Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/09/23
Area Forecast Discussion
National Weather Service La Crosse WI
1015 PM CDT Tue Aug 8 2023
.DISCUSSION...(This evening through Tuesday)
Issued at 206 PM CDT Tue Aug 8 2023
Key Messages:
- Shower/storm chances (40-50%) mainly north of I-90 Wednesday
afternoon- evening
- Higher probability of showers/storms (60-80%) for more of the
area Thursday night into Friday
- Periodic lower confidence rain chances this weekend and beyond
Wednesday - Wednesday Night Rain Chances...
Split flow aloft will bring bifurcated rain chances to the
forecast area on Wednesday. A prominent shortwave is expected to
cut across Iowa during the day, with some of the latest guidance
suggesting a subtle southward shift. This will keep the highest
rain chances from this first shortwave just to our south, as most
of the CAMs would suggest. Will keep small chances (20 to 30%) for
now across a portion of northeast IA and far southwest WI, but
those may have to be trimmed further back over the next 12 to 24
hours.
Meanwhile, a second wave and associated cold front will sag in
from the north Wednesday afternoon-evening. Still a decent signal
for rain chances (40 to 50%) from these features and it will be the
better opportunity for any rain in the short-term within our
forecast area. Main timeframe for any showers and thunderstorms
looks to come in the 2 to 10pm timeframe per most CAM solutions.
Forecast soundings out ahead of the front show very steep low
level lapse rates developing in the afternoon, but a subtle nose
of warmer temperatures in the mid-levels should help keep
instability and updraft strength mostly in check. RAP suggests
1000-1500 J/kg SBCAPE, but not much wind shear to support
organized storm development. Better chances will be mainly north
of I-90, though latest CAM guidance suggests isolated to scattered
activity may linger along the front as it sags further south
Wednesday night.
Thursday Night - Friday Rain Chances...
Next opportunity for much-needed rain will come Thursday night into
Friday. While questions remain about the strength of the shortwave
trough and therefore don`t want to "oversell" the rain potential,
there is good agreement and decent consistency among GEFS/EPS/CMC
ensemble guidance for a weakening convective complex to pass through
the area. Looks like modest moisture transport takes aim at the
area, but overnight timing is unfavorable for much instability to be
in play. Meager wind shear is also a limiting factor for organized
confection. Better potential for any overlap between instability and
shear would be west of the Mississippi River. Overall ensemble
consensus suggests a 60 to 80+% probability for most of the area to
see at least 0.1 inch of rain from this complex. Higher amounts
would be likely within any thunderstorms.
Weekend and Beyond...
Still a somewhat active quasi-northwest flow pattern aloft that
brings a few additional shortwaves through the region over the
weekend into early next week. Low confidence in any attendant rain
chances, though Sunday night into Monday brings the strongest wave
through the area and greatest potential for rain of the later
forecast periods. Temperatures look to remain seasonable for heading
into mid-August.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1015 PM CDT Tue Aug 8 2023
CIGS: sct-bkn clouds overnight-Wed. Could see a thicker BKN VFR cig
moving into Wed evening, associated with an upper level
shortwave/sfc front.
WX/vsby: no impacts through Wed morning. Some of the short term
guidance triggers a few showers/storms along a sfc front late
afternoon, sagging in from the north. Spotty, and could run out of
daytime heating/instability before forcing could near the TAF sites.
Will leave out of the forecast for now.
WINDS: mostly light west/southwest through the day Wed. KLSE could
decouple overnight and swing to southeast for direction until mixing
kicks in later Wed morning. Passage of a cold front Wed evening will
swing winds to the northwest, but still looks to stay sub 10 kts.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...Kurz
AVIATION...Rieck
Area Forecast Discussion
National Weather Service Boston/Norton MA
1000 PM EDT Tue Aug 8 2023
.SYNOPSIS...
Remaining showers come to an end this evening. Sunny, warm and
dry for Wednesday. Unsettled conditions back to the region
Thursday, and then again over this weekend into early next
week. The highest chances for rain being Thursday afternoon,
with generally scattered afternoon showers or thunderstorms over
this weekend. An increased risk for showers and thunderstorms
early next week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Mainly minor tweaks this evening to keep up with observed
trends. The loss of daytime heating has taken the punch out of
the convection late this evening. Still, quite a few of the
near-term guidance, namely the latest RAP and the 18Z 3-kn NAM,
still depicted isolated showers through the night. Based on what
is observed now, thinking the RAP is overdone with its coverage,
and the 3-km NAM not quite as much. Did like the HRRR and latest
NatonalBlend guidance best. As such, those two pieces of
guidance were used to trend the forecast overnight. The greatest
risk for any showers looks to be right where we don`t want it,
across northeast MA. Fortunately, not looking at heavy rainfall
amounts, still certain sections can only handle some much
additional rainfall.
Very minor tweaks to temperatures. A cold front had finally
reached eastern MA, and should be moving offshore towards
midnight, albeit a little later across the Cape and islands.
Dewpoints were only dropping into the lower to mid 60s, so that
would be the floor for low temperatures for most.
8 PM Update...
Showers have certainly become more scattered at this hour, but
some of the strongest cells, particularly across Essex/Middlesex
counties are still robust enough to support lightning. While
there will be a general drying trend overnight, some showers are
possible through daybreak tomorrow, with the highest confidence
in coverage again north of Boston and from Fitchburg, east.
Slow moving cold front is currently draped across central MA,
with winds turning westerly from Worcester, west, and remaining
SE across eastern MA and portions of RI, but we expect winds
will shift W/NW across these areas over the next two to three
hours.
Previous Update...
Still some surface based instability, but as discussed earlier,
some subsidence aloft should keep the development of
thunderstorms to a minimum, so expecting just scattered showers
for the most part. Expect convective activity to wane quickly
after sunset. Will have a weak front pass across the region by
mid evening, with a windshift to the west, resulting in a quiet
overnight period.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
All guidance still showing a dry day tomorrow. Plenty of sun
will promote excellent boundary layer mixing, perhaps up to
800mb (6000ft or so). We should be able to tap into some
stronger winds aloft of 20-30kt to result in a breezy day
tomorrow. Given all the weather today, I stuck with the model
blend for tomorrow`s forecast. Wednesday night should be
continued quiet. With rather low dewpoints, and the winds
expected to drop off after midnight, it should be a good night
to open up the windows. Lows in the 50s to lower 60s.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Highlights
* Unsettled conditions into this weekend
Overall synoptic pattern trending more active as we head into
the second half of this week into this weekend. A mid level low
should move over Ontario and Quebec Provinces in Canada towards
Thursday. The result of this is a shifting of the main mid level
steering flow to be right over southern New England into this
weekend. Essentially, our region will be impacted by just about
every mid level shortwave passing through the larger flow. Thus,
looking at a prolonged risk for at least some showers, and
possibly some thunderstorms, at times during this portion of
the forecast. It will not be raining this entire time. In fact,
am thinking we may get through most of Friday and Saturday rain-
free, at least for now. The timing of these smaller features in
near zonal flow is one of the sources of error. The timing may
shift with later forecasts.
Another mid level low moving farther south over the Great Lakes
early next week, will lead to a more favorable pattern for
showers and possible thunderstorms.
Anticipating near normal temperatures through this portion of
the forecast, expect perhaps for some below normal low
temperatures Friday night.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z update...
Overall high confidence
Tonight...
Generally VFR tonight, though scattered showers and
thunderstorms may briefly degrade cigs and vsby to MVFR,
especially at terminals across central and eastern, southern New
England. Wind shift in progress currently from the SW to the
W/NW. All terminals to shift to the NW by 05Z. Winds remain
gusty overnight, generally 10-15kt with gusts to 20kt.
Wednesday and Wednesday night...
Gusty NW flow prevails again for Wednesday with gusts to 25kt
possible. Clearing trend, with VFR all day. Mostly sunny skies
expected region wide by Wednesday afternoon. VFR persists into
Wednesday night as winds calm slightly, generally 5-10kt.
KBOS TAF...High Confidence. VFR through the period, very low
risk of shower through 06Z, which may briefly degrade cigs to
MVFR. Otherwise, winds shift from SW to W/NW by 02Z tonight.
Gusty conditions persist through late Wednesday, generally
10-15G25kt. Winds subside to 5-10kt overnight Wednesday.
KBDL TAF...High confidence in TAF.
VFR through the period, though risk of VCTS through 06Z, which
may briefly degrade cigs to MVFR. Otherwise, winds shift from SW
to W/NW by 02Z tonight. Gusty conditions persist through late
Wednesday, generally 10-15G25kt. Winds subside to 5-10kt
overnight Wednesday.
Outlook /Thursday through Sunday/...
Thursday: Mainly VFR, with local IFR possible. Chance SHRA,
isolated TSRA.
Thursday Night: MVFR/IFR conditions possible. Breezy. Chance
SHRA, isolated TSRA.
Friday: VFR. Windy with local gusts up to 30 kt.
Friday Night: VFR. Breezy.
Saturday: VFR.
Saturday Night: Mainly VFR, with areas MVFR possible. Slight
chance SHRA.
Sunday: Mainly VFR, with areas MVFR possible. Breezy. Slight
chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Based on latest reports, seas were taking longer to subside
across the RI coastal waters. Reissued Small Craft Advisories
for these waters through the overnight. It is possible that
these advisories will need to be extended in time with later
forecasts. Will let the next shift take a closer look.
Previous Discussion...
Will continue the Small Craft Advisory for the outer waters
overnight due to marginal wind and sea conditions, may need to
extend that advisory into Wednesday, especially across the
southern waters, as waves may take their time to subside. Weak
cold front pushes across the waters tonight with winds turning
more westerly behind that front with frequent gust 20-25kt.
Winds start to subside later Wednesday.
Outlook /Thursday through Sunday/...
Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers, isolated thunderstorms.
Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Chance of rain showers, isolated
thunderstorms. Local visibility 1 to 3 nm.
Friday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Saturday: Winds less than 25 kt.
Saturday Night through Sunday: Winds less than 25 kt. Slight
chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 AM EDT Wednesday for ANZ235-237-
250-254>256.
&&
$$
SYNOPSIS...Belk
NEAR TERM...Belk/KS/Nash
SHORT TERM...Nash
LONG TERM...Belk
AVIATION...Belk/KS/Nash
MARINE...Belk/Nash
Area Forecast Discussion
National Weather Service Columbia SC
749 PM EDT Tue Aug 8 2023
.SYNOPSIS...
A few showers this evening mainly in the CSRA near a stalled
frontal boundary. A dry day is expected on Wednesday as high
pressure passes overhead. A series of potent shortwaves bring
the risk for showers and thunderstorms on Thursday. Diurnally
driven convection returns Friday and into the weekend with
typical summertime heat.
&&
.NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/...
At 23z, the frontal boundary appears to be stationary across the
southeast Midlands. Instability is moderate near the
front...especially in east-central GA. Deep layer shear is
strong in the CSRA with effective shear near 45 kt based on rap
analysis. Based on the latest radar trends, the strong to
severe thunderstorms are expected to remain just to the south of
Burke county early this evening. However, stratiform rain is
moving toward the CSRA so raised pops to chance there.
A strong short wave trough is evident on water vapor over
western GA/AL. This short wave will move through the region this
evening and should be east by around 06z. Lift appears to be
increasing in east-central GA ahead of the short wave, so went
with slight chance pops mainly this evening into the Midlands as
the short wave approaches. Despite dew points in the 60s
overnight in mainly areas, low temps in the low 70s appears on
target with considerable high clouds to limit nocturnal cooling.
&&
.SHORT TERM /7 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Wednesday and Wednesday Night: Wednesday is expected to be
another dry day for most of the forecast area. PWATs are
forecast to decrease into the 1" to 1.25" range as surface high
pressure passes overhead. The latest guidance suggests clouds
will increase later in the day associated with a decaying MCS to
our west. Keeping the region dry during the daytime hours as any
precipitation should hold off until the overnight. Highs will
generally be in the lower 90s. The aforementioned MCS should
continue to weaken as it approaches us Wednesday evening
therefore opted to keep PoPs out of the forecast until near
daybreak with the next system approaches. The clouds limit
cooling Wednesday Night with forecast lows in the lower to mid
70s.
Thursday and Thursday Night: A series of shortwaves will move
through the forecast area on Thursday bringing a renewed threat
for showers and thunderstorms. Showers associated with the first
shortwave are expected to move into the northwestern CWA
Tuesday morning but there is disagreement in the guidance
regarding how far into the forecast area the rain will reach.
The SPC Day 3 outlook places the entire CWA in a Marginal (1/5)
risk for severe weather and given the upper-level support, the
main inhibiting factor will likely be the extent of the clouds
and precipitation in the morning. Temperatures are also
questionable given the morning rain and cloudiness. Highs
currently range from the lower to mid 90s. Clouds and showers
could linger into Thursday Night with forecast lows in the lower
to mid 70s.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
A more typical summer pattern sets up during the extended
period. Heights gradually rise through the weekend as the
potent ridge over the Western CONUS edges eastward. The
combination of high temperatures in the mid-90s and dewpoints in
the mid-70s will result in Heat Index values in excess of 100
degrees. Will need to access conditions as we get closer to
determine if a Heat Advisory will be needed for some or all of
the CWA. In terms of precipitation, expecting afternoon and
evening convective chances primarily focused along the sea
breeze and any other mesoscale boundaries. Temperatures through
the period will be above normal.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
With a frontal boundary to the south some light rain will spread
into the CSRA this evening which may bring visibility
reductions to AGS and DNL. The rain is expected to diminish
during the evening with sites returning to VFR by 03Z.
A shortwave trough will move across the tonight. Expect an
increase in mid and upper level clouds and possibly a few
showers overnight. Confidence is low but the timing would be
between 03z and 09z. With crossover temperatures in the mid 60s
and increasing cloud cover the fog threat appears low. Winds
will pick up out of the west on Wednesday morning but will not
be as breezy as the previous day. With drier air over the area
convective activity should be minimal but we can`t rule out an
isolated shower.
EXTENDED AVIATION OUTLOOK...Restrictions possible in generally
diurnal convection Thursday through the extended.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Cheyenne WY
527 PM MDT Tue Aug 8 2023
.SHORT TERM...(Today through Wednesday night)
Issued at 215 PM MDT Tue Aug 8 2023
...SEVERE THUNDERSTORMS expected this afternoon and this evening
for most of southeast Wyoming and western Nebraska...
Severe Thunderstorm Watch in effect until 1000 PM MDT for far
southeast Wyoming (Laramie, Goshen, and Niobrara Counties) and all
of western Nebraska.
Primary forecast concern will be over the next 12 hours as a
potent shortwave trough, currently over western Wyoming, pushes
eastward over the state. This feature is a bit of an anomaly this
time of the year with 500mb heights 3 to 4 standard deviations
below seasonal averages. In fact, this same trough was responsible
for some mountain snowfall across northwest Wyoming last night
and early this morning. Current KCYS radar loop shows lines and
single cell discrete thunderstorms developing at this hour across
most of the area with another round already pushing into Carbon
County. Looks to be a busy afternoon and evening with multiple
rounds of strong to possibly severe thunderstorms. The first
round, currently developing across far eastern Wyoming and the
central/southern Nebraska panhandle, is expected to be the primary
large hail/tornado threat while the 2nd round (further west
coming into Carbon County) should be the primary strong wind
threat. Can not rule out a few tornadoes with 0-1km boundary layer
helicity around 150 to 250, but any additional outflow boundaries
may enhance this potential through early this evening. The main
area of interest for tornadoes is near the
Nebraska/Wyoming/Colorado triple point and points east due to the
stationary front in that generally location and winds backing into
the east towards Sidney Nebraska.
Although the Severe Thunderstorm Watch is in effect until 10 PM,
one additional concern is how many lines of thunderstorms are
expected to form further west and push east across the area late
this evening. HRRR and NAMNEST, which are initializing pretty good
so far, show some of this activity lingering past midnight...just
as the trough axis pushes through the area. Increased POP through
midnight along and east of the I-25 corridor.
Thankfully, once this upper level trough swings through the area
later tonight/early Wednesday morning, weather conditions will
quickly improve for Wednesday. All models show stable conditions
in the low to midlevels with high LI`s above +2c and a solid
temperatures inversion just above 700mb. Strong subsidence behind
the potent shortwave will likely be enough to prevent deep
convection through the afternoon and evening hours.
.LONG TERM...(Thursday through Monday)
Issued at 300 AM MDT Tue Aug 8 2023
Starting off Thursday...we have upper level ridging over the CWA.
