Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/14/20

Area Forecast Discussion
National Weather Service La Crosse WI
556 PM CST Sun Dec 13 2020 .SHORT TERM...(This evening through Monday) Issued at 251 PM CST Sun Dec 13 2020 Early afternoon analysis showed plenty of low clouds across the region and upstream into northwest Minnesota with some shortwave energy inching into western Minnesota. At the surface, a cold front was seen stretching from southwest Ontario, through northwest Minnesota and into the Dakotas. Radar/surface obs show light snow falling along said front. In addition, good isentropic ascent has led to another band of snow developing well ahead of the front (over the eastern MN/northwest WI) and will continue eastward into the forecast area. However, still a fair amount of dry air to overcome over our forecast area, isentropic ascent is is progged to weaken a bit, and frontogenesis looks to remain weak as the snow enters the forecast area (mainly along and north of Interstate 94). Still, RAP soundings at Medford, WI, do show a fairly deep dendritic growth zone, along with a few hour period this evening (roughly 00Z to 03Z) of deep enough saturation for some light snow. At this point, accumulation of 1/2 inch or less seems reasonable and HREF guidance supports that. With better forcing and/or moisture, this could be a sneaky 1 to 2" event, but given current model data, looking like it`ll remain lower than that. Even so, looks like there could be enough snow to lead to some slick spots. Behind the front tonight, expect a period of gustier winds (around 20 kts or so) out of the northwest, with drier air working in and clouds scattering out. This should set the stage for a mostly sunny, but cooler day on Monday, with high temperatures generally in the 20s. .LONG TERM...(Monday night through Sunday) Issued at 251 PM CST Sun Dec 13 2020 Quiet weather and dry conditions are expected through the week. Monday night into Tuesday, the upper-level flow begins to split as a surface high-pressure system moves eastward towards the Great Lakes Region. An upper-level low and associated mid-level short- wave trough dips into the southern Great Plains. Cloud cover increases throughout the day on Tuesday as the trough continues progressing eastward through the region by mid-week. No precipitation expected with its passing as plenty of dry air remains above the surface to around the 850 mb layer in wake of the departing surface high- pressure system. Upper-level flow becomes southwesterly ahead of the next approaching shortwave with chances for precipitation returning Friday night into Saturday. NBM guidance was mostly dry with this system. Decided to use a blended 50th percentile model guidance for precipitation chances as confidence has been increasing that there will be some precipitation this weekend. Ensemble model guidance have continued to show precipitation this weekend across the region. Although, chances are still relatively low as there are some differences between deterministic models and ensemble members with the exact placement and progression of this system. Temperatures will be impacted by cloud cover and recent snowfall accumulations in the southern portions of the region. Currently anticipating Tuesday morning low temperatures to dip into the single digits and teens then increasing into the 20s for the afternoon. Otherwise through the rest of the week and into the weekend, temperatures will be slightly above the seasonal average with afternoon highs in the 30s with overnight lows in the teens and 20s. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 556 PM CST Sun Dec 13 2020 MVFR ceilings are expected tonight, with improvement to VFR possible by Monday morning. A brief period of light snow might also impact KLSE early this evening, with brief visibility reductions. Radar shows a very narrow band of light snow/flurries moving toward KLSE at the beginning of the TAF period. This may very briefly impact visibility, but should not last very long. While some guidance would suggest MVFR ceilings improve to VFR later this evening, models have been tending to improve ceilings too quickly lately and will go with the more pessimistic guidance for the overnight, keeping MVFR in the TAFs. There is a gap in the MVFR several counties to the west of KRST which may briefly bring things back up to VFR, but more MVFR clouds are sinking southward behind a cold front moving toward the area. Winds will become more northwesterly tonight behind the front, with gusts near 20 kts possible. Skies should clear out Monday morning as high pressure works into the area, with northwest winds gradually decreasing. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...CA LONG TERM...Peters AVIATION...Lee
Area Forecast Discussion
National Weather Service Fort Worth TX
545 PM CST Sun Dec 13 2020 ...New Short Term, Aviation... .SHORT TERM... /NEW/ /Tonight through Monday Night/ Water vapor imagery and the latest RAP analysis indicates the core of the mid level shortwave trough is tracking eastward just north of I-20 this evening. Strong mid level forcing for ascent associated with this feature and sufficient moisture where this forcing is occurring is resulting in continued areas of rain along with some rain/snow mix mainly north of I-20 from the Metroplex northeastward. This will continue for another few hours before pushing off to the east with the upper trough. No significant accumulations are expected this evening. Behind the front, gusty winds prevail across much of the region and this will also continue at least through late evening before higher pressure settles in and the gradient relaxes a bit. The current wind advisory will remain