Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/13/21
Area Forecast Discussion
National Weather Service Denver/Boulder CO
600 PM MDT Tue Oct 12 2021
.UPDATE...
Issued at 553 PM MDT Tue Oct 12 2021
Strong winds expected along the the Wyoming/Nebraska border
Wednesday morning. HRRR indicating wind gusts to 60 mph at least
through the morning and into early afternoon. Therefore a High
Wind Warning had been issued for northeast Weld, Logan, Phillips
and Sedgwick counties from 6 AM to 6 PM Wednesday.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 245 PM MDT Tue Oct 12 2021
The center of upper low is currently over southwestern Utah.
There is some convection breaking out over the forecast area this
afternoon. The snowfall was slow to get going over the high
mountains through today. In the lower levels there is an elongated
circulation just east of Fort Morgan to south central Elbert
County. The best convection is firing just to the east of this.
Winds over the eastern plains are south and southeasterly from 20
to 40 knots.
Models show the upper low center to track into the far southwest
corner of Nebraska by 06Z tonight. After that, west-southwesterly
flow aloft will increase over the CWA overnight into Wednesday
morning. There looks to be enough moisture to keep widespread pops
going in the mountains and foothills with scattered coverage over
the plains through around midnight tonight. Will leave the snow
advisory going in Zones 31 and 33 through 12Z Wednesday morning
with enough moisture lingering along with orographic help.
For winds, will leave the High Wind Warning going over the Palmer
Ridge through 6 PM this evening. Will up the High Wind Watch to a
Warning over the northern foothills from 06Z to 18Z based on the
a decent mountain top stable layer, strong subsidence and a
pretty strong low level pressure gradient expected. For
temperatures, Wednesday`s highs will be close to today`s readings.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 223 PM MDT Tue Oct 12 2021
A quick moving system Thursday-Friday will bring another round of
snowfall for the mountains/foothills, Palmer Divide and perhaps a
few flakes further east for the Urban Corridor. Amounts for the
mountains will likely be lighter (couple inches) than the
previous system.
Thursday through Thursday night...
There is good agreement among model guidance that trough will push
into the region Thursday into Thursday evening. Moisture will be
fairly limited; however, QG fields indicate an area of weaker ascent
which should support another round of light to moderate snowfall for
the mountains. The Foothills also display potential for light
snowfall with even a chance for the Urban Corridor still being
advertised by some model solutions. As the trough pushes east into
the area Thursday, precip. chances increase towards the afternoon
and spread eastward into the evening hours. There is a signal for a
few inches of snowfall over the Palmer Divide supported by upslope
component flow. There is more uncertainty in regards to snowfall
potential for the plains/I-25 corridor. Models are consistent
with cool air advecting in given northerly component flow and
snow levels will resultantly drop through Thursday evening.
However, there is disagreement among model guidance with respect
to the amount of cooling. Wet bulb freezing level heights vary
from model to model with some solutions being too warm to support
snowfall. Ensembles continue to display a split in members for
snowfall in the Urban Corridor. Overall, there is sufficient
confidence for snowfall over the higher elevations into the
Foothills overnight Thursday while potential remains for light
snow along the Urban Corridor.
Friday through early next week...
Cool, below normal temperatures continue Friday with NW flow
aloft. Although winds won`t favor the optimal cross-barrier flow
for strong downslope winds, could see increased winds with gusts
to 30 mph over portions of the mountains/foothills. Ridging builds
in Saturday which initiate a warming trend and dry conditions. By
Sunday, temperatures rebound to 60s and low 70s across the
plains. Less confidence in the pattern next week as there is a
spread in solutions among deterministic and ensemble guidance. No
major signal for active weather and temperatures continue to trend
slightly above normal.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 523 PM MDT Tue Oct 12 2021
VFR conditions will continue through 05Z. Rain showers will keep
the environment humid enough to bring down visibility levels to
MVFR conditions starting 05Z to 08Z at KDEN and KBJC. BKN skies
will prevail through 09Z clearing to SCT or FEW Wednesday morning.
A wind boundary may develop shown on a few short term models near
22Z at KDEN which could potentially make the wind direction and
wind speeds tricky. Forecast confidence is higher in gusty
westerly winds due to upper levels occurring a KAPA and KDEN
through 0Z.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from 6 AM to 6 PM MDT Wednesday for COZ042-048-
050-051.
High Wind Warning until 6 PM MDT this evening for COZ041-046-047.
High Wind Warning from midnight tonight to noon MDT Wednesday
for COZ035.
Winter Weather Advisory until 6 AM MDT Wednesday for COZ031-033.
&&
$$
UPDATE...Cooper
SHORT TERM...RJK
LONG TERM....Mensch
AVIATION...AD
Area Forecast Discussion
National Weather Service Dodge City KS
835 PM CDT Tue Oct 12 2021
.MESOSCALE DISCUSSION...
Issued at 824 PM CDT Tue Oct 12 2021
Key Messages...
Damaging winds, hail to quarter size and brief, weak tornado
spinups will continue to be the primary concerns this evening
unless we see the development of discrete supercells. The storm
line will sweep across western Kansas and into central Kansas
after midnight.
Technical discussion...
Convective mode has been mainly linear this evening despite the
strong shear profile. It`s still possible for discrete storms to
develop; but the later we get into the evening the smaller the
chances. However, given the strong shear, any bows in the line
could result in enhanced storm relative shear and a brief tornado
spinup. But as long as convection stays linear, the primary
concern will be damaging straight line winds and hail to quarter
size.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 212 PM CDT Tue Oct 12 2021
...Significant Severe Weather Tonight, Including Tornadoes...
