Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/20/18
Area Forecast Discussion
National Weather Service Denver/Boulder CO
845 PM MDT Thu Jul 19 2018
.UPDATE...
Issued at 832 PM MDT Thu Jul 19 2018
Radar showing multiple boundaries over the northeast plains this
evening but too dry and subsident for thunderstorms. The RAP and
HRRR do show the surface rh increasing (90-95%) toward 12z Friday.
Enough there to warrant the mention of patchy fog primarily north
and east of Denver for 2-4 hours. Otherwise, no other updates
planned.
&&
.SHORT TERM...(This evening through Friday)
Issued at 253 PM MDT Thu Jul 19 2018
Our hot and dry day continues under mostly clear skies. Dewpoints
are in the 20s and 30s across the mountains and urban corridor,
with 40s and 50s along the South Platte River Valley out to the
eastern plains. Fire weather conditions continue to be flirting
with warning criteria levels, however not an extended period of
time, and are more critical up north where fuels aren`t as dry. Northwesterly
winds moving off the mountains will continue to spread southeast
across the area.
Tonights temperatures will continue to be warmer than normal after
today`s near record warm temperatures, and with a surface lee
trough and warming at 700 mb.
On Friday, even through 700 mb temperatures will be warmer, a low
level cooler airmass will push in from the Great Plains.
Temperatures will be 3 to 7 degrees cooler over the plains, and
up to 4 degrees cooler in the mountains. Moisture will be moving
up from the southwest for a return to a chance of afternoon storms
over the mountains mainly south of I70. The plains should remain
capped, however, some forecast soundings showing areas over the
east plains with a weaker cap. Will stick with a dry forecast
with the weather pattern in mind of a cooler airmass sliding under
warmer temperatures.
.LONG TERM...(Friday night through Thursday)
Issued at 253 PM MDT Thu Jul 19 2018
An upper level ridge will be the predominant factor leading to
continued very warm temperatures Friday and Saturday. Friday evening
a short wave trough will dip into northeast Colorado. The GFS and
European solutions are indicating potential for evening convection
over the Palmer Divide region. Saturday precipitation will become
more likely over the higher terrain, spreading onto the plains in
the afternoon. For the past couple of days the GFS has continued to
forecast high PWs Friday night through the middle of next week.
Sunday is expected to bring a cool down as the ridge flattens and
with more moisture moving into the region and allowing for cloud
cover. This should keep temperatures about 10 degrees F lower than
the previous day.
Monday through Wednesday cooler, stormy conditions are expected to
continue. High PWs with low instability will reduce the chances for
severe weather but could lead to a heavy rainfall threat.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 832 PM MDT Thu Jul 19 2018
East/southeast winds at KDEN will switch to east/northeast around
0330z this evening. Could see some gusts to 20 kts as the boundary
pushes into the Denver area from the northeast. Still anticipate
VFR conditions to prevail through the period. The boundary layer
rh over 90 percent however suggests potential for low stratus or
fog around 10-14z Friday. Confidence not high enough to include
it in the terminals but will need to keep an eye on it. The HRRR
keeps most of it north and east of Denver while the RAP has it
further east.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Cooper
SHORT TERM...Kriederman
LONG TERM...Sullivan
AVIATION...Cooper
Area Forecast Discussion
National Weather Service Dodge City KS
705 PM CDT Thu Jul 19 2018
...Updated for aviation discussion...
.SHORT TERM...(This evening through Friday)
Issued at 1231 PM CDT Thu Jul 19 2018
Scattered storms and heat will continue to be the main forecast
points in the short term. A surface low located in southeast
Colorado along with a weak frontal boundary in southwest Kansas
will be the focus for the potential development of storms late
this afternoon into tonight. HRRR and RAP have been fairly
consistent showing isolated to widely scattered storms developing
after 4pm and moving east to southeast through the forecast area
before dying off shortly after sunset. Main risk with these storms
will be strong downburst winds given the environment of around
100 degree highs and dewpoints in the mid to upper 60s. CAPE
values are forecast to be ~3000 J/kg ahead of the thunderstorm
development. It looks like better potential for storm development
tonight given the lack of widespread morning convection...however
a few isolated thunderstorms from Syracuse to Garden City that
developed this morning may provide a more stable airmass for
thunderstorm development to overcome.
