Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/19/18
Area Forecast Discussion
National Weather Service Des Moines IA
633 PM CDT Tue Sep 18 2018
.DISCUSSION.../Tonight through Tuesday/
Issued at 414 PM CDT Tue Sep 18 2018
At 20z Tue, a somewhat broad, stretched more northerly-southerly,
area of anticyclonic flow was centered over eastern Oklahoma.
Meanwhile height falls were noted across the western Plains as low
pressure has begun to try to establish itself off the Rockies.
With this synoptic setup, moisture was being transported from the
Gulf of Mexico through West Texas and into Kansas. As this
anticyclone propagates eastward the next couple of days, low-
level moisture transport will make it into Iowa.
Mesoscale has dominated as an outflow boundary went pushed southward
all the way from northern Iowa into Missouri. Behind this boundary,
clouds kept temperatures down... confining highs to the 60s... where
southern Iowa made it into the low 90s before the boundary arrived
there. The RAP has had the best handle on the progression of this
boundary, so have leaned towards it much of the day.
For this evening into tonight...
PWAT values continue to push 2 inches across most of Iowa through
the next couple of days. A Theta- e ridge has begun to build over
eastern Nebraska, with the ribbon cutting right through western
Iowa. A 30 KT 850mb LLJ pokes its way into NW Iowa after 06z Wed.
In short, severe threat will diminish to nil overnight as MUCAPE
values drop to around 500 J/KG. Main focus is on flooding
potential. Northern/NW Iowa has had generally 1 to 2 inches of
rain the past 48 hours, with some locations closer to Mason City
approaching 3 to 4 inches this morning alone. The GFS is excited
about orienting a band of E-W oriented 925mb frontogenetical
forcing to serve as a focusing mechanism for where reinforcing
precip could set up and dump itself. At this time, think NW Iowa
is the most likely location for best phasing. Again, if this
shifts eastward closer to I-35 and especially Mason City, would
need to be quick on trigger for Flash Flooding headlines.
Tomorrow...
May be somewhat a repeat of today. Will be watching for
an outflow boundary to kick off the overnight convection and sag
southward. The difference in the setup tomorrow is that as the LLJ
cuts into Iowa, this boundary will not drop all the way into
Missouri. Rather, it will take a slightly more NW-SE orientation.
There will be a remarkable temperature difference north/south of the
boundary. Highs south of the boundary will be into the 90s, highs
north of the boundary may struggle to make it into the 70s again.
Heat index values south of the boundary will likely be in the low to
upper 90s... opening the door for possible heat-related issues in
southern Iowa.
Instability south of the boundary very high as MUCAPE values
approach 3000 J/KG. Low-level lapse rates also very steep, so hail
would be a primary threat, along with damaging winds. Like today,
thunderstorms may produce periods of heavy rain.
Thursday into the weekend...
All eyes shift to the cold fropa as a sfc low finally gets its
act together and pushes through the upper midwest. The past
several 12z/00z model runs have trended to slow the progression of
the cold front. This is notable as the timing of the fropa may
now not be until 03z Fri-09z Fri at the earliest... which would
put us out of a lot of the daytime heating convection.
Thunderstorms are very likely with this fropa, including severe
weather. With the focus on the near-term... the Thursday fropa
will be detailed in higher resolution over time.
Seasonable temperatures return to Iowa this weekend as conditions
should dry out through Saturday.
&&
.AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/
Issued at 633 PM CDT Tue Sep 18 2018
Main challenge will be onset of next round of convection and
duration through Wednesday. Last area of -shra/-tsra moving
southeast sections of Iowa now and break from storms until 05-07z
expected when storms begin to refire over northwest Iowa.
Meanwhile cigs will begin to lower northwest and along with storms
moving east southeast affecting KFOD/KMCW/KALO and to a lesser
extent KDSM/KOTM from 07z north sites to near 15z southeast sites.
Another break/lessening of activity may follow until end of
period. Will need to evaluate meso trends with each package./rev
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Kotenberg
AVIATION...REV
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1002 PM CDT Tue Sep 18 2018
.UPDATE...
Just sent a forecast update to remove low PoPs for western Val Verde
County late tonight and early Wednesday, as diurnal convection has
shut down for the night and return Gulf flow should not result in
more than light drizzle if anything at all. Otherwise, we re-trended
the hourly forecast values through 12Z to reflect expected trends.
&&
.PREV DISCUSSION... /ISSUED 639 PM CDT Tue Sep 18 2018/
UPDATE...
00Z Aviation forecast below.
AVIATION...
VFR conditions through the evening hours. Stratus is forecast to
develop from DRT-SAT and north into the Hill Country 07Z-10Z
resulting in IFR ceilings. HRRR indicating the stratus could advect
north to near or just south of the AUS area around daybreak. Current
SCT010 for AUS reflects uncertainty, but if trends continue northward
BKN IFR or MVFR ceiling may be needed for AUS in the 06Z TAF cycle.
The stratus will gradually scatter out 14Z-17Z, perhaps a little
longer near the Rio Grande. S to SE winds diminishing to under
10 kts tonight.
PREV DISCUSSION... /ISSUED 303 PM CDT Tue Sep 18 2018/
SHORT TERM (Tonight through Wednesday Night)...
The latest water vapor imagery shows an upper low centered in the
northwest Gulf of Mexico, with broad cyclonic flow in the mid and upper
levels across roughly the southern half of Texas. In the low-
levels, weak high pressure was located over southeast Texas with
southerly winds in place across our region. Late afternoon
temperatures across the region were generally in the 80s with a few
readings in the lower 90s.
For the remainder of this afternoon and early evening, we will maintain
a low chance for convection along the Rio Grande. The latest hi-res
models are not very aggressive in coverage and will keep rain chances
limited to 20%. Most activity is expected to diminish with daytime
heating, although a few showers can`t be ruled out during the early
morning hours as the low-level jet strengthens. Elsewhere, look for a
rain-free forecast tonight with some patchy fog developing after
midnight along and east of the I-35/I-37 corridor. The coastal plains
will be favored for lower visibilities during the overnight hours
into early Wednesday morning as winds will be lightest here.
On Wednesday, the overall pattern will change little as the upper low
in the northwest Gulf drifts northward. We still expect some isolated
showers and thunderstorms to develop, mainly in the afternoon hours
along the Rio Grande. The latest suite of hi-res models do not show
much coverage of showers and storms and we will limit rain chances to
20%.
LONG TERM (Thursday through Tuesday)...
On Thursday, the weather pattern will begin to change as the subtropical
high shifts eastward and strengthens over the eastern U.S., while a
broad trough approaches from the west. The latest round of model data
continues to advertise a good chance of rain for south central Texas
during the latter half of the week. The remnants of a weak tropical
disturbance in the eastern Pacific are still not handled too well by
the models. However, it does appear we can expect some increase in
moisture from the Pacific along with southerly flow in the lower and
mid-levels, leading to increasing moisture from the Gulf of Mexico.
Rain chances on Thursday will initially be favored across the Rio
Grande plains where low-level upslope flow and a weak upper
disturbance moving in from the west will be found. As weak upper
disturbances continue to filter in from the west, rain chances will
spread eastward and increase on Friday and Saturday. The models
continue to show precipitation will be fairly widespread and have
also increased rainfall amounts in the latest MOS data. With a lack
of a well-defined surface feature, it will be difficult to pinpoint
which areas will see the heaviest rains as we head into late this
week and the upcoming weekend. For now, we have increased rain
chances across all areas on Friday and Saturday. If subsequent model
data remains consistent, we will need to increase the chance of rain
for all areas on Saturday, with the focus for rainfall expected to
shift eastward to along and east of the I-35 corridor on Sunday. We
have included the mention of locally heavy rainfall in the Hazardous
Weather Outlook for Thursday through the weekend.
For early next week, we should see a gradual decrease in rain chances
with only a very minimal decrease in moisture. Areas east of I-35
will remain favored for some afternoon seabreeze convection on Monday
and Tuesday. The medium range models also show potential for an
inverted trough moving in from the Gulf early next week, but differ
on the timing.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 74 92 74 88 75 / 0 - - 30 20
Austin Bergstrom Intl Airport 72 92 73 89 75 / 0 - - 30 20
New Braunfels Muni Airport 72 90 73 88 74 / 0 - 10 30 30
Burnet Muni Airport 71 90 72 86 73 / 0 - 0 30 20
Del Rio Intl Airport 74 87 74 85 74 / 10 20 20 40 50
Georgetown Muni Airport 73 92 72 89 74 / 0 - - 30 20
Hondo Muni Airport 72 88 73 88 74 / 0 - 10 40 50
San Marcos Muni Airport 72 91 73 88 74 / 0 - 10 30 30
La Grange - Fayette Regional 74 93 74 90 75 / 0 10 - 30 20
San Antonio Intl Airport 73 89 74 88 75 / 0 - 10 30 40
Stinson Muni Airport 74 90 74 89 76 / 0 - 10 30 40
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale/Aviation...Runyen
Synoptic/Grids...26
Area Forecast Discussion
National Weather Service Green Bay WI
1036 PM CDT Tue Sep 18 2018
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Wednesday
Issued at 233 PM CDT Tue Sep 18 2018
What a difference a day makes! Temperatures in the 80s to
around 90 yesterday were replace with temperatures this
afternoon in the middle 50s to the 60s at most places. The
warm spot was 70 at Wisconsin Rapids.
The first band of showers has shifted south of the area this
morning. Cloudy skies remained. The main question for tonight is
when the next round of showers and a few thunderstorms will move
across the area, especially across the southern half of the
forecast area. The latest HRRR run has backed off on the timing of
the next round of showers and perhaps a few thunderstorms until
late tonight.
