845
FXUS62 KILM 131437
AFDILM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1037 AM EDT THU AUG 13 2020
SYNOPSIS
HIGH PRESSURE ACROSS THE WESTERN ATLANTIC WILL MAINTAIN SOUTHERLY
WINDS, ALONG WITH SEASONABLY WARM AND HUMID CONDITIONS. WEAK LOW
PRESSURE WILL PRODUCE GREATER COVERAGE OF STORMS INTO THE
WEEKEND.
UPDATE
FORECAST ON TRACK AS WEAK LOW JUST EAST AND LOW LEVEL TROUGH,
EVIDENT RUNNING FROM SW TO NE JUST INLAND OF THE COAST, DRIFTS
NORTHEAST THROUGH TODAY ALONG WITH UPPER LEVEL LOW. FOCUS WILL
REMAIN ON LOCALIZED FLOODING IN STORM DEVELOPMENT TODAY WITH
WEAK STEERING FLOW AND VERY HIGH PCP WATER VALUES.
NEAR TERM /THROUGH FRIDAY/
GOES-EAST IN GEOSTATIONARY ORBIT, PRESENTLY SAMPLING A STREAM OF
PRECIPITABLE WATER VALUES IN EXCESS OF 2 INCHES STREWN ABOUT THE
AREA, AND LIFTED INDICES OF -1 TO -2. AN UPPER WEAKNESS WITH EQUALLY
FAINT CYCLONIC CIRCULATION WAS SUPPORTING DEEP CONVECTION OFFSHORE.
THIS FEATURE IS EXPECTED TO DRIFT NE TO OFFSHORE OF NC OUTER BANKS
BY FRIDAY, AS AN UPPER TROUGH WEST OF THE AREA SLOWLY MIGRATES EAST.
MARINE OUTFLOWS INTO UNSTABLE AIR WITH LIGHT STEERING CURRENTS WILL
LEAD TO ISOLATED WATERSPOUTS BENEATH RAPIDLY DEVELOPING CONVECTION,
SOME OF WHICH COULD MOVE ASHORE LATER THIS MORNING. THIS MAY ENHANCE
COASTAL CONVERGENCE, LEADING TO DECENT SHOWERS CHANCES FOR COASTAL
ZONES, ESPECIALLY CAPE FEAR REGION THIS MORNING.
NEW CONVECTION INLAND, ASIDE FROM THE COASTAL ACTIVITY, SHOULD BEGAN
TO FLARE UP AROUND 1 PM, SCATTERING THE LANDSCAPE THROUGH EARLY
EVENING WITH SHOWERS AND TSTMS, RAIN BRIEFLY HEAVY IN SPOTS. THERE
IS NO DISCERNIBLE MOTION TO STORMS TODAY, AND PERIPHERAL
OUTFLOWS WITH NEWLY SPAWNED CONVECTION WILL OUTPACE ANY SINGLE
STORM MOVEMENT. THE STORM STAGNANCY AND HIGH PWAT INDICES MAY
LEAD TO EXCESS WATER IN SPOTS, AND PONDING ON HIGHWAYS.
FRIDAY SIMILAR, EXCEPT THE UPPER WEAKNESS OFFSHORE MAY HAVE LESS
IMPACT OVER THE COASTAL INTERIOR, AS IT BECOMES POSITIONED SOUTH OF
CAPE LOOKOUT, BUT STILL CLOSE ENOUGH FOR COASTAL SHOWERS FRIDAY
MORNING. BECAUSE OF CLOUDS AND RAIN, MAX-T NEAR TO A COUPLE DEGREES
BELOW NORMAL THIS PERIOD.
SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/
WEAK UPPER LOW WILL PUSH OFF TO THE NE ON FRIDAY EVENING AS A DEEPER
UPPER-TROUGH APPROACHES THE AREA FROM THE WEST. THUNDERSTORM
COVERAGE WILL BE SCATTERED TO WIDESPREAD ON SATURDAY AS THE APEX OF
THE TROUGH AND AN ASSOCIATED FRONTAL BOUNDARY APPROACH THE SOUTHERN
APPALACHIANS. LOCALLY, WIND FIELD THROUGHOUT THE SOUNDING SHOWS VERY
LITTLE SPEED OR DIRECTIONAL SHEAR AND STORM MOTION WILL BE ON THE
ORDER OF 10-20 KNOTS. WITH THESE PARAMETERS, IT IS LIKELY THAT
SEVERE WEATHER WILL BE LIMITED TO ONE OR TWO EXCEPTIONAL PERFORMERS
WITH A RELATIVELY LOW FLOODING THREAT. WITH THE UPPER-LEVEL ENERGY
AVAILABLE AND THE MOISTURE-LADEN ATMOSPHERE AHEAD OF THE FRONT,
EXPECT WIDESPREAD THUNDERSTORM COVERAGE TO LINGER INTO THE OVERNIGHT
HOURS.
LONG TERM /SUNDAY THROUGH WEDNESDAY/
UPPER TROUGH WILL SHIFT EASTWARD ON SUNDAY AND PUSH A WEAK FRONTAL
BOUNDARY THROUGH THE AREA. THUNDERSTORM ACTIVITY SHOULD BE LIMITED
TO THE COAST ON SUNDAY AFTERNOON WITH AFTERNOON STORMS BATTLING MUCH
DRIER MID- AND UPPER-LEVEL AIR. MOSTLY QUIET ON MONDAY BEFORE THE
UPPER TROUGH DIGS SOUTHWARD OVER THE CENTRAL PART OF THE CONUS AGAIN
ON TUESDAY. THIS WILL BRING A PATTERN OF ELEVATED STORM CHANCES EACH
AFTERNOON THROUGH THE MIDDLE OF NEXT WEEK. TEMPERATURES WILL
GENERALLY REMAIN IN THE UPPER 80S TO NEAR 90, RIGHT AT THE CLIMO
MARK FOR MID-AUGUST.
AVIATION /14Z THURSDAY THROUGH MONDAY/
VCSH AND VCTS MUCH OF THIS 12Z TAF CYCLE, GENERALLY ISOLATED TO
SCATTERED IN COVERAGE, BUT IMPACTING MOST TERMINALS TODAY.
A DISTURBANCE LOCATED OFFSHORE OF THE CAPE FEAR REGION WILL
SUSTAIN A CHANCE OF SHRA AND TSTM AT COASTAL TERMINALS THROUGH
THE PERIOD. SOME RESIDUAL MVFR/BRIEF IFR FOG THIS MORNING MAY
PERSIST THROUGH 13-14Z, THE THICKEST OF IT BEING AT THE MORE
INLAND TERMINALS. WOULDN'T BE SURPRISED TO SEE BRIEF IFR IN AND
AROUND STORMS THIS AFTERNOON. CONVECTION SETTLES DOWN AFTER
SUNSET. THINK KFLO AND KLBT COULD SEE SOME PERSISTENT AREAS OF
MVFR/IFR FOG BEFORE SUNRISE FRIDAY MORNING. FOG MAY ALSO FORM
ALONG THE COAST, BUT NOT AS THICK.
EXTENDED OUTLOOK...TSTMS, ISOLATED TO SCATTERED WILL CONTINUE
THROUGH THE EXTENDED PERIOD. PATCHES OF MORNING FOG GENERALLY
BETWEEN 8Z-11Z SHOULD BE EXPECTED, OR LOCALIZED MVFR STRATUS.
WINDS OUTSIDE OF TSTMS SHOULD REMAIN LIGHT, AND SOUTHERLY.
MARINE
TSTMS OFFSHORE POSING AN EARLY HAZARD OVER THE 0-20 NM WATERS, AS
OUTFLOWS ARE APT TO BRING MORE TSTMS CLOSER TO SHORE THIS MORNING.
ISOLATED WATERSPOUTS AND DANGEROUS CLOUD TO SEA LIGHTNING IS THE
EXPECTATION THROUGH MOST OF MORNING, AND MARINERS SHOULD OBTAIN
RADAR UPDATES BEFORE A VENTURE OUT. AWAY FROM TSTMS, LIGHT S WINDS
IN GENERAL THIS PERIOD. THE SEA SPECTRUM WILL BE COMPOSED OF S-SSW
WAVES 1 FOOT EVERY 4-5 SECONDS AND SE WAVES 1-2 FEET EVERY 9 SEC.
ELEVATED TSTM COVERAGE SHOULD BE EXPECTED THROUGH FRIDAY AS AN UPPER
LOW JUST OFFSHORE DRIFTS SLOWLY TO THE NE, OFFSHORE OF THE OUTER
BANKS BY FRIDAY. STRONG TSTMS OFFSHORE COULD PRODUCE LOCALLY HIGHER
SEAS THAN FORECAST, AND MAY BE LOCALIZED. LIGHTNING ACTIVITY TO RUN
HIGH THIS PERIOD, WITH A HIGHER THAN NORMAL RISK OF A WATER
SPOUT.
SOUTHERLY BERMUDA-DRIVEN FLOW WILL CONTINUE THROUGH THE WEEKEND AND
INTO EARLY NEXT WEEK. A WEAK FRONTAL BOUNDARY WILL APPROACH THE AREA
THIS WEEKEND AND LEAD TO A TIGHTENING OF THE PRESSURE FIELD. SHOWERS
AND THUNDERSTORMS APPEAR LIKELY THROUGH THE END OF THIS WEEK AND
INTO THE WEEKEND. THE AFOREMENTIONED FRONT WILL PRODUCE WINDS 10-15
KNOTS WITH GUSTS TO 20 KNOTS ON FRIDAY AND SATURDAY. THIS BRIEF
FETCH WILL BE ENOUGH TO PUSH WAVES TO 2-4 FEET THROUGH THE WEEKEND.
THE BOUNDARY IS EXPECTED TO MOVE THROUGH THE AREA ON SUNDAY AND MAY
PRODUCE OFFSHORE WINDS FOR A BRIEF PERIOD INTO SUNDAY EVENING.
THUNDERSTORM CHANCES DIMINISH ON SUNDAY NIGHT AND INTO MONDAY BEFORE
RAMPING BACK UP AGAIN BY THE MIDDLE OF NEXT WEEK. SEAS WILL
GENERALLY BE 2 TO 3 FEET WITH NO SIGNIFICANT SWELL NEXT WEEK.
ILM WATCHES/WARNINGS/ADVISORIES
SC...NONE.
NC...NONE.
MARINE...NONE.
SYNOPSIS...ILM
UPDATE...RGZ
NEAR TERM...MJC
SHORT TERM...21
LONG TERM...21
AVIATION...IGB
MARINE...MJC/21
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