Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/28/23
Area Forecast Discussion
National Weather Service La Crosse WI
1047 PM CDT Thu Jul 27 2023
.UPDATE...
Issued at 1045 PM CDT Thu Jul 27 2023
Strong to severe storms pushed across north central Wisconsin
earlier this evening with 1 to 3 inches of rainfall across parts
of Taylor and Clark counties. With continued storm development
expected as the low level jet increases and a low level boundary
with moisture pooling along the boundary, storms repeating over
the same area additional locally heavy rain is possible. As a
result, a flood watch was issued north of I90 earlier this
evening. Over the last hour, an outflow boundary has pushed south
with additional shower and thunderstorms development along with
gusty winds.
&&
.DISCUSSION...(Tonight through Thursday)
Issued at 245 PM CDT Thu Jul 27 2023
Key Messages:
- Scattered strong/severe storms north of I-94 this evening, but
threat could spread south to I-90 corridor. Large hail, damaging
winds and locally heavy rain the threats.
- Another round of strong/severe storms for parts of the region Fri
afternoon/night. However, location is highly dependent on where
tonight`s convection moves. Expect refinement to expectations over
the next 12-24 hours. Currently, local severe risk would generally
be along/south of I-90 for the late afternoon/early evening hours.
Large hail, damaging winds and locally heavy rain remain the threats.
- One more hot day generally south of I-90 Friday. Seasonable
temperatures for the weekend into next week.
* STORM CHANCES TONIGHT - mostly north of I-94 with a strong/severe
threat, but could spread into the I-90 corridor. Severe threat has
increased in the north.
West-east running sfc front will layout from north-central MN into
northwest WI this afternoon. Moderate/strong pool of instability
building around/south of the front (4+K J/kg of SBCAPE via the RAP)
with 40-50 kts of 0-6 km shear to support updraft, storm
development. Ripe environment for quick upscale once storms fire -
which CAMS continue to favor between 20-22z from north-central MN
spreading into northwest WI. Supercells at first, gradually evolving
into line segments as they dive southeast. The storms would quickly
become severe, with the severe threat dropping to at least the I-94
corridor, possible down to I-90 locally. Meanwhile, there is an
upper level shortwave trough churning over SD (per watervapor
satellite imagery) at early afternoon. This is progged to shift east
through the rest of the day and work into the mix of forcing for
storm development tonight. Mixed messages in the CAMS on how this
evolves, but current trends favor the shortwave working on the
western portions of the front, firing storms over southern/southeast
MN in the early evening. Along with the severe threat, storms could
continue to generate and repeat along the frontal boundary as the
low level jet starts to focus into and across it. Training storms
could result. With a juicy atmosphere to tap, locally heavy rains
likely...with a threat for localized flooding if repeated rounds are
realized.
In addition: some convection could pop along various lingering
boundaries earlier than the "main" convective expectations to the
north. And, with that said, radar does show some convection popping
along a sfc front over southeast MN, western WI. Deep layer shear
lies well north but ample instability for any storm that can sustain
itself to pose some hail and locally heavy rain threat. Might act
more pulsy in nature.
* STORM CHANCES FRI AFT/EVENING - strong/severe potential mostly
south of I-90.
Overnight convection will push a west-east running frontal boundary
southward across the local forecast area with the RAP/HRRR/NAM12
laying out roughly from the IA/MN border across southern WI at 21z
Fri. Some bits of upper level energy could ripple across the front
for the afternoon/early evening while a weak low looks to
develop/move over the boundary across IA. The pool of moderate/high
unstable air continues around and south of the boundary (upwards of
4+K J/kg MUCAPE in the RAP/NAM12) with around 40 kts of 0-6 km shear
along and just south of the front. The deeper, better shear is
progged to lie northward, in the cooler air.
Stout cap to contend with through most of the day which could erode
enough to reach convective temp just south of the sfc front by late
afternoon. RAP increases convergence along the sfc boundary in the
afternoon, with aspects of the overnight mcs/clouds to the north and
heating to the south. Meanwhile, another source for forcing looks to
move almost parallel to the front with the low level jet/moisture
transport focused east/northeast into northern IL/southeast WI by
21Z.
CAMs not showing much for agreement on timing/location of convective
initiation, but per the expected setup, some sparking along, just
south of the boundary by mid/late afternoon would be reasonable.
Currently, this would suggest over northern/northeast IA, gradually
spreading-moving east. With the juicy atmosphere in place, once
above the cap explosive development would occur with sustained
updrafts thanks to the shear. Large hail, damaging winds and locally
heavy rains are the main threats.
Where the front lays up is of paramount importance as the
convection, and potential for severe storms, will be closely
associated with. Confidence is shaky at this time with where that
boundary will lie, although there is a good amount of support via
short term guidance to hold it south of I-90.
Will follow the model blends, leaning into CAMS output, for related
pcpn chances. Expect some refinement to the chances/severe threat -
more likely tomorrow morning as the outlay of the overnight
convection presents a better idea on how/where convection will spark
later in the day. For timing - a local severe threat would be
favored in the mid afternoon/early evening hours.
One more thing to consider - NAM/GFS drive a shortwave trough
eastward from the northern plains to across MN and northern WI Fri
night. This could/would serve as another source for convective
development...OR...it could advance quick enough east/southeast to
interact with the west-east running front. Medium range guidance not
clear on that. If north of the front, there could still be 1-1.5K
J/kg of MUCAPE to work on, along with favorable shear a loft to
promote at least a few stronger storms (maybe isolated severe). If
catching the front, further enhancement of the storms there would be
likely well into the evening hours.
* COOLER WEEKEND, MORE SEASONABLE NEXT WEEK. TRENDING DRY.
FIRST...heat will continue to pool south of a west-east running cold
front Friday. Where the front lies exactly is in question, dependent
much on what happens overnight with showers/storms. As it currently
sits though, hot and humid conditions will continue favored over
northeast IA/southwest WI - with afternoon heat indices around 100.
Due to lower confidence in some of the details, will not issue a
heat advisory for those areas at this time.
Medium range guidance still in step with a change in the upper level
pattern for the weekend, pushing the ridge axis back westward as a
trough carves over the eastern great lakes/new england states.
Cooler, less humid air returns to the region as a result. The GFS
and EC then hint that a bit of shortwave ridging could return for
the latter half of the new week, which could bump temps back up -
not like today - but above normal. Operational runs at the high end
of their ensemble guidance though and might be outliers when it
comes to temps.
With the upper mississippi river valley under the influence of
northwest flow, there will be the opportunity for bits of shortwave
energy to top the ridge and slide across the region. There has been
good consensus between the medium/long range guidance to keep the
weekend dry with uncertainties to potential rain chances as we move
through the new work week. Some trends in the EPS/GEFS members that
Wed night could harbor a decent shot for showers/storms. Will let
the blend dictate rain chances for now.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 648 PM CDT Thu Jul 27 2023
A cluster of storms is pushing across northern Wisconsin and
additional storms have developed to the west along a boundary in
south central Minnesota and also along an outflow boundary. The
short range models tend to bring an increased chance for storms at
the TAF sites after 04 or 05Z, however due to the uncertainty of
how far south the storms will make it or if this area will fall
apart and convection arrives later. Included vcts at this time at
both sites beginning around 04-05Z with the boundary approaching
and the shortwave trough moving through. Timing will need to be
adjusted through the night. VFR conditions outside of storms along
with some potential fog Friday morning. Gusty winds and
torrential rains could accompany the storms.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch until 5 AM CDT Friday for WIZ017-029-032>034.
MN...Flood Watch until 5 AM CDT Friday for MNZ079.
IA...NONE.
&&
$$
UPDATE...Zapotocny
DISCUSSION...Rieck
AVIATION...Zapotocny
Area Forecast Discussion
National Weather Service Cheyenne WY
552 PM MDT Thu Jul 27 2023
.UPDATE...
Issued at 442 PM MDT Thu Jul 27 2023
Based on the latest radar trends, we are sending out a quick
update to expand the showers and thunderstorms further east to
cover the Chadron and Alliance area late this afternoon.
Otherwise, current forecast looks to be on track.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 255 PM MDT Thu Jul 27 2023
An active next few days are expected, including this afternoon where
showers and thunderstorms will continue through the evening. Hi-Res
guidance shows widely scattered showers and thunderstorms impacting
most corners of the CWA. Main concern to keep an eye on with these
storms are strong winds. Model soundings show very dry low-levels
with the passage of a dryline. Current observations do show the
dryline currently trekking eastward, so the inverted-V profiles are
believable with over 1000 J/kg of DCAPE. Since severe gusts were
seen with yesterday`s storms with moister low-levels, then it is
very plausible that storms today could produce 60 MPH wind gusts. Hi-
Res shows storms tapering off by midnight tonight.
On Friday, the upper-level ridge starts to retrograde back westward,
allowing for drier conditions to persist west of the Laramie Range
and for higher dewpoints to sneak back into the High Plains. A weak
shortwave Friday afternoon will push a cool front into the northern
counties of the CWA which may usher in even higher dewpoints. This
extra lift and moisture will likely produce another round of storms
Friday afternoon. Hi-Res shows much less precipitation coverage than
the last few days, however, what few isolated storms pop up may be
more intense than what has been seen the last few days. GFS
soundings from the Nebraska panhandle show ~1000 J/kg of MUCAPE and
pretty good shear of 30 to 40 kts. Wind will still be a primary
threat with these storms as DCAPEs are still elevated, but large
hail could also be possible with storms.
As the upper-level ridge over the Four Corners region strengthens
again to nearly a 600 decameter high on Saturday, the ridge axis
will shift back westward, putting the CWA in more unsettled
northwesterly flow. On top of this, a surface low sitting over the
panhandle of Texas will help advect moist southeasterly flow into
the CWA. The northwest flow aloft and southeast flow at the surface
will create a greatly sheared environment east of the Laramie
Range. This, combined with dewpoints potentially in the 60s, could
lead to severe weather. GFS soundings in the Nebraska panhandle
on Saturday show ample instability with greater than 1300 J/kg of
MLCAPE, 1800 J/kg of MUCAPE, inverted-V profiles, and ~45 kts of
shear. These ingredients make all severe weather hazards possible.
.LONG TERM...(Sunday through Thursday)
Issued at 230 PM MDT Thu Jul 27 2023
A significant (596-598 dam) H5 ridge is expected to translate east
from the Four Corners into the southern and central plains late in
the weekend through the early to mid portions of next week. Active
west-southwest flow aloft will persist across southeast WY and the
western NE Panhandle along the western & northern periphery of the
ridge. Numerous mid and upper-level disturbances will pivot around
the expansive ridge, along with plentiful moisture availability w/
the development of a more favorable monsoonal pattern. As such, do
expect daily chances for showers and thunderstorms for much of the
area although the timing & intensity of individual waves cannot be
discerned at this time. Hot conditions are likely for a large part
of the area early in the forecast period (Sunday/Monday) with day-
time highs likely in the 90s as the center of the ridge axis makes
its closest approach. However, a dramatic increase in mid and high
level moisture associated with the monsoon, as well as much cooler
thermal profiles, should support a substantial cooling trend later
in the forecast period around Wed/Thu.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 535 PM MDT Thu Jul 27 2023
The main concern with this TAF issuance is when the thunderstorms
will move out of the picture this evening.
The latest radar loop was showing numerous outflow boundaries from
various thunderstorm complexes affecting areas from Chadron
southwest through Scottsbluff into Cheyenne and Laramie. Latest
HRRR guidance is showing this convection lingering through much of the
evening, but with these storms working over the environment
things may conclude a little sooner. The only fly in the ointment
is more convection continues to develop over the Sierra Madre
mountain range. If this persist, this may allow for things to
recover and allow for convection to last through the night.
Otherwise, thunderstorm coverage should be a little less tomorrow
afternoon.
&&
.FIRE WEATHER...
Issued at 255 PM MDT Thu Jul 27 2023
Main fire weather concerns this afternoon will be scattered showers
and thunderstorms producing gusty winds and frequent lightning.
Cannot rule out erratic gusts to 60 MPH with any stronger storms.
Slightly cooler temperatures are expected over the next few days
which will also help keep minimum RHs above 20 percent for most
locations. Conditions will remain fairly dry in Carbon County
through the weekend. Expect near daily chances for showers and
thunderstorms Friday through Sunday. A push of monsoon moisture will
come Monday through Wednesday which will also diminish fire weather
concerns next week.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...REC
SHORT TERM...SF
LONG TERM...CLH
AVIATION...REC
FIRE WEATHER...SF
Area Forecast Discussion
National Weather Service Grand Rapids MI
751 PM EDT Thu Jul 27 2023
LATEST UPDATE...
Aviation
.SHORT TERM...(This evening through Friday night)
Issued at 305 PM EDT Thu Jul 27 2023
Low confidence forecast for late tonight into Friday as
guidance/CAMs continue to struggle with eventual behavior of the
strong/severe convection expected to develop across nrn WI later
today or this evening (SPC Day 1 ENH risk area). There is some
suggestion that this activity maintains to some extent while
sliding southeast in our direction, and latest update to the SPC
Day1 outlook now has a marginal risk covering much of wrn Lwr MI
through 12Z Friday to cover this potential.
Even if the upstream convection early Friday morning is in a
decaying mode as it enters lwr MI, there may be some
redevelopment/re-intensification that occurs by mid/late morning
as sfc instability builds. RAP shows MLCapes exceeding 3000 J/KG
already by 15Z Fri in hot/humid air mass with low 70 dew pts,
and deep layer shear near 50 kts arriving by afternoon. While
coverage of storms may not be too high on Friday afternoon in the
wake of any earlier day activity or an old outflow boundary, the
environment will support severe storms.
Latest HREF guidance indicates that the highest coverage of
storms and best potential for severe weather will be on Friday
evening with arrival of a 50 kt mid level jet streak from the
west. Will also have to monitor a risk for locally heavy rain and
flooding during this time, especially given that some swaths of
2-3" occurred on Wednesday. Some showers and storms will probably
linger into the overnight period as well, especially over srn
sections, as sfc boundary will be slow to sink southward.
Considered posting a Heat Advisory for the area south of I-96 on
Friday but given the expected debris clouds from upstream
convection and possible morning convection or outflow boundary
slipping through decided to hold off for now.
.LONG TERM...(Saturday through Thursday)
Issued at 305 PM EDT Thu Jul 27 2023
An upper low across southern Canada moves east and reloads the
persistent troughing across eastern Canada, resulting in lower
heights and northwest flow across the Great Lakes for much of next
week.
As heights fall, a cold front sags south of the forecast area on
Saturday, with showers and a few thunderstorms clearing the southern
zones during the afternoon. Then fair weather prevails until a
shortwave trough axis moves through with the potential for a chance
of showers Sunday. This is followed by a stretch of cool and drier
weather as a Canadian surface high is centered over Lower Michigan.
The high moves east by mid-week with southerly flow and enough
moisture return pooling ahead of the next shortwave trough and
surface cold front advancing in the fast northwest flow to bring a
chance of showers and thunderstorms Thursday afternoon.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 740 PM EDT Thu Jul 27 2023
A complex of thunderstorms across northern Wisconsin will be
diving southeast late tonight into early Friday across Lake
Michigan and western Lower Michigan. The expectation is for an
outflow boundary to race out ahead of these storms and impact most
of the terminals with a sudden wind gust from the NW. Whether
there is much lightning left in this complex by the time it
arrives is still in question. Will go with SHRA for now.
Heading into the rest of Friday, there is greater than normal
uncertainty with wind speed and direction. We are seeing the
possibility for highly variable wind directions throughout the day
at the terminals based on uncertain location and timing of any
convection that develops. In general, an easterly or ESE flow may
be favored from MKG to LAN and more of a southerly flow from AZO
to JXN. There is a signal, however, for northerly flow to begin
impacting MKG/GRR/LAN by mid to late afternoon. Much depends on
convective activity during the day and where mesoscale boundaries
develop.
Just beyond this TAF period, thunderstorms with very strong wind
gusts may develop in the 00z-06z Saturday time frame. There is
certainly potential for gusts to 50 kts or greater during this
period, along with IFR or LIFR due to low ceilings developing
given abundant low level moisture.
&&
.MARINE...
Issued at 305 PM EDT Thu Jul 27 2023
The wind forecast is complicated tonight by the possibility of a
cluster of thunderstorms moving south down the Lake after midnight.
If this occurs the prevailing Winds will be shifting tonight from
the prevailing southerly flow to east or northeast with locally
higher gusts and waves in the vicinity of those storms.
South winds should return Friday morning as the storms dissipate and
then veer northwest as another round of showers and thunderstorms
arrive in the afternoon. These storms could have wind gusts over 40
knots and even higher as they move through, along with heavy rain and
hail. They should be moving south and east of Lake Michigan during
Friday evening.
Winds go north as high pressure advances in from the north on
Saturday and a Small Craft Advisory and Beach Hazards Statement may
be needed. Conditions will improve on Sunday as the high
builds in and winds and waves diminish.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
SHORT TERM...Meade
LONG TERM...Ostuno
AVIATION...Hoving
MARINE...Ostuno
Area Forecast Discussion
National Weather Service Indianapolis IN
954 PM EDT Thu Jul 27 2023
.Forecast Update...
Issued at 954 PM EDT Thu Jul 27 2023
Much of the isolated showers and thunderstorms that were across
central Indiana earlier this evening have dissipated with loss of
heating. Most of the convection is now southeast of the area,
associated with a low level convergence axis.
Confidence is lower than desired in chances for convection
overnight. Much of the convection earlier was driven by outflow
boundaries moving through unstable air.
However, some weak upper energy may move across the area into the
early overnight, sparking additional isolated convection. The latest
HRRR has been hinting at this possibility. For now, have just
extended the isolated PoPs a few more hours than the previous
forecast, since confidence is low in specifics of the weak upper
energy. Will keep a close eye on whether they need to be extended
longer.
Additionally, a little stronger push of upper energy will approach
the area late tonight from the west. This will generate convection
that may move into the forecast area in the 09-12Z time frame.
Convective allowing models are struggling with this, and there is no
clear signal yet on how this will develop. Will have to play a
waiting game with this as well. Kept the forecast dry for now.
Adjusted hourly temperatures and dewpoints based on latest
observations, but made no significant changes to low temperatures.
Dewpoints are quite high with many observations showing 79/80 degree
readings.
&&
.Short Term...(This evening through Friday)
Issued at 251 PM EDT Thu Jul 27 2023
* Heat Advisory in effect today and Friday
* Hottest temperatures and heat indices of the Summer expected Friday
* Isolated to scattered storms possible near and south of I-70
through early evening
Sultry afternoon across the region with a few lucky locations
getting a drink from isolated downpours...including KIND. Where rain
has not fallen...afternoon temps have soared into the lower 90s.
Meanwhile here at KIND...temps have been unable to rise above 85 due
to the few downpours that have tracked across the SW Indy metro
since around 16Z. Regardless of the temps...the dewpoints are
absurdly high this afternoon...with much of the area in the mid and
upper 70s. KHUF has even made it the rare 80 deg dewpoint as of 18Z.
Heat indices have maxed in the 105 to 110 range as a result...
especially across the Wabash Valley.
The convection component so far has been a result of some form of a
convergence boundary which has shown up very nicely on satellite as
an axis of towering cu from Vermillion Co E/SE across the southern
Indy metro continuing into Shelby and Rush Cos before persisting
further east into southwest Ohio. There have been a few storms but
as discussed earlier...the lack of shear and storm motions generally
hovering around 10kts at best have led to slow moving and pulse
intensity convection with soaking downpours which has had difficulty
maintaining intensity for any extended period of time. Away from
this boundary...it has been dry so far today across the forecast
area.
Going forward for the rest of the afternoon and evening...this
boundary should shift slowly southeast with additional convection
likely to focus in its vicinity into the evening before diminishing.
Really hard to place much higher than chance pops over the southern
half of the forecast area as coverage is not expected to exceed
scattered in nature with much of the area remaining dry. However...
locations that can get underneath the broken line of convection will
get a respite from the heat (but not the humidity) and a nice drink
of water. Not out of the question to see isolated activity elsewhere
driven by heating and instability. As is typical with mid summer
pulse intensity convection...any stronger cells aloft will be
capable of producing localized damaging winds when their cores
collapse. We have not seen that to this point so far this afternoon
but enough DCAPE present that this remains a possibility.
ACARS soundings out of KIND have continued to show a shallow but
potent inversion present below 850mb for much of the day. While that
has not been enough to limit convection...it has led to a much more
extensive level of lower ceilings that have had some difficulty
mixing out. The bulk of the cloud cover will remain in the vicinity
of the boundary through the afternoon but in general skies should
trend towards mainly clear by mid to late evening as lingering
convection shifts into southern Indiana and eventually diminishes.
It still appears that Friday will be the hottest day of the summer
so far for the forecast area as the heat ridge anchored to our
southwest nudges into the Ohio Valley. That being said...there is a
wild card in play that may stunt temp rises initially in the
morning...and that is what remains of the expected robust convective
development later this evening over the upper Midwest. That complex
is expected to turn right and dive southeast around the ridge
periphery overnight and into Friday morning before weakening. Some
of the CAMs data attempts to pull that even more south into northern
Indiana around daybreak before completely diminishing. Confidence
remains low in that potential at this point but even if that did not
occur...remnant cloud debris could be drawn into the region during
the morning before scattering out for Friday afternoon. That could
also have a downstream impact on convective risks later Friday
afternoon and especially Friday night if any remnant boundaries
drift into the forecast area from earlier activity to our north.
More on this threat for Friday night in particular in the Long Term
section below.
Temps...most locations will make it or already have made it to 90
this afternoon except for those impacted by convection and the
clouds. Pulled high temps down for the remainder of the afternoon at
KIND because of this reason but increased sun is not that far to the
north and even a short period with more sun could help boost KIND
near 90 late. Overnight lows will only drop into the mid and upper
70s with heat indices likely lingering in the low 80s in many
locations all night.
Friday remains a bit of a challenge based on the points made above.
While morning cloud debris may limit temp rises initially...the
combination of increasing southwest flow and slightly lower
dewpoints in tandem with warmer boundary layer air should enable
temps to peak at higher levels than today. Still feel that the bulk
of the model guidance is too warm in general with highs especially
considering how temperatures have performed the last few days.
Nudged highs down a few degrees from the previous forecast but still
expect low to mid 90s for the entire area with some locations in
western counties into the upper 90s. Max heat indices will be
solidly in advisory criteria for Friday and those headlines will be
continued.
