Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/20/21
Area Forecast Discussion
National Weather Service La Crosse WI
1051 PM CDT Tue Oct 19 2021
.SHORT TERM...(This evening through Wednesday)
Issued at 154 PM CDT Tue Oct 19 2021
High pressure continues it`s reign of today`s sensible weather with
clear skies and unseasonably warm temperatures. The National Blend
has been having a difficult time with surface warming strength the
previous few days, and have subsequently used 90th percentile max
temps for today, which lines up with how yesterday`s max temps
panned out containing similar conditions.
Precipitation chances begin tomorrow as a closed low crosses the
Northern Plains. Initial precipitation chances early tomorrow
morning seem to be elevated and showery in nature as isentropic
ascent ramps up within the warm conveyor belt downstream of the low
center. The next chance of precipitation tomorrow occurs during the
afternoon as the low center gets dry slotted and a north-south band
of instability works its way across our forecast area. As this
happens and the low wraps itself up, a mid-level frontogenetical
deformation band soaks north of the low center, north of interstate
94. The third and final precipitation chance for our forecast area
occurs tomorrow night as the deformation band sweeps behind the low.
Severe threat remains low with a stout 800 mb cap inhibiting any
surface-based CAPE for most of our area. The best instability occurs
in the afternoon, with MUCAPE values near 1000 J/kg in both the RAP
& NAM, along a north-south Mississippi River based band. Overall,
small severe threat remains for potential marginal 1" hailers.
Precipitation amounts remain 0.25"-0.50" from south to north with
higher amounts possible within potential mesoscale banding.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 154 PM CDT Tue Oct 19 2021
The low continues east Wednesday night with the main deformation
rain band along I-94, and lowering rain chances southward. The
rain will take much of the night to clear and this is a slower
exit than previously forecast. By sunrise Thursday, the rain
should be ending in central WI.
The just-below normal air mass then moves into the area through
Saturday with frosts/freezes likely across much of the area. There
is pretty good agreement on a stronger shortwave trough /current
wave off West Coast/ shifting through the northwest flow and
bringing in some mid- level cloud late Thursday night which may
hinder lows that morning from getting too cold. But, Saturday
morning should be colder with clear skies expected overnight. An
end to the growing season is expected this weekend in many areas.
Stronger warm advection and moisture transport from the south
shift in for Sunday rain chances. The deterministic ECMWF
solutions the last 12 hours are an outlier dry solution versus
their ensemble and also the GEFS members. About 40% of the members
in the 19.00Z EC ens rain Sunday and it is a higher number in the
19.00Z GEFS. The 19.00Z GEFS is certainly the northern outlier on
the moisture surge`s northward extent. The rain chances continue
into Sunday night.
As the CONUS long wave pattern becomes more amplified again with
West Coast troughing, early next week looks like it should bring
above normal temperatures after Monday.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1051 PM CDT Tue Oct 19 2021
VFR conditions are expected to continue through this coming
afternoon, then rainfall and accompanying lower ceilings return by
the evening.
Exact timing of the initial band of showers is uncertain, but
confidence increases later in the day as showers are anticipated to
become more widespread around 18z. There is a chance for
thunderstorms, but was not confident enough to include in the TAF at
this time. At KRST, MVFR ceilings become more likely towards the end
of the forecast period after 00z. Winds will be from the south into
the early morning hours, from the west through the afternoon, and
then become more northerly after 00z remaining around 10 knots
or less.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...JAR
LONG TERM...Baumgardt
AVIATION...Peters
Area Forecast Discussion
National Weather Service Bismarck ND
953 PM CDT Tue Oct 19 2021
.UPDATE...
Issued at 953 PM CDT Tue Oct 19 2021
Changes with this update were to 1) lower temperatures into the
upper teens F in far northwestern ND, using the 10th percentile
of NBM guidance, and 2) refreshing hourly PoPs through Wednesday
using recent NBM output. As of early evening, clear skies in the
dry air mass are allowing for efficient radiational cooling over
northwestern ND, while the northern extent of deformation-driven
high-level clouds and low-level stratus persists over southern ND.
Radar trends suggest the deformation associated with the upper low
in southeastern WY at this hour is producing an initial band of
light rain a bit further north than earlier HRRR cycles suggested,
so we have only made minor changes to the northern extent of PoPs
with this update cycle. That said, it still appears the southern
James River valley stands the best odds of precipitation from late
tonight into Wednesday, with a mix of light rain and snow possible
in some areas given marginal thermal profiles.
UPDATE Issued at 630 PM CDT Tue Oct 19 2021
Only minor changes were made with this update, mainly blending
observed trends into the the evening forecast. Satellite images
show continued southward advancement of the back edge of stratus
into southern and central ND, and early data from the 00 UTC RAOB
from Bismarck suggests the cloud layer is thin. However, guidance
suggests the stratus will develop back northward overnight, so we
will be monitoring its evolution after sunset. Otherwise, CAMs
through the 22 UTC HRRR suggest the northern edge of precipitation
late tonight and Wednesday may remain further south than earlier
anticipated. The exception is the 18 UTC NAM Nest, but that model
core/configuration has a tendency to be too far north with its QPF
signature. Thus, if trends in successive guidance continue with
the southward trend, our PoPs may follow suite in the next update.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 240 PM CDT Tue Oct 19 2021
Forecast highlights in the short term period will be lingering
clouds today/tonight, along with rain and snow chances south
tonight into early Wednesday.
Currently, upper level low centered along the Colorado/Wyoming
border area, with sfc high pressure to our north. Extensive cloud
cover across much of the state, with clearing from north to south
across the northwest and north central. Clouds associated with the
upper low streaming north towards our area.
Model guidance continues to show the low clouds dissipating slowly
from north to south this afternoon into the evening to around the
I94 corridor, then halting/redeveloping back to the north later
tonight. Upper low moves into central South Dakota/Nebraska region
overnight, with chances for rain or snow developing across our far
south along the ND/SD border. Best chances for precpitation will
not arrive till after 09Z and last through the morning hours
before dissipating across the James River Valley during the day.
Surface high pressure to the north will settle into western and
eventually central ND as well late tonight through Wednesday
morning, so how far north precip chances get to remain uncertain.
Latest NBM did lower QPF by about 30-50% compared to the forecast
issued earlier this morning.
Precipitation type will depend on surface temperatures and how the
atmospheric profile cools with time. Expect a rain/snow mix
becoming mainly snow south central, possibly remaining all rain
across the southeast. Some potential for a mix of rain/snow/sleet
for a period around sunrise but not expecting any impacts from
this at this time. A few tenths of an inch of snowfall will be
possible dependent if we can get a snow band to develop. Global
models say maybe, CAMs keep best DivQ/frontogensis linkage to our
south.
Another cool day tomorrow with highs in the 40s. Breezy south
central and east, but not as windy west closer to the surface
high.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 240 PM CDT Tue Oct 19 2021
Upper low continues to push to the east through the day
Wednesday, pushing over the Iowa/Minnesota border by evening. This
allows surface high pressure to build across the Dakotas Wednesday
night, setting the stage for a widespread hard freeze for much of
western and central areas of the state, with forecast lows in the
lower to mid 20s.
Mainly quiet weather expected through the rest of the work week
with northwest flow over the area. The southwest may push into the
50s for highs, 40s elsewhere. A weak clipper could bring some
light precip chances Thursday night-Friday morning, but opted to
maintain NBM and a dry forecast for now.
A variety of systems off the west coast are expected to shift
upper level flow southwest for the weekend into the start of next
week, resulting in occasional precipitation chances. Should also
see a nice moderation in temperatures early next week (highs back
into the 60s) with all models showing strong WAA into the area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 953 PM CDT Tue Oct 19 2021
MVFR ceilings in stratus are expected in southwest and south
central ND tonight, with local IFR ceilings possible. The main
uncertainty is how far north and west the low clouds may expand,
including whether they will reach KMOT or not. Otherwise, rain is
likely near the ND-SD border along with a chance of snow overnight
and Wednesday. The highest probability of precipitation and MVFR
to IFR visibilities will be south of KJMS, closer to KABR.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...CJS
SHORT TERM...NH
LONG TERM...NH
AVIATION...CJS
Area Forecast Discussion
National Weather Service Grand Forks ND
1017 PM CDT Tue Oct 19 2021
.UPDATE...
Issued at 1002 PM CDT Tue Oct 19 2021
Clearing is working slowly south/east but becoming more east-west
vs southwest to northeast. Clearing line is Hallock to west of
Grafton to Devils Lake to Harvey. HRRR/NAM insist on clearing
southward at a decent clip late tonight into Wed as rain moves
into far SE ND/WC MN. Tweeked sky/pops a bit earlier in the
evening and no further changes needed.
UPDATE Issued at 706 PM CDT Tue Oct 19 2021
Monitoring cloud trends this evening. Clearing is near a Walhalla
to Devils Lake to Harvey line at 23z. HRRR/NAM is more agressive
in bringing clearing southeast toward GFK overnight and then
southward Wednesday. This will set up a tight gradient from clouds
to clearer sky and rain to no rain Wednesday as system moves to
our south. HRRR is farthest south with rain and barely brushes our
far south vs NCEP models are farther north and brushes Fargo-Park
Rapids which is what the current fcst has.
.SHORT TERM...(This evening through Wednesday night)
Issued at 321 PM CDT Tue Oct 19 2021
Impacts in the short term will be rain across the southern valley
Wednesday with good agreement on placement as low pressure system
slides across Nebraska and South Dakota into Iowa and Minnesota.
The pressure gradient will of the low to the south and Canadian
high pressure to the north will keep wind speeds up overnight with
gradual clearing pushing into the northern valley. Temps overnight
will range from upper 20s to low 40s. Given the track of the sfc
low the northern fringe of the precip shield will bring rain to
the southern valley with a sharp gradient on the northern edge
expected with dry air entraining into the system from the north.
12Z HREF probability matched means indicate less than a tenth of
an inch for areas along and south of a Lisbon to Wahpeton to
Fergus Falls to Wadena line with higher amounts confined to Grant
Co MN where 0.50 to 0.75" is likely. Temps tomorrow will be cool
again with highs in the 40s even with some sun in the northern
valley. Winds will again be breezy with northerly gusts of 30 to
35 mph as tight pressure gradient persists. Skies will clear and
winds relax tomorrow night with temps falling into the 20s as the
sfc high axis moves over eastern ND overnight.
.LONG TERM...(Thursday through Tuesday)
Issued at 321 PM CDT Tue Oct 19 2021
The wide influence of an upper trough within southern ON into the
Great Lakes region is expected to move east late this week. Rising
heights are expected in the wake of the departing upper trough, but
not before being gifted with a backdoor cold front continuing
seasonably cool temperatures with lows dipping into the 20s.
