Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/12/23
Area Forecast Discussion
National Weather Service La Crosse WI
1043 PM CDT Tue Jul 11 2023
.DISCUSSION...(This evening through Tuesday)
Issued at 212 PM CDT Tue Jul 11 2023
Key Messages:
- Another round of showers and storms tonight. Highest rain
chances (40-74%) along and south of Interstate 90.
- Periodic rain chances from Wednesday through Tuesday. Rainfall
amounts with any of these systems look on the light side.
Tonight and Wednesday...
The cold front that pushed through the area Monday night has
progressed almost to the Iowa/Missouri border into northern
Illinois. This boundary will be the focus for more convection
overnight as a short wave trough comes out of the High Plains and
moves across the region. The concern becomes how much convection
will extend north of the boundary and just how far north it will
be. Most of the high-resolutions models today are focusing the
bulk of the activity to stay to the south with the possibility of
the northern fringe moving across portions of northeast Iowa and
southwest Wisconsin. The RAP indicates there will only be between
500 and 1000 J/kg of MU CAPE with maybe 30 to 35 knots of shear in
the 0-3 km layer. Forecast soundings would suggest the CAPE will
be up to 700 mb with a very skinny profile that would only
support some general thunder from this activity. Any showers and
storms that do make into the area overnight should push off to the
east Wednesday morning. Another weak short wave trough may work
across the region Wednesday with some scattered activity possible.
This does not look to be all that organized at this point.
Wednesday Night through Tuesday...
A closed low pressure area will move slowly south from Hudson Bay
into the Great Lakes. Meanwhile, a strong high system will remain
over the southwest United States. This will keep the area in west
northwest flow aloft. As a result, the heat and the greatest
instability will remain southwest of the Upper Mississippi River
Valley through this time period. As a result, temperatures will
range from below to near normal. The 11.12z models continue to
show that there will be some weak embedded shortwaves in this
flow. These will bring periodic showers and storms. As is the case
in these flow patterns, the timing of these waves are highly
uncertain, so low precipitation chances (15-30%) covered much of
this time period. Looking at the model ensembles and clusters,
rainfall amounts with these systems look to be mainly less than a
tenth of an inch. The one exception was from Friday into Friday
night where there was better agreement in the ensembles and
clusters for higher rain chances (30-60%). In addition, the
chances for rainfall greater than 0.10 inches was also higher with
it ranging 30-60%. Meanwhile, the probabilities for a 0.50 inches
is less than 10% was less than 8%. While 0-1 km CAPES are up to
1500 J/km, the 0-3 km and 0-6 km shear are weak, so not
anticipating any organized severe weather at this time.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1040 PM CDT Tue Jul 11 2023
Very light showers move through overnight from west to east, but
impacts to aviation should be minimal with VFR ceilings. A second
band of showers and storms progresses quickly across the area
early in the morning between 08-15Z, affecting mainly areas south
of an AUM to LNR line, which may bring MVFR to IFR restrictions
in heavier rain. Scattered storms redevelop in the afternoon, but
confidence in impacting a TAF site is low. Ceilings in the
afternoon may also lower close to MVFR levels at times. Winds will
generally be light and veer to the east/southeast by the morning,
with sites west of the Mississippi River switching to the
northwest in the afternoon.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...Boyne/04
AVIATION...Skow
Area Forecast Discussion
National Weather Service Des Moines IA
1024 PM CDT Tue Jul 11 2023
.UPDATE...
Issued at 953 PM CDT Tue Jul 11 2023
Models continue to show convective development beginning shortly
after midnight and lasting through the morning hours along an
elevated boundary draped from north central SD through NW IA and
into north central Iowa. This convection will intersect with an
approaching mesoscale convective system (MCS) resulting from
convection in the Dakotas. While heavy rainfall and gusty winds
are possible with the elevated convection, the primary severe
threat will be with the developing MCS.
The origin and evolution of this MCS remains a bit uncertain, but
the leading solution is for it to develop out of storms firing in
central SD. This MCS will then ride along the
instability/moisture gradient, with its sights set on western IA.
Strong effective bulk shear will promote upscale growth of this
system and a developing LLJ over the southern Great Plains region
will sustain it through the night. Given this environment, and
recent model output, it is apparent that strong winds of 50 to
60kts or more will be possible as this system matures. However,
where these winds occur will depend on which pocket of convection
the MCS develops out of as well as what occurs along the boundary
downstream from it.
If elevated convection develops soon enough in northern Iowa, it
would push the boundary south and prevent the developing MCS out
west from making it into the state. While some severe weather
would still be possible with this solution, the widespread wind
threat would be lower. However, if convection holds off long
enough for the MCS to arrive, damaging winds would be possible in
western and southwestern Iowa as the MCS matures and moves
through.
In addition to the winds, elevated convection developing out
ahead of the MCS could also result in a hydrological threat. We
have been fairly dry across the area, which should limit most
flash flooding impacts. However, if the boundary lights up over an
urban area and then the MCS were to track over that area as well,
locally heavy rainfall could lead to ponding of water in poor
drainage or low lying areas.
All this being said, the solution is not cut and dry. The
environment should show its hand over the next few hours, and the
likley solution should become apparent once the MCS begins to
develop and/or the elevated convection starts to fester.
Regardless, the chance for strong winds in western Iowa and
locally heavy rainfall seems like a possibility as this complex
scenario unfolds.
