Area Forecast Discussion
Issued by NWS Topeka, KS
Issued by NWS Topeka, KS
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117 FXUS63 KTOP 020730 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 230 AM CDT Tue Jul 2 2024 .KEY MESSAGES... - Heat advisory in effect today and unchanged from previous forecasts. - The first of several potential severe weather threats sets up across the area today by mid afternoon as a modified cold front enters northeast and north central Kansas. - Severe weather may be possible in at least some form through much of the 4th of July week due to little change in the overall weather pattern. && .DISCUSSION... Issued at 226 AM CDT Tue Jul 2 2024 The overall upper air pattern continues to exhibit gradual changes over the past 12 hrs. The eastern long wave trough has worked off shore into the Canadian maritime region. A semipermanent anticyclone remains over the southern and southeastern CONUS. Return of subtropical moisture and a LLJ is set up on the northwestern flank of this anticyclone and in between a broadening cyclonic flow regime which is setting up across the northern CONUS. A modified surface cold front is positioned through central Nebraska within and inverted pressure trough and surface low pressure back into southeastern Colorado and southwestern Kansas vicinity. An embedded vort max continues to work through eastern Nebraska into Iowa at this hour. Storms associated with resultant DCVA ahead of this feature have been trending down below severe limits early this morning. Parallel mean winds have led to a series of flash flood warnings along the Platte River valley over southeastern into east central Nebraska areas. This is also along the cold frontal boundary which will advance southeast into the area later today. A few showers continue to form along the 305K surface from north central Kansas areas and mainly along the KS/NE border region. This is expected to continue through early morning with the LLJ streaming across the region before it veers slightly and weakens after sunrise today. Not anticipating this area to broaden in coverage substantially with convergence being limited across the area and lapse rates not very conducive to convective development being favored. Deeper moisture looks to be in place across the forecast area for this afternoon. Moist flux convergence increases by this afternoon along the frontal boundary as it sags into the area. This will support intense heating today with insolation being intense into the afternoon. The front working into northern areas should keep the cooler side over Hwy 36 areas so the heat advisory remains unchanged at this point. Severe weather looks most favorable across much of the area this afternoon. Initiation could be mid to late afternoon along the modified cold front as heating erodes the cap and MLCAPES have a chance to reach to around 4000 J/kg especially along the boundary into northeastern Kansas areas. The next vort max working across the central Rockies into the central Plains should arrive by late afternoon. This may help foster scattered to more widespread coverage of storms into the evening hours across the area. Still anticipate the primary hazards to remain damaging wind potential due to the intense heating aspects leading to DCAPE well in excess of 900 J/kg. Mean flow will be mostly boundary parallel suggestive of potential for flooding concerns as storm interactions increase with coverage. Can`t rule out low potential for a tornado but this looks potentially best northeast of the area into southwestern into central Iowa areas where potential surface low pressure may cause locally backed winds where northeast Kansas low level winds appear to suggest a better setup for southwesterly flow within the BL. Freezing levels likely around 15kft which would require a strongly rotating storm or intense updraft for large hail production. Each day through the 4th of July looks to have potential for severe weather and additional flood potential across at least portions of the area with central and east central zones having the best potential for the modified boundary to stall and waiver back and forth. Mesoscale details such as outflow boundaries should ultimately determine where the boundary sets up and thus differential heating, etc. may become a focus for daily storms development to take place primarily in concern with the heating of the day. Thursday (unfortunately on the 4th of July) with broad cyclonic flow regime still in place overhead, a more significant shortwave appears to emerge from the northern Rockies and slip into the central Plains. This may help push a more organized baroclinic zone through the area by the evening of the 4th of July. This could lead to the next best organized severe weather threat should it ultimately materialize. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1220 AM CDT Tue Jul 2 2024 Expect VFR conditions to hold outside of any showers or storms that develop across the area by late afternoon. Uncertain on the coverage at this time for any storms along the front so have gone with a VCSH element to suggest there will be a time frame where storms may form around the terminals. Wind shear conditions may be present around FL015 this morning as a strong LLJ is set up across the area. A few gusts may continue overnight with a partially mixed boundary layer, however, low level winds just off the deck may be substantially higher causing speed shear. FROPA takes place later this evening as the front moves through the area. && .TOP WATCHES/WARNINGS/ADVISORIES... Heat Advisory from noon today to 8 PM CDT this evening for KSZ021-KSZ022-KSZ023-KSZ024-KSZ026-KSZ034-KSZ035-KSZ036-KSZ037- KSZ038-KSZ039-KSZ040-KSZ054-KSZ055-KSZ056-KSZ058-KSZ059. && $$ DISCUSSION...Drake AVIATION...Drake