Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/15/16
Area Forecast Discussion
National Weather Service Wakefield VA
1057 PM EST Wed Dec 14 2016
.SYNOPSIS...
A dry cold front crosses the area tonight and ushers in an arctic
airmass for Thursday and Friday. Low pressure tracks across the
Great Lakes region this weekend. A warm front will move north
across the area Saturday with the trailing cold front crossing the
region Sunday.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Latest surface analysis depicts a ridge axis along the Southeast
coast with the approaching Arctic cold front across northern
Virginia. Aloft...latest water vapor imagery depicts the
associated wave over northern Ohio. Beginning to see an area of
light precip and mid level clouds developing over northeast
Maryland into southeast Pennsylvania. However, ceilings over the
local area remain above 12k feet AGL. Temperatures range from the
upper 30`s to low 40`s. A few locales have actually warmed the
past few hours thanks to a southwest wind. Trends have slowed
slightly with the onset of the Arctic air mass, with the RAP
handling the current obs/trends well. Have followed suit and
delayed the cold/dry air mass a few hours. The front still progged
to drop into the area late tonight, pushing offshore around day
break. The upstream air mass will begin to advect into the region
late tonight as low level thicknesses drop rapidly. Models still
in good agreement with dropping the area of light precip over
northeast Maryland southeast into the Delmarva. However, the
latest trends keep the best chances for measurable precip north of
the Wakefield area. Will keep mention of slight chance to low end
chance POPs after midnight. Temperatures will be dropping into the
upper 20`s to low 30`s so expect light snow. No accumulation is
expected. A dry northwest flow will result in decreasing clouds
west to east behind the front. Lows from the low to mid 20`s
northwest to the mid 30`s southeast coast.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
Mostly sunny, blustery and cold Thursday. Strong CAA and falling
H85 temps suggest highs peak out around noon with falling readings
there after. Highs lwr 30s N/NW to lwr 40s SE coast. Wind chills
in the teens and 20s.
Clear / very cold Thursday night with slowly diminishing winds west
of the Ches Bay. Winds do stay up along the coast. The coldest air
of the season expected with lows 10-15...except near 20 at the
beaches. Wind chills drop into the single digits most areas except
the lower MD ern shore where a wind chill advisory may be needed
for values aob zero. Only record low that might be challenged will
be at ORF. See climate section below.
Ridge axis overhead at 12Z Fri will slowly move east throughout the
day. Sunny skies to start with high level clouds in the afternoon ahead
of next system. H85 support highs between 30-35, pretty impressive for
these parts given no snow cover.
Well advertised overrunning event shaping up for late Friday night
into early Saturday. Models keep it dry through 06Z with light pcpn
breaking out between 06Z-09Z. Thicknesses suggest a wintry mix of
snow, sleet and freezing rain to start as the column saturates.
Boundary layer temps begin to warm along the SE coast as the high
pressure tracks further offshore and winds become SSE. Expect a
quick changeover to rain there before 12Z Sat. Despite QPF being
only a few hundredths of an inch and given how cold surfaces will
be, could very well see a light ice accum mainly along/west of
I-95 prior to 12Z and have noted this in the ice accum forecast.
Best chance for a minimal snow accumulation will be from Caroline
County and the Northern Neck over to the lower MD Eastern Shore
where the coldest air aloft will hold on the longest before the
changeover to rain. If these forecast trends hold, a winter
weather advisory may be needed. Lows in the low-mid 20s except
upr 20s-lwr 30s along the coast with temps rising after midnight
along the coast.
Warm air quickly floods north across the area shortly after 12Z Sat
changing all pcpn to rain. Will continue to indicate a mix for a few
hour period, but expect most areas to see just plain rain by 15Z,
last to go over would be Louisa/Fluvanna counties. Best lift and
support for steady pcpn into the aftn will be across the north as
the warm front lifts north of the area. Thus, kept chc pops across
the south with likely to categorical pops (rain) across the north.
Highs Sat from nr 50 to the low 60s SE coast.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Warm front to lift well NE of the FA Sat night resulting in a drop
in PoPs and steady to rising temperatures. Lo pres will be
tracking through the ern lakes Sat night...then continue NE along
the St Lawrence River Sun...pushing its associated cold front
through much of the FA by Sun eve. Starting out mild Sun...then
cooling during the afternoon as winds shift to NNW. There will
also be an increase in PoPs from NW-SE throughout the day.
Colder air will continue to press into the FA Sun night into Mon
morning. Models continue to suggest possible wintry mix (mainly
IP)...especially NNW 1/2 by 12Z/19 as cold air will initially be
shallow. Dry/partial clearing expected NW-SE by Mon
afternoon...though will keep chc PoPs invof far SE VA-NE NC. Sfc
hi pres builds into the region Mon night through Tue while an area
of moisture lingers invof coastal NC. Models push the moisture
farther S by Wed.
Lows in the m-u40s NW to u50s SE Sat night...but rising. Highs Sun
from the u50s NW to the u60s-around 70F SE...though possibly
trending cooler NW during the day. Lows Sun night from the u20s NW
to the u30s SE. Highs Mon in the m30s NW to the m40s far SE. Low
Mon night from the l20s NW to the l30s SE. Highs Tue in the u30s
NW to the m40s SE. Highs Wed in the l40s NW to the l50s in coastal
NE NC.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
VFR conditions with mostly high clouds movg across the region. An
arctic front will move through the region during the overnight.
The front will bring some lower ceilings...2500 to 5000
ft...across the Delmarva during the overnight. Winds will pick up
behind the front and will gust to 25-40 kt during the day with the
strongest gusts in the northern half of the CWA. There is a slight
chance of a few snow showers for SBY but did not mention due to
lack of confidence. Believe that most precip will remain north of
SBY.
Outlook: A complex area of low pressure and its associated
frontal boundaries will affect the region over the weekend. Some
wintry pcpn possible early Sat with rain expected most areas by
noon. More showery weather expected Sunday ahead of yet another
strong cold front.
&&
.MARINE...
Starting out w/ weak sfc hi pres over the waters this
afternoon...remaining so this eve. Strong cold front late
tonight/Thu morning with strong hi sfc pres building in behind
it. Gale warning in effect all waters except rivers for Thu w/
solid 20-30 kt sustained...gusts 35 kt (potential 40 kt nrn ocean
waters. SCA elsewhere with gusts up to 25-30 kt expected.
Strongest winds will be daytime Thu...slowly subsiding
afterwards w/ sfc hi pres becoming centered directly over the
area by Fri aftn. Expect waves over the Bay of 3-5 ft Thu/Thu
night with 4-6 ft seas over coastal wtrs. Warm front lifts N
across the waters Sat w/ increasing SSW winds to at least solid
SCA. SSW winds continue (though a tad lower in speed Sun) then
become NNW w/ another period of lo level CAA late Sun/Sun night.
Possible for a short period of at least gale gusts w/ that arrival
of cold air very late in the weekend.
&&
.CLIMATE...
Record low min temps for Dec 16th:
RIC...1 in 1958
ORF...15 in 1958
SBY...-6 in 1958
ECG...11 in 1958
Record low max temps for Dec 16th:
RIC...25 in 1951
ORF...27 in 1901
SBY...26 in 1951
ECG...29 in 1951
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory from 4 AM Thursday to 1 AM EST Friday for
ANZ635>638.
Gale Warning from 7 AM to 7 PM EST Thursday for ANZ630>632-634.
Small Craft Advisory from 4 AM Thursday to 4 AM EST Friday for
ANZ633.
Gale Warning from 7 AM to 10 PM EST Thursday for ANZ650-652-
654-656-658.
&&
$$
SYNOPSIS...JDM
NEAR TERM...JDM/SAM
SHORT TERM...JDM
LONG TERM...ALB
AVIATION...JDM/JEF
MARINE...ALB
CLIMATE...
Area Forecast Discussion
National Weather Service State College PA
1102 PM EST Wed Dec 14 2016
.SYNOPSIS...
Arctic air arrives late tonight and Thursday and lasts through
Friday. Snow showers and a few heavy squalls will occur tonight
and thursday as the front moves through. Lake effect snows will
pile up over the northwest and north-central mountains. Wind
chills will get very low Thursday into Friday morning. A more
significant weather system will bring a variety of precipitation
types to central Pennsylvania beginning Friday night and lasting
into Sunday.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Minor changes made to overnight temps, and the timing of snow
showers. Little or no snow is expected SE of the Allegheny Front
until around 10-12Z based on the last few runs of the HRRR
which coincides well with the NAM and RAP timesections which show
the subsidence inversion base shooting up over 5 kft agl.
Previous Discussion Below...
