Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/30/21
Area Forecast Discussion
National Weather Service Denver/Boulder CO
841 PM MDT Sat May 29 2021
.UPDATE...
Issued at 828 PM MDT Sat May 29 2021
Scattered showers and thunderstorms will continue this evening
across the county warning area, especially across Douglas and
Elbert counties. The severe threat has diminished but could still
see some brief heavy rain and small hail with the stronger storms
across the Palmer Divide where the best instability still resides.
Elsewhere, mainly scattered light rain showers over the mountains
and locations further north towards the Wyoming border. Northern
Colorado will remain under weak synoptic scale ascent for the rest
of tonight with continued showers. Have lowered rain chances over
the I-25 corridor this evening with more stability in place.
Upslope flow will deepen a bit overnight with some increase in low
level moisture. Could see some light rain showers/drizzle as well
especially later tonight. Best chances of widespread showers will
delay until Sunday afternoon as upslope continues to deepen and
strengthen.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 324 PM MDT Sat May 29 2021
Only a couple of storms have managed to develop this afternoon,
with a cluster near the Douglas/Elbert county line along with a
single cell in far northern Weld county. The rest of the urban
corridor has actually seen some decent clearing outside the few
convective cells, though temperatures are generally still in the
low to mid 60s. Day cloud phase also shows an area of low stratus
over our far northeast, stretching from Limon and into
Julesburg/Holyoke. Underneath this cloud deck, temperatures have
remained near or below 60. Over the higher terrain, generally
light rain showers have been noted, with only a few of these
producing any lightning activity. One recent cell has produced
some heavy rain over the Cameron Peak burn area, while most of the
higher terrain has been quiet.
A recent ACARS sounding from KDEN and a special sounding released
by CSU illustrate why convection has struggled over the plains
thus far... with a robust capping layer evident near 750-700mb. It
will be difficult to get widespread surface-based convection to
develop over the urban corridor this afternoon unless strong
surface heating can occur in the next couple of hours. The HRRR
and a few other CAMs try to warm us up to near 70F in the next few
hours, with another round of stronger convection moving off the
southern Foothills, but it`s worth noting that high-resolution
guidance has struggled with the overall convective evolution so
far. This makes the forecast for the next several hours pretty
uncertain. Given the clear skies over the southwestern metro into
portions of the southern Foothills, this would probably be the
most likely area to see stronger storms initiating again sometime
in the next few hours, with continued scattered showers and weak
storms for most of other higher terrain.
We should see showers persist through most of the overnight hours
as weak upslope flow deepens a bit across the area. Models do
show a skinny CAPE profile overnight so even a few rumbles of
thunder will be possible as we head towards daybreak. With the
light/moist upslope flow there could be some patchy fog across the
area near daybreak, which has been added into the grids. Tomorrow
morning should see precipitation blossom yet again with continued
upslope flow. Confidence is low on how this precip sets up. It`s
difficult to say what exactly the models are keying into, as
there`s not a whole lot of synoptic scale lift around.
Nonetheless, the good agreement in ensemble guidance is hard to
ignore and we expect widespread light to moderate rainfall for
much of the day. It wouldn`t be surprising to see daytime rainfall
amounts near an inch in some spots. Showers will continue into
the evening hours and overnight. Details on the rest of the rain
below.
.LONG TERM...(Sunday night through Saturday)
Issued at 324 PM MDT Sat May 29 2021
The models continue to gradually slow the departure of the trough
and the steady rain. Most solutions keep at least a little rain on
the plains into Monday. While the forcing for the heavier rain is
probably past, there`s no drying yet and weak upslope winds
continue. This means we`ll stay cool as well. Monday may be a
transition day with a little drying for areas west of the Front
Range, but for the east side it`s just less rain. We`ll slow the
whole thing down another 6 hours and drop temperatures Monday by a
couple of degrees.
After that, the trend is toward a little sharper transition from
trough to ridge. This means there`s some drying but still enough
moisture for scattered mainly diurnally/terrain driven storms on
Tuesday, then quicker and stronger warming Wednesday into
Thursday. These days look relatively dry, but with the surface
moist and some southerly low level flow on the plains there will
probably still be low grade convection. It may well stay warm and
dry into next weekend, but there are some differences with a weak
short wave that pushes a weak boundary southward at least into
Wyoming. If it comes further south it could set up some increase
in storms and a little cooling for Friday and Saturday. For now
our model blend looks appropriate, which is still warm with a
little below average thunderstorm activity for early June.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 828 PM MDT Sat May 29 2021
MVFR ceilings have developed over DEN/APA in the past hour with
continued shallow northeast flow. Isolated showers/TS also
developing near APA and will include until 05z. Expect mainly
isolated/scattered coverage of showers overnight with expected
lowering ceilings later tonight. Best chance of widespread
showers will be Sunday afternoon through Monday.
&&
.HYDROLOGY...
Issued at 324 PM MDT Sat May 29 2021
Flooding threat will continue through the rest of today. A few
heavier showers and storms have started to re-develop this
afternoon, which could pose a brief flash flooding risk over the
burn areas. A more widespread rainfall event is expected early
tomorrow morning through much of the day. Precipitation rates will
likely be light to moderate, leading to a low flash flooding
risk. Rainfall totals through tomorrow evening will be close to an
inch, which will fall over a 6 to 12 hour period.
