418
FXUS62 KRAH 181526
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1026 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 1025 AM WEDNESDAY...
* DENSE FOG ADVISORY WAS ALLOWED TO EXPIRE AS CONDITIONS BEGIN
TO IMPROVE ALTHOUGH PATCHES OF THICK FOG WILL BE SLOW TO
COMPLETELY ERODE ACROSS THE SANDHILLS AND SOUTHERN COASTAL
PLAIN.
QUICK UPDATE THIS MORNING AS WIDESPREAD DENSE FOG EARLY THIS
MORNING IS BEGINNING TO ERODE ALTHOUGH SOME AREAS OF FOG WILL
PERSIST THROUGH MIDDAY. FOG WILL BE MOST STUBBORN AND PERSISTENT
ACROSS SOUTHERN AND SOUTHEASTERN AREAS IN THE SANDHILLS AND
SOUTHERN COASTAL PLAIN WHERE VISIBILITIES MAY BE LESS THAN A 1/2
MILE AT TIMES THROUGH MIDDAY. IN THESE AREAS A LAYER OF STRATUS
AND EVEN A FEW SPRINKLES MOVING NORTHEAST OUT OF NORTHEASTERN
SC MAY PROVIDE COVER AND REDUCE THE AMOUNT OF SUNSHINE AVAILABLE
TO ERODE THE FOG. ADDED A SLIGHT CHANCE OF A SHOWER ACROSS
SOUTHEASTERN AREAS LATE THIS MORNING AND EARLY THIS AFTERNOON AS
WARM ADVECTION SPRINKLES/SHOWERS SPREAD INTO THE SANDHILLS AND
COASTAL PLAIN. MADE LITTLE ADJUSTMENT TO TEMPERATURES WHICH WILL
BE A WILD RIDE TODAY DEPENDING ON FOG AND CLOUD COVER WITH THE
POTENTIAL FOR TEMPS TO BE TOO WARM ACROSS THE SOUTHEASTERN
AREAS. -BLAES
PREVIOUS DISCUSSION FROM 310 AM...
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 THROUGH 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 /15Z WEDNESDAY THROUGH SUNDAY/
AS OF 635 AM WEDNESDAY...
TAF PERIOD: WIDESPREAD CIG/VIS RESTRICTIONS ARE PRESENT AT ALL
TERMINALS - DO NOT BELIEVE THAT THE CURRENT VFR CONDITIONS AT
INT/GSO WILL PERSIST. IT WILL LIKELY TAKE MUCH OF THE MORNING FOR
CONDITIONS TO RETURN TO MVFR, WITH VFR RETURNING DURING THE
AFTERNOON. THERE WILL BE A CHANCE OF SHOWERS AT ALL SITES BY LATE
AFTERNOON, WITH PREVAILING RAIN FOR A FEW HOURS AT CENTRAL/EASTERN
TERMINALS. THESE SITES ALSO HAVE A SLIGHT CHANCE OF A THUNDERSTORM
AS WELL, BUT CONFIDENCE IS NOT HIGH ENOUGH TO INCLUDE IN THE
FORECAST. IN ADVANCE OF AN APPROACHING COLD FRONT, GUSTS COULD REACH
20 KT OUT OF THE SOUTHWEST THIS AFTERNOON, THEN WINDS WILL VEER AS
THE FRONT MOVES THROUGH AFTER MIDNIGHT.
OUTLOOK: THERE WILL BE A CHANCE OF SHOWERS AND MVFR RESTRICTIONS AT
ALL TERMINALS FRIDAY. OTHERWISE VFR CONDITIONS ARE EXPECTED.
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...GREEN
NEAR TERM...BLAES/GREEN
SHORT TERM...KREN
LONG TERM...KREN
AVIATION...MWS
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