Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 152102
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
402 PM CDT WED APR 15 2015

.DISCUSSION...
A DAY OF LITTLE ACTION WEATHER-WISE WILL TRANSITION TO A COUPLE OF
DAYS OF WHAT IS FORECAST TO BE A VERY ACTIVE WEATHER PATTERN. AN
UPPER LOW CURRENTLY CHURNING OVER THE GREAT BASIN WILL SLOWLY
DESCEND INTO THE LOWER-CENTRAL ROCKIES OF CO-NM THROUGH TOMORROW...
OPENING UP A MORE SOUTHWESTERLY FLOW PATTERN OVER EASTERN TEXAS.
RETURN FLOW SETTING UP OVERNIGHT WILL BEGIN THE MOISTURE PUMP THAT
HAS PWATS INCREASING TO OVER 1.6-1.7 INCHES BY FRIDAY AFTERNOON.
SHORTWAVE DISTURBANCES TRAVELING WITHIN MID-UPPER LEVEL SOUTHWESTERLY
FLOW WILL INITIALIZE PERIODS OF RAIN AND STORMS...WITH THE MORE
AGGRESSIVE GFS HINTING AT DEVELOPING A WESTERN AREA MCS ON FRIDAY
AFTERNOON AND PUSHING IT ACROSS THE CWA THROUGH SATURDAY MORNING.

THURSDAY AFTERNOON INTO FRIDAY EVENING`S THERMO AND SHEAR INDICES
HAVE MET AND/OR ACHIEVED THE THRESHOLDS NEEDED IN MENTIONING
ISOLATED SEVERE BOTH DAYS. HIGH SRH VALUES IN THE 200 TO 400S
FRIDAY WARRANT THE MENTION OF MESOCYCLONES THAT COULD PRODUCE
ISOLATED TORNADOES. A HIGH PWAT AIR MASS...WITH A POSSIBLE MCV OR
TWO PASSING SLOWLY OFF TO THE EAST-NORTHEAST...STRENGTHENS THE
ARGUMENT FOR MENTIONING LOCALIZED HEAVY RAINFALL. PER THE SATURATED
SOILS FROM RECENT RAINFALL...ANY HEAVY RAIN THAT FALLS GENERALLY
ALONG AND SOUTH OF THE I-10 CORRIDOR WILL SIGNIFICANTLY INCREASE
THE THREAT FOR FLASH FLOODING. PROG SOUNDINGS ARE DEPICTING MID-
LEVEL DRY AIR WITH A SOMEWHAT INVERTED-V STRUCTURE THAT WOULD
SIGNAL ANY BOWED LINE SEGMENT...OR SUBSEQUENT CONVECTIVE OUTFLOW...
GUSTING WINDS IN EXCESS OF 50 MPH. IF AND WHEN STRONG STORMS
AFFECT AN AREA...THE USUAL SUSPECTS OF FREQUENT LIGHTNING AND HAIL
WILL ALSO BE IN PLAY THROUGHOUT THE NEXT SEVERAL DAYS. THE MAIN
NEAR TERM FORECAST CHALLENGE WILL BE IN THE TIMING OF ONSET AND
LOCATION OF HIGHEST RAINFALL...ESPECIALLY WITH ROUND 2 ONCE THE
FIRST ROUND MOVES THROUGH AND STABILIZES THE ATMOSPHERE A BIT.

THE 5H TROUGH AXIS ROTATES ACROSS THE SOUTHERN PLAINS...WITH ITS
AXIS EAST OF THE REGION...ON SUNDAY. THUS...WITH THE IMPROVED
DOWNSTREAM UPPER LEVEL DIFFULENCE...THIS COMING WEEKEND MAY BE AS
WET (OR MORE WET) THAN THIS PREVIOUS WEEKEND AS A SERIES OF
DISTURBANCES FOLLOW ONE ANOTHER THROUGH A CONTINUED UNSEASONABLY
MOIST AND UNSTABLE SE TX ENVIRONMENT. THE GFS AND EURO SOLUTIONS
SIGNIFICANTLY DIVERGE EARLY NEXT WEEK. THE GFS DEVELOPS AND HOLDS
BACK AN UPPER BAJA REGION LOW WHILE THE EURO PROGRESSIVELY SWEEPS
A SHALLOW OPEN WAVE TROUGH ACROSS THE STATE TUESDAY INTO WEDNESDAY.
EITHER SCENARIO SUGGESTS AT LEAST LOW TO MODERATE POPS IN CLOSING
OUT THE PERIOD. MAXIMUM TEMPERATURES THROUGHOUT THE PERIOD WILL
RANGE IN THE UPPER 70S TO LOWER 80S...MAYBE LOW TO MID 70S ON
THOSE DAYS WITH LATE MORNING TO EARLY AFTERNOON CONVECTION. VERY
MILD MORNINGS PER HUMIDITY/OVERCAST...AVERAGE MID 60 TO LOW 70S.
31

&&

.MARINE...
A WEAK PRESSURE GRADIENT WILL GRADUALLY STRENGTHEN AS HIGH
PRESSURE OVER THE WESTERN GULF MOVES EAST AND LOW PRESSURE OVER
EASTERN COLORADO. ONSHORE WINDS WILL PREVAIL THROUGH SUNDAY NIGHT.
A COLD FRONT WILL CROSS THE COASTAL WATERS ON SUNDAY NIGHT WITH
OFFSHORE WINDS LINGERING THROUGH TUESDAY MORNING. A STRONG UPPER
LEVEL DISTURBANCE WILL TRIGGER SHRA/TSRA THURSDAY MORNING. SOME OF
THE STORMS WILL PRODUCE STRONG GUSTY WINDS AND MARINERS SHOULD
REMAIN ALERT FOR RAPIDLY CHANGE CONDITIONS THURSDAY MORNING. 43

&&

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      63  74  66  76  63 /  20  60  60  70  50
HOUSTON (IAH)              65  76  67  76  66 /  30  70  70  70  60
GALVESTON (GLS)            71  75  70  75  69 /  20  70  70  70  50

&&

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

$$

DISCUSSION...31/43


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