Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 252020

Area Forecast Discussion
National Weather Service Houston/Galveston TX
320 PM CDT WED MAY 25 2016

Another warm and very humid day across SE TX. Heat index values
approached 100 degrees in a few locations. Moisture streaming into
the region beneath a weak capping inversion will keep skies mostly
cloudy overnight. The cloud cover and winds will keep min temps
on the warm side once again. Can`t rule out an isolated shower
beneath the cap but dry air in the 850-700 mb layer will preclude
much in the way of widespread or heavy rain.

A deep upper trough over S CA will approach the southern Rockies
on Thursday. A weak disturbance embedded in a sharpening southwest
upper flow will trigger scattered showers and thunderstorms over
SE TX. There are some significant model differences on Thursday
with the NAM, ECMWF and the Texas Tech WRF all more bullish with
rain chances. The GFS and Canadian are drier primarily because
they both maintain capping and dry air at the 850-700 level. PW
values remain high, between 1.80 and 2.10 inches. Jet dynamics
still look strong on Thursday with a splitting jet structure noted
over most of E-SE TX. Best rain chances should be over the
northern zones where model consensus is in good agreement with
little to no capping, high moisture and strong jet dynamics. Have
tapered highest PoPs over the NW zones and lower PoPs toward the
coast. Have added locally heavy rain to the wx grids over the NW
zones with PW values over 2.00 inches and some training of storms
looks likely. CAPE values will approach 2500 J/kg and LI values
around -6 suggest that some of the storms could be strong during
the afternoon.

The upper trough will move into the southern plains on Friday
with the upper flow remaining S-SW. Another upper level
disturbance will move across SE TX on Friday and this feature will
trigger another round of showers and thunderstorms. The NAM
continues to show no capping and a nearly saturated forecast
sounding. Locally heavy rain will again be likely on Friday over
the northwest half of the region. Again, further south and toward
the coast, models diverge with the amount of dry air at the
850-700 layer and the strength of the cap. Will again taper higher
PoPs over the northwest and trend lower toward the coast. Jet
dynamics look stronger on Friday with a well defined split in the
upper level winds and SE TX possibly falling into a jet couplet
during the afternoon. CAPE values increase to around 3600 J/kg
with LI values around -10. Shear values also look a bit stronger
on Friday. These ingredients coupled with stronger jet dynamics
would support a better chance of strong/severe storms on Friday.
Feel both the threat for severe storms and locally heavy rain will
be more widespread than on Thursday but the best chance will still
remain over the NW zones.

Conditions begin to dry out on Saturday afternoon as PW values
drop to 1.40 inches. A weak s/wv will move across the region
Saturday morning with PW values till on the high side thru 18z.
Will maintain chance PoPs on Saturday but feel the best chance
will be in the morning. Upper level ridging tries to reestablish
over the region Sun/Mon with PW values remaining below 1.60
inches. Forecast soundings show weak capping and a dry layer near
850 mb so not expecting much more than isolated showers through
early next week. Another weak upper level trough develops over the
southern Rockies on Wednesday and this feature begins to suppress
the ridge with rain chances returning for the latter half of next
week. 43


Moderate to occasionally strong southeast winds and building seas
are expected through the end of the week as the upper Texas Coast
remains pinched in a tightening pressure gradient between a large
ridge of high pressure over the Eastern US and a deepening storm
system over the Great Plains states.

Small craft advisories will be needed Thursday night through Friday
night. Improving conditions are expected over the Memorial Day
weekend as the storm system moves away from Texas.   44


College Station (CLL)      75  82  73  82  70 /  30  70  40  80  50
Houston (IAH)              76  84  75  84  72 /  20  50  30  60  40
Galveston (GLS)            78  82  78  82  77 /  10  40  20  30  20



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