Area Forecast Discussion
Issued by NWS
FXAK67 PAJK 241515 CCA
Southeast Alaska Forecast Discussion...Corrected
National Weather Service Juneau AK
547 AM AKDT SUN JUL 24 2016
.SHORT TERM...Surface analysis shows low pressure centered around
57.5N/139W early this morning. The low will continue to dissipate
this morning, with the southerly pressure gradient remaining strong
enough to maintain small craft advisories over Lynn Canal, Stephens
Passage and Sumner Strait this morning. The upper low will move
inland this afternoon/evening resulting in a tightening gradient
over the northern panhandle as a surface reflection develops.
This will keep advisory level winds over N Lynn through late
tonight. Model solutions remain in good agreement through the
period with a low deepening over the west gulf inducing ridging
into the southern panhandle with an overall trend for diminishing
showers today from S to N. As the low deepens to the W, the flow
will turn more towards the north gulf coast. This will bring
another round of precip to AKZ017 this evening and overnight.
The other challenge will be potential for fog development
overnight into Mon morning. Current thinking is that cloud cover
will persist overnight inhibiting fog development so kept mention
out of forecast at this time. Any clearing will increase the
potential and trends will need to be monitored this evening and
.LONG TERM.../ Monday to Saturday / Model consistency continues to
agree generally well and all seemed to pick up on a wetter pattern
shift for Southeast Alaska. Monday`s forecast still on track with
ridge building over the panhandle and a surface low with a
vertically stacked upper level support system drifting south to be
south of Cold Bay by Tuesday where the low will slowly weaken into
midweek. The main ridge of high pressure is positively tilted with
an axis curving along the panhandle. Aloft the main flow pattern
will be a moist onshore pattern.
The models agree that there will be a developing wave that will move
northeast and into the panhandle. Expect this wave to bring
between 1 and 3 inches to the panhandle...better amounts at the
higher elevations. As a result raised pops and rainfall amounts
Tuesday and Wednesday and then blended into the continued wet
extended part of the forecast. Used the ECMWF for rain amounts and
added some GEM to assist with wind updates. With the added rain
for early part of the week, hydrology will play a part as the
rivers will still be at an elevated state. So we will need to keep
an eye on them the first part of the week. Confidence is average
to above average through roughly mid week.
In the far extended forecast, hints that the start of next month
may start off with dry weather...though that will bear watching.
.HYDROLOGY...The Taiya River near Skagway rose above moderate flood
stage late Saturday afternoon, crested late in the evening and
continues to recede. Although heaviest rain ended, shower
activity over the basin could produce up to 1/2 inch rainfall
today. The forecast is to fall to near bankfull and rise again to
just near minor flood stage this afternoon/evening. Mendenhall
Lake also rose to bankfull from Saturday`s rain, cresting around
8.2 feet this morning, and, given the diminishing precipitation
trends, will recede through the morning.
MARINE...Small Craft Advisory for PKZ012-031-034-042.
Small Craft Advisory due to Seas for PKZ022-041-043-051-052.
Visit us at http://www.weather.gov/Juneau