Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/11/19
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
957 PM EDT Wed Jul 10 2019
The 00Z DTX sounding tells the story of afternoon and early evening
convective potential for SE Michigan. It shows a well mixed boundary
layer with generous moisture supply but just not enough to break
through the cap in the 800-750 mb layer. A few late developing
updrafts made an attempt but quickly dissipated while storms
developed more fully to the east where moisture was deeper and much
more strongly to the south where surface based instability was
For the rest of tonight, thunderstorm potential shifts to the upper
level trough and surface cold front moving across the northern and
western Great Lakes. A window for storms remains open for SE
Michigan as the mid level thermal trough is nudged eastward and
replaced by modest cooling aloft. This is proving adequate for
continued expansion over northern Lower and for new convection near
the south end of Lake Michigan where slightly greater mid level
lapse rate overlaps with the MLCAPE axis and stronger SW flow aloft.
A secondary surge of low level theta-e ahead of the cold front is
expected to maintain moderate elevated instability during the night
that could support additional isolated to scattered coverage along
and ahead of the cold front. Marginal and conditional is a good way
to describe severe potential as storms, if they develop, are limited
by the loss of surface based instability while gaining access to a
slightly better wind profile. Slightly stronger shear could support
a marginal hail risk along with a localized downburst wind gust and
locally heavy rainfall before the front exits into Ontario toward
Issued at 710 PM EDT Wed Jul 10 2019
Increased convective potential shifts to the cold front advancing
from Wisconsin into Lower Michigan tonight. Southward development
along the front has been limited so far but a window does remain for
activity reaching the MBS to FNT area during late evening and early
overnight. Conditions outside of any storms remain VFR upon passage
of the initial cold front through early Thursday morning. A trailing
pressure trough brings a stronger NW wind shift by late morning
through Thursday afternoon. Substantial cumulus coverage is expected
in the cooler but still relatively humid air mass into Thursday
For DTW... A stray shower or thunderstorm remains possible near the
Canadian and Ohio borders through early evening moving eastward and
away from DTW. Storms along the cold front also appear to remain
north of DTW tonight although new development near the south end of
Lake Michigan will be monitored during the evening.
DTW THRESHOLD PROBABILITIES...
* Low for thunderstorms tonight.
* Moderate for ceiling 5000 ft or less Thursday.
Issued at 351 PM EDT Wed Jul 10 2019
Forecast reasoning laid out in previous discussions remains valid
going into this afternoon. An instability axis is moving in from the
west with latest RAP guidance indicating MLCAPEs of 1500+ J/kg
present west of US-23. Weak midlevel capping in place (evidenced by
lack of stronger vertical development in the cumulus field) and weak
forcing will hinder much convective development, but isolated
showers and storms will be possible in the 6-10pm window given the
unstable air mass. 0-6km bulk shear of about 15-20 kt is currently
in place and will increase to about 30 kt this evening as the low
pressure system moves into northern lower Michigan, which will allow
for a marginal risk of strong to severe storms. The main threats
will be 50-60 mph wind gusts, small hail, and heavy rain given
potential PWATs in excess of 1.5 inches. After diurnal support is
lost and the boundary layer stabilizes, severe threat diminishes.
However, a broken line of showers or storms ahead of the incoming
cold front may extend/survive into the Saginaw Valley and Thumb
tonight in the 11pm-3am time frame.
Dew points in the upper 60s to lower 70s will remain in place much
of the night ahead of the cold front. With cold frontal passage late
in the overnight period and weak/delayed cold advection, lows will
be held in the upper 60s to lower 70s as well. The overall result
will be a very muggy night.
Tomorrow will be a more comfortable day across the region as cooler
and slightly less humid air advects in from the northwest. Mixing
depths expand to around 850mb and tap into slightly elevated
gradient flow, resulting in a breezy afternoon. 850mb temps around
13-15C will allow for highs to climb into the lower 80s across much
of the region and mid 80s in the Detroit urban corridor and south of
the glacial ridge. Isolated to widely scattered showers will be
possible during the afternoon as the thermal trough passes overhead
coincident with a weak surface trough. Lows tomorrow night will fall
to around 60 degrees (mid 60s in Metro Detroit) with any lingering
showers having tapered off by evening.
Quiet weather on Friday as weak height rises move in with a ridge
expanding in from the upper Midwest. Surface high pressure will
build in from the mid-Mississippi Valley with light northerly flow
keeping temperatures seasonable in the 80s with mostly sunny to
partly cloudy skies.
Saturday morning a low moves south of the Hudson Bay which brings a
slight chance for some scattered storms and showers Saturday evening
as its weak cold front moves across SE MI. Before the fropa, hot
humid air returns to the area with Saturday highs near 90 and
dewpoints in the 60`s. Post fropa highs Sunday will be average, in
the mid 80`s. Another large ridge of high pressure sets up over the
Great Plains and moves over SE MI by Monday bringing a very hot
humid airmass. Highs the first half of the next work week will be in
the low to mid 90`s and dewpoints in the mid 60`s.
Though still uncertain given how far out it is, models are taking
the remnants of what is currently Potential Tropical Cyclone Two up
the Mississippi valley and over SE MI by Thursday next week which
could bring heavy rain to the area if the track pans out.
Light wind within resident high pressure will continue through
today. There is a chance for severe thunderstorms this evening
mainly over the southern waters. Light to moderate northwest flow
fills in behind the cold front on Thursday.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
You can obtain your latest National Weather Service forecasts online
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
700 PM CDT Wed Jul 10 2019
1237 PM CDT
Thunderstorm chances continue to be the main forecast question,
though heat indices around 100 degrees this afternoon may be
causing the bigger impacts. Regarding convective trends, most of
the latest CAMs have at best some spotty development for the rest
of the day into the evening, with the southeast portion of the
forecast area most favored. Cumulus development is very sparse
across our western half and just upstream of the area so far. This
is probably related to the nose of warm air just above 800mb being
seen in late morning AMDAR data and reflected in the latest RAP
soundings. The RAP shows this cap eroding somewhat but not
completely this afternoon, so have held onto a slight chance of
storms mainly across our southeast where the cumulus field is more
robust and the passing cold front will coincide with the best
diurnal support. Expect that anything that does manage to develop
this afternoon to wane during the evening and then dry conditions
to prevail into tomorrow morning.
With dewpoints in the 60s by morning rather than lower 70s like
this morning, low temperatures tonight behind the cold front
should also be a few degrees cooler than this morning.
218 PM CDT
Thursday through Wednesday...
A relatively quiet period is setting up for the long term forecast
period. The upper level pattern is transitioning to a broad low
amplitude long wave pattern with an upper high parked over the
Southern Rockies/Four Corners region and the western extent of the
Bermuda high staying east of the Florida Peninsula. Meanwhile, a
series of upper troughs will dig through the Eastern Great Lakes and
southeastern Canada. Broad wnwly flow aloft will persist from
Thursday into early next week. Weak shortwave energy dropping
through the wnwly flow aloft may bring a few chances for some
showers and thunderstorms, but with the main upper forcing shunted
north of the Wisconsin border, and pcpn chances will be low, and
likely be glancing the far nrn portions of the CWA.
For Thursday and through the weekend, sfc high pressure will also be
firmly established across the region, leading to warm, but less
humid conditions. By Friday night, a weak cold front from an
associated low over northern Ontario will sag southward across the
Upper Mississippi River Valley. This weak front may skirt the
northern extent of the sfc high pressure. Latest guidance still
suggests that the front will stall over or just north of the CWA
late Friday night into Saturday, supporting at least small chances
of convective activity during this time, mainly for the northern
portions of the CWA.
Through the weekend and into early next week, a weakness in the
upper level flow between the upper ridge over the swrn CONUS and the
Bermuda high east of FL may allow a potential tropical system to
sneak north into the Lower Mississippi Valley. While there is still
considerable uncertainty as to how this system will develop and
where it may track, it will need to be watched over the next few
days to see if any moisture associated with this system can get
into, at least, the southeastern portions of the CWA by the middle
of next week.
For the 00Z TAFs...
700 PM...Forecast concerns include...
Isolated thunderstorms this evening...southeast of the terminals.
Wind shift to northeast Thursday morning.
Mvfr cigs Thursday morning.
A weak cool front is moving across the area currently and isolated
thunderstorms will be possible southeast of the terminals for the
next few hours. Westerly winds will turn northwesterly this
evening with gusts into the lower 20kt range possible through
Winds will continue to turn northerly by daybreak and will become
northeast Thursday morning. Confidence on timing is only medium
and its possible that winds will shift northeast earlier than
currently advertised in this forecast. Gusts into the mid/upper
teen kt range will be possible Thursday afternoon diminishing
Much of the guidance is suggesting mvfr cigs will develop after
sunrise across the area with cigs near 1kft across much of
northwest IL. Followed these trends and introduced mvfr cigs with
this forecast but confidence on specific heights is low. Cigs
should begin to lift by late morning with scattering expected in
the afternoon. cms
IN...Beach Hazards Statement...INZ001-INZ002...2 PM Thursday to 4 AM
LM...Small Craft Advisory...LMZ743-LMZ744-LMZ745...2 PM Thursday to 4
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
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Area Forecast Discussion
National Weather Service Marquette MI
811 PM EDT Wed Jul 10 2019
Issued at 322 PM EDT WED JUL 10 2019
Still a tricky forecast this afternoon. A few showers developed
along what appears to be an enhanced Lake Michigan breeze boundary
pushed all the way up to Lake Superior by prevailing southerlies. An
additional light shower popped up near Ironwood in the last hour in
the neighborhood of enhanced 925mb fgen. None of these have been
able to sustain any strength to the updrafts as of yet. Now, after
19Z, a few cells are becoming more organized just north of the
The main event is still expected to get going after 4pm EDT,
increasing in coverage and intensity into the early evening and then
moving out east of Luce County by about 10pm. Coverage will likely
be better over the northern tier of counties than further south
owing to stronger forcing, and will still be scattered at best
rather than widespread. In fact most CAMs are indicating better
coverage over eastern Lake Superior than the UP.
Mixing down of dry air has led to steep low level lapse rates over
the central UP, but this has allowed ample dry air to mix down there
and thus an instability minima exists over MQT, Iron, and Dickinson
Counties. It does appear that the best deep layer shear will be a
little out ahead of the forcing through this event, but may still
maximize at around 40 kts. Thus, a rotating updraft is still not out
of the question, but is not exactly likely. Low level shear is weak
in a 0-1km sense, but picks up to 30-35 kts for 0-3km. With some
south and even southeasterly component to the 5-10 knot sfc winds
out in the east, still can`t completely rule out a brief spin up
east of a Marquette to Iron Mountain line. More likely hazards will
be isolated large hail and some gusty winds with any stronger cells
that do develop.
Some lingering isolated drizzle or light showers are likely to stick
around through tonight over the north where onshore/upslope flow
will keep the lower levels moist before drier air can fully filter
in behind the front. Marine fog over Lake Superior will also stick
around this evening, perhaps pushing south towards the shoreline
ahead of the front, and then gradually dissipate as this drier air
.SHORT TERM...(This afternoon through Thursday evening)
Issued at 1138 AM EDT WED JUL 10 2019
...STRONG TO SEVERE THUNDERSTORMS POSSIBLE MAINLY FROM MARQUETTE AND
DICKINSON COUNTY EASTWARD AFTER 4PM EDT...
Lingering low clouds over Schoolcraft and Luce Counties this morning
have exited, and skies across the Upper Peninsula have been partly
cloudy through the day with only daytime cumulus. The warm front has
already pushed through the region with even 15Z readings of 81/66 at
IMT and 79/71 at MNM. At IMT, those dew points have already started
to mix downwards thanks to relatively dry air aloft.
Per RAP analysis, the sfc low was located north of Isle Royal late
this morning and it is expected to pick up the pace northeastward
this afternoon. The cold front, located out over the arrowhead of MN
at 15Z, will continue it`s trek across the area relatively quickly
through this evening. 12Z GRB sounding matched up pretty well with
the NAM fcast, with a near sfc inversion and a number of smaller
ones up the column. These should mix out by about 18Z.
CAMs have trended later with convective initiation, and the
expectation is for most of the activity to be centered along and
east of a line from about Iron Mountain to Big Bay. West of there,
some scattered showers and an isolated thunderstorm or two are
possible, but better parameters for strong to severe storms will be
to the east.
HRRR seems to be underdoing both instability and shear in relation
to most other CAMS and SREF members, and thus the depiction of model
reflectivity is a bit more cellular than expected. A plume of 1500-
2000 J/kg SBCAPE over the east this afternoon seems likely, and
isolated pockets of slightly higher values cannot be ruled out.
This, in combination with 50 kts bulk shear per RAP analysis, will
allow for the possibility of robust convection. East of Munising to
Escanaba looks to be where the best chance for low level southerlies
early on, with strong southwesterlies aloft, and thus rotating
updrafts remain possible for at least the first couple hours before
storms grow upscale into a more linear configuration. More likely
hazards will be brief heavy downpours as well as the potential for
large hail (supported by WBZ heights near 9-9.5 kft and at least
some dry air aloft for entrainment) and gusty winds (supported by
the aforementioned dry air and DCAPE values per RAP soundings near
1200 J/kg). Storms are expected to exit the region by about 03Z.
.LONG TERM...(Thursday night through Wednesday)
Issued at 220 PM EDT WED JUL 10 2019
Not to many changes in the extended with fluctuating temperatures,
with highs in the 70s on cooler days and 80s on warmer days, through
the end of the week and throughout the weekend a couple of cold
fronts push across the area. Upper-level ridging is progged to build
in next week and push over the eastern half of the CONUS, placing us
under persistent warm air advection and the return of persistent
above-normal heat. While we will remain on the northern periphery of
the ridging, it still looks like we will get back into an active
period of weather as shortwaves crests the upper-level ridge. While
it is certainly too far out to talk specifics, we could be looking
at decent chances for MCSs rolling across the region.
