Tag: Chip Redmond

November is typically characterized by increases in cold air intrusions across much of the United States. This also begins what is considered the dry season for much of the Plains and portions of the inter-mountain west. Rainfall begins to become more prevalent further south along the Gulf and where Gulf flow (southerly winds carrying moisture from the Gulf into the US) can become established before a storm system. This flow typically becomes established ahead of an advancing cold front, but is pushed further east than during the summer months. Multiple cold fronts with very little moisture/flow recovery time between can greatly influence fire activity for the Mississippi Valley and eastward. Wide sweeping cold fronts are common and typically drier as moisture becomes more limited, dominated by Canadian/Arctic air masses.

Vegetation is now dormant across most of the continental US and foliage/grasses can cure easily. The Appalachians have a vigorous deciduous tree canopy and provide new debris and additional uncompacted litter for increased fire occurrence/sustainability. Strong cold fronts tend to bring much drier air and windy conditions that only fuel fire conditions along these slopes and further to the east/southeast. The fuel load depends greatly on the water received from tropical systems during the late summer/early fall. If there is an active tropical season, fuel loads can be greatly enhanced. Therefore, the region is greatly dependent on the tropical/drought status of the area and their subsequent influences on the fire season.

Overnight relative humidity recovery is typically much higher across the US than the summer. This is due in part to the lack of solar radiation. Less sunlight reaches the earth’s surface in the Northern Hemisphere during winter. This in turn prevents the surface from warming, allowing the surface temperature to drop during the overnight, approaching saturation much easier, and providing increased humidity. Therefore, often fires in late fall/early winter may make a big run in the afternoon when the surface is warm, but then easily/quickly lay down once the sun sets. There are some exceptions including strong storm systems and terrain influences, but typically this is the case.

Complicated weather pattern currently across the US. A large high pressure sits over the inter-mountain West, an elongated front extends from Texas northeast into the Great Lakes, and another cold front is sweeping south into the northern Plains.

Fire weather focus is for southwestern California, where breezy off-shore winds continue Wed/Thurs in response to diverging winds of the high pressure centered over northern Utah. Sustained winds along higher terrain are expected up to 20-25mph with gusts to 45-50 (see graphic below). With these downsloping winds, very dry/warm conditions are expected with RHs in the mid-to-upper single digits. In combination with ongoing drought conditions, this will create explosive fire weather conditions Wed afternoon and Red Flag Warnings are posted. Winds are expected to weaken Thurs as high pressure moves northward. However, some areas will still see aggravated fire weather conditions with gusts exceeding 20mph in southern CA. After Thurs, winds will be much calmer for the remainder of the period but conditions will remain very dry. Daytime RH isn’t expected to exceed 15% for the entire period with very poor overnight recoveries into the weekend.

Elsewhere, several cold fronts are expected to traverse the Plains and Eastern US through the period. With these frontal systems, quick periods of dry and/or windy conditions are possible. The first front is currently entering the northern Plains and will bring a period of windy conditions for central South Dakota with RH dropping to 20-25% Wed afternoon. Overnight Wed the front moves further southeast into the Mississippi Valley, reaching the Appalachians Thurs. Friday, it reaches the southeastern US and windy conditions move offshore. However, enhanced fire concerns exist with RHs ranging 20-25% from east Texas to northern Florida. Friday afternoon, another quick moving cold front enters the Plains with strong winds across the northern Plains. This second front will move eastward and repeats the process through Sunday.

A third, much stronger cold front moves south from Canada on Sunday evening. This front will bring much colder air to much of the central and eastern US early week. Very strong winds are possible with this front on Sunday/Monday in the central Plains both ahead and behind the cold front. Enhanced fire conditions are possible across the central Plains through this 48 hour period, especially for portions of eastern Colorado, Kansas, Nebraska, and Oklahoma.

Some rainfall is likely from these fronts, however, much of it will avoid the southeastern, central, and southwestern US. Image from NWS Weather Prediction Center – 5 day rain predicted rainfall total.

Weather Highlights:

Southern CA: Red Flag Warnings for Wed, critical fire weather with strong winds (gusting to near 50mph) and very low RH (4-9%). Winds will weaken Thurs (gusting to 20mph), and become calm Fri-remaining very dry. Poor overnight RH recovery through the week, and into the weekend.

ND/SD: Enhanced fire weather conditions on Wed & Fri afternoon with strong northwest winds (gusting to 60mph) and low RH (20-25%).

