Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/16/21
AREA FORECAST DISCUSSION
National Weather Service Albany NY
954 PM EST Wed Dec 15 2021
.SYNOPSIS...
Precipitation will move across the region this afternoon
and evening. Most areas will see rain, but the higher elevations of
the Adirondacks and southern Greens may see a wintry mix of snow,
sleet, and/or freezing rain for a few hours this evening before
changing to all rain. Precipitation ends tonight. Thursday and
Friday look mainly dry, and near record warmth is possible Thursday.
We are watching the potential for a wintry storm system this weekend
which could bring a light to moderate snowfall to some portions of
the region.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Areas of rain mainly south of the Adirondacks and temperatures
have risen above freezing in areas seeing the precipitation.
Temperatures continue to slowly rise, so the threat of any
freezing rain is about ended. Continuing rain through the night
with the best chances in the Mohawk Valley, Lake George Saratoga
Region to southern VT and Berkshires, with solid chances
elsewhere. So, some adjustments to temperatures and rain chances
through the night. Previous AFD has a few more details and is
below...
PREVIOUS DISCUSSION:
GOES 16 water vapor imagery shows and upper-level disturbance
moving into our region, and precipitation has developed in
response to this upper impulse and additional forcing from
isentropic lift on the 295 K theta surface. As the disturbance
continues moving to the east and ridging aloft builds in from
the west, precipitation becomes more showery in nature after
midnight, and showers should taper off by 12z Thursday. With a
warm front moving to the north and east of our area by Thursday
morning, we will see warm air advection into the region, so
temperatures may actually rise overnight after low temperatures
are achieved this evening. What minimal snow and/or ice
accumulation we see will likely melt overnight tonight after
temperatures begin to warm up.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/...
We begin the day Thursday under upper-level ridging, but the
ridge crest will slowly move eastward during the day. Ridging
aloft should promote subsidence which will keep our area mainly
dry during the day. At the surface, the warm front will have
lifted well to the north and east of our region, while a
deepening low pressure system tracks from Minnesota up towards
Hudson Bay in Canada. This will place our region in the storm`s
warm sector. Here, 850 mb temperatures will be approaching
+12-14C during the day. Guidance also suggests some partial
clearing, especially during the late morning and early
afternoon. It will also be breezy thanks to a tight pressure
gradient over the region. The aforementioned conditions will set
the stage for an anomalously warm day Thursday (not out of the
question we see some new daily record highs set). The degree of
mixing is still in question as there are uncertainties in a) the
degree of cloud cover and b) how deeply we will mix with a
sharp inversion near 925 mb. Even with shallow mixing depths,
temperatures should still climb into the upper 50s and low 60s
outside of the higher elevations. Temperatures could be even
warmer if more sun and deeper mixing occurs. A
west/southwesterly flow may lead to downslope warming in the
Capital District and portions of the Hudson Valley as well.
Thursday night, the ridge moves off to the east and heights fall
aloft as a trough approaches from upstream. As the surface
cyclone continues to track well to our north across Quebec, the
trailing cold front will move into our region Thursday night
after midnight. Despite PWATs in excess of 1.1", the best
upper-level forcing looks to pass to our north. Therefore, while
some showers are possible ahead of and along this cold front,
not expecting widespread and/or heavy precip with this frontal
passage. However, it will become windy behind the front. With a
strong pressure gradient over the region, winds aloft will be
mixed down as we switch to a cold air advection regime behind
the front and mix to around 850 mb. While 850 mb winds will be
in excess of 50 kts ahead of the frontal passage, winds aloft
look to decrease behind the frontal passage. The highest wind
gusts look to occur in the high terrain of the southern Greens,
where the HRRR and 3 km NAM both show some wind gusts in excess
of 50 kt for the southern Greens. But these pieces of guidance
have been overdone by 5-10 kt with wind gusts for the past few
wind events in our cwa. Therefore, confidence is not high enough
at this time for a wind advisory for this area, but it is not
out of the question that one could be needed in the future if
confidence in higher gusts increases. Elsewhere, mainly sub-
advisory criteria gusts expected, although some higher
elevations in the Adirondacks could possibly see some gusts
approach advisory criteria behind the cold front.
It remains breezy Friday, although winds will be decreasing
during the afternoon. The cold front looks to stall/wash out
over our region, so there may end up being a stronger than
normal temperature gradient between our northern and southern
zones. At this time, expecting highs in the 30s for the high
terrain of the Adirondacks and southern Greens to mid/upper 50s
in the Mid Hudson Valley. Any showers associated with the cold
front should diminish by 12z Friday. Friday night, a surface
pressure ridge builds in from the northwest, which should help
temperatures fall into the 20s and 30s region-wide. High clouds
will be on the increase ahead of our next weather system for
Saturday. As of right now, the bulk of precip looks to hold off
until around daybreak Saturday or later, so did cut back on NBM
PoPs for Saturday night.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Main question this period will be details with the storm system
forecast to move across the area on Saturday. Low pressure will
track northeast from the Ohio Valley toward western Pa / western
NY with redevelopment off of the northern mid-Atlantic coast.
Precipitation will overspread the area, likely starting as snow
in many places, however there will be a warm layer aloft with
this system which will probably result in a change-over to sleet
and freezing rain during the day Saturday especially along and
south of I-90. The location of the rain vs. mixed precipitation
vs. snow cannot yet be determined with much confidence at this
point, as there remains some discrepancy in the details of the
model storm track and resultant temperature profiles. For now
the ECMWF looks to be far enough south so that much of the area
would see snow on Saturday, while other models and especially
the NAM are farther north bringing mixed precipitation farther
north. With cold high pressure forecast over Quebec through
Saturday it will be hard to get surface temperatures much above
freezing during the day Saturday, so if warm air moves in aloft
there will certainly be icing potential. Confidence with this
event should be increasing in the next couple of days and
forecasts will be refined.
Beyond Saturday the forecast gets more straightforward. Sunday
will be cold and blustery with modest amounts of lake effect
snow west of the Hudson Valley and over the higher terrain in
western New England. High pressure will move southeast to the
mid- Atlantic coast on Monday bringing dry, seasonably cold
weather. There will be low pressure developing over the
southeastern states on Tuesday but for now there does not appear
to be phasing with the northern branch sufficient to bring this
storm up the coast. If that continues, Tuesday should be dry
with continued seasonable temperatures, although with this
situation still 6 days away we will have to continue to monitor
model trends.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
VFR ceilings and visibilities persist this evening despite
ongoing scattered areas of showers including some periods of
sleet/snow. Temperatures will be warming overnight so any wintry
mix should occur before Midnight and be mainly limited to GFL
where dew points remain below freezing. During periods of
steadier showers from 00 - 06 UTC, MVFR ceilings are possible
at all TAF sites. After 06 UTC, the most organized areas of rain
exit into the New England with some lingering showers ending by
10 - 12 UTC. Then, VFR conditions remain in place through the
end of the TAF period.
Light and variable winds expected tonight except at ALB where
sustained winds will remain near 10 - 12kts. Where the winds are
light, low level wind shear looks possible as winds at 2000ft
reach 40 - 50kts. POU and PSF look to have the best potential to
observe LLWS. Then, tomorrow, southeast winds shift to the
south-southwest and become sustained near 8 - 15kts with gusts
up to 20kts in the afternoon. Breezier winds could be observed
in the afternoon should more sunshine occur.
Outlook...
Thursday Night: Low Operational Impact. Breezy. Slight Chance of SHRA.
Friday: No Operational Impact. NO SIG WX.
Friday Night: Moderate Operational Impact. Chance of SHSN.
Saturday: High Operational Impact. Definite RA...SN.
Saturday Night: High Operational Impact. Likely RA...SN...FZRA.
Sunday: No Operational Impact. NO SIG WX.
Sunday Night: No Operational Impact. NO SIG WX.
Monday: No Operational Impact. NO SIG WX.
&&
.HYDROLOGY...
A period of showers this evening into tonight will result in
about 0.15 - 0.30 inches of liquid precipitation. Some light
snow/sleet accumulations are possible in the southern
Adirondacks and southern VT. These QPF amounts will not be
enough to elicit a response from streams and rivers in our
region. Then, the next main disturbance to watch arrives
Saturday and continues into Saturday night. This may result in
both snow and wintry mix.
Temperatures will be above normal through much of the week, which
will limit the potential for ice formation.
