Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/16/23
Area Forecast Discussion
National Weather Service La Crosse WI
1041 PM CDT Sun Oct 15 2023
.DISCUSSION...(This evening through Sunday)
Issued at 250 PM CDT Sun Oct 15 2023
Key Messages:
- Periods of clouds continue with seasonably cool temperatures
- Breezy and warmer Wednesday with rain chances returning
Wednesday into the end of the week. Still rain timing
challenges with the storm system, but amounts remain light, now
only a 30-50% chance for more than 0.05"
- Temperatures with highs in the 50s Thursday-Sunday
Through Monday:
Latest water satellite imagery indicates closed upper level low over
the northeast United States. Latest visible satellite imagery shows
low level stratus clouds rotating around the closed upper level low
and into the Great Lakes region. The area will remain under
northerly flow aloft on the backside of the closed upper level low
tonight into Monday. Latest 15.12z GFS/NAM indicate 925 to 850mb
moisture...in association with low stratus deck of clouds...to
advect into the forecast area this evening/tonight. Expect mostly
cloudy skies tonight across much of the forecast area. Due to
subsidence and daytime heating...low level stratus deck of clouds
will slowly erode during the day Monday.
With northerly flow aloft over the Great Lakes region...cooler air
will filter into the region. The 15.12z GFS/NAM suggest 925mb
temperatures plus 2 to plus 5 degrees Celsius by 18z Monday
across the forecast area. With the possibility of cloud cover and
cooler temperatures over the region...temperatures will be below
normal. High temperatures are expected to be mainly in the 50s.
Monday night through Sunday:
The HRRR/RAP forecast soundings continue to show enough low level
moisture for clouds and possibly patchy drizzle Monday night.
We`ll have to see how the cloud forecast evolves as this would
impact low temperatures Tuesday morning and how cold temperatures
will get/potential for frost.
Tuesday through Thursday night, a shortwave trough over
Alberta/Montana pushes southeast into the Dakotas and the Upper
Mississippi Valley and Great Lakes region. There continue to be
locations/timing differences related to rainfall between the
deterministic models for Wednesday. Moisture transport increases
along with enhanced lift with the left exit region of the upper
level jet. Precipitable water values increase to around 150% of
normal ahead of the cold front; around 0.80 or .90". The NAEFS
standard anomalies are around 1.5. The rain looks light though as
the frontogenesis weakens as it moves through. Scattered showers
continue until the low exits the area Friday night. Rain amounts
still look light with only 25 to 50% probabilities of 0.05" or
more.
Brisk south winds are forecast for Wednesday with temperatures
warming into the 60s. Temperatures for the rest of the extended
hold in the 50s for highs.
&&
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1040 PM CDT Sun Oct 15 2023
MVFR cigs are expected to begin at both TAF sites with some
incoming low-level stratus during the pre-dawn hours and persist
into the afternoon. However, uncertainty remains for how long MVFR
cigs will persist at KLSE when considering the 16.00z HRRR
soundings and with the 16.00z HREF cig probs showing medium
confidence (30-60% chance) for category reductions to persist at
KLSE later into the evening, opted to leave out of current TAF
issuance due to lower predictability. Winds will be predominantly
from the N/NW between 5-10 kts and lessening towards the end of
the TAF period.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...DTJ/Zapotocny
AVIATION...Naylor
Area Forecast Discussion
National Weather Service Grand Forks ND
1035 PM CDT Sun Oct 15 2023
.UPDATE...
Issued at 1032 PM CDT Sun Oct 15 2023
02z HRRR and 02z NBM data still show some fog forming late tonight
in a narrow zone from eastern Manitoba thru Roseau/Hallock to near
Bemidji/Bagley then toward Wadena. This area in the patchy fog
forecast and will leave as is. Some hints too in the short term
models of patchy fog Devils Lake or Langdon area. See no reason to
alter any of the sky or patchy fog area tonight. Temps look
reasonable.