&&
.DISCUSSION.../Tonight through Tuesday/
Issued at 236 PM CDT Tue Jul 11 2023
Key Messages:
- Storms likely overnight, with the potential for severe wind
gusts south.
- Additional storms possible Wednesday, although the severe
potential is uncertain.
19z surface analysis shows a weak boundary draped over the CWA near
I-80. Wind fields and convergence along the boundary are weak, but
the moisture gradient is pronounced. Dewpoints are in the upper
60s/low 70s near and south of the boundary axis. Much drier air with
dewpoints in the 40s and 50s north thanks a dry airmass nosing south
around a Canadian high pressure. Radar has detected a few light
showers as instability builds near boundary today, but have
struggled to survive given the weak low level convergence and little
to no support aloft. A few light showers are also possible into
northwest Iowa by early evening as weakening remnant convection
pushes out of South Dakota and Nebraska. Otherwise most folks will
still dry for at least the next handful of hours.
Conditions become more for favorable for convection later this
evening into tonight as a shortwave trough within the northwesterly
flow aloft drops into the northern Plains. A few hi-res models
suggest low level thermal forcing may be strong enough to generate a
elevated storms closer to the 850mb boundary after 03z, set up
generally near the Hwy 20 corridor. Much more robust convection tied
closer to the deep kinematic forcing with the parent wave develops
over north central Nebraska this evening, then feeds south and east
into the moisture transport and along the instability axis into Iowa
overnight. The overall severe threat wanes as MUCAPE weakens
overnight, but could still see some strong to severe wind gusts
south if a deep cold pool can remain organized. HRRR maintains a
stronger cold pool and has shown several consecutive runs with 50-60
kt gusts clipping southwest Iowa, so this will need to be closely
watched. 0-3km shear is quite strong and nearly orthogonal to the
mean storm motion. This would be favorable for QLCS type spin
ups. However, most soundings show a stable boundary layer and
diminished low level thermal profile by this time, favoring
elevated convection and a minimal tor threat. Typical mid-summer
environment will be primed for heavier rainfall rates, given PWATS
near 1.75" and warm cloud depths pushing 4000m. Progressive
nature of the overnight convection + antecedent dry conditions
will limit the flash flood threat outside of urban areas.
Considerable uncertainty going into Wednesday in the wake of the
overnight convective episode. Model differ on boundary placement,
with some pushing it south with the cold pool, scouring out our
instability with little to no recovery through the day. A separate
model camp pulls the boundary back north in response to another
shortwave passing through the active northwest flow aloft. This
would build the humid and unstable airmass back into at least the
southern half of the state. If the latter solution is realized then
additional showers and storms are likely, including the potential
for severe storms as deep layer shear increases to near 50 kts.
Active northwesterly flow remains in place through the end of the
week and into the weekend. This will keep periodic chances for
showers and thunderstorms in the forecast. Timing the most likely
opportunities is difficult due to model differences, but ensemble
data points to Fri-Fri night as the most likely candidate.
&&
.AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/
Issued at 642 PM CDT Tue Jul 11 2023
Mostly VFR conditions continue across the area this evening. The
primary challenge through the TAF period continues to be
thunderstorm trends through the night. A large amount of
uncertainty exists on timing of both isolated showers and the main
system of storms. As of right now, anticipating the main system to
enter the area early tomorrow morning with some isolated showers
and storms popping up throughout this evening and overnight. TAFs
have been timed out accordingly, but confidence in timing is low,
so trends will be monitored and TAFs will be updated if any
changes are expected. Storms may produce gusty winds and reduced
visibility as they move through the area, especially at KFOD, KDSM
and KOTM.
Tomorrow morning, some MVFR clouds may accompany the storm
system as it moves through, especially in the northern and
eastern portions of the area. Have only included this in the KALO
TAF for now and will reassess with the next issuance.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Dodson/Small
DISCUSSION...Martin
AVIATION...Dodson
Area Forecast Discussion
National Weather Service Quad Cities IA IL
648 PM CDT Tue Jul 11 2023
...AVIATION UPDATE...
.SHORT TERM...(This evening through Wednesday)
Issued at 149 PM CDT Tue Jul 11 2023
Key Messages
1. Dry initially before shower & storm chances increase overnight
2. Severe risk along with a risk for torrential rainfall
Discussion
A quiet start will turn fairly active overnight as shower and storm
chances increase areawide. Initial analysis shows a west to east
oriented frontal boundary draped along the Interstate 80 corridor
from central Nebraska into northern Illinois. Along and south of
this boundary, temperatures were well into the mid and upper 80s
to near 90 with a rather muggy dewpoint in the upper 60s.
Meanwhile to the north, conditions were more comfortable with
dewpoints in the 40s and even 50s analyzed from northeast Iowa
into Wisconsin.
The main short term forecast challenge is the progression of this
boundary, as this will be the determining factor in precipitation
chances and timing for our area Wednesday morning.
Conditions will be primarily dry and hot for much of eastern Iowa,
northwest Illinois and northeast this afternoon and evening. Will
make note, however, of a risk of an isolated thunderstorm mainly
around the Interstate 80 and Hwy 30 corridor near the enhanced
surface convergence with the frontal boundary. Ample instability
from the heat and marginal shear will favor stronger cores capable
of producing localized wind gusts and hail. This threat should
diminish by sunset.
