Small Craft Advisory 432, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
1228 PM AKDT Wed May 31 2017

.ANALYSIS AND UPPER LEVELS...
Clear skies prevail across the southern mainland this morning as
an upper level ridge continues to build over the state from the
southwest. This is promoting very quiet weather conditions area
wide, with dry air in the low levels and weak offshore flow
helping to limit any fog development. A broad low pressure system
centered north of Adak is gradually weakening as it makes slow
eastward progress, bringing benign cloudy and showery conditions
to much of the Bering Sea.

&&

.MODEL DISCUSSION...
Models remain in good synoptic agreement in the short term as
high pressure lingers over mainland Alaska through the end of the
work week. Continued to utilize hi-res guidance to better capture
localized features.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist through the TAF
period.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

General offshore flow along with afternoon coastal sea breezes
will continue through Thursday. Fairly warm and dry conditions
will prevail with afternoon temperatures warming well into the 60s
with even a few 70s inland today. With warming 850 mb temps and
general dry offshore flow/weak downslope continuing, expect
widespread mid to upper 60s with a sprinkling of low to mid 70s
inland. Afternoon and evening sea breezes today and Thursday will
keep temperatures cooler along the coasts. Gusty outflow winds
are expected near Whittier and in the Valdez areas this morning.
Outflow conditions could linger on into the afternoon near Valdez
delaying the onset of the seabreeze. Outflow conditions are likely
to develop again in the Valdez area, but should not be as strong.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2...Wed and Thu)...
Quiet weather will continue for the next couple of days. High
pressure will remain firmly over the area today before drifting
north late Thu. Lower pressure passing to the south of the Alaska
Peninsula will serve to tighten up the offshore gradient. This in
turn will help cause an uptick on the east to northwest winds.
Offshore winds and clear skies will make for some of the warmest
days of the Spring/Summer so far.

As the high slips north Thu, a few showers could form along the
higher terrain, but not looking for any widespread development at
all. The thermal trough builds in much stronger Fri and into the
weekend. It will provide a better forcing mechanism for
widespread showers and some isolated thunderstorms.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2...Wed and
Thu)...
The low (and associated front) over the Bering will hold on for
one more day before finally moving off into the North Pacific on
Thu. For today, the front remains draped through the Central
Aleutians. East of the boundary (Dutch Harbor), gusty southeast
winds and steady rain persist. West of it (Adak), flow switches
around to more west to northwest and precipitation is much more
showery in nature. A weak upstream ridge and a 100-kt jet will
help to nudge out and carry away the low pressure center. Rain
will subside for the Central Aleutians Thu, but will remain over
the Eastern Aleutians and especially on the south side of the
Alaska Peninsula. A new weak low will clip the very western-most
Aleutians on Thu. It will bring another round of rain and easterly
winds as it slides along south of the chain to end the week.

&&

.FIRE WEATHER...While convective indices are looking slightly
less impressive and moisture more limited for Friday, with a well
defined thermal trough stretching from interior Alaska into
Southwest Alaska providing good instability, still think isolated
thunderstorms in the Kuskokwim Valley and along the western Alaska
Range are a possibility Friday. Shower and thunderstorm chances
will increase for the weekend as easterly waves propagate from
the Yukon Territory across southern Alaska. These could pose a
fire weather concern, but this of course depends on how rapidly
fuels dry during the warm, dry spell this week.

&&

.LONG TERM FORECAST (Days 3 through 7)...

The long range forecast Saturday through Monday brings increasing
chances for rain showers for the southern mainland and along the
gulf with a Pacific low taking a westward track across the gulf.
It is still unclear how much ridging spreads over the Bering to
the west of this system, as another dominant low over Kamchatka
tries to swing energy south and east. If the ridge centers near
the Kuskokwim Delta, very dry conditions would develop with
seasonally warm temperatures instead of the showery conditions
currently advertised. The last challenge in the forecast deals
with a fast paced low moving up from the Eastern Pacific. This
system races up toward the western Aleutians on Monday.
Conservative edits were made in the extended forecast with the
most significant changes along the gulf where models are in better
agreement with westward moving low. Only minor edits were made
across the southwest mainland and Bering as large models
discrepancies lend little need for adjustments.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...CB
SOUTHCENTRAL ALASKA...RMC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MSO
FIRE WEATHER...JR/MSO
LONG TERM...KH