Eventually warmer air aloft is expected to start encroaching the
region pushed by southwesterly flow getting into late this weekend
and early next week. While temperatures should be on the increasing
trend into next week, it is unclear how much warmth will be drawn
in. Ensemble spread also increases into early next week, even
showing differing variation of upper pattern. Variations in timing
and amplification of trough/ridge pattern into early next week
results in this spread, although there is a general trend for
increased precipitation next week, as well as potential for above
seasonal average temps. But again, spread is high and confidence is
low in details with next week`s forecast.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 321 PM CDT Tue Oct 19 2021
Impacts in the short term will be rain across the southern valley
Wednesday with good agreement on placement as low pressure system
slides across Nebraska and South Dakota into Iowa and Minnesota.
The pressure gradient will of the low to the south and Canadian
high pressure to the north will keep wind speeds up overnight with
gradual clearing pushing into the northern valley. Temps overnight
will range from upper 20s to low 40s. Given the track of the sfc
low the northern fringe of the precip shield will bring rain to
the southern valley with a sharp gradient on the northern edge
expected with dry air entraining into the system from the north.
12Z HREF probability matched means indicate less than a tenth of
an inch for areas along and south of a Lisbon to Wahpeton to
Fergus Falls to Wadena line with higher amounts confined to Grant
Co MN where 0.50 to 0.75" is likely. Temps tomorrow will be cool
again with highs in the 40s even with some sun in the northern
valley. Winds will again be breezy with northerly gusts of 30 to
35 mph as tight pressure gradient persists. Skies will clear and
winds relax tomorrow night with temps falling into the 20s as the
sfc high axis moves over eastern ND overnight.
.LONG TERM...(Thursday through Tuesday)
Issued at 321 PM CDT Tue Oct 19 2021
The wide influence of an upper trough within southern ON into the
Great Lakes region is expected to move east late this week. Rising
heights are expected in the wake of the departing upper trough, but
not before being gifted with a backdoor cold front continuing
seasonably cool temperatures with lows dipping into the 20s.
Eventually warmer air aloft is expected to start encroaching the
region pushed by southwesterly flow getting into late this weekend
and early next week. While temperatures should be on the increasing
trend into next week, it is unclear how much warmth will be drawn
in. Ensemble spread also increases into early next week, even
showing differing variation of upper pattern. Variations in timing
and amplification of trough/ridge pattern into early next week
results in this spread, although there is a general trend for
increased precipitation next week, as well as potential for above
seasonal average temps. But again, spread is high and confidence is
low in details with next week`s forecast.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 706 PM CDT Tue Oct 19 2021
MVFR cloud deck over most areas tonight, though clearing that is
now working into DVL basin will spread east and south thru the
night into Wednesday, making timing of clearing the main forecast
issue this TAF period. North-northeast winds gusts will die down
some overnight and then pick up Wednesday in the 25 kt range over
E ND/RRV...lowest wind speeds thru the pd Bemidji area.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...Riddle
SHORT TERM...JK
LONG TERM...CJ
AVIATION...Riddle
Area Forecast Discussion
National Weather Service Grand Rapids MI
923 PM EDT Tue Oct 19 2021
LATEST UPDATE...
Marine
.SYNOPSIS...
Issued at 322 PM EDT Tue Oct 19 2021
- Quiet weather again tonight
- Showers, few thunderstorms for late Wed into Thu
- Seasonably cooler weather for Fri into the weekend
- Somewhat active weather for next week
&&
.DISCUSSION...(This evening through next Tuesday)
Issued at 322 PM EDT Tue Oct 19 2021
- Quiet weather again tonight
Another sunny and unseasonably warm day has passed for much of the
region today. The broad surface anticyclone over the southern
Appalachians will move off the coast tonight. To our west, recent
lee cyclogenesis has yielded a 1005-mb surface cyclone, having now
reached southwestern Nebraska. A closed mid/upper-level low and
associated vort maximum is noted in WV-channel imagery across NW
Colorado, associated with somewhat modest 500-mb height falls of
60 m per 12 h, as shown in RAP mesoanalysis. The northward return
of low-level moisture has been somewhat delayed, owing to the
aforementioned anticyclone over the gulf states, but is
nevertheless underway across the plains. Another fairly quiet
night is expect under some passing high clouds, with warmer low
temps than previous nights.
- Showers, few thunderstorms for late Wed into Thu
For Wed, our attention turns to this aforementioned system and
its associated impacts. HREF ensemble mean suggests the surface
cyclone will reach the vicinity of central Lower Michigan by 12z
Thu, with a trailing cold front to its south. In advance of this
cold front, low 50s F surface dewpoints should be common in the
area (dewpoints currently near 50F inland are noted), and PWAT
will climb to 1.0-1.2 inches. Aloft, an elevated mixed layer--
recently transported from the Rockies--may glance southern
Michigan, perhaps providing 700-500-mb lapse rates of 7 C/km in
our southern counties by late Wed night. This environment is
expected to yield 500-1000 J/kg of MUCAPE--mainly along/south of
I-96--for tomorrow night, per HREF mean. Effective bulk shear of
20-30 kt is expected--not terribly impressive--and SW Lower
Michigan is positioned on the nose of a 35-kt LLJ. QG forcing for
ascent increases considerably for Wed night/early Thu morning, as
manifest by 850-400-mb Q-vector convergence downshear of compact
midlevel vort max.