unchanged and allowed to expire at 9 pm. Low clouds will clear out later tonight, and temperatures will fall rapidly as clearing fills in from northwest to southeast. Overnight lows are expected to fall into the low/mid 20s west and northwest of the Metroplex by early Monday morning with temps near freezing elsewhere. Strong north winds will diminish through the overnight to less than 5 mph. High pressure will traverse the region on Monday with winds becoming more southeasterly late in the day ahead of the next system on Tuesday. It`ll be a chilly day with highs in the upper 40s and lower 50s under abundant sunshine. Dunn && .LONG TERM... /Issued 314 PM CST Sun Dec 13 2020/ /Monday Night Onward/ Another chilly night is expected Monday night with lows dipping into the upper 20s to mid 30s. Another cold front is expected to cross our western border midday Tuesday. The front will slowly sweep eastward across the area with the center of the surface low passing directly over North Texas. As the low exits to the east Tuesday night, wrap around moisture may be sufficient for a rain/snow mix to occur near and along the Red River. Confidence in wintry precipitation is considerably low at this time as moisture will be quite shallow and temperature profiles may be slightly too warm. However, the potential will continue to be monitored in future updates. Another cold night is expected Wednesday night with lows dropping into the mid 20s to low 30s. Chilly conditions will continue into Wednesday with highs only in the 40s to mid 50s. As southerly flow is re-established early Thursday, temperatures will quickly rebound into the 50s and low 60s late this week. Rain chances will be on the rise for areas near and east of Highway 281 beginning Friday evening as isentropic ascent increases ahead of our next cold front. The front is expected to enter the area overnight Friday night. Showers will continue throughout the day Saturday for areas east of I-35 until dry air behind the front brings an end to the rain from west to east. The only noticeable change behind this front will be a couple of cooler mornings in the 30s both Sunday and Monday. Otherwise, rain-free weather and above- normal temperatures are expected as we head into next week. Barnes && .AVIATION... /NEW/ /00Z TAFs/ MVFR conditions prevail this evening at all sites with lingering precipitation. This light rain will continue to move east over the next few hours and we`ll hang on to a TEMPO for 5SM -RA through 2Z. Otherwise, low clouds will remain in place for much of the overnight with clearing expected before sunrise. Gusty north winds will diminish overnight and become southeasterly by late Tuesday. VFR will prevail on Tuesday at all sites. Dunn && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 30 50 35 52 34 / 20 0 0 10 5 Waco 32 51 35 56 32 / 0 0 0 5 0 Paris 29 48 31 44 32 / 70 0 0 10 20 Denton 24 50 31 51 33 / 20 0 0 10 5 McKinney 28 49 32 50 34 / 40 0 0 10 5 Dallas 31 51 37 52 33 / 20 0 0 10 5 Terrell 29 50 32 51 33 / 30 0 0 5 5 Corsicana 33 51 37 53 34 / 5 0 0 5 5 Temple 31 51 34 60 33 / 0 0 0 5 0 Mineral Wells 25 50 32 53 29 / 5 0 0 5 0 && .FWD WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 9 PM CST this evening for TXZ115>118-129>133- 141>145-156>160-174. && $$
Area Forecast Discussion
National Weather Service Lincoln IL
829 PM CST Sun Dec 13 2020 .SYNOPSIS... Issued at 220 PM CST Sun Dec 13 2020 While a storm system spreads rain and snow across the Ohio Valley tonight, much of our area will remain mostly cloudy but dry. Skies are expected to clear on Monday, as high pressure drifts into the Great Lakes region. The next storm system will spread some light snow across areas near and south of I-70 Tuesday night. && .UPDATE... Issued at 829 PM CST Sun Dec 13 2020 Overcast conditions will prevail for the next several hours before clearing currently over central/western Iowa tries to work into central Illinois late tonight. HRRR cloud forecast has been varying run to run, so confidence in any one solution is low. Based on latest satellite loops, it appears partial clearing could arrive across the Illinois River Valley between 09z and 12z. However as a storm system passes well south of Illinois, the boundary layer flow will likely lead to a slowing trend. As a result, think skies will remain mostly cloudy across the KILX CWA through the night, followed by a gradual west to east clearing on Monday. Low temperatures tonight will be in the middle to upper 20s. && .SHORT TERM...(This evening through Monday) ISSUED AT 220 PM CST Sun Dec 13 2020 Early afternoon water vapor imagery shows a well defined upper low sliding along the Texas/Oklahoma border, with a separate shortwave moving across Minnesota and western Ontario. While radar mosaics show widespread echoes across southern Missouri and up the Ohio River, surface observations indicate that much of the precipitation is from south central Missouri and areas to the south/southwest. Nearly all the model guidance is in agreement that this should largely slide to our south, though a few sprinkles or flurries can`t be ruled out in areas from Flora to Lawrenceville. Main challenge in this period will be with cloud cover. Plenty of stratocumulus continues across the region, with earlier holes filling in. There is also an expansion of the cloud shield across Iowa, nearly to the Mississippi River now. 925 mb relative humidity plot off the RAP, close to the level which would correspond to the cloud heights, indicates these clouds should be slower to clear out than earlier projections. Will go more pessimistic with the sky cover tonight, keeping it mostly cloudy in most areas. A little more uncertainty northwest of the Illinois River, but will go partly cloudy there and monitor for updates over the next few hours. .LONG TERM...