Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/27/20
Area Forecast Discussion
National Weather Service Denver/Boulder CO
802 PM MDT Sat Sep 26 2020
.UPDATE...
Issued at 756 PM MDT Sat Sep 26 2020
Smoke has move into the I-25 Corridor behind a cold front. The
smoke will linger much of the night in and near the foothills
but should diminish across the plains. Otherwise no changes
needed to previous forecast.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 302 PM MDT Sat Sep 26 2020
Short wave associated with a passing jet max north of Colorado
will push a weak front into the northeast plains this evening.
Strong gusty winds in the mountains and foothills with 50-60 mph
above timberline and in the foothills of Larimer County. HRRR
still shows the potential for a few showers late this evening, but
likely just some brief sprinkles. Another warm afternoon with
temperatures in the mid 80s in spite of a persist shield of high
cloudiness over the urban corridor and northeast plains. Late
tonight and Sunday, a stronger system will drop out of the
northern Rockies. There will be weak mid/upper level QG omega
through Sunday morning then increasing subsidence as a 110 kt
upper level jet orients itself northwest/southeast over the
plains. Some jet dynamics coupled with low level instability will
allow for scattered showers in the afternoon. 700 mb temperatures
ranging from +12 to +15C this afternoon, will range from -3 to +2C
across the northeast plains Sunday afternoon. High temperatures
on Sunday will be 20-25F cooler than today. Gusty northerly winds
25-35 mph can be expected over the urban corridor/northeast plains
Sunday, strongest to the north and east of Denver. Models show a
fairly decent north-south surface pressure gradient around from
0900-1500 mdt Sunday. In the foothills, gusty northwest winds but
Sunday afternoon but nothing to the degree of this afternoon,
coupled with cooler temperatures and a chance of showers should
help improve the fire weather conditions.
.LONG TERM...(Sunday night through Saturday)
Issued at 302 PM MDT Sat Sep 26 2020
A 135kt jet on the backside of the upper trough laid across the
Rockies in Wyoming will continue digging the trough to the
southeast Sunday night. High surface pressure pushing down from
that region as well will keep the northerly winds across the
forecast area with them veering to the northeast to east up to 700
mb into the southern Foothills through midnight. This, combined
with the plains being in the left exit region of the incoming jet
will keep a slight chance of showers over the northeastern plains,
and a better chance of light showers over the high Front Range mountains,
foothills and Palmer Divide area. However, with QG forcing being
downward, and much drier Precipitable Water values of 0.1-0.4
inches being advected in, very little precipitation is expected.
Models have all been trending downward/drier as well, so backed
off on PoPs, QPF and snowfall forecasts. Best moisture will be
found south of I-70, mainly east of the Palmer Ridge. Therefore,
with snow levels down around 7000ft by midnight, down to 65,00 by
Monday morning, only expecting less than an inch of snow to fall
over the Front Range mountains, foothills and South Park. With
clearing skies, overnight lows will be in the teens to 20s in the
mountains, and in the 30s over the plains.
Stiff northerly flow will be across the state Monday as the upper
trough heads into the Great Plains and into the Mississippi
Valley and a high amplitude upper ridge builds over the western
US. Therefore with help of the cold morning temperatures,
Monday`s max temperatures will only be in the mid 50s to mid 60s
across the plains and in the 40s to 50s in the mountains. Winds
will remain gusty out of the northwest.
The West Coast ridge and East Coast trough weather pattern will
stay for the rest of the week, with models agreeing on a dry
northwesterly flow over the state. Tuesday will have a quick warm
up as a surface lee trough develops and warmer air is mixed down,
resulting in temperatures near 80 over the plains and in the 60s
in the mountains. Then a few ripples in the flow aloft dropping
south across the Great Plains will push in cooler temperatures.
Friday and Saturday`s temperatures will warm back to normal for
early October.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 756 PM MDT Sat Sep 26 2020
Gusty east winds along with smoke will continue for the next few
hours. Winds should decrease by 05z with improving visibilities
by 06z. Winds after midnight will be light east or southeast.
&&
.FIRE WEATHER...
Issued at 302 PM MDT Sat Sep 26 2020
A cold front has moved across the plains with cooler
temperatures and increasing humidity. Over the higher
terrain winds have decreased with some increase in humidity.
A stronger cold front will push in on Sunday bringing little more
than a dusting of snow over the higher elevations of the Front
Range Mountains while the plains receive very spotty areas of
little more than a trace of rain. The one exception may be closer
to Lincoln County where better moisture will exist. Temperatures
20 degrees cooler and gusty northerly winds of 20 to 35 mph will
occur.
For the rest of the week, a dry northwesterly flow will be aloft,
resulting in near normal temperatures and humidity returning to
levels between the teens to mid 20 percent range. Winds will come
close to criteria especially over the plains as the jet stream
remains nearby. At this time, conditions don`t seem to need any
sort of highlight.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
&&
$$
UPDATE...RPK
SHORT TERM...Cooper
LONG TERM...Kriederman
AVIATION...RPK
FIRE WEATHER...RPK/Kriederman
Area Forecast Discussion
National Weather Service Columbia SC
839 PM EDT Sat Sep 26 2020
.SYNOPSIS...
Drier conditions for the weekend before a more unsettled and
wet beginning of the week. Cooler temperatures are expected by
the middle of the week.
&&
.NEAR TERM /UNTIL 7 AM SUNDAY MORNING/...
Mid and upper level dry air across the area with PWATs dropping to
below an inch. This deep layer of dry air continues to promote
subsidence which has prevented drier air mixing down to the
surface today. While there has been some erosion of the low
clouds that are in place currently, this will allow for more
favorable radiational cooling conditions which will support fog
developing late tonight, with crossover temps only in the mid
60s. Fog may become locally dense in fog prone areas.
Temperatures drop into the low to mid 60s.
&&
.SHORT TERM /7 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
Southerly flow will increase through the day Sunday as an upper
level trough digs into the central US. Moisture will mainly
impact the eastern Midlands with pwat values rapidly increasing
during the late morning and early afternoon hours. This will
bring showers and a few thunderstorms to the area with the
highest chances in the eastern Midlands and lower chances in the
central and western Midlands. Monday another push of moisture
from the Gulf will be moving into the forecast area with
increasing chances of showers and a few thunderstorms again for
the late morning through the afternoon hours. The upper level
trough will dig deeply through the central US Monday with the
trough axis moving into the far western Gulf States Monday
night. Concern for the forecast area Monday night will be with
pops as the area will be between the departing moisture to the
east and an approaching cold front to the west. Have remained
with chance pops overnight however subsidence between the
features may be stronger and result in limited precip.
Temperatures will be in the low 80s each day with overnight lows
in the mid 60s to around 70.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
All of the models continue to advertise a deep upper trough
centered west of the region by Tuesday. Model time section show
a deep south/southwest flow from the Gulf ahead of this system.
At the surface a cold front along with good surface convergence
will be moving across the region throughout the day into Tuesday
night. Some differences begin to appear between the
GFS/ECMWF with how deep and when the trough will close of
across the Southeast. This will affect the timing as to how
quickly the moisture will push east of the CWA on Wednesday.
Models do show good instability ahead of the front, so have
continued with mention of thunderstorms Tuesday into Tuesday
night. By Wednesday, models begin to push system and moisture
farther east and away from the area. Have still kept some low
chance pops through Wednesday night for any showers. With closed
low/cold pool aloft would expect clouds along with a few showers
around.
As the trough moves east of the area by midweek, should see
dry and cooler weather for Thursday through Saturday. Another
reinforcing s/w will move across the area Thursday night into
Friday. A moisture limited front will cross the area Thursday
night and reinforce the cooler airmass into the weekend.
Near normal high temperatures in the low to mid 80s Tuesday
will cool into the 70s for the latter half of next week into the
weekend. Overnight lows around 60 Tuesday night will cool into
the 50s Wednesday night through Saturday morning.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Challenging forecast with lingering stratus in place and
abundant low level moisture in place beneath very dry mid
levels. Reasonably high confidence in restrictions later tonight
but low confidence in whether it will be from fog or stratus.
