SPC Day 1 Fire Weather Outlook

By Newsroom America Feeds at 20 Mar 2017

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0217 AM CDT Mon Mar 20 2017 Valid 201200Z - 211200Z ...CRITICAL FIRE WEATHER AREA FOR PARTS OF CENTRAL AND SOUTHWEST OK... ...Synopsis... The primary belt of strong mid-level westerlies is associated with a jet streak over the northern Great Plains/Upper Midwest and this belt of stronger flow will generally be confined to the northern tier of states and West Coast. Surface high pressure located over the northern Great Plains will strengthen during the period as a cold front moves southward across the lower MO Valley and a trailing portion of the front over the central High Plains. A southern-Plains dryline will extend from northwest TX northeastward into west-central OK. ...for northwest and western north-central TX into southwest-central-northeast OK... A weak area of low pressure over northwest TX and a surface high over the Gulf of Mexico will contribute to a belt of appreciably strong southwesterly 925-850 mb flow (25-35 kt) being maintained during the diurnal heating cycle near the I-44 corridor in OK and farther east across eastern OK and parts of north-central TX. The development of a very deeply mixed boundary layer is forecast to the west of the dryline over northwest TX into far southwestern OK where RH will plummet into the 7-15 percent range. Weak flow to the west of the dryline will likely limit the overall risk. However, there appears to be an area of overlap with near-critical RH (20-25 percent) from near Wichita Falls northeast into the greater OKC area ---modifying HRRR forecast soundings for expected high temperatures--- with 18-25 mph sustained winds (higher gusts). Record-breaking temperatures are forecast for parts of this area and the near-critical RH and sufficiently strong winds seem to suggest several hours of critical fire weather conditions. ...southeast WY into far north-central CO and a small part of the NE Panhandle... A very dry low-level airmass over the central Rockies and High Plains will heat considerably during the day to the west of a front with trajectories emanating from the continental-polar high located farther north. The area west of the low-level confluence will feature west winds ranging from around 20 mph in southeast WY and weakening to only 10 mph farther south north of the Palmer Divide. However, model guidance shows a minimum RH axis extending north from east-central CO into southeastern WY with values in the upper single digits mainly south of I-76 to 13-20 percent in southeastern WY. Forecast soundings show inverted-V profiles associated with dry-adiabatic lapse rates in the lowest 5-10 kft AGL. Despite the relatively weaker flow fields across CO, the very steep lapse rates will promote gusty winds around 20 mph. ..Smith.. 03/20/2017 ...Please see www.spc.noaa.gov/fire for graphic product... Read more



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