&&
.Long Term...(Friday night through Thursday)
Issued at 251 PM EDT Thu Jul 27 2023
Hot and humid conditions should persist into the long range as
surface ridging to our south remains. Upper-level ridging across the
southern Plains and Four Corners region is expected to amplify,
allowing a trough to dig across the northeastern US. The trough will
lead to a cold front sliding into Indiana from the north late
Saturday into early Sunday, which will bring cooler conditions
Sunday and early next week. Gradual warming is likely by late week,
with humid conditions returning along with a chance of storms.
Storm chances continue on and off Friday night through Saturday
night as some embedded disturbances in the flow aloft pass nearby.
These waves may trigger some upstream convection which may
consolidate into an MCS or loosely organized cluster. Flow aloft is
weak for the most part, but guidance does tend to increase winds
above 500mb later Friday into Saturday. Given the warm and humid air
ahead of the aforementioned cold front, plenty of instability will
exist through Saturday. In the lower levels, guidance shows a decent
low-level jet persisting through Saturday (20 to 30 kts at 850mb),
which may allow activity to sustain somewhat.
Any cluster or MCS approaching from the north will likely persist
where upper-flow is maximized. Though the system, if it develops,
could also propagate into the LLJ which would give it a slight
southwesterly component. However, by that point, the system would
probably be out of cold pool shear balance and enter into a
weakening phase. Convective redevelopment is again possible later
Saturday afternoon along any residual outflow boundaries. Given the
convective dependence on mesoscale forcing, convection-allowing
models will struggle with storm placement and propagation. Expect
wildly different solutions, particularly in simulated reflectivity,
depending on the model...even run-to-run with the same model.
By Sunday, the cold front should be through and cooler and drier air
(dew points into the 50s) will spread in from the north. 850mb temps
should fall by 10 to 15 degrees C, which will correspond to highs
only in the 80s Sunday through Tuesday. Northerly flow could persist
through mid-week as surface high pressure slides east over the Great
Lakes. Some slight airmass modification should allow temperatures to
rebound into the upper 80s by Thursday and Friday. Return flow on
the back side of the high brings southerly flow back by the end of
the week. Simultaneously, a system diving in from the north may
bring a renewed threat for showers and storms Thursday and Friday.
&&
.Aviation...(00Z TAF Issuance)
Issued at 700 PM EDT Thu Jul 27 2023
Impacts:
* Isolated convection possible this evening mainly at KHUF/KBMG
* Low confidence chance for convection north near sunrise
Discussion:
A few showers are near KBMG but at the moment most convection is
away from the TAF sites. Will watch some storms across central IL to
see if they can make it to KHUF between 00-02Z. For now will just
mention VCSH at KBMG and KHUF this evening. Can`t rule out
convection elsewhere, but odds are too low to mention.
Otherwise VFR conditions are expected. Some localized fog is
possible late tonight, but odds are too low to mention. Also, some
storms may move into northern Indiana toward sunrise. Confidence is
much too low to mention these at this time. Additional isolated
convection will fire after 18Z Friday, mainly east.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until midnight EDT Friday night for INZ021-028>031-
035>049-051>057-060>065-067>072.
&&
$$
Update...50
Short Term...Ryan
Long Term...Eckhoff
Aviation...50
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
953 PM EDT Thu Jul 27 2023
.SYNOPSIS...
Bermuda high pressure will continue to drive excessive heat,
humidity, and diurnal thunderstorm chances through Friday. A strong
cold front will push across the region late Saturday into Sunday.
Drier conditions with slightly cooler temperatures and lower
humidity return with high pressure early next week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
The Severe Thunderstorm Watch has been allowed to expire early as
convection continues to wane across the region. SPC mesoanalysis
continues to show increasing CIN over a majority of the region
outside of the southern Shenandoah Valley, southern MD, and the
northern neck of Virginia. CAPE values remain between 1500-3500 j/kg
in these locations with DCAPE values between 1200-1400 j/kg. The
current 00z HRRR, ConShort, and RAP continue to show weakening
and decreasing coverage of storms as we head into the overnight
hours. This aligns well with current radar trends keeping the
bulk of the convection tied to areas west of Allegheny Front.
As a a result, an isolated strong thunderstorm cannot be ruled
out before midnight although confidence continues to increase
for dry/muggy conditions overnight.
Areas that did see rain today can expect some patchy dense fog.
The same can be said, for river valleys along and west of the
Blue Ridge heading into sunrise Friday morning. Overnight low
temperatures will remain in the low to mid 70s for most
locations. City centers will bottom out around 80 degrees with
mountain locations falling into the upper 60s.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
Bermuda high pressure will continue to cause hot and humid
conditions Friday. In fact, it should turn out even hotter due
to more sunshine (less mid-level clouds than what occurred
today). For that reason, an Excessive Heat Warning is in effect
for the I-95 corridor to the Bay, with Heat Advisories for most
other locations to the west (except the ridges).
The heat and humidity will lead to higher CAPE, and a surface
trough will remain overhead. Therefore, more scattered severe
storms are possible during the afternoon and evening with
damaging winds and large hail being the primary threat. The best
chance for stronger storms will be east of the Blue Ridge
Mountains.
Convection should wane Friday evening, but an upper-level
disturbance may trigger more convection overnight into Saturday
morning. A cold front will drop closer to the area from the
north later Saturday while the flow aloft strengthens. Hot and
humid conditions will likely persist (assuming we can get enough
of a break behind the morning activity), and Heat Advisories
may be needed for heat indices around 100 to 105 degrees.
Additional thunderstorms are possible Saturday afternoon and
evening, and some may be severe due to stronger shear profiles
and moderate to higher CAPE. The front will likely drop into the
region Saturday, and more convection may persist through the
night.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
A frontal passage is expected Saturday night into Sunday morning,
bringing potentially unsettled weather. Uncertainty remains with
this disturbance, especially with cloud debris ahead of the line
serving as a limiting factor. Nonetheless, showers and thunderstorms
will be possible Sunday during the day. Shortly thereafter, high
pressure will build into the Mid-Atlantic, bringing drier conditions
across the area through midweek next week. Highs after Sunday will
begin to trend towards normal or even slightly below normal for late
July/early August.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
VFR conditions will prevail overnight into Friday. Some patchy
fog is possible at terminals along and west of a line from
KIAD/KFDK south to KCHO. Highest confidence for fog will be
across the river valleys between 09-13z/5-9am Friday morning.
For now, opted out of putting fog at IAD and MRB despite the
recent rainfall from this evening. Residual cloud cover in the
area may limit fog formation per the latest 00z hi-res guidance.
Will need to revisit the opportunity for fog in the 03z TAF
amendments of 06z TAF package pending how things clear out. Any
fog looks to burn off beyond 13z/9am with mostly sunny skies
prevailing Friday morning into Friday afternoon.
Additional showers and thunderstorms are likely to provide
brief restrictions to the terminals Friday afternoon. With the
surface trough nearby expect convection to fire between
18-23z/2-7pm. Coverage once again will be isolated to scattered
with a focus on the eastern terminals. Current 00z hi-res
guidance seems to focus on an area from I-81/Shenadoah Valley
and east of Blue Ridge into the urban corridor between
19-01z/3-9pm. For now, will put a mention of VCTS in at all
terminals based upon the uncertainty in tracking down where the
convection may form. VFR conditions will return with patchy
areas of fog late Friday night before a better chance of storms
arrives Saturday into Saturday night as a cold front crosses the
region. The coverage of storms looks better on Saturday
compared to Friday with further organization expected as the
front drops through.
VFR conditions are expected Sunday and Monday with some isolated
instances of sub-VFR conditions Sunday with any passing showers and
thunderstorms across the terminals. Northwesterly wind gusts on
Sunday may be 15-20 knots Sunday afternoon before subsiding by
Monday.
&&
.MARINE...
A Small Craft Advisory is in effect through Friday morning for
the open waters of the southern Bay and lower Tidal Potomac
River.
Scattered storms are possible Friday afternoon and evening, and
some may produce strong winds. More storms are possible Saturday
into Saturday night with strong winds possible. SMWs may be
needed during the afternoon and evening hours on both days to
encompass the thunderstorm threat.
Winds may approach SCA criteria Saturday ahead of a cold front.
Small Craft Advisories may be needed Saturday ahead of the front
and Sunday behind the front as northwesterly winds increase.
High pressure builds in for the beginning of the workweek and
into midweek next week, leading to weakened winds.
&&
.TIDES/COASTAL FLOODING...
A southerly component to the wind may cause water levels to
reach action stages over the next couple days, but confidence
for minor flooding is low.
&&
.CLIMATE...
Potential for daily temperature records Thu (7/27) through Sat (7/29)
Washington/Reagan National:
7/27 high 100 (1940)
7/27 low 81 (2016)
7/28 high 100 (1997)
7/28 low 80 (1949)
7/29 high 104 (2011)
7/29 low 80 (2011)
Washington Dulles Airport:
7/27 high 98 (1993)
7/27 low 75 (2016)
7/28 high 99 (1993)
7/28 low 75 (1963)
7/29 high 103 (2011)
7/29 low 74 (2002)
Baltimore/Washington Arpt:
7/27 high 101 (1940)
7/27 low 82 (1930)
7/28 high 103 (1941)
7/28 low 82 (1949)
7/29 high 101 (2011)
7/29 low 82 (1949)
Martinsburg Airport:
7/27 high 105 (1930)
7/27 low 76 (1892)
7/28 high 101 (1952)
7/28 low 75 (1892)
7/29 high 103 (1941)
7/29 low 77 (1941)
LENGTH OF CLIMATE RECORDS:
Washington/Reagan National: Since 1872 Washington Dulles
Airport: Since 1960 Baltimore/Washington Arpt: Since 1872
Martinsburg Airport: Since 1891
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Excessive Heat Warning from 11 AM to 8 PM EDT Friday for
DCZ001.
