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Area forecast discussion...corrected...resent 
National Weather Service Buffalo New York
428 am EDT Sat may 23 2015

Synopsis...
a sprawling Canadian high pressure system will drift across the
Middle Atlantic States today...and while it will provide our region
with abundant sunshine...temperatures will remain below normal.
This will change after today as a significant day to day warming
trend will become established. The Mercury will climb to above
normal levels by Monday and will remain there through the
upcoming week. The warmth will be accompanied by a noticeable
increase in humidity...which will encourage the potential for
showers and thunderstorms.

&&

Near term /through tonight/...
a sprawling Canadian high pressure system centered over western
Pennsylvania at 08z will keep starlit skies and light winds in
place through daybreak. This will encourage strong radiational
cooling that will result in widespread areas of frost by daybreak
with parts of the region experiencing a rare late may freeze.
Temperatures around the region at 08z were in the low to middle 30s
away from the lakes...with increasingly widespread 20s showing up
across Cattaraugus and Allegany counties as well as the north
country.

As we push through today...the Canadian high will drift across
the Middle Atlantic States. The subsidence provided by this feature
combined with a Bone dry airmass will guarantee a sun filled sky
for most areas...with the only exception coming across the north
country where some nuisance Alto-cumulus will drift by during the
afternoon.

Despite the wealth of sunshine...it will remain cool with
afternoon temperatures generally ranging from 60 to 65. The
Mercury is not expected to make it out of the 50s though across
the north country...and also in downtown Buffalo where a southwest
wind off Lake Erie will be in place.

Tonight...the surface high will drop anchor off the middle Atlantic
coast while riding in the middle levels will build across the Great
Lakes. This will keep fair dry weather in place over western and
north central New York. Temperatures in most areas will not be
nearly as chilly as those experienced early this morning...as weak
warm advection will help hold overnight lows in the 40s for most
areas. The exception will be found in the deeper valleys of the
southern tier where good radiational cooling will encourage the Mercury
to fall into the low to middle 30s. This will lead to some patchy
frost. Since confidence is not high enough to issue an advisory
for this risk at this time...the dayshift will re-examine for a
possible issuance later today.

&&

Short term /Sunday through Monday night/...
on Sunday...surface high pressure will remain anchored just
offshore of the middle Atlantic coastline...while a surface warm
front extending from low pressure over the plains states slowly
lifts northeastward across the Ohio Valley and into the central
Great Lakes. While this latter feature will bring some increase in
cirrus-level cloudiness to western New York during the
afternoon...we still expect a dry and predominantly sunny
day...along with temperatures climbing back to above average as
the aforementioned ridge circulates progressively warmer air into
our region. More specifically...850 mb temperatures climbing to between
+10 and +11c should translate into surface temperatures reaching into the
middle to upper 70s in many areas...with cooler readings found across
the higher terrain and in areas immediately northeast of the
lakes...where a west-southwesterly surface flow should keep
readings significantly cooler. All in all...it will be a fine day
for outdoor activities.

Sunday night and Monday...the large surface ridge will remain
firmly anchored over the far western Atlantic...while the plains
states low bodily lifts northeastward to Lake Superior. In the
process...this latter feature will push its attendant warm front
northeastward across our region between later Sunday night and
Monday.

Compared to earlier guidance cycles...the 00z guidance suite has
continued to trend toward a drier overall warm frontal passage...
with the NAM/GFS/Gem and even the European model (ecmwf) now all suggesting that
the best isentropic lift and deepest moisture will tend to remain
more over the central Great Lakes and Ontario province as opposed
to over our region. Consequently...have elected to cut back probability of precipitation
noticeably later Sunday night and Monday in collaboration with
neighboring weather forecast offices...with any noteworthy precipitation chances now
appearing to be largely confined to areas from the I-90 corridor
northeastward... and primarily over the far eastern Finger
Lakes/north country at that. Should current trends continue...much
of the Memorial Day Holiday could in fact turn out to be dry south
of Lake Ontario. With the approach and passage of the warm front
and the arrival of a warmer and more humid airmass...temperatures
will also continue to trend warmer both Sunday night and Monday.
Lows Sunday night will likely only fall to between 55 and 60 and
will thus average some 10 to 15 degrees higher than those of the
preceding night... while highs on Monday will likely reach the
upper 70s across the north country...while surging into the lower
and middle 80s south of Lake Ontario as 850 mb temperatures there climb to
between +14c and +15c.

As we get into Monday night...the surface warm front will most
likely finish clearing our region during the evening hours...while
a very modest elongated shortwave slowly eases into the region
from the central Great Lakes. As this feature interacts with the
warm and more humid airmass that will be in place over our
region...it will probably help to generate an additional round of
scattered convection...for which some broadbrush chance probability of precipitation will
be in play. Otherwise expect a warm and humid night to close out
the period... with lows mostly ranging in the lower to middle 60s.

&&

Long term /Tuesday through Friday/...
the dominant weather feature in the extended portion of the
forecast will be a persistent Bermuda high that will remain firmly
entrenched over the western Atlantic...while pumping a continual
feed of warm and humid air northeastward across the Great Lakes
and northeast. This will guarantee our region well above average
temperatures throughout...with daily highs generally ranging
between the upper 70s and middle 80s each day...or some 10 to 15
degrees above late may normals. At the same time...dewpoints will
range in the lower to middle 60s and make for more uncomfortable
sleeping conditions at night...when overnight lows will likely
remain a little above such levels.

With respect to precipitation chances...these will be tied both
to the passage of a number of hard-to-time shortwave impulses
riding around the northern periphery of the dominant East
Coast/western Atlantic ridge...as well as the diurnal heating
cycle which will lead to greater amounts of afternoon
instability...when lake breeze circulations and orographic
influences will probably also come into play. Given the inherent
difficulty in resolving and timing the responsible synoptic
features this far out...broadbrush low to middle chance-range probability of precipitation
appear to be in order for the entire period at present...even
though considerable portions of it will likely be rainfree.

&&

Aviation /09z Saturday through Wednesday/...
high pressure centered over western Pennsylvania during the
remaining pre dawn hours will drift southeast across the Middle
Atlantic States today before making its way off the coast this
evening. This will keep wide open VFR conditions in place
across our region through the taf period.

The only concern will be the potential for some low level
wind shear at kart and kgtb later in the upcoming night. This
will be covered in greater detail in the next taf update.

Outlook...
Sunday...VFR.
Monday...VFR/MVFR with showers likely and a chance of thunderstorms.
Tuesday and Wednesday...VFR with a chance of showers and
thunderstorms/attendant MVFR.

&&

Marine...
sprawling high pressure will drift across the Middle Atlantic States
today...then will make its way off the Virginia coast this evening
and become nearly stationary through Monday. This will result in
light to moderate winds and negligible waves across lakes Erie
and Ontario through the weekend.

While winds and waves will likely remain below Small Craft
Advisory criteria early in the upcoming week...there will be an
increasing risk for mainly afternoon and evening thunderstorm
activity.

&&

Buf watches/warnings/advisories...
New York...freeze warning until 9 am EDT this morning for nyz005>008-012-
013-019>021-085.
Frost advisory until 9 am EDT this morning for nyz001>004-010-
011-014.
Marine...none.

&&

$$

Synopsis...rsh
near term...rsh
short term...jjr
long term...jjr
aviation...rsh
marine...rsh

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