040
FXUS62 KMHX 230532
AFDMHX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEWPORT/MOREHEAD CITY NC
1232 AM EST MON DEC 23 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 /THROUGH TODAY/
AS OF 1900...NO CHANGES REQUIRED TO THE NEAR TERM WITH
EVERYTHING ON TRACK.
PREVIOUS DISCO...LATEST ANALYSIS SHOWS 1036MB CENTERED OVER
SOUTHERN ONTARIO/QUEBEC AND THE GREAT LAKES RIDGING SOUTHWARD
THROUGH THE EASTERN US. THE HIGH WILL GRADUALLY SHIFT EASTWARD
OVERNIGHT. NNE FLOW WILL LIKELY KEEP SCU STREAMING OVER THE
OUTER BANKS, WITH MOSTLY CLEAR SKIES EXPECTED ELSEWHERE.
CONTINUED TO GO BELOW GUIDANCE GIVEN THE GOOD RADIATIONAL
COOLING SETUP INLAND WITH CALM/LIGHT WINDS, CLEAR SKIES AND
DEWPOINTS IN THE TEENS THIS AFTERNOON. EXPECT LOWS TO FALL INTO
THE UPPER TEENS TO LOW 20S INLAND AND UPPER 20S/LOW 30S FOR THE
BEACHES.
SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/
AS OF 230 PM SUN...HIGH PRESSURE OVER NEW ENGLAND WILL CONTINUE
TO SHIFT EASTWARD AND OFFSHORE, WHILE UPPER RIDGE GRAD BUILDS
OVER THE CAROLINAS. TEMPS WILL REMAIN BELOW NORMAL, BUT WARMING
SEVERAL DEGREES FROM THE PAST FEW DAYS. LOW LEVEL THICKNESS
VALUES AND NE FLOW SUPPORT HIGHS IN THE MID 40S TO LOW 50S. THE
NE FLOW WILL LIKELY KEEP SCT-BKN SCU ALONG THE IMMEDIATE COAST
WITH MOSTLY SUNNY SKIES ELSEWHERE.
LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/
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 /06Z MONDAY THROUGH FRIDAY/
SHORT TERM /THROUGH 06Z TUESDAY/...
AS OF 1230 AM MONDAY...VFR FLIGHT CATS EXPECTED THROUGH THE TAF
PERIOD WITH HIGH PRESSURE IN CONTROL. WINDS RELAX OVERNIGHT,
PERHAPS DECOUPLING INLAND, BEFORE BECOMING LIGHT AGAIN FROM THE
NORTH DURING THE DAY MONDAY. LOW LEVEL CLOUD COVER AND RAIN
CHANCED START MOVING INTO THE REGION FROM THE SOUTH JUST BEYOND
THE TAF PERIOD AS A COASTAL TROUGH OFFSHORE SPINS UP A WEAK
COASTAL LOW. SEE THE LONG TERM SECTION FOR MORE INFORMATION.
LONG TERM /06Z TUESDAY THROUGH FRIDAY/...
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 MONDAY/...
AS OF 1900 SUNDAY...WAS ABLE TO CANCEL THE NERN WATERS SCA
EARLY. REST OF THE FORECAST REMAINS ON TRACK.
PREVIOUS DISCO...LATEST OBS SHOW NNE WINDS 10-20 KT WITH SEAS
4-5 FT NERN WATERS, 4-6FT CENTRAL, AND 3-5 FT SOUTH OF OCRACOKE.
HIGH PRESSURE TO THE NORTH WILL REMAIN IN CONTROL THROUGH THE
PERIOD, SLOWLY PUSHING OFF THE NEW ENGLAND COAST MONDAY, KEEPING
NE WINDS 10-20 KT THROUGH MONDAY. SCAS CONTINUE FOR THE
CENTRAL WATERS THROUGH THIS EVENING AND TONIGHT FOR ELEVATED
SEAS, WITH SEAS GRADUALLY SUBSIDING TO 2-5 FT LATE TONIGHT AND
MON.
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
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...NONE.
SYNOPSIS...MHX
NEAR TERM...CQD/CEB
SHORT TERM...CQD
LONG TERM...RM
AVIATION...RM/RJ
MARINE...RM/CQD/CEB
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