Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/24/17

Area Forecast Discussion
National Weather Service Dodge City KS
549 PM CST Thu Feb 23 2017 ...Updated aviation discussion... .SHORT TERM...(This evening through Friday) Issued at 305 PM CST Thu Feb 23 2017 Our area is in the middle of 2 competing airmasses this afternoon. A cool airmass to the north is holding off the further advancement of higher terrain dry downslope air that has made it into Elkhart, Hugoton and Liberal by early this afternoon. The HRRR and RAP13km models showed a narrow area of convective development anywhere from Dodge City eastward through Stafford/Great Bend and northward, corresponding to a band of moderate CAPE values ahead of the warm front and frontal forcing zone. Given the environmental parameters, a brief marginally severe hail storm couldn`t be ruled out in this area during the very late afternoon. Meanwhile, the wave responsible for developing the large scale lift and winter storm across Nebraska will continue lifting northeast, with some potential for rain and snow showers to clip the northern sections of our area (namely the I-70 corridor and the Wakeeney and Hays area). Little more than a dusting to a half inch of snow looks possible form the most optimistic model runs. The area will remain under the influence of cold northerly surface winds through the day Friday. Low level overcast clouds should influence central Kansas through the day, however sun should be returning from southwest to east through the day. Much of the area won`t exceed the mid 30s for afternoon highs. .LONG TERM...(Friday night through Thursday) Issued at 305 PM CST Thu Feb 23 2017 Much colder temperatures returning by Saturday morning, as cold surface high pressure settles over the area. The entire area could be in the the teens, with low teens in the extreme western counties. Models indicate a slow moderation in temperatures through the early part of next week, with a couple of westerly waves along the way bringing outside chances for precipitation, Sunday night and Tuesday. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 549 PM CST Thu Feb 23 2017 Strong low pressure system moving out of southwest into south central Kansas early this evening. North winds gusting to 35-40 knots at the beginning of this period should diminish somewhat after sunset but will continue at 15-25 knots overnight. MVFR to occasional IFR cigs are expected at the terminals overnight but should improve to VFR by Friday morning. In addition, snow showers will be possible around the Hays terminal later this evening. && .FIRE WEATHER... Issued at 130 PM CST Wed Feb 22 2017 It will be tough to see true red flag conditions across the extreme northern sections of the warned area, like Scott County, northern Finney and Lane. However farther south the conditions will easily be met with stronger winds than forecast earlier and the latest HRRR model runs taking the windy dry conditions across the entire southern tier to Barber county. Lane and Scott counties dropped from red flag. && .PRELIMINARY POINT TEMPS/POPS... DDC 27 41 17 46 / 10 0 0 0 GCK 26 38 16 46 / 10 0 0 0 EHA 27 42 19 48 / 10 0 0 0 LBL 29 44 19 47 / 10 0 0 0 HYS 29 34 18 44 / 40 20 0 0 P28 34 46 21 47 / 10 0 0 0 && .DDC WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 8 PM CST this evening for KSZ063-064- 074>080-084>090. && $$ SHORT TERM...Russell LONG TERM...Russell AVIATION...Gerard FIRE WEATHER...Russell
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
924 PM CST Thu Feb 23 2017 .UPDATE... Southeasterly flow off the Gulf of Mexico has returned faster this evening bringing higher dewpoints to across the I-35 corridor and Escarpment. HRRR and RAP indicated this better than the other models and have updated to generally follow their trends. Stratus has also developed near the Coastal Plains. Expect it will push further to the northwest and may approach the I-35 corridor overnight. Then, a Pacific cold front will surge east pushing this deeper, yet shallow moisture back to the Coastal Plains early in the morning. Otherwise, no significant changes to the South Central Texas forecast. && .PREV DISCUSSION... /ISSUED 531 PM CST Thu Feb 23 2017/ AVIATION DISCUSSION...FOR 00Z TAF PERIOD... VFR conditions expected to prevail through midnight. An approaching cold front may result in some BR prior to frontal passage forecast to reach the I-35 terminals just before dawn. Then winds will shift to the northwest becoming gusty in the afternoon. May cause some impacts to north/south oriented runways. PREV DISCUSSION... /ISSUED 252 PM CST Thu Feb 23 2017/ SHORT TERM (Tonight through Friday Night)... Upper air analysis this morning showed nearly zonal flow across the southwestern US with a trough over the northern Rockies. At the surface, high pressure was centered over the Gulf and winds were from the southeast to southwest. The upper level trough over the northern Rockies will swing down through the southern plains. A cold front will move through north Texas tonight and our CWA Friday morning. The atmosphere is still very dry and the front will not generate any precipitation. Behind the front, drier