Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/15/20
Area Forecast Discussion
National Weather Service Caribou ME
936 PM EST Sat Nov 14 2020
.SYNOPSIS...
High pressure will build this evening and crest over the region
tonight. Low pressure approaches on Sunday with a frontal system
crossing Sunday night. Cold Canadian high pressure then
gradually builds through the middle of the week.
&&
.NEAR TERM /THROUGH SUNDAY/...
9:36 PM Update: Satellite imagery, observations and a couple
webcams indicate that the sky is mostly cloudy to cloudy across
most of the FA. Skies are mainly clear along the Downeast Coast
up the Penobscot River Valley to near the Milo area. There will
be an overall clearing trend overnight as high pressure builds
into the region but I have adjusted that clearing for most based
on the trends. Radar & observations indicate some snow showers
and flurries in parts of Aroostook, Northern Washington &
Northern Penobscot counties. We observed a brief period of
flurries here at the office about 20 minutes ago. Expect this
activity to end over the next few hours but we have adjusted the
pops for the next few hours. The overall forecast remains in
good shape with only minor tweaks based on the latest
observations, webcams, radar images, and trends.
Previous discussion:
Tonight...Upper disturbance will be moving across the region
this evening as seen on satl imagery w/this feature residing in
Quebec attm. CAA and NW flow coming off the St. Lawrence and
deep moisture available will be enough to allow for some
streamer action in the form of light snow/flurries. The GEM and
GFS matched up well w/this setup. The 12z NAM and HRRR show a
line of activity running from NW ME down across the Baxter State
Park region into Nrn Washington County. The llvl convergence
shown by the NAM matches up well w/this as well. Not expecting
more than at best 0.5 inches and this will be across the higher
terrain. Clearing to take place overnight w/NW winds dropping
off as high pres from the ridges across the region. It will be
much colder than Friday night`s mins w/temps generally getting
down into the 20s w/the far northern areas seeing upper teens
and even some lower teens back toward the Allagash and N Woods
region.
Sunday will be starting out mostly sunny as the upper ridge
moves right over the area and then passes east later in the
afternoon. This will allow for some warming of the temps after a
chilly start to the morning. Temps will be capped off though by
early afternoon as clouds advance from the wsw. Many locations
across the northern 1/2 of the CWA will top out in the mid 30s,
while central and downeast areas will see upper 30s to lower
40s. A frontal system apchg from the w later in day will bring
the leading edge of precip in wrn areas by later in the
afternoon. Attm, stayed w/the midnight crew`s assessment of a
mention of rain/snow in aforementioned area.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
updated to change Monday night to Sunday night...
Guidance for the Sunday night storm has trended a bit slower and
warmer with less QPF. This resulted in snowfall amounts being
cut back in northern zones, but there`s still decent potential
for an advisory in NW Aroostook County. Accumulations may be
further reduced by sleet too, but have stuck with rain/snow in
the forecast for now. The secondary low along the warm occlusion
doesn`t really take over and cut off warm advection. As a
result, warmer boundary layer temperatures are pushed northward
towards the northern border with a changeover to rain later
Sunday night...a relatively mild day following Monday. The
southerly low level jet is now more the focus of our attention
rather than snow. With 70 kts at 925mb shown by all the models,
a High Wind Watch has been issued to advertise the threat for
Monday night. Stability does not appear to be a big impediment
and mixing up towards 925mb or higher is a big concern. Power
outages could be a problem. Wind advisories may be needed
further north to include the Bangor area, but will let the night
crew make that call. The precip will sweep across the area
fairly quickly Sunday night with most falling within a six hour
period and amounting to around a half inch to three quarters of
an inch of QPF. For Monday, the milder air in the wake of the
occlusion continues until Monday night when a cold front brings
much cooler air for Tuesday into Thursday. Highs on Tuesday will
be some 10 degrees cooler with a brisk west wind. With a decent
supply of low level moisture and instability, snow showers will
be a possibility in the western mts Monday night and Tuesday,
but no accumulations are forecast at this time.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A trough of low pressure crosses Tuesday night into early Wednesday
and brings the coldest air of the season for Wednesday into
Thursday. Highs will only be in the 20s to lower 30s...some 40
to 50 degrees cooler than the record highs early this week. The
cold advection will bring a lot of cu/stratocu fields with some
upslope snow showers into Wednesday. High pressure builds
Wednesday night, but since it`s a rather narrow ridge, it may be
hard to get rid of low clouds for much of the night and this
scenario favors the coldest temps in the North Woods where
subzero temps will be possible. The ridge will be short-lived
early Thursday as a rather dry northern stream warm front brings
rapidly increasing clouds and the threat of snow or mixed
precip later Thursday into Thursday night. Can`t see any snow
accumulations more than an inch and some freezing rain or sleet
seems possible by later Thursday night. Did not include in the
forecast at this point due to timing uncertainties. A milder
zonal flow emerges for late week with a return to more
seasonable temperatures.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
NEAR TERM: Basically VFR for terminals into Sunday. The caveat
will be this evening across some of the northern terminals, such
as KPQI, KCAR and perhaps KHUL as a brief period of MVFR cigs &
possibly some flurry activity. A more prolonger period of MVFR
ceilings at KFVE through the evening. NNW winds 5-10 mph
tonight becoming light overnight. Light and variable winds
Sunday morning becoming SE 5-10 mph.