On Wednesday, clouds and easterly flow combined with the chances
of showers and storms will continue throughout the day. The best
chances of rain will be across central Wisconsin. Severe storms
are not expected. Did lower max temps down a degree due to cloud
cover and easterly flow.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 233 PM CDT Tue Sep 18 2018
The main weather impacts through the extended will be the potential
for heavier rainfall Wednesday night through Thursday evening and
the potential for strong to severe storms Thursday afternoon and
evening. Attention then turns to frost potential over the north half
of the area Friday night.
Wednesday night through Thursday night: A warm front is expected to
lift northward through the CWA as it initially stretches from around
the NE/SD border eastward to southern WI/northern IL. This will be
ahead of a low pressure system that is expected to eject into/deepen
across Colorado. Ahead of the low and along the warm front, moisture
and warm air advection will increase across the area Wednesday
night into Thursday.
The warm front is expected to continue to lift through the CWA
Wednesday night. This will be the main focus for precipitation
through Thursday morning, before the warm front lifts north of the
area. Models continue to show a LLJ developing ahead of the
deepening low. This would help to increase moisture flow and forcing
up and over the warm front, which would lead to the potential for
heavier rainfall. Current thinking is that a widespread 1 to 3
inches of rain may fall across much of CWA Wednesday night through
Thursday night, heaviest late Wednesday night into mid Thursday
morning and again late Thursday afternoon into Thursday night. PWAT
values are progged to be around 1 - 2 inches for this time period,
which is around 150% to 250% of normal for this time of year. The
CWA is in a slight risk outlook for excessive rainfall Wednesday
night and again on Thursday. The latest 12Z model guidance is in
good agreement that the low pressure center will slide over north-
central WI late Thursday afternoon into Thursday evening. Much of
the CWA, especially the southeastern 2/3 of the area, will be in
the warmer/more moist (dewpoints in the low 70s) sector to the
southeast of the low and ahead of the cold front. Instability is
expected to increase with up to 1000-2000 J/kg ahead of the front
along with deep-layer shear values in the 45 to 55 kt range. Shear
vectors also look to be perpendicular to the cold front favoring
a more organized severe event along and ahead of the cold
front late Thursday afternoon and evening. This setup would favor
more of a linear convective system with the potential for some
bowing segments along the line. While wind gusts will be the main
threat, largely due to rapid storm motions of around 50 kts,
there will also be an isolated tornado threat along the line and
with any storms that pop up in the warm sector ahead of the cold
front. Any isolated storms ahead of the front will also have the
potential to produce large hail. Continued to mention in the HWO.
SPC has highlighted most of the area in a slight risk for severe
storm during that time period.
Rest of the extended: Friday morning, the cold front will be to the
east and southeast of the area as dry high pressure builds in,
allowing for more tranquil and cooler conditions. In fact, provided
that skies clear, chilly overnight lows may allow for patchy to
widespread frost development over the north half of the CWA Friday
night. Otherwise, quiet conditions and drier weather will be in
place through the upcoming weekend as zonal flow remains in place
and only minor disturbances push through the area. The next chance
of showers would be late Sunday into early Monday as a weak low
pressure system quickly slides across the CWA. Consensus worked
well for the weekend into early next week.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1034 PM CDT Tue Sep 18 2018
Cool moist northeast flow will result in plenty of low clouds
across the area. Cloud coverage and ceiling height has become more
variable, and that will probably continue until a more organized
area of rain arrives on Wednesday. Expect some fog tonight as
well. Showers and along with some scattered thunderstorms will
overspread the area tomorrow.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....Eckberg
LONG TERM......Cooley
AVIATION.......Skowronski
Area Forecast Discussion
National Weather Service Grand Rapids MI
755 PM EDT Tue Sep 18 2018
LATEST UPDATE...
Aviation
.SYNOPSIS...
Issued at 300 PM EDT Tue Sep 18 2018
A few showers and thunderstorms are forecast tonight through
Wednesday afternoon. A warm front will lift northward across our
area Wednesday night and bring a much better chance for widespread
thunderstorms late Wednesday night into early Thursday. A cold
front moving in from the west will bring more thunderstorms
Thursday night. Some severe storms with damaging winds and hail
and heavy rain are possible early Thursday and then again Thursday
night. A much cooler and drier airmass will move in behind that
system for Friday through the weekend.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 300 PM EDT Tue Sep 18 2018
Primary short term fcst concerns involve determining potential for
convection through the short term fcst period.
A few showers and perhaps an isolated storm will continue to
develop late this afternoon into this evening along and south of the
weakening cold front that is moving in from the north and is located
near the I-96 corridor attm. Scattered showers and thunderstorms
will develop Wednesday as elevated instability begins to increase
to the north of the warm front.
A much better chance for widespread rain and convection will come
late Wednesday night into Thursday morning as the warm front
lifts to the north and elevated instability ramps up significantly
north of that boundary.
Convection will also develop on the nose of a 30-35 kt llj off to
our west Wednesday night and then roll east along the boundary
into our area. The strongest convection will contain heavy rain
and potentially hail and gusty winds. A few marginally severe
storms are possible overnight.
On Thursday after early morning convection clears out it will
become very warm and humid as the warm front moves north of our
fcst area. Increasing instability out ahead of the approaching
cold front in conjunction with strong deep layer shear and lift
from the approaching front with ample low level moisture in place
will set the stage for convective development Thursday night.
Strongest convection will bring potential for damaging wind gusts
and large hail and heavy rain. There is also potential for an
isolated tornado given ample deep layer shear and favorable speed
and directional wind shear along with low lcl heights. However
the severe wx threat is mitigated by unfavorable cold frontal
timing as well as lack of pva or favorable upper level dynamics.
.LONG TERM...(Friday through Tuesday)
Issued at 300 PM EDT Tue Sep 18 2018
A few showers and storms will linger Friday morning until fropa.
After fropa occurs we expect some instability showers to develop
in the afternoon and evening before high pressure builds in to
bring fair wx Saturday. Temps will average pretty close to normal
for this time of year late in the weekend into early next weekend
as the upper pattern becomes very zonal before ridging begins to
amplify over the eastern CONUS again by Tuesday/Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 756 PM EDT Tue Sep 18 2018
This may end up being one of those nights were low clouds come in
from the east and northeast (off Lake Huron) and cause MVFR cigs
to most of not all of our CWA. I put the low clouds in the LAN
taf site and after midnight in the JXN taf site but those clouds
may be in there much sooner than that. It was questionable if
those clouds would make to GRR, AZO and BTl. That is what the 12z
and 18z run of the NAM is in fact showing. Since the RAP and HRRR
did not show that I did not forecast those clouds to come in but
it is possible. If the clouds do come in they should lift out by
midday Wednesday as the warm air tries to push back in. Convection
should result of the warm air pushing back but that should be
after 00z Thursday.
&&
.MARINE...
Issued at 300 PM EDT Tue Sep 18 2018
Wave heights of around 1 to 3 feet are forecast tonight and
Wednesday and winds will become offshore tonight through
Wednesday. Strong southerly winds will develop Thursday by which
time a small craft advisory will be required through Friday.
Winds could potentially reach gale force Thursday night and
Friday.
&&
.HYDROLOGY...
Issued at 300 PM EDT Tue Sep 18 2018
River levels remain steady following mostly dry weather over the
past week and a half. Coverage of showers and thunderstorms through
Wednesday evening will be isolated to scattered. Although individual
storms may contain heavy rain, flooding is not anticipated through
Wednesday evening.
A higher coverage of rain and thunderstorms is expected late
Wednesday night into Thursday morning. This round looks to bring
between one-half inch and one inch of rain to areas near and north
of a line from Holland to Grand Rapids to Mt Pleasant. Local totals
will be higher in thunderstorms, which will be capable of producing
rainfall rates in excess of one inch per hour. There looks to be
relative lull in activity Thursday afternoon before another round of
showers and thunderstorms moves through the area Thursday night into
early Friday morning. This round will also have the potential
produce rainfall rates in excess of one inch per hour.
The quick-hitting nature of these rounds of heavy rain will be more
likely to cause localized flooding on roads, in low-lying areas, and
along small creeks, than flooding of streams and rivers. Drier
weather is expected Friday afternoon through Sunday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...Laurens
AVIATION...WDM
HYDROLOGY...HLO
MARINE...Laurens
Area Forecast Discussion
National Weather Service Gray ME
1044 PM EDT Tue Sep 18 2018
.SYNOPSIS...
Low pressure will shift east into the maritimes overnight. High
pressure will build in from the north on Wednesday and will hold
over the region on Thursday. A warm front will lift northeast
through the region Thursday night and early Friday followed by a
strong cold front Friday night. High pressure will build over
the area Saturday and will shift east on Sunday.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
1030 pm...Cold front moving SW across ME attm in classic back
door front action, with gusty NE winds as it moves thru, and
low clouds filling in quickly behind it. Models still show it
losing some its forward motion overnight, and greatest cooling
will be in the NE zones, but overall this has been reasonably by
previous forecast, and just some minor changes made.
730 PM...Sfc cold front really slowing as it crosses the CWA,
and producing some showers, most prevalent across central ME and
moving to the mid-coast. Think the front will mosey its way
offshore this evening, but will have to wait for secondary weak
wave aloft to move through to allow enough of a pres gradient to
develop and allow sfc flow to shift NE, which should a more
significant drop in Td and temps after midnight. The somewhat
shallow NE flow behind the front, and beneath weak flow aloft
will allow stratus to develop so, while there may be some
clearing this evening clouds will return later tonight and it
looks like a cloudy Wed morning. Some light showers or sprks
/other than those associated with the front this eve/ are
possible as well tonight, but nothing that would do much more
than wet the ground at best. Lows will range form the low to mid
50s in the N, to the low 60s in srn NH.
Previously...After a busy day tonight will be much more tame. A
S/WV trof and attendant front will push thru the region. At the
surface a cold surge is moving down the St. Lawrence
Valley...and down from The County towards Downeast ME. This will
continue to creep towards our forecast area thru the evening
and overnight. Some low clouds are possible along the coast as
the cooler NE flow arrives...while inland may seem some fog this
evening while it remains clear. Most likely to see the longest
period of clear would be the CT River Valley...where I have
areas of fog in the forecast. Elsewhere is more uncertain...as
clouds move in from the NE.
We will also see continued shower activity along the approaching
cold front...but the majority of these will likely dissipate
after dark.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Lingering trof overhead Wed will provide a focus for some
afternoon clouds and scattered showers...especially early on.
Generally used the multi-model consensus blend for PoP...but
precip will be relatively hit and miss. In NE flow temps will be
much cooler...with readings hanging in the 60s. In the far
SW...near EEN...temps may run at 70...while closer to Moosehead
Lake will struggle into the 50s. Wed night widespread 40s and
50s are expected.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
High pressure will crest over the region on Thursday producing a mix
of sun and clouds and temperatures slightly below normal for a
change. Expect highs to range through the 60s from north to
south.
High pressure will shift east Thursday night as a warm front approaches
the region from the southwest. Will see increasing clouds
during the evening hours and showers will move into the region
from the southwest after midnight. Highest pops will be found in
the better dynamics to the north and west of the forecast area
with rainfall amounts in the .25 to .50 inch range through mid
afternoon Friday in the mountains. Lows overnight will range
from the mid 40s north to the mid 50s south.
Rain will gradually taper to showers from southwest to northeast Friday
morning but expect skies to remain mostly cloudy as abundant
low level moisture lingers behind the warm front. Even though
850 mb temps support upper 70s to lower 80s...clouds will hold
high temps in the mid 60s to mid 70s from north to south.
A cold front will push in from the west Friday evening bringing
another round of showers and some thunderstorms...mainly after
midnight. Good forcing along the front and marginal instability
will produce scattered convection ahead of this boundary. Very
strong shear with the associated shortwave may produce isolated
severe cells with wind damage being the main threat. PWAT`s
ahead of the front will max out in the 1.5 to 2.00 inch range
contributing to heavy downpours and possible downbursts in
heavier cells. Expect the front to quickly push offshore by
daybreak Saturday taking any lingering shower activity with it.
Lows will range from the upper 40s north to the lower 60s in the
south.
Saturday will feature breezy and much cooler conditions as high
pressure builds in from the west. Expect variable clouds in the
morning to give way to mostly sunny skies in the afternoon.
High temps will generally range through the 60s from north to
south.
High pressure will crest over the region Saturday night producing
mostly clear skies and light winds. Low temperatures will range
from the mid 30s in the north to the upper 40s in the south.
High pressure forecast to shift east on Sunday with increasing
onshore flow setting up. This will produce a mix of sun and clouds
in southwest zones and mostly sunny skies elsewhere.
Temperatures will top out below normal ranging from the mid 50s
in the north to the mid 60s in the south.
Models diverge significantly for the latter periods of the
forecast with timing of the next cold front and associated
precipitation...so have generally stuck close to SB numbers.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Short Term...00Z TAF update...Starting to think with shallow NE
flow undercutting, weak flow, and perhaps more moist air aloft,
some MVFR-IFR cigs are possible after midnight tonight and into
Wed morning. They will likely lift somewhat in the afternoon,
but perhaps only to 3500-400 ft.
Previously...Still some areas of broken MVFR CIGs as drier air
filters in from the N. Will likely see all terminals go to VFR
eventually. After sunset the NE flow will bring cooler air down
the coast...and models forecast IFR CIGs to move down from
RKD/AUG thru PWM to PSM. I am not totally sold on widespread IFR
or lower...especially as quick as models like the HRRR show
it...but I have included SCT007 CIGs to show the potential.
Winds will likely be calm enough to see some valley fog in the
CT River Valley...so LEB and HIE have LIFR tonight. Lingering
trof overhead into Wed will lead to some widely scattered
SHRA...but not likely enough at any terminal to include in the
TAF.
Long Term...VFR Thursday. Areas of MVFR/IFR Ceilings developing
Thursday night and persisting through Friday. VFR Saturday and
Sunday.
&&
.MARINE...
Short Term...NE surge is forecast to work down the coast
tonight. Model guidance suggests some gusts above 25 kts and
seas building to 5 ft...so I have issued a SCA into early Wed
afternoon.
Long Term...SCA`s likely Friday through Saturday.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory from 2 AM to noon EDT Wednesday for
ANZ150-152-154.