Satellite showing the last of the stratus holding out at CAE/CUB
with a brief patch of it at OGB. Expect all terminals should be
VFR by 03z. Some higher clouds are developing along the Gulf
Coast, east of an upper low, and they will continue to stream
northeastward overnight. The dilemma for this forecast will be
the return of stratus or development of fog during the predawn
hours. Soundings indicate a significant amount of mid level dry
air which is confirmed by the water vapor imagery, while at the
surface dewpoints are in the mid to upper 60s. Winds will be
light to calm overnight and this is a favorable set up for fog,
and possibly dense fog. Also, there is moisture trapped beneath
the subsidence inversion which may reform into stratus as the
HRRR suggests.
While I believe restrictions are likely, the uncertainty comes
with whether it will be from fog or stratus. Introduce MVFR
vsbys after 06z all terminals and mention potential for IFR
stratus and brief IFR/LIFR fog during the 08z-12z time frame.
Expect vsbys to improve by 14z but some lingering stratus may
linger until 16z-17z before cigs improve to VFR. Winds will pick
up from the southwest around 5 knots. Isolated showers possible
late afternoon but not including in this forecast.
EXTENDED AVIATION OUTLOOK...Morning fog/stratus possible
Monday. Periods of flight restrictions expected in scattered to
numerous showers and thunderstorms Sunday night through
Wednesday.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Grand Junction CO
521 PM MDT Sat Sep 26 2020
.SHORT TERM...(Tonight through Sunday night)
Issued at 347 PM MDT Sat Sep 26 2020
Strong gusty westerly winds are occurring across much of the CWA
ahead of a strong cold front expected to move through Sunday. The
southern edge of a 120 kt jet is dipping southward across the
northern half of the CWA. This in combination with low relative
humidity is allowing for critical fire weather conditions across
east-central Utah and west-central Colorado. High temperatures are
currently around 10 degrees above normal and near record highs in
some areas. Big changes are on the way as a much cooler air mass
ushers in behind a strong cold front on Sunday. Daytime
temperatures on Sunday will be near to slightly below seasonal
with even cooler temperatures Monday. As this trough and cold
front drop southward, the backside of the trough will brush by the
northern divide mountains allowing for some isolated showers and
light snow at the higher peaks. Most of this precipitation looks
to stay east of our CWA but may squeeze in along the far eastern
side along the Park and Gore Ranges. Relative humidities will come
up quite a bit Sunday in this cooler air mass with the Four
Corners valleys potentially seeing elevated fire weather concerns
in the post front/trough northwest flow. More details in the Fire
Weather section below.
This trough and cold front look to finally push the smoke and
haze out of the region for some cleaner skies on Sunday according
to the HRRR smoke model. The big story though will be the much
colder temperatures Sunday night. Widespread below freezing
temperatures look possible across the northwest Colorado and upper
Colorado River valleys, with low temperatures Sunday night in the
20 to 28 degree range. If this verifies, this would be a
widespread season ending killing hard freeze. We didn`t quite hit
it with the last cold push due to the abundance of cloud cover but
it looks like skies will be clear for this push of cold air.
Therefore, decided to issue a Freeze Watch for Colorado zones 1,
2, 5, and 8 for Sunday night into Monday morning. Efficient
radiational cooling has been occurring each night with clear skies
and dry air, with overnight lows in some areas, several degrees
below forecast and model guidance. So, also adjusted towards the
10th percentile and lower end of most model guidance for overnight
lows both tonight and Sunday night.
.LONG TERM...(Monday through Saturday)
Issued at 347 PM MDT Sat Sep 26 2020
The entire forecast area will be in a post-frontal regime to start
the day on Monday with the coldest air aloft settling in by mid to
late morning. 700mb temperatures will range from -3C up north to
around +5C down south. This quick shot of cool air will translate to
high temperatures several degrees below average, which will actually
make it feel like fall for a change. Combined with diminishing winds
and a mostly sunny sky, it will be a near picture-perfect fall day
across the Western Slope.
