Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/21/20
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
528 PM MDT Sun Sep 20 2020
.AVIATION...
00Z TAF CYCLE
Scattered cu field over western and northern NM this afternoon with
breezy sly winds across the eastern plains. VFR prevails with some
smoke likely to mix down to the sfc tonight again over the eastern
half to two-thirds of the state. Light terrain drive wind tonight
into Monday morning.
24
&&
.PREV DISCUSSION...306 PM MDT Sun Sep 20 2020...
.SYNOPSIS...
Calm, dry, and warm conditions will prevail this week, as high
pressure remains over New Mexico. A weak upper level disturbance
will enhance the potential for showers and thunderstorms Monday
through Wednesday, with coverage favoring the northern mountains and
western NM. High pressure will build over the state by mid week,
diminishing rain chances and causing temperatures to climb above
normal. A backdoor front is forecast to impact northern and eastern
New Mexico on Saturday, bringing temperatures near to below normal
across eastern New Mexico by Sunday.
&&
.DISCUSSION...
SHORT TERM...(TONIGHT THROUGH MONDAY NIGHT)...
Areas of haze from wildfire smoke will persist, with the HRRR Smoke
model indicating areas along and east of I-25 and along and south of
I-40 will be most affected tonight and Monday.
Cumulus cloud coverage is slightly greater this afternoon compared
to the last couple of afternoons at this time, although chances for
any appreciable rainfall remain slim to unmentionable for the rest
of the afternoon and this evening. Any cells that do develop should
move to the east and will be mostly dry with gusty winds. Chances
for rain from showers and storms over the western and northern high
terrain will be a bit higher on Monday as some mid level moisture
remains forecast to leak into the northwest third to half of the
state. Temperatures will be near to above average.
LONG TERM...(TUESDAY THROUGH SUNDAY)...
A weak upper level disturbance will drop down through the central
Rockies Tuesday, bringing with it the increased potential for showers
and thunderstorms across the northern mts and western NM. By
midweek, an upper ridge will build over the southwestern CONUS,
driving drier air into the Desert Southwest, and this will work to
diminish any chances for precipitation through the remainder of the
week. The upper high will migrate east, centering over NM by
Thursday, weakening somewhat in its course. Temperatures across the
Land of Enchantment will climb a few to several degrees above normal
by Friday. Saturday, a backdoor front dips down from southeast CO.
Models are not yet in agreement whether sufficient moisture will be
present to fuel showers and thunderstorms in the wake of this front,
but so far, the plume looks modest at best. Temperatures however
will dip below normal across the eastern plains and return near to
slightly above normal for the central mts and westward.
12
&&
.FIRE WEATHER...
Potential for a few mostly dry showers and possibly a short lived
thunderstorm with gusty winds will be focused over portions of the
western and northern mountains this afternoon. Best chances for
localized wetting rain will be with convection over the northern and
portions of the western mountains Monday and Tuesday as some mid
level moisture works into the northwest third to half of the state.
If any cells develop this afternoon they will move to the northeast
and east. Cells on Monday will move slowly to the south or
erratically.
Widespread fair to poor ventilation expected central and west Monday
with overall improvement Tuesday and Wednesday as winds aloft become
north to northwesterly. A strong ridge builds late this week, with
dry weather anticipated. Temperatures will be near to above average.
Areas of poor to fair overnight humidity recoveries are forecast
over portions of the Rio Grande Valley westward tonight then again
Wednesday through Friday nights.
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
552 PM CDT Sun Sep 20 2020
.AVIATION...
Southerly winds from 10 to 15 knots overnight will increase and
get gusty by late morning at DHT and GUY. It will take until mid
afternoon for the winds to get gusty at AMA. Visibilities may
become MVFR at DHT and AMA for a brief time with haze Monday
morning. Otherwise, skies will be VFR.
&&
.PREV DISCUSSION... /Issued 221 PM CDT Sun Sep 20 2020/
SHORT TERM...Tonight through Monday...
Persistent SFC high pressure ridge axis near or just south of the
SRN TX Panhandle will remain in place through Monday which means
little change in weather from what we have seen the past few days.
So, winds will be relatively light in the SE but pushing breezy
levels in the far NW where pgrad is strongest. With dry
atmosphere, diurnal range will also remain on the large side with
lows mostly in the low 50s and highs rebounding into the upper
70s to mid 80s. Haze from smoke may be a tad little less
prevalent, in the east, but HRRR smoke products certainly keep it
in place across the west.
Gittinger
LONG TERM...Tomorrow night through Saturday...
Dry weather conditions expected to continue with temperatures
warming up through the week into the first half of this coming
weekend.
Tropical Storm Beta in the Gulf continues to make its way towards
the Texas Gulf coastline to perhaps make landfall by Tuesday
morning. A weak ridge across the SE CONUS will bring the tropical
system into SE TX and will lose tropical characteristics and
become an open H500 wave by Wednesday morning and move east into
the lower Mississippi River Valley by Wednesday night. As it does
so, some Gulf moisture may wrap around into parts of the SE TX
Panhandle providing just some additional cloud cover with no rain
expected at this time. This will keep the SE TX Panhandle a bit
cooler with the higher Td and cloud cover over the aforementioned
region. High temperatures Tuesday and Wednesday will range from
the upper 70s in the SE to mid 80s elsewhere.
Weak northwest H500 flow to eventually light and variable flow
will continue through the remainder of the forecast period with
dry conditions continuing. Temperatures will warm up through the
week topping out in the lower to mid 90s by Friday and Saturday as
a ridge builds over the Panhandles from the SW bringing
downsloping winds.
Meccariello
&&
.AMA Watches/Warnings/Advisories...
TX...None.
OK...None.
&&
$$
15/88
Area Forecast Discussion
National Weather Service Burlington VT
735 PM EDT Sun Sep 20 2020
.SYNOPSIS...
One more night of frost and freeze conditions across the North
Country tonight as high pressure persists over the region. A gradual
warming trend is expected to start the new week off with highs
getting back to seasonal normals by midweek. The threat of frost and
freeze conditions will also come to an end. Expect plenty of
sunshine through Wednesday and no precipitation. The next chance for
some rain will be later Thursday into early Friday as a cold front
moves into the region. At this time rainfall amounts look to be less
than a quarter inch.
&&
.NEAR TERM /THROUGH MONDAY NIGHT/...
As of 735 PM EDT Sunday...No major changes made to the forecast
at this time. Temps are dropping fast similar to previous nights
so a slight adjustment was made to cool temps a little faster.
Otherwise, last visible satellite images of the day showed some
thin smoke aloft moving in from the north, and peeking at the
HRRR experimental smoke model it seems more smoke will likely
filter in from the north through tonight and into Monday. Did
make a slight adjustment to increase cloud cover just to say
partly sunny for tomorrow even though it`s not cloud related,
sunshine will be filtered through the smoke. Could have an
impact on high temps depending on how thick the smoke becomes,
but will allow the next shift to assess that. Have a good night!
Previous Discussion...Looks like another night of frost and
freeze conditions for much of the North Country. A Frost
Advisory is in effect from midnight to 8am for areas where the
Frost/Freeze program remains in effect...which is much of the
Champlain Valley minus Grand Isle County and the eastern
portions of Addison and Rutland counties. Winds and very shallow
cumulus clouds will dissipate by evening and clear skies and
light winds are expected to develop. This will allow
temperatures to fall into the middle 20s to middle 30s and
create the frost and freeze conditions.
