May 2017: Memorial Day/End Of May Outlook

General Weather Discussions and Analysis

Re: May 2017: Quiet WX Pattern Continues For Now

Postby tireman4 » Mon May 15, 2017 12:43 pm

000
FXUS64 KHGX 151731
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1231 PM CDT Mon May 15 2017

.AVIATION...
Not a lot of changes from previous TAF forecast thinking that the
intrusion of BKN/OVC mid/high clouds from the west overnight will
help temper the development of patchy fog through early Tues morn-
ing. Otherwise the quiet weather pattern will remain in place and
VFR conditions will prevail. 41

&&

.PREV DISCUSSION... /ISSUED 1037 AM CDT Mon May 15 2017/

Today is shaping up to be another quiet day weather-wise with
temperatures in the upper 70s and dewpoints in the low/mid 60s.
Moisture should only increase with southerly winds today. Upper
level ridge over much of Texas should suppress convection over the
area so only expecting flat cumulus development today. High
temperatures should reach the mid/upper 80s again and look for a
repeat tomorrow.

Afternoon forecast update will take a look at rain chances
Wednesday through the weekend. Only changes to the forecast for
this morning are to ongoing temperature, dewpoint and sky trends.

Overpeck

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 88 67 89 71 84 / 0 0 10 20 40
Houston (IAH) 87 68 87 73 85 / 0 0 10 10 40
Galveston (GLS) 81 74 83 77 83 / 0 0 10 10 20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$
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Re: May 2017: Quiet WX Pattern Continues For Now

Postby DoctorMu » Mon May 15, 2017 2:51 pm

The GFS has changes its tune a bit and has a more dynamic weather pattern by the end of the month, including a couple of cold fronts. Trough sets up in the west with the block to our east. While the greatest chance of pricip in the next 2 weeks is allegedly in the NW HGX area, the outlook is more hopeful than yesterday. Wednesday and Sunday appear to have the best chance of rain this week.
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Re: May 2017: Quiet WX Pattern Continues For Now

Postby Katdaddy » Tue May 16, 2017 5:39 am

GOM moisture inflow will continue to increase across SE TX through the rest of the week with some scattered thunderstorms possible tomorrow and Thursday across portions of SE TX. The upcoming weekend is looking more unsettled but will be mesoscale driven.
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Re: May 2017: Quiet WX Pattern Continues For Now

Postby srainhoutx » Tue May 16, 2017 7:04 am

Best chance of showers and storms looks to be along and West of the I-35 Corridor into the weekend where there are several days of severe storm chances before the frontal boundary slowly sags SE into Central Texas. I still believe it is too soon to know with any certainty where the greatest chance of rainfall will occur regarding our sensible weather in SE Texas other than the College Station to Lake Livingston areas which have been the lucky locations the past several events. I will wait until Friday before believing any of the models predicting heavy rainfall across Metro Houston to the Coast... ;)

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Re: May 2017: Quiet WX Pattern Continues For Now

Postby srainhoutx » Tue May 16, 2017 11:36 am

Tuesday midday weather briefing from Jeff:

Upper air pattern continues to transition toward one of a much more active period of weather coming to TX compared to the recent week.

First upper level trough will eject into the plains today and Wednesday only to be replaced with a secondary upper trough over the SW US by this weekend. While the air mass is certainly moistening over the area, it is capped off to deep convection via a warm layer of air in the mid levels. A surge of deeper moisture on Wednesday may help to promote a few showers under the capping inversion along with the arrival of an outflow boundary from today’s dryline convection over W TX. Meso models general show the arrival of the west TX convective line into the western counties of SE TX early Wednesday before forcing weakens and the line generally collapses.

Calm weather on Thursday and Friday although dryline storms will likely erupt each afternoon and will have to at least watch for any potential for any sort of thunderstorm complex to approach from the W/NW during this period.