Unfortunately, this fall-like weather will be short-lived as warm
advection ramps back up late Monday afternoon into Tuesday. This is
in response to a trough axis exiting to our southeast and an
anomalously strong mid-level ridge building in from the west over
the Great Basin. High temperatures on Tuesday will quickly rebound
back to near seasonal norms, if not a few degrees above. This
warming trend will continue through the remainder of the long term
period with temperatures climbing to 5 to as much as 15 degrees
above normal by mid to late week.
No good news in the precipitation department as the strong, highly
amplified ridge will be very effective at preventing any source of
moisture from reaching into eastern Utah or western Colorado. In
fact, modeled precipitable water from the 00Z EC ensemble is progged
to be a paltry 0.20 inches on average through next Saturday. PWAT
values that low would be near daily record minimums. As a result,
it`s safe to say that precipitation chances will essentially be near
zero through at least the end of next week. It`s also reasonable to
think that the dry and unseasonably warm pattern extends into the
first full week of October as well.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 520 PM MDT Sat Sep 26 2020
VFR conditions will continue through the forecast period with only
high clouds expected. Expect west to northwest winds to subside
this evening, and winds of 10-15 mph on Sunday afternoon.
&&
.FIRE WEATHER...
Issued at 347 PM MDT Sat Sep 26 2020
Dry and warm conditions in combination with gusty winds will
allow for critical fire weather conditions across portions of
east-central Utah and west-central Colorado ahead of a strong
cold front today. Therefore, the Red Flag Warning remains in
effect. Localized conditions will occur elsewhere like Durango and
Moab but do not appear widespread enough across those zones. This
cold front will move through Sunday, bringing much cooler weather.
Strong winds and dry conditions may create elevated fire weather
concerns across southwest Colorado Sunday afternoon. Still some
uncertainty in terms of the relative humidity as it looks very
borderline with higher relative humidities expected in the cooler
post frontal airmass. Will let the evening shift re-evaluate.
High pressure builds in for the coming week with dry conditions
and a slow warming trend towards mid to late week.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Red Flag Warning until 8 PM MDT this evening for COZ202-203-205-
293.
Fire Weather Watch from Sunday afternoon through Sunday evening
for COZ207.
Freeze Watch from Sunday evening through Monday morning for
COZ001-002-005-008.
UT...Red Flag Warning until 8 PM MDT this evening for UTZ487.
&&
$$
SHORT TERM...MDA
LONG TERM...MDM
AVIATION...MAC
FIRE WEATHER...TGJT
Area Forecast Discussion
National Weather Service Lincoln IL
908 PM CDT Sat Sep 26 2020
.SYNOPSIS...
Issued at 331 PM CDT Sat Sep 26 2020
An approaching cold front will bring an abrupt end to the
summer-like weather across central Illinois by early next week.
After one more warm day on Sunday, high temperatures will drop
into the middle 60s by Monday.
&&
.SHORT TERM...(This evening through Sunday)
ISSUED AT 331 PM CDT Sat Sep 26 2020
Breezy and warm conditions will be the rule tonight, with
overnight lows remaining in the lower to middle 60s. The main
short-term forecast challenge will be the potential re-development
of low clouds late tonight into Sunday morning. Models had a poor
handle on the clouds earlier today, so am skeptical of solutions
that suggest clear skies. The HRRR has been hinting at low clouds
after midnight, mainly along/east of a Champaign to Shelbyville
line. Given increasing boundary layer moisture and a persistence
forecast, have gone with overcast conditions across the E/SE KILX
CWA after midnight. Further west, have maintained partly cloudy
conditions due to increasing/thickening high clouds.
