Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/25/21

Area Forecast Discussion
National Weather Service Denver/Boulder CO
832 PM MST Sun Jan 24 2021 .UPDATE... Issued at 819 PM MST Sun Jan 24 2021 Forecast appears to be on track this evening. Some weak showers have drifted off the foothills earlier this evening but dissipated as they moved into the Denver area. Additional showers upstream as they next system moves toward the OK/TX panhandles tonight into Monday morning. Generally light snowfall expected overnight with the best chance of accumulating snow over the plains of ecentral and northeast CO late tonight into Monday morning. Still do not expect much impact from this system in metro Denver at this time, with isolated to scattered showers overnight. && .SHORT TERM...(This evening through Monday) Issued at 229 PM MST Sun Jan 24 2021 Satellite and radar showing shallow convective showers spreading northeast across the high country, and some virga across the plains. One weak wave has already moved through Summit County, but expect a couple more waves late this afternoon into early evening per upstream observations. Accumulations of an inch or two will be possible with these in the Summit/Park County areas. Some of the showers will be spreading down through the foothills, and we`re still seeing a large variation in potential for showers stretching across the plains. At this point, think the convective allowing models (CAMs) like the HRRR are still overdone given the dry downslope layer just above the boundary layer, while the global models look underdone. The 12Z NAMNEST looked most realistic with scattered showers but not much accumulation across the plains, although the latest NAMNEST was more bullish. In any case, it may end up like last night where a couple spots in the lower elevations get a quick half inch of snow, but most places would only see a dusting or brief flurries. Later tonight, we`ll start dealing with the effects of the main weather system ejecting out of the Desert Southwest. QG lift will be increasing with the best lift organizing over the eastern plains. There has been slight trends to the northwest and a stronger, earlier development. That will be favorable for more snow across the plains late tonight and Monday morning. Right now, it looks like widespread snow will stay just east and southeast of Denver, but place like Limon and Akron to around Julesburg should be able to pick up a couple inches of snow from this first wave. Snow will then decrease tomorrow afternoon, except in the mountains where another round of showers develops with sufficient moisture and instability. .LONG TERM...(Monday night through Sunday) Issued at 229 PM MST Sun Jan 24 2021 Our continued long duration light snowfall will be ongoing at the start of the forecast period. Initially, there should be two areas of more widespread snow - over our far northeast plains, and across most of the Front Range/Foothills on Monday night. There`s not a ton of synoptic scale lift overnight, though there is enough of a weak upslope component and steep enough lapse rates to promote at least scattered snow showers through the night. Accumulations overnight will generally be 1-3 inches in the aforementioned locations, with little to no snowfall between I-25 and a line from roughly Sterling to Limon. A second shortwave will swing across the state Tuesday, bringing another round of widespread light snowfall to the area. Most guidance is in good agreement showing increasing QG ascent and shallow upslope flow through the day. Best timing seems to be late morning to late afternoon for the plains, with another inch or two likely, and the best chance of accumulating snow for metro Denver and Fort Collins. Snow departs the area from west to east overnight as moisture and lift rapidly shift away from the state. The only exception to this may be over the Park Range overnight where shallow moist layer and weak upslope flow over a deep layer of steep lapse rates could allow for snow showers to continue through early Wednesday morning. By Wednesday, ridging begins to take over and a warmer and drier trend starts. There`s still some cold air overhead on Wednesday, and combined with a fresh (but shallow) snowpack, we probably won`t see highs any warmer than 40F. Temperatures look much warmer on Thursday and Friday, with highs in the low to upper 50s over the plains. Another trough finally begins to impact the weather by next weekend, though for now it looks like most of the impacts would be limited to the higher terrain. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 819 PM MST Sun Jan 24 2021 Ceilings are expected to lower again through the course of this evening. Isolated light snow showers will be possible this evening but a trace at best. Ceiling heights are expected to lower into the 1000-1500 foot range 05Z-09Z, but timing and certainty of this is difficult as it revolves around evolution of the Denver Cyclone. Latest satellite this evening show these low clouds east of FNL and around Limon. The cyclone should in effect pull low clouds and stratus back southward across the Denver area TAF sites. Later tonight, there is a chance of light snow redeveloping toward 12Z as a storm system begins to organize to our southeast. At this time, only expect a dusting of light snow possible once again through Monday morning as the bulk of the snow should stay over the eastern plains of Colorado. Expect some lifting and breaking of the stratus deck toward 18Z Monday. Lowering ceilings and some light snow will return to the terminals Monday evening. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Cooper SHORT TERM...Barjenbruch LONG TERM...Hiris AVIATION...Cooper
