Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
FXUS64 KHGX 192050
Area Forecast Discussion
National Weather Service Houston/Galveston TX
250 PM CST Sun Feb 19 2017
Cloud cover starting to break up this afternoon with some mixing.
Where we are seeing the sun, temps have already made it to the
upper 70s, so SE areas will likely see some 80 degree temps this
aft. It is breezy and very humid as well for Feb with sfc dw pts
in the mid/upper 60s areawide.
Model guidance is in fairly good agreement that widespread showers
and storms will develop early this eve well west of SE TX across
central/north TX ahead of a slow eastward moving longwave
mid/upper level trough. Meso models show that an area of showers
and storms will develop out ahead of this main precip. band across
western portions of Se Texas just after midnight and this lead
band will be a slow mover across our W/NW areas during the early
morning hours. With PW values peaking around 1.8 inches Mon
morning, and upper level divergence increasing Mon morning as well
as a split jet structure develops, key parameters are in place
for heavy rainfall. The fairly unidirectional s/sw flow in the
low-mid layers of the atmosphere points to the possibility of
cell training in this very moist airmass. Think this all equates
to widespread 1 to 3 inches late tonight and tomorrow as well as
the threat for localized 4 to 6 amounts. Given that the ground is
fairly moist from previous rainfall, have issued a flash flood
watch for most of SE TX beginning during the early morning hours
on Mon and continuing through most of the aft.
The heavy rainfall threat should end by the eve hours. A trailing
mid/upper low that hangs around on Tue and this feature will
extend the chc of showers into Tues, but no heavy rainfall is
expected with this feature. Dry conditions with above normal
temperatures are expected on Wednesday and Thursday. A cold front
will move through on Friday aft/eve and bring a brief cooler
airmass to the region early next weekend. 33
Southeasterly flow very slow to come up this afternoon. Throughout
the evening hours expect winds to increase and will continue with
the SCEC for winds increasing to 15-20 knots...lighter in the bays.
Moisture still rich but with shorter residency over the warming
shelf waters and more mixing expect fog to be lighter throughout the
night with areas from around Freeport to Galveston probably dropping
to 1 to 3 miles. Will hold off on a Marine Dense Fog Advisory as it
isn`t as clear cut as last night. Seas building to 5 to 6 feet
toward morning. Storms will move in from the west and will be
capable of gusty conditions and significant reduction in visibility
in heavy downpours. Shear is a little higher over the southwest
waters between midnight and 8 am and will have to keep an eye out
for fast moving spinners/waterspouts over the far waters. Pacific
cold front eventually pushes through Monday night with a gusty
northwesterly winds probably below SCEC. Another Pacific cold front
late Friday may boost offshore winds to SCEC for Saturday morning.
Long southeasterly fetch develops Sunday and may see a period of
elevated seas/tides/sea fog late Sunday through Tuesday.
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 64 72 57 76 55 / 90 70 10 20 10
Houston (IAH) 69 72 61 76 59 / 80 100 30 30 10
Galveston (GLS) 68 70 63 72 62 / 60 90 50 30 10
TX...Flash Flood Watch from late tonight through Monday afternoon for
the following zones: Austin...Brazoria...Brazos...
GM...SMALL CRAFT SHOULD EXERCISE CAUTION from 6 PM CST this evening
through late tonight 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...Waters from Freeport to the Matagorda Ship Channel
from 20 to 60 NM...Waters from High Island to Freeport from
20 to 60 NM.