Friday could bring with it similar conditions with more heat
through the forecast area as highs in the lower 100s with heat
index values around 105 for the counties along the Oklahoma border
looking like a good bet. The surface low in eastern Colorado will
continue to have a weak frontal boundary in southwest Kansas and
with northwest flow another 500-700 mb shortwave will move in late
afternoon. Depending on where the boundary sets up more isolated
to widely scattered late afternoon storms could develop. A lot
will depend on if the CAP can be broken ahead of the boundary so
the chance nothing develops is also in the cards.
.LONG TERM...(Friday night through Thursday)
Issued at 140 PM CDT Thu Jul 19 2018
More chances of spotty storms will continue in the long term as
the upper level pattern will continue to stay mainly in northwest
flow between an upper level low in the southeast and a ridge in
the desert southwest.
A 500-700 mb shortwave is forecast to come into western Kansas
Saturday afternoon into Saturday night and combining with upslope
flow we could once again see isolated to widely scattered
thunderstorms develop.
Sunday with the ridge moving a little more eastward at this point
this should keep us dry through most of the day.
Monday the long term models have the hints of a MCS developing in
eastern Colorado with a shortwave propagating along the ridge and
moving into western Kansas in the overnight.
Tuesday through Thursday continue with the upper level flow in a
northwest pattern with periodic shortwaves rotating around the
ridge in the Rockies providing more chances of isolated to widely
scattered storms.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 704 PM CDT Thu Jul 19 2018
Aside from isolated evening t-storms, VFR conditions will presist.
With a light pressure gradient, winds will be generally light and
less than 10 kts except in vicinity of t-storms through 02z.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 68 101 70 93 / 20 0 20 10
GCK 68 102 69 94 / 20 10 20 10
EHA 70 104 70 98 / 20 20 20 0
LBL 71 106 71 97 / 20 20 20 0
HYS 70 96 68 91 / 10 0 10 0
P28 73 102 73 94 / 20 0 20 10
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 1 PM to 7 PM CDT Friday for KSZ088>090.
&&
$$
SHORT TERM...Tatro
LONG TERM...Tatro
AVIATION...Finch
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
1059 PM CDT Thu Jul 19 2018
.Discussion...
Issued at 311 PM CDT THU JUL 19 2018
Active afternoon across west-central Missouri and eastern Kansas
as a strongly unstable airmass interacts with passing midlevel
vort maxes and numerous outflow boundaries. EAX radar shows
multiple outflow boundaries from ongoing and earlier convection
across the immediate KC Metro and points south, with numerous
splitting supercells across southern portions of the Metro. In
fact, we just received a healthy dose of golf ball sized hail here
at the office, with baseball sized hail reported over in Lone
Jack. Further to the west, TWX radar showing the next inbound
cluster or organized storms moving into the Topeka area which if
current movement trends persist, should arrive into the immediate
KC Metro by 4 PM. Large hail and damaging winds will be possible
with this cluster of storms as well, with latest radar trends
suggesting the line of storms is beginning to take on bowing
characteristics. If this upstream cluster maintains its intensity,
its possible winds in excess of 75 mph will be possible over the
KC Metro. Please refer to SPC Mesoscale Discussion #1087 for
additional details. And if this were not enough, the region north-
central Missouri is also being monitored for another watch as
latest SPC mesoanalysis shows a well-defined instability axis
extending up into southern Iowa. Southward extent of this activity
remains in question, but latest CAMs to include the HRRR suggest
isolated activity with increased ascent thanks to incoming
shortwave energy in west-northwest flow aloft. By this evening,
activity should gradually come to an end as main cold front off to
our northwest moves through and eventually stalls south of our
region. Between now and then however, the radar will remain active
with all severe weather threats possible considering ample
buoyancy and increased forcing for ascent as upper shortwave
energy approaches.
