Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/19/23
See below for an aviation forecast discussion for the 00Z TAFs.
&&
.SHORT TERM...(This Evening through Friday Night)
Issued at 331 PM CDT Thu May 18 2023
The main forecast challenges in this period will initially revolve
around the sfc smoke that continues to persist this afternoon
followed by temperatures tonight into tomorrow. A sfc cold front is
currently sweeping southward across our CWA. Wind speeds have been
relatively light ahead of this feature today, helping to keep sfc
smoke from Canadian wildfires and resultant low visibility
persisting. Behind this sfc boundary, an increasing northwest wind
is beginning to mix things up so to speak and slowly improving
visibility in a few areas. Anticipate these improving conditions
will become more noticeable toward late afternoon through this
evening. Also, a couple of afternoon showers may develop across our
northeast in association with this passing sfc front and and upper
trough swinging down across the eastern Dakotas into western
Minnesota. The low levels remain pretty dry however, but if any
activity materializes it should be fairly short lived.
Cold air advection in the lower levels this afternoon and evening
will help usher in a much cooler air mass tonight. Chilly
temperature readings are expected by daybreak Friday morning. Just
how cool we could get may be a bit tricky. All dependent on sky
cover and wind speeds going through the overnight hours. A sfc high
is progged to build across the western Dakotas overnight and remain
centered there. Feel this will give our central and eastern zones
enough of a gradient that northwest winds will stay up enough and
not allow readings to fall as significantly as if there were very
little wind and clear skies. Some of our eastern zones will see
increasing cloud cover toward daybreak which would help keep
temperatures warmer as well. Farther across our western zones,
moreso West River, winds will be lighter, skies potentially more
clear. So, anticipate temps will fall in the mid-upper 30s range in
some of our northwest zones briefly where some frost could be
possible prior to daybreak. Passed on a frost headline at this point
because of the uncertainly in wind speeds but this will be a trend
we`ll have to monitor going through this evening into the early
overnight.
Conditions of Friday will be improved in terms of the wildfire
smoke. There could be some leftover smoke aloft through the morning
hours before that gets swept to the south during the afternoon. A
cool air mass remains as the sfc high shifts over our CWA through
the day. Highs on Friday could be stuck in the upper 50s to around
60 in our east thanks to more cloud cover while zones from the James
Valley and points west see readings in the 60s.
.LONG TERM...(Saturday through Thursday)
Issued at 331 PM CDT Thu May 18 2023
The long term portion of the forecast begins on Saturday with a
surface high pressure drifting south and east of the region with
warmer air moving in from the west. While the lower levels of the
atmosphere favor a southerly flow, the upper levels suggest the
possibility for near surface smoke on Saturday, mainly along and
west of the Missouri River. While the latest RAP vertically
integrated smoke only goes out to 18Z Saturday, another round of a
smoky sky appears likely Saturday afternoon over much of the CWA.
The smoke may limit high temperatures on Saturday. Above average
temperatures should move into the area early next week as ridging
aloft moves into the region. Highs on Monday should reach the low to
mid 80s for most locations. The NBM shows a 50 to 60 probability for
the Missouri River to reach 90 degrees. The probability is higher on
Tuesday, reaching 60 to 80 percent.
By mid week, an area of low pressure and a weak upper level trough
should track across the region, bringing the potential for showers
and thunderstorms. The deterministic ECMWF and Canadian support
drier conditions midweek, with the GFS still advertising wetter
conditions. The latest rendition of the NBM has reduced the mention
of pops on Wednesday, and now favors a better pcpn chance Thursday
afternoon into Thursday night.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 621 PM CDT Thu May 18 2023
Terminals KABR,KATY,KPIR,KMBG
The prevailing flight category at KMBG, KPIR and KABR over the
next 24 hours is forecast to be VFR. The blustery north-
northwesterly winds will draw down within a few hours of sundown.
Same thing for KATY over the next 24 hours, except that on Friday
between ~13Z and ~21Z, low stratus is forecast to back into KATY
from the north-northeast; sticking around until daytime
heating/mixing can scatter it out.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...Dorn
SHORT TERM...Vipond
LONG TERM...SD
AVIATION...Dorn
Area Forecast Discussion
National Weather Service La Crosse WI
1052 PM CDT Thu May 18 2023
.DISCUSSION...(This evening through Thursday)
Issued at 257 PM CDT Thu May 18 2023
Key Messages:
- Showers and scattered storms are expected from late this
afternoon into tonight.
- Smoke will affect visibilities from late this afternoon into
Tonight
- Patchy frost possible in central Wisconsin Friday Night
- After a cool Friday, temperatures will warm into next week
Late This Afternoon and Tonight...
At 250 PM, radar shows scattered showers and thunderstorms
developing along a pre-frontal trough from St. Ansgar, IA
northeast to Wabasha, MN. A more widespread band of showers is
located from south-central Minnesota northeast toward the western
tip of Upper Michigan. Surface-based CAPES have climbed into the
500 to 1000 J/kg range west of the Mississippi River. For the
remainder of the afternoon and early evening, these CAPES are
forecast to spread east into western Wisconsin. The NAM CAM is a
bit too robust with its CAPES (climbing into the 1500-2000 J/kg
range). This is due to its surfaces dew points climbing into the
lower and mid-60s. Meanwhile, the HRRR has better dew points, but
its surface temperatures look to be too warm, so its CAPES of 1000
to 1500 J/kg also look to be a bit too high. Much of the shear is
located in the 0-3 km (up to 30 knots) layer along and behind the
surface front. As a result, not anticipating any widespread
severe weather. However, could not rule out an isolated strong
storm. The main threats would be lightning and wind gusts up to 35
mph.
Subsidence in the wake of this front will bring the smoke from
aloft to the surface. This smoke is reducing visibilities into the
1 to 3 mile range in South Dakota and in western Minnesota. The
RAP is showing that this smoke will reduce visibilities in our
area into the 3 to 5 mile range. This is likely not low enough so
went with visibilities around 2 miles based on the visibilities
upstream. Due to this smoke, Air Quality Alerts have been issued
by the Minnesota Pollution Control Agency and the Wisconsin DNR.
The particulates from this smoke will be unhealthy for sensitive
groups such as those with cardiovascular and lung disease.
Friday Night...
With clearing skies and decreasing winds on Friday night,
low temperatures will range from the mid-30s to mid-40s. The
coldest temperatures will be in central Wisconsin where they will
be cold enough that there could be some scattered frost in the
typical cold areas.
This Weekend into Early Next Week...
High pressure will gradually build across the area on Friday. This
high pressure system will produce dry weather into early next
week. As this high pressure moves east of the area, temperatures
will gradually warm. High temperatures will be around 70 on
Saturday and then gradually warm to around 80 by Tuesday.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1050 PM CDT Thu May 18 2023
A band of showers was progressing through northeast Iowa into
western Wisconsin this evening in conjunction with a cold front.
Behind this front, smoke from Canadian wildfires was reducing
visibilities to MVFR and these conditions should remain until a
secondary front sweeps south late tonight between 05 and 09Z.
Light WNW winds of 5-10 kts this evening behind the initial front
will increase from the NW behind the second front to 10-15kts
with gusts over 20-25 kt through the daytime hours tomorrow. MVFR
to low VFR ceilings are expected to develop by mid to late
morning and linger through the rest of tomorrow afternoon.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...Boyne
AVIATION...Skow
Area Forecast Discussion
National Weather Service Boise ID
824 PM MDT Thu May 18 2023
.DISCUSSION...Smoke layers aloft from wildfires in the Western
Canada will remain in place through at least Saturday. Smoke could
mix down to the surface tonight across Southwest Idaho and expand
westward Friday afternoon. Latest RAP guidance remains unchanged
with keeping near surface smoke trapped in the lower valleys as
the upper level ridge moves over the forecast area. In addition to
the reduce in visibility, the smoke could keep high temperatures
a few degrees cooler than previously forecast. NBM and HREF
probabilities still favor temperatures in the valley reaching 90
F or above both Saturday and Sunday (70% chance). This is about
15% lower probabilities in the latest run possibly signally the
smoke could be an issue. Thunderstorms could return as early as
Saturday evening in Southeast Oregon with a potential for stronger
storms on Sunday as the upper level trough moves in. Models have
remain consistent with a deep moisture plume (in 95% percentile)
from the Gulf of Mexico along with substantial destabilization
and increased shear with the approaching trough on Sunday. This
could support organized thunderstorms across much of the area.
Updated forecast for increased smoke/hazy conditions in Southwest
Idaho overnight. Update will be out shortly.
&&
.AVIATION...Mainly VFR. Areas of wildfire smoke from Canada will
continue to degrade visibility aloft. Isolated evening showers and
thunderstorms in Harney County, OR and the Central ID Mountains
tomorrow. MVFR conditions, gusty winds to 30 kt, and small hail are
possible with stronger storms. Surface winds outside of storms:
variable 10 kt or less. Winds aloft at 10k feet MSL: variable 5-10
kt.
Weekend Outlook...Isolated afternoon-evening showers and
thunderstorms this weekend, mainly in SE OR and central ID. A higher
chance of widespread thunderstorms expected Sunday, with some severe
storms expected mainly in SE OR. MVFR conditions, gusty winds and
hail are possible with stronger storms. Outside of storms, expect
VFR conditions and light winds. Areas of smoke.
&&
.PREV DISCUSSION...
SHORT TERM...Tonight through Saturday night...
Near-record warm temperatures, thunderstorm chances, and
smoke/haze from Canadian fires are the primary forecast concerns
through Saturday night.
*HEAT: The well-advertised warm up remains on track across the
entire forecast area amidst an anomalously strong upper-ridge.
The position of this feature will remain nearly fixed into this
weekend. Forecast trends suggest temperatures will likely peak on
Saturday across the entire area, with upper 80s through low 90s
expected through most of the Snake Valley and other lower
elevation locations. Latest probabilities for exceeding 90
degrees on Saturday are 83% for Boise, 24% for Twin Falls, and
16% for Baker City, OR. There is the possibility that lofted
smoke/haze could reduce heating by a couple degrees, but current
forecasts suggest the plume will primarily remain situated to the
north and east on Saturday.
