textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

The upper level pattern continues to show a northeast-southwest oriented progressive tilt of an amplified ridge extending from south of the Aleutians over the North Pacific into much of mainland Alaska. In doing so, the main jet has shifted eastward, weakening upper level support for strong winds and gap winds to continue across Southcentral Alaska. At the surface, a strong 1040 mb high remains anchored across the Aleutians as a surface low in the Gulf pulls away from the area, which in turn has weakened the pressure gradient - and winds across Southcentral. The 500 mb ridge's influence over Southcentral will increase overnight and through the rest of the short term by causing adiabatic warming from sinking motion in the upper atmosphere. The sinking motion combined with relatively breezy conditions will keep temperatures warmer than they have been over the last few days. 850 mb temperature anomalies suggest that much of mainland Alaska will be well above average for this time of year through the end of the short term forecast period.

Attention then shifts to Monday morning, where the sharp ridging aloft begins to deamplify and zonal flow becomes enhanced across the region as a shortwave trough upstream of the region begins to dig eastward with time. There are some differences in the models in the progression of the shortwave. The NAM seems to be somewhat of an outlier at this time as it wants to dig the shortwave faster and is a bit more robust than the GFS, EC, and Canadian-NH. That said, it does look likely that with this influx of energy that Southcentral will see light snow return Tuesday morning. Forecaster confidence does decrease closer to the event, particularly for the Kenai Peninsula, Anchorage area, and Matanuska-Susitna valleys as some models show this more of a situation of precipitation just clipping the area, with confidence much higher that the Copper River Basin will see more widespread snowfall from the system.

Looking ahead, the upper level pattern becomes characterized by a deep upper level trough/low complex, spilling a colder airmass over the region. At the surface, enhancement from the trough develops a surface low somewhere over the northern Gulf, which combined with higher pressure across the Interior, will cause gap winds to return to the region.

-AM

AVIATION

PANC...Northerly winds will continue to diminish this evening, becoming calm and variable tomorrow. VFR cigs and vis will persist.