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Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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327 FXUS66 KPDT 172115 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 215 PM PDT Wed Jul 17 2024 .SHORT TERM...Today through Saturday...All eyes are on radar and satellite this afternoon as a low pressure system currently centered on the OR/WA border around Portland slowly lurches its way NNE-ward, bringing with it a round of broken showers and some isolated thunderstorms. So far, activity this afternoon has been concentrated primarily along the spine of the southern WA Cascades, but even then lightning strikes have been relatively infrequent. Across the eastern mountains and portions of the Basin, light showers to virga have prevailed thus far. With clearing on the back end of this morning`s showers, there is a potential for another round of isolated showers and storms to form heading into the evening hours tonight, namely across the Washington Columbia Basin and even into the eastern mountains. Or at least that is what is being suggested by recent runs from CAMs such as the 18z NAMNest and HRRR. Confidence is shaky, however, as latest SPC mesoanalysis keeps instability concentrated primarily over the Cascades, with moisture still being pretty limited. It doesn`t take much moisture or instability to trigger convection given the right pattern, however this system`s performance outside of central Oregon does not particularly inspire confidence. Either way, the 4-10pm time window will be key, and we`ll have to keep a close eye on how convection develops under clearer skies. Until then, Red Flag Warnings remain in effect for both Basin zones and zones around the east slopes of the Washington Cascades. Quieter, albeit hotter, weather prevails Friday onward. Once the low moves out, high pressure stemming from the Four Corners will slowly begin to dominate, fighting against a weak shortwave trailing today`s low on Friday. Not seeing much of any impacts in the way of this wave, so looking at primarily increasing temps, the usual gap flows, and continued dry conditions. Heat headlines remain in effect, with more possible over the weekend should models prove correct in depicting the influence of this building Four Corners high. Evans/74 .LONG TERM...Saturday through Wednesday...A ridge continues to amplify across the PacNW on Saturday and Sunday. Hot temperatures are expected (70-90%) with HeatRisk demonstrating wide swaths of Moderate risk by Saturday, and developing pockets of Extreme risk on Sunday, especially across the lower elevations. Audiences susceptible to heat should consider preparations ahead of this incoming heat. This round of heat is anticipated to be shorter than the one experienced in early July, though additional audiences could be impacted with the weekend. Sunday is expected to be the hottest day through the forecast period. Currently, analysis is demonstrating a 80-100% chance of temperatures of at least 100 degrees F for the lower elevations of Sunday, with a low chance (10- 30%) chance of temperatures of 110 or greater. To offer support, the ECMWF Extreme Forecast Index also highlights a significant portion of the forecast area as abnormally warm for the weekend. As the ridge amplifies, it does produce a tightened pressure gradient for Sunday, with gusty wind developing across the western half of the forecast area by the afternoon/evening hours. This gradient will receive an extra boost from a passing wave to help produce additional gusty winds on Sunday. The favored areas of Yakima and Kittitas Valleys are current showing a 30-50% chance of wind gusts of 30-35 mph. Generally quiet conditions anticipated for Monday with this pattern with a return of gusty afternoon wind possible (30-50%). Another area of low pressure will influence conditions across the PacNW by Tuesday. This system will help to flatten the ridge allowing temperatures to cool down to near normal values. Meanwhile, this system will again result in a tightened pressure gradient across the forecast area, with gusty winds possible (20-50%). Influences from this system will continue through the remainder of the forecast period, with near yo slightly above normal(within 5 degrees) temperatures forecast. Cluster analysis through the later forecast periods all remain fairly supportive of the progression of this area of low pressure. Branham/76 && .AVIATION...18z TAFs (Previous Discussion)...Mostly VFR with the exception for instances of MVFR to IFR conditions through around 02z due to showers and thunderstorms. KDLS, KYKM, and KALW are the favored terminals to see this continued shower or storm development through the late afternoon hours. Thunderstorm probabilities are low (10-20%) for development across the terminals. Otherwise, VFR conditions will be found. Surface wind across the western terminals (KDLS, KRDM, KBDN) will be 10-20 kts after 20z today, with locally higher gusts. The remainder of the area should see generally light wind at less than 10 kts, with the exception of gusty and erratic wind near any thunderstorm development. Branham/76 && .PRELIMINARY POINT TEMPS/POPS... PDT 63 98 63 97 / 20 0 0 0 ALW 67 102 68 101 / 20 0 0 0 PSC 67 103 67 102 / 20 0 0 0 YKM 63 101 63 100 / 20 0 0 0 HRI 67 103 67 102 / 20 0 0 0 ELN 66 101 65 98 / 20 0 0 0 RDM 54 95 54 94 / 0 0 0 0 LGD 60 97 60 96 / 10 0 0 0 GCD 58 98 59 98 / 0 0 0 0 DLS 66 96 66 98 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Red Flag Warning until 10 PM PDT this evening for ORZ641. Heat Advisory until 10 PM PDT this evening for ORZ041-505-507- 508-510. Heat Advisory until 10 PM PDT Thursday for ORZ044. WA...Red Flag Warning until 10 PM PDT this evening for WAZ690-691-694- 695. Heat Advisory until 10 PM PDT this evening for WAZ024-029-521. Heat Advisory until 10 PM PDT Thursday for WAZ028. Excessive Heat Warning until 10 PM PDT Thursday for WAZ026-027. && $$ SHORT TERM...74 LONG TERM....76 AVIATION...76