Temperatures will rebound quickly Monday morning as full sun and
very dry air mass promote warming. Flow aloft is weaker and despite
deeper mixing winds should be under 10 mph. The deeper mixing will
allow dew points to drop in the afternoon and lower relative
humidities. With high pressure over the area no precipitation is
expected on Monday and as the high begins to move to the east we
should start to see some return flow from the south and southwest,
which will result in lows Monday night not being as cold as they
have been. Frost threat will definitely be limited.
&&
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 338 PM EDT Sunday...Warming trend continues Tuesday into
Tuesday night with highs on Tuesday in the 60s and lows Tuesday
night in the 40s. Once again no precipitation is expected as
area`s weather remains controlled by high pressure over the
region.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 338 PM EDT Sunday...Still looking like a warmer,
breezier, and cloudier period for Wednesday and Thursday. 850 mb
temperatures rising from around 8 to 10C, good mixing, and
partly cloudy skies supports highs both days generally near 70
on Wednesday and 75 on Thursday. However, areas with more
sunshine on Wednesday, most likely in parts of the Champlain
Valley and southern Vermont, could see highs in mid-70s both
days. On Wednesday morning, winds upwards of 20 mph with a few
stronger gusts should be commonly observed in eastern and
southern Vermont. By afternoon, winds in the Champlain Valley
should gradually pick up and peak in the 10 to 15 mph range.
These winds will be stronger on the New York side due to a
downslope component. Meanwhile winds will be fairly light in the
St. Lawrence Valley and Adirondacks.
A cold front passage on Thursday evening continues to look quite
unimpressive with the newest forecast data. In fact, with the trend
towards a weaker surface low, it no longer looks particularly breezy
in the pre-frontal air mass during the day. Other than a wind shift
and increase in clouds, the front will not be very noticeable. The
chance for measurable rainfall has trended even lower with only a 15
to 25% in northern and western areas diminishing to near 0% in
southern areas. Behind the front, a weak area of convergence may
linger over the Adirondacks with some low-level moisture in place.
For now expect no precipitation given upper-level forcing is progged
to be well south of the area, but this feature bears watching for
Friday. Otherwise, quiet weather and near normal temperatures will
be in place as surface high pressure slides eastward near or just to
our north.
Warm weather is looking good for the weekend and have further raised
maximum temperatures for both Saturday and Sunday above the blended
guidance given the trends in global models. This is consistent with
the Climate Prediction Center`s 6-10 day outlook favoring above
normal temperatures in northern New England. We will likely see high
pressure off to our east over the weekend, which would promote
breezy south winds and temperatures reaching into the 70s in most
areas. This scenario would favor moderately windy and choppy
conditions on Lake Champlain over the weekend.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Through 00Z Tuesday...VFR conditions will persist through the
period under mainly clear skies. Some smoke will filter into the
region from the north overnight and through Tuesday, but will
remain aloft above 20,000 feet. No restriction to flight
category is expected a the surface. Winds will be light through
the period, except 5-10kts from the southeast at KRUT
overnight, and during the day at KPBG.
Outlook...
Monday Night: VFR. Patchy frost.
Tuesday: VFR. NO SIG WX.
Tuesday Night: VFR. NO SIG WX.
Wednesday: Mainly VFR, with local MVFR possible. NO SIG WX.
Wednesday Night: Mainly VFR, with local MVFR possible. NO SIG WX.
Thursday: Mainly VFR, with local IFR possible. Slight chance
SHRA.
Thursday Night: MVFR/IFR conditions possible. Slight chance SHRA.
Friday: VFR. NO SIG WX.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Frost Advisory from midnight tonight to 8 AM EDT Monday for
VTZ005-009-018-019.
NY...Frost Advisory from midnight tonight to 8 AM EDT Monday for
NYZ028-035.
&&
$$
SYNOPSIS...Evenson
NEAR TERM...Evenson/Lahiff
SHORT TERM...Evenson
LONG TERM...Kutikoff
AVIATION...Lahiff
Area Forecast Discussion
National Weather Service State College PA
1129 PM EDT Sun Sep 20 2020
.SYNOPSIS...
An anomalous surface high will remain over Pennsylvania through
Monday, then shift south of the state during midweek. A weak
cold front is likely to cross the state late Thursday, followed
by ridging along the east coast next weekend.
&&
.NEAR TERM /UNTIL 8 AM MONDAY MORNING/...
Sky is clear. Temps are jumping down here and there. Overall,
mins look good. Will make only minor tweaks. Don`t expect
any new areas with a widespread freeze with dewpoints mainly a
couple of degs higher than last night at this time. The wind is
lighter, though, and should go calm all over. Will keep the
frost advy as is. Have mentioned patchy frost pretty much
everywhere. With micrometeorology in control overnight, it is
tough to get the mins perfect in everyone`s own backyard.
Prev...
Interesting cu over the eastern counties earlier almost looked
like they had blow-off/anvil tops per satellite loops. But,
they were really flat. Anyway, temps are on track and the sky
has cleared out. Will hold the frost advy where it is for now.
Prev..
Clear skies, a calm wind and dry air will once again result in
efficient radiational cooling tonight, with readings tumbling
after sunset. Overnight lows will be very close to those of
Sunday morning over the eastern half of the state and perhaps a
degree or two milder over the western counties. Areas of frost
will again be a concern from late tonight through Monday
morning, and have issued widespread Frost Advisories for most of
the same places which saw frost on Sunday morning.
&&
.SHORT TERM /8 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
Air mass will moderate a bit on Monday, resulting in a slightly
warmer afternoon. Otherwise, expect a repeat of abundant
sunshine and light wind under the influence of anomalous surface
high. Expect highs to range from around 60 north to the upper
60s south.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
This evening`s update brings, at the most, minor changes. Still
looks to stay dry through the entire forecast - until Day 7.5 or
8. Did dink the maxes down a deg Tues-Thurs with an eye toward
the smoke layer perhaps returning.
Prev...
Monday night looks like another chilly one with potential frost
concerns. After that, center of surface high will drift south
of Pa, resulting in a warmer westerly flow. Plenty of sunshine
should push readings back to near seasonal averages with highs
from the mid 60s to mid 70s. Latest HRRR smoke model suggests
lingering smoke from western fires could be drawn over central
Pa Tuesday PM ahead of shortwave crossing the Grt Lks. If this
happens temperatures could be a bit cooler than forecast.
Still looking very dry in the long term. Multiple waves moving
along the US/Canadian border will be starved of moisture. The
only one of note would be passing us Thursday night or Friday.
The GFS is wetter, making a few hundreths here and there, versus
the EC with this upper trough passage. However, the lack of
moisture will keep us from mentioning PoPs until we can get
some GOMEX or Atlantic moisture up into PA.
&&
.AVIATION /04Z MONDAY THROUGH FRIDAY/...
TAFS in good shape as of 1125 PM.
Earlier discussion below.
00Z TAFS sent.
Very dry air in place, with record low temperatures in a few
spots the last few days. While the temperature drops off quickly
after sunset, it is too dry for fog at the TAF sites.
Expect less of a breeze on Monday, than on Saturday or today.
Thus looking at VFR conditions for Monday and with no change
in the airmass, right into at least Tuesday.
Outlook...
Tue-Wed...VFR conditions.
Thu-Fri...Mainly VFR, with patchy river valley fog possible
early each morning.
&&
.CLIMATE...
Cold temperatures were noted across the region the last 2
nights. Another cold night is in store for the region tonight.
The low of 32 degrees at Altoona this morning broke the old
record of 33 degrees set in 1956.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 9 AM EDT Monday for PAZ017-019-024>028-
033>036-042-045-046-049>053-056-057-063>065.
