Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/26/19
Area Forecast Discussion
National Weather Service Houston/Galveston TX
545 PM CST Mon Feb 25 2019
.AVIATION...
A difficult set of TAFs to write this evening considering much of
the guidance doesn`t even know what`s going on in the present.
That being said, forecast confidence is moderate with the general
trends expected but quite low on specific details/and timing.
General thinking at this point is the disturbance and associated
precip impacting the Houston and coastal terminals will slide off
the the east in the next hour or two and we get a break from the
precip for a while. The low level moisture further deepens
overnight...ceilings fall into MVFR the IFR overnight and pockets
of -ra/dz develop to the southwest and fill in across the region
toward morning. Ceilings further fall by mid morning with IFR/LIFR
condition persisting for the remainder of the day as a warm front
nudges inland. Added VCTS for inland sites during the late
morning and afternoon hours as there should be enough instability
for some iso/sct elevated storms. 47
&&
.PREV DISCUSSION... /ISSUED 410 PM CST Mon Feb 25 2019/
Key dynamical and thermodynamical ingredients came together at
the right time earlier this afternoon to produce scattered
thunderstorms from roughly south of Highway 290 and along and east
of Interstate 45. Discrete cells that produced small hail moved
quickly off to the east at around 40 mph. A jet level speed max
/northeast-exiting jet, along with a passing shortwave disturbance
embedded in the southwest flow, initialized the lift that sent
parcels into very skinny CAPE (per regional ACARS soundings). Very
low WBZ heights of under 10k ft set the stage for these quick
pulsers to quickly produce small pea to dime size hail. Subsidence
behind this wave should dry everyone out through the early
Tuesday morning hours...slight chance for showers along the coast
and points offshore through the sunrise hour. Weak onshore flow
and mostly overcast will regulate interior temperatures to the
lower to middle 50s/around 60 F at the immediate coastline come 6
or 7 AM.
High to likely rain probabilities tomorrow will arise from the
approach of an offshore warm frontal boundary. There should be
enough lift along and north of a weak nearshore coastal trough/wf
to produce periods of light morning rain further out west with a
gradual movement east and northward to the more organized rain
clusters through the remainder of the day. While likely not like
today`s behavior of more discrete fast-movers, rumbles of thunder
will occasionally be heard as there should be ample elevated
instability. Lower layer moistening not only will keep rain/storm
chances high but will also aid in the return development of sea
fog...likely beginning over the western nearshore waters tomorrow
morning and slowly forming over the Galveston Bay regional waters
by the evening. Uncertain as to the extent or intensity of this
latest round of sea fog mainly due to the wind field. Winds are
forecast to primarily be out of the south. Without an easterly
component to the winds, even middle 60 F Td air atop near 60 F SSTs
could struggle to produce and maintain dense sea fog.
A coastal southeast Texas vicinity warm front will keep slight
chance low-end QPF POPs around on Wednesday. Steering flow may
veer a bit more west of south at mid-week and this will be the
impetus to warming back into the 70s during a mostly overcast day
on Wednesday. Forecast begins to becomes much less certain from
Thursday onward as the model suite all differ on the strength and
timing of a series of late week cold fronts. The current forecast
has a weak diffuse boundary barely making its way into our CWA
Thursday with a stronger front making it to the coast Saturday
during the day. Weather conditions should remain warmer and more
humid with low (30 or below) POPS during the Thursday through
Saturday time frame. The actual bad news of all of this is in the
post-frontal early next week. Skies will partially clear in the
wake of Saturday`s frontal passage but then again become overcast
from Sunday through at least Tuesday with more persistent light
rain and drizzle (think a few days ago and this is how March will
open up). Cool northeast winds below warmer, more moist mid-level
southwesterly winds will produce overcast and wet days from
periods of light rain, showers or drizzle. This early week post-
frontal, isentropic upglide pattern will have days starting off in
the lower to middle 40s with very sluggish daytime warmth into
the low to middle 50s. Got Sun? 31
MARINE...
Winds have finally started to relax so will only maintain the SCA
for the 20-60nm waters through 6 pm with SCEC in the nearshore
waters. Scattered showers and thunderstorms over the waters this
afternoon shifting away to the east on the departing upper level
exit region. Easterly winds tonight should continue and as warm
front well out over the Gulf starts to drift back north expect the
continued moistening of the LL and increasing chance for fog/sea fog
to spread into the area Tuesday. Tuesday night through Wednesday
look foggy. Some breaks may be possible at times but overall the
pattern looks favorable for sea fog Wednesday through the cold
frontal passage on Saturday. SCA conditions a high likelihood in the
wake of the cold front with northerly winds of 15 to 25 knots.
