Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 262017 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 417 PM EDT SAT JUL 26 2014 .SYNOPSIS... HIGH PRESSURE OFFSHORE WILL RIDGE BACK INTO THE CAROLINAS THROUGH MONDAY...CREATING VERY HOT AND HUMID CONDITIONS. A HEAT ADVISORY IS IN EFFECT FOR PORTIONS OF THE AREA SUNDAY...AND MAY BE NEEDED AGAIN ON MONDAY. AN UNUSUALLY STRONG COLD WILL CROSS ON MONDAY...BRINGING A GOOD CHANCE FOR THUNDERSTORMS...SOME OF WHICH MAY BE SEVERE. MUCH COOLER AND DRIER WEATHER WILL DEVELOP TUESDAY...AND CONTINUE THROUGH THE UPCOMING WEEK. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... AS OF 330 PM SATURDAY...OUR ATMOSPHERE IS BECOMING PROGRESSIVELY RESISTANT TO PROSPECTS OF DEEP CONVECTION AS DRY AIR CONTINUES TO DIG INTO THE LOWER PORTIONS OF THE TROPOSPHERE ON NORTHWEST WIND TRAJECTORIES. NO SHORTAGE OF LOW-LEVEL VAPOR CONTENT WITH MUGGY HEAT BOOSTING LOCAL HEAT INDICES TO 100 DEGREES CURRENTLY. THIS WAS RESULTING IN A VIGOROUS BUT SUPPRESSED CUMULUS FIELD AND AN OVERALL SWELTERING TONE TO OUTSIDE CONDITIONS INLAND. SINCE OUR LOCAL ATMOSPHERE IS BECOMING INCREASINGLY UNFAVORABLE FOR MATERIALIZATION OF SHOWERS/TSTMS...POP VALUES WILL BE LOWERED BELOW MENTIONABLE THRESH-HOLDS IN MOST AREAS AWAY FROM SEA BREEZE CONVERGENCE BASED ON RADAR TRENDS PRIOR TO ZFP/CWF DISSEMINATION. TONIGHT A MILD ONE ANTICIPATED ROUGHLY 3 DEGREES MILDER THAN LAST NIGHT...PARTIALLY A RESULT OF SW BOUNDARY LAYER WINDS INCREASING AS THE LOWER ATMOSPHERE DECOUPLES AMIDST A SLIGHTLY TIGHTENING LOW-LEVEL PRESSURE GRADIENT...AND ALSO BECAUSE OF RELATIVELY HIGH TD VALUES LIMITING OVERNIGHT TEMPERATURE FALLS. EXPECTING MIDDLE 70S AT DAYBREAK INLAND TO THE UPPER 70S TO NEAR 80 AT THE COAST. CLOSER TO THE ICW/SEA...SUSTAINED SW WINDS OVERNIGHT WILL LIKELY KEEP TEMPERATURES LEVELED OFF IN THE LOWER 80S. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... AS OF 330 PM SATURDAY...AN INTERESTING PERIOD ON TAP FOR THE SHORT-TERM PERIOD AS BOTH EXTREME HEAT/HEAT INDICES AND SPRING-LIKE SEVERE WEATHER IS ANTICIPATED. WITH HIGH PRESSURE IN PLACE OVER THE ATLANTIC AND A MID-LEVEL RIDGE...VERY WARM AND HUMID AIR WILL CONTINUE TO BE USHERED INTO THE AREA. WITH A HEAT ADVISORY NOW IN PLACE FOR ALL SOUTH CAROLINA INLAND COUNTIES...ALONG WITH ROBESON...COLUMBUS...AND BRUNSWICK COUNTIES IN NORTH CAROLINA...WILL ALSO FOCUS ON THE POSSIBILITY OF HEAT ADVISORY FOR MONDAY AS WELL WITH APPARENT TEMPS BOTH DAYS NEARING/AT/OR JUST ABOVE HEAT ADVISORY CRITERIA OF 105 DEGREES THANKS TO HIGHS IN THE UPPER 90S AND DEWPOINTS IN THE LOWER 70S. GIVEN FAIRLY DRY ATMOSPHERE AND SUBSIDENCE ALOFT...DO NOT ANTICIPATE ANY CONVECTION ON SUNDAY...THOUGH WILL NOT ENTIRELY RULE OUT AN ISOLATED SHOWER OR THUNDERSTORM ON THE AFTERNOON SEA BREEZE...BUT CONFIDENCE IS VERY LOW. REGARDING SEVERE WEATHER...WE WILL LOOK CLOSELY AT MONDAY LATE AFTERNOON/EVENING AS SPC HAS ALREADY HIGHLIGHTED THE AREA IN A SLIGHT RISK ON DAY 3. A STRONG AND VERY SPRING-LIKE DIGGING TROUGH/SFC COLD FRONT WILL PROPAGATE INTO THE CAROLINAS LATE SUNDAY AND THROUGHOUT THE DAY ON MONDAY AS ITS ASSOCIATED DEEPENING LOW PRESSURE MOVES EASTWARD ACROSS THE GREAT LAKES AND INTO NEW ENGLAND. WHILE THE AREA IS NOT USUALLY SUSCEPTIBLE TO FRONTAL BOUNDARIES AS SUCH DURING THE MID-SUMMER MONTHS...THE SETUP IS BECOMING MUCH MORE INTERESTING ESPECIALLY GIVEN THE 95+ TEMPERATURES ANTICIPATED FOR MONDAY...WHICH IS MUCH WARMER THAN WHAT WE WOULD SEE IN A TYPICAL SETUP LIKE THIS FOR APRIL/MAY. WHILE THE LATEST GUIDANCE SUGGESTS A SLIGHT LACK OF SUPPORT IN THE UPPER LEVELS WITH THE UNFAVORABLE LOCATION/NATURE OF THE JET...FOCUS TURNS TO THE MID AND LOWER LEVELS. LATEST GUIDANCE SEEMS TO BE IN PRETTY GOOD AGREEMENT WITH THE TIMING OF THE FRONT/CONVECTION ACROSS OUR AREA (MONDAY AFTERNOON/EVENING)...AND HAVE DECIDED TO UTILIZE GFS MORE IN FORECAST ESPECIALLY IN ANALYZING SEVERE WEATHER PARAMETER VALUES. PRECIPITABLE WATER VALUES WILL INCREASE THROUGHOUT THE DAY ON MONDAY...REACHING UP TO 2 INCHES BY 18Z. WHILE TIME-HEIGHT ANALYSIS SUGGESTS FEW/SCT HIGH CLOUDS SUNDAY NIGHT INTO MORNING...TEMPERATURES WILL ALREADY BE AROUND 80 DEGREES TO KICK-START MONDAY MORNING AND THUS AM NOT OVERLY CONCERNED WITH THE AFTERNOON HIGH TEMPS POTENTIALLY NOT CLIMBING INTO THE MID TO UPPER 90S. PER LATEST 12Z GFS FCST SOUNDINGS...A SLIGHT THERMAL RIDGE IS PRESENT...BUT AGAIN GIVEN ANTICIPATED HIGH TEMPERATURES FOR THE DAY...AN ADJUSTED SKEW-T WOULD MAKE THIS OBSOLETE AND PRESENT ITSELF AS A NEARLY-CLASSIC INVERTED-V SOUNDING...SUPPORTIVE OF SEVERE WEATHER. LOOKING AT OTHER PARAMETERS...BOTH LOW AND MID-LEVEL LAPSE RATES ARE FAIRLY STEEP...WITH VALUES OF 6-7 C/KM AND LIFTED INDEX VALUES ARE SHOWING TO BE ROUGHLY -6 TO -8. THIS WITH CAPE VALUES INCREASING TO NEAR 2000+ AS 500 MB HEIGHTS CONTINUE TO FALL WILL CREATE QUITE AN UNSTABLE AIRMASS FOR THE AREA. ALSO...DCAPE VALUES WILL BE 300+...ESPECIALLY CLOSER TO THE COAST PER LATEST GUIDANCE. FCST HODOGRAPHS ARE ILLUSTRATING A MORE FAVORABLE SETUP FOR SPEED SHEAR VERSUS DIRECTIONAL SHEAR...SO WHILE EXPECT A LOW TORNADO THREAT...COULD BE LOOKING AT THE POSSIBILITY OF DISCRETE CELLS/SPLITTING SUPERCELLS. LOCATION-WISE...WHILE WILL FOCUS ON THE FRONTAL BOUNDARY FOR LIFT...EXPECT THE SEA BREEZE TO PLAY A ROLE IN CONVECTIVE INITIATION AS WELL (LATE AFTERNOON/EARLY EVENING) AS IT WILL BE PINNED TO THE COAST GIVEN THE DECENT MID LEVEL WESTERLY FLOW AND THE FRONT ITSELF MOVES CLOSER INTO THE EARLY EVENING. GIVEN THE LATEST GUIDANCE AND THE ANTICIPATION OF CONVECTIVE DEVELOPMENT...EXPECT DAMAGING WINDS AND HAIL TO BE THE PRIMARY THREAT. WOULD NOT ENTIRELY RULE OUT THE POSSIBILITY OF LARGE HAIL GIVEN THE FAVORABLE AMOUNT OF CAPE IN THE HAIL GROWTH ZONE...BUT BEING THAT THE EVENT IS STILL A FEW DAYS AWAY...WILL REMIND THAT THIS IS A POSSIBILITY. ANY DECREASE/INCREASE IN SPEED OF THE SYSTEM COULD CHANGE THINGS ENTIRELY. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 330 PM SATURDAY...FALL COMES EARLY THIS YEAR...OR SO IT SEEMS...AS THE END OF JULY AND BEGINNING OF AUGUST FEATURE A PATTERN RARELY SEEN IN MID-SUMMER. THIS FALL LIKE PATTERN IS DUE TO A VERY STRONG MID-LEVEL TROUGH...PROGGED TO REACH -4 SD`S FROM CLIMO...DIVING ACROSS THE EASTERN CONUS AND THEN SITTING IN PLACE THROUGH THE UPCOMING WEEK. WHILE THIS WILL BRING A PERIOD OF MUCH DRIER AIR...AS SHOWN BY PWATS AROUND OR BELOW 1 INCH TUE-THU...AND A THETA-E RIDGE DISPLACED WELL EAST OF THE AREA...TEMPS WILL ALSO STRUGGLE TO VALUES WELL BELOW NORMAL FOR LATE JULY. 850MB TEMPS DROP TO AROUND -2 SD`S...AND HIGHS AND LOWS THROUGH THE WEEK WILL BE 5-10 DEGREES BELOW NORMAL. PRECIP CHANCES WILL BE MINIMAL THROUGH FRIDAY...AND ALTHOUGH ISOLATED SHOWERS WILL BE POSSIBLE LATE WEEK...WILL KEEP POP SILENT ATTM. BY THE END OF THE PERIOD THE HIGHLY AMPLIFIED RIDGE ACROSS THE ATLANTIC WILL TRY TO BACK UP TOWARDS THE COAST...CREATING SLIGHTLY WARMER TEMPS AND HIGHER POP FOR SATURDAY. && .AVIATION /20Z SATURDAY THROUGH THURSDAY/... AS OF 18Z...VFR THIS AFTERNOON. WINDS WILL BE SW WITH STRONGEST AVERAGE WINDS OF 8-15 KTS AT THE COASTAL TERMINALS. THROUGH EARLY EVENING TWO SFC BASED FEATURES...THE SEA BREEZE AND THE PIEDMONT TROF...WILL BE THE DRIVING FORCE FOR POSSIBLE CONVECTION. HOWEVER THE ENVIRONMENT WILL BECOME MORE HOSTILE AS THE EVENING APPROACHES. ANY ACTIVITY WILL BE ISOLATED...AND AS SUCH WILL NOT MENTION ANY CONVECTION IN TAFS EXCEPT FOR VCSH AT KILM EARLY THIS AFTERNOON. WINDS DECREASE THIS EVENING AS ANY CONVECTION DISSIPATES. ALTHOUGH WINDS DECREASE THEY SHOULD REMAIN SOMEWHAT ELEVATED OVERNIGHT. THIS SHOULD PREVENT ANY DENSE FOG FROM DEVELOPING...BUT SCT IFR STRATUS AND MVFR VSBYS IN BR ARE POSSIBLE IN THE PRE-DAWN HOURS MAINLY AT THE INLAND TERMINALS. OTHERWISE VFR THROUGH THE END OF THE TAF VALID PERIOD. BY 14-16Z WINDS WILL BECOME SSW 10-15 KTS. EXTENDED OUTLOOK...SHOWERS/TSTMS/TEMPO MVFR POSSIBLE SUNDAY AND MONDAY. OTHERWISE EXPECT VFR. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 330 PM SATURDAY...MODERATE SW WINDS WILL HOLD OVERNIGHT DUE TO INTERACTION OF A SURFACE TROUGH OVER THE CENTRAL CAROLINAS AND HIGH PRESSURE CIRCULATING OFFSHORE...EQUATING TO A STEADY SW 10-15 KT TONIGHT INTO DAYBREAK SUNDAY. SEAS 2-3 FOOT SEAS CAN BE EXPECTED IN A MIX OF S WAVES OF 1-1.5 FEET EVERY 4-5 SECONDS AND SE WAVES 1 TO 2 FEET EVERY 8-9 SECONDS. ANY SHOWERS OR TSTMS WILL BE FAVORED FOR LATE TONIGHT INTO EARLY SUNDAY MORNING...BUT ISOLATED AT BEST. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 330 PM SATURDAY...SCEC POSSIBLE SUNDAY NIGHT...WITH SMALL CRAFT ADVISORY ANTICIPATED MONDAY AND MONDAY NIGHT. SOUTH-SOUTHWEST WINDS WILL INCREASE SUNDAY INTO MONDAY AHEAD OF AN APPROACHING STRONG COLD FRONT. ON SUNDAY WILL SEE SUSTAINED WINDS 15 TO 20 KTS ...INCREASING TO AROUND 20 KTS LATE SUNDAY NIGHT AND INTO MONDAY. SEAS OF 2 TO 4 FT WILL INCREASE TO 4 TO 6 FT OVERNIGHT SUNDAY INTO MONDAY. LATE MONDAY NIGHT SEAS WILL BEGIN TO DECREASE TO 2 TO 4 FT WITH WEST-SOUTHWEST WINDS REMAINING AROUND 15 KTS. LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 330 PM SATURDAY...COLD FRONT WILL BE OFFSHORE AT THE START OF THE PERIOD...LEAVING GUSTY NW WINDS OF 10-15 KTS EARLY TUESDAY. THESE WINDS WILL EASE AND VEER TO THE NE DURING TUESDAY AS RIDGE OF HIGH PRESSURE BUILDS DOWN THE COAST...LEAVING A RELATIVE WEAK PRESSURE GRADIENT ACROSS THE AREA. WINDS WILL REMAIN FROM THE NE THROUGH THE REMAINDER OF THE EXTENDED...INCREASING SLOWLY TO 10-15 KTS BY THURSDAY. SEAS TUESDAY WILL BE 1-3 FT ON THE NW WINDS...BUT THEN BECOME A MORE STEADY 2-3 FT LATE TUESDAY....WEDNESDAY...AND INTO THURSDAY WITH A SLOWLY AMPLIFYING NE WIND WAVE DOMINATING THE WAVE SPECTRUM. SEAS THURSDAY WILL RISE SLIGHTLY HIGHER ON THE STRONGER WINDS...BECOMING 3-4 FT. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...HEAT ADVISORY FROM NOON TO 7 PM EDT SUNDAY FOR SCZ017-023-024- 032-033-039-053-055. NC...HEAT ADVISORY FROM NOON TO 7 PM EDT SUNDAY FOR NCZ087-099-109. MARINE...NONE. && $$ SYNOPSIS...JDW NEAR TERM...MJC SHORT TERM...SGL LONG TERM...JDW AVIATION...MJC/MRR MARINE...MJC/JDW/SGL

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