120
FXUS62 KRAH 152029
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
329 PM EST WED JAN 15 2025
SYNOPSIS
ARCTIC HIGH PRESSURE WILL BUILD INTO THE AREA THROUGH TONIGHT BEFORE
SHIFTING SOUTH INTO THE GULF STATES LATE IN THE WEEK. A FRONTAL
SYSTEM WILL MOVE ACROSS THE REGION THIS WEEKEND.
NEAR TERM /THROUGH TONIGHT/
AS OF 325 PM WEDNESDAY...
WITHIN SPLIT STREAM FLOW AROUND A REX BLOCK NEAR THE ERN PACIFIC/
WEST COAST, A POSITIVE TILT SRN STREAM SHORTWAVE TROUGH WILL PIVOT
ACROSS THE SOUTHEAST TONIGHT, WHILE A MOBILE NRN STREAM SHORTWAVE
TROUGH IN NW FLOW ALOFT WILL DIG ACROSS THE UPR GREAT LAKES AND OH
VALLEY. CNTL NC WILL BE NESTLED BETWEEN RELATED AREAS OF STRONGER
FORCING FOR ASCENT TO THE SOUTH AND NORTHWEST AND WITHIN A MINIMUM
OF MID-LEVEL HEIGHT FALLS (~40 METERS/12 HR). DESPITE THOSE WEAK-
MODEST HEIGHT FALLS, DEEP DRYNESS AND STABILITY SHOULD MAINTAIN
MAINLY CLEAR SKIES OVER CNTL NC.
AT THE SURFACE, ~1034 MB ARCTIC HIGH PRESSURE CENTERED THIS
AFTERNOON OVER ERN MO WILL WEAKEN CONSIDERABLY, BY ABOUT 10 MB AS IT
MIGRATES SEWD BENEATH THE FALLING HEIGHTS ALOFT, ACROSS NC TONIGHT.
A COMBINATION OF THE (MAINLY) CLEAR AND CALM NOTED ABOVE WILL FAVOR
EXCELLENT RADIATIONAL COOLING OF A VERY DRY, ARCTIC AIR MASS
CHARACTERIZED BY SURFACE DEWPOINTS IN THE SINGLE DIGITS OVER CNTL NC
THIS AFTERNOON, WITH LOW TEMPERATURES MOSTLY BETWEEN 17-22 F.
SHORT TERM /THURSDAY AND THURSDAY NIGHT/
AS OF 300 AM WEDNESDAY...
..SLIGHT MODERATION BUT REMAINING BELOW NORMAL
SURFACE HIGH WILL SINK SOUTH OF THE AREA WITH SFC WINDS BECOMING
SWLY AS A PIEDMONT TROUGH DEVELOPS IN THE LEE OF THE MTNS.
MEANWHILE, AN AMPLIFYING NORTHERN STREAM SHORT-WAVE TROUGH DIVING
SOUTHEASTWARD INTO THE REGION WILL LEAD TO RENEWED H5 HEIGHT FALLS
(30-60 METERS) AND A FLEETING PERIOD OF BROKEN MID-LEVEL CEILINGS
DURING THE DAY, MAINLY ACROSS NORTH CENTRAL PORTIONS OF THE FORECAST
AREA. THE SOUTHERLY FLOW WILL ALLOW A MODEST WARM UP, WITH LOW-LEVEL
THICKNESSES GENERALLY IN THE SAME BALL PARK AS WHAT WE SAW
YESTERDAY(TUESDAY). HIGHS RANGING FROM MID 40S NORTH TO LOWER 50S
SOUTH, WITH BREEZY CONDITIONS OF 20 TO 25 MPH DURING THE AFTERNOON.
NOT AS COLD THURSDAY NIGHT, WITH A STRONG LLJ NOTED JUST ABOVE THE
NEAR SFC INVERSION LAYER. LOWS 25-30.
LONG TERM /FRIDAY THROUGH WEDNESDAY/
AS OF 315 PM WEDNESDAY...
HIGHLIGHTS:
-THERE ARE TWO POTENTIAL WEATHER SYSTEMS THAT COULD
CREATE WINTRY WEATHER BETWEEN FRIDAY AND THE MIDDLE TO LATE NEXT
WEEK, WITH AN ARCTIC BLAST IN BETWEEN.
-THE FIRST WEATHER SYSTEM COMES ON SATURDAY WITH A HIGH PROBABILITY
OF RAIN, FOLLOWED BY THE POTENTIAL FOR ANOTHER PERIOD OF LIGHTER
RAIN THAT COULD MIX WITH SOME SNOW, ESPECIALLY ACROSS NORTHERN AREAS
ON SUNDAY.
-BEHIND THIS SYSTEM WILL BE AN ARCTIC BLAST THAT MAY RIVAL
TEMPERATURES IN LATE DECEMBER 2022 WHEN LOW TEMPERATURES REACHED THE
SINGLE DIGITS AND HIGHS WERE IN THE 20S.
-THE NEXT WEATHER SYSTEM HAS THE POTENTIAL TO BE A COASTAL LOW WITH
WINTRY PRECIPITATION ACROSS INTERIOR NORTH CAROLINA MID TO LATE
WEEK. HOWEVER, CONFIDENCE IS VERY LOW AT THIS POINT DUE TO
SIGNIFICANT DIFFERENCES IN MODEL RUNS REGARDING HOW FAR EAST OR WEST
THE LOW TRACKS
MORE DETAILS:
THE OVERALL WEATHER PATTERN WILL FEATURE A BRIEF PERIOD OF SHORTWAVE
RIDGING ON FRIDAY AHEAD OF THE REESTABLISHMENT OF A VERY DEEP AND
COLD LONGWAVE TROUGH OVER THE EASTERN US THAT PERSISTS THROUGH NEXT
WEEK. ON THE FRONT END, A LEAD SOUTHERN STREAM SHORTWAVE IS
FORECAST TO RACE ACROSS THE DEEP SOUTH ON FRIDAY AND BRING
WIDESPREAD RAIN TO THE REGION SATURDAY. MODELS HAVE BEEN CONSISTENT
AND INDICATING THAT THE HEAVIER QPF WILL SPREAD ACROSS GEORGIA AND
SOUTH CAROLINA, MORE ASSOCIATED WITH A WAVE OF LOW PRESSURE TRACKING
ACROSS A SLOWLY NORTHWARD RETREATING POLAR FRONT AND EVENTUALLY
DEVELOPING INTO A SURFACE LOW OFF THE CAROLINA COAST SATURDAY NIGHT,
WHILE THERE IS A DRYING TREND AS THE PRECIPITATION REACHES NORTH
CAROLINA INTO VIRGINIA. OVERALL QPF IS FORECAST TO BE IN THE 0.25-
0.5 RANGE ON SATURDAY.
BEHIND THIS AREA OF RAIN THE ARCTIC FRONT IS FORECAST TO CROSS
CENTRAL NORTH CAROLINA ON SUNDAY. MODELS HAVE BEEN FAIRLY CONSISTENT
IN SHOWING A WAVE OF LOW PRESSURE DEVELOPING ALONG THE FRONT IN
RESPONSE TO THE DEEP UPPER LEVEL TROUGH, WHICH CONSEQUENTLY CAUSES
PRECIPITATION TO BREAK OUT OVER THE PIEDMONT SUNDAY OR SUNDAY NIGHT.
THIS IS TYPICALLY A SCENARIO WHERE THE ARRIVAL OF COLD AIR THAT
COULD CAUSE A CHANGE OVER TO SNOW IS TOO LATE, BUT GIVEN THE
POTENTIAL FOR A WAVE OF LOW PRESSURE AND STRONG DEEP LAYER LIFT, IT
SEEMS MORE PLAUSIBLE THAT A MIX OF RAIN AND SNOW COULD DEVELOP,
ESPECIALLY ACROSS COUNTIES CLOSER TO VIRGINIA. THE GFS EVEN
INDICATES SOME LOCALLY HIGHER QPF NEAR A QUARTER OF AN INCH ACROSS
NORTHEAST NORTH CAROLINA, SO THERE ARE DETAILS THAT WILL BE WORTH
WATCHING OVER THE NEXT SEVERAL MODEL RUNS.
FOLLOWING THE ARCTIC FRONT, THE ARCTIC AIR MASS USHERED IN AHEAD OF
A 1050 MB HIGH-PRESSURE OVER THE CENTRAL PLAINS IS FORECAST TO HAVE
THICKNESSES THAT BOTTOM OUT BELOW 1230 M. GUIDANCE IS INDICATING
LOWS WELL INTO THE TEENS IF NOT NOT SINGLE DIGITS IN SOME AREAS BY
TUESDAY AND HIGHS IN THE 20S.
THE NEXT BIG QUESTION IS HOW SHORTWAVES MOVING THROUGH THE LONGWAVE
TROUGH COULD CAUSE CYCLOGENESIS IN THE GULF OF MEXICO OR ALONG THE
SOUTH EAST COAST, AND HOW FAR WEST PRECIPITATION EXTENDS INTO A
SIGNIFICANTLY COLD AIR MASS ACROSS THE CAROLINAS. MODELS HAVE BEEN
BACK-AND-FORTH BETWEEN OFFSHORE PRECIPITATION AND PRECIPITATION
EXTENDING WELL INTO NORTH CAROLINA, WITH ALMOST REGULAR FLIP-
FLOPPING BETWEEN MODEL CYCLES. PROBABILISTIC FORECASTS BASICALLY
SHOW AT LEAST A SLIGHT CHANCE OF SNOW BETWEEN TUESDAY AND THURSDAY,
WHICH HIGHLIGHTS THE UNCERTAINTY, AS IS VERY UNLIKELY TO SNOW FOR
THAT LONG. INSTEAD, THE MODELS ARE HAVING A HARD TIME, FOCUSING ON
ONE SPECIFIC PERIOD OF PRECIPITATION. FOR NOW, WE WILL CONTINUE TO
INDICATE A SLIGHT CHANCE OF SNOW WITH THE CAVEAT THAT THIS WILL
DEFINITELY CHANGE AND THE SYSTEM COULD HAVE ANYWHERE FROM NO IMPACT
TO SIGNIFICANT IMPACT.
AVIATION /18Z WEDNESDAY THROUGH MONDAY/
AS OF 125 PM WEDNESDAY...
ARCTIC HIGH PRESSURE WILL FAVOR VFR CONDITIONS, AND LIGHT NWLY TO
CALM SURFACE WINDS, AS IT BUILDS ACROSS CNTL NC THROUGH THU MORNING.
THE PASSAGE OF A WARM FRONT THU AFTERNOON WILL RESULT IN THE
DEVELOPMENT OF STRONG SWLY SURFACE WINDS THAT WILL GUST UP TO 25-30
KTS DURING THE AFTERNOON. WHILE THOSE SWLY SURFACE WINDS WILL
DIMINISH AROUND SUNSET, VEERING WINDS JUST ABOVE THE SURFACE, TO WLY
AT 2000 FT AGL, WILL BRIEFLY STRENGTHEN AND RESULT IN A CHANCE OF
LOW-LEVEL WIND SHEAR EARLY THU NIGHT.
A COUPLE OF FRONTAL SYSTEMS AND ACCOMPANYING RAIN, FLIGHT
RESTRICTIONS, AND MARGINAL LOW-LEVEL WIND SHEAR WILL WILL MOVE
ACROSS CNTL NC THIS WEEKEND.
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...KREN/BLAES
NEAR TERM...MWS
SHORT TERM...CBL
LONG TERM...BLS
AVIATION...MWS
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