Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/12/25
Area Forecast Discussion
National Weather Service Cheyenne WY
435 PM MST Tue Feb 11 2025
.KEY MESSAGES...
- Widespread snow continues throughout the day today. 1-3
inches of snow possible in the lower terrain, 2-6 inches
possible in the mountains.
- Arctic air mass will bring very cold temperatures with
overnight wind chills into the negative 10-20`s through
Thursday morning.
- A warm-up on Thursday and Friday will be accompanied by a
return of strong winds and the potential for blowing snow in
the wind prone areas.
&&
.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 210 PM MST Tue Feb 11 2025
Current observations from across the CWA show scattered light snow
showers. Light snow is expected to continue this afternoon, before
becoming a bit more widespread and likely more intense. As the upper-
level trough axis swings into Wyoming this evening, cyclogenesis
will occur in lee of the Rockies. Both the GFS and ECMWF develop the
low in far southern Colorado and track it east into Texas. Placement
and track of this low does not cause major concerns for the forecast
area, however it will likely lead to accumulating snow in portions
of the CWA. Hi-Res guidance does show snow becoming more widespread
this evening and overnight. An easterly component to surface winds
will lead to weak upslope flow, favoring the South Laramie Range and
Cheyenne Ridge for a few inches of snow accumulation. Later tonight,
the Interstate 80 corridor east of Cheyenne into Nebraska will be
under an area of brief frontogenesis. Combined with a saturated DGZ,
some fairly decent, but brief, snowfall rates could be possible.
Most models, including ensembles, give the Interstate 80 corridor
between Laramie and Sidney about 1 to 3 inches of accumulation.
Higher amounts are likely in the South Laramie Range, but should
stay below 6 inches for the most part. The HRRR has been a bit of an
outlier, showing higher totals than GFS and ECMWF ensemble members,
so cannot rule out some of the aforementioned locations seeing 3+
inches of snow overnight.
Snow will likely taper off early Wednesday morning, with a few
lingering showers possible along the Interstate 80 corridor
throughout the day. Any additional snow accumulations will remain
below an inch as this progressive system kicks eastward. Once snow
tapers off Wednesday morning, bitter cold temperatures will be left
in its wake. The arctic frontal boundary will still be far enough
south in Colorado for the forecast area to be locked in cold air.
Many locations will see below zero low temperatures and wind chills
Wednesday morning. Some areas, notably high valleys and peaks,
could get close to Cold Weather Advisory criteria, however cloud
cover and lack of winds will likely keep wind chills just warm
enough. High temperatures during the day Wednesday will be in
the teens and single digits as 700 mb temperatures sit at -24C.
With the trough exiting the Rockies Wednesday night, clear skies and
drier conditions are expected. With decent snowpack likely after
this system and clear skies, temperatures overnight could tank.
Again, low temperatures for most locations will be below zero,
however stronger winds are expected to develop overnight which
could lead to cooler wind chills Thursday morning. As currently
forecast, wind chills across a good chunk of the CWA could fall
into Cold Weather Advisory territory, so this will need to be
considered in the coming shifts.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 210 PM MST Tue Feb 11 2025
Thursday...The Arctic airmass begins to retreat to our east as the
flow aloft backs from northwest to west and strengthens. High winds
may be continuing across our Wyoming wind prone locations such as
Arlington, Bordeaux and the I-80 Summit based on 700 mb winds
approaching 50 knots and our local wind model suggesting possible
high winds for Arlington. Thus, went ahead and bumped up wind speeds
for the wind prone locations. 700 mb temperatures near -5 Celsius
yield maximum temperatures in the 30s to near 40 degrees.
Friday...The warming trend continues with westerly flow aloft. Moist
flow aloft will produce widespread orographic snows for the Snowy
and Sierra Madre Ranges, with snow spreading to nearby areas as well
in the afternoon.
Saturday...Another arctic cold front moves southward into our
counties, although with temperatures not quite as cold as the
current arctic airmass. With cyclonic northwest flow aloft, combined
with the moist upslope in the wake of the cold front, we expect to
see scattered to numerous snow showers, most numerous south of a
Douglas to Sidney line.
Sunday...Chances for snow will decrease significantly as the flow
turns northwest and some drier air is advected into our region. A
warming trend will develop as the arctic air retreats to our east.
Low and mid level gradients look sufficient to produce a windy day
for the wind prone locations of southeast Wyoming and places west of
I-25.
Monday...Moist cyclonic flow aloft will help increase chances for
snow, especially for orographically favored locations like our Snowy
and Sierra Madre Ranges.
Tuesday...Colder again with 700 mb temperatures near -9 Celsius,
yielding high temperatures from the mid 20s to mid 30s. Looks like
enough low and mid level moisture, combined with lift, to produce a
chance of snow, with best coverage south of a Douglas to Scottsbluff
line.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 440 PM MST Tue Feb 11 2025
A potent upper level disturbance is forecast to push southeast across
the area tonight as a surface arctic cold front stalls to our south.
This will result in widespread snow for the southern terminals, and
periods of snow for terminals north of Interstate 80.
HAZARDS/WEATHER TRENDS: Conditions will gradually deteriorate to IFR
or LIFR for KLAR, KCYS, KSNY, and possibly KBFF this evening and
continue tonight with VIS between 1/2 mile and 2 miles in light to
occasionally moderate snow. These conditions should persist after
06z with snow eventually tapering off after 12z. For KRWL, KAIA, and
KCDR, periods of snow and IFR conditions are possible (25% to 40%
chance) between 03z and 09z, but MVFR conditions will prevail with
even some breaks in the low clouds possible at KCDR and KRWL
tonight. Although snow should taper off between 12z and 18z, expect
MVFR or near IFR CIGS to persist into the late morning hours on
Wednesday.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until 11 AM MST Wednesday for
WYZ117>119.
Winter Weather Advisory until 2 PM MST Wednesday for WYZ116.
NE...Winter Weather Advisory until 11 AM MST Wednesday for NEZ054-
055.
&&
$$
SHORT TERM...SF
LONG TERM...RUBIN
AVIATION...TJT
Area Forecast Discussion
National Weather Service Peachtree City GA
703 PM EST Tue Feb 11 2025
...New 00Z Aviation Discussion...
.UPDATE...
Issued at 641 PM EST Tue Feb 11 2025
Adjustments were made to the forecast this evening to capture the
character of the CAD wedge over much of the forecast area.
Evaporative cooling of light rain and drizzle that fell through
the wedge this afternoon served to reinforce the dome of colder
air underneath. Most locations to the north of a line from
LaGrange to Macon to Swainsboro did not see temperatures rise
above 50 this afternoon, which indicates the current southward
extent of the wedge boundary. Furthermore, locations in far
northeast Georgia still has temperatures in the mid 30s, though
this will warm slightly over the next few hours as heavier rain
moves into the area and mixes out some of this colder air. Raw
conditions, with temperatures in the upper 30s and 40s combined
with low clouds, mist, and drizzle will persist through the
overnight hours into Wednesday morning to the north of the
aforementioned wedge boundary. Moreover, moderate rain has begun
to spread into far northwest Georgia and will continue to advance
southeast through the overnight period.
&&
.SHORT TERM...
(This evening through Wednesday)
Issued at 343 PM EST Tue Feb 11 2025
Key Messages:
- A Flood Watch remains in effect for north Georgia and the
northern portions of the Atlanta metro from Tuesday afternoon until
Thursday morning. Several waves of precipitation move through the
area on tonight and Wednesday/Wednesday night. 3-5" of rain is
expected to fall with locally higher amounts of up to 6" possible
where repeated rounds of precipitation occur.
- Some very light ice accumulation has been noted in higher
elevations of north Georgia on elevated surfaces. This will likely
continue for next few hours until heavier rain mixes the cold air
out a bit. Only very minor impacts expected to trees and powerlines.
No impacts to roadways.
- A few strong to severe storms may be possible overnight
Wednesday in primarily west central Georgia. Slight risk into metro
is likely overdone, given wedge should make surface based convection
challenging, though if wedge does erode, environment will certainly
be favorable.
Forecast:
The forecast for today and tomorrow is quite the washout for north
Georgia and potentially parts of the Atlanta metro, and wet a dreary
set of days for everyone else. Aloft, zonal flow is slowly being
replaced by SW flow as an initial PV anomaly ejects out of large
scale trough over western Coast. This deep trough has already tapped
into subtropical moisture and is bringing moisture flowing into the
southeast. This moisture is overrunning a previous surface front
towards the gulf coast and is being lifted isentropically, bringing
copious cloud cover and showers to north and central Georgia.
Compounding this is a CAD/wedge that has been driven into the area
and is cool enough with enough moisture being driven into it to lead
to some soupy, misty, and in some places, foggy conditions.
Temperatures are equally dreary, with temps in the wedge still in
the upper 30s to low 40s and only in the upper 40s and 50s outside
of it down in central Georgia.
The exception to those temps is in the higher elevations of NE GA
(generally above 3000 ft), where a few patches of freezing to
subfreezing temps have been able to hang on this afternoon. These
areas have seen some very light ice accumulations that have occurred
as a result of freezing fog/freezing drizzle. This may continue for
a few more hours until heavier rain moves into the area and mixes
out the colder temps with some warmer air aloft. Impacts should be
very minor, limited to just some branches falling and maybe a few
sporadic power outages.
Moderate push of rain is expected to move in tonight as a frontal
boundary approaches with the first system. This should bring an
additional 1-2" across the area for our first round, with the
heaviest rain likely across north Georgia where the upper level
frontogenesis may push into ahead of the main surface frontal
system. Rivers and creeks will likely be able to handle the first
wave okay, though some isolated flooding will be possible.
Tomorrow, larger wave begins to kick out into the southeast bringing
yet another round of precip into the area. Wedge looks like it will
remain stoutly in place, especially given how current observations
are in some cases 10 degrees below what models expected at this time
yesterday. Wedge will be reinforced by both surface high over the
northeast and active precip expected to be falling in it through the
day. This will create sharp temperature gradient, with northern
Georgia in the 40s and 50s and central Georgia potentially rising
into the 60s and 70s (and maybe warmer, if the sun can poke through
during the afternoon hours).
Speaking of the precip, of concern is what a few models such as the
HRRR has shown for the potential for repeated rounds of afternoon
convection into the metro Atlanta area. This leads to tremendously
higher values of QPF than currently in the deterministic QPF output.
HREF probabilities of > 4" in and around the I-85 corridor are in
the 30-40% range. These amounts would certainly lead to issues with
local creeks, rivers, and streams, especially within the urban areas
where runoff will be quicker and more intense. As such, have made a
slight southward expansion of the Flood Watch to account for this.
Otherwise, forecast is on track to see another heavy push of precip
with the main system Wednesday evening into Wednesday night with a
front pushing through the area that will bring widespread 2-3"
across north Georgia and another 1-2" into central Georgia. Given
rainfall on Tuesday, this will likely lead to flooding of rivers,
creeks, and streams in northern Georgia and portions of the metro.
Numerous river gauges are forecast to go to at least Minor flood
stage, and HEFS probabilities for several gages to go to Moderate
flood stage over the next several days are in the 30-40% range at
some locations.
The last thing to discuss is severe potential on Wednesday night as
the frontal system moves through. Models show some decent moisture
return into at least central Georgia ahead of the line as a mass
response to the deepening surface low to the north. Decent vertical
shear will be in place. SRH values are being driven in part by the
position of the wedge front, which will allow for some local surface
backing of winds. The models are likely going to struggle with
erosion of the wedge. This is a well known bias, where many of them
will begin to erode it to the north far too quickly. General
experience/research says these tend to hold on until the cold front
actually arrives, making surface based storms ahead of the front
challenging. This is a big reason why the northern end of the SPC
slight risk is likely a bit overdone. However, if the wedge does
push back a bit, the parameter space will certainly allow for a few
strong to severe concerns as described next. In central Georgia, a
QLCS mode will be possible, though the threat is a low end one. SRH
is high, but is being enhanced by the wedge boundary. Models do
struggle to bring in surface based instability, but it won`t take
much provided a storm can become rooted enough to tap into the shear
profiles. STP values in the HREF show probabilities of being greater
than 1 at about 30-40% in central Georgia.
Lusk
&&
.LONG TERM...
(Thursday morning through next Monday)
Issued at 343 PM EST Tue Feb 11 2025
At a glance:
- Brief reprieve from rainfall on Friday
- Second round of heavy rain and yet another conditional severe
threat overnight Saturday into Sunday
As we kick off the extended range on Thursday morning, a cold front
will be making its way through the southern half of the forecast
area, accompanied by moderate to heavy showers and isolated embedded
thunderstorms. In the wake of the aforementioned front, a strong
(nearly 1040mb) surface high will move in across the Southeast,
shifting slowly eastward until its center is off the coast of the
Eastern Seaboard at the start of the weekend. Perhaps unsurprisingly
with such strong forcing at the surface, classic cold air damming is
progged to set up throughout the course of the day Friday -- with
characteristic U-shaped isobars banking up against the Appalachians.
The combination of high pressure at the surface and a swath of dry
air rounding the base of a broader trough present at the mid-levels
will support a fleeting period of dry weather on Friday. Highs in
the mid-50s to lower-70s and dewpoints in the 30s to 40s by the
afternoon will make for a pleasant end to the week...
...but don`t get too comfortable. A mid-level trough is progged to
dig across the Mountain West and into the ArkLaTex Saturday into
Sunday. Coincident with the strongest shortwave embedded within the
broader trough, resultant mass response supports the development of
a low pressure system at the surface. We`re expecting a final,
punctuating round of rainfall and conditional chances for severe
weather as the associated line of convection makes its way across
north and central Georgia overnight Saturday into Sunday.
Severe chances: Much like Wednesday/Thursday`s event, the brunt of
the favorable forcing overlap will occur late Saturday night/early
Sunday morning, making this a primarily nocturnal event (changes in
timing are possible, perhaps even likely as this event enters the
short term). We`re not yet in range of HiRes or intermediary
guidance, but global models suggest the presence of a 40-50kt low
level jet at 925 mb as the line is trekking southeastward. As has
been the case recently, we`ll be fighting against a lingering wedge
for areas along and east of the Atlanta Metro for thermodynamics.
Wind profile differences along the outer edge of the wedge boundary
will serve to further locally enhance hodograph curvature. Dewpoints
look to be in the 60s outside of the wedge airmass, but it remains
to be seen if we materialize any surface-based instability. It won`t
take much with the forecast kinematics, and we`re currently sitting
on a very narrow corridor on the order of 50-100 J/kg SBCAPE. We`re
solidly within high-shear, low-CAPE season, and if trends continue,
it appears that we`ll be looking at primarily QLCS-type hazards
(isolated damaging wind gusts and the potential for a tornado within
any bulges, kinks, or breaks in the line of convection). The SPC has
outlined a 15% area in their Day 5 (7AM Saturday through 7AM Sunday)
Convective Outlook, and we`ll be keeping an eye on potential
upgrades and specific hazard probabilities over the next few days.
Precipitation/flooding chances: The rebound period between our
midweek rainfall and our weekend rainfall looks to be approximately
48 hours or so, and rivers are likely to remain at elevated stages
at the onset of this final round of precipitation. Highest NBM
probabilities for an inch or more rainfall over the 48-hour period
ending 7AM Monday are once again focused across locales in north
Georgia: 63% for Atlanta, 74% for Rome, 77% for Gainesville, 79% for
Dalton, and 84% for Ellijay. For 2 inches or greater over the same
48-hour period, 45-50% probabilities for portions of far north
Georgia. In general, blanket totals of an additional 1-2" are
possible CWA-wide late Saturday through early Monday, with terrain-
enhanced locally higher amounts up to a reasonable worst case (90th
percentile) of 3-4".
Moving into Monday and beyond, yet another surface high moves in on
the heels of the precipitation, which will support another period of
dry and relatively tranquil weather. Phew.
96
&&
.AVIATION...
(00Z TAFS)
Issued at 641 PM EST Tue Feb 11 2025
IFR/LIFR ceilings have developed at all TAF sites and will persist
through the overnight hours into Wednesday. A gradual, brief
scattering of low clouds may return CSG/MCN to VFR in the mid to
late afternoon on Wednesday, but the ATL metro sites and AHN will
see no such improvement. Visibilities amid mist and drizzle will
drop to 2-3 SM tonight and persist through the morning hours on
Wednesday. -RA DZ is impacting all sites and also expected to
continue through tomorrow, with moderate RA anticipated to
impact sites overnight between 01Z-09Z. Winds will be primarily E
to SE through the period at 6-10 kts, though a shift to SW
between 10-13 kts with occasional gusts of 20-25 kts will be
possible at CSG/MCN by 21Z.
//ATL Confidence...00Z Update...
Medium confidence on ceiling trends.
High confidence on all other elements.
King
&&
.PRELIMINARY POINT TEMPS/POPS...
Athens 38 43 43 66 / 100 80 100 100
Atlanta 41 49 49 66 / 100 90 100 100
Blairsville 36 47 43 58 / 100 100 100 100
Cartersville 41 47 47 62 / 100 100 100 100
Columbus 57 78 61 72 / 70 70 100 100
Gainesville 36 42 42 63 / 100 90 100 100
Macon 49 75 60 72 / 50 60 80 100
Rome 42 52 48 61 / 100 100 100 90
Peachtree City 45 62 55 68 / 90 90 100 100
Vidalia 53 81 65 75 / 20 10 20 80
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Thursday morning for GAZ001>009-011>016-
019>025-030>035-041>048-052>057-066>068.
&&
$$
SHORT TERM...Lusk
LONG TERM....96
AVIATION...King
Area Forecast Discussion
National Weather Service Green Bay WI
539 PM CST Tue Feb 11 2025
Updated aviation portion for 00Z TAF issuance
.KEY MESSAGES...
- Accumulating snow is expected on Wednesday and Wednesday night.
While most of the area will receive some snowfall, there is a
greater than 70% chance of 2+ inches east of a line from Wautoma
to Sister Bay. Areas over east-central Wisconsin are forecast to
receive the most snowfall (greater than 60% chance of at least
4+ inches). A Winter Storm Warning has been issued for Manitowoc
County where lake enhancement will locally increase snow amounts.
- There is a 40-60% chance of greater than 3 inches of snow on Friday
afternoon and Friday evening. Hazardous winter travel is
expected across most of the area.
- Cold wind chills from 10 below to 25 below zero are possible on
Thursday night into Friday morning, and also from Sunday night
through Tuesday morning. The coldest wind chills will be found
over central and north-central Wisconsin.
&&
.DISCUSSION...
Issued at 231 PM CST Tue Feb 11 2025
Short Term...Tonight and Wednesday
High pressure currently centered over MN will bring quite and clear
conditions to for the remainder of today. Temperatures, especially
across north-central WI will start to cool quickly after sunset
given the clear skies and light winds. High and mid-level clouds
will start to overspread the region tonight ahead of a low pressure
system currently developing over CO/NM, as shown by 20Z RAP analysis
and satellite imagery. Increasing clouds overnight should slow the
rate of cooling with lows bottoming out near -15 degrees across
northern WI to around 5 degrees along the lakeshore. If clouds are
slower to develop than forecast may have to drop lows a few more
degrees.
Main focus of the short-term then become a round of accumulating
snow forecast to arrive mid Wednesday morning and continue through
early Thursday morning. While the main surface low is forecast to
track well south across the mid Mississippi/Ohio Valley a coupled
upper jet and push of mid-level WAA will lead to a favorable 18 hour
period of light to moderate snow across the southeastern half of the
forecast area. Periods of moderate to heavy snowfall look possible
Wednesday afternoon/evening as the lift associated with the mid-
level WAA is maximized through a deep and saturated DGZ. Snowfall
rates may peak around 0.75-1"/hour during this time. CAMs also show
the potential for localized lake enhancement in Manitowoc and
southern Kewaunee counties as a lake enhanced inverted trough develops
and winds become convergence along the lakeshore. One caveat with
the potential lake enhancement is the strength of the land breeze
during the morning as land/lake delta Ts will be near 30F degrees
which may keep any lake enhancement offshore into the afternoon
hours.
By Thursday morning snowfall amounts are forecast to range from 2-5"
south and east of a Wisconsin Rapids to Marinette line with locally
higher amounts of 6-8" possible east of I-43 in Manitowoc Co.
Headlines wise a Winter Weather Advisory is in effect across east-
central WI from noon Wednesday through 6am Thursday. A Winter Storm
Warning is in effect for Manitowoc Co. to account for the potential
of those locally higher amounts along the lakeshore.
Long Term...Wednesday Night Through Tuesday
Focus of this forecast remains on potential snow accumulations for
Friday and Friday night, followed by very cold wind chills.
Friday and Friday night...Shortwave energy moving across the
Plains will lead to strong warm advection developing across the
western Great Lakes. With some models indicating a coupled jet
structure, a 35-45 kt low level jet will lead a swath of precip
pushing east into northeast Wisconsin on Friday afternoon before
departing late Friday night.
In addition to moderate to strong dynamics, models also indicate
an impressive DGZ that is 200-300 mb thick with strong lift
occurring within this thermal regime. This is most obvious over
central and east-central WI where thermal profiles are relatively
warmer than far northern WI. There it appears that most of the
strong lift is above the DGZ. As a result, efficient snowfall
production is very possible over central and east-central WI with
this system.
Models are trending faster with this system, but precip amount
trends are rather noisy over the past 24-48 hours. Probabilities
do seem to be gradually increasing for 3" and 6" of snow in the
NBM and now sit at 40-60% and 20-40% respectively. With strong
dynamics and favorable thermal profiles, concern seems warranted
for a headline worthy event.
Very Cold Wind Chills: Arctic high pressure will be nosing into
the region at times over the next 7 days. The coldest periods
appear to be Thursday morning (10 below to 20 below wind chills)
and Sunday night through Monday night (15 below to 30 below wind
chills). Cold weather headlines are possible early next week.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 539 PM CST Tue Feb 11 2025
VFR flying conditions will continue this evening across the
region as a weak high pressure system builds over the region.
Flying conditions will begin to deteriorate Wednesday morning as a
series of strong upper-level disturbances beginning to move
across the upper Midwest. CIGs will gradually lower during the
morning, becoming MVFR mid-morning and likely IFR across much of
the region by Wednesday afternoon. Snow will also spread across
the southern and eastern halves of Wisconsin from southwest to
northeast Wednesday morning. Expect the snow to reach the central
Wisconsin TAF sites (AUW and CWA) around 14-15Z and the east-
central TAF sites (ATW, GRB, MTW) around 16-17Z. Initially snow
should be light with little impact on vsbys. Snowfall intensity
will increase during the afternoon likely leading to periods of
MVFR/IFR vsbys into Wednesday night.
Overall snow amounts are expected to range from 2-5" south and
east of a ISW to SUE line with locally higher amounts near 6"
possible at MTW. Areas across central and northern Wisconsin will
likely see a dusting to 1".
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from noon Wednesday to 6 AM CST Thursday
for WIZ022-037>040-045-048-049.
Winter Storm Warning from noon Wednesday to 6 AM CST Thursday
for WIZ050.
&&
$$
DISCUSSION.....GK/MPC
AVIATION.......Kurimski
Area Forecast Discussion
National Weather Service Houston/Galveston TX
526 PM CST Tue Feb 11 2025
...New AVIATION...
.SHORT TERM...
(This evening through Wednesday Night)
Issued at 247 PM CST Tue Feb 11 2025
Light to moderate rainfall continues across Southeast Texas this
afternoon and evening as clusters of showers and thunderstorms
continue to push through. Expecting a lull in activity this
evening through around midnight as the front sits just offshore.
It will make another northward progression overnight through
Wednesday morning, placing Southeast Texas in a warm and unstable
airmass once again.
Taking a closer look at the overnight hours...As this front moves
northward, a mid- level shortwave will cut NE across the state
from the Baja area. This will send pulses of energy in the 500mb
level through Southeast Texas providing an aid in upward air
movement and convergence at the surface. In other words, it would
contribute to thunderstorm development with helping warm moist air
to rise and cool. Mid-level lapse rates are not terribly steep,
so the hail threat looks to be minimal with these storms. SRH and
Bulk Shear, however, looks more impressive. Overnight 0-1 SRH
values get well above 200 m2/s2 and Bulk Shear values fall between
30-50 kts, and for portions of SE Texas the bulk shear vectors
lie perpendicular to the forcing mechanism (in this case the
frontal boundary that has been triggering showers and storms the
last couple of days). Essentially, what this means is that with
these SRH values and Bulk Shear values we are looking at the
potential for storms to become organized and potentially have some
rotation within. The vectors lying perpendicular to the forcing
mechanism suggest that the storm mode may start out less linear
and more discrete (18Z HRRR seems to catch onto this idea ahead of
the main line of storms). As the main line moves through, could
see gusty winds and brief spin ups occur.
Activity will diminish Wednesday evening as the front is pushed
offshore and cooler drier northerly winds fill in from behind.
So what is the timing of all of this? HRRR seems to be doing a
good job with the activity today, so going to use that as a loose
timeline of how things will play out for the rest of the day
through Wednesday.
We should see a lull in showers and storms this evening through
around midnight...generally light showers during this time. Around
midnight we will see the first cluster of storms move in from
Central Texas, entering the Brazos Valley and SW sector around 1
AM. A few showers and storms may develop out ahead of this
cluster. Around 3-4 AM the cluster of showers and storms will move
through the Houston Metro, bringing heavy rainfall near the
beginning of the morning rush hour. Showers and storms will move
east out of the area shortly after sunrise.
...But wait...there`s more...Just as the first cluster of showers
and storms moves out towards the Lake Charles area, more cells pop
up and move across SE Texas along and ahead of the frontal
boundary during the mid- morning to early afternoon hours. The
front will push offshore overnight Wednesday into Thursday
morning, bringing a cooler start to the long-term period.
To summarize...Window of potential severe weather (most favorable
dynamics) will be from 3 AM Wednesday through 3 PM Wednesday.
Gusty winds will be the main threat, but with the high shear and
decent 0-1km SRH there is also an isolated tornado threat. These
storms could also produce heavy rainfall, and with soils already
wet from today`s rainfall, low-lying and urban areas could
experience flooding. WPC has a line along and north of Colorado
County to northern Galveston County in a Slight Risk for Excessive
Rainfall (level 2 of 4). Inland areas of Jackson, Matagorda, and
Brazoria Counties as well as Wharton and Southern Galveston County
are in a Marginal Risk for Excessive Rainfall (level 1 of 4). SPC
has most of Southeast Texas in a Marginal Risk for severe weather.
Temperature wise, lows for tonight will be in the 50s to low 60s.
Tomorrow will feature warmer weather as that front moves in and
brings the return of warmer air. Highs will be in the 70s area
wide. Lows will cool off significantly Wednesday night as cooler
air moves in and skies clear. Temperatures will be in the mid 30s
to near 50 north of I-10 and in the upper 40s to near 50 south of
I-10.
Adams
&&
.LONG TERM...
(Thursday through next Monday)
Issued at 247 PM CST Tue Feb 11 2025
A cooler airmass will move in behind the front. Temperatures for
Thursday morning will be in the 30s across the Brazos Valley and
portions of the Piney Woods. For the rest of Southeast Texas
expect lows to be in the 40s. Northerly winds and cloudy skies
will keep temperatures from rising too much during the day
Thursday. Wind chills will be in the 40s and 50s. Highs will be in
the upper 40s to 50s.
Cool weather continues for Friday, but a coastal trough
approaching from the south will allow temperatures to be a bit
warmer with highs in the 60s area wide. This coastal trough will
also bring the potential for isolated showers. Southerly winds
will prevail going into the weekend, bringing highs into the 70s
on Saturday. Another FROPA is expected over the weekend with
another round of showers and storms expected with the front. Below
normal temperatures return behind the frontal boundary as breezy
north winds prevail and a more arctic airmass filters in. Sunday
night into Monday will feature much colder weather than what has
been observed over the last couple of weeks as temperatures dip
into the 30s inland and into the 40s along the coast. Below
freezing temperatures will be possible across the far NW counties.
Adams
&&
.AVIATION...
(00Z TAF Issuance)
Issued at 524 PM CST Tue Feb 11 2025
Widely scattered SHRA activity is expected to become more
widespread overnight, with locally heavy TSRA expected by the
morning hours. SHRA/TSRA activity is expected to diminish as
tomorrow morning progresses. Widespread IFR conditions are
expected through tomorrow morning. Some areas of LIFR are likely.
Flight conditions are expected to begin improving tomorrow
afternoon behind a front. But conditions may be slow to improve.
&&
.MARINE...
Issued at 247 PM CST Tue Feb 11 2025
A very active wx period. Weak front sagged off the coast earlier
today as showers & isolated storms passed. This boundary should
drift back north tonight. With onshore winds resuming, look for
patchy sea fog to re-develop at some point but confidence as to
exactly when is low. Anticipate that the lowest visibilites will
again be in the nearshore Gulf and lower bays.
Late tonight, we`ll see another disturbance move in from the west.
Look for showers and thunderstorms to accompany this disturbance,
possibly consolidating into a line that`ll push into the portions
of the coastal waters, especially east of Sargent sometime in the
3am- 9am timeframe. Some of theses storms will have the potential
to become strong-severe with strong winds, hail and isolated
waterspouts a possibility. May see a 2-5 hour break followed by
possible redevelopment near the Houston/Galveston Bay area in the
afternoon. Things should wind down in the evening.
A cold front is expected to push off the coast Wednesday night. This
will end storm/fog threat...but winds/seas will increase and Small
Craft Advisories will be required into Thursday Night. Onshore flow
resumes and increases late Friday in advance of the next cold front
Saturday night. Look for more storms with this front and even
stronger winds & higher seas in its wake. 47
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 55 50 75 37 / 90 90 30 0
Houston (IAH) 70 60 76 47 / 70 80 80 0
Galveston (GLS) 72 64 71 53 / 50 50 60 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Should Exercise Caution until 3 AM CST Wednesday for
GMZ370-375.
