Initial Target: O'Neill, NE to Plankinton, SD (Based on a blend of the NAM-WRF, GFS, SREF and ECMWF)
Forecast Discussion: A trough is digging onto the west coast with severel shortwaves visible at the midlevels. Several of these shortwaves will round the base of the trough and eject into the northern plains during the period. One thing to note is the trough remains well west of the modest instability axis leaving any forcing to occur along the dryline Saturday afternoon and evening.
Another concern is the EML forecasted to be strengthening over the target area throughout the day on Saturday. Absent any large scale ascent this could be problematic for convection to initiate. However, the NAM is breaking precipitation out over south central SD and north central NE at 0Z/23, albeit it has been pushed further north from run to run. Any storms that do form will quickly go severe and with a warm front in the area and the potential for outflow boundaries the tornado risk should be enhanced with the more robust supercells.
Another concern for this forecast period is the on-going thunderstorms over the high terrain of eastern Wyoming and the residual cloud cover. These parameters will need to be resolved with tomorrow mornings forecast and nowcasting throughout the morning on Saturday.
Areas of surface low pressure are forecasted to be over eastern Montana (992mb) and NE Colorado (1000mb) with a developing surface low (996mb) over central Nebraska Saturday afternoon and evening. This developing surface low is forecasted to deepen by 0Z/23.
A warm front will be draped southeastward from the developing central Nebraska low back across south central and southeastern Nebraska. A dryline will be positioned along and south of the low pressure center from the central Dakota's into Kansas. These areas of low pressure and attendant boundaries will interact with a very broad warm sector and will provide the focus for severe thunderstorm development from north central Kansas into the Dakota's Saturday afternoon and evening.
Warm air advection is currently on-going over the target area with deep gulf moisture being transported northward into the forecasted warm sector. A very broad warm sector will develop from central Kansas all the way into the Dakota's tomorrow afternoon and evening. Surface temperatures are forecasted to be in the upper 70's to low 80's across the target area. Here is a look at current dewpoints and forecasted dewpoints over the target area (0Z/22):
Surface based CAPE is forecasted in the 3000 to 3500 J/kg range over the target area by the NAM-WRF and GFS. There will be a moderate to strong cap over the target area most of the day with 700mb temps in the 12C-14C range. Howevver, the NAM-WRF and GFS show the cap begining to erode between 18Z/22 and 0Z/23 over the target area with 700mb temps dropping to the 9C range as well.
Modest shear values are also present with bulk shear in the 40 to 50 kt range with shear vectors being perpindicualr to the dryline/boundary. SRH and EHI values are maximized across the target area at 0Z/23. Low level shear, 0-1km, is also appreciable for an attendant tornado threat with large, looping hodographs in the target area.
Forecast Discussion: A trough is digging onto the west coast with severel shortwaves visible at the midlevels. Several of these shortwaves will round the base of the trough and eject into the northern plains during the period. One thing to note is the trough remains well west of the modest instability axis leaving any forcing to occur along the dryline Saturday afternoon and evening.
Another concern is the EML forecasted to be strengthening over the target area throughout the day on Saturday. Absent any large scale ascent this could be problematic for convection to initiate. However, the NAM is breaking precipitation out over south central SD and north central NE at 0Z/23, albeit it has been pushed further north from run to run. Any storms that do form will quickly go severe and with a warm front in the area and the potential for outflow boundaries the tornado risk should be enhanced with the more robust supercells.
Another concern for this forecast period is the on-going thunderstorms over the high terrain of eastern Wyoming and the residual cloud cover. These parameters will need to be resolved with tomorrow mornings forecast and nowcasting throughout the morning on Saturday.
Areas of surface low pressure are forecasted to be over eastern Montana (992mb) and NE Colorado (1000mb) with a developing surface low (996mb) over central Nebraska Saturday afternoon and evening. This developing surface low is forecasted to deepen by 0Z/23.
A warm front will be draped southeastward from the developing central Nebraska low back across south central and southeastern Nebraska. A dryline will be positioned along and south of the low pressure center from the central Dakota's into Kansas. These areas of low pressure and attendant boundaries will interact with a very broad warm sector and will provide the focus for severe thunderstorm development from north central Kansas into the Dakota's Saturday afternoon and evening.
Warm air advection is currently on-going over the target area with deep gulf moisture being transported northward into the forecasted warm sector. A very broad warm sector will develop from central Kansas all the way into the Dakota's tomorrow afternoon and evening. Surface temperatures are forecasted to be in the upper 70's to low 80's across the target area. Here is a look at current dewpoints and forecasted dewpoints over the target area (0Z/22):
Surface based CAPE is forecasted in the 3000 to 3500 J/kg range over the target area by the NAM-WRF and GFS. There will be a moderate to strong cap over the target area most of the day with 700mb temps in the 12C-14C range. Howevver, the NAM-WRF and GFS show the cap begining to erode between 18Z/22 and 0Z/23 over the target area with 700mb temps dropping to the 9C range as well.
Modest shear values are also present with bulk shear in the 40 to 50 kt range with shear vectors being perpindicualr to the dryline/boundary. SRH and EHI values are maximized across the target area at 0Z/23. Low level shear, 0-1km, is also appreciable for an attendant tornado threat with large, looping hodographs in the target area.
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