Fire Danger raised to high in Mineral County

MINERAL COUNTY – The fire danger level in Mineral County was again raised last week this time reaching high as temperatures in the area soared to nearly 100 degrees and little precipitation fell in forested areas.

According to information supplied by Superior Ranger District Fire Prevention Officer Jim Ward, Mineral County is abnormally dry for this time of year. The report stated, dry conditions were expected to intensify over large parts of the western U.S. including parts of Northwest Montana. In July, the report indicated an above normal fire forecast for areas including Mineral County.

Michael Richmond, Meteorologist with the U.S. Forest Service Predictive Services, further stated, “it has been very warm and dry all spring throughout North Idaho and Western Montana, when

May and June are climatologically the wettest months in the lower elevations. We had two days of record-warmth last week, Monday-Tuesday the 8th/9th, with every other day remaining above average. In fact,looking at (2) you can see how much warmer than average it has been throughout the West as a whole.

Our precip. over the last week (1) has been slim to none, in the areas that need it the most, and that have been the driest all spring, west of the Continental Divide.

Now we are faced with long-range model forecasts continuing and even amplifying these trends, for the next 10-14 days.  But first let’s look at the shorter term. A dry cold front will sweep across North Idaho

and Western Montana tomorrow, bringing gusty winds, some cooling, but low RHs (3).

Thus, continued faster than normal fuels drying/curing will continue from the Front Range, westward. Fuels status is not quite to requiring high-risk status for this event, or NWS Red Flag Warnings. Further east in Eastern Montana and

North Dakota Friday, access to moisture from the Plains and Gulf of Mexico will continue to allow scattered strong to severe Thunderstorms with large hail and heavy rain to develop. This potential will remain over Eastern North Dakota on Saturday, until drier, more stable air moves in.

Thereafter, high pressure ridging will re-build over North Idaho Sunday/Monday, returning temperatures to well-above average there (but not quite as hot as what occurred June 08-09). There may be enough moisture and instability present in the WSW flow aloft to bring at least isolated DRY thunderstorms west of the Divide as well. Central/Eastern Montana during this time will continue to see periodic scattered strong wet thunderstorms.

A weak low pressure trough is forecast to skim across North Idaho/Western Montana late Tuesday and Wednesday next week, which will bring some cooling, but only limited, if any, precipitation. Then, the long-range models

(both the European and US) show high-pressure ridging returning, and amplifying starting Thursday of next week, to the point that extreme heat could occur over North Idaho and Western/Central Montana by Friday

and Saturday. (4) shows forecast 7-Day precipitation totals, ending 25 June, again, very little west of the Divide, and an upper-air forecast chart for Friday 26 June.

What this forecast chart depicts (this is the US Model, the European model shows this pattern starting even earlier next week) is the typical summer-time 4-Corners upper-ridge amplifying northward over the western NRGA. This

is the pattern that brings the most extreme heat west of the Divide, as hot air from the desert southwest moves northward, with no maritime influence. Temperatures near 100F would be possible in Missoula/Kalispell, 105F in

Libby, and 102-110F the lower elevations in North Idaho (Lewiston/Riggins, etc..), accompanied by very low RHs.

These heat waves can last anywhere from 4-14 days. This is borne out in the NOAA/Climate Prediction Center 8-14 Day Temperature/Precipitation outlooks (5), for 26 June – 02 July.

May has already been the driest ever recorded in Kalispell. If model forecast dryness continues west of the Divide, and little or no precipitation occurs, Kalispell and Missoula both will experience their driest ever May/June period,

as (6) depicts. Assuming none occurs, that would be 0.82 for Kalispell (1981-2010 average 4.54), and 1.23 for Missoula (1981-2010 average 4.08). Of course, this reflects conditions throughout North Idaho and Western

Montana.

I’ve been discussing how Fire Danger Indices and Fuel Moistures have been trending throughout North Idaho and Western Montana for some time, because of our mild low snow/early-snowmelt winter, and warm, dry Spring.

Now we need to look at what this actually means for potential fire behavior, because as we heat up, especially at the end of next week, the probability of drier or dry thunderstorms and ignitions will also increase. Just looking

at the ERC trends to date, and trying to informally extrapolate these based on forecast weather, to 04 July, gives this very conservative estimate (7). What it shows though is the likelihood we will be reaching 90th Percentile

ERCs in PSA 04, and most of the other ones west of the Continental Divide, and possibly even the 97th Percentile.

Both of which would be drier than the driest average values of the entire summer. 1000 hour and 100 hour fuel moistures would show similar trends/values. And since live fuel moisture will be decreasing substantially at the

same time, and fine fuels curing completely at lower and middle elevations, overall fire danger will approach or reach peak summer levels by 04 July weekend, most areas west of the Continental Divide.

Central and Eastern Montana will see strong warming and drying at the end of next week as well, if model forecasts are correct. But at least fuel moistures are at more seasonal values there, as they are also in North Dakota.