Models have trended a bit cooler and breezier on Thursday behind the
exiting cold front. Didn`t make too many changes to the forecast
other then bumping up the sustained and gust wind fields. Given the
onshore flow east of Marquette, it certainly looks like tomorrow we
will see a moderate to high swim risk along the beaches of Lake
Superior for Marquette and Alger County. Temperatures look borderline
as they should be a bit cooler near the shoreline; however, with
models also trending dry with clearing earlier in the morning hours
near the shoreline a beach hazards statement may be required. Winds
will relax overnight Thursday as high pressure moves overhead. This
also will lead to a pleasant night with overnight lows dropping
into the mid to upper 40s inland, and 50s near the Great Lakes.
On Friday, shortwave energy tracking east across the Dakotas will
traverses the Upper Great Lakes, pushing another cold front across
the region. Ahead of this cold front, it will get warm and humid yet
again, with daytime highs in the 80s, except downwind of Lake
Michigan where 70s will prevail. With the main axis of deeper
moisture and return flow shifting east across the area Friday
afternoon, depending on how early morning convection plays out,
medium-range models are showing the potential for thunderstorms that
afternoon and evening. With increasing moisture throughout the day,
the GFS and NAM show an axis of 1500-2000+ J/kg of SBCAPE. The
instability coupled with boundary perpendicular deep-layer shear of
30-40 knots, is cause for concern for the potential for severe
thunderstorms. Given the subtle nature of the shortwave, thinking
any thunderstorm activity should be more isolated/scattered in
nature, which would increased chances of updrafts maintaining better
organization/strength. Given the environment in place, large hail
and damaging winds look to be the main hazards. Cannot rule out a
tornado if any boundaries develop locally; however, low-level shear
and surfaces winds veering westerly are not favorable for tornadic
Much of the upcoming weekend looks nice as another area of high
pressure drops south across the area. Saturday will be the coolest
day of the weekend behind the departing cold front. However, Sunday
the main area high pressure starts to shift southeast of the region
and we will find ourselves back under warm/moisture return flow. As
high pressure continues to push eastward and upper-level ridging
builds across the central CONUS through the early/middle parts of
next week, this will push us back into a hot and humid spell. As we
remain on the northern-edge of the upper-level ridging Sunday
through next week, this will put us in the potential zone for MCS
activity. However, this far out there is still a lot of uncertainty
in regards to where and when the best chances for precipitation and
thunderstorms will be late weekend/next week. To make things more
complicated in the extended, tropical activity well to our south
will certainly have an impacted on the overall pattern and play a
role in making next weeks forecast a bit more complicated until we
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 809 PM EDT WED JUL 10 2019
Isolated showers are possible near KSAW through 03z. Otherwise, MVFR
cigs are expected overnight as low level moisture moves in overnight
behind a cold front moving through Upper Michigan. VFR
conditions will return by mid to late Thursday morning as drier air
setttles across the area.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 219 PM EDT WED JUL 10 2019
Areas of fog have been observed on the lake today over primarily
locations 30+ miles north of Upper Michigan, which is expected to
gradually dissipate this evening and tonight as a cold front brings
a cooler, drier air mass to the region. Strong thunderstorms are
possible across eastern Lake Superior late this afternoon and
evening. Hail and strong winds are the primary threats. Winds have
come down this afternoon over the lake, but the cold front coming
across tonight will cause winds to increase out of the west and then
northwest, gusting in the 20 to 25 knots range, with some gusts up
to 30 knots across higher platforms. Winds will diminish tomorrow
evening, but may reach up to 25 knots again on Friday from the west
to northwest as another weak cold front passes across Lake Superior.
After Friday, winds should remain below 20 knots.
Area Forecast Discussion
National Weather Service Phoenix AZ
358 PM MST Wed Jul 10 2019
.UPDATE...Updated Aviation Discussion...
The Monsoon High will be the predominant weather feature through
next week, resulting in a continuation of the above normal
temperatures. Moisture will also steadily increase, resulting in
a threat of isolated storms each afternoon through next week,
particularly from Phoenix north and eastward.
Streamline analysis clearly depicts anticyclonic flow across the
Desert Southwest associated with the Monsoon High building
northward through New Mexico. Further west, a vort max is evident
across central Arizona, which is helping to transport richer
moisture northward. Latest surface observations indicate that
temperatures and dewpoints in particular are several degrees
higher than they were this time yesterday. Meanwhile, temperatures
in the mid-levels are relatively cool, owing to the presence of
the vort max and corresponding inverted trough. PSR sounding
climatology suggests this morning`s 500 mb temperature of -10 deg
C is near the all-time record low. Mid-level lapse rates are
consequently quite steep, which is supporting a CU field across
the Mogollon Rim. Given the limited moisture, only isolated
showers are likely across the higher terrain. Latest HRRR
indicates any light showers that develop this afternoon will lift
northward, with no impact across the lower deserts.
Latest NAM-WRF simulated satellite imagery suggests that broken
cloudiness will overspread the region Thursday and Friday as PWATs
steadily climb above 1.0 inches. This will certainly affect
insolation and the NBM MaxT has trended 1 to 2 degrees cooler than
previous runs. Although the forecast high temperature for Phoenix is
111 degrees, the ECMWF and GEFS ensembles are exhibiting
relatively high variability, suggesting that if there are enough
breaks in the clouds, the temperature could potentially climb a few
degrees higher. The persistent clouds will linger into Friday
morning, resulting in well above normal temperatures overnight when
people are anticipating a reprieve from the heat. Bottom line is
that the Excessive Heat Warning will continue through Saturday
evening for most lower desert locations.
The cloudiness will also inhibit instability Thursday and hi-res
CAMs suggest that only a sprinkle or perhaps an isolated shower will
be possible. Less clouds are likely for Friday, resulting in
somewhat more CAPE in the afternoon and an increased threat of
showers and thunderstorms. Conditions will also be favorable for a
dust storm south and east of Phoenix.
In addition to the continued heat Saturday, there will be a
continued increase in the chances for convection over south-central
Arizona. While PWAT and CAPE continue to climb and are elevated over
the western deserts, low levels look to be too dry to support any
significant storms and thus POPs out west will stay in single digits.
We raised POPs a bit for south-central and have slight chances for
storms south and east of Phoenix. Of course, dust storm potential
will also climb over the deserts.
For the rest of the forecast period, Sunday through Tuesday, we will
remain in a somewhat low grade monsoon pattern; the upper high will
remain near or a bit south of the 4 corners area keeping a general
southerly steering flow in place and moisture will remain modest.
CAPE values will also be modest with highest values east of the
lower Colorado River Valley. Steering flow actually starts to turn
more to the south/southwest by Tuesday further confining storms that
develop to south-central Arizona and mainly high terrain locations
east of Phoenix. With moisture still only at moderate levels we will
see high temperatures remain elevated each day with hotter deserts
running around 110 and just below heat warning thresholds.
.AVIATION...Updated at 2300 UTC
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Westerly winds will remain breezy at times through early evening,
diminishing some after sunset but remaining out of the west
through at least midnight. Winds at KPHX should stay out of the
west through the overnight with only a brief period of easterly
winds early Thu morning. Clouds will be increasing tonight, but
generally above 15K feet. Some pockets of virga are also possible
mostly south and southwest of the metro early Thursday morning.
West winds Thu afternoon will again be gusty at times.
Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation impacts through the TAF period with mostly clear
skies. Winds will follow typical diurnal trends with speeds
generally less than 10 kts. Periodic afternoon breeziness will
occur at KBLH with gusts mostly around 15 kts.
Aviation Discussion not updated for amended TAFs.
Saturday through Wednesday:
Above normal temperatures and humidity will persist through next
week. Isolated storms will be possible each day, particularly across
the higher terrain of Arizona. However, the chance for wetting
rains will be somewhat lower. Winds will generally be light, except
in the vicinity of thunderstorms.
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
AZ...Excessive Heat Warning from 10 AM Thursday to 8 PM MST Saturday
Excessive Heat Warning from 10 AM to 8 PM MST Friday for AZZ532-
CA...Excessive Heat Warning from 10 AM to 8 PM PDT Friday for CAZ565-
Area Forecast Discussion
National Weather Service Pueblo CO
555 PM MDT Wed Jul 10 2019
Issued at 549 PM MDT Wed Jul 10 2019
Ran a quick update to bring in the latest observations and adjust
precipitation chances for this evening. The latest high-res model
solutions develop isolated activity over the Sangre de Cristo
range through sunset, with more isolated activity developing over
a pocket of higher instability over Baca County. Mozley
.SHORT TERM...(This evening through Thursday)
Issued at 343 PM MDT Wed Jul 10 2019
Tonight and Tomorrow:
Upper level high pressure system is currently centered over
southwestern Colorado and northwestern New Mexico. Any isolated
convection that developed over the mountains will dissipate by
sundown as downslope flow stabilizes the atmosphere. The surface
flow over the plains is from the southeast, which will advect some
moisture originating from the Gulf of Mexico over the eastern
plains. That moisture plume will be responsible for an increased
chance at an isolated thunderstorm that may develops over the Wet
Mountains this evening. The HRRR model trends are consistent in
developing a thunderstorm over the Wet Mountains and for the storm
to propagate along the theta-e ribbon south towards New Mexico. The
GFS is in agreement in that outcome as well. The NAM has isolated
thunderstorms along the main theta-e plume, but there is no
organized convection. The European model has no convection during
the overnight hours, whatsoever. The weather grids will have
isolated POPs over the lower Arkansas River Valley and will have
QPF. If the thunderstorm develops, it will be out of Pueblo`s CWA
The higher dew points will increase the minimum temperature
overnight over the plains. So expect low temperatures over the
plains to be in the mid-to-upper 60s, the mountain valleys in the
upper 40s to lower 50s, and the mountains in the upper 30s to low
The upper level ridge remains over Colorado tomorrow, which will
slowly bring Pacific based moisture towards the region. The added
moisture combined with diurnal winds up the mountains will spark
scattered (as compared to isolated the day before) thunderstorms
over the mountains. PW values, though higher than the previous
day, are still relatively low, which will put a limit on how
liquid will fall and how strong the storms will be.
The "La Junta low" will develop over the plains tomorrow afternoon,
creating a moisture boundary east of La Junta. CAPE values east of
the moisture boundary will be around 2500-3000 J/kg, but bulk shear
values are less that 30 kts. The only lifting mechanism that seems
to be around is the upslope flow towards the Palmer Divide. An
isolated thunderstorm may develop along that boundary, but it is
anticipated to be a pulse thunderstorm, meaning that the storm will
be brief but may produce isolated gusts up to 60 mph and hail larger
.LONG TERM...(Thursday night through Wednesday)
Issued at 343 PM MDT Wed Jul 10 2019
Recent forecast model soundings, PV analysis and computer
simulations indicate that varying degrees of upper level ridging
will impact southern Colorado during the balance of the longer
In addition, projected increased atmospheric moisture in
combination with occasional weak upper impulses and surface
northerly surges will allow for elevated precipitation chances at
times during the balance of the longer term.
At this time, it appears that the highest potential for more
widespread shower and thunderstorm coverage(including the
potential for locally heavy storms, capable of producing localized
flooding, including but not limited to recent burn scars) should
be realized this weekend and possibly continue into next week(with
the latest GFS solution signaling more aggressive storm activity
than the recent EC solution).
Overall, near to above seasonal mid-July maximum and minimum
temperatures are anticipated over the majority of the CWA during
the balance of the longer term with warmest conditions anticipated
Thursday and Friday(with maximum temperatures challenging 100F
over select southeastern Colorado plains locations) and then
again by next Wednesday. Finally, generally low-grade gradient
winds are projected during the balance of the longer term over
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 343 PM MDT Wed Jul 10 2019
VFR conditions are expected for KALS, KCOS, and KPUB throughout the
forecast period. There is a chance for an isolated thunderstorms to
develop over the Wet Mountains and travel in the vicinity of KPUB
during the overnight hours. Scattered thunderstorms are anticipated
over the higher elevations, so thunderstorms will be in the vicinity
of all of the forecast points. If a thunderstorm does develop over
KALS, KCOS, and KPUB, expect locally heavy rainfall which would
lower visibility and erratic and gusty winds.
Area Forecast Discussion
National Weather Service Blacksburg VA
905 PM EDT Wed Jul 10 2019
A cold front will approach from the west overnight into Friday.
This front should push south of the Mid Atlantic by this
weekend as high pressure builds overhead. Hot and humid weather
should continue into early next week.
.NEAR TERM /THROUGH THURSDAY/...
As of 900 PM EDT Wednesday...
Isolated slow moving convection continuing in spots this
evening, mainly north of Roanoke and across the southwest
mountains into NC. This in association with lingering
instability and a quick return in deeper moisture per high Pwats
off evening soundings. Latest HRRR seems to have the best handle
on current coverage with some isolated showers persisting into
the overnight off residual outflow. Thus leaving in 20ish pops
espcly mountains into the overnight after current showers fade,
while boosting fog where heavier rain did occur earlier on. Lows
to remain muggy given so much moisture around with eastern
locations likely staying above 70 with mid/upper 60s west.
Previous discussion as of 230 PM EDT Wednesday...
