Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/26/18
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
638 PM EDT Tue Sep 25 2018
.AVIATION...
A moist and weakly unstable environment lies across Se Mi,
preceding a cold front now over the western Great Lakes. Multiple
convergence areas ahead of the front will pose the risk for
thunderstorms prior to frontal passage, which will not occur until
05-09z tonight. Ample low level moisture will also support continued
intervals of MVFR (perhaps some IFR) cigs and showers. The passage
of the front will end the risk of additional thunderstorms late
tonight. Post frontal cold air advection will boost westerly wind
gusts (20 knots or greater at times). A gradual lifting of the post
frontal inversion due to cold air advection will also result in a
slow but steady lifting of the strato cu during the course of Wed
morning, like VFR by early afternoon.
For DTW...An expansion of a mid cloud deck and embedded showers have
worked into metro Detroit, which may be enough to hold off the threat
for thunderstorms an hour or two after TAF issuance. The cold front
will advance across metro between 09Z and 10Z, veering the winds to
the west. There will at least be a chance of thunderstorms at anytime
prior to fropa.
.DTW THRESHOLD PROBABILITIES...
* High for ceiling aob 5000 ft tonight and Wednesday morning.
Moderate Wednesday afternoon.
* Moderate confidence that thunderstorms will occur through the
night but low confidence on timing/coverage.
* Low confidence that westerly winds will exceed crosswind
thresholds Wednesday morning.
&&
.PREV DISCUSSION...
Issued at 403 PM EDT Tue Sep 25 2018
DISCUSSION...
Severe weather potential for late afternoon through tonight remains
the primary focus for the afternoon forecast package. The overall
scenario continues to be strongly conditional on adequate recovery
of instability which remains possible but with low confidence. The
bottom line is that hourly monitoring of instability trends will be
required to continually assess severe weather potential or the lack
thereof. That being said, instability is about the only element
missing as large scale support and a strong wind field otherwise are
more than adequate to support and/or sustain organized convection.
Showers and ordinary thunderstorms that moved in from Indiana and NW
Ohio continue to fade during mid afternoon while cloud debris further
inhibits daytime heating over SE Michigan. This sets up target areas
for new development over SW Lower Michigan moving eastward from the
lee of Lake Michigan, and over Illinois and western Indiana moving
toward the Ohio border region of SE Michigan later in the evening.
Expect this would be more discrete convection occuring ahead of the
surviving portion of the Iowa MCS that would approach SE Michigan
shortly after midnight if adequate downstream instability can be
maintained.
Mid afternoon hourly mesoanalysis indicates MLCAPE rising slowly
from values mostly less than 1000 J/kg across the mid Mississippi
Valley into Lower Michigan. This is expected to reach the 1000-1500
J/kg range during the 21-00Z time period as a corridor of steeper
mid level lapse rates moves into Lower Michigan from the Midwest.
RAP projections indicate 700-500 mb lapse rates in the 7.0-7.5 C/km
range along the leading edge of height falls ahead of the advancing
upper level trough. The associated cooling aloft could be enough to
maintain MLCAPE near 1500 J/kg well into the night along and shortly
ahead of the cold front and should be considered the target range to
hold for severe potential. It also suggests an advective component of
instability into SE Michigan is possible which would be required for
new storm development and to maintain storms moving into our area
from the west. Other than concerns for instability trends, discrete
convection that is able to develop ahead of the Midwest MCS will be
within a strong wind profile having both some low level curvature and
some mid level length. RAP and NAM sounding projections advertise
0-3 km SRH exceeding 150 m2/s2 and 0-6 km bulk shear exceeding 40
knots, 0-1 km helicity also exceeds 100 m2/s2 with 0-3 km CAPE
exceeding 150 J/kg with cloud base on the low side of 3000 ft. These
are all thresholds for supercell characteristics and for
tornadogenesis, even in low topped convection. This again is strongly
conditional on development of adequate instability, which is in
doubt, but combined with the other elements of the storm environment
remains worthy of the slight risk outlook. Tornado and small hail
potential would be secondary to damaging wind if the upstream MCS can
hold together.
The cold front with this system exits quickly around sunrise
Wednesday followed by dry and cooler mid week conditions leading into
the extended period characterized by periodic shortwaves ushering
in transient shots of cooler temps and attendant opportunities for
showers. This will occur within a slowly retrograding background
state most evident by the motion of the 591dm high centered near
Florida this Friday potentially migrating toward western Texas after
Day 7, a scenario that would offer a better opportunity for sustained
longwave troughing locally. In the meantime, a steady stream of
Pacific energy will keep heights at bay over the Great Lakes as this
evolution unfolds. Chance of rain accompanying Friday`s fropa will be
followed by highs at least 10 degrees below normal for the weekend.
A brief warmup will then be tempered by another chance for rain under
similar circumstances early next week.
MARINE...
A cold front will track through the region tonight which will prompt
a notable change in conditions over the lakes. Currently, southerly
winds are ushering in a warm and moist airmass which will result in
scattered showers and thunderstorms into the overnight. Winds will
quickly flip around to the northwest late tonight while
strengthening as colder air filters in behind the front. The
strongest winds remain across the northern Lake Huron basin where
gusts will reach around 30 knots Wednesday morning into the
afternoon hours. Though a few gusts to gale force are possible, it`s
appears to be over a very short window so we will continue to hold
off on any gale headlines. These elevated northerly winds will build
wave heights along a portion of the Lake Huron shoreline prompting a
small craft advisory. Northwest winds diminish late Wednesday and
Wednesday night as high pressure builds into the region. Winds
become southwesterly and strengthen again Thursday in advance of the
next cold front.
