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FXUS61 KBUF 230604

Area Forecast Discussion
National Weather Service Buffalo NY
204 AM EDT Wed Oct 23 2019

Lake effect rain will fall and a gusty southwest wind will howl to 
the northeast and east of the Great Lakes today. Surface high 
pressure will build towards our region this evening and tonight, 
with surface winds becoming lighter and lake effect rain ending.  A 
cold front will then slowly sag across the region Thursday and 
Friday while bringing some additional scattered showers, with cool 
and mainly dry weather then following for the first half of the 


Favorable lake effect conditions will continue into this morning 
within a southwest flow across Lake Erie. A southwest flow of 30-
40kts will also bring the lake effect showers as far northeast as 
the Rochester Metro by Wednesday morning. Rainfall amounts will be 
localized due to the nature of the band and amounts of up to a 
quarter to half inch are possible within the band. There will be 
some clearing outside of the lake effect activity. Low temperatures 
will reach the upper 30's across the higher terrain to the low to 
mid 40's across the Lake Plains and possibly the upper 40's under 
the influence of the lake band. Lake effect will just be starting 
late tonight northeast of Lake Ontario.


Lake induced rain showers will already be in place northeast of Lake 
Erie as we open this period on Wednesday morning. A well aligned 240 
flow of -1c H85 air will place a well defined band of steady rain 
over the Buffalo metro area with a 30-40kt cloud bearing flow 
extending the activity northeast to the western suburbs of 
Rochester. A cap in the vcnty of 8kft and lack of background 
synoptic deeper moisture and lift should keep the band from 
producing significant rainfall amounts...although the rain showers 
could be moderately heavy at times during the first few hours of the 
day. As the base of a shortwave trough passes east of our 
region...subtle warm advection during the afternoon will further 
lower the limiting cap below 5kft. This should substantially weaken 
the lake effect showers...although the axis of the activity will 
move very little as winds persist from the southwest.

Off Lake Ontario...the base of the aforementioned shortwave trough 
will still be the west as the day begins. A moderately sheared 
airmass within a general 240 flow will focus disorganized lake rain 
showers near or immediately north of Watertown...although an upslope 
flow will support scattered showers throughout much of the Eastern 
Lake Ontario region. Once the base of the mid level trough passes... 
the lake response should become more pronounced across the northern 
half of Jefferson county and Thousand Islands region. Given the 
'late' start and shorter fetch...forecast rainfall amounts in this 
region (as compared to Lake Erie's activity) should be significantly 

Outside of these two lake effect areas...cold advection strato-cu 
within the cyclonic flow during the early morning will thin out 
during the course of the day as weak warm advection becomes 
established. This will especially be the case across the Southern 
Tier and Finger Lakes regions...where partial sunshine may make an 
appearance all day away from the influences of the additional lake 
moisture. Temperatures in the low to mid 50s will be quite close to 
where we should be for the later stages of October. However, gusty 
southwest winds, reaching 30 to 35 mph at times especially from the 
Niagara Frontier toward Rochester and along the eastern shoreline of 
Lake Ontario, will add a chill to the air. 

Lake effect will end on Wednesday evening with continual warm air 
advection, lowering inversions and anticyclonic flow as sfc ridge 
expands from southeast CONUS to the Mid Atlantic States. Attention 
later Wednesday night into Thursday morning will be on broad and 
flat troughing sweeping across the Great Lakes. Weak sfc cold front 
tied to the upper level trough will remain moisture starved as it 
limps across our forecast area later Thursday. While it will 
generate a fair amount of cloud cover...the paltry mid level 
moisture and general lack of forcing continue to only warrant 
slight to low chc pops, with best chances closer to Lake Ontario. 
Looks like with gusty sw wind, though not as strong as what occurs
on Wednesday, temps on Thursday may be able to warm into the lower
60s, especially toward Finger Lakes. 

Forecast confidence remains on the lower side later Thursday night 
and the various guidance packages continue to have 
timing issues with the next shortwave trough moving in from the 
nations mid section. Whether this trough is more amplified or 
flatter has bearing on if showers impact mainly western NY or more 
over the Southern Tier into eastern NY. Maintained continuity and 
kept chc pops to avoid significant flip flopping. Temps on Friday 
should reach around 50F or into the lower 50s. Behind this system 
does appear we'll see a minor lake response off Lake Ontario with 
wnw winds sfc-H85 and sufficient instability as H85 temps drop to 
around 0c to -2c, leading to delta t/s toward 13c with Lake Ontario 
water temps of 52F (11C).


Any limited lake response off Lake Ontario will end later Saturday 
afternoon as surface high pressure and associated dry air move into 
the eastern Great Lakes. Looks like another day with highs mainly 
into the lower 50s, with upper 40s across higher terrain.

Medium range guidance continues to diverge Saturday night and 
Sunday. The latest 12Z/22 ECMWF and GEM bring a substantial southern 
stream system through the Ohio Valley and eastern Great Lakes 
Saturday night into Sunday with the GEM on the quicker side of the 
two. Meanwhile, recent GFS runs keep this system more suppressed 
over the southeast states and Mid Atlantic, only grazing our 
southern and eastern forecast areas with any light QPF. Given the 
consensus between the ECMWF and GEM and recent pattern/model trends, 
have continued to increase POPS for later Saturday night and Sunday. 
If the surface low track ends up passing to our northwest such as 
the ECMWF solution, it may turn fairly mild on Sunday despite the 
clouds and showers.

Following this system weak high pressure will build into the Ohio 
Valley and New England from Monday through Tuesday. The GFS is again 
faster with the next trough coming into the Great Lakes, and again 
appears too fast when compared to ECMWF/GEM solutions and ensemble 
means. Given this, kept the Monday through Tuesday period dry and 
turning gradually cooler.


For the 06Z TAFS, as a pool of cold air aloft deepens across the 
Eastern Great Lakes region bands of lake effect rain will develop 
this morning, bringing MVFR flight conditions. A more favorable 
setup will be off Lake Erie, with several hours of rain at KBUF, and 
slightly less at KIAG on the northern side of the band. A strong 
wind will bring at least lake clouds, and possibly a shower as far 
inland as KROC. 

Mid-afternoon lake effect rain will begin to diminish on Lake Erie, 
while still nearing a peak east of Lake Ontario. A less favorable 
setup may leave KART with just a few scattered showers.

Winds to the northeast of the Lakes will gust up to 35 knots before 
high pressure tonight brings a weakening pressure gradient. Though 
surface winds weaken, there will still be a LLJ around 2K feet of 
near 35 to 40 knots that will bring limited LLWS. 

Tonight drier air associated with this surface high pressure to our 
south will end lake rains and clouds...with VFR flight conditions 


Thursday...Mainly VFR with a chance of showers. 
Thursday night and Friday...MVFR/VFR with scattered showers.
Saturday and Sunday...Mainly VFR.


A round of stronger southwest winds will develop on Lake Erie and 
western Lake Ontario this early morning, then spread across the rest 
of Lake Ontario during the course of Wednesday. This will result in 
another round of advisory-worthy conditions that will last into 
Wednesday night or Thursday, with the strongest winds and higher 
waves persisting the longest at the eastern ends of both lakes. 

Small Craft headlines are outlined below.

Looking further out in time, winds and waves will steadily diminish 
from later Thursday through the end of the week as the pressure 
gradient slackens across the Lower Great Lakes.


MARINE...Small Craft Advisory until 5 PM EDT Thursday for LEZ040-041.
         Small Craft Advisory until 11 PM EDT this evening for 
         Small Craft Advisory from 8 AM this morning to 2 AM 
         EDT Thursday for LOZ043-044.
         Small Craft Advisory from 8 AM this morning to 11 PM EDT 
         this evening for LOZ042.
         Small Craft Advisory until 5 PM EDT Thursday for LOZ045.




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