


Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
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052 FXUS02 KWBC 150747 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 347 AM EDT Wed Oct 15 2025 Valid 12Z Sat Oct 18 2025 - 12Z Wed Oct 22 2025 ...Guidance/Predictability Assessment... Model guidance remains in relatively good agreement during the medium range period, handling the evolution of several large scale trough/ridge features across the CONUS reasonably well despite a highly amplified 500mb flow pattern. Only minor differences were noted for Days 3 and 4, so a composite blend of the 00Z EC, 00Z UKMET, 00Z CMC and 06Z GFS deterministic runs sufficed to begin the period. However, larger discrepancies started cropping up by Day 5, most notably with the evolution of a potent Pacific trough that is progged to push inland over British Columbia and the Pacific Northwest late in the weekend into early next week. While the EC/GFS/UKMET all had similar solutions depicting the trough digging deeper along the West Coast, the CMC shows the trough becoming completely sheared apart as it moves across the Pacific Northwest. As a result of being much faster and flatter than consensus, the 00Z CMC was removed from the blend starting on Day 5 and was not considered for the remainder of the forecast. To compensate, more weighting was placed on the EPS and GEFS ensemble means, which ultimately made up slightly more than 50% of the blend for Day 6 and 7. The greater weighting of the ensemble means resulted in a more stable forecast that preserved continuity while reducing some of the timing and positional differences that are typical for the latter half of the medium range forecast period. ...Weather/Hazards Highlights... As an upper trough supported and wavy cold front passes through the Plains, moisture/instability return will increase in advance of it through the Mid-MS Valley where rainfall should significantly increase by Saturday. The WPC Day 4/Saturday Excessive Rainfall Outlook (ERO) introduced a new Slight Risk area centered over the Mid-South given favorable upper support, moisture and instability. SPC also shows a threat for severe weather in this pattern. The slowly progressive nature of the upper-level and surface features will spread organized rainfall eastward into the East/Northeast later weekend into early next week, particularly near and along the track of a deepening/consolidating coastal low pressure system (and more modestly into the Southeast ahead of the cold front). A Day 5/Sunday ERO Maringal Risk area was introduced to capture local runoff potenital into the Appalachians. Temperatures will be mild ahead of the cold front with highs well into the 70s/80s Friday from the Corn Belt to the Ozarks with 90s across South Texas. Out West, another deepened system will approach/enter the Pacific Northwest/West Coast over the weekend to produce a period of moderately heavy coastal and valley rains along with higher mountain snow. Activity will then dig and spread across the West and downstream to the Rockies. The WPC Day4/Saturday ERO maintains a coastal Washington Marginal Risk area given a favorable signal and our Winter Weather Outlook shows mountain snow potenial inland from the Northwest to the Northern Rockies into Monday with passage. Schichtel Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation forecast (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml https://www.wpc.ncep.noaa.gov/#page=ovw $$