Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/01/19
Area Forecast Discussion
National Weather Service Buffalo NY
1052 PM EDT Thu Oct 31 2019
Low pressure will strengthen as it moves across the eastern
Great Lakes this evening and into southern Quebec by Friday
morning. Heavy rain will taper to showers from west to east
tonight. Meanwhile, a strong cold front will sweep east across
the region this evening, with damaging winds developing in the
wake of the cold front tonight through Friday. Much colder air
will move into the region Friday through the weekend, with the
first snowflakes of the season possible in some areas east of
.NEAR TERM /THROUGH FRIDAY/...
At 10 p.m. a 991 surface low was centered across southern
Ontario province with a cold front extending southward from
this low just west of Watertown. There is a gust front with
this front producing gusts of 40 to 50 mph. This front will
continue to move eastward across Watertown and to the east of
the cwa around midnight. The strongest winds will arrive around
midnight across far western New York, and spread eastward from
Rochester to Watertown between 1 a.m. and 4 a.m. The feature
causing this is a secondary trough axis which is still across
central Lake Erie late this evening. This coincides with a
strong 60 knot low level jet, a good part of which will mix to
the surface due to a well aligned WSW cold air advection flow.
The HRRR has been useful in timing each of these features.
A line of convection which developed east of Lake Ontario late
this afternoon has moved to the east, which will end our severe
weather threat. The steady rain will effectively end with the
passage of the cold front, and then rain will transition to lake
effect showers. This combined with previous rainfall will pose
a risk for flooding east of Lake Ontario which is further
discussed in the hydrology section.
Following the passage of the secondary trough late tonight and
Friday morning, the boundary layer flow will veer more westerly
as the low reaches southern Quebec. Following the wind direction
change to westerly, there will be a period of a few hours with
60+ knot winds at 850mb. Past events have shown this strong
westerly flow signaling wind damage spreading well inland across
the interior Southern Tier and western Finger Lakes, rather
than staying in the typical lake plain locations.
Potential Vorticity analysis of this system is impressive, with
the 1.5 PVU surface descending to below 700mb. This suggests a
tropopause fold and intrusion of stratospheric air into the
troposphere, which will enhance lapse rates and mixing
potential. Furthermore, a fairly impressive isallobaric
fall/rise couplet will pass across the eastern Great Lakes.
Based on the lastest model guidance, thinking has changed little
with the strongest winds occurring tonight northeast of Lake Erie,
centered around the 11 pm to 5 am time frame, and Friday
morning farther east once the flow veers more westerly, centered
around the 4 am to 10 am time frame. Peak wind gusts will
likely reach 60-65 mph in many areas, with some potential for 70
mph gusts especially near the eastern shores of Lake Ontario.
The strong winds will diminish fairly quickly from west to east
Friday morning into the early afternoon as the surface low and
stronger winds aloft move east of the area.
Following the cold front, the airmass will grow rapidly cold enough
to support a lake response off Lake Erie later tonight, and by
Friday morning off Lake Ontario. The boundary layer may become cold
enough to support some wet snowflakes across higher terrain by early
Friday morning, but marginal temperatures and a rapidly drying
synoptic scale airmass should prevent accumulation. The lake effect
rain/snow showers will taper off later Friday, but may not end
.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
Surface high pressure across the Ohio Valley will build
northeastward across PA into eastern NY Friday night. This will
cause winds to shift out of the southwest, causing any light lake
effect rain and snow showers to shift northeast of both lakes then
diminish through the night as drier air and subsidence work in
across the area. Cool temperatures expected Friday night with lows
ranging from the upper 20s across the higher terrain to the mid 30s
across the lake plains.
There will be a break in the weather Saturday, with just the chance
for a few rainshowers across far western NY by late in the day ahead
of the next deepening shortwave trough and attendant surface cold
front that will move across western and northcentral NY Saturday
evening through the early overnight. Some warmer air will advect
across the region on a southwesterly flow ahead the approaching
system, which will help to boost temperatures a bit with highs
mainly in the mid to upper 40s.
