Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/13/23
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
849 PM CDT Wed Jul 12 2023
.UPDATE...
Issued at 848 PM CDT Wed Jul 12 2023
See no reason to make any major changes to the forecast this
evening, it looks just fine.
&&
.SHORT TERM...(This Evening through Thursday Night)
Issued at 306 PM CDT Wed Jul 12 2023
Water vapor imagery shows shortwave energy / vort max moving across
eastern ND into northern MN. Still cannot rule out a stray shower or
two into early evening across the eastern CWA, but expect most
everyone to stay dry. Quiet conditions expected for the overnight as
clouds decrease and winds go light. May want to watch for slim
potential for fog in the Big Sioux valley, but confidence is too low
at this point to include in forecast, but something to monitor.
On Thursday, air mass across the region becomes somewhat unstable,
with around 1000 J/KG MLCAPE potentially being realized, all the
while low to mid level lapse rates become fairly steep. 0-6km bulk
shear increases to over 35 or 40 knots as well. Only thing lacking
is an overall focus for forcing to work with all this. That said, a
handful of CAMs do show widely scattered activity moving southeast
across the Dakotas during the late afternoon and early evening, with
perhaps some of these cells becoming strong to severe given the
above conditions. Areal coverage doesn`t look the greatest, and it`s
hard to pinpoint exactly where in the overall broader air mass these
storms will form. Surface wind field does show a very subtle/weak
wind shift/front moving eastward during the day, which may be a
focus if convergence along this manages to produce anything. POP
forecast is generally 20-40 percent from late afternoon Thursday
into Thursday evening.
.LONG TERM...(Friday through Wednesday)
Issued at 306 PM CDT Wed Jul 12 2023
The upper pattern will remain dominated by an upper trough migrating
from central/eastern Canada and across the Great Lakes region, while
an upstream ridge builds to the west. This upstream ridge will
migrate east, over the Northern Plains for at least a brief
transition out of a northwest flow regime during the middle of next
week. In the interim, that leaves us with a few weak systems, the
first departing in the morning hours Friday, a possible weak wave
moving through the Western Lakes region early Saturday, and one late
Sunday. The initial setup for the day Friday features strong
unidirectional flow with some CAPE though with low level dry/cold
air advection. The Saturday system will probably be far enough east
to avoid any upper level support, with strong unidirectional shear
but negligible CAPE. Of note with this system is the backdoor cold
front which will usher in a shot of Canadian air, with 850mb
temperatures falling close to +9C for far northeast South Dakota and
western Minnesota. The wave Sunday will provide for another backdoor
front knocking 850mb temperatures down to as low as +5C, but under
more stable profiles and moisture with any associated wave up around
12-15kft.
Unfortunately with these cool Canadian airmasses, we have to concern
ourselves with smoke from the unceasing northwest Canada forest
fires. HRRR and RUC show both vertically integrated and near surface
smoke plumes on a trajectory towards the Dakotas Friday. Will
increase sky cover to account for a veil of high smoke expected but
given uncertainty for now will forgo any mention as a surface
obscuration.
Already mentioned the details behind why it will be so cool around
here through the weekend, but will also note some temperature
moderation towards the end of the extended to more summer-like
readings.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 615 PM CDT Wed Jul 12 2023
Terminals KABR,KATY,KPIR,KMBG
VFR skies/vsbys are expected through tonight regionwide.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...TDK
SHORT TERM...TMT
LONG TERM...Connelly
AVIATION...TDK
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
936 PM EDT Wed Jul 12 2023
.SYNOPSIS...
High pressure continues to gradually move offshore through the rest
of the week. Several disturbances will bring the chance for
scattered showers and thunderstorms from Thursday evening into early
next week before a cold front pushes through by midweek. Heat
indices will reach around 100 degrees from Thursday into early next
week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 935 PM EDT Wednesday...
The forecast remains on track this evening with only minor
changes needed. Temperatures have fallen into the mid 70s-lower
80s although there has been an increase in humidity with dew
points around 70F. Expect mostly clear skies/light southerly
winds with broad sfc high pressure to our south. Lows will fall
into the upper 60s-lower 70s in most areas.
Previous Discussion as of 320 PM EDT...
The latest analysis indicates a broad area of sfc high pressure
centered over the SE coast. Aloft, A deep upper low is centered over
Hudson Bay, Canada, with a broad upper ridge across the SW CONUS,
allowing for a WNW flow through the FA. Temps as of 300 PM ranged
from the upper 80s to lower 90s. Expect afternoon highs a couple
degrees warmer. Dew points have dropped into the low-mid 60s for
most and even upper 50s in some spots which has keep heat indices
close to actual air temperatures. Tonight, a shortwave passes well N
of the FA across the Great Lakes and OH Valley, allowing for
scattered clouds to continue until around 2 AM with clearing late.
Lows tonight in the upper 60s to lower 70s (most in the lower 70s)
apart from mid 70s along the coast.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY NIGHT/...
As of 350 PM EDT Wednesday...
High pressure continues to slowly move offshore through the end of
the week, allowing for S winds and hot conditions to continue
(particularly Thurs). Thurs looks to be the hottest day of the year
(so far) with highs in the mid 90s for most with heat indices of 97-
102F. Cannot rule out some upper 90s if enough clearing occurs.
Expect mostly sunny skies Thurs morning with partly sunny skies
developing by the afternoon as widespread Cu develop. A shortwave
passes through the Northeast late Thurs afternoon with the S portion
of the trough tilted to the SW and not moving through our area until
Thurs night. As such, Thurs looks to remain dry with PoPs likely
holding off until after 6PM across the far NW Piedmont and after
sunset for the rest of the FA. CAMs show considerable uncertainty
with regards to areal extent and timing of showers/storms Thurs
night. The HRRR was the most aggressive with the NAM the least
aggressive and most hi res CAMs leaning towards the drier NAM.
Therefore, capped PoPs at chance (40-44%) with the expectation that
a line or broken line of showers and storms weakens as it moves SE
into the FA Thurs night. However, given the forcing of the shortwave
and moisture advection overnight allowing for CAPE to be present
through the night, will keep thunder in the forecast through the
night. Lows Thurs night in the mid 70s for most.
A loosely organized line of showers/storms may reinvigorate Fri
morning as it slowly moves E. If the line moves E quick enough,
increasing moisture Fri afternoon (dew points in the mid 70s)
may allow for enough instability for lee trough storms to
develop in the late afternoon and evening and move from the mnts
SE into the Piedmont. Given modest CAPE and sufficient shear
(for mid July), a few strong to severe storms are possible. As
such, SPC has a marginal risk for severe storms Fri across the
FA. Convection tapers off overnight. A stronger shortwave pivots
into the TN Valley and towards the local area Sat providing
another chance for scattered afternoon showers/storms. The best
chance Sat looks to be generally S of I-64 (50-54% PoPs). Given
an environment similar to Fri but with stronger forcing, a few
storms may become strong to severe. Total QPF through Sat of
0.5-1.0" of rain with locally heavier amounts expected where
multiple storms track over the same areas. WPC has a marginal
risk for excessive rainfall Fri-Sun across the area with
localized ponding of water on roadways or flash flooding in
mainly urban areas possible (where flash flood guidance is
lower). Highs in the lower 90s Fri and Sat with heat indices of
97- 102F Fri and 100-104F Sat. Lows in the upper 60s to lower
70s Fri night and lower 70s Sat night.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 400 PM Wednesday...
Unsettled weather continues through early next week with diurnal
afternoon showers/storms possible each day. A large ULL moves from
Canada into the Great Lakes Sun-Mon before slowly moving E across S
Canada into Wed. This will try and push a cold front into the area
Sun night into Mon before stalling. The ULL will then push a
slightly stronger cold front into the area Tues night which may be
able to make it to the coast by Wed and bring some somewhat drier
conditions. The best chance for showers/storms is Sun with 50-54%
PoPs. PoPs decrease below 35% Mon-Wed (apart from 40% PoPs across NE
NC Mon afternoon). Highs in the lower 90s Sun, low-mid 90s Mon, mid
90s Tues, and low-mid 90s Wed. Max heat indices of 100-104F (~105F
across far SE VA/NE NC) Sun, 95-103F Mon and Wed, and 100F W to 107F
E Tues. Lows in the lower 70s W to mid 70s E Sat night and upper 60s
W to lower 70s E Sun through Wed nights.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
As of 740 PM EDT Wednesday...
VFR conditions are expected through the 00z/12 TAF period with
clear skies (outside of high clouds) tonight-Thu AM. Scattered
CU develops again by late Thursday morning with any
showers/storms very likely holding off until Thu night. There is
a 10-15% chc of tstms at RIC after 21z Thu evening, with a
30-40% chc of showers/tstms area-wide Thu night-early Fri AM.
Light S-SW winds are expected tonight, with speeds increasing to
10-15 kt on Thu (gusts to 20 kt possible).
Outlook: Mainly afternoon/evening showers/storms then continue
Friday into early next week with brief flight restrictions
possible.
&&
.MARINE...
As of 305 PM EDT Wednesday...
The benign weather continues over area this afternoon as high
pressure anchored over the Southeastern US continues to slowly
slide eastward into the Western Atlantic. The winds will
gradually increase out of the south tonight into the 10 - 15 kt
with gust to 20 kt as the pressure gradient increases with the
sfc high off the coast and an approaching cold front from the NW
begins to approach from the Ohio Valley toward the Mid-Atlantic
states. The front should weaken as it moves into the strong
ridge of high pressure that becomes stationary off the coast on
Thursday. This should keep winds in the 10 - 15 kt range on
Thursday. Overall expect conditions to remain below SCA levels
tonight into Thursday.
A new wave of low pressure moving from the central plains
eastward along the stalled cold front will reinvigorate the
front Thursday night into Friday, bringing more showers and also
enhancing the southerly winds over the waters. This enhancement
might get the wind gust into the 20 - 25 range and kick seas in
the coastal waters up to 5 FT. For now with the marginal SCA
conditions and it being in still about 30 - 36 hours away, have
elected to not raise SCA flags with this forecast package and
continue to monitor the conditions, but SCA may be need for at
least a portion of the area waters for Thursday night into
Friday.
The winds should relax some on Friday afternoon into Friday
night as the surface high slides farther off the coast and the
cold front stalls and gradually dissipates over the Mid-Atlantic
states. This should get winds down to the 10 - 15 KT range and
low seas below 5 Ft in the coastal waters.
Conditions remain a bit unsettled over the coming weekend as the
southerly flow remains in place as another cold front tries to
push into the Mid-Atlantic states Saturday evening into Sunday.