*THUNDERSTORMS: Substantial destabilization (CAPE values near 1000
J/kg) has occurred across eastern Oregon and far western Idaho
amidst ample daytime heating. The 12Z BOI sounding this morning
showed a near-record PW value of 0.86". Despite the favorable
thermodynamic environment, the proximity of the upper ridge to
the west over Oregon should keep convection somewhat suppressed
today through Saturday over Valley locations. One exception today
will be across the Boise/Sawtooth Mountains, Owyhee Mountains,
and east-central Oregon, where thunderstorm chances are roughly
15-25% this afternoon and evening. Less activity is expected on
Friday (less than a 15% chance), but a gradual increase in
moisture on Saturday should lead to an uptick in thunderstorm
chances in eastern Oregon (20-40%) and over the Boise Mountains
(15-20%). Locally gusty winds to 40 mph and brief heavy rain are
likely to accompany the strongest thunderstorms.
*SMOKE/HAZE: A substantial plume of primarily lofted smoke
continues to meander erratically over the Pacific Northwest. The
most significant surface visibility reductions today have been
near Baker City, OR. Additional areas of visibility reductions
are possible (30-40% chance) overnight into the west-central
Mountains and Magic Valleys. Both the RAP-based smoke output and
NASA biomass output indicate smoke will spread westward across
the Snake Valley Friday morning.
LONG TERM...Sunday through Thursday...Southwest flow will develop
aloft over the Pacific Northwest as an upper trough approaches on
Sunday. With forecast precipitable water values reaching over the
90th percentile on Sunday, combined with increased lift ahead of the
trough, showers and thunderstorms are expected to generate during
the afternoon and evening. The best chance (35-50%) for enhanced
instability and wind shear for stronger thunderstorms in the
afternoon will be over central and eastern Oregon. However,
thunderstorms over the mountains of southwest Idaho also become more
likely (30-45% chance) by the evening as the trough tracks eastward.
Storms that develop will be capable of heavy rains, hail, and gusty
outflow winds. GFS guidance is currently the most bullish with the
amount of precipitation that will impact the area, whereas other
guidance members are more conservative and limiting. Thereafter, a
cold front is forecast to move through the area on Monday, creating
increase wind speeds for the Snake Plain. Temperatures will also
cool to around 5 to 10 degrees above normal, which is roughly 10
degrees cooler than the forecast high temps on Sunday. Ensemble
guidance agrees that the region will continue to be influenced by
the trough passing through the NW U.S. on Tuesday and Wednesday, and
therefore the threat of thunderstorms will remain a possibility each
afternoon. Currently, the best location for storms will be closer to
the NV border and over central Idaho, with a 20-30% chance of
occurrence. Lastly, forecast smoke models are predicting that areas
of Canadian wildfire smoke will waft in and out of Oregon and Idaho
next week, so hazy skies may continue to be in our future.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.
&&
$$
www.weather.gov/Boise
www.facebook.com/NWSBoise
www.twitter.com/NWSBoise
DISCUSSION...JDS
AVIATION.....SA
PREV SHORT TERM...JR
PREV LONG TERM....SH
Area Forecast Discussion
National Weather Service Cheyenne WY
949 PM MDT Thu May 18 2023
.SHORT TERM...(This evening through Friday night)
Issued at 302 PM MDT Thu May 18 2023
A very active weather pattern will be coming to a close for the
short-term forecast package. Heavy rainfall from thundershowers,
severe weather, and gusty winds should come to a close here this
afternoon. Light to moderate rain showers behind the main cluster
of convection is anticipated to linger along and behind the cold
frontal passage today and tonight, in conjunction with upslope
flow along the higher terrain. The more important concern remains
with the visibility and air quality reductions from wildfire
smoke. The source region from the wildfire smoke is from Alberta,
Canada. Once the northerly winds behind the slow-moving cold
front pushed through, significant visibility reductions remain
present. Several sites across our cwa have reported observations
between 1/2 mile and 2 miles. Went ahead with an Air Quality
Alert for the NE Panhandle, and an SPS for southeast WY through
11am FRI. We have also recorded observations with rainfall being
present while smoke was still in the vicinity of our automated
reporting stations.
Overnight, we should see gradual clearing of the cloud cover from
north to south. The mostly cloudy conditions are expected to
persist through daybreak Friday for areas along and south of
Interstate 80. However, the wildfire smoke may linger not only
into Friday morning, but the majority of the day. Hi-res models
have struggled to handle the near-surface smoke aspect via the
HRRR due to the wildfire source point being too far north outside
of the domain. Have gone with a combination of the RAP and
international models to assess how long, and the concentration
levels for smoke to be included in the short term forecast. Will
have to re-assess on the next forecast package if smoke needs to
be included into the forecast through potentially early Saturday.
Daytime highs should begin to moderate back into the 60s for
Friday, with slightly cooler temperatures in the higher terrain. A
few locations may creep into the lower 70s if the smoke does begin
to wane in concentrations near the surface. High pressure will
take hold by Friday night as overnight lows creep down into the
upper 30s to middle 40s. We will begin to see a dry pattern take
hold for the beginning of the weekend as warmer temperatures begin
to make a return to the area.
.LONG TERM...(Saturday through Thursday) Issued at 302 PM MDT Thu
May 18 2023
The only concern with the portion of the forecast is the potential
for convection at the beginning of the week continuing through mid
week.
It is looking look like a mild and fairly dry weekend across the
forecast area as the upper level ridge keeps its grip over the
region. The models are hinting at a weak shortwave moving through
the Nebraska panhandle on Saturday night into Sunday, but it appears
like the moisture will be quite limited for any convective
development. Next week, the models/ensembles are showing the
precipitable water values increasing through the week. At this
point, it appears like the better moisture return will take place
over Wyoming on Monday and Tuesday with this moisture spreading
further east into the Nebraska panhandle on Wednesday and Thursday.
The models are also showing the shear increasing over the area
especially around mid week in response to the closed low moving into
northern Montana. Overall, the trends are pointing to a chance of
scattered afternoon thunderstorms through much of the week
especially over Wyoming with lesser coverage over the Nebraska
panhandle. Temperatures will also be on the mild side with highs in
the 70s and lows in the upper 40s to mid 50s.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 948 PM MDT Thu May 18 2023
Wyoming TAFS...Northerly flow at the surface and aloft will help
bring in smoke from fires, reducing visibilities to 2 to 6 miles
at Laramie and Cheyenne, and 4 miles at Rawlins until 08Z. Clouds
will generally remain scattered to broken between 5000 and 8000
feet AGL, although Laramie and Cheyenne will see broken clouds at
2500 feet AGL until 15Z.
Nebraska TAFS...Northerly flow at the surface and aloft will help
bring in smoke from fires, reducing visibilities to 1 to 4 miles at
times. Broken clouds from 3000 to 5000 feet AGL will prevail through
early morning, with broken clouds below 1000 feet AGL at Sidney from
09Z to 14Z. Skies will become mostly clear after 14Z Friday.
&&
.FIRE WEATHER...
Issued at 302 PM MDT Thu May 18 2023
Fire weather concerns will remain low for the short-term forecast
as a cold front and recent precipitation keep fuels and humidity
values away from critical thresholds. Light winds will also be
present for the short term forecast. Rain showers and isolated
thunderstorms are possible this evening into Friday morning, with
the potential for a few gusty and erratic winds to 30-40mph.
&&
.HYDROLOGY...
Issued at 302 PM MDT Thu May 18 2023
Latest radar loop was showing the showers and thunderstorms mainly
tracking across the I-80 corridor this afternoon which is
fortunately north of the Snowy and Sierra Madre ranges. Therefore,
we will most likely not see too much in the way of rapid rises on
the mountains streams and rivers this afternoon. However, we will
continue to see some snowmelt during the next couple of days.
Fortunately, temperatures will be on the cool side tonight and
Friday which will slow down the melting process a bit. The snowmelt
process will pickup again this weekend and early next week which may
aid in pushing the upper North Platte River close to flood stage at
Saratoga. At this point, it still looks likely that Saratoga which
will reach minor flood stage on Sunday. Still a little uncertain on
whether Encampment and Sinclair will reach minor flood stage, but
would not be surprised that they could creep to minor flood stage
early next week. Meanwhile, the Little Snake River basin will
continue to have steady flow which will result in more minor to
moderate flooding near Baggs and Savery.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...BW
LONG TERM...REC
AVIATION...RUBIN
FIRE WEATHER...BW
HYDROLOGY...REC
Area Forecast Discussion
National Weather Service Duluth MN
641 PM CDT Thu May 18 2023
.DISCUSSION...(This evening through Wednesday)
Issued at 241 PM CDT Thu May 18 2023
Key messages:
* Air Quality Alerts continue into Friday due to near surface
smoke from Canadian wildfires.
* Numerous rain showers with a few thunderstorms this afternoon
and tonight before a dry weekend for the Northland.
* Patchy frost is possible for the Iron Range Saturday morning.
* Warming up for most areas next week.
Per the MN Pollution Control Agency, and the WI DNR, an Air
Quality Alert remains in effect for northeast Minnesota until 600
am Friday, and until noon Friday for northwest Wisconsin. Near
surface smoke behind a cold front will spread across the area this
afternoon and into tonight. Visibilities of 1 to 3 miles in smoke
have been observed upstream. Per the RAP Smoke forecast, near
surface smoke will decrease from west to east tonight into Friday
morning as low level air trajectories become less favorable with
the passage of the upper level low.
For this afternoon, an area of rain showers with embedded
thunderstorms will move across northwest Wisconsin ahead of a cold
front. While Price county is in a Marginal Risk for severe
storms, the overall threat is very low given very modest buoyancy.
Additional scattered rain shower and thunderstorm activity will
spread across northeast Minnesota late this afternoon, and more so
into this evening and tonight as the cold core aloft associated
with the upper level low propagates east-southeast. After a brief
lull across northwest Wisconsin, this next round of rain showers
and a few thunderstorms will spread across the region this evening
and tonight. Severe weather is not expected. Precipitation
activity will diminish from west to east Friday morning and into
the early afternoon as the low propagates into the central Great
Lakes region.
With light winds and clear skies in surface high pressure, we will
be on the lookout for frost Friday night into Saturday morning.
However, the 12 UTC guidance suggests the coldest portion of the
airmass to be exiting the region through the afternoon and
evening. At this time, the Iron Range has the best potential for
patchy frost Saturday morning.
Looking ahead to next week, surface high pressure across the
eastern US will support a warming trend with high temperatures
solidly into the 70s, and potentially in the 80s, with southerly
surface flow. Of course, the caveat will be lake breezes for
especially the North Shore and Twin Ports.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 637 PM CDT Thu May 18 2023
A cold front is passing through the Northland this evening. Winds
will shift from southwest to northwest at remaining terminals in
northwest Wisconsin. The Arrowhead will experience a few
thunderstorms as well over the next few hours. Off and on shower
chances continue through tonight and may require future amendments
to lengthen the shower and or rain chances at some terminals. MVFR
cigs should then clear towards the late morning to afternoon hours
tomorrow.
&&
.MARINE...
Issued at 325 PM CDT Thu May 18 2023
Southwest winds around 5kts this afternoon will increase to west
at 10-15 kts late tonight across western Lake Superior. A localized
area of northwest winds with gusts to near 25 kts will develop late
tonight into Friday morning between Silver Bay and Grand Marais,
and a Small Craft Advisory has been issued. Patchy fog and areas
of smoke will reduce visibilities on the lake tonight. Scattered
rain showers and a few thunderstorms are also expected. Winds will
turn northwest at 10-15kts on Friday. For this weekend,
conditions hazardous to small craft are forecast in strong
southwest winds on Saturday, and strong northeast winds on Sunday.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 42 58 41 70 / 60 10 0 0
INL 39 66 38 73 / 60 0 0 0
BRD 41 60 38 72 / 20 0 0 0
HYR 42 58 37 73 / 50 20 0 0
ASX 44 55 40 71 / 70 30 0 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory from 4 AM to 10 AM CDT Friday for LSZ141-
142.
&&
$$
DISCUSSION...PA
AVIATION...NLY
MARINE...PA
Area Forecast Discussion
National Weather Service Des Moines IA
619 PM CDT Thu May 18 2023
...Updated for the 00z Aviation Discussion...
.DISCUSSION.../Tonight through Thursday/
Issued at 321 PM CDT Thu May 18 2023
Key Messages:
- Scattered showers and thunderstorms through the overnight. The
overall severe weather threat is low.
- Areas of smoke passing through this evening may reduce surface
visibilities at times.
- Pleasant weekend ahead.
Cold front is situated across central Iowa from near Mason City to
Webster City to Carroll this afternoon. Weak instability has
developed in vicinity of the boundary with MLCAPEs below 1000
J/kg and weak shear/flow aloft will limit any strong storm
potential. The hail threat is minimized by the lack of instability
and where there is an, narrow CAPE profiles. The non-supercell
tornado parameter is non zero but LCL heights are quite high and
the potential for vorticity stretching is no great again with
lower 0-3 km CAPE values generally 50 J/kg or less. The showers
and storms will bubble along the boundary for much of the night
with cell movements nearly parallel to the boundary. Still that
will not pose a heavy rain threat.
Smoke is the other issue in the near term. Subsidence behind the
cold front has allowed the smoke from the Canadian wildfires to
make it to the ground into northwest Iowa with visibilities
dropping to 2 miles or less. Some of these visibilities have
improved this afternoon with mixing. For the forecast, followed
the RAP near surface smoke solution for visibility restrictions.
The near surface smoke will diminish overnight as the wind becomes
more northerly. The upper level smoke however will have another
wave pass across the state on Friday.
Friday will be cooler then a very pleasant weekend is on tap with
high pressure moving into the region. That high pressure system
will have a big influence on the Iowa weather into mid next week.
Temperatures will gradually rise into the 80s next week as Iowa is
in the return flow though dew points will remain on the dry side
as the source region of the air flow will be originating from the
high pressure system. The next chance of precipitation as of now
is around late Wednesday.
&&
.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 619 PM CDT Thu May 18 2023
A narrow line of showers and thunderstorms will move across the
area tonight, and may briefly impact ALO/DSM/OTM at times. Highest
probability is at ALO where a TEMPO has been included, whereas the
other two terminals are covered with VC groups due to lower
confidence. Amendments are possible. Also, a broad swath of
smoke/haze is advecting across the area and will produce multiple
hours of MVFR visibility overnight, and possibly IFR at times
mainly in the north, before easing early Friday morning.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Donavon
AVIATION...Lee
Area Forecast Discussion
National Weather Service Quad Cities IA IL
646 PM CDT Thu May 18 2023
...AVIATION UPDATE...
.SYNOPSIS...
Issued at 239 PM CDT Thu May 18 2023
A surface low is near the western tip of Lake Superior this
afternoon with a cold front extending southwestward into northwest
Iowa to near KOMA. Visibility restrictions due to smoke are
occurring behind this front. A second cold front extends from
near International Falls southwestward into South Dakota then
westward to southeast Montana. Satellite shows a developing
cumulus field ahead of the first front with radar showing
convective development across southeast Minnesota. Locally, at 3
PM temperatures ranged from 74 degrees at Freeport and Sterling to
81 degrees at Washington Iowa. Dewpoints are in 50s across the
area. Surface based CAPE across Iowa 250 to 500 J/KG across Iowa
with 0 to 6 km shear was around 25 knots.
&&
.SHORT TERM...(This evening through Friday)
Issued at 239 PM CDT Thu May 18 2023
Key Messages:
1. There is a low risk for severe thunderstorms this evening from 4
to 8 PM north of Highway 20 in Buchanan, Delaware, and Dubuque
Counties.
2. There is a chance for wildfire smoke to make it to the surface
behind a cold front Friday morning. This will have to be monitored
for impacts to air quality and visibility.
Discussion:
The main forecast concerns were timing of precipitation and smoke
reaching the surface behind a cold front on Friday morning.
A positively tilted 500 MB trough is forecast to move
southeastward into northeast Minnesota and western Lake Superior
tonight then into Michigan by 00 UTC on Saturday. At the surface,
a surface low is forecast to follow a similar track with a
prefrontal trough and cold front moving across eastern Iowa,
northwest Illinois, and far northeast Missouri. There is a narrow
axis of moisture and instability developing along the prefrontal
trough late this afternoon and into this evening this evening and
overnight. 500 to 1000 J/kg of CAPE are forecast across the area
late this afternoon into this evening with 20 to 30 knots of 0 to
6 km shear. Scattered showers and isolated thunderstorms are
possible this evening An isolated severe storm is possible late
this afternoon into the early evening but confidence is low in
this occurring. The better shear moves into the area after 03 UTC.
CAMS have showers and storms moving into the area after 03 UTC
when instability is decreasing. Rainfall amounts will be light
with 0.20 to 0.40 inches possible especially north of Highway 30.
Low temperatures on Friday will range from the mid 50s along
Highway 20 to the lower 60s south of a Fairfield to Burlington to
Galesburg line.
Precipitation will quickly exit the area after 12 UTC on Friday. the
RAP continues to show the potential for smoke aloft to mix to the
surface along and behind the cold front in a short 3 hour window
as gusty northwest winds behind front mix to the surface. Clouds
and smoke aloft will be slow to clear on Friday behind the front.
High temperatures on Friday will range from the mid 60s along the
Highway 20 corridor to the lower 70s in far southeast Iowa, west
central Illinois, and far northeast Missouri.
.LONG TERM...(Friday night through Thursday)
Issued at 239 PM CDT Thu May 18 2023
Key messages:
1) Well above normal temperatures for much of the extended period.
2) Small chance for rain late next week.
Details:
Global models indicate a blocking ridge of high pressure developing
from the Plains to the Ohio Valley and to New England. The polar jet
will be well up into Canada, with an upper low in the PacNW.
This means much of the extended will have very warm temperatures
with no significant rainfall.
Temperatures will be into the 80s with the potential for 90+ later
next week. However, as of now this doesn`t appear to be record
breaking heat. ECMWF has H8 temps in the 16 to 18C range which would
support well above normal readings.
Toward the end of next week we`ll see moisture increase on the
backside of the high and stronger mid level flow encroach from the
northwest, which should bring with it some rain chances. However,
chances look to be small and possibly could remain off to our west.
Haase
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 645 PM CDT Thu May 18 2023
VFR cigs are expected through the period as MVFR vsbys due to shra
and smoke are expected overnight and into the morning. A cold
front will sweep through the area and mix down smoke from a loft.
Currently have MVFR vsbys, but cams upstream have LIFR vsbys. Some
mixing out is expected, but could see some brief IFR vsbys from
the smoke. Otherwise, expect improving vsbys later in the period.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SYNOPSIS...Cousins
SHORT TERM...Cousins
LONG TERM...Haase
AVIATION...Gibbs
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
636 PM CDT Thu May 18 2023
...Updated 00z Aviation...
.Discussion...
Issued at 301 PM CDT THU MAY 18 2023
Key messages:
- Thunderstorms will be possible tonight and into Friday
morning...severe weather is not expected.
Discussion:
Low pressure system moving into the upper Great Lakes region will
push a sagging front through the region. This front is currently
situated across western Kansas up into central Wisconsin. Along the
front, scattered showers have started to develop with some embedded
thunderstorms. Anticipate showers and thunderstorms to continue to
develop and expand in coverage ahead of sunset due to the
favorable instability and upper level forcing.
Through the overnight and into tomorrow morning, showers will
continue to spread across the area as the front continues to sag.
Severe weather is not expected due to limited forcing and
instability overnight and into the morning along the front. One
caveat is a secondary shortwave ejected across the four corners
which will ride along the sagging front. This could bring a better
chance for some heavy downpours across the southern half of the CWA
tomorrow morning. OVerall not expecting any flooding concerns for
with this event.
Northern high pressure will quickly move into the region behind the
front later in the day tomorrow and bring in cooler weather thanks
to CAA. One thing to watch is the smoke across the Northern Plains
and its trajectory. RAP smoke guidance does have the potential for
some thick smoke moving in north of US-36 by tomorrow morning behind
the front thanks to due north winds. We can see this happening
already across Nebraska where vsbys are down below 5sm. Will have to
keep an eye on the smoke and its potential impacts across the region
over the next 12-24 hours.
Otherwise cooler temperatures and very pleasant weekend is on tap for
the region. By next week, upper level ridge and associated high
pressure will build across the eastern half of the CONUS keeping the
area in southwest flow. Temperatures will increase each day with dry
weather for much of next week.
&&
.Aviation...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 632 PM CDT THU MAY 18 2023
A cold front will be moving across eastern Kansas and western
Missouri overnight. There are two things to watch with this. The
first, is smoke associated with the Canadian Wildfires. This
afternoon over Nebraska, several sites dropped below 2 mile
visibility. However, since 22z this afternoon, conditions have
been improving. Expecting mixing to weaken this evening, thus will
keep visibility VFR with respect to smoke issues. The second
factor to watch will be shower and storm development along the
front. Expecting precipitation to start around 09-10z in the KC
metro. Thunderstorm coverage will be isolated along the front,
therefore will place VCTS for a couple of hours in the TAF and
will monitor lightning trends overnight for the 06z TAF issuance.
Winds shift north-northwest after the cold front passes.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&
$$
Discussion...Sipprell
Aviation...Krull
Area Forecast Discussion...UPDATED
National Weather Service Glasgow MT
711 PM MDT Thu May 18 2023
.DISCUSSION...
Evening update: As visibility observations now show 10SM or
better across all of NE Montana, felt it was best to update the
forecast for now through the next 24 hours to better represent the
location and movement of smoke from Canadian wildfires. Currently,
the smoke seems to have retreated to along the Rocky Mountain
front range of central and western Montana. Operational HRRR / RAP
smoke models show this area of smoke slowly moving east through
the night tonight. I adjusted the weather grids to show this
gradual movement. By this time tomorrow, a brief rain shower or
two is showing up in a few convection-allowing models, skirting
along the southern Saskatchewan / northern Montana border.
Probably will not amount to much. -----BMickelson
Previous discussion: Smoke was not as bad today as yesterday and
it looks to stay that way according to the RAP Smoke products.
However, a surface high will drift over the area tonight, allowing
for radiational cooling and that could trap smoke close to ground
level. Smoke should mix out Friday as the surface high moves to
our east and southerly winds bring in cleaner air.
Look for a cool night tonight as clear skies and light winds will
allow temps to drop into the 30s to low 40s. There is a 5-20%
chance that a location in the eastern zones reaches 32F.
On Friday, southerly winds and an upper ridge will start a warming
trend. Look for temps to reach the upper 60s and 70s. Saturday`s
highs look to be mainly in the 80s. Some instability over Alberta
could fire up some showers Friday evening that should die before
reaching NE MT Saturday.
Another impulse looks to fire off thunderstorms over central
Montana late Monday that could bring gusty winds as they move into
the western zones. Hail doesn`t look likely at this point as the
airmass looks a bit dry (dewpoints mainly in the 40s).
An upper trough over the Pacific NW associated with the
instability Monday looks to remain in place into the middle of
next week, keeping the chance of showers around through Wednesday.
TFJ
&&
.AVIATION...
VFR, possibly MVFR Friday 09-16z.
Even though smoke seems to have dissipated across the NE MT
region, some smoke models are showing it returning to the area
from west to east through the overnight hours. A nighttime
inversion could help keep current smoke from clearing away from
some locations.
Otherwise, skies will be clear tonight with light winds. Look
for South winds at 5-15 kts at all TAF sites by Friday afternoon.
TFJ/BMickelson
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
weather.gov/glasgow
Area Forecast Discussion
National Weather Service Green Bay WI
1044 PM CDT Thu May 18 2023
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Friday
Issued at 345 PM CDT Thu May 18 2023
There are numerous forecast issues, including thunderstorm/severe
potential for late this afternoon/early evening, precipitation
trends, air quality/smoke concerns, and cooler temperatures for
Friday.
Thunderstorm/severe potential...instability has been slow to
develop this afternoon, but local mesoanalysis page showed
SBCAPE building to 400-800 j/kg in SE MN/NE IA. Satellite and
radar showed new convection developing in SE MN, along the
approaching cold front. Expect instability to increase in
central WI as the front approaches late this afternoon, so
thunderstorms appear most likely there. Cannot rule out an
isolated severe storm or two in central WI, as deep layer shear
of 35 to 40 knots and low wet-bulb zero heights (8-9k feet) favors
hail, and inverted-v soundings and 40-50 kt winds in the mid-
levels support strong gusts. The overall lack of instability will
be a limiting factor. The severe threat should occur in a small
time window, mainly 5 pm to 9 pm.
Precipitation trends...showers and embedded storms will arrive in
north central WI with the cold front between 4 pm and 5 pm, then
spread southeast to the lakeshore by around midnight. Expect the
thunderstorm threat to wane before the precipitation makes it into
NE/EC WI, as instability weakens. As the main frontal
precipitation exits eastern WI overnight, additional showers will
move into north central WI as the upper level low arrives.
Scattered showers will persist across mainly NC/NE WI into
Friday. Have lowered QPF amounts a bit for late this afternoon and
tonight, given recent trends.
Air Quality/Smoke concerns...Wisconsin DNR issued Air Quality
Advisories for all of WI earlier today, and these continue through
midday Friday over the northwest two-thirds of the CWA, and until
midnight Friday night for the Fox Valley/lakeshore areas. RAP
near-surface smoke forecasts show smoke mixing to the surface
in the wake of the cold frontal passage tonight, and lingering
into the day on Friday. The latest forecasts show this occurring
in NC/C WI later this evening, and during the overnight hours in
the east, with some clearing occurring from west to east on
Friday. Added patchy smoke in the forecast, and stayed close to
the RAP timing trends. It remains to be seen if vsbys will be
greatly reduced anywhere in the forecast area, but models seem to
suggest that the smoke will disperse some as it shifts east.
Cooler Temperatures on Friday...H8 temperatures are expected to
drop to near zero C on Friday as the upper low moves through the
region. Lowered high temperatures considerably, with readings in
the upper 40s and 50s expected over most of the region.
.LONG TERM...Friday Night Through Thursday
Issued at 345 PM CDT Thu May 18 2023
A less active pattern will set up for this forecast period and bring
dry and warmer weather to the region. Afternoon high temperatures
will be above normal throughout the extended with values in the low
to middle 70s for the weekend and Monday, then increase to the upper
70s to low 80s for midweek next week.
Friday night through Saturday...Moisture wrapping around a departing
upper-level low over northern Lake Michigan will keep a few showers
across far northeast WI from Friday night into Saturday morning.
Meanwhile, high pressure will be moving into the state from the
west. The combination of the departing low and the incoming high
will cause clouds and an elevated smoke layer to also decrease and
exit. The remainder of Saturday will be dry and mostly sunny.
Rest of the extended...Dry and mostly sunny conditions are also
anticipated for Sunday. However, models indicate a possible backdoor
cold front dropping south across the region sometime Sunday
afternoon/evening. If anything, this would cause temperatures to
decrease quickly behind the front. Models have also continued to
lower the potential for precip development due to the amount of dry
air already in place. Temperatures will rebound on Monday and
Tuesday as low-level winds switch to the southwest and lift warmer
air into the region. Models then show signs of the next chance for
some precip sometime midweek or towards the end of the week.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1039 PM CDT Thu May 18 2023
Showers and a few thunderstorms will end overnight as a cold
front moves across the region. IFR conditions are likely late
tonight and early Friday west of a IMT to CWA line, with MVFR
conditions to the east. Conditions should improve to VFR by
Friday afternoon east of a IMT to STE line and be MVFR to the
west. Scattered showers are possible in the north Friday.
The layer of smoke that was far above the ground the last several
days may mix down to the ground late tonight and Friday, and
produce visibilities of 3 to 5 miles.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM.....Kieckbusch
LONG TERM......Kruk
AVIATION.......RDM
Area Forecast Discussion
National Weather Service Grand Rapids MI
1045 PM EDT Thu May 18 2023
LATEST UPDATE...
Update
.UPDATE...
Issued at 1044 PM EDT Thu May 18 2023
Cold front located upstream this evening will make steady
progress tonight moving out of Minnesota and Wisconsin and
approach Lake Michigan towards 12Z. The front will then push
through the forecast area on Friday. For tonight though, the bulk
of the area will remain dry, the exception being the northwest
CWA up towards Ludington. The precipitation upstream at the
present time though is not impressive in coverage or intensity.
The HREF both the 12Z run and the 00Z run trickling show some
light precipitation moving into West Central Lower Michigan near
and after 09Z. Again, precipitation amounts are not expected to be
heavy from this entire frontal passage and only a few hundredths
are likely by 12Z.
&&
.DISCUSSION...(This evening through next Thursday)
Issued at 147 PM EDT Thu May 18 2023
- Showers Friday
The mid level low is still shown to track eastward through MI
Friday. Favorable moisture depth and lift are shown to support
showers as it tracks through the state Friday. Although trends
are for a slightly weaker system with a dip in the qpf shown.
Ensemble forecasts of qpf still show most members in the various
models with measurable qpf and we will continue to feature
relatively high POPs. There is a small risk for thunderstorms and
the region is still in a general thunder risk from SPC`s site. The
HRRR looked to be the most aggressive with the thunder potential
showing 500 to 1000 J/kg of CAPE in the afternoon along the
frontal zone. The other models show less CAPE but enough for an
isolated storm or two. If we do develop some better instability,
given the 500 mb jet streak over the state Friday afternoon, the
storms could take on some organization with gusty winds the main
risk.
- Warming up early next week but will it last
Most models still show a significant warm up next week, although
the 12z GFS brings down a cold front from the north by Thursday.
This model then keeps the temperatures much lower than the other
models. It looks like an outlier and this model also shows
considerable spread in the ensemble forecasts with the high
temperatures for the end of next week. The CMC and ECMWF ensemble
mean max temperatures are at or above 80 degrees for the end of
the week at Grand Rapids. These two models are either holding
steady with the warmth or trending higher.
- Looking dry next week
The axis of moisture along with the location of the low level jet
are shown to be well west of the CWA. This will act to focus the
convective development away from MI. Bufkit overviews for Grand
Rapids show next week featuring an unsaturated DGZ and mainly
subsidence. As a result we will feature dry conditions.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 811 PM EDT Thu May 18 2023
VFR conditions are in place area wide this evening and that will
remain the case through the night. An upstream cold front
stretching from portions of Western Wisconsin southwest into Iowa
will bring lower ceilings and rain into the area on Friday.
Tonight though, ceilings will remain VFR and we will be dry at the
TAF sites. Ceilings will lower to around 5,000ft at MKG at 12Z
with higher cloud bases at the other TAF sites. By 18Z however
widespread MVFR ceilings will overspread the area. A band of rain
showers and possibly an isolated thunderstorm will move through
between 11Z and 00Z on Friday. The lower ceilings will begin to
lift out quickly in the afternoon as the front progresses to the
southeast. Winds will veer from southeast tonight to south by
morning and then southwest and west on Friday. Winds 5 to 15 knots
will increase to 10 to 20 knots on Friday.
&&
.MARINE...
Issued at 147 PM EDT Thu May 18 2023
It looks like it will get close to small craft conditions tonight
up around Little and Big Sable Points. However given the stable
conditions over the cooler waters of Lake Michigan, we will hold
off on a small craft advisory. Bufkit Overviews for wind and
mixing height suggest that we may struggle to reach criteria as
well. For now we will feature winds topping out at 20 knots for
those locations.
Another shot for small craft conditions exists later Friday
night into Saturday morning. The mixing height deepens up with
cold air advection and the winds at those levels are progged to be
near or above criteria. In addition, waves of 3 to 4 feet are
progged south of Grand Haven. Thus we will need to monitor
trends closely.
&&
.FIRE WEATHER...
Issued at 147 PM EDT Thu May 18 2023
The southeast flow continues with temperatures rising now into the
mid to upper 60s. Relative humidity values continue to fall with
values currently showing 25 to 35 percent at most locations. With
surface temperatures likely to go up a few more degrees, the
humidity levels will fall off as well. Wind gusts were mostly in
the 10 to 20 knot range. Based on all this we will maintain the
Red Flag Warning for northern zones into the early evening hours.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...Duke
DISCUSSION...MJS
AVIATION...Duke
FIRE WEATHER...MJS
MARINE...MJS
Area Forecast Discussion
National Weather Service Wichita KS
711 PM CDT Thu May 18 2023
.SHORT TERM...(This evening through Sunday night)
Issued at 201 PM CDT Thu May 18 2023
A mid/upper trough over Manitoba was digging southeast into the
Northern Plains/Upper Mississippi Valley area this afternoon. A cold
front extended from this system south and southwestward from the
arrowhead of Minnesota to the Central High Plains. Widespread smoke
was evident on GOES imagery in the post-frontal airmass stretching
across all of the Northern Plains and moving southward into the
Central Plains this afternoon. The smoke was reducing visibilities
across southern Nebraska and northwest KS to MVFR with visibilities
in the 1-3 mile range (lower at times in some areas). This smoke may
gradually build southward in the wake of the front as we move
through the day on Friday but rainfall over southern KS leads to low
confidence in the exact impacts which are not being handled well
from the HRRR since it`s domain does not extend into Canada where
the origin of the smoke is.
Tonight-Friday...as the front sinks southward late this afternoon
and evening we are expecting showers and storms to develop as the
airmass remains weakly capped. Much of this activity may be
diurnally driven and tend to fade away as we move through the
evening hours impacting portions of central and northern KS.
Organized strong/severe storms continue to appear unlikely given
weak deep layer shear and mid-level lapse rates. We expect to see a
break until late tonight or into the early morning hours on Friday
when low level moisture transport ramps up with storms focusing
across northern Oklahoma and perhaps into far southern KS during the
morning hours on Friday. There still appears to be better support
for heavy rain just south of the forecast area but some of this
activity could spill into far southern KS given a very moist column
with PWATS progged in the 1.5 inch range for above the 90th
percentile for mid May and relatively slow storm motions anticipated.
Sat-Sun...a stable post-frontal regime is anticipated as we move
through the weekend. Seasonably cool temperatures on Sat will rise
to near normal on Sunday. We may see some shallow radiational fog
develop each morning, especially where the soil remains moist or
across southern Kansas. With high pressure overhead, light winds and
mostly clear conditions are expected to prevail.
.LONG TERM...(Monday through Thursday)
Issued at 201 PM CDT Thu May 18 2023
Seasonal and dry conditions should persist over the region for much
of the period. There remains a small chance of precipitation Tuesday
and Wednesday thanks to uncertainty among model outlooks for upper-
level flow. Look for this to change with future model runs, but for
the time being, this weak and uncertain flow aloft does not appear
to be overly convincing for significant pops.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 657 PM CDT Thu May 18 2023
Main aviation concerns will be shower and storm chances, along
with some smoke reducing visibility.
Currently have a series of upper waves moving out of the Rockies
and into the Plains. In addition, a cold front extends from north
of KDDC, through northern KS and into southeast Nebraska. Numerous
storms are currently over eastern CO with some additional sct
activity over west/central KS. While we may see some decrease in
coverage after sunset, feel there will be enough 850mb moisture
transport to keep some activity going overnight. Locations
generally west of I-135 will have the best chance to see something
before 06z with KICT`s higher chances after 06z. Not expecting
any severe weather with the storms overnight into Fri morning.
Widespread smoke from wildfires in Canada has made it as far south
as Nebraska and feel some of this will also make it into KS,
especially the northern portion. So will lower visibilities at
most sties to account for this. However, with some convection
around, confidence is low on how much smoke will have an impact.
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 60 70 47 75 / 70 70 0 0
Hutchinson 59 71 44 75 / 60 50 0 0
Newton 60 71 44 74 / 60 60 0 0
ElDorado 60 70 45 74 / 60 70 0 0
Winfield-KWLD 60 71 45 73 / 80 90 10 0
Russell 55 73 41 77 / 60 10 0 0
Great Bend 56 71 41 75 / 60 20 0 0
Salina 58 74 44 76 / 50 30 0 0
McPherson 58 71 43 74 / 60 50 0 0
Coffeyville 62 71 47 73 / 40 90 10 0
Chanute 62 72 46 74 / 30 90 10 0
Iola 61 72 45 74 / 30 90 10 0
Parsons-KPPF 62 71 46 73 / 40 90 10 0
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...MWM
LONG TERM...JK
AVIATION...RBL
Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1104 PM CDT Thu May 18 2023
.SYNOPSIS...
Issued at 1104 PM CDT Thu May 18 2023
Smoke aloft will remain widespread through Friday, but will be
less visible as clouds increase ahead of a cold front. This front
is expected to bring showers and scattered thunderstorms on
Friday, but some may occur west of the Illinois River late
tonight. Behind the front, high pressure will bring dry weather
for the weekend, and after a brief cooldown, temperatures return
to near 80 degrees on Sunday.
&&
.UPDATE...
Issued at 824 PM CDT Thu May 18 2023
Going forecast is on track this evening with only minor tweaks
needed. Continue to monitor a cold front that stretches from
central Wisconsin SW to near Kansas City this hour. A very
narrow corridor of diminishing instability in the vicinity of this
front will support a few storms to our west this evening, but
should weaken to just scattered showers as it moves into the
Illinois River Valley late tonight/early Friday morning.
Deubelbeiss
&&
.SHORT TERM... (Through Saturday Night)
Issued at 243 PM CDT Thu May 18 2023
Key messages:
1) The smoke layer aloft is likely to persist through at least
Friday night, though a period of near-surface smoke can`t be ruled
out as a front passes through the area.
2) Scattered thunderstorms will be most likely near and south of
I-70, though severe weather is not expected.
Other than some diurnal cumulus, most of the sky obstructions this
afternoon remain with the smoke. Geocolor satellite imagery shows
quite the expansive area of smoke across the northern third or so
of the CONUS, as far south as the Ohio Valley. Surface
obstructions have been most extensive from South Dakota and
Nebraska east to near Minneapolis, with widespread visibility of
1-3 miles as air is drawn downward behind the cold front. Midday
RAP near-surface smoke guidance does show a period on Friday with
some potential for smoky air over Illinois, though in general, the
threat is not expected to be as widespread as it is now to our
west. However, with the upper low currently just south of Lake
Winnipeg only making it to lower Michigan by early Saturday, a
wholesale upper level pattern change is not expected yet. Thus,
will linger the higher sky grids behind the front through Friday
evening, before gradually phasing them out by early Saturday.
In terms of the convective activity, the high-res models are in
good agreement with bringing the front to the Illinois/Iowa border
by about 4 am, the I-55 region by late morning, and exiting areas
south of I-70 very late in the afternoon. Areas east of the
Illinois River appear likely to remain dry through the night.
Highest rain chances before midday Friday will be west of I-55,
then east of there through the afternoon. In terms of thunder
potential, HREF shows some meager CAPE to around 500 J/kg in the
afternoon across the southeast third of the forecast area, with
the best chances of any thunder in that area. However, will
maintain some isolated thunder chances as far back as the Illinois
River late morning as the front passes.
Behind the front, surface high pressure builds across the central
U.S. on Saturday, edging into Illinois by evening. Will overall be
a pleasant start to the weekend, with highs in the lower 70s and
some less smoke-filtered sunshine.
Geelhart
&&
.LONG TERM... (Sunday through Next Thursday)
Issued at 243 PM CDT Thu May 18 2023
Precipitation chances during this period look to be rather meager,
as upper level ridging gradually amplifies over the central U.S.
The GFS tries to get some nearby convection going on Tuesday due
to a weak upper low over the middle Mississippi Valley, though
this appears to be an outlier at the moment and the forecast will
be kept dry. Main impact from this ridging will be a gradual
building of warmth as the week progresses, with highs in the mid
80s Tuesday-Thursday. However, periodic convection near the Gulf
Coast should keep any meaningful moisture advection cut off from
us, so heat index levels should not be an issue.
Geelhart
&&
.AVIATION... (For the 06z TAFs through 06z Friday Night)
Issued at 1104 PM CDT Thu May 18 2023
A cold front will slowly move across central Illinois through the
day Friday. Ahead of the front, VFR conditions and S/SSW winds
will prevail overnight. Winds will back to the SW Friday morning
and afternoon with scattered showers near the front. A few
isolated storms may develop during the afternoon, but low coverage
precludes any mention in the forecast at this time. Winds will
turn northwesterly behind the front and precip chances will
diminish. Will have to continue to monitor for MVFR vsby behind
the front as smoke overspreads the region. For now confidence
remains low, but upstream sites over Iowa and Nebraska continue to
show widespread 3- 5SM visibility.
Deubelbeiss
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
WFO ILX
Area Forecast Discussion
National Weather Service Louisville KY
930 PM EDT Thu May 18 2023
.Forecast Update...
Issued at 930 PM EDT Thu May 18 2023
Skies at mid-evening were partly cloudy across the region.
Temperatures varied a bit with mainly lower 70s across much south-
central and east-central KY. A small portion of north-central KY
had temperatures in the low-mid 60s. Convection continues to wind
down across the Tennessee plateau this evening. Convective outflows
heading northward will produce some isolated-scattered showers and
storms across portions of south-central KY (mainly along and east of
I-65) for the next few hours. Latest HRRR and RAP runs agree with
this, and some of the activity may make it as far north as the BG
Parkway before fading away due to the loss of heating.
For the remainder of the overnight, combination of the weak warm
advection aloft along with some slight isentropic lift will result
in stratus development. So most spots will see mostly cloudy
conditions develop after midnight. Lows will range from the upper
50s over southern IN to the lower 60s over KY.
&&
.Short Term...(Tonight through Friday evening)
Issued at 310 PM EDT Thu May 18 2023
Synopsis...Mid-level water vapor imagery depicts a small shortwave
currently moving through the Tennessee and lower Ohio Valleys while
a shortwave ridge occupies the rest of the Ohio Valley. Progressive
flow aloft will allow the current features to continue moving to the
east while an upper low and attendant frontal surface swing from the
Upper Midwest to the Great Lakes.
Tonight...Rest of the afternoon will exhibit quiet conditions for
most of the region except the Lake Cumberland region and surrounding
areas where a chance of showers and isolated storms still exist.
Current satellite imagery shows increasing cloud coverage in
response to the weak moisture advection ahead of the small
shortwave. RAP-based guidance still indicates 1000-1500 J/kg of
SBCAPE, weak deep-layer shear and low-level dry air. As a result,
there could be a non-zero chance of pulse convection with brief but
strong downdrafts as DCAPE values range anywhere between 600-800
J/kg during the late afternoon. This convective activity will be
decaying after sunset while it moves northward with a few leftover
showers around Lexington before midnight. Rest of the night should
stay dry with light southerly winds while a low-level stratus layer
build over the western half of the area.
Friday...Winds will keep rotating to the southwest with a gradual
increase in moisture as the cold front approaches from the
northwest. A mostly cloudy day is anticipated with some low-topped,
isolated showers and spotty lightning strikes during the afternoon;
however, the deeper convection are expected after 20/00Z (see Long
Term section below for more details). Overall, decided to trend down
precipitation chances and coverage during the afternoon compare to
NBM following the HREF and NAM guidance. Temperature wise, lows will
be in the upper 50s to low 60s while afternoon highs will probably
reach the low 80s.
&&
.Long Term...(After midnight Friday night through Thursday)
Issued at 300 PM EDT Thu May 18 2023
Friday Night - Saturday...
A positive tilt trough axis and associated cold front will be
pushing into and through our region Friday night. Expect fairly
widespread showers, and a few thunderstorms possible. In general,
coverage should be increasing from sunset onward across our NW CWA,
spreading slowly southeastward through the night. Overall, not
expecting much strength to any storms due to several limiting
factors. 1.) Already meager instability will be steadily waning
after sunset. 2.) Mid level lapse rates will remain quite poor
(~5.5C/Km). 3.) Deep layer shear will be modest at best, and most of
that is from 500mb upwards thanks to a speed max. However, if you
look at soundings, convective clouds tops would probably peak
between 15-20 K feet. So, again most of that shear likely wouldn`t
even be realized. Even thunder/lightning may be hard to come by with
such shallow convection.
The cold front will be pushing through by Saturday morning, however
the upper trough axis will linger just a bit. As a result, we will
likely have to hang onto some lingering pops, at least the first
part of the day, and especially over our south and east. Thereafter,
expect drier conditions heading into the later part of the day from
NW to SE as Canadian high pressure begins to build in behind the
front. Highs Saturday are tricky given cool advection, cloud cover
uncertainty, and lingering precipitation, but low to mid 70s seems
reasonable.
Later Saturday - Thursday...
Looking for a mostly dry pattern to set up for the late weekend and
into the first half of next week as Canadian high pressure centered
to our north dominates the surface. Aloft, there are a few question
marks about the upper pattern as we get toward the middle of next
week, and this is hurting confidence a bit. A weak disturbance
within an overall benign upper pattern could be enough to keep
mention of some slight chance pops for Tuesday. Outside of that,
will stay with dry mention. Mid to upper 70s rule for Sunday, with
temps trending milder into early next week. Mid 80s should be common
by mid week.
&&
.Aviation...(00Z TAF Issuance)
Issued at 720 PM EDT Thu May 18 2023
VFR conditions are expected this evening and into the overnight
hours at the TAF sites. Winds this evening will be light and
variable at times, but the overall winds should be out of the
northeast with speeds of less than 5 knots. Winds overnight will
shift to the southeast and eventually the southwest after sunrise.
Low stratus is expected to develop across the region overnight. Cigs
will likely remain VFR though a drop to MVFR looks likely after
19/12Z at the terminals. Winds on Friday during the day will be out
of the southwest at 5-10 knots. Some scattered showers and possible
storms will be possible across the region after 19/18Z, though the
most widespread precip will likely occur after 20/00Z.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update.......MJ
Short Term...ALL
Long Term....BJS
Aviation.....MJ
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
835 PM CDT Thu May 18 2023
.UPDATE...
Issued at 835 PM CDT Thu May 18 2023
Going forecast is in good shape this evening, with some only minor
adjustments made to add some hourly detail in pop trends from after
midnight tonight into Friday with the approaching cold front.
Evening GOES vapor imagery depicts a deep mid-level trough and
embedded closed low centered near the Minnesota/Saskatchewan/Ontario
border. At the surface, an elongated area of low pressure was noted
from Ontario into the upper Mississippi Valley, with a cold front
trailing southwest across Iowa and into southwest Kansas. The mid-
level trough is progged to propagate southeast across the upper
Great Lakes through Friday, with the cold front pushing east across
the WFO LOT forecast area through the day. Scattered showers and a
few thunderstorms were evident in regional radar data along and
ahead of the cold front, and these are expected to move into
northern Illinois after midnight tonight then work their way
southeast during the day Friday with the front. Instability is
limited, with forecast soundings from various guidance generally
less than 500 J/kg. Precip should largely clear areas northwest of
the I-55 corridor by early afternoon, exiting the southeastern parts
of the cwa by early Friday evening. Winds turn breezy from the
northwest behind the front, bringing in drier air.
Current RAP near-surface smoke forecasts suggest there could be some
low-level Canadian wildfire smoke in the area immediately behind the
front Friday afternoon/evening. Current surface obs depict smoke
behind the front across MN/IA/NE, with visibilities less than 5 miles
in spots. Don`t have a good feel for how impactful this will be
here, with RAP forecasts indicating decreasing smoke concentrations
farther east, but would not be surprised to have smoke in lower
levels in the wake of the front Friday/Friday evening.
Ratzer
&&
.SHORT TERM...
Issued at 256 PM CDT Thu May 18 2023
Through Friday night...
While we have primarily cloud free skies across the area this
afternoon, smoke from Canadian wildfires continues to result in a
milky sky with filter sunshine. This will be the general theme
through the remainder of the day as temperatures climb through the
70s inland from the lake. An onshore wind will keep temperatures
cooler along the IL lakeshore areas.
Our next weather maker is a cold front currently shifting across
the Upper Midwest. This front will shift eastward across our area
during the day Friday. A modest increase in low-level moisture
(lower 50s dewpoints) accompanying this frontal boundary will
support increasing cloud cover late tonight, followed by a period
of showery precipitation (possibly a few embedded thunderstorms)
on Friday. The prime time for this activity is expected to be
during the morning hours, through around midday for much of far
northern IL, with the focus for these showers and embedded storms
gradually sagging southeastward across east central IL and
northwestern IN into the afternoon. Drier weather, with breezy
northwesterly winds are expected to develop across the area in
the wake of the frontal passage Friday afternoon.
While otherwise quiet weather is likely in the wake of the frontal
passage tomorrow afternoon, the potential exists for some reduced
surface VSBYs to develop due to wildfire smoke reaching closer to
the surface. This has, and continues to be the case within the
post cold frontal airmass, with current upstream surface
observations across the Dakotas into parts of the Upper Midwest
indicating reduced visibilities from wildfire smoke reaching the
surface. It still remains a bit unclear how extensive this smoke
will be at the surface in our area as the front moves through
tomorrow. However, I would not be surprised to see more hazy
conditions closer to the surface tomorrow afternoon.
KJB
&&
.LONG TERM...
Issued at 256 PM CDT Thu May 18 2023
Saturday through Thursday...
Upper-level ridging will begin to establish itself over the central
and eastern CONUS beginning this weekend, and correspondingly,
positive MSLP anomalies will be the rule over the Great Lakes and
northeast through at least this middle of next week. Accordingly, we
will find ourselves in a quiet and dry pattern over this time frame
which should feature no precipitation, plenty of sunshine, and
moderating temperatures without a notable increase in humidity.
Saturday should be the coolest day of the current extended forecast
period with highs ranging from the mid 60s to mid 70s for most.
Temperatures should then climb well into the 70s at most locations
on Sunday before continuing their ascent into the 80s as we head
into the upcoming work week. Temperatures should be cooler near
the lake each day, though, as daily lake breezes can be expected
with the progged mean positioning of dominant eastern CONUS surface
high pressure regions over this time frame not really being
conducive to offshore flow. It should also be said that high
temperatures may end up being a bit lower than what`s currently in
our forecast grids if prevailing northwest flow continues to
funnel smoke from Canadian wildfires in our general direction that
ends up filtering some of the otherwise abundant sunshine that we
are expected to see over the next several days.
On a final note, with the richer Gulf moisture likely to be steered
into the Great Plains next week, dew points here are expected to
primarily remain in the 40s and 50s through the entirety of the long
term forecast period. This will lead to comfortable humidity levels
during the daytime, so go out and enjoy the great weather over
the next several days!
Ogorek
&&
.AVIATION...
For the 00Z TAFs...
644 PM...Forecast concerns include...
Wind shift to southwest tonight.
Scattered showers, possible mvfr cigs Friday morning.
Gusty northwest winds Friday afternoon.
Possible haze/smoke Friday.
Possible wind shift/lake breeze late Friday afternoon.
A lake breeze has moved west of the terminals, shifting winds
east/southeast. Winds will turn back southeasterly this evening
and are expected to shift to the southwest overnight. A cold front
will move across the area late Friday morning shifting winds to
the west/northwest. Winds will continue turning northwest and then
likely to the north/northwest by late Friday afternoon. Gusts to
20kts will be possible Friday afternoon. A lake breeze may develop
Friday afternoon and move inland through GYY and possibly to MDW.
Confidence is low for how far inland in IL this lake breeze would
move. For now, have not included this lake breeze in the MDW or
ORD taf.
Scattered showers are expected along and ahead of the cold front
Friday morning. Current tempo mention seems reasonable for the
best time period and expected coverage. There is a small chance
for an isolated thunderstorm along the front, but no mention at
this time given the expected isolated coverage and short
duration. Some mvfr cigs are possible with the showers and the
front though guidance has been slowly lifting cigs as this time
period approaches and has mainly low vfr cigs.
Smoke, being reported as haze, from Canadian wildfires is
widespread across the midwest, behind the cold front noted above.
There is limited skill and guidance for forecasting smoke but
there is some potential that this smoke will move across northern
IL Friday, behind the cold front, possibly reducing visibilities
into the 3-5sm range. Confidence is low and for now have not
included smoke but its possible it will be needed with later
forecasts. cms
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1051 PM CDT Thu May 18 2023
.UPDATE...
Issued at 1048 PM CDT Thu May 18 2023
Updated for 06z Aviation Discussion below.
&&
.DISCUSSION...(This evening through Thursday)
Issued at 137 PM CDT Thu May 18 2023
KEY MESSAGES: (optional)
- A couple of strong to severe storms possible over from far southeast
Minnesota into west central Wisconsin later this afternoon.
- Poor air quality due to wildfire smoke from Canada will linger into
tonight, but will improve overnight into Friday. Some smoke will
still be present aloft on Friday.
- Dry and pleasant weather for this weekend.
- A warming trend is expected from the weekend onward into next week.
A line of showers in association with a surface cold front will
continue to push east across the remainder of the forecast area this
afternoon, with a few thunderstorms possible over the far eastern
portion of the area after 4 PM. Widespread severe weather is not
expected, but there may be sufficient instability and shear for some
marginally severe hail. Low-level smoke affecting visibility and air
quality will persist for about eight hours after frontal passage at
any given location based on observations and RAP smoke forecasts.
However, smoke aloft looks to stick around into Friday evening as it
rotates around the upper low as it moves across northern Minnesota
late tonight and into the eastern Great Lakes Friday night.
The weather looks benign once we get the current issues out of the
way, with dry weather and warming temperatures expected from the
weekend through most of next week. Northwest upper flow looks to
become zonal by the end of the weekend, and will transition to
southwest flow by midweek. We`ll see a prolonged period of warm
advection through the week, with the surface trough remaining well to
our west through at least Wednesday. The ensemble guidance starts to
exhibit more spread after Wednesday, with some solutions bringing the
surface trough eastward, which would bring chances for SHRA/TSRA
Thursday into Friday. Can`t argue with the consensus approach at this
point, so included chance PoPs at the end of the period, but given
the large scale pattern it wouldn`t be surprising if things progress
more slowly and we remain precipitation free until Friday or later
across most of the area.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1048 PM CDT Thu May 18 2023
By the beginning of the period, the front will have moved through all
but the EAU area, with winds from 310-340 at 10-15kts with some
occasional 20-25kt gusts through the night. We begin VFR with the
exception of some smoke in EAU, but likely see many sites dropping to
borderline MVFR with cigs between 025-035 for much of the day
tomorrow. Skies scatter out as cigs lift by tomorrow afternoon, with
clearing skies towards the end of the period.
KMSP...Winds will be the primary concern alongside potential for MVFR
conditions to begin the daylight hours tomorrow. We trended a bit
lower for CIGS compared to the 00z TAF due to higher confidence in
the low level moisture.
/OUTLOOK FOR KMSP/
SAT...VFR. Wind SW 10-15kts.
SUN...VFR. Wind SW to NE 5-10kts.
MON...VFR. Wind SE 10-15kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
DISCUSSION...WFO MPX
AVIATION...TDH
Area Forecast Discussion
National Weather Service Marquette MI
635 PM EDT Thu May 18 2023
.SHORT TERM...(Into Tonight)
Issued at 346 PM EDT THU MAY 18 2023
Latest water vapor imagery and RAP analysis show a closed low
centered over southern Manitoba with shortwave ridging over the
Upper Great Lakes. Gusty southerly winds have developed today ahead
of the approaching cold front from the Northern Plains with gusts
reaching 30-35 mph over many east half portions of the U.P with a
few downsloping locations along Lake Superior reaching over 40 mph.
However, abundant smoke at mid-upper levels from the Western
wildfires has limited mixing across the area today keeping temps
cooler than expected and thus RHs have not dropped as low as
originally forecast. While temps have reached into the mid 60s over
the central counties, eastern counties have thus far have struggled
to reach 60F at many locations given the thick smoke aloft and
onshore flow off Lake Michigan. This has resulted in RHs
generally 35 percent or above across much of the forecast area
where Red Flag Warnings are currently posted. There could still
be a chance of increased heating and mixing over the next hour or
two which could lower RHs a bit more so will keep the RFW headline
going into early evening over the east half counties, but
confidence is waning that RFW criteria will be reached for RH
values.
The focus then shifts to the mid-level low over southern Manitoba
which is fcst to move into the western fcst area later tonight. The
associated cold front out ahead of this feature will reach western
Upper MI in the next few hours and then push e thru the rest of the
cwa tonight, accompanied by showers which will last roughly 3hrs or
so. Given little or no instability as noted on SPC mesoanalysis
fields have taken thunder chcs out of the fcst late this afternoon
into tonight. There will be a break in the showers over the western
counties after the main band along the front passes through late
afternoon/early evening. Showers tied closely to the mid-level low
center will then arrive over western Upper MI, mostly after
midnight. Model consensus suggests rainfall amounts generally on the
order of 0.10-0.75 inches by 12z Fri, greatest over the western
counties and least over the east half. Under mostly cloudy skies,
expect min temps in the 40s tonight, possibly near 50F far south
central.
.LONG TERM...(Friday through Thursday)
Issued at 354 PM EDT THU MAY 18 2023
Amplified upper level flow regime across northern North America
becomes more zonal over the next week. During this time, troughing
across eastern Canada consolidates across the Baffin Island and
Greenland region as western Canada and Pac NW ridging shifts east
toward the Great Lakes region. This allows for slightly below normal
temperatures to transition to a much above normal regime by the end
of next week. After rain chances end Friday night, 4-5 days of dry
weather are expected before precip chances return late next week.
Starting with Friday morning, most of our area will be between waves
of precip as the initial cool front exits stage right and a
secondary trough enters stage left. There could be a few light
showers during the morning, but I think most places will have broken
low level cloud cover that increases/thickens through mid to late
afternoon. Decent upper level support suggests a few hours of fairly
widespread rain showers, but by the late afternoon or evening
clearing should begin spreading eastward across our area.
By Saturday morning, our whole area should be mostly clear with
mostly sunny skies leading to a pleasant day with most places
warming to around 70F. Deep mixing up to around ~6kft is expected
especially for south-central locations where northwest downsloping
should be maximized leading to gusty winds and low RH values. A
somewhat stronger wind field across the Keweenaw and winds
backing to a more favorable westerly wind direction may result in
a few hours of a breezy conditions there Friday evening. Shortwave
ridging arriving around sunset allows the boundary layer to
stabilize with winds diminishing.
Another Hudson Bay high approaches on Saturday behind a seasonably
strong cold front dropping south into our area late Saturday
night/early Sunday morning. Gusty north to northeast winds off Lake
Superior prevent temperatures from warming much through the day with
fairly steady temps in the upper 40s, but temps should be able to
warm up to around 60F farther inland. The high pressure system sinks
southeast toward the Ontario/Quebec border by Monday morning when
light winds and clear skies may allow for another round of frost or
freeze across the UP. The interior west seems most likely to get
below freezing, but patchy frost appears possible across our entire
area. Temperatures warm into the 60s and 70s under sunny skies and
light winds across the UP with RH values likely to get below 30% for
most spots.
A weak front approaches on Tuesday with an increasing pressure
gradient ahead of it allowing for gusty winds and potential for more
elevated fire wx conditions. While precip with this frontal boundary
cant be ruled out, chances are more likely on the other side of Lake
Superior. The upper level ridge axis shifts overhead on Wednesday
then to our east on Thursday allowing for a more amplified WAA
regime late next week with moisture and precip chances increasing
accordingly.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 635 PM EDT THU MAY 18 2023
A narrow band of showers will move through the area overnight.
Wraparound moisture will move in after a cold front moves through
late tonight. Conditions will start off VFR at IWD and SAW and then
will deteriorate to high IFR/low MVFR tonight into Fri. CMX will be
a different story as rain over Lake Superior could bring in some fog
and they will go from MVFR to IFR later tonight.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 354 PM EDT THU MAY 18 2023
Low pres and the associated cold front are currently dropping se
across far western Lake Superior with southerly winds ahead of the
front. The strongest southerlies up to around 30 kt are across the
eastern half of the lake at higher elevation platforms where a few
gale force gusts to 35 kts are possible late this aftn/evening. This
cold front reaches the far eastern lake early Friday morning with
lighter westerly winds generally gusting below 20kt behind the
front. A few northwesterly wind gusts up to 25kt are possible across
the central Lake Friday afternoon before light winds return and
continue through Saturday morning as brief ridging moves across the
lake. Ahead of the next cold front dropping s toward Lake Superior,
wsw wind gusts will increase to 20-25kt across w and central Lake
Superior Sat aftn/evening, especially around the w and n side of the
Keweenaw. As the front sweeps s across Lake Superior Sat night,
winds will shift to n to ne, and there could be a period of gusts to
around 30kt for a few hrs after the front passes due to colder air
pushing into the area and incoming pres rises. Winds will diminish
to mostly under 15kt Sun night as high pres ridge arrives. The ridge
will shift toward the Lwr Great Lakes and New England on Mon. SE to
S gusts increase to 20-25kt Monday evening or overnight, especially
across the eastern half of the lake.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Red Flag Warning until 8 PM EDT this evening for MIZ005>007-013-
014-085>088-095-096.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Voss
LONG TERM...EK
AVIATION...07
MARINE...EK
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 353 PM CDT Thu May 18 2023
Key Messages:
- Shower and non-severe thunderstorm chances this afternoon and
evening as a cold front moves through.
- Smoke from wildfires has reached the surface behind the front
and has lead to reduced visibility and air quality.
- Quiet and pleasant weather Friday through Tuesday.
Have been working to keep track of smoke and its impacts
throughout the day. Worst conditions have generally been directly
behind the front, but visibilities below 2 miles stretch all the
way back into South Dakota. A second reinforcing cold front has
brought cooler temps and some refreshingly smokeless skies to
northern South Dakota. We look forward to that.
Guidance has been pretty terrible with picking up on the reduced
visibility. HRRR has not found the smoke at all and the RAP has
been doing well for smoke placement but not visibility. I`ll
lean on the RAPs trends while ignoring its actual numbers. Expect
the smoke to grow denser after dark - especially south of I-80.
OAX NEXRAD has picked up on a few updrafts along the front, just
south of the Lincoln and Omaha metros. A few bolts of (intra-cloud)
IC lightning have been detected. Expect those
showers/thunderstorms to remain on the weak side. No severe
weather is anticipated with negligible CAPE and shear. Some gusty
winds may be noted. Some light and sparse showers may continue
along the NE/KS state line overnight, but very little QPF is
expected.
Winds will pick up behind the secondary front that will push into
the CWA around 10pm. Gusts up to 28mph or so are expected. Again,
this will bring a supply of clear air to the area as the upper low
tied to the front meanders east toward Detroit. CAA at nearly -3C
degrees an hour at 850 hPa will leave us with highs mostly falling
below 70F on Friday afternoon, with the breezy winds making it
feel a touch cooler.
With high pressure overhead on Saturday, winds will be veering
from north to southwest with return flow developing, but will
remain negligible in speed. Add in sunny skies and highs in the
mid-70s, I think it will be quite the pleasant day.
Widespread 80s develop by Sunday afternoon as the southerly return
flow becomes a little quicker. A weak piece of shortwave energy
traverses the area on Sunday, but it`ll be hard pressed to bring
much more than an uptick in cloud cover.
80s continue through the work week and weather remains dry under
the high pressure ridge over the central CONUS. The pattern breaks
down toward the end of next week as a trof approaches from the
west. Scattered POPs are warranted for Thursday with the first
piece of energy ejecting ahead of the main low. Next weekend
brings more chances of showers and storms.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 623 PM CDT Thu May 18 2023
Considerable smoke has descended to ground-level this afternoon in
the wake of a weak front that has now shifted south of IA.
Resultant IFR to MVFR visibilities, and at times vertical
visibility restrictions, are expected to continue into the
overnight hours. By late tonight into Friday morning, visibilities
should begin to improve as a secondary, stronger cold front moves
through the area with gusty north winds.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...Nicolaisen
AVIATION...Mead
Area Forecast Discussion
National Weather Service Pendleton OR
820 PM PDT Thu May 18 2023
.EVENING UPDATE...Thunderstorm activity is gradually winding down
this evening, however there are still a few cells in southern
Deschutes county that continue to restrengthen. So far, most of
the storms that have developed have produced heavy rain with small
hail. Tonight, thunderstorm activity will wane with quiet
conditions through tomorrow morning. Tomorrow, the forecast area
will continue to be under a south to southwest flow aloft with
high pressure aloft. Firstly, afternoon temperatures are expected
to warm into the upper 80s to mid 90s across the lower elevations,
with 70s to mid 80s mountains. Secondly, another round of isolated
to scattered thunderstorms/rain showers are anticipated tomorrow
afternoon and evening over the OR Cascades, central and north
central OR, as well as the Ochoco-John Day Highlands. Lawhorn/82
&&
.SHORT TERM...Tonight through Saturday Night...A complex forecast
has gotten even trickier with the addition of smoke aloft from
wildfires in British Columbia and Alberta. Overall, hot
temperatures are expected tomorrow and Saturday but perhaps a bit
cooler than previously thought. Still expecting isolated to
scattered thunderstorms each afternoon, especially on Saturday.
A ridge continues to build over the area with an upper low in the
Gulf of Alaska sending a moist south to southwest flow into the
interior Pacific Northwest. This is expected to remain the pattern
through Saturday night. A cumulus field is developing over the
mountains and central Oregon this afternoon and continue to expect
isolated thunderstorms over the Cascades and central Oregon as
well as the higher terrain of the eastern mountains. Instability
is around 500-1000 j/kg this afternoon and will be a bit stronger
Friday. Precipitable water remains around 1 inch which is well
above normal and is expected to remain at this level through
Saturday. Shear is only about 5-10 kts this afternoon and
tomorrow, so pulse type cells that form and quickly weaken are
expected. Shear increases to around 20 kts and instability rises
to 1000-2000 j/kg Saturday, so storms Saturday may be better
organized and stronger, though do not expect any severe
thunderstorms. Rain amounts in the mountains and central Oregon
this afternoon and evening should be fairly light and generally
no more than a tenth of an inch though thunderstorms will be slow
moving and could locally drop a quarter of an inch.
Tonight will see thunderstorms end this evening and weather should
be quiet overnight and tomorrow morning. Lows tonight will be warm
and in the mid 50s to lower 60s with upper 40s to mid 50s in the
mountains.
Friday will have warmer temperatures in the upper 80s and lower
90s with mid 70s to mid 80s in the mountains. Guidance is even
warmer than this, though have lowered temperatures a couple of
degrees due to a recent warm bias in the models and the
possibility of continued smoke aloft. The focus for thunderstorms
will be mainly in the Oregon Cascades, central and north central
Oregon and the Ochoco-John Day Highlands and have scattered
thunderstorms there and a slight chance of thunderstorms
elsewhere. Rain amounts of up to a quarter inch are expected with
up to a half inch with the heavier storms. Showers and
thunderstorms should end during the evening.
Saturday will be both the warmest day and the day with the most
thunderstorm activity. Temperatures will be 20 to 25 degrees above
normal with highs in the mid 80s to mid 90s and in the low to mid
80s in the mountains. Record high temperatures will be possible
in the Columbia Basin, Yakima and Kittitas Valleys, Blue Mountain
Foothills and the Grande Ronde Valley. The NBM is giving
probabilities of 90-100% of at least 90 degree temperatures in
those areas and a 35-40% chance of 100 degrees around the Tri-
Cities. Thunderstorms will begin developing in the afternoon in
the Cascades, Ochoco-John Day Highlands and central Oregon and
increase and spread over most of the rest of the area in the late
afternoon and evening. Rain amounts will be heavier over the
Ochoco-John Day Highlands and southern Blue Mountains with amounts
of up to a half inch expected. The stronger cells may have even
heavier amounts than that. Amounts will be up to a quarter inch
elsewhere. Thunderstorms may also have small hail and gusty
outflow winds to 40 mph. Perry/83
.LONG TERM...Sunday through Thursday...The long term will be
characterized by a pattern change. An upper level trough will begin
to break down the ridge that is in place. A leading cold front will
cross the region ahead of the upper level trough dropping the
temperatures over the area by about 20 degrees from the current
temperatures. Some lingering showers will remain and be primarily
over the Cascades however, the eastern portion of the area will see
an increase in thunderstorm activity as the front passes. Once the
upper level low is in place, conditions will return to more
seasonable weather with temperatures in the 60s and 70s and dry
conditions.
Sunday the models are in firm agreement with the placement and
timing of the upper level trough. The cold front will be mostly
offshore and will move overhead by late Sunday afternoon. EFI shows
CAPE values to be above seasonal normal as the front passes over
with the HRRR and CAMs models showing the values to be between 1000-
2000 J/kg. Shear will remain low causing these storms to be more
pulse like in nature but high enough that an enhanced threat of
larger hail and stronger winds could be associated with them. NBM
shows the probability of thunderstorms to be >35% and mainly across
Central Or through the Ochoco-John Day highlands and the southern
Blues. Chances pf rain associated with the front range between 30-
40% and again will be primarily over the aforementioned area.
Despite the pattern shift, temperatures on Sunday will remain above
seasonal average as the front is not expected to cross over the
Cascades until late afternoon. NBM and ensembles show the
temperatures to be in the 80s through the Gorge, along the foothills
of the Blues, the Basin and adjacent valleys while elsewhere will be
in the mid to upper 70s.
Models keep the upper level trough in place overhead through Monday
night before diverging. The cold front will have already passed over
the region bringing with it cooler temperatures and dry conditions
through the end of the period. Clusters show that the models begin to
struggle with both the position and timing of the next incoming
system. The GFS has an upper level closed low moving in from British
Columbia and while the ECMWF has the upper level trough already in
place deepening. Regardless of the divergence, the majority of the
models show a shift in the pattern. EFI continues to show the
temperatures to be near normal and the NBM and ensembles show the
temperatures to steadily rise. Temperatures on Monday will drop back
into the mid to high 70s through the majority of the region with
some of the higher terrains in the mid 60s. By the end of the period
temperatures will be back in the mid 70s to 80s. Bennese/90
&&
.AVIATION...Previous Discussion...00Z TAFS...VFR conditions to
prevail through the period. Isolated thunderstorms will continue
to develop across the mountains through this evening, then
redevelop by tomorrow afternoon. Only sites expected to be
impacted by vicinity thunderstorms are RDM/BDN. Winds will be
light, less than 12kts through the period, except at sites RDM/BDN
where gusty erratic winds from nearby thunderstorms may be
possible. Lawhorn/82
&&
.PREV DISCUSSION... /issued 436 PM PDT Thu May 18 2023/
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 59 89 60 90 / 0 0 10 10
ALW 62 91 62 94 / 0 0 0 0
PSC 64 95 65 97 / 0 0 0 0
YKM 59 91 62 92 / 10 10 10 10
HRI 62 94 63 96 / 0 0 10 0
ELN 57 89 58 89 / 20 10 10 20
RDM 53 87 54 85 / 20 30 30 20
LGD 54 84 55 87 / 10 10 10 10
GCD 53 85 55 87 / 10 10 20 20
DLS 61 94 62 90 / 10 0 10 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&
$$
EVENING UPDATE...82
SHORT TERM...83
LONG TERM....90
AVIATION...82