Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 221714
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1214 PM CDT FRI MAY 22 2015

.DISCUSSION...
SEE THE 18Z AVIATION DISCUSSION BELOW.

40

&&

.AVIATION...
THE WARM FRONT WAS ALONG OR JUST INLAND OF THE COAST AT 17Z...
ALTHOUGH THE FRONT DID SWING INLAND FROM NEAR FREEPORT THROUGH
COLUMBUS. THE 12Z NAM12 MODEL PUSHES THE FRONT INLAND DURING THE
EARLY AND MID AFTERNOON PERIOD. IFR CONDITIONS TO THE NORTH OF THE
FRONTAL BOUNDARY WILL LIKELY LIFT AS THE FRONT MOVES THROUGH ANY
PARTICULAR SITE. BEST RAIN CHANCES WILL LIKELY BE AT KCLL BY MID
AFTERNOON AS WELL.

FOR TONIGHT...MVFR CONDITIONS WILL DEVELOP TONIGHT OVER MOST OF
THE INLAND SITES. ALONG THE COAST THE MODEL WAS ADVERTISING MORE
VFR CONDITIONS. THE NAM12 WAS ALSO FORECASTING RAIN CHANCES
SATURDAY AFTERNOON.

40

&&

.PREV DISCUSSION... /ISSUED 1038 AM CDT FRI MAY 22 2015/

UPDATE...
SEE MORNING UPDATE.

DISCUSSION...
AT 9 AM...A WEAK FRONTAL BOUNDARY EXTENDED ACROSS THE NORTH
CENTRAL GULF TOWARD VICTORIA AND THEN ACROSS SOUTH CENTRAL TEXAS.
THE FRONT WAS ACTING MORE LIKE A WARM FRONT OVER TEXAS AS SFC DEW
PTS HAVE CLIMBED BACK INTO THE MID 70S WITH HIGH TEMPS SOUTH OF
THE BOUNDARY NEAR 80...AND NORTH OF THE BOUNDARY...TEMPS ARE IN
THE MID 60S. MOISTURE IS PLENTIFUL AT BOTH 850 AND 700 MB WITH 850
MB DEW PTS NEAR 15 C. A WEAK 850 MB TROUGH AXIS EXTENDED N-S
ACROSS EAST TEXAS INTO DEEP SOUTH TEXAS. AT 300 MB...UPPER LEVEL
WINDS REMAIN DIVERGENT WITH A WEAK SPEED MAX OVER NORTHERN MEXICO.
SURFACE CONVERGENCE APPEARS TO BE STRONGEST OVER THE SW ZONES
ALONG THE DEVELOPING WARM FRONT. CONVECTIVE TEMPS ARE AROUND 82
DEGREES AT CRP...85 DEGREES AT LCH AND 89 DEGREES AT SHV. WILL
MAINTAIN HIGHER POPS OVER THE W-SW ZONES TODAY DUE TO THE
PROXIMITY OF THE 850 TROUGH AXIS...DEEPER LOW LEVEL MSTR...THE
NORTHWARD MOVING BOUNDARY...LOW CONVECTIVE TEMPS AND THE
APPROACHING SPEED MAX. TEMPS ARE TRICKY WITH THE COOL START AND
CLOUD COVER. TRENDED TEMPS A LITTLER COOLER OVER THE EAST CENTRAL
ZONES AND BUMPED TEMPS UP A LITTLE OVER THE SW ZONES. AT 10
AM...TEMPS WERE 77 AT PALACIOS AND 63 AT HUNTSVILLE SO QUITE A
CONTRAST THIS MORNING.  43

PREV DISCUSSION... /ISSUED 650 AM CDT FRI MAY 22 2015/

AVIATION...
FOR THE 12Z TAFS... VARIED FLIGHT CONDITIONS IN PLACE THIS MORNING
/LIFR TO VFR CEILINGS/ WILL IMPROVE TO VFR BY THIS AFTERNOON AS A
WARM FRONT LIFTS NORTH. EXPECT SHOWERS AND THUNDERSTORMS
TO FORM ALONG THIS FEATURE BUT SOME UNCERTAINTY EXISTS ON
COVERAGE AND WHERE BEST HEATING WILL OCCUR. MOST LIKELY AREAS FOR
IMPACTS APPEAR TO BE WEST AND SOUTHWEST OF THE INTERSTATE 45
CORRIDOR THIS AFTERNOON BUT CONFIDENCE IS NOT HIGH ENOUGH TO
INCLUDE MORE THAN VCSH/VCTS MENTIONS ATTM. AS WARM FRONT LIFTS...
EXPECT EASTERLY WINDS TO BECOME SOUTHEASTERLY AND REMAIN GENERALLY
AT OR UNDER 10 KNOTS /WITH SLIGHTLY HIGHER WINDS AT GALVESTON/.
CEILINGS EXPECTED TO DETERIORATE TO AT LEAST MVFR AGAIN OVERNIGHT.

HUFFMAN

PREV DISCUSSION... /ISSUED 501 AM CDT FRI MAY 22 2015/

SHORT TERM...
TODAY THROUGH SATURDAY.

MORNING SURFACE ANALYSIS SHOWS YESTERDAY/S COLD FRONT DRAPED FROM
THE TEXAS COASTAL BEND EASTWARD TO THE FLORIDA PANHANDLE... WITH
AN EXPANSIVE SURFACE RIDGE SLIDING INTO THE SOUTHERN PLAINS. THE
COLD FRONT IS EXPECTED TO LIFT NORTH AS WARM FRONT TODAY AS THE
SURFACE RIDGE SHIFTS OVER EASTERN CONUS... WITH THE FRONT SLOWLY
CLIMBING NORTH THROUGHOUT THE DAY /REACHING THE PINEY WOODS REGION
SATURDAY MORNING/. EXPECT SHOWER AND THUNDERSTORM ACTIVITY TODAY
TO PRIMARILY BE CONCENTRATED ALONG THIS FEATURE WITH COVERAGE
INCREASING WITH A BIT WITH SURFACE HEATING. CONVECTIVE
TEMPERATURES ARE GENERALLY AROUND 80 DEGREES F THIS AFTERNOON AND
THE MAIN INHIBITOR TO REACHING THESE TEMPERATURES WILL BE CLOUDS
/COURTESY MOISTURE TRAPPED UNDERNEATH A FRONTAL INVERSION/. RH
PROGS DO SHOW SOME LOW LEVEL DRIER AIR WORKING ITS WAY OVER THE
AREA AROUND THE SURFACE RIDGE... AND THIS SHOULD ALLOW FOR ENOUGH
BREAKS IN THE CLOUDS TO ALLOW HIGH TEMPERATURES TO REACH THE LOW
80S. OTHERWISE... CARRYING THE HIGHEST POPS OVER THE WESTERN AND
SOUTHWESTERN ZONES WHERE FRONT WILL LIFT FARTHER INLAND.

RAIN WILL TAPER OFF OVERNIGHT WITH LOSS OF DAYTIME HEATING BUT
ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE AGAIN
ON SATURDAY AS SMALLER WAVES AHEAD OF THE UPPER LOW OVERSPREAD THE
REGION ON SATURDAY. WITH BETTER INSTABILITY IN PLACE SATURDAY
AFTERNOON /SBCAPE VALUES 2500-3000 J/KG/ AND FORECAST SOUNDINGS
SHOWING AN INVERTED-V SIGNATURE... COULD SEE A STRONG STORM OR TWO
NORTH OF THE HIGHWAY 59 CORRIDOR BUT WITH 0-6 KM BULK SHEAR VALUES
AROUND 20 TO 25 KNOTS STORMS WILL STRUGGLE TO MAINTAIN
ORGANIZATION. MAIN THREAT WITH ANY ACTIVITY THAT DEVELOPS DOES
APPEAR TO BE HEAVY RAINFALL WITH PRECIPITABLE WATER VALUES AROUND
1.8 TO 1.9 INCHES.

14

MARINE...

UNSETTLED WEATHER WILL PREVAIL ACROSS THE BAYS AND COASTAL WATERS
THROUGH MEMORIAL DAY WEEKEND WITH SHOWERS AND THUNDERSTORMS OVER
THE COASTAL WATERS PROVIDING PERIODS OF HEAVY RAIN... INCREASED
RIP CURRENT RISK WITH ELEVATED ONSHORE FLOW... AND SMALL CRAFT
ADVISORY CONDITIONS EXPECTED OVER PARTS OF THE WEEKEND AND INTO
THE NEXT WEEK.

A COLD FRONT LOCATED OFF THE UPPER TEXAS COAST AS OF 3 AM CDT
WILL LIFT NORTH TODAY AS A WARM FRONT WITH WINDS BECOMING EASTERLY
IN ITS WAKE... RESULTING IN SOME SLIGHTLY ABOVE NORMAL TIDES
BEFORE VEERING TO THE SOUTHEAST BY SATURDAY AFTERNOON AND THEN
SOUTH IN RESPONSE TO AN EJECTING LEE SURFACE LOW OVER THE HIGH
PLAINS. SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ALONG
THIS BOUNDARY TODAY... WITH ANOTHER ROUND POSSIBLE ON SATURDAY. AN
INCREASING SURFACE PRESSURE GRADIENT IN RESPONSE TO THE SYSTEM
OVER THE HIGH PLAINS WILL ALSO RESULT IN ELEVATED WINDS /20 TO 25
KNOTS/ OVER THE MARINE ZONES BY SATURDAY EVENING... WITH SEAS
BUILDING ACCORDINGLY /REACHING 7 TO 8 FEET/. THIS WILL CREATE
CHALLENGING CONDITIONS FOR SMALL CRAFT OVER THE REMAINDER OF THE
MEMORIAL DAY WEEKEND AND MARINERS ARE ADVISED TO CHECK CURRENT AND
FORECAST CONDITIONS BEFORE ANY OUTING... AS SMALL CRAFT ADVISORIES
MAY BE NEEDED AS EARLY AS SATURDAY EVENING. ADDITIONALLY...
INCREASING WINDS WILL ALSO PROMOTE AN INCREASING RIP CURRENT RISK
ALONG THE UPPER TEXAS COAST. THUNDERSTORM CHANCES WILL PERSIST
SUNDAY INTO MONDAY AS A POTENT UPPER LEVEL SYSTEM CROSSES THE
GREAT PLAINS... WITH A THUNDERSTORM COMPLEX POSSIBLY CROSSING INTO
THE COASTAL WATERS LATE SUNDAY INTO EARLY MONDAY.

DETERIORATED CONDITIONS ARE EXPECTED TO PERSIST THROUGH THE REMAINDER
OF THE WEEKEND... WITH SOME IMPROVEMENT POSSIBLE IN THE TUESDAY/WEDNESDAY
TIMEFRAME AS WIND SPEEDS DECREASE AS THE GRADIENT RELAXES.

14

LONG TERM...
SATURDAY NIGHT THROUGH THURSDAY.

AN ACTIVE HEAVY RAIN PERIOD LIES AHEAD. SATURDAY NIGHT A 4
CORNERS LOW WILL BE DRIFTING THROUGH COLORADO AS SSW FLOW ALOFT
STRENGTHENS ACROSS SETX. AN IMPRESSIVE DIVERGENCE SIGNATURE SETS
UP OVERHEAD WITH A S/W MOVING INTO THE REGION. THIS SHOULD BRING A
ROUND OF HEAVY RAIN TO THE REGION. LLJ STRENGTHENS FOR SUNDAY AND
FAST TRAINING STORMS LOOK LIKELY ACROSS THE AREA. SEVERE THREAT
MAY ALSO BE ON THE INCREASE FOR SUNDAY AS WELL WITH IMPRESSIVE LL
SHEAR. PERIODS OF HEAVY RAIN SPREAD ACROSS THE REGION SUNDAY NIGHT
AND MONDAY. THE INGREDIENTS OF UNUSUALLY HIGH PW
(1.9-2.1")/K-INDEX VALUES OF 32-38/CAPE OF 1800-3000J/KG DURING
THE DAYLIGHT HOURS/SRH 120-220 ALL PRESENT SATURDAY NIGHT THROUGH
TUESDAY. THE POTENTIAL FOR AN EXTENDED PERIOD OF HEAVY RAIN AND
FLOODING IS ON TAP PRIMARILY FROM AROUND 3 AM SUNDAY BEGINNING IN
THE WEST THEN SHIFTING AND EXPANDING EAST ACROSS THE ENTIRE REGION
SUNDAY BY LATE IN THE MORNING AND ON THROUGH MONDAY NIGHT. A
FLASH FLOOD WATCH WILL BE NEEDED AS WE GET CLOSER TO THE EVENT AND
MAINSTEM FLOODING ALSO A THREAT WITH THE WET GROUND AND THE
ALREADY ELEVATED RIVER LEVELS. SIGNIFICANT AVIATION IMPACTS WILL
BE ON TAP FROM TEXAS UP THROUGH AR INTO MO AND POSSIBLY EVEN
CHICAGO FOR THIS EVENT.

THE RAINS AND INTENSITY SHOULD TAPER DOWN LATE TUESDAY AS THE
UPPER TROUGH LIFTS OUT AND UPPER RIDGING TRIES TO TAKE HOLD ACROSS
MEXICO/TX. RAINS MAY BECOME MORE DIURNAL IN NATURE ON WEDNESDAY
NEEDING THE DAYTIME HEATING AND CONTINUING THROUGH THURSDAY. FOR
WHAT IT IS WORTH NEXT WEEKEND ALSO LOOKS WET BUT NOT WITH SUCH A
POTENT SYSTEM. THE ECMWF ALSO TRYING TO DEVELOP A TROPICAL SYSTEM
IN THE EAST PAC FOR AT LEAST 2 RUNS IN A ROW.

45

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      78  71  83  71  79 /  30  20  50  30  90
HOUSTON (IAH)              77  72  84  74  82 /  20  20  40  20  90
GALVESTON (GLS)            78  77  81  78  82 /  30  30  30  20  60

&&

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

$$

DISCUSSION...43
AVIATION/MARINE...40


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