Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
417 PM akdt Sat may 2 2015
Analysis and upper levels...
a broadening high pressure ridge is building across the northern
Gulf and the southcentral Mainland. Areas of stratus and Strata-cumulus
are evident across the north Gulf and Prince William Sound.
Generally fair skies are present over the reminder of southcentral
Mainland. A stacked and weakening low well south of Kodiak Island
and an associated front over the far southern Gulf are producing
broad east to northeast flow over the western Gulf. Showers caught
up in this flow are spreading west across Kodiak Island. Further
west...an upper level low over the eastern Bering Sea and a trough
to its east are producing generally cloudy conditions across much
of Bristol Bay and the Kuskokwim Delta. Radar returns across these
areas were fairly light and observation stations did not report
any measurable precipitation. High pressure was located to the
west of the trough with lower pressure and a weakening low near
the western Aleutians.
models across the Gulf and southcentral Alaska are in fairly good
agreement on the handling of the eastward moving low over the
southern Gulf and the building ridge to the north. Out west...the
global models (gfs/ecmwf) are in fairly good agreement with the
development and movement of the storm force low moving to the
central Aleutians on sun. Global models also have a similar
handling of the low center as it weakens and drifts southeast on
Monday. Models have a similar quantitative precipitation forecast pattern over the SW Mainland as
the upper low moves across the area.
Short term forecast southcentral Alaska (days 1 and 2)...
Weak high pressure aloft is really beginning to assert its
dominance over southcentral Alaska today. This pattern will
continue to slowly dry and stabilize the atmosphere through
Monday...limiting showers to near the mountains around the Alaska
Range...Talkeetna Mountains...and the northern Copper Basin. Sea
breezes will be prominent across all coastal locations...with
interior locations warming well above average. Northerly gap
winds will develop Sunday evening into Monday morning across the
northern Prince William Sound region...but winds will not exceed
10 to 15 miles per hour.
Near Kodiak Island...a glancing blow from the weakening front
moving through the southern Gulf will continue to support rain
showers across the island through the weekend...although they will
become increasingly sparse by Monday as the front falls apart and
Short term forecast southwest Alaska (days 1 and 2)...
rain showers will continue to develop over interior Bristol Bay
and the Kuskokwim Delta this evening and continue through the
overnight hours. The responsible upper level low pressure will
also move the area of rain from the Alaska Peninsula toward King
Salmon and inland overnight. The system will stall overhead
through the weekend and into early next week keeping at least
afternoon showers in the forecast for most areas.
Short term forecast Bering Sea/Aleutians (days 1 and 2)...
a developing low pressure system in the western Aleutians will
spread a storm force front over the western and central chain
overnight tonight into Sunday. This front will bring especially
gusty winds to Adak and Atka on Sunday as the thermal profile
should allow for mixing down of winds up to 70 miles per hour from aloft. The
front will stall over the southern Bering and weaken early next
Long term forecast (days 3 through 7)...
mostly sunny skies will prevail across southcentral Alaska
through the beginning of the week before giving way to a wetter
pattern late Tuesday into Wednesday as ridging over the eastern
Mainland is replaced by deep southerly flow and a front
approaching the Gulf Coast. This will be followed by a North
Pacific low that looks to approach the western Gulf by
Friday...keeping a chance of rain in the forecast through the end
of the week. The bulk of the precipitation will be along the Gulf
Coast...with a more showery regime setting up farther inland. Out
west...windy and rainy conditions will gradually improve from west
to east across the Aleutian chain as the North Pacific low passes
to the south and moves towards the western Gulf. This will be
replaced by weak high pressure which will yield benign conditions
dominated by fog and stratus through the end of next week.
Marine...gale 172 173 174 177 178.
Storm 175 176.
Synopsis and model discussion...British Columbia
southwest Alaska/Bering Sea/Aleutians...ml