638
FXUS62 KRAH 170652 RRA
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
150 AM EST SUN NOV 17 2024
SYNOPSIS
HIGH PRESSURE WILL BUILD ACROSS THE MIDDLE AND SOUTH ATLANTIC STATES
THROUGH MONDAY, THEN MOVE OFFSHORE MONDAY NIGHT. A STRONG COLD FRONT
WILL MOVE THROUGH THE REGION MID-WEEK.
NEAR TERM /TONIGHT/
AS OF 905 PM SATURDAY...
* FROST ADVISORY EXPANDED ACROSS THE REST OF THE (CLIMATOLOGICALLY-
FAVORED) PIEDMONT AND INTO THE NORTHWESTERN SANDHILLS AND CENTRAL
COASTAL PLAIN
IN THE MID/UPPER-LEVELS, A HIGH AMPLITUDE RIDGE EVIDENT IN 00Z UPPER
AIR CHARTS FROM THE CNTL GULF OF MEXICO TO ERN ON WILL PROGRESS
SLOWLY EWD ACROSS THE SOUTHEAST AND MIDDLE ATLANTIC TONIGHT. DEEP
SUBSIDENCE WILL RESULT WITHIN AN ALREADY DEEPLY DRY PROFILE DEPICTED
IN THE 00Z-OBSERVED GSO AND RNK SOUNDINGS, WHERE PWS OF AROUND A
QUARTER INCH WERE MEASURED. FARTHER UPSTREAM, MAINLY THIN, HIGH-
LEVEL MOISTURE EVIDENT IN BOTH SATELLITE AND OBSERVED SOUNDING DATA
OVER THE OH VALLEY AND UPR MIDWEST WILL STREAM SEWD AND ACROSS CNTL
NC SUNDAY MORNING.
AT THE SURFACE, A RIDGE, SURROUNDING PACIFIC HIGH PRESSURE NOW
CENTERED AT 1023 MB OVER THE LWR GREAT LAKES AND EXTENDING
THROUGHOUT THE SOUTHEAST AND NRN GULF OF MEXICO, WILL BECOME
CENTERED OVER THE MIDDLE AND SOUTH ATLANTIC (FROM PA TO NC) BY
SUNDAY MORNING. ASSOCIATED CALM HAS ALREADY BECOME ESTABLISHED
ACROSS CNTL NC THIS EVENING AND WILL CONTINUE THROUGHOUT THE NIGHT
AND EARLY TO MID-MORNING SUNDAY.
THE COMBINATION OF CALM AND CLEAR, ASIDE FROM THE AFOREMENTIONED
HIGH CLOUDS SUNDAY MORNING, WILL FAVOR EXCELLENT RADIATIONAL COOLING.
GIVEN THAT TEMPERATURES AWAY FROM URBAN AREAS REACHED THE 30S THIS
PAST (SAT) MORNING OVER ALL BUT PARTS OF THE COASTAL PLAIN AND
SANDHILLS (SEE THE LATEST PUBLIC INFORMATION STATEMENT - PNSRAH),
TEMPERATURES WITH MORE-PROLONGED AND IDEAL RADIATIONAL COOLING
TONIGHT SHOULD BE EVEN LOWER AND SUPPORTIVE OF FROST IN MOST ALL OF
RURAL, CNTL NC. THE FROST ADVISORY WAS CONSEQUENTLY EXPANDED TO
INCLUDE ALL BUT THE SRN COASTAL PLAIN AND ERN SANDHILLS. EVEN THE
TYPICALLY COLDER LOCATIONS OF THE LATTER COUNTIES MAY EXPERIENCE
PATCHY FROST SUNDAY MORNING.
SHORT TERM /SUNDAY AND SUNDAY NIGHT/
AS OF 205 PM SATURDAY...
ALOFT, THE SUB-TROPICAL RIDGE WILL SIT OVER THE SOUTHEAST US THROUGH
SUN NIGHT. A S/W WILL MOVE EWD THROUGH THE OH VALLEY AND NORTHEAST
US SUN NIGHT, CLIPPING THE MID-ATLANTIC/NC ALONG THE WAY. AT THE
SURFACE, HIGH PRESSURE WILL DRIFT SEWD THROUGH THE CAROLINAS TO OVER
THE SOUTHEAST US COAST MON, WITH SURFACE WINDS BECOMING MORE SWLY
OVER CENTRAL NC. AS THE HIGH MOVES OFF THE SOUTHEAST US COAST SUN
NIGHT, A LEE TROUGH WILL SET UP OVER CENTRAL NC AND SURFACE WINDS
COULD BECOME MORE WLY, OR EVEN NWLY THROUGH THE NIGHT, ESPECIALLY
ACROSS THE NORTHWEST. THE WEATHER SHOULD REMAIN DRY THROUGH SUN
NIGHT, WITH SOME INCREASING HIGH CLOUDS AS THE S/W PASSES TO THE
NORTH. AS FOR TEMPERATURES, HIGHS SHOULD RANGE FROM LOW 60S NE TO
UPPER 60S SW. LOWS COULD BE A BIT TRICKIER. LOW-LEVEL THICKNESSES
ARE FORECAST TO BE IN THE 1360-1370 METER RANGE BY 12Z MON AND WINDS
SHOULD GRADUALLY TAPER OFF THROUGH THE NIGHT, BECOMING LIGHT (0-4
KTS) BY 12Z MON. THE POTENTIAL FOR INCREASING HIGH CLOUDS COULD BE
THE LIMITING FACTOR FOR RADIATIONAL COOLING, HOWEVER IF THEY ARE
THINNER OR OF LESS COVERAGE THAN EXPECTED FORECAST LOWS MAY BE TOO
HIGH. ALL THAT SAID, FOR NOW HAVE LOWS FORECAST IN THE LOW TO MID
40S.
LONG TERM /TUESDAY THROUGH SATURDAY/
AS OF 150 AM SUNDAY...
RIDGING OVER THE AREA TUE AND WED AHEAD OF A STRONG TROUGH TRACKING
INTO THE OH VALLEY WILL SPELL OUT MILD HIGHS TO START THE EXTENDED.
HIGHS ON TUE AND WED ARE STILL PROGGED TO BE IN THE UPPER 60S TO LOW
70S, ABOUT 8-10 DEGREES ABOVE NORMAL.
WE CONTINUE TO WATCH FOR THE CHANCE OF PRECIPITATION IN THE LATE TUE
THROUGH WED TIME FRAME. MOST DETERMINISTIC AND ENSEMBLE GUIDANCE
SHOWS LIGHT BUT MEASURABLE RAINFALL TUE NIGHT AS DEEP MOISTURE FROM
REMNANT TC SARA ADVECTS INTO THE SE US. PW'S REACH OVER 250-PERCENT
OF NORMAL AROUND 1.5 INCHES DURING THIS TIME. LIFT IS NOT OVERLY
IMPRESSIVE, DRIVEN LARGELY BY SOME WEAK ISENTROPIC ASCENT IN THE 700-
500 MB LAYER. THE PRIOR GEFS WAS A DRIER OUTLIER COMPARED TO THE 12Z
EPS/GEPS, BUT APPEARS A SMIDGE WETTER IN LINE WITH THE LATEST 00Z
GUIDANCE. EVEN WITH THAT, AMOUNTS ARE ABOUT A TENTH OF AN INCH OR
LESS.
A SECOND CHANCE OF PRECIPITATION, IN THE FORM OF SHOWERS, WILL THEN
BE POSSIBLE WED INTO LATE WED NIGHT, AS A STRONG TROUGH OVER THE MS
VALLEY TRACKS INTO THE OH VALLEY. A STRONG COLD FRONT WILL ACCOMPANY
THIS SYSTEM, MOVING THROUGH LATE WED NIGHT. SOME MORNING LIGHT RAIN
IS POSSIBLE WITH LINGERING ISENTROPIC ASCENT. A SECOND BATCH OF
SHOWERS ARE THEN POSSIBLE WED AFTN INTO THE LATE EVENING AS GUIDANCE
SHOWS PERHAPS AN AREA OF LOW PRESSURE TRACKING ALONG THE FRONT.
THERE ARE SOME SUBTLE DIFFERENCES IN THE LOCATION OF THE TROUGH,
WITH THE ECMWF/CMC WETTER AND FURTHER SOUTH THAN THE GFS. THERE
MIGHT BE A VERY SHORT WINDOW WHERE SOME ISOLATED STORMS COULD FORM
AHEAD OF THE FRONT GIVEN STRONG SHEAR, THOUGH INSTABILITY STILL
APPEARS LIMITED. TOTAL PRECIPITATION AMOUNTS ARE ABOUT A QUARTER
INCH, GIVE OR TAKE IN EITHER DIRECTION.
BEHIND THE FRONT, BRISK WSW TO WNW WINDS WILL BE IN PLACE THU
THROUGH SAT AS THE TROUGH OVER THE REGION SLOWLY LIFTS INTO THE NE
US. SUSTAINED WINDS OF 10-15 COULD GUSTS BETWEEN 25-35 MPH. HIGHS
WILL BE MUCH COOLER AND BELOW NORMAL IN THE LOW TO MID/UPPER 50S
THU/FRI, WITH SOME SLIGHT MODERATION IN THE MID 50S TO AROUND 60 BY
SAT. LOWS WILL BE NEAR NORMAL IN THE MID/UPPER 30S DUE TO PERSISTENT
STIRRING. IN REGARDS TO THE UPPER-TROUGH LATE THU THROUGH FRI, THE
ECMWF/CMC SHOW A RATHER IMPRESSIVE VORT MAX ROTATING THROUGH, WHICH
COULD PRODUCE SOME SPRINKLES/CLOUDS WITH THE STEEP LAPSE RATES. THE
GFS/GEFS ARE FURTHER NORTH WITH THIS FEATURE, SO STILL ENOUGH SPREAD
IN THE GUIDANCE TO LEAVE THE FORECAST DRY AT THE MOMENT.
AVIATION /06Z SUNDAY THROUGH THURSDAY/
AS OF 1230 AM SUNDAY...
VFR CONDITIONS EXPECTED AT ALL SITES THROUGH THE PERIOD. HIGH
PRESSURE OVERHEAD WILL ALLOW FOR CALM (OR NEARLY CALM) WINDS THROUGH
THE OVERNIGHT HOURS. A LIGHT SW SURFACE FLOW UNDER 10KT IS EXPECTED
SUNDAY AFTERNOON.
OUTLOOK: VFR WEATHER EXPECTED SUNDAY NIGHT THROUGH MONDAY. A STRONG
COLD FRONT MOVING THROUGH THE REGION ON TUESDAY AND TUESDAY NIGHT
WITH A PERIOD OF SUB-VFR CONDITIONS WITH SHOWERS/GUSTY WINDS.
RAH WATCHES/WARNINGS/ADVISORIES
FROST ADVISORY FROM 4 AM TO 8 AM EST SUNDAY FOR NCZ007>011-021>028-
038>043-073>078-083-084.
SYNOPSIS...BADGETT/MWS
NEAR TERM...MWS
SHORT TERM...KC
LONG TERM...KREN
AVIATION...BADGETT
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