Elevated tide levels Tuesday afternoon through Friday night as well.
45
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 52 64 57 74 60 / 30 50 30 20 20
Houston (IAH) 54 65 60 76 62 / 40 50 30 20 20
Galveston (GLS) 60 67 61 71 63 / 40 40 20 20 20
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 9 PM CST this evening
for the following zones: Coastal waters from Freeport to
Matagorda Ship Channel TX out 20 NM...Coastal waters from
High Island to Freeport TX out 20 NM.
Small Craft Advisory until 6 PM CST this evening for the
following zones: Waters from Freeport to Matagorda Ship
Channel TX from 20 to 60 NM...Waters from High Island to
Freeport TX from 20 to 60 NM.
SMALL CRAFT SHOULD EXERCISE CAUTION until 9 PM CST this evening
for the following zones: Waters from Freeport to Matagorda
Ship Channel TX from 20 to 60 NM...Waters from High Island
to Freeport TX from 20 to 60 NM.
&&
$$
Area Forecast Discussion
National Weather Service Lake Charles LA
941 PM CST Mon Feb 25 2019
.UPDATE...
As mentioned in earlier AFDs, the coverage of precipitation has
remained more widespread than originally anticipated due to a weak
mid-level disturbance moving across the region. This disturbance
and the upper level divergence which supported the precipitation
are moving to the east and northeast and the precipitation has
become more showery in nature to the west.
While a brief lull in the precipitation will likely occur over
western portions of the CWA through 06Z, moist isentropic ascent
is expected to increase later tonight resulting in the
redevelopment of showers. This will result in showers redeveloping
after midnight. Subjectively, the 12Z HREF and 18Z nested NAM
have had the best handle on the precipitation thus far and were
blended into the official forecast. This resulted in overnight
PoPs increasing slightly from the previous forecast.
The rest of the forecast remains representative with no changes
needed at this time.
&&
.PREV DISCUSSION... /issued 614 PM CST Mon Feb 25 2019/
AVIATION...
Showers and isolated thunderstorms dominate the wx this eve as a
shrtwv ripples ovr the rgn this eve pulling mstr up and ovr the
stalled frntl bndry in the gulf. Cld deck running about around 040
to 080 w/ sctd deck noted around 026 this eve. The sys is xpcd to
exit before midnight only to be replace. Cld deck xpcd to drop
twrds sr down along the coast to around 025 while inld ceilings
hold around 050 thru sr. Rains to lwr vsby somewhat for aircraft
operations to greater than 5sm.
PREV DISCUSSION... /issued 335 PM CST Mon Feb 25 2019/
DISCUSSION...
Somewhat surprisingly, widespread light rainfall with embedded
heavier precipitation has developed across the region this
afternoon in response to a poorly identified mid level
disturbance. We have received several reports of small hail across
parts of southeast Texas within discreet stronger storms.
Fortunately, all of the hail has, to our knowledge, remained below
severe criteria with the largest report being three quarters of
an inch.
Expecting a brief window of weakening/dissipating storms late this
afternoon into early this evening ahead of the next upper level
disturbance progged to move across the area later tonight.
Precipitation coverage is expected to begin increasing once again
late this evening and especially after midnight with widespread
showers and more isolated thunderstorms expected through the day,
Tuesday. SPC continues to highlight the region in a marginal risk
for severe weather with the primary threat being large hail. Given
the relatively modest environment in which hail was observed
today, this certainly seems plausible.
While there is relatively poor agreement amongst most guidance in
the medium to long range with regards to the exact evolution of
precipitation, there is higher confidence in the overall pattern
of a deep layer of moisture sitting over the region through the
week being lifted by a series of upper level disturbances each
day. The forecast is generally a blend of the most reliable
guidance which results in scattered to numerous PoPs each day
through the end of the week.
The GFS, Euro and Canadian all show the next frontal boundary
moving through the area sometime on Friday although there is
considerable divergence on strength and speed. All show a quick
rebound of the gulf airmass and precipitation by next Sunday.
MARINE...
Moderate easterly to east southeasterly winds and elevated seas
are expected to continue through the evening with winds and seas
gradually subsiding tonight into Tuesday. Showers and isolated
thunderstorms are expected to continue through the overnight
hours, increasing in coverage after midnight. Several additional
rounds of precipitation will develop across the area through the
remainder of the week as a series of upper level disturbances
move across the region. Areas of dense fog will be possible
across the nearshore waters and inland lakes and bays Tuesday
night through Friday with patchy fog possible across the outer
coastal waters.
