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000
FXUS61 KBUF 182036
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
436 PM EDT Tue Jun 18 2019

.SYNOPSIS...
Through Wednesday weak high pressure will linger across the Lower
Great Lakes...while a stalled out frontal boundary will remain
draped across Pennsylvania. Weak impulses sliding eastward along the
front may generate some widely scattered showers across far interior
sections at times through early Wednesday...with increasing daytime
heating then allowing showers and perhaps a few thunderstorms to
expand a bit across areas inland from the lakes Wednesday afternoon
into Wednesday evening. Low pressure advancing into the Lower Great
Lakes will then bring a widespread soaking rainfall Thursday into
Thursday night which could be heavy at times.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
As of 430 pm a cumulus field persists inland from the lakes...
however shower coverage within this region remains very spotty
on area radars...with any echoes confined to interior portions
of the Southern Tier and Finger Lakes. Still could see a few
additional showers and perhaps an isolated thunderstorm develop
within the above areas through early this evening given SBCAPES
of 500-1000 J/kg and the potential for localized convergence/lift
along lake breeze boundaries and terrain features...however
coverage will likely remain fairly limited. After that there
should be a relative break for at least part of the night...
before a few more isolated showers become possible across the
Southern Tier as an impulse along front currently causing
showers and t-storms over central Indiana to central Ohio slides
along PA/NY border...as is hinted at by a majority of the higher
resolution models (WRF-ARW, NMM, NSSL- WRF and even NAM- nest).


On Wednesday, diurnal instability and local convergence from lake
breezes, terrain, and differential heating will support a chance of
a few showers or an isolated thunderstorm especially in the
afternoon and evening hours, mainly inland from the lakes. Stable
lake shadows will likely keep most lake plain locations dry. High
temperatures will be in the upper 70s in most areas, but it will be
cooler along the immediate lakeshores as lake breeze circulations
develop. Still appears that most of the diurnal showers will taper
off Wednesday evening. Then late Wednesday night, larger scale
ascent in form of pva/q-vector convergence ahead of approaching
shortwave trough and warm air advection/moisture flux convergence in
advance of approaching sfc-H85 lows will support increase in showers
and possibly a thunderstorm toward western portions of forecast
area.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
Thursday, a surface low will be found near Ohio, this within a
progressive, zonal shortwave trough that will eventually merge with
an upper level low well to our east this weekend. Ahead of this low,
a southerly stream will transport deep moisture northward, with
PWATS rising to near 1.5 inches during the day over our region.
While moisture will surge northward, it will not become very
warm...with temperatures at 850 hPa around 10-13C. The surface low
is forecasted to track eastward across Pennsylvania, and the greater
warmth and instability will remain along and to the south of this
low.

In light of this, will narrow in the area for heavy rain, and
thunderstorms to the southern two tiers of counties in our CWA.
While moderate rain is still possible to the north of the thruway,
the position of the surface low (which will continue a steady
eastward track), greatest instability, and southward push of the
axis of deeper moisture will allow the removal of heavy rain. Still
with the upper level shortwave passing through, deep accent will
allow for rain showers for the entire region and will continue with
the categorical PoPs.

Rainfall of over an inch is likely south of the NYS thruway Thursday-
Thursday night, while closer to the Saint Lawrence Valley total
rainfall will average around a quarter of an inch.

This surface low will track towards the Jersey Shore Thursday night.
This will carry the bulk of the rain showers eastward, though moist
cyclonic flow aloft will maintain chances for light rain showers or
drizzle deep into the overnight time period. A northerly wind behind
the surface trough aloft may bring some lower ceiling heights, and
areas of fog across the hills of the Southern Tier.

High temperatures on Thursday will range from the upper 60s, to
lower 70s or about 5 to 10 degrees below normal. A late night push
of drier and cooler air will allow for temperatures to drop into the
mid 50s late.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
After Thursday`s rains...Friday will become much nicer with a
surface low now over New England and heading out to sea. Under
cyclonic flow aloft, a dry northerly flow will bring increasing
amounts of sunshine and much lower humidity. There will likely be a
decent cumulus field forming through the afternoon under the
cyclonic flow, though there should still be plenty of sunshine.
Temperatures through the afternoon will be in the 60s, with highs
peaking around 70F.

Saturday and Sunday an upper level ridge will begin to amplify over
our region, with 500 hPa heights peaking Sunday around 576-580 dm.
This upper level ridge and strengthening lower level inversion will
limit any shower or thunderstorm activity, while also allowing for
day to day warming into the mid 70s Saturday and around 80F Sunday.

The ridge axis will slide to our east Sunday night and this will
allow for increasing chances for showers and perhaps a thunderstorm.
The greatest chances will be Monday and Monday night as an upper
level trough axis swings across the region. The GFS is much sharper
with this trough than the operational ECMWF/Canadian and much of the
GFS`s 12Z ensemble members. If a slower progression to this trough
occurs, then a sharper trough as suggested by the GFS could be
possible with prospects for stronger thunderstorms Monday
night/Tuesday. Monday will likely still remain warm, with
temperatures well into the 70s to lower 80s, with Tuesday behind the
trough a few degrees cooler.

&&

.AVIATION /21Z TUESDAY THROUGH SUNDAY/...
Daytime VFR cumulus clouds will fade into the evening. Overall
VFR conditions will continue into Wednesday morning, though
should see some fog (IFR/MVFR conditions) and an isolated
shower at KJHW late tonight into Wednesday morning. Additional
showers could develop over more areas during peak heating on
Wednesday afternoon, though again especially at KJHW.
Conditions Wednesday afternoon into Wednesday night should
remain VFR.

Outlook...

Thursday...MVFR/IFR with periods of rain and a chance of a
thunderstorm.

Friday...MVFR/VFR. AM chance of showers.

Saturday and Sunday...VFR.

&&

.MARINE...
Weak surface high and weak pressure gradient will reside across the
Lower Lakes through Wednesday maintaining light winds and minimal
wave action.

A low pressure is expected to track across the Lower Great Lakes on
Thursday, but the exact track and strength of the low still is
uncertain. Winds and waves may approach Small Craft levels Thursday
into Friday depending on the track and eventual strength of this
system.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...JLA/JJR
NEAR TERM...Hitchcock/JLA/JJR
SHORT TERM...Thomas
LONG TERM...Thomas
AVIATION...JLA
MARINE...AR/JLA