Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 262323
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
723 PM EDT SAT JUL 26 2014

.SYNOPSIS...

AS LOW PRESSURE DEEPENS FROM THE GREAT LAKES TO SOUTHEAST CANADA
AND EVENTUALLY OCCLUDES ACROSS NEW ENGLAND...ANTICIPATE WAVES OF
SHOWERS AND THUNDERSTORMS...BEGINNING SUNDAY MORNING AND
CONTINUING THROUGH LATE MONDAY. A FEW OF THESE STORMS COULD BE
STRONG TO SEVERE. HIGH PRESSURE FOLLOWS WITH COOLER AND DRIER
WEATHER INTO THE END OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...

730 PM UPDATE...

INITIAL MID-LEVEL DISTURBANCE THROUGH THE ZONAL FLOW IS EXITING TO
THE E WITH ACCOMPANYING DRIZZLE. ABUNDANCE OF LOW-LEVEL DRY AIR
HAS LIMITED ACTIVITY FROM REACHING THE GROUND. EXPECTING A MOSTLY
QUIET NIGHT WITH S/SW FLOW. SOME GUSTS POSSIBLE DURING THE EVENING
HOURS...BUT OVERALL EXPECT GUSTS TO REMAIN SUBDUED. S-FLOW WILL
RESULT IN INCREASING DEWPOINTS. T-D SPREADS ON THE ORDER OF
SEVERAL DEGREES ALONG THE S-COAST. COULD SEE THE DEVELOPMENT OF
LOW-CLOUDS AND/OR FOG FOR SUCH REGIONS BY MORNING. NOT A LOT OF
CONFIDENCE. WILL SEE HIGH CLOUDS BUILDING INTO THE REGION AHEAD OF
THE MORNING LINE OF SHOWERS AND THUNDERSTORMS.

SPEAKING OF WHICH...EVALUATING FORECAST GUIDANCE FOR WHAT
SOLUTIONS ARE HANDLING THE CONVECTION OUT W WELL...IT APPEARS THE
WRF-ARW IS DOING THE BEST. SUBSEQUENT TRENDS PUT A LINE OF
CONVECTION ACROSS THE FORECAST REGION INTO THE CT-RIVER VALLEY BY
12Z...ACROSS WORCESTER INTO E NEW ENGLAND BY 18Z. SEE DISCUSSION
BELOW FOR FURTHER DETAILS.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...

SUNDAY...

ALL MODELS INDICATE A JET MAX OF 80 KT AT 300 MB PASSING OVER NJ
WHICH PLACES SOUTHERN NEW ENGLAND IN THE LEFT FRONT QUADRANT... A
POSITION FAVORABLE FOR RISING MOTION. IN ADDITION...AN ELEVATED
MIXED LAYER WILL BE PRESENT WITH 500-700 MB LAPSE RATES AROUND
7C/KM. THUS...WITH THE WARM FRONT APPROACHING...THE BAND OF
THUNDERSTORMS THAT WILL BE APPROACHING THE BERKSHIRES AROUND
DAYBREAK SHOULD CONTINUE TO PROGRESS EASTWARD...ESPECIALLY OVER
SOUTHERN NH AND NORTHERN MA...PERHAPS EXITING THE REGION AROUND
NOON OR 1 PM. LOW LEVEL WIND FIELDS WILL BE STRENGTHENING DURING
THE MORNING...TO 30-40 KT AT 5000 FT...AND THIS MEANS THAT ANY
REMAINING STORMS COULD PRODUCE STRONG TO POTENTIALLY DAMAGING
WINDS BEFORE EXITING NORTHEAST MA.