A low pressure system is tracking across the southern Alberta and
Saskatchewan Provinces Thursday morning with a cold front draped
across southern Montana. Ahead of this front...looking at breezy
wind conditions over the CWA. GFS showing 30-35kts at 700 and
750mbs...so had to increase winds over guidance across southeast
Wyoming.
Surface cold front never really makes it through our CWA Thursday
night into Friday. It looks to wash out over southern Montana
Friday as parent upper low tracks east. Friday looks mainly dry.
Layered PWATS over southeast Wyoming down under a half inch...with
0.7 inch in the Panhandle. The exception may be some showers over
the Snowy and Sierra Madre Ranges in southern Carbon County.
GFS forecasting increased PWATS over the CWA for the weekend. So
afternoon and evening convection looks to return. By Saturday
afternoon...PWATS in the Panhandle back up near 1.25 inches and
near an inch along the Laramie Range. At the same time...a
backdoor cold front looks to move into the area from the northeast
Sunday. Could be looking at severe thunderstorms once again
Saturday and Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 522 PM MDT Tue Aug 8 2023
A passing weather disturbance will produce isolated to scattered strong
thunderstorms through early this evening, especially for far
southeast Wyoming and the Nebraska Panhandle.
Wyoming TAFS...Isolated thunderstorms will produce gusty winds,
primarily at Rawlins through 01Z, with wind gusts to 45 knots,
visibilities to 2 miles and ceilings near 3500 feet AGL.
Thunderstorms will be in the vicinity of Laramie and Cheyenne
until 01Z. Otherwise, expect scattered to broken clouds around
10000 feet AGL.
Nebraska TAFS...Occasional thunderstorms will affect the terminals
through 02Z, producing wind gusts to 50 knots, visibilities of
1 to 4 miles and ceilings from 2500 to 5000 feet AGL. Otherwise,
scattered to broken clouds around 10000 feet AGL will prevail.
&&
.FIRE WEATHER...
Issued at 113 PM MDT Tue Aug 8 2023
No fire weather concerns through the rest of the week due
to recent wetting rainfall across many areas, cooler than normal
temperatures, and daytime minimum humidities above 20 percent.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...TJT
LONG TERM...GCC
AVIATION...RUBIN
FIRE WEATHER...TJT
Area Forecast Discussion
National Weather Service Duluth MN
947 PM CDT Tue Aug 8 2023
.UPDATE...
Issued at 946 PM CDT Tue Aug 8 2023
Thunderstorm coverage has decreased pretty dramatically after
sunset this evening, though there has been some new convection in
the past hour in Koochiching county around the cold front and
coinciding with an area of ~45 kt of effective bulk shear.
However, instability is quickly diminishing and so are those
storms. Strong to severe storms are not expected for the rest of
the night, though isolated showers and storms lingering from pre-
existing outflow boundaries and weak instability will be possible.
&&
.DISCUSSION...(This evening through Monday)
Issued at 354 PM CDT Tue Aug 8 2023
Key Messages:
1. Scattered showers and thunderstorms this afternoon into
tonight, with strong to severe storms (large hail/wind gusts to 60
mph) between now and 10 PM.
2. Lingering showers/storms across NW WI Wednesday. Slightly
cooler weather returns starting Wednesday.
3. Additional shower and thunderstorm chances from late Thursday through
Friday. Additional severe thunderstorm potential Thursday evening
and again on Friday.
Rest of Today/Evening:
Scattered diurnal storms have developed across the Arrowhead
region in an area of a surface trough where the atmosphere has
become uncapped. MLCAPE around 400-700 J/kg and effective bulk
shear around 20-25 knots has led to some of these pulse storms
become strong to marginally severe, albeit short-lived. Generally
seeing most of these storm hazards being wind gusts in the 30-40
mph range, hail to the size of pennies, frequent lightning, and
locally heavy rain, though a few more robust cells could see wind
gusts up to 60 mph and hail to the size of quarters.
As we get into the 4 PM to 7 PM timeframe, MLCAPE maxes out around
500-1000 J/kg along with improving effective shear to 25 to 40
knots in portions of north-central and northeastern Minnesota as a
shortwave trough currently over southern Manitoba and northwest
Minnesota moves into the northern reaches of the CWA. This
combination of shear and instability would support more
multicellular, less vertically upright thunderstorms developing
along a southeastward moving cold front with maximum hail sizes up
to a quarter to half dollar in size as well as wind gusts up to 60
mph. Secondary threats include frequent lightning and efficient,
localized higher rainfall rates that could lead to localized
flooding. Storms along the front will continue to push southeast
into this evening into the Iron Range and Arrowhead regions,
though severe potential drops off around 9 to 10 pm as instability
decreases this evening. Therefore, expect the storm intensities to
gradually weaken as the cold front approaches the Brainerd Lakes
into Twin Ports late this evening into the overnight hours.
Outside of thunderstorms, some hazy conditions near the surface
will continue to linger given some near-surface smoke from
Canadian wildfires. An Air Quality Alert remains in effect across
Minnesota portions of our CWA through Noon CDT on Wednesday for
poorer air-quality associated with this near-surface smoke.
Wednesday:
The cold front continues to slide southward into NW Wisconsin by
Wednesday morning, with HRRR smoke guidance indicating near-
surface smoke conditions will improve for areas behind the front.
Some uncertainty amongst hi-res model guidance with regard to
coverage and duration of convection Wednesday, but a lingering
threat for scattered showers and thunderstorms should continue
across portions of NW Wisconsin during the morning and afternoon
Wednesday. May see the potential for a few stronger storms
Wednesday afternoon across our most southern tier of counties in
NW Wisconsin given bulk shear around 30-40 knots and 400-900 J/kg
of MLCAPE. However, if the front moves through the area faster
than currently forecast, this area of stronger storm potential
may remain south of our CWA completely.
Thursday - Friday:
Slightly cooler weather with highs in the 70s arrives for the late
part of the week. Northwesterly flow aloft on Thursday will keep
dry conditions across the area through most of the day before an
additional upper-level trough and associated vorticity move across
southern Manitoba and far SW Ontario into northeastern Minnesota
by late Thursday into Friday. Global ensemble guidance has come
into better agreement regarding the timing and better forcing with
this feature, so have kept the NBM PoPs of 60-80% in place during
this timeframe. Coverage looks to be more widespread than today`s
storms, but any rainfall, while likely beneficial, won`t be enough
to alleviate drought conditions. Severe weather remains possible
with this next round of storms given the general CAPE/Shear
combinations coming out of the GFS/ECMWF ensemble members,
particularly on Friday afternoon and evening. Will need to monitor
this situation closely as it gets into the range of higher
resolution model guidance in the next 24-36 hours.
This Weekend - Mid Next Week:
A generally active pattern this weekend into early next week as a
series of shortwaves moves across the northern Plains and
Wisconsin, with the first occurring on Saturday night into Sunday
leading to additional showers and thunderstorm potential during
that timeframe. Global ensembles then diverge into next week with
regard to the timing of these shortwaves and associated showers
and thunderstorms, leading to a lower confidence in the forecast
PoPs and temperatures.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 704 PM CDT Tue Aug 8 2023
Continuing to see scattered showers/storms affect far northern and
northeastern MN as of 00Z. The intensity on these storms should
continue to weaken through the evening as the storms slowly
progress southeastward ahead of an approaching cold front. Main
concern for showers and vicinity TS this evening are BRD and HIB,
with brief MVFR visibilities possible if any shower or storm
moves directly over the TAF site. Severe weather is no longer
expected this evening. May still see some sporadic showers
overnight, mainly at HIB and BRD. The patchy fog is still possible
tonight, but left out of current TAF mention due to lower
confidence amid lingering cloud cover.
Winds will weaken and turn light out of the west tonight ahead of
the front and northwest behind the cold front as the front slowly
sinks south through the area. Should see winds turn completely
northwesterly by Wednesday morning. Additional showers and
possibly a few storms return again for HYR on Wednesday morning
into afternoon as the front pushes south across Wisconsin.
&&
.MARINE...
Issued at 354 PM CDT Tue Aug 8 2023
Occasional wind gusts today to around 15 to 20 knots over the
North Shore Waters and waves of 1 to 3 feet outside of
thunderstorms. However, ongoing scattered thunderstorms over the
SW arm of Lake Superior could lead to erratic gusts up to 25 to 35
knots at times as well as hail up to penny size and frequent
lightning the rest of this afternoon into evening.
Wind gusts turn northwesterly at around 10 knots with gusts up to
around 15 knots during the day on Wednesday with waves heights of
less than 2 feet before turning light overnight. Winds increase
again out of the south to southwest by Thursday afternoon, with
gusts to 10 to 15 knots and wave heights around 1-2 feet along the
north shore.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 58 76 51 75 / 30 10 10 0
INL 51 70 47 71 / 40 10 10 10
BRD 58 79 51 77 / 50 20 10 10
HYR 57 80 49 77 / 30 40 30 0
ASX 60 80 53 75 / 40 30 10 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
UPDATE...JDS
DISCUSSION...Rothstein
AVIATION...Rothstein
MARINE...Rothstein
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
627 PM CDT Tue Aug 8 2023
.Discussion...
Issued at 407 PM CDT TUE AUG 8 2023
Key Messages:
- Thunderstorms Early Wednesday Morning; Severe Possible
- Scattered Redevelopment Wednesday Afternoon Possible
- Temperatures Upper 80s This Week
Discussion:
Quasi-zonal flow characterizes the mid-level flow this afternoon
with a few notable short-waves. The first is over the Northwest
Great Lakes Region and will not have much influence over the pattern
for our area. The second is vort max currently moving into the High
Plains of Nebraska. This feature will be the one to watch. In the
short term for this evening, eastern and western Missouri have
actually seen subtle H5 height rises and weak subsidence that have
kept skies mostly clear. There is a weak jet max that has moved
eastward but helped to force a few weak showers in northern Missouri
early this afternoon. With insolation, expecting boundary layer
destabilization to result in some cumulus clouds late this afternoon
but with no other forcing will not be expected to result in
widespread showers. Therefore, POPs remain dry through the remainder
of the evening.
Attention turns to the short-wave trough and vort max coming out of
the High Plains. Over the past 24 hours, increasing dCVA over the
High Plains and Front Range has resulted in surface cyclogenesis,
and as of late this afternoon is analyzed over eastern Colorado.
During this evening, H5 height falls will start across the Central
Plains developing numerous thunderstorms. Eventually the low-level
jet ramps up this evening and most of the convection will congeal by
the time it reaches south-central Nebraska and central Kansas. The
timing of when a potential MCS or line of storms enters our forecast
area has been difficult to pinpoint. The primary short-wave has
already developed and can be seen on water-vapor imagery just east
of the Rockies. However, there is potential for vorticity to break
off from the main wave, and develop a secondary wave ahead of it
that may provide enough kinematic forcing for additional
development, and thus moves activity into the area earlier. However,
the 12z HRRR slowed down the eastern progression of the storm
cluster by a few hours, and the 18z HRRR has slowed this even
further, now bringing in the line closer to 12z Wednesday morning.
There is potential for the surface troughing to expand eastward into
the region ahead of the primary short-wave, which may be able to
increase convergence a few hours earlier on Wednesday morning. This
may also line up with weak isentropic ascent and a few WAA showers,
especially south of Interstate 70. However, if there is no secondary
short-wave or vort max, the lower troposphere will be too capped to
support any convection. As the MCS or line of storms move eastward,
RAP soundings indicate mid-level lapse rates around 8.0 C/km,
meaning for elevated parcels there will not be much inhibition as
long as they are above the boundary layer. HREF mean MUCAPE values
range around 1500-2000 J/kg across our area and back into Central
Kansas. In addition, deep layer shear will increase in the presence
the main short-wave, with 0-6km bulk shear values around 40-45 kts
and 0-8km closer to 50 kts. Storms though will likely not realize
much in the 0-1km layer, but with EBWD around 35-40 kts should still
support storm organization. Overall, the hodograph shape is
relatively straight. Once the storms congeal, would expect an MCS
storm mode remain in cold-pool/ambient shear vorticity balance for
several hours. Confidence is medium that this holds up as it
approaches the KS-MO stateline. Most of the CAM solutions (even with
the timing discrepancies) has the MCS decaying as it gets east of
Interstate 35. If it releases a strong outflow boundary and falls
out of balance, the system may decay bringing just heavier rain
showers to much of eastern Kansas and western Missouri. If it holds
up though, DCAPE values off of RAP soundings are around 1000 J/kg
with decent theta-e deficits between 900-700mb, which could support
downdrafts capable of damaging winds. While there is stable layer it
would have to punch through, this layer is rather shallow. Isolated
pockets of hail are possible given the stronger wind shear available
and healthy mid-level lapse rates, though with freezing levels near
15kft would expect a large degree of melting.
The strongest portion of storms simulated in High Resolution
guidance exits the area or dissipates around 15-16z, though may
leave lingering stratiform rain shield that lasts longer especially
if cold-pool vorticity becomes most dominant. The question than
becomes redevelopment potential during Wednesday afternoon into the
early evening. If an MCS is able to get ahead of the main short-
wave, there may still be a mid-level vort max and surface cyclone
over the Central Plains that could provide additional lift. 0-6km
bulk wind shear will be quite strong in the presence of this vort
max which could support storm organization. However, if there is an
expansive stratiform field, this may greatly limit boundary layer
recovery and overall instability parameters on Wednesday. A stalled
remnant outflow boundary though could help overcome this if one is
present. Given these factors, redevelopment for most of the forecast
area is uncertain. Current RAP/HRRR solutions have an area of
stronger surface troughing closer to Interstate 44 and into the
Ozarks Region that might be able to do more even if thermodynamic
recovery is weak. This also concentrates an H5 vort max further
south of area. However, there are solutions such as the NAM Nest
which keep the forcing further northward and impact our area later
into Wednesday afternoon. Given the current trends amongst most of
the HREF members, would think that south of Interstate 70 is the
most favorable for redevelopment Wednesday afternoon, but these
chances could certainly shift if the morning activity turns out
differently than currently progged.
For the remainder of the week, mid-level flow remains in a quasi-
zonal pattern. There are multiple PV anomalies across North America
that will likely send a few enhanced jet maxes that should present
additional rain shower and thunderstorm chances. Temperatures will be
in the mid to upper 80s for most of this week, with modest increases
in humidity but should not be nearly as oppressive as temperature and
dewpoint conditions experienced toward the end of July and the first
week of August.
&&
.Aviation...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 618 PM CDT TUE AUG 8 2023
Cluster of thunderstorms across Kansas is expected to develop into
a complex affecting the region after 11Z Wednesday. Potential for
gusty winds with the complex, as well as locally heavy rain.
Complex may create outflow, which would be the focus for renewed
thunderstorms Monday afternoon across the region. Best chances for
outflow are along and south of I-70. Areas farther north,
including KSTJ terminal will likely experience MVFR status behind
the storms.
&&
.Hydrology...
Issued at 407 PM CDT TUE AUG 8 2023
Locally heavy rainfall is expected with showers and thunderstorm
activity Wednesday morning. Current HREF mean has a widespread 0.75
to 1.00 inch of QPF across most of the forecast area, with a band of
1.00 to 1.50 inches from the KC metro and southeastward. This higher
stripe seems to be centered around where an MCS is likely to track
and decay with eventual redevelopment along an outflow. The
probability matched mean values from the 12z HREF projects values of
2.00 to 2.50 inches from areas south of the Interstate 435 loop
toward the Ozarks Region. The good news is that this heaviest band
is forecast to miss the areas east of Hwy 65 in our counties that
were hit hard last week. However, 1.00 inch of rainfall in our
eastern counties could still result in hydro issues, including river
flooding and areal flooding. For synoptic scale ensembles such as
the GEFS, probabilities for exceeding 0.50 inches is around 40
percent for most of the area. This likely is coming in lower than
the HREF, as the secondary short-wave ahead of the main is being
resolved by some of the non-CAM models but is not producing much
QPF. Given the uncertainty of how far early morning convection
travels, and that the heaviest QPF is not over the same area as last
week, have not issued any Flood Watch products on this shift.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&
$$
Discussion...Krull
Aviation...BT
Hydrology...Krull
Area Forecast Discussion
National Weather Service Grand Forks ND
855 PM CDT Tue Aug 8 2023
.UPDATE...
Issued at 855 PM CDT Tue Aug 8 2023
Low levels are decoupling and MLCIN has increased, with
hoers/thunderstorms becoming weaker and elevated where they are
tracking along the frontal zone. This matches the expected trend
with sunset and while shower/storms may remain possible near the
front through Midnight, the severe threat is greatly diminished.