UPDATE Issued at 705 PM CDT Sun Oct 15 2023
Skies clear across the area at 00z. Some thin cirrus in central ND
moving east and some cirrus moving west thru Duluth and NW
Wisconsin. So clear sky tonight with some increase in cirrus but
more areas of cirrus vs widespread. HRRR and other short term
ceiling/vsby models backing off a bit in fog chances, but do
highlight a narrow zone where patchy dense fog may occur 10z-13z
from Roseau to Bagley. Will keep the larger area of patchy fog
that is in there as with light winds overnight some ground fog
could form just about anywhere.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 208 PM CDT Sun Oct 15 2023
Key Messages:
-Quiet and dry conditions throughout today, with temps in the 50s to
lower 60s.
-Patchy dense fog during the morning hours on Monday, within the Red
River Valley towards the east.
-Continued warm and dry conditions Monday afternoon and into
Tuesday.
Discussion:
Clouds linger across parts of lakes country this afternoon, with a
majority of the region seeing mostly sunny skies. Thanks to the sun
temperatures are easily climbing into the upper 50s to lower 60s
this afternoon. Quiet and dry conditions continue overnight, with
temperatures dropping down into the low to mid 30s for lows. Dew
points remain in the low to mid 30s for the Red River Valley towards
the east, with light and variable winds. Mostly clear skies
overnight, combined with dew point depressions near zero, and light
and variable winds means patchy dense fog potential 10z through 16z.
Fog could become more widespread depending on cloud coverage from
the east. Short range guidance wants to bring clouds into lakes
country overnight which could limit fog potential from becoming
widespread. None the less, patchy dense fog will be possible Monday
morning, within the Red River Valley points eastward. Visibility
reductions down to a quarter of a mile will be possible on an
isolated basis.
As the sun rises Monday and temperatures warm, chances for fog begin
to diminish. This occurs late morning and into the early afternoon.
Another dry and quiet day is expected on Monday, with highs in the
upper 50s to lower 60s once again. This is all thanks to an upper
level ridge shifting through the region and warm air advection
moving into the northern plains. Clouds begin to move in for Monday
night, which will help limit fog potentials for Tuesday morning by
keeping overnight lows warmer.
.LONG TERM...(Tuesday through Sunday)
Issued at 208 PM CDT Sun Oct 15 2023
Key Messages:
-Ridge breaks down mid week, with an upper level trough digging into
the northern plains.
-Light precipitation chances Tuesday evening through Thursday
morning, with up to quarter of an inch possible (30-50%). Windy
conditions behind the upper level trough Wednesday afternoon and
evening.
-Ridge builds back in end of the week, with above normal
temperatures.
Discussion:
Ridge continues to shift east across the area Tuesday, with an upper
level trough translating through the region. Main forcing across the
region will be synoptic, with little frontogentic forcing. The
systems residence time is high, and lacks moisture content from the
Gulf of Mexico as a ridge remains in the southern United States.
This keeps precipitation amounts lower over a 24 hour period.
Precipitation chances increase Tuesday evening and last through the
early morning hours on Thursday. QPF probabilities of up to 0.25
inches is 30-50% across the region. Cold air advection wraps around
the system Wednesday afternoon/evening, with lapse rates approaching
8 C/km. This combined with a NW wind direction will help increase
wind potential Wednesday afternoon and evening. The strong pressure
gradients remain further towards western ND and eastern MT, but up
to 30kt gusts are possible within the valley points westward.
A building ridge out in the Pacific NW helps increase 1000-500mb
thickness levels end of the work week and into the new weekend. NW
flow aloft is pushed into southern Canada, with above normal temps
expected. Highs reach the mid 50s to lower 60s end of the work week
and into the new weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 705 PM CDT Sun Oct 15 2023
Question will be ground fog potential 10z-13z across RRV into MN.
Notoriously these are difficult to forecast and impacts vary
greatly. But some risk of fog, higher BJI. But otherwise kept out
per latest aviation short term vsby grids which keep chance only
in a part of NW MN. Light winds overnight turning south 5 to 8 kts
Monday.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Riddle
SHORT TERM...Spender
LONG TERM...Spender
AVIATION...Riddle
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
641 PM CDT Sun Oct 15 2023
.SHORT TERM...
Issued at 202 PM CDT Sun Oct 15 2023
Through Monday night...
Forecast concerns include lake effect rain showers through the
period and patchy frost across northwest IL late Monday night.
The first round of lake effect rain showers are moving southeast
and may completely end for a few hours later this afternoon into
early this evening. An upper trough will move south across the
region tonight bringing a chance of showers for mainly northwest
IN tonight, but then allowing for another lake effect setup that
will persist through Monday and possibly Monday evening. There is
some uncertainty with how far inland into IL the lake effect will
extend. General consensus is roughly an O`Hare Airport to Kankakee
line will be the western extent and this matches up well with the
current forecast. Will still have a narrow axis west of this line
for low chance pops, but east of that line, including Chicago and
northwest IN, have pops increasing to likely tonight into Monday
morning, then the lake effect looks to shift back east into
northwest Indiana, similar to today`s trends. Conditions may
become unfavorable rather quickly Monday evening, ending the lake
effect rain showers but both the HRRR and RAP now continue showers
into Monday evening and added low chance pop for this potential.
Where some sunshine persisted today, temps were able to warm into
the upper 50s. Expect the same for Monday, if enough sunshine
develops in the afternoon, expect highs in the upper 50s, perhaps
a few locations tagging 60.
A ridge of high pressure will move into the area Monday night with
light winds and clearing skies across IL. Low temps by Tuesday
morning will likely fall into the mid/upper 30s away from Chicago,
allowing for at least some patchy frost across northwest IL. cms
&&
.LONG TERM...
Issued at 245 PM CDT Sun Oct 15 2023
Tuesday through Sunday...
Key Forecast Messages:
* Seasonably mild Tuesday and Wednesday with an uncertain chance
of afternoon and evening showers on Wednesday
* Higher confidence in showers on Thursday then turning cooler to
close out the work week and into next weekend with some shower
chances continuing, especially near the lake in Indiana
Following a chilly and locally frosty start to Tuesday, southwest
winds, modest warm air advection, and plenty of sun will boost
afternoon temperatures back to near seasonable (lower 60s).
Persistent light to moderate southerly winds on Tuesday night
will result in overnight lows a few to several degrees milder
than Monday night, albeit still seasonably chilly in the low-mid
40s (upper 40s downtown Chicago). If winds diminish a bit more
than forecast, the dry air mass in place may enable favored
northern Illinois cool spots to dip into the upper 30s.
The main feature of interest for the Wednesday-Friday period is a
compact and strong closed mid-upper low forecast to dive southeast
from the Northern Plains to the western Great Lakes by early Thursday
and then slowly weaken and rotate northeast through Friday. Surface
low pressure associated with this short-wave will track to our north,
dragging its trailing cold front across the area late Wednesday night
into Thursday. Strengthening southwesterly warm advection in
response to the aforementioned short-wave will translate to breezy
south-southwest surface winds combining to boost high temperatures
well into the mid to upper 60s. This will be despite skies becoming
partly sunny/mostly cloudy.
For Wednesday afternoon and evening, the ECMWF suite of guidance
has been consistently depicting a QPF response as the system
warm front lifts north, while the other guidance has just as
consistently shown a dry depiction for the daytime hours. Large
scale ascent will be in the upswing from the onset of mid-level
height falls along with increased mid-level moisture and clouds.
However, the thinking is the main limiting factor will be the deep
layer of dry air below 10kft from the antecedent dry air mass
over the area.
On the above note, even the ECMWF forecast soundings are
suspiciously dry for its QPF depiction. While the ECMWF and EPS
can`t be ignored, given the dry low-mid levels on the ECMWF
soundings, the dry look on the other guidance, slight chance PoPs
Wednesday afternoon across parts of northern Illinois appear
reasonable. It may end up being a scenario with spotty high-
based sprinkles later in the day. Then in the evening, another
possible scenario to watch for will be the better deep moisture
focusing east of I-57 and keeping better shower chances over the
eastern CWA and/or points east. Given the overall uncertainty and
likelihood of spotty shower coverage Wednesday night, low chance
PoPs in the official forecast suffice for now.
Suspect the brunt of the shower chances will be tied closer to
the cold frontal forcing arriving on Thursday morning. Post-
frontal scattered showers also look to be a decent bet in the
afternoon as the mid- upper low shifts overhead, supporting high
chance PoPs. Temperatures will cool down a bit as the front moves
across the area on Thursday (upper 50s-low 60s) and then more-so
on Friday (mid-upper 50s) as the upper trough slowly progresses
east. The cold advection cyclonic flow aloft regime with steepened
low-level lapse rates may still support spotty showers inland on
Friday, but the brunt of the activity may transition to lake effect
showers through Friday night with breezy north-northwest winds.
Uncertainty increases in the large scale pattern over the weekend
into early next week, as the eastern trough should get kicked
east, but how quickly it does so is a question mark. Some recent
operational runs have had a clipper-like feature on Saturday that
could bring a quick bout of light rain and then reinforcing cold
air advection, lake effect into northwest Indiana, and cool
conditions through Sunday. On the other hand, some guidance, such
as the 12z ECMWF, kicks the trough out faster and moderates us
more quickly to close out next weekend.
Castro
&&
.AVIATION...
For the 00Z TAFs...
The main aviation weather concerns are:
* Brief NE wind shift at ORD, MDW, and GYY this evening.
* Potential for lake effect rain showers to spread back west into
KGYY, KMDW, and possibly KORD tonight into Monday morning.
* MVFR cigs spreading back across all of the terminals tonight and
Monday.
A surface boundary is currently traversing the ORD airfield and
will result in a brief period of northeasterly winds (020 to 050
directions). Wind speeds generally will remain below 10 knots and
are expected to come back around to a northwesterly direction
after about 01z.
Cloud cover will continue to increase across the region this
evening, and cigs will eventually build down to MVFR tonight,
first at the Chicago-area terminals, and then at RFD towards
daybreak. While there is some potential for cigs to build under
020/low-MVFR Monday morning, confidence was not high enough to
include a mention at this time.
Lake effect showers are expected to re-develop with time tonight,
and will back westward across the lake, impacting GYY, and
possibly MDW and ORD, although confidence in showers making it as
far west at ORD is lowering. Have maintained a PROB30 for MVFR
SHRA at MDW tonight/Monday morning, and will make adjustments to
this as lake effect develops this evening. Intermittent -shra will
likely impact GYY through the day on Monday.
Carlaw
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...IL nearshore waters until 10 PM Monday.
Small Craft Advisory...IN nearshore waters until 4 AM Tuesday.
&&
$$
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Area Forecast Discussion
National Weather Service Marquette MI
645 PM EDT Sun Oct 15 2023
.SHORT TERM...(Through Tonight)
Issued at 304 PM EDT SUN OCT 15 2023
Key Messages:
-Lake aided low cloudiness persists.
Water vapor imagery and RAP analysis show mid-level ridging
extending from the southern Rockies ne to Hudson Bay and n central
Canada with a strong 500mb positive height anomaly at ~+400m
centered over western Hudson Bay. Deep, elongated troffing exists
downstream from the Canadian Maritimes across the ne U.S. and back
toward the southern Plains. Result is continued n to ne flow into
the Upper Great Lakes today. Weak shortwave that passed earlier
today combined with a sfc trof/wind shift dropping across Lake
Superior into Upper MI triggered a few -shra/patchy -dz into n
central Upper MI mid morning to early aftn. Last of that pcpn is
currently in Baraga County and is in the process of ending.
Otherwise, abundant low-level cloudiness is the rule. However,
with moisture/clouds confined to a shallow low layer, downsloping
off of the Canadian shield is breaking up low clouds over ne and e
Lake Superior into far eastern Upper MI.
Little change in the low-levels is expected thru tonight. Models
show a low inversion at 3-4kft with NAM on the lower end of that
range and even lowering it a little more during the night. With
temps at the base of inversion 0 to -1C, overlake instability is not
quite there for lake effect pcpn with Lake Superior water sfc T
averaging 11C. Given such a low inversion, marginal at best
overwater instability and no passing sfc trof or shortwave of note,
doubt that any lake effect -shra or drizzly pcpn will develop
tonight despite most of the CAMS showing such development. If
anything did develop, maybe the far w would see it with potential
streamline back to Lake Nipigon. However, even there, low
inversion/marginal instability at best suggest development is highly
unlikely. Fcst tonight will only keep a barely mentionable schc in
that area. With low clouds likely to dominate along with winds
stirring, expect low temps in the upper 30s to mid 40s F.
.LONG TERM...(Monday through Sunday)
Issued at 321 PM EDT SUN OCT 15 2023
Key Messages:
-Significant weather is not expected this week, although widespread
light rain is expected later in the week.
-Near normal temperatures trend above normal by mid-week.
-Temperatures fall below normal for weekend.
Guidance packages continue to suggest a drier start to the coming
work week with a wetter finish going into the weekend. The main item
of interest continues to be the coming clipper/closed low later this
week. Specific to it, model agreement on the overall structure and
evolution is mixed, but the same general impacts of light rain are
still expected.
Starting off on Monday, there`s consensus that the pattern across
CONUS and Canada will involve a broad trough across their eastern
third while the western two thirds sits under ridging. The ridging
actually extends well into Hudson Bay on Monday. As we progress
through Monday and Tuesday, this ridge and attendant surface high
will press southeast through the Great Lakes. This benevolent
feature will support a couple of dry fall days. There`s questions
about how much sunshine we`ll see but overall, expecting highs to
climb in the low-mid 50s. Overnight lows Monday night may dip into
the 20s away from the lakeshores if we are able to clear out, but
lakeshore communities should expect to stay in the 30s or low 40s.
There`s a low chance (25% or less) early Monday that a lingering
saturated near-surface environment may support some isolated pockets
of rain near Lake Superior in the west and north-central where
upslope flow may enhance lift. Much like tonight though, over lake
instability isn`t very strong and there may not be enough to support
lake effect.
Surface ridge axis shifts through the forecast area early Tuesday
followed by southerly flow developing across the area. This warm air
advection regime should support increasing cloud cover overnight and
a return to overnight lows in the mid-upper 30s inland and low-mid
40s lake-side. Upstream, the noted clipper is expected to dip into
CONUS by Wednesday morning then progress through our region as the
cutoff mid-level low drops further southeast or broadens out and
gets caught up in a trailing cold front. Regardless, the trailing
cold front looks to push through the region Thursday night and
Friday, allowing a cooler airmass to advect into the region. This
evolution should support a warmer Wednesday with temps in the upper
50s, maybe near 60 in downslope regions near Lake Superior. Rain
chances increase on Wednesday. Despite the differences in evolution
of the system, there appears to be good agreement on the cooler air
building in behind the cold front. Between yesterday and today,
guidance has trended a few degrees colder at 850mb to -2 to -5C by
Friday afternoon, so I`d expect any precip should transition to lake-
enhanced and then lake-effect rain showers through the day. Some
guidance appears open minded about the clipper deepening along the
cold front and passing near the Straits of Mackinac. If this ends up
being realized, some breezy winds may accompany the system Thursday
night into Friday.
Beyond the clipper and this weekend, there`s mixed solutions on
whether we`ll continue lake effect rain through the weekend or if
another clipper will dive through the Upper Great Lakes. While
confidence in this is lacking, there`s better agreement that the
cooler airmass behind the front will support a return to cooler than
normal temperatures for the weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 644 PM EDT SUN OCT 15 2023
A cool northerly flow across Lake Superior will continue to support
lake effect cloudiness, aided by upsloping. With a low inversion,
MVFR cigs are likely to prevail at IWD/CMX/SAW thru this fcst
period. Winds will be strongest at SAW early this evening,
gusting over 20kt.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 321 PM EDT SUN OCT 15 2023
20-30kts winds are expected this afternoon and evening (strongest
east half) thanks to continued stronger pressure gradient forces.
Ridging begins to build into the region tonight though, supporting a
gradual decrease in winds across Lake Superior. By morning, winds
are expected to have fallen to 20kts or less lake-wide. Expecting
these light winds to persist through at least Tuesday night.
Wednesday, a clipper system is expected to approach from the west.
There`s still some questions about timing, but pressure falls
through the day should support increasing winds out of the south or
southeast to 20-25kts. Winds should continue increasing to around
30kts by evening. As the system moves through, there may be a few
hours of lighter winds during the day Thursday. A cold front will
follow the system beginning Thursday night and its possible the low
may deepen some near the Straits of Mackinac, supporting an increase
in winds. This will be something to watch since models don`t quiet
have a good handle on this yet. After the front, winds of 25-30kts
should be expected as colder air builds in across Lake Superior out
of the north or northwest. These stronger winds may persist into the
weekend, but there`s some questions about when and where another
system may track
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...JTP
AVIATION...Voss
MARINE...JTP