Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 251900

Area Forecast Discussion
National Weather Service Buffalo NY
300 PM EDT Thu May 25 2017

An upper level low will track just to the south of the region
tonight and tomorrow, maintaining cool, cloudy conditions with
scattered light rain showers. Temperatures will moderate back to
normal for the weekend, though there will remain a chance for a
shower early Saturday, and then more widespread showers and perhaps
a thunderstorm later Sunday and Sunday night.


Water vapor imagery displays a closed upper level low near OH/PA
this afternoon with a surface low near Lake Erie. Regional radars
display the main axis of rain now to the north of Lake Ontario and
across the North Country.

This main shield of rain will continue to slowly advance northward
tonight as the upper level low tracks just to the south of our
region. Rain showers, and a few thunderstorms over Ohio, under the
upper level low will largely stay just to the south of the state
border tonight. That said, we will still have low chance PoPs in the
forecast as the influences of the upper level low passes through.
Saturated lower levels tonight and a soaked ground will allow for
some patchy fog formation, thickest across the hills of SW NYS where
low clouds will drop to the hill tops.

Tomorrow the surface low will become better organized off the mid-
Atlantic coastline, though a surface trough will linger westward
behind this low. Within this trough, and under a west to northwest
flow will remain chances for a few sprinkles/light rain showers
through the day Friday. As the deeper moisture slides eastward
tomorrow the light shower activity will end through the day.

Temperatures tonight under thick clouds will not drop much from the
afternoon readings, with lows in the lower 50s. With the upper level
trough still overhead, highs tomorrow will only rebound back to the
low to mid 60s.


Weak surface-based ridging will slide eastward into our region from
the Central Great Lakes and Ohio Valley Friday night and Saturday.
In addition, heights aloft will build over the region as shortwave
ridge pushes east into the region. A wave embedded within the
northern edge will slide across the region with the possibility of a
few stray showers Friday night and Saturday morning with the
Southern Tier having the best chance to see any measurable
precipitation. The arrival of somewhat drier air behind the wave
from mid day through the afternoon should help to bring some partial
sunshine. Weak warm air advection and sunshine should allow
afternoon highs to reach the upper 60s to lower 70s.

Surface and upper ridging remains over the area for much of Saturday
night. Lead wave ahead of main upper trough will drop into the Great
Lakes as associated surface wave moves into the Ohio Valley. For the
most part Saturday night will be dry, before the leading edge of
some scattered shower activity returns to far western sections
toward Sunday morning.

Latest models continuing to highlight the Sunday and Sunday time
frame with increasing chances for showers and embedded
thunderstorms, as the deepen trough moves in from the west. Models
remaining inconsistent on timing, but with the combination of
falling heights and warm air advection on the eastern flank we
should see showers and embedded thunderstorms fill in during the
day, especially by afternoon and continuing into Sunday night.
Temperatures look to remain above average with highs in the lower to
mid 70s Sunday followed by lows in the mid to upper 50s Sunday night.


Moving on into next appears that our region will remain
under the influence of the large upper level low...which will only
slowly meander its way across the Great Lakes and adjoining portions
of southern Canada through midweek. Numerous shortwave impulses
rotating around the large cyclonic gyre aloft will result in frequent
opportunities for showers across our region...with some embedded
thunderstorms again not out of the question each day with diurnal
heating/destabilization of our slowly cooling airmass.

Temperature-wise...highs in the lower to mid 70s on Monday should
pull back to the mid to upper 60s by midweek as progressively cooler
air filters into our region...while nighttime lows gradually settle
back through the 50s.


For the 18Z TAFS flight conditions remain IFR/MVFR as an area of
rain exits northward from the region. There will likely be some
modest improvements this evening, though still with the threat for a
shower. Later tonight as winds become westerly we will see CIGS fall
within a saturated lower atmosphere with flight conditions returning
to IFR for the TAF sites.

Friday, with a still light westerly flow flight conditions will
slowly improve back to MVFR with daytime mixing and deeper moisture
exits to the east.

Friday afternoon...MVFR/VFR with isolated showers.
Saturday...Mainly VFR. chc of showers early to the west.
Sunday...MVFR/VFR with showers likely.
Monday and Tuesday...MVFR/VFR with a chance of showers.


An easterly wind will continue across Lake Ontario this
afternoon and evening producing small craft advisory worthy
waves and winds on the western shoreline. A slight northerly
component to the wind will also create some eddies in the wind
field across the lower Niagara River, near the Lake Ontario
shoreline...and will maintain the SCA here as well.

Otherwise an upper level low will track across Lake Erie and to the
south of Lake Ontario tonight and tomorrow. Winds will relax under
this feature and this will allow for the SCA to end overnight.


A deepening low pressure system will move closer with an
increasing ENE flow on Lake Ontario. Winds will remain 15 to 25
knots today and this evening...allowing waves of 3 to 6 feet. Given
the high lake levels...this is expected to generate lakeshore
flooding from Monroe county west to the Niagara River, with
additional shoreline erosion likely. A Lakeshore Flood Warning
is in effect from Thursday morning through Thursday evening.

The higher wave action and associated flooding risk should be
relatively short-lived, however. The low will move over head
Western New York by late this evening, resulting in sharply
diminishing winds, with waves subsiding shortly thereafter. A
baggy pressure gradient on the back side of the departing low
means that while northwesterly flow behind the low should
generate some choppy conditions Friday along the southern shores
of Lake Ontario, waves should remain in the 1-2 foot range, and
additional flooding issues are not expected.


Buffalo has exceeded the daily precipitation record of 1.21
inches established in 1874. Rochester is close to a recorded
rainfall, while the rain continues across Watertown. Daily
record rainfall for Rochester is 1.74 inches set back in 1943
and Watertown`s record for today is 1.13 inches set back in
1979. With rain continuing east of Lake Ontario, and possible
showers across Buffalo and Rochester final daily totals be known
after the climatic day (1 AM EDT to 1 AM EDT) ends.


NY...Lakeshore Flood Warning until 2 AM EDT Friday for NYZ001>003.
     Beach Hazards Statement until 10 PM EDT this evening for
MARINE...Small Craft Advisory until 9 PM EDT this evening for LOZ030.
         Small Craft Advisory until 11 PM EDT this evening for
         Small Craft Advisory until 2 AM EDT Friday for LOZ042.



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