Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 300146 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 946 PM EDT Mon May 29 2017 .SYNOPSIS... A stationary front will remain over the Maine coast overnight. An weakening occluded front will cross the region Tuesday morning. Another frontal boundary is expected to slowly cross the region late Tuesday night and wednesday. && .NEAR TERM /THROUGH TUESDAY/... 9:30pm Update... As expected, did adjust POPs to lower them for the area south of Piscataquis County, as only a passing shower appears likely for the Bangor metro. Minor adjustments to QPF as well, as a result. Kept the day shift`s patchy fog in the grids between 06z and 12z, as a combination of moistening from the showers and onshore winds will increase the RH across much of the area. Didn`t need to change temps much this update. Original Discussion... A weakening occluded front will apch and cross the Rgn from the W as a s/wv alf from QB shears apart. This front will wash out whats left of a weakening stationary front currently near the Downeast Maine coast. Rnfl amts will be lgt, with the most ovr NW ptns of the Rgn where the shwr band will be a little more organized before weakening further E. Patchy fog will be possible late tngt with the llvls of the atmosphere becoming more moist with any additional lgt rn and winds becoming lgt. With shwrs already E of the Rgn by Tue morn, any remaining fog should lift by mid morn with breaks in the ovc possible by Tue aftn. Fcst warmer aftn 925 temps suggest warmer hi temps across Nrn and Cntrl ptns of the Rgn Tue with Downeast areas tempered by a geostrophically enhanced sea breeze. The next round of shwrs with the next s/wv rotating SW to NE arnd upper lvl low pres ovr Ont Prov will just be entering Wrn ptns of the Rgn later in the aftn. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... Widespread showers are expected Tuesday night and Wednesday as a shortwave rotates around an upper low situated over Ontario. South flow will keep marine air in place across much of the region on Wednesday, thereby limiting the potential for thunderstorms. The exception will be across the North Woods, where model guidance is indicating 300-800 J/kg of CAPE will be available by afternoon. Have kept a chance of thunder for these areas. This CAPE will wane overnight as daytime heating is lost, and guidance is not very generous with elevated instability, so don`t expect any thunder much past sunset. Showers will wind down after midnight Wednesday night, but additional precipitation will be possible Thursday as a weak cold front moves through. Moisture will be lacking with this fropa, so any showers will be scattered and light in nature. Wednesday will be another cool day across the region owing to marine air and plentiful cloud cover, but increasing sunshine and west winds behind the front will allow temperatures to reach into the mid 60s to around 70 on Thursday. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Differences in model solutions making a tough forecast for Friday. The aforementioned upper low will draw closer Thursday night and Friday with another, stronger shortwave to lift across New England. However, the latest GFS now has a nearly stationary front lying stretched across Downeast Maine, which would limit most precipitation, particularly thunderstorms, to inland regions from Bangor south. It also swings the shortwave through early on Friday. Meanwhile, the ECMWF and Canadian are 6-12 hours slower with the shortwave and also allow surface instability to develop across the entire interior forecast area. Noted that while the ECWMF now lags the highest instability behind the best shear, the GFS has them timed more concurrently. As such, should its frontal position be incorrect, the potential is there for strong storms to develop. Given the uncertainty, have reduced mention of any convection to slight chance. This uncertainty continues right through the weekend, with the GFS and ECMWF not agreeing in timing, placement, or strength of shortwaves rotating around the departing upper low. Given this, have stayed close to a blend through the extended, which resulted in slight chance/chance PoPs for much of the period. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... NEAR TERM: Mainly MVFR clgs ovrngt for our TAF sites with intermittent IFR clgs/vsbys possible late tngt with shwrs and patchy fog. Conditions will gradually improve to low VFR by Tues aftn, with the possible xcptn being KFVE. SHORT TERM: Widespread MVFR conditions will prevail Tuesday night through Wednesday due to low ceilings, rain, and patchy fog. IFR will be likely 00z-12z Wed and Thu, particularly at the southern terminals. Conditions will gradually improve after 12z Thu as drier air works in behind a passing frontal boundary. Scattered showers will be possible Thu afternoon, but they should be light and expect VFR conditions at all terminals after 16z. VFR conditions continue Thu night, then more showers, along with MVFR ceilings and visibilities, are possible Friday. && .MARINE... NEAR TERM: No Hdlns xpctd thru Tue with wv hts 2 to 3 ft ovr the outer MZ waters and 1 to 2 ft ovr the intracoastal MZ waters. We went with about 85 to 90 percent of WW3 wv guidance for fcst wv hts which is advertising a 5 to 8 sec primary wv pd. SHORT TERM: Headlines are expected to be needed through Thursday. South winds will increase Tuesday night into Wednesday and again Wednesday night and Thursday. These increasing winds will allow seas to build to around 4 feet, but both winds and waves will remain below Small Craft Advisory levels. A better chance for possible SCA conditions arrives Friday and Friday night. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Kredensor/VJN Short Term...Hastings Long Term...Hastings Aviation...Kredensor/VJN/Hastings Marine...Kredensor/VJN/Hastings is the U.S. government's official web portal to all federal, state and local government web resources and services.