HYDROLOGY...
Potential exists for scattered showers and thunderstorms this
evening into tonight ahead of a cold front that will sweep through
the region early Wednesday morning. Rainfall totals will average
around one third of an inch, although any thunderstorm activity
could bring very localized higher amounts.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory from 6 AM to 4 PM EDT Wednesday for LHZ421-441.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....SC
DISCUSSION...BT/JVC
MARINE.......DRK
HYDROLOGY....DRK
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Quad Cities IA IL
926 PM CDT Tue Sep 25 2018
.UPDATE...
Issued at 924 PM CDT Tue Sep 25 2018
Elevated post frontal showers have developed across Missouri and
are now reaching into northeast Missouri. Most of the activity
should remain south of the area. However, I would not be surprised
if some showers get into Hancock and McDonough counties later
tonight and have added pops there.
Updated forecast to be available shortly.
&&
.SYNOPSIS...
Issued at 1135 AM CDT Tue Sep 25 2018
Strong cold front was bisecting the state of Iowa late this
morning. Temperatures across the area ranged from the upper 70s
to low 80s across the southeast to the lower 60s to upper 50s
across the northwest. Showers and thunderstorms were located
across Iowa. Some of these storms could be severe with damaging
winds, hail and tornadoes all possible threats.
Update at 10AM this morning continues to have the current thought
for this afternoon`s event. As a result, have attached it here for
brevity.
Severe Potential: Looks as though elevated convection will begin to
overtake the warm sector and become rooted in the BL. This should
occur shortly before noon and likely just west of the CWA.
Overall convection speed will slow down and begin to move into our
area. This will give time for CAPE to build this afternoon across
the CWA. Synoptic models show that shear doesn`t support
tornadogenesis, due to SW sfc winds. It appears that a sfc wave is
forming across SW IA. This wave will back winds, much like the HRRR
shows. I believe that we will have a tornado threat from any
mesovortex that develops. I also believe that shear will be greater
than what synoptic models forecast due to this low. As far as severe
parameters go, tend to favor CAM solutions related to shear. Severe
threat for winds to 70 mph, hail and tornadoes remains for the area.
&&
.SHORT TERM...(This Afternoon through Tonight)
ISSUED AT 1135 AM CDT Tue Sep 25 2018
Showers and storms will be exiting the area at the beginning of the
period. It appears that the overall severe risk will be waning
after 00z across the area. Main forecast concern for the overnight
period will be how low to go with temperatures as strong CAA brings
cool air into the area. Currently, most of the area will see lows
in the 50s to the upper 40s.
.LONG TERM...(Wednesday through Monday)
ISSUED AT 150 PM CDT Tue Sep 25 2018
Dry conditions will be seen through Friday morning, as high pressure
builds into the mid and lower MS River valley. Cool and breezy NW
winds will be expected Wednesday, with highs struggling into the low
to mid 60s. A chilly night with light winds will allow temperatures
to fall into the low to mid 40s. Warmer temperatures are expected
Thursday as the high departs and gusty southwest return flow sets
up. Highs are slated to be in the mid 60s to lower 70s Thu.
From Friday through Tuesday, there is some uncertainty in models. In
short, there are slight to chance PoPs, mainly rain showery type,
through most of the day4 through day7 period focused on a meandering
boundary across the region.
A re-enforcing cold front will sweep through Friday with highs in the
upper 50s and 60s. Even colder temps are expected Saturday with
highs in the mid 50s to low 60s. Saturday may end up being mostly
dry with a surface high building in.
A warm front and low pressure system lifts across the area Monday,
with highs in the 70s to near 80 along with some chance/likely
thunderstorm chances mainly over the northern part of the CWA.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
ISSUED AT 625 PM CDT Tue Sep 25 2018
Strong cold front just east of the Mississippi will move into the
Ohio Valley overnight. Behind the front IFR/MVFR conditions be
seen through 06z/26 with scattered SHRA. After 06z/26 conditions
will improve to VFR as high pressure builds into the Midwest.
&&
.HYDROLOGY...
Issued at 1022 AM CDT Tue Sep 25 2018
Not much change to river forecasts. The Cedar River at Vinton has
crested with Cedar Rapids expected to crest this evening near
17.5 feet. On the Wapsipinicon River near De Witt Major flooding
is expected to begin tomorrow, with a crest expected Friday night
into Saturday. Moderate flooding is still forecast for the Cedar
River at Conesville and the Iowa River at Marengo, Columbus
Junction, Wapello, and Oakville.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
UPDATE...08
SYNOPSIS...Gibbs
SHORT TERM...Gibbs
LONG TERM...Sheets
AVIATION...08
HYDROLOGY...14
Area Forecast Discussion
National Weather Service Green Bay WI
1055 PM CDT Tue Sep 25 2018
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Wednesday
Issued at 241 PM CDT Tue Sep 25 2018
The latest RAP analysis and satellite/radar imagery show a cold
front extending from around Marinette to Wautoma early this
afternoon. Partial clearing over northeast WI has allowed some
instability to develop up to the 600-1000 j/kg range. Meanwhile,
a shortwave trough over Minnesota, and associated surface low over
Iowa continue to push an area of showers and storms to the
northeast and across southwest Wisconsin. This area of
precipitation remains on track to pass over the area from mid-
afternoon through the evening. Given the instability over east-
central WI, concern remains for a few strong storms to develop,
mainly from about 21-00z time period. The main threat will likely
be strong, gusty winds from any storms.
Tonight...Cold front, and weak surface low, will be departing over
central Lake Michigan at the start of the period. Although the
potential for strong storms will likely have passed on to the
east by 00z, deformation showers and a few embedded storms are
expected to continue across the region through the evening before
exiting northeast WI shortly after midnight. Partial clearing is
possible overnight, mainly over central and east- central WI, but
additional cloud cover from a trailing shortwave will approach
late. With gusty northwest winds developing behind the front, lows
will fall back into the 40s at most locations.
Wednesday...Upper troughing will be moving across the region.
Progged soundings indicate the thermal profile will be supportive
of an ample cu field developing at locations that clear overnight.
With a breezy west wind and scattered to broken cloud cover, temps
will range from the mid 50s north to low 60s south.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 241 PM CDT Tue Sep 25 2018
Another cold front is forecast to arrive late Wednesday night
into Thursday, along with the next chance of showers. Models show
little instability with this system, so will hold off on any
mention of thunder at this time. Drier weather is anticipated
Thursday night, but a short-wave trof and secondary cold front
could bring scattered showers on Friday.
Canadian high pressure is expected to be the dominant weather
feature over the weekend, and the 00z ECMWF would suggest that
the high would keep mainly dry conditions in place through Sunday
morning. The GFS is dry Friday night into Saturday, but quickly
shifts the Canadian high east on Saturday night, allowing showers
to develop due to increasing WAA/isentropic lift.
An unseasonably cool air mass will arrive Friday night, with
850 mb temperatures dropping to -5 to -6 C over north central WI
by Saturday morning. Will need to keep an eye on Friday night and
Saturday night, as forecast lows are cold enough to be concerned
about frost potential. However, sky cover and wind will play a
significant role in whether or not frost forms, and it is too far
out to ascertain those details.
A significant isentropic lift/overrunning event is possible
across the forecast area from Sunday night into Monday night.
There may be enough elevated instability to support thunderstorm
development, especially over the south half of the forecast area.
This is shaping up as a potentially very wet period.
Temperatures should be near normal on Thursday, drop below normal
over the weekend, then recover to near normal early in the work
week.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1055 PM CDT Tue Sep 25 2018
As the cold front continues to shift off to the east of the area,
winds will remain out of the west and northwest through the rest
of the night into Wednesday. The winds could gust to the 15 to 20
knot range tonight and again Wednesday afternoon. Lower clouds
will linger through late tonight before lifting overnight into
Wednesday morning. GRB, ATW and MTW may lift a bit earlier with
the downsloping winds into those sites. As cooler air linger aloft
Wednesday afternoon, could easily see some afternoon CU giving a
broken MVFR ceiling.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......Kieckbusch
AVIATION.......Cooley
Area Forecast Discussion
National Weather Service Huntsville AL
852 PM CDT Tue Sep 25 2018
.NEAR TERM...(Tonight)
Issued at 852 PM CDT Tue Sep 25 2018
The line of storms has moved off into NE AL and portions of southern
middle TN. Radar, lightning observations and GLM data all suggest a
few stronger storms continue to be embedded in this line. With
precipitable water values of 2+inches over the area these storms have
been producing very high rainfall rates between 2-4 inches per hour.
Thankfully, wind flow through the atmosphere has kept these moving
and the flash flood threat down. Some brief wind gusts of 30 to 40
mph are possible as the storms shift into GA and E TN.
We`ll likely see a break in activity through about 3 or 4 AM. Then,
a weak wave moving north up the MS River Valley will combine with a
frontal boundary shifting E/SE out of the plains to generate another
round of showers and storms. Hires guidance has been handling these
features pretty well and also have a good handle on current radar
trends. The HRRR brings the batch of showers currently over the
ArkLaMiss into NW AL a little after midnight. So in terms of PoPs
over the next several hours, we initially have a decreasing trend as
the current line exits east. Then around midnight start to raise PoPs
back up out west and spread these higher values eastward through
sunrise.
With the little bit of clearing before the next round of rain arrives
temps may be able to cool a few more degrees. Lows around 70 degrees
seem reasonable for much of the area.
.SHORT TERM...(Wednesday through Thursday)
Issued at 245 PM CDT Tue Sep 25 2018
The front should continue to drift swd starting Wed, and gradually
make its way into the area later in the day. Abundant moisture flow
ahead of the front coupled with an increase in synoptic forcing
should allow for num/widespread showers/tstms to develop along/ahead
of the advancing boundary. With unseasonably high PWAT`s xpcted to
remain near/just above 2 inches, multiple episodes of heavy rainfall
are possible with these showers/tstms. A Flash Flood Watch may be
required for Wed/Wed night and perhaps into Thu. With the front
xpcted to remain invof the gen area, total rainfall amounts look to
be right around 2-2.5 inches, with locally higher amounts certainly
possible. Areas east of I-65 into NE AL will have the highest prob of
any localized/flash flooding Wed into Thu. Latest model suites are
then fairly consistent with moving the boundary south of the area
later in the day Thu, with a somewhat weakening trend. This will
translate into rainfall gradually tapering off from the west during
the day Thu. Rain chances look to remain fairly high across the ern
zones thru Thu, although total rainfall amounts will be on a
diminishing trend. Given the abundant cloud cover/rainfall in the
area, afternoon highs Wed/Thu may struggle to climb any higher than
the mid/upper 70s range. Lows Wed night look to fall more into the
mid/upper 60s given the influx of some cooler air.
.LONG TERM...(Thursday night through Monday)
Issued at 245 PM CDT Tue Sep 25 2018
Rainfall will continue to be on a gradual diminishing trend near the
end of the work week, with the front perhaps just south of the area
and continuing to weaken. This may at least allow afternoon temps on
Fri to climb more into the lower 80s for most spots. The wx across
the region will then be dependent on another frontal boundary
approaching from the NW this weekend. However, the latest global
models are not clear on this boundary moving into the area as with
the front Wed. As such, rain chances will mainly be iso/sct in nature
starting this weekend, with much of this activity dependent on the
strength of the moisture return back into the region. Highs look to
rebound more into the lower/mid 80s for much of the period, while
lows trend predom in the mid 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 624 PM CDT Tue Sep 25 2018
A line of showers and storms at the HSV terminal as of 23z but should
be east by 01z. Brief drop to MVFR cigs/vis possible with these
storms. Some clearing is noted in satellite behind the storms and
cigs should improve to VFR. Then late tonight into early Wednesday a
frontal boundary is forecast to approach the area. Scattered to
numerous showers/storms are forecast after 12z Wednesday. IFR
cigs/vis are possible under the heavier activity during the day
Wednesday.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...Stumpf
SHORT TERM...09
LONG TERM...09
AVIATION...Stumpf
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Lincoln IL
855 PM CDT Tue Sep 25 2018
.UPDATE...
Issued at 855 PM CDT Tue Sep 25 2018
0130z/830pm surface analysis shows cold front just east of the
I-55 corridor...with a broken line of convection just ahead of the
boundary from near Rantoul S/SW to Taylorville. These storms will
continue to progress eastward over the next couple of hours,
eventually exiting into Indiana by around midnight. Behind the
front, breezy and much cooler conditions are spilling into the
western KILX CWA where temperatures have already dropped into the
lower to middle 60s. HRRR continues to suggest a line of post-
frontal showers will develop from Missouri into portions of
central Illinois later this evening into the overnight hours.
Latest radar mosaic is showing these showers already materializing
across central and western Missouri, so will be keeping a close
eye on radar trends to see how far N/NE these showers will expand.
Have updated hourly PoPs to focus likely showers/thunder across
east-central Illinois through midnight, then have added chance
PoPs for showers along/south of a Macomb...to Lincoln...to Paris
line overnight.
&&
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 330 PM CDT Tue Sep 25 2018
Severe Thunderstorm Watch is ongoing across the northern third of
the CWA late this afternoon and is set to continue til 10 pm. The
strongest storms are north of the CWA but additional showers and
storms will continue to develop across portions of central IL
along I-72 and move northeast. Will keep highest pops to the north
through the evening hours and then have pops getting lower as
moving to the southeast and south. Based on HiRes models and other
models, back edge of the precip should move through rather quickly
this evening with precip ending across most areas around midnight
and then in the east and southeast late tonight. Once the precip
moves through tonight dry weather is expected on Wednesday.
As the front moves through tonight winds will become northwesterly
and this should usher in cooler temps for tonight. Overnight lows
are expected to drop into the upper 40s in the northwest to around
60 in the southeast. Most areas will see temps of around 50 mid
50s. Wed temps will be much cooler tomorrow with northwest
flow...with 60s possible across the CWA.
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 330 PM CDT Tue Sep 25 2018
The extended period will predominately be dry as a northwest flow
pattern takes over the area for the rest of the week and then more
zonal during the weekend. Any precip chances will remain north of
the CWA the rest of the week and into the weekend as weak waves
move through the flow and across the Great Lakes region. However,
small chances of precip will be seen across the extreme northern
tier of the CWA through the period. The pattern begins to slowly
change to more southwest/zonal for the beginning of next week and
this results in the models differing with timing and position of
precip across the CWA. A blend of the models brings precip chances
for Mon night and Tue and this seems fine for now.
Temps will vary through the period with 70s expected Thur and Fri,
60s for Sat, 70s again for Sun, and then 80s for Mon and Tue.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 724 PM CDT Tue Sep 25 2018
Line of broken showers and isolated storms will continue to move
through the area with only thunder seen on radar/satellite near
BMI. Will keep VCSH at all other sites and VCTS at BMI...all for
a few hours. Then clouds will become MVFR at around 2.5kft on back
side of the front. These clouds are expected to hang around until
morning...then clear out during the morning hours. Winds will
become northwest behind the front.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Barnes
SHORT TERM...Auten
LONG TERM...Auten
AVIATION...Auten
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
840 PM CDT Tue Sep 25 2018
.UPDATE...
Issued at 840 PM CDT Tue Sep 25 2018
At 8pm, the surface cold front extended from just east of
Springfield, IL (KSPI) to southern Lincoln County Missouri to near
Jefferson City, MO (KJEF). Surprisingly very little convection has
developed along this front in our forecast area from earlier and
the front is currently precipitation-free. Examination of
soundings showed a bit stronger mid level cap that led to much of
the frontal scale forcing being suppressed. A slight chance token
PoP will be retained until 06z as this cold front continues to
push southeast through our region.
Of a more important forecast change is the HRRR/RAP have really
picked up on post-frontal development of showers with isolated
thunderstorms currently over western Missouri due to
frontogenetical forcing (welcome to the COOL season!) and
broadscale forcing aloft. Have decided to run with this depiction
for overnight PoPs, which places many areas in likely category.
Instability will be quite limited when this does enter our
forecast area late this evening and have showers going instead.
These showers are expected to exit the forecast area to the east by
mid-morning Wednesday.
Otherwise, the rest of the forecast is on track with only minor
cosmetic changes made.
TES
&&
.SHORT TERM... (Through Late Wednesday Afternoon)
Issued at 330 PM CDT Tue Sep 25 2018
Isolated showers and a lone thunderstorm have developed over the
area this afternoon. Am surprised there hasn`t been more lighting
as of yet given the 1500-2000 J/Kg MLCAPE on indicated by SPC
Mesoanalysis over eastern Missouri and southern Illinois. RAP
soundings are showing some low level CAPE with a mid level wedge of
warmer air around 10,000 feet. While the soundings are uncapped by
the warm mid levels, it`s possible the RAP is a little too cool
aloft and updrafts aren`t able to punch up high enough to cause
glaciation and lightning production. I expect that between the
instability and the approaching shortwave the convection should
eventually be able to grow tall enough to produce lightning later
this afternoon. 0-6km shear is in the 40-50kt range, with the
higher end of those values over northeast Missouri and west central
Illinois. With the aforementioned MLCAPE values and shear, will
have to remain vigilant through the early evening for severe
thunderstorms. The greatest potential should be over northeast
Missouri and west central Illinois where the highest shear and CAPE
values are superimposed. CAMS have been too strong/too widespread
with convection so far this afternoon...so I can`t say I have a lot
of faith in them for the evening. That being said, the operational
HRRR seems to finally be figuring out that there may not be as much
convection this afternoon and evening as originally thought, so am
leaning toward it for guidance on coverage tonight.
Instability drops off very quickly behind the cold front tonight
which should pass from central into east central Missouri between 00-
04Z, and from there through our southeast Missouri and south central
Illinois counties by 07-08Z according to the RAP. This should put
an end to the threat for thunderstorms, but short-range models are
showing some moderate low-mid level frontogenesis behind the front
into early Wednesday morning. Will keep low chance/slight chance
PoPs in the forecast behind the front tonight, ending from northwest
to southeast through 12Z Wednesday to cover this. This looks like a
nice strong cold front, with temperatures dropping 20 degrees or
more in the cold sector. Expect lows Wednesday to be 15-20 degrees
below this morning`s readings in the upper 40s to mid 50s, and highs
similarly around 15 degrees cooler in the upper 60s to low 70s.
Carney
.LONG TERM... (Wednesday Night through Next Tuesday)
Issued at 330 PM CDT Tue Sep 25 2018
By early Wed night, the ridge axis of a broad surface high
pressure center will stretch from southwest to northeast across the
region. Looking aloft, one PV anomaly is forecast to remain in TX/OK
near the base of an upper trough axis while a much stronger one
sinks southward into ND/MN and eventually develops into a low
pressure system. The surface ridge axis will be nearly overhead for
most of the night, but mid/high cloudiness associated with the TX/OK
disturbance will interfere with what would otherwise be good
radiational cooling conditions. Overnight lows are forecast to fall
into the mid-40s to low/mid-50s across the area with the coldest
temperatures in the northwestern CWA where the least cloudiness is
expected. This will likely be the coolest night out of the next
several, especially if less cloud cover occurs and leads to better
radiational cooling conditions.
The aforementioned strong PV anomaly over ND/MN continues moving
southeastward into the western Great Lakes on Thu/Thu night and
develops into a low pressure system before lifting northeastward
into Canada. This low pressure system will send a cold front into
MO/IL on Friday, but the upper forcing across our area appears
limited due to the distance from the surface and upper lows. Any
rain showers associated with this front would be limited to the
northern CWA and likely sparse to widely scattered in coverage.
Models then depict a 1025+ hPa surface high settling into the region
behind this front which will ensure quiet and mostly dry conditions
over the weekend.
Models diverge late this weekend regarding their handling of a
closed upper low which approaches the northern California coast.
Despite the timing and evolution differences, models are in vague
agreement that lee cyclogenesis associated with this system produces
a developing surface low near the Rockies which lifts the effective
frontal boundary northeastward through the CWA on Sunday/Monday. The
combination of the warm frontal passage and rising heights aloft
downstream of the upper trough will lead to warming temperatures for
Sunday through next Tuesday. Moisture convergence associated with a
low-level jet could produce isolated to scattered SHRA/TSRA early
next week.
Kanofsky
&&
.AVIATION... (For the 00z TAFs through 00z Wednesday Evening)
Issued at 655 PM CDT Tue Sep 25 2018
Showers and thunderstorms are struggling to develop along a cold
front now just east of UIN and COU. This is looking less likely to
directly impact the STL metro TAF sites during the evening.
Another interesting development from some model guidance is
development of an area of showers behind the front that could
affect all TAF sites during the late evening and overnight hours.
Will be evaluating this soon and updating rain chances as needed.
Look for a period of MVFR ceilings behind the cold frontal passage
this evening, otherwise, VFR conditions will prevail at the TAF
sites through the valid period. Light SW surface winds will veer
NW and become gusty to 20-25kts behind the front, diminishing some
during Wednesday.
SPECIFICS FOR KSTL: Kept a token VCTS mention for now through 03z
although it is looking less likely with time. Otherwise, the cold
front is set to move through around 03z followed by surface winds
veering NW and becoming gusty with several hours of MVFR ceilings
as well. We are looking into the potential for another better
round of showers overnight between 07-11z and may need to upgrade
to prevailing or TEMPO as needed. Otherwise, VFR conditions will
settle in by sunrise Wednesday and continue through the remainder
of the valid period.
TES
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Nashville TN
755 PM CDT Tue Sep 25 2018
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Lower level convergence zone appears to be working slowly across
eastern middle TN at this time. Rainfall rates of up to an inch
per hour are falling along the central Plateau. Movement is rather
slow to the east. Will go ahead and increase pops for areas along
that central Plateau.
Otw, the western two thirds of the mid state is experiencing a
break right now. But looking up stream, a cold front stretches
from IL southwest through eastern OK. Pressure rises are indicated
in the post frontal sector, so the front is on the way.
Currently, vort advection is neutral over our western two thirds.
Later tonight, curvature and shear spikes will become more n-s
oriented. This will enhance a positive tilt in regard to the vort
advection fields. As the developing pva aligns with the frontal
and pre frontal forcing, convection coverage will pick up later
tonight. At 12z, frontal position progs are such that the boundary
will be working through our northwestern counties. Latest HRRR
data shows the marked precip covg increase holding off until aft
09z. Will adjust weather and pop grids accordingly.
Remainder of the grids appear to be in good shape. Update out
shortly.
&&
.AVIATION...
00Z TAF DISCUSSION.
CKV/BNA/MQY/CSV...Expecting only some VCSH potentially for
CKV/BNA/MQY thru 26/08Z. As sfc front approaches mid state
after 26/06Z and then sags slowly sewd into cntrl portions of
mid state by 26/18Z, another round of shwrs/tstms is likely to
occur. As sfc front is expected to push well southeast of mid
state region by 26/24Z, look for some drier air to work into at
least northwestern parts of mid state region. However, with a
continuance of southwesterly flow aloft anticipated, look for the
potential of shwrs to hang around all terminals expect CKV thru
26/24Z. Current VFR ceilings will degrade to generally low end
MVFR/IFR ceilings. CKV may see a return to VFR ceilings by 26/21Z.
SW sfc winds will veer slowly to the NW as sfc front progresses
thru the mid state region.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......21
AVIATION........31
Area Forecast Discussion
National Weather Service New York NY
1035 PM EDT Tue Sep 25 2018
.SYNOPSIS...
A warm front will slowly move north of the area tonight,
followed by a cold front Wednesday and Wednesday night. High
pressure returns on Thursday and then builds to the north on
Friday as a wave of low pressure passes to the south. A stronger
high pressure builds from the west over the weekend and then
offshore early next week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Significant flash flooding continues across New Haven,
Middlesex, and New London Counties in CT. Once the heavy rain
band moves to the east in the next hour or two, the flash
flooding threat will diminish. However, it will take some time
for the water to recede as rainfall amounts have been quite
impressive. Several locations in SE CT have reported over 6
inches of rain in a relatively short amount of time.
A Public Information Statement has been issued listing some
rainfall totals so far with this event.
There will be a more limited threat for heavy downpours after
midnight. PoPs will be decreased accordingly, but with a
continued moist southerly flow and warm front nearby, PoPs will
still remain in the chance range.
Will need to watch the early morning hours as the HRRR and 3-km
NAM show some regeneration of heavy rain, mainly along Long
Island and SE CT.
Winds should remain high enough at the coast to keep fog from
becoming widespread tonight. Inland areas north of the warm
front may see fog become more widespread and possibly dense.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Areas of fog during the early morning hours will dissipate as
heating and mixing commences. Scattered showered in the morning
will become more widespread as the day progresses with a pre-
frontal trough developing and followed by a cold front during
the eve. Moderate instability and 30-40kt of 0-6km bulk shear
has warranted SPC to place the entire area in a slight risk for
severe weather on Wed. The main threat is damaging winds. Heavy
rain will once again be a concern although the storms should be
moving and the upper pattern does not appear to be conducive for
training storms. However, urban and small stream flooding cannot
be ruled out.
Showers/tstms end from W to E Wed night with dry weather
returning behind it.
There is a high rip current risk for the Atlantic beaches
Wednesday.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
The synoptic pattern through the long term will be characterized by
a large, mean trough over the northern CONUS. The upper trough may
flatten later this weekend and lift back into Canada early next week
as ridging rebuilds over the east.
High pressure will briefly build over the region on Thursday and
then lift to our north on Friday. The cold front that moves across
late Wednesday into Wednesday night stalls to our south.