Again this could lead to an period of enhanced southerly flow.
For now have kept winds in the 10 - 15 kt range for that period
due to timing differences in the models, but expect that with
better timing could see a brief period of 15 - 20 kt winds
develop ahead of this front. Also, models show that front has
enough energy to get through the waters by Monday morning, but
with it being July, not confident the front will have enough
push to clears the area.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...None.
&&
$$
SYNOPSIS...RMM
NEAR TERM...ERI/RMM
SHORT TERM...RMM
LONG TERM...RMM
AVIATION...ERI/RMM
MARINE...ESS
Area Forecast Discussion
National Weather Service Boston/Norton MA
1006 PM EDT Wed Jul 12 2023
.SYNOPSIS...
Scattered showers and thunderstorms with heavy downpours possible
across western MA this evening, and again tomorrow. Otherwise,
mainly dry and warm conditions persist through Thursday afternoon.
More impactful precipitation approaches for Friday. Periodic showers
and thunderstorms then continue through this weekend and into early
next week with seasonable temperatures.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
10 PM Update...
Any rain showers that survived the trek over the Berkshires
after 00Z have dissipated as forecast after sunset. Fog has
already begun to form across the typical radiators, and we
anticipate that fog will become more widespread as the evening
continues given very high dewpoints and near zero dewpoint
depressions. OVernight lows will struggle to fall out of the 70s
in most areas, with urban heat islands expected to only bottom
out in the mid 70s! It is summer, after all!
8 PM Update...
Mainly used the latest runs of the HRRR, RAP and NationalBlend
to update rainfall chances this evening. Modest shear, but poor
instability, in place. Thunderstorms already weakened as we
approached sunset, and the showers are not likely to linger much
longer either.
Minor tweaks to temperatures and winds to reflect observed
trends. Otherwise, the overall forecast remained on track.
Previous Discussion...
Highlights
* Any lingering shower/storm activity diminishes this evening.
* Mostly clear with patchy fog development across portions of
the interior.
Stuck under cyclonic flow through this period with a shortwave
trough lifting through during the evening. A shortwave ridge
briefly builds in behind the shortwave tonight, while another
trough/shortwave lifts into the eastern Great Lakes. A cold
front slides into the region and stall nearby/over us tonight.
Anticipate that any shower/storms that develop late this
afternoon to taper off this evening. Expecting the cold front
that is sliding in to stall out as the shortwave associated with
it lifts into northern New England. Still will need to be
vigilant as SPC Mesoanalysis currently showing 30-35 kts of
effective shear, 1000-2000 J/kg of surface based CAPE, nearly
adiabatic low level lapse rates and DCAPES around 1000 J/kg.
Mid level lapses rates per usual are meh around 5-6 degrees
Celsius per km and we are trying to overcome some drier air per
the 1.2-1.4 inch PWATs. Main concern this evening with any of
the stronger storms are strong/gusty winds, especially NW of
ORH. Given our wet antecedent conditions also have a flash
flood risk given the 1 hr FFG is between 1.5 to 2 inches. Have
leaned quite heavily on HREF guidance, but in particular the
NSSL WRF. This is doing well based on current radar trends.
Winds will become light and skies relatively clear tonight,
which will result in patch fog development. At this point am
thinking risk is highest across northern portions of the CT
River Valley where the QPF is anticipated to be the highest.
However, still could potentially be an issue in other areas as
well. Low temps bottom out in the mid 60s to the low 70s.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Highlights
* Any fog burns off early in the day. Increasing chances of
showers and thunderstorms late on Thu through Thu night.
* Cannot rule out a few strong/severe storms. Locally heavy
downpours may still bring flash flooding, but could also see
some hail/gusty winds as well.
A trough/shortwave will lift from the eastern Great Lakes early
on Thu into Quebec by late in the day. Another shortwave lifts
in from the Mid Atlantic Thu night. Still anticipating the
frontal boundary to be nearby/overhead. This turns into a warm
front and lifts northward on Thu and a cold front sags toward
the region late on Thu into early Fri.
Some uncertainty during the day with convective activity/timing.
At this point am leaning toward much of the day to be dry, but
there may be a few showers around early in the day as the
stalled front begins lifting northward. This is indicated by the
NAM/ARW/NSSL at this point, but confidence is a bit lower than
would like being less than 24 hrs out. Think that the better
opportunity for shower/storms comes late in the afternoon, but
especially overnight. Will have a pre-frontal trough in place as
well as a cold front sliding in from the west. Expecting
increasing deep layer shear with 0-6 km bulk shear increasing to
roughly 40 kts by Thu night. Will have roughly 1000-1500 J/kg of
MLCAPE with a few hundred J/kg within the hail growth region and
some DCAPE. Think that the SPC Outlook highlights the severe
risk well, but at this point mostly concerned with damaging
winds and hail especially heading into Thu night/Fri AM as a
line potentially moves in.
On top of the severe risk will have the threat of locally heavy
downpours as PWATs increase to roughly 1.5-2 inches. At this
point blended WPC and NERFC guidance for QPF, but think that it
is not out of the question we get higher amounts. This is
typically the case especially if multiple thunderstorms fall
over the same area.
High temps similar to tough with readings generally in the 80s,
but will also see some lower 90s across the Merrimack and CT
River Valley.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
* Wet, unsettled weather continues Friday through this weekend with
no prolonged dry stretch likely during this extended forecast.
* Seasonable temperatures throughout, with highs in the 80s but
quite muggy given dewpoints in the upper 60s and lower 70s
Details...
No real changes to the synoptic pattern are expected during most
of this portion of the forecast. A persistent upper low lingers
over Canada, maintaining a preferred mid level storm track
through or near southern New England right into the middle of
next week. The end result is generally near to above normal
temperatures with high humidity during this time.
The main concern will remain the location and amount of rainfall
through the upcoming week. Much of interior southern New England
cannot handle much additional rainfall, so those details will be
crucial. Unfortunately, the predictability of something that
specific at this time range is rather low. We will need to
monitor these details carefully, and make adjustments to the
forecast as new information arrives.
Am still thinking it will not be raining this entire time,
except perhaps for much of Friday. Rainfall looking more
scattered into Saturday, before ramping up again Saturday night
into Sunday ahead of an approaching front. Then questions remain
on where exactly this front stalls across southern New England
sometime Monday into Tuesday. That will play a significant role
in focusing additional rainfall in our region.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High confidence away from ACK. Moderate confidence
late at ACK.
Should see any shower/storm activity tapering off roughly
00-02Z. For most, will have VFR conditions, but expect radiation
fog to develop especially across the northern portions where
earlier day convective activity is anticipated to be more
widespread. Less confident a bit further S/SE, but could lower
to MVFR/IFR. May see stratus/fog advect into ACK late tonight,
but not overly confident on it, so continued to only hint at
for now. Winds becoming light and variable.
Thursday...High confidence in trends moderate in exact timing.
Any area of fog burning off by roughly 13-15Z. Otherwise will be
VFR with scattered showers and thunderstorms possible during the
afternoon, especially across the interior. Modest S/SSW flow of
10-15kt. Winds out of the S/SSW at 5-10 initially increasing to
10-15 kt during the afternoon as a low level jet moves in. Think
BOS may sea breeze early in the day until that low level jet
pushes in 19-21Z. Could have some 15-20 kt gusts during the
afternoon.
Thursday Night...Moderate confidence.
MVFR to IFR conditions with scattered showers and thunderstorms.
Winds out of the S at 5-10 kts.
BOS Terminal... High confidence. Could see a stray shower before
02Z, but confidence too low in coverage to include in latest
forecast. Will need to monitor radar trends. VFR overnight, but
sea breeze around 13-15Z before LLJ shifts winds to S roughly
18-21Z.
BDL Terminal...High confidence. VFR. Not out of the question
patchy fog develops late, but confidence higher across northern
portions of the CT River Valley.
Outlook /Friday through Monday/...
Saturday through Saturday Night: Mainly VFR, with local MVFR
possible. Breezy. Chance SHRA, isolated TSRA.
Sunday: MVFR/IFR conditions possible. Breezy. Chance SHRA,
chance TSRA.
Sunday Night: MVFR/IFR conditions possible. Breezy. Chance
SHRA, slight chance TSRA.
Monday: VFR. Breezy. Chance SHRA, isolated TSRA.
Monday Night: VFR. Slight chance SHRA.
Tuesday: Chance SHRA, isolated TSRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Thursday...High confidence.
Generally quiet marine conditions tonight through Thu. Will have
S/SSW flow generally around 5-10 kts. Though winds increase to
10-15 kts Thu afternoon as a low level jet pushes in. Could see
a few gusts to around 20 kts during the afternoon. May see some
marine fog push into portions of the south coast tonight. Seas
between 1-3 ft.
Thursday Night...High confidence.
Will have increasing chances of showers and thunderstorms as the
night goes on. Winds remain out of the S at 10-15 kts with gusts
around 20 kts. Seas 1-3 ft for the eastern waters and building
2-4 ft across the far southern waters.
Outlook /Friday through Monday/...
Saturday: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers, isolated thunderstorms.
Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Chance of rain showers, isolated thunderstorms.
Sunday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft. Chance of rain
showers, isolated thunderstorms.
Sunday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers,
isolated thunderstorms.
Monday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Chance of rain showers.
Monday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.
Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers.
&&
.HYDROLOGY...
Flood Warnings remain in place for many locations along the CT
River from the MA/VT border to the Long Island Sound, except for
a small portion of the river near Springfield, MA. Many sites
along the CT River crested overnight, though it will take
several days for river levels to fall below flood stage.
Additional rainfall late this week into this weekend may
exacerbate existing flooding, or lead to new flooding elsewhere.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Air Quality Alert until 11 PM EDT this evening for MAZ020>024.
RI...Air Quality Alert until 11 PM EDT this evening for RIZ001>008.
MARINE...None.
&&
$$
SYNOPSIS...Belk/BL
NEAR TERM...Belk/BL/KS
SHORT TERM...BL
LONG TERM...Belk
AVIATION...Belk/BL
MARINE...Belk/BL
HYDROLOGY...
Area Forecast Discussion
National Weather Service Burlington VT
1040 PM EDT Wed Jul 12 2023
.SYNOPSIS...
A weak cold front passing through this evening will retreat
northward as a warm front on Thursday, setting the stage for
possible severe thunderstorms Thursday afternoon and evening.
Torrential rain and saturated soils will likely lead to numerous
flash floods. A seasonably warm and humid air mass will bring
continued chances for showers and thunderstorms on Friday and
through the upcoming weekend.
