Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/29/23
See below for an aviation forecast discussion for the 00Z TAFs.
&&
.SHORT TERM...(This Evening through Saturday Night)
Issued at 322 PM CDT Fri Jul 28 2023
As of 3 PM CDT, the showers and storms from this morning have moved
east and out of the area but there is a storm still moving southeast
through the central part of our CWA. Temperatures are in the 80s to
low 90s.
A weak shortwave makes its way across the area this afternoon and
evening bringing a chance for some storms. Most of our CWA is in a
marginal risk (1 of 5) for severe weather but our far southern
counties are included in a slight risk (2 of 5) afternoon and
evening mostly for a possibility of large hail. 0-6km bulk shear
from the HRRR shows around 40 to 50 kts which pushes things into the
supercell realm of possibility. Low level wind shear is relatively
low which increases the potential for large hail. Higher MUCAPE
values are concentrated in the southeastern portion of the CWA as
well with values around 1500 J/kg. CAMs aren`t sending a clear
message on where storms will be forming today, but most have at
least some sort of activity in the slight risk area. Bottom line, if
storms do form this afternoon some could become strong to severe
with large hail as the biggest threat.
Tomorrow, things are expected to be a little quieter, with a
marginal risk (1 of 5) just reaching into the southern portions of
Jones and Lyman counties. Areas west of the James River Valley are
in a general thunderstorm outlook. Bulk shear values are favorable
for storms but the instability isn`t there. Models are showing
MUCAPE values less than 500 J/kg. Lapse rates fall to between 6 and
6.5 C/km during the day. So, if storms do form, no severe weather is
expected.
Temperatures will cool back down to around to slightly below normal.
There is a little bit of near surface smoke, but not enough to
reduce visibilities. Another plume of elevated smoke will reach
northern SD this afternoon but moves out pretty quickly overnight.
Winds could get pretty gusty in and around thunderstorms if they
form later this afternoon, but otherwise gusts up to 25 mph across
the area through the period.
.LONG TERM...(Sunday through Friday)
Issued at 322 PM CDT Fri Jul 28 2023
The main forecast challenge in the extended period revolves around
the chances for showers and thunderstorms. An upper level ridge will
be over the Rockies through a majority of the period, with northwest
flow over the Northern Plains. Will see a series of shortwaves ride
through this flow and across the CWA.
At the surface, high pressure will be over the eastern CWA into
Minnesota Sunday and Sunday night, with a trough over the lee of the
Rockies. The high then slides slightly to the east along with the
trough to the west, with the CWA becoming situated between the two
systems. The boundary to the west then looks to finally track across
the CWA on Wednesday, with high pressure settling back in at the end
of the period. The best chances for potential precipitation look to
be Sunday night into early Monday, and again Monday night, with
smaller chances later in the period. No real confidence on severe
weather chances at this time. Temperatures will be a bit cooler to
start the period, but will warm up again for the latter half of the
period.
High temperatures will be in the 80s Sunday and Monday, in the upper
80s to mid 90s Tuesday and Wednesday, and in the mid to upper 80s
Thursday. Overnight lows will be in the upper 50s to mid 60s Sunday
night, then in the 60s Monday night, Tuesday night and Wednesday
night.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 618 PM CDT Fri Jul 28 2023
Terminals KABR,KATY,KPIR,KMBG
VFR conditions are forecast during the TAF period. It`s possible a
thunderstorm or two could be rolling up to the Missouri River
valley (KPIR/KMBG?) later tonight after 06Z, perhaps closer to 12Z
Saturday.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...Dorn
SHORT TERM...KK
LONG TERM...Parkin
AVIATION...Dorn
Area Forecast Discussion
National Weather Service La Crosse WI
1050 PM CDT Fri Jul 28 2023
.DISCUSSION...(Tonight through Friday)
Issued at 140 PM CDT Fri Jul 28 2023
Key Messages:
- Scattered strong/severe storms tonight with large hail and
damaging wind threat...generally along/south of I-94. Higher end
threats focused across northeast IA/southwest WI.
- Seasonable, dry for the weekend...continuing into the new week
with some rain chances near mid week.
* STORMS THIS AFT/EVENING: some severe with wind, hail threat
Somewhat chaotic atmosphere to deal with with a front and variety of
other boundaries leftover from last night/this morning`s convection
laying across/near the local forecast area. Bits of upper level
shortwave energy currently over the northern plains on track to
shift east across the region this evening, interacting with the
boundaries and any ongoing convection.
Latest RAP suggests main sfc boundary will layout from northern IA
into southern WI by 21z, with a weak low developing over northeast
IA. 3500+ J/kg of SBCAPE pool into the boundary while 40-50 kts of 0-
6km develops along/near the front. The deep layer shear does hold
farther north, dropping off as you move southward into the higher
instability. Broad low level moisture transport into/across the
front, but more a northeast fetch focuses into northern
ILL/southeast WI.
CAMS generally favoring sparking storms as convective temps are
neared/reached, with the sfc boundaries acting as focuses ~ 5 to 7 pm
time frame. With the moderate/strong instability, fairly explosive
convection is likely, the kind that could go from zero to severe in
a 1/2 hour. Depending on where development originates, large hail
and wind would be the threats, gradually morphing into line
segments/clusters of damaging winds. If development originates on
top of the local area, the hail threat is heighten. If storms kick
off farther west, the wind threat would become the primary threat. A
lot of uncertainties still.
Outside of the sfc boundaries, one shortwave of note is currently
pushing east across the dakotas, moving into MN. Persistent area of
showers and a few thunderstorms with this feature, which is progged
to move east/southeast over northern WI. This will push over the
northern extent of the instability gradient with RAP MUCAPES of 1-
1.5K J/kg. Storms should get more punchy with 40+ kts of 1-7 km
shear aiding storm development. Some strong/severe storm risk with
these too, although the higher risk/likely severe will lie a bit
more south (with the sfc boundary).
* COOLER, DRIER WEEKEND...stay seasonable for the new work week,
trending dry.
The upper level flow becomes more northwesterly for the upper
mississippi river valley on Sat as the upper level ridge re-
establishes westward and a trough carves out over the new england
states. Cooler (comparatively) and less humid air flows in from
Canada with highs about 10 to 15 degrees cooler than the past few
days.
Long range guidance hints that the upper level ridging could bulge a
bit eastward from its setup up over the rockies, which could push
temps a few degrees upward for the start of the work week - but
still cooler than the current warm up. Seasonable temps are then
favored for the rest of the new week.
As for pcpn chances, the only consensus in the GEFS/EPS ensembles
is to bring a shortwave trough across the region Wed/Wed night. Shot
for showers and storms would accompany the system. Otherwise, no
clear signals for rain chances into next weekend.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1039 PM CDT Fri Jul 28 2023
Dry conditions with light winds are expected during this TAF
period. Models are suggesting that a MVFR stratus ceiling develops
during the morning hours across the region, but confidence on this
potential is low. At LSE, there is a 50% chance for 2kft ceilings
or lower by 8-10Z, with a 30 to 40% chance for IFR ceilings
during that same time. There are smaller chances at RST, with a
30% chance for ceilings around 2kft and a 20% chance for IFR
ceilings. Opted to bring a prevailing MVFR ceiling at LSE for a
few hours this morning and have left RST at a sct020 and will
monitor trends. By late morning, VFR conditions will prevail
through the rest of the period.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...Rieck
AVIATION...JAW
Area Forecast Discussion
National Weather Service Boston/Norton MA
1042 PM EDT Fri Jul 28 2023
.SYNOPSIS...
Another round of strong to severe thunderstorms and flash
flooding is possible Saturday as a cold front slides through.
Mostly dry with cooler and more comfortable weather Sunday through
Wednesday. Unsettled weather returns late next week with showers and
thunderstorms likely Friday as a slow-moving cold front approaches.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
1035 PM update...
Following observational trends and some loose consensus and
increasing trend in the higher res guidance, I`ve made a few
changes to the forecast, more notably to include a mention of
isolated to scattered t-storms into CT and coastal RI overnight
to early Sat AM.
Currently tranquil if warm and quite humid for most of SNE given
the late hour. That should continue at least for the next few
hrs or so. However focus turns to active cluster of t-storms
across central PA and into western NJ, seemingly being
initiated by a subtle shortwave trough seen in WV imagery coming
out of northern WV and western PA. This complex of storms should
weaken, but storms in isolated to widely scattered coverage may
re- develop and/or arrive in a degraded state around later
overnight into CT, southern RI and the southern coastal waters.
Did look at a few point fcst soundings from the RAP and NAM for
the overnight at BID and WST as well as PVD and IJD, and what
somewhat notable is that progged elevated CAPE values are higher
over the waters/along the immediate coast than further north.
Not thinking severe weather from these but if storms can develop
as indicated, lightning, heavy rain and perhaps small hail (in
any intense storm) are possible. The risk increases for storms
early in the overnight - perhaps as soon as 2 AM, but more
likely in the 4-9 AM window for parts of northern CT, central
and southern RI and the southern waters. With weakening CAPE
values further northward, would think a lesser but not zero risk
for t-storms may exist. Will be monitoring trends for
adjustments for the overnight hrs. So, some potential to be
woken up by thunder for the southern coast and into part of CT,
but thinking otherwise dry weather elsewhere.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
440 pm update...
12z suite of guidance isn`t really changing our expectations for
tomorrow. Looks to be an active day convection-wise. As is
usually the case, hi-res CAMs are all over the place in
resolving what will happen (where, when and what). Tried to take
a more blended approach, leaning on HREF for this stab at the
forecast. Certainly many ingredients supportive of strong to
perhaps a few severe t-storms: 35-45kts of shear to promote
organized convection (especially later in the day), cold front
to focus development, decent instability (MLCAPE over 1000
J/kg). Of course there are downsides, biggest being especially
rather meager mid-level lapse rates of just 5-6C/km. There is
also a big question of timing -- as in, does the location of
the front line up with afternoon peak heating in the same place
that shear aloft is strengthening?
So the best estimates at this time, again relying on the HREF,
is that we will have enough of the ingredients to line up,
especially mid/late afternoon across more eastern/southern parts
of southern New England to generate some strong to potentially
severe t-storms. The HREF 4-hr max updraft output from SPC
probably best shows that area, with highest probabilities of
strongest updrafts tending to be centered in an area from OWD to
IJD to HFD. Right in line with what SPC has highlighted for it`s
slight risk area. Timing in general seems to be about noon to
9pm, with the main period probably in the 3p-6p timeframe.
That said, CAMs suggest that we may actually see two or three
rounds of convection during the afternoon. And to make things a
little more complex, a few hi-res models (like the 18z HRRR)
suggest there could be some elevated convection moving across CT
and perhaps RI during the early to mid morning hours.
Though there is a non-zero risk for a tornado, do think the
primary risk is localized straight line winds. Locally heavy
rain/minor flooding is also up there. Can`t rule out some hail
too.
Regarding the heavy rain threat, again guidance would suggest
that the heavier rain might be more across eastern areas. Which
is good, since that area can handle more. HREF Probability Match
Mean values show upwards of 3", so that indicates that is
probably a max spot value. Have held off on issuing any sort of
Flood Watch at this point. Think any heavy rain will be so
localized that only minor flooding of poor drainage areas will
be the issue. Concern will be if we get "training" of cells
across the same location, which is a possibility. Did
coordinate with WPC to highlight much of the area in a Slight
Risk for Excessive Rainfall. Later shifts can review the aspect
of the need for a Flood Watch.
Have left the Heat Advisory in place. Certainly an earlier start
to the convection will mean we won`t reach the current forecast
highs and max apparent temperatures. Even so, it will be humid
and rather uncomfortable, so no need to slice things so thin to
take down the advisory at this time.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
440 pm update...
Highlights
* Cooler, mainly dry, and less humid Sunday through Wednesday.
* Warmer and more humid with showers and thunderstorms returning
late in the week. A few strong storms possible Friday.
Sunday through Tuesday...
At upper levels, there will be a weak trough over the region from
Sunday through Tuesday. Weak high pressure at the surface Sunday and
Monday becomes stronger Tuesday as high pressure moves in from the
west. Much drier air will be the rule, with dewpoints in the 50s
northwest to lower 60s southeast coast. Highs mainly in the upper
70s to lower 80s each day. Mainly sunny days and clear nights.
However, it is summer, so a very isolated diurnal shower cannot be
ruled out.
Wednesday...
The upper trough moves off the coast by Wednesday with a ridge axis
building in from the eastern Great Lakes. With high pressure at the
surface, too, expecting full sunshine and highs in the 75 to 80.
Thursday and Friday...
Another trough digs toward the Great Lakes region. High pressure at
the surface moves off the coast, allowing moist south to southwest
winds to return. Dewpoints will steadily rise, reaching sultry
levels again...near or above 70...by Friday. A cold front will
slowly be approaching from the west and it could have waves of low
pressure along it as it moves through the Appalachians. Thursday
will start out sunny, but clouds will be on the increase in the
afternoon and there is a chance of showers or a few thunderstorms,
mainly in western MA and northern CT.
Although it is still a full week away, at this time, it looks like
Friday would be the day for the most numerous showers and
thunderstorms ahead of that slow-moving cold front. GFS wind fields
are strong, with 40-50 knots of bulk shear and potentially high low-
level helicity. Will need to keep an eye on the potential for severe
weather, as well as the potential for localized flooding.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00Z update...
High confidence through tonight. Moderate confidence Saturday.
VFR currently, and for most of the region that will continue
through tonight as well. Expect some IFR to develop after 04z
or so due to fog and low ceilings forming just offshore to our
south. Primarily an impact to ACK, FMH and HYA late tonight.
Small potential that some low clouds make their way up to PVD
prior to 12z.
Will need to pay close attention to whether a cluster of
thunderstorms moves across the south coast early to mid morning
on Saturday, as forecast by some models. Have added some VCTS to
southern terminals in the 12Z-15Z time frame to account for this
possibility.
Previous discussion...
More difficult part of the forecast revolves around the
evolution of the showers and thunderstorms for tomorrow.
Model guidance all show varying solutions, so stuck with a
blend. Best guess is that SHRA and TSRA start developing 14-17z
timeframe and continue through 00-03z or so. In general, looks
like northern sections will be earlier, with convection
eventually transitioning further south. Probably going to be
several rounds. With all the uncertainty, kept the TAFs fairly
general, but did introduce VCTS for the TAFs in the northern
half of the area. Think better chances for TSRA will be after
18z in places like PVD. Would expect MVFR to brief IFR to
accompany the SHRA/TSRA, with interludes of VFR outside of the
heaviest rains. IFR ceilings may persist much of the morning
along the south coast, primarily impacting ACK.
Winds will generally be from the southwest, but a front will be
moving across during the late afternoon and evening, producing a
wind shift to the NW to N. Uncertainty in timing of this front
remains, but best estimate is roughly 20-22z for places like
BOS, ORH, BDL to 22-01z for locations further south and east
like PVD, HYA, ACK
Improving conditions from west to east Saturday evening behind
that front. Should see primarily VFR conditions by 12z Sunday.
KBOS TAF...High confidence in TAF rest of today. Sea breeze
should push out in the 21-22z range. Moderate confidence for
tomorrow as it relates to timing of TSRA.
KBDL TAF...High confidence in TAF through tomorrow morning.
Moderate confidence Saturday with timing of TSRA.
Outlook /Sunday through Wednesday/...
Sunday: VFR. Slight chance SHRA.
Sunday Night through Wednesday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
755 PM update...
Overall high confidence. Rather tranquil overnight, although
some fog is expected to develop across the waters around the
Islands. Cold front moves through tomorrow, bringing showers
and thunderstorms to the region. Current forecasts are for
marginal wave heights to develop late Saturday into early
Sunday, especially for waters south of RI and the Cape. May need
to have a Small Craft Advisory hoisted at some point. Otherwise
high pressure will build in for Sunday and into early next week.
Outlook /Sunday through Wednesday/...
Sunday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers.
Sunday Night through Wednesday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 8 PM EDT Saturday for CTZ002>004.
MA...Heat Advisory until 8 PM EDT Saturday for MAZ005-010>021.
Air Quality Alert until 11 PM EDT this evening for MAZ020>024.
RI...Heat Advisory until 8 PM EDT Saturday for RIZ001>007.
Air Quality Alert until 11 PM EDT this evening for RIZ001>008.
MARINE...None.
&&
$$
SYNOPSIS...GAF/Nash
NEAR TERM...Loconto/GAF/Nash
SHORT TERM...Nash
LONG TERM...GAF
AVIATION...Loconto/GAF/Nash
MARINE...Loconto/GAF/Nash
Area Forecast Discussion
National Weather Service Cheyenne WY
535 PM MDT Fri Jul 28 2023
.SHORT TERM...(This evening through Saturday)
Issued at 220 PM MDT Fri Jul 28 2023
Main forecast concerns in the short term will be strong to severe
thunderstorms today and Saturday with strong winds and hail
possible.
Convection over the high terrain of southern WY has been ongoing
since around noon today with a few showers and storms developing.
Latest GOES WV imagery shows multiple shortwave passing over the
upper level high to the south that will continue to support storm
development with steep mid-level lapse rates. Initial updrafts may
struggle with drier air aloft, but better low-level moisture and
instability sits along the eastern slopes of the Laramie Range.
Latest dew point at KCYS is 54F degrees (higher than RAP analysis)
while KLAR is observing 34F degrees. CAPE in the hail growth zone is
700-900 J/kg over the eastern half of Laramie Co and southern Goshen
Co with enough wind shear for organized storms. SPC continues the
Day 1 Marginal Risk for the general area with quarter size hail
possible with the strongest storms through early this evening.
Additional storms will be possible farther north from Wheatland
through Alliance with an additional shortwave passage overnight as
well with any overnight MCSs that develop farther north in the
vicinity of the Black Hills.
Looking ahead to Saturday, expecting another round of afternoon
thunderstorms with the potential for a few strong to severe storms
capable of producing large hail and strong winds. Yet another subtle
shortwave will pass over the upper level high centered over the
southwest CONUS with surface southeasterly flow increasing low level
moisture. Could see early afternoon convection along the higher
terrain, but forecast soundings across the adjacent plains have been
pretty consistent with a capping inversion that should limit storm
coverage until mid-afternoon. The best moisture and greatest
instability looks to be placed along and north of the North Platte
River valley which should be where storms intensify with 0-6 km
shear over 40 kt. Fairly straight hodographs will favor splitting
storms with left-movers from initial convection off the Laramie
Range more likely to drift towards the greater instability where the
latest RAP has 2000-3000 J/kg of MLCAPE. CAMs are still split on the
evolution at this time with the HRRR showing a few discrete storms
moving into the NE Panhandle into the evening hours, while the
NAMNest tracks a line of storms down into northern CO closer to the
surface low. Will need to continue to monitor trends tonight,
especially with potential storms to the north and east as that could
alter the environment for storms tomorrow.
.LONG TERM...(Saturday night through Friday)
Issued at 220 PM MDT Fri Jul 28 2023
Minimal changes made from the overnight forecast. Continuing to
see trends indicating warmest temperatures at the beginning of the
week (highs in the 80s to low 90s), specifically Monday.
Temperatures then cool throughout the week (highs 70s to low 80s)
as widespread precipitation chances increase.
The location of the High Pressure System across the CONUS will be
the main factor in how hot and how wet southeast Wyoming and the
Nebraska panhandle will be next week. Currently, long range models
show the ridge axis positioned directly over southeast Wyoming
Sunday into Monday, beginning to shift east Monday night into
Tuesday. This shift east allows a deep plume of moisture to push
around the high pressure system, and into southeast Wyoming and the
Nebraska panhandle. GFS and ECMWF Ensemble mean PWATs are 0.7 to
0.95 inches west of the Laramie Range and 1.0 to 1.3 inches east of
the Laramie Range. These values are in the 150-200 percent of normal
range for west of the Laramie Range and 120-160 percent of normal
east of the Laramie Range. This drastic increase in moisture will
definitely encourage more shower and thunderstorm development. In
addition, more clouds and moisture would also result in temperatures
being a few degrees cooler in the afternoon. Thunderstorms that do
develop could be strong to severe. Seeing this high of PWAT values
as the Ensemble Mean does increase confidence in the ridge axis
shifting east allowing this plume of moisture to enter the region,
however, there is always the possibility that it remains stationary
longer, which would decrease precipitation chances and increase
temperatures.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 526 PM MDT Fri Jul 28 2023
Wyoming Terminals... Isolated showers and storms are currently
present across southeast Wyoming. VFR conditions at all terminals
at this time, though VCTS continues for KCYS for the next several
hours. Calm winds expected overnight with scattered cloud decks.
Winds begin to increase in the afternoon tomorrow, with
thunderstorm potential ramping up near the end of the 00Z TAF
period. Timing of these storms will be determined over the next
several hours.
Nebraska Terminals... Mostly clear skies across most of western
Nebraska with VFR conditions at all terminals. KSNY may see some
light rain showers over the next hour or two with VCTS in the TAF.
Isolated showers and thunderstorms across southeast Wyoming will
move into western Nebraska and begin impacting KBFF in the next
hour or two. Thunderstorms currently expected to increase in
coverage across western Nebraska, so included VCTS for all
terminals during the late evening and overnight hours.
Thunderstorms should move off to the east by 06Z. Gusty winds
return tomorrow afternoon.
&&
.FIRE WEATHER...
Issued at 220 PM MDT Fri Jul 28 2023
Showers and thunderstorms continue today across the area with
another round east of the Laramie Range Saturday. Warm and dry
conditions will continue across much of Carbon Co Saturday with
afternoon RHs dropping to around 15 percent. By late in the
weekend, cooler and wetter weather will arrive continuing into
early next week with daily chances for thunderstorms with wetting
rainfall.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...MB
LONG TERM...LEG
AVIATION...AM
FIRE WEATHER...MB
Area Forecast Discussion
National Weather Service Des Moines IA
1055 PM CDT Fri Jul 28 2023
...Updated for the 06z Aviation Discussion...
.DISCUSSION.../Tonight through Friday/
Issued at 158 PM CDT Fri Jul 28 2023
FORECAST HIGHLIGHTS:
--Hot, humid today with heat headlines persisting into tonight.
--Storm chances later this afternoon into tonight and/or overnight
into Saturday. Some strong to severe storms possible this
afternoon/evening with large hail and damaging wind gusts the
primary threats.
--Cooler temperatures this weekend.
--Periodic storm chances at times into next week.
DISCUSSION:
Not a clear-cut forecast heading into the rest of the day and
tomorrow with models continuing to suggest multiple scenarios and
flip-flopping between most likely solutions run to run.
Let`s start with what we know already. Upper-level pattern features
a strong high pressure over the southwest U.S. with near zonal flow
this morning that is expected to amplify into tomorrow as the ridge
builds over the western U.S. and a trough starts to deepen over the
eastern U.S. This leaves Iowa in west to northwest flow with
multiple waves continuing to drift through the overarching flow and
providing multiple opportunities for storms over the next several
days.
Focusing on the short term, midday surface analysis shows the
boundary near the IA/MN border in the north/east arching back
towards the IA/SD/NE border in the northwest. As expected, a warm,
moist airmass is south of this boundary with dew points well into
the 70s, some AWOS stations once again suggesting dew points in the
80s. Temperatures have also warmed into the upper 80s to 90s as of
midday resulting in heat indices well into the 100s, or overall
generally unpleasant. Midday satellite imagery shows two waves of
note, one moving eastward across northern Nebraska and the other
diving south out of the Upper Northern Plains with a second frontal
boundary associated with it. Mid-level temperatures in the +12 to
+14 range would suggest a capped environment is still in place over
much of the state as of ~18Z with 850mb analysis showing plentiful
moisture pooling in northern Iowa up towards the IA/MN border and
frontal boundary. The warm, moist airmass is leading to the
development of strong instability with ~18Z SPC mesoanalysis showing
3000-6000 J/kg of MUCAPE with equally impressive (though still
capped) MLCAPES in the 3000-4000 J/kg range. Given our abundant
CAPE, steepening lapse rates and bulk shear values in the 30-50 knot
range, the environment is absolutely supportive of strong to severe
storms this afternoon into tonight, with large hail, potentially 2"
or larger, a threat with initial, more discrete storms, before
storms likely congeal into more of a forward propagating convective
system(s) with damaging winds gusts becoming a greater concern as
storms continue into the evening. Although won`t rule out
completely, the threat for tornadoes is low with LCL heights
generally too high and lower SRH values overall. Thus, any tornado
threat looks highly dependent on boundary interactions.
When and where the storms form is not quite as straightforward. The
most likely location for storms will be near the frontal boundary
with the incoming waves helping to provide the forcing to erode the
cap. Some 12Z data, like the 12Z HRRR seems to not be modeling the
environment well with dew points likely too low by later this
afternoon and thus not kicking storms off despite suggesting we`ll
break through part of the cap by 21-23Z. Best guesses at this point
for storm formation location/timing are closer to some of the HRW
cores and/or NAMNest with storms forming through central/northern
Iowa and moving eastward with time into this evening.
Whether or not storms are able to form this afternoon into evening,
storm chances continue into tomorrow as the front shifts south with
the second wave/front coming into the area off of the Northern
Plains with yet another wave behind it incoming from WY/MT. What
happens with all of these waves is highly dependent on what happens
this afternoon/evening and whether or not the environment is worked
over into tomorrow morning. Do want to emphasize the possibilitiy
for additional storms overnight into early Saturday, especially
southwest/south which could have a conditional wind threat.
Influence of the low level jet overnight seems more uncertain with
models not consistent in location/strength and some models, like
the NAM, generally slower with the secondary wave which would
have storms not arriving until closer to midday Saturday.
With the uncertainty of storm timing/location, exact temperatures
tonight into tomorrow are more uncertain as well but we will at
least be able to ditch the heat headlines by/before the 9pm time
frame tonight with temperatures cooling through the weekend behind
the passage of the fronts as highs drop into the 80s again. A
surface high pressure does move towards the state from the north
into Sunday with a period of dry weather later this weekend though
as mentioned previously, periodic chances for storms continue off
and on into next week as waves round the overarching northwest flow
with additional details to be provided in future forecast
updates.
&&
.AVIATION.../For the 06Z TAFS through 06Z Saturday night/
Issued at 1054 PM CDT Fri Jul 28 2023
Storms to exit southeast near OTM by 07z with lingering strong
storms though 05-06z. Most sites sct mid to high level behind
boundary with NW/NE winds generally under 12kts most of remainder
of period. Aft storms pass, expecting VFR conditions. Some
potential for storms aft 12z Sat, but at this time expect them to
miss any TAF sites. /rev
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...KCM
AVIATION...REV
Area Forecast Discussion
National Weather Service Goodland KS
815 PM MDT Fri Jul 28 2023
.UPDATE...
Issued at 809 PM MDT Fri Jul 28 2023
The Heat Advisory has been allowed to expire at 02z as
temperatures have dropped with sunset and increasing cloud cover
from the west. This has lowered heat indices below criteria.
&&
.SHORT TERM...(This evening through Monday)
Issued at 315 PM MDT Fri Jul 28 2023
Tonight...a potentially high impact event is in store for a small
portion of the area through about 10 PM MDT (11 PM CDT) this
evening. Convection moving off the Cheyenne Ridge and Palmer Divide
is forecast to move toward each other this evening, creating a
line/broken line of strong to potentially severe thunderstorms
moving generally east along and north of Interstate 70.
The 12z GFS model (which does very well with our dust storm events
the past few years, both convective and non-convective) is showing
support for blowing dust/dust storm conditions, supported by local
office research. 0.5-1km wind speeds of at least 43kts (one key
parameter) are forecast to move toward the Yuma/Cheyenne (CO) border
by 00z, continuing east toward KS Highway 27 by 02z/03z then
weakening. Strong 3 hour pressure rises are forecast behind this
feature which would be associated with a cluster of thunderstorms.
The latest HRRR model runs are emphasizing locations closer to the
Nebraska/Kansas border would be impacted by the higher winds.
Hopefully, the 18z GFS will shed some light on where the higher
wind/dust threat exists. Regardless, conditions are favorable for
thunderstorms producing strong wind gusts and blowing dust from
around 00z-03z/04z generally along and west of KS Highway 25 and
along/north of I-70.
Low temperatures are forecast to range from 60 to 70 degrees.
Saturday-Saturday night...the forecast area remains under northwest
flow aloft, in between an upper level ridge centered over the Palmer
Divide and low pressure over eastern Canada. It appears there will
be another weather system moving through parts of the area from the
northwest during the overnight hours, supporting a chance for strong
to potentially severe thunderstorms. High temperatures finally cool
a bit with lower to middle 90s advertised, in line with typical
mixing at 850mb and a blend of the better performing temperature
guidance from the past 7 days. Low temperatures are forecast to be
in the lower to upper 60s.
Sunday-Sunday night...upper level ridging strengthens over the area
with limited chances for thunderstorms as moisture is lacking.
Slight chance pops are confined to the northwest through northern
counties where a weather system moves across from the southwest, on
the backside of the upper ridge center. High temperatures are
forecast to be in the lower to middle 90s. Low temperatures are
forecast to be in the middle 60s to around 70.
Monday...dry weather is expected during the day. High temperatures
return back into the lower 90s to around 102 degrees. Heat index
values are currently forecast to remain in the 90s, maybe a few
spots hitting 100 degrees.
.LONG TERM...(Tuesday through Friday)
Issued at 211 PM MDT Fri Jul 28 2023
For the long term, the mid part of the week is forecasted to see a
continuance of the hot temperatures. However, a system may move
through around Thursday that could cool us to a few degrees below
average.
For Tuesday and Wednesday, the hot temperatures continue with high
temperatures forecasted to be in the 90`s and 100`s. There will
still be the potential for afternoon/evening thunderstorms, maybe
more so than prior days as the ridge over the Central CONUS flattens
and the Tri-state area returns to more northwesterly flow. With a
few shortwaves potentially moving through, the area could see storms
that will generally come from the west and move east into the area.
Heavy rain could be possible with PWATs climbing into the 75th or
higher percentile. Strong wind gusts would also be possible as there
could be drier areas (especially southwest) that will lead to an
inverted V sounding and higher DCAPE.
For Thursday and beyond, a system and cold front with the upper low
moving across the Northern CONUS will help increase storm chances
and potentially bring cooler temperatures. Currently, it looks like
the passage would be early Thursday, but ensemble surface pressure
spreads show a variation of 24 hours in either direction, but
favoring later into Thursday. When the front does move through,
storms should fire and heavy rain and flooding could be a
possibility if the front stalls over the area. Otherwise, cooler
temperatures in the 80`s are possible going into the weekend.
However, 500mb spreads are showing the potential for the ridge over
the rockies to amplify which could bring warmer temperatures and
lower storm chances by pushing shortwaves further north.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 503 PM MDT Fri Jul 28 2023
For KGLD, VFR conditions currently expected, but from 03z-06z
storms are possible. Guidance not putting a storm close to the
terminal so VCTS for now. Also, blowing dust may also occur that
may drop visibility to 5sm at times.
Winds may be gusty and will augment if conditions warrant. Winds
in general will meander from southeast to northeast 10kts or
less. Some light/variable possible between 03z-15z Saturday.
For KMCK, VFR conditions through the forecast period with mainly
SCT-BKN mid and high clouds. Winds, meandering from the north
through east around 10kts or less.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...JN
SHORT TERM...DDT
LONG TERM...KAK
AVIATION...JN
Area Forecast Discussion
National Weather Service Green Bay WI
1044 PM CDT Fri Jul 28 2023
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Saturday
Issued at 337 PM CDT Fri Jul 28 2023
Complex/messy mesoscale/synoptic set-up making for a complicated
forecast this afternoon into tonight. Main focus will be timing
best chances for storms and if any will be on the strong side.
For this afternoon into tonight...weak surface boundary,
instability gradient and FGEN centered around 850mb, combined
with daytime heating generating MUCAPEs of 1000-2000 J/kg will
continue to produce isolated to scattered showers and storms
extending east-west over parts of central and east-central WI.
Main threats with this activity will be heavy rain and small hail
as they should mainly remain elevated. Then attention turns to
this evening as a more potent shortwave tracks into WI, likely
kicking off additional showers and storms. Instability gradient
still expected to be in place, with the pool of very instability
well to our south in southern WI. Think the strongest of the
storms, along with the main threat for severe weather, will build
south/east into the better instability. We will be on the northern
part of this and it may clip the southern CWA. Models are mixed
on if and how widespread activity north of the main complex will
behave tonight, with the HRRR very aggressive with more widespread
activity, but other models have little to no activity. So
confidence not great on how it will play out as you work to the
north. Plenty of bulk shear to work with (around 50 kts) so any
storms could be well organized and have the chance to produce hail
and some brief gusty winds (especially if a cold pool can get
established with the complex and it clips the southern counties).
Some fog is expected later tonight as temps cool, especially in
central and north central WI where winds are lighter in the
boundary layer. Lows will drop into the 50s to low 60s for most
spots.
For Saturday...some lingering showers will be possible over north
central WI in the early morning, then additional showers will be
possible in the later morning and afternoon as a weak secondary
frontal boundary drops south across northeast WI within a
northwest upper flow, along with a weak shortwave and departing
upper jet. A narrow ribbon of moisture and instability be just
enough to touch off a storm, but will just mention showers for
now. If models continue to trend more aggressive with this
activity, PoPs will need to be expanded. It will be a little
cooler and noticeably less humid with highs in the mid 70s to mid
80s.
.LONG TERM...Saturday Night Through Friday
Issued at 337 PM CDT Fri Jul 28 2023
Summary: Generally quiet weather will prevail Sunday into
Tuesday, outside of warming temperatures. There may be a period of
strong thunderstorms again Wednesday PM as southerly flow returns
and a low pressure system in northern Ontario crosses the Upper
Great Lakes region.
Deep low pressure centered over northern Quebec on Sunday and
amplifying ridging over the northern High Plains keeps the central
United States under mild northwest flow Sunday into Monday. This
is generally expected to be a dry period for north-central and
northeast Wisconsin. Temperatures aloft warm by a degree or two
from Sunday into Monday, but largely support near-normal daytime
high temperatures for the beginning of next week.
The ridge axis aloft shifts eastward into the Missouri Valley
Monday night into Tuesday as lower-level high pressure over the
Upper Midwest drops into the Ohio River Valley. This creates a
return flow into northeast Wisconsin by Tuesday morning. Expect
an increase in daytime high temperatures for Tuesday as a result.
Low pressure over northern Manitoba breaks down the central CONUS
ridge Tuesday night to further increase temperatures Wednesday
ahead of the next chance of possible stronger thunderstorms to
work into northeast Wisconsin later Wednesday. There may be a
chance of severe thunderstorms in this time period as well, but
further analysis will be needed over the next few days pending
similar guidance trends.
Northwest flow may then return behind the cold front later
Thursday as the low then centered in northeast Ontario moves
further eastward.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1044 PM CDT Fri Jul 28 2023
Rain and thunder will be out of the area by the start of the 06Z
TAF period. Behind this, recent rainfall may produce some fog
across the area, especially across north-central WI where skies
have begun to clear. Kept the fog mention for RHI in previous
TAFs. Some fog may yet be added to central WI as well, but
confidence was low. Then, good flying conditions are expected for
the region through Saturday. VFR conditions should prevail across
the area.
.KOSH...
Rain and storms will exit the airfield area by the beginning of
the TAF period. Currently expect temperatures to be too warm
overnight to allow for any fog by the morning. Saturday then bring
clear skies, relatively light winds, and good flying conditions
for the area. A few mid level clouds could yet develop in the
afternoon, but no active weather is expected in Oshkosh.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM.....Bersch
LONG TERM......NLY
AVIATION.......Uhlmann
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
930 PM EDT Fri Jul 28 2023
.SYNOPSIS...
High pressure remains over the area Saturday with hot and humid
conditions. A cold front approaches the region on Sunday, moving
south of the area on Monday. High pressure returns through next week
with another frontal boundary approaching on Friday.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 930 PM EDT Friday: For this update, pulse convection has
subsided throughout the CWA, with a few lingering showers continuing
to dwindle as air becomes more stable. Scattered mid-level clouds
remain over the NC mountains and the SW counties. Temperatures along
the foothills and far western Piedmont have cooled well below
forecasted due to the ongoing convection from this evening. Added
moisture will keep dewpoints in the 70s and make for a somewhat
muggy night. Mountain valley fog and low stratus look to return
overnight into daybreak Saturday. With cloud cover expected to
linger overnight, lows will be around 5-7 degrees above climo.
Another round of convection can be expected Saturday afternoon into
the evening. CAMs are not in good agreement regarding the timing of
activity. The HRRR shows activity early afternoon to early evening
while the NAMNEST has activity early to late evening. With
confidence on the timing of storms being low, capped PoPs to chance
on Saturday. The Day 2 SPC Severe Weather Outlook has the northern
half of the CWA in a Marginal Risk for severe storms. So, a few
strong to severe storms will be possible again tomorrow. The main
threat will be damaging wind gusts. Highs look to be a few degrees
cooler Saturday afternoon thanks to cloud cover lingering. However,
highs should still be around 3-5 degrees above climo. Heat indices
could reach into the lower 100s east of the mtns, but will remain
below Heat Advisory criteria.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 220 PM EDT Friday: The forecast area will be under NW flow
with a trough axis near or just east of the area. A series of short
wave troughs will move through the flow and over or near the area. A
weak frontal boundary also moves toward the area from the NW Sunday
and will be over or just south of the area Monday. The atmosphere
will be moist and unstable both days with MCS activity potentially
moving over or near the area as well. The result is mainly diurnal
PoP through the period, with higher PoP Sunday than Monday and
favoring mountains both days. A few pulse storms, or perhaps some
loosely organized multicell clusters, could produce localized/brief
severe weather, mainly in the form of microbursts. Temps will be
above normal Sunday with Piedmont Heat Index values near or over
100. Temps drop a few degrees on Monday keeping Heat Index values
generally below 100.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 155 PM EDT Friday: A long wave trough axis starts the period
over the area then moves slowly east through Wednesday. A short wave
moving into the NW flow Thursday digs a new trough over the eastern
CONUS by Friday. At the surface, high pressure over the Great Lakes
moves eastward through the period with a moist southerly flow
developing by Thursday into Friday. The result is a slowly increase
in diurnal convective chances through the period, with generally
higher PoP over the mountains and lower over the Piedmont. Temps
will be near or slightly below normal until Friday when the rise
back above normal.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: TS activity continues to decrease as the
evening progresses, with temporary restrictions still possible at
KCLT. Once storms dissipate, VFR conditions expected to prevail
at all sites. Given the addition of rainfall this evening, mountain
valley fog is possible close to KAVL and KHKY. Confidence is medium
that brief MVFR/IFR for VSBY will likely occur between 09z-11z at
KAVL. KHKY could have brief IFR CIG restrictions with lower stratus
between 08z-10z. For Saturday afternoon, a higher chance for strong
to severe pulse-like thunderstorms across the region. Therefore,
PROB30 for TSRA at all terminals ranging from 20z-24z. Some upper
cloud cover is expected to increase during the day, but remain VFR.
Winds will prevail S/SW east of the mountains and WNW/NW at KAVL.
Outlook: Shower and thunderstorm coverage with associated
restrictions will increase over the weekend. Morning fog/low stratus
will be possible each day across the mountain valleys.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...RWH
NEAR TERM...AR/CP
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...CP
Area Forecast Discussion
National Weather Service Gray ME
1029 PM EDT Fri Jul 28 2023
.SYNOPSIS...
A cold front will settle across the region tonight with a few
showers and possibly a thunderstorm...especially over the mountains.
A wave of low pressure will move along this front on Saturday
bringing a renewed chance for showers and storms with some locally
heavy rain possible over southern New Hampshire. This low pressure
will help push a cold front south of the area Saturday night with
much cooler and drier air arriving for Sunday. The cooler and drier
weather pattern looks to hold across the region into early next
week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
1030 PM Update...Adjusted PoPs upward slightly in northern Coos
County and the wrn ME mountains for the next couple of hours
based on latest radar mosaics. Otherwise, very little change to
the forecast for the overnight hours. We expect it to continue
to be warm and muggy.
715 PM Update...Little change to the going forecast for this
evening. Mostly clear and muggy for most, with an isolated
shower or thunderstorm in the mountains as heights fall and a
cold front approaches.
Previously...
High Impact Weather Potential: An isolated strong thunderstorm
is possible near the international border this evening.
Pattern: Early afternoon water vapor imagery shows a shortwave
trough moving east across southern Quebec with scattered
showers/thunderstorms along the cold front associated with this
wave. West southwest flow exists across the northeastern United
States with another day of very warm temperatures and elevated
relative humidity values. Through the near term forecast period
the aforementioned cold front will settle overhead with our
primary forecast concerns centered on the survival of any
shower/storm activity as it reaches northern New Hampshire and
western Maine.
Through this Evening: Guidance has trended a bit later with the
arrival time of any convection associated with the front...which
lowers any potential for a strong storm...but given a good
ribbon of westerly winds...some gusty winds are possible with
any showers/storms that make a run at northern areas after 00Z.
It will remain warm this evening with 8pm temperatures still in
the mid 70s to lower 80s from north to south.
Tonight: MUCAPEs quickly diminish as cold front slowly sags overhead
tonight...with any storms tapering to a few showers that will sink
across northern zones as the front arrives and stalls overhead with
as the mid level flow becomes parallel to the boundary. Llevel
moisture looks sufficient to keep a good bit of cloudiness in the
upslope regime north of the Whites with a mix of mid/high cloudiness
to the south with clouds thickening towards daybreak as the next
shortwave approaches from the Great Lakes...backing the mid level
flow. Low temperatures will be in the 60s in the foothills and
mountains...remaining near 70 across southern NH and along the
coastal plain of Maine.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
High Impact Weather Potential:
* Potential for locally heavy rain and an isolated severe
thunderstorm over southern NH / far southwestern ME Saturday
afternoon.
Pattern: Shortwave trough over the Great Lakes region moves east
towards New England during the day Saturday...passing east of the
region Saturday night. This will spawn a wave of low pressure along
the stalled frontal boundary overhead with low pressure moving from
west to east across New England through the day and into the Gulf of
Maine Saturday night. This wave and surface reflection will renew
lift over the boundary resulting in another round of shower activity
and possible thunderstorms before drier air arrives Saturday night.
The primary forecast focus will be the track of this low and the
amount of instability that will be realized to determine the threat
for severe thunderstorms or excessive rainfall.
Saturday: Challenging forecast with a pretty good spread in the
guidance even at a 24 hour lead time with the spread largely
stemming from what occurs with developing convection over the
northern Mississippi Valley this evening that will cross the
southern Great Lakes region overnight and them move east
towards New England for Saturday. The 12Z HRRR and high res FV3
are on the northern edge of the envelope which brings
significant instability into the southern half of the forecast
area with a not too dissimilar setup as to yesterday albeit with
weaker llevel shear profiles. The NAM and much of the global
guidance camp is significantly further south...keeping any
significant instability south of our forecast area with more of
a modest QPF event for the southern half of the forecast area.
Good moisture will again be available with PWATs south of the
front around 2 inches. With lower than normal confidence at this
range...a consensus...HREF-like solution was followed which
aligns well with SPC Day 2 SWO as well as the ERO from WPC which
brings some SVR/FF potential to far southern NH but not further
north at this time. This reduced confidence also suggests
holding off on any flood watch headlines. To the south of the
frontal boundary SBCAPES may push to around 1000J/kg with 40kts
of deep shear...so there is a conditional threat for severe
given sufficient instability. Storm motions should be rather
steady from west to east...but there will be a flash flood
threat for any storms that track over the same area. Frontal
location and uncertainly makes the temperature forecast tricky
as well. Could push back into the upper 80s across southern NH
with lower 80s in the foothills and 70s further north.
Saturday Night: Wave of low pressure pulls east of southern New
England taking all shower/storm activity with it by late evening
with cool/dry advection taking over in it/s wake. PWATs fall back
towards 0.75" by daybreak Sunday. Some moisture remains beneath
developing subsidence inversion overnight which will likely allow
for some scattered cloudiness. Expect temperatures to fall to the
lower 50s in the mountains and the upper 50s to just above 60 to the
south as the cP airmass pushes overhead.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
A longwave trough will be persistent through the long term with a
cooler airmass until northwest flow. A few scattered light
upslope showers across the international boundary are possible,
but generally the moisture profiles look insufficient for more
than isolated coverage. Cold advection will continue through
the day with highs in the 70s and lows in the 50s, cooler in the
higher terrain. With the broader cyclonic flow moving over the
area, a few shortwaves are likely to move through the CWA
triggering some occasional light showers during the first half
of the week. Looking particularly at Monday as a weakening mid
level shortwave looks to move through. This will allow for
increased ascent, supportive of showers with some higher POPs in
higher elevations due to upslope. Any showers Monday are likely
to form during peak heating in the afternoon. This airmass will
however be much drier than what we have been dealing with over
the last few weeks, so rainfall amounts will be limited due to
lack of moisture depth. High temperatures on Monday should
remain in the 70s, with near 70 further inland and upper 70`s
near the coast.
Beyond Monday, deep northwesterly flow settles into the region for
the first time in recent memory, bringing with it a cooler and drier
airmass than we have seen in some time, with both PWATs and
temperatures significantly lower than recent weeks. Through Tuesday
and Wednesday, high temperatures look to stay around the mid-70s,
with some northern locations likely even staying in the upper-60s,
especially if any of the impulses rotating through can aide in cloud
formation in upslope regions. Overnight Tuesday and Wednesday, dew
points will fall substantially from where they have been into the
40s and 50s, allowing low temperatures to get down into the 50s for
most locations, with perhaps even low to mid 40s for northern
locations on Wednesday morning.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Short Term...
Summary: A cold front will drop towards the region late this
afternoon and evening with a wave of low pressure moving along this
front on Saturday bringing showers and some thunderstorms Saturday
afternoon and evening before improving conditions Saturday night.
Restrictions: VFR should persist through this evening with some fog
developing with IFR/LIFR conditions after midnight at
HIE/LEB/AUG/RKD. Shower chances increase after noon on Saturday
with local MVFR/IFR restrictions before conditions improve to
VFR Saturday evening with another round of valley fog Saturday
night.
Winds: Westerly winds 5-10kts with southerly seabreezes at PWM/RKD
through this evening with winds becoming calm/light-variable
tonight. Variable winds early Saturday given a front overhead
before winds become light northwesterly /<10kts/ Saturday
night.
LLWS: No LLWS is expected through Saturday Night.
Lightning: There is some potential for isolated-scattered
thunderstorms for MHT-PSM-CON-PWM on Saturday afternoon with lesser
chances further north.
Long Term...Dry conditions on Sunday will favor VFR into Sunday
night. Some scattered showers on Monday could cause brief MVFR
conditions.
&&
.MARINE...
