Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/18/18

Area Forecast Discussion

National Weather Service Gaylord MI

 1150 PM EDT Fri Aug 17 2018

.UPDATE...
Issued at 957 PM EDT Fri Aug 17 2018

Last of the diurnal convection (near and s of W Branch) has faded
out over the last hour. Maybe a small shower can still fire for
another hour or so, but otherwise we are mostly done with precip
for the night. Most recent Rap run does pop a few showers over
Saginaw Bay toward morning, perhaps due to converging land
breezes. This does not require a mention of shower, at least over
land.

Have expanded the mention of fog across all of northern MI
overnight. Airmass remains plenty soupy (especially in northern
lower), and cloud cover is exiting east (though we might have
enough smoke overhead to inhibit cooling to some degree).

No big changes to temps.

&&

.NEAR TERM...(Through Tonight)
Issued at 340 PM EDT Fri Aug 17 2018

...Showers and Thunderstorms Into the Evening...

High Impact Weather Potential: Thunderstorms through early evening.
Mostly non-severe, although a stronger storm/updraft could produce
hail...along with heavy rain.

Pattern Synopsis/Forecast: Slow moving closed low is over
Chicago/southern Lake Michigan, associated broad surface low
pressure is across far southern Ontario. Showers and some
thunderstorms with this system continue across central lower
Michigan back into Wisconsin within the associated deformation
axis, just skirting our far southern counties.

Further north, lots of mid/high cloud cover has spread up into
northern lower Michigan, mainly south of M-32. SPC mesoanalysis
reveals in excess of 500 J/KG MLCAPE across the southern counties.
Some convection is now developing along the differential heating
boundary that bisects northern lower MI currently. Strongest
updrafts so far (supporting some elevated hail cores in the last
hour) have been (of all places) in Benzie/Manistee counties,
where the intersection of the Lake Michigan marine boundary has
helped.

Tonight: Closed mid-level circulation over the Chicago area still
expected to open up and advance through lower Michigan through
this evening. Band of showers/thunder associated with attending
deformation axis will largely stay to our south, clipping the
Gladwin/Arenac counties area.

Meanwhile to the north, as noted, convection has started along
the differential heating boundary that bisects northern lower
Michigan and will likely continue to percolate/meander across
northern lower Michigan over the next few hours before diminishing
this evening. Always tough to know exactly how convection will
ultimately unfold. But I suspect the bulk of showers/storms will
tend to contract inland and south over the next few hours.

Severe weather potential: Relatively light winds aloft, minimal
ambient shear, and higher freezing levels suggest a low severe
storm threat. But, as we`ve seen, strongest updrafts can support
marginally severe hail. And, slow moving/back building updrafts
will result in localized heavy rain. Will mention those in the
HWO.

&&

.SHORT TERM...(Saturday through Monday)
Issued at 340 PM EDT Fri Aug 17 2018

Saturday through Sunday

...Despite the Small Rain Chances Saturday the next Round of Dryness
Begins...

High Impact Weather Potential...Thunderstorms, but nothing severe
expected.

Pattern Synopsis/Forecast...Models then begin to show another
"wiggle" in the 500 mb height fields for rain to be possible, but it
looks a lot less impressive than today`s convection, and yesterday`s
convection. Things diminish quickly by the evening and dry out
overnight. On Sunday, the high is built into the region, drying out
the state. The high continues over the region through the night.

Primary Forecast Concerns...Again is the thunder potential on
Saturday, Most of the models are pegging the area near M-55 and I-75
as where the convection would occur. While the consensus is in that
area, the ECMWF and the GFS have a broader coverage to the
convection Saturday. So, there is a lower chance that it will be
over portions of N Lower.

.LONG TERM...(Monday night through Friday)
Issued at 340 PM EDT Fri Aug 17 2018

...Rain on Monday night/Tuesday then Pretty Much Dry through
Friday...

Extended (Monday through Friday)...The ridge breaks down Monday,
allowing a cold front and the 500 mb low trough to move into the
region. It looks like thunder will be possible as the cold front
moves into the area Monday night/Tuesday morning. Then the models
show a decent band of rain on the north side of the sfc low in a
deformation zone producing some rain, possibly heavy at times, as
the system move NE through the State. Will continue the cautious
optimism as the models are holding onto this feature, but details
are still a little less certain. As the GEFS plumes show the mean
over GLR just under 0.5", but the GFS model, itself showing 1.4" and
is the furtherest outlier. However, the latest ECMWF is also showing
over an 1" of rain in Gaylord, as well. So it looks like a good
soaker, but not sure about the heavy amounts that the deterministic
models are trying to produce. Wednesday through Thursday are dry,
then scattered rain on Friday so low chance pops there.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1150 PM EDT Fri Aug 17 2018

Some fog again overnight, otherwise VFR.

Still expecting some fog overnight, with similar conditions to
last night progged (IFR at times PLN, MVFR MBL/APN, no issues at
TVC). Airmass remains muggy, and though some smoke aloft will
limit cooling, ground fog is still expected. Additional showers/
storms will fire Saturday afternoon in some interior sections of
northern lower MI, but these should be inland from all of the TAF
sites.

Light northerly breezes.

&&

.MARINE...
Issued at 340 PM EDT Fri Aug 17 2018

Lighter winds and waves will continue to dominate over the next
few days. No marine headlines anticipated.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...JZ
NEAR TERM...BA
SHORT TERM...JL
LONG TERM...JL
AVIATION...JZ
MARINE...BA



Area Forecast Discussion

National Weather Service Bismarck ND

 949 PM CDT Fri Aug 17 2018

.UPDATE...
Issued at 945 PM CDT Fri Aug 17 2018

Did add a mention of fog to the James River Valley tonight into
early Saturday morning with greater moisture in place with
dewpoints in the lower 60s. Otherwise, little change to the
forecast from the previous update.


UPDATE Issued at 654 PM CDT Fri Aug 17 2018

Little change with this update. It would appear that smoke will
remain for the most part lofted across the area through at least
Saturday, with perhaps an increase in near surface smoke possible
behind a surface trough and cold front that will enter western
North Dakota Saturday afternoon, and continue to propagate east
into the evening. This is favored by the 18 UTC experimental HRRR
smoke forecast. Smoke impacts to surface temperatures and
convection initiation will continue to be evaluated for Saturday.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 240 PM CDT Fri Aug 17 2018

The main concerns for the short-term forecast are smoke and
increasing chances for showers and thunderstorms Saturday afternoon.

Surface observations, webcams, and satellite imagery show a thick
veil of smoke covering all of North Dakota this afternoon. The most
dense smoke is located aloft - around 10,000 ft above the surface
per pilot reports. So while surface visibility has not been reduced
below 5 miles by the smoke, the sky has had a partly to mostly
cloudy appearance all day, despite few clouds to speak of. In
addition, the smoke has kept temperatures as much as 5-10 F below
model guidance this afternoon. It is not entirely clear how long the
smoke will remain this thick. Conditions look slightly improved
upstream across northern MT and southern SK, but recent HRRR and RAP
vertically integrated smoke actually increase concentrations tonight
into Saturday. Will maintain up to widespread smoke mention through
this afternoon, areas of smoke tonight, and patchy smoke Saturday,
though adjustments may be needed.

Upper-level ridge currently sits over the Northern High Plains. A
weak disturbance is forecast to move across southern Saskatchewan
into southern Manitoba tonight. A few CAMs and the GFS have been
producing some QPF associated with this wave across northwest into
north-central North Dakota. However, model soundings show a very dry
boundary layer with CCL heights above 10,000 feet. Very low
confidence that any precipitation would make it to the ground before
evaporating, so will maintain a dry forecast for now.

Farther upstream, a deepening upper-level low has made its way into
the Pacific Northwest and will continue to propagate eastward toward
the Northern Plains on Saturday. Surface cyclogenesis, low-level
frontogenesis, and increasing moisture ahead of the upper low should
lead to shower and thunderstorm development over the western Dakotas
late Saturday afternoon. Instability (1500-2500 MUCAPE) will be
sufficient for strong, possibly isolated severe storms, but weak
deep layer shear (around 20 kts) will be a limiting factor for
severe weather.

Meanwhile, a surface cold front attendant to a shortwave trough
crossing central Saskatchewan will move southeastward into northwest
and north central North Dakota by Saturday evening. Could see
isolated to scattered storms along this boundary as well, but
stronger storms appear less likely here due to weaker instability.

.LONG TERM...(Saturday night through Friday)
Issued at 240 PM CDT Fri Aug 17 2018

The southeast-advancing surface cold front will interact with the
upper-level low slowly drifting eastward across SD/NE Saturday night
into Sunday. This will keep shower and thunderstorm chances in the
forecast for all but northwest ND Saturday night, then decreasing to
the southeast for Sunday. With cool, Canadian high pressure settling
in and a transition to northwest flow aloft, highs will be limited
to the 70s Sunday through Tuesday, with widespread lows in the mid
to upper 40s.

Long-range guidance is in agreement with a shortwave trough moving
through the area late Monday. With a stable air mass in place,
only showers would be possible, and it`s a slight chance at best.
Tuesday and Wednesday look to be dry as an upper-level ridge axis
approaches the Northern Plains. Another shortwave trough is then
forecast to move through late Wednesday into Thursday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 945 PM CDT Fri Aug 17 2018

Patchy fog may develop across the James River Valley tonight into
early Saturday morning where dewpoints are highest across western
and central North Dakota, possibly impacting KJMS. Significant,
thick lofted smoke will continue across western and central North
Dakota into Saturday. Near surface smoke reducing surface
visibility may increase from west to east Saturday afternoon and
evening behind a surface trough and cold front. Scattered rain
showers and thunderstorms will also develop along these surface
features Saturday afternoon and into the night.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...PA
SHORT TERM...Hollan
LONG TERM...Hollan
AVIATION...PA



Area Forecast Discussion

National Weather Service Detroit/Pontiac MI

 1158 PM EDT Fri Aug 17 2018


.AVIATION...

Wind directions have uniformly turned to the northwest or west in
all location which has begun the drying out process of the
atmosphere. Plan view progs suggest a slow drying response this
evening, increasing now after 06Z. Deep downward motion is
forecasted with building surface high pressure. However, subsidence
inversion is not overly impressive and some diurnal instability will
exist Saturday afternoon. Model trends are now suggesting some
greater static stability in the midlevels. Dry conditions
anticipated today.

.DTW THRESHOLD PROBABILITIES...

* Low for cigs aob 5kft overnight, medium Sat afternoon.

&&

.PREV DISCUSSION...
Issued at 338 PM EDT Fri Aug 17 2018

DISCUSSION...

Extensive cloud cover remains in place over the area as the upper
low near Chicago slowly makes its way east. Clearing over northern
IN and southwest Lower MI has fostered modest destabilization and
subsequently allowed showers and thunderstorms to develop in that
area. This activity will spread into the the Detroit Metro area and
points south and west into the evening as renewed warm and moist
advection lifts into the area and larger scale dynamic forcing
increases. In the meantime, mediocre convection will likely continue
to flare up at times within areas of enhanced boundary layer
convergence. Further north, more organized mesoscale forcing will
still pose a threat for locally persistent heavy rain. However, the
lack of destabilization to this point, HRRR analysis indicates just
a few hundred J/KG MLCAPE, suggests the outcomes indicated by the
12z suite are highly unlikely. Instead, maintained likely to
categorical pops and will simply highlight a locally heavy rain
threat potentially leading to poor drainage or urban flooding.

Little in the way of airmass change between now and Sunday as H850
temps hover in the mid teens within mean troughing regime. Scouring
out of today`s moisture will limit convective potential,
particularly as mid-level temperatures warm, favoring just diurnal
cu-up Sat and Sun aftn as high temps settle in the low 80s with a
decent coverage of upper atmosphere smoke worthy of an upward nudge
in the sky grid.

Midlevel ridging will remain in place on Monday as surface high
pressure drifts northeast into New England, allowing for a dry
Monday morning and afternoon for our area. Highs near normal in the
lower 80s and light southeasterly winds expected. A shortwave
currently moving over the Pacific Northwest will make its way into
the central Plains by this weekend and interact with additional
upper energy dropping in from the Canadian Prairie provinces on
Tuesday, resulting in a strengthening mid-latitude cyclone moving
into the Great Lakes by late Monday night. Long range guidance has
begun to converge on a solution suggesting the center will track
through lower Michigan during the day Tuesday. Chance for showers
and thunderstorms increases Monday evening and lasts through the day
Tuesday.

A broad area of high pressure will build back in on Wednesday and
maintain influence over the area through the rest of the work week,
allowing quiet weather to prevail. The early week system will pull a
good amount of cooler and drier air southward from Canada, leading
to highs in the mid to upper 70s Tuesday through the end of the week.

MARINE...

A weak secondary area of low pressure tracking across Lower Michigan
will maintain showers and thunderstorms this evening before exiting
the region tonight. In its wake, weak high pressure will build
across the Great Lakes bring dry weather for the weekend. Light to
moderate northerly flow will prevail through the weekend, with peak
gusts limited to around 15 knots.

HYDROLOGY...

A secondary low pressure system moving across Lower Michigan will
bring scattered to numerous showers and thunderstorms through this
evening. Rainfall amounts will generally range from a quarter to a
half of an inch, with locally higher amounts associated with
thunderstorms. The flooding threat will be minimal, with ponding of
water on roadways and localized minor poor drainage flooding briefly
possible where the heaviest rainfall occurs. Outside of an isolated
shower Saturday afternoon, the weekend will feature dry weather with
weak high pressure building across the region.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

AVIATION.....CB
DISCUSSION...JVC/TF
MARINE.......JD
HYDROLOGY....JD


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.




Area Forecast Discussion

National Weather Service Glasgow MT

 852 PM MDT Fri Aug 17 2018

.DISCUSSION...
Previous forecast was generally in good shape. Main changes were
to add "patchy smoke" wording in for tomorrow and tomorrow night,
and lower/remove the POPs that were in there in/around Roosevelt
and northeastern McCone Counties. The experimental HRRR Smoke
model continues to suggest smoky/hazy conditions persisting, with
upper level winds continuing to direct whatever smoke their is
aloft coming from Washington and California towards us.

Temperatures got a slight touchup, too, but nothing extraordinary.

Avery

Previous Discussion...
There will be a change in the weather pattern by Saturday as a
short-wave upper-level trough moves across the Divide. This
pattern will bring a cold front to the area that will generate
isolated to scattered general thunderstorms, and rain showers.
With winds shifting to the north and diminishing heights,
temperatures will trend back closer to normal for Saturday. As the
short-wave trough and storms further descend into the Central
Prairie, cooler air flows in behind, with temperatures dropping
below normal. Expect highs in the mid to upper 70s for Sunday.
Templer

Previous Discussion for next week:
For Monday, current high temperature forecasts show readings into
the lower 70s, some 10 degrees below average or so. Thus,
northeast Montana can expect a little relief from the above
average temperatures late this week that are presently underway.

For the middle of next week and beyond, due to the usual increase
in model solution spread and associated uncertainties, the
forecast was trended toward consensus model blends. This resulted
in a gradual uptick in temperatures along with dry weather across
the CWA. Maliawco


&&

.AVIATION...
VFR conditions are expected. Also hazy conditions are expected at
times with patchy smoke across the region from upstream
wildfires. It is possible that the smoke could lead to MVFR
visibilities at times over area terminals, but prolonged periods
of reduced visibility are not currently expected. A change will
occur Saturday with a short-wave trough and cold front moving over
the Divide. There will be the possibility of isolated to scattered
thunderstorms and rain showers.
Wind: southerly tonight at 10-15kt becoming VRB. Saturday wind
will shift to the north and increase to 10-15kt.


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

weather.gov/glasgow



Area Forecast Discussion

National Weather Service Hastings NE

 659 PM CDT Fri Aug 17 2018

.SHORT TERM...(This evening through Saturday)
Issued at 203 PM CDT Fri Aug 17 2018

Aloft: RAP dynamic tropopause maps and upr-air data show fairly
weak flow over the CONUS with the main belt of Westerlies zonal
over Canada. Low-amplitude NW was over the Cntrl Plns with a
shortwave ridge over the Nrn Rckys and a shortwave trof over the
Pac NW. These features will progress E thru tomorrow...with the
ridge moving overhead tonight and tomorrow...as the trof crosses
the Nrn Rckys.

Surface: High pres extended from Ontario SW to OK. There was
little else to speak of. This high will weaken and slowly creep E
of the CWA tomorrow AM.

Rest of this afternoon: p-m/sunny. Light winds. Another day of
cooler than normal temps.

Tonight: M/clear with just a few patches of cirrostratus drifting
thru. Probably some patches/areas of fog again toward sunrise.
Lows near normal. Very light/calm winds.

Sat: Any early fog dissipates by 9 AM. Should be p-m/sunny again.
Near normal temps. Light winds.

.LONG TERM...(Saturday night through Friday)
Issued at 203 PM CDT Fri Aug 17 2018

Aloft: The flow will be progressive thru next Fri. The mdls are
in good agreement that the Nrn Rckys trof will deepen as it slides
SE...forming a low that will cross Neb/KS Sun. Moderately-
amplified NW flow will then develop Mon-Tue as the low moves into
the Ern USA. A new low will form over the Pac NW this wknd. This
low (or its remnant trof) is fcst to be kicked E Wed and into the
Nrn Plns Thu. A shortwave ridge will precede it here on the Cntrl
Plns Wed followed by zonal flow Thu-Fri...as the trof will remain
N of the rgn.

The last 2 runs of the EC/GFS/UKMET/GEM are in good agreement...
suggesting above normal confidence.

Surface: A stationary front currently extended from the TX
Panhandle to MI. Low pres will form on this front over OK Sat
night. This low will move NE across the mid MS vly Sun-Mon and
into the GtLks Tue. Meanwhile...a Canadian cool front will
gradually sink S and merge with the low pres sys...probably
crossing the CWA Sun night. Cool sector Mon. High pres arrives
Tue. Return flow will develop Wed as the high departs into the OH
Vly. Low pres is fcst to form over SD by 12Z/Thu with a developing
warm front extending S thru Neb/KS. The warm front will move thru
putting the CWA into the warm sector Fri while the low moves E.
The associated cool front is currently fcst to remain N of the
CWA. This scenario Thu-Fri is a bit shaky and will probably change
a bit based on what happens aloft.

Temps: The way things look now...much cooler than normal Sun-Tue
with widespread 70s with high confidence. Some recovery Wed-
Thu...but still a bit below normal. Then near or possibly above
normal Fri. Confidence is medium Wed-Fri.

Tue is looking like a gem of a day...with low humidity/dwpts in
the 50s to near 60.

Precip: widespread beneficial rain is probable for much of the
CWA...but as always some locations will get more than others. Some
localized pockets/swaths of 1.5-2.0" are on the table. Mesoscale
details will determine where...including where the deformation
zone/comma head precip sets up...and convective elements/
downpours. WPC is highlighting the SE 1/3 of the CWA for the
heaviest rainfall.

Most of the rain will fall Sunday into Sunday night. Spotty
mostly diurnal shwrs could linger into Mon.

Instability/shear Sun will be insufficient for svr tstms due to
extensive cloudiness and light winds. SREF MLCAPE is fcst to
remain below 1000 J/kg and 0-6 km shear will be 10-15 kt.

The fcst may not have enough POPs/thunder Tue night thru Thu as
warmer air and rich moisture return to the area. Watch for changes
as spotty tstms will be possible at times.

&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday)
Issued at 636 PM CDT Fri Aug 17 2018

A few passing clouds are expected overnight with the convection to
our west expected to fizzle out well before it reaches the local
terminals. With mostly clear skies and light winds expected
overnight...could see some patchy BR develop...and maintained
some MVFR VSBYS for a few hours overnight to account for this.
Otherwise...a weak pressure gradient will remain in place to start
the day Saturday...with increasing clouds late in the period
ahead of the next disturbance forecast to impact portions of the
local area late Saturday night through Sunday.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&

$$

SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...Rossi




Area Forecast Discussion

National Weather Service Grand Junction CO

 536 PM MDT Fri Aug 17 2018

.SHORT TERM...(Tonight through Saturday night)
Issued at 330 PM MDT Fri Aug 17 2018

Active weather is expected over eastern Utah and western Colorado
from tonight through Saturday night. PWAT values have finally
risen to over 1 inch as of today`s morning sounding at GJT with
higher values farther south. This increase in moisture content has
allowed for numerous showers and thunderstorms to develop
throughout much of the higher terrain as expected. Convection
will diminish in intensity this evening, but short-term guidance
does indicate some instability lingering through the night
especially south of US 50. Cloud cover as well as shower activity
will likely linger for much of the night.

Early on Saturday morning, a shortwave trough will approach from
the northwest. A frontal boundary associated with this trough
will dive south and eastward through Utah and Colorado, entering
the Uinta mountain range just after midnight and exiting to the
south of the San Juan Mountains by around 4pm on Saturday
afternoon. If this front were only a handful of hours slower, this
system would pose a legitimate severe weather threat across the
western slope given strong forcing along the front, upper- level
support for lift, and stronger wind shear due to an approaching
jet streak aloft. However, the missing ingredient tomorrow will be
instability, as this trough/front will pass too early in the day
to take advantage of peak heating and prefrontal moisture content.
That being said, a low-CAPE/high-shear threat (relatively
speaking for the western slope) will evolve during the morning
hours as this front marches southeastward. CAMs are in excellent
agreement on the timing of this system, indicating FROPA in Grand
Junction around 8am, Montrose by 10am, and Durango by 1pm or so.
The potential for strong, gusty winds along this boundary and
briefly heavy rain will still exist, despite lower instability
values in the early morning. Farther south, enough heating will
occur through late morning to result in a potential severe weather
threat from Montrose southward through the San Juan Mountains.
CAM guidance indicates anywhere from 1000-1500 j/kg of SBCAPE by
noon, with around 25 knots of 0-6 km speed shear at the same time.
The threat for stronger thunderstorms will end after the front
exits east of the Continental Divide after 4pm. Overall,
confidence in both the timing and thunderstorm threats on Saturday
is high. As is usually the case with very defined frontal
boundaries, dProg/dT analysis of recent HRRR and NAM Nest runs was
essential for timing this event.

.LONG TERM...(Sunday through Friday)
Issued at 330 PM MDT Fri Aug 17 2018

Dry weather works in behind this front for Sunday and Monday as
northwesterly flow resumes behind the departing trough. By
midweek, high pressure redevelops in the southwestern CONUS and a
more typical monsoon flow pattern becomes established. PWAT values
in the medium range steadily rise through the period as
southwesterly to westerly flow builds over the Four Corners. After
a dry start to the week, increasing chances for shower and
thunderstorm activity will be the main weather concern by midweek.
Another shortwave trough skirts by to the north on Friday evening,
but at this time it appears as though this system will have a
limited impact on monsoonal flow.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 533 PM MDT Fri Aug 17 2018

Overall VFR conditions will dominate the forecast over the next 24
hours. There are still some passing showers and storms which could
impact a few TAF sites through sunset before clearing. Expect
early morning showers to move back in from the East...associated
with a system passing through. Again isolated to scattered showers
and storms are possible through mid to late afternoon. Confidence
not high for impacts to specific TAF sites attm so vicinity will
have to pass for now.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

SHORT TERM...MAC
LONG TERM...MAC
AVIATION...TGJT



Area Forecast Discussion

National Weather Service Grand Rapids MI

 1159 PM EDT Fri Aug 17 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EDT Fri Aug 17 2018

Low pressure passing across southern Lower Michigan this evening
will bring scattered showers and thunderstorms, some containing
torrential downpours. The showers will end overnight, then a
mainly dry and warm weekend is expected.

A significant storm by August standards will pass through the
Great Lakes Region Monday night and Tuesday, bringing widespread
rain and thunderstorms followed by windy conditions. Dry, cooler,
and comfortable late summer weather will follow behind that
system for the rest of next week.

&&

.UPDATE...
Issued at 1008 PM EDT Fri Aug 17 2018

Showers have all but ended across the forecast area at 1000pm. An
isolated shower will remain possible for another hour or two from
roughly I-96 to the south, but for the most part expecting dry
conditions.

Next question will be cloud cover, which is more widespread across
the south at this time. The cloud cover in the south is directly
related to the upper trough being situated across that area. In
general expect clouds to decrease even across the south, at least
initially. The concern is that as the cloud associated with the
upper trough begin to push south we develop stratus in a cooling
but moist boundary layer. Hi-res models are becoming more bullish
on low clouds filling in from AZO to LAN and points to the east of
that line. Patchy fog is also expected as the surface winds will
be light through the night.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 330 PM EDT Fri Aug 17 2018

Combination of the upper low tracking through this evening and
very moist air mass with PWATs around 1.7 inches will result in
a continuation of showers and tstms with torrential rain. The
showers will be very slow movers so a localized flooding risk
will exist over the next several hours as diurnal heating cycle
peaks. Hard to nail down where best threat of flooding may be,
although latest radar trends and HRRR suggest one area along/near
I-94 and another from roughly Ionia to Flint.

System moving out overnight so showers ending with decreasing
clouds from northwest to southeast. The north flow behind the
system is rather weak so doubt that the current dew points near
70 will drop off much overnight. That may lead to areas of fog
developing again as skies clear, particularly where heavy rain
occurs through 10 PM.

On Saturday full sun is not expected. The combination of diurnal
cumulus clouds and a relatively thick smoke layer aloft should
lead to a partly cloudy/hazy sunshine type of day. Isolated
afternoon/early evening showers cannot be completely ruled out on
Saturday. Less risk of diurnal clouds and isolated showers on
Sunday, although some smoke may still be present aloft.

.LONG TERM...(Monday through Friday)
Issued at 330 PM EDT Fri Aug 17 2018

Confidence continues to increase that a deepening sfc low
will be tracking through the area on Monday night and Tuesday.
Impacts will be widespread much needed rain then windy
conditions as the low pulls away. A severe weather threat may
develop Tuesday as the sfc cold front comes through, but timing
of things and specifics still uncertain. Deep layer shear of
around 35 kts is progged, although amount of instability unclear
given expected high coverage of clouds/precip. This will be
something to watch in the coming days. Regardless of cold frontal
timing, marine impacts should be significant in the strong NW flow
and cold advection behind the front Tuesday afternoon and Tuesday
night. Weather then turns quiet for mid to late week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1153 PM EDT Fri Aug 17 2018

A mix of VFR/MVFR conditions at the moment will gradually
deteriorate to primarily MVFR during the early morning hours
Saturday due to development of low clouds and patchy fog. Some
patchy IFR is also possible early Saturday morning due to
potential for some locally denser fog and/or low clouds.

Conditions will gradually improve to mainly VFR by mid to late
Saturday morning as patchy fog dissipates. VFR conditions will
then continue at all the terminals Saturday afternoon through
Saturday evening.

&&

.MARINE...
Issued at 330 PM EDT Fri Aug 17 2018

North-northwest flow over Lk MI looks to be remaining on the
lighter side this afternoon, although it could be briefly
stronger on Saturday from mid afternoon through early evening
resulting a some choppier conditions for a time. Sunday looks like
a tranquil day on the lake, and the winds on Monday should be
mostly offshore. However hazardous winds are waves are a good bet
on Tuesday into Tuesday night as deepening sfc low tracks through.
Small Craft Advisories and Beach Hazard Statements will likely be
needed, and gales/beach erosion are not out of the question
either.


&&

.HYDROLOGY...
Issued at 154 PM EDT Fri Aug 17 2018

Rainfall over the past 24 hours...per MRMS with gage correction...
has been more widespread than in recent days...with locations south
of Grand Rapids showing one tenth of an inch or less.  More isolated
coverage of rainfall was indicated over northern sections of Central
Lower Michigan...with some amounts in excess of one inch.  The low
amounts to the south and the isolated nature of the heavy rain to
the north have produced little to no impact to area river levels.
Heavy rain of 4 to 6 inches fell across east central Wisconsin since
Thursday morning.

Quite a bit of uncertainty as to the expected coverage and location
of rainfall this afternoon and evening.  Atmosphere has plenty of
moisture to work with as precipitable water values in excess of 1.5
inches over most of Lower Michigan.  Slow movement of showers and
thunderstorms will also aid in producing increased amounts in areas
that receive rainfall.

Threat for significant impacts to area rivers is highly conditional
over the next 48 hours...mainly due to the recent dry conditions.
If precipitation can develop over a basin with appreciable areal
coverage and persist long enough for significant runoff to
develop...river stages could show significant rises.  Combination of
factors results in a low confidence forecast for river impacts over
the next 48 hours.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

UPDATE...Duke
SYNOPSIS...Meade
SHORT TERM...Meade
LONG TERM...Meade
AVIATION...Laurens
HYDROLOGY...MWS
MARINE...Meade




Area Forecast Discussion

National Weather Service Lincoln IL

 902 PM CDT Fri Aug 17 2018

.UPDATE...
Issued at 901 PM CDT Fri Aug 17 2018

The upper trough axis resides over central IL this evening with
surface cold front near I-70. Instability is weakening with the
last remaining thunderstorms currently south of I-70, although an
isolated shower or thunderstorm is still possible the next few
hours to the north. The upper trough and front will continue to
progress ESE overnight, with light and variable winds and skies
clearing overnight, especially west of I-57. As a result, patchy
fog should develop across the area after midnight. Currently, a
large variety of depictions of the fog exist among several models,
from minimal coverage to fairly widespread. Will therefore continue
with patchy coverage. Lows ranging from 65 in Galesburg to 69 in
Lawrenceville continue to look good for tonight. Updates sent this
evening mainly to remove mention of precipitation over
northwestern portions of the area, and continue isolated showers
and thunderstorms SE.

&&

.SHORT TERM...(This evening through Saturday)
ISSUED AT 324 PM CDT Fri Aug 17 2018

Vigorous upper low currently centered over southwest lower
Michigan continues to be the primary weather-maker across central
Illinois this afternoon. With upper troughing in place and MLCAPEs
analyzed from 1000-1500J/kg, widely scattered thunderstorms have
developed...with the most concentrated area setting up along I-70.
HRRR has been handling the situation quite well today, so will be
following its solution closely in the short-term. As such, will
linger chance PoPs along/south of I-70 through mid-evening...with
just slight chance PoPs further north across the remainder of the
ILX CWA. The showers will be largely diurnally-driven, so am
expecting them to completely fade away toward midnight. Skies will
clear in the wake of the short-wave trough overnight, particularly
across the western half of the CWA. With clear skies, nearly calm
winds, and plenty of boundary layer moisture...think patchy fog
will once again develop late tonight. Low temperatures will drop
into the middle to upper 60s. With the trough axis east of
Illinois, synoptic forcing for scattered convection Saturday
afternoon will be focused across the Ohio River Valley. While
synoptic models such as the GFS/ECMWF hint at a few showers across
E/SE Illinois, higher-res models are mostly dry. Will therefore scale
back the PoPs for Saturday, with only slight chance PoPs during
the afternoon across the far SE. Elsewhere, partly sunny and dry
weather will be the rule with highs in the middle 80s.

.LONG TERM...(Saturday night through Friday)
ISSUED AT 324 PM CDT Fri Aug 17 2018

Short-wave ridging will develop across Illinois on Sunday in
advance of the next upper disturbance digging into the central
Plains. Given overall subsidence, am expecting mostly sunny and
very warm conditions with highs in the middle to upper 80s. All
models agree that the Plains wave will track eastward into
Illinois on Monday, with only minor timing differences noted. It
appears quite a bit of precip will develop along/ahead of a
developing warm front late Sunday night into Monday...warranting
high chance to likely PoPs at that time. The amount of cloud cover
and ongoing convection Monday morning will play a major role in
the potential for severe weather later in the day...as the exact
extent of destabilization remains unknown. If enough breaks in the
overcast can occur and moderate instability develops, would not be
surprised to see a round of strong to potentially severe
convection develop across central Illinois Monday afternoon and
evening as strong upper dynamics traverse the region.

