Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/06/24
Area Forecast Discussion
National Weather Service La Crosse WI
809 PM CST Thu Dec 5 2024
.KEY MESSAGES...
- A light wintry mix possible north central WI Friday morning.
- Warmer through the weekend.
- Precipitation chances continue Sunday night into Monday.
&&
.UPDATE...
Issued at 805 PM CST Thu Dec 5 2024
Recent forecast profiles from both the HRRR and RAP show
saturation deepening Friday morning after 12Z below 700 mb to
over 1-km in depth in advance of a mid-tropospheric shortwave
dropping southeastward from Canada. While the raw omega plots
from these CAMs are not overly impressive, there is enough
background 280-290K isentropic lift to possibly result in light
precipitation from this low stratus deck. The moisture profiles
are mostly confined between -7 and -10 C, raising the concern
that any precipitate could come in the form of freezing drizzle.
Have added some mention of a wintry mix to the forecast north
of Interstate 94 and this will need further assessment through
the night. The main uncertainty in the forecast is the depth of
the stratus deck with the recent HRRR runs coming in slightly
more mixed and thinner than the RAP. The good news is that this
threat will be relatively transient and depart with the
850-700-mb wave by the early afternoon hours.
&&
.DISCUSSION...
Issued at 250 PM CST Thu Dec 5 2024
Overview:
A little bit quieter weather today, but still cold! At 19Z, a
1038mb area of surface high pressure was centered over the
Missouri River Valley with a gradient remaining over the local
area. 19Z temperatures were in the teens and 20s with brisk
northwest winds 5 to 15 mph and some gusts over 20 mph west of
the Mississippi River. Once the clouds cleared, visible
satellite imagery showed some lingering snow streets from the
snow showers yesterday! Latest vapor satellite imagery, and
heights showed the center of closed low pressure that brought
all the wind and cold Wednesday over the New England States. A
larger ridge was located around 115 deg W longitude over the
western U.S. with a closed center of low pressure over Arizona.
We had some flurries this morning and additional snow showers
were noted from the Missouri River into the Dakotas.
Flurries possible north central WI Friday/Warmer through the
weekend:
The pattern through Sunday remains under northwest flow aloft,
however the 925mb/850mb pattern shows more of a westerly or
southwesterly flow through the weekend. Generally temperatures
will be on a warming trend with highs in the 20s and 30s for
Friday and in the 30s and 40s through the weekend. Normal highs
for this time of year are mostly in the 30s. The NAEFS
standardized anomalies show 850mb anomalies of 0-1 standard
deviations, with higher 500mb anomalies across Minnesota. The
latest nohrsc snow depth map has light snowcover over parts of
Minnesota and northern Wisconsin, thus warmer daytime
temperatures will work to melt some of the snow.
Still some chances for flurries for parts of the area. Tonight
into Friday, a trough will track through the U.P./Great Lakes
with an 850mb boundary passing through. The RAP has warm
advection mid clouds that are currently seen on visible
satellite imagery across the Dakotas into the forecast area
04-12Z...with lower level saturation mainly across WI later
Friday morning into the afternoon. There is weak moisture
transport and isentropic upglide during this time. Friday night
into Saturday a weak wave moves across southern MN into IA with
a stronger shortwave tracking through the U.P./Great Lakes.
There may be enough low level moisture in place Friday night/
morning for some patchy freezing drizzle. With surface
temperatures below freezing, we`ll need to monitor this as we
get closer.
Precipitation chances continue Sunday night into Monday:
A couple of areas of low pressure over the Southwest U.S. and
Saskatchewan are forecast to deepen over the Northern Plains
and lift northeast through the Mid-Mississippi River Valley
region late this weekend. The deterministic GFS/EC are similar
with the primary forcing north...east...and southeast of the
forecast area. 05.12Z LREF probabilities for measurable
precipitation ending 12Z Monday range from 5% near DEH to 45%
near Medford. Our current pops (0 to 30%) reflect these low
precipitation chances for a rain/snow mix. Friday night we`ll
see the Pacific Northwest wave moving onshore, so should have
better data sampling by 12Z Sat. Highs Monday remain mild in the
30s and 40s, but return to cooler in the 20s for Tuesday and
Wednesday.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 545 PM CST Thu Dec 5 2024
Clear skies early this evening give way to mid to high clouds
overnight, with bases lowering through the day on Friday. These
bases lower to MVFR (possibly borderline IFR) in central WI in
the morning, with these clouds spreading south through the day.
The big forecast uncertainty is how far south these lower
ceilings spread with the higher confidence north of RST/LSE.
Also cannot rule out a wintry mix for central WI in the morning
(<20% confidence). Winds will generally be around 5-10 kts
backing to the W/SW for the day on Friday.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
UPDATE...Skow
DISCUSSION...Zapotocny
AVIATION...Skow
Area Forecast Discussion
National Weather Service Bismarck ND
931 PM CST Thu Dec 5 2024
.KEY MESSAGES...
- Below normal temperatures will continue this afternoon, with
seasonable temperatures in the southwest. Temperatures will
warm to above average for the weekend, peaking on Saturday.
- Mainly dry conditions are expected tonight through Saturday,
with widespread medium to high chances (40 to 80 percent) for
precipitation returning Sunday and Monday.
- Light snow accumulations are possible Sunday night into Monday
morning, with a medium chance of at least one inch of snow.
