####018004510####
FXAK02 KWNH 082356

PMDAK 



Alaska Extended Forecast Discussion

NWS Weather Prediction Center College Park MD

755 PM EDT Wed May 08 2024



Valid 12Z Sun May 12 2024 - 12Z Thu May 16 2024



...Overview...



A mean trough aloft atop Alaska will be persistent through the

weekend and lasting through at least the first part of next week.

A couple features of note should be present within the broad

trough pattern, including a weakening upper/surface low moving

into the Gulf over the weekend, and troughing extending into the

northern Pacific that has trended stronger over the past day that

supports another low in the Gulf Tuesday-Wednesday. Lingering

heavy precipitation is forecast across favored portions of the

Kenai Peninsula on Saturday, while the pattern will favor multiple

rounds of precipitation across Southeast Alaska next week.





...Guidance Evaluation and Preferences...



Model guidance is agreeable with the overall mid-upper trough

pattern atop the state into early next week, and show reasonable

agreement with the upper/surface lows coming into the Gulf while

weakening Sunday. Most model guidance also continues to show

reinforcing energy into the trough as additional energy drops

south into the northern Pacific, positively tilting the southern

portion of the trough Monday-Tuesday. For the most part, recent

models indicate that a potential upper low forming within the

trough could be stronger than models a day ago suggested, though

there remains some spread. The 12Z CMC was weaker and more

progressive with the troughing/energy, while the 06Z GFS was quite

strong with the upper low as it moved into the Gulf midweek and

also produced a stronger surface low that was an outlier. But the

12Z ECMWF and GFS runs seemed to be a good middle ground. Behind

these systems, rounds of troughing and energy emerging from

Siberia remain uncertain in timing and strength for

Tuesday-Thursday. The flat ensemble means and the spread in the

ensemble members themselves yield low confidence in these

features, so this will continue to be monitored as it could be

impactful to western Alaska later next week.



The WPC forecast was based on a blend of the deterministic 12Z

models favoring the GFS and ECMWF early in the period, and

increased the proportion of the GEFS and EC ensemble means to half

while maintaining some GFS/EC components late period. This yielded

deeper/sharper troughing in parts of southern Alaska than the

previous forecast, but otherwise maintained reasonable continuity.





...Weather/Hazards Highlights...



Into the weekend, upper and surface lows tracking into the Gulf of

Alaska will lead to lingering heavy precipitation across the

eastern Kenai Peninsula that continues to be shown on the Hazards

product for Saturday. Gusty winds are possible for the

northeastern Pacific ahead of the low. As the lows weaken over the

Gulf, moist flow will be directed into Southeast Alaska for some

generally moderate precipitation totals into Sunday-Monday. Then

by Tuesday-Wednesday, another low system shifting into the Gulf

should renew precipitation chances. Precipitation amounts could be

moderate to heavy and will be partially dependent on the eventual

strength of the surface low. Some lighter precipitation in the

form of rain showers and higher elevation snow showers could

extend into the Interior as well. The Aleutians and the western

Mainland may see precipitation chances and winds increase for the

middle of next week, but with considerable uncertainty.



The unsettled pattern will tend to keep diurnal temperature ranges

more narrow than climatology, with daytime highs most likely to be

below normal and morning lows averaging above normal. However,

some pockets of modestly above normal highs may be possible over

the Interior, while various locations depending on the day may see

slightly below normal lows.





Tate





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



$$