For details on specific area rivers and lakes, including observed
and forecast river stages and lake elevations, please visit the
Advanced Hydrologic Prediction Service /AHPS/ graphs on our
website.
&&
.CLIMATE...
Record high temperatures for December 16:
Glens Falls, NY: 56 degrees, 1982
Albany, NY: 55 degrees, 1971
Poughkeepsie, NY: 59 degrees, 1971
Record high minimum temperatures for December 16:
Glens Falls, NY: 37 degrees, 2011
Albany, NY: 40 degrees, 1971
Poughkeepsie, NY: 38 degrees, 2015
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.
&&
$$
SYNOPSIS...Main
NEAR TERM...Main/NAS
SHORT TERM...Main
LONG TERM...MSE
AVIATION...Speciale
HYDROLOGY...Main/Speciale
CLIMATE...
Area Forecast Discussion
National Weather Service Denver/Boulder CO
714 PM MST Wed Dec 15 2021
.UPDATE...
Issued at 702 PM MST Wed Dec 15 2021
Winds have clamed down in most areas. However, satellite
data shows enhanced subsidence in the nrn foothills. This is
allowing for wind gusts in the 50 to 60 mph range in the normal
windy areas. Cross-sections show gusty winds may last through the
night with a few gusts up to 70 mph possible in and down to the
base of the foothills. Can`t rule out an isold higher gust or two,
however, don`t think these gusts will be widespread enough for
reissuing a high wind warning at this point.
Meanwhile, areas of light snow continue in some higher mtn areas
with blowing snow. Doesn`t appear to be that widespread so will
let advisory expire at 8 pm.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 108 PM MST Wed Dec 15 2021
GOES-16 Water Vapor shows the comma head moving across western
Kansas. Broad and strong subsidence has taken over eastern
Colorado and will continue through this evening. The DEBRA dust
satellite product shows the extent of the dust across SE CO and
all of W. KS. There is a fair amount of dust across the northeast
corner of Colorado, but with mid level clouds we can`t see it on
satellite but ASOS and trained spotters have been all over it.
Will keep dust in the forecast through this evening across mainly
the northeast corner. With the strong subsidence and departing
short wave trough, the mountain wave is in the process of breaking
down, and by 3-5 PM winds in the foothills and west of I-25 will
weaken significantly. Winds across the far eastern plains will
remain up for a few more hours than that because those areas are
more dependent on the surface pressure gradient, which will take
longer to relax. Expect a few more hours of gusts to 80 mph in the
favored windy spots west of I-25, and gusts across the far
eastern plains around 70 mph through 5-7 PM. Elsewhere, like much
of central metro Denver north to Fort Collins and Greeley, should
see gusts 30-50 mph through 5 PM. The RFW will continue through 5
PM given the high winds and relatively low RH.
In the mountains, snow rates have come down this afternoon but
with upslope and moisture, light snow will continue through about
midnight with another 1-3" possible. With the wind and light snow,
roads have been slow to recover across the less traveled mountain
passes, so will keep the advisory going through 8 PM. Expect it
to be seasonably cold across much of the area tonight with
weakening winds, mostly clear skies, and snow cover in the
mountain valleys. Lows tonight should be in the single digits in
the mountain valleys, and teens across the plains other than the
urban heat islands where lows should remain in the low 20s.
Southwest flow aloft is expected Thursday ahead of another trough
moving across the northern Rockies. Lapse rates improve
significantly above the mountains vs today, and combined with
some moisture in the upslope flow, light snow is possible starting
late Thursday morning across the higher elevations. Very little
accumulation is expected most areas though the higher totals
should be for the Park Range where several inches look likely
Thursday into Friday.
Across the plains, southwest low-level flow combined with
southwest flow aloft will result in a decent warm up. It will be
very dry across the plains with RH dropping to 15-20 percent below
6,000 ft elevation. Elevated fire wx conditions are expected
along and east of the Palmer Divide but winds may remain just
below RFW criteria during the afternoon hours. It should be breezy
along and southeast of I-76 during the afternoon. Highs should be
in the low 50s across the plains, with 30s in the mountain
valleys.
.LONG TERM...(Thursday night through Wednesday)
Issued at 108 PM MST Wed Dec 15 2021
Thursday night and Friday, an upper level trough will move across
the Central and Northern Rockies. Increasing moisture combined with
cold air advection and orographic lift will produce snow in the
Mountains Thursday night and Friday. The best chance for
accumulating snow should be before midnight due to a 100KT upper
level jet over the area. Snowfall amounts are expected to range
between 1 and 6 inches, heaviest over the Northern Gore and Park
Ranges. Dry conditions are expected east of the mountains due to a
downsloping flow. Cooler temperatures and breezy conditions
(northern and eastern sections) of the plains are expected on Friday
behind the passage of a weak cold front.
Dry and warmer weather is expected on Saturday as an upper level
ridge of high pressure builds over the Rocky Mountain Region. For
Sunday through Tuesday, an upper level trough of low pressure is
progged to develop just off the west coast of the U.S. with a dry
west to southwesterly flow aloft over Colorado. This pattern should
result in continued dry weather and above normal temperatures across
the forecast area.
On Wednesday, the mountains could see another round of snow as
energy and moisture from the Pacific start to make its way into
Western Colorado.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 702 PM MST Wed Dec 15 2021
Winds have been all over the place but have gone back to a more
westerly direction. HRRR has been all over the place with
directions this evening and overnight. Confidence in wind
forecast overnight is low at best. Would think they would
eventually go more SSW in the 04z-06z timeframe.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 8 PM MST this evening for COZ031-
033-034.
&&
$$
UPDATE...RPK
SHORT TERM...Schlatter
LONG TERM...jk
AVIATION...RPK
Area Forecast Discussion
National Weather Service Burlington VT
1013 PM EST Wed Dec 15 2021
.SYNOPSIS...
A warm front will produce a period of mixed precipitation this
evening, with a minor snow and ice accumulation expected east of the
Green Mountains, along with some slippery travel. Record warmth will
build across the North Country on Thursday associated with breezy
southerly winds. These winds will increase overnight Thursday into
Friday morning with isolated to scattered power outages possible
across northern New York into parts of southern Vermont. A brief
break is anticipated on Friday, before our next system arrives for
the weekend with a period of light snow likely.
&&
.NEAR TERM /THROUGH THURSDAY NIGHT/...
As of 1003 PM EST Wednesday...Forecast conditions continue to go
according to plan. Most of the forecast area quickly made the
flip over to rain, while areas in the Northeast Kingdom continue
to produce freezing drizzle or sleet. Slightly tweaked the
precipitation types again to capture the latest trends, and then
modified PoPs, as it seems there should be some more widespread
activity that passes through the area in the 5 AM to 9 AM time
frame. All of is expected to be rain. Have noted that outside of
the immediate area near Lake Champlain, winds have not been as
strong as anticipated. So for areas outside of the Champlain
Valley, slightly reduced wind gusts, which can be noted in a
brief reduction in low-level flow until the cold front
approaches tomorrow afternoon. These changes were minor, and lie
outside the wind advisory for tomorrow. So, with that, have a
great night!
Previous Discussion...
Winter wx advisory continues from 22z this evening until 12z
Thursday for light wintry mix east of the Greens and slippery
travel.
Wind advisory has been expanded to include most of northern NY and
parts of southern VT for gusts up to 55 mph and isolated to
scattered power outages expected.
Tonight...very little change in our thinking as crnt radar shows
band of light precip expanding acrs northern NY attm with a mix of
rain/snow falling. MSS down to 1 1/4sm in -sn as of 236 PM. This wl
continue to push eastward this evening and given thermal profiles
east of the Green Mtns a 3 to 6 hour window of mixed precip is
anticipated. Soundings show llvl east-southeast flow wl help to keep
sfc to 900mb temps at or below 0C as most of the heavier precip
falls associated with initial band of 850 to 700mb fgen forcing.
Expect snow/sleet accumulations a dusting to 2 inches possible, with
a light glaze of ice possible, which wl cause some areas of slippery
travel overnight. Coolest temps occur btwn 00-03z with sfc temps
warming overnight as south/southwest 925mb to 850mb winds of 45 to
55 knots develop and advect much warmer air northward. Meanwhile,
over northern NY and the CPV after a brief period of rain/snow,
expect mainly a cold rain to develop aft 00z, as thermal profiles
show the entire column warming above 0C. Very minimal impacts
anticipated as temps warm back into the mid 30s to lower 40s by late
evening.