&&
$$
SYNOPSIS...DeVoir
NEAR TERM...DeVoir/Fitzgerald/Dangelo
SHORT TERM...DeVoir/Fitzgerald
LONG TERM...Dangelo/Gartner
AVIATION...Martin
CLIMATE...Martin
Area Forecast Discussion
National Weather Service Grand Forks ND
935 PM CDT Sun Sep 20 2020
.UPDATE...
Issued at 934 PM CDT Sun Sep 20 2020
Did increase cloud cover over NE ND and into far NW MN thru the
overnight as clouds move east along and north of Hwy 2. Gusty
winds to continue in the DVL basin otherwise winds had decoupled
from aloft and remain southerly in the RRV and east.
UPDATE Issued at 651 PM CDT Sun Sep 20 2020
Mid level showers exiting the far eastern fcst area at 2330z.
Very light rain noted as they move thru Bemidji and Park Rapids
and likely other areas as well. Skies clear behind this area, with
surge of mid level CU/clouds eastward on south side of upper low
moving into the DVL basin. Few showers/sprinkles noted moving into
the Bottineau area with some chance into far NW fcst area this
evening.
&&
.SHORT TERM...(This afternoon through Monday night)
Issued at 331 PM CDT Sun Sep 20 2020
Minimal impacts from weather expected through the short term
periods, with main focus on passing very light precip potential
and isolated thunderstorm potential thorugh sunset.
This afternoon-evening: Cold front and parent trough axis are
actively moving over our CWA and immediately ahead of this cold front
within area of 925-850 MB WAA a narrow region of light showers
(mainly virga and sprinkles) have developed. Instability is
increasing some with objective RAP analysis now indicating around
500 J/KG of MUCAPE. While lightning activity has been non existent
in our area to this point, I couldn`t rule out an isolated
thunderstorms before sunset as this transitions eastward. Latest
HREF for example as less than 10% probability for measurable
through this evening and NBM 24hr probably is less than 15%. Not a
lot of confidence we see measurable, though the slight chance is
probably still warranted considering the forcing/instability
present.
Tonight-Monday night: Strong subsidence as PV height anomaly
transitions over our CWA, and then drier/more stable air arrives
through Monday. This pattern favors dry conditions and is supported
by all guidance during these periods. though there is a lull in
winds aloft immediately along the upper trough a secondary low level
jet moves across the region overnight tonight through Monday
afternoon, so we are likely to see gusty winds continue (just a
shift from south-southeast to west-southwest). Momentum
transfer/mixing should support daytime gusts 30-35 mph over parts of
the region continuing (further north/northwest in our CWA Monday).
Regarding temps: The gusty winds will tend to keep low levels mixed
and limit cooling (lows tonight in the 50/lower 60s again) despite
weak CAA. Only a minor change in temps aloft as the cold front
passes, and with sunny skies and axis of smoke aloft shifted south
and east of our CWA, we should see good diurnal heating Monday
(highs in the mid 70s to lower 80s). Better radiational cooling on
Monday night with seasonal lows in the upper 40s/lower 50s.
.LONG TERM...(Tuesday through Sunday)
Issued at 331 PM CDT Sun Sep 20 2020
Main highlight in the long term period remains the high
confidence in above normal temperatures through the work week.
Confidence has decreased in the continued warmth going into next
weekend. One or more cold fronts bring a slight chance for precip
mid this week into next weekend.
Ensemble and deterministic guidance are in relatively good agreement
of above normal temperatures early this week, especially ahead of
the mid week cold front expected to move through the region late
Tuesday into Wednesday. Temperatures on Tuesday have a good chance
of reaching into the 80s for the majority of the area, around 10-20
degrees above normal. While temps decrease behind this front, there
is still a chance for temps to remain above normal going through the
rest of the work week. This mid week cold front continues to bring a
slight chance for showers and perhaps some thunderstorms given the
signal for weak instability to collect ahead and near the front.
Capping will be an issue given expected warm low/mid level temps,
along with majority of forcing expected to remain in Canada. Still
couldn`t rule out some elevated convection atop the cap should
forcing be enough.
Confidence has decreased in this warmth lasting into the weekend
though as most guidance is speeding up the development of upper
troughing to move out of the PacNW into the Upper Midwest/Great
Lakes region. This eventual troughing also increases the chance for
precip late next week, although details on timing, location, and
amounts are far from certain due to spread within guidance.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 651 PM CDT Sun Sep 20 2020
VFR thru the pd. But windy this evening with south to southwest
thru 02z then west winds picking up Monday midday/aftn with gusts
30 kts psbl mainly near the Manitoba border.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...Riddle
SHORT TERM...DJR
LONG TERM...CJ
AVIATION...Riddle
Area Forecast Discussion
National Weather Service Glasgow MT
718 PM MDT Sun Sep 20 2020
.DISCUSSION...
Evening Update: Scattered showers over the northeastern corner of
the area are starting to decrease and should clear from the area
before midnight. Winds are starting to decrease in many locations,
but is still breezier than originally expected. The updated
forecast this evening reflects POP lingering and wind speeds
diminishing slowly (by an extra hour or two). With winds at Fort
Peck still above Lake Wind criteria after 6PM, the Lake Wind
Advisory has been extended from 7PM to 9PM tonight. The rest of
the forecast is in good shape, with skies clearing overnight and a
return to dry weather. Smoke from California may bring haze back
to area tomorrow per the HRRR smoke model. Roxy
Afternoon Update: Updates were confined mostly to cleaning up the
precipitation forecast for the exiting system. The rest of the
forecast is well on track due to the fairly stagnant pattern that
will re-emerge over the region through the week.
Cliff
PREVIOUS DISCUSSION:
The first wave of precipitation with this storm system came
through the region overnight from south to north and was fairly
quick-moving. Today, the second wave of precipitation will move
through the region from west to east, probably slower, which will
allow for higher amounts of rainfall, especially north of the Hi-
Line. This will also push through some stronger surface winds from
the west behind the cold front. The Lake Wind Advisory is well in
place. Expecting 25 to 35 mph winds, with maybe a few higher
gusts.
Our automated tools for determining the chance for thunderstorms
today were not very helpful, so I felt it was best to try and
depict thunderstorms, where I expect the best chances for
more convective activity to develop, following the trends in the
hourly convective allowing models. Overall, I feel that
thunderstorms are possible, but will not be widespread - more like
hit and miss or isolated. So tried to manually paint the weather
grids in that manner today.
After tonight, as the storm system lifts away toward the
northeast, a drier and warming weather pattern will begin to take
over across the region. High temperatures will warm back up to 80
degrees as early as Tuesday.
Through most of the week, the general weather flow pattern will
be from the west, with barely the passing chance of some isolated
rain showers here or there - nothing very organized.
&&
.AVIATION...
Scheduled maintainence from 06-09Z tonight has been rescheduled
for September 28th.
Expected Flight Conditions: VFR-MVFR
Synopsis: Showers will slowly come to an end over the next several
hours. Low ceilings associated with these showers will climb back
out into VFR conditions by this evening. Dry conditions return to
the region by Monday.
Winds: West winds of 15-25 kts gusting 35 kts will relax back
down to light and variable overnight and remain under 10 kts
mostly out of the west Monday.
Cliff/Roxy
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Lake Wind Advisory until 9 PM MDT this evening For Fort Peck
Lake for Central and Southeast Phillips...Central and Southern
Valley...Garfield...McCone...Petroleum.
&&
$$
weather.gov/glasgow
Area Forecast Discussion
National Weather Service Grand Rapids MI
749 PM EDT Sun Sep 20 2020
LATEST UPDATE...
Aviation
.SYNOPSIS...