Aforementioned cold front to stall south of our region tonight,
with latest models suggesting additional shwr/storm activity
possible south of Route 50 through the predawn hours. Hydro
concerns should remain low through the overnight as the terminus
of the low-level jet is directed away from our region, but radar
trends will need to be monitored. By tomorrow, a ridge of high
pressure should start extending south into our region from the
northern Plains, however models indicate low chance pops along the
lingering front during the afternoon and evening hours. Beyond
this, high pressure should take hold of the weather pattern with
dry and pleasant conditions expected through much of the upcoming
weekend as winds remain from the north and northeast. In fact,
high temps through the weekend look to be mid to upper 80s, which
will feel more than welcomed for many.
&&
.Aviation...(For the 06Z TAFS through 06Z Friday Night)
Issued at 1059 PM CDT THU JUL 19 2018
VFR conditions are expected to prevail over the next 24 hours. A
few showers may be possible early this morning, but we do not
expect them to impact the terminals. Lastly, while it`s not
included in the TAF at this time, we may have to amend in a bit of
ground fog due to Wednesday`s rain.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&
$$
Discussion...32
Aviation...Cutter
Area Forecast Discussion
National Weather Service Glasgow MT
649 PM MDT Thu Jul 19 2018
.DISCUSSION...
Evening update...
Going forecast looked good. Made some tweaks to clouds in Phillips
County to cover whatever is left of the storms that have been
ongoing in southern SK drifting in. POPs looked fine to cover the
possibility of them holding together.
Avery
Previous discussion...
Upper ridge over the area tonight has some disturbances moving
through. But 500 mb heights don`t really fall, so not all that
confident that storms will fire from southern Alberta/SW Sask/NC
Montana and move into the NW zones as advertised by the HRRR
tonight. Do have slight chance of storms to account for this.
Storms over the SW corner of the CWA will dissipate soon as they
move away from their elevated heat source (Big Snowy Mountains).
Eyes then turn to large closed upper low over British Columbia. EC
continues to show more of a split with a piece of upper energy
moving into Montana while GFS keeps the system cohesive. Both
models do show slight chances of storms Saturday into Sunday, but
wind being more of an impact Sunday. GFS stronger with winds than
other models, but with models generally too light on cold frontal
passages, increased speeds over model consensus. Speeds of 20-30
mph look to be a sure bet with gusts to 35 mph.
Thereafter, temperatures for the rest of the period will be 5 to
10 degrees below normal as the upper low deepens as it moves into
Manitoba. The cool air mass will extend back to the Canadian
Rockies while NW winds will bring that into NE MT. TFJ
&&
.AVIATION...
Expected Flight Category: VFR, possible low clouds early Friday
morning.
Synopsis: Mainly clear skies are expected tonight, but some sub-
VFR clouds may blow in from the east late tonight/early Friday
morning: however, there is too much uncertainty to include them in
the TAFs. Any clouds that do move in should quickly clear off by
noon.
Winds: Northerly around 10 kts, then becoming variable overnight
and diminishing to 5-10 kts. Winds become easterly tomorrow around
10 kts. with higher gusts near GGW. MDA
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
weather.gov/glasgow
Area Forecast Discussion
National Weather Service Huntsville AL
908 PM CDT Thu Jul 19 2018
.NEAR TERM...(Tonight)
Issued at 908 PM CDT Thu Jul 19 2018
The overall forecast is on track. With a loss of daytime heating and
a more stable atmosphere, have removed rain chances for the rest of
the night. This was based mainly on output from the more recent HRRR
and RAP, which have remained consistent in lowering rain chances. The
18Z version of the NAM/GFS were trending that way too. But that being
said, future interaction between numerous outflow boundaries spawned
by recent convection - cannot totally rule out a stray shower or
storm; but those chances should remain on the lower side.
Will further evaluate if adding patchy fog will be needed for the
late night, mainly in/near areas that received a "wetting" rain
earlier today. Parts of NW Alabama (Franklin county) and NE Alabama
(Jackson/DeKalb) will be considered for a patchy fog mention per
recent MRMS rainfall data. A warmer west to slightly cooler east
gradient as was already in place, stayed with that thinking for
overnight low temperatures.
.SHORT TERM...(Friday through Saturday Night)
Issued at 219 PM CDT Thu Jul 19 2018
On Friday, we have gone with a low chance PoP through most of the
day, to account for the decaying MCS or MCV (much like today) that
may enter the area from our west. There could be some subsidence
behind this feature (rain or not) that may squelch afternoon
convection.
Very warm temperatures (with highs ranging into the low/mid 90s and
dewpoints into the mid 70s) will produce apparent temperatures as
high as 107 over NW Alabama. As such, have added Lauderdale, Colbert,
Franklin and Lawrence counties to a Heat Advisory - valid from Noon
to 6 PM on Friday.
Then attention turns to the severe weather threat Friday night into
Saturday morning. Not much to argue about on the new SPC outlook,
other than uncertainty with coverage of storms. There continues to
be varied solutions on timing and coverage with this as unseasonably
strong NW flow develops and an upper low deepens over the Great
Lakes. Multiple clusters of convection, including HP supercells, will
likely initiate over the lower OH valley into the Ozarks Friday
afternoon. These will rapidly drop southeast feeding off an
increasing west-southwest LLJ. As noted yesterday, forecast
soundings today continue to indicate a lengthening sharply curved
hodograph which yields 1km SRH values of 300+ later Friday evening as
these storms drop south-southeast into the region. Obviously,
thermodynamics will be favorable for severe convection, including
very large hail and damaging winds, and perhaps tornadoes. The main
issue is coverage of the cells. The NAM in particular is showing a
large gap in coverage of thunderstorms over southern middle TN and
north AL Friday night. The GFS seems to point to better coverage of
supercells/clusters over western TN, northwest AL and northern MS,
with less coverage further east. The previous and current ECMWF have
been focusing more on KY and TN into far northeast AL into north GA,
with lesser coverage further south and west. In either case, will go
with chance to likely PoPs on Friday night into Saturday, favoring
our eastern areas on Saturday. Details on Saturday thunderstorms will
likely be dictated somewhat by what occurs late Friday night. Will
maintain chances with the cold front into Saturday as well, then dry
things out by late Saturday evening.
.LONG TERM...(Saturday night through Wednesday)
Issued at 653 PM CDT Thu Jul 19 2018
There remains a decent amount of uncertainty to start the extended as
model differences for timing of precip continue. The overall pattern
consists of an upper ridge centered over the desert SW, a trough
over the Great Lakes, and a Bermuda high shifting westward slightly.
The result is the trough north of the area has no where to go and
models indicate it should drop south as a cutoff low. These types of
systems are never handled well by models and explains the issues. A
few waves rotating around the backside of this cutoff low may be
enough for isolated to scattered convection on Sunday with the
highest chances closer to the center of the system (NE AL and TN).
Then as the core of the system drops south near the area on Monday
could start to see more scattered to numerous showers and storms.
The system shifts to the S/SW away from the area on Tuesday but upper
level flow suggests we might be under a deformation axis and could
see another round of scattered to numerous showers and storms. An
elongated shear axis remains over the area Wed/Thu and we might see
continued showers/storms both days. But with the uncertainty in some
of the positioning and just how widespread some of this precip might
actually be, have nudged PoPs down below guidance from Tuesday
onward.
The one thing the system will bring is some relief from the heat as
the increased cloud cover and rain chances each day should keep temps
in the 80s. Those temps combined with slightly drier air at the
surface, and modest lapse rates aloft will result in CAPE values
between 1,000 to 1,500 J/kg each day based on latest GFS soundings.
Afternoon highs begin to climb back up towards the 90 degree mark
Thu/Fri. But again as mentioned above, models have trouble with the
cutoff type of systems and uncertainty in the forecast is a bit
higher than normal.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 653 PM CDT Thu Jul 19 2018
Surface high pressure to the east of the region will result in VFR
flying weather continuing into the late night. Night time cooling and
moisture pooling aloft could result in late night MVFR CIGs before
daybreak Friday. S-SW winds otherwise will continue on Friday. The
period right after this TAF could become very interesting, as some of
the mesoscale and longer term models depict thunderstorm complexes
moving southward, affecting the terminals Friday evening.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Heat Advisory from noon to 6 PM CDT Friday for ALZ001>004.
TN...NONE.
&&
$$
NEAR TERM...RSB
SHORT TERM...17/RSB
LONG TERM...Stumpf
AVIATION...RSB
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Jacksonville FL
952 PM EDT Thu Jul 19 2018
.UPDATE...
Tried to blend the NAM12 and HRRR with the NAM12 indicating the
meso-low across southeastern Georgia overnight and the HRRR
depiction of convection developing over the Suwannee Valley area
and Nature Coast moving inland during the overnight hours.
Looking at the radar and satellite imagery can see both happening
although the meso-low over Georgia is beginning to wind down a
bit.
&&
.AVIATION...
Overall looking at a mid deck in the 5-10 kft range at the Florida
fields overnight with a low 1-3 kft range deck at KSSI. Tomorrow
the convection should begin early with the thunderstorms between
14-20 utc and then with a worked over atmosphere more light rain
to showers after 20 utc. Some rain may be heavy with visibility
reduced to 1-3sm in storms.
&&
.MARINE...
The region will remain between troughing to the northwest and
high pressure to the east/southeast through the weekend. The
waters will be between high pressure to the east/northeast and a
weak low to the West early next week.
Rip Currents: Low risk through Friday.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 74 88 73 92 / 60 70 50 30
SSI 78 87 77 90 / 50 70 60 30
JAX 76 89 74 92 / 40 60 50 40
SGJ 76 88 74 89 / 40 60 50 60
GNV 76 86 74 91 / 50 70 50 60
OCF 75 87 74 89 / 50 70 50 60
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&
$$
Sandrik/Kennedy/Cordero
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
914 PM CDT Thu Jul 19 2018
.UPDATE...
913 PM CDT
A cluster of storms in northwest Illinois had matured quickly as
it moved into Ogle County in north central Illinois early this
evening, but has since weakened some. Isolated cores occasionally
strengthen, with likely some small hail, and the overall
footprint of the storms and associated cold pool likely are
producing some 40+ mph gusts in central Ogle County. In addition,
rain amounts near an inch in an hour are occurring under these
slow-moving and semi-training storms, though antecedent
conditions in this area, mainly rural, are not overly wet.
These storms are north of the warm front, however the effective
air mass is not that far southwest of the CWA per mesoanalysis
and 00Z DVN sounding. This along with strong 0-1 and 0-3km shear
is likely why these sustained storms have been able to acquire
some cold pool development and occasional wind surges. Will need
to watch for this behavior, but would think it might be trending
less favorable in this northern part of north central Illinois.
Further south toward LaSalle and Livingston Counties if any
isolated storms were to develop in the gradually increasing
forcing/warm advection, they could have a better potential to be
strong.
It is challenging to say how many more storms will develop south
of I-88 for the rest of tonight. There is strengthening ascent
ahead of the closed upper low and impinging mid-level jet into the
area. Countering that is that some moisture transport over the
front is being robbed by very deep convection over the northeast
MO/western IL border. The HRRR and its experimental run generally
develop little additional convection in the southern two-thirds
of the CWA, which could indicate our likely storms including into
at least part of the Chicago area overnight are overdone. Suspect
these solutions could be somewhat underdone, but middle of the
road from current forecast and that solution may be the better
route (i.e. scattered storms overnight).
Forecast for Friday still looks on track with good coverage of
showers and embedded isolated/scattered deeper cores with
lightning potential, all forced by the upper vorticity maximum
swinging into the area. If there were to be deeper late
morning/early afternoon convection in the east/southeast CWA it
would have to be watched for a severe weather threat.
MTF
&&
.SHORT TERM...
249 PM CDT
Through Friday...
The line of showers and storms over Western IL is slowly advancing
east. There should be sufficient CAPE to keep the line going with
embedded thunderstorms. I`m not expecting any severe storms with
this line.
I kept a chance of scattered showers and storms behind the line as
CAPE values should still be supportive of storms and the upper level
forcing will be on the increase. PWAT values are 1-1.6 inches so any
thunderstorm will produce heavy rain. If storms train over the same
area, localized flooding could occur.