Thurs/Thurs Night...water vapor shows a potent 700 to 500mb vort
entering the central Plains this aftn, which wl enhance sfc low
pres/wind fields and svr wx threat acrs this area. Meanwhile, as sub-
975mb sfc low pres races toward Hudson Bay, a strong pres gradient
develops btwn this system and 1032mb high pres over the western
Atlantic. Guidance continues to increase 925mb to 850mb wind fields
acrs our fa, especially northern NY/SLV on Thurs Night with values
now in the 60 to 75 knots range. Sounding indicate boundary layer
mixing increases sharply aft a sfc trof/cold frnt moves acrs our
region, promoting steepening lapse rates and deeper mixing. NAM 3km
and BTV 4km show bottom of the mixed layer of 45 to 50 knots acrs
the SLV and northern slopes of the Dacks along route 11 from Malone
to Altona.
Based on this information have expanded wind advisory and
mention gusts up to 55 mph possible with isolated to scattered power
outages. Also, BTV 4km shows favorable downslope wind gusts near
Ludlow, so have included eastern Rutland/Windsor Counties in
advisory. For the SLV expecting two periods of gusty winds, first is
btwn 1 PM and 4 PM Thurs with deeper mixing on warming sfc temps in
the mid/upper 50s to near 60F, followed by increasing wind fields
and additional mixing behind boundary from 9 PM to 2 AM Thurs Night.
Have continued with schc/chc pops for showers maybe even a rumble of
thunder on Thurs aftn, as HRRR and NAM3KM show a weak axis of most
unstable cape of 100 to 250 j/kg over slv/western dacks around 18z
Thurs. Still anticipating record breaking temps on Thurs,
supported by progged 925mb temps btwn 8-12C, with warmest values
around 15z on the southwest downslope side of the eastern/northern
Dacks. Interesting how 925mb cool btwn 15z-21z Thurs, behind
departing s/w energy, but 1000 to 500mb thickness parameter
increase, maybe some mixing of cooler air aloft. Thinking temps
range from l/m 50s NEK/eastern VT to lower 60s downslope locations
of the northern dacks, which is supported by upstream temps in the
l/m 60s near Chicago. Bottom line many records should be broken on
Thurs.
&&
.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
High pres builds into our fa with modest llvl caa prevailing on
brisk west/northwest winds. Progged 925mb temps btwn -2C and -5C
support highs mainly in the mid 30s to mid 40s on Friday, with
warmest values over the lower CT River Valley. Expect dry conditions
to prevail during this time frame.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 348 PM EST Wednesday...Widespread light to possibly moderate
snowfall continues to be grow more likely for Saturday across the
North Country based on decreasing spread in model guidance. The
National Blend of Models probability of 24 hour snowfall in excess
of 2 inches exceeds 60% areawide, and in excess of 4 inches is
between 30 and 50% for nearly all of the North Country. Snowfall
amounts will be dictated by where the axis of 700 millibar
frontogenesis sets up as a focus for heavier rates of precipitation.
Otherwise, a broad area of steady overrunning precipitation should
lift northward into the North Country during the day ahead of a
surface low tracking through central New York, which will give way
to a coastal low that will move northeastward in the vicinity of
Cape Cod Saturday night. This storm track will tend to keep a large
layer of air above the ground relatively warm, such that cloud ice
may not be present in the clouds towards the end of the event. As a
result, snow will tend to mix or change to freezing drizzle
resulting in a crusty top to the snow accumulation Saturday night.
At this time, it is hard to evaluate when and where this will occur,
but based on the expected storm track it should be more likely over
southern and western portions of the area and spread through much of
central Vermont overnight.
In the wake of Saturday`s storm system, it still looks like some
snow showers throughout northern Vermont could develop with
cyclonic, upslope flow battling strong cold and dry air advection.
Eventually the dry air will win out with some bitterly cold wind
chills developing, especially by Sunday night. Current values
forecast fall below zero in most areas after midnight. High pressure
builds in on Monday to help relax winds with temperatures remaining
below freezing but with sunshine it should feel more pleasant than
on Sunday.
A split flow in the jet stream will support relatively dry and cold
conditions next week as our area sees shots of polar air come
through the region. Have maintained some chances for snow on Tuesday
associated with a relatively weak cold front that reinforces colder
air for Wednesday following some moderation Monday night into early
Tuesday.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Through 00Z Friday...Changeable weather remains the theme. Area
of snow remains east of the Greens, like EFK and MPV, while
areas west have now seen a transition to rain. At this time,
only EFK is reporting a wintry mix. Visibilities around 4 to 8
miles in precipitation. Precipitation will become more isolated
and confined to terrain after 06Z, with a brief resurgence
around 10Z-15Z across the area before trending drier. Ceilings
will also range between about 1500 ft agl and 3500 ft agl for
the next several hours, before gradually lifting after 15Z.
Anticipate LLWS at most terminals in the next 24 hours, with
south winds at 35 to 50 knots at 2000 ft agl, becoming
southwesterly beyond 08Z. LLWS could briefly abate, mainly north
at MSS, PBG, BTV, and EFK before increasing again after 13Z.
Nevertheless, turbulent conditions off the mountain ranges will
remain likely, regardless of wind shear criteria. At the
surface, winds will be from the south to southwest about 7 to 14
knots with gusts 15 to 25 knots at times, especially now through
06Z and again after 18Z Thursday. Wind gusts are expected to
increase behind a cold front beyond 00Z Friday.
Outlook...
Thursday Night: VFR. Strong winds with gusts to 45 kt. Slight
chance SHRA.
Friday: VFR. Windy with gusts to 30 kt. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: Mainly VFR, with local MVFR and IFR possible. Likely
SN, Slight chance FZRA.
Saturday Night: Mainly MVFR, with local IFR possible. Chance SN,
Chance FZRA.
Sunday: Mainly MVFR, with areas VFR possible. Slight chance SN.
Sunday Night: Mainly VFR, with local MVFR possible. NO SIG WX.
Monday: VFR. NO SIG WX.
&&
.MARINE...
Strong winds continue to be observed over Lake Champlain.
Sustained winds have ranged between 20 and 30 knots. Based on
the latest data, these winds should briefly decrease to 15 to 25
knots sustained after midnight, and then pick back up tomorrow
afternoon and into Thursday night with winds in the 20 to 30
knot range with gusts around 35 knots. Waves will be 3 to 6 feet
across the open waters.
&&
.CLIMATE...
High temperatures across the North Country will be well above
normal on Thursday with daily records expected. Here are the
records on 12/16 that may be broken:
Date KBTV KMPV KMSS KPBG KSLK
12-16 54|1982 53|1982 54|1992 51|2011 47|1992
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Winter Weather Advisory until 7 AM EST Thursday for VTZ003-004-
006>008-010-012-016-018-019.
Wind Advisory from 7 PM Thursday to 10 AM EST Friday for
VTZ012-019.
NY...Wind Advisory from 1 PM Thursday to 7 AM EST Friday for NYZ026-
027-087.
Wind Advisory from 7 PM Thursday to 10 AM EST Friday for
NYZ028>031-034.
&&
$$
SYNOPSIS...Taber
NEAR TERM...Haynes/Taber
SHORT TERM...Taber
LONG TERM...Kutikoff
AVIATION...Haynes
MARINE...Evenson/Taber
CLIMATE...Kutikoff
Area Forecast Discussion
National Weather Service Grand Rapids MI
951 PM EST Wed Dec 15 2021
LATEST UPDATE...
Update
.UPDATE...
Issued at 951 PM EST Wed Dec 15 2021
No changes to the existing wind/marine headlines. Winds will
continue to ramp up over the next few hours with arrival of the
low level jet core related to deepening sfc low tracking north
through MN. Gusts of 40 to 60 mph have been noted in recent sfc
observation in Illinois underneath that approaching LLJ which
strengthens as it moves north. Highest gusts so far have been
around 45 mph along the lakeshore between Muskegon and Pentwater.
Hourly HRRR wind gust fcsts, which performed quite well in last
Saturday`s high wind event, have remained consistent in each run
showing 60-65 mph impacting areas north and west of GRR overnight.
The peak of the highest winds occurs in the northwest CWFA
between roughly Midnight and 4 am, whereas the peak over inland
areas is more like 5 am to 10 am Thursday. This is when the colder
low level air will be arriving from the southwest, increasing the
depth of the mixed layer just before the core of highest winds
at 925 mb departs.
Fortunately the worst of this storm stays to our west where the
svr convective line and trop fold/sting jet components of the
cyclone are located and causing wind gusts of around 80 mph.
Latest CAM updates continue to weaken the line of svr convection
as it outruns the instability and will only be a line of scattered
showers by the time it gets here overnight.
The increasing southerly flow continues to send milder air into
the state this evening, and current readings are near or above
the record values for today (see Climate section below). Records
for 12/15 have been recently broken at Grand Rapids, Muskegon,
Kalamazoo, and Holland.
&&
.DISCUSSION...(This evening through next Wednesday)
Issued at 342 PM EST Wed Dec 15 2021
- Strong Winds Early Thursday
The storm we have been forecasting for several days now is
developing as expected. The surface low (985 mb) is currently in
western Nebraska and will track north of Lake Superior by sunrise
on Thursday as a 975 mb, and still deepening low. The upper wave
goes seriously negative tilt so we get a trop fold and strong
cyclogensis as a result of this. strong isallobaric wind
component will resulting in 45 to 55 knots in the mixing layer
between midnight and mid morning on Thursday. The HREF continues
to forecast 60 to 65 mph winds gusts for several hours near the
Lake Michigan shore (near US-31). Gusts in the 45 to 55 mph range
are expected inland.
With the track of the storm to our west, the strongest winds will
be in our northwest CWA but all area will see strong winds once
the cold front comes into the area. Some of the strongest winds
are just above the mixed layer, prior to the passage of the cold
front so there is some question as to if we can really mix down
some those really strong winds. Still, the wind field with this
storm is significantly stronger than what happened Saturday. I
would expect power outages due to falling tree limbs and even
falling trees.
- Record Highs Today
The strong southerly winds have already brought enough warm air
into the area so that Muskegon has already broken their record
high of 58 degrees today by reaching 61 at 3 pm. As the warmer air
continues to move in (temperature are in the mid to upper 60s by
Chicago) most of our climate sites have a good chance to break
their records (see our climate section below for detail). Most
locations south of Route 10 should get into the 60s by this
evening.
- Not Much Rain on the Cold front
There is not a lot of deep layer instability with this system as
the cold front comes into the area. While the 1000/850 moisture
transport vectors are pointed directly at our County Warning Area,
there is not a significant increase in precipitable water tonight,
actually the perceptible water starts to decrease after midnight.
Still there is lift and surface convergence with the cold front
and the HREF has a 70 to 90 percent chance of measurable
precipitation with the frontal rain band. The HRRR does show some
shallow convection moving across at least our western CWA in the 4
to 7 am time frame. Remember if you get rain from this it will be
very brief,less than 15 minutes as any one location. There is not
enough instability for thunderstorms so that is out of play for
us. Even so the shallow convection that does come through will be
deep enough to mix down very strong winds so if nothing else you`d
get wind gusts over 50 mph as this moves through.
Once that is done we get a lot of subsidence behind this system so
skies should clear nicely by midday Thursday.
- Quiet Weather Friday and Cooler
There is a trailing 140 knot jet streak that crosses our area on
Friday. Initially being in the right front exit region of that
jet streak we will see mostly clear skies to start the day. We
also have a surface high pressure ridge moving across the area
too, which will help the cause for some sunshine Friday.
Temperatures will be closer to normal too.
- Possible Snow Saturday into Early Sunday
The same jet streak that helped result in a Friday with a fair
amount of sunshine will lead to clouds and possible snow Saturday.
Of course if you have to go through the right exit region of the
jet you should expect to have the right entrance region of that
jet impact you too. So that does happen on Saturday. That entrance
region lift causes a wave on the front which will be stalled
south of us by then. At the same time we have northern stream
shortwave heading our way too.
We then get snow on the north edge of that surface lows
precipitation shield Saturday morning. That may just get far
enough north to impact the I-94 area with a dusting of snow.
The northern stream wave brings is -10c air at 850 so that will be
just cold enough for lake effect snow showers late in the day
Saturday over western sections. Not much of event there either but
just enough to say it snowed.
- Mostly Quiet Weather into Christmas
Next week we have to wait for the impact of Typhoon Rai (140
knots max wind 18z) in the western Pacific to allow the
hemispheric wave pattern to re- adjust to a more phase 7 looking
pattern. That would bring the arctic air into our area, but it may
take until after Christmas for that to happen. Meanwhile some
minor waves on the polar jet may cause a little snow or rain
midweek and possibly near Christmas. It is not out of the question
we could see snow for Christmas yet!
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 704 PM EST Wed Dec 15 2021
Obviously the main story is the strong southerly winds tonight
into early Thursday which will gust to at or above 40 kts at
times. (Exception being MKG which should gust to near 50 kts at
times).
The highest gusts are expected to occur between 06Z and 12Z, give
or take a few hours. Expect to encounter LLWS during landing and
take off as the winds at 2000 ft will be 50-70 kts out of the
southwest tonight, resulting in loss or gain of 20 kts or more.
Expect numerous MVFR cigs tonight and a few scattered showers,
with conditions improving to mainly VFR for Thursday as southwest
winds lower into the 15-30 kt range.
&&
.MARINE...
Issued at 342 PM EST Wed Dec 15 2021
No changes have been made to our marine headlines. All indications
are we will have storm force winds between midnight and sunrise
Thursday morning. The 10 to 15 foot waves are expected to cause
some beach erosion so we will continue the Lake Short Flood
Statement based mostly on the erosion aspect since the water
levels will likely not come within 2 feet of our advisory
criteria base on the GLERL water level model forecast.
We will likely replace the storm warnings with gales into early
Friday then we will also likely need a small craft advisory for
the cold air push Saturday.
&&
.CLIMATE...
Issued at 342 PM EST Wed Dec 15 2021
With the warm temperatures forecast for later today into early
Thursday, we took a look at the records for each day. Some of
these records could be broken. Here are the records:
Wednesday Thursday
Grand Rapids: 60 degrees - 1971 61 degrees - 1984
Lansing: 64 degrees - 1971 61 degrees - 1984
Muskegon: 58 degrees - 1971 58 degrees - 1984
Kalamazoo: 62 degrees - 1975 60 degrees - 1984
Battle Creek: 63 degrees - 1971 61 degrees - 1984
Holland: 61 degrees - 1971 55 degrees - 1992
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Wind Advisory until 4 PM EST Thursday for MIZ046-051-052-057>059-
064>067-071>074.
Lakeshore Flood Advisory until 10 AM EST Thursday for MIZ037-043-
050-056-064-071.
High Wind Warning until 4 PM EST Thursday for MIZ037>040-043>045-
050-056.
LM...Storm Warning until 10 AM EST Thursday for LMZ844>849.
&&
$$
UPDATE...Meade
DISCUSSION...WDM
AVIATION...Meade
CLIMATE...WDM
MARINE...WDM
Area Forecast Discussion
National Weather Service Northern Indiana
623 PM EST Wed Dec 15 2021
.SYNOPSIS...
Issued at 1244 PM EST Wed Dec 15 2021
A cold front will sweep across the area late tonight into
Thursday with a chance for showers along with very gusty winds
between 45 and 50 mph. There will be another chance for rain and
snow Friday night into Saturday. It will then be dry for the first
half of next week.
&&
.SHORT TERM...(This Evening through Thursday)
Issued at 308 PM EST Wed Dec 15 2021
A very strong low pressure system continues to move from southwest
to northeast from the Southern Plains into the Western Great Lakes
area from this afternoon into tonight. A very warm and moist airmass
will be draped across the area as a result. Temperatures will be
able to stall around the upper 50s to near 60 degrees ahead of the
front this evening, which is around 20 degrees above average for
this time of year. Temperatures will wait until Thursday night to
observe a true diurnal low and that will fall into the upper 20s to
low 30s in some spots. When it comes to the moisture column, a mid
level dry slot has eroded precipitation chances except for along any
immediate forcing like the cold front. While there will be a thin
band of 1 inch PWATs and 10C 850 mb dew points, feel the cold front
is so progressive and with limited instability to allow for even
less than 0.25 inch of QPF as it moves through.
