If you’re like me – and I know I am – you love trying to understand and predict the weather. On the off chance you’re not like me, I’m reposting below my favorite recent “Area Forecast Discussion” product from the National Weather Service’s Taunton, MA office. Even with the jargon and peculiar typographic conventions, you can get a pretty keen sense of how weather systems and forecasts work by reading this discussion:

838
FXUS61 KBOX 220357
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1057 PM EST SUN FEB 21 2010

.SYNOPSIS…
TWO LOW PRESSURE SYSTEMS ARE FORECAST TO DEVELOP OFF THE MID ATLANTIC COAST THIS WEEK AND COULD BRING PERIODS OF WINTRY WEATHER…MAINLY TO THE INTERIOR. THE FIRST SYSTEM IS LIKELY TO AFFECT THE REGION TUESDAY AND WEDNESDAY AS IT TRACKS ACROSS SOUTHERN NEW ENGLAND. A SECOND COASTAL STORM MAY AFFECT THE AREA LATE THURSDAY INTO FRIDAY AS IT TAKES A SIMILAR TRACK THROUGH OUR AREA.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/… FOR THE OVERNIGHT FORECAST…HAVE LOWERED SKY COVER GRIDS TO ALMOST CLEAR OVER MOST OF THE AREA. SOME CIRRUS ADVANCING THROUGH EASTERN NY…SOME LOW CLOUDS IN THE HIGHER ELEVATIONS OF CHESHIRE COUNTY ARE THE TWO EXCEPTIONS. SATELLITE IMAGERY SHOWS HIGH CLOUDINESS SPILLING SOUTHWESTWARD OVER THE GULF OF MAINE AS ANOTHER SPOKE OF VORTICITY ROTATES AROUND THE UPPER LOW. 00Z NAM BRINGS THE CLOUD COVER INTO MASS BAY BY DAYBREAK THEN BACK EASTWARD OUT TO SEA…SO ADDED THIS TO SKY COVER GRIDS. NO CHANGES TO TEMPERATURE FORECAST OVERNIGHT. LOWERED WIND GUSTS IN WESTERN MA BUT KEPT WINDS AS FORECAST ALONG THE COAST OVERNIGHT SINCE BOS STILL GUSTING TO 24 KTS AS OF 10 PM.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/…
MONDAY…THE FORECAST AREA WILL RESIDE WITHIN A COL AREA BETWEEN HIGH AND LOW PRESSURE SYSTEMS. ANTICYCLONIC FLOW ALOFT WILL ALLOW FOR SUBSIDENCE AND MOSTLY CLEAR SKIES. WILL NOTE SOME INCREASING HIGH CLOUDS LATE IN THE DAY WELL AHEAD OF ADVANCING LOW PRESSURE ACROSS THE GREAT LAKES.

TEMPERATURES ARE EXPECTED TO REBOUND TO ABOVE SEASONAL NORMS…IN THE 40S MOST LOCATIONS. DEVELOPING LIGHT ONSHORE FLOW WILL ALLOW FOR COOLING TEMPERATURES ALONG THE COAST DURING THE AFTERNOON. STAYED FAIRLY CLOSE TO THE MILDER MAV MOS GUIDANCE MOST AREAS.

MONDAY NIGHT…THE WEAK H5 RIDGE WILL BE MOVING EAST OF THE AREA. NOTED AN APPROACHING H7 MID LEVEL JET PROVIDING INCREASING MID LEVEL CONVERGENCE ACROSS THE SOUTHWESTERN ZONES APPROACHING DAYBREAK FROM THE LATEST OPERATIONAL NAM/GFS. A LOW LEVEL ESE JET AHEAD OF DEVELOPING LOW PRESSURE OFF THE NORTH CAROLINA COAST WILL PROVIDE SOME INCREASING LOW LEVEL CONVERGENCE AND ATLANTIC MOISTURE AFTER 06Z ACROSS THE SOUTHWEST ZONES. THE MAIN FOCUS FOR DEEP LIFT WILL LIKELY OCCUR WELL AFTER 06Z.

THERE ARE TIMING ISSUES REGARDING THE ARRIVAL TIME OF PRECIPITATION BUT FEEL IT WILL TAKE SOME TIME FOR THE LOWER LEVELS FROM H85 TO THE SURFACE TO MOISTEN. THUS HAVE CHANCE POPS ADVERTISED FROM 06Z THROUGH 12Z ACROSS THE WESTERN ZONES…BUT REMAINING DRY UNTIL AFTER DAYBREAK ACROSS THE EAST. TEMPERATURE PROFILES REMAIN COLD ENOUGH TO SUPPORT MOSTLY SNOW THROUGH DAYBREAK.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/…
VERY COMPLEX WX PATTERN DURING THIS EXTENDED PERIOD WITH PERSISTENT NORTH ATLANTIC BLOCKING REMAINING IN PLACE. SIGNIFICANT TROF AMPLIFICATION OCCURS OVER MIDWEST AND OHIO VALLEY EARLY IN THE PERIOD AS PIECE OF ENERGY BREAKS OFF FROM HUDSON BAY VORTEX AND FORMS ANOTHER CLOSED VORTEX WHICH DROPS SWD ACROSS OHIO VALLEY EVENTUALLY SHIFTING EAST OVER NEW ENG TOWARD THE END OF THE WEEK. POTENTIAL FOR 2 STORMS TO AFFECT SNE DURING THE PERIOD.

HIGH CONFIDENCE IN A PROLONGED WINTER WEATHER EVENT ACROSS SNE THROUGH AT LEAST WED ALTHOUGH THERE REMAINS CONSIDERABLE UNCERTAINTY IN DETAILS OF QPF AND PTYPE. GREATEST PROABILITY FOR SIGNIFICANT SNOW ACCUM DURING TUE-WED PERIOD WILL MOST LIKELY BE OVER NW HIGH TERRAIN.

COASTAL STORM DEVELOPS OFF MID ATLC COAST TUE AS PIECE OF SHORTWAVE ENERGY BREAKS OFF FROM DEVELOPING VORTEX DROPPING SOUTH INTO THE MIDWEST. THERE IS CONSIDERABLE MODEL SPREAD WITH THE TRACK OF THIS STORM SO CONFIDENCE IN THE DETAILS OF QPF/PTYPE IS LOW. GFS/NAM FURTHEST EAST AS THEY DEVELOP THE STORM WELL OFFSHORE ALTHOUGH INVERTED TROF HANGING BACK TO THE WEST ENSURES PRECIP ACROSS SNE. OP GFS HAS NO SUPPORT FROM MAJORITY OF ITS ENSEMBLE MEMBERS WHICH ARE FURTHER WEST BUT ALSO CONDISERABLE SPREAD AMONG ALL MEMBERS. GGEM ON WESTERN ENVELOPE OF SOLUTIONS TRACKING STORM NWD THROUGH NYS. ANSWER PROBABLY LIES SOMEWHERE IN BETWEEN MORE IN LINE WITH ECMWF/GEFS MEAN/SREF BLEND WHICH TRACK STORM SLOWLY NWD INTO E NEW ENG DURING WED.

CURRENT THINKING IS PRECIP WILL OVERSPREAD THE REGION FROM WEST TO EAST DURING TUE…BUT HEAVIER QPF WILL PROBABLY BE FOCUSED ACROSS LOWER CT VALLEY TUE WITH STEADIER PRECIP MOVING EAST ACROSS REST OF SNE TUE NIGHT.

PTYPE IS TRICKY. PRECIP COULD BEGIN AS A PERIOD OF SNOW IN THE COASTAL PLAIN BUT WE THINK THERE IS TOO MUCH LOW LEVEL ELY FLOW WHICH SHOULD OVERWHELM THE BOUNDARY LAYER RESULTING IN MOSTLY RAIN FROM BOS-PVD SEWD WITH SOME MIXING POSSIBLE TUE NIGHT. NOT BUYING THE COLD NAM SOLUTION FOR BOS/PVD AS MAIN STORM IS LIKELY TOO FAR EAST. BEST CHANCE FOR ALL SNOW WILL BE OVER ELEVATED TERRAIN IN BERKSHIRES…MONADNOCKS AND HILLS ACROSS NORTHERN ORH COUNTY. IN BETWEEN THESE 2 AREAS FROM N CT AND MASS PIKE REGION NORTHWARD ALONG I495 BELT IS WHERE CONFIDENCE IS LOWEST IN PTYPE. WILL PROBABLY SEE A PERIOD OF SNOW THEN MIXED RAIN/SNOW AS BOUNDARY LAYER WARMS.

PRECIP CONTINUES INTO WED…BUT SHOULD BEGIN TO TAPER OFF FROM SOUTH TO NORTH DURING AFTERNOON/EVENING AS DRY SLOT MOVES IN WITH APPROACH OF SFC LOW. HIGHEST PROBABILITY FOR GREATER THAN 6″ WITH LOCALLY UP TO A FOOT WILL BE OVER NW HIGHER TERRAIN…WITH ADVSY SNOWFALL POSSIBLE IN INTERIOR NW OF I95. FOR THE COASTAL PLAIN…THINKING RIGHT NOW IS LITTLE ACCUM EXPECTED.

THEN THERE IS THE SECOND COASTAL STORM WHICH DEVELOPS IN RESPONSE TO VORTEX MOVING EWD FROM OHIO VALLEY AND OFF THE MID ATLC COAST THU INTO FRI. AGAIN THERE IS CONSIDERABLE UNCERTAINTY ON THE EVOLUTION OF THIS STORM AS THE INTERACTION OF SEVERAL SHORTWAVES WILL ULTIMATELY DETERMINE THE POSITION OF THE VORTEX AND EVENTUAL DEVELOPMENT/TRACK OF COASTAL STORM. STILL WAY TOO EARLY TO EVEN ATTEMPT TO PIN ANYTHING DOWN SO WE JUST HAVE CHC POPS FOR NOW.

UNSETTLED WEATHER COULD LINGER INTO SAT WITH SOME IMPROVEMENT POSSIBLE BY NEXT SUNDAY.

&&

.AVIATION /04Z MONDAY THROUGH FRIDAY/…
OVERNIGHT…HIGH CONFIDENCE VFR.

MONDAY…HIGH CONFIDENCE VFR.

MONDAY NIGHT…VFR CEILINGS EXCEPT LOW TO MODERATE CONFIDENCE MVFR/IFR CEILINGS AND VSBYS IN DEVELOPING -SN KBAF-KBDL-WST BY 09Z.

OUTLOOK…TUESDAY THROUGH FRIDAY…

TUE-WED…HIGH CONFIDENCE OF MVFR CIGS/VSBYS IN MIXED RAIN/SNOW WITH PERIODS OF IFR POSSIBLE. GUSTY EASTERLY WINDS ALONG THE COAST.

THU-FRI…CONDITIONS DEPEND ON DEVELOPMENT/TRACK OF SECOND COASTAL STORM. THERE COULD BE MORE MVFR/IFR CONDITIONS AND GUSTY WINDS BUT CONFIDENCE IS VERY LOW.

&&

.MARINE…
OVERNIGHT…SMALL CRAFT ADVISORIES REMAIN IN EFFECT FOR THE OFFSHORE WATERS AS OF 10 PM…STILL HAD GUSTS TO 29 KTS AT BUOY 44018 AND TO 27 KTS AT 44013. ALSO SEAS WILL AVERAGE 4 TO 6 FEET OVERNIGHT.

MONDAY…A SMALL CRAFT ADVISORY WILL MAY NEED TO BE EXTENDED UNTIL AROUND NOON FOR LEFTOVER HAZARDOUS SEAS ACROSS THE OUTER COASTAL WATERS.

MONDAY NIGHT…A SMALL CRAFT ADVISORY MAY BE NECESSARY APPROACHING DAYBREAK TUESDAY ACROSS THE SOUTHWESTERN WATERS AS LOW PRESSURE DEVELOPS OFF THE NORTH CAROLINA COAST.

OUTLOOK…TUESDAY THROUGH FRIDAY…

TUE-WED…INCREASING E-NE WINDS WITH PROLONGED PERIOD OF GUSTS TO 30 KT EXPECTED. LOWER PROB OF GALE FORCE GUSTS DEPENDING ON TRACK/DEVLOPMENT OF THE FIRST COASTAL STORM. ECMWF WOULD BRING STRONG GALES TUE NIGHT INTO WED FOR EASTERN WATERS BUT GFS IS WEAKER. SEAS LIKELY BUILDING TO OVER 10 FEET OVER OUTER WATERS BY WED…POTENTIALLY STRONGER IF ECMWF SOLUTION VERIFIES.

THU-FRI…WINDS/SEAS WILL DEPEND ON DEVELOPMENT/TRACK OF POSSIBLE SECOND COASTAL STORM. THERE IS CONSIDERABLE MODEL SPREAD WHICH RESULTS IN VERY LOW CONFIDENCE ON WIND SPEED AND DIRECTION.

&&

.TIDES/COASTAL FLOODING…
COASTAL FLOOD TREAT IS LOW THROUGH TUE DUE TO LOW ASTRO TIDES AND SEAS NOT HAVING BUILT UP ENOUGH BY THEN. COASTAL FLOOD POTENTIAL INCREASES FOR THE WED MORNING HIGH TIDE. STORM SURGE OF 2 FEET COMBINED WITH 10-15 FT SEAS OFFSHORE COULD YIELD WORST CASE SCENARIO OF MINOR FLOODING.

HOWEVER…BEACH EROSION MAY BECOME A PROBLEM ON EAST FACING BEACHES DUE TO PERSISTENT EASTERLY FLOW OVER MULTIPLE HIGH TIDE CYCLES.

NEXT STORM AFFECTING REGION TOWARD END OF WEEK ALSO BEARS WATCHING AS ASTRO TIDES ARE HIGHER.

&&

.BOX WATCHES/WARNINGS/ADVISORIES…
CT…NONE.
MA…NONE.
NH…NONE.
RI…NONE.
MARINE…SMALL CRAFT ADVISORY UNTIL 6 AM EST MONDAY FOR ANZ250-254>256.

&&

$$
SYNOPSIS…KJC/STRAUSS/GAF
NEAR TERM…GAF
SHORT TERM…STRAUSS
LONG TERM…KJC
AVIATION…KJC/STRAUSS
MARINE…KJC/STRAUSS
TIDES/COASTAL FLOODING…KJC