MD...Excessive Heat Warning from 11 AM to 8 PM EDT Friday for
MDZ008-011-013-014-016>018-504-506-508.
Heat Advisory from 11 AM to 8 PM EDT Friday for MDZ003>006-502-
503-505-507.
VA...Excessive Heat Warning from 11 AM to 8 PM EDT Friday for
VAZ053>057-527.
Heat Advisory from 11 AM to 8 PM EDT Friday for VAZ025>031-
036>040-050-051-501-502-505-506-526.
WV...Heat Advisory from 11 AM to 8 PM EDT Friday for WVZ050>053-055-
502-504.
MARINE...Small Craft Advisory until 10 AM EDT Friday for ANZ533-534-537-
543.
&&
$$
SYNOPSIS...EST
NEAR TERM...EST
SHORT TERM...BJL
LONG TERM...ADM
AVIATION...BJL/ADM/EST
MARINE...BJL/ADM/EST
TIDES/COASTAL FLOODING...BJL
CLIMATE...LWX
Area Forecast Discussion
National Weather Service Tucson AZ
147 PM MST Thu Jul 27 2023
.SYNOPSIS...An excessive heat warning remains in effect across
portions of the region through tomorrow. Isolated to scattered
mainly afternoon and evening showers and thunderstorms through
Friday, then an increase in moisture this weekend into early next
week should result in cooler afternoon temperatures and more
numerous and wetter showers and thunderstorms.
hereafter.
&&
.DISCUSSION...Mostly sunny skies across most of southeast
Arizona early this afternoon with some cloud build-ups across the
mountains east of Tucson. Latest GOES total PWAT values are around
0.9-1.00" for areas east of Tucson and up to around 1.5" for the
western deserts. Latest forecast trends based on CAMS/HREF for
isolated to scattered showers and thunderstorms later this afternoon
into this evening continue to look good, mainly east of a Sells-San
Carlos line. Latest SPC RAP mesoanalysis shows MLCAPE values around
500-1000 J/KG, upwards of 2000 J/KG of DCAPE and around 20 kts of
effective bulk shear. Main concerns with storms today will be strong
gusty winds and locally heavy downpours. Blowing dust is also
possible in the usual areas prone to blowing dust but it`s not
expected to be widespread today.
A fairly similar setup for Friday with scattered afternoon and
evening showers and thunderstorms. Then for this weekend, as an
inverted trough in the easterly flow approaches Saturday and moves
through Sunday, we expect more widespread shower and thunderstorm
activity. It`s a bit too early to say which of the weekend days will
be the most active but an overall busier period is in store as the
first system of this type impacts our region for the season.
For next work week, storm chances will start to diminish back to
more typical levels for early August as southeast Arizona resides on
the back side of the wave and our flow becomes more south to
southwest as drier air advects in from the west.
Hot temperatures will continue through Friday, lowering to near
normal values by Sunday and Monday briefly, with a gradual warming
trend thereafter next week.
&&
.AVIATION...valid through 29/00Z.
Isolated-Scatered SHRA/TSRA will continue thru 28/06Z, most likely
impacting KOLS but also potentially impacting KTUS and KDUG. Gusty
outflow winds to 40+ kts along with VSBY reductions to 3SM or less
are possible with TSRA. Outside of thunderstorm outflows, SFC winds
will be NWLY this afternoon and again Friday afternoon. Aviation
discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Isolated to scattered afternoon and evening
showers and thunderstorms are expected across portions of southeast
Arizona this afternoon and Friday before an increase in coverage and
rainfall potential is expected this weekend. Storms will be capable
of producing strong, gusty and erratic outflow winds of 45 mph or
more. Although sustained 20-foot winds will generally be less than
15 mph through the remainder of the week, afternoon gusts to around
25 mph may occur. Hot temperatures with near record to record
readings will continue through Friday, with temperatures
lowering a few degrees over the weekend. Valley min RH readings will
generally range between 10-20% this afternoon, 15-25% Friday
through Sunday, then 20-30% Monday through Wednesday.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 10 PM MST Friday for AZZ504>506-509.
&&
$$
Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson