Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/10/23
Area Forecast Discussion
National Weather Service La Crosse WI
1040 PM CDT Sun Jul 9 2023
.DISCUSSION...(This evening through Sunday)
Issued at 144 PM CDT Sun Jul 9 2023
Key Messages:
- Scattered storms expected very late Monday into Monday night.
An isolated severe storm possible, mainly north of I-94 with
strong winds or small/marginally severe hail.
- Another round of showers/storms possible (40-60%) Tuesday night
into Wednesday with higher chances favoring southwest
WI/northeast IA.
This evening-Tuesday:
The main focus early this week will be on thunderstorm chances and
hazards late Monday into Monday night as a front drops south across
the Upper Mississippi Valley. Ahead of the front, relatively deep
diurnal mixing with breezy southwest winds should help boost temps
well into the 80s or low 90s on Monday.
Much if not all of the day should be dry with scattered storms
possible by late in the afternoon/early evening across southern into
central MN/northern WI near the front as the stronger shortwave
forcing arrives, with scattered storms developing southeast into the
evening/overnight ahead of the front as large scale forcing
increases.
Little has changed in overall thinking regarding the storm
threat. Some moisture transport/pooling is expected ahead of the
front, but this is not expected to be particularly strong. In
contrast, deep boundary layer mixing could cut into low-level
moisture and instability. The RAP suggests MLCAPE in the 1000-2000
J/kg range ahead of the front. However, stronger deep layer
effective shear lags the front, so storm organization and
longevity should be limited. Overall, the severe storm risk is
expected to be low given this environment with the highest chances
for an isolated strong/severe storm near initiation late
afternoon/evening, especially north of I-94. Given the deep mixing
and veered surface winds with modest shear, locally strong winds
and perhaps marginally severe hail appear to be the main hazards
with a general weakening trend as storms work south overnight. The
front is forecast to pass south through Tuesday morning, so drier
and cooler conditions are expected for Tuesday.
Tuesday night-Wednesday:
A low amplitude shortwave trough is forecast to eject from the
plains Tuesday night into Wednesday toward the Mid/Upper Mississippi
Valley. Models have been showing MCS development in association with
this wave given favorable low-level moisture transport/warm
advection topped by seasonably strong mid-level flow. Models
generally show storms organizing across the northern high plains
late Tuesday and dropping east/southeast along the instability axis
with the shortwave trough.
Locally, the higher rain chances (50-60%) late Tuesday
night/Wednesday favor northeast IA/southwest WI, but the exact
track of shortwave trough and placement of the low-level
baroclinic zone/instability axis will likely impact where the
possible storm complex tracks, and this could shift north a bit,
or, more likely south into the higher instability. Predictability
of the details in these scenarios is typically not resolved until
closer to the event. About 40% of the 00Z global ensemble members
(GEFS/EPS/CMC) favor a slightly more zonal flow which would
support a more northern track of the shortwave trough and bring
higher rain chances south of I-90. The remaining solutions
indicate lesser instability/stronger northwest flow with a more
southerly solution and less impact to the local area. Wherever it
tracks, a pool of elevated CAPE and and a deep warm cloud layer
with a low-level jet feeding moisture northward would support a
locally heavy rain threat. Some wind threat could exist depending
on how convection evolves, but with the higher instability still
expected to be farther south, the higher chances for stronger
storms (and heavy rain) right now would look to be south of the
local area.
Rest of the Week:
There is good overall agreement among global ensembles for a
northwest flow pattern aloft across the Upper Midwest through late
week and next weekend downstream from strong, persistent ridging
over the western US. Differences exist with the amplitude of the
troughing over the Great Lakes and placement/strength of shortwave
troughs passing through the flow. All in all, though, the pattern
favors near to below average temps and only lower end precip chances
given the limited predictability of smaller scale features.
&&
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1040 PM CDT Sun Jul 9 2023
Surface ridge builds south of into the Central Plains States tonight
into Monday. VFR conditions are expected to prevail at the RST/LSE
taf sites through late Monday afternoon. Winds aloft will mix down
to the surface and pressure gradient tightens across the area
Monday. This allows southwesterly winds to increase to 10 to 15
knots with gusts possibly 20 to 25 knots at both RST/LSE taf sites.
A cold front will push south across the area late Monday
afternoon/Monday night. A line of showers or storms will develop
along the front and move over the RST/LSE taf sites...mainly after
00z Tuesday. Will introduce VCSH/VCTS at both taf sites after 00z
Tuesday.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...JM
AVIATION...DTJ
AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
1005 PM CDT Sun Jul 9 2023
.UPDATE...
Issued at 1005 PM CDT Sun Jul 9 2023
A back door cold front continues to slowly progress southwestward
from Manitoba. Slight visibility reductions have been observed
upstream of the cold front. Therefore, patchy smoke was added to
the grids to match these trends. RAP has visibility reductions
from near surface smoke tomorrow morning with conditions improving
in the afternoon. Other then adding smoke to the grids no other
updates are needed.
UPDATE Issued at 650 PM CDT Sun Jul 9 2023
Outflow from thunderstorms that moved north of Bismarck this
afternoon continue to push across Dickey county initiating short
lived thunderstorms. A back door cold front is forecast to move
through the region tonight bringing in a slight chance of
thunderstorms to the Turtle Mountains this evening and tomorrow
morning. Smoke aloft is being transported in from the northwest
due an upper low over the Hudson Bay. Near-surface smoke is
possible tomorrow morning as the back door cold front moves
through the region. However, widespread visibility reductions are
not anticipated at this time.
&&
.SHORT TERM...(This Evening through Monday Night)
Issued at 204 PM CDT Sun Jul 9 2023
Expect a mainly quiet night tonight with an isolated severe
thunderstorm threat southwest on Monday.
Western and central North Dakota is situated under northwest flow
aloft, which will lead to plenty of sunshine for the rest of today
and some fair weather cumulus. Highs will be much warmer than in
recent days, in the mid 80s to lower 90s. We will see breezy
conditions this afternoon across the north and into the James
River Valley with gusts up to 35 mph or so.
At the surface a backdoor cold front will approach the North
Dakota/Manitoba border this evening around 00z to 06z time frame.
A weak wave will ride down the ridge tonight and clip our area in
the vicinity of the Turtle Mountains. Thus, we could see a brief
window for an isolated shower or thunderstorm here in the evening
or overnight. Lows will be around normal for the year, in the
lower 50s to lower 60s.
We remain in northwest flow aloft on Monday, but the ridge axis to
our west will slowly move towards eastern Montana by late in the
day. At the surface, the backdoor cold front will stall out
across southwest North Dakota or maybe even into western South
Dakota. By the afternoon hours, the southwest will start to
destabilize but quality moisture will be limited. Still, the
southwest should see MLCAPE values at least in the 500 to 1000
J/kg range and deep layer shear values ranging from 35 to 45
knots. These parameters would likely support isolated severe
thunderstorms (most likely elevated). However, there is a very
real scenario where storms do not form at all. There will be some
capping present, neutral heights, and an absence of any obvious
upper level forcing. However, if a storm or two can pop (as some
CAMs are showing), the environment would support large hail to the
size of quarters and 60 mph wind gusts. At the moment, the threat
looks conditional, so SPC`s Day 2 Marginal Risk seems reasonable.
Height falls approach the west with the flattening ridge axis
late Monday night and into Tuesday morning. This will mean
increasing chances of showers and thunderstorms west but severe
weather is not likely with this second round of activity.
With the backdoor front moving through on Monday, there will be
quite the gradient in the high temperature forecast in the
afternoon. Areas across the eastern Turtle Mountains will see
highs in the upper 60s and lower 70s, while areas across the
southwest will see highs in the mid to upper 80s. Elsewhere,
expect values in the mid 70s to lower 80s. Lows will be chilly
north and east Monday night, mainly in the 40s, with values in
the 50s west and south.
.LONG TERM...(Tuesday through Sunday)
Issued at 204 PM CDT Sun Jul 9 2023
Scattered to numerous showers and thunderstorms are possible
Tuesday and Wednesday with lower chances through the rest of the
long term. Temperatures will remain either around normal or
slightly below normal.
A couple of stronger waves will move through Tuesday into
Wednesday, flattening the ridge more. These waves will bring
scattered to numerous showers and storms to the area with the best
chances across the west and south. While this won`t be a washout,
some folks across the west will likely see a quarter to half inch
of rain and some locally higher amounts will be possible under
any heavier showers or storms. In general, severe weather is not
anticipated on Tuesday but most guidance keeps the better
instability well to our west and south. If we can see a bit more
instability across the far southwest, a stronger storm or two will
be possible here as strong shear will also be present.
Through the rest of the long term, the ridge pops back up to our
west and we remain in northwest flow aloft. Various weak waves
will move through the flow, bringing small chances of showers and
storms here and there mid to late week. Temperatures on Tuesday
will be cool, with highs in the mid 60s to mid 70s, but we warm
back into the mid 70s to mid 80s by Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 650 PM CDT Sun Jul 9 2023
VFR conditions will continue through the period. Winds out of the
northwest will continue persist until a back door cold front
moves into the region early tomorrow morning. Showers and
thunderstorms are possible tomorrow morning along the back door
cold front.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Johnson
SHORT TERM...ZH
LONG TERM...ZH
AVIATION...Johnson
Area Forecast Discussion
National Weather Service Burlington VT
1012 PM EDT Sun Jul 9 2023
.SYNOPSIS...
A round of widespread heavy rain arrives this evening into the
overnight hours, with another round expected during the day on
Monday. Expect widespread 2 to 5 inches of rain with locally 7
inches through Monday night. With saturated soil and elevated
river levels from recent rainfall, widespread significant to
potentially catastrophic flash flooding are expected overnight
tonight into Monday night. The heavy rainfall will also lead to
sharp river rises, leading to widespread area and river flooding
through Tuesday. Muggy and unsettled conditions continue
through the rest of the week. The next system to bring rain will
be Thursday into Friday.
&&
.NEAR TERM /THROUGH MONDAY NIGHT/...
As of 1008 PM EDT Sunday...We`ve reached a bit of a lull in
precipitation, but portions of eastern Vermont are still
experiencing some heavy rain. Made only minor changes with this
updates as we are still busy here in operations. Temperatures
have fallen to the upper 60s to around 70 for most spots with
forecast lows in the mid- to upper 60s, another muggy and mild
night. Expect rain to intensify again after midnight tonight.
Previous discussion below:
Previous discussion...
* Expect significant to potentially catastrophic widespread
flash flooding through Monday evening, with possible impacts
not seen since Irene.
* Widespread heavy rainfall of 2-5 inches with localized 7+
inches will be exacerbated by the saturated soil and elevated
river levels from all the recent rainfall.
* Scattered strong storms are possible Monday afternoon with the
risk of an isolated downburst.
The steady rain is already knocking on our doorstep, with dozens of
Flash Flood Warnings just to our south. Heading into this evening,
showers and thunderstorms this afternoon will result in brief heavy
or torrential downpours. It is not out of the question that we could
see isolated 1 to 2 inches of rainfall in as little as 30 minutes,
exacerbating saturated ground conditions in areas that have seen a
lot of rain in the last few days. In addition, there will also be
isolated strong to locally severe storms capable of producing
localized damaging winds or downbursts. So be sure to stay weather
aware even prior to the main show.
A combination of satellite imagery and RAP mesoanalysis shows just
how dynamic this system is. Visible satellite shows a mesolow
feature south of Nova Scotia. RAP analysis depicts a deepening
negatively tilted 500mb trough digging into Tennessee. Of note is
that the trough is a little more amplified than modeled. Out
ahead of the digging trough, a line of thunderstorms now
stretches from far southwestern New York to the western Piedmont
region of North Carolina. Then out ahead of it, there is
another blossoming cluster stretching from southeast PA through
the Taconics of northwestern CT. These two features have
developed along a particularly wavy quasistationary front draped
across the Mason-Dixon line to Long Island. The negative H5
trough means that these two clusters will combine and head our
way later this evening into the overnight hours. That`s a lot of
precipitation that will have to move through our region from
south to north. In addition, terrain will help enhance the
rainfall, leading to locally higher rainfall rates near and
along the spine of the Green Mountains. Unfortunately, this also
means that areas that saw damaging flash flooding just a couple
of days ago and are undergoing recovery will get another deluge
of rain. With saturated grounds and elevated stream levels, the
rain will go straight to runoff and lead to widespread
significant, potentially catastrophic flooding. The widespread
rain will overspread the entire CWA overnight tonight, tapering
off towards daybreak tomorrow.
Then, another piece of the stalled boundary south of Long Island
will lift northwards during the day on Monday, leading to the second
round of deluge. This will coincide with an amplified upper trough
right over the spine of the Greens Monday night. The probability of
the 3 hour rainfall exceeding 3 inches according to the HREF
probability matched mean is quite high for this time frame. This
appears to be slightly west than the first deluge overnight tonight,
going up an axis near or along the Hudson Valley into the Champlain
Valley, including the western slopes of the Greens into the
Adirondack area. By Monday night, this becomes more wraparound
precipitation as a cold front crosses northern NY and VT, which
could lead to another inch or two of rain. It almost looks like a
cold season deformation band developing which could lead to a third
round of deluge late Monday into overnight Monday. When it is all
said and done, some locations that get two if not three rounds of
heavy rain could see localized 7 to 8 if not upwards of 10 inches
through Tuesday or in a 48 hour period. This is extremely rare to
historical rainfall, with the HREF 24 hour QPF exceeding 100 year
Average Recurrence Interval (ARI) at 60 to 70 percent probability.