Area Forecast Discussion
National Weather Service Grand Forks ND
900 PM CST Sun Jan 24 2021 .UPDATE... Issued at 850 PM CST Sun Jan 24 2021 Light snow continues to slowly expand overcoming dry northeasterly air. The strongest radar returns and lowest visibility this evening have been in the Harvey to Carrington area just southwest of the FA. Expecting that area of moderate snowfall to slowly work to the east northeast into southern Devils Lake basin. Still expecting 1 to 3 inches in the southern Devils Lake basin with under an inch in the Red River valley. UPDATE Issued at 621 PM CST Sun Jan 24 2021 Light snow beginning to develop as expected across central ND and into the western portions of the Devils Lake basin. Accumulations will depend on saturation with dry easterly flow slowing the eastward progression of the snow area this evening. HRRR solns continue to keep much of the valley dry from this easterly flow whereas the RAP continues to bring about an inch to GF. Will need to monitor radar trends and the CAMs this evening to refine PoPs and snow amount for the overnight. && .SHORT TERM...(This evening through Monday night) Issued at 237 PM CST Sun Jan 24 2021 Main focus within the short term will be snow tonight into Monday AM within Devils Lake basin into northern/central RRV. This may impact the Monday morning commute. Wind chills dip below -25 F for international border counties, hence a Wind Chill Advisory has been issued. Forcing mechanisms that will be responsible for tonight`s snowfall are manifesting themselves nicely on satellite, radar, and objective mesoanalysis. Synoptic lift assoc with a subtle mid level wave driven by entrance region jet dynamics is shown through textured, colder cloud tops in western ND via satellite. With the jet progressing east, synoptic lift will also trek east into eastern ND later tonight. Ahead of the wave, low level WAA and increasing theta-e (also apparent on satellite through northward moving stratus out of SD) is lending to isentropic lift already apparent over central ND through radar returns. This initial snow is battling dry near surface layer as apparent through virga on area webcams, but should help pave the way of saturation for when better upper support moves over the area. As the wave nears, snow production is expected to be near the head of a weak but advertised H8 LLJ nosing into the Devils Lake basin by 06 UTC. This will help focus lift in the H8-H7, feeding a small area and progressive area of fgen. Additionally, forecast soundings suggest deep saturation within the DGZ between 100-200 mb collocated with maximum lift. This lends confidence in high snow ratios greater than 20:1, esp with a lack of wind shear expected. While QPF amounts will be light, this efficient snow production should lead to a fluffy 1-3 inches of snow near the Devils Lake basin. Lesser amounts are expected into the central and northern RRV as synoptic lift decreases and the H8 jet dissipates. Most snowfall should fall within the 00 - 12 UTC timeframe Sunday night into early Monday morning. Impacts to travel may be possible through moderate snowfall rates leading to reduced visibility to a half mile at times, as well as slick travel conditions from accumulating snow. This is especially true within the Devils Lake basin during the Monday morning commute. Winds will be relatively light keeping drifting/blowing snow concerns low. While accumulating snow is expected to end around 12 UTC, lingering flurries will be possible for northern counties throughout the day tomorrow. Cold temps already in place near the international border will combine with just enough of a light wind to present wind chill values near or below -25 F. Thus a wind chill advisory has been issued for these counties starting midnight tonight lasting through Monday morning. Cold conditions continue into Monday night. May need to re- evaluate for another night of wind chill headlines for northern counties Monday night into Tuesday morning. .LONG TERM...(Tuesday through Sunday) Issued at 237 PM CST Sun Jan 24 2021 The probability for weather related impacts for Tuesday through Thursday will be minimal. Temperatures will struggle to climb out of the single digits Tuesday and Wednesday, with low temperatures in the single digits to teens below zero. Heading into Thursday, temperatures moderate slightly, with near average teens for highs and lows in the single digits either side of zero. For Friday and the weekend, unsettled weather is possible, with a chance for snow; although much uncertainty surrounds the exact scenario, impacts are possible through the weekend. Low H5 heights and 850 mb temperatures in the -22C to -12C range are expected Tuesday and Wednesday. The biggest challenge will be the low temperature forecast, as cloud cover will impact radiative cooling potential. Overall, lows will fall into the -14 to -3 degree range across the area. The lower H5 heights push to the east heading into Thursday, with somewhat strong shortwave ridging filling into the region late in the day. Some temperature rebound is possible; however, with a strong southwest to northeast jet, situated across the Central Plains, WAA will be minimal. This translates to highs generally in the teens to middle 20s with split flow across the Northern Plains and Upper Midwest. As the H5 split flow pushes east, we see the upper flow turn more southwesterly, allowing temperatures to rebound into the middle to upper 20s Friday and Saturday. Moisture advection will also take place, with precipitation chances increasing ahead of an upper trough, that will move southeastward out of Alberta Saturday afternoon and evening. As previously mentioned, confidence in this solution remains low; however, there is growing ensemble support for an increased chance for snow Saturday into Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 621 PM CST Sun Jan 24 2021 FAR and BJI are expected to remain VFR for the period with light snow and MVFR CIGs expected at DVL and GFK tonight into tomorrow. TVF may see MVFR CIGs and light snow though this location is much more uncertain as drier easterly winds create less confidence of snow reaching that far east. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...Wind Chill Advisory from midnight tonight to noon CST Monday for NDZ006>008-015-054. MN...Wind Chill Advisory from midnight tonight to noon CST Monday for MNZ004-005. $$ UPDATE...JK SHORT TERM...CJ LONG TERM...Lynch AVIATION...JK
