Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KBOX 031800
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
100 PM EST TUE MAR 3 2015

.SYNOPSIS...
A STORM SYSTEM ACROSS SOUTHERN CANADA WITH A TRAILING COLD FRONT
WILL BE THE FOCUS FOR WINTRY WEATHER LATE TODAY INTO EARLY
TOMORROW. A WEAK WAVE OF LOW PRESSURE WILL MOVE ALONG A STALLED
FRONT WED NIGHT AND THU...BRINGING ANOTHER ROUND OF SNOW. HIGH
PRESSURE MOVES IN FOR FRIDAY THROUGH THIS WEEKEND...BRINGING DRY
BUT COLD CONDITIONS. A WEAKENING FRONT MAY BRING SOME LIGHT SNOW
SHOWERS ON MONDAY.

&&

.NEAR TERM /UNTIL 3 PM THIS AFTERNOON/...
1 PM UPDATE...WARM ADVECTION ALOFT IS BRINGING MID AND HIGH
CLOUDS INTO THE REGION WITH THICKER SKY COVER STARTING TO CREEP
EASTWARD TOWARDS SOUTHERN NEW ENGLAND. GROUND OBSERVATIONS OF SNOW
ARE STILL BACK OVER EAST CENTRAL PENNSYLVANIA CURRENTLY. STILL
LOOKING AT ROUGHLY AN ARRIVAL TIME IN THE BERKSHIRES AND
CONNECTICUT VALLEY OF 4-5 PM. DEWPOINTS IN THE SINGLE DIGITS
ACROSS MOST OF SOUTHERN NEW ENGLAND WILL ALLOW THE INITIAL SNOW TO
EVAPORATE UNTIL THE LOWER LEVELS CAN MOISTEN UP.

MORNING SOUNDINGS AT ALY AND CHH SHOW MIXING TO 900-925 MB. TEMPS
AT THE TOP OF THIS MIXED LAYER WILL SUPPORT MAX TEMPS IN THE MID
20S TO NEAR 30.

&&

.SHORT TERM /3 PM THIS AFTERNOON THROUGH 6 PM WEDNESDAY/...
** MIXED WINTRY PRECIP EVENT BEGINS LATE TODAY **

HIGHLIGHTS...
 - SNOW BEGINS EVERYWHERE BY EVENING...1-4 INCHES EXPECTED.
 - SNOW CHANGES TO SLEET AND FREEZING RAIN OVERNIGHT.
 - ALL RAIN EXPECTED BY MORNING.

OVERVIEW...
LOW PRES WILL BE GRADUALLY SLIDING ACROSS SRN ONTARIO AND QUEBEC
TONIGHT INTO TOMORROW MORNING. STRONG WARM ADVECTION ON THE
LEADING EDGE...COINCIDENT WITH 50+ KT SLY LLJ AT H92 SUGGESTS
STRONG OVERRUNNING EVENT AS SUBTROPICAL MOISTURE ASSOCIATED WITH
THE SRN STREAM INITIATING WAVE SLIDES INTO THE AREA. WITH PWATS
ABOUT 1-2 STD DEVIATIONS ABOVE NORMAL..THERE WILL BE PLENTY OF
MOISTURE TO WORK WITH AS THE ISENTROPIC LIFT COMMENCES. INITIALLY
THE COLUMN THROUGH ABOUT H8 IS COLD ENOUGH FOR SNOW...AND
TIME/HEIGHT PROFILES SHOW A FAIR AMOUNT OF THE OMEGA BEGINS
WITHIN THE DENDRITE ZONE. THEREFORE...MODERATE SNOWFALL IS
EXPECTED AS THE PRECIP SHIELD MOVES IN LATE TODAY...WITH THE
POSSIBILITY OF 1+ INCH/HOUR SNOWFALL RATES AT TIMES.

