Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/04/19
Area Forecast Discussion
National Weather Service Gaylord MI
1145 PM EDT Tue Sep 3 2019
.UPDATE...
Issued at 1013 PM EDT Tue Sep 3 2019
Low pressure center has pushed east into SE Ontario late this
evening...with the associated cold front now extending from NE
Lower Michigan to the Wisconsin/Illinois border. Last vestiges of
convection have pushed off shore into Northern Lake Huron. A look
at upstream satellite...radar and surface obs indicated a large
area of low clouds and scattered light shower activity rotating
into the Western Great Lakes region in the wake of this system.
Much of our CWA is currently experiencing a temporary clearing in
between the front and this wrap-around moisture. Expect these low
clouds and scattered light showers will slide into our CWA
overnight. Going forecast handles this well...so no major changes
needed to the near term forecast. CAA behind the front will be
offset by increasing low clouds. Still expect overnight lows in
the upper 40s to lower 50s.
&&
.NEAR TERM...(Through Tonight)
Issued at 311 PM EDT Tue Sep 3 2019
...Breezy Evening Diminishing Overnight...
High Impact Weather Potential...Thunderstorms sure, but severe
weather, well there`s a chance.
Pattern Synopsis/Forecast...Sfc low over W Upper This afternoon,
with a warm front over N lower and a cold front along the Lake
Michigan shoreline of Wisconsin. The last of the warm front
thunderstorms is making its way out of E Upper near ANJ, at the
moment with showers trailing across the warm sector. Thunderstorms
are beginning to break out along the cold front along the
Wisconsin shoreline. These showers and thunderstorms will move
across Lake Michigan and into portions of NW Lower and cross the
forecast area, between 00z and 03z/Wed. Winds will remain gusty
this afternoon, and then veer NW and remain gusty until about
06z/Wed, when the winds will diminish overnight.
850 mb temperatures will cool overnight to around +5C with 850 mb
moisture, will expect another round of rain showers, as the LE
rain machine gets going for a short period of time.
Primary Forecast Concerns...Severe potential for the rest of the
afternoon and early evening. 18z/Tue upper air release (in support
of Dorian) showing sfc based CAPE around 750J/kg, while the KGRB
is around 2500 J/kg. The main difference is the cloud cover is
still sticking into most of NW/NC lower attm. Latest satellite
images showing clearing line begin to move in from Lake Michigan.
Looking at the more conservative MLCAPE here it is 76J/kg, while
while GRB is 1000J/KG. So the main issue will be if the clouds
continue to move east, while the sunshine destabilize the boundary
layer enough to get anything going. HRRR (18z) is showing that by
21z showers and thunderstorms should make it across the region,
from Wisconsin, and with the LFQ of the500 mb Jet over us, will
have to watch. but thinking that most of the region will have
general thunder as the cloud cover continues to keep the boundary
from destabilizing to its potential.
&&
.SHORT TERM...(Wednesday through Friday)
Issued at 311 PM EDT Tue Sep 3 2019
...Cooler Wednesday; chances for showers Friday...
High Impact Weather...None is expected.
Primary Forecast Concerns...Pops early Wed and Thu night/Fri.
Much cooler and drier air continues to advect in Wednesday. Over
lake instability (the difference between 850 mb and lake
temperatures is in the mid teens) would normally be sufficient for
lake effect but this will be offset by the drier air (850-700 mb
relative humidity falling from about 50 percent at 12z to 25 percent
at 15z). The drier air should win out here squelching any lake
effect rain bands in the morning (slight chance pops through 15z).
High pressure then builds in Wednesday afternoon and holds through
the day Thursday yielding rain free conditions. An upper level
trough and associated surface cold front will then bring chances for
showers Thursday night into Friday.
Temperatures will be several degrees below normal Wednesday before
rebounding to close to normal Thursday and Friday.
.LONG TERM...(Friday night through Tuesday)
Issued at 311 PM EDT Tue Sep 3 2019
...Cool over the weekend then moderating temperatures...
High Impact Weather...None is expected.
West northwest flow aloft is expected to lead to cool but
precipitation free conditions this weekend. Increasing warm air
advection should then lead to moderating temperatures and chances
for showers early next week.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1145 PM EDT Tue Sep 3 2019
Low clouds and MVFR cigs will move into Northern Michigan
overnight into early Wednesday morning behind the cold front.
Scattered showers are also expected overnight into early
Wednesday...but chances are too small to include in the TAF
forecast for now. Winds will remain from the NW at 15 to 25 kts
thru Wednesday.
&&
.MARINE...
Issued at 311 PM EDT Tue Sep 3 2019
tonight through Thursday...Wind will continue to be at gale
force into the evening, as the cold front in Wisconsin crosses
Lake Michigan, and Whitefish Bay. Winds will diminish to 10-15
knots after 06z/Wed. Lake Huron may take a little longer. High
pressure then builds into the region and wind continue to be
variable at less than 10 knots over most of the region.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT through Wednesday afternoon for
MIZ016>018-020-021-024-025-030-031-036-042-099.
LH...SMALL CRAFT ADVISORY until 5 PM EDT Wednesday for LHZ345>349.
LM...BEACH HAZARDS STATEMENT through Wednesday afternoon for LMZ346.
SMALL CRAFT ADVISORY until 5 PM EDT Wednesday for LMZ323-341-342-
344>346.
LS...SMALL CRAFT ADVISORY until 5 PM EDT Wednesday for LSZ321-322.
&&
$$
UPDATE...MR
NEAR TERM...JL
SHORT TERM...AS
LONG TERM...AS
AVIATION...MR
MARINE...JL
Area Forecast Discussion
National Weather Service Cleveland OH
1023 PM EDT Tue Sep 3 2019
.SYNOPSIS...
Low pressure over the upper Midwest will continue east across
the northern Great Lakes today. This low will extend a cold
front across the region on Wednesday. High pressure will build
in behind the cold front on Wednesday night and will remain in
place through Friday.
&&
.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
Update...Wind chills went rogue on zone product with -120 chills
but did correct, sorry. Otherwise radar now showing
thunderstorms developing in southern lower MI, southwest into
central IL. Expect this activity to increase over the next
couple hours as a strong short wave interacts with favorable low
level instability with mixed layer capes around 3000j/kg to our
west. Adjusted pops based at the time mainly ion the HRRR which
did show this development moving east across the area although
after 06Z or so expect activity to thin and weaken. SPC has
indicated a watch is possible for isolated severe threat.
Original...A surface low was located just north of Michigan
with a cold front extending southwest into Illinois. This cold
front is forecast to rapidly move southeast, arriving in
northwest Ohio later this evening. Showers and thunderstorms
will move into the area just ahead of the cold front, now
looking to enter the Toledo area around 9 or 10 pm, moving
southeast through the area around 3 to 5 am. This timing is
slightly slower compared to earlier forecasts, but the short
term high res models are in good agreement so forecast
confidence is pretty high.
Areas generally along and west of I-71 are in a slight risk for
severe weather while areas east are in a marginal risk of severe
weather. Wind and hail are the main concerns, however an
isolated tornado can`t be ruled out especially for northwest
Ohio. Please see spc.noaa.gov for additional information.
Dry weather is expected by around noon tomorrow for the entire
area as surface high pressure begins to build east over Ohio.
Much cooler weather is expected tomorrow across the region as a
result of the cold front expected tonight. Temperatures
tomorrow afternoon are expected to top out generally in upper
60s to low 70s, about 10 to 15 degrees cooler compared to
today. Temperatures tomorrow are expected to be between 5 and 10
degrees cooler than normal values for the beginning of
September.
