Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/24/19
Area Forecast Discussion
National Weather Service Denver/Boulder CO
908 PM MDT Wed Oct 23 2019
.UPDATE...
Issued at 903 PM MDT Wed Oct 23 2019
Starting to see the low level drying from relatively drier
northerly winds off the Cheyenne ridge expand southward this
evening. Snowfall overnight will be primarily confined to the
higher terrain of the southern Front Range and Palmer ridge areas
where the upslope flow is most optimal. Will expect this trend to
gradually continue through the overnight period as best jet
dynamics exit the state to the east and mid and upper level QG
ascent diminishes with time. Current timing of the Winter Storm
Warning and Winter Weather Advisory still looks good with a
termination at 8am. Believe much of the snow will have decreased
by then, however with wintry impacts related to travel conditions
and the morning commute, the 8am termination looks fine. A fairly
rapid improvement is still expected for Thursday with dry
conditions, light winds and mostly sunny skies expected.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 322 PM MDT Wed Oct 23 2019
The storm system that will bring snow to our area (and is bringing
snow to the high country now) is beginning to take shape this
afternoon. A secondary push of cold air from Wyoming has moved
across our area this afternoon, with north winds 20-25 gusting
over 35 mph. The air behind this frontal surge is still not
terribly cold yet, with wet bulb temperatures hovering in the mid
30s. Thus, precipitation so far has fallen as rain or a rain/snow
mix below 6,000 feet elevation. Above 6,000 feet elevation, and
especially above 7,000 feet, it`s been all snow and it`s sticking
to the northern mountain passes from Berthoud to Cameron to Rabbit
Ears to Gore to Willow Creek passes. It`s also snowing presently
along I-70 in the mountains and points south. With the QG forcing
aloft and the arrival of the 700 mb cold front yet to some, we
expect the snow to continue through the overnight hours in the
mountains. Travel is already adversely impacted across the
northern mountains, and this will quickly spread south along the
I-70 corridor and into Park County by late afternoon. Orographics
are weak, so once the forcing from the short wave trough exits the
area after midnight, the snow rates will reduce and will keep the
snow totals in check for the higher terrain. Advisory level
amounts look like a safe bet in most mountain areas north of I-70
and across Park County.
Along the east slopes and Palmer Divide, strong upslope is
underway out of the north, and eventually out of the northeast.
With north to northeast upslope and strong QG forcing passing over
the southern foothills and Palmer Divide this evening, the
heaviest snow is expected in those areas starting after 6 PM or so
and continuing overnight. The Winter Storm Warning has this well
in hand, with 4-8" expected, possibly up to 10-12" for the
foothills of Jefferson County and near the summit of the Palmer
Divide near Monument Hill. Travel is discouraged after 6 or 7 PM
given the increasing snow rates and chance for slick roads heading
up I-70 west of Golden and I-25 south out of Castle Rock.
For metro Denver, we still feel the HRRR and HRRRX have a good
handle on the precipitation timing and fall patterns. So far this
afternoon it has done a nice job predicting the rain/snow band
going on now, and the upslope flow patterns behind the most recent
frontal surge. Thus, we continue to predict a pretty steep
snowfall gradient across metro Denver. From DIA and Brighton,
probably not much more than a trace to an inch and a half of
snow. The amounts will increase towards the west and southwest
across metro Denver, with as much as 3-6" for the southwest metro
from Golden to Highlands Ranch. Most impacts to travel should hold
off until after this evening`s rush hour unless you are driving
up over 6,000 feet elevation.
For the eastern plains north and northeast of Denver, the best
forcing stays to the west, and downslope flow off the Cheyenne
Ridge will impact snowfall potential across Weld and Morgan
Counties, limiting snowfall accumulation in those areas. Far
Northeast corner may just see some light rain/show showers with
little accumulation of either this evening.
Jet dynamics shouldn`t come into play until the moisture is gone
during the day on Thursday. Thus, the main forcing will be the
short wave trough and upslope, perhaps augmented with a bit of
potential instability. Areas not favorable for northeast upslope
will likely stop snowing between midnight and 2 AM or so. The
Palmer Divide and southern foothills may see snow through 5 AM as
shallow upslope continues. Clouds will be on the decrease
throughout the day on Thursday but northerly flow will keep
temperatures in check, with right around 40 degrees I-25 urban
corridor, mid 40s eastern Plains, and 20s to low 30s in the high
country. Winds will be much weaker Thursday afternoon. With much
drier air and strong subsidence, all areas should be dry by
Thursday afternoon.
