743  
FXUS62 KRAH 161346  
AFDRAH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RALEIGH NC  
945 AM EDT TUE JUL 16 2019  
   
SYNOPSIS
 
 
A HOT, SUB-TROPICAL RIDGE ALOFT WILL REMAIN OVER THE SOUTHEASTERN US  
THROUGH WED. A TROUGH, INCLUDING THE SIGNIFICANTLY WEAKENED REMNANTS  
OF BARRY, WILL DRIFT ACROSS THE CENTRAL APPALACHIANS AND SOUTHERN  
MIDDLE ATLANTIC STATES WED NIGHT THROUGH THU NIGHT. THE SUB-TROPICAL  
RIDGE WILL THEN REDEVELOP NORTHWARD ACROSS THE CENTRAL APPALACHIANS  
AND VIRGNIAS THROUGH THE WEEKEND.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 945 AM TUESDAY...  
 
ONLY MINOR ADJUSTMENTS TO TEMPS, CLOUD COVER, AND POP TIMING WITH  
THIS ITERATION. HIGH THIN CLOUDS OVER THE AREA HAVE THINNED FURTHER  
THIS MORNING AND SHOULD ALLOW FOR PLENTY OF INSOLATION TODAY. CINH  
PERSISTS BUT IS QUICKLY DWINDLING, AND WITH ELEVATED MLCAPE ALREADY  
EXCEEDING 1000 J/KG OVER THE E HALF, WE SHOULD START DEVELOPING  
SURFACE-ROOTED CONVECTIVE TOWERS PRIOR TO NOON, PARTICULARLY IN THE  
E WHERE BOTH PW AND DEWPOINTS ARE A BIT HIGHER. WITH NO OBVIOUS  
FOCUS FOR CONVECTIVE INITIATION, WE'LL NEED TO CLOSELY WATCH FOR  
SUBTLE BOUNDARIES AND PERHAPS OLD OUTFLOWS THAT MAY ONLY REVEAL  
THEMSELVES WITH UNIFORM MIXING OVER THE NEXT COUPLE OF HOURS. GIVEN  
THIS, IT'S TOUGH TO DETERMINE EXACTLY WHERE THE BEST STORM CHANCES  
WILL BE, BUT HAVE MAINTAINED A BIT BETTER CHANCE E THAN W  
CONSIDERING THE GREATER MOISTURE DEPTH THERE. STILL EXPECT TEMPS TO  
PEAK IN THE MID-UPPER 90S, AS OBSERVED 850 MB TEMPS ARE WELL ABOVE  
NORMAL, IN THE 90TH PERCENTILE, AT GSO (~19C). PEAK HEAT INDICES  
WILL BE FIRMLY IN THE 102-105F RANGE IN THE E, A BIT LOWER W, SO NO  
CHANGES AT THIS TIME TO THE HEAT ADVISORY. -GIH  
 
PREVIOUS DISCUSSION FROM 345 AM: ANOTHER HEAT ADVISORY HAS BEEN  
ISSUED FOR THE NC COASTAL PLAIN AND ERN SANDHILLS FOR THIS  
AFTERNOON. NOTE THAT IN ADDITION TO THE EASTERN REGION DIRECTIVE FOR  
HEAT ADVISORY CRITERIA OF 105 DEGREES FOR TWO CONSECUTIVE HOURS OR  
MORE, WFO RAH'S POLICY IS ALSO FOR THREE OR MORE CONSECUTIVE DAYS OF  
102 TO 105 DEGREES. TODAY/TUESDAY WILL MARK THE SIXTH DAY OF (AT  
LEAST) THAT CRITERIA IN THE ADVISORY AREA.  
 
THE FORECAST WILL BE GENERALLY A PERSISTENCE ONE, WITH PERHAPS A  
SLIGHT INCREASE IN COVERAGE OF DIURNAL, PULSE CONVECTION THROUGH  
THIS EVENING.  
 
A SUBTROPICAL RIDGE --A STRONG ONE AT 594 DM AND 324 DM AT 500 MB  
AND 700 MB, RESPECTIVELY-- WILL REMAIN SITUATED OVER THE SERN US  
THROUGH TONIGHT. A MID LEVEL SHEAR AXIS THAT WAS DRAPED ACROSS SC  
AND SWRN NC DURING THE PAST 36 HOURS LEFT BEHIND A RELATIVE MAXIMUM  
IN MOISTURE AROUND 700 MB; AND THIS MOIST AXIS WILL DRIFT AROUND THE  
NRN PERIPHERY OF THE FOREGOING SUBTROPICAL RIDGE AND ACROSS CNTL NC  
AND VA THROUGH THIS EVENING.  
 