Overall, we will carry likely PoPs for many areas on Wed night,
with thunder also possible, particularly across our
central/southern counties. Organized severe thunderstorms are not
expected (see also SPC day-2 outlook), but the proximity of the
aforementioned steep midlevel lapse rates and LLJ suggest that
some transient stronger storms are possible with elevated
convection. Heavy rainfall is not a major concern, given the
fairly progressive motion of this system, and HREF ensemble-max
QPF generally stays below 1 inch through 12z Thu.
- Seasonably cooler weather for Fri into the weekend
Precip coverage will generally taper away after 12z Thu as
subsidence arrives behind departing wave. Modest low-level cold
advection will commence for Thu afternoon and persist through Fri
morning, with the 850-mb 0C isotherm may reach southern Lake
Michigan. A good deal of cloudiness should linger on Friday,
especially for the lakeshore counties. Moreover, recent
deterministic GFS runs suggest a fast-moving shortwave trough and
associated vort max may clip our southwestern counties on Fri
evening, with another bout of modest cold advection and
cyclonicly-curved low-level flow in its wake. Thus, will maintain
PoPs through Sat morning.
- Somewhat active weather for next week
Looking ahead to next week, a somewhat active patten may be in
store for the Great Lakes. Yet another system will approach for
late Sun into Mon, but details are uncertain. Meanwhile, a 500-mb
anticyclone will over Northern Canada will begin to deamplify on
Sunday, with significant height falls off the Pacific coast on
Mon, with possible implications for our region later in the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 638 PM EDT Tue Oct 19 2021
I am expecting another VFR night for our TAF sites. There will be
some layered mid and high clouds tonight into Wednesday. The
precipitation is not expected until after sunset Wednesday. It
would not be out of the question there could be some light rain
showers by mid to late afternoon near MKG but at this point the
odds are rather low.
&&
.MARINE...
Issued at 923 PM EDT Tue Oct 19 2021
I have expunged the Small Craft Advisory. I did that since the
winds and waves have not reach criteria. The latest model data
does no show winds or waves reaching the threshold for and
advisory tonight or most of the day on Wednesday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
SYNOPSIS...Kenyon
DISCUSSION...Kenyon
AVIATION...WDM
MARINE...WDM
Area Forecast Discussion
National Weather Service New Orleans LA
619 PM CDT Tue Oct 19 2021
.AVIATION... (00Z TAF Discussion)
Conditions remain in VFR overnight for most locations, with some
gusty winds confined to coastal and near coastal sites. Patchy
fog and increase ceilings are possible for locations west and
along the I-55 corridor, to include BTR and MCB. With these
conditions expect decreases in flight categories overnight, down
to the LIFR range. Tomorrow expect showers and thunderstorms to
develop along the coast and work inland during the day. -KO
&&
.PREV DISCUSSION... /issued 327 PM CDT Tue Oct 19 2021/
SHORT TERM (This evening through Friday Night)...
The nice string of weather continues with another beautiful day
in the books. As mentioned in the morning update, a low-level Cu
field developed following afternoon mixing, even with a nice
westward stretching lake shadow west of Lake
Pontchartrain/Maurepas with easterly surface winds. These clouds
were a bit elevated with LCL heights in the 3500-4500ft AGL range,
with diurnal mixing helping to promote just enough positive
energy at the LCL ~860mb to the base of a strong subsidence
inversion ~810mb to pop spotty clouds. This inversion,and the
lack of any environmental dynamic ascent at play helped to prevent
shower activity today. Taking a step back and analyzing the
regional surface /upper-air maps shows the surface high,
responsible for the previous days cool and pleasant weather has
shifted east into the mid-Atlantic states, promoting easterly
winds along a tight SLP gradient over the northern Gulf. This has
led to breezy conditions for coastal locations, especially east-
facing shorelines. Jumping up aloft into the lower troposphere
shows a large pocket of deep Gulf moisture well south of
Louisiana, coincided with mild curvature/troughing rotating
northwest around the periphery of the low-height ridge center
nearby/stacked with the high at the surface along the Mid-
Atlantic coastline. This moisture gradient, aligned with
increasing low-level winds and modest isentropic ascent will
continue to develop coastal showers and storms this evening
through tonight. When going through short-range guidance, noticed
the NAM coming in way too strong developing some sort of meso-low
tracking northwest into SE LA, associated with a 30-40kt 925mb
wind maximum. This appears to be some convective feedback that is
not initializing well based out of radar trends. What is actually
occuring is a nearly stationary cluster of storms south of GMZ570
(far southwestern marine zone), producing 38kt gusts from recent
KGRY observations. Alternatively, recent HRRR runs do not
initialize this cluster which could influence downstream short-
range trends with this cluster either tracking north, or
dissipating with time. Overall, short-range guidance is not in the
best agreement over small-scale features but the general idea
will be increasing marine convection throughout the night, making
it to coastal areas with time and pushing inland through early
Wednesday. We will quickly moisten at the surface as well, with
areas either along or south of I-10/12 back into the upper 60 to
lower 70 dewpoints around daybreak Wednesday.
