Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/11/18
Area Forecast Discussion
National Weather Service Burlington VT
756 PM EST Sat Feb 10 2018
A quasi-stationary frontal zone extending from western New York
into far northern Vermont will maintain cloudy skies with
periods of snow across the North Country through this evening.
A wave of low pressure moving into the region along the frontal
boundary will bring warmer air aloft, with periods of sleet and
freezing rain mixing in with the snow tonight into Sunday. The
best chance for mixed precipitation will be across central and
southern Vermont tonight. High pressure will ultimately bring
drier air to the region Monday and Tuesday.
.NEAR TERM /THROUGH SUNDAY/...
As of 612 PM EST Saturday...Latest radar shows central and
southern portions of the CWA are now precipitation free south of
the front with more widespread snow persisting across northern
New York and portions of northern Vermont. Hi-res models such as
the NAM3, HRRR and locally run 4km WRF all handling the current
trends very well, and show mainly dry weather persisting south
with a brief period of rain possible as the front sags southward
and weak low pressure tracks along the boundary through the
mid-Atlantic and southern New England states. To the north snow
remains widespread through the midnight hour, but rapidly
decreases in coverage thereafter through the remainder of the
night. With this in mind, have cancelled the winter weather
advisory for central and southern Vermont, while continuing it
northward where additional snow accumulations of up to 2 inches
is possible through midnight. No other changes made to the
forecast at this time.
Previous Discussion...The Winter Weather Advisory remains in
effect through 7 am Sunday. Snow is spreading back across the
North Country this afternoon as weak low pressure moves along a
nearly stationary boundary. This boundary has lifted just to our
north today, allowing temperatures to warm into the 30s in many
spots away from the Saint Lawrence Valley, but it will slowly
sink south overnight. In fact, it has already begun its
southward trek as evidenced by northwest winds at Plattsburgh
and Burlington. As such, although precipitation may initially
start as rain or a rain/snow mix, it should transition over to
all snow by sunset. The snow will continue through this evening,
particularly over the north until the low moves east.
Meanwhile, another low will move to our south later tonight,
which will transition the precipitation more toward southern
sections of the forecast area. Cold air at the surface will
undercut warmer air moving in aloft, resulting in a wintry mix
of precipitation, mainly south of a St Johnsbury to Montpelier
to Elizabethtown line. Additional snow accumulation through
tonight will be 1 to 3 inches, with a glaze of ice possible.
For Sunday...expect a good part of the area will be dry as we remain
sandwiched between low pressure to our south and a second low
approaching to the west. Far southern areas will see a wintry mix
continuing early in the morning, but warm advection will begin in
earnest by early afternoon, turning the mix over to rain as
temperatures rise above freezing. This wintry mix will shift
northward through the afternoon as the more northern low approaches.
The low will slide along the St Lawrence Valley toward evening, and
temperatures will rise into the mid and upper 30s away from the St
Lawrence Valley by early evening. As such, precipitation will likely
change over to rain just about everywhere for a time Sunday
afternoon/evening. Once the low moves to the east, colder air will
rush in from northwest to southeast, turning precipitation back over
to all snow, starting roughly around midnight. However, moisture
will quickly get shut off, so snow will taper to showers and then
come to an end by daybreak Monday. Additional snow accumulations
overnight Sunday night will be less than an inch.
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 255 PM EST Saturday...Quiet weather is then expected
Monday and Monday night in a post- frontal airmass under
northwesterly flow which will trend light as 1040 mb polar high
settles overhead by Tuesday morning. Outside a lingering
mountain flurry early mainly dry weather is expected with
increasingly sunny/clear skies. Temperatures to generally range
within a few degrees of mid-February seasonal norms with highs
in the upper 20s to lower 30s and corresponding lows in the
single digits to around 10 above in warmer locations of the
Champlain and southern Vermont valleys.
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 255 PM EST Saturday... A seasonal, though fairly active
weather pattern looks to continue for the middle and later
portions of next week as near-zonal flow becomes slightly more
amplified over time. The polar front will be draped across the
northern tier of the lower 48 and waffle north and south across
our area through these periods. Decent stretches of dry weather
are expected, but given the proximity of the frontal boundary
clouds will be more common than sunshine. No large-scale
precipitation events are expected with the best shot of light
precipitation occurring Tuesday night as the boundary pushes
north with accompanying warm thermal advection, and then again
by Thursday/Thursday night as it passes back through as a cold
front. Temperatures should top out in the 20s to lower 30s on
Tuesday, Friday and Saturday, though trend milder into the upper
30s/lower 40s during Wednesday/early Thursday with the front
lying to our immediate north. Given these temperatures lie
either side of the 32F mark, precipitation will be characterized
as rain/snow showers at this point with some minor additional
snowpack additions to mainly higher terrain locales.
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Through 00Z Monday...Light snow continues across the region as
of 00z. IFR conditions will be likely through 06z Sunday due to
snow and mixed precipitation. Precip will wind down thereafter
as drier air works into the region, allowing conditions to
improve to MVFR. Mixed precipitation will spread northward
through Sunday 18z, with the wider valleys turning to plain rain
Sunday afternoon. MVFR conditions will prevail through then,
though local IFR will be possible.
Sunday Night: MVFR/IFR conditions possible. Chance RA, Likely
FZRA, Slight chance SHSN.
Monday: VFR. NO SIG WX.
Monday Night: Mainly VFR, with local MVFR possible. NO SIG WX.
Tuesday: VFR. NO SIG WX.
Tuesday Night: VFR. Chance SHSN.
Wednesday: Mainly MVFR, with local IFR possible. Slight chance
SHRA, Slight chance SHSN.