Issued at 320 PM EDT Sun Sep 20 2020
- Warmer but dry weather most of this week
- Smoke aloft returns
- Looking better for widespread rain Sunday into Tuesday
&&
.DISCUSSION...(This evening through next Sunday)
Issued at 320 PM EDT Sun Sep 20 2020
-- Warmer but dry weather most of this week--
We are expecting above normal temperature through this coming week
into next weekend. We can thank that system from Russia I have
been writing about for the past few days for that. A near zonal
polar jet near the dateline back west to 140E (Korea) is causing a
rossby wave interaction that will cause a split upper flow near
the Great Lakes most of this week. Most of the Pacific wave energy
that would create meaningful precipitation is passing north of the
Great Lakes.
Two fronts actually do come through this area. The first one is
Pacific system that got booted out of the Gulf of Alaska by the
system from Russia. That system as northern and southern stream
component to it. It is the southern stream part that tracks into
the northern Great Lakes and southern Ontario tomorrow. However
the cold front does not get here since the northern stream part of
the system trails the southern stream wave so that causes a wave
on the front and drags it north before it can get here.
Later in the week the system from Russia gets pushed inland over
the western CONUS as a trailing system from Russia causes a
significant deepening of the upper wave pattern over both the
Pacific and North America. That Russian system will cause a surge
of warming late in the week but at this point most of the energy
from that stays mostly north of here so still no rain is expected.
In fact as the next upstream system gets east of the dateline a
western upper ridge builds causing deepening of the downstream
trough. That will be over the Western Plains by Saturday. Which is
a great place for us to get a really strong surge of warm air. I
would think we could see highs in the 80s if this really works out
this way.
-- Smoke aloft returns --
As the winds become more westerly at mid levels the smoke aloft
returns. Cross sections from the model show the deep is from
around 8000 ft to near 18000 ft. The smoke moves in this evening
and will likely be with us most of this week. This may decease the
daily temperature range some.
--Looking better for widespread rain Sunday into Tuesday --
It is looking better for a widespread rain event late next
weekend into the first few days of the following week. Our second
system from Russia builds a large ridge over the western CONUS and
a 180 knot jet climbs the ridge and dives into the down stream
trough, which because there is yet a third system which helps
keep the upper wave near the Gulf of Alaska deep, forces a deep
trough over the central CONUS into the western Great Lakes. The
polar get south down to Arkansas by Monday Night (29th). With
that deep of a trough with developing closes low, it makes sense
we would finally get rain. Both the GFS and ECMWF ensembles are
now in better agreement with nearly all of the 50 members of the
ECMWF and 20 members of the GFS giving us rain in that time frame.
It will turn shapely colder then too.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 749 PM EDT Sun Sep 20 2020
VFR weather will prevail tonight and Monday. A smoke layer
aloft (above 8000 ft) will overspread the area from the west and
there will also be some cirrus above 20K ft. Southeast sfc winds
around 5 kts tonight becoming south around 10 kts on Monday.
Latest RAP guidance indicates winds of 25 kts at around 1000 ft
AGL between 03z and 10z tonight, but that`s not quite enough to
include LLWS in the TAFs.
&&
.MARINE...
Issued at 320 PM EDT Sun Sep 20 2020
We will continue the small craft advisory for our two northern
marine zones as well as the beach hazard for late tonight into
Monday evening.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from 5 AM EDT Monday through Monday
evening for MIZ037-043.
LM...Small Craft Advisory from midnight tonight to 8 PM EDT Monday
for LMZ848-849.
&&
$$
SYNOPSIS...WDM
DISCUSSION...WDM
AVIATION...Meade
MARINE...WDM
Area Forecast Discussion
National Weather Service Lincoln IL
724 PM CDT Sun Sep 20 2020
.SYNOPSIS...
Issued at 223 PM CDT Sun Sep 20 2020
Mostly clear skies will continue through the night and into
tomorrow. However, smoke from the fires in the west will also
remain over the region. Overnight lows are expected to fall into
the middle 40s but then rebound into the middle to upper 70s
tomorrow afternoon.
&&
.UPDATE...
Issued at 724 PM CDT Sun Sep 20 2020
Last vestiges of visible satellite imagery show the thicker areas
of the smoke layer roughly from about Decatur westward, though
some legitimate high clouds are in portions of east central
Illinois. 18Z run of the HRRR-smoke model indicates this should
begin to pivot some overnight and be more focused across the
northwest half of Illinois. Sky grids have been updated to
emphasize more of a mention of this layer, though only around 30%
or so. Temperature-wise, while dew points overnight will generally
be around 40 degrees from I-72 north, winds are expected to stay
up enough to keep temperatures from falling too far, so low
temperatures only saw some minor adjustments.
&&
.SHORT TERM...(This evening through Monday)
ISSUED AT 223 PM CDT Sun Sep 20 2020
Smokey conditions will continue tonight through tomorrow. However,
skies should be mostly clear as surface ridging remains in place
over central Illinois. East to southeast winds should become
lighter tonight, allowing enough cooling that overnight lows in
the middle 40s seems reasonable. Lots of sunshine tomorrow and
winds out of the southeast should allow temps to rebound into the
middle to upper 70s by tomorrow afternoon.
.LONG TERM...(Monday night through Sunday)
ISSUED AT 223 PM CDT Sun Sep 20 2020
Dry weather will continue into Wed and across most of the CWA
through the entire week. However, remnants of tropical storm Beta
are forecast to advect northward, west of the Mississippi river,
and reach into southern IL during the middle of the week. Some of
this precip could reach southeast IL...southeast of I-70...for
Wednesday night through Thursday. For now, chance of precip will
be below the chance criteria...only in the 20pct range. Will wait
to see if models bring more confidence next couple of days to
consider raising pops higher. The next best chance of precip will
be this weekend as a weather system approaches from the northwest
and reaches central IL by Sat night and continuing through Sunday.
Models show enough agreement with this system at the moment, that
mentionable pops is warranted. Temps through the extended period
will mainly be in the middle to upper 70s, but Sat will be a
little warmer as warm air advection moves into the area allowing
temps to rise into the lower to middle 80s. Overnight lows should
mainly be in the 50s through the period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 608 PM CDT Sun Sep 20 2020
VFR conditions to continue the next 24 hours. Main feature will
be with the smoke layer, which should persist into Monday mainly
from KBMI-KSPI westward per HRRR smoke model. Winds have been
alternating between east and southeast today, but are expected to
become more solidly southeast to south on Monday.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Geelhart
SYNOPSIS...Auten
SHORT TERM...Auten
LONG TERM...Auten
AVIATION...Geelhart
Area Forecast Discussion
National Weather Service Indianapolis IN
1140 PM EDT Sun Sep 20 2020
.UPDATE...
The AVIATION Section has been updated below.
&&
.SYNOPSIS...
Issued at 352 PM EDT Sun Sep 20 2020
High pressure at the surface and aloft will be the dominant force
across the area through at least mid week, keeping the weather dry
and temperatures near or slightly above seasonal normals. An upper
level wave and the influence of the fringe of tropical remnants
may bring a shower or two to far southern portions of the area
Thursday, with slightly more substantial rain chances accompanying
a low pressure system very late in the period.
&&
.NEAR TERM /Rest of Tonight/...
Issued at 948 PM EDT Sun Sep 20 2020
Going forecast is on track. High pressure continues to provide dry
and mostly clear conditions to central Indiana with light easterly
winds. Previous discussion follows...
Another quiet and cool night on tap across central Indiana under
the influence of high pressure. Skies will remain clear overnight
aside from a very small amount of passing high cloud across the
north. Near ideal radiational cooling conditions, low dewpoints,
and dry ground will allow temperatures to cool easily, even with
winds staying up a bit. Have lowered blend numbers to account for
this, while accounting for easterly winds off the city at
IND/urban heat island effect by keeping IND temp up.
