Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/28/23
Area Forecast Discussion
National Weather Service La Crosse WI
1056 PM CDT Fri Oct 27 2023
.DISCUSSION...(This evening through Friday)
Issued at 300 PM CDT Fri Oct 27 2023
Key Messages:
- Overnight lows tonight will dip below the freezing mark
areawide, ending the growing season.
- Increasing confidence in a band of light snow across portions
of our region tomorrow but uncertainty still remains in its
exact position. Accumulations will be very minor with drier air
further east limiting precipitation amounts.
- Temperatures will remain well below normal through the first
half of next week with highs stuck in the 30s on Monday and
Tuesday.
FREEZE WARNING TONIGHT:
Bitterly cold temperatures, compared to the previous days, are
heading into the region with many observations in the middle 30s to
50 degree range. The coldest area is over southeast Minnesota where
wind chill values are in the lower 20s! This cold air will continue
streaming in tonight and even if clouds dont clear, morning lows
will be near freezing in the river valleys, southwest WI and
northeast IA for a freeze. Clearing would only help temperatures get
lower. So, the Freeze Warning for those areas seems on track.
WEEKEND SNOW POTENTIAL:
With a longwave trough presenting itself for the weekend behind the
a cold frontal passage, temperatures will remain below normal this
weekend. With a shortwave riding through the southwesterly flow
around the base of the trough, expecting some precipitation to push
through the region during the afternoon and evening Saturday. The
short-range guidance has been painting a fairly dynamic setup where
a narrow band of light to moderate snow could develop as a result of
some mid-level frontogenesis and resulting lift. Subtle differences
between the 27.15z RAP and 27.12z NAM in their forcing regime show
the main forecast challenge with this disturbance as the positions
and intensity of the lift differ. The 27.15z RAP shows the idea
of keeping the stronger frontogenesis further south with a more
robust frontogenesis/frontolysis couplet that could enhance lift
in the mid-levels, which may be a reason the RAP has been trending
higher in its model reflectivity. The 27.12z NAM keeps the
frontogenesis and lift further north with a more messy structure.
As a result, the NAM solution has tended to show a weaker and
further north snow band.
As far as accumulations are concerned there are a few trouble
points. The first challenge with this disturbance will be location
and size of the band itself. Guidance generally agrees that this
snowband may only be a county or two in width with a sharp gradient
on the southern extent where the forcing diminishes rapidly.
Consequently, a situation will likely arise where a couple of miles
could be the difference between moderate snow and green grass.
Additionally, with maximum temperatures reaching into the upper 30s
across western Wisconsin and warm soil temperatures from the
previous weeks warmth, surface conditions will become increasingly
unfavorable for snow accumulation east of the river and would
require heavier snowfall rates to overcome. Another point of
consideration is how much dry air is present in the low-levels.
Forecast model soundings across guidance generally show a prevalent
dry layer across western Wisconsin that generally does not saturate
until the evening hours. As a result, some of the stronger forcing
may be spent on achieving low-level saturation rather than
precipitating which will limit QPF. The 27.12z HREF generally
shows high probability (60-80% chance) of seeing at least 0.01" of
precipitation east of the Mississippi River with guidance
struggling to have QPF higher than a few hundredths for much of
the region. As a result, accumulations would likely be very
minimal for many when considering the previously mentioned
limiting factors. If precipitation onset occurs later into the
evening than forecast, surface conditions would be more favorable
for accumulation and we could overachieve. Otherwise, this could
be a setup where ridgetops in the driftless region see minor
snowfall accumulation but the valleys do not.
COLD WEEK AHEAD:
A secondary shot of reinforcing cold air advection will be present
Monday with a broad upper-level wave progressing north of our
region. Blustery winds during the morning Monday combined with lows
in the upper teens to middle 20s across the region could lead to
wind chills in the teens and single digits. With a longwave trough
still in place to our north, expecting temperatures for the first
half of the week to remain well below normal. A passing upper-level
trough Tuesday could sneak in some light snow for our region,
however with major differences in the position of the trough between
the EC ensembles and GEFS, confidence remains low, especially
considering how dry the airmass is with precipitable waters being
30-50% of normal around 0.1" to 0.2".
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1100 PM CDT Fri Oct 27 2023
Monitoring MVFR ceilings over nearly the entire area from
northeast Iowa, southeast Minnesota, and western into central
Wisconsin. High resolution models have been poor at picking up
this thick, wide stratus band over the last few hours. Upstream
satellite imagery shows this band stretching through north-central
Minnesota towards the international border. Therefore, given
observations, opted against model guidance and continued MVFR
cigs for the next few hours. Given proclivity for KLSE to lift
out over KRST, have introduced FM group for VFR cigs, and a TEMPO
at KRST. Also, upstream trends over the last 2-3 hours have been
slightly lifting to just above MVFR cigs from western into central
Wisconsin. Big potential forecast buster will be dry slot evident
in satellite imagery over west-central Minnesota.
The drier lower level air is farther to the southwest, from
central into western Iowa. Forecast difficulty through Saturday
will be extent of this dry air through northeast Iowa into
Wisconsin and Minnesota. Again, models have little to no agreement
on behavior of potential mixing out to VFR ceilings. Given
difficulties at 28.06Z forecast issuance, have continued to keep
KRST MVFR and KLSE VFR. Outside of the TAF sites, expect much of
the same, with higher confidence for dry air (potential VFR) at
smaller airports to the south and west. Otherwise, light snow
expected to move in Saturday evening within a narrow band.
Lifting mechanism will keep the band quite tight. The extent of
the aforementioned dry air will also limit onset and extent of
snow impacts. Therefore, have included PROB30 at KLSE with limited
confidence for impacts that far east. Any accumulations expected
to primarily remain on elevated or grassy surfaces.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Freeze Warning until 9 AM CDT Saturday for WIZ032-033-041-
053>055-061.
MN...Freeze Warning until 9 AM CDT Saturday for MNZ079-088-096.
IA...Freeze Warning until 9 AM CDT Saturday for IAZ008>011-018-019-
029-030.
&&
$$
DISCUSSION...Baumgardt/Naylor
AVIATION...JAR
Area Forecast Discussion
National Weather Service Columbia SC
719 PM EDT Fri Oct 27 2023
.SYNOPSIS...
Strong high pressure will persist over the forecast area into this
weekend, generating above normal temperatures and dry conditions.
Expect scattered daytime clouds and light winds through Monday
before a frontal passage brings more Autumn-like temperatures back
to the region next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Fair weather with above normal temps as high pressure, surface
and aloft, continues over the region. Satellite indicates some
mid and high level cloud cover could stream across northern
areas. Guidance favors any fog across southern areas. Bumped min
temps down just a tad. Lows in the 50s.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY NIGHT/...
Surface high pressure remains across the area through Sunday,
then will begin to push east as a surface cold front begins to
approach the area on Monday. Aloft, ridging remains into Sunday,
then is suppressed southward as a deepening upper trough
approaches. Dry conditions are still expected to occur ahead of
the front through Monday night. Temperatures continue to be more
Summerlike, with both highs and lows well above normal through
Monday. Highs in the middle 80s, with lows in the mid to upper
50s.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
Beginning Tuesday, the pattern shifts from Summertime back into
Autumn as a cold front moves through the area during the day.
Best cold advection occurs across the northwestern cwa during
the day, with cold air lagging some across the southeast until
late in the afternoon. This will create a good spread of
temperatures across forecast area throughout the day, with highs
only reaching the middle 60s north, but the southern counties
will see the middle to possibly upper 70s. Moisture is still
going to be somewhat limited, especially as the front moves east
of the mountains. Best chance for rainfall may occur over the
northwestern cwa along the front as it moves through. Much of
the remaining counties will remain dry.
Behind the front for the remainder of the week, a much colder
airmass will settle into the region, with some of the coldest
air so far moving into the cwa. Highs turn much colder, with
readings in the mid to upper 50s Wed/Thu, and possible reaching
back into the 60s by Fri with a little airmass modification.
Bigger temperature issue will be the overnight lows. Coldest air
will not be hear Tuesday night, and with good mixing overnight
lows will still only fall into the 40s. Much colder temperatures
will occur Wednesday night as strong cold advection really takes
hold. Wind out of the north between 5 and 10 mph, with higher
gusts, will keep good mixing near the surface. This will limit
any frost potential at this time. However, guidance is showing
the first real threat of freezing temperatures across a large
portion of the cwa by Thurs morning, especially over the
northern and central Midlands, and northern CSRA. The southern
CSRA and Midlands may be able to remain above freezing. So, late
Wednesday night/early Thursday morning has the potential to see
the first Freeze Warning of the season for freezing temperatures
for portions of the area, which would thus end the growing
season. Will continue to monitor trends over the weekend and
into next week. Thursday night/Friday morning may see a slight
moderation in lows to just above freezing.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Satellite showing diminishing strato-cumulus across the region
and expect mainly a few high clouds overnight. Surface high
pressure across the area and near calm winds overnight. Shallow
near surface moisture may lead to shallow fog late tonight
especially at AGS with fewer strato-cumulus clouds expected
overnight to limit development. Some ground fog possible at
times at other taf sites but latest HRRR suggest most areas of
fog in the coastal plain toward morning. So will go with a
period of LIFR at AGS 08z-12z and MVFR at other sites through
around 12z. A few cumulus expected by 15z-18z with light and
variable winds.
EXTENDED AVIATION OUTLOOK...Chances of late night/early morning
VSBY/CIG restrictions.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Cheyenne WY
505 PM MDT Fri Oct 27 2023
.SHORT TERM...(This evening through Saturday)
Issued at 316 PM MDT Fri Oct 27 2023
Key Messages:
*Snow expected to begin across higher terrain late Friday evening.
*Moderately strong snowband expected to develop Saturday and will be
the primary snow producer for the lower elevations.
*Very cold air moves in behind the system.
Current Weather: Clouds have finally cleared out of the region this
afternoon after a long period of low clouds across most of the
region and freezing fog across southeast Wyoming. GOES-16 visible
imagery shows some clouds remaining over portions of the Panhandle
and northern portions of the CWA. Temperatures are cool today with
highs ranging from the low-50s in Laramie to the upper-20s in
Alliance. Winds are relatively calm, leading to a calm, but cool day
ahead of the incoming winter system this evening.
Discussion: After a mostly quiet day thus far, things begin to
change quickly as the evening hours approach. The 250mb trough
begins to push towards the region this evening with a large and
strong jetstream across much of the central CONUS. The CWA is
primarily in the right entrance region of the jet this afternoon and
evening before transitioning towards less favorable jet dynamics by
the overnight hours. However, southwesterly flow dominates
throughout the atmosphere overnight and promotes upslope development
across the high terrain of Carbon and Albany counties. With cold
temperatures, especially at 700mb, snow is expected to begin across
the Snowy and Sierra Madre ranges by late this evening and continue
through most of the day Saturday. Snow is not expected in the lower
terrain until around midnight tonight and any snow that falls will
be light in nature due to less favorable jet dynamics and weak
isentropic lift across the area.
The most favorable time frame for snow across most of the CWA will
be between 12 and 18Z on Saturday. By this time, jet dynamics are
not favorable for synoptic lift across the region as the jet stream
migrates off to the east and the CWA loses the right entrance
region. However, a 500mb vorticity maximum is progged to eject out
ahead of the incoming trough and traverse across the region between
12 and 18Z. This vorticity maximum will support some synoptic lift
across the region. In addition to this synoptic lift, moderate
isentropic upglide on the 300K isentropic surface is present along
with some weak, positive 650mb theta-e advection across much of the
CWA. With the vorticity maximum, isentropic upglide, positive theta-
e advection, and upslope surface flow being collocated, a moderately
strong snow band is expected to develop from a line from
southwestern Laramie County to the northeast through southeastern
Scotts Bluff County during this time frame. This band will likely
have the best chance at producing the most snowfall for these
regions, as synoptic lifting mechanisms are nearly non-existent
through Saturday evening. The HRRR has recently started oscillating
towards a slightly further north position of this snow band, which
could give central portions of the Panhandle a better shot at snow,
but this is a recent trend and all previous runs trended the band
further south. Should any of these potential lifting mechanisms
dissipate in the next few model runs, only surface upslope flow will
be providing lift, which may not be enough to get significant
snowfall accumulations in the lower elevations. Currently, snow
totals around 1-3 inches are expected for the lower elevations, with
6-8 inches possible in the higher terrain. Snow totals for
southeastern portions of the CWA are dependent on where the snow
bands sets up, so any change in this location will change the snow
totals over the next several model runs.
Snow is expected to come to an end late Saturday evening into late
Saturday night, as the trough axis approaches the region. The CWA is
under the left entrance region of the jet stream by Sunday morning
and isentropic downglide develops as flow turns northwesterly. Very
cold air is expected behind this system with high temperatures in
the 20s and 30s for Sunday and Sunday morning lows sit in the teens
and single digits. Drier conditions expected behind this system for
the remainder of the weekend and into next week.
.LONG TERM...(Saturday night through Friday)
Issued at 316 PM MDT Fri Oct 27 2023
Overview: The overall long term forecast period looks quiet in
regards to precipitation chances as the region will be under the
influence of a large ridge before transitioning to a more zonal flow
that will open the door multiple days of elevated to potentially
high winds across the region. The main weather hazard of note, will
be the bitterly cold temperatures expected Sunday night into Monday.
Looking way out, the next potential weather maker may on tap toward
the end of next week.
Discussion: As mentioned above, the highest impactful weather will
be the cold temperatures expected Sunday night into Monday morning.
The mesoscale setup still supports some varying degree of
radiational cooling to occur across the region. Geographically the
sheltered mountain valleys and higher elevation valleys will see the
greatest net radiational cooling where everyone else will be
dependent on prior snowfall and remaining snow pack and the both the
speed and direction of the wind. Very high confidence that
substantial clearing will occur on the backs of the persistent dry
air advection into the region which will allow for both clearer
skies and low dew points to help accelerate the cooling. The weather
element to watch will be the winds. Most guidance keeps winds
relatively light but winds should be out of the west which will be
in the downsloping regime which will aid in keeping those downstream
areas a few degrees warmer.
One more cold day on tap as the last of the cold air advection
filters into the region as a secondary low drops out of central
Canada into the central Dakotas. Winds will also turn breezy
primarily across the northeastern portions of the Nebraska
Panhandle. After Monday that overall synoptic pattern and 500mb
pattern will begin to transition toward a west to east zonal flow
which favors a return of multiple days of breezy conditions and
the threat of high winds.
Both long range models and in-house parameter guidances are hinting
at a return of much winder conditions beginning Tuesday and
continuing through the rest of the long term forecast period. The
setup will be the zonal flow with the jet streak planted overhead
with subtle shortwaves though moving through the mean flow to our
north. This is a very common setup for the area to see prolonged
breezy conditions with episodes of high winds to occur. Details
regarding just how strong these winds are emerging, especially in
our in house products. The approach is to begin to increase winds
where in house guidance is showing the strongest signals through the
time period which already gives forecast wind gusts around 45 mph
across the wind prone areas and locations east of the Laramie Range
for next Thursday into Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 501 PM MDT Fri Oct 27 2023
Evening VFR conditions across southeast Wyoming and Nebraska
Panhandle airports. Conditions deteriorate after midnight as low
clouds and stratus develop. Used HRRR guidance for timing and
locations for lowering conditions...as the HRRR model has been
doing a superb job the past several days. Snow beginning from west
to east towards 12Z Saturday and continuing through the day
Saturday.
&&
.FIRE WEATHER...
Issued at 316 PM MDT Fri Oct 27 2023
Minimal fire weather concerns for the next several days. Much
colder temperatures expected through the weekend and into the
middle of next week. Accumulating snow expected late this evening
through much of the day Saturday. Warmer conditions expected
Wednesday with the next chance of precipitation arriving Friday.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until noon MDT Sunday for WYZ112-114.
Winter Weather Advisory from 6 AM Saturday to noon MDT Sunday
for WYZ116>118.
NE...None.
&&
$$
SHORT TERM...AM
LONG TERM...AW
AVIATION...GCC
FIRE WEATHER...AM
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1152 PM EDT Fri Oct 27 2023
.AVIATION...
The cold front will be east of the terminals by TAF issuance.
Observations indicate a region of post frontal showers/drizzle which
will affect the area for the first couple hours after TAF issuance.
Post frontal cold air advection will deepen the inversion and trap
low level moisture in place, causing the low clouds to persist
through at least daybreak. A northerly wind flow on Saturday,
minimizing the lake fetch, in advance of inbound high pressure will
support the potential for clearing by afternoon.
.DTW THRESHOLD PROBABILITIES...
* High in ceilings aob 5000 feet overnight and Saturday morning.
&&
.PREV DISCUSSION...
Issued at 831 PM EDT Fri Oct 27 2023
UPDATE...
A line of broken showers has developed along the cold front now over
SW Lower Mi. There has even been some prefrontal showers out ahead of
this front. SPC meso analysis shows waning instability as expected.
This will prove a big limiting factor for anything other than
isolatedthunderstorms as this front tracks across the area late
this evening. Overall, the current forecast remains valid.
PREV DISCUSSION...
Issued at 357 PM EDT Fri Oct 27 2023
DISCUSSION...
Some breaks of sun are nicely topping off a warm late October day
around SE Mi as afternoon highs reach the lower and mid 70s. Record
highs are 78 at Detroit, 76 Flint, and 79 Tri Cities, all set in
1927. The extra warm sector influence across SE Mi is thanks to the
Midwest cold front being a few hours slower compared to recent model
cycles. This gives the borderline summer air mass a chance to build
some surface based instability prior to the front as the most recent
RAP projects CAPE around 1000 J/kg by 21Z based on early afternoon
hourly mesoanalysis. An isolated prefrontal thunderstorm then
remains possible toward the Tri Cities until the cold front brings
ongoing activity farther east and south across SE Mi. Surface based
CAPE decreases with the loss of daytime instability in exchange for
stronger low level convergence along the front. The system is
otherwise weakly forced but has a constructive wind profile in
deep/moderate intensity SW mid level flow. Model soundings indicate
a unidirectional profile with about 40 knots of effective bulk shear
during late afternoon and evening. Stronger cells then command some
respect for gusty wind potential as 500 mb wind speed is shown to
hover around 50 knots, although there is equal concern the wind
profile will be too strong for updrafts as surface based CAPE wanes
below 1000 J/kg. The later arriving front favors a less organized
scenario, although trends will be closely monitored through the
evening.
The cold front exits into Ontario/Ohio shortly after midnight while
carrying remaining showers out of the area and possibly leaving a
few hours of patchy drizzle during the late night. Impressive low
level cold advection will be the main story as midnight high
temperatures in the upper 50s to lower 60s drop well down into the
40s by sunrise. Readings then struggle to warm out of the 40s until
breaks of sun develop Saturday afternoon and NW wind diminishes to
around 10 knots. Guidance highs in the lower to mid 50s are
reachable with the boost of sunshine before high clouds thicken mid
to late afternoon.
The surface cold front maintains intensity while stalling in the
Ohio valley by Saturday night with a shallow profile extending back
north into the Great Lakes. Elevated portions of this front then
strengthen considerably under a textbook increase in organization of
right entrance region upper jet dynamics. In addition to strong mid
level Fgen, there is also a component of isentropic ascent and
moisture transport organizing in backed boundary layer to 850 mb
wind flow. This occurs with reasonable model agreement on Ohio
valley surface cyclogenesis leading to a band of rain showers
expanding into southern Lower Mi later Saturday night through
Sunday. There is also a separate area of light rain showing up in
the northern Great Lakes, also with reasonable agreement among the
deterministic solutions but which does bring into question the
predictability of smaller scale features during Sunday. For now, a
dry pocket in central Lower Mi is expected to fill in during the
afternoon and then last through Sunday night across the area.
Falling temperatures are on track for the early to middle portion of
next week. Colder air arrives in two stages; the first being with
Plains high pressure building eastward post Sunday front, the second
being with a strong northern stream system low pressure system on
Tuesday. Sub freezing 1000-850 mb thickness will likely force
daytime temperatures down into the 30s with a few snow showers
possible as the system sweeps through the region.
MARINE...
Warmer southwest flow has limited the degree of overlake mixing with
stronger gusts being confined to land or directly along the shore. A
cold front tied to low pressure over the northern Great Lakes is
then set to sweep across the region overnight bringing numerous
showers as well as a chance for an isolated thunderstorm. Main
impact of this frontal passage instead is an abrupt temperature
shift as a cold Canadian airmass is drawn into the Great Lakes. A
modest gradient is expected to cap NW wind gusts sub-gales, in the
25-30kt range, over the northern half of Lake Huron (weaker south)
however flow direction will be enough to lead to rougher waves
around the tip of the Thumb daytime Saturday. As a result, a Small
Craft Advisory is in effect from Outer Saginaw Bay to Port Sanilac.
Northerly winds gradually weaken Saturday night into Sunday as high
pressure briefly expands over the central Great Lakes before
unsettled weather returns late Sunday into Monday as developing low
pressure tracks into the northern Ohio Valley/southern Great Lakes.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from 5 AM to 4 PM EDT Saturday for LHZ421-441-
442.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....SC
UPDATE.......SC
DISCUSSION...BT
MARINE.......KDK
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Rapids MI
1037 PM EDT Fri Oct 27 2023
LATEST UPDATE...
Update
.UPDATE...
Issued at 1037 PM EDT Fri Oct 27 2023
Removed thunder from the forecast for this evening as deep
convection has failed to occur and the front will be clearing the
southeast zones by midnight. Post-frontal stratiform rain will
linger an hour or two later.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 334 PM EDT Fri Oct 27 2023
An increase in shower coverage and intensity is expected over the
next few hours as a sfc cold front currently over ern WI presses
east. A few thunderstorms are also possible as SB Capes have
risen to around 500 J/KG ahead of the front with deep layer shear
values around 50 kts.
However HRRR fcst soundings continue to show very skinny cape
profiles through a deep layer and poor mid level lapse rates
which are expected to limit updraft strength (despite recent
pockets of sun and sfc temps now 70-75 south and east of GRR).
So, the strong to severe thunderstorm threat (for gusty winds) is
not zero with the fropa this evening given strong kinematics and
frontal forcing but the thermodynamic environment is quite
lacking.
Shower threat gradually ends tonight from northwest to southeast
with frontal passage and commencement of cold/dry advection, but
considerable low clouds likely lingering into Saturday morning
before peeks of sun emerge in the afternoon. A much cooler day
with highs only 48-53, but really not too bad of an autumn day
considering no rain, some sun and lighter winds.
The next chance of rain arrives near/south of I-94 late Saturday
night as a wave rides up the stalled frontal boundary situated to
our south. Also some low pops Sat ngt in the nw CWFA near
secondary baroclinic zone.
.LONG TERM...(Sunday through Friday)
Issued at 334 PM EDT Fri Oct 27 2023
We are looking at two general periods of precipitation in the long
term that our focus will be on. The first will be a couple of waves
of rain that will continue Sunday through Sunday night. The second
will be some rain, then snow showers from Monday night through
Tuesday night.
We may be in a relative lull in precipitation at the beginning of
the long term period on Sunday morning. The Saturday night system
mentioned in the short term will be pulling out, and leaving some
short wave ridging in place Sunday morning. This will not last long
as will we see some additional precipitation the will redevelop
Sunday afternoon, and continue through Sunday night. The forcing
responsible for this will be the right rear quad of a 150 knot upper
level jet. This precipitation will not be heavy, as the deep and
rich moisture will be swept out well before this. Also, the
precipitation should be mainly in the form of rain with thermal
profiles cool, but still warm enough for mostly liquid. There may be
a few flakes that develop as the event is ending with just enough
cold air coming in by then.
We will see a mainly dry day then on Monday, and quite cool with
highs in the 40s. A fresh canadian air mass will move in behind the
Sunday system, with a flow from the North.
The most interesting system then arrives for Tuesday and Tuesday
night. The models and ensembles have all been keying in on a strong
short wave diving SSE into the area for this period. This short wave
has origins near the North Pole, and is being driven down here by a
long fetch from the NNW.
Precipitation will break out ahead of the associated sfc low most
likely Tuesday morning. The air mass looks initially cold enough to
support mainly snow with 850 mb temps around -7 to -8C, and freezing
levels no more than 1-2k ft agl. There could be a bit of a boost to
the initial precipitation with instability over the lake almost
extreme with delta t`s likely around or over 20C. Then, lake effect
will be likely from later Tuesday and Tuesday night behind the
system. The flow behind the system is likely to be from the NNE, so
most of the lake effect may end up over the lake.
Once the strong wave moves out for Wednesday, we should see much
quieter weather settle in with ridging building in. Temperatures
should also moderate from the much below temps on Mon-Wed.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 625 PM EDT Fri Oct 27 2023
Low clouds and scattered showers as well as a narrow cold frontal
rain band with potential for embedded thunderstorms mainly
southeast of KGRR will cause reductions to MVFR/IFR this evening
at all the terminals.
Showers will taper off after fropa and winds will veer to the
northwest overnight. Primarily MVFR conditions due to low clouds
are expected overnight into Saturday morning. Conditions will
improve to VFR at all the terminals by late Saturday
morning/Saturday afternoon as cigs improve and northerly winds
continue to advect a drier airmass into our area.
&&
.MARINE...
Issued at 334 PM EDT Fri Oct 27 2023
Cold frontal passage this evening brings a brief thunderstorm
threat then a wind shift to the northwest with waves building to
4-7 feet. Winds subsiding Saturday while turning more northerly,
allowing waves to fall off below advisory levels by late in the
day. The current Small Craft Advisory may need to be extended in
time a bit, particularly south of Grand Haven.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 11 AM EDT Saturday for LMZ844>849.
&&
$$
UPDATE...Ostuno
SHORT TERM...Meade
LONG TERM...NJJ
AVIATION...Laurens
MARINE...Meade
Area Forecast Discussion
National Weather Service Northern Indiana
748 PM EDT Fri Oct 27 2023
.SYNOPSIS...
Issued at 742 PM EDT Fri Oct 27 2023
Chances exist for showers and perhaps a thunderstorm this evening
as a cold front pushes through. Chances for rain return Saturday
night and continue through Sunday night. Between now and the
weekend, the most noticeable change will be the cooler
temperatures coming in with highs in the 40s and 50s expect
Saturday and Sunday, but low temperatures in the 30s and 20s
likely for Monday morning and Tuesday morning. Snow is possible
Tuesday night.
&&
.SHORT TERM...(This Evening through Saturday)
Issued at 320 PM EDT Fri Oct 27 2023
With a high pressure ridge in the southeastern US and a trough in
the northwestern US, this sets up the area to be in a favorable
environment for warm weather with a chance for showers. As such, we
do have a cold front approaching for this evening with a strong
temperature gradient associated with it. The theta-e plume seems to
have a connection to the Gulf of Mexico and looks to bring in mid
60s dew points and around 10C 850 mb dew points, which may be
adequate for thunderstorm creation, but the best moisture of the
plume looks to pass by just to our south and east. Models do seem to
have some differences on where the better low level lapse rates set
up across the area with the NAM hastening them in the same area
where it brings in the better instability (arriving around 21z),
whereas the RAP appears to have the better instability (arriving
around 17z) created across west of I-69, but the better lapse rates
appear to be along I-69 on north and east. The main low level jet
dissipates across the US-24 corridor during the day today and
orients itself from northeast IL into Michigan. This provides some
effective shear for thunderstorms this evening to tap into and wind
shear does seem to arrive ahead of the main instability axis, at
18z. So, there is some misalignment of ingredients that may play a
role in weakening the chance for stronger storms this evening in
addition to the 20 to 06z window area-wide where the greatest
potential for stronger storms appears to occur. All told, think we
have the greatest potential to see gusty winds and hail from
thunderstorms in addition to locally heavy rain. There is around 100
m2/s2 of helicity for thunderstorms to tap into that may allow for
slight rotation in thunderstorms that form in areas where LCLs
remain below 1000m, but the question remains around if the
instability is stout enough to allow for more than just signs of
weak rotation.
The main moisture/instability axis exits the forecast area not too
long after 6z spelling the end to the thunder chance tonight. Then,
cool air begins to move into the area, as evidenced by the 850 mb
temperatures dropping into the single digits Celsius, allowing
temperatures to drop into the 40s overnight. Gusts are expected to
be weaker on Saturday than this afternoon, despite some mixing
occurring, as the pressure gradient and low level jet relax. Highs
only reach the 50s. Saturday is also expected to be dry as
subsidence behind the departing wave acts to suppress any
activity.
&&
.LONG TERM...(Saturday Night through Friday)
Issued at 320 PM EDT Fri Oct 27 2023
For Sunday, the aforementioned trough over the western US pivots
towards the area and a wave of low pressure forms along the
baroclinic zone just to our south. This reloads a chance for showers
Saturday night into Sunday, but instability is low enough to keep
thunder chances out. There is a period of dryness that comes in
midday Sunday that may provide a brief lull in the precipitation or
potential just a drizzle setup for areas closer to I-69. Whereas
areas closer to Lake MI may actually continue to precipitation due
to the affects of an f-gen band. Either way, it looks like showers
return Sunday afternoon into Sunday with a renewed push of low level
moisture in a sort of anafrontal type setup north of the front, but
with enough upper divergence to provide lift. With the front not
moving too far during this period, expect only a small diurnal
increase in temperatures Sunday from the 40s Saturday night to the
mid 40s to low 50s Sunday daytime.
Subsidence follows again for Monday as surface high pressure noses
in. 850 mb temperatures also continue to drop into the below 0C
range indicating our next chance for low temperatures in the 30s.
Although we`ll need to see if lingering cloud cover and excited
winds can limit evaporational cooling and, therefore, the potential
for frost formation. Highs on Monday only reach the low to mid 40s
despite the clearing of cloud cover.
Our first chance at a widespread freeze arrives Tuesday morning as
temperatures drop into the 20s for lows ahead of a cold front from a
clipper-like system. Moisture appears very limited, but we may have
a chance at producing our first snow of the season Tuesday night,
which is Halloween night. Any light system snow would transition to
lake enhancement Tuesday night into Wednesday, but inversions appear
shallow enough to restrict overall severity of the lake enhanced
snowfall. Through this, the potential to accumulate on roadways from
the snow also appears limited as the 70s and 80s temperatures we are
having now, will be in the too recent past.
Surface high pressure keeps us dry through the rest of the work
week. We trend warmer from Wednesday`s upper 30s to low 40s to
Friday`s either side of 50 degrees, which is still a few degrees
below normal for that time of year.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 742 PM EDT Fri Oct 27 2023
Predominantly MVFR to VFR conditions expected at the TAF sites.
IFR conditions are possible briefly within any heavier showers. As
of this writing a cold front is draped from NE Lower Michigan down
through eastern Lake MI and into IL/MO. So far, thunderstorm
activity has been limited to the southern IL/MO area--and has
decreased in intensity with the loss of daytime heating. Expect
WSW winds to shift to the NW through the night, eventually
becoming N-NE by tomorrow. There are chances for rain showers,
with the lower visibilities and ceilings confined to stronger
cells. Thunder is possible, but don`t expect it to become
widespread thus left out of the TAF for now. Otherwise, rain
(currently over Chicago area and just south of KFWA) should move
in tonight, then exit the area by morning (KSBN after 6z).
Improvement to VFR is expected tomorrow afternoon.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory until 2 PM EDT Saturday for LMZ043-046.
&&
$$
SYNOPSIS...Roller
SHORT TERM...Roller
LONG TERM...Roller
AVIATION...MCD
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Area Forecast Discussion
National Weather Service North Platte NE
622 PM CDT Fri Oct 27 2023
...AVIATION UPDATE...
.SYNOPSIS...
Issued at 321 PM CDT Fri Oct 27 2023
Key Messages:
- Significant snow appears likely and the threat of snow has
increased across southwest Nebraska.
- A significant blast of cold air will move into Nebraska Monday
night and near or subfreezing high temperatures appear likely
Tuesday.
- A warming trend is likely Wednesday through Friday leading to
near or above average temperatures by Friday.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 321 PM CDT Fri Oct 27 2023
The models are showing 2 or 3 banded snow structures developing
Saturday morning through Saturday evening. If the bands overlap,
heavy snow accumulations over 6 inches will develop. Most models
don`t show this and the forecast suggests an initial band forming
later tonight and early Saturday morning across the wrn Sandhills
followed by a second band later in the morning across the srn
Panhandle, east northeast into the srn Sandhills. A third band is
expected to develop along and south of Interstate 80 Saturday
evening. The models suggest each of these bands will be capable of
producing 2 to 3 inches of snow.
The NAM and RAP show convective enhancement at times which could
lead to snowfall rates near 1 inch per hour. There are hints of CSI
developing in the banded structures where theta-e lapse rates are
negative. The very strong midlevel winds aloft, 70-100kts, and 850-
300mb RH near 85 percent combined with cooling temperatures aloft
suggest the potential for significant snowfall. The 15z SREF looks
lofty showing plumes clustering 0.5-0.6 inches of storm total liquid
from near KOGA to KTIF. In summary, snowfall amounts could be
increased in the next forecast later tonight and the location of the
bands is by no means certain.
The forecast assumes less QPF concentration leading to amounts of 2
to 5 inches spread out across much of wrn and ncntl Nebraska. Winter
Weather Advisories are now in place beginning late tonight across
the north and Saturday afternoon across the far south. The winter
weather should exit the region overnight Saturday and Sunday morning.
It is worth noting the location of the predicted snow bands is
uncertain given the 15z RAP places all three along and south of
highway 2 while the NAM, SREF and HREF spread the bands north and
south. The QPF centroid for this forecast has drifted south about 50
miles and is now from KOGA east northeast to KTIF.
.LONG TERM...(Sunday through Friday)
Issued at 321 PM CDT Fri Oct 27 2023
Attention is drawn toward an arctic high pressure system moving
off Siberia into AK this afternoon. The models are in excellent
agreement building the high to near 1035mb and moving it rapidly
south south through the Great Plains Monday and Tuesday. The
models show temperatures at the h850mb level around -5C to -10C
and the risk of near of below freezing high temperatures Tuesday
continues. The 20-30 percent RH in the h850-300mb layer suggests
clear skies and the high centered over Nebraska Tuesday afternoon
would maintain light winds until the high moves south Tuesday
evening.
Heights aloft and h850mb temperatures will rise rapidly Wednesday
through Friday leading to near or above average temperatures. The
forecast is dry Monday through Friday and other than Tuesday, no
significant weather features are predicted by the models.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 622 PM CDT Fri Oct 27 2023
The main aviation weather concerns for western and north central
Nebraska terminals include low ceilings and snow, primarily
tomorrow morning onward. Lower clouds in northern Neb (VTN) will
scour out briefly this evening before a more solid deck builds in
ahead of the snow. Expect bands of snow to develop by mid-morning
tomorrow as north/northeast winds remain generally light. Tempo
visby drops to 1SM are expected during bursts of heavier snow,
resulting in IFR conditions at times.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 1 AM CDT /midnight MDT/ Saturday to
7 AM CDT /6 AM MDT/ Sunday for NEZ004>010-022>029-035>038-094.
Winter Weather Advisory from 7 AM CDT /6 AM MDT/ Saturday to 10
AM CDT /9 AM MDT/ Sunday for NEZ056>059.
Winter Weather Advisory from 1 PM CDT /noon MDT/ Saturday to 10
AM CDT /9 AM MDT/ Sunday for NEZ069>071.
&&
$$
SYNOPSIS...CDC
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Snively
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
918 PM CDT Fri Oct 27 2023
.UPDATE...
Issued at 918 PM CDT Fri Oct 27 2023
Couple tweaks to forecast this evening. GOES nighttime
microphysics RGB imagery shows an expansive post frontal stratus
deck upstream blanketing most of WI, MN, and about the northeast
half of IA. A couple PIREPS this evening have reported this deck
to be about 1000ft thick with evening soundings showing a sharp
frontal inversion beneath which this stratus is trapped. HRRR
seems to have the best handle of this status and suggests it will
overspread the CWA tonight and that it`ll be pretty locked across
the area Saturday. It is a bit on the early side for post frontal
stratus to linger for days, so confidence is low on how extensive
the cloud cover will be tomorrow. For now, bumped up sky cover
tonight through mid-morning Saturday, but potential is certainly
there for stratus to stick around all day Saturday.
Other minor change was to nudge tonight`s low temps upward a bit.
Given the cloud cover and wind, temp drop tonight will be
strictly advective in nature and with sfc winds not terribly
strong and the temp gradient to the northwest pretty baggy, seems
like mid-upper 30s will be more common for lows tonight west and
north of Chicago and 40/lower 40s in the city and points south
including NW IN. If stratus hangs around tomorrow, that would
likely keep temps from rising very much and forecast highs for
tomorrow would need to be lowered. At this point, confidence in
stratus tomorrow is too low to make any big changes to tomorrow`s
temps.
- Izzi
&&
.SHORT TERM...
Issued at 230 PM CDT Fri Oct 27 2023
Through Saturday...
Key Points:
* Temperatures will drop behind a cold front this afternoon and
evening with overnight lows expected to fall into lower 30s (west)
to around 40 (east).
* Isolated to scattered showers will accompany the front. The
threat for severe weather remains low (<5%).
* Saturday will be dry with highs either in the upper 40s or lower
50s, depending on cloud cover.
Discussion:
The low-level baroclinic zone responsible for waves of showers over
the past few days is finally on the move, thanks to the eastward-
advancement of the much-anticipated cold front now crossing northern
Illinois. The passage of the front is marked by a stark temperature
drop from the upper 60s to the lower 50s, as well as a brisk
westerly wind shift. Meager low-level instability continues to limit
the coverage and intensity of showers along the front, though a
gradual increase is expected this afternoon across northeastern
Illinois and especially northwestern Indiana where pockets of
clearing have helped temperatures jump into the low to mid 70s. With
a strong low-level kinematic field in place, the tallest showers may
produce gusty winds and even a funnel cloud or two, particularly in
northwestern Indiana where low-level instability will be greatest
and most able to facilitate downward momentum transfer. With that
said, the severe weather threat continues to look quite low (<5%).
After front clears the area this evening, increasing DCVA ahead of a
subtle upper-level shortwave lifting northeast toward the Great
Lakes should support scattered showers more or less near I-55 before
shifting eastward into northwestern Indiana before midnight. Showers
should wane before daybreak Saturday. Continued CAA bolstered by
blustery west winds overnight will drop temperatures into the low to
mid 30s, save for around 40 in northwestern Indiana.
Tomorrow, lowering inversion heights and the advection of dry air
from the west will make an earnest attempt to erode low-level
stratus, though confidence is low if sun will actually make an
appearance (e.g. low-level moisture can easily get trapped beneath
inversions this time of year, though the incoming airmass is quite
dry). With that said, if clouds clear, temperatures tomorrow will
have the opportunity to bounce into the low to 50s. If clouds hold
tight, temperatures may be restricted to the mid to upper 40s. Our
forecast will take the middle of the road approach with partly
cloudy skies and highs near 50.
Borchardt
&&
.LONG TERM...
Issued at 330 PM CDT Fri Oct 27 2023
Saturday Night through Friday...
Key Messages:
* Periods of primarily light rain Saturday night into Sunday
* Growing-season ending freeze likely Sunday and Monday nights
* Blustery and cold with a chance of scattered snow showers on Halloween
A fairly deep wedge of dry air between 850 and 700 mb will be in place
to start Saturday evening, which will at least initially offset an
uptick in large scale forcing from low amplitude impulses in southwest
flow aloft, and mesoscale forcing from a developing lower to mid-level
f-gen circulation. The antecedent dry wedge and also a feed of drier
air from the north have added uncertainty to how precipitation trends
play out Saturday evening through the overnight. All in all, this
has resulted in a slowing of precip onset (a primarily dry evening
north of I-80), and the focus of highest (categorical) PoPs being
near and south of I-80 in the late evening and overnight.
Given the likelihood of a sharp cut-off on the northern periphery
of the precip, there`s a growing chance for portions of far
northern Illinois to remain dry through the night. There`s enough
wiggle room in the exact position of banded rain to keep
mentionable PoPs in, but have trended areas near and north of I-90
down into the chance range (30-50%). The likely banded nature of
the precip with at least transient stronger f-gen suggests some
occasional moderate rainfall rates are possible where it does
rain, though all in all QPF should top out at no more than 0.2 to
0.3" by Sunday morning. Forecast lows range from about 35-40F for
the northwest half of the CWA and about 40-45F for the southeast
half of the CWA.
On Sunday, any lingering banded rain in the morning could be on
its way out if it didn`t move out already prior to sunrise. Have
noted that the ECMWF consistently has indicated the morning-mid
day period of Sunday being mainly dry. This isn`t unanimous among
the guidance, though it looks like we`re headed to at least lower
rain coverage through the morning for a good chunk of the CWA,
especially our Illinois counties. One possible exception to this
would be the potential for lake effect showers or lake enhancement
into parts of northeast Illinois and northwest Indiana. The previous
discussion mentioned a potentially more robust follow-up wave
(with conditional instability) interacting with the baroclinic
zone across the region Sunday afternoon, though this feature also
showed a generally southward trend among the 12z guidance members.
Confined likely PoPs to generally I-88 and south (except near the
lake in IL for some possible continued lake enhancement) and
categorical PoPs to south of the Kankakee River. Highs will only
be in the low-mid 40s for the northwest half of the CWA and mid-
upper 40s southeast.
On Sunday night, the first plunge of modified Arctic air being
driven southward by Pacific coast amplified ridging and downstream
deep troughing will send 850 mb temps down to -4 to -9C by around
sunrise Monday. Still can`t completely rule out the cold enough
air for snow "catching up" to the lingering showers tapering
steadily southeastward, though still think this is a less likely
outcome and have kept precip. mention in the form of light rain.
How long clouds take to clear will determine how cold it can get
in a more cold advection driven cool-down, and have highest
confidence in this outside of Chicago and northwest of the I-55
corridor where mid-upper 20s lows appear reasonable. Meanwhile,
for Chicago and southeast of I-55, low-mid 30s suggest a chance of
needing to wait another night for a true killing freeze.
Monday will be mostly sunny and unseasonably chilly, with a
moderate west-northwest breeze and highs in the upper 30s to lower
40s and a few mid 40s possible. High pressure ridging centered to
our south should be close enough for radiational cooling to bring
low temps on Monday night outside of Chicago down into the low-
mid 20s, with upper 20s to around 30F in and near the city.
This brings us to our main period of interest in the long term,
Halloween Tuesday. Guidance remains in solid agreement conceptually
in a unseasonably deep/cold PV lobe (with 500 mb heights near 530
DaM) diving southeastward. If the wave dives far enough south,
there could be some bonafide bursts of accumulating snow into
parts of northern Illinois, though at this time the thinking is
Wisconsin will have a better chance of this playing out. A
sufficiently far enough north track of our wave of interest would
result in bursts of primarily non-accumulating snow showers along
a modified Arctic front. Maintained chance PoPs for this
potential, followed by a solid lake effect setup into Porter
County and especially points east Tuesday night as any lingering
snow showers or flurries to the west wind down on Tuesday evening.
The main message continues to be to plan for a blustery and cold
afternoon and evening for your trick or treaters with temps in the
30s and wind chills in the 20s and the potential for the novelty
of some snowflakes in the air.
Wednesday, while featuring solidly below normal temps (low-mid 40s
highs) will start a moderating trend, along with dry conditions,
lasting through the end of next work week as the mid and upper
pattern becomes more zonal. High temperatures are forecast to
return to near/around 50F on Thursday and the low-mid 50s on
Friday. Overnight lows will trend upward as well.
Castro
&&
.AVIATION...
For the 00Z TAFs...
649 PM...Forecast concerns include...
Rain with mvfr vis early this evening.
Gusty northwest winds into the overnight hours.
Mvfr cigs through at least Saturday morning.
An area of rain is moving across the Chicago terminals currently
and may briefly reduce visibility into the 3-5sm range. Once this
rain ends this evening, dry weather is expected through early
Saturday evening. There will be another chance of rain late
Saturday evening into early Sunday and it may remain just south of
the terminals through the end of the new 30hr ORD/MDW taf period
and for now have only prob mention.
Prevailing cigs may be somewhat variable this evening. There are
patches of vfr along with areas of low mvfr cigs and there is a
narrow area where clouds have scattered across northwest IL.
Maintained prevailing mvfr cigs through late Saturday morning
given the expansive area of mvfr clouds across WI and MN. Its
possible mvfr cigs continue into Saturday afternoon and evening.
Northwest winds will gust into the lower 20kt range this evening
as they slowly turn more north/northwest. Winds will eventually
shift to north/northeast Saturday morning and then are expected to
remain northeast into Saturday evening. cms
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...IL nearshore waters until 4 AM Saturday.
Small Craft Advisory...IN nearshore waters until 1 PM Saturday.
&&
$$
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Area Forecast Discussion
National Weather Service Norman OK
1043 PM CDT Fri Oct 27 2023
...New AVIATION...
.SHORT TERM...
(This evening through Saturday)
Issued at 318 PM CDT Fri Oct 27 2023
Short-term observations and forecast trends will be absolutely
critical to the upcoming forecast. Multiple waves of precipitation,
as well as multiple shots of cold air, will occur this weekend, and
this forecast will attempt to address each impactful concern. For
tonight and tomorrow, the concerns will be:
-Colder highs tomorrow (high confidence)
-Widespread rain tomorrow (high confidence), with some flooding
potential in southeast Oklahoma (medium-low confidence) and the
potential for a few stronger storms capable of small hail (medium
confidence).
The postfrontal stratus deck is mixing out this afternoon, and
temperatures are trying to climb back into the low 60s in the face
of cold advection. It will be interesting to see what, if any,
effect this has on temperatures over the next 24-48 hours. At least
tonight, cold advection should weaken to a degree as cloud cover
begins to build in and northerly winds weaken.
Widespread precipitation chances will begin tomorrow, with
isentropic ascent increasing near daybreak in the Red River region
and spreading northward throughout the day. Models still maintain a
significant discrepancy in the nature of this precipitation. NAM
model forecast soundings are suggesting perhaps a deeper moist layer
than they did yesterday, which may be more conducive to a
precipitation shield. In all likelihood, this shield will develop
across southern and southeastern Oklahoma tomorrow during the day in
advance of a weak impulse moving northeastward out of the Texas Hill
Country. 6-hour rain values are likely to stay below 2 inches per
HREF guidance, but there may be a band in the Bryan/Atoka/Coal
County region that sees some convective enhancement, with localized
flooding possible. Given the current expectation that most areas
will see rain totals below GFFG thresholds, have opted not to issue
a flood watch.
To the north, precipitation may be more sporadic and rooted within
the zone of the strongest 850-700 mb warm advection. Notably, CAMs
in this area develop a zone of elevated instability tomorrow
afternoon, with some HRRR soundings suggesting MUCAPE values could
reach nearly 1,000 J/Kg. Between that and veering wind profiles,
this looks like a classic case of fast-moving, rather high-coverage
"cold" thunderstorms throughout the afternoon in western, central
and northern Oklahoma that will contain the risk of lightning and
small hail. A few strong to severe thunderstorms would not be a
massive shock, either. Temperatures are expected to largely remain
steady underneath the shallow cold airmass with widespread
cloudiness, rain, and wet-bulbing in place.
Meister
&&
.LONG TERM...
(Saturday night through next Thursday)
Issued at 318 PM CDT Fri Oct 27 2023
The multi-faceted fall cold snap will continue into next week. A
summary of hazards:
-Rain continues Saturday night (high confidence)
-A cold front will bring colder temperatures Saturday night (high
confidence), with a chance of freezing rain (medium-low confidence)
and sleet (medium-low confidence) in northwest Oklahoma Sunday
morning.
-Cold conditions from Sunday afternoon through Wednesday (high
confidence).
While the area of steadier rain will likely depart southeast
Oklahoma before nightfall Saturday night, isentropic ascent will
continue across the northern half of the area. Thus, scattered to
numerous cellular showers and thunderstorms will continue in the
area throughout the night.
Overnight, another cold front will enter the area. This one will
bring a source airmass which NAM HYPSLIT analysis suggests is
over North Dakota right now. If that`s true, then the widespread
mid-20s temperatures over North Dakota this afternoon offer a
pretty cold comfort. It is unlikely that we see temperatures drop
into the low 20s in northern and northwestern Oklahoma, but with
observations largely trending colder, it seems plausible that we
have an area of 28-32 degree temperatures near daybreak. Some
lingering WAA near 700 mb at the top of the warm nose, and a
continuation of convective instability, would seem to suggest that
in addition to a threat of some freezing rain, convective
sleet/graupel is also a possibility. Indeed, we often see in
events like this that while we may cue in on freezing rain as the
primary hazard, convective cells tend to produce sleet/graupel
that have the greatest impacts. Added IP to the grids in northwest
Oklahoma in addition to RA/FZRA.
The 700 mb cold front will arrive by Sunday afternoon, and apart
from maybe some flurries with lingering saturation in the boundary
layer, our precip event should draw to a close by Monday morning.
Sunday`s highs will be the coldest of the year so far, with some
areas failing to make it out of the mid-30s and sub-50 temperatures
area-wide.
With drier weather expected by Monday, we should be able to
efficiently cool off with a hard freeze expected in northern
Oklahoma and freezing conditions possible as far south as the Red
River. One final cold front will arrive on Tuesday, with a
widespread hard freeze signaling an end to the growing season
Wednesday morning. The end of the Arctic snap should occur
sometime toward mid-to-late next week, with largely dry weather
expected.
Meister
&&
.AVIATION...
(06Z TAFS)
Issued at 1040 PM CDT Fri Oct 27 2023
MVFR stratus continues to slowly spread northward over OK tonight.
This trend will continue well into the forecast period, as drizzle
and rain develop after ~12Z for most terminals. Most of the
precipitation should remain light until ~18Z. A few thunderstorms
still appear possible, but it`s unclear how widespread they will
be so we will keep TS out of the TAFs for now. Winds will
generally remain north to northeasterly around 10 to 15 kt.
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 60 46 46 36 / 20 30 80 80
Hobart OK 60 46 48 33 / 10 30 90 90
Wichita Falls TX 71 48 52 40 / 50 70 90 80
Gage OK 57 37 42 27 / 0 40 80 90
Ponca City OK 54 41 46 33 / 10 30 70 80
Durant OK 82 51 56 46 / 60 70 90 90
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&
$$
SHORT TERM...04
LONG TERM....04
AVIATION...03
Area Forecast Discussion
National Weather Service Tucson AZ
Issued by National Weather Service Phoenix AZ
140 PM MST Fri Oct 27 2023
.SYNOPSIS...Slightly above normal temperatures will persist
through Saturday. Another weather system will bring occasionally
gusty winds and even cooler conditions to the area beginning
Sunday and continuing through Tuesday. A warming trend is expected
late in the week as high pressure returns to the Desert
Southwest.
&&
.DISCUSSION...
Clear skies predominate across southeastern Arizona this
afternoon. Surface temperatures and dewpoints are both running
near or slightly above normal for this time of year. Further
upstream, latest RAP analysis reveals a broad trough across the
northern Rockies, while a much colder air mass plunges southward
down the east side of the Rockies.
Latest model ensembles indicate another trough across western
Canada will amplify as it drops southward into the Great Basin
Saturday. Slightly above normal temperatures will continue
tomorrow followed by cooler conditions Sunday as the trough axis
sweeps through the area. Another trough moving through the Four
Corners will likely reinforce the cooler conditions Monday and
Tuesday and there is a 50-60 percent chance high temperatures each
day will fail to reach 76 degrees in Tucson, which would make it
the coolest day so far this fall. Windy conditions are also
anticipated Monday and Tuesday in spots, though ECMWF Ensemble
EFIs generally below 70 percent do not suggest anything anomalous,
except for some pockets in Graham County, where gusts could reach
40 mph.
Further northeast, latest NBM indicates a 25 percent chance of
precipitation across the White Mountains Monday. Precipitation
could fall in the form of snow, but accumulations are not
anticipated. Meanwhile, latest NBM also indicates a 50-90 percent
chance of freezing conditions Tuesday and Wednesday morning,
particularly in the eastern valleys extending from 20 miles north
of Willcox to Douglas.
High pressure in the eastern Pacific will build across the
intermountain West midweek. Latest ensembles indicate positive
height anomalies will increase in coverage and magnitude,
translating into a warming trend late in the week.
&&
.AVIATION...Valid through 29/00Z.
SKC. Sustained SFC winds remain light AOB 8 kts through tomorrow
morning. Predominant SW winds pick up at KDUG and KOLS between 18-
20Z, with gusts in the mid to upper teens. WNW directions will be
favored at KTUS tomorrow afternoon, with gusts in the mid teens as
early as 19Z. Aviation discussion not updated for TAF amendments.
&&
.FIRE WEATHER....Mostly clear and dry into this weekend with a
warming trend resulting in high temperatures a few degrees warmer
than average and minimum RHs dropping into the teens most valley
locations through Saturday. 20 foot winds generally light and
following diurnal trends through Saturday. Then a dry and cool
weather system will affect the area next week with breezy to
locally windy conditions and cooler temperatures, especially the
night time low temperatures.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
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DISCUSSION...Hirsch