Scientific Forecaster Discussion
000 FXUS61 KGYX 232145 AFDGYX Area Forecast Discussion National Weather Service Gray ME 545 PM EDT Tue May 23 2017 .SYNOPSIS... Weak high pressure will hold over the region through Wednesday as low pressure passes well offshore. A complex area of low pressure will approach from the southwest Wednesday night and Thursday and will slowly move northeast through southern New England and the Gulf of Maine Thursday night and Friday. High pressure will build in from the west Friday night and Saturday. A cold front will drop south through the region Saturday night and Sunday. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Update... Have issued a quick update to account for current observational trends and mesoscale models. CS shield continues over southern areas, while skies remain mainly clear further inland. Expect much of the CU fields to dissipate around sunset over the mountains. Prev Disc... A stratus deck has moved offshore but it did take a while for coastal locations to clear out today. After some clearing over the coastal plain and variable sun across the area, moderately dense cirrus blow off from the west has covered southern NH and much of western Maine. Elsewhere cumulus had developed over the mountains. All this developed in WSW/weak ridging aloft and in advance of a warm front over the Great Lakes region. Expect more cloudy skies tonight with light and variable winds. Overnight lows will range from the mid 40s to mid 50s. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Wednesday will be similar to today but with increasing moisture due to an increased onshore flow. We'll see a weak sea breeze develop tomorrow afternoon with low pressure passing well south of the Gulf of Maine. That said there may be a stray shower associated with this low across southern NH or SW Maine. In addition, isolated mountain showers are possible as the elevated warm front nears tomorrow. Highs will generally be in the lower to mid 70s. Overnight lows will be a little warmer for northern zones in the upper 40s with lower 50s to the south. && .LONG TERM /THURSDAY THROUGH TUESDAY/... A broad upper level ridge currently over the eastern portion of the US will shift eastward as the trough moves through the midwest and onto the east coast. This will set us up for an active pattern with a series of waves moving along the upper low and up the east coast. Thursday will start off partly sunny but quickly cloud over as low pressure develops to our south and moves up the east coast. This storm will deepen and pass across Cape Cod on Friday bringing widespread rain. While there is a fairly good consensus there will be a coastal low, the strength of the storm is still seeing quite a bit of spread with QPF amounts as high as 2 inches possible along the coast for the stronger solution and as low as 0.5 inch. Have leaned a bit on the higher QPF both due to favoring the stronger solution and because of the long tropical fetch for the moisture source. The storm departs into the maritimes on Saturday with some scattered upslope showers. Saturday afternoon and evening will be a brief break from the rain. The next low will move through the Great Lakes on Sunday pushing a warm front and overunning precipitation through the area Sunday night. Another coastal low will spin up on Monday pushing another round of widespread precipitation through to start the week. && .AVIATION /22Z TUESDAY THROUGH SUNDAY/... Short Term...VFR conditions will prevail with some possible IFR/MVFR in low stratus and fog once again near RKD...AUG...and PWM late tonight into Wednesday morning. A low deck is lurking just offshore and should move back towards shore tonight. Additional fog or drizzle is possible late Wednesday night into Thursday morning. Long Term... Thursday will begin with VFR and MVFR but rapidly drop to IFR on Thursday night as low pressure approaches the region. IFR with rain and fog will continue through the day on Friday with gusty winds along the coast. Conditions will improve to VFR with MVFR ceilings in the mountains for Saturday. && .MARINE... Short Term...Conditions should remain below SCA thresholds today through early Thursday morning. Long Term... A coastal low will cross the waters on Thursday into Friday with Small Craft Advisories likely and gale force winds possible ahead of the storm. Winds and seas will subside on Saturday and remain fairly calm through the start of next week. && .TIDES/COASTAL FLOODING... In addition to the potential for a lot of rain on Friday morning, the easterly flow and winds associated with a coastal low will create a risk for coastal flooding. Onshore flow will develop Thursday ahead of the storm and strengthen through the day on Friday. This will result in a storm surge of around 0.5 ft Thursday night. The highest tides of the year will occur Friday, with the onshore component plus the storm surge resulting in coastal flooding. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None.