National Weather Service Sioux Falls SD
929 PM CST Sun Jan 24 2021 .UPDATE... Issued at 922 PM CST Sun Jan 24 2021 Challenging forecast for the significant winter storm expected across portions of Nebraska and Iowa Monday and Monday night. Influx of dry air on the northern edge is expected to produce a very sharp gradient in snowfall totals. Previous guidance suggested this cutoff would largely be south of our forecast area, however a slight northward trend in the 18z guidance has continued/maintained in the 00z guidance and leaves some doubt that the Hwy 20 corridor will be spared impactful snowfall. 00z HRRR and WRFs still more robust with this dry push and largely reflect the previous forecast. 00z NAM/NAM Nest and 21z RAP/SREF are much more concerning bringing at least Advisory level snow into the Hwy 20 corridor in Iowa. There is also a notable trend upward in the SREF mean plume diagram for Sioux City over the last several runs. Still believe a pronounced push of dry air will keep the northern edge of the snowfall in check but confidence is far lower than it was a day or two ago. Have increased POPs and QPF somewhat but will wait for the full suite of 00z guidance to come in to make any whole-sale changes (if even necessary). && .SHORT TERM...(This Evening through Monday) Issued at 221 PM CST Sun Jan 24 2021 Stratus will be the main concern for the next couple of days as a very strong system passes to the south. Drier air still wrapped in place across the area and will play a roll in stratus expectations through tomorrow. Going into tonight expect the stratus near the Missouri River into northwest IA to expand a bit north as low pressure develops to the south. By late morning into the afternoon low pressure will move to the southeast of the area and start to advect this dry air more southwest. This should really eat away at the stratus and bring improving sky conditions to many locations. May even see some slightly quicker drying and slightly stronger winds just west of the Buffalo Ridge where a bit of a downslope flow develops. As for snowfall the chances are pretty much confined to locations along and south of a Sioux City to Sioux Rapids line. The GFS is a little farther north with saturation and lift compared to the Nam but neither bring too much activity into the area. Overall a chance for an inch or so along and south of that line. Low temperatures will be tricky with clear skies in some locations before cloud cover increases. Will go towards the 75th to 90th percentile where clouds are expected to remain through the night and colder in southwest MN where clouds should be last to develop. Highs on Monday pretty cold, especially with a breezy east and northeast wind, only climbing into the teens to lower 20s, maybe a little warmer under the cloud cover to the south. .LONG TERM...(Monday Night through Sunday) Issued at 221 PM CST Sun Jan 24 2021 High pressure remains well to the north Monday night into Tuesday so while temperatures will be on the cold side, not as cold as the might be if the high pressure was farther south. Lows near zero along highway 14 to around 10 above closer to the MO River into northwest IA.Highs only in the teens to around 20 on Tuesday with cold air locked in place. The next system of interest will move into the area on Tuesday night but for now not looking like much of an issue. Any lift that can generate some snow will be fighting through some lower level dry air. So will keep the chance for snow at slight and chance. After this system passes through upper level ridging will build into the area through the end of the week. This will bring temperatures back to above normal Thursday into the weekend. Some hints of a system moving into the area again next weekend but temperatures will be much warmer so if precipitation can develop it would not be a guarantee for snowfall. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 440 PM CST Sun Jan 24 2021 Arcing area of MVFR to IFR ceilings trying to fill back in on KFSD and KHON as of late afternoon and will likely succeed over the next couple/few hours. Could also see some fog form at the edge of this stratus through the overnight hours although will likely be fleeting depending on where this cloud cover ends up. For Monday, lower ceilings will likely linger at least until the afternoon as mid and upper level clouds also stream northward with the arrival of a significant winter storm to our south. Latest 18z GFS and nested NAM guidance somewhat concerning for KSUX for the potential of impactful accumulating snow. Will monitor this trend thru the evening as 00z guidance arrives. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ UPDATE...Kalin SHORT TERM...08 LONG TERM...08 AVIATION...Kalin
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
