132 FXUS63 KGID 131237 AFDGID AREA FORECAST DISCUSSION National Weather Service Hastings NE 637 AM CST Sun Feb 13 2022 ...Aviation Update... .DISCUSSION...(Today through Saturday) Issued at 509 AM CST Sun Feb 13 2022 Before getting into the main topics of interest for most readers, please note that all discussion of at least near-critical fire weather conditions for both this afternoon and Tues afternoon can be found in the separate Fire Weather section at the bottom. --- Main highlights/messages of the entire 7-day forecast in chronological order: - Today-Monday: 1) With essentially zero risk of precipitation, the primary challenges these next couple days involve somewhat tricky temp forecasts (especially today), due mainly to our coverage area (CWA) residing squarely within the "battle zone" between colder air east and warmer air west. In fact today technically features a 24-degree difference in forecast highs between northeast Polk County and southwestern Furnas County! 2) Secondary concerns in the short term (especially for today) involve whether we have aimed strong enough with southwesterly breezes this afternoon (especially after seeing winds yesterday generally exceed forecast expectations by around 5 MPH). - Tuesday-Thursday: 1) For those who maybe "checked out" of monitoring the mid-week forecast over the weekend, the main message for you is that the "possible big storm" that once looked like it could produce legitimate wintry precip/travel issues across at least parts of our CWA Wed night-Thurs continues to fizzle out for us locally and look less and less impactful. In fact, at least for now, essentially all precip chances (PoPs) associated with this system have been removed by the default model blend (NBM) used to populate our mid-long term forecast. That being said, it's also still too early to declare this thing a complete dud as well, as various models suggest that later forecasts may have to re- introduce at least limited chances for flurries and/or light measurable snow to parts of the area. But as things currently stand, the trend in models that generally started 24-36 hours ago continues, as both the latest ECMWF/GFS are depicting the main southern stream wave ejecting out into the central CONUS as a quick-moving open wave, while in turn, a faster cold frontal invasion into our area Tues night-Wed severely limits the northward surge of Gulf moisture, with growing consensus that the primary swath of heavy precip will ultimately focus along a corridor from the Southern Plains toward the Great Lakes (and points east). 2) Even if precipitation in our CWA is little-to-none Wed-Thurs (as currently expected), these still look to be the crummiest days of the week (especially Wed), with high both days no better than mid 30s-low 40s and with Wed featuring moderately strong north winds (likely gusting at least 30-35 MPH). 3) Backing up to Tuesday, this is most certainly the warmest upcoming day (until at least Friday), as strengthening southerly winds ahead of the incoming system should boost highs well into the 50s across most of the CWA, with 60s more probable especially near/south of the state line (see below for fire weather concerns). That being said, forecast highs have trended down a few degrees from previous forecast, as there are still some question marks, including whether what appears to be fairly extensive high clouds could temper full heating potential to some degree. - Friday-Saturday: 1) Confidence is fairly high in the going dry forecast (especially for Saturday) as broad/low-amplitude ridging develops in the wake of the mid-week system, although the latest ECMWF suggests that a band of light snow/flurries could at least flirt with our northern zones Fri night along a cold front so this will be something to watch to see if any trends develop with it. 2) Temperature-wise, confidence is pretty high (at least by Day 6 standards) that Fri will at least be the 2nd-warmest day of the week, as we're currently calling for a big 15-20 degree jump from Thurs with highs mid 50s to around 60. With breezy westerly winds anticipated, this could unfortunately be a fire weather day as well (too soon to get into those details). As for Saturday, those already looking forward to next weekend may have already taken notice that we are calling for a pretty nice day with highs at least low-mid 50s. That being said, this is currently the most uncertain temperature forecast of the entire 7-day, as some of the latest raw model data/guidance suggests that Sat could only make it into the 40s. Obviously plenty of uncertainty being Day 7. -- With the main high points of the entire 7-day forecast period covered, will conclude by focusing more detail solely on the current and shorter-term weather situation (through the next 36 hours/3 periods): - Current/recent weather scene as of 430 AM: No big surprises overnight. As expected, parts of the area saw a brief "surge" of northwesterly winds (gusting to around 35 MPH) around midnight behind a passing cold front and associated compact surface low pressure center that passed southeastward through our area (and is now centered in far east-central KS). Following a bit of a lull in wind speeds behind this initial surge, steadier north breezes have kicked in, with most of the CWA reporting sustained 10-15 MPH/some gusts 20+ MPH. These north winds are advecting in increasingly cold air from north-to-south, with overnight lows eventually expected to range from 10-15 degrees across roughly the north half of the CWA, to more so 15-20 south half. So not as cold as yesterday morning, but still quite a change from the seasonably-mild readings last evening. Fortunately, wind speeds will slowly decline over the next several hours, likely keeping wind chill readings at least slightly above zero this morning for at least the vast majority of the CWA. One pesky thing early this AM is a fairly narrow, east-west oriented band of low clouds that is just now invading our extreme northern CWA (meanwhile the remainder of the CWA is all but pristinely clear). Although not a total surprise (some models suggesting a limited area of low clouds moving in 24 hrs ago), one of the bigger question marks of the next 4-8 hours involves how far southward into the CWA these low clouds get, and whether they could at least briefly hinder diurnal warming (more on this below). - Today: As touched on in the highlights above, today's temperature forecast features an impressive gradient and thus is certainly subject to modest "bust potential" at any given location. Wind- wise, decreasing northerly breezes this morning will give way to a brief period of very light/variable direction around mid-day as a ridge axis slides through. But then, as the afternoon wears on, south-southwesterly breezes will be on the increase, although to what degree is a bit in question. After seeing wind speeds exceed our forecast a bit yesterday (not uncommon of course), tried to account for this a little more proactively today by boosting speeds roughly 5 MPH from previous forecast most areas, now calling for mid-late afternoon speeds around 15+ MPH/gusts 20-25 MPH in roughly the northwest half of the CWA, while speeds in the southeast half should be roughly 5 MPH weaker. For sure, the degree of how quickly winds flip around to southwesterly and their strength will play a definite role in setting up today's sharp temperature gradient, as warmer air will obviously have a much easier time boosting readings over our western zones versus our east where the low-level cold air will remain entrenched the longest. Sky cover could also play a role in defining how sharp the temp gradient ultimately is, as not only might we be dealing with the aforementioned narrow stripe of low clouds (currently expected to settle into mainly parts of our Neb zones this morning in some yet-to-be seen configuration before eventually scattering out by mid-day), but also at least a modest increase in mid-high clouds invading from the northwest this afternoon (likely most abundant over the northeast half of the CWA). So all in all, various competing factors favoring colder versus warmer afternoon highs, depending on where you are. If anything, current feeling is that our going forecast may be aiming a touch too warm, but the last few days things have ended up on the slightly warmer-side of expectations so plan to run with the following: coolest highs in the mid-upper 30s along and near the Hwy 81 corridor far east ...low-mid 40s central counties near Hwy 281...upper 40s-low 50s within several far western counties and MAYBE even some upper 50s especially far western Furnas County. - This evening-overnight: In many ways, this will be somewhat of a "replay" of the current overnight, featuring yet another weak cold frontal passage thanks to a glancing blow of upper forcing from a quick-moving wave diving southeastward from northern MN toward the Midwest as the night wears on. However, unlike the ongoing night, tonight's front will be weaker, both in terms of lighter winds and less-aggressive cold air advection in its wake. Getting into specifics, the first part of the evening will feature light south-southwesterly breezes before the front passes through from north-to-south a few hours either side of midnight, but with wind speeds only 10-15 MPH/maybe gusting 20 MPH briefly. With winds easing under 10 MPH by sunrise Monday and skies largely clear, temps will drop fairly efficiently, but lows should hold up a good 5-ish degrees warmer than this morning...currently aimed into the low 20s across most of the CWA. - Monday daytime: Although there will be another northeast-to-southwest temperature gradient across the CWA, it should not be as dramatic as today. Aloft, our flow will flatten somewhat, transitioning from sharp northwesterly to more zonal (west-to-east) as the pattern starts to shift in response to the strong upstream trough arriving into the Pacific Northwest. At the surface, this will be a relatively light wind day for our area (at least the majority of it), as ridging will keep speeds near to under 10 MPH much of the day especially within the eastern half of the CWA as direction transitions from northerly, to easterly and eventually southeasterly. The strongest daytime breezes (mid-late afternoon) of 10-15 MPH/gusts around 20 MPH will occur in our far western counties (mainly Dawson/Gosper/Furnas). Sky cover wise, the day as a whole will be sunny/mostly sunny, although high clouds will increase from the north by mid-late afternoon. Getting back to temps, highs were kept similar to previous forecast, with most of the CWA aimed into the upper 40s-low 50s, but ranging from as cool as the mid 40s far north-northeast (counties such as Greeley/Nance/Polk) to as warm as the mid 50s far southwest (especially Furnas/Phillips/Rooks). && .AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Monday) Issued at 637 AM CST Sun Feb 13 2022 General overview: High confidence in VFR ceiling through the vast majority of the period and in VFR visibility/precipitation-free conditions throughout (save for maybe a few flurries under any lower clouds this AM), although there is at least a 2-hour period right away this morning that will likely feature a "sneaky" MVFR ceiling for sure at KGRI and possibly KEAR as well. Otherwise, by far the main issue through the period is winds, not so much intense speeds (albeit a little breezy especially mid-late afternoon), but more so various directional changes and also a brief period of marginal low level wind shear (LLWS) mainly at KGRI tonight. Read on for more element-specific details. Ceiling: As was previously discussed as a sneaky possibility (only subtle hints/low probability in most models/guidance), a narrow band of MVFR clouds (around 1,500 ft. AGL) has indeed sunk southward into the area and as of this writing is knocking on the doorstep of KGRI and is only about 30 miles from KEAR (and slowly approaching). Although confidence is only medium regarding how long this small- scale feature might last once it arrives, am currently aiming for only a 2-hour window that is being addressed with a TEMPO (12-14Z KGRI/14-16Z KEAR). However, there is some concern that these low clouds could get "strung out" within a ridge axis and linger a touch later into the morning especially at KEAR, so stay tuned as amendments are very possible. No matter what, confidence is at least fairly high that any MVFR concerns should abate no later than 17-18Z, with the remainder of the period featuring varying degrees of passing mid-high clouds. Winds (including LLWS): Surface winds: Sustained wind speeds will be fairly tame through the majority of the period, averaging around 10KT-or-less through most of it. The main exception will be mainly 19-00Z this afternoon, during which time breezes will kick up out of the south-southwest with sustained speeds closer to 15KT/gusts to around 20KT. Direction- wise, there will be various shifts: 1) Starting off north- northeasterly this morning...2) becoming variable especially 16-19Z within a ridge axis...3) turning south-southwesterly this afternoon into this evening...4) turning north-northwesterly again late tonight behind a weak cold front. LLWS: Although confidence is only medium regarding timing/magnitude details, have maintained a 3-hour period of LLWS at KGRI from 03-06Z as winds within roughly the lowest 1K ft. AGL look to accelerate to around 35-40KT as they swing around from southwesterly to northerly. For now have "split the difference" on the direction with westerly, and will obviously defer to later issuances to better pin down details. For now have omitted a formal LLWS mention from KEAR as the stronger shear looks to focus slightly east of there. && .FIRE WEATHER... Issued at 509 AM CST Sun Feb 13 2022 - A decent bet for near-critical fire weather conditions THIS AFTERNOON mainly in our far west-southwestern CWA: Compared to the previous forecast, this one has trended "worse" for near-critical fire weather conditions this afternoon, particularly southwest of a Lexington-Alma-Osborne KS line (roughly the southwest 1/3 of the CWA), and this concern has been introduced to our Hazardous Weather Outlook (HWO). This is due to the forecast trending toward slightly stronger winds/gusts and slightly lower relative humidity (RH)...mainly a function of raising high temps a bit. More specifically, expect much of this area to realize at least a few- hours overlap of BOTH southwest winds gusting at least 20-25 MPH and RH as low as 20-25 percent, with these conditions most favored between 2-6 PM. As is almost always the case, areas farther east- northeast into the CWA will certainly not have "zero" fire danger, especially considering that several counties will experience the same 20-25 MPH gusts as west- southwest areas will. However, these areas will hold onto higher RH due to cooler temperatures, with values likely no lower than 25-35 percent, and thus falling short of near-critical thresholds. Fortunately, outright-critical conditions that might necessitate Warning issuance are not anticipated today. - Fire weather concerns continue increasing for TUESDAY AFTERNOON mainly within our KS zones: As touched on by previous forecaster, Tuesday afternoon is likely our next-best chance for solidly near-critical (and at least limited outright-critical) conditions within our CWA, with eventual Warning issuance a possibility particularly within KS zones which look to feature the "worst" combo of gusty south winds and lowest RH. More specifically, Tuesday will be the warmest of the next several days, with highs well into the 60s near and especially south of the state line driving RH values down into the 18-25 percent range. At the same time, southerly winds will on the increase out ahead of an approaching low pressure system, with sustained speeds currently looking to average 15-25 MPH/gusts 25-35 MPH. Farther north into the majority of our Nebraska CWA, while certainly not "zero", fire weather concerns should not be quite as high given slightly cooler temps helping to keep RH values up closer to 25-30 percent. Obviously there is some uncertainty in the details with Tues afternoon still being 3 days out, but definitely a period to monitor for fire weather concerns, especially south. Please Note: NWS Hastings generally defines CRITICAL fire weather as the overlap of BOTH 20-percent-or-lower RH and sustained winds/gusts at least 20 MPH/25 MPH. NWS Hastings generally defines NEAR-CRITICAL fire weather as the overlap of BOTH 25-percent-or-lower RH and sustained winds/gusts at least 15 MPH/20 MPH. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ DISCUSSION...Pfannkuch AVIATION...Pfannkuch FIRE WEATHER...Pfannkuch