235 FXUS21 KWNC 131828 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT March 13 2026 SYNOPSIS: Very strong mid-level high pressure is forecast over the western and central Contiguous United States (CONUS), promoting unseasonably warm weather across much of the region through the first half of week-2. Spring extreme heat conditions may briefly continue into week-2 over parts of the Desert Southwest and potentially portions of Texas. The early-season warmth is likely to accelerate spring snowmelt where seasonal snowpack has been well below normal. Meanwhile, persistent mid-level high pressure centered over the western Aleutians in concert with downstream troughing across eastern and southern Alaska support Arctic surface high pressure over much of the state. This raises the potential for much below normal temperatures across central and southern Alaska. At the same time, the mid-level trough is expected to induce surface low pressure near the Gulf of Alaska, creating a pressure gradient that sets up a slight risk of high winds in south-central Mainland Alaska and Southeast Alaska for the first half of week-2. HAZARDS Moderate risk of much above-normal temperatures for portions of the Great Basin, California, Desert Southwest, Rockies, and Plains, Sat-Sun, Mar 21-22. Slight risk of much above-normal temperatures from much of the western CONUS into the central and southern Plains, Sat-Tue, Mar 21-24. Slight risk of much below-normal temperatures over much of central and southern Alaska, Sat-Tue, Mar 21-24. Slight risk of high winds over portions of coastal southern Alaska and Southeast Alaska, Sat-Tue, Mar 21-24. DETAILED SUMMARY FOR MONDAY MARCH 16 - FRIDAY MARCH 20: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR SATURDAY MARCH 21 - FRIDAY MARCH 27: The latest 0z GEFS, European ensemble (ECENS), and Canadian ensemble (CMCE) daily means start week-2 with a highly amplified ridge centered over the Interior West, and a 500-hPa trough downstream over the northeastern CONUS. According to these ensembles, the peak heights are predicted on Day 6 or 7 (Mar 19 or 20), with a gradual decline thereafter. Today, the CMCE mean is the slightly stronger model, indicating 589 dm heights just south of the Four Corners Region on Mar 21 at the start of week-2. Peak heights at this time on the GEFS and ECENS means are 1 to 3 dm lower. The northward-extending ridge axis is also slightly farther west in the CMCE mean, centered over the Rockies, while the axis has more of a positive tilt on the ECENS and GEFS means, reaching into the northern Great Plains. These relatively minor differences aside, there continues to be good model agreement on the evolution of this mid-level feature gradually sliding eastward into the central CONUS and deamplifying. Consequently, heights are forecast to rise across the central and southeastern CONUS in week-2, accompanied by increasing coverage of above-normal temperatures. In the wake of this eastward-drifting mid-level ridge, heights are expected to fall across the Northwest as a weakening 500-hPa trough broadens and drifts toward the region from the Gulf of Alaska. This is expected to limit the northward extent of the unseasonable warmth, keeping it out of the northern tier of the western CONUS for the most part. The Probabilistic Extremes Tools (PETs) from all ensembles are very bullish on unusual warmth in terms of percentiles for this time of year, but the extent of excessive heat appears to be very limited. The PETs from the GEFS, ECENS, and CMCE all depict greater than 90 percent chances that temperatures will end up in the top 15th percentile historically at the start of week-2 across most of the Four Corners Region and Desert Southwest, but non-trivial chances for temperatures above 90 deg. F are restricted to the climatologically-warmest areas in the Desert Southwest (where odds are high early week-2) and in a band across southern, west-central, and north central Texas, along with adjacent parts of Oklahoma (20 to 40 percent). Still, the extreme climatological nature of the early-season warmth justifies a moderate risk of much above normal temperatures early week-2 through much of the interior western CONUS, reaching as far east as the central and south-central Great Plains. The PETs show chances for unusual warmth declining over the course of week-2, with chances for temperatures exceeding 90 deg. F dropping below 50 percent even in the Desert Southwest in all three PETs by mid-week. The likelihood of temperatures in the top 15 percent historically drop below 50 percent by the middle of the period, and only marginally tops climatology by the end of week-2. This justifies a slight risk of much above normal temperatures through the middle of the period across a large part of the western CONUS outside the northern tier, reaching as far east as the fringes of the Lower Mississippi Valley. The pattern across the CONUS favors unusually dry conditions in most locations, with potential exceptions in the northeastern and northwestern CONUS at times. Amounts are forecast to remain below hazards thresholds, so no precipitation hazards are posted at this time. Similarly, PETs for strong winds are unremarkable today, and deterministic models are inconsistent in depicting when and where there might be short-lived high wind threats. Given this guidance, no risks for high winds are posted today, but the situation will be monitored for increased consistency in the deterministic models, and more bullish odds in the PETs. Over Alaska, anomalous 500-hPa ridging from the western Aleutians into eastern Siberia is forecast in concert with downstream troughing over south-central through eastern Alaska, along with the adjacent Gulf of Alaska, where the greatest negative height anomalies are expected early week-2. This pattern favors Arctic high pressure dominating most of the state. As a result, a slight risk of much below normal temperatures is posted for a large portion of central and southern Alaska over the first half of week-2. The PETs all show large parts of Alaska with a better than 50 percent chance for temperatures to drop into the lowest 15 percent of the climatological envelope at the start of the period, with the GEFS showing such conditions across roughly the southern half of the Mainland and adjacent parts of the Aleutians and Panhandle. PETs from the ECENS cover a larger area (southern two-thirds) with similar odds for much below normal temperatures, while the CNENS depicts this across the entire Mainland, along with adjacent parts of the Aleutians and the Panhandle. This prompted an expansion of the slight risk area for much below normal temperatures across the entirety of the southern two-thirds of the state. There is increasing uncertainty on the evolution of the temperature pattern as week-2 progresses, but all guidance favors moderating temperatures around the middle of week-2, as both the mid-level ridge and downstream trough weaken and drift southward, reducing their impacts on the state. With support waning, the slight risk for much below normal temperatures is discontinued after the middle of week-2. Across southern Mainland Alaska and Southeast Alaska, surface low pressure is expected in or near the Gulf of Alaska in response to the aforementioned mid-level trough. The pressure gradient between this system and the Arctic high dominating most of Alaska raises the chances for high winds along the southern tier of the Mainland and Southeast Alaska through the middle of week-2. This is expected to bring substantial precipitation to parts of Southeast Alaska as well, but amounts are expected to remain below hazardous thresholds. Following a Kona low event ongoing over the Central Pacific that looks to bring heavy rains, high winds and flooding to Hawaii, ensembles depict some potential for the mid-level trough to reload temporarily to the west of the state by early week-2, which may induce additional heavy precipitation. The ECENS and GEFS PETs continue to highlight 20% to 50% chances for 3-day precipitation amounts exceeding the 85th percentile over much of the island chain during the first half of week-2. If it materializes as expected, the additional rainfall will exacerbate any flooding ongoing at the start of the period. FORECASTER: Rich Tinker $$