Cold front currently across the Dakotas will push into central
Illinois on Sunday. There are some notable differences among the
models concerning the exact speed of the boundary, with the 12z
NAM appearing to be the slowest model. With a vigorous short-wave
trough evident on latest water vapor imagery over the Northern
Plains, think the front will get a solid push southeastward. As a
result, prefer the faster GFS/ECMWF/HRRR solution. Given expected
position of front approaching I-70 by mid-afternoon, have featured
a strong NW/SE temp gradient across the area...with highs ranging
from the lower 70s far northwest around Galesburg to the lower
80s along/south of I-70. While models have been consistently
showing most of the precip developing behind the front Sunday
evening through Monday morning, a few solutions are suggesting
widely scattered showers will form immediately along the boundary.
HRRR shows MLCAPEs reaching 500-800J/kg along the front by
afternoon, so have decided to add isolated thunder. Best rain
chances will remain along/west of the Illinois River until evening
when widespread showers advance further eastward.
.LONG TERM...(Sunday night through Saturday)
ISSUED AT 331 PM CDT Sat Sep 26 2020
Frontogenetic forcing behind the cold front will serve as the
primary focus for showers Sunday night. With forecast soundings
showing deep-layer moisture increasing markedly, have gone with
likely to categorical PoPs as the band of forcing passes through
the region. A few showers will linger into Monday morning,
followed by mostly dry weather by afternoon. Total rainfall with
this system will range from one quarter to three quarters of an
inch.
Once the front exits, showers will taper off and come to an end by
Monday night, followed by cooler conditions with highs only in the
60s for Monday/Tuesday. After a brief warm-up on Wednesday, a
reinforcing surge of cool, Canadian air will drop highs into the
upper 50s and lower 60s by Thursday and Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 908 PM CDT Sat Sep 26 2020
Scattered cirrus continues to spread across the CWA this evening,
along with models still forecasting some lower moisture/clouds
advecting northward into southeast and eastern IL toward morning.
Dewpoints are in the upper 50s to around 60 across the area and
with increasing cloud cover, overnight lows in the 60-65 degree
range still seem reasonable. Winds are still a little breezy out
of the south and current forecast has good handle on this too.
Therefore no update planned at this time.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...Barnes
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Auten
Area Forecast Discussion
National Weather Service New York NY
1117 PM EDT Sat Sep 26 2020
.SYNOPSIS...
A weak low passes offshore tonight through Sunday but on the
larger scale the region remains on the western side of a weak
high pressure area based in the Western Atlantic. A cold front
approaches the area Monday and Tuesday then stalls nearby.
Disturbances ride along the front before it pushes east by
Thursday or Friday.
&&
.NEAR TERM /UNTIL 10 AM SUNDAY MORNING/...
Some slight adjustments were made to forecast temperatures and
cloud to better match observed trends. Smoothed out the minimum
temperature field to convey less spatial spread with the
abundant clouds and light onshore flow mitigating radiational
cooling. Forecast lows range from the low to upper 60s. Lower
clouds are developing and expanding within parts of the area.
Mesoscale models including the HRRR and NARRE expand the lower
clouds across the entire area overnight with some fog
development as well. In addition, models show some light
moisture across mainly the coast towards early Sunday morning
and with forecast soundings showing most moisture in the low
levels, so added in areas of fog and drizzle along the coast for
late tonight into early Sunday morning. Kept fog more patchy
farther away from the coast.
&&
.SHORT TERM /10 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
A warmer than normal Sunday is expected. Following the passage
of a weakening low in the morning, the high pressure system over
the Atlantic Ocean becomes the dominate synoptic forcing for
the Northeast. Persistent southerly winds continue to advect
warm moist air into the forecast region. Could see precipitable
water values around 1.5 inches which is enough for slight chance
pop in the afternoon. Temperatures should reach the mid to
upper 70s.
In the late afternoon and into the evening, an approaching
shortwave from the Appalachian Mountains will have to be
monitored. As this shortwave nears southern New York it could
initiate light showers late Sunday evening and into the
overnight hours. Regardless muggy conditions late Sunday may
lead to another round of fog. Temperatures overnight should hold
in the mid 60s throughout the Long Island and Southern
Connecticut.
A moderate risk of rip currents at the Atlantic Ocean beaches
will continue on Sunday due to a continued E-SE swell and E-SE
winds.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
A shortwave disturbance moves through the area on Monday and
Monday night from the southwest ahead of an amplifying longwave
trough digging into the Midwest and Great Lakes region. A large
surface low pressure system develops over the Great Lakes and
Southeastern Canada allowing for the flow over the area to be
south-southwesterly through much of the first half of the week
as we will be ahead of the associated cold front. This flow will
allow ample moisture to advect into the region priming the
environment for the potential of rain through much of the week.
The cold front associated with this surface low will push east
into the area but then looks to stall somewhere in the vicinity
by mid-week. This will allow for disturbances to ride along the
front from southwest to northeast allowing for the potential of
showers and periods of rain through much of the week.
Models vary a bit as to how the areas of vorticity interact
with each other as the longwave trough slows its progression
east. The thinking is that an area of vorticity digs into the
Southeastern US before rounding the base of the longwave trough
and pushing through the region in the Wednesday to Thursday
timeframe. The ECMWF is a bit slower in the passage of this
disturbance as the area of vorticity gets cut off from the
large-scale flow for a bit on Wednesday. The GFS and CMC have
similar solutions with the main disturbance passing through on
Wednesday night into early Thursday.
Regardless of the timing of this disturbance, ample moisture
will be present under S-SW flow and since we will be positioned
downstream of the large-scale trough, disturbances will
continually move through the area allowing for the chance for
rain showers, some of which may be heavy, through much of the
week along with some embedded thunderstorms possible.
There is a moderate risk of rip currents at Atlantic Ocean
beaches on Monday.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
A weak low passes offshore tonight through Sunday but on the
larger scale the region remains on the western side of a weak
high pressure area based in the Western Atlantic.
A continuous SE flow will help bring in lower stratus across
the terminals tonight. SE winds of 10 kts or less are expected
through the TAF period.
In terms of category forecast, mainly IFR conditions are
expected tonight into Sunday morning, mostly due to ceilings but
also expecting some fog to form overnight into early Sunday
morning. KGON and KISP have a higher probability of getting
sub-IFR visibilities overnight into daybreak Sunday.
For Sunday, expecting a gradual lifting of the ceilings back to
MVFR and then VFR in the afternoon but ceilings may very well
stay MVFR to IFR for KISP and KGON. There will also be a
possibility of rain showers as well mainly east of NYC terminals.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Moderate confidence in magnitude of flight restrictions
tonight. Timing of lowering flight categories and improvement
on Sunday could be off by a few hours.
.OUTLOOK FOR 00Z MONDAY THROUGH THURSDAY...
.Sunday night...Chance of IFR/MVFR conditions. Slight chance
of showers.
.Monday...Chance of IFR/MVFR conditions. Chance of showers,
mainly during the day.
.Tuesday...Chance of IFR/MVFR conditions. A chance of showers. A
slight chance of thunderstorms. S-SW wind gusts around 20 kt.
.Wednesday...IFR/MVFR with showers likely. SW wind gusts
15-20kt day into early evening.
.Thursday...Chance of MVFR. Chance of showers. SW wind gusts
15-20kt day into early evening.
Detailed information, including hourly TAF wind component
forecasts, can be found at:
http:/www.weather.gov/zny/n90
&&
.MARINE...
Below SCA conditions are forecast through Tuesday with S to SE
winds. Winds on the ocean approach SCA criteria ahead of a cold
front on Tuesday night and seas rise above SCA criteria by
Wednesday. SCA conditions on the ocean waters are forecast from
Tuesday night through Thursday.
&&
.HYDROLOGY...
No hydrologic impacts are anticipated at this time.
However, a frontal boundary may stall close to the area midweek,
increasing the chance for a more significant rainfall event.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...DJ/MW
NEAR TERM...JM
SHORT TERM...DJ
LONG TERM...MW
AVIATION...JM
MARINE...DJ/MW
HYDROLOGY...DJ/MW