AFTER THAT...THE FORECAST BECOMES MORE UNCERTAIN. MODELS CONTINUE
TO STRUGGLE WITH THE LOCATION AND TIMING OF MESOSCALE FEATURES.
FOR EXAMPLE...IT DOES DRY OUT IN THE MID LEVELS AND K INDICES
CORRESPONDINGLY DROP TO NEAR 20 OR LESS. THIS WOULD IMPLY THAT
THERE COULD BE BREAKS OF SUNSHINE FORMING HOWEVER AND IT COULD
MAKE THINGS MORE UNSTABLE. THE GFS SHOWED TOTAL TOTALS INDICES OF
50 TO 55 LURKING CLOSE BY IN SOUTHEAST NY AND THIS UNSTABLE AXIS
COULD MOVE INTO CT AND WESTERN MA IN THE LATE AFTERNOON. HODOGRAPH
PROFILES DO SHOW SIGNIFICANT TURNING IN THE LOWEST 1 KM...SO
ALTHOUGH STORMS MAY BE ONLY SCATTERED ABOUT IN THE AFTERNOON...THERE
IS THE POTENTIAL FOR ROTATION AND EVEN AN ISOLATED TORNADO.
BY FAR...THE MOST SEVERE WEATHER ACTION WILL BE TAKING PLACE WELL
TO OUR SOUTHWEST. IT REMAINS TO BE SEEN IF THAT ACTIVITY WILL TAKE
AWAY FROM ENERGY IN OUR REGION OR WHETHER IT WILL ATTEMPT TO MOVE
IN OUR DIRECTION BY SUNDAY NIGHT.

HIGHS SHOULD REACH INTO THE LOWER 80S BUT COULD BE A FEW DEGREES
HIGHER IF THERE ARE MORE BREAKS OF SUN. SOUTH TO SOUTHWEST WINDS
SHOULD GUST TO 20 TO 25 MPH ESPECIALLY ACROSS RI AND SOUTHEAST MA.
A FEW GUSTS TO 30 MPH ARE POSSIBLE SUNDAY AFTERNOON.

SUNDAY NIGHT...

SECOND WAVE OF ACTIVITY ANTICIPATED. FOCUS IS ALONG THE CONVERGENCE
OF LOW- TO MID-LEVEL THERMAL/MOIST AXES COLLOCATED WITH AN ATTENDANT
MID-LEVEL IMPULSE WITHIN THE LFQ OF THE UPPER-LEVEL JET. FALLING
HEIGHTS ACROSS THE REGION AS NEARLY-STACKED LOW PRESSURE SHIFTS INTO
W NEW ENGLAND BY MORNING. WILL HAVE TO MONITOR ACTIVITY OUT OF THE
OH-RIVER VALLEY LIKELY AS A MCS AS IT ROUNDS THE UPPER-LOW...HOW IT
WILL TREND WITH 0-6 KM MEAN WIND AND CORFIDI VECTOR FLOW. TRENDS
BEGIN TO IMPROVE BY MORNING WITH THE INTRUSION OF MID- TO UPPER-
LEVEL DRY AIR.

MAIN CONCERN IS WITH A HEAVY RAIN THREAT ACROSS S/E PORTIONS OF NEW
ENGLAND CENTERED AROUND MIDNIGHT. SURFACE DEWPOINTS SURGING INTO THE
70S. PWATS INCREASE TO +2-INCHES ACROSS S/SE COASTLINES. ATMOSPHERIC
PROFILES BECOME SATURATED MOIST-ADIABATICALLY FROM THE SURFACE ON UP
TO H3 FOR A SHORT-PERIOD OF TIME. AND FINALLY...THE MAJORITY OF THE
ACTIVITY IS FOCUSED ON THE NOSE OF A H925/85 LOW-LEVEL-JET SWEEPING
ROUGHLY S OF LONG-ISLAND INTO THE GULF OF MAINE. IT IS POSSIBLE THAT
MOST OF THE ACTIVITY REMAINS OFFSHORE. NEVERTHELESS...THE PROXIMITY
TO AREAS WHICH ARE SUSCEPTIBLE TO FLASH FLOODING /I.E. NEW BEDFORD
AND FALL RIVER/ AS THEY ARE LOW-LYING WARRANTS THE CONCERN MENTIONED
ABOVE.

AS FOR SEVERE POTENTIAL WITH THE SECOND WAVE...AGAIN...WILL NEED TO
WATCH ACTIVITY OUT OF THE OH-RIVER VALLEY. OTHERWISE...CONCLUSION OF
DAYTIME HEATING LENDS TO A CAP JUST ABOVE THE SURFACE. BUT AT ONSET
INSTABILITY IS IMPRESSIVE UP TO 2K J/KG PRIOR TO MIDNIGHT WEAKENING
AS THE ATMOSPHERIC PROFILE SATURATES. DECENT AVERAGE SW-NE SHEAR
WITH SOME SLIGHT TURNING WITHIN 0-1 KM...MAY HAVE TO WATCH FOR AN
ELEVATED SEVERE WEATHER POTENTIAL INITIALLY IN THE FORECAST PERIOD
WITH THE THREAT OF DAMAGING WIND GUSTS. WITH THE CAP...FEEL ANY
THREAT OF TORNADOES WILL BE DIMINISHED.

MONDAY...

NEARLY STACKED LOW AND MAIN TROUGH AXIS LIFTS INTO NEW ENGLAND AS
THE MID-LEVEL DRY PUNCH AHEAD SWEEPS NE ACROSS THE FORECAST REGION.
MOST NOTABLY...TROWALING PROCEEDS REARWARD OF THE LOW /NW-QUAD/
CONVERGING WITH THE COLD-CONVEYER-BELT LENDING TO A REGION OF LOW-
TO MID-LEVEL FRONTOGENESIS ACROSS UPSTATE NY INTO THE W-SLOPES OF
HIGH TERRAIN OF NEW ENGLAND.

WITH OVERNIGHT ACTIVITY AND DYNAMICS SHIFTING N/E FOLLOWED BY A MID-
LEVEL DRY-PUNCH...S/E PORTIONS OF NEW ENGLAND SHOULD BECOME DRY AND
QUIET. SHOULD SEE CLOUDS SCOUR OUT. SOME LOW-CLOUDS AND FOG ISSUES
MAY LINGER FROM OVERNIGHT.

AS TO THE N/W NEW ENGLAND...CONSIDERING THE FORCING ASSOCIATED WITH
LOW- TO MID-LEVEL CONVERGENCE WITHIN THE TROWAL...INSTABILITY ON THE
ORDER OF 2K J/KG...DECENT AVERAGE SW-NE SHEAR...AND PWATS UP TO 1.5-
INCHES...ANTICIPATE SCATTERED STORM ACTIVITY WITH THE THREAT OF
HEAVY RAIN...LARGE HAIL /LOWER FREEZING LEVEL HEIGHTS/...AND
DAMAGING WINDS. MUCH OF THIS ACTIVITY LOOKS TO REMAIN OVER UPSTATE-
NY INTO N NEW ENGLAND...BUT THERE IS A THREAT FOR THE W-SLOPES OF
HIGHER TERRAIN IN W MA AND SW NH. 26.12Z NAM HINTS AT SOME ACTIVITY
ACROSS THE CT-VALLEY ON UP INTO SW NH. QUITE POSSIBLE WITH THE
FALLING HEIGHTS AND PROXIMITY OF THE LOW. CAN NOT RULE IT OUT...WILL
HOLD WITH LIKELY POPS AS SUCH.

MONDAY NIGHT...

DIURNAL HEATING CONCLUDES AS THE LOW LIFTS OUT OF THE REGION. EXPECT
ACTIVITY WITHIN THE TROWAL STRUCTURE REARWARD OF THE LOW TO DIMINISH
RESULTING IN A MOSTLY QUIET NIGHT. SCATTERED SHOWER ACTIVITY MAY
LINGER ALONG THE W-SLOPES OF HIGHER TERRAIN INITIALLY IN THE PERIOD.
BUT WITH HEIGHTS RISING AS HIGH PRESSURE BUILDS INTO THE REGION...
EXPECT CONDITIONS TO IMPROVE INTO TUESDAY.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...

OVERVIEW...

SHORTWAVE FROM MONDAY SLOW LIFTS NORTHEAST AS IT MERGES WITH AN
UPPER LEVEL LOW IN NORTHEAST CANADA. MEANWHILE AIR CONTINUES TO FLOW
INTO THE REGION FROM THE SOUTHWEST AFTER THE COLD FRONT PASSES AND
STALLS JUST OFF THE EAST COAST. THE STALLING IS CAUSED BY BLOCKING
IN THE WESTERN UNITED STATES AND NORTHWESTERN ATLANTIC. SO FLOW
CONTINUES TO BE MERIDIONAL RATHER THAN ZONAL OVER THE UNITED STATES.
THIS IS ALSO HINTED AT BY THE PNA WHICH HAS HAD A BETTER HANDLE ON
THE BLOCKING THAN THE NAO OF LATE.

AM ALSO NOTICING SOME DISCREPANCIES IN THE HANDLING OF THE UPPER
LEVEL LOW IN NORTHEAST CANADA. THE ECMWF WANTS TO CLOSE OFF A LOW IN
THE EASTERN CENTRAL US WHILE THE GFS HAS SMALLER PACKETS OF ENERGY.
THESE LEAD TO THE DIFFERENCES IN PRECIPITATION. FEEL A MODEL BLEND
IS THE BEST TO HANDLE THE LATER PERIOD.

DAILIES...

TUESDAY...A SHORTWAVE PINWHEELS AROUND THE UPPER LEVEL LOW HELPING
TO DIG THE TROUGH FURTHER SOUTH. AS MENTIONED BEFORE...A COLD FRONT
STALLS JUST EAST OF CAPE COD KEEPING SURFACE FLOW MOSTLY FROM THE
WEST. THIS ALLOWS FOR DRYING OVER THE INTERIOR. HOWEVER...CLOSER TO
THE FRONT...NEAR THE CAPE AND ISLANDS...CAN/T RULE OUT SEEING MORE
HIGH LEVEL CLOUDS.

WEDNESDAY AND THURSDAY...WITH THE FLOW BEING STALLED...CAN/T RULE
OUT PERIODS OF MORNING AND EVENING FOG ALONG SOUTHERN AND EASTERN
SECTIONS ESPECIALLY AS THE LOW LEVEL WINDS GO BELOW 10KTS AND DEW PT
DEPRESSIONS GO LESS THAN 5F. ENERGETIC WAVES WILL ALSO CONTINUE TO
MOVE NORTHEAST ALONG THE FRONT CHANGING WIND DIRECTION AS THE THEY
GO THROUGH. SOME PERIODS OF NORTHEAST WINDS CAN BE SEEN WHERE THE
MOISTURE CAN BE BROUGHT INTO THE CAPE AND ISLANDS ALLOWING FOR SOME
CLOUDS THERE. PROFILES STILL LOOK PRETTY DRY THOUGH.

FRIDAY AND SATURDAY... AS THE UPPER LEVEL LOW IN SOUTHEAST CANADA
LIFTS NORTH DURING FRIDAY...CAN EXPECT THE FRONT TO BACK CLOSER TO
THE EAST COAST ALLOWING MORE RAIN ON THE CAPE AND ISLANDS. HAVE
ALLOWED FOR POPS FOR THIS TIME PERIOD.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...

FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...

* MODERATE CONFIDENCE WITH RESPECT TO TRENDS
* LOW CONFIDENCE IN REGARDS TO SPECIFICS /IMPACTS AND TIMING/

VSBY IMPACTS WITH FOG POSSIBLE TOWARDS MORNING PRIOR TO LOWERING
CIGS ASSSOCIATED WITH THE APPROACH OF SHRA/TSRA THAT SHALL LINGER
INTO THE AFTERNOON. WILL GO CONSERVATIVE AND HOLD MVFR FOR NOW.

MAY SEE A LULL IN ACTIVITY DURING THE EVENING YET OVERNIGHT
ANTICIPATE THE INCREASE IN AREAL COVERAGE OF SHRA/TSRA ALONG WITH
THE POTENTIAL OF COASTAL FOG FOR THE S/SE SHORELINE TERMINALS. A
MIX OF MVFR-IFR CONDITIONS SUBSEQUENT TO SHRA/TSRA ACTIVITY IS
POSSIBLE...BUT WILL HOLD OFF IN MENTIONING DUE TO LOW CONFIDENCE.

AS CONDITIONS QUIET DOWN INTO MONDAY MORNING...SHRA/TSRA ARE
ANTICIPATED TO BE ON THE INCREASE OVER INTERIOR NEW ENGLAND
THROUGHOUT THE DAY...WEATHER CONCLUDING INTO THE EVENING AND
IMPROVING. WITH ANY SHRA/TSRA ACTIVITY...MIX OF MVFR-IFR POSSIBLE
BUT WILL HOLD OFF ON ANY MENTION DUE TO LOW CONFIDENCE.

BREEZY S/SW FLOW THROUGHOUT THE PERIOD.

KBOS TAF...MODERATE CONFIDENCE. SHRA/TSRA ANTICIPATED AROUND
16-18Z AND LIKELY TO BE ACCOMPANIED WITH A MIX OF MVFR-IFR
IMPACTS...THOUGH UNCERTAIN TIMING RESULTS IN LACK OF MENTION.

KBDL TAF...MODERATE CONFIDENCE. LINE OF SHRA/TSRA SHOULD SWEEP THE
TERMINALS DURING THE MORNING HOURS. A MIX OF MVFR-IFR IMPACTS
POSSIBLE...BUT LOW CONFIDENCE LIMITS A PREVAILING MENTION.

OUTLOOK...MONDAY NIGHT THROUGH THURSDAY...MODERATE CONFIDENCE.

MONDAY NIGHT...

IMPROVING VFR AS WINDS BACK W/SW AND ACTIVITY MOVES OUT OF THE
REGION. SHOULD SEE CIGS/VSBYS LIFT.

TUESDAY THROUGH THURSDAY...VFR WITH DRYING WEST WINDS. LOW
CONFIDENCE ON A POSSIBILITY OF MVFR WITH ANY FOG IN THE MORNING AND
EVENING HOURS.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /TONIGHT THROUGH MONDAY...HIGH CONFIDENCE INTO THIS
EVENING AND THEN LOWERING CONFIDENCE LATER TONIGHT THROUGH MONDAY
REGARDING TIMING AND AREAL COVERAGE OF SHOWERS/T-STORMS.

TONIGHT...QUIET TO START BUT AN APPROACHING WARM FRONT WILL LEAD TO
PATCHY FOG/LOW CLOUDS POTENTIALLY REDUCING VSBY TOWARD DAYBREAK
SUNDAY.

SUNDAY...A SMALL CRAFT ADVISORY HAS BEEN ISSUED. S TO SW WINDS
INCREASE TO 15-20 KT WITH GUSTS TO 25 KT ACROSS ALL WATERS. SEAS
WILL BE BUILDING TO 5 TO 6 FT OVER THE SOUTHERN OUTER WATERS BY
SUNDAY EVENING. SCATTERED T-STORMS POSSIBLE AT ANY TIME DURING
THE DAY. ANY STORMS COULD PRODUCE STRONG WIND GUSTS AND LOCALLY
HIGHER SEAS.

SUNDAY NIGHT INTO MONDAY...

BREEZY SW WINDS WITH GUSTS UP TO 25 KTS WITH WAVE HEIGHTS BUILDING
UP TO 7 FEET ON THE S/SE OUTER WATERS. SMALL-CRAFT ADVISORIES LIKELY
NEEDED TO BE EXTENDED. WIDESPREAD RAIN...HEAVY AT TIMES...WITH
EMBEDDED THUNDERSTORMS. ANTICIPATE VISIBILITY RESTRICTIONS DOWN TO A
MILE AS FOG IS ALSO POSSIBLE.

OUTLOOK...MONDAY NIGHT THROUGH THURSDAY...MODERATE CONFIDENCE.

MONDAY NIGHT...

WINDS SHIFTING W/SW AND DECREASING. SHOULD SEE CONDITIONS IMPROVE AS
WAVES DEAMPLIFY. LIKELY WAVE HEIGHTS OVER 5 FEET ON THE OUTER WATERS
WILL RESULT IN A PROLONGED PERIOD OF SMALL-CRAFT ADVISORIES.

TUESDAY...THE COLD FRONT PUSHES AWAY FROM SOUTHERN NEW ENGLAND...
BUT STALLS OFFSHORE SO WATERS WILL BEGIN TO LESSEN FROM 5 TO 6 FT
WAVES TO JUST AROUND 5 IN THE OUTER WATERS NEAR WHERE THE FRONT
STALLS. A SMALL CRAFT ADVISORY MAY BE NEEDED FOR SOME OF THE WATERS
ESPECIALLY THE OUTER WATERS.

WEDNESDAY AND THURSDAY...LIGHTER WINDS AND SEAS AS HIGH PRESSURE
BUILDS OVER THE WATERS.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 1 PM TO 8 PM EDT SUNDAY FOR
     ANZ230>234-236-237-251.
     SMALL CRAFT ADVISORY FROM 1 PM SUNDAY TO 6 AM EDT MONDAY FOR
     ANZ235-250-254>256.

&&

$$
SYNOPSIS...SIPPRELL/GAF
NEAR TERM...SIPPRELL/GAF
SHORT TERM...SIPPRELL/GAF
LONG TERM...99
AVIATION...SIPPRELL/GAF/99
MARINE...SIPPRELL/GAF/99



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