The upper level and surface low move over southern WI Friday.
Forcing aloft should allow scattered showers and thunderstorms
throughout the day. There will be dry hours, but I have low
confidence in exactly when and where due to the scattered nature of
the showers/storms.
Increased cloud cover should limit warming, so I lowered high temps
into the 70s.
JEE
&&
.LONG TERM...
255 PM CDT
Friday night through Thursday...
A vertically stacked storm system will continue to gradually
shift over the region into Sunday. This will generally result in
cloudy and seasonably cool temperatures through the weekend, with
periods of showers. A couple of thunderstorms will also be
possible, especially near Lake Michigan late Saturday and Saturday
night. Also, as mentioned in the previous discussion, some funnel
clouds will be possible, especially given the proximately to the
mid-level circulation. With extensive cloud cover likely, expect
cool high temperatures in the 70s to around 80 both Saturday and
Sunday.
A high risk for swimming is also likely to set up for the weekend
for most of the southern Lake Michigan beaches as stout northerly
winds over the lake result in high waves.
It still appears this upper level system will finally move out of
the area early next week. This will likely set up a few dry days
with more sun across the area into the middle of next week.
Expect temperatures to warm back to around seasonal normals into
the mid 80s.
KJB
&&
.AVIATION...
For the 00Z TAFs...
645 pm...Forecast concerns include thunderstorm chances tonight
and Friday...mvfr cigs Friday and possible ifr cigs Friday night.
A few showers are possible across the Chicago area terminals for
the next hour or so along with an isolated thunderstorm. This
activity will continue lifting northeast early this evening.
A line of thunderstorms extends from southwest WI into far
northwest IL early this evening and while short term guidance has
so far not handled this activity well...this is expected to
continue to slowly move east/northeast this evening. There remains
uncertainty regarding how much more development will occur south
of this line and how much will occur/move across the Chicago area
terminals later this evening into early Friday morning. Adjusted
tempo for thunder a few hours later based on current movement but
further timing tweaks can be expected as trends emerge over the
next few hours. A lull is then expected around sunrise with
additional showers expected to spread into northwest IL by mid
morning and the rest of the area by late morning. By this time...
the best instability is expected to be south of the terminals.
While an isolated thunderstorm will be possible...the potential
looks low so no thunder mention during this time period with this
forecast. Showers are expected to slowly diminish through Friday
afternoon with perhaps much of Friday evening being dry.
Brief mvfr cigs will be possible with any thunderstorms tonight
but prevailing cigs are expected to remain vfr. Mvfr cigs will
begin to move into northwest IL by sunrise and then spread across
the rest of the area Friday morning. Possible cigs may drop as low
as 1kft at times. Mvfr cigs are then expected into Friday night
with ifr cigs possible Friday evening into Saturday morning.
An outflow boundary moved across the terminals in the past few
hours...briefly shifting winds to the west/southwest. Winds are
expected to settle back to south/southeast this evening and then
slowly turning southerly overnight and shift west/southwest by
mid/late Friday morning. Speeds likely to remain 10kts overnight
with gusts 16-20kts developing on Friday. A wind shift to the
north is possible Friday evening. Confidence is low that this
shift will occur so no mention with this forecast. cms
&&
.MARINE...
321 PM CDT
A slow moving storm system is expected to shift over southern
Lake Michigan Friday night and then gradually meander over the
southern half of the lake through early Sunday. This system is
expected to produce hazardous conditions over the lake,
especially tonight through early Sunday. Expect southeast winds
over the lake (15-25 KT) to develop tonight as the surface low
approaches from the west. The winds will then shift northeasterly
on Friday over the northern half of the lake and southwesterly
over the southern tip of the lake as the low begins to move over
central and southern sections of the lake. Finally, winds will
likely become north-northeasterly lake-wide for the weekend, with
speeds of 25 to 30 kt likely for a period on Saturday. This will
likely produce high waves of 5 to 8 feet over southern Lake
Michigan, which will likely result in the need for another small
craft advisory for the weekend. Winds and waves should subside
early next week as the system shifts out of the region.
Periods of showers and thunderstorms can also be expected on the
lake into the weekend. Waterspouts also appear possible over the
southern end of the lake.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement...ILZ006-ILZ014...midnight Friday to 10
AM Friday.
IN...None.
LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742...midnight Friday to
10 AM Friday.
&&
$$
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Area Forecast Discussion
National Weather Service Marquette MI
750 PM EDT Thu Jul 19 2018
.SHORT TERM...(This evening through Friday)
Issued at 414 PM EDT THU JUL 19 2018
WV imagery and RAP analysis indicated a mid/upper and sfc low over
sw MN. The leading edge of pcpn with WAA/isentropic ascent ahead of
the low was slowly lifting to the ne through wrn WI. Any
thunderstorms remained farther south over ern IA, where MUCAPE
values were near 1k J/Kg. Otherwise, srly low level flow
prevailed through Upper Michigan with sct cu and a few high clouds.
Tonight, model trends with fcst moisture advection, isentropic lift,
and QPF suggest that the best rain chances/coverage will move into
wrn Upper Michigan overnight. However, instability to support tsra
will remain south of the area. Pcpn amounts should also remain
light, generally at or below 0.10 inch.
Friday, as the low slowly moves through srn WI, the heaviest pcpn
will continue to remain to the south of Upper Michigan and the
highest POPs will remain over the wrn CWA, closest to the stronger
700-300mb qvector conv. Expect enough diurnal heating to boost
MLCAPE values into the 500-1000 J/Kg range with potential of isold
thunderstorms over the south and east. Highs should climb into the
lower 70s near the WI border to around 80 east.
.LONG TERM...(Friday night through Thursday)
Issued at 347 PM EDT THU JUL 19 2018
Main concerns in the long-term forecast will be the precipitation
potential Friday night through the weekend along with the associated
cooler than normal temperatures.
Friday night through Sunday, Models are showing very similar
evolutions of a closed low moving through the Upper Great Lakes
through this time period. The models have converged on the upper-
level and surface low sliding across WI. This will lead to
increasing shower and thunderstorm chances for Friday; however,
dwindling instability will keep mainly rain showers and cloud cover
in place from Friday night through at least Sunday morning. The
increased cloud cover and intermittent precipitation through the
weekend, will keep temperatures below normal for this time period,
generally in the upper 60s to mid 70s, coolest downwind of the Great
Lakes. Doesn`t look like a lot of rain, but the southeast half of
the U.P. could see rainfall totals around a quarter to a half inch.
That`s good news as those locations have been especially dry over
the past couple months.
Monday through Thursday, models are depicting a surface low and
and upper level trough sliding across Canada. The main impact this
would have is perhaps an increase in cloud cover Monday into
Tuesday as a weak, moisture starved front slides through the area.
Another small chance of rain showers is possible Tuesday night
into Wednesday as the aforementioned lows sink a bit farther south
across Ontario. This will allow a stronger cold front to slide
through the area along with some additional moisture. At this
point, with timing and placement similar among the models, will
stick with the consensus blend, bringing a few scattered showers
for Tuesday night into Wednesday. Temperatures will likely be in
the 70s for most locations with a few 80 degree readings possible
for inland locations.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 750 PM EDT THU JUL 19 2018
Low pressure system moves across Wisconsin Friday. Winds back from
southeasterly this evening to easterly Friday morning and eventually
northeasterly late Friday. Rain chances also come with it. Northward
extent of any heavier showers remains a bit uncertain but will
dictate where low ceilings will end up being an issue. Have kept
prevailing ceilings at IWD in low-end MVFR, but upstream obs over
central Minnesota and hi-res model consensus support a few hour
period of IFR cigs mid-morning Friday so have covered that with a
TEMPO. Have kept cigs low-end VFR at CMX and SAW throughout the TAF
period as they will be farther removed from the system. Rain should
be light enough to prevent any category reductions to vis.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 414 PM EDT THU JUL 19 2018
Expect winds generally 15-20 kts with a few times of gusts over 20
kts through Saturday as a low pressure system slowly crosses the
western Great Lakes. High pressure building in Sunday through early
next week will result in winds staying mostly 15 kts or less.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...KEC
AVIATION...RJC
MARINE...JLB
Area Forecast Discussion
National Weather Service Las Vegas NV
600 PM PDT Thu Jul 19 2018
.SYNOPSIS...Moist and unstable air will remain over the region
through the end of the week providing fuel for afternoon and evening
thunderstorms...especially over the mountains. Next week, a heatwave
will be building with very hot temperatures expected and lowering
thunderstorm chances.
&&
.UPDATE...The POP/WX grids were updated through 11 PM PDT this
evening to reflect the latest trends. A cold pool could be seen on
satellite imagery pushing out of southwest Utah into nearby Lincoln
and Mohave counties. This will likely lead to isolated to scattered
thunderstorms over northeast Clark County this evening. This was the
main change to the forecast. Thunderstorm coverage was also
increased over Esmeralda and central Nye counties. -Adair
&&
.PREV DISCUSSION...
242 PM PDT Thu Jul 19 2018
.SHORT TERM...Tonight through Saturday.
Radar returns as of 2 PM show isolated to scattered deep, moist
convection north of Interstate 15. Most storms have developed over
terrain and remained anchored. Daytime heating combined with
differential heating circulations due to anvil shadowing have
allowed strong storms to develop over Nye and Lincoln Counties. HRRR
is indicating that storms will develop further eastward into Lincoln
County late this afternoon then transition to outflow-dominant and
move southwestward toward Clark County this evening. There has
decent run-to-run consistency, so PoPs were increased slightly for
Las Vegas and northern Clark County. Without a dynamic influence,
most convection should wane after sunset, the exception would be
convection maintained along outflow.
As far as synoptic evolution goes, ridging will continue to move
eastward and eventually settle across the Southern Plains by
Saturday. As it moves east, southerly flow will increase along the
western periphery of the ridge allowing slightly drier air to push
northward into the southern Great Basin. This will lead to lowering
rain/thunderstorm chances across the forecast area. Rain chances
will be limited to higher terrain (Spring and Sierra Mtns.) and
Mohave County through Saturday where the best instability,
although only moderate, will exist. Temperatures will remain at or
just above normal through Saturday.
.LONG TERM...Sunday through Thursday.
High pressure centered over New Mexico/Texas over the weekend will
gradually propagate west early next week. As this happens,
temperatures will be on the increase each day. Las Vegas may see 110
as early as Monday, but the more excessive heat will arrive Tuesday
and Wednesday as readings will be about 8-10 degrees above normal.
This will put places like Las Vegas in the 110-114 degree range, 115-
120 down the Colorado River, and 120-125 in Death Valley. With these
readings and little relief expected overnight an Excessive Heat
Watch has been issued for much of southern Nevada, southeast
California, and northwest Arizona for Tuesday and Wednesday.
Moisture is also expected to be rather limited with any thunderstorm
chances mainly confined to the higher terrain of central Nevada and
the Sierra with only slight chances over the higher terrain of
southern Nevada and northwest Arizona Sunday through Thursday.
&&
.AVIATION...For McCarran...Outflow winds from distant
thunderstorms could still influence the terminal area this evening,
but confidence is low in any direct impacts. Clouds will diminish
after sunset. Similar unstable conditions are expected Friday, but
confidence is low in a thunderstorm developing within the terminal
area. Cloud bases at or above 10k feet.
For the rest of southern Nevada, northwest Arizona and southeast
California...Scattered to isolated thunderstorms, mainly over the
higher terrain across the southern Great Basin and eastern Mojave
Desert. Storms will wane this evening. Convection may persist later
into the evening across Lincoln, northern Clark, and southern Mohave
Counties along outflow boundaries. Outside of thunderstorm
influences, southerly winds with speeds of 10-15 knots and gusts to
20 knots should prevail. CIGs at or above 10k feet; CIGs may drop to
5-7 k feet with convection that develops near a terminal. Similar
conditions expected Friday, with slightly less thunderstorm coverage.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
SHORT TERM/AVIATION...Boothe
LONG TERM.............Gorelow
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