(Monday night through Sunday) ISSUED AT 220 PM CST Sun Dec 13 2020 Upper level pattern will remain in a split flow through midweek, with the trough currently off the Pacific Northwest coast our next weather maker. Morning model guidance in decent agreement with the trough deepening as it advances across Missouri Tuesday night. Main surface low expected to track just southeast of Illinois, with our area more on the fringes of the precipitation. Initialized guidance from the NBM seemed too low with PoP`s Tuesday night and Wednesday morning, so a forecast closer to a blend of the GFS and the previous grids will be used. That continues to concentrate light snow chances near and south of I-70, with potential for some flurries as far northwest as a Taylorville-Danville line. Some 20% PoP`s will linger into early Wednesday morning east of I-57. Upcoming weekend storm system continues to have some continuity difficulties. GFS remains on the wetter side of the guidance, and while last night`s European run was close to that, the morning run significantly backs away from the PoP`s until the front has passed east of Illinois. Consequently, no changes were made to the NBM guidance, which has widespread slight chance PoP`s. No significant cold surges are expected this week, with temperatures moderating late week ahead of the developing storm system. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 529 PM CST Sun Dec 13 2020 Low clouds blanket all of Illinois and much of Iowa/Missouri late this afternoon. With light boundary layer from the northwest, it appears clearing will be delayed until Monday morning at the earliest. Based on satellite trends and latest HRRR forecast, have carried MVFR ceilings at all terminals through the entire night. Have scattered the overcast at KPIA by 15z...then further east to KCMI by around 18z. Winds will initially be NW at 5-10kt tonight, then will increase to 10-15kt on Monday. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Barnes SYNOPSIS...Geelhart SHORT TERM...Geelhart LONG TERM...Geelhart AVIATION...Barnes
National Weather Service Jackson KY
937 PM EST Sun Dec 13 2020 .UPDATE... Issued at 936 PM EST SUN DEC 13 2020 At 230z, an ~1008mb surface low was located near Jackson, Mississippi with a broad area of rain across much of the Lower Mississippi Valley and spreading across the Lower Ohio and Tennessee valleys. Some snow is also noted over the Ozarks along the NW periphery of the system. Across eastern Kentucky, reflectivity echoes continue to spread ENE in across the forecast area from central Kentucky. However, most of this precipitation is evaporating as it falls into a very dry layer of air between 850 and 700mb, as per RAP, HRRR, and 00z BNA soundings. As the better mid-level frontogenesis and ascent, evidenced by a stronger band of reflectivity from south central Kentucky to northeast Arkansas, pushes eastward, the dry layer should rapidly saturate and cool to its wet-bulb temperature. For areas closer to central KY light showers and sprinkles will develop over the next couple of hours, but should hold off until 6 to 7z across the far east. Recent T, Td trends suggest that the dry layer is located just above Black Mountain. Therefore, expect a rapid temperature drop to near freezing via wet-bulb cooling aloft and a shallow layer of dynamic cooling near the mountain top there soon after the onset of precipitation. This will lead to a quick transition from rain over to snow atop Black Mountain. Thereafter, soundings indicate that the dynamic cooling will initially cause a fairly quick lowering of the snow level to between 2,000 and 3,000 feet. Current expectations are for up to 1-4 inches of snow between 2,000 and 4,000 feet. Given this potential, a Winter Weather Advisory has been issued for elevations above 2,000 feet in Bell, Harlan, Letcher, and Pike counties. Some minor accumulations are also possible across the highest elevations in adjacent counties. At elevations below 2,000 feet, the 2-3k foot layer of above freezing dew points will take longer to overcome by latent heat and melting. However, with that being said, the HRRR and other CAMS do suggest the potential for banding and localized QPF rates of 0.3+ inches. If precipitation rates of this intensity materialize, it is possible for the dynamic cooling processes to prevail, causing the rain to change over to moderate snow, especially toward sunrise as the above freezing near-surface air layer becomes shallower. Any heavier banding that occurs early Monday morning could lay down a quick slushy coating to inch, especially over the ridges. && .SHORT TERM...(This evening through Monday night) Issued at 424 PM EST SUN DEC 13 2020 A mid/upper level low currently over the OK/TX border will weaken and get absorbed by the prevailing flow as it moves east across the TN valley tonight and early Monday. It is prompting surface low development near the east TX coast this afternoon. As the upper level support tracks east, so will the surface low, reaching the Carolinas Monday morning. The model consensus is for a cold stratiform rain to overspread the JKL forecast area on the north side of the system tonight. As temperatures cool, it will mix snow late tonight and Monday morning, first at higher elevations. Temperatures are expected to bottom out near or just below freezing at the highest elevations near the VA border on Monday morning. With temperatures marginally cold enough for accumulations at the highest elevations toward the end of the event, a small change up or down could make a substantial difference for amounts. Based on blended models, the best estimate is for an inch or two above about 2500 feet. The system pulls out to the east during the day Monday. Much drier air tries to advect in behind the system, but will be battling cold air advection and upslope flow. The best shot at seeing sun will be in our western counties, with clouds remaining more prominent near the VA border, but confidence in the sky forecast is not high. As the frontal inversion behind the system lowers on Monday night, the coverage of low clouds will continue to shrink, but high clouds may offset this somewhat overnight. .LONG TERM...