Preview of NWS' New Version of Forecast
This preview is not operational and should not be used for support decisions.

Area Forecast Discussion (AFD)

Issued by Buffalo, NY (BUF)

FXUS61 KBUF 200105

Area Forecast Discussion
National Weather Service Buffalo NY
905 PM EDT Sun May 19 2019

Mild and humid conditions will support another round of showers and 
possibly a stray thunderstorm tonight. A cold front will cross the 
area Monday with a few more scattered showers. Much cooler and drier 
air will move into the region Tuesday and Wednesday as high pressure 
builds into the Great Lakes.


The next round of convection is rolling east across the forecast 
area tonight. Local radars shows mainly light showers with a few 
thunderstorms popping up east of Rochester which could continue to 
strengthen and produce strong gusty winds and hail as it heads into 
North Central NY.  Otherwise, not expected too much in the way of 
SVR storms with instability waning across the eastern Great Lakes. 
This second round of showers and thunderstorms will continue to move 
east with rain showers tapering off from west to east behind the pre-
frontal trough. After that, there will yet again be another lull in 
shower activity for a good chunk of the night behind the pre-frontal 
trough, then the cold front arrives on Monday. Otherwise, it will be 
a mild and a muggy night with lows nudging back only into 60s across 
the forecast area overnight.

Monday the mid level trough will move east across the eastern Great 
Lakes, with a surface cold front moving east across the area. The 
majority of the better moisture and convergence will be found along 
the pre-frontal trough tonight, with much less in the way of deep 
moisture and forcing for the actual cold front to work with. 
Nonetheless, the cold front will produce a few scattered showers as 
it crosses the area from morning through early to mid afternoon. 
Enough instability may develop across Central NY and east of Lake 
Ontario to support a few thunderstorms during the early to mid 
afternoon. Western NY will dry out during the afternoon behind the 
cold front, with clearing and drying aided by an expansive lake 
shadow developing northeast of Lake Erie.

It will become quite windy Monday along and behind the cold front 
given the favorable low track across southern Quebec, and a 50+ knot 
low level jet lingering behind the cold front. Expect gusts of at 
least 40 mph, with the strongest winds northeast of Lake Erie. If 
enough sunshine develops prior to the stronger winds aloft moving 
out, wind gusts may reach advisory criteria in some areas.


One last lobe of moisture is set to rotate through the North
Country on Monday night, allowing for a continuation of
chances for showers there as much cooler air advances into the
region behind the cold front. This will be short lived, however,
as the upper low will quickly transition into maritime Canada
with a sprawling upper anticyclone builds in the southeastern
U.S. The pronounced upper ridge along the northern periphery of
this will be the dominant player in our weather through midweek,
resulting in decidedly dry conditions over our area as surface
high pressure and the attendant subsidence rule the roost
through the interval.

With the progression of the surface high across the area, low
level flow will quickly back of from the brisk 20-25 kt boundary
layer flow of early Tuesday, toward much lighter flow by 
Tuesday evening, and eventually to southerly flow as the surface
high pushes to the east on Wednesday. This will allow for warm
advection to resume by midweek, as well, which will allow
temperatures to come out of the cool values of Tuesday morning
and rebound above normal by midweek.


A sprawling upper level anti-cyclone will continue to take
residence over the southeast U.S. through the long term period.
A deepening trough over the west coast and intermountain west 
will initiate active weather over the western half of the 
country. Active weather from the western trough will trek 
northeast over the ridge resulting in mostly weak waves of low 
pressure to pass over/near the western and north central NY area
for most of this period. At the moment, the best timing for
showers to move through our region seems to be centered around
Saturday from this activity.

Temperatures will warm from the low to mid 60s on Wednesday to the 
upper 60s and 70s for the rest of this period through the weekend.


The next round of showers and thunderstorms is rolling east across 
the forecast area tonight. While VFR condition are likely to 
continue for most terminals, a few stronger storms may develop and 
produce brief periods of lower CIGS and VSBYS at area airports 
tonight. Otherwise, later tonight with the passage of the pre-
frontal trough low level moisture will increase likely bringing 
about a period of lower CIGS overnight into Monday morning with the 
approach of the cold front. This cold front as it moves through will 
also likely produce a few scattered showers Monday. It will also 
become quite windy Monday, with gusts of over 35 knots from late 
morning through the afternoon, especially northeast of Lake Erie.


Tuesday and Wednesday...Mainly VFR.
Thursday and Friday...Mainly VFR with a chance of showers and 


Pre-frontal trough will cross the lower Great Lakes with showers and 
a stray thunderstorms into the first half of tonight. Low pressure 
will then move across southern Ontario and Quebec late tonight and 
Monday, with a trailing cold front crossing the eastern Great Lakes 
Monday. Southwest winds will increase as the low passes by to our 
north, likely producing southwest-west winds of 20-25 knots and 
Small Craft conditions on Lakes Erie and Ontario. The moderate winds 
will last into Monday night and early Tuesday before diminishing by 
Tuesday as high pressure builds into the Great Lakes.


A cold front will move across the eastern Great Lakes Monday as
low pressure moves east across Ontario and Quebec. Southwest
winds will increase around midday Monday across Lake Ontario, 
then become more westerly during the afternoon and evening 
following the cold frontal passage. The increase in westerly 
winds will bring higher waves on Lake Ontario, combining with 
very high lake levels to bring an increased risk of lakeshore 
flooding on the east half of Lake Ontario.

For Monroe, Orleans, and Niagara counties, the westerly winds
will be shore parallel Monday and early Monday night, which 
will likely not increase lakeshore flooding and erosion as much 
as the eastern portion of the lake.

There still is a slight chance that the winds may become more 
northwest late Monday night and Tuesday. The GFS is strongest 
and also most northwest, which would bring lakeshore flood 
potential to the entire south shore of the lake, but it all by
itself in forecasting this scenario. The rest of the model
guidance maintains more westerly flow. Thus, the lakeshore flood
warning will only be issued for the eastern end of the lake at
this time and the western half of the lake will continue to be
watched as further guidance rolls in.


NY...Lakeshore Flood Warning from 2 PM Monday to 8 AM EDT Tuesday 
     for NYZ007.
     Lakeshore Flood Warning from 5 PM Monday to 11 AM EDT Tuesday 
     for NYZ004>006.
MARINE...Small Craft Advisory from 10 AM to 11 PM EDT Monday for LEZ020.
         Small Craft Advisory from 8 AM to 11 PM EDT Monday for 
         Small Craft Advisory from 10 AM to 11 PM EDT Monday 
         for LOZ030.
         Small Craft Advisory from 1 PM Monday to 8 AM EDT Tuesday 
         for LOZ043>045.
         Small Craft Advisory from 10 AM Monday to 8 AM EDT Tuesday 
         for LOZ042.
         Small Craft Advisory from 1 PM to 8 PM EDT Monday for 



NEAR TERM...AR/Hitchcock