Early this afternoon, a major mid-latitude cyclone was maturing out
across western Colorado. A surface low continued to rapidly deepen
just lee of the Colorado Rockies, and the surface winds were
responding nicely with widespread south-southeast winds in the 20 to
25 knot range with higher gusts. Rapid northward transport of 60-65F
surface dewpoints were underway across the eastern Texas Panhandle
into west central Oklahoma.
Everything that was discussed in yesterday afternoon`s Short Term
discussion remains valid as of this forecast update. A significant
severe weather event is about to unfold later on this evening. The
only thing that has really changed, and has become increasingly
concerning, is that the low level moisture (62-65F dewpoints) will
be making a run on southwest Kansas a little bit quicker than
previously forecast...and a bit farther west...such that areas along
and event a bit west of Highway 83 now have an increased risk of
significant severe weather, including tornadoes. The 02-05Z (9 PM to
Midnight CDT) time frame is of particular concern, as the latest
HRRR and RAP low level thermodynamic and shear parameters are well
into the tornado category...even significant tornado category...as a
large region will have 0-1km AGL storm-relative helicity in the 300-
400 m2/s2 during the 02-05Z time frame. This is also the best time
frame for discrete supercell mode.
If the storm mode remains primarily supercellular in the critical 02-
05Z time frame, we have to face the possibility of long-track
significant tornadoes covering potentially 10s of miles. This is
extremely unusual for far western Kansas to see tornadic storms
racing northeast at 50+ mph, but this is exactly what we may be
dealing with tonight. This puts much more land at risk, obviously,
with such fast storm motions. This will also present a challenge for
warning forecasters tonight given such fast, forward storm (tornado)
motion. Eventually, the primary severe weather mode will become more
linear in nature as the risk shifts east by/shortly after midnight.
All in all, a dangerous night of severe storms is still on track for
much of the southwest Kansas region.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 346 PM CDT Tue Oct 12 2021
The next storm system slated to impact the region will move across
late Thursday into early Friday, however the surface front is
expected to remain just south of the DDC forecast area, so the
severe weather potential will remain south and east of southwest
Kansas. That said, we will need to watch our far southeast CWA
(mainly Barber County) as a surface wave along the front will be
pretty close to south central Kansas. We will keep some POPs in
Barber county area as a result. Light cold sector precipitation is
still expected across the remainder of our forecast area along the
mid level frontal zone late Thursday Night, but widespread moderate
or heavy rainfall is not expected. Fairly cool air behind the front
will filter in on Friday, and afternoon temperatures will struggle
to get out of the 50s. It still looks like there is the potential
for a frost/freeze across mainly far west central Kansas.
Frost/freeze headlines may be required if these model trends
continue out west. A high pressure ridge in the mid/upper
troposphere will move across western Kansas over the weekend with
much quieter weather forecast.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 630 PM CDT Tue Oct 12 2021
Low level stratus in central and south central Kansas will continue
to develop slowly northwestward into portions of southwest and west
central Kansas within a prevailing southeasterly upslope flow,
resulting in MVFR cigs in vicinity of KDDC, KHYS, and potentially
KGCK through mid/late evening. IFR cigs cannot be ruled out at KDDC.
Strong to severe thunderstorms are expected to develop along and
ahead of a strong frontal boundary edging into extreme southwest
Kansas generally after 01Z, then spread eastward across the remainder
of southwest Kansas into central/south central Kansas through 07Z,
affecting all TAF sites. The main impacts will be damaging winds,
large hail, and isolated tornadoes. Prevailing southeasterly winds
15 to 30kt will continue ahead of the aformentioned approaching
frontal boundary, then turn west-southwesterly around 10-20kt
behind the boundary as it pushes eastward overnight.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 44 67 42 67 / 90 0 0 10
GCK 40 65 38 63 / 80 0 0 0
EHA 42 70 39 66 / 30 0 0 0
LBL 41 69 38 68 / 60 0 0 0
HYS 46 65 40 62 / 90 0 0 10
P28 53 70 48 73 / 90 10 0 20
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
MESOSCALE...Finch
SHORT TERM...Umscheid
LONG TERM...Umscheid
AVIATION...JJohnson
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
631 PM CDT Tue Oct 12 2021
.AVIATION (00Z TAFs)...
VFR conditions prevail across South Central Texas this evening. A
band of scattered SHRAs and isolated TSRAs will persist over the next
hour or two near SSF to just east of AUS. Guidance indicates MVFR
ceilings developing along the I-35 corridor and into the Hill Country
03Z-06Z, including at AUS/SAT/SSF, and eventually into portions of
the Rio Grande near DRT, where possible IFR conditions may occur,
11Z-13Z. Earlier convective allowing model runs were indicating a
complex of SHRAs and TSRAs developing along the Rio Grande early this
evening. So far there is no indication of this taking place on radar.
Latest HRRR runs have delayed this into the late evening, developing
around the Rio Grande 03Z-06Z and moving through the Hill Country
overnight and into early Wednesday morning. We have followed this
trend with the DRT TAF.
&&
.PREV DISCUSSION... /ISSUED 315 PM CDT Tue Oct 12 2021/
SHORT TERM (Tonight through Wednesday Night)...
A very moist and moderately unstable atmosphere will remain in place
through the next 48-60 hours. The primary issue then is what lifting
mechanisms will be in place, when, and where. Diurnal heating has
sparked isolated thunderstorms amongst widespread scattered light
showers this afternoon. The storms should remain along/east of I-35,
primarily over the coastal plains. Otherwise, another shortwave
trough will eject from northern Mexico into west central Texas
overnight. This trough and the diurnal uptrend in the low level jet
should provide the lift for another round of storms to develop in
Mexico, then develop/propagate into our area after midnight.
Rainfall will be spotty and generally under one inch, although a few
spots may receive more than one inch by daybreak Wednesday.
Wednesday will feature a pattern similar to today, with light to
moderate rain at many locations in the morning, then tapering off
and skies partially clearing by early afternoon. Again, rainfall
amounts will be generally under 1/4 inch, but a few locations could
receive 1/2 to one inch by noon.
The main action period will be Wednesday night into Thursday
afternoon, as the remnants from Hurricane Pamela, a slow moving cold
front dropping south from northwest Texas, and moist Gulf air all
converge on central Texas. It is not just the near record levels of
moist air, but the remnants of Pamela actually interact with the jet
stream and help create upper level divergence, which induces strong
lifting motion, and thus the potential for heavy rain. There is also
a marginal risk for damaging winds or brief tornadoes, especially
late Wednesday night/early Thursday morning, as low level shear and
buoyancy may be strong enough for some storms to develop rotation.
Total rainfall amounts from Wednesday morning through Thursday
afternoon will average 2 to 4 inches across the area. A number of
spots may receive 5-6 inches in the Hill Country, and one or two
spots may receive just over 7 inches of rain near the Highland Lakes.
A Flash Flood Watch is in effect from 7 am Wednesday through 7 pm
Thursday for locations generally along and west of I-35/I-37.
LONG TERM (Thursday through Tuesday)...
The remnant low associated with Pamela is forecast to push across
the northern part of South Central Texas on Thursday between 7 am
and 1 pm. An upper level long wave trough axis pushing across the
Intermountain West is expected to push to the southeast and east and
over the Southern Plains through the period. This feature will help
the remnant low to push toward eastern Texas on Thursday afternoon
with dry weather conditions spreading across the area from west to
east. However, locally heavy rain is still possible across part of
the Hill Country through early Thursday afternoon. Can`t ruled out
some areas getting one half to one inch of rainfall during this
particular time frame. With that said, the Flash Flood Watch remains
in effect for the Hill Country through 7 pm Thursday.
As the day progresses, a drier airmass is forecast to push across
the area from the west ahead of a surface trough/dry-line. A break
from the rain is expected as mentioned above Thursday afternoon into
the evening. Then, a cold front is forecast to push across South
Central Texas on Friday morning with little moisture to work with but
with some instability in place as the boundary nears the I-35
corridor. Therefore, decided to go with slight chance of showers and
thunderstorms mainly along and southeast of I-35.
In the wake of the cold front expect dry weather conditions mainly
Friday evening through the upcoming weekend. The dry and cooler
airmass will keep South Central Texas around the upper 60s across
the Hill Country with 70s elsewhere.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 74 87 71 84 69 / 40 60 70 70 10
Austin Bergstrom Intl Airport 73 88 70 84 68 / 30 50 70 60 10
New Braunfels Muni Airport 73 90 71 86 68 / 30 50 70 60 10
Burnet Muni Airport 73 84 69 81 66 / 50 80 80 60 10
Del Rio Intl Airport 74 85 69 91 68 / 70 80 60 10 -
Georgetown Muni Airport 72 87 70 83 68 / 40 70 80 60 10
Hondo Muni Airport 73 88 70 87 67 / 50 60 80 40 -
San Marcos Muni Airport 73 89 70 86 68 / 30 50 70 60 10
La Grange - Fayette Regional 75 90 73 86 71 / 20 30 40 60 10
San Antonio Intl Airport 74 88 72 86 71 / 40 60 80 60 -
Stinson Muni Airport 76 91 74 88 71 / 20 50 70 50 -
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from Wednesday morning through Thursday evening
for Atascosa-Bandera-Bexar-Blanco-Burnet-Comal-Dimmit-Edwards-Frio-
Gillespie-Hays-Kendall-Kerr-Kinney-Llano-Maverick-Medina-Real-
Travis-Uvalde-Val Verde-Williamson-Zavala.
&&
$$
Short-Term/Aviation...76
Long-Term...04
Area Forecast Discussion
National Weather Service Goodland KS
848 PM MDT Tue Oct 12 2021
.UPDATE...
Issued at 847 PM MDT Tue Oct 12 2021
Have removed all counties along Highway 25 from the Tornado Watch
based on current radar trends. East of there, the Watch remains
for another couple hours.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 245 PM MDT Tue Oct 12 2021
500mb RAP analysis and satellite imagery showed a low centered over
eastern Utah and western Colorado, placing the High Plains under
southwest flow out ahead. This system is causing quite the variety
of weather today. South to southeast winds have been sustained at
approximately 25 to 45 mph, with gusts up to 60 mph observed so far.
These winds have produced patchy blowing dust this afternoon,
producing some slight reductions in visibility across portions of
the region. At 2 PM MT, temperatures ranged in the mid 60s to mid
70s. Some cumulus clouds and showers had developed in northeastern
Colorado.
A severe weather event is expected to occur this afternoon and
evening. Isolated thunderstorms will form in the vicinity of the
Colorado border in the next couple of hours. Activity will then
gradually shift to the east, increasing in coverage and intensity
through the evening.
Storm mode will play a large role in hazards through the event.
Initially, when storms are discrete, (while damaging winds will be
possible) large hail and tornadoes will be the main threats. Low
level parameters as well as hodograph profiles and 0-1km helicity
suggest that the timeframe that is most favorable for tornadoes is
generally from sunset to a few hours afterwards. The area of most
concern is east of the Colorado border, particularly south of
Interstate 70. The threat of tornadoes is made even more dangerous
by a potential for long-track tornadoes occurring at nighttime when
they are more difficult to see.
As a frontal boundary pushes eastward, discrete storms will evolve
into a line of thunderstorms in the late evening. As this occurs,
hazards will transition to predominantly a wind threat. Storms are
anticipated to move rather quickly, minimizing the concern for flash
flooding. Severe thunderstorm activity should exit to the east
around midnight; however, some showers/non-severe storms may linger
in the eastern zones overnight.
Quiet weather is expected to return tonight behind the severe
threat, with low temperatures falling into the upper 20s to low 40s
(from west to east). Patchy frost will be possible in eastern
Colorado early Wednesday morning.
On Wednesday, our system tracks north of the region, leaving behind
dry weather. Breezy northwest winds are forecast north of Interstate
70 on the backside of the low through the morning and into the
afternoon hours as temperatures climb into the low to mid 60s.
Relative humidities may fall as low as 18 percent in eastern
Colorado in the afternoon; fortunately, the lowest values do not
seem to be collocated with the higher wind gusts at this time.
Southwest flow resumes aloft Wednesday night, with lows in the 30s.
Overall, quiet weather is expected. Clear skies and light winds do
allow for a potential of patchy frost north of Interstate 70.
.LONG TERM...(Thursday through Tuesday)
Issued at 324 PM MDT Tue Oct 12 2021
At the beginning of the extended period, long-term models show the
CWA having a southwesterly flow aloft as the CWA is underneath the
front part of an upper air trough over the western CONUS on
Thursday. Going into Friday, the upper air trough moves slowly
eastward with the upper air flow turning northwesterly by the
evening hours as the back part of the trough moves over the CWA with
a ridge moving behind it in the western CONUS. On Saturday, models
show the upper air ridge moving eastward over the CWA. Going into
Sunday, long term models show the ridge remaining over the CWA
and then the models start to deviate from their solutions in how
the upper air pattern develops behind it. The GFS has an upper air
low developing over southern CA during the evening with another
trough moving over the Pacific Northwest. On Monday, the GFS has
the southern low moving east into AZ with the trough moving over
central Canada along with a ridge moving over the western CONUS.
On Tuesday, the GFS shows the CWA between the ridge in the west
and the upper air trough to the east which makes its way over the
Great Lakes area. As an alternate solution, the ECMWF shows a
trough reaching down to northern CA behind the ridge on Sunday
evening. For Monday, the ECMWF moves the trough eastward over the
Rockies and starts to close off into a low. By Tuesday, the ECMWF
looks to move the low over the CWA. As there is a good amount of
uncertainty between long term models beginning Sunday and beyond,
this situation will be monitored for better agreement in future
runs.
At the surface, the CWA looks to see chances for precipitation
Thursday evening into Friday morning with the remainder of the long
term period staying relatively dry. Chances for precipitation are
expected to begin on Thursday evening west of a line from
Benkelman, NE to Hoxie, KS with these chances increasing going
westward. Precipitation starts as rain for a P-type across the
aforementioned area with chances for snow mixing in starting
during the nighttime hours along and west of the CO border. Areas
in CO may see light snow showers instead of a mixed P-type
overnight though snowfall amounts look to be negligible at this
time. With overnight temperatures getting colder, the Tri-State
area may see frost develop during the long term period. Friday,
Saturday, and Monday nights look to have the best chances for
frost development within the Tri-State area. At or below freezing
temperatures can be expected as well along and west of the CO
border on Thursday night, across most of the Tri-State area on
Friday night, and Yuma county on Monday night.
The Tri-State area expects daytime highs on Thursday in the lower
50s to lower 60s followed by highs on Friday being in the middle to
upper 50s. The Tri-State area sees daytime highs on Saturday warming
to the middle to upper 60s before highs increase to the lower to
middle 70s on Sunday. Monday looks to be the warmest day in the long
term period with highs in the middle to upper 70s with Tuesday`s
highs expect to be in the middle 60s to lower 70s. The Tri-State
area expects to see overnight lows on Thursday between the upper 20s
and upper 30s while Friday sees lows ranging from the middle 20s to
lower 30s. Overnight lows on Saturday look to be in the middle 30s
followed by Sunday night seeing lows in the upper 30s to middle 40s.
Overnight lows for the remainder of the long term expect to range
between the lower 30s to the lower 40s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 529 PM MDT Tue Oct 12 2021
The passage of a strong cold front thru the region will affect
both terminals at least for the first half of the forecast.
For KGLD, mainly VFR ceilings with some thunderstorms, some large
hail with some reduction to visibility thru about 07z Wednesday.
Low ceilings around BKN-OVC040-050 will give way to SKC-
SCT150-200 during this time. The frontal passage will have
southeast winds currently around 25-35kts become west-southwest
15-30kts by 05z. Some reduction to 5-15kts from 05z-15z. LLWS
13z-15z 300@40kts.