In other words, expect widespread significant to pockets of
catastrophic flooding to unfold in the next 48 hours. All things
considered, upon coordination with WPC and neighboring WFOs, we have
a Day 2 High risk ERO for much of our CWA (Monday 8 AM to Tuesday 8
AM), which means that widespread flash flooding is expected.
The main takeaway is that if you are in a Flood Watch and especially
inside the WPC Moderate and High risk Day 1/2 ERO, please take this
flooding event seriously, have multiple ways to receive real-time
NWS weather alerts and have contingency plans in place.
&&
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 345 PM EDT Sunday...
By Tuesday, the threat transitions into more of an areal and
river flood threat. Refer to the hydrology section for more
details.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 345 PM EDT Sunday...Overall, the unsettled weather pattern
continues as the region stays under the influence of an upper low
centered near the Hudson Bay. Shortwave troughs will rotate about
this low, resulting in bouts of showers and thunderstorms. While the
timing of these events is tricky to pinpoint this far out, model
guidance supports the idea of a disturbance passing through the
region Thursday afternoon into evening. GFS model soundings support
decent instability both Thursday and Friday afternoon, so trends
will need to be monitored as we get closer. Temperatures will be
rather seasonable, with highs generally in the 80s and lows in the
60s, although it will depend on precipitation and sky cover. It will
continue to feel warm and muggy, as dewpoints continue to sit in the
upper 50s to mid 60s.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Through 00Z Tuesday...TAFs have been slightly challenging with
heavy showers and t-storms in the mix. Thunder is waning,
however, so main concern for the next 24 hours will be heavy
rain and showers lowering vis as well as associated low clouds.
We are anticipating MVFR ceilings and vis for most sites with
vis 4-6SM outside of heaviest t-storms, but KMPV, KRUT, and SLK
could have IFR ceilings at times. Thunderstorms could also bring
brief gusts to 20-30 knots, and cigs/vis should stay MVFR or
below for most of the TAF period as rain continues, potentially
for the next couple days.
Outlook...
Monday Night: MVFR/IFR conditions possible. Likely SHRA, Patchy
BR.
Tuesday: Mainly VFR, with local MVFR possible. Chance SHRA,
Slight chance TSRA.
Tuesday Night: VFR. Slight chance SHRA.
Wednesday: VFR. Slight chance SHRA, Slight chance TSRA.
Wednesday Night: VFR. Slight chance SHRA.
Thursday: Mainly MVFR, with local IFR possible. Chance SHRA,
Slight chance TSRA.
Thursday Night: MVFR/IFR conditions possible. Chance SHRA, Slight
chance TSRA.
Friday: MVFR/IFR conditions possible. Chance SHRA, Slight chance
TSRA.
&&
.HYDROLOGY...
In coordination with WPC, most of our region is now in a Day 1
Moderate risk Excessive Rainfall Outlook (ERO) and Day 2 High risk
ERO. A Moderate risk ERO (level 3 of 4) indicates that numerous
flash flooding is likely while a High risk ERO (level 4 of 4) means
that numerous flash flooding is likely. There will be two rounds of
widespread heavy rainfall, one overnight tonight into early Monday
morning. After a brief lull, rainfall will once again blossom during
the day on Monday, peaking Monday afternoon into evening. There is
even potential for a third round of moderate rainfall Monday evening
into the overnight hours. Given the saturated ground and antecedent
high river/creek levels, bottom line is that it will not take a
whole lot of rain to cause widespread issues. Overall, we are
forecasting widespread 2 to 5 inches of rain with locally 7+ inches
especially along and near the spine of the Green Mountains. Expect
washed out roads and culverts, fast-responding creeks spilling out
of their banks, as well as widespread poor drainage urban area
flooding. Even outside of the stratiform widespread rainfall,
convective elements will be possible on Monday afternoon, leading to
locally enhanced rainfall with a quick inch or two in as little as
30 minutes. By Monday evening into overnight hours, and heading into
Tuesday, the flooding mode will transition from flash flooding to
more of area and main stem river flooding. Typically vulnerable
basins including the Mad River in Moretown, Otter Creek in Center
Rutland, Winooski River in Essex Junction and Ausable River at
Ausable Forks are expected to reach minor and moderate flood stage
on Monday, Tuesday and even into Wednesday.
The main takeaway is that if you are in a Flood Watch, please take
this flooding event seriously, have multiple ways to receive real-
time NWS weather alerts and have contingency plans in place.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Flood Watch through Tuesday evening for VTZ001>011-016>021.
NY...Flood Watch through Tuesday evening for NYZ027-028-030-031-034-
035.
&&
$$
SYNOPSIS...Chai
NEAR TERM...Chai/Storm
SHORT TERM...Chai
LONG TERM...Kremer
AVIATION...Storm
HYDROLOGY...Chai/Hastings
Area Forecast Discussion
National Weather Service Duluth MN
630 PM CDT Sun Jul 9 2023
.MESOSCALE UPDATE...
Issued at 630 PM CDT Sun Jul 9 2023
Strong thunderstorms were occurring this evening along the
International Border near Voyageurs National Park on east. These
were occurring ahead of a cold front in a favorable environment
with MUCAPE values around 1000 J/KG, effective shear of 40-45 KT,
and 0-1KM shear of 20-25 KT. Other showers and storms have
developed much further south in an area of low level convergence
in the Brainerd Lakes region. RAP forecast soundings at KINL were
inverted-V with DCAPE values of 800-900 J/KG. There will be a
threat for severe storms over the next few hours, mainly in far
north to northeast Minnesota with damaging wind the main threat.
There will also be a threat for large hail as we`ve observed some
three body scattering with a couple of the cells. The storms were
developing into a line so the hail threat will be secondary to the
wind. Although not likely, the 0-3KM shear along the
International Border supports a chance for a QLCS tornado.
&&
.DISCUSSION...(This evening through Saturday)
Issued at 330 PM CDT Sun Jul 9 2023
Summary: Thunderstorms and rain showers are expected to move into
the Minnesota Borderlands between 6-8 PM this evening, with storms
as far south as MN Hwy 210 and possibly limited coverage into
northwest Wisconsin later tonight. The strongest storms could
produce wind gusts of 40-50 mph, but an isolated severe wind gust
to 60 mph cannot be entirely ruled out for far northern Minnesota.
These overnight rain chances end last in the Arrowhead by very
early Monday morning. The next chance at rain and thunderstorms
sets up Monday late afternoon in inland northwest Wisconsin around
eastern Sawyer, Price and southern Iron Counties. The strongest
storms in this area could also be a period of isolated severe
thunderstorms producing large hail and strong wind gusts into late
Monday evening. Cooler temperatures in north-central Minnesota
Monday spread areawide by Tuesday.
Deep low pressure remains entrenched over far northern Manitoba
today. A low to mid-level shortwave trough is seen rotating
through this feature on afternoon infrared imagery. This has
already produced daytime showers and isolated thunderstorms in
northwest Ontario, per CASDR radar imagery. The trailing cold
front is expected to slowly move southward this evening and create
increasing precip chances first over the Minnesota Borderlands
between 6-8 PM today. Forecast model soundings show a period of
500 to 1000 J/kg of CAPE with a fairly dry environment aloft. That
dry air aloft and fairly dry mixed layer late this afternoon,
expected to last into this evening, may create gusty and erratic
winds as the main thunderstorm threat through 03-04Z tonight
mainly for northeast Minnesota. Most wind gusts are expected to be
from 40-50 mph, but an isolated severe thunderstorm gust to 60
mph cannot be entirely ruled out. The best forcing lining up with
available instability and very limited shear keeps the severe
threat mainly to the Iron Range, Arrowhead and Borderlands, but
scattered showers and thunderstorms may be observed as far south
as the MN Hwy 210 corridor and into lake shore counties of NW WI
through tonight. Showers chances decrease last in the Arrowhead by
early Monday morning. So the main message for this evening
continues of widely scattered strong thunderstorms in northeast
Minnesota through very early tonight, but an isolated severe
thunderstorms has a low probability of occurring too.
Lighter northwesterly flow behind the front allows cooler
temperatures to set up over north-central Minnesota Monday, while
much of far eastern Minnesota remains seasonable and still warm
into northwest Wisconsin.
Monday late afternoon looks to be the next chance for severe
weather in northwest Wisconsin as the trough aloft moves
southeastward tomorrow daytime. Inland northwest Wisconsin
counties including eastern Sawyer, all of Price and across
southern Iron Counties have the best chance at seeing isolated
severe thunderstorms in the late afternoon to mid-evening hours
Monday. Southern Price County could even see more like a
scattered severe thunderstorm regime. This is largely conditional
on just how far north the warm air is able to keep around in our
far southeast counties as the front moves southward tomorrow ...
right now the severe threat is there but this could easily push
just south of our forecast area over the next 12-18 hours. At this
point the 25-or-so knots of effective shear, CAPE to 1700 J/kg
and steeper lapse rates promote the potential of large hail around
1" in diameter as a primary severe threat for Monday late
afternoon into mid-evening. Some guidance has non-severe
thunderstorms back into the lakeshore counties of NW WI, but
confidence remains low on any development at this time so the
forecast remains limited to only isolated to scattered storm
mentions over just a few hour period tomorrow in those counties.
Temperatures were dropped for Monday night from the base national
blend guidance over northeast Minnesota as clearing skies, calm
winds and dryer sounding profiles are expected to promote
efficient cool-basin radiational cooling. Temperatures may have to
be further lowered over the next 24 hours from current
expectations of most locations north of US Hwy 2 in MN reaching a
few degrees either side of 40 F by sunrise Tuesday morning.
Fog was added to Price County in northwest Wisconsin for the
expected localized late-evening heavier rainfall tomorrow night
creating pockets of low-basin fog throughout Monday night after
the showers and storms taper off.
Those cooler temperatures set up areawide by Tuesday predominant
northwest flow. Surface winds should be fairly light.
The pattern of west to northwest flow persists into the middle to
the end of this week as the low pressure is stationary over
Manitoba. The next shortwave could move over our area Wednesday
evening and bring an overnight rain chances into Thursday. Similar
low PoPs remain in the forecast into next weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 630 PM CDT Sun Jul 9 2023
A cold front from northwest Ontario into far northern North Dakota
will continue south tonight. There will be a chance for showers
and thunderstorms both ahead and behind the front with the
stronger storms ahead and especially affecting far
northern/northeast Minnesota through the late evening hours. A
dip to MVFR or IFR will occur with the thunderstorms and gusty
winds will be likely with the storms as well. Coverage of
showers/storms are expected to diminish overnight but some are
expected to hold together. We highlighted the most likely time in
the TAFs and will update as necessary. A brief dip to MVFR
ceilings will also occur right along the front but they should
only last a few hours.
Gusty southwest winds will gradually diminish this evening. A low
level jet will cause low level wind shear at KBRD/KHYR tonight.
The front may kick off more thunderstorms in southern parts of the
Northland including northwest Wisconsin on Monday. We left the
mention out of KHYR for now as confidence is too low to include.
&&
.MARINE...
Issued at 310 PM CDT Sun Jul 9 2023
Gusty southwest winds will persist over the head of the lake
through the mid-evening hours today as the strong winds shift east
towards the Apostle Islands and near Saxon Harbor. The earlier
Small Craft Advisories remain in effect for those conditions, with
a new set now in effect until early tonight covering the Apostles,
Chequamegon Bay and up till Saxon Harbor. The low level jet moves
out of the western waters after Midnight tonight, with a cold front
eventually moving southeastward. Scattered showers and thunderstorms
associated with the front may produce a lightning and gusty wind
hazard over the Arrowhead through much of tonight. Winds will
shift westerly Monday morning and midday behind the front. There
may be another period of limited thunderstorm coverage along the
South Shore late Monday afternoon and evening, but confidence is
not high on just how far north the storms will travel away from
inland northwest Wisconsin.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 61 75 47 71 / 40 10 10 0
INL 53 69 41 70 / 60 10 0 0
BRD 63 77 47 72 / 20 20 0 0
HYR 62 81 45 73 / 20 40 30 0
ASX 63 76 46 71 / 40 30 20 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory until 1 AM CDT Monday for LSZ121-147-148-
150.
Small Craft Advisory until 7 PM CDT this evening for LSZ143>146.
&&
$$
MESOSCALE UPDATE...Melde
DISCUSSION...NLY
AVIATION...Melde
MARINE...NLY
Area Forecast Discussion
National Weather Service Des Moines IA
632 PM CDT Sun Jul 9 2023
...Updated for the 00z Aviation Discussion...
.DISCUSSION.../Tonight through Sunday/
Issued at 352 PM CDT Sun Jul 9 2023
Key messaging highlights:
* Mostly clear and pleasant tonight into Monday morning
* More seasonal temps and humidity returning starting tomorrow
* Thunderstorm chances back in the forecast to start the work
week. Mainly northwest tomorrow afternoon and southwest Tue
night into Wed morning
With a very dry airmass in place and surface high pressure
passing through the lower MO Valley, it should be another pleasant
night across IA with mostly clear skies. The trailing lobe
extending south from the Ontario upper low has exited and will
soon give way to a prolonged period with varied degrees of active
northwest flow turning our pattern back to something more typical
for mid July. Southwest low level flow will be back in place by
tomorrow morning, boosting our highs well into the 80s, with and
axis of 60s dewpoints through the Siouxland area into northern IA.
This will set the stage for thunderstorm development during the
afternoon, triggered by an approaching front driven by a strong
western Great Lakes short wave falling into the persistent Ontario
trough. There is fairly strong agreement among recent HRRR runs
and 12Z HREF members that scattered storms will develop in peak
heating north, and then dissipate north and east with the loss of
insolation and increased CINH. MLCAPEs look to approach 1500 J/kg
with nil inhibition. Wind and hail would be the primary threats
in what may be a small strong to severe window. Even though low
level moisture will increase, temps will at an equal or faster
rate allow for relatively dry low levels and steep lapse rates
with DCAPEs +/- 1000 J/kg. Deep shear suggests organization and at
least discrete cells at onset, and elongated hodographs 1km and
above would support large hail.