Next, we turn our attention to the west. Over the next several
hours, clusters of strong to severe thunderstorms will be developing
across the western Dakotas in response to a robust vortmax/shortwave
moving into the High Plains. Latest CAMs and deterministic model
guidance progs this activity evolving into an MCS and eventually
latching on to the aforementioned frontal boundary, with a track
southeast into the eastern Dakotas, northeast Nebraska and western
Iowa favored heading into tonight. Additional showers and storms may
form out ahead of the MCS along the 850-700 hPa frontal boundary,
with some assistance from a 925-850 hPa 35-45 kt LLJ that will be
oriented across the region perpendicular to the boundary.
Now we turn back to the position of the surface boundary. There are
a couple of potential scenarios we could see here: 1) The frontal
boundary retreats south of the Quad Cities from its current position
to around the IA/MO border, with it stalling across this area into
the overnight. This scenario is supported by previous 18z of the 00z
guidance. A setup like this favors the bulk of the MCS track nearer
to the state borders, with impacts felt mainly across southeast
Iowa, west central Illinois and northeast Missouri. This also keeps
the majority of severe potential further south into Missouri. The
next scenario 2) favors the frontal boundary setting up around the
Interstate 80 corridor, with impacts felt more CWA-wide vs. the
first scenario. This also appears to be the way latest guidance is
trending per the latest HREF and several deterministic CAMs, likely
due to early runs being too aggressive on cold pool processes
driving the front further south, and the incoming shortwave aloft
ushering the front further north. This scenario is higher confidence
vs. the first, and will be focusing more on this for the rest of the
discussion.
Aforementioned MCS will track along the surface front and boundaries
aloft into the area later tonight, with much of the area seeing
impacts from this beginning around 10-12z Wednesday morning. Storms
should remain well maintained and organized with the LLJ supplying
plentiful amounts of moisture (PWATs climbing to around 1.60"-2.00")
and vertical shear as they arrive, with a gradual diminishing trend
expected through the morning as the LLJ weakens. Storms initially
could pose a severe threat if they are well maintained, with cold
pool dynamics supporting a damaging wind threat and ample shear
posing a threat for large hail in stronger cores. In addition,
thanks to the very high PWATs, storms could be capable of producing
heavy rain with rainfall rates around 1-2/hr possible. Latest
HREF/NBM probabilities focus along and north of Interstate 80 for
heavier rain amounts, likely due to higher probs of this area seeing
more elevated activity initially.
Once the MCS exits the area by mid to late morning, we will see a
brief lull in precipitation before another shortwave arrives for the
afternoon and evening. This should help fire an additional round of
showers and thunderstorms mainly across southern Iowa and northern
Missouri along the 925-700 hPa frontal boundary. There remains
uncertainty on severe weather potential with this activity, as much
will be dependent on how the AM MCS evolves. For much of the area
post MCS, look for dry conditions with clouds slowly clearing and
temperatures ranging from the upper 70s to mid 80s. Any remnant
outflow boundary from the morning MCS could produce an afternoon
shower or storm.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 149 PM CDT Tue Jul 11 2023
Key Messages:
1. Additional showers and thunderstorms are possible Wednesday
night across southeast IA, northeast MO, west central IL. Small
hail, brief heavy rain, and lightning will be main threats.
2. Active weather pattern remains on track through the latter half
of the work week, with several chances of showers/storms. However,
there will be plenty of dry hours as well.
3. Trending cooler and drier for the upcoming weekend, with near
normal temperatures.
Discussion:
Lingering convection from morning/afternoon storms will be just to
our south in Missouri at 00z Thursday. Attention then turns to
another weak shortwave moving across southern IA, as shown by the
latest RAP and HRRR runs. This wave along with an increasing LLJ and
upper jet support should allow for more storms to develop
overnight. With instability a limiting factor, only expecting a
few elevated storms capable of small hail and heavy rain.
Overnight lows Wednesday night, will drop in the lower to middle
60s.
Thursday-Friday night...unsettled weather pattern to bring periodic
chances of rain, with the region between the upper high across the
southwest CONUS and the closed low in northern Manitoba. Several low
amplitude waves will move through the west-northwest flow aloft
owing to the rain chances. While there is still some timing
differences of these waves, there is some consenus that Friday
afternoon will see the best chances for rain. With the Gulf closed
moisture advection will be low, but with a mature corn crop should
still see enough moisture locally for diurnal storm development.
Severe weather is not out of the question, but still too low
confidence to determine location/threats. High temperatures will
be in the upper 80s and lows in the middle 60s. In addition,
dewpoints increasing into the upper 60s and lower 70s will bring
humid conditions Friday and afternoon heat indices will rise in
the lower to middle 90s.
Saturday-Sunday night...the closed low in Manitoba to drop near the
US-Canada border on Sunday, putting the region into northwest flow
aloft. This will drag a cold front through the area and usher in a
cooler and less humid airmass to the region, along with mostly dry
conditions. The latest deterministic and ensemble data is trending
drier for this period and I expect this trend to continue. While the
forecast still has slight chance PoPs in the afternoon each day, the
1000-500mb RH progs are less than 50% suggesting a drier period.
Highs in the lower 80s and lows in the lower 60s are forecast.
Monday-Monday night...upper low drops further south into the upper
Great Lakes. This will bring an increase in clouds and perhaps some
diurnal showers to the region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 636 PM CDT Tue Jul 11 2023
Main concern for the next 24 hours is potential for thunderstorm
complex to move through eastern Iowa and northwest Illinois
Wednesday morning. Additionally, scattered storms may develop out
ahead of the main line of convection late tonight/early Wed. AM,
especially along and north of I-80. Anticipate conditions to
deteriorate in vicinity of storms to MVFR and possibly brief IFR.
