Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/26/21


Area Forecast Discussion
National Weather Service La Crosse WI
532 PM CST Thu Feb 25 2021 .SHORT TERM...(This evening through Friday) Issued at 240 PM CST Thu Feb 25 2021 Latest visible satellite imagery shows a patch of stratus deck over southeast Minnesota and north central Iowa overtopping a weak surface ridge axis...as depicted by latest 19z surface analysis...with mostly sunny skies seen elsewhere. Surface ridge will build to the east of the forecast area tonight. However...surface ridge will continue to be the dominant weather feature tonight and provide dry weather/mostly clear to partly cloudy skies across the region. Friday...as the surface ridge builds east of the forecast area...pressure gradient tightens on backside of surface ridge will allow for winds to increase across the forecast area. The 25.12z deterministic models indicate 30 to 35 knots at the top of the mixed layer near the inversion across the northwest part of the forecast area. For now...sustained wind speeds will be 10 to 20 knots and gusts 25 to 35 knots across much of the forecast area. With the increased in southerly winds aloft...warmer air advects into the region...as the 25.12z GFS/NAM indicate 925mb temps warming to minus 2 to near plus 1 degree celsius by 21z Friday. Expect high temperatures to be in the upper 30s to lower to middle 40s...if more sunshine occurs...temps could be slightly warmer. .LONG TERM...(Friday night through Thursday) Issued at 240 PM CST Thu Feb 25 2021 For the extended, we continue to see a shortwave trough Friday night with attendant light snow/wintry mix, however the system for Saturday night into Sunday morning it looking a bit more promising for more snow/wintry mix. Temperatures through the extended mostly remain at or above normal except for a cooler shot of air Sunday and Monday. A 500mb trough will be swinging through the forecast area Friday night. The 12Z NAM takes an embedded shortwave across the county warning forecast area. There is upper level jet support with a somewhat coupled jet and left front exit region lift, with positive vorticity advection. Since yesterday, the NAM has decreased liquid equivalents. The models in general are not as robust with the precipitation. The GFS/EC are a little more shifted toward the southeast half of the forecast area to receive the higher liquid equivalents/light snow/mix. The GEFs plumes are only about 0.05" with half an inch of snow. The forecast soundings show robust lift through the dendritic growth zone, however the low levels are drier to start and the lift is quick to push through. The main storm track to the south is limiting moisture from the south being advected into the system, however as the shortwave does push east, there is some limited connection. As the lift decreases, could see some patchy freezing drizzle should the low levels remain saturated with the loss of ice. Westerly flow aloft continues Saturday and the SREF stratus probabilities are around 70 percent in the morning which improve to 20 percent in the afternoon. Other hi-res models hint at these low clouds as well, however the RAP is more optimistic. This will be important should there be enough moisture for drizzle/freezing drizzle. Saturday night into Sunday is looking a lot more interesting. There is good model agreement that within the longwave flow, another shortwave will swing through the area. The NAM has it more tied to the wave coming across the Central Plains, where the GFS/EC has it tied closer to the shortwave tracking across the Northern Plains. The NAM/GFS now paint a stripe of potentially heavy snow either in MPX`s area or our county warning forecast area. The EC is more to the northeast of our area with the moderate to heavy snow. We`ll need to keep and eye on this as temperatures, strength, precipitation type, and liquid equivalent will be affected. The HREF/Forecast soundings show some freezing precipitation across parts of the forecast area. Cooling arrives later Sunday into Monday with highs from the 30s/40s dropping to the 20s/30s. The cooling is short-lived as highs return to the 30s/40s for the rest of the week Tue-Thu. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 532 PM CST Thu Feb 25 2021 VFR conditions expected through the TAF period, though will need to keep an eye on MVFR deck approaching LSE. It has been consistently scattering out through the afternoon so keeping SCT015 mention, but can`t completely rule out a brief period of BKN ceilings at the beginning of the period followed by clear skies later this evening. Always need to keep an eye on fog/low cloud potential with any snow melting, but latest guidance seems to confine this to portions of northeast Iowa into far southwest Wisconsin tonight...well south of the TAF sites. Otherwise, main concern heading into Friday will be southerly winds gusting in the 25 to 35 kt range, highest west of the Mississippi River. Winds should pick up by 14 to 15Z before tapering off right at the end of the TAF period. Looking ahead, expect some light snow to be approaching the TAF sites toward the end of the period, but model consensus holds it off until after 00Z. Will need to monitor timing trends on future issuances. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...DTJ LONG TERM...Zapotocny AVIATION...CA
Area Forecast Discussion
National Weather Service Grand Forks ND
652 PM CST Thu Feb 25 2021 .UPDATE... Issued at 651 PM CST Thu Feb 25 2021 Opaque high clouds are increasing a bit faster than forecast, but overall forecast is on track with ongoing breezy conditions continuing and mostly cloudy skies overnight. Result of the clouds/winds may be less radiational cooling and there is potential that some locations hold steady around or above freezing. Colder spots would be in the 20s, still warmer than previous nights. && .SHORT TERM...(This evening through Friday night) Issued at 306 PM CST Thu Feb 25 2021 Minimal to no impacts are expected today through tonight as the probability for widespread hazardous weather is very low (less than 10 percent). Any impacts would come from brief, scattered snow showers assoc with a cold front moving into the area Friday night into Saturday. Mid level troughing nears the area Saturday with an attendant cold front expected to move into the area from the north Friday night. Several hires deterministic models reveal CAA aloft Friday as the mid level trough axis moves over the area. This initial mid level CAA steepens mid level lapse rates some, which may introduce some condition instability for the cold front and mid level shortwave forcing to utilize. However this isn`t too much of a concern given the lack of overall moisture and forcing to work with. Ensemble guidance like ENS and GEFS along with hires guidance like NAM3K and HRRR show the majority of members keeping QPF through Friday night under 0.01 inches and largely behind the cold front, likely owing to just enough of a kick from low level CAA behind the front to introduce the mention of scattered light snow showers. Due to lack of coverage and more QPF, chances of impacts from this activity will to remain very low. Low level temps tonight through Friday remain warm ahead of the cold front. This translates to afternoons with above freezing temps into the 30s and 40s , which will likely continue to melt snowpack outside of areas that received several inches early this week. Fog concerns from snowmelt are nill due to overnight cloud cover and elevated winds overnight. Winds will remain breezy out of the southwest and west tonight and Friday, also aiding in downslope warming in typical areas like the western Valley. .LONG TERM...(Saturday through Thursday) Issued at 306 PM CST Thu Feb 25 2021 Besides a short wave bringing some chances for light snow to the area Sunday evening the extended forecast continues to look dry and above normal leading to minimal weather impacts. Saturday will see temps either steady to falling behind a cold front with flurries or light snow in the morning. Highs in the teens can be expected with similar values on Sunday. The last weak wave in the NW flow aloft will bring another round of light snow Sunday evening for locations along and north of Hwy 2. Will see the upper air pattern flattens and become more zonal thereafter. As a result temps will climb into the 30s and 40s for Monday and onward which is above normal for the first week of March when normal highs are in the upper 20s. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 532 PM CST Thu Feb 25 2021 VFR conditions should prevail through the TAF period across eastern ND and northwest MN. Southerly winds 13-18kt with gusts occasionally 20-30kt will be possible through the TAF period though better chances for gusts are during the daytime periods. A low level jet should result in a period of low level wind shear 40-45kt this evening into the early morning hours Friday. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...DJR SHORT TERM...CJ LONG TERM...JK AVIATION...DJR
Area Forecast Discussion
National Weather Service Lincoln IL
