MARCH-APRIL-MAY-JUNE OUTLOOK
Geographic Area: Northern Rockies
Past Weather and
Drought:
A cold but also fairly moist
pattern took hold over the region during February, which helped to moderate
incipient very dry conditions over portions of North Idaho, Southwest and Northwest
Montana, and Eastern North Dakota. This cold pattern also has established and
maintained solid snow cover east of the Continental Divide in the plains, with
the bulk of that region now covered with a snowpack containing 1-3 inches of
water equivalent. In terms of the past 90 days however, precipitation still has
been somewhat below average over portions of North Idaho, Southwest Montana,
and spotty areas in North Dakota. Mountain snowpacks in the western PSAs have
registered substantial gains during February as well, and basin-average SWE’s
are now near to slightly above-average region-wide. The latest US Drought
Monitor shows that drought conditions have eased, with only areas of
“Abnormally Dry” conditions persisting in North Idaho, Northwest Montana, and
Northeast North Dakota.
Weather and Climate Outlook:
Weak El Niño conditions are still
present according to the latest update from the NOAA Climate Prediction Center
(CPC). Their long-term forecast calls for a moderation back to ENSO neutral conditions
by summer. Seasonal temperature outlooks from the CPC depict above-average
temperature likelihood for the entire outlook period through June in the Western
PSAs, but near-average further east. This
could lead to a faster spring snowmelt in the Western PSAs. The CPC outlooks are
depicting equal chances of below or above-average precipitation during the
outlook period region-wide. Although the cold, moist pattern currently in place
over the region will likely moderate by mid-March, mountain snowpack
accumulations should persist. And so basin-average SWE’s by April 1st
will likely end up being closer to long-term average values than what often
occurs during weak El Niño winters.
Fuel Conditions:
Currently fuels are snow-covered
across most of the Northern Rockies. When dry, warmer, windy periods return to
the plains areas by mid-March, the melting snowpack moisture will help delay
significant fire potential until the end of the month. With an outlook of
near-average temperatures and precipitation for April in the plains, extended
periods of very low fine dead fuel moistures caused by gusty chinook winds
would be unlikely. If near-average temperatures and precipitation persist
through the green-up months of May and June in the plains, live and dead fuel
moistures would remain at near normal levels there. A slightly faster snowmelt
in the western PSAs during April and May from the possibility of warmer than
average temperatures would be offset by near-average precipitation, in terms of
producing very low dead fuel moisture values.
Fire Season Timing/Discussion:
Typically during March and April
in El Niño winters, the NRGA can see enhanced plains pre-greenup fire potential
caused by more frequent and extended dry windy chinook flow periods. This is
looking to be unlikely there until at least Mid-March, and the absence of
drought conditions there combined with above-average precipitation for most of
this region during the last 90 days will help limit significant fire potential
until early April. Fire potential in the western PSAs typically is low in early
spring except during dry windy periods in Southwest Montana, but these will
likely not occur until at least the latter half of March, if not later. In May,
through most of June, green-up conditions occur region-wide, and with the
near-average precipitation outlooks then, live and dead fuel moistures should
remain at near normal levels. Thus, “Normal”
fire potential will be forecast for each month region-wide, March through June.
