216
FXUS62 KRAH 131046
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
645 AM EDT TUE APR 13 2021
SYNOPSIS
WEAK HIGH PRESSURE WILL SETTLE OVER THE AREA TODAY AS A COLD FRONT
STALLS SOUTH OF THE AREA. AN AREA OF LOW PRESSURE IS EXPECTED TO
TRACK ACROSS NC ON WEDNESDAY, FOLLOWED BY THE PASSAGE OF A COLD FRONT
LATE WEDNESDAY NIGHT AND EARLY THURSDAY MORNING. COOLER AND DRIER
HIGH PRESSURE WILL FOLLOW FOR LATE WEEK.
NEAR TERM /THROUGH TONIGHT/
AS OF 400 AM TUESDAY...
MID AND UPPER LEVEL HEIGHTS WILL INCREASE ALOFT AS SHORTWAVE RIDGING
MOVES INTO THE REGION, DOWNSTREAM OF YET ANOTHER SLOW MOVING UPPER
LEVEL LOW MOVING OVER THE GREAT LAKES REGION. WEAK UPPER LEVEL
IMPULSES AND ASSOCIATED MID-LEVEL WAA SPILLING ATOP THE BUILDING
RIDGE AXIS WILL LEAD TO AN INFLUX OF MID AND HIGH CLOUDS BY THE
AFTERNOON. IT'S POSSIBLE SOME VERY LIGHT SPRINKLES COULD REACH THE
GROUND ACROSS THE FAR NW ZONES, BUT GIVEN RIDGING ALOFT, ANY
MEASURABLE PRECIP WILL BE HARD TO COME BY.
OTHERWISE, CONTINUED DRY WITH SLIGHTLY COOLER DAYTIME HIGHS, THANKS
TO THE LOW-LEVEL NORTHERLY FLOW AND AFOREMENTIONED CLOUD OVER. HIGHS
RANGING FROM LOWER 70S NE TO UPPER 70S SOUTH. LOWS 50 TO 55, WITH
SOME MID/UPPER 40S POSSIBLE ACROSS THE FAR NE ZONES.
SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/
AS OF 400 AM TUESDAY...
...A FEW STRONG TO SEVERE STORMS POSSIBLE WEDNESDAY AFTERNOON AND
EVENING...
THE UPPER LOW OVER THE UPPER GREAT LAKES WILL DEEPEN AS IT MOVES
SLOWLY SEWD TOWARD THE UPPER OHIO VALLEY. A SERIES OF SHORTWAVE
IMPULSES EMBEDDED WITHIN THE BROADENING CYCLONIC FLOW ALOFT WILL
EJECT EAST ACROSS THE AREA DURING THE LATE AFTERNOON AND INTO THE
OVERNIGHT HOURS. AT THE SURFACE, A COLD FRONT WILL BE DRAPED FROM
THE CENTRAL/SOUTHERN APPALACHIANS TO THE LOWER MS VALLEY TO START
THE DAY. HOWEVER, AS THE UPPER LOW DEEPENS AND THE ASSOCIATED MODEST
H5 FALLS BEGIN TO OVERSPREAD THE AREA FROM THE WEST, AN AREA OF LOW
PRESSURE IS FORECAST TO DEVELOP INVOF THE CAROLINAS, ALONG/AHEAD OF
THE COLD FRONT. THIS SURFACE LOW AND COLD FRONT WILL MOVE EAST
THROUGH THE AREA DURING THE EVENING AND OVERNIGHT HOURS, BEFORE
MOVING OFFSHORE EARLY THURSDAY MORNING.
SURPRISINGLY, MODELS ARE INDICATING RATHER ROBUST HEATING/INSOLATION
BEFORE THE ARRIVAL OF THE DEEPER MOISTURE/CLOUD COVER, WITH STEEP
LOW-LEVEL LAPSE RATES OF 8-8.5 C/KM ACROSS THE AREA BY 18Z AS
AFTERNOON TEMPS WARM IN THE MID/UPPER 70S NORTH TO LOWER 80S SE.
HOWEVER, MODELS INDICATE ONLY WEAK LOW-LEVEL MOISTURE ADVECTION INTO
THE AREA, WITH BL DEWPOINTS FORECAST TO REMAIN IN THE 50S. THESE
LOWER DEWPOINTS WILL LIKELY LIMIT DESTABILIZATION TO WEAK
INSTABILITY.
CONVECTIVE RAIN CHANCES WILL INCREASE FROM WEST TO EAST DURING THE
AFTERNOON AND EVENING, WITH THE HIGHEST QPF AND BEST COVERAGE OF
SHOWERS AND STORMS EXPECTED NEAR THE VA BORDER WHERE MODELS INDICATE
THE DEEPEST MOISTURE AND ALONG JUST NORTH OF THE WARM/OCCLUDED FRONT
AND POTENTIAL LOW TRACK. THIS WILL ALSO BE THE FAVORED AREA FOR A
FEW STRONG TO SEVERE STORMS, ESPECIALLY WITH ANY STORMS THAT RIDE
EAST ALONG THE FRONT DRAPED ACROSS THE AREA. DESPITE THE WEAK
INSTABILITY, 0-1KM SHEAR OF 20 TO 25 KTS COUPLED WITH THE POTENTIAL
FOR LOCALLY ENHANCED LOW-LEVEL SHEAR/HELICITY ALONG THE FRONT, COULD
SUPPORT A FEW SUPERCELLS CAPABLE OF PRODUCING ISOLATED DAMAGING
WINDS AND HAIL. AT THIS TIME IT IS BELIEVED THAT HIGHER LCL HEIGHTS,
DUE TO THE DRIER AIR IN THE LOW-LEVELS, WILL GREATLY REDUCE THE RISK
OF ANY STORM'S CIRCULATION OF REACHING THE GROUND. THUS, MAKING
FUNNEL CLOUD SIGHTINGS A REAL POSSIBILITY WEDNESDAY
AFTERNOON/EVENING.
WHILE THE SEVERE THREAT LOOKS TO BE OVER BY LATE EVENING, RAIN
CHANCES WILL LINGER THROUGH THURSDAY MORNING UNTIL THE PASSAGE OF
THE COLD FRONT AND UNDER THE CONTINUED MOIST PERTURBED FLOW ALOFT.
LOWS RANGING FROM LOWER/MID 50S NW TO LOWER 60S SE.
LONG TERM /THURSDAY THROUGH MONDAY/
AS OF 330 AM TUESDAY...
AS THE SURFACE LOW MOVES OFF THE NEW ENGLAND COAST THURSDAY
AFTERNOON, DRIER AND COOLER AIR MASS TAKES OVER CENTRAL NC THURSDAY
AND FRIDAY. RELATIVE HUMIDITIES WILL BE DOWN AS WELL TO AROUND 30-
40 PERCENT IN THE AFTERNOONS THURSDAY AND FRIDAY. EXPECT FRIDAY AND
SATURDAY TO BE DRY (BESIDES A FEW SPRINKLES POSSIBLE IN THE SOUTHERN
PART OF THE CWA ON SATURDAY) BEFORE THE NEXT SYSTEM MOVES INTO THE
REGION FOR THE LATTER HALF OF THE WEEKEND. ANOTHER RIDGE, WEAKER
THAN THE LAST, WILL MOVES ACROSS THE REGION SATURDAY NIGHT/SUNDAY
MORNING AHEAD OF A DEEPENING LOW IN THE MIDWEST MOVING IN FROM
CANADA. MODEL DISCREPANCY CONTINUES FOR TIMING AND AMOUNT OF PRECIP
FOR SATURDAY ONWARD THEREFORE CONFIDENCE IS STILL TOO LOW FOR ANY
FORECAST SPECIFICS. ALTHOUGH, SHOWERS SHOULD REMAIN WEAK AND
SCATTERED THROUGH THE LATTER PART OF THE WEEKEND AS ZONAL FLOW KEEPS
WEAK MOISTURE AROUND. THERE IS A SLIGHT CHANCE OF RAIN SUNDAY
MORNING THROUGH AT LEAST MONDAY EVENING. TEMPERATURES FOR THE
WEEKEND WILL BE A TAD BELOW NORMAL WITH HIGHS IN THE UPPER 60S IN
THE NORTH AND LOW 70S IN THE SOUTH. MONDAYS TEMPERATURES WILL WARM
UP TO LOW/MID 70S DURING THE DAY AND CONTINUE WITH MID 40S LOW 50S
AT NIGHT.
AVIATION /12Z TUESDAY THROUGH SATURDAY/
AS OF 645 AM TUESDAY...
NELY LOW-FLOW IN THE WAKE OF THE BACK-DOOR COLD FRONT IS PRODUCING
BRIEF PERIOD OF IFR TO MVFR RESTRICTIONS IN FOG AND/OR CEILINGS AT
RWI. OTHERWISE, CONDITIONS SHOULD REMAIN VFR THROUGH THE TAF PERIOD
WITH INTERMITTENT MID AND HIGH CLOUDS STREAMING ACROSS THE AREA,
ESPECIALLY AT KGSO/KINT THE LOWER MID-LEVEL CEILINGS COULD ALSO
SUPPORT SOME SPRINKLES.
OUTLOOK: AN AREA OF LOW PRESSURE WILL TRACK ACROSS THE REGION
WEDNESDAY AFTERNOON AND EVENING, BRINGING WIDESPREAD SHOWERS, ALONG
WITH AND A FEW STORMS TO THE AREA. A COLD FRONTAL PASSAGE THURSDAY
MORNING WILL USHER IN MUCH DRIER AND WILL MARK A RETURN TO VFR
CONDITIONS THAT WILL LAST THROUGH SATURDAY.
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...CBL
NEAR TERM...CBL
SHORT TERM...CBL
LONG TERM...CA
AVIATION...CBL
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