AT THE SURFACE, A LEE TROUGH WILL SHARPEN OVER THE PIEDMONT WITH  
DIURNAL HEATING, WHILE A ANOTHER WEAK CONVERGENCE AXIS/WIND SHIFT  
MAY LINGER OVER NERN NC/SERN VA, IN THE VICINITY OF THE WEAK FRONTAL  
ZONE THAT SETTLED INTO THAT REGION EARLY MONDAY, AND SINCE WEAKENED.  
 
A CONTINUED SLIGHT UPTICK IN LOW LEVEL MOISTURE/SURFACE DEWPOINTS  
WILL OCCUR TODAY, OWING TO A MORE-SLY/ONSHORE COMPONENT TO THE LOW  
LVL FLOW ACROSS THE CAROLINAS. WITH GENERALLY PERSISTENCE HIGH  
TEMPERATURES, THAT UPTICK IN LOW LEVEL MOISTURE WILL FAVOR HIGHER  
HEAT INDEX VALUES (THAN PREVIOUS DAYS) THROUGHOUT CNTL NC, WITH NEAR  
100 DEGREE READINGS CREEPING WWD ACROSS ALL BUT THE NRN AND NW  
PIEDMONT, AND WITH ANOTHER DAY OF 102 TO 107 DEGREES ACROSS THE  
ADVISORY AREA. THAT UPTICK IN LOW LVL MOISTURE, AND THE EWD DRIFT OF  
THE AFOREMENTIONED MID LEVEL MOIST AXIS, WILL FAVOR THE DEVELOPMENT  
OF ISOLATED TO LOCALLY SCATTERED PULSE CONVECTION THIS AFTERNOON,  
SOME OF WHICH MAY LINGER OVER MAINLY THE NE PIEDMONT AND NRN COASTAL  
PLAIN THROUGH MIDNIGHT. THE PRESENCE OF HIGH DCAPE VALUES, TO AS  
MUCH AS 1200-1400 J/KG, MAY SUPPORT A COUPLE OF EPISODES OF SEVERE  
WIND GUSTS.  
 
PERSISTENCE LOWS IN THE 70S, COOLEST WHERE EARLIER CONVECTION  
OCCURS.  
 

 
   
SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/
 
 
AS OF 410 AM TUESDAY...  
 
A MID AND UPR LOW OVER MO/AR THIS MORNING, AND WHICH INCLUDES THE  
REMNANTS OF BARRY, WILL DEVOLVE INTO AN OPEN WAVE, POSITIVELY-TILTED  
TROUGH THROUGH EARLY TONIGHT, THEN DRIFT EWD ACROSS THE NRN MIDDLE  
ATLANTIC AND CNTL APPALACHIANS WED THROUGH EARLY THU. WEAK MID LEVEL  
HEIGHT FALLS OF 10 TO PERHAPS 20 METERS, AND THE RIGHT ENTRANCE  
REGION OF A RELATED WEAK SWLY UPR JET STREAK, WILL CONSEQUENTLY  
OVERSPREAD CNTL NC LATE WED AFTERNOON AND WED NIGHT.  
 
AT THE SURFACE, THE APPALACHIAN-LEE TROUGH WILL AGAIN SHARPEN OVER  
THE PIEDMONT, WITH UPR 60S TO AROUND 70 DEGREES SURFACE DEWPOINTS TO  
THE WEST OF THAT TROUGH, AND LWR TO MIDDLE 70S ONES TO THE EAST.  
 
LOW LVL THICKNESS VALUES ARE FORECAST TO INCREASE BY ABOUT 5 METERS  
OVER THOSE OF MON AND FORECAST FOR TUE; AND THIS SHOULD TRANSLATE TO  
A DEGREE OR TWO HOTTER TEMPERATURES. WHEN COMBINED WITH SLIGHTLY  
HIGHER SURFACE DEWPOINTS THAN THOSE FORECAST FOR TUE, HEAT INDEX  
VALUES WILL LIKELY NEAR 105 DEGREES OVER ALL BUT THE NRN AND NWRN NC  
PIEDMONT, WITH 105-109 DEGREE VALUES COMMON IN THE COASTAL PLAIN AND  
ERN SANDHILLS. CONSEQUENTLY, THE HEAT ADVISORY AREA WILL LIKELY BE  
EXPANDED WWD TO INCLUDE AT LEAST ANOTHER TIER OF COUNTIES IN CNTL NC  
FOR WED.  
 
SCATTERED SHOWERS AND STORMS WILL AGAIN LOOSELY FOCUS IN THE  
LEE/PIEDMONT TROUGH, AND THE SEA BREEZE, WITH SUBSEQUENT  
DEVELOPMENT/OUTFLOW PROPAGATION THROUGHOUT CNTL NC THROUGH WED  
EVENING. SLIGHTLY GREATER COVERAGE MAY OCCUR OVER THE NWRN AND NRN  
PIEDMONT AFTER 6 PM, THEN CONTINUE THROUGH EARLY WED NIGHT, OWING TO  
THE BEST OVERLAP THERE OF THE INCOMING WEAK FORCING FOR ASCENT  
ACCOMPANYING THE SHORTWAVE TROUGH ALOFT WITH MAXIMUM DIURNAL  
HEATING. THE INFLUENCE OF THE SHORTWAVE TROUGH AND JET STREAK WILL  
ALSO YIELD EFFECTIVE BULK SHEAR VALUES IN THE 20-30 KT RANGE, WHICH  
MAY PROVIDE FOR MULTI-CELL STORM AND COLD POOL ORGANIZATION, AND  
STRONG TO MARGINALLY SEVERE WIND GUSTS.  
 
GENERALLY PERSISTENCE LOWS IN THE 70S.  
 

 
   
LONG TERM /THURSDAY THROUGH MONDAY/
 
 
AS OF 100 AM TUESDAY...  
 
STRONG MID AND UPPER LEVEL RIDGING WILL FOLLOW THE WEAK, REMNANT  
TROUGH THAT WAS BARRY LATE IN THE WEEK THROUGH THE WEEKEND. HOT  
TEMPERATURES WILL PREVAIL THURSDAY THROUGH SUNDAY, WITH SOME COOLING  
WITH INCREASED THUNDERSTORM AND ASSOCIATED CLOUDINESS BY SUNDAY AND  
MONDAY.  
 
AS THE WEAK MID/UPPER TROUGH (BARRY REMNANTS) PULLS OUT TO THE NE  
AND OFF THE NORTHERN MID-ATLANTIC COAST/NEW ENGLAND THURSDAY, THE  
HEIGHTS AGAIN RISE ALOFT THU-SAT LEADING TO A LARGE UPPER RIDGE OVER  
THE REGION AGAIN. THIS WILL LEAVE ONLY A WEAK SURFACE TROUGH, STRONG  
SURFACE HEATING, AND DAILY INTENSE INSTABILITY TO FOCUS ISOLATED TO  
WIDELY SCATTERED PM THUNDERSTORMS.  
 
DAILY HIGHS SHOULD REACH THE MID TO UPPER 90S, WITH LOWS IN THE 70S.  
HEAT INDICES OF 105-108 WILL BE LIKELY INTO THE WEEKEND.  
 
THE CHANCES OF MUCH NEEDED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO  
INCREASE BY SUNDAY INTO EARLY NEXT WEEK AS A PATTERN CHANGE TO LESS  
RIDGING AND MORE TROUGHING OVER THE REGION OCCURS. A COLD FRONT OR  
TWO SHOULD STALL OVER THE REGION DURING THIS TIME FRAME ACTING AS A  
FOCUS FOR CONVECTION.  
 

 
   
AVIATION /11Z TUESDAY THROUGH SATURDAY/
 
 
AS OF 655 AM TUESDAY...  
 
MAINLY VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. HOWEVER,  
WIDELY SCATTERED SHOWERS AND STORMS ARE EXPECTED TO DEVELOP WITH  
DIURNAL HEATING THIS AFTERNOON, BUT GIVEN A LACK OF FOCUSING  
MECHANISMS, SUCH DEVELOPMENT IS APT TO BE RANDOM AND WITH A  
PROBABILITY OF OCCURRENCE AT ANY GIVEN POINT ONLY AROUND 20 OR SO  
PERCENT.  
 
OUTLOOK: INCREASING MOISTURE AHEAD OF THE TROUGH ALOFT AND RELATED  
REMNANTS OF BARRY WILL PROVIDE A BETTER CHANCE OF MAINLY DIURNAL  
(AFTERNOON-EVENING) CONVECTION WED-FRI, AND ALSO PATCHES OF EARLY  
MORNING STRATUS.  
 

 
   
RAH WATCHES/WARNINGS/ADVISORIES
 
 
HEAT ADVISORY FROM NOON TODAY TO 7 PM EDT THIS EVENING FOR NCZ011-  
027-028-042-043-078-088-089.  
 

 
 

 
SYNOPSIS...MWS  
NEAR TERM...HARTFIELD/MWS  
SHORT TERM...MWS  
LONG TERM...BADGETT  
AVIATION...MWS  
 
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