Now, for the winds, a 75+ kt low level jet will pass to our
northwest around 6z tonight. However, with the low-mid level warmth,
a low level inversion appears to be in place and will limit
consistent gusts to the 40s of kts at most. Even the pressure rise-
fall couplet is well north of the area where the track of the low
is. As a result, the best gusts will have to come from the forcing
of the front itself or just out in front of it. Could see a few
gusts near to around 50 kts from the front with its additional
forcing. Short range guidance has been increasing gusts in the last
few runs and that presents a little bit more confidence on the
higher gusts in the upper advisory level range, but still struggle
to see more than sporadic gusts at that range. Even at 12z, the core
of the low level jet is now into the northern Great Lakes area and
the cold front forcing is near I-69. Often, our best wind gusts come
from favorable low level lapse rates as the cold air comes rushing
behind the cold front, but with this event the pressure gradient
relaxes during the afternoon and the jet ascends making it harder to
get those stronger winds with the weaker lapse rates.
&&
.LONG TERM...(Thursday Night through Wednesday)
Issued at 308 PM EST Wed Dec 15 2021
Another trough follows the one for the Wed-Thu time period and, as
such, another surge in moisture occurs for later Fri-Fri night time
period. The theta-e plume is much farther south than the Wed-Thu
plume and the QPF output is much farther south as well with areas
south of US-24 really being the only ones seeing any wetting precip
output. Unlike the Wed-Thu time period, this event may have a brief
lake effect snow response later Saturday into Saturday evening.
There is also a stronger surge of colder air with this event as 850
mb temps drop to the upper single digits below zero.
High pressure and ridging follows for Sunday allowing us to dry out
and return to more seasonable temperatures. Models diverge on where
to bring an upper level low pressure system early next week, but
will continue with the blend on carrying null PoPs through the rest
of the period. Upper level lows like this one often bring low
PoPs/QPF anyway.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 622 PM EST Wed Dec 15 2021
Focus on intensifying low pressure system lifting northeast
through the Upper Midwest tonight and then to near James Bay by
the end of the forecast period. Strong south-southwest low level
flow in advance of frontal passage with some mixing in lowest
2kft to bring 40-45 knot gusts to northern Indiana terminal sites
later tonight. Timed highest gusts at KSBN 05-08 UTC and a few
hours later at KFWA per latest hrrr wind gust guidance. Will
continue low level wind shear mention with higher sustained winds
at base of 2 kft inversion. Most intense post-frontal surface
pressure rises to track well northwest through north of region and
core of low level jet tracking eastward into Ohio suggests
lesser/g25-30 knots for much of daytime hours with gradual
veering.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Wind Advisory until 4 PM EST /3 PM CST/ Thursday for INZ003>009-
012>018-020-022>027-032>034.
MI...Wind Advisory until 4 PM EST Thursday for MIZ077>081.
OH...Wind Advisory until 4 PM EST Thursday for OHZ001-002-004-005-015-
016-024-025.
LM...Small Craft Advisory until 7 PM EST this evening for LMZ043-046.
Gale Warning until 11 AM EST Thursday for LMZ043-046.
&&
$$
SYNOPSIS...Fisher/Roller
SHORT TERM...Roller
LONG TERM...Roller
AVIATION...Murphy
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Area Forecast Discussion
National Weather Service Jackson MS
920 PM CST Wed Dec 15 2021
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
Plenty of cirrus overhead, but only patchy stratus as part of that
cloud cover moved quickly to the north. Now, some moisture
advecting into the south is developing clouds into the region as
well. Many varied depictions of how tonight will play out. HRRR in
the latest runs have picked up on the development of the clouds to
the south and spreads them northward over the next few hours.
Given the SREF more or less agrees with the placement...and
therefore where the best chances for fog are (east central and
southeast)...will leave the forecast and the fog graphic alone.
Updating for minor adjustments, but no large scale changes
anticipated at this time.
Prior discussion below:
Tonight through Thursday: Surface and upper high pressure ridging
will prevail tonight into Thursday across the area. Lows tonight
will range from the low 50s in the east to low 60s in the west.
Stratus clouds will once again develop over the area tonight,
along with areas of fog, especially across the Pine Belt area.
Will have to monitor this area for the potential for a dense fog
advisory. A frontal boundary will sag south into northwest
Mississippi and southeast Arkansas on Thursday, with increasing
chances for showers and possibly a thunderstorm across the Delta.
Expect most of the area to remain dry though, as surface ridging
continues to prevail. High temperatures on Thursday will mostly be
in the mid/upper 70s./15/
Thursday night through Tuesday: Low to mid level south to southwest
flow will promote widespread warm advection cloud cover and showers
focused along quasi-stationary surface boundary just to the
northwest of the area at the beginning of the period. While this
boundary looks to retreat to the north as a warm front Friday,
moisture does look to become deep enough over the south by afternoon
for a few showers there. Mid level energy moving out of the Rockies
into the Plains Saturday will bring the cold air back to the
southeast in the form of a cold front. As this occurs, increasing
ascent will promote widespread rain and a few thunderstorms in the
south mainly Saturday afternoon and evening.
Shortwave ridging over the area Sunday will quickly shift east by
Monday as persistent energy over the southwest US, begins to shift
to the east. Flat surface ridge over the southeast US will be slow
to aid in low level moisture return as the mid level system
approaches Monday night. Nevertheless, sufficient ascent and mid
level moisture will still allow for light showers Monday night,
tapering off from the west Tuesday morning./GG/
&&
.AVIATION...
00Z TAF discussion:
VFR in most locations for now, though a swath of lower clouds is
expanding on sat imagery this evening...and GLAMP data seems to be
picking up on it. HRRR has a similar cloud development, but not
until just prior to 05Z. Have pushed more of the forecast to agree
with GLAMP instead of other guidance. Given more stratus
possible...keeping the worst fog in MEI/HBG/PIB for the morning
hours. Cold front approaching from the NW tomorrow may result in
some SHRA for GLH/GWO...but confidence too low for a predominant
condition.
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 59 78 59 77 / 5 13 5 5
Meridian 55 75 58 75 / 3 6 2 9
Vicksburg 60 80 61 78 / 5 18 8 3
Hattiesburg 59 78 59 78 / 5 9 3 23
Natchez 61 79 61 77 / 4 14 3 8
Greenville 60 77 63 75 / 5 35 23 4
Greenwood 62 77 62 75 / 2 23 15 2
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
HJS
Area Forecast Discussion
National Weather Service Jacksonville FL
850 PM EST Wed Dec 15 2021
.UPDATE...
Well-defined sfc coastal trough is noted this evening with fairly
pronounced veering with height per JAX 00Z sounding. Isentropic
ascent is occurring with more cloud cover developing and lift
happening over the northeast FL zones. Shower activity is
persistent and has expanded further since the late afternoon
hours. Latest HRRR shows shower activity continuing late tonight
and then may decrease toward the early morning over the area. Have
confined chance POPs for parts of northeast FL and brought slight
chance POPs northward into southeast GA as well for late tonight.
Rainfall amounts will be light. Main updates tonight were to
increase the POPs and sky cover given the current conditions.
Low temps on track with only gradual fall given the increased
cloud cover and light sfc wind. Patchy fog still expected for
inland southeast GA late tonight.
.MARINE...
Seas and winds look to be a little higher than guidance, so for
the update have extended the SCA overnight for the southeast
marine zone and also included SCEC headline for rest of the
waters.
&&
.PREV DISCUSSION [700 PM EST]...
.NEAR TERM [Through Tonight]...
Surface high pressure well to the north will maintain onshore
flow pattern Tonight. Light winds and clear/partly cloudy skies
expected. Radar has been showing a narrow band of showers just S
of Flagler Co...latest guidance tries to shift this band NW over
Flagler, Putnam and eastern Marion Co through the evening while
gradually diminishing. Will maintain low POPs in that area
Tonight. Latest short-range ensemble guidance suggests potential
for fog across srn GA late Tonight...and have this in forecast.
.SHORT TERM [Thursday Through Friday Night]...
Upper ridge axis over n-ctrl FL early Thursday will shift slowly
SE through this period, while surface ridge of high pressure
gradually shifts southward over the forecast area Friday.
Well above normal temperatures will continue this period, with
high temperatures in the upper 70s to lower 80s, and morning
lows in the 55-60 range.
.LONG TERM [Saturday Through Wednesday]...
