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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

                            
000
FXUS64 KHGX 240837
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
337 AM CDT Mon Jun 24 2019

.DISCUSSION...

- Severe thunderstorm watch to expire at 4AM. Severe threat if any
  looks rather small. Line of storms mainly producing 30-40 mph
  wind gusts. Main concern the next 3 to 6 hours will be locally
  heavy rainfall with showers in the low level jet axis merging
  with the line causing an increase in rain rates.

- Tuesday there is the potential for more heavy rainfall due to a
  combination of several factors. There could be another solid
  inch of rain to occur but likely depend upon convective
  evolution on the mesoscale.

.SHORT TERM [Today Through Tuesday]...

A ragged line of early morning showers and thunderstorms moving 
across the northern forecast area with thin lines of precipitation
feeding into this activity. So far, this activity is behaving 
itself. The near term forecast still calls for the southern 
advancement of a cold pool-driven broken line of showers and 
thunderstorms to pass across the region this morning. Current 
timing has a somewhat disorganized QLCS impacting the city just 
before sunrise and then reaching the coast in the late morning 
hours. Not anticipating severe with this activity although the 
strongest storms could put down greater than 30 knot wind gusts 
and small hail. After a couple of warm mornings in the lower 80s, 
this passing rain will 'cool' many north of the city to the middle
70s. A mainly overcast day with slight to low end chances for 
spotty return precipitation. The highest chances for shower and 
storm coverage will be near the coast and points just offshore, or
where the remnants of this morning's outflow boundary will hang 
up. The afternoon will warm up into the upper 80s to lower 90s 
and, with dew points in the middle 70s, this will produce 100 to 
105 F afternoon heat indices. 

The models want to develop a shortwave trough across central 
state later today and then pull this feature across the eastern 
Texas early Tuesday. Couple the lift provided by weak PVA with 
higher bouts of greater than 1.8 inch pwat air advecting in from 
the Gulf and you have some of the ingredients needed to place 
moderate to high end rain chances in for Tuesday. An uncapped 
Tuesday daytime environment will produce low level 7 to 8 deg C 
rates leading to near 4k J/kg CAPE and -11 L.I.s. The GFS as well 
as the WRF solutions want to fire convection ahead of the west 
central Texas dry line boundary. They push this activity east into
our area during peak heating so, if this scenario stays 
consistent through tonight, Tuesday's POPs will be on the rise. A 
backing LLJ and weak upshear Corfidi vectors indicate slow(ing) 
storm motions. This increases the potential for higher rainfall 
rates making the storm threat mode that of flooding on Tuesday. 31

.LONG TERM [Wednesday Through Monday]...

Wednesday into Thursday upper level ridging should become more 
pronounced over northern Mexico, southern Rockies and into the 
Plains. SE Texas will be on the edge of this ridge so we will need
to carry at least 10 to 20 PoPs as there will still be some 
decent moisture over the area. Any showers and storms will be 
diurnally driven with low end threats of brief heavy rain, 
lightning and gusty winds.

The weekend still looks to feature the development of an inverted
upper level trough or weakness in the ridge over the NW Gulf into
Texas. The problem is that all the models show differing 
evolutions and timing for this trough development. For now we will
go with a climo 20 to 30 PoP across the area seeing that the 
atmosphere by this time should be more favorable for convection 
than not. Towards day 8/9 the GFS shows a surge in tropical 
moisture along the lower TX coast so this may be worth watching 
for an increase in thunderstorm chances.

Overpeck

&&

.MARINE...

The main marine hazards of strong southerly winds and rough seas 
will continue this morning. A squall line should push off the 
coast later this morning and this should allow for winds to 
decrease after it moves through the upper Texas coast. Small craft
advisories will continue until the late morning hours when winds 
should decrease. Seas will be slow to decrease but should begin to
happen this afternoon and tonight. Winds should remain around 
moderate levels for much of the week and then decrease late in the
week. This will allow for seas to slowly decrease to less than 3 
feet by the end of the week.

The other concern will be rip currents for Gulf facing beaches. 
We will need to take this hazard day by day as winds should be 
decreasing and cause less wave run up. Rip current threat should 
be on the decline but we will coordinate with area beach patrols 
to determine the risk.

Overpeck

&&



.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  91  75  91  73  92 /  50  30  60  40  20 
Houston (IAH)          92  78  91  76  93 /  50  30  50  50  10 
Galveston (GLS)        87  83  89  81  90 / 100  30  30  20  10 

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...High Rip Current Risk until 10 AM CDT this morning for the 
     following zones: Brazoria Islands...Galveston Island and 
     Bolivar Peninsula...Matagorda Islands.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 10 AM CDT this morning 
     for the following zones: Galveston Bay...Matagorda Bay.

     Small Craft Advisory until 10 AM CDT this morning 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.


&&

$$

DISCUSSION...Overpeck
SHORT TERM...31
LONG TERM...Overpeck
AVIATION...31
MARINE...Overpeck