952 PM CST Sun Jan 24 2021 .UPDATE... Updated for evening discussion. && .DISCUSSION... Regional surface analysis had a 1000mb low over west central Texas with a warm front stretching east across the central portions of our CWA. Lower 60F dew points have spread as far north as Interstate 20 this evening and are progged to continue spreading north the remainder of the night. Similar to last night, temperatures across our northern zones will warm through the night. Local radar shows the bulk of the measurable rain has moved north of our CWA. Pops have been lowered significantly the remainder of the night maintaining low pops in the northwest and east through sunrise. Patchy fog development is likely in the east and northwest as well but dense fog development is not currently anticipated. /22/ Prior discussion below: Tonight and Monday: The mid level wave responsible for the showery activity over northeast MS continues moving east as seen in latest WV imagery. The bulk of this activity will move into AL before sunset. Very little precipitation noted behind the departing mid level wave as drying/warming occuring its subsident wake. Elsewhere, mainly just isolated light showers were observed along the weak warm front from central MS into north LA. The boundary will begin to gather some northward speed this evening as the mid level system over AZ begins to lift out to the northeast. At the same time, the coastal baroclinic zone, where dewpoints in the mid to upper 60s exist, will begin to surge northward tonight. While showers may become concentrated again this evening along the warm front over north LA/south AR/northwest MS, they will not persist as the forcing lifts northward with the boundary before midnight. As the mid level system ejects to the northeast and weakens, it will drag a cold front through the area during the day Monday. The tightening pressure gradient will increase surface wind speeds enough to warrant a limited wind hazard in the HWO. Forcing along this boundary may be adequate for showers, but the lack of sufficient low level moisture (dewpoints in the lower 60s) and the strengthening warm layer will make deep convection difficult to materialize. The majority of the CAM data show this scenario, although the HRRR is the only model showing convective potential and that over southeast portions during the afternoon. HRRR model soundings show a bit more moisture and a bit less cap compared to others. Will have to watch this trend to see if other models catch on to this possibility./GG/ Monday night through next weekend... Showers and storms will be moving out of most of the area Monday night as a frontal system moves through and stalls near the coast. Dry weather will return to much of the area Tuesday, although some showers and possible storms look to linger across the south in the vicinity of the stalled frontal system. Highs Tuesday will range from the lower 60s northwest to the lower 70s southeast. Rain chances will return to the entire area Tuesday night into Wednesday as a shortwave moves across the area. Highs Wednesday will range from the mid 50s northwest to around 70 southeast. Dry weather returns to the entire area Wednesday night through the remainder of the week under the influence of high pressure. Temperatures will be cooler, with highs Thursday ranging from the mid 40s northwest to the mid 50s southeast. Highs will be slightly warmer Friday, ranging from the lower 50s northwest to the lower 60s south. Rain chances look to return Saturday as another frontal system approaches the region. /27/ && .AVIATION... 00Z TAF discussion: At 2330Z IFR cigs were observed in the north while MVFR cigs were observed cntrl and south. Cigs will lower to IFR at most sites this evening and continue until after 12Z. Cigs are expected to improve to MVFR by 15Z and MVFR cigs are expected to prevail through Monday aftn. A se wind will increase Monday morning becoming sustained around 12 knots with gusts around 20 knots. Monday aftn TSRA may come in vcty of GLH-GWO. /22/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 63 75 51 69 / 21 66 49 13 Meridian 59 75 54 69 / 36 62 79 18 Vicksburg 63 74 49 68 / 21 70 22 10 Hattiesburg 62 77 59 71 / 18 54 74 36 Natchez 64 73 51 68 / 12 69 30 16 Greenville 55 71 46 63 / 21 73 8 3 Greenwood 58 73 48 65 / 23 77 24 4 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ 22/GG/27
National Weather Service Jackson KY
940 PM EST Sun Jan 24 2021 .UPDATE... Issued at 940 PM EST SUN JAN 24 2021 Visibilities have gone down significantly over the past few hours in areas north of the mountain parkway. For this reason, opted to issue a special weather statement to cover the fog threat for the rest of the night. The fog threat could creep farther south, but for now, will just focus the dense fog on the areas where it currently resides. Updated the forecast to reflect dense fog in these areas and also to expand the drizzle to more areas. UPDATE Issued at 848 PM EST SUN JAN 24 2021 The earlier shower activity is exiting to our southeast as the frontal boundary continues to sag southward across the area. This is allowing some of the lower ceilings, fog, and drizzle to build into the area from the north. Given the trends, will cut back on the pops through about 10z, and go with more patchy drizzle and fog through this period. The better rain potential should begin to push into and across the area around or after 10z with pops quickly ramping back up. Did make some adjustments to temperatures as we have quite the gradient over the area right now ranging from the low to mid 30s in the north to the mid 40s in the south. As the boundary shifts southward, we should see those cooler temperatures also slip a bit farther south. It looks like the prospects of freezing drizzle should remain just north of our coverage area as Fleming-Mason airport currently sits at 33 degrees. We`ll watch it closely, but we do not anticipate temperatures dropping much across the north tonight. It just looks like a very cold drizzle. && .SHORT TERM...(This evening through Monday night) Issued at 435 PM EST SUN JAN 24 2021 20z sfc analysis shows a developing area of low pressure to the southwest as the first wave of moisture is rolling across eastern Kentucky this afternoon. Temperatures have warmed through the day and above freezing most places early in the afternoon ending the mixed pcpn threat from the morning. Readings now vary sharply across the CWA - from around 33 degrees in the northeast to the lower 50s in the southwest. Dewpoints, meanwhile, range from the low 30s in the southwest to the mid 20s in the northeast. For the most part, winds have been running at 5 to 10 mph from the southeast to southwest beneath a deck of thickening and lowering clouds. The models are in a bit better agreement aloft through the short term short term portion of the forecast compared to yesterday for the Monday time frame. They all depict deep layer southwest flow for Kentucky atop a broad Southeast ridge while a pair of shortwaves dig troughing in the Desert Southwest on Monday. The lead shortwave of this will dampen as it moves into the Central Plains tonight with some of its energy making it into the mid level flow and riding over the Bluegrass State. A close passing of this lead trough on Monday night will push some height falls into our northern counties by Tuesday morning, along with more in the way of energy. This is where the models diverge a bit with the NAM and ECMWF quicker to take the wave east compared to the GFS. Favored a consensus model solution with the NBM as a starting point along with details from the HRRR and NAM12 - for the forecast grids. Sensible weather will feature a wet and milder 48 hours with light rain showers around tonight along with some fog. Temperatures will basically hold steady or slowly rise. More substantial rain showers then arrive during the day Monday with locally heavy rains possible across eastern Kentucky as the system`s sfc trough kicks off some deeper convection with thunder a decent bet for parts of the area Monday afternoon and evening. Depending on instability, some of these storms could become strong in the western parts of the Cumberland Valley. Winds will also become breezy on Monday with some gusts to over 30 mph possible in our highest terrain near the Virginia border. The soaking rains will fall onto relatively dry grounds with antecedent conditions nearing D0 and minimal stream flow through the bulk of eastern Kentucky. Accordingly, have left this event as just a mention in the HWO with not enough of flood potential to warrant a Flood Watch at this time. Mild conditions hold through Monday night and into Tuesday morning with pockets of light rain around. Made only point based adjustments to temperatures through the period outside of the near term adjustments based on current obs. As for PoPs: ended up generally wetter than the NBM tonight - closer to the CONSShort values. .LONG TERM...(Tuesday through Sunday) Issued at 303 PM EST SUN JAN 24 2021 A few stray rain showers will be exiting far eastern Kentucky early Tuesday morning, as a large area of low pressure continues to move away to our east. A ridge of high pressure will briefly move through the region Tuesday and Tuesday, and will bring a short period of dry and warm weather to eastern Kentucky. However, this respite will be short lived, as a fast moving area of low pressure is forecast to move through the region Wednesday through late Thursday morning. Precipitation with this system will begin as rain during the day on Wednesday, as warmer air will be in place. The rain will mix with and then change over to snow Wednesday night, with light snow expected to linger around the area through Thursday morning. Light snow accumulations will be possible, especially north of the Mountain Parkway, and along the I-64 corridor in particular. Temperatures will start off well above normal, with highs in the upper 50s to lower 60s on tap for Tuesday, and the mid 40s to mid 50s on Wednesday. Below normal temperatures are forecast for Thursday, in the wake of a passing area of low pressure. Highs on that day will likely max out in the 30s around the area. Gradual warming is expected to begin again on Friday, and we could see well above normal temperatures over the weekend, as another ridge of high pressure sets up over the region, and winds swing around to the south. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) ISSUED AT 848 PM EST SUN JAN 24 2021 Ceilings will continue to lower from the north through the overnight hours tonight as a frontal boundary slips farther southward. Patchy to areas of fog will be seen along with some drizzle through the overnight hours. As the frontal boundary begins to lift back to the north late tonight and Monday morning, widespread rain should develop areawide and continue through the day on Monday. A few thunderstorms may be possible very late in the period at KSME and KLOZ as the boundary pushes north and we get some unstable conditions to develop as milder air pushes north into the area. We will take a closer look at this potential in future TAF issuances. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...KAS SHORT TERM...GREIF LONG TERM...AR AVIATION...KAS
Area Forecast Discussion
National Weather Service North Platte NE
