Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/19/19


Area Forecast Discussion
National Weather Service La Crosse WI
454 PM CST Wed Dec 18 2019 .SHORT TERM...(This evening through Thursday) Issued at 237 PM CST Wed Dec 18 2019 Fairly quiet weather is expected in the short term, with the main forecasting challenge being cloud potential overnight. Afternoon surface analysis showed a ridge of high pressure centered over Wisconsin. Temperatures were below normal, with many areas in the single digits or low teens. Mid to high level clouds were streaming southeastward across the area, with clearing noted across western portions of the area. As the high continues to slide east tonight, winds will turn southerly with warm air advection kicking in. This will likely help to limit how far temperatures fall this evening, even as clearing works east. While the overall atmospheric profile looks pretty dry still this afternoon, some guidance is hinting at enough moistening in a narrow chunk of the low levels late tonight/early Thursday morning to produce low clouds or even patchy fog. With dry air in place and winds staying up for a portion of the night, confidence is not high in the extent of clouds or whether patchy fog will occur, but it will have to be monitored. Thursday looks much warmer than today, as cold air aloft scoots east of the area allowing highs to reach the 20s and 30s. Other than the aforementioned possibility of morning clouds, there could be some partly cloudy skies/sunshine for a while Thursday under mid-level ridging before high clouds begin to fill back in. .LONG TERM...(Thursday night through Wednesday) Issued at 237 PM CST Wed Dec 18 2019 Mid-level ridge moves east of the region Thu N/Fri, pushed off by fairly strong pv-anomaly passing through the Northern Plains. NAM/GFS/ECMWF/GEM all showing surface cyclogenesis over MN by Friday morning with warm air advection/isentropic upglide taking place across our area. This system gets quickly shunted northeast of the area by Friday evening. Could see a brief bout of freezing drizzle in the morning mainly north of our forecast area where better saturation from forcing takes place. For now, will keep a dry forecast going but will definitely keep a close eye on how far south/possibly into our area this freezing potential gets. Otherwise, plan on highs Friday pushing well into the 30s, maybe even a few lower 40s across portions of far northeast IA/southwest WI in snow-free areas. The weekend into early next week looks quiet and mild as mid-level ridging dominates the central CONUS. Temperatures look to be some 10 degrees above normal with highs in the 30s/40s and lows in the mid 20s/lower 30s. Deepening southwest flow aloft/digging trough out west will start sending moisture/chance of precipitation toward the area Tuesday night/Christmas Day. ECMWF would keep our area dry through Christmas with ridging holding in place whereas the GFS would bring an area low pressure/chance of rain through the region. Will go with model consensus for now which yields low-end chances. Otherwise, remaining above normal temperature-wise with highs Christmas Day in the 30s/lower 40s. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 454 PM CST Wed Dec 18 2019 Southwest low level flow was developing across the area as an area of high pressure was moving into the Ohio River Valley. Both the 18.18Z NAM and 18.21Z RAP show an area of higher relative humidity at 925 mb over western Minnesota and Iowa and move this east/northeast while expanding it through the overnight hours as it moves across the local area. Right now, there are no clouds associated with this moisture and the suggestion in the hi-res meso-models and forecast soundings is that clouds will form in this moisture field overnight resulting in a MVFR ceiling. However, confidence is not high in this scenario and will continue the trend from the previous forecast of showing some scattered lower clouds but no ceiling. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Lee LONG TERM...DAS AVIATION...04
Area Forecast Discussion
National Weather Service North Platte NE
540 PM CST Wed Dec 18 2019 .SHORT TERM...(This evening through Thursday night) Issued at 248 PM CST Wed Dec 18 2019 Near term concerns revolve around temperatures the next few days. Otherwise, quiet weather is expected from now through the weekend as the area falls under the influence of shortwave ridging in a split- flow pattern before transitioning to high-amplitude northerly flow for the start of the weekend as additional ridging approaches from the west. Ridging overhead at the present moment is centered over the Texas Panhandle and will be kicked out by an approaching shortwave trough currently moving onshore southern California with it moving across the Rockies and onto the southern Plains late tomorrow. Ridge axis will pass late tonight into early Thursday with low-level winds backing to the southwest in response. Winds never really go light tonight with h85 flow increase from midnight to sunrise on Thursday, limiting any concerns for fog Thursday morning. Given recent snowmelt and forecast lows, however, cannot rule out some patchy fog developing for portions of western Nebraska. Favored locations would be low-lying areas shielded from winds like river valleys. Crossover temperatures further support this thought with some hi-res guidance such as the NAM and NAM Nest painting lowered visibilities across the area but the RAP and HRRR aren`t overly optimistic and the SREF only shows 40% or less probabilities. Will leave out of the forecast for now but pass on the subsequent shifts to monitor overnight. Have had a stretch of mornings where low temperature forecasts have not been cold enough and given non-zero snow depth across much of the area have lower temperatures tonight as a result with values generally in the teens and low teens for some. Thursday is a tricky forecast regarding high temperatures. Will see the day start with southerly-southwesterly flow in the low-levels and similar if not slightly warmer h85 temperatures. In addition, a weak surface cool front associated with northern stream system will move into the area and push through during peak heating of the day. This may help lead to a degree or two of warming thanks to compressional heating but lingering snow and a slow rise to temperatures seen Wednesday makes the temperature forecast medium confidence at best. Thinking tomorrow is a good day for beating our stretch of cooler than expected temperatures and so have increased daytime highs slightly with values generally in the 40s to near 50 across the far southern tier of counties. Winds will shift from southwest to west-northwest during the daytime as the frontal boundary pushes through but fropa is expected to be dry as little in the way of appreciable moisture is available. Temperatures Thursday night will be similar if not slightly warmer than Wednesday night as values fall into the teens to low 20s. .LONG TERM...(Friday through Wednesday) Issued at 248 PM CST Wed Dec 18 2019 Beginning 12z Friday. Little in the way of sensible weather is expected Friday through the start of the holiday week. Mid-level height rises begin during the daytime on Friday and persist through the weekend right into late Sunday night. Dry conditions will continue with temperatures climbing to well-above normal values for late December. Normal highs for this time of year are generally in the mid to upper 30s with forecast highs generally reaching the 50s for all locations. Some NWP guidance even hints at locations hitting 60+ degrees at least Sunday if not Saturday and Sunday, but will hold off on forecasting near record territory for the time being but look for these temperatures to increase should there be any trend. Thereafter guidance begins to diverge and the forecast becomes more murky. Modest height falls will begin by Monday locally, however, without any large impulse of energy/lift we should expect to see dry conditions continue Monday and right on into Christmas Eve on Tuesday. This will be about as favorable a scenario for little if any travel impacts prior to the holiday itself we`ve seen in recent years but attention turns quickly to what various ensemble solutions and global deterministic models have hinted at for the past 24-48 hours. A deep trough will move onshore southern California late Tuesday night and get caught up in the southwest flow which will steer it onto the central Plains sometime in the late Tuesday into Wednesday timeframe. This trough will look to take on more of a negative tilt open wave as it passes through our region. Model discrepancies abound which is putting it modestly but general thinking is that precipitation chances will be on the increase towards mid-week and Christmas Day. These aforementioned discrepancies greatly limit confidence in precipitation type and timing and as a result, what impacts may occur. Consider this forecast very low confidence at the present time but just know that those with travel plans for the Holiday anywhere in the Central Plains post-Christmas will need to monitor the forecast between now and then to potentially adjust plans as necessary. Worth mentioning again this is a low confidence forecast and impacts to the local area are far from guaranteed so stay tuned. Beyond that, the pattern looks to remain fairly active as additional troughing in the west will allow more disturbances move into the area and bring more shots at precipitation. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 538 PM CST Wed Dec 18 2019 Over the next 24 hours, scattered high clouds will track across western and north central Nebraska with ceilings around 25000 FT AGL. Ceilings will fall to 20000 FT AGL Thursday afternoon. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Jurgensen LONG TERM...Jurgensen AVIATION...Buttler
Area Forecast Discussion
National Weather Service Paducah KY
111 PM CST Wed Dec 18 2019 .SHORT TERM...(Tonight through Friday night) Issued at 110 PM CST Wed Dec 18 2019 Low clouds across the area should diminish in coverage through the afternoon and possibly early evening (for west KY). We had to rely fairly heavily on prior runs of the HRRR and Daytime Snow/Fog GOES- 16 imagery to time the slow decrease in clouds. At the surface high pressure will move across the region tonight, and set up to our east Thursday and Friday, allowing for modest return flow. NW flow aloft will be replaced by s/wv ridge that will move slowly east over the area, followed by SW flow ahead of southern Plains low Friday. With a generally dry airmass in place, no precipitation is anticipated. Just an increase in clouds by Friday. Temperatures tonight should fall quickly once the clouds are gone early on. Temperatures will moderate into the mid to upper 40s Thursday and Friday, with lows in the upper 20s to lower 30s. .LONG TERM...(Saturday through Wednesday) Issued at 110 PM CST Wed Dec 18 2019 From this weekend through Christmas Eve or so, the PAH forecast area will be more or less under a ridge axis of high surface pressure, roughly oriented southwest-northeast, which should keep the surface winds in check and make it more difficult for measurable pcpn to occur. Meanwhile, slack mid level flow in a larger scale split pattern will initially prevail over us well to the north of a low pressure system moving through the Gulf Coast states. There continues to be the occasional hint that some measurable pcpn associated with the system may creep just across the TN state line over the weekend, whether it be the 12Z deterministic ECMWF or a few GEFS members, but it is believed that model consensus continues to be strong enough for a dry forecast over the weekend at this time. Whatever cloudiness occurs should be most prevalent in the Pennyrile region of KY. By Mon, strong mid level ridging induced by a strongly amplified shortwave in the western CONUS is forecast to dominate the country`s midsection. These height rises should translate to afternoon surface temps in the 50s for us, perhaps attaining 60 degrees near the TN state line. Lows are forecast to be above freezing everywhere on Day 6 and Day 7. Just beyond the Day 7 period, deep moist southwesterly flow may bring some showers back to the forecast, but for now, Christmas Day (Wed) looks dry, mostly cloudy, and unseasonably warm. && .AVIATION... Issued at 1119 AM CST Wed Dec 18 2019 Stratus lingers across much of the area at midday. Clearing was working into southern IL and will make into southwest IN through mid afternoon. It may take until the end of the day to shrink in coverage over west KY into SEMO. Once the clouds go away, should be mostly clear through Thursday. Light northwest winds will become variable overnight, then south 5 to 10 kts Thursday. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ SHORT TERM...08 LONG TERM...DB AVIATION...08
Area Forecast Discussion
National Weather Service Pocatello ID
145 PM MST Wed Dec 18 2019 .SHORT TERM...Tonight through Saturday. Early afternoon satellite imagery was showing a weak upper trough lifting NE across the region this afternoon with very little in the way of sensible weather impacts noted across SE Idaho. Further upstream, a very moist west flow/Atmospheric River was advancing east through the Pacific toward the Oregon/Washington coast. Numerical models continue to show the brunt of the Atmospheric River impacting Washington, Oregon and the Idaho panhandle and with each successive model run showing less and less impact on the CNTRL mountains. Storm total accumulations for Thursday and Friday currently fall below advisory levels for the Sun Valley and Sawtooth region and thus no highlights are planned for this forecast cycle. For Friday night into Saturday, a ridge expands northward through Wyoming into ERN Montana as the next Pacific trough takes shape off the NW coast with mostly dry conditions anticipated across SE Idaho. The main moisture plume extends from NRN California north-northwestward ahead of the trough into the Canadian Rockies, however there may be enough advance moisture to squeeze out a shower or two over the CNTRL mountains. For now the National Blend of Models was dry and we have trended in that direction until we see a change. With the onset of unsettled conditions over the next several days, temperatures are expected to warm through climatological norms and the going forecast reflects this current thinking. Huston .LONG TERM...SATURDAY NIGHT THROUGH CHRISTMAS DAY. Strong consensus continues among the long-range models that SE Idaho will reside on the western edge of (yet still under the influence of) a longwave ridge of high pressure through Sun, with dry conditions. With a SW flow throughout the atmospheric column ahead of our next trough, temps will moderate into the upper 30s/low 40s, about 10-15 degrees above climatological norms for this time of year. Forecast confidence remains high for Sun. The ridge is still forecast to more definitively move east starting Mon, allowing longwave troughing to become established across much of the western half of the US, signaling a return to a more active weather pattern for our region. Indeed we waste no time, as a shortwave ejects NE across the northern Rockies Mon/Mon night, while a stronger shortwave or even weak closed low pressure center works SE down the Pacific coast, rounds the base of the trough across southern CA, and then tracks NE across NV/UT/WY Tues into Christmas Day. The GFS/ECMWF/Canadian all differ a bit with respect to strength of both features, and how to handle potential messy interactions between them in the form of timing and placement of various rounds of precip. Thus, confidence in the details remains quite low from Mon into Christmas Day. Overall trends over these 3 days favor temps cooling a few degrees each day back closer to seasonal norms (highs topping out in the 30s by Christmas Day), and at least a chance of (largely snow) showers each day just about anywhere, highest as usual in the mntns vs. the Snake Plain. We took NBM guidance for PoPs, increased them by about 5-7%, and broadbrushed them a bit more from Mon eve onward to account for the low confidence/model differences and ensure we keep a mention of snow showers in the forecast. As far as SE Idaho seeing a white Christmas, overall chances aren`t bad at all with the cooling temps, active large-scale pattern, and a couple systems/features to play with. Stay tuned and jolly! - KSmith && .AVIATION...Quiet and low-impact conditions for aviation are expected for the next 24 hours or so, with VFR cigs/vsbys and high forecast confidence through tonight. Some BKN to almost OVC high- level cloud cover continues to drift across the region this afternoon. This should thin out a bit tonight, with the focus then shifting to increasing mid-level clouds working in from the west as a dry shortwave trough works across the region, especially after 10- 13z or so depending on the terminal. We massaged this into the TAFs as a BKN deck using mostly NAM time-heights and HRRR guidance...the 12z MAV/MET suite seems perhaps a bit too aggressive (shoving decks down below VFR tomorrow for some sites) compared to the rest of our preferred guidance, so we avoided that for now. For several days now models have also trended a little drier for our area with regards to the atmospheric river of moisture forecast to hit the Central Idaho Mountains, with the bulk of that flow perhaps now directed further north toward the panhandle of Idaho. We still can`t rule out a few snow showers getting into our CWA Thurs afternoon through Fri afternoon (mostly just beyond the end of the current 18z TAF period), but the activity may be fairly hit-and-miss, and confidence is low on impacts to any given terminal. For now, we initiate VCSH at KSUN after 10z tonight and will monitor forecast trends especially among the high-res guidance, but even here there may not be a ton of activity making into the Wood River Valley. Still, cigs could drop into MVFR starting Thurs afternoon. - KSmith && .PIH WATCHES/WARNINGS/ADVISORIES...None. && $$