Scientific Forecaster Discussion
fxak67 pajk 242305
Southeast Alaska forecast discussion
National Weather Service Juneau Alaska
305 PM akdt Mon Jul 24 2017
Synopsis...high pressure persists over the Gulf into Tuesday. A
weak low pressure system and its associated weather front will
impact the southern Panhandle Tuesday and Wednesday.
Short term...widespread low status continues to plague a wide
swatch of the Gulf, which advances inland and into the inner
channel waters that have entrances to the open waters. Cloudy
skies with a fair amount of sunny breaks occurred over the
northern half of the Panhandle while the south had more clouds.
The outer coastal areas from Icy Bay down to Cross Sound area kept
the clouds all day and even had light precipitation fall.
Forecasting with a heavy hand on persistence this evening before
the low starts to influence our area, starting in the south
Tuesday and progressing northward into Wednesday.
With the advance of the low, the rain chances will increase in the
southern half of the Panhandle through Wednesday with the
Ketchikan-Prince of Wales are receiving the most rainfall.
Staying with only chance pops for the northern half as we reach
I feel like a broken record with the winds being 15 kt or less,
but alas that is what continues. The exception also continues to
be a late afternoon/evening enhancement in Lynn Canal and Skagway
area. Directions will be changing significantly as the low moves
up from off the coast of haida gwaii to off the coast of Prince of
Overall good model agreement between the ECMWF/NAM/GFS. Used the
GFS with more NAM when dealing with the precipitation moving in.
Slight divergence with the pop with the GFS being drier, while the
NAM is wetter.
Long term.../Thursday through Sunday/...as of 1030pm Sunday...
the upper level low that we've been watching for the start of next
week has strengthened in the models now to the point that there
is a surface low/trough reflection...where there used to be
weak/broad high pressure. The placement of the low should allow
for lower chances for showers across the far northern Panhandle,
however cannot rule out isolated/scattered showers.
After that upper level troughs look to continue to pass over the
region with southerly onshore flow, thus keeping the potential for
showers in the forecast. At the surface, expect a very weak
pressure gradient over the region develops due to broad high
pressure while low pressure settles over the south central Gulf.
Have decreased wind speeds over the Inner Channels some to reflect
the weaker pressure pattern. Will have to watch where the new low
tracks for next weekend.
Used a blend of the GFS/European model (ecmwf) and wpc for updates to this forecast
package. Forecast confidence is average.
Aviation...fairly widespread clouds over Southeast Alaska with
only a few breaks. Expect to see clouds lower overnight to the
MVFR with ceilings 1500 to 2500 ft. Clouds should be lifting
through the morning. A small front/wave looks to be lifting some
rain north into southern and central by late afternoon.