928 PM CST Thu Feb 25 2021 .SYNOPSIS... Issued at 313 PM CST Thu Feb 25 2021 High pressure will move through Illinois this evening. Patchy fog is possible overnight north of I-74. A warming trend continues through Saturday, with high temperatures in the upper 40s or low 50s on Friday, then the upper 50s on Saturday. Light rain is possible Friday night. Additional rain is possible Saturday night into Sunday, especially south of I-70. && .UPDATE... Issued at 925 PM CST Thu Feb 25 2021 Relatively benign weather conditions are expected the rest of tonight as the surface high pressure center departs to the east of Illinois. Patchy fog could affect our northern counties where snowmelt occurred recently. Light and variable winds and moisture trapped near the ground under a subsidence inversion will help support that scenario. High res guidance is pointing toward better chances of fog remaining north of Peoria, where we currently have fog in the forecast. Low temps will dip below freezing in our entire CWA by sunrise, so any fog that does develop could deposit some moisture and produce icy conditions. Frost in the ground will also give support for slippery conditions in some areas. Overall the forecast is on track, and only minor updates were needed this evening. && .SHORT TERM...(This evening through Friday) ISSUED AT 313 PM CST Thu Feb 25 2021 A 1030mb surface high pressure located over northwestern Missouri this afternoon will shift briskly to the east, translating through Illinois this evening and exiting the area overnight. In its wake, light southeasterly flow will develop. The lack of truly calm winds should be enough to limit fog potential across much of the area, except north of I-74 where the snowpack enhances low- level moisture and cooling. With overnight lows in the mid 20s, some freezing fog is possible where fog develops. On Friday, two waves of forcing will induce precipitation chances. The first comes as a shortwave moves through the ArkLaTex region during the day Friday. Most of the precipitation with this wave should be confined to far southern Illinois and further south from there, but the southernmost counties of the ILX CWA (Clay, Richland, Lawrence) could see some light precip Fri afternoon. A better chance for precip comes Fri evening, as a shortwave lifts from the central Plains into the Great Lakes. The best forcing with this wave will remain north of the ILX CWA, and moisture advection may be limited due to convection expected to be ongoing across Kentucky and Tennessee at the time, but models have been consistent in developing scattered precip across the area in the 00z-06z Saturday time frame. With surface temps in the mid 30s, no wintry precip is expected. .LONG TERM...(Friday night through Thursday) ISSUED AT 313 PM CST Thu Feb 25 2021 The warming trend will continue through Saturday, as clear skies, lack of snow cover, and winds with a southerly component boost temperatures well above average. Adjusted the Saturday highs to the 75th percentile of the blended guidance. The Sunday high temp forecast is more uncertain than Saturday, as a cold front moves through in the afternoon and clouds limit insolation. GEFS member spread increases considerably Sunday afternoon. Nudged forecast highs slightly warmer than the blended guidance in coordination with surrounding offices, but confidence in that adjustment is low. Another precip chance comes overnight Saturday into Sunday. Models have been consistent in indicating that the heaviest precip will fall over Kentucky, with a very sharp gradient in QPF amounts. The current forecast calls for a half inch of QPF in Lawrence county, with amounts in excess of 1.5 inches across Kentucky. For ILX counties south of I-70, small shifts in the storm track will result in significant changes to the amount of rainfall received with this system. Multiple additional precip chances exist into next week, but model solutions diverge after Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 553 PM CST Thu Feb 25 2021 A stream of cirrus clouds advancing across Illinois will be the primary clouds of note tonight, as high pressure advances across Illinois. The weak pressure gradient under the surface ridge axis will create light and variable wind conditions. Friday morning, after the ridge axis passes to the east of Illinois, winds will become southeast and increase into the 10-15kt range by late morning through the afternoon. RAP guidance continues to point toward locally dense fog developing north of Peoria later tonight. Forecast soundings in most other models do not support much in the way of fog at PIA, or the other I-74 TAF sites. Have stayed the course with a mention of MVFR vis for a couple hours late tonight. However, if model and observational trends continue, will likely pull that out with the 06z TAF update. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Shimon SYNOPSIS...Deubelbeiss/Erwin SHORT TERM...Deubelbeiss/Erwin LONG TERM...Deubelbeiss/Erwin AVIATION...Shimon
Area Forecast Discussion
National Weather Service Northern Indiana
614 PM EST Thu Feb 25 2021 .SYNOPSIS... Issued at 355 PM EST Thu Feb 25 2021 Partly cloudy and cold conditions are in store for tonight with some patchy fog development expected. Slightly warmer conditions are expected for Friday as clouds increase in advance of a system that will bring a brief period of rain late Friday night. The weekend will feature much warmer conditions. && .SHORT TERM...(This Evening through Friday) Issued at 355 PM EST Thu Feb 25 2021 The next sheared upper level wave will approach the Mid MS Rvr Valley later tonight with just some increasing high cloud this evening. Currently not expecting clouds to be much impediment to radiational cooling tonight as winds slacken off with approach of low level anticyclone. High clouds may also tend to thin/drop south of the area during the overnight hours. Fog forecast a bit of a challenge tonight with near term guidance differing quite a bit on the handling strength of nocturnal inversion. In leaning toward lessening clouds overnight and snowmelt possibly providing near sfc moisture source, have opted to include patchy fog mention across most of the area with greatest confidence across the northwest half of the area where snow cover is greater. Departure of low level anticyclone on Friday will allow for return warm advection Friday afternoon. Did slightly nudge up high temps for Friday with forecast soundings indicating respectable low level mixing. Cloud cover will be on the increase from south to north during the afternoon however. Warmer conditions for Friday will allow for continued melting of snowpack and continued rises on some area rivers. Some ice action has been observed on area rivers today, and going forward into the weekend will need to continue to monitor for some localized minor flooding due to runoff from snowmelt and isolated ice jam activity. && .LONG TERM...(Friday Night through Thursday) Issued at 355 PM EST Thu Feb 25 2021 The next fast moving eastern Pacific wave is still poised to affect the area Friday night. As has been the case many times over the past several weeks, this upper level short wave will tend to dampen under the influence of northern stream confluence. Nevertheless, good advective forcing will overspread the southern Great Lakes and Ohio Valley late Friday afternoon into Friday night. The best chances of precip now appear to be focused across northern third of the area, which will be in closer proximity to stronger pocket of isentropic ascent and stronger 850-700 hPa fgen forcing with tighter low-mid level thermal ribbon late Friday evening into the overnight. Strength of advective forcing still seems to support idea of mainly all rain with light precip amounts of a tenth of an inch or less given progressive nature of this forcing and rapid eastward translation of dry slot. No significant changes to the forecast post-Friday as a broader western CONUS Pacific wave allows for quick resurgence of low level thermal ridging back into the Ohio Valley and southern Great Lakes. Highs by Sunday in the mid 50s appear likely across many locations as lingering snowpack erodes. A rather complex combination of positively tilted northern stream trough and sheared southern stream forcing appears likely for Saturday night- Sunday. Positively tilted nature will keep heavier rainfall south of the local area, but will continue to carry low-mid range chance light rain PoPs across the south Saturday night into Sunday. Temps cool down for Monday to slightly below normal, but low amplitude flow downstream of western CONUS upper ridging should allow for quick moderation back to above normal by middle of next week. && .AVIATION...(For the 00Z TAFS through 00Z Friday Evening) Issued at 610 PM EST Thu Feb 25 2021 Decidedly difficult forecast with respect to BR/FZFG potential near sunup. Have sided more optimistic per latest trends of HRRR versus moister NAM boundary layer. This, in part, due to shallow trough passage with surface dewpoints on order of 5-10F lower over past 24 hours. With a few more hours of dry advection remaining and opacity of cirrus shield, at least for first part of the night, should hold br formation at bay. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SYNOPSIS...Marsili SHORT TERM...Marsili LONG TERM...Marsili AVIATION...Murphy Visit us at www.weather.gov/iwx Follow us on Facebook...Twitter...and YouTube at: www.facebook.com/NWSNorthernIndiana www.twitter.com/nwsiwx www.youtube.com/NWSNorthernIndiana
