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FXAK02 KWNH 132309

PMDAK 



Alaska Extended Forecast Discussion

NWS Weather Prediction Center College Park MD

709 PM EDT Mon May 13 2024



Valid 12Z Fri May 17 2024 - 12Z Tue May 21 2024



...Guidance Evaluation and Preferences...



As early as this weekend there is a lot of uncertainty in the

overall flow pattern across Alaska into early next week. Friday

into Saturday, there is general consensus that an amplified trough

will split sending a shortwave across northern Alaska and another

into the Gulf. The GFS is the major outlier here with a much

stronger and faster Gulf of Alaska system. The UKMET was different

as it brought the northern stream energy south into the Bering

with a deep closed low and little to no support from any other

guidance. The early period blend was heavily based on the better

agreeable ECMWF and CMC, with the ensemble means. This also had

support from the ECMWF-initialized ML models as well.



After Saturday and into next week, uncertainty in the pattern

evolution over Alaska significantly increases. There is some

general consensus that at least weak ridging should build behind

the early period Mainland troughing, along with a weak shortwave

moving into the Bering Sea. The ECMWF has been fairly consistent

in this shortwave amplifying as it moves into the Mainland early

next week, while the GFS suggests it shifts more northward and

weakens towards the Bering Strait as strong ridging builds over

the Mainland/Gulf. A quick look at the ensembles and ML models

shows better support for some sort of ridging or flatter flow, but

there is a considerable amount of spread lending to a very low

confidence forecast. However, given no clear guidance on which

deterministic solution may be more plausible, the WPC Alaska blend

for today trended significantly towards the ensemble means, but

did incorporate back in some of the GFS just for a little bit of

added definition. The next system will move across the western

Aleutians around Monday-Tuesday but with some discrepancies in

timing.





...General Overview and Weather/Hazards Highlights...



A weak surface low into the Gulf Friday-Saturday should allow for

some general light to moderate rainfall along the coast. Mean low

pressure across the Mainland should also result in light showers

through the weekend and maybe into next week farther inland as

well. Total rainfall along the coast should be on the order of

maybe 1-2 inches, which would not reach hazards level criteria.

Upper ridging building in behind this initial system would help

the Southern Coast/Southeast region dry out some going into next

week. A cold front will also begin spreading showers from west to

east across the Aleutians by next Monday.



Western to southern Alaska should be modestly below normal to

start the period underneath amplified ridging. By the weekend and

beyond, temperatures should regulate back towards normal but still

cool. The Eastern interior and North Slope will be 10-20 degrees

above normal for this time of the year, but should gradually shift

back towards normal by next week.





Santorelli





Additional 3-7 Day Hazard Information can be found on the WPC

medium range hazards outlook chart at:

https://www.wpc.ncep.noaa.gov/threats/threats.php



WPC medium range Alaskan products including 500mb, surface

fronts/pressures progs and sensible weather grids can also be

found at:

https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif

https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml

https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html



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