For KMCK, thru 05z Wednesday, ceilings will range from VFR down
to IFR in thunderstorms, with some large hail. After 05z, BKN035
giving way to scattered high cloud by 12z Wednesday. Visibility
in precip will range 2-5sm at worse. Winds southeast 15-30kts
with gusts to 40kts thru 01z. By 05z, a shift to the west-
southwest 10-15kts with gusts back up to 25kts by 12z. LLWS 03z-
05z 160@45kts.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...JN
SHORT TERM...JBH
LONG TERM...MRC
AVIATION...JN
Area Forecast Discussion
National Weather Service Grand Rapids MI
914 PM EDT Tue Oct 12 2021
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 330 PM EDT Tue Oct 12 2021
-Dry, warmer Wednesday but considerable clouds
-Showers/storms Wednesday night into Thursday morning
-More rain Friday into Saturday, turning cool/breezy
&&
.UPDATE...
Issued at 914 PM EDT Tue Oct 12 2021
Minimal changes this evening. Will keep low chances for drizzle
going through the night mainly north of I-94. Models are pointing
to an occasional saturated and weakly unstable layer between 1000
ft and the cap at 3500 ft, with very dry air above the cap. While
omega in the moist layer is departing, a slight thermal and
moisture contribution from Lake Michigan and downwind zone of
confluence (early hints of lake-effect banding) may be enough to
keep very light precipitation going overnight.
&&
.DISCUSSION...(This evening through next Tuesday)
Issued at 330 PM EDT Tue Oct 12 2021
-Dry, warmer Wednesday but considerable clouds
Sfc low over ern upr MI responsible for all the low clouds and
showers today continues to fill tonight and Wednesday while
moving slowly away. Low clouds and areas of light rain/drizzle
will be rather slow to depart and will likely linger through at
least midday Wednesday.
Once the low clouds finally do break up/lift out Wednesday,
considerable mid and high clouds associated with the next system
will be streaming in. However renewed warm advection pattern and
southerly flow ahead of that system sends high temps back up into
the lower or mid 70s.
-Showers/storms Wednesday night into Thursday morning
Unlike the last few systems from the wrn longwave trough, which
passed near or through MI, the next upper low passes well west of
Michigan through the nrn Plains Region on Wednesday. That
occluding system still pushes a frontal boundary in our direction,
with some semblance of a triple point coming across srn lwr MI on
Wednesday night.
Most guidance, with the exception of the 12Z HRRR, keeps the area
dry until after midnight which would keep any severe weather
threat quite low. Actually the highest MUCapes may stay south of
MI overnight per NAM and newer RAP guidance. Highest pops will be
featured overnight into Thursday morning, with some drying
arriving in the afternoon into Thursday night as the sfc frontal
boundary nudges just south and east of the area.
-More rain Friday into Saturday, turning cool/breezy
Wrn longwave trough moves in our direction for the end of the week
and a shortwave in the base that trough moves along the stalled
frontal boundary just south of MI. Ensemble guidance favors the
axis of heaviest QPF closer to the frontal zone from Indiana into
se lwr MI, but still shows lighter rains falling across our area
much of the time Friday into Friday night.
Then, as cold advection sweeps in behind that shortwave on
Saturday, we should see a continuation of clouds and sct`d showers
with an H8 thermal trough near 0C overhead. (Lake effect should
become a factor with air that cool.) High temps will be held in
the 50s Saturday, before a return to sunshine on Sunday allows a
recovery back into the 60s. Tight pressure gradient over the
weekend keeps a breezy westerly flow over the GrtLks, so
definitely a more normal fall-like pattern coming in by then.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 752 PM EDT Tue Oct 12 2021
Belts of IFR ceilings and localized MVFR to IFR visibility
containing drizzle continue to stream from west to east this
evening, primarily affecting MKG, GRR, and LAN. Low level
moisture and pockets of rising air are shown in the models through
Wednesday morning, so MVFR ceilings should prevail through then.
However there may be a tendency toward scattering out to VFR at
times. Drier air makes a pronounced arrival Wed afternoon, so VFR
seems likely then. Showers and and lowering ceilings should move
back into West Michigan Wed evening.
&&
.MARINE...
Issued at 330 PM EDT Tue Oct 12 2021
Westerly flow gradually diminishes later tonight as the sfc low
to our north over upr MI continues to weaken and is replaced by
high pressure. No change to the expiration time of the Small Craft
Advisory at 11 PM. The next chance of higher winds and waves
develops on Wednesday night due to increased southerly flow ahead
of the next system, with the main concern for advisory criteria
being north of Holland. After a period of weaker flow for Thursday
into Friday, hazardous conditions appear likely again for the
weekend - especially Saturday - as colder air arrives.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 11 PM EDT this evening for LMZ844>849.
&&
$$
UPDATE...CAS
SYNOPSIS...Meade
DISCUSSION...Meade
AVIATION...CAS
MARINE...Meade
Area Forecast Discussion
National Weather Service Wilmington NC
1011 PM EDT Tue Oct 12 2021
.SYNOPSIS...
High pressure continues to build into the area this evening and
this week. Skies will start to clear out midweek, and
temperatures will begin to warm, potentially to near record
values by Friday. A cold front moves through Saturday, bringing
a slight chance of showers to the area. After the front, fall
returns, bringing much more seasonal temperatures to the area by
the end of this weekend.
&&
.UPDATE...
No big changes necessary from the ongoing forecast with this
update. Continued to raise Sky cover overnight.
&&
.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
Persistent low clouds have been the big forecast story again today.