TX/LA/MS/AL/GA/FL: Locally enhanced fire weather conditions on Fri-Sun afternoons with low RHs (25-35%).

Western KS, NE, OK/Eastern CO, WY: Beginning Sun morning and continuing until a cold front passage Monday afternoon, very windy conditions (gusting to 55mph) and low RHs (5-15% increasing Mon afternoon).

Chip

Yet another upper level trough providing some active fire weather conditions today across northern CA/southern OR and most of WY/western SD. With this trough, a lack of mid-level moisture is preventing any thunderstorm activity across the northwestern US. However, very dry conditions (aggravated by drought in CA/OR) combined with windy conditions are developing critical fire weather conditions in both these regions. A surface cold front associated with the trough will slide southeast across the northern Rockies Wed evening and into Thurs. This front will increase humidity across WY/SD lessening fire danger and shifting winds to the north for Thurs.

The same cold front will push south/west across OR/CA overnight Wed. This front will continue mixing overnight with breezy winds and poor RH recovery-continuing elevated fire danger through Wed night. Through late week and into the early weekend, easterly winds will provide additional downsloping off the Rockies and continue increased fire risk with poor overnight RH recovery through Sun. With an off-shore trough developing late-week and weak ridging over the Rockies, temperatures will increase to 90F+ across much of CA/OR/WA. Very dry conditions and RHs at/below 20% will expand eastward/northward across the region and into the central Rockies through the weekend. Breezy easterly winds will continue through Fri for much of OR/northern CA/NV and gradually diminish overnight Fri. As the off-shore upper level trough approaches the West Coast Sun/Mon, westerly winds will increase for much of the northern CA/OR/WA/ID, which may develop widespread critical fire weather conditions. No precipitation is expected for northern CA/NV and WA/OR/ID through the period.

The other major weather highlight will be soon-to-be Hurricane Norbert near the California Peninsula. Current forecast model trends depict moisture streaming northward into the southwestern US by late weekend. Developing monsoonal conditions across AZ/NM/UT/CO late week will provide chances of scattered thunderstorms. However, much more widespread rains/storms could develop for portions of southern CA/NV and much of AZ/UT/CO with the influence of Norbert. Great uncertainty still exists on the exact track of this system, though confidence is increasing on widespread heavy rains late weekend/early next week.

Weather Highlights:

WY/western SD/northern CO/NE Panhandle: Critical fire weather Wed with breezy westerly winds, RH’s <20%, and warm conditions. Cold front crossing region tonight increasing RH and winds increasing and turning northerly post-front. Becoming very dry/warm Sun/Mon with increasing fire weather threat.

OR/northern CA/northern NV: Critical fire weather Wed through Thurs with breezy northerly wind, turning easterly Thurs AM. Very warm/dry with poor overnight RH recoveries expected through Sat with continued enhanced fire weather conditions. Additional critical fire weather conditions possible Mon/Tues with breezy westerly winds.

WA/ID/MT: Increasing fire weather threat as temperatures warm into the weekend with breezy westerly winds possible late weekend. Continued dry conditions with no precipitation expected (with exception of northern ID/MT Wed/Thurs).

AZ/UT/NM/southern CO: Monsoonal flow returning Thurs/Fri/Sat with scattered thunderstorms, rain becoming more numerous over the weekend, especially across AZ/UT with flooding possible.

Southern CA/southern NV: Very dry and warm through late week. Increasing showers/storms Sun/Mon with flooding possible.

Chip

A large, slow-progressing upper level trough has brought copious moisture to much of the northern Rockies and Eastern Great Basin. Even some winter weather advisories with very a cool air mass over MT. Widespread fire weather threats have been minimal across much of the western US and will likely remain quiet through the weekend. Despite the lack of optimal large fire conditions, several areas will need to be monitored for developing potential into mid-week.

As the trough begins to lift northeast into the northern Plains and Canada early week, another final shortwave will rotate around the apex on Monday. This will bring a slight chance of showers and thunderstorms across portions of NV/UT. With lack of low level moisture and drying taking place over the weekend, a few isolated dry thunderstorms are possible. No strong winds are anticipated outside of thunderstorm outflows. The threat will diminish Tuesday evening.

A big story will be developing, with upper level ridging along the West Coast and subsequent drying conditions and warming temperatures early week. These conditions will aggravate already drought stricken regions and provide ripe conditions for fire growth for CA and northward into OR/WA. No widespread thunderstorms or wind events are anticipated. However, temperatures above 90F and widespread RHs <20% with some <10% for central OR and northern CA by Wednesday will promote extreme fire behavior.

Weather Highlights:

NV/UT/southern ID: Isolated dry thunderstorms Mon/Tues. Becoming hot and mid-week.

OR/WA: A few scattered showers on Sun, lingering into Mon. Becoming very hot and dry Tues and continuing into late week.

CA: Warm and dry Sat/Sun. Becoming very hot and critically dry by mid-week.

Chip

Lack of widespread critical fire weather has kept fire starts down across much of the western US. Expect fire weather to become more critical today in OR/CA and spread eastward into ID/WY through late-week.

A cut-off upper level low off the coast of north CA will provide enough moisture and instability for scattered dry thunderstorms over high elevations. Very dry surface conditions combined with hot temperatures will make fuels very receptive to dry lightning. Tues, the low will drift southward along the coast, but lose ample moisture to provide widespread storms, however a few isolated storms are possible in central/north CA through Tues evening.

A more potent upper level trough will enter dig into the Pacific Northwest Tues, and begin to eject over the Northern Rockies on Wed. In advance of this trough, surface pressure falls are expected across central OR/WY creating breezy westerly winds Tues and Wed. Combined with warm temperatures and dry conditions, fire suppression will become difficult. Higher moisture across extreme northern WA/ID/MT will develop scattered rain and wet thunderstorms over higher elevations bringing some relief mid-week, with a higher heavy rain threat for eastern MT late week.

Surface low pressure will begin to develop across the central Plains in response to the eastward movement of these upper level features. With high pressure over the Rockies and the western US, a strong pressure gradient will set up over WY and southern ID, and northern CO late week. This gradient will develop breezy conditions across these areas leading to critical fire weather. In addition, increased upper level moisture will provide ample conditions for scattered dry thunderstorms across the same areas, especially over higher terrain. Cooler conditions will develop across the northern Rockies late weekend. Meanwhile, warm and dry conditions will continue for CA and western/central OR/WA with isolated locations of gusty winds through the weekend.

Weather Highlights:

CA: Critical fire weather Monday due to dry lightning, warm temperatures and dry conditions. Threat will lessen and drift southward on Tues/Wed. Continued hot and dry through the period.

OR/WA: Scattered dry thunderstorms across higher elevations of southern OR Monday. Increasing winds Tues/Wed with critical fire weather conditions expected Wed. A few wet thunderstorms over higher terrain of extreme nrthern WA.

Southern ID/WY/northern CO: Very breezy conditions developing with warm temperatures and dry conditions continuing into the weekend. Scattered dry thunderstorms possible through the period over higher terrain. Critical fire weather expected Wed through Fri.
MT: Isolated dry thunderstorms possible Wed through Fri for southern MT, with wet thunderstorm chances across northern MT. Otherwise warm and dry through Thurs with heavy rain possible Fri across eastern MT.

Chip

Upper level low centered over OR/WA will continue to weaken over the next few days, before finally drifting northeast into Canada by the weekend. Conditions should gradually improve as thunderstorms become less numerous across the Pacific northwest on Thurs and even less on Fri. Moisture has become abundant around the low and with that, storm modes are expected to be mainly wet. Warm and dry conditions, with an isolated dry thunderstorm threat is possible Thurs across central MT. As the system drifts northeast across portions of MT on Fri, heavy rains are possible across E MT. Other scattered storms across the state are possible through Sat with mainly wet storm modes expected. No widespread critical fire conditions expected.

High pressure is already building into portions of CA, in the wake of the low. Dry, hot, but calm conditions have developed across much of CA and will continue to build north and eastward into OR/WA/NV/ID into the weekend. Temperatures will be above average for much of the western US Sat and Sun and into early next week. Some isolated pockets of breezy conditions are possible in central ID and MT, however, no widespread wind events are expected.

Long term, another upper level low makes an attempt to push onshore to OR/CA early next week. Not overly confident of any widespread thunderstorm activity at this time, though a few storms over higher terrain of north CA Mon and Tues are possible. There are hints at a larger pattern change for mid-week next week which will need to be watched for a possible wind event.

Weather Highlights:

MT: A few dry thunderstorms across portions of central MT Thurs with hot and dry conditions present. Heavy rain possible across eastern MT on Fri, otherwise scattered storms across much of the state. Warming and drying out Sun.

CA: Above average temperatures with dry conditions.

OR: Some showers and wet thunderstorms Thurs. A few lingering showers/storms north on Fri. Drying gradually from south to north, with increasing temperatures.

ID/WA: Scattered showers and wet thunderstorms through Sat, gradually waning and drying out from south to north through the period. Localized breezy conditions Sat/Sun.

WY: Becoming very warm Sat/Sun with breezy conditions.

Chip

Today meteorologist Chip Redmond sent us another fire weather outlook, for August 10 through 15.

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Upper level ridging across the western US has returned, resulting in warming temperatures and much less thunderstorm activity. Most fire activity has been limited to portions of OR/WA where breezy westerly winds have became prevalent along the Columbia Gorge and western slopes of the Cascades. Though these localized conditions are expected to wane, widespread critical fire weather conditions are expected to develop across the region late weekend and continue through much of next week.

A slow moving upper level low will develop on the west coast of CA/OR by Sunday evening. As it progress towards the coast, upper level moisture will begin pushing northward across much of the western US. This increase in moisture aloft and subsequent instability, will contribute to the development of afternoon thunderstorms. Surface moisture will remain minimal however, providing the ideal ingredients for dry thunderstorms. With very dry, drought-stricken surface fuels, widespread fire starts are possible. Though no widespread winds are forecasted, gusty winds can be expected around any thunderstorm activity.

The nearly stationary upper-level low will make this a prolonged event, with thunderstorm activity through the entire period. Storms will become prevalent in OR/CA on Sunday, and expanding north into WA on Monday/Tuesday, and eastward into ID/MT on Tuesday and Wednesday. By mid-week, enough upper level moisture may advect northward into CA/OR/ID/WA for some wet thunderstorms, however, dry thunderstorms will still be possible across much of the region. As the low shifts eastward by late-week, a break in the activity is expected across portions of OR/CA. However, warm and dry weather is expected to continue.

Weather Highlights:

OR/northern CA/southern ID: Critical fire weather through Wednesday. Daily dry thunderstorms with hot and dry surface conditions expected. Isolated wet thunderstorms by Tues/Wed.

WA: Critical fire weather Monday through Wednesday. Very hot across central portions of the state and with critically low RH Sun through Tues. Dry thunderstorms likely Mon and Tues with a few wet thunderstorms Wed.

Northern ID/western MT: Critical fire weather Monday through Wednesday. Hot and dry Mon and Tues with scattered dry thunderstorms. Increased chances of wet thunderstorms with slightly cooler temperatures Wed.

Chip

Today we have another article from Incident Meteorologist Chip Redmond.

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2014 August fire weather

Typical fire season for August is focused greatly on the western US and Pacific NW. This time of year a summer upper level ridge is usually prevalent across the western US. This leads to hot and dry conditions reaching into Canada. However, monsoonal rains creep northward into much of the inter-mountain west from Mexico bringing a break to fire season in much of Colorado, Arizona, California, Utah and other nearby states. These monsoonal rains are the wet season for many, and besides the winter snows, are a large source of water.

In the recent weeks, we have seen quite a bit of large fire activity in Washington, Oregon, and California. For this time of the year, it is fairly typical to expect hot spots in these regions. However, the size and vigor of these fires has been greatly magnified with already a record fire season (Carlton Complex). The main driver of these impressive fires has been the significant drought impacting the western US, which has been developing over the previous years. Despite some recent rains in many areas, especially inter-mountain West (thanks to seasonal monsoonal moisture), much of it has fallen to the east of the greatest Exceptional Drought. This drought has substantial impacts on both short and long term vegetation and fuel conditions. It has made the region very susceptible to very large fires with extreme fire behavior.

The big question is, will these conditions continue? Long-term it appears that they will. This persistent pattern is showing signs of weakening short term, but after this weekend, forecast models hint at more prolonged ridging much like we have had the previous weeks. A very active Western Pacific typhoon season is somewhat to blame. As systems move north, and eventually northeast past Japan, they amplify the large upper level ridge assisting in the continued hot and dry weather for the western US. With numerous typhoons still across the western Pacific, it appears this may continue to occur. Long-term models also suggest continued below normal rainfall and above normal temperatures for the next 1-3 months for the W US. There is some suggestion of El Nino development this fall which could bring some much needed relief to portions of southern California. However, should it develop, it would also suggest warmer than normal conditions across regions of Washington and Oregon.

It appears that it likely be a very long, and dragged out fire season for many in WA, OR, and CA.