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   QPFERD   
      
   Excessive Rainfall Discussion   
   NWS Weather Prediction Center College Park MD   
   1236 PM EST Thu Jan 22 2026   
      
   Day 1   
   Valid 16Z Thu Jan 22 2026 - 12Z Fri Jan 23 2026   
      
   The probability of rainfall exceeding flash flood guidance is less   
   than 5 percent.   
      
   A mesoscale cyclone appears to have formed near the intersection   
   of a weak surface trough/front east to northeast of Biscayne Bay.   
   This combination has led to thunderstorm development with heavy   
   rainfall, which up until this point has only impacted southern   
   portions of Key Biscayne though some cells recently are   
   threatening to move ashore a little farther north across Key   
   Biscayne and near Fisher Island. The airmass along and east of the   
   coast is sufficiently moist and unstable for thunderstorms with   
   heavy rainfall, and effective bulk shear supports the formation of   
   random mesocyclones. The low-level inflow to the east north of the   
   mesocyclone runs counter to the westerly flow aloft, with the   
   combination leading to minimal cell movement. The overall threat of   
   heavier rainfall materializing over urban areas of the I-95   
   corridor still appears to be fairly isolated. The overall threat   
   appears to wane after 19z/2 pm EST when the guidance implies that   
   the mesocyclone near South Florida drifts eastward. A non- zero   
   threat of flash flooding exists, but convective coverage and the   
   brevity of the thunderstorm risk precludes any addition of Marginal   
   areas at this time.   
      
   Isolated showers across southern California may also impact   
   portions of the Transverse and Peninsular Ranges as well, with   
   brief heavy rain occurring near burn scars across the area. The air   
   mass should be sufficiently moist, with precipitable water values   
   in the 0.75-1" range. Bubbles of 100+ J/kg of MU CAPE lie offshore   
   at the present time. This should maximize hourly rain amounts in   
   the 0.4" neighborhood. The 12z HREF probabilities of 0.5"+ in an   
   area are below 15%, also implying that lesser hourly amounts are   
   expected. The threat for flash flooding here is also less than 5%   
   although an isolated instance of excessive runoff cannot be   
   completely ruled out.   
      
   Roth/Cook   
      
      
   Day 2   
   Valid 12Z Fri Jan 23 2026 - 12Z Sat Jan 24 2026   
      
   ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE TEXAS   
   HILL COUNTRY...   
      
   Gulf inflow ahead of an incoming upper level trough across the=20   
   Northern Plains/West brings overrunning moisture into South-Central   
   TX, with precipitable water values rising to 1.25" within a cool=20   
   atmosphere with 5610 m 1000-500 hPa thickness, implying complete=20   
   saturation. RAP forecasts show MU CAPE rising to 500+ J/kg,=20   
   implying a heavy rain threat. The 12z HREF/06z REFS agree, showing=20   
   high enough probabilities of 0.5"+ an hour and 3"+ in 24 hours to=20   
   be of concern to the Hill Country, where there is limited topsoil   
   to prevent runoff. This new Marginal Risk was added in=20   
   collaboration with the EWX/New Braunfels TX, SJT/San Angelo TX,=20   
   and FWD/Fort Worth TX forecast offices.   
      
   Roth   
      
      
   Day 3   
   Valid 12Z Sat Jan 24 2026 - 12Z Sun Jan 25 2026   
      
   ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL NEAR THE   
   NORTHWEST GULF COAST...   
      
   An upper level trough phasing as it moves through the Rockies lures   
   sufficient Gulf moisture into Southeast TX/the Upper TX Coast and   
   southwest Louisiana, with precipitable water values rising to   
   1.25-1.75". Considering the coolness of the environment, this   
   should lead to atmospheric saturation. The region is diffluent=20   
   aloft and does not appear to be capped...700 hPa temperatures are   
   forecast to be below 6C. MU CAPE rises above 1000 J/kg, at times.=20   
   Inflow at 850 hPa/effective bulk shear appears sufficient for=20   
   convective organization. Hourly rain amounts to 2.5" with local=20   
   totals to 5" are possible, given the above ingredients. The 12z=20   
   UKMET, 12z Canadian Regional/RDPM, and 00z ECMWF have a signal for=20   
   heavy rainfall in this region, though the 12z GFS does not. Enough=20   
   of a signal exists for a Marginal Risk area to be hoisted this=20   
   cycle. Over the past week, it has been wet across portions of   
   Jefferson, Orange, & Galveston Counties in TX as well as portions=20   
   of southwest LA south of I-10. Isolated to widely scattered issues=20   
   would be mostly confined to urban areas.   
      
   Roth   
      
      
   Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/94epoints.txt__;!!DZ3fjg!7ESEwQjP6l0ddiDKpbckZF5M_vqB9TFPzru7FR97hUey=   
   5dUOGGWskzC0YIGgmkt-EaGb8qB8wTebH-iyp29l6AT6ucg$=20   
   Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/98epoints.txt__;!!DZ3fjg!7ESEwQjP6l0ddiDKpbckZF5M_vqB9TFPzru7FR97hUey=   
   5dUOGGWskzC0YIGgmkt-EaGb8qB8wTebH-iyp29lx_Wf7Vc$=20   
   Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/99epoints.txt__;!!DZ3fjg!7ESEwQjP6l0ddiDKpbckZF5M_vqB9TFPzru7FR97hUey=   
   5dUOGGWskzC0YIGgmkt-EaGb8qB8wTebH-iyp29llAcGhKw$=20   
      
   =3D =3D =3D   
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