&&
.SHORT TERM /Monday through Wednesday/...
Issued at 352 PM EDT Sun Sep 20 2020
Dry weather will persist throughout the short term under the
continued influence of high pressure both surface and aloft. With
the continued influence of very dry ground, have lowered min temps
and raised max temps across the board to account for likely
enhanced diurnal range.
Additionally, have increased sky grids a bit beginning tomorrow
into tomorrow night before cloud associated with disturbance to
our south/southwest begin to move into the area later in the
period. HRRR smoke suggests hazy smoke layer aloft, which has been
bottled up to our west throughout the day, will begin to shift
northeast and overspread central Indiana from the northwest
tomorrow. While there will be little cloud cover, this will bring
a return of the milky/hazy sunshine as was experienced last week.
&&
.LONG TERM (Wednesday Night Through Sunday)...
Issued at 225 PM EDT Sun Sep 20 2020
The National Blend of Models initialization was accepted for most
items.
An upper level low moving into the vicinity on Thursday now looks
to perhaps bring in enough moisture from the south for a few
showers to reach the southern forecast area. Confidence is low
though on the moisture return.
Friday looks to be dry, but an approaching stronger upper level
trough will pull moisture north into the area for the weekend. Not
sure that much moisture will be able to make it into the area on
Saturday, but don`t want to really flip-flop on the forecast. Thus
will keep slight chance PoPs for Saturday.
On Sunday the upper trough will be closer and more moisture will
have moved into the area on southerly flow ahead of it, so chance
category PoPs look reasonable.
Above normal temperatures will continue through the period.
&&
.AVIATION /Discussion for 210600z TAF issuance/...
Issued at 1140 PM EDT Sun Sep 20 2020
VFR through the period. Easterly winds around 3 to 7 kts will
increase in speed to 8 to 12 kts and become more southeasterly by
mid morning. Only a few cirrus overnight and through much of
Monday, with a layer of smoke around 15000 to 20000 ft moving in
during the afternoon and evening.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...Nield
NEAR TERM...Nield/CP
SHORT TERM...Nield
LONG TERM...50
AVIATION...CP
Area Forecast Discussion...UPDATED
National Weather Service Miami FL
830 PM EDT Sun Sep 20 2020
...00z Aviation Update...
.Aviation...
VFR conditions initially could come down to MVFR during the day
on Monday as a cold front moves into the region. CIGs will lower,
especially in heavier showers and T`storms that develop.
Otherwise, subVFR cigs will be possible even behind the front
through the end of the cycle. Additionally, winds will begin to
shift to the north or northeast with a few gusts up to around
30kts, especially for the coastal terminals (PBI, FXE, and FLL).
&&
.Prev Discussion... /issued 335 PM EDT Sun Sep 20 2020/
Short Term (Now through Monday)...
This Afternoon...
A complex pattern evolving today, with several features/impacts
to discuss. First, there is a notable mesoscale low, currently WNW
of Lake Okeechobee, which is evident in latest visible satellite
imagery. While model guidance has been somewhat disparate
regarding this feature, A SW track is forecast to occur, which
should bring the meso-low over near the western interior and
eventually into the Gulf waters. As this progression takes place
this afternoon, a broad surface trough is forecast to develop over
South Florida this afternoon. This isobaric gradient (trough)
becomes induced by both the relative convergent cyclonic wind flow
accompanying the meso-low as well as sufficient differential
heating that takes place, as portions of the interior are forecast
to reach up into the lower to mid 90s this afternoon. The
environment is characterized by deep tropical moisture (2.0-2.3
PWI) and weak steering flow (850-300 hPa mean winds < 5 kts).
Areas where high theta-e air intercepts localized sea-breeze
convergent wind maxima will be favorable for deep convection, of
which may be capable of producing torrential rainfall and strong
wind gusts. For this afternoon, the signal for highest storm
potential is presently over the interior, though activity is
forecast to increase over the Atlantic metros late this afternoon
and into the evening.
Tonight Through Monday...
The concern for heavy rainfall and flooding lingers overnight into
Monday morning. A vigorous shortwave impulse is forecast to
propagate from north to south, around the eastern portion of 500 hPa
anticyclone located in the Gulf of Mexico. A frontal boundary is
attendant with this feature, oriented across south central Florida
with a gradual southerly propagation. A narrow NE convergent wind
field exists ahead of this boundary. Additionally, a swath of high
precipitable water congeals over the Atlantic waters/metros Monday
morning. Higher boundary layer wind speeds associated with the
tightening pressure gradient will yield impressive moisture fluxes,
likely resulting in showers/thunderstorms over the Atlantic waters
overnight and into the morning. This activity may propagate into the
metros, which could present a localized flooding threat.
Furthermore, RAP prognostic data is parsing SFC-3km bulk shear
values of 15-20 kts. This could favor strong bowing segments, which
may be further enhanced by the uptick in synoptic wind speeds.
Therefore, the main impacts of concern tonight into Monday are
strong wind gusts and localized flooding.
Temperatures will be uncomfortable this afternoon, with max
temperatures in the lower to mid 90s across the region. Some relief
is anticipated for Monday, likely owing to widespread cloud cover
tomorrow morning as well as advection of a slightly cooler maritime
airmass. High temperatures for Monday are forecast to be in the mid
to upper 80s across the region.
Long Term (Tuesday through Sunday)...
A drier air mass will move into the region for Tuesday and
Wednesday as high pressure continues to build in from the north.
At the same time, Hurricane Teddy will interact with the frontal
boundary well off to the northeast in the Atlantic. This will help
to continue the strong pressure gradient over South Florida which
will allow for the gusty conditions to continue throughout the
day on Tuesday. There will be a slight chance of showers as
enough lower level moisture will remain in place, however, any
shower that does develop will be fast moving and rather shallow.
The pressure gradient across the region will begin to decrease on
Wednesday and the dry air mass will remain in place. A slight
chance of showers cannot be ruled out during the day on Wednesday
as enough low level moisture still will be in place. Temperatures
during this time frame will be in the mid 80s across the east
coast metro areas to around 90 across the interior sections.
On Thursday, the weather pattern begins to change as the latest
computer model guidance show a mid level disturbance over the
central portion of the country beginning to interact with Tropical
Storm Beta in the western Gulf of Mexico. This interaction will
help to draw the frontal boundary in the Florida Straits back
northward slowly as a warm front as the mid level disturbance
moves eastward. This will allow for additional moisture to return
to the region which will increase the chances of showers and
thunderstorms from Thursday through the end of the week. The
timing of this frontal boundary moving northward is still
uncertain as the ECMWF is a bit slower then then GFS is. The
slower solution would delay the onset of increased chances of
showers and thunderstorms. With the increased amount of moisture,
locally strong convection could lead to heavy rainfall and gusty
towards the end of the week and into next weekend. This will
continue to be monitored as the week progresses.
Marine...
An approaching frontal boundary will result in an uptick in winds
speeds over the Atlantic waters. A surge of moisture will advance
ahead of the front tomorrow as well, which will increase the chance
for showers and storms across the region, mainly overnight into
Monday morning. Breezy NE winds in association with the front will
phase with swell emanating from Hurricane Teddy to produce hazardous
seas beginning this afternoon. The highest swell and wave heights
are forecast to be over the Palm beach waters initially, but will
protrude southward into Broward/Miami-Dade waters as well. Given the
aforementioned conditions, a Small Craft Advisory is currently in
effect. There could be periods where wind speeds meet gale force
criteria, however this does not currently merit a Gale Watch. Will
monitor and update as necessary.
Beach Forecast...