Wednesday Night: Mainly VFR, with areas MVFR possible. Slight
Thursday: Mainly MVFR, with local IFR possible. Chance SHRA,
VT...Winter Weather Advisory until 7 AM EST Sunday for VTZ003-004-
NY...Winter Weather Advisory until 7 AM EST Sunday for NYZ026-027-
Area Forecast Discussion
National Weather Service Wilmington OH
940 PM EST Sat Feb 10 2018
A cold front will continue to push slowly southeast. Meanwhile,
a series of low pressure systems riding northeast along the
front will lead to occasional chances for precipitation through
Sunday night. With cooler air moving in behind the front, there
is chance for a wintery mix of pcpn northwest of I-71. Drier
conditions will work in for Monday.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Temperatures have dropped off in the early evening. But it
appears that they should become fairly steady until closer to
morning. At that point, expect temperatures to start to slowly
rise as low pressure approaches.
There will be another surge of rain across southeast counties
overnight, and it is not out of the question that the northern
edge of this could be freezing rain. Not a lot of confidence in
this, but it will have to be monitored. North of the
precipitation shield there may be some drizzle which could
increase in coverage later in the night as the low gets closer.
Will not make any changes to the advisory at this time. If
sufficient drizzle breaks out in sub freezing temperatures, this
may have to be expanded for a period of time.
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Rain will develop early in the period along and behind low
pressure and a cold front that will track northeast across the
area. HRRR and RAP runs show that the precipitation will be
rather transient, likely only lasting a few hours at any one
location. But it appears that there will be a lingering chance
of precipitation through the afternoon as additional energy
lifts across the area. Details of temperature forecast become
more uncertain further out in time, but boundary of winter
weather advisory seem sufficient to capture the area where
freezing rain is likely. Temperatures will rise into midday and
then start dropping from west to east starting in the early to
After 00Z Monday, a shortwave in the northern stream will be
swing through the flow. Models are trying to develop a streak of
snow with the feature Sunday night, but are differing on the
exact placement. THe NAM has it across ne KY and the lower
Scioto valley, while the other models keep it farther se. Will
keep low chance PoPs in the se Sunday night. Temperatures and
thicknesses will be cool enough that the pcpn should be snow,
with a quick half inch possible.
.LONG TERM /MONDAY THROUGH SATURDAY/...
A system will be exiting the region at the start of the long term
Monday morning. High pressure and dry conditions will then work
into the region. Some off and on drizzle or light rain will move
across the region Tuesday through Thursday with southerly flow.
Cannot rule out some brief snow across northern portions of the
Better precipitation chances will be present Thursday evening into
Friday as a cold front approaches and moves through. There will
also be some snow with the front as colder air works in.
A frontal boundary with additional disturbances will linger around
the region for the weekend keeping precipitation chances in the
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
While there could be a few breaks in the lower clouds early,
IFR conditions will prevail through much of the period. Some
locations are expected to fall to LIFR late tonight into Sunday
morning. At the terminals there may be some drizzle from time
to time, and temperatures may get cold enough for this to be
As low pressure tracks across the region on Sunday, there will
be a period of rain associated with it. Ceilings and
visibilities will improve slightly and winds will shift to west
to west northwest. KDAY to KCVG/KLUK may rise to MVFR late in
OUTLOOK...MVFR conditions are possible Wednesday into Thursday.
OH...Winter Weather Advisory from 1 AM to 4 PM EST Sunday for
IN...Winter Weather Advisory from 1 AM to 4 PM EST Sunday for
Area Forecast Discussion
National Weather Service Jacksonville FL
837 PM EST Sat Feb 10 2018
.UPDATE...Marine fog will continue for the nearshore waters along
the First Coast and Coastal Southeast Georgia, so the Dense Fog
Advisory for the marine waters through Sunday afternoon. With the
lowest level winds becoming southerly, have hoisted a Dense Fog
Advisory for Coastal Glynn County with the areas that will be
most susceptible to the lowered visibilities include: Saint
Simons Island, Wesley Oaks, Glynn Haven, Sea Island, Wimberly on
the Marsh and Jekyll Island. Sea fog will develop over the western
peninsula coastal waters overnight. A southerly wind will make for
a peninsular flow, and good mixing immediately above the surface
at 20 to 25 knots combined with plentiful moisture above 550 mb is
not ideal for radiational fog. The best chance of fog will be
more maritime advection fog over southern part of coastal Glynn
due to the nature of the southerly flow. The HRRR hourly runs over
the last few hours continues to indicate that marine fog will
continue over our coastal waters and along much of western Florida
without much advection inland across our region but rather up the
U.S. Route 319 corridor north of the Big Bend area well west of
the region due to the southerly flow. Over most the region, a
hybrid of low stratus and patchy fog looks like the best bet,
except near the immediate coast. During the rest of the night, we
will continue to monitor area observations if fog develop deviates
from this latest thinking. There could be an influx of moisture
moving through Atlanta by early morning, translating south and
east through the pre-dawn hours where a few showers can reach near
or just west of the door step of the far NW interior zones of SE
Georgia by daybreak. Otherwise, the rest of the region will remain
dry. Overnight lows will be mild in the lower 60s.
.AVIATION...Sea fog will continue to impact KSSI through most of
the TAF period. Light southerly surface winds anticipated overnight.
Plenty of high level clouds will prevail through the period. Low
stratus and patchy MVFR fog is forecast to develop a couple hours
after midnight through the early daylight hours, with southerly
LLJ increasing around 20 to 25 knots. Daytime mixing and heating
will scour stratus between 16 and 18z with southerly surface
winds at 10 to 15 knots. While sea fog will continue at SSI
through late morning or early afternoon. Isolated to widely
scattered showers with a couple thunderstorms are possible in
during the mid to later part of the afternoon over area terminals.
