Area Forecast Discussion
Issued by NWS Caribou, ME
Issued by NWS Caribou, ME
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234 FXUS61 KCAR 061923 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 323 PM EDT Sat Jul 6 2024 .SYNOPSIS... Weak low pressure will drag a cold front across the area tonight. High pressure builds Sunday into Monday. A weak surface boundary approaches from the north Tuesday with a cold front crossing the area Wednesday night. && .NEAR TERM /THROUGH SUNDAY/... A weak and disorganized surface low will move across the area tonight in concert with a weakening upper level shortwave. These features will help provide enough lift to produce another round of showers and thunderstorms this evening. Clearing to the southwest of the forecast area this afternoon may just nose into southern Piscataquis and Penobscot counties late this afternoon. The persistent inversion and low clouds will remain elsewhere in the CWA. The clearing may allow enough instabilty for heavy thunderstorms to form...or at least move into the area from more unstable areas upstream. Given the low FFG, juicy PWs nearing 2 inches, dew points in the lower 70s, and the history of heavy rainfall in the past two days, another round of locally heavy precipitation seems quite possible this evening. Training cells along the line currently stretching from northern New Hampshire towards Piscataquis County are another reason for concern. WPC maintains a marginal risk in the ERO. Enough rainfall for localized flash flooding is possible into this evening. The primary area of concern is southern Piscataquis. The other diminishing concern, if storms can organize in the next few hours would be winds. Shear is quite favorable this evening, but decent instability has been very slow to materialize upstream of the area. Low LCLs and the shear present a little worry for weak rotation. SPC has a marginal risk for severe storms grazing the far southwestern portion of the forecast area. Otherwise, the main story remains low clouds, drizzle and fog under the inversion for most of the forecast area. The fog will be thickest near the coast and a Dense Fog Advisory will have to be a consideration as we move into the evening. For Sunday, a slightly drier west wind and drier mid/upper levels will allow fog and stratus to burn off fairly quickly in the morning. Most of the area will see some sunshine. Residual 850mb moisture remains for cumulus. This moisture and instability will allow development of scattered afternoon showers and isolated thunderstorms. The very dry air aloft will likely limit coverage and duration of any activity. A weak upper trough arriving later in the afternoon will help provide cooling aloft. The warm and humid air mass remains in place for Sunday. The sunshine will propel highs well into the 80s with continued unpleasant humidity levels. Dew points will remain in the mid to upper 60s. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... Weak ridging remains over the area Sunday night into the day on Monday, with the forecast area situated in the right entrance region of the upper level jet streak. Though this jet streak will quickly propagate eastward, lessening the influence, enough instability may exist along with diurnal heating on Monday to develop a few isolated showers Monday afternoon. Otherwise, a drier pattern in terms of precipitation to start the week. That said, warm muggy air will remain in place, with forecast highs on Monday reaching into the mid 80s while dewpoints remain in the mid to upper 60s. Monday night into Tuesday, another jet streak of around 120 kts aloft will approach from the west, with the forecast area entering the right exit region of this streak. Some 500 mb vorticity will approach from the west during this time as well. With southwest return flow wrapping around the exiting ridge of high pressure, the next wave of rain showers begin to enter the forecast area from the south and west, aided by orographic lift into the Central Highlands late in the day on Tuesday. Warm and muggy conditions will continue, with highs lifting into the upper 80s to near 90 during the day on Tuesday and dewpoints remaining in the mid 60s across the north and approaching 70 Downeast. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... The next low pressure system is likely to cross through the area Wednesday into Wednesday night, with full support from the upper levels all the way down through the surface. Showers should move in from the southwest as the low crosses the area, passing into New Brunswick by late Wednesday night. There is some uncertainty with just how much moisture will be available at this point, with the GFS pointing towards the leading edge of Beryl moisture moving in at this point, while the ECMWF continues to suggest that the pattern will not be quite so amplified, and that the moisture will be confined to the southern CONUS through the middle of the week. There seems to be good agreement that the moisture from Beryl will reach the forecast area at some point through the end of the week, and this will support a generally unsettled pattern with more showers and storms through the second half of the week. Temperatures may remain around or just above average for this time of the year, with dewpoints remaining steady in the 60s to lower 70s due to the continued moisture advection. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... NEAR TERM: IFR to LIFR vis and cig persist through the night for all sites. BHB will be near VLIFR most of the night. Thunderstorms are possible this evening...mostly from GNR and HUL southward, but not near BHB and the coast. For Sunday, IFR/VLIFR fog and stratus will break up by mid- morning for all sites and VFR follows by early afternoon for all terminals. An isolated thunderstorm is possible north of HUL and GNR. SHORT TERM: Sun night...IFR in low clouds/patchy fog. Winds light and variable. Mon...Improving towards VFR. Winds SW around 5 kts. Mon night...Generally VFR, with brief IFR/LIFR possible in patchy fog. Light SW winds. Tues...VFR cigs, with showers moving in late from the SW. SW winds 5 to 10 kts. Tues night - Wed...MVFR with scattered rain showers. Light W winds. Wed night - Thurs...MVFR with lingering showers. Winds light and variable. && .MARINE... NEAR TERM: Winds and seas will slowly diminish tonight into Sunday. Although some gusts have reached over 20 kt today, do not anticipate the need for a Small Craft Advisory. Fog remains the greatest problem with little improvement expected through tomorrow...except along the immediate coast by later Sunday morning. SHORT TERM: Winds and seas are expected to remain below small craft advisory levels through the middle of the week. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...MCW Short Term...AStrauser Long Term...AStrauser Aviation...MCW/AStrauser Marine...MCW/AStrauser