(Tuesday through Sunday) Issued at 405 PM EST SUN DEC 13 2020 Quite a complicated forecast, if only for a short period of time. Tuesday will start off dry with strong high pressure located to our north taking hold of the region as it progresses eastward. Meanwhile, a strong upper level shortwave will be deepening across the Southern Plains, proving strong SW flow aloft. The result will be cool northerly flow at the surface vs. stronger and warmer SWrly flow in the mid and upper levels...keeping temperatures in the upper 30s to low 40 degree range. As we head into the overnight, this is where things start to get very tricky very fast. The shortwave and a surface low pressure system are expected to push eastward quickly. Precip will accompany, but will have a lot of dry air to overcome. However, as the center of the low pressure system passes just to our SE, this should be enough to saturate, and allow precip to begin falling in the JKL by around 6Z, quickly increasing in coverage and strength as we head into the morning hours. Between 6 and 12Z, JKL will be located on the NW of the surface low as it passes by, according to all the models, which is generally the coldest sector. Meanwhile, the upper level shortwave will be to our west, across the Mississippi River Valley during this time, with strengthening S to SW flow across the region, result in WAA. The fact that the system is moving in during the colder overnight also complicates things. It seems as though there has been a trend in the models to increase a degree or few based on previous runs, likely given the strong southerly flow in the mid and upper levels. However, the NBM samples from some of the older models, and is also incorporating some lower values such as the Canadian and previous ECMWF. With that in mind, my personal opinion is that the NBM lows are perhaps a degree or two too low...however after chatting with neighboring offices, there was no desire to increase the temps at this point, and so the NBM will stand for now. This will put lows in the upper 20s across much of eastern Kentucky. So as the precip moves in, and temperatures drop to the upper 20s at the surface, but warmer air above freezing exists aloft, this creates a set up that could lead to some mixed precip and more so...freezing rain. As was noted before, the NBM temps do seem a bit too low, so if this is true, the amount of freezing rain could be overdone a bit. However, if the temps do hold true...which granted we are still period 5 for this event...freezing rain is a definite possibility. Will continue to monitor this next system closely as things continue to evolve. Precip will change back to rain on Wednesday as temperatures warm back to just above freezing. The only exception will be the high terrain, which may struggle to increase throughout the day as the upper level shortwave passes over, and we start to cool aloft. The question, however, is will the highest mountains remain in freezing rain, or transition to rain/snow or snow. This much is still up in the air. The system should exit almost as quickly as it arrived, with all precip out of the region by Wednesday evening. Strong high pressure will then take hold from the SW this time, centering across the state by Thursday evening. Meanwhile, there will be an upper level shortwave moving across the state as well. The GFS and, to some degree, the ECMWF, show some isolated to scattered light pops across the far eastern CWA...but these did not translate to the NBM, and given the amount of dry air in place, did not change the NBM to account for any pops at this time. By Thursday night, with the high pressure system directly overhead, and the backside of the shortwave passing through (NW flow), expect temperatures to drop quite substantially overnight. Lows are forecast in the low 20s. Temperatures are then expected to start a warming trend heading into the weekend as upper level ridging takes hold, followed by SW flow ahead of the next shortwave that will approach and pass over Saturday. There remains considerably good agreement in the models with this shortwave, even this far in the extended, as it passes across the Ohio Valley and points to our south Saturday and the first part of the day Sunday. Both the GFS and ECMWF show widespread precip moving through during this time, which is starting to be reflected in the NBM with chance to likely pops. Expect these will continue to increase over the coming runs. High temperatures for Saturday will be in the upper 40s to around 50 head of this next system, dropping a few degrees for Sunday as it passes over. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) ISSUED AT 700 PM EST SUN DEC 13 2020 Conditions at TAF issuance were mainly VFR, except near and north of I-64 where some high-end MVFR was noted at SYM and IOB. Some virga will be possible north of the Hal Rogers Parkway this evening before a steady rain develops between 3-6z. After the rain begins, visibilities and ceilings will quickly drop to IFR or potentially lower through the rest of the night. The rain is expected to mix with or change to snow toward sunrise over southeastern Kentucky and the higher elevations before tapering off Monday morning. Gradual improvement to MVFR is expected during Monday afternoon. && .JKL WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 3 AM to 10 AM EST Monday for KYZ087- 088-118-120. && $$ UPDATE...GEERTSON SHORT TERM...HAL LONG TERM...JMW AVIATION...GEERTSON/HAL