.MARINE...Sea fog will continue for the nearshore waters, especially from
St. Augustine northward. The flow will shift to the south and southwest
overnight tonight, which should keep the sea fog away from the
immediate coast of northeast Florida, but still along the coast of
southeast Georgia. Dense sea fog will likely continue over the
nearshore waters during the next few days as high dewpoints stream
over relatively cold waters. Scattered shower and thunderstorm
activity will increase Monday, and especially Tuesday as a weak
backdoor cold front moves into the region. Surface high pressure
will then build over the waters in the middle of the week.
Rip Currents: Moderate risk will continue in the onshore flow.
.PRELIMINARY POINT TEMPS/POPS...
AMG 63 77 63 75 / 10 40 50 70
SSI 62 74 62 70 / 10 10 30 60
JAX 62 82 62 76 / 10 20 30 70
SGJ 62 80 63 75 / 10 30 40 60
GNV 62 80 64 79 / 10 20 30 60
OCF 63 82 64 80 / 10 20 30 60
GA...Dense Fog Advisory until 9 AM EST Sunday for Coastal Glynn.
AM...Dense Fog Advisory until 1 PM EST Sunday for Coastal waters from
Altamaha Sound to Fernandina Beach FL out 20 NM-Coastal
waters from Fernandina Beach to St. Augustine FL out 20 NM-
Coastal waters from St. Augustine to Flagler Beach FL out
Area Forecast Discussion
National Weather Service North Platte NE
710 PM CST Sat Feb 10 2018
Issued at 710 PM CST Sat Feb 10 2018
Based on current radar trends, as well as the latest HRRR and 4KM
NAM nest model, have decided to cancel the winter weather advisory
for Hayes and Frontier counties. The back edge of the
precipitation has moved east of the area, with some flurries/very
light snow occurring across Frontier county. This should come to
an end in the 9 to 10 PM CST time frame. Elsewhere, will probably
need to evaluate low temps for tonight, given the degree of
clearing. Fortunately with light winds, the threat for dangerous
wind chills appears minimal attm.
.SHORT TERM...(This evening through Sunday)
Issued at 213 PM CST Sat Feb 10 2018
The latest model consensus places the deformation band just south
of our southern three counties across southwest Nebraska. The
band has largely set up in that location, and based off of
upstream obs, moderate to heavy snow is occurring. Expected
snowfall as the band lifts east northeast will produce an
additional 2-3" across eastern Hayes and Frontier Counties late
afternoon and evening. The frontogenesis is strong aloft with some
omega in the DGZ and indications of weak slantwise instability.
Under the right conditions, snow accumulations of an inch per hour
would be possible. Along I80, light snow is possible under much
weaker lift and lesser moisture. Snow amounts will remain at a
half inch or less. Will continue the WWA for Hayes and Frontier
counties due to the expected snow late this afternoon and evening.
The advisory expires at 06z tonight.
The overnight temperature forecast was derived from a blend of
guidance with the WFR_ARW. This produces sub zero lows across
our north with single digits elsewhere. This seems reasonable
given weak downsloping winds and waa from the west. Am a bit
concerned though that the recent snows with clear skies will yield
much cooler lows like we saw last night. Will need to monitor.
The temperature forecast has big implications as cooler
temperatures would allow for dangerously cold wind chills. Given
the latest data, we feel that wind chills will remain warmer than
minus 19 F, but will monitor closely. Otherwise dry conditions and
slightly warmer temperatures are forecast for Sunday. The
temperature forecast is a result of blended guidance, but then
lowered to account for the deep snow pack.
.LONG TERM...(Sunday night through Saturday)
Issued at 213 PM CST Sat Feb 10 2018
Minimal to low sensible weather concerns in the long term period.
The main weather highlights include: cold wind chills early
Monday morning in far northern NEB, flurries/light snow possible
Monday, well-below normal highs Monday, and temperatures warm up
peaking into the lower 50s Wednesday.
Large scale pattern will feature an amplified longwave trough
over much of the CONUS early Sunday evening with shortwave
troughs near northern CA and another digging into the Pacific
Northwest. Meanwhile, west northwest flow prevails overhead. An
elongated upper level trough will then form over the West Coast-
Northern Rockies Monday. Deterministic guidance are in fair
agreement with the development of a closed low over the Pacific
offshore waters off CA by Tuesday, elsewhere a sheared disturbance
will be moving east through the Northern/Central Plains. A cold
front will advance into western NEB from the north by early
Sunday evening and should exit by late Sunday night. Meanwhile,
surface high pressure builds across the Missouri Valley and Upper
Midwest overnight with colder air filtering in.
While high clouds are anticipated, lows 5 to 15 degrees below
seasonable normals are expected with most locations expected to
see lows in the single digits above zero Sunday night. Winds will
be light and breezy as well so there are heightened wind chill
concerns across far northern NEB wherein wind chills approach the
upper teens below zero early Monday morning. However, wind chills
do not appear to reach advisory levels at this time. Monday will
be cold with highs forecast in the teens to 20s, warmest across
far southwest NEB. There are also low-end chances for light snow
Monday as well. Winds become westerly from the surface up to the
lower-levels with the passing of 850 hPa shortwave trough early
Tuesday. This will promote warming temperatures, albeit highs are
expected to read slightly below- normal Tuesday. Warm up trend
continues Wednesday with highs mostly 10 degrees above seasonable
normal values at this time.
Wednesday night and beyond, a weak surface cold front advances
across the local forecast area late Wednesday and that will drop
temperatures for Thursday. Highs Thursday and beyond are forecast
to generally by slightly below to near-normal. Differences between
guidance in the large scale pattern become more apparent with
differences in both phase and amplitude noted. While there are
low-end chances Friday-Saturday, confidence in timing and
location is below-average.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 549 PM CST Sat Feb 10 2018
Cloudiness will gradually shift south and east of the area
overnight with clearing expected across northern Nebraska by mid
evening and across southwestern Nebraska overnight. In the
meantime, expect ceilings of 5000 FT AGL at the KLBF terminal
through mid evening, with scattered clouds around 15000 FT AGL
through the overnight. Clear skies are expected on Sunday. For the
KVTN terminal, expect clearing skies after mid evening. Clear
skies will persist through Sunday.
