652
FXUS62 KRAH 091811
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
111 PM EST FRI DEC 9 2022
SYNOPSIS
HIGH PRESSURE WILL EXTEND ACROSS THE MID ATLANTIC AND SOUTHERN
APPALACHIANS, WHILE BEING OVERSPREAD BY WEAKLY-PERTURBED FLOW ALOFT,
THROUGH THE WEEKEND.
NEAR TERM /THROUGH TONIGHT/
AS OF 1000 AM FRIDAY...
THE MORNING FORECAST UPDATE WAS SENT WITH MINIMAL CHANGE FROM THE
PREVIOUS FORECAST. UPSLOPE STRATUS, BASED AS LOW AS 200-400 FT AGL
AT INT AND GSO, AND LIGHT RAIN AND DRIZZLE, MAY PERSIST INTO THE
EARLY AFTERNOON OVER THE NW PIEDMONT. THE DAYLIGHT HOURS WILL BE DRY
OTHERWISE AND ELSEWHERE, AS DRIER AIR WILL CONTINUE TO ADVECT IN
NELY FLOW INTO CNTL NC, AROUND HIGH PRESSURE OVER THE MID ATLANTIC.
GIVEN THE COMBINATION OF CONTINUED COOL, DRY ADVECTION, AND ALSO
CLOUDY OR MOSTLY SO CONDITIONS THROUGHOUT THE DAY, TEMPERATURES ARE
ONLY EXPECTED TO RISE A CATEGORY OR TWO FROM MID-MORNING READINGS
MOSTLY IN THE UPR 40S TO AROUND 50.
PREV DISCUSSION
/ISSUED 318 AM EST FRI DEC 09 2022/
LIGHT RAIN HAS BLOSSOMED IN THE LAST FEW HOURS, ESPECIALLY OVER THE
SOUTHERN PIEDMONT AND SANDHILLS, OWING TO LOW-LEVEL FRONTOGENESIS
AND ISENTROPIC ASCENT ATOP THE SURFACE BOUNDARY. THE BOUNDARY IS
CURRENTLY LOCATED NEAR THE NC/SC BORDER, BUT WITH TIME IT WILL SAG
SOUTH INTO SOUTHERN SC THIS MORNING AND SOUTHERN GA BY EARLY SAT.
THE FRONTOGENETICAL FORCING AND ISENTROPIC ASCENT WILL SLOWLY WANE
BY SUNRISE AS SURFACE HIGH PRESSURE OVER CANADA CONTINUES TO FURTHER
EXTEND INTO THE CAROLINAS. AS SUCH, A DRY DAY WILL TAKE OVER OVER
MOST OF CENTRAL NC. THE BUILDING HIGH WILL REINFORCE A CAD WEDGE OF
COOL/MOIST ENE FLOW, RESULTING IN PERIODS OF STRATOCUMULUS, MOST
DENSE OVER THE WESTERN PIEDMONT WITH WEAK SURFACE UPSLOPE FLOW. THIS
WEAK UPSLOPE FLOW FOR THE MORNING HOURS WILL ALSO FAVOR A FEW HOURS
OF LIGHT DRIZZLE OVER THE TRIAD AND WESTERN/SOUTHERN PIEDMONT THIS
MORNING. WHILE SOME BREAKS MAY OCCUR IN THE CLOUDS OVER THE
NORTHEAST PIEDMONT AND COASTAL PLAIN, CONSIDERABLE CLOUDS WILL FAVOR
A SMALL DIURNAL TREND WITH HIGHS BELOW NORMAL IN THE LOW TO MIDDLE
50S, COOLEST IN THE NORTH AND WEST.
ALOFT, A MID-LEVEL SHORTWAVE CURRENTLY OVER IA WILL BECOME SHEARED
OUT AS IT MOVES INTO THE OHIO VALLEY AND LOWER GREAT LAKES. A RIDGE
OVER THE CENTRAL PLAINS WILL BUILD INTO THE OHIO VALLEY BY EARLY
SAT. SOME ENERGY TIED TO THE AFOREMENTIONED SHORTWAVE CURRENTLY OVER
AR WILL DRIFT ESE INTO GA/SC THIS AFTERNOON AND TONIGHT, LARGELY
MISSING CENTRAL NC. HOWEVER, LOW-LEVEL WAA/UPGLIDE CONFINED NEAR THE
850MB LAYER, LIFTING ATOP THE LOW-LEVEL FRONTAL ZONE, WILL DEVELOP
LATE TODAY AND MAINLY TONIGHT OVER WESTERN NC, WANING AFTER
MIDNIGHT. THIS WILL FAVOR LOW-END CHANCES OF LIGHT RAIN/DRIZZLE OVER
THE WESTERN PIEDMONT, LARGELY WEST OF US-1. AMOUNTS WOULD BE VERY
LIGHT, AS EVIDENCE FROM THE LATEST HRRR/NAM-NEST AND HREF.