SHORT TERM:
Sunday night...Will feature IFR cigs and IFR vis in snow north
of HUL. LLWS is expected...especially for BGR, BHB and coastal
sites.
Monday...IFR cigs north of HUL dissipate early and give way to
MVFR cigs north of HUL. VFR is forecast further south.
Monday night into Wednesday...Frequent MVFR cigs and a few snsh
north of a GNR to HUL line. Otherwise VFR.
Thursday...Chance of IFR vis in snow north of HUL by
afternoon...otherwise VFR.
&&
.MARINE...
NEAR TERM: NW winds 15-20 kt this evening will gradually drop
off tonight as high pres to the s apchs the waters. Seas 3-4 ft.
N winds around 10 kt on Sun becoming SE and increasing to around
15 kt w/some higher gusts.
SHORT TERM: A strong gale is expected Sunday night and have
converted the watch to a warning. Can`t rule out a few gusts to
storm, but confidence not high enough for a storm watch or
warning at this time. The gale will probably continue in the
outer waters all of Monday. Advisory conditions are expected
mostly non-stop into Friday.
&&
.TIDES/COASTAL FLOODING...
High astronomical tides are expected Sunday into Monday. The
very highest tides will be Sunday morning around 10 AM EST and
again Monday morning near 11 AM EST. The Sunday evening tide is
just a bit lower, but will be enhanced by a potentially strong
storm surge that could make it the highest tide of the three.
While all three tides could cause minor issues at prone areas
such as Machias, the Sunday evening tide near 1040 PM EST could
cause the greatest issues if the max surge coincides with the
high tide. Using ESTOFS with the southeasterly winds rather
than ETSS. With the elevated water levels, seas over 10 ft and
an increasing wave period, wave runup could be an problem with
the Monday morning high tide.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...High Wind Watch from Sunday evening through Monday morning for
MEZ029-030.
MARINE...Gale Warning from 7 PM Sunday to 7 AM EST Monday for
ANZ050>052.
&&
$$
Near Term...Hewitt/Sinko
Short Term...MCW
Long Term...MCW
Aviation...Hewitt/Sinko/MCW
Marine...Hewitt/Sinko/MCW
Tides/Coastal Flooding...
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
532 PM CST Sat Nov 14 2020
.Short Term...(This Evening through Sunday)
Issued at 329 PM CST SAT NOV 14 2020
Short term filled with challenges as strong winds and thunderstorms
impact the area.
As stratus across eastern Kansas erodes, am seeing winds approach
wind advisory criteria. South of the Missouri, it may be a struggle
to reach full advisory level winds with the stratus expected to hang
tough. With that said, conditions will be quite close to advisory,
so will leave headline as is for the time being.
CAMs have delayed convective initiation across central and eastern
Missouri this evening closer to 00Z. Capping inversion near 800 mb
looks to remain in place a bit longer, limiting convective potential
through the late afternoon hours. With strongly sheared
environment, effective bulk shear is expected to be in 50-60 knot
range. With tongue of 500-1000 J/kg of CAPE, may be enough to
result in scattered shower/storm development early this evening
across central Missouri. Latest runs of the HRRR (18-19Z) are also
suggesting development along the surface cold front towards 01-03Z.
Surface inversion looks to be weakest across south central Missouri,
suggesting that if convection is able to form, there may be a small
window for convection to become near surface based near Clinton, MO
early this evening. Outside of this area, expect the main severe
weather threat to be severe wind gusts with 50-60 knots of wind
poised just above the surface.
As cold air advection increases behind the cold front after 03Z,
1000-900 mb lapse rates increase to near 8.5 degrees/km. This along
with pressure rises of 3-5 mb/hr will likely result in a second
period of increased winds. The increased winds are expected to only
last 3-5 hours in any particular location, but have issued a wind
advisory for much of the forecast area through the overnight hours.
Strong westerly-northwesterly winds of 40-50 knots are expected to
follow behind the cold front, and with the steepening low level
lapse rates, expect wind gusts to surface for a period.
Breezy conditions are expected to develop Sunday morning and slowly
decrease through the day as winds in the mixed layer slowly
decrease. With that said, expect wind gusts of 30-35 mph throughout
the morning hours, decreasing through the afternoon hours. Have
left the wind advisory as is for now, but will need to closely watch
the top of the mixed layer and make sure mixing doesn`t climb into
the stronger winds aloft.
.Long Term...(Sunday Night through Saturday)
Issued at 329 PM CST SAT NOV 14 2020
Jet stream is expected to buckle northward early next week with
relatively quiet weather and above normal temperatures through the
week. Potential for rain showers increases next Saturday as
deepening trough across the west creates the chance for warm air
advection showers.
&&
.Aviation...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 520 PM CST SAT NOV 14 2020
A strong cold front will move through the terminals early in the
prevailing period. Southwesterly winds of 10 to 20kt with gusts up
to 30kt will continue out ahead of the approaching front. Post-
frontal, winds will veer to more westerly in direction but
maintain a similar wind speed into early Sunday morning. Storms
are beginning to develop ahead of the front, but are expected to
remain south and east of the terminals KSTJ/KMCI/MKC. KIXD may see
a brief period of VCTS between 00-01Z but given how quickly the
storms are moving...any storms should quickly clear out of east-
central Kansas and far west-central Missouri. Ceilings will
predominantly be VFR with a possible scattered MVFR deck ahead of
the front that will quickly rise to 9-12 kft behind the front.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
KS...Wind Advisory from 9 PM this evening to 4 AM CST Sunday for
KSZ025-057-102>105.
Wind Advisory until 6 PM CST this evening for KSZ057-060-105.
MO...Wind Advisory from 9 PM this evening to 4 AM CST Sunday for
MOZ001>006-011>015-020>023-028>031-037>039-043-044.
Wind Advisory until 6 PM CST this evening for MOZ037-043-044-053-
054.
Wind Advisory from midnight tonight to 3 PM CST Sunday for
MOZ007-008-016-017-024-025-032-033-040.
&&
$$
Short Term...BT
Long Term...BT
Aviation...PietrychaP
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
814 PM CST Sat Nov 14 2020
.UPDATE...
814 PM CST
Evening update:
No significant changes to going forecast this evening. Gusty
showers and thunderstorms and very strong winds later tonight and
Sunday continue to be the primary forecast concerns. No changes to
wind advisory or marine headlines at this time.
Evening surface analysis shows 996 mb low pressure over central
IA, with a cold front trailing through Missouri into far
southeastern KS at 01Z. East of the low, blustery southeast winds
were across the western Great Lakes region within a tight pressure
gradient maintained by a broad area of pressure falls in excess
of 2-3 mb/3 hrs. An area of showers and isolated thunderstorms was
working east- northeast over southern Lake Michigan and the IL/IN
state line region, generally along the leading edge of stronger
H8 moisture advection/convergence while patchy light rain/drizzle
was occurring farther to the west over north central IL.
Going forecast captures the expected trends nicely through the
remainder of the evening/overnight hours. Forcing for ascent will
continue to strengthen through late evening, in advance of a deep
upper trough and a strong vort/jet streak transiting the region
overnight. Showers and thunderstorms are expected to increase in
coverage again mid-late evening, with the potential for a stronger
line of low-topped convection ahead of the approaching cold front
toward and just after midnight. Earlier cluster of low-topped
cells produced a 40 kt wind gust at Rochelle, and with 50+ kts of
SSW winds only about 1500 feet above ground level, any additional
strong convection will have to be watched for some stronger gusty
wind potential overnight. Surface cold front pushes through during
the pre-dawn hours, which will then shift the concern to very
strong synoptic (non-convective) winds as low level cold advection
kicks in and steepens low level lapse rates, deepens the boundary
layer and mixes down higher momentum from aloft. Surface gusts
45+ mph are likely to develop behind the cold front, as this
deeper mixing and strong isallobaric gradient forcing aid in
increasing westerly winds.
Despite complexities of the weather scenario, going forecast has
things handled very well, with wind advisory beginning at midnight
and thunder chances quickly diminishing behind the cold front.
Gradual slight warming of temps up until cold fropa also depicted
nicely in hourly grids.
Ratzer
&&
.SHORT TERM...
300 PM CST
Through Sunday night...
The shower and thunderstorm chances tonight, followed by the
likelihood of strong and potentially damaging wind gusts of 50-60
mph on Sunday are the primary forecast concerns during the short
term period.
...Showers and storm chances Tonight into Sunday morning...
Showers have been slow to develop early this afternoon, with much
of the activity currently confined well to our south. However,
more scattered activity has recently been developing just to our
west near the Mississippi River. This uptick in showers, and even
some storms will be the rule as we head into the early evening
hours. This uptick in activity will be driven by the combination
of increasing upper level jet dynamics over the area associated
with the approaching upper trough to our west, and a strong
northward surge occurring thanks to a strong lower-level mass
response (Southerly low-level jet 50+ KT). With this in mind,
confidence continues to be high with periods of showers through
the evening, along with some thunderstorms given the steepening
mid-level lapse rates. We also may have to watch for a strongly
forced line of low topped convection around, or just after
midnight ahead of an approaching cold front. This could produce
some small hail, and/or help locally drag down some stronger wind
gusts ahead of the approaching cold front.
The upper level dynamics associated with the approaching upper
level impulse will drive a fast northeastward moving and deepening
area of low pressure from eastern IA early this evening to near
the Straits of Mackinac by early Sunday morning. Gusty southerly
surface winds will be the rule through the evening ahead of this
area of low pressure, and its associated cold front. Because the
area will be in the warm sector of this storm system tonight,
expect temperatures to continue rising through the evening, with
readings likely reaching into the low to middle 50s overnight
before the strong cold front shifts eastward across the area
overnight. The time of this frontal passage is likely to result
in both todays and Sundays high temperatures occurring right
around midnight tonight. Temperatures during the day on Sunday
will likely remain nearly steady in the upper 30s to low 40s.
After the cold front pushes across the area overnight the strong
winds will become the main weather story, see more on this below.
However, it appears that another batch of precipitation will
occur across the area Sunday morning as a secondary disturbance,
now over South Dakota, rotates through the larger scale trough.
This will have to be watched as it could mix with, or even change
to a period of snow over far northern IL during the morning. Given
steep mid- level lapse rates remaining in place, this could fall
a decent clip for a short period of time, potentially even leading
to some minor accums in some areas. Confidence is not the highest
with this changing to snow due to uncertainties on how warm the
near surface airmass will remain. This activity should largely
come to an end by midday Sunday.
...Strong Winds late Tonight and Sunday...
For tonight`s winds, a tightening pressure gradient will develop
between high pressure of 1023 mb over the east coast and a
strengthening low pressure over Iowa. There will be pressure
falls around 4-5 mb per 3 hr over the CWA. In addition, an 850-925
mb low level jet (LLJ) of 55-65 kt will develop later this
evening. Tapping into these stronger gusts will be limited with
indications of a stronger inversion with clouds and showers. Still
some sporadic gusts of around 35 mph are likely, and a few higher
are possible especially with any convection that is near the
front.
As the enclosed 990 mb low develops over Wisconsin overnight and
progresses to Lake Superior Sunday morning, further deepening to sub
980 mb as it does so, the pattern will favor at least Wind Advisory
conditions (45+ mph gusts) over the region with potential for a
window of time to High Wind Warning (58+ mph gusts). Pressure rises
of +7 mb per 3 hours just behind the front will create a very tight
gradient and be assisted by cold air advection. This looks to maximize
Sunday morning, right after daybreak, and persist through early to
mid afternoon. One uncertainty to reach that 60 mph threshold will be
the amount of clouds, but feel high confidence in 50 mph gusts with
that degree of wind forecast on model soundings at cloud base layer.
Also the HRRR and experimental HRRR continue to indicate gusts
nearing or even reaching 50 kt across much of the CWA during that
morning period, further adding confidence and suggesting we may at
least temporarily reach 60 mph for gusts.
While gusty winds look to continue into Sunday evening, expect
the speeds to begin to ease.
In addition to the wind advisory a lake shore flood advisory has
been issued for Porter county IN for Sunday and early Sunday
evening. The strong westerly winds are also expected on Lake
Michigan, and this is likely to result in large waves up to 11
feet impacting the Porter county shoreline.
KJB/BKL/MTF
&&
.LONG TERM...
313 PM CST
Monday through Friday...
The forecast thinking for the extended period has not changed.
Please reference the previous discussion below for more
information.
Overall quiescent conditions are expected next week as fast
northwesterly flow continues overhead. A fast-moving disturbance
is forecast to zip along the northern fringes of the fast polar
jet on Monday. Most guidance tonight continues to suggest the core
of this feature remaining north of the Wisconsin state line, but
some ensemble members do suggest this getting close enough to at
least thicken up the mid-level cloud deck. Main issue with this
feature is that it will be accompanied by very cold temperatures
aloft (getting towards -30 C at 500 mb) which will result in a
plume of steep mid-level lapse rates as the main corridor of
forcing for ascent arrives. At this time, the strongest isentropic
upglide associated with this disturbance looks to be displaced
enough from the main lapse rate plume to justify keeping the
forecast dry (plus the rather dry sub-cloud layer in the place),
but a feature to watch nonetheless as wet bulb temperatures would
support column cooling to favor (convective) snow.