Rain will likely continue over the east slopes of the Front Range
Sunday night and Monday but the intensity should be less. On the
west side of the Front Range there may still be some thunderstorms
on Monday afternoon, but again the intensity is expected to be
less. The threat of flooding should be low during this time,
although if there are issues on larger streams from Sunday`s rains
the additional rain would prolong the problems. Lighter rain is
expected on the plains and flooding is not expected.
From Tuesday on through the week a low level of thunderstorm
activity is expected over the mountains, and storms should be
moving faster. The threat of flooding will be low.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Entrekin
SHORT TERM...Hiris
LONG TERM...Gimmestad
AVIATION...Entrekin
HYDROLOGY...Gimmestad/Hiris
Area Forecast Discussion
National Weather Service Houston/Galveston TX
646 PM CDT Sat May 29 2021
.AVIATION [00Z TAF Issuance]...
There is still an outside chance of a stray shower or even a weak
thunderstorm in the next hour or two, but trends strongly favor
sky becoming mostly clear as the sun goes down, with all
convection staying well east. Expect winds to become
light/variable with some high MVFR clouds, and even a brief CIG
expected around dawn. After that, we should see another fair
weather day in VFR with winds roughly easterly to around 10 knots.
&&
.PREV DISCUSSION /Issued 322 PM CDT Sat May 29 2021/...
.DISCUSSION...
.NEAR TERM [Tonight Through Sunday Night]...
With skies clearing faster than anticipated, temperatures are
climbing into the mid-to-upper 80s with fair weather cumulus clouds
starting to fill in across Southeast Texas. Therefore, we can expect
pulse-like thunderstorms this afternoon that will dissipate shortly
after sunset. Short-term models have not been initializing well and
so far seem to be too aggressive regarding storm development this
afternoon. Local AMDAR soundings show little to no convective
inhibition overhead, but low-level dry air and ample mid-to-upper
level dry air should be enough to suppress severe convection and
once again, limit convection to more pulse-like afternoon
thunderstorms. However, with activity definitely picking up across
western Louisiana for our neighbors in Lake Charles, any type of
outflow boundary pushing west into our CWA or westward propagation
of their storms might be enough to kick up some stronger storms,
primarily east of I-45.
Tonight, both global and hi-res models are indicating some onshore
showers overnight and into tomorrow morning. However, forecast
soundings still look dry, CIN looks strong with a nocturnal
inversion, and CAPE dwindles, so not placing too much confidence
again with how hi-res models are treating precipitation. At most,
shallow onshore showers might push onto the coast and into our
southern counties. As the day progresses tomorrow and into the
afternoon, daytime heating, onshore flow, along with decent low-
level warm air/moisture advection to our southwestern counties will
help initiate showers and thunderstorms once again. However,
favorable ingredients are primarily west of I-45 in our southwestern
counties. By tomorrow night, cooling temps and a nocturnal inversion
will inhibit convection, leaving tomorrow night relatively dry.
Areas to the east of I-45 tomorrow will see easterly winds, partly
cloudy skies, highs in the low-to-mid 80s, and dewpoints in a
reasonably pleasant mid-60s. Areas to the west of I-45 will have
southeast winds, mostly cloudy skies, and warmer temps in the mid-
80s due to this warm, Gulf moisture pushing inland. KBL
.LONG TERM [Monday Through Saturday]...
Expecting a warm...humid period with persistent onshore flow. At
upper levels a longwave trough sets up over the West...and an
upper ridge over the Southeastern U.S...with shortwave
disturbances lifting NEWD across TX in SW flow in between.
Given this pattern rain chance forecast over SE Texas a little
tricky but would appear higher chances of thunderstorms should be
over NW counties...more in the path of these periodic
shortwaves...and with less limiting influence of the SE ridge
with its associated weak convective inhibition. Will really
depend on the details of the flow pattern and positioning of
these large scale features how much and how widespread the
thunderstorms are. For now...followed the National Blend of Models
for rain chances pretty closely which favor more higher chances
over NW counties especially as we get to Tuesday and beyond. Think
at least isolated diurnal activity still a good bet for coastal
counties as well...just more of a question whether will be any
more than that. Should upper ridge build in from the SE more than
expected...would imply a drier scenario especially for coastal
counties. Should the SE ridge be weaker and the upper trough a
little farther east...would be a wetter scenario. Uncertainly
above average.
DHR
.MARINE...
With high pressure in place over the Eastern U.S. and a cold front
positioned over West and Central TX...expect persistent E to SE
flow through the period in between these features. Wind speeds and
seas will fluctuate with the pressure gradient between these two
features. Looks like onshore flow will increase through midweek
then decrease slightly as ridge builds some from the east and the
gradient slackens. There will be chance of thunderstorms but more
isolated to scattered than we`ve seen over the past week.
DHR
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 69 87 68 85 69 / 20 20 0 20 10
Houston (IAH) 69 86 69 86 70 / 20 10 10 10 10
Galveston (GLS) 74 83 75 83 77 / 20 20 0 0 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
DISCUSSION...DHR
SHORT TERM...KBL
LONG TERM...DHR
AVIATION...Luchs
MARINE...DHR