531 PM CST Sun Jan 24 2021 .SHORT TERM...(This evening through Monday night) Issued at 313 PM CST Sun Jan 24 2021 The synoptic and mesoscale models continue to converge on a storm track for the storm system affecting Arizona this afternoon. The system will track through the srn Rockies tonight and then through ern Colo, KS and southeast Nebraska Monday. The model blended QPF forecast increased liquid a few hundredths across wrn and ncntl Nebraska which translates to a slight increase in snowfall; most noticeable across wrn Nebraska where an upslope snow event will occur Monday night once the upper level energy moves east of Nebraska Monday evening. The higher snowfall amounts across southwest Nebraska have also been shifted south toward KS slightly. The system is now in range of the HRRR and RAP models which are only predicting slightly more than half as much liquid as the synoptic mesoscale model blend. Thus, there is still a fair amount of uncertainty with the snowfall for this portion of the storm event. The predicted snowfall across wrn and ncntl Nebraska will occur as a result of a moist and favorable environment for snow growth with h700mb temperatures around -13C and layer mean RH between 70 and 90 percent. Lift, however, is very modest, presumably producing light to briefly moderate snow. Snowfall totals of 2 to almost 6 inches are in place tonight through Monday night affecting areas along and south of highway 2 west of Dunning and along and south of highway 91 east of Dunning. SLR numbers are close to climo for this event; 12 to 15 to 1 which might be too low but out of respect for the drier RAP and HRRR models, these SLR numbers will be used. The ECM continues to suggest strong forcing across southwest Nebraska and continues to trend north. Just a 50 mile error in the forecast would place parts Custer county, Lincoln county and parts of Frontier county in a winter storm condition. The Winter Storm Watch will be converted to a Winter Weather Advisory and a few counties will be added to the highlight. The tandem storms will produce around 2 to 5 inches of snow each day Monday and Tuesday. The temperature forecast tonight through Monday night uses the short term model blend plus bias correction which handles the radiative effects of overcast skies better than the guidance blend. .LONG TERM...(Tuesday through Sunday) Issued at 313 PM CST Sun Jan 24 2021 A second storm off the nrn California coast this afternoon will swing south through the Great Basin and then east through the cntl Rockies arriving on the ern Colorado plains Tuesday afternoon. This system has the potential to produce a few additional inches of snow. The models are in reasonably good agreement tracking the h700mb low through wrn KS and southeast Nebraska Tuesday night. Likely POPs are in place Tuesday afternoon and Tuesday evening for this system. Clearing skies will begin to advance east through wrn Nebraska Tuesday night which could set the stage for subzero lows in the some areas Wednesday morning and again Thursday morning when most of the region will be clear. Wrn and ncntl Nebraska will still be under the influence of arctic high pressure Wednesday and Thursday morning. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 531 PM CST Sun Jan 24 2021 An approaching winter storm will result in several aviation weather hazards across western and north central Nebraska. Widespread stratus is already in place with MVFR cigs, likely lowering to IFR overnight. Snow will develop toward sunrise across the far southwest and spread north through the day. Expect considerable visby reductions at times during the afternoon. Wind will primarily be from the east tonight, then northeast tomorrow. && .LBF WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from midnight CST /11 PM MST/ tonight to midnight CST /11 PM MST/ Tuesday night for NEZ022>029-035>038- 056>059-069>071. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Snively
Area Forecast Discussion
National Weather Service Marquette MI
733 PM EST Sun Jan 24 2021 .SHORT TERM...(This evening through Monday) Issued at 212 PM EST SUN JAN 24 2021 Water vapor imagery and RAP analysis show a shortwave moving across northern Ontario and northern Lake Superior. Additional shortwave energy is streaking from the mid-Mississippi Valley toward the Lower Great Lakes. In response, waa/isentropic ascent has led to a large area of -sn across the central Great Lakes into this afternoon. Some weak enhancement to snow appears to be occurring along Lake Mi, but it`s hard to tell from sfc obs/webcams alone as radar is inoperable right now. Will keep advisory going through 21Z as a few of the models indicate isentropic ascent increasing on the 280K sfc from 18Z-21Z with the approach of the sfc-h85 trough. Expect snow to end out east by early evening as shortwave and associated sfc trough push east of the U.P. CAA behind the trough/front has led to some light wnw flow LES over the western counties late this afternoon. Tonight and Monday, sfc high pres centered over northern Saskatchewan will build a ridge se toward the Upper Mississippi Valley as low-level winds veer nw tonight and then more northerly late Monday. Fcst soundings indicate a low inversion around 3kft setting up off western Lake Superior and 3-4kft off eastern Lake Superior. The DGZ is favorably situated mostly within this shallow convective layer. Thus, expect -shsn and flurries off Lake Superior tonight into Mon morning under a nw flow and then into Mon afternoon as flow becomes more northerly. However, only a dusting to maybe as much as an inch of accumulation is anticipated given the shallow convection and dry air as noted on fcst soundings with inverted-v look toward the sfc. As for temps, there may be enough breaks in the cloud cover to allow min temps to fall toward zero over interior western Upper MI tonight. Under a northerly onshore flow and mostly cloudy skies for much of the area, Monday`s max temps will range from the upper teens to lower 20s west half to the mid 20s east half. .LONG TERM...(Monday night through Sunday) Issued at 324 PM EST SUN JAN 24 2021 Trending a little warmer through the week, with a few chances for light lake-effect snow, and nothing too significant the week. Strong positive height anomalies across the Arctic and the Pacific, with negative height anomalies along the West Coast and just off New England are leading to a split flow pattern across NOAM with a more active southern stream progged to bring much needed pcpn across the west, though maybe too much at once, and add`l pcpn across the southern Mississippi Valley eastward through the Ohio River Valley and Appalachians. This southern stream will bring an active storm track with it as troffing sets up in the west with rising heights and weaker ridging in the east. Global ens means suggest this pattern to continue through at least the longterm period, which is expected to bring a slow warm up through the week, with temperatures trending just above normal by this weekend As a shrtwv moves through the central CONUS Monday evening through Tuesday, high pressure drops south on the leeside of the Canadian Rockies. With split flow in place and this high pressure influencing much of the Northern Plains, the Central Plains shrtwv will remain south of Upper Michigan. The shrtwv passes Tuesday evening as cooler air slowing moves across Superior from the Canadian high pressure. This pattern will support some light LES through Wednesday before coming to an end by Thursday. With light northerly flow and model 850mb temps in the -13 to -16C range. A brief peek at model soundings show rather low inversions, with an inverted V profile, and the DGZ remaining closer to the sfc. This should keep any accumulations on the lighter side as Arctic high pressure remains to the north of Lake Superior. Through Wednesday night could see 2 to 4 inches total in the higher terrain of west of Marquette and across the Porkies. The NAM has been hinting at a stronger convergence band on Wednesday for Alger County the last few days, but sounding profiles still don`t allow much better conditions for the usual heavy snowfall amts seen within these bands, stay tuned. As another shrtwv moves through the southern stream across the Appalachians on Thursday, rising heights and SW return flow increase Thurs aftn across Upper Michigan. This pattern will bring the end of any LES and a slight increase in temperatures. Another wave moving onshore across the desert SW Saturday shifts into the central US on Sunday, which will need to be monitored over the coming days for potential shifts in the track. Models are trending towards wrapping up a sfc low that looks to impact the Great Lakes region somewhere, but details have several days before they can be ironed out. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 727 PM EST SUN JAN 24 2021 VFR conditions are expected at KIWD and KSAW until Mon morning when north winds develop and bring MVFR cigs from lake clouds back into the area. Onshore flow into KCMX will support mainly VFR cigs in the dry airmass over the region. Slightly greater moisture moving in Mon morning should also result in MVFR cigs with some flurries. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 212 PM EST SUN JAN 24 2021 Expect w to nw winds 20-30kt in the wake of the front this evening. High pres will then slowly build toward Lake Superior with ridge axis crossing Lake Superior on Thu. Ahead of the ridge, expect nw winds to diminish to 15 to 25 knots later tonight into early Monday. Northerly winds will be mostly under 20kt into Thursday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...JAW AVIATION...JLB MARINE...Voss
Area Forecast Discussion
National Weather Service Phoenix AZ
410 PM MST Sun Jan 24 2021 .UPDATE...Updated Aviation Discussion. && .SYNOPSIS... An active weather pattern featuring a series of storm systems will bring chances for rain and thunderstorms, high elevation snowfall, and much colder temperatures over the next several days. The first storm system will move through the area today, followed by a second colder system Monday and Tuesday. Below normal temperatures are expected through at least next weekend with possible freezing conditions Wednesday morning. && .DISCUSSION... Latest water vapor imagery reveals a well-defined closed low traversing a bit faster eastward through Arizona. Cold pool associated with this system juxtaposed atop anomalously high moisture has resulted in objectively analyzed area of 250+ J/kg MLCAPE. This has lead to the development of numerous small cells across Maricopa County, with several producing pea-sized hail. Latest consensus from the CAMs suggests this activity will persist through this evening, before eventually fizzling out in the ephemeral subsidence behind the departing low. Quick on the heels of the aforementioned low will be another stronger low pressure system diving down the west coast with its anomalous low height anomalies. Given the antecedent low-level moisture, shower activity will quickly redevelop in the orographically favored areas north and east of Phoenix after midnight. Successive runs of the HRRR and local CAMs indicate strong vorticity-forced ascent will then give way to a developing pre-frontal line of showers and thunderstorms during the early morning across southeastern California. Latest CAMs suggest this line will become more organized as it marches eastward through Arizona during the morning. Sufficient deep