&&
.NEAR TERM /THROUGH THURSDAY NIGHT/...
As of 1039 PM EDT Wednesday...Bottom line up front:
* A Flood Watch is in effect for much of Vermont and northeastern
New York from tomorrow afternoon through late tomorrow night.
* Numerous flash floods are likely tomorrow afternoon and evening,
especially in central and southern Vermont from Route 2 southward
in Vermont. However, not looking at the kind of widespread impacts
we saw earlier in the week.
* Scattered Severe Thunderstorms are possible tomorrow afternoon
and evening. Expect organized thunderstorms with some intense
storms possible. These stronger storms will be capable of
damaging winds and large hail. There is also a low, but non-
zero, chance for an isolated tornado tomorrow.
With the evening update, added in mention of damaging winds and
heavy rainfall within tomorrow`s thunderstorms given increasing
confidence as additional model data comes in. Adjusted the QPF
forecast for tomorrow slightly, with newest forecast really
keying in on the heaviest rainfall totals for tomorrow afternoon
in southern and central Vermont (1-2 inches), with generally
under an inch expected in most of northern NY along with the
northern half of Vermont. Previous discussion follows...
A weak cold front is currently sagging southeastward through central
Vermont in the vicinity of central Addison and Washington
counties at this time. The isolated showers and thunderstorms
ahead of the front will tend to diminish and be south of our
area through the remainder of the day as relatively quiet
weather builds in. Our attention then turns to a vigorous
shortwave moving eastward over the Midwest. As this upper level
feature pushes eastward and rounds the base of a trough over the
eastern Great Lakes, low level flow over our region will
strengthen, advecting deep moisture back into northern New York
and Vermont after a brief break in moisture overnight. The
synoptic setup suggests a warm front will be in our vicinity,
which will help to generate low level spin. As we get into the
warm sector of the system, ample heat and humidity will build
back into the area, especially from the Champlain Valley and
points east.
With that said, an increasingly likely and impactful, severe weather
event is shaping up for Thursday afternoon and evening with a
combination of moderate to high shear and CAPE line up over most of
our region. A concerning level of low-level wind shear in
particular, including 0-1 km bulk shear near 30 knots, provides
confidence in severe thunderstorms. Although deep layer shear/upper
level winds are not as favorable, storm mode may include supercells,
which should also grow upscale into lines. In support of the severe
potential, the latest NCAR HRRR Neural Network Convective Hazard
Forecast suggests a 30-45% chance of severe thunderstorms associated
with thunderstorms in the 5 PM to 9 PM timeframe in much of our
region. Damaging winds associated with wet microbursts are the most
likely hazard. However, the low-level environment will be favorable
for supercell development, which supports chances (under 5%) for a
tornado as well.
The evolution to a more upscale scenario in the evening will lead to
a gradual shift from severe threat to a heavy rain threat tomorrow
night. Best case scenario will be that thunderstorms move through a
single location, but even with that happening rainfall intensity
could produce urban flash flooding. Otherwise, training/slow cell
propagation of showers and thunderstorms will be possible in
central and southern Vermont (Rutland and Windsor counties most
favored) as southwesterly shear vectors become parallel to cell
motion. Repeated heavy rain in central and south central Vermont
will lead to excessive rain, especially given the still ongoing
flooding. Flash flood guidance of roughly 1.2 -1.5" in 3 hours
will be exceeded with the type of intense rainfall that these
thunderstorms can produce.
&&
.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
As of 418 PM EDT Wednesday...Showers with a few embedded thunderstorms
will continue into Friday as a moisture boundary stalls over
the area. At this point, it appears the boundary will stall near
the Vermont/New Hampshire border during the day on Friday,
resulting in a strong moisture gradient across Vermont.
Precipitable water values along the Connecticut River Valley
will be around 1.6 inch, while PW values further north and west
will only be 1.2 inch. Some showers and thunderstorms are
expected to stream through Vermont during the day along the
boundary, potentially bringing another round of rainfall to
waterlogged areas. Initial QPF estimates for the Friday
precipitation are in the 0.1 to 0.5 inch range. Usually these
amounts would not be any issue, but given the current
saturated/flooded conditions within Vermont, the Weather
Prediction Center has included most of the State of Vermont in a
Slight Risk for excessive rainfall in their Excessive Rainfall
Outlook. Some embedded thunderstorms are possible during the day
on Friday, though the upper-level wind fields are weak enough
that the main storm threat looks to be locally heavy rainfall.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 418 PM EDT Wednesday...Unfortunately for those looking for a
break in the active weather, there will be little change for
the weekend with warm and muggy conditions continuing with
additional rounds of showers and thunderstorms. The focus at
this point continues to be on Sunday, when we are seeing the
best ingredients come together for potentially another round of
heavy rain.
Saturday will be the warmest day of the weekend, with forecast highs
in the mid to upper 80s and dewpoints in the mid to upper
60s...resulting in apparent temperatures in the low 90s in the
Champlain and Connecticut River Valleys. Elsewhere, apparent
temperatures will be in the mid 80s. Once again, ample instability
will support the development of scattered showers and thunderstorms
during the afternoon on Saturday.
Once we get into Saturday night/Sunday, an impressive moisture plume
will be directed into our area, funneling up Atlantic moisture into
our area. PW values have the potential to rise in excess of 2.0
inches in our southern VT counties, priming the atmosphere for
another round of potentially heavy rainfall. The tropical
atmosphere with deep warm cloud layers, modest instability, and
high moisture content means that any shower/thunderstorms that
develop will be highly efficient rainers. While difficult to
forecast exact details 5 days out, the synoptic pattern will be
favorable for several rounds of moderate to heavy rainfall with
broad cyclonic flow remaining overhead. It`s too early to go
into details on QPF this far out, but we are certainly keeping
an eye on Sunday for the potential for additional hydro concerns
if current forecast pans out.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Through 00Z Friday...VFR conditions will prevail through most
of the period. Mid to high level cirrus should generally
minimize fog coverage overnight tonight despite light and
variable winds at the surface. Winds increase from the south and
southeast at 5 to 12 kt after Thursday 12z, with some VCSH but
generally no reduction in vsby or cig categories. Then after
18z, we are expecting a line of strong to severe thunderstorms
to cross the region. Generally, the timing is between 18-21z
across the northern NY terminals, arriving in the Champlain
Valley terminals around 20-23z and then finally central/eastern
VT terminals by 22-00z. These thunderstorms are capable of
producing locally damaging straight line winds with isolated
large hail.
Outlook...
Thursday Night: VFR. Chance SHRA, Chance TSRA.
Friday: Mainly VFR, with local MVFR possible. Likely SHRA, Chance
TSRA.
Friday Night: Mainly VFR, with local MVFR possible. Chance SHRA,
Chance TSRA.
Saturday: Mainly VFR, with local MVFR possible. Chance SHRA,
Chance TSRA.
Saturday Night: VFR. Chance SHRA, Slight chance TSRA.
Sunday: Mainly VFR, with local IFR possible. Likely SHRA, Chance
TSRA.
Sunday Night: MVFR/IFR conditions possible. Chance SHRA, Slight
chance TSRA.
Monday: Mainly VFR, with local MVFR possible. Chance SHRA, Chance
TSRA.
&&
.HYDROLOGY...
As of 349 AM EDT Wednesday...River levels will continue to
slowly fall today with flooding continuing along the Winooski,
Otter Creek, Lamoille, Missisquoi, and Barton Rivers. The
Winooski at Essex Junction appears to have a hung float as the
level has flatlined, but it should be lowering below Major flood
today, and all rivers should drop below flood stage by the days
end. Drainage into Lake Champlain is expected to result in lake
rises of 1 to 1.5 feet by Friday morning but isn`t expected to
reach flood stage, likely staying at least 2 feet below.
Please continue to take this flooding event seriously and heed
all road closures. Know safe zones or higher ground that you can
reach in case of high waters. Have multiple ways to receive
real-time NWS weather alerts and have contingency plans in
place. See our current flood warnings for the latest details,
especially for individual points along our rivers.
For details on specific area rivers and lakes, including observed
and forecast river stages and lake elevations, please visit the
Advanced Hydrologic Prediction Service /AHPS/ graphs on our
website.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Flood Watch from Thursday afternoon through late Thursday
night for VTZ003-004-006>011-016>021.
NY...Flood Watch from Thursday afternoon through late Thursday
night for NYZ028-031-034-035.
&&
$$
SYNOPSIS...Kutikoff
NEAR TERM...Duell/Kutikoff
SHORT TERM...Duell
LONG TERM...Duell
AVIATION...Chai/Kutikoff
HYDROLOGY...Banacos/Storm
Area Forecast Discussion
National Weather Service Billings MT
344 PM MDT Wed Jul 12 2023
.DISCUSSION...
Through Friday night...
An upper ridge is bringing mostly clear skies and dry conditions
to the Northern Rockies this afternoon. The dry conditions should
persist into Thursday morning for most of the area. There is a 20%
chance of a shower or thunderstorm over the Beartooth/Absaroka to
northern Bighorn Mountains this afternoon into the early evening
as suggested by the high-resolution model data. Any showers or
storms that develop should diminish late this evening.
On Thursday, a weak upper air shortwave trough will move
east/southeastward over northern Montana and bring a weak surface
cold front/wind shift over our area. This disturbance will
facilitate isolated to scattered shower and thunderstorm
development (20-60% chance) especially over the higher terrain
west of Billings in the afternoon, with the showers and storms
moving east/southeastward over the lower elevations. The primary
hazard concern from the thunderstorms will be isolated wind gusts
to 40-50 mph due to high cloud bases with sleep lapse rates below
the cloud bases. Any showers and storms should dissipate Thursday
night from northwest to southeast with the loss of solar heating.
Friday looks similar as the area will be under northwesterly flow
aloft, which tends to produce an unstable atmosphere in our area.
Isolated to scattered showers and thunderstorms (20-30% chance)
should develop over the higher terrain of central MT Friday
afternoon then move southeastward over the lower elevations into
the early evening. The primary hazard concern again will be
isolated strong wind gusts to 40-50 mph. Any showers and storms
should dissipate Friday evening with the loss of solar heating.
Smoke: The HRRR model brings smoke aloft southeastward into
central and eastern Montana Thursday night. As of now there looks
to be a gradient in the smoke from west to east across our area.
