Weather Service Report

FXAK67 PAJK 202256

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
256 PM AKDT Fri Jul 20 2018

.SHORT TERM... Our main forecast challenge for today is the warm 
up occurring across the panhandle this weekend. A building ridge 
will aid in raising temperatures and keeping skies clear (for the 
most part). Models are in relatively good agreement, and thus, no
major changes to pressure were necessary. There will be some 
increasing northwesterlies associated with the building ridge, but
otherwise, a few small crafts along the coast through late 
tonight and a few local effects.

Maximum temperatures were adjusted upwards by a degree or two,
mainly using local effects. The biggest temperature increase was made
on Sunday with the inverted trough. Even temperatures at the 850
mb level were upwards of 15 C (60 F) over the northern panhandle.
Mixing that down to the surface yields temperatures in the 70
degree+ range across the panhandle. Temperatures were slightly 
above or near the top of the model spectrum spreads and just above
MOS Guidance. While MOS guidance is based on both climatology and
takes into past history (i.e. the last several days), models 
often struggle with surface temperatures (hence the need for model
spectrum spreads). However, this only accounts for "average" 
events, and doesn't include extreme outliers. Several locations 
(possibly Hoonah, Hyder, and Craig) could reach record 
temperatures or close to. The sea breeze will be the only 
limitation for warming in the Haines and Skagway areas. Minimal 
changes were made to minimum temperatures.

Widespread precipitation won't return to the panhandle at least 
until Wednesday, depending on how long it takes for the ridge to 
break down. POP's were updated with the NAMdng and the current 
APrfc for QPF. Another challenge was sky cover. With the marine 
stratus along the coast, it could also keep some coastal 
locations cooler. 

As of this afternoon, there are no current hydro concerns. Mendenhall
Lake has receded below action stage following yesterday's glacier
dam release. There could be some concerns in other rivers (i.e.
the Taiya) with the warming temperatures. In addition, warm temps
and low relative humidities may lend to some fire weather concerns
with dry fuels in the Juneau area and along the Haines highway.
Any residual showers in the Hyder area this afternoon could lead 
to the potential for thunderstorm activity, with lapse rates
nearing 7 C/km and CAPE nearing 600-800 J/kg. 

Overall, a warm, dry pattern persisting through the short term 
and small changes in the pressure pattern weren't enough to boost 
our confidence even higher. 

.LONG TERM.../Sunday through Wednesday/ The warming in Southeast 
Alaska interior this weekend has been well proclaimed. The marine 
stratus that we also told you about now lies indeed across the 
gulf and presses against our coastal areas and will do so through 
the weekend. So this begs the real question of the evening 
regarding the extended. When will this ridge tip over, end, or 
retreat? And the answer is not clear. Do we have complaints? 

Our forecast essentially lies unchanged. We will see a gradually 
weakening ridge by mid next week bringing in a chance of rain by 
Wednesday. The strongest winds will likely be along the outer 
coast over the gulf with the potential for strong westerlies at 
times through Cross Sound and Cape Decision. Finally, the warmth 
may need to be extended into Tuesday. 

This is all. 


.HYDROLOGY...The glacier dammed release from Suicide Basin stopped
yesterday afternoon and the lake level crested at 430 pm evening
at just over 10 ft. The Mendenhall lake level has continued to
fall overnight. As of 415 am today the lake gauge is at 7.75 ft
and will continue to fall through the day.


.AJK Watches/Warnings/Advisories...
MARINE...Small Craft Advisory for PKZ022-041>043. 




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