Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/31/19
Area Forecast Discussion
National Weather Service Bismarck ND
923 PM CST Mon Dec 30 2019
Issued at 922 PM CST Mon Dec 30 2019
Main concern this update is developing stratus and fog potential for
western and central North Dakota tonight. The main focus is on
aviation interests...see aviation section below for those details.
Otherwise, earlier forecast had a mention of the stratus and fog
developing...the tricky issue is how widespread they will be. Latest
iterations of short term high res models do not pick up on the
stratus forming in the southwest near Beach/Dickinson. However
models are persistent in depicting the stratus/fog developing in the
northwest, then moving/expanding into central ND overnight and
finally reaching the James Valley towards daybreak.
Thus expect western ND to increase in clouds through the early hours
of Tuesday...then clearing from the west. Increasing clouds central,
maintaining clouds and fog for most of the nighttime hours. Low
clouds and patchy fog lingering in the James Valley after
UPDATE Issued at 600 PM CST Mon Dec 30 2019
Winter Weather Advisory for much of the James River Basin counties
will be allowed to expire at 6 pm CST. Northwest winds of around 20
mph with gusts to around 30 mph at times will continue in the James
Valley area early this evening, then decrease gradually tonight.
Visibilities have improved through the afternoon, with only
occasional dips in visibility to 6 miles or so in some patch blowing
snow between now and midnight.
Otherwise, attention then turns to the possibility of stratus clouds
and some fog developing northwest, spreading into central North
Dakota. Short term models continue to indicate this possibility, and
satellite loops indicated some stratus forming over parts of
southern Saskatchewan and northeastern Montana that were advancing
southward. Will continue to monitor any progression/expansion of
stratus and fog and send updates as needed.
UPDATE Issued at 229 PM CST Mon Dec 30 2019
Visibilities just outside of the southern James River Valley have
improved per webcams, thus the winter weather advisory has been
cancelled for Wells, Foster, Kidder, and Emmons counties. Webcams
still show quite a bit of blowing and drifting in the southern
James River Valley and will maintain Stutsman, Logan, LaMoure,
McIntosh, and Dickey counties in the winter weather advisory until
6 PM CST Monday.
.SHORT TERM...(This evening through Tuesday)
Issued at 210 PM CST Mon Dec 30 2019
The winter weather advisory addressing blowing/drifting snow and
lower visibilities especially in open country remains in good
standing this afternoon and will let it continue until the
original expiration time of 6PM CST Monday. Northwest winds
between 20kt and 30kt atop of a large area of total snowfall
between 15 inches and 26 inches continues to create blowing and
drifting snow with low visibilities, per a couple of Emergency
Management officials in the James River Valley. Some light
flurries (no accumulation) through early evening in the James
River Valley, but that would be it as dry conditions will prevail
For tonight, latest RAP/HRRR/GFSLAMP push an area of stratus now
located in central Saskatchewan and Alberta into northern and
central North Dakota tonight. The NBM was much less aggressive, so
used a blend of the warmer RAP low temperatures and colder NBM
temperatures to get some compensation between the two possible
solutions. The evening shift can adjust as satellite trends
dictate how things are progressing and verifying. Areas of fog
also predicted along and east of the Missouri River by all high
resolution models, so have used this and populated the fog grids
with this mention. Lows tonight expected in then upper single
digits to mid teens. However if stratus does not materialize as
expected, then much colder (widespread single digits) low
temperatures will occur.
Dry Tuesday with weak low level warm air advection in the morning.
A weak/subtle shortwave with no surface reflection, but some
reflection at 850mb as a cold pocket (-2C to -4C) swings across
Tuesday afternoon and evening. Overall expect partly cloudy to
mostly sunny conditions after the morning low clouds and residual
areas of fog. Highs will range from the upper teens in the Turtle
Mountains and southern James River Valley, to mid 20s central,
and mid 30s southwest.
.LONG TERM...(Tuesday night through Monday)
Issued at 210 PM CST Mon Dec 30 2019
Upper level flow is predominately west to northwest, so quick
moving clipper systems with brief warm ups, then a cool down, and
some light precipitation with each. And with each clipper cold
frontal passage, expect gusty northwest winds between 20 and 35
First clipper sends its warm front across western and central ND
Wednesday with a chance for rain or snow. Decent warm air
advection will help boost high temperatures into the 30s, with
lower 40s in the west Wednesday afternoon. The clippers cold
front slides through Wednesday night into Thursday morning. Here
we may see a light wintry mix. There are periods that we lose ice
aloft in the top/down approach per NAM/GFS/ECMWF, but precipitation
chances remain on the low side. In addition, NAM/GFS BUFKIT
soundings show some potential for a chance of light freezing rain
as well, but most of the vertical motion resides above the low
level saturated region, so not real confident at this time we
will realize any widespread areas of light freezing rain
The next clipper already slides into western North Dakota Thursday
evening, and soundings show better saturation with height and
colder temperatures through the column, so will see strictly a
chance for snow. Snowfall accumulations of around one inch
certainly possible with this one along with patchy areas of
Colder for Friday behind the clipper with highs in the 20s, than
warming back into the 30s for the weekend. Another surge of cold
air with highs in the 20s returns Monday.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 922 PM CST Mon Dec 30 2019
Update for the 00z TAF cycle:
Gusty northwest winds continued at KJMS with ceilings improving to
VFR. Visibility went to 7sm during a recent gust to around 35 mph.
Winds should decrease gradually through the night.
Main concern at all TAF sites is developing IFR/MVFR stratus over
western North Dakota the past couple of hours. Crosby station in the
far northwest corner of the state reported 1200 ft
ceiling...followed by a 900 ft ceiling. Latest high res models
continue to depict IFR ceilings and visibilities, but not as far
west as KISN and KDIK. Unfortunately, stratus has developed farther
west...and have amended TAF at KISN and KDIK to reflect this.
Further development of stratus and fog expected...expanding to KMOT
before 04z...and perhaps at KBIS by around 08z...and in KJMS by
around 12z. It is expected that the stratus and fog would linger at
KISN and KDIK for around 3-5 hours, improving overnight after
Area Forecast Discussion
National Weather Service Boston/Norton MA
1059 PM EST Mon Dec 30 2019
A deep low will linger across the central Great Lakes. The
secondary low south of Long Island will move across Cape Cod
early Tuesday morning, then push across Gulf of Maine Tuesday
afternoon. Light rain will linger across the coastal plain into
northern Connecticut overnight, while a wintry mix will
gradually change to snow across the central Massachusetts into
the Connecticut Valley. Precipitation will slowly taper off
from south to north from overnight into Tuesday morning. A few
intermittent snow showers are possible for New Years Eve night
across western Massachusetts into the Connecticut River Valley.
Pattern trends drier moving into the first week of the New Year.
Next chance for precipitation is with a frontal system Friday
into Saturday, with even warmer temperatures. Above normal
temperatures look to continue into the upcoming weekend.
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
1015 PM Update...
...Ice Storm Warnings and Winter Weather Advisories remain in
effect through 7 AM Tuesday...
Low pressure lingers south of Long Island at 03Z. Easterly
winds have increased along the S coast over the last couple of
hours, gusting up to 25-30 kt across most of the S coast, up to
39 kt at 03Z at KACK. Temps were running in the mid 30s to mid
40s, mildest across the islands. Further N and W, winds have
been gradually backing to N-NE, except mainly N across the mid
and lower CT valley where a wintry mix continues as temperatures
hover from 32 to 34 degrees. Across the Worcester Hills and
portions of the Berkshires, light snow was reported with reduced
Have held on to the ice storm warnings for now across central
Mass and the E slopes of the Berkshires as temps linger near and
below freezing. Could see some mixed precip develop over the
next few hours across the Worcester hills, where it is mainly
snow at 03Z, while noting freezing rain reports at KBDL, KBAF
Latest NE regional radar imagery showing the precip field
tending to become rather scattered especially across W Mass
into N central CT, as well as across steadier precipitation
continues across central and eastern areas. Another steadier
precip field heading NE toward the S coast as the low begins to
push in that direction.
With the onshore winds across eastern areas, temps are forecast
to remain steady or slowly rise through the remainder of the
night. Further inland, may hold steady or fall a degree or two,
then could begin a gradual rise around or after 06Z, and could
reach the lower-mid 30s across central Mass into N central and
NE CT, but readings across the E slopes of the Berkshires and
the northern Worcester hills may hold at around freezing through
Short range models and near term trends continue to signal the
back edge of the precip shifting slowly NE overnight, but may
see steady precip across N central/NE Mass linger through the
Mesoanalysis shows the elevated instability responsible for our
convection this afternoon has decreased over the past hour or
so, with the axis of just ~250 J/kg lingering over central MA
into northeast MA. Here we may continue to get some strikes in
the next hour or so as the back edge of the heavier precip moves
through, but the stronger storms we saw earlier should be done
as storms exit the favorable effective shear over western MA/CT.
Observations along the south and east coast continue to show
wind gusts 30-40 kts at this hour, but these will steadily
decrease as the secondary low crosses overhead and the pressure
gradient relaxes on Tuesday.
Synoptically we have a large cutoff system located across the
central Great Lakes. A secondary low will spawn east of New
Jersey this evening and lift northeastward across Cape Cod
tonight. As the secondary low develops, expect another slug of
precipitation to move across.
