Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/21/22
Area Forecast Discussion
National Weather Service Cleveland OH
931 PM EDT Tue Sep 20 2022
A warm front located over eastern Indiana this evening will
move northeastward across northern Ohio and northwestern
Pennsylvania through sunrise. A strong cold front then moves
southeastward across the region late Wednesday afternoon into
the evening. A secondary cold front crosses the region Thursday
with high pressure building overhead Thursday night into Friday.
.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
Only minor changes to hourly temperatures and sky cover to
reflect current trends. Otherwise previous thoughts still look
to be on track:
Made some timing changes to the forecast through the overnight
as the warm front and its lift move across the region. In the
wake of this morning convection we will see how fast the
environment can recover. Ended up focusing the best chances of
strong to severe thunderstorms near and east of a line from
Cleveland to Canton. The western areas should see limited
coverage with 7H temperatures around 10 C. This is likely the
indication of the EML mentioned in the previous discussion.
IR satellite and water vapor loops this afternoon show a
mid/upper trough beginning to sharpen over Manitoba, and this
feature will bring the potential for severe weather Wednesday
afternoon, as well as a major change in the pattern that will
usher in some true Autumn air. First off...this evening,
clusters of showers and thunderstorms are currently progressing
southeastward across southern lower MI and northern IN, with
another cluster developing farther north over central Lake
Michigan and WI. This convection is developing and riding along
a warm front where strong warm/moist advection on the nose of a
WSW oriented low-level jet is maximizing ascent along the
resultant theta e gradient. This warm front/theta e gradient
currently stretches from southern MN and central WI through
southern IN which is holding all of the instability west of our
region. As a result, this initial round of convection will miss
our area this evening, but added slight chance PoPs for NW Ohio
to cover the decaying showers starting to reach that area. Most
of the region will just see increased cloud cover this evening.
Moving into tonight, the aforementioned warm front will lift ENE
across the region in response to the mid/upper trough digging into
the Upper Midwest. A nocturnal WSW oriented low-level jet developing
in response to the increasing upper forcing will nose into MI and
the vicinity of western Lake Erie igniting new clusters of showers
and thunderstorms along the eastward advancing instability gradient.
Forecast soundings suggest that this convection will be elevated
above a pretty strong 850-900 mb stable layer, so the main impact
will be locally heavy downpours, but small hail is possible too
given an upstream EML (mid-level lapse rates 7-8 C/km) that will be
encroaching on the region from IN and western MI behind the warm
front. HREF members are not in good agreement on the coverage and
location of this nocturnal convection, but consensus points toward
it sliding SE across Lake Erie from north central Ohio into NW PA,
with the greatest chances in NE Ohio and NW PA, so have the highest
PoPs out there. Lows tonight will stay in the mid/upper 60s in most
areas, with a few upper 50s/low 60s in NW PA.
Now for the most interesting part of the forecast...severe potential
Wednesday afternoon. Much of what happens depends on how quickly
lingering clouds and showers exit in the morning. All HREF members
show this exiting by 12 to 13Z at the latest, which is supported by
the warm frontal boundary making steady progress into New York in
the morning, but there could be lingering outflow boundaries at play
that influence where the new convection initiates during the
afternoon. The mid/upper trough will dive into the central Great
Lakes during the day with strong height falls taking place over the
lower Great Lakes by early to mid afternoon. These height falls, as
well as a 100-110 knot H3 jet streak approaching the central Great
Lakes in the afternoon, will lead to strong forcing for ascent
allowing a line of convection to erupt ahead of the cold front and
along any outflow boundaries/prefrontal troughs. HREF members show
large spread in where this convection initiates, with the NAMNEST
initiating a solid line over southern Ontario in the early afternoon
that progresses across Lake Erie through much of the area, while the
HRRR and WRF ARW suggests everything developing on a boundary in far
eastern Ohio/western PA in the early to mid afternoon that would
quickly exit, and miss most of the area. Some of this is also due to
differences in the degree of capping as a stout EML advects over the
region during the morning. The greatest forcing for ascent is
definitely north and east of the region, but if convection can build
along the front westward into our area, a favorable environment will
be in place for severe weather. Clearing skies behind the morning
activity combined with the EML (very steep mid-level lapse rates of
7 to 8 C/Km) and strong low-level warm/moist advection in the warm
sector (upper 60s to low 70s F dew points) will allow for strong
instability. RAP and NAM soundings suggest MLCAPE could reach as
high as 2500-3000 J/Kg with the surface heating and dry mid levels
also supporting over 1300 joules of DCAPE. This combined with
impressive deep layer effective shear over 40 knots will support
robust, organized updrafts with good potential for damaging winds,
as well as large hail given the steep mid-level lapse rates. Deep
layer shear oriented fairly parallel to the sagging cold front
support mainly a squall line, further enhancing wind potential
within bow segments, but low-level shear over 30 knots and low-level
SRH values potentially over 250 m2/s2 also support embedded
supercells, especially given the favorable effective shear and
moderate to strong instability. 0-3 Km shear over 30 knots certainly
could support isolated QLCS tornadoes where the line is normal to
the shear vector. Timing of all this has trended faster with
consensus initiating the convection after 17Z and generally exiting
out of the region by 22 or 23Z, but again, this is uncertain given
the degree of capping and other factors described above. If the cap
holds, it will be a few hours slower. Overall, the main threats are
damaging winds and large hail, but isolated tornadoes are certainly
possible, and again, coverage of convection is uncertain. Finally,
PWATs increasing to 1.7 to 1.8 inches will allow for torrential
rainfall within the thunderstorms, but rapid movement will limit any
flash flooding to any localized areas where/if training develops.
