184
FXUS61 KBOX 211729
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
129 PM EDT TUE APR 21 2026
WHAT HAS CHANGED
NO SIGNIFICANT CHANGES.
KEY MESSAGES
- SCATTERED SHOWERS WED AND THU. SOME WET SNOW POSSIBLE WED
MORNING IN THE HIGHER ELEVATIONS, THEN A THUNDERSTORM WITH
SMALL HAIL POSSIBLE THU.
- MAINLY DRY AND SEASONABLE FRI THROUGH THE WEEKEND, THEN
PATTERN LOOKS TO TURN MORE UNSETTLED NEXT WEEK.
DISCUSSION
KEY MESSAGE 1...SCATTERED SHOWERS WED AND THU. SOME WET SNOW
POSSIBLE WED MORNING IN THE HIGHER ELEVATIONS, THEN A THUNDERSTORM
WITH SMALL HAIL POSSIBLE THU.
YOU KNOW IT'S APRIL IN SOUTHERN NEW ENGLAND WHEN YOU HAVE TO REFER
TO YOUR WINTER WEATHER AND CONVECTIVE FORECAST PROCEDURES ON THE
SAME DAY.
BROAD NW FLOW ALOFT DOMINATES AS UPPER LOW OVER MARITIMES DROPS
SOUTHWARD TOWARD GULF OF MAINE WED AND THU. THIS WILL HELP SUPPRESS
A WEAK SHORT WAVE AND SURFACE LOW APPROACHING FROM THE LOWER GREAT
LAKES WHICH EVENTUALLY PASSES OFF NJ COAST AND SOUTH OF NEW ENGLAND
WED. THERE IS ENOUGH LOW LEVEL MOISTURE CONVERGENCE TO BRING
SCATTERED SHOWERS TO SOUTHERN NEW ENGLAND LATE TONIGHT INTO WED
MORNING, ESPECIALLY FOR WESTERN MA AND MUCH OF CT WHICH ARE CLOSER
TO THE BETTER LIFT AND MOISTURE CONVERGENCE. WE ALSO CAN'T RULE OUT
SOME WET SNOW ACROSS THE HIGHER ELEVATIONS AT ONSET DUE TO MARGINAL
TEMPERATURE PROFILES BUT AT MOST THERE SHOULD ONLY BE A COATING ON
THE GRASS.
KIND OF AN INTERESTING SETUP FOR THU AND GUIDANCE MAY BE
UNDERPLAYING CONVECTIVE POTENTIAL A BIT, SOMETHING TYPICAL IN THESE
SITUATIONS WITH COLD AIR ALOFT AND CLOSED LOW LURKING NEARBY.
THERE'S ENOUGH CYCLONIC FLOW COUPLED WITH DAYTIME HEATING AND AMPLE
MOISTURE TO AT LEAST GENERATE DIURNALLY DRIVEN CLOUDS AND PERHAPS A
FEW SHOWERS. CERTAINLY SEEING SOME SIGNALS IN THE HIGH-RES MODELS
FOR A FEW LOW-TOPPED SHOWERS OR THUNDERSTORMS, ESPECIALLY IN EASTERN
MA WHERE THERE SHOULD BE ADDITIONAL SUPPORT FROM POTENT MID LEVEL
SHORT WAVE ROTATING THROUGH ALONG WITH MINIMAL LOWER LEVEL
INSTABILITY. SMALL HAIL OR GRAUPEL IS POSSIBLE SHOULD CORES
GROW TALL ENOUGH GIVEN PRESENCE OF COLD AIR ALOFT.
KEY MESSAGE 2...MAINLY DRY AND SEASONABLE FRI THROUGH THE WEEKEND,
THEN PATTERN LOOKS TO TURN MORE UNSETTLED NEXT WEEK.
BROAD CYCLONIC FLOW DOMINATES LATER THIS WEEK AND THROUGH THE
WEEKEND AS UPPER LOW MEANDERS AROUND ATLANTIC CANADA. THIS
ESSENTIALLY BLOCKS ANY SYSTEMS APPROACHING OUR AREA FROM THE
PLAINS AND GREAT LAKES AND MAINTAINS DRY WEATHER, ALTHOUGH IT'S
CERTAINLY POSSIBLE THAT WE SEE DIURNAL CLOUDS AND PERHAPS A
BRIEF SHOWER FROM COMBINATION OF DAYTIME HEATING AND COLD AIR
ALOFT. TEMPERATURES SHOULD END UP NEAR OR JUST BELOW AVERAGE
HIGHS FOR LATE APRIL WHICH ARE IN THE UPPER 50S TO LOWER 60S.
THERE ARE SOME SIGNALS IN LONGER RANGE GUIDANCE THAT BLOCKY PATTERN
BREAKS DOWN EARLY NEXT WEEK WHICH ALLOWS A SERIES OF CLOSED UPPER
LOWS TO TRACK THROUGH REGION, EACH BRINGING ROUNDS OF STEADIER
RAINFALL, SO IT'S POSSIBLE WE SEE A RETURN TO A WETTER PATTERN
TOWARD THE MIDDLE OF NEXT WEEK.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
18Z TAF UPDATE: HIGH CONFIDENCE.
VFR THROUGH EARLY TONIGHT BEFORE MVFR CEILINGS ARRIVE AFTER MIDNIGHT
WITH SCATTERED SHOWERS. MOST LOCATIONS WILL HAVE A FEW HOURS OF
SHOWERS WED MORNING WITH MVFR CEILINGS AND VISIBILITIES. IT'S
POSSIBLE SOME TERMINALS LOWER TO IFR CEILINGS DURING THE DAY BUT
CONFIDENCE WASN'T HIGH ENOUGH TO INCLUDE THAT YET. SHOWERS COME TO
AND END BY WED AFTERNOON BUT MVFR (OR PERHAPS IFR) CEILINGS SHOULD
PERSIST ALL DAY.
LIGHT WINDS WITH COASTAL SEA BREEZES BECOME S/SW TONIGHT AND WED.
MAY SEE A FEW 20-25KT GUSTS WED AFTERNOON, ESPECIALLY CLOSER TO
SOUTH COAST.
OUTLOOK /THURSDAY THROUGH SUNDAY/...
THURSDAY: VFR. BREEZY. SLIGHT CHANCE SHRA.
THURSDAY NIGHT THROUGH FRIDAY NIGHT: VFR.
SATURDAY: VFR. SLIGHT CHANCE SHRA.
SATURDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. SLIGHT
CHANCE SHRA.
SUNDAY: VFR. SLIGHT CHANCE SHRA.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
HIGH CONFIDENCE THROUGH THE WEEKEND.
EXPECTING WINDS AND SEAS TO REMAIN BELOW SCA THROUGH THE WEEKEND.
WEAK LOW PRESSURE PASSES SOUTH OF NEW ENGLAND WED. WE MAY SEE SOME
SOUTHERLY 20KT GUSTS AHEAD OF IT ON SOUTH COASTAL WATERS WED MORNING
ALONG WITH 3-4 FT SEAS, BEFORE WINDS SHIFT TO N/NE AND SUBSIDE LATER
WED AND WED NIGHT.
OVERALL, LIGHT WINDS AND CALM SEAS WILL PREVAIL INTO THE WEEKEND AS
HIGH PRESSURE REMAINS NEAR MARITIMES AND A SERIES OF LOW PRESSURE
SYSTEMS TRACK WEST AND SOUTH OF NEW ENGLAND.
OUTLOOK /THURSDAY THROUGH SUNDAY/...
THURSDAY: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN SHOWERS.
THURSDAY NIGHT THROUGH FRIDAY NIGHT: WINDS LESS THAN 25 KT.
SATURDAY THROUGH SUNDAY: WINDS LESS THAN 25 KT. SLIGHT CHANCE
OF RAIN SHOWERS.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...NONE.
DISCUSSION...JWD
AVIATION...JWD
MARINE...JWD
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