Hail in Texas, May 24, 2020

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1040 AM CDT Sun May 24 2020

.SHORT TERM [Tonight Through Tuesday]...
A quick update...s/w over the Hill Country before sunset shifting
east and now bringing a little more lift across SETX with the
additional heating we are reaching the deep convective
temperatures of 84-85 so from here on out a thunderstorms should
become more common. Moistening up through 800 mb per AMDAR
soundings so dry entrainment should be to much of a hamper for
development nor cap. Have raised POPs across the west and central
corridors this morning and then shifting eastward and
northeastward through the afternoon. Still the potential for heavy
rain as storm motion is likely to be less than 25 mph this morning
diminishing to less than 20 this afternoon.

45

&&

.PREV DISCUSSION /Issued 622 AM CDT Sun May 24 2020/...

.DISCUSSION...

The much more pronounced appearance of streamer showers very
early this morning on radar shows we are finally transitioning
from last week's persistent ridging and hot weather to a more
unsettled pattern. This new pattern will likely persist for a
while as well, bringing us several opportunities for periods of
showers and thunderstorms for much of the week.

We'll continue to have to watch for the potential of heavy
rainfall creating flooding issues, as the large-scale environment
will remain supportive of efficient rain processes. Fortunately,
confidence is a little higher that rains today will not realize
high end potential, though the strongest storms will be able to
produce localized issues in spots with poor drainage with rain
rates of up to an inch per hour.

As the environment does not look to change significantly in the
coming days, we will have to evaluate mesoscale features day to
day to see if each day's setup may be able to result in more
significant rainfall.

.LONG TERM [Tuesday Through Sunday]...

An upper level trough over the western plains will extend into west
and central Texas. A strong short wave rotating around the base of
the trough and strong moisture transport will provide the region
with a good chance of showers and thunderstorms. A well defined
upper level low develops in the base of the trough and gets cut-off
from the main flow and generally just sits and waffles back and
forth across the state through the end of the week. Global models
are in better agreement with the general placement of the upper low
but there are enough differences that to pinpoint who will get rain,
when it'll occur and how much will fall is still a bit of a folly at
this time. Certainly rain chances are in order since SE TX will lie
on the east side of the low and upper level winds remain broadly
divergent. The EC is further east with the low on it's 00z run and
this shunts more of the precip eastward on Wed/Thu. The GFS also
looks a bit further east before it takes the low back to the central
part of the state. Although fcst soundings show some drier air working
into the moisture profile, convective temps look reachable day with
Tc around 84-85 degrees with PW values hanging around 1.65-1.75
inches. Will carry chance to likely PoPs every day as diurnally
driven showers and thunderstorms should develop. Any embedded s/wv
rotating around the low will enhance rainfall but timing on that is
uncertain at this time. An upper level ridge is expected to develop
next Sunday or Monday and things should begin to dry out during the
the first week of June. 43

.AVIATION [12Z TAF Issuance]...

Messy, messy forecast period ahead. Widespread MVFR CIGs with
isolated spots of IFR, as well as scattered SHRA and isolated TS
to start. Should see activity briefly come to an end later this
morning as we improve to VFR. TSRA to erupt this afternoon, fading
after sunset. MVFR CIGs return, as well as more potential for
rain later tonight. Specifics will be very hard to pin
down...multiple amendments seem virtually certain.

.MARINE...

Moderate onshore winds will persist, keeping elevated seas through
the holiday weekend. Caution flags for the Gulf, and at times the
bays will likely continue to be needed. Thunderstorm chances will
increase today as a series of shortwave troughs aloft passes
through. This more active pattern of showers and thunderstorms
will continue well into the upcoming week as an upper low looks to
be cutoff over the region and move little over the next several
days. However, towards mid-week, we may see much more variable
winds, which should break the persistent onshore fetch, and allow
for diminished, but more confused seas to emerge.

.CLIMATE...

Both Houston and Galveston set new high minimum temperature records
yesterday and this was second day in a row Galveston achieved a high
minimum record. The low yesterday at Galveston was only 81 degrees.
This was the warmest overnight low temperature for so early in the
year and also tied for the warmest overnight low temperature for the
month of May. 43

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  84  70  82  69  82 /  60  70  80  60  60
Houston (IAH)          88  73  83  72  84 /  50  60  80  50  60
Galveston (GLS)        83  76  83  76  83 /  30  50  70  40  60

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...High Rip Current Risk through this evening for the following
     zones: Brazoria Islands...Galveston Island and Bolivar
     Peninsula...Matagorda Islands.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION through late tonight 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.

&&

SHORT TERM...45
LONG TERM...Fowler