Areas to the west such as Livingston may get little to no smoke
while areas farther east such as Miles City and Baker may get much
greater smoke concentrations aloft, with areas in between like
Billings getting a concentration between the Livingston and Miles
City/Baker levels. Through Thursday night the model keeps much of
the near-surface smoke over northern Montana, but this will need
to be watched as any northerly or northeasterly wind could bring
the near-surface smoke more south- or southwest-ward into our
area.
Low temperatures will generally be in the 50s to lower 60s tonight
through Friday night. High temperatures will mostly be in the 70s
and 80s, coolest in the foothills. RMS
Saturday through Wednesday...
Ridging in the west and troughing in the east will keep the
forecast area under the influence of northwest flow through
Sunday and may bring smoke from the Canadian wildfires back into
our region, with some near surface smoke. Occasional weak
disturbances will bring low (5-10%) chances of isolated showers
and thunderstorms in the afternoons and evenings over the weekend.
On Monday, the ridge axis will move across the region as a low
moves into the Pacific Northwest, bringing 10-20% chances for
precipitation Monday afternoon through late Monday night. Tuesday
and Wednesday will be warm and mostly dry, but afternoon showers
and thunderstorms will remain a possibility under zonal flow.
High temperatures will be in the 80s Saturday and Sunday, warming
into the upper 80s and low 90s Monday through Wednesday.
Overnight lows will remain in the 50s to mid 60s through the
extended. Arends/Archer
&&
.AVIATION...
Wind gusts at 20-25 kt will continue into the evening. Weak
isolated showers and thunderstorms are possible over the
Absaroka/Beartooth mountains this afternoon and evening. VFR
conditions will prevail. Archer
&&
.PRELIMINARY POINT TEMP/POPS...
Thu Fri Sat Sun Mon Tue Wed
-----------------------------------------------------------
BIL 059/086 059/084 059/085 060/087 060/090 063/090 060/087
02/T 22/T 00/U 00/U 00/U 10/U 10/U
LVM 054/083 053/082 052/086 054/089 055/090 056/087 052/085
12/T 22/T 00/U 00/U 00/U 10/U 00/U
HDN 057/088 056/084 058/085 056/088 059/093 062/091 058/088
02/T 22/T 00/U 00/U 00/U 10/U 10/U
MLS 060/087 060/084 059/084 058/084 058/088 062/090 061/087
02/T 22/T 10/U 00/U 00/U 11/U 21/U
4BQ 060/087 060/083 059/083 058/085 057/089 062/091 062/088
02/T 22/T 00/U 00/U 00/U 11/U 21/U
BHK 057/086 055/081 056/081 053/080 052/082 057/087 059/085
02/T 22/T 10/N 00/U 00/U 11/U 21/U
SHR 056/084 054/081 053/082 054/085 055/090 059/090 056/085
02/T 22/T 00/U 00/U 00/U 11/U 10/U
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service Cheyenne WY
545 PM MDT Wed Jul 12 2023
.SHORT TERM...(This evening through Friday night)
Issued at 330 PM MDT Wed Jul 12 2023
Fairly quiet weather exists this afternoon across most of the area.
On the synoptic scale, the quieter weather is related to the strong
but shallow ridge whose axis is just to our west. Satellite imagery
indicates some shallow, high-based cumulus development over the
mountains and starting to spread over southern Wyoming. Surface
observations show a fairly sharp dryline straddling the area at this
hour, positioned generally from near Pine Bluffs to Wheatland to
Douglas. To the west, dewpoints are stuck in the mid 30s around
Cheyenne, but quickly climb to the mid 50s by Kimball and Sidney.
This feature is positioned a little further west than indicated by
earlier model runs, which has resulted in some minor changes to the
near term forecast. Modest instability has crept in as far west
as Laramie county per RAP analysis, and the latest few HRRR runs
are now showing some convection flaring up across Laramie county
and the southern panhandle later this evening, between about 02z
and 06z. Models indicate some lingering elevated instability and
decent shear continuing as the dryline crashes back westward.
Therefore, this seemed likely enough to at least warrant
introduction of slight chance PoPs for these areas through
midnight tonight.
Nocturnal convection associated with elevated instability and a very
weak vort max traversing overhead may continue through the
morning, but should be mainly east of our area. Still can`t rule
out this activity creeping westward, so maintained low end PoPs
for the far eastern counties. However, even if the convection
remains off to the east, it could be important for potential wild
cards in the forecast for Thursday. We will need to watch for
outflow boundaries from the nocturnal/morning convection lingering
over portions of the area Thursday morning as they compare to the
current model forecasts, since this could alter how Thursday
afternoon`s storm potential. The challenging aspect of the
forecast will be the dryline position. Most models show the
dryline setting up fairly close to the CWA boundary by the time
convection can get going, but if this ends up just a little bit
further west, a favorable storm environment may exist in our area.
Most guidance shows substantial instability and steep lapse rates
setting up in the morning, but then the advancing dryline cuts
this off by mid-afternoon before anything is able to kick up. This
could be the kind of day where we may only get one storm, if at
all, but if the dryline is further west we may need to look out
for severe potential. Otherwise, look for another hot day across
the area and breezy conditions along and west of I-25.
The strong ridge over the southwest CONUS is expected to retrograde
westward on Friday, allowing for more shortwave activity to creep
into our area in the northwest flow aloft. This will knock down
temperatures a bit especially east of the Laramie range. Look for
Friday highs to be about 8-10F cooler than Thursday in these areas.
The passing shortwave may also add enough lift to kick off some
showers and thunderstorms through the day. However, instability and
lapse rates both look modest so the probability of severe weather is
fairly low, but nonzero. Precipitation chances may continue into
Friday evening or overnight. The GFS, for example, shows the surface
front pushing well westward, leading to a region of modest
frontogenesis and showers/storms through the evening hours.
.LONG TERM...(Saturday through Wednesday)
Issued at 330 PM MDT Wed Jul 12 2023
The medium range to extended forecast will include near to slightly
above average temperatures, and a couple of upper level disturbances
moving along a persisting upper level ridge across our cwa. The
northwest flow aloft will provide an opportunity for passing weak
wave features to bring chances of showers and isolated thunderstorms
to the cwa. As the upper level ridge amplifies across our cwa, we
can expect a much warmer trend of temperatures from Sunday to
Tuesday before we have a transition to slightly cooler temperatures
behind a weak cool frontal passage.
Saturday will bring a contrast of CAA to our northern zones due to a
passing upper level wave, and WAA for our western zones by the late
afternoon ours. The dividing feature between the two air masses will
be the Laramie Range. However, with the lower elevations seeing
decent atmospheric mixing, daytime maximum temperatures for the
eastern forecast zones will be similar to those for areas west of
the Laramie Range. The coolest temperatures are likely across the
CO/WY border for Saturday as daytime highs there will hover in the
middle to upper 70s, with the remainder of the cwa seeing daytime
maximums in the low to middle 80s. There will be an isolated chance
of thunderstorms on Saturday along the I-80 corridor from Albany
County towards the NE Panhandle, but severe weather isn`t expected.
Sunday and Monday will bring warmer temperatures to our cwa due to
the upper level ridge amplifying across the desert Southwest towards
the Central and Northern Rockies/Central Plains. The lower and mid-
levels of the atmosphere will warm considerably. 700mb temperatures
on Sunday will be 5C to 7C warmer than Saturday. This will translate
to afternoon highs being 5 to 10 degrees F warmer for Sunday
afternoon. Most locations should see middle 80s to lower 90s for
highs in the lower terrain, and slightly cooler temperatures in the
higher terrain. The axis of the upper level ridge will propagate to
the east from the Great Basin area towards the Central/Northern
Rockies by Monday. 700mb temperatures by Monday afternoon will range
from 15C to 20C, and will mix to the surface easily. Because of the
very warm temperatures being present, isolated showers and a
thunderstorm may be possible as the elevated mixed layer has weak
instability within it. Severe weather is not expected, but afternoon
and evening showers and thunderstorms can`t be ruled out. Widespread
80s and 90s can be anticipated for the lower terrain to start next
week on Monday.
Tuesday will be the warmest day of next week. Ensemble members for
daytime highs for locations east of the Laramie Range are favoring
low to upper 90s. Some cities along the North Platte River Valley
from approximately Torrington to Sidney are the highest favored for
potentially reaching the century mark for high temperatures. This
will be a little tricky to fine tune as we approach Tuesday due to
the model guidance favoring an approaching shortwave disturbance to
our north. If this shortwave disturbance treks further to the south,
then we will see a higher probability of showers and thunderstorms.
This could easily impact daytime highs by having additional cloud
cover over the area, and slightly cooler temperatures. However, have
gone with an aggressive approach to daytime highs, with several
areas seeing the highest forecast maximums of the summer period:
Widespread 80s and 90s. Have kept the century mark out of the
forecast as it is 6 days away at this time of inspection.
Wednesday has the signals to be nearly as warm as Tuesday, with
isolated chances of showers and thunderstorms as well. We
recommend paying attention to the extended forecast as it
transitions to the short term desk by early next week. There may
be a need to issue headlines due to the very warm to hot
temperatures expected by early next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 537 PM MDT Wed Jul 12 2023
VFR conditions expected across area terminals through the forecast
period. The main update to the latest TAFs has been the inclusion
of VCTS to KBFF and KAIA early this evening. Latest radar imagery
has shown development of a storm near the WY/NE border north of
Torrington with hi-res guidance suggesting additional development
along a retreating dryline early this evening is possible as well.
Moderate rainfall and occasional lightning will be possible if
storms move near any terminals, but coverage should remain fairly
isolated through 06z.
&&
.FIRE WEATHER...
Issued at 330 PM MDT Wed Jul 12 2023
Near critical fire weather conditions continue along and west of
the I-25 corridor through Thursday, though fuels remain non-
critical which will prevent any fire weather headlines. Still, hot
temperatures, low RH, and breezy conditions will return again
tomorrow for the same areas. A few isolated thunderstorms are
possible over the high plains and could produce locally gusty
winds.
The dryline is expected to push back westward by Friday,
boosting humidity for all except western Carbon county lower
elevations. Isolated to scattered thunderstorms are possible
Friday and Saturday with cooler temperatures returning. Expect a
warming trend to begin Sunday through Tuesday with near critical
fire weather conditions possible for areas along and west of I-25.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...MN
LONG TERM...BW
AVIATION...MB
FIRE WEATHER...MN
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
800 PM EDT Wed Jul 12 2023
.UPDATE...
No changes will be necessary to the current flood watch headlines or
the severe weather threat in the south tonight. A lead short wave
impulse now tracking into the thumb region initiated the lead batch
of primarily light rain showers. Although a bit of a lull in the
shower coverage is immediately following this wave, the stronger
compact short wave/MCV now traversing southern Lake Mi will drive
the more widespread rain and convection across the forecast area
tonight. Increased inflow along the nose of a strengthening low
level jet will drive the resident instability plume along/south of
the state line northward into the southern portions of the forecast
area by late evening. This will sustain the region of convection
upstream if not initiate additional convective clusters across far
southern Lower Mi in the 02Z to 07Z time frame. The expected
shear/instability profiles continue to look favorable for a severe
weather threat in the far south tonight, particularly mini
supercells. The moisture advection and region of mid level
deformation will sustain widespread moderate to occasionally heavy
rain across the northern half of the forecast area.
&&
.PREV DISCUSSION...
Issued at 647 PM EDT Wed Jul 12 2023
AVIATION...
A compact mid level short wave will traverse Se Mi this evening into
the early overnight hours. Strengthening SSW flow in advance of this
system is already driving rain across Se Mi. The intensification of
the low level inflow during the evening will transport the
instability reservoir now over the northern Ohio Valley into Se Mi
later this evening. This instability plume will accompany the
passage of the associated surface low across Se Mi in the 02Z to 07Z
time frame. This will be the most probable time period for
thunderstorms at the terminals. While the better chances for more
widespread thunderstorms will be from FNT south, prolonged rain will
affect MBS well into the overnight. The combination of low level
moisture transport and periodic heavy rainfall will cause ceilings
to drop into the lower end MVFR and IFR range late
evening/overnight.
For DTW...The instability plume is forecast to be driven into metro
around or shortly after 02Z. This is likely to result in the
development and/or intensification of thunderstorm activity across
metro airspace. Timing of the exit of the convection carries a
little bit of uncertainty, but should be in the 05Z to 07Z time
frame based on the expected departure of the forcing and instability
axis.
DTW THRESHOLD PROBABILITIES...
* Moderate in thunderstorms tonight.
* High in ceilings below 5000 feet tonight
PREV DISCUSSION...
Issued at 410 PM EDT Wed Jul 12 2023
DISCUSSION...
The late afternoon and early evening forecast keeps a close eye on
thunderstorm trends along the stalled front near the Ohio border in
the area under a Marginal to Slight risk of severe intensity. The
upgrade to Slight risk is due to an increased tornado probability
very close to the Ohio border as the front starts moving northward
this evening and before the transition to the larger scale weather
features supporting heavy rainfall. A Flood Watch remains in effect
for that potential tonight along the north of I-94 through the Tri
Cities and northern Thumb.
The primary concern for severe intensity thunderstorms is tied to
increasing wind shear brought by the decaying MCS/MCV ahead of which
new discrete storm development is possible. The strengthening shear
profile with strong low level curvature favors supercell potential
given adequate instability. The latest hourly mesoanalysis measures
surface based CAPE in the 1000-1500 J/kg range along and south of
the front which nudges north of the Ohio border into Lenawee and
Monroe counties for any new cells able to form on the leading edge
of the MCS/MCV. The hybrid meso/surface low also appears deep enough
to support SW flow capable of some recovery of instability along the
surface trough trailing the MCV as well. Locally backed surface flow
ahead of the MCV and a longer straight-line hodograph behind it
support organized storms. Adequate instability is the main limiting
factor which will be monitored through the evening.
Moisture on the other hand is not a limiting factor which fuels
increasing probability for the excessive rainfall scenario tonight.
Part of the increasing confidence is the stronger forcing that
results due to interaction between the MCV and upper Midwest short
wave circulation as they move eastward. The first sign of that is
the deepening and organizing meso/surface low over IA which supports
model depictions of the strengthening low level jet early tonight.
Even the ECMWF has SW wind reaching 50 knots at 850 mb 00-06Z
tonight. The resulting powerful moisture transport and nocturnal
elevated instability fills in the current "dry slot" from northern
IL into Lower Mi. A consensus of deterministic model QPF and the 12Z
HREF PMM favor the I-69 corridor to the Tri Cities and northern
Thumb for heavy rainfall axis while the Canadian models and latest
RAP point farther south toward metro Detroit. This variability is
the primary reasoning for a larger Flood Watch footprint until near
term convective trends can guide later refinement. Average rainfall
around 1 inch with localized totals around 3 inches on 1 inch/hr
rates look reachable given this strongly forced larger scale
environment fueled by PW holding around 1.75 inches.
The primary wave of low pressure moves east of Lower Mi Thursday
morning leaving the Great Lakes in a more weakly forced large scale
pattern on the southern fringe of the large mid level low in central
Canada. Scattered showers and thunderstorms are possible both
Thursday afternoon and Friday with temperatures in the lower to mid
80s finishing the week. The long wave pattern aloft remains blocked
which holds the Canadian low in place this weekend. Various short
wave features roll through the Great Lakes in this pattern to keeps
showers and thunderstorms active through the period.
MARINE...
Developing low pressure currently over the WI/IL/IA area will track
along a stalled frontal boundary into the central/southern Great
Lakes this evening into tonight. Compared to guidance yesterday,
this low is already more developed than what was advertised by this
time today. Because of this, expectation is for a more mature,
slightly deeper low to track over southern lower MI into southern
Ontario resulting in stronger east turning northeast flow over Lake
Huron and east turning southwest flow over Lakes St Clair and Erie.
While winds over these southern lakes could briefly touch 25kts late
night, have held off on a small craft advisory due to the quick
rotation toward weaker offshore flow. As for Lake Huron, funneling
of winds down the Saginaw Bay likely supports gusts up around 25kts
with some overachievement attempting to push near 30kts not
completely out of the question. Similar gusts up around 25kts
possible around the tip of the Thumb as the low tracks just to the
south late tonight. Forecast soundings show a brief couple hour
period where peak winds aloft overlap with slightly unstable
overlake thermal profiles further supporting these moderate to
strong gusts. As such, have issued small craft advisories for these
nearshore waters tonight into Thursday morning.
In addition to winds, widespread showers with scattered embedded
thunderstorms are likely with this system. An isolated strong to
severe storm still can`t be ruled out. Low vacates the central Great
Lakes by Thursday afternoon however additional unsettled weather
possible by late week/this weekend as an upper level trough settles
over the Great Lakes.
HYDROLOGY...
A Flood Watch is now in effect until 4 AM tonight from the I-94
corridor northward through the Tri Cities and northern Thumb due to
increasing probability of excessive rainfall and flooding. A large
organization of thunderstorms and its parent low pressure system
continue to feed off of a high moisture environment tonight along
with the potential for training or repeated rounds of storms.
Average rainfall around 1 inch is likely with the range extended
toward 2 to 3 inches where training of convective cells occurs.
Rainfall rate of 1 inch per hour is possible at times. Flooding
could include area roads, urban locations, along with significant
rises in area streams and rivers. The unsettled pattern may also
result in additional showers and thunderstorms Thursday and Friday
but with lower coverage and intensity.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Flood Watch until 4 AM EDT Thursday for MIZ047>049-053>055-060>063-
068>070-075-076.
Lake Huron...Small Craft Advisory from 2 AM to 10 AM EDT Thursday for LHZ421-422-
441-442.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
UPDATE.......SC
AVIATION.....SC
DISCUSSION...BT
MARINE.......KDK
HYDROLOGY....BT
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Quad Cities IA IL
654 PM CDT Wed Jul 12 2023
...AVIATION UPDATE...
.SHORT TERM...(This evening through Tonight)
Issued at 217 PM CDT Wed Jul 12 2023
Key Messages:
1. A few scattered showers and isolated thunderstorms are
possible in northwest IL and northeast IA the rest of this
afternoon. Otherwise, quiet conditions expected through tonight.
2. Patchy fog will be possible early Thursday from recent
rainfall.
Latest GOES 16 water vapor imagery shows a strong shortwave
responsible for the active weather this morning, tracking into
southwest WI. Two weaker waves were shown upstream with one over
south central MN and another dropping south into northwest MO.
Visible satellite loops show some clearing taking place across IA,
allowing for some temperature recovery from precip/clouds this
AM. 18Z MSAS analysis depicts a surface low near KVTI and
dewpoints in the upper 60s/lower 70s across the CWA.
Active weather this morning has exited to our east. While some
strong storms were observed, severe reports were minimal with
winds generally between 30-50 mph in the strongest cells. However,
much of the area received some beneficial rain in the past 36
hours, especially in areas that have missed out over the last
week. Rain totals over 1.5 inches were common in the central
portions of the CWA, mainly 25 miles north and south of I-80. The
highest totals over 3 inches likely fell in northern Henry county
and western Bureau county in IL based on radar estimates.
Turning to additional chances for showers/storms this
afternoon/evening. The above mentioned shortwave over south
central MN and strong mid level flow will support some
redevelopment of showers and storms northeast of a line from
Cascade IA to Morrison IL. Extensive cloud cover from morning
convection has kept the atmosphere recovery and subsequent
instability from rising much in this area. This will be the
limiting factor and am not anticipating strong storms this evening.
This is also supported by recent HRRR runs and SPC mesoanalysis.
The entire area should be dry by 6-7 PM this evening.
Tonight...weak high pressure, light to calm winds, and abundant
BL moisture will bring some patchy fog to the forecast area
overnight. Some model guidance keeps low clouds lingering through
sunrise and thus keeps fog formation limited. Nonetheless, have
added patchy fog to the forecast for now and the evening shift can
update as needed. Overnight lows will drop into the Lower to
middle 60s.
.LONG TERM...(Thursday through Wednesday)
Issued at 206 PM CDT Wed Jul 12 2023
Overall pattern looks to remain very active well into next week with
disturbances lined up across the Pacific. The area will remain in
west northwest flow aloft until the intense system in the Gulf of
Alaska rebuilds the west coast ridge. Once this occurs northwest
flow aloft will dominate.
Thursday
Assessment...medium confidence
The morning hours should remain dry as a weak upper level
disturbance approaches from the Plains. As the disturbance moves
into the area during peak afternoon heating, some isolated showers
and storms are possible east of the Mississippi and north of I-80.
If the disturbance would slow down, isolated showers and storms
north of I-80 on both sides of the river cannot be ruled out.
Thursday night through Saturday
Assessment...medium confidence
Any diurnal convection that develops Thursday afternoon will
dissipate with sunset leaving the area dry during the evening hours.
After midnight another upper level disturbance will approach from
the northern Plains. Internally the models are suggesting a possible
thunderstorm complex late Thursday night and into Friday morning.
The signal is weak and the better potential is across
Minnesota/Wisconsin. However given the nonlinear aspects of
thunderstorm complex formation and evolution, if the complex would
develop further south then the area would be in the path of the
organized storm complex.
The model consensus is suggesting this with slight chance to chance
pops in the northwest parts of the area late Thursday night and
chance to likely pops on Friday.
Boundaries left over from this nocturnal complex would then provide
the focus for diurnal redevelopment Friday afternoon. The
question then becomes whether or not the Friday afternoon
development grows upscale into another storm complex Friday night.
Here the internal signals from the models are not clear. The GFS
says yes, the ECMWF says no while the CMC is in-between.
A `possible` scenario is a very loose cluster of storms that persist
through Friday night as the upper level disturbance moves through
with convection slowly dissipating on Saturday. The model
consensus is somewhat supportive of the this scenario with chance
to likely pops Friday night and slight chance to chance pops on
Saturday.
Saturday night through Monday night
Assessment...low to medium confidence
The upper level high rebuilds on the west coast changing the flow
pattern aloft to more northwest. As a result a storm system will
push a cold front into the area that slowly dissipates with time.
The front combined with passing upper level disturbances will
provide a focus for storm development. Locally heavy rainfall will
also be possible as the airmass south of the front will have high
amounts of moisture to aid in storm development.
The model consensus currently has Saturday night dry ahead of the
approaching front, and then slight chance to chance pops Sunday
into early next week.
Tuesday through Wednesday
Assessment...low confidence
Starting Tuesday the overall sensible weather picture becomes more
unclear with northwest flow established. At least one upper level
disturbance will move through the area but moisture will initially
be limited before better moisture arrives Tuesday night/Wednesday.
Thus Tuesday is more likely to remain dry compared to Wednesday.
The model consensus suggests this with Tuesday being mainly dry. For
Tuesday night/Wednesday the model consensus has slight chance
pops.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 654 PM CDT Wed Jul 12 2023
Latest Surface analysis had low pressure across far northwest
Illinois with a stationary boundary across parts of the CWA.
Latest satellite has a mix of clouds with breaks across the CWA.
We had plenty of precipitation today and with breaks in the clouds
coming later in the day concerned about fog potential tonight when
winds decrease. Brought in fog a little earlier northeast with
lower cigs. Expect mostly places in the IFR/LIFR vsbys with the
fog. Visibilities may not get as low in the BRL region. Placed a
little more fog and lower ceiling this forecast period based on
recent data and rainfall.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SHORT TERM...Gross
LONG TERM...08
AVIATION...Holicky
Area Forecast Discussion
National Weather Service Grand Forks ND
714 PM CDT Wed Jul 12 2023
.UPDATE...
Issued at 710 PM CDT Wed Jul 12 2023
Partly to mostly cloudy skies prevail this evening with impacts
not expected through Thursday morning. Temperatures are hovering
in the upper 60s to low 70s and will fall slowly through the
remainder of the overnight period due to cloud cover. Overnight
lows could be a bit warmer than the forecast, depending on how
persistent the cloud cover is, but will hold off on modifying at
this point.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 232 PM CDT Wed Jul 12 2023
The Hudson Bay Low continues to spin around to our north, bringing
through little shortwaves here and there to give us some chances of
rain. We could see another round of showers and/or thunderstorms
this afternoon, as some CAMs have some form of activity traversing
the area later this afternoon. This is a lower probability outcome
though, and depends on daytime heating in the area as they will be
diurnally driven.
Into Thursday, A shortwave will give the area chances for strong to
severe storms. With MLCAPE around 2000 J/kg in the southern Red
River Valley, sufficient shear and lapse rates, severe weather is
definitely possible. Hazards include wind gusts up to 60 MPH, and
given the environment supercells capable of producing hail as well
as damaging wind gusts will be possible. Forcing is not really there
in the area, so it`s hard to pinpoint where exactly supercells are
more likely. For now, the most likely area to receive strong to
severe storms looks to be SE North Dakota and MN Lakes country.
Hopefully things will become more clear on location in further
updates.
Temperatures will warm from the 60s and 70s today into the 70s and
80s tomorrow, making for a warmer end to the week before a Friday
cold front comes and cools us back down.
.LONG TERM...(Friday through Wednesday)
Issued at 232 PM CDT Wed Jul 12 2023
Friday looks to be a bit breezy and possibly smokey. Around 43% of
guidance shows sustained winds around 10 - 15 knots or higher for
the Devils Lake Basin and the northern Valley. In addition, more
smoke will be filtering south into our area, with both HRRR & RAP
smoke showing some decent concentrations of near-surface smoke.
Friday night looks to have the possibility for some showers and
thunderstorms early, with areas being the most likely to see some
thunderstorms being east of the Red River Valley. Precipitation from
these showers and storms looks to be minimal, around a trace to
0.10" in the areas affected.
Not much else to add for the long-term period. The Hudson Bay Low to
our north will continue to spin around, bringing possible
precipitation chances as it does. In the four corners region, a
ridge is setting up shop and this will begin to affect us in the
beginning of the new work week. Our area will begin to see some
850mb WAA into the area through mid-week next week, which will help
our highs rise into the low 80s by Wednesday. However, the ridge
flattening mid-week means more precipitation chances to come due to
ridge riders.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 605 PM CDT Wed Jul 12 2023
VFR conditions are expected through much of the TAF period at all
sites. Winds remain light through early Thursday morning, then
increase slightly heading into the midday and afternoon hours.
Overall, no impacts expected through the TAF period.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Lynch
SHORT TERM...AK
LONG TERM...AK
AVIATION...Lynch/TT
Area Forecast Discussion
National Weather Service Green Bay WI
1101 PM CDT Wed Jul 12 2023
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Thursday
Issued at 239 PM CDT Wed Jul 12 2023
The latest RAP analysis and satellite/radar imagery show an MCV
moving across southern Wisconsin early this afternoon. While the
strongest storms and heaviest rainfall will pass well south of
northeast Wisconsin, rain and a few embedded storms on the
northern edge of the system will pass over central to northeast
Wisconsin this afternoon before exiting early this evening. Areas
along HWY 10 may receive over a half inch of rain. A trailing wave
is moving into northern Minnesota and poised to pass across
north- central WI tonight. Forecast concerns mainly revolve around
precip trends.
Tonight...With the exception of far northeast WI, showers and
embedded thunderstorms will have exited the region by the start of
the evening. Then the shortwave over northern Minnesota will pass
across northern WI for the rest of the evening. This wave will
bring scattered showers, mainly north of HWY 29. Precip activity
will generally decrease in coverage and intensity after midnight,
but low clouds will likely hang around overnight. Lows tonight
are expected to range from the lower 50s across the north to
around 60 across east- central Wisconsin.
Thursday...Under flattened troughing, weak, embedded shortwaves
may bring additional showers and thunderstorms to northeast
Wisconsin during the afternoon. However, forecast soundings show
quite a bit of dry air in the atmosphere along with a capping
inversion. Therefore, precipitation chances will be much lower on
Thursday with less confidence in seeing storms given the weak
dynamics and low instability in place. Highs on Thursday will be
warmer ranging from the middle to upper 70s across the north with
highs around 80 across central and east- central Wisconsin.
.LONG TERM...Thursday Night Through Wednesday
Issued at 239 PM CDT Wed Jul 12 2023
Synopsis: The upper air pattern will generally remain relatively
stable and consist of a trough stretching from Hudson Bay to the
Great Lakes over the period. This pattern will bring occasional
showers and thunderstorms and near to slightly below temperatures
for the next week. Precip amounts will also likely be near to
below normal over the next week as well.
Thursday night through Friday night...After a relatively quiet
Thursday night, models continue to point towards a shortwave
impulse traversing the region on Friday. While there could be a
few showers during the morning, daytime instability growing
upwards of 1000 j/kg should lead to an uptick in shower and
thunderstorm development in the afternoon. Convective parameters
suggest a few strong storms are possible, mainly from central to
east-central WI. Storms should then weaken through the evening as
instability is lost. No significant changes to temps.
Rest of the forecast...The chance of showers and storms will
continue at times through the weekend, as the region will be on
the southern periphery of the upper trough. Sunday appears to
offer a higher chance of rainfall rather than Saturday. Then the
chance of rain will continue on Monday as the upper trough passes
directly overhead. Cooler and drier weather follows for Tuesday
behind the system.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1100 PM CDT Wed Jul 12 2023
A mix of MVFR/VFR conditions were found across the area this evening,
as the last of the shower activity exit into Lake MI. A few
sprinkles or light showers could linger overnight, mainly over
northern WI, but most of the night looks dry. Still some
differences in the models regarding if/where we will get some
lower CIGs tonight, along with if any fog will form. Stayed pretty
close to the previous TAFs, with the better chance of the lower
CIGs at CWA/AUW and RHI but some lower BKN/OVC CIGs might be
needed. As for fog, if/where any clearing occurs, some thicker fog
is expected.
On Thursday, any low clouds and fog will lift with mainly higher
end MVFR and VFR ceilings expected through the day. A few showers
or possibly a stray storm will be possible, especially in the
afternoon/evening, but confidence and coverage too low to include.
West winds will become a little gusty, up to around 20 kts, in
the late morning and afternoon, then diminish in the evening.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM.....MPC
LONG TERM......MPC
AVIATION.......Bersch
Area Forecast Discussion
National Weather Service Grand Rapids MI
940 PM EDT Wed Jul 12 2023
LATEST UPDATE...
Update
.UPDATE...
Issued at 940 PM EDT Wed Jul 12 2023
Sfc low now entering far sw Lwr MI and will track east along the
sfc boundary over the next few hours. Convection has congealed
into a line as it comes onshore and has taken on some QLCS
characteristics.
RAP shows the low level jet ramping up over 40 kts ahead of this
feature over next few hrs and effective bulk shear values near 50
kts. Sig tor values of 2-3 moving along/south of the I-94
corridor as well.
Damaging wind/tornado threat will exist with compact bowing
feature as it continues east next few hours. While the TOR watch
goes til 3 AM, much of sw Lwr MI will see the threat end by
midnight with passage of this feature.
Max rainfall reports so far have been 1 to 1.5" and radar shows
axis of heavy rain setting up/continuing from Ottawa and Kent
Counties toward the east-northeast-- as projected in earlier
HREF/CAM QPF fcsts. No changes to the flood watch as this time
although back edge is already sweeping toward MKG.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 303 PM EDT Wed Jul 12 2023
...Impactful weather likely tonight...
