Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/13/22
AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
844 PM CST Mon Dec 12 2022
.UPDATE...
Issued at 844 PM CST Mon Dec 12 2022
Dual-polarization radar data and surface webcams indicate snow as a
precipitation type along the South Dakota border from near Strasburg
to Ellendale, moving north-northwest. The snow generally coincides
with an area of cooler cloud tops depicted by 3.9 micron infrared
satellite imagery, steep mid level lapse rates, and the nose of a
low-level jet. 00Z RAOBs at both Bismarck and Aberdeen showed a dry
mid-level layer of air that the increasing forcing for ascent
appears to have eroded, at least to some extent, allowing ice
crystals aloft to act as seeder feeders through the low-level
saturated layer. Recent runs of the HRRR did hint at this potential,
but not to the spatial extent it is being observed. A mention of
scattered snow showers was added to the forecast from south central
into southeast North Dakota for the late evening.
Freezing drizzle is still a major concern across all of central and
most of western North Dakota. The 00Z Bismarck RAOB shows the near-
surface saturated layer extends up to 1.5 km AGL, about 0.5 km
greater than had been advertised by deterministic model soundings.
No changes to headlines are needed for this update.
UPDATE Issued at 624 PM CST Mon Dec 12 2022
Surface observations and webcams show persistent freezing drizzle
across much of western and central North Dakota this evening. ASOS
ice accretion sensors at Bismarck, Jamestown, Minot, and Dickinson
have all reported a few hundredths of an inch over the past few
hours. Dense fog also remains an issue, mainly for areas to the
south and west of the Missouri River, as well as near the Turtle
Mountains. No major changes in forecast messaging are needed for
this update. The afternoon Winter Weather Advisory for freezing
drizzle in south central and southeast North Dakota has expired,
and all other headlines are now in effect.
&&
.SHORT TERM...(This Evening through Tuesday Night)
Issued at 312 PM CST Mon Dec 12 2022
Freezing drizzle will remain a threat through the night across
much of the central and portions of the west. Snow then begins in
earnest overnight into Tuesday morning, lifting from the south to
the north out of South Dakota.
Western and central North Dakota is currently situated under
nearly meridional flow aloft as a closed low and mid level trough
digs into the Great Basin region well to our southwest. At the
surface, a low continues to deepen over eastern Colorado to the
lee of the Rockies under the left exit region of a strong upper
level jet.
Low level moisture pooling this afternoon and tonight will
continue along and in the vicinity of an inverted surface trough,
extending north northeast into the Dakotas from the surface low.
Given dry mid levels, this will mean periods of light freezing
drizzle/mist across much of western and central North Dakota the
rest of today through at least Tuesday morning. The most
significant icing generally looks to take place across the south
central and into the James River Valley where we could see a tenth
of an inch or two of accumulation. However, anywhere along and
east of the Highway 83 corridor could see ice accumulations
leading to significant impacts. Further west, a light glaze to a
few hundredths of a inch seems reasonable. Ice potential lessens
approaching the Montana border.
A strong wave will rotate around the base of the mid level low,
ejecting north and approaching southern North Dakota late tonight
into Tuesday morning, which should help to gradually moisten the
mid levels. The latest suite of CAM runs suggest a transition from
freezing drizzle/light freezing rain to snow along the South
Dakota border area in the 06z to 12z time frame Tuesday morning
depending on how vertical profiles evolve. An initial band of
moderate to heavy snow will develop around the border and rotate
into portions of central North Dakota by late morning/early
afternoon. NAM soundings continue to suggest a possible dry slot
and loss of cloud ice behind this band which could mean a brief
lull in the snow for some during the early to mid afternoon hours.
This could also mean some more freezing drizzle under any dry
slot. By later in the afternoon, this dry slot should start to
fill in as the main deformation band rotates up from South Dakota,
leading to more widespread moderate to heavy snow across much of
western and central North Dakota through Tuesday night.
While snow will continue well into Wednesday and light snow
probably even into Thursday, we can talk about storm totals here
in the short term. Forecast totals remain steady with widespread
totals of 6 to 14 inches expected with the highest totals
generally west and south. Some uncertainty remains however, given
potential dry slotting/periodic loss of saturation in the
dendritic growth zone. However, it is worth noting that the NBM
v4.1 continues to advertise 12 inches of snow or greater in the
50 to 90 percentile range for much of western and central North
Dakota. So potential scenarios for an even higher end event are
certainly not out of the question.
.LONG TERM...(Wednesday through Monday)
Issued at 312 PM CST Mon Dec 12 2022
By Wednesday morning, the low kicks up into southeastern South
Dakota. As the surface low starts to fill, heavy banding will
start to become a bit more disorganized through the day. This will
mean more of a transition to periodic light to moderate snow
instead of heavy banding (although some transient heavy pockets
will remain possible, especially across the west under the
weakening deformation band). Portions of the central may also
experience some more dry slotting during the day on Wednesday but
periodic light snow should continue to rotate around the low in
cyclonic flow aloft through Thursday, likely into Friday and
maybe even into early Saturday. Only light accumulations are
likely in the Thursday through Saturday time frame but winds will
increase, leading to some areas of blowing snow. Therefore, an
eventual Winter Weather Advisory for blowing snow is possible at
some point towards the end of the week after all current headlines
expire. The other story will be the next arctic push through the
weekend and into next week. Forecast highs on Friday will be in
the low to mid teens, the single digits Saturday, closer to zero
Sunday and maybe even single digits below zero on Monday. Thus
wind chill headlines are also probably on the far horizon around
the end of the weekend and into next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 844 PM CST Mon Dec 12 2022
A winter storm will bring IFR/LIFR conditions to all terminals
through the forecast period. Visibility restrictions this evening
through much of the night will be primarily driven by freezing
drizzle/light freezing rain. The greatest icing concerns are at
KJMS. Dense fog is also possible at KDIK this evening. Precipitation
will transition to snow late tonight into Tuesday morning, but
freezing drizzle could still mix in at times through Tuesday
afternoon. Expect LIFR visibility under falling snow for much of
the day Tuesday. Northerly winds across western North Dakota and
east to northeast winds across central North Dakota will increase
to 15-20 kts on Tuesday, gusting near 30 kts.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM CST Thursday for NDZ001>005-
009>013.
Winter Storm Warning until 6 AM CST /5 AM MST/ Thursday for
NDZ017>023-025-031>037-040>048-050-051.
&&
$$
UPDATE...AE/Hollan
SHORT TERM...ZH
LONG TERM...ZH
AVIATION...Hollan
Area Forecast Discussion
National Weather Service Dodge City KS
607 PM CST Mon Dec 12 2022
...Updated for aviation discussion...
.SHORT TERM...(This evening through Tuesday night)
Issued at 250 PM CST Mon Dec 12 2022
Multiple hazards impacting the area now and through the
overnight. First, fog and areas of dense fog will persist in an
enhanced dew point/upslope region across the south central Kansas
counties , where early afternoon highway cams were showing dense
fog. Based on saturated point HRRR forecast soundings and the
general HREF trend for visibility at 1/4mi, some areas of dense
fog are likely to continue through the evening across Ford, Kiowa
and Pratt counties, southward to the OK line and even northward
into Hodgeman and Pawnee. The uncertainty in widespread nature
will preclude extension of the earlier dense fog advisory.
Attention then turns to convection chances and threats this
evening. An intense upper jet across the AZ and NM/Mexico border
arced into southwest Kansas will lift a sharp PV anomaly max into
the SE CO/TX Panhandle and southwest Kansas area through mid
evening, juxtaposed across an ever increasingly moist boundary
layer noted in SPC 850 moisture transport fields. With the north-
south oriented surface based CAPE axis and generally parallel wind
field, the convection that may or may not develop in the western
counties should become quickly linear. Very skinny CAPE profiles
above the surface layer doesn’t support hail, and the qlcs nature
could support mesovorices (swaths of wind damage) in the 9pm to
midnight time frame. SPC’s 5% Tornado risk outlines the added risk
very quick moving mesovotices that may develop. Not all the CAMS
are all that keen with the more robust storms in that window,
namely the FV3 does support it while many others dry slot the
local area. All models have the more widespread showers and
storms moving into the eastern counties with a generally lessening
surface CAPE with time. PoPs increase significantly west to east
and the front should clear out the entire area after about 7z/1AM
or so. Beyond the convective risks tonight, the westerly momentum
Tuesday morning will lead to strong gusty westerly winds for the
entire forecast area, probably falling below the High wind
threshold, but at least making for a difficult north – south
travel Tuesday morning.
.LONG TERM...(Wednesday through Monday)
Issued at 250 PM CST Mon Dec 12 2022
We changed up NBM’s winds to the 90th percentile which better
supports the weather trends given the pipeline of cold air we`ll
be seeing in the coming days. Colder air will limit highs to the
30s over most of the area through the weekend, but more impactful
will be the apparent temperatures or wind chills during the
overnight and early morning periods. Official forecast
calculations for wind chill area commonly in the single digits
every morning beginning Wednesday and lasting through the rest of
the current long term. Any slight moderation in real temperatures
through the weekend will be reinforced by more cold air into
early next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 603 PM CST Mon Dec 12 2022
Moist southerly winds will result in widespread low MVFR/LIFR/IFR
CIGS through 6z. A strong disturbance will approach this evening,
with thunderstorms possible between 02 and 7z. These could be
severe with high winds. After the cold front passes between 09 and
12z, VFR CIGS will return. Winds will shift to the west and
southwest behind the front and become gusty.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 34 47 21 41 / 60 0 0 0
GCK 30 42 19 39 / 50 0 0 0
EHA 29 46 19 43 / 10 0 0 0
LBL 31 48 19 43 / 20 0 0 0
HYS 35 47 19 37 / 80 10 0 0
P28 42 55 25 43 / 100 10 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Russell
LONG TERM...Russell
AVIATION...Finch
Area Forecast Discussion
National Weather Service Flagstaff AZ
305 PM MST Mon Dec 12 2022
.SYNOPSIS...Occasional snow showers are forecast for the rest of
this afternoon and again Tuesday afternoon. These snow showers may
result in quick snow accumulations and hazardous driving
conditions on a highly localized scale. Otherwise, the main theme
will be unseasonably cold conditions, with widespread single digit
temperatures for morning lows on Wednesday.
&&
.DISCUSSION...Our anticipated winter weather episode has unfolded
as expected, however, we may not be done with the wintry
precipitation just yet. Regional satellite imagery revealed a pair
of shortwave troughs rotating around the main longwave feature
this afternoon. The lead shortwave trough, across southern
California, will eject eastward this afternoon and spread modest
ascent across the southern half of the High Country. The region
with the greatest chance for additional snowfall this afternoon
and tonight will be for locations near and south of the I-40
corridor (PoPs are 20-40%). Areas north of I-40 generally have a
less than 10% chance for precipitation. With that in mind, I`ve
shaved off the western half of the Winter Weather Advisory (the
Kaibab Plateau, Grand Canyon Country, and the Flagstaff area).
Farther south and east, ascent will be maximized and the Winter
Weather Advisory for central/eastern Rim and White Mountains areas
will run through 06 UTC.
The most noteworthy changes to the forecast were on Tuesday.
Recent runs of the HRRR and HRRR-Time Lagged Ensemble suggest that
more pronounced synoptic scale ascent will accompany the second
shortwave trough that will dive southward around the back end of
the aforementioned longwave feature. This feature is forecast to
slide into the area, induce westerly to northwesterly upslope flow
during peak heating on Tuesday. Forecast soundings (even from the
coarser NWP) indicate a MAUL or moist adiabatic unstable layer
with a saturated lower half of the troposphere characterized by
nearly 8 C/km lapse rates. With even modest ascent, this will
likely be enough to encourage pockets of deeper convection. CAPE
values actually approach 100-200 J/kg across portions of the area
suggesting a non-zero risk for thunder. As a result, I`ve inserted
isolated thunder into the worded forecast and boosted PoPs
considerably.
The greatest PoPs for Tuesday reside along the SF Volcanic Field,
down the Mogollon Rim and into the White Mountains with values
ranging between 50 and 80 percent. The North Rim of the Grand
Canyon, over to the Black Mesa, and Defiance Plateau have around
a 30-50% chance for precipitation. Snow levels will be quite low
(around 3,500 feet), so areas such as the LCR may see a few flakes
fly. In terms of snowfall amounts, there`s a broad swath of 1 to
7 inches. Areas across the Kaibab Plateau and Central Mogollon Rim
could experience 1-3 inches of snow, with the Eastern Rim and
White Mountains looking at 3-7 inches of snow. It should be noted,
that because of the convective nature of activity, not all
locations advertised with mentionable PoPs will experience
accumulating snowfall. In fact, snow may be highly localized in
spots and as a result, this will result in very rapid changes in
driving conditions!
By midnight Wednesday, most areas will be clear and with light
winds and a fresh snowpack, temperatures will crater. Many
locations across the higher terrain will experience Wednesday
morning low temperatures in the single digits, with "freezing"
conditions all the way down across the Yavapai County deserts.
The rest of the outlook period appears cold and the NBM appears to
be on track in terms of temperatures---though we may need to nudge
things down by a degree or two depending on trends.
&&
.AVIATION...For the 00Z TAF package...Periods of LIFR/IFR conditions
are possible through the period. Expect scattered snow showers this
evening and again tomorrow afternoon. These convective snow showers
may rapidly reduce visibility and lower cloud ceilings, especially
along a KGCN-KFLG-KINW line. Mostly VFR conditions are expected
elsewhere. Winds stay generally light out of the west-southwest
around 10 kts. Aviation discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Unseasonably cold. Scattered snow showers are
expected Tuesday afternoon, before skies clear on Wednesday. Expect
west-southwest breezes Tuesday, shifting to west-northwest breezes
on Wednesday.
Thursday through Saturday...Dry weather prevails and winds stay
light. Temperatures broadly 10-15 degrees below average will allow
snow cover to persist over the high country.
&&
.FGZ WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 PM MST this evening for
AZZ016>018-116>118.
&&
$$
PUBLIC...Bain
AVIATION...BAJ
FIRE WEATHER...BAJ
For Northern Arizona weather information visit
weather.gov/flagstaff
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
725 PM CST Mon Dec 12 2022
.UPDATE...
Issued at 715 PM CST Mon Dec 12 2022
* Dense Fog Advisory has been cancelled.
Appears the window for dense fog has passed us for the rest of the
evening and overnight. Observational trends have been steady in
the 1-3+ range, and hi-res models such as the HRRR (which is
already overdoing the fog) suggests gradually improving conditions
for the rest of the evening.
No other changes to the overnight forecast at this time. Expect
convection to incr substantially in the 02-04Z time frame as upper
forcing attendent to mid level jet streak noses in from the SW.
Still appears greatest severe threat will remain just SW of the
CWA, closer to primary MUCAPE plume of 500-1000 J/kg. Nonetheless,
with continued moisture advection and steepening mid-upper lapse
rates, could still see up to 500-750 J/kg of MUCAPE edge into
portions of the area, esp. SW of the Tri-Cities. Elevated
instability combined with strong cloud layer shear and cool low
level temps could be enough for marginally severe hail with the
strongest cores. Stable near-sfc layer should preclude too much of
a strong wind threat.
While not explicitly shown in the Day 2 severe weather outlook,
can`t completely rule out some hail concerns Tue from low-topped
convection as the sfc-500mb low becomes deep and vertically
stacked over central Neb. Narrow tongue of higher low level
theta-e air will wrap W back into the sfc low as it moves from
near MCK to LXN and BBW during the daylight hrs. In conjunction
with very cold H5 temps of -26 to -28C, expect another small area
of MUCAPE of around 500 J/kg to build and move SW to NE through W
2/3rds of CWA. Small hail would be main concern, but if instability
trends any higher then could conceivably get some nickels and
quarters. High ambient vorticity and cold mid level temps also
argue for perhaps some cold air funnel clouds, too. Don`t have
high confidence one way or the other, and very maginal sfc temps
(likely less than 50F) argue against strong storms... but with the
deep low nearly overhead I wouldn`t be shocked if some convection
"overachieves" tomorrow, as sometimes happens with intense cold
season low pressure systems. Will let night shift evaluate whether
these concerns are worthy of further messaging.
&&
.DISCUSSION...(This evening through Monday)
Issued at 317 PM CST Mon Dec 12 2022
Key Messages:
* Fog persists this afternoon and into the evening.
* Rain and thunderstorms expected tonight into Tuesday. There is
a marginal risk for severe weather.
* Some snow moves from the west/northwest late Tuesday afternoon.
Periods of flurries and light snow continuing through Wednesday
and even into Thursday morning.
* Strong northwest winds (gusts 40-50 MPH) expected Tuesday night
through Thursday.
* Below-normal temperatures likely through the weekend and most
(if not all) of next week.
Details:
Despite the gusty southeast wind, we`ve actually seen an uptick in
dense fog this afternoon as higher dewpoints advect into the area.
As such, a Dense Fog Advisory was issued through 9pm. It is
possible that this will need to be expanded.
This evening, drizzle should transition to more rain showers as
we see increasing lift arrive ahead of the upper low. CAMs
indicate that the main risk for thunderstorms will be after 8pm
(but cannot totally rule some out before that). The best
instability (especially in the low levels) is initially well to
the southwest of the area. As such, expect that the strongest
updrafts will initiate in this area. These may approach our
southwestern zones after midnight but will probably be on a
weakening trend. Nevertheless, a few strong to marginally storms
cannot be ruled out through Tuesday morning given the strong shear
and dynamic lift.
On Tuesday, the surface low moves through the area. A few
thunderstorms are expected to persist through the morning and
early afternoon, gradually pushing to the northeast. The severe
threat is decreased due to decreasing instability. Rain totals
are expected to range from just around a tenth in our southwest to
over an inch in parts of central and north-central Nebraska.
Temperatures will crash behind the cold front on Tuesday
afternoon. Some light snow may push in from the northwest, but
most of the area will only see a dusting through Wednesday
morning. Far northwestern zones may pick up 1-2". The low moves
eastward very slowly through Wednesday, meaning that we will
continue to see flurries and light snow over portions of Nebraska
through Wednesday and even into Thursday morning. More notable
than the snow will be the strong northwest winds (gusts 40-50 MPH)
that will persist through Thursday.
After this system departs, we will see a much colder pattern
continue through the weekend and into next week. Single digit
highs and subzero lows are completely possible. There will be
spotty chances for light snow, but there is not enough model
agreement to really pinpoint any timeframe as particularly
concerning at this point.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 545 PM CST Mon Dec 12 2022
Significant weather: LIFR CIGs, MVFR-IFR VSBYs, strong wind, and
scattered thunderstorms.
Tonight: LIFR CIGs are likely here to stay through the overnight
period. VSBY has been, and will continue to be, quite tricky. With
that said, appears per ob/model trends that TAF sites may be past
the lowest VSBYs and that we`ll be primarily in the 1-4sm range.
Will probably oscillate back and forth between IFR and MVFR, but
think we`re done with any dense fog. Expect shower, and eventually
t-storm, activity to build over the next few hrs, with overall
best chances coming in the 03Z-12Z time frame. Can`t rule out some
small hail with the strongest cores, but best chc for svr looks to
be SW of the terminals. Finally, strong SE winds will continue all
night, generally sustained near 20kt, and gusts 30-35kt.
Confidence: CIGs/Wind - High, VSBYs - medium.
Tuesday: Complex TAF forecast will continue through this period as
well. Will start off with continued LIFR CIGs and perhaps a break
from steady shwrs/storms. Some model evidence that VSBYs could dip
around daybreak as winds back slightly in response to deepening
sfc low off to the SW. This slight incr in upslope component could
give VSBYs a chc to fall back to around 1sm, but this is
uncertain. If VSBYs do drop, don`t think it will be to LIFR
levels. The dry slot from the major storm system will wrap into
the area around late AM, and provide a distinct, but brief,
reprieve from solid IFR CIGs and shwr/storm chcs. However, wrap
around flow will quickly bring at least BKN MVFR CIGs and
possibly more iso-sct tstm chcs for the aftn hrs. Winds will start
off SE, then veer to S and eventually SW with arrival of dry slot
around midday, and remain strong - sustained 20-25kt, gusts up to
around 35kt. Confidence: Medium.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
UPDATE...Thies
DISCUSSION...Mangels
AVIATION...Thies
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
949 PM EST Mon Dec 12 2022
.SYNOPSIS...
Dry conditions are expected through Tuesday before rain impacts
the Ohio Valley midweek. Temperatures will generally be very
close to normal to slightly above normal for the first half of
the workweek before trending below normal for the end of the
workweek. Unsettled conditions will be possible Friday into the
weekend, with some snow showers possible.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Despite surface ridging extending across the Great Lakes and
Ohio Valley, stubborn stratocumulus clouds beneath a subsidence
inversion continues to plague the region. However, there appears
to be some erosion taking place on the southern edge of the
cloud deck per latest GOES-16 nighttime microphysics loop. Per
latest RAP run, am expecting drier air between 900 mb and 875
mb to gradually nudge its way northward overnight as the flow in
this layer turns southeast. Where the low level cloud deck
erodes, some high level clouds will take its place above. The
process will be slowly going and will continue from south to
north into the first part of Tuesday. Lows tonight will be
somewhat uniform given easterly flow between 5 and 15 mph. Lows
will range from the upper 20s to the lower 30s.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
The influence of surface high pressure begins to wane on
Tuesday as a low pressure system ejects into the high Plains
from the Rockies. Easterly/southeasterly flow increases through
the day and temperatures moderate with upper level ridging
building over the region. The most welcome change to the weather
pattern on Tuesday is a sharp reduction in low level moisture
allowing for temporary clearing of low level cloud cover.
Filtered sunshine is expected through the building cirrus with
some peeks of blue sky being possible. Forecast highs reach into
the 40s.
Partial clearing in the cloud cover does not last long since
Tuesday night features increasing moisture, cloud cover, and
increasing rain chances ahead of the approaching low to the
west. Any precipitation that falls late Tuesday night is likely
to be rain since increasing WAA aloft shifts the profile well
above freezing by the time any chance for precipitation starts.
Surface temperatures are also likely to be above freezing by
precipitation onset. Forecast lows are near freezing overnight.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Strong low pressure over the central Plains will slowly shift
into the upper Midwest from Wednesday through Thursday. Initial
shortwave Wednesday morning and its accompanying rain will exit
to the northeast by afternoon, leaving a few hour break and
lower PoPs.
A second stronger shortwave lifts into the region Wednesday
night along with a surface low and cold front. The region will
be well into the warm sector, so expecting all rain with any
precipitation that falls Wednesday night through Thursday.
Behind the front colder temperatures advect into the Ohio
Valley late Thursday into Friday. At the same time, the core of
the mid- level low drifts into the Great Lakes. With the cold
air aloft and surface temperatures in the mid to upper 30s
Friday afternoon, can`t rule out a few rain/snow showers.
Mostly cloudy skies will still be present through Saturday as
the mid-level low continues to wobble over the Great Lakes. The
low shifts east Sunday so the region may see a few peaks of
sunshine at that time. Temperatures will be below seasonal norms
from Friday through the end of the extended period on Monday.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Surface ridging extends from Hudson Bay southward into the Ohio
Valley this evening. This ridge axis will gradually move east
through the TAF period while a mid level ridge axis moves
briefly east into the region.
Stubborn low level stratocumulus trapped underneath a
subsidence inversion is expected to show some signs of
erosion/movement over the next 12 to 18 hours. Before then, MVFR
ceilings are expected. The erosion/movement should gradually
occur from south to north overnight into the first part of
Tuesday. By Tuesday afternoon, any stratocumulus left over near
the northern terminals should eventually mix out and dissipate.
In its wake will be some high level clouds spilling through the
mid level ridge.
Winds will generally be from the east between 5 and 10 knots.
OUTLOOK...MVFR/IFR conditions likely late Tuesday night into
Thursday. MVFR ceilings possible Thursday night into Saturday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...Campbell/KC
NEAR TERM...Hickman
SHORT TERM...Campbell
LONG TERM...
AVIATION...Hickman
Area Forecast Discussion
National Weather Service Indianapolis IN
937 PM EST Mon Dec 12 2022
.Forecast Update...
Issued at 936 PM EST Mon Dec 12 2022
* Evening Update
Dry air subsidence in the axis of an approaching ridge is aiding in
the erosion of a thick low level cloud layer over the NE half of
central Indiana. This should continue over the next several hours,
eventually leading to a two part cloud deck; FEW at 3000FT, and a
more broad cloud deck above 20000 feet associated with a diffluent
upper level jet.
Due to a delay in diurnal cooling over NE central Indiana, morning
lows have been increased slightly. Otherwise, forecast looks on
track, minus a few observational based changes.
&&
.Short Term...(This evening through Tuesday)
Issued at 237 PM EST Mon Dec 12 2022
Cloud cover and temperatures remain only concern in this tranquil
short term period before large scale pattern change begins to take
shape in later periods.
High pressure over Great Lakes providing a light easterly flow
across central Indiana today. Surprisingly we have seen low perma
cloud deck slowly erode this morning over southern and southwest CWA
despite easterly flow and strong inversion. Model and ACAR soundings
tell the story with a very shallow layer of moisture near inversion
that has been eroded today by drier air and subsidence associated
with high pressure. HRRR shows this clearing to continue working
west and north across western portions of central Indiana, with east
to northeast areas likely remaining mostly cloudy. The question is
whether enough residual moisture remains to allow clouds to fill
back in this evening across the areas that have cleared and what the
southern fringe of cloud cover in the north will do. Previous
forecast trended toward some clearing tonight and with these
observational trends see no reason to deviate from that thinking
south and west with support of HRRR. However, will remain more
pessimistic in the north and northeast where satellite and
observations suggest clouds will linger.
Any clearing will be short lived as ridge axis quickly passes and
warm air advection begins ahead of next system. Mid and high clouds
to spread back in later on Tuesday but deeper moisture and large
scale lift ahead of potent short wave remains west so expect the day
to be dry. With fewer clouds around and 850mb temps warming to
between +5C to +7C in the southwest, expect high temps to respond
into 50s there. A bit more uncertainty as you go north and east with
uncertainty on cloud cover so trended toward lower to middle 40s
with consensus guidance.
&&
.Long Term...(Tuesday night through Monday)
Issued at 237 PM EST Mon Dec 12 2022
If you were in search of a pattern change...wait a few days and
winter weather will return to the Ohio Valley later this week. But
before we dive into the extended pattern change, we have a potent
well-developed system poised to impact many areas on the lee-side of
the Rockies Tue/Wed.
Highlights for the extended:
* Periods of rain early Wed through midday...again late Wed into
early Thur.
* Quick flirt of mild temps in the 50s Wed...enjoy it while it lasts.
* Winter knocks at the door Sat...with a wide-open door to close-out
the weekend.
Tue Night/Wed: As is common with well-developed systems, adjustments
to the timing of arrival continues to be refined. Before we look at
the upcoming system, we first need to look downstream and the block
that is developing across the North Atlantic. This will set the
stage for an amplified upstream wave, ie next weather system.
Guidance has continued to lean towards more amplification to the
heights across the Ohio Valley Tue eve, with persistent diffluent
conditions within the lower 3km of the atmosphere. The low-level jet
will begin to ramp up, but it doesn`t appear to be the case until
after 6Z Wed for Central Indiana. Meridional flow has trended
stronger, which is essentially the south to north flow of parcels,
and this is supported by the amplification of heights. This should
allow a rapid moistening along isentropic surfaces, with parcels
likely becoming saturated quickly from southwest to northeast Wed
early morning. The axis of deep moisture begins to pivot east around
12Z Wed, which should help to usher in a dry nose in the 925-800mb
layer likely helping to diminish the steadier rain coverage
marginally. Temps Tue ngt, likely will not budge much...so will hold
onto mild air heading into Wed. The challenge for Wed highs temps
will depend on cloud cover and precip coverage. But at this time it
does appear we can lean slightly warmer, and could see Wed highs
touching the low 50s, perhaps in the far south even a few spots
could hit 60 briefly.
Wed aftn-Thur: There is another jet maxima that points northeast Wed
aftn, which could help to lift parcels modestly and re-engage the
precip coverage Wed aftn/eve. Given the continued strong meridional
flow in the sfc-850mb layer, some better organization to the precip
coverage could occur before the trough axis arrives and kicks the
rain east. Isallobaric pressure gradient quickly arrives Wed
aftn/eve, and depending on mixing heights, we could see gusty
conditions develop. Have nudged winds/gusts up and may flirt with
higher gusts between 35-40 mph for a period Wed.
Guidance continues to fluctuate with timing of the potent 500mb
shortwave late Wed to early Thur, which will dictate the back edge
to the precip. Dry boundary finally arrives early Thur morning, with
temps likely falling throughout the day.
Fri-Sun: As was eluded to earlier, Winter will be knocking at the
door late this week but especially over the weekend. The 500mb
trough axis finally arrives Fri across the Ohio valley, as the
thermal trough dives south from the Upper Midwest. Cold air
advection will rapidly pour into the Ohio Valley late Fri, being
sensed Sat/Sun as temps struggle to push beyond the mid/upr 20s. At
the present time, there doesn`t appear to be any lingering northwest
flow shortwaves that could trigger light snow. So for now it appears
perhaps flurries would be the extent of winter precipitation for the
weekend. The deep trough will then linger through the weekend with
a continued winter pattern.
&&
.Aviation...(00Z TAF Issuance)
Issued at 628 PM EST Mon Dec 12 2022
Impacts:
* MVFR ceilings likely at LAF, intermittent at KIND through 03Z
* Gusts up to 20kts possible tomorrow afternoon.
Discussion:
Shallow moisture near a strong inversion leading to thin layer of
stratocu clouds that have thinned further and cleared in areas
across central Indiana. Satellite shows this trend with drier air
and subsidence associated with high pressure slowly eroding cloud
deck. There has been a slight trend westward within the eastward
winds. But this should erode before impacts are seen at KIND.
Still, have left a tempo for BKN025 for the possibility of
intermittent MVFR ceilings.
VFR conditions expected for the remainder of the TAF period. Gusts
up to 20kts are possible tomorrow afternoon. Have only included at
KIND and KBMG, with confidence higher at these locations. SE dry air
should lead to brief periods of clearing at these locations,
increasing PBL mixing.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...Updike
Short Term...Lashley
Long Term...Beach
Aviation...Updike
Area Forecast Discussion
National Weather Service North Platte NE
535 PM CST Mon Dec 12 2022
.SYNOPSIS...
Issued at 355 PM CST Mon Dec 12 2022
H5 analysis this morning has a closed low over far
northeastern Nevada with a trough extending to a secondary, strong
shortwave over southern California. East of this feature, a highly
amplified ridge extended from the Ozarks north into western Ontario.
West of the western CONUS trough, another highly amplified ridge
extended from the eastern Pacific into the Yukon. Current WV
imagery has a nice plume of upper level moisture, streaming into
the rockies and high plains from northwestern Mexico. At the
surface, a lee side trough of low pressure extended from
southeastern Wyoming along the front ranges of eastern Colorado. A
warm front was present along the Kansas/Nebraska border and a cold
front extended from central Wyoming, into southwestern, then north
central South Dakota. Southeasterly and easterly winds extended east
of the trough across western and north central Nebraska this
afternoon. These winds have led to increasing low level moisture
across the area overnight with continued low level moisture
advection this afternoon. Skies remained cloudy across the area as a
shroud of low level clouds continued across the area. Temperatures
as of 2 PM CST ranged from 33 at Gordon to 45 degrees at North
Platte and Imperial.
Key Messages:
-A major winter storm is expected to impact the area starting
tonight and continuing into Thursday.
-Early this evening, there is a threat for severe thunderstorms
south of Interstate 80.
-Dangerous blizzard conditions are expected for much of the
Panhandle, western Sandhills, and portions of northern Nebraska.
-Potentially life threatening travel conditions are expected to
develop Monday night into Thursday, especially in the Blizzard
Warning area.
-Ice accumulations of a light glaze to around a tenth of an inch are
expected for much of western and north central Nebraska.
-Strong northwest wind gusts of 45 to 50 mph, with gusts approaching
60mph will lead to significant blowing and drifting snow.
-Much colder temperatures persist into the weekend, with the
potential for well below zero wind chills each morning into next
week.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 355 PM CST Mon Dec 12 2022
A significant storm system
will impact western and north central Nebraska over the next 24 to
72 hours with several hazards expected. Synoptically, an upper level
low will emerge and deepen over southeastern Colorado overnight.
This feature will then track from western Kansas into central
Nebraska Tuesday, then will decelerate as it tracks from central
Nebraska into southeastern South Dakota Tuesday night through
Wednesday night. The low will then track east southeast, finally
exiting northern Iowa late Thursday. Strong surface cyclogenesis is
currently underway over eastern Colorado. This area of surface low
pressure will track slowly east northeast on Tuesday, then north
northeast Tuesday night into Wednesday, ending up as an occluded low
over sern South Dakota Wednesday into Wednesday evening. The very
slow movement of the upper level low and surface low is a result of
a blocking ridge of high pressure anchored over the eastern CONUS.
As mentioned before, this storm system will be multifaceted with a
significant number of hazards over the next 72 hours.
With respect to the thunderstorm threat this evening. Surface
analysis this afternoon has a nice tongue of 40+ degree dew points
extending as far north as Thedford Nebraska. Further south, 50+
degree dew points had pushed into southwestern Kansas this
afternoon. With the approach of the H5 low this afternoon, increased
instability has led to a band of convective cloudiness over the
northern TX panhandle and OK panhandle over the past hour. Looking
at the latest NAM12 soln, a tongue of SB capes (750-1000J/KG lifts
north into western Kansas this evening. As an area of very steep mid
level lapse rates approaches the area of increased CAPE early
evening, thunderstorm development appears likely over western
Kansas. The latest HRRR lifts this convection into southwestern
Nebraska during the 00z-02z time frame. Strong mid level flow and
anticipated linear storm structure across southwestern Nebraska may
would favor strong winds as the main severe threat. Wouldn`t be
surprised if we saw some dime to quarter sized hail with any of the
stronger storms given the very steep lapse rates.
Storms will continue to track north into the Sandhills this evening,
weakening north of I-80. As these showers and embedded thunderstorms
lift over the approaching cold front this evening, we will see our
greatest threat for freezing precipitation over northwestern
portions of the forecast area. ATTM, based on forecast soundings,
this appears to be a narrow corridor of light to briefly moderate
freezing precipitation this evening into the early overnight hours.
Further north of the front, thermal profiles are indicative of snow
which may be heavy at times, thanks to the degree of instability and
upright/not slantwise lift. Overnight, the cold front will track
slowly east, becoming oriented from Ogallala to near Valentine by
12z Tuesday. The surface low will track east northeast across
southern Nebraska, occluding over northeastern portions of the
forecast area Tuesday afternoon. Strong isentropic lift will
continue Tuesday behind the front with deep lift in the dendritic
zone noted west of a line from Ogallala to Bassett. Given the degree
of mid level lift, am expecting the heaviest snow to fly Tuesday
into Tuesday evening. For the most part, the current snowfall
forecast was on track with the previous forecast. With some minor
changes noted with the surface low track, heavier precipitation was
carried east into northeastern portions of the forecast area. This
necessitated expansion of the blizzard warning into Keya Paha and
Brown counties, and a winter storm warning into Rock, Blaine and
Logan counties. In the expanded blizzard area, snow accumulations
were increased with up to 10 inches in western Keya Paha and
northern Brown counties. In the expanded winter storm warning
counties listed above, accumulations of 2 to 6 inches are forecast.
I realize this falls short of warning criteria but with expected wind
gusts of 50+ MPH, blowing snow will be a major issue. Left Boyd and
Holt counties in a watch as the surface low tracks over these
counties and will probably limit snow accumulations. Will have the
night shift look at this and determine if the forecast low track
shifts further east. Snow will linger across northern Nebraska
Wednesday night into Thursday as weak mid level isentropic lift
lingers.
Strong winds will accompany this system and will be an impact
through Thursday. With the anticipated snowfall, blowing snow will
remain impactful, well after snowfall ends. Current headlines end at
6 AM CT on Thursday morning. Current model trends indicate strong
winds persisting well into Thursday with H85 winds of 40+ KTS. If
this materializes, we will possibly need to extend, or replace
winter headlines for the threat for blowing snow.
.LONG TERM...(Thursday night through Monday)
Issued at 355 PM CST Mon Dec 12 2022
Upper level low pressure, will remain entrenched over the
northern Great Lakes Friday through Saturday. This feature will
finally transition east into the eastern Great Lakes Sunday. On
its heels, a secondary upper level low and arctic trough, will
track south from western Canada into the northwestern CONUS early
next week. Cold and mainly dry conditions will persist through
Monday with even colder air arriving midweek next week. Highs
through Sunday will be in the teens and 20s with single digits to
teens for next Monday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 535 PM CST Mon Dec 12 2022
Fairly widespread IFR/LIFR in fog and low or very low ceilings is
expected tonight. Rain, showers, snow and isolated thunderstorms
are expected to develop later this evening which will continue
Tuesday.
Some improvement in flight conditions is possible along and south
of Interstate 80 Tuesday afternoon where MVFR/IFR ceilings and
vsbys may develop.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Blizzard Warning from midnight CST /11 PM MST/ tonight to 6 AM
CST /5 AM MST/ Thursday for NEZ004-005-022>024-035-056-094.
Blizzard Warning from 6 AM Tuesday to 6 AM CST Thursday for
NEZ006-008.
Winter Storm Watch from Tuesday morning through late Wednesday
night for NEZ007-010.
Winter Storm Warning from 6 AM CST /5 AM MST/ Tuesday to 6 AM
CST /5 AM MST/ Thursday for NEZ009-025-026-036-037-057-058.
Winter Weather Advisory from 6 AM CST /5 AM MST/ Tuesday to 6 AM
CST /5 AM MST/ Thursday for NEZ059-069.
&&
$$
SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...CDC
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
537 PM CST Mon Dec 12 2022
.SHORT TERM... (Through Late Tuesday Night)
Issued at 229 PM CST Mon Dec 12 2022
the Mid Mississippi Valley remains under an upper level ridge
sandwiched between to long wave troughs over the western Atlantic
and the western U.S. The subsidence inversion beneath the ridge has
trapped low level moisture over the area which has kept us socked in
with low clouds and patchy fog. There has been some drying in
southeast Missouri and southern Illinois due to east-southeast low
level flow which is pushing somewhat drier air in from the Tennessee
Valley, however I think this break in the clouds will be short lived
as the next system gets wound up over the Plains.
There has been little change to the forecast for tonight through
Tuesday. Low pressure will advance into the central Plains by
Tuesday afternoon, with a strong low level jet developing ahead of
it. Moisture convergence associated with the jet is expected to
produce widespread showers and a few thunderstorms which will
overspread the area from west to east through the day and into
Tuesday evening. All guidance shows widespread precip in response
to the moisture convergence and as a mentor of mine said in these
situations, "if the entire area doesn`t get some rain, it`s going
to miss a darn good chance." Have therefore continued with
unconditional PoPs ahead of the front Tuesday afternoon and evening.
Latest storm total QPF is for around 0.75 and 1.25 inches, with the
lion`s share of that falling Tuesday afternoon and evening.
RAP MUCAPE shows a tongue of weak instability creeping up into our
forecast area late Tuesday afternoon into the evening ahead of the
cold front. Highest values are hovering around 500 J/Kg, but
there`s little if any SBCAPE. The latest GFS doesn`t even have 100
J/Kg MUCAPE during that period. This morning`s HREF SBCAPE max has
around 100 J/Kg ahead of the front, and mean MUCAPE is likewise
around 100 J/Kg. All this means I cannot rule out a few rumbles of
thunder, but there seems to be little if any chance the storms could
be strong or severe. That being said, the gradient wind ahead of
the system will be pretty strong on Tuesday and Tuesday evening.
Sustained winds of 15-20kts with gusts of 30-40kts look likely until
around 03-06Z Wednesday.
Carney
.LONG TERM... (Wednesday through Next Monday)
Issued at 229 PM CST Mon Dec 12 2022
The stacked closed low will meander across the eastern Plains
Wednesday and into the Upper Midwest Thursday. Medium range
deterministic guidance stalls the low over Minnesota/Wisconsin
through Saturday and then ejects it east across the Great Lakes on
Sunday. GEFS and ECE open the low up somewhat more quickly, but the
general pattern is the same. West-northwest flow on the west side
of the low will bring progressively colder air south from Canada to
spread across the Missouri Valley. The cold air won`t really start
filtering into our area until Wednesday night so highs Wednesday
will be mild in the 50s. However Thursday through Saturday will get
progressively colder with highs dropping into the 30s and 40s.
Saturday will be the coldest day of the bunch with parts of northern
Missouri and west central Illinois struggling to reach 30. Mid
teens to low 20s will be the rule for lows. Deterministic guidance
shows another fast-moving short wave moving across the Plains into
the Mid Mississippi Valley Sunday night into Monday. It gets washed
out in the ensembles, and/or masked by the next huge upper low. At
any rate, the deterministic guidance prints out some QPF which the
NBM picked up on and inserted PoPs Sunday night and Monday. The low
chance/slight chance PoPs look reasonable at this time given the
movement of the wave so we`ll keep them for now. Temperatures
suggest that some of this precip could be a brief wintry mix before
warm advection turns the precip to all rain.
Carney
&&
.AVIATION... (For the 00z TAFs through 00z Tuesday Evening)
Issued at 532 PM CST Mon Dec 12 2022
The clearing trend has worked from southeast to northwest just
about reaching sections of central MO. Metro terminals have gone
VFR, although broken high clouds continue to stream overhead. MVFR
conditions will likely move back in as temperatures cool this
evening with all sites under MVFR ceilings around and after 04z.
Greatest impacts will stem from an approaching system that will
lead to gusty southeast winds from mid-morning Tuesday onward.
Ceiling will continue to lower into IFR as rain potential
increases through late morning/early afternoon. Reduced visibilities
are expected to accompany rainfall through the end of the period.
Maples
&&
.PRELIMINARY POINT TEMPS/POPS...
Saint Louis 36 55 48 58 / 0 100 100 20
Quincy 35 50 43 52 / 0 100 100 5
Columbia 37 54 41 51 / 20 100 70 0
Jefferson City 37 56 41 53 / 20 100 70 0
Salem 33 52 48 58 / 0 50 100 50
Farmington 33 56 45 57 / 0 100 100 20
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
952 PM EST Mon Dec 12 2022
.SYNOPSIS...
High pressure ridge continues to nose south into the Carolinas
through mid week. A strong cold front will then approach the
area Wednesday night and Thursday with an excellent chance of
appreciable rain. Cold high pressure will build over the area
over the weekend.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
As of 950 PM Mon...Cloud cover has quickly eroded over the
coastal plain and in response temperatures have already
plummeted into the 30s as radiational cooling has taken hold.
There are likely colder spots in well sheltered areas. Latest
HRRR is capturing temperature trend well and blended some of
this in for this update with little effect to the overnight low
forecast.
Prev disc...A synoptic cold front pushed well offshore to the
south of the Carolinas earlier today, with high pressure nosing
in from the Great Lakes. Behind the front, satellite imagery
reveals a well-defined surface trough pivoting south through the
far western Atlantic. While it is very dry aloft, the low-
levels are fairly moist within the cyclonic flow around the SFC
trough. This is leading to a broad area of low clouds streaming
south along, and off, the Mid-Atlantic Coast at this time. Short
term guidance have struggled with the western extent of the
clouds, which have ended up fairly far inland this afternoon.
Some of this is probably diurnally- enhanced, and it appears the
extent of clouds will thin some after sunset. That said, the
moist confluent flow will continue to support periods of low
clouds through tonight, especially east of HWY 17. Consequently,
this will have a big impact on temperatures overnight. For
areas east of HWY 17, temperatures won`t drop as much as areas
to the west. However, if the clouds end up not being as
widespread, lows will be colder than currently forecast and
vice-versa.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
As of 1200 PM Monday...High pressure will continue to be wedged
south from the Great Lakes into the Carolinas on Tuesday. With
time, a more significant push of drier low-level air should help
to scatter out any lingering low clouds during the day. Given
the potential for lingering clouds early in the day, and with a
chilly start to the diurnal curve, highs Tuesday may actually be
colder than today, despite gradually rising low-level
thicknesses.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
As of 330 AM Monday...Cool and dry conditions expected into
Wednesday. The next storm system and cold front which will bring
next chance of appreciable rain will arrive late Wednesday
evening or Thursday.
Tuesday night through Wednesday...Reinforcing shortwave troughs
rotating around an upper low centered over northern New England
will bringing renewed nrly surge and CAA with cool temps
continuing, albeit mostly sunny skies with dry high pres ridging
in. Brief ridging aloft builds over the area Tuesday night into
Wednesday ahead of another upper low across the central plains.
Clouds will thicken and lower Wednesday as the system
approaches but guidance is a bit slower bringing precip into ENC
and expect dry conditions through the afternoon. Highs expected
around 50-55 with lows around freezing or lower inland to upper
30s to lower 40 coast.
Wednesday Night through Thursday Night...Aforementioned upper
low over the Central Plains slides into the western Great Lakes
through this period while an attendant strong cold front
approaches the area Thursday. Sfc low press develops along the
front as it pushes across the Southeast and is progged to track
across the coastal plain late Thursday afternoon and evening,
which may lead to some marginal destabilization along the coast
and continue slight chance of thunderstorms. Stronger forcing
and SW flow aloft brings a better feed of moisture from the Gulf
of Mexico and expect appreciable rain with this system with 1
to 2+ inches possible. Cool temps continue Wed night with lows
generally in the 40s. WAA ahead of the front and sfc low will
bring warmer temps Thursday with highs expected around 60-65,
warmest along the coast. CAA ramps up behind the departing low
Thursday night with lows in the 40s expected.
Friday through Sunday...Cyclonic flow continues aloft through
the weekend with the upper low remaining centered over the Great
Lakes Friday and Saturday before sliding into the northern New
England Sunday. A series of shortwave trough will transition
through the flow aloft bringing reinforcing shots of CAA but
with limited moisture not expecting any precip. Temps near
normal Friday with highs in the mid to upper 50s with about 5
degrees of cooling each day Saturday and Sunday. Lows mainly in
the mid 30s inland to around 40 coast Friday night with many
inland areas likely see sub-freezing temps Saturday night and
Sunday night.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
SHORT TERM /through Tuesday/...
As of 705 PM Mon...VFR conditions persist at all terminals this
evening although periods of MVFR are likely especially for the
Outer Banks.
Healthy amount of low-level moisture advection continues to sock
the Outer Banks in low stratus, which has bounced between MVFR
and VFR levels most of the afternoon. Current expectation,
following guidance, is a gradual lowering of cigs to a
predominant MVFR overnight before returning to a mix of VFR and
MVFR tomorrow. Further west over the TAF terminals, cloud cover
is beginning to erode and expect only a few clouds. EWN is close
enough to the coastal stratus deck that some lower cigs could
sneak over the terminal, although no IFR is anticipated.
Combination of elevated winds and Td depressions suggest little
in the way of fog.
After sunrise, VFR conditions prevail with high clouds across
all terminals. Lower stratus will continue to plague OBX
terminals. Northerly winds continue at 5-10 kt, except 10-15 kt
along the coast.
LONG TERM /Tuesday night through Friday/...
As of 4 AM Monday...High pressure builds through Wednesday
with pred VFR conditions expected. A frontal system will
approach rtes Wednesday with clouds thickening and lowering
throughout the day but should remain VFR into the evening hours.
Periods of sub-VFR conditions expected late Wednesday night
through Thursday night with precip along and ahead of the cold
front and sfc low lifting across the coastal plain. VFR
conditions should return Friday and cooler and drier air builds
in.
&&
.MARINE...
SHORT TERM /through Tuesday/...
As of 950 PM Mon...Northerly winds have eased over the sounds
this evening as the pressure gradient continues to relax, and
opted to drop the SCA slightly early. Dangerous offshore seas
continue through the rest of the week.
Prev disc...Late this afternoon, seas of 7-9 ft and north winds
of 10-20kt are common across the coastal waters. For the sounds
and inland rivers, north winds have underperformed some, and
have generally held in the 10-15kt range with occasional gusts
to 20kt. For the sounds, I`ll hold onto the SCA for another few
hours in case there is a bump on the western edge of the modest
pressure gradient associated with a surface trough moving south
offshore. For the inland rivers, I decided to go ahead and
cancel the SCA early given the lower wind speeds that have been
observed today. Additionally, that area should be further
removed from the tighter gradient located offshore. Modest north
winds continue into Tuesday, but will decrease some, even over
the coastal waters.
LONG TERM /Tuesday night through Friday/...
As of 415 AM Monday...SCA conditions will prevail across the
coastal waters through the much of the week with a strong low
pres system well out in the open Atlantic bringing long period
swell and elevated seas to around 6-10 ft much of the period.
Nly winds diminish late Tuesday through Wednesday but a strong
frontal system will approach the area Wednesday night with a
developing low pressure area lifting along the front just west
of the waters Thursday evening. Winds to SCA expected to develop
Thursday morning in sely flow which veers to sly during the
afternoon. There is a potential for a period of Gales late
Thursday afternoon and evening just ahead of the low. Winds
become wly around 15-25 kt late Thursday night and Friday behind
the departing low.
&&
.TIDES/COASTAL FLOODING...
As of 330 PM Monday...High Surf Advisories remain in effect for
the Outer Banks, now until early Wednesday morning. Powerful
swell from distant low pressure systems out in the Atlantic
will continue to impact the Outer Banks beaches with wave run
up over the next couple of days. As a result, rough surf is
expected to continue for east facing area beaches. This will
continue to support an elevated risk of minor ocean overwash
and beach erosion for the Outer Banks. Main impacts will be
felt from Oregon Inlet to Cape Hatteras, with the greatest
impacts coming Tuesday. Impacts may also extend to the Northern
Outer Banks and Ocracoke Island. Portions of Hwy 12 with
vulnerable dune structure may be impacted, mainly during times
of high tide.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...High Surf Advisory until 7 AM EST Wednesday for NCZ203>205.
MARINE...Small Craft Advisory until 6 AM EST Saturday for AMZ150-152-
154-156-158.
&&
$$
SYNOPSIS...MHX
NEAR TERM...RM/MS
SHORT TERM...RM
LONG TERM...SK/CEB
AVIATION...RM/SK
MARINE...RM/SK/CEB
TIDES/COASTAL FLOODING...MHX
Area Forecast Discussion
National Weather Service Portland OR
239 PM PST Mon Dec 12 2022
.SYNOPSIS...The forecast is highlighted by an extended stretch of dry
and cold weather with increasing east winds late in the week as
low-level offshore flow strengthens.
&&
.DISCUSSION...Tonight through Sunday night...A few light snow showers
were still being observed over the Cascades early Monday afternoon,
however the coverage of showers was quickly decreasing as high
pressure continues building into the area from the west. As a result,
still expecting showers to end completely tonight. The main forecast
challenge for tonight is determining the potential for fog
development. If cloud cover clears out this evening, then areas of
fog are likely to develop as winds will be calm. If cloud cover does
not clear out, would only expect patchy fog at best. The latest
iteration of the HREF suggests cloud cover will clear out to some
degree tonight, but mainly over the southern and central Willamette
Valley rather than the northern valley into southwest WA. Sure
enough, this is exactly where the HRRR and the RAP depict fog
development. Current satellite imagery already shows cloud cover
attempting to break up over the southern valley, so this outcome
seems very reasonable. Cannot completely rule out fog in the
northern valley, but the chance is lowest to the north of Aurora and
highest in the Eugene area.
Then, a prolonged period of dry weather with gradually cooling
temperatures will occur Tuesday through at least Saturday. This is
due to what appears to be an omega blocking pattern, as the
GEFS/EPS/CMC ensemble mean for 500 mb heights are all showing a
quasi-stationary ridge over the Gulf of Alaska being blocked by an
upper low to the west and east of this ridge. This synoptic scale
setup will result in a prolonged period of northerly flow aloft
across WA/OR, allowing for several shots of relatively cold air from
Canada to dive southward into the region. This will also result in
strengthening offshore flow at the surface, especially on Thursday
and Friday when the cold pool east of the Cascades is set to deepen
and east winds begin to ramp up. Until then, it is worth mentioning
that there are some air stagnation concerns over southwest
WA/northwest OR Tuesday night through Wednesday morning. Initially
considered issuing an Air Stagnation Advisory for Tuesday night
through Wednesday night, but after taking a closer look at GFS/NAM
model soundings, have determined that transport winds will be above
our 5 kt threshold Wednesday afternoon and then well above that
threshold on Thursday and Friday. Air Stagnation Advisories are only
issued when mixing heights are below 2000 feet and transport winds
are below 5 kt for at least 48 hours straight. Currently, it looks
like criteria will only be met for approximately 36 hours, so have
decided not to issue an Air Stagnation Advisory.
How cold will it get this week? Well, the NBM continues to suggest
high temperatures on Tuesday and Wednesday will be in the low to mid
40s, except mid to upper 40s at the coast. Even colder Thursday
through Sunday when the NBM is suggesting highs in the mid 30s to
around 40 degrees, except mid 40s at the coast. Overnight lows will
be significantly colder, with widespread lows in the 20s expected
each night beginning Wednesday night. Cannot rule out lows in the
upper teens for typical cool spots such as Hillsboro, Battle Ground,
and Corvallis. Even colder over the Cascades with lows in the single
digits to teens. In addition, breezy east winds on Thursday and
Friday will make it feel even colder. Expecting widespread wind
chills in the upper teens across the lowlands, except 20s at the
coast.
Model spread on the NBM 1D Viewer is very small for temperatures,
suggesting confidence is high that the cold weather will materialize.
Model spread increases drastically Sunday into early next week as
models and their ensembles struggle to determine when the omega
blocking pattern will break down. A few of the GEFS ensemble members
are even hinting at low elevation snow on Sunday, but most members
maintain the dry conditions at this time. For now, have left the NBM
v4.0 PoPs for Sunday, which seem reasonable at 15-25%. -TK
&&
.AVIATION...00Z TAF preliminary thoughts: Region is squeezed
between high pressure to the west and a departing low pressure
center to the east. A persistent cloud deck at FL045-055 remains
over the area but seems to be more driven by daylight mixing
versus other methods.Feel these should somewhat break up with
sunset. Isolated MVFR cigs remain across the central Willamette
Valley, to include KUAO AND KSLE, but think these will also
dissipate with the loss of sun. Then, conditions should remain
VFR through roughly 08Z tonight when stable conditions will
promote another stratus deck forming. Cigs will initially in the
FL015-025 layer with many areas lowering to cigs 005-015. KHIO,
KUAO, KEUG, and maybe KSLE will drop to LIFR fog later overnight.
Conditions across the board will then change little through 13/18Z
given very little wind and minimal daytime mixing. Areas with fog
will be very slow to improve but could lift above IFR for a short
time Tuesday afternoon. Other areas should improve closer to 20Z.
For detailed Pac NW aviation weather information, go online to:
http://weather.gov/zse
KPDX AND APPROACHES...Cigs 015-020 will linger the next couple
hours at most. Then expect VFR conds with cigs above FL040 until
around 13/08Z when calm stable conditions will promote cigs
020-025 through the Tuesday morning arrivals. /JBonk
&&
.MARINE...Seas have been slow to subside with the inner buoys
bouncing between 7 and 10 feet. The peaks have become more spaced
out in recent hours, so will keep the SCA in place through 3 PM
with the expectation seas will continue to subside and become more
consistently below criteria shortly thereafter, if not by then.
High pressure and northerly flow over the waters will eventually
develop into a thermal low along the SW Oregon coast as higher
pressure builds inland. Winds will will eventually become a
consistent easterly across the waters Thursday. However, sustained
speeds appear to remain 15 kts or less through the forecast.
Seas subside further tonight and then remain 5 to 7 ft for the
next several days. /JBonk
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 3 PM PST this afternoon for coastal
waters from Cape Shoalwater WA to Florence OR out 60 nm.
&&
$$
www.weather.gov/portland
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Area Forecast Discussion
National Weather Service Pueblo CO
319 PM MST Mon Dec 12 2022
.SHORT TERM...(This evening through Tuesday)
Issued at 316 PM MST Mon Dec 12 2022
...Impactful storm will bring snow, blowing snow, along with strong
and gusty winds for portions of southeast Colorado through tomorrow
morning...
Key messages:
1) Snow and blowing snow will develop over the Palmer Divide late
this evening through early tomorrow morning which may result in high
impacts to travel over this area. Portions of southern El Paso
County and northern Pueblo County could also be impacted.
2) It will become very windy on the backside of this low, with areas
that could potentially reach High Wind Warning Criteria during the
early morning hours through afternoon tomorrow over the eastern
plains.
3) Snow will continue over the high elevations and portions of the
central and eastern plains though the afternoon tomorrow with a few
additional inches possible. Locally higher amounts can be expected
north of the US-50.
Detailed discussion:
Currently and tonight...
Current satellite imagery shows a band of mid and high level clouds
advecting in over the region from the baroclinic leaf associated
with the major shortwave trough, which continues to propagate
towards the region. There have been some strong and gusty SW`ly
winds over much of the plains, which as led to some critical fire
weather conditions this afternoon over portions of the southern I-25
corridor. These winds will continue to subside into the evening
hours over the plains, but remain stronger over the higher
elevations.
There is very low confidence of thunderstorms initiating over our
extreme southeastern portion of the CWA later this evening. If they
do, it will likely be right where the current moisture axis is
located, in the very southeastern portion of Baca County. There is a
very high amount of bulk shear, although higher CAPE values of 1000
J/k or more tend to remain just to the east of the KS/Co border, and
most CAM`s keep potential development east of the border with only a
few having cells develop right along the border and then racing off
to the northeast. That being said, if the moisture axis retorgrades
back to the west, there could be a rogue storm could fire right over
the very eastern fringes of our CWA between 6 and 9 PM.
As the low ejects out over the plains this evening, it will undergo
rapid lee-side cyclogenesis, resulting in a tightening of the
pressure gradient and will produce very strong winds on the backside
of this low as it does. The latest models in recent days have been
trending southward where this low pressure center spins up, and now
the general consensus appears to be somewhere over northeastern
Pueblo County to Kiowa County. The deformation zone will back into
the I-25 corridor and as it does, the TROWAL (Trough of Warm Air
Aloft) will establish itself. As this does, it will allow for some
heavier bands of snow to set up, especially on the northern facing
slopes of the Palmer Divide where there will be some upsloping
aiding in the development of these bands. With winds increasing to
near High Wind Warning criteria for some locations, coupled with the
heavier bands of snow, there could be a brief window of near-
blizzard like, or near white-out conditions, with treacherous travel
possible over portions of the northern I-25 corridor.
The latest HRRR also reflects a heavier band developing due to the
cyclogenesis over northeastern Pueblo for increased upward vertical
motions around the low and higher omega forcing, that will produce a
heavier band later this evening over northern Pueblo County and
extending into Otero County by around 10 PM and lasting until
midnight or shortly thereafter. When looking at soundings for
Pueblo, the HRRR tends to bring in more moisture in the lower
levels, either from mixing down to the surface from the mid levels
or as the trough axis moves over, that results in a very saturated
PBL and mist adiabatically up to the 700 mb level for a window of a
few hours that convectively induced snow hangs out over Pueblo and
Otero Counties. Another element will be possible heavier bands of
snow produced by the TROWAL that will make its way over into the I-
25 corridor over southern El Paso County, as some of the high
resolution models have been suggesting. Lows will continue to drop
into the 20s over the plains, and single digits to teens for high
county after passage of the trough.
Tomorrow...
The TROWAL will continue to produce snow over the Palmer Divide into
the early morning hours, while the wrap around moisture over the
lower Arkansas River Valley continues to provide so additional snow
into the late morning hours. The main story for tomorrow will be the
winds on the backside of this low, along with much colder
temperatures being advected in. Some of the high resolution models
have been depicting winds near High Wind Warning criteria over the
eastern portion of Kiowa County and northern portions of Prowers
County. If models continue to trend towards stronger winds over this
area, the High Wind Watch currently in place may need to be upgraded
to a warning for tomorrow afternoon and evening. Snow will continue
over the higher terrain, but should let up by the afternoon hours
and the wrap around moisture will continue to move east and diminish
as the surface low does with clearing skies. With the cold NNW`ly
winds over much of the plains, temperatures will only max out in the
30s and low 40s for most locations. In the higher terrain, upper 20s
low 30s are expected for the upper Arkansas River Valley and San
Luis Valley. Teens and 20s are expected for highs across the rest of
the high terrain with even some single digits for the fourteeners.
-Stewey
.LONG TERM...(Tuesday night through Monday)
Issued at 316 PM MST Mon Dec 12 2022
Key Messages:
1. High Wind Watch for Kiowa and Prowers counties late Tuesday
night.
2. Winter Weather Advisory for the Sawatch Mountains 8 PM Tuesday
until 5 AM Wednesday.
Tuesday night into Wednesday...
Low pressure system to our Northeast will be making a slow trek to
the east, bringing a Northwest flow to our area. The pressure
gradients will be a little on the tight side towards the northeast
counties in the area. Winds are expected to be gusty with winds 35
to 40 MPH in Prowers and Kiowa Counties. This prompted a High Wind
Watch for Tuesday night.
The westerly flow will also cause some upsloping in portions of the
Continental Divide, which will bring some snow in Lake and Chaffee
counties, necessitating continuation of a Winter Weather Advisory
from Tuesday night into Wednesday Morning.
The area will have a blanket of cloud cover Tuesday night into
Wednesday morning, hindering any radiational cooling. This will
keep overnight low temperatures in check with lows in the teens and
20s in the plains and single digits to teens in the Mountains and
Mountain Valleys. For Wednesday`s highs, downsloping will be
occuring along the mountains adjacent to the I-25 Corridor and the
Palmer divide. This will keep temperatures just a little above
seasonal norms with highs in the 40s in the Plains and 20s and 30s
in the Mountains and Mountain Valleys.
Thursday and beyond...
As the low pressure system to our northeast finally makes its move
to the east, there will be more gusty winds in the eastern counties,
but certainty not high enough to issue highlights for high winds.
The movement of the low will bring a cold front through the area
Thursday night into Friday, bringing winds to a more northerly
component, and dropping overnight low temperatures and daytime high
temperatures close to seasonal norms. The continued influx of cold
air will continue into Friday night as lows will drop even lower to
below seasonal norms. This should hold through the weekend.
As the new work week starts on Monday, a slight warming trend will
occur. For next week, a few models are hinting at a deep trough
pushing through, and with it a cold front bringing in arctic air
crossing the Canadian border, and possibly dipping into our area. If
this occurs, there is a possibility of bitter cold temperatures in
the area with highs only reaching the teens and lows possibly in the
negative single digits or even in the negative teens. This of
course is a worst case scenario, but a development definitely worth
watching.
-Riser
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 316 PM MST Mon Dec 12 2022
VFR conditions are expected to prevail for all TAF sites (KALS,
KCOS, and KPUB) throughout the forecast period. Winds will become
influenced by the approaching low pressure system at all terminals
with a SW`ly direction and gusts up to 29 kts at KALS, and 25 kts at
KCOS and KPUB. Wind will eventually shift to the WNW at KALS, and
out of the NNW at KCOS and KPUB later this evening after FROPA
occurs. This looks to occur around 03Z at KALS and KCOS, and 04Z at
KPUB, but could occur slightly sooner at KCOS and KPUB if the cold
air descends quicker down the Palmer Divide. This will produce very
strong winds for KCOS and KPUB, with gusts as high as 40 kts
possible through the early morning hours. -SHSN is expected to begin
for KCOS around 07Z, and may also impact the terminal of KPUB, which
would reduce VIS down to 5SM and CIGs into MVFR criteria. Some of
the lastest CAM models have also been hinting at a heavier
convective band of snow developing over KPUB between 03Z and 10Z.
VIS could also be further reduced if heavier bands develop, which
would be more likely to occur at KCOS, and may drop into IFR
criteria if it does. Winds will weaken early tomorrow morning at
KALS. Winds will still be very strong and gusty out of the NW at
KCOS and KPUB later in the morning tomorrow, yet begin to become
somewhat reduced in strength. VCSH could still be present at both
KCOS and KPUB through the later part of the morning, towards the end
of the forecast period, but should begin to clear out after 18Z.
-Stewey
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 AM MST Wednesday for COZ058-060.
Winter Weather Advisory until 5 PM MST Tuesday for COZ059-061.
Winter Weather Advisory until 11 PM MST this evening for COZ066.
Winter Storm Warning until 11 PM MST this evening for COZ068.
Winter Weather Advisory from 9 PM this evening to 8 AM MST
Tuesday for COZ084.
Red Flag Warning until 5 PM MST this afternoon for COZ228>230-
232-233-235.
High Wind Watch from late tonight through Tuesday evening for
COZ095-096-098.
&&
$$
SHORT TERM...STEWARD
LONG TERM...RISER
AVIATION...STEWARD