Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
757 PM EDT Friday Sep 19 2014
high pressure will drift off the New England coast tonight.
Increasing southerly winds in the wake of this high pressure will
boost temperatures to well above average for Saturday under partial
sunshine. A cold front and wave of low pressure will then cross the
region later Saturday night and Sunday with occasional showers and a
few isolated thunderstorms. This cold front will usher in much
cooler air again for early next week.
Near term /through Saturday/...
surface high pressure will continue to drift east off the New
England coast overnight with satellite imagery showing some
high/thin cirrus over western and central New York ahead of a
storm system in the upper Great Lakes. Increasing southerly return
flow around the western periphery of the departing high will allow a
plume of enhanced low level moisture over the middle Atlantic to advect
northward and into portions of New York state overnight. This will likely
produce an expanding area of low stratus clouds across the higher
terrain of the southern tier and Finger Lakes late tonight...and
eventually the higher terrain east of Lake Ontario as well. On the
lake plains increasing south-southwest downslope flow should prevent the low
clouds from developing.
South-southwest winds will increase notably overnight as the pressure
gradient tightens between the departing high and low pressure moving
from Lake Superior to western Quebec...and a 35-45 knot low level
jet crosses the region. This will produce gusts of 15 to 20 knots
later tonight with 20 to 25 knots on the hills and Lake Erie shore.
The increasing winds and mixing will also keep temperatures much
milder than last night...with lows in the middle to upper 50s on the
lake plains of western New York and lower 50s well inland...with some middle
40s across the Tug Hill region. These lows should occur early...with
slowly rising temperatures after midnight.
On Saturday the gusty south-southwest winds will continue...with wind gusts of
20 to 25 knots common across much of the area...and 25-30 knots
across the Niagara Frontier with some added acceleration from
downslope flow. The low stratus which develops across the higher
terrain will still be around for the morning...but should break by
midday as strong mixing dilutes the relatively shallow low level
moisture. For the lower elevations expect partly to mostly sunny
skies for most of the day with just some middle/high clouds at times
ahead of the next system. Any showers will remain to the northwest
of our region through early evening.
850mb temperatures soar to around +13c west and +11c east during the
afternoon. This will support highs in the upper 70s to around 80 on
the lake plains of western New York with an added boost from Stout south-southwest
downslope flow. Expect low to middle 70s across the higher terrain and
east of Lake Ontario where the potential for low morning clouds may
initially hinder warming.
Short term /Saturday night through Monday night/...
Saturday night will likely start dry across the region. Ahead of a
central Great Lakes cold front a ribbon of moisture will reach
western New York later overnight. This moisture coupled with a
strengthening low level jet upwards to 40 knots and elevated instability
between 100 and 500 j/kg will allow for showers with embedded
thunderstorms to become likely overnight...especially across far
wny which will lie closer to the right entrance region of an upper
level 110 knot jet at 250 hpa.
Expect showers and a few embedded thunderstorms to become more
numerous Sunday as lift ahead of a vigorous upper level shortwave
and surface cold front nears the region. This upper level shortwave
will bring another surge of moisture. A surface wave forming and
deepening along this surface cold front will bring added low level
convergence to produce rain showers...and thus we will raise probability of precipitation to
categorical for Sunday. Though weak instability...enough wind shear
aloft and ahead of this surface wave may form line segments of
stronger showers and thunderstorms that will bring gusty winds down
to the surface.
This cold front will reach far wny early Sunday afternoon and our
eastern zones by early evening. Expect the main slug of showers and
thunderstorms to be along and ahead of the front. Behind the surface
cold front the lagging upper level trough and cold pool overhead
will maintain chances for scattered showers Sunday night. Clouds
will hang tough through the day Monday as moisture becomes trapped
beneath a subsidence inversion and winds become northwesterly. These
northwest winds will bring cold air across the lower lakes with
temperatures at 850 hpa dropping to near zero celsius. This...along
with cloudy skies will keep most areas in the 50s through the
afternoon Monday. Any lingering showers Monday towards the east will
end by early afternoon. The cool northwest flow Monday night will
likely maintain stratus and lake effect clouds across the region. If
there is ample clearing Monday night the interior southern tier and
north country will again be prone to frost overnight.
Long term /Tuesday through Friday/...
aloft to start this time period there will be two long wave
troughs of low pressure...one just off the Pacific northwest
coastline and a second over eastern Canada and the northeast US.
An upper level disturbance will be cresting over a Central Plains
ridge of high pressure on Tuesday.
A few showers are possible across the north country Tuesday in
association with the trough...both aloft and also reflected at the
surface over eastern Canada and the northeast. This trough will be
lifting eastward through the day such that warmer and drier air will
build eastward across our region along with an area of surface high
As the western longwave trough deepens across the western US...broad
upper level ridging will be found east of The Rockies...save for the
dampening upper level shortwave trough. This pattern will bring
dry...building warmth and abundant amounts of sunshine Wednesday and
on through the remainder of the week. The passing upper level
shortwave on Thursday night and Friday may only bring some clouds to
interrupt the fair weather.
Temperatures will warm from the low to middle 60s Tuesday up to the
lower 70s by the end of the week.
Aviation /00z Saturday through Wednesday/...
VFR will prevail through this evening with only some cirrus clouds
streaming overhead ahead of a storm system over the upper Great
Lakes. Later tonight a plume of low level moisture over Pennsylvania
will be drawn northward on increasing southerly flow. This may
produce some low stratus across the higher terrain of the southern
tier and Finger Lakes...and also east of Lake Ontario with areas of
MVFR/IFR ceilings. Some of this may impact kjhw as well. Increasing south-southwest
downslope flow will prevent the lower clouds from making it to the
lower elevations...with VFR prevailing at the rest of the taf sites.
A 45 knots southwesterly low level jet will cross the region tonight
into early Saturday. Surface winds will run 10-15 knots out of the
south which will create some low level wind shear overnight. Have
updated the 00z tafs to include low level wind shear.
On Saturday the low stratus across the higher terrain should mix out
by midday...and leave VFR across the entire region for the afternoon
with a mix of some cumulus around 5k feet and increasing middle/high
clouds. It will become quite breezy with south-southwest winds gusting to 20-25
knots across much of the region...and 25-30 knots northeast of Lake
Erie from kbuf-kiag.
Sunday...areas of MVFR and spotty IFR with occasional showers and a
chance of a thunderstorm.
Monday and Tuesday...mainly VFR with a slight chance of a shower.
Wednesday...VFR except for local IFR in southern tier valley fog in
surface high pressure will continue to drift off the New England
coast tonight and Saturday. A tight pressure gradient between the
departing high and low pressure moving from Lake Superior to western
Quebec will produce moderate south-southwest winds across the lower lakes later
tonight through Saturday. This will produce small craft conditions
on Lake Erie and Western Lake Ontario...and also at the northeast
end of Lake Ontario with winds around 20 knots sustained. Winds will
diminish by late afternoon and early evening on Lake Erie and
Western Lake Ontario. Another period of stronger south-southwest winds may
develop at the northeast end of Lake Ontario Saturday night before
winds diminish areawide on Sunday as the pressure gradient weakens.
A period of stronger northwest winds will develop Sunday night into
Monday morning behind a cold front crossing the region Sunday. This
may produce another round of Small Craft Advisory conditions on Lake
Marine...Small Craft Advisory from 9 am to 7 PM EDT Saturday for lez020.
Small Craft Advisory from 1 am to 4 PM EDT Saturday for
Small Craft Advisory from 9 am to 7 PM EDT Saturday
Small Craft Advisory from 11 am to 7 PM EDT Saturday for
Small Craft Advisory from 1 am to 4 PM EDT Saturday for