GRADUALLY...MID LVL TEMPS WILL WARM THROUGH THE EVENING. WITH H92
TEMPS REACHING +4C AND H85 TEMPS +8C AT THE WARMEST DURING THE
EARLY MORNING HOURS NEAR THE S COAST. THE WARMING IS EXPECTED TO
BE MUCH FASTER ALOFT THANKS TO THE LLJ AND DEEP SNOWPACK ACROSS
THE REGION...SLOWING THE SFC TEMP INCREASES. THEREFORE...EXPECT A
TRANSITION FIRST TO SLEET...AS LOW LVL SOUNDINGS REMAIN COLD
BENEATH THE INITIAL WARM LAYER...THEN A GRADUAL SHIFT TO FREEZING
RAIN ESPECIALLY OVER THE INTERIOR. AS A TRANSITION TO STRAIGHT
RAIN OCCURS FURTHER E AND AT THE COASTLINES THROUGH THE EARLY
MORNING HOURS. 2M TEMPS WILL WARM...BUT IT/S LIKELY THAT SOME ICE
ACCRETION WILL OCCUR AS SFC TEMPS AND SNOW REMAINS COLD...SO A
LAYER OF LIGHT ICE CANNOT BE RULED OUT.

TIMING...
SNOW WILL BEGIN IN W MA AND CT BY LATE AFTERNOON...THEN BEGIN
SHIFT E WITH TIME. EXPECT IT TO ARRIVE IN CENTRAL MA/RI AND E CT
BY ABOUT 6PM...THEN SPREAD TO E MA WITHIN AN HOUR OR SO AFTER
THAT. IT WILL REMAIN ALL SNOW...EVEN FOR THE CAPE AND ISLANDS OVER
THE NEXT FEW HOURS...THEN A GRADUAL TRANSITION FROM 10PM THROUGH
EARL MORNING WED TO SLEET AND FREEZING RAIN...TO ALL RAIN IS
EXPECTED. FOR A TIME...IT WILL BE ALL RAIN DURING THE EARLY
MORNING. THEN...DRIER AIR IS EXPECTED TO SPILL INTO THE NW AS A
SFC COLD FRONT SLIDES ACROSS THE AREA...THIS WILL ALLOW PRECIP TO
END GRADUALLY FROM NW TO SE AFTER SUNRISE...POSSIBLY ENDING ALMOST
EVERYWHERE BY ABOUT MID MORNING. RECENT TREND IN HI-RES GUIDANCE
SUGGESTS PRECIP COULD BE DONE ALMOST EVERYWHERE AWAY FROM THE S
COAST BY 12Z...BUT WILL TAPER THIS SOMEWHAT. LOOKS LIKE AREAS S OF
THE MASS PIKE MAY DEAL WITH SOME FOG OR POSSIBLY EVEN DRIZZLE AS
THE DRY AIR COMES IN ALOFT FIRST...TRAPPING THE LOW LVL MOISTURE.
THE LIGHT RAIN/DRIZZLE THREAT CONTINUES IN THIS AREA MUCH OF THE
DAY.

PRECIP TYPE/AMOUNTS...
0.2-0.4 OF THE TOTAL QPF THROUGHOUT WED WILL FALL IN THE REGIME
COLD ENOUGH FOR SNOW. HOWEVER...WITH WARM AIR EXPECTED TO MOVE IN
QUICKLY ALOFT...LIFTING THE DENDRITE ZONE AWAY FROM THE PEAK
OMEGA...AGREE WITH PREVIOUS FORECASTER/S THINKING THAT 10-12 TO 1
SLR/S ARE ABOUT AS HIGH AS SLR/S WILL GET. THEREFORE...SOLID
ADVISORY LVL SNOWFALL RANGING FROM 1-3 INCHES ACROSS THE AREA IS
EXPECTED BEFORE TRANSITION THIS EVENING. MAYBE A BIT MORE IN THE E
SLOPES OF THE BERKSHIRES WHERE ADDED LIFT COULD YIELD A FEW SPOTS
OF 4+. AS THE WX TRANSITIONS TO SLEET AND FREEZING RAIN...GIVEN
THE RAPID ADVANCEMENT OF WARM AIR ALOFT...AND WARMING 2M
TEMPS...IT WILL BE DIFFICULT TO ACCRETE EXCEPT ON COLD
SFCS...THEREFORE...SWATH OF A TRACE TO ABOUT A TENTH OF AN INCH OF
ICE IS EXPECTED LATE TONIGHT AND EARLY TOMORROW MORNING BEFORE ALL
RAIN IS EXPECTED FOR A TIME. TOTAL LIQUID AMOUNTS OF 0.5-0.75
INCHES IS EXPECTED...SO ABOUT A QUARTER OF AN INCH OF LIQUID RAIN
IS LIKELY BY THE TIME IT ENDS.

IMPACTS...
THE SNOW THIS EVENING COULD BEGIN MID-COMMUTE FOR FOLKS IN WRN MA
AND CT. AND TOWARD THE LATER HALF OF THE COMMUTE FOR AREAS FURTHER
E. THIS WILL LEAD TO SLICK CONDITIONS INTO THE OVERNIGHT HOURS AS
MODERATE ACCUMS OCCUR. FOLLOW THAT WITH SOME ICE...AND COLD SFC
MAY DEVELOP A GLAZE ON TOP OF THE SNOW...EXACERBATING THE SLIPPERY
CONDITIONS. AS THE TRANSITION TO RAIN OCCURS...THE COMBINATION OF
NEW SNOW...SOME ICE...AND LIQUID WATER WILL CAUSE PROBLEMS
ESPECIALLY ON UNCLEARED ROOFS ACROSS THE AREA AS THE WEIGHT WILL
INCREASE QUITE RAPIDLY. WITH SOME SNOWMELT LIKELY AND RAIN...AREA
DRAINS COULD BECOME CLOGGED...LEADING TO PONDING ON ROADWAYS AND
SOME POOR DRAINAGE FLOODING LEADING INTO THE COMMUTE TOMORROW.

HEADLINES/FINAL THOUGHTS...
ADVISORIES LOOK SOLID...SO NO PLANS TO EXPAND OR UPGRADE. WILL BE
BREAKING THEM UP INTO A FEW DISCRETE SECTIONS WHERE MORE
SNOW...ICE OR LESS OF EITHER ARE EXPECTED. OTHERWISE...WILL SEE A
GRADUAL END TO THE PRECIP EXCEPT FOR THE REMNANT DRIZZLE OR FOG
THROUGH THE MORNING HOURS ON WED. ONE ISSUE OF NOTE IS IF THE SUN
BREAKS OUT IN PARTS OF NRN MA ESPECIALLY...TEMPS COULD RISE QUITE
RAPIDLY...SO HIGHS MAY BE A BIT TOO LOW.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
OVERVIEW...

UPPER LEVEL PATTERN BEGINNING TO SHOW A FEW SIGNS OF CHANGE WITH THE
CHANGING SEASON...THOUGH DOES LOOK LIKE SIMILAR COLD PATTERN REMAINS
FOR MUCH OF THE NORTHEAST U.S. THROUGH A GOOD PORTION OF THIS LONG
TERM TIMEFRAME. ONE NOTICEABLE CHANGE IS THE DRYING OF THE SAME
PATTERN.

NE-SW ELONGATED LONG WAVE TROUGH WORKS E WED NIGHT...BUT WILL STAY
IN SW FLOW ALOFT. BY THU...THOUGH...SHORT WAVE DIGS IN THIS GENERAL
LONG WAVE PATTERN AND PUSHES E DURING THU. LONG WAVE TROUGH SHIFTS
OFFSHORE LATE THU/THU NIGHT...SO EXPECT PRECIP TO END. FOR FRIDAY
INTO THIS WEEKEND...UPPER PATTERN FLATTENS OUT ACROSS THE NORTHERN
STREAM...SO EXPECT GENERALLY DRY CONDITIONS EXCEPT FOR A FEW QUICK
MOVING CLIPPER TYPE SYSTEMS WHICH APPEAR TO KEEP MOST OF THEIR
PRECIP N OF THE REGION. WILL STILL SEE COLDER THAN NORMAL TEMPS
HOWEVER.

USED A BLEND OF AVAILABLE GUIDANCE FOR THIS FORECAST...WHICH HAD
GOOD CONTINUITY TO THE PREVIOUS PACKAGE.

DETAILS...

WEDNESDAY NIGHT-THURSDAY...

STALLED FRONTAL SYSTEM JUST OFF THE SOUTHERN NEW ENGLAND COAST WILL
KEEP PRECIP LINGERING ACROSS MOST OF THE REGION AS COLDER AIR
RETURNS. MIXED PRECIP CHANGES BACK TO SNOW OVERNIGHT...THOUGH COULD
SEE A PERIOD OF FREEZING RAIN/SLEET THROUGH ABOUT MIDNIGHT OR SO.

GOOD BAROCLINIC ZONE REMAINS ESPECIALLY FROM THE MASS PIKE SOUTH
DURING THIS TIMEFRAME ALONG WITH PRETTY GOOD MOISTURE CONVERGENCE
AND OVERRUNNING RETURNS. SLIGHTLY HIGHER QPF FROM THE PREVIOUS
FORECAST...RANGING FROM 0.2 TO 0.3 INCHES ACROSS N MA TO 0.5 TO 0.8
INCHES FROM N CT/RI/SE MA.

SURFACE REFLECTION/WEAK WAVE WILL RIDE ALONG THE STALLED FRONT LATE
WED NIGHT/THU. THIS...ALONG WITH COLDER AIR WORKING IN...WILL SEE
SNOW PICK UP IN INTENSITY AFTER MIDNIGHT THROUGH THU MORNING WHERE
THE BEST LIFT AND MOISTURE ARE LOCATED...GENERALLY S OF THE MASS
PIKE.

WILL LIKELY NEED HEADLINES FOR THIS EVENT...THOUGH HOLDING OFF
CONSIDERING TODAY/S HEADLINES ALREADY IN PLACE. CONTINUE TO
HIGHLIGHT IN THE HAZARDOUS WEATHER OUTLOOK.

THURSDAY NIGHT...

UPPER TROUGH SHIFTS E...PUSHING THE FRONT OFFSHORE OVERNIGHT. SOME
MODEL TIMING DIFFERENCES THOUGH ALL DO TEND TO PUSH PRECIP OFFSHORE
RATHER QUICKLY OVERNIGHT. ANOTHER SHOT OF ARCTIC AIR WORKS IN WITH
OVERNIGHT LOWS IN THE SINGLE DIGITS FOR MOST AREAS EXCEPT THE TEENS
ALONG THE S COAST.

FRIDAY THROUGH MONDAY...

A BROAD UPPER TROUGH CONTINUES ACROSS CENTRAL AND EASTERN CANADA...
KEEPING THE REGION IN BELOW NORMAL TEMPS THROUGH THIS TIMEFRAME.
FAST FLOW ALOFT ALSO BRINGS WEAK SYSTEMS TOWARD THE REGION...THOUGH
LOOKS LIKE ONLY LIGHT PRECIP WITH W-NW FLOW IN PLACE WITH THESE
CLIPPER TYPE SYSTEMS.

LARGE HIGH PRES BUILDS TO THE SW OF THE REGION FRI WITH TEMPS
RUNNING 15 TO 20 DEGS BELOW THOUGH NOT CLOSE TO LOW MAX TEMP RECORDS
EXCEPT FOR PROVIDENCE /VERY LOW MAX TEMP RECORDS FOR MARCH 6/.

AS THE HIGH SHIFTS S OF THE REGION THIS WEEKEND...TEMPS REBOUND A
BIT. THEY LOOK REMAIN BELOW NORMAL BUT WILL PROBABLY SEE HIGHS IN
THE 30S AS WINDS BACK TO SW.

A COLD FRONT APPROACHES LATE SAT/SAT NIGHT BUT MOST OF THE ENERGY
AND PRECIP LOOKS TO REMAIN ACROSS NORTHERN NEW ENGLAND. WILL SEE
SOME CLOUDS AND A WIND SHIFT TO W MOVES ACROSS BY SUNDAY MORNING AS
THE FRONT WEAKENS.

ANOTHER CLIPPER SYSTEM QUICKLY MOVES N OF THE GREAT LAKES BY MONDAY
MORNING...WITH ANOTHER FRONT CROSSING LATE MON/MON NIGHT. CARRIED
SLIGHT CHANCE POPS FOR MAINLY SNOW SHOWERS...BUT MAY SEE PRECIP
MAY WASH OUT AS IT APPROACHES IN THE DRY W-NW FLOW.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /THROUGH WEDNESDAY/...

18Z TAF UPDATE... NO MAJOR ADJUSTMENTS.

THROUGH ABOUT 22Z /5PM/...HIGH CONFIDENCE.
MAINLY VFR CONDITIONS ACROSS THE AREA. WINDS SLOWLY SHIFT TO
SOUTHERLY BUT LIGHT.

THIS EVENING INTO EARLY TOMORROW...MODERATE CONFIDENCE.
ALTHOUGH THERE IS HIGH CONFIDENCE IN OVERALL TRENDS...THERE IS
LOWER CONFIDENCE IN EXACT TIMING.

CIGS WILL LOWER TO MVFR THIS EVENING AND AREAS OF SNOW WILL
DEVELOP FROM W-E FROM 21Z-01Z. ACCUMS RANGE FROM 1-3 INCHES
WIDESPREAD ALTHOUGH SOME 4+ IS POSSIBLY IN THE HIGHER TERRAIN OF
THE EAST SLOPES OF THE BERKSHIRES AND THE WORCESTER HILLS. IFR
CONDITIONS AT TIMES LIKELY ESPECIALLY IN LOWER VSBYS. THE SNOW
TRANSITIONS TO A PERIOD OF SLEET...TO FREEZING RAIN...TO STRAIGHT
RAIN THROUGH THE OVERNIGHT HOURS FROM S-N. SOME ICE ACCUMS
POSSIBLE...MAINLY IFR/MVFR CONDITIONS.

TOMORROW...MODERATE CONFIDENCE.
SOME GRADUAL IMPROVEMENT IS EXPECTED DURING THE MORNING HOURS FROM
N-S ALTHOUGH IT/S LIKELY MVFR/IFR CONDITIONS LINGER CLOSER TO THE
S COAST EVEN AS RAIN SLOWS AND FOG/DRIZZLE DEVELOPS. SOME VFR IS
NOT OUT OF THE QUESTION DURING THE DAY FOR TAF SITES N OF THE
MASS PIKE.

KBOS TAF...HIGH CONFIDENCE IN OVERALL TRENDS...LOWER CONFIDENCE IN
EXACT TIMING.

KBDL TAF...HIGH CONFIDENCE IN OVERALL TRENDS...LOWER CONFIDENCE IN
EXACT TIMING.

OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY...

WEDNESDAY NIGHT AND THURSDAY...MODERATE CONFIDENCE.

EXPECT CONDITIONS TO DETERIORATE TO MVFR BY 05Z IN MIXED PRECIP
CHANGING OVER TO SNOW FROM N-S. WILL VSBYS LOWER TO IFR-VLIFR ACROSS
N CT/RI/SE MA IN PERIODS OF SN/+SN AFTER 06Z-08Z AND CONTINUE
THROUGH THU MORNING. CONDITIONS SHOULD SLOWLY IMPROVE FROM N-S
DURING THU AFTERNOON...BUT LOWER CIGS/VSBYS CONTINUE ALONG S COAST
INTO THU EVENING. NW WINDS GUSTING TO 20-25 KT ALONG THE COAST.

THURSDAY NIGHT...MODERATE CONFIDENCE.

MAINLY VFR ACROSS MOST AREAS. RI/SE MA...IFR CONDITIONS EARLY IN
LEFTOVER -SN...THEN IMPROVING TO VFR. N-NW GUSTING TO 25-30 KT FOR
ALONG THE COAST...DIMINISHING AFTER MIDNIGHT.

FRIDAY THROUGH SATURDAY...MODERATE CONFIDENCE.

EXPECT VFR CONDITIONS.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /THROUGH WEDNESDAY/...

THROUGH THIS EVENING...HIGH CONFIDENCE.
HIGH PRES WILL CREST OVER THE WATERS ALLOWING SEAS AND WINDS TO
DIMINISH RAPIDLY THIS MORNING. WINDS WILL SHIFT TO THE S...BUT
REMAIN BELOW SMALL CRAFT THRESHOLDS UNTIL THIS EVENING.

TONIGHT...MODERATE CONFIDENCE.
S-SW WINDS INCREASE WITH A FEW GUSTS TO AROUND 25 KT EXPECTED. S
SWELL ALSO BUILDS...REACHING ABOUT 8-10 FT BY TOMORROW MORNING.
SMALL CRAFT ADVISORIES WILL BE ISSUED FOR ALL WATERS.

TOMORROW...MODERATE CONFIDENCE.
WINDS WILL SHIFT MORE TO THE W ESPECIALLY ON THE E COASTAL
WATERS. A FEW GUSTS MAY STILL REACH 25 KT AT TIMES AND THE SWELL
WILL LINGER SOME THROUGH THE DAY. THEREFORE...SMALL CRAFT
ADVISORIES ARE LIKELY TO CONTINUE ON THE OCEAN WATERS...BUT MAY BE
ABLE TO BE DROPPED FOR NEAR SHORE WATERS.

OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY...

WEDNESDAY NIGHT-THURSDAY...

W WIND WILL GUST UP TO 20 KT WED NIGHT...THEN SHIFT TO NW AND
INCREASE DURING THU...GUSTING UP TO 25-30 KT BY LATE IN THE DAY.
SEAS BUILD UP TO 5-6 FT ON THE OUTER WATERS. VSBYS REDUCED IN AREAS
OF FOG AND PATCHY FOG.

THURSDAY NIGHT...

EXPECT N-NW WINDS GUSTING TO 25-30 KT THROUGH AROUND MIDNIGHT...
HIGHEST ACROSS THE EASTERN WATERS...THEN WILL DIMINISH. SEAS WILL
REMAIN AOA 5 FT OVER THE OPEN WATERS. REDUCED VSBYS EARLY THU NIGHT
MAINLY FROM E OF CAPE COD SOUTHWARD THROUGH AROUND MIDNIGHT THEN
SHOULD IMPROVE.

FRIDAY AND SATURDAY...

NW GUSTS TO AROUND 25 KT CONTINUE ON THE OPEN WATERS THROUGH FRI
NIGHT...THEN BACK TO SW BUT WILL STILL GUST UP TO 25-30 KT DURING
SAT. SEAS REMAIN AOA 5 FT THROUGH LATE FRI...THEN BRIEFLY SUBSIDE
BEFORE BUILDING AGAIN ON THE SW WINDS DURING SAT.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...WINTER WEATHER ADVISORY UNTIL 10 AM EST WEDNESDAY FOR
     CTZ002>004.
MA...WINTER WEATHER ADVISORY UNTIL 10 AM EST WEDNESDAY FOR
     MAZ002>022-026.
RI...WINTER WEATHER ADVISORY UNTIL 10 AM EST WEDNESDAY FOR
     RIZ001>007.
MARINE...SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 4 AM EST
     WEDNESDAY FOR ANZ230>234-236.
     SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 7 PM EST
     WEDNESDAY FOR ANZ235-237-250-254>256.
     SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 1 PM EST
     WEDNESDAY FOR ANZ251.

&&

$$
SYNOPSIS...DOODY/EVT
NEAR TERM...WTB/DOODY/RLG
SHORT TERM...DOODY
LONG TERM...EVT
AVIATION...WTB/RLG/EVT
MARINE...DOODY/EVT


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.