A broad SW flow aloft and some shortwave energy may interact
with this front and develop a wave of low pressure along it
Thursday night. This wave likely passes to our south and east on
Friday. Have continued to keep PoPs in the slight to low chance
range. Thinking the surface high will continue to ridge down
into the region preventing much in the way of precipitation. The
low moves offshore late Friday into Friday night with a
stronger high building into the region for the rest of the
weekend. This high will likely move offshore early next week
with the approach of the next frontal system.
Temperatures should average near normal through the long term period
with highs in the upper 60s and lower 70s and nighttime
temperatures mainly in the lower and middle 50s.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Warm front will clear nrn portions of the area by 12-14z. A
cold front passes Wed eve.
Rain tapers off thru 5-6z from w to e. Heaviest shwrs invof
KGON. Cigs still expected to lower to ifr all areas overnight,
with some brief breaks to vfr thru 4-6z.
Winds will continue to diminish this tngt. Light and variable
winds likely across the Lower Hudson Valley. S-SW winds of 10
to 15 kt expected on Wed, becoming nw behind the cold front Wed
ngt.
.OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY...
.Wednesday night...Showers/tstms with MVFR or lower at times,
mainly in the evening.
.Thursday...VFR.
.Thursday night-Friday morning...MVFR possible, low chance of
showers.
.Friday afternoon-Sunday...VFR.
&&
.MARINE...
SCA remains in effect through 1am for the Eastern Sound and
Eastern LI Bays. Winds will continue to diminish there and
should be below 25 kt around or just after midnight. Gusts on
the ocean waters have diminished below 25 kt, although seas will
remain above 5 ft through Wed night.
Winds are likely to remain below SCA levels Thursday through the
weekend on all area waters. Ocean seas on Thursday into Thursday
night will remain elevated above 5 ft, but then should remain 3-4 ft
from Friday into the weekend.
&&
.HYDROLOGY...
The potential for significant flash flooding remains for the
next few hours across southeastern Connecticut. Additional
rainfall amounts of 2 to 3 inches with locally higher amounts
cannot be ruled out in the heaviest band of showers across New
London County. Outside of the heaviest band of showers, rainfall
amounts will be significantly less.
Scattered tstms Wed/Wed eve have the potential to produce heavy
rainfall however urban and small stream flooding appears to be
the potential threat at this point.
&&
.EQUIPMENT...
NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off
the air for an extended period of time.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Rip Current Risk through Wednesday evening for NYZ075-080-
081-178-179.
NJ...None.
MARINE...Small Craft Advisory until 1 AM EDT Wednesday for ANZ330-340.
Small Craft Advisory until 6 AM EDT Thursday for ANZ350-353-
355.
&&
$$
SYNOPSIS...24/DS
NEAR TERM...24/DS
SHORT TERM...24
LONG TERM...DS
AVIATION...JMC
MARINE...24/DS
HYDROLOGY...24/DS
EQUIPMENT...
Area Forecast Discussion
National Weather Service Paducah KY
853 PM CDT Tue Sep 25 2018
.UPDATE...
Issued at 851 PM CDT Tue Sep 25 2018
Performed a second iteration of PoPs/Weather/Sky/QPF adjustments
for the rest of tonight. Surface/low level moisture convergence
remains weak and the lack of deep layer moisture and instability
inhibiting deep convection this evening. The HRRR and RAP guidance
appear to have consistent signals regarding convective development
overnight. Some slight spatial adjustments were made to the model
output to reflect current rainfall trends this evening and
overnight.
Plan to remove mention of damaging winds associated with
convection in the Hazardous Weather Outlook. The best potential
for any wind damage concerns would be isolated to wind gusts
associated with the cold frontal passage late tonight impacting
trees or other weakened structures in areas with saturated ground
the past couple of days.
UPDATE Issued at 616 PM CDT Tue Sep 25 2018
Aviation update. See section below for the public forecast
update.
UPDATE Issued at 602 PM CDT Tue Sep 25 2018
Made some significant short term adjustments to PoPs/Weather/QPF
for the WFO PAH forecast area this evening and overnight. At this
point, could not justify keeping 40-50% PoPs in the forecast for
the next few hours.
From a surface based perspective, there is some decent theta-e
convergence and up to 2700 j/kg LAPS surface based CAPE over
southeast Illinois and southwest Indiana in ahead of the
convection in southeast Illinois, but this area has been worked
over fairly well, so temperatures for surface lift and renewed
convection are marginal. Elsewhere, theta-e convergence is weak
and there is lower dewpoints advecting into southeast Missouri.
Will not rule out pockets of scattered showers and isolated to
scattered thunderstorms in advance of the cold front tonight.
Until more organized lift and forcing can be in place, cannot
rationalize widespread coverage of chance POPs at least through
the midnight hour. Will make adjustments as the front gets closer
to the WFO PAH forecast area.
The HRRR/ESRL HRRR convection allowing models (CAM`s) have shown
quite a bit of consistency since yesterday evening on the
progression of the convective, heavy rain producing, band today
and the widely scattered convection this evening.
&&
.SHORT TERM...(Tonight through Thursday night)
Issued at 114 PM CDT Tue Sep 25 2018
Warm front that has pivoted northeast of FA has allowed warm
conveyor belt of high theta-e air to train across southeast
IL/southwest IN with efficient rains. Embedded elevated
instability resulting in occasional thunderstorms has heightened
the locally heavy rain risk, which continues this pm. Afterwards,
we`ll be warm sectored, and watching pm destabilization in the
west. Marginal risk day1 svr still exists for our north/west.
