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Area forecast discussion
National Weather Service Buffalo New York
649 am EDT Sat Oct 19 2019

Synopsis...
it will be a beautiful weekend for viewing the peak of the fall
foliage...as high pressure passing to our east will provide US with
US with sun filled skies today and fair dry weather through Monday.
The pleasant weather will be accompanied by day to day warming with
temperatures climbing as high as the lower 70s across the western
counties for Monday. A dramatic change back to more seasonable Fall
weather will then take place for the remainder of the week.

&&

Near term /through tonight/...
an elongated area of high pressure centered over the region this
morning will push away to the east during the course of the day.
This feature will provide US with a spectacular day...complete with
sun filled skies and afternoon temperatures that will climb to near
60 across many of the western counties. It will be a shade cooler
east of Lake Ontario where the Mercury will top out in the mid 50s.
Interestingly...if we were able to fully mix our airmass within this
warm advective pattern...temperatures would push well into the 60s
to near 70. A staunch 4 deg subsidence inversion though will prevent
that from happening...but take heart...that kind of warmth is 'just
around the corner'.

Fair dry weather will continue across our region tonight...as the
area of high pressure will make its way across New England. While
skies will generally remain clear across the far western counties...
some mid level clouds could move over parts of the southern tier and
Finger Lakes region in response to a storm system over the
Carolinas. A flow of Atlantic moisture around the northern periphery
of this southern system could make its way up The Spine of the
Appalachians and glance our forecast area by daybreak. Otherwise it
is not expected to be quite as chilly...especially over the western
counties...as mins will range from the lower 30s across the north
country to the low 40s for much of western New York.

&&

Short term /Sunday through Monday night/...
on Sunday our area will be situated in between a shortwave and its
attendant surface trough lifting northeastward across the upper
Great Lakes and central Ontario province...and a compact surface low
tracking northeast along the Carolina and Delmarva coastlines. While
this latter system may temporarily throw some partial cloud cover
back across our southeastern periphery as it passes by well to our
southeast...relatively drier air and compensating subsidence across
our region should result in a dry and quiet day. Otherwise...
continued airmass modification will result in an even milder day
than Saturday...with highs ranging from the upper 50s/near 60 across
the north country to the lower to mid 60s across western New York.

Sunday night ridging will build eastward across our region at all
levels...with the axis of the ridge then only slowly sliding off to
our east during the day Monday. This will result in fair dry weather
continuing right through this 24-hour period. With good conditions
for radiational cooling present under the surface ridge...lows
Sunday night should range from the upper 30s across the north
country to the lower to mid 40s south of Lake Ontario. Strengthening
warm advection/southeasterly flow in between the departing ridge and
the next frontal system pushing into the western Great Lakes will
then allow monday's highs to trend even warmer than those of the day
before...with readings mostly peaking in the mid to upper 60s. This
said...it could well be even warmer in areas of favored downslope
flow in far western New York...where highs could reach or even break
the 70 degree mark. Compared to late October averages...such highs
will be a solid 10 to 15 degrees above normal.

As the aforementioned ridging slides out across New England Monday
night...it will gradually give way to the next strong upper level
trough and associated cold front approaching from the upper Great
Lakes. While this system will remain far enough away to allow for a
mainly dry start to the night...over time increasing moisture
transport...low level convergence...and mid/upper level height
falls/DCVA on its front flank will eventually bring increasing
chances for showers from west to east overnight...particularly
across far western New York where likely probabilities for these
remain in the forecast. Otherwise...increasing cloud cover and warm
advection/southerly flow out ahead of this system will result in
overnight lows much more typical of late Spring than mid-autumn...
with these expected to range from the mid to upper 40s east of Lake
Ontario to the lower to mid 50s across western New York.

&&

Long term /Tuesday through Friday/...
a mature...vertically stacked cyclone will meander its way across
central Ontario province on Tuesday...and in the process will slowly
pivot its trailing front eastward across New York state. With the
00z/19 guidance suite...the GFS (as typical) remains on the fast
side of the guidance envelope and once again appears too fast with
the cold frontal passage compared to the slower Gem and European model (ecmwf)
solutions. This said...even the more favored slower timing of the
latter packages would still suggest a swath of widespread rain
crossing the area from west to east during Tuesday...for which
categorical pops remain in the forecast.

With regard to potential rainfall amounts...by this time this system
will have already occluded and will be in a weakening phase...with
any secondary coastal wave development along the advancing cold
front likely to remain to our south and east across the mid Atlantic
and New England states. Given all this...rainfall amounts across our
region should remain under an inch...and therefore unlikely to
produce any hydrologic impacts.

While the bulk of the steadier rain will taper off following the
passage of the cold front Tuesday night...broad mid/upper level
troughing and associated wraparound moisture may still produce a few
more scattered synoptically-driven showers...while our airmass also
grows cold enough to support another round of scattered to numerous
lake effect rain showers downwind of the lakes Tuesday night into
Wednesday. At this point steering winds for this time frame
generally look to start out southwesterly before gradually veering a
little more west-southwesterly...which would place the best chances
for lake effect showers northeast and then east-northeast of both
lakes.

Looking further out into the latter portions of next week...the
medium range guidance becomes increasingly divergent for Thursday
and Friday...with the GFS/Gem both still showing another weak to
modest trough crossing the area on Thursday followed by high
pressure on Friday...while the European model (ecmwf) keeps high pressure and dry
weather over our area on Thursday...before bringing a notably
stronger system into our area during Friday. Given the resulting
forecast uncertainty...for now have kept a mix of slight chance to
lower-end chance pops in play for these two days.

With respect to temperatures...these should remain relatively close
to late October normals through this period...with the coolest
conditions expected on Wednesday in the wake of the preceding day's
cold front. Depending upon the strength and timing of the late week
system...at least some semblance of warmup appears possible between
Thursday and Friday.

&&

Aviation /12z Saturday through Wednesday/...
high pressure overhead this morning will move east of the region
during the course of the afternoon. This will keep mainly clear
skies and light winds in place...ideal flying weather. The only real
issue for this taf period will be the potential for some low stratus
and fog across parts of the srn tier before 13z. The stratus and
patchy fog could result in a few hours of MVFR to IFR conditions for
sites like kjhw and kelz.

VFR conditions with light winds will remain in place through tonight.

Outlook...
Monday...VFR.
Tuesday...MVFR with areas of rain and fog.
Wednesday...mainly VFR with scattered lake effect rain showers
northeast of lakes Erie and Ontario.

&&

Marine...
the axis of an elongated area of high pressure will move east of the
region today. Variable winds this morning will become light from the
east later today as a result with waves only averaging a foot or
two.

As the surface high moves across New England tonight and Sunday...a
weak pressure gradient will remain in place across the lower Great
Lakes. This will maintain light winds and negligible waves through
the remainder of the weekend.

East to southeast winds will begin to freshen on Monday...well ahead
of a slow moving cold front that will be crossing the mid-western
states.

&&

Hydrology...
2-3 inches of rain fell in the Black River basin between late
Wednesday and Thursday...and this has resulted in high water levels
on area waterways. While it will remain below flood stage...Black
River forecast points have (or are expected to) reach action
stage. Boonville has already crested and is now steadily falling...
while farther downstream Watertown is expected to reach action
stage late today...and should crest below flood stage during
Sunday.

&&

Buf watches/warnings/advisories...
New York...frost advisory until 9 am EDT this morning for nyz001>006-010-
011-013-014-019-085.
Marine...none.

&&

$$

Synopsis...rsh
near term...rsh
short term...jjr

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