&&
$$
SYNOPSIS...
NEAR TERM...Cempa/Legro
SHORT TERM...Legro
LONG TERM...Sinsabaugh
AVIATION...
MARINE...
Area Forecast Discussion
National Weather Service Jacksonville FL
847 PM EDT Tue Sep 18 2018
.UPDATE...Isolated showers and storms continue this evening ahead
of a prefrontal trough to the north. Storms are still producing
strong gusty winds with heavy downpours and frequent lightning
strikes. Outflow boundaries with a moist and unstable airmass will
keep a chance of storms til at least midnight across the area.
Latest HRRR model shows storms moving se and finally dissipating
near the ne Fl coast around 07z. Warm and muggy conditions will
result in low temperatures mostly in the mid/upper 70s tonight.
&&
.AVIATION...Have VCTS in forecast til 02z this evening due to
isolated shower and thunderstorm activity continuing...may need
to amend and extend til 04z. Otherwise VFR conditions will prevail
tonight and Wednesday morning. Have VCTS in again Tuesday
afternoon.
&&
.MARINE...Southwest winds up to 15 knot tonight with seas 2 to 4
feet. Winds will become northeast on Wednesday as high pressure
builds to the north.
Rip Currents: Moderate risk through Wednesday.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 72 94 72 92 / 10 10 10 10
SSI 76 91 77 88 / 40 10 10 10
JAX 75 94 75 89 / 40 30 10 10
SGJ 75 91 75 87 / 30 30 10 10
GNV 75 94 73 92 / 10 30 20 30
OCF 74 93 73 92 / 10 30 20 40
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&
$$
Zibura/Sandrik/Enyedi
Area Forecast Discussion
National Weather Service Louisville KY
945 PM EDT Tue Sep 18 2018
.Forecast Update...
Issued at 945 PM EDT Tue Sep 18 2018
Isolated showers have all but dissipated this evening. IR satellite
imagery shows a clear sky over much of our eastern forecast area
(Bluegrass region) with a partly cloudy sky over western counties.
Meanwhile, remnant mid and high clouds are pushing southeast over
eastern MO, IL, and northern IN, and some of these could arrive
overnight into our northern and western counties. Looks like skies
overnight will vary from clear at times to partly cloudy.
The 18z NAM and GFS and an earlier HRRR run suggested that isolated
showers could redevelop over or move southeast into parts of our
west-central KY counties overnight, with possibly some weak forcing
associated with the exit region of an upper-level jet streak as it
pushes E and SE into the Great Lakes and parts of OH Valley.
However, later HRRR runs and the WRF-NMM and WRF-ARW suggest dry
conditions, and model soundings show little low-level or elevated
instability. Thus, will leave our west-central KY counties dry for
now, but cannot rule out an isolated shower late tonight/Wed
morning. A few other showers could occur well N and E of our
forecast area by morning.
Still looks like patchy fog will occur toward daybreak, especially
in river valleys. Model statistical guidance overdid their fog
potential for this morning, and may again be overdone for Wed
morning given model low-level sounding data. Nevertheless, beware of
ground fog and especially near bodies of water before dissipating
quickly after sunrise Wed.
Another very warm/hot day in storm for Wed with afternoon highs near
90 and the lower 90s, a couple/few degrees above guidance.
&&
.Short Term...(This evening through Wednesday)
Issued at 301 PM EDT Tue Sep 18 2018
Afternoon satellite imagery revealed partly cloudy skies across
southern Indiana and central Kentucky. The Cu field was in full
swing and an arc of agitated Cu was seen from SW IN through central
Kentucky. Radar showed isolated-scattered showers from near
Evansville over to just south of Lexington. These storms will
continue to develop through the heat of the afternoon and move
eastward. Afternoon highs will top out in the upper 80s in areas
east of I-65. For points west of I-65, highs in the upper 80s to
the lower 90s are expected. The urban areas will be slightly warmer
with Louisville likely topping out in the 92-93 degree range.
As we move into the evening hours, instability will decrease with
the setting sun. Temperatures should cool into the upper 70s to the
lower 80s by mid-late evening with skies clearing out overnight.
Models still hinting at fog towards dawn. Have gone ahead and added
patchy fog to many locations, but hit the river valley locations
harder as they should fog up overnight. Lows are expected to drop
into the mid-upper 60s.
For Wednesday, upper level ridging is forecast to build into the
region from the west. This should result in a drier weather pattern
for much of the region. Still could see an isolated storm develop
during the afternoon, but coverage should be less than what we saw
this afternoon. Right now, coverage looks to be less than 15
percent, so we plan on going with a dry forecast for now. Wednesday
will be another warm/muggy day with afternoon highs in the 85-90
degree range east of I-65. In areas along and west of I-65, highs
in the upper 80s to the lower 90s are expected again.