NE swell off the Atlantic coast will be increasing across the
Atlantic waters through at least the middle of this week allowing
for an elevated risk of rip currents to persist, with the highest
risk along the Palm Beach coastline. Therefore, a High Surf Advisory
is in effect for the beaches of Palm Beach County and a High Risk of
Rip Currents in effect for the east coast beaches of South Florida.
Astronomically higher than normal tides may result in minor coastal
flooding along coastal Miami-Dade, Broward, and Palm Beach counties
and isolated minor coastal flooding in Collier County through Sunday
evening. Considering this risk, a Coastal Flood Advisory is in
effect for the Atlantic coast and a Coastal Flood Statement in
effect for the beaches of Collier County.
&&
.Preliminary Point Temps/PoPs...
West Palm Beach 90 78 86 76 / 70 70 50 20
Fort Lauderdale 91 79 86 77 / 40 50 50 30
Miami 92 78 86 76 / 40 50 50 30
Naples 90 76 88 73 / 70 60 50 20
&&
.MFL WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through Tuesday evening for FLZ168-172-173.
High Surf Advisory until 8 PM EDT Tuesday for FLZ168.
AM...Small Craft Advisory until 8 PM EDT Tuesday for AMZ610-650-651-
670-671.
Small Craft Advisory from 2 AM Monday to 8 PM EDT Tuesday for
AMZ630.
GM...Small Craft Advisory until 8 PM EDT Tuesday for GMZ656-657-676.
&&
Marine...09/Bhatti
Aviation...28/Frye
Beach Forecast...09/Bhatti
Short Term...09/Bhatti
Long Term...55/CWC
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1054 PM CDT Sun Sep 20 2020
.SHORT TERM...(This evening through Monday night)
Issued at 256 PM CDT Sun Sep 20 2020
The main message of the forecast is that most locations will be dry
and warm this coming week. However, confidence is increasing in
showers and thunderstorms moving across the region on Saturday. Did
increase pops higher than the blended guidance during this time
period for parts of the forecast area.
Early afternoon GOES GeoColor satellite imagery showed clouds and
smoke across the region. A weak frontal boundary was approaching
from the west, and southerly winds were gusting 25 to 35 mph ahead
of the front in the warm sector.
This front will gradually lose its identity as it drifts eastward
while the upper level forcing lifts northeast into Canada. As a
result, expect less showers and thunderstorms this evening and
overnight. The HiRes models have backed off on the precipitation,
so suspect that this will be more of a scenario with radar echoes
but nothing more than sprinkles for most location. Monday`s
weather looks to be similar only with lighter winds. Have
decreased pops slightly as this too seem to be more of a light
showers or sprinkles type set up.
.LONG TERM...(Tuesday through Sunday)
Issued at 256 PM CDT Sun Sep 20 2020
The only noteworthy change to the extended part of the forecast was
to increase pops on Saturday. Until then, the central United States
will be in a split flow regime with above normal temperatures. A
shortwave trough will slide across the north on Wednesday, but the
strongest forcing and highest chances for precipitation will be
north of the forecast area.
Later in the week this split flow becomes better organized into a
stronger upper level jet. On Saturday the models are in good
agreement that a longwave trough will develop over the Upper
Mississippi River Valley. Rising air ahead of this trough should
lead to a large area of clouds and precipitation. If this current
pattern holds, expect most locations to see measurable rainfall. For
now, due to timing and location uncertainties, only have a 30-40
percent chance of rain. The most likely timeframe would be
Saturday.
&&
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1054 PM CDT Sun Sep 20 2020
No changes to going TAFs, with nothing more than the occasional
sprinkle within the best moisture transport of the LLJ, but dry
air below 700mb (as seen on MPX 00z sounding), will keep things
from getting any worse than that. Given the LLJ overhead, it will
be another night of wind shear as well. This LLJ really starts to
fade Monday morning, so winds will not be as strong on Monday as
they were on Sunday. In addition, there will be potential for a
batch of virga/sprinkles to continue much of the day from south
central MN into western WI where a weak convergence zone will
stall out. Again, chances for precip are to low to include any
mention in the TAFs.
KMSP...Not much more to add. The threat for occasional sprinkles
should be ending as this TAF period gets going, with the HRRR
about the only model that continues to try and generate some
showers near MSP on Monday.
/OUTLOOK FOR KMSP/
TUE...VFR. Wind S 5-10 kts.
WED...VFR. Wind SW 10G20 kts.
THU...Chc MVFR. Wind S 5 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
SHORT TERM...JRB
LONG TERM...JRB
AVIATION...MPG
Area Forecast Discussion
National Weather Service Marquette MI
745 PM EDT Sun Sep 20 2020
.SHORT TERM...(This evening through Monday)
Issued at 423 PM EDT SUN SEP 20 2020
Water vapor imagery and RAP analysis show a mid-level ridge
extending n across the western Great Lakes and northern Ontario.
Upstream, a well-defined mid-level low was over far southern
Saskatchewan with a shortwave pivoting across the Dakatos on its se
side. Sct radar returns are noted ahead of the wave, but have not
seen any obs indicating pcpn reaching the ground. 12z raobs showed
abundant dry air dominating blo 500mb, which is hindering the pcpn
development. Closer to home, it`s been a dry day under the arriving
mid-level ridge. Patch of mid-level clouds has lingered across
portions of western and n central Upper MI. Even though the clouds
are thinning out, smoke layer aloft from the western forest fires
has returned, giving the sky a hazy look. Temps have risen into the
60s across the board, but a few spots over the w are now at 70F.
Winds have become gusty to 20-30mph.
Mid-level low over southern Saskatchewan will open up as it shifts
to northern Ontario by Mon evening. Shortwave over the Dakotas will
pivot ne ahead of it, posing a small risk of -shra later tonight
into Mon morning. As is currently the case, dry air at the lower
levels will continue to be a significant issue. In addition, the
shortwave will be weakening. However, 850mb theta-e ridge/theta-e
adv accompanying the eastward translating low-level jet along with
some instability avbl for parcels lifted from above the stable sfc
based layer may still be sufficient to generate isold -shra. If in
fact a few -shra do develop, suppose that it`s not totally out of
the question that a rumble of thunder could occur as well as there
is the potential of mucape upwards of a few hundred j/kg in the 1-
3km layer. Only schc pops were utilized far w late tonight,
spreading to the Keweenaw Mon morning then e across Lake Superior in
the aftn.
With low-level jet shifting into Upper MI during the night, winds
should remain gusty w and n and especially in the downslope areas to
Lake Superior. Where southerly winds favorably downslope, gusts to
35mph may occur at times. As mixed layer then builds with daytime
heating on Mon, sustained winds and gusts will increase. Gusts of 25-
35mph should generally be the rule. With the wind, min temps tonight
will be held up into the upper 40s to upper 50s, warmest w. Expect
highs on Mon in the upper 60s to mid 70s.
.LONG TERM...(Monday night through Sunday)
Issued at 416 PM EDT SUN SEP 20 2020
Relatively zonal pattern with slight ridging across the mid levels
this week is expected with the first decent chance at precipitation
coming with a shortwave and weak cold front Wednesday night. Heights
rebound briefly Thursday into Friday before another wave and cold
front the UP heading into next weekend. A more significant feature
has shown up in the 3 main deterministic models for the 12Z run...a
highly amplified trough is progged to develop behind the fropa on
Saturday as it digs south from the Great Lakes region into the Gulf
Coast states, persisting into the start of next week.
Monday night, weak boundary and front will be passing through the
UP, bringing just a slight chance of some showers across the central
UP, shifting east through the night. Not overly impressed with the
chances given the abundant dry air, but some models are also picking
up on it, so kept the prevailing fcst and trimmed it back a bit.