Heavily relied on the 12Z HREF and latest RAP guidance which is
doing well compared to the latest obs. Temperatures will remain
nearly steady with lows in the 30s.
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
Precipitation ending from south to north during the morning.
Temperatures warm up into the mid 30s and 40s during the day.
Could see some scattered snow showers across the Berkshires, CT
River Valley and western Worcester Hills for New Years Eve.
The secondary low lifts from Cape Cod into southern Maine by Tuesday
afternoon. Winds will shift from easterly/northerly to westerly.
Expect precipitation to taper off from south to north. Most areas
will see rain, but there may be a wintry mix across the Berkshires
as things are ending.
Expect some clearing as a weak 850 hPa ridge builds in during the
afternoon. This will be short lived, but should be enough to bring a
mix of sunshine and clouds across southern New England. Temperatures
will rebound into the mid 30s across the Berkshires and the mid to
upper 40s across the coastal plain.
The upper level cutoff will lift into southern Quebec and keep us
under cyclonic flow. Good agreement amongst guidance for scattered
snow shower activity across the Berkshires, CT River Valley and
western Worcester Hills for New Years Eve. Could see anywhere from a
half an inch to 1 inch of snow accumulation across the Berkshires.
Low temperatures range from the mid 20s across the Berkshires to the
upper 30s along Cape Cod and the Islands.
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
* Dry and milder-than-normal weather through Thursday night.
* Frontal system Friday into Saturday; may see brief wintry mix at
onset in northern MA but mainly a rain event. Well above normal
temperatures thru Sat.
* Drier weather for the weekend, with temps trending just less above-
New Year`s Day and night...
Sfc and upper low continue to pull north of the area Wednesday. Dry
weather and increasing sunshine through the day as drier air filters
in on generally zonal flow. Rising heights ahead of an incoming high
pressure ridge. High temps reach into the upper 30s/low 40s,
slightly above normal. Overall a pleasant start to 2020.
Thursday and Thursday night...
Pleasant weather Thursday under high pressure with temperatures
reaching the mid 40s. Sunny skies persist on dry NW flow much of the
day. The sfc ridge axis by late evening. As we move to the
backside of the ridge WAA and moisture advection will begin in
earnest. This brings the return of cloud cover and WAA on SW
flow, so a combination of warm advection and limited radiation
should keep lows a bit milder than the night previous, in the
upper 20s/low 30s.
Friday and Saturday...
This will be the most active weather of the extended forecast. A
digging shortwave in the plains will shift east beginning Friday
with a surface reflection lifting from the mid Mississippi Valley
into the central Great Lakes by late Friday/early Saturday. This
brings a very warm plume of moisture up the coast with PWATs
approaching an inch along our south coast by Friday morning. Given
the track of the parent low well to our NW over the Great Lakes this
will be a very warm, nearly all rain event for southern New England.
The only exception would be on the front end of the precip in
northern MA where model soundings show shallow subfreezing air
holding on beneath 850mb temps above freezing, so we could see some
light icing issues briefly before transitioning to rain. However,
confidence is low that this cold air will hold on long enough to
cause issues. Stay tuned. The warm sector overspreads Friday and
Saturday with 850 mb temps >10C spreading into southern New England
by Friday night. Along the cold frontal boundary models are
beginning to hint at a secondary low forming and moving along our
south coast which could increase QPF but by then temps are so warm
that even if winds do turn out of the NE Saturday precip will remain
as rain. Heaviest rain looks to fall south of SNE and along our
south coast where the nose of the LLJ and plume of moisture
coincide. High temperatures will be well above normal (10 to 15
degrees), in the upper 40s on Friday and into the mid 50s on
Sunday into next week...
Cold front moves through Saturday night bringing a drying airmass
and high pressure for Sunday and Monday with moderating temps back
toward normal; highs in the 30s and 40s on Sunday and down into the
30s by Monday.
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight.. IFR/LIFR, but expect VSBYS to gradually improve
across the interior as precipitation becomes lighter. Along the
south coast VSBYs come down to LIFR by 12Z and should last for a
few hours. Expect mainly rain except for freezing rain and
sleet at ORH until roughly 08Z. Gusty winds will diminish
across interior locations. The only exception is across Cape Cod
and the Islands where strong winds continue through 06Z to 12Z.
Tuesday ...Precipitation tapering off from south to north early
on Tuesday. Gradually expect conditions to improve. IFR/LIFR at
12Z but trending toward MVFR/VFR in the afternoon from south to
north. Expect gusty winds to develop at BOS, ACK and FMH by late
morning/early afternoon as the mixed layer grows.
Tuesday Night: VFR. Windy with local gusts up to 30 kt.
KBOS Terminal...High confidence in TAFs.
KBDL Terminal...Moderate confidence in TAFs.
Outlook /Tuesday Night through Saturday/...