.Long Term...(Wednesday night through Tuesday)
Issued at 300 PM EDT Tue Sep 18 2018
At the beginning of this time period models are in agreement with an
upper level ridge placed over Arkansas and a longwave trough along
the West Coast. Model agreement continues through the week as the
aforementioned ridging builds toward the East Coast, and the
upstream upper level trough makes its way to the Great Lakes. At
this point the models diverge as to the placement of a stalled front
extending across our region.
Wednesday Evening and Thursday...Expect unseasonably warm with high
temps in the upper 80s and lower 90s. Dew points in the upper 60s to
low 70s will continue our summer trend of muggy discomfort. Expect
mostly sunny skies with diurnally driven cu to develop each day.
Friday and Saturday...The upper level trough will sweep across the
Great Lakes on Friday. In doing so, it will degrade the ridging over
the SE U.S. allowing for increased chances of showers and storms
ahead of a surface cold front extending NE to SW across the region.
Severe weather is not expected at this time as buoyancy and shear
values are low with most of the energy remaining well to our north.
SPC shows a 15% chance of severe weather just north of our forecast
area, stretching from central IN through OH and clipping northern
KY. Here`s where the models start to disagree. GFS and Canadian
models stall the frontal boundary to our south over TN, whereas
ECMWF stalls the boundary over KY. Each scenario allows for short
waves to influence our forecast area by way of increased chances of
showers and storms...a bit less with GFS/Canadian and a bit more
with ECMWF. Will side with WPC`s decision to blend the GFS and ECMWF
at this time. Expect temperatures to lower towards climo with
increased cloud cover and precipitation.
Sunday through Tuesday...The stalled frontal boundary across the
region will allow short waves to pulse through bringing chances of
showers and storms each day, especially during periods of diurnal
heating.
&&
.Aviation...(00Z TAF Issuance)
Issued at 730 PM EDT Tue Sep 18 2018
The current clouds and showers around the CWA should start to
diminish as sunset nears. Kept things VFR at all TAF sites through
the forecast period. Don`t expect fog to be much of an issue. If fog
forms, it is expected to be light with little impact to aviation.
Winds will remain light to calm.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update.......TWF
Short Term...MJ
Long Term....CG
Aviation.....KDW
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1032 PM CDT Tue Sep 18 2018
.Updated for 06Z Aviation discussion...
Issued at 1029 PM CDT Tue Sep 18 2018
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 350 PM CDT Tue Sep 18 2018
Dry conditions resumed by the afternoon after the widespread 0.5-
1.0" of rainfall over Southern MN. Northern Renville County received
3+ inches of rainfall this morning. Widespread stratus has been in
place over Central MN and West Central WI this afternoon with an
inversion above a moist boundary layer. Skies are expected to remain
mostly cloudy through the overnight with precipitation expected
across Southern Minnesota by early Wednesday morning.
Warm air advection will continue overnight with a mid-level
shortwave expected to cause elevated thunderstorm development. The
18Z RAP has 1000-1500 J/kg of MUCAPE for Southern MN. There is a
possibility for hail over the South Central MN Wednesday morning,
but the RAP and NAM indicate that the 8 C/km mid level lapse rates
may remain to the east and south of the forecast area. The largest
concern will be excessive rainfall with 1.5-2" precipitable water
values. Precipitation chances continue throughout the day as a cold
front approaches from the north and the boundary over Iowa
progresses toward the MN/IA border.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 345 PM CDT Tue Sep 18 2018
...Potential of Several Inches of Rainfall Wednesday night, through
Thursday night...
Atmospheric conditions are coming together for allowing several
rounds of very heavy rainfall from Wednesday night, through Thursday
night. The only concern is where the focus of the heaviest rainfall
will occur, especially once the main bands of convection develop
along and north of a warm front Wednesday night, and Thursday.
Based on the latest information, the initial wave of storms will
focus just north of the warm front late Wednesday afternoon/evening
across southern Minnesota. Once the low level jet intensifies, the
warm front will likely lift northward with the heaviest bands
developing in central/east central Minnesota, and west central
Wisconsin by Thursday morning. There are always differences of where
the low level jet develops, where the warm/cold front lie, and where
some of the earlier outflow boundaries from convection remains. But,
but confidence in this forecast has increased that several inches of
rain will occur over the region before Friday morning.
One of the main reason for high confidence in the excessive rainfall
probability was the aspect of the relatively very moisture and
anomalous precipitable water values developing. Currently, -NAEFS-
precipitable water anomalies are 3-4 standard deviations above
normal, which equates to 200-250% above normal for this time of
year. Thus, any storms that develop will be very efficient for high
rainfall rates.
Behind this system, a couple of cool days are forecast with highs
back in the 50s/60s, and lows in the 30s/40s. I wouldn`t be
surprised to see patchy frost in central, east central Minnesota,
and west central Wisconsin Saturday morning where high pressure will
settle over the region.
The cool period will be short lived as another storm system begins
to organize across the Rockies, and into the Plains, Upper Midwest
early next week. Temperatures will likely rebound into the 60s/70s
with increasing humidity levels. This pattern of a fast west to east
flow aloft will continue through at least early next week.
Beyond the 7 day period, there are signs and trends in the models
that a pattern change is possible. The models are advertising a
western North America ridge developing (+PNA) by late next week.
This will allow northwest flow aloft to develop across the Rockies,
and into most of the northern tier of the nation. This type of
pattern is conducive for cooler, and drier weather.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1029 PM CDT Tue Sep 18 2018
No major changes to the TAF. MVFR/IFR conditions expected as low
clouds linger across the region tonight. Showers and thunderstorms
should develop later tonight. There are chances for thunderstorms
most of the day on Wednesday, but the best chance will be across
the south at KRWF and KMKT. The main threat is Wednesday evening
and night. Winds will be east/northeast.
KMSP...
MVFR/IFR conditions. Ceilings should stay below 1700ft for most of
the TAF duration. Best chance for showers and thunderstorms is
Wednesday morning. Most of the storms should be to the south, so
did not mention thunder in the TAF during the morning. We expect
storms to redevelop again Wednesday evening.
/OUTLOOK FOR KMSP/
Thu...MVFR with IFR/RA possible. Wind ENE becoming NW at 20G25
kts.
Fri...MVFR. Wind NW 15G25 kts.
Sat...VFR. Wind S at 10G20 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...AMK
LONG TERM...JLT
AVIATION...JRB
Area Forecast Discussion
National Weather Service Tucson AZ
350 PM MST Tue Sep 18 2018
.SYNOPSIS...Abundant moisture will provide widespread showers and
thunderstorms especially Wednesday into Wednesday night. Heavy
rainfall should occur at times. Rainfall chances decreasing Thursday
before dry conditions return across much of the area this weekend
into early next week. Much cooler temperatures Wednesday into
Thursday followed by a warming trend this weekend.
&&
.DISCUSSION...Isolated to scattered showers and thunderstorms were
occurring east to south of Tucson at this time. The best
concentration of showers and thunderstorms was across Santa Cruz
County as per several HRRR solutions earlier today. Isolated to
scattered showers and thunderstorms will occur tonight, with the
greatest coverage likely southeast to south of Tucson.
Various 18/12Z numerical weather prediction models suggest that
numerous showers with at least embedded thunderstorms will occur
Wednesday into Wednesday evening. The NAEFS total precip water
anomaly depicts generally 1.5" - 2.0" across this forecast area
Wednesday, and these values are in the 99th percentile for
Wednesday.
In addition to the abundant moisture progged across the area, a deep
southerly flow regime should occur Wednesday as strong high pressure
aloft shifts eastward into Arkansas, and an upper trough moves
eastward into the Great Basin. Diffluence aloft ahead of the
approaching trough in combination with abundant moisture prompted
the issuance of a Flash Flood Watch earlier today for all of
southeast Arizona, in effect from Wednesday morning through
Wednesday evening.
As flow aloft becomes more westerly Thursday, precip chances and
coverage should decrease especially from Tucson westward into
western Pima County. Expect scattered showers/tstms Thursday
especially east of Tucson, then isolated showers/tstms Friday mainly
east of Tucson. Thereafter, global models depict high pressure aloft
to build over the southwestern CONUS Saturday, then somewhat
stronger westerly flow aloft is progged to occur next Monday into
Tuesday. This flow regime should support markedly drier conditions
across the area. Thus, have opted for precip-free conditions Sunday
into next Tuesday.
Markedly cooler temps will occur Wednesday given the increased
moisture and rain chances. Forecast confidence is somewhat low
regarding high temps Wednesday due to a continued fairly wide range
amongst guidance values. A warming trend will then occur Thursday
into Sunday followed by no significant change in daytime temps
Monday and Tuesday.
&&
.AVIATION...Valid through 20/00Z.
Scattered -TSRA/-SHRA mainly east to south of KTUS through tonight,
then numerous TSRA/SHRA across much of southeast Arizona Wednesday.
Expect MVFR and possible brief IFR conditions Wednesday with the
stronger TSRA. Otherwise few to broken clouds around 8k-12k ft AGL
tonight then cloud decks generally 5k-10k ft AGL Wednesday. Surface
wind variable in direction mainly less than 12 kts except gusts near
40 kts with TSRA. Aviation discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Scattered to numerous showers and thunderstorms
Wednesday into Wednesday night. Heavy rainfall should occur at
times. Scattered showers and thunderstorms Thursday especially east
of Tucson followed by isolated showers and thunderstorms Friday into
Saturday mainly east of Tucson. Dry conditions to occur Sunday into
next Tuesday. 20-foot winds will be terrain driven mainly less than
15 mph. However, gusty and erratic winds with thunderstorms may
occur at times.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from Wednesday morning through Wednesday
evening for AZZ501>515.
&&
$$
Francis
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