Red Flag Warning
Issued by NWS Seattle/Tacoma, WA

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000
WWUS86 KSEW 202140
RFWSEW

URGENT - FIRE WEATHER MESSAGE
NATIONAL WEATHER SERVICE SEATTLE WA
240 PM PDT SAT AUG 20 2016

...A RED FLAG WARNING REMAINS IN EFFECT FOR FIRE WEATHER ZONES
652...658...659 AND 661 UNTIL 10 PM PDT THIS EVENING FOR LOW
RELATIVE HUMIDITY AND A MID-LEVEL UNSTABLE AIR MASS...

.A THERMAL SURFACE PRESSURE TROUGH IN THE WESTERN INTERIOR THIS
AFTERNOON IS EXPECTED TO SHIFT EAST OF THE CASCADES TONIGHT. THIS
FEATURE IS ACCOMPANIED BY AN EXTREMELY DRY AND UNSTABLE AIR MASS
ABOVE 2000 FEET. LOW LEVEL ONSHORE FLOW WITH A MUCH COOLER AIR
MASS WILL SURGE ONSHORE AND INTO THE INTERIOR THROUGH THE NIGHT.

WAZ652-658-659-661-210500-
/O.CON.KSEW.FW.W.0001.000000T0000Z-160821T0500Z/
WEST PORTION OF THE OLYMPIC MOUNTAINS-
WEST SLOPES OF THE NORTH CASCADES GENERALLY ABOVE 1500 FEET-
WEST SLOPES OF THE CENTRAL CASCADES GENERALLY ABOVE 1500 FEET-
EAST PORTION OF THE OLYMPIC MOUNTAINS-
240 PM PDT SAT AUG 20 2016

...RED FLAG WARNING REMAINS IN EFFECT UNTIL 10 PM PDT THIS
EVENING FOR A DRY AND UNSTABLE AIR MASS...

* AFFECTED AREA...FIRE WEATHER ZONES 652...661...658 AND 659.
  THIS INCLUDES THE OLYMPIC MOUNTAINS ABOVE 1500 FEET AS WELL AS
  THE WEST SIDE OF THE CASCADES ABOVE 1500 FEET.

* HUMIDITY...15 TO 25 PERCENT WILL BE COMMON INTO THIS EVENING.

* INSTABILITY...THE AIR MASS WILL BE UNSTABLE THROUGH THIS
  EVENING. MID-LEVEL HAINES 5 AND 6 CONDITIONS EXPECTED.

* IMPACTS...CRITICAL FIRE WEATHER CONDITIONS CONTINUE. WEATHER
  WILL BE A SIGNIFICANT AGGRAVATING FACTOR ON ANY FIRES THAT
  GET STARTED.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A RED FLAG WARNING MEANS THAT CRITICAL FIRE WEATHER CONDITIONS ARE
IN PLACE. A DRY AND UNSTABLE AIR MASS WITH WARM TEMPERATURES CAN
CONTRIBUTE TO ACTIVE FIRE BEHAVIOR. IN WESTERN WASHINGTON...
SIGNIFICANT GROWTH ON EXISTING FIRES TAKES PLACE UNDER SUCH
CONDITIONS.

ONCE THE RED FLAG WARNING EXPIRES TONIGHT...BACKGROUND FIRE
DANGER DUE TO DRY FUELS WILL REMAIN. HOWEVER...THE WEATHER WILL BE
LESS OF AN AGGRAVATING FACTOR.

&&

$$

WAZ662-210500-
/O.CON.KSEW.FW.W.0002.000000T0000Z-160821T0500Z/
EAST PORTION OF NORTH CASCADES NATIONAL PARK/LAKE CHELAN NATIONAL
RECREATIONAL AREA-
240 PM PDT SAT AUG 20 2016

...RED FLAG WARNING REMAINS IN EFFECT UNTIL 10 PM PDT THIS
EVENING FOR DRY AND UNSTABLE CONDITIONS...

* AFFECTED AREA...FIRE WEATHER ZONE 662. THIS IS THE PORTION OF
  THE NORTH CASCADES NATIONAL PARK COMPLEX EAST OF THE CASCADE
  CREST...INCLUDING STEHEKIN.

* HUMIDITY...LOW RELATIVE HUMIDITIES BETWEEN 10 AND 20 PERCENT.

* INSTABILITY...A DEEP COLUMN OF DRY AND UNSTABLE AIR. THE MID-
  LEVEL HAINES INDEX OF 6 INDICATING A DRY AND UNSTABLE AIR MASS
  CAPABLE OF SUPPORTING LARGE FIRE GROWTH.

* IMPACTS...WEATHER WILL BE A SIGNIFICANT AGGRAVATING FACTOR ON
  ANY FIRES THAT GET STARTED. FIRE DANGER IS HIGH TODAY DUE TO DRY
  FUELS AND LOW HUMIDITY...BUT INSTABILITY WILL ADD AN AGGRAVATING
  FACTOR THROUGH THIS EVENING.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A RED FLAG WARNING MEANS THAT CRITICAL FIRE WEATHER CONDITIONS
ARE EITHER OCCURRING NOW... OR WILL SHORTLY. A DRY AND UNSTABLE
AIR MASS WITH WARM TEMPERATURES CAN CONTRIBUTE TO ACTIVE FIRE
BEHAVIOR. SIGNIFICANT GROWTH ON EXISTING FIRES TAKES PLACE UNDER
SUCH CONDITIONS.

&&

$$



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