Scientific Forecaster Discussion
000 FXUS66 KPDT 121328 AAB AFDPDT Area Forecast Discussion...Updated National Weather Service Pendleton OR 527 AM PST Tue Dec 12 2017 Updated short tern discussion .SHORT TERM...Today through Thursday...The current weather pattern will remain over the area for the next few days with only a few subtle changes expected. Low clouds remain over the Columbia Basin and adjacent valleys and into North Central Oregon but has not returned to Bend and Redmond. A weak low level flow from the southwest to southeast appears to have pushed the clouds north. Clouds have been moving back into Madras, Prineville and Redmond but at around 5000 feet, so it is probably due to a weak wave crossing the area rather than the low stratus returning. Have the low clouds returning to central Oregon tonight though without a northerly flow to push it, confidence is low. The rest of the Columbia Basin and most northerly areas will see the low clouds continue through Thursday. A freezing fog advisory remains in effect for north central Oregon and the southern Blue Mountain Foothills through noon today. However, the freezing fog advisory for central Oregon was dropped earlier and do not see any sign it is reforming early this morning, so I will not issue a new advisory. The low clouds in the lower elevations will keep temperatures in the current small range from the mid 20s to lower 30s. Elsewhere skies will be partly cloudy with highs in the mid 30s to lower 40s and lows mainly in the upper single digits and teens. There will be a weak wave moving through the flow late tonight and early tomorrow morning so have added very light snow flurries to the area under the inversion and low clouds. Do not expect any locations will see more than a dusting of snow and precipitation will be just a trace. Perry .LONG TERM...Thursday night through Monday...A weak disturbance looks to begin the process of weakening the upper ridge over the Pacific Northwest late Thursday night into Friday. As such will see the slow, but gradual elimination of the fog/low clouds across the lower levels of the Interior Northwest. Some light precip will be possible as this system moves through the region Friday and Friday night. Precip Friday morning may be in the form of freezing rain at many locations. Friday afternoon into Friday night snow levels will lower, but the low levels should warm due to an intrusion of marine air. Thus the lower levels would see rain by late Friday while the higher elevations would see snow. A more westerly flow pattern looks possible Saturday through Monday. Thus would see periods of precip with snow in the mountains and rain or snow at the lower elevations depending on the time of day. 90 && .AVIATION...12Z TAFS...Low level inversions trapping moisture will continue to affect the Interior Northwest through the next 24 hours. As such ceilings will generally run between 1000 and 2500 feet AGL at KDLS, KYKM, KPSC, KALW and KPDT through the period. Tops of this cloud/fog area will generally run between 3500 and 4500 feet MSL. Highest surface pressure is over southeast Oregon. This has been causing an east to west pressure force into central Oregon that has been limiting fog/stratus at KBDN and KRDM. This condition looks to last another 24 hours. Yet fog/stratus has made it to KS33 (Madras), thus will indicate the potential for brief a appearance at KRDM around daybreak into mid morning. Winds will remain light. 90 && .PRELIMINARY POINT TEMPS/POPS... PDT 29 26 29 26 / 0 10 10 0 ALW 34 29 34 29 / 0 10 10 0 PSC 34 30 34 30 / 0 10 10 0 YKM 34 30 33 30 / 0 10 10 0 HRI 33 29 32 29 / 0 10 10 0 ELN 31 25 30 25 / 0 10 10 0 RDM 34 21 31 21 / 0 10 10 0 LGD 35 22 33 24 / 0 0 0 0 GCD 44 27 46 27 / 0 0 0 0 DLS 36 31 36 31 / 0 10 10 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Air Stagnation Advisory until 10 AM PST Friday for ORZ041-044- 050-505-507>511. Freezing Fog Advisory until noon PST today for ORZ508-510. WA...Air Stagnation Advisory until 10 AM PST Friday for WAZ024- 026>029-520-521.