Showers and thunderstorms will continue to slowly develop
during the remainder of this afternoon. However, instability
has only increased somewhat due to peristent cloud cover left
over from a retreating cool wedge. The atmosphere should
gradually destabilize with time, but weak steering currents
will not allow much organization of any convection. DCAPE
exceeds 1,000 J/kg due to notable dry air aloft in the model
soundings. Thus, if any storms can obtain some vertical depth
later this evening, there could be a threat of gusty winds.
Precipitable water values near 1.50 inches also indicates some
heavy rainfall may be possible in the stronger storms.
Tonight should remain quite humid with dewpoints staying in the
mid 60s to the lower 70s. Any convection from the evening should
taper off before midnight. Patchy fog was included in the
forecast along some river valleys for early Thursday morning,
but most locations will probably witness just low clouds. The
threat for heavy rainfall and severe will be more notable during
tomorrow afternoon with high temperatures expected to be a few
degrees warmer compared to today. CAPE during Thursday will
likely reach 1,500-2,000 J/kg, and an approaching cold front
from the Ohio River Valley should provide more synoptic lift to
increase the coverage and organization of the storms. Damaging
winds and localized flooding from heavy rain will be the main
threats. However, confidence is too low to provide more refined
location details other than mentioning that the greatest severe
threat appears to be north of Route 460.
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 215 PM EDT Wednesday...
There will be lingering convection as we head into Thursday
evening with front slowing down with another upper vort moving
across the central Appalachians. The front will be east of us
by Friday morning with lingering upslope showers possible.
The front will linger south of the VA/NC border into Friday,
while another area of shortwave energy passes across. The
models showing at least fair 40-50 percent chance of
showers/storms Friday across our southern area, with high
pressure keeping the northeast CWA dry.
Drier air should push across the region by Saturday, although
the front stays situated from the Gulf Coast stats into
eastern NC while TC Barry enters the lower MS Valley. May see
just enough buckling in the flow and moisture advection across
the mountains to keep chance pops in Saturday in the southwest.
Temps will stay elevated despite front as not much change in low
level thicknesses though RH drops off Saturday.
Confidence is medium on how far south the front goes and chance
of storms especially Saturday.
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 130 PM EDT Wednesday...
The forecast will center on the track of what is expected to be
Tropical Storm, possibly Hurricane Barry. Numerous models are
close in general direction of this storm, with it situated
across the mid- lower MS Valley next week, while weakening.
Meanwhile, 500 trough is situated over the northeast U.S. with
broad ridge over the southeast. Some differences by day 7-Wed
with GFS allowing for Barry to picked up by the westerlies and
shifted east toward KY, while the Ecmwf keeps the remnants
further west across mid MS valley with a stronger ridge in the
southeast. Ensembles showing a blend of these two.
For our area, will see less threat of storms although a back
door front edges close to the area Sunday-Monday, models have
backed off on rain chances, mainly diurnal widely scattered
threat. Will remain very warm to hot and humid and mainly dry
through the period.
Confidence is medium on track of Barry and impact on our area.
.AVIATION /01Z THURSDAY THROUGH MONDAY/...
As of 645 PM EDT Wednesday...
Conditions should remain mostly VFR through this evening, but
the potential for MVFR exists from lingering cloud cover and a
chance for showers and thunderstorms mainly along/west of the
Blue Ridge. However given very isolated coverage attm, will only
keep a VCTS mention around KLWB/KBCB and KROA into this
evening. Winds should stay light from the south to southwest
this evening into the overnight.
Tonight a combination of damp ground and a humid atmosphere
will make low clouds and/or patchy fog a good possibility. The
best chance for IFR resides at KLWB, while MVFR could occur at
other valley locations but likely wont include elsewhere at this
point at other sites. KROA has the highest confidence of
staying VFR through the night. Conditions should recover to VFR
for all sites during Thursday, but showers and thunderstorms
could impact aviation concerns during the afternoon as a cold
front approaches from the northwest. Appears could see
convection develop in the KBLF-KLWB corridor by midday and
elsewhere during the afternoon. Models also suggest some lighter
showers during the morning across the mountains so something to
watch. Therefore given the high probability of all sites seeing
showers/storms have included a prevailing shower and/or VCTS
mention Thursday afternoon with at least brief MVFR or worse
possible into the early evening.
.Extended Aviation Discussion...
A cold front should cross overhead during Thursday night. MVFR
conditions may accompany the showers and thunderstorms before
the convection decreases toward early Friday morning. Some
showers could linger into Friday before drier air arrives by
Friday night. High pressure should arrive and maintain control
to provide overall VFR through the weekend into Monday.
Area Forecast Discussion...UPDATED
National Weather Service Shreveport LA
1028 PM CDT Wed Jul 10 2019
The strongest convection has exited the forecast area to the
southwest into Central Texas. However, additional showers and
thunderstorms are developing across Northern and Central Louisiana
along an outflow boundary that is moving south and southeast
across the area. This new convection will likely persist through
the overnight hours, but intensity and coverage should gradually
diminish. PoPs were updated to account for this.
The storms helped to cool several locations below the forecast low
temperatures, particularly along and north of Interstate 30.
Temperatures will likely hold steady, possibly even warm a degree
or two in these areas through the overnight hours.
Updated text products will be sent shortly.
.PREV DISCUSSION... /issued 659 PM CDT Wed Jul 10 2019/
For the 11/00z TAFs, a line of strong to severe convection will
progress southward across the area early in the period. These
storms should very slowly weaken by 11/06z. Most of the TAF sites
will be affected, but the latest model guidance suggests the
convection will greatly diminish before reaching KLFK. Otherwise,
VFR conditions should prevail. More scattered convection is
possible after 11/16z, mainly across Louisiana and East Texas
south of Interstate 20.
PREV DISCUSSION... /issued 417 PM CDT Wed Jul 10 2019/
This evening, the HRRR indicates that isolated thunderstorms will
continue to develop in an environment with strong instability
(SBCAPE 3000-5000 J/kg) and abundant moisture (PWATs near 2
inches) this afternoon into the evening. As the weak cold front
approaches from the north, lingering convection and outflow from
upstream convection will help increase chances of showers and
thunderstorms this evening for locations along the I-20 corridor
Showers and thunderstorms will mostly diminish tonight with
chances decreasing to a slight chance overnight. Remnant clouds
from earlier thunderstorms along with cirrus continuing to filter
in ahead of the tropical system should keep skies partly to mostly
cloudy. The chance of showers and thunderstorms will increase
again tomorrow afternoon with daytime heating. With the lingering
frontal boundary there is the potential for locally heavy rainfall
For temps, another oppressively hot afternoon is expected tomorrow
with highs in the mid 90s and heat indices warming into the 105 to
110 degree range. With this in mind, a Heat Advisory remains in
place for everywhere except Red River and McCurtain counties
through tomorrow. Tonight and tomorrow night, lows will be in the
mid to upper 70s. /04-Woodrum/
The National Hurricane Center commenced advisories on Potential
Tropical Cyclone Two at 10 am CDT this Wednesday morning. For
information concerning this developing system, please refer to the
discussions and graphics from the NHC.
For Friday, with the forecast, strengthening, tropical system in
the northern Gulf of Mexico, SCT TSTMS begin to affect central LA
and deep E TX as the outer bands of the tropical system spread N
The tropical system is then forecast by NHC to slowly move NW
through WRN LA, and center over extreme NW LA by Monday morning
shortly after daybreak. This scenario results in unsettled weather
into at least the middle of next week with SCT to numerous showers
and TSTMS. A deep tropical moisture airmass would of course result
in the potential for flash flooding issues. The main threat of
heavy rainfall will be over the eastern semicircle of the
Fortunately, this July commenced with typical very warm conditions
with only scanty rainfall. This trend allowed antecedent soil
moisture conditions to dry and area rivers, bayous, and lakes to
recede after our rather wet winter and springtime of 2019. In any
case, our dryer than normal spell that began this July will end this
weekend into the middle of next week.
As for winds with this system, the NHC currently forecasts a
hurricane to be inland in SW LA during Sunday morning just after
daybreak. By Monday morning, NHC then forecasts a tropical
depression over extreme NA LA. Current thinking is that tropical
storm force winds during Sunday afternoon may affect our southern
sections of our southern parishes: Natchitoches, Grant LaSalle, and
possibly Sabine. Have blended our SFC winds for this weekend with
the wind forecasts from LCH. /VIII/.
.PRELIMINARY POINT TEMPS/POPS...
SHV 76 94 76 92 / 40 30 10 30
MLU 78 94 76 92 / 40 30 30 40
DEQ 73 94 71 92 / 50 20 0 0
TXK 73 92 73 90 / 60 20 10 10
ELD 76 94 74 90 / 40 20 10 30
TYR 73 93 74 92 / 40 20 10 10
GGG 76 94 75 92 / 40 30 10 20
LFK 77 94 77 93 / 20 40 20 30
AR...Heat Advisory until 7 PM CDT Thursday for ARZ070>073.
LA...Heat Advisory until 7 PM CDT Thursday for LAZ001>006-010>014-
TX...Heat Advisory until 7 PM CDT Thursday for TXZ097-108>112-124>126-