Little change in the weather pattern through Wednesday night as
surface high pressure remains the dominant weather feature.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
A relatively quiet end of the week expected as high pressure
builds east across the Great Lakes region into New
England/Quebec by Friday. A shortwave and attendant surface low
will dive southeast through the Great Lakes on Friday, with the
mid/upper wave weakening through the Great Lakes and the surface
low weakening and lingering across the central part of the Great
Lakes through Friday night. The models are showing some
inconsistency with the strength and timing of the system, but
most of the area should be dry during this period. A stray
shower is possible downstream of the lake across northeast OH
and northwest PA, but only warrants a slight chance at this
point. Highs in the low 70s Thursday will warm into the mid 70s
Friday.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
A low confidence long term period is forecast with models solution
differences. A cold front will sink south across the Great Lakes
Saturday night into Sunday as a surface low swing around James Bay.
A stray diurnally driven shower cannot be ruled out Saturday across
the snow belt with the lingering trough in the region ahead of the
front. Most of the guidance is suggesting a dry fropa Saturday night
into Sunday. The ECMWF suggest the front stalling out across the
southern part of the area, with a shortwave bringing precip chances
into the area Sunday night through Monday. The rest of the guidance
clears the area of the front and keeps precip chances south and west
of the area. Have opted for slight chance pops Sunday night, with a
dry forecast Monday and beyond. Near normal temps Saturday will cool
behind the front on Sunday, with moderating temps through Tuesday,
when 80s return to the forecast.
&&
.AVIATION /00Z Wednesday THROUGH Sunday/...
Outflow boundaries to our west have initiated convection across
southern MI and northern Indiana this afternoon but so far this
activity has not really taken off. HRRR guidance, which has
missed the initial convection, still develops convection to our
northwest ahead of the approaching cold front within the next
few hours and then drops it ese across the area through the
early overnight. Will keep conditions VFR across the area
through the evening but with convection will drop conditions, at
this point, to MVFR. IFR however will be possible and with
development any update may contain lower conditions. VFR
expected Wednesday.
.OUTLOOK...Non-VFR possible Friday night.
&&
.MARINE...
Southerly winds will increase through this evening across the lake
as a cold front sinks southeast through the central Lakes. A line of
storms is expected to cross the lake this evening just ahead of the
front, with the front pushing across the lake overnight and moving
east of the lake by Wednesday morning. Have left the headlines in
tact, although winds may not ramp up to near small craft criteria
until closer to 00Z. Winds will quickly shift to the west behind the
storms, then increasing out of the southwest for a few hours
overnight before the frontal passage. Winds will become northwest
across the lake by Wednesday morning. Winds will slowly veer
northerly Wedneday night to northeasterly Thursday as high pressure
builds across the Great Lakes. Another weak front will cross the
lake on Saturday.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Beach Hazards Statement from 5 AM EDT Wednesday through
Wednesday morning for OHZ011-012-089.
PA...Beach Hazards Statement from 5 AM EDT Wednesday through
Wednesday morning for PAZ001.
MARINE...Small Craft Advisory until noon EDT Wednesday for LEZ146>149.
Small Craft Advisory until 5 AM EDT Wednesday for LEZ142>145.
&&
$$
SYNOPSIS...Riley
NEAR TERM...TK/Riley
SHORT TERM...Greenawalt
LONG TERM...Greenawalt
AVIATION...TK
MARINE...Greenawalt
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
928 PM EDT Tue Sep 3 2019
.UPDATE...
Attention this evening remains centered on the thunderstorm
potential ahead of 925-850mb cold front that is now pushing onshore
across far western Lower Michigan. 00Z KDTX raob highlighted the
environment well with a midlevel capping inversion at 6.0 kft agl and
very steep 800-600mb lapse rates. Sounding did capture lower quality
boundary layer moisture that corresponds to surface dewpoints that
have struggled to even hit the mid 60s. No surprise then with a
somewhat slower than expected development of shower and thunderstorm
activity given combination of lower boundary layer moisture and high
CIN between 3.0-6.0 kft agl. HREF output places a tongue of ML
instability from SW Lower Michigan to the northeast into sections of
the northwest cwa that is corroborated by this evening`s RAP based
mesosanalysis. The thunderstorm in Clare Co. was on the apex of this
instability axis while the shower/elevated thunderstorm activity from
Lansing eastward through Shiawassee/Genesee counties has been on the
eastern flank. HREF solution shows that peak of instability locally
will last through 02Z before shrinking/withering away with the loss
of daytime heating.
A strongly sheared environment remains in place with 0-3km SRH in
excess of 350 m2/s2 and environmental wind of 50 knots at 2750 ft
agl, see 00Z KDTX raob. Given this shear and steep midlevel lapse
rates the potential still exists for strong to severe thunderstorm
development before midnight. Will likely see convective updrafts
weaken as the activity pushes eastward away from the main instability
axis. This suggests less of a strong thunderstorm potential east and
north of I 75. Low level equivalent potential temperature progs and
HREF output shows strong to severe thunderstorm potential ending
quickly by 4Z.
&&
.PREV DISCUSSION...
Issued at 819 PM EDT Tue Sep 3 2019
AVIATION...
Strong kinematic field and resultant instability advection spreading
south of strong surface low pressure system over western Lake
Superior will bring a period of thunderstorm activity to Southeast
Michigan in the 00-04Z timeframe. Initial thunderstorm activity
developed along the front flank of 900-700mb theta e advection that
will exit the forecast area by the start of the 00Z taf period.
Model soundings show a stout capping inversion for a brief moment
this evening before midlevel dry air punches into the cwa and
steepens lapse rates aloft. The focus for the nearterm will shift to
the potential for strong to possibly severe thunderstorms along the
950-800mb cold front that will impact the area before 04Z.
Orientation of the trough supports similar timing for all the taf
sites. Strong to severe wind gusts with large hail will be possible
with thunderstorm activity this evening. Abrupt windshift to the west
northwest, 290-300, expected around 05-06Z. Wednesday forecast
soundings showing saturation remaining trapped below midlevel
subsidence inversion. Prefer BKN030 cigs Wednesday morning
transitioning to BKN050 for the afternoon. Northwest winds of 10 to
20 knots.
For DTW...Timing for convection this evening remains centered on 01-
04z with strong to severe storms possible. Abrupt windshift to the
northwest at approximately 06Z.
DTW THRESHOLD PROBABILITIES...
* Moderate for cigs aob 5000 ft late this evening, and again
Wednesday morning.
* Moderate for thunderstorms this evening with the most likely
timing around 01-04z.
PREV DISCUSSION...
Issued at 337 PM EDT Tue Sep 3 2019
DISCUSSION...
A high degree of effective bulk shear (60 KTS) will present a severe
threat this evening.
Upper level jet core (90 knots at 250 MB) tracking through northern
Lower Michigan/north half of Lake Huron presenting a window of right
entrance forcing over southeast Michigan around 00z, as a strong
cold front tracks through this evening, with the seasonably strong
low pressure system (aob 1000 MB) tracking into northeastern
Ontario.
Southwest winds gusting 35 mph this afternoon within the boundary
layer gives a glimpse of the strong wind fields. Despite the limited
destabilization over southeast Michigan thus far, seeing surface dew
pts around 70 degrees over southeastern Wisconsin and good
instability (MLcapes 2000+ J/KG), with pocket of steep mid level
lapse rates (8 C/km) noted over northern Illinois. Latest RAP
suggests this instability and steeper lapse rates will advect/work
its way into southern Lower Michigan, with SBCAPES increasing to
between 2000-2500 J/kg over the CWA during the mid evening hours (8-
10 PM). With 0-1 KM bulk shear 30+ knots, cells will have a tendency
to rotate supporting embedded supercells capable of producing large
hail, damaging winds, and even possible tornadoes before the front
clears the State around/shortly after Midnight. Right now, the warm
layer/cap at 750 MB (temp 12-14 C) is the biggest concern of the
forecast going astray (limited activity with the front), but is
expected to cool/erode as the forcing kicks in.
