Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/17/18
Area Forecast Discussion
National Weather Service Albany NY
956 PM EST Tue Jan 16 2018
.SYNOPSIS...
A developing coastal low pressure system will form
southeast of the Delmarva region overnight and track northeast to
near Cape Cod late Wednesday morning. This system is expected to
bring a moderate to heavy snowfall to much of the region overnight
into Wednesday. Seasonably cold and mainly dry weather is expected
Thursday with some lake effect snowfall northwest of the Capital
District.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 945 PM EST...The latest RAP guidance with the GOES-16
Clean IR /10.35 micron band/ satellite imagery overlaid
continues to show cloud tops cooling over much of the forecast
area with the a positively tilted mid and upper level trough
centered over the central-eastern Great Lakes Region. A decaying
primary sfc low has drifted over the central NY-PA border. A
secondary sfc/coastal low is continuing to form southeast of the
Delmarva corridor. Over running moisture ahead of the coastal
low continues to spill into the region with a baroclinic zone
set-up over eastern NY and western New England. The snowshield
continues to fill in, and the latest KENX and regional radar is
showing an enhancement in the radar echoes with a bandlet/band
setting up north and west of the best low- mid level FGEN over
the southeast Catskills, mid-Hudson Valley, Berkshires and
central and southern Taconics. Snow rates may start to reach the
0.50-1.0 inch/hr rate shortly before midnight there. Some
slight adjustments were done with the PoPs and snow amounts. The
current headlines look good with Warning for 5-10" of snow from
the Mid-Hudson Valley of Dutchess Co., the Taconics into
eastern Rensselaer County eastward into western New England.
West of the warning area, advisories remain up for 4-8" in the
Capital Region, eastern Catskills, Schoharie Valley, and the
Lake George Region northern Saratoga Region, and 2-6" further
west.
With the approaching mid and upper level trough and a strong mid
and upper left front quadrant of a jet-streak nearby, recent
Northeast CSTAR research would suggest the potential for a
quasi- stationary mesoscale band of snowfall on the northwestern
side of this developing low pressure area especially after
midnight to continue. The latest mesoscale models, including the
3-km HRRR and NAM do suggest the heaviest snowfall amounts
extending from the Poconos northeast across the Catskills, mid
Hudson Valley and into NW CT/Berkshires overnight.
Previous near term...
The morning commute will likely be fairly difficult across much
of the area on Wednesday morning due to the snow covered
roadways and low visibility. As the low pressure lifts up
towards eastern New England, snowfall will start to taper off
from west to east during the day on Wednesday. We will have to
monitor for a brief period of Mohawk-Hudson Convergence /MHC/
in the late morning based on some of the mesoscale model trends
including the latest NAM12. Based on the track of the cyclone,
and the local flow patterns in the adjoining valley, it is
possible referring to the MHC CSTAR conceptual model. Snowfall
should be done in the Capital Region and mid- Hudson Valley by
the mid to late morning and should be ending in western New
England by the late morning or early afternoon hours. Winds will
switch to the northwest behind the storm, but shouldn`t be too
strong since the surface low is fairly weak, so blowing/drifting
doesn`t look like a concern with this event. Temps on Wednesday
will generally be in the 20s, with a few spots in the mid-
Hudson Valley and NW CT reaching the low 30s. Clouds should be
breaking for some sun on Wednesday afternoon from west to east
as well.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
A ridge of high pressure will build in Wednesday night
providing mainly dry conditions. However, due to well aligned
westerly flow and borderline conditional lake induced
instability, there will be some lake effect snow showers across
the western Adirondacks. Any accumulations should be light, with
shallow inversion heights of only around 850 mb are expected.
Temperatures will be near normal, with lows in the single digits
and teens.
Similar conditions should prevail on Thursday, with a flat
ridge in place and a westerly flow continuing. Again, some light
lake effect snow showers may affect the western Adirondacks,
but dry conditions should prevail elsewhere. Snow showers may be
a bit more enhanced with greater coverage Thursday night across
the western/southern Adirondacks, as a fast-moving short wave
trough is expected to move through. Still, only minor
accumulations are forecast with mainly dry conditions elsewhere.
Temperatures will remain near normal during this time. Highs on
Thursday will be in the upper teens to lower 30s with lows
Thursday night in the mid teens to lower 20s.
On Friday, any lingering lake effect should end during the
morning with dry conditions expected Friday afternoon. Highs on
Friday will be in the mid 20s to mid 30s.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
This period will mark a turn toward much above normal
temperatures...with highs mainly in the 30s and 40s each day, and
lows stating out mostly around 20 degrees Friday night, with mostly
upper 20s and lower 30s by Sunday and Monday nights. With mid-
January being Albany`s coldest time of the year, on average, lows
there are normally in the mid teens, with highs around 30 degrees.