A strong subsidence inversion with a base measured by 12z weather
balloons at 2500 feet AGL over MHX and 3000 feet AGL over CHS has
very effectively trapped low level moisture and created dense
stratocumulus clouds. This morning`s 12z GFS and NAM erroneously
showed the base of the inversion near 4000 feet AGL. This left too
little depth of saturation for opaque clouds in the model
initialization, and the rest of the model forecast quickly fell
apart with sunshine and warm temperatures indicated.
The inversion will continue tonight, therefore I am forecasting
clouds to continue as well. Sky cover forecasts are based on a blend
of the HRRR and the 90th percentile of the NBM, with some upward
revisions still needed across coastal North Carolina where boundary
layer dewpoints remain highest. This gives "partly cloudy" across
the Pee Dee and Grand Strand region, and "mostly cloudy" near
Wilmington. Forecast lows (60-65 degrees) have been adjusted up
above all MOS guidance under the densest cloud cover across coastal
NC.
I do expect some sunshine to finally arrive Wednesday, although
there may be quite a few stratocumulus clouds still dotting the sky,
especially near the coast. Forecast highs (80-83) are a little below
guidance consensus. It`s unclear if the inversion erodes enough
Wednesday night to finally let the clouds dissipate entirely. As a
hedge I`m forecasting lows a little above the clear sky MOS forecast
with 60-65 degrees.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Ridging brings very warm and dry weather through this period.
Thursday sees highs in the mid-to-upper 80s, with lows that night in
the mid 60s.
Big story focuses on Friday, when the ridge axis shifts a little to
east such that is is directly overhead the Carolinas. This cranks up
the heat a few degrees more from the previous day. Still looking at
potentially record tying/breaking high temperatures at this point.
MOS data is starting to sniff this out, and shows some of these high
temperatures potentially kissing 90 on Friday. Official forecast
does *not* reflect this yet, as I have capped it at 89. But with
some SSE flow building in, I wouldn`t be surprised if this milestone
is achieved, particularly somewhere along and north of a line from
Darlington County, SC to Pender County, NC.
Since there`s a greater curve in the diurnal trends on Friday, lows
that night should be 2-3 degrees warmer than the previous night.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
Cold front approaches from the west Saturday, quickly moving to the
offshore waters by Sunday morning. The bulk of the dynamics appears
to remain to the north, and this front seems to be rather moisture-
starved. As a result, keeping a mostly slight chance of showers
Saturday afternoon for the SC counties, with those chances moving
eastward towards the coast by Saturday evening. Showers taper off
overnight.
Welcome fall! This cold front chops down temperatures and dewpoints
alike, just in time for pumpkin carving. Expect more seasonal highs
in the low-to-mid 70s Sunday through Tuesday. Lows should dip down
into the low-to-mid 50s Saturday night, with the lower end of the
range likely found in the SC counties. Sunday and Monday nights,
with plentiful radiational cooling, wouldn`t be surprised to see
lows dip down into the upper 40s in the usual cold spots in Pender
and Bladen Counties.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Ceilings will linger this evening near the coast, remaining at
MVFR at ILM and mainly VFR elsewhere. Clouds should gradually scatter
tonight, but in general guidance continues to erode the clouds
too quickly. Fog not likely tonight, with any patchy fog limited
to far western areas. VFR on Wednesday with continued light
northerly flow.
Extended Outlook...VFR expected to dominate during the mid to
late week period due to high pressure. However, patchy early
morning fog/stratus could lead to MVFR/IFR ceilings/vsby.
&&
.MARINE...
Through Wednesday Night...High pressure centered across the
southern Appalachians will move little through Wednesday night.
Light northerly winds should continue across the Carolina
coastal waters, veering northeasterly Wednesday night. Seas are
currently 2 to locally 3 feet primarily in two easterly swells
with 10 and 15 seconds period. Wavewatch and local NWPS models
show little change anticipated over the next 36 hours.
Thursday through Sunday...Variable winds at 5-10kts will be the
trend Thursday and early Friday. By Friday afternoon, winds have a
more southerly component, as a cold front approaches. Winds continue
to veer more southwesterly by Friday night, increasing to 10-15kts
by Saturday morning. The front moves offshore by Sunday morning, and
winds veer northerly at 15kts, with a few gusts up to 20kts
possible. Seas are tame Thursday through Saturday, with 1-2ft waves
at the coast, slightly increasing to 2ft waves away from shore. By
Sunday, as the cold front arrives to the waters, wind waves increase
to 2-3ft seas at the coast and 3-4ft waves spotted 20nm away from
shore.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...ILM
UPDATE...MAS
NEAR TERM...TRA
SHORT TERM...IGB
LONG TERM...IGB
AVIATION...MAS/43
MARINE...TRA/IGB
Area Forecast Discussion
National Weather Service Marquette MI
625 PM EDT Tue Oct 12 2021
.SHORT TERM...(This evening through Wednesday)
Issued at 434 PM EDT TUE OCT 12 2021
Water vapor imagery and RAP analysis show a trof over the Rockies
with a well-defined, deep shortwave in the base over the 4 Corners
(500mb height anomaly of 340m). Downstream, ridging is over the
eastern Lower 48. In the ne flow btwn the 2 features, the vigorous
shortwave that was over MO 24hrs ago has weakened and is currently
over the Upper Great Lakes. This wave brought widespread rainfall to
the fcst area last night and today, but the heavier rainfall
(generally 1-2 inches) ended up more limited, affecting only the
eastern fcst area. Sfc low pres is currently located over eastern
Lake Superior btwn Caribou Island, Grand Marais and Whitefish Pt.
