Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 222022
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
322 PM CDT FRI MAY 22 2015

...LOCALLY HEAVY RAIN EXPECTED SUNDAY AND MONDAY...

.DISCUSSION...
AT 2 PM...A WARM FRONT ACROSS CENTRAL/SOUTHEAST TEXAS WILL
CONTINUE TO MOVE SLOWLY NORTH THIS EVENING. SCATTERED SHRA/TSRA
WILL CONTINUE TO DEVELOP OVER THE W/SW ZONES THROUGH THE EVENING
WITH PRECIP WANING AFTER MIDNIGHT. A WEAK UPPER LEVEL DISTURBANCE
COUPLED WITH PW VALUES INCREASING TO 1.80 INCHES...CONVECTIVE
TEMPS BETWEEN 79-81 DEGREES AND INCREASING UPPER LEVEL
DISTURBANCE WILL PRODUCE SCATTERED SHRA/TSRA ON SATURDAY. THE NAM
LOOKS OVERLY AGGRESSIVE SO WILL LEAN TOWARD A GFS/ECMWF BLEND. PW
VALUES SURGE TO 1.9-2.0 INCHES LATE SATURDAY NIGHT. AN UPPER LEVEL
TROUGH OVER THE INTERMOUNTAIN WEST WILL MOVE EAST SAT NITE/SUNDAY.
FCST SOUNDINGS SHOW A SATURATED PROFILE DEVELOPING ON SUNDAY WITH
SE TX LYING IN A STRONG RRQ AND A S-SE 40-45 KT LOW LEVEL JET.
NUMEROUS SHRA/TSRA ARE EXPECTED ON SUNDAY. ALTHO STORM MOTION WILL
BE PRETTY QUICK...TRAINING OF STORMS WILL LEAD TO SOME HEAVY
RAINFALL TOTALS ON SUNDAY. HELICITY VALUES WILL RANGE BETWEEN
170-200 SO THERE IS A THREAT FOR ISOLATED TORNADOES AS WELL.

ANOTHER UPPER LEVEL TROUGH WILL DIG FURTHER SOUTH TOWARD EL PASO BY
MONDAY MORNING AND THEN MOVE E-NE ACROSS TEXAS ON MONDAY NIGHT.
SOME SIGNIFICANT DIFFERENCES BETWEEN THE GFS AND THE ECMWF WITH
THEIR RESPECTIVE QPF BULLSEYE MON AFTN THROUGH TUESDAY. THE ECMWF
IS FURTHER SOUTH WITH A SPLITTING JET STRUCTURE AND FAVORS THE MAX
QPF OVER SE TX WHILE THE GFS SHOWS THE BETTER DIVERGENCE OVER N
TEXAS. THE GEM FAVORS THE ECMWF SO LEANED TOWARD THE FURTHER SOUTH
SOLUTION AND WILL MAINTAIN HIGH RAIN CHANCES MON NIGHT/TUESDAY.
TRAINING OF STORMS IS AGAIN EXPECTED WITH SOME HEAVY RAINFALL
TOTALS EXPECTED. THE ECMWF QPF OUTPUT EXCEEDS 7 INCHES OVER
HOUSTON BETWEEN SUNDAY AND TUESDAY. UNLESS FCST CONDITIONS CHANGE
SIGNIFICANTLY...A FLASH FLOOD WATCH IS EXPECTED TO BE ISSUED EARLY
SATURDAY MORNING.

PW VALUES REMAIN BETWEEN 1.7-1.8 INCHES THROUGH THE END OF THE
WEEK. DAYTIME HEATING SHOULD TRIGGER SCT SHRA/TSRA EACH DAY WITH
PRECIP WANING WITH THE LOSS OF HEATING. A WARM UP WILL ENSUE WED-
FRI WITH MAX TEMPS WARMING INTO THE UPPER 80S. ANOTHER UPPER LEVEL
TROUGH WILL APPROACH THE STATE NEXT WEEKEND WITH MORE RAIN
EXPECTED NEXT FRI-SUN. 43

&&

.HYDROLOGY...
THE TRINITY RIVER AT LIBERTY REMAINS IN MAJOR FLOOD AND WILL
REMAIN IN FLOOD FOR THE NEXT COUPLE OF DAYS. THE FLOOD WARNING AT
STRANE PARK ENDED EARLIER TODAY AND THE RIVER LEVEL WILL CONTINUE
TO DROP. RIVER LEVELS ALSO CONTINUE TO DROP ON THE W FORK OF THE
SAN JAC NEAR HUMBLE AND PORTER. ALTHO CONDITIONS ARE IMPROVING IN
THE SHORT TERM...IF HEAVY RAIN DEVELOPS OVER THE WEEKEND...
HYDROLOGIC ISSUES COULD BECOME A PROBLEM. AREAS OF POSSIBLE
CONCERN INCLUDE THE W FORK OF THE SAN JACINTO...THE TRINITY
RIVER AND THE LOWER END OF THE BRAZOS RIVER. FLASH FLOOD GUIDANCE
HAS ALSO IMPROVED. RAINFALL RATES WILL NEED TO EXCEED THREE INCHES
PER HOUR TO PRODUCE FLASH FLOODING. 43

&&

.CLIMATE...
HUNTSVILLE HAS ALMOST 11 INCHES OF RAIN THIS MONTH AND TODAY WAS
THE FIRST DAY IN THE LAST 13 DAYS WITHOUT MEASURABLE RAIN.
HUNTSVILLE RECORDED 12 CONSECUTIVE DAYS WITH RAINFALL 0.01 INCHES
OR GREATER (5/10-5/21). THE CONROE ASOS HAS ALSO TALLIED OVER 10
INCHES OF RAIN THIS MONTH. ON THE FLIP SIDE...GALVESTON HAS ONLY
MEASURED 1.40 INCHES OF RAIN DURING MAY WHICH IS ABOUT AN INCH
BELOW NORMAL. 43

&&

.MARINE...
CONDITIONS OVER THE WEEKEND ARE EXPECTED TO DETERIORATE AS THE
PRESSURE GRADIENT TIGHTENS AND THE PERSISTENT MODERATE ONSHORE WINDS
BECOME STRONGER. CURRENT THINKING IS THAT SMALL CRAFT CONDITIONS MAY
DEVELOP AS EARLY AS OVERNIGHT SATURDAY NIGHT AND PERSIST THROUGH
SUNDAY AFTERNOON. ALTHOUGH THE WINDS SHOULD DROP OFF A BIT ON
MONDAY...STORMY CONDITIONS MAY KEEP SEAS ELEVATED.

THE TIDES MAY ALSO BECOME AN ISSUE ON SUNDAY. THE TIDE LEVELS WERE
FROM 0.5 TO 1.0 FEET ABOVE THE PREDICTED MEAN LOWER LOW WATER
/MLLW/ LEVELS THIS AFTERNOON. THESE ARE EXPECTED TO SLOWLY INCREASE
TO ABOUT 1 TO 1.5 FEET ABOVE THE PREDICTED MLLW LEVELS BY SUNDAY...
AND POSSIBLY LEVEL OFF OR EVEN SLOWLY DIMINISH ON MONDAY IF THE
WINDS DIMINISH. HOWEVER...SWELLS ON TOP OF THE ABOVE NORMAL TIDE
LEVELS MAY LEAD TO MINOR FLOODING ISSUES ON THE GULF FACING BEACHES
OF THE BOLIVAR PENINSULA...ESPECIALLY LOW-LYING AREAS OF HIGHWAY 87.

40

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      71  83  71  79  70 /  20  50  70  90  70
HOUSTON (IAH)              72  84  75  81  73 /  20  40  40  90  70
GALVESTON (GLS)            78  83  78  83  77 /  30  30  30  60  70

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$


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