The threat for severe storms and heavy rainfall continues to be the
primary focus tonight. Late this afternoon, a warm front extends
from northern Illinois to southern Lake Michigan to far southeast
Lower Michigan. This front will lift north across the I-94
corridor this evening /approaching GRR-LAN/ as convective complex
over parts of WI/IL moves east into the region - along with an
associated surface low. These features are forecast to be east of
the area by around midnight, but until then, there will be a
potential for locally heavy rainfall and severe storms.
- Heavy rainfall threat tonight
A Flood Watch has already been issued for a multi-county section of
West/Central Lower Michigan, as the juxtaposition of several key
dynamic/thermodynamic ingredients likely support a heavy rain
scenario. In addition to aforementioned front and surface low,
the advancing convective complex /and rainfall rates/ will be
further enhanced by PWATs increasing to near 2 inches, a coupled
jet structure aloft that will serve to enhance vertical motions,
and strong moisture transport into the area aided by 30-40 kt 850
mb LLJ and said PWATs.
Bottom line: Repeated rounds of rain and thunderstorms are possible
along and north of the surface front. Storm total rainfall amounts
of 2"-4" are expected, with locally higher amounts possible. While
the recent dry weather *potentially* reduces the overall flood
risk, urban areas and areas that have experienced rainfall
recently will still be prone to flooding given the expected
rainfall.
- Severe weather threat tonight
Latest SPC Severe Weather Outlook places extreme southern Lower
Michigan in the Slight Risk area, with the Marginal Risk area
north to roughly the I-96 corridor. Confidence is growing that
severe storms /particularly strong winds/ will be possible near
I-94 (and also just to the north of this area) thanks to modest
MUCAPES of 500-1000 J/kg creeping into southern Lower Michigan and
0-6 km shear values nearing 40 kts. **Tornado threat** is non-
zero, given backed low level flow near warm front coupled with the
deep layer shear. Ultimately, instability may be an inhibitor,
but this evolving situation will need to be closely monitored.
The greatest risk for severe weather, including tornadoes, will
be south of I-96 corridor between 7 pm and Midnight.
- Relatively quiet Thursday and Thursday night
Quieter weather is expected Thursday in the wake of tonights storms,
though some residual instability is expected to lead to scattered
non-severe storms away from Lake Michigan /mainly in the
afternoon/ that will end by Thursday evening.
.LONG TERM...(Friday through Wednesday)
Issued at 303 PM EDT Wed Jul 12 2023
- Risk for for storms Friday into Saturday
Broad cyclonic flow aloft will be in place late this week, and
energy rotating around this trough /along with an associated cold
front/ will potentially set the stage for another round of
thunderstorms in West Michigan Friday/Saturday. 35-40 kt 500 mb
flow, synoptic forcing, daytime heating, and cold front may once
again support some severe storms.
- Modest cooling trend by early next week
This upcoming weekend and into early next week will be dominated by
a continued troughing pattern aloft, with increasing height falls
expected into early next week. In fact, some model guidance is
increasingly showing a respectable closed upper low north of Lake
Superior by late Sunday/Monday. This pattern will support
temperatures falling to a bit below normal by Monday/Tuesday,
along with a periodic risk for convective showers/storms -- given
mid summer sun angle and colder air aloft.
Seasonable high temperatures this weekend in the lower to mid 80s
will moderate back into the upper 70s to near early next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 740 PM EDT Wed Jul 12 2023
The area of thunderstorms around Chicago and extending to near
KMKG will build east through the evening leading to widespread
impacts. The MVFR conditions associated with the showers and
storms will go down to IFR in the heavier cells with local sub IFR
possible. The stronger cells could lead to local winds over 40
knots as well. A frontal zone extended through the TAF sites with
a east northeast flow for KMKG to KGRR and into KLAN and southeast
south of these sites. The winds will swing around as the wave
passes through later this evening into the overnight hours. While
the bulk of the showers and storms will wind down by 06z an area
of IFR cloud cover will linger through the night. VFR conditions
will gradually arrive during the day on Thursday.
&&
.MARINE...
Issued at 303 PM EDT Wed Jul 12 2023
Winds/waves are generally expected to remain below Small Craft
Advisory criteria tonight, though there are signals in some model
output of a period of enhanced winds for a several hour period
this evening /perhaps resembling wake low dynamics/ in association
with this evenings convective complex. This will need to be
monitored.
A weak ridge of high pressure will then nudge into the western Great
Lakes Thursday, supporting a general north flow that will become
more northwesterly/onshore during the day. Based on guidance and
anticipated pressure gradient, winds/waves will likely remain below
headline criteria - in spite of advancing high situation.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Flood Watch until 2 AM EDT Thursday for MIZ044-050>052-056>059-
064>067.
LM...None.
&&
$$
UPDATE...Meade
SHORT TERM...Smith
LONG TERM...Smith
AVIATION...MJS
MARINE...Smith
Area Forecast Discussion
National Weather Service Marquette MI
938 PM EDT Wed Jul 12 2023
.UPDATE...
Issued at 938 PM EDT WED JUL 12 2023
The forecast remains largely on track tonight, with just some
isolated showers mainly across the western UP so far courtesy of
another shortwave rippling through northern WI. Minor updates have
been made to adjust PoPs downward in order to capture the more
isolated nature of showers expected the rest of the night, more in
line with what most of the high-res simulated reflectivity suggests.
Otherwise, skies remain mostly cloudy, with temperatures in the
lower 60s so far and still on track to bottom out in the 50s by
early Thursday morning.
&&
.SHORT TERM...(This afternoon and tonight)
Issued at 125 PM EDT WED JUL 12 2023
Broad troughing noted across much of eastern Canada has supported a
couple shortwaves embedded in near-zonal, slightly northwesterly
flow over the northern Plains and Upper Midwest per RAP analysis and
GOES water vapor imagery today. A more potent wave tied to a
decaying MCV has been observed pressing east/east-southeast into
southern Wisconsin/northern Illinois while an upstream shortwave has
been observed migrating eastward through North Dakota/western
Minnesota. Together isentropic lift between the features has
resulted in skies gradually filling in through the day. Temperatures
so far have warmed into the 60s and low 70s.
As forcing continues this afternoon, moisture advection will
support top down column saturation and showers spreading into the
west and south by late afternoon/early evening. Instability and
QPF isn`t expected to be notable given our proximity of the more
southern system though. Showers should press west to east through
the night with maybe some patchy fog developing across the central
late. Overnight lows are expected to be mostly in upper 40s to
mid 50s.
.LONG TERM...(Thursday through Wednesday)
Issued at 337 PM EDT WED JUL 12 2023
A few low-amplitude shortwaves move across our region during the
latter half of this week before the anomalously strong parent low
over Canada drops down late this weekend into early next week. As
this occurs, expect to see showers and thunderstorms across our
area, with a strong storm or two being plausible Saturday should all
the conditions come together just right. While we should have
multiple shots at rainfall these next several days, don`t expect a
soaking rainfall as the better Gulf of Mexico moisture should be
kept out of our area. Moving to the end of the period, models show
some ridging building back in over the UP behind the closed low.
CAMs guidance hints at scattered to isolated rain showers ending
over the east Thursday morning while continuing over the far west.
However, with model soundings showing dry air hanging on in the
lowest levels of the atmosphere, rain will likely struggle to hit
the sfc. Therefore, capped most chances at slight Thursday morning.
Moving into the afternoon hours, some breaks here and there in the
cloud coverage may create enough instability to produce diurnal
showers and thunderstorms, mainly over the interior west half.
However, given the weakness of the instability, expect rainfall
amounts to be fairly light. We could see a brief pause in the
rainfall late Thursday evening before another shortwave brings
additional showers and thunderstorms to the area late Thursday night
through Friday morning. Now, given that the consensus of the CAMs
has a line of storms developing over the central UP early Friday
morning and moving over the eastern half through the rest of the
morning, thinking that the severe weather threat should be pretty
limited since diurnal instability will close to its daily minimum.
Any CAPE that is there should be very skinny and limited to the mid
to upper levels of the atmosphere. Therefore, while we may see some
gusty winds well below severe criteria with the line of storms, I
don`t think we will see much else besides some heavy downpours
Friday morning. Behind the line, some isolated to scattered showers
and storms look possible over the area as we move into Friday
afternoon and evening.
Moving into this weekend, an additional low-amplitude shortwave
looks to move through the region, bringing more showers and
thunderstorms to the area. With mostly sunny to partly cloudy skies
expected, 0-6 km bulk shear around 30 kts, and CAPE up to around
1500 J/kg, we could see a strong storm or two over the eastern half
of the UP. However, that`s if the convection over the east half
waits until the afternoon hours and the shortwave low doesn`t shift
further south than currently expected, so there is quite a bit of
uncertainty even for this very marginal event.
As we head into Sunday and Monday, rain showers and maybe some
thunderstorms look to move back over the area as an impressive low
pressure dips southwards towards Lake Superior. With some robust
CAA on the backside of the low, ensemble guidance such as the EFI
and NAEFs have hinted at well below normal temps, especially maxTs
due to the cloud cover associated with the low. As we move into the
middle of next week, expect ridging from the Plains to creep into
the area, bringing with it some drier weather and near normal temps.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 716 PM EDT WED JUL 12 2023
VFR ceilings prevail at all sites in this TAF period. Hit and miss
showers continue through the evening and first half of the night,
mainly in the western UP, but restrictions are not expected. Some
fog/mist is expected to develop overnight and lift out beginning
around sunrise Thursday. Most likely to be impacted is KSAW, which
may dip into MVFR. Otherwise, expect light and variable winds
overnight to turn to the southwest Thursday, peaking at around 5 to
8 knots.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 337 PM EDT WED JUL 12 2023
Fairly calm winds of 20 kts or less continue throughout most of the
fcst period, although westerly winds above 20 kts could be seen
across the lake Monday as an impressive low pressure moves over the
region. Otherwise, some thunderstorms could be seen late Thursday
night through Sunday, but most of them should be seen near the
shoreline.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
UPDATE...LC
SHORT TERM...JTP
LONG TERM...TAP
AVIATION...LC
MARINE...TAP
Area Forecast Discussion
National Weather Service Springfield MO
615 PM CDT Wed Jul 12 2023
Key Messages:
1. Heat Advisory for the entire area this afternoon and for
locations along and south of a Columbus, KS to Ava, MO line for
Thursday afternoon. Heat indices of 100 to 109.
2. Enhanced risk for severe thunderstorms tonight. The main
potential hazards include damaging wind gusts to 75 mph, hail to
two-inches in diameter, and flash flooding.
3. Potential for additional thunderstorms from Thursday night
into Saturday morning.
.SHORT TERM...(This evening through Thursday)
Issued at 212 PM CDT Wed Jul 12 2023
Synoptic Scale Pattern and Current Conditions: Water vapor imagery
depicts a rather flat west-northwest flow aloft across the central
U.S. One distinct short wave trough is noted in the flow across
northern Minnesota. A subtle short wave trough is also noted across
northeast Colorado.
At the surface, a stationary frontal boundary extends from low
pressure in the Texas Panhandle northeast to around Topeka. The
front then continues in an east-northeast fashion to weak surface
low pressure in eastern Iowa. An east to west outflow boundary from
a morning MCS has now pushed south into southeastern Kansas and
central Missouri. The boundary is becoming increasingly diffuse as
it approaches the Stockton Lake to Fort Leonard Wood corridor.
Morning regional soundings showed strong convective inhibition
across the region with convective temperatures on the order of 100-
106 degrees. The 12Z KSGF sounding measured a convective temperature
of 102 degrees. This has resulted in the Missouri Ozarks and
southeast Kansas remaining convection-free this afternoon beneath
mostly sunny skies.
The big story this afternoon is the excessive heat that has set up
across the area. Temperatures at the 850 mb level have warmed into
the 20-24 Celsius range which is supportive of highs in the middle
90s to around the 100 degree mark. The dry air just above the
surface that was evident on the 12Z KSGF sounding has been able to
mix down to the surface, thus offering slightly lower dew point
temperatures over some areas. Nevertheless, afternoon heat
indices are running in the 98-108 degree range. The current Heat
Advisory will be left intact.
Potential for Severe Storms and Flash Flooding Tonight: Convective
initiation is expected from late this afternoon into early this
evening from central Kansas into northern Missouri. Initial
thunderstorm development will occur in response to weak frontal
convergence and that subtle short wave trough emerging from the
central Rockies.
MLCAPE values of 3000-4500 J/kg and 0-6 km bulk shear magnitudes
around 40 knots will initially favor supercells capable of very
large hail. Some of these supercells may make it into portions of
extreme southeastern Kansas and west-central Missouri later this
evening with an attendant threat of 2" diameter hail and locally
damaging winds.
As we get from mid to late evening, a low-level jet will begin to
strengthen and nose into southeast Kansas and northeast Oklahoma.
This may result in a continued threat for either surface-based or
slightly elevated supercells, especially west of Highway 65 and
north of Highway 60 (where deep layer shear will be stronger).
Supercellular characteristics would generally be within the first
hour or two of cell development. Large hail would again be the
primary threat with any supercells.
A greater concern for the overnight period will be the likelihood
for individual cells to merge and grow upscale into one, or
multiple bowing MCSs that track southeast or south across portions
of the Missouri Ozarks and southeast Kansas. Wind fields are
supportive of southeastward movement for any MCS activity that
develops across central Missouri. Activity that develops across
eastern Kansas may tend to drop more south-southeast or even due
south.
The 12Z CAMs do indeed support this notion with pretty much every
member either showing one or multiple bowing structures impacting
portions of the Missouri Ozarks and southeast Kansas. Damaging
straight line winds of 60-70 mph would be the primary hazard with
bowing structures that are able to develop. Isolated gusts up to
75 mph are possible with established bowing structures. These
magnitudes are also supported by the CAMs.
The SPC Enhanced and Slight Risks cover these expectations well,
including the hatched areas for both wind and hail.
The tornado threat for tonight looks very low (SPC 2% risk) given a
lack of low-level shear. We will have to watch the four state border
region (KS/MO/OK/AR) as that low-level jet attempts to nose in.
There may be some locally higher amounts of 0-1 km SRH with the last
few runs of the RAP depicting values in the 150-200 m2/s2 range. A
supercell in this area would stand that very low chance for a
tornado. As for the bowing segments, we are expecting those to be
largely outflow dominant which would tend to mitigate the tornado
threat.
Another potential hazard we will be closely monitoring overnight is
flash flooding. The atmosphere will become very moist across the
region starting this evening with short term ensembles giving us
high confidence that precipitable water values will increase into
the 1.8" to 2.1" range. Any training of thunderstorms and/or
back-building characteristics on the southwestern flanks of any
MCSs would result in torrential rainfall. The 12Z HREF localized
probability-matched mean product is showing small pockets of
rainfall amounts in the 3-5" range with member maximum amounts in
the 5-8" range over very localized regions.
Even with the drought worsening across the region, any basins that
see 3-5"+ amounts would experience flash flooding. We considered a
Flood Watch for portions of the area, but it is very hard to pin
down what particular basins would be at the greatest risk for flash
flooding. This will be a short term forecast challenge with a short-
fused watch an option.
Quieter Thursday with the Potential for Excessive Heat: Any
remaining thunderstorm complexes should exit southern Missouri
around or shortly after daybreak. The one potential "gotcha" would
be that low-level jet continuing to induce isentropic upglide and
resultant elevated convection later into Thursday morning. This low
confidence scenario would only occur if overnight MCS activity does
not sufficiently clear out instability.
The big question then becomes how quickly we can clear out and how
much we will heat up Thursday afternoon. NBM statistical data shows
some rather large ranges in potential high temperatures considering
that we are only 24-hours out. More in the way of cloud cover
would keep highs in the upper 80s to lower 90s. Less in the way of
cloud cover would support highs returning to the middle to upper
90s.
We have gone with NBM deterministic numbers for now which have
highs ranging from the lower 90s across central Missouri to the
upper 90s along the I-49 corridor near and south of Joplin. With
dew points expected to mostly be in the upper 60s and lower 70s,
afternoon heat indices would range from the upper 90s across
central Missouri to the 103-109 degree range over our far
southwest. We have issued another Heat Advisory for locations
generally along and south of a Columbus, Kansas to Ava, Missouri
line where our confidence is highest in 105+ heat indices.
One final note regarding Thursday will be the potential for isolated
late afternoon convection across extreme southeastern Kansas and
southwestern Missouri. Weak short wave energy is forecast by short
term models to track across the central Plains from mid to late
afternoon with the atmosphere becoming highly unstable (MLCAPE
values of 3000-4000 J/kg). Convective temperatures will once again
be around 100 degrees, thus it will take some sort of lift
(perhaps that short wave) to result in deep convection. We have
kept PoPs in the 10-20% range to account for this potential.
If storms can manage to develop late Thursday afternoon, there will
be an attendant marginal severe risk given the high instability and
0-6 km bulk shear magnitudes running around 30 knots. Hail to the
size of quarters and locally damaging wind gusts would be the
primary potential severe weather hazards.
.LONG TERM...(Thursday Night through Wednesday)
Issued at 212 PM CDT Wed Jul 12 2023
Thursday Night into Friday Morning: The risk for widely scattered
thunderstorms will persist into Thursday evening across extreme
southeastern Kansas and southwestern Missouri, however that risk
will tend to diminish by 03Z with the loss of daytime heating.
Meanwhile, another complex (or two) of thunderstorms is expected to
develop across the central High Plains. As we have seen in this
pattern, there is a considerable amount of variability in the
models regarding where these MCSs will track. Several ensemble
members do indeed track activity through the Missouri Ozarks
either late Thursday night and/or Friday morning. NBM
deterministic data suggests 50-70% PoPs for this time period.
Interestingly, the outer hours of the CAMs paint a much quieter
picture, at least through 12Z Friday. Adjustments to PoPs are
highly likely for this time period.
Friday Afternoon into Saturday: Shorter term ensembles depict a
slightly more amplified short wave trough diving southeast across
the northern and central Plains with the upper level flow becoming
more diffluent in nature over the Missouri Ozarks. This bodes
well for additional thunderstorm potential Friday afternoon and
evening as well as the potential for another MCS from Friday night
into Saturday morning.
There will be an attendant risk for a few strong to severe storms
from Friday afternoon into Friday night. SPC has placed almost the
entire area in a Marginal Risk for Friday and Friday night. A
Slight Risk does clip our southeastern Kansas counties. The
eventual severe risk will be highly dependent on how much we can
destabilize Friday afternoon and then how much elevated
instability can develop Friday night ahead of any potential MCSs.
Locally heavy rainfall and flash flooding potential will also have
to be monitored for Friday/Friday night as the atmosphere remains
very moist. Ensemble data continues to suggest that PWATs of 1.7" to
2.0" are likely. WPC has placed nearly the entire area under a
Slight Risk for excessive rainfall.
Sunday: WPC cluster scenarios indicate that the upper level pattern
will temporarily become more amplified as strong upper level energy
dives into the northern Great Lakes. The upper level flow will veer
to more northwesterly across the central U.S. That should result in
a frontal boundary settling south towards the I-40 corridor. This
should then push most (if not all) potential convection south of
the Missouri Ozarks.
We are not looking for too much relief from the heat this weekend
despite the front eventually getting south of the area. A few
locations across the Missouri Ozarks may remain below the 90
degree mark on Saturday if clouds and precipitation hang around
long enough. Otherwise, NBM statistical data indicates that highs
Sunday afternoon should return to the lower 90s over all areas.
Monday through Wednesday: Cluster scenarios all indicate that the
upper level flow will transition right back to west-northwesterly
as that trough over the Great Lakes lifts out of that region.
This will put us right back into a pattern that favors nocturnal
MCS potential. That front will also lift back north through the
area and will likely support a return to excessive heat.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 608 PM CDT Wed Jul 12 2023
For the 00z TAFS, still expecting a thunderstorm complex to
develop later this evening and push through the forecast area and
affecting the 3 forecast TAF sites. While there is some
differences with the CAMS on timing, there is a chance for some
development prior to 06z, but the most likely scenario is for the
majority of convection at SGF/BBG/JLN to be after 06z. Prior to
then, we are expecting VFR conditions. Within the strong to
possibly severe convection, MVFR and IFR conditions are expected
along with variable wind directions and gusty winds. We are going
with 20 to 30 kts in the TAFS, but if storms become severe, then
some 50 to 60 kts will be possible. Storms may backbuild
overnight and linger to around 12-13z.
&&
.SGF WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory until 7 PM CDT this evening for MOZ055>058-066>071-
077>083-088>098-101>106.
Heat Advisory from 1 PM to 7 PM CDT Thursday for MOZ088-093>096-
101>105.
KS...Heat Advisory until 7 PM CDT this evening for KSZ073-097-101.
Heat Advisory from 1 PM to 7 PM CDT Thursday for KSZ101.
&&
$$
SHORT TERM...Schaumann
LONG TERM...Schaumann
AVIATION...Lindenberg