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FXUS06 KWBC 151902PMDMRDPrognostic Discussion for 6 to 10 and 8 to 14 day outlooksNWS Climate Prediction Center College Park, MD300 PM EDT Mon March 15 20216-10 DAY OUTLOOK FOR MAR 21 - 25 2021Today's models are in good agreement on the longwave pattern across the domainduring the 6-10 day period. An amplified pattern is predicted, featuringanomalous ridging over the Aleutians, in the Eastern Pacific and across theeastern CONUS, with anomalous troughing forecast over Mainland Alaska and theAlaskan Peninsula, and over the southwest CONUS.A strong west-to-east mid-level flow over the Bering Sea and into southwestAlaska is expected to support an active storm track across much of Alaska,increasing chances of above normal precipitation south of the Brooks Range, andfor the Aleutians and Peninsula. North of this storm track, negative heightanomalies are predicted, which, coupled with relatively cold easterly low-levelflow from Canada, favor below normal temperatures across the state.Downstream of ridging over the eastern Pacific, storm activity is forecast tobe suppressed, enhancing the likelihood of near to below normal precipitationfor western parts of the Lower 48. A trough is forecast to amplify downstreamof this ridge, favoring near to below normal temperatures for much of thewestern CONUS. Within this trough a storm system is predicted to develop overparts of the Four Corners region, amplifying and moving eastward during theperiod. This leads to increased chances of above normal precipitation for theSouthwest and across the central U.S. Ahead of the trough, strong southerlylow-level flow favors above normal temperatures for most of the eastern half ofthe CONUS. Probabilities are especially high across the Great Lakes region andNortheast, where forecast positive height anomalies are highest. The cold frontpredicted to move eastward during the period is expected to encounter anomalousridging in the eastern U.S., which would help to suppress precipitation as itapproaches the coast. This increases chances of near to below normalprecipitation along the Eastern Seaboard.The official 6-10 day 500-hPa height blend consists of 50% of Today's 0zEuropean Ensemble Mean centered on Day 8, and 50% of Today's operational 0zECMWF centered on Day 8FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Well above average, 5 out of 5,due to excellent model agreement on the large-scale pattern, combined with goodagreement among the temperature and precipitation tools.8-14 DAY OUTLOOK FOR MAR 23 - 29 2021Models remain in good agreement on the large-scale pattern forecast across thedomain during the week-2 period. The pattern over the CONUS is forecast toshift eastward, compared to the 6-10 day period, as well as deamplify somewhat(due to natural uncertainty in longer leads, coupled with a more progressivepattern). The height pattern forecast over the Alaska region is very similar tothe 6-10 day period.The week-2 forecast temperature and precipitation probabilities across Alaskaalign closely with the 6-10 day forecast, as the 500-hPa pattern is expected topersist into week-2. Ridging and positive height anomalies are forecast to moveonshore over the western CONUS, leading to increased chances of above normaltemperatures in the West, and favoring above normal temperatures from the WestCoast, east to the Northern Plains. Troughing forecast in the central U.S.enhances the likelihood of near to below normal temperatures from the FourCorners region to the Central and Southern Plains. One or more storm systemspredicted to form near the trough, and expand east and north, favor abovenormal precipitation for parts of the Southwest, Southern Plains, Lower andMiddle Mississippi Valley, and Great Lakes region. Ridging is forecast topersist along the Eastern Seaboard, leading to an increased chance of near tobelow normal precipitation along the East Coast. Ahead of the trough in thecentral U.S., southerly low-level flow favors above normal temperatures acrossmost of the eastern half of the CONUSFXUS02 KWBC 151928PMDEPDExtended Forecast DiscussionNWS Weather Prediction Center College Park MD327 PM EDT Mon Mar 15 2021Valid 12Z Thu Mar 18 2021 - 12Z Mon Mar 22 202119Z Update: Similar to yesterday, the 12Z models are in very goodagreement across the continental U.S. through most of the mediumrange period, and therefore a general multi-deterministic modelblend was used as a starting point in the forecast process. Forthe building western trough this weekend and into next Monday,there are some modest timing differences with the shortwavetracking across the Desert Southwest, with the 12Z GFS slightlyahead of the consensus. Greater differences are apparent onMonday with the next shortwave trough approaching the PacificNorthwest with the 12Z CMC/ECMWF more amplified and faster thanthe GFS. Otherwise the rest of the forecast remains on track andthe previous discussion is appended below for reference. /Hamrick...Overview...Upper ridging initially over the northern Rockies and southernCanada will translate eastward through the period, allowing aclosed low to linger over the Southeast. Troughing in thenortheastern Pacific will move ashore through the West thisweekend, setting up another round of snow for parts of the centralRockies....Model Guidance/Predictability Assessment...Through the 12Z/18Z guidance, a deterministic/consensus blendsufficed for the Thu-Fri period as an area of low pressure movesthrough the Ohio River/Tennessee valleys and off the Carolinacoast. By next weekend, guidance continues to indicate lingeringtroughing over the Southeast, supporting surface wave developmentalong the front just offshore. Upper pattern (Rex block) wouldallow for such a feature but its proximity to the coast andstrength remain unclear. For now, kept most of its associatedprecipitation just offshore but strong northeast flow aided byhigh pressure to the north could pose some marine hazards (seeproducts from OPC and TAFB).Over the West, upper trough is poised to move inland a bit quickerthan forecast 24 hrs ago (ECMWF EPS trended quicker towards thefaster GEFS mean) but a blended solution between the GFS/GEFS andECMWF/ECMWF ensemble mean was a good starting point as the 12ZCanadian was on the quicker side of the spread (possible outcomebut not preferred at this time). Split between northern andsouthern portions of the trough could allow for a close low in theGreat Basin/Four Corners region by early next week....Weather/Threats Highlights...Rainfall will slip eastward to the Mid-Atlantic ahead of the warmfront on Thursday, perhaps with a bit of snow on the northernfringe of the precipitation shield. Much of the region has seenlittle to no precipitation the past 7-14 days. Rainfall may beconfined to coastal portions of the Southeast into Florida nextweekend as long as the offshore system stays far enough away. Highpressure over the Northeast will maintain cool temperatures thisweekend.Approaching Pacific systems will spread low elevation rain andhigher elevation snow to the West Coast (NorCal and northernSierra into coastal OR/WA) Thu-Sat until the upper trough axismoves inland. Another system may bring in light rain/snow late Suninto early Mon. Farther east, light to modest snow is likely forthe terrain in the Great Basin to the central Rockies as thesouthern portion of the upper trough slows the system progression.Question will be how much moisture can be tapped from the Gulfearly next week as the system pulls into the Plains.Mild temperatures over Florida (record highs in the upper 80s tonear 90 are possible) will give way to 60s/70s behind the coldfront over the Southeast/Florida Friday into the weekend.Temperatures will moderate in the northern tier by Sunday intoMonday to about 5-10 degrees above normal. Over the West, coolerthan normal temperatures behind the front are forecast for muchof the region this weekend into Monday. East of the Rockies, wellabove normal temperatures are expected for the High Plains intothe Upper Midwest and Great Lakes (p