Things get a bit more interesting Saturday night as cold air deepens
across western and northcentral NY with temperatures aloft at 850mb
dipping to around -6 to -7C overnight. There will be mix of rain and
snow showers initially across the higher terrain, with just plain
rain at lower elevations Saturday evening. Precipitation will
transition to all snow across the higher elevations overnight, with
a mix of rain and snow showers across the lower terrain. Lake effect
rain and snow showers will initially be northeast of the lakes,
transitioning to east of the lakes for the second half of the night.
Increasing lake induced instability combined with equilibrium levels
up to 15 Kft and saturation through the dendritic snow growth zone
may lead to the first accumulating snows across the higher terrain,
with possibly a sloppy coating in a few spots across the lower
terrain. Temperatures will again fall into the upper 20s across the
higher terrain, with mainly low 30s elsewhere.
.LONG TERM /SUNDAY THROUGH THURSDAY/...
Lake snows will be ongoing but in the process of slowly weakening
early Sunday. As we move through the day Sunday, lake snows will
rapidly begin to shut down as equilibrium levels fall with a
strengthening subsidence inversion. Lake snow will also be hampered
by weak warm advection occuring in the mid-level. Additionally, air
temperatures will be gradually warming over the course of the day,
so any additional accumulations will be minor after sunrise Sunday.
With that said, surface high pressure is forecast to build into the
Mid-Atlantic which will bring dry and quiet weather to the Lower
Lakes as we head into Monday.
Monday, surface high pressure over the Mid-Atlantic will be the main
player influencing our weather. This feature will bring dry and a
bit warmer conditions to the region with highs rebounding into the
50s. Although, a weak low does race by just to our west and
northwest as it heads into Canada. This feature may introduce some
cloud cover across far Western New York. Tuesday into Tuesday night,
precipitation chances again increase as another low races by to our
west dragging its associated cold front across the region. Behind
the cold front, a much colder air mass filters in across the Lower
Lakes with some lake response. After Wednesday, significant
differences arise with the ECMWF showing high pressure building in
across the Lower Lakes with cold conditions(H850T -12C/-14C). While
the GFS brings another weak weak wave across the forecast area with
some light snow for late Thursday into Friday. Either way, it
appears that the later half of the week will be colder at this
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
A cold front located near KART at 02Z will push eastward across
the region. This will produce a dramatic increase in wind
speed, and also roughly mark the end of the steady rain and
LLWS. Expect windy conditions behind the front, with mainly MVFR
flight conditions. A secondary trough of low pressure will move
through from west to east between 05Z and 10Z and this will
trigger the start of the VERY WINDY conditions. Gusts of 50 to
55 kts can be expected at KBUF/KIAG/KROC/KART with slightly less
windy conditions at KJHW.
Expect strong winds to last into Friday morning before gradually
diminishing from west to east mid-day Friday through Friday
afternoon. There also will be some lake effect rain showers,
mainly late tonight and early Friday morning. It will be cold
enough that these may actually change over to snow at KJHW and
may mix with snow at times elsewhere. These will taper off
Friday afternoon and giveway to mainly VFR flight conditions.
Friday night and Saturday...Mainly VFR. A Chance of showers.
Saturday night and Sunday...Mainly VFR, except IFR in lake
effect rain and snow showers east of the lakes.
Monday and Tuesday...VFR/MVFR with a chance of showers.
Low pressure will track from southern Ontario into southern
Quebec overnight. A strong cold front will push east of Lake
Ontario just before midnight. A secondary surface trough will
move across the lakes after midnight, and this will key the
onset of the strongest winds. This will result in storms and
The strongest winds will be found on the eastern end of Lake
Erie and Lake Ontario, where a brief period of storm force winds
is likely very late tonight and Friday morning. Waves will
reach the 16-20 foot range on both lakes Erie and Ontario. The
wind event will be relatively short lived, with winds quickly
diminishing Friday afternoon.
Generally 1-2 inches of rain has fallen across the region with
the bulk of the rain over west of Watertown. The exception is
southern Oswego and Lewis counties where observations and radar
estimates suggest totals already around 2 inches, with an
additional half inch likely before the rain ends after midnight.