Cold fropa entering nrn MO at this writing, and we`ll see height
falls/speed shear aloft increasing in difluent upper flow as front
approaches. However, it won`t be reaching PAH FA/making passage
til later tonight, when surface destabilization wanes. Anticipate
showers/some continuing risk of thunder, with main impact gusty
frontal shift winds/maybe locally heavy rains.
Fropa brings Fall like change to airmass, with dew points still
poised to drop thru the 50s Wednesday, and upper 40s to invade the
entirety of the FA by 12z Thursday. This will be our first true
taste of Fall.
.LONG TERM...(Friday through Tuesday)
Issued at 221 PM CDT Tue Sep 25 2018
Models are in fairly good agreement showing a surface high over
the upper Mississippi valley Friday night, then centering it over
the southern Great lakes region by 00z Sunday. The overall trend
of a slower moving high results in a slower warm up for the
weekend, with winds remaining easterly into Saturday night and
becoming southerly on Sunday. Temperatures will now remain below
seasonal normals through Saturday, moderating back to seasonal
values by Sunday.
A frontal boundary situated to our north early in the work week
and increasing low level moisture due to our southerly winds will
give us a gradual increase in shower and thunderstorm chances
Monday into Tuesday. Our slight to low chances on Monday will be
primarily diurnally driven, then chances will increase late Monday
night into Tuesday as the boundary sinks a little farther south.
Our early week temperatures will be few degrees above normal,
with readings in the lower 80s, and dew points will climb into the
upper 60s to around 70 degrees.
&&
.AVIATION...
Issued at 616 PM CDT Tue Sep 25 2018
Front will push southeast across the area overnight. SSW winds up
to 10 kts ahead of it, NW winds becoming N, with some gusts 18 to
22 kts or so expected behind the front. Around 09z the front
should be along a KEVV- KPAH line, clearing west KY by 12z.
Scattered showers and a few storms possible up to fropa, but
chance too low to include in the terminals. There may be a period
of MVFR cigs along and behind the front for a few hours. Otherwise
expect mainly VFR conditions ahead of the front, and from mid
morning Wednesday on into the afternoon hours.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
UPDATE...Smith
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Wednesday)
Issued at 308 PM CDT Tue Sep 25 2018
As of 18Z Tuesday afternoon a neutrally tilted, midlevel trough was
positioned across the northern Plains with broad cyclonic flow across
the central Plains. An attendant surface trough extended from
eastern WI through northeast KS into west TX. Scattered
thunderstorms have developed within the last hour across northern
MO/southern IA where better midlevel moisture and forcing for ascent
reside. Scattered showers and storms are possible across northeast
KS through the afternoon and early evening. RAP and HRRR forecast
soundings suggest upwards of 2,000 J/kg of MLCAPE will reside across
east-central KS by mid to late afternoon, along with 40-50 kts of
effective shear. This combination could pose a damaging wind and
hail threat. Additional elevated thunderstorms are possible behind
the surface trough as sufficient residual low level moisture will
reside for upwards of 1,000 MUCAPE to reside across northeast KS.
Sufficient effective shear values will remain greater than 30 kts,
which could support a large hail potential into the early evening
hours. As the main midlevel trough moves east and the surface trough
exits the area to the southeast, all shower and thunderstorm
activity will come to an end from northwest to southeast early this
evening.
Gusty northerly winds between 20 and 30 MPH will decrease after
sunset to below 10 MPH. Cold air advection combined with plentiful
radiational cooling due to clear skies should yield a cool start to
Wednesday morning with lows in the mid to upper 40s.
A pleasant Wednesday is expected as the surface ridge axis moves
overhead, yielding sunny skies and light winds. High temperatures
are progged to remain in the upper 60s to near 70.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 308 PM CDT Tue Sep 25 2018
PV anomaly diving south-southeast along the northern Rockies helps
reinforce the surface ridge over the southern Plains Wednesday night
into Thursday keeps the lower troposphere dry despite a return of
southerly winds. Modest warm air advection should bring highs back
into the mid 70s for most areas Thursday.
The next upper wave rotating southeast through the mean trough
brings another Canadian cold front through the area Thursday night
and Friday with precipitation chances low with precipitable water
values remaining below normal. Best chances again look to be in
northeastern areas closer to the deeper forcing with the upper wave.
Chances do increase Friday night into Saturday with isentropic
upglide developing over the front as mid/upper flow becomes more
zonal. Differences on the post-frontal anticyclone`s intensity give
rise to varying solutions on precipitation potential but any amounts
look to be light. Confidence in temperatures for these periods is not
high with timing differences on the front Friday, persistence and
depth of cloud cover, and cloud/precip potential Saturday.
The mean upper trough shifts east early next week though confidence
in the pattern in the western U.S. in specifics in the timing and
location of waves there is not high. West to southwest upper flow
over the central and northern Plains should bring predominantly
southerly winds and above normal temps in place.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 633 PM CDT Tue Sep 25 2018
For the 00z TAFs, VFR conditions are expected with diminishing
winds and gradually scattering cloud cover this evening.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Baerg
LONG TERM...65
AVIATION...Hennecke