212  
FXUS64 KHGX 272055  
AFDHGX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX  
355 PM CDT THU APR 27 2017  
   
SHORT TERM
 
 
TODAY'S NICE WEATHER WITH LOW HUMIDITY AND MOSTLY CLEAR SKIES WILL  
COME TO AN END TONIGHT AND TOMORROW. SOUTHERLY WINDS ARE ALREADY  
DEVELOPING ACROSS SE TEXAS BASED ON LATEST SURFACE ANALYSIS. DEEP  
GULF MOISTURE IS NOT FAR AWAY AND SHOULD RETURN TONIGHT. SHORT  
TERM GUIDANCE SHOWS TEMPERATURES FALLING AFTER SUNSET BUT MAY  
ACTUALLY WARM OVERNIGHT AS MOISTURE RETURN INCREASES. LOW  
TEMPERATURES IN THE 60S WILL BE COMMON BUT EVEN LOW 70S WILL BE  
POSSIBLE ALONG THE COAST. PATCHY FOG MAY ALSO DEVELOP TONIGHT WITH  
THE INCREASE IN MOISTURE.  
 

 
   
LONG TERM
 
 
MAIN FOCUS OF THE FORECAST UPDATE WAS ON SATURDAY AND SUNDAY WITH  
A DEEP TROUGH DEVELOPING OVER THE SOUTHERN PORTIONS OF THE 4  
CORNERS REGION. MODELS SHOW THIS UPPER LOW MOVING TOWARDS TEXAS  
PANHANDLE AND SOUTHERN PLAINS BY 12Z SUNDAY. GFS/NAM SEEM 3-6 HRS  
FASTER WITH THE TROUGH THAN THE ECMWF/CMC. A COLD FRONT ASSOCIATED  
WITH THE SYSTEM SHOULD PUSH INTO SE TEXAS 00-03Z SUNDAY, ABOUT 12  
HOURS IN ADVANCE OF ANY STRONG PVA OR LARGE SCALE ASCENT. FRONTAL  
FORCING MAY BE ENOUGH TO GET A STRONG OR SEVERE STORM TO DEVELOP  
LATE EVENING THROUGH THE OVERNIGHT. MODELS ALL MAINTAIN WEAK  
CAPPING IF ANY WHICH EXPERIENCE SAYS THE ELEVATED MIXED LAYER WILL  
BE STRONGER THAN FORECAST. ALSO VERY FEW MODELS ARE ACTUALLY  
PRODUCING STORMS DURING THE DAY SATURDAY SUGGESTING THE CAP  
HOLDING. BY SATURDAY NIGHT, INSTABILITY SHOULD BE DECREASING WITH  
LOSS OF HEATING AND WITHOUT STRONG COOLING ALOFT SINCE UPPER  
DYNAMICS ARE OUT OF PHASE WITH THE SURFACE FORCING, THE SEVERE  
THREAT MAY END UP BEING MORE ISOLATED. SPC HAS ELEVATED/SLIGHT  
RISKS FOR THE AREA WHICH IF A STORM FORMS IN THE ENVIRONMENT, IT WOULD  
LIKELY BECOME SEVERE WITH HAIL/WIND THREATS. TORNADO THREAT WILL  
BE HAMPERED BY THE LACK OF STRONG UPPER LEVEL WINDS WHICH ONLY  
INCREASE AFTER 06Z SUNDAY (OUT OF PHASE UPPER TROUGH FINALLY  
MAKING ITS PRESENCE FELT). THIS MEANS DEEP LAYER SHEAR MAY NOT BE  
STRONG ENOUGH TO SUPPORT ROTATING UPDRAFTS. LOW LEVEL SHEAR MAY  
SUPPORT SOME ROTATION BUT OVERALL HELICITY VALUES ARE ONLY  
BORDERLINE SUPPORTIVE OF ROTATION. STORM MODE WILL BE ANOTHER  
ISSUE AND EXPECT LINEAR CONVECTION TO FORM ALONG THE FRONT. THERE  
MIGHT BE A STRONG ENOUGH SQUALL LINE TO BRIEFLY SUPPORT WIND/HAIL  
THREATS BUT THE CONVECTION WILL BE FIGHTING LACK OF INSTABILITY  
AND CAPPING. THERE IS JUST ENOUGH FACTORS THAT SUPPORT SEVERE  
WEATHER THAT IT DESERVES MENTION AND NO LET OUR GUARD DOWN.  
 
MOISTURE WILL BE INCREASING SO THERE MAY BE A LOCALLY HEAVY  
RAINFALL THREAT. THIS APPEARS TO BE MORE NORTH OF HOUSTON WHERE  
THERE WILL BETTER FORCING. ALSO MODELS SHOW MAIN MOISTURE AXIS  
SHIFTING EAST SATURDAY NIGHT WITH ONLY ENOUGH MOISTURE CONVERGENCE  
ALONG THE FRONT TO INCREASE PRECIPITABLE WATER VALUES. PWAT VALUES  
OF 1.8-2 INCHES IS NOTHING TO SNEEZE AT, BUT WITH STORMS EXPECTED  
TO BE MOVING ALONG A COLD FRONT THE FLOOD THREAT LOOKS RATHER  
SMALL AT THIS TIME FOR MUCH OF SE TEXAS. WHERE STORMS CAN TRAIN  
ALONG THE FRONT AS THEY MOVE NE ALONG IT LIKE IN NE TEXAS INTO  
LOUISIANA, FLOODING WILL BE MORE LIKELY. OVERALL LOOKING AT 1-2  
INCHES OF RAINFALL FOR THE NORTHERN THIRD OF THE FORECAST AREA AND  
LESS THAN AN INCH FOR MUCH OF THE AREA.  
 
THE COLD FRONT PUSHES THROUGH OFF THE COAST SUNDAY MORNING WHICH  
WILL PROVIDE A GOOD COOL DOWN FOR SUNDAY THROUGH TUESDAY. TUESDAY  
SOUTHERLY RETURN FLOW RAMPS UP AGAIN AHEAD OF THE NEXT UPPER LEVEL  
SYSTEM CRASHING DOWN THROUGH THE ROCKIES INTO THE PLAINS. MODELS  
SHOW STRONG MOISTURE RETURN ON WEDNESDAY SO INCREASE RAIN CHANCES  
FOR THE AREA. COLD FRONT SHOULD PUSH THROUGH WEDNESDAY NIGHT INTO  
THURSDAY. THIS WILL LIKELY BE THE NEXT TIME FRAME TO MONITOR FOR  
SEVERE WEATHER AND PERHAPS HEAVY RAINFALL.  
 
OVERPECK  
 

 
   
MARINE
 
 
WINDS OVER THE COASTAL WATERS ARE CONTINUING TO SHIFT TO THE E/SE  
THIS AFTERNOON AS THE SURFACE HIGH MOVES FURTHER EAST. AN ONSHORE  
FLOW IS EXPECTED TO BE IN PLACE AREAWIDE THIS EVENING WITH SPEEDS  
PICKING UP OVERNIGHT. HAVE ISSUED AN SCEC FOR THE OFFSHORE WATERS  
FOR AFTER MIDNIGHT AND THIS COULD BE EXPANDED TO INCLUDE THE NEAR-  
SHORE WATERS BY TOMORROW MORNING. SMALL CRAFT ADVISORIES MIGHT BE  
NEEDED BY TOMORROW AFTERNOON AS THE PRESSURE GRADIENT TIGHTENS IN  
RESPONSE TO DEEP LOW PRESSURE OVER SOUTH TX. THE LOW WILL MOVE NE  
AND DRAG ANOTHER COLD FRONT ACROSS SE TX BY EARLY SUN MORNING. AN  
ABRUPT WIND SHIFT TO THE NNW IS EXPECTED IN THE WAKE OF THE FRONT  
AND ANOTHER SCA WILL LIKELY BE REQUIRED ON SUN. A LIGHT/MODERATE  
ONSHORE FLOW WILL PREVAIL MON/TUES.  
 
WILL NEED TO KEEP AN EYE ON ELEVATED WATER LEVELS AND RISK OF RIP  
CURRENTS GOING INTO THE WEEKEND. TIDE LEVELS COULD POTENTIALLY EX-  
CEED 3.5 FEET AROUND HIGH TIDE EARLY SAT MORNING. A COASTAL FLOOD  
WATCH OR ADVISORY MAY BE REQUIRED LATE FRI NIGHT INTO EARLY SAT.  
41  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
COLLEGE STATION (CLL) 81 68 91 75 87 / 0 10 10 20 30  
HOUSTON (IAH) 83 70 90 77 85 / 0 10 10 20 30  
GALVESTON (GLS) 75 72 84 77 83 / 0 10 10 20 30  
 

 
   
HGX WATCHES/WARNINGS/ADVISORIES
 
 
TX...NONE.  
GM...SMALL CRAFT SHOULD EXERCISE CAUTION FROM 1 AM CDT FRIDAY THROUGH  
FRIDAY MORNING FOR THE FOLLOWING ZONES: WATERS FROM  
FREEPORT TO THE MATAGORDA SHIP CHANNEL FROM 20 TO 60 NM...  
WATERS FROM HIGH ISLAND TO FREEPORT FROM 20 TO 60 NM.  
 

 
 

 
 
DISCUSSION...39  
AVIATION/MARINE...41  
 
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