Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 041529 AAB AFDGYX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GRAY ME 1129 AM EDT TUE AUG 4 2015 .SYNOPSIS... PERSISTENT LOW PRESSURE ALOFT...SITUATED OVER QUEBEC...WILL BRING THE THREAT OF SHOWERS AND THUNDERSTORMS BOTH TODAY AND WEDNESDAY. A FEW STORMS COULD BE SEVERE LATER TODAY WITH STRONG WINDS AND LARGE HAIL...WITH ANOTHER ROUND OF STRONG STORMS POSSIBLE WEDNESDAY AFTERNOON. COOLER AIR MOVES IN FOR THE MID TO LATE WEEK PERIOD...AND IT WILL BE MAINLY DRY...ALTHOUGH SCATTERED SHOWERS WILL BE POSSIBLE IN THE MOUNTAINS THURSDAY. FRIDAY LOOKS MOSTLY DRY FOR NOW. THERE IS CHANCE FOR SOME RAIN OVER THE WEEKEND AS LOW PRESSURE JUST OFF THE COAST. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... MESOSCALE UPDATE...SOME MINOR ADJUSTMENTS TO SET FORECAST UP BEFORE THINGS GET BUSY WITH TSTMS. AT THIS TIME CU FIELD IN NRN NEW ENGLAND IS QUICKLY BECOMING AGITATED...AND BANDS OF TSTMS ARE ALREADY IN DEVELOPMENT ACROSS VT. INITIALLY STORMS WILL CARRY A LARGE HAIL THREAT...GRADUALLY BUILDING UPSCALE INTO CLUSTERS WITH A WIND THREAT. THETA-E AXIS IS BUILDING INTO SRN NH AND FAR SWRN ME...THIS IS WHERE INSTABILITY WILL BE THE GREATEST TODAY. LIKEWISE...THE HIGHEST THREAT FOR SIGNIFICANT SEVERE WX WILL EXIST IN THESE REGIONS OF THE FORECAST AREA. AS FOR THIS AFTERNOON...BASED ON LATEST AVAILABLE GUIDANCE...THE THREAT FOR SEVERE TSTMS CONTINUES FOR MUCH OF THE FORECAST AREA S OF THE MTNS. DRIER AIR IS ADVECTING IN FROM THE N...THOUGH MID 60S DEWPOINTS RESIDE ALONG THE COASTAL PLAIN. IN THE WAKE OF MORNING MCS ABUNDANT SUNSHINE WILL WARM THOSE AREAS INTO THE 80S. RESIDUAL MID LEVEL LAPSE RATES ON THE ORDER OF 6.5 C/KM WILL SUPPORT CAPE VALUES INCREASING TO AT LEAST 1500 J/KG NEAR THE COAST. STRONGER FORCING ARRIVES THIS AFTERNOON IN THE FORM OF THE LEFT EXIT REGION OF A NEAR 90 KT UPPER JET. THE END RESULT IS AT LEAST SCATTERED TSTMS ARE EXPECTED TO DEVELOP ACROSS CENTRAL PORTIONS OF THE FORECAST AREA...AND MOVE TOWARDS THE COAST...AS INDIVIDUAL CELLS PROPAGATE NEWD. SHEAR IS FORECAST TO BE STRONGER THAN YESTERDAY...SO STORMS WILL BE ORGANIZED WITH ALL MODES POSSIBLE...INCLUDING DISCRETE CELLS AND CLUSTERS. STRONG FLOW ALOFT WILL SUPPORT A DAMAGING WIND THREAT...AND LOWERED FREEZING LEVELS WILL AID IN DISCRETE CELLS POSSESSING A HAIL THREAT AS WELL. RESIDUAL BOUNDARIES FROM PREVIOUS NIGHT/S CONVECTION AND ANY MARINE/SEA BREEZE FRONT WILL ALSO CARRY A NON- ZERO TORNADO THREAT...BUT WIND AND HAIL APPEAR TO BE THE MAIN CONCERN. THE MOIST ENVIRONMENT AND STRONG FORCING WILL ALSO RESULT IN EFFICIENT RNFL IN STRONGER STORMS. FORECAST WILL BE UPDATED AS NECESSARY WITH ANY CHANGES TO THE EXPECTED EVOLUTION THIS AFTERNOON. PREV DISC... AT 06Z...A PREFRONTAL TROUGH WAS DRAPED ACROSS THE FORECAST AREA WITH A COLD FRONT OVER THE EASTERN GREAT LAKES. FOR TODAY...THE FRONT WILL INCH EASTWARD WITH CONVECTION INCREASING IN COVERAGE WITH DAYTIME HEATING AND APPROACH OF UPPER IMPULSE AND ASSOCIATED SURFACE COLD FRONT. MODIFIED BUFKIT FORECAST SOUNDINGS FROM NAM/GFS YIELD CAPES NEAR 2000 J/KG AND MODERATE SHEAR. EXPECT ORGANIZED STORMS AND LINE SEGMENTS ONCE AGAIN TODAY WITH DAMAGING WINDS AND LARGE HAIL THE PRIMARY THREATS. HIGHS WILL RANGE FROM 70S IN THE MOUNTAINS TO THE 80S ELSEWHERE. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... THE COLD FRONT WILL CLEAR THE AREA OVERNIGHT...BRINGING COOLER AND DRIER AIR BACK TO THE REGION. WITH LOWS IN THE 50S AND LOWER 60S. WEDNESDAY WILL PROVE TO BE ANOTHER INTERESTING DAY AS COOL CYCLONIC FLOW..DAYTIME HEATING AND PASSING IMPULSE PRODUCE ANOTHER ROUND OF CONVECTION WITH POTENTIAL FOR SMALL HAIL AND GUSTY WINDS. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... HIGH IMPACT WEATHER: NONE. 500 MB PATTERN STARTS WITH STRENGTHENING RIDGES OVER THE SRN CONUS AND MEAN TOUGHING IN THE NERN US. WHILE THERE IS SOME FLATTENING OF THE TROUGH TOWARD THE END OF THE WEEK...THE GENERAL TREND IS FOR THE TROUGH TO HOLD TO SOME DEGREE THRU EARLY NEXT WEEK. THIS PATTERN WOULD KEEP THE HOT AIR TO OUT WEST BUT SURPRISINGLY THE AIR IN THE TROUGH IS NOT ALL COOL. THIS WOULD KEEP TEMPS NEAR NORMAL WITH UNSETTLED CONDITIONS. SPECIFICALLY...WED NIGHT SHOULD FEATURE A SECONDARY PUSH OF THE COOLER AND DRIER SFC AIR IN NW FLOW...WITH PERHAPS A FEW SHRA IN THE MTNS. THU AND FRI LOOK MAINLY DRY AS WEAK SFC HIGH BUILDS IN BENEATH NEARLY ZONAL FLOW ALOFT. THE FORECAST BECOMES MUCH MORE MUDDLED FOR THE WEEKEND AS THE 00Z MEDIUM RANGE MODELS SHOW QUITE DIVERGENT SOLNS...WHICH RANGE FROM THE GEMS COMPLETE MISS OF A COASTAL LOW WELL TO THE SOUTH...TO THE EUROS WINTER-LIKE COASTAL BOMB. NOT MUCH CONFIDENCE IN THE FORECAST BEYOND FRIDAY AT THIS POINT. GIVEN THAT ALL MODELS LOOK TO BE DEALING WITH CONVECTIVE SCALING ISSUES AND AT TIMES DO NOT MAKE METEOROLOGICAL SENSE...HAVE OPTED TO GO WITH JUST CHC POPS SAT-SUN...WITH THE BEST CHC SAT NIGHT...AS THIS IS CLOSEST TO WHAT MIGHT CALLED MODEL CONSENSUS...AND AGREES WITH SUPERBLEND. SEE WPC EXTENDED FORECAST DISCUSSION /PMDEPD/ FOR A GOOD EXPLANATION OF THE MODEL ISSUES WITH THIS SYSTEM. STILL...ONE THING TO TAKE HOME ABOUT THE MODELS IN THE MEDIUM TO LONG RANGE IS THAT THEY ARE PROBABLY PICKING UP ON SOMETHING...BUT HOW THAT PANS OUT AND WHAT ITS IMPACTS WILL BE NEED TO BEEN FROM A SHORTER TIMEFRAME THAN DAYS 5 AND 6. TEMPERATURES THU AND FRI WILL SEE HIGHS IN THE LOW 70S NORTH TO AROUND 80 IN INTERIOR SW ME AND SRN NH...WITH OVERNIGHT MOSTLY IN THE 50S. DEPENDING ON HOW THE SYSTEM OVER THE WEEKEND PLAYS...AND ASSUMING IT AMOUNTS MORE TO SHOWERS AND SOME COOLER N-NE FLOW...DAYTIME HIGHS WILL BE IN THE 70S AND OVERNIGHT LOWS IN THE MID 50S TO LOW 60S. SHOULD SEE AT LEAST SLIGHT WARM UP EARLY NEXT WEEK. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/... SHORT TERM /THROUGH WED/ ... AREAS OF MVFR IN SHRA/TSRA WITH LCL IFR PSBL IN +TSRA ALONG WITH STRONG WIND GUSTS AND LARGE HAIL THROUGH 02Z. AREAS OF STRATUS AND FOG WITH LCL IFR TONIGHT. AREAS OF MVFR WED IN SHRA/TSRA. LONG TERM...MAINLY VFR THURSDAY THROUGH SATURDAY...ALTHOUGH HIGH PROBABILITY OF VLY FOG AT KHIE/KLEB WED AND THU NIGHT. && .MARINE... SHORT TERM...PERSISTENT SSW FLOW AHEAD OF SLOWLY APPROACHING COLD FRONT WILL KEEP WINDS AND SEAS JUST BELOW SCA THRESHOLDS THRU THIS EVENING. SCA WAS DROPPED WITH NEW MARINE PACKAGE THIS MORNING. LONG TERM...THU AND FRI WILL SEE CONDS COMFORTABLY BELOW SCA LVLS. DEPENDING ON TRACK OF LOW PRESSURE THIS WEEKEND COULD SEE A PERIOD OF SCA WINDS SEAS OVER THE WEEKEND. .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ NEAR TERM...LEGRO

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