Under northerly cyclonic flow to the w of the low this aftn, low
clouds have dominated the fcst area along with some -shra/dz.
Pcpn has become increasingly confined to the upslope areas of
western and northern Upper MI.
The weakening shortwave over the Upper Great Lakes will continue to
weaken as it lifts to the ne tonight. However, with the weakening
sfc low moving little, low-level cyclonic upslope n to nw flow will
linger, likely resulting in continued patchy -ra/-dz and some fog
across portions of the w and n thru much of the night. Weak sfc
ridge axis does reach western Upper MI late in the night, and that
should work to end whatever light pcpn remains there. With
expectation of abundant cloud cover, opted for min temps near raw
model guidance consensus, 50s F across the board, coolest w. Should
clouds break anywhere, temps will fall back into the 40s.
Any lingering -dz should end by 12z Wed as winds go light/vrb before
becoming se in response to a strong sfc low pres lifting across the
Dakotas. Waa/isentropic ascent will spread ne toward Upper MI in the
aftn, but the thermal gradient and thus pres gradient on the
isentropic surfaces is rather weak, leading to overall weak ascent.
Bulk of model guidance appears on track delaying development of pcpn
into Upper MI. Best chc would be over the w, closer to better deep
layer forcing. Fcst will reflect chc pops far w late in the aftn
with a dry aftn prevailing to the central and eastern fcst area.
Should be quite a bit of cloud cover thru the day. Even if low
clouds clear out anywhere, high and mid clouds will overspread the
area during the day. Expect high temps in the low/mid 60s F across
the board.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 337 PM EDT TUE OCT 12 2021
A progressive weather pattern across the CONUS will allow for the
active weather pattern to continue for the Great Lakes. Temperatures
will be on somewhat of a roller coaster, which is typical for Upper
Michigan in the fall as multiple waves of warm and cool air will
swing across the cwa in the extended forecast. Above average
temperatures will quickly change to seasonal temperatures for autumn
by the end of the week, and then beginning to rise to slightly above
average readings once again to start next week. Due to the
progressive nature of the weather systems moving through the Great
Lakes, precipitation is not expected to heavy with any of the weather
disturbances.
On Wednesday night, the strong surface low will continue its trek to
the north from the Dakotas toward Manitoba. The warm conveyor belt
of moisture will propagate northward from the Gulf of Mexico, ahead
of the surface cold front. Instability looks to be marginal for
organized convection as the rain showers move to the northeast
quickly across Upper Michigan. The GFS and Euro model show the nose
of a strong 110+ knot jet streak making its way over Upper Michigan
overnight, so we can expect gusty winds to be present as the system
moves through the area at the surface. It will be a mild and muggy
night for several areas as dew point values will remain in the 50s
to lower 60s ahead of the approaching surface cold front from the
west. Rain showers should push through the area by Thursday morning.
The cold front will move from west to east quickly on Thursday.
850mb temperatures in the single digits will mix down to the surface
with the help of the breezy winds at times, making temperatures fall
behind the front quickly. Ultimately, seasonal temperatures will
have arrived for this time of October across Upper Michigan by
Thursday evening.
The CAA behind the front, and dry air will cause sky cover to
decrease Thursday on a temporary basis. Surface temperatures will
quickly decrease after sunset to the 40s across the interior. The
next shortwave trough riding along the upper level flow/ULL over the
Canadian Provinces will propagate toward Upper Michigan late
Thursday night into Friday. This will usher in another round of
cloud cover from the west, and help limit overnight lows to around
40 degrees across the interior west. Throughout the remainder of
Friday, the upper level shortwave will propagate to the east, and
another surface frontal passage will occur, reinforcing the cooler
air across the UP. This will cause the west half to struggle to
reach the lower 50s for a high temperatures by late afternoon on
Friday when combined with the cloud cover.
Friday night through Sunday, the ULL will slowly propagate toward
James Bay. Multiple embedded shortwave disturbances will propagate
along the upper level northwest flow. Lake effect rain showers look
plausible via nw flow at the surface through the weekend. Seasonal
temperatures will remain across the area as well. 850mb between +2C
to -2C will assist with lake enhanced initiation of precipitation
during the weekend, thus cloud cover will assist with keeping
temperatures cool. Early next week, upper level ridging will amplify
across the Northern Plains, and bring warmer temperatures back to
Upper Michigan. Afternoon highs will creep back up toward the upper
50s to middle 60s, which is about 10-15 degrees above normal.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 625 PM EDT TUE OCT 12 2021
Abundant low-level moisture will result in LIFR conditions
prevailing at SAW until late Wed morning when improvement to low
MVFR is expected. LIFR conditions at IWD/CMX will continue. Both
terminals will improve to MVFR near the end of the fcst period. All
terminals will see some periods -dz/-shra at least into the evening
hrs.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 434 PM EDT TUE OCT 12 2021
Thru Wed morning, sfc low pres over eastern Lake Superior will
meander, weaken and eventually dissipate. W of the weakening low,
expect a corridor of northerly winds gusting to 20-25kt across a
swath of central Lake Superior thru this evening. Winds will fall
off blo 20kt by daybreak Wed. Winds will then begin to ramp up on
Wed aftn, particularly over western Lake Superior, as strong low
pres lifts n thru the Dakotas. Expect easterly winds gusting to 30kt
by late aftn over western Lake Superior. Could be some gale force
gusts to 35kt for a few hrs over the far w late aftn/early evening.
SE winds will increase to 20-30kt across eastern Lake Superior Wed
night. At high obs platforms, there could be some gale gusts to 35kt
for a time. Front associated with the low pres will sweep across
Lake Superior late Wed night/Thu morning, bringing a wind shift to
the sw. These sw winds will gust to 20-30kt, strongest over western
Lake Superior where there could be a few gale force gusts to 35kt.
As a more seasonal air mass arrives over the Upper Lakes into the
weekend, winds will likely frequently gust to 25-30kt.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...BW
AVIATION...07
MARINE...Rolfson
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 313 PM CDT Tue Oct 12 2021
.Forecast Summary:
Showers and thunderstorms developing tonight with some risk for
damaging winds and large hail. Breezy to windy on Wednesday.
Trending cooler through Friday. Warmer daytime temperatures this
weekend into early next week. Potential for freezing temperatures
on Friday night into Saturday morning.
.Tonight and Wednesday:
An intense mid/upper-level low situated along the UT-CO border as
of early afternoon is forecast to undergo further intensification
while developing into western parts of NE and SD by 12z Wednesday.
Meanwhile, an attendant shortwave trough and accompanying 90-100
kt jet streak at 500 mb are expected to pivot through the
southeast periphery of the parent low, and across the mid MO
Valley on Wednesday morning. At the surface, a deepening lee
cyclone over eastern CO will develop through western NE tonight
and into central SD by 18z Wednesday with a trailing cold front
sweeping east through our area on Wednesday morning.
The vigorous, synoptic cyclone that moved through the Great
Plains on Sunday and Monday shunted substantive, low-level
moisture to the TX coastal plain. That moisture is now in the
process of being advected poleward along a 40+ kt LLJ, which
extends from central TX through western parts of KS and NE, per
plan-view WSR-88D VWP observations. How rapidly that moisture
returns north through the central Plains tonight will largely
dictate the magnitude of severe-weather threat across our area.
Latest CAM solutions remain relatively consistent in suggesting
that initial, surface-based storm development will occur later
this afternoon into evening over the central High Plains with
that activity subsequently growing upscale into a QLCS while
tracking into central NE/KS by around midnight. Thereafter, the
models indicate a warm-advection-related cluster of thunderstorms
developing over portions of eastern NE ahead of the QLCS, which
is projected to weaken while moving through our area in the 2-6 AM
time frame. Finally, the models also hint at the potential for a
secondary, broken band of showers and storms forming along the
cold front moving through eastern NE in the 7-9 AM time frame
with all convection moving out of the area by 10 or 11 AM.
In regard to the pre-storm environment, the models suggest that
warming and moistening along a 50+ kt LLJ and atop a stable, near-
surface inversion will contribute to a corridor of moderate
instability (i.e., MUCAPE of 1000-1500 J/kg). The initial, warm-
advection storms are expected to develop in that thermodynamic
environment, which should support a few strong updrafts capable of
hail approaching one-inch in diameter. HRRR forecast soundings
suggest that the near-surface inversion will likely be maintained
ahead of the QLCS, which is expected to limit the potential for an
organized, damaging-wind threat. Nonetheless, any stronger,
longer-lived downdrafts may be sufficient to promote sporadic
pockets of 50-60 mph wind gusts at ground level. Finally, there is
some suggestion that parcels may become close to surface-based
along and just ahead of any showers and thunderstorms that may
form along the cold front on Wednesday morning. Here too, locally
strong wind gusts appear to be the primary hazard owing to the
high-momentum flow field just above the ground.
Steepening, low-level lapse rates coupled with a tight pressure
gradient on the south side of the surface low over central SD are
expected to foster breezy to windy conditions from late Wednesday
morning into afternoon. Wind gusts of 35 to 40 mph appear
possible, especially across northeast NE. High temperatures will
range from around 60 northwest to lower 70s in far southeast NE
and southwest IA.
.Thursday and Friday:
Another mid-level trough is forecast to amplify over the High
Plains on Thursday with that feature tracking east through the
remainder of the Great Plains on Thursday night and Friday. The
primary surface baroclinic zone is forecast to reside well to the
south of our area from the Ozarks into southern Plains. And that
is where the majority of precipitation is expected to fall. The
northern extent of that precipitation shield could extend north
into portions of southeast NE and southwest IA on Thursday night,
where we will indicate chance PoPs.
Highs in the upper 50s to upper 60s on Thursday will fall back
into the 50s areawide on Friday.
.Saturday through Monday:
Latest model data indicate an increased potential for freezing
temperatures at preferred locations in northeast NE and west-
central IA late Friday night into Saturday morning. Widespread
frost appears probable elsewhere in our area. Lows on Sunday
morning are expected to be a bit warmer, but areas of frost still
appear possible. Otherwise, mid-level heights are expected to
build ahead of the next trough evolving over the western U.S.,
which will translate to warming high temperatures through the
weekend into early next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 617 PM CDT Tue Oct 12 2021
Deteriorating conditions are expected later tonight ahead of a
storm system moving into the region. Should see conditions drop to
MVFR towards 06Z with increase of areal coverage of TSRA. Models
do show some signal for small hail accompanying a few storms
passing through KOMA/KLNK sometime between 07z-09z mainly
affecting. However, did not include in latest TAFs given low
confidence. Expect TSRA activity to eventually push east of the
terminals toward 14z with VFR conditions prevailing the remainder
of the period. Also, LLWS threat will be in play late this
evening through early Wednesday morning at all terminals.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...Mead
AVIATION...DEE