These may linger to some degree central and south into Tuesday,
with our attention turning upstream to the central Plains. The
front from Monday should push just to our south and west by
Tuesday afternoon with a sharp theta-e and instability gradient
setting up NE/SW across IA along or just southwest of the
immediate MO River Valley. Thunderstorms are expected to develop
upstream across NE during peak heating and reach southwest IA into
the night. The severe potential this far north and east remains
in question with low confidence. The model guidance suite suggests
much of the instability should remain just southwest of the
forecast area, however the NAM and some other members suggest a
less aggressive frontal push and better instability into the
state, especially southwest. Examination of forecast soundings and
hodographs are somewhat disconcerting through the MO Valley if
greater instability is realized with looping low level hodographs
which become elongated above supporting damaging wind, large hail,
and even some QLCS potential in the Slight Risk area, although
that seems a bit too aggressive to the north and east at them
moment. Regardless, the NBM and ensemble guidances suggest some
form of MCS Tue night into Wed, although the strength and severity
is certainly still in question. Something to definitely keep
watching.
For the remainder of the period, the active northwest flow will
remain in place, but as is often the cause during these regimes
confidence in details is low. This leads to an extended period of
ill-defined slight to chance PoPs and seasonal temperatures into
next weekend.
&&
.AVIATION.../For the 00Z TAFS through 00Z Monday evening/
Issued at 630 PM CDT Sun Jul 9 2023
VFR conditions through the period for most locations though a few
thunderstorms are possible across northern Iowa Monday afternoon.
Mainly SKC overnight then some cumulus development by mid-morning
Monday. Light wind tonight will become breezy from the southwest
as well Monday.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Small
AVIATION...Donavon
Area Forecast Discussion
National Weather Service Gray ME
1011 PM EDT Sun Jul 9 2023
.SYNOPSIS...
A frontal boundary remains stalled west of the region through
Monday, with showers, thunderstorms, and heavy rainfall possible
Monday night. Flash flooding is possible across western and
northern NH today through tomorrow night with the heavy
rainfall. Conditions likely won`t dry out again until at least
the middle of the week once the front finally drifts east of New
England. Humid conditions continue with moderating temperatures
behind the front for the middle and later portions of the week.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
1000 PM Update... Convective showers are continuing to stream
northward across western NH. Gauge reports and radar
reflectivity indicates rainfall rates are lower than earlier
this evening though, which should help to mitigate the flash
flood threat some. Patchy dense fog has developed along the
coast and therefore based on these observations and the latest
HREF probabilities went ahead and issued a dense fog advisory
for visibility down to 1/4SM at times through 10am. Otherwise
only minor adjustments were made to the forecast at this time.
Previously...
730 PM...Some minor changes to the POPs overnight into early
Monday, but the overall forecast is very similar. Marine air
has kept everything from the mtns S and E mainly dry /other than
some patch DZ/, while all the convective activity and heavy
rains are around the western and northern perimeter of the CWA.
I think this it where it will mostly stay through much of the
night. Eventually will get more in the way of synoptic forcing
Monday which will allow the rain to move to the east, bit
heaviest rain is still expected across W and N NH.
Previously...The worst of the rains and thunderstorms will be
from the point through Monday, and the main focus is over the
western portions of NH. A weak 500 mb trough is moving N-S
through N New England this afternoon and is responsible for the
current convection and heavy rain this afternoon. Practically
all of the convection is N or W of the mtns and terrain, which
suggests the marine layer as covered much of the rest of the
CWA, and this should protect these areas form anything
significant into tonight. Models still showing some spread as to
where the heaviest rain, but the 12Z HREF, seems like a good
compromise /although the HRRR has been doing OK as well/. Think
the ongoing convection will continue at least into the first
part of the evening, and then will see a break until close to
daybreak. Otherwise the threat of showers moves very slowly east
into ME late tonight, with the return of fog in those places
where it has dissipated. Areas near the coast are likely to some
patch dense fog as well. Lows will once again be mostly in the
mid to upper 60s, cooler on the mid- coast.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
The heaviest rains still looks to remain to our west, over VT,
but the Whites, the CT valley and Monadnock region will be on
the fringe of that, and are the in the area of greatest concern,
but flash flooding is possible for much of NH. Localized rain
amounts of up to 4” will be possible in the flood watch as
convective storms back build over the area. Also, will see some
mid level deformation and could see banding of heavy rain
showers as well. In SE NH and Maine will see showers increase in
frequency through the day, with heavy downpours as well, and
while there is no watch, could see a few warnings in that area
tomorrow afternoon and night. Otherwise it should be very much
like Sunday with patch fog and overcast skies. Highs will be in
the upper 60s to low 70s.
