Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/20/23
Area Forecast Discussion
National Weather Service La Crosse WI
640 PM CDT Wed Jul 19 2023
.DISCUSSION...(Tonight through Wednesday)
Issued at 220 PM CDT Wed Jul 19 2023
Key Messages:
- Scattered storms tonight, mostly focused north of I-94 but
increasing potential for development to spread southward.
Strong/severe threat mainly mid/late evening (hail). Mix of forcing
mechanisms make for a bit of mess environment-wise so close eye on
development with adjustments to forecast as needed.
- Shower, storm chances for the weekend. Lower end chances.
- Heat for next week - could get quite hot.
* STORMS TONIGHT - some strong to severe potential.
Narrow ribbon of instability continues to build across western MN
early this afternoon, between a warm front stretching north-south
across central MN and a cold front across the eastern Rockies. A
stationary front/trough hangs across parts of the MN arrowhead into
northwest WI. Meanwhile, the driver of it all (the upper level
trough) is churning over eastern ND, pushing east.
CAMS models takes this blend of lift and instability and spark
clusters of storms across MN, more focused northward. The majority
of the CAMS suggest the higher storm chances would hold north of I-
94. However, the HRRR has been painting a different picture...firing
up more convection across southern MN as it develops a focused area
of lift from a branch of the 850 mb jet/moisture transport
ahead/across the cold front. RAP hints at this too. If this does
manifest, that southern cluster could/would track across southeast
MN and move east/southeast across southwest WI overnight.
Around 1500+ J/kg of MUCAPE per the RAP with 40-50 kts of 0-6km
shear...mostly longer, straight line hodographs (some curvature
though). Strong-severe threat with larger hail favored.
A lot of moving parts here with interactions adjusting environment,
providing additional focuses/or deterrents to convection. Obviously a
close eye will be paid to the evolution tonight with adjustments to
the forecast as needed. Locally, the severe threat is focused on the
mid to late evening hours.
* WEEKEND RAIN CHANCES? a few disturbance will bring mostly small
rain chances to the area
With the upper level ridge axis still holding to the west, the upper
mississippi river valley continues under the influence of northwest
flow. Medium range guidance has a few ripples in the flow top the
ridge, spinning southeast across the region this weekend...perhaps
into the start of the new work week. Pinpointing location/timing of
these small scale features are problematic...while the surface
pattern also fairly weak. So will continue to broad brush the rain
chances with lower end pops areawide. The GFS suggests 500-1000 J/kg
of MUCAPE, mostly skinny longer profiles. Could support some storm
development. Not much for wind shear. Severe threat looks low.
* HEAT RETURNS - latter half of next week looking like a hot one.
The GEFS/EPS have been steadfast in bringing the west coast ridge
(the one responsible for the record/extreme heat) eastward next
week, eventually shifting over the upper mississippi river valley.
When and how amplified the ridge will be remains in question. SPC
cluster analysis has a quick solution, slower, more amplified and a
flatter one. GEFS members are fairly spread out between all the
possible outcomes while the EPS favors a flatter more "middle of the
road" speed. The operational runs of both models are stronger with
the ridge with the GFS about a day quicker compared to the EC. The
tendency has been to move the ridge in too quickly, with later model
runs then holding it back. The last couple days have shown a bit
more consistency though, and despite the current differences,
eventually getting the local area under the ridge`s influence by
Wed.
While we may not experience the extreme heat many over the western
states are, highs into the 90s are looking like a safe bet - even a
week away. Nearly 75% of the GEFS and EPS ensemble members push
highs of 90+ for the mid/latter part of next week. Top end extends
to 100+. Of note is that the operational runs of both models are on
the hotter side of their ensembles...especially the GFS. So some
moderation from those runs is likely necessary. All said, we should
be ready for higher heat and humidity (and the related heat impacts)
next week...and if the scenario plays out as it currently is progged
to...heat headlines could/would be needed.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 635 PM CDT Wed Jul 19 2023
A shortwave trough and cold front will push through the area
tonight. Scattered showers and thunderstorms are forecast to
accompany the cold front. The short range models tend to take the
more robust convection north of the TAF sites. Deeper mixing this
afternoon has provided some drying with dewpoints in the upper 50s
and more stable looking clouds. Will continue to monitor storm
development through should storms approach KRST/KLSE. Will also
watch potential for gusty winds and have included gusty winds with
showers/near storms. Ceilings are mostly VFR with patchy MVFR
conditions with storms. MVFR ceilings do increase from the north
Thursday morning for a few hours. Southwest winds becoming
northwest and increase Thursday with gusts 20 to 25kts.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...Rieck
AVIATION...Zapotocny
Area Forecast Discussion
National Weather Service Columbia SC
1048 PM EDT Wed Jul 19 2023
.SYNOPSIS...
Northwest flow aloft will continue across the area the next
couple of days. Thunderstorms expected to develop each afternoon
through the end of the week with the highest potential for
severe weather Thursday. Temperatures slightly above average
through the end of the week becoming cooler for the weekend as a
cold front moves into the area.
&&
.NEAR TERM /UNTIL 7 AM THURSDAY MORNING/...
A shortwave is moving through the region this evening, which
has kicked off some shower and thunderstorm activity mainly in
the CSRA. The convection has since moved out of the forecast
area, leaving gradually clearing skies behind it. With the axis
of the shortwave moving through the region now, don`t expect any
widespread activity through much of the night. However, cannot
rule out an isolated shower or two over the far eastern Midlands
as suggested by some CAMs or the far western Midlands near
daybreak as the next shortwave begins to approach the region.
Overnight temperatures fall into the lower to mid 70s.
&&
.SHORT TERM /7 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Additional shortwave moving through the NW flow along the
periphery of the upper ridging to our west, although HiRes
guidance is indicating a bit of a lull in convective activity
tomorrow morning. Does appear that the HRRR performed reasonably
well today with convection that developed well west which
indicates moderate to strong destabilization, especially in the
southern portion of the area into the afternoon with cooling
aloft. Additional cloud coverage and potential for some showers
or storms earlier may keep the northern portion of the area a
little more stable and possibly a bit cooler with MOS guidance
trending a bit cooler for Columbia and areas north. The
northern area will have the strongest deep layer shear, however,
likely above 30 knots which would support organized storms
developing. Still a bit of uncertainty in the timing, especially
with not a ton of agreement among the CAMs but if we can stay
dry Thursday morning, will be a severe threat in the afternoon,
especially where the strongest instability and shear overlap.
SPC maintained the slight risk basically for the central and
northern portion of the forecast area, which will be the highest
potential for organized severe storms, although cannot rule out
an isolated severe storm elsewhere. Biggest threat will be
damaging wind gusts with any storms and maybe some small hail,
although wbz heights remain high. High temperatures will be
extremely dependent on convective coverage, especially in the
morning, with highs generally in the low to mid 90s. With plenty
of convective debris cloudiness and low level moisture
overnight, low temperatures in the mid 70s across most of the
area.
Friday, upper flow may become a bit more zonal with global
models indicating no significant shortwaves. Fairly significant
850mb temperature anomalies remain present with a bit of
downsloping developing during the afternoon which will lead to
temperatures rising a bit but should also mix out our dew points
compared to what blended guidance is indicating. High
temperatures expected to be mostly in the mid 90s with max heat
indices around 105F, below heat advisory criteria. Convection
likely more limited compared to Thursday but cannot rule out
isolated to scattered storms developing during the afternoon.
Low temperatures in the low to mid 70s Friday night.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
By Saturday, ensemble means show that the upper ridging over the
forecast area will break down with NAEFS indicating that 500mb
heights will be below the tenth percentile across the entire
forecast area with below average temperatures as a result. At
the surface, a cold front will push into the area with a fairly
significant moisture gradient in place from south to north with
majority of GEFS members indicating PWATs will exceed 2 inches
in the south. Showers and storms will be focused along the
front, although ensembles do indicate instability may be a bit
on the weaker side. Does appear that some drier air moves in
late weekend into early next week with ensembles indicating the
axis of highest PWATs shifts offshore. Heights also expected to
recover as temperatures return to near average with limited
afternoon convection.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
VFR conditions expected outside of diurnal scattered
showers/storms.
Afternoon convection has diminished but lingering convective
debris clouds will remain in place over the region tonight with
winds diminishing to less than 5 knots.
Do not expect smoke or fog to be an issue overnight although
there is some uncertainty at AGS given over a half inch of rain
occurred there, so included a tempo for MVFR vsbys 07z-11z.
Otherwise, some higher clouds may continue to move over the area
through the period in northwesterly flow aloft. Winds will pick
up from the west around 8 to 10 knots after 15z. Expect another
round of scattered afternoon convection on Thursday, driven by
an upper disturbance. However, timing and location remains
uncertain so will not include in this forecast.
EXTENDED AVIATION OUTLOOK...Increasing probabilities of diurnal
thunderstorms and late night/early morning fog/stratus through
Sunday. Smoke/Haze from distant wildfires may continue to reduce
flight VSBYS and possibly affect surface VSBYs at times.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Charleston SC
1026 PM EDT Wed Jul 19 2023
.SYNOPSIS...
A weak front will stall over the area late week into the
weekend, then high pressure will rebuild early next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
The temperature hit 97F degrees at KSAV on Wednesday, tying it
for the hottest at that location so far this summer season.
Lingering outflow boundaries from previous convection plus a
short wave aloft will still generate isolated to scattered
convection over the South Carolina counties into the overnight.
This is mainly derived from a combination of the HREF and
NAMnest. Nocturnal CINH along with MLCAPE just 1000-1500 J/kg
suggests that any strong or severe storms like earlier has
ended.
While the HRRR Smoke products imply there still could be some
places with haze or smoke, recent trends aren`t showing any of
these weather elements. Thus we don`t have it mention in the
forecast.
Persistence is a good forecast regarding min temps; down into
the lower and middle 70s far inland, upper 70s to even near 80F
degrees along the coastal corridor.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
A broad upper ridge will remain west of the area on Thursday.
Weak shortwave energy is forecast to drop through the northern
zones late Thursday afternoon into the evening which could spur
clusters of thunderstorms. Bulk shear values may increase to
30-35 kt late in the day and CAPE values will be above 2,000
J/kg in this area. There will therefore be a risk for severe
thunderstorms, mainly in the Charleston Tri-County area.
Damaging winds look to be the main threat. High temps in the mid
to upper 90s and mid-70s dewpoints will result in heat indices
of 106-112F, so a Heat Advisory may be needed for a portion of
the area.
A deep layered ridge will exist on Friday, with hot temperatures
persisting. Highs in portions of southeast GA could exceed 100F,
while upper 90s will prevail elsewhere. Strong mid-level
subsidence should limit convective development during the day
and the sea breeze will likely struggle to move inland. Late in
the afternoon through the evening, a weak shortwave could
ripple through, bringing a better chance for convective
development. The main issue will be heat indices potentially
exceeding 110F. A Heat Advisory will probably be needed for at
least the coastal counties.
Upper height falls expected on Saturday as a broad upper trough
shifts into the eastern United States. Decreasing thicknesses
should bring a slight break from the heat, though highs will
still reach the low to mid 90s. Upper levels will be much more
favorable for afternoon convection, so we have 50-65% PoPs
Saturday afternoon.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
A weak surface front stalled over the area Sunday will support
better coverage of showers and thunderstorms during the day. A
more typical summer pattern will then exist Monday through
Wednesday with near-normal highs and scattered diurnal
convection.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Keeping watch on convection not far upstream from KCHS and
KJZI. Not yet certain it will reach these terminals, but will
amend if necessary, Otherwise, mainly VFR expected through the
remainder of the night into Thursday. Some chance of haze/smoke
through the period. Relatively little convective activity
expected during the day Thursday but another impulse could bring
some convection Thursday evening.
Extended Aviation Outlook: Mainly VFR. Brief flight
restrictions possible Saturday and Sunday due to a greater
coverage of showers and tstms.
&&
.MARINE...
Tonight: A modest gradient will exist much of the night between
the Bermuda-Azores High across Florida and a trough inland over
the Southeast. This will result in S or SW winds as high as
15-20 kt with some stronger gusts. Not enough frequency nor
coverage though for any Small Craft Advisory. Seas will run 2
to 3 feet.
South to southwest winds will prevail Thursday through Tuesday.
For the most part, conditions will remain below advisory
criteria, though we could see some 25 kt gusts Thursday evening
due to a brief tightening of the gradient.
&&
.EQUIPMENT...
Maintenance is being performed on the Awendaw NOAA Weather All
Hazards transmitter KHB-29 operating on a frequency of 162.550
MHz. This can result in a degradation of the broadcast or even
the transmitter being off air.
In the meantime, you can tune to station WXM-93 at Cross on a
frequency of 162.475 MHz, WNG-628 at Georgetown on a frequency
of 162.500 MHz or station WXJ-23 at Green Pond on a frequency of
162.450 MHz to get your latest weather information.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...
SHORT TERM...JRL
LONG TERM...JRL
AVIATION...JRL
MARINE...
EQUIPMENT...
Area Forecast Discussion
National Weather Service Cleveland OH
802 PM EDT Wed Jul 19 2023
.SYNOPSIS...
High pressure will move into New England tonight allowing a warm
front to lift across the region Thursday morning. This will be
quickly followed by a cold front Thursday night. A trough will
linger across the Great Lakes Friday before high pressure tries
to build in by the weekend.
&&
.NEAR TERM /THROUGH THURSDAY NIGHT/...