High pressure centered over the deep south will build up into the
mid-Atlantic region. An east-west frontal boundary will stay just
north of our zones as low pressure over the center of the contiguous
U.S. develops and tracks across the Great Lakes and into southern
Quebec through Monday night, displacing the high pressure and
bringing a good chance of rain showers throughout the area as early
as Sunday night, which could start as snow. By midday Monday, all
areas outside of the high peaks of the Adirondacks will likely
experience pure rain shower activity ahead of a cold front which
will move quickly east across our zones Monday night. It will be
overcast with low instability. Only a modest decline in
temperatures will be experienced behind the front...to as low as
near normal.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
A double barrel low pressure system will impact eastern NY and
western New England tonight into tomorrow with snow. The primary
low over upstate NY will weaken tonight, as the secondary
coastal low moves along the Atlantic Coast towards eastern Long
Island by daybreak tomorrow. The coastal low will quickly move
northeast of Cape Cod by the afternoon with the snow tapering to
snow showers and flurries.
In the developing snow shield conditions will continue to lower
from MVFR/IFR levels in terms of cigs/vsbys. Expect the
cigs/vsbys to lower to widespread IFR and some LIFR levels with
vsbys down to 1/2SM to 3/4SM with moderate snow between 04Z-
08Z. The best chance for sustained moderate snow with vsbys a
1/2SM will be from KALB/KGFL/KPSF/KPOU from 07Z-13Z/WED. The
snow will begin to taper and lighten prior to 16Z/WED with
lingering MVFR cigs/vsbys thereafter. As the system moves
northeast expect widespread VFR conditions after 18Z/WED with
cigs BKN-OVC 3.5-4.0 kft AGL.
The winds will be calm tonight or light and variable at 4 kts or
less. The winds will increase from the N to NW at around 5 kts
after 12Z/WED, and will continue to strengthen from the
northwest at around 10 kts by the afternoon with some gusts
16-20 kts at KPOU/KALB/KPSF.
Outlook...
Wednesday Night to Saturday: No Operational Impact. NO SIG WX.
Saturday Night to Sunday: Moderate Operational Impact. Chance
of SHRA...SHSN.
&&
.HYDROLOGY...
Ongoing flooding due to ice jams will continue to be addressed
with areal flood warnings. There could still be some lingering
issues as any existing ice jams may tend to become frozen in
place due to the continued cold temperatures expected over the
next few days. Warmer weather is not expected until the weekend.
In terms of precipitation, a moderate snowfall is expected for
much of the area from today into Wednesday, with heavy snowfall
from the mid Hudson Valley and Taconics eastward across western
New England.
For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...Winter Storm Warning until 3 PM EST Wednesday for CTZ001-013.
NY...Winter Weather Advisory until 3 PM EST Wednesday for NYZ032-
033-038>043-047>053-058>060-063-082>084.
Winter Storm Warning until 3 PM EST Wednesday for NYZ054-061-
064>066.
MA...Winter Storm Warning until 3 PM EST Wednesday for MAZ001-025.
VT...Winter Storm Warning until 3 PM EST Wednesday for VTZ013>015.
&&
$$
SYNOPSIS...JPV/Wasula
NEAR TERM...Frugis/Wasula
SHORT TERM...11/JPV
LONG TERM...ELH
AVIATION...Wasula
HYDROLOGY...11/JPV
Area Forecast Discussion
National Weather Service Taunton MA
713 PM EST Tue Jan 16 2018
.SYNOPSIS...
A developing coastal low pressure will emerge off the Delmarva
tonight and track northeast to near Cape Cod Wednesday morning.
This system is expected to bring a moderate to heavy snowfall to
western and central MA and northern CT late tonight into Wednesday.
Snow, with a likely transition to rain for the BOS-PVD corridor
by the mid-morning. However, impacts to the morning commute are
likely. Mainly dry weather likely Wednesday night into Sunday,
with a warming trend during this weekend. Another low pressure
should affect our region early next week with mostly rain.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
* Potent Winter Storm expected late tonight into Wednesday
* Hazardous Morning commute expected
713 PM Update...
Overall trend in the forecast remains on track this evening.
Some light snow ahead of the main low pressure already moved
into portions of north central and western MA. Visibility was
down as low as 1 mile, so expecting this snow will be
accumulating at least a little.
Mainly tweaks to the forecast this evening to reflect observed
trends. Expecting precipitation to not overspread the rest of
southern New England until after midnight. Last few runs of the
HRRR seem to have a decent handle on timing, so used it as a
basis for this update.
Tonight into Wednesday...
Overview...
More substantial snowfall is expected starting this evening into
tonight, as a coastal low pressure system is forecast to emerge
off the Delmarva and track northeast along a baroclinic zone
close to the NJ/Long Island coast. At the same time, the
positive tilt mid/upper level trough will migrate eastward.
