Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/17/21
Area Forecast Discussion
National Weather Service Burlington VT
931 PM EST Thu Dec 16 2021
After recording breaking temperatures today, a cold front will
sweep across the region tonight with gusty westerly winds and
cooler temperatures by Friday. Localized gusts up to 55 mph are
expected over northern New York with 35 to 45 mph over much of
Vermont with some isolated to scattered power outages. A
widespread light to moderate snow is anticipated this weekend
across most of the North Country, which could end as a period of
freezing drizzle early Sunday morning. Temperatures will be
trending back toward normal, especially by this upcoming
.NEAR TERM /THROUGH FRIDAY NIGHT/...
As of 928 PM EST Thursday...Wind gusts between 45 and 55 mph
have materialized this evening across the St. Lawrence Valley.
Based on high resolution model data and upstream observations,
we will continue to see these strong gusty winds through
midnight or 1 AM before we begin to see winds weaken slightly.
There are still some signs that winds could exceed 60 mph but as
mentioned earlier, these would be the exception and not the
rule. Over the next hour or so we should get a good idea on the
extent of the mixed layer and will be able to fine-tune winds a
little more if need be if winds are expected to be stronger
than currently forecast.
A high end wind advisory for gusts between 55 and 59 mph
continues for most of northern NY and parts of central-southern
VT tonight with scattered power outages expected.
Water vapor shows mid/upper lvl trof and embedded 5h vort moving
acrs the northern/central Great Lakes this aftn, while a strong sfc
cold frnt is approaching the eastern Great Lakes with ribbon of mid
lvl moisture. This boundary wl quickly approach the SLV by 00z and
sweep acrs our cwa btwn 02z-06z with a period of very gusty winds
expected, especially acrs northern NY. Soundings continue to support
bottom of mixed layer winds of 45 to 50 knots with favorable mixing
profiles as lapse rates steepen under moderately strong caa. This
combined with unidirectional and well aligned sw to ne flow support
localized gusts in the SLV up to 55 mph with some values near 60 mph
possible at Massena and Malone. Have continued with strongly worded
wind advisory, as the probability of widespread gusts over 60 mph is
relatively low. The core of strongest 925mb to 850mb winds of 55 to
65 knots moves acrs the SLV/northern NY btwn 00z and 05z tonight and
shifts into VT btwn 03z-10z. Outside advisory still anticipating
some gusts in the 30 to 40 mph range with some isolated gusts up to
45 mph in favorable downslope regions east of the Greens into parts
of the NEK. A few power outages are possible.
Have noted the HRRR and NAM3km shows a very weak broken line of fast
moving showers developing just ahead of boundary tonight. Have
continued to mention chc to low likely pops mainly northern NY, with
any convective showers having the potential to transfer gusty winds
aloft toward the sfc. This would be covered in a sps type product if
this scenario was to develop. The threat of rain showers weakens
further east, as better dynamics slide to our north and ribbon of
moisture dissipates, but 700mb fgen forcing is still rather strong
Record warm temps have occurred acrs the region today with values in
the mid 50s to lower 60s and expect many values to hold steady this
evening, given the gusty winds. Sfc wl begin to fall sharply aft
fropa with lows generally in the mid 30s to lower 40s, which is
still well above normal for this time of year. For Friday cwa
remains on under modest llvl caa on westerly winds, so anticipate
temps only warming a few degrees into the mid/upper 30s to mid 40s,
warmest in the CPV and lower CT River Valley. Weak high pres tries
to build southward on Friday Night with cooler temps and dry
.SHORT TERM /SATURDAY THROUGH SUNDAY/...
As of 308 PM EST Thursday...A developing low pressure system will
track up the Ohio River Valley during the day on Saturday,
eventually moving into southern New York State Saturday evening
before transferring it`s energy to an offshore low. Our forecast
area will be in a favorable location for a brief burst of warm air
advection driven snowfall Saturday evening into Saturday night,
briefly additionally supported by some enhanced mid-level
frontogenesis. Models continue to indicate a dry slot wrapping into
the system around midnight Saturday night/Sunday morning, which will
bring a rapid end to the steady snow and allow conditions to turn
more showery. In addition, continues to appear the snow growth zone
will lose saturation as the dry-slot wraps in, which may support
some brief freezing drizzle early Sunday morning with the loss of
ice nuclei. Any ice accumulations at the surface would be minimal,
but conditions may briefly become slick overnight into Sunday
morning. Storm total snowfall amounts from Saturday afternoon
through Sunday morning range from 3 to 6 inches...with the lower
amounts expected over the Saint Lawrence Valley and increasing
amounts towards 4-6 inches expected eastward into eastern Vermont.