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
808 PM CST Sat Feb 10 2018
808 PM CST
Moved up start time to the southern portion of the winter weather
advisory to 9 pm CST, with light mixed precip already developing
across central IL. No other significant changes made to going
forecast for overnight/early Sunday.
Surface stationary front was analyzed from the Arklatex to south
of the Ohio River this evening. 00Z upper air analysis continues
to show a very strong thermal gradient aloft north of the surface
front over our region, associated with the elevated frontal zone.
This baroclinic zone will continue to be the focus for another
round of wintery weather tonight through Sunday morning, as a
short wave trough propagates across the region. Low level warm
advection/isentropic ascent was already occurring across MO into
central IL, which was working to enhance the already strong
thermal boundary and force ascent. 00Z ILX sounding shows temps
near 0C around/above H8, and RAP forecast soundings depict this
warm layer increasing across the southeastern tier of LOT cwa
counties overnight. Already seeing mixed precip (snow, freezing
rain and the dreaded "unknown precip") reported from SPI to CMI,
along the ILX/LOT border. Thus have adjusted start time for winter
weather advisory a few hours earlier, due to the potential for the
potential for some light glazing in any freezing rain.
Farther north, mid-level frontogenetic forcing was producing
banded light snow from Nebraska/Kansas northeast across Iowa.
Radar returns over northern IL likely not reaching the ground just
yet, with cloud bases still generally above 10 kft. Guidance
indicates frontogenesis will strengthen across the area overnight,
with gradual top-down saturation leading to snow developing
toward or just after midnight. New 00Z NAM data is arriving, and
see nothing from it to change much of going forecast at this
Thus, moved southern cwa counties advisory start time to 9 pm,
and otherwise have only made minor tweaks to hourly temp trends
and pops here this evening based on observations/radar trends.
310 PM CST
In collaboration with surrounding WFOs, have issued a Winter
Weather Advisory for the whole CWA, in effect from midnight CST
tonight to noon CST on Sunday. For most of the area, looking at a
2-5" snowfall range. This appears to be another set-up where low
and mid level frontogentically driven banding component will play
a role, along with fairly steep midlevel lapse rates aiding in
snow intensity in at least transient more intense bands. Should a
persistent more intense band develop, currently appearing to most
likely to happen if it occurs north of I-80 in IL and IN, then a
narrow swath of localized 5-6" amounts will be possible. Expecting
snow rates to max out generally in the moderate intensity half
inch to inch per hour range, though again if a more persistent
intense band forms, then heavy rates of 1-2" per hour are possible
at least briefly. Model forecast soundings do indicate favorable
overlap of moderate to strong lift with the DGZ to support the
For the southeast CWA counties (Ford, Iroquois, Newton, Jasper,
Benton), have concern for mixed precipitation overnight,
including sleet and even freezing rain/freezing drizzle. NAM
soundings (using LAF as a proxy on BUFKIT) indicate an isothermal
warm nose of about 2-3 Celsius for a few hours, with GFS only
about +1 Celsius. Assuming enough ice crystal presence in the DGZ,
then it appears that low level cold wedge would be enough for more
of a sleet concern. However, the ice presence issue is an
uncertain one as the DGZ remains on the drier side/marginal.
Therefore, it`s also possible that freezing drizzle/light freezing
rain could occur at times, with freezing rain also possible if
refreezing of hydrometeors is less than anticipated. Have a second
segment of the Winter Weather Advisory for these counties with
1-3" of snow/sleet accumulation and light glaze of ice potential
The snow/precip will overspread the area late this evening into
the overnight and continue through Sunday morning before ending by
around mid day. Would like to note that there is a bit of
uncertainty on the start time of the snow/precip, with latest NAM
and short-range guidance on the slower side. For now felt
comfortable with 06z/12am CST start time, as most of the steady
light/moderate to briefly heavy snow should be confined to the
overnight through early-mid Sunday morning. The snow will come to
an end after the passage of a mid-level short-wave trough, though
it`s possible flurries could hang on through early afternoon.
Temperatures will be in the teens to around 20 tonight and top out
in low-mid 20s on Sunday. Wind will be fairly light northerly
10-15 mph or less tonight, shifting to northwest then west-
northwest on Sunday, so blowing/drifting is not expected to be an
220 PM CST
Sunday night through Saturday...
The main concern early in the period will be with the very cold
temperatures Sunday night into Monday. However, a quiet and mainly
dry period of weather is looking likely Monday through at least
A surface ridge of high pressure is expected to build into the
region Sunday night. However, the center of this high is likely to
remain well northwest of the area in the Dakotas into Monday.
While clear skies and a fresh deep snow pack certainly point to a
very cold night across the area Sunday night, there remains
uncertainty on how low temperatures will drop. This is mainly due
to the fact that a light northerly wind component may continue
through the night and this could keep temperatures from tanking
into the teens below. However, if the winds do become very light,
expect temperatures in the favored cold spots to possibly drop
several degrees colder than the current forecast. Either way, it
will still be a cold night across the area.
Temperatures on Monday are likely to remain in the 20s for highs
as the surface high gradually sags southeastward over the Lower
Great Lakes. As this high shifts to New England by Tuesday, expect
the surface flow to turn southerly, which should result in warmer
temperatures over the area for the middle of the week. The main
concern I have is that the models may be warming things to fast
at the surface over the area. With snow depths across much of
northern IL in excess of a foot, this does not bode well for a
quick warm-up response in temperatures too far above freezing. For
this reason, I have backed off on highs a bit for Wednesday and
Thursday. Generally, I am keeping areas with the highest snow
cover in the mid to upper 30s instead of into the 40s. Our warmest
period may end up being Wednesday evening right ahead of the next
cold front. This is the time when the highest dewpoints, possible
into the upper 30s will try to advect northward into the area
just ahead of the approaching frontal boundary. This may also set
the stage for a period of very low clouds and visibilities with
fog and drizzle Wednesday evening.