Well-advertised arctic boundary will enter the northwest by
midnight, but will be slowing/losing steam as it presses farther
into Central PA overnight as it will become more-parallel to the
flow. However, the 25-30unit vort max rolling over the nc mtns
will help the front to pack a bit of a punch. This punch will
probably be tempered a bit by the lack of surface instability
overnight. However, snow showers and a few heavy squalls (snow
showers accompanied by gusty winds) will drop 1-3 inches overnight
in the northwestern third of the area. After the front goes by
there, the flow becomes better-aligned for lake effect. It may be
fluffy stuff with very dry air in place. SLRs in the 15:1 or 17:1
range are most likely. QPF is light from the models most likely
due to the transitory nature of the bands. Temps drop into the
single digits overnight with help from the snow pack already on
the ground. The wind will pick up and by morning, some wind chills
will be 5 to 15 below. The valley locations should not be all that
bad wind-chill wise as the strongest winds should be on the hill
tops. However, the wind will blow the fluffy snow around and will
make it difficult to keep the roads cleared. The southeast has an
interesting forecast for tonight as a very minor jet streak moves
overhead and briefly enhances lift over MD and far SErn PA. Have
continued to paint chc POPs in the far SE and even hinted at a
dusting of snow south of route 30. This feature moves very quickly
and no snow should linger into the morning.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Active wx continues with multiple headlines. Lake effect snow will
continue through the day and into Thursday night in the snow belt.
A few bands could stretch quite far into the CWA, so have
continued chc POPs into the aftn for the central mtns. Winds will
back and shsn will taper off over the Laurels before sunset -
perhaps even before 2 or 3 PM. Bands will continue to produce
heavy snow for at least the first half of Thursday night with
fetch favorable for multi-lake connections to be made. The biggest
snow totals will be in NW Warren Co where eventual numbers will be
8-10 inches and perhaps near a foot. Other places will be at the
whim of how long the bands linger, but expect a general 2-5 in
the nc mtns and perhaps a little less in the Laurels. Again, the
winds will be a factor, and have contributed to the issuance of
the LES advy and WW advy. Winds will pick up during the day on
Thursday - and last much of Thurs night. Wind chills will get into
the 5 to 15 below range for many places and the higher elevations
and west-facing slopes where the wind will be strongest will get
to 15 or 20 below on Thursday night. Have tried to place the
ending times of the LES flags at the end of the snow and lowest
wind chills Fri AM. The low wind chills may linger into mid-
morning before temps warm and winds slacken a bit.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Fair and dry (but very cold) weather is expected to persist
Friday and Friday night. However, a moisture-laden storm will
likely impact a large chunk of the region (beginning Friday night
or Saturday) with snow changing to mixed precip or rain from the
SW as a strong and rapidly warming southerly jet overruns the
colder surface air (850mb temps may rise as much as 20-25C over a
36hr period from 12z Fri through 00z Sun). Although it`s still too
early to give specifics on that storm w/resp to snowfall, both the
EC and GEFS do show the parent storm heading NE from the mid
Mississippi to the Upper Great Lakes. Since this storm track is so
far to the NW, the deep valleys in Central PA could easily trap
the cold, sub- freezing air into Saturday afternoon, bringing a
slower or only partial changeover further north and east.
As trough on back side of this system lifts across the Great
Lakes, could see a period of light snow Sat night before high
pressure builds in again on Sunday.
&&
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
Arctic front pushing through tonight will shift winds to the
west northwest, and bring increasingly windy conditions as speeds
pick up to 15-25 mph with frequent gusts into the 30s by Thursday.
Other notable impacts will be a return to a lake effect snow
regime. This will affect KBFD and KJST the most with IFR ceiling
reductions in frequent snow showers. KAOO, KUNV and KIPT will
drop to MVFR conditions toward morning mainly from ceiling
restrictions, with -SHSN being mainly flurries or infrequent
showers. KMDT and KLNS will only see ceilings drop to BKN050.
Northwest flow and lake snow bands, both depicted by the HRRR and
NAM 4km, establish over the northwest/KBFD starting after 07z and
in the Laurel Highlands/KJST after 10-12Z. A few heavier snow
squalls will be possible into the central mtns Thu morning.
Outlook...
Thu...MVFR/IFR with frequent snow showers west; MVFR to low VFR
ceilings central and east with ocnl snow showers and flurries.
Windy with 25-35kt gusts from 280-310. Snow squalls possible.
Fri...Decreasing winds. No sig wx.
Fri night...Restrictions with light snow becoming likely. LLWS
developing.
Sat...MVFR/IFR. Wintry mix transitioning to rain from south to
north. Increasing winds from the south with LLWS likely into
Saturday night.
Sun...MVFR/IFR. Rain early...ending as mix/snow.
Mon...No sig wx.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Lake Effect Snow Advisory until 7 AM EST Friday FOR PAZ005-006-
010-011.
Lake Effect Snow Warning until 7 AM EST Friday FOR PAZ004.
Wind Chill Advisory from 3 PM Thursday to 10 AM EST Friday FOR
PAZ012-017-018-024-025-033-034-037-041-042.
Winter Weather Advisory until 3 PM EST Thursday FOR PAZ017-024-
033.
&&
$$
Synopsis...Dangelo/Lambert
Near Term...Dangelo/Lambert
Short Term...Dangelo
Long Term...Gartner
Aviation...RXR
Area Forecast Discussion
National Weather Service Cheyenne WY
424 PM MST Wed Dec 14 2016
.SHORT TERM...(Tonight - Thursday Night)
Issued at 323 PM MST Wed Dec 14 2016
We are still on track for widespread snow across southeast Wyoming
and the western Nebraska panhandle tonight. Copious amounts of mid
and high level moisture continue to stream into the area late this
afternoon courtesy of the Pineapple Express. An impressive 160-170
knot H25 jet streak extends from central Montana southeast through
eastern Wyoming, setting up strong upper-level divergence over the
I-80 corridor in southeast WY. Low-level warm air advection should
increase markedly during the evening/overnight, likely setting the
stage for significant overrunning. The latest radar loop shows W-E
oriented bands of snow increasing in coverage in response to these
mechanisms. Forecast soundings continue to show good potential for
excellent dendritic growth in the overrunning layer along w/ quite
deep saturation. That said, we expect snow to become heavy but the
duration will likely not last long enough for significant snowfall
accumulations. Snow should end around sunrise, as the arctic front
retreats to the northeast. Winds will increase overnight and could
become rather strong over our wind corridors on Thursday. Both the
H85 and H7 CAG-CPR gradients climb above 70 meters, but the 850 mb
gradient continues to lag behind the 700 mb gradient by 3 hours or
so. The H7 gradient first climbs above 70 meters by 06z, so we may
see winds markedly at Arlington after midnight tonight w/ stronger
winds occurring mid-day Thursday. Bordeaux should eventually reach
High Wind Warning criteria per in-house probabilistic guidance and
60 knot H75 flow once surface winds go westerly. The south Laramie
Range and adjacent foothills will be extremely windy too, and high
wind highlights may eventually be required. Do not believe the 700
mb subsidence will spread far enough east to initiate strong winds
in CYS, especially w/ warm advection contributing to a shallow sfc
inversion. Warming temperatures are still expected tonight, w/high
temperatures in the 40s for many areas on Thursday.
The impacts of winter weather tonight are uncertain. The Arlington
area will see snow through about 2 AM, but very strong winds might
not arrive until closer to sunrise. However, winds should begin to
increase by midnight with a few hours of significantly reduced vis
in falling/blowing snow. The question is whether or not the Winter
Weather Advisory is enough to cover the impacts, but prefer to let
the next shift monitor conditions and make that decision since the
snow amounts are still uncertain. Although high winds are possible
from sunrise and beyond, rapidly warming surface temperatures over
night could limit the blowing snow potential. Nonetheless, we have
extended the Winter Weather Advisory for ARL until 18z Thursday as
hazardous travel has potential to persist. Same story for the I-80
summit. We will maintain a 12z expiration for the remaining winter
headlines as blowing snow is not expected to be as impactful. High
Wind Warnings may be required on Thursday, but will let the winter
threats pass first.
.LONG TERM...(Friday - Wednesday)
Issued at 323 PM MST Wed Dec 14 2016
Main weather this period will be the winter storm system that will
affect the area Friday thru Friday night. Models remain in pretty
good agreement with the evolution of the system. Arctic cold front
will move south over the CWA Friday morning. Max temperatures over
southern parts of the CWA will occur late morning with temperatures
falling through the afternoon across the CWA. Overrunning pattern
and upslope flow will allow snow to expand across the CWA during
the day Friday. Areas close to the Colorado border from roughly
Cheyenne to Sidney may not see much snow until Friday evening.
