387 FXUS63 KLSX 241018 CCA AFDLSX Area Forecast Discussion...CORRECTED National Weather Service Saint Louis MO 418 AM CST Fri Nov 24 2017 .SHORT TERM... (Through Late Tonight) Issued at 404 AM CST Fri Nov 24 2017 The upper air pattern will be progressive but will undergo a good deal of amplification over the next 30 hours. The short wave trof currently exiting the Northern Rockies will amplify as it moves east and into the MS Valley be early this evening. Accompanying this short wave will be a cold front which should extend from eastern IA through NW MO into SE KS at 00Z tonight. Mild temperatures and breezy conditions will be the story for today. A batch of high clouds will slide southeast across the area this morning, while the surface pressure gradient and low level height gradient tighten. This will result in increasing and gusty south-southwest winds from mid-late morning into the afternoon and prominent low level WAA. Highs today will be quite mild ranging from 15-20 degrees above normal. The short wave trof will continue to move east tonight and into the OH/TN Valleys sending the cold front through the area. There is some weak large scale forcing accompanying the upper trof and cold front, as well a band of mid level moisture. Interestingly, a few of the CAMS also have a little light precipitation. We previously had some sprinkles in the forecast and the new forecast expands the coverage in a swath that migrates southeast tonight coincident with the weak forcing and moisture. Even though we will see a cold fropa tonight, the air is not particularly cold, and mins will be above normal. Glass .LONG TERM... (Saturday through Thursday) Issued at 404 AM CST Fri Nov 24 2017 Corrected Long Term Discussion. The first part of the long-term forecast will continue to be tranquil as a longwave trof remains in place over the eastern U.S. This will keep the Mid Mississippi Valley in northwest flow through much of the troposphere and lock a relatively mild ridge of high pressure at the surface over the area through at least Sunday night into Monday. Temperatures for Saturday and Sunday will continue to be above normal in the mid and upper 50s with plenty of sunshine. Guidance is in good agreement in beginning a pattern shift on Monday in building an upper ridge east into the Mississippi Valley. The surface high will be shunted further east as this happens resulting in low level southwest flow. Guidance members are in generally good agreement on this shift, though the ECMWF is a bit slower than the GFS and Canadian. Am siding a little bit with the warmer and breezier solution in this case since highs on Sunday will already be running as much as 10 degrees above normal and Monday should be even warmer than that. The upper pattern becomes quasi-zonal on Tuesday with a shortwave moving across the U.S. Canadian border and another wave moving off the Rockies by around 00Z Wednesday. The northern wave will push a cold front into the Midwest Tuesday night and Wednesday morning. While the atmosphere looks pretty dry, there may be enough moisture convergence ahead of the front to squeeze out some light rain before sunrise Tuesday over western/northern portions of the forecast area, though QPF looks pretty meager. Guidance is in decent synoptic agreement with the second wave moving from the Rockies into the Plains Tuesday night and Wednesday. The ECMWF is about 6 hrs behind the GFS and Canadian models, and it's also around 100-150 miles further north with base of the shortwave and the associated surface low. Backed PoPs off a bit on Wednesday to give a nod to the ECMWF's slightly slower and more northerly solution, though it does look like the much of the area should see a chance of precip at some point on Wednesday into Wednesday night. The system should be through the area on Thursday with high pressure building across the Plains into the Midwest. The ECMWF keeps some light precip over eastern portions of the area Thursday, but with drier air pouring into the region the chance for precip should be minimal. Carney && .AVIATION... (For the 06z TAFs through 06z Friday Night) Issued at 1145 PM CST Thu Nov 23 2017 VFR conditions to prevail through the period. High clouds over northwest MO will continue to stream southeast overnight and into the day on Friday. Southwesterly winds will increase late Friday morning into Friday afternoon, with gusts of 20-25 knots likely ahead of a cold front. This cold front will push through all sites Friday evening, bringing a wind shift to the northwest along with some enhanced mid/high cloudiness. SPECIFICS FOR KSTL: Main TAF concern will be crosswind potential on the parallel runways Friday afternoon. Southwest winds will increase by late Friday morning, with gusts of 20-25 knots possible Friday afternoon. Otherwise, a cold front will bring a wind shift to the WNW Friday evening with some increase in mid/high cloudiness. KD && .CLIMATE... Issued at 404 AM CST Fri Nov 24 2017 Record High Temperatures for Nov 24 STL...74 1966 COU...70 1966 UIN...69 1931 && .PRELIMINARY POINT TEMPS/POPS... Saint Louis 71 46 57 36 / 0 10 0 0 Quincy 68 40 55 33 / 5 10 0 0 Columbia 70 41 58 34 / 5 10 0 0 Jefferson City 72 42 59 34 / 0 10 0 0 Salem 61 43 56 34 / 0 10 0 0 Farmington 66 44 59 34 / 0 10 0 0 && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX