Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 261558
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1058 AM CDT THU MAR 26 2015

.DISCUSSION...
COLD FRONT AND ASSOCIATED SHOWERS AND THUNDERSTORMS ARE CURRENTLY
MOVING OFF THE COAST AND ACROSS THE COASTAL WATERS. WHILE THE
GREATEST CONCENTRATION IS OFF THE COAST...SOME LINGERING LIGHT/
MODERATE RAIN AREAS WILL HANG AROUND FOR ANOTHER HOUR OR SO.
THE FORECAST PACKAGE HAS THINGS COVERED...AND MIGHT UPDATE EVERYTHING
ONCE THE RAINS EXIT OUR AREA.  42
&&

PREV DISCUSSION... /ISSUED 401 AM CDT THU MAR 26 2015/

DISCUSSION...
AT 08Z SFC ANALYSIS SHOWS THE COLD FRONT STRETCHING FROM THE
ARKLATEX SW TO C TX AND NW HILL COUNTRY. A THIN LINE OF SHOWERS
HAS DEVELOPED ALONG AND JUST AHEAD OF THE FRONT. LLJ AT 850MB
STRETCHES FROM THE LOWER TX COAST NE THROUGH E TX AND TOWARDS THE
MISS RIVER VALLEY. WATER VAPOR AND 500MB ANALYSIS SHOW TROUGH AXIS
STRETCHING FROM THE N GREAT LAKES THROUGH THE PLAINS. POLAR JET
STRETCHES FROM THE S PLAINS NE TOWARDS THE GREAT LAKES WITH RIGHT
ENTRANCE REGION OVER OK MOVING EAST TOWARDS ARK. ANOTHER JET
STREAK WAS FOUND OVER THE N ROCKIES WHICH SHOULD FURTHER DEEPEN
THE TROUGH WITH UPPER LEVEL RIDGING OVER THE PAC COAST.

LATEST RAP/HRRR/3KM TXTECH WRF/4 KM WRF ARW ALL HAVE A PRETTY
GOOD HANDLE ON COLD FRONTAL PASSAGE ACROSS SE TX. LATEST 07Z HRRR
HAS INITIALIZED WELL AND BASED THE FIRST DAY FORECAST ON A BLEND
OF THESE TRENDS WITH THE RAP AND 3KM TX TECH WRF. FRONT SHOULD
REACH KCLL/KUTS 10-11Z...KIAH/KSGR/KHOU AROUND 13Z AND THEN OFF
THE COAST 15-16Z. MODELS DO SUPPORT CONVECTION INCREASING IN
COVERAGE MAINLY SOUTH OF HOUSTON AND ALONG THE COAST WHERE THE
FRONT INTERACTS WITH HIGHER MOISTURE. FORECAST WILL KEEP HIGHER
POPS FOR THE COASTAL AREAS AND OFFSHORE THROUGH 18Z. RAIN CHANCES
CLEAR OUT QUICKLY FROM 15-18Z INLAND. ANY THUNDERSTORM ACTIVITY
MAY BECOME STRONG BUT NOT LIKELY SEVERE DUE TO CAPPING AND LIMITED
INSTABILITY. THE 00Z CRP SOUNDING SHOWS A PRETTY GOOD CAP AT
800-750MB.

TEMP FORECAST WILL BE A CHALLENGE BECAUSE OF STRONG COLD
ADVECTION BEHIND THE FRONT. TEMPS ARE IN THE LOW/MID 60S THIS
MORNING AND MAY INCREASE A FEW DEGREES AHEAD OF THE FRONT MAINLY
ALONG THE COAST. TEMPS MAY DROP INTO THE 50S BEHIND THE FRONT BUT
AS CONVECTION/CLOUD COVER CLEARS...MAY GET SOME SLIGHT HEATING IN
THE AFTERNOON TO OFF SET COLD ADVECTION. SHORT RANGE MODELS KEEP
TEMPS IN THE 60S WHICH LOOKS REASONABLE.

FRI MORNING SHOULD BE A COOL START TO THE DAY WITH MIN TEMPS BACK
INTO THE 40S BUT MAX TEMPS SHOULD TOP OUT IN THE 70S. TEMPS
INCREASE OVER THE WEEKEND WITH WEAK UPPER LEVEL RIDGING OVER TX.
THE GFS/ECMWF DIVERGE IN THEIR SOLUTIONS OVER THE WEEKEND AND INTO
NEXT WEEK. WHILE THE MODELS THEMSELVES HAVE HAD RUN TO RUN
CONSISTENCY...THERE HAS NOT BEEN ANY CONSISTENCY WITH EACH OTHER.
THE PROBLEM SEEMS TO BE HOW EACH MODEL IS HANDLING A TROUGH THAT
PUSHES INTO THE PACIFIC COAST LATE FRI INTO SAT. THE ECMWF CUTS
OFF SOME VORTICITY FROM THIS TROUGH AND HAS IT RETROGRADE BACK
INTO THE PACIFIC WITH THE MAIN WAVE MOVING ACROSS THE PAC NW AND
INTO THE PLAINS BY SUNDAY. THE GFS DOES SIMILARLY WITH THE MAIN
WAVE BUT HAS A MORE COHERENT CLOSED OFF UPPER LOW OVER
CALIFORNIA/BAJA LATE SUNDAY. THIS SYSTEM THEN MOVES ACROSS THE S
ROCKIES INTO TX ON TUE. THE ECMWF HAS A MUCH WEAKER SYSTEM AND HAS
A STALLED FRONT ACROSS THE AREA. THIS MAKES THE FORECAST
CHALLENGING BECAUSE IF THE ECMWF VERIFIES THERE WILL BE LITTLE
WEATHER IMPACT. IF THE GFS IS CORRECT THEN THE TROUGH SWINGS OVER
SE TX WITH NEG TILT AND VERY FAVORABLE FOR HEAVY RAINFALL/SEVERE
WEATHER. FOR WHAT IT IS WORTH THE CANADIAN MODEL MIGHT BE A
COMPROMISE BETWEEN THE GFS/ECMWF BUT PERHAPS SUPPORTING THE ECMWF
A BIT MORE. FORECAST WILL KEEP 30/40 POPS AND MAX TEMPS WILL BE A
COUPLE DEGREES COOLER DUE TO POSSIBLE RAIN CHANCES AND CLOUD
COVER. THE SYSTEM CLEARS OUT EARLY NEXT WED WITH NO REAL CHANGE IN
AIRMASS. TEMPS NEXT WEEK COULD BE A GOOD 5-8 DEGREES ABOVE NORMAL.

39

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      65  45  74  51  78 /  20   0   0   0   0
HOUSTON (IAH)              67  49  75  54  79 /  50   0   0   0   0
GALVESTON (GLS)            68  54  70  60  73 /  60   0   0   0   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 1 AM CDT FRIDAY FOR THE FOLLOWING
     ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL
     OUT 20 NM...WATERS FROM HIGH ISLAND TO FREEPORT OUT 20 NM.

     SMALL CRAFT ADVISORY UNTIL 4 AM CDT FRIDAY FOR THE FOLLOWING
     ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL
     20 NM TO 60 NM...WATERS FROM HIGH ISLAND TO FREEPORT 20 TO
     60 NM.

&&

$$

DISCUSSION...42
AVIATION/MARINE...31


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