Next feature to monitor will be low-level stratus developing and
building into the area later tonight/early Wednesday with the
increase in surface moisture/lowering LCL heights/ceilings. The
degree of coverage is in question, with guidance coming in good
agreement with the potential for some patchy surface fog along and
west of I-55. Will let this ride, refraining from mentioning
dense fog at this time until confidence increases. Otherwise, as
we see low-level moisture advection/deep moist ascent continue to
lift/erode the subsidence inversion aloft, we will see building
instability regardless of a thick layer of moisture in the
925-700mb layer keeps mostly cloudy skies in place. Not entirely
impressed looking at low-level directional shear/shear magnitudes
glancing at sounding hodographs, but a strong storm or two cannot
be ruled out given SB/MU CAPE in the 1800-2000J/kg range and
enough deep-moist ascent to act as a trigger to keep convection
scattered and going throughout the day. The tropospheric profile
shows (some) subtle cooling aloft bringing H7 to H5 lapse rates
nearing the 6C/km range, with H5 temps in the -8C to -9C range
that could help grow tall enough updrafts to downward transfer
some sub-severe wind gusts to the surface. Definitely a day to
watch the radar, but for now... not anticipating any widespread
severe weather issues but a few SPS`s cannot be ruled out
highlighting any locally stronger updrafts for gusty wind
potential.
Convection should come to an end Wednesday evening into the
overnight hours as we lose daytime instability and decouple, but
as we reside in a deep-moist tropical environment, cant really
rule out an isolated shower overnight. Meanwhile, a cold front
will approach the area from the northwest helping to squeeze out
more showers and storms during the day on Thursday, out ahead of a
northeastward surging tongue of enhanced PW. Nothing overly
impactful on Thursday with no real strong dynamic trigger in
place other than plenty of Gulf moisture and instability during
peak heating - leading to only a few areas of disorganized showers
and storms.
This front will slowly try to push its way south through our area
during the day on Friday, getting to coastal areas late in the
day. Not seeing much in the way of rain with it, as NBM PoPs come
in the 20-25% range but PW`s will fall quickly back below the 1"
range revealing dry conditions to end the week as we approach the
upcoming weekend. KLG
LONG TERM (Saturday through Tuesday)...
The beginning of the extended period looks to be rather dry and
quiet as we sit in upper level zonal flow most of Saturday, with SE
flow at the surface expected to arrive into Sunday. This helps to
bring a bit of moisture into our CWA, making for some diurnally
driven very isolated PoPs on Sunday, limited to coastal areas.
Temperatures will continue to be above average for this time of
year, with highs in the mid 80s and lows in the mid to upper 60s
inland and the low 70s for coastal areas.
Into Monday an upper level ridge will build over the central CONUS
as a deep upper level trough digs over the far west CONUS. Although
models agree we will be under the ridge on Monday, they also agree
that some moisture will be hanging around our area due to the SE
flow at the surface. With some isolated PoPs for much of the CWA
both Monday and Tuesday, this may end up being more of a dirty
ridge. Temperatures still looking above average early next week,
with highs in the mid 80s and lows in the upper 60s to low 70s.
Dewpoints also look to remain above average in the upper 60s to even
mid 70s at times, making for continuing high RH values as well.
-HL
AVIATION (18Z DISCUSSION)...
Expect VFR conditions for all area terminals today through this
evening, with only some patchy low-level Cu nearby a few terminals
with upper-level cirrus spreading in from the west. Otherwise,
expect generally light to occasionally breezy east-northeasterly
surface winds today, with higher winds primarily confined to
coastal and near-coastal TAF sites.
Clouds will increase tonight, with patchy surface fog possible
primarily for western areas after midnight tonight, or for TAF
sites along and west of I-55 including KMCB and KBTR. Expect
periodic reduced VIS/CIGs leading to lower flight categories in
these areas, otherwise SHRA/TSRA will increase across coastal
areas around daybreak, spreading inland throughout the morning
with prevailing conditions mentioned in TAF sites with higher
rain/storm chances. KLG
MARINE...
Easterly winds will persist across marine areas this evening and
tonight, with surface high pressure over the Mid-Atlantic states
and a tight surface pressure gradient. These winds may be breezy,
especially over outer 20-60nm zones through tonight and have
introduce Exercise Caution headlines through Wednesday morning.
Otherwise, scattered showers and storms will be possible across
all marine zones tonight, extending into the day on Wednesday.
Surface winds will continue to lighten and transition out of the
southeast, with wave/seas peak in the 3 to 5ft range around midday
Wednesday for offshore Gulf zones, but remain in the 1-3ft range
for protected waters. Conditions become more calm going into late
week, then dry this weekend with the passage of a weak cold front.
Calm conditions will persist into next week beyond the upcoming
weekend but may increase in southeasterly flow Monday and Tuesday
back up to the 10-15kt sustained range. KLG
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 60 79 66 83 / 0 70 20 40
BTR 63 81 67 84 / 0 70 20 50
ASD 65 82 69 83 / 30 80 50 70
MSY 71 83 72 83 / 30 90 50 70
GPT 68 81 70 81 / 40 70 50 80
PQL 66 81 69 81 / 30 60 50 80
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
746 PM EDT Tue Oct 19 2021
.SHORT TERM...(This evening through Wednesday)
Issued at 439 PM EDT TUE OCT 19 2021
Water vapor imagery and RAP analysis show split flow across much of
N America. In the northern stream, a shortwave is moving over
western Hudson Bay and adjacent Manitoba/far northern Ontario.