Area Forecast Discussion
National Weather Service Memphis TN
908 PM CST Sun Dec 13 2020 .UPDATE... Rain associated with a deepening low pressure system continues to fall over the Mid-South at this time. This will begin to change shortly. Snow should begin to mix in with the rain over Northeast Arkansas as Walnut Ridge just reported snow. Also, just saw a report of rain changing to snow in Piggott, AR. The latest HRRR shows all snow at Jonesboro by 11 PM CST and possibly at Memphis by 1 AM CST. Still expecting little to no accumulations as ground temperatures remain warm. Current forecast is on track. Will only update to remove evening wording. KRM && .DISCUSSION... /issued 355 PM CST Sun Dec 13 2020/ Radar shows rain increasing across the area. Surface analysis charts show a low pressure center located over souther TX/souther LA with the warm front stretching into central AL. Temperatures are in the low 40s to low 50s across the Mid-South. Clouds are increasing across the region with mostly cloudy skies over the Mid-South. Rain coverage will continue to increase across the County Warning Area this evening and into the overnight hours as the upper-level trough moves through southern AR and central TN overnight. Temperatures will drop overnight which means snow mixed with rain will be possible after midnight - mainly over areas north of I-40. The best chance for snow will be over northeast AR, the MO Bootheel, and northwest TN. At this time, the only accumulations expected would be on grassy surfaces as well as bridges/overpasses as ground temps are still well above freezing. If we can get heavy enough snow and enough evaporational cooling, we could see light accumulations over the northwestern counties of the CWA. Temperatures will drop down into the 30s overnight. High pressure will move in to start off the workweek. We`ll stay dry and cold through Tuesday. Temperatures will remain below normal with highs reaching the 40s and lows dipping down into the 20s. Another trough will dig down from the northwest and bring another shot of cold air Tuesday night. This system is a tricky forecast due to model inconsistencies and uncertainties of where the dry air will set up. This system certainly has a bust potential. At this time, the trough is expected to track through KY with most of the moisture developing south of I-40 and north of I-22. Once again, rain mixed with rain will be possible but over a larger portion of the Mid-South as the 540 line reaches northern MS. Temperatures will remain in the 40s and 50s for highs with lows in the 20s and 30s. Dry weather will move in behind the system. KRF && .AVIATION... Conds are lowering across the Mid-South as rain moves into the region. Expect cigs to lower to IFR across the Mid-South with MVFR ocnl IFR vsbys in moderate to heavy rain. Winds will be increasing out of the NNE and becoming gusty at times. Expect some mixing with snow across the northern part of the area overnight and perhaps a brief change to all snow at KJBR before ending. Warm ground and surface temps remaining above freezing = little to no impacts. There is some uncertainty with regard to clouds clearing out Monday morning. The majority of the guidance is quick to clear but will hold on to a MVFR deck for a few extra hours given the NAM soundings and HRRR. SJM && && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
619 PM CST Sun Dec 13 2020 .SHORT TERM...(This evening through Monday night) Issued at 257 PM CST Sun Dec 13 2020 A few respectable bands of snow showers are continuing eastward across the Upper Mississippi Valley this afternoon ahead of a cold front pushing through western Minnesota. Accumulations have been minor overall, but a few reports of over an inch have been received near Milaca and Mora where the snow has been most persistent. The cold front will progress across the remainder of the area by early this evening with gusty northwest winds and strong CAA developing behind it. Much drier air will scour out the cloud cover late this evening, setting up a clear overnight and Monday morning. Lows tonight will reach the single digits across central and western Minnesota, with low teens across southern Minnesota and western WI. Thermal troughing overhead Monday will make it difficult to reach 20 for a high. Increasing clouds and light return flow will keep temps steady or allow them to rise slowly Monday night in most areas. The exception may be across central Minnesota and western WI where calm winds and clear skies will persist well into Monday evening. Here, temperatures may drop lower than currently forecast, but it will depend on the timing of the high and mid level clouds. .LONG TERM...