Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/01/20
Area Forecast Discussion
National Weather Service Grand Rapids MI
1156 PM EDT Sat Oct 31 2020
LATEST UPDATE...
Aviation
.SYNOPSIS...
Issued at 258 PM EDT Sat Oct 31 2020
- High winds and snow showers Sunday and Sunday night
- Cold early week, moderating by mid-week
&&
.UPDATE...
Issued at 705 PM EDT Sat Oct 31 2020
For the most part our ongoing forecast looks fine. I did fine tune
the precipitation to show a break between the showers ahead of the
cold front and the wrap around snow showers behind the front.
There is enough cold air with this system to bring the freezing
level to the ground or very near to the ground by early afternoon
so I could see grassy surfaces down wind of the better fetch snow
showers getting and inch or so Sunday. The higher terrain areas
north of Grand Rapids would see the most. There seems to be a
preferred area of snow accumulations near US-131 just south of
Grand Raids. In that area we have good lift in the DGZ and
cloud tops look to be near 9000 ft, so these could be decent snow
showers.
The gusty winds look very much on track too. The latest HRRR is
still showing gusts in the 40 to 45 mph, the ECMWF has gusts in
the 45 to 50 mph range.
&&
.DISCUSSION...(This evening through next Saturday)
Issued at 258 PM EDT Sat Oct 31 2020
- High winds and snow showers Sunday and Sunday night
Forecast wind profiles continue to show 40 to 45 knots in the
mixing layer for Sunday afternoon and evening so we expect the
potential for wind gusts over 45 mph. We have expanded the wind
advisory across the entire CWA.
Sharp thermal trough with 850 mb temps plunging to minus 10C or
lower Sunday afternoon and evening. Strong CAA will mean
temperatures actually falling through the 30s during the day and
surfaces should be cold enough for any snow to stick, with
accumulations an inch or two possible across the northern interior
zones.
Model soundings show inversion heights generally above the DGZ
with cyclonic flow and lake-generated instability helping create
some decent updrafts, although strong winds will tend to disrupt
stronger bands from forming. Some rain will mix in near the shore
because of the warmer lake temps. The trough axis moves east with
drying early Monday.
- Cold early week, moderating by mid-week
Trough moves out early next week with rising heights and moderating
temperatures by mid-week. 850 mb temps go from about 0C on Monday
to about 14C on Wednesday. No precip expected through the end of
the week as western CONUS trough amplifies keeping ridging across
the east.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1156 PM EDT Sat Oct 31 2020
The primary story with this system coming through is strong winds.
The GRR VAD wind profiler shows 50 knots at 2000 ft AGL. Many
locations near the Lake Michigan shore are getting gusts to 35 to
45 mph already. We are expecting the strongest surface winds
behind the cold front Sunday. I am thinking surface wind gusts in
any open location like an airport could see gusts to 40 mph with
no problem at all a good part of the day. Winds will diminish by
mid evening Sunday.
The area of showers is starting to develop now and will become
widespread by 06z and last until around 10z. It is questionable
now how much MVFR there will be with these showers as there is a
lot of dry air at low levels ahead of the front. Still it is
possible we could locally see some heavier rain and MVFR cigs/vsby
for a time.
There will be about a 3 to 6 hour break between the frontal rain
band and the lake enhanced snow showers that will follow Sunday
during the day. These snow showers will be light mostly but in the
15z to 21z time frame locations near and inland of US-131 could
see some local IFR in snow showers. These conditions would be
brief.
After 21z enough dry air comes in to end the snow showers and
bring VFR cigs. Skies may clear by 06z Monday.
&&
.MARINE...
Issued at 258 PM EDT Sat Oct 31 2020
Gale Warning and Lakeshore Flood Warning in effect and are
unchanged from previous forecast. South gales to 40 knots are
expected tonight then going west and northwest on Sunday and
increasing to 45 knots during the afternoon and evening. A few
gusts to Storm force are possible north of Pentwater. Waves are
expected to build over 10 feet tonight and up to 14 feet on
Sunday. This will cause some erosion of dunes and flooding of
areas adjacent to the lake.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Lakeshore Flood Warning until 1 AM EST Monday for MIZ037-043-050-
056-064-071.
Wind Advisory until 7 PM EST Sunday for MIZ037-043-050-056-064-
071.
Wind Advisory from 9 AM to 7 PM EST Sunday for MIZ038>040-
044>046-051-052-057>059-065>067-072>074.
LM...Gale Warning until 1 AM EST Monday for LMZ844>849.
&&
$$
UPDATE...WDM
SYNOPSIS...Ostuno
DISCUSSION...Ostuno
AVIATION...WDM
MARINE...Ostuno
Area Forecast Discussion
National Weather Service Lincoln IL
852 PM CDT Sat Oct 31 2020
.SYNOPSIS...
Issued at 240 PM CDT Sat Oct 31 2020
A cold front will move across Illinois tonight bringing gusty
northwest winds and much cooler temperatures for Sunday. The chill
will be short-lived however, as temperatures are expected to make
it back into the 60s for highs by midweek. Weather is expected to
remain dry through the week.
&&
.UPDATE...
Issued at 852 PM CDT Sat Oct 31 2020
Cold front is still on track to move into the CWA late this
evening and move across the state overnight. Winds may be on the
lighter side as the front moves through, but strong gusty
northwest winds are expected a couple of hours after FROPA and as
colder air advects into the region. HiRes model guidance suggests
sustained winds around 25 mph with gusts of 35-40 mph and possibly
45 mph. So, forecast winds will be just below wind advisory
criteria for this CWA. Therefore will continue the current
SPS...but adjust to have winds slightly stronger at times during
the morning hours. Update for stronger winds is necessary for late
tonight into tomorrow morning and will be out shortly.
