National Weather Service Raw Text Product

941 
FXUS61 KBUF 071426
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1026 AM EDT Fri Sep 7 2018

.SYNOPSIS...
High pressure will move north of the region this weekend, bringing 
dry and cool weather across the region. Widespread rain will then 
approach the region late Sunday and into Monday, with soaking 
rainfall expected for much of the area.

&&

.NEAR TERM /THROUGH TONIGHT/...
The region remains with a fair amount of clouds, especially across 
southern areas which lie closer to a mid level frontal boundary. 
Latest visible satellite imagery displays clearing across the North 
Country. 

As we progress through the day today, Canadian high pressure will 
become the dominating feature, helping to slide the frontal boundary 
southward across the region. This will usher in cooler and drier air 
along with clear skies today and into this evening as the stream of 
mid-high level clouds is shunted southward. Temperatures will top 
out in the mid 70s today with diurnal heating and mixing, while dew 
points fall through the 50s today and tonight with some 40s pushing 
into the North Country later tonight. This will result in good 
radiational cooling conditions tonight where the low-level flow 
decouples, thus valley locations will see lows in the low 50s to the 
mid-upper 40s in the North Country. Northeast winds will pick up 
behind the frontal passage tonight across the Great Lakes where the 
relatively warmer water temperatures help to support mixing of 
higher momentum air to the surface.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
Saturday and Saturday night high pressure will build from northern 
Ontario into Quebec. Meanwhile a frontal zone will remain stalled 
well south of our area, from the lower Ohio Valley to the Mid 
Atlantic states. The frontal zone will remain far enough south of 
the area to keep the majority of the thicker clouds south of the 
NY/PA border, with just some thin cirrus crossing the western 
Southern Tier at times. Some lake effect clouds Saturday morning 
south of Lake Ontario will transition into a diurnal cumulus field 
over the land by Saturday afternoon, with partly to mostly sunny 
skies in most locations. 

The coolest airmass since June will build into the area over the 
weekend, with highs on Saturday in the mid to upper 60s at lower 
elevations, and lower 60s for the higher terrain. Lows Saturday 
night will drop into the 40s across the entire region except for the 
immediate lakeshores. Some of the normally cooler locations east of 
Lake Ontario such as the Tug Hill and western foothills of the 
Adirondacks may even drop into the upper 30s.

Sunday the surface high will continue to move east across Quebec, 
with increasing southeast flow in its wake allowing the frontal zone 
to bulge northward through the Ohio Valley. Clouds will increase 
from southwest to northeast as warm advection and moisture transport 
ramp up. Rain will develop first across the western Southern Tier, 
then spread slowly northward towards the Niagara Frontier and 
Genesee Valley by later in the afternoon. The rain may become steady 
and heavier in the afternoon across the western Southern Tier. With 
the cool airmass still in place, and increasing cloud cover and 
precipitation, it will remain quite cool on Sunday. Expect highs in 
the mid 60s on the lake plains, and only upper 50s across the higher 
terrain.

Sunday night through Monday will become very active across our 
region, with a risk of heavy rainfall and strong southeasterly 
downslope winds. The remnants of Gordon will have merged with a mid 
latitude system, with the resultant upper level closed low and 
deepening surface low moving from the Ohio Valley into the central 
Great Lakes. The dynamics will become stronger with time as the 
upper level jet and low level jet mature. Our region will be in the 
favored right entrance region of the upper level jet, and near the 
nose of a strong 60+ knot low level jet, combining with the 
approaching trough to provide impressive moisture transport and 
forcing for ascent. Abundant moisture will be available given the 
tropical origins of the remnants of Gordon. 

Flooding may become a concern by late Sunday night and especially 
Monday with 2-3+ inches of rain a possibility. Our area has been 
relatively dry over the past few weeks, with below normal 
precipitation from late August into early September. With this in 
mind, we can likely handle a few inches of rain, but if rainfall 
amounts approach or exceed 3 inches flooding would become more 
likely. We have continued to mention this possibility in the HWO.

Strong downslope winds may also be a concern later Sunday night into 
Monday morning along the Lake Erie shore and other northwest facing 
slopes in Western NY. Latest GFS and NAM soundings show 60 knots at 
about 3K feet, with a sufficient inversion to produce the necessary 
stability for downslope winds. The orientation of the low level jet 
is ideal, nearly perpendicular to the Chautauqua Ridge. The one 
mitigating factor may be the potential for steady rain through the 
period. Typically, we see the strongest downslope winds occur when 
there is no precipitation falling. Nonetheless, the potential has 
grown enough to introduce mention into the HWO.

Monday night the surface low will move into southern Quebec, with a 
trailing cold front crossing our region from west to east. The 
steadier rain will taper off to scattered showers with the passage 
of the cold front.

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
Tuesday through Thursday an upper level ridge will build back into 
the Ohio Valley and Great Lakes. This will promote a rapid return to 
above normal temperatures. Highs will be back into the mid 70s by 
Tuesday, and then 80s at lower elevations for Wednesday and 
Thursday. Humidity will also return rapidly, with dewpoints well 
into the 60s for Tuesday and Wednesday, and possibly pushing 70 by 
Thursday.

A weak remnant stalled frontal zone will be located near the 
Appalachians Tuesday through Thursday, where a better chance of 
showers and a few thunderstorms will be found. For our area, there 
may be a few showers or isolated thunderstorms at times, especially 
over the higher terrain inland from the lakes, but much of the time 
should be rain free.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
Mainly VFR conditions are expected as surface high pressure slowly 
moves east through the upper Great Lakes region.  Some 
limited/isolated MVFR and IFR is possible later tonight, 
particularly over the higher terrain in the Southern Tier under a 
northerly to northeasterly upslope flow where abundant moisture will 
remain trapped below about 5000'. Additionally, some limited fog 
and/or low clouds may be possible in interior valleys if enough 
clearing takes places. 

Any inland cloud cover should steadily clear out and be replaced by 
an afternoon cumulus field on Friday, with VFR conditions.  

Outlook... 

Saturday...VFR.
Sunday...Mainly VFR with a chance of showers and thunderstorms late.
Monday...MVFR with rain.
Tuesday...VFR or MVFR with a chance of showers.

&&

.MARINE...
Today, dry weather, light winds, and 2 foot or less wave heights are 
expected as surface high pressure moves slowly east over the upper 
Great Lakes. The high will continue east on Saturday, but this will 
result in a strengthening NE flow with Small Craft Advisory 
conditions on the south shore of Lake Ontario on Saturday.  The flow 
will become easterly on Sunday.  Then expect a low to move up the 
Ohio Valley, across lower MI and into Lake Huron Sunday night into 
Monday.  This will likely bring more widespread rain, wind, and 
associated Small Craft Advisory conditions across much or all of the 
lower Great Lakes region.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory from 2 AM Saturday to 8 PM EDT Sunday for 
         LOZ042-043.
         Small Craft Advisory from 2 AM Saturday to 2 AM EDT Sunday 
         for LOZ044.

&&

$$

SYNOPSIS...Church
NEAR TERM...Church/Thomas
SHORT TERM...Hitchcock
LONG TERM...Hitchcock
AVIATION...Church
MARINE...Church