Surface high pressure centered over Lake Huron and Georgian Bay this
afternoon is holding an active quasi-stationary frontal boundary
well to our south over the lower Ohio Valley. This is allowing for
pleasant northerly flow of relatively cool, dry air across our
region. Mid afternoon temperatures range from the upper 70s/low 80s
with dew points generally in the mid/upper 50s, so it will be a very
pleasant evening. The surface high will shift into New England
tonight ahead of a strong northern stream mid/upper shortwave trough
diving into the Upper Midwest. This shortwave has an impressive
visible satellite presence across northern portions of North Dakota
and Minnesota this afternoon and will be the main weather maker for
Thursday. Before that arrives, the lingering effects of the
retreating surface high will maintain dry conditions tonight with
low temperatures cooling into the upper 50s/low 60s in NE Ohio and
NW PA and low/mid 60s elsewhere.
The main weather story continues to be a potential severe weather
outbreak Thursday afternoon and evening. Confidence in the timing
and exact evolution/intensity of the convection remains low because
it is conditional on the amount of morning showers and debris clouds
(as is often the case around here in the summer), but we can
certainly say that there will be at least scattered strong to severe
thunderstorms capable of damaging winds and large hail in the
afternoon and evening hours.
Synoptic and Mesoscale Details:
The strong mid/upper shortwave trough mentioned above will progress
from the western Great Lakes Thursday morning through the southern
Great Lakes and Ohio Valley by late evening. As this occurs, a nice
75-90 knot H3 jet streak rounding the base of the shortwave trough
will place much of the Ohio Valley and Lake Erie vicinity in the
left exit region, favorable for strong and abundant synoptic scale
lift. A surface low, strengthening in response to the upper forcing,
will track east across northern lower Michigan and Lake Huron during
the late afternoon and evening before lifting north of Lake Ontario
Thursday night. This is a favorable low track for northern Ohio and
NW PA to get into the triple point, where warm/moist advection is
maximized in the warm sector. Indeed, the associated warm front will
lift northeastward through the area in the morning before slowing in
the vincity of far NE Ohio, eastern Lake Erie, and NW PA by late
afternoon as the trailing cold front sweeps east/southeast from
Michigan and Indiana. This cold front will sweep through the entire
area by early Thursday night and begin to occlude as the mid/upper
trough axis becomes negatively tiled across the Great Lakes.
Warm/moist advection will quickly strengthen during the morning into
the afternoon as a southwesterly low-level jet strengthens to over
20 knots in response to the increasing upper forcing. This will pump
rich low-level moisture characterized by dew points in the upper
60s/low 70s into the area. This warm/moist advection and isentropic
ascent will likely generate at least scattered showers and possibly
rumbles of thunder as the warm front lifts northeastward Thursday
morning. Most of the HREF members are suggesting this potential with
varying degrees of coverage. That is where the uncertainty comes
from regarding what will happen ahead of the cold front in the
afternoon and evening. Extensive coverage of showers and cloud
debris in the morning and midday hours will inhibit surface heating
and resultant instability, but if this clears by late morning
allowing for quite a bit of sunshine, then surface temps will easily
rise into the upper 80s. A tongue of steep mid-level lapse rates
(6.8 to 7.2 C/Km) advecting across the region overtop of the rich
low-level moisture will help to generate at least 1500-2000 J/Kg of
MLCAPE by late afternoon regardless of the early day debris, but if
sunshine increases earlier, then MLCAPE values could exceed 3000
J/Kg, especially across NW and north central Ohio, as indicated by
the NAM. This possibility would also generate close to 4000 J/Kg of
SBCAPE. Deep layer bulk shear (0-6 Km) will increase to 40-50 knots
by late afternoon and evening as the cold front approaches, and this
combined with low-level shear (0-1 Km) over 20 knots is favorable
for organized convection capable of all hazards (damaging winds,
hail, and isolated tornadoes). Again, storm coverage and intensity
depends on what happens in the morning hours, but there should at
least be scattered severe storms in the afternoon and evening given
the above mentioned parameters. My gut feeling is that the morning
activity will not be as widespread as some of the HREF members are
indicating because both NAM and RAP forecast soundings are showing
capping in the 900-800 mb layer holding until mid afternoon when mid-
levels start to cool in response to the approaching shortwave. If
this is true, then higher instability could be realized until the
cap breaks in the mid afternoon. So overall, my gut feeling is that
the severe weather risk is increasing.
Storm mode and timing:
As briefly discussed above, timing and coverage is uncertain due to
questions about what happens in the morning. Assuming that most of
the debris showers and clouds exit by late morning and the capping
holds until mid afternoon, the feeling is that initiation will occur
on a pre-frontal trough or outflow boundaries after 18Z across SE
Michigan, northern and eastern Indiana, and NW Ohio. The
aforementioned shear profiles and at least moderate instability
support both multicell clusters and supercells early on capable of
all hazards (damaging winds, large hail, and isolated tornadoes)
before a veering and strengthening low-level jet grows the
convection upscale into a QLCS during the evening. Most HREF members
propagate this possible QLCS east and east-southeastward across Lake
Erie, most of northern Ohio, and NW PA in the roughly 22Z to 03Z
timeframe. Damaging winds will be the biggest threat if this
materizes, with some signicant gusts over 75 mph associated with
bowing/surging segments possible given deep layer shear vectors
oriented perpendicular to the line. Large hail should be more of a
threat early on in the storm mode evolution in NW and north central
Ohio when the activity has a better chance to be multicells and
embedded supercells. Brief spin up tornadoes are possible everywhere
because low-level SRH looks to increase to around 100 m2/s2 near the
line, LCL heights will be low (500-1000 m), and 0-3 Km shear will be
over 30 knots and oriented mostly perpendicular to the line. For
these reasons, the SWODY2 has been upgraded to Slight Risk areawide
with a 2% tornado risk and 15% wind and hail risks. In terms of
flash flooding potential, PWATs will be at seasonable levels (1.50
to 1.75 inches) which will support torrential rainfall within the
storms, but the shear vectors generally perpendicular to the
approaching cold front should keep the convective cells moving at a
good clip (at least 30-40 knots). This will keep any flooding
localized to urban and poor drainage areas, or places that see
repeated storms.
In summary, there will definitely be scattered severe storms with
damaging winds and hail later tomorrow afternoon and evening, and it
will be busy, but the exact timing, coverage, and intensity is
uncertain, so this forecast is low to medium confidence. Stay tuned
for updates, review severe weather safety plans, and have multiple
ways to receive watches and warnings.
The showers and thunderstorms should exit by Midnight Thursday night
with the cold front pushing east, but wraparound moisture and a
surface trough as the parent mid/upper trough deepens overhead will
bring some scattered showers back toward sunrise Friday morning,
especially in NE Ohio and NW PA. Lows Thursday night will range
from the low to mid 60s.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
A cooler rather pleasant start to the weekend is in store for the
lower Great Lakes as a somewhat strong short wave for July exits the
region. The upper level trough axis will be just east of the region
Friday and a few lingering showers can be expected mainly in the
morning over extreme northeast Ohio and northwest PA. Cooler and
less humid air will spread into the region with 850 mb temperatures
dropping to the 10-12C range as high pressure builds over the region
by Saturday night. High temperatures will mainly range from the mid
70s to lower 80s. Overnight lows will range from the lower 60s at
the lakeshore to the 50s inland.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
The upper level pattern persists through this period with a broad
trough over the eastern states and high amplitude ridge in the 4
corner states. Another short wave will drop into the base of the
trough over the region Sunday night and linger into Tuesday.
There may be sufficient instability for widely scattered to
scattered showers with some embedded thunder with coverage of 15-30
percent mainly diurnally with an afternoon maximum. The highest POPs
are expected on Monday. High temperatures will gradually warm from
the mid 70s to lower 80 on Sunday to the 80s on Wednesday. Low
temperatures will be in the 60s with mid to upper 50s inland over
northeast Ohio and northwest PA on Sunday night.
&&
.AVIATION /00Z Thursday THROUGH Monday/...
VFR conditions can be expected through the first part of
Thursday morning before showers and thunderstorms develop and
move in along and ahead of a cold front pushing southeast out of
the Great Lakes Thursday afternoon and evening.
There are two potential windows of activity...one is from mid
morning (after 13-14z) into the afternoon from west to east as
at least some pre-frontal scattered showers and storms may
develop. Greater potential appears to be after 19-20z from west-
northwest to southeast as storms develop and move in with the
cold front itself. Of the two rounds, confidence is higher in
the second round, with this second round bringing greatest
concern for lightning, vsby restrictions and wind gusts
potentially over 40 knots with more organized or intense
convection. With that said, how activity with the first round
behaves will influnece the timing and intensity of the second
round. Included VCSH at most TAF sites to account for the
potential earlier round and began including VCTS with more
focused/aggressive TEMPOs for the second round. Did not yet put
the more aggressive TEMPO in at ERI and YNG since activity would
get there right around the end of the TAF period and because
confidence is somewhat lower that far east.
Winds will be light and variable tonight before picking up out
of the south-southwest at 6 to 12 knots on Thursday.
Outlook...Non-VFR possible in scattered lingering showers
Thursday night and Friday. Non-VFR also possible in isolated
thunderstorms Saturday afternoon and Sunday afternoon.
&&
.MARINE...
Generally quiet marine conditions are expected during this period on
Lake Erie with the possible need of a small craft advisory on
Friday. High pressure over Lake Erie will shift east of the region
by Thursday morning. Low pressure will pass by north of the lake on
Thursday and a cold front will cross the lake Thursday night. Light
winds tonight will become southwest ahead of the cold front on
Thursday at 10-15 knots. After the frontal passage on Thursday
night, winds will shift to the northwest and increase to 13-18 knots
on Friday before diminishing Friday night. SCA conditions may
develop on Friday. High pressure will build over the lake for the
weekend and linger into Monday with light winds.
SYNOPSIS... High pressure 30.10 inches over Lake Erie will shift
east of the region by Thursday morning. Low pressure will pass by
north of the lake on Thursday and a cold front will cross the lake
Thursday night and early Friday. High pressure will build over the
lake for the weekend and linger into Monday.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.
&&
$$
SYNOPSIS...Garuckas
NEAR TERM...Garuckas
SHORT TERM...LaPlante
LONG TERM...LaPlante
AVIATION...Sullivan
MARINE...LaPlante
Area Forecast Discussion
National Weather Service Corpus Christi TX
653 PM CDT Wed Jul 19 2023
...New AVIATION...
.SHORT TERM...
(Tonight through Thursday night)
Issued at 315 PM CDT Wed Jul 19 2023
Hot. That`s still the key word in the forecast. The ridge has
stretched out across the region, but it`s not making any
difference in our forecast. We`re still very hot today with heat
index values reaching 120 at KCRP, and close at KNQI so far.
Models are underdoing dewpoints along the coast especially in the
afternoon periods, for instance only RAP and NAM are anywhere
close to the 80 dpt we have here at time of writing, but those two
models are also far too high over the waters. Having to manually
pull in some of the higher dewpoints behind the seabreeze to get
appropriate values. Not expecting to see much difference tomorrow,
and thus will keep similar heat headlines with Heat advisory for a
lot of the area and excessive heat warning for primarily the
southern Coastal Bend.
Overnight lows remain in the mid to upper 70s and some lower 80s
right along the coast with lighter winds in the overnight hours.
Daytime winds tomorrow will be gusty again, especially near the
coast.
&&
.LONG TERM...
(Friday through next Tuesday)
Issued at 315 PM CDT Wed Jul 19 2023
Key Messages:
- Dangerous heat continues
Not much change from the previous few forecast. The upper-level
ridge will hang tight Friday before beginning to gradually erode
Saturday from the north as a trough digs into the Southeast. By
Sunday, the trough is expected to have collapsed the ridge leading
to some weaknesses in the upper-levels, which when combined with an
increase in moisture could lead to isolated showers and
thunderstorms each afternoon Sunday through Tuesday.
Despite winds expected to remain below 20 mph, elevated fire weather
conditions will be possible this weekend and into next week. Due to
the combination of recent dryness and above-normal temperatures, the
Climate Prediction Center (CPC) has majority of South Texas in a
rapid onset drought risk next week, which when combined with dry to
critically dry fuels could result in rapid fire growth despite the
weaker winds.
Temperatures are expected to remain above-average for this time of
the the year with temperatures ranging from the mid 90s to near 110
degrees, with the coolest temperatures near the coast. Dangerous
heat indices will continue this weekend and into next week with heat
index values ranging from 110-114 degrees, with isolated areas
across the Coastal Bend possibly reaching up to 117 degrees. Please
remember to stay hydrated, limit outdoor strenuous outdoor activity,
and look before you lock your vehicle.
&&
.AVIATION...
(00Z TAFS)
Issued at 648 PM CDT Wed Jul 19 2023
VFR conditions expected this evening/early tonight, followed by a
transition to a mixture of MVFR and VFR conditions after 06z
Thursday. Expect predominate VFR conditions by mid/late Thursday
morning. Moderate/breezy onshore flow this evening/early tonight,
becoming light south/variable overnight/early Thursday morning,
followed by a transition to moderate onshore flow near the end of
the TAF period.
&&
.MARINE...
Issued at 315 PM CDT Wed Jul 19 2023
Light to moderate southerly flow is expected into early next week,
with moderate to strong gusts possible this evening and Thursday
for the bays and nearshore waters south of Port Aransas.
Isolated to scattered showers and thunderstorms will be possible
each afternoon from Saturday to Tuesday across the Gulf waters.
&&
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 79 98 77 98 / 0 0 0 0
Victoria 77 100 76 101 / 0 0 0 10
Laredo 79 108 76 106 / 0 0 0 0
Alice 77 103 75 103 / 0 0 0 0
Rockport 81 93 81 91 / 0 0 0 10
Cotulla 79 108 75 106 / 0 0 0 0
Kingsville 77 103 76 101 / 0 0 0 0
Navy Corpus 81 96 81 96 / 0 0 0 10
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory until 8 PM CDT this evening for TXZ229>234-239>241-
245>247-346-347.
Heat Advisory from noon to 8 PM CDT Thursday for TXZ229>234-
239>241-245>247-344-346-347-442-443.
Excessive Heat Warning until 8 PM CDT this evening for
TXZ242>244-342>344.
Excessive Heat Warning from noon to 8 PM CDT Thursday for
TXZ242>244-342-343.
GM...None.
&&
$$
SHORT TERM...PH
LONG TERM....JCP
AVIATION...WC/87
Area Forecast Discussion
National Weather Service Cheyenne WY
940 PM MDT Wed Jul 19 2023
.SHORT TERM...(This evening through Friday)
Issued at 215 PM MDT Wed Jul 19 2023
Showers and thunderstorms ongoing since early this afternoon as
weak shortwave energy passes east along the WY/CO border today.
Overall, seeing dry boundary layers west of the Laramie Range
across Carbon and Albany Co as forecast sounding have LCLs above
the freezing level. This will likely lead to gusty outflow winds
with any storms that develop. Could even have a few gusts to 60
mph like what has been seen the last few days with storms moving
over the Arlington/Elk Mountain area. Farther east, latest RAP has
MLCAPE near 1000-1400 J/kg with 40 kt of shear which would be
enough for severe hail to develop through early this evening.
Fairly straight hodographs will favor splitting storms which has
already been observed with initial storms today. Storms could move
into the NE Panhandle late this afternoon and early this evening
before dissipating and a cold front approaches from the north. Expecting
cooler temperatures Thursday behind the trailing cold front
passing through the CWA late tonight that will drop 700mb temps to
around 6C. This, in addition to widespread precipitation (see
next paragraph) will lead to afternoon highs 10-15F degrees below
normal for mid-July being in the upper 60s to mid-70s.
Beginning Thursday morning, a compact progressive shortwave
will move across southern WY providing ample lift in addition to
the post-frontal easterly upslope flow. Looking at sfc dewpoints
east of the Laramie Range in the 50s with very moist profiles.
Widespread PW values over 1" with spots east of the Laramie Range
and along/south of the North Platte River valley climbing near
1.25". Latest NAEFS guidance places this over 2 sigma anomaly for
mid-July while WPC has much of the area under a marginal risk for
excessive rainfall with a slight risk area drawn into Laramie and
Kimball Co. CAMs are depicting showers and storms entering Carbon
Co early Thursday morning moving east of I-25 by mid-morning with
additional storm development possible early in the afternoon
within a few pockets of instability reaching 800-1000 J/kg. With
the anomalously high moisture content, mainly looking at heavy
rain as the main hazard with the storms on Thursday. 1-hr FFG
across the area hovers around 1.5" which hi-res guidance suggests
is very reasonable through the early evening.
Friday will begin a warmup headed into the weekend with increasing
700mb temps as the upper level ridge builds over the
Intermountain-West. Will still remain in northwest flow throughout
the day with marginal instability/shear parameters capable of a
few strong storms from east-central WY into the NE Panhandle.
.LONG TERM...(Friday night through Wednesday)
Issued at 215 PM MDT Wed Jul 19 2023
Overall, the long term forecast looks much warmer and drier over
the weekend and into next week. Starting on Saturday, the ridge
over the desert southwest will gradually strengthen and slowly
push eastward. By Monday afternoon, a 600 decameter high/ridge
will be positioned over the Rockies. This will usher in much
warmer and drier air to the CWA. The warmer temperatures stay
locked over the region through much of next week, even as the
ridge flattens and becomes more broad. During this time,
temperatures will be on the hot side. Over the weekend,
temperatures will range from the upper 80s to upper 90s, with
Saturday being the cooler of both days as the ridge axis sits
farther off to the west. Monday and Tuesday will likely be the
hottest days of the week as 700 mb temperatures make it up to the
+16 to +20C range! As a result, did nudge high temperatures
towards the NBM 75th percentile, especially Monday and Tuesday
with the ridge axis almost directly overhead. This will lead to
most cities in the CWA having high temperatures in the 90s to low
100s! As we head into next week, will have to keep an eye on the
temperatures as we enter into county fair season.
The hot and dry weather will keep most storms away, but cannot rule
out an isolated thunderstorm or two during the afternoon hours as
weak vort maxes pass through the ridge aloft. This weekend looks
like the driest of the long term with maybe an isolated shower or
two over the high terrain. Precipitation chances are a bit better
Monday and Tuesday with slightly stronger disturbances moving
through the ridge. Again, any storms that do form will be isolated
and will likely stay below severe criteria.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 939 PM MDT Wed Jul 19 2023
Wyoming TAFS...A passing cold front and weather disturbance will
produce widespread rain and showers from 10Z until early Thursday
evening with visibilities from 1 to 4 miles in rain, along with
ceilings from 800 to 1500 feet AGL at Cheyenne, and 3500 to 5000
feet AGL at Rawlins and Laramie. Before 10Z, scattered to broken
clouds from 9000 to 12000 feet AGL will occur. After 01Z Thursday
evening, scattered to broken clouds from 3500 to 8000 feet AGL will
prevail.
Nebraska TAFS...A passing cold front and weather disturbance will
produce numerous showers at Alliance, Scottsbluff and Sidney from
15Z to 01Z, reducing visibilities to 3 to 4 miles, along with
ceilings from 3500 to 4000 feet. Before 15Z, scattered to broken
clouds from 10000 to 15000 feet AGL will prevail. After 01Z Thursday
evening, expect scattered to broken clouds from 4000 to 6000 feet
AGL. Chadron will see scattered to broken clouds near 15000 feet AGL
until 17Z, then scattered to broken clouds around 6000 feet AGL.
&&
.FIRE WEATHER...
Issued at 215 PM MDT Wed Jul 19 2023
Minimal fire weather concerns through the rest of this week as
conditions turn cooler headed into Thursday with widespread
rainfall likely. Temperatures will remain below average Thursday
behind a cold front before warming up headed into the weekend.
Afternoon temperatures will climb into the 90s by Sunday
continuing into early next week that could lead to afternoon RHs
reaching critical levels.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...MB
LONG TERM...SF
AVIATION...RUBIN
FIRE WEATHER...MB
Area Forecast Discussion
National Weather Service Des Moines IA
627 PM CDT Wed Jul 19 2023
...Updated for the 00z Aviation Discussion...
.SHORT TERM.../Tonight through Thursday Night/
Issued at 222 PM CDT Wed Jul 19 2023
Forecast Impacts for the week:
...Storm chances into early tonight
...Storm chances return Sat >> Mon
...Heat returns by midweek next week
Confidence Short Term: Medium to High
Not much change in the pattern so far into early this period as a
weak area of low pressure over western MN and an attendant warm and
cool front extend from the low; the warm front over MN into far
northeast Iowa while the cool front extends southwest into a second,
weak low over northern Nebraska. Convection has been most active in
the arrowhead of MN overnight with another area of showers/storms
beginning to develop along the cool front in southeast South Dakota
and central Nebraska at 14z. Subjective H850 analysis shows a weak
wave in central/eastern Iowa now with a more pronounced wave over
Nebraska south to Kansas. The airmass over central to eastern Iowa
remains rather dry at H850 at 12z with the bulk of the moisture
resides over Nebraska to Oklahoma. As the northern stream low pulls
northeast and the southern low tracks just south of the state this
afternoon, we remain in between the best forcing and surface
convergence as the lows pass south/north of our area and the storms
begin to move into some of the drier air by late day and evening.
These trends are mirrored by the synoptic models as well as earlier
runs of the HRRR model around 06z. This afternoon will see some
convection, but it should be trending down by late afternoon and
early evening. A secondary area of convection will develop near the
Iowa MN border around 21-00z and move nearly due east with some
impact possibly in our far northern counties. As we move into the
evening hours, the cool front will begin to trek south across the
region and gradually displace the warmer air today with cooler air
by Thursday morning. H850 temperatures in the upper teens to lower
20s today will cool to 13C north and 18C south by morning. Lows
tonight will remain rather mild south in the mid to upper 60s while
the north cools to about 60 by morning. Tomorrow will be a very
pleasant, but somewhat breezy day, as northwest winds mix to 15 to
25 mph early and then begin to relax a bit by evening. Highs will
recover a bit and reach the upper 70s north to the lower to mid 80s
in the far south. As a ridge of high pressure settles into the area
for Thursday night, we cool to 12C to 14C at H850 with overnight
lows rather comfortable in the mid to upper 50s.
&&
.LONG TERM.../Friday through Wednesday/
Issued at 212 PM CDT Wed Jul 19 2023
Confidence: High through Monday & Low/Medium Tue-Wed
By later Friday, the high will begin to slide east with weak warm
air advection returning to northwest sections of the state. There
may be some scattered late day convection in the far northwest,
though nothing sustained. Saturday appears to be a repeat of Friday
with a few scattered storms farther into the region. By Sunday a
front will develop on the leading edge of the hotter air over the
Western Plains. This will bring some additional chances for isolated
to scattered daytime convection to the region, but at this time
nothing appears to organized. Highs during the period will be
warming from the 70s/lower 80s Friday to the lower 80s/upper 80s by
Sunday. Monday should be the day we see highs rising to the lower
90s over much of the south. Though we continue to heat up, our
forecast dew points are not expected to rise beyond the 60s
initially as most of the moisture replacement will be due at first,
to evapotranspiration. With no organized low pressure in the region
and the airmass in the boundary layer not mixing too much, humidity
levels will probably increase as we move into Tuesday.
We continue to see an increasing signal for hot weather to return to
the Central Plains by Wednesday. Differences on the arrival of the
heat continues with inter-model variations between the operational
and ensemble systems of the GFS and Euro. Yesterdays 12z run, the
Euro had backed off a bit on the arrival, favoring a lingering
Great Lakes high pressure ridge. The consensus, given a little
wiggle room, has temperatures at H850 building back to ~20C to 24C
by 00z Wednesday with a strong H700 cap and little chance for any
rain. Todays Euro is still trying to delay the hotter airmass
until at least Wednesday as well, keeping storm chances along a
northwest to southeast boundary bisecting the region Tuesday
evening. By 00z Thursday, Euro temps aloft now fall to 21C to 24C
with +13C cap at H700 as convection is attempting to knock back
the ridge. A trough will be near or south of the region by
Wednesday afternoon. GFS forecasts H850 temps around 30C for 00z
Thursday with much stronger winds at H850. In addition to the
deterministic runs, the ensemble systems also differ with the Euro
still cooler than the GFS for the period of expected hot weather
over our area next week. Forecast highs would certainly vary
between current solutions; Euro cooler with highs hitting the 90
to 94 range and the GFS over 100F at these forecast temperatures
aloft. Given the tendency for the GFS to be too fast, siding with
the slightly less hot solution for now is warranted. Regardless of
result, the period from Wednesday to Friday is appearing to be
the hottest stretch of the season for our area so far. One aspect
of the pattern that will need to be monitored is if the H500 ridge
buckles with any wave tracking into our area. This could lower
temps and bring storms back as the Euro is suggesting, versus the
GFS which is more bullish on building the ridge farther north and
east.
&&
.AVIATION.../For the 00Z TAFS through 00Z Thursday evening/
Issued at 621 PM CDT Wed Jul 19 2023
Mostly VFR conditions prevail through the period. Low cumulus have
begun to dissipate early this evening leaving only mid to upper
level clouds along with remnant showers from the storms to our
north and west. Shower and storm chances for this evening are on
a downward trend, but there still remains the chance for a stray
storm or two over the next few hours. This is not represented in
the TAFs due to the low probability of occurrence and isolated
nature, but will be added if any impacts are anticipated.
Otherwise, light winds out of the west southwest will shift to
more northwesterly overnight and then more northerly during the
day tomorrow. Wind speeds will also pick up tomorrow with gusts
up to 20 kts possible.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...REV
LONG TERM...REV
AVIATION...Dodson
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
300 PM PDT Wed Jul 19 2023
.SYNOPSIS...Hot interior temperatures will continue through
Saturday, with the hottest temperatures expected on Friday.
Temperatures will then gradually cool through early next week, but
interior temperatures will remain near to above normal through
the rest of the period. Temperatures along the coast will remain
near normal. No rain is forecast to occur during the next seven
days.
&&
.DISCUSSION...Coastal stratus has been slow to clear out in many
areas today, but most areas are seeing at least some peaks of sun
this afternoon. However, clouds are more stubborn across the Eel
River Delta and along the S Mendocino coast. Across the interior,
sunny skies prevail. Temperatures this afternoon range from some
lingering 50s in cloudier coastal areas to the lower to mid 90s
across portions of the interior.
A large upper low continues over the Gulf of Alaska with a
trailing week trough extending S to the North Coast. A sprawling
upper ridge persists across the S from N Mexico to the S MS
Valley. Through the end of the week, the upper low will slowly
sink S over the E Pacific. However, the S ridge will also nose
farther to the N over the Desert SW and 4 Corners area. This
pattern will allow temperatures to warm across the interior, with
the hottest temperatures in our area expected over Lake and
extreme E Mendocino counties. The hottest day is expected to be
on Friday. Have hoisted a Heat Advisory for Lake County from
midday Friday through late Saturday evening. The Saturday portion
of the advisory is a bit more marginal. Temperatures will start a
slow decline beginning Saturday, the interior temperatures closer
to normal by the early to middle portion of next week.
Along the coast, stratus will continue through most of the period,
although at least partial clearing is expected in many locales
each day. Patchy drizzle is possible tonight from Cape Mendocino N
to Humboldt Bay. Local tools suggest that this will continue to be
possibility most nights and mornings into the weekend. Mostly
trace amounts of rainfall are expected, with locally a hundredth
or two.
Have continued to populate HRRR smoke guidance to account for
visibility reductions from the Flat Fire in SW OR. The smoke is
forecast to expand and shift a bit eastward on Thursday. /SEC
&&
.AVIATION...Apart from any brief periods of scattering, ceiling
heights will range in the IFR to MVFR level this afternoon. The
stratus will swiftly fill back in overnight. Ceiling heights will
lower to IFR overnight, with movement into LIFR levels, particularly
through the early morning hours. High pressure is building back in,
and there will be brief opportunity for periods low visibility
Thursday morning. UKI will remain dry and VFR with generally light
NW to N afternoon wind.
&&
.MARINE...Northerly winds are generally on a weakening trend through
much of Thursday. Thursday winds look to be the lightest of any day
this week. The northern waters will see winds of 15 to 20 kt in the
outer waters with 5 to 10 kt in the inner waters. The southern
waters will see winds of 15 to 25 kt with a few gusts to gale force
just downwind of Cape Mendocino. Short period seas will lower to 3
to 5 in the northern zones, and 6 to 8 ft in the southern zone on
Thursday. The northerlies will begin restrengthening Thursday night.
By Friday, the southern waters will see winds of 20 to 25 kt with
gusts to gale force just downwind of Cape Mendocino. Areas of
southerly wind reversal will develop overnights along the immediate
coast north of Trinidad.
&&
.FIRE WEATHER...Interior winds are forecast to remain fairly
light, but W to NW up-valley winds may become gusty through
channeled terrain and exposed ridges each afternoon this week.
This will also be accompanied by increasing temperatures through
Friday. The driest air and poorest nighttime recoveries are
expected across E portions of fire wx zones 264 and 277. Have
continued near-critical headlines in both these zones. Dry
weather will continue through the weekend, but with a gradual
cooling trend. /ZVS&SEC
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory from 11 AM Friday to 11 PM Saturday for
CAZ114-115.
NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory until 3 AM Friday for PZZ455-475.
Small Craft Advisory until 3 AM Thursday for PZZ470.
$$
Visit us at https://www.weather.gov/eureka
Follow us on Facebook and Twitter at:
https://www.facebook.com/NWSEureka
https://www.twitter.com/NWSEureka
For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
647 PM CDT Wed Jul 19 2023
...Aviation Update...
.DISCUSSION...(This evening through Wednesday)
Issued at 507 PM CDT Wed Jul 19 2023
-- KEY MESSAGES FOR THE ENTIRE 7-DAY FORECAST (generally
chronological):
* A few severe storms probable this evening: BY FAR the main
"forecast focus" right now is on the threat for likely at least
a few severe storms this evening (particularly during the 5 PM-
Midnight time frame), including the possibility for an intense
supercell or two (probably most favoring our far southwestern
coverage area (CWA) if anywhere). Large hail up to around 2"
diameter and damaging winds the main threats.
* Thursday rain/thunderstorm potential: Although the severe
weather threat will be considerably lower versus this evening
(the "main show" should impact western/south central KS and
points south), the overall chances for rain and mainly non-
severe storms is proving to be a bit of a challenge, as some
models keep all but our southern/southwest fringes dry, while
others bring decent chance for at least some measurable rain to
at least the southwest half of our CWA. These chances/PoPs will
obviously need better refined during the next few shifts.
* Friday afternoon-night storm chances?: Although still only
slight (20 percent) chances, these chances have been expanded a
bit more to include more of our Nebraska coverage area than
before. Based on latest raw model data, the afternoon chances in
our far north are very "iffy", with the overnight chances a bit
more supported by a few models. IF any convection does occur,
there is a non-zero chance that it could be marginally-severe,
so this will need monitored going forward (SPC currently does
not have our CWA "outlooked" on the latest Day 3).
* Saturday-Wednesday overview: Somewhat to this forecaster`s
surprise (but also with a bit more model support than
yesterday), this entire time frame continues to feature a dry
forecast (although still cannot rule out some slight PoPs
working into the mix at some point). Of higher confidence is
that it will start to feel like "true summer" again, as a
northward/eastward expansion of the current southern CONUS
upper ridge brings up the heat. Saturday looks to be the final
day for a while with highs mainly in the 80s, as temps Sun-Wed
look to gradually creep upward from low-mid 90s initially to
perhaps mid-upper 90s by mid-week. At least for now, the
heat/humidity combo through Wed does not look overly-oppressive,
but increasing parts of the area will likely see 100+ heat
index each afternoon.
-- MORE DETAILS/FURTHER INFO BUILDING UPON THE KEY MESSAGES ABOVE
(including all further discussion of Friday daytime-Wednesday):
- General overview of the large scale upper air/surface pattern:
Overall, and like this time yesterday, the latest ECMWF/GFS
solutions are in overall-great agreement regarding the "big
picture" through the entire 7-day (as also reflected by very
similar temperature values on their respective MEX/ECX numerical
guidance products). Thus, the general situation is as follows:
1) Tonight-Friday:
We remain in the same general situation as currently. This means
we reside under broad, seasonably-strong west-northwesterly flow
aloft, sandwiched between dominant large-scale ridging centered
over the southwestern CONUS, and persistent large-scale troughing
centered from the Great Lakes/northeast CONUS and northward. At
the surface, by far the main synoptic feature is a weak
(temperature-wise) but somewhat stronger (moisture/humidity-wise)
cold front dropping southward through our region overnight into
Thursday, that will drop dewpoints/humidity back to more
comfortable levels, accompanied by a north-northeast breeze.
2) Saturday-Sunday:
At least for now, our weekend forecast is a dry and warming one,
but various models (NAM/ECMWF/GFS) hint that especially Sat
afternoon-evening bear watching for at least limited thunderstorm
potential. Of higher confidence though is that temps will start
trending upward, as the heart of upper ridging climbs northward
from its current west-east axis over AZ/NM/TX to more of a north-
south orientation centered over the Four Corners area. This
northward/eastward nudge will raise mid level heights over our
area, with highs in at least the low 90s looking probable by
Sunday.
3) Mon-Wed:
The pattern changes very little, as our region resides along the
northeast periphery of the Four Corners area ridge, and with the
going dry forecast better supported by increasingly-warm mid level
temperatures (capping). Highs in the mid 90s will prevail in most
areas, with upper 90s more common in KS zones.
-- SHORTER TERM DETAILS FOCUSED SOLELY ON THESE NEXT 36 HOURS
(through late Thurs night/Fri AM):
- CURRENT/RECENT WEATHER SITUATION AS OF 415 PM:
Overall, today has turned out largely as expected SO FAR, as most
of the featured rather extensive mid-high level cloud cover
(following patchy dense fog to start the day), accompanied by
passing, high based light showers/sprinkles that have since
largely exited most of our CWA. Obviously this regime held down
temperatures quite a bit even into the first part of the
afternoon, but enough filtered sunshine has gotten through that
most of the CWA should end up realizing official highs into at
least the 80-85 range (still a touch cooler than expected 24 hours
ago). In the mid-upper levels, water vapor satellite and short
term model data confirm the same, seasonably-strong west-
northwesterly flow that we have been under lately, along the
interface between the aforementioned southwestern upper ridge and
northeastern/Canada upper troughing. At the surface, if anything
the weak cold front whose leading edges have now made it into
north central/western Nebraska is creeping southward a bit
slower/less aggressively than depicted 24 hours ago (summer fronts
tend to arrive slower, winter fronts the opposite). Meanwhile over
our CWA, light east-southeasterly breezes (generally 5-10 MPH)
have prevailed this afternoon, maintaining a humid airmass with
widespread dewpoints into the upper 60s/low 70s.
- LATE THIS AFTERNOON-EVENING (through around midnight):
Obviously severe storm potential is our #1 concern, but honestly
the magnitude (and for sure the potential areal coverage) of the
threat appears to be at least a bit muted from how things stood 24
hours ago. In short, the widespread clouds (and earlier light
showers) today have at the very least delayed and to some degree
held down convective instability over especially the southeast
half to 2/3rd of our CWA, as even with gradually cooling mid level
temps, mesoanalysis reveals plentiful lingering inhibition (CINH)
to near-surface based parcels. Also working against "explosive"
convective development is that upper forcing is fairly weak,
especially in the wake of the low amplitude wave that passed
through earlier today. However, looking just to our west-
northwest, it`s a bit more favorable for robust thunderstorm
development, as latest mesoanalysis depicts 2000-3000 J/kg mixed-
layer CAPE over southwest/west central Nebraska, along with some
weak low level convergence into a weak low pressure center. Deep
layer shear is definitely NOT a limiting factor anywhere, with
40-50KT common. Leaning into the latest HRRR as much as anything,
it is looking increasingly-probable that the MAIN severe threat
(assuming you does eventually materialize) will focus within the
southwestern 1/3 of our CWA (mainly west-through-south of the Tri
Cities), where at least a few supercells could develop mainly in
the 6-9 PM time frame before tracking southeast into/near our KS
zones and perhaps growing upscale into more of convective complex.
Meanwhile, the severe threat now seems more muted especially in
our northern/northeast zones, as despite some storm development
along the cold front along the NE/SD border, storms may struggle
to develop/maintain intensity heading southeastward toward that
part of our CWA this evening. Despite these limiting factors,
officially our entire CWA remains in an SPC Slight Risk, and the
potential still exists (especially west-southwest) for a few
intense storms with mainly a large hail/damaging wind threat),
with the main threat for severe likely winding down by around
midnight.
- LATE TONIGHT (midnight-sunrise):
In the wake of whatever does (or doesn`t) transpire this evening,
the vast majority of the CWA will likely see a storm-free late
night as the cold front gradually slides through, its passage
marked by a transition to light northerly breezes. Have small
PoPs/storm chances confined mainly near/south of the NE/KS border
during this time, as do not necessarily the HRRR`s totally
dry/storm-free late night solution for our south. Skies should
clear somewhat (especially north) and the setup should be at
least weakly supportive of some late night/early AM fog (albeit
likely not nearly as much as this morning). Have introduced some
generic "patchy fog" to mainly a few of our far southwestern Neb
counties. Low temps were changed little, ranging from around 60
far north to upper 60s far south (mid 60s for most).
- THURSDAY DAYTIME-EVENING (pre-midnight):
Will have to keep this a little shorter than usual, so in brief:
Have maintained a dry forecast sunrise-noon, although latest
RAP/HRRR suggest that some light showers could actually arrive by
mid-late morning especially in our west-central (something to
watch). Of higher confidence is that better chances for
showers/largely weak storms will arrive into especially our
southwestern (but perhaps as far northeast as our central?) CWA
during the afternoon, as we reside in a fairly stable airmass
along the far north-northeast fringes of what could be a somewhat
significant severe storm event taking aim on western into south
central KS and points south. The latest HRRR is actually the most
aggressive in brushing the Rooks County KS area in our extreme
southwest with a strong to perhaps marginally-severe storm late in
the afternoon, but for the vast majority of our area that does
see rain, it should come in the form of generic showers with
embedded thunder. SPC officially removed our extreme south-
southwest from the Marginal Risk on the latest Day 2 outlook and
feel it will probably remain so (albeit very near the edge of it).
Otherwise, the day will likely start with partly cloudy to mostly
sunny skies most areas, but trend toward mostly cloudy with time
(mainly mid- high level). At the surface, the passing cold front
will be more apparent, marked by sustained north-northeast breezes
10-15 MPH and slightly higher gusts. Temperature-wise, highs will
actually be very similar to today (80-86 most areas with any
upper 80s most favored far southeast), but dewpoints will be
noticeably lower versus today in the afternoon (mainly upper
50s-low 60s).
- LATE THURS NIGHT-EARLY FRI AM:
If anything the north-northeastward extent of our rain
chances/PoPs are probably overdone, as latest models suggest the
majority of any lingering showers/weak storms post-midnight should
be near-south of the NE/KS border at best. Skies will gradually
clear form north-to-south, and in the presence of light north-
northwesterly breezes only around 5 MPH, overnight low temps
should fall a few degrees cooler than tonight (upper 50s far
north/west-central to mid 60s far southeast).
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 647 PM CDT Wed Jul 19 2023
- General overview:
Although there is non-zero chance for some light fog (perhaps MVFR
visibility) or even a brief MVFR ceiling (especially at KEAR) at
some point overnight, confidence is relatively high in VFR
ceiling/visibility throughout with mainly just varying degrees of
mid-high level clouds, and have issued TAFs as such. Although the
overall likelihood of occurrence has trended down a bit since 18Z
issuance, the main issue is still a roughly 5-hour window of
opportunity for a passing thunderstorm through around 05Z. Aside
from any possible thunderstorm-outflow surges in speed/directional
changes, winds should not be a significant issue. There will,
however, be a directional change due to the passage of a weak cold
front, with breezes this evening mainly easterly, then
transitioning to northerly overnight and north-northeasterly
during the day Thursday. Sustained speeds (again aside from
possible storm outflow) will largely prevail near-to- below 10KT,
although some 15+KT gusts will be most probable especially 15-20Z.
- Thunderstorm/rain potential:
Although the threat for a truly severe storm does not look as high
as it did with the 18Z issuance, both sites (probably favoring
KEAR) at least stand a low chance of a storm passing through this
evening mainly before 05Z. Because confidence in occurrence is
still not overly-high, have opted to maintain a generic "vicinity
thunderstorm" (VCTS) group and allow any possible amendments to
handle any need for a TEMPO/prevailing group. Should any storms
directly impact either site this evening, large hail/damaging
winds are in the realm of possibility.
Once any chance for possible storms ends this evening, odds favor
the remainder of the period being dry/storm-free. However,
especially KEAR could reside near the north-northeast fringes of a
possible swath of rain shower/weak thunderstorm activity later in
the period Thursday afternoon, and have introduced a basic
"vicinity shower" (VCSH) for now to cover this low-confidence
possibility.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
DISCUSSION...Pfannkuch
AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Goodland KS
505 PM MDT Wed Jul 19 2023
.SHORT TERM...(This evening through Thursday)
Issued at 136 PM MDT Wed Jul 19 2023
The short term period calls for active weather with severe storms
and potential flooding.
The remainder of this afternoon, storms are expected to develop
across the area. The first round is already forming in Eastern
Colorado along a surface wind convergence boundary. These storms are
expected to continue to form and move east/southeast. Forms are then
forecasted to form during the mid afternoon in far Northwest Kansas
and Southwestern Nebraska along an area of surface wind convergence
and differential heating from earlier cloud cover. These storms will
also move east to southeast. Storms could be severe as effective
shear is around 40 to 50 kts with boundaries forming the storms.
However, the other severe parameters (1000-1500 J/KG of MLCAPE, 7 to
7.5 C/KM, and DCAPE around 1000 J/KG) are sufficient for severe
weather but a bit lacking. Recent cases with parameters like these
have produced marginally severe hail and wind gusts. Current
forecast reflects this with a few severe storms producing up to 1.5
inch hail and wind gusts up to 65 mph. If an isolated supercell can
develop, hail up to 2 inches would be possible. The severe threat
should diminish by 02-03Z.
Tonight, there could be a few showers and storms that develop
similar to recent night depending on how much lift and moisture
remain. If a storm did form, it would be unlikely to be severe with
limited instability available (MUCAPE around 1000 or less).
Otherwise, skies should clear across most of the area with lows
dropping into the 60`s. Similar to recent days, fog is again
possible mainly for areas along and east of Highway 83.
Tomorrow, the daylight hours could see cloud cover linger across the
area, especially with a cold front lingering near the area. The
passage should occur later in the day and when it passes could
determine the storm chances for the area. Otherwise, the additional
cloud cover and progress of the cold front will help most of the
area stay in the 70`s and 80`s for high temperatures.
In regards to storms, there could be a few that form ahead of the
main batch along a lingering outflow or pre-frontal trough. These
would form in Eastern Colorado and move east and could be the areas
best chance for hail. However, instability is forecasted to be
lacking again with MLCAPE around 1500 or less so the hail threat may
be spotty if it occurs at all. The main batch is then forecasted to
move off the Front Range, potentially along with the cold front.
This batch is forecasted to form either a storm cluster, squall line
or MCS that moves southeast. This would favor counties generally
west of Highway 83 and south of US 34. With the uncertainty in mode
and how progressed the front will be, there is some uncertainty
where the greatest threats would be. The main threats with the
storms that move through would be flooding and damaging wind gusts.
Most deterministic and ensemble guidance has at least 2+ inches of
rain falling in the main part of the storm complex. However, fast
downstream motion is limiting the accumulations and flooding threat
as storms are forecasted to move 30+ kts. Even if the storms form a
fairly large complex or take advantage of the very high PWATs
(generally 1.5 inches or higher which is near to above the 90th
percentile), the storms wouldn`t be over a spot long enough to
produce flooding unless the spot had poor drainage. That being said,
if the storms move slower or form and MCS that rotates around an
area, flooding chances would increase a fair amount.
Tomorrow night, with the complex moving out of the area, showers and
storms should end though the cloud cover may linger for a majority
of the night. Lows are forecasted to be cooler with a few locales
nearing 60 or less.
.LONG TERM...(Friday through Wednesday)
Issued at 1250 PM MDT Wed Jul 19 2023
Showers may linger into Friday morning with MCS exiting to the
south. Afterwards, looking at dry conditions from Friday afternoon
into early next week as ridge builds over the Rockies from the
west. Temperatures will warm well into the 90s, with some pockets
of triple digits for Monday through Wednesday. Precipitation
chances will be slim to none, with perhaps an isolated shower or
thunderstorm in eastern Colorado towards the end of the period
provided the ridge axis moves a little further east.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 505 PM MDT Wed Jul 19 2023
KGLD...VFR conditions are currently forecast through the period.
Convection in the vicinity and/or over the terminal at taf
issuance looks to continue through maybe 02z before moving away
from the terminal. Winds generally from the southwest to southeast
at speeds under 12kts except around any showers/thunderstorms.
From 02z-06z VFR conditions are expected with winds generally from
the south around 10kts. From 07z-14z, sub VFR conditions are
possible in stratus and maybe some fog/br as winds become light
and variable. Updated forecasts may have to introduce sub VFR
conditions. After 15z, winds generally from the east, slowly
increasing about 12kts in the afternoon. Cant rule out a
shower/thunderstorm over 21z (if the HRRR model is correct) but
other models delay convection around the terminal until the end of
the taf period.
KMCK...VFR conditions are currently forecast through the period.
Winds at taf issuance from the east around 10kts, becoming light
and variable from 04z-13z. After 14z, winds generally from the
east or east-northeast at speeds under 12kts. Regarding
precipitation chances, cant rule out a thunderstorm impacting the
terminal from taf issuance through 04z. Otherwise, it currently
looks like chances are rather low through the rest of the taf
period. Will have to watch for sub VFR cigs and maybe visibilities
in the 09z-15z timeframe.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...KAK
LONG TERM...024
AVIATION...99
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
837 PM CDT Wed Jul 19 2023
.SYNOPSIS...
Issued at 837 PM CDT Wed Jul 19 2023
The weather pattern will remain conducive to periodic precipitation
opportunities for parts of the area on Thursday and again on Sunday,
though by and large the next seven days will be on the dry side.
Seasonable temperatures are expected the next few days.
&&
.UPDATE...
Issued at 837 PM CDT Wed Jul 19 2023
00z surface map indicated a very moist low level airmass had crept
north into central IL, with mid 70s dewpoints south of a Macomb to
Decatur to Paris line. Plenty of high clouds were streaming east
across the area and patches of lower clouds were developing near
the I-72 corridor. These factors will result in much warmer
temperatures tonight, as lows only drop to the low 70s for most
locations. Due to the moist airmass and light winds, areas of fog
are expected to develop after midnight, primarily east of the IL
river. Some high-res guidance shows patches of dense fog after 4
am over eastern IL, so will be monitoring visibility trends
overnight. Cannot rule out an isolated shower or storm later this
evening with a subtle upstream shortwave noted on water vapor
imagery over southeast IA, though expected coverage is too low to
include in the forecast. CAMs show somewhat better probabilities
of isolated shower/storm over east central IL after 4 am, and this
is where low chance PoPs remain in the forecast.
25
&&
.DISCUSSION...
Issued at 324 PM CDT Wed Jul 19 2023
------------------------- [Key Messages] -------------------------
1. 50-70% chance for thunderstorms late tonight-tomorrow east of I-
57, tapering to sub 30% west of I-55. Low, albeit nonzero, chance
for severe storms in the morning south of I-72 and early afternoon
east of I-57.
2. Multiple slight (20-30%) chances for precipitation temporally
scattered throughout the forecast period, though chances for more
than half an inch between now and mid next week is less than 20%.
3. Temperatures on a warming trend next week. Predictability at that
time range is low, but there is concern for excessive heat by next
weekend.
-------------------------- [Discussion] --------------------------
3 PM composite reflectivity shows a few showers across southeast
Missouri and west Kentucky, along with a few well upstream across
central and western Iowa. Otherwise, the coast is clear with little
(10%) chance for an isolated storm until later tonight/tomorrow
morning when the cold front comes through. The 18z HRRR suggests a
plume of 2000-3500 J/kg of MUCAPE will surge northward from the I-70
corridor this afternoon to the I-74 corridor by around 11z/6am when
the cold front is forecast to be positioned near or along the
Illinois River. This latest iteration is a little more aggressive
than the 06z and 12z runs in developing a few cells along the I-72
corridor in the early to mid morning hours tomorrow, however it`s
still less bullish than the 00z iteration which had intense
convection exploding over our southeast half. The run to run
inconsistency reflects the difficulty the models are having in
pinning down where outflow from this evening/tonight`s convection
will reside to fuel redevelopment ahead of the front in the morning.
Ultimately, the best forcing for storms will be associated with a
belt of 40-45kt 925mb westerlies which will overspread areas along
and south of I-64 late tonight to fuel one or more MCSs which could
worsen the flooding situation in western KY. Nonetheless, this
latest HRRR iteration is slower in having the cold front clear our
area to the east tomorrow afternoon, which suggests the convective
potential may not be over after the early-mid morning
isolated/scattered storms - which at this point are looking hard
pressed to become severe given (1) the nocturnal inversion should
prevent momentum transport to the surface for strong winds and (2) a
lack of steep lapse rates in the 700-500mb layer should inhibit
sufficiently fast updrafts to suspend large hail. The time period
we`ll need to carefully watch for severe storms clipping our
southeastern counties would be 1-5 PM, during which time the HRRR is
suggesting explosive convective development south of I-72 in an
environment characterized by 3000 to 4000 J/kg of SBCAPE (and 1200
to 1400 J/kg of DCAPE!) and 10m to 500mb EBWD of 35-45 kt. SPC has
maintained the level 1 of 5 "marginal" risk for severe storms for
areas east of I-57 tomorrow, which seems reasonable given the
uncertainty in how far west storms will develop in the afternoon
along the southeastward moving cold front. One should not be
surprised to see an upgrade to slight on day one if model trends for
convective development further west continue.
Behind the front, dewpoints will plummet from the low to mid 70s to
mid 50s within the span of just a couple hours, which, given the
lack of clouds, could help optimize surface heating for temperatures
in the upper 80s to perhaps 90 in a few spots - the only limiting
factor being blustery northwest winds which will be gusting 20 to 25
mph during the late afternoon/evening.
On the back side of the exiting trough, perpetual northwest flow
will bring into the region a cooler-than-normal air mass which
should keep highs in the upper 70s to low 80s Friday and 80 to 85
degree range Saturday with less than 10% chances for rain showers.
The next shortwave could brush us sometime Saturday night to Monday
for some chance of precip, but at this point the deterministic
models are in disarray in the placement of shower activity and hence
NBM`s PoPs only peak around 40% Sunday night. NBM mean surface CAPE
comes up to around 1500 J/kg SBCAPE by Sunday afternoon, when 30-
40kt of 0-6km bulk shear associated with the trough could result in
some storm organization for a marginal severe threat.
The biggest story in the extended period, however, will be the
potential for heat to build into the region as an already expansive
upper ridge which has resulted in excessive heat across much of the
West Coast and Desert Southwest builds into the country`s
midsection. It`s far too early to get excited (or frightened) by the
prospect of a major heatwave, but some degree of warmth is on the
horizon beginning around the end of the forecast period. One
interesting thing to bear in mind is that probabilities for
temperatures warming above certain thresholds (e.g., 100, 105,
etc.) on particular days may be slightly lower than the cumulative
probability for temperatures to warm above that threshold during
the several day time period over which this heat is expected to
evolve. Each ensemble member in the low resolution ensemble
forecast (LREF) system is different in when precisely the peak of
the heat begins, but most have it getting "hot" by Illinois
standards between next Tuesday (July 25th) and the following
Tuesday (August 1st). On the whole, the GEFS, for some reason, is
much more extreme in its high temp forecast for central Illinois
compared to the CMCE and EPS - both of which are warm but not
necessarily record-breaking. Only 5 (10) out of 30 of the GEFS`
members have highs failing to exceed 100 (105) degF during this
time period in Lincoln, while by comparison only 17 (1) of 50 EPS
members have temps exceeding 100 (105) degF there. This may be
driven by how each ensemble system is handling boundary layer
moisture, but it`s difficult to say. The deterministic GFS`s
dewpoints have been consistently 5 to 10 degF lower than the
ECMWF`s. At this point, it`s difficult to say whether the GFS is
on to something given the ongoing rainfall deficit across much of
the region which should theoretically tamper
evapotranspiration...or the ECMWF has a better handle on those
higher dewpoints, but moisture will likely be key in determining
just how hot we can get during the day. One caveat will be
potential for storms. If the GFS is correct in its forecast for
vast temp to dewpoint spreads at the surface, then we`ll be
lacking in moisture available for convection (though any
convection that does develop would be efficient at producing gusty
winds given the steep low level lapse rates and dry boundary
layer conducive to evaporational cooling), while the ECMWF
solution would suggest greater coverage in storms given any
trigger - especially if we`re near the periphery of the ridge.
Stay tuned as we continue to monitor.
Bumgardner
&&
.AVIATION... (For the 00z TAFs through 00z Thursday Evening)
Issued at 620 PM CDT Wed Jul 19 2023
Short range guidance develops MVFR to IFR cigs/vsby late tonight
for the central IL terminals east of KPIA as light winds and a
moistening airmass overspread the region. These should lift/dissipate
within 1-2 hours after sunrise. A cold front is forecast to track
southeast across the terminals from 15-19z, followed by northwest
winds gusting up to 20 kt. A few storms could develop along/ahead
of the front during the early afternoon over eastern IL, so added
PROB30 for TSRA at KDEC-KCMI.
25
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1040 PM EDT Wed Jul 19 2023
.UPDATE...
Issued at 1040 PM EDT WED JUL 19 2023
There has been some good news this evening as the 00Z guidance
trickling in indicates the earlier noted southwest trend is still
showing up and overall lower QPF amounts in our area through the
night. Even so many of the CAMs still show some convective activity
toward our southwest counties later tonight especially toward
dawn and therefore slowed PoP development this evening. Even so,
kept 60 to 80 percent chances of rain in a narrow area toward the
Lake Cumberland region late tonight into earlier Thursday morning.
Another challenge this evening has been some lower cloud cover
developing and exactly how this spreads across the region. Given
the complexity and lack of better guidance had to make manual
adjustments to align better with obs and satellite trends. Outside
of these changes mostly minor adjustments to latest obs and
trends.
UPDATE Issued at 713 PM EDT WED JUL 19 2023
The late afternoon surface analysis shows a weak stationary
boundary north of Kentucky across the Upper Ohio Valley and high
pressure off to the south across parts of the Tennessee Valley.
Meanwhile, a weaker low pressure is forming across Missouri. Ample
cloud cover this afternoon has left the area largely dry most of
the day, but diurnally limited due to the cloud cover. The SPC
mesoanalysis show maybe 1000 J/kg of MLCAPE this afternoon and
this has built in largely as we have seen some late afternoon
sunshine. Outside a spotty shower not much is expected early this
evening and most of the thunderstorms will be to the north and
east.
Lots of uncertainty remains with how convection plays out tonight
or doesn`t play out. We are watching a mid-level shortwave across
Missouri that is expected to ride southeast into the Lower Ohio
Valley later this evening into tonight. The question remains how
much convection develops with this wave and where does it track.
The CAMs are a bit of a mess with where this develops or doesn`t
and there where it tracks. Some of the CAMs hold on to a more bow
and arrow MCS structure tonight, which is a similar structure seen
in western Kentucky last night. The biggest difference among the
guidance is timing and placement of this structure. The trend I
have seen so far this afternoon has been southwest with the
greater precipitation amounts. The 20Z HRRR has been most
surprising, as it depicts quite a differing solution compared to
earlier runs leading to more uncertainty. Now comparing this one
to one to last night doesn`t work because we are seeing a much
different parameter space this afternoon and evening. Now looking
at the 18Z run of the HREF and comparing it to the 12Z run there
has been a shift southwest with the higher precipitation amounts.
This favors the Cumberland Plateau and Tennessee Valley more and
we see shift of the probability of exceeding 6 hour FFGs from the
HREF at around 10 percent lower to around 10-20 percent in Wayne
County from the 12Z to the 18Z runs. Given this trend not
expecting to need a watch at this time, but will be monitoring
this closely through the evening.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 530 PM EDT WED JUL 19 2023
Key Points:
* Unsettled weather continues through Thursday night.
* Locally heavy rainfall and isolated flash flooding as well as
the potential for severe weather Thursday into Thursday night.
The latest upper level map features an anomalously strong ridge
sprawled from the southern Plains through the Desert Southwest,
with a persistent low spiraling just north of Hudson Bay. Plenty
of perturbations are traversing the flow between the two
aforementioned features, with pockets of seasonably to anomalously
strong wind speed throughout the atmosphere noted. At the
surface, a quasi-stationary frontal boundary is aligned from
portions of New England through the Ohio Valley, and then from the
Midwest through the southern Plains. High pressure is seen from
portions of the southern Appalachians down through the eastern
Gulf of Mexico. Clouds associated with a very persistent MCS to
our west and southwest have just thinned out across eastern
Kentucky late in the day, with a few sites now reaching the lower
80s. The lack of instability and forcing has only allowed for
some isolated showers this afternoon.
The models remain in good agreement with the upper level features
through the short term, with the core of the ridge to our south
becoming more confined to the Desert Southwest with time.
Meanwhile, a potent short wave trough will swing from the Upper
Midwest to the northern Great Lakes Thursday into Thursday night.
At the surface, a low pressure system will track in a similar
path, with a cold front making a better push southeast across the
Ohio Valley through the end of the period. This will result in a
continued stormier pattern across our area, although confidence in
the evolution of the details is not high, particularly for
tomorrow, with CAM guidance varying in solutions.
In general, expect a fairly quiet start to the night, with
any isolated convection that manages to initiate between now and
sunset to diminish with the loss of heating. A more moderate low
level jet then begins to nose in from the west southwest between
midnight and daybreak. This will allow for increasing chances of
convection across our far southwest counties. Some locally heavy
rainfall will be possible, given the higher PWATs in place. On the
other hand, there has been a relative minimum of rain over those
locations in the past several days, generally an inch or less, and
in some cases less than a half inch. As such, feel that most
locations would be able to take the forecast convective rainfall.
Lows tonight will range from the upper 60s to around 70.
Convection will dissipate through mid-morning, as the low level
jet and associated moisture transport relax. The question then
remains how much instability can build back into the region for
the afternoon, with perhaps more persistent low clouds to contend
with once again, with guidance trending lower with high
temperatures compared to yesterday. 12z HREF is also less
confident on more organized convection making it in, with lower
probabilities of updraft helicity noted compared to the 00z run.
Have maintained likely PoPs in the afternoon, with better forcing
moving in from the northwest ahead of a more potent short wave
trough. This will allow for some 500 mb height falls downstream
and the advection of more moderate effect shear values into the
region. The main threat with any stronger storms would be wind,
with a secondary threat of large hail and a non-zero, but overall
very low tornado threat. Again, CAM guidance is varying with
solutions, and confidence is not high, given the more seemingly
conditional threat. Highs on Thursday will be in the lower 80s.
Convection will diminish into tonight, before a slight uptick
towards dawn with the approach of the cold front. Lows will range
from the mid to upper 60s.
.LONG TERM...(Friday through Wednesday)
Issued at 346 PM EDT WED JUL 19 2023
Key Points:
* Conditions gradually dry out on Friday as a cold front sinks
southward across the area; lingering rain chances will be found
primarily south of the Mountain Parkway.
* A vast majority, if not all, of eastern Kentucky remains dry on
Saturday and Sunday.
* Another upper level disturbance and perhaps a weak frontal
boundary will spark more chances for showers and storms from
Monday onward, especially during the afternoon and evening.
Analysis: The long term period will start off Friday morning with an
~597 dam ridge centered over Arizona. A ridge axis extends
eastward to along the Gulf Coast and another axis extending
northward across the Canadian Rockies. To the northeast, mean
500H troughing, associated with an ~543 dam parent low over
northern Quebec, prevails across the Ohio Valley, Midwest, Great
Lakes, Mid-Atlantic and New England. Shortwave troughs will be
passing around the parent low, the first of which will be over the
Lower Great Lakes/Ottawa Valley at the start of the period. At
the surface, this shortwave trough supports a weak double-
barreled low with centers near the Delmarva Peninsula and Lake
Ontario. A cold frontal boundary extends WSW from the lows across
the Ohio Valley. Behind the front, an ~1020 mb high pressure is
resides across much of the Central and Northern Great Plains.
The aforementioned shortwave trough will pivot from the Great Lakes
into the St. Lawrence Valley/Northeast US early in the weekend,
nudging the surface cold front south of the JKL forecast area on
Friday. A cooler and drier northerly flow will bring some relief
from the humidity on Saturday, as the surface high builds
eastward into the Ohio Valley. The high continues to shift east
and becomes diffuse on Sunday and Monday. Southerly flow returns
on the back side of the high early next week, once again bringing
a return of more humid conditions, though still within the
typical values for this time of year. Another shortwave trough
passing through the mean trough aloft will bring a renewed
diurnally-modulated threat for showers and thunderstorms Monday
through Wednesday. An associated cold front may also approach,
but it is not certain that the front will actually reach our
area. Overall, the second half of the long-term does not look to
be a washout -- partly cloudy skies should be the norm along with
hit-or-miss, garden-variety thunderstorms. An isolated storm
pushing severe thresholds (primarily due to wind gusts) cannot be
ruled out if mid-level dry air aids the generation of stronger
downdrafts.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 758 PM EDT WED JUL 19 2023
VFR is the story this evening as the clouds finally cleared late
this afternoon. There remains some question into how cloud cover
will fill in tonight and given the diurnally limited day do we see
fog form easily in the valleys. Overall with the TAFs did lean
toward MVFR skies, with probabilties at 40 percent or so for MVFR
Cigs late tonight around 9Z or a little later. These Cigs will
slowly burn off through the day, but fair amount of uncertainty
remain on convection through the afternoon. The winds will be calm
tonight and increase to around 5-10 knots through the day
Thursday.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...DJ
SHORT TERM...GEOGERIAN
LONG TERM...GEERTSON
AVIATION...DJ
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1034 PM CDT Wed Jul 19 2023
.UPDATE...
Issued at 959 PM CDT Wed Jul 19 2023
Overall the convective threat tonight has decreased from earlier
expectations. That said, there`s still a threat for isolated
severe storms (hail, wind) and localized flooding. This threat
does not look very widespread, though. A shortwave trough is
crossing the area currently without much fanfare. Although many
CAMs assessed a strongly unstable environment and tried to flare
up a few thunderstorms this evening, a subtle capping inversion
kept this from happening. This was evidenced by the persistent low
level cloud cover that lasted into the early evening. Overnight a
westerly low level jet sets up over southern Missouri. Within
this jet is where we are more likely to see warm advection trigger
mostly elevated convection. The westerly orientation of the jet
aligns it fairly well with the overall deep layer flow which
should result in somewhat progressive storm movement. High
moisture levels indicated by PWAT of over 2 inches in southeast MO
indicates heavy rainfall rates will be possible.
The HRRR has been the most aggressive with developing convection
overnight, remaining somewhat consistent within its hourly runs
suggesting storms form near St Louis and train southeast along the
Mississippi River. While the HRRR has been mostly consistent with
itself in this idea, it remains an outlier in relation to most of
the other CAMs in this idea as well as the southeasterly
orientation of convection. Elsewhere to our west multiple
convective clusters over Kansas could evolve into a broader MCS
which should slide through southwestern MO and miss our forecast
area. The primary focus for us will be within the low level jet.
On the extreme end, training storms could lead to several inches
of rain in localized areas mainly after 3AM. But even if training
doesn`t happen, any thunderstorm will have heavy instantaneous
rainfall rates and could lead to localized flash flooding
especially in areas which have received recent heavy rainfall.
Kimble
&&
.SHORT TERM... (Through Late Thursday Night)
Issued at 242 PM CDT Wed Jul 19 2023
Key Messages:
1) Thunderstorms are once again expected along and south of I-70
overnight and tomorrow morning, with heavy rain and localized
flash flooding, damaging wind gusts, and occasional large hail
all possible.
2) A cold front may produce a few thunderstorms during the afternoon
tomorrow, but coverage and strength are expected to be limited.
3) Milder and mostly dry conditions are expected Friday and
Saturday, with a few showers possible Sunday.
4) Another warming trend is expected from early to mid week.
While a few weak showers continue to percolate across mainly the
core of the Ozarks this afternoon, precipitation has largely ended
in most areas. However, a deep cold pool remnant from this morning`s
thunderstorms continues to suppress temperatures across much of the
area, and while high humidity remains in place, this will help to
keep heat index values below 100 degrees for all but a few locations
in central Missouri for the remainder of the afternoon.
Later tonight, a shortwave trough is expected to approach the area
from the west, while a compact low level jet once again
strengthens ahead of it. While this iteration of the LLJ is not
likely to be quite as strong as last night (25 to 35 kt), forcing
from the approaching shortwave should be enough to produce another
round of thunderstorms across mainly areas along and south of
I-70. While this setup shares some similarities to last night,
there are a few key differences as well.
First, convection is more likely to occur in the form of a forward
propagating MCS arriving from the west, as opposed to locally
developing thunderstorms anchored to a boundary. While very high
PWATS approaching 2 inches will once again support efficient rain
rates, the progressive nature of such a complex would likely
limit the overall potential for more impactful, flood-producing
rain. This scenario is not yet a certainty, but latest CAM
solutions seem to be trending this way. While it shouldn`t be
discounted that the 12Z HREF LPMM data once again produces a
narrow stripe of 2 to 4 inches of rain across these areas tonight,
these higher totals appear less likely to occur than they did
last night.
On the other hand, instability projections during the overnight
period have increased when compared to previous forecasts, with HREF
probabilities of 1000 J/kg of surface based CAPE now reaching 20 to
40 percent, with some more recent CAMS exceeding 2000 J/kg. Even if
a shallow stable layer develops overnight and storms remain
elevated, MUCAPE is likely to remain at least 1500-2500 J/kg as
thunderstorms either arrive from the west or develop locally. Wind
fields are expected to be weaker overall than the previous night in
spite of an arriving shortwave, but sufficient deep layer shear is
nonetheless expected to be in place to support thunderstorm
organization (25 to 35 kt of 0-6km shear). HREF ensemble mean 0-1km
SRH is also likely to approach 100 to 200 m2/s2, although it`s
unclear how accessible these near-surface parcels will be. Given all
of these considerations, there will be at least a limited potential
for thunderstorms to produce damaging straight line wind gusts and
occasionally large hailstones with any complex that moves through
the area very late tonight and early tomorrow morning, with a
slightly increased potential for damaging winds should this complex
remain surface-based.
Morning thunderstorms are likely to clear the area to the east by
shortly after sunrise. This will be followed by a break in
thunderstorm activity, along with another warm and humid afternoon
across the area. Once again though, the potential for a deep cold
pool may keep areas slightly cooler through the day, although this
remains to be seen. Likewise, what also remains somewhat uncertain
is just how quickly the atmosphere can destabilize in the afternoon
in the wake of morning storms. A cold is expected to push into the
area through the day, and by mid afternoon this may provide enough
of a focus for additional thunderstorm development. Exactly where
these storms develop, along with their potential strength, will
largely depend on how effectively the atmosphere can destabilize in
the afternoon. On the bullish end of the spectrum, it would be
reasonable for around 2000 J/kg of SBCAPE to develop in spite of the
slightly drier and worked-over airmass, which would occur in tandem
with around 25 to 35 kt of 0-6km bulk shear. Should this level of
destabilization occur, a few thunderstorm clusters may be capable
of producing marginally severe hail and strong downburst winds.
This potential is limited overall, both due to the uncertainties
described above and the expected limited coverage (only 20 to
30%).
Thunderstorms will diminish in the evening, and the cold front will
continue to push south of the area, placing the entire region within
a regime of northerly flow by Friday morning.
BRC
.LONG TERM... (Friday through Next Wednesday)
Issued at 242 PM CDT Wed Jul 19 2023
Overnight Thursday, yet another shortwave is expected to dig into
the area, although the track of this wave continues to trend towards
a slightly more southerly track. When combined with the expected
progression of the previously discussed cold front, this is is
expected to shunt another round of thunderstorms farther south into
southern Missouri and northern Arkansas. As a result, most local
areas are more likely to remain dry through the night and into
Friday, with most of our local area experiencing comfortable below-
average temperatures and low humidity throughout the day Friday. The
lone exception could be parts of the Ozarks, which still have a low
potential (20 to 30%) for a few showers and thunderstorms early in
the day. These comfortable temperatures and generally low humidity
are likely to continue into Saturday as a northerly flow regime
persists, although a few weak showers can`t be ruled out in the
afternoon. On Sunday, a weak cold front will sink into the area, and
as a result precipitation chances have incrementally increased to
around 20 to 40 %, although the chances for significant rain or
noteworthy thunderstorms remains low.
Monday through mid-week, a longwave ridge is expected to slowly inch
eastward, and southwest to southerly flow will return. This will
likely result in a quick warming trend, although ensemble members of
both the LREF and NBM display a non-trivial amount of spread in
the temperature forecast during this period. In other words,
confidence is high that temperatures will be noticeably warmer
early to mid week, but it`s unclear whether it will get hot enough
to produce noteworthy heat impacts.
BRC
&&
.AVIATION... (For the 06z TAFs through 06z Thursday Night)
Issued at 1032 PM CDT Wed Jul 19 2023
VFR conditions expected overnight with light winds. There`s an
outside chance of a thunderstorm mainly in the St Louis metro, but
the chances are too low to mention in the TAF. A cold front moves
through from northwest to southeast during the day on Thursday,
shifting winds to the WNW behind it. A thunderstorm could form
along the front especially in the St Louis metro around midday
but again the chances of this are too low to mention in the TAF.
If thunderstorms do occur, brief heavy rain and lower visibility
are likely, but otherwise VFR should continue.
Kimble
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 314 PM CDT Wed Jul 19 2023
Key Messages:
- Still a threat of a strong storm or two across portions of
eastern NE through the evening.
- Turning hot and dry toward the end of the weekend and beyond.
Severe weather trends are the first concern, and based on clouds
and showers hanging tough this afternoon, that threat may be
diminishing. Scattered showers continue to move through some of the
area this afternoon. A cold front remains draped from northwest NE
through eastern SD, and stronger storms have fired across portions
of SD within the last couple of hours. The latest HRRR model runs
show continued development possible along the frontal boundary
from eastern SD through central NE into the early evening, but all
of that remains west or north of our forecast area. There does
still appear to be a window of opportunity if those storms can
hold together and perhaps impact northeast NE if they hold
together in the 23-01z period. This trend is also supported by
the 18z Nam Nest as well. But storms across central NE may remain
far enough west to not be able to hold together to reach other
areas of eastern NE this evening. So overall, the severe threat
seems low for most of our area. SPC did just trim the slight risk
area a little bit with these thoughts in mind. Otherwise, the
cold front will make slow progress through the forecast area from
north to south of overnight, gradually pushing rain chances out of
the area by about 1 am and beyond.
Thursday looks like a beautiful day with a lot of sunshine with
highs in the lower to middle 80s.
There is a weather system coming out of the Rockies Thursday
night, but it slides to the south, and most of the rain associated
with that system will likely remain south of the forecast area.
There is one more weather disturbance that looks to move through
the region Friday night into Saturday, which could trigger a
spotty storm or two. Highs Friday in the lower 80s, and mid to
upper 80s for Saturday.
And then it turns hotter and dry from Sunday and beyond. High
temperatures reach the lower to mid 90s each day, but could reach
the mid to upper 90s by Tuesday and Wednesday. And a location or
two have a good chance of reaching 100. It will also be
increasingly humid with dewpoints in the upper 60s to lower 70s,
which could help push heat index values to 100 to 105 by Tuesday
and Wednesday as well.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 549 PM CDT Wed Jul 19 2023
VFR conditions are still forecast to prevail through the period,
with low confidence that any showers or storms make it to the
terminals this evening. Some scattered rain showers with an
isolated rumble of thunder or two could end up diminishing by the
time they reach near KOMA, but close eyes will be kept on any
development for in-between TAF issuance amendments. Tonight a
slow-moving cold front will pass through with north-northwesterly
winds settling in.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...DeWald
AVIATION...Petersen
Area Forecast Discussion
National Weather Service Nashville TN
857 PM CDT Wed Jul 19 2023
...New UPDATE...
.UPDATE...
Issued at 835 PM CDT Wed Jul 19 2023
The radar is quiet across Middle Tennessee this evening as the
atmosphere is still recovering from this morning`s round of
showers and storms. Mesoanalysis shows this well with MLCAPE
values 500 J/kg or less east of I-65 and PWAT values ranging from
1.5-1.75 east of I-65. West of I-65, some better moisture has
worked in from the west with PWAT values approaching 1.9 in the
far northwest. The richer moisture will be advected eastward
throughout the night with another surface boundary oriented NW to
SE near our northwestern counties toward Cumberland county. This
will be the focus of development for the next round of showers
and storms. Storms are expected to develop around 08z and become
more widespread through the rest of the overnight hours. Showers
and storms will continue through Thursday morning. When all is
said and done, rainfall totals of 3+ inches will be likely for
some areas. A couple of runs of the HRRR have shown the potential
for isolated amounts of 5+ inches. This will require storms to
train over the same area for a period of time. Looking at the
storm motions, they appear to be slightly less parallel to the
surface boundary in comparison to this morning`s wave. As far as
the area of highest rainfall amounts, CAMS have varied in the
location of the bullseye but generally along and north of I-40 has
been the focus. As mentioned in the afternoon discussion, if
these higher amounts fall along and west of I-24, this would cause
the biggest issues given the high rain totals from today`s round.
Overall, the forecast remains on track. No major changes were
made.
&&
.SHORT TERM...
(This afternoon through Friday night)
Issued at 151 PM CDT Wed Jul 19 2023
Once again we are concerned about the potential for flash
flooding. We have issued a Flood Watch for the north half of our
area valid from midnight to noon Thursday.
Portions of the Mid State have been soaked in the past 24 hours.
The band of greatest rainfall has occurred from Dover and Waverly,
southeast across the Franklin area. Many spots have had more than
3 inches of rain. Some spots near the Tennessee River have had
more than 5 inches. Thankfully, we have not heard of any
fatalities, and we have not heard of major property impacts like
they have seen in parts of western KY.
For tonight, we will see a setup similar to last night. Warm
advection will develop along a low level boundary from western KY,
east southeast into northern TN. A very moist air mass will remain
in place with precipitable water values over 2 inches and adequate
cape through a deep vertical layer to bolster deep convection with
efficient rainfall production. A couple of waves will move along
the zone helping to initiate the storms. Unfortunately, our
confidence on the coverage and location of rainfall is low. Some
models are focusing over far northwest area. This would be bad
because of all the rain that has already fallen. Other models are
focused on our northeast quadrant. This would probably not be as
bad since this area has not had recent heavy rainfall. But, several
models are signaling potential for very heavy downpours in our
northeast counties. More than 3 inches of rain could fall within a
short period from the stronger storms, which would certainly
exceed flash flood guidance. Heavy downpours could continue
throughout the morning hours. It looks like coverage and intensity
will drop off significantly for Thursday afternoon.
Chances for on and off thunderstorms will continue Thursday night
through Friday night. There will continue to be potential for
localized flooding and marginally severe storms as we remain
within the same very warm and humid air mass, but for now we do
not expect anything widespread in terms of flash flooding or
severe storms Thursday night through Friday night.
&&
.LONG TERM...
(Saturday through next Wednesday)
Issued at 151 PM CDT Wed Jul 19 2023
After showers move out late Friday night or very early Saturday
morning, the weekend looks great. It will mainly clear with
cooler, below normal temperatures and much lower humidity levels.
Weekend highs will be mainly in the low to mid 80s with lows
mostly lower 60s. This will occur as more northerly flow aloft
brings a surface high pressure system down across the Mid State.
Looking ahead to next week, the upper ridge from the mid section
of the country will expand eastward. This will bring a warming
trend. Humidity levels will creep up, but it will not be as soupy
as the past few days. A few weak impulses rounding the ridge
could bring some scattered thunderstorm chances, mainly in the
afternoon hours each day. By midweek, many areas will be up in the
low to mid 90s for highs.
&&
.AVIATION...
(00Z TAFS)
Issued at 633 PM CDT Wed Jul 19 2023
Another round of thunderstorms is expected to move through the
area overnight tonight and impact all terminals. Tempos are in for
the best timing of impact at each terminal. MVFR cigs/vsbys are
possible during storm passage, especially over CSV/SRB. Once the
line of storms clears the area, VCSH will linger through 20Z.
Winds are currently southerly and will shift westerly once the
front moves through. Some isolated wind gusts of up to 20kts are
possible during frontal passage.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 75 89 73 88 / 60 80 30 40
Clarksville 75 88 72 86 / 80 80 20 30
Crossville 67 80 66 81 / 60 90 40 50
Columbia 74 91 72 88 / 20 60 50 50
Cookeville 70 82 69 83 / 80 90 40 40
Jamestown 68 80 68 81 / 80 90 40 40
Lawrenceburg 73 90 72 87 / 20 50 50 60
Murfreesboro 73 89 72 89 / 40 70 40 50
Waverly 74 88 71 85 / 30 70 30 40
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
Flood Watch from midnight CDT tonight through Thursday morning
for Cannon-Cheatham-Clay-Cumberland-Davidson-De Kalb-Dickson-
Fentress-Houston-Humphreys-Jackson-Macon-Montgomery-Overton-
Pickett-Putnam-Robertson-Rutherford-Smith-Stewart-Sumner-
Trousdale-Van Buren-Warren-White-Williamson-Wilson.
&&
$$
UPDATE.......Reagan
SHORT TERM...13
LONG TERM....13
AVIATION.....Baggett
Area Forecast Discussion
National Weather Service Paducah KY
1025 PM CDT Wed Jul 19 2023
.UPDATE...
Issued at 1025 PM CDT Wed Jul 19 2023
KPAH radar estimates are already approaching an inch between KCGI
and KPAH, so went ahead and started the Flood Watch a bit early.
UPDATE Issued at 859 PM CDT Wed Jul 19 2023
Just updated PoPs and Wx to bring the forecast into line with the
00Z HRRR model.
Convection is expected to develop around 3 AM in the Cairo to
Paducah areas. The initial development will progress southeast,
but trailing convection is expected to train over the Purchase
area around daybreak, so additional flooding problems will be
possible in those areas hardest hit by last night/this morning`s
flooding. Hopefully, the heavy rains will hold off until daybreak.
A few severe storms with isolated damaging winds and large hail
cannot be ruled out, but the primary threat will be heavy rainfall
and flooding.
UPDATE Issued at 637 PM CDT Wed Jul 19 2023
We are watching a disturbance currently moving across
central/northern Missouri to see if it can touch off our next
round of convection later this evening. If it doesn`t, the next
round may be overnight into Thursday. However, there is the
possibility that nothing of significance develops through
Thursday.
The AVIATION section has been updated for the 00Z TAF issuance.
&&
.SHORT TERM...(Tonight through Friday night)
Issued at 320 PM CDT Wed Jul 19 2023
Lingering light showers continue over portions of Southeast
Missouri and far Western Kentucky this afternoon. Torrential
rainfall from training storms last night through this morning has
resulted in severe flooding, mainly in far Western Kentucky and
areas just to the northwest in far Southern Illinois. The Kentucky
state daily rainfall record appears to have been broken. Multiple
flash flood warning products remain in effect. With the boundary
remaining a little southwest of expectations in yesterdays` model
runs and, with cloud cover lingering, temperatures peaked in the
upper 70s to lower 80s today.
