547
FXUS62 KMHX 221421
AFDMHX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEWPORT/MOREHEAD CITY NC
921 AM EST SUN DEC 22 2024
SYNOPSIS
HIGH PRESSURE BUILDS IN THROUGH MONDAY BRINGING COLD, DRY
CONDITIONS. A COASTAL LOW IS NOW FORECAST TO IMPACT THE AREA
MONDAY NIGHT AND TUESDAY. HIGH PRESSURE THEN REBUILDS INTO THE
AREA THROUGH THE REMAINDER OF THE WEEK.
NEAR TERM /TODAY/
AS OF 920 AM SUNDAY...STRONG HIGH PRESSURE RIDGE REMAINS
CENTERED ACROSS THE GREAT LAKES AND EXTENDS SOUTH AND WEST
ACROSS THE CAROLINAS. COLD HIGH PRESSURE WILL CONTINUE TO BUILD
OVER THE CAROLINAS TODAY, MAKING FOR A COLD/DRY DAY. LOW LEVEL
THICKNESS VALUES AND NNE FLOW WILL RESULT IN BELOW NORMAL TEMPS,
WITH HIGHS IN THE UPPER 30S TO LOW 40S. NORTHERLY FLOW WILL
LIKELY KEEP SCU STREAMING OVER THE OUTER BANKS, WITH MOSTLY
SUNNY SKIES EXPECTED ELSEWHERE.
SHORT TERM /TONIGHT/
AS OF 300 AM SUNDAY... COLD AIRMASS IN PLACE WILL SUPPORT WELL
BELOW NORMAL TEMPERATURES TONIGHT. HIGH PRESSURE SHIFTS EAST
OVER NEW ENGLAND TONIGHT, WITH RIDGING EXTENDING SOUTHWARD OVER
THE COASTAL PLAIN AND PIEDMONT REGIONS OF NC. IT IS LIKELY THAT
WINDS GO CALM TONIGHT ALONG AND WEST OF HWY 17 WHERE RIDGING IS
PREVALENT. GRADIENT DOES BECOME A BIT MORE PINCHED EAST OF HWY
17, AS HIGH INTERACTS WITH A COASTAL TROUGH SETTING UP TO OUR
SOUTH. DESPITE THE SLIGHTLY STRONGER GRADIENT, CURRENT FORECAST
(ALBEIT WITH SOME UNCERTAINTY) CALLS FOR DECOUPLING, AND
THEREFORE CALM WINDS EAST OF HWY 17 AS WELL (EXCEPT FOR
BEACHES). IN A RADIATIONAL COOLING SETUP WITH LOW DEWPOINTS,
LOWS OFTEN END UP BELOW BOTH MOS, AND DETERMINISTIC GUIDANCE.
CONSIDERING THIS, MOST LIKELY SCENARIO IS LOWS TONIGHT REACH THE
UPPER TEENS INLAND, LOW 30S FOR BEACHES. IF INLAND AREAS EAST
OF HWY 17 REMAIN MIXED THROUGH THE NIGHT, THEY WOULD END UP
SEEING TEMPS IN THE LOW TO MID 20S INSTEAD OF THE UPPER TEENS
CURRENTLY FORECAST. WITH APPARENT TEMPS FORECAST TO REMAIN ABOVE
15F, A COLD WEATHER ADVISORY IS NOT EXPECTED TO BE ISSUED FOR
TONIGHT. HEADLINE OR NOT, THE KEY MESSAGE IS STILL THE SAME...IT
WILL BE COLD.
LONG TERM /MONDAY THROUGH SATURDAY/
AS OF 230 AM SUNDAY...
KEY MESSAGES
- TUESDAY (CHRISTMAS EVE) IS BEGINNING TO TREND WETTER
ASSOCIATED WITH A WEAK COASTAL LOW MOVING THROUGH ENC
- CONTINUED UNCERTAINTY REGARDING TEMPS AND PRECIP OVER THE
REMAINDER OF THE HOLIDAYS
FROM A 50,000 FT VIEW, GUIDANCE CONTINUES TO POINT TOWARDS UPPER
LEVEL RIDGING BECOMING A DOMINANT FEATURE ACROSS THE EASTERN U.S.
OVER MUCH OF THE UPCOMING WEEK. AT THE SFC, A NOTABLY STRONG AREA OF
HIGH PRESSURE LOOKS TO SETUP SHOP ACROSS THE NORTHEAST U.S. THIS
TYPE OF PATTERN OFTEN FAVORS LOW-IMPACT, QUIET WEATHER. HOWEVER,
THERE ARE SOME NOTABLE CAVEATS THAT POTENTIALLY COMPLICATE THE
FORECAST.
MOST NOTABLY IS THE POTENTIAL FOR A WEAK COASTAL LOW TO DEVELOP OFF
THE NC COAST MONDAY NIGHT OR TUESDAY. OVER THE PAST FEW DAYS, SOME
MODELS HAVE SHOWN THIS FEATURE OFF AND ON, BUT RECENT 12Z AND 00Z
GUIDANCE HAVE SHOWN A NOTABLY STRONGER SIGNAL WITH THIS FEATURE. THE
POTENTIAL LOW IS TIED TO A WEAK SOUTHERN STREAM SHORTWAVE THAT IS
FORECAST TO MOVE THROUGH THE SOUTHEAST U.S. PRIOR TO UPPER LEVEL
RIDGING GETTING ESTABLISHED. THIS WAVE, WHILE WEAK, SHOULD INDUCE
WEAK CYCLOGENESIS (~1020MB SFC LOW) ALONG A COASTAL TROUGH BY MONDAY
NIGHT. THE SUBSEQUENT TRACK OF THE LOW REMAINS LESS CERTAIN, BUT
THERE IS DECENT CONSENSUS WITH BRINGING THE LOW UP ALONG THE NC
COAST TUESDAY, THEN OFFSHORE BY TUESDAY NIGHT.
IN LIGHT OF THAT, THE LATEST EXPECTATION IS THAT AN AREA OF MODEST
LOW-MID LEVEL FRONTOGENESIS PLUS INCREASING LOW-LEVEL FORCING SHOULD
SUPPORT A PERIOD OF MODERATE RAIN FOCUSED FROM SE NC NORTHEAST
THROUGH MUCH OF ENC. A NARROW PLUME OF INSTABILITY GETTING PULLED
NORTH WITH THE SYSTEM MAY LEAD TO A PERIOD OF HIGHER PRECIP RATES
RIGHT ALONG THE COAST. ENSEMBLE MEAN QPF GUIDANCE NOW SHOWS A 30-50%
CHANCE OF EXCEEDING 0.25" OF RAIN, WITH A 10-20% CHANCE OF EXCEEDING
1" OF RAIN (MAINLY ALONG THE COAST). WHILE THERE ARE DIFFERENCES
WITH THE STRENGTH OF THE LOW, THERE CERTAINLY APPEARS TO BE AN
INCREASING SIGNAL FOR A QUICK-HITTING ROUND OF RAIN ACROSS ENC
MONDAY NIGHT INTO TUESDAY.
ONE OTHER NOTE WITH THIS SYSTEM IS THAT THE INITIAL PRECIP WILL BE
MOVING INTO A DEPARTING COLD AIRMASS FROM THE PAST COUPLE OF DAYS.
FORECAST SOUNDING SHOW A VERY SHALLOW COLD LAYER, WITH WET-BULB
TEMPS AROUND 31-33F ACROSS PORTIONS OF THE COASTAL PLAIN MONDAY
NIGHT. TEMPS ALOFT WILL BE VERY WARM (5-10C), SO FROZEN
PRECIPITATION (IE. SLEET/SNOW) IS NOT EXPECTED. HOWEVER, DEPENDING
ON HOW QUICKLY THE PRECIP MOVES IN, THERE COULD BE A VERY BRIEF (1-2
HR) PERIOD OF VERY LIGHT FREEZING RAIN AT THE ONSET. BECAUSE OF THE
LOW PROBABILITY, THE FORECAST WILL REFLECT ALL RAIN WITH LOWS AROUND
33F ACROSS THE COASTAL PLAIN, BUT STAY TUNED IN CASE THIS RISK WERE
TO INCREASE. ONE OTHER CONSIDERATION IS THAT EVEN WITH LIGHT RAIN AT
33F, THERE IS A SCENARIO WHERE THE COLD RAIN FALLS ON ROADS WITH
COLD TEMPS FROM THE RECENT COLD SNAP, AND THIS COULD LEAD TO SOME
SLICK SPOTS, EVEN WHERE TEMPS AREN'T BELOW 32F.
ONCE THIS SYSTEM MOVES AWAY FROM THE AREA, A GENERAL DRYING TREND
APPEARS LIKELY AS THE ABOVE-MENTIONED UPPER RIDGE BUILDS
OVERHEAD. HOWEVER, THERE ARE STILL MODEL DIFFERENCES REGARDING
THE STRENGTH OF THE RIDGE, AND WHETHER OR NOT ANOTHER COASTAL
TROUGH WILL SUPPORT SHOWER ACTIVITY. FOR THIS REASON, WE'LL
CONTINUE TO LEAVE A LOW-END CHANCE OF SHOWERS IN THE FORECAST. LATE
IN THE WEEK, THE UPPER RIDGE IS FORECAST TO SHIFT OFFSHORE,
WITH A MOISTENING RETURN FLOW DEVELOPING. THIS MAY SUPPORT A
HIGHER CHANCE OF RAIN SHOWERS BY THE WEEKEND.
TEMPERATURES ARE STILL EXPECTED TO MODERATE THROUGH THE WEEK. HOWEVER,
WITH SFC RIDGING IN PLACE, AND PERSISTENT NORTHEASTERLY LOW-
LEVEL FLOW, GUIDANCE HAS TRENDED SLOWER WITH THE MODERATION.
AVIATION /14Z SUNDAY THROUGH THURSDAY/
SHORT TERM /THROUGH TONIGHT/...
AS OF 655 AM SUNDAY... VFR CONDITIONS WITH SKC AND P6SM VIS
EXPECTED THROUGH THE PERIOD FOR ALL TAF TERMINALS AS HIGH
PRESSURE BUILDS. LIGHT TO CALM WINDS TONIGHT REMAIN LIGHT OUT OF
THE NORTH THROUGH THE DAY BEFORE BECOMING CALM TONIGHT. COASTAL
WATERS AND PORTIONS OF OBX COULD SEE MVFR MARINE STRATOCUMULUS
THROUGH THE PERIOD, STARTING OFF OFFSHORE AND SHIFTING OVER OBX
THROUGH THE DAY AS WINDS VEER FROM NNW TO N.
LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 230 AM SUNDAY...
KEY MESSAGES
- RISK OF SUB VFR CONDITIONS INCREASING MONDAY NIGHT - TUESDAY
A WEAK COASTAL LOW IS FORECAST TO MOVE ALONG, OR VERY NEAR, THE
COAST OF EASTERN NC MONDAY NIGHT THROUGH TUESDAY, AND GUIDANCE HAS
TRENDED WETTER WITH THIS SYSTEM. FOR AVIATION PURPOSES, THIS EQUATES
TO AN INCREASING RISK OF SUB VFR CONDITIONS, INCLUDING A RISK OF
LIFR/IFR CONDITIONS. THERE MAY ALSO BE A RISK OF A FEW TSRA, MAINLY
ALONG THE IMMEDIATE COAST. INLAND, THE INITIAL PRECIP MONDAY NIGHT
WILL COME AS THE RECENT COLD AIR DEPARTS, AND THIS MAY OPEN THE DOOR
FOR A VERY BRIEF PERIOD OF LIGHT FZRA. RIGHT NOW, THE CHANCE APPEARS
LOW (<5% CHANCE), BUT IS WORTH NOTING. A MIX OF MVFR AND VFR
CONDITIONS THEN APPEARS LIKELY FROM CHRISTMAS DAY ON.
MARINE
SHORT TERM /THROUGH TONIGHT/...
AS OF 920 AM SUNDAY...A BRIEF PERIOD OF TIGHTENED PRESSURE
GRADIENT WINDS COULD CONTINUE TO PRODUCE GUSTS OF 25 KTS OR
GREATER THROUGH THE EARLY MORNING HOURS FOR THE COASTAL WATERS.
WILL DROP SCA FOR THE PAMLICO SOUND AND SOUTHERN WATERS IN THE
NEXT HOUR OR TWO. LATEST OBS SHOW N-NNE WINDS 15-20 KT WITH
OCCASIONAL GUSTS OF 25 KT AND SEAS 5-6 FT NORTH OF OCRACOKE AND
3-5 FT SOUTH. SCAS CONTINUE FOR THE COASTAL WATERS. STRONG HIGH
PRESSURE TO THE NORTH WILL CONTINUE TO BUILD INTO THE CAROLINAS
THROUGH TONIGHT, KEEPING A MODEST GRADIENT OVER THE WATERS.
N/NNE WINDS WILL DIMINISH TO 10-20 KT TODAY AND TONIGHT WHILE
SEAS DROP TO 2-5 FT, HIGHEST N OF OCRACOKE.
LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 230 AM SUNDAY...
KEY MESSAGES
- MONITORING POTENTIAL MINOR IMPACTS FROM A WEAK COASTAL LOW
MONDAY NIGHT - TUESDAY
GUIDANCE CONTINUES TO SHOW A FAIRLY GOOD SIGNAL FOR THE DEVELOPMENT
OF A WEAK COASTAL LOW MONDAY NIGHT AND TUESDAY. AT THE MOMENT, THE
WEAK NATURE OF THE LOW LOOKS TO KEEP MARINE IMPACTS AT A MINIMUM.
HOWEVER, STAY TUNED AS A STRONGER LOW WOULD INTRODUCE AN INCREASED
RISK OF ELEVATED WINDS AND SEAS. BEYOND TUESDAY, NORTHEASTERLY FLOW
OF 10-20KT IS EXPECTED, WITH SEAS OF 2-4 FT FOR MOST COASTAL WATERS.
MHX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EST THIS MORNING FOR AMZ135.
SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR AMZ150.
SMALL CRAFT ADVISORY UNTIL 4 AM EST MONDAY FOR AMZ152-154.
SMALL CRAFT ADVISORY UNTIL 10 AM EST THIS MORNING FOR AMZ156-
158.
SYNOPSIS...MHX
NEAR TERM...CQD/RJ
SHORT TERM...RJ
LONG TERM...RM
AVIATION...RM/RJ
MARINE...RM/CQD/RJ
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