This is likely to result in general flooding, and also may push
several forecast points in the Black River basin above flood
With current rainfall amounts in line with what was modeled by
the RFC, there appears a good chance that one or more forecast
points in the Black River basin will reach flood stage. Another
factor is that the bulk of the rain fell in a 6 hour period,
which can speed up and maximize the crest. This will be closely
Otherwise, basin averages are around 1.5 inches for the Buffalo
creeks. These will be monitored too, with Lancaster likely to
crest near flood stage but just about every other forecast point
expected to crest near or below action stage.
A strong cold front will move across the waters earlier this
evening, and this caused a dramatic increase in winds which
pushed Lake Erie over 9 feet earlier this evening.
This is an unusual situation, with this initial rise shortly
following the passage of the cold front, and then a secondary
rise expected with the strongest winds which will be after
midnight. Typically the highest levels for Lake Erie are with
the initial surge, but in this case its likely that the second
surge will exceed the first. Expect levels to hold steady
before rising again after midnight. Expect a peak around 10
feet above low water datum at Buffalo, which would result in
lakeshore flooding along the Lake Erie shore. Flooding is also
likely along the Niagara River. The elevated Lake Erie water
results in more water flowing down the Niagara River, which can
cause flooding along the riverside in locations such as Cayuga
Island in the City of Niagara Falls.
Strong southwest to west winds combined with high lake levels
will result in lakeshore flooding and shoreline erosion across
Jefferson and Oswego counties. Flooding may also develop across
the Thousand Islands region of the Saint Lawrence River as water
is pushed down the river from Lake Ontario.
NY...High Wind Warning until 1 PM EDT Friday for NYZ001>003-010>012-
Lakeshore Flood Warning until 1 PM EDT Friday for NYZ001-010-
High Wind Warning until 4 PM EDT Friday for NYZ004>008.
Lakeshore Flood Warning until 8 PM EDT Friday for NYZ006-007.
Flood Watch through Friday evening for NYZ006>008.
High Wind Warning until 1 PM EDT Friday for NYZ013-014-021.
MARINE...Gale Warning until 5 PM EDT Friday for LEZ020.
Storm Warning until 5 AM EDT Friday for LEZ040-041.
Gale Warning until 11 PM EDT this evening for LEZ040-041.
Gale Warning until 5 PM EDT Friday for LOZ030.
Gale Warning until 5 PM EDT Friday for LOZ042-043-062.
Storm Warning until 1 PM EDT Friday for LOZ044-045-063>065.
Gale Warning from 3 AM to 5 PM EDT Friday for SLZ022-
Area Forecast Discussion
National Weather Service Caribou ME
1031 PM EDT Thu Oct 31 2019
Low pressure will lift across the St. Lawrence Valley tonight,
and then cross the region on Friday. High pressure will build
across the area Saturday. A cold front will cross the region
Sunday. High pressure will build across the region Monday and
.NEAR TERM /THROUGH FRIDAY NIGHT/...
1030 pm update...
Sfc low sits ovr the far ern end of Lk Ontario with sfc wmfront
extending up thru swrn Quebec. This front is separating moist
and humid air with temps and dwpts in the u50s/l60s ovr nern
Maine and 40 temps and dwpts south of the St. Lawrence. It
appears as tho the far nrn tip of nw Aroostook is on the cold
side of the bndry with a temp at Estcourt Station of 41F.
Still looking for near steady temps ovrngt and maybe even a
slight rise thru daybreak. Convective squall line continues to
race thru ern NY and PA and latest HRRR indicates it will go
thru in a weakened state btwn 10z-12z Fri mrng. Hv adjusted pops
drg the course of the ovrngt to show more of a dry slot and
reduced pops ovr Downeast areas btwn 05z and 10z ahead of the
main cold front.
Still expecting LLJ to strengthen rapidly in the next few hrs
with wind gusts to nr 60 MPH along the coast thru daybreak bfr
jet moves eastward into NB. Still expecting strong mixing in
wake of front to near 750mb fm about mid-mrng into the aftn hrs.