Cold advection overnight through the day tomorrow, as 850 MB temps
lower into the high single numbers (Celsius), holding maxes
predominately in the lower 70s, as there will likely be a stratus
deck trapped underneath the stout subsidence inversion around 850
MB. The inversion height is forecasted to lower Wednesday evening,
which suggests skies will clear out as surface high (1023 MB) builds
over southeast Michigan. Low temperatures in the 40s seems
reasonable with the good radiating conditions expected, outside of
the urban heat island of Detroit where temps hold in lower 50s. It
is possible there may be enough lingering surface moisture to
support some fog, but will see how well we dry out tomorrow before
introducing.
Still under the influence of upper level northwest confluence flow
on Thursday, leading to dry and seasonably cool conditions.
Passage of an upper-level trough and embedded PV anomaly in
conjunction with slightly favorable jet streak dynamics, as the nose
of a weak upper-level jet pushes across SE MI from the Midwest, will
bring the chance for rain showers across the region Friday morning
and afternoon. As a result, have increased rain chances slightly
during this time frame to account for the more favorable dynamics.
Otherwise, upper-level flow to turn more zonal as surface high
pressure expands from the Midwest into the Ohio Valley to finish off
the week. This will bring dry weather and relatively little change
to day-to-day highs and lows Friday and Saturday, where slightly
below normal values with hold -- Highs in the 70s and lows in the
50s. The passage of a weak cold front will then move through on
Sunday, reducing temperatures slightly down into the 60s to lower
70s for a high and possibly even down into the 40s for a low
temperature leading into Monday. This frontal boundary that is
pushing south is set to settle across the Ohio Valley which will set
up a a nice baroclinic zone, which may be the focal point for
ongoing precipitation due to overruning along the front. At this
time, rain and thunderstorm chances are expected to take place just
south of the Michigan border, however, any slightly deviation from
the projected model runs to the north could bring much higher (and
extended period) precipitation chances to southern Michigan.
Surface low and a weakening upper-level shortwave is projected to
travel east across the northern Plains Monday into Tuesday and in
turn will lift the stalled frontal boundary north across SE MI. This
will be the next chance for a potential warm up in addition to rain
and thunderstorm chances.
MARINE...
Seasonably strong low pressure is moving eastward across Lake
Superior with a tightened pressure gradient set up across the
central Great Lakes. Strong south and southwest winds will continue
through this afternoon, weakening slightly this evening before the
associated strong cold front approaches. Northwest winds then
strengthen tonight after frontal passage with northwest gales
expected late tonight through Wednesday morning over central and
northern Lake Huron, where a Gale Warning remains in effect. Small
Craft Advisories also continue tonight into Wednesday morning for
the nearshore zones as winds in excess of 25 kt and increased wave
action create hazardous marine conditions. Tonight`s front will also
bring numerous showers and storms, some of which may be strong to
severe. Storms will move out by early Wednesday morning. Winds begin
to weaken late in the morning as high pressure moves into the
western Great Lakes. Improved marine conditions will persist into
the late week as this high moves overhead.
HYDROLOGY...
Numerous showers and thunderstorms are expected this evening and
tonight ahead of and along a strong cold front. Storms are expected
to be progressive and move west to east at about 45 mph and thus
will likely not linger over one area, but precipitable water values
reaching and possibly exceeding 1.50 inches will result in
relatively brief but heavy downpours. Rainfall totals of a quarter
to three quarters of an inch will be possible before the front
clears the area by around 2am. As is usually the case with
thunderstorms, total precipitation amounts will likely show a high
variability across the area. The potential for flooding will be
equally variable and limited to ponding of water on roads and in
poor drainage areas.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Lakeshore Flood Warning until 4 AM EDT Wednesday for MIZ063-070.
Lake Huron...Small Craft Advisory until 4 PM EDT Wednesday for LHZ441>443.
Gale Warning until 11 AM EDT Wednesday for LHZ361>363.
Small Craft Advisory until 10 AM EDT Wednesday for LHZ421-422.
Lake St Clair...Small Craft Advisory until 4 AM EDT Wednesday for LCZ460.
Michigan waters of Lake Erie...Small Craft Advisory until 4 AM EDT
Wednesday for LEZ444.
&&
$$
UPDATE.......CB
AVIATION.....CB
DISCUSSION...SF/AM
MARINE.......TF
HYDROLOGY....TF
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Rapids MI
1022 PM EDT Tue Sep 3 2019
LATEST UPDATE...
Mesoscale Discussion
.MESOSCALE DISCUSSION...
Issued at 1024 PM EDT Tue Sep 3 2019
The thunderstorms are now becoming more active as a shortwave
rotates in on the upper level trough. The axis of MU cape is over
Southwest Michigan from near Grand Rapids to South Haven at 10
pm. There is around 3000 j/kg of MU cape south of I-94 and around
2500 j/kg of MU cape over the I-94 area. The axis of the low
level jet (LLJ) was from near South Bend to Detroit with the core
of the LLJ near Detriot. There is around 50 knots of effective
bulk shear near the front front where the storms currently are.
The early inversion seen on AMDAR sounding as gone now so
convection is now surface based ahead of the front. We expect the
storms to continue to develop and move east. It may take till
midnight now for the storms to clear our CWA. So, the area near
I-94 is still at risk for severe storms till midnight.
&&
.SYNOPSIS...
Issued at 308 PM EDT Tue Sep 3 2019
- Slight risk for severe thunderstorms this evening
- Cooler for Wednesday
- Some showers possible for Thursday Night into Friday
&&
.UPDATE...
Issued at 754 PM EDT Tue Sep 3 2019
We are watching for development on the cold front and it is
looking less and likely for severe storms. Actually it is becoming
questionable that there will be much in the way of thunderstorms.
I still think given the MU cape, and elevated mixed layer with a
shortwave moving through with the cold front it is still possible
a line of storms my form south or near I-94. No matter what this
should all be done by 10 pm.
&&
.DISCUSSION...(This evening through next Tuesday)
Issued at 308 PM EDT Tue Sep 3 2019
The atmosphere continues to gradually destabilize through mid
afternoon with a southwesterly flow advecting in considerable
moisture. The clouds have delayed/slowed the heating somewhat. At
the same time deep layer and low level shear were impressive. How
much if any severe weather we see will likely be determined by
the amount of destabilization from now until the cold front pushes
through this evening. Based on satellite imagery there will be a
window of an hour or two when decent destabilization could occur
just ahead of the cold frontal passage. HRRR does forecast surface
based CAPE values up over 2000 j/kg ahead of the frontal passage.
Even if we end up short of these values...given the strong shear
in place and lift with the wave moving in...a risk for severe
weather exists. Damaging winds...large hail and a risk for
tornadoes are possible.
By 10 pm the main area of instability should shift southeast of
the area. This is when I drop off the thunderstorm potential. A
much cooler airmass moves in overnight and into Wednesday. A few
showers could clip northern parts of the CWA late tonight.
A weakening wave of low pressure arrives for Thursday night into
Friday. We will only feature a low chance for a few showers given
the weakening trend noted in the models.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 754 PM EDT Tue Sep 3 2019
The threat for severe storms has decreased but it is still
possible between now and say 02z that there could be a storm.
Whether or not that happens, there is an area of MVFR cigs near
the front. That will be cleared out by the front so by 04z or so
all TAF sites are VFR. There is a secondary surge of cold air that
will have an area of MVFR cigs with it and that moves through in
in the 12z to 16z time frame. After that enough cool dry air moves
in to once again clear the skies.
Winds will not be as strong behind the cold front as it was ahead
of the cold front, for the most part winds will in the 5 to 15
knot range Wednesday during the day.
&&
.MARINE...