Tuesday night may feature the coolest temperatures of the upcoming
stretch as high pressure builds (briefly) directly overhead and
winds go light and variable for a time. However, warm advection
returns with gusto on Wednesday and especially Thursday which
should allow temperatures to climb back to above normal values
with some low to even mid 60 degree readings in place come
Thursday.
Thereafter, some low-grade precipitation chances get re-introduced
over the weekend, as the next disturbance--a southern stream
wave--scoots east across the CONUS. Lots of model spread with this
one, and did not stray from the offered slight chance to low-end
chance PoPs from the blended guidance.
Carlaw
&&
.AVIATION...
For the 00Z TAFs...
547 PM...Several forecast concerns this period including...
Strong/gusty southeast winds this evening.
Very strong/gusty westerly winds Sunday.
Chance of thunder this evening and again around 06z.
Showers through Sunday morning...chance of snow Sunday morning.
Possible ifr cigs this evening.
Southeast winds gusting to 30kt will continue this evening...
slowly turning more southerly by late evening and then to the
south/southwest after midnight. Despite the these strong surface
winds...winds aloft are strong enough to continue low level wind
shear mention...especially when surface winds may be lower than
expected. Speeds/gusts will increase overnight with gusts into the
mid 30kt range possible. Winds will shift westerly before or
around daybreak and by this time period...gusts will increase into
the mid 40kt range. These very strong gusts will continue through
the morning and will slowly relax into the 40kt range Sunday
afternoon. Wind speeds/gust will slowly diminish Sunday evening
but will remain gusty through much of the evening.
Showers will continue to spread across the area this evening
though there will likely be some dry periods. Isolated
thunderstorms will remain possible but the duration of thunder
should be short-lived at any one location but maintained the
vicinity mention this evening. A better chance of thunderstorms
is expected ahead of the cold front late this evening into early
Sunday morning and tempo thunder still on track for this time
period. Any of the stronger showers or storms may produce brief
moderate/heavy rain and some vis reductions. There appears to be a
break in the precipitation in the predawn hours but another wave
will move across the area Sunday morning bringing rain showers to
the area. It will turn cold enough that some snowflakes may mix
with the rain especially at rfd. If there were a period of mainly
all snow...ifr vis can be expected.
Mvfr cigs have scattered out across part of the area early this
evening and guidance has been backing away from ifr cigs this
evening across northeast IL. Prevailing mvfr cigs are still
expected though with showers moving through...cigs may remain
somewhat variable over the next few hours. Ifr cigs are still
possible across northwest IL including at rfd but even here...
confidence is low. Mvfr cigs will continue through late Sunday
morning...possibly into early Sunday afternoon before lifting to
low vfr. Its possible another period of ifr cigs may develop with
the rain or rain/snow showers Sunday morning and did include ifr
cigs with the tempo at rfd. cms
&&
.MARINE...
313 PM CST
A strong storm system will produce a significant wind event on
Lake Michigan late tonight through though Sunday. A period of
storm force winds to 50 kt appears likely following a strong cold
front, which will move across southern Lake Michigan late tonight.
Westerly winds will quickly increase to 50 kt in its wake, and
these strong winds will continue through much of the day Sunday.
Winds will gradually ease below storm force late Sunday afternoon
and evening, but some gale force winds could continue during the
evening. A storm warning has been issued from late tonight through
Sunday afternoon, during the period of strongest winds. The gale
warning also remains in effect through 09z Monday. Expect the
weather to improve for Monday.
Carlaw/KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-
ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-
ILZ039-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108...midnight
Sunday to 6 PM Sunday.
IN...Wind Advisory...INZ001-INZ002-INZ010-INZ011-INZ019...midnight
Sunday to 6 PM Sunday.
Lakeshore Flood Advisory...INZ002...9 AM Sunday to 9 PM Sunday.
LM...Gale Warning...nearshore waters until 3
AM Sunday.
Gale Warning...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...3 PM
Sunday to 3 AM Monday.
Storm Warning...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...3 AM
Sunday to 3 PM Sunday.
&&
$$
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Area Forecast Discussion
National Weather Service Blacksburg VA
950 PM EST Sat Nov 14 2020
.SYNOPSIS...
Increasing clouds tonight as high pressure departs to our east.
Windy conditions with showers Sunday as a strong cold front pulls
through. Our next front arrives Tuesday bringing another round of
wind and cooler conditions midweek.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 946 PM Saturday
A broken to scattered deck of mid to high level clouds continues to
stream in from the southwest. These clouds will continue to increase
overnight as warm air advection takes over. Winds have also
started to pick up with gusts close to 20 mph back toward
Beckley and Charleston as our surface low over the Great Plains
starts to deepen ejecting rather stout south to southwest low
level jet our way. Precipitation wise, I have opted to back off
on PoPs a bit through the early morning hours of Sunday by 1-2
hours based on how dry the low levels remain per the 0z
sounding. Hi- res models continue to show this as well with a
slower precipitation arrival time from the front itself and any
shower activity that develops out ahead on south to
southeasterly flow. Otherwise, no additional forecast changes at
this time.