Still, a few brief updrafts capable of smaller hail will remain
possible due to lingering elevated instability/forcing/increased
shear. I made some adjustments to capture coverage/trends with
this update, otherwise forecast is on track. Smoke has been
reported behind the front, but so far vis has been 5-9sm. I`ve
left patchy smoke in the forecast for now.
UPDATE Issued at 659 PM CDT Tue Aug 8 2023
The slow moving cold front continues to progress over our
southern CWA with clusters of showers/thunderstorms which are
tracking west to east. Instability along the frontal zone is
still decent (1000-2000 J/G MLCAPE) and effective shear is
starting to increase closer to the frontal zone (25-35kt) most
activity is showing marginal/pulse type behavior, but there had
been a few discrete cells with brief supercellular
characteristics. Due to enhanced low level shear/vorticity there
was a window before deep layer shear increased where landspout
type tornadoes were possible but with the sun starting to set/low
levels start to decouple this threat may be waning. General trend
should be for stabilization to occur overall with all activity as
RAP indicates, though elevated showers/storms (non-severe) may
linger beyond sunset as the front moves out of our CWA.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 332 PM CDT Tue Aug 8 2023
Convective strength this afternoon and evening will be the main
challenges for the period.
Upper low continues to spin over southern Manitoba/Ontario, with a
decent vort coming down and bringing a cold front for our CWA. Pre-
frontal trough has been swinging through east central ND and
northwestern MN, with thunderstorms across much of our southern
and eastern CWA. The first round that developed along the Highway
2 corridor earlier has nearly fizzled out, but some additional
storms have been developing further south near Highway 200 and
Highway 10 where ML CAPE values have been getting to around 2000
J/kg. Effective bulk shear is around 20 kts with the better values
further north, and low level shear is even less impressive,
around 10 kts. Cannot completely rule out an isolated storm
pulsing upward and producing some marginal hail around an inch or
a quick downburst, but not very impressed with widespread severe
risk at this point. Storms will continue into this evening as the
main cold front comes down into region. Some smoke getting mixed
down behind the frontal boundary, so will keep patchy mention
going.
Northwesterly flow will continue into tomorrow, with a reinforcing
vort on the backside of the low moving through Canada. CAMs as
well as global models have some shower activity tomorrow as the
vort moves through, so have some 20 to 30 POPs going. Instability
behind the cold front is pretty weak, so thunder chances will be
mainly near the SD border. Overall, Wednesday should be cool and
breezy with highs in the 70s and chances for showers.
.LONG TERM...(Thursday through Tuesday)
Issued at 332 PM CDT Tue Aug 8 2023
Thursday and Friday...A fairly vigorous shortwave is expected to
move through southern Canada and ND Thursday, with a another
reinforcing shortwave coming down out of Canada on Friday as the
first system pulls east. Southeasterly winds at the surface get
going on Thursday ahead of the surface trough which will swing
through Thursday night. Many of the ensemble members are not too
impressive with surface based CAPE over our CWA except in a very
limited area near the SD border. There is some sign of elevated CAPE
around 1500 J/kg possible during the overnight hours as the system
swings through, along with some 40 to 50 kts of deep layer bulk
shear. Of course, that is only one model solution and even the
elevated instability is fairly conditional, but think there could be
some isolated severe cells possible Thursday. There is a strong
signal from the GEFS and ECMWF, and NBM probabilities of at least a
tenth of an inch in 12 hours is at least 60 to 70 percent.
Precipitation chances continue to be fairly decent into Friday as
the reinforcing shortwave comes through. The NBM mean surface based
CAPE is even higher Friday afternoon than Thursday for portions of
our CWA, but seems odd with northwesterly flow at the surface on the
backside of the surface trough. Will continue to monitor as the
period grows closer.
Saturday through Tuesday...Northwesterly flow returns with various
weak shortwaves coming through. There isn`t much in the clusters to
hang our hat on and predictability is pretty low for these kind
of features his far out. Near seasonal temps and POPs in the 20 to
50 percent range as various shortwaves move through seems
reasonable.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 659 PM CDT Tue Aug 8 2023
A front continues to move over southeast ND and west central MN,
with additional showers/thunderstorms developing where this front
is slowly moving. Main impacts are in the KFAR area, and guidance
supports decreasing trends in coverage/chances after sunset this
evening. Behind the front a period of smoke may impacts the TAF
sites with 3-6sm vis (upstream trends favor 6sm or higher), but
this should be brief with most smoke remaining aloft through the
rest of the TAF period. Winds are shifting to the northwest
behind the front but will becoming variable overnight, before
gradually increasing again (10-15kt range).
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...DJR
SHORT TERM...JR
LONG TERM...JR
AVIATION...DJR
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
702 PM CDT Tue Aug 8 2023
...Aviation Update...
.DISCUSSION...(This evening through Tuesday)
Issued at 415 PM CDT Tue Aug 8 2023
Key Messages:
* Scattered to widespread thunderstorms expected late this evening
into the overnight, some of which will likely be strong to
severe. Most of the forecast area remains in a Slight Risk
(level 2 of 5) of severe weather.
* Generally dry and mild Wednesday into Thursday, though isolated
to widely scattered thunderstorms could linger and/or redevelop
over portions of the area on Wednesday, depending on how
tonight`s activity plays out.
* Off and on, relatively minor, rain chances return Thursday night
and Saturday night through Sunday night. Temperatures warm back
up into the upper 80s to mid 90s Friday-Saturday, then cool off
a bit Sunday into early next week.
Forecast Details:
Main story this forecast period is the potential for scattered to
widespread thunderstorms this evening into the overnight, some of
which will probably be strong to severe. Overall, not a ton of
change to overall forecast as still expect a fairly large area of
convective development over the next 1-2hrs over the central High
Plains ahead of potent shortwave seen very clearly on aftn WV loop
over W WY. In fact, have already seen some development near CYS,
and appears explosive development is just getting underway in NE
CO. This activity should gradually consolidate and grow upscale
later this aftn and eve, generally W of the CWA, then propagate
E and probably at some point even SE. Am skeptical of recent HRRR
runs that suggest an entirely W to E track of one or two primary
MCSs, which, if true, would present a greater risk for primarily
damaging winds for nearly entire CWA, even areas N and E of Tri-
Cities. However, this seems unlikely IMO, though, as it wants to
hang onto higher storm intensities later into the overnight (and
also further N/E), despite the propagation into much lower
instability environment. Lack of CU field currently in areas from
around HSI, S and E, seems to confirm latest SPC Meso analysis of
a significant minimum in deep layer moisture and instability, and
most guidance keeps primary LLJ advection and convergence zone
from NW into south central KS. Just doesn`t seem like a good setup
to support an MCS rolling through the entire Slight Risk area.
Instead, my gut feeling is that the orientation of the various
deep layer flow vectors to the main instability axis - which is
currently analyzed N to S from Nebraska Sandhills to around DDC -
will keep the brunt of strongest convection confined to areas W
and S of the Tri-Cities, perhaps even mostly S/SW of an Elwood to
Beloit line. This is the general scenario suggested by last
couple runs of the NAMNest, as well as the 12Z HREF, and would be
the area most at risk for up to 70 MPH wind gusts associated with
mature QLCS. Main time frame of concern looks to be about 03Z to
09Z, though sometimes these MCSs organize and mature more quickly
than even the CAMs anticipate, so 09Z could be a bit on the long
end of the main potential. Thus, with all that said, feel the
Slight Risk area could end up being a bit overdone, esp. for areas
N and E of Hastings. Most CAMs agree that a secondary, less
intense, band of convection should develop W to E through central
NE after 03Z, generally along zone of mid level WAA/ascent. Much
weaker instability should keep the severe threat with this
activity on the low side.
The above scenario is what I believe to be most likely. However,
there`s a non- zero chc for sfc based tstms to develop on nose of
northward advecting instability axis/theta-e ridge, which appears
to be depicted well in recent visible sat imagery by agitated CU
on northern end of N-S axis of large field of convective roll
clouds. Storms in NE CO developed very quickly when leading edge
of cirrus - which likely denotes leading edge up upper
ascent/cooling - impinged on the instability gradient there. Will
have to watch if this happens again over the next few hrs as the
cirrus continues to spread E towards the North Platte area where
CU is most agitated. This is a low probability, but potentially
high-impact scenario, given combination of steep mid level lapse
rates near 7.5 C/km, strong deep layer shear around 45-50kt, and
moderate instability...as sampled by 19Z LBF special sounding.
Very large hail and damaging RFD wind gusts would accompany
initial likely supercells, and present a much earlier start time
to svr weather potential. This seems unlikely, but again, non-
zero, given this area is further away from upper low and doesn`t
have quite the upslope component to low level lift like NE CO.
Wednesday continues to be a bit of a question mark in terms of
lingering shwr/tstm potential as some guidance (such as HRRR)
dries the area out early and keeps any redevelopment well E of the
area during the aftn...whereas other guidance (such as NAMNest/EC)
linger some mid-level energy/trough axis slower and further W, and
develop iso-scat tstms beneath it during aftn peak heating. Since
I prefer the NAMNest solution tonight, it needs to be taken into
consideration for Wed, as well. However, would also not be
surprised if organized MCV evolves out of tonight`s convection and
simply carries the "effective" trough axis through the area
quicker, essentially keeping main threat area for redevelopment
during peak heating (modest CAPE, weak CINH) further E. Will just
have to see how things evolve tonight, but kept the ongoing low
end PoPs in mainly E/SE zones through Wed aftn to account for the
potential. Outside of any lingering rain potential, should be a
nice day with comfortable temps in the 70s/80s and lgt wind.
Didn`t spend a ton of time of middle to later portions of the
forecast as impactful weather appears minimal. Generally speaking,
should see a bit of a warm-up Thu thru Sat, though this is
basically just taking temps back closer to normal. Nothing too
terribly hot. Off and on rain chances will continue, though
specific timing/placement details are too difficult to pin down
this far out. Appears best chcs will be with a weak front Thu
eve/night, and again Sat PM with a somewhat stronger front that
could push temps back below normal early next week.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday)
Issued at 652 PM CDT Tue Aug 8 2023
We have a few more quiet hours to go this evening, but eventually
the developing line of thunderstorms to the west will push through
our TAF sites. Gusty winds, possibly severe winds are the biggest
threat with this line of storms as it pushes through mainly
between 10 PM and 1 AM. We could see some brief lower ceilings
and visibility reductions, primarily MVFR conditions during the
worst of the thunderstorms and then improvement as the storms move
out. The wind should be fairly light and variable most of the
time except for in and around the thunderstorms when strong gusts
to over 40 mph will be possible.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
DISCUSSION...Thies
AVIATION...Wesely
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
752 PM CDT Tue Aug 8 2023
.SYNOPSIS...
Issued at 752 PM CDT Tue Aug 8 2023
While isolated thunderstorms fade off tonight, additional and
more widespread thunderstorm activity is then anticipated
Wednesday and Wednesday night. Localized areas of severe weather
and flash flooding will be possible with these Wednesday storms.
&&
.UPDATE...
Issued at 752 PM CDT Tue Aug 8 2023
Narrow axis of heavy rain has been occurring south of Newton to
near Lawrenceville the last couple hours, but otherwise the
earlier convection has been on the wane. Latest HRRR runs have
been lingering light showers a bit longer than past sunset, so
PoP`s have been updated to extend them to about midnight
near/south of I-70. Temperatures are generally on track this
evening.
Geelhart
&&
.SHORT TERM... (Through Late Wednesday Night)
Issued at 145 PM CDT Tue Aug 8 2023
Subtle mid-level shortwave energy and a weak surface trough
positioned across northern Illinois are providing the forcing
mechanisms needed to yield isolated thunderstorms this afternoon.
Weak deep-layer shear (< 25 kts) will preclude a severe weather
threat despite healthy MLCAPE values (1000-1500 J/kg). And yet,
we cannot completely rule out a funnel cloud or two late this
afternoon as stretching potential increases in the face of
appreciable low-level CAPE and some degree of surface vorticity.
Any such activity should be confined north of a Quincy-to-Danville
line.
As today`s isolated showers and storms fizzle with the loss of
daytime heating, the attention shifts towards Wednesday and
Wednesday night as a convectively-augmented mid-level shortwave
moves across the Mid-Mississippi Valley. In the low levels, good
WAA and an influx of theta-e will help boost buoyancy despite
abundant cloud cover. The parameter space across central Illinois
by tomorrow afternoon, per today`s 15z RAP analysis, offers
uncapped MLCAPE values between 1500-2000 J/kg while deep-layer
shear remains a bit of an enigma. On the one hand, mid-level flow
will actually be decreasing around midday -- suggesting
diminishing deep-layer shear (< 30 kts). On the other hand, low-
resolution models often don`t resolve localized shear enhancements
associated with decaying MCVs.
With some uncertainty surrounding the shear profile, Wednesday`s
severe weather threat is marginal at best for much of central
Illinois. Should the latter scenario play out (i.e. locally
enhanced shear in the vicinity of the decaying MCV), a few severe
storms may develop throughout the afternoon hours. We will
continue to monitor short-term, hi-resolution guidance tonight,
but we may not have a good handle on this system until it`s on our
doorstep Wednesday midday.
Perhaps the greater impact will be localized flooding. Robust
moisture transport, characterized by PWATS approaching 2", will
aid in very efficient rainfall rates as the MCV slowly pushes
across central Illinois. The latest HREF 3-hr QPF PMM guidance
advertises the potential for 2" + in such a time span, while the
HREF 3-hr QPF max teases values of 3" in that same 3-hr time span.
Either of those scenarios would threaten our flash flood
guidance, perhaps resulting in widespread ponding of small streams
and urban street ways.
MJA
&&
.LONG TERM... (Thursday through Next Tuesday)
Issued at 145 PM CDT Tue Aug 8 2023
After a bit of a lull on Thursday, spare the fog potential
Thursday night, central Illinois will have another shot for
scattered showers and storms Friday and Friday night. While the
strongest forcing appears to be displaced northward across the
Great Lakes, we maintain a 20-30% chance for storms as a cold
front makes its passage beneath hostile mid-level dry air.
After the Friday/Friday night period, another chance for
widespread showers and storms arrives Sunday/Sunday Night as the
upper jet stream buckles over the Midwest and helps send a
surface cold front through central Illinois. We`ll spare you the
mesoscale parameters at this point, but it`s not out of the
question that the severe weather potential will return late this
weekend.
Global models then show good semblance of a much drier airmass
spreading in early next work week with seasonably hot
temperatures.
MJA
&&
.AVIATION... (For the 00z TAFs through 00z Wednesday Evening)
Issued at 631 PM CDT Tue Aug 8 2023
Scattered storms will continue for a couple more hours generally
in the KSPI-KCMI corridor, but will fade out with sunset.
VFR conditions are expected until about mid afternoon, but
ceilings should steadily deteriorate behind an area of showers and
thunderstorms Wednesday afternoon. By the end of the period,
ceilings should be near or below 2,000 feet at all sites.
Geelhart
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
1016 PM CDT Tue Aug 8 2023
...New UPDATE...
.UPDATE...
Issued at 1016 PM CDT Tue Aug 8 2023
Midevening GOES IR imagery shows thunderstorms over the high
plains of NE, KS and eastern CO, downstream of a compact upper
trough over southern WY. This upper trough and associated
downstream convection will move southeast through the central
plains overnight. By daybreak, bulk of the thunderstorms will have
arrived to the Ozark plateau. By the time this convection reaches
eastern AR around midmorning, additional storms will develop
south of I-40, associated with a warm front surging north from the
Arklamiss. PWat values will increase from 1.6 to 2.3 inches
following the passage of the warm front. This will enhance heavy
rain potential Wednesday morning over east central AR, southwest
TN and much of north MS. Damaging wind threat should be marginal
through the morning, limited mainly by marginal instability.
The heavy rain threat will shift north into northeast AR, the MO
bootheel and northwest TN Wednesday afternoon, as the additional
convective clusters track east, north of the slowing surface warm
front.
The aforementioned thunderstorm activity will be associated with a
series of shortwaves, perhaps an MCV or two, ejecting ahead of the
main upper trough. 00Z HRRR suggests stabilization from early day
storms may be sufficient to offset afternoon heating, limiting
thunderstorm coverage and severe threat late Wednesday afternoon.
However, this optimistic solution is not corroborated by the
00Z NSSL-WRF or the 3km NAM.
CAMs and global models agree on the arrival of additional storms
late Wednesday evening and early Thursday morning, associated with
an upper trough. Boundary layer instability will be strongly
capped by late evening, but the lower atmosphere will be buoyant
at 925mb, with around 2000 J/kg CAPE. 00Z HRRR depicts a 700mb
speed max in excess of 70 knots rotating through far northeast AR,
the MO bootheel and west TN, just north of Memphis, through 3am
Thursday. With DCAPE nearing 1000 J/kg this may be an indicative
of a pronounced damaging wind threat into the early morning hours
Thursday. It may be long night.
PWB
&&
.SYNOPSIS...
Issued at 342 PM CDT Tue Aug 8 2023
An unsettled weather pattern continues across the Mid-South with
the threat of severe weather returning on Wednesday. Otherwise,
the relief from the heat will be short-lived with hot and humid
conditions building throughout the week.
&&
.DISCUSSION...
(This evening through next Monday)
Issued at 342 PM CDT Tue Aug 8 2023
The immediate forecast concerns will revolve around the chances
for severe weather Wednesday into Wednesday night. Some
uncertainties in the forecast remain though as morning/early
afternoon convection may impact additional severe weather chances
later in the afternoon and evening.
Most of tonight should be fairly quiet with low temperatures in
the upper 60s to low 70s. Patchy fog will once again be possible
tonight across parts of West TN and N/NE MS and have included fog
in the latest forecast.
Latest CAMs develop convection by mid-morning on Wednesday across
northeast AR with one or more clusters moving across West TN into
the afternoon hours. Point soundings out ahead of this activity
supports a severe weather threat with damaging winds being the
primary hazard along with a non-zero tornado threat. Hot and humid
conditions will be possible across the southwest part of the CWA
in the MS Delta and a heat advisory may become necessary for these
areas.
Another cluster/complex of storms may sweep across the Mid-South
during the evening hours into the early overnight hours as a
boundary approaches the region. This activity will also have the
potential to become severe but the confidence on the exact
details are on the lower side at this time due to the threat of
storms earlier in the day. Damaging winds will once again be the
primary threat but a low tornado threat will be in place due to
sufficient wind shear profiles.
Overall - the flash flooding threat should be on the limited side
as storms should be progressive in nature. However, intense
rainfall rates and multiple rounds of storms may result in some
isolated flooding across the region.
The heat and humidity will begin to build towards the latter of
the half of the week with heat headlines increasingly likely
Friday into the weekend. Daily chances of isolated to scattered
showers and storms will continue a result of day time heating and
additional upper level disturbances moving along northern
periphery of upper level ridge.
&&
.AVIATION...
(00Z TAFS)
Issued at 608 PM CDT Tue Aug 8 2023
There is a chance for BR/FG conditions to develop overnight for
low lying areas and for areas near river basins. MVFR/IFR
conditions are expected for the sites effected by BR/FG, with VFR
conditions expected elsewhere.
A convection filled forecast is expected tomorrow with multiple
rounds effecting the terminals. Timing to the terminals is the
challenging aspect this forecast as guidance lacks agreement.
TEMPOS/PROB30S were warranted for the most likely timing to impact
the terminals. Brief periods of MVFR conditions and gusty winds are
likely during direct impact times. Winds will generally stay from
the south throughout the forecast and begin to back to the SE
towards the end of the period.
DNM
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
PUBLIC FORECAST...TAB
AVIATION...DNM
Area Forecast Discussion
National Weather Service Phoenix AZ
405 PM MST Tue Aug 8 2023
.UPDATE...
Updated Aviation
&&
.SYNOPSIS...
Monsoonal moisture will lead to continued rain chances of 10 to 30
percent on the lower deserts and 30 to 50 percent over the higher
terrain through Thursday. A gradual decline will take place from
west to east beginning Friday with storm chances limited to south-
central Arizona. Anticipate high temperatures to be lower than they
have been in several weeks but still near, to slightly above,
normal. A warming trend is anticipated for early next week with
highs climbing above 110 at most lower desert locations by next
Tuesday.
&&
.DISCUSSION...
Deep southwesterly flow remains in place which is aiding coherent
storm movement to the northeast. The development areas have been
over higher terrain locales of the eastern third of AZ plus Pima
County west of Tucson. With the storm movement to the northeast, it
will be hard to get storms to advect to our forecast area. However,
outflow from Pima County storms could aid propagation to the north.
Latest aircraft soundings indicate there isn`t a lot of CIN over the
Phoenix area. We may wind up having something of a repeat of last
night/this morning with a passing disturbance tapping into the
convective potential. This time, the models are picking up on a weak
short wave emanating from the upper trough where the remnant
circulation of former TS Eugene is. There is also a moisture
convergence boundary over the Mohave Desert that is over/near our
CWA border with VEF CWA. That boundary is anticipated to nudge
further north and may be another aid to convection. Most of the
deterministic CAMs are depicting relatively weak echoes/showers late
tonight - mainly over VEF and FGZ CWAs. The HRRR has had run- to-run
variations in showing very isolated storms over La Paz County with
better coverage just north. The NBM PoPs once again has a late
night/morning peak over the whole forecast area (except for portions
of Gila County which peak this afternoon/eve). That being said, the
numbers aren`t overwhelmingly high but definitely higher than
seasonal climatology. Though not convection related, model data
shows strong winds for late afternoon and tonight over western
portions of Imperial County extending into the Imperial Valley.
Thus, a Wind Advisory was issued.
The convective outlook for later Wednesday has a lot of uncertainty.
The moisture availability will be relatively good. But, being on the
back side of the disturbance, there may be some subsidence to hinder
things. Also, where/if there is prior precip, that will hinder
destabilization as well. But, if the preceding wave isn`t much, then
potential will be better. Global models are depicting a gradual
downtrend in moisture availability beginning Thursday but not a
dramatic drop off. The NBM PoPs reflect this with an eastward
retreat - most noticeable on Friday - but lingering over south-
central AZ through next Tuesday.
Temperatures are expected to be within a few degrees of normal for
the next several days thanks to the influence of troughing and
eastward retreat of the strongest high pressure. But, that still
means moderate HeatRisk as opposed to no issues at all. Early next
week, the ridge slowly expands westward again leading to an uptrend
in temperatures - potentially back to excessive thresholds by next
Tuesday. Of note, the NBM deterministic value for next Tuesday is at
the 75th percentile.
&&
.AVIATION...Updated at 2305Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major weather impacts are expected though Wednesday afternoon
under occasional mid/high cloud decks. Confidence is only moderate
with respect to timing overnight wind shifts as most evidence shows
a somewhat earlier shift to easterly versus the past several days.
Chances for outflows and any storm development affecting terminals
are too low to mention in this TAF package. Otherwise, west winds
with a few higher gusts should be common again Wednesday afternoon.
Southeast California/Southwest Arizona including KIPL and KBLH:
Gusty winds, particularly at KIPL will be the greatest weather issue
under periods of mid/high cloud decks. Winds will tend to stay
westerly at KIPL through Wednesday afternoon with gusts ~30kt common
this evening resulting in some lofted dust. Directions at KBLH will
vary more between SE and SW with gusts more muted 20-25kt.
&&
.FIRE WEATHER...
Monsoonal moisture will linger through Thursday for ongoing, though
modest, potential for thunderstorms at any given location. High
temperatures will be at, or a few degrees above, normal. MinRH
values will be in the 20-30% range and MaxRH values in the 40-60%
range most places. Eastern Riverside County will see the most
significant increases in humidity. Late in the week and over the
weekend, anticipate a gradual decline of humidity as well as storm
chances. Temperatures trend upward early next week to well above
normal. Apart from thunderstorms, winds will favor familiar warm
season patterns - except over Imperial County with late afternoon
and nighttime windiness from the west today and Wednesday.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Wind Advisory from 5 PM this afternoon to 8 AM PDT Wednesday for
CAZ562.
Wind Advisory from 5 PM this afternoon to 2 AM PDT Wednesday for
CAZ563-566-567.
&&
$$
DISCUSSION...AJ
AVIATION...18
FIRE WEATHER...AJ
Area Forecast Discussion
National Weather Service Raleigh NC
1001 PM EDT Tue Aug 8 2023
.SYNOPSIS...
A cold front will stall to our south tonight and early Wednesday.
The front will be followed by weak high pressure today through
Wednesday. Another system should affect the region Thursday from the
west.
&&
.NEAR TERM /TONIGHT/...
As of 955 PM Tuesday...
A complex of thunderstorms is currently moving east across eastern
GA/SC. The northern extent of it is reaching the NC mountains, but
radar returns are very light and most of it is likely virga based on
surface observations. Furthermore, the cold front appears to have
cleared all of central NC as surface winds have shifted W/NW, and
dew points have dropped into the 60s everywhere except the
central/southern Coastal Plain. Meanwhile, a strong shortwave trough
is seen on water vapor imagery over northern GA/AL. This will push
east across central NC between 03z and 09z tonight, resulting in a
brief increase in mid and upper level moisture across southern
portions of the region. This is where the 00z RAP shows roughly 1.5-
1.8" PW values and 500-1000 J/kg of MUCAPE overnight. So think this
could enhance the coverage and intensity of the aforementioned
showers as they move across the south, particularly between 03z and
09z. The latest HRRR/RAP/NAM runs are consistent in showing some
measurable rain as well. So added some low chance POPs across
roughly the southern two tiers of counties, with slight chance
extending a bit north of that. The relatively dry air in the low
levels behind the cold front should keep amounts fairly light,
around a tenth of an inch or less. Widespread mid and high clouds
will gradually clear overnight from NW to SE, keeping lows in the
lower-70s SE, while temps drop to the mid-60s in the far north.
&&
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of 225 PM TUESDAY...
Wednesday will begin with surface high pressure over western North
Carolina which will weaken through the day. A warm front will push
into the state from south to north overnight, but the main forcing
for any precipitation would likely come from a strengthening upper-
level shortwave. The daytime hours should be mostly sunny, but
clouds will move in from the west overnight. Have not strayed too
far from the previous forecast, but slightly increased the coverage
of precipitation late in the overnight hours, having it reach Durham
and Chapel Hill. With northwesterly wind, at least to start the day,
highs will likely be a degree or two cooler than today. Meanwhile,
increased cloud cover overnight should keep lows a degree or two
warmer than tonight.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
As of 310 PM Tuesday...
A mid/upper level trough will move across the region Thursday into
Friday and then another weak upper level disturbance will move
across the region Sunday and Monday before clearing out late
Tuesday. Meanwhile at the surface, a low pressure centered over the
OH valley will slowly shift into New England Thursday. A surface
boundary to the south of NC will shift across NC Thursday bringing
WAA and ample moisture to Central NC. As this boundary moves across
the region, expect isolated showers in the morning becoming more
scattered to numerous in the afternoon and evening. With increased
instability in the expected Thursday afternoon, SPC has all of
Central NC in a Marginal Risk for Severe weather. Organized
convection with the main hazard of damaging wind gusts could be
possible as the frontal boundary passes over the region. WPC also
has portions of the NW Piedmont in a Marginal ERO because of the
seasonal dynamics in place with rainfall rates sufficient enough to
produce minor flooding in some areas. Temperatures for Thursday will
be mainly dependent on cloud coverage and how early precipitation
begins to move across the region for now, it will be the most
seasonable day of the long range forecast with highs in the mid to
upper 80s and a few spots reaching 90 degrees.
For the weekend and into early next week, expect a more summertime
pattern with isolated afternoon showers and storms with the best
chance in the Coastal Plain and Sandhills regions, but cannot rule
out areas around the Triangle. Model agreement has been inconsistent
the past few runs with specific weather features influencing our
area. Temperatures for the weekend and Monday will be in the low to
mid 90s. However, with some moisture still in the atmosphere, heat
indices will be in the range of 100 to 106 degrees in areas of the
Triangle, Sandhills, and Southern Coastal Plain Saturday Sunday and
Monday. Tuesday will still be warm but with temps a few degrees less
with highs in the upper 80s NW to low 90s SE, for now as things dry
out a tad, heat indices will be spotty with only a few areas
reaching 100.
&&
.AVIATION /00z WEDNESDAY THROUGH SUNDAY/...
As of 730 PM Tuesday...
Through 00Z Thursday:
Broken/overcast mid and high clouds will overspread the area through
the evening and overnight hours as a upper level disturbance and
associated convective complex passes just south of the area. While a
passing shower cannot be ruled out at KFAY, no restrictions are
expected. The mid/high clouds will thin out after daybreak with dry
VFR conditions expected. Gustiness has subsided. Winds will remain
light and predominately out of the W-NWLY through the forecast
period.
After 00Z Wednesday: A mid-level shortwave trough and attendant cold
front/composite outflow boundary traversing the region will bring a
good/high chance of showers and thunderstorms(potentially two rounds
of convection) and associated restrictions to the area throughout
the day on Thursday. Scattered showers and storms are possible into
the weekend. Fog/low stratus restrictions will also be possible each
morning.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...np
NEAR TERM...Danco
SHORT TERM...Green
LONG TERM...CA
AVIATION...CBL
Area Forecast Discussion
National Weather Service Las Vegas NV
Issued by National Weather Service Flagstaff AZ
142 PM PDT Tue Aug 8 2023
.SYNOPSIS...Dry and breezy conditions will persist through this
evening with seasonable temperatures. Slight cooling is expected
the next few days as increasing mid and high level cloud cover and
an increase in thunderstorm activity is expected Wednesday
through Friday. Thereafter, storm chances will persist in the
higher terrain of Northwest Arizona and southern Nevada, but
coverage of precipitation should trend downward.
&&
.SHORT TERM...through Friday.
Dry and gusty conditions prevail this afternoon across the Mojave
Desert and southern Great Basin as a rather strong shortwave
pushes through Utah and Wyoming. Synoptically, the pattern aloft
is more representative of what we would expect in September or
October than early August, and the spatial coverage of dry and
gusty southwesterlies today is rather unusual.
Some changes are lurking to our south however, with mid-level
remnants of what was once Tropical Storm Eugene now banking up
against the coastal ranges of SoCal and Baja California. This
moisture will work north overnight, on track to enter into our
southern border zones by daybreak and lift into Southern Nevada by
midday. HREF and some runs of the HRRR suggest the arrival of
this remnant moisture sparking some strong morning convection
between 5am - 11am across Southern Mohave County, and NBM PoPs
seem to capture this potential well. PoPs will spread north in the
afternoon and slight chances exist across most of the eastern
Mojave Desert including Las Vegas, with substantially higher
chances further east in Mohave County.
The remnant tropical moisture will linger into Thursday and
Friday, with storm chances spreading west into Inyo County where
some of the higher precipitable water anomalies will exist as the
remnant moisture begins to get absorbed into a larger low
pressure system off the central California coast. Given the brunt
of the moisture is focused in the mid-levels (as opposed to a
strong low level moisture surge), gusty winds will be the greatest
concern with thunderstorms that form - but stronger cores will
still be capable of producing localized heavy rainfall and even a
few instances of flash flooding in more sensitive basins.
The increase in cloud cover and gradual upward trend in surface
dewpoints will keep our regional temperatures a few degrees cooler
than normal starting tomorrow through the remainder of the week.
.LONG TERM...Saturday through Tuesday.
Weak cut off low will remain parked over central California over
the weekend and will only slowly weaken and drift away early next
week. This will keep a southerly or south-southwesterly flow aloft
over the region with our Monsoon High still somewhat suppressed
to the east. This should result in a thinning of our moisture
profile and a slowly decreasing trend in thunderstorm coverage
each day, along with temperatures returning to near seasonal
normals.
&&
.FIRE WEATHER...Dry and gusty conditions across the northern half
of Mohave County will result in a period of critical fire
conditions and a Red Flag Warning remains in effect through 8 pm.
Elsewhere, dry and breezy conditions are expected as well but
surface wind speeds will not be quite as strong. Increasing
moisture will arrive from south to north Wednesday into Thursday
with improving RH and increasing shower and thunderstorm chances.
&&
.AVIATION...For Harry Reid...Breezy south-southwest winds this
afternoon and evening, with gusts 20-25 knots. Gusts fall off late
tonight as mid-level and high clouds move in. Southerly breezes
resume late tomorrow morning along with rain chances. Some
discrepancies remain in the likelihood of thunderstorm impacts at
the airfield, so opted to just put VCTS in for now. Trends in the
afternoon suite of hi-res guidance will likely determine whether any
PROB30 groups are needed for storms or outflow. Regardless, expect
scattered mid-level and high clouds tomorrow afternoon.
For the rest of southern Nevada, northwest Arizona and southeast
California...Breezy south-southwest winds across most of the area
today, with gusts generally 20-25 knots this afternoon. In the
Colorado River Valley, gusts should taper off around sunset. In the
Las Vegas Valley and at KDAG, gusts like persist later into the
night. At KBIH, light and variable winds this afternoon, returning
to their typical northwesterly direction tonight. VFR conditions
across the region with some mid-level and high clouds moving in late
tonight.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
DISCUSSION...Outler
AVIATION...Woods
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