833
FXUS62 KRAH 211744
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1244 PM 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
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 /THROUGH TONIGHT/
AS OF 1240 PM TUESDAY...
* WINTER STORM WARNING HAS BEEN ISSUED FOR A PORTION OF THE COASTAL
PLAIN AND EASTERN SANDHILLS FROM 5 PM UNTIL 7 AM WEDNESDAY.
* WINTER WEATHER ADVISORY HAS BEEN EXPANDED SLIGHTLY FARTHER WEST TO
INCLUDE STANLY, MONTGOMERY, AND CHATHAM.
* COLD WEATHER ADVISORY REMAINS IN EFFECT FOR TONIGHT INTO EARLY
WEDNESDAY MORNING.
THE WINTER STORM THAT IS EXPECTED TO IMPACT OUR AREA LATER THIS
EVENING INTO THE OVERNIGHT HOURS IS WELL UNDERWAY OVER LA, SOUTHERN
MS, AND AL. A POTENT 180 KT 250MB JET WILL CONTINUE TO STRENGTHEN TO
AROUND 200 KTS AS THE RIGHT-ENTRANCE REGION SAGS OVER THE SOUTHERN
MID-ATLANTIC AND SOUTHEAST. THIS WILL BE THE MAIN PLAYER IN BRINGING
IN VERY LIGHT SNOW LATER THIS AFTERNOON AND EVENING. SNOW RATES ARE
EXPECTED TO INCREASE AS THE COLUMN BEGINS TO FURTHER SATURATE AND
STRONG LOW/MID-LEVEL FORCING BEGINS TO SPREAD INTO OUR AREA AFTER
00Z.
TRENDS IN THE LATEST MODEL GUIDANCE SHOWS A STEADY INCREASE THE
LIQUID EQUIVALENT AMOUNTS OVER OUR AREA. NOW, WE ARE ONLY TALKING
ABOUT ON THE ORDER OF A HUNDREDTHS TO A TENTH, BUT ANOMALOUSLY HIGH
SNOW-LIQUID RATIOS FOR THE CAROLINAS RESULTS IN DRASTIC DIFFERENCES
IN THE EVENTUAL SNOWFALL AMOUNTS. A COMBINATION OF MORE LIQUID
EQUIVALENT AND HIGHER SNOWFALL RATIO HAS RESULTED IN 2 TO 4 INCHES
OF SNOW POSSIBLE IN THE WINTER STORM WARNING AREA WITH A DUSTING TO
2 INCHES IN THE ADVISORY AREA. GREATEST ACCUMULATIONS WILL LIKELY BE
FROM 9 PM TO 3 AM.
A COUPLE VERY IMPORTANT POINTS TO REMEMBER FOR THIS EVENT. THE VERY
COLD ANTECEDENT CONDITIONS AHEAD OF THIS SYSTEM WILL RESULT IN
HIGHLY EFFICIENT ACCUMULATIONS AS SOON AS SNOW BEGINS TO FALL. FIRST
FLURRIES WILL LIKELY BEGIN VERY LIGHT AND NOT RESULT IN MUCH IMPACT
UNTIL THIS EVENING WHEN RATES ARE EXPECTED TO INCREASE. HOWEVER,
ONCE SNOW BEGINS TO FALL ON ANY UNTREATED SURFACE, EXPECT SURFACES
TO BECOME IMMEDIATELY SLIPPERY. ALSO, WITH HIGH SNOW-LIQUID RATIOS
RESULTING IN DRY AND POWDERY SNOW, WE ARE NOT EXPECTING MUCH IMPACT
FROM SNOW LOAD, OR STRESS ON TREES TO RESULT IN MANY POWER OUTAGES
WITH THE MAIN IMPACT FROM HAZARDOUS DRIVING CONDITIONS.
OVERNIGHT LOWS WILL BE WELL BELOW NORMAL WITH APPARENT TEMPERATURES
IN THE SINGLE DIGITS FOR MOST LOCATIONS GIVEN THE CONTINUED MIXED
BOUNDARY LAYER. AS SUCH, THE COLD WEATHER ADVISORY REMAINS IN EFFECT
FOR TONIGHT.
SHORT TERM /WEDNESDAY THROUGH THURSDAY 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.
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.
LONG TERM /FRIDAY THROUGH TUESDAY/
AS OF 1240 PM TUESDAY...
NO MAJOR CHANGES IN THE EXTENDED AT THIS TIME. THE MEAN, POSITIVELY
TILTED LONG WAVE TROUGH BRIEFLY GIVES WAY TO FLATTER ZONAL FLOW
ACROSS THE SOUTHERN USA AND HIGH MIGRATING ACROSS THE SOUTHEAST.
THIS WILL PROVIDE A WELCOME OPPORTUNITY FOR MODERATING TEMPERATURES
WITH NEAR NORMAL CONDITIONS BY SUN/MON. MEANWHILE AN UPPER LOW IS
EXPECTED TO DEVELOP OVER THE SOUTHWESTERN US WITH SPLIT FLOW
EVOLVING DOWNSTREAM ACROSS THE CENTRAL US. THE NEXT CHANCE OF
PRECIPITATION LOOKS TO COME EARLY NEXT WEEK AS A NORTHERN STREAM
WAVE IS FORECAST DIVE INTO THE MIDWEST, WHICH RESULTS IN A WAVE OF
LOW PRESSURE AND PRECIPITATION BREAKING ACROSS THE DEEP SOUTH.
LATEST MODEL RUNS SUGGEST THE BEST TIMING FOR PRECIP ACROSS NC WILL
BE SUNDAY NIGHT INTO MONDAY, WITH A RELATIVELY LIGHT EVENT THAT
SHOULD BE ALL LIQUID GIVEN THE LACK OF A PARENT HIGH AND COLD
ADVECTION FROM THE NORTH. THAT SAID THE ARCTIC AIRMASS WILL STILL
BE JUST TO THE NORTH AND CRITICAL THICKNESSES ARE CLOSE ENOUGH THAT
THIS SYSTEM WILL BE MONITORED FOR PTYPES. THERE'S STILL ENOUGH MODEL
DISCREPANCY TO WARRANT JUST CHANCE POPS AT THIS TIME.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
AS OF 1240 PM TUESDAY...
VFR CONDITIONS TO START THE TAF PERIOD BUT AN AREA OF LIGHT SNOW IS
EXPECTED TO OVERSPREAD CENTRAL NC LATER THIS AFTERNOON. ALL 5 TAF
SITES SHOULD SEE SOME DEGREE OF AVIATION IMPACTS, PRIMARILY IN THE
FORM OF REDUCED VSBYS. DETAILS AS FOLLOWS:
INT AND GSO: LIKELY TO BE ON THE FAR WESTERN EDGE OF THE SNOW. SNOW
ARRIVING BETWEEN 20-22Z, AND WHILE RESTRICTIONS TO MVFR ARE POSSIBLE
THIS EVENING, THEY SHOULD BE SHORT LIVED. RECOVERING TO VFR BEFORE
MIDNIGHT WITH SKIES CLEARING OUT ENTIRELY BEFORE DAYBREAK.
RDU: EXPECT LIGHT SNOWFALL ONSET JUST BEFORE 00Z, WITH A FEW
HOURS OF IFR SNOW BETWEEN 00Z AND 04Z. THIS SHOULD ALSO WRAP UP
QUICKLY WITH DRY WEATHER AND VFR CONDITIONS RETURNING SHORTLY
AFTER MIDNIGHT, WITH CLEAR SKIES BY DAYBREAK.
FAY/RWI: LIKELY TO SEE THE LONGEST DURATION OF SNOW WITH THE LOWEST
VSBYS AND CEILINGS. SNOW ARRIVING AROUND 21-22Z, HEAVIEST FROM 00Z
TO 06Z, TAPERING OFF AROUND 08Z, CLEARING OUT ENTIRELY AFTER 14Z.
GUSTY NORTH WINDS AROUND 15-18KTS POSSIBLE AT ALL SITES THROUGH
WEDNESDAY MORNING.
OUTLOOK: VFR IS EXPECTED TO RETURN WED MORNING. A SYSTEM IS FORECAST
TO CROSS THE REGION THU 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 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 NCZ011-026-027-040>042-073>077-083-084.
WINTER STORM WARNING FROM 5 PM THIS AFTERNOON TO 7 AM EST
WEDNESDAY FOR NCZ028-043-078-085-086-088-089.
SYNOPSIS...KREN/HARTFIELD
NEAR TERM...SWIGGETT
SHORT TERM...KREN/KC
LONG TERM...SMITH
AVIATION...LEINS
CLIMATE...RAH
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