&&
$$
SHORT TERM...Adams
LONG TERM....Adams
AVIATION...Self
MARINE...47
Area Forecast Discussion
National Weather Service Wichita KS
619 PM CST Tue Feb 11 2025
.KEY MESSAGES...
- Slight chance for freezing drizzle across southeast KS this evening
- Widespread snow arrives late this evening into Wednesday; highest
accumulations along the Interstate 70 corridor
- Bitter wind chills as cold as -15 Wednesday and Thursday mornings;
coldest across central KS
- Additional chances for snow late Friday into Saturday
&&
.DISCUSSION...
Issued at 228 PM CST Tue Feb 11 2025
As of 230 PM Tuesday afternoon, broad southwesterly midlevel flow
has established across the entire central and southern Plains.
Strong, surface, cold air advection continues across the region
with temperatures hovering in the upper 10s and 20s across
central KS to the 30s across southeast KS. An initial push of
midlevel WAA is overspreading portions of western and northern
KS ahead of a broad trough across the southwest US. Latest RAP
forecast soundings suggest convective instability upwards of
20-40 J/kg. Based on agitated midlevel clouds it appears this
instability is being realized and snow showers will continue
predominately north and west of the forecast area. Transitioning
into the evening hours, weak, low-level, WAA is progged across
southeast KS. Cloud bases are forecast to gradually drop below
1kft. The combination of the 2 may create patchy drizzle. With
temperatures dropping below freezing after sunset, freezing
drizzle may become a concern. This concern should be brief as
deeper midlevel moisture advects overhead to transition
precipitation types to snow.
Further west, an area of snow has developed across the high Plains
of CO as the initial 700 mb shortwave trough progresses from the
Rockies. This axis of snow will gradually spread east and northeast
throughout the evening and nighttime hours. Moderate and even heavy
snow is expected late tonight into Wednesday morning on the nose of
a 700 mb jet. 12Z guidance remains largely unchanged with the nose
anchoring in the vicinity of Interstate 70 across central KS.
Forecast soundings from the RAP, NAM, ECMWF, and GFS all depict a
deep isothermal layer through ~600 mb. In addition, this isothermal
layer is positioned within the dendritic growth zone (DGZ). This
should support efficient snowfall rates with snow-to-liquid ratios
approaching 20:1. The overlap of the deep DGZ and strong lift look
to persist along the I-70 corridor for 4-6 hours. With snowfall
rates likely to approach or exceed 1" per hour, this still
translates to 5-8" of snow accumulation for areas along/near I-70.
This convergence zone will gradually weaken and slide to the east as
the main deformation zone expands across eastern KS.
Further south across south central into southeast KS, the main 700mb
speed max is progged to eject into the state late tonight into
Wednesday morning. Steep midlevel lapse rates on the order of 7-8C
will contribute to instability up to 200 J/kg above 650 mb. This
will most certainly result in banded snowfall across south central
and southeast KS with snow rates exceeding 1" per hour at times.
Furthermore, this instability may allow for ice pellets from
time to time and even a rumble of thunder. Unfortunately, these
snow bands may overlap with the morning commute, including
across the Wichita metro area. Visibility of 1/2 mile or less
can be anticipated within these bands. While overall snow
amounts are less across southern and southeast KS, hazardous
travel conditions are still probable. As the main midlevel
trough slides through the Wednesday afternoon into Wednesday
evening, all snowfall will progress east of the area, setting
the stage for a very cold night.
In regards to the cold, bitterly cold wind chills are expected
Wednesday and Thursday morning as temperatures plunge towards zero
and even below zero. The coldest temperatures are expected across
central KS. Coupling in a brisk north wind up to 25 mph will create
wind chill values as cold as -15. A Cold Weather Advisory may be
needed with subsequent forecast packages.
Beyond Thursday, shortwave ridging will slide across the central US
in-advance of the next trough progged to arrive late Friday into
Saturday. Winds on Friday will likely be strong as a tight pressure
gradient develops across the area combined with strong winds
approaching 70 mph at 850mb. This may result in blowing snow
conditions from Wednesday`s snowfall. Temperatures on Friday are
expected to rise above freezing which may help with snow melting;
though, these warmer temperatures will be short-lived as we move
into Saturday. Temperatures are expected to drop again as the
Arctic air with the next upper level wave moves into the area.
This wave could bring another round of snow to central KS and
rain to southeast KS. Timing and evolution of this system will
be monitored closely.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 619 PM CST Tue Feb 11 2025
SUMMARY...Widespread snow and IFR to LIFR conditions will
spread across the region tonight into Wednesday morning.
DETAILS...A strong storm system approaching from the west will
spread areas of light-moderate to occasional heavy snow west to
east across the region from about 06-09z through 13-17z later
tonight into Wednesday morning. Only went prevailing 1SM in
light snow at this time, but there will likely be pockets of 1/2
to 3/4SM or lower in moderate to heavy snow. Additionally,
cannot completely rule out a few lightning strikes (i.e. thunder
snow) between 06-12z or so, given some elevated instability,
which would locally enhance snowfall rates. Furthermore, gusty
north winds will develop later tonight and persist through
Wednesday.
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 6 PM CST Wednesday for KSZ032-033-
047>053.
Winter Weather Advisory until 6 PM CST Wednesday for
KSZ067>072-082-083-091>096-098>100.
&&
$$
DISCUSSION...BRF/GC
AVIATION...ADK
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
837 PM CST Tue Feb 11 2025
.KEY MESSAGES...
- While the mid week storm system will still have impacts,
especially to the Wednesday afternoon commute, snowfall amounts
have trended downward.
- The highest threat for freezing rain remains centered just north
of the I-70 corridor, with amounts around a tenth inch or so
expected. Wednesday afternoon and early evening is most favored
for this accumulation.
- The next storm system will bring a wintry mix to the region this
weekend, though starting off as rain in many areas near and
south of I-72/Danville.
&&
.UPDATE...
Issued at 836 PM CST Tue Feb 11 2025
First of the 00Z models are rolling in and continue to support the
lower snow totals as forecasted by the previous shift. NAM and
HRRR both indicate 2-4 inch snow totals will be common across
central Illinois Wednesday with some hints of mesoscale banding
that will drive locally higher totals. Both also indicate a sharp
cutoff on the southeast side of the system (near I-70 per the
HRRR and near a Shelbyville to Danville line per the NAM) where
some sleet and freezing rain will cut down on snow totals. Timing
still looks on track for the heaviest precip to overspread the
Illinois River Valley mid to late in the morning and the remainder
of central Illinois late morning into the afternoon. Will let
going headlines ride this evening, but if remainder of 00Z
guidance continues to pull back on snow, may be able to convert
more of the warning to advisory overnight.
Deubelbeiss
&&
.SHORT TERM... (Through Wednesday Night)
Issued at 220 PM CST Tue Feb 11 2025
Some significant shifts have been noted in the morning model
suite, a trend which was first noted overnight. Most notably,
precipitation amounts have dropped a couple tenths, which results
in lower snowfall amounts. Timing-wise, the arrival still appears
early to mid morning, holding off until after 9 am over southeast
Illinois. Heaviest rates of a half to 1 inch per hour are most
favored near and north of Peoria in the afternoon. However, the
highest snow amounts are now more favored from southern Iowa to
the Illinois/Wisconsin border. HREF probabilities of snow over 4
inches (although based on a 10:1 ratio which is a little low in
this particular area) dropped to around 20%. On the whole, the
traditional Winter Storm Warning criteria for that area (6 inches)
currently doesn`t appear to be within reach. However, the greatest
impact times do line up with the afternoon commute, so most of the
warning will be maintained at this point. However, areas near
Jacksonville and Petersburg will be downgraded to an advisory, as
amounts in that area are expected to be closer to 3 inches.
On the ice front, placement of freezing rain and sleet still
appears most likely near and just north of I-70. Amounts have come
up a tad, with HREF probabilities of over 1/10 inch around 40%
from around Shelbyville northeast to Paris. Winter Weather
Advisory in this area still appears good. The midday run of the
HRRR has shifted the line just south of I-70, but the trend will
need to be watched to see if it is consistent.
Geelhart
.LONG TERM... (Thursday through Next Tuesday)
Issued at 220 PM CST Tue Feb 11 2025
Temperatures will be on a roller coaster during this period.
While wind chills below zero are expected early Thursday west of
I-55, temperatures over central Illinois rebound into the 30s
Friday, and 40s are within reach Saturday near and south of I-70.
Another surge of Arctic air follows as a large upper low settles
across Ontario early next week. NBM probabilities of lows below
zero are over 60% north of a Macomb- Bloomington line Monday
morning.
No significant changes were noted in the morning model suite
regarding the weekend storm system. With warmer temperatures, a
rain/snow mix will be common, with the mix line potentially as far
north as Peoria before a changeover from rain to snow moves from
northwest to southeast over the forecast area. NBM probabilities
of more than 2 inches of snow are highest north of I-72, around
30-35%. Further out, a fast-moving system will streak out of South
Dakota early next week, though moisture will be more starved as it
tracks into the high pressure axis that will extend into Illinois.
Consequently, snow chances for this feature are around 30% in the
current forecast package.
Geelhart
&&
.AVIATION... (For the 00z TAFs through 00z Wednesday Evening)
Issued at 519 PM CST Tue Feb 11 2025
Low pressure will develop over the lower Mississippi Valley
tonight and lift to the Ohio Valley by Wednesday evening. Ahead
of the system, lowering ceilings and snow are expected across
central Illinois. Conditions will quickly deteriorate to IFR as
the onset of snow occurs mid to late Wednesday morning and
continues much of the day. Snow is expected to taper off around
00Z Wednesday evening.
Deubelbeiss
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from 6 AM Wednesday to 3 AM CST Thursday
for ILZ027>031-036-037-040-041.
Winter Weather Advisory from 6 AM Wednesday to 3 AM CST Thursday
for ILZ038-042>057-061>063-066.
&&
$$
Area Forecast Discussion
National Weather Service Indianapolis IN
1000 PM EST Tue Feb 11 2025
.KEY MESSAGES...
- Winter Weather Advisory for combination of freezing rain and snow
Wednesday into Wednesday night
- Total snow up to 3 inches near Lafayette, ice accumulations up to
0.2 inches north of I-70
- Widespread Precipitation expected Friday night through early
Sunday AM; Predominately rain with snow mixing in Fri/Sat night
- Well below normal temperatures likely early next week
&&
.FORECAST UPDATE...
Issued at 1000 PM EST Tue Feb 11 2025
No major changes to the overnight grids with brief break now starting
between departing/weaker disturbance and tomorrow`s approaching/
stronger system. Made slight increase to POPs along region`s southern
tier through 06Z where slowly-fading -SN has been hanging on this
evening. Also decided prudent to issue a corresponding SPS for
isolated black ice following 500P North Vernon COOP snowfall ob (0.2
inches) and MRMS PCPN guidance toward CWA`s southern boundary implying
upwards of 1.0" snowfall...especially across southern portions of Knox,
Daviess, Martin zones. SPS set to expire at 04Z.
Otherwise thickening clouds will slowly drop ceilings through the late
night...and will combine with light to moderate ENE breezes to drop
readings about 5 degrees from current obs in mainly the low 30s.
Expect morning lows by daybreak in the upper 20s along the I-70
corridor...with marks about 5 degrees lower around Kokomo...and 5
higher along the US-50 corridor.
No changes to forecast for system to impact central/northern counties
through PM hours tomorrow...with Winter Weather Advisory along/north
of I-70 for 100P Wednesday to 400A Thursday.
&&
.SHORT TERM (This evening through Wednesday night)...
Issued at 242 PM EST Tue Feb 11 2025
Summary:
An impactful winter system is expected to impact portions of central
Indiana starting Wednesday afternoon with greatest impacts ending
around midnight. A low pressure system will bring a combination of
snow, freezing rain, and rain with snow generally isolated to areas
near Lafayette while an area of icing occurs in the corridor north
of I-70 and along/west of I-69. Areas to the south will see
primarily rain with short periods of freezing rain. Total snow of 1-
3 inches along with freezing rain of up to 0.2" expected.
Tonight Through Wednesday Night:
Synoptically a broad upper level trough will move through the Ohio
Valley Wednesday into Wednesday night with increasing confidence in
the track of the surface low generally moving along to just south of
the Ohio River while the 850mb low tracks across Missouri into the
Great Lakes. Precipitation onset looks to be during the early
afternoon hours but there is just enough forcing during the morning
hours for additional isolated precipitation.
Model soundings continue to show a strong warm nose in the 4-8kft
level which will be discussed in more detail below along with near
to below freezing surface temperatures. A mix of freezing rain and
snow is likely in the Lafayette area while freezing rain looks to be
the predominant precipitation type elsewhere in areas approximately
north of I-70 and west of I-69.
Surface temperatures will remain steady-state through the day with
weak CAA near the surface counteracting the latent heat of fusion in
areas of ice accumulation. Total ice accumulations of around 0.1"
with locally higher amounts to 0.2" continue to look reasonable with
snow amounts of 1-3 inches near Lafayette. While an argument can be
made with the combination of ice and snow to issue a Winter Storm
Warning, with some of the continued uncertainties on p-type,
elected to issue a higher end Winter Weather Advisory.
One key caveat that is leading to the differing outcomes is how the
models are handling a subtle but important secondary low just ahead
of the main surface low which the NAM is keying in on as a source
for a strengthened LLJ ahead of the main LLJ during the late
evening into early overnight hours. This is pushing a stronger
surge of warm air and creating a stronger warm nose vs the GFS and
HRRR which show this localized LLJ, but not to the same degree.
If this verifies, the freezing rain threat may push as far
northwest as Lafayette with higher end ice accumulations. If the
GFS solution of a weaker and more isothermal warm nose verifies,
the snow axis will move 20-25 miles further southeast with snow
amounts as high as 4 inches near Lafayette.
&&
.LONG TERM (Thursday through Tuesday)...
Issued at 242 PM EST Tue Feb 11 2025
Thursday through Friday...
Surface high pressure builds in early in the extended behind the
departing midweek system. Large scale subsidence will provide quiet
weather conditions during this period. Temperatures are also going
to below normal due to cold air advection. Overnight temperature are
going to be particularly cold Thursday night into Friday morning
with lows ranging from the single digits to teens. A few locations
across the far northwest could even fall to near zero. Excessively
cold wind chills are not expected as winds should be very light due
to surface high pressure directly overhead.
Friday night onward...
The quiet pattern comes to an end by this weekend as another system
tracks across the region. Latest guidance has come into slightly
better agreement showing a developing surface across the central
CONUS and tracking near TN/KY. Expect anomalous moisture to surge
northward within a strong-broad LLJ. This combined with increasing
dynamics will favor heavy precipitation for areas south of the Ohio
River.
Widespread precipitation is favored across central Indiana as well,
but with weaker forcing towards the north and west, QPF amounts
should be much lower compared to those in Kentucky or Tennessee. The
lowest QPF amounts are expected over N/NW portions of the area. The
warmer trend in guidance continues to support rain as the
predominant precipitation type though wintry precipitation is still
expected to mix in at times.
Increasing positive vorticity and warm-air advection should allow
for precipitation to begin Friday night. Precipitation may begin as
snow or a rain/snow mix briefly before quickly transitioning to rain
due to increasing warm air advection. Mostly rain is expected during
the Saturday as temperatures warm into the upper 30s and 40s. Some
uncertainty remains on temperatures for Saturday due to model spread
in the surface low track, but most guidance keeps temperatures well
above freezing.
Colder air filtering in on the backside of the system Saturday night
will likely promote a Cloudy skies continued across central Indiana this evening. ACARS
soundings show very dry air below the mid cloud deck. Surface
dewpoints were still in the mid teens to lower 20s most areas.
Weak isentropic lift was occurring in the mid levels, but any
precipitation is not reaching the ground thanks to the very dry air
in the lower levels.
As the night progresses, lift will increase and the lower levels
will begin moisten up. This perhaps will allow some flurries in the
northern two-thirds or so of the area, while better forcing and
moisture could lead to some light snow in the far south later
tonight.
Ongoing forecast reflected the above pretty well so only made some
tweaks to PoPs/flurry coverage. Little or no snow accumulation is
expected in the far south by 12Z.
Adjusted dewpoints as necessary given the stubborn dry air in place.
Tweaked hourly temperatures but low temperatures look good.transition
back to snow. However, questions remain on how much moisture
lingers overnight as the colder air moves in. There is at least a
low chance for some snowfall accumulation during this event, but
given the dominant precipitation type will be rain, confidence is
low.
Expect a cold airmass to settle in behind the weekend system with
well below normal temperatures early next week. Long range guidance
supports this cold airmass sticking around for much of next week
with a gradual moderation in temperatures.
&&
.AVIATION (00Z TAF Issuance)...
Issued at 625 PM EST Tue Feb 11 2025
Impacts:
-MVFR CIGs after 06Z...falling to IFR around 15Z Wednesday
-Precipitation after 15Z Wednesday...-SN/-FZRA at KLAF, -RA at KBMG,
-RA/possible -FZRA at KIND/KHUF
-Mainly east-northeast winds at 5-12KT through TAF period
Discussion:
Zonal, wintry pattern will support weak, departing disturbance
sliding up the Ohio Valley this evening...and a more impressive,
approaching weather system that will lower ceilings to MVFR after
06Z tonight...before -RA/-ZR/-SN arrives from west to east during
midday hours Wednesday.
Expect overcast VFR to continue this evening from drier air present
through the lower levels. CIGs to slowly drop from south to north,
with MVFR reaching TAF sites 07Z-12Z...with further deterioration to
IFR CIG/MVFR VIS from south to north during 13Z-18Z. Precipitation
to then arrive west to east within 16Z-20Z, and continue into
Wednesday evening. IFR/LIFR to be the rule after 18Z, with only
slight improvement expect at KLAF by end of TAF period. -SN/-FZRA
will prevail at KLAF...-RA/possible -FZRA at KIND/KHUF...and -RA at
KBMG.
Winds should remain more uniform through late Wednesday as surface
low pressure tracks from TX to central KY....from 040-080 degrees at
5-12KT.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 1 PM Wednesday to 4 AM EST Thursday
for INZ021-028>031-035>049-051-052.
&&
$$
UPDATE...AGM
SHORT TERM...White
LONG TERM...Melo
AVIATION...AGM
Area Forecast Discussion
National Weather Service New York NY
948 PM EST Tue Feb 11 2025
.SYNOPSIS...
Low pressure passes well south of the area tonight into early
Wednesday morning. Another low pressure and its associated frontal
system moves across the area Wednesday night into Thursday.
Strong high pressure approaches Thursday night through Friday.
High pressure moves directly over the local region Friday night,
and moves out into the Atlantic on Saturday. An associated strong
low moves across Sunday into Sunday night. High pressure
returns thereafter, gradually building in for early next week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Forecast on track, increased probabilities to near 100% across
NE NJ, NYC, and Long Island where snow has been falling for a
couple of hours. Just some minor adjustments to temperatures,
dewpoints to better match observed and short term forecast
trends.
Winter Weather Advisory remains in effect for Nassau and
Suffolk Counties through 7am EST Wednesday morning.
Low pressure will push ENE off the southern Middle Atlantic
into late tonight. The region will continue to lie on the
northern periphery of the precip shield. The latest model trends
all support a bump up in liquid equivalent with around a few
hundredths well inland, around a tenth southern portions of the
Lower Hudson Valley and coastal CT, 0.15-0.20" in the NYC metro,
and around 0.25" across Long Island. The NAM still appears to
be the wettest of the guidance across the area, especially
across the southern half with as much as 0.3" in NYC and near
0.4" across eastern Long Island. The 18z NAM has lowered QPF
just slightly, but overall remains consistent with its last
several cycles. Most of the 12z CAMs have come into better
agreement with the rest of the model consensus. The HRRR is one
of the drier models, but have noted it be to dry at times in
previous events when the region is on the northern periphery.
There are also several key ingredients that support the trend
upward in liquid equivalent and resulting snow accumulation
including a stronger 700mb frontogenesis signal combining with
strong upper divergence from a 170-190 kt departing polar jet
streak to our north. Models do tend to struggle with the
combination of these features and have seen several past events
over perform with lift accompanying a strong upper jet. The
other factor is the majority of the model suite is indicating
enhancement of the precip shield from Southern NJ up into the
area at least the southeast portion of the area tonight as the
coastal low emerges off the coast. Thermal profiles are also
supporting an all snow event. Soundings indicate deep ice
saturation within the dendritic growth zone for several hours
tonight, especially across Long Island and portions of the NYC
metro. The strongest lift appears to occur between 10pm and 2am
with a decrease the rest of the night.
There is a period between about 10pm and 2am where snowfall
rates could run between 0.25-0.50" per hour. There is even a low
probability snowfall rates could briefly approach 1" per hour
across Long Island from around 11pm-1am as the strongest forcing
and deepest moisture combine. Snowfall rates will drop off from
west to east from 3am to 5am. Some flurries may linger towards
day break, but accumulating snow should end before sunrise.
Snow to liquid ratios look higher with this event given we are
on the northern periphery of the low and soundings show more of
an ice saturation signal over one with deeper supercooled water
saturation signal. For these reasons have gone closer to a
12-13:1 ratio.
Updated snow totals are around 3 inches with potential of a few
spots approaching 4 inches across Long Island. Elsewhere across
the NYC metro and much of NE NJ and coastal CT, generally 1-2
inches are forecast. Locations closer to the south shore in
Staten Island and southern Brooklyn and southern Queens could
see up to 3 inches. More locations could see closer to 3 inches
in the NYC metro and NE NJ if a wetter and further north trend
continues. Amounts across the interior will be lower and
generally less than an inch as this area is closer to subsidence
from the high building in from the north.
A Special Weather Statement for areas outside the advisory where
amounts over an inch are expected to account for potential of
slick conditions tonight.
Lows generally in the upper 20s along the coast and lower to
mid 20s interior.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/...
The offshore low pressure moves further out into the Atlantic
Wednesday morning. Heights aloft along the eastern seaboard
will rise through the day in response to an amplifying upper
trough over the Plains. High pressure will briefly build down
across New England from southeast Canada. Another strong upper
jet streak will pass over New England so mid and high level
clouds are likely to persist through the day. The day time hours
are expected to be dry as subsidence from the high pressure to
the north dominates. High temperatures range from the lower and
middle 30s inland to the middle and upper 30s near the coast.
The next low pressure and its associated frontal system fast
approach Wednesday night. Warm advection precip north of the
warm front will expand across the region Wednesday evening and
Wednesday night. SW flow aloft will increase helping to drive
warmer air over the region. The latest model trends have
indicated an overall warmer solution with a brief window for a
wintry mix of snow/sleet changing to liquid overnight. There is
still potential for some freezing rain across the interior late
at night into early Thursday morning. For the NYC metro and Long
Island, warmer air at the surface and aloft will change any
brief snow to plain rain late in the evening and night.
Snow/sleet accumulations look light and generally a coating near
the NYC metro to around an inch well inland. Ice accumulations
for the interior could be several hundredths.
The warm front and associated weak secondary low lift north over
the area on Thursday. It is always difficult to forecast the
exact placement of these features. However, the guidance has
been trending warmer with a much stronger parent low passing
well to our northwest Thursday. This should be able to scour out
some of the low level cold air across the interior by Thursday
morning. The bulk of any remaining precip occurs in the morning
with drier air beginning to move in late in the day as the
associated cold front moves through. Latest model consensus
indicates highs in the 40s. With potential of dew points in the
40s as well, there may some fog around with lingering melting of
the recent snow pack. This is something that may need to be
added into the forecast in future updates.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
The key feature of the long term will be the evolution of a
strong quite deep mid and upper level cutoff low in Southern
Canada. The mid and upper level pattern is expected to be more
amplified as a result. The active upper jet stream remains
across the region much of the long term period with more periods
of strong meridional SW flow.
The overall forecast trend, POPs went up this weekend compared to
previously forecast and temperatures on average cooled compared to
previously forecast. Forecast followed NBM but did blend in
consensus of raw model data for temperatures this weekend. For the
precipitation, greater weight was given to utilize a precipitation
type from thickness method for Saturday night into Sunday using the
GFS with some manual cooling of layers.
Dry conditions expected with strong high pressure building in
Thursday night through Friday night. Lows at night are forecast to
be near normal and highs forecast on Friday are slightly below
normal.
Precipitation event, this weekend, warm front followed by strong
low and associated occluded front. The strong low moves across
Sunday into Sunday night along with its occluded front. Warm air
advection makes for plain rain for entire region pretty much
all of Sunday afternoon.
However, with onset (Saturday) and tapering off of precipitation
(Sunday night), snow will be probable for all of the region. In
between, mainly Saturday night into Sunday, warming aloft in
advance of the strong low will present a potential transition
to a wintry mix, including freezing rain across the interior.
There is uncertainty and subsequent forecasts may have northward
or southward shifts with this wintry mix and snow line and its
timing.
Too much uncertainty at this point for any exact rain, snow and/or
ice amounts.
Behind this front, strong cold air advection is expected with jet
max south of the region. Coldest temperatures of the forecast period
are expected for Monday and Tuesday of next week. Forecast highs
struggle to approach the freezing mark and are well below
normal.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Low pressure passes south of the terminals tonight. High
pressure briefly builds to the north Wednesday before yet
another low approaches from the west late Wednesday afternoon
into the evening.
Conditions have lowered to IFR to LIFR with light snow across
the New Jersey terminals, New York City, and Long Island, with
MVFR to VFR farther to the north, with some light snow, except
at KSWF, which may remain dry, with just a chance of MVFR in
light snow. IFR to LIFR continues into late tonight, until
08Z/09Z when the snow is expected to end. Conditions improve
back to MVFR with snow ending toward morning, with MVFR
continuing through Wednesday, with a chance Wednesday afternoon
with a brief period of VFR, however, confidence is low. A wintry
mix is possible toward 23Z Wednesday.
Snow accumulations 1-2 inches with locally up to 3 inches from
metro NYC across Long Island, 1/2 to 1 inch west and north.
Light S to light and variable wind into late tonight, then
becoming NE 10-15 kt as the low begins to depart. Highest winds
will be along the coast.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Amendments for the timing of flight category changes in snow
into the overnight period. Snowfall amounts of 1-2 inches
expected with locally up to 3 inches.
Likely remaining MVFR Wednesday. Another round of wintry
weather, snow and sleet, may begin to 23Z Wednesday.
.OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY...
Wednesday Night-Thursday: Snow/wintry mix developing Wednesday
evening with conditions lowering to IFR/LIFR. At the coast,
wintry mix for a brief period before becoming plain rain.
Further north, wintry mix becoming plain rain Thursday morning.
Rain ending from the west during Thursday afternoon. LLWS east
of the NYC terminals Thursday, SW 45-55 kt, ending during the
afternoon. E gusts 15-20 kt Wednesday night.
Friday: VFR. NW wind gusts 15-20 kt during the day.
Saturday: VFR early. MVFR or lower possible with rain/snow mix near
coast and snow inland late. Becoming all rain at the coast by early
evening, and a bit later at the inland terminals.
Sunday: MVFR for much of the day in rain; winds SW 5-10kts.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
Conditions will remain below SCA levels on all waters tonight.
E/NE winds on Wednesday with marginal SCA gusts and seas likely
in the morning then higher confidence in winds and seas at SCA
levels in the afternoon and at night. Winds will also increase
to SCA levels on the LI Bays and eastern Sound Wednesday night.
SCA conditions likely linger on the ocean Thursday and could
also expand to the Sound, Bays, and Harbor.
SCA conditions are probable on the local waters Thursday night
into Friday. Sub-SCA conditions then probable Friday night
through Saturday night. SCA conditions potentially return for
Sunday and Sunday night.
&&
.HYDROLOGY...
There are no hydrologic concerns through early next week.
&&
.TIDES/COASTAL FLOODING...
With full moon on Wednesday and SCA easterly flow Wed Night into
Thu AM ahead of approaching frontal system, there is potential
for scattered areas of minor coastal flooding with Thu morning
high tide for vulnerable areas along Jamaica Bay, western Great
South Bay and western LI Sound, and more isolated along NY/NJ
harbor.
Tidal departures needed for minor coastal flooding are
near 2 to 2.5 feet of surge. An average of model surge guidance
shows localized departures up to near 2 feet for parts of the
Long Island shoreline, particularly within the South Shore
Bays as well as within the Southern Fairfield CT shorelines.
However, with the aforementioned SCA easterly flow leading into
the early Thursday high tide, the surge might end up being on
the higher side and above surge model averages. Therefore, the
minor coastal flooding may well be more widespread early
Thursday, especially within the South Shore Bays and along
portions of Western Long Island Sound.
Some beach flooding and escarpment possible during the Thu AM high
tide with elevated water levels and e to w sweep of 4 to 6 ft
breaking surf, but dune erosion threat appears limited at this
point.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Winter Weather Advisory until 7 AM EST Wednesday for
NYZ078>081-177-179.
NJ...None.
MARINE...Small Craft Advisory from 6 PM Wednesday to 6 AM EST Thursday
for ANZ332-340-345.
Small Craft Advisory from 6 AM Wednesday to 7 PM EST Thursday
for ANZ350-353-355.
&&
$$
SYNOPSIS...JM/DS
NEAR TERM...JM/DS/MET
SHORT TERM...DS
LONG TERM...JM
AVIATION...MET
MARINE...JM/DS
HYDROLOGY...JM/DS
TIDES/COASTAL FLOODING...