Area Forecast Discussion
National Weather Service Spokane WA
344 PM PST Thu Feb 25 2021 .SYNOPSIS... Windy weather will continue into Friday with periods of moderate to heavy mountain snow. Snow showers will also impact portions of the Palouse and Camas Prairie. Quieter weather is expected this weekend then more light mountain snow is possible Sunday into Monday. && .DISCUSSION... Remainder of the afternoon and this evening: Cold upper-level trough with 500mb temperatures around -32C coupled with afternoon sunshine will create steep lapse rates across the region leading to convective hit or miss showers. A majority of these showers will be chaotic and short-lived however meso-scale models continue to show convergence zones extending well east of the Cascades (typically tied to the larger volcanoes) resulting in more organized bands of east to west showers. HRRR even showing a few low 40 dbZ echoes with this activity which could extend anywhere from around Plain-Wenatchee to Pullman-Lewiston. This will likely fall as a mix of rain, snow, and graupel but with gusty winds pushing temperatures into the 40s, it will be difficult for this to impact travel. As you go into the rising terrain of the Idaho Panhandle, temperatures are cooler and we may see snow start to stick to roads, especially after sunset. Snow shower activity will be more concentrated on the mountains due to the strong west flow with an additional 1-2 feet of snow possible at Stevens Pass and 4 to 8 inches for Lookout Pass. Winds will remain breezy across the region with gusts of 25-35 mph common across our wind prone Basin, Palouse, and West Plains. Friday: A second shortwave will drop into the region early Friday morning. Forcing along this shortwave will be quite strong with Div Q values on the order of -20 to -30. This forcing along with the aforementioned steep lapse rates will likely lead to bands of moderate precipitation. Exact placement of these bands could change but general consensus for the last few model runs were from southern Shoshone County...across the Palouse, and into the Blue Mountains. Northwest flow feeding into this area will also enhance lift for the Blue Mountains and Camas Prairie. Consequently, periods of light to moderate snow will be possible early Friday morning just prior to sunrise before ending in the afternoon. The challenge with this event will be temperatures. Gusty winds have pushed temperatures near 40F around Pullman and mid 30s in the Idaho Palouse. With the winds expected to blow through the night, there is modest uncertainty if these locations will cool enough to efficiently accumulate snow. Perhaps the showers this evening will cool the environment. Confidence is higher for the Camas Prairie where temperatures at this hour are in the mid 30s and thinking the Lewiston Area will certainty remain too warm. With this being said, we have issued snow advisories for the Camas Prairie. Will have the evening shift monitor temperature trends for the Palouse zones and if these locations can cool into the mid 30s before midnight, likely expand the advisories for locations like Pullman, Uniontown, Troy, and Moscow where another 2-4" will be possible. Snow showers will continue in these areas into Friday afternoon but the forcing will be shifting south and intensities will become lighter and largely driven by afternoon heating and upsloping flow. The late February sun angle will also make it challenging for snow to accumulate on roads. One impact that could be problematic on the Camas Prairie, Blue Mountains, and Central Panhandle Mountains will be blowing and drifting snow. Steady winds of 15-25 mph from the west could create heavy drifting for several hours Friday morning after snow falls and before the sun crusts the snow. Winds: Southwest winds remain breezy from the East Slopes of the Cascades, across the Basin, and into the Palouse and West Plains today. We saw a quick punch of advisory winds (30 G 45 mph) with the cold front passage earlier this morning and now the winds are being driven by a PDX-GPI pressure gradient of 13 mb...which is expected to increase closer to 17-18mb. Gusts of 30-38 mph have been common the last few hours and could approach 40-45 mph before sunset. The winds will remain breezy into the early evening then begin to come down, especially across the Upper Columbia Basin between Wilbur and Spokane. May be able to remove these areas from the advisory if this comes to fruition. A second surge of winds will come from the west and northwest Friday morning and afternoon with the passage of the next shortwave. This push of winds will mainly focus from the East Slopes to Waterville Plateau to Tri- Cities and into the foothills of the Blue Mountains and L-C Valley. Sustained winds of 20-30 mph coupled with gusts 40-50 mph will be a concern. Minor tree damage and challenging cross winds will be a concern. Stronger winds gusting near 60 mph or stronger are expected on the ridgetops of the Cascades. There is little evidence in the hi-res models that these winds will descend into the valleys like Leavenworth, and Plain but something we will need to monitor. /sb Saturday: Light mountain snowfall may linger into the morning, and morning fog/stratus is still a possibility. Northerly flow is expected to funnel down the Okanogan valley causing somewhat breezy winds into the Columbia Basin. Winds are expected to calm Saturday evening. Relatively clear skies for much of the region, though not as much of a break from cloud cover is expected for the mountains. Forecast uncertainty for next week remains significant. This is due to a split flow pattern aloft which has resulted in very different model solutions. Additionally, for the rest of the period, every morning currently holds the potential of fog/low stratus development according to weather models, and actual development depends largely on which routes next week`s systems take. Sunday: A weak system will drop down from the North and likely bring light snow to the Cascades and Idaho Panhandle mountains at some point Sunday. Monday: Not much has changed for the low confidence Monday forecast. New model runs have not brought much clarity; they continue to have large differences and have not been trending toward agreement as of yet. Currently, there is the possibility of light lowland precip, light to moderate mountain snow, breezy winds, and a decent cold frontal passage. This is generally what the European model suite has been suggesting. Lowland precip type would still weigh heavily on the actual arrival time of the system. On the other hand, the GFS suggests only some flurries and sprinkles for the northern mountains and valleys on Monday. Will continue to examine new model runs... Tuesday and Wednesday: More flip-a-coin type scenarios are possible. Fortunately, major impacts are not currently expected. Tuesday model solutions are leaning towards mainly mountain snow, if anything. Wednesday is similar to Monday in that there may be widespread lowland precipitation or nothing at all, even for the mountains. RC && .AVIATION... 00Z TAFS: Bands of convective showers of rain, snow, and graupel will impact much of Eastern WA and North Idaho through 03z. Local conditions under the heaviest showers could fall near marginal VFR or lower. A few stray lightning strikes will also be possible from Spokane to Lewiston westward toward Moses Lake however confidence is too low to include in the forecast at this point and any storms will be very brief. Winds will be the other aviation concern. Gusty west to southwest winds of 30-40 mph will be common. Winds could increase further closer to 50 mph Fri AM around Wenatchee, Moses Lake, Waterville, and along the East Slopes of the Cascades. We are also looking at another wave bringing clusters of snow showers to SE WA and the lower ID Panhandle overnight early Friday morning roughly 09-13z. A few inches of accumulation will be possible at Pullman, Winchester, and Deary. Lewiston could also see a mix of rain/snow with lower confidence for any accumulation. /sb && .PRELIMINARY POINT TEMPS/POPS... Spokane 31 42 24 39 26 41 / 10 20 10 10 10 10 Coeur d`Alene 30 39 21 38 22 39 / 50 70 20 10 10 10 Pullman 30 36 24 35 22 37 / 80 90 40 20 10 10 Lewiston 36 43 29 42 27 43 / 20 60 40 20 0 10 Colville 28 42 21 40 21 41 / 20 30 10 0 10 10 Sandpoint 31 39 22 36 23 37 / 70 60 20 10 10 20 Kellogg 29 35 22 34 22 36 / 80 80 30 30 10 30 Moses Lake 34 49 28 48 30 51 / 10 0 0 0 10 0 Wenatchee 32 43 27 44 30 47 / 30 20 10 0 10 0 Omak 29 44 24 43 25 43 / 10 0 10 0 10 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Winter Weather Advisory until 4 PM PST Friday for Central Panhandle Mountains. Winter Weather Advisory from 1 AM to noon PST Friday for Lewis and Southern Nez Perce Counties. WA...Winter Storm Warning until 10 PM PST Friday for East Slopes Northern Cascades. Wind Advisory until 4 PM PST Friday for Lower Garfield and Asotin Counties-Moses Lake Area-Spokane Area-Upper Columbia Basin-Washington Palouse-Waterville Plateau-Wenatchee Area. Winter Storm Warning until 10 AM PST Saturday for Northeast Blue Mountains. && $$