There is potential for the line of storms to bring strong gusty
winds, potentially up to 50+ kts, and very heavy rainfall rates.
Estimated time of arrival for the squall line is between 7 - 9 AM
CDT west of the Mississippi River and 9 - 11 AM CDT to the east.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SHORT TERM...Speck
LONG TERM...Gross
AVIATION...Uttech
Area Forecast Discussion
National Weather Service Grand Rapids MI
1055 PM EDT Tue Jul 11 2023
LATEST UPDATE...
Update
.UPDATE...
Issued at 1054 PM EDT Tue Jul 11 2023
No changes planned to the going forecast tonight. The cold front
is positioned from Southeast Lower Michigan back to the west
across Northern Indiana. Much drier air has pushed into Southwest
Lower Michigan behind the front with dew points in the 40s and 50s
across most of the area. The drier air should keep low clouds and
fog from forming. Models hint at some low clouds over Southeast
Lower, but these should stay east of our area. Skies will
generally be partly cloudy tonight as mid and high clouds stream
into the area. The general trend in cloud cover though will be an
increase through the night.
There is an area of returns on regional radar loops over IA that
is headed our direction but very little is reaching the ground at
this time. We have some scattered pops in the far south, but it
may end up being a bit drier than that. Early 00z models look like
the precipitation on Wednesday may be delayed by 3-6 hours. The
wave driving the precip is in South Dakota at this time, so it has
a ways to go to make it into Southwest Lower Michigan.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 230 PM EDT Tue Jul 11 2023
- Risk for a few storms this evening
The cold front was slipping south southeast through the CWA at
this time. SPC Meso page shows surface based CAPE values up to
over 2000 J/kg near and south of I-96. Deep layer shear showed
values over 35 knots, but that axis of higher values is located
north of the stronger instability. DCAPE was near 1000 J/kg.
Surface convergence was maximized near and east of Lansing, but
some still existed further west. The HRRR keeps most of the area
dry this evening, but RAP and more so the NAM 3km suggest we will
see a scattered to broken line of convection mainly over the
southern half of the CWA. SPC HREF pops remain low, which is where
we will keep them for now. An isolated strong/svr storm is
possible given the above parameters.
- Several rounds of storms possible overnight into Wednesday night
The coupled upper jet is still shown in the models for Wednesday.
PWAT values are progged to climb up over 1.75 inches. Most models
show a 925/850 mb low level jet moving in/forming into southwest
Lower MI during the day. Thus showers and storms will likely
become numerous with some containing locally heavy rain. We could
see showers/storm forming later tonight along the returning
frontal zone but other than the front, there is not much to focus
widespread rain. The low level flow remain convergent into
Wednesday evening as we get on the backside of the wave and the
atmosphere remains unstable. As a result the risk for showers and
storms will persist. Give the focus for multiple rounds of showers
and storm along with increasing precipitation efficiency as PWAT
values climb, we could see locally excessive rainfall.
Deep layer shear is forecast to increase later Wednesday afternoon
into the evening, along with the instability, mainly near and
south of I-96. Thus the afternoon storms could organize with an
increased risk for severe weather. There is still a lot of
uncertainty in terms of how much instability we can generate but
several models like the GFS, ECMWF and NAM 3km suggest we would
top 2000 J/kg of surface based CAPE. Mean MU CAPE values from the
SPC HREF show that we will likely remain under 1000 J/kg of
instability.
.LONG TERM...(Thursday through Tuesday)
Issued at 230 PM EDT Tue Jul 11 2023
- Gradually Drying Out on Thursday from W to E
Upper jet divergence will be exiting the region early Thursday and
low level speed divergence coupled with W/NW trajectories off the
more stable marine layer of Lake Michigan should favor a winding
down of leftover rain from Wednesday night. The best chance for some
scattered showers and thunderstorms will be east of US 131 where
primarily elevated instability will be present. Coverage is expected
to be low at this time.
- Next Round of Storms Late Friday into Saturday
Medium range guidance is indicating the potential for another
coupled upper level jet scenario Friday afternoon into Saturday
morning. This occurs with another 500 mb shortwave vorticity maximum
swinging through and a possible 30 kt LLJ developing. With 40-50 kts
of potential deep layer shear and sufficient SBCAPE, some stronger
thunderstorms may develop during this time frame.
- Additional Risk for Thunderstorms Into Early next Week
Models continue to advertise an anomalously deep upper low over
central Ontario late in the weekend and early next week. This
feature is shown to dive south toward Lake Superior by early next
week. Given the strength of this system with a solid mid level jet
of 50 knots, and the possibility of a surface cold front pushing
through early next week, any sort of destabilizing ahead of this
feature could spell the risk for additional strong to severe
thunderstorms.- Gradually Drying Out on Thursday from W to E
Upper jet divergence will be exiting the region early Thursday and
low level speed divergence coupled with W/NW trajectories off the
more stable marine layer of Lake Michigan should favor a winding
down of leftover rain from Wednesday night. The best chance for some
scattered showers and thunderstorms will be east of US 131 where
primarily elevated instability will be present. Coverage is expected
to be low at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 808 PM EDT Tue Jul 11 2023
Cold front and its associated showers and thunderstorms have
pressed south of the TAF sites as of 00Z, including JXN. The
boundary will sag a bit further south into Northern Indiana and
Ohio tonight before coming back north as a warm front on
Wednesday. We are not expecting low clouds tonight in the wake of
the front as drier air is pushing in and 10-20 knot winds at 1000
feet should keep any fog at bay.
Focus is truly on tomorrow (Wed) now as the warm front lifts back
north bringing low clouds (potentially to IFR levels), showers as
well as thunderstorms. MVFR ceilings should spread into the TAF
sites beginning around 18Z, with IFR potentially developing
around 20Z. We are expecting scattered thunderstorms between
roughly 18Z and 23Z as a weather disturbance rotates through the
area. Worst of the aviation conditions is most likely between 18Z
and 00Z tomorrow afternoon and evening.
&&
.MARINE...
Issued at 912 PM EDT Tue Jul 11 2023
High pressure building into the region this evening has allowed
winds to drop off and that trend will continue even further after
sunset. We have therefore allowed both the Beach Hazards Statement and
Small Craft Advisory to expire as of 900pm. Waves are still around
3 feet at South Haven, but the trend should be down over the
course of the next hour or two.
North winds of 5 to 15 knots this evening should become light and
variable overnight. Winds on Wednesday will likely have an off
shore which will result in minimal waves near the shoreline.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...Duke
SHORT TERM...MJS
LONG TERM...Hoving
AVIATION...Duke
MARINE...Duke
Area Forecast Discussion
National Weather Service Gray ME
1050 PM EDT Tue Jul 11 2023
.SYNOPSIS...
Drying continues tonight into Wednesday morning before a front
brings isolated thunderstorms into the forecast Wednesday
afternoon. Active weather returns on Thursday and persists
through the weekend as upper disturbances and surface fronts
cross the area. These fronts could bring scattered
thunderstorms and periods of heavy rainfall, particularly on
Friday.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
1045 PM...MAde some adjustments to T/Td overnight. Currently,
warmer than expected, and this may be because of moist ground
as well as some weak W flow persisting. Anyway, raised mins by
a degree or two, especially in the S.
745 PM...Just made some minor changes to T/Td/sky based on
current obs for the evening. Looks like all showers have
cleared the mid coast, and it will be mainly clear and dry
through the night with patchy ground and valley fog likely given
the wet ground.
Previously...Per latest RAP analysis, the upper trough axis is
just east of the ME/NH state line with good mixing and drier air
behind it allowing for mostly sunny skies across NH into far
western ME. For the rest of this afternoon into early evening,
have generally kept mentionable showers east of the trough axis
where there is lift and decent enough moisture. This meshes well
with the growth in the cumulus field see on satellite toward
the Augusta and Midcoast regions in addition to a few showers
being seen on latest radar imagery. There may be a storm or two
as well, but the potential seems very low. As the trough keeps
progressing eastward, these areas should see cloud cover start
to diminish as well.
Showers will then diminish this evening with the loss of
daytime heating. With drier air continuing to enter the region,
we`ll have less cloud cover, allowing more radiative cooling.
Models aren`t hitting much in the way of fog tonight, but given
the light winds and how much rain we`ve had recently, patchy fog
seems possible pretty much anywhere. Lows mainly in the 60s, but
northern areas could fall into the 50s.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Weak high pressure that builds in tonight will give way to an
approaching but weakening cold front on Wednesday. This front will
provide focus for scattered showers along with a slight chance of
thunderstorms. Good mixing and warming temperatures aloft will
support highs getting into the 80s, even at the coast with opposing
southwest flow delaying the seabreeze and keeping it from getting
too far inland. A few spots may even hit the low 90s.
These warm temperatures will provide instability and there will be
some shear to work with, but the limiting factor will a pocket of
dry air aloft as seen on forecast soundings from the NAM and GFS.
This dry air should keep convective coverage on the lower side and
short-lived but will also add a small strong to marginally severe
wind gust threat. Brief heavy downpours could accompany showers and
storms but am not overly concerned about any additional hydro
issues with more storm motion.
Not expecting any precip Wednesday night, but we`ll see increasing
cloudiness ahead of a wave that will cross through on Thursday.
Lows again mainly in the 60s with some 50s mixed in across the
north.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Overview: An upper low will remain anchored in the vicinity of
Hudson Bay through this weekend. This feature will keep the
Northeast in the grip of an unsettled pattern into next week.
Upstream blocking associated with a negative NAO will keep this
upper low from making much eastward progress into early next
week. Ensembles do however, suggest upstream blocking will
weaken towards the middle of next week with the NAO trending
towards neutral. This will allow the upper low to shift over
eastern Canada towards the second half of next week with a
slight signal for high pressure moving in towards the end of
next week.
Details: Low pressure over the Great Lakes Thursday morning is
likely to approach upstate NY Thursday afternoon and bring a
front across the Northeast. This front arrives in New Hampshire
late Thursday evening. The environment shows around 500-1000
J/kg of CAPE, and some directional wind shear lasting pretty
well through the night. This type of environment could endorse a
few thunderstorms with some gusty winds along the passing
front. Storms look to occur after peak heating and brings a
degree of uncertainty in storm intensity this evening. As storms
move across New Hampshire due to loss of daylight and as it
approaches the coast and interacts with the marine layer.
Unidirectional flow parallel to the front will support storm
training in New Hampshire Thursday night and into Friday
morning. Flooding is a concern in western and southern NH where
antecedent soils are saturated and flash flood guidance is as
low as 1 inch in 3 hours.
On Friday, another front will approach form the west, and provide a
potentially more robust severe weather threat. At this time, there
is a great amount of uncertainty about timing and general storm
track. However, ensembles suggest a 50% chance of CAPE exceeding
2000 J/kg on Friday afternoon and some wind shear will create an
environment that could be favorable for strong updrafts and intense
thunderstorms. Storms could contain damaging winds.
In addition, a weak low-level jet initiates on Friday. Corfidi
vectors appear to run along the direction of the low-level jet, and
PWATs are expected to exceed 1.5 inches. Just like Thursday,
flooding is also a concern through the day on Friday. The Weather
Prediction Center has much of western and Southern New Hampshire in
a Slight Risk for excessive rainfall on Friday (Day 4). With soils
being saturated, it won`t take much for flooding to occur.
A relentless wet pattern continues into next week. Ensembles are
currently showing solid probabilities for modest rainfall on Sunday,
and perhaps again towards the middle of next week. Some guidance is
showing some drier weather *might* be possible towards the second
half of next week, but time will tell how this guidance evolves over
the next week.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Short Term...Low coverage of showers this afternoon, mainly in
the vicinity of AUG and RKD. These could bring brief
restrictions, but potential is low. Otherwise, generally VFR
into tonight, but given the recent widespread rainfall, light
winds, and clearer skies, fog is certainly possible tonight.
What develops should clear out early to mid morning with VFR the
rest of Wednesday, although a few showers and/or storms are
possible in the afternoon and evening. Mostly VFR through
Wednesday night.
Long Term...
VFR will likely prevail on Thursday. Thursday evening,
cigs and visibility will decrease as SHRA/TSRA move across the
region. Cigs and visibility will most likely stay down through the
day on Friday with thunderstorms in the region. Flight conditions
could improve on Saturday, but conditions should deteriorate on
Sunday as another system crosses the region. &&
&&
.MARINE...
Short Term...Conditions remain below SCA criteria through Wednesday
night. Winds will be out of the west to southwest tonight before
becoming southerly on Wednesday and then more light and variable
Wednesday night. Seas 2-3 ft outside of the bays and 1-2 ft in the
bays.
Long Term...
An low pressure system crosses the region on Thursday night
through Saturday morning. Onshore flow at 15-20kts is expected
through the day on Friday. Otherwise, seas and winds will stay below
SCA criteria although there will be chances for showers and
storms across the waters.
&&
.HYDROLOGY...
Flooded rivers have crested. Elevated levels on tributaries of
the CT River in southwest New Hampshire will continue to drain
into river, but a downward trend is expected to continue. The
Merrimack River will continue to see rises through tonight and
Wednesday, but flooding is not expected. Current gauge obs and
forecast suggest that everything, but the Warner River will fall
below flood this evening, and the Warner should fall below
flood stage in the pre-dawn hours.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
SYNOPSIS...
NEAR TERM...Cempa/Combs
SHORT TERM...Combs
LONG TERM...Palmer/Schroeter
AVIATION...Combs/Palmer
MARINE...Combs/Palmer
HYDROLOGY...
Area Forecast Discussion
National Weather Service Wichita KS
633 PM CDT Tue Jul 11 2023
.SYNOPSIS...
Issued at 345 PM CDT Tue Jul 11 2023
The hottest day of the year appears likely for Wednesday with heat
index values ranging from 105 to 110 degrees with localized values
up to 115 degrees possible. With this being the first big heat day
of the year be sure to take necessary heat precautions. Some good
practices are limiting strenuous outdoor activities, staying
hydrated and taking breaks from the heat as often as possible, and
never leave kids or pets unattended in vehicles.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 345 PM CDT Tue Jul 11 2023
Upper level ridging will briefly build into the Central Plains on
Wednesday ahead of a shortwave trough that will approach the
Northern Plains tonight. A cold front will move southward during the
day on Wednesday and will approach our region sometime Wednesday
afternoon and evening. Timing of the front will have significant
impacts on heat indices and the potential for storms across our CWA.
If the front is faster than expected we could see an enhanced
pooling of moisture across the region which would allow for heat
indices to likely exceed 110 degrees. This scenario could become
more likely if convection that is expected to occur over Nebraska
tonight is stronger than expected and allows for a stronger cold
pool that sends the front further south. An excessive heat warning
would likely be needed for portions of central, south-central, and
southeast Kansas with this scenario. On the other hand, a slower
moving front would allow for most of our region to mix out and could
keep our heat indices closer to 105, which would only support a heat
advisory. Latest RAP and HRRR trends have been slower with the front
so with the additional uncertainty we`ve gone with a heat advisory
for now with the potential for an upgrade with a future forecast
package.
The timing of the front on Wednesday will also influence our storm
chances. A faster solution would allow for a maximization of CAPE,
shear, and lift. With the potential for extremely high CAPE values
well above 3000 j/kg, effective shear of 40kt, and a frontal
boundary for lift, Wednesday could be a conditional severe day with
the potential for significant hail greater than 2" near and just
south of the front. However, with the slower solution of the front
there will likely be not enough forcing and shear for organized
severe storms. A strong to severe pulse storm couldn`t be ruled out
due to some locations potentially reaching their convective
temperatures and high instability in place. For now will just
mention slight PoPs for portions of south-central and southeast
Kansas tomorrow and the chance for strong to severe storms.
