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 1114 AM CDT Mon Mar 20 2017 Valid 201700Z - 211200Z ...CRITICAL FIRE WEATHER AREA FOR CENTRAL AND SOUTHWEST OK... ...Northwest TX...Southwest/Central/Northeast OK... Regional 12Z soundings sampled the very warm airmass over the region well with MAF, AMA, OUN, LMN, and DDC all reporting 850 mb temperatures at or above 22 deg C. Based on SPC climatology, these 850 mb temperatures are near record values for each location. This very warm airmass with support well-above-average high temperatures this afternoon, with values across the region expected to reach the low to mid 90s. Additionally, deep boundary-layer mixing will contribute to significant low-level drying, with afternoon RH values in the low 20s likely. These warm and dry conditions, coupled with increasing winds associated with a tightening of the surface pressure gradient ahead of the approaching cold front, will support elevated to critical fire weather conditions across the region. Most likely location for critical fire weather conditions is across southwest/central OK, roughly in the corridor between I-44 and I-35. ...FL Panhandle...Northern/Central FL Peninsula...GA...Carolinas... Warm and dry airmass over the region will support RH values in the mid 20s across much of the region this afternoon. Fuels across the region are also very dry. However, high pressure over the area, will keep the wind speeds down, mitigating a higher fire weather risk. Even so, some locally elevated fire weather conditions are possible. ...Southwest WY and adjacent far north-central CO and far southwest NE Panhandle... Scenario outlined in the previous forecast discussion (below) remains valid with no changes needed to the ongoing outlook area. ..Mosier.. 03/20/2017 .PREV DISCUSSION... /ISSUED 0217 AM CDT Mon Mar 20 2017/ ...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. ...Please see www.spc.noaa.gov/fire for graphic product... Read more



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