Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 311717
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1217 PM CDT Sun May 31 2020

.AVIATION...
Fcst soundings show convective temperatures between 82-85 degrees
today and this threshold will be met shortly so would expect an
increase in showers and thunderstorms this afternoon. Some of the
rain could be briefly heavy as PW values are near 2.00 inches.
Ceilings are expected to remain VFR for the most part with a brief
dip to MVFR in heavier showers. Upper level ridging will build
into the area from the east on Monday so would expect the higher
rain chances to be over the western half of SE TX. That said,
convective temps on Monday will again be in the lower 80`s so will
keep VCSH/VCTS in area TAFs. Cigs are expected to remain VFR. 43

&&

PREV DISCUSSION /Issued 446 AM CDT Sun May 31 2020/...

SHORT TERM [Through Monday]...

Water vapor imagery this morning shows a large upper-level low
spinning across northern Mexico ushering in a moist southerly flow
into SE Texas. A short wave moving around this upper level
disturbance will help to trigger scattered strong thunderstorms
across the southwestern portion of the CWA through the day today.
Jackson, Matagorda, and Wharton counties high the highest chance of
experiencing stronger thunderstorms from around noon through sunset
as that disturbance moves through the area. PWATs increasing to near
2 inches will mean that the thunderstorms that do form will have the
potential to produce locally heavy rainfall. The high pressure that
has been sitting over northern Texas the past few days has retreated
northwards. This will allow for higher PWATs to make their way
northward, so isolated showers are possible this afternoon up
through Harris County. A lull in the shower activity is expected
after sunset this evening, but return on Monday thanks to daytime
heating and continuing high PWATs. Although coverage and intensity
of Monday`s storms will be less than today due to less favorable
upper level support.

High temperatures today and Monday will be in the mid to upper 80s
north of I-10 and in the low 80s south of I-10 due to increased
cloud cover. Low temperature tonight will be in the low 70s across
most of the area, and in the mid to upper 70s along the coast.

Fowler

LONG TERM [Monday night through Sunday]...

Upper ridging will dominant early June`s weather pattern by
providing the subsidence needed in keeping this period`s
areal precipitation chances low and temperatures trending above
normal.

While rain chances will be low, most everyone will pick up
measurable rain from Tuesday through Thursday. The mid to upper
level ridge enveloping the Southern Plains will display a subtle
weakness over Eastern Texas and the western Gulf of Mexico. 85H to
5H ridging will focus over the southeastern U.S. with a longwave
ridge axis over the Rocky Mountains. This places Texas within the
relatively weaker height channel. Traditionally, within this set up,
any disturbed weather forming over the Bay of Campeche gets caught
up within this channel and brought northward towards the Upper Texas
coastline...or gets caught within the east to southeast 7H steering
flow between two aforementioned mid to upper ridges. In essence,
this height weakness channel also becomes a moisture channel as
higher moist air masses over the warmer southwestern Gulf are
advected northward into the region.

The surface pressure gradient with high pressure generally
stationed over Georgia and Florida in relation to lowering
pressures (due to daily heating) over the Rocky lees and western
Texas will maintain an onshore orientation through the week. This
will keep pwats high, in the 1.6 to near 2 inch range...these
numbers fall into the 75 percentile by early June standards.
Convective temperatures in the lower 90s will likely be achieved
so, if lift is either provided along the local breezes or from a
landfalling weak Gulf disturbance, expect at least low end PoPs to
be in place for (at least) the southern 2/3rds of the forecast
area through a good part of the week.

Heat will also be a topic this coming week. Ambient temperatures
not falling much overnight (only the low to mid 70s) will quickly
warm into the early afternoon lower 90s within a more humid air
mass with little to no mixing per weak lower level southerlies
will produce "feels like" mid to late week temperatures in the
upper 90s to lower 100s. Thus, be aware and take the proper
precautions to avoid heat exhaustion if outside exercising or
working between the hours of Noon to 4 PM.

The global deterministic models are still developing a closed off
circulation from the current broad disturbance over southern
Mexico and the northern countries of Central America. The GFS
solution is to bring a weak tropical system (near 1000 mb low) to
Galveston Bay next Tuesday while the ECMWF is a faster solution of
taking its weak low of around 1000 mb up the Sabine Pass late
Sunday. The NHC has placed a 30% chance of it developing into a
tropical cyclone within the next 5 days. Obviously, due to the
disagreement amongst models, confidence is very low but it will
still be wise to pay attention to what becomes of this potential
system. Tomorrow is the official start of the 2020 Hurricane
Season so now is a good time to review your hurricane plan! 31

MARINE...

Occasional early day showers and an isolated thunderstorm can be
expected over the maritime the next several days. Funnels and/or
waterspouts are likely within the strongest cells. High pressure
positioned over the southeastern U.S./Florida, along with a weak
surface boundary paralleling the upper Texas coastline, will
maintain a general (north)east wind today. Inland heating will
cause a slight nearshore veering of winds to the southeast later
in the afternoon. Nearshore significant wave heights will remain
in the average near 2 foot range...3 to near 4 feet over the far
offshore waters. The early week pressure gradient will favor a
typical onshore wind orientation so southeasterly winds will
become the dominant wind by Tuesday. The approach of a southern
Gulf low into the northern Gulf early next week will back
strengthened winds to the east-northeast and increase
precipitation chances. 31

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      86  70  85  72  91 /  20  20  30  20  20
Houston (IAH)              87  72  87  73  90 /  40  40  20  20  20
Galveston (GLS)            83  77  84  78  86 /  60  30  30  10  20

&&

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

$$

Discussion...43
Aviation/Marine...43


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