Heavier snows still look to be over the mtns and the northern
parts of the CWA where over 6 inches a decent bet so the current
winter storm watch looks to be in good shape. Snow should be most
widespread over the CWA Friday evening then taper off after
midnight as much colder and drier air filters down and the main
upper trough axis moves by. A few lingering flurries still
possible Saturday morning but main story Saturday through Sunday
will be the very cold temperatures. After mins below zero Saturday
morning highs Saturday will struggle to get above zero in many
areas. Still bitterly cold Sunday morning with wind chills likely
to become dangerously low in some areas. The cold surface airmass
begins to pull out Sunday allowing for warmer temperatures to
return through Tuesday. Mainly dry weather expected once the snow
ends Saturday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 422 PM MST Wed Dec 14 2016
Snow to become pretty widespread this evening with IFR/LIFR
spreading out into the Nebraska Panhandle. Generally followed
latest HRRR guidance on onset and dissipation times of IFR/LIFR.
There will be an end time to snow from west to east later this
evening, generally after 06-07Z across southeast Wyoming as
stronger westerly winds kick in.
&&
.FIRE WEATHER...
Issued at 238 AM MST Wed Dec 14 2016
No Fire Weather Concerns this week and into the weekend as a
series of weather disturbances bring accumulating snowfall to the
area through Saturday morning. Bitter cold temperatures and high
relative humidities are expected...especially across the High
Plains.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Watch from late Thursday night through late Friday
night for WYZ101>105-110-112-114.
Winter Weather Advisory until 11 AM MST Thursday for WYZ110-116.
Winter Weather Advisory until 5 AM MST Thursday for WYZ103-
105>107-112>115-117>119.
NE...Winter Storm Watch from late Thursday night through late Friday
night for NEZ002-095.
&&
$$
SHORT TERM...CLH
LONG TERM...RE
AVIATION...GCC
FIRE WEATHER...TJT
Area Forecast Discussion
National Weather Service Grand Forks ND
657 PM CST Wed Dec 14 2016
.UPDATE...
Issued at 653 PM CST Wed Dec 14 2016
Winds are diminishing as anticipated and will continue to do more
this evening. But with high pressure ridge to our west they will
remain up enough to keep wind chills in the advisory range into
Thursday. Kept lows the same with likely coldest readings just
east of the RRV Fosston-Park Rapids area wh ere temps nearing
-10F. Some pesky thin stratocu showing up around Bemidji and
Baudette. Overall they will dissipate or move out this evening.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 211 PM CST Wed Dec 14 2016
Forecast challenge for tonight will be overnight lows and wind
chills. Blustery winds continue across the Devils Lake basin with
breezy conditions across much of remaining zones in eastern North
Dakota. A shallow adiabatic layer up to about the H900 level
should begin to dissipate around 23Z to 00Z, based on the latest
HRRR soundings from around the area. This will help winds and any
patchy drifting snow taper off but will prevent the sharp drop in
temperatures common with the snow pack and early sunset. Will slow
down the diurnal curve through about 03Z to 06Z timeframe. Modest
cold advection with temps falling into the teens below zero will
keep 5 to 10 mph winds throughout the night, however, as the
surface high over eastern MT undercuts the valley and moves across
SD...keeping a light westerly wind throughout the night. This will
keep apparent temperatures in the 25 to 40 below range and no
plans to change any headlines. The coldest apparent temps should
be after midnight in northwest Minnesota, where winds will be
light enough to allow ambient temps to approach 20 below zero.
Clear skies will continue thorugh tomorrow morning with increasing
clouds in the afternoon, as the next low pressure system begins to
develop and move into the plains. Have generally preferred the
BCCONSHORTTL today which brings daytime highs just above zero
across southeastern ND yet maintains sub zero temperatures across
northwest MN.
.LONG TERM...(Thursday night through Wednesday)
Issued at 211 PM CST Wed Dec 14 2016
The long term starts off with generally zonal flow aloft and a low
pressure system developing in the lee of the Rockies in eastern CO.
An area of warm air advection producing snow will precede this
low...as warm air pushes north into the cold high pressure
dominating the region. Snowfall amounts Thursday night in the
Wahpeton/Fergus Falls region are expected to be rather light...under
a half an inch. As the low moves out of CO and across KS Friday and
Friday night and a mid level wave moves through the area...a large
area of snow is expected across SD/southern ND and central/southern
MN. Currently expecting 2-4 inches across an area south of Fargo and
Park Rapids Fri aftn/Fri night.
Cold high pressure then fills in behind this low on Saturday and
Saturday night. Some of the coldest air of the year will make its
way across the Canadian border...with highs expected to range from
-14 to -5 F based on the current forecast. Lows Saturday night will
be mostly in the 20s below zero. The high moves east into the
eastern US by Monday...allowing temps to rebound closer to average
by Monday and above average by Tuesday when highs in the mid to
upper 20s are expected. The warm up will continue into Wednesday
...with minor precipitation chances expected as well.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 653 PM CST Wed Dec 14 2016
West-northwest winds to continue tonight 8 to 18 kts then turn
southerly on Thursday. Some thin stratocu/ice crystals resulting
in brief MVFR cigs at Bemidji and surrounding areas early this
evening, but for the most part clear tonight with increasing high
clouds by Thursday afternoon.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Wind Chill Advisory until 9 AM CST Thursday for NDZ049-052-053.
Wind Chill Advisory until noon CST Thursday for NDZ006>008-
014>016-024-026>030-038-039-054.
MN...Wind Chill Advisory until 9 AM CST Thursday for MNZ029>032-040.
Wind Chill Advisory until noon CST Thursday for MNZ001>009-
013>017-022>024-027-028.
&&
$$
UPDATE...Riddle
SHORT TERM...Speicher
LONG TERM...Knutsvig
AVIATION...Riddle
Area Forecast Discussion
National Weather Service Huntsville AL
859 PM CST Wed Dec 14 2016
.NEAR TERM...(Tonight)
Issued at 859 PM CST Wed Dec 14 2016
An Arctic surface high in the 1035mb range across the South Dakota
and Nebraska region was building to the southeast, bringing another
shot of very cold air toward this region. Current temperatures near
and north of this high were generally near or below zero Fahrenheit
from Montana to Lake Superior. Close to home, an area of stratus was
moving in a NNW-SSE manner across the region, producing MVFR ceilings
(cloud bases < 3000` above the ground) from near Tupelo, across the
greater Huntsville area, and the western Cumberland Plateau in
Tennessee. Temperatures across this region were in the mid 30s to low
40s, with northerly winds of 5-15 mph. Some higher gusts were being
realized as the stratus deck moves by.
Changes for tonights forecast were mainly minor timing and cloud
coverage this evening. Stayed with more clouds over our northern
areas, especially Tennessee as short term guidance suggests more low
clouds will affect them before daybreak Thu. Also made minor tweaks
to night time lows and wind, with higher winds (and lower apparent
temperatures) in the higher terrain.
Precautions will be needed for outdoor pets and exposed water pipes,
as night time lows fall into the mid 20s, and 5-15 mph winds (gusts
to 25 mph in the higher terrain) during most of tonight.
.SHORT TERM...(Thursday through Friday)
Issued at 315 PM CST Wed Dec 14 2016
The Arctic high settles in on Thursday and with the strong CAA
occurring, afternoon highs will only be in the low to mid 30s. It
will be a blustery/chilly morning with wind chills remaining in the
teens through the morning hours. Winds finally begin to weaken by the
afternoon but it will still feel quite cold.
The Arctic high will also bring very dry air into the region sending
dewpoints into the single digits for the northern half of the area.
Decreasing winds and mostly clear skies will allow temps to drop
rather quickly Thursday night. NAM/GFS forecast soundings suggest
some possible mid and high level clouds moving in early Friday
morning ahead of our next system. But believe that this is probably
optimistic, given how dry it will be with this Arctic high. With all
of that said, decided to knock temps down a couple of degrees across
the board for Friday morning with most places in the lower 20s. Our
TN counties could see temps drop into the teens.
Both of these nights people may want to take some pre-cautionary
measures to protect household pipes and ensure you dress warmly as
it will feel quite cold Thursday/Friday mornings.
The other concern is with the dry air is Fire Wx. The recent rainfall
has helped to increase fuel moistures but as we saw with the last
shot of dry Arctic air there is still a potential for fire starts.
So, extra caution is still advised for any outdoor burning.
Especially, during the day Thursday with the increased winds.
.LONG TERM...(Friday night through Tuesday)
Issued at 315 PM CST Wed Dec 14 2016
Increasingly southerly flow on Friday should help to warm
temperatures back up into the mid to upper 40s, as a surface low
develops in Colorado and Oklahoma. This surface low should begin to
advect increasingly more moist air northeast towards the Tennessee
Valley. Strong low level jets (850 and 925 mb) ahead of the surface
low and a much more saturated boundary layer develop in response on
Friday night over the Tennessee Valley. As a weak shortwave develops
ahead of the front Friday night and into Saturday morning, steady
light rain development is expected. Lows on Saturday morning should
be much warmer as well west of I-65 (lows in the 45 to 50 degree
range).
East of those areas lows drop into the upper 30s to lower 40s (effect
of cold air damming).
New model runs converge on this low pushing eastward quickly into
the Ohio Valley/eastern Great Lakes region during the afternoon on
Saturday. A developing cold front extends southwest from this low
into western Tennessee and northern Louisiana. West of I-65, 925 mb
winds increase to between 40 and 50 KTS. This should advect much
warmer temperatures and moist air into the area by the
afternoon/evening hours.
By Saturday night, as the front moves into northern Alabama and
Southern Middle Tennessee, upper level energy swings eastward and
aids in cyclogenesis. This should steepen lapse rates slightly and
models show ~ 500 J/KG of elevated CAPE. Abundant shear will be in
place as well, but much of this looks linear in nature. However,
there may be just enough surface based CAPE and helicity in place
Saturday night for an isolated tornado near the MS/AL border.
However, confidence is very low. A wind advisory may be needed on
Saturday.
Very cold air will push into the area behind the front on Sunday.
Temperatures could drop to 32-34 degrees in Southern Middle
Tennessee/extreme Northwest Alabama by late morning and early
afternoon. However, the models diverge on how quickly this pushes
eastward. The ECMWF continues to be the quicker moving solution,
pushing precipitation east of the area after 15Z. However, the GFS
holds onto rainfall through the early afternoon hours, before slowly
pushing it east of the area by Sunday evening. Kept a compromise in
the forecast, with the POP closer to ECMWF. At this point, think it
will end as rain as much drier air quickly moves in behind the front,
which exits the area by noon.
Went with Superblend through the rest of the forecast due to model
divergence as multiple disturbances move through the area. Main
takeaway is that it will be a warmer and rainy pattern through
Wednesday night.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 536 PM CST Wed Dec 14 2016
MVFR clouds present north of the region were showing a southward
drift per low cloud/fog satellite imagery. Rough timing of these
clouds moving southward and output from the RAP suggests that local
terminals could be impacted in the early/mid evening. Timing has the
clouds reaching KMSL around 15/0200Z, and KHSV an hour later. Right
now, stayed with a TEMPO MVFR CIGs, as drier air moving southward
should bring VFR CIGs in for the overnight. Winds should continue
from the north around 10kt tonight, but increase into the 10-15kt,
gusting to 20kt as a reinforcing shot of cold air moves across the
region. NNE winds should diminish somewhat late Thur afternoon.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...RSB
SHORT TERM...Stumpf
LONG TERM...KTW
AVIATION...RSB
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Wilmington OH
855 PM EST Wed Dec 14 2016
.SYNOPSIS...
Another last push of arctic air will descend into the area
tonight, bringing some gusty winds tonight and continued bitterly
cold temperatures through early Friday. A vigorous low pressure
system approaching the area late Friday bringing first light snow
and then a mix of sleet and freezing rain before changing to rain
for Saturday.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Winds behind the arctic front have increased slightly stronger
than expected and the forecast has been adjusted to reflect this
for the next few hours. HRRR timelag temperatures were also
showing a cooler air surge by a bit. Did not shave more than a
degree or three off of the temperatures tonight but did not cool
as much as aforementioned guidance. Thought that the fresh snow
would also trend the temps colder than most guidance would
support.
The increased wind and cooler temperatures necessitated an
expansion of the wind chill advisory for almost another tier of
counties to the south. Did not include Clermont/Brown in this
expansion as the southern halves of them did not reach the -10
criteria and the northern sections only had these apparent
temperatures for a brief period in time.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
As the arctic high settles into the area for Thursday,
temperatures well below normal. The center of the high passes
through the forecast area Thursday night, bringing in some
overrunning clouds in the western forecast area. With clouds
reaching through the area, radiational cooling scenario not quite
as efficient as tonight, and with winds very light, did not meet
the minimum 6kt wind criteria for a wind chill advisory for
Friday morning.
Increasing clouds through the day on Friday with the area under
southeast flow.
A complex weather scenario late Friday into Friday night, with
and initial overrunning snow set up affecting especially the
western and northern forecast area bringing light snow.
Through the overnight though, very strong warm air advection will
warm the mid then low levels, but with the area coming off of an
arctic airmass and very cold surface temperatures with a snowpack
in place through the northern 2/3 of the forecast area, warming
may not occur as quickly as some of the more aggressive solutions
like the GFS/ECMWF. It`s interesting to note that the NAM seems to
recognize the very cold surface conditions in place, which could
make for greater ice accumulations in especially the central and
northern forecast area. By daybreak the entire area should succumb
to this strong push of warm air with all rain by 12z Saturday.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
With surface low pressure located over Illinois on Saturday morning,
the entire ILN forecast area is likely to be within a regime of
strong warm / positive theta-e advection, leading to moderate to
high confidence in rain as the dominant p-type through Saturday
afternoon/evening. While the majority of the warm frontal forcing
will be shifting north and northeast of the middle Ohio Valley by
Saturday morning, continued strong moisture convergence will lead to
patchy/showery precipitation through the day.
The situation begins to change again late in the day and during the
evening, as the approaching cold front undergoes impressive
frontogenesis (strengthening) over the ILN forecast area, in advance
of a mid-level wave. Precipitation is expected to become more
widespread in the vicinity of this front, with some concerns
regarding precipitation type, as the sharp surface cold front may
actually undercut the slower-to-modify air in the 850mb/700mb layer.
This may result in a period of mixed precipitation, rather than an
orderly rain-to-snow switch near the time of the frontal passage.
Regardless, the push of cold air will be significant and sharp,
bringing temperatures down significantly through Saturday night and
into Sunday morning. Models have come in slightly faster with the
end of precipitation during the day on Sunday, but with continued
strong cold advection, there may be little diurnal rise in
temperatures. The coldest air aloft with this air mass is expected
to be in place over the region on Monday morning, which may end up
as the coldest morning of the extended forecast period.
Surface high pressure is expected to settle into the Ohio Valley
through Monday, Tuesday, and Wednesday. This will allow for a
gradual modification in temperatures, and weak warm advection
through the period, under zonal 500mb flow.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
An Arctic front will be crossing the region in the next few hours.
Mid level altostratus deck will give way to generally clear skies
as the drier air behind the front pushes in. Earlier sct
cu/stratocu around 3kft in forecast behind front does not appear
to be seen upstream with the drier air winning out. Expect wnw
winds to be sustained at 15kt with higher gusts up to 25kt through
about daybreak - lasting a bit further into the morning in central
Ohio taf sites of KCMH/KLCK. Sustained winds in the cold air will
still be 13-15kt through much of the day Thursday but the gusts
will subside early.
Towards 0z Friday - winds will go slack and cirrostratus or a high
altostratus deck will encroach on the region.
OUTLOOK...MVFR conditions possible Friday night into Sunday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Wind Chill Advisory from 2 AM to noon EST Thursday for OHZ046-
055-056-060>065-070>074-077-080.
Wind Chill Advisory until 2 PM EST Thursday for OHZ026-034-035-
042>045-051>054.
KY...None.
IN...Wind Chill Advisory from 2 AM to noon EST Thursday for INZ050-
058-059-066-073-074.
&&
$$
SYNOPSIS...Coniglio
NEAR TERM...JDR/Franks
SHORT TERM...JDR
LONG TERM...Hatzos
AVIATION...Franks
Area Forecast Discussion
National Weather Service Louisville KY
943 PM EST Wed Dec 14 2016
.Forecast Update...
Issued at 945 PM EST Wed Dec 14 2016
Updated the forecast to increase wind gusts overnight. Upstream obs
are still quite breezy with gusts as high as 20-25 mph. The latest
soundings indicate our area will be gusty overnight as well. The
higher gusts and slightly lower forecast temps for tonight resulted
in lower wind chill values. Low temps should range from 8-13
degrees over southern Indiana/north central KY with the lowest wind
chills in the -5 to 0 degree range late tonight. Low temps over
south central KY will range from 13-19 degrees with lowest wind
chills in the 0 to 5 degree range.
&&
.Short Term...(This evening through Thursday night)
Issued at 310 PM EST Wed Dec 14 2016
Extensive mid/high-level cloud cover streaking across the Ohio
Valley, but low-level moisture is lacking ahead of the secondary
Arctic front diving across Illinois and Indiana. This front will
push through overnight, and finally could tap enough low-level
moisture in a mixy boundary-layer to generate a few bands of
flurries. No accums or impacts expected. Winds should stay up enough
to keep temps from bottoming out, with most locations reaching mins
in the teens. However, those winds will drop wind chills to around
zero along and north of I-64.
Arctic high pressure will slide by to our north on Thursday, with
continued mid/high clouds under a fast upper jet. The cold will hang
on as 900mb temps around -16C will limit max temps to the lower/mid
20s, around 20 degrees below normal for mid-December. By Thu night
the high will be far enough east to open up weak return flow, so
expect a quick drop in temps Thu evening with flat or slowly rising
temps after midnight.
.Long Term...(Friday through Wednesday)
Issued at 315 PM EST Wed Dec 14 2016
...Very Dynamic Storm System to Affect the Region Friday night
through Sunday...
Friday will be a transition day with a gradual thickening and
lowering of cloud cover as the low levels take all day to saturate.
Temps recover noticeably from Thursday`s big chill, but still a
solid 10 degrees below climo.
POPs really ramp up on Friday evening as the low-level jet sets up
ahead of the main low kicking out of the OK/TX Panhandle. Early drop
in temps will present precip type issues at onset, with a brief
wintry mix possible mainly along and north of the I-64 corridor.
Temps will rise significantly overnight, so any issues will be short-
lived. Widespread showers expected on Saturday in the warm sector,
with just enough moisture and instability for isolated thunder in
south-central Kentucky. Some hint that an upper dry slot may cut in,
limiting QPF during the day on Sat, with the higher totals now
skewed toward Sat night.
Surface front swings through on Saturday evening, but another wave
riding up behind the front will keep precip chances going through
the night and even into Sunday. Biggest challenge is presented by a
very sharp drop in temperatures, from Sat afternoon highs around 60
(if not warmer) all the way into the 20s by daybreak Sunday, and the
accompanying changeover in precip type. Cold air arrives slowly
enough that a freezing rain transition is possible at some point,
but it`s still too early to get caught up in multiple P-types. For
now will carry a rain-to-snow transition in the official forecast
products, but a more general wintry mix mention in our other
messaging. Travel impacts are likely for at least some part of the
area late Sat night/Sun morning.
Low-amplitude pattern aloft through the first half of next week, but
Arctic high pressure will keep us dry and cold. Temps gradually
recover to climo by Wednesday, but a southern stream system could
bring rain chances back into the picture by the end of Day 7.
&&
.Aviation...(0Z TAF Issuance)
Issued at 625 PM EST Wed Dec 14 2016
VFR conditions are expected through the TAF period as Arctic high
pressure builds into the region. A strong pressure gradient on the
east side of the high will result in gusty NW winds tonight. The
latest RAP and NAM soundings are in favor of a well mixed boundary
layer through the overnight hours which will result in gusts between
16-20 kts at the TAF sites. The pressure gradient should relax
after sunrise tomorrow causing gusts to diminish.
&&
.LMK Watches/Warnings/Advisories...
IN...None.
KY...None.
&&
$$
Update...AMS
Short Term...RAS
Long Term...RAS
Aviation...AMS
Area Forecast Discussion
National Weather Service Medford OR
800 PM PST Wed Dec 14 2016
.UPDATE...No major changes were necessary this evening as the
current forecast appears to be on track. Rainfall continues across
the area as the cold front begins to push east over the coast and
across the forecast area. Standing water and full ditches will
continue to be a concern until the rain ends later tonight, and a
flood warning continues for Deer Creek at Roseburg. For more
information, see the previous discussion below. -BPN
&&
.AVIATION...15/00Z TAF CYCLE...Freezing levels will drop to around
2000 to 3000 feet by midnight. IFR to LIFR conditions are expected
to return to most of the west side this evening. east of the
Cascades will see mostly MVFR ceilings, but with warmer air moving
over the recently heavy snowfall some areas of fog are possible.
Ceilings are not expected to rise to vfr over almost all of the
region tomorrow. Sven
&&
.MARINE...Updated 800 PM PST Wednesday 14 December 2016...The front
has moved through the area and weaker north winds have moved in
behind. The fresh south swell generated by the south winds ahead of
the upper low are expected to migrate northward through the northern
waters this evening and continue through Thursday. North winds will
increase some with borderline small craft possible in the southern
outer waters late Thursday afternoon and evening. Calmer conditions
are expected Friday into next weekend. Very high and very long
period swell may possibly move into the waters Tuesday. -Sven/BPN
&&
.PREV DISCUSSION... /Issued 322 PM PST Wed Dec 14 2016/
DISCUSSION...A high-impact winter storm continues to affect
Northern California and Southern Oregon with heavy rain at the
coast and west of the Cascades, snow east of the Cascades from
Chiloquin northward, and some high winds in the Shasta Valley and
areas east of the Cascades.
A Winter Storm Warning will expire around 4pm as snow levels
continue to rise over the Cascades and portions of the East Side.
After that time, the most significant impacts will be confined to
areas east of the Cascades north of Chiloquin where lingering
cold air at the surface will help maintain snow or a mix of
snow/rain/freezing rain through the afternoon, potentially
changing to all rain this evening, then transitioning back to snow
tonight with snow expected through early Thursday morning. We have
relied on HRRR surface temperature output to provide an idea on
where the freezing temperatures will last the longest and have
adjusted based on observations. A Winter Weather Advisory at WSW
has been issued to cover this. Snow is also expected to impact the
highest elevations of the Cascades through the night, like the
Crater Lake Rim. Lower elevations in the mountains will likely
receive sub- advisory snow amounts but still expect some snow
accumulation in the mountain passes as the cold front moves
through quickly Thursday morning.
The heavy rain threat continues through Thursday morning, and an
Areal Flood Watch has been maintained at FFAMFR to highlight the
potential impacts from the rain. We have added most of Jackson
County given the already-impressive rainfall received last night and
today. Also, we have issued a flood advisory for some areas of the
West Side to include the Applegate and Highway 238 and the Illinois
Valley area. Models suggest that when the front pushes back to the
south tonight, the duration of heavy rain won`t be long-duration, so
the threat for flooding does diminish some tonight. Still, rivers
and streams are rising sharply this afternoon, and drivers should
use caution when traveling in flood-prone areas. -NSK
Winds in the short term will be another major concern in the
forecast. The strongest winds are expected to be across the
Cascades and eastward this afternoon and evening. Current
observations indicate that winds are following the forecast well
in the Shasta valley as well as in Modoc County, but are slow to
increase across the Eastside in Oregon. Winds are still forecast
to pick up later this evening, around 4:00 PM PST. They will begin
to come down around 7 or 8 PM PST and become lighter after 4 AM
PST. While winds are strong, visibilities may be reduced due to
rainfall and possible blowing snow. Otherwise, winds will be
relatively light for the next few days.
Temperatures are going to be the main concern after this system
moves out of the area. Although temperatures are going to be heavily
moderated due to cloud cover tonight through tomorrow, skies are
expected to clear out and this will allow temperatures to plummet,
especially across areas which are snow-covered beginning Friday
night. West of the Cascades including the coast, temperatures are
going to range in the 20s and 30s with a few isolated higher
elevation places reaching into the teens. Meanwhile on the Eastside
and across Modoc County, temperatures are expected to reach into the
teens and single digits.
The coldest night will be on Friday night. Guidance is showing
frigid temperatures across the Eastside, but the clear skies and
cloud cover will likely mean even colder temperatures than what
guidance is showing. This means that temperatures will reach near
zero and below zero in many locations including Klamath Falls,
Lakeview, and Alturas. More northerly places like Chemult may even
see temperatures plummeting to negative 10 degrees. West of the
cascades, temperatures will remain similar with lows reaching the
20s and 30s with the warmer of these temperatures occurring near the
coast. Temperatures will be slow to recover, and will continue the
cold trends through the weekend. -Schaaf
Saturday through Wednesday...It will be a cold start to the
weekend Saturday morning with at least freezing temperatures over
the entire area inland from the immediate coast. With mainly clear
skies, fresh snow cover, and a 1030 mb surface high parked just to
the east, the east side will be quite cold. Lows Saturday morning
will be below zero over much of the east side, with lows
potentially 10 to 15 degrees below zero over northern Klamath and
Lake counties. On Sunday, the GFS shows a weak disturbance
bringing some snow showers to the north Cascades and portions of
the east side. The ECMWF and GEM show the disturbance much further
north and not affecting us at all. It`s worthy of some low pops,
but we`ve definitely skewed it toward the drier solutions. Monday
should be dry as a weak ridge pokes in over us, but by Tuesday and
Wednesday, another system is likely to bring precipitation to our
area. All the models show a moderately wet system during this
timeframe, but there are some timing differences with the ECMWF
being about 12 hours faster than any other model. Snow levels
should be high enough (4000 feet plus) that impacts will be mostly
in the mountains. However, the east side may see snow in places.
-Wright
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning until 10 PM PST this evening for ORZ030-031.
Winter Weather Advisory until 10 AM PST Thursday for ORZ030-031.
Wind Advisory until 10 PM PST this evening for ORZ030-031.
Flood Watch until 4 AM PST Thursday for ORZ021-022-024-026-028.
Wind Advisory until 10 PM PST this evening for ORZ029.
CA...High Wind Warning until 10 PM PST this evening for CAZ085.
Wind Advisory until 10 PM PST this evening for CAZ085.
Wind Advisory until 10 PM PST this evening for CAZ084.
Flood Watch through Thursday afternoon for CAZ080>083.
Flash Flood Watch until 10 PM PST this evening for CAZ080.
Flood Watch from 4 AM PST Thursday through Thursday evening for
CAZ084-085.
Pacific Coastal Waters...Flood Watch until 4 AM PST Thursday for PZZ356.
Small Craft Advisory until 10 PM PST this evening for
PZZ356-376.
$$
BPN/SBN/BMS/NSK
Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
955 PM EST Wed Dec 14 2016
.DISCUSSION...
MRMS is showing light precip from WV across KY, moving east. Dual-
pol from KJKL shows that it is snow, but so far no obs in that area
show it reaching the ground. The HRRR and RAP maintain light
precip across SW VA and NE TN from 06Z to 08Z, so the current
forecast of snow flurries in that area appears on track. Cold front
passage in our area will occur between 09Z and 12Z. Winds will
increase behind the front but should stay below advisory criteria
in the mountains. Forecast low temps in the lower to mid 20s looks
on track, but will tweak the hourly temp/dewpt grids for the
update.
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...None.
VA...None.
&&
$$
DGS
Area Forecast Discussion
National Weather Service Mount Holly NJ
944 PM EST Wed Dec 14 2016
.SYNOPSIS...
A strong cold frontal boundary will move from northeast to southwest
across the region tonight. High pressure will then build eastward
into the region by Friday and then move offshore by Saturday. A
strong low pressure system will develop in the midwest tracking into
the Great Lakes. This will be followed by a cold frontal passage by
Monday. High pressure will then build eastward toward the region in
the Tuesday and Wednesday timeframe with areas of low pressure
tracking to our south.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Latest KDIX and KDOX radars showing some light returns over
extreme SE PA, and into N and E MD. However, dewpoint depressions
are still fairly high, generally from 10 to 20 degrees F, so that
precip is evaporating before reaching the ground. This light
precip will help to moisten up the atmosphere, so snow will be
able to develop later tonight.
Latest HRRR continues to indicate a swath of snow across the
Delmarva and into S NJ, where around 1" with as much as 2" in
banding of snow is possible. This should be a relatively quick
shot of snow, generally from around 11 pm to 3 am. Highest snow
amounts possible in S NJ.
NW winds behind the arctic front will become breezy toward early
morning. Forecast lows range from the teens N/W of the Fall Line to
the mid 20s along the coast.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
Arctic air will make its presence felt on Thursday. The pressure
gradient between low pressure over southeastern Canada and high
pressure building in from the Midwest states will yield a brisk W-NW
winds tomorrow. Steep lapse rates owing to strong CAA in the
boundary layer will yield deep mixing of stronger winds aloft down
to the surface. We were on the fence about issuing a wind advisory
for tomorrow as wind gusts should generally be in the 35-45 mph
range. However, forecast soundings (particularly off the GFS) in
BUFKIT show the potential for higher gusts to 50 mph if the upper
bound values of momentum transfer are realized with deep mixing.
Will let later shifts re-evaluate the need for a wind advisory.
In addition to the cold and wind, the other concern is for localized
snow squalls. The environment becomes conditionally supportive of
snow squalls with steep lapse rates in the boundary layer and mid-
level moisture streaming in from the Great Lakes. A mean W-NW (300
degrees) wind direction in the boundary layer will direct lake
effect moisture toward NE PA and NW NJ (I-78 and I-80 corridors).
The BTV snow squall parameter from the NAM/GFS/RAP highlight these
areas as being conducive for maintaining snow squalls. Timing is
uncertain, but it looks like the first snow bands could reach our
northern zones during the morning rush. Even though the threat will
be very localized, it could potentially be a high impact on travel;
which is why we have kept it in the HWO.
&&
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Lengthy long term AFD today, summary listed first then body of long
term section.
1. Bitter cold Thursday night with wind chills near or below zero.
2. Potential burst of moderate to heavy snow late Friday night into
Saturday morning and uncertainty with changeover timing from south
to north.
3. Likely temperature spike Sunday morning before rapidly falling
temperatures later Sunday.
4. Prospects for a secondary area of low pressure to keep
precipitation going Sunday night, leading to a changeover back to
sleet and snow from northwest to southeast.
5. Another cold shot and ensemble signal of another low
pressure system at some point Monday through Wednesday.
A very active long term period. In the mid levels a predominant
staple of the winter season so far is a potent ridge over the
Southeastern United States. Teleconnections such as the EPO and WPO
will allow for a few shots of very cold air to move southward into
the country from Canada as well. In between these features, there
will be an extremely active storm track and a surface frontal
boundary for the weekend and early next week. Temperature extremes
will potentially vary as much as 50 degrees on either side of the
boundary leading to more uncertainty than usual.
Thursday night and Friday: We could still have a few lingering snow
showers or flurries in the northwest flow aided by the higher
terrain. These should dwindle down once the steepness of the lapse
rates decrease in the evening. The main story will be the cold
temperatures which will fall into the single digits or low teens for
many as skies clear some. Bufkit soundings show the potential for
35-40 mph gusts with the highest gusts in the evening. This would
send wind chills below zero for most of the region and close to
advisory criteria in spots. Please refer to our facebook and
twitter pages for tips on how to stay safe during the cold. Winds
will decrease and temperatures will warm well into the 20`s on
Friday as a high pressure system moves over the region making it
less harsh overall.
Friday night through Saturday night:
A high impact wintry event will move through the region. A strong
low pressure system will track northeast from the Southern Plains
into the midwest. With the high offshore, warm air advection will
increase and correspond with a warm front pushing northward.
Isentropic lift will combine with increased mid level vertical
velocities and frontogenesis forcing leading to the development
of precipitation late Friday night and Saturday which is highly
probable to become moderate or heavy at times. Wind gusts of 20
mph are possible as well in this timeframe.
The precipitation should start everywhere as snow but the warm air
advection will be potent (strong LLJ) with the high not in an ideal
place to keep cold air around for an extended period. The snow
should quickly change to rain Saturday morning across Delmarva and
coastal New Jersey south of Atlantic City. Further north the snow
will last a few hours longer in the Philadelphia and central New
Jersey regions changing over by noon. In Northern New Jersey, the
Lehigh Valley and Southern Poconos cold air is likely to hang on
throughout most of the day before seeing a changeover to rain. A
period of sleet and freezing rain is also probable at many
locations in the transition as the mid-levels warm faster than the
surface. For some of the valleys north and west, it may be more
of a challenge to scour out the low level cold resulting in an
extended period of ice. Models are notorious for getting rid of
low level cold too quick. One thing that could allow the cold to
hang on longer would be the formation of a secondary low off the
NJ coastline, which is a possibility shown on some ensemble
members.
First guess snow totals with a few locations listed for each
range. Will likely change based on track and intensity of system
in the coming days. Ratios may start out in the 10-15:1 as snow
growth looks favorable in the -10 to 20C layer along with the
favorable lift described above.
4-6 for Mount Pocono, Wantage, Reading, Allentown and Somerville.
2-4 for Wilmington, Philadelphia, Mount Holly and New Brunswick
1-2 for Dover, Millville northeast into the Pine Barrens
Less than an inch is currently expected for Georgetown and Cape
May.
Temperatures will continue to rise Saturday night in the warm
sector. However, the forcing which results in widespread rain and
snow Saturday takes a break Saturday night resulting in a dry slot
or just some scattered rain showers. An 8-9 Standard deviation
spread with the ensembles for temperatures is present in this
timeframe, really high uncertainty.
Sunday and Sunday night: Another low pressure system will develop
along the frontal boundary as additional mid-level energy moves
northeast from the southern Plains. A slight majority of ensemble
members show a progressive frontal passage, which has been the
trend on most of the operational models as well. However a group
of ensemble members slow the front with an additional area of low
pressure riding northeast along it. That would result in
precipitation through Sunday night with the highest amounts south.
Regardless, high temperatures will be early in the day with
falling temperatures during the day. Temperatures are likely to
quickly spike into the 40`s and 50`s but that depends on how
entrenched into the warm sector we are. The cold air behind the
front will be faster to move in just above surface than further
up in the atmosphere. If precipitation continues into Sunday
afternoon and evening a change to sleet would occur based on the
expected depth of the cold air and then change to snow from
northwest to southeast. Additional snow and sleet accumulation
could occur with the highest odds for accumulation on the
ensembles across Delmarva currently.
Monday through Wednesday: Quite a bit of ensemble spread depending
on where the front which moves through Sunday stalls. Some members
develop additional areas of low pressure with prospects for more
wintry precipitation. This included the 12Z/14 operational ECMWF.
Other models and ensemble members allow a stronger high pressure
system to move into the region with the front far enough offshore
to keep us dry. Stuck close to the ensemble blend on temperatures
in this timeframe. Pops will be highest in southern portions of
the region with colder mid-levels to result in mainly or all snow.
Longer term: The mid-level ridge is expected to strengthen across the
Eastern United States heading into the holiday travel period along
with the EPO and WPO reversing to more of a positive phase. As a
result, milder temperatures are favored by the CPC in the 8-14 day
period. Although it may remain quite a bit wet as well, further
denting the ongoing drought.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Generally a VFR forecast. W winds 5-10 KT initially will increase
to 15-20 KT with 25-35 KT gusts after midnight and towards
daybreak.
A band of snow is expected to develop over the Delmarva and S NJ
overnight. This could bring a period of IFR conditions and steadier
snows to MIV and ACY for a 2-3 hr period. ILG and PHL may be on the
northern fringe of the snow, so impacts will be less. VFR elsewhere
overnight.
Mainly VFR on Thursday. Breezy W-NW 15 to 25 knots will gust to
30-35 kt during the day. Isolated higher gusts approaching 40 kt
are possible. There is still a slight risk of localized snow
showers/squalls that could bring brief restrictions to our
northwestern TAF sites such as ABE and RDG during the day.
OUTLOOK...
Thursday night and Friday: Mainly VFR, could be a brief lower
restriction in any snow shower or snow flurry activity north.
Northwest wind gusts 20-30 knots Thursday night decreasing to
under 10 knots and becoming more southerly on Friday.
Friday night and Saturday: Celings and visibilities decreasing to
IFR or lower with snow developing from south to north. Could be
moderate or heavy for a few hours around 12Z Saturday. Gradual
change to rain from SE to NW with KMIV and KACY changing over by
14z and PHL by 16z with KABE closer to 18z. Southerly wind gusts
increasing to 20 knots on Saturday. Transition may include a brief
period of sleet and freezing rain.
Saturday night: IFR or lower celings and visibilities, in light rain
and patchy fog. Southwest Winds of around 20 knots may prevent
widespread fog formation.
Sunday and Sunday night: IFR or lower still likely with rain
potentially changing to snow from northwest to southeast in the
afternoon and evening. Winds shifting to northwest and gusting from
15-25 knots.
Monday: More uncertain but improvement to VFR is currently
anticipated for most terminals. A chance is present that snow may
impact southern terminals with lower restrictions. Northerly
wind gusts 10-15 knots.
&&
.MARINE...
W-NW winds 10-15 KT with gusts to 20 KT will increase late
tonight into Thursday morning behind a cold front. Expect gale
force gusts of 35-40 kt to develop shortly before daybreak
Thursday and become more numerous during the daytime hours.
There could also be locally reduced visibility on Thursday
farther offshore with ocean-effect snow bands developing.
OUTLOOK...
Seas will generally be just above five feet through the outlook
period with a lull in the Friday/Friday night time period.
Northwesterly wind gusts of 25-30 knots behind a cold front Thursday
night then a period of southerly wind gusts Saturday and Saturday
night that may approach gale force with warm air advection. Winds
still 25 knots on Sunday but shifting to the northwest after a
frontal passage.
&&
.CLIMATE...
Our first true shot of winter air will move into the region later
this week with near record or record cold highs on Thursday and
Friday. Low temperatures the morning of the 16th look to stay
above record values.
Daily record min temperatures (F) December 16th...
ACY: 8 1968
PHL: 9 1876
ILG: 5 1910
ABE: 1 1951
TTN: 9 1917
RDG: 5 1917
GED: -7 1958
MPO: -7 1917
Daily record coldest max temperatures (F) for December 15th and
16th...
ACY: 22 (1915) and 23 (1916)
PHL: 22 (1914) and 22 (1917)
ILG: 24 (1904) and 21 (1917)
ABE: 22 (1943) and 15 (1951)
TTN: 29 (2010) and 29 (2010)
GED: 30 (2010) and 26 (2010)
RDG: 30 (2010) and 26 (2010)
MPO: 19 (2010) and 21 (2010)
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Gale Warning from 2 AM Thursday to 1 AM EST Friday for ANZ430-
431-450>455.
&&
$$
Synopsis...Gaines
Near Term...Klein/MPS
Short Term...Klein
Long Term...Gaines
Aviation...Gaines/Klein/MPS
Marine...Gaines/Klein
Climate...
Area Forecast Discussion
National Weather Service Raleigh NC
950 PM EST Wed Dec 14 2016
.SYNOPSIS...
Weak high pressure will remain overhead tonight, in advance of an
arctic cold front that will surge through VA and NC early Thursday.
Arctic high pressure will follow and crest over our region on
Friday.
&&
.NEAR TERM /TODAY AND TONIGHT/...
As of 950 PM Wednesday...
Skies have cleared pretty rapidly from the southwest this evening,
and will remain mostly clear except for some jet and orographically
enhanced cirrus skirting along the NC/VA border. A 1033mb arctic
high over the Central Plains will continue to build east tonight,
though the associated cold air looks as though it will remain pent
up against he western side of the Appalachians until closer to 09-
12, at which time northwest winds and cold advection will begin to
pick up. In the meantime, weak pressure gradient in the lee of
mountains and good radiational cooling conditions has led to temps
quickly falling into the mid and upper 30s. Patchy fog seems
plausible, mainly over the coastal plain where dewpoint depressions
are low. HRRR soundings suggest fog potential is best between 04Z
and 09Z prior to the onset of northwest winds. Overnight lows have
been tweaked a little to reflect current trends and rural urban
variability...29-35.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
As of 130 PM Wednesday...
Brisk NW wind and cold. Strong cold advection in the wake of the
arctic cold frontal passage Thu morning will result in mostly clear
skies and a brisk NW wind sustained at 15-25 mph with gusts as high
as 35 mph during the day (particularly along/east of Hwy 1). Expect
highs ranging from the mid 30s NW to mid 40s SE, plus or minus a few
degrees depending on precise fropa timing. With Canadian high
pressure building over the Mid-Atlantic/Carolinas by 12Z Friday
morning, expect very cold overnight lows in the teens to lower 20s,
coldest in the N/NW Piedmont where the MSLP gradient will slacken
the earliest. -Vincent
Friday:Modified Arctic high pressure will be centered over the
region to start the day on Friday and will shift east, off the Mid-
Atlantic seaboard Friday evening. With the h8 thermal trough
lingering over the area, expect another day of frigid temperatures
on Friday, with afternoon temperatures struggling to climb above
freezing across the northern piedmont and coastal plain, to upper
30s across the south. -CBL
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
As of 350 PM WEDNESDAY...
Friday night through Saturday night:
Next batch of northern Pacific energy will will lead to re-
amplification of the mean trough in place over the Conus and the
development of a surface low over the Central Plains on Friday. This
low will track northeast through the Middle MS and Ohio Valleys
Friday night and Saturday, and then accelerate across the NE and New
England by early Sunday. Strong 850mb WAA ahead of the system,
fueled by a 50-60kt SWLY LLJ will support a period of
overrunning/isentropic lift late Friday night/Saturday morning.
Near to sub-freezing temperatures Friday night/early Saturday may
support a few wet snowflakes or sleet at precip onset, but will
quickly change-over to light freezing rain and then rain from SE to
NW between 06 to 15z Saturday as a stout/prominent 10 to 12 C warm
nose overspreads the sub-freezing near surface layer.
Without a favorably located parent high to supply a steady feed of
CAA, the freezing rain/drizzle will be short-lived and a self-
limiting process. Additionally, with only 0.10" of liquid-equivalent
expected, and all of that not going towards ice accrual, expect a
light glaze at best(1/16" or 0.05") across the far NW Piedmont/Triad
area where the the longest duration(~6hr) of freezing rain is
possible. Lows Friday night in the upper 20s north to lower 30s
south.
Could see light patchy rain through the afternoon, but once the warm
front lifts north through the area by noon Saturday, we could see a
lull in rain until Sunday as the front approaches from the west.
High temps Saturday will depend on the timing of the warm front
lifting north through the area and resultant In-situ CAD erosion
across the Piedmont. Highs ranging from mid/upper 40s NW to around
60 SE. Temperatures Saturday evening/night are expected to either
hold steady or slowly rise in advance of the front.
Sunday through Monday: The southern end of the trailing cold front
attendant to the surface low moving through the Canadian maritimes
will move slowly east through the area late Sunday afternoon and
Sunday night. Forecast models are in fairly good agreement in
showing a healthy band of ana-frontal precip with the system,
bringing some much needed-widespread rainfall of 0.50-1.0" to
central NC. Pre-frontal warm sector highs on Sunday will be mild,
ranging from near 60 NW to lower 70s SE. Much cooler behind the
front on Monday, and continued cloudy and potentially wet,
especially across the east in proximity to the stalled front
offshore.
Monday night through Wednesday: In response to the development of a
closed low over the SW US and resultant continued SWLY flow aloft,
the front is forecast to stall off the Southeast Coast through
Tuesday. Ana-frontal precip could linger across eastern NC through
early Tuesday, but otherwise models have trended drier and cooler as
another strong ~1040mb surface high builds into the area from the
West.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 740 PM Wednesday..
An upper level disturbance and associated mid level ceilings and
virga will continue to move E and offshore this evening, followed by
clearing and calm/light and variable winds overnight. Consequent
radiational cooling may result in the occurrence of patchy fog in
Ern NC, including a small chance at KRWI and KFAY, between 04-10Z.
Otherwise, VFR conditions are expected; and an arctic cold front
will move SE across the forecast area early Thu, with following
blustery NW winds that are expected to gust up to 25 kts Thu
afternoon.
Outlook: Sub-VFR conditions, and light precipitation, will develop
late Fri night and early Sat, and continue at times throughout the
weekend, as a storm system approaching from the west interacts with
lingering arctic high pressure. The precipitation will likely begin
as a period of light freezing rain early Sat, with the highest
probability and relative greatest impacts from a light glaze, at
Piedmont sites.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...MWS
NEAR TERM...Vincent/Smith
SHORT TERM...Vincent/CBL
LONG TERM...CBL
AVIATION...MWS
Area Forecast Discussion
National Weather Service Charleston WV
1036 PM EST Wed Dec 14 2016
.SYNOPSIS...
Cold front crosses tonight, followed by very cold weather Thursday
and Friday. Storm system this weekend starts as wintry mix, then
becomes all rain. Colder again to start next week.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 1035 PM Wednesday...
Burst of snow has indeed developed along I79 corridor over the
last hour with some reductions in vsby to 1 mile or less. Have
upped the snow accumulation a few tenths along this
corridor...still below 1 inch until reaching the high terrain,
where an inch or so is possible over the next 3 hours. Things
quickly wind down after 06Z as drier air works thru the column.
As of 635 PM Wednesday...
Forecast generally on track. We are awaiting the arrival of arctic
air as the night progresses, with some flurries breaking out.
Near term models are continuing to suggest a burst of snow showers
across the central mountains in the the 4 to 6Z time frame which
may put down a coating.
Tweaked hourly temp/wind grids using latest HRRR and Nam as a
base. Winds will become gusty as strong CAA ensues overnight,
sending wind chill values into the low single digits to below
zero by morning. Current headlines still look good, so no changes
anticipated this evening with those.
As of 335 PM Wednesday...
Cold front, just entering IN and western MI this afternoon,
charges eastward across the forecast area tonight. The
polar/pacific air in place, and the polar/arctic air mass behind
it, together with a subtle southwest to northwest wind shift,
spells little inflow, and thus little moisture and precipitation
with the front itself. However, winds pick up behind the front,
strengthening the upslope flow given increased contribution based
on both speed and direction. This will lead to snow showers in
the mountains, mainly the windward side. With primarily only
upslope and good crystal growth, only looking at an inch to an
inch and a half accumulation tonight in the most favored higher
windward terrain.
The snow showers quit Thursday morning as the arctic air is also
very dry, but the last flurry will not be gone almost until the
last cloud is gone given the very low temperatures Thursday.
Guidance has been handling temperatures well in this pattern, and
the near term update did not result in much change. Temperatures
will be very slow to start recovering Thursday morning, typical
of arctic air masses.
The combination of low temperatures and the wind will lead to wind
chill advisory criteria in the northwest corner of the county
warning area, and across the higher terrain. For Perry county, 10
kt winds will drive wind chills to around ten degrees below zero
Thursday morning, beginning well before dawn. Have wind gusts up
to 25 kts. For the higher terrain, 10 to 25 kt sustained winds,
with gusts 25 to 40 kts, will drive wind chills to 10 to 20 below
zero, the worst values across the highest terrain, also starting
well before dawn Thursday, but lasting through Thursday night.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 345 PM Wednesday...
A very cold night expected across the region as we head into
Friday morning. For now it appears that cloud cover will not start
to increase until early Friday morning so that will allow plenty
of time for radiational cooling. Some sites will likely drop
below zero in the coldest spots of Pocahontas and Randolph
Counties. Elsewhere it is looking like widespread single digits
with near zero lows in the Northern Forecast Area.
Clouds will be on the increase Friday as moisture begins to
return. Strong WAA/overrunning pushing northward Friday night.
Cold air will remain entrenched at the surface, however aloft
temperatures will climb well above freezing by Midnight. With
dewpoints in the teens I would expect evaporational cooling will keep
temperatures below freezing across the region into early Saturday
morning. A wintry mix or plain freezing rain will be a high
probability from I64 northward and there is a could chance
locations further south will also see a period of frozen
precipitation. Winter weather advisories will probably be need,
but due to some uncertainty with how fast surface temperatures
will warm we have decided to just continue to highlight in the
HWO and hold off any headlines until we get a bit closer to the
event.
Eventually by mid morning on Saturday the temps should be warm
enough everywhere for precipitation to turn to all rain. Light rain
will continue through the day with about a quarter of an inch
expected.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 345 PM Wednesday...
A cold front pushes into the region Saturday night with a heavier
shot of rain expected. Colder air filters in behind the front
fairly quickly, and rain should turn over to snow early Saturday
morning as all guidance is in fairly good agreement with this now.
However, how much moisture lags behind the front is where the
spread in the guidance increases. Light snow accumulations will
be possible for the entire area, but how much will depend on how
fast the changeover occurs and if enough moisture lingers behind
the front.
&&
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
As of 645 PM Wednesday...
An arctic front will cross tonight with MVFR stratocu developing
along the boundary. This will be brief out across the lowlands,
or not even occur at all along the Ohio River. Snow showers are
possible in the mountains overnight, with flurries over the
lowlands, mainly east of the Ohio River, in the arriving arctic
air. There looks to be a 1 to 2 hour window centered on 04Z for a
burst of snow in the central mountains, affecting KEKN/KBKW with
brief IFR vsby which has been handled with tempo groups.
Snow showers, flurries and clouds will break up Friday morning as
very dry air moves in.
Surface winds will strengthen and become gusty from the west to
northwest overnight and remain so on Friday, as the arctic air
moves in. Moderate west flow aloft will veer to moderate northwest
tonight and remain so on Friday.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z FRIDAY...
FORECAST CONFIDENCE: Medium to high.
ALTERNATE SCENARIOS: IFR vsby may not materialize in the 4 to 6Z
time frame at KEKN/KBKW should expected snow burst not occur.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE THU 12/15/16
UTC 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14
EST 1HRLY 22 23 00 01 02 03 04 05 06 07 08 09
CRW CONSISTENCY L H H H H H H H H H H M
HTS CONSISTENCY H H H H H H H H H H H M
BKW CONSISTENCY M M L M M M H H H H H M
EKN CONSISTENCY L L M H H H H H M M M L
PKB CONSISTENCY H H H H H H H H M M H M
CKB CONSISTENCY H H H H H H H H M M M M
AFTER 06Z FRIDAY...
IFR possible in mixed wintry precipitation Friday night into Saturday.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Wind Chill Advisory from 2 AM Thursday to 6 AM EST Friday for
WVZ520-522>526.
OH...Wind Chill Advisory from 2 AM to noon EST Thursday for OHZ066.
KY...None.
VA...None.
&&
$$
SYNOPSIS...TRM/MPK
NEAR TERM...TRM/30
SHORT TERM...MPK
LONG TERM...MPK
AVIATION...30