784
FXUS62 KRAH 180812
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
312 AM EST WED DEC 18 2024
SYNOPSIS
LOW PRESSURE MOVING ACROSS THE OHIO VALLEY INTO NEW ENGLAND WILL
DRAG A COLD FRONT THROUGH NORTH CAROLINA TONIGHT, BRINGING A COOLER
PATTERN FOR THE REST OF THE WEEK.
NEAR TERM /THROUGH TONIGHT/
AS OF 310 AM WEDNESDAY...
AS OF EARLY THIS MORNING, DENSE FOG IS PRIMARILY CONTAINED TO
NORTHERN AND SOUTHERN COUNTIES, WITH VISIBILITIES STILL 5-10 MILES
ACROSS CENTRAL COUNTIES, BUT MODEL GUIDANCE INDICATES THAT AREAS OF
DENSE FOG ARE LIKELY ACROSS THE ENTIRE FORECAST AREA BY SUNRISE.
THEREFORE, HAVE ISSUED A DENSE FOG ADVISORY THROUGH MID-MORNING.
LOW PRESSURE IS CURRENTLY ACROSS WESTERN KENTUCKY AND WILL CONTINUE
TO MOVE NORTHEAST THROUGH THE DAY, REACHING THE NEW YORK CITY METRO
AREA BY THIS EVENING AND MOVING EAST OF MAINE BY THURSDAY MORNING.
HIGH-RESOLUTION GUIDANCE SUGGESTS THAT THERE COULD BE SOME SPOTTY
SHOWERS THROUGH MUCH OF THE DAY, BUT DO NOT SEE MUCH OF A FORCING
MECHANISM IN PLACE ACROSS THE REGION. HAVE KEPT THE FORECAST DRY
THIS MORNING, THEN HAVE POPS BEGIN TO INCREASE FROM BOTH NORTHWEST
AND SOUTHEAST ACROSS THE AREA. THE COLD FRONT APPROACHING THE REGION
FROM THE NORTHWEST WILL BRING A HIGHER POTENTIAL FOR RAINFALL, BUT
ACROSS THE SOUTHEAST, THERE WILL BE GREATER INSTABILITY, AT LEAST
500 J/KG OF MUCAPE, AND WILL HAVE A CHANCE OF THUNDERSTORMS ACROSS
THE SOUTHEAST LATE THIS AFTERNOON INTO TONIGHT. THINK THAT THE
HIGHEST CHANCE FOR SHOWERS WILL COME LATE THIS EVENING, AND BELIEVE
THAT THE BULK OF THE RAINFALL WILL OCCUR EAST OF THE TRIAD. RAINFALL
TOTALS CONTINUE TO COME DOWN - OUTSIDE OF AN ISOLATED HEAVY
SHOWER/THUNDERSTORM, MOST LOCATIONS WON'T RECEIVE MORE THAN A TENTH
OF AN INCH OF RAIN. MODELS HAVE REMAINED CONSISTENT IN PUSHING ALL
THE RAIN TO THE EAST OF THE REGION BY DAYBREAK. ANOTHER UNSEASONABLY
WARM DAY IS EXPECTED, WITH HIGHS RANGING FROM THE MID 60S NEAR THE
VIRGINIA BORDER TO THE MID 70S ACROSS THE SOUTH. THERE WILL BE A
WIDE RANGE OF OVERNIGHT LOWS WITH THE COLD AIR NOT IMMEDIATELY
ARRIVING EVERYWHERE BEHIND THE FRONTAL PASSAGE - LOCATIONS IN THE
NORTHWEST WILL FALL INTO THE LOWER 40S, WHILE IN THE SOUTHEAST,
TEMPERATURES WILL ONLY FALL INTO THE MID 50S.
SHORT TERM /THURSDAY AND THURSDAY NIGHT/
AS OF 230 AM WEDNESDAY...
A SHEAR AXIS AT MID-LEVELS STRETCHING FROM THE SE US AND CAROLINAS
AND NEAR DELMARVA WILL MOVE EAST OF OUR REGION DURING THE AFTERNOON
TO EARLY EVENING. THE PASSAGE WILL BE RATHER QUIET AS MOISTURE TIED
TO THE FRONT WILL BE MOVING OFFSHORE DURING THE MORNING. AT THE
SURFACE, THE COLD FRONT WILL CONTINUE ITS MARCH SOUTH, REACHING THE
FAR SE TIP OF NC BY MIDDAY. WINDS WILL SWITCH FROM NNW TO ENE AS THE
DAY WEARS ON AS A CAD WEDGE TRIES TO REDEVELOP. THIS ALONG WITH THE
FACT THAT THE LOW-LEVEL 925-850 MB MOISTURE LINGERS MEANS WE COULD
STILL SEE A FAIR AMOUNT OF LOW STRATUS DURING THE DAY. THE 850 MB
FRONT ACTUALLY LOOKS TO GET HUNG UP ALONG THE APPALACHIANS. HIGHS
WILL BE NOTICEABLY COOLER AND CLOSER TO SEASONAL NORMS WITH LOW 50S
IN THE NORTH AND UPPER 50S IN THE SOUTH. THESE HIGHS MAY BE FELT
EARLIER IN THE DAY GIVEN CAA ENSUING THROUGH THE AFTERNOON.
A STRONG TROUGH DIGS INTO THE LOWER OH VALLEY AND EASTERN TN
OVERNIGHT. AT THE SAME TIME, 850 MB SW MOIST FLOW WILL PERSIST ATOP
THE CAD DOME TRYING TO SETUP. THERE COULD BE SOME LOW-END SPRINKLES
OR PATCHY LIGHT RAIN ACROSS OUR SE ZONES OVERNIGHT, BUT IT APPEARS
DEEP SATURATION FOR WIDESPREAD ACTIVITY IS MINIMAL IN FORECAST
SOUNDINGS. NEVERTHELESS, THE LOW STRATUS EXPECTED OVER MUCH OF THE
AREA WILL KEEP TEMPERATURES WARMER THAN EXPECTED UNDER THE AIRMASS,
WITH LOW TO MID 30S N AND UPPER 30S TO NEAR 40 IN THE SOUTH.
LONG TERM /FRIDAY THROUGH TUESDAY/
AS OF 230 AM WEDNESDAY...
THE STRONG TROUGH FROM THU NIGHT IS FORECAST TO STRENGTHEN AS IT
MOVES ACROSS OUR REGION FRI AFTERNOON AND EVENING. MUCH OF THE 00Z
SUITE OF THE GFS/CMC/ECMWF ARE IN VERY GOOD AGREEMENT WITH THE TRACK
AND TIMING OF THE VORT MAX MOVING SOUTHEAST. THE VORT MAX IS LARGELY
FORECAST TO MOVE DIRECTLY OVERHEAD CENTRAL NC CENTERED AROUND EARLY
EVENING, WITH IMPRESSIVE 180+ M HEIGHT FALLS. THERE IS A CHANCE OF
SOME LIGHT RAIN OR DRIZZLE EAST OF US-1 FRI MORNING TO EARLY
AFTERNOON ASSOCIATED WITH LOW-LEVEL ISENTROPIC ASCENT ATOP THE
SURFACE WEDGE. HOWEVER, FEEL THE BETTER CHANCE OF LIGHT RAIN WILL BE
LATE FRI AFTN AND EVENING WITH THE VORT MAX. MODELS ALSO SHOW A
SURFACE TROUGH AXIS AND PERHAPS A WEAK SURFACE LOW ALONG SC,
TRACKING SE WITH THE MID-LEVEL VORT MAXIMA. ENSEMBLE GUIDANCE WAS
ALSO TRENDING WITH HIGHER POP CHANCES. WE RAISED POPS ACCORDINGLY
(30-PERCENT) IN THE LATE AFTN/EVE AREA-WIDE EXCEPT THE FAR SOUTHERN
PIEDMONT. HIGHS FRI IN THE LOW/MID 50S. IT LOOKS LIKE THE VORT MAX
MOVES EAST BEFORE THE MUCH COLDER AIR MOVES IN. MODEL SOUNDINGS AND
PTYPE NOMOGRAMS ALSO SHOW THIS, SUCH THAT ANY PTYPE CONCERNS ARE NOT
ANTICIPATED THUS FAR.
IT IS ALL ABOUT MUCH COLDER AIR SAT TO EARLY NEXT WEEK AS COLD HIGH
PRESSURE OVER THE UPPER MS VALLEY SAT EVENTUALLY SETTLES INTO THE
MID-ATLANTIC COME MONDAY. AN ARCTIC FRONT WILL MOVE THROUGH SAT
NIGHT. LOW-LEVEL THICKNESSES BECOMING LOWEST SUN INTO MON AROUND
1265-1270 M, SOME 40-45 M BELOW AVERAGE. ANOTHER VORT MAX IS
FORECAST IN THE GUIDANCE/ENSEMBLES TO MOVE THROUGH LATE SAT INTO SUN
WITH THE NW FLOW ALOFT, BUT CURRENT INDICATIONS POINT TO A FURTHER
SOUTH AND WEST TRACK SUCH THAT WE KEPT THE FORECAST DRY FOR NOW.
HIGHS SAT WILL FALL FURTHER INTO THE LOW TO MID/UPPER 40S. HIGHS
SUN/MON WILL BE SOME 12-16 DEGREES BELOW AVERAGE IN THE UPPER 30S TO
LOW 40S AND LOWS IN THE MID TEENS TO LOW 20S, COLDEST MON MORNING
UNDER THE ANOMALOUSLY STRONG 1040 MB SURFACE HIGH.
ENSEMBLE DATA SHOWS THAT RIDGING TO QUASI-ZONAL FLOW IS FORECAST TO
BUILD IN MON AND TUE AT MID-LEVELS, WHILE THE COLD SURFACE HIGH
SLOWLY RETREATS NORTHWARD. THIS SHOULD FAVOR WARMER HIGHS BY TUE IN
THE MID 40S TO LOW 50S.
AVIATION /06Z WEDNESDAY THROUGH SUNDAY/
AS OF 1230 AM WEDNESDAY...
TAF PERIOD: SIMILAR TO 24 HOURS AGO, THERE ARE WIDELY VARYING
CONDITIONS ACROSS THE TERMINALS. THINK THAT GSO AND FAY ARE LIKELY
SOCKED IN WITH DENSE FOG FOR THE REST OF THE NIGHT, WHILE THE OTHER
THREE TERMINALS WILL TAKE A LITTLE LONGER FOR IFR/LIFR RESTRICTIONS
TO DEVELOP. THE DEVELOPMENT OF ADDITIONAL RESTRICTIONS WILL BE
COMPLICATED BY HIGHER CLOUDS MOVING IN FROM THE SOUTHWEST, ALTHOUGH
WITH NO CHANGE IN AIR MASS OVER THE LAST FEW DAYS, THERE IS PLENTY
OF LOW-LEVEL MOISTURE PRESENT FOR FOG/LOW CLOUDS TO DEVELOP. ALL
SITES SHOULD RETURN TO VFR CONDITIONS BY MID AFTERNOON, AND SOME
RESTRICTIONS COULD DEVELOP AT KFAY/KRWI WITH THE NEXT ROUND OF RAIN
THAT IS EXPECTED. THE WIND WILL BE CALM TONIGHT, WITH SOUTHWESTERLY
WIND DEVELOPING LATE THIS MORNING THAT COULD GUST AS HIGH AS 20 KT.
OUTLOOK: SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE POSSIBLE,
PRIMARILY AT RDU/RWI/FAY, THE REST OF WEDNESDAY NIGHT. AN ISOLATED
SHOWER CANNOT BE RULED OUT THURSDAY NIGHT AT ANY SITE. OTHER THAN
THESE TIME PERIODS, VFR CONDITIONS ARE EXPECTED.
RAH WATCHES/WARNINGS/ADVISORIES
DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR NCZ007>011-
021>028-038>043-073>078-083>086-088-089.
SYNOPSIS...GREEN
NEAR TERM...GREEN
SHORT TERM...KREN
LONG TERM...KREN
AVIATION...GREEN
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