380
FXUS62 KRAH 181021
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
620 AM EDT MON MAY 18 2026
WHAT HAS CHANGED
* NO SIGNIFICANT CHANGES.
KEY MESSAGES
AS OF 120 AM MONDAY...
1) HOT AND MAINLY DRY THROUGH WEDNESDAY.
2) INCREASINGLY UNSETTLED STARTING WED NIGHT, WITH HIGHEST RAIN
CHANCES EXPECTED TO BE THU. LOW CONFIDENCE IN HIGH TEMPS THU AND FRI.
DISCUSSION
AS OF 120 AM MONDAY...
KEY MESSAGE 1... HOT AND MAINLY DRY THROUGH WEDNESDAY.
STILL ANTICIPATE MULTIPLE DAYS OF ANOMALOUSLY HOT TEMPERATURES. MID-
UPPER LEVEL TROUGHING FROM SASKATCHEWAN/MANITOBA DOWN THROUGH THE N
PLAINS AND ROCKIES WILL ENSURE MAINTENANCE OF STRONG RIDGING OVER
AND OFF THE SOUTHEAST COAST THROUGH MIDWEEK (ALTHOUGH THIS IS
COMPLICATED BY A WEAK BUT PERSISTENT UPPER LOW NW OF THE BAHAMAS).
THE LREF CONTINUES TO SHOW 500 MB HEIGHTS OVER NC REACHING THE 95TH-
99TH PERCENTILE INTO WED. MEANWHILE, AT THE SURFACE, BERMUDA HIGH
PRESSURE CONTINUES TO EXTEND WESTWARD ACROSS NC, KEEPING LOW LEVEL
MOISTURE RETURN LIMITED, WITH DEEP MIXING EACH DAY AND MINIMAL
CLOUDINESS OVERALL. MULTI-MODEL LOW LEVEL THICKNESSES CONTINUE TO BE
AROUND 20 M ABOVE NORMAL TODAY THROUGH WED, SUPPORTING HIGHS FROM
AROUND 90 TO THE MID 90S GIVEN HIGH INSOLATION. EARLY-DAY DEWPOINTS
IN THE 60S ARE LIKELY TO MIX OUT AND DROP INTO THE 50S DURING THE
HOTTEST PARTS OF EACH DAY, WHICH SHOULD KEEP HEAT INDEX VALUES FROM
RISING INTO THE TRIPLE DIGITS. HOWEVER, THIS KIND OF EARLY-SEASON
HEAT CAN STILL BE UNEXPECTEDLY DANGEROUS, AS PEOPLE HAVE NOT YET
BECOME ACCLIMATED TO THE HOT WEATHER. THE DAILY EXPERIMENTAL HEAT
RISK IS EXPECTED TO PEAK AT MODERATE (LEVEL 2 OF 4) TODAY THROUGH
WED, INDICATING THAT THIS KIND OF HEAT IS QUITE UNUSUAL FOR THIS
TIME OF YEAR AND HAS HISTORICALLY LED TO HIGH LEVELS OF HEAT
ILLNESS, WITH SENSITIVE INDIVIDUALS AND THOSE WITHOUT ADEQUATE
COOLING PARTICULARLY VULNERABLE. AND WITH JUST A MODEST BREEZE AND
LOTS OF SUNSHINE EACH DAY, THE WBGT INDEX WILL ALSO BE ELEVATED, SO
SPENDING TIME IN THE SHADE IS ENCOURAGED, ESPECIALLY FOR THOSE
WORKING OR EXERCISING OUTDOORS.
KEY MESSAGE 2... INCREASINGLY UNSETTLED STARTING WED NIGHT, WITH
HIGHEST RAIN CHANCES EXPECTED TO BE THU. LOW CONFIDENCE IN HIGH
TEMPS THU AND FRI.
CONFIDENCE IS HIGH THAT THE SOUTHERN CANADA PORTION OF THE MID-UPPER
LEVEL TROUGH WILL SHIFT E OVER ONTARIO/QUEBEC AND FAR E CANADA TUE
THROUGH THU, ALLOWING A COOL SURFACE HIGH TO SPREAD ACROSS THE N
GREAT LAKES AND ST LAWRENCE VALLEY, REINFORCED BY CONFLUENT FLOW
ALOFT OVER THE NORTHEAST, WHICH WILL HELP PUSH A BACKDOOR FRONT
SOUTHWARD INTO NC THU. PRECISELY WHEN THIS FRONT ARRIVES WILL DRIVE
BOTH THU HIGH TEMPS AND PRECIP CHANCES. THE DETERMINISTIC GFS AND
ECMWF HAVE TRENDED TOWARD A SLIGHTLY SLOWER ARRIVAL IN THEIR LAST
FEW RUNS AND ARE A BIT SLOWER THAN THE LATEST LREF MEAN, INDICATING
THAT AT LEAST OUR SOUTHERN AREAS WILL LIKELY STAY IN THE WARM SECTOR
LONGER, SUGGESTING HIGHS IN THE LOW 90S. NORTHERN AREAS, ESPECIALLY
NEAR THE VA BORDER, HAVE THE LARGEST TEMP SPREAD AMONG DETERMINISTIC
MODELS AND ENSEMBLE MEMBERS, INCLUDING THE NBM'S 15-20 DEGREE 25TH-
75TH PERCENTILE SPREAD FOR HIGHS AT ROXBORO. EXPECT HIGHS IN THE
LOWER TO UPPER 80S N OF HWY 64, BUT CONFIDENCE IN TEMPS AT ANY
PARTICULAR LOCATION IS LOW. BY FRI MORNING, THE FRONT IS EXPECTED TO
SETTLE ACROSS THE S PIEDMONT AND S SANDHILLS THROUGH THE S/E COASTAL
PLAIN AS THE SURFACE HIGH CENTER SHIFTS ESE OVER THE NORTHEAST
STATES, SETTING UP A SHORT-LIVED COLD-AIR DAMMING SCENARIO, WITH
STABILITY REINFORCED BY OVERRUNNING FLOW (ALBEIT SHALLOW) ATOP THE
WEDGING RIDGE. HIGHS NW OF HWY 1 ARE LIKELY TO BE NO WARMER THAN THE
70S, WITH SOME UPPER 60S FOR HIGHS EXPECTED IN THE FAR N AND NW
PIEDMONT, WHILE THE FAR SE CWA SHOULD REACH THE LOW 80S. THE
GREATEST UNCERTAINTY WITH FRI HIGH TEMPS, HOWEVER, WILL BE THROUGH
THE HEART OF THE CWA, INCLUDING IN THE TRIANGLE, AS TEMPS WILL
DEPEND ON WHERE THE WEDGE BOUNDARY SETS UP. THIS HIGH TO OUR N AND
NE WILL BE TRANSITORY, AND AS SUCH WE SHOULD SEE THIS WEDGE DISSOLVE
BY SAT, LEADING TO REBOUNDING TEMPS BACK TO NEAR TO ABOVE NORMAL
VALUES BY THE WEEKEND AS MID-UPPER RIDGING BUILDS BACK OVER THE
CAROLINAS.
REGARDING POPS, THE HIGHEST RAIN CHANCES LOOK TO BE WITH AND JUST
BEHIND THE FRONT, PEAKING THU AFTERNOON AND NIGHT WITH AN UPTICK IN
MOIST UPGLIDE, ESPECIALLY OVER THE NW CWA WITHIN THE DEEPEST
OVERRUNNING FLOW. OVERALL, THE CHANCE FOR SHOWERS AND ISOLATED TO
SCATTERED STORMS WILL BE ABOVE CLIMATOLOGY THU THROUGH THE UPCOMING
WEEKEND, AS OUR 925-850 MB FLOW STRENGTHENS FROM THE SE AND S,
DRAWING IN BOTH GULF AND ATLANTIC MOISTURE WHILE WEAK PERTURBATIONS
RIDE WITHIN THE SW FLOW FROM N MEXICO AND THE TX GULF COAST INTO THE
CAROLINAS. COVERAGE SHOULD BE HIGHEST OVERALL FROM THE NW PIEDMONT
TO OUR W, WHERE PW IS EXPECTED TO BE HIGHEST WITHIN LOW LEVEL
CONFLUENT FLOW AND BENEATH WEAK DPVA AND MINOR JET STREAKS TO FORCE
ASCENT. ISOLATED POCKETS OF HEAVY RAIN CAN'T BE RULED OUT, ALTHOUGH
GENERALLY SPEAKING, THESE HIGH POPS ARE GOOD NEWS FOR OUR DROUGHT-
RAVAGED REGION.
AVIATION /10Z MONDAY THROUGH FRIDAY/
AS OF 620 AM MONDAY...
TAF PERIOD: WITH HIGH PRESSURE OFFSHORE, THE FORECAST SHOULD BE
QUIET WITH VFR ALMOST A CERTAINTY. THE ONE EXCEPTION WILL BE FAY -
YESTERDAY THERE WAS AN MVFR CEILING FOR ABOUT 90 MINUTES, AND
VERTICAL SOUNDINGS SHOW THIS SHOULD BE A POSSIBILITY AGAIN THIS
MORNING. IN ADDITION, STATISTICAL GUIDANCE IS SUGGESTING THAT SOME
MVFR FOG COULD DEVELOP LATE TONIGHT INTO EARLY TUESDAY MORNING.
OTHERWISE, CONDITIONS SHOULD BE MOSTLY CLEAR WITH SOUTHWEST WIND.
OUTLOOK: MVFR RESTRICTIONS WILL BE POSSIBLE BRIEFLY AT FAY AND RWI
TUESDAY AND WEDNESDAY MORNINGS. DRY VFR CONDITIONS ARE FORECAST
THROUGH WEDNESDAY. THE CHANCE OF RAIN WILL INCREASE FROM NORTHWEST
TO SOUTHEAST WEDNESDAY NIGHT, WITH RESTRICTIONS AND SHOWERS EXPECTED
THURSDAY AND FRIDAY.
CLIMATE
RECORD HIGH TEMPERATURES:
MAY 18: KGSO: 95/1911 KRDU: 95/1906 KFAY: 96/1911
MAY 19: KGSO: 96/1911 KRDU: 95/1962 KFAY: 96/2022
MAY 20: KGSO: 95/1917 KRDU: 96/2022 KFAY: 99/2022
RECORD HIGH MINIMUM TEMPERATURES:
MAY 18: KGSO: 70/2015 KRDU: 72/1896 KFAY: 71/2018
MAY 19: KGSO: 68/2018 KRDU: 70/2022
MAY 20: KGSO: 68/2022 KRDU: 69/2019 KFAY: 71/2022
MAY 21: KGSO: 67/2022 KRDU: 71/1898 KFAY: 71/2025
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...HARTFIELD
AVIATION...GREEN
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