Appears that a transfer of energy as coastal low jet structure
begins to take hold early tomorrow morning will help phase the
clipper system. This coastal low track has been key for this
forecast as it is projected to track across the Cape and up
towards the Maritimes. At the same time, open wave at 700 mb and
surface high situated over the Maritimes will help allow the
warm air to push into southern New England. The lack of
blocking, also allows for this system to be quite progressive.
So with the progressive nature, closer surface low track and
warm air mixing into the I-95 corridor went ahead and adjusted
snowfall amounts and sped the system up.
P-type...
Ongoing snowfall this evening will overspread across the region
as cold front from the west approaches. Coastal low will move
up the coast by the morning hours resulting a perhaps a good
thump of snow right around the morning commute. Trended the
onset of the snowfall with wet-bulbing to help indicate some
moderate lift in the snow growth region. However, decent warm
air at 925mb and at 950mb pushes into the I-95 corridor right
after the rush which will transition any snow into rain. This
will help undercut snowfall totals.
Several model p-type algorithms also keeps the precip more as
snow. However, that does not agree with current synoptics and
climatology, especially with a low tracking over the Cape. The
other thing we noticed is Hi-res guidance including the HRRR and
RAP show a snow hole moving across RI and southeast MA towards
the morning commute. This minimum in the guidance is a suggested
in jet energy transfer towards the coastal low. Snow will
eventually fill into that region, but there could be some lower
amounts between 06-12z.
Mixing could reach as far as Windham county and up into coastal
Essex which is in agreement with EC, GFS and NAM. As the storm
moves up towards the Maritimes later in the day, it does
strengthen, allowing for any rain to transition back to snow
by the late afternoon hours. This is all depending on where
precip will be ongoing, with our highest confidence right now
for NE MA.
Snow Amounts/Hazards...
Higher snow amounts remain across western MA for this evening
which is climatology supported. Appears to be a good swath of
over 0.5 inches across Hartford county and up into northern
Middlesex county. Thereafter QPF amounts will be lower towards
the Canal, with a secondary max across the Cape and Islands.
With higher snowfall ratios, expect about 5-8 inches of snowfall
within the current warning, with isolated higher amounts near 9
or 10 inches as you get closer to the Berkshires. This area
appears to have good forcing within the snow growth region also
some banding near the Berks down into Hartford county as shown
by packed thermals in the mid-levels. Thus could see some higher
amounts. Thus will keep the current winter storm warning for
Western and Central MA as well as Hartford and tolland CT.
As you get closer to the I-95 corridor expect around 2-5 as this
region has a better shot of mixing during the mid-morning hours.
This as well as the snow hole will keep amounts lower and thus
have downgraded the I-95 corridor to an advisory. Did not have
the confidence to keep the warning up, especially with the
warmer trends in all of the models. Closer to the south coast
and near the Canal, amounts will be less than 2 inches. Most of
the snow will fall tonight into the early morning hours, but
will quickly transition to rain by the morning. Thus went ahead
an dropped the advisory.
Even though amounts and hazards have been lowered, the timing of
this system is not ideal as it brings accumulating snow during
the morning commute. Motorists should use caution and take their
time if heading out in the morning.
&&
.SHORT TERM /WEDNESDAY NIGHT/...
Coastal low will continue to move towards the Maritimes
Wednesday night. This will pull all the moisture with is so
any lingering snow showers will come to an end. Thus will not
expect much in the way of issues with the evening commute.
Cloud cover will improve by the later half of the night, and if
we decouple then temps will bottom out during the overnight
hours. Low temps will range from 20s across the Cape and Islands
to single digits across Western MA where fresh snow pack
resides.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Highlights...
* Cold and dry Thursday
* Continued dry with a warming trend through this weekend
* Another storm may bring mostly rain Monday into Monday Night
16/12Z guidance is in reasonable agreement moving a deeper mid
level trough offshore Thursday, with the mid level flow becoming
more zonal across the eastern USA by Saturday. Still expecting a
modest mid level ridge to build over the Eastern Seaboard this
weekend. This should set the stage for a modest mid level trough
to pass through early next week.
Overall, this is looking like a rather quiet period of the
forecast. Dry weather should prevail Thursday into Sunday, with
a gradual warming trend and above normal temperatures.
A low pressure is expected to move through the Great Lakes
sometime early next week, and swing a cold front across our
region. The timing is still uncertain, since it is still 6-7
days away. It does appear the most likely precipitation type
will be rain. However, some light snow, or even freezing rain,
will be possible if precipitation were to have a longer duration
at night. It will likely be several more days to work out these
sorts of details. The most likely period for precipitation
would be from Monday afternoon into Tuesday morning.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Wednesday Night/...
Tonight and Wednesday...High confidence in trends. Moderate
confidence in timing. Mainly IFR-LIFR CIGS/VSBYS in snow, with
areas of heavy snow north of a KBOS-KHFD line. Snow may mix
with or change to rain south of a KGHG-KPVD-KWST line during
Wednesday. Conditions improve to VFR across CT and western MA
Wednesday afternoon, and across RI and eastern/central MA
Wednesday night. Wind gusts 20-25 knots around Nantucket and
parts of Cape Cod.
Wednesday Night...High confidence. Any lingering IFR/LIFR will
improve to VFR from west to east during the overnight.
KBOS Terminal...Moderate to high confidence in TAF. Morning push
will be impacted.
KBDL Terminal...High confidence in TAF. Morning push will be
impacted.
Outlook /Thursday through Sunday/...
Thursday through Friday Night: VFR. Breezy.
Saturday: VFR. Windy with local gusts to 30 kt.
Saturday Night: VFR. Breezy.
Sunday: VFR.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Wednesday Night/...High confidence.
Easterly swell will continue to keep seas up tonight across the
eastern waters. However seas will slowly relax late tonight.
Approaching coastal low tomorrow will build seas and winds for
all of the waters. Low pressure system will track over Cape and
head towards the Gulf of Maine. Could see some gusts near 20-25
kts but seas will build near 5-8 feet. Thus have extended SCA
for outer waters into Wednesday night.
Outlook /Thursday through Sunday/...
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Chance of freezing spray.
Thursday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Local rough seas.
Friday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas.
Friday Night: Winds less than 25 kt. Areas of seas approaching
5 ft.
Saturday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Seas up to 5 ft.
Saturday Night: Winds less than 25 kt. Local rough seas.
Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
&&
.HYDROLOGY...
Minor flooding continues along the Taunton River, where a Flood
Warning remains in effect. A Flood Warning is also in effect
for the Connecticut River at Middle Haddam, where ice is causing
some river fluctuations.
Colder weather will persist through midweek which will limit
additional runoff. Continued ice jams expected on some of the
rivers. There will be an increase of snow pack for a portion of
southern New England through Wednesday as several inches of
snow will fall.
For details on specific area rivers, including observed and
forecast river stages, please visit the Advanced Hydrologic
Prediction Service (AHPS) graphs on our website.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory from 1 AM to 6 PM EST Wednesday for
CTZ004.
Winter Storm Warning until 3 PM EST Wednesday for CTZ002-003.
MA...Winter Weather Advisory from 1 AM to 1 PM EST Wednesday for
MAZ017>019.
Winter Weather Advisory from 1 AM to 6 PM EST Wednesday for
MAZ007-013>016.
Winter Storm Warning until 3 PM EST Wednesday for MAZ002-003-
008>011.
Winter Storm Warning from 1 AM to 6 PM EST Wednesday for
MAZ004>006-012-026.
RI...Winter Weather Advisory from 1 AM to 1 PM EST Wednesday for
RIZ002>004.
Winter Weather Advisory from 1 AM to 6 PM EST Wednesday for
RIZ001.
MARINE...Small Craft Advisory from 7 AM to 7 PM EST Wednesday for
ANZ235-237.
Small Craft Advisory until 8 AM EST Thursday for ANZ250-
254>256.
Small Craft Advisory until 1 AM EST Wednesday for ANZ251.
&&
$$
SYNOPSIS...Belk/Dunten
NEAR TERM...Belk/Dunten
SHORT TERM...Dunten
LONG TERM...Belk
AVIATION...Belk/Dunten
MARINE...Belk/Dunten
HYDROLOGY...
Area Forecast Discussion
National Weather Service Key West FL
943 PM EST Tue Jan 16 2018
.DISCUSSION...
KBYX Doppler radar shows a large swatch of chaff north of the Keys
island chain extending into southwest Florida. Very weak echoes
continue to drift northward in the Atlantic, mainly offshore from
the Upper and Middle Keys. These echoes are elevated, and it is
unlikely that any precipitation is making it to the surface. If it
is, it is very light. And, the trend is for these echoes to wane
as they approach the island chain.
The evening local sounding showed the winds up to nearly 4000 feet
remained fresh from the northeast. Flow above that has
strengthened from the southwest/west. Moisture remains low in a
relative sense, but there is a sense of increase in a layer from
4000 to 7000 feet nudging northward. Have already sent a zone
update to increase the cloud cover for the overnight period,
maintain just a slight chance of light showers, and trimmed our
northeasterly breezes to gentle to moderate.
&&
.MARINE...
Sent a coastal waters forecast update out a little early this
evening to account for lower winds being reported along and north
of the reef. The local HRRR suggests a wind surge over the next
hour or so, but even with this, the overall wind field for most
locations will be sustained below the small craft advisory
criteria, save for the Straits. That headline has been preserved
through the early morning hours there, but an exercise caution for
small craft has replaced the advisory from the afternoon package
elsewhere.
&&
.AVIATION...
VFR ceilings are expected through the overnight period. Winds will
be sustained moderately through tonight from the north/northeast,
then freshen from the north with less overall cloud coverage
expected through the day on Wednesday at both the KEYW and KMTH
terminals.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...Small Craft Advisory GMZ052>055-072>075.
&&
$$
Public/Marine/Fire...04
Aviation/Nowcasts....04
Data Collection......L. Kasper
Visit us on the web at weather.gov/key
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Area Forecast Discussion
National Weather Service Memphis TN
638 PM CST Tue Jan 16 2018
.UPDATE...
Update to add light snow showers along and downwind of Kentucky
Lake and Tennessee River.
&&
.DISCUSSION...
A another very cold night is in store for the Mid South as an
upper level shortwave rotates across the region and surface high
pressure builds in from the west. It appears that conditions will
again be favorable for lake/river effect snow along and downwind
of Kentucky Lake/Tennessee River. It appears that as winds shift
north-northeast later this evening will set up a favorable fetch
along the lake/river. Latest high resolution HRRR soundings
suggest a moist layer will develop between 1.5-2.0kft beneath an
inversion. This moisture layer is well within the prime dendritic
snow growth zone. In addition, the temperature difference between
the water temperature and air temperature should create near dry
adiabatic lapse rates through this moisture profile. Light
accumulations will be possible along and downwind of the best
fetch along the lake/river system. This may also occur along
smaller lakes across eastern sections of the forecast area.
Further west, there is a smaller potential for this set up along
the Mississippi River. Although winds and lift are not as
impressive, therefore will leave it out of the forecast for now.
Increased low level clouds will be possible and a few snow
flurries cannot be completely ruled out.
Further north across northwest Tennessee, there may also be enough
lift and moisture associated with the upper level shortwave to
produce a few flurries. This has been left out of the forecast for
now as confidence is not high enough at this time.
One thing is for certain, very cold temperatures will continue
tonight across the forecast area. Low temperatures will range from
zero to five above in many locations. Temperatures may go even
lower if cloud cover can clear out and winds die out earlier than
expected. This will be monitored closely throughout the evening
and additional updates will be provided as needed. Wind chills
will likely range from zero to ten degrees below zero across the
Mid South and a wind chill advisory remains in place.
Updates have been sent and additional updates to temperatures will
be provided, if needed.
JLH
&&
.PREV DISCUSSION... /issued 308 PM CST Tue Jan 16 2018/
Surface analysis this afternoon places a cold front from East
Tennessee back through Northern Georgia, the Florida Panhandle,
and the Northern Gulf of Mexico. Regional WSR-88D radar trends
indicate snow has moved out of the North Mississippi and any
remaining Winter Weather Advisories have been cancelled. As of 3
PM CST, temperatures across the Mid-South are predominantly in the
teens at most locations.
A ridge of arctic high pressure will build in across the Lower
Mississippi Valley tonight into Wednesday. Leftover precipitation
from last night`s/today`s winter storm will refreeze, especially
on untreated surfaces as temperatures remain below freezing.
Temperatures are expected to fall into the single digits below
zero tonight across many locations and went below MOS guidance
with the addition of snow cover across the forecast area. A
combination of these very cold temperatures and winds will result
in wind chill values falling between zero and 10 degrees below
zero tonight across the entire Mid-South with the coldest wind
chill values over the northern one third of the area.
Not much recovery in temperatures is expected on Wednesday with
high pressure overhead. There is a possibility of an additional
Wind Chill Advisory being needed Wednesday night into Thursday
morning, especially north of I-40.
A gradual warming trend will begin towards Friday as the high
pressure moves east and southerly winds on the backside of high
pressure returns. Temperatures by the end of the weekend will
range from the upper 50s to lower 60s. Long term models indicate
rain chances and perhaps an isolated thunderstorm or two will
return for the latter half of the upcoming weekend into early next
week as another front moves through the region. High pressure will
build in behind this front for the remainder of the long term
forecast into next week.
CJC
&&
.AVIATION...
00z TAFs
VFR conditions to prevail for the majority of the TAF set as
Arctic high pressure builds in. However, some uncertainty exists
in the short term in regard to low-level cloud formation and
possible MVFR ceilings as an upper-level disturbance pivots
through the Midsouth over the next 12 hours. Highest confidence at
JBR where a 4k ft broken deck looks to arrive shortly, while MEM
and MKL are lower confidence with a TEMPO group to handle. Winds
remain light at 5-10 kts out of the north.
WLC
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Wind Chill Advisory until 10 AM CST Wednesday for Clay-Craighead-
Crittenden-Cross-Greene-Lawrence-Lee AR-Mississippi-
Poinsett-Randolph-St. Francis.
Wind Chill Advisory until 10 AM CST Wednesday for Phillips.
MO...Wind Chill Advisory until 10 AM CST Wednesday for Dunklin-
Pemiscot.
MS...Wind Chill Advisory until 10 AM CST Wednesday for DeSoto-Tunica.
Wind Chill Advisory until 10 AM CST Wednesday for Alcorn-Benton
MS-Calhoun-Chickasaw-Coahoma-Itawamba-Lafayette-Lee MS-
Marshall-Monroe-Panola-Pontotoc-Prentiss-Quitman-
Tallahatchie-Tate-Tippah-Tishomingo-Union-Yalobusha.
TN...Wind Chill Advisory until 10 AM CST Wednesday for Carroll-
Crockett-Dyer-Gibson-Haywood-Henry-Lake-Lauderdale-Madison-
Obion-Shelby-Tipton-Weakley.
Wind Chill Advisory until 10 AM CST Wednesday for Benton TN-
Chester-Decatur-Fayette-Hardeman-Hardin-Henderson-McNairy.
&&
$$
Area Forecast Discussion
National Weather Service New York NY
941 PM EST Tue Jan 16 2018
.SYNOPSIS...
Low pressure develops along the Mid Atlantic coast tonight and
then passes near or just east of Long Island on Wednesday before
moving up the coast into the Canadian Maritimes Wednesday
night. High pressure will then build to the south through Friday
and move into the western Atlantic this weekend. A cold front
then passes through Monday night into Tuesday morning.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
No significant changes were made to the forecast with this
update except to delay precip timing a bit from NYC on east. It
looks like precip will blossom after 06-08z as the upper trough
dynamics interact with the developing secondary low. No changes
were made to the winter weather headlines.
Light snow continues to fall across NW Orange County. Starting
to see reflectivity increase as better dynamics begin to move
into this area. Steadier precipitation will continue to
overspread from the west through the night and then blossom
across the rest of the area towards day break.
Have taken an initial look at the 00z NAM12, 00z 3-KM NAM and
they generally support the current forecast. QPF may be a bit
lower than previous runs, but overall looks close. The latest
HRRR also is in general agreement with the ongoing forecast.
The biggest challenge continues to lie with the northward
extent of the warmer air and how far the rain/snow line works.
Despite temperatures currently running a bit cooler than
previously forecast in the NYC metro area, a surge of warmer air
at the surface to just above 925 mb is anticipated. This is due
to a prolonged period of S-SE winds ahead of the developing low.
The transition of energy from upper trough/weakening primary low
is to the secondary low is slow such that an inverted trough is
expected to extend back into the Hudson Valley of New York.
This should allow the rain snow line to make it about 10-20
miles north and west of I-95 corridor in New Jersey to near or
just south of a line from HPN to DXR.
Temperatures will remain nearly steady overnight and even slowly
rise. Lows will range from the upper 20s in the interior to the
mid 30s along the coast.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Low pressure near Long Island in the morning lifts northeast
during the day and up into the Canadian Maritimes by Wednesday
night. Precipitation shuts down across most of the area by late
morning/early afternoon and perhaps ends as period of snow at
the coast. Even if the changeover to snow occurs a bit faster
than indicated in the city/at the coast, limited duration of
precipitation on the backside of the low will limit any
accumulation. Highs will top out in the mid to upper 30s with
NW winds developing on the backside of the storm. Gust up to 20
mph develop late in the day and possibly linger into first half
of the night.
Cold air will follow for Wednesday night with lows in the teens
inland and around 20 at the coast. This is slightly below
normal.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Surface high pressure will build to our south on Thursday and
Friday. Meanwhile, an upper trough shifts through with some
shortwave energy Thursday night into Friday. Moisture looks
insufficient for any PCPN, so dry weather is expected. Highs a few
degrees below normal for Thursday, returning to near normal on
Friday. Ridging aloft will then keep the weekend dry with warming
temperatures.
Low pressure enters the Great Lakes Region Sunday night, eventually
tracking through Quebec on Tuesday. Some warm advection PCPN may
reach some of the northern zones Sunday night into Monday morning,
which could be in the form of a wintry mix. A cold front otherwise
approaches with increasing chances of rain during the afternoon and
night. Some timing differences still exist among the global models
with the cold front passage, so have capped PoPs at chance through
Tuesday morning. Rain chances otherwise diminish Tuesday afternoon
with dry weather likely returning Tuesday night. Temperatures Sunday
through Tuesday will remain above normal.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
A developing coastal low with move north towards the region
overnight, tracking just southeast of Long Island on Wednesday,
and then into the Canadian Maritimes by Wednesday evening.