For Saturday, broad SW flow aloft expected with surface cold
front approaching the area from the NW. The front moves across the
forecast area Sunday with scattered showers along it. A weak upper
ridge will move over the area Mon/Mon night. Consensus guidance
has it rather wet (50-60 POP) over our area, despite very little
QPF in new models and low MOS POP. Will maintain consensus
guidance, but would not be surprised to see subsequent forecasts
end up drier Mon/Mon night. Strong upper trough approaches
Tuesday and moves over the area Tuesday night. Latest guidance
suggests good rain chance with this system, but consensus guidance
currently has it coming in 12 hrs earlier. Good confidence on
rain potential, but low confidence on timing...better rain chances
could end up Tue night rather than Mon night/Tue. After a warm
weekend, temperatures will cool down to just slightly above normal
during the first half of next week.
.AVIATION...
[Through 00Z Friday]
VFR ceilings around the area at 4-5 kft, except for SSI which
went down to IFR earlier and now has LIFR. Satellite imagery shows
increasing cloudiness moving northwest to west through most of
northeast FL and the low clouds streaming northeast to southwest
around SSI. The low stratus at SSI is anticipated to push slowly
back to the west later tonight with improvement in the sky there
later on, and went with a VFR ceiling by 06Z, though confidence is
only moderate. Light isolated and scattered shower activity this
evening from just east of GNV to just south of SGJ will likely
lift northwest tonight and slowly break up. Kept VCSH around the
JAX metro TAFs and GNV with TEMPO MVFR SHRA for SGJ based on HRRR
run. Otherwise, chances of MVFR ceilings tonight, and possible
IFR around GNV and also near VQQ late. Sky conditions improve
Thursday morning after 12Z-13Z with VFR clouds. Sfc winds will be
northeast 5-10 kt this evening, and then diminish later tonight.
East then southeast winds of 5-10 kt expected on Thursday.
.MARINE...
High pressure well N of the area will weaken Tonight, allowing
winds to weaken over the next few days. Will have the current
SCA, mainly for seas up to 7 ft, expire this evening as
scheduled. The next cold front will move across the waters late
Sunday with scattered showers.
Rip Currents: Moderate through Thursday.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 54 78 56 79 58 / 20 20 10 10 0
SSI 59 74 59 74 60 / 10 10 0 10 10
JAX 60 78 59 78 60 / 30 10 0 10 0
SGJ 63 76 61 77 61 / 30 10 0 10 10
GNV 61 81 59 82 60 / 30 10 10 0 0
OCF 62 81 61 83 62 / 20 10 10 0 0
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...Small Craft Advisory until 3 AM EST Thursday for Waters from St.
Augustine to Flagler Beach FL from 20 to 60 NM.
&&
Area Forecast Discussion
National Weather Service Melbourne FL
1017 PM EST Wed Dec 15 2021
.UPDATE...
Current-Tonight...Stubborn marine showers continue to spread towards
I-95 this evening with highest concentration of rainfall occurring
from Port Canaveral north to the Volusia County coast. Activity is
aided by a flattening inverted trough that has stretched along the
coast most of the day. Most coastal sites have measured rather hefty
rain amounts for mid December but most falling short of rather low
record values. HRRR keeps light to moderate showers continuing
through at least midnight east of I-95 south of Melbourne and inland
to the Saint Johns River for areas north. Have adjusted the PoP
forecast to reflect this, increasing to a chance of showers (30-40%)
for Volusia and a portion of the Space Coast. A bit of low stratus
has already developed over portions of north central FL, so lower
ceilings may filter southward towards Orlando over the next several
hours. Updated sky cover forecast as well to reflect this potential.
Lows tonight in the low to mid 60s, near 70 along the Treasure
Coast.
&&
.AVIATION...
Onshore moving showers will bring brief MVFR conditions to coastal
sites through at least midnight, with meso models ending most precip
by 06Z. KDAB has the highest potential for showers over the next
several hours, so continuing TEMPO mentions with update. Low stratus
has begun to fill in along Nature Coast terminals towards Northeast
FL, so added IFR/MVFR reductions to KLEE/KDAB through the overnight
which will likely need further adjustment.
&&
.MARINE...
Tonight-Thu night...(modified previous) Hazardous marine
conditions will continue through tonight, with overall winds and
seas gradually improving. Onshore winds up to 20 knots will
subside with seas of 5-6 ft nearshore and up to 7 ft offshore.
Seas of 5-6 ft will remain on Thu morning and 4-5 ft by afternoon.
As these continue with this trend, seas of 3-4 ft are expected
Thu night with east winds 10-15 kt. Any shower activity through
midnight across the waters could produce localized higher gusts
and seas, although most activity is on a downward trend.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 77 66 79 63 / 40 40 10 0
MCO 80 66 83 65 / 30 20 10 0
MLB 79 69 81 65 / 60 30 10 10
VRB 79 70 83 66 / 50 30 20 10
LEE 81 65 83 65 / 20 20 10 0
SFB 79 66 83 64 / 30 30 10 0
ORL 80 66 83 65 / 30 20 10 0
FPR 78 69 81 65 / 50 30 20 10
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory until 3 AM EST Thursday for Flagler Beach
to Volusia-Brevard County Line 20-60 nm-Sebastian Inlet to
Jupiter Inlet 20-60 nm-Volusia-Brevard County Line to
Sebastian Inlet 20-60 nm.
&&
$$
SHORT TERM...Smith
LONG TERM....Pendergrast
AVIATION...Smith
Area Forecast Discussion
National Weather Service Pendleton OR
801 PM PST Wed Dec 15 2021
.EVENING UPDATE...Satellite imagery this evening showing extensive
cloud cover continuing to move northeast across the inland PacNW,
while radar is indicating embedded bands of light precipitation
moving across northeast OR and southeast WA. Some of this light
precipitation is falling as rain in those areas warm enough in the
Basin, while a rain/snow mix has been reported in the Gorge, and
snow being reported in high elevation valleys including the Yakima
valley. Tonight, surface frontal system coupled with an offshore
upper closed low will continue to push these bands of
precipitation northeast across the forecast area overnight, with
chances of snow in the mountains and chances of snow and a
rain/snow mix in the lower elevations. In the northern Blues,
Wallowas, and the OR Cascades additional accumulations of 2 to 4
inches will be possible overnight, while everywhere else a trace
to half an inch of snow will be possible. Tomorrow, snow showers
will taper off into the mountains as the upper closed low weakens
into an open wave. This will provide another 1 to 3 inches across
our mountain zones with a dusting possible along foothill
locations. Lawhorn/82
&&
.PREV DISCUSSION... /issued 358 PM PST Wed Dec 15 2021/
AVIATION...00Z TAFs...VFR to IFR conditions to prevail through
the period. A weather system will continue to spread a band of
precipitation northeastward across the forecast area. The heaviest
precipitation is expected across the Blues overnight, while sites
PDT/YKM/ALW/PSC will see chances of a rain and snow mix
transitioning over to snow late this evening. By sunrise tomorrow,
precipitation will have moved out of the region with dry
conditions returning. Ceilings and vsby will become MVFR to IFR at
sites DLS/PDT/BDN/YKM/ALW/PSC behind the band of precipitation,
with these conditions persisting overnight. Sites RDM/BDN/YKM
will improve to VFR by tomorrow morning. Breezy winds 10 to 15 kts
will continue into the evening at sites PDT/RDM/BDN/ALW, but will
become light after 03Z. Otherwise, winds will be light at all
sites through the rest of the period.
PREV DISCUSSION... /issued 244 PM PST Wed Dec 15 2021/
SHORT TERM...Tonight through Friday Night...The main sensible
weather concerns revolve around winter weather over the next 24-30
hrs. While no change in the winter headlines, there is increased
potential for light snow in the lower WA Basin. Latest water
vapor imagery shows an broad upper level trough over the western
US with an closed low apparent offshore the PacNW coast. This
upper-level closed low is anticipated to weaken into an open wave
tonight while it moves across OR to NV by early tomorrow. This
will set the stage for predominantly likely to definite PoPs
overnight across the Cascades, eastern mountains and the Basin.
The area will see modest upward moisture transport and isentropic
ascent tonight, especially across south central WA. Meantime, the
Grande Ronde Valley and Foothills of the Blues will continue to
see moderate gusts early tonight, peaking ~35 mph, with
downsloping flow in the foothills. Main concerns initially will
be p-type and amounts in the lower Basin wherein hi-res guidance,
recent HRRR runs and HREF, continue to show potential for light
snowfall late tonight through the small hours in the Lower WA
Basin to northern Blues. Of which, there will be less dry air in
the lower troposphere to overcome in tandem with the sufficient
ascent. Current thinking is around a half inch. Confidence is
moderate there with a high-end amount of around an inch reasonable
in the Tri-Cities. Otherwise, the northern Blues will see start
seeing snow tonight with the heaviest amounts above 4500 ft with
this event. Current thinking is 5-8 in the northern Blues.