Highs Wednesday will reach the upper 80s/low 90s, and went above
Most areas will dry out quickly behind the cold front Wednesday
night, with the front progged to cross quickly during the late
evening hours. Strong cold air advection and some lingering wrap
around moisture will however keep some lake-effect or lake enhanced
showers going in NE Ohio and NW PA through the night, so kept chance
PoPs in those areas. Lows Wednesday night will fall into the
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Deep digging upper level trough will dive into the Great Lakes
region Thursday forcing strong cold air advection into the local
area. Strong surface high pressure is expected to build in from the
west aiding in funneling the cold air south. Moisture associated
with the upper level trough is expected to move southeast into the
area Thursday afternoon and evening. The combination of the this
synoptic moisture and the lake moisture support will aid the
development of lake effect rain showers across the northeast
portions of the forecast area. Due to lake to air temperature at
850 mb difference, expecting Moderate instability. Can`t rule out
the possibility for some thunderstorms as equilibrium level tops out
around 12000 feet by Thursday evening. Rest of the forecast area
should begin to dry out during this period. Drier air pushes into
the area from the west in association with the surface high pressure
and gradually diminishes the lake effect threat. Fair weather is
expected Friday afternoon into Friday night. Strong cold air
advection expected during this forecast period and will keep
temperatures on the cooler side.
.LONG TERM /SATURDAY THROUGH TUESDAY/...
Upper level trough will gradually push east allowing an upper level
ridge to build east over the forecast area during the period. This
will bring fair weather to the region Saturday. Another upper level
trough is expected to dive southeast toward the area Saturday night
into Sunday with associated moisture. This feature along with
surface low pressure will bring another threat for showers into the
area Saturday night into Monday. Unfortunately, a return to warm
air advection over the weekend will quickly give way to another
round of cold air advection behind a surface cold front Sunday
night. This round of cold air will persist through Tuesday. However,
moderating temperatures are expected by Tuesday as surface ridge
begins to bring a return back to fair weather for the early part of
.AVIATION /00Z Wednesday THROUGH Sunday/...
Convection over NW OH at 23Z should continue to sink southward
and weaken through the evening. We will then monitor for
additional rounds of thunderstorms along and northeast of a warm
front that moves across northern OH and northwestern PA through
the overnight. This convection should lower ceilings but may
not get them below 3000 feet. However visibilities should
briefly drop to MVFR/IFR levels.
The region should get a lull through the morning hours with
skies trying to clear. NW OH may not see anything more than an
isolated thunderstorm along/ahead of the cold front that moves
into the region during the afternoon. Best chances of strong to
severe thunderstorms looks to be near and east of a line from
KCLE to KCAK. Any of the convection will produce brief MVFR/IFR
conditions during the afternoon and evening. Gusty winds from
the thunderstorms in excess of 40 knots definitely possible
across the east. All of the thunderstorm activity should be east
of the region by 02Z. We will then see how much lake enhanced
cloudiness and showers develops through the overnight.
