997
FXUS62 KRAH 200741
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
240 AM EST MON JAN 20 2025
SYNOPSIS
ARCTIC HIGH PRESSURE WILL REMAIN ENTRENCHED ACROSS THE REGION TODAY
THROUGH MIDWEEK, BRINGING BITTER COLD TEMPERATURES. A WAVE OF LOW
PRESSURE WILL TRACK NORTHEAST OFF THE COAST OF THE CAROLINAS
THURSDAY INTO FRIDAY.
NEAR TERM /TODAY AND TONIGHT/
AS OF 240 AM MONDAY...
* COLD WEATHER ADVISORY IN EFFECT FOR ALL OF CENTRAL NC 10 PM
TONIGHT THROUGH 10 AM TUESDAY WITH WIND CHILLS RANGING FROM 2 TO 9
DEGREES
VERY COLD TEMPERATURES ARE EXPECTED TODAY AND ESPECIALLY TONIGHT
INTO TUE MORNING AS 1038 MB ARCTIC HIGH PRESSURE OVER THE MID MS
VALLEY SETTLES INTO THE EASTERN TN VALLEY AND SOUTHERN APPALACHIANS.
ALOFT, WSW FLOW WILL PERSIST MOST OF THE DAY AND NIGHT AHEAD OF A
SHORTWAVE TROUGH OVER THE UPPER MS VALLEY AND NORTHERN PLAINS THAT
WILL REACH THE MID MS VALLEY AND GREAT LAKES BY 12Z TUE.
NORTHWEST WINDS TODAY WILL GUST AT TIMES TO 15 TO 20 MPH. ALONG WITH
SURFACE TEMPERATURES RANGING FROM THE UPPER 20S NW TO MID 30S SE
WILL PRODUCE WIND CHILLS INTO THE AFTERNOON OF UPPER TEENS IN THE NW
TO AROUND 30 IN THE SOUTH AND SOUTHEAST. TONIGHT, THE PRESSURE
GRADIENT RELAXES, ALTHOUGH A 5 MPH OR SO WIND WILL LIKELY PERSIST.
ON TOP OF THAT, THE AIRMASS IS SOME 60 M COLDER THAN AVERAGE UNDER
THE ARCTIC AIR. THIS AIRMASS SUPPORTS LOWS RANGING FROM THE LOW
TEENS IN THE NORTHWEST PIEDMONT TO THE MID TEENS IN THE EASTERN
SANDHILLS AND SOUTHERN COASTAL PLAIN. WIND CHILLS TONIGHT COMBINED
WITH LOW TEMPERATURES WILL RANGE FROM 2 TO 9 DEGREES. WHILE SOME
LOCATIONS IN THE NORTH AND NORTHWEST MAY NOT REACH CRITERIA, GIVEN
THE COLDEST AIRMASS OF THE SEASON, DECIDED TO OPT FOR A COLD
ADVISORY FOR ALL OF CENTRAL NC. IT WOULD BE GOOD PRACTICE TO CHECK
ON NEIGHBORS, WEAR APPROPRIATE CLOTHING, AND KEEP PETS INDOORS.
SHORT TERM /TUESDAY AND TUESDAY NIGHT/
AS OF 240 AM MONDAY...
* LIGHT SNOW POTENTIAL STILL UNCERTAIN, BUT GUIDANCE APPEARS TO
CONTINUE TO TREND SOUTH WITH LIMITED SNOW ACCUMULATION
* ARCTIC AIR REMAINS WELL ENTRENCHED AND A COLD WEATHER ADVISORY MAY
AGAIN BE NEEDED TUE NIGHT INTO WED MORNING
ON THE SYNOPTIC SCALE, MOST GUIDANCE INDICATES TWO SHORTWAVE SYSTEMS
WILL DIRECTLY OR INDIRECTLY IMPACT CENTRAL NC TUE NIGHT INTO EARLY
WED. THE FIRST IS A SHORTWAVE TROUGH OVER THE MID MS VALLEY THAT
LOOKS TO BECOME INCREASINGLY SHEARED ON ITS SOUTHERN FLANK AS IT
TRACKS INTO THE MID-ATLANTIC TUE NIGHT AND INTO NEW ENGLAND
OVERNIGHT. A SECOND SHORTWAVE, PRESENTLY ACROSS CA/NV, TAKES A MORE
SOUTHERN TRACK ACROSS THE NORTHERN GULF AND PORTIONS OF NORTHERN FL
AND THE FAR SOUTHEAST US. THE MAIN FORCING WITH THE SYSTEM WILL
LARGELY BE FROM A 180-200 KT JET STREAK ORIENTED SW TO NE FROM THE
CAROLINAS INTO DELMARVA AND OFFSHORE IN THE ATLANTIC. AS OUR AREA
BECOMES SITUATED IN THE RIGHT-ENTRANCE REGION OF THE JET, MAINLY TUE
NIGHT, THERE LOOKS TO BE A ROUGHLY 6 HR PERIOD WHERE FRONTOGENETICAL
FORCING COULD FAVOR LIGHT SNOW. THIS TIME FRAME APPEARS CENTERED ON
ROUGHLY 5-6 PM TUE UNTIL 12-1 AM WED, STARTING EARLIEST IN THE FAR
SOUTHERN PIEDMONT AND ENDING ACROSS THE FAR SOUTHERN COASTAL PLAIN
AFTER MIDNIGHT.
THE DEVIL IN THE DETAILS REMAINS HOW MUCH, IF ANY, WE WILL GET. THE
00Z SUITE OF DETERMINISTIC MODELS, NAMELY THE NAM/GFS/CMC, INDICATE
LESS FRONTOGENESIS WITH THE JET AND FOCUSING MEASURABLE SNOW
CONFINED MAINLY TO THE COASTAL AREAS OF NC. THE GEFS ENSEMBLE MEAN
ALSO SHOWS THIS. THE 00Z ECMWF REMAINS FURTHER NORTH AND WEST WITH
ITS BAND AND APPEARS RELATED TO STRONGER FRONTOGENETICAL FORCING
ALONG/EAST OF US-1 AND ESPECIALLY ALONG/EAST OF I-95. TRYING TO MAKE
A FORECAST DUE TO THESE DIFFERENCES IS DIFFICULT. THE 12Z LREF
SUGGESTS ABOUT A 30-45 PERCENT CHANCE OF AN INCH OVER THE FAR
EASTERN SANDHILLS TO SOUTHERN COASTAL PLAIN, MAINLY DRIVEN BY THE
EPS AND PARTLY THE GEPS. THE COMPETING FACTOR TO ANY LIFT ALOFT IS
THE VERY DRY AIR SEEN IN FORECAST SOUNDINGS FROM THE NAM/GFS.
SNOWFLAKES MAY SUBLIMATE BEFORE REACHING THE GROUND. OUR LATEST
FORECAST DOES NOT REMOVE SNOW POTENTIAL BUT DOES TREND LOWER GIVEN
THE LATEST MODEL TRENDS, WITH ABOUT A HALF INCH OR LESS ALONG/EAST
OF US-1, WITH HALF INCH POTENTIAL CLOSER TO THE COASTAL PLAIN AND
EASTERN SANDHILLS. HOPEFULLY THE MODELS WILL COME INTO BETTER
AGREEMENT LATER TODAY. HIGH-RES CAMS WILL ALSO BE TELLING, BUT THE
00Z NAM-NEST IS ALSO VERY DRY.
HIGH TEMPERATURES TUE WILL BE VERY COLD IN THE UPPER 20S NW TO LOW
30S SE. LOWS WILL RANGE FROM THE MID/UPPER TEENS TO LOW 20S, WITH
WIND CHILLS IN THE SINGLE DIGITS TO LOWER TEENS. AS A RESULT, A COLD
WEATHER ADVISORY MAY BE NEEDED AGAIN.
LONG TERM /TUESDAY THROUGH SUNDAY/
AS OF 420 PM SUNDAY...
* FORECAST CONFIDENCE REMAINS HIGH FOR A CONTINUATION OF WELL BELOW
AVERAGE TEMPERATURES AND DANGEROUSLY COLD CONDITIONS THROUGH MOST
OF THE WORK WEEK, MAXIMIZED WITH DEPARTURES FROM NORMAL OF 15-25 F
TUE-THU.
* FORECAST CONFIDENCE HAS INCREASED REGARDING THE NORTHERN EXTENT OF
(WINTRY) PRECIPITATION ACROSS E-CNTL NC --WITH ABOVE AVERAGE
CONFIDENCE OF ONLY LIGHT ACCUMULATIONS-- AS WEAK AND SOUTHWARD-
SUPPRESSED LOW PRESSURE TRACKS FROM THE GULF OF MEXICO TO WELL
OFFSHORE THE SOUTH AND SOUTHERN MIDDLE ATLANTIC COASTS TUE-EARLY
WED.
A HIGHLY AMPLIFIED MID/UPR-LEVEL PATTERN WILL BE CHARACTERIZED BY A
REX BLOCKING RIDGE OVER THE ERN PACIFIC AND MEAN TROUGHS THAT WILL
PIVOT ACROSS THE CNTL-ERN US, THE DEEPEST OF WHICH --AND MOST
INFLUENTIAL FOR MAINLY LIGHT SNOW OVER E-CNTL NC-- WILL BE THE LEAD
ONE OVER THE ERN US TUE-WED. THE ASSOCIATED, POSITIVELY-TILTED AND
AT LEAST PARTIALLY PHASED TROUGH WILL EXTEND FROM THE UPR GREAT
LAKES TO THE GULF OF CA AT 12Z TUE AND PIVOT ACROSS AND OFFSHORE THE
SOUTH AND SRN MIDDLE ATLANTIC THROUGH WED. IN THE SWLY FLOW
DOWNSTREAM OF THAT TROUGH, AN INTENSE UPR-LEVEL JET IS FORECAST TO
STRENGTHEN AND NEAR OR EXCEED 200 KTS FROM THE SRN MIDDLE ATLANTIC
TO JUST OFFSHORE ATLANTIC CANADA. A BROAD ZONE OF DIVERGENCE WITHIN
THE ELONGATED RIGHT ENTRANCE REGION OF THIS JET WILL BE PRINCIPALLY
RESPONSIBLE FOR DEEP ASCENT ACROSS AND OFFSHORE THE SOUTHEAST TUE-
TUE NIGHT, WHERE LOW-LEVEL AGEOSTROPHIC RESPONSE WILL FOCUS
CONVERGENCE AND ISENTROPIC LIFT. LOW AMPLITUDE SHORTWAVE RIDGING
WILL THEN PROGRESS ACROSS AND OFFSHORE THE MIDDLE AND SOUTH ATLANTIC
LATER WED-WED NIGHT, DOWNSTREAM OF A TROUGH THAT WILL RELOAD AND
PIVOT FROM THE GREAT PLAINS AND MS VALLEY TO THE EAST COAST THROUGH
FRI. RISING HEIGHTS BUT CONTINUED STRONG/FAST, QUASI-ZONAL WILL THEN
PREVAIL ACROSS THE SRN US AND CAROLINAS NEXT WEEKEND.
AT THE SURFACE, ARCTIC HIGH PRESSURE WILL INITIALLY SPRAWL FROM THE
CNTL GREAT BASIN TO THE MIDDLE ATLANTIC, THEN GRADUALLY WEAKEN AS IT
MIGRATES EWD AND BECOMES CENTERED OVER THE MIDDLE ATLANTIC THROUGH
THE END OF THE WEEK. A WAVY FRONTAL ZONE WILL BE SUPPRESSED WELL-
SOUTHWARD ACROSS THE SUB-TROPICS, FROM THE GULF OF MEXICO TO THE
SWRN N. ATLANTIC, ALONG THE SRN/EQUATORWARD DRAPE OF THE EXPANSIVE
ARCTIC HIGH AND AIRMASS THROUGH MID-WEEK; AND MODEL AGREEMENT
REMAINS HIGH REGARDING ONLY WEAK/FLAT FRONTAL WAVE DEVELOPMENT ALONG
THAT FRONTAL ZONE FROM THE GULF OF MEXICO TO OFFSHORE THE SOUTH
ATLANTIC COAST TUE-TUE NIGHT. THE AFOREMENTIONED RE-LOADING OF THE
TROUGH ALOFT INITIALLY INTO THE CNTL US MAY ALLOW THE SURFACE
FRONTAL ZONE AND SUBSEQUENT CYCLOGENESIS TO BUCKLE POLEWARD AND
NEARER THE MIDDLE ATLANTIC COAST LATER IN THE WEEK, WITH POSSIBLE
ADDITIONAL, LOW CONFIDENCE PRECIPITATION IMPACTS INTO CNTL NC
CENTERED AROUND THU-THU NIGHT. THE GFS AND GEM DETERMINISTIC MODELS
AND A SMALL PERCENTAGE OF THEIR ENSEMBLE MEMBERS ARE MOST BULLISH/
WESTWARD ACROSS THE ERN HALF OF NC WITH THIS SYSTEM, WHILE THEIR
OTHER MEMBERS, AND MOST OF THE EC AND ECS, ARE FARTHER OFFSHORE.
UNCERTAINTY WILL LIKELY REMAIN HIGH UNTIL THAT TROUGH ALOFT IS
BETTER SAMPLED ACROSS NOAM AND ASSIMILATED INTO FORECAST MODELS IN
THE NEXT COUPLE OF DAYS.
MODEL GUIDANCE HAS BECOME MUCH MORE TIGHTLY-CLUSTERED WITH THE TUE
NIGHT SYSTEM AND FOCUS MAINLY LIGHT MEASURABLE SNOW ACROSS THE ERN
CAROLINAS, WITH A LIGHT DUSTING POSSIBLE AS FAR NORTHWEST AS A LINE
FROM NEAR ALBEMARLE TO RALEIGH TO ROANOKE RAPIDS, RANGING TO AROUND
AN INCH OR TWO ALONG THE COAST. THE GREATEST CHANCE OF AROUND ONE
INCH ACCUMULATION IN CNTL NC WILL BE IN SAMPSON AND WAYNE COUNTIES,
WHERE LATEST PROBABILITIES OF GREATER THAN AN INCH ARE AROUND 60
PERCENT. ANY ACCUMULATION, HOWEVER LIGHT, MAY RESULT IN SLICK AND
LOCALIZED HAZARDOUS TRAVEL CONDITIONS DUE TO VERY COLD, ANTECEDENT
AIR AND GROUND TEMPERATURES.
VERY COLD CONDITIONS, AND DRY ONES WED-WED NIGHT, WILL THEN
GRADUALLY MODERATE INTO THE UPCOMING WEEKEND, AS THE ARCTIC HIGH AND
AIRMASS GRADUALLY WEAKEN AND LOSE INFLUENCE. AS THE ARCTIC AIR DOES
SO, HOWEVER, SUFFICIENTLY COLD AIR MAY REMAIN IN PLACE TO PRESENT
ADDITIONAL P-TYPE CONCERNS AS MOISTURE IS DRAWN NWWD WITH THE
AFOREMENTIONED OFFSHORE FRONTAL ZONE AND POSSIBLE RENEWED
CYCLOGENESIS NEAR THE MIDDLE ATLANTIC COAST THU-THU NIGHT. GIVEN THE
AFOREMENTIONED HIGH UNCERTAINTY DURING THAT TIME, JUST A SLIGHT TO
SMALL CHANCE OF A WINTRY MIX WILL BE ADVERTISED MAINLY OVER THE ERN
HALF OF CNTL NC THU-THU NIGHT, WITH FOLLOWING DRY CONDITIONS FRI
THROUGH THE WEEKEND.
AVIATION /06Z MONDAY THROUGH FRIDAY/
AS OF 1210 AM MONDAY...
THERE IS HIGH CONFIDENCE IN VFR CONDITIONS THROUGH THE 24-HOUR TAF
PERIOD. WINDS IN THE LAST HOUR HAVE DIMINISHED AT MOST SITES, THOUGH
GUSTS STILL PERSIST AT GSO/INT. INTERMITTENT GUSTS ARE STILL FAVORED
AT MOST TERMINALS INTO MONDAY MORNING, MOST FAVORED AT GSO/INT/RWI.
GUSTS OF 15-20 KT OUT OF THE NW ARE FAVORED AT ALL SITES MONDAY
DAYTIME INTO THE AFTERNOON, BEFORE DIMINISHING MONDAY EVENING.
OUTLOOK: ALTHOUGH UNCERTAINTY REMAINS HIGH, LIGHT SNOW IS POSSIBLE
TUE NIGHT INTO EARLY WED, MOST FAVORED AT FAY. OTHERWISE, VFR
CONDITIONS ARE EXPECTED THROUGH THE PERIOD.
CLIMATE
RECORD LOW MAXIMUM TEMPERATURES:
JANUARY 20:
KGSO: 29/1983
KRDU: 28/1970
JANUARY 21:
KFAY: 31/1983
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
NONE.
SYNOPSIS...KREN
NEAR TERM...KREN
SHORT TERM...KREN
LONG TERM...MWS
AVIATION...KREN
CLIMATE...RAH
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