Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 525 PM EST Tue Nov 03 2020 Valid 12Z Sat Nov 07 2020 - 12Z Wed Nov 11 2020 ...Guidance/Predictability Assessment... Successive troughing is forecast to push through much of the state in progressive flow, squashing upper ridging in the northeastern Pacific but at times nosing into southeastern areas. The 12Z guidance offered good clustering to start the period Saturday as a system lifts northward toward the eastern Aleutians and a boundary lingers astride the North Slope. By early Sun, 12Z GFS slips the surface low just east of the other models (closer to Kodiak) that maintained a more defined parent low across the AKPen into Bristol Bay and southwestern Alaska. With some wavering in recent runs east-west, preferred to blend the 12Z guidance which keeps a modest parent and triple point low before the triple point low develops into the Gulf late Sun. The will approach the Panhandle early Monday and head into Canada thereafter. Along the North Slope, surface boundary may waver north-south as a weak upper trough dips through late Sun into Mon. Next system of interest will enter the western Bering around late Sun, moving eastward next week. 12Z guidance paired the ECMWF/Canadian closer to the ensemble means as the GFS spun up a wave along the cold front, but then all diverged from the ensemble means by late in the period. With no clear signal on which model may have a better handle on the pattern/evolution, trended to solely and ensemble mean blend between the 12Z GEFS mean and 00Z ECMWF ensemble mean for lack of anything better. This would take the parent low toward the Bering Strait next Wed as its triple point takes over in the Gulf between Kodiak and the Kenai peninsula. At the least, this was close to continuity from 24 hrs ago but is a rather simplified depiction. ...Weather/Threats Highlights... Approaching Pacific system will bring increasing coastal rain and inland snow to southwestern portions of the state late Sat into Sun on southerly to southeasterly flow. Precipitation may be heavy with several inches (liquid) possible in favored areas. Heavy snow is possible in some areas that stay cold enough. In-house bias-corrected QPF shows 3-5 inches over southeastern Kenai eastward toward Yakutat and some locally higher amounts into Mon (5-8"). Next system over/near the western to central Bering Sea Mon-Tue should spread another area of precipitation and strong winds across the Bering Sea/Aleutians. This will move into Southcentral by mid week next week but perhaps with less precipitation than the lead system Sunday. However, this may bring significant precipitation to western areas from the Y-K Delta northward to Kotzebue. Well above normal temperatures are forecast near the Brooks Range on Saturday (anomalies about +20F) but this will trend less above normal next week as the boundary slips southward. Above normal temperatures are expected over the rest of the Interior (generally west and north of the Alaska Range) next week. By contrast, below normal temperatures are expected over the Panhandle and southeastern areas Saturday with high pressure over Canada. Temperatures will only moderate a bit next week as the lead system approaches and moves through. Fracasso Additional 3-7 Day Hazard information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sat-Mon, Nov 7-Nov 9. WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can also be found at: https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html