Ice accumulations look to be a trace or less at this point, but will
continue to monitor. Winds are not expected to be a concern for the
system, although we will see some brisk northwesterly winds behind
the system on Sunday afternoon. Snow ratios will be generally
between 10:1 and 15:1, so not expecting many negative impacts with
the system unless ice amounts trend upwards. For now looks like a
beneficial quick snowfall for a snow-starved area.
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 308 PM EST Thursday...The forecast for Monday onward features
generally unblocked, progressive zonal flow, which will prevent the
development of any large storm systems. Will see a few clipper-type
systems zip through, notably Monday night/Tuesday morning, and again
Wednesday night/Thursday morning timeframe. Expect some brief,
light snow with the initial system Monday night/Tuesday morning with
only very light accumulations (lower elevations may not see any snow
at all). Precipitation type for the next system (thinking Wednesday
night/Thursday time frame) is a little more up in the air as models
struggle with the track of the low this far out. For now
forecasting snow, but this may change. Between the quick clipper
systems, will see brief ridges of high pressure build in that will
support some seasonably cold overnight lows in the single digits for
a few nights. Highs will generally be in the mid 20s to mid 30s next
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Through 00Z Sunday...Strong and gusty winds will continue to be
the major aviation concern at all TAF sites through tonight.
Associated with these strong winds will be areas of moderate to
severe turbulence and LLWS. 850mb LLJ ~50 to 65 knt continues
to strengthen this evening and into the overnight hours, with
the core of strongest winds occurring between 02z and 08z. This
will cause localized gusts 40-45 kt at KMSS, near 40 kt at KSLK,
and 25-30 kt at KPBG/KBTV/KMPV sites overnight. A strong cold
front will produce scattered showers, mainly over northern NY,
with ceilings trending toward MVFR conditions at SLK late tonight.
Winds decrease on Friday with VFR conditions prevailing at all
sites except KSLK by 18z.
Friday Night: VFR. NO SIG WX.
Saturday: Mainly VFR, with local MVFR possible. Slight chance SN.
Saturday Night: MVFR and IFR. Definite SN, Likely SHSN, Chance
Sunday: Mainly MVFR, with areas VFR possible. Chance SHSN, Chance
Sunday Night: VFR. NO SIG WX.
Monday: VFR. NO SIG WX.
Monday Night: Mainly VFR, with local MVFR possible. Slight chance
Tuesday: Mainly MVFR, with areas VFR possible. NO SIG WX.
Expect gusty winds to continue over Lake Champlain right
through Friday. Look for south winds in the 15 to 25 knot range,
but increasing into the 20 to 30 knot range with gusts to 40
knots tonight. The winds will shift to the west later tonight
and begin to gradually taper off through the day on Friday.
Waves will be in the 2 to 4 foot range, but increase at time
into the 3 to 6 foot range. This will create very choppy
conditions across the lake, especially the north half of the
lake give the strong southerly wind expected.
High temperatures across the North Country will be well above
normal today 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
VT...Wind Advisory until 10 AM EST Friday for VTZ012-019.
NY...Wind Advisory until 7 AM EST Friday for NYZ026-027-087.
Wind Advisory until 10 AM EST Friday for NYZ028>031-034.
Area Forecast Discussion
National Weather Service Medford OR
455 PM PST Thu Dec 16 2021
The Marine and Aviation sections have been updated...
.DISCUSSION...Today through Friday night. Today`s weather is much
quieter than yesterday, and we expect mostly dry conditions to
continue through much of Saturday at least. We`re forecasting
temperatures to be lower tonight than dynamical models statistical
guidance suggests, mainly because of widespread snowpack, partial
clearing, and light winds. Single digit low temperatures are
possible anywhere east of the Cascades where clouds clear tonight.
Latest RAP model data suggests the best chance for clouds
clearing and very cold temperatures are in southeastern Modoc
County, western Lake County, and much of Siskiyou County. West of
the Cascades on the Oregon side, we expect fog and low clouds to
linger through much of the night, but low temperatures will still
be below freezing most places.