Wl continue High Wind Warning for all areas thru all areas thru
Prev discussion blo...
The third and final phase will be strong WSW pres grad winds on
the back side of the low as it conts N toward Labrador from the
St Lawrence vly of QB, with steep sfc-850mb lapse rates able to
tap momentum transfer from left ovr 45 to 50 kt winds alf form
late morn thru late aftn. Winds will begin to subside after 5 pm
Fri with the loss of dytm htg.
Latest 12z model trends shifted the axis of hvy rnfl a bit
further NW than indicated from last ngt`s model guidance, with
heaviest rnfl now xpctd ovr the far NW. Still, though, sig rnfl
rates will be experienced ovr the N later this eve into the
ovrngt hrs before msly migrating into Ern QB durg the lat ngt
hrs, with the aforementioned quick band of shwrs with the the
cold front shortly after day break Fri. Aftwrds, shwrs will
become sct to isold SW to NE durg the late morn then end from
the same direction Fri aftn.
Temps will also be interesting, with most of the FA
experiencing steady or even a little bit of rise in temps
ovrngt, with only the NW receiving falling temps very late tngt
and erly Fri morn behind the cold front. All other lctns in the
FA will experience falling temps later Fri morn and aftn as the
cold front moves E into the Can Maritimes.
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
A low over Eastern Quebec will continue to move away from our
area. Higher pressure will build across the area. And will
remain over the area through Sunday morning. A low over James
Bay with a trough extending south into Southern Quebec and a
weak low in the Gulf of Maine will be the next systems to affect
our area. The trough will move into Northwestern Maine Sunday
afternoon bringing showers to the area. The low will track
across the Gulf of Maine early Sunday morning bringing showers
to Downeast Maine. Interior Downeast and the Central Highlands
could see a trace of snow before sunrise Sunday morning. By the
end of period, the low in the Gulf of Maine and the trough will
both be east of our area, and higher pressure will build in.
Loaded a blend of the GFS/NAM/ECMWF/GEM to smooth out the minor
differences in the models.
.LONG TERM /MONDAY THROUGH THURSDAY/...
Unsettled weather north of our area, a high pressure ridge
built into the southern portions of the state will be the main
weather features early in the extended period. The high pressure
will dominate through early morning Wednesday. Minor troughs
will move through the northern portions of Aroostook County
bringing a few showers Sunday evening through early Wednesday. A
low moving through the upper Great Lakes region Tuesday evening
will move to the east of James Bay Wednesday morning bringing a
trough into central Maine. The trough will move east of Maine
Wednesday evening, keeping Northern Maine in wrap around
precipitation. Higher pressure will build across the area early
Thursday morning A new low in the Midwest Thursday evening,
will move east to the coast by the end of the period. The
associated frontal system will affect the SW Coast of Maine by
the end of the period.
Loaded a blend of models to smooth out the minor differences.
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
NEAR TERM: Restrictions will range from IFR to MVFR thru the
overnight period as light to locally heavy rainfall moves
through the region. IFR vsbys appear most likely over northern
terminals where moderate-hvy rain will likely fall, especially
at FVE. Cold front moves through around daybreak with winds
gusting to 40-45 kts in wake of fropa thru the aftn.
LLWS will plague all terminals thru the overnight hours with BHB
likely seeing 75kts LLWS just before 12z, BGR experiencing 70kts
of LLWS around 08z. 50-65kts of LLWS further to the north,
mainly from 190-200 degrees.
SHORT TERM: Friday night through Sunday morning...VFR
conditions with increasing clouds and decreasing ceilings Sunday
Sunday morning through Sunday evening...MVFR to Low MVFR with
Sunday evening through Tuesday...VFR conditions with increasing
clouds and decreasing ceilings Tuesday afternoon.
NEAR TERM: We opt`d to increase hdlns to stm wrng ovr the waters
with pretty good potential of wind gusts of 50 kt reaching to
10m abv sfc by late tngt and contg into the morn hrs Fri.
Aftwrds, we will need a gale wrng for the remainder of day Fri.
Went with about 110 percent of WW3/NWPS blended guidance for
fcst wv hts.