Weekend-Early Next Week:

Main attention is starting to focus on this time period as the secondary very slow moving upper level trough lifts into TX allowing a surface frontal boundary to slowly advance into the region. Surface front will act as a trigger for deep convection as early as Saturday, but more likely on Sunday. Mesoscale processes will likely begin to take over and drive convective events during this period as outflow boundaries override the frontal boundary. Air mass will remain very moist (PWS of 1.8-2.0 inches) and unstable throughout the entire period which will support numerous thunderstorms. Heavy rainfall signal continues to show up in model forecast and confidence is starting to grow given the increasingly favorable setup that flash flooding could be possible. Combination of a surface boundary nearly parallel to the upper level SW flow aloft, deep tropical moisture in place, and an upper level storm system nearly stalled just to our west allowing good upper level divergence are some classic heavy rainfall parameters for this area. Would like to see a stronger 850mb transport flow off the Gulf and if then begins to show up in the model guidance this would suggest an even stronger flash flood signal. Concern would be some sort of slow moving thunderstorm complex either Saturday night or Sunday night perpendicular to the 850mb low level jet.

Severe threat also looks possible this weekend with good instability in place. Main threat would likely be large hail and wind damage given the potential for lines of storms versus tornadic supercells.

Forecast into early next week is of low confidence as models attempt to resolve the meso scale influences over the local area. Looks like another surface boundary may approach the area sometime around Tuesday which would only serve promote additional thunderstorms.
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Re: May 2017: Quiet WX Pattern Continues For Now

Postby jasons » Tue May 16, 2017 12:23 pm

From the NWS:

May has been relatively cool when compared to the past couple of months with the average monthly temperature (through the 14th) about 2 degrees cooler than normal. 10 out of the first 15 days of the month have been cooler than normal.

However, the year to date average temperatures are still the warmest on record for all four first order climate sites.
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Re: May 2017: Quiet WX Pattern Continues For Now

Postby Katdaddy » Wed May 17, 2017 6:01 am

Partly sunny skies and breezy across SE TX today. A weakening line of scattered showers and thunderstorms across Central TX will continue to fall apart as they approach NW portions of SE TX this morning. Thunderstorm chances will increase through the weekend with a potential for heavy rainfall.

The big weather story will be the continued severe weather across the Plains through the rest of the week. 27 tornadoes reported yesterday across the Plain with loss of life in WI and significant damage in Elk City, OK The SPC has another Moderate Risk area tomorrow across NW OK and SW KS. If you have friends and family in that area; make sure the are weather aware.
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Re: May 2017: Quiet WX Pattern Continues For Now

Postby jasons » Wed May 17, 2017 7:26 am

Rain chances for today went poof!
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Re: May 2017: Quiet WX Pattern Continues For Now

Postby DoctorMu » Wed May 17, 2017 10:24 am

jasons wrote:Rain chances for today went poof!



Looks like another bust here as well with the dryline. NW Harris Co could see a few midday showers. Maybe some daytime heating shower tomorrow for CLL.
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Re: May 2017: Quiet WX Pattern Continues For Now

Postby tireman4 » Wed May 17, 2017 10:25 am

000
FXUS64 KHGX 171444
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
944 AM CDT Wed May 17 2017

.UPDATE...
Morning soundings from the neighbors showed fairly dry atmosphere
above a pretty stout cap this morning. This can also be easily
inferred from the appearance of radar, where most rain approaching
Southeast Texas is fizzling before moving into our area of
responsibility. CRP`s sounding looked a bit more saturated, so
that showers are better holding together to our west is not a big
surprise.

Have reconfigured PoPs to match these trends a little better for
today and tonight. Best chance for some showers going forward will
be along our western boundary where the environment is a little
more supportive. Also tweaked temps to match obs, but changes here
were not very substantial. Changes to winds include keeping winds
up a little more over the water and immediate coast, which
necessitated a longer small craft advisory. However, winds are low
enough on the coast that the wind advisory was able to expire.

Luchs


&&


.PREV DISCUSSION... /ISSUED 458 AM CDT Wed May 17 2017/

DISCUSSION...
A very tight onshore pressure gradient between the Bermuda
Subtropical High and a deepening low (trough/cold front) over the
western South Plains states has created an overnight moderate to
strong surface wind field. Strongest winds are closer to the coast
where a Wind Advisory will be in effect through 8 AM this morning.
Convection that fired along the west Texas dry line yesterday is
falling apart as it runs into a more dry and capped downstream
environment over Central Texas. There are slight to low chances
that some discrete cells from this activity nearing I-35 this hour
may hold together and enter our warming and becoming increasingly
unstable northwestern forecast area during the morning daytime
hours. Another element to consider will be jet placement as the
southern branch comes right across the state this afternoon...possibly
overlaying more favorable diffluence over the region during peak
heating. Today`s maximum temperatures should achieve the mid to
upper 80s once again...with overnight overcast and a well-mixed
near surface layer keeping regional minimum temperatures in the 70s.

The northeastern ejection of this morning`s Desert SW upper trough
will allow a secondary upper low moving south out of the northern
Rockies to fall into its wake Thursday. This upper low will meander
over the Rockies through Saturday before exiting north into the
Great Northern Plains states. As this occurs...a weak cold front
will slowly travel across the state this weekend. A general unsettled
pattern will evolve through the weekend...with a modest chance of
more widespread rain occurring from late Saturday through as late
as Monday. Not particularly confident on the `where` and `why` as
of this morning...but precipitation forming along or just ahead
of a Central Texas frontal boundary/low level area of convergence
will slowly advance into our area going into Sunday. Overall
moisture should not be a problem with progged greater than 1.5 inch
pwats within an unstable downstream air mass. If the aforementioned
boundary does sag into the region Sunday...there should be enough
focus within a modeled weakly-sheared regional atmosphere with 5.5
to 7 C/km lapse rates (near 2.5k J/kg CAPE) leading to -7 to
-9 lifted indices and lower 30 K indices. Inverted V soundings
indicate that the strongest storms may put down some decent wind
but slow clustering cell movement depict the highest threat being
that of high rainfall leading to early week flooding concerns.

Late period general troughiness over the Southern Plains (ridging
remains over Mexico) signals that unsettled weather will likely
linger on into mid-week. Shortwave disturbances rotating around
the base of the trough Tuesday and Wednesday keep POPS in the low
category range. A more wet and overcast pattern from Sunday onward
into late May will shave a few degrees off daily maxT readings...closer
to the middle 80s...with downward trending minTs eventually falling
back into the interior 60s after several days in the lower to
middle 70s. 31

MARINE...
Localized tight pressure gradient is allowing for some strong
onshore winds this morning, with gusts to close to gale force at
times. These should slightly diminish later this morning, but in the
meantime small craft advisories will remain in effect. In addition,
we plan on issuing a beach hazards statement for strong rip currents
& elevated tide & surf thru the early afternoon hours. Tide levels
are running 1 ft above normal. With high tide at 1018am along the
Galveston beachfront, we may see water get right to the HWY 87/124
intersection with the assistance of wave runup. But not expecting
substantial problems elsewhere. The remainder of the fcst looks
about the same w/ moderate onshore winds & elevated seas continuing
into Sat. May see a combo of caution/advisory flags between now and
then. A weak frontal boundary will approach the coast late Sunday,
but it`s unclear if or how far offshore it`ll push just yet. 47

AVIATION...
MVFR cigs have settled in across the region. These should lift back
above 3000ft by lunchtime. Remnants of the precip currently to our
nw will be making its way into se tx 13-16z, but should be weakening
as it does so. There`s a pretty good chance it dissipates before making
it into the Houston terminals. There may be some lingering spotty shra
around into the aftn hours. Otherwise, expect a transition back to
MVFR ceilings later this evening. 47

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 85 73 90 73 90 / 20 10 20 20 20
Houston (IAH) 85 74 88 74 88 / 10 10 10 10 20
Galveston (GLS) 82 77 85 78 85 / 10 10 10 10 10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 6 PM CDT this evening
for the following zones: Galveston Bay...Matagorda Bay.

Small Craft Advisory until 4 AM CDT Thursday for the following
zones: Coastal waters from Freeport to the Matagorda Ship
Channel out 20 NM...Coastal waters from High Island to
Freeport out 20 NM...Waters from Freeport to the Matagorda
Ship Channel from 20 to 60 NM...Waters from High Island to
Freeport from 20 to 60 NM.

&&

$$

Discussion...25
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