Heights begin to rise as SW flow moves in on Tuesday. This will
bring above normal temperatures across Upper Michigan Tuesday and
Wednesday with highs in the mid to upper 70s for the west half and
70s elsewhere. With a ridge of high pressure extending northward
from the Appalachians, dry weather will prevail.
The next chance for precipitation will come Wednesday night as a
shortwave and associated cold front pass through Upper Michigan.
There is some instability with this wave as it pushes through, but
it is elevated. Models have backed off as well with the coverage and
chances of precipitation, so chance pops will continue and capped
thunder chances at slight chance given the lack of deeper forcing
with the elevated CAPE.
Temperatures fall closer to normal then for Thursday before
rebounding above normal again on Friday. Beyond Friday, into the
weekend, another shortwave and associated cold front look to bring a
decent shot at precipitation across the UP. With stronger ridging
upstream across the West Coast, this fropa brings with it colder air
and develops an amplified trough across much of the Great Lakes and
into the Appalachians and even further south early next week. It`s
too far out to go into much detail yet, but the 850mb EC temperatures
get quite cold, as low as -6C by Wednesday, which could put a damper
on the going fcst of abv normal temperatures going into October.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 736 PM EDT SUN SEP 20 2020
With the lower level air mass remaining dry, VFR conditions will
prevail thru the fcst period at KIWD/KCMX/KSAW. Not out of the
question that isold shra could develop over western Upper MI late
tonight, spreading to central Upper MI during Mon, but potential is
too low to include any mention in fcst. Winds on Mon will be
gusty to 20-30kt, strongest at KIWD/KSAW. Some gustiness may
continue tonight as low-level winds increase, but expect LLWS due
to the presence of a stablizing sfc based layer and a low-level
jet just above the sfc. &&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 423 PM EDT SUN SEP 20 2020
With fairly strong high pres over southern Quebec/New England and
low pres tracking from southern Saskatchewan to Hudson Bay, brisk
southerly winds gusting to 20-30kt will generally be the rule across
Lake Superior tonight/Mon. As is typical for southerly winds, the
strongest winds will occur mainly over the e half of Lake Superior.
Some gale gusts to 35kt will be possible at high obs platforms and
also toward and into the nearshore zones e of Marquette, especially
on Mon. Winds will then diminish from w to e Mon night and will fall
off to under 15kt Tue into Tue night as a high pres ridge arrives. A
weakening cold front will cross Lake Superior Wed night with high
pres following, tracking se across far northern Ontario on Thu.
Winds should stay mostly under 20kt during this period. Southerly
winds will increase on Fri as the high moves to the Canadian
Maritimes and low pres tracks e to Hudson Bay. Winds could reach 20-
30kt over the east half of Lake Superior.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Beach Hazards Statement from 5 AM EDT Monday through Monday
evening for MIZ014.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...JAW
AVIATION...Voss
MARINE...Rolfson
Area Forecast Discussion
National Weather Service Phoenix AZ
502 PM MST Sun Sep 20 2020
.UPDATE...Updated Aviation discussion.
&&
.SYNOPSIS...
A weak slow moving disturbance will bring occasional scattered
clouds and very slight chances of isolated light showers and
sprinkles early this week. There is also a very slight chance of a
stray or isolated thunderstorm. The best chances will be in
southwest Arizona and some remote lower deserts outside of Phoenix.
Drier conditions return for the second half of the week. High
temperatures will fluctuate and also remain at least several degrees
above normal through the week.
&&
.DISCUSSION...
The upper air analysis depicts the anticipated weak, nearly
stationary closed low pressure disturbance centered over NW Baja
with a weak cold air trough over SW AZ at H5. Weak southerly
cyclonic flow dominated SW AZ ahead of the low with slightly stronger
southerly anticyclonic flow controlling SE-E AZ on the west flank of
the high to the east. The converging southerly flow was supporting
an axis of elevated/increasing PWs across SW AZ and the lower
Colorado river of 0.8-1.0" and some slightly elevated MUCAPE. The
latest midday ACARs sounding showed PW at 0.73" (near the same as
12Z) although with some elevated mid level moisture near 600-650 mb
and southeasterly flow through the lower BL. Low and mid-level GOES
WV and imagery showed an axis of slightly elevated moisture with sct
Cu across S-SE AZ and the borderland slowly drifting northwest in
advance of the low. Early afternoon radar had some isolated
light showers developing well south of Gila Bend.
The weak and relatively/mostly dry low pressure will linger over SW
and S-central AZ through Tuesday evening and bring a slight chance
of isolated, mostly light showers and sprinkles/virga, especially to
SW AZ and remote lower desert locations outside of Phoenix. GEFS PW
anomaly indicates moisture advection in advance of the low will
gradually increase PWs across SW and S-central AZ through Tuesday
somewhere near 0.9-1.0". There will be a minor increase in patchy
mid-level moisture and sct cloud cover near H6. Together with weak
vorticity and forecast weak CAPE/instability, a slight chance of a stray
or isolated thunderstorm can not be precluded--especially for the
aforementioned areas on Monday afternoon. The slightly more bullish
HRRR and ARW of the HREF family depict any isolated heavier showers
or an isolated storm as being very short-lived. Although most
members keep activity much more subdued. As such no significant
impacts are currently in the forecast with the exception of a slight
chance of dry lightning.
The day 3 and 4 NCEP/WPC 500 mb heights clusters and ensembles are
in good agreement on a progressive ridge of high pressure building
across S CA and the SW US through the Central Plains/US on Wednesday
and Thursday. By Friday the ridge flattens in response to a
progressive low and troughing zonal jet stream to the north. Drier
and slightly warmer conditions are on tap for the second half of the
week. With only a couple degrees of warming, highs will remain in
the low-mid 100s through the end of the week.
The weekend favors continued dry conditions with dry northwesterly
flow aloft and a chance of high pressure building across the West
Coast late in the period.
&&
.AVIATION...Updated at 0000Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Moisture will increase overnight ahead of a weak low pressure system
across the northern Baja Peninsula. Consequently, areas of
SCT-BKN mid clouds could persist into Monday. There is also a slight
chance of showers, though any cells that develop would be light and
brief. The focus for mid clouds and isolated showers will generally
shift into western Arizona Monday. Winds will also remain light and
diurnal at the TAF sites. Otherwise, areas of elevated haze
associated with distant wildfires will persist. Reductions in
surface visibilities are not anticipated, however slant range
visibilities may be affected around sunrise and sunset.
Southeast California/Southwest Arizona including KIPL and KBLH:
A corridor of deeper moisture will be transported into western
Arizona and extreme southeastern California through Monday. A brief
shower may be possible near KBLH Monday afternoon, however
probabilities are too low to include in the TAF. Otherwise, areas of
elevated haze associated with distant wildfires will persist.
Reductions in surface visibilities are not anticipated, however slant
range visibilities may be affected around sunrise and sunset.
&&
.FIRE WEATHER...
Wednesday through Sunday:
A lingering slight chance of afternoon convection will continue
outside of the forecast area (White Mountains) Wednesday. Highs will
be slightly warmer on Thursday and Friday although still remain at
least a few degrees above normal through the period. Min RH values
trend down slightly through Thursday but will generally remain
in the 10-15% range most places. Max RH values trend down through
Thursday as well, especially over southeast CA and southwest AZ with
decreases of as much as 30%. But readings are expected to generally
remain above 25% across the forecast area. Winds will be mostly
light and favor normal diurnal pattern with periods of typical
afternoon breeziness.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Sawtelle
AVIATION...Hirsch
FIRE WEATHER...Sawtelle/AJ
Area Forecast Discussion
National Weather Service Reno NV
1256 PM PDT Sun Sep 20 2020
.SYNOPSIS...