Issued at 844 PM EDT Tue Sep 3 2019
I have downgraded our Gale Warning to a Small Craft Advisory since
we have not had gales since prior to noon. We have winds of 15 to
25 knots into mid morning Wednesday and with the cold air coming
in it makes sense to continue the Small Craft Advisory till late
afternoon. I through it good to keep the beach hazard and flood
advisory for the same time period.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Lakeshore Flood Warning until 4 PM EDT Wednesday for MIZ037-043-
050-056-064-071.
Beach Hazards Statement through Wednesday afternoon for MIZ037-
043-050-056-064-071.
LM...Small Craft Advisory until 4 PM EDT Wednesday for LMZ844>849.
&&
$$
MESOSCALE...WDM
UPDATE...WDM
SYNOPSIS...MJS
DISCUSSION...MJS
AVIATION...WDM
MARINE...WDM
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1009 PM CDT Tue Sep 3 2019
.DISCUSSION...
Tropical Storm Fernand continues to move west toward the Mexican
coast and it`s impacts on SE TX will be minimal and confined to
mainly the marine zones. Radar is quiet at the moment but am
expecting some showers to redevelop around 09z over the Gulf
waters and move toward the coast prior to sunrise. The 02z HRRR is
showing some of the showers clipping the coast and bumped PoPs up
a bit along the immediate coast. made a few minor tweaks to MinT
grids and it`s going to be a warm night across the region with low
temps near 80 in Houston and mid 70`s inland. A 594 dm upper level
high will build into Texas and high temps Wed/Thu/Fri look to be
very hot. The calendar might say September but the thermometer is
stuck in August.
Water levels are near 3.0 feet at high tide but should begin to
fall overnight. Water levels should reach similar values on
Wednesday night. No coastal flooding is expected. A SCEC was
issued earlier this evening for all of the Gulf waters and
Matagorda Bay as east winds increase. 43
&&
.PREV DISCUSSION... /ISSUED 635 PM CDT Tue Sep 3 2019/
AVIATION [00Z TAF Issuance]...
No major changes in this TAF package, with VFR ceilings expected
to prevail through the TAF period. Some light showers will be
possible along the coast, potentially impacting LBX and GLS in the
morning hours. Mostly a wind forecast, with winds light and out
of the east overnight, increasing to between 7 to 12 knots by mid
morning and turning more out of the southeast. Winds could become
gusty once again tomorrow afternoon as we have seen today.
Otherwise, expect a scattered deck overhead once again around
6000 feet tomorrow afternoon.
Hathaway
PREV DISCUSSION /Issued 323 PM CDT Tue Sep 3 2019/...
SHORT TERM [Tonight through Wednesday]...
Convection around TS Fernand has become more robust this
afternoon with at least one flare up of deep convection around the
circulation. Fernand is not far from the Mexican coast and will
likely make landfall tomorrow. This means impacts from Fernand for
SE Texas will be minimal. The main concerns will be a far outer
rainbands that happens to brush along the coast causing brief
heavy rain along with gusty easterly winds, building seas, tide
levels about 1 foot above normal and rip currents. Otherwise upper
level ridging over the central Rockies and central Plains will
provide enough subsidence to keep deep convection from forming
inland. Precipitable water values are running above 2 inches just
along the coast so this area may be the lone exception for deep
convection for this afternoon through tomorrow.
The other concern will be the hot conditions expected tomorrow.
Today temperatures have reached the upper 90s in several locations
but temperatures at or just above 100F will be more common tomorrow.
There should be enough winds to mix the boundary layer so dewpoints
should decrease in the afternoon holding heat index values in the
low 100s as well.
Overpeck
LONG TERM [Wednesday Night through Tuesday]...
Based on the current track of Fernand, its effects over SE TX (which
are expected to be mainly along the coast/coastal waters) will be de-
creasing further by this time frame. Hot/dry weather to prevail over
much of the CWFA as the strong upper ridge lingers over the Southern
Plains. While high temperatures are progged to be in the 98F to 102F
range, drier air moving into the region (from the NE/E) will help to
mix dewpoints out during the afternoons. This should keep heat index
values just under advisory criteria(108F) for the latter half of the
week.
Some relief is possible by the end of the weekend/early next week as
the upper ridge weakens in response to a series of strong trofs move
in from the west coast across into the Northern Plains. This will be
helping to re-open the Gulf to us as E/SE winds return to the area.
Have kept with the mention of low POPs for next Mon/Tues. 41
MARINE...
No major changes for the short-term with the development of Tropical
Storm Fernand in the western Gulf. We will continue to see the outer
bands associated with this system move into our coastal waters along
with moderate to strong east winds and 3 to 6 foot swells. Did main-
tain the SCEC for the offshore waters through tomorrow evening based
on its current track into the eastern coast of Mexico. After this...
seas will be slowly decreasing as winds shift briefly to the N/NE. A
weak surface high building over the area will keep winds very light/
variable late Thurs through Sat. Onshore winds are set to return Sun
night/early Mon. 41
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 75 100 74 102 75 / 0 0 0 0 0
Houston (IAH) 78 99 77 101 78 / 0 0 0 0 0
Galveston (GLS) 84 93 81 95 81 / 20 20 10 10 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk through Wednesday morning for the
following zones: Brazoria Islands...Galveston Island and
Bolivar Peninsula...Matagorda Islands.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION through Wednesday morning
for the following zones: Coastal waters from Freeport to
Matagorda Ship Channel TX out 20 NM...Coastal waters from
High Island to Freeport TX out 20 NM...Matagorda Bay.
SMALL CRAFT SHOULD EXERCISE CAUTION through Wednesday evening
for the following zones: Waters from Freeport to Matagorda
Ship Channel TX from 20 to 60 NM...Waters from High Island
to Freeport TX from 20 to 60 NM.
&&
$$
Discussion...43
Area Forecast Discussion
National Weather Service Lincoln IL
809 PM CDT Tue Sep 3 2019
.SYNOPSIS...
Issued at 253 PM CDT Tue Sep 3 2019
A cold front will move across central and southeast Illinois
tonight. Ahead of the front, there is a chance for strong to
storms north of I-70. High pressure will push into the region in
the wake of the front bringing dry and cooler weather for the next
few days.
&&
.UPDATE...
Issued at 808 PM CDT Tue Sep 3 2019
Radar imagery showed the cold front pushing across the
northwestern CWA, generally from near Macomb to northwest of
Pontiac. Storms, or even clouds, have been struggling to get going
over the last few hours, despite CAPE`s above 3500 J/kg. However,
a few showers have recently starting developing along the boundary
from northeast of Peoria to Chicago. Latest HRRR is starting to
back off a bit from its earlier aggressive stance a couple hours
ago, but increases and pushes the showers/storms across mainly the
northeast half of the CWA through midnight. Latest SPC Day1 backed
off on the slight risk in our area, but kept a marginal risk in
an area from Peoria to Lincoln to Danville. Have worked on
refining the PoP trends, and have recently sent out a grid update
for it. Updated zones will follow shortly.
&&
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 251 PM CDT Tue Sep 3 2019
Sounding from 18z indicates cap still in place with -60 J/kg.
Abundant cloud cover north of I-72 is inhibiting heating. With 700
temp of 12C, it will likely take approach of a cold front
currently from SW WI to SE IA to provide sufficient convergence
to initiate significant convection. Effective bulk shear is 30-40
kts across the northern portions of the forecast area early this
afternoon, which should be sufficient for rotating storms if the
cap can be broken before the boundary layer decouples later this
evening. The best chances for severe weather would be in our
northeast forecast area which has received more insolation and is
concurrent with the elevated shear. This area likely also has a
antecedent boundary from this morning`s MCS. Over the remainder
of the area the window should be small both spatially and
temporally for any strong convection.
Any isolated remnant convection should be out of the area by
sunrise. Temperatures following the frontal passage on Wednesday
should be about 10 degrees cooler with much lower humidity.