SHORT TO LONG TERM: Gale force winds and seas will be ongoing
at the start of the period. Winds will subside to Small Craft
Advisory levels in the early morning hours Saturday morning.
Seas will diminish below SCA criteria Saturday afternoon. Higher
pressure will build across the waters Saturday, winds and seas
will remain below SCA through Tuesday.
Heavy rainfall is expected tonight into early Friday msly across
the N and Cntrl ME mtns which will allow rivers and streams to
rise sharply. Soil moisture rates will increase w/the initial
slug of rain being absorbed, but more heavy rainfall will lead
to runoff. Major rivers of the N and W will see some good
rises, but they should be able to handle the latest projected
additional rainfall of 1-2 inches as they had been trending
downward. Some smaller streams and brooks over the NW could
fill up w/some reaching near bankfull with some minor flooding
of lowlands possible here, but nothing significant is expected
attm. Some minor urban flooding is possible due to culverts
filling up and clogged storm drains.
Strong southerly winds pushing a surge up the Penobscot River
at Bangor and heavy rainfall may may result in nearby parking
areas in downtown Bangor at the time of high tide late tonight,
but it is uncertain attm, with minor flooding a worst case
With seas building to between 5 to 10 feet tonight, minor
splashover is possible around the time of high tide late
ME...High Wind Warning from 6 AM to 6 PM EDT Friday for MEZ001>006-
High Wind Warning from 2 AM to 6 PM EDT Friday for MEZ015>017-
MARINE...Storm Warning from 2 AM to 2 PM EDT Friday for ANZ050>052.
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
948 PM EDT Thu Oct 31 2019
A strong cold front moved through the area early this morning
bringing widespread rain and now gusty winds. Gusty winds and
occasional rain showers will continue through the evening hours
before diminishing after midnight. A much colder airmass will
settle into the area for later tonight and remain through the
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Eight ASOS/AWOS sites in the ILN CWA recorded gusts to advisory
criteria, in addition to an observation at the NWS Wilmington
office. After about 830 PM, a gradual drop in wind speeds
started becoming apparent across the forecast area, with less
gusts in the upper 30 knot range, and more gusts in the 30-35
knot range instead. If this trend continues for another hour or
two -- and it is expected to -- the wind advisory may be able to
be cancelled before its planned 200 AM expiration time. SPC
Mesoanalysis shows that a weakening of the pressure gradient is
beginning to occur, and HRRR forecasts indicate that this will
become more pronounced in the 02Z-04Z time frame.
Aside from the wind, some tweaks for timing were made to PoP
(snow) and sky cover grids, though min temps were generally left
close to the previous forecast. Despite the strong winds on the
cold side of this system, and the big drop in temperatures
earlier today, the cold advection is not expected to be overly
strong through the overnight hour. Temperatures may only fall
another 5-6 degrees or so from current values as of 9PM.
Previous discussion >
Much of the widespread precipitation has moved on to the east as
the cold front pushes out of the area. In the wake of the front,
a deepening surface low pressure currently positioned over the
southern Great Lakes promotes increasing winds throughout the
afternoon and into the evening before gradually decreasing after
midnight. Scattered showers potentially mixing with snow at
times are possible later this evening as cold air advection
ushers in much colder air.
Anyone venturing outdoors for this evening`s Trick or Treat
activities should use extreme caution. Rapidly falling
temperatures will be uncomfortable for those not dressed for
warmer weather and intensifying wind gusts could lead to falling
limbs and power lines. Isolated rain showers mixing with snow
may also lead to uncomfortable conditions at times.
With the rain off to the east, the main focus for the near term
is on the wind. Steep pressure falls have been occurring to the
northeast throughout the afternoon, resulting in a surge in
winds the last couple of hours as the pressure gradient
increases. Observations revealed several sustained winds
between 25-35 mph to the north with gusts around 40 mph. As of
330 PM, the peak wind gust was 43 mph at Dayton International.
With pressure falls continuing through the evening, model
consensus is that winds will increase over the next few hours
before peaking during the evening. HREF mean wind gust
probabilities show a large swath of 45-50 mph with a few
isolated pockets of 50 to 55 mph. This is in good agreement
with ECMWF ensemble mean peak gusts in the mid 50s for the same
areas. Therefore, updated wind advisory this afternoon for
occasional gusts around 55 mph, primarily for northern portions
of the forecast area along I-70 and northward. Further south,
wind gusts around 45 mph are expected with sustained winds
between 20-30 mph. With these numbers in mind, the wind advisory
was also updated by extending it southward to the Cincinnati
Metro area and Ohio River. Wind gusts to 40 mph are still
possible in northern Kentucky, but chose not to include these
areas in the advisory due to distance from the low pressure and
frictional effects. As the low pressure pulls away overnight,
winds gradually decrease toward Friday morning.
The strong CAA is leading to rapidly falling temperatures from
west to east this afternoon and this will continue through the
evening. Temperatures have already dropped nearly 20 degrees
around the Dayton and Cincinnati. Wrap around moisture is also
advancing into central Indiana and this will brush across at
least northwest portions of our area heading toward this
evening. With the colder air moving in, any pcpn will mix
with/change to snow showers heading through this evening before
precipitation moves out. With the ground still warm, any
accumulation across our northwest should be minor and generally
limited to elevated surfaces or possibly grassy areas.
Finally, temperatures are expected to fall below freezing by
later tonight. Freeze warning remains in place as temperatures
drop to the mid to upper 20s by Friday morning.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Surface high pressure will build northeast across the Ohio
Valley through the day on Friday. This will provide for dry but
continued cool conditions. Temperatures will be well below
normal on Friday with afternoon highs mostly in the mid 40s.
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Saturday starts with a longwave trough crossing east through the
Ohio Valley as high pressure builds in the mid section of the
country. Some cold pool showers may be present during the day,
primarily in the northern sections of the CWA, roughly the I-70
corridor. These will be sparked by the combination of the cold air
overturning, vorticity within the l/w trough and sunshine hitting
the column, if there is any sun available. Daytime insolation will
at least come into account, and any showers lingering by afternoon
will quickly wane to nothing by nightfall.
Temperatures for the weekend will generally be static - upper 40s
for highs and overnight lows Saturday night being similar to what is
expected tonight - upper 20s. Lows Sunday night will be a bit warmer
in the lower 30s, with some slightly milder mid 30s in the northwest
due to a southerly flow kicking in overnight.
This south flow will continue over the region and warm temperatures
to the mid and upper 50s Monday and Tuesday. A front will cross
later Tuesday and showers will occur as it passes. High pressure in
the Upper Midwest then builds in and gives reinforcing shots of cold
air from Tuesday night onward. Models diverge in the late portions
of the forecast which gives a lower confidence but is entirely
typical in cold and more active patterns of fall.
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Gusty winds remain the primary concern for the TAFs, with all
six airports currently experiencing gusts into the 30-40 knot
range. This should continue through the 02Z-04Z time frame,
after which the wind gusts will begin a marked diminishing
trend, ending up below 10 knots by 12Z and through the day
While there have been a few reports this evening of very light
wintry precipitation -- snow or sleet -- this is not expected to
have much of an impact on aviation conditions. A couple TEMPO
groups were included to add some brief MVFR visibilities.
Otherwise, the only item to discuss is the cloud forecast, with
MVFR ceilings expected to persist through much of the overnight.
There is high confidence that these MVFR ceilings will scour out
by 12Z at the latest, with VFR conditions after that occurs.
OUTLOOK...MVFR ceilings are possible again Saturday night.
OH...Freeze Warning until 11 AM EDT Friday for OHZ026-034-035-
Wind Advisory until 2 AM EDT Friday for OHZ026-034-035-042>046-
KY...Freeze Warning until 11 AM EDT Friday for KYZ089>100.
Wind Advisory until 2 AM EDT Friday for KYZ091>093.
IN...Freeze Warning until 11 AM EDT Friday for INZ050-058-059-066-
Wind Advisory until 2 AM EDT Friday for INZ050-058-059-066-