Short Term...Winds/waves are expected to remain below small
craft levels through Saturday night. Some showers/thunderstorms
on Saturday afternoon may bring some locally gusty winds to the
waters south of Portland.
Long Term...Winds and seas remain below SCA through mid week.
Return flow late in the forecast will favor building seas by the
end of the work week which will likely reach 5ft or higher. High
astronomical tides expected at the end of the month.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR TERM...Ekster
SHORT TERM...Arnott
LONG TERM...Jamison
Area Forecast Discussion
National Weather Service Lubbock TX
551 PM CDT Fri Jul 28 2023
...New AVIATION...
.SHORT TERM...
(This evening through Saturday)
Issued at 130 PM CDT Fri Jul 28 2023
Current satellite and RAP analysis has the upper high spinning over
western New Mexico with temperatures warming across the area today
into the upper 90s to triple digits. A scant amount of mid-level
moisture may lead to a few high clouds this afternoon and tonight.
Otherwise, breezy southerly winds and dry conditions are expected
for the remainder of today. Tonight, temperatures will be very
similar to last night in the upper 60s to mid 70s across the
forecast area. There is a very small potential (< 10 percent chance)
of a showery echoes to develop on radar early tomorrow morning with
the shallow mid-level moisture. However, no precipitation is likely
to make it to the surface with the extremely dry boundary layer
below. Tomorrow, the high will begin to meander northward towards
the Colorado border. This shift in the high will result in little
change to the high temperatures with once again upper 90s along the
Caprock and lower triple digits (100-105 degrees) off the Caprock.
Skies will be mostly clear with light southerly winds and dry
conditions.
&&
.LONG TERM...
(Saturday night through next Thursday)
Issued at 130 PM CDT Fri Jul 28 2023
Upper level high pressure to remain over the forecast area through
the forecast period. The main center of the high will rotate
northeastward this weekend from its current position over New Mexico
toward southwestern Kansas followed by a movement southeastward to
the Red River valley by Wednesday. At this point the models begin to
diverge some with the GFS favoring a more aggressive westward shift
and a more aggressive and higher-amplitude trough over the eastern
CONUS. This solution would favor cooler temperatures at the end of
the period and possibly some thunderstorms edging into the
northwestern part of the forecast area in northwest flow. However,
the majority of solutions trend more toward a lower amplitude
pattern and slower retrogression of the upper high. Will continue to
favor NBM precip chances and low temperatures while edging slightly
warmer with high temperatures using bias-corrected CONSMOS through
the period.
&&
.AVIATION...
(00Z TAFS)
Issued at 550 PM CDT Fri Jul 28 2023
VFR conditions and generally light winds will persist through the
TAF period.
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...11
LONG TERM....07
AVIATION...19
Area Forecast Discussion
National Weather Service Paducah KY
644 PM CDT Fri Jul 28 2023
.UPDATE...
Issued at 645 PM CDT Fri Jul 28 2023
Updated aviation discussion for 00Z TAFs.
&&
.SHORT TERM...(Tonight through Sunday night)
Issued at 341 PM CDT Fri Jul 28 2023
There will be no changes to the heat headlines at this time. The
110+ heat indices are clustered over the northern half of the area.
Dewpoints have indeed not mixed out across the region, but
temperatures, as has been the case the last few days, have
struggled to get into the middle 90s, let alone the upper 90s.
However, we are still getting the heat indices to 105+ to support
the headlines.
Much of the 12Z guidance has trended drier for tonight and even
much of Saturday. However, the 18Z HRRR does show a decaying MCS
with a nice outflow boundary slipping south through southwest
Indiana and west Kentucky in the morning. It washes out the
boundary and does not blow up any convection in the area until
another MCS approaches from the northwest in the late afternoon.
The general consensus is that convection will develop north of
the area and move southeast through the region, mainly to the east
of the Mississippi, from the late afternoon through the evening.
A cold front is expected to move into/through the area Saturday
night and there certainly would be potential for convective
development along it or any outflows late Saturday night into
Sunday. This later development would be most likely over southeast
Missouri.
As for severe weather, NAM and GFS soundings across the region
Saturday afternoon show different scenarios. Neither model
indicates much shear, so convection will struggle to get organized
and any linear system that approaches the area will struggle to
maintain its level of organization as it moves through the Quad
State. The GFS has a deeper mixed layer than the NAM and mixes
out dewpoints more. It does have very steep low-level lapse rates
which would promote more gusty/damaging winds, but not much hail
threat. The NAM develops extreme instability and would support
some hail threat to go along with the damaging wind threat. In
either case, severe storms are likely to be isolated due to the
lack of shear. Precipitable water values will be pushing 2", so
any decent storm will produce torrential rainfall, but it will be
rather isolated and short-lived which should limit any significant
flash flooding threat. However, the extreme rain rates could
briefly overwhelm drainage systems.
We will continue to favor the shallower mixed layer of the NAM
until it doesn`t verify, so we will continue to go with as high a
dewpoint grid as we can find for Saturday, which should support
heat indices in the 105-110 range throughout the region. Of
course, if we do get some outflow into the area in the morning,
that could muddle up the thermodynamics and limit the heat indices
in the east. The Heat Advisory looks good for Saturday.
Beyond Saturday night, the convective forecast is rather murky and
dependent on boundary locations and disturbances in developing
northwest flow aloft. Certainly cannot rule out some strong to
severe storms Sunday over southeast Missouri if we get heat of
the day storms with mainly a damaging wind threat.
Leaned toward the cooler NAM/MOS guidance for highs on Sunday, as
the GFS looks too hot, but if the front hangs up, it could still
get awfully hot in southeast Missouri.
.LONG TERM...(Monday through Friday)
Issued at 341 PM CDT Fri Jul 28 2023
Northwest flow aloft will be the rule over the Quad State through
the week. At the surface, northeasterly flow will prevail through
Tuesday, then winds will attempt to turn back to the south
Wednesday. There is a decent signal for a cold front to move back
through the region Friday.
So we will be dealing with the potential for convection with any
disturbances in the northwest flow aloft through the week. Any
convection Monday and Tuesday will likely be confined to southeast
Missouri. There will be some shear, so we cannot rule out the
potential for some more organized convection with mainly a
damaging wind threat.
As the low-level flow becomes southerly Wednesday, it will lead to
a hotter and more humid air mass, but the upper ridge will attempt
to push closer to the region, as well. This could set the stage
for some periods of stronger convection and heavy rainfall across
the region until the cold front passes next Friday.
High temperatures will be near normal levels in the upper 80s to
around 90 degrees Monday through Wednesday, but will climb into
the lower and middle 90s Thursday and Friday. Heat indices
Thursday and Friday could climb back into the triple digits.
&&
.AVIATION...
Issued at 645 PM CDT Fri Jul 28 2023
VFR conditions will prevail through Saturday. Scattered mid level
clouds tonight will give way to scattered high based cumulus by
Saturday afternoon. Isolated/scattered thunderstorms are possible
across northern/eastern portions of the region Saturday afternoon,
mainly impacting KMVN/KEVV/KOWB. Southwest winds 5 to 10 knots
tonight will increase to 10 knots with gusts to 15 knots by late
morning and afternoon Saturday.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Excessive Heat Warning until 8 PM CDT this evening for
ILZ075>078-080>087.
Heat Advisory until 7 PM CDT Saturday for ILZ075>078-080>087.
Heat Advisory until 7 PM CDT Saturday for ILZ088>094.
MO...Excessive Heat Warning until 8 PM CDT this evening for MOZ076.
Heat Advisory until 7 PM CDT Saturday for MOZ076.
Heat Advisory until 7 PM CDT Saturday for MOZ086-087-100-107>112-
114.
IN...Excessive Heat Warning until 8 PM CDT /9 PM EDT/ this evening
for INZ081-082-085>087.
Heat Advisory until 7 PM CDT /8 PM EDT/ Saturday for INZ081-082-
085>087.
Heat Advisory until 7 PM CDT Saturday for INZ088.
KY...Heat Advisory until 7 PM CDT Saturday for KYZ001>022.
&&
$$
UPDATE...RJP
SHORT TERM...DRS
LONG TERM...DRS
AVIATION...RJP
Area Forecast Discussion
National Weather Service Phoenix AZ
514 PM MST Fri Jul 28 2023
.UPDATE...
Updated Aviation discussion.
&&
.SYNOPSIS...
Strong high pressure will continue to hover over the region with
Excessive Heat persisting into the weekend. Scattered afternoon
thunderstorm development will also continue over higher terrain
areas with the main impacts in lower elevation communities being
strong, gusty winds and blowing dust. However, an area of low
pressure will migrate northward out of Mexico over the weekend
bringing significantly increased chances of thunderstorms and cooler
temperatures to the entire area.
&&
.DISCUSSION...
Latest RAP analysis places the center of the Monsoon High along
the Arizona/New Mexico border. This is resulting in a light
southeasterly flow across central Arizona. Meanwhile, dewpoints in
the upper 50s and lower 60s are running a few degrees higher than
at this time yesterday. The high temperature has also eclipsed
the 110 degree mark in Phoenix for the 29th consecutive day.
Showers and thunderstorms developed early across northern Arizona
while satellite imagery reveals convection bubbling across the
White Mountains. The latest HREF suggests this activity will build
further south later today, particularly across Gila and Pinal
Counties.
Latest ACARS KPHX sounding depicts a layer of relatively dry air
near 800 mb, resulting in significant MLCIN across the lower
deserts, similar to yesterday. However, temperatures remain
relatively cool aloft, yielding steep mid-level lapse rates. There
is a 60 percent chance of an outflow boundary reaching the Valley
this evening from the northeast, but with abundant inhibition,
only isolated convection is possible along the boundary.
Nevertheless, there is a 30-50 percent chance the outflow boundary
will produce wind gusts of 35+ mph across central Arizona and
this is depicted well in the HRRR. There is an even higher
likelihood of gusty winds further south across Pinal County this
evening along with a 10 percent chance of severe wind gusts. Winds
of this magnitude will also be capable of producing areas of
blowing dust.
&&
.PREVIOUS DISCUSSION...
A well defined negative PV anomaly is already quite evident in WV
satellite imagery over eastern Mexico, and models continue to
propagate this feature westward into Sonora, and eventually up the
lower Colorado River valley over the weekend through early next
week. This classic late July inverted trough will enhance synoptic
scale ascent over the region resulting in markedly increased
thunderstorm chances and the likelihood of at least one organized
convective complex blasting through the region. The first vestiges
of this system will enter the picture Saturday with multi-model
output indicating a high probability (50-70% chance) of an intense
convective complex developing over northern Sonora/southern AZ. In
concert with other terrain forced storms and outflows, deeper
moisture should be thrust north and west into the forecast area with
the primary uncertainty as to whether downstream thermodynamic
profiles will be receptive to additional deep convection along and
behind the boundary. Given the probable thunderstorm intensity and
outflow depth, feel at least scattered storms are possible into
lower elevations Saturday evening with damaging winds and dense
blowing dust the main threats.
The most outstanding signal still hinges on Sunday as many favorable
conceptual aspects appear to be present for a complex of organized
storms in the CWA. Assuming the convective mass Saturday does not
fully contaminate and overturn the environment Sunday, deep boundary
layer mixing ratios of 10-11 g/kg should be available in a strongly
forced synoptic regime. Although model trends have shown the
aforementioned PV anomaly tracking a little farther south than
previously forecast and locally capping effective deep layer shear
around 30kt, a favorable coupling of MLCape/DCape around 1500 J/kg
still portends storms reaching strong to severe thresholds. Overall,
the pattern still looks to match some historical monsoon severe
events for the region.
Convective evolution beyond Sunday becomes more chaotic based on
mesoscale processes and the easterly wave weakening and becoming
stretched/sheared in southwest flow over the lower Colorado River.
Not surprisingly, the official NBM continues to spread relatively
high POPs over a large temporal and areal range Monday and Tuesday
not necessarily realistic of a monsoon pattern. Conceptually, the
focus for thunderstorm activity should shift into SE California and
NW Arizona Monday, then towards southern NV/UT Tuesday in advance of
the remnant circulation center. However with lingering moisture and
favorable ascent structure still over the region, cannot discount a
few storms anywhere in the CWA early next week. Thereafter, model
trends suggest a revision back to more limited deep convection
scenario as initially strong SW flow aloft acts to scour away better
moisture with mixing ratios perhaps falling back to an unsupportive
7-8 g/kg range. It`s possible during the latter half of the week
that strong subtropical ridging (598dm H5 heights) retrogrades back
over the forecast area further inhibiting thunderstorms, and also
reintroducing 110F temperatures into the forecast.
&&
.AVIATION...Updated at 0013Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Thunderstorms that are currently over Yavapai County and areas
further east/southeast are anticipated to have complex effects on
the surface winds over the Valley floor this evening. But, there
is a high degree of uncertainty on just how outflow driven wind
shifts will evolve. There is already outflow approaching far
northern portions of the Greater Phoenix area from the north and
northeast. One or two follow-on outflows from the east/southwest
are anticipated after that. Timing, strength, and precise
directions are all uncertain. The TAFs reflect the best estimate
of those parameters and subsequent updates are likely as things
unfold. Potential for new storm development over the Valley floor
itself (initiated by the outflows from distant storms) looks to be
limited but isolated storms are still possible. If any
development, follow-on wind shifts are likely. Apart from
outflows, surface winds will continue to favor westerly winds
through the evening (gusts 15-20kts early evening) and eventually
trend to light easterly before westerly breeziness resumes
Saturday evening. As for cloud cover, anticipate bases remaining
AOA FL120 (if not higher) except for the near vicinity of any
thunderstorms (dipping to FL090).
Southeast California/Southwest Arizona including KIPL and KBLH:
Thunderstorm activity is expected to remain far removed from the
TAF sites such that typical warm season wind patterns will
continue along with minor mid to high level cloudiness.
&&
.FIRE WEATHER...
Well above normal temperatures will continue into the weekend as
scattered afternoon thunderstorms develop over higher terrain
locations in the eastern districts. Wetting rainfall is likely with
a few of these storms, however a greater concern will be gusty and
erratic winds as well as the potential for new ignitions from
lightning strikes. Afternoon minimum humidity levels will continue
to fall into a 10-20% range following fair to good overnight
recovery of 25-50%. Periods of afternoon upslope gustiness will also
be common across all districts. A pattern shift with a marked
increase in moisture and thunderstorm chances will sweep into the
region over the weekend. Outside of the far western districts,
widespread wetting rainfall will be possible with potentially
repeated rounds of storms. This pattern shift will allow humidity
levels to moisten substantially while also tempering much of the
recent excessive heat. However by the middle of next week, drier and
warmer weather may return to most districts.
&&
.CLIMATE...
Record High Temperatures:
PHOENIX YUMA EL CENTRO
July 28 121 (1995) 124 (1995) 121 (1995)
July 29 115 (2020) 118 (1878) 115 (1954)
Active Streaks:
PHOENIX
1. Consecutive days of high temperatures 110F or greater: longest
on record at 28 days (previous record: 18 days in June 1974)
2. Consecutive days of no measurable precipitation: 4th longest on
record at 127 days
YUMA
1. Consecutive days of low temperatures 85F or greater: tied
3rd longest on record at 17 days
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Saturday for AZZ530-532-
534-537-538-540>544-546-548>551.
Heat Advisory until 8 PM MST this evening for AZZ557-558-563.
Excessive Heat Warning until 8 PM MST this evening for AZZ531-
533-535-536-539-545-547-552>556-559>562.
CA...Excessive Heat Warning until 8 PM PDT Saturday for CAZ562-563-
565>567-569-570.
Excessive Heat Warning until 8 PM PDT this evening for CAZ560-
561-564-568.
&&
$$
$$
DISCUSSION...Hirsch
PREVIOUS DISCUSSION...18
AVIATION...AJ
FIRE WEATHER...18
CLIMATE...Young