Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 231400 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 900 AM EST FRI JAN 23 2015 .SYNOPSIS... HIGH PRESSURE DEPARTS THE EAST COAST TODAY. THIS GIVES WAY TO DEVELOPING LOW PRESSURE MOVING UP THE COAST. THIS LOW WILL BRING A PERIOD OF SNOW SATURDAY AND SATURDAY EVENING BEFORE EXITING INTO THE MARITIMES SATURDAY NIGHT. AFTER A BRIEF BREAK SUNDAY ANOTHER LOW PRESSURE SYSTEM MOVES OUT OF THE OHIO VALLEY AND QUICKLY DEVELOPS WELL SOUTH OF NEW ENGLAND. A SHOT OF COLDER AIR FOLLOWS BEHIND THIS SYSTEM...AS COLD CANADIAN HIGH PRESSURE BUILDS IN. && .NEAR TERM /THROUGH TONIGHT/... ---900 AM UPDATE--- NOT MUCH IN THE WAY OF CHANGES THIS MORNING. A MIX OF SUN AND CLOUDS WITH TEMPERATURES CLIMBING INTO THE UPPER 20S AND LOWER 30S. CURRENT PACKAGE HAS THIS COVER WELL. WILL ONLY TWEAK MINOR THINGS TO ACCOUNT FOR CURRENT TRENDS. 630 AM UPDATE...LITTLE CHANGE TO THE PREVIOUS FORECAST. JUST A FEW MINOR ADJUSTMENTS BASED ON LATEST TRENDS IN OBSERVATIONAL DATA. PREVIOUSLY... HIGH PRESSURE RIDGING CRESTS OVER MUCH OF THE REGION TODAY AND SHOULD DELIVER AND FAIR WEATHER DAY. WAA CLOUDS MAY HANG TOUGH IN THE INTERIOR BUT IT SHOULD REMAIN MOSTLY DRY. BUMPED UP HIGH TEMPERATURES A LITTLE BIT FOR TODAY AS SWLY FLOW DEVELOPS AT THE SFC ALONG WITH AMPLE SUNSHINE. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... A STRONG SOUTHERN STREAM SHORT WAVE TROUGH WILL EJECT EASTWARD OUT OF THE SOUTHERN PLAINS AND INTO THE DEEP SOUTH TONIGHT. THIS WILL AID IN THE DEVELOPMENT OF SFC LOW PRESSURE OVER THE MID ATLANTIC STATES. AS THE SOUTHERN STREAM TROUGH LIFTS NORTHEASTWARD...THE SFC LOW WILL FOLLOW SUIT WHILE INTENSIFYING. MODEL TRENDS OVERNIGHT HAVE BEEN SLIGHTLY MORE NORTHWEST WITH THE LOW TRACK...MOVING IT VERY NEAR OR OVER NANTUCKET ISLAND LATE SATURDAY AFTERNOON. THIS IS LIKELY DUE TO THE NORTHERN STREAM TROUGH LAGGING A BIT AND ALLOWING THE SOUTHERN STREAM TROUGH TO COME UNDERNEATH/WESTWARD SOME. THIS SHOULD ALLOW THE SNOW SHIELD TO MOVE FURTHER WEST AS WELL. AS FOR THE QPF AND SUBSEQUENTLY THE SNOWFALL FORECAST...HAVE BLENDED SEVERAL OF THE LATEST MODELS AND ENSEMBLE DATA...WITH MOST WEIGHT GIVEN THE THE 00Z ECMWF /WHICH HAPPENS TO BE THE MOST NORTHWESTERN SOLUTION BUT IS STRONGLY SUPPORTED BY IT/S ENSEMBLE MEMBERS/. THE RESULT IS AT LEAST A 50/50 CHANCE AT REACHING WARNING CRITERIA SNOWFALL SATURDAY INTO SATURDAY EVENING FOR SE NEW HAMPSHIRE AND THE COASTAL PLAIN OF MAINE. THE BEST CHANCE AT REACHING WARNING CRITERIA WILL BE THE IMMEDIATE COAST UNLESS THE NW TREND CONTINUES AND MORE OF A MIX ENTERS THE PICTURE. WHILE THE BULK OF THE PRECIPITATION IS EXPECTED TO BE IN THE FORM OF SNOW...A BRIEF MIX WITH SLEET AND FREEZING RAIN WILL BE POSSIBLE ACROSS SOUTHEAST ZONES WHERE A LITTLE WARM AIR ALOFT WILL SNEAK IN. ALONG THE IMMEDIATE COAST AND SOUTHEASTERN NH...THE SNOW COULD BECOME WET ENOUGH FOR A TIME TO WEIGH DOWN TREE BRANCHES AND POWER LINES. WE ARE STILL EXPECTING A VERY TIGHT SNOWFALL GRADIENT WITH THIS SYSTEM...JUST A BIT FURTHER WEST...PROBABLY NEAR THE WESTERN EDGE OR JUST WEST OF THE CURRENT WATCH AREA. IT`S POSSIBLE THAT LITTLE IF ANY SNOW FALLS IN THE NORTHERN WHITES NORTHEASTWARD INTO THE WESTERN MAINE MOUNTAINS. WINDS SHOULDN/T BE A BIG ISSUE OVER LAND WITH THIS SYSTEM...PERHAPS SOME GUSTS AROUND 25 MPH OR SO. THE BULK OF THE SNOWFALL WILL END BY EARLY SATURDAY EVENING ACROSS SOUTHERN ZONES AND AROUND MIDNIGHT ON THE MID COAST. && .LONG TERM /SUNDAY THROUGH THURSDAY/... ON SUN COASTAL STORM DEPARTS THE AREA...BUT WE REMAIN UNDER CYCLONIC FLOW ALOFT. COLD FRONT WILL BE EDGING THRU THE AREA...WITH LINGERING LOW LEVEL MOISTURE. SO SHSN REMAIN A POSSIBILITY IN THE MTNS...BUT DOWNSLOPING OVER THE REST OF THE FORECAST AREA SHOULD KEEP THINGS MAINLY DRY. LATE IN THE DAY A NRN STREAM S/WV WILL BE DIVING THRU THE CANADIAN PRAIRIES. CUTTING THRU THE OH VALLEY IT ARRIVES AT THE MID ATLANTIC COAST EARLY MON. LOW PRES WILL DEEPEN RAPIDLY ONCE OVER THE WATER...EXPANDING THE PCPN SHIELD. AT THIS TIME THERE REMAIN SOME CONSIDERABLE UNCERTAINTY JUST HOW FAR N THIS PCPN MAKES IT. WILL MAINTAIN CHANCE POP ALONG THE SRN HALF OF THE FORECAST AREA TO ACCOUNT FOR THIS. MUCH OF THE OUTCOME DEPENDS ON THE STRENGTH AND POSITION OF THE LOW PRES TO AFFECT THE REGION SAT. BEHIND THIS SYSTEM A STRONG SHOT OF CAA IS LIKELY. TEMPS SHOULD BE SEASONABLY COOL FOR THE FIRST HALF OF THE WEEK AT LEAST...AS COLD CANADIAN HIGH PRES SETTLES INTO THE ERN CONUS. IT SHOULD ALSO LEAVE THE MIDDLE PART OF THE WEEK MOSTLY DRY AS WELL. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... SHORT TERM...VFR TODAY EXCEPT PATCHES OF MVFR IN THE MOUNTAINS. VFR TONIGHT WILL GIVE WAY TO IFR OR LOWER CONDITIONS ACROSS SOUTHERN NH AND COASTAL MAINE SATURDAY AND SATURDAY EVENING IN SNOW. FURTHER INLAND...CONDITIONS WILL BE BETTER BUT STILL LIKELY MVFR. VFR CONDITIONS RETURN SATURDAY NIGHT. LONG TERM...CONDITIONS WILL BE IMPROVING TO VFR BEHIND LOW PRES ON SUN. NRN STREAM LOW PRES SYSTEM WILL RAPIDLY DEVELOP OFF THE NORTHEAST COAST MON. THIS COULD BRING A PERIOD OF IFR IN SNWFL ALONG THE COAST...THOUGH CONFIDENCE IS LOW AT THIS TIME. GUSTY WLY WINDS WILL FOLLOW BEHIND THIS SYSTEM. && .MARINE... SHORT TERM...MARGINAL SCA CONDITIONS POSSIBLE TODAY THROUGH TONIGHT. GALE WATCH IN EFFECT FOR ALL EXCEPT CASCO BAY LATE SATURDAY AND ESPECIALLY FOR SATURDAY NIGHT AS LOW PRESSURE MAKES ITS CLOSEST APPROACH. LONG TERM...SCA CONDITIONS ARE STILL LIKELY EARLY SUN BEHIND DEPARTING LOW PRES. A NRN STREAM LOW PRES WILL EXIT THE EAST COAST AND RAPIDLY DEVELOP MON...WITH A STRONG SHOT OF CAA IN ITS WAKE. THERE IS A LOW CHANCE FOR A PERIOD OF GALE FORCE GUSTS LATE MON BEHIND IT. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...WINTER STORM WATCH FROM SATURDAY MORNING THROUGH SATURDAY EVENING FOR MEZ018>028. NH...WINTER STORM WATCH FROM LATE TONIGHT THROUGH SATURDAY EVENING FOR NHZ010-012>015. MARINE...GALE WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY MORNING FOR ANZ150>152-154. && $$ SYNOPSIS... NEAR TERM...POHL SHORT TERM...EKSTER LONG TERM...LEGRO AVIATION...EKSTER/LEGRO MARINE...EKSTER/LEGRO

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