267
FXUS62 KRAH 230110
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
810 PM EST FRI FEB 22 2019
SYNOPSIS
CHILLY HIGH PRESSURE WILL BUILD SOUTHWARD INTO CENTRAL NC THROUGH
SATURDAY, RESULTING IN ANOTHER PROLONGED EPISODE OF APPALACHIAN COLD
AIR DAMMING. A COLD FRONT WILL CROSS THE REGION ON SUNDAY, FOLLOWED
BY TRANQUIL WEATHER AND SEASONABLE TEMPERATURES FOR EARLY NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
AS OF 810 PM FRIDAY...
BULK OF PRECIP SO FAR THIS EVENING HAS REMAINED ALONG AND NORTH OF
HIGHWAY 64, IN CLOSER PROXIMITY TO THE WEAK S/W IMPULSES MOVING NE
ACROSS THE REGION. EXPECT THIS TREND TO LARGELY CONTINUE DURING THE
REMAINDER OF THE EVENING AND MUCH OF THE OVERNIGHT HOURS, BEFORE THE
NEXT BATCH OF DISTURBANCES FROM THE SW BRINGS MORE EQUITABLE RAIN
CHANCES AREA-WIDE AROUND DAYBREAK AND CONTINUING THROUGH THE LATE
MORNING/EARLY AFTERNOON HOURS. OTHERWISE, EXPECT NEARLY STEADY
TEMPERATURES OVERNIGHT.
PREVIOUS DISCUSSION: UNSETTLED WEATHER PATTERN TO CONTINUE DURING
THE NEAR TERM WITH EXTENSIVE CLOUDINESS AND PERIODS OF RAIN/DRIZZLE
CONTINUING TONIGHT THROUGH EARLY SATURDAY. A SERIES OF PERTURBATIONS
IN THE SW FLOW ALOFT WILL CONTINUE TO STREAM FROM THE LOWER MS
VALLEY INTO THE TN VALLEY/CENTRAL APPALACHIANS. MEANWHILE, A CHILLY
SFC HIGH CENTERED OVER NEW ENGLAND WILL BUILD SOUTHWARD INTO THE
CAROLINA PIEDMONT, SETTING UP A CLASSICAL COLD AIR DAMMING EPISODE.
THE WARM MOIST AIR OVERRUNNING THE COLD STABLE AIR NEAR THE SURFACE
WILL MAINTAIN THE EXTENSIVE CLOUD COVER AND PERIODS OF LIGHT
RAIN/DRIZZLE. THE LOW LEVEL NORTHEAST FLOW WILL CONTINUE TO ADVECT
COLD AIR INTO THE REGION OVERNIGHT. BY EARLY SATURDAY, TEMPERATURES
SHOULD VARY FROM THE UPPER 30S/NEAR 40 NORTH TO THE LOWER 40S SOUTH.
BULK OF THE PRECIPITATION WILL OCCUR ACROSS THE NORTHERN COUNTIES
WHICH WILL BE IN CLOSER PROXIMITY TO THE BETTER LIFT ASSOCIATED WITH
THE PERTURBATIONS AND THE UPPER JET LIFTING OVER THE OH VALLEY INTO
SOUTHERN NEW ENGLAND.
SHORT TERM /SATURDAY AND SATURDAY NIGHT/
AS OF 330 PM FRIDAY...
LITTLE CHANGE IN THE OVERALL WEATHER PATTERN SATURDAY INTO SATURDAY
NIGHT AS PERIODS OF RAIN WILL PERSIST WITH THE GREATEST COVERAGE
ACROSS THE NORTHERN COUNTIES. EXPECT LITTLE CHANGE IN THE
TEMPERATURES THROUGHOUT THE DAY WITH THE DIURNAL TREND LIKELY NO
MORE THAN 3-5 DEGREES. CURRENTLY APPEARS THAT A LULL IN THE
PRECIPITATION MAY OCCUR LATE IN THE DAY SATURDAY INTO SATURDAY
EVENING THOUGH PATCHY DRIZZLE AND AREAS OF FOG APPEAR HIGHLY
PROBABLE. LATER SATURDAY NIGHT, THE APPROACH OF A STRONG COLD FRONT
ASSOCIATED WITH A DEEP LOW PRESSURE SYSTEM LIFTING ACROSS THE UPPER
MIDWEST WILL INDUCE A SLY NEAR SFC WIND FLOW OVER OUR COASTAL PLAIN
COUNTIES, EVENTUALLY SPREADING INTO THE PIEDMONT TOWARD DAYBREAK
SUNDAY. THIS FLOW WILL SPREAD A WARM AIR OVER THE COOL SFC, LEADING
TO THE DEVELOPMENT OF FOG, SOME OF WHICH MAY BE DENSE. CURRENTLY,
THE DENSE FOG POTENTIAL APPEARS HIGHEST FOR LOCATIONS SOUTH AND
SOUTHEAST OF RALEIGH. IN ADDITION, SHOULD START TO SEE AN INCREASE
IN RAIN OR SHOWER ACTIVITY TOWARD DAYBREAK SUNDAY IN THE WESTERN
PIEDMONT ATTRIBUTED TO THE CONVERGENCE AHEAD OF THE APPROACHING SFC
COLD FRONT. OVERNIGHT TEMPERATURES WILL HOLD STEADY THROUGH THE BULK
OF THE EVENING, THEN SLOWLY RISE, ESPECIALLY SOUTHEAST OF RALEIGH,
AFTER MIDNIGHT.
LONG TERM /SUNDAY THROUGH THURSDAY/
AS OF 300 PM FRIDAY...
SUNDAY AND SUNDAY NIGHT: THE SURFACE LOW WILL DEEPEN AS IT
ACCELERATES NORTHEASTWARD THROUGH THE WESTERN GREAT LAKES ON SUNDAY.
SINCE THE LOW (AND THUS BEST FORCING) WILL BE WELL TO THE NORTH, THE
FRONT WILL SLOW AS IT IMPINGES ON THE APPALACHIANS. THE BIG QUESTION
IS HOW LONG THE WEDGE WILL HOLD AND HOW FAR NORTHWEST THE WARM FRONT
ADVANCES THROUGH THE AREA. THE LATEST MODELS SUGGEST THE WEDGE COULD
BREAK JUST PRIOR TO THE ARRIVAL OF THE FRONT EARLY SUNDAY. BEST
CHANCES FOR CONVECTION WILL BE ALONG AND AHEAD OF THE FRONT BETWEEN
12Z SUNDAY AND 00Z MONDAY. THE FRONT SHOULD BE THROUGH THE AREA BY
SUNDAY EVENING. SOMEWHAT LOW CONFIDENCE IN THE HIGH TEMPERATURE
FORECAST AS IT WILL DEPEND ON WHETHER/HOW LONG THE WEDGE HOLDS AND
THE TIMING OF THE FRONT. FOR NOW GENERALLY EXPECT HIGHS IN THE MID
60S NW TO MID 70S SE. LOWS BEHIND THE FRONT IN THE MID 30S TO AROUND
40 DEGREES SUNDAY NIGHT.
MONDAY THROUGH THURSDAY: SURFACE HIGH PRESSURE WILL BUILD INTO AND
THROUGH THE REGION BEHIND THE FRONT, WITH DRY, SEASONABLE CONDITIONS
EXPECTED THROUGH TUESDAY NIGHT. THE UPPER LEVEL TROUGH AMPLIFIES
TUESDAY NIGHT INTO WEDNESDAY AS THE SURFACE HIGH PUSHES OFFSHORE. A
WEAK SHORTWAVE COULD PASS OVER THE AREA, HOWEVER CHANCES FOR ANY
PRECIPITATION WITH THAT ARE SMALL. THE SOUTHERLY RETURN FLOW AT THE
SURFACE ON WEDNESDAY MAY CONTRIBUTE TO INCREASING CHANCES FOR RAIN,
PRIMARILY ACROSS THE SOUTH, ON WEDNESDAY. FORECAST CONFIDENCE FOR
WEDNESDAY AND THURSDAY IS VERY LOW AT THIS TIME.
AVIATION /00Z SATURDAY THROUGH WEDNESDAY/
AS OF 650 PM FRIDAY...
24 HOUR TAF PERIOD: ANOTHER DAY OF VERY UNATTRACTIVE AVIATION
CONDITIONS ACROSS CENTRAL NC. MOST SITES AT THIS HOUR REPORTING IFR
CONDITIONS WITH SOME BOUNCING AROUND BETWEEN FLIGHT CATEGORIES STILL
OCCURRING AS POCKETS OF RAIN AND DRIZZLE MOVING THROUGH ALL OF THE
NORTHERN TAF SITES WITH KFAY THE ONLY ONE SOUTH OF THE MAIN RAIN
SHIELD. CEILINGS MAY BOUNCE AROUND BUT WILL EVENTUALLY LOCK IN AT
IFR/LIFR LEVELS FOR MUCH OF THE TAF PERIOD AS RAIN AND DRIZZLE
CONTINUE AND FLOW BECOMES MORE PRONOUNCED OUT OF THE NORTHEAST ON
SATURDAY. NOT EXPECTING ANYWHERE TO SCATTER OUT THROUGH THE DAY ON
SATURDAY.
LONG TERM: A FRONT WILL MOVE THROUGH SATURDAY NIGHT AND SUNDAY
MORNING FINALLY BRINGING AN END TO THIS WET PERIOD AT LEAST FOR THE
EARLY PART OF NEXT WEEK. ONCE CONDITIONS RETURN TO VFR ON SUNDAY
THEY SHOULD REMAIN THERE THROUGH AT LEAST TUESDAY AND MAYBE MOST OF
WEDNESDAY BEFORE A SHORTWAVE APPROACHES FROM THE SOUTH WEDNESDAY
NIGHT.
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...WSS
NEAR TERM...CBL/WSS
SHORT TERM...WSS
LONG TERM...KC
AVIATION...ELLIS
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