Short Term Forecast Southcentral Alaska (Days 1 Through 3)
Discussion:
The main story is the drier and much colder conditions through Friday morning as an upper ridge strengthens over Southcentral. The next 24 hours will be well below normal, as the cold airmass lingers in place over Southcentral. Although daytime highs will range from the 20s in the Copper River Basin and mid 30s elsewhere, overnight lows Saturday morning are expected to fall well below normal, with low temperatures dipping into the teens and 20s and into the single digits to near zero degrees for portions of the Copper River Valley if skies remain clear.
Beginning Saturday afternoon, the front of a strong Bering low will increase chances for rain across Kodiak and the southeastern Kenai Peninsula and by Saturday evening across the far western Susitna Valley. Chances for rain overnight from Saturday to Sunday range from 35 to 50% for the Anchorage Bowl and Palmer, up to 75% to 85% for the Gulf coast, Homer, and the Susitna Valley. Daytime temperatures across Southcentral warm back up into the mid 30s to low 40s by Sunday with nighttime lows in the low 30s, with the Copper River Basin dipping to the low 20s and high teens.
Short Term Forecast Southwest Alaska/Bering Sea/Aleutians (Days 1 Through 3)
Key Messages:
* A High Wind Warning remains in effect for the Kuskokwim Delta/Coast, northern Bristol Bay coast, and Platinum to Goodnews Bay from 7 AM Friday to 4 AM Saturday. South to southeast 35 to 50 mph winds with gusts up to 75 mph are expected.
* A High Wind Warning remains in effect for Cold Bay, King Cove, and Akutan from 10 PM Thursday to 10 PM Friday. South to southeast 35 to 50 mph winds with gusts up to 75 mph are expected.
* A Wind Advisory remains in effect for Unalaska and Nikolski from 10 PM Thursday to 4 PM Friday. South 25 to 40 mph winds with gusts up to 55 mph are expected.
* A Coastal Flood Advisory remains in effect for the Kuskokwim Delta coast, including Kipnuk, Kwigillingok, and Kongiganak from 8 AM Friday through 1 AM Saturday, particularly around high tides near 10 AM and 10 PM Friday. The most likely scenario continues to be for water levels 2 to 3 feet above the normal highest tide line.
* A High Surf Advisory remains in effect for the northern Bristol Bay coast from 10 AM Friday to 7 AM Saturday. Water levels will most likely be around 1 to 2 feet above the normal highest tide line. Nuisance flooding of lying areas and coastal erosion is possible.
Discussion:
A strong, storm-force front will be the main weather focus through the weekend as it moves eastward towards a ridge which is currently over the eastern Bering and Southwest Alaska. The front from extends from a Kamchatka low and is progged to move eastward across the Bering and sweep the Aleutian Chain through Saturday morning. The front is to track to begin to move across Unalaska and the Pribilofs by late this evening, while the timing for the Kuskokwim Delta and southern Alaska Peninsula is early Friday morning, and Bristol Bay, the northern Alaska Peninsula, and more interior portions of Southwest Alaska by Friday afternoon. Sustained southerly winds of gale to storm force with higher gusts and moderate to heavy precipitation is expected along the front. As the front pushes east, the pressure gradient tightens with the ridge to the east which will help strengthen the winds. With high confidence for strong winds, multiple wind hazards have been issued across the region. This includes a wind advisory for Unalaska and Nikolski, where gusts up to 55 mph are expected Thursday night into Friday, a High Wind Warning for Cold Bay, King Cove and Akutan on Friday, where gusts up to 75 mph are expected, and a High Wind Warning for the Kuskokwim Delta and northern Bristol Bay coast Friday morning through Saturday morning, where winds are expected to gust up to 60 to 70 mph inland and up to 75 mph along the Kuskokwim Coast. Southerly winds will bring in warmer air to the region. Initially, precipitation across lower elevations of Southwest may be a mix of rain and snow. Precipitation quickly transitions to rain by Friday afternoon along the coast and Friday evening inland as temperatures continue to warm to the upper 30s to 40s and snow levels rise to 2500 feet. For the AKPen, Aleutians, and Bering, precipitation will fall as rain outside of the highest mountains.
Once the front passes through, both winds and chances for precipitation rapidly decrease. Timing of this is Friday morning for Adak, Friday afternoon for Unalaska and Nikolski, and Friday evening for the southern Alaska Peninsula (Cold Bay). The front slows over Southwest, Bristol Bay, and the northern Alaska Peninsula Friday night and begins to weaken as high pressure persists to the east. Winds begin to decrease. However, showers and gusty winds will persist through Saturday across Southwest and the northern Alaska Peninsula, especially for eastern Bristol Bay and north to the Kuskokwim Valley. Behind the front, showers and southwesterly gale force winds persist across the western Aleutians and Bering on Friday. As the low moves north and continues to weaken, winds weaken to small-craft force in the western Aleutians and Bering by Saturday morning.
Along with winds and rain, coastal flooding concerns remain. A Coastal Flood Advisory remains in effect for the Kuskokwim Delta Coast, including Kipnuk Kwigillingok, and Kongiganak from 8 AM Friday through 1 AM Saturday, particularly around high tides near 10 AM and 10 PM Friday. The most likely scenario continues to be for water levels 2 to 3 feet above the normal highest tide line. In contrast to previous storms with southwesterly winds, although very strong, the southerly to south-southeasterly wind direction with this system will limit the fetch of wind pointed towards the Kuskokwim Delta Coast due to the shape of the coastline from Quinhagak southward. Coastal flooding concerns decrease farther southeast toward Togiak. However, a High Surf Advisory remains in effect for the northern Bristol Bay coast from 10 AM Friday to 7 AM Saturday as southerly winds likely push water levels 1 to 2 feet above the normal highest tide line. Water levels are expected to drop off Saturday morning as winds decrease and the front slowly moves inland, alleviating coastal concerns.
-AM/PA
Long Term Forecast (Days 4 Through 7: Monday Through Thursday)
Discussion:
The long term forecast continues to remain focused on a series of systems that will lift up across the Bering Sea. Forecast confidence has remained fairly steady, with most model solutions showing decent continuity on general placement and timing of these systems riding along on southwesterly flow. Meanwhile, high pressure will take up residence on the Gulf side with ridging in place for much of the week. Several of these aforementioned systems may try to ride up the western periphery of the ridge...helping to flatten it some before it rebuilds over the Gulf. As such, Southcentral looks fairly quiet through midweek with best chances for some precipitation on Monday.
Most of the systems over the Bering will be rotating around a complex Kamchatka low. These systems will swing around the base of the low, moving across the Bering, and lifting up towards the Southwest Alaska coast and Bering Strait area. Strong winds and moderate to heavy precipitation will accompany each of these systems, strongest along the coast then dropping off as the front moves inland. Rain looks to be the primary precipitation type for lower elevations, but some locations across the Kuskokwim Delta / Nunivak Island area down towards the Greater Bristol Bay area could possibly see a changeover to a mix of rain and snow, or all snow at times. One feature to keep an eye on next week will be a strong North Pacific low moving into the western Aleutian Islands and Bering Sea.
- PP
Aviation
PANC...High pressure over the region will result in generally clear skies and light northerly winds through the TAF period.