As of 713 PM EST Saturday
Some minor adjustments to temperatures and sky coverage through the
overnight as well as precipitation chances early Sunday morning.
Leaning toward a later start Sunday morning in overall rain chances
along the southern crest of Blue ridge and back into the North
Carolina mountains. Both the 12z and 18z model suites illustrate
this with the NSSL, NAMnest, and CONShort the most aggressive in
moistening the column due to isentropic lift from south to southeast
return flow. For now opted for the 8-10z (3am-5am Sunday)window
which lines up better with the current HRRR and ARW solutions.
Overall the latest hi-res guidance pegs our front coming in between
15-19z Sunday before clearing the area Sunday evening. The front
will bring with it several hours of sustained winds between 15-30
mph with gusts over 40 to 50 mph at times especially across the
higher elevations. With that said a Wind Advisory will continue from
6am-7pm Sunday for the Greenbrier Valley, Alleghany Highlands, and
North Carolina mountains. These areas are likely to see the highest
winds across the regions starting around sunrise Sunday and
continuing into the afternoon. Will reevaluate the advisory and look
to see if we need to expand further east as the cold frontal
boundary works in.
As for temperature we look to warm a bit out ahead of the
boundary as low level warm air advection builds with south to
southeasterly return flow. On top of this high level clouds will
continue to filter in acting as a thermal blanket overnight. Lows
tonight will generally be in the mid to upper 40s. Highs tomorrow
will top off mainly in the 60s for the west, near 70 for the
east.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 130 PM EST Saturday...
Frontal passage Sunday will be followed by strong pressure rises,
cold advection and decent gradient, low level jet. Soundings suggest
that our normal mountain counties could get to advisory level winds
of gusts over 45 mph Sunday night. Seeing the wind advisory ahead of
the front, will wait another run of the models and ascertain where
there will be a need for one Sunday night.
Otherwise, high pressure works in from the southwest Monday but will
still have some wind lingering, with colder temperatures with broad
trough in the east. Next front arrives Tuesday and will likely see
clouds increase with threat of rain/snow showers in the higher
terrain of WV, but nothing of consequence for now, as fast flow and
drier air limit precip.
Another shot of colder air, with winds accelerating again, but
models are not as strong with the low level jet, so sub-advisory
winds anticipated Tuesday-Tuesday night.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 138 PM EST Saturday...
Building heights as ridge sets up over the southeast this period
will bring milder temperatures and dry weather. A backdoor front
edges toward the mid-Atlantic Saturday but not seeing enough of a
push with the stronger high over the Carolinas. Temperatures should
rise to at and above normal toward the end of the week.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
As of 713 PM EST Saturday...
VFR conditions persists through this evening before the focus shifts
to strong winds and precipitation impacting aviation concerns Sunday.
Winds will start to increase beyond 6z-8z out of the south to
southeasterly building high clouds and giving way to sub-VFR ceilings
and LLWS at most of the TAF sites early Sunday morning. Confidence
is a bit lower on the extent of clouds east of the Blue Ridge from
KLYH to KDAN opening the door for an additional period of VFR around
sunrise Sunday morning.
Overall sub-VFR conditions are expected in the west throughout the
TAF period as a cold frontal boundary enters the area. With strong
south to southeasterly flow out ahead of the boundary an opportunity
for VCSH or even a period of SHRA remains possible at KBCB, KROA
,KDAN, and KLYH early Sunday morning. Rain chances increase for KBLF
and KLWB beyond the early morning period as the cold frontal
boundary works into the region. Shower activity wraps up as the
front looks to clear the area by 20-22z Sunday. Winds will persist
though well into the afternoon sustained at 10 to 15 knots out of
the south/southeast gradually shifting to the south/southwesterly
direction. Gusts will also hang between 20-25 knots through latter
half of the TAF period.
Extended Aviation Discussion...
A cold front will cross the region early Sunday evening. Expect
limited sub-VFR conditions associated with this feature. Winds will
become very gusty from the northwest by Sunday afternoon and remain
gusty through early Monday morning.
After a brief visit by high pressure on Monday night, another cold
front will cross the region Tuesday into Tuesday night.
Very gusty winds will again follow the passage of the cold front.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Wind Advisory from 6 AM to 7 PM EST Sunday for VAZ007-009>011-
015-019-020.
NC...Wind Advisory from 6 AM to 7 PM EST Sunday for NCZ001-002-018.
WV...Wind Advisory from 6 AM to 7 PM EST Sunday for WVZ042>044-507-
508.