Meanwhile, in the southern stream, a well-defined shortwave is over
the central Rockies. Downstream of these features, mid-level ridging
extends from Lower Mississippi Valley to eastern Hudson Bay. Sfc
cold front associated with the northern stream wave extends from
northern Ontario se across MN to low pres associated with the
southern wave over sw Nebraska. Out ahead of the front, it`s
another warm day (unseasonably warm at that) across Upper MI, the
overall theme of Oct so far. Temps are mostly in the lwr to middle
70s F, except mid/upper 60s along Lake MI. Here at NWS Marquette,
the first 18 days of Oct (will be able to include today as well)
are the warmest first 18 days of Oct on record with the average
temp (11.1 degrees above normal) exceeding the #2 spot (1963) by
an impressive 2.0 degrees. Across Upper MI, the average temps for
the month so far are running 8-12 degrees above normal.
Cold front to the nw will sweep se across the fcst area tonight,
bringing a sharp return to more typical Oct weather for Wed. This
front will reach the Keweenaw this evening and exit s central Upper
MI btwn 09-12z. Behind the front, low clouds will follow. Post
frontal cigs are in the 1000-1500ft range. With cooling air,
arriving low-level moisture and upslope northerly winds, there could
be some upslope -dz overnight in the higher terrain areas favored by
n to ne winds. Temps tonight will fall back into the 40s,
but locally lwr 50s along Lake Superior.
On Wed, some patchy -dz may linger thru the morning in areas favored
by n to ne upslope winds (mainly portions of Baraga/Marquette
counties). Otherwise, shortwave currently over the central Rockies
will weaken as it moves toward the Upper Mississippi Valley.
Associated sfc low will track to far n central IA. Meanwhile, the
shortwave/developing mid-level low over sw Hudson Bay will settle
over far northern Ontario. In the confluent flow btwn the 2 waves,
the resulting upper jet streak will bring right entrance upper
diffluence into northern WI/Upper MI. Streaks of low-mid level fgen
and modest isentropic ascent are noted in the morning, which may
support some -shra, but somewhat better fgen and isentropic
ascent developing in the aftn will bring a better potential of
-shra. Fcst will reflect increasing pops in the aftn, reaching
likely late from KESC toward KIWD. Keweenaw will likely see dry
weather thru the day. With the clouds and n to ne winds, expect a
much cooler day with highs ranging from around 50F w and n central
to the upper 50s s closer to Lake MI.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 433 PM EDT TUE OCT 19 2021
The extended period begins with near to below normal temperatures
and multiple chances for generally light precipitation. Overall,
Thursday through Tuesday should average to below normal temperatures
and near normal precipitation. Lake effect/enhanced rain along the
Lake Superior shoreline may result in localized areas of above
normal precipitation.
A surface low tracks just south of our area Wednesday evening into
Thursday. This surface low tracks along a remnant surface front that
stalls across northern Lower Michigan on Wednesday. Warm air
advection atop the surface front increases as the surface low
approaches resulting in an east-west axis of frontogenesis in the
favored baroclinic zone between Lakes MI and Superior. The post-
frontal air mass appears quite dry so a sharp northern precip
gradient seems likely.
A seasonably chilly air mass moves in as the surface low moves out
Thursday evening. Ensemble means of the major model suites indicates
850 mb temperatures dropping into the -3C to -6C range. This colder
air mass supports lake-850 delta Ts in the 15-20C range that is more
than adequate for lake effect precipitation. There appears to be
at least one noteworthy shortwave passage Friday night, but
lake effect should be active through at least Saturday. Marginal
850 mb temperatures suggest a mixture of drizzle, rain, graupel,
and snow depending on time of day, elevation, and precipitation
intensity. While some snowflakes/mixed precip is possible at
higher elevations it might as well be rain since any frozen
hydrometeors should melt on contact with no accumulations expected
at this time.
Surface ridging moves in Saturday night into Sunday and the drier
air mass should bring an end to lake effect precipitation. With
surface ridging overhead on Sunday and Monday, sunny skies and light
winds support large diurnal temperature ranges. Warm air advection
ramps up ahead on Monday ahead of the next trough/surface low. There
seems to be good agreement among ensemble guidance for this surface
low to track well to our northwest resulting in a return to above
normal temperatures for Monday/Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 735 PM EDT TUE OCT 19 2021
VFR conditions currently persisting at all three terminals will be
short-lived with incoming LL cloud deck. Observations behind an
approaching cold front indicate ceilings in the MVFR and IFR
categories. These low clouds look to linger through the remainder
of this TAF period once they take over the skies. Add in moisture
courtesy of the Great Lake of Superior and drizzle looks probable
at KSAW by early Wednesday morning. Winds initially out of the SW
this evening will become northerly to eventually northeasterly,
with the wind shift already underway at KCMX. Some gusts can be
expected, but currently appears to perhaps remain below the 10
knot over sustained threshold; will update this though if appears
warranted in the next TAF issuance.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 439 PM EDT TUE OCT 19 2021
A cold front will sweep across Lake Superior tonight, bringing a
wind shift to stronger n to ne winds. Expect winds to gust to 20-
30kt, strongest over the w half of Lake Superior. Given the
magnitude of the incoming pres rises, 4-5mb/3hr, some gale force
gusts to 35kt could occur for a few hrs over the w half after the
frontal passage. As low pres moves toward n central IA and high pres
ridges into northern Ontario on Wed, ne winds will continue to gust
to 20-30kt, again strongest over the w half. Winds will settle back
Wed night, gusting to around 20kt, as weakening low pres tracks
toward Lower MI. N to nw winds up to 20kt will continue Thu. Winds
should then settle back to mostly 15kt or less for Fri/Sat. Some
increase in winds may occur late Sun, but there is considerable
uncertainty in whether a low pres system will be moving toward the
Midwest at that time.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...EK
AVIATION...lg
MARINE...Rolfson
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 249 PM CDT Tue Oct 19 2021
Main feature per water vapor imagery is closed low migrating
along the WY/CO border with a mix of precip expanding across WY.
Surface reflection was centered over western KS with attendant
boundary extending from southwest NE to northern MN.
Models in agreement precip activity will begin to spread eastward
out of the NE panhandle/western SD early this evening and expand
across the rest of SD as well as northern NE. RAP/HRRR time the
precip to reach the northern CWA toward midnight.SPC has placed us
in a marginal risk for tonight. However, latest RAP suggests
composite parameters including instability and shear will not be
maximized over our area until after midnight. At this point
serious doubt and severe storms will develop. But cannot
completely rule out some storms accompanied by small hail.
A few locations may see rainfall amounts of a quarter inch or so by
events end Wednesday afternoon. But overall, expect amounts to
generally range from 0.05" to 0.10".
Otherwise, the air mass filling in behind the exiting system will
noticeable cool down Wednesday and Thursday. Dry period then from
Wednesday night through Saturday. Models still hinting precip
chances will return Saturday night through Sunday ahead of a
system ejecting from the central Rockies. Have noted that if the
latest GFS/CMC solutions verify, next weekends storms may be more
intense than previously thought.
Wed - mid 50s/lower 60s
Thu - mid/upper 50s
Fri - low 60s
Sat - low/mid 60s
Sun - mid 60s/low 70s
Mon -upper 60s/low 70s
Tue - mid 70s
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 651 PM CDT Tue Oct 19 2021
Showers and thunderstorms are possible over central and northeast
Nebraska between 04Z and 18Z Wednesday. Storms may affect KOFK
for a time between 05Z and 08Z, but confidence is to low for
inclusion in the TAF at this time. Ceilings should fall into the
MVFR (1,500 to 2,500 ft AGL) range over northeast Nebraska post
04Z, with isolated IFR (1/2 to 5 SM) conditions due to lower
visibility in any rain. Can`t rule out some lower ceilings a KOMA
or KOFK post 08Z, but the potential is lower. Winds should remain
breezy from the south through around 04Z, then transition to
prevailing northwesterly by 15Z Wednesday.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...DEE
AVIATION...Albright
Area Forecast Discussion
National Weather Service Portland OR
344 PM PDT Tue Oct 19 2021
.SYNOPSIS...Expect a very active weather pattern to bring valley rain
and high mountain snow every 12-24 hours through early next week. A
brief burst in wind is likely late tonight and Wednesday morning with
additional stronger bouts of wind possible over the weekend and/or
early next week.
&&
.SHORT TERM...THIS EVENING THROUGH FRIDAY...The cloudy day
continues, with precipitation already beginning in the southwestern
portion of our area (Florence and Newport points west). Now, the
rain will spread northeast across the area as warm air advection
ahead of an approaching surface low results in isentropic lift.
Precipitation with this wave is not looking problematic, as the rain
will be gentle and rainfall totals are looking to generally fall
between one and three tenths of an inch, though some of the higher
terrain in the Coast Rain will see a little more (perhaps 0.5" +).
What is potentially impactful about this system is the gusty wind
threat associated with it. Both the upper trough and its attendant
surface low will have a negative orientation, and a tight gradient
appears likely with an isallobaric push extending east/southeast of
the low as it moves north along the coast. This seems likely to
result in a burst of strong winds area-wide tomorrow morning, with
gusts even in the Willamette Valley reaching the 35 to 45 mph range.
With winds of around 50 knots present at around 850mb, NAM and GFS
forecast soundings suggest efficient momentum transfer through the
mixed layer could produce gusts to ~30-35 knots at PDX. However, any
showers this system produces could tap into stronger winds even
higher up (with the NAM depicting an equilibrium level at nearly
500mb by 11 AM as daytime surface heating begins), which is likely
the reason that the HRRR and NAMNest are suggesting isolated to
scattered gusts to more than 45 mph for a brief period tomorrow
morning. The duration and arrival time of these winds is not
completely agreed upon by the high resolution guidance, but it
appears that the strongest gusts at any location will last only 1.5 -
3 hours, and that this burst of strong winds will move across the
area between 1 AM and 9 AM Wednesday.
The pattern will also turn showery tomorrow morning, and, with
forecast soundings suggesting a couple hundred J/kg of MLCAPE,
sufficient instability should exist to support the slight chance for
thunder that the NBM is forecasting. The area where that risk exists
has been expanded slightly to include much of the Willamette Valley.
It`s not a forecasting decision that was made based on high
confidence, but given (1) the showery pattern depicted by the
convective allowing models, (2) the strongly sheared environment,
and (3) the cold air aloft favoring marginal instability, thunder
seems plausible - especially west of I-5. With any heavier showers
and/or thunderstorms, strong winds and possibly small hail will be
possible; the greatest chance for this would be over the waters,
along the coast, and in the Coast Range through tomorrow afternoon.
Chances for rain subsequently diminish everywhere, with the best
opportunity for a break in precipitation Wednesday evening through
Thursday morning. Thereafter, models are in good agreement that a
remarkably strong surface low in the Gulf of Alaska will bring a
weakening cold/occluded front into our area late Thursday night.
