187
FXUS62 KRAH 210950
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
450 AM EST TUE JAN 21 2025
SYNOPSIS
ARCTIC HIGH PRESSURE WILL REMAIN ENTRENCHED ACROSS THE REGION
THROUGH EARLY THURSDAY. AN UPPER LEVEL DISTURBANCE WILL MOVE OVER
THE SOUTHEAST STATES TONIGHT INTO WEDNESDAY MORNING, BRINGING LIGHT
SNOW TO THE REGION. LATER IN THE WEEK, A WAVE OF LOW PRESSURE WILL
TRACK NORTHEAST OFF THE COAST OF THE CAROLINAS THURSDAY INTO FRIDAY.
NEAR TERM /TODAY AND TONIGHT/
AS OF 450 AM TUESDAY...
* COLD WEATHER ADVISORY CONTINUES INTO MID-MORNING, THEN AGAIN
TONIGHT INTO WED MORNING FOR ALL OF CENTRAL NC
* WINTER WEATHER ADVISORY EXPANDED FOR AREAS ALONG/EAST OF THE US-1
CORRIDOR GIVEN RECENT HIGH-RES MODEL TRENDS
DID A QUICK UPDATE TO THE FORECAST TONIGHT TO ADD A WINTER WEATHER
ADVISORY FOR ALL AREAS ALONG/EAST OF US-1 GIVEN THE INCREASE IN QPF
FROM THE HRRR/NEST/ECMWF MODEL GUIDANCE. EVEN IF MODEL TRENDS DO NOT
REACH 1 INCH OF SNOW ACCUMULATION, COLD GROUND TEMPS AND THE EVENING
COMMUTE WILL MAKE FOR HAZARDOUS IMPACTS. THE PRIOR DISCUSSION
FOLLOWS IN THE NEXT SEVERAL PARAGRAPHS.
FORECAST CONFIDENCE REMAINS ON THE LOW END, BUT THERE HAS BEEN A
NOTICEABLE NORTH AND WESTWARD SHIFT OF THE EXPECTED SNOW SHIELD THIS
EVENING TO EARLY WED. GUIDANCE HAS ALSO TRENDED HIGHER WITH ITS QPF
AND INDICATES POTENTIAL BANDING THAT COULD SET UP.
ON THE GENERAL SPECIFICS, A SHORTWAVE TROUGH AXIS OVER THE MID MS
VALLEY AND SOUTHERN PLAINS WILL TRACK EAST AND OVER THE AREA THIS
EVENING BEFORE MOVING TOWARD THE COAST WED MORNING. THE NORTHERN
BRANCH OF THE SHORTWAVE TROUGH WILL TRACK TO OUR NORTH INTO THE MID-
ATLANTIC, WHILE A SOUTHERN STREAM SHORTWAVE TRACKS INTO THE FAR SE
US. AS HAS BEEN ADVERTISED, AN IMPRESSIVE 180-200 KT JET STREAK WILL
BE ORIENTED SW TO NE FROM NC INTO DELMARVA AND OFF THE MID-ATLANTIC
COAST. CENTRAL NC TO THE COAST WILL BE UNDER THE RIGHT ENTRANCE
REGION OF THIS JET STREAK FROM ROUGHLY THIS EVENING INTO THE EARLY
OVERNIGHT HOURS OF WED. AT THE SURFACE, A FRONTAL ZONE WILL BE WELL
SOUTH OF OUR REGION AS ARCTIC HIGH PRESSURE OVER THE MIDWEST AND TN
VALLEY SLOWLY SHIFTS INTO THE SOUTHERN APPALACHIANS BY EARLY WED. A
WAVE OF LOW PRESSURE IS FORECAST TO TRACK FROM OFF THE COAST OF
CENTRAL FL INTO THE SOUTHWEST ATLANTIC.
THE COLD WEATHER ADVISORY WILL BE IN EFFECT THROUGH 10 AM. CLOUDS
WILL BUILD IN THIS MORNING AND BECOME OVERCAST AHEAD OF THE MID-
LEVEL ENERGY. WITH THE COLD ARCTIC AIRMASS STILL IN PLACE WITH
LITTLE SUN, WE WILL NOT WARM UP MUCH. WE WENT WITH THE COLDER
GUIDANCE FOR HIGHS, WITH ONLY UPPER 20S NW TO LOW TO MID 30S IN THE
TRIANGLE AND IN THE SOUTHEAST.
THE BIG UNCERTAINTY IS STILL HOW FAR WEST THE BAND OF SNOWFALL WILL
DEVELOP. THERE IS LIKELY TO BE A SHARP GRADIENT DUE TO THE EXTENSIVE
DRY AIR OVER THE REGION. DEWPOINTS ARE PRESENTLY IN THE SINGLE
DIGITS TO BELOW ZERO, WITH LITTLE RECOVERY UNTIL SATURATION RAISES
THESE CLOSER TO WEB-BULB VALUES. THE 00Z SUITE OF MODEL GUIDANCE HAS
COME IN FURTHER NORTH AND WEST, AS WELL AS WITH HIGHER QPF, WITH THE
PRECIPITATION SHIELD. THE NAM AND ITS HIGH-RES COUNTERPART, NAM-
NEST, APPEAR THE MOST BULLISH, WITH AN INCH OR SO ALONG/EAST OF US-1
AND UPWARDS OF 3 OR MORE INCHES FROM SAMPSON COUNTY TO THE CENTRAL
COASTAL PLAIN EAST OF I-95. THE GFS/GEFS AND 03Z RAP ARE NOT AS HIGH
BUT DO SHOW ADVISORY CRITERIA OF AN INCH OR MORE FROM CUMBERLAND
INTO THE COASTAL PLAIN. THE ECMWF REMAINS FAIRLY CONSISTENT, BUT
DOES SHOW HIGHER TOTALS IN THE AFOREMENTIONED AREAS. THE CANADIAN IS
THE DRIEST, ALONG WITH THE 00Z HREF/HRRR. MOST RECENTLY, THE
HRRR/NEST AND NAM CONTINUE TO BE TRENDING FURTHER NORTH AND WESTWARD
WITH THE SNOW TOTALS, WITH THEIR 06Z RUNS SHOWING ADVISORY OR EVEN
WARNING CRITERIA ALONG OR JUST EAST OF THE TRIANGLE. GIVEN ALL OF
THIS, IT CERTAINLY APPEARS THE DRIER SOLUTIONS ARE BECOMING FEW AND
FAR BETWEEN. GUIDANCE IS LIKELY PICKING UP ON A STRONG 70-80 KT
SOUTHWESTERLY JET AT 700 MB. THIS IS TIED TO THE UPPER-JET AND
LIKELY PRODUCING STRONG FRONTOGENETICAL FORCING OVER OUR CENTRAL AND
EASTERN COUNTIES THAT WOULD FAVOR BANDED SNOW. WHERE THE BAND
ULTIMATELY SETS UP IS STILL DIFFICULT TO DISCERN AT THIS POINT GIVEN
THE DRY AIR TO ITS WEST THAT WILL MAKE FOR A SHARP CUTOFF. UPSTREAM
RADAR RETURNS IN MS/AL, THOUGH, DO SHOW SOME NICE BLOSSOMING OF THE
PRECIPITATION SHIELD AND IS CONCERNING. RIGHT NOW, CONFIDENCE ON HOW
FAR WEST THE BAND SETS UP IS TOO LOW TO INTRODUCE ADVISORIES AS FAR
WEST AS THE US-1 CORRIDOR GIVEN THE SEEMINGLY ABRUPT CHANGE IN MODEL
GUIDANCE. HOWEVER, THERE IS ENOUGH OF A SIGNAL AND ENSEMBLE SUPPORT
FROM THE HREF/LREF TO ADD CUMBERLAND TO EDGECOMBE INTO AN ADVISORY
FOR 1 TO 1.5 INCHES OF SNOW. IF MODEL TRENDS CONTINUE TO PROGRESS
WESTWARD, ADVISORIES OR EVEN WARNINGS MAY BE ADDITIONALLY ISSUED AND
EXPECTED AMOUNTS WILL BE INCREASED. INTERESTED PARTIES ALONG/EAST OF
US-1 SHOULD STAY UP TO DATE WITH THE FORECAST AS IT IS LIKELY TO
CHANGE AS THE DAY WEARS ON GIVEN THIS VERY DYNAMIC SITUATION TAKING
SHAPE.
LIGHT SNOW MAY START AS EARLY AS THE LATE AFTERNOON IN OUR
SOUTHWEST, BUT SHOULD BECOME MORE PREVALENT AFTER SUNSET AS ENOUGH
SATURATION ALOFT ALLOWS THE SNOWFLAKES TO REACH THE GROUND. THIS IS
STILL A RATHER QUICK EVENT, WITH ONSET AROUND 6-7 PM AND ENDING
EARLY WED BETWEEN 3-5 AM. SOME GUSTS MAY DEVELOP OVERNIGHT WITH THE
PRESSURE GRADIENT BETWEEN THE ARCTIC HIGH AND OFFSHORE LOW. THIS
ALONG WITH LOWS IN THE LOWER TEENS TO AROUND 20 WILL PRODUCE WIND
CHILLS IN COLD ADVISORY CRITERIA.
SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/
AS OF 338 AM TUESDAY...
* COLD WEATHER ADVISORY INTO MID-MORNING WED, BUT REMAINING COLD
WITH UPPER 20S TO LOW TO MIDDLE 30S FOR HIGHS. OVERNIGHT LOWS IN
THE LOWER TO MIDDLE TEENS UNDER CLEAR SKIES, LIGHT WINDS, AND
POSSIBLE FRESH SNOW COVER
WESTERLY ZONAL FLOW WILL TAKE OVER ALOFT ON WED, AHEAD OF ANOTHER
SHORTWAVE TROUGH DIGGING INTO THE TN/OH VALLEY REGION. AT THE
SURFACE, ARCTIC HIGH PRESSURE WILL RESIDE TO OUR NORTH IN THE
SOUTHERN MID-ATLANTIC, WHILE AN OFFSHORE FRONTAL ZONE RESIDES OFF
THE NC COAST. WE ARE COLD UNDER SUNNY SKIES WITH UPPER 20S TO LOW TO
MID 30S DURING THE AFTERNOON. CLOUDS WILL INCREASE TOWARD EARLY THU,
BUT MOST OF THE NIGHT SHOULD BE CLEAR AND CALM, SUPPORTING VERY COLD
LOWS IN THE LOW TO MIDDLE TEENS. NO PRECIPITATION IS EXPECTED ON WED.
LONG TERM /THURSDAY THROUGH MONDAY/
AS OF 320 AM TUESDAY...
* HIGH CONFIDENCE BELOW TO WELL BELOW NORMAL TEMPERATURES WILL
CONTINUE THROUGH SAT, WITH GREATEST DEPARTURES FROM NORMAL
EXPECTED THU.
* ANOTHER COASTAL SYSTEM COULD RESULT IN SOME BRIEF WINTRY
PRECIPITATION ACROSS THE SOUTHERN AND CENTRAL COASTAL PLAIN
THU/THU NIGHT, HOWEVER CONFIDENCE IN OCCURRENCE REMAINS LOW AND NO
ACCUMULATION IS EXPECTED AT THIS TIME.
THURSDAY: ALOFT, SWLY FLOW WILL PREVAIL OVER CENTRAL NC. AS A PAIR
OF NRN STREAM SHORTWAVES SWING THROUGH THE UPPER MS VALLEY, OH
VALLEY, AND INTO THE NORTHEAST THU/THU NIGHT, THE PARENT TROUGH AXIS
WILL SHARPEN WEST OF THE APPALACHIANS. AT THE SURFACE, THE RIDGE
SHOULD QUICKLY WEAKEN AND RETREAT OUT OF THE REGION THU AS THE
ARCTIC HIGH MOVES EWD OUT OVER THE NRN ATLANTIC. MEANWHILE, AN
INVERTED TROUGH WILL AMPLIFY OFF THE CAROLINA COAST ON THU, WITH A
LOW DEVELOPING OFF THE CENTRAL FL COAST. MODEL GUIDANCE VARIES WRT
THE TIMING AND STRENGTH OF THIS LOW, CONTRIBUTING TO THE FORECAST
UNCERTAINTY. THE NAM IS QUICKEST TO DEVELOP THE LOW AND BRINGS IT
CLOSEST TO THE NC COAST. IF THE NAM VERIFIES, MOISTURE COULD GET
PULLED INLAND AS FAR AS THE COASTAL PLAIN AND POSSIBLY FAR ERN
PIEDMONT OF CENTRAL NC. THERE IS CONTINUED UNCERTAINTY WRT
TEMPERATURES AS THE HIGH MOVES AWAY FROM THE NORTHEAST AND CLOUD
COVER INCREASES. FOR NOW, EXPECT HIGHS IN THE MID 30S TO LOW 40S AND
LOWS IN THE UPPER TEENS TO MID 20S. WILL MAINTAIN A SLIGHT CHANCE
FOR SOME WINTRY PRECIPITATION, ALBEIT WITH LOW CONFIDENCE AND NO
ACCUMULATION, MAINLY ACROSS THE SRN AND CNTL COASTAL PLAIN.
FRIDAY ONWARD: FORECAST SHOULD REMAIN DRY THROUGH SAT NIGHT, WITH
INCREASING UNCERTAINTY AND CHANCES FOR PRECIPITATION THEREAFTER.
ALOFT, THE PARENT TROUGH WILL GRADUALLY WEAKEN AS IT MOVES EWD
THROUGH THE EASTERN US AND OFF THE EAST COAST FRI/FRI NIGHT, WITH
THE FLOW BECOMING BRIEFLY ZONAL SAT/SAT NIGHT. MEANWHILE OUT WEST, A
NRN STREAM S/W WILL DROP SWD THROUGH THE PACIFIC NORTHWEST FRI/FRI
NIGHT, THEN CLOSE OFF AS IT CONTINUES SWD THROUGH NV/CA SAT AND SUN.
THE PARENT LOW AND ITS EMBEDDED SHORTWAVES WILL MOVE THROUGH CENTRAL
AND EASTERN CANADA SAT AND SUN. A SRN STREAM DISTURBANCE WILL LIFT
NWD INTO AND BLOSSOMS OVER THE SRN PLAINS/LOWER MS VALLEY SAT AND
SUN. THE MEDIUM-RANGE MODEL SOLUTIONS BEGIN TO DIVERGE THEREAFTER.
EVENTUALLY THE SRN STREAM DISTURBANCE SHOULD MIGRATE EWD, BUT
HOW/WHEN IT IMPACTS CENTRAL NC WILL DEPEND ON THE EVOLUTION OF A NRN
STREAM S/W EXPECTED TO MOVE THROUGH THE UPPER MS VALLEY/WRN GREAT
LAKES SUN/MON. AT THE SURFACE, AS THE LOW MOVES AWAY FROM THE
SOUTHEAST US COAST, HIGH PRESSURE WILL MOVE EWD THROUGH THE DEEP
SOUTH AND SOUTHEAST FRI/FRI NIGHT. THE HIGH WILL SIT OVER THE
SOUTHEAST US/CAROLINAS SAT, THEN WEAKEN AND SHIFT EWD ON SUN. THE
GUIDANCE BEYOND SUN DIVERGES SIGNIFICANTLY, ESPECIALLY WRT A
POTENTIAL LOW PRESSURE SYSTEM DEVELOPING OVER THE SOUTHERN
PLAINS/LOWER MS VALLEY. CONFIDENCE IS LOW WRT THIS SYSTEM AND ITS
IMPACTS, BUT FOR NOW EXPECT PRIMARILY LIQUID PRECIPITATION IF/WHERE
IT OCCURS, WITH THE COLD AIR CHASING IT ON THE BACK SIDE.
AVIATION /06Z TUESDAY THROUGH SATURDAY/
AS OF 1242 AM TUESDAY...
THERE IS HIGH CONFIDENCE IN VFR TO START THE TAF PERIOD. WHILE MOST
OF THE PERIOD THROUGH 18-21Z TUE IS EXPECTED TO ALSO BE VFR, THERE
ARE INCREASING SIGNALS IN THE MODEL GUIDANCE THAT LIGHT SNOW WILL
OVERSPREAD THE TERMINALS FROM THE SOUTHWEST TO NORTHEAST. SEVERAL OF
THE 00Z MODEL DATA HAVE COME IN WITH HIGHER PROBABILITIES OF SNOW
ACROSS THE EASTERN TERMINALS (RDU/FAY/RWI), WITH HIGHEST
PROBABILITIES FROM FAY TO RWI. GIVEN A MORE CONSISTENT SIGNAL FOR
SNOW IN BOTH PROBABILISTIC AND DETERMINISTIC GUIDANCE, OUR
CONFIDENCE IS HIGHEST THAT FAY/RWI ARE LIKELY TO SEE IFR OR LOWER
RESTRICTIONS. THE CURRENT TIMING FOR THE SNOW IS ROUGHLY FROM 22-23Z
TUE TO 05-06Z WED. AT RDU, THE BAND OF LIGHT SNOW MAY SKIRT JUST TO
THE EAST BUT CONFIDENCE WAS HIGH ENOUGH TO INCLUDE AT LEAST MVFR VIS
RESTRICTIONS. AT GSO/INT, CONFIDENCE IS TOO LOW TO INTRODUCE SNOW OR
SUB-VFR RESTRICTIONS, BUT DID INCLUDE A PROB30 FOR POTENTIAL LIGHT
SNOW BETWEEN 21 AND 24Z. SOME GUSTS TO 16 KT ARE POSSIBLE LATE IN
THE TAF PERIOD FROM THE N AND NW.
OUTLOOK: LIGHT SNOW SHOULD END AT THE EASTERN TERMINALS EARLY WED,
WITH VFR RETURNING. A SYSTEM IS FORECAST TO CROSS THE REGION FRI
INTO SAT, BUT CONFIDENCE ON ANY SUB-VFR RESTRICTIONS IN WINTRY
PRECIPITATION IS TOO LOW AT THE MOMENT.
CLIMATE
RECORD LOW MAXIMUM TEMPERATURES:
JANUARY 22:
KGSO: 29/2014
KRDU: 27/1970
JANUARY 23:
KGSO: 28/1954
KFAY: 30/1970
RECORD LOW MINIMUM TEMPERATURES:
JANUARY 23:
KRDU: 8/1977
KFAY: 9/1970
RAH WATCHES/WARNINGS/ADVISORIES
COLD WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR NCZ007>011-
021>028-038>043-073>078-083>086-088-089.
COLD WEATHER ADVISORY FROM 3 AM TO 10 AM EST WEDNESDAY FOR
NCZ007>011-021>028-038>043-073>078-083>086-088-089.
WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 7 AM EST
WEDNESDAY FOR NCZ011-026>028-041>043-075>078-083>086-088-089.
SYNOPSIS...KREN/HARTFIELD
NEAR TERM...KREN
SHORT TERM...KREN
LONG TERM...KC
AVIATION...KREN
CLIMATE...RAH
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