Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 210447
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1147 PM CDT MON APR 20 2015

.AVIATION...
FOR THE 21/06Z TAFS...WILL BE KEEPING VFR CONDITIONS TONIGHT THROUGH
TOMORROW EVENING WITH GRADUALLY LOWERING CEILINGS. MODELS ARE BEGINNING
TO INDICATE MVFR LEVELS POSSIBLE TOMORROW EVENING...BUT FOR NOW WILL
HOLD OFF ON THAT HAPPENING UNTIL TOMORROW NIGHT. WITH LIGHT WINDS AND
INCREASING LOW LEVEL MOISTURE...COULD EVEN SEE SOME IFR CEILINGS DEVELOP
BEFORE SUNRISE ON WEDNESDAY MORNING. AND FOR THE WINDS...MADE LITTLE
CHANGE TO THE PREVIOUS TAF PACKAGE. SURFACE HIGH PRESSURE CENTERED TO
THE N AND NE OF THE AREA TONIGHT WILL MOVE OFF TO THE EAST TOMORROW.
THIS WILL ALLOW FOR THE LIGHT WINDS TONIGHT TO INCREASE TOMORROW AND
BE MORE OUT OF THE EAST AND SOUTHEAST. STILL THINK THAT THE AREA`S NEXT
BEST SHOT OF SEEING SOME SHRA/TSRA BACK IN THE TAFS COULD POSSIBLY BE
SOME TIME ON WEDNESDAY.  42
&&

.PREV DISCUSSION... /ISSUED 941 PM CDT MON APR 20 2015/

UPDATE...
EVENING FORECAST UPDATE.

DISCUSSION...
STILL A FAIRLY STRONG SOUTHERN JET STREAM OVER THE REGION WHICH
HAS BEEN PRODUCING SOME HIGH LEVEL RADAR RETURNS. DOUBT ANY OF THE
PRECIPITATION IS HITTING THE GROUND. HIGH CLOUDS WILL BE
THICKENING OVER THE REGION TONIGHT BASED ON WATER VAPOR/IR
SATELLITE IMAGERY. MIN TEMPS MAY NOT GET QUITE AS COOL AS FORECAST
BUT THINK FORECAST IS CLOSE ENOUGH. OVERALL NO REAL CHANGES IN THE
FORECAST AS IT LOOKS ON TRACK.

39

PREV DISCUSSION... /ISSUED 344 PM CDT MON APR 20 2015/

DISCUSSION...
AN AREA OF HIGH PRESSURE AT THE SURFACE HAS BROUGHT A PLEASANT DAY
ACROSS SOUTHEAST TEXAS. PARTLY TO MOSTLY CLOUDY SKIES HAVE BEEN
COMPLIMENTS OF THE SUBTROPICAL JET MOVING HIGH LEVEL CLOUDINESS
OVERHEAD. THE WEST-SOUTHWESTERLY PATTERN ALOFT WILL PERSIST
THROUGH THE UPCOMING WEEKEND.

THE SURFACE HIGH WILL MOVE EAST OF THE AREA AND ONSHORE WINDS
WILL RETURN LATE TOMORROW. A WEAK DISTURBANCE ALOFT WILL FIRST
BRING A SLIGHT CHANCE FOR THUNDERSTORMS OVER THE NORTHERN COUNTIES
DURING THE AFTERNOON AND EARLY EVENING. BOTH THE TEXAS TECH WRF
AND THE NAM12 AGREE WITH THIS SCENARIO. A MODEL CONSENSUS ALSO
BRINGS CHANCES OF RAIN TO THE OFFSHORE WATERS AS WELL. EXPECT
SLIGHTLY BETTER RAIN AND THUNDERSTORM CHANCES ON WEDNESDAY WITH
BETTER ONSHORE FLOW. THE GFS MODEL PW/S APPROACH 1.9 INCHES OVER
THE SOUTHERN THIRD OF THE FORECAST AREA ON WEDNESDAY AS WELL.

A DEEPENING UPPER LEVEL TROUGH OVER THE SOUTHERN ROCKIES INTO
WESTERN MEXICO WILL THEN PROVIDE A DOWNSTREAM RIDGE OVER THE STATE
LATE ON WEDNESDAY INTO THURSDAY. THIS SHOULD PROVIDE FOR A MORE
SUBSIDENT FLOW ALOFT AND LESS CHANCES FOR DAYTIME RAIN AND
THUNDERSTORMS. AS THE RIDGE MOVES OVERHEAD AND EAST ON THURSDAY
NIGHT AND FRIDAY...A DIFFLUENT FLOW ALOFT WILL COMBINE WITH A
SHORTWAVE TROUGH ON FRIDAY. MODEL PW/S ALSO APPROACH 2 INCHES ON
FRIDAY...AND AM EXPECTING MORE WIDESPREAD SHOWERS AND
THUNDERSTORMS.

ANOTHER LESS POTENT UPPER LEVEL SYSTEM MOVES OVERHEAD LATE SUNDAY
INTO MONDAY. HOWEVER...BOTH THE GFS AND ECMWF DIFFER FOR MONDAY.
AM LEANING TOWARD THE ECMWF GIVEN THAT THE GFS IS MOVING A COLD
FRONT OFF THE COAST EARLY ON MONDAY WHILE THE ECMWF MOVING A
WEAKER FRONT THROUGH LATE ON MONDAY AND INTO THE MONDAY NIGHT
PERIOD.

40

CLIMATE...
JUST ISSUED A PUBLIC INFORMATION STATEMENT FOR THE RAINFALL
THROUGH APRIL 19TH. TO SUMMARIZE...ALL OF THE CLIMATE SITES HAVE
REPORTED ABOVE NORMAL RAINFALL TO DATE...WITH ALL NOW REPORTING
ABOVE NORMAL RAINFALL FOR THE YEAR-TO-DATE. HERE IS A SUMMARY
TABLE FOR THE FIRST- AND SECOND-ORDER SITES.

                       RAINFALL FOR APRIL   YEAR-TO-DATE RAINFALL
SITE                    TOTAL   DEPARTURE     TOTAL    DEPARTURE

CITY OF HOUSTON         6.40      +3.91       16.57      +4.09
GALVESTON               4.51      +2.44       18.34      +6.34
HOBBY AIRPORT           8.07      +5.84       20.20      +7.69
COLLEGE STATION         2.36      +0.82       15.60      +4.80
CONROE                  2.20      +0.82       12.17      +0.56
HUNTSVILLE              4.68      +2.76       17.73      +5.52
DW HOOKS AIRPORT        5.93      +3.83       16.19      +3.92
SUGAR LAND              8.67      +6.44       17.85      +5.55
ANGLETON                2.95      +1.34       15.94      +3.47
PALACIOS                3.02      +2.36       10.70      +1.32
CLOVER FIELD            4.39      +2.17       16.30      +3.65

40

MARINE...
SHOULD BE ABLE TO DROP THE CAUTION FLAGS OFFSHORE LATE THIS
AFTERNOON OR EARLY EVENING AS SPEEDS CONTINUE TO SLIGHTLY
DIMINISH. WINDS WILL SWING AROUND TO THE EAST AND REMAIN AROUND
15KT FOR MOST OF THE WATERS TUE. MAY BE BORDERLINE CAUTION
CRITERIA AT TIMES BEFORE 2 PM. OTHERWISE...WINDS WILL CONTINUE TO
VEER BACK TO THE SE BY MIDWEEK AND GENERALLY REMAIN IN THE 10-15KT
RANGE FOR THE REMAINDER OF THE WORK WEEK WITH SEAS MAINLY 4FT OR
LESS. 47

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      54  78  64  82  69 /  10  20  10  30  30
HOUSTON (IAH)              58  79  65  81  70 /   0  10  10  30  30
GALVESTON (GLS)            67  77  71  80  72 /  10  10  10  20  20

&&

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

$$

DISCUSSION...39
AVIATION/MARINE...42



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