Scientific Forecaster Discussion
Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
1156 am akdt Monday Jul 27 2015
models initialized well and verified well against the 12 analysis.
Minimal spread in the short term on synoptic scale feature
positions and strengths. In the middle term the 12z models remain in
good agreement but exhibit large spread in the extended range.
Cool and moist onshore flow continues on the North Slope with low
stratus and fog taking visibility to under one quarter mile at
times over night and this morning. Expect brief improvement this
afternoon but a return to low ceilings and visibilities in fog
this evening trough at least noon tomorrow.
Low stratus and fog will continue along portions of the West
Coast where weak northwest flow around a 1024 mb high north of
the wrangle island is creating on shore flow. Generally light
winds and fair skies are found along the West Coast where the 1024
mb high north of wrangle island is creating off shore flow over
the southern Seward Peninsula.
A broad area of low pressure continues over the interior and in
conjunction with the thermal trough which extends from near Old
Crow in the Yukon to near Bettles and extending northwest to near
Ambler will be be the Focal Point for rain showers and isolated
thunderstorms. A very moist and airmass has settled in over the
southern interior with near saturation from boundary layer to over
near 500 mb has resulted in precipitable water values on the 12z
sounding of around .9 inches over McGrath and just over 1 inch on
the Fairbanks sounding.
Very weak upper level winds will limit movement of the heavy
showers and isolated thunderstorms that develop this afternoon and
continue into tonight. The potential for slow moving and heavy
rain producing thunderstorms and showers will continue over the
southern interior through Wednesday. The heavy rain will continue
to be localized and cause rapid rises on smaller streams in steep
terrain and in recently burned areas. Flooding is not expected at
this time but as the region becomes more saturated the likelihood
of smaller streams reaching bankfull will increase over the next
several days. Larger rivers and streams will see gradual rises
but are expected to remain below bankfull at this time.
Coastal hazard potential days 3 and 4...none
Fire weather...relatively wet regime set up for today and the
next couple days. Thermal trough persists in the upper Yukon.
Weather front over southeast interior today will linger around for
the next couple days...with another weather front dropping out of
the Arctic over the northern areas. Driest areas will be in the
Kobuk and Noatak valleys and the middle Yukon. Isolated
thunderstorms across the area with some being embedded with the
heavier rainfall around the front. Relative humidity values will
remain above 30 percent during the day with winds generally less
than 15 miles per hour and excellent overnight recovery.
precipitable water on this mornings sounding was just over 1.0
inches. Upper level winds remain light combined with lifted
indices in the minus 1 to minus 2 range and convective available potential energy in the 500 to
750 joules range will provide potential for slow moving and heavy
rain producing thunderstorms over much of the southern interior.
Best areas for heavy rain producing thunderstorms will be in the
Alaska Range and northern slopes of the Alaska Range between the
Parks Highway and the Richardson Highway and the Salcha...the
upper chena...and the goodpaster river basins and in the fortymile
country. Potential for thunderstorms and showers to drop heavy
rain will continue through the middle of the week. Will need to
closely monitor for water rises on small streams and rivers. See
Special Weather Statement or hydrologic statement for additional
Ccc Jul 15