Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/23/23
Area Forecast Discussion
National Weather Service Corpus Christi TX
520 PM CST Fri Dec 22 2023
...New AVIATION...
.SHORT TERM...
(Tonight through Saturday night)
Issued at 336 PM CST Fri Dec 22 2023
Moist air mass in place as GOES imagery of total precipitable
water shows values around 1.5 inches from the Coastal Bend into
the Victoria Crossroads. Scattered showers between CRP and VCT
are in a region of weak low level convergence according to the
latest MSAS analysis with a weak mid level short wave trough
providing assistance for lift. This shower activity will linger
over the coastal waters into the Victoria Crossroads early this
evening, then diminish as the short wave trough exits to the east.
With high boundary layer moisture and relatively light low level
southeasterly flow, environment looks favorable for fog formation
tonight. SREF probabilities for visibility below 1 mile range from
70-90 percent over the inland Coastal Bend into the eastern Brush
Country. HREF forecast for dense fog (vsby 1/4 mile) shows a
60-80 percent probability in this region for early Saturday
morning. Will show areas of fog after midnight in this region with
patchy fog for the remainder of the area. Looks like a good chance
there will be an advisory issued for dense fog overnight.
The mid level low will move into Arizona tonight and over the
Rockies east of the Four Corners region by Saturday afternoon.
Low pressure strengthening over the southern high plains ahead of
this system will lead to increasing onshore flow. This will bring
in deeper moisture to the region on Saturday with PW values up to
1.6-1.7 inches. This will be near 2 standard deviations above
normal for this time of year. As the upper low moves through the
Rockies Saturday, a strong upper level jet streak will move into
central Texas with the south Texas region in the favorable right
entrance region of the upper jet leading to increasing upper level
divergence. With moisture influx Saturday, instability will be a
little better with HRRR model showing MLCAPE values slightly above
1000 J/kg from the eastern Brush Country into the coastal plains
Saturday afternoon. Large scale lift will enter the region during
the afternoon and expect an increase in coverage of convection to
numerous showers with scattered embedded thunderstorms that will
linger into the evening over the northeast part of the area.
As the upper jet/short wave trough moves east late in the evening,
there could be a decrease in convection. But a very impressive
upper level jet moving across northern Mexico will approach south
Texas late Saturday night with the left exit region/increasing
upper divergence moving into south Texas. With increasing lift,
expect convective trend will show another uptick during the
overnight hours over the coastal waters into Victoria Crossroads.
WPC shows a marginal risk for excessive rainfall over the Victoria
area for the period Saturday into Saturday night.
&&
.LONG TERM...
(Sunday through next Thursday)
Issued at 336 PM CST Fri Dec 22 2023
Deterministic NWP models continue to predict that an upper level
disturbance, and associated weak surface boundary, to move across
the region Sunday and combine with above normal moisture (PWAT per
the GFS) to generate isolated/scattered convection over the Coastal
Plains. Continue to expect subsidence/drier conditions to commence
Sunday night/Monday as the foregoing disturbance moves east.
However, the GFS/ECMWF predict a developing quasi-stationary upper
low centered over the central Plains, with disturbances rotating
around it. The combination of these disturbances, isentropic lift
over the CWA (GFS 300K level as proxy), and/or the proximity of a
250-mb jet streak, will contribute to partly/mostly cloudy
conditions over the CWA Monday/Tuesday. However, no precipitation
expected during this period owing to dry conditions (below normal
PWAT values per the GFS/ECMWF.) Less cloud cover expected afterward.
Concur with NBM prediction that cool/cold early morning conditions
will occur Tuesday through Friday. Concur with the NBM that lows in
the mid 30s will occur over portions of the northern Brush
Country/Victoria Crossroads early Thursday morning owing to very dry
conditions (lower GFS/ECMWF PWAT values than Tuesday/Wednesday
morning) and mostly clear skies. P-ETSS output suggest that minor
coastal flooding may occur during the high tidal cycles
Sunday/Monday. Low minimum relative humidity values Monday through
Friday over at least the Rio Grande Plains/Brush County. However,
Elevated fire weather conditions are not expected as wind speeds
remain below the threshold.
&&
.AVIATION...
(00Z TAFS)
Issued at 512 PM CST Fri Dec 22 2023
MVFR to VFR ceilings are expected this evening with periods of
rain possible across South Texas. There could be some isolated
thunderstorms over the Victoria Crossroads and along the coast,
but confidence in thunder is very low. Low stratus and fog are
expected to develop overnight, with dense fog possible. LIFR/IFR
ceilings and visibility is possible for the inland areas. Expect
conditions will begin to improve by mid-morning as showers begin
to redevelop along the coast and the Victoria Crossroads, with
conditions improving to MVFR/VFR for the inland Coastal Plains and
points west in the early afternoon.
&&
.MARINE...
Issued at 336 PM CST Fri Dec 22 2023
A weak easterly flow this evening will become southeasterly
overnight. Isolated showers are expected to diminish by late this
evening but redevelop toward daybreak. Southeast winds will be
weak to moderate Saturday and Saturday night. Showers are expected
to increase to numerous with scattered thunderstorms Saturday
afternoon as an upper level disturbance moves across south Texas.
Scattered to numerous showers and scattered thunderstorms will
continue into Saturday night as another disturbance approaches
from the west.
