714 FXUS63 KEAX 271124 AFDEAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO 624 AM CDT Fri Jul 27 2012 ...UPDATED AVIATION DISCUSSION... .DISCUSSION... Short Term (Today through Sunday Night)... It's nice to have a quasi-normal July flow pattern for once -- aka "morning surprise". Water vapor imagery shows several well defined vorticity lobes pivoting southward in advance of an upper trough now over nrn Wisconsin. The leading wave is presently pushing into northern Missouri. 00Z KOAX sounding was clearly uncapped and simply needed some lift/mid level moistening to get the job done, and this impulse is providing that necessary support. A large plume of ACCAS has turned into widely scattered showers/thunderstorms, and this activity has gained some traction over the past hour or two. Sufficient MUCAPEs for a 750-700mb parcel on the order of 500-700 J/kg will yield a continuation of widely scattered thunderstorms overnight, focused especially over the northeast half of the CWA, The more robust cells could produce some small hail, while a very dry/deep sub-cloud layer will likely support surface wind gusts on the order of 30-35 mph accounting for the low level inversion. Meanwhile, the actual surface front which I expected to be along the AR border by now, has not budged from last night and is still located along the IA/NE border. This stall was due to the upper trough over northern Wisconsin, awaiting its forward progression which will force a surface high southward from the Dakotas. Based on recent trends and the aforementioned convection, the boundary should move fairly quickly this morning allowing much lower dewpoints to advect/mix into the area for this afternoon. This will occur in concert with enhanced low-mid level baroclinity that will increase over the area in response to a realignment of the stronger upper flow along the periphery of the Rockies ridge. As such, forecast temperatures today will be a bit tricky resulting from this thermal gradient and cannot argue with the previous forecast of upper 80s across northeast Missouri to around 100 across west central MO/east central KS. This gradient will tighten even further tomorrow, with afternoon 850mb temps ranging from the upper teens Celsius in NE MO to the mid 20s over the SW zones, yielding forecast highs ranging from 90 NE MO to near 105 south of Kansas City. Easterly low level flow will maintain very dry air across the region, so heat index values will generally be at/below the ambient temperature. As we head into Saturday Night and Sunday, the upper ridge center is expected to shift back into Oklahoma, while low level flow begins to veer back into the south and southwest. The strong low level baroclinic zone will likely begin to return northward as a warm front, aided by a nocturnal low level jet. A few plausible scenarios exist as a modest instability axis will be co-located along this gradient, including nocturnal convection developing across srn IA/NE MO. Another scenario would evolve an organized MCS across the Central Plains that would track through this region late Saturday Night or Sunday morning. Will continue to carry low chance POPs across this area with uncertainty regarding both the placement of the edge of the cap as well as questionable boundary layer moisture. Further southwest, very hot air will spread eastward into the forecast area on favorable low level westerlies along the northern periphery of the upper ridge. The NAM remains the most aggressive, featuring record breaking 30C 850mb temps in the afternoon. Let's hope this is overdone. Nevertheless, even the other more temperate solutions still suggest that 105-106F highs may be fairly widespread on Sunday. With some modest moisture recovery in the boundary layer, heat headlines may have to make a return. Another concern is that convective temperatures could be breached Sunday afternoon within the thermal ridge axis across western MO/ern KS. Without forcing for ascent, do not feel that even 20 POPs are warranted, but a few high-based storms could be sent skyward through 50Kft, with an attendant threat of dry microbursts. Bookbinder Medium Range (Monday - Thursday)... For the extended, the upper ridge is expected to build across the Southern Plains and into the Rockies by the middle of the week. This leaves the area in a rather difficult spot as we could have a large variation of temperatures on any given day from the southwestern forecast area to the northeastern forecast area. The region will predominantly be under northwest flow which is notoriously unpredictable with regards to precipitation chances. There could be several rounds of storms track mainly through from the Northern Plains into Iowa and spread convection or some convective debris that could really inhibit temperatures across mainly the northeastern half of the forecast area. On the opposite side, the southwestern half of the forecast area could see daily highs around or just above the century mark based forecast 850mb temperatures. With the drought not relenting, despite several nights of scattered convection, decided to remove POPs through most of the extended. With limited confidence in timing any wave that may trigger any convection feel the more likely outcome is the be dry. Forecasting any precipitation, in a regime like this, is better left to short to near term analysis of any short waves. With no real evidence of any wave and the anticyclonic curvature prevailing, there is just more evidence to keep the forecast dry. Overall, raised temperatures from the forecast initialization by a degree or two which brings temperatures from the low 100s in the southwestern forecast area to the mid and upper 90s in our northeastern zones. Throwing the dewpoint, the heat indices through the extended approach 105 in our south and southwestern zones. CDB && .AVIATION... For the 12Z TAFs, a few high based showers will move through the vicinity of the terminals this morning. Have included a VCSH through 14Z at the Kansas City terminals. Otherwise, VFR conditions are expected through the forecast as dry air filters into the region behinds a cold front. This will also allow for winds to prevail from the north but they should remain light through the period. Winds will transitions to the southeast late in the period but still remain light through 12Z Saturday. CDB && .EAX WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ WFO EAX