layer shear of 40 kt will be present and insolation could yield a few hundred joules of CAPE, per the latest HREF. Meanwhile, pressure gradient will will be strong enough to produce breezy conditions on its own, particularly across southeastern California and southwestern Arizona. The line will only enhance the potential for wind gusts up to 40 mph, as suggested by the ECMWF ensembles. Although gusts to 40 mph are not anticipated throughout the entire day and over a widespread area, latest HREF max ensemble hints at this threat and a Wind Advisory has been hoisted across Maricopa County to address the potential. Given the steep lapse rates, conditions will also be favorable for small hail within the strongest cells. The other noteworthy component of Monday`s low pressure system will be the winter storm impacts. While lower desert activity will generally taper off Monday evening, rain and snow showers will persist across the higher terrain through Tuesday. Critical thicknesses will be low enough to support snow as low as 2000-2500 ft in elevation. Wrap-around precipitation Tuesday morning could very well take the form of snow across north Scottsdale and Cave Creek, and possibly graupel a bit lower in elevation. Across the higher terrain north and east of Phoenix, total snow accumulations will likely amount to 1 to 2 feet above 5000 ft in elevation and 3 to 6 inches near Globe above 3500 ft, where the Winter Storm Watch has been upgraded to a Warning. Considering the uncertainties often inherent with moisture and low pressure systems, overall GEFS and ECMWF ensemble spread remains relatively low, even with regard to total QPF. Although amounts have trended downward, latest EMCWF ensemble mean indicates around three quarters of an inch in the Phoenix area, while the WPC deterministic amount is lower and closer to the GEFS mean. The prolonged moist southwesterly flow is conducive for even higher amounts in the foothills, where as much 1 to 2 inches in liquid or SWE is possible. This could lead to runoff into Tonto Creek near Tonto Basin, where increases are again forecast. && .PREVIOUS DISCUSSION... Otherwise, colder temperatures will become entrenched, save for southeast California, which may be be fortunate enough to hold onto the low 60s through the week. The cold air mass will cause high temps to drop into the 50s across the lower Arizona desert through Thursday. On Tuesday afternoon, the high in Phoenix will struggle to reach the low 50s, potentially setting up for freezing Tuesday night/Wednesday morning lows in many places. Fog could also emerge as a possibility on this night, or of these nights, after rain and modest sky clearing. By Thursday, afternoon highs should warm nicely into the mid to upper 60s. Guidance remains consistent portraying a quick moving weather system passing through the Southwest late this week that could bring another round of rain and high elevation snow. && .AVIATION...Updated at 2305Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Scattered showers and isolated thunderstorms will continue through this evening and to a lesser degree through the night as well. The strongest storms will be capable of producing localized winds up to 25 kt and pea- sized hail. Meanwhile, abundant low-level moisture is resulting in CIGS of 4-6 kft. In general, CIGS should remain in this general range through the morning, but may briefly drop lower in any showers. Westerly winds of 8-15 kts will gradually weaken and veer to southerly overnight as well. Scattered showers will increase once again Monday morning. Monday late morning (about 18-20Z) a strong line of showers and thunderstorms will move through. Accompanying this line of showers will be gusty southerly winds of 20-25 kts with a few gusts to 35 kts possible. Behind the band of showers, breezy westerly wind with scattered showers will continue for several hours. CIGS will drop to 2-4 kft with reductions in visibility also possible during the heaviest showers, but CIGS will rise again to 4-6 kft behind them. Southeast California/Southwest Arizona including KIPL and KBLH: Light westerly wind will shift to light southerly overnight with FEW-SCT coverage near 5-8 kft. Monday morning CIGS will lower to 4-8 kft with scattered showers expected. The biggest aviation issue will be the wind. Gusty westerly wind of 15-20 kts with gusts to 30 kts will develop at KIPL. Expect similar windy conditions at KBLH, but out of the south. && .FIRE WEATHER... Tuesday through Saturday: Lingering rain and snow showers possible in the wake of a departing weather system Tuesday and snow levels could drop below 3000 feet. Otherwise, a clearing and drying trend will begin. Colder temperatures and lingering moisture should keep min RH values above 25% every day. Overnight recoveries will reach the 40-80% range. Afternoon breeziness will be common, especially over any higher terrain features. Another weather system could bring rain chances again by Friday-Saturday. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Wind Advisory from 10 AM to 4 PM MST Monday for AZZ534-537>563. Winter Storm Warning from 5 PM Monday to 3 PM MST Tuesday for AZZ562. Winter Weather Advisory until 11 PM MST this evening for AZZ557- 558-563. Winter Weather Advisory from 5 AM to 5 PM MST Tuesday for AZZ557- 558-563. Winter Storm Warning from 11 AM Monday to 5 PM MST Tuesday for AZZ557-558-563. Wind Advisory from 11 AM to 11 PM MST Monday for AZZ530>533-535- 536. CA...Wind Advisory from 10 AM to 10 PM PST Monday for CAZ560-561- 563>570. Wind Advisory from 10 AM Monday to 4 AM PST Tuesday for CAZ562. && $$ DISCUSSION...Hirsch PREVIOUS DISCUSSION...AD AVIATION...Hodges FIRE WEATHER...AD