&&
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 251 PM CDT Tue Sep 3 2019
Northwest flow will dominate the Midwest through the end of the
week as ridging develops over the Rockies/High Plains. A
reinforcing cold front is expected to move through the region
Friday, but with mostly north flow over the SE US, moisture should
be limited prior to the front. At this time, will be keeping
Friday dry.
Following the Friday front, models diverge significantly in the
evolution of the ridge to our west and the upstream trof over the
Great Basin. Will stick with a model blend for the weekend until
we have a better idea on which way the pattern will change.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 610 PM CDT Tue Sep 3 2019
VFR conditions expected the next 24 hours. Main concern will be
with any thunderstorms that manage to fire this evening.
Atmosphere has been struggling with getting anything going ahead
of the cold front, though latest RAP/HRRR models do show some
activity in the 02-04Z time frame. Don`t have confidence to go any
higher than a VC mention at this point. Any convective activity
should be past the TAF sites by 06Z. Winds will swing around to
the northwest between 02-06Z as the front drops through the area.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Geelhart
SHORT TERM...Barker
LONG TERM...Barker
AVIATION...Geelhart
Area Forecast Discussion
National Weather Service Indianapolis IN
1151 PM EDT Tue Sep 3 2019
.UPDATE...
The AVIATION section has been updated below.
&&
.SYNOPSIS...
Issued at 137 PM EDT Tue Sep 3 2019
A quick moving cold front will sweep across Indiana this evening
and Overnight. This may result in isolated to scattered showers
and thunderstorms to Central Indiana overnight.
High pressure is then expected to build across Indiana for the
middle of the week...bringing dry weather and slightly below
normal temperatures for the rest of the work week.
Rain chances...albeit small...will return this weekend with
continued cool temperatures.
&&
.NEAR TERM /Tonight/...
Issued at 915 PM EDT Tue Sep 3 2019
Slowed down timing of PoPs a couple hours based on trends and
updated the Weather Story and Hazardous Weather Outlook due to the
Storm Prediction Center pulling the Slight Risk out of our area and
taking the Marginal Risk near and north of Muncie and
Crawfordsville.
Previous discussion follows...
Issued at 137 PM EDT Tue Sep 3 2019
Surface Analysis early this afternoon shows SW flow in place
across Indiana between High pressure over SE OH and an approaching
cold front across Wisconsin and Iowa. Radar shows a convective
cluster within the SW flow aloft over NW Indiana.
HRRR advects the convective cluster slightly southeast and
gradually results in dissipation within the next few hours. Still
some minimal chances for showers this afternoon across the north
forecast area appear prudent at this juncture.
The GFS and NAM bring a weak short wave aloft along with the
surface cold front across Indiana late tonight. Timing for daytime
heating appears unfavorable...with a late overnight passage. HRRR
suggests light scattered precip overnight with the frontal
passage. Moisture with this system continues to be a problem. Time
heights and forecast soundings never really show deep moisture
available. Deep gulf moisture remains cut off by high pressure in
place over Tennessee and the deep south. However some lift
remains as the front passes and dew point temps are in the 60s.
Thus will keep some low chance pops for very light rain amounts
overnight. Given the rain and expected change in air mass will
trend lows close to the NBM.
&&
.SHORT TERM /Wednesday through Friday/...
Issued at 137 PM EDT Tue Sep 3 2019
The GFS and NAM keep and similar and stable weather pattern in
place on Wednesday through Friday. Strong ridging is indicated
aloft over the Western United States...resulting om NW flow from
the northern plains into the Ohio Valley. This lee side flow also
result in subsidence and drying across the region. the result at
the surface is a rather large area of high pressure in place
across the upper midwest...great lakes and Ohio Valley. Generally
northerly flow will be in place through at least Thursday
night...allowing cooler Canadian air to spill across Indiana. This
will also continue to prevent any gulf moisture from arriving in
Central Indiana. Finally through Thursday night...forecast
soundings show a dry column with unreachable convective
temperatures through Friday. Thus will trend toward mostly sunny
days and mostly clear nights through Thursday night. Will
generally stick close to the NBM on temps.
Forecast soundings are hinting at some lower level moisture
arriving on Friday with a passing area of surface low pressure
within the NW flow. Again moisture remains a problem here as the
NW flow aloft remains prevalent. Thus confidence for pops on
Friday is low and will try to trend toward a dry forecast.
&&
.LONG TERM (Friday Night Through Tuesday)...
Issued at 205 PM EDT Tue Sep 3 2019
Models are close enough that the National Blend of Models
initialization was accepted for most items.
Much of the long term will be quiet. A cold front will move through
Friday night but have no moisture to work with, so went dry. High
pressure will keep Saturday dry, but as alluded to yesterday, an
upper disturbance will now bring chances for rain around Sunday.
Have some low PoPs in around then.
A warm front will be in the area on Monday and Tuesday, but heights
will be rising during that period. Thus, without upper support, kept
those days dry for now.
Below normal temperatures at the start of the long term period will
give way to above normal readings by the end of the period.
&&
.AVIATION (Discussion for the 040600Z TAF Issuance)...
Issued at 1151 PM EDT Tue Sep 3 2019
Good confidence any convection and brief MVFR or worse conditions in
thunderstorms will be south of the terminals after 07z-08z. Then,
should see VFR conditions the remainder of the TAF period per the
SREF and GFS LAMP.
Winds will start off northwest at LAF and southwest elsewhere to
near 10 knots and then shift to northwest and north in the wake of
the cold front after 07z-08z.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...Puma
NEAR TERM...Puma/MK
SHORT TERM...Puma
LONG TERM...50
AVIATION...MK
Area Forecast Discussion
National Weather Service Key West FL
1025 PM EDT Tue Sep 3 2019
.DISCUSSION...In the middle and upper levels(700-200 MB), latest
available satellite imagery overlaid with model streamline
analysis as of 900 pm, depict the axis of a middle and upper
trough extending from Lake Superior down to the Tennessee Valley.
South of that, a northwest to southeast oriented ridge is centered
over the Western Gulf near 28N 94W, with the eastern flank of the
ridge poking SE into the Florida Straits and Central and Western
Cuba attm. Well east of that feature the western flank of a ridge
centered over the Central Tropical Atlantic pokes northwest to
just east of the Carolina Outer banks. In betwixt these large
scale features sits Hurricane Dorian, located as of 800 pm, at
28.1 N, 78.8 W, or about 110 miles east of Cape Canaveral, moving
NW at 6 mph.
At the surface and in the lower to middle levels(Surface to 700
mb), latest available land and marine surface observations and
analysis as of 900 pm, detail Tropical Storm Fernand over the far
Southwest Gulf of Mexico, and of course aforementioned Hurricane
Dorian. The Florida Keys remain in the far southwest circulation
of departing Hurricane Dorian.
&&
.CURRENTLY...As of 900 pm, skies are partly to mostly cloudy
across the islands and surrounding waters. Radar detects isolated
showers with an occasional thunderstorms that are confined to
banding features that are moving across the Florida Straits attm.
Maybe some sprinkles would be impacting a few of the islands at
best attm. Temperatures across the Keys are in the middle to upper
80s with dewpoints in the middle to upper 70s. C-man stations
along the Florida Reef are strongest over the Upper Keys with
Alligator Reef and Carysfort Reef with near near 20 knot west
southwest to west winds with higher gusts. Traveling down the
Reef, winds are 15 to 20 or near 20 knots at Sombrero Key, and
near 15 knots off the Lower Keys and 10 to 15 knots out at the Dry
Tortugas. As a result, the 00Z evening sounding illustrated a
quite moist with columnar PWAT at 2.27 inches and moderate to west
west to northwest flow off the surface to 500 mb, indicative of
confluent lower to middle level flow typical of the outermost
circulation of a category 2 Hurricane well to the northeast of the
Florida Keys.
.SHORT TERM...Overnight and Wednesday, Hurricane Dorian will
continue to pull away from the Keys, reaching approx 100 miles
east of the GA/FL line by 800 pm Wed. The Keys will remain in the
circulation of this storm, however, much drier air may already
mixing down from above 500 mb this evening. Local/Caribbean HRRR
is still indicating slightly more robust banding features could
impact the Keys with heavier showers (within redeveloping
rainbands again after 0600Z). However, overall coverage has been
isolated to widely scattered at best this evening. Hence, have
already lowered rain chances down to 40%, middle of the road, for
the overnight period for the islands.
Better low level confluence may be available Wednesday morning
thru Wednesday afternoon, as ridging south of Cuba begins to pull
northwards across the Straits. As for local breezes tonight, they
will continue to vary greatly across the region, with the highest
winds in the upper Keys, and the lowest across the Lower Keys and
out at the Dry Tortugas, which are more distant from the gradient
of Hurricane Dorian.
&&
.MARINE...A Small Craft Advisory remains in effect for the
eastern coastal waters of the Florida Keys due to southwest to
west winds 20 to 25 knots.
Hurricane Dorian will continue to the northwest and track east
of, and parallel to the Florida east coast overnight. Moderate to
fresh, southwest to west breezes are expected across the coastal
waters of the Florida Keys overnight and Wednesday. Confused seas
can be expected off the Upper Keys due to locally driven wind
waves and long period swells emanating southward from Dorian.
Winds and seas will begin to subside Wednesday night and Thursday
&&
.AVIATION...VFR conditions will prevail at both the Key West and
Marathon terminals overnight and through tomorrow morning. There
is a possibility of isolated quickly moving showers passing over
either terminal, and this will be reflected by the inclusion of
vicinity showers in the terminal forecast. If showers do cross the
terminals, they should bring only very brief MVFR conditions. Any
showers that do develop will be moving towards the east at 15 to
20 knots. Surface winds will be out of the west near 10 knots,
with occasional gusts near 15 knots.
&&
.COASTAL FLOODING...
High tides are expected to run about a half foot to a foot above
the predicted tides, including the Lower, Middle, and Upper
Florida Keys. The total water level at high tide will result in
minor saltwater flooding in the Florida Keys. Saltwater flooding
of low elevation streets and lots is likely. Some storm drains
will overflow and some seawalls and docks will be overtopped.
Motorists should remember, persistent puddles around the times of
high tide is almost certain to be saltwater. Reports from the
Bayside communities of the Upper Keys indicate some of the low-
lying neighborhoods have about a foot of water over the streets.
These conditions likely will persist through Wednesday night.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...Small Craft Advisory until 6 AM EDT Wednesday for GMZ042-043-052-
053-072-073.
&&
$$
Public/Marine...Futterman
Aviation/Nowcasts....Devanas
Upper Air/Data Collection/Social Media......DR/KL/Devanas
Visit us on the web at weather.gov/key
Follow us on Facebook and Twitter at:
www.facebook.com/nwskeywest
www.twitter.com/nwskeywest
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
620 PM CDT Tue Sep 3 2019
.MESOSCALE DISCUSSION...
500 PM CDT
Convective evolution continues to be monitored, with capping
from the morning convection and lingering clouds severely
impeding any mature development thus far. This will likely prevent
any rapid development and may very well keep any development that
can occur isolated, such as has been the case. A conditional
severe risk does exist though if any sustained mode can develop.
Convection in the southeast CWA over the past hour to hour and a
half will have moved mainly east of the area by 530 pm. This
activity is along an old outflow boundary and pseudo warm
front advancing higher theta-e air into the area. While this
convection has fair potential to be supercellular, it has
struggled to be mature and sustaining thus far, likely owing to
the cap.
Further northwest along the cold front -- our now best chance for
storms -- convection has been isolated in southern Wisconsin with
agitated cumulus struggling along the boundary. Aircraft
soundings from across northern Illinois and even into Wisconsin
show capping around 850 mb, that had weakened little since ILX`s
18Z sounding. In Wisconsin there are more noteworthy height falls
and associated cooling with the ascent that looks to only just
graze far northern Illinois. This is why we think development is
likely only to be isolated at least for the next few hours.
Observational trends indicate the front is slower than forecast
trends, and so did slow the forecast timing of chances slightly,
along with lower them some. The nature of development should
continue to be discrete given the orthogonal flow and shear with
respect to the front. Given the values of deep layer shear (50+
kt) and CAPE, including in the low-levels thanks to the high
moisture ahead of the front, supercellular mode is still favored
and a conditional severe threat if sustained enough. If convection
can grow more scattered into early evening as the front works
into eastern Illinois and northwest Indiana, it`s possible some
segments/clustering may develop and have a little more potential
for wind.
MTF
&&
.SHORT TERM...
300 PM CDT
Wednesday...
Primary concern for Wednesday will focus on winds.
As high pressure continues to slide into the Upper Missouri Valley
and the deep low and associated cold front continue to push to the
east, an area of moderate pressure rises and deep layer cold
advection will continue the strengthening north winds. the gradient
should be strongest over Lake Michigan and a little weaker over
land. So, while winds over land should remain in the 5-10 mph
range, winds over the lake should be in the 15 to 20 mph range, with
an occasional higher gust. Winds along the Lake County IL shore
should be mainly along shore while winds approaching the Cook County
and Lake/Porter Counties should be more directly on shore,
generating higher waves and a greater rip current threat. So, have
issued a Beach Hazard Statement for Cook County IL and Lake County
IN for the late morning through early evening hours and a bit longer
for Porter County IN, from early morning through early evening.
Otherwise, conditions Wednesday will be dry with below normal
temperatures. Lows in the morning should be in the middle to upper
50s, and low 60s for the Chicago area urban heat island. Highs
will, generally, be in the lower 70s, except along the lake where
temperatures should only reach the middle to upper 60s.
&&
.LONG TERM...
203 PM CDT
Wednesday Night through Tuesday...
Main weather concerns this period include a chance of showers and
storms with a cold front late Thursday and/or early Friday...
followed by a possible additional period of high swim risk at Lake
Michigan beaches Friday in the northeast flow behind the front.
Then possibly an unsettled pattern with periodic thunderstorm
chances Saturday night through Tuesday.
Sprawling high pressure moves overhead Wednesday night bringing
light winds and mainly clear skies along with very September like
temperatures with overnight lows in the upper 40s to lower 50s for
locations outside of the Chicago metro. Thursday sees a return to a
milder southerly flow but only marginally increased moisture ahead
of a cold front expected to move across the area late Thursday or
early Friday. Rain/storm chances are better north coincident with
stronger upper level forcing... with central and southern sections
of the CWFA quite possibly staying dry.
Northeast surface flow on the back side of this cold front may set
up yet another period of waves sufficient to produce a high swim
risk at Lake Michigan beaches before high pressure riding moves over
the area Friday night into Saturday.
Models then continue to diverge in solutions for Saturday night
through Tuesday with the GFS bringing a stronger area of surface
high pressure southeast out of the Canadian prairies and into the
northern Great Lakes Sunday into Monday. Meanwhile the Canadian
takes a more northward track of this high... and the ECMWF even more
so. Both hence shift the ribbon of shortwave energy in the
northwest flow aloft farther north... to include northern IL and
northwest IN. This would place the area under periodic chances of
thunderstorms Saturday night through Monday... until most of the
area comes under the warm sector with low pressure tracking along
the U.S.-Canadian border into the northern Great Lakes by late
Tuesday. Will continue to carry low pops in the forecast pending
further inter-model consistency.
Ed F
&&
.AVIATION...
For the 00Z TAFs...