Winds should be southerly through the overnight away from the
convection. Southwest winds develop by late Wednesday morning
into the afternoon. Deep mixing across the west should allow
wind gust to reach 25 knots. As the cold front passes during
the evening winds shift to the northwest at 10 to 15 knots.
Outlook...Non-VFR in showers and lower lake effect cloud cover
Wednesday night through Thursday night, mainly near and east of
a line from Sandusky to K4I3.
Winds will be gradually increasing tonight into Wednesday ahead of a
cold front expected to move east across the lake Wednesday evening.
After southwest flow develops ahead of the front, winds should shift
around to a northwest direction Wednesday night. Expecting
northwest flow to support the possibility for small craft advisory
conditions Wednesday night persisting through at least Friday
morning when winds diminish. High pressure will gradually build east
and keep winds fairly light until Saturday night. Southwest flow
develops again pushing winds up to around 15 knots Sunday.
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
750 PM EDT Tue Sep 20 2022
Elevated showers and convection will continue in a broad line from
northwest to southwest, extending from KFNT - KDTW. Showers and
thunderstorms are expected through roughly 02Z, before coverage
shifts out of the area. Near surface conditions remain relatively
stable, thus stronger wind gusts are not expected with the current
thunderstorm activity. Some renewed activity will be possible
centered 03-09Z as a warm front starts to extend across SE MI.
Confidence remains low regarding the development and location of any
new showers and thunderstorms. More organized development will be
possible with any overnight precipitation as elevated instability
moves into SE MI. The main threat with any overnight thunderstorms
will be heavy downpours and possibly large hail. Model guidance
suggests some clearing of clouds will be possible after the passage
of the warm front, which can lead to the quick development of low
stratus (satellite imagery shows ~3kft across western MI with the
For DTW...High confidence for thunderstorm activity to persist
through roughly 02Z. A second round of elevated thunderstorms will
be possible centered 03Z - 09Z with the passage of a warm front, but
confidence remains low regarding development of this second round.
Any overnight clearing may provide a window for stratus development
DTW THRESHOLD PROBABILITIES...
* High for thundestorms to impact the terminal through 02Z. Low
between 03Z - 09Z.
* Low for ceilings at or below 5000 feet mid to late Wednesday
Issued at 414 PM EDT Tue Sep 20 2022
Initial stage of midlevel warm advection is occurring over Southeast
Michigan this afternoon driven by the increase in latent heat
content from the old mesoscale convective system. Models do show
this moistening at/above 10.0 kft agl will now be good for MUCAPE
above this level so shower and scattered/isolated thunderstorm will
be possible moving forward. There is a good amount of work that
needs to be done yet, however, as moisture remains lean in the sfc-
8.0 kft layer. Models show substantial H8-H6 warm advection crashing
into the northern cwa between 00-06Z this evening which will help to
erase out some of the lower column stability that is in place.
Latest RAP based mesoanalysis has the Oceana/Mason county activity
outpacing the MLCAPE reservoir thats hanging back across Lake
Michigan. So while its going to take a few hours, do think that
meaningful elevated instability, MUCAPE of 1000-1500 J/kg, will
flood rapidly across the cwa after 00Z tonight. 0-6km bulk shear is
progged to range out around 35 knots particularly across the
northern and eastern cwa. The weather feature that will need to be
monitored tonight is a sharp 950-925mb warm front that will push
west to east across the forecast area in the 03-09Z timeframe. The
directional shear, veering environmental wind profile with height,
becomes outstanding which will be more than adequate for organized
updraft potential including elevated supercells. Lapse rates are
certainly questionable, but inherent low confidence always exists in
higher end warm advection scenarios. The potential exists for severe
weather tonight, primarily in and around the surface warm front as
it lifts through the area. The threat for tonight is large, damaging
hail greater than 1 inch with little to no surface based threats
outside of locally heavy rainfall. Latest Swody1 has a Marginal
designation for severe weather across Southeast Michigan tonight.
A low confidence conditional threat for severe weather exists
Wednesday. Too much model variance and spread exists to discount the
potential for thunderstorm development. Just note the differences
between the HREF mean vs. the 12Z ECMWF. Two big factors on how
Wednesday plays out. 1. To what extent the coverage of overnight
activity becomes and whether or not a substantial amount of
mesoscale subsidence can develop. 2. How significant the capping
inversion persists between 3.0-7.0 kft agl. A majority of the
guidance keeps activity outside of the cwa, but a little subset of
the 12Z NAM and 12Z ECMWF brings a line feature southward through
the eastern half of the cwa between 15-19Z. 0-6km bulk shear remains
at 35 knots so an organized severe weather threat, damaging wind
gusts and large hail, will exist.
Pattern change then in store for Thursday as Autumn catches the
area. A strong cold front with 850mb temperatures dropping from 19C
down to 1C by Thursday afternoon. Steep surface based lapse rates
will be good for shower activity Thursday. A cool stable anticyclone
will then lead to quiet and below normal weather Friday and Saturday.
Warm front is beginning to lift north into the region late this
afternoon which has begun to generate scattered to numerous showers
and thunderstorms over central Lake Michigan. This activity is
expected to track east-southeast into the southern half of the
central Great Lakes this evening/early tonight. Parent low pressure
quickly lifts from the upper Midwest into northern Ontario early
Wednesday sending a strong cold front across the Great Lakes.
Additional showers and storms are likely ahead of this front over
the northern half of the region late tonight-early Wednesday morning
before chances expand over the southern half by Wednesday afternoon-
evening. A couple strong to severe thunderstorms are possible during
this timeframe focused over Lakes St Clair and Erie.
Cold front clears Lake Huron by Wednesday afternoon and Lakes St
Clair/Erie by Wednesday evening ushering in a significantly cooler
airmass. Decreasing overlake thermal stability as strong cold air
advection develops latter half of Wednesday supports strong NW winds
particularly over the northern half of Lake Huron. Gusts up around
30kts are likely for this area with the potential for low-end gales.
Wind strength has continued to trend gradually upward in successive
model runs to support a long enough duration of entry-level gales to
warrant the issuance of a Gale Watch for Wednesday evening/early
Lake Huron...Gale Watch from Wednesday evening through late Wednesday night for
Lake St Clair...None.
Michigan waters of Lake Erie...None.
You can obtain your latest National Weather Service forecasts online
Area Forecast Discussion
National Weather Service Goodland KS
542 PM MDT Tue Sep 20 2022
Issued at 538 PM MDT Tue Sep 20 2022
Isolated thunderstorms have developed along the pre-frontal trough
during the late afternoon. There is not much CAPE to work with,
and the upper level trough overhead is rather shallow. Am
expecting the storm activity to end as the sun sets. There could
be gusts around 50 MPH with the strongest storms.
.SHORT TERM...(This evening through Thursday night)
Issued at 335 PM MDT Tue Sep 20 2022
Synoptic Overview: The mid-latitude westerlies.. initially
relegated to higher latitudes (> 40N).. will descend to lower
latitudes (shift southward over the Tri-State area) Wed-Thu as a
pronounced upper level low.. presently stalled offshore the
northern California coast.. tracks slowly ENE /inland/ over the
PAC NW (Wed) and northern Rockies (Thu) -- suppressing the
pronounced upper level ridge over the central CONUS.
Through Sunset: Isolated diurnal convection cannot be ruled out
on the moist side /eastern periphery/ of a SW-NE oriented low-
level convergence zone extending from Tribune- Oakley-Norton (as
of 21Z). While substantial deep/moist convection is not
anticipated.. given the presence of strong DCAPE (~1500 J/kg)..
brief/localized marginally severe downbursts cannot be ruled out
in association with any updrafts capable of producing lightning..
mainly between 22-02Z.
Tonight-Wed Morning: Synoptic subsidence / surface pressure rises
on the western periphery of an upper level trough progressing
eastward from Alberta/Saskatchewan to Manitoba/Ontario will drive
surface high pressure /a cooler airmass/ southward along the lee
of the northern/central Rockies -- the leading edge of which will
manifest as a northerly wind shift /effective cold frontal
passage/ late tonight and Wed morning. Guidance suggests that a
broad/persistent lee cyclone in southeast CO may act to
[initially] slow/delay the frontal passage. This and other
factors, for example -- whether or not (and if so, to what extent)
post-frontal precipitation /elevated convection/ may develop in
western NE and northeast CO (evaporative cooling could
augment/enhance the surface ridge extending into the region from
the north.. resulting in relatively stronger pressure rises..
propelling the front southward faster than what would otherwise be
the case) -- continue to lend uncertainty to FROPA timing. Based
on the latest available guidance.. the front is anticipated to
reach the I-70 corridor by sunrise (~12Z Wed).. progressing south
of Greeley/Wichita counties by noon (~18Z Wed). Forecast
soundings suggest that northeasterly winds will increase to ~20-30
mph for a few hours immediately after the frontal passage.
