woefully too low with their Thursday afternoon temperature

A typical summer day is not complete without the threat of late
afternoon or evening thunderstorms...and this will certainly NOT be
an exception. The very warm and somewhat humid airmass (Tds near 60
and PWAT values approaching 1.5") will not only support MLCAPE
values over 1000 j/kg...but will have bulk shear values as high as
40 kts. This environment will be lying in wait ahead of a cold front
that will move through the region between 00z and 06z. The nocturnal
timing of this fropa will be one of the few limiting factors for
strong to severe convection for the bulk of the region...but as is
usually the case with warm season cold frontal passages in the Lower
Great Lakes...the main threat could come with convection within a
pre frontal trough. Some of the guidance packages are picking up on
this subtle boundary...which would likely cross the far western
counties between 21z and 03z...several hours ahead of the actual
(and likely anticlimactic) cold front.

Twenty four hours ago...guidance was suggesting a slower frontal
passage with a higher risk for training storms. While a strong
southerly flow will still keep this potential in place...a greater
concern may now be strong and potentially damaging wind gusts with
the initial round of convection. The latter has become more of a
threat because of an earlier frontal passage...which will encourage
a possible pre-frontal trough to pass through at the time of maximum
diurnal instability. Will continue to highlight the concerns in the
Hazardous Weather outlook (HWO).

To summarize...strong to possibly severe convection will likely
break out across the far western counties around 21z Thursday
afternoon in the vcnty of a pre frontal trough. This convection will
push east during the evening while gradually weakening as it makes
its way to the eastern Lake Ontario region near/just after midnight.
A second area of showers and possible weak thunderstorms will move
through the region about two hours after the initial line.
Conditions will improve from west to east after midnight with
moderately strong cold advection pushing our temperatures back
through the 50s.

As one would will be notably cooler in the wake of the
cold front on Friday. It is worth pointing out though that while it
will be cooler than the previous two days...temperatures will STILL
be above normal. H85 temps will be in the high single digits for the
majority of the afternoon temperatures should top out in
the mid 60s to lower 70s. The trend back TOWARDS normal temperatures
will be accompanied by the return of at least partial sunshine...
courtesy of a bubble of high pressure that will cross the region.

The next cold front will settle to the south across our forecast
area Friday night. Guidance is suggesting that moisture and general
forcing will be somewhat limited with the will only use
low chc to cover the minimal opportunity for showers. In fact...
while there is agreement with the passage of a sfc front...guidance
is split on whether there even be any hgt falls. As we push through
the weekend though...this front will return to the north and should
be much more active.

On Saturday...high pressure over the province of Ontario will help
to push the cold front south across Pennsylvania. There could be
enough of a baroclinic zone on its northern side to support chc pops
over the southern portions of our forecast area...generally south of
a line from the hills of southern Erie County and Warsaw to the
heart of the Finger Lakes. In other words...the metro areas of Buf-
Roc and Art should be rain-free but cloudy for Saturday.


Time for a change in the pattern.

A hemispheric WV loop clearly depicts a robust shortwave rotating
around the base of an expansive Aleutian low early this morning.
This feature will eject to the east this afternoon and is forecast
to make landfall along the British Columbia coast Thursday evening
before diving into a persistent longwave trough over the western
half of the country. This will lead to significant cyclogenesis
across the southern Plains during the course of the weekend...with a
deep `cutter` low lifting north and eventually closing off in the
vicinity of the Upper Great Lakes early next week. This will
encourage the base of the persistent longwave trough over the west
to become centered over the center of the continent...setting the
stage for notably cooler air to make its way to the Lower Great
Lakes. As is usually the case...the pattern change will be marked by
a round of very unsettled weather. More on that in a moment.

As we open this period on Sunday...the aforementioned `cutter` low
will be in the process of lifting north across the plains states. A
burgeoning downstream ridge ahead of this storm system will help to
lift the old frontal boundary from Friday night back across our
region as a warm front. This could touch off some showers...but more will usher in another round of very mild weather.
This will be realized by highs that will mainly be in the 70s for
Sunday...particularly across the Southern Tier where it is not out
of the question that some spots could reach 80. This would depend on
the speed of the warm front and the amount of clearing in its wake.
In any case...this will set the stage for a warm night with mins
across the western counties struggling to fall below 60.

The stacked low over the Upper Great Lakes will swing its associated
cold front across our region on Monday. This will produce a round of
showers and thunderstorms...and again...pending the timing of the
actual fropa...the mercury could re-visit the 70s.

Notably cooler weather can then be expected on the
opening longwave trough will pass to our north. H85 temps will
settle into at least the lower single digits...and possibly below
zero c. This will translate into high temperatures Tuesday afternoon
that will be in the 50s...which is actually below normal. A novelty.

A look further down the road suggests that temperatures may stay
near to below normal for much of the remainder of the
general troughiness if preferred by the majority of the medium range
ensemble members of the GEFS and ECMWF. This agrees with the 8 to 14
day temp forecast from CPC...which favors cooler than normal weather
for the first week or two of May.


For the 06Z TAFS flight conditions will start MVFR/low end VFR as a
deck of stratus passes across the region, this from a coastal low
edging northward up the Atlantic coastline. This deck of MVFR CIGS
will persist across most TAF sites through the morning hours (lowest
across KJHW) before drier air from the west pushes eastward with an
improving trend starting this afternoon.

For tonight winds will veer to southeast to southerly, while
remaining light. VFR flight conditions will prevail through the
night. There may be a little IFR CIGS developing across interior So.
Tier, but at this point confidence for these low CIGS to expand
westward across JHW is too low to place in the TAFS.


Thursday...Mainly VFR during the day...with showers/thunderstorms and
attendant MVFR then becoming likely late Thursday and Thursday night.
Friday...Mainly VFR.
Saturday...VFR/MVFR with a chance of showers.
Sunday...VFR/MVFR with a chance of showers and thunderstorms.


A light easterly wind will produce waves one to two feet on the
western waters of Lake Ontario this morning, before a weak bubble of
high pressure crosses the lake this afternoon and evening. Light and
variable winds this evening will become southeast to southerly
tonight and into tomorrow ahead of a cold front. Winds and waves
will continue to be well below small craft thresholds into Thursday

Behind a cold front Thursday night winds and waves will increase
some, but likely remain below SCA thresholds on the Eastern Great


The last days of April will finish with above normal
temperatures, warm enough that it will send our climate sites
towards a top 10 warmest April on record. The degree of
anomalous warmth has been greater towards the west, where
climate site Buffalo may reach the warmest April on record.
Below are the warmest Aprils on record.


Rank.....Value (F)....Year


Current April average temperature through April 25th: 49.0F


Rank.....Value (F)....Year


Current April average temperature through April 25th: 49.9F


Rank.....Value (F)....Year


Current April average temperature through April 25th: 45.9F

Temperture records for Buffalo and Rochester begin 1871, while
Watertown`s history is a bit shorter, with temperature records
beginning in 1949.





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