055 FXUS63 KEAX 291728 AFDEAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO 1228 PM CDT Fri Aug 29 2014 .UPDATE... Issued at 1012 AM CDT FRI AUG 29 2014 Quick update this morning to account for latest radar and satellite trends. Fairly potent upper-level wave inbound this morning as seen on latest water vapor imagery. Ahead of this feature...upper- level pressure along the 1.5 PVU surface showing a nice "treble clef" signature with latest RUC analysis showing the trop undulation down to almost 500-mb...not bad for this time of year! Pressure advection in advance of this feature combined with decent upper divergence aloft should continue to support organized shwrs and thunderstorms. As this feature continues sliding east this morning...expect a gradual increase in precip chances from west to east which should result in very beneficial rainfall for a good portion of the area. In general...QPF totals will likely range from a quarter to half inch...with localized higher amounts possible with thunderstorm activity. Pop/wx grids updated to reflect a slightly delayed arrival time...but overall fcst trends remain unchanged. && .SHORT TERM...(Today through Sunday) Issued at 326 AM CDT FRI AUG 29 2014 For today, areas of scattered thunderstorms will continue to develop along and ahead of an eastward-moving shortwave trough, resulting in slowly increasing chances of precipitation this morning into the evening across the CWA. The best chance of storms will spread from early afternoon across eastern KS and far western MO to late evening in central MO. Afternoon temperatures will be held down by clouds and precipitation, keeping highs mainly in the 80s and the highest readings in central MO where storms will be later to arrive. Not much instability is expected to develop today with clouds arriving early and temperatures aloft and no real significant temperature perturbation along the trough to increase lapse rates, so do not expect much of a strong/severe storm threat this afternoon or this evening. However, if areas of central MO see a few peeks of sun through early afternoon, an isolated more robust storm could develop and could produce briefly gusty winds. Precipitation will generally clear out from northwest to southeast on Friday night, but may linger into Saturday across portions of central MO as a second weak shortwave trough rides up over central MO, especially if the weak surface boundary associated with today's shortwave trough can stall over the region and support convective initiation on Saturday. High temperatures should be several degrees warmer for Saturday and especially Sunday as skies clear, southerly surface flow returns, and 850 hPa temperatures remain in the 18 to 21 C range. The next round of thunderstorms is expected to be a bit more robust Sunday night into early Monday morning along a southeastward moving cold front. General model consensus brings the front through the CWA between midnight and 9 AM Monday morning, although timing could change a bit. MUCAPE values in the 1000-2000 J/kg range and bulk shear values as high as 40 kts could support organized, potentially strong multicell storms especially across northwest MO. Heavy rain is also a threat with PWATs climbing to around 2 inches and bulk shear vectors orienting parallel to the front to support training storms. The overall severe threat will depend on timing of frontal passage as storms should become elevated with time and instability will decrease, but is expected mainly across northwest and northern MO where upper-level forcing and flow is a bit stronger. .LONG TERM...(Monday through Thursday) Issued at 326 AM CDT FRI AUG 29 2014 A complex of showers and thunderstorms will likely be ongoing over portions of the forecast area Monday morning as a cold front settles into northwest Missouri. While not an optimal diurnal time for severe weather with only modest instability forecast, will need to monitor potential as dynamics from the large upper trough over the northern tier of the country will yield moderate shear in advance of the cold front. The upper trough will gradually deamplify, leaving the surface cold front largely stationary Monday into Tuesday across the northern half of the CWA. Periodic thunderstorm chances will remain possible through Tuesday night as the region remains on the southern periphery of strong upper dynamics and associated embedded shortwave troughs traversing the area. A few storms may be strong with moderate shear and instability, especially during the afternoon and evening hours. With the boundary layer winds expected to remain weak, the primary threat would be brief periods of damaging wind gusts and hail to quarter-size. Pinpointing the timing and specific locations of highest precipitation potential remains challenging at this stage with convective details that will play some role in frontal position and windows of strongest ascent both unresolved. The surface boundary is expected to retreat northward as a warm front by Wednesday as heights begin to rise across the region. Only a slight chance of thunderstorms is anticipated on Wednesday, with dry conditions for the remainder of the work week. Likewise, temperatures will return to above normal readings, with afternoon highs in the upper 80s to lower 90s. && .AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon) Issued at 1227 PM CDT FRI AUG 29 2014 Complicated fcst this afternoon as large scale upper trough and associated cold front will move through the area this afternoon/evening. That said...latest radar trends showing a decent swath of rain inbound to MCI with upstream obs over eastern KS supporting a tempo IFR mention out of the gate. As this activity clears to the north by 20z or so...attention then shifts to areas upstream which are now destabilizing thanks to mostly clear skies. As result...expect renewed shwr/storm activity later this afternoon with a second tempo group added at all sites to account for this possibility. Skies to slowly clear from west to east overnight which should give rise to developing VSBY and low CIG restrictions. For now...IFR restrictions offered at STJ with MVFR elsewhere. && .EAX WATCHES/WARNINGS/ADVISORIES... KS...NONE. MO...NONE. && $$ UPDATE...32 SHORT TERM...Laflin LONG TERM...Blair AVIATION...32