air will move in with breezy northwesterly winds. Temperatures will be cooler behind the front, but still above normal. LONG TERM (Saturday through Thursday)... Dry weather will continue Saturday. Low level winds will become southeasterly bringing moist air back to the region. Sunday there may be sufficient moisture and isentropic lift to produce showers and thunderstorms. Monday another cold front will move through the region bringing a chance for showers and thunderstorms Monday and Tuesday. High pressure will build back in behind the front with dry weather through the remainder of the period. FIRE WEATHER... Relative humidity will drop below 20 percent across all of our CWA Friday afternoon. Breezy northerly winds between 10 and 15 mph will lead to near critical fire weather conditions. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 57 80 42 65 45 / - 0 0 0 0 Austin Bergstrom Intl Airport 56 80 41 65 43 / - 0 0 0 0 New Braunfels Muni Airport 56 82 42 66 45 / 0 0 0 0 0 Burnet Muni Airport 52 75 37 61 42 / 0 0 0 0 0 Del Rio Intl Airport 54 80 44 74 51 / 0 0 0 0 - Georgetown Muni Airport 55 77 39 62 42 / 0 0 0 0 0 Hondo Muni Airport 53 83 41 70 46 / 0 0 0 0 0 San Marcos Muni Airport 56 81 41 65 44 / - 0 0 0 0 La Grange - Fayette Regional 59 81 43 66 45 / - 0 0 0 0 San Antonio Intl Airport 56 83 44 67 47 / 0 0 0 0 0 Stinson Muni Airport 57 83 45 69 48 / 0 0 0 0 0 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Mesoscale/Aviation...TB3 Synoptic/Grids...04 Public Service/Data Collection...Williams
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
844 PM CST Thu Feb 23 2017 .UPDATE... 844 PM CST Primary change to going forecast this evening was to sharpen up the temperature gradient across the area tomorrow. Strong warm front is looking increasingly likely to make it as far north as about I-80, with areas north of the front likely to see low clouds, fog, drizzle, and occasional showers with stiff northeast winds likely to hold temps in the upper 30s or lower 40s. GFS and NAM have been consistent their past few runs with this, though RAP and HRRR are a bit more gung-ho on bringing the front a bit farther north, especially given the tendency for the cold lake to retard northward advancing warm fronts this time of year. To the south of the boundary temperatures should climb well into the 60s with 70 not out of the question far south if the sun breaks out. Big question convectively for tomorrow is how far west will initiation occur. Impressive EML advecting into the area should provide for a strong capping inversion that will take some work to overcome, though strong forcing and heating in the warm sector should eventually cause cap to break, just a matter of whether it is over our eastern CWA or just to our east. Unusually strong instability for this time of is progged tomorrow with very strong shear as well, leading to the potential for supercells and damaging wind producing line segments. At this distance, too hard to say exactly where initiation will take place, so no changes made to that aspect of the forecast this evening. Continued isentropic ascent tonight should lead to continued development of scattered showers and eventually some thunderstorms too as steeper lapse rates advect north and lead to increasing elevated instability. Overall, forecast for tonight appears to be in good shape. Did add some fog to the forecast for late tonight and especially Friday morning north of the warm front, where some locally dense fog could form, especially north of the warm front close to the surface low. Izzi && .SHORT TERM... 230 PM CST Tonight through Friday... Several forecast concerns through the short term period, including large north-south temperature gradient, locally heavy rainfall, timing/extent of thunderstorms, and the potential for severe weather Friday afternoon across the southeastern parts of the cwa. Deepening surface low pressure was over far southwestern Kansas this afternoon, with a nearly stationary frontal boundary extending northeast into central IL and IN. This low is expected to propagate to near far southern Lake Michigan by mid-afternoon Friday, in response to a strong mid-level short wave ejecting from the central Rockies. Isentropic upglide was already developing into the region this afternoon, as indicated by rain spreading into western IL per regional radar mosaic. Increasing south winds above the warm frontal inversion into this evening will support strengthening moisture transport, and an increase the coverage and intensity of showers/rain. Guidance focuses the greatest pops and rainfall amounts generally along/north of the I-88 corridor across northern IL, with high-res members eventually shifting focus mainly across and north of the IL/WI border area early Friday morning. Forecast soundings depict precipitable water values approaching 1.00" late tonight, with blended guidance QPF of 0.75-0.95 inches north of I-88 indicated through Friday. Thunderstorm potential appears fairly high for late February, with a plume of steep mid-level lapse rates (700-500 mb >7.5 C/km) atop 40-50 kt southwest low-level jet late this evening into early Friday morning. Forecast soundings depict anywhere from 150-450 J/kg of elevated mucape which should support embedded thunder especially across the aforementioned area overnight. The surface low is progged to be over far northeast MO/western IL near Quincy by 12Z Friday, with general model agreement in taking it across the southern parts of the Chicago metro/far southern Lake Michigan during the mid-late afternoon hours. With the mid- level dry slot spreading across the cwa from the southwest during the afternoon, the focus for surface-based thunderstorm development is across the southeast parts of the cwa, especially east of I-55 and along/south of I-80 (with much of the high res CAM guidance highlighting areas from I-57 east). SPC has appropriately tightened up the western part of the day 2 slight risk a little further east of their previous outlook. WRF and GFS soundings indicate fairly substantial capping around 750 mb, though large scale height falls associated with ascent with approaching mid-level wave, divergent left exit region of upper jet and surface cold front should be enough to force a narrow band of convection along/just ahead of the front during the afternoon. While mlcapes are fairly week (<500 J/kg for the most part), 40-50 kts of effective shear will support storm organization. While some supercell structures are possible, the primary severe threat should be damaging winds from convection within gusty southwesterly 25-35 kt background wind field. Storms should exit the cwa prior to sunset. Back to the west, the southeastern periphery of the synoptic deformation precip should spread in during the afternoon, but should remain all liquid through sunset. Occasional light rain/drizzle is possible earlier in the day as well across much of the area as low levels remain moist beneath the mid-level dry slot and increasing deep layer ascent. Temperatures will continue to depict a large north-south variance across the forecast area. Cool northeast winds north of the warm front and low track will produce temps mainly in the 30s and 40s this evening, but will slowly rise into the 40s-50s by Friday as the low approaches. Farther south 50s overnight will warm to the 60s Friday before colder air surges in late. Ratzer && .LONG TERM... Friday night through Thursday... 214 pm...Main forecast concern is the potential for accumulating snow early Saturday morning...mainly across the northern half of the cwa...along with much colder temps. Active pattern next week with various systems but with low confidence. Much if not all of the convection is expected to be east of the area by early Friday evening as colder air spreads across the region and a dry slot moves across the area in the evening. Wrap around moisture on the back side of the departing low will move across the area late Friday night into Saturday morning. Qpf amounts by Saturday morning could approach a tenth of an inch across the north...lowering to trace amounts across the south. With the colder air arriving a bit faster...precip should transition to mainly snow by late evening and continue through mid morning on Saturday. While snow amounts have gone up...generally around an inch north of I-88...trailing to a few tenths along I-80...there is still quite a bit of uncertainty as to how much snow may accumulate on pavement. While the ground will be warm... air temps will be falling into the mid/upper 20s by sunrise Saturday. If the snow is able to fall quickly and heavy enough... there could be some accumulation on pavement but confidence is low from this distance. Northwest winds will become strong/gusty Friday night and continue into Saturday but there remains differences as to how strong winds will become. Gusts into the 30-35 mph look reasonable currently with speeds/gusts diminishing with sunset Saturday evening as a ridge of high pressures moves across the area Saturday night. Southerly winds could become breezy/gusty Sunday as the gradient tightens between the departing ridge and a trough moving across the western Great Lakes with low pressure moving from the southern plains Sunday to the Ohio Valley it weakens. The Ecmwf remains dry with system while the Gfs lifts precip into the southern cwa and maintained chance pops for this potential. And if precip did could be a mix of rain/snow but confidence remains low. Another ridge of high pressure moves across the area Monday night as the next low moves from the central plains Monday night to the upper Great Lakes Wednesday though the Gfs favors a weaker low tracking through the Ohio Valley. Trended more toward the Ecmwf which would suggest mainly rain Tuesday/Wednesday with precip ending before colder air arrives. Confidence remains low with this system as well. Both models then show a clipper system moving across the area Thursday night and from this distance...are in fair agreement. Thermal profiles would support mainly snow with this clipper. cms && .AVIATION... For the 00Z TAFs... Multiple potential weather related aviation problems over the next 24 hours. First, SHRA will continue to develop and move across the terminals this evening. MVFR CIGS partially a result of the lake should hold and eventually develop farther inland and build down to IFR this evening. Isolated to scattered thunderstorms expected to develop later this evening and there`s a reasonably good chance that SCTD TSRA will affect or be close to the terminals at times tonight. Latest high-res guidance would continue to support most likely timing for potential thunder in the late evening/early overnight timing from the previous TAFs. Continued moistening of the low levels and slowly approaching warm front favor lowering CIGS and VSBY, with cold wind off the lake further favoring very low CIGS and potential for dense fog Friday morning as warm front attempts to lift north. For now, kept the denser fog potential in a PROB30 group due to inherent uncertainties in forecasting fog, however synoptic pattern quite favorable for dense fog north of a strong warm front and MOS guidance is hitting the threat fairly hard as well. Latest guidance would support surface low tracking just south of the terminals, except perhaps GYY could pop into the warm sector Friday. North of the surface low track, very little improvement in CIGS expected and dense fog potential could even linger into the afternoon until winds back to northwest later in the afternoon. Largely followed the trends of previous TAFs which showing improvement in the afternoon, but feel this is an optimistic solution assuming the sfc low tracks to our south. Winds should swing around to the west or northwest late in the afternoon or early in the evening, but stronger/gustier winds will likely hold off until later in the evening with the better push of cold air. Izzi && .MARINE... 214 pm...Low pressure over the south/central plains will move northeast to the southern tip of Lake Michigan Friday evening and then into Quebec Saturday. Strong northeasterly winds will increase to gale force tonight as the gradient tightens ahead of this approaching low. While gales will diminish Friday evening... speeds will remain in the 30kt range and then as colder air spreads across the region and the gradient tightens...northwest gale force winds are possible from early Saturday morning through Saturday afternoon. A ridge of high pressure will move across the southern lakes region Saturday night with winds shifting southerly Sunday and a period of 30 kts is possible especially on the southern half of the lake. Another strong area of low pressure may move across the upper midwest and northern lakes region Tuesday into Wednesday next week. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...Small Craft Advisory...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 3 PM Friday. Small Craft Advisory...LMZ741-LMZ742-LMZ743-LMZ744 UNTIL 9 AM Friday. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
816 PM CST Thu Feb 23 2017 .UPDATE... Issued at 815 PM CST Thu Feb 23 2017 Will downgrade northern portions of the headlines shortly. Now that the event is underway and hi-res models are getting a relatively good handle on the dry air and where the snow shield will advance, feel confident on tightening the PoP, QPF, and snow amount gradients. Global model resolution is too coarse to resolve the ridiculously tight gradient expected which results in bleeding the snow too far northward. This means locations like Redwood Falls and the Twin Cities proper may not see a flake. The 00Z NAM has shifted south slightly again which confirms this idea. As for the area that will see snow, we are still not seeing widespread steady snow, and it appears the models are too eager to break things out this evening, particularly the NAM. However, it is still expected to become intense tonight near the Iowa border. Visibilities are 1/4 mile in several locations of northwest Iowa and thunderstorms are breaking out just south of there so a maturing snow shield is under development. Expecting this snow shield to shift mostly east northeastward tonight, then pivot more northeast Friday. Amounts on the northern periphery of the Blizzard Warning may be a little high if the HRRR was to verify, but can`t get too cute. This southward shift in the past couple days has been a little surprising to say the least considering the monster totals advertised on all the models and their ensembles at one point. Suspect this is due to the very large upper low over Florida which deamplified the eastern ridge and resulted in a flatter pattern, sending the low eastward and taking a more southerly track. The mid level features aren`t as strong and compact either and are instead more sheared which will prevent the monster totals (15-18"+) from falling where the heavy band does set up. The WSW and the rest of the product suite will be issued shortly. && .SHORT TERM...(This evening through Friday night) Issued at 342 PM CST Thu Feb 23 2017 Surface analysis this afternoon shows development of a classic mid-latitude cyclone over the TX/KS panhandles with an extended surface front from the center of this system ENE into lower MI and a trailing cold front over NM/AZ. Aloft, a large longwave trough which moved onshore the lower CA coast has shifts atop the central-southern Rockies. The upper trough is expected to deepen over the central-northern Plains during the day tomorrow through tomorrow night, helping add plenty of energy to the developing surface low. The surface low will shift across KS tonight and over northern MO tomorrow morning, on its way to lower Lake Michigan by tomorrow evening then Lake Huron by Saturday morning. Deep Pacific moisture will accompany this system, so much so that QPF amounts for southern MN look to range 1.00-1.50" by the conclusion of this system. Though there continues to be good model agreement (outside of the NAM which has and remains a significant outlier) that SE MN will be in the crosshairs for the highest snowfall totals, the consensus track took another slight shift to the SE, thus lowering the snow amounts and hence the impacts mainly N and W of the Twin Cities metro. As such, some minor reconfiguring of the headline products were made but the point must still be made that there will be a very tight NW-SE gradient of snow amounts just to the south of the Twin Cities metro. As an example, counties like Le Sueur or Nicollet or Dakota or Brown could see as much as a 6" difference in snow totals from NW to SE across each respective county. Snow has commenced in far SW MN this afternoon and snow will gradually spread mainly E and slightly N as the overnight progresses. There may even be a slight mixture with rain at the immediate onset but any mixture of precipitation will have a short duration before become all snow. As the surface low shifts ENE and the upper level trough pivots to help enhance the surface feature, snow coverage and intensity will increase during the early morning hours, likely with rates increasing to 1-2"/hr for several hours in far southern MN and into SW WI. The morning commute for southern/eastern MN into western WI will likely have ongoing snow then the snowfall will steadily diminish as the day progresses. However, strong winds for much of the region will contribute to the blowing snow issues, making for hazardous travel conditions for much of southern MN. Another concern is isolated thunderstorms could develop over far southern MN into southwestern WI. Instability levels are not entirely zero given the antecedent moisture levels plus the incoming surge and that additional lift will be created by the pivoting upper level trough. Confidence not high enough to include mention at this point but some thunder cannot be ruled out. Precipitation will end from west to east late tomorrow afternoon through tomorrow night and the wind speeds will decrease as well, resulting in partly to mostly cloudy skies for the start of the weekend. As for temperatures, once temperatures drop below freezing later this evening, they will remain below freezing throughout the duration of this event. Lows tonight to highs tomorrow will have a very small diurnal range, potentially 5 degrees or less from tonight through tomorrow. As colder air wraps around this system as it departs, lows will drop into the teens tomorrow night, temperatures this area has not seen in some time but will be actually right on par with climatological norms. .LONG TERM...(Saturday through Thursday) Issued at 342 PM CST Thu Feb 23 2017 Temperatures will warm through early next week. A fairly large storm will develop over the Upper Midwest, but thermal profiles should be warm enough to have mostly rain, especially if the system translates westward with time. A weak clipper system will sweep through the region on Sunday and could bring some snow across MN/WI. On Monday the southern stream will develop a storm to the southeast over the Ohio river valley. This will be followed by a third system Tuesday into Wednesday. This mid-week storm will have a favorable temperature gradient to work with and should develop strong cyclone. However, there is a lot of warm air with this storm, so the primary p-type will be rain, with perhaps some snow mixed in. There is still uncertainty with this storm, but as of now it appears that the chance is quite low for this system to develop into a winter storm for the Upper Midwest. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 553 PM CST Thu Feb 23 2017 There have been rather significant changes to the 00Z set of TAFs. Per a plethora of latest guidance, the northern edge of the snow will be very sharp and may miss KRWF, KMSP, and KRNH entirely. Unfortunately each of these locations is on the edge and it can shift either way so wasn`t confident in completely removing the snow but it is possible that will need to be done in the next several hours. Outside of the snow, VFR conditions will prevail through the period. KMSP...As discussed above, KMSP will be on the northern fringe of the snow later tonight and Friday. Depending where it does set up, further adjustments to the TAF may be necessary. /OUTLOOK FOR KMSP/ Sat...VFR. Wind NW 10-15 kts becoming W. Sun...VFR. Chc MVFR/-SN. Wind SW-W 5-10 kts. Mon...VFR becoming MVFR. Chance afternoon -RASN. Wind S 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...Winter Weather Advisory until 6 PM CST Friday for WIZ015-023. Winter Storm Warning until 6 AM CST Saturday for WIZ016-024>028. MN...Winter Weather Advisory until 6 PM CST Friday for MNZ063-069-070. Winter Weather Advisory until noon CST Friday for MNZ067-073. Blizzard Warning until 6 AM CST Saturday for MNZ074>078-082>085- 091>093. && $$ UPDATE...BORGHOFF SHORT TERM...JPC LONG TERM...JRB AVIATION...BORGHOFF
Area Forecast Discussion
National Weather Service Marquette MI
943 PM EST Thu Feb 23 2017 .UPDATE... Issued at 943 PM EST THU FEB 23 2017 Due to the very dry llvl airmass shown on local 00Z raobs as well as general diffluent llvl flow associated with weak sfc rdg axis over the Upr Lks, removed the potential for any lk effect pcpn near Lk Sup. A quick look at the incoming 00Z NAM and 01Z RAP shows sn spreading into the scentral cwa late tngt, so wl maintain the 09Z start to the advy time for that area. && .SHORT TERM...(This evening through Friday) Issued at 341 PM EST THU FEB 23 2017 The main forecast concern through Friday evening will be the arrival of system snow across the area on Friday, with the potential for upslope/lake enhancement snow in the northeast wind snow belts Friday afternoon/evening. The initial system snow looks like it will be on the wet and heavy side, especially across central and eastern portions of the area. In the afternoon hours, the snow is expected to transition over to a mixture of freezing drizzle/ice pellets across the east. Afternoon water vapor imagery shows a strong, deep upper-level trough beginning to lift out of the southern Rockies with a strengthening lee cyclone developing in far southwest Kansas/southeast Colorado. Tonight, expect mid and upper level clouds to stream back northward as the above mentioned system begins to lift northeast towards the Great Lakes region. Do not expect any precipitation tonight; however, through the early morning and morning hours as surface to 850mb flow veers to the north-northeast expect light lake effect snows to develop in the north and northeast wind snow belts. 850mb temperatures do not look terribly cold and the inversions are quite low, so not expecting much in the way of lake effect accumulations across the north through the early morning hours on Friday. However, further south across south central portions of Upper Michigan were 850-700mb warm air advection begins to lift north through the early morning hours, a fairly strong mid- level front will strengthen and may allow for a quick 1 to 2 inches of wet, heavy snow to fall through the early morning hours. As we progress through the mid-late morning through the afternoon hours, the models are fairly consistent with the warm air advection wing to lift north across the area allowing system snow to spread north across the remainder of Upper Michigan. Temperature profiles are on the warmer side of things, especially across eastern and central portions of the area, so the snow should keep wet and heavy characteristics. As we progress through the afternoon hours, the models are fairly consistent with a dry slot moving over at least eastern portions of the area. Forecast soundings show cloud ice dissipating within the dry slot; however, given the depth of the low- level cold air would not be surprised the freezing drizzle is able to refreeze before reaching the ground. Therefore, may see a mixture of freezing drizzle/ice pellets. Further west across central and western portions of the area through the afternoon hours, things are a bit more uncertain. The GFS would favor a much drier solution and would hold off additional precipitation chances until the evening hours, but given the onshore flow and cooling 850mb temperatures behind the system tend to favor the high-res models guidance that favor higher QPF, especially across the higher terrain in the northeast wind snow belts. .LONG TERM...(Friday night through Thursday) Issued at 406 PM EST THU FEB 23 2017 Beginning Fri night, 4 km NAM and CMC regional soundings still indicate mid-level drying into at least the east half of Upper Mi through much of Friday night which could cut off ice nucleation until cold advection at lower-levels reintroduces ice back into the cloud for some lake enhanced snow. For now, fcst will continue to reflect some mix with -fzra, more likely just -fzdz, which will cut down snow accumulations over the e half to just 1-3 inches Fri night. If the mid level moisture does not cut out, snow accumulations will be higher than currently fcst Fri night. To the n central and especially w, the air mass will be cold enough to support lake enhancement as winds back more northerly. However, the far w will be near the edge of deep layer moisture with the system, making for a challenging fcst. The 4km NAM and Canadian sounding maintain deeper moisture near KIWD through much of Fri night while the GFS sounding shows deeper moisture cutting out already by late Fri evening. This model difference could range from 6-12hrs of heavy snow to mainly just light snow. Will continue to lean toward the more conservative side with fcst for the n central and w with snow accumulations Fri night in the 3-6 inch range. System will exit on Sat with a transition to light LES from w to e. Finally, gusty winds up to 30mph, higher at times in exposed areas near Lake Superior, will lead to blsn, mainly Fri night into early Sat afