Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/20/22
Area Forecast Discussion
National Weather Service La Crosse WI
1000 PM CST Sat Nov 19 2022
.DISCUSSION...(This evening through Saturday)
Issued at 213 PM CST Sat Nov 19 2022
- Remaining cold through Sunday
- Potential for some precipitation Thanksgiving into Friday
Tonight and Sunday...
Arctic air mass continues sagging southeast with the upper level
trough evident on satellite water vapor imagery. With the cracking
cold air advection, low level lapse rates steepened providing
slight instability and some heavier bouts of snowfall rates
temporarily traversed the area this morning. Now that low level
CAA has weakened, upstream conditions suggest lighter snowfall
rates within scattered snow showers into tonight. Temperatures in
the teens extend from western Wisconsin into central Minnesota.
Slight clearing overnight will allow temperatures to reach the
single digits area wide. While wind gusts wane overnight, wind
chill temperatures still expected to be below zero area wide. A
meager low level trough will scoot by Sunday morning, providing
precipitation chances primarily in central Wisconsin. Have
increased PoPs in Clark & Taylor counties, with HRRR (19.12Z) and
RAP (19.15Z) soundings showing a seriously stout dendritic growth
zone. Snow will be transient, lasting only a couple hours, but
given the potential for such a thick DGZ with mid level warming,
something to keep an eye on. With short term model consensus
lacking, HREF (19.12Z) highest confidence for at least 0.1". Winds
remain increased primarily west of the Mississippi River during
the day Sunday with highest confidence peaking above 30 mph
according to HREF (19.12Z) probabilities.
Thanksgiving Holiday week...
The models are showing a pattern shift to occur ahead of
Thanksgiving. The current northwest flow looks to transition
through a period of zonal flow to having a long wave trough
develop over the central part of the country by Thanksgiving.
Within this broad scale signal, there are some differences on how
the long wave trough develops. The 19.12Z GFS suggests the whole
trough will have a positive tilt extending from an upper level low
over Hudsons Bay. The 19.00Z ECMWF and 19.12Z CMC suggest a
stronger short wave trough coming through the zonal flow looks to
dig into the mid-Mississippi River Valley leading to the
development of an upper level low within the long wave trough.
Looking at the cluster analysis for this time frame, all four
clusters show some anomalies for lower heights across the mid to
lower Mississippi River Valley with the two clusters predominantly
made of ECMWF and CMC solutions have stronger anomalies. With the
uncertainty on where the upper level low may develop, the overall
probabilities for precipitation still look to be on the low side.
Data from the 19.00Z EPS would suggest the probabilities of
getting 0.01" Thanksgiving day are in the 30 to 40 range and drop
to under 10 for 0.1". Right now, surface temperatures look to be
warm enough for any precipitation that occurs to mainly be rain,
but some concern that colder air could get drawn in for a light
snow event for at least parts of the area. Fortunately, given the
current expectation of light qpf amounts, any snow should also be
on the lighter side. With the ECMWF being the most aggressive with
the upper level low development, it also then lingers some light
precipitation chances across parts of the area into Friday but
these probabilities look to be on the downswing during the day
with a slow eastward movement of the overall system.
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1000 PM CST Sat Nov 19 2022
CIGS: low/mid level warm air advection moves in overnight, ushering
in a few hours of a VFR mid deck. It should clear by 18z-ish Sun
with SCT/SKC condition then for the rest of the day/Sun night.
WX/vsby: no impacts anticipated.
WINDS: winds becoming southerly overnight and holding under 10 kts.
They will pick up a bit for Sunday with mixing promoting a few gusts
into the lower 20 kts - not nearly as windy as Saturday.
Area Forecast Discussion
National Weather Service Goodland KS
415 PM MST Sat Nov 19 2022
.SHORT TERM...(This evening through Monday)
Issued at 147 PM MST Sat Nov 19 2022
At the start of the short term period, the latest RAP analysis has a
north-northwesterly upper air flow over the CWA being underneath the
rear portion of an upper air trough with a ridge over the Pacific
coast. Current satellite imagery and surface observations show clear
skies over the region with surface winds blowing out of the north-
northwest gusting up to around 25 mph. Forecast models show the
ridge moving eastward a bit as the trough departs towards the east
coast keeping the same flow through the remainder of the day. At
the surface, the CWA sees dry conditions throughout the rest of Saturday
with some elevated fire weather concerns for areas west of a
Wray-Goodland-Leoti line for a few more hours before the evening.
Minimum RH values look to be in the upper teens in the
southwestern quadrant with the occasional gust around 25 mph
expected in this western region. Daytime highs for today look to
be in the upper 30s to middle 40s with overnight lows being in the
lower to middle teens.
On Sunday, forecast guidance shows the CWA remaining underneath the
front part of the upper air ridge with a weak subtropical trough
over the NM/TX border giving the CWA a generally northerly weak
upper air flow throughout the day. At the surface, dry conditions
expect to continue across the CWA with little to no cloud cover.
While forecast minimum RH values look to be in the middle teens
across the CWA, light winds due to the axis of a surface trough
being in the region may hinder fire weather potential. Daytime
highs for Sunday look to be in the lower to upper 50s while the
overnight lows range between the middle teens and lower 20s.
For Monday, the CWA looks to get a west-northwesterly flow over the
CWA as models show the subtropical weak trough moving eastward. At
the surface, dry conditions are expected once again with clear
skies expected throughout the day. Forecasted minimum RH values
for the afternoon hours west of a line from Joes, CO to Russell
Springs, KS look to be in the middle teens. Similar to the
previous day, light winds will hinder any fire weather concerns.
Monday`s daytime highs expect to be in the upper 40s to middle 50s
with overnight lows in the middle teens to lower 20s.
.LONG TERM...(Tuesday through Saturday)
Issued at 113 PM MST Sat Nov 19 2022
The extended period looks to feature mainly above normal
temperatures with a quick shot of cooler air over the Thanksgiving
Tuesday, the upper level pattern looks to remain zonal allowing
sunny skies and above normal temperatures to be prominent across the
entire area. I opted to up temperatures a few degrees as 850mb
temperatures reach around 11C in part to southwesterly surface
flow as a result the entire area looks to see highs in the 50s
along with overnight lows falling into the low 20s.
Wednesday, will another nice for mid to late November with even
warmer temperatures in the upper 50s to mid 60s developing across
the area. A dry air mass will be in place which will allow RH
values to fall rather low into the low to upper teens. Winds will
however be less than 10 knots across the area with the exception
being across east Colorado (Kit Carson/Yuma counties) where winds
may become northwesterly around 15-20 mph for an hour or two
before sunset ahead of the next shortwave. As a result elevated
fire weather conditions may become realized for a few hours.
Wednesday night and into Thursday morning, a quick shot of cooler
air as the shortwave mentioned above moves into the area. The
overall track of the shortwave remains a bit murky at this time as
the ECMWF keeps the colder air and precipitation chances further
east out of our area. The GFS has a more southern track which favors
cooler temperatures for the area and perhaps some light
precipitation along and west of the Colorado border. I have left
the forecast dry for now until some consistency shows itself in
guidance. Winds will become breezy to gusty behind the
trough/front as NW winds around 20 mph will expected along with
gusts up to 30 mph.
Thanksgiving Day, will be cooler with highs in the mid 40s to low
50s across the area. Gusty winds up to 50 mph at times still look
like a possibility however guidance has brought down the strength
of the overall wind field; cloud cover may hinder how strong
winds do become as well. I didn`t want to stray away from previous
forecasts in case the 12Z data is an outlier so the overall
forecast remains relatively the same. A blend of the NBM and 90th
percentile NBM was used for wind speeds. The remainder of the
extended is a bit uncertain as guidance varies quite a bit
between the GFS and ECMWF as the GFS develops a compact low over
the southern Plains and the ECMWF develops a larger low over the
upper Midwest. Ensemble guidance however continues to indicate
above normal temperatures continuing to end November.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 413 PM MST Sat Nov 19 2022
For KGLD & KMCK... VFR conditions are forecasted for the period.
Winds will pick up this evening out of the west and become more
northwesterly around sunrise. The GLD ASOS outage remains.
Area Forecast Discussion
National Weather Service Grand Rapids MI
837 PM EST Sat Nov 19 2022
Issued at 836 PM EST Sat Nov 19 2022
So far the forecast largely remains on track. I see no reason to
change our headlines at this point. We still continue to get
locally heavy snow shower and winds continue to gust to around 40
mph near the lake shore and even inland gusts are still in the 25
to 35 mph range. The latest MDOT road conditions show slow travel
on just about all area roads from Lansing west to the Lake
Michigan shore on I-96 and also on I-94, US-131, US-31, US-127
(Lansing and south) and other major travel routes. While the
snowfall rates will be diminishing over the next few hours, we
will continue to see accumulating snow, some blowing snow in open
area and temperatures will remain well below freezing. Likely in
many parts of Southwest Michigan it will be the coldest night of
the month so far.
The latest run of the RAP model shows the best lift in the DGZ at
8 am was between I-80 and I-94 and currently that is where the
strongest snow shower are. That area will continue to pivot
southward and be south of I-94 by midnight. There is yet one more
area of lift in the DGZ that must come through before this record
breaking snow event comes to and end Sunday morning. That one is
currently over northern Lower Michigan. That will also slowly
rotate southward but this time it will also spread inland. This
band of enhanced snow showers is the back edge of the better lift
in the DGZ. Once that is through the event is done. We will still
see snow showers into midday Sunday but they will be more like
snow flurries than anything meaningful for accumulations.
As for snow accumulations, I expect 1 to 2 inches of snow yet over
ares west of US-127, with the greatest amounts near Kalamazoo and
north of Reed City, near US-131. Locations east of US-127 will
likely see less than an inch of snow overnight.
.DISCUSSION...(This evening through next Saturday)
Issued at 328 PM EST Sat Nov 19 2022
-- Winter storm conditions winding down overnight --
The main change in forecast thinking from previous AFD updates is
that poor travel conditions will persist after midnight for the
Ludington area. This is where the Lake Superior connection will keep
lake effect snow robust. No changes to headlines planned at this
Most solid area of enhanced reflectivity on the KGRR radar at 245 PM
extended from Kalamazoo to east of Hastings. Even though radar looks
less impressive farther west with a broken cellular appearance, this
area still features visibility well below a mile in many locations
including the lakeshore and GRR itself. This is expected to continue
the rest of this afternoon.
Although not in the SPC Day 1 outlook, there are solid chances for
thundersnow late afternoon into early tonight over and adjacent to
southeastern Lake Michigan, where SBCAPE will climb towards 500 J
per kg in magnitude. Much of this SBCAPE will be realized within the
full extent of the -10C to -30C layer, meaning that sufficient ice
production will co-mingle with supercooled water and graupel to
achieve the differential fall speeds required for charge separation
By the 9 PM time frame, in addition to ongoing activity around
Ludington, lake effect snow will consolidate roughly south of a
Grand Rapids to Jackson line and continue well past midnight. By
sunrise Sunday, this area will spread east and become diffuse, with
perhaps a brief final salute of concentrated snow for the I-94
-- Recovery weather Sunday, quieter weather thereafter --
Fortunately, the better part of Sunday looks dry with lighter winds.
Wind chills will never climb out of the teens however. Our next
chance of precipitation will be of the liquid variety on
Thanksgiving Day. Precipitation remains in the forecast throughout
the Thanksgiving holiday weekend. Given that minimum temperatures
will often drop below freezing during this time, there is the
possibility for at least some impactful travel conditions.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 659 PM EST Sat Nov 19 2022
We have transitioned from widespread IFR due to the frontal band
snow area, to a more lake effect scenario. This will mean VFR at
times and LIFR at other times. For example MKG was 9sm BKN055 at
2255z then 30 minutes later they were 2sm -sn blsn bkn028. This is
classical for lake effect snow showers. This cellure snow shower
pattern will likely continue through about 04z. After that
inversions heights fall so snow shower intensity should lessen.
Between 06z and 12z I would think we`d vary between VFR cigs and
MVFR / IFR in snow showers. After 12z most of our TAF sites should
be VFR as the system continues to pull away. The I-94 TAF sites
may hold on to MVFR cigs into mid morning.
Winds will become less gusty after 06z but there may still be
gusts into the 15 to 25 knot range into early evening Sunday.
Issued at 328 PM EST Sat Nov 19 2022
After coordination with surrounding offices, will extend the current
Gale Warning to Monday morning. There will be a relative lull
during day Sunday and will message that accordingly.
MI...Winter Storm Warning until 7 AM EST Sunday for MIZ037>039-
Winter Weather Advisory until 7 AM EST Sunday for MIZ040-046-052-
LM...Gale Warning until 10 AM EST Monday for LMZ844>849.
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
738 PM EST Sat Nov 19 2022
Issued at 730 PM EST SAT NOV 19 2022
Mainly minor adjustments have been made to the grids for this
evening into the overnight. The main adjustment was to increase
sky cover a bit from the previous forecast as the band of low and
mid level clouds near an approaching cold front has been a bit
more robust than the previous forecast. No other changes were
needed at this time other than minor adjustments to hourly
temperatures based on observations.
.SHORT TERM...(This evening through Sunday night)
Issued at 410 PM EST SAT NOV 19 2022
* Record-breaking low temperatures (10s to low 20s) likely
* Wind chill temperatures between 0 and 15 above around sunrise
* Upper single digit lows possible Sunday night in a few sheltered
At 2055z, satellite showed clear skies over all of eastern Kentucky.
This has allowed temperatures to rebound into the mid 30s north of
I-75 to the mid 40s in the deeper valleys near the Virginia and
Tennessee borders. Winds have also picked up out of the southwest
and dew points have dropped as the diurnal heating has allowed
momentum and dry air to mix down from aloft. Weather station
networks show peak southwesterly gusts on the order of 15 to 30
mph while dew points have settled into the 5 to 15 degree range.
Looking upstream, the latest analyses shows another rapidly
approaching cold front now aligned from Lower Michigan to
southeast Indiana and on into northern Arkansas. This boundary is
evident from a leading band of clouds and trailing field of post-
frontal cumulus visible on satellite imagery.
Through the short-term, guidance is in good synoptic agreement. The
cold front will sweep through tonight, likely between 3 and 7z.
Moisture is almost nonexistent (PWATS are only near 0.10 ahead of
the boundary), and will fall further once the front passes. Thus
nothing more than a period of low clouds and possibly a flake are
expected, mainly over the northern half of the CWA and also along
the highest mountains near the Virginia border. Overnight
temperature trends are a bit challenging as winds decouple to
varying degrees this evening, particularly in the sheltered
valleys. However, strong cold air advection and the stronger
pressure gradient along and immediately behind the front should
reengage the winds at all locations for at least part of the
night. The HRRR gusts and BUFKIT Momentum Transfer products show
potential wind gusts of 15 to 30 mph. The gradient relaxes later
in the night allowing winds to die down and the valleys to
decouple again over the Lake Cumberland and Bluegrass first,
during the early morning hours, and then further east through
sunrise. Current thinking is that temperatures drop off quickly at
those location which decouple (particularly sheltered valleys)
this evening before rising slightly with the frontal passage. The
ridges and less sheltered locations will likely stay mixed through
most of the night with the more significant temperature drop off
occurring behind the front. Expect low temperatures of 10F to 15F
in the in valleys and sheltered locations west of the Pottsville
Escarpment and 15F to 20F in the Coalfield Valleys. The thermal
belt should see a northwest to southeast temperature gradient
ranging from the mid teens along the Escarpment to lower 20s over
far eastern Coalfield ridges. Wind chills/apparent temperatures
in the 0 to 15F range are expected by sunrise.
On Sunday, high pressure of modified arctic origins will build
eastward across the Commonwealth and crest over eastern
Kentucky/Central Appalachians on Sunday night. Early afternoon
temperatures in the -5 to -8C range at 925mb will only support daily
maximum temperatures in the 30 to 38 degree range, north to south,
even with bright sunshine. Winds will be much weaker though, thanks
to the relaxing pressure gradient. Dew points will drop off to -5F
to +5F with afternoon mixing. This dry air in combination with clear
high pressure cresting overhead will set the stage for another
unseasonably cold Sunday night. Look for widespread lows in the
10 to 15 degree range through the valleys and in the upper teens
to lower 20s over the ridges. COOP MOS shows the potential for
upper single digit lows in the coldest sheltered valleys.
.LONG TERM...(Monday through Saturday)
Issued at 402 PM EST SAT NOV 19 2022
* Moderating temperatures with large diurnal swings expected
* A cold front approaches Thanksgiving and brings a round of
precipitation Thursday night into Friday.
* Turning colder behind the front with a chance of snow showers
mainly Friday night into early Saturday morning.
The models are in good agreement through early next week
regarding a quasi-zonal long wave flow pattern to be the rule
across the CONUS. Model agreement then breaks down by the middle
and end of the week, as vigorous inbound short wave energy from
the eastern Pacific allows for significant downstream
amplification. Deep troughing will evolve across the middle of the
nation and then gradually shift towards the eastern CONUS by next
weekend. There still remains a lot of spread in the ensemble data
regarding the intensity, timing, and positioning of this feature.
This of course translates to lower confidence in the surface
details, and have generally stuck pretty close to the blended
Moderating temperatures will be the main story through Wednesday,
as high pressure gradually weakens and shifts off to our east with
time. Monday will feature a very dry day, as dew point
depressions likely push the 40 degree mark, with highs around 50.
This will set the stage for another night of teens in the colder
valleys Monday night, while ridges stay up closer to 30 degrees.
Lows will be a little more tempered across our southeast, as some
higher clouds increase out ahead of a southern stream transiting
short wave trough. Readings will continue to modify through the
middle of next week, with highs in the low to mid 50s Tuesday,
and mid to upper 50s Wednesday. Lingering dry air will continue to
allow for valleys in our east and northeast to retreat to the 20s
The cold front will approach on Thanksgiving, with increasing rain
chances in the afternoon. Overall, the best chance of more
sustained shower activity appears to arrive late Thursday night
into early Friday morning, where rain chances peak in the likely
range. As the deep trough axis shifts east across the Ohio and
Tennessee valleys Friday into Saturday, chances of precipitation
will be maintained, with cold air advection eventually allowing
for a chance of flakes across the area. Again, this is still low
confidence at this stage, given the aforementioned model spread.
Highs will retreat from the 50s Thursday, to the 40s for Friday
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 738 PM EST SAT NOV 19 2022
A moisture-starved cold front is approaching the area with a
rather persistent. but narrow band of clouds in the 6 to 8kft AGL
range. This band of clouds should work across the northern two
thirds of the area during the first 6 hours or so of the period.
However, even with this band of clouds to affect KSYM and probably
JKL and SJS, VFR conditions are expected to prevail through the
period. Southwest to west winds up to 10KT are expected ahead of
the front, before becoming west to northwest generally between 7
and 12KT immediately behind the front. Winds should then slacken
toward 12Z to the 3 to 8KT range.
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
823 PM CST Sat Nov 19 2022
Issued at 823 PM CST Sat Nov 19 2022
No significant changes to going forecast this evening, with dry but
cold and blustery weather persisting into early Sunday. Lake effect
flurries and snow showers will likely affect far northeast Porter
county overnight, and may produce reduced visibility and wind-blown
minor accumulations though the worst of these conditions will be
focused off to the east of the forecast area.
Evening GOES vapor imagery depicts a strong mid-level short wave
digging across the Midwest, with the core of the mid-level vorticity
maxima now east of the forecast area across northern IN/OH. At the
surface, a sharp cold front was evident also well east of the cwa
stretching from near Cleveland OH to the MO Bootheel. Cold, blustery
cyclonic low level flow persisted across northern IL and northwest
IN behind the front, with surface dew points in the single digits
evidence of the arctic origins of the air mass. While patchy wind-
rows of low level strato-cu lingered across parts of the area
(mainly far NE IL, LM and NW IN), the combination of deep-layer
subsidence in the wake of the mid-level vort and the dry low level
advection was working to erode these lingering clouds. While a few
isolated or scattered flurries can`t be ruled out of the remaining
shallow cloud layer, these should be inconsequential (no vis
reductions and no accumulations) and will come to an end as the
clouds fully erode through late evening/midnight. The exception to
this will be across far northeast Porter county in northwest IN,
where a slight northwesterly low level wind component may allow for
lake-induced flurries and snow showers to clip areas mainly east and
northeast of Chesterton. Radar trends indicate heavier snow showers
have been focused east of the Porter/LaPorte county line so far,
though RAP and other high-res guidance do suggest a slight veering
of the low level winds may maintain some potential for snow showers
to affect northeast Porter during the late evening/early overnight
hours. Will update the Special Weather Statement for that area
shortly, with no significant changes planned to the forecast.
Conditions will generally be worse east of our forecast area along
the I-94 and I-80 corridors across northern IN and southwest MI.
Otherwise, dry but blustery and cold conditions will continue across
the area overnight. Westerly winds still gusting 25-30 mph as of 8
pm CST will ease gradually and back southwest overnight, but with
temperatures eventually settling into the 5-10 above range (10-15
above in the core of the Chicago metro), wind chills will be in the
negative single digits in most spots by early Sunday morning.
Issued at 300 PM CST Sat Nov 19 2022
Through Sunday night...
* A period of heavier lake effect snow and wind into northeast
Porter County through this evening
* Bitterly cold tonight into early Sunday with lowest wind chills
of 0 to -10F
* Gusty winds Sunday PM and especially Sunday night, when gusts
up to 35-40 mph will be possible
The mid-winter pattern of daily flurries and snow showers has
again not disappointed today, with scattered bursts of heavy snow
in the most robust snow showers over northeast Illinois and northwest
Indiana. Given this behavior, we probably weren`t far off moisture
depth wise from higher end type snow squalls. The threat for additional
brief heavier snow bursts will be winding down and focus closer to
the lake through about 5 PM CST.
Concern then shifts to a period of very favorable lake effect
parameters for northeastern Porter County this evening. The
extreme lake induced instability with such a cold air mass (-17C
at 850 mb at KMPX at 12z) overhead will compensate for the non-
classic 290-300 deg wind direction for multi-cellular LES into
northeast Porter and particularly LaPorte Counties.
Well below freezing air temperatures, winds still gusting up to 35
mph or so and falling snow suggests some hazardous travel conditions
could develop. Explicitly forecasting 1-1.5" accumulation for the
area of concern. Contemplated issuing a short-fused Winter
Weather Advisory for Porter County, but opted to hold off with
some uncertainty on magnitude of any impacts and higher confidence
in them for northern LaPorte County. Planning to issue a SPS and
hitting the the threat in one of the afternoon Weather Story graphics.
Will continue to monitor trends over the next few hours.
Otherwise, the main story for the rest of the area will be the
mid-winter cold. Very low dew points in the dry Arctic air mass
supports some mid-high (positive) single digit lows, especially in
favored cold spots of northern Illinois. The surface high passing
well to the south will mean some wind (but certainly not like
what`s occurring as of this writing) through the night, yielding
minimum wind chills early Sunday of 0 to -10F.
The PV anomaly responsible for the bitterly cold weather will
quickly kick out on Sunday, with southwesterly warm advection in
its wake. May see some mid clouds through early afternoon followed
by clearing. Southwesterly winds will increase in response to
pressure falls from an approaching frontal trough, with afternoon
gusts up to 25-30 mph. Warm advection in this setup with no
antecedent cloud cover will enable high temps to recover to the
lower to mid 30s, though the wind means it certainly won`t be
pleasant outside. A robust low level jet (45-50 kt at 950 mb) will
develop Sunday night, so gusty winds will continue and in all
likelihood increase in the late evening and overnight. With the
low base of the LLJ, could see some sporadic gusts up to 35-40
mph, highest in/near Chicago and points north. After any small
temperature drop in the evening, temperatures will slowly rise
overnight into early Monday.
Issued at 204 PM CST Sat Nov 19 2022
Monday through Saturday...
The week of Thanksgiving will start off on a warmer and drier note
compared to what we`ve been dealing with the past couple of days.
Monday will likely see many areas reach the 40s for the first time
in about a week with a relatively "warmer" starting point for
temperatures in the 20s at daybreak and mostly sunny to partly
cloudy skies through most of the day contributing to the likelihood
of that occurring. How many areas get to 40 and just how warm our
warmest locations will be on Monday will depend upon how long warm
air advection off of southwesterly winds will be able to persist
over the course of the day before a surface trough axis shifts
across the region and veers winds around to a westerly and
eventually northwesterly direction. With high pressure to our
southeast on Tuesday and Wednesday, southwesterly winds will
return for a more prolonged stay and will help high temperatures
to climb to seasonable readings for this time of year in the 40s
and 50s on both days. A couple of subtle shortwave disturbances
will also swing through the region between Monday and Wednesday,
but an overall lack of moisture through the atmospheric column
should keep us precipitation-free through this time period, with
increasing high cloud cover being the only discernible sign of the
passage of these waves.
A potentially different story could play over the latter half of the
week as a potent upper-level northern stream trough enters the
Pacific Northwest and digs southeastward. However, confidence in the
forecast for Thanksgiving and beyond remains quite low with guidance
continuing to offer up a hodgepodge of possible solutions and not
much consistency being exhibited between successive operational runs
of most global models at this point. The main forecast uncertainties
revolve around how much phasing will occur with this northern stream
wave as it interacts with the southern stream and any embedded
perturbations within it, as well as where the northern stream wave
intercepts the southern stream. As can be implied, models remain all
over the place with how they resolve this interaction. Some operational
runs suggest that the northern and southern stream waves will phase
favorably and induce surface cyclogenesis that will eventually
see a relatively deep surface low track into and occlude over the
Great Lakes, Mid-Atlantic, or New England, presumably resulting
in a healthy dose of precipitation somewhere in these regions over
the holiday weekend. In a scenario like this, precipitation types
of both rain and snow appear to be in play for our forecast area,
though the exact precipitation type evolution and amount of
precipitation that we will receive will depend on where exactly we
end up relative to the track of the surface low, as well as how
much this low ultimately deepens. Other solutions suggest that
there will be little to no constructive phasing of the northern
and southern stream waves, or that it will occur far enough away
from us where the exact degree of phasing may not matter much for
the purpose of our late week forecast anyways. If a scenario like
this were to verify, then we could get through the holiday weekend
without seeing much of any precipitation at all.
Considering all of the existing uncertainties, did not stray from
the NBM, whose chance PoPs for the Thanksgiving afternoon through
late Friday time frame appear to be reasonable and more or less
in line with ensemble mean guidance. The main message for now
remains that there`s still a chance for rain and/or snow to occur
in our forecast area over the holiday weekend, but that confidence
in the exact specifics of how things will play out remains quite
low at the moment. Nevertheless, continue to keep an eye on the
forecast in the coming days, especially if you have travel plans
for the holiday, as there is a possibility that weather could
cause impacts over a good chunk of the eastern CONUS this holiday
For the 00Z TAFs...
Aviation Forecast Concerns:
* Isolated to widely scattered flurries/light snow showers ending
early this evening. No accumulation.
* Blustery west winds gusting near 30 kt gradually easing early
this evening. Winds become southwest Sunday, then increase again
Sunday evening with gusts increasing above 25 kts.
Digging upper level trough will move quickly east of the region
this evening, with blustery west winds continuing to pull drier
air into the region. This will allow lingering isolated to widely
scattered flurries/light snow showers to end early, and these are
not expected to produce impacts to visibility or accumulations.
Will see a scattered to broken VFR deck linger through the evening,
before clearing out late. VFR conditions are expected through the
West winds were still gusting near 30 kts at both ORD/MDW as of
23Z, though these will gradually ease early this evening. Winds
back southwesterly Sunday and become a bit gusty again during the
afternoon. Winds look to strengthen Sunday evening as another
area of low pressure deepens north of the Great Lakes, with gusts
again approaching 30 kts from the southwest.
Issued at 426 PM CST Sat Nov 19 2022
Westerly gales will diminish late this evening from Winthrop
Harbor to Gary and in the pre-dawn hours of Sunday from Gary to
Michigan City. Hazardous waves for small craft will persist
through the morning from Gary to Michigan City, with hazardous
southwesterly winds up to 30 kt developing in the afternoon for
the entire nearshore. These southwest winds will further increase
to gales Sunday evening in response to low pressure passing well
to the north as conditions remain unstable over the lake. The
strongest winds in this setup will probably occur from 2-3 miles
from shore and out to the open waters. Issued a new Gale Warning
from 6PM Sunday to 4AM Monday.
LM...Gale Warning...Winthrop Harbor to Gary IN until 9 PM Saturday.
Small Craft Advisory...Winthrop Harbor to Gary IN until 3 AM
Small Craft Advisory...LMZ740-LMZ741-LMZ742-LMZ743...noon Sunday
to 6 PM Sunday.
Gale Warning...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...6 PM
Sunday to 4 AM Monday.
Gale Warning...Gary to Michigan City IN until 3 AM Sunday.
Small Craft Advisory...LMZ744-LMZ745...3 AM Sunday to 6 PM
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Area Forecast Discussion
National Weather Service Phoenix AZ
424 PM MST Sat Nov 19 2022
A weak and dry weather system passing through the region today
will bring another round of breezy winds, particularly across
portions of southeastern California today and then tonight into
Sunday morning for higher terrain areas east of Phoenix.
Dry conditions and near to slightly below normal temperatures
will continue through the middle of next week before even warmer
temperatures are likely late next week as a stronger high
pressure system moves over the region.
Latest water vapor imagery and streamline analysis reveal a
closed low in the mid-levels atop south-central Arizona. Surface
winds also suggest the presence of an inverted trough at the lower
levels. Weak vorticity-forced ascent is situated across
southeastern Arizona, though PWATs remain too low for organized
precipitation and only a few clouds are expected across far
eastern Gila County.
Biggest sensible impact across the forecast area has been some
windy conditions, mainly across portions of southeastern
California, and the Chocolate Mountains in particular, where the
flow is largely perpendicular to the terrain. Observations suggest
gusts likely reached 40 mph earlier this morning, however winds
will continue to taper off early this afternoon. Further east
across central Arizona, stronger northeasterly winds just above
the surface continue to mix out, resulting in gusts of 20 to 25
mph across the Valley. Latest HRRR also suggests the windy
conditions will dissipate this afternoon as the surface high
across the Great Basin weakens.
The focus for windy conditions will shift into southeastern
Arizona Sunday as the low-level flow acquires more of an easterly
component around the weakening low-level trough. However, ECMWF
EFI values indicate the strongest gusts will mainly be confined to
the higher terrain south and east of Phoenix early Sunday
morning. Nevertheless, latest ECMWF indicates gusts of 15 to 20
mph are still likely in the Phoenix area.
Ensemble suites are in good agreement indicating the flow will
become more zonal early next week. This will translate into near
normal temperatures through Wednesday. Thereafter, 90 percent of
the multi-model ensemble members suggest the flow will become more
amplified across the CONUS with a ridge building eastward from
the Eastern Pacific into the Desert Southwest. This will yield
above normal temperatures, likely reaching at least the upper 70s
across the Phoenix area Thursday-Saturday. There is also a 40
percent chance of reaching the 80 degree mark in Phoenix and El
Centro Friday. However, this would still fall well short of daily
records, which are in the upper 80s.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Northeasterly winds will persist this evening and through the
overnight hours. LLWS concerns are possible overnight but
currently expect this to remain just below TAF thresholds. A
period of breezes will be possible late Sunday morning as the
inversion breaks. Skies will remain mostly clear.
Southeast California/Southwest Arizona including KIPL and KBLH:
Northwesterly winds will persist through the forecast period,
weakening quickly this evening then mostly below 10 kt through
Sunday afternoon. Skies will remain mostly clear.
A dry weak upper level disturbance moving through the region
today will bring another round of breezy conditions for much of
the area. Locally windy conditions with wind gusts of 30-45 mph
will be possible across southeast California today, mainly over
ridgetops, and easterly winds of 30-40 mph possible tonight
through Sunday morning across the Arizona high terrain east of
Phoenix. By Monday, tranquil weather conditions are expected,
lasting through most if not all of next week. Temperatures will
be near to slightly below normal through the middle of next week
before warming to slightly above normal late next week. Moisture
levels will remain quite low through the period with daily MinRHs
in the teens across the western districts to 15-25% across the