Rain will overspread the area in weak forcing for ascent ahead of
the front beginning Thursday afternoon - first along the Coast, then
later in the Willamette Valley and eventually the Cascades as the
front moves east. Precipitation totals with this system will be a
little beefier than with the tonight/Wednesday afternoon system,
with rainfall amounts Thursday afternoon through Friday evening
looking to be in the 0.5-1.0" range (but a bit higher along the
coast). Though this system will have an intense wind field, that
will remain far enough away from the Coast to have few, if any,
impacts on our county warning area (at least, when compared to
Wednesday morning`s blustery weather). -Bumgardner
.LONG TERM..FRIDAY NIGHT THROUGH MONDAY...Saturday the deep surface
low in the Gulf of Alaska moves north and congeals with another
southeastward moving low rotating about the same parent 500mb
trough. An occluded front associated with this feature will approach
the area Saturday to bring another chance for rain, though the
timing of arrival for this wave of precipitation is looking quite
ambiguous at this time. The deterministic GFS, along with several
ECMWF members, is hinting that one or more weak lows could develop
along this frontal boundary, but the uncertainty in this is high. If
a low can develop in closer proximity to the coast, and with the
proper orientation, another round of gusty winds might be possible
with its passage, but for now we`ll need to wait and see if and when
model agreement increases in a given scenario. One thing that does
look likely with this feature is more widespread precipitation
Saturday into Saturday night.
Sunday and beyond, guidance is just a mess, with only one thing that
seems certain at this time: That the pattern will remain unsettled.
The timing, strength, location, movement, and orientation of the
pressure field associated with any feature is just impossible to pin
down at this time, with virtually every ensemble solution showing a
scenario vastly different from other ensembles. However, heavy
precipitation and strong winds would be possible with one or more of
these lows with excellent dynamical support for cyclogenesis in the
left exit region of a strong upper jet to our south. This being
said, many ensemble members indicate one or more systems that would
stay far enough away from our area (or that would be weak enough) to
result in very little, if any, impacts to any part of our area. For
now, we`ll just have to handle this as has been done the past
several shifts: Watch for patterns and trends in model guidance that
would suggest necessary forecast adjustments during the time period
spanning the latter half of the weekend through the middle of next
week. -Bumgardner.
&&
.AVIATION...Generally VFR with mid and high clouds over the
region early this afternoon. The 12Z HREF ensemble mean cloud
cover guidance and model soundings suggest thickening mid-level
clouds through the evening. The incoming frontal system is
expected to elongate and weaken as it approaches the coast this
evening. Expect rain to reach the coast between 04Z and 07Z,
earliest south of KONP. Rain gradually spreads inland after 07Z,
but low-level offshore flow through the Columbia Gorge will delay
onset of rainfall closer to 12Z Wed. The front reaches the coast
south of KONP around 12Z Wed, but not until 15Z or so along the
south Washington and north Oregon coast. Increasing MVFR
conditions will be likely for the coastal TAF sites overnight.
Expect south wind gusts 25-35 kt along the coast associated with
the frontal passage. Gusts 20-30kt likely inland between 12Z and
18Z Wed, especially south of a KTMK to KSLE line.
For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse
KPDX AND APPROACHES...VFR conditions are expected to continue
through Wed morning, but cigs gradually lower to 100 by 06Z Wed
and then 035-045 by 12Z. Rain develops between 07Z and 10Z. East
wind gusts to 30 kt likely near KTTD and the west end of the
Gorge through 12Z Wed. Weishaar
&&
.MARINE...A strong front continues to move toward the outer
waters this afternoon. The latest models show this front
elongating/weakening as it moves through the outer waters tonight
into Wed morning. The 12Z model guidance maintains the trend of
depicting the strongest wind speeds over the outer waters (beyond
20 nm). Will maintain the current gale warnings. Some models
show a strong wave on the front early Wed morning, but vary on
the strength and timing of this feature. About 25 of 50 ECMWF
ensemble members show gusts 40-48 kts at 12Z Wed for buoy 46050.
The favored time frame for gale force gusts over the inner waters
appears to be between 12Z and 18Z Wed.
A second, potentially stronger, system is forecast to impact the
waters Wed night and Thu. Confidence is fairly high gale force
gusts will occur over PZZ270 and PZZ275. Less confidence in gale
force gusts over the inner zones. The parent low remains well
offshore with a majority of the individual ensemble members
showing the surface low tracking to the south British Columbia
coast Thu. The active pattern continues through the weekend with
additional gale force wind periods likely.
Total wave heights will begin to ramp up over the outer waters
the remainder of the afternoon and spread to the inner waters
this evening. There will be a substantial south wind wave
component, up to 10-12 ft over the far southwest portion of
PZZ275, tonight. This will result in combined seas into the upper
teens for the outer waters. Wave heights will be several feet
lower over the inner zones tonight, but still exceed 10 ft. Seas
gradually subside late tonight and Wed. The expected gales
Thursday will allow seas to rise into the 15 to 20 ft range with
highest seas offshore. Seas subside beginning Fri afternoon, but
will remain above 10 ft through the weekend.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Gale Warning until 11 AM PDT Wednesday for coastal waters from
Cape Shoalwater WA to Florence OR from 10 to 60 nm.
Small Craft Advisory from 8 PM this evening to 2 AM PDT
Wednesday for coastal waters from Cape Shoalwater WA to Florence
OR out 10 nm.
Gale Warning from 2 AM to 11 AM PDT Wednesday for coastal waters
from Cape Shoalwater WA to Florence OR out 10 nm.
Small Craft Advisory from 5 AM to 7 PM PDT Wednesday for
Columbia River Bar.
&&
$$