946 FXUS63 KGID 140540 AFDGID AREA FORECAST DISCUSSION National Weather Service Hastings NE 1140 PM CST Fri Jan 13 2023 ...AVIATION UPDATE... .DISCUSSION...(This evening through Friday) Issued at 403 PM CST Fri Jan 13 2023 -- Key Messages for the entire 7-day forecast (see end of discussion for short term forecast details): * Although our forecast remains high-confidence dry through Sunday afternoon, the Sun night-Fri time frame turns somewhat active as THREE distinct disturbances bring at least small precip chances (PoPs). More details on each below, but the "middle one" (Wed- Wed night) still appears to bear the most watching for maybe a few inches of accumulating snow (still plenty of uncertainty though). * The first/weaker system Sun night-Mon AM bears watching for perhaps a "sneaky" round of light freezing rain, but have kept this out of the official forecast for now given some modest uncertainty in especially surface temperatures. * Temperature-wise, these next 7 days as a whole look to lean toward the seasonably-chilly (but not OVERLY cold) side, with highs on most days (especially next week) mid-30s to mid-40s However, the mildest two days just happen to correspond to this weekend, with widespread mid-40s to low-50s. * Despite the aforementioned parade of weather system next week, no days/nights look particularly windy, with Monday currently looking to feature the overall-highest speeds (gusts to around 30 MPH out of the northwest). -- More detailed overview/highlights of the entire 7-day forecast (including ALL discussion of 4th period and beyond...Sun-Fri): 1) Any changes worth noting with this forecast versus previous: Honestly nothing of particular significance. However, those watching closely will note that: - PoPs have trended down slightly (roughly by 10 percent) for the Wed-Wed night system given a slight southward trend to the main system (but still "only" 20 percent far north to 40-50 percent in KS). - High temps for Monday trended generally 2-3 degrees cooler and highs for Thursday upward 2-4 degrees (although any POSSIBLE new snow cover by then could easily reverse that trend). 2) General overview of the large-scale upper air/surface pattern (and any notable model differences): All things considered, the latest ECMWF/GFS are actually in pretty remarkable agreement on "the basics" through the entire 7-day. Aloft, this weekend starts with broad ridging aloft (hence a nice warm-up), with flow aloft then turning southwesterly Sunday before "system #1" swings directly over our area Sun night-Monday. In its wake a brief stretch of dry quasi-zonal (west-east) flow ensues most of Mon night-Tues night, before "system #2" tracks through the Plains mainly Wed-Wed night (bringing perhaps a decent chance of snow to mainly our southern zones). In its wake, another brief period of ridging/dry conditions Thurs-Thurs night before "system #3" arrives Friday, bringing at least small chances for mainly snow. At the surface, not surprisingly there is a lot of model agreement as well (boosting confidence in the forecast), with Saturday really the only day to feature modestly-breezy SOUTHERLY winds, as most days thereafter will feature prevailing northerlies or a fairly light/variable direction regime. 3) Precipitation overview (a little more on all 3 systems): - System 1 (Sun night-Mon AM): Although this does not look like a "major event" by any means, it is obviously the closest-in-time, and thus will likely need increasing forecast attention over the next 24-36 hours, especially if it ends up creating some minor wintry impacts. Various models (NAM/GFS/ECMWF) are in pretty good agreement in taking the mid level low right over the heart of our coverage area (CWA), likely intensifying somewhat into a progressive closed low as it passes. For sure, this system appears fairly moisture starved and we are not expecting significant precip amounts (likely less than 0.10"). It also appears likely that precip will start out as "regular rain" showers given above-freezing air at both the surface and 850 millibars (probably can't even rule out a few rumbles of thunder given weak elevated instability, although better chances for this would focus just east of our CWA per latest NAM). However, as colder air filters in behind a cold front late Sun night-Mon AM, chances for a brief period of light freezing rain and/or snow just cannot be ruled out. Because this system is still a 4th-5th period "problem" and modest uncertainty remains in the temperature profile details, maintained trend from previous forecaster in keeping the ever-concerning freezing rain out of the official forecast for now. However, with this system now barely creeping into the range of higher-res models (such as 18Z NAMNest), there are at least modest hints of light icing potential, so this bears watching going forward. No matter what happens, our forecast dries back out by Monday afternoon (although could see a few lingering flurries added in later forecasts). - System 2 (Tues night-Wed night): As noted above, PoPs have trended a little bit lower with this system, for Tues night because it is appears to be moving in slower (oh-so typical) and for Wed because it appears to be trending a bit south, with both the latest ECMWF/GFS tracking the main mid level low through southern KS/northern OK. That being said, this track would still bring a threat for SOME snow accumulation to especially our southern zones (mainly KS). Far too early for "official" snow amount forecasts, but 12Z ECMWF ensemble would suggest a modest (not major) snow event, perhaps ranging from around 1" in our north to around 3" in our south. Unlike system #1, precip type looks more clear-cut/uniform due to colder air at the surface and aloft (thus snow). - System 3 (Friday): Not gonna say much about a system a full week out, but with both ECMWF/GFS indicating another round of light QPF (mainly would be snow), the slight PoPs in our latest forecast for parts of our CWA appear very justified (and probably could be expanded to include the entire CWA). 4) Temperature overview: As touched on in the opening bullets, these next 7 days as a whole look to lean toward the seasonably-chilly (but not OVERLY cold) side. Confidence is high that the overall-two warmest days are right away this weekend (widespread mid-40s to low-50s and even some upper 50s far southeast on Sunday). Thereafter, once our parade of upper level waves start passing through, an overall- cooler regime settles in, with highs mainly mid-30s to mid-40s at best. In concert with our overall best snow chances, Wed features the overall-coldest highs with mid-30s most everywhere. As for overnight lows, again nothing unusual for January with most nights bottoming out in the teens or 20s. The overall mildest night looks to be Sunday night (lows a few degrees either side of freezing), which plays into the tricky precip type possibilities. -- With the main messages through the entire 7-day forecast outlined above, will conclude with shorter term details focused solely on the first 36 hours/3 forecast periods: - Current/recent weather scene as of 330 PM: Upper air and satellite data show a well amplified pattern across the CONUS, with ridging extending northward through the Rockies and troughing through the Midwest/Gulf Coast regions. This is keeping sharp north-northwesterly flow in place across the Central Plains, with a lack of notable disturbances keeping things quiet today...though there have been a few spots of flurries/light snow scattered around, mainly around/downstream of industrial locations. The day started out with widespread dense fog and low level stratus, and wasn't too big of a surprise that the fog lingered in many areas through midday. The low level stratus has been slow to diminish, but outside of a narrow swath roughly along an Ord-Kearney-Holdrege line, only cloud cover is from some upper level cirrus passing through. Surface high pressure set up through the area kept winds light/variable this morning, but winds have been gradually turning more southerly with time as that sfc high shifts east. Speeds have been peaking around 10 MPH. In general forecast highs have worked out fairly well, if anything a few spots may end up a bit cooler than expected...obs at 3 PM range from the upper 20s in far NNErn areas, with low-mid 40s in the far SW. - Tonight through Saturday night... Overall there weren't any significant changes made to the forecast for start of this weekend, which is still looking to be dry. Models continue to be in good agreement showing the main upper level ridge axis currently off to our west sliding east with time, moving through the Plains during the day on Saturday. Did increase sky cover across the entire region, as models are showing the potential for more upper level cirrus to keep skies through Saturday partly if not mostly cloudy. At the surface, the CWA looks to remain set up between the gradually departing high to our ESE and a trough axis over the High Plains...keeping winds southerly. A tightening pressure gradient could bring more breezy conditions during the day Saturday, mainly across southern and eastern areas. Speeds closer to 15 MPH and gusts closer to 20 MPH will be possible. Didn't make any notable changes to forecast highs, and confidence is not overly high with just how much of a bump up occurs. Models show a warmer airmass building into the region, but am a little concern about the impact thicker sky cover, if it pans out, would affect those temps. Even with clouds am expecting a nice increase, with current forecast highs in the 40s across most of south central NE and 50s across north central KS. && .AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Sunday) Issued at 1134 PM CST Fri Jan 13 2023 This should be a rather quiet TAF forecast period with southerly winds and broken high clouds expected throughout the period. The wind will remain light early this morning and then pick up a bit by this afternoon with some gusts to around 20 mph before becoming light again by evening. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ DISCUSSION...ADP/Pfannkuch AVIATION...Wesely