&&
.SHORT TERM...(This evening through Sunday)
ISSUED AT 240 PM CDT Sat Oct 31 2020
Breezy conditions should subside somewhat this evening ahead of an
approaching cold front currently over southeast Minnesota into
western Iowa. The front is associated with a strong northern
stream wave digging into the eastern U.S. Models are in good
agreement in bringing the front through between 04z and 09z. With
strong cold advection and height rises behind the front and
enhance subsidence on the backside of the wave, winds should come
up before sunrise west of I-55 and by mid-morning elsewhere.
Extended HRRR and SREF suggest wind speeds just below advisory
levels. By middle afternoon, the gradient is already exiting the
state and heights are rising so expect winds to gradually
decrease.
Strong cold advection behind the front, should keep temps from
rising much on Sunday. 850 temperatures are progged to fall into
the -5C to -10C by range by Sunday evening. This should keep temps
in the 40s despite abundant sunshine.
.LONG TERM...(Sunday night through Saturday)
ISSUED AT 240 PM CDT Sat Oct 31 2020
Clear skies, cold Canadian air mass, and diminishing winds should
set up the region for low temperatures in the 20s Sunday Night.
However heights start to rise quickly in the wake of the
departing shortwave and 850 temps respond increasing some 20C by
Tuesday evening. Temperatures are expected to be around 10 degrees
above normal for an extended period.
Models are in unusually good agreement in building a broad ridge
across much of the U.S. next week. A weakness in the ridge does
move across the Midwest midweek, but the Gulf of Mexico remains
cutoff and the weak wave should have little impact on our weather.
Next significant system amplifies over the western U.S. toward
the end of the week, but is not expected to bring any chances of
precip until after the valid period of this forecast.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 612 PM CDT Sat Oct 31 2020
VFR conditions will prevail at all TAF sites next 24hrs. Mid and
high clouds are advecting into the area and will bring broken cigs
around 8kft to PIA and BMI this evening, but this should scatter
out around midnight. SPI/DEC/CMI will just see scattered cloud
later this evening and overnight. Skies will then become clear
early morning and continue through rest of TAF period. Winds will
be out of the south-southwest this evening, but as a front moves
into and through the area, wind direction will shift to westerly
around or just after midnight with gusts up to 22kts. After the
front moves through overnight, wind direction will become
northwest and wind gusts will increase to 25kts...then increase to
over 30kts during the early morning hours. This will continue into
the afternoon.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Auten
SYNOPSIS...Auten
SHORT TERM...Barker
LONG TERM...Barker
AVIATION...Auten
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 315 PM CDT Sat Oct 31 2020
Mild temperatures, gusty winds and decreasing relative humidity
values have bumped the fire danger up into the very high category
for much of the local area this afternoon. That should continue
until near sunset. Otherwise temperatures are the main forecast
concern for the next several days. Precipitation chances from now
through next Saturday are very low.
Upper air maps from this morning showed the following features of
interest. At 850 mb and 700 mb, thermal ridges were in place from
KS and NE through MN and the eastern parts of the Dakotas. Colder
air was starting to push in from the northwest though with 850 mb
temps colder than 5 C from northern MT and western ND northward.
Strong 12 hour height falls of up to 150 meters were noted in
southern Manitoba, associated with a shortwave trough. Water vapor
satellite imagery, in combination with recent RUC model
initializations indicated that the trough stretched from Manitoba
down to the TX panhandle. Some variable mid and high level clouds
should move through the area over the next 12 hours.
Winds will gradually decrease tonight as the atmosphere decouples
and high pressure builds east across the northern and central
parts of the Plains. Ridge axis should stretch from central ND to
the TX panhandle by sunrise Sunday. That ridge will build
east/southeast over our area during the day Sunday, with much
lighter winds than today. So poor mixing will help keep
temperatures down. We expect highs to range from 46 to 49 in
southwest IA and 47 to 52 in eastern NE. Winds will turn to the
south or southeast in eastern NE by early evening.
Winds will not be from the south the whole week, but from Monday
through Friday they should mainly have a southerly component. A
weak cold front pushing through could turn winds to the northwest
on Thursday. We look for a warming trend Monday into Tuesday, and
then a pretty mild rest of the week with highs in the mid 60s to
lower 70s. Tuesday will probably be the warmest day, with highs
from 67 to 70 in southwest IA and 70 to 75 in eastern NE. The
warmest readings Tuesday should be west of a line from Beatrice to
Albion. Fire danger could be high or very high that day, so will
have to monitor that with later forecasts.
Gusty south winds are forecast for Friday afternoon, and even
moreso on Saturday, as low pressure deepens over the High Plains
in response to the digging mid level trough over the Rockies.
There is fairly good model agreement with the large scale pattern
until Sunday, then differences increase dramatically with pretty
big spreads shown in both the high and low temperature forecasts
from the National Blend of Models (NBM). For the 8 to 14 day
period, it looks like there will be some precipitation chances
with temperatures trending cooler than normal.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 628 PM CDT Sat Oct 31 2020
LLWS threat will persist through tonight at all terminals.
Otherwise, VFR conditions will prevail.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...Miller
AVIATION...DEE