Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/19/23
Area Forecast Discussion
National Weather Service Burlington VT
1017 PM EDT Sat Mar 18 2023
.SYNOPSIS...
Scattered to numerous gusty snow showers will move through the
region through the evening, and again tomorrow morning ahead of
a couple of frontal boundaries. In between, a lake-effect snow
band is expected to produce locally heavy snowfall in
southeastern St. Lawrence County in New York. Blustery
conditions reminiscent of mid-winter will occur Sunday with
areas of blowing snow. A return to more seasonable weather is
expected on Monday with some light valley rain and mountain
snow at times through the first part of the week, followed by more
widespread precipitation later in the week.
&&
.NEAR TERM /THROUGH SUNDAY NIGHT/...
As of 1016 PM EDT Saturday...The forecast remains in good shape
for the overnight hours with the initial surge of snow showers
occurring over southern portions of St. Lawrence County as
expected, but the main lake effect event remains on track to
take shape later tonight, which continues to be supported by
the incoming 00Z guidance. So after the current radar activity
wanes over the next hour or two, a brief lull is expected before
the true lake effect band develops after 2-3AM and still looks
to deposit a quick 3-6" across southern portions of St. Lawrence
and Franklin Counties of New York.
Previous Discussion...Snow shower activity has blossomed in
response to daytime instability, height falls, and increasing
surface convergence in advance of a weak surface cold front. The
amount of instability and moisture is more than sufficient for
convection, and as such the snow squall parameter in the western
Adirondacks is greater than a value of 2 per RAP mesoanalysis
late this afternoon. Relatively high cloud bases are supporting
strong downdrafts with brief gusts in excess of 35 MPH possible;
these stronger winds should be mainly in the St. Lawrence
Valley through the rest of the daytime hours associated with a
southwesterly low level jet. These winds should diminish
somewhat tonight as flow becomes more west- southwesterly. As
such, cold winds moving along Lake Ontario will support the
lake-effect snow band into the favored downstream area of far
southeastern St. Lawrence County and southern Franklin County in
New York, where a Winter Weather Advisory remains in effect.
Model guidance has honed in on roughly a six hour period with
best chances for heavy lake effect snow, roughly 2 AM to 8 AM,
before wind shear increases and the band diminishes tomorrow
morning. Still expect locally as much as 8 inches with sharply
lower amounts heading farther north into the Advisory area,
although this region will see snow showers aside from the lake
effect band tonight into tomorrow.
Relatively mild temperatures today will trend much cooler
tonight as low level temperatures drop sharply. This well below
normal air mass, featuring surface temperatures in the twenties,
will help steepen low level lapse rates again. As such, expect
gusty westerly winds, and any snow showers will be prone to
blowing around given their low density. Even when scattered snow
showers diminish in the afternoon, have indicated areas of
blowing snow to continue primarily in higher elevations. Again,
with lack of a strong surface front tomorrow morning, the
organization and intensity of snow showers will likely be
limited, but are generally from the northern Adirondacks
eastward through the northern two-thirds of Vermont some briefly
heavy and gusty snow showers are possible. Lingering showers
should tend to diminish during the afternoon and be focused
along and east of the spine of the Greens due to strongly
unblocked flow. With a continued pressure gradient through the
night and some cloud cover possible overnight, have not shown
much of a temperature change moving through the night. In fact,
by Monday morning some locations may be a bit milder than in the
evening as some warm air advection develops.
&&
.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 338 PM EDT Saturday...With a trough passing north of the
international border along with lingering 700mb moisture, light
showers could linger in the Adirondacks, northern Greens, and the
Northeast Kingdom throughout the day Monday. Any additional lake
effect snow falling in northern New York is expected to drop off by
the end of the morning. PoPs are in the 25-30% range at most.
West/southwesterly winds will draw in milder air, allowing highs to
rebound into the upper 30s to lower 40s, around average for this
time of year. Due to this, any snow accumulations with this light
snow will be limited to a dusting to couple tenths of an inch at
higher elevations. The precipitation reaching the valleys will most
likely be rain. Including in the St. Lawrence Valley, where
conditions could become gusty with up to around 25 mph gusts, and in
general the forecast area will have good mixing and gusty winds. The
southern half of the area could even have a good amount of sunshine
in the afternoon as high pressure expands northward from the mid-
Atlantic.
A shortwave is expected to move toward/into our forecast area Monday
night, returning the potential for snow showers along the
international border/Adirondacks, where best moisture will traverse.
PoPs capped at around 20-30% for this period, and clouds start
increasing from the northwest to southeast. Winds out of the
southwest are anticipated to calm slightly throughout the night with
lows in the 20s, again around average. Thanks to these colder temps,
any showers are expected to be snow showers overnight, with just
another few tenths of accumulations in the Adirondacks.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 338 PM EDT Saturday...A shortwave passing through the region as
a jet streak sets us in its left exit region on Tuesday will produce
more shower activity and mostly cloudy skies, mainly for the
northern half of the forecast area with PoPs 25-30% at most. Showers
could start as snow early, but rain will likely take over as
dominant p-type throughout the day as temperatures rise into the
40s. Winds are expected to turn more westerly Tuesday morning, then
calm and variable Tuesday afternoon as shortwave energy departs and
ridging builds in into Wednesday.
This ridging will produce briefly dry weather Tuesday night/early
Wednesday, but another shortwave will head into the Great Lakes with
a larger trough following it across Manitoba. Late Wednesday into
Thursday, these features look to combine in Ontario as they head
into Quebec, associated with a low pressure at the surface. Our
forecast area will initially receive an influx of milder air and
precipitation Wednesday night as the system occludes to our north.
Best chances for precip occur Wednesday night-Thursday, so
widespread 30%+ chances with 50-65% chances mostly in terrain-driven
upslope areas. Thursday night, chances linger in the 30-40% range.
Temperatures Wednesday and Thursday will rise into the 40s, while
south-central Vermont could even flirt with the lower 50s. This will
mean mostly rain again for the valleys as snow mixes in at higher
elevations. As warmer air affects the atmospheric column, model
soundings show warm nose bending toward the 0 C line in some spots,
like the Northeast Kingdom and the Greens, so there`s the potential
for a bit of wintry mix, but overall it looks isolated and low
confidence at this time. We are also monitoring the potential for
minor river flooding, but with this being the extended period, much
can change between now and the event. Currently ensemble models are
indicating a few not-insignificant river rises across the forecast
area. We will have to see how models handle QPF with this system in
the coming days.
A frontal boundary is expected to drag through the forecast area
following the initial midweek batch of precip, so PoPs remain
around 30-50% into Saturday night with the potential for showers
as a shortwave rides the front. Highs could come down slightly
Friday and Saturday, but overall still looking to stay in the
40s. Once again valley rain, snow mixing to the summits,
however, at night, there`s the chance for more snow than rain
showers with this front as temps drop.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Through 00z Monday...Mainly VFR, although isolated to scattered
snow showers will result in occasional MVFR and IFR
visibilities. Timing of these showers is challenging with
multiple boundaries moving eastward through the region. Have
utilized the 00z hi-res guidance to better time the snow
showers, which could briefly drop vsby to MVFR although cigs
should stay mainly VFR between 3500 to 4500 ft. The exception is
KSLK, where more persistent snow from a lake effect band off
Lake Ontario looks to impact the terminal between 06z and 10z
with IFR vsby and perhaps MVFR cigs.
Winds will be predominantly southwest through 12z Sunday then
turning more westerly. It will be quite breezy with winds
gusting to 25 kt and even a few isolated 30 kt gusts possible.
Outlook...
Sunday Night: VFR. Slight chance SHSN.
Monday: VFR. Slight chance SHRA, Slight chance SHSN.
Monday Night: VFR. Slight chance SHSN.
Tuesday: Mainly VFR, with local MVFR possible. NO SIG WX.
Tuesday Night: Mainly VFR, with areas MVFR possible. NO SIG WX.
Wednesday: VFR. Slight chance SHRA.
Wednesday Night: Mainly VFR, with areas MVFR possible. Chance
SHRA, Chance SHSN.
Thursday: Mainly MVFR, with local IFR possible. Chance SHRA.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...Winter Weather Advisory until 2 PM EDT Sunday for NYZ029-030-
034.
&&
$$
SYNOPSIS...Kutikoff
NEAR TERM...Kutikoff/Lahiff
SHORT TERM...Storm
LONG TERM...Storm
AVIATION...Chai
Area Forecast Discussion...UPDATED
National Weather Service Indianapolis IN
1030 PM EDT Sat Mar 18 2023
.Mesoscale Update...
Issued at 1030 PM EDT Sat Mar 18 2023
Residual shallow layer of instability is supporting a narrow band of
moderate to heavy snow showers from near Crawfordsville to
Westfield and Carmel to northern Hancock County. This band is
organizing west-northwest to east-southeast parallel to mean PBL
flow and may bring a brief burst of significantly reduced
visibility and cause a few slick spots on roads over the next hour
or so, before decreasing in intensity through midnight. Northern
portions of Indianapolis will be impacted as this band moves
southeastward at around 25 mph. We have sent a localized Special
Weather Statement to describe travel impact potential, since we`re
seeing some reduced traffic speeds on Google Maps traffic data
under this snow band.
Elsewhere, flurries are still likely into the first part of the
night as a shallow convective layer remains optimally placed within
the dendritic growth temperature range. These will be
inconsequential and nonmeasurable, however. Impacts should be
limited to the narrow corridor described above, and will be minor.
&&
.Forecast Update...
Issued at 635 PM EDT Sat Mar 18 2023
CIRA layered precipitable water product shows a drier lower
troposphere advecting into northern Illinois. This will reach
central Indiana later tonight, and bring an end to the flurries and
snow showers. In fact, even before then, minimal surface heating
contributing to a layer of shallow convective instability should
slowly diminish through the evening. Thus, the cellular convective
snow showers should steadily/slowly decrease early-mid evening.
There may be just enough residual convective instability and
optimally-placed convective cloud within the dendritic growth zone
for a few flurries to persist the first half of the night.
MSLP gradient, mechanical mixing, and clouds should prevent a sharp
temperature drop tonight. However, temperatures have been roughly
around the 25th percentile of models this afternoon. So, the
magnitude of this Arctic air mass isn`t fully captured and we will
follow day shift`s lead and keep temperatures in the lower
percentile range (i.e., around the 25th percentile, or roughly on
par with the HRRR though maybe a degree colder) through the night.
All that is to say the current forecast is largely on track with
only nitpicky details addressed in this update. Have a good evening.
&&
.Short Term...(This evening through Sunday)
Issued at 302 PM EDT Sat Mar 18 2023
* Very cold for mid March tonight
* Scattered snow showers and flurries end this evening
* Dry and a little warmer Sunday
Arctic air continued to flow into central Indiana this afternoon.
This is resulting in clouds reestablishing themselves across the
area, and the additional development of flurries and scattered snow
showers. Temperatures were from near 20 into the upper 20s.
Rest of this afternoon...
Cold advection will continue along with cyclonic flow. This will
keep the scattered snow showers and flurries going, especially
north. Not expecting much if any accumulation with these as the
atmosphere overall is pretty dry. With the low water content of the
snow, it will blow around easily.
Gusty winds will persist with a decent pressure gradient across the
area, with gusts over 30 mph common. This will make it feel even
colder.
Tonight...
The core of the cold air will move into the area during the first
half of the Tonight period. Some flurries will linger into the
evening with this, but with loss of heating, expect the snow showers
to end by early tonight. Clouds will continue with the cold still
aloft, but more holes may develop as heating is lost.
Overnight, the southern forecast area should see skies become
partly cloudy. However, lower clouds will linger in the remaining
cyclonic flow north.
Winds will remain up around 10mph, so radiational cooling with not
be strong. However, the Arctic nature of the airmass will still
allow temperatures to fall into the teens most areas. Will trend
below blended guidance given the strength of the cold air.
Sunday...
The upper trough will exit the area as surface high pressure builds
in with drier air. This should erode the remaining clouds during the
morning hours. Sunshine and some warmer air moving in will bring
highs back into the mid and upper 30s. This is still much below the
normal highs in the 50s.
&&
.Long Term...(Sunday night through Saturday)
Issued at 300 PM EDT Sat Mar 18 2023
* Noticeable Moderation Monday through Thursday
* More Active Pattern Wednesday-Friday, Potential For Heavy Rainfall
Sunday Night through Tuesday...
The long term will start dry amid a noticeable moderating trend as
rather broad surface high pressure slowly slides from the
Mississippi Valley to the Mid-Atlantic. Ample March sun will shine
through the dry column through much of the early week. Coupled with
increasing south-southwesterly breezes, a noticeable transition
Monday should find temperatures climbing at least 25 degrees to
around 50F. Moderation will continue into Tuesday, with surface low
pressure slowly approaching from the central High Plains...backing
the robust fetch to southerly, promoting thickening clouds. Fairly
certain no organized rain reaches the CWA through the late Tuesday
timeframe given the dry lower levels. Appears temp/dewpoint combos
will promote daily minimum relative humidity values near 25-35
percent both Monday and Tuesday which could briefly present marginal
fire weather concerns during afternoon hours...with this potential
to be refined in updated packages. Readings are expected to peak in
the 50s Tuesday.
Tuesday Night through Saturday...
The pattern will then turn more active for the midweek through
Friday amid above normal temperatures and perhaps at least brief
anomalously high humidity. Surface low pressure expected to pass
well to the north/west of the region should bring a decent slug of
light-moderate rainfall into the Wednesday timeframe. Greater
impacts will likely accompany a nearly-stationary frontal boundary
as it slowly crosses the Midwest in the Thursday-Friday period, with
at the very least potential for extended rain. A subtropical upper
ridge strengthening along the Gulf coast will build northward while
sliding into the southeastern United States. Above normal readings
will be pumped into Indiana on gusty southerly breezes. Adequate
instability for thunderstorms so far appears most likely on Thursday
when highs in the 60s could couple with dewpoints in the 50s...with
the possibility of additional moderate/heavy rainfall to close out
the workweek as the boundary finally crosses to the Ohio Valley.
So far appears the long term will end with another area of surface
high pressure advancing drier conditions into the Midwest, although
with a less pronounced ridge of more seasonable temperatures than
the current cold blast.
&&
.Aviation...(00Z TAF Issuance)
Issued at 425 PM EDT Sat Mar 18 2023
Impacts:
* Flurries with scattered snow showers producing brief bursts of
reduced visibility through early evening
* Gusts 25-30 knots subsiding this evening
Discussion:
Cyclonic moist flow and influence from an eastward migrating weather
system centered over the Great Lakes will keep occasional snow
flurries and scattered snow showers through early evening. Once the
diurnal convective cycle subsides winds will become less gusty and
snow showers will decrease. Brief MVFR ceilings and sub-VFR
visibility can be expected with passing more significant snow
showers until then. Afterwards, improving flying conditions are
expected.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale...BRB
Update...BRB
Short Term...50
Long Term...AGM
Aviation...BRB
Area Forecast Discussion
National Weather Service Northern Indiana
732 PM EDT Sat Mar 18 2023
.SYNOPSIS...
Issued at 156 PM EDT Sat Mar 18 2023
Lake effect snow showers will persist through this evening, with
the greatest intensity and accumulation potential north of the
Toll Road. Expect 1 to 3 inches of snow, with localized amounts up
to 4 inches in the advisory. It will remain windy and cold
through tonight before warmer temperatures return Sunday and into
next week.
&&
.SHORT TERM...(This Evening through Sunday)
Issued at 242 PM EDT Sat Mar 18 2023
A upper low pressure system moving east across southern Canada and
the upper Great Lakes is the weather-maker for today and tonight.
Snow showers forced along by a cold front front brought 1 to 2
inches of accumulations to the 1st and second tiers of counties in
our south this morning. Additionally, the lake effect snow belts
were invigorated with the fresh shot of cold air. Lake induced
temperature differences of 25 to 30 degrees will become more like 20
to 25 degrees tonight as the back side of the area of vorticity
associated with the upper low exits the forecast area. Lake induced
inversions will rise up to about 700 mb or 8.5 to 9 kft today before
slowly falling overnight. Low level moisture today appears the best
within Michigan on those mainly 290 degree trajectories before a
more northwest wind triggered by a departing surface instability
trough this evening starts the slow dissipation process over of the
moisture overnight. All through this, a particular problem is the
sub-950 dryness apparent in forecast soundings. Additionally, strong
gusty winds between 25 and 40 mph during the afternoon are expected
to taper off tonight as the gradient relaxes causing the low level
jet to relax. But these winds will serve to break up the snowflakes
as they fall likely reducing their influence on accumulations, but
lowering visibility due to their greater reflectivity within the
daytime light.
One concern for the late afternoon into tonight period will be that
aforementioned shift in the low level wind trajectories. This would
change the direction of convergent boundaries located in the wind
field and the RAP in particular wants to set up a single band
through the Michigan counties and into a few Northern Indiana
counties. Have noted a similar shift in the other model output QPF
as well. The aforementioned issues with the snowfall accumulation
have kept totals down during the daytime, but we`ll lose the
sunlight`s influence tonight and the winds die down slightly
allowing for flake size to trend larger. All these factors taken
into consideration, have allowed for an additional 1 to 3 inches of
lake effect snowfall within the advisory area and perhaps into St.
Joseph, Elkhart, and Lagrange Indiana counties. A stray 4 inch area
of snowfall will be most possible between Cass and St Joseph,
Michigan counties, which may be where the lake effect snow band
has its largest residence time. Lowered visibility will again be
possible and may briefly hamper travel within the heavier lake
effect snow bands.
Temperatures tonight will be able to drop back to the upper teens to
low 20s as the dry/cool air begins an attempt to shut off the lake
induced cloud/precip plumes.
Height rises begin to come in and low level moisture will be mostly
gutted after 00z tonight, but will take a dissipation of the low
level wind convergence and swivel of the wind trajectories to a more
southerly wind component to shut off lake effect snowfall. That
change doesn`t look to occur until Sunday morning and so will hang
on to cloud cover and at least 15 to 20 PoPs into this period to
track the dissipation. Highs Sunday reach into the mid 30s.
&&
.LONG TERM...(Sunday Night through Saturday)
Issued at 242 PM EDT Sat Mar 18 2023
With the upper low pulling away and the aforementioned warming low
level temperatures we start the warming trend back towards
seasonable temperatures and reach those by Monday. But above normal
50 degree temperatures will be common on Tuesday through Friday with
60s also possible. The one problem for reaching these above normal
temperatures would be the rain chances that enter the area Tuesday
night and continue at times into the next work week. The Tuesday
through Wednesday rain chances would be from various weak vort maxes
moving by to our northwest with the warm advection wing. Models have
attributed a bit more moisture to these and have produced more light
precipitation with them as a result. Thereafter, a baroclinic zone
stalls nearby the area likely as a result of the southeast CONUS
ridge setting up. Various weak waves of low pressure ride along it
each providing a dose of moisture/rainfall to the area. These extra
doses of rainfall would serve to provide an uptick to the recently
saturated ground likely reinvigorating the river flooding.
We`ll need to watch the track of a low pressure system late week
into the weekend. The NAO flips neutral to negative and may allow a
more southward track to the low, but by how much is unsure this far
out.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 724 PM EDT Sat Mar 18 2023
Strongest lake effect snow bands appear to be north of SBN, where
there is also better low level moisture. Yet still expect rapid
fluctuations between VFR and IFR as cellular snow snow continue to
pass over the terminal. Will account for this with a wide range in
visibility between dominant conditions and tempo group. Concerns
much lower at KFWA which is seeing much lighter snow
showers/flurries with only brief MVFR conditions possible.
Snow showers look to quickly wind down overnight as deepest
moisture and lift departs with a return to VFR conditions expected
and eventually clearing of the cloud cover on Sunday.
Gusty west wind this evening will subside some overnight but
likely to remain above 10 kts through the day Sunday.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...Winter Weather Advisory until 5 AM EDT Sunday for MIZ078>080-177-
277.
OH...NONE.
LM...Small Craft Advisory until 5 PM EDT Sunday for LMZ043-046.
&&
$$
SYNOPSIS...MCD/Fisher
SHORT TERM...Roller
LONG TERM...Roller
AVIATION...Cobb
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Area Forecast Discussion
National Weather Service New Orleans LA
814 PM CDT Sat Mar 18 2023
...New EVENING UPDATE...
.EVENING UPDATE...
Issued at 759 PM CDT Sat Mar 18 2023
Performed a gridded forecast update this evening to reflect
observations and recent model guidance. Forecast is looking on
track generally with little adjustments required. Main focus in
the next 12 hours will be the cold, and how cloud cover and a
passing front will impact the diurnal trends and attendant MinT`s.
Can`t sway too far away from the earlier forecast with good
consensus continuing. Hanging on the idea that winds will pick up
later tonight enhancing low-level mixing, disrupting the plunge of
temperatures which is also impacted by cloud cover leading to
modest insulation. Am seeing a brief window of freezing
temperatures for atelast portions of SW MS however regardless of
these limiting factors as CAA intensifies but be aware - a warmer
bias would be meteorologically plausible especially if guidance is
not picking up on the degree of winds/cloud cover offsetting the
strong CAA which may prevent areas to reach freezing. Overall -
mid to upper 30`s for the northern half of the CWA is looking
good and sits right around deterministic with very little, if any
adjustments required.
As for winds, can`t ignore the potential for winds to remain up
enough throughout the night given this reinforcing frontal
passage. Winds near calm to 0-3kt is well below the NBM10th
percentile. Did increase winds a notch tonight above the 10th but
lower than the deterministic which again, further supports the
potential warmer bias in the forecast and will be monitored. Could
very well be a case where the diurnal trend drops faster ahead of
the front throughout the night, then flat lines/slows around
daybreak as mixing kicks up.
Sunshine attempts at returning in intervals tomorrow, but may not
be completely done with the clouds as the base of a strongly
positive-tilted trough axis to our north swings down the MS river
valley, meeting up a weak/subtle impulse pressing ENE from the
Mexican plateau into SE TX. Enough downstream divergence and
moisture feed will support mid to upper-level clouds.
Deterministic NBM settled well into the higher end of ensemble
guidance and I like this. It`s important to note simply the time
of the year - keeping temperatures cold all day requires very
strong CAA and thick clouds. Any degree of offset would explain a
warmer bias as well for highs. Blended in the 75th for highs
bringing many areas in the mid 50`s. Aware this sticks out a bit,
but wanted to make sure we are on the right track given the
synoptic setup and time of the year. Otherwise, winds remain
breezy at times tomorrow especially over marine areas and across
north- facing shorelines. Introduced the NBM10th percentile in
dewpoints in the afternoon to account for strong mixing per HRRR
soundings as deterministic NBM is notorious at under doing. No
other additional impacts expected. KLG
&&
.SHORT TERM...
(This evening through Monday night)
Issued at 235 PM CDT Sat Mar 18 2023
Not much change from the previous forecasts. Biggest concern and
challenge in the short term is trying to determine overnight lows
for tonight and tomorrow night.
At the risk of continuing to repeat, the temperature forecast for
tonight is a bit tricky. Much of the guidance indicates potential
for freezing temperatures across our southwest MS counties as
well as some northern portions of the adjacent LA parishes, and
even down the Pearl and Pascagoula drainages. The limiting factors
are going to be lingering clouds at least through the first part
of the night, as well as some mixing owing to a secondary shot of
cold air advection associated with a fast moving shortwave. Both
of these factors will cut down on the radiational component of
overnight cooling. Most likely freeze locations still look to be
across our southwestern Mississippi counties from Wilkinson across
to Walthall. In these areas, even the warmer NBM guidance
continues to indicate freezing temperatures for at least the
northern half of each county. Another factor playing a supporting
role is that these areas only warmed to right around 50 degrees
today. Current temperatures are even still in the upper 40s at
some observation sites in these counties. That being said, the
temperature doesn`t need to drop quite as far to reach the
freezing mark. Have gone ahead and upgraded the freeze watch for
SW MS to a freeze warning for tonight.
Sunday will be another rather chilly day for March with afternoon
temperatures only rising into the low to mid 50s. It won`t feel
quite as raw as today though as there will be fewer clouds. Winds
will still be a little breezy, but not quite as strong as today,
either.
Sunday night there is high confidence that we will see widespread
light freeze impacts for much of the area. Conditions appear much
more favorable for an efficient radiative cooling night with
mostly clear skies, winds easing to 5 mph or lower in places away
from the south shore of the tidal lakes, and dewpoints in the low
to mid 20s for much of the area. With those factors in mind,
temperatures should begin to plummet after sunset. At this point
the biggest question continues to be how far south will it freeze?
At this time the main portion of the New Orleans metro looks to
remain above freezing as winds off the lake will moderate the
temperatures somewhat. Am generally forecasting upper 30s for
these areas. Similarly, areas closest to the Louisiana coast
should remain above freezing. The question is for areas from Belle
Chasse across the west bank through upper portions of Terrebonne
and Lafourche Parishes. MOS numbers continue to be several
degrees lower than the NBM forecast in these areas. For example,
the 12z MAV and MET indicate lows of 32 and 30, respectively, at
KNBG. The 12z Euro ensemble mean is 32 with a 50th percentile of
31 and a low member of 26 (LOL). The latest run of the NBM comes
in at 37. A similar story unfolds at Houma, though even the NBM
has come in at 34 there with the latest run. I do think the MOS
guidance, especially the ECM, is a little too cool, so I didn`t
make a lot of adjustment to the NBM numbers except in the Belle
Chasse and west bank areas where the NBM tends to struggle more.
This results in min temperatures generally in the mid 30s for
these areas. However, there are some isolated spots in portions of
northern Terrebonne and Lafourche, and on the west banks of St.
John and St. Charles Parishes that could touch the freezing mark.
Confidence in this happening is low so I`ve opted not to expand
the area of the freeze headline at this time, but the next couple
shifts will need to take a close look at some of these areas to
make a more informed decision. Given the high confidence of
freezing conditions elsewhere, though, have upgraded the previous
freeze watch to a freeze warning for areas that are generally
along and north of a line from Morgan City to Lake Maurepas, and
eastward across the north shore and Mississippi coast.
After starting out quite chilly, temperatures Monday should
rebound into the upper 50s to even lower 60s in some places as we
lose the influence of cold air advection. Monday night
temperatures look to stay above freezing but will still dip into
the mid to upper 30s across northern areas.
&&
.LONG TERM...
(Tuesday through Friday night)
Issued at 235 PM CDT Sat Mar 18 2023
Zonal flow will dominate the upper level pattern Tuesday,
transitioning to strong ridging and high pressure influencing
the area Wednesday and Thursday. Southerly surface winds will
advect warm air and moist air into the area throughout the week.
Tuesday through Thursday, looking at the models, will be pretty
dry with above average temperatures. We will warm up considerably
from Tuesday through the end of the week. There was not good model
consensus on the high temperatures, but given the calm winds and
mostly sunny skies, it could be possible to overachieve on
guidance. It will be something we may need to adjust in the
forecast down the road, but for now, NBM was left in the forecast
due to the numerous model uncertainties. Generally, highs in the
low 80s could be expected Wednesday/Thursday timeframe thanks to
the strong ridging and extra daylight hours.
Friday, a shortwave system will move through the area. It is too
soon to discuss many details. But strong warm air advection ahead of
the system will help enhance instability. Weak upper level
divergence will help to enhance lifting in the environment. Some
strong storms may be possible, if there is decent shear. But that
will depend on how far north the best forcing ends up, and the
models cannot agree on that at the moment. Looking at the current
pattern in the models, there could also be some concern for flash
flooding given the orientation of the line and the slower
shear/movement. It will be something worth monitoring as we get
closer to the event.
&&
.AVIATION...
(00Z TAFS)
Issued at 620 PM CDT Sat Mar 18 2023
Expect VFR conditions through the TAF period for all local sites.
Seeing mid to upper-level BKN to OVC clouds across the area which
will break up going into tonight. Some FEW to SKC during the day
tomorrow. Otherwise, main impacts will be a reinforcing cold front
sliding south overnight, which will increase winds around daybreak
lasting into the day on Sunday. Wind direction bearing 350 to 010
can be expected with occasional sfc gusts to 15 to 20kts. Stronger
winds can be expected for terminals near north-facing shorelines
including KNEW where winds may gust upwards of 20-30kts by the
time the front passes early Sunday, lasting through the day but
otherwise, no additional impacts are anticipated.
&&
.MARINE...
Issued at 235 PM CDT Sat Mar 18 2023
Hazardous conditions persist across the coastal waters through
Sunday afternoon owing to cold air advection and a tight pressure
gradient between low pressure between the frontal trough extending
through Florida and into the central Gulf, and high pressure
centered over the Rockies. The high will finally build in enough
by Sunday evening to hopefully end headlines and then winds will
slowly veer back around to the southeast as the high lifts
northeastward through the work week.
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 31 49 26 56 / 0 0 0 0
BTR 37 54 31 59 / 0 0 0 0
ASD 37 56 30 60 / 0 0 0 0
MSY 43 54 39 56 / 0 0 0 0
GPT 38 54 32 57 / 0 0 0 0
PQL 35 56 28 60 / 0 0 0 0
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Freeze Warning from 10 PM Sunday to 10 AM CDT Monday for
LAZ034>037-039-046>048-056-057-071-076-079>086.
GM...Small Craft Advisory until 1 PM CDT Sunday for GMZ530-532-534-
536-538-550-552-555-557-570-572-575-577.
MS...Freeze Warning from 10 PM Sunday to 10 AM CDT Monday for
MSZ068>071-077-083>088.
Freeze Warning from 2 AM to 9 AM CDT Sunday for MSZ068>071.
GM...Small Craft Advisory until 1 PM CDT Sunday for GMZ532-534-536-
538-550-552-555-557-570-572-575-577.
&&
$$
SHORT TERM...DM
LONG TERM....MSW
AVIATION...KLG
MARINE...DM
Area Forecast Discussion
National Weather Service Marquette MI
746 PM EDT Sat Mar 18 2023
.SHORT TERM...(Through Tonight)
Issued at 359 PM EDT SAT MAR 18 2023
Water vapor imagery and RAP analysis show a deep mid-level low over
the Great Lakes region, centered n of Georgian Bay, with 500mb
height anomalies around 360m over northern MI. 850mb trof passed
across the area late last night, reinvigorating lake enhanced snow
off of Lake Superior under deep cyclonic northerly flow per KMQT VAD
wind profile. Per latest RAP analysis, 850mb thermal trof at around
-18C currently extends ne to sw across the area. Lake enhanced snow
this morning into the aftn has not well-organized, which limited
snow accumulations to some degree by limiting the duration of hvy
snow. Nonetheless, the deep moisture to near 20kft and healthy
overlake instability has resulted in frequent bursts of hvy
snowfall. KMQT radar has shown +28dbz echoes scattered throughout
the lake effect regime, suggesting at least 1 inch/hr snowfall rates
at times. Webcams have also shown periodic very low vis in the heavy
snow showers. Gusty winds to 25-40mph, strongest at exposed
locations near Lake Superior (Copper Harbor ASOS peaked at 51mph),
are also creating blsn and sharply reduced vis. Increasingly
stronger solar insolation at this time of year has also supported
land based development of -shsn/flurries outside of the lake effect
areas, well inland in s central Upper MI. Back edge of deep moisture
is currently pushing se with drying at the lower levels as well.
With this drying spreading across western and northern Lake
Superior, LES has taken a notable hit out w with LES ending close to
the lake. It`s a cold aftn for mid Mar with temps currently running
in the mid teens to lwr 20s F. So far, temp has only reached 15F
here at the NWS office. The record low max temp for the day at this
location is 19F. That will likely be broken.
As drying continues to spread se thru the late aftn/evening, expect
a rapid diminishing of LES from w to e across the area. There may
not even be any flurries lingering over the w by late aftn.
Diurnally aided flurries/-shsn over the s central will end quickly
toward sunset. Lingering LES over the e will wind down to mostly
just flurries this evening. With the DGZ dominating the shallow
convective layer, will probably see some flurries linger well into
the overnight hrs. To the w, skies will become mostly clear. With
high pres well to the sw over the Plains and a shortwave and
associated sfc trof dropping into northern Ontario, it won`t be a
great radiational cooling night by any means as winds won`t
completely decouple. However, given the cold conditions leading to
sunset and a new layer of fresh snow cover, will lean toward the
lower side of guidance for the interior. MET/MAV have a min temp of
0F and 1F, respectively, at KLNL which is often a good indicator of
where traditional cold spots over the w will end up. Won`t go quite
that cold, but interior cold spots will likely fall to about 5F.
Otherwise, 10 to 15F will generally be the rule.
.LONG TERM...(Sunday through Saturday)
Issued at 344 PM EDT SAT MAR 18 2023
Starting Sunday, we get a little bit of a breather from the active
weather pattern as the low pressure bringing the LES over us this
afternoon continues to lift away into northern Quebec tomorrow. This
allows a quick reprieve from snowfall Sunday, with mostly sunny
skies expected across the area. With high pressure ridging skirting
by to our southwest Sunday, expect some WAA which, combined with the
sunny skies, should give us high temps in the mid 30s to around 40F
over the south central. Therefore, if you have the winter blues or
are tired of being stuck inside the past few days, Sunday would be a
great day to enjoy the outdoors! As we move into Sunday night, a
cold front from northern Ontario drops south over Lake Superior and
moves over the area. Model guidance, particularly CAMs, are hinting
at a line of convection forming over the lake from west to east
along the frontal boundary due to some weak fgen along the front. As
the front moves southwards over the northern portion of the UP, a
quick burst of snowfall could be seen over the area, with possibly
moderate to heavy snowfall being seen for a few minutes along the
band. However, as the fgen band dies out, marginal and light LES
sets up over the north to northeast snow belts late tonight into
early Monday. Light, weak, and pulse-y LES could continue over the
northeast snow belts throughout the rest of the day. Overall,
thinking impacts associated with this cold front will be fairly
minimal, as snow totals should range from a dusting to around an
inch. The only concern would be when the band of snowfall associated
with the fgen comes onshore, as snowfall rates then may greatly
reduce visibility and quickly accumulate on roads (albeit only for a
short while); however, these concerns are relieved a bit due to this
occurring overnight though.
The next system that looks to impact us is expected to come around
Tuesday evening. With model guidance projecting a Colorado low to
move through MN Tuesday night, expect the warm front of this low to
bring some wet snowfall and rain to the area. Most of the area
should start out as pure snowfall, save for maybe southern Menominee
County. However, as the warm front slowly lifts through the area
Tuesday night into Wednesday, expect the transition from snowfall to
rain from the south and west to the north and east. Ahead of the
transition, it looks like we could see up to moderate snowfall at
times, with sloppy accumulations that may be enough for a low-end
winter weather headline, particularly over the north and west. Model
guidance has QPF for this event ranging from around 0.20 to 0.60
inches (this includes the rain and snow); the greatest QPF totals
look to occur along the southeast upslope areas. Once the warm front
moves through Wednesday, expect high temps to get into the 40s
across the area before the cold front pushes in Wednesday afternoon
and evening; some additional light rain/snowfall is expected with
the cold front`s passage.
Recent model solutions have shifted northward a second low pressure
that was previously slated to move through the Lower Midwest late
this work week. While the Euro keeps the low along the MI/IN line
and the GFS has it slightly further north, the Canadian, UKMET, and
NBM seem to highlight the possibility of the low lifting through
Lake MI or northern Lower MI into northern Ontario Thursday.
However, confidence in the most northerly solutions is fairly low,
as the previous runs and the current GFS and Euro keep the low well
south of the area; it will depend on the strength and speed of the
high pressure dropping from Canada into the Plains during the middle
of next week. However, given how the previous storm system lifted
drastically north and westward last week, solutions with precip
occuring over the UP are still on the table. Should the more
northerly solutions win, we could see some more snowfall across the
area late Wednesday night into possibly Thursday. Meanwhile, the
chance for precip heading into next weekend isn`t looking all that
great; while the Euro keeps the strong low pressure solution moving
through Lake Erie Friday night, other medium range guidance keeps
nominal ridging over us. Nevertheless, it still looks possible that
a weak cold front from northern Ontario could drop down over the
area and bring some snowfall back across the UP this weekend.
Overall, temps look to be around normal over the course of this next
week, although we can expect to see some swings from above normal
(like Sunday and Wednesday) to below normal (like Monday and
Tuesday) throughout the week as the generally active weather pattern
continues.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 726 PM EDT SAT MAR 18 2023
High pressure building in from the west and associated much drier
air will quickly diminish any remaining lake effect -shsn this
evening as the terminals improve to VFR. Northwest winds will also
be diminishing through the night and backing west. As winds back
west late tonight into Sunday west winds will become gusty at CMX
with gusts to around 30 kts during the day on Sunday. West-
southwest winds between 20 to 25 knots are expected at IWD on
Sunday.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 404 PM EDT SAT MAR 18 2023
As a low pressure system continues to pull away into northern Quebec
tonight into Sunday morning, expect winds to diminish this evening
as they back with time, with NNW gales up to 40 kts over the eastern
lake early becoming NW winds 20 to 30 kts by Sunday morning.
Likewise, any heavy freezing spray continuing over the eastern half
of Lake Superior this evening ends not too long after midnight,
although some moderate freezing spray could be seen still across the
lake into Sunday. However, with a cold front moving down from
northern Ontario late tonight, expect winds to begin increasing from
the W/WSW early Sunday morning ahead of the front, becoming gales of
35 to 40 kts by around noon EDT. However, when the cold front moves
across the lake Sunday evening, expect the gales to quickly die
down, with north to northeasterly winds of 20 to 25 kts becoming
dominant across the lake late Sunday night. As a weak shortwave
moves through the UP and northern Lake MI Monday, expect winds to
remain northeasterly at 20 to 25 kts over the far western lake
before lightening up to around 20 kts or less Monday evening.
However, as a low pressure system over the Central Plains Tuesday
lifts into MN Tuesday night, expect winds to pick up again from the
east, with gales of 35 to 40 kts being possible over the far western
lake. As the low moves through the lake Wednesday, expect the higher
winds to move over the eastern half of the lake before the cold
sector of the low brings northwesterly winds of 20 to 25 kts back
across the lake Wednesday night into Thursday. Moving into next
weekend, expect winds to be fairly light.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Lakeshore Flood Advisory until 2 AM EDT Sunday for MIZ005>007.
Winter Weather Advisory until 8 PM EDT this evening for
MIZ005>007-013-014-085.
Lake Superior...
Heavy Freezing Spray Warning until 8 PM EDT /7 PM CDT/ this
evening for LSZ162-240>242-263.
Gale Warning from 11 AM EDT /10 AM CDT/ to 8 PM EDT /7 PM CDT/
Sunday for LSZ162-242>244-263-264.
Heavy Freezing Spray Warning until 2 AM EDT Sunday for
LSZ243>251-264>267.
Gale Warning until 8 PM EDT this evening for LSZ243>248-264-265.
Gale Warning until 2 AM EDT Sunday for LSZ249>251-266-267.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...TAP
AVIATION...Voss
MARINE...TAP
Area Forecast Discussion
National Weather Service Blacksburg VA
856 PM EDT Sat Mar 18 2023
.SYNOPSIS...
Gusty winds are expected tonight behind a cold front. Much
colder air will move in overnight and Sunday. Even colder
temperatures are forecast for Sunday night. Temperatures
increase to above normal by Tuesday, becoming very warm by
Thursday. The next widespread chance of rain may come Friday.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 845 PM EDT Saturday...
...Front moving through ushering in cold and gusty weather...
Radar shows echoes associated with a frontal passage, but so far
not seeing anything reach the ground with dry air still in the
low and mid levels. The lowest cloud deck is around 6kft and
should be low enough to produce some seeder-feeder type snow
showers for the Greenbrier Valley, with a few sprinkles or
flurries downwind into the overnight hours. Did increase wind
gusts just a bit to 15-25 mph for the valleys and 25-35 mph for
the ridges as the front moves through and bumps up mixing
heights for a few hours. Winds should decrease closer to the
10-15 mph range by morning. Still expecting very cold wind
chills on the mountains, ranging for 0 to +10F in the valleys,
and as low as
-12F on top of the ridges.
As of 445 PM EDT Saturday...
Colder with light mountain snow and
flurries/sprinkles...winds lowering some overnight...
A cold front was entering the northwestern sections of the
forecast area, accompanied by plenty of altocumulus and light
snow showers. Expect these clouds to spill into the rest of the
region tonight as the front continues pushing SE.
After looking at the snow squall parameters from the NAM and
HRRR tonight, have added either snow flurries or a cold rain for
a few hours this evening. It will be plenty cold (-8 to -10C at
850mb) for upslope showers to drift to or even past the Blue
Ridge, so we may see some light sprinkles/flurries reach as far
south as Boone to Roanoke to Lynchburg, resulting in a few
hundredths precip at most.
Also adjusted snow ratios and thus snow amounts tonight for the
Greenbrier Valley. Just an increase of a few tenths, giving max
snow amounts just under an inch for the northeastern part of the
Greenbrier County.
As of 200 PM EDT Saturday...
Cold and windy with light mountain snow...
With the cold front safely to our east, most areas have broken
to partly cloudy skies thanks to the dry air. Later this
evening into the overnight period, as the upper trough
associated with the front makes its pass over southwest VA,
winds will have a slight resurgence in strength and induce some
upslope clouds for most of the CWA, and some light snow
showers/flurries along the western slopes of the mountains. It
will only be for a few hours, and accumulation will be scant.
Most will see no accumulation or a dusting, and the higher
elevations of Greenbrier County, WV could see up to an inch.
Winds will gust between 25-35 MPH in the mountains overnight,
and up to 25 MPH for the rest of the CWA, with weaker winds
towards Southside VA. With low overnight temperatures in the
teens and low 20s overnight west of the Blue Ridge, wind chills
will be in the teens and single digits. Some limited portions of
ridgetops and peak elevation locations above 3500ft could
experience a brief period of wind chills below zero. These spots
are the exception rather than the rule for this forecast period
though. East of the Blue Ridge, overnight lows will be in the
mid 20s/low 30s.
On Sunday winds will start to calm and the skies will clear and
make way for considerable sunshine. Things will be slow to
warm up with many west of the Blue Ridge not getting out of the
30s, and east of the Blue Ridge high temps just getting into the
mid 40s.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 151 PM EDT Saturday...
Significant cold to start Sunday night, then temperatures
moderate into Tuesday.
Closed upper low near New Brunswick Sunday night will lift
northeast into the Atlantic ocean by Tuesday. Trailing band of
vorticity will result in some high clouds Sunday night into
Monday. A more zonal flow aloft establishes Monday into Tuesday
night. At the surface, high pressure will build across our
region and shift east offshore by Tuesday night.
Low temperatures Sunday night will be very cold with readings
from the single digits to the lower 20s. PWATs drop to
0.05-0.10" by Monday morning, and close to the climatological
daily minimum recorded for the day at RNK. High temperatures
will remain below normal from the mid 30s in the mountains to
around 50 degrees in the Piedmont. Low temperature Monday night
will generally be in the 20s. Clouds increase Tuesday allowing
temperatures to moderate to highs from the mid 40s in the
northwest mountains to near 60 in the Piedmont. Skies become
cloudy Tuesday night as a cold front approaches from the west.
Low temperatures Tuesday night will range from the lower 30s in
the west to the mid 30s in the east.
Confidence in the Short Term Forecast is high.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 151 PM EDT Saturday...
Much warmer with showers possible especially late in the
workweek, then drier for Weekend.
High pressure over the Gulf of Mexico build north across our
region Wednesday into Friday. With rising heights temperatures
will moderate Thursday and Friday. High temperatures will be
warm with readings in the 60s and 70s. Several shortwaves pass
to our north and may bring some clouds and a few showers. Models
continue to have differences in timing. However, southeast West
Virginia has the best chance for showers in the Medium range.
The first opportunity for rain will be Wednesday.
Confidence is moderate for the long term forecast.
&&
.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
As of 840 PM EDT Saturday...
Gusty NW winds are developing along and behind a cold front
which is moving through this evening. Expect gusts to 20 kts
for the valleys, and 25 to maybe 30 kts for a few hours in the
mountains. Winds decrease some by daybreak as mixing weakens for
a few hours. VFR conditions will remain in place for most TAF
sites through the TAF valid period with the exception of BLF/LWB
which may drop to MVFR in snow showers. Expect the mountain
clouds to hang on towards 15-18Z Sunday before clearing.
.Extended Aviation Outlook...
Winds will subside completely Sunday night. Confidence is high
that good flying weather will continue through Monday and
Tuesday. Clouds will increase by Tuesday night as a warm front
approaches from the west to bring a chance of rain showers and
sub-VFR conditions on Wednesday.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...SH
NEAR TERM...SH/VFJ
SHORT TERM...KK
LONG TERM...KK
AVIATION...SH