The primary aviation weather concerns through the period revolve
mainly around a brief window of TS potential with a cold front
followed by breezy northwesterly winds. A cold front is about to
pass through RFD and will be through ORD and MDW around 0130 and
0200 respectively. Recent AMDAR soundings out of ORD and MDW
indicate capping remains in place with a plume of warm air in the
850-700 mb layer. Thus far, convection near the state line has
struggled to maintain itself in this very strongly sheared and
capped environment. However, the Cu field remains agitated
entering our CWA, and RAP forecast soundings reveal a rather quick
lifting/cooling of the aforementioned warm nose shortly after 00z
as the front makes its approaches to the Chicago-area terminals.
As a result, convective initiation remains possible, although
still conditional on erosion of the remaining warm layer just off
the surface. It may be that storms begin to initiate more
cohesively as the front begins to pass the Chicago area terminals
as better height falls overspread the region through the mid-
evening hours. As a result, will be maintaining a VCTS mention at
ORD, MDW, and DPA up through FROPA, and will continue a TEMPO for
TSRA at GYY. Any TS potential should be relatively short-lived,
however, as much drier air will invade the region quickly behind
the front. Northwesterly breezes will gradually abate through the
night, with winds trending to light northerly on Wednesday. A
modest push off the lake will turn the winds more northeasterly at
ORD and MDW through the afternoon.
Carlaw
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement...ILZ014...11 AM Wednesday to 7 PM
Wednesday.
IN...Beach Hazards Statement...INZ001...11 AM Wednesday to 7 PM
Wednesday.
Beach Hazards Statement...INZ002...7 AM Wednesday to 7 PM
Wednesday.
LM...Small Craft Advisory...nearshore waters
until 10 PM Wednesday.
&&
$$
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Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
946 PM CDT Tue Sep 3 2019
.UPDATE...
Issued at 936 PM CDT Tue Sep 3 2019
The cold front was located near a Chicago to Quincy to Kansas City
line at 02z. Warm air aloft was resulting in signficant capping
and the only convection was located just ahead of the front across
NE IL where CIN was much less. The cold front will continue to
move southward through the remainder of the CWA tonight. The
chances of surface-based storms appears pretty remote given the
current CIN and forecast CIN. I can`t completely rule out the
possibility of an isolated and short-lived elevated shower or
storm forming associated with increasing clouds/moisture in the
850-700 layer spanning the frontal zone, but even that chance
seems rather low at this point.
Glass
&&
.SHORT TERM... (Through Late Wednesday Night)
Issued at 335 PM CDT Tue Sep 3 2019
Latest surface analysis indicates that the front extends from
eastern Iowa into far northwest Missouri. Satellite trends
continue to show extensive mid clouds along the front, but a
limited cumulus along the front with the only thunderstorms over
northeast Illinois and Indiana. Convective development farther
westward as been hindered by stout cap shown well by the RAP
soundings today, and this trend is expected to continue into this
evening. CAMS have kept shower/thunderstorm development over
Illinois tonight, so will do the same. Have only isolated showers
and thunderstorms over west/south central Illinois during the
evening hours. If updrafts are stout enough to develop and remain
upright, then there will be sufficient CAPE/shear parameters for a
few severe storms, particularly over Illinois. These storms will
be capable of producing large hail and damaging winds. The cold
front will push south of the CWA late tonight.
Then dry weather is expected Wednesday and Wednesday night as a
surface ridge moves in from the upper Midwest and the atmosphere
becomes dry through a deep layer. Highs on Wednesday will be
cooler behind front with cold air advection.
Britt
.LONG TERM... (Thursday through Next Tuesday)
Issued at 335 PM CDT Tue Sep 3 2019
Expect mainly dry weather from Thursday into Saturday as a large
surface high moves across Missouri and Illinois under generally
dry northwesterly upper flow aloft. This will change by Saturday
night into early next week as the deterministic global models and
GEFS mean show a pair of shortwave troughs dropping southward out
of the Northern Plains. These troughs will combine with a stalled
front over southern Missouri and Illinois to bring a chance a
showers and thunderstorms late in the period.
Temperatures will be close to normal on Thursday, but will then warm
up above normal on Friday ahead of a cold front with 850mb
temperatures close to 20C. Temperatures behind the front will
likely be at or below normal behind the cold front with a chance
rain, but the spread on the GEFS ensemble temperatures is showing
an increasing spread which lowers the confidence in the overall
forecast in early next week. Overall trend in guidance is showing
temperatures going back above normal by next Tuesday.
Britt
&&
.AVIATION... (For the 00z TAFs through 00z Wednesday Evening)
Issued at 659 PM CDT Tue Sep 3 2019
A cold front currently stretches from northwest IL across
southeast IA into northwest MO early this evening. This front will
move southward tonight and will be accompanied by a increasing
swath of VFR clouds with bases from 4,000 to 5,000 feet.
Precipitation chances with the front look iffy and if a shower or
thunderstorm does develop this evening, then the coverage should
be rather isolated. The TAFs reflect the wind shift with the cold
front and clouds, and are void of any precipitation given the
aforementioned low probability.
SPECIFICS FOR KSTL:
A cold front currently stretches from northwest IL across
southeast IA into northwest MO early this evening. This front will
move southward tonight and should move through the terminal around
05-06z. The front will be accompanied by VFR clouds with bases
from 4,000 to 5,000 feet. Precipitation chances with the front
look iffy and if a shower or thunderstorm does develop this
evening, then the coverage should be rather isolated. The TAF
reflects the wind shift with the cold front and clouds, and are
void of any precipitation given the aforementioned low probability.
Glass
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service San Francisco Bay Area
855 PM PDT Tue Sep 3 2019
.SYNOPSIS...Monsoonal moisture arriving from the south late
tonight and Wednesday will result in a slight chance of
thunderstorms on Wednesday and Wednesday evening, mainly across
northern portions of our forecast area. Temperatures are not
expected to change much through Wednesday, meaning warm conditions
will persist inland. A gradual inland cooling trend is then
forecast from Thursday on through the weekend as the marine layer
slowly deepens and onshore flow increases.
&&
.DISCUSSION...As of 8:55 PM PDT Tuesday...Primary forecast
concern in the short term continues to be the possibility of
showers and/or thunderstorms tomorrow and tomorrow evening,
especially the potential for dry lightning. Monsoon moisture
continued to flow across southern California today, resulting in
widespread thunderstorms across southern California as well as the
southern Sierra Nevada. Both the NAM and GFS continue to forecast
scattered light precipitation in the SF Bay Area tomorrow and
tomorrow evening (mostly across the North Bay) as an approaching
upper trough interacts with the plume of monsoon moisture flowing
in from our south. Forecast soundings indicate that most of the
moisture will be above 10K feet, with dry air below. Thus, any
thunderstorms that may develop could produce dry lightning as much
of the rainfall will likely evaporate before reaching the ground.
Shower/thunderstorm potential will end by Wednesday night as the
flow aloft takes on a more westerly component, bringing in a drier
airmass. It should be noted that neither the HRRR or ECMWF
forecast precipitation on Wednesday. Thus, slight chances for
showers and thunderstorms seems sufficient.
The Fort Ord profiler shows that the marine layer remains shallow
this evening with a depth of only about 1000 feet. The profiler
also indicates recent warming of the airmass above the marine
layer. Model guidance indicates little change in temperatures
through Wednesday, which seems reasonable given current
conditions. Cooling is then likely on Thursday, especially inland,
as the upper trough finally reaches the coast, enhancing onshore
flow and bringing with it a slightly cooler airmass.
Little change is forecast for Friday, but then additional cooling
is expected over the weekend as a second upper trough sweeps
across California. Inland temperatures over the weekend are
forecast to be 7 to 15 degrees cooler than they were today.
The trough forecast for the weekend looks to be strong enough to
mix out the marine layer which will mean more sun and thus warmer
temps in coastal areas, especially on Sunday.
It`s looking less likely that moisture from Hurricane Juliette
will have any impact on our weather. Both the GFS and ECMWF now
forecast Juliette`s moisture to mostly remain south of 30N and not
be drawn northward ahead of the weekend trough.
&&
.AVIATION...As of 4:45 PM PDT Tuesday...Enough stratus has
cleared from the coast to prevent early intrusion into the SFO Bay
Area. Ft Ord Profiler shows marine layer is shallow at 1000 feet
which also works against the stratus. Latest tafs have delayed
the cigs over SFO and the approach until after 06Z but it could be
even later than that.
Vicinity of KSFO...VFR conditions through at least 06Z. Becoming
IFR with bases 800-1000 feet sometime after 06Z. West winds to 20
kt decreasing after 04Z.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...A patch of stratus is developing off
Point Pinos and forming a wave cloud. This cloud is expected to
push into MRY by 04Z then spread into SNS after 06Z.
&&
.FIRE WEATHER...as 2:16 PM PDT Tuesday...A noted above the biggest
concern over the next 36 hours is possible dry lightning for
portions of NorCal, including the Bay Area. Dry lightning is
always tricky to forecast and this slight chance is no different.
However, unlike the last dry lightning event (which resulted in no
lightning for the Bay Area) this one has a better trigger (jet
streak). That being said, it is not a slam dunk and will not issue
a Red Flag Warning at this time. If thunderstorms do develop dry
lightning seems pretty certain with how dry the low levels will
initially be. Gusty winds may also be possible with the right
outflow boundary. Lastly, fuels are definitely dry and will be
receptive to allow for possible fire starts. Persons with fire
weather interests should monitor the forecast over the next day.
&&
.MARINE...As of 8:49 PM PDT Tuesday...Northwesterly winds will
strengthen over the coastal waters through mid-week, with the
strongest winds occuring in the afternoon and evening hours. Long
period forerunners will enter the coastal waters from the
northwest on Tuesday. A shorter period southerly swell will mix in
through the remainder of the week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...SCA...SF Bay until 9 PM
SCA...Mry Bay until 9 PM
SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 9 PM
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Reyes to Pigeon Pt 0-10 nm until 3 AM
&&
$$
PUBLIC FORECAST: Dykema
AVIATION: W Pi
MARINE: W Pi
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Area Forecast Discussion
National Weather Service Phoenix AZ
413 PM MST Tue Sep 3 2019
.UPDATE...aviation discussion.
&&
.SYNOPSIS...
Very limited storm activity is expected over the region through
Saturday. Temperatures will be above normal during this time. The
warmest day looks to be Wednesday. In fact, Excessive Heat
conditions are expected on Wednesday over south-central Arizona. A
change in the weather pattern early next week will lead to a
cooling trend. It lead to an uptrend in storm activity over
Arizona.
&&
.DISCUSSION...
Rest of Today and Tonight...
Modest storm activity is in progress as of mid-afternoon. Of
note, surface dew points are running higher than initially
projected given the 12Z PSR sounding. SPC mesoanalysis shows 1000+
J/kg of MLCAPE over the south-central AZ deserts (500-1000
elsewhere) and 1800+ J/kg DCAPE (seems overdone given dew
points). Plus, there is about 15kts of easterly steering flow. But
there is also noteworthy CIN to be dealt with. HRRR has been
depicting isolated to scattered storms moving across Gila County
and into far northeast Maricopa and northern Pinal County before
dissipating. But not without spreading some outflow wind into at
least eastern portions of the metro area. Other CAMs are
supportive of this scenario with the 18Z NAM Nest trending closer
to that than what the 12Z run was depicting. Given the
mesoanalysis, this scenario is reasonable. Dry advection
advertised by the RAP should help preclude storms from
maintaining/regenerating themselves all the way across the metro
area.
Wednesday through Friday...
There is good model agreement on dry advection from the east on
Wednesday. This will lead to warmer temperatures Wednesday. Expect
temperatures to reach high Heat Risk levels over portions of
south-central AZ and thus Excessive Heat Warning remains in
effect. On Thursday, the center of the ridge drifts eastward a
little bit and temperatures cool slightly - just enough to dip
below excessive heat thresholds. A bit better moisture remains
over southwest AZ and southeast CA. By Friday, a trough
approaching the West Coast begins a change to southwesterly flow
aloft. Still a very low grade Monsoon situation due to lack of
moisture. Little change in temps. Meanwhile, Hurricane Juliette
will have no discernible effect on our forecast area. There is
also an inverted trough moving through northern Mexico during this
time which may help to reinforce moisture levels over Sonora.
Saturday through Tuesday...
There`s somewhat better operational and ensemble member agreement
depicting a progressive, and rather deep northern stream trough
depressing the ridge axis into northern Mexico late in the
weekend, then sweeping into the four corners and Great Basin early
next week. While the increased strength and depth of westerly
flow would typically dislodge moisture from the forecast area,
substantial incoming height and pressure falls may actually create
stronger low level southerly flow and transport better moisture
profiles northward ahead of a frontal boundary. Add in cooling
aloft with this trough and shortwave, along with dynamical
forcing, and forecast soundings actually look quite enticing for
the eastern portions of the CWA during this transition season type
event. Details regarding timing and depth of this system remain
somewhat elusive preventing a more resounding POP mention for any
given time frame, but certainly the signals are present that a
more convectively active day may be in the offing sometime early
next week. Regardless, there is consistency that much lower
heights and cooling will spread into the region allowing
temperatures to finally fall near or below average (and many lower
elevation communities possibly not even hitting 100F for a day or
two).
&&
.AVIATION...Updated at 2315Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Storms will continue to develop in Gila and extreme eastern
Pinal/Maricopa counties this afternoon. Although storm activity
is still not anticipated to actually make its way into the
terminals (better chances at SDL), it is now looking likely that
outflows from these storms will switch the winds to east-
northeast around 01Z at SDL and DVT and between 0130Z and 02Z at
PHX and IWA, with gusts as high as 20-25 kts possible. Given the
wind direction, do not think blowing dust will be an issue, except
possibly at KIWA. There`s a lot of uncertainty as to what the
wind direction will be after the possible outflow boundary moves
through, but guidance is suggesting that winds will try to veer to
the south/southwest before completely switching back to the east
after 07-09Z. Easterly winds will then persist through most, or
all of Wednesday. FEW mid-level clouds through this afternoon
should become SCT-BKN this evening with bases around 10k feet.
Southeast California/Southwest Arizona including KIPL and KBLH:
KBLH will favor a southerly to southerly wind through the TAF
period, with speeds mainly aob 10 kts. KIPL should see a
southwesterly wind before switching to the southeast after
midnight with speeds aob 8 kts. A vicinity shower or thunderstorm
cannot be ruled out at KIPL in the afternoon, but activity should
stick mostly to the mountains to the west. Chances are better to
see brief gusty outflow winds from the west in the early evening
hours. FEW-SCT mid-level clouds and cumulus are expected though
the TAF period with bases remaining aoa 10 kft.
Aviation Discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Friday through Tuesday:
Expect low grade Monsoon conditions Friday and Saturday along with
high temperatures several degrees above normal. Humidities trend
down over southeast California on Saturday with little change east
of there. Sunday through Tuesday, high pressure weakens as a low
pressure system moves through the western CONUS. Temperatures
trend down and humidities trend upward. This will also lead to an
uptrend in storm potential for south-central Arizona.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning from 10 AM to 8 PM MST Wednesday for
AZZ530-532-534-536-537-540>544-546-548-550-551-553-555-556.
CA...Excessive Heat Warning from 10 AM to 8 PM PDT Wednesday for
CAZ567-569-570.
&&
$$
DISCUSSION...AJ/MO
AVIATION...Hernandez
FIRE WEATHER...AJ