(Tuesday through Sunday) Issued at 257 PM CST Sun Dec 13 2020 Thicknesses and heights will increase into late week with pesky, weak disturbances remaining confined to Canada or the far northern CONUS. A trough over the west midweek should eject into the Plains and Midwest Friday and Friday night. This feature appears to shear out as it does so, but it could bring a little light rain or snow (less than a tenth of QPF), much like the system currently impacting the area. Not really impressive at all. Highs ahead of the front could reach 40 Friday. A brief cool down would then follow Saturday before thicknesses rise again into early next week. Could see low 40s again Sunday. ECMWF even has 50s by Monday. Too early to say what could transpire closer to Christmas, but deterministic models are adverting some sort of system in the center of the CONUS on the 23rd and 24th. Ensemble QPF spread increases during this time with some members showing a more active period finally developing. Ensembles have been showing that for the past several weeks now, only to see the spread shrink back down to zero by day 7 or 8 though. It does look rather likely, however, that no arctic airmasses are in store through at least the rest of the month. It`s very hard to get a prolonged period of below normal temperatures in winter without a stout snowpack. Snowpack is so common this time of year that its influence is significant in climatological temperature normals. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 619 PM CST Sun Dec 13 2020 Snow band that moved through earlier will clear EAU by 2z. That won`t be the end for snow though. Right behind the front we`ve seen sites get about an hour of light snow, while in central MN, the cloud deck is completely within the dendritic snow growth zone, so we continue to see snow easily get generated across central into northern MN. Biggest change with this TAF package was to delay the clearing by several hours at all terminals based on moisture we see through the night pretty much at all terminals in forecast soundings. In central MN, these clouds will likely be MVFR, but expect this stratus to move up to around 4k feet through the night everywhere else before clearing out. High pressure moves in on Monday, resulting in mainly clear skies and wind speeds that will be diminishing during the day. KMSP...Cold front is just now moving through MSP. Radar and upstream obs show we`ll have a brief period of flurries/light snow right behind the front, but no significant vis restrictions are expected. NAM shows clouds clearing MSP around 7z and the RAP not until around 12z. With some back filling of clouds noted along the MN/SD border, pushed out the clearing to 10z, though do expect heights to be VFR much of the night. /OUTLOOK FOR KMSP/ Tue...VFR. Winds SSE 5-10kts. Wed...VFR. Winds S 5-10 kts. Thu...VFR. Winds S 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ SHORT TERM...Borghoff LONG TERM...Borghoff AVIATION...MPG
Area Forecast Discussion
National Weather Service Paducah KY
711 PM CST Sun Dec 13 2020 .UPDATE... Issued at 711 PM CST Sun Dec 13 2020 Updated aviation discussion. && .SHORT TERM...(Tonight through Tuesday) Issued at 216 PM CST Sun Dec 13 2020 Precip has been expanding rapidly northeast across the Ozarks today, mostly in the form of snow in Missouri and the higher elevations of north Arkansas. In the near term, hrrr and other high res guidance blossoms precip across se Missouri and the lower Ohio Valley by 00z. This precip correlates well with strong mid level frontogenetic forcing on the northeast side of an approaching mid level low. The high res models indicate a band of moderate precip will focus from the Ozark foothills east-northeast into the lower Ohio Valley by 00z. This band will sink southeastward across western Kentucky tonight. The freezing level is forecast to remain just a little too high for appreciable snow, ranging from 1500 to 2000 ft at kpah this evening. The exception is in the Ozark foothills, where the higher elevations will likely have some minor impacts from snow this evening. Brief periods of wet snow or a snow/rain mix are possible anywhere in the forecast area tonight. The highest chances of snow will be associated with bands of heavier precip and associated dragging down of colder air. However, any impacts are likely to be restricted to the Ozark foothills region, where an advisory remains in effect. Ground temps are still quite warm, and surface temps will also be above freezing until after the precip ends. Where and when snow occurs, model soundings indicate large wet snowflakes. A rather deep and saturated dendritic growth zone, combined with a near-freezing isothermal layer in the low levels, should result in ideal conditions for large flakes. The high reflectivity values on radar to our west are indications of these large wet targets. Clearing skies will occur late tonight and Monday morning as the system pulls away to our northeast and weakens. North winds around 10 knots will keep temps from climbing out of the lower 40s in most areas Monday. Overnight lows will be in the 20s Monday night as winds slacken and skies become partly cloudy. Clouds will increase Tuesday ahead of the next system. .LONG TERM...(Tuesday night through Sunday) Issued at 216 PM CST Sun Dec 13 2020 Forecast confidence is moderate through the period, as the medium range guidance is in good agreement in the larger-scale details. However, there is some spread in the finer details of precipitation amounts and type especially Tuesday night into Wednesday and again Saturday. The 12Z guidance in general has trended farther north with the surface trough/low early Wednesday, and that has pushed the surface freezing line farther north and west. As for QPF the models have trended almost completely dry for Tuesday evening. The focus for 06Z- 15Z Wednesday is over the eastern half of the region with the greatest QPF over the Tri State and Pennyrile. Although the model soundings are warming in the low-levels, there still is no significant warm layer off the surface, so a good bit of the precipitation will fall as snow, with the exception of the southern Pennyrile where it may be all rain. The impact, if any, will be determined by the surface temperatures. The GFS and ECMWF ensembles continue to lower the probability of sub-freezing surface air over the Tri State with the 