The cold front looks to push over the area sometime on Thursday.
While it then looks to get colder again later in the period, there
are uncertainties on how active the weather pattern will be over
the area going into next weekend. Due to these uncertainties, I
will continue with a small chance of precipitation going into next
Saturday. However, this chance may be able to be removed with
For the 00Z TAFs...
Primary weather related aviation concern this TAF cycle is with
the snow overnight into Sunday morning. Previous TAF had a good
handle on what looks to be the evolution with snow starting toward
or just after midnight with snow picking up enough to knock VSBYs
down to primarily IFR. There will likely be some variation in the
snow intensity which could result in periods of light snow (MVFR
VSBY) and perhaps some brief periods of heavier snow (LIFR VSBY).
The model consensus would favor 09-14z time frame for best chance
of heavier snow and have nudged the TEMPO for LIFR VSBY forward
just a bit, though suspect that LIFR VSBY would be the exception
not the rule, if it happens. After picking up a couple/few inches
of snow, look for snow to end later Sunday morning with guidance
strongly suggesting skies clearing out in the wake of the snow
A trough of low pressure will shift eastward across the Ohio
Valley Sunday into Monday. Another area of low pressure will
quickly shift east across Ontario on Sunday, while a potent area
of high pressure sets up over the northern Plains by Monday.
These two pressure systems will tighten the gradient across Lake
Michigan Sunday night with a period of 30kts expected. The high
will move across the lakes region Monday and Monday night. Another
area of low pressure is expected to quickly move across Ontario
Wednesday night. This system will likely push a cold front over
the western lakes region sometime on Thursday.
IL...Winter Weather Advisory...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ022-ILZ023-ILZ032...midnight Sunday to noon Sunday.
Winter Weather Advisory...ILZ033-ILZ039 until noon Sunday.
IN...Winter Weather Advisory...INZ001-INZ002...midnight Sunday to
Winter Weather Advisory...INZ010-INZ011-INZ019 until noon Sunday.
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Area Forecast Discussion
National Weather Service Mount Holly NJ
954 PM EST Sat Feb 10 2018
Low pressure organizing over the Lower Mississippi Valley will lift
to the north starting tonight, and then propagate through the region
tomorrow. A cold front slides through the region Monday, and then
high pressure passes north of the region Tuesday. A warm front moves
into the region Wednesday before stalling. Another cold front is
expected late in the week.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Several waves of rain will continue to track northeast into the
region along a stalled frontal boundary. Through the overnight,
the new 00z NAM and the HRRR are concentrating the heaviest rain
across southern New Jersey south into Delmarva. Another inch or
so of rain could fall which could create some local high water
issues, see hydro section.
Another concern overnight is fog. It has become widespread and
locally dense in spots. A look at the NARRE indicates the fog
will reach peak intensity and coverage during the early morning
hours. However, I suspect the fog may remain widespread through
most of the overnight given light winds and a high amount of
moisture around. Locally heavier downpours could mix/lift the
fog as well in a few spots.
Temperatures should be steady throughout most of the overnight
or even slowly rise with most locations in the 40`s and 50`s,
some upper 30`s for the southern Poconos and northwest New
Given this is my last scheduled forecast shift (departing for
WFO BGM next weekend) I want to say thank you to everyone for
giving me the opportunity to serve and provide updated weather
information to you. It has been a great honor.
.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
The axis of a positively tilted trough will approach the central
Great Lakes and Ohio Valley by late Sunday. A southwest flow aloft
will continue downstream with continued low-level warm air
advection. The thermal advection is the most pronounced along and
east of the I-95 corridor. A more pronounced short wave within the
southwest flow aloft looks to move across our area through about
midday. It is this feature in combination with upper-level jet
forcing along with frontogenetic and frontal forcing when a band or
bands of heavy rain occur. In addition, a more pronounced wave of
low pressure will track along an incoming front through early
afternoon. The more widespread heavier rain looks to occur through
An initial warm front or coastal front looks to be lifting northward
across Delmarva into southeastern New Jersey in the morning, however
this feature may dissipate as the aformentioned main surface low
arrives. However, the placement of boundaries will be key as bands
of enhanced rainfall is quite possible in the vicinity of them. Some
of the guidance continues to show some weak instability working
northward, however this may end up not being enough to produce
lightning. Despite this, the presence of a low-level jet and
stronger theta-e advection may allow for some rumbles of thunder
especially in Delmarva to southern New Jersey. Any convective
elements will enhance the local rainfall. Given the meager look to
the instability and after collaborating with WFO`s Sterling and
Wakefield, we did not add thunder. For the flooding potential, see
the hydrology section below and also the flood watch product.
High temperatures were mostly a blend of several pieces of guidance
and continuity. There may very well be a decent temperature gradient
somewhere in the I-95 corridor based on the thermal fields and the
placement of low-level jets.
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Thanks to a progressive mostly split flow pattern, much of the long
term period, especially with respect to timing of fronts and
precipitation, is uncertain.
Sunday night into Monday...Cold front is expected to sweep through
late Sunday night. There is considerable cold air advection behind
the front, with temperatures on Monday 10 to 15 degrees lower than
Sunday (this is still at or slightly above normal). An even more
impressive part of this front is the dry air advection behind the
front. Dewpoint temperatures could be 30 degrees lower behind the
front than what we saw on Sunday. Consequently, we should see the
rain come to a quick end with the front. Expect a non-diurnal
temperature trend through this period with the highs likely being
reached early in the day.
Monday night and Tuesday...A high builds closer, though the center
of the high will actually pass to the north of our region. Still
close enough to give us mostly dry conditions through this period.
Temperatures should be near or slightly below normal.
Wednesday...A warm front is expected to move into the region, but
may stall over or just north of our area. As mentioned previously, a
split flow pattern is expected through this period and the latest
model runs show our area in between the northern and southern
streams. If this trend continues, there may be little if any
synoptic scale lift. Though there may be enough weak low level lift
along the front for light precipitation.
Thursday...One surface low may pass east through Ontario and Quebec
early in the day, bringing the first chance for precipitation.
However, the main focus, for now is on the second low, moving from
the Ohio Valley into New England, which could not only bring another
chance for precipitation late in the day, but also a strong cold
front Thursday night.
Friday through Saturday...Precipitation should move out of the area,
at least temporarily behind the cold front. However, some long range
models depict the front stalling to our south. If it stalls close
enough to our area, and if we are in a favored area for lift
underneath the upper level jet, we could have another period of
precipitation to start the weekend. For now, there remains poor
model agreement so have stayed close to the previous forecast.
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Tonight...IFR and LIFR as moderate to heavy rain occurs
especially overnight along with some fog. Light and variable
surface winds to generally light southerly. Southwest winds near
2,000 feet increase gradually overnight to between 30 and 45
knots from about the I-95 corridor terminals on eastward,
therefore low- level wind shear is maintained in the 00z TAFS.
Sunday...Generally IFR or LIFR conditions with periods of rain
some of which will be heavy at times through about midday. Some
fog also expected. Southwest surface winds mainly less than 10
knots through the morning, however low- level wind shear due to
winds at 2,000 feet around 45 knots from mainly the PHL area
eastward. Surface winds increase in the afternoon, lowering LLWS
risk in the afternoon. A few 20-25 knot gusts possible at KACY
with a window for raised ceilings to MVFR for a few hours.
Monday and Tuesday...Mostly VFR conditions. Northwesterly winds
decreasing through the morning Monday, should be less than 10 KT.
Tuesday night through Thursday...VFR conditions with periods of MVFR
as rain moves in. Winds less than 10 KT through the period, though
direction will be variable. Low confidence.
South-southwest winds are expected to increase overnight as a low-
level jet arrives and continues on Sunday. However, warmer air over
the colder waters will reduce the overall mixing. Given the warmer
air and higher dew points over the colder waters, some fog should
occur although there is low confidence regarding the extent of it
given the flow just above the surface. Seas have been slow to build
tonight and continued to slow this trend with the evening update.
A Small Craft Advisory is effect starting at 4 AM Sunday for
the Atlantic waters, with conditions expected to remain below
criteria in Delaware Bay through the night. Small Craft Advisory
conditions Sunday on all zones with gusts 25-30 knots.
Areas of fog have developed and may become locally dense
overnight. Given the likelihood for visibilities below a mile,
a marine dense fog advisory has been issued which runs through
Sunday night...Winds and seas are forecast to slowly decrease
through the overnight hours. Moderate confidence.
Monday...Lingering showers over southern NJ/DE waters in the
morning. Winds and seas should be mostly below SCA criteria. High
Tuesday through Thursday...winds and seas should be mostly below SCA
criteria. Moderate confidence.
Some flooding is possible later tonight and Sunday, and a Flood
Watch remain effect through Sunday evening for much of the region.
Rainfall amounts of 2-3 inches are forecast along the I-95 corridor.
While the first few inches of soil may be soft, a frozen ground lies
underneath mainly along and north of I-78. Given this and the
moisture in the ground, runoff will be very efficient.
The heaviest rain is expected to occur later tonight through about
midday Sunday. The potential for low-lying flooding will begin later
tonight and continue as long as the rain falls. The potential for
river flooding exists Sunday and Monday.
The heaviest axis of precipitation is expected to be along or near
the I-95 corridor. Rivers in southeast Pennsylvania including the
lower Schuylkill, and rivers in central and northern New Jersey
including the Raritan and Passaic could all approach flood stage or
experience minor flooding. If the Raritan basin sees the brunt of
the rainfall, the Millstone River could experience moderate flooding.
Visit the AHPS web site to see where our main concerns are.
Record highs for today, 2/10...
ACY 60 in 2001
GED 70 in 1960
For February 11th, at this time the only climate site that may have
their record high temperature challenged is Georgetown, Delaware.
The current record high temperature for this location is 71 in 2009.
We are also looking at possible record daily rainfall for either
today or Sunday. The records are below for reference.
ACY 0.90 2010 1.70 1886
PHl 1.10 2010 1.85 1983
ILG 0.90 2010 1.62 1983
ABE 1.40 2010 1.40 1983
TTN 1.20 2010 1.60 1983
GED 1.30 1967 2.10 1994
RDG 1.50 2010 1.26 1886
MPO 2.74 1998 2.47 1960
For 2/10 the water equivalent is probably just that, an estimate
from a snowstorm in 2010.
PA...Flood Watch through Sunday evening for PAZ060>062-070-071-
NJ...Flood Watch through Sunday evening for NJZ007>010-012>027.
DE...Flood Watch through Sunday evening for DEZ001-002.
MD...Flood Watch through Sunday evening for MDZ008-012-015-019-020.
MARINE...Dense Fog Advisory until 6 AM EST Sunday for ANZ430-431-
Small Craft Advisory from 4 AM Sunday to 6 AM EST Monday for
Small Craft Advisory from 10 AM to 6 PM EST Sunday for ANZ430-
Area Forecast Discussion
National Weather Service Blacksburg VA
910 PM EST Sat Feb 10 2018
A front to the west will stall overnight allowing for a
soaking rain to impact the region into Monday. The front will
eventually move through on Monday and be replaced by high pressure
for Tuesday and Wednesday. Another cold front will move through the
forecast area late in the week.
.NEAR TERM /THROUGH SUNDAY/...
As of 905 PM EST Saturday...
Rain remains widespread across the region with the heaviest
axis now out along the Blue Ridge where seeing some elevated
convective elements embedded within the main shield of rain.
However this where flash flood guidance remains higher so plan
to keep the going watch where already in place and not expand
east at this point. Otherwise main threat continues over the far
west where have seen nearly continuous rainfall since late this
afternoon with totals now around 1.5 inches in spots. Latest
short term guidance showing perhaps a slight diminishing trend
over the next few hours as an initial wave exits before more
fills in overnight. Appears rates may also decrease a bit but
something to watch. Temps remain slow to rise given heavier
rainfall and the southwest jet aloft basically stuck above a
decent low level inversion. Thus have lowered readings to start
and cut back on rises some until late when the inversion may
finally mix out.
Previous update as of 638 PM EST Saturday...
Many locations in the VA/NC Piedmont are currently experiencing
a good amount of fog, as these areas have cleared from rain at
least temporarily. Lynchburg, Danville and Brookneal have seen
visibilities in fog as low as 1/4 SM, and this fog also extends
down into the NC Triad, especially in the Greensboro area.
Further west, we also see some patchy mist or fog interspersed
with light/moderate rains, but visibilities here are expected to
be a little greater given start of heavier rains (mentioned
below). I`ve added patchy fog across essentially much of the
forecast area through tonight, and also issued a special weather
statement to address fog potential, with stronger wording for
occasional, though transient, dense fog in the Piedmont.
Steady light to moderate rain has now overspread most locations
from the VA/NC foothills westward. However, an uptick in
rainfall intensity is anticipated for these locations through 8
PM through extrapolation of heavier bands of rain in the TN
Valley and per high-resolution model guidance. Do think that the
WRF-NMM model is a bit aggressive in terms of simulated
reflectivity and rain totals. For timing purposes, I shaped
PoPs using a blend of some of the better-performing HRRR and
3-km NAM into the current forecast. Would expect onset of
steadiest moderate to heavy rain to be around 01-02z in the far
southwest and advancing to the northeast/east as the overnight
progresses. Main message is that the first burst of heavier
rains is expected during the late-evening/overnight hours.
At least in the next 3-6 hrs, will need to keep close watch on
rivers/streams in Tazewell County and into the upper reaches of
the Tennessee River with the approach of steadier/heavier
rainfall. Already noting some modest to moderate response on
some of these river gages in the Clinch and Holston basins.
No other changes needed to other elements attm.
Previous discussion issued at 345 PM...
Cloud cover will continue to be persistent over the region
through the forecast period. Temperatures will struggle to warm
as high as previously forecast however there really is no
diurnal trend to speak of during this time period. That being
said, temperatures may continue to warm a few more degrees after
the typical peak heating time under strong southerly flow, per
high resolution guidance. During the evening, forecast lows will
not vary much from the forecast highs with several high-minimum
temperature records in play for the 11th. Winds will be light
for much of the forecast period but will tick up a bit in the
early morning hours into the day Sunday as the low center passes
just to the west of the region.
The band of rain that traversed the forecast area earlier in the day
continues to pour on the northern counties. A surface boundary to
the west will stall near the region overnight. The baroclinic zone
associated with that boundary will begin to impact the region this
afternoon as it enters from the west. This combination will make for
conditions of regularly moderate or heavier intensity rain across
much of the forecast period through Sunday.
During the afternoon on Sunday, a significant warmup into the 60s
for many under continued strong southerly flow can be expected.
Further, as the low passes nearest the region early morning into the
day tomorrow shear will increase and slight chances for
thunderstorms will exist, mainly in the piedmont.
The flood watch remains for areas near the Blue Ridge and west
through 7AM Monday.
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 240 PM EST Saturday...
Overall little change this period as front stays situated along and
just south of the forecast area Sunday night into Monday. Question
will be drying out on the northwest side before colder air works in
changing any precip to a wintry type. At the moment models are
leaning toward little wintry precip across the Alleghanys into WV,
with the colder air staying further north, so all rain for us.
The rain will be more numerous Sunday evening, then in the southeast
Monday as another wave of low pressure moves along the front across
GA/SC with easterly flow keeping deeper moisture in the Carolinas
and southern VA.
Strong high over the Great Lakes looks to push the precip further
south by Monday night, but on the backside an inverted trough sets
up along the southern Appalachians. Though deeper moisture is gone,
low level moisture remains so kept chance pops around for most of
the forecast area. May start to see wintry precip, light in intensity
by late Monday night/early Tuesday as colder air works into the low
levels as a wedge sets up. At the moment, have it as rain vs snow.
Temps this period will be close to normal.
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 300 PM EST Saturday...
Somewhat active pattern as southwest flow becomes more zonal
midweek. High pressure works over the area but models are slow in
dispelling all the moisture such that will keep low chance pops
around. Front arriving Thursday will slide in from the northwest,
then orient itself from east to west keeping a fairly decent threat
of rain Thursday into possibly Friday. Still a lot of variability in
the models on this set up. Therefore kept pops around into Saturday.
If colder air can push in with the front set up to our south, we
could see another shot of wintry wx, though upper pattern favors
more rain vs wintry mix as opposed to snow, with wedge in place, but
for now keeping it rain vs snow.
Temperatures will be seasonably cool Tuesday with wedge, then we
warm up Wed-Thu, with some cool down Fri-Sat.
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
As of 638 PM EST Saturday...
Significant impact to aviation operations in the 00z TAF period
from IFR to LIFR conditions from both ceilings, fog and heavier
rains, mtn obscuration as well as low-level wind shear.
With very few exceptions, most TAFs are presently IFR to LIFR.