Hi-res models generally agree on additional shower and storm
chances tonight into tomorrow morning, though differ in timing and
positioning. The NAM-Nest and FV3 lean towards evening development
in the Pennyrile and Central Kentucky respectively, while the
others remain fairly dry. Most agree on storms from
Kansas/Missouri progressing towards the forecast area late in the
night varying with trajectory either far Southeast Missouri or
across Southern Illinois to the Evansville Tri-State. Backbuilding
training is, fortunately, unlikely with these storms so rainfall
amounts will generally stay in the half inch to 1.5 inch range
with locally higher amounts possible. A Flood Watch has been
issued for locations hit by the torrential rainfall last night
into today, as saturated soils will make subsequent rounds of
flooding faster to develop. A slight risk ERO covers much of the
same area as the Flood Watch along with the Evansville Tri-State.
PWs remain very high, albeit not to the extremes last night into
today. CAPE and shear will be adequate for a few strong storms and
a severe storm cannot be ruled out. A marginal risk of severe
weather covers the Quad State tomorrow aside from a slight risk
barely clipping SWIN.
A cold front pushes through Thursday evening, which should limit
the slight chance to chance PoPs Friday to southern portions of
the forecast area, with the NAM the northern outlier. The other
models keep rainfall light on Friday.
Humid conditions will keep lows in the 70s tonight. The passage of
a storm system by midday should lead to some afternoon heating
tomorrow to the upper 80s with 90 possible in the western half.
Highs drop off to the lower 80s Friday following the cold front
with lows in the lower 60s Friday night as dry air moves in.
.LONG TERM...(Saturday through Wednesday)
Issued at 320 PM CDT Wed Jul 19 2023
Mostly clear skies and dry air Saturday will allow for warming to
the mid-80s. Highs lift to the upper 80s Sunday with
southwesterly winds ahead of a trough passage. Models keep
precipitation minimal with the trough late Sunday with the GFS the
wetter exception. PoPs are limited to the slight chance to chance
range in the northwest but further adjustments are likely in
later model cycles. Northwesterly flow aloft continues early next
week with southerly flow at the surface. Progression of the upper
ridge slightly northeastward from the Desert Southwest along with
southerly flow and dry conditions will lift high temperatures to
the lower half of the 90s early next week.
&&
.AVIATION...
Issued at 637 PM CDT Wed Jul 19 2023
MVFR ceilings will linger at KMVN through the evening. With lots
of uncertainty in the convective forecast over the next 24 hours,
the mention of VCTS was limited to KPAH late tonight into the
morning. This is based on the latest HRRR which generally keeps
its convection between the other sites. Otherwise, there is some
potential for low clouds, IFR or lower, over the northern sites
late tonight through the morning, but confidence is too low to add
the low ceiling at this time.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Flood Watch through Thursday morning for ILZ080-081-084>086-
088>094.
MO...Flood Watch through Thursday morning for MOZ076-086-087-111-112.
IN...None.
KY...Flood Watch through Thursday morning for KYZ001>013-017-022.
&&
$$
UPDATE...DRS
SHORT TERM...ATL
LONG TERM...ATL
AVIATION...DRS
Area Forecast Discussion
National Weather Service Portland OR
845 PM PDT Wed Jul 19 2023
Updated aviation discussion
.SYNOPSIS...Dry southwest flow aloft and low-level onshore flow will
persist through the upcoming weekend, resulting in slightly above
normal temperatures and continued dry weather. An upper level trough
will approach the Pacific Northwest early next week, bringing
relatively cooler temperatures and a 10-30% chance of light rain
across southwest Washington.
&&
.DISCUSSION...Wednesday night through Tuesday night...Satellite
imagery from 3 PM PDT Wednesday showed an area of upper level smoke
extending across the central OR coast range into much of the
Willamette Valley and Columbia River Gorge. This smoke layer
originated from the Flat fire burning in southwest Oregon. The HRRR
Smoke model suggests upper level smoke will continue to produce hazy
skies across much of the area through Thursday afternoon/evening
before pushing eastward over the Cascades Thursday night. This smoke
layer was thick enough to cool temperatures by a couple of degrees
across the Salem area on Wednesday, but aside from that there have
been little to no impacts from this smoke layer. Air quality has
already improved significantly for most locations.
Otherwise, expect very little change to the overall weather pattern
through the weekend. The strong upper level ridge bringing record
heat to the Four Corners region will expand northward along the
Rockies into Canada, persisting through Friday. Meanwhile, low
pressure presently over the Gulf of Alaska will drift southeastward,
settling off the coast of British Columbia Thursday. The Pac NW will
remain in between these two features for the next several days, with
stable southwesterly flow through at least the weekend and possibly
into early next week. This setup will result in the continuation of
above normal temperatures over southwest WA and northwest OR, however
onshore flow will help modify the airmass and keep temperatures from
climbing well above seasonal normals. The deterministic NBM generally
suggests the interior lowlands will warm well into the 80s Thursday
through Saturday. With the lack of significant offshore flow, the
coast will remain much cooler as usual with occasional low clouds and
fog.
Conditions will most likely begin to cool slightly Sunday into early
next week as an upper trough currently over the Gulf of Alaska slowly
begins moving inland. Deterministic models mostly bring the upper low
into British Columbia, but WPC`s cluster analyses reveal that a
minority of ensembles (30-50%) are considerably slower/weaker than
the others with the upper trough. Given the strength of the upper
ridge, we would likely put the chances a bit higher than that.
However, if this trough does wind up deep enough to extend into
northwest OR, then light rain would likely materialize over southwest
WA and far northwest OR. NBM PoPs are currently rather low at 10-30%
over southwest WA, and there is a 5-10% chance for rain amounts of
0.25 inches or greater. -TK/Weagle
&&
.AVIATION...Dry, southwest flow aloft through Thursday with
predominately VFR conditions expected inland. The onshore push
has brought IFR to LIFR marine stratus back to the coast this
evening and is expected to persist overnight through Thu morning.
Guidance suggests there is a 60-70% chance of cigs remaining IFR
along the central coast, and low MVFR at the north coast, through
Thu evening. Visibility along the central coast is also expected
to deteriorate with a 50-70% chance of vsbys dropping below 1 SM
between 04-12z Thu. As of 03z Thu, marine stratus is already
pushing into the Coast Range gaps, and probabilities of MVFR
stratus pushing into the southern Willamette Valley have increased
to around 40-50% at KEUG between 10-16z Thu.
For detailed Pac NW aviation weather information, go online to:
http://weather.gov/zse
KPDX AND APPROACHES...VFR with mostly clear skies. Northwest winds
becoming light overnight. /DH
&&
.MARINE...Gusty northerly winds will continue through the
majority of the week with a surface high pressure offshore and a
thermally induced trough inland. Wind driven seas 2 to 5 feet
through the week. Winds will peak in the afternoon and will
diminish during the overnight hours. Towards the latter part of
the week, a slowly approaching Alaskan low will cause a change in
the overall synoptic pattern, but will result in minimal change in
the current observed weather pattern. -BMuhlestein/42
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&
$$
www.weather.gov/portland
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Area Forecast Discussion
National Weather Service Tallahassee FL
930 PM EDT Wed Jul 19 2023
...New UPDATE...
.UPDATE...
Issued at 924 PM EDT Wed Jul 19 2023
Outflow from an upstream decaying MCS helped initiate convection
around 20z Wednesday just north of our CWA. Some of these storms
progressed southeastward into our GA/AL counties through about 23z
when the lack of instability led to their dissipation. Since that
time, the radar is quiet and with no upstream convection, expect
a storm-free overnight.
Hazy conditions will continue, however. In fact, a few sites
around the region are already reporting decreasing visibilities,
so this trend will need to be monitored through night. The
inherited forecast is largely on track, so no significant
adjustments were needed.
&&
.NEAR TERM...
(Through Thursday)
Issued at 408 PM EDT Wed Jul 19 2023
For the remainder of today and tonight, hazy conditions look to
stick around while some isolated convection ahead of a decaying
upstream MCS attempts to brush through our northern-tier GA
counties. Patchy fog is then possible roughly along/west of the
Apalachicola River in the early AM hrs. Overnight lows are in the
sultry mid-70s. The HRRR Smoke Vertically Integrated Smoke suggests
the haze plume mostly shifts offshore after sunrise, but extends
across parts of the Forgotten Coast.
The main highlight for tomorrow is the hot weather thanks to strong
subtropical ridging that stretches from the SW US into the Western
Atlantic. This feature is slated to be accompanied by anomalously
high 500-mb heights modeled around 595 dm, which ties the daily max,
per SPC sounding climatology for TLH! In addition forecast 850-mb
afternoon temperatures are nearly 22C, which would be about a degree
above the daily max. When you then factor in large-scale subsidence
that should limit convective coverage, all signs point towards
hazardous heat.
Forecast highs are in the mid to upper 90s away from the immediate
coast. Widespread dew points in the 70s push peak heat indices well
above 100 degrees, with isolated pockets of 108-112-degree readings
focused over the Central FL Big Bend and along the east to SE
fringes of our service area with JAX. Given that our local criteria
values are not extensive, we decided to hold off on issuing on a
Heat Advisory for this package and have the evening-midnight shift
re-assess.
&&
.SHORT TERM...
(Thursday night through Friday night)
Issued at 408 PM EDT Wed Jul 19 2023
The persistent upper ridge will continue
gradually eroding Thursday evening through Friday as troughing over
the Great Lakes / Ohio Valley persists. The short term will be
generally similar to what we have been dealing with as of late with
subsidence aloft suppressing showers and storms from forming across
the area despite a moist boundary layer remaining in place via WSW
surface flow. PoP`s have been capped around 10-20% as an isolated
brief shower or two may form given the moist environment, though it
still appears quite unlikely at this time.
Thursday evening into Friday will see temperatures drop into the mid
to upper 70s overnight before rebounding back into the upper 90s
during the day. Though temps across most areas should stay contained
in the upper 90s, apparent temperatures are forecast to reach 108-
111 across the majority of the CWA, likely warranting a heat
advisory. Following this, temperatures will once again fall to the
mid 70s overnight.
&&
.LONG TERM...
(Saturday through Tuesday)
Issued at 408 PM EDT Wed Jul 19 2023
Saturday will abruptly usher in a pattern shift
as the upper ridge axis erodes with the aforementioned troughing
to the north. Additionally, this will enable shortwave
disturbances to pass through the area which will provide
sufficient lift for storms across the area in the afternoon hours
with robust moisture at the surface. At least some severe appears
possible given 0-500mb bulk shear ranging from 30-40kts, MLLR`s
approaching 7C/km, and SBCAPE approaching 3000J/kg, with a few
severe wind gusts appearing possible and perhaps some small hail.
Sunday and Monday both appear similar to Saturday, though there
remains some model inconsistencies regarding parameter spaces.
Regardless, this weekend into next week will be quite wet with
storms expected each day areawide.
Maximum temperatures will start off the period in the upper 90s,
gradually decreasing to the low 90s through Monday. Tuesday may
usher another pattern shift with warmer temperatures making another
appearance as ridging builds back in. Overnight lows through the
period should hover around the low to mid 70s.
&&
.AVIATION...
(00Z TAFS)
Issued at 745 PM EDT Wed Jul 19 2023
The thickest of the haze stemming from Canadian wildfires is
probably behind us. Haze will continue to some extent through
Thursday, but it should not lower vsbys enough on Thu to include
in TAFs.
Similar to today, a few short hours of fog and low stratus are
possible around sunrise on Thursday morning. Used persistence from
Wed morning as a major indicator for timing and amount of cig/vsby
reduction on Thu morning.
Otherwise, Thursday afternoon should feature isolated
thunderstorms along the seabreeze front, possibly bringing short-
duration impacts for ECP and TLH. Coverage and timing uncertainty
preclude mention in the TAFs at this time. Elsewhere at DHN, ABY,
and VLD, warm air aloft will nearly shut down the usual chance of
afternoon storms.
&&
.MARINE...
Issued at 408 PM EDT Wed Jul 19 2023
A light to moderate breeze out of the west southwest will
remain persistent across our waters over the next few days with seas
generally 2 feet or less. There will be low chances for isolated
showers over the next few days, although chances and coverage will
begin to increase Friday into the weekend. Locally intense and
erratic wind gusts are likely near and within thunderstorms.
&&
.FIRE WEATHER...
Issued at 408 PM EDT Wed Jul 19 2023
Hot and humid conditions are expected the next 3 days with peak
afternoon heat indices well above 100 degrees. Appreciable rain
chances hold off until Saturday. A wet pattern is forecast by then
and spill over into early next week with a return of scattered to
widespread showers and thunderstorms. As far as dispersions,
forecast values are at or above 75 for portions of SW GA tomorrow
and Friday and high areawide on Saturday.
&&
.HYDROLOGY...
Issued at 408 PM EDT Wed Jul 19 2023
Dry conditions are expected through the end of the workweek.
Chances for rain increase substantially this weekend with rain
expected daily through Monday with around 1 inch in the forecast.
Thus, there are no flooding concerns for the next 5-7 days at this
time.
&&
.SPOTTER INFORMATION STATEMENT...
Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur by calling the office or tweeting us @NWSTallahassee.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 75 97 76 98 / 10 20 0 10
Panama City 79 92 78 91 / 10 10 0 10
Dothan 75 95 74 96 / 10 10 0 20
Albany 75 97 76 97 / 10 10 0 20
Valdosta 75 98 76 98 / 10 10 0 10
Cross City 74 95 77 94 / 10 30 0 20
Apalachicola 77 91 78 91 / 0 10 0 10
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...None.
&&
$$
NEAR TERM...Godsey
SHORT TERM...Worster
LONG TERM....Worster
AVIATION...Haner
MARINE...Worster
FIRE WEATHER...IG3
HYDROLOGY...Worster