50% threshold being near I-64. Figure that any potential for travel impacts early Wednesday will be along and north of I-64 in southwest Indiana and then on the back edge of the precipitation shield over southeast Illinois. We still have up to near an inch of snowfall in the grids, but the current expectation is that the surface will be warm enough in most places to limit any accumulations to grassy areas. We will remain dry and cool Wednesday afternoon through Thursday, but then short wave ridging aloft will push the surface high east of the area and allow south winds to develop Thursday night into Friday. Forecast confidence dwindles as we head into next weekend, as there is considerable variation in the timing of our next storm system. There will be southerly low-level flow ahead of it, and no fresh cold air coming into the back side of the system, so wintry impacts are not expected. There is no instability in the GFS, so thunder is not a concern either. We will have PoPs spread out from late Saturday through Sunday due to the spread in the model timing, but in reality it will likely be a 12 to 18 hour event. && .AVIATION... Issued at 711 PM Sun Dec 13 2020 A low pressure system will pass well to our south tonight. Its associated widespread precipitation will be spread across mainly western KY and parts of se Missouri until not long after midnight. IFR conditions are expected in the precip, mainly from 00z to 08z. Farther north around KMVN, little if any precip is expected, so there is no mention of IFR conditions there. In the wake of the system, clearing skies are expected between 09z and 12z at most locations. Light north winds will increase to around 10 knots late tonight. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...Winter Weather Advisory until midnight CST tonight for MOZ100- 107-108. IN...None. KY...None. && $$ SHORT TERM...MY LONG TERM...DRS AVIATION...MY/DB
Area Forecast Discussion
National Weather Service Pendleton OR
230 PM PST Sun Dec 13 2020 .Updated Aviation Discussion. .SHORT TERM...The main sensible weather concerns begin with the current winter weather event with advisories in the eastern Cascades, southern Blues, and the Grande Ronde Valley with a winter storm warning in effect for the Northwest Blues and Northern Blues of OR. Otherwise, next round of winter weather is expected Tuesday-Tuesday night with generally light snowfall in the mountains. Wintry mix to light snow possible Tuesday morning elsewhere with rain then more so possible in the afternoon. Light breezes will also be possible in the foothills and northeast OR Tuesday afternoon-Tuesday night as well. Latest water vapor imagery shows a upper trough extending across the eastern North Pacific southeast into the Pacific Northwest and offshore with the main shortwave trough approaching the northern CA coast. Recent radar display shows precip mainly confined to the foothills of the Blues and the Blues with a few spotty showers in parts of the Basin. Snowfall rates generally look to be light though there has been some instances with visibilities down to a half mile to a mile suggesting 1 to 0.25 per hr rates at times, though not for a longer duration or frequent in nature. The aforementioned upper trough will weaken as the primary shortwave moves onto northern CA and dives southward over the Central Great Basin overnight. Current thinking is we will continue to see snow at times in the eastern Cascades and parts of the Blues tonight with upslope enhancement favoring the northern Blues. While we may see some spotty precip (mix or snow) at times in the OR Basin and foothills tonight, precip chances there and south central WA will be low. Most recent HREF and recent runs of the HRRR continue to depict occasional to periods of snow in the Blues put coverage looks limited elsewhere by and large. Shortwave ridge builds upstream Monday and moves into the region late. This should provide fair conditions by and large tomorrow through tomorrow night ahead of the next system. Of which, ensembles and deterministic guidance in good agreement with a upper closed low developing late Monday-Monday night offshore British Columbia and its warm front moving onto the OR coast Tuesday morning. Decent moisture with this system with precipitable waters increasing 125-150% of normal Tuesday and modest transport seen via IVT directed eastward into the region. Moderate-high confidence in the placement and location of IVT given closeness of the GEFS and GFS thus moisture should be sufficient for some wintry conditions in the higher terrain. Greatest snowfall amounts look to be seen 4,000 ft and higher with amounts peaking 2-4 in the northern Blues of OR into WA. Elsewhere, 2-6 are forecast in parts of the WA/OR Cascades generally above 3,000 ft with increasing snow levels then late Tuesday. .LONG TERM...WEDNESDAY THROUGH SUNDAY...The extended period will be rather active, as several systems are expected to drive through the PacNW. A transient upper level ridge will be departing our area through Wednesday morning, opening the door to an incoming system that will be increasing rain and snow chances through the afternoon and evening hours on Wednesday. Expect light valley rain and mountain snow to occur with the passing of this system, producing the majority of the associated precip Wednesday evening through Thursday morning. Areas of higher elevations will continue to see light snow through much of the day on Thursday, while lower elevation rain should taper off by Thursday morning. Models are still in disagreement with timing and intensity, but they are slowly coming to a compromise. The ECMWF is still the wetter and slightly earlier product by about 3 hours, which is