Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/16/21
Area Forecast Discussion
National Weather Service Houston/Galveston TX
648 PM CDT Thu Apr 15 2021
.AVIATION [00Z TAF Issuance]...
Thunderstorms moving across the northern flying areas this evening
producing around pea size hail. As of 2340z, radar indicate the
northern portion of the line of cells weakening as it approaches
UTS/CXO area. Further to the south, a strong storm is moving towards
the IAH flying area and is expected around 0030z. This storm has
produced pea size hail and winds around 30kts. By around 01z, the
storms will be out of the flying areas with some scatted showers
left behind through the night. Tomorrow morning, IFR to LIFR
conditions are expected to return with lower ceilings at most TAF
sites. 35
&&
.PREV DISCUSSION /Issued 345 PM CDT Thu Apr 15 2021/...
.SHORT TERM [Today Through Friday Night]...
Upper disturbance and associated shra and elevated tstms moving
across ncntl Tx. Guidance is a mixed bag in regards to precip
coverage and intensity across se Tx in the next 6-9 hours. Previous
24 hours worth of CAMs showed a fair bit of consistency with a
cluster of strong elevated tstms developing and moving into the
Brazos Valley and sinking to the southeast toward the I-10 corridor
before weakening. Some of the recent runs aren`t quite as bullish,
though some of the global models are still holding out hope for
fairly decent coverage across parts of the area (mainly north of I-
10). Developing cluster north of Marble falls (340pm) may be the one
earlier guidance was pinging on.
Overall forecast confidence isn`t particularly very high. Will
taper POPs very slightly, but mainly ride with the ongoing fcst into
the evening and monitor trends. Recent aircraft soundings in the
area show a saturated warm nose between H95-H7 so confidence is
fairly high that any convective activity sagging into the CWA will
remain mostly elevated with large hail being the primary threat into
the mid-evening hours. Coverage/intensity diminishes a few hours
after sunset.
Otherwise, llvl flow will gradually veer to the se/s going into
Friday as high pressure edges ewd. A very messy zonal pattern
continues and the expectation is that another disturbance will
move into the region during the day and generate some shra and
possibly a few tstms. Better rain chances situated north of I-10.
This impulse is fcst to move east of the area before a cold front
moves into northern parts of the area Fri evening and off the
coast before sunrise Sat. Though there will be some decent llvl
convergence associated along the boundary, the deeper moisture
axis will likely have moved out of the area w/ the passing
disturbance. Suspect we`ll just see a narrow band of shra right
along the front as it passes through. 47
.LONG TERM [Saturday Through Thursday]...
Cold air advection and lingering cloud cover will keep temperatures
over the weekend below normal with highs in the mid-to-upper 60s for
Saturday and Sunday. Rain chances persist along the coast through
Saturday night due to lingering moisture (PW values around 1") along
with favorable jet mechanics (right entrance region) that will
provide the upper-level support. With virtually no instability in
place and dry air encompassing the atmospheric profile from the
surface up to 700mb, expecting only isolated to widely scattered
rain showers for Saturday. If anything, may have been too generous
on the PoPs, but the highest probabilities will remain over the Gulf
waters. Back to the CAA, overnight lows for Saturday and Sunday will
feature temperatures that are 7-10 degrees below normal. Lows will
dip down into the upper 40s/low 50s on each of these nights. CAA
comes to an early Monday morning as surface high pressure slides off
to the east and places the region in onshore flow by Tuesday.
Resultingly, highs will be back in the upper 70s for Tuesday. Want
to briefly mention that a shortwave trough will swing through the
region on Monday night, but forecast soundings indicate a profile
that is too dry aloft to support notable precipitation reaching the
surface.
GFS/ECMWF are in agreement on a surface cold front briefly pushing
into the region on Tuesday night, which will help bring overnight
lows back into the upper 40s/low 50s. Models agree that there will
not be much moisture in place ahead of this front, but there is a
bit of disagreement on if upper-level support will be present that
could try to squeeze out some rain showers along the boundary. For
now, leaned towards keeping PoPs out for this FROPA. Speaking of
model disagreements, there isn`t a clear answer as to how long the
CAA with this front will last but it will definitely be shorter than
Friday night`s front. ECMWF/Canadian keep CAA lingering through
Wednesday evening, while the GFS ends the CAA on early Wednesday
afternoon. This makes Wednesday`s high temperature forecast tricky
since one model shows afternoon WAA while others show persisting
CAA. Surface high pressure pushes off to the east by Thursday and
with strong onshore flow likely, moisture increases quickly with PW
values reaching 1.3"-1.7" by Thursday night. A shortwave trough
swinging down into the Southern Plains along with a developing
surface low pressure in north TX will combine to develop showers and
thunderstorms in the area going into Thursday afternoon.
Batiste
.MARINE...
Moderate northeasterly to easterly winds will prevail for the Gulf
waters through the evening hours. Onshore flow returns on Friday
morning ahead of our next cold front that will push through the
coastal waters on early Saturday morning. Anticipating moderate to
strong northeasterly winds in the wake of this front that will
prevail through the weekend. Resultingly, offshore seas will elevate
to 6-7 feet by Saturday afternoon and persisting through Sunday.
Rain showers will linger along the coast and Gulf waters through
Sunday morning with dry conditions following going into early next
week. Winds will gradually transition back to easterly on Monday and
southeasterly on Tuesday as surface high pressure slides off to the
east.
Batiste
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 63 76 53 65 49 / 80 80 40 10 10
Houston (IAH) 65 75 59 68 53 / 60 60 50 20 10
Galveston (GLS) 69 77 64 70 60 / 50 30 50 30 20
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory until 7 PM CDT 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...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...UPDATED
National Weather Service Los Angeles/Oxnard CA
553 PM PDT Thu Apr 15 2021
.SYNOPSIS...15/342 AM.
A warming trend is expected today and will continue through early
next week. The marine layer will gradually shrink through the
period. Temperatures should begin to lower again by next Tuesday
and Wednesday.
&&
.SHORT TERM (TDY-SUN)...15/153 PM.
Overall, 12Z models in good synoptic agreement through the short
term period. At upper levels, weak low will gradually drop south
across the Great Basin through the weekend, keeping cyclonic flow
over the area through Saturday then northeasterly on Sunday. Near
the surface, weakening onshore flow through Saturday (with some
northerly offshore flow during the overnight hours) with the flow
turning weakly northeasterly on Sunday.
Forecast-wise, no significant changes to the previous forecast
thinking with main concerns marine layer stratus, temperatures
and offshore winds. With respect to marine layer stratus, current
AMDAR soundings indicate marine inversion settling down to a depth
of 2000-2500 feet this afternoon. So, with continued onshore flow,
will anticipate an extensive stratus deck overnight and Friday
morning, extending into the coastal valleys (although northerly
flow will keep stratus less extensive along the SBA South Coast).
For Friday night/Saturday, will expect relatively persistent
stratus development/dissipation. For Saturday night/Sunday, expect
most areas to be stratus-free as weak offshore flow develops. Only
exception may be the LA coastal plain as offshore flow will likely
be too weak to prevent some stratus development. Other than all of
this stratus. skies should remain mostly clear through the
weekend.
As for temperatures,the combination of decreasing onshore flow and
rising thicknesses/H5 heights will bring a gradual warming trend
to the area through Saturday. On Sunday, more pronounced warming
is anticipated as weak Santa Ana winds develop. Based on available
model guidance (deterministic/ensembles) and local TEMP STUDY
database, widespread upper 70s and 80s can be expected (meaning
most areas 6-12 degrees above climatic normals). There could even
be a isolated 90+ high temperature or two across the valleys.
As for winds, do not anticipate any issues with onshore winds as
onshore gradients will continue to weaken. As mentioned earlier,
there will be some increase in northerly gradients through
Saturday evening. Therefore, some locally gusty north winds can be
expected across the Santa Ynez Range (in areas such as Refugio and
Gaviota). For late Saturday night/Sunday, flow turns northeasterly
and weak Santa Ana winds are expected across the usual spots in
Ventura/LA counties. Gradients aren`t too strong and upper support
is not great, so northeasterly winds are expected to generally
remain below advisory levels (likely gusting 30-40 MPH in the
windier spots).
.LONG TERM (MON-THU)...15/153 PM.
For the extended, 12Z models have the same general synoptic idea,
but differ in details. Fortunately, the differences in details
will have limited impact on the sensible weather.
For Monday, another warm and dry day is expected. Offshore flow
will be weaker in the morning with a switch to onshore flow Monday
afternoon. So, do not anticipate any significant offshore winds in
the morning, given the weak gradients. However, it will be enough
to generate another warm and dry day. Interior sections will
actually be a couple degrees warmer. However, the coastal plain
will be several degrees cooler due to the return of onshore flow.
However all areas will still be above climatic normals.
For Tuesday through Wednesday, models keep a cyclonic flow aloft
in place over the area while onshore flow increases near the
surface. So, will expect a cooling trend for all areas with an
increase in night/morning stratus and fog.
For Thursday, onshore flow decreases a bit and thicknesses/H5
heights increase. So, expect slightly warmer temperatures and
likely a little less marine layer stratus.
&&
.AVIATION...16/0052Z.
At 2354Z at KLAX, the marine layer was 1000 feet deep. The top of
the inversion was around 2500 feet with a temperature of 12 C.
High confidence in desert TAFs. Moderate to low confidence in
remaining TAFs with limited marine layer clouds expected, and
early burn off times. The best chance for cigs will be over L.A.
County.
KLAX... Moderate confidence in the 00z TAF due to uncertainty in
timing of cigs. There will be no east wind component greater than
6 kt.
KBUR...Moderate confidence in TAF with a chance for brief cigs
from 10-15Z.
&&
.MARINE...15/116 PM.
Other than some local Small Craft Advisory (SCA) level gusts from
around the Channel Islands to San Nicolas Island this afternoon
and evening, good confidence that winds and seas will largely
remain below SCA level today. Gusty northwest winds will develop
over much of the waters by late Friday afternoon leading to likely
SCA level conditions for the waters along the Central Coast to
San Nicolas Island and into the western portion of the Santa
Barbara Channel. High confidence in SCA level conditions lasting
through Saturday. Confidence in SCA level conditions starts to
lower on Sunday as offshore flow develops over the land and upper
support is lost, but then rises again on Monday through at least
mid-week.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
.HAZARD POTENTIAL OUTLOOK (SUN-THU).
No significant hazards expected.
&&
$$
PUBLIC...Thompson
AVIATION...Phillips/Sweet
MARINE...Sweet
SYNOPSIS...Smith/Stewart
weather.gov/losangeles