TONIGHT, CLOUDS WILL REMAIN SOCKED IN, THOUGH SOME BREAKS IN THE
CLOUDS IN THE NORTHEAST ARE POSSIBLE AS DRY ADVECTION CONTINUES TO
FILTER IN, WITH DEWPOINTS LOWERING TO THE MID 30S TO AROUND 40 BY
EARLY SAT. CAA WILL FAVOR COLDER OVERNIGHT LOWS BUT ABOVE NORMAL.
CLOUDS WILL TEMPER THE RADIATIONAL COOLING WITH LOWS IN THE UPPER
30S IN THE NE TO THE LOWER 40S IN THE SW.
SHORT TERM /SATURDAY AND SATURDAY NIGHT/
AS OF 318 AM FRIDAY...
HIGH PRESSURE OVER SE CANADA WILL CONTINUE TO EXTEND INTO THE MID-
ATLANTIC AND CENTRAL NC SAT AND SAT NIGHT, KEEPING THE CAD WEDGE IN
PLACE. AT MID-LEVELS, A RIDGE OVER THE OHIO VALLEY WILL MOVE EAST
INTO OUR AREA DURING THE AFTERNOON/EVENING. CAA WILL RESULT IN LOW-
LEVEL THICKNESSES ABOUT 10M LOWER THAN FRI, RESULTING IN ANOTHER
COOL AND BELOW NORMAL DAY WITH HIGHS IN THE UPPER 40S IN THE NORTH
TO THE LOW/MID 50S IN THE SOUTH. MOST OF SAT WILL BE DRY WITH PW'S
DECREASING TO 90-PERCENT OF NORMAL, BUT WITH EXTENSIVE CLOUD COVER -
THOUGH CANNOT RULE OUT SOME PARTIAL SUNSHINE ACROSS THE COASTAL
PLAIN WITH LOW-LEVEL MOISTURE DECREASING IN THE NE FLOW.
BY SAT NIGHT INTO EARLY SUN, OUR NEXT MID-LEVEL SHORTWAVE OVER THE
UPPER MISSISSIPPI VALLEY AND GREAT LAKES REGION WILL TRACK INTO THE
LOWER GREAT LAKES AND WESTERN NY, SENDING SHORTWAVE ENERGY INTO
VA/NC. PW'S INCREASE ABOVE NORMAL TO ABOUT 0.9 INCHES. ISENTROPIC
ASCENT/FRONTOGENETICAL FORCING WILL DEVELOP TOWARD EARLY SUN AS A
SURFACE WAVE TRACKS ALONG THE TN VALLEY, WITH THE FRONTAL ZONE
SLOWLY EDGING NORTH AS A WARM FRONT OVER CENTRAL GA. THIS WILL FAVOR
DEVELOPMENT OF LIGHT RAIN COME EARLY SUN, BUT MOST FAVORED OVER THE
WESTERN PIEDMONT. MODEL GUIDANCE HAS SLOWED THE START TIME OF THE
PRECIPITATION SHIELD, WITH MOST ENERGY NOW COMING IN SUN MORNING
INTO THE EVENING. THIS COUPLED WITH DRY AIR IN PLACE EVIDENT IN
FORECAST SOUNDINGS SHOULD KEEP ANY PRECIPITATION AMOUNTS RATHER
LIGHT BY EARLY SUN. OVERNIGHT LOWS WILL BE SIMILAR TO FRI NIGHT WITH
CLOUD COVER IN PLACE, UPPER 30S TO LOWER 40S, LOWEST IN THE NORTH.
LONG TERM /SUNDAY THROUGH THURSDAY/
AS OF 300 AM FRIDAY...
SUNDAY: A SOUTHERN STREAM WAVE INVOF ARKLATEX REGION EARLY SUNDAY
WILL CONTINUE TO EJECT ESEWD THROUGH THE DEEP SOUTH THROUGH EARLY
MONDAY. ASSOCIATED ISENTROPIC LIFT AND WAA OVER THE SE US WILL
RESULT IN ANOTHER WET AND GRAY DAY OVER CENTRAL NC, WITH LATEST
ROUND OF MODEL GUIDANCE KEEPING THE BULK OF THE PRECIPITATION ALONG
AND SOUTH OF US 1, IN PROXIMITY TO THE QUASI-STATIONARY FRONTAL ZONE
DRAPED OVER AL, GA AND SOUTHERN PARTS OF SC. RAINFALL AMOUNTS ARE
EXPECTED TO BE LIGHT. RAIN SHOULD GRADUALLY TAPER OFF FROM NORTH TO
SOUTH DURING THE LATE AFTERNOON AND EVENING WITH THE EVENTUAL
EROSION OF THE CAD AIRMASS SUNDAY NIGHT/EARLY MONDAY VIA POST-
FRONTAL DRY, COLD AIR ADVECTION,
THE CAD REGIME IN PLACE WILL BE MAINTAINED AND THUS WILL FEATURE
ANOTHER COOL/CHILLY DAY. HIGHS RANGING FROM MID/UPPER 40S NORTH TO
LOWER 50S SOUTH. LOWS SUNDAY NIGHT IN THE LOWER/MID 30S NORTH TO
UPPER 30S/LOWER 40S SOUTH.
MONDAY THROUGH TUESDAY: STRONG HIGH PRESSURE OVER EASTERN CANADA
WILL EXTEND SOUTH DOWN THE EASTERN SEABOARD RESULTING IN DRY, SUNNY
CONDITIONS TO START THE WORK WEEK AS UPPER LEVEL RIDGING BUILDS OVER
THE EASTERN US, IN ADVANCE OF A SPRAWLING UPPER LOW OVER THE
NATION'S MID SECTION. TEMPERATURES WILL AVERAGE NEAR TO SLIGHTLY
BELOW NORMAL
WEDNESDAY THROUGH THURSDAY: THE DEEP, MATURE LOW PRESSURE OVER THE
CENTRAL US PLAINS IS FORECAST TO MOVE VERY LITTLE ON WEDNESDAY,
BEFORE FINALLY EJECTING EASTWARD INTO THE OHIO VALLEY BY THURSDAY
NIGHT. CLOUDS WILL OVERSPREAD THE AREA DURING THE DAY ON WEDNESDAY
WITH RAIN LIKELY DELAYED UNTIL THE ARRIVAL OF THE OCCLUDED FRONTAL
ZONE INTO THE TN VALLEY WEDNESDAY EVENING/NIGHT. DRIVEN BY A 50 KT
LLJ, A POTENTIAL MILLER B STORM SYSTEM WILL BRING A HIGH CHANCE OF A
SOAKING RAIN EVENT TO MUCH OF THE SE US DURING THE WEDNESDAY NIGHT-
THURSDAY AFTERNOON/EVENING TIME FRAME. WILL ALSO HAVE TO CLOSELY
MONITOR THE THREAT FOR SEVERE STORMS, PARTICULARLY THE
TRACK/LOCATION OF THE SECONDARY SFC LOW/WARM FRONT AND ASSOCIATED
MARITIME AIR THAT COULD BRIEFLY ADVECT INTO OUR SE COUNTIES. WRT TO
TEMPERATURES, ANOTHER CAD EVENT LOOKS PROBABLE OVER THE
WESTERN/CENTRAL PIEDMONT, WHICH WILL SET THE STAGE FOR A SHARP NW TO
SE TEMPERATURE GRADIENT OVER THE CAROLINAS.
AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
AS OF 105 PM FRIDAY...
GENTLE LIFT ATOP COOL SURFACE PRESSURE RIDGING SOUTH ACROSS THE MID
ATLANTIC WILL MAINTAIN GENERALLY BROKEN TO OVERCAST STRATOCUMULUS
LAYERS (LOW VFR CEILINGS) BASED BETWEEN 3500-5000 FT AGL THROUGH THE
TAF PERIOD. THE EXCEPTION WILL BE AT INT/GSO, WHERE ELY UPSLOPE FLOW
TODAY WILL FAVOR CURRENT LIFR-IFR CONDITIONS THAT SHOULD LIFT TO
MVFR THROUGH EARLY THIS EVENING, AS THE DRIER AIR TO THE EAST AND
NORTHEAST IS ADVECTED IN THEIR DIRECTION. WHILE A BRIEF SCATTERING
TO VFR CANNOT BE RULED OUT DURING THAT TIME, THE ARRIVAL OF PATCHY
LIGHT RAIN OVER THE WRN NC PIEDMONT WILL LIKELY REINFORCE THE MVFR
MOIST LAYER, OR CAUSE IT TO LOWER INTO IFR RANGE ONCE AGAIN,
OVERNIGHT. HOWEVER, THE BETTER CHANCE OF THOSE LIFR-IFR CONDITIONS
WILL REMAIN ENTRENCHED ACROSS THE WRN CAROLINAS, NEAR AND JUST TO
THE WEST OF INT.
OUTLOOK: PERSISTENT COOL AND MOIST NELY FLOW AROUND SURFACE HIGH
PRESSURE ACROSS THE MID ATLANTIC WILL FAVOR CONTINUED LOW VFR
CEILINGS, TO OCCASIONAL SUB-VFR CONDITIONS MAINLY EACH NIGHT-
MORNING, THROUGH MONDAY. PATCHY LIGHT RAIN WILL ALSO BE POSSIBLE AS
A DISTURBANCE ALOFT CROSSES THE REGION EARLY SUNDAY.
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...KREN/MWS
NEAR TERM...MWS/KREN
SHORT TERM...KREN
LONG TERM...CBL
AVIATION...MWS
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