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Area Forecast Discussion
Issued by NWS Caribou, ME
Issued by NWS Caribou, ME
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839 FXUS61 KCAR 180134 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 934 PM EDT Sat Aug 17 2024 .SYNOPSIS... Surface high pressure drifts east of Nova Scotia tonight. Ernesto will track well east of the region Sunday through Monday. Low pressure will also approach from the west Monday, cross the region Monday night through Tuesday, then exit across the Maritimes Wednesday while high pressure begins to build into the area on Thursday. && .NEAR TERM /THROUGH SUNDAY/... 930 PM Update... No significant changes were needed with this update. Cloud cover continues to increase, particularly across the southwestern portion of the forecast area as southerly flow continues. With the increasing cloud cover, fog will be more influenced by advection rather than radiation tonight, and is expected to be mostly confined to Downeast areas and south facing slopes further inland. It remains hazy across the area due to smoke, mainly aloft, from distant wildfires. However, slightly higher surface smoke concentrations exist across the Saint John Valley. Previous Discussion... Tonight high pressure will drift E of Nova Scotia as a 500mb upper low works into the Eastern Great Lakes. Return southerly flow increases and turns S-SSE over the area with moisture advecting northward. RAP/HRRR vertically integrated smoke models continue to show haze caused by smoke continuing through tonight into Sunday morning. Expecting patchy to areas of fog to develop again tonight and may become dense along the Downeast coast given the wind direction flow turning S-SSE & boundary layer moisture increases. Temperatures fall back into the upper 50s to low 60s across the area with calm or light and variable winds. Sunday will turn partly sunny after morning fog but expecting smoke to dissipate with increasing SW flow aloft pushing it mostly out of the area. Expecting more stubborn clouds Sunday with highs generally in the low to mid 70s and a touch more humidity. Cool spots along the Downeast coast will only reach the mid to upper 60s. A few showers will be possible along the Quebec border by afternoon, perhaps dipping down into the Moosehead Region, which is ahead of our next weather maker described below. Lastly, main concerns is from Ernesto causing increasing wave heights making it to the coast and rip current risks increasing which is talked about in the Marine section below. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... As Ernesto moves further northwards, well to the east of the forecast area, the system will begin to transition to an extratropical system, which in part would be seen by the expansion of the wind field and circulation. The core of the system will remain completely out of our region, passing east of the Canadian Maritimes, however, recent model runs suggest that as Ernesto transitions, moisture from this expanding system may get wrapped around the stalled ridge of high pressure over the CWA, leading to increased moisture and cloud cover through Sunday night into Monday ahead of the next frontal passage. As the next longwave trough begins to slide eastward into the area on Monday, the left exit region of a jet streak aloft will aid in providing lift for scattered showers across the area, capitalizing on the additional moisture provided from Ernesto as outlined above. For Monday night into Tuesday, a cold front will finally, slowly, push through the area as the blocking pattern begins to release with Ernesto moving east and the ridge of high pressure sliding eastward in pursuit. An upper level longwave trough, with connections to deep Gulf of Mexico moisture, will support the surface low and cold front, bringing the next widespread rain event to the region. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... The upper level trough remains in the area through the middle of the week, which will persist a general area of instability and lead to the slight chance for showers to linger Tuesday night into the day on Wednesday. That said, plenty of dry air will be ushered in aloft, which will limit how extensive rain showers may become through the middle of the week. High pressure is likely to return by the end of the week, but some uncertainty remains in how deep the ridge of high pressure will be, with a few models resolving a more progressive pattern and another shortwave moving into the region by the end of the week. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... NEAR TERM: Already IFR at BHB and expected to become MVFR/IFR tonight with LIFR possible due to low ceilings and visibility at all airfields. BR/FG and low ceilings are likely at BGR and Downeast airfields. Ceilings and visibility improve to VFR at northern airfields and MVFR and BGR and Downeast airfields by midday Sunday. Winds S around 5kts becoming light and variable tonight, increasing to 5-15kt Sunday. SHORT TERM: Sunday night...Variable conditions with low clouds and patchy fog late. Otherwise, VFR. A slight chance of showers across western areas. South/southeast winds 5 to 10 kts. Monday...Variable conditions with low clouds and patchy fog early, then VFR/MVFR. Increasing shower chances. South/southwest winds 5 to 10 kts. Monday night...IFR likely across all terminals with rain and a slight chance of thunderstorms. Winds shifting NW at 5 to 10 kts. Tuesday...IFR early, potentially improving to MVFR through the day. Rain, tapering to showers. NW winds 10 to 15 kts. Tuesday night...VFR/MVFR. A slight chance/chance of showers. North/northwest winds 5 to 10 kts. Wednesday...VFR. Slight chance of a shower. North/northwest winds 5 to 10 kts. Thursday...VFR across all terminals. Light NW winds around 5 kts. && .MARINE... NEAR TERM: Ernesto tracking well E of the waters through Mon is causing long period swells of 12-15 seconds to continue building tonight. Small Craft Advisory has gone into effect for the Coastal Waters out 25nm and East to the Hague Line. S swells will increase to 6-7ft tonight. Areas of fog will reduce visibility tonight. Sunday, wave heights will increase to 5-8ft at 14-15sec periods. These waves will reach the Downeast coast posing a serious concern for dangerous high surf hitting the coast and rip currents. High Surf Advisory will be in effect from 8PM tonight through Monday night. Sea surface temperatures from the Downeast coast out 25nm and east to the Hague Line range from 55-60F including Passamaquoddy Bay. SHORT TERM: A Small Craft Advisory is in effect through Monday due to seas from swells generated from Ernesto. Meanwhile, Ernesto will pass well to the east of the waters. Seas 4 to 7 ft may linger into Monday night as well. A chance of showers Monday, then rain Monday night into Tuesday. Patchy fog Sunday into Tuesday. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...High Surf Advisory until 8 PM EDT Monday for MEZ029-030. MARINE...Small Craft Advisory until 8 PM EDT Monday for ANZ050>052. && $$ Near Term...MStrauser/Sinko Short Term...AStrauser Long Term...AStrauser Aviation...MStrauser/Sinko/AStrauser Marine...MStrauser/Sinko/AStrauser