Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 281144
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
644 AM CDT TUE APR 28 2015

.DISCUSSION...
SEE THE AVIATION DISCUSSION BELOW.

40

&&

.AVIATION...
GENERALLY MVFR CEILINGS WILL HANG AROUND FOR MOST OF THE DAY AS AN
UPPER LEVEL LOW PRESSURE AREA OVER NORTH TEXAS SLOWLY MOVES
EASTWARD. MODEL SOUNDINGS FORECAST A GRADUAL LIFTING OF THE
CEILINGS AND POSSIBLY SCATTERING OUT THE DECK LATER THIS EVENING.
WENT WITH THIS GENERAL SCENARIO IN THE PACKAGE.

THE WIND SPEEDS WILL BE THE OTHER ISSUE. GUIDANCE WAS SPLIT
BETWEEN STRONGER WINDS IN THE GFS AND SLIGHTLY LIGHTER CONDITIONS
IN THE NAM. DECIDED TO LEAN TOWARD THE NAM GUIDANCE WITH THE
CAVEAT THAT GUSTY WINDS TO AROUND 20 KNOTS MAY DEVELOP DURING THE
AFTERNOON.

40

&&

.PREV DISCUSSION... /ISSUED 355 AM CDT TUE APR 28 2015/

DISCUSSION...
THE LARGE UPPER-MID LEVEL LOW IS BECOMING SLIGHTLY SHEARED AS IT
ROTATES PARALLEL TO THE RED RIVER VALLEY AND IS PROGGED BY THE
NWP GLOBAL MODEL ENSEMBLE TO BE OVER THE ARKLATEX BY SUNSET
TONIGHT. AN UNSEASONABLY COLD AND DRY AIR MASS (AROUND 2 STD DEV
I.R.T. MID-LEVEL COOLING) IS DESCENDING UPON THIS UPPER LOW`S
WESTERN FLANK...WITH THE SOUTHERN EXTENT OF THE AIR MASS THE COLD
FRONT THAT WILL BE ADVANCING SOUTH TO THE COAST OVER THE NEXT FEW
HOURS...THE BOUNDARY TO BE WELL OFFSHORE BY LATE MORNING. THE
GENERAL SYNOPTIC SOUTHERN PLAINS FLOW PATTERN WILL BECOME MORE
NORTH AND WEST AS TEXAS FALLS BETWEEN RETREATING EASTERN TROUGHING
AND AMPLIFYING WESTERN CONUS RIDGING. THIS DRY AND STABLE PATTERN
WILL PERSIST FOR THE REMAINDER OF THE WEEK.

LINGERING CLOUD COVER UNDER THE POST-FRONTAL INVERSION...IN
TANDEM WITH COLD AIR ADVECTION...WILL REGULATE TODAY`S WARMTH TO
ONLY THE UPPER 60S TO NEAR 70F. COMBINE THIS LATE SEASON CAA WITH
A NEAR 15 MB OFFSHORE PRESSURE GRADIENT CREATED BY A DESCENDING
1025 MB CENTRAL PLAINS HIGH AND THE GENERATION OF A FRESH NEAR 15
KT SUSTAINED NORTH WIND WILL BE THE RESULT. AS EVIDENCED BY UPPER
40 DEW POINT AIR SPILLING INTO THE STATE THIS MORNING...THE ONCE
OVERLY-SATURATED RESIDENT AIR MASS WILL TRANSITION TO A MUCH DRIER
ONE THROUGH THE DAY...BEST REALIZED BY THIS TIME TOMORROW MORNING
AS MINIMUM TEMPERATURES FALL INTO THE MEAN LOWER 50S (OR ABOUT 10
DEGREES BELOW NORMAL LATE APRIL STANDARDS). A DRY REINFORCING
FRONTAL PASSAGE WEDNESDAY AS WESTERN HIGH PRESSURE BUILDS IN AND
FORTIFIES THE TAUNT OFFSHORE GRADIENT...WITH MORE MID-WEEK SUN TO
WARM WEDNESDAY PM INTO THE LOWER TO MIDDLE 70S. HIGH PRESSURE AT
THE SURFACE AND UPPER SOUTHWESTERN U.S.-BASED RIDGING THROUGH THE
END OF THE WEEK WILL GUARANTEE SUBSEQUENT DAY WARMING BACK INTO
THE LOWER 80S BY THE WEEKEND WITH CONTINUED LOW TO NIL POPS. LATE
WEEK EASTERN TEXAS HIGH PRESSURE TRANSITIONING EAST WILL ALLOW
RETURN FLOW TO RE-DEVELOP BY FRIDAY AFTERNOON. THE REGION WILL
STILL BE THE GRIP OF UPPER RIDGING NEXT WEEKEND. THIS EQUATES TO
NEAR NORMAL EARLY MAY CONDITIONS....MANAGEABLE HUMIDITIES AND ONLY
SLIGHT RAIN CHANCES PER WEAK DISTURBANCE PASSAGES AS UPPER-MID
RIDGING BEGINS TO BREAK DOWN ABOUT A WEEK FROM NOW. 31

MARINE...
A COLD FRONT WILL MOVE OFF THE COAST LATER THIS MORNING AND USHER
MODERATE TO STRONG OFFSHORE WINDS IN ITS WAKE. SMALL CRAFT ADVISORY
CONDITIONS SHOULD DEVELOP BETWEEN 9 AM AND NOON OVER MOST OF THE
GULF WATERS...AND POSSIBLY OVER MATAGORDA BAY. THESE CONDITIONS ARE
EXPECTED TO DIMINISH LATE TONIGHT AND WEDNESDAY...ALTHOUGH THE
OFFSHORE WATERS BEYOND 20 NM MAY SEE WIND SPEEDS AROUND ADVISORY
LEVELS THROUGH WEDNESDAY AFTERNOON. 40

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      66  50  72  52  77 /  20   0   0   0   0
HOUSTON (IAH)              70  50  74  53  79 /  20   0   0   0   0
GALVESTON (GLS)            73  57  71  62  75 /  20   0   0   0   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION THROUGH THIS EVENING FOR THE
     FOLLOWING ZONES: GALVESTON BAY...MATAGORDA BAY.

     SMALL CRAFT ADVISORY UNTIL 7 AM CDT WEDNESDAY FOR THE FOLLOWING
     ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL
     20 NM TO 60 NM...WATERS FROM FREEPORT TO THE MATAGORDA SHIP
     CHANNEL OUT 20 NM...WATERS FROM HIGH ISLAND TO FREEPORT 20
     TO 60 NM...WATERS FROM HIGH ISLAND TO FREEPORT OUT 20 NM.

&&

$$

DISCUSSION...14
AVIATION/MARINE...40



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