LIFR fog is most common in the Piedmont (affecting Lynchburg
and Danville) as these areas have cleared of rain, while MVFR-
IFR visibilities in rain/fog more common across the rest of the
TAFs. Would expect fog to thin as heavier rains move in after
02z, but visbys still commonly 2-4 SM in moderate to at times
heavy rain overnight. Ceilings generally expected to be rather
stable LIFR/IFR. Strong winds aloft will also contribute to
areas of low-level wind shear tonight into early morning Sunday
as winds will be light to calm.
Likely to have continued moderate/heavy rain lingering into the
early morning hours, but a little bit of a break should allow
for more IFR to MVFR conditions by late morning. Next round of
rain and even some possible thunder toward Sunday afternoon.
Timing this next round of rain is low and will only leave VCSH
or a VFR -RA late in the TAF period. South winds increase to
6-12 kts Sunday.
Moderate confidence in ceilings. Low to moderate confidence in
visbys. High confidence in winds.
Extended Aviation Discussion...
Mainly MVFR ceilings and reduced visibilities will continue
through Sunday night. High pressure begins to build into the
region Monday and ceilings are expected to lift to VFR at most
locations, with some upslope low clouds still probable at
A low level wedge will then develop by Tuesday as a
weak system scoots by to the south and helps low level moisture
return into Tuesday night. This may keep sub- VFR around wit
low ceilings again Tuesday/Tuesday night before some slow
improvement occurs as the wedge weakens on Wednesday.
As of 350 PM EST Saturday...
Flood watch remains in effect from this evening through Monday
morning for areas near the Blue Ridge and West.
The entire forecast area is expected to get 1-4 inches of rain
from Saturday through Monday, with the heaviest rain expected to
occur on Sunday. Streams across the entire service area are
expected to rise, with significant rises anticipated for
mountain streams. The headwaters of the Greenbrier River and
upper reaches of the James River will also receive contributions
from snowmelt. This will add to the flood potential.
At this time, the river basin which will likely be most effected
from snowmelt is the Greenbrier. Upwards of an inch of liquid
equivalent water is suspended within the snowpack. If this snow
melts at the same time as the occurrence of the heaviest rain,
then flooding will become likely along the Greenbrier River.
Confidence is increasing that minor to potentially moderate
flooding may occur during the Sunday to Monday time frame for
the Greenbrier River at Alderson.
Those living particularly along the Greenbrier River should
begin taking precautions. The river level at Alderson is already
half bank full from the previous rain event, which means it
will not take as long to reach flood stage if heavy rain occurs
You should monitor later forecasts and be alert for possible
Flood Warnings. Those living in areas prone to flooding should be
prepared to take action should flooding develop.
VA...Flood Watch through Monday morning for VAZ007-009>020-022>024-
NC...Flood Watch through Monday morning for NCZ001>003-018-019.
WV...Flood Watch through Monday morning for WVZ042>044-507-508.
Area Forecast Discussion
National Weather Service Shreveport LA
807 PM CST Sat Feb 10 2018
For the 11/00Z terminal forecast will prevail all the sites across
the Four State Region with IFR and below for the overnight and
through most of the first of Sunday. MVFR ceilings will be
returning during the early to middle morning for parts of
East and Northeast Texas and the more Eastern sites in the middle
to late afternoon Sunday. Surface winds will be light Southeast
out to the East of a cold front and to the West and Northwest
10-15 knots in wake of the boundary. /06/
.PREV DISCUSSION... /issued 331 PM CST Sat Feb 10 2018/
Large area of shwrs associated with a series of shortwaves and a
cold front has pushed ewd, and is only affecting our far sern
parishes. Meanwhile, shallow cold airmass continues to bend around
the Ouachita Mountains of SE OK/SW AR and spill into N TX. As a
result, cold air has begun to spill in to portions of E TX, while
leaving our SW AR counties still in the upper 50s and lower 60s.
Model solutions vary, and in general do not handle the shallow
cold airmass damming across our nrn areas, but the cold air will
eventually get deep enough to overcome the terrain tonight. HRRR
seems to be handling the hourly evolution of temps well, so have
used this in the short term.
Patchy light rain and drizzle will continue to be possible
through the overnight hours, as sw flow aloft overruns the cold
air at the sfc. This will coincide with temperatures near or just
below the 32 degree mark across portions of NE TX, SE OK, and SW
AR, especially after midnight. Any accumulation will be very light
and mostly confined to elevated surfaces, including bridges and
overpasses. The potential impact to travel across these areas has
led to the issuance of a Winter Weather Advisory from midnight
through 10 am Sunday. Temps should warm above freezing Sunday
morning, ending any ongoing travel impacts.
Isold to sct shwrs will continue to be possible Sunday and Sunday
night before a drier airmass sinks swd Monday. However, swly
flow aloft will keep us in an unsettled pattern, with rain chances
returning Tuesday and remaining through the work week. Chances for
more widespread, heavier rain will come into play Friday through
the weekend, as a strong disturbance over the Desert SW moves ewd
into the Southern Plains.
Temperature trends this pd will be below normal through Monday,
but a warming trend will take us into the 70s for some areas by
mid week. /12/
.PRELIMINARY POINT TEMPS/POPS...
SHV 39 47 37 51 / 50 40 20 10
MLU 50 53 38 48 / 60 50 30 20
DEQ 31 42 29 52 / 40 20 20 0
TXK 35 43 32 50 / 50 20 20 0
ELD 43 47 34 50 / 60 40 20 10
TYR 32 40 32 53 / 30 30 20 10
GGG 34 43 34 53 / 40 30 20 10
LFK 40 47 37 55 / 50 30 20 10
AR...Winter Weather Advisory from midnight tonight to 10 AM CST
Sunday for ARZ050-051.
OK...Winter Weather Advisory from midnight tonight to 10 AM CST
Sunday for OKZ077.
TX...Winter Weather Advisory from midnight tonight to 10 AM CST
Sunday for TXZ096-108>111-124-125-136.