Simulated reflectivity forecasts via recent runs of the HRRR and
NAM NEST suggest that dry conditions will prevail over the
majority of the area in this period -- with the relative greatest
potential for elevated convection largely confined to Yuma County
(CO) and Dundy-Hitchcock-Red Willow Counties (NE) after 15Z (9 AM
MDT). No significant/impactful weather is presently anticipated.
Wed-Thu night: A synoptic pattern reminiscent of Cold Air Damming
in the Mid-Atlantic/Carolinas -- i.e. high pressure anchored to
the north, a pronounced inverted surface ridge extending southward
into the region on the lee side of a mountain range, SW flow
aloft -- will prevail in this period. With this in mind.. expect
widespread cloud cover, below normal temperatures, and a
relatively small diurnal range in temperatures (especially for the
High Plains). It appears that precipitation chances may largely
be dictated by (1) mesoscale features /MCVs/ emanating from
persistent convection in the Rockies, (2) small amplitude waves at
the southern periphery of the westerlies (WSW-SW flow aloft), and
(3) low-mid level (850-700 mb) warm advection. Simulated
reflectivity forecasts via recent runs of the HRRR/NAM NEST
suggest that elevated convection may be most-prevalent along/north
of I-70 Wednesday evening through mid-day Thursday. Precipitation
(and associated evaporative cooling) may significantly affect
temperatures across portions of the area -- particularly
along/north of I-70 on Thursday -- when forecast soundings hint
that temperatures may struggle to exceed the upper 40s to lower
While locally heavy rainfall / isold flash flooding are certainly
a possibility (mainly along/north of I-70).. given antecedent
conditions characterized by severe to extreme drought.. widespread
and/or significant hydrological issues are not anticipated.
Thermodynamic profiles characterized by near moist-adiabatic mid-
level lapse rates /marginal elevated instability/ -- and the
absence of substantial upper forcing -- suggest that severe
convection is unlikely.
.LONG TERM...(Friday through Tuesday)
Issued at 111 PM MDT Tue Sep 20 2022
Friday and Saturday - Northern Plains shortwave trough will rapidly
move to the east with flow aloft becoming subsident and westerly
flow scouring out any lingering moisture and precipitation
relatively quickly, leading to mostly sunny skies and allowing
temperatures to rebound after several relatively chilly days.
Overall expect weather to be fairly tranquil during this period with
winds remaining light and gradually becoming southerly. Another
strong cold front will sweep across the region during the evening
hours Saturday. Ensembles showing a surprising amount of
consistency with respect to timing of this feature, which should
minimize potential impacts overnight even as winds gusts to 40
mph. Only concern with this system will be potential for it to
slow down and sweep through during peak heating, but this threat
looks very low at this point in time.
Sunday-Tuesday...Quiet weather will continue as broad H5 ridge
begins to amplify over the Rockies. Temperatures will gradually
climb through the period, reaching around 10 degrees above normal by
the start of next week. With position of ridge axis and expected
downward motion, do not anticipate any chances for meaningful
precipitation through the start of the week.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 538 PM MDT Tue Sep 20 2022
VFR conditions forecast for the TAFs. Main impact will be the
northeast winds becoming gusty behind the cold front after 12z
tomorrow. Rainfall will move in during the afternoon.
Issued at 230 PM MDT Tue Sep 20 2022
Record or near record high temperatures are possible across
portions of the area today (Sept 20).
Goodland......95 set back in 2010 and previous years
Hill City.....99 set back in 1935
McCook........98 set back in 1937
Burlington....97 set back in 2010
Tribune.......97 set back in 1980
Colby.........101 set back in 1980
Yuma..........98 set back in 1956
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
755 PM CDT Tue Sep 20 2022
Issued at 748 PM CDT Tue Sep 20 2022
Updated to include 00z aviation discussion below.
.SHORT TERM...(This evening through Wednesday night)
Issued at 219 PM CDT Tue Sep 20 2022
- Chance for thunderstorms this evening, mainly in west central
- Much cooler air arrives tonight and sticks around for a while.
Surface low pressure will move from central Minnesota into northwest
Wisconsin this evening. As it does it will bring a cold front across
the area that may be the focus for a few showers and thunderstorms
later this evening, mainly in west central Wisconsin. Low clouds
have hung on stubbornly in west central Wisconsin today and that may
lessen the chance of any strong sustained convection. Most of the
CAMs try to develop some storms, but are unable to sustain them,
except for the HRRR which has been showing thunderstorms initiating
late this evening in west central Wisconsin, with the counties of
Barron and Rusk looking to have the best chance of a thunderstorm.
Should any storms develop in this area, large hail will be the main
hazard and SPC has maintained the slight risk for for this
conditional setup. Much cooler and drier air will filter into the
forecast area behind the cold front with lows tonight falling into
the 50s for most with dewpoints falling through the 60s and 50s into
the 40s by tomorrow. Cool Canadian high pressure moving in behind
the departing system will leave us with highs only in the 60s
tomorrow, and with gusty northwest winds it will feel more like
fall. Lows tomorrow night should fall into the 40s area wide, with
even an upper 30 or two possible in the northwestern portion of the
CWA. Some guidance wants to bring some isolated showers across
southern Minnesota tomorrow morning, but precipitation should stay
just to our south as the baroclinic zone sinks to the south.
.LONG TERM...(Thursday through Tuesday)
Issued at 219 PM CDT Tue Sep 20 2022
- Chance for rain showers Friday and Friday night.
Cooler, more Fall-like air will continue to advect into the Great
Lakes region into Thursday. While building surface high pressure
should allow for mostly sunny skies, temperatures Thursday will only
reach the upper 50s to lower 60s. Southerly return flow should take
place from west to east across our MN counties Friday night as an
upper-level trough nears from the west. This will allow lows to only
fall to the mid to lower 40s. However, calmer conditions across our
WI counties mean mid to upper 30s are expected. Localized areas of
patchy frost may even occur in our extreme eastern CWA.
While the southerly return flow will strengthen and overspread the
area during Friday, forecast models strongly suggest overcast skies
and rain developing ahead and along a cold front, keeping highs a
couple of degrees cooler than Thursday. The front and rain will push
west to east through the CWA early Friday morning through Friday
night. PoPs are maximized in western MN (likely to definite) where
strongest forcing and most vertically saturated forecast soundings
occur Friday morning. PoPs do slightly lower with eastward extent
where saturation depth and forcing become slightly more uncertain.
But, the entire CWA should see rain drops. Guidance keeps heaviest
QPF over western MN with upwards of 0.50" possible while areas east
may only see a few tenths. Southerly winds look also quite gusty,
especially across western MN as an LLJ and strong surface pressure
gradient move over the region. Have increased winds with gusts
nearing 30 knots during Friday using a blend of the NBM 4.1 and NBM
Aside from our far east, rain showers should largely end by Saturday
morning with the aforementioned trough axis to our east. A small
lobe of the 850 mb thermal ridge over the Central Plains will
actually warm highs into the mid 60s to lower 70s Saturday. However,
a second trough Sunday morning will bring another cold front causing
cooler temperatures and a small chance of rain in our eastern-most
WI counties Sunday. Proceeding the second trough, enhanced
northwesterly flow will develop and persist through the early half
of next week. This should allow for dry weather and temperatures a
couple degrees below normal. Long-range forecast models hint that
this cooler regime may not last long, though. Most long-range
guidance advances a sprawling 850 mb thermal ridge over the western
CONUS slowly towards the Northern Plains the second half of next
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 748 PM CDT Tue Sep 20 2022
Cold front is slowly making its way SE across southern MN into
western WI this evening, with isolated convection developing along it
in far eastern MN into western WI. Any activity looks to stay north
of the MN TAFs but the WI TAFs are in line to see at least VC if not
directly into the terminals. That said, chances are 40% at best that
any one location may see convection so have opted to keep the
initialized TAFs dry and monitor radar trends for amendments.
Rainfall potential will last thru roughly 06z then only high clouds
are expected thereafter, with plenty of sunshine expected for
Wednesday. However, a tightened pressure gradient after sunrise will
make for breezy/gusty northerly winds Wednesday.
KMSP...Still a chance that isolated convection could reach MSP
airport but the expectation is that the activity will remain to the
north. Still, will monitor radar trends to see if any SHRA/TSRA may
reach MSP and will amend accordingly.
/OUTLOOK FOR KMSP/
Thu...VFR. Wind N 5-10 kts.
Fri...MVFR/SHRA likely, chc IFR/SHRA. Wind S 5-10 kts.
Sat...VFR. Wind SW 5-10 kts, becoming NW 5-10 kts.
Area Forecast Discussion
National Weather Service Marquette MI
757 PM EDT Tue Sep 20 2022
.SHORT TERM...(Through tonight)
Issued at 238 PM EDT TUE SEP 20 2022
A warm day for mid-September across Upper Michigan this afternoon as
skies remain mostly clear with an ongoing convective complex to our
south in WI. This complex did limit some of the warming potential
across the UP today, eating into the WAA and bringing some morning
clouds across parts of the UP. Looking upstream, you can see the
advertised cold front making its way through northwest MN with some
weak convection along it. This will be the main focus heading into
tonight; however, chances have been decreased quite a bit with this
fcst update compared to this mornings package.
As for thunderstorm potential tonight, the elevated warm layer will
be difficult to overcome. 12Z CAMs have backed off considerably
across the area with the lack of a LLJ and capping in place, model
soundings would suggest convection will need to be tied directly to
the frontal axis. The issue will be how narrow a window will be for
instability to remain as convection is progged for after sunset.
While there is certainly enough deep-layer shear to support any
convection that does occur, I am skeptical of initiation chances.
All but the HRRR has suggested thunderstorms will not occur this
evening, and each subsequent HRRR update this morning and afternoon
has been slowly trimming back chances as well. Hail is the primary
threat with the elevated storms. Cut back pops to low-end chc
initially at 03Z across the west and diminishing quickly to just
slights as the front shifts from W to E across the UP through 12Z.
Behind the front, CAA will start to bring in some lake-effect clouds
and gusty NW winds by tomorrow morning.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 315 PM EDT TUE SEP 20 2022
Upper air pattern will consist of a closed 500 mb low in the western
U.S. with a ridge over the southern and central plains and a trough
in the upper Great Lakes 12z Wed. This trough digs into the ern U.S.
on Thu with the west coast system moving to the northern plains on
Fri. Will continue with some lake effect pops in for Wed into Wed
night and then carry some over to Thu morning in the central cwa.
This is the only change made to the going forecast. Does look like
there will be a high swim risk for Wed for Alger and Marquette
County beaches, but temperatures will be on the cool side and could
be showery in the afternoon.
In the extended, the GFS and ECMWF show a broad 500 mb ridge across
the southern half of the U.S. and a trough in the upper Great Lakes
12z Sat. The ridge then builds into the western U.S. 12z Sun and
into the Rockies 12z Mon as a trough digs into the ern U.S. through
Tue. Temperatures look to be below normal for this forecast period.
Looks unsettled as well with chances for showers almost every day
with a little lake effect thrown in there.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 757 PM EDT TUE SEP 20 2022
VFR will prevail at IWD/CMX/SAW tonight despite a cold front
passing. There is a schc that a few shra/tsra will develop vcnty of
the front. Right now, potential appears quite low that any of the
terminals will be directly impacted. Only included VCSH mention at
IWD later this evening. With fropa, winds will shift wnw and will
become gusty soon after sunrise. Expect IWD/SAW to gust to 25-30kt
on Wed. At CMX, gusts will reach 35-40kt. Cyclonic flow and
increasingly colder air will result in considerable stratocu
development. Cigs will likely be in the 3000-4000ft range with CMX
more likely than IWD/SAW to see high MVFR cigs. Isold to sct -shra
should develop mid to late aftn across w and central Upper MI.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 315 PM EDT TUE SEP 20 2022
Hoisted a gale warning for the east half of Lake Superior Wed
afternoon and evening for west to northwest gales up to 40 knots
across the east half of Lake Superior behind a strong cold front
that will move through late tonight. The wind drops to below 20
knots by Thu evening as high pressure approaches and remains below
20 knots through the rest of the forecast period.
Gale Warning from 1 PM to 8 PM EDT Wednesday for LSZ244-248-264-
Gale Warning from 6 PM to 10 PM EDT Wednesday for LSZ249>251.
Gale Warning from 1 PM Wednesday to midnight EDT Wednesday night
Area Forecast Discussion
National Weather Service Raleigh NC
947 PM EDT Tue Sep 20 2022
Hot and dry high pressure will extend across the South ahead of a
strong cold front that will cross the region Thursday afternoon and
.NEAR TERM /THROUGH TONIGHT/...
As of 947 PM Tuesday...
The latest sfc analysis shows a weak cold front has mostly cleared
our CWA and is off to our east and south. For the rest of tonight,
expect mainly clear skies and very light winds...perhaps a very
light NE low level wind across our northeast and Coastal Plain
zones. This direction and magnitude of low level flow usually sets
the stage for pre-sunrise fog and/or stratus, and the latest HRRR
suggests such fog/stratus may indeed occur particularly northeast of
RDU and across the Coastal Plain. Otherwise, farther to the west,
any low level flow will be more northerly, so I wouldn`t expect much
if any fog west and southwest of RDU. Latest sfc analysis also
shows a NW to SE dwpt gradient with highest dwpts SE closer to the
front. While dwpts may still fall some overnight particularly where
flow is more northerly, the latest obs suggest overnight lows
ranging from the upper 50s along and north of I-85, lower 60s
between I-85 and the HWY 24 corridor, to mid 60s south and east of
.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
As of 355 PM Tuesday...
A very similar synoptic pattern will continue tomorrow, with a
strong mid-level ridge over TX and dry NW flow aloft across central
NC. While a weak surface trough may develop again tomorrow,
instability looks less impressive and the CAMS are entirely dry.
Thus have no POPs anywhere tomorrow. Similar thicknesses will again
support above-normal highs in the upper-80s to lower-90s. As
southwesterly flow increases on Wednesday night ahead of a strong
cold front, lows will be milder (mostly mid-to-upper-60s).
..LONG TERM /THURSDAY THROUGH TUESDAY/...
As of 300 PM Tuesday...
Upper-level ridging near TX will generate another unseasonably hot
day across central NC Thursday as 1000-850mb thicknesses increase to
near 1430m. Highs have trended down a few degrees since yesterday,
due to enhanced cloud cover expected in the afternoon. Highs in the
low to mid 90s will still be just over 10 degrees above seasonal
normals for this time of the year. An upper trough and associated
surface cold front will traverse across the region by the afternoon,
however models and their ensembles still differ somewhat in the
timing and precipitation amounts. A broken line of showers and
isolated thunderstorms will likely develop and move NW to SE Thu
afternoon, with the greatest coverage and best chance for precip
near the VA border. SBCAPE near 2000 J/kg and 0-6km shear near 35 kt
could help generate some strong storms along the front, and some
possibly severe with damaging wind gusts and small hail. SPC
currently has the northern half of central NC under a Marginal Risk
(level 1/5) for severe storms in the afternoon. Conditions will
improve Thursday evening and overnight.
Northwest flow aloft and cold air advection with northerly surface
flow will create a much more fall-like day on Friday with highs in
the 70s and dewpoints dipping into the 40s. A surface high will move
from the Midwest area on Friday to over NC by Saturday morning.
Clear skies and light winds will make excellent conditions for
radiational cooling, and help lows dip into the 40s across most
areas Saturday morning. The surface high will push offshore Saturday
afternoon, and create warm air advection with southerly flow for the
remainder of the weekend. Highs will increase to seasonal normals on
Saturday, with southern areas near 80 degrees, and then increase to
above normal again on Sunday with highs in the low to mid-80s.
A trough will deepen across the the OH Valley and move across the
Mid-Atlantic late Sunday into Monday, then a secondary and weaker
trough will quickly follow late Monday into Tuesday. Ensembles are
in slightly less agreement with these systems compared to yesterday
in terms of timing and strength, however precipitation amounts will
likely be higher late Sunday into Monday than the front moving
through on Thursday.
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 743 PM Tuesday...
Through 00Z Thursday: Scattered mid and high clouds are drifting
south across central NC attm; however flt conditions will remain VFR
through the night. Just before sunrise, some fog or stratus will
develop over the Coastal Plain, thanks to a light NE wind overnight
which typically supports such fog and stratus. West of the Coastal
Plain, any low level light wind will be more from the north, which
should preclude any fog at KINT/KGSO. Otherwise, VFR conditions
will persist on Wednesday through the rest of the TAF forecast
period after any fog or stratus lifts, along with light and variable
winds through mid-day which will be SSW 10kt or less during the
Outlook: A strong cold front will cross the region with accompanying
scattered showers/storms and brief sub-VFR conditions and gusty
surface winds Thu afternoon and evening. VFR conditions and dry
weather will prevail for the rest of the period.