&&
$$
SYNOPSIS...ET
NEAR TERM...ET/RR
SHORT TERM...WP
LONG TERM...WP
AVIATION...ET/RR
...Update to aviation forecast discussion...
.UPDATE...
Issued at 545 PM CST Sat Nov 14 2020
Forecast for a push of stronger winds remains on track for tonight
based on upstream observations and CAM progs. Wind gusts of 40 to
45 kts are likely as the front pushes through between 01-04Z,
decreasing from west to east after several hours. The presence of
elevated precipitate lends some concern that additional momentum
transport could be lent to the winds as they work through the area
and will monitor trends closely in case winds approach warning
levels.
&&
.DISCUSSION...
Issued at 217 PM CST Sat Nov 14 2020
20Z water vapor imagery showed a longwave trough over the
northern and central plains. There was still signs of
amplification of this trough as the trough was moving out into the
plains. Further upstream a shortwave was noted off the Pacific
northwest coast moving towards British Columbia. At the surface, a
prefrontal trough bisected the forecast area north to south.
Temps have warmed into the lower 70s ahead of this boundary while
areas across north central KS have struggled to warm into the
lower 60s.
For this afternoon and tonight, the main concern is with the winds.
Models show the pressure gradient relaxing across east central KS
this afternoon as the prefrontal trough continues moving east. So I
anticipated being able to let the initial wind advisory expire on
schedule. The bigger concern is with strong pressure rises behind the
front tonight. The RAP and HRRR continue to show the potential for
wind gusts near 50KT which is strong enough for a high wind warning.
Confidence in gusts this strong is not high enough to go with a
warning at this time. The models show the pressure rises weakening
through the night and statistically the gusts shown by the HRRR and
RAP have about a 10 percent chance of happening. So will continue
with the advisory. Have extended the advisories tonight to expire at
11 pm and 1 am since the overall progression of the upper trough and
associated pressure rise have trended slower.
Some of the guidance is trying to spit out some light QPF this
evening. Forcing from the upper trough looks to be pretty strong,
but moisture may be limited. Have been monitoring the radar returns
across northwest KS and surface obs have not reported any precip
while ceilings generally remained around 10 KFT. So have kept POPs
below 20 percent with only a mention of sprinkles through the
evening. Lows tonight will be cooler, but a strong pressure gradient
is likely to keep the boundary layer mixed through the night. This
is expected to hold lows in the middle to upper 30s.
For Sunday through Friday, dry weather is forecast to persist.
Models are in good agreement for northwest flow to develop for
Sunday and Monday where there could be some perturbations within the
flow. However a dry airmass is expected to preclude any POPs. Then
an upper level ridging amplifies over the central U.S. through mid
week. So rain chances any time soon do not look promising. Temps for
Wed and Thu have trended warmed with the GFS and ECMWF showing good
low level warm air advection. In fact Wednesday looks to be pretty
breezy as the pressure gradient potentially strengthens again.
There are some indications from the operational models for the next
upper trough to move from the southwestern U.S. into the plains next
weekend as a cold front sags south. So have some small POPs going
for Saturday. The forecast this far out has some uncertainty as
models differ on the timing and location of the frontal boundary.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 545 PM CST Sat Nov 14 2020
VFR conditions are forecast for the TAF period with scattered
thunderstorms currently southeast of an EMP to LWC line rapidly
exiting the area by 02-03Z. Westerly winds of 15-20 kts will
rapidly increase out of the northwest between 01-04Z tonight with
gusts of 40-45 kts likely at times. These winds lessen after
05-07Z, but remain gusty out of the west through the remainder of
the TAF period. Should any decoupling happen tonight, LLWS would
ensue, but confidence was not high enough to mention in the TAFs.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 1 AM CST Sunday for KSZ011-012-023-024-026-
038>040-054>056-058-059.
Wind Advisory until 11 PM CST this evening for KSZ008>010-
020>022-034>037.
&&
$$
UPDATE...Skow
DISCUSSION...Wolters
AVIATION...Skow
Area Forecast Discussion
National Weather Service Tulsa OK
923 PM CST Sat Nov 14 2020
.DISCUSSION...
Scattered low-topped supercells continue over parts of western
Arkansas near the nose of 700mb jet in unstable pre-frontal
environment, and will continue to pose a severe threat for a
couple more hours. Cold front currently located near Checotah to
Gravette and will continue to sweep through the remainder of the
area by Midnight. Front is forcing a broken line of storms,
however updrafts quickly being undercut and as such, these storms
pose little severe threat. Gusty northwest winds immediately in
the wake of the front have been enhanced by convective cells
immediately behind it, with brief gusts in the 40-45 mph range
noted. Severe threat will end once the front clears the forecast
area.
Additional updates will mainly be to clear more counties from
tornado watch behind the front...and have also upped wind speeds
behind the front for tonight.
&&
.PREV DISCUSSION... /Issued 506 PM CST Sat Nov 14 2020/
AVIATION...
CONCERNING TAF SITES KTUL/KRVS/KBVO/KMLC/KXNA/KFYV/KFSM/KROG.
The main concern with the potential for thunderstorms
to impact the western Arkansas sites through 06z as a
cold front sweeps through the region rather quickly. After 6z...
the gusty northwest winds will be concern as ceilings
clear out.
PREV DISCUSSION... /Issued 145 PM CST Sat Nov 14 2020/
DISCUSSION...
Primary concerns will be the convection trend the remainder of the
afternoon and into the evening.
Current visible satl imagery shows the back edge of the clouds
over the part western parts of the forecast area, with
considerable breaks in the overcast noted across parts of
southeast into far eastern OK. If these trends continue, then
afternoon instability may a bit higher than earlier anticipated.
Recent runs of the HRRR appear to latch on to this idea, with
scattered pre-frontal convection developing along OK/AR border
around 21-22Z. A few of these storms could become severe, with
forecast wind fields showing the potential for rotating storms.
This activity would likely shift east of the area by early
evening, although expect additional development as the cold front
enters northwest AR around 03-04Z. This activity may pose a small
severe threat, with storms quickly exiting the area by midnight.
Will keep an eye on wind gusts over the next few hours, but
anticipate leaving the current Wind Advisory as is.
Sunday will be seasonally cool and dry, although temperatures will
bounce back to above normal readings next week as mid-level
heights rise. Went a touch above NBM guidance, with afternoon
temps likely pushing the mid 70s in some spots by Thursday and
possibly into Friday. Shower and thunderstorm chances look to
increase next weekend as the upper flow becomes southwesterly and
a cold front approaches.
&&
.PRELIMINARY POINT TEMPS/POPS...
TUL 40 61 38 67 / 10 0 0 0
FSM 44 62 36 68 / 30 0 0 0
MLC 42 60 36 66 / 10 0 0 0
BVO 39 60 35 66 / 0 0 0 0
FYV 39 58 32 65 / 50 0 0 0
BYV 41 57 37 65 / 60 0 0 0
MKO 40 59 36 64 / 30 0 0 0
MIO 37 58 35 64 / 30 0 0 0
F10 40 60 36 66 / 0 0 0 0
HHW 45 62 36 65 / 10 0 0 0
&&
.TSA WATCHES/WARNINGS/ADVISORIES...
OK...None.
AR...None.
&&
$$
SHORT TERM...14
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
756 PM MST Sat Nov 14 2020
.UPDATE...
Issued at 753 PM MST Sat Nov 14 2020
Extended the wind adv in the lee of the Black Hills where
CAA/pressure rise squeeze will continue for another hour or 2,
supporting wind gusts up to 50 mph. Rap H8-H750 winds highlight
this well.
&&
.DISCUSSION...Water vapor shows upper trof over the Northern Plains.
Band of rain/snow along the cold front is shifting into central SD,
with a bit of snow beginning to increase in our western zones with
secondary cold front. Windy conditions across much of the region,
although not quite as windy as initially expected. Cold advection
with secondary front may push winds closer to high wind criteria
from northeast WY into northwest SD briefly later this afternoon and
early evening, but given winds have already been less than
anticipated and the mid/late afternoon arrival of front may be a
tad too late diurnally, have cancelled the Warning for northeast
WY and downgraded to Advisory for northwest SD.
Winds decrease by later this evening and overnight, with mostly
sunny conditions for Sunday and highs mainly in the 40s. Another
wave embedded in northwest flow aloft crosses the Northern Plains on
Monday and will kick up the winds a bit more, but dry conditions
expected. Upper ridge then builds in through mid week with dry and
much warmer conditions likely. Temps into the 60s and even some 70s
expected Wednesday, warmest south/east of the Black Hills. Flow may
become a bit more unsettled towards the end of the week as ridge
axis shifts east, with temps generally or slightly above average.
&&
.AVIATION...(For the 00Z TAFS Through 00Z Sunday Evening)
Issued At 415 PM MST Sat Nov 14 2020
Breezy NW winds will continue this evening, with ISOLD-SCT snow
showers ending. MVFR to local IFR conds will be possible in the
heavier snow showers. Conditions will improve late this evening to
VFR, except possibly across parts of NW SD and the Black Hills,
where MVFR CIGS may linger overnight.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory until 8 PM MST /9 PM CST/ this evening for SDZ001-
002-012>014-025-027-030-032-041>044-046-047-049-074.
Wind Advisory until 10 PM MST this evening for SDZ026-031-072-
073.
WY...None.
&&
$$
Update...JC
DISCUSSION...Johnson
AVIATION...JC