.LONG TERM...(Thursday through Tuesday)
Issued at 345 PM CDT Tue Jul 11 2023
The frontal boundary looks to stay draped across central or south-
central Kansas Thursday and Friday with an additional cold front
expected to move southward across the area on Friday afternoon and
night. A few subtle shortwaves will round the ridge on Thursday and
again on Friday, which should allow for a better chance for storms
near the frontal boundary. Instability is expected to remain high
across south-central and southeast Kansas while EFI continues to
show anomalously high shear for this time of year over the same
areas. This will allow for the chance for organized severe storms on
Thursday and Friday.
Global models show an anomalously deep upper low swinging south-
southeastward out of Canada into the Northern Plains and Upper
Mississippi Valley on Sunday into Monday. This could send a much
stronger cold front into the region on Monday. There is support on
the global ensembles, but there is still uncertainty on how far east
the low may track before it dives southward. Stay tuned as we
continue to refine the long term forecast.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 620 PM CDT Tue Jul 11 2023
Main aviation concern will be storm chances Wed evening.
Clear skies and very hot temperatures will be in place on Wed
across the entire area. A cold front will make its down to near
I-70 by the late afternoon and will continue tracking south during
the evening. For now left mention of storms out of the TAFs with
the thinking if anything affects a TAF site, it would likely be
after 00z. If we do end up inserting storms at a TAF site, feel
confident it would most likely be KCNU.
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 74 100 73 94 / 0 10 30 20
Hutchinson 73 100 72 96 / 10 10 20 20
Newton 73 100 72 94 / 10 10 30 20
ElDorado 73 98 72 94 / 10 10 30 20
Winfield-KWLD 74 99 74 95 / 0 0 30 20
Russell 72 99 69 96 / 10 0 10 10
Great Bend 72 99 70 95 / 10 0 10 10
Salina 74 101 71 98 / 10 10 20 10
McPherson 73 100 71 96 / 10 10 20 20
Coffeyville 73 100 75 97 / 10 10 40 30
Chanute 74 102 74 97 / 10 10 50 30
Iola 73 101 72 96 / 10 10 50 30
Parsons-KPPF 73 101 74 97 / 10 10 40 20
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon to 9 PM CDT Wednesday for KSZ032-033-
047>053-067>072-082-083-091>096-098>100.
&&
$$
SYNOPSIS...CRW
SHORT TERM...CRW
LONG TERM...CRW
AVIATION...RBL
Area Forecast Discussion
National Weather Service Louisville KY
941 PM EDT Tue Jul 11 2023
.Forecast Update...
Issued 940 PM EDT Tue Jul 11 2023
Latest nighttime microphysics satellite imagery reveals clear skies
across much of southern Indiana and central Kentucky at this hour,
with a few thin high clouds thus far unsuccessfully trying to push
into southern IN. Clear skies and high pressure in the vicinity has
allowed for the development of a widening range in temperatures
between urban heat islands and cool rural valleys. This suggests
that river valleys stand a fair chance of decoupling enough tonight
for another chance of pre-dawn patchy fog. After comparing tonight`s
setup to continuity from last night, have decided to include patchy
fog mention, but only in sheltered river valleys. Would place
forecast confidence in patchy fog development at 60-70%, because
while the setup generally favors some fog development, we may have
mixed out enough this afternoon such that crossover temps may be
unreachable tomorrow morning.
Will send updated products to reflect addition of fog shortly.
Otherwise, the forecast remains on track at this hour.
&&
.Short Term...(Tonight through Wednesday evening)
Issued at 300 PM EDT Tue Jul 11 2023
Afternoon satellite imagery shows partly to mostly sunny skies
across the region. A Cu field was in full swing across the central
and eastern parts of KY and far SE Indiana. Temperatures were in
the lower 80s in most spots, though a few locations had warmed to 84-
85. For the remainder of the afternoon, no significant weather is
expected.
Moving into this evening and into the overnight, winds will slacken
off toward sunset and skies will become mostly clear once again.
Mostly clear skies are expected overnight. Some patchy valley fog
can`t be ruled out toward dawn on Wednesday. A light southerly flow
is expected overnight and that should keep temps a bit milder than
last night. Overnight lows will be in the lower 60s, though a few
of the cooler valley locations could fall back into the upper 50s.
For Wednesday, southwest flow will continue across the region.
Increasing moisture will bring dewpoints up about 4-6 degrees which
will make it feel a bit more muggy. Skies look to remain mostly
sunny with highs in the 84-89 degree range.
&&
.Long Term...(After midnight Wednesday night through Tuesday)
Issued at 300 PM EDT Tue Jul 11 2023
The forecast remains on track for an active and unsettled weather
pattern for the end of the week and into the weekend. Upper low over
Hudson Bay will slowly sink southward towards the Great Lakes by the
end of the weekend. Upper ridging over the Desert Southwest of AZ/NM
will shift westward and amplify pushing northward into the Pacific
NW over the same time period. These two features will establish a
northwest flow aloft as a series of disturbances move within the
flow as well as a couple of cold front for the end of the week and
weekend. This will result in daily chances of showers and
thunderstorms through the entire long term along with warm and muggy
conditions.
Wednesday night into Thursday morning, some of the hi-res convective
allowing models are indicating the development of a MCS over IA/MO.