Scattered to numerous showers and isolated/scattered thunderstorms
anticipated for Sunday in response to an upper disturbance/corresponding
frontal boundary. Drier Sunday night/Monday as the boundary moves
offshore/surface high pressure builds. Moderate offshore flow
expected Monday/Monday night. No precipitation expected
Monday/Tuesday. However, an upper level disturbance (GFS/ECMWF
upper jet dynamics and 700-300 Q-vector convergence) is predicted
to move across the region Wednesday, and combine with moisture
(near normal PWAT values) to generate isolated showers. Drier
Thursday/Friday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 64 77 64 78 / 20 60 20 10
Victoria 61 75 62 75 / 30 70 60 60
Laredo 62 75 61 78 / 10 20 20 0
Alice 61 78 62 80 / 10 60 10 10
Rockport 63 74 63 75 / 20 60 30 20
Cotulla 62 74 60 78 / 10 30 20 10
Kingsville 62 78 64 79 / 10 50 10 10
Navy Corpus 66 75 66 76 / 20 60 20 10
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
SHORT TERM...TMT
LONG TERM....WC
AVIATION...LS/77
Area Forecast Discussion
National Weather Service Des Moines IA
542 PM CST Fri Dec 22 2023
...Updated for the 00z Aviation Discussion...
.DISCUSSION.../Tonight through Friday/
Issued at 333 PM CST Fri Dec 22 2023
Key Messages:
- Potential for areas of Dense Fog tonight into Saturday morning.
- Widespread rain on Sunday.
- Cooler trend for Christmas Day. There is some potential for
wintry precipitation across parts of western Iowa.
Widespread stratus with some areas of fog continue across much of
central Iowa this afternoon. A few senors are registering 1/4sm or
less visibilities in fog in some areas though webcams in those areas
suggest the visibility is greater than those measurements. The rain
over the southeast is diminishing but patches of drizzle are
beginning to appear on radar in central Iowa though likely
overshooting any drizzle that is over 40 miles from the radar.
Fog is the first order of business for tonight. The aforementioned
locally dense fog measurements this afternoon will likely persist
into the overnight though headlight refraction and the darkness will
amplify visibility restrictions. The HRRR and other high resolution
solutions are again greatly over done with the dense fog expansion
under the stratus field. The stratus has been eroding through the
Missouri Valley over western Iowa this afternoon with the clearing
line gradually advancing eastward. This area should quickly fill in
overnight with dense fog and some of this may reach parts of the
forecast area. With the current reduced visibilities north and
greater potential for widespread dense fog later tonight, will be
issuing a dense fog advisory along with adjacent NWS neighbors in
those areas tonight into Saturday morning. Confidence in widespread
dense fog elsewhere is not high enough for headlines and any
headlines will have to be of a short lead time.
Otherwise, mid-level moisture is continuing to dry this afternoon
and into the overnight in the wake of the passing upper level short
wave that moved through earlier today. While some patches of drizzle
could linger, especially east overnight, the stratus field depth
should be thinning and lower the drizzle potential. There is the
potential for some of the stratus to thin enough for some peaks at
the sun later Saturday morning and into the early afternoon. Clouds
will be on the increase though as mid-level theta-e advection kicks
in followed by a strong surge of Gulf moisture from the south later
in the day. Enough saturation will occur, especially after midnight
Saturday night over the west for precipitation chances to increase
then spreading into central and eastern Iowa on Sunday. Sunday will
be quite wet for much of the forecast area and event totals with
widespread 1 inch plus totals are still looking likely. There is
some embedded thunderstorm potential. Lapse rates are mostly
saturated adiabatic but static stability is low and it won`t take
much of a nudge to get some thunder.
The phasing of the strong northern and southern stream systems and
an eventually merge into an intense upper low is still suffering for
temporal and spatial issues that probably won`t be resolved well
through the next 48 hrs though this should gradually get better with
time. The overall colder trend of colder air entering the system
faster as the northern stream short wave dives south and siphons
more cold air from the north before being cut off by the upper
ridge. This in addition to any dynamic cooling taking place with the
upper low evolution and associated vertical ascent. Finally the warm
conveyor wrapping around the north side of the system will have a
significant impact as well on how this storm system evolves. For a
broad expectation, a cold front will undercut the warm air on the
south side of the system which will lead to cooler conditions
Christmas Day than previously advertised. There will be a transition
to snow somewhere on the west/southwest side of the system that
could include good dendritic growth. How far east this gets into
Iowa is certainly in question but much of central and eastern Iowa
should remain on the warm precipitation side of this. Have
introduced more snow west with some accumulations by late Christmas
Day. More widespread light snow could occur on Tuesday. Mid next
week should be near to above normal with a stronger push of cold air
still on track to arrive late next week.
&&
.AVIATION.../For the 00Z TAFS through 00Z Saturday evening/
Issued at 542 PM CST Fri Dec 22 2023
Widespread IFR to LIFR conditions are expected overnight with
restrictions in both visibility from fog and very low ceilings.
These poor conditions are expected to persist until Saturday
morning before some gradual improvement begins. MVFR to VFR
conditions are expected by the end of the period. Surface winds
remain light and somewhat variable overnight but increase from the
southeast on Saturday.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory from 11 PM this evening to 11 AM CST Saturday
for IAZ004>006-015-023.
&&
$$
DISCUSSION...Donavon
AVIATION...Cogil
Area Forecast Discussion
National Weather Service Hastings NE
502 PM CST Fri Dec 22 2023
.KEY MESSAGES...
- Patchy dense fog is possible again tonight, mainly south and
east of the tri-cities.
- Storm system arrives Saturday evening, bringing rain and
thunderstorms to the area Saturday night through Sunday
morning.
- Rain transitions to snow on Sunday. But snow amounts during
the day on Sunday are expected to be minimal.
- Additional rounds of moderate snow could move into the area on
Monday, but timing and amounts remain somewhat uncertain.
&&
.DISCUSSION...
Issued at 242 PM CST Fri Dec 22 2023
Skies are clear across the area this afternoon, and will remain
mostly clear into the overnight hours. Unfortunately, the clear
skies and light winds may allow radiational fog to develop. HREF
and HRRR highlight the southeastern 1/3 to 1/2 of our area with
the potential for patchy dense fog.
Increasing southerly winds on Saturday should mix out any fog
that develops by late morning. By afternoon, temperatures
should be able to climb into the 50s. Get out and enjoy it if
you can, because we almost definitely won`t see any more 50s
until sometime in 2024.
A complex storm system moves into the picture late Saturday
afternoon through the evening. Rain and thunderstorms are likely
Saturday night into Sunday morning, with highly variable rain
amounts generally ranging from 0.10" to 1.00" by midday Sunday.
A cold front sweeps through the area Sunday morning, and as
cold air arrives, this rain will gradually transition to snow
from west to east Sunday into Sunday night. There is some
uncertainty on timing of this changeover, with some guidance
showing a more rapid transition occurring mostly during the day
on Sunday. Fortunately, regardless of model solution, the
probability for significant winter impacts on Sunday (Christmas
Eve) is relatively low. The latest NBM shows only a 10 to 20%
chance for even 1" of snow accumulation through Sunday night.
The forecast for Monday (Christmas Day) and Tuesday is still
rather uncertain. The upper low is expected to stall as it moves
over the central Plains, but the specific timing and location
varies widely from model run to model run. Unfortunately, this
significantly reduces our confidence in expected snowfall. Some
runs have several inches of snow on the backside of the low,
while others keep it progressive and largely skip our area
entirely. Looking at ensembles, the highest probabilities for 3"
or more of snow is focused over northern Nebraska. Both the 12Z
EPS and GEFS trended upwards slightly from the 00Z runs. The
latest NBM has a 20 to 50 percent chance for 4" or more snowfall
through Tuesday for much of our Nebraska counties, with
decreasing probabilities as you move further south into Kansas.
The other thing to mention with this system are the winds. While
not overly strong, we could see gusts over 35 MPH Sunday into
Monday, potentially leading to some blowing and drifting snow.
Depending on model solution, some snow could linger into
Wednesday, but at the very least it should be winding down at
that point. After this system moves out, dry conditions are
expected through the end of next week with daily highs in the
30s to low 40s.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 435 PM CST Fri Dec 22 2023
The models are dry tonight, but SE of GRI there could be some
patchy fog and with the southerly winds I would not be surprised
if GRI had some vis issues later night due to drifting patches
of BR/FG.(Will amend if needed) Tomorrow morning some marginal
LLWS looks possible so will keep a mention for it in the 00z
TAFs. The gradient tightens as the area of low pressure
approaches the region, so have gusts into the low 20s for now.
Tomorrow evening IFR will likely return to the TAF sites, so put
in a SCT020 for now as low clouds will begin to move into the
TAF sites around the 00z time frame.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
DISCUSSION...Mangels
AVIATION...Beda
Area Forecast Discussion
National Weather Service Gray ME
717 PM EST Fri Dec 22 2023
.SYNOPSIS...
High pressure will bring dry conditions with chilly nights and
seasonable daytime highs through Saturday. A weak system will
bring clouds and the chance for some light rain or snow showers by
Saturday night and Sunday with significant impacts not
expected. Mild and dry conditions are expected on Christmas Day
and Tuesday before the weather turns unsettled again by midweek.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
717 PM Update...Going forecast is in good shape with
temperatures tracking well with observations. Have only made
minor tweaks to dew points based on observed trends.
Previously...
High pressure will continue to build overhead into this evening and
the early portions of tonight allowing winds to go light to calm by
sunset. Skies are expected to remain mostly clear through at least
this period, so temperatures are expected to rapidly drop once the
sun goes down and through evening hours. After that, we`ll see some
mid and high clouds stream in through the overnight hours and if the
cloud deck is thick enough, it could level off cooling or even cause
temps to go up a degree or so. My approach for forecast lows is to
go colder than the NBM as it`s always too warm during radiational
cooling and also going warmer than MOS as it has had a cold bias the
last couple of nights, likely due to it assuming we have snow on the
ground with it being late December. So for the time being, forecast
lows range from the single digits above to the teens.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
After the chilly start, the light south to southwest flow brought on
by the high pressure moving east will usher in slightly warmer
temperatures with most seeing highs in the mid to upper 30s. There
will be more moisture aloft, and while there won`t be any precip
during the day Saturday, we will have some clouds around.
Clouds increase Saturday evening into Saturday night ahead of a weak
shortwave that will push high pressure farther off to the east. Most
model guidance is showing light QPF with this system on the order of
trace amounts to a few hundredths of QPF with snow, rain, or even a
mix possible. The general consensus of this occurring looks to be
mostly across NH, especially the southern half, but this morning`s
12Z HRRR is suggesting some light precip could also make into SW
Maine. There could be a few slick spots out there for those getting
an early start on holiday travel, but all in all little if any
impacts are expected out of this.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
The 500 MB pattern across the middle latitudes of NOAM and its
surroundings oceans continues to remain mostly progressive,
despite the signals that favor a trend toward a +PNA pattern.
This is not new as this has been the trend since the cold-season
began. However, we start the period with a building ridge over
the ern CONUS, which will persists through mid -late week,
bringing above normal temps, before a deepening trough moves in
and provides a threat for more significant precip.
On Sunday, weak 500 MB wave will push through the top of a
ridge as it crosses the CWA, and may bring a few SHRASN to the
srn half of NH Sunday morning, but the system is losing most of
its dynamic forcing at that times, and this will likely only
lead to scattered showers at best. By Sunday afternoon, should
be dry although clouds will linger through the day, but some
breaks of sun will be possible in the afternoon. Highs range
from the mid to upper 30s in the mtns to the low 40s in the S.
Friday will see a fair mount of clouds and lows range from the
mid 20s N to the low 30s S.
On Monday, there is some weak ridging that wants push into the
region from the S, and this may be enough to bring some partly
sunny skies, although with light SW flow there is some
uncertainty to how well things mix out. Still, expecting highs
above normal and generally running from near 40 in the mountains
to the mid 40s on the coast and in srn NH. Tuesday looks
similar to Monday, although better ridging aloft should bring a
better chance of at least partly sunny skies, and highs a few
degrees warmer.
The unsettled period arrives for mid-late week, with a
persistent signal for some precip as closed low to our W does
some phasing, which drives it a bit equatorward and produces sfc
low. The variability comes in how the 500 MB moves as it phases
and where the sfc low forms, and although the 12Z Op Euro and
GFS differ quite a bit, they do agree that it will be warm
enough that this should be all rain across most of the CWA. Some
mid level cooling as the system moves could change higher
elevations in the N to some SN, but this is uncertain. Also the
timing of when the steadiest precip may occur is uncertain as
well, and this why there are CHC-LKLY POPs Tue night into Thu.
Areally, this is a big system, so it is possible that there
could be some showers through this whole period, however, there
will be roughly a an 18-24 hour period of steadier rain for
which for now I have focused on Wed and Wed night, although
this can change. Friday remains uncertain as well, although it
should be cooler behind this system, but the coldest air will
likely be delayed until next weekend.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Short Term...VFR with light winds through Saturday. A weak area of
low pressure may bring a brief period of light rain or snow showers
Saturday night along with MVFR ceilings. This looks to be mainly
for the NH terminals.
Long Term...Mainly VFR expected Sunday-Tuesday but could see
some MVFR cigs possible as warm front moves through Sunday into
Sunday night. Flight restrictions expected Tue night or Wed as
the next system moves in from the W.
&&
.MARINE...
Short Term...SCA conditions are not expected through Saturday night.
Light northerly flow across the waters this afternoon will become
light and variable as high pressure builds overhead this evening.
The high slides east tonight, allowing winds to take on a
southwesterly direction through Saturday night.
Long Term...Winds/seas expected to generally stay below SCA
criteria Sunday through Tuesday. May need SCAs Tuesday night or
Wed as low pressure approaches from the W.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR TERM...Combs/Schroeter
SHORT TERM...Combs
LONG TERM...Cempa
Area Forecast Discussion
National Weather Service Memphis TN
930 PM CST Fri Dec 22 2023
...New UPDATE...
.UPDATE...
Issued at 930 PM CST Fri Dec 22 2023
00Z upper air analysis depicts southwest flow aloft with a
shortwave trough located over the Middle Mississippi Valley, and a
second shortwave over Oklahoma. Meanwhile, shortwave ridging
still remains in place across much of the Lower Mississippi Valley
this evening. 00Z KLZK upper air sounding showed a substantial
amount of dry air present with a shallow moist layer present
between 850-700 mb. KNQA/KLZK WSR-88D radar trends show some
light low-level warm air advection rain showers are occurring
across portions of extreme northeast Arkansas, and east Arkansas.
Otherwise, confidence is low overall once this band of rain
showers departs the Mid-South as short-term isentropic analysis
shows very high condensation pressure deficits (dry air), and
neutral to isentropic descent. These conditions will result in
less than ideal conditions for rain showers for the remainder of
the night into Saturday morning.
Some adjustments will be made to the remainder of tonight`s
forecast to lower rain chances. Otherwise, the remainder of the
forecast is in decent shape.
CJC
&&
.SYNOPSIS...
Issued at 237 PM CST Fri Dec 22 2023
Scattered showers will pick up throughout the day and last through
tomorrow afternoon. Another system will approach on Sunday,
bringing widespread rain for the holiday weekend. The heaviest
rain should move out by Monday afternoon, but scattered showers
will linger on the back side of an upper low through Tuesday. Cool
and dry weather returns midweek.
&&
.DISCUSSION...
(This evening through next Thursday)
Issued at 237 PM CST Fri Dec 22 2023
A weak shortwave trough is currently making its way across eastern
AR. KNQA radar is already picking up a few light showers ahead of
this feature as of 3PM CDT. Expect these showers to remain very
light but increase in areal coverage through tomorrow morning. A
weak frontal boundary should keep most of this first round of
precip confined to areas north of I-40. Most of the column looks
quite dry for the next 24 hours, so QPF through tomorrow is only
about a tenth of an inch, if that.
Another, more robust synoptic system is expected to impact the
Mid-South starting Sunday to kick off a wet holiday weekend. A
Colorado Low looks to deepen as it approaches the area on Sunday
afternoon, quickly increasing PoPs to the 80-90% range by sunset
on Christmas Eve. Above normal PWATs around 1 inch should help
bring drought-relieving rain to the entire area. However, this is
a very progressive system in its initial approach so the heaviest
rain overnight Sunday into Monday will clear out very quickly by
Monday afternoon. Total QPF through Monday night is now only
looking to be about 0.5 to 1 inch.
Instability ahead of the aforementioned low pressure system looks
essentially negligible across most of the Mid-South due to its
deeply occluded state this far north. Ensemble guidance depicts a
brief surge of 10-20% probability of CAPE > 500 J/kg on Monday
afternoon, but this will most likely not be colocated with the
most favorable kinematics ahead of the system. Forecast soundings
also suggest a weak EML for most of the day Monday, so any
thunderstorms would most likely be elevated and short-lived.
Rain chances will gradually decrease from west to east while the
upper low churns toward the east coast on Tuesday. Temperatures
have trended slightly cooler in the wake of the system for
the rest of the week; expect slightly below normal temperatures
in the upper 40s Wednesday through Friday afternoons. The same
upper low may retrograde a bit late week and bring a few scattered
showers back to west Tennessee, but confidence in this is fairly
low.
CAD
&&
.AVIATION...
(00Z TAFS)
Issued at 553 PM CST Fri Dec 22 2023
Primary forecast concern is onset timing of MVFR CIGs. GLAMP
guidance has been consistent in delaying MVFR development at MEM
until after completion of the late evening inbound push. 22Z NBM
and HRRR guidance maintains VFR CIGs the entirety of the
overnight. Central AR METARs show MVFR CIGs already making
progress into SRC and M19, ahead of guidance and with a
northeastward development tendency. Official TAF is relatively
close to GLAMP guidance.
In any case, impacts should be minimal, both with respect to CIGs
and VIS reductions due to isolated -SHRA.
PWB
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
PUBLIC FORECAST...CAD
AVIATION...PWB
Area Forecast Discussion
National Weather Service Marquette MI
751 PM EST Fri Dec 22 2023
.UPDATE...
Issued at 741 PM EST FRI DEC 22 2023
Poor visibility in dense fog noted on webcams and observations
supported adding Delta County to the Dense Fog Advisory until 16Z
Saturday. The combination of weak upslope moist flow combined with
high dew points (above freezing) over a melting snowpack and/or
frozen ground has led to dense fog across much of the central U.P.
this evening. Do not expect much improvement in visibilities from
fog until late Saturday morning. &&
.SHORT TERM...(This evening through Saturday)
Issued at 314 PM EST FRI DEC 22 2023
Key Messages:
-Dense fog tonight, especially for the interior central portions of
the Upper Peninsula
-Chances of drizzle with some patchy freezing drizzle, but no
impacts expected
-Record warm low tonight possible (32 set in 2015, current forecast:
33)
RAP analysis shows a 1032 mb high over the St Lawrence Seaway
while a weak surface trough approaches the Upper Mississippi
Valley. A subtle 500mb trough is providing enough lift for some
drizzle in some locations, but the primary weather impact so far
has been the low cloud ceilings and fog. IMT and SAW seem to be
the hardest hit, frequently reporting obs of 1/4SM and ceilings in
the 100-300 ft range. Dew points have soared into the mid 30s,
which is bad news for the snowpack and the odds of it holding on
until Christmas. The snowpack will continue to melt through the
night and continue to add to the boundary layer moisture, which
will make low clouds and fog linger through the overnight period.
With these strong insulating low clouds, overnight lows will be
pretty close to the daytime highs, and the record warm low
temperature of 32 (set in 2015) is in serious jeopardy. The 50th
percentile of the NBM has 31 with a 25th-75th percentile range of
31-33. This forecast package will reflect 33 given some of the
complexities in moisture contributions in scales smaller than
model resolution. The Grand Ensemble has probabilities of 1/4 SM
visibility or less at 80-100% for wide swaths of the interior
central UP with probabilities in the 30-70% range along the spine
of the Keweenaw and the interior eastern UP. While forecast
soundings show that the boundary layer should be too warm for
freezing drizzle, the NBM shows that some minimal patchy freezing
precip may fall in the interior west and interior far east, so
some FZDZ mention has been kept in the grids.
.LONG TERM...(Saturday night through Friday)
Issued at 349 PM EST FRI DEC 22 2023
Key Messages:
- Periods of dense fog can be expected at times through at least
Sunday
- Periods of rain are expected late Sunday through Tuesday, with a
20-30% chance of freezing rain late Christmas Day into Tuesday
morning over the interior central and west
- Temperatures remain much warmer than normal through at least the
middle of next week
Massive 500 mb time-mean height anomaly will continue to encompass
most of Canada and the northern tier of the CONUS through at least
the middle of next week, which will prevent any incursions of
significant cold air. A narrow midlevel trough now coming onshore in
the Pacific Northwest will split as it moves east, with a portion
heading north to Hudson Bay by Sunday, and a portion joining the
cutoff low now over southern CA. In advance of this latter feature,
ridging will build over the Great Lakes Saturday into Sunday. This
will result in a seasonably mild airmass becoming even warmer with
time, accompanied by plentiful low clouds and areas of fog and
drizzle. The accompanying anomalous moisture will be drawn poleward,
interacting with an eastward-moving front associated with the
northern stream wave. That will allow rain to move in from west to
east possibly late Sunday but more likely Sunday night. That area of
forcing dissipates as the parent wave shifts into Hudson Bay, but
any break in the precipitation will likely be short lived as
overrunning begins in association with the evolving sprawling cutoff
low taking shape over the Plains. This should result in a cold rain
continuing into Christmas Day for many, lingering into Monday night
or Tuesday with some timing differences noted in the guidance. The
main moisture plume will likely exit east by Wednesday with PoPs
trending down accordingly. There is potential for a northern stream
low to drop into the Great Lakes by Thursday resulting a cool down
and possibly some lake effect snow, but this is uncertain at this
time.
In terms of impactful weather, periods of fog, locally dense, will
continue at times through at least Sunday. On Christmas Day into
Monday night, there is some concern about freezing rain as colder
air near the surface drains south from a high building over southern
Ontario, while strong southeasterly flow keeps temperatures warm
aloft. A small subset of guidance has temperatures aloft cold enough
for snow over the west as well. Unconditional probabilities of
freezing rain from the latest NBM are in the 20-30% range over the
interior central and western UP. However, NBM lows are likely biased
too low, and some of the incoming airmass will be modified by the
warmer Lake Superior. Will mention chances for freezing rain in the
official forecast but refrain from any other messaging efforts at
this time until more certainty can be gained.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 732 PM EST FRI DEC 22 2023
The combination of some upslope moist flow combined with dew points
above freezing residing above a melting snowpack will leave
ceilings and visibilities from fog near or below the SAW airport
minimums for much of the TAF. MVFR conditions should prevail
through much of the period at CMX and IWD although there is an
opportunity that either cigs or vsbys could lower for a time into
the IFR range late tonight into Saturday.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 349 PM EST FRI DEC 22 2023
A weak pressure gradient should result in winds remaining less than
20 kt through Saturday night. On Sunday, southeasterly winds
increase ahead of low pressure approaching from the southwest. Wind
gusts of 20-30 kt are expected late Sunday into Sunday night, but
increased stability due to warm air aloft should limit the higher
end of that range to higher observing platforms. Winds turn
northerly behind this low from west to east late Sunday night into
Monday, with gusts of 20-30 kt expected with this round as well.
There is about a 20-30% chance of gales Monday morning near the
eastern end of Isle Royale.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Dense Fog Advisory until 11 AM EST /10 AM CST/ Saturday for
MIZ004-005-010>013.
Lake Superior...
None.
Lake Michigan...
Dense Fog Advisory until noon EST Saturday for LMZ221-248-250.
&&
$$
UPDATE...Voss
SHORT TERM...GS
LONG TERM...Thompson
AVIATION...Voss
MARINE...Thompson
Area Forecast Discussion
National Weather Service Raleigh NC
935 PM EST Fri Dec 22 2023
.SYNOPSIS...
Dry high pressure will extend across the eastern US through the
weekend. A slow-moving frontal system will move across the Carolinas
early to mid next week.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 935 PM Friday...
Included within a larger-scale mid/upr-level trough extending from
the upr and mid MS Valleys sewd and across the wrn OH and TN
Valleys, a shortwave trough now over IL will move east and across
the OH Valley tonight and cntl Appalachians and middle Atlantic on
Sat. Varying amounts of mid and high clouds (between 12-25 thousand
ft AGL) will result across cntl NC and yield variable sky conditions
ranging from mostly clear to mostly cloudy through Sat afternoon.
Otherwise, modified, continental Polar surface high pressure and
associated dry air will continue to extend across the middle
Atlantic and directly across cntl NC, with associated calm tonight
and light ely through sly winds around the ridge axis on Sat.
Forecast low temperatures in the upr 20s to lwr 30s on average
appear on track, despite rapid radiational cooling into the 30s away
from urban areas that occurred after sunset. Based upon observed
high temperatures and a cool bias in the official forecast Fri,
forecast high temperatures for Sat have been raised 3-4 F to reflect
mid/upper 50s north to lwr/mid 60s south.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 345 PM Friday...
A mid-level ridge will extend from the Deep South into the Upper
Great Lakes on Saturday night. This ridge will amplify and push east
into the Appalachians and OH Valley on Sunday, with the ridge axis
moving across central NC on Sunday night. This is in response to a
shortwave moving from TX into the lower MS Valley that becomes
negatively tilted, as a closed mid/upper low develops over the
Central Plains. At the surface, high pressure will remain centered
over the North Atlantic to the east of New England. Associated
ridging extending down the Eastern Seaboard will gradually weaken
through Sunday night as surface low pressure moves east across the
Southern/Central Plains.
All of the above means quiet weather and mostly clear skies are
expected for central NC from Saturday night through Sunday. Less
cloud cover on Saturday night should help lows drop into the upper-
20s (outlying areas) to upper-30s (urban areas) despite low-level
thicknesses about 10-15 m higher than tonight. Temperatures will be
7-10 degrees above normal on Sunday with highs in the upper-50s to
mid-60s. It certainly won`t feel like Christmas Eve and will be far
different from last year`s frigid one.
Mid and high clouds will then be on the increase overnight Sunday
night as the flow aloft begins to turn southwesterly ahead of the
aforementioned system, and we begin to get some isentropic lift.
However, any rain will hold off until after the end of the period.
Lows Sunday night will be milder, upper-30s to mid-40s, and
temperatures should remain nearly steady once the clouds move in.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 240 PM Friday...
High pressure will be centered over the Atlantic Ocean to the east
of New England and will continue to move off to the east. Meanwhile,
a surface low will drift north from Missouri into Iowa and then over
Michigan by Wednesday morning while an upper low remains nearly
stationary. An occluded front will inch to the east, still remaining
west of the Appalachian Mountains Tuesday morning, and a secondary
wave of low pressure along the front should be just offshore North
Carolina Wednesday morning.
There has not been much change to the forecast over the last 12
hours. Rain will be slow to move in from west to east Monday and
Monday night, with easternmost locations possibly dry all the way
through Monday night. The overall rainfall should be on the light
side Christmas day itself, with the heaviest rainfall likely between
midnight and noon on Tuesday. While an isolated thunderstorm cannot
be ruled out on Tuesday, did not see enough instability in the
thermal profiles to warrant keeping the slight chance of
thunderstorms in the forecast. Likely pops continue from the
Triangle to the northeast Tuesday night, then drier air will move
into the region from the west. The GFS/GEFS show another coastal low
developing by Friday morning off the North Carolina coast, but this
seems an unlikely scenario and will stick closer to the ECMWF
solution, which has slowly decreasing pops through the rest of the
forecast.
Monday and Tuesday remain the warmest days, with highs ranging from
the mid 50s in the Triad to the upper 60s in the east. Temperatures
will even remain mild into Wednesday, but highs should fall into the
50s everywhere on Thursday with some upper 40s across the northwest
Friday. Lows only fall near the freezing mark Thursday night, so
precipitation should fall as all rain.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
As of 705 PM Friday...
The approach and passage of a mid/upr-level trough and associated
disturbances now extending across the TN through mid and upr MS
Valleys will result in varying amounts of mid and high clouds
(mostly between 12-25 thousand ft AGL) over cntl NC through early
Sat afternoon. Otherwise, continental Polar surface high pressure
and associated dry air across the Northeast and middle Atlantic will
favor VFR conditions in cntl NC through Sat. While a short period of
radiation fog cannot be entirely ruled out from RWI and especially
points newd through nern NC and ern VA Sat morning, as some high-
resolution model guidance suggests (ie. HRRR and NAM3KM), dew/frost
are considered more likely owing to the otherwise dry air related to
the aforementioned high pressure extending across the region.
Outlook: Gradually modifying/moistening low-levels will increase the
probability for fog at RWI through Mon, followed by a high
probability of prolonged flight restrictions and rain accompanying a
slow-moving frontal system early to mid next week.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...Danco
LONG TERM...Green
AVIATION...MWS
Area Forecast Discussion
National Weather Service Shreveport LA
929 PM CST Fri Dec 22 2023
...New UPDATE...
.UPDATE...
Issued at 923 PM CST Fri Dec 22 2023
Posted a Dense Fog Advisory which is valid overnight through 10am
Saturday Morning and the fog may continue through close to Noon
on Saturday across portions of the Middle Red River Valley of NE
TX, SE OK and SW AR. While we are still dealing with some very
light precipitation returns across most of Northern Louisiana
attm, much of the upper level forcing is slowly trying to move out
of the area and thus, the precipitation should move with it. In
the wake of this upper forcing is areas of Dense Fog which has
formed across the Middle Red River Valley of NE TX, SE OK and SW
AR as well as portions of Deep East Texas. As we go through the
remainder of the night, there is good model consensus that Dense
Fog should fill in across the remainder of NE TX, while just
remaining patchy across Northern Louisiana. For this reason, went
ahead and posted the Dense Fog Advisory and will allow oncoming
shift to add to it or subtract from it if necessary. Temperatures
should fall through the dewpoint where dense fog forms and for
that reason, had to lower temperatures slightly across our western
and northern half where some locations were already at their
fcst overnight min temps or below the forecast as of 03z.
All other grids were in pretty good shape so no additional
changes were necessary.
13
&&
.SHORT TERM...
(This evening through Saturday Night)
Issued at 239 PM CST Fri Dec 22 2023
Areas of light rain showers continue to shift ENE across the area
this afternoon as a weak short-wave trough continues to push
across the region. Models haven`t handled this precip very well
today, with most suggesting things will dry out by late this
afternoon. But with it being wetter than guidance today, thinking
some light precip may linger across portions of East Texas, North
Louisiana, and SW Arkansas through the early evening hours. Things
eventually dry out overnight with the departure of the short-
wave trough, along with drier air expected to spread into the
region from the west.
Upper ridging will build into the region tonight before
transitioning to SW Flow aloft ahead of a closed trough ejecting
across the SW CONUS into the Rockies. As this system continues to
push eastward, we will see a quick return of showers by Saturday
afternoon from the south, as isentropic forcing will be on the
increase. Rain will continue to increase in coverage and intensity
Saturday night into Sunday morning, as the closed trough ejects
into the Central Plains, and its associated cold front slides
eastward across Oklahoma and Texas. Moderate to heavy rainfall
could be in our East Texas and SE Oklahoma zones by daybreak
Sunday, with that activity spreading eastward during the remainder
of Sunday.
Above normal temps are expected to remain over the region, with
lows in the 50s over the next couple of nights, and highs on
Saturday ranging from the mid 60s to around 70 degrees. /20/
&&
.LONG TERM...
(Sunday through next Thursday)
Issued at 239 PM CST Fri Dec 22 2023
The start of the long-term takes us right into Christmas Eve, and
the bulk of our rainfall that we`ve been messaging the last few
days. Here, widespread rain and thunderstorms will be ongoing and
expanding across the region, with most of this rain being on the
moderate to heavy side. During the day on Sunday, most locations
will record 1-2 inches of rainfall, with some isolated pockets of 2+
inches possible. It also looks like widespread flash flooding won`t
be a large threat, given how dry everything is across the region.
Instead, a flash flooding threat will likely remain limited to poor
drainage, and the usual problem spots. The severe weather prospects
on Sunday also still look on the marginal side, with no outlook for
severe weather in our region for the time being. Thus my mentioning
of a marginal risk, as it would most likely be the type of outlook
introduced, if one were to be.
Conditions will quickly dry out into Christmas, as the trough and
low pressure move off to the NE. In turn, temperatures will begin to
fall across the region behind the front, with high temperatures on
Monday split N to S. Highs south will range in the mid-60s, with
highs N ranging in the low-50s. That will be the story for the
remainder of the long-term, as dry conditions and seasonable
temperatures remain through the rest of the week.
/44/
&&
.AVIATION...
(00Z TAFS)
Issued at 516 PM CST Fri Dec 22 2023
Light precipitation continues across portions of Deep East Texas
into Northwest Louisiana and Southwest Arkansas this evening so
prevailed VCSH at the SHV/ELD and MLU terminals through the
remainder of the evening. Added patchy fog to go along with
developing IFR and perhaps LIFR ceilings overnight across our
western terminals if the HRRR is to be believed overnight with the
possibility of widespread advection fog developing. Did not go
below 1 mile later tonight through mid morning on Saturday but
will better define this with the 06z TAF package. Also introduced
VCTS during the afternoon on Saturday across our NE TX terminals
given the forcing expected in advance of our shortwave trough
expected to continue impacting all our terminal airspace just
beyond this 24hr TAF cycle.
13
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 57 69 59 66 / 20 30 80 100
MLU 54 72 57 66 / 20 20 40 100
DEQ 52 66 54 62 / 20 20 90 100
TXK 53 67 57 62 / 20 20 90 100
ELD 54 69 54 64 / 20 20 60 100
TYR 55 68 60 66 / 20 40 90 100
GGG 57 69 58 66 / 20 30 90 100
LFK 58 69 59 67 / 20 50 90 100
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...Dense Fog Advisory until 10 AM CST Saturday for ARZ050-051-
059>061-070>073.
LA...None.
OK...Dense Fog Advisory until 10 AM CST Saturday for OKZ077.
TX...Dense Fog Advisory until 10 AM CST Saturday for TXZ096-097-
108>112-124>126-136>138-149>153-165>167.
&&
$$
SHORT TERM...20
LONG TERM....44
AVIATION...13
Area Forecast Discussion
National Weather Service Tucson AZ
219 PM MST Fri Dec 22 2023
.SYNOPSIS...A wet Pacific storm will continue to move across
Southeast Arizona tonight into the weekend. This storm will bring
widespread rain and high elevation snow tonight into Saturday.
Isolated to scattered thunderstorms are possible late afternoon
into the late evening. A few showers possible on Sunday and then
dry and cooler temperatures for the new week.
&&
.DISCUSSION...Rain showers and high elevation snow can be observed
across Southeast Arizona today and will continue through the
night. A low pressure center off the southern California coast
will bring three forecast elements for the region:
rain, thunderstorms, and high elevation snow.
The Total Precipitable Water satellite imagery shows the low
pressure center tapping into the subtropical jet (PWAT values of
1.5 inches) which will continue to bring the anomalous amount of
rain for the region. The ECMWF Extreme Forecast Index shows this
anomalous amount of rain on a order of 1-2 shift of tails through
Saturday night. The current 12 hour rainfall amounts have been 0.5
inches to several locations in the 1+ inch territory. Those
locations have the upslope dynamics and more efficient rain
process so far. As the afternoon progresses, more storms will
start to train over a corridor from the northern limits of Tucson
to the southern limits of Sonoita. The storms will be traveling
between the two limits in a northeasterly direction. The HREF 3
Hour ensemble Probability Match Mean shows the corridor has 30-50%
of receiving an 1 or more by the later afternoon and early
evening. This can make the evening travel a challenge as roads
will be ponding to some minor flooding issues in low lying areas
and washes will be flowing. So far, only a handful of washes are
flowing in the Tucson metro. The will lead to more flow in other
washes as the soils have become more saturated from the morning
rains. Reminder, Turn Around Don`t Drown!
As the low pressure center moves across the region this afternoon,
the jet axis will be a favorable position as well with good
diffluence aloft to support organized thunderstorms. The RAP
analysis has shear values of 50 kts and some low CAPE values, but
that can increase over the course of several hours if there is
enough break in clouds to get solar heating or minor disturbance
to jump start storms. SPC has a marginal risk for thunderstorms
for wind and hail which can be possible due to the upper level
support. Once thunderstorms form, especially within the previously
stated corridor, it can bring locally heavy rainfall, gusty and
erratic winds, and possibly small hail.
The snow levels are currently around 8500-9000 feet based on the
cameras on the radio ridge on Mt Lemmon. The snow has been
accumulating to about an inch as of this writing. As the
low pressure center moves, the 700mb temperatures will drop from
0 degrees celsius to close to -4 degrees and possibly to -5 by the
late evening. This will bring snow levels down close to
6,500-7,000 feet by tomorrow morning. The ridgetops and higher
upslope will see the heavier side of the snow. Thus, there is a
Winter Weather Advisory for locations above 8000 feet to highlight
this snow.
Looking ahead, a 500 mb ridge will build behind the storm system
by Sunday and into the new week. Temperatures will stay several
degrees below normal (eastern locations will be below freezing
for the mornings) for a few days after the storm system moves out.
Then, dry and temperatures being near seasonal normal for the
week.
&&
.AVIATION...valid through 24/00Z.
SCT-BKN clouds AOA 4K-8K ft AGL across the forecast area and
through the majority of the forecast period. -SHRA and embedded
-TSRA continuing through the after and clearing west to east by
24/18Z. MVFR ceilings/vsby conditions across all of southeast
Arizona through the end of the forecast period, along with
mountain obscurations. Any -TSRA is capable of wind gusts to 30
kts. Otherwise, SFC wind will generally be less than 12 kts and
from the south/southwest through the end of the period. Aviation
discussion not updated for TAF amendments.
&&
.FIRE WEATHER...A strong and wet storm system will move across the
area tonight into Sunday, with cooler temperatures and widespread
precipitation. Relative humidity values will increase
substantially starting tonight and remain well above critical
thresholds into at least the middle of next week. 20-foot winds
will generally remain below 15 mph through the period. Widespread
wetting rain is likely with this system, along with high elevation
snow above 8k ft.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 8 PM this evening to 5 PM MST
Saturday for AZZ510-511-514.
&&
$$
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