down from 6 hours from yesterday`s model comparison. The GFS is much drier because it holds onto a relatively strong high pressure center over western Colorado which helps to break up the incoming system, where the ECMWF slides the high more east and south, delaying its influence until the system begins to reach Idaho. Forecast is leaning toward the ECMWF with snow levels between 3000-4500 feet, snow amounts of 1-5 inches, and valley rain amounts hovering around 0.1-0.2 inches. Another transient upper level ridge and associated surface high will move onshore Thursday night. This ridge will continue to move quickly east through our area overnight before driving into southern Idaho and northern Utah by Friday evening, which should coincide with another approaching system from the NW. The initial wave of this system will be rather weak, and should bring rain and snow showers to the Cascades and west of the Cascade crest Saturday morning. Models are also having a tough time with this system as well, as the GFS pushes moisture over and into the Basin, but the ECMWF keeps it confined along the Cascades. The initial wave will be reinforced by the main trough late Saturday into Sunday, which looks rather robust. At this time, snow levels should be high enough to warrant rain showers across the area, with the exception of mountain snow above 4000 feet. This system will be a slow mover, keeping mountain snow and low elevation rain in the forecast into the beginning of the workweek. Snow levels will initially be between 3000-4500 feet, but are expected to increase along with the frontal passage to 5000-6500 feet. Guidance on rain/snow amounts are currently quite erratic, but the hypothesized results could be double what we experienced earlier in the week due to this lingering, slow moving system. 75 && .AVIATION...00Z TAFS...Variable conditions currently across all sites, with LIFR for PDT/ALW, MVFR at DLS/YKM, and VFR for RDM/BDN/PSC. Conditions will continue to degrade to LIFR/IFR for all sites except for RDM/BDN, which should bottom out in MVFR after 03Z. LIFR expected to continue for PDT/ALW until 18Z due to the low cigs and vsby associated with the frontal passage and developing fog overnight into tomorrow morning. PSC also will be wondering into LIFR land near 10Z as cigs drop and haze develops into the morning hours. 75 && .PRELIMINARY POINT TEMPS/POPS... PDT 29 41 28 43 / 40 10 0 50 ALW 30 40 31 43 / 50 10 0 60 PSC 30 38 31 43 / 20 10 0 20 YKM 25 39 26 39 / 10 0 0 30 HRI 30 42 29 43 / 20 10 0 30 ELN 25 38 26 37 / 10 0 0 50 RDM 26 44 26 46 / 30 0 0 30 LGD 28 40 24 36 / 60 20 0 70 GCD 29 40 25 39 / 60 20 0 60 DLS 34 45 33 43 / 30 10 0 50 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory until 4 AM PST Monday for ORZ049-503-509. Winter Storm Warning until 4 AM PST Monday for ORZ502. WA...Winter Weather Advisory until 4 AM PST Monday for WAZ520. Winter Storm Warning until 4 AM PST Monday for WAZ030. && $$ SHORT TERM...80 LONG TERM....75 AVIATION...75 UPDATE... FIRE WEATHER...
Area Forecast Discussion
National Weather Service Springfield MO
455 PM CST Sun Dec 13 2020 .SHORT TERM...(This evening through Monday) Issued at 221 PM CST Sun Dec 13 2020 Near term forecast: Snow over far se KS and southern MO will end later this afternoon and this evening. We have had some reports of road impacts right along the nw AR/southwest MO border region where a few inches have fallen so far. No plans to make big changes to the advisory, but may knock out a few counties over the northern and western part where warm temperatures have limited accumulation. KSGF airport area has seen snow for a couple of hours with no accumulation. Will have to watch trends in our eastern counties going into the evening hours with temperatures dropping a degree or two. Overnight into Monday: HRRR and some other guidance is slower to clear shallow stratus out tonight, and hedged a little bit that way with the forecast, a bit warmer and cloudy/mostly cloudy. Moist layer looks too shallow for much drizzle, but will need to watch. We should clear out any stratus very early Monday leaving a sunny sky and light winds with a sfc ridge moving through. .LONG TERM...(Tuesday through Sunday) Issued at 221 PM CST Sun Dec 13 2020 Tuesday: Another shortwave moving onshore along the northern CA coast will shift quickly into the southern Plains Tuesday supporting a chance for some light snow/flurries late Tuesday/Tuesday evening. Moisture will be lacking for this system, and progged accumulation looks limited. Wednesday-Sunday: A progressive pattern will continue, but a lack of low level moisture will limit precip chances for the rest of the work week. Should see a nice warmup by Friday with gusty south-southwest winds and a sharp upper level ridge. There is good general agreement for another frontal passage early next weekend with a brief window of opportunity for some showers, but again, only limited/modified Gulf moisture looks to be available for us with better chances for rain expected to be to our east. Sunday looks dry. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 453 PM CST Sun Dec 13 2020 For the 00z TAFS, light to moderate snow will gradually diminish over the next few hours at the TAF sites and then come to an end from northwest to southeast by mid to late evening. A clearing sky is expected overnight from west to east. Until then, we are expecting IFR conditions to continue. && .SGF WATCHES/WARNINGS/ADVISORIES... MO...Winter Weather Advisory until midnight CST tonight for MOZ082- 083-091-092-096>098-104>106. Winter Weather Advisory until 9 PM CST this evening for MOZ090- 093>095-101>103. KS...NONE. && $$ SHORT TERM...DSA LONG TERM...DSA AVIATION...Lindenberg