Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 211450 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 1050 AM EDT MON APR 21 2014 .SYNOPSIS... HIGH PRESSURE CONTINUES TO SLOWLY SHIFT EAST TODAY WITH FAIR WEATHER EXPECTED. LOW PRESSURE APPROACHES FROM THE WEST TUESDAY...CROSSING THE AREA TUESDAY NIGHT AND WEDNESDAY. HIGH PRESSURE BUILDING ACROSS THE REGION WILL BRING FAIR WEATHER MID TO LATE WEEK. ANOTHER AREA OF LOW PRESSURE TRACKING TO OUR NORTH BRINGS A THREAT OF SHOWERS SATURDAY. && .NEAR TERM /THROUGH TONIGHT/...
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1045 PM UPDATE...NO SIGNIFICANT CHANGES TO THE GOING FORECAST. MADE MINOR ADJUSTMENTS BASED ON TRENDS IN OBSERVATIONAL DATA. PREVIOUSLY... UPDATE...A FEW MINOR CHANGES TO ACCOUNT FOR CURRENT OBSERVATIONAL TRENDS. PREVIOUS DISCUSSION...MID LEVEL FRONTAL BOUNDARY ACROSS THE INTERNATIONAL BORDER IS PROVIDING THE FOCUS FOR SOME CLOUDS AND SPRINKLES THIS MORNING. HAVE TO LOOK ALL THE WAY BACK TO SRN ONTARIO TO FIND ANYTHING REACHING THE GROUND OR CIGS BELOW 8 KFT. HAVE KEPT POP BELOW 15 ATTM EXPECTING NO MEASURABLE PCPN...BUT A SPRINKLE OR FLURRY IS POSSIBLE. PATCHES OF MID LEVEL CLOUDS WILL PLAY WITH TEMPS IN THE NEAR TERM. CLEARING WILL ALLOW AREAS TO DROP INTO THE 20S...WHILE CLOUDS WILL BOUNCE READINGS BACK INTO THE 30S. SHOULD BE A FAIR DAY TODAY...ESPECIALLY AWAY FROM THE COAST. DEPARTING HIGH WILL ALLOW SLY RETURN FLOW TO DEVELOP. THIS ONSHORE COMPONENT WILL KEEP COASTAL ME IN THE 50S...WHILE INTERIOR SECTIONS WARM INTO THE 60S TO NEAR 70. WARMING TEMPS AND DRY AIR MASS WILL PRODUCE RH VALUES CLOSE TO 25 PERCENT ACROSS MUCH OF NH TODAY. WINDS SHOULD REMAIN BELOW 20 MPH ON GUSTS...BUT THIS WILL STILL LEAD TO AN ELEVATED FIRE DANGER. NOT ENOUGH FOR A RED FLAG...BUT WILL MENTION HERE AND IN THE HWO TO HIGHLIGHT DRY CONDITIONS.
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&& .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... CONTINUED SLY/SWLY FLOW SHOULD YIELD A MILD NIGHT...WITH READINGS IN THE 40S. SOME SHRA MAY SPILL INTO NRN ZONES FROM CANADA AS FNT PRESSES CLOSER TO THE REGION. LOW PRES WILL CONTINUE TO PUSH FNT TOWARDS NEW ENGLAND TUE. EXPECT A MAINLY DRY DAY FOR AREAS SE OF THE MTNS...WITH SHRA BECOMING MORE NUMEROUS ACROSS THE N AS THE DAY WEARS ON. HIGH TEMPS SHOULD BE SIMILAR TO TODAY...COOLER AT THE COAST AND FAR N UNDER CLOUD COVER...WARMING NICELY INLAND. LATE IN THE DAY COASTAL STRATUS MAY BEGIN TO FORM...AS DEEPER SLY FLOW DEVELOPS OVER THE WATERS. HOWEVER...THIS LOOKS MORE LIKELY TO HOLD OFF UNTIL TUE NIGHT. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... 00Z MODELS IN FAIR AGREEMENT THAT THE NEAR ZONAL FLOW AT 500MB...BREAKS DOWN AND BECOMES QUITE AMPLIFIED AND BLOCKY BY THE WEEKEND. HOWEVER...THERE DETAILS VARY QUITE A BIT...AND THIS WILL MEAN LOWERING FORECAST CONFIDENCE AS WE MOVE INTO NEXT WEEKEND AND BEYOND. FAIRLY HIGH CONFIDENCE EARLY IN THE PERIOD AS SHRA MOVE THROUGH THE CWA TUE NIGHT INTO WED MORNING AS WEAK LOW AND COLD FRONT TRACK ACROSS THE AREA. TUE NIGHTS TEMPS WARM ENOUGH THAT PRECIP WILL BE RAIN EVERYWHERE BUT THE HIGHEST TERRAIN. UNCERTAINTY ALREADY BEGINS TO ENTER THE FORECAST LATE WED AND WED NIGHT...AS UPPR LVL LOW CLOSES OFF TO OUR SE AND COULD SLOW SFC LOW OR HANG SFC TROUGH BACK TO THE WEST. THIS COULD LINGER SOME SHRA THU AFT INTO THU NIGHT ALONG THE MID-COAST AND INTO THE KENNEBEC AND PENOBSCOT VLYS. AS THAT LOW INTENSIFIES OFFSHORE...WILL SEE N-NW WINDS PICK UP ON THE BACK SIDE...WITH SOME BREEZY CONDS IN STORE WED INTO THU. DECENT RIDGING ALOFT BUILDS BEHIND THE LOW THU INTO FRI...SO EXPECTING A DRY PERIOD...WITH TEMPS NEAR TO SLIGHTLY ABV NORMAL. ITS AFTER THIS WHEN WE START TO GET INTO MULTIPLE STRONG BLOCKS AND GYRES AT 500 MB...AND CONFIDENCE IN ANY MODELS ABILITY TO HANDLE THESE FEATURES IS LOW...BUT FOR NOW LOOK FOR A CHC OF SHOWERS AT SOME POINT OVER THE WEEKEND. && .AVIATION /11Z MONDAY THROUGH FRIDAY/... SHORT TERM...VFR CONDITIONS EXPECTED TO PREVAIL INTO EARLY TUE. EVENTUALLY APPROACHING TROF WILL SPREAD SHRA AND POSSIBLE MVFR CONDITIONS INTO NH TERMINALS BY TUE AFTERNOON. WILL HAVE TO WATCH FOR COASTAL STRATUS DEVELOPING LATE IN THE PERIOD IN ONSHORE FLOW. LONG TERM...EXPECT A PERIOD OF IFR OR LOWER TUE NIGHT INTO EARLY WED...WITH CONDS IMPROVING TO VFR DURING THE DAY WED. THEN...VFR IS EXPECTED TO HOLD THROUGH FRI. && .MARINE... SHORT TERM...PERSISTENT ONSHORE...SLY FLOW WILL EVENTUALLY BUILD SEAS TO NEAR 5 FT BY TUE AFTERNOON. A SCA MAY BE REQUIRED. LONG TERM...N-NW FLOW INCREASES ON WED AS LOW PRES INTENSIFIES E OF THE WATERS. WILL LKLY SEE SCA CONDS LATE WED INTO THU...AND COULD SEE GALES IN THE OPENS WATERS. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$

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