&&
.PRELIMINARY POINT TEMPS/POPS...
AEX 47 63 52 71 / 30 50 50 50
LCH 51 66 59 73 / 50 70 60 50
LFT 52 67 58 75 / 60 70 70 60
BPT 53 66 59 73 / 60 70 60 40
&&
.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...Small Craft Exercise Caution until midnight CST tonight for
GMZ450-452-455-470-472-475.
&&
$$
PUBLIC...26
Area Forecast Discussion
National Weather Service Reno NV
250 PM PST Mon Feb 25 2019
.SYNOPSIS...
A major Pacific storm system will be on-going through Thursday
morning. Heavy mountain snow and valley rain spreads south while
strong winds persist east of the Sierra. After a brief break
late Thursday into Friday, another storm system brings more rain
and mountain snow next weekend.
&&
.SHORT TERM...
* Changes were generally minor, but some details are becoming
clearer as a strong winter storm lingers in the Sierra through
at least early Thursday. The main trends for this forecast cycle
were to shift the heaviest QPF and storm-focus slightly
northward while increasing winds Tuesday and Wednesday as waves
move through the region. However, the story remains generally
unchanged with multiple feet of wet snow forecast for the Sierra
and ample wind with brief spillover for western Nevada.
* Impacts will increase over the duration of this storm as heavy,
wet snow accumulates in the Sierra and as Winds remain gusty -
both are cumulative in terms of mounting damage as duration
increases. There have been reports already of high profile
vehicles being blown over in more wind prone locations where
sensors report gusts in the 70-85 mph range. As snow continues
to fall in the Sierra, loading on structures will increase while
trafficability will greatly decrease. Couple snowfall with wind,
and periods of white-out conditions are a threat with road
closures possible; unstable slope conditions will also be a
result and avalanche activity could increase.
The initial wave has moved into the Sierra earlier this
afternoon. Current radar imagery shows a wide swath of moisture
extending from around Alpine County northward through the northern
reaches of Lassen County. There is an obvious core of heavy
precipitation directed towards the Lassen/Plumas County border at
this time of this writing. Expect this core to shift slightly
southward through the evening and overnight hours bringing a
period of heavier snowfall with rates possibly exceeding 3 inches
per hour.
Meanwhile, downsloping conditions are prevalent to the
lee of the Sierra with pronounced drying with strong wind gusts
across much of the Sierra Front into the Basin and Range. There
have been many reports of Low Level Wind Shear(LLWS), severe
turbulence, and surface wind gusts over 60 mph. Unsurprisingly,
the strongest winds have occurred along the foothills and in wind-
prone locations like Washoe Valley, Hwy 395 from the North Valleys
to Janesville, and along Hwy 95 in the vicinity of Walker Lake.
While these conditions will continue to a varying degree through
early Thursday, there are a few details to note.
* Winds will slow a little late tonight into early Tuesday, but
remain gusty in the 40-50 mph range for the Sierra Front.
However, a frontal boundary will increase winds again as it
pushes through the region. There will be a period of spill-over
where heavier rainfall will be possible for western Nevada as
the front moves through as well. This pattern will repeat
Wednesday as another wave moves through.
* Snow levels will remain 5-6000 feet, but are expected to rise
during the day on Wednesday with levels peaking in the
6000-7000 ft range bringing a period of rain to locations in
the Tahoe Basin and around Truckee. Local areas of flooding are
possible if and when this occurs from blocked storm drains.
Bottom line: Hazardous travel conditions will continue in the
Sierra through at least Thursday morning due to heavy snow and
strong winds. Into western Nevada, periods of strong winds and
moderate rain will continue, but with lighter amounts. Generally
up to 1 inch of rain with 2-4 inches in the foothills. Virginia
City will be an exception as it will remain above the snow level
for most of the storm and several inches are possible. -Boyd/X
.LONG TERM...Friday and beyond...
We are on track to see yet a couple more systems this weekend going
into next week and it should be noted that the forecast is subject
to changes due to timing and track of these storms.
Friday will be a quiet day with light winds and minimal chances for
precipitation. A few models indicate a weak disturbance passing
across northern CA and northern NV. So we maintained a slight chance
of light snow for western Lassen County up into the Surprise Valley.
Any snowfall would be very light.
For this weekend, the next system is forecast to move onshore and
then across CA-NV. Some timing issues have crept into the
deterministic model runs from the ensemble suite with the 12Z ECMWF
faster. We maintained overall high pops both Saturday-Sunday before
tapering them Sunday night. But Sunday could be drier if the faster
scenario plays out.
There is a good moisture tap as this system arrives, its trajectory
is farther south than the current storm. This would favor the
southern Sierra, especially Alpine County south to Mammoth and
beyond. Being on the north side of the main jet, the frontal
boundary will be draped across the area with temperatures and snow
levels colder from about I-80 north and warmer to the south. The
current forecast has them ranging from 4500-5500 feet across
northeast CA and northwest NV to 6000-7000 feet farther south. Some
decent snow could fall down to valley floors north of Susanville to
Gerlach as well as along the Sierra above 7000 feet. Current
projections (subject to change) range from up to 6 inches north of
Susanville to Gerlach and upwards to 3 feet or more for the high
Sierra. For the Lake Tahoe Basin and Sierra below 7000 feet as well
as the foothills of the Sierra Front, snow amounts will be trickier
due to the eventual snow level. Current forecast shows 6 to 12
inches, but this could be bit more or less. Also, there is a chance
that the cold front could slide farther south in some of the colder
scenarios which could bring snow even to lower elevations along the
I-80 corridor including Reno-Carson City. The good news with this
one will be less wind. Ridges will still see gusty winds, but it
will mainly be breezy for a lot of locales.
After gusty northwest winds and brisk conditions on the back side of
the weekend storm (either Sunday or Monday), we will see a brief
break. The AR tools indicate another wave moving into the region for
Tue-Thu of next week with the potential for more rain/snow.
Confidence is too low to project on details at this time with the
track and speed varying considerably. Hohmann
&&
.AVIATION...
...LLWS, rotors and strong winds will create dangerous travel for
aviators through this evening...
Strong winds will continue with the peak winds through mid evening.
Widespread south-southwest winds 20-35 kts and gusts to 40-45 kts
are expected along the eastern Sierra, even as far south as KMMH.
LLWS and rotors will result in moderate to occasionally severe
turbulence and sounding profiles indicate a window between now and
03Z Tue where winds 19040G55KT may occur at times. Aircraft
soundings near KRNO have showed a backing wind to about 160 degree
and 10-15 kts around 1500-2000 ft AGL today and pilot reports have
indicated LLWS as low as 400-900 ft AGL.
As moisture and precipitation increase tonight through Wednesday,
the more extreme wind threat will decrease although gradients and
winds aloft are still going to be quite strong. So widespread
turbulence is likely to persist across the region. In fact there
could be a period Tuesday morning between the individual waves where
winds and LLWS could see another peak along the eastern Sierra as
precipitation lightens a bit in the Sierra ahead of the next wave.
As far as snowfall, periods of light to moderate snow accumulations
can be expected for the Sierra terminals through Wednesday
night/Thursday morning with CIGS/VSBYS varying between IFR-MVFR most
of the time. Lower elevations terminals will see no accumulation and
CIGS may briefly lower enough to obscure ridges outside the Sierra.
Hohmann
&&
.HYDROLOGY...
Impacts to rivers and streams are generally expected to be less
than the 2/13 - 2/14/19 event. This is due mostly to somewhat
lower rain/snow elevations and greater shadowing along the Sierra
Front. Periods of higher rain/snow elevations may cause minor
road and urban flooding in mountain communities, especially
around Tahoe and Truckee where deep snow will channel runoff.
Flows on the Pit River and Middle Fork of the Feather are both
expected to reach monitor stage, but no flooding is expected. The
Truckee River will be running high, but well below flood stages,
due to a combination of increased runoff and elevated released
from Lake Tahoe. Rises are also expected in lower elevation rivers
and streams as well as terminal lakes, with some minor flooding
in poor drainage areas.
&&
.REV Watches/Warnings/Advisories...
NV...High Wind Warning until 10 PM PST this evening NVZ003.
Winter Weather Advisory from 10 PM this evening to 4 PM PST
Tuesday NVZ005.
Wind Advisory until 10 PM PST this evening NVZ005.
Winter Storm Warning until 4 AM PST Thursday NVZ002.
Wind Advisory until 10 PM PST this evening NVZ001.
Lake Wind Advisory until 10 PM PST this evening for Pyramid Lake
in NVZ004.
CA...High Wind Warning until 10 PM PST this evening CAZ071.
Winter Storm Warning until 4 AM PST Thursday above 4500 feet in
CAZ071.
Winter Weather Advisory from 10 PM this evening to 4 PM PST
Tuesday CAZ070.
Wind Advisory until 10 PM PST this evening CAZ070.
High Wind Warning until 10 PM PST this evening CAZ073.
Winter Weather Advisory from 10 PM this evening to 4 AM PST
Thursday CAZ073.
Winter Storm Warning until 4 AM PST Thursday CAZ072.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno