789
FXUS62 KRAH 040450
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1250 AM EDT SAT JUL 4 2020
SYNOPSIS
A WEAK BACKDOOR FRONT WILL MOVE SOUTHWARD THROUGH THE REGION TODAY,
BRINGING SCATTERED LATE DAY SHOWERS AND STORMS. BEHIND THIS FRONT,
HIGH PRESSURE WILL EXTEND INTO THE AREA FROM THE NORTH TONIGHT
THROUGH SUNDAY BEFORE MOVING OFFSHORE. LOW PRESSURE WILL DEVELOP
OVER THE LOWER MISSISSIPPI VALLEY AND GULF COAST STATES MONDAY,
ALLOWING MOISTURE TO RETURN TO THE CAROLINAS WITH INCREASING RAIN
CHANCES EARLY TO MID WEEK.
NEAR TERM /THROUGH TONIGHT/
AS OF 837 PM FRIDAY...
QUIET WEATHER REMAINS IN PLACE THIS EVENING AS THE AREA SITS UNDER
THE INFLUENCE OF A DRY SUBSIDENT AIRMASS. LINGERING CU FROM LATE
AFTERNOON HAS DISSIPATED, LEAVING BEHIND CLEAR/MOSTLY CLEAR SKIES.
SOME HIGHER CLOUDS ARE STILL MAKING THEIR WAY OVER THE APPALACHIAN
MTNS AND THEY WILL EVENTUALLY MAKE IT INTO NC BEFORE DAYBREAK, BUT
SHOULD BE OF LITTLE CONSEQUENCE TO THE FORECAST.
QUICK LOOK AT INCOMING MODEL DATA YIELDS VERY LITTLE CHANGE FROM THE
INHERITED FORECAST OR PREVIOUS FORECAST THINKING. OVERNIGHT LOWS IN
THE LOWER 70S IS A SOLID BET WITH PRECIP-FREE SKIES. I ONLY MADE
SOME MINOR CHANGES TO TEMPS/DEWPOINTS BASED ON OBSERVATIONAL TRENDS,
OTHERWISE THINGS ARE IN GOOD SHAPE.
SHORT TERM /SATURDAY AND SATURDAY NIGHT/
AS OF 400 PM FRIDAY...
A COUPLE OF MINOR SHORTWAVE TROUGHS OVER SWRN QC AND NRN MI THIS
AFTERNOON WILL SETTLE SEWD ACROSS AND OFFSHORE THE MIDDLE ATLANTIC
ON SAT, WITH GENERALLY NEUTRAL MID LEVEL HEIGHT TENDENCY AND FORCING
FOR VERTICAL MOTION OVER CNTL NC THROUGH SAT NIGHT.
AT THE SURFACE, A COLD FRONT ANALYZED FROM CT NWWD ACROSS CNTL NY
WILL SAG SWD ACROSS SRN/SERN VA AND NRN/NERN NC ON SAT, IMMEDIATELY
PRECEDED BY A PRE-FRONTAL TROUGH.
CONVERGENCE AND LOW LEVEL MOISTURE POOLING ALONG AND IMMEDIATELY
BEHIND THOSE BOUNDARIES WILL CONTRIBUTE TO THE DEVELOPMENT OF
MODERATE INSTABILITY AND PROBABLE DEVELOPMENT OF SCATTERED SHOWERS
AND STORMS ACROSS MAINLY THE NRN/NERN HALF OF CNTL NC SAT AFTERNOON-
EVENING. OTHERWISE, THE WARM SECTOR OVER THE CAROLINAS WILL BE A HOT
AND DEEPLY MIXED ONE WITH SURFACE DEWPOINTS LIKELY TO MIX OUT INTO
THE LWR-MID 60S AHEAD OF THE TROUGH/FRONT. HIGH TEMPERATURES WILL BE
NEAR TO PERHAPS A DEGREE OR TWO HOTTER THAN THOSE OF FRI, GIVEN
FORECAST 850 MB TEMPERATURES NEAR 19-20 C. GIVEN THE MIXING OUT OF
SURFACE MOISTURE IN THE WARM SECTOR, HEAT INDEX VALUES ARE EXPECTED
TO TOP OUT BETWEEN 93 AND 98 DEGREES - MARGINALLY HAZARDOUS.
THE COMBINATION OF POST-FRONTAL ELY FLOW AND RAIN-COOLED AIR/OUTFLOW
AND LOCALLY MAXIMIZED RELATIVE HUMIDITY VALUES SAT NIGHT WILL FAVOR
THE DEVELOPMENT OF AREAS OF STRATUS AND/OR FOG ACROSS THE NE
PIEDMONT AND NRN-CNTL COASTAL PLAIN THROUGH SUN MORNING, WITH LOW
TEMPERATURES GENERALLY AROUND 70 DEGREES.
LONG TERM /SUNDAY THROUGH FRIDAY/
AS OF 320 PM FRIDAY...
THE UPPER LEVEL TROUGH AXIS WILL LARGELY REMAIN SOUTH OF THE AREA
THROUGH THE WEEKEND, WITH MEDIUM-RANGE MODELS STILL DEVELOPING A LOW
OVER THE DEEP SOUTH/ARKLATEX BY SUNDAY OR MONDAY. OTHERWISE, THE
FLOW ALOFT WILL BE SOMEWHAT DIFFUSE, WITH THE AFOREMENTIONED LOW
SLOWLY DRIFTING EAST-NORTHEAST AND AMPLIFYING A WEAK TROUGH BEFORE
MOVING EAST THROUGH THE REGION MID- TO LATE-WEEK. AT THE SURFACE,
SOUTH-SOUTHEASTERLY FLOW INTO THE AREA OFF THE ATLANTIC WILL
PERSIST, WITH HIGH PRESSURE CENTERED WELL TO THE NORTHEAST OFF THE
NEW ENGLAND/NORTHEAST US COAST. THERE IS NOT VERY GOOD AGREEMENT
WITH THE DEVELOPMENT AND SUBSEQUENT PROGRESSION OF A LOW DEVELOPING
IN RESPONSE TO THE LOW ALOFT, THUS CONFIDENCE WITH EXACTLY IF AND
WHEN IT WOULD IMPACT CENTRAL NC IS LOW AT THIS TIME. REGARDLESS OF
THE COVERAGE, STILL EXPECT SHOWER AND THUNDERSTORM ACTIVITY TO BE
DIURNALLY DRIVEN AND BEST CHANCES TO BE ACROSS THE SOUTHERN PORTIONS
OF THE AREA. TEMPERATURES SHOULD BE NEAR NORMAL ON SUNDAY, WITH THE
POTENTIAL FOR SOME BELOW NORMAL HIGHS ON THE DAYS WITH MORE
EXTENSIVE CLOUD COVER AND CONVECTION. HIGHS WILL GENERALLY BE IN THE
MID 80S TO LOW 90S AND LOWS IN THE UPPER 60S TO MID 70S.
AVIATION /06Z SATURDAY THROUGH WEDNESDAY/
AS OF 1250 AM SATURDAY...
VFR CONDITIONS ARE LIKELY TO DOMINATE THROUGH THE NEXT 24 HOURS
ACROSS CENTRAL NC. FAIRLY DRY AIR IN PLACE NEAR THE GROUND WILL
LIMIT POTENTIAL FOR FOG/STRATUS, PARTICULARLY WITH A BATCH OF MID
AND HIGH CLOUDS SPREADING IN FROM THE WEST THIS MORNING TO SLIGHTLY
LIMIT RADIATIONAL COOLING, BUT ISOLATED PATCHES OF GROUND FOG REMAIN
POSSIBLE IN THE E AND FAR S 08Z-12Z THIS MORNING. JUST A FEW MID AND
HIGH CLOUDS AT MOST ARE EXPECTED FOR MUCH OF THE DAY, BUT BROKEN
HIGH-BASED CU IS EXPECTED WITH HEATING THIS AFTERNOON, AND THERE IS
A CHANCE FOR STORMS MAINLY IMPACTING (BUT NOT LIMITED TO) RWI/RDU
18Z TO 00Z, LEADING TO ISOLATED SUB-VFR CONDITIONS AND GUSTY WINDS
IN/NEAR STORMS. SURFACE WINDS OVERALL WILL REMAIN LIGHT/VARIABLE.
LOOKING BEYOND 06Z SUN, THERE IS A RISK FOR SUB-VFR FOG AND STRATUS
PARTICULARLY NEAR RDU/RWI/FAY 08Z-12Z SUN MORNING. DAILY AFTERNOON
AND EVENING SCATTERED STORMS AND THE RESULTANT RISK OF BRIEF SUB-VFR
CONDITIONS AND GUSTY WINDS WILL RETURN SUN AFTERNOON AND BE THE NORM
THROUGH MID WEEK, AS WEAK BUT PERSISTENT MID LEVEL LOW PRESSURE SITS
OVER THE MID MISS VALLEY ACROSS THE MID SOUTH AND CAROLINAS. THERE
IS A GOOD CHANCE FOR EARLY-MORNING SUB-VFR FOG AND STRATUS AREAWIDE
BOTH TUE MORNING AND WED MORNING. -GIH
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...HARTFIELD
NEAR TERM...LEINS
SHORT TERM...MWS
LONG TERM...KC
AVIATION...HARTFIELD
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