More uncertainty for Monday night as some models end the heavy
rain faster than others. But still looks like showers will
continue through most of the night across the CWA with fog
moving in to most places once again.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
The negatively-tilted upper-level low will be centered across VT/NH
to start off Tuesday morning. As this low slowly shifts to the north
and east through the day, the threat for heavy rain fall will go
along with it as the deepest moisture and forcing also shift east.
Based on latest guidance, any lingering potential for locally heavy
rainfall would be confined across northern NH and/or western ME
during the morning while a dry slot moves in for most everywhere
else in the area. It should be noted that this is based on the NAM
and GFS solutions, and the ECWMF is a little slower in the movement
of the upper-level low.
As we get this drier air, we should be able to achieve some
clearing, and the instability from this should allow additional
showers and a couple of storms to develop the rest of the day. These
look to be more isolated to scattered in nature but could still
produce heavy downpours, which could bring a localized flooding
threat should they fall on areas that see heavy rainfall today
and Monday. Some area rivers could continue to rise through the
day on Tuesday. Other than a few showers Tuesday night across
northern areas, the rest of the area should stay dry, although
patchy fog will be possible given the light winds and recent
rains.
The weather pattern stays active right through the rest of the week
and into next weekend thanks to an upper low hanging around the
Hudson Bay region, keeping mean troughing into the Northeast U.S.
This will allow several waves to cross through and given the
sufficient moisture, there will be at least a chance of showers and
storm each day. Wednesday or Thursday could be potentially be drier
than what`s currently in the forecast, with the GFS favoring
Wednesday for the drier day while the ECMWF is going with Thursday.
With differences in the timing/location of the waves, will maintain
chance PoPs in the forecast.
There is better agreement going into Friday and next weekend with
southerly flow ramping up and again increasing the moisture across
the region. Multiple waves ahead of another slow-moving frontal
boundary will bring back even higher chances for showers and storms,
especially Friday and/or Saturday. Shortwave ridging could provide a
mostly dry day for next Sunday, but confidence on this is low given
that is right at the end of the forecast period.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Short Term...IFR-LIFR is expected through tonight and into
Monday at most terminals. KHIE may stay MVFR trough much of the
night, except in TSRA. Like Sunday, could see a few hours of
slight improvement during the afternoon, but expect a return to
IFR or lower Monday night.
Long Term...Scattered to numerous showers continue on Tuesday,
especially farther north, along with a slight chance of storms
as low pressure continues to move across the area. However, conditions
are expected to improve to VFR from west to east later in the
day. Fog and low ceilings could being flight restrictions again
for Tuesday night (especially the ME terminals) with improvement
by Wednesday morning. Mostly VFR expected for Wednesday with
lower chances for showers and storms, but the potential for
flight restrictions and showers/storms increase again toward the
later part of this week.
&&
.MARINE...
Short Term...No issues with winds/seas through Monday night. Fog
remains the main hazard as it likely becomes dense at times.
Long Term...Weak low pressure will move across
the waters Tuesday, with showers and fog remaining possible.
Showers diminish Tuesday night and Wednesday, but the potential
for fog stays put. Fog then remains possible through at least
late week as warm and humid southerly flow returns for the later
part of this week into next weekend as a series of low
pressures moving along a slow-moving frontal boundary to our
west. In general, conditions are anticipated to stay below SCA
levels, but can`t rule out a brief period of southerly gusts
approaching 25 kt Friday into next weekend.
&&
.HYDROLOGY...
Weak low pressure develops South of New England and tracks
northward tonight into Monday night, which will add some
dynamics to a very moist atmosphere. This is likely to produce
heavy downpours and back building storms late today through
Monday night, especially across western and northern New
Hampshire. The areas at greatest risk for flash flooding will be
across the higher terrain of western and northern New Hampshire
and along the CT River Valley.
As the heavy rainfall and any flash flooding runs off, flooding
on some larger rivers is also possible early this week.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Dense Fog Advisory until 10 AM EDT Monday for MEZ023>028.
NH...Dense Fog Advisory until 10 AM EDT Monday for NHZ014.
Flood Watch until 5 AM EDT Monday for NHZ001>003-005-007-008-
011-015.
Flood Watch from 6 AM EDT Monday through Tuesday morning for
NHZ001>009-011-015.
MARINE...None.
&&
$$
NEAR TERM...Tubbs
SHORT TERM...Cempa
LONG TERM...Combs