Conditions expected to gradually lower to MVFR this evening, then
lower to IFR late tonight as precipitation develops across region.
Expect all snow at KSWF, which may be moderate at times between
06z and 12z. Rain expected to develop for NYC/NJ terminals after
midnight, likely mixing with snow towards daybreak, and then
briefly changing to all snow Wed morning. KHPN/KBDR may see a
mix of rain/snow overnight, before changing to all snow towards
daybreak. All rain expected to for KISP/KGON. Precip taper off
from W to E Wed morning into early afternoon, with conditions
improving to VFR.
E/NE winds less than 10 kt overnight, becoming N/NNW towards
daybreak. Winds become WNW with gusts 20 to 25 kt Wed afternoon
continuing into Wed eve push, likely averaging just right of
310 magnetic.
.OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY...
.Wednesday night-Thursday...VFR. WNW winds G20-25KT for Wed Eve
push and on Thursday.
.Thursday night-Friday...VFR. W-SW winds G20KT possible.
.Saturday-Sunday...VFR.
&&
.MARINE...
SCA in effect for the ocean waters as seas remain 4-5 ft. Ocean
seas increase a bit more tonight. Flow returns to a NW direction
and begins to gust late on Wednesday.
SCA conditions continue on the ocean for Thursday through Friday
morning, then sub-advisory conditions are expected for a brief
period Friday afternoon and night. Winds and seas then pick up with
marginal advisory conditions on the ocean during Saturday and
Saturday night. A weaker pressure gradient then returns relatively
tranquil conditions for Sunday.
&&
.HYDROLOGY...
No significant hydrologic impacts are expected.
&&
.EQUIPMENT...
NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the
air for an extended period of time.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory until 1 PM EST Wednesday for
CTZ005>008.
NY...Winter Weather Advisory until noon EST Wednesday for NYZ069-
070.
Winter Storm Warning until noon EST Wednesday for NYZ067-068.
NJ...Winter Weather Advisory until noon EST Wednesday for NJZ002-
004-103>105-107.
MARINE...Small Craft Advisory until 6 AM EST Thursday for ANZ355.
Small Craft Advisory until 6 AM EST Thursday for ANZ350-353.
&&
$$
SYNOPSIS...JC/DW
NEAR TERM...DW/DS
SHORT TERM...DW/DS
LONG TERM...JC
AVIATION...NV
MARINE...JC/DW
HYDROLOGY...JC/DW
EQUIPMENT...
Area Forecast Discussion
National Weather Service Raleigh NC
740 PM EST Tue Jan 16 2018
.SYNOPSIS...
A strong Arctic cold front will approach from the west, crossing our
region very late tonight through Wednesday morning. High pressure
will build into the Carolinas Thursday, then remain anchored over
the Deep South through the weekend, leading to a warming trend.
&&
.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
As of 740 PM Tuesday...
Upper trof edging east is right on track, with mid cloudiness
reaching the Triad during the past hour. Timing of the precip is on
track as well, with latest HRRR soundings in the Triad indicative of
saturation in the -12 to -18 growth zone a little before midnight,
with the Triangle area following suit a couple of hours later.
Initial light precip will begin to blossom behind the front as it
moves into the western Piedmont after midnight, but may not reach
the ground for a couple of hours afterwards, with coverage
continuing to spread east through morning. Any changes prior to
arrival of 00Z guidance will be to update hourly grid trends.
Previous Discussion:
Summary and Main Points:
NWP models have trended wetter over the past couple of runs, which
has boosted forecast confidence that the strong dynamic support
aloft associated with the vigorous shortwave trough will support a
quick burst of significant snowfall across central NC between 12 to
18z Wednesday, with an increasing likelihood of seeing a broad snow
swath of 2 to 4 inches, with locally higher amounts of 5 to 6
possible across the interior portions of the RAH CWA. As such, have
upgraded all but the 2 most SE counties(Sampson, Wayne)to a Winter
Storm Warning. Due to the west-east difference in onset and ending
timing of precip, will segment the warning/advisories maps, with an
earlier start in the west and later ending in the east.
Details:
The well-advertised blast of Arctic air, that`s currently supporting
daytime highs in the teens and 20s across central and eastern TN, is
well on it`s way. There has been little change in the model timing
of the frontal passage through the area; between 06z-09 through the
NW Piedmont, to 12 to 15z across the southern Coastal Plain. On the
heels of this front, the high-amplitude positively-tilted trough
that currently extends from SE Canada back into the Southern Plains,
will assume a neutral tilt as it traverses the region on Wednesday,
a signal of the strengthening deep layer lift(coupled ascent from
strong s/w dynamics, vigorous jet divergence and deep layer f-gen)as
depicted by bufkit soundings that shows a classic cross-hair
signature(moderate to strong lift intersecting with the dendritic
growth zone(-10C to -18C))across central NC between 12 to 18z. As
such, expect the ana-frontal precip band to fill in and blossom
across the area during that time frame. So, it`s not a surprise to
see that models have trended wetter over the last 24 hours, with
average liquid equivalents now in the 0.20 to 0.40"range.
While we could see a brief period of rain or rain-snow mix at onset,
especially east of the US 1 where precip will move in after
daybreak, deep layer cooling will result in a quick change-over to
snow, with high snow:liquid ratios of 12:18 expected in the 3 to 6
hour window of strongest forcing, similar to the upstream ratios we
saw across Middle Tn and Central-Eastern Tn earlier this morning.
This would support a broad swath of 2 to 4 inches(0.5-1.0"/hour
rate)across interior sections of the state, with localized higher
amounts of 5 to 6 inches certainly possible given the favorable set
up for banding precip. Elsewhere, along the western and SE fringes,
1 to 3 inches are possible. Aggressive drying aloft will overwhelm
the area as early as late morning in the west to mid afternoon in
the east. This would support a brief transition of freezing drizzle
before ending, resulting in only trace ice amounts. The drying and
subsidence aloft is so strong and abrupt, that western portions of
the forecast could see sunshine by the afternoon, indeed a quick
hitting system.
Additionally, the Arctic high building in the Southern US in the
wake of this system will support very cold temperatures and wind
chills Wednesday and Wednesday night. Daytime highs will likely
occur during the early morning at most locations, with wet-bulb
cooling and CAA leading to a quick drop into the 20s by midday. NWLY
wind gusts of 15 to 20 kts will make it feel even colder, producing
wind chills in the teens and 20s.
Lows Wednesday night are expected to be in the teens, with wind
chill values approaching the single digits across much of central
NC. Given these frigid temperatures, any snow or slush on roads and
bridges/overpasses will freeze, making for treacherous road
conditions Thursday morning.
&&
.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
As of 200 PM Tuesday...
In the wake of the exiting system Thu, expect blustery and cold
conditions with afternoon temperatures 10-15 degrees below normal.
Dependent upon the extent of the snowpack, min temps Thu night may
end up a few degrees colder, possibly ranging from the mid teens to
around 20.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 200 PM Tuesday...
The extended forecast will feature a warming trend across the
Carolinas as the upper level pattern transitions from a highly
amplitude pattern with a west coast ridge and east coast trough, to
one of feature a broad, low amplitude trough across the entire U.S.
Moderation in the atmosphere begins in earnest Friday and continue
through the weekend. The dry air mass coupled with a wly flow should
result in a wide diurnal temperature swing of 25-30 degrees. Highs
Friday will be close to normal in the upper 40s and lower 50s, then
warm well into the 50s Saturday, and near 60-lower 60s Sunday.
The mild conditions will persist into early next week as the flow in
the mid-upper levels remain zonal. An upper level disturbance will
be lifting well to our nw Monday. This system`s attendant cold front
will approach and cross our region Monday and Monday night,
increasing the threat for scattered showers.
&&
.AVIATION /00z WEDNESDAY THROUGH MONDAY/...
As of 640 PM Tuesday...
24-Hour TAF Period: No major changes aviation-wise for the next 24
hours. Still expect snow to develop across Central NC tonight,
reducing ceilings and visibilities into the MVFR/IFR range along
with it. Light and variable winds early tonight will become north-
northwesterly and gusty Wednesday morning into the afternoon. -KC
Previous discussion: Precipitation falling through the dry sub cloud
layer will initially evaporate before reaching the surface but will
aid to lower ceilings into the MVFR category after 06Z Wed in the
Triad, and between 09Z-13Z elsewhere across central NC. The
precipitation will initially start out as rain but will quickly
change over to snow. the snow will pick-up in intensity across the
west after 09Z, and across the east after 12Z, with visibilities 1-
2SM common. The snow will taper off over the western Piedmont after
15Z, and by early-mid afternoon across the eastern counties. Sfc
winds will be light and variable through 10Z, then increase out of
the north with gusts 18-23kts probable. -WSS
Looking ahead: Aviation conditions will improve west-to-east late by
Wednesday night as a drier colder air mass overspreads the region.
VFR parameters expected Wednesday night through Sunday. -WSS
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 4 AM to 9 PM EST Wednesday for NCZ078-
089.
Winter Storm Warning from 11 PM this evening to 4 PM EST Wednesday
for NCZ007-021>025-038>040-073>076-083-084.
Winter Storm Warning from 4 AM to 9 PM EST Wednesday for NCZ008>011-
026>028-041>043-077-085-086-088.
&&
$$
SYNOPSIS...WSS
NEAR TERM...CBL/mlm
SHORT TERM...WSS
LONG TERM...WSS
AVIATION...KC/WSS