Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/09/22
AREA FORECAST DISCUSSION
National Weather Service Albany NY
919 PM EST Thu Dec 8 2022
.SYNOPSIS...
Clouds gradually clear tonight giving way to a chillier night.
Expect abundant sunshine tomorrow with seasonably cool
temperatures and a slight northerly breeze. Sunshine on Saturday
will slowly fade behind increasing clouds late Saturday into
Saturday night. Our next disturbance arrives Sunday into Sunday
night resulting in a period of snow and light snow
accumulations which may give us slippery travel conditions.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
As of 915 pm, stratus remains trapped over the western
Adirondacks, with a few patches also around the Lake George
Saratoga area and eastern Catskills. Updated sky grids to
reflect a more pessimistic scenario for the next several hours
over the ADKs; otherwise, no changes needed.
Previous discussion...
Cloudy skies this evening will gradually give way to clearing;
however, guidance still suggests clouds linger in western New
England and into parts of the Capital Region and the eastern
Catskills. Temperatures will likely be contingent on cloud
coverage meaning where clouds can clear out (likely
southern/western Adirondacks and Upper Hudson Valley)
temperatures will fall well into the 20s and even upper teens.
Where clouds are stubborn to erode, temperatures will stay a bit
elevated and may only fall into the mid to upper 20s. Adjusted
cloud coverage to better match the high resolution guidance (i.e
HRRR and NAM) which is catching on to the fact that clouds may
linger in parts of the region. Otherwise, northwest winds shift
to the north and decrease to under 5kts. Northerly flow will
help funnel cooler and a much drier air mass into eastern NY and
western New England.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
Quiet and seasonably cool temperatures will ensue for Friday
and Saturday as high pressure centered near the Hudson Bay in
Canada strengthens impressively towards 1045 - 1050hPa. Despite
the center of the high displaced well to our north, it will nose
southward into the Northeast. Under the influence of the high,
expect abundant sunshine tomorrow throughout the day with
northerly winds funneling seasonably cool and very dry air down
the north-south oriented Champlain and Hudson Valley. With a
coastal low off the New England coast, the pressure gradient
overhead will tighten resulting in slightly breezy winds,
especially down the valley, ranging 5 - 10kts with gusts up to
15-20kts at times.
Clear skies and northerly flow continuing to funnel chilly and
very dry air down the valley will likely result in a cold night
Friday night. We trended temperatures downward compared to the
NBM guidance given the clear skies and northerly flow. Normally
clear skies and any kind of wind usually impedes temperatures
from cooling as much as they could but in this situation, the
northerly winds will be advecting in a chilly air mass. Thus, we
felt confident enough to blend in NBM25th percentile and trend
temperatures lower. Dew points in the teens and clear skies
will also assist cooling. We show lows reaching into the mid to
upper teens with near 20 degrees in the valley. The MET/MOS
guidance actually show even cooler values in the low to mid
teens but we did not feel confident to go that cold given the
somewhat breezy winds.
Sunny skies and chilly temperatures continue into Saturday as
the ~1045hPa maintains control. The low subsidence inversion
height will likely limit boundary layer mixing and thus keep
high temperatures seasonably cool with highs in the mid to
upper 30s despite the sunshine. Luckily, the pressure gradient
relaxes so northerly winds will be weaker compared to Friday.
Clear skies Saturday night will gradually fade behind intruding
cirrus clouds from southwest to northeast. Temperatures should
not be as cold as Friday night but still end up chilly from
radiational cooling during the first half of the night
(especially for areas north of I-90 where skies stay clear
longer). Expect lows in the low to mid 20s with upper teens in
the southern Adirondacks where radiational cooling will have a
longer influence.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
Main focus for the long term is a system that will bring a period of
light snow to the region Sunday and Sunday night. Then, the first
half of next week loos tranquil and dry with below normal
temperatures. Another weather system is possible towards the end of
next week, but confidence is low surrounding this system. More
details below...
Long term period begins Sunday with a strong 1040+mb surface high
located over Quebec, with a surface pressure ridge extending
southwards into our region. At the same time, an uper-level
disturbance and associated area of low pressure will be tracking
across the Great Lakes Sunday and over our region Sunday night. This
clipper system should have enough moisture and forcing for ascent
(cyclonic vorticity advection, left exit of an upper jet streak over
our area) to produce a light snowfall for much of the region. It is
still early to talk about snowfall amounts, but a general 1-3/2-4"
snowfall seems plausible. Some rain may mix in in the valleys during
the afternoon, but all areas should see a change to snow by the
evening, so even valley areas could see light snowfall
accumulations. Onset timing of snow looks to range from mid-day in
the western Mohawk Valley to mid to late afternoon in western New
England.
Now, there are still some forecast intricacies that have to be
ironed out. First, as the upper disturbance emerges over the
Atlantic ocean Sunday night, the primary low will weaken and a new
surface low forms off the Mid-Atlantic coast. A Norlun/inverted
trough is expected to extend back from the coastal low towards the
decaying primary low, which will become vertically stacked beneath
the upper low. Locally heavier snow is possible with this feature,
but where exactly this feature sets up remains uncertain, and these
inverted troughs often end up further south than modeled.
Additionally, recent forecast trends have been for more amplified
ridging over the center of the country, which would lead to a
further north track of the surface low. The other feature that will
need to be monitored is a closed upper low diving southwards over
southeast Atlantic Canada on Sunday. If this feature is
faster/further south, then it could force the clipper system to
track further south, potentially limiting snowfall accumulations for
northern areas. At this time, will continue to mention light
snowfall, with a few areas potentially needing winter weather
advisories. Highest confidence in accumulating snow remains for
areas along and south of I-90.
As the system pulls away from our area Monday, a ridge of high
pressure builds back into the region from the north. This will
result in cool but tranquil weather for the first half of the week.
Then, a more impressive storm system may approach the region towards
the end of the week, but due to low confidence will just mention
chances for rain and snow at this point in time.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Through 00z Saturday...A ridge of high pressure building over the
region from the north will result in dry and tranquil weather
through at least the end of the TAF period. FEW to SCT mid-level
clouds are expected through tonight, especially at GFL and PSF, but
still expecting conditions to remain VFR. Tomorrow morning, any mid-
level clouds dissipate during the morning with clear skies through
at least 00z. Winds will be at 5-10 kt from the north/northwest at
all TAF sites tonight, then will become more north/northeasterly at
5-10 kt through the day tomorrow while remaining northwesterly at 5-
10 kt at PSF.
Outlook...
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Moderate Operational Impact. Likely SHSN...SN.
Sunday Night: High Operational Impact. Likely SHSN.
Monday: No Operational Impact. NO SIG WX.
Monday Night: No Operational Impact. NO SIG WX.
Tuesday: No Operational Impact. NO SIG WX.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.
&&
$$
SYNOPSIS...Speciale
NEAR TERM...Thompson/Speciale
SHORT TERM...Speciale
LONG TERM...Main
AVIATION...Main
Area Forecast Discussion
National Weather Service La Crosse WI
518 PM CST Thu Dec 8 2022
.DISCUSSION...(This evening through Thursday)
Issued at 246 PM CST Thu Dec 8 2022
Key Messages:
- Mixed precipitation, while slightly later than previous
forecasts, still on track for late tonight lasting into Friday.
- Light precipitation chances lingering through Saturday. Minimal
accumulations possible with less than 1" of snow to a light
glaze of ice.
- Monitoring the impending system for early/mid next week.
Several details still need to be worked out, but this
rain/snow/wintry mix system has the potential to be fairly
impactful for the region.
This Afternoon:
Water vapor satellite imagery exhibits cyclonic circulation lee of
the Rocky Mountains with an equatorward subtropical jet propagating
it eastward; deadset on the Upper Mississippi River Valley. Quite a
steep low level temperature inversion this morning over the forecast
area evident in neighboring 12Z soundings and the local ARX webcam
trapping boundary surface exhaust. Vad Wind Profiles from
neighboring profiles have anticyclonic flow centered over the hat of
Illinois. As this anticyclonic flow shifts downstream with the
aforementioned progressive upper level pattern, low level warm air
advection ramps up and winds turn southwesterly as the warm sector
of the impending low affects the forecast area. Where the warm
sector is as of 12Z (OAX), a stout low level entrained dry air layer
has been inhibiting initial reflectivities.
Estimated Time of Arrival:
This entrained dry air expected to be in place over our forecast
area as initial precipitation shield traverses Iowa later tonight.
As saturation occurs, temperature profile expected to dip below the
0C isotherm, limiting initial icing impacts. Have decreased
initial freezing rain mentioning and messaging in current
forecast. Also have delayed initial onset/advisory by a couple of
hours with updated guidance.
Increased Snowfall:
According to high resolution ensembles, highest confidence for
snowfall rates above 1"/hr will occur near the IA/MN boundary from
4am in our western counties to 10am in our eastern counties.
Deterministic high res models vary spatially by about a county
thickness, potentially placing this increased snowfall band from
interstate 90 to Nrn Floyd/Chickasaw counties. National Blend snow
ratios have been trending a little low !7:1), therefore have
increased slightly to near 10:1 which is climatologically
average. This band would be tied to the best low level fgen lobe
upstream of the surface low. This band is currently (20Z) shifting
north across northeast NE.
Drizzle/Freezing Drizzle concerns:
As the low passes into Friday morning, upper/mid level dry air
erodes ice nucleation falling out of central Minnesota. Therefore,
have increased and introduced drizzle/freezing drizzle in weather
grids based on high resolution soundings and lack of NBM ice
nucleation. RAP (08.15Z) analysis keeps low level moisture
(0-1.5km) through Friday afternoon, with passing omega providing
moderate forcing. Later into the early evening , subsidence and
passing positive omega likely to inhibit drizzle. Have scooted
drizzle out to the southeast as it erodes from northwest to
southeast.
Tonight`s Storm Summary:
Similar to previous forecasts, anomalous water content, 90th
percentile PWATs, entering the forecast area late tonight and
lasting into tomorrow providing higher snowfalls. The deformation
band and its attendant fgen band will produce increase snowfall
rates from northeast Iowa into southwest Wisconsin late tonight to
early tomorrow morning. Overall snowfall amounts will be a few
inches for our southern counties. Limited residence within the
primary -12 to -18C DGZ zone will limit intensity but we the
second DGZ near 0C will provide big, wet flakes. Will be a wet,
compactful snow so may be difficult for higher measurements to
come to fruition. As the snow exits, drizzle/freezing drizzle
concern increases with loss of ice Friday late morning. Should
fall on already fallen snow across most of the area, ideally
minimizing freezing on roads impacts and again compacting snowfall
limiting higher measurements.
Friday night - Saturday: Light precipitation accumulations
As this system exits the region it fills and lifts into the
general flow pattern. Lingering shortwave trough energy from this
system will result in precipitation chances to continue through
the overnight. The broad isentropic ascent with decent low level
saturation as suggested by forecast soundings will support drizzle
as the main liquid precipitation type. Cannot rule out some
patchy areas of freezing drizzle with surface temperatures below
freezing, but once ice gets reintroduced aloft then snow would be
expected. Precipitation chances increase into the day closer to
30-40% with an increasing frontogenetic forcing as a longer wave
trough slides eastward through the northern plains pushing a
surface boundary through the area. Overall, the accumulations will
be light, especially compared to the previous system. The highest
snow amounts across north central Wisconsin north of I-94 are
still anticipated to be less than 1". Weekend travelers should
still be aware of potential lingering impacts in wake of the
Friday system, but even a light glaze of ice would case issues.
Early/Mid next week: Next impactful system targets the region
While much of the focus has been on tonight`s impactful winter
weather system, there has already been plenty of discussion for an
anticipated impactful system early next week. Looking at the big
picture a low pressure system is slated to slide southward along the
west coast over the weekend. As the associated upper long wave
trough edges through the Rocky Mountains, the surface low developing
on the leeward side begins on its eastward track towards the region
pushing through over midweek.
There are still plenty of specific details (timing, location,
precipitation type) that will be hammered out as the event draws
closer with varying differences among the model guidance. Will be
looking at the model trends to see if there is a strong signal on
which solution appears to be more favored, but will stick with the
blended model guidance as details will continue to be refined over
the next several days. Specifically looking the deterministic GFS
guidance, the 08.12z run has the system track further to the south
and delayed when compared to the previous 2 runs which would hint
for more snow accumulations across the region falling more under the
cold/northern sectors of the system. Now looking at the GEFS
guidance, the probabilities have increased (low end teens to up to
30%) from the previous run across the forecast area for impactful
(4+") snow accumulations. However the deterministic EC remains
fairly similar to the previous run with the low center tracking from
central Iowa through the Wisconsin/Illinois border. The EPS guidance
has tightened the snow total gradient compared to the previous run
keeping the probabilities nearly the same across the region leaving
the highest chances off to the northwest. The track of the system
will play into the precipitation type the area receives from this
messy wintry mix system. Precipitation chances will be on the decline
the further away the system moves heading into the end of the
week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 515 PM CST Thu Dec 8 2022
Low-level clouds will increase in coverage across the area this
evening ahead of a quick-moving system that will bring a round of
snow tonight followed by light freezing drizzle as the system
departs Friday morning. Snowfall onset time has shifted back with
this forecast and so has the transition to freezing drizzle. Will
leave freezing drizzle out of LSE TAF as it falls near the end of
the period, will reexamine the need for fzdz at the 06Z forecast.
Conditions are expected to remain on the cusp of MVFR/IFR at LSE
through much of the night before they deteriorate into IFR early
Friday morning. Visibilities are expected to fall to IFR as a
round of snow shifts over the terminal Friday morning. There is a
40% chance for a brief window of LIFR where snowfall restricts
visibilities further around 12-15Z.
At RST, IFR ceilings are ongoing at the start of this TAF
period. These conditions will remain through the night, though there
is a 35-40% chance of LIFR ceilings between 3-6Z tonight. Upstream
observations at KEST and KMJQ support these chances, but other
terminals upstream are around 5-700 feet ceilings. Ceilings may go
back and forth between LIFR and IFR for a few hours at RST overnight
and have included a tempo group for this chance. Chances are higher
(62%) at RST for visibilities to fall into LIFR than at LSE (40%) on
Friday morning during the heavier snowfall.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from midnight tonight to 3 PM CST Friday
for WIZ032>034-041>044-053>055-061.
MN...Winter Weather Advisory from 9 PM this evening to noon CST
Friday for MNZ086-087-094-095.
Winter Weather Advisory from midnight tonight to 3 PM CST Friday
for MNZ079-088-096.
IA...Winter Weather Advisory from 9 PM this evening to noon CST
Friday for IAZ008>011-018-019-029-030.
&&
$$
DISCUSSION...Peters/JAR
AVIATION...JAW
Area Forecast Discussion...Corrected
National Weather Service Detroit/Pontiac MI
656 PM EST Thu Dec 8 2022
.AVIATION...
Conflicting guidance exists with regards to the persistence of MVFR
stratus across Southeast Michigan tonight and into the day Friday.
MOS is in strong disagreement and much lower on potential for cloud
than both the saturation within the deterministic model soundings
and HREF probabilities for low cloud. Preference sides with a more
pessimistic perspective keeping MVFR OVC throughout the period given
structure of inversion and relatively moist easterly flow. A rapidly
weakening shortwave will push towards Southeast Michigan from the west
after 18Z Friday. Model trends are backing off on the coverage
of activity here in Southeast Michigan. Have pushed the PROB30 group
back in time until after 01Z. East flow of 10 to 20 knots expected
late Friday.
DTW THRESHOLD PROBABILITIES...
* Medium for ceilings at or below 5000 ft tonight through Friday.
* Moderate for ptype as rain/snow mix Friday evening.
&&
.PREV DISCUSSION...
Issued at 307 PM EST Thu Dec 8 2022
DISCUSSION...
The high pressure system located across nrn Ontario and Quebec is
forecast to strengthen during the night. This will reinforce shallow
cold air advection across Se MI and will maintain the deep low level
inversion noted on the 12Z DTX sounding. While there has been some
clearing across NE Lower Mi, the low level flow (now divergent in NE
Lower) will turn more north-northeasterly off Lake Huron. The added
lake moisture flux under the inversion should sustain ample stratus
through the night, limiting the degree of nocturnal cooling to the
upper 20s/low 30s.
An upper wave now over the central Rockies is forecast to move to
the WI/IL border region by early Friday afternoon, then track across
Lower Mi late Fri afternoon and evening. While there is strong model
support showing this wave remaining a compact mid level low as it
approaches the western Great Lakes on Friday, there is a decent
spread among various model solutions in depicting how quickly this
wave dampen/shears apart as it slides across Lower Mi late Fri/Fri
night. The NAM/Canadian/ARW are faster in dampening this wave. The
result is that these solutions weaken the ascent significantly by
the time the mid level height falls advance into Se Mi. So the
moisture transport and ascent is not adequate enough to overcome the
wedge of mid level dry air associated with the large anticyclone to
the northeast, thus barely bringing any precip at all to Se Mi.
The GFS, ECMWF and latest HRRR are slower in weakening this wave,
which results in a more compact system traversing srn Mi. These
systems maintain a decent moisture surge into Se Mi within a layer
of good mid level system relative isentropic ascent. This ascent
would overcome the mid level dry air and result in a period of
precipitation late Fri afternoon through Fri evening. Noting a
weaker trend in both the 12Z GFS and ECMWF, the afternoon forecast
will not veer too significantly from the previous one with respect
to the better precip chances being southwest of a Saginaw to Mount
Clemens line. Overall, precip chances will simply be lowered
slightly. Obviously, even though this event is only 24-32 hours out,
there is still a fair amount of model spread over Se Mi and
additional forecast adjustments are likely. Based on forecast wet
bulb zero heights on GFS soundings, precip type will be mainly wet
snow. Warm ground temps, boundary layer temps expected to hold in
the 30s and compaction still only justifies minimal snow accums (if
any) for late Friday at this time.
Mid level subsidence will ensure a dry (albeit cloudy) day on
Saturday. Another mid level wave forecast to emerge in the lee of
the central Rockies is forecast to evolve into a closed mid level
circulation as it rotates into the Great Lakes Sat night into
Sunday. Expect there will also be additional model adjustments with
this system over the next few model runs. Current indications are
that the better moisture transport will be deflected south of the
state. Respectable mid level height falls will still however warrant
precip chances. There will not be as much wet bulb cooling
influences from the high parked over nrn Quebec with this second
system. So boundary layer temps within this event will be more
favorable of a rain/melting snow mix, with a little colder thermal
profiles favoring all snow across the Saginaw Valley and thumb
region (with some minor accumulations possible).
MARINE...
A high pressure system will wash out across western Quebec tonight
with a secondary high pressure system then filling in across Ontario
through Friday morning. This will bring continued light winds for
the remainder of the day. A low pressure system is then expected to
travel from the Plains into the Ohio Valley through tomorrow
afternoon and evening, which will strengthen the pressure gradient,
resulting in an uptick in wind speeds and gust potential, between 20
to 25 knots. The placement of the low will reinforce easterly flow
which will bring elevated wave action to the shorelines, especially
across Lake Huron. A Small Craft Advisory for waves will be likely
for portions of Lake Huron and Lake Erie Friday evening into
Saturday as a result. Wind speeds gradually diminish late Saturday
into Sunday as low pressure vacates the region.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....CB
DISCUSSION...SC
MARINE.......AM
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Wilmington NC
959 PM EST Thu Dec 8 2022
.SYNOPSIS...
Surface high pressure will prevail through early next week,
although a few upper disturbances will bring a few chances of
rain. A stronger storm system could then impact the area for
the middle of next week.
&&
.UPDATE...
MVFR ceilings hold over the area with the exception of some
clearing along Horry`s coastal terminals. Obs show MVFR ceilings
around, and these should start to fill in within the coming
hours. Precip to the west will also start to move into the area
within the next couple hours. Otherwise, forecast appears to be
on track.
&&
.NEAR TERM /THROUGH FRIDAY/...
E-W oriented surface front remained located near CHS early this
afternoon, with a shallow and "relatively" cool airmass in place
across the CWA. The frontal boundary may waffle north into
southern Georgetown and Williamsburg counties this evening and
overnight, which would have implications the diurnal curve in
that area. Otherwise, moisture will begin to overspread the
surface wedge this evening, with potential for light showers
increasing from west to east, beginning 02-03Z. Precip will be
weakly forced, and latest HRRR suggests a possible lull in
activity Friday after 12-13Z, before additional overrunning
showers start spreading in from the west after 20Z.
Will also note that long period (15 sec) swells arrive north of
Cape Fear just after 12Z Friday, and spread to the NE SC coast
during the afternoon. This will produce rough surf, particularly
north of Cape Fear, with some 5 ft breaking waves. Criteria for
a High Surf Advisory is 6 ft breakers, and we will be on the cusp
along the beaches of New Hanover and Pender counties.
Lows tonight generally within a degree or two of 50 north, to mid
50s south, with the caveat that warmer air could slip northward
into southern Georgetown and Williamsburg counties at some point.
Highs Friday will remain a tad on the cool side of climo, ranging
from upper 50s inland to around 60 southern and eastern sections,
under mostly cloudy skies and the influence of scattered light
showers.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
Forecast confidence is moderate to high this period.
Inland high pressure at the surface centered north of the area will
prevail through the period while some upper disturbances move
through the generally zonal flow aloft. Some light rain will be
possible Friday night into early Saturday with a bit better
chances/amounts Sunday, possibly starting late Saturday night
and even lasting into early Sunday night. High temperatures
should stay below normal while low temps stay above normal.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
Forecast confidence is moderate to high through Tuesday night, then
low to moderate thereafter. The period should start off dry with
high pressure prevailing, except for a few lingering light showers
in SC early Monday. The next rain chances could come as early as
Wednesday across inland areas as deeper moisture begins to encroach
on the area ahead of the next storm system, although it appears the
best chances should be Wednesday night into Thursday as a potent
storm system likely impacts the area. Some locations could pick up
an inch or more. Also will need to monitor for a low-end severe
storm risk given the likely high shear/low instability setup.
Temperatures should be near to below normal until Wednesday night
with the coldest night being Monday night when some of the normally
colder inland locales possibly get to near freezing.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Ceilings MVFR to start out the period with showers expected to move
in at KFLO/KLBT from the west around 05Z. IFR is expected for
KFLO but confidence was lower for the NC sites so decided to
keep MVFR conditions for KLBT at this time. IFR ceilings could
be possible and conditions will continue to be monitored as this
cloud deck moves in. For KMYR/KCRE, IFR ceilings and precip are
looking to arrive closer to 10Z. MVFR is then expected to
persist into Friday morning.
Extended Outlook...Moderate confidence Fri night through Tue.
Restrictions mostly from low clouds Fri night (possibly into early
Sat), especially SC terminals. The risk of restrictions increases
Sat night into maybe early Mon due to low clouds and some rain. VFR
should then return through Tue.
&&
.MARINE...
Through Friday: Surface front was laying just south of the South
Santee this afternoon and is expected to remain quasi-stationary
through Friday. The result will be continued NE flow across the
waters through the period. The gradient will tighten up overnight
with surface pressure rises across the interior Carolinas, and
winds will surge as a result. A Small Craft Advisory will be raised
with this forecast package, as mixing should produce gusts of 20
to 25 knots after 09Z. Winds will begin to diminish after 15Z
Friday, but seas will stay up through the day, as NE wind waves
blend in with a long period (up to 15 sec) E swell.
Friday night through Tuesday: Confidence is moderate through the
period. High pressure to the north should prevail most of the period
keeping winds mainly from the north/northeast 20 kt or less. Small
Craft Advisory conditions likely into early Saturday for at least
part of the area, mainly due to moderate swells from a distant
Atlantic low. SCA conditions could return Monday/Tuesday, at least
for the SC waters.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory from 1 AM Friday to 1 PM EST Saturday for
AMZ250-252-254-256.
&&
$$
SYNOPSIS...ILM
UPDATE...LEW
NEAR TERM...CRM
SHORT TERM...RJB
LONG TERM...RJB
AVIATION...LEW
MARINE...SHK/CRM
Area Forecast Discussion
National Weather Service Indianapolis IN
931 PM EST Thu Dec 8 2022
.Forecast Update...
Issued at 929 PM EST Thu Dec 8 2022
Surface analysis this evening shows high pressure in place over
Ontario, allowing a cool easterly surface flow across Central
Indiana. Low pressure was found over NB, along with an associated
warm front that stretched across MO. Radar mosaics show an area of
associated precipitation over IA as earlier rain over Central
Indiana has exited to the east. GOES16 continues to show abundant
cloud cover across Central Indiana as the cool dirty easterly flow
continues. Temperatures remained in the lower 40s and dew point
depressions remained low. This will be favorable for continued cloud
cover and patchy fog as we have seen the past several nights.
Models fail to show much in the way of forcing aloft overnight as
the warm front and associated low is expected to approach on for
Friday. Forecast soundings and time heights show continued lower
level moisture through the night. Models do hint at some moisture
pushing into western Central Indiana after 10Z…but given radar
trends and the progression of the low, better forcing should arrive
after 12Z Fri. Thus will keep the forecast mainly dry tonight with
lows mainly around 40.
&&
.Short Term...(This evening through Friday)
Issued at 255 PM EST Thu Dec 8 2022
The widespread light rain, with the back edge lined up back to the
Ozarks per radar mosaic, will continue to move over areas south of I-
70 into the evening. The rain was associated with isentropic lift to
the north of a Tennessee Valley quasi-stationary front and impulses
in fast southwest flow aloft. The somewhat heavier rain was limited
to areas south of the Ohio River associated with moisture
convergence closer to the stalled, northward sloping front. This
should remain the case through the evening. Isentropic support will
be ending early and lead to short mostly dry period overnight save
perhaps some patchy drizzle. That said, moisture will be
plentiful under a steep inversion which will lead to some more
patchy fog and low stratus overnight.
Then, an upper low will track from Nebraska to Iowa tonight and Lake
Michigan late Friday. Meanwhile, an occluded frontal system
associated with the upper low will move across central Indiana on
Friday and bring more rain to mainly northern sections Friday. 125+
knot jet streaks may also contribute to a few heavier pockets of
rain. Went likely PoPs north of I-70 with chance Pops over southern
sections. Combo of synoptic lift and moisture will keep the clouds
around and limit diurnal temperature curve with overnight lows
tonight in the upper 30s to middle 40s tonight and afternoon highs
Friday in the middle 40s north to middle 50s south.
&&
.Long Term...(Friday night through Thursday)
Issued at 255 PM EST Thu Dec 8 2022
Extended periods synoptic overview...
Pattern adjustments appear to be the general theme for the extended
periods, kicking off Friday night as some mid-lvl height rises are
progged to arrive for the Mid-Missouri Valley. Items worth taking
notes on will be a beefy lobe of vorticity progged to dig south of
the Pac-NW Saturday, which will help to create greater longwave
volatility in the later periods or more specifically Tuesday into
Wednesday. As the aforementioned trough gets its act together and
begins to drift east, the response from the downstream wave will be
modest return flow from GOMEX. Once this system arrives in the Ohio
Valley sometime mid/late next week, the cold conveyor appears to
become active with a northwest flow.
Friday night through Sunday... Guidance has been relatively
consistent with height rises for the Ohio Valley Fri ngt in the wake
of a weak mid-lvl shortwave lifting into Ontario. Ensembles have
been indicating some anti-cyclonic flow in the lower levels, which
should assist with providing a period or two of benign weather
Saturday; however, as noted earlier with the volatility within the
longwave pattern, there is still a quasi-zonal orientation to the
upper level flow. This is supportive in what some of the operational
solutions are indicating, with precip chances quickly returning
Saturday evening. The caveat will be how quickly the lower levels
can moisten backup, given the lack of omega and a conveyor to bring
ascending parcels to help kick-off the precip. There will be
stronger ascent to parcels further south across KY/TN perhaps
southern IN, but confidence just isn`t there to bring higher POPs
further north at this time. This could easily be one of those setups
where clouds return from a weak southeasterly low-level flow and
provide a thick stratus shield inhibiting the surface from warming.
Weak boundary pushes east across the region Sat eve, with some weak
cold air advection returning from the leading edge of an elongated
surface ridge. This could be setting the stage for trapped low-level
stratus early Sun, but more likely late Sun into Mon morning. Think
an ideal inversion setup in this case, which could allow for a foggy
start to next week given the lack of a gradient in the lowest levels
and also minimal mixing to scour out the trapped stratus layer.
Monday through Tuesday... A few days ago the focus was turning
towards Tue, and while that still appears to be an interesting
setup, its the setup prior that will dictate how the later periods
will unfold. Ensembles membership has continued to highlight with
minimal spread/noise in a robust trough beginning to pivot east
through the Southern Rockies Mon aftn/eve. This will result in
downstream strong meridional flow from the Western GOMEX pointing
due north through ArkLaTex into the Missouri Valley Mon ngt. This
strong ascent to parcels coupled with contrasting airmasses set the
stage for a very dynamical setup for Tue/Wed periods. Quick
amplification to heights across the Ohio Valley has been a trending
feature Tue, as the downstream shortwave over Eastern Quebec likely
slows the forward progression the next system. Thus leading a nudge
towards Tue ngt/Wed as the more favored timing for the possible
convection/heavy rainfall concerns.
Wednesday through Thursday... Well developed shortwave continues to
be the main focus for Wed somewhere east of the Rockies. There is
some uncertainty with respect to the placement, given the equally
robust downstream wave exiting the Northeast CONUS. Considerable
instability still appears to be the main course, but
placement/timing is still the elusive element. We are still somewhat
confident that convection and heavy rainfall are possible given the
current track of a surface feature displaced to the northwest of
Central Indiana. This does appear to be a consistent feature, thanks
to the slower evolution and arrival.
Confidence in heavy rainfall Wednesday...medium.
&&
.Aviation...(00Z TAF Issuance)
Issued at 555 PM EST Thu Dec 8 2022
Impacts:
- MVFR or worse conditions are expected for much of the TAF period.
Discussion:
A wave of precipitation was exiting central Indiana early this
evening. This will bring a brief break of precipitation as a frontal
boundary continues to linger south of Indiana. Extensive lower level
moisture is expected to persist overnight along with light northeast
surface flow ahead of the approaching low. This will lead to
ongoing MVFR cigs and visibilities this evening and overnight.
An area of low pressure is expected to push across Central Indiana
on Friday, led by a warm front pushing across the state by late
morning and early afternoon. HRRR shows an associated band of
showers expected to push across the TAF sites. As this passes
continued MVFR or worse conditions will be expected. Forecast
soundings continue to suggest abundant lower level moisture as these
features pass.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...Puma
Short Term...MK
Long Term...Beach
Aviation...Puma
Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
741 PM PST Thu Dec 8 2022
.SYNOPSIS...08/145 PM.
A weak weather system will bring light showers to the Central
Coast tonight into very early Friday. Then a stronger system will
bring periods of heavy precipitation to all areas Saturday
afternoon through Sunday night. Lingering showers are possible
Monday, otherwise a drying trend with below normal temperatures is
expected through the middle of next week.
&&
.SHORT TERM (THU-SUN)...08/740 PM.
***UPDATE***
Another benign weather day today with partly cloudy skies. Max
temps across csts/vlys again came in within 2 degrees of 60 today
or 5 to 10 degrees blo normal.
The latest NAM and HRRR are downplaying the tonight`s trof even
more than the earlier runs and its doubtful that SLO county will
see anything more than a sprinkles.
00Z does not deviate much at all from 12Z runs and all systems are
green and go for a moderate rain event over the weekend.
Will issue a forecast update to reduce SLO county POPs tonight and
Friday morning.
***From Previous Discussion***
A weakening cold front is just offshore and will be moving inland
tonight. Hi res models continue to show further weakening
overnight with only a very light amount of rain at best and
generally just across the northwest portion of SLO County.
Elsewhere, just an increase in clouds but no rain. The remainder
of Friday will be quiet with a few clouds but also plenty of
sunshine. Temps will continue to be on the cool side with highs
4-8 degrees below normal.
The fun begins Saturday as a cold 522dam upper low drops out of
the Gulf of Alaska. Models have been speeding up the arrival of
pre-frontal showers the last few runs and there could be rain
reaching the Central Coast as early as sunrise Saturday and into
LA County by noon Saturday.
As the low and associated cold front continues to march southeast
towards California later in the afternoon, southerly winds will
start increasing and good diffluence aloft will generate strong
upward motion, which in turn will increase rain rates. That
combined with 850mb southwest winds of 50kt generating additional
orographic enhancement near the coastal mountains will push rain
rates up to at least a half inch per hour and locally higher. The
peak of the storm still appears to be during the overnight hours
Saturday night into Sunday morning when the best low level
forcing and jet dynamics come together. Models are still showing
a fairly rapid movement through the area so the period of heaviest
rain should be limited to a 3 to 6 hour period in any one area.
By Sunday morning the steady rain should be through LA County with
still a fair amount of shower activity behind it. While the air
mass isn`t particularly unstable an isolated thunderstorm or two
can`t be ruled out. So while rain rates will be quite high during
the peak of the event, no significant flooding or debris flows are
expected. Showers will continue behind the front but will be
decreasing with time Sunday into Sunday night.
As is typical with strong low level jet scenarios like this snow
levels will jump quite a bit as the heavy precip approaches.
Latest models are showing snow levels between above 7500 feet for
a large portion of this event, meaning significant snow
accumulations will be confined to very high elevations. Snow
levels will lower rapidly Sunday into Sunday night but showers
will be short lived with minimal impacts at that point. One
exception may be the Grapevine on Interstate 5 where by late
Sunday night there is a chance of light accumulating snow at pass
level which could lead to travel delays.
Southerly winds will be picking up quickly Saturday ahead of the
front and advisory level winds are likely across interior SLO
County, the Antelope Valley, and the mountains. It will be breezy
across the coast and valleys as well but likely below advisory
levels.
.LONG TERM (MON-THU)...08/141 PM.
The upper low will be over the northern San Joaquin Valley Monday
with still ample moisture and forcing over southern California to
squeeze out scattered showers just about anywhere. At the very
least it will be a cool day with highs mostly in the 50s at lower
elevations and 20s and 30s in the mountains.
Dry weather expected Tuesday through Thursday with slowly warming
temps, but still generally below normal through the period.
Overnight lows will likely drop to near or below freezing in many
valleys and even some coastal areas.
&&
.AVIATION...08/2315Z.
At 23Z at KLAX, there was no marine layer or marine inversion.
60 percent chance of LIFR conditions at KPRB by 10-15Z Fri.
Light -SHRA with MVFR ceilings possible 12-18Z Fri at KPRB KSBP
(30%), and KSMX (20%). SCT015-25 likely at all other sites 12-18Z
Fri, but without an inversion the chance of ceilings is only
20-30%. High confidence in generally light winds.
KLAX...Moderate confidence in VFR through Friday, except for a 30%
chance of MVFR ceilings 12-18Z. Lighter than usual winds expected,
with high confidence in NO significant east winds.
KBUR...Moderate confidence in VFR through Friday, except for a 30%
chance of MVFR ceilings 12-18Z. Lighter than usual winds expected.
&&
.MARINE...08/643 PM.
For the Outer Waters, moderate to high confidence in current
forecast. Tonight through Friday afternoon, high confidence in
winds and seas remaining below Small Craft Advisory (SCA) levels.
For Friday night and Saturday, high confidence in southerly winds
increasing to SCA levels as well as seas with a 60-70% chance of
Gale force winds developing Saturday afternoon across PZZ670/673.
The strong southerly winds will continue Saturday, before
shifting to the west and northwest on Sunday with SCA level
winds/seas continuing. For Monday and Tuesday, seas will gradually
diminish below SCA levels, but there will remain a 50% chance of
SCA level winds.
For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. Tonight through Friday night,
high confidence in winds and seas remaining below SCA levels.
On Saturday and Saturday night, high confidence in SCA level
southerly winds and seas with a 50-60% chance of Gale force winds.
On Sunday, high confidence in SCA-level westerly winds and seas.
For Monday and Tuesday, high confidence in winds and seas
remaining below SCA levels.
For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. Tonight through Saturday
afternoon, high confidence in winds and seas remaining below SCA
levels. For Saturday afternoon and night, high confidence in SCA
level southerly winds with a 40% chance of SCA level seas. On
Sunday, winds will shift to a westerly direction with high
confidence in continued SCA level speeds and the 40% chance of SCA
level seas. On Monday and Tuesday, high confidence in winds and
seas remaining below SCA levels.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Gale Watch in effect from Saturday afternoon through Saturday
evening for zones 645-670. (See LAXMWWLOX).
&&
$$
PUBLIC...MW/Rorke
AVIATION...Kittell
MARINE...RAT
SYNOPSIS...MW
weather.gov/losangeles
Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox
Area Forecast Discussion
National Weather Service Lubbock TX
527 PM CST Thu Dec 8 2022
...New AVIATION...
.SHORT TERM...
(This evening through Friday)
Issued at 220 PM CST Thu Dec 8 2022
Early afternoon surface analysis showed a surface cyclone moving
east across the Oklahoma Panhandle, bringing breezy westerly winds
to the CWA this afternoon. These downslope winds will result in
drying and warming over the region through today. Temperatures are
still on track for highs in the 60s on the Caprock and low-70s off
the Caprock.
Upper-level water vapor imagery and RAP analysis showed a shortwave
trough moving across the Intermountain West. A weak "cold" front is
expected to push through the region late this evening, mainly
bringing slightly drier surface conditions to the area. However, a
surface cyclone is expected to form over southeastern Colorado,
resulting in moisture being advected into the CWA through the night,
helping to increase precipitable water values to near the daily max
for the area once again. This could result in patchy fog over parts
of the Rolling Plains early tomorrow morning. As the aforementioned
upper trough moves into the Plains, moist isentropic ascent is
expected to increase over our region, bringing the potential for
light rain over the forecast area tomorrow afternoon through the
evening. GKendrick
&&
.LONG TERM...
(Friday night through next Wednesday)
Issued at 220 PM CST Thu Dec 8 2022
The next shortwave expected to impact the area tomorrow night can
already be seen on mid-level water vapor analysis entering the
Pacific Northwest. With a surface high over the GoM, south
southeasterly winds will give way to low level moisture advection
across Texas. Weak lift ahead of the shortwave, along with a narrow
window of Pacific moisture will lead to the continued chance for
some rain showers across portions of the Rolling Plains and
southeast Panhandle into the evening hours tomorrow. However, there
is a dry layer around 700-600mb, which will keep any precipitation
light in nature with mostly light amounts of accumulation expected.
With the abundance of low level moisture tomorrow night, a low deck
of stratus is expected to persist through the night before clearing
out from northwest to southeast following a weak frontal passage
Saturday morning. A few additional showers may linger across the
southern Rolling Plains Saturday morning before the dry air behind
the front filters in across the forecast area.
Another weak and dry shortwave will follow in behind the previous on
Saturday into Saturday night, with little to no affect to the
forecast. Therefore temperatures are actually expected to warm
slightly through the weekend and into Monday with highs approaching
the lower 70s off the Caprock. The next system will creep into
northern Cali Sunday with surface troughing developing leeward of
the Rockies and breezy southwest winds returning to West Texas. By
Monday, the upper closed low will be entering the Great Basin region
with the lee trough deepening into a surface low over eastern
Colorado. A tightening of pressure gradients across the area
combined with daytime heating and momentum transfer of 40 knot 700mb
winds to the surface will allude to breezy to windy conditions
Monday. In addition, there is a slight chance for rain showers to
return across the southeast Panhandle and Rolling Plains Monday with
southerly surface winds pulling in Gulf moisture across much of
eastern and central Texas combined with isentropic lift ahead of the
upper low. Winds will remain breezy overnight with the approaching
system, along with the deepening surface low in the Central Plains.
By Tuesday morning the Pacific front will move through with windy
west surface winds expected throughout the day with the passing
upper low to the north and 100 knot 500mb jet axis overhead. Some
model discrepancies still exist on the exact location of the passing
jet axis, but overall the trend is windy conditions following the
Pacific front Tuesday. Cooler air will begin to also filter in
Tuesday with highs in the 40s along the Caprock and 50s off the
Caprock. The cold front is then expected Wednesday with an
additional surge of cool Canadian air in the 40s and lower 50s
across the area. In addition to cooler highs, overnight temperatures
by the middle of next week will dip into the 20s. With breezy
overnight winds, morning wind chills may also be in the single
digits to teens across portions of the area.
&&
.AVIATION...
(00Z TAFS)
Issued at 520 PM CST Thu Dec 8 2022
VFR through the night will give way to MVFR CIGs by morning as
deeper moisture spreads W-NW across the terminals. CDS should see
a brief bout of IFR CIGs and maybe some fog toward daybreak
before widespread MVFR decks arrive later in the morning. Some
SHRA are likely at times from LBB-PVW by the afternoon.
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...10
LONG TERM....11
AVIATION...93