Once the early week short-wave passes to the east, northwesterly
flow will take hold and temperatures will drop into the 70s for
Tuesday and Wednesday. After that, all model solutions are
suggesting rapidly rising heights by the end of the
week...signaling a return to more typical summertime weather by
Friday into next weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 633 PM CDT Fri Aug 17 2018

Patchy fog is expected to develop overnight after isolated evening
showers diminish this evening. VFR conditions are expected until
around 07-09Z then MVFR or worse visibility is expected as fog
develops, continuing until 14Z. VFR conditions are then expected
the remainder of the TAF forecast period, with scattered cloud
cover around 3000 ft AGL. Winds NW less than 10 kts this evening,
becoming light and variable overnight, then NE less than 10 kts
after 14Z.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...37
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...37



Area Forecast Discussion

National Weather Service Indianapolis IN

 1137 PM EDT Fri Aug 17 2018

.UPDATE...
The AVIATION Section has been updated below.

&&

.SYNOPSIS...
Issued at 225 PM EDT Fri Aug 17 2018

Rain chances will continue tonight as low pressure moves across
and exits the area. A few lingering showers will be possible early
on Saturday as the low departs. High pressure is expected to
build across Central Indiana on Saturday afternoon and Saturday
Night. This will bring dry weather for the latter parts of the
weekend.

Another low pressure system is expected to arrive in the area on
Monday and Tuesday. This will bring more rain chances to Central
Indiana early next week. That low will depart by mid
week...bringing a return to dry weather for the end of the next
work week.

Look for temperatures to remain at or below seasonal normals over
the next week.

&&

.NEAR TERM /Tonight/...
Issued at 837 PM EDT Fri Aug 17 2018

Scattered convection continues across the area, as a mid level
vorticity lobe and diffuse surface cold front drift south through
the area.

Expecting a gradual decrease in coverage of shower activity from
this point on as heating is lost. However, the presence of the mid
and level and surface features suggests the potential for some
showers and thunderstorms will linger into the early morning hours
of Saturday.

Previous discussion follows.

Surface analysis early this afternoon shows Low Pressure over
Lower Michigan and Northern Indiana. Broad cyclonic flow was in
place across the region GOES16 shows a swirling clouds across the
region...denoting the circulation. Pop up cumulus clouds were
found filling in any clear gaps as convective temperatures were
reached. Surface flow was generally southerly or southwesterly and
dew points remained in the very moist upper 60s and lower 70s.
Radar shows shower development over western central Indiana as
convective temperatures were being reached.

Models this afternoon suggest a weak short wave embedded within
the troughy flow aloft passing across Central Indiana. This
combined with some afternoon heating should lead to some scattered
showers lasting into the evening hours. Time height sections
continue to shows good lift through the late afternoon and past
00Z with good lower level moisture available. Forecast soundings
again show favorable lapse rates for afternoon convection. HRRR
also suggests shower and storm development this
afternoon...continuing into the evening. Thus will trend pops at
or above the forecast builder blends with this favorable set-up
for rain.

Trough axis is expected to pivot southeast across the forecast
area overnight...and rain chances  should diminish as this axis
passes along with the loss if daytime heating. Thus for now...will
focus best pops in the 20Z-04Z time frame...trending downward
after that. Given the expected clouds and rain...will trend lows
at or above the forecast builder blends.

&&

.SHORT TERM /Saturday through Monday/...

Issued at 225 PM EDT Fri Aug 17 2018

Models show the trough axis sagging southeast of Central Indiana
on Saturday morning as NW flow develops aloft. Forecast soundings
respond with a dry column as the GFS shows a good mid level
inversion arriving by 12Z. Time heights show subsidence arriving
by 15Z. Thus forecast builder willing...will try and trend toward
a dry forecast for saturday with decreasing clouds in the wake of
the front. With minimal temperature advection in place...will
trend highs close to the forecast builder blends.

On Saturday night through Sunday night the models clearly show
strong high pressure in place across the region...stretching from
Ontario...across the Great lakes to the Ohio valley. Forecast
soundings again show a dry column and subsidence is depicted
within the middle levels. Thus will trend toward a dry forecast
here and stick close to the forecast builder temperatures for
highs and lows.

On Monday the GFS suggests low pressure pushing toward Indiana
from the Central Mississippi River valley. Models suggest by mid
to late in the day on Monday...a warm front will arrive in
Central Indiana ahead of the deepening Low over Illinois.
Aloft...the GFS show a favorable upper level trough with ample
forcing. Thus will trend toward high pops late in the day as these
feature arrive.

&&

.LONG TERM /Monday Night through Friday/...
Issued at 330 PM EDT Fri Aug 17 2018

Primary focus of the long term will be early in the period as a low
pressure system moves through the Great Lakes. This will necessitate
precipitation chances in the first 48 hours or so before a large and
somewhat fall-like high pressure system pushes into the region,
bringing dry and somewhat cooler weather right on time mid to late
week as meteorological summer nears its close.

Blended initialization was generally acceptable minus removing some
spotty slight chances late in the week.

&&

.AVIATION /Discussion for the 180600Z TAFS/...
Issued at 1136 PM EDT Fri Aug 17 2018

Light winds and a humid air mass may lead to the development of
IFR ceilings, along with some fog, overnight. Some lingering mid
level cloud may work against the low ceilings becoming too
widespread. If these lower ceilings form, they will likely into
the mid to late morning hours of Saturday.

Light winds overnight will become 010-030 degrees at 7-10 kts by
midday Saturday.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS...Puma
NEAR TERM...Puma/JAS
SHORT TERM...Puma
LONG TERM...Nield
AVIATION...JAS



AREA FORECAST DISCUSSION...UPDATED

National Weather Service Jackson KY

 1055 PM EDT Fri Aug 17 2018

.UPDATE...
Issued at 1055 PM EDT FRI AUG 17 2018

Updated the grids mainly to reflect the latest radar trends and
aggregate CAMs forecast through the night. This entailed a slower
ramp up to likely PoPs after midnight across our southeast
counties. Did also add in the latest obs and trends for the T/Td
grids. These updated grids have been sent to the NDFD and web
servers. Additionally, a freshened set of zones and HWO was
issued.

UPDATE Issued at 745 PM EDT FRI AUG 17 2018

23z sfc analysis shows a slowly moving cold front and general low
pressure off to the northwest of the CWA with a meso high located
over the Cumberland Plateau. The bulk of the storms in the region
are taking place well to the south in Tennessee while a few
scattered ones are trying to develop over central parts of eastern
Kentucky taking advantage of the 2000+ J/kg CAPE available for
the next couple of hours. Most of the CAMs keep these evening
storms limited favoring development later tonight similar to the
ones that took off last night. Have nudged the grids in this
direction allowing for more in the way of thunderstorms with the
convection that develops. Again we will have to watch for
excessive rainfall in any locations that see training from these.
If a larger scale cluster of storms manages to develop a short
fuse flash flood watch may be warranted. For now will maintain the
mention of heavy rain in the HWO and social media messaging.
Currently, readings are in the mid to upper 70s most places with
dewpoints well up there in the low to mid 70s. Winds are mainly
from the southwest at 5 to 10 mph. Have also updated the near term
T and Td grids per the latest obs and trends. These freshened
grids have been sent to the NDFD and web servers.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 435 PM EDT FRI AUG 17 2018

Aloft, long wave trough is found over the upper Midwest with
eastern Kentucky under a southwest flow regime. At the surface a
series of weak low pressure waves appear along a semi-stationary
frontal boundary draped roughly from the Great Lakes southwest to
St. Louis, and further southwest to about Oklahoma City. Another
upstream cold frontal system is dropping out of the Northern Tier
and appears to make it no further south than the Great Lakes
Region. The southernmost surface front makes an honest move
eastward through the short term and may have enough support aloft
from the aforementioned trough to push through our area late
Saturday into Saturday night. Regardless our area remains in an
unsettled pattern until the frontal zone passes entirely through
the Commonwealth.

The lull in activity this afternoon is coming to an end as strong
diurnal heating is beginning to kick off some isolated activity
across our forecast area late this afternoon. The HRRR showed a
general and gradual increase in activity through the late
afternoon and evening, mainly from the southwest and across the
south. Activity continues through the overnight as it appears
more organized convection takes shape, similarly to the previous
few nights except just a bit futher east each night. This activity
appears to take shape as a result of the typical increase in the
H850 winds through the overnight period just above the boundary
layer. Synoptic setup allows for some pockets of increased
convergence in spots as weak but distinct H850 LLJ maxes help in
generating the bands of more organized convection. Our area
remains in a slight risk for heavy rain with any hydro issues
being mainly confined to areas where training cells set up,
similarly to the last few days.

Temperatures remain generally at or just below normals due to
precipitation and additional cloud cover as afternoon highs climb
into the low to mid 80s and overnight lows drop into the 60s.

.LONG TERM...(Sunday through Friday)
Issued at 352 PM EDT FRI AUG 17 2018

The models are in fairly good agreement with the overall pattern
for the extended. Weak upper level ridging, formed by an upper
level cutoff low located in the Central Plains digging to the
southeast, will help bring a brief lull in precipitation for
eastern Kentucky late Sunday into early Monday. The cutoff low
will evolve into a deep trough and progress across the eastern
CONUS through midweek before moving off to the northeast Thursday.
Southeastern Kentucky will see chances of showers and
thunderstorms Sunday afternoon into the evening as a surface
boundary passes to the south of the Commonwealth. A warm front
associated with a surface low pressure system in Missouri will set
up over Kentucky early Monday. This low pressure system will
migrate to the northeast and settle over the Great Lakes by Monday
evening, lifting the warm front to the northeast and keep chances
of showers and thunderstorms Monday into Tuesday. A cold front
will begin progressing through western Kentucky during this time
as well. This cold front will move through the Commonwealth,
bringing increased chances of showers and thunderstorms through
midweek. By Thursday, a surface high pressure will build in over
the Ohio Valley, ushering in drier conditions for the end of the
work week.

High temperatures will generally be in the mid 80s Sunday and
Monday with low temps in the upper 60s through Tuesday morning.
High temps will cool down to around 80 degrees by midweek with
lows temps in the lower 60s Thursday and Friday mornings due to
frontal passage. Temperatures will then be on the rise Friday
afternoon.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 820 PM EDT FRI AUG 17 2018

A few scattered showers and thunderstorms are around this evening
but it is generally quiet. Expect convection to redevelop during
overnight hours due to some pockets of H850 convergence and with
the advancement of a cold front toward the state. Will add
thunder into the TAF for the limited activity this evening and
that better development later tonight. Ceilings and visibilities
will likely lower with convection redeveloping into Saturday
morning. The convection chances will taper off from north to south
during the day, Saturday, as the cold front drops through the
forecast area. Winds will generally be out of the south/southwest
around 5 to 10 knots during the daylight hours, but could be
higher in stronger showers and thunderstorms. Otherwise, generally
light winds are expected overnight.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GREIF
SHORT TERM...RAY
LONG TERM...CGAL
AVIATION...GREIF