.LONG TERM...(Thursday night through Wednesday)
Issued at 322 PM MDT Wed Oct 23 2019
There`s good model agreement with the westerly flow aloft bringing
dry and warmer air over Colorado Friday and Saturday, then a sharp
cold front as the pattern buckles with cold air dropping south out
of western Canada. After that, the models diverge quickly. There`s
only a little better agreement than yesterday with the main
difference how much cold air comes down Sunday and drags the
bottom of the trough into the southwest. Solutions that are
weaker with this wind up less amplified and push a reinforcing
blast of cold air further east toward the Great Lakes with
Colorado on the edge, then gradual warming over the Rockies by
midweek. The models that keep the trough further west have less
cooling for Sunday, but the bring an even colder air mass
straight at Colorado on Tuesday with a possible prolonged
overrunning snow event.
Weatherwise for our area, not much to worry about through
Saturday. It still looks like there`s some threat of a South Park
mountain wave around 12z Friday, but this just looks like a low
threat of high winds for the US 285 corridor. There`s a consistent
trend of faster timing with the cold air coming down, now more
like Saturday night instead of Sunday. Model blend seems to
capture this alright with likely PoPs across most of the area as
there is lift over the initial front into Sunday night.
Monday looks like a bit of an in between day whichever set of
solutions you look at, as the first forcing should be past. There
probably won`t be much warming and it may even be a little cooler,
and some cloud cover is still likely as well, but the chance of
snow should be less.
There`s better agreement now on the existence of the Tuesday
front, which should bring additional cooling and some chance of
snow. The models that direct this further east have less forcing
for precip over Colorado, while the stronger ones like the
operational EC have another sharp front with an upstream trough
producing overrunning snow for 24 hours. The operational EC has
about three-quarters of an inch of precip with this, while the
operational GFS is dry. By Wednesday, there`s quite a range of
temperatures as the further east solutions are already warming us
up again. 700 mb temperatures over Denver are +2 C in the
operational GFS with -24 C in the ECMWF. MOS based on these
ensembles ranges from a near record low around zero, to a high
near 70. We`ll hedge our blend down a little bit figuring the cold
air is usually a bit more persistent over the plains and again
note that it could be a significant cold and snowy day or two if
the slower/stronger/further west solutions are right, or somewhat
warmer if not.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 903 PM MDT Wed Oct 23 2019
Persistent northerly winds will gradually bring drier air across
northeast Colorado and into the vicinity of the Denver Metro
terminals for the overnight period. Will expect a gradual
diminishment of snowfall coverage and intensity through 08z with
higher ceilings and decreasing clouds mainly after 10z. VFR
conditions will be expected for Thursday morning and persist
through the day. Winds will be primarily from a northerly
component through the morning hours before trending to the east by
late afternoon. A normal light wind drainage patter is expected
for Thursday night.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 8 AM MDT Thursday for COZ034-035-
037-039-040.
Winter Storm Warning until 8 AM MDT Thursday for COZ036-041.
&&
$$
UPDATE...Fredin
SHORT TERM...Schlatter
LONG TERM...Gimmestad
AVIATION...Fredin
Area Forecast Discussion
National Weather Service Melbourne FL
1032 PM EDT Wed Oct 23 2019
.UPDATE...
Tonight...Latest sfc analysis drapes a stalled frontal boundary
across the southern FL peninsula from Stuart to south of Ft Myers.
This feature is clearly highlighted in GOES Total PW, with peak
values of 1.9-2.0" right along the boundary, with the rest of
central FL at 1.5-1.7". Isolated to scattered showers with the
occasional lightning strike continuing near the boundary in the
Atlantic waters south of Cape Canaveral, with activity just now
reaching the northern Palm Beach County coast. Cape wind profilers
indicate a slight E/NE shift, which may allow for showers to push
toward the interior early tonight for the Treasure Coast counties.
Slight change to the precip forecast overnight, limiting PoPs to
less than 50%. Latest HRRR has significantly tapered back on a
convergent line of showers/storms moving northward overnight,
although will continue a chance for showers south of Cape Canaveral
to Lake Okeechobee and a slight chance just to the north, with
mentions of thunder remaining over the Atlantic. Low stratus will
fill in south to north overnight, mainly along the coast. No other
significant changes to forecast.
&&
.AVIATION...
Stalled frontal boundary across Lake Okeechobee has led to a deep
moisture concentration across south FL this evening, leading to
occasional ceiling drops <3000 for KSUA/KFPR/KVRB. Low stratus,
along with low shower chances, should expand northward overnight
leading to MVFR conditions thru daybreak at most terminals.
Developing onshore flow overnight may allow iso SHRA to push
inland, with higher coverage expected thru tomorrow.
&&
.MARINE...
Tonight...(modified previous) Winds will veer toward the ENE
tonight and will keep caution headlines up for most of the area
with 15-20kt winds initially, then decreasing to 10-15 kts after
midnight. Seas up to 4 to 6 feet offshore legs and southern
nearshore leg, with 3-5 ft elsewhere. Scattered showers and a few
storms through the overnight hours mainly south of Cape Canaveral.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 70 82 74 83 / 10 50 40 50
MCO 70 85 72 87 / 10 50 20 50
MLB 74 84 76 85 / 40 50 40 50
VRB 75 85 76 85 / 40 50 30 50
LEE 66 85 71 87 / 10 40 20 40
SFB 69 85 72 87 / 10 50 30 50
ORL 70 85 72 88 / 10 50 20 50
FPR 74 85 76 85 / 40 30 30 40
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Smith/Sharp/Combs
Area Forecast Discussion
National Weather Service Marquette MI
743 PM EDT Wed Oct 23 2019
.SHORT TERM...(This evening through Thursday)
Issued at 422 PM EDT WED OCT 23 2019
WV imagery and RAP analysis indicated a mid/upper level low near
James Bay with a trough through much of the north central CONUS. A
shortwave trough into western IA supported an area of rain through
northeast IA with thickening clouds into western WI. Otherwise,
cyclonic low level westerly flow persisted through the northern
Great Lakes on the periphery of a filling low over far northern
Ontario. 850 temps to around -6C (lake temps around near 9C)
provided marginal instability for any lake effect pcpn. However,
diurnal heating was still great enough to support sct/isold
showers/sprinkles/drizzle over mainly the west half of Upper
Michigan.
Tonight, although temps in the moist layer were marginal to support
ice nuclei, expect enough cooling tonight with lingering 850-700
moisture to reduce drizzle potential. 850 mb temps also dropping to
near -7C will continue to bring sct lake effect rain showers
changing to snow for west wind favored snow belts. However, any
accumulations should be minimal. As winds veer slightly to the wnw,
pcpn will also move into northeast Upper Michigan. Given the
marginal instability and dry low levels. Clouds/wind will keep temps
from dropping off too far with min readings in the lower 30s west to
the mid 30s east and along the Great Lakes.
Thursday, the gradually departing 850-700 moisture along with
daytime heating disrupting any banding will bring a diminishing
trend with the pcpn even as 850 mb temps remain near -7C. Highs
will struggle to reach 40 over the west while mid 40s are expected
over the south and east.
.LONG TERM...(Thursday night through Wednesday)
Issued at 353 PM EDT WED OCT 23 2019
Storm system near James Bay which impacted the Upper Great Lakes
with widespread rain and lakeshore flooding earlier this week will
continue to lift north and east through the end of the week.
Lingering CAA will continue isolated lake effect showers over the
west wind belts of Lake Superior into Thu night. Ridging and the
onset of a WAA southerly flow will result in a drying/warming trend
later Fri into Sat. Models trending farther se with track of
developing southern Plains low which now looks like it will track
through the Lower Great Lakes later this weekend with little impact
on our weather here. Strong ridging into the Gulf of Alaska and
Alaska this weekend into early next week will support the
development of a deep downstream trough across much of central
Canada into much of the west and central CONUS for the early and
middle portion of next week. This deep troughing across the
continent will provide a conduit for much colder Arctic air and
below normal temperatures to work into the central CONUS and western
Great Lakes, especially by the middle of next week.
Thu night into Fri, NAM fcst soundings would support at least some
lingering isolated west flow lake effect rain and snow showers into
Thu night as inversion heights remain from around 5 kft west to 7kft
far east and 850 mb temps around -7C would yield a lake-h85 delta-t
of at least 15C. Inversion heights will begin lowering from west to
east late Thu night into Fri as the sfc ridge builds in from the
west which should diminish or end any remaining lake effect showers.
Min temps Thu night will likely become quite chilly, especially with
clearing skies way from Lake Superior. Expect readings ranging from
the lower 20s over the interior west to near along the Great Lakes
shorelines. With 850 mb thermal trough of -8C still moving through
the area, expect highs Friday to be only in the lower to mid 40s.
More prominent mid-level ridging building in from the west along
with the onset of WAA in a breezy s-sw flow will allow temps to
rebound back into the 50s on Sat under generally sunny skies.
A cold front moving through into the area late Sat night into Sunday
may produce a narrow band of showers along the front but moisture
inflow is limited. Models now indicate that low pressure evolving
over the southern Plains should track well south and east of the
region and not impact the Upper Great Lakes.
The big story for next week is the likely return of below normal
temperatures as the pattern strongly amplifies across North America.
A trough from central Canada is expected to dig deeply into the west
and central CONUS in response to a strong positive height anomaly
over Alaska. This will pave the way for colder Arctic air to work
into the west and central CONUS and eventually into the Upper
Great Lakes for early to mid next week. Models also indicate the
potential for an early season winter storm to develop somewhere
over the central CONUS by the middle of next week, but agreement
is poor at this time on evolution, timing and track of this
potential storm. Will need to stay tuned and closely monitor model
trends heading into next week to determine what, if any, impact
this potential storm will have on the Upper Great Lakes region. At
this point, chance pops for mainly w-nw flow lake effect rain and
snow will be utilized in the forecast for the early part of next
week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 743 PM EDT WED OCT 23 2019
Ceilings at KIWD/KCMX look to flirt with the high-end MVFR to low-
end VFR categories this evening and overnight, along with nearby
showers have included mentions of VCSH for tonight. Winds have
relaxed at KIWD; however, KCMX will continue to see gusty west-
northwest winds overnight. Further west, diurnally driven showers
near KSAW are expected to further dissipate, leaving behind VFR
ceilings.
Early to mid Thursday morning, as a shortwave pivots across the
region, lake-effect showers and MVFR ceilings will move into the
northwest wind belts mostly impacted KIWD/KCMX. Thermal profiles
look cold enough to support some light snow throughout a good
portion of the day on Thursday, before switching over to a light
rain/snow mix in the afternoon. Further west, KSAW may see some
diurnally driven showers on Thursday; however, given the wind
direction not totally sold on the terminal itself being impacted so
have included at least mentions of VCSH for now. Otherwise, gusty
west-northwest winds are expected at all terminals tomorrow, but
there should be a decreasing trend in wind speeds towards Thursday
evening. Ceilings look to scatter out towards the end of the day on
Thursday as well.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 422 PM EDT WED OCT 23 2019
The pressure gradient will only gradually relax as the strong
October low pressure system continues to weaken and pull away to the
north. So, the strong west winds will also only gradually diminish
into Thursday. A few gale force west wind gusts may be possible into
this evening over the east. Otherwise W winds of 25 kts become NW
tonight then back to WNW late Thursday afternoon as they weaken
below 20 kts. High pressure moving through the Central Plains later
this week will switch winds more from the SW for this upcoming
weekend with winds increasing back to 25 kts across the lake on
Saturday then becoming W on Sunday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...Voss
AVIATION...Ritzman
MARINE...JLB
Area Forecast Discussion
National Weather Service Pueblo CO
613 PM MDT Wed Oct 23 2019
.UPDATE...
Issued at 610 PM MDT Wed Oct 23 2019
The following updates were made to the forecast:
Added Otero and Crowley counties to the winter weather advisories
Added the San Luis Valley and the San Juans to the winter weather
advisory. Most of the snow in the SLV will occur over the far western
part of the valley floor, and the eastern slopes of the San Juans
and La Garita mtns. /Hodanish
&&
.SHORT TERM...(This evening through Thursday)
Issued at 240 PM MDT Wed Oct 23 2019
...Winter returns to southern Colorado tonight and Thursday...
Upper trough diving south through the Rockies this afternoon will
move across Colorado from tonight into Thursday morning, with closed
upper low forming near the CO/NM border by 12z Thu. At the surface,
cold front already south of the Palmer Divide at 21z will race south
through the area in the evening, turning winds to the north-
northeast along and east of the mountains by 02z-04z. Models all
produce a period of intense upward vertical motion across much of
the area from roughly 22z through 12z, while dendritic growth region
quickly saturates as 700mb temps plunge and cold air deepens. Still
the usual questions about location of heavy banded snow on the
plains late this evening and overnight, with latest HRRR suggesting
one band across El Paso County this evening and another along or
just south of the Arkansas River beginning around 06z. Overall, set-
up still looks very good for heavy snow over all the eastern
mountains and back up the Arkansas Valley toward Salida, while
portions of the I-25 corridor and eastern Las Animas counties also
see at least some bands of heavier (6-8+ inches) as well. Precip
will start as rain briefly this evening, with a quick change-over to
snow after sunset many areas. Suspect models are a couple hrs slow
to change rain to snow around Pueblo, as evaporative cooling ahead
of heavier precip will likely drive temps down toward 32f by
midnight. Overall, current set of highlights and snow amounts from
forecast earlier this morning look on track, and few changes made in
the afternoon package. San Luis Valley looks tricky for snow amounts
as easterly flow will likely deepen enough to spill over most
eastern mountains passes early Thu morning, leading to perhaps some
higher snowfall amounts due to locally enhanced upslope flow on the
western edge of the valley. Roads will become slushy/icy and
snowpacked in spots many areas after midnight as temps fall into the
20s, leading to a slow commute most locations Thu morning.
Snow ends from north to south Thu morning, though srn Sangres/Raton
Mesa area will hang on to at least light snow through much of the
afternoon as deep upslope flow persists. Storm totals over a foot
look likely over most of the eastern mountains, higher elevations of
western/central Fremont County and near the Raton Mesa, with 4+
likely over much of the I-25 corridor. Roads should improve at lower
elevations Thu afternoon at most lower elevations as snowfall wanes
and temps creep back above freezing, though mountain highways and
passes will see snowpacked roads through the day as temps up high
remain below freezing.
.LONG TERM...(Thursday night through Wednesday)
Issued at 240 PM MDT Wed Oct 23 2019
High disagreement among ensemble members in regards to the
extended forecast. The one certain thing, is there will be an
upper ridge off the west coast, while longwave troughing sets up
somewhere in the Missouri Valley or Ohio Valley. The
inconsistencies look to be in upper systems dropping down the
back side of the longwave trough and what impacts they will have
on southern Colorado. Confidence is currently low beyond Sunday.
Thursday night through Sunday...the upper system that is currently
dropping across the area today, will continue southeast away from
the area Thursday night. Expect any snow showers lingering over
the Raton Mesa to come to an end during the early evening hours.
Broad northerly flow will persist across the area on Friday, with
cool temperatures across the region.
By Saturday, flow aloft will begin to transition more westerly
with warmer air mixing across Colorado. Temperatures will well
through the 60s with perhaps a few lower 70s possible. A cold
front will arrive late Saturday night into Sunday morning with
much cooler air advecting across the Plains. Highs on Sunday will
only reach into the 40s. As far as precipitation, models develop
isolated to scattered rain and snow showers, initially over the
Palmer Divide, spreading south down the Eastern Mountains Sunday
night. Snow will be possible for the whole area as the night
progresses, but accumulations should remain light.
Monday into Wednesday...models and ensembles really diverge early
next week. The GFS has a longwave trough over the Missouri Valley
with a ridge off the west coast. This will put southern Colorado
under broad northwesterly flow. Several weak disturbances in the
flow may move across the area with not much in the way of snow
except for the Central Mountains. The ECMWF on the other hand,
develops an upper low over Nevada and shifts it east across the
region. This would bring another round of moderate to heavy
snowfall to southern Colorado Monday into Wednesday with decent
accumulations possible. Forecast high temperatures favor the GFS
at this time with upper 40s to lower 50s. If the ECMWF becomes the
favorable model, it could be much colder. We will continue to
monitor the evolution of the finer details for early next week.
Mozley
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 240 PM MDT Wed Oct 23 2019
Snow will begin in the KCOS area probably between 23Z and 01Z this
evening, although there could be a mix of rain and snow, with IFR or
LIFR conditions expected this evening thru late tonight, but toward
morning improving conditions are expected, with a return to VFR
conditions by mid to late morning.
KPUB will probably see a rain and snow mix this evening, before
changing over to all snow in the mid-evening. The chances for the
heaviest snow will likely come between about 03Z and 07Z, with some
light snow continuing into early Thu morning and then conditions
will improve. IFR or LIFR conditions should be expected later this
evening and into early Thu. VFR conditions will likely return by
mid to late morning Thu. Both KCOS and KPUB will see periods of
strong east to northeast winds this evening and overnight.
It looks KALS will see gusty easterly winds move into the area early
this evening and continue into Thu morning. Chances for snow will
likely hold off until toward Thu morning, and then ceilings will
drop and so will the visibility. Chances for snow should end by
about 18Z Thu.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 10 PM this evening to 8 AM MDT
Thursday for COZ089-093.
Winter Storm Warning until noon MDT Thursday for COZ072>075-079-
080-087-088.
Winter Storm Warning until 10 AM MDT Thursday for COZ076>078-083-
085-086.
Winter Weather Advisory until 8 AM MDT Thursday for COZ058-
060>063.
Winter Weather Advisory from midnight tonight to noon MDT
Thursday for COZ065>071.
Winter Storm Warning from 10 PM this evening to noon MDT
Thursday for COZ094.
Winter Storm Warning until 8 AM MDT Thursday for COZ081-082-084.
&&
$$
UPDATE...HODANISH
SHORT TERM...PETERSEN
LONG TERM...MOZLEY
AVIATION...28