Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/15/17
Area Forecast Discussion
National Weather Service Grand Rapids MI
953 PM EDT Sat Oct 14 2017
Issued at 953 PM EDT Sat Oct 14 2017
Have extended the areal flood warning northward to include
Allegan, Barry, and Eaton counties. Radar currently shows an
impressive feed of showers and thunderstorms coming into this
region from the Chicago area. This convection was recently able
to achieve radar estimated precipitation rates well in excess of
an inch per hour just north of metro Chicago. It appears that in
general, DualPol / MRMS QPE values correlate best to rainfall
reports we have received thus far. These radar estimates show a
maximum just south of Paw Paw and Mattawan, and we have recently
received a credible report of 5.9" near Mattawan. This suggests
that even the DualPol/MRMS QPE might be a bit low.
Aircraft soundings out of Chicago imply elevated convection rooted
around the 850mb level. This would limit the wind threat for our
area in spite of impressive looking bow structures seen on the LOT
radar. There is little to suggest the instability plume will work
its way much further east than it already has.
Issued at 327 PM EDT Sat Oct 14 2017
A strong fall storm system will affect the area through Sunday. This
storm will bring a good deal of rain to the whole area through
tonight. Some of this rain will be accompanied by embedded storms,
some of which could become locally strong to severe. Winds and
localized flooding will be the main threats. Strong winds will
develop late tonight and last through much of Sunday as colder air
flows into the area.
Once lingering showers end on Sunday night, much of the upcoming
week looks dry and increasingly warmer. Monday will still be a bit
cool after some possible frost across Central Lower Sunday night.
Highs could reach up into the 70s by the end of the week.
.SHORT TERM...(This evening through Monday night)
Issued at 327 PM EDT Sat Oct 14 2017
No major changes for the forecast this afternoon as the table has
been well set for all of the weather expected through Sunday. The
flood watch still looks well justified, as does the wind advisory
for late tonight and on Sunday.
We are thinking that we have three organized waves of showers/storms
that will work through the area between now and Sunday morning when
the front moves through. The first is coming into the CWFA right
now, the next one is south of the Quad Cities, and the third and
strongest one is over NW MO and SW IA.
The first two are expected to bring mainly heavy rainfall to the
area with only some embedded storms. We are watching the track of
these, as heavy rain has already fallen from Van Buren county to
Calhoun county. If these areas see additional heavier rain, we may
have to upgrade to a flood warning there. We will be watching any
other areas for possible advisories/warnings if too much training
over one area occurs.
The third wave continues to be our main concern for tonight. This
looks to arrive mid-late evening, and last into the early morning
hours on Sunday. This wave is the one that is being fueled by the
RRQ of the strengthening upper jet to our NW, and the resulting 60+
knot low level jet zipping up through here. Instability is limited
in our area to as much as 400-500 j/kg of MU Cape. The concern is
that with the strong wind fields, any downdraft reaching the sfc
could bring down the 50-60 knots winds only 1500-3000 ft up.
Then once the convection moves out, the concern focuses to the
frontal passage, and the strong synoptic winds that will ensue.
Models are fairly similar in showing the ability to mix 45 knots
down from late tonight and lasting through much of Sunday. There
will be a few showers on Sunday with the wind. The showers could be
enhanced a bit along the lakeshore with land/lake delta t/s in the
mid to upper teens C. The showers will then end late Sunday night as
ridging builds in. Inland areas could see some patchy frost up in
the normally colder locations toward Mt. Pleasant and Clare.
After Sunday night, the weather quiets down. We will remain rather
cool on Mon in comparison to the recent weeks with highs only in the
.LONG TERM...(Tuesday through Saturday)
Issued at 327 PM EDT Sat Oct 14 2017
A steady warmup is on tap for the middle and latter portion of next
week as upper level heights build and H850 warm air advection
settles in. We`re looking at the warmest days likely being toward
the end of the week and weekend as H500 heights surge back into the
580s dm. H850 flow will advect temps in the 14C to 16C range, or
possibly higher, if the Ohio Valley ridge develops as advertised.
This equates to a few things for our region. First, if this pattern
materializes, high temperatures late in the week and weekend may
overachieve given the anomalous pattern and the challenges that
numerical models can have resolving the degree of warmth. For now,
we have low 70s featured from Thursday through Saturday. Actual
highs may be several degrees warmer. With average highs around 60
degrees this time of year, we are expecting temperatures to be 10 to
15 degrees above normal by late next week. Secondly, we will likely
be precipitation free through Saturday with a good amount of
sunshine for the region. It should be a quiet stretch.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 810 PM EDT Sat Oct 14 2017
Some IFR will still be possible for the I-96 TAF sites early this
evening, but then MVFR will be predominate. Winds will be
increasing and that will help hold ceilings and vsbys up as we
work through the overnight.
A round of thunderstorms is expected to roll through, mainly
between 02Z and 06Z and may impact all TAF sites. After this
departs much of the TAFs should remain VFR.
Southwest winds will begin gusts to around 30 knots after 06Z and
continue much of Sunday. These winds should finally simmer down
Issued at 327 PM EDT Sat Oct 14 2017
No changes needed to the marine headlines with this forecast
package. The latest data continues to support solid gales for the
waters this evening ahead of the front, through Sunday with the
strong cold air advection. The chance for Storm Force winds is not
zero, but looks way too low for now to consider an upgrade at this
Issued at 1217 PM EDT Sat Oct 14 2017
Multiple waves of convection, some of it training, are expected to
provide the entire area with a soaking rainfall by Sunday morning.
PW values will be at or above 1.5 inches for the entire day, which
are about as high as they can get this time of year (based on DTX
sounding climatology). With elevated instability being maintained
through a thick layer of this deep atmospheric moisture, rain
production will be efficient in convection.
Mesoscale models have been consistent with providing 1 to 3 inches
of rain to the area, but have reasonable disagreement on where the
axis of heaviest rain will fall. There could be two heavy rain
swaths that end up falling, as convection this morning and afternoon
will focus south of I-96, then convection will tend to blossom north
of I-96 later this evening and tonight. Several runs of the HRRRX
have shown the potential for isolated 4 to 6 inch totals. Already
southern Van Buren and Kalamazoo counties are approaching 2.0
inches in the past 6 hours.
A flood watch has been issued through late Saturday night. River
flood advisories or warnings may be needed if heavy rain falls in
flood-prone drainage basins. With basin-average totals between 2 to
3 inches plugged into river models in the lower Kalamazoo and upper
Grand basins, several river points climb above bankfull (the usual
suspects: Holt, Eagle, Maple Rapids, Ionia, Hastings).
MI...Flood Watch until 4 AM EDT Sunday for MIZ043>046-050>052-056>059-
Wind Advisory from 2 AM to 8 PM EDT Sunday for MIZ037>040-
LM...Gale Warning until 8 PM EDT Sunday for LMZ844>849.
Area Forecast Discussion
National Weather Service San Diego CA
813 PM PDT Sat Oct 14 2017
High pressure aloft over Southern California will bring a warming
trend through Monday, when temperatures will be in the nineties
from near the coast to the mountains. Surface high pressure over
the Great Basin will bring periods of gusty northeast winds near
the coastal foothills and below passes and canyons...mostly
through Sunday morning. Weak onshore flow will return on Tuesday
and strengthen on Thursday and Friday. Slow cooling will begin on
Tuesday and Wednesday with greater cooling on Thursday and Friday
along with a chance of precipitation and periods of stronger and
gusty west winds for the mountains and deserts.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
Extremely low dewpoints lie across inland locales away from the
sea breeze, which has made it into western portions of the Inland
Empire. Dewpoints where the sea breeze has passed are in the 50s
and 60s, while ahead of the sea breeze, insanely low dewpoints in
the single digits and teens prevail. In the mountains, dewpoints
are even lower in the -10s to -30s! The San Diego sounding this
evening shows -20s to -30F dewpoint at the level of the ob
(~8000FT), so looks reasonable. The extremely dry air will remain
in place on Sunday.
Dewpoints are 60-65F along the coast with ACARS data showing a
surface inversion developing. This presents the potential of
patchy fog developing along the coast, so have added this to the
forecast. Confidence is very low on dense fog. Fog could not form
at all, but given a possibility, patchy fog mention near the
coast is prudent.
...Previous Discussion (Issued at 152 PM PDT Sat Oct 14 2017)...
Mostly clear this afternoon, except for a few high clouds. Sfc
pressure gradients are now -11.3 mb SAN-TPH, and the offshore
winds are surfacing in the I.E. So far today, the strongest gust
reported is 45 mph at Highland Springs last hour. Highland Springs
is at 2233 ft, a few miles south of Beaumont. The driest
conditions west of the mtns are in the northern I.E. where
relative humidities are less than 10 percent.
A ridge of high pressure aloft will strengthen over Southern
California into Monday with surface high pressure over the Great
Basin. This combination will bring a warming trend with very dry
conditions and periods of gusty northeast to east winds. The
offshore winds will continue through Sunday morning before
weakening Sunday Afternoon. The strongest winds will be near the
coastal foothills and below passes and canyons where gusts to 45
mph will be possible. Monday will likely be the warmest day, with
90+ degree temps from within 1-2 miles of the coast inland to the
foothills. The very warmest locations for inland coastal areas
into the western valleys could have high temperatures near 100 on
For Tuesday and Wednesday...the high pressure aloft over Southern
California will begin to weaken in response to a low pressure
trough moving in from the northwest. This will bring a return of onshore
flow which slowly strengthens. Temperatures will begin to decrease
near the coast and spread inland with night and morning coastal
low clouds and fog returning and spreading farther inland later in
For Thursday and Friday...Temperatures continue to decrease and
onshore flow strengthens as the approaching trough deepens off the
California coast. The increasing onshore flow could bring periods
of gusty west winds to the mtns and adjacent desert areas.
Medium-range deterministic models show a chance for some precip
on Fri. This is dependent on whether or not moisture from the sub-
tropics gets entrained as the trough absorbs an upper level low
currently located at about 35N 140W.
Chances of precip should end next Saturday as the trough axis
150300Z...Areas of east to northeast winds 15-25 KT will continue
through 18Z Sunday with local surface gusts 30-40 KT through/below
passes and canyons of the San Bernardino and Riverside County
Mountains and Santa Ana Mountains producing MDT-STG UDDFS and LLWS
over and west of the mtns, including near KONT and KSBD. Winds will
be mostly below 25 KT after 18Z Sunday.
Near the coast, there is a small chance of fog with visibilities
below 1 mile 05Z-13Z Sun. This could occur near KSAN and KCRQ though
confidence is low. Otherwise, skies will be clear with unrestricted
vis through Sun evening.
No hazardous marine weather is expected through Thursday.
High pressure aloft will strengthen over Southern California
bringing a warming trend through Monday. Mostly weak offshore flow
will continue into Sunday. Winds will then weaken late Sunday
into Monday. Lowest daytime humidities will be 5 to 10 percent
each afternoon through Monday...with Sunday being the driest day.
Overnight recovery will be poorest near the coastal foothills
where mixing from winds continues overnight. Periods of gusty
northeast to east winds near the coastal foothills and below
passes and canyons will continue at times through Sunday morning.
The stronger winds are expected to be in the Inland Empire below
the Cajon and Banning Passes and near the coastal foothills of the
Santa Ana Mountains. The strongest gusts will be mostly around 45
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
CA...Red Flag Warning until noon PDT Sunday for Orange County Inland
Areas-San Bernardino County Mountains-Including The
Mountain Top And Front Country Ranger Districts Of The San
Bernardino National Forest-San Bernardino and Riverside
County Valleys -The Inland Empire-Santa Ana Mountains-
Including The Trabuco Ranger District of the Cleveland
PUBLIC...Gregoria (Update)/PG(Previous Discussion)