Elsewhere, new snow in the OR Cascades will amount to 4-8,
highest near the crest. Snow should initially start winding down
in the OR Cascades tomorrow with snow likely to continue in the
northern Blues through the PM owing to orographic ascent. The
latter should see snow end by late evening presently. A reprieve
in the pattern is expected Friday as an upper-level ridge builds
in. This will be accompanied by seasonable temperatures tomorrow
night and Friday.
LONG TERM...Saturday through Wednesday...Guidance suggests that the
extended period will be dominated by deep troughing offshore with
southwesterly flow aloft, though both ensemble means and cluster
analysis reveal differences in timing and amplitude of the wave.
Moreover, deterministic runs favor forming multiple cut-off lows and
are inconsistent in their tracks and when the cut-off low will re-
open into an open wave. Currently, the EFI is highlighting Saturday
night and Sunday morning as a period of interest for winds across
the Blues, Foothills of the Blues, and the Grande Ronde Valley. The
ECMWF ensemble has a 50-90 percent chance of winds reaching or
exceeding 34 kts across the aforementioned region Saturday night and
Sunday morning. Otherwise, the period will continue the recent trend
of active weather across the Pacific Northwest with mountain snow
and potentially some light low-elevation rain/snow. Plunkett/86
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 28 39 26 38 / 50 30 10 0
ALW 30 40 30 40 / 70 50 20 0
PSC 31 40 27 37 / 50 10 0 0
YKM 24 36 21 38 / 60 10 0 0
HRI 29 41 28 38 / 50 20 0 0
ELN 20 33 22 36 / 40 10 0 0
RDM 25 43 22 41 / 30 20 0 0
LGD 27 37 23 37 / 50 40 40 0
GCD 25 37 23 39 / 80 30 20 0
DLS 31 42 32 43 / 70 30 10 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 10 PM PST Thursday for ORZ502.
Winter Weather Advisory until 4 PM PST Thursday for ORZ509.
WA...Winter Weather Advisory until 10 PM PST Thursday for WAZ030.
&&
$$
EVENING UPDATE...82
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
915 PM EST Wed Dec 15 2021
.SYNOPSIS...
High pressure will extend across the Carolinas and Mid Atlantic
through tonight. Warm return flow will develop Thursday as the high
moves offshore and a cold front begins to approach from the west.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 915 PM Wednesday...
915PM Update...Latest satellite imagery shows a low cloud deck
slowly meandering along the Coastal Plain. Patchy fog is expected
across central NC overnight with reduced visibilities until after
sunrise Thursday morning. Temperatures overnight will slowly drop
into the low/mid 30s in the NW and upper 30s low 40s in the SE.
Otherwise high pressure will dominate the region tonight and
Thursday, before moving offshore on Friday.
As of 240PM...A strong upper ridge is centered roughly over the SE
US today, with a strong but slowly weakening surface high pressure
ridge extending down the mid-Atlantic states its parent 1035mb high
departs to the east of Maine. Skies have cleared since this
morning, and except for some thin cirrus and cirrocu drifting over
the upper ridge, will remain so this evening. As the surface
continues to weaken, light swrly wind will attempt to develop,
though the pressure gradient should remain sufficiently weak for
calm conditions and good radiational cooling tonight. Given the
increase in low-level moisture last night and increased moisture
over the Savannah River Basin/Upstate SC, there should be some low
clouds to develop across the piedmont and coastal plain after
midnight, or be advected in from Upstate SC into the western
Piedmont by sunrise. Guidance suggests a smattering of clouds but
not completely overcast everywhere. Fog may also develop in spots
around the Piedmont and coastal plain, though confidence in a large
area of dense fog is low. Lows will be in the mid to upper 30s,
though lower 30s are possible in the western Piedmont on the edge of
the low clouds...if they do develop in the east.
&&
.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
As of 240 PM Wednesday...
Warm swrly flow will develop on Thursday between the offshore
surface high and a cold front moving through the Midwest. Mixing
will be deeper in this flow regime, though still relatively shallow,
and 925mb temps climbing back to 11-12C suggest highs in the upper
60s to lower 70s, with wind gusts to 15-20kt in the afternoon. The
NAM shows stratus lingering much longer than the GFS, but without a
supporting surface high, prefer to hedge toward warmer NBM/GFS-like
temps. However there is some forecast bust potential.
Stratus is plausible again Thursday night as moisture continues to
advect around the offshore high. Pre-frontal low-level winds are
forecast to have a little more westerly component across the western
Piedmont as the cold front in the Midwest begins to pivot to more SW
to NE, so perhaps the stratus may be focused more in the east.
However, the split between the GFS and NAM handling of the moisture
continues, so confidence remains low on the favored area for clouds.
Lows will be much milder in the upper 40s and lower 50s.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
As of 355 PM Wednesday...
A subtropical ridge aloft will remain off the Southeast US coast on
Friday and Friday night, resulting in dry weather for central NC as
a quasi-stationary front remains hung up well to our west and north
from Texas to the northern Mid-Atlantic. At the surface, high
pressure that had been centered over the area today will have
shifted east and offshore, resulting in southwesterly flow and
temperatures well above normal on Friday and Saturday. Forecast
highs on Friday and Saturday are in the lower-to-mid-70s, or roughly
20 degrees above normal. Thus the record high of 72F at RDU on 12/17
(Friday) could be in jeopardy. The return flow around the high will
keep some low-level moisture/cloudiness in place particularly on
Friday and Saturday mornings and in the NW Piedmont. This will help
keep temperatures very mild on Friday night with lows only in the
lower-to-mid-50s (20-25 degrees above normal).
Precipitation chances will increase for the weekend as a strong cold
front crosses the region late Saturday night into early Sunday
morning. Medium-range guidance generally agrees that it will have
enough moisture with it to be accompanied by some showers,
particularly in the south and east, so have likely POPs there and
high chance in the NW. However, similar to recent frontal passages,
there is no wave along the front and it does not look to have a ton
of moisture associated with it. Thus rainfall amounts do not look
impressive at this time, and WPC QPF continues to be a quarter of an
inch or less. Also continue to leave out any mention of thunder as
instability looks virtually non-existent, especially with the timing
of the front being at night. There is high confidence in a period of
no precipitation chances behind the front with dry NW flow aloft,
from later Sunday into Monday, with much cooler temperatures. Highs
will only be in the upper-40s to 50s, with lows Monday morning in
the mid-20s to lower-30s.
However, uncertainty then increases for the rest of the period as
models continue to struggle with the evolution of a potential
coastal low early next week. A southern-stream shortwave trough over
the Baja region will finally get ejected eastward by a closed
mid/upper low moving towards the Pacific NW. Models continue to be
slower and slower with the shortwave, with both the GFS and ECMWF
bringing it across Texas on Monday, along the Gulf Coast on Tuesday,
and off the Southeast US coast on Wednesday. At the surface, both
models also show a coastal low developing off the Southeast US coast
on Wednesday. However, while the 00z runs came back north a bit, the
12z GFS and ECMWF are much more suppressed with this low than they
were previously, mainly dry for central NC. The vast majority of
ECWMF ensembles are dry as are roughly two-thirds of GFS ensembles,
even for the south. Thus just have low chance POPs in the far south
on Tuesday and Tuesday night, with slight chance elsewhere, and if
these trends continue, POPs will need to be lowered even more. It`s
also looking increasingly like an all-rain event with no ptype
issues if it does occur, as the later timing of the system means
there will be no high to the north to supply cold air. Temperatures
on Tuesday and Wednesday will begin to moderate with highs in the
mid-to-upper-50s.
&&
.AVIATION /00Z WEDNESDAY THROUGH MONDAY/...
As of 640 PM Wednesday...
High confidence in VFR conditions through the evening into the
overnight hours, but confidence drops for the period around sunrise.
Both MOS guidance and model soundings show varying situations. The
NAM and RAP soundings show seemingly non-meteorological soundings,
with exceptionally strong and shallow inversions present at the
surface across eastern terminals. Meanwhile the GFS shows minimal
saturation through the profile. With such widely varying model
solutions, do not have the confidence to make any changes to the
flight category forecasts, which includes a MVFR tempo at sunrise at
INT/GSO and prevailing LIFR conditions at RDU/RWI/FAY. In addition,
there is a marginal threat for low-level wind shear, primarily near
the Virginia-North Carolina border, but wind speeds at 2000 ft are
not quite high enough to include LLWS in the TAFs. Finally, the
primary change to the forecast with the 00Z TAF package was to
slightly lower wind forecasts Thursday afternoon, as gusts do not
appear to be as strong as previously forecast.
Outlook: Areas of stratus and fog are expected to redevelop Thu
night-Fri morning, followed by a chance of rain/showers Sat-Sat
night.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Smith
NEAR TERM...CA/Smith
SHORT TERM...Smith
LONG TERM...Danco
AVIATION...Green/Smith/MWS
Area Forecast Discussion
National Weather Service Reno NV
155 PM PST Wed Dec 15 2021
.SYNOPSIS...
Another winter storm will bring moderate to heavy snowfall with
windy conditions this afternoon through Thursday morning. Whiteout
conditions are possible in the Sierra. We should see a break from
significant storms Friday through Sunday, but a weak system
possible by late Sunday. An active storm pattern is likely for
next week. Plan on delays and impacts for holiday travel.
&&
.SHORT TERM...
After a very brief break in the action, our next winter storm is
already affecting portions of northeast California and will be
moving into the Sierra and western Nevada this afternoon and
evening. The commutes this evening and again Thursday morning will
be slow with periods of near impossible mountain travel overnight
in the Sierra due to white out conditions. If you can avoid
traveling, that`s best. Otherwise, allow plenty of extra time and
be sure to have a winter travel kit. Check with CalTrans, CHP,
NDOT, and NHP for the latest on road conditions. Here are the
storm highlights:
*WINDS*
S-SW winds have begun to increase across ridgelines, with winds
anticipated to mix down to valley areas this afternoon and evening.
HREF guidance still shows the strongest winds late this evening and
overnight along the Sierra Front and Eastern Sierra, mainly along
the 395 corridor from Reno south through Mammoth. Per NBM
probabilities, there is a 40% chance to see wind gusts exceed 50 mph
in wind prone locations along the Sierra Front (which is down 10%),
increasing to around 70% chance (down 5%) in the Eastern Sierra.
This is also reflected in the ENS meteograms as well.
*SNOW LEVELS*
A rather complicated snow level forecast for lower valleys with
our incoming system. While there is plenty of cold air in place
for all elevations, the aforementioned S-SW winds will bring some
warming to the region, actually leading to snow levels potentially
rising after sunset Wednesday night. Looking at probabilities,
the 25th-75th percentiles keep snow levels in the 4400-4800` range
during the "warmest" portion of the storm overnight. However,
looking at wet bulb temperatures, it would suggest keeping snow
levels at all valley floors. One other "fun" item to contend with
is if we go convective (lightning is being observed off the Oregon
coast as of the time of writing), which could also drag snow
levels down. One final complication is that sheltered valleys
which do not mix out overnight may stay snow the entire time. So,
we could end up with valleys at the same elevation receiving
different precipitation types simultaneously. The big takeaway
here is there is a large boom or bust potential in snow totals for
the lower elevations of the Sierra Front, including the Greater
Reno-Sparks- Carson metro areas. For areas above 5000 feet, it
should be all snow tonight.
*SNOW TOTALS*
Official forecast is 1-2.5 feet in the high Sierra, with a 20%
chance to exceed 3 feet along the Sierra crest. Per the NBM, there
is an 95% chance for at least 8 inches in the Tahoe Basin and a 70%
chance for 1 foot; these probabilities are up from yesterday.
Lesser amounts are anticipated along the US-395 corridor in
northeast California and the Eastern Sierra of Mono County where
totals should range from 2-6" per probabilistic guidance. For
western Nevada, the varying snow levels could lead to lower
elevation totals ranging from a dusting upwards to several inches.
If the precipitation type remains snow, a boom scenario of 3-4"
for the lower valleys is possible with 6-8" in the foothills,
about a 20% chance of this occurring. The highest rates will be
from sunset Wednesday through daybreak Thursday where the Sierra
could see 1-3"/hour snowfall rates. In western Nevada, HRRR
guidance suggest the highest rates will be from about 9 pm through
4 am. Snow showers could continue through midday Thursday. -Dawn
.LONG TERM...(Friday Onward)...
Friday will be a good day to continue digging ourselves out of
this past week`s impressive snowfall. With a fresh round of snow
falling most places in the short term, expect some travel impacts
due to icy roads once again Friday morning as teens and single
digit lows will refreeze road surfaces. With cold surface
inversions and not much in the way of winds (except for breezy
ridges), we will fail to completely mix out during the afternoon
and only warm up into the 20s and 30s.
Moving along to the weekend, Saturday looks to be another quiet
day with pleasant weather as a cutoff trough meanders over the
Baja of California and "weak" ridging moves over our area. Calm
winds and a slight uptick in high temperatures (30s and 40s)
during the day with mid/high level clouds pivoting around the
ridge.
Ensemble guidance continues to be in very good agreement of a
large omega blocking pattern over the Central Pacific with
anomalous high pressure extending well into Alaska. Cluster
analysis allows for high confidence that this pattern will persist
through the forecast period (next Thursday) and a medium
confidence it`ll continue through Christmas; with the variation in
days 8-11 mostly with respect to the placement of the ridge. For
the next 7 days at least, this puts the West coast of the US in a
favorable location (to the east of the omega block) for longwave
troughing to bring us bouts of winter weather.
The first of these systems may arrive as early as Sunday
afternoon/evening with an increase in winds bringing the chance of
some recreational disruptions to the Sierra. Lower confidence on
the onset, and type of precipitation for lower elevations below
lake level. Simulations at this time suggest accumulating snow may
begin by late Sunday evening into the overnight hours for the
Sierra, with a low chance (30%) of measurable snowfall working
it`s way down to valley floors by Monday morning commute. Higher
confidence increases in precipitation chances through the day on
Monday through Tuesday with a big question mark on precip type
below 4500ft during the afternoon hours. Plan on travel &
commuting impacts but definitely stay tuned to the forecast going
through the weekend so you can prepare/adjust accordingly.
It`s a bit challenging to split up, or differentiate storms next
week at this point as the "storm door" will stay wide open for us
with numerous shortwaves pivoting along the longwave trough. It`s
safe to say that we have a guaranteed chance to see appreciable
snow & QPF amounts by the end of the work week. Which part of the
Sierra will receive the most, and what our impacts look like
across Western Nevada, will have to be ironed out in the coming
days.
-Dustin
&&
.AVIATION...
Winds are already increasing aloft ahead of our next winter storm
with wave clouds evident on satellite and out the window and
turbulence and wind shear likely through tonight. SW-W FL100 winds
should be sustained at 55-65 kts tonight, decreasing slowly
through the day tomorrow.
Snow is already affecting NE CA terminals, spreading into the Tahoe
Basin between 22-02z and across into western Nevada between 00-02z.
It will reach west central Nevada and Mono County 04-08z tonight.
Anticipate 10-16" of snow accumulation at KTRK and KTVL overnight
with 4-8" for KMMH. There will be widespread mountain obscuration
through midday Thursday.
For western Nevada, including KRNO/KCXP/KMEV/KNFL the precipitation
type is going to be rather tricky tonight. Looking at probabilities,
the 25th-75th percentiles keep snow levels in the 4400-4800` range
during the "warmest" portion of the storm overnight. However,
looking at wetbulb temperatures, it would suggest keeping snow
levels at all valley floors. So, we could see anywhere from a
dusting up to several inches at airport sites. Widespread MVFR-IFR
conditions are anticipated overnight.
Flying conditions will be much improved Friday and Saturday. -Dawn
&&
.REV Watches/Warnings/Advisories...
NV... Winter Storm Warning until 10 AM PST Thursday NVZ002.
Winter Weather Advisory until 10 AM PST Thursday NVZ005.
Winter Weather Advisory until 10 AM PST Thursday NVZ003.
CA...Winter Storm Warning until 10 AM PST Thursday CAZ072.
Winter Weather Advisory until 10 AM PST Thursday CAZ070-071.
Winter Weather Advisory from 7 PM this evening to 1 PM PST
Thursday CAZ073.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno