Area Forecast Discussion
Issued by NWS Caribou, ME
Issued by NWS Caribou, ME
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946 FXUS61 KCAR 130445 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 1245 AM EDT Sat Jul 13 2024 .SYNOPSIS... A frontal boundary will remain stalled across the region tonight. A disturbance will cross the region Saturday. High pressure will cross the region Sunday. A cold front will begin to approach Tuesday. The front stalls over the region on Wednesday. && .NEAR TERM /THROUGH TODAY/... 12:30 AM Update... Isolated showers are moving across the Central Highlands and the Crown of Maine this morning, so have updated the current forecast to reflect this. Not expecting much rainfall from these showers. This instability may also help lift some patchy fog seen mostly over the eastern portion of the forecast area. Previous Discussion... The upper level ridge over the Mid Atlantic and the weak upper level trof over the Great Lakes will continue to funnel tropical moisture into the region tonight and Saturday. For Saturday, showers will start to increase and spread across the north as the upper level trof starts to move over the state. This trof will create a frontal boundary at the surface, where instability can develop in the afternoon. Model guidance shows the boundary setting up across the Bangor Region and Interior Downeast where the majority of instability is. Upper air model sounding show CAPE >1000 J/kg, steep lapse rates, upper level divergence. Thunderstorms are expected to be pulse storms with the weaker bulk shear across the area. However, with the higher lapse rates, moderate DCAPE, and higher PWATS, some thunderstorms could produce heavy rain and gusty winds. && .SHORT TERM /TONIGHT THROUGH MONDAY/... For Saturday night, the upper trough will quickly move through the area and convection will end during the evening. There are some signs of elevated instability persisting through the evening and have maintained mention of thunderstorms until about 10 pm. Clearing skies develop as the night progresses, but do not foresee temperatures dropping below the low to mid 60s in the humid air mass. The moisture will help produce patchy fog inland and more expansive areas of fog for the Downeast coast. On Sunday, a dry upper ridge moves through the area. The lack of clouds and subsidence will help propel temperatures back into the mid to upper 80s across the area. A deep mixed layer may even allow a few 90s. Expect little relief even at the coast with the west-southwest flow. Will probably need to issue a Beach Hazards Statement due to the cold water temps. Heat indices will likely remain a few degrees below advisory criteria. In terms of convection, expect the subsidence and a cap to inhibit formation of any storms. High pressure and clear skies remain in place Sunday night, but so will the humid air mass. Once again, lows will only drop into the mid 60s for most of the area...a bit warmer than the previous night. High temperatures on Monday will again climb into the upper 80s with a few 90F readings possible. No change in humidity means another day close to Heat Advisory criteria. The only differences from Sunday will be a cooler day on the coast due to a more onshore flow, and the possibility of afternoon convection. A weak, compact shortwave propagating in a fast northern stream flow would be the culprit to destabilize the atmosphere, but there is little agreement in guidance on the evolution and timing of this feature...possibly because it may be an MCS that has yet to form. Therefore, confidence is not high and have generally only assigned 15 to 30 percent PoPs for Monday afternoon with an eye towards further reductions. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... There are signs of a temporary break in the heat later next week as a fairly strong upper trough digs southward from Canada towards the northeastern US. However, the price for the cool off will be continued heat early next week and the potential for strong thunderstorms Tuesday and Wednesday. Upper level ridging starts to break down Tuesday, but not before the most of the area experiences another day in the upper 80s. It may end up as the warmest day of the week, and the most likely day for any heat advisories. Onshore southerly winds will provide some relief for the Downeast coast. As the vigorous upper trough digs southward towards the Great Lakes region, a weakening occlusion will approach the area late day with the potential for afternoon thunderstorms. The risk will be greatest in the northern zones. Deep layer shear will increase during the afternoon and the potential for strong storms is there. The front tends to hang up over the area Tuesday night into Wednesday as the upper trough continues to dig southward into the Great Lakes region. The stalled front seems likely to become a conduit for strong thunderstorms on Wednesday afternoon. Impressive deep layer shear and steep low level lapse rates are two factors that prompt concerns for even more severe potential than Tuesday. The front is expected to sweep across the area later Wednesday and a markedly cooler air mass with dew points back in more comfortable 50s seems likely. High temps will trend back towards seasonable readings for Thursday and Friday. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... NEAR TERM: VFR/MVFR tonight with isolated to scattered showers. Variable conditions with any fog across northern areas overnight into early Saturday, otherwise VFR. IFR/LIFR develops Downeast overnight with isolated to scattered showers along with low clouds and areas of fog, which persists early Saturday. VFR/MVFR across the entire region Saturday afternoon with scattered to numerous showers. Variable conditions with any afternoon thunderstorms. Variable winds 5 to 10 knots tonight through Saturday. SHORT TERM: Saturday night...Chance of IFR to LIFR vis in fog for BHB, coastal sites and possibly as far north as BGR. Expect generally VFR further north with light winds. Sunday...VFR with light SW winds. Sunday night...Chance of IFR to LIFR vis in fog for BHB and coastal sites. Monday...Generally VFR. Slight chance of afternoon thunderstorms, mostly west of a GNR to HUL line. Light winds. Monday night...Slight chance of IFR to LIFR vis in fog for BHB and coastal sites. Otherwise, VFR with light winds. Tuesday...VFR outside of scattered afternoon thunderstorms, mostly north of GNR and HUL. Light winds. && .MARINE... NEAR TERM: Seas have subsided below Small Craft Advisory levels. Thus, the SCA for the outer waters has been dropped. Winds/seas will remain small craft advisory criteria overnight through Saturday. Scattered showers later tonight, with scattered/numerous showers Saturday. Areas of fog tonight through Saturday. SHORT TERM: Fog will be the primary concern until a strong cold front moves through later Wednesday. Thunderstorms will become a slight concern Tuesday evening, and a bigger concern later Wednesday with a strong cold front moving across the waters. Continued to adjust guidance winds and seas down due to strong low level stability. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Clark/Norcross Short Term...MCW Long Term...MCW Aviation...Clark/Norcross/MCW Marine...Clark/Norcross/MCW