Small Craft Advisory 18, NWS Fairbanks, AK

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
1228 PM AKDT Sat May 13 2017

.DISCUSSION...
The 12z model suite initialized well against the 12z surface
analysis and verified well against the 18z surface analysis. Model
spread in minimal between model families and from run to run in
the short range as well as the mid range. Model spread remains
very reasonable in the extended range.

Aloft at 500 HPA, a 529 DAM low over Bristol Bay will move east
today to be located over Cook Inlet this evening and over Yakutat
Sunday morning. The upper level low then moves southeast over the
panhandle Monday. The upper level low pumps ample moisture into
the southern portions of the the central and especially eastern
interior as it moves east. A lee side low develops at 700 HPA
down to the surface over the eastern Alaska Range and Fortymile
Country tonight and moves slowly into the southwestern Yukon
Sunday and to near Whitehorse Monday morning. Significant upslope
aided rains develop on the west and northwest portions of the low
tonight and will continue Sunday before tapering off Monday
morning over the Upper Tanana Valley, the Eastern Alaska Range,
and the southern Forty Mile Country including the Salcha and
Goodpaster river basins. Storm total rainfall of one half inch to
nearly 1 inch are expected in these areas beginning tonight and
continuing through Monday morning. See hydro section for
additional details on concerns for rainfall and snowmelt runoff
aiding rises on small streams and rivers in these areas.

A thermal trough will lie from the Seward Peninsula to McGrath to
Fairbanks line today and combined with Lifted Indices in the minus
1 to minus 2 range and Capes in the 200 to 400 Joules range will
be the focus for isolated thunderstorms and scattered rain showers
this afternoon and evening.

Low ceilings, fog and flurries continue on the north slope. Gusty
northeast winds will continue to reinforce the low ceilings today
and will continue through Sunday. The winds will diminish and
switch to the southeast over the eastern north slope late on
Sunday.

As the upper level low passes to the southeast over the panhandle
an upper level ridge builds over the interior beginning Monday
and will continue to build over the area into the middle of next
week. Much warmer temperatures with highs in the lower and middle
70s are expected by the middle of next week over the southern
interior and combined with drying conditions will elevate fire
weather concerns.

&&

.FIRE WEATHER...
Minimal fire weather concerns today, Sunday and Monday other than
moderate instability along the thermal trough that will lie along
a Seward Peninsula to McGrath to Fairbanks line this afternoon.
Expect isolated thunderstorms and scattered rain showers in these
areas. Min Rh values will drop into the upper 20s and lower 30s
this afternoon before afternoon thunderstorms develop over the
western and central interior. Similar values are expected in the
middle and upper Tanana Valley this afternoon before wetting rains
envelop the area tonight and continue through Sunday especially
east of Fairbanks. Min RH values in the Middle and Upper Tanana
Valley will remain well above 40 percent tomorrow east of
Fairbanks. Fire weather concerns will build by the middle of next
week as a ridge builds over the interior bringing much warmer
conditions with low to mid 70s possible over much of the southern
interior next week. RH values will drop through the week under
mostly clear skies and limited thunderstorm or shower activity.

&&

.HYDROLOGY...
Thermal breakup continues along interior rivers with no significant
ice jams or flooding noted at this time.

Focus turns to significant wetting rains developing over the
Upper Tanana Valley, the Fortymile Country and eastern Alaska
Range. One half inch to nearly one inch is forecast to fall
beginning tonight and continuing through Sunday and into early
Monday. The rainfall combined with freezing levels around 5 to 6
thousand feet aiding ongoing snowmelt and many small rivers and
streams already running moderately high with the snowmelt will
likely make small streams run very high and swift especially in
the steep terrain of the eastern Alaska Range. Rivers such as the
Salcha and GoodPaster River near Big Dela will likely see rises
Monday and Tuesday with the additional rain and snowmelt runoff.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Brisk Wind Advisory for PKZ230-PKZ235-PKZ240-PKZ245.
&&

CCC MAY 17