A general haze should linger for most locations with worse smoke
and degraded air quality expected for portions of northeast
California and the eastern Sierra tonight. Some degree of smoke
and haze should affect the region through the week, but it will be
dependent on fire activity. High temperatures return to slightly
above average with dry conditions and breezy afternoon winds the
week ahead.
&&
.DISCUSSION...
Not much in the way of changes to the forecast thinking with the
main concerns being dry and breezy conditions this week in addition
to smoke/haze impacts.
* WINDS: A trough approaches the PacNW this week which will
enhance gradients and bring breezy afternoon winds each day. At
this point, Tuesday and Friday could feature slightly stronger
winds, but overall speeds this week will be similar to a typical
zephyr. This will bring increased fire concerns, choppy
conditions on area lakes, and could be a bit bumpy for aviation
interests each afternoon. For more details on the fire weather
concerns, please see the fire discussion below. Lighter winds
are looking likely Sunday into the start of next week as high
pressure strengthens over the west.
* SMOKE/HAZE: Ongoing wildfires aren`t burning quite as
aggressively as what we saw last week, with satellite imagery
showing much less smoke present across the west. With the dry
and breezy conditions this week, it`s possible fires could burn
more actively again, but that isn`t something we can say with
certainty. Expect general smoke/haze across the region this week
with the potential for unhealthy air quality and reduced
visibility to return to the Mammoth/June Lake/Mono Lake areas
starting tonight from the Creek Fire. Air quality may also be
degraded in northeast California between Quincy and Susanville
due to the North Complex.
* ANY RAIN?: The aforementioned trough brings a chance for very
light rain Thursday into Friday in far northeast CA near the
Oregon border based on ensemble chances for 0.01" or greater.
Wetting rains, however, are unlikely. Otherwise, the forecast
remains dry through the end of September.
* TEMPS: Temperatures will be warm during the day, running just
slightly above normal, with seasonably cool nights. Frosts/
freezes remain likely in Sierra valleys with spotty frost
potential for rural western Nevada valleys. - Dawn
&&
.AVIATION...
* After todays light and variable winds, southwesterly breezes kick
in each afternoon and evening starting Monday. No major aviation
impacts from the winds alone - mainly gusts 20-25 kts at their
peak through Thursday at airports such as RNO, CXP, TRK, TVL, NFL,
SVE.
* Smoke models are really focusing smoke closer and more directly
downwind of ongoing fires such as the Creek and North Complex.
As such the trend in the HRRR Smoke guidance has been for more
of a general haze at most airfields into Monday and possibly
beyond. Generally 6-10 mile type stuff. So while not included in
the TAF explicitly, there will be haze in the region affecting
slantwise visibility making terrain harder to see at a
distance.
* The one big exception is MMH where smoke models bring in slugs of
dense smoke each afternoon-night from the Creek Fire as winds turn
more westerly. HRRR Smoke showing IFR conditions at times this
evening into Monday morning which is noted in the TAF. SVE could
see some occasional MVFR conditions from North Complex smoke.
-Chris
&&
.FIRE WEATHER...
* Winds increase starting Monday as an upper trough sets up shop
off the Pac NW coast helping increase gradients in our region
slightly. These are not big winds, closer to what a typical
zephyr would bring in the summer. ECMWF Extreme Forecast Index
guidance keeps strongest winds up into Oregon. Also humidity
values are low but not super dry. So that sets up a scenario
each afternoon Monday-Thursday where we could see critical
conditions in wind prone areas for 1-2 hours, mainly from the
Sierra Front northward into NE California and far N Washoe
County. Not widespread nor long enough duration for any watches
or warnings but will highlight in our briefings and in the FWF.
* Otherwise were watching a decent ridge signal in the ECMWF
ensemble guidance for next week, which would set up another round
of unusually warm temperatures and more drying. With that feature
in place, wetting rains are looking extremely unlikely in our
region through at least October 4th. The GFS ensemble is looking
less amplified with somewhat flatter flow, but still skimpy on the
offerings of wetting rains into early October. Fire season
continues.
-Chris
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Las Vegas NV
805 PM PDT Sun Sep 20 2020
.SYNOPSIS...A weak disturbance with limited moisture moving up
from northern Baja will produce isolated thunderstorms over Mohave
county Monday afternoon and even a slight chance for the mountains
of Clark County and eastern San Bernardino counties. A dry southwest
flow then redevelops Tuesday into next weekend with temperatures
holding several degrees above normal.
&&
.UPDATE...Mostly clear skies and light winds dominate the region
this evening. Greatest smoke density today has been focused across
far western San Bern and Inyo counties, and Mammoth`s visibility has
dropped into the 2-5 mile rage in the past few hours, with some of
this smoke likely to filter into the Owens Valley later tonight.
Overall, the forecast has things well handled and no updates are
needed tonight.
-Outler-
.SHORT TERM...through Tuesday.
Satellite loops showed cumulus fields over Mohave County this
afternoon and more vertical cloud development could be seen over
southwest Arizona and northern Sonora. Moisture from this region
will continue to be pulled up across northwest Arizona and there may
be sufficient moisture and instability over eastern San Bernardino
and Clark counties by Monday afternoon for a slight chance of
showers or thunderstorms. This will combine with a weak disturbance
being pulled from northern Baja to western Arizona in the base of
broad trough developing along the West Coast. The 12Z HREF indicates
the latest HRRR indicate the potential for some convection over the
Mojave National Preserve, McCullough Range and possibly the Spring
Mountains. A slight chance of thunderstorms was added to the Wx
grids for these areas. Any rainfall should be quite light...less
than a tenth of an inch. Some thunderstorms may continue into Monday
evening over Mohave County. Increasingly dry southwest flow Tuesday
should stabilize the air mass. Breezes will pick up each afternoon
out of the south-southwest generally 10-20 mph with occasional gusts
25-30 mph. Daytime and overnight temps won`t vary more than a couple
degrees from today`s readings.
.LONG TERM...Wednesday through Sunday.
The latest models are in fairly good agreement that a ridge will
briefly amplify over the region Wednesday ahead of another broad
trough moving across the northern Great Basin Thursday and Friday
followed by a large ridge building over the western states next
weekend. This will provide a dry weather pattern with breezy
afternoons Thursday and Friday. Temps will remain 5-7 degrees above
normal.
&&
.AVIATION...For McCarran...Generally light winds expected today
following typical diurnal trends. South-southwest winds expected
later this afternoon into the evening, generally remaining below 10
knots. Light and variable winds are expected overnight through early
tomorrow morning. Similar winds expected tomorrow with light
easterly winds developing late morning and a push of southerly winds
late afternoon. There is a slight chance for distant thunderstorms
to develop south and east of Las Vegas tomorrow afternoon, which may
push outflow boundaries in the valley, but confidence low on this
occurring. Varying amounts of haze will continue to contribute to
slight reductions in visibility, potentially obscuring surrounding
mountains at times. Mid to high clouds expected tomorrow afternoon,
remaining aoa 12-15 Kft.
For the rest of southern Nevada, northwest Arizona and southeast
California...Southerly winds 10-12 knots with occasional gusts to 15-
20 knots expected this afternoon across the region. Southeasterly
winds at KBIH may bring an increase of smoke/haze potentially
reducing visibility`s this afternoon. Light, diurnal winds will
resume shortly after sunset. Similar winds expected tomorrow across
the region. Mid to high clouds expected tomorrow afternoon generally
across southern NV, the Colorado River Valley, and northwest AZ
remaining aoa 12-15 Kft.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
SHORT TERM/LONG TERM...Adair
AVIATION...Kryston
For more forecast information...see us on our webpage:
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