Tomorrow, conditions will be dry, and given we`re in the middle of
December and following recent precipitation, it will be tough for
valleys to clear out from any low clouds, so expect plenty of
clouds in valleys west of the Cascades through at least the
Saturday through Wednesday...The timing on the next system
appears to be happening later and later with the next system
arriving some time Saturday afternoon. This system, however, will
keep the active pattern going. This system will mimic that of a
front/atmospheric river hybrid. Precipitation will begin with low
snow levels around 1500 to 2500 feet and rise to around 6000 to
7000 with the start of precipitation. Then the front moves inland
and snow levels fall to around 3000 feet by Saturday night. This
system has been interesting to watch as the projected impacts will
depend strongly on the timing of the snow level drop. As of this
iteration of the National Blend of Models, the heaviest
precipitation looks to coincide with the drop in snow levels.
Yesterday, the heaviest precipitation west of the Cascades came
with 7000 foot snow levels, and now it comes with around 4000 foot
snow levels. This inspires low confidence in the details of the
forecast. Still, this could mean some impacts for passes for folks
traveling the weekend before the Christmas and Kwanzaa holidays.
The other thing worth noting here is that snow levels look to only
rise in areas along and west of the Cascades with a sharp drop in
snow levels for areas east of the Cascades, and precipitation
seems to follow suit with markedly less precipitation expected
east of the Cascades with this system.
Then, a brief break is expected Sunday night into Monday before the
active weather pattern continues as a low pressure system offshore
spins up moisture and rainfall into southern Oregon and northern
California for most of the rest of the week. Precipitation is
expected to be relatively light, and snow levels will hover between
3000 and 5000 feet with impacts possible for passes as travel begins
increasing ahead of winter holidays. In fact, for the remainder of
the year, ensembles are trending towards a wetter and cooler pattern
overall for southern Oregon and northern California. -Schaaf
MVFR across many valley areas and partial terrain obscurations will
continue this evening. IFR to LIFR is expected to develop in most
valley areas tonight as the higher terrain clears. Mid level clouds
are expected to move in Friday afternoon as IFR to LIFR improve to a
mix of MVFR and VFR. ~BTL
.MARINE...Updated 300 PM PST Thursday, 16 December, 2021...
Steep seas dominated by a westerly swell are likely to remain at
advisory level through late this evening. Light winds and low seas
are then likely Friday and Friday night. A frontal system will then
move in Saturday into Sunday with gales possible and very steep,
hazardous seas likely Saturday afternoon through early Monday.
Active weather is then likely to continue through next week as broad
low pressure stalls along and near the Pacific northwest coast. ~BTL
Pacific Coastal Waters...
Small Craft Advisory until 10 PM PST this evening for
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
539 PM CST Thu Dec 16 2021
.DISCUSSION...(This evening through Wednesday)
Issued at 322 PM CST Thu Dec 16 2021
A rather uneventful forecast is upon us, especially in comparison to
the past several days. High pressure will make slow inroads into the
area tonight but will be on the weak side, just enough to allow an
inverted trough of low pressure to drift across the region Friday
afternoon through Friday night. While limited in moisture, the cold
residual air in place will be able to squeeze out some light snow
over western and northern portions of the WFO MPX coverage area late
Friday afternoon through Friday night. Though moisture will not be
overly deep, it will be located mainly within the DGZ, thus allowing
for some minor accumulations should duration allow as such.
Accumulations will be limited to roughly along and west of a line
from Cambridge to St. Michael to New Ulm. And even then,
accumulations won`t be much, up to around an inch. Once this trough
ejects off to the east Saturday morning, the remainder of the
forecast period remains dry. This includes the potential of a frontal
passage Sunday night to early Monday, but the lack of upper level
support plus a dearth of moisture forces a dry forecast to be
Along with a dry forecast being maintained, temperatures will have
little day to day variation throughout this forecast. While a few
minor perturbations daily can be expected, overall temperatures will
remain fairly steady and near-to-above normal. Through the first half
of next week, highs will run in the teens and 20s while lows bottom
out in the single digits and teens. Even some sub-zero temperatures
are possible during the early mornings Sunday and Tuesday.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 527 PM CST Thu Dec 16 2021
Mainly clear skies are expected tonight, but Friday morning, an
inverted surface trough will move up along the SD/MN border. This
looks to provide enough forcing to produce an area of light snow.
There`s quite a bit of spread with how quickly snow will develop, but
followed the idea of the RAP and HRRR with snow developing around 15z
to the west of RWF that lifts north toward AXN by the afternoon.
Other than that potential area of snow, dry conditions are expected,
with skies remaining VFR.
KMSP...There`s a small chance of seeing snow around 18z as the
western MN snow band lifts north into central MN. Otherwise any
additional snow and sub VFR chances hold off until closer to 12z
/OUTLOOK FOR KMSP/
Sat...MVFR cigs. Wind NW 10-15 kts.
Sun...VFR. Wind S 10-15 kts.
Mon...VFR. Wind NW 10-15 kts.
Area Forecast Discussion
National Weather Service Mount Holly NJ
922 PM EST Thu Dec 16 2021
A cold front will approach the region tonight and pass through early
Friday morning. High pressure will return briefly from the north
through Friday night, then a warm front will lift north and stall
across the forecast area on Saturday. Associated low pressure will
pass over the region Saturday evening then high pressure will return
through early next week. A coastal system will pass well south of
the area during the middle of next week.
.NEAR TERM /THROUGH FRIDAY/...
Forecast mostly on track. Some weak shortwave energy will pass
through the region this evening ahead of an approaching cold
front. Now the 00Z/17 NAM and 01Z/17 HRRR both fairly dry, so
will keep no PoPs in the forecast and will keep a few hours of
sprinkles throughout the region with the passage of that
The front`s main effects will be rapidly decreasing dew points
Friday morning and a switch in wind direction from southwest to
west or northwest. Fortunately, the surface pressure gradient will
be fairly modest, so despite minimum relative humidity values
near or perhaps even slightly below 30 percent, wind speeds look
marginal at best for meeting fire-weather thresholds. See more in
the fire-weather discussion below. The origins of the system are
warm, so only modest cooling is expected for Friday. Statistical
guidance has trended a little cooler from previous forecasts, but
consensus still has highs a good 10-15+ degrees above seasonal
averages for Friday.
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
A broad mid-level ridge axis and an associated jet streak will
build over the area Friday night into Saturday. This axis will
shift offshore late Saturday then the main trough axis will move
offshore on Sunday. At the surface, cold high pressure will be
just north of New England on Saturday resulting in a cold air
damming setup for our northern zones. A surface low across the
Ohio Valley will pass over the area Saturday evening with a warm
front lifting north and stalling near the I-95 corridor ahead
of it during the day. This is expected to result in a
significant temperature gradient from north to south, with
temperatures in the 30s and low 40s across the higher terrain
near and north of I-78 with 60s across much of Delmarva.
The upper-level support is not particularly strong for
precipitation, however there will be strong overrunning and
isentropic ascent near and north of the baroclinic zone lifting
north and eventually stalling across the area on Saturday. Thus,
we are still expecting periods of rain to move into the area
late Friday night and early Saturday. The greatest ascent and
thus coverage of precipitation is expected to be near and north
of I-95 and this will lift north a bit throughout the day.
Portions of far southern New Jersey and much of the Delmarva
peninsula may actually remain largely dry during the daytime on
Saturday, but a few rouge showers cannot be ruled out.
The latest mesoscale guidance has trended stronger with the
surface ridging (cold air damming) Saturday morning near and
north of the Lehigh Valley. The RGEM and NAM tend to handle
these shallow cold air patterns fairly well (in some cases a
little too strongly), but this trend was considered in the
latest forecast. Thermal profiles will not be supportive of snow
with a warm nose building in quickly across the north as
precipitation begins late Friday night and early Saturday.
However, depending on the depth of the cold air damming, we very
well could see a mix of freezing rain and/or sleet across the
higher elevations north of I-78. If the surface temperature is
able to remain near freezing, we could see some minor ice
accretion or possibly some very minor sleet accumulation in some
spots. Given the uncertainty and marginal setup for any
impacts, we have opted not to issue any Winter Weather
Advisories at this time, but this will need to be reevaluated.
The greatest chance of any accretion/accumulation would be
Saturday morning, generally before noon, as temperatures will
begin rising into the afternoon.
The surface low will pass directly over the forecast area
Saturday evening, and surface temperatures will generally rise
through much of the evening. High pressure and cold advection
will ramp up quickly behind it Saturday night as a cold front of
sorts passes through. The rain will end from north to south by
late evening. Lows will be mainly in the 30s as northwest winds
High pressure will continue building into the area into Sunday
and initially breezy conditions will abate into the afternoon
and evening along with clear skies. Expect high temperatures in
the 40s in most locations and in the mid to upper 30s north of
I-78. High pressure overhead Sunday night will yield ideal
radiational cooling conditions, thus went a bit cooler than
guidance for this period. Low temperatures will be in the low to
mid 20s with upper teens across the higher terrain and typical
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Mostly zonal mid-level flow will prevail through the middle of
next week, then a southerly stream trough will move across the
Gulf Coast on Tuesday and off the Southeast coast on Wednesday.
This will likely result in a coastal low forming and staying
well south of our region with high pressure largely dominating
the sensible weather. The cold high pressure initially over the
area will result in a rather chilly day Monday with highs around
40, then temperatures will rebound to near normal with highs in
the mid to upper 40s and lows in the 20s to around 30 degrees
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE,
KRDG, KILG, KMIV, KACY and surrounding areas.
Tonight...VFR. Light S winds, veering to the SW less than 10 kt
through 06Z, and then winds continue to veer to the NW by 12Z.
LLWS concerns at 1500 feet with SW winds 45-50 kt through
05-07Z. Moderate confidence.
Friday...VFR. NW winds around 10 kt with gusts up to 20 kt in
the afternoon. High confidence.
Friday night...Initially VFR ceilings will quickly drop to MVFR or
IFR near and after 09Z. Light rain is also likely to reduce
visibility to MVFR at times. Initially northwesterly winds around 5
kts will become northerly then easterly after 06Z. Moderate
Saturday...Ceilings near MVFR or IFR, likely lowering throughout the
day near and north of PHL. Periods of light rain expected much of
the day, especially near and north of PHL, likely causing MVFR
visibility restrictions. Winds east to southeasterly around 5-10 kts.
Moderate confidence overall.
Saturday night...A cold front will pass through the area around 06Z
with a wind shift to northwesterly. Speeds increase to around 10-15
kts with gusts around 25 kts. Initially MVFR to IFR ceilings with
showers will become VFR behind the front. Moderate confidence.
Sunday...VFR/SKC. Winds northwesterly around 10-15 kts with gusts up
to around 25 kts, especially before 18Z. Winds diminish to around 5
kts after 00Z. High confidence.
Monday...VFR/SKC. Winds west to northwesterly around 5 kts. High
There may be a few occasional gusts to 25 kt around midnight
tonight, on DE Bay but do not think they will be widespread
enough or frequent enough to warrant a SCA.
SCA remains in effect on the ocean through 7 am due to SW winds
15-20 kt with gusts to 25 kt. Seas will average around 5 feet.
A cold front passes across the waters on Friday. Winds diminish
and seas subside. Conditions should be below SCA criteria by
Friday night through Saturday...Sub-advisory conditions expected.
Initially northerly winds around 5-10 kts will shift east then
southeasterly around 10-15 kts on Saturday. Seas 2-3 feet. Periods
of showers Saturday.
Saturday night...Advisory conditions likely developing near or after
midnight as winds shift northwesterly and increase to 15-20 kts with
gusts to 25-30 kts. Some guidance suggests gusts to near gale force
of 35 kts in the Atlantic waters near Cape May and Lewes and across
Delaware Bay. Seas 3-5 feet. Showers early.
Sunday...Lingering elevated seas around 3-5 feet and winds gusting
up to 25 kts will probably warrant an advisory through much of the
Monday...Sub-advisory conditions expected. Winds west to
northwesterly around 10-15 kts with gusts up to 20 kts early
diminishing to around 10 kts late. Seas 2-3 feet.
A cold front will move through the region tonight, with dew points
expected to drop rapidly after its passage. With west winds of 10 to
15 mph and occasional gusts to 20+ mph, minimum relative humidity
likely approaching 30 percent during the afternoon, and dry
antecedent conditions across the area, conditions for enhanced fire
spread will at least be approached on Friday (primarily in southeast
Pennsylvania, most of New Jersey, and northern Delaware). No special
weather statements are planned at this time, though we will continue
MARINE...Small Craft Advisory until 7 AM EST Friday for ANZ450>455.
Fire Weather...WFO PHI