&&
.UPDATE...
Issued at 930 PM CST Thu Dec 5 2024
The stratus deck has finally started to show some appreciable
eastern movement over the past few hours with some scattering on
the western edge. Updated the sky cover forecast to better
reflect these trends. Otherwise, just blended in the latest
observations to the going forecast and updated the aviation
forecast below.
UPDATE
Issued at 521 PM CST Thu Dec 5 2024
Guidance continues to perform poorly with regards to stratus
coverage and trends, but do not think it will be going away
anytime soon. Forecast soundings suggest that there is a low
chance that we could see some light freezing drizzle under the
stratus across the northwest later tonight, but confidence is
not high enough to add to the gridded forecast just yet. For
this update, just blended in the latest observations to the
sensible weather fields.
&&
.DISCUSSION...
Issued at 320 PM CST Thu Dec 5 2024
Deep troughing aloft was analyzed over the Ohio Valley and
northeast CONUS this afternoon, while upper ridging was
beginning to build over the Northern Rockies, leading to
northwest flow across the Northern Plains. At the surface, a
stout high pressure was sliding across the central CONUS in the
wake of yesterday`s Arctic front, with seasonably cold air still
in place across most of the region.
Low stratus has been persistent and extends over most of
western and central North Dakota, with high-res guidance not
having a great handle on the temporal evolution of this cloud
deck. Underneath the stratus, temperatures are in the lower
teens to lower 20s, while the southwest, under mostly sunny
skies, has warmed into the lower to mid 30s. At this point,
would not expect most of the cloud cover to clear much, with
recent runs of the RAP having the best handle on current
conditions. Various high-res guidance has been advertising
potential for patchy fog in the northwest and north central
tonight, so we do have that mention in the gridded forecast.
We begin warming up on Friday as higher heights try to push
further into the region. A few of the recent CAMs runs want to
bring in some scattered light radar returns across central North
Dakota during the day, although confidence in this is rather
low as forecast soundings are showing moisture to be pretty
shallow. However, there is some potential for fog to persist and
expand, especially if the stratus deck does not erode much on
Friday. Forecast highs currently range from the lower to mid 30s
north and east, where cloud cover is likely to persist, while
the southwest with mostly clear skies could warm into the mid
40s.
Temperatures will peak on Saturday as the axis of an upper ridge
approaches, with forecast highs ranging from the upper 30s in the
Turtle Mountains area to the mid 50s in the southwest. There is
a low but non-zero chance of highs reaching the 60 degrees F
threshold in the Hettinger area, with the latest NBM putting
this probability around 10 percent. Winds will be increasing
ahead of an approaching system, with cloud cover increasing as
well.
There is high confidence among ensemble guidance of a shortwave
trough moving onshore and over the Northern Rockies, flattening the
aforementioned ridge and bringing widespread medium to high
precipitation chances to North Dakota on Sunday and Monday, along
with strong winds and cooler temperatures. The expectation is that
it stays an open wave and does not close off, which favors a
more transient nature and less forcing, thus less QPF.
Probabilities for rain and snow amounts have stayed pretty
consistent the past few runs of the NBM, with the chance of
48-hour QPF exceeding 0.25 inches generally 25 percent or less.
The probability of at least one inch of snow is broadly 40 to
70 percent, dropping off modestly when increasing to the 2 inch
or more threshold, which only has a low chance of occurring. The
bulk of this will fall Sunday night into Monday morning, with
some dependency on the timing of the transition from rain to
snow as cooler air moves in. We cannot rule out the potential
for some light freezing rain across parts of northern North
Dakota as this p-type transition takes place, although this is a
low probability solution. The EFI is highlighting parts of
western North Dakota on Sunday and southern North Dakota on
Monday, although only in the lower categories that would imply
winds would max out around advisory criteria. Forecast highs on
Sunday are in the upper 30s to upper 40s, cooling to mainly the
20s on Monday.
Northwest flow is favored for the synoptic pattern next week,
with broad ridging over the western CONUS and troughing centered
over the Ohio Valley region. This will lead to an active
pattern through next work week, with low-predictability
shortwaves moving through the mean flow aloft. NBM temperature
spread signals a slow but steady warming trend into next
weekend, with above normal temperatures favored through most of
the week 2 period.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 930 PM CST Thu Dec 5 2024
Widespread VFR to MVFR stratus continues to blanket much of
western and central North Dakota. Model guidance does not have a
great handle on these clouds but there should be a gradual
eroding from west to east through the night. Ceilings have
scattered out at KXWA and should start to scatter out again at
KDIK in the next hour or two. All other sites may be dealing
with this cloud cover through Friday morning. For now, will keep
MVFR stratus in place over KMOT and KBIS through 12z. Low VFR
ceilings should also lower eventually into MVFR categories over
the next few hours at KJMS. Stratus will likely remain in place
at KJMS through the period. Overnight patchy fog also continues
to be possible across portions of the northwest and north
central although confidence remains rather low as model
guidance has continued the trend of backing off.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...ZH
DISCUSSION...Jones
AVIATION...ZH
Area Forecast Discussion
National Weather Service Gray ME
1056 PM EST Thu Dec 5 2024
.SYNOPSIS...
Winds will be gusty tonight and Friday as low pressure
intensifies to our east. A ridge of high pressure will build
towards New England on Saturday before cresting over the region
Saturday night. A weak area of low pressure will cross New
Hampshire and Maine on Sunday. Drier conditions will follow
early Monday before another low pressure system late Monday into
Tuesday. Yet another system will slowly approach New England
from the west during the midweek period.
&&
.NEAR TERM /THROUGH FRIDAY/...
1000 PM...Cold and blustery conditions are expected to move
through the region with a passing cold front tonight. In fact,
temperatures are likely to continue falling through the day
tomorrow because the fresh snowpack will reflect more sunlight
and northwesterly winds will being substantial CAA to the
region.
Mostly clear skies tomorrow will allow temperatures south of
the mountains to rebound into the upper 20s/lower 30s. Upslope
snow and mostly overcast skies will make it difficult for most
places north of the mountains to get above 20F. Don`t be fooled
by these seemingly average winter high temperatures - wind
chills across NH and ME will range from single digits below zero
to teens above and will feel progressively colder throughout
the day. Upslope snowfall will likely skew visibility as well,
and opted to add a little blowing snow into the forecast across
some parts of northern NH/western ME. Also lowered temperatures
overnight and tomorrow and blended in some more recent model
guidance to winds.
725 PM...Still waiting for the sfc cold front and slight wind
shift, but notable increase in winds, and colder air moving in.
That looks like it won`t happen until later this evening in NH
and midnight or shortly thereafter in ME. Upslope SHSN ahead of
the front are occuring but should a surge in these behind the
front later tonight. Also could some SHSN with the front track
past the mtns and into the foothills as well as the inland part
of the ME coastal plain, although these will likely be brief and
light that far S and E. It won;t be too cold this evening but
once the from comes through and the winds pick up temps will
fall quickly with lows mid to upper to teens in the mtns and low
to mid 20s in the S. Wind chills for the morning commute will
be from around +5 in the N to +15 in the S.
Previously...The HRRR and the NAMnest have done quite well in
advertising the swath of light to occasionally moderate snow
(and rain along the immediate coast) currently advancing east
across western ME associated with the upper low overhead. Latest
observations show readings mostly just above freezing, so this
should struggle to accumulate except mostly on grassy surfaces
for the next hour or so but could still reduce visibility down
to a half mile at times. As we get closer to sunset though it`s
possible that the snow starts collecting on roads to cause some
slick roadways for the afternoon and evening commute in addition
to the reduce visibility. Where snow does accumulate up to an
inch is possible.
Looking to the west, snow showers have struggled to reach beyond
the Green Mountains, but western NH could start seeing a few
(possibly heavy) as flow becomes more unblocked over the next
few hours although CAMs have kind of backed off on this.
Going into the evening, winds will become breezy behind a strong
cold front and with the tightening pressure gradient as the
deepening low pressure starts to lift northward into the
Canadian Maritimes. Wind gusts of 25 to 35 mph are likely per
forecast soundings with a few up to 40 mph possible. Snow
showers will largely wind down south of the mountains, but will
remain likely in the mountains with upslope flow. As the evening
and night go on, flow will gradually become more unblocked, and
I have extended some PoPs downwind of the mountains to account
for this. Temperatures will fall mostly into the 20s with wind
chills in the teens.
&&
.SHORT TERM /FRIDAY NIGHT/...
Cold air advection will be in full force on Friday with the gusty W-
WNW continuing, making for a blustery and chilly day. Forecast
soundings support 30-35 mph and occasionally up to or just over 40
mph. Some areas could start the day with wind chills in the single
digits but will likely remain in the teens the rest of the day
with temperatures struggling to get above 30 degrees. Scattered
upslope snow showers will continue in the mountains through at
least the morning or early afternoon, and these may see somewhat
of a lull later in the day with the low levels drying out.
Froude numbers will be high enough to support snow showers making it
downwind of the mountains in the morning, but the low-level drying
may lower this potential going into the afternoon.
Even though winds will steadily diminish Friday night, continued
cold advection will make for a chilly night with temperatures
dropping into the single digits across the north and mostly in the
teens to the south. Winds chills below zero are possible
across the north as well as the single digits to the south. Models
are advertising an additional wave and increasing low-level moisture
so another uptick in upslope snow showers is possible, and Froude
numbers remain high enough to warrant keeping a slight chance of
snow showers downwind.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
1050 PM...Overall not much change for next week, with higher
confidence on the wave and precip centered around Monday night,
and then less confidence, especially on the timing of waves and
location of said waves along the front. MAybe some snow in the
N on Monday night, but for the most part should be rain, except
on the higher mountain terrain into mid-week.
3 PM...The long range portion of the forecast begins with just
a few remaining snow showers over the White Mountains on
Saturday as a cyclonic flow continues aloft. This ridge may
allow for radiational cooling with light winds and mainly clear
skies Saturday evening. This will allow for temperatures to drop
quickly into the single numbers across the north to the teens
in the south. Thereafter, clouds will allow for a moderation in
temperatures during the night.
A clipper type system will move east from the Great Lakes late
Saturday night before crossing the region on Sunday. This will
allow for light snow to fall in Maine and New Hampshire.
A weak ridge of high pressure will allow for a dry day to start
out the work week on Monday. Thereafter, 12Z operational models
and ensemble solutions suggest a weak wave of low pressure will
form along a baroclinic zone on to bring light rain in the south
and rain and snow to the north by Tuesday. By later in the
midweek period, a large scale system will approach the region
from the west, potentially bringing heavier precipitation to the
region. Mixed freezing rain, sleet and snow will combine with
rain, however timing and details are highly uncertain at this
time.
&&
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
Short Term...Most sites will trend toward VFR and remain there
tonight through Friday night except HIE could continue to see
MVFR ceilings and snow showers at times through tonight or part
of Friday. Westerly winds will pick up this afternoon and will
continue to be gusty through tonight and through the day on
Friday. The expectation is that these will be mostly in the 25
to 30 kt range but could be around 35 kt at times.
Long Term...Mainly VFR conditions on Saturday will be replaced
with low clouds and IFR conditions Saturday night into Sunday in
precipitation. A brief ridge of high pressure will build into
the region on Monday with mostly VFR conditions. A weak area of
low pressure will follow on Tuesday with low clouds and mostly
rainfall.
&&
.MARINE...
Short Term...Deepening low pressure lifting into the Canadian
Maritimes will support westerly Gales tonight through most of
Friday. Winds and seas will diminish Friday night but will
probably need a Small Craft Advisory once the Gales subside.
Long Term...A brisk westerly flow will continue during the long
range portion of the forecast. The flow will back to the
southwest by Sunday and continue into early next week.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Gale Warning until 7 PM EST Friday for ANZ150>152.
Gale Warning until noon EST Friday for ANZ153-154.
&&
$$
SYNOPSIS...
NEAR TERM...Combs/Palmer
SHORT TERM...Combs
LONG TERM...Cannon/Cempa
AVIATION...
MARINE...
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1034 PM EST Thu Dec 5 2024
.KEY MESSAGES...
- Below normal temperatures are expected through Saturday night.
- Temperatures will warm over the weekend, with above normal
readings expected early next week, along with wet weather.
&&
.UPDATE...
Issued at 1034 PM EST THU DEC 5 2024
Not many wholesale changes made to the forecast grids aside from
loading the latest surface observations and making tweaks to the
cooling trends across the area. Also, updated evening text and
radio products to reflect those changes. Grids have been saved and
sent.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 359 PM EST THU DEC 5 2024
Late this afternoon, a mid and upper level trough extended from
north of Hudson Bay into eastern Canada and the eastern Conus.
An upper level low was over the St Lawrence Valley vicinity with
an associated shortwave south into New England. An upper level
ridge extended from the eastern Pacific north and then northeast
into portions of the western Conus to western Canada. A couple of
shortwaves were in northwest flow between the upper trough and
the ridging, with the first over the upper MS Valley and another
upstream of that over Manitoba. At the surface, an area of low
pressure was working into the Maritimes with a cold front east of
the eastern seaboard to near the GA/FL border and into the Gulf of
Mexico. Further west a ridge of high pressure at the sfc extended
through the Plains to the mid and upper MS Valley with ridging
extending east into the Lower OH Valley to portions of the
southern Appalachians. Some cumulus and stratocumulus lingers
across the area, with these more prevalent nearer to the WV
border and then east into WV.
This evening through Friday, the first of the upstream shortwaves
will approach the Lower and Middle OH Valley late tonight and then
pass east of the area on Friday with the shortwave further
upstream progged to cross the Great Lakes. Once this first
shortwave crosses eastern KY, the axis of the upper level trough
will move east of the area on Friday afternoon with gradual height
rises through Friday night. At the surface, the ridge of high
pressure will build south and east and become centered in the
vicinity of the Ozarks late tonight and then the TN
Valley/Memphis TN areas through Friday evening. This ridge of high
pressure will settle southeast of the area Friday night.
With high pressure building into the area, dry weather is
anticipated along with continued temperatures on the order of 15
to 20 degrees below normal all the way into Friday night. Some
linger of stratocumulus may occur this evening and into tonight or
redevelopment near the VA border and perhaps WV border per some
recent RAP and NAM runs with some moisture remaining in the 925 to
850 mb layer. This could affect low temperatures tonight/hold them
up in some of the more southeastern locations. Otherwise, with
afternoon mixed dewpoints in the single digits above zero, the
upper single digits in the normally colder locations to low to mid
teens are attainable for lows tonight assuming sufficient
decoupling. Temperatures, especially during the afternoon will
moderate about 5 to 7 degrees for Friday compared to today.
The pattern of ridging settling southeast of the area and west to
southwest flow for ridgetops will be favorable for a potentially
larger ridge/valley split on Friday night compared to tonight.
For now we have continued with mid teens deeper valleys to low 20s
coalfield ridges, though the normally colder spots could end up
closer to 10.
.LONG TERM...(Saturday through Thursday)
Issued at 326 PM EST THU DEC 5 2024
Saturday, high pressure builds in over eastern Kentucky. This will
lead to mostly sunny skies, dry weather, and highs in the low to mid
40s. Lows will generally remain in the mid 20s, with warm spots
around 30.
Sunday, warmer weather can be expected, with clouds increasing
through the afternoon. Highs generally in the low to mid 50s. An
upper level low will work its way across Mexico/Texas and advect
moisture north and east. The cold front will arrive around sunset,
bringing showers to the area. Rain will continue through Monday.
Lows Sunday night are expected to be warmer, in the lower 40s.
Monday, rain continues through the evening, with highs in the upper
50s to low 60s, and lows in the upper 40s, nearing 50 in spots.
During the day Monday, a secondary trough begins to dig southeast
out of the Pacific Northwest. This trough will follow the same
track as the previous, digging as far south as Mexico and Texas,
and drawing moisture poleward from the Gulf Of Mexico. Shower
chances will remain through mid week.
Tuesday, highs will warm into the mid 50s to low 60s, with rain
showers continuing through the day. Temperatures at night drop into
the low to mid 30s. A wintry mix could result heading into
Wednesday. Little to no impacts are currently expected at this time.
Highs Wednesday will remain chilly, in the upper 30s to low 40s.
Rain and snow showers continue with breezy conditions. Lows Wednesday
are expected to dip into the low to mid 20s.
Thursday, snow showers look to taper off as the frontal system is
modeled to push east of the state by mid afternoon. Highs are
forecasted in the mid to upper 30s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 623 PM EST THU DEC 5 2024
VFR conditions are prevailing across all TAF sites and will remain
VFR through the TAF period. Passing high clouds may move across
the area tomorrow afternoon but nothing of consequence. Light and
variable winds will persist through the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...VORST
SHORT TERM...JP
LONG TERM...GINNICK
AVIATION...VORST
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
558 PM CST Thu Dec 5 2024
.KEY MESSAGES...
- Single digit wind chills expected through tonight, with wind
chills rising to the teens and 20s on Friday.
- Much warmer temperatures expected over the weekend, followed
by another cooldown early-to-mid next week.
- Little to no additional precipitation expected through at
least the middle of next week.
&&
.DISCUSSION...
Issued at 1200 PM CST Thu Dec 5 2024
Surface analysis early this afternoon shows the center of high
pressure sitting over eastern SD/NE, with pronounced NW flow
advecting cold air into the region. The center of the high will
shift into central MO tonight, bringing an end to effective CAA
into the Upper Mississippi River Valley. Thus, bringing an end
to the single digit wind chills by the time sunrise Friday
morning comes. A more broad southerly flow regime will develop
tomorrow as the high moves into the southeast CONUS, opening up
a pathway for warmer western CONUS air, held under a stalled
ridge, to start making its way eastward Friday and into the
weekend. This deeper ridge will start to slide across the
Rockies over the weekend and while flattening by the time its
axis reaches the Northern Plains, effective warming will be felt
across the Upper Midwest over the weekend. Highs will jump to
the upper 30s to mid 40s, with any precipitation being mostly
confined to northern portions of the state although a few
rain/snow showers are possible north of I-94. The main active
timeframe will be late Sunday night through Monday with the most
expansive PoPs dropping as far south as Mankato, but even so,
are only in the 20-40 percent range with very little QPF. More
tranquil conditions return going into the middle of next week as
another arctic high pressure airmass drops into the central
CONUS from north-central Canada. At this point, highs will only
drop into the 20s with lows into the teens, but temperatures
could vary slightly either way. That said, no major storm
systems are apparent to impact the Upper Midwest through at
least next weekend.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 534 PM CST Thu Dec 5 2024
Main change from the going TAFs was to beef up the mention of
MVFR cigs on Friday. Forecast soundings for the RAP/HRRR/NAM all
point a rather gloomy picture for the development of stratus
across the region tomorrow, which is backed up by 18z HRRR cigs
and HREF probs for cigs less than 3k feet. There`s still a good
deal of spread though with just how widespread stratus will be,
but for now, leaned toward the RAP & HRRR solution.
KMSP...RAP soundings have MVFR cigs moving into MSP around 15z.
With the 00z TAFs, decided to move the TAF toward having MVFR
cigs, but haven`t jumped completely into the MVFR stratus
scenario yet given the spread seen in the models with how low
cigs will get (see 5k foot cigs in LAV guidance).
/OUTLOOK FOR KMSP/
SAT...VFR. Wind SW 5-10 kts.
SUN...Mainly VFR. Wind S 5-10 kts.
MON...MVFR likely. Chc -RASN. Wind WNW 10-15G25-30 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
DISCUSSION...JPC
AVIATION...MPG
Area Forecast Discussion
National Weather Service Marquette MI
649 PM EST Thu Dec 5 2024
.KEY MESSAGES...
- Moderate lake effect snow will continue at least this evening
for Alger, Schoolcraft, and Luce Counties. Blustery winds may
lead to blowing snow, as well as wind chills in the single
digits above and below zero.
- West wind lake effect snow picks up in the Keweenaw Peninsula
early Friday where 3 to 6 inches of snow is possible. A
Winter Weather Advisory has been issued for Northern Houghton
and Keweenaw counties through Friday evening.
- Warmer than normal temperatures return late weekend into
early next week.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 351 PM EST Thu Dec 5 2024
GOES-16 visible imagery shows a typical northerly to northwesterly
lake effect scene, highlighted at 20Z by a semi-dominant band
stretching from Lake Nipigon across Lake Superior to just west of
Marquette and then all the way down Lake Michigan to southwest lower
Michigan. This band was marked by 1/4 mile visibility or less
(WFO obs and KSAW METAR) and snowfall rates of 1-2"/hr (multiple
reports). As a 1032mb surface high that the RAP Analysis has
centered over northern Missouri continues to slide southeast,
winds over the UP and the Upper Great Lakes will continue to
back west and then southwest overnight. While the general anti-
cyclonic flow will suppress snowfall somewhat, the Nipigon band
and surrounding bands (which themselves have shown to be capable
of 1/2SM to 1SM visibility) will shift east, bringing an
additional 0.5 to 2 inches to the east half with areas north of
M-28 seeing 2-4 additional inches of snowfall tonight.
Additionally, CAMs show another lake effect band setting up over
western Lake Superior as northwesterly flow over the north half
of the lake and the southwesterly flow near the UP shores
converge for a single band targeting the vicinity of KCMX around
07Z tonight and lifting north to the remainder of the Keweenaw
Peninsula through 12Z. Winter Weather Advisories have been
hoisted for impacts related to that band, as snowfall rates of
1-2 inches per 6 hours are possible (~50%) within that band
prior to the morning commute. Winds will decrease overnight as
the winds shift in response to the high pressure going
unchallenged with the clipper low now exiting Maine. However,
given the low temperatures falling to the single digits tonight
for the interior west, wind chills could (~50%) still reach the
negatives by 12Z.
&&
.LONG TERM /FRIDAY THROUGH THURSDAY/...
Issued at 430 PM EST Thu Dec 5 2024
Active weather remains in the long term forecast beginning tomorrow
morning. A weak shortwave embedded within the broad northwest flow
aloft reflects a surface trough across Lake Superior, veering lake
effect snow to the west wind snowbelts early Friday. Guidance has
been consistent depicting a Bayfield Peninsula convergent band
extending from the western lake into the Keweenaw Peninsula by the
morning commute hours where snowfall rates upwards of 0.5-1" are
possible before winds back to the northwest wind snowbelts in the
afternoon. Opted to issue a Winter Storm Advisory for Northern
Houghton and Keweenaw counties where snow totals could reach 3-6"
through the evening. Areas in the east half could pick up an inch or
two through Friday evening with the NW wind shift, however lowering
inversion heights will work to weaken LES into Saturday.
The western CONUS ridge starts to flatten out Saturday, sending a
ridge riding clipper across central Canada into the Upper Great
Lakes. Subtle WAA/isentropic ascent will spread light snowfall
across the UP. Snowfall should be on the sloppier side as SLRs
lessen through the day to below 10:1. Mid-level temperatures will be
warming to above 0C by the evening, perhaps changing snow to a
wintry mix or all rain over the west half late in the, although
confidence is low on the timing and spatial extent of precip type
changeover. High temperatures on Saturday will be at or just above
freezing, marking the start of a brief pattern change where above
normal temperatures will prevail through the end of the weekend into
early next week.
Deterministic and ensemble guidance begin to diverge beyond the
weekend on the evolution and phasing of a pair of shortwaves that
could bring accumulating precipitation (both rain and or snow)
Monday into Tuesday. ECMWF suite continues to be the colder
solution, clustering surface low pressure locations by Monday
afternoon somewhere in the vicinity of Lake Michigan, while GEFS
has the faster and warmer solution to the north of Lake Superior.
This split leaves confidence on expected precip early next week
quite low. Into the mid-week, there is general agreement on negative
height anomalies and below normal 850 mb temps returning to the
Upper Great Lakes, suggesting another round of northwest LES
across the UP, though not as prolonged as the recent stretch.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 637 PM EST Thu Dec 5 2024
VFR conditions for much of tonight will trend toward MVFR in
light snow around sunrise at IWD and IFR in possible moderate
snow at CMX as a westerly convergent flow develops across the
Copper Country in advance of a Clipper system dropping south
from Manitoba and Ontario. It looks like the worst conditions
will likely be late tonight into Friday morning at CMX. SAW will
see VFR conditions lower to MVFR late Friday morning into the
afternoon, although the less favorable west to northwest flow
will likely only yield flurries there.
&&
.MARINE...
Issued at 430 PM EST Thu Dec 5 2024
North winds 25 to 30 knots diminish through the evening before
backing to the southwest early Friday morning and west by the
afternoon, gusting in the western lake to around 30 knots. Wave
heights build to 6 to 9 feet during this time period. This brief
pick up will be short lived, however, as winds veer to the northwest
and fall below 20 knots into Saturday, remaining calm through the
morning. A weak surface low pressure passes northeast of Lake
Superior Saturday, increasing southwest winds mostly across the
western lake upwards of 25 knots before weakening late Sunday and
throughout Monday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory from 1 AM to 1 PM EST Friday for
MIZ001-003.
Winter Storm Warning until 7 PM EST this evening for MIZ005.
Winter Storm Warning until 7 AM EST Friday for MIZ006-007-014-
085.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...GS
LONG TERM...BW
AVIATION...Voss
MARINE...BW
Area Forecast Discussion
National Weather Service New York NY
925 PM EST Thu Dec 5 2024
.SYNOPSIS...
A cold front moves through this evening, with a couple of
reinforcing cold frontal passages through Friday evening. The
region will remain in-between intense low pressure over
NewFoundland and high pressure to the southwest into Saturday.
High pressure passes to the south this weekend as a weak low
passes to the north on Sunday. A warm front pressure impacts the
region on Monday with low pressure. A slow moving cold front
will then approach from the west from Tuesday into Wednesday.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Continued to lower winds speeds based on current observations.
This has prompted the cancellation of the Wind Advisory. There
may be isolated gusts that reach advisory criteria over the next
couple of hours, but it is not expected to be widespread.
Otherwise, look for dry, breezy, chilly conditions for the rest
of the night.
Polar upper low slides through northern New England tonight,
with associated trough axis crossing this evening. At the
surface, secondary cold front passes though by early evening
with reinforcing shot of cold air and invigoration of WNW winds.
BUFKIT soundings and HRRR wind gusts continued to suggest 20-30
gusts 45-50 mph through this evening, with occasional 30-35 with
gusts to 55 mph behind reinforcing cold frontal passage. Wind
Advisory remains in place for the entire area through 10pm.
Winds gradually come down overnight as pressure gradient
gradually weakens and low level lapse rates stabilizes, closer
to 15-20 gusts to 30-35 mph by early Friday Am.
Dry conditions expected overnight, with sct to locally bkn
strato cu under cyclonic flow.
Coldest wind chills of the season so far late tonight into
early Fri morning, with lower to mid teens for city/coast and
single digits interior.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Deep upper trough remains over the region on Friday, with
cyclonic flow around intense Nova Scotia low Friday AM giving
way to surface ridging building in from the SW late Fri/ Fri
Night.
Cold advection continues on gusty WNW flow (15-25 mph with
gusts of 30-35 mph) through the day Friday, with surface temps
likely hard pressed to get out of the 20s interior and above
freezing for the city/coast with 850mb temps dropping to close
to -15c. Windchills only rising into the upper teens interior
and lower 20s city/coast.
Otherwise, scattered to locally bkn strato-cu under slow to
relent cyclonic flow and approach of late day backside
shortwave/surface trough.
Winds slowly subside Fri Night with high pressure building to
the southwest, but still appears to be enough of a gradient and
low- level mixing to preclude widespread radiational cooling.
Most places will get down into the lower 20s, with upper teens
interior, and mid 20s for NYC/NJ metro. Windchills once again
dropping into the lower to mid teens.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Key Points:
* Chilly, dry Saturday.
* Warming Sunday into next week.
* Next round of rain on Monday.
* Another shot of getting wet mid-week, next week. Low chances for
frozen precip.
Heights aloft gradually rise through the weekend as a ridge builds
in from the west. Winds remain from the west 10-15 mph on Saturday,
gusting 15-20 mph. Cold air remains aloft, with highs only expected
to be in the mid-30s to around 40 with lows Saturday night in the
low-20s to low-30s. Saturday remains mostly sunny, but cloud cover
increases Saturday night as gradual warm air advection starts up at
850mb.
A weak surface low passes to the north in Canada on Sunday. Its far
enough removed from the area for most of us to remain dry, but a few
isolated light snow showers are possible for northern interior
locations closer to the low on Sunday. No accumulation expected.
Highs on Sunday will be in the mid-40s to low-50s with lows in the
upper-20s for the northern interior to near 40 for southern coastal
locations.
As a ridge centers over the region on Monday, as small shortwave
trough embedded within the the longwave ridge with pass through on
Monday. This occurs in tandem with a warm front advecting in
moisture from a low in the lower plains and gulf states as another
low deepens over the northern Great Lakes. Rain showers look likely
across the area due to warmer temperatures in place following the
warm frontal passage. The rain will taper Monday evening and early
night west to east.
Tuesday night into Wednesday night a trough approaches from the
west, which also pulls in a low from the souther plains and brings
it across the northeast. Widespread showers look likely, particularly
ahead of and along a frontal passage. Model guidance still varies on
the timing of the front, so exact timing for the best chance of
showers is still lower confidence, but the chance for rain looks
good. Warmer temperatures in place will prevent chances for frozen
precipitation until the exit of the front where a window of
opportunity for frozen precip is possible in the interior Wednesday
night. This, however, is still subject to change given this is at
the end of the forecast period.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
The terminals will remain between strong low pressure to the
northeast and high pressure to the south and west through Friday.
VFR through the TAF period.
Strong, gusty W-WNW winds expected through this evening. Sustained
speeds 15-25 kt with gusts 25-35 kt are likely. Winds may
diminish somewhat overnight. WNW- NW winds 15-20 kt with gusts
25-30 kt are forecast on Friday, with winds diminishing late in
the afternoon, but still gusting 15 to 20 kt by Friday evening.
...NY Metro (KEWR/KLGA/KJFK/KTEB)TAF Uncertainty...
An isolated gust to 40 kt possible until around 02z.
Winds could be a bit weaker at times overnight.
OUTLOOK FOR 00Z SATURDAY THROUGH TUESDAY...
Friday Night: VFR. NW winds diminishing through the night,
gusts 15 to 20 kt early in the evening.
Saturday. VFR. W wind gusts 15-20 kt.
Sunday. VFR. SW wind gusts 15-20 kt.
Monday: MVFR-IFR in showers.
Tuesday: Mainly VFR. Chance of showers and MVFR at night.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
Gale warnings continue across all waters into tonight. In
response rough seas on the ocean (8-13 ft) and LI Sound (3-7 ft)
continue to build through this evening.
After midnight gales will gradually give way to small crafts for NY
Harbor and W LI Sound, and eventually the south shore and
eastern LI Sound and bays. Marginal gale conditions possible
for the ocean waters Friday morning, otherwise expect small
craft conditions to prevail across all waters through the day.
SCA winds relent on nearshore waters Fri evening, but likely
continue into early Sat Am for ocean waters.
Winds drop below 25 kts on Saturday with waves already below SCA-
level criteria. We remain below SCA levels until Sunday morning.
Waves on the ocean will build to 5-7 feet with wind gusts 25-30 kts.
WInds may also reach SCA levels on south shore bays and the sound
entrance and possibly the eastern sound. Winds and waves gradually
drop below SCA levels Sunday night. Sub-SCA conditions remain
thereafter through Tuesday except for waves coming close to 5 feet
on ocean waters Monday evening through Tuesday morning.
&&
.HYDROLOGY...
No hydrologic impacts are anticipated through mid-week next
week.
&&
.TIDES/COASTAL FLOODING...
Strong W winds will drop water levels to 1.5 to 2 ft below MLLW
during times of low tide late this aft/eve, but appears
marginal for low water advisory.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Gale Warning until 6 AM EST Friday for ANZ331-332-340-345-350-
353-355.
Gale Warning until 1 AM EST Friday for ANZ335-338.
&&
$$
SYNOPSIS...BR/NV
NEAR TERM...JP/BR/NV
SHORT TERM...NV
LONG TERM...BR
AVIATION...JP
MARINE...BR/NV
HYDROLOGY...BR/NV
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Pocatello ID
526 PM MST Thu Dec 5 2024
.UPDATE...
Updated forecast for dense fog advisory for Bear Lake area. Fog
looks to be expanding already with several sensors showing 1/4
mile or less visibility. See no reason what would cause conditions
to improve. Advisory in effect until 10am Friday, when day shift
can reevaluate.
13
&&
.PREV DISCUSSION... /issued 246 PM MST Thu Dec 5 2024/
SHORT TERM...TODAY THROUGH FRIDAY NIGHT...
High pressure and attendant quiet, low-impact weather continue, with
freezing fog continuing to be our only concern. The airmass really
hasn`t changed at all compared to last night/this morning, winds
will be VERY light, and both the NBM and HRRR are supporting another
round of localized dense freezing fog in areas similar to what we
saw this morning (like Bear Lake, just west of Pocatello along I-86,
perhaps the Arco Desert, etc.)...with support from some other
guidance sources as well for some spots. Thus, will carry freezing
fog in the forecast once again in many valley and plain locales. It
likely won`t be widespread, but where it does occur, motorists
should be prepared for sudden drops in visibility...SLOW DOWN and
use extra caution accordingly! Temperatures will hold steady a bit
above normal for early December...modestly mild (upper 30s to upper
40s) during the day and quite cold at night. Unfortunately many of
us without garages will need to continue melting/scraping our car
windows each morning. This meteorologist is not a fan. - KSmith
LONG TERM...Saturday through Thursday. Ridge axis still projected
to weaken and tilt east during the day Saturday, allowing light
precipitation to work across East Idaho through Sunday. Models have
trended drier with the latest runs, and it wasn`t an exceptionally
impactful system to begin with. That said, have kept expected QPF
similar to prior runs, with the highest snow totals through Sunday
night across the Sawtooths, Tetons and Big Hole Mountains.
Probabilistic means support 4-6" across these areas through Sunday
night. Those totals drop off almost exponentially down to the 25th
percentile, nearly half of the means. 90th percentile (1 in 10
chance of exceedance) shows maybe another inch or two at higher
elevations above the means, but the real change occurs at valley
locations, with around an inch in the I-15 corridor. Passage of the
frontal boundary Saturday night will bring colder temperatures to
valley floors especially daytime, and gusty winds on Sunday. Another
ridge of high pressure shifts across the western states Monday
through Tuesday, though there is less agreement in ensemble clusters
this far out. By mid week, ensemble means favor a flat-ish ridge
over the intermountain west, while at least two of the clusters try
to push another trough into the coastal states. Blend keeps
conditions dry with temperatures near normal over East Idaho until
late Wednesday into Thursday with onset of increased PoPs. DMH
AVIATION...
Stagnant high pressure will continue to support dry, mostly
sunny/clear, low-impact VFR conditions across southeast Idaho with
VERY light winds (only 0-4kts except a bit higher at times at KSUN),
WITH THE EXCEPTION of continued patchy dense freezing fog concerns.
As expected, fog was a bit more problematic this morning in a few
spots (affecting KPIH in particular) despite mixed signals on
development in the guidance yesterday. Looking ahead to Friday
morning, the HRRR and NBM are both supporting another similar round
of development, with even MOS guidance jumping on board for impacts
once again at KPIH. Where freezing fog does develop, LIFR cigs AND
vsbys are almost certain. Will hold/continue with 6SM BR VCFG SCT002
at KIDA and KBYI where impacts can`t be ruled out but confidence is
low at the immediate terminals, and have adjusted start times in the
TAFs based on HRRR and NBM guidance. Potential is higher at KPIH
where we`ve verified impacts each of the last two mornings and
conditions will be very similar tonight, so have introduced a TEMPO
with LIFR impacts starting at 11z/4am Friday (a dense fog bank
should be lurking somewhere very close to the terminal and may drift
in/out), with the main threat continuing through about 18z/11am.
Timing here is a blend between NBM/HRRR guidance, but then weighted
toward "persistence" based on how fog evolved this morning. Future
shifts will continue to evaluate this potential and associated
timing. Fog is least likely at KSUN and KDIJ. Looking ahead...for
anyone tired of the high pressure...a storm system with at least
some light snow is forecast to arrive Saturday night! - KSmith
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM MST Friday for IDZ061.
&&
$$