SACRUS

12Z GGEM:

1/22 12z GFS AI AIGFS: Total QPF storm Total Snow / Sleet (10:1)

1/22 12z GFS total QPF: Total snow/sleet (10:1) - again with a long / linger snow duration through Monday afternoon:

Snow starts between 2 - 6 am Sunday morning

12Z GFS is updating

1/22 12Z : NYC area Total QPF / (Snow/Sleet) using 10:1 NAM (84H) : 0.7 / (6.7) RGEM (84H): 1.0 / (9.0) ICON : 1.4 / (8.5) GFS: 1.4 / (12.5) GGEM: 1.2 / (8.2) UKMET: 0.8 - 1.0 / (8.5) GEFS: 1.4 / (12.8) Euro AI AIFS: 1.2 / (11.1)

1/22 12z ICON Total QPF - storm 1/22 12z ICON Snow / Sleet

RGEM RGEM Total QPF through 84 H (Sunday 8PM) RGEM Snow/Sleet through 84H

RGEM: snow arrives by 4 AM Sunday

ICON wrap around on Monday morning

ICON 12Z

RGEM next up

Snow/ sleet through 84

From my review the NBM General weighting philosophy Time RangeHeavier Weight 0–24hHRRR, RAP, obs 24–48hNAM, HRRR, HREF 48–72hNAM + globals 3–5 daysEuro, CMC, ensembles 5–7 daysEnsembles dominate It’s NOAA/NWS’s official blended forecast system, designed to combine many models, ensembles, and observations into a single, statistically optimized forecast for sensible weather (temps, precip, wind, snow, etc.). What goes into the NBM (Inputs)? Global Models ECMWF (Euro) GFS CMC (GGEM) UKMET ICON (limited elements) Ensembles EPS GEFS GEPS HREF (short range) Regional / Mesoscale HRRR NAM / NAM-Nest RAP RGEM Observations & Post-Processing Surface observations Climatology MOS-style bias correction Downscaling to fine grids (~2.5 km)

EPS mean 850 MB