The current consensus in the 12z models is this activity develops
and then shifts south into the area of higher instability across
southern MO/northern AR. The one thing we will have to watch is some
models do indicate a ribbon of higher MUCAPE values (1500-2000 J/kg)
setting up across southern IN/central KY overnight into early
Thursday morning. The 12z run of the HRRR was indicating the
possibility of some convection in our southern IN/northern KY areas
daybreak Thursday. Details are still in question but if we were to
see some of this activity, gusty winds and heavy rain would be the
main threat. This is in line with the SPC Day 2 Convective Outlook
which as locations along and west of the I-65 corridor under a
marginal (1 out 5) risk for severe weather Wednesday night into
Thursday morning.
The forecast for Thursday and Thursday night will be depended on
what happens with the potential MCS Wed night/Thu AM. While model
soundings show plenty of instability and some moderate deep layer
shear Thu afternoon/evening, they also indicate some possible
capping. Any activity could be dependent on lingering outflow
boundaries across the area. SPC Day 3 Outlook has a broad MRGL
across the Ohio Valley for Thurs and Thurs Night. Dew points will be
in the mid 70s and PWAT values ranging from 1.75" to 2.00" localized
heavy rain and gusty winds with small hail will be the main threat.
Shower and storm chances continue Friday into the weekend as a
series of embedded disturbances as well as a sfc cold front work
across the Ohio Valley. Continued with the chance to likely PoPs
Friday and Saturday. Weak cold front is prog to pass through late in
the weekend into early next week with little over change in airmass.
For now, will keep chance of showers and storms for Sunday into
early next week with highs remaining in the mid/upper 80s.
&&
.Aviation...(00Z TAF Issuance)
Issued at 712 PM EDT Tue Jul 11 2023
IMPACTS:
- None (VFR conditions)
DISCUSSION:
Light SW winds will transition to light and variable quickly after
sunset tonight with high pressure remaining fairly close to the
region. Scattered cu field should likewise dissipate as the boundary
layer stabilizes overnight. While mostly clear skies and light winds
overnight will help temperatures cool efficiently, forecast low
temps are at least 3-5 degrees above crossover temps from this
afternoon, and dewpoint depressions are expected to be large enough
that morning fog is not expected. After sunrise tomorrow, winds will
again pick up out of the S/SW, with sustained winds generally
between 6-12 kt tomorrow afternoon. Any diurnal cu which develops
should have 5+ kft bases, and VFR conditions are expected throughout
the current forecast period.
CONFIDENCE:
High on all elements.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...CSG
Short Term...MJ
Long Term...BTN
Aviation...CSG
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 333 PM CDT Tue Jul 11 2023
Key Messages:
- Potential MCS to roll through the forecast overnight capable of
producing damaging winds and large hail in addition to locally
heavy rainfall as some storms may train.
- Dry conditions expected from later Wednesday through Thursday
- Small chances for continued precipitation Friday into the
weekend
Elevated showers continue to push east across eastern Nebraska along
weak outflow from ongoing thunderstorms across southern SD. In
addition, a weak frontal boundary extends east/west across
northeastern Nebraska. Aloft, a weak upper trough continues to move
east across southeast South Dakota/northeast Nebraska. These ongoing
showers are expected to continue eastward through the afternoon and
we will continue to watch closely for any vertical development
and/or thunderstorm development through the afternoon. Latest
trends have shown the showers begin to fall apart the farther east
they get, likely due to weak mid-level lapse rates and more cloud
cover farther to the east and this goes along well with latest
CAM guidance. As long as these showers do not become anything
more, a warm/muggy evening looks in store with dewpoints in the
low 70s south of the warm front with more comfortable and cooler
conditions to the north of the boundary.
A cluster of thunderstorms is forecast to develop over western SD
this evening and the latest CAM guidance continues to vary greatly
on the evolution of this thunderstorm activity overnight. For now,
this office is forecasting the overnight activity more closely to
the latest runs of the HRRR which has been more consistent from
run to run. A veering low-level jet should sustain the
thunderstorm activity as it moves across central Nebraska and into
our forecast area. This scenario would bring a line of storms
into our far northwestern counties by 5-6z and would quickly make
a swath of strong winds toward I-80 by 9z. Some of the runs have
been showing 70-90+ knots so all eyes of course on a scenario
such as this. We are hitting messaging hard with the potential for
this scenario to play out during the middle of the night. Behind
the line, a linear extension of thunderstorms is forecast to
extend northwest to southeast and would lead to training and
localized heavy rainfall. If this scenario does play out as the
18z HRRR indicates, we could be seeing isolated flash flooding
potential overnight and into daybreak Wednesday. There are still
many things to play out so forecaster confidence is somewhat
moderate to low on placement and timing.
On Wednesday, thunderstorms are expected to eventually push
southeast of the area toward 15-18z. Surface high pressure will
build in from the north behind this providing a fairly nice day for
much of the region continuing through Thursday. Another round of
thunderstorms looks possible Thursday night into early Friday with
on and off small chances for thunderstorms throughout the
weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 640 PM CDT Tue Jul 11 2023
The primary concern is the timing of a cluster of thunderstorms
moving into eastern Nebraska overnight. Recent weather model
guidance has slowed down the arrival time. Because of this, the
latest forecast has the storms moving in after 6z with very strong
winds a possibility.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...Kern
AVIATION...Pearson