Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 221723
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1223 PM CDT Mon May 22 2017

.AVIATION...
General trend this afternoon is for SHRA/TSRA to move off to the east
with some ceiling improvement. Could see patchy fog/low CIGS tonight/
early tomorrow morning. Might see some additional SHRA/TSRA development
tomorrow as another front moves through the area.  42
&&

.PREV DISCUSSION... /ISSUED 1113 AM CDT Mon May 22 2017/

UPDATE...
Main update to the ongoing forecast was to update rain chances and
the Flash Flood Watch based on latest trends. Have removed
Jackson, Fort Bend, and Matagorda from the watch as the heaviest
rain threat continues to shift eastward as a surface low/MCV lifts
along the Upper Texas Coast. Morning soundings from Lake Charles
and Corpus Christi both showed precipitable water values in the
1.75-2 inch range, which combined with about 1000 j/KG of CAPE
along the coast, has been sufficient to produce peak rain rates
around 2-2.5 inches an hour. Expect the flooding threat to
gradually shift east with this main complex with time, but
extensions or adjustments to the ongoing Flash Flood Watch are
possible based on short term trends. With surface winds ahead of
this surface low/MCV slightly backed, cannot rule out a brief,
weak tornado or two as a line of storms associated with it
continues to lift across Galveston and Chambers counties.

Farther north, divergent flow aloft and low level speed/direction
convergence across the northern half of the forecast area is
resulting in a secondary area of moderate to occasionally heavy
rain. Minor flooding issues will be possible across these areas
through mid afternoon as high rain rates contribute to ponding of
water on roads. Expect all activity to continue to move east to
the region by mid to late afternoon as an associated shortwave
trough also pushes east of the region.

Huffman

PREV DISCUSSION... /ISSUED 501 AM CDT Mon May 22 2017/

Forecast remains pretty much on track and made just minor tweaks
to the ongoing package.

An MCV has developed with the large cluster of precip west of
Matagorda Bay. This should continue trekking mostly eastward
today. Surface boundary situated just offshore focused some 5"+
totals overnight. The hope was it would stay there but has since
edged closer to the coast and into the Galveston Bay area.
Convergent zone appears to be setting up from roughly Liberty to
Matagorda Bay. Inflow has really ramped up offshore with sustained
25-30 knot llvl SE winds perpendicular to this zone. Hopefully
the MCV takes a more ese track in the coming hours and pulls this
boundary back offshore. But there`s considerable uncertainty and
with resident 2-2.3" PW`s, felt is was best to issue a short fused
Flash Flood Watch and re-evaluate trends in the coming hours.
Those details are in that product that`s already been sent.

Bulk of precip should be headed off to the east later in the
afternoon and early evening. With the exception of offshore
areas, most of the region should see a break in the action
tonight. Rain and isolated storm chances return Tue aftn and evng
as a cold front makes its way into the region. The remainder of
the work week should be dry in the wake of the front. Pleasant
temps on Wed will gradually modify back into the 70s/90s Thursday
and into the weekend as onshore winds resume. Next shot of rain
looks to be late Sunday or early next week with the approach of
another weak front. 47

MARINE...
Strong and gusty onshore winds will prevail today into this evening
as low-level jet develops over SE TX. Scattered showers and thunder-
storms are possible thru Tues night as a series of upper level dist-
urbances move in from the west and interacts with left-over surface
boundaries lingering over the region. Models remain on track with a
cold front moving into the coastal waters Tues...with the stronger/
deeper northerly flow not making it into the Gulf until Tues night/
Weds morning. Caution flags may be needed during this time. Onshore
winds are set to return to the area by Weds night and then strength-
ening the rest of the week. 41

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      75  65  80  57  81 /  80  20  50  40   0
Houston (IAH)              77  67  82  60  83 /  90  20  40  40   0
Galveston (GLS)            81  73  82  66  81 / 100  50  30  40   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flash Flood Watch until 1 PM CDT this afternoon for the
     following zones: Brazoria...Chambers...Fort Bend...
     Galveston...Harris...Liberty.

GM...Small Craft Advisory until 5 PM CDT this afternoon 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...Galveston Bay...Matagorda
     Bay...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...14
Aviation/Marine...42


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