New Years Day through Wednesday Night: VFR. Windy with local
gusts up to 30 kt.
Thursday: VFR. Breezy.
Thursday Night: VFR. Chance SHRA, chance FZRA.
Friday: Mainly VFR, with areas IFR possible. Chance SHRA,
Friday Night: Mainly VFR, with areas IFR possible. Chance SHRA.
Saturday: Mainly VFR, with local IFR possible. Breezy. Chance
/09Z MONDAY THROUGH FRIDAY/...
Easterly gales continue as low pres tracks from the NJ coast to Cape
Cod. Poor visibility continues in rain/drizzle and fog.
Gradual improvement as low exits Cape Cod and tracks into coastal
ME. Winds become westerly during the morning. Expect improving
visibility and dry weather during the afternoon. Leftover
easterly swells continue.
Outlook /Tuesday Night through Saturday/...
Tuesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Rough seas up to 9 ft.
New Years Day through Wednesday Night: Moderate risk for Small
Craft Advisory winds with gusts up to 30 kt. Areas of rough
Thursday: Winds less than 25 kt. Local rough seas.
Thursday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Chance of rain showers.
Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Rain showers likely.
Friday Night: Winds less than 25 kt. Local rough seas. Rain
Saturday: Winds less than 25 kt. Areas of rough seas. Chance of
CT...Winter Weather Advisory until 7 AM EST Tuesday for CTZ002>004.
MA...Winter Weather Advisory until 7 AM EST Tuesday for MAZ003-005-
Ice Storm Warning until 7 AM EST Tuesday for MAZ002-004-008-
RI...Winter Weather Advisory until 7 AM EST Tuesday for RIZ001.
MARINE...Gale Warning until 7 AM EST Tuesday for ANZ231-232-251-255.
Small Craft Advisory until 7 AM EST Tuesday for ANZ230-233>237-
Gale Warning until 9 AM EST Tuesday for ANZ250-254.
Area Forecast Discussion
National Weather Service Marquette MI
1021 PM EST Mon Dec 30 2019
Issued at 1018 PM EST MON DEC 30 2019
Water vapor imagery and RAP analysis show a well-defined mid-level
low over the western Great Lakes with the center over the middle of
eastern Lake Superior. Sfc low pres associated with the vigorous
shortwave that redeveloped the mid-level low to Lake Superior has
slipped out over Lake Superior near Munising this evening. While the
synoptic snow is gradually diminishing as the system fills, lake
enhancement will continue tonight. Latest RAP analysis has 850mb
temps around -8C over s central Lake Superior to the w of the low
pres and closer to -10C over western Lake Superior, more than
sufficient for lake enhancement. In fact over the last couple of
hrs, KMQT radar has shown a healthy uptick in reflectivity across
Marquette County under unidirectional 15-20kt northerly flow to
around 7kft per KMQT VAD wind profile. The greater than 28dbz
returns are suggestive of at least 1in/hr snowfall rates, and that
seems on track based visually on how heavily the snow has been
falling here at the office. Snow has definitely taken on better
dendrite/fluffier characteristics as well. With the slightly colder
air over the western lake, areas where low-level northerly winds are
most perpendicular to the terrain are likely experiencing snowfall
at least as heavy as we are seeing here at the office.
During the night, latest RAP and NAM suggest 850mb temps will fall
about 2C from western Lake Superior to s central Lake Superior,
increasing support for lake enhancement. Winds generally blo 850mb
tend to back toward the nw during the night which will weaken the
upslope that is strongly aiding the snowfall currently increasing in
Marquette County. However, a little higher up winds remain more
northerly, so that should maintain a lake enhanced component thru
the night as 850mb temps fall a little more. Low-level water vapor
imagery suggests the snow may briefly diminish in the next hr or
two across Marquette County as some drying arrives, but that
drying is then driven out under another push of moisture as the
mid-level low center drops s. Out over western Upper MI,
conditions will remain favorable thru the night for locally hvy
snowfall at times.
With headlines scheduled to expire at 06z, will need to work on some
extensions. Will opt to extend winter storm warnings across the Lake
Superior border counties over the w into the n central. Alger/Luce
are more challenging, especially Luce. Alger should see an increase
in snow overnight as nnw winds develop. Luce may not get under nnw
winds until morning when synoptic support really falls off. However,
models indicate a sharp low-level convergence zone setting up that
includes a moisture tap off Lake MI as winds over the eastern part
of northern Lake MI are backing southerly. Result could be enhanced
snowfall there as well. So in the end, will be extending winter
storm warnings for all of the Lake Superior border counties until
12z Tue. Other warnings will expire as previously scheduled.
Hopefully, new statement will be out around 0345z.
.SHORT TERM...(This evening through Tuesday)
Issued at 347 PM EST MON DEC 30 2019
Radar this afternoon shows moderate to heavy snow moving through the
U.P. from east to west. The primary fgen band set up farther east
than anticipated, keeping snowfall rates lighter to the west than
expected yesterday. Therefore, have only measured 3.3" through 18z,
though rates are picking up somewhat now as the band pivots
westward. Water vapor satellite shows the dry slot now wrapped
almost all the way around the cyclone. But as that dry air continues
to lift over the warm conveyor belt, convective-looking radar echoes
are now filling back in over Luce County. All in all, the rest of
this evening is mostly what you see is what you get. The big band
will continue to decay as the system occludes and we lose the fgen
forcing. But at the same time, this colder air wrapping in (850 mb
temps dropping to as low as -14 C tonight) will increase lake-based
instability and keep the snow going in the NNW wind snow belts.
Although lake-based instability parameters are nothing too extreme,
the lingering moisture and lift should allow for moderate to heavy
snow to continue straight through the night in these areas with a
majority of the accumulation from this storm yet to come. Some CAMs
also suggest that as the surface cyclone "landfalls" (so to speak)
early Tuesday morning (roughly 08z-12z), convergence may tighten up
and create a brief but intense shoreline convergence LES band into
Marquette County, generally for the city and points south and east.
All in all, expecting about 3-6" of additional snow outside of the
NNW wind LES belts through tonight, with 5-10" still to come in
those LES areas (including Ironwood, Houghton, and the city of
Marquette). Should note however that reports indicate snowfall has
disappointed so far along the immediate Lake Superior lakeshore
given the marginal temps and wind off the water. As temps drop into
the 20s tonight that should become less of an issue, allowing those
folks to catch up somewhat.
Lake effect snow showers will continue in the NW wind LES belts
through most of the day tomorrow, ending from west to east as the
cyclone finally departs to the east and drier air works in, dropping
inversion heights. As usual, the eastern LES belts of Alger and Luce
counties will be the last to see the snow come to an end. Snow
showers will linger past sunset tomorrow in those areas.
.LONG TERM...(Tuesday night through Monday)
Issued at 405 PM EST MON DEC 30 2019
A fairly progressive weather pattern continues through much of this
week into early next week. There is a system late this week that
models show tracking from the Central Plains/mid Mississippi Valley
into Lower Mi that could bring some light widespread snow or
snow/rain mix to Upper Mi on Friday. Temperatures are expected to be
above normal through this weekend and then begin trend below normal
toward the middle part of next week as a mid-upper level ridge
amplifying over the West Coast forces a broad downstream trough
across much of the central CONUS, including the western Great Lakes.
In association with the deepening trough across the central
CONUS/Upper Great Lakes region, a couple of clipper systems will
likely move through late weekend into early next week which could
bring another shot of system snow and then much colder temps to
support nw lake effect snow in its wake into the middle of next
Tuesday night, increased ridging and associated subsidence and
lowering inversion heights from the west along with the onset of
warmer 850 mb temps should quickly diminish any remaining nw flow
LES from west to east during the evening hours as the occluding
storm system finally lifts ne out the area.
Wed-Thu, surface ridging takes over and wind flow begins to back sw
so any lingering lake-effect snow should be over by early Wed. It
then remains quiet into Thu, although southwest winds could get
breezy on Thu as the surface pressure gradient tightens ahead of an
incoming trough/cold front from the Plains.
Fri into Sat, things get more interesting as models indicate the
development of a secondary surface low on the tail-end of the cold
frontal passage with the low lifting up through the Central
Plains/mid Mississippi Valley into central/southern portions of
Lower MI Fri into Fri night. With models trending farther southward
with track of the low, impacts with this system may be fairly
limited with a light mix of snow/rain on Fri and then marginal CAA
for scattered lake effect snow showers behind the system into Sat.
Will continue to monitor model trends with this system over the next
few days, but right now it appears like a low-impact system for our
The active weather pattern looks to continue into the tail-end of
the weekend and early next week as a couple of clipper systems dig
south from Canada down into parts of the Great Lakes. The exact
track and timing of the initial clipper system remains very
uncertain, but it appears the 12Z ECMWF and GFS may be trending
farther north which would mitigate or delay impacts for our area Sun
into Mon. Some of the models indicate a second and stronger clipper
system moving through on Tue which could bring a better chance for
widespread snow and likely enough Arctic air in its wake to sustain
nw flow into the middle part of next week, but again, we will have
to wait and see on this as model trends and fcst details could
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 656 PM EST MON DEC 30 2019
Gradual improvement will occur tonight and then accelerate on Tue as
low pres over the Upper Great Lakes weakens and shifts e. At
KIWD/KCMX, colder air moving across western Lake Superior will
enhance the snow, keeping somewhat heavier snow in place thru the
most, if not all, of the night and resulting in prevailing LIFR
conditions. Not out of the question that conditions could fall blo
landing mins at times. At KSAW, IFR conditions should prevail
tonight, though some periods of MVFR are expected along with
possibly some brief LIFR. Winds will become gusty to 20-30kt at all
terminals, leading to some blsn, especially at KCMX. On Tue,
conditions will improve to VFR by late aftn at KIWD and to MVFR at
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 356 PM EST MON DEC 30 2019
NNE gales up to 40 kts continue on the western half of the lake this
evening, spreading east to the eastern half and becoming NNW late
tonight. There could be some freezing spray tonight as well, mainly
on the north-central lake by isle Royale, but this is not expected
to hit warning-criteria. Winds across the lake subside below gale
force by tomorrow afternoon and below 20 kts by Wednesday morning.
Right now it looks like the next period of stronger wind should not
be until the weekend when 25-30 kt N winds are possible behind a
Winter Storm Warning until 7 AM EST /6 AM CST/ Tuesday for
Lakeshore Flood Advisory until 7 AM EST Tuesday for MIZ002-003.
Lakeshore Flood Warning until 7 AM EST Tuesday for MIZ001.
Winter Storm Warning until 1 AM EST /midnight CST/ Tuesday for
Gale Warning until 1 PM EST Tuesday for LSZ265-266.
Gale Warning until 10 AM EST /9 AM CST/ Tuesday for LSZ162-
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
945 PM EST Mon Dec 30 2019
Cooler air will move in tonight behind a cold front, followed by
high pressure for the middle of the week. The chance for rain will
return to the forecast Thursday afternoon and night.
.NEAR TERM /THROUGH TONIGHT/...
As of 935 PM Monday...
01Z surface analysis shows the cold front now east of the CWA, with
clear skies between the departing cold front and the expansive
stratocu in the upper trough over the Midwest. Not making any
changes to the forecast this evening as most everything appears to
be on track for lows in the 40s under continued clear skies. Will
be watching an area of low stratus over northern VA that is making a
fairly aggressive push southward in response to northerly flow
between a triple point low east of NJ and the occluded surface low
over the Upper Peninsula of Michigan. The HRRR suggests some of low
clouds could drift as far south as Emporia VA by sunrise, but
there`s not enough support to alter the forecast. -Smith
A cold front is currently moving through the region, with two
primary distinctions - a noticeable drop in dewpoints as well as
clearing skies. While the clearing behind the front is more gradual,
most locations are reporting a 5-10 degree drop in dewpoints in an
hour time span. Across the state, dewpoints are in the upper 20s to
the northwest but still near 70 across the southeast. Although many
locations only dropped into the 60s this morning, and the AFD
includes a climate section for record warm minimum temperatures, air
temperatures should drop to near 50 by midnight, preventing any warm
minimum records from being set. Skies will completely clear out
tonight, and between the clear skies and colder air behind the
front, temperatures will tumble between 20 and 25 degrees from last
night`s values. Nearly all locations will bottom out in the lower
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 245 PM Monday...
Surface high pressure will drift along the Gulf Coast Tuesday and
Tuesday night. Between the high to the southwest and low pressure
across the Great Lakes, this will funnel westerly winds to the
region. Another 24 hours of clear skies are expected. Temperatures
will be slightly above normal, which are generally in the lower 50s
and lower 30s for this time of year.
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 355 PM Monday...
A compact closed low now rotating along and offshore the srn CA and
nrn Baja coast will pivot sewd, then ewd across n-cntl Mexico
through early Thu, then become increasingly srn stream-influenced
and lift/deamplify rapidly newd across the lwr and mid MS Valleys
and lwr Great Lakes through Fri. A series of upstream shortwave
troughs in nwly flow aloft will re-carve/amplify a longwave trough
across the cntl US through the same time, while anomalous
subtropical high pressure expands from the swrn N. Atlantic nwd
along the East Coast. The foregoing trough initially over the cntl
US will then migrate ewd in progressive flow aloft, across the
Appalachians and ern US, then offshore, through the weekend and
early next week.
At the surface, weak high pressure will crest over the sern US Wed-
Wed night, then drift offshore. Meanwhile, a srn stream
cyclogenesis/frontogenesis will occur from the wrn Gulf of Mexico
newd across the TN Valley and Carolinas/srn middle Atlantic through
early Fri, downstream of a stronger cyclone that will track and
occlude from the cntl US to the Great Lakes. The aforementioned warm
front will retreat nwd across the Carolinas Thu night and early Fri,
with some degree of cold air damming that will likely slow/retard
that retreat over nrn/nwrn NC and VA. A cold front related to the
stronger, occluding low will then sweep east across NC Fri night,
with following high pressure that will gradually build ewd through
early next week.
The sensible weather related to the pattern described above will
feature dry and near average temperatures New Year`s Day and night,
with increasing mid-high cloudiness (to cloudy or mostly so) on Thu;
and that cloudiness will result in near persistence temperatures --
well shy of most guidance-- again Thu. That cloudiness will also
promote increasing rain chances late Thu and Thu night, some of
which will linger in saturated cold air damming over the nw Piedmont
Otherwise, the period from late Thu night through the first half of
Fri may prove to simply be a dry and warm one, as the aforementioned
subtropical ridge expands up the East Coast. The presence of that
ridge and related backing of the flow aloft to swly will also favor
a slower surface frontal progression across NC Fri night - closer to
EC (vs GFS) solutions during that time. Any clearing Fri night-early
will be short-lived, with cyclonic flow aloft and lift --and mostly
cloudy conditions and a small chance of showers-- accompanying the
longwave trough progression across cntl NC Sat afternoon-early
evening. Dry, with near average temperatures will then follow for
.AVIATION /00Z TUESDAY THROUGH FRIDAY/...
As of 600 PM Monday...
A cold front moved across the state today, and in its wake, dry air
has moved in and will allow clear skies through the TAF period. Some
wind gusts up to 15 kt are possible Tuesday afternoon, but did not
add another line to the TAFs to account for that at this time.
Beyond 00Z Wednesday: VFR conditions will continue into Thursday
before restrictions arrive in showers and lower clouds Thursday
night into Friday.
Area Forecast Discussion
National Weather Service Reno NV
314 PM PST Mon Dec 30 2019
Near normal temperatures Tuesday will warm to 5 to 10 degrees above
normal for the beginning of the new year. A weak system will bring
increased breezes Wednesday with a chance for light rain and snow
showers well north of Interstate 80. Quieter weather returns
Thursday and Friday, with a system possibly bringing light mountain
snow and valley rain and snow showers over the weekend.
Regarding lake effect off of Mono Lake, cameras from Lee Vining to
June Mountain don`t appear to show much instability for lake effect
with rather flat clouds near Lee Vining and what looks like just
stratus at June Mountain ski area. This makes sense with lake
surface to 700 mb temperature differences marginal for lake effect.
However, several HREF members still show hints at a few hours of
lake effect to the south and southwest of Mono County late this
evening so have left a low chance for snow showers this evening.
As far as the lake wind advisory for Lake Tahoe, right now winds are
running 10 to 20 mph (below lake wind advisory criteria). However,
the HRRR continues to show increasing winds this evening off of the
Carson Range as pressure gradients intensify, so have continued
the advisory (but will mention timing of increased winds in
High pressure builds over the region tonight and Tuesday. North to
east winds aloft and surface high pressure sitting in the western
Great Basin will bring seasonably cool temperatures Tuesday, with
moderate winds over the Sierra crest relaxing during the day as
gradients decrease across the Sierra. The ridge is expected to be
rather dirty with mid and high level clouds Tuesday.
A fast-moving system will brush by over the Northwest CONUS for
New Years` Day. This is not expected to bring too much impact to
most of northeast California and western Nevada; however, there
will be an increase in ridge winds and valley breezes, with light
shower chances (low impact) well north of Interstate 80. A very light
snowfall will be possible above about 5500 feet across northern
Washoe County and extreme northeast CA.
Thursday, high pressure builds back overhead with temperatures
topping out in the mid 40s to mid 50s for valleys. -Snyder
.LONG TERM...Friday through next Monday...
Not too many changes to the long term forecast this cycle. Long
range ensemble guidance shows the western half of the country in a
shortwave ridge to trough pattern through the first week of the
new year with most storm activity for the Pacific NW region. This
translates to periods of light showers with typical winds and patchy
cloud cover for the Sierra and western Nevada. No significant storms
are on the horizon at this time.
Friday looks to be a tranquil weather day as a shortwave ridge
remains over the region. This ridge is shoved quickly to the east
by a shortwave trough from the west possibly producing light
rain/snow showers for northeast California and northern Washoe
County on Saturday. Confidence is higher in both Friday and
Saturday looking to be above normal in terms of temperature with
highs in the 50s and overnight lows in the low 30s.
For Sunday into Monday of next week...a deeper, secondary trough
looks possible. Deterministic and ensemble model guidance does
shows this feature around this time frame, but there are
disagreements in overall forcing and strength of the shortwave.
Westerly winds are expected to increase on Sunday ahead of the
trough and its associated cold front. Precipitation is possible at
this time, but uncertainty exists in where most of the forcing
will take place. Will the trough dig deeper into our region
(deterministic guidance) generating more widespread precip or will
it track more northerly with the main impacts to the Pacific NW
and areas along the Oregon border (ensemble guidance)? As of now,
we have introduced slight chances for showers mainly north of I-80
for Sunday evening.
Temperatures drop back to normal Sunday and Monday as another
shortwave ridge builds in, bringing less cloud cover and light
For the most part, the low clouds experienced this morning have
broken up and will continue to do so as the low pressure system
that trekked along the California coast last night dives southward
into the Baja Peninsula.
Mainly VFR conditions, besides for some FZFG at KTRK early Tuesday
morning, from here on out for the rest of the year with light
northeasterly flow. Winds are expected to be stronger along the
Sierra ridgeline and KCXP/KTVL as northeast winds typically respond
better in these locations. Winds look to become light and variable
by Tuesday evening.
The next system for Wednesday will bring gusty afternoon WNW winds
up to 25 kts along with strong ridge winds and mountain wave turbulence.
Localized areas of LLWS are also possible. Any -SHRASN will be well
north of I-80, with some MVFR CIGS likely near the Oregon border.
NV...Lake Wind Advisory until 7 AM PST Tuesday for Lake Tahoe in
CA...Lake Wind Advisory until 7 AM PST Tuesday for Lake Tahoe in
For more information from the National Weather Service visit...
Area Forecast Discussion
National Weather Service San Diego CA
215 PM PST Mon Dec 30 2019
An upper low off the northern Baja will move further away from the
area through Tuesday. Gusty north to northeast winds are expected
over portions of the mountains, canyons and inland valleys through
Tuesday morning. Strong high pressure over the Pacific will build
east over southern California, resulting in fair, dry weather with
a warming trend for the remainder of the week and this weekend.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
After a period of light snow this morning, there has been little
in the way of reports over the San Bernardino County mountains the
last few hours. The latest GFS and short-term models including
the HRRR and local WRF indicate a continued downward trend in
precip potential through the evening. Given radar and model trends
and the lack of significant travel issues have gone ahead and
cancelled the Winter Weather Advisory.
The main concern in the short term period will be the winds. Winds
have been gusty over all of the mountain areas, Banning Pass, the
eastern valleys of San Diego County, the inland portion of Orange
County, and the upper part of the Inland Empire north of Fontana
and San Bernardino. Issued a Wind Advisory for portions of these
areas this morning and have expanded it to include the mountains.
Expect wind gusts as high as 65 mph over the mountains, and 50 mph
over the rest of the Advisory area, with the peak winds occurring
overnight tonight. The Advisory will run until 18Z Tuesday,
though winds over San Diego County will subside a few hours
earlier than that. Winds area wide should subside Tuesday
afternoon and Tuesday night.
Another upper trough passes well east of southern California late
Wednesday and Thursday. Should see some marine layer influence
both Wednesday and Thursday night with some night/morning low
clouds possible mainly near the coast. Upper ridging develops
directly over the area Friday and Saturday, resulting in further
drying of the atmosphere. Will see a nice warming trend by the
weekend with highs in the 70s likely over the deserts and valleys.
Generally used NBM guidance for the days 3 through 7 forecast. For
what it`s worth, the GFS ensembles show the next potential for
precipitation in the area late next week, beyond 10 days.
302100Z...BKN high clouds AOA 8000 ft, becoming SCT overnight. Low
confidence in -SHRA west of the mtns and -SHSN in the mountains. No
VIS or CIG restrictions are anticipated. East winds peaking at 15-25
kt sustained with local gusts to 35 kt expected at times over and
west of the mtns through 18Z Tue. Strongest winds will be through
passes and in the foothills. Areas of LLWS and MOD UDDFTS likely
through tonight west of the mtns.
Southeast winds with gusts near 20 kt will begin to diminish by late
afternoon. No marine hazards are expected for Tuesday and Wednesday.
An increasing long- period WNW swell will generate combined seas of
8-10 ft Thursday. Highest seas will be in southern portions of the
Outer Waters. High seas will likely continue into Friday morning
before gradually subsiding.
Locally elevated surf can be expected at San Diego County beaches
Tuesday due to a medium-period WNW swell from 290 degrees. An
incoming WNW swell with a long 19-second period will build into
Thursday. Confidence is high that widespread high surf conditions
will impact the area beginning Thursday. Surf will be highest in San
Diego County, at 8-10 ft. Orange County will likely see elevated
surf of 6-9 ft. High surf may linger into Friday, particularly in
San Diego County. Lower, but still elevated, surf is expected over
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
CA...Wind Advisory until 10 AM PST Tuesday for Orange County Inland
Areas-Riverside County Mountains-San Bernardino County
Mountains-San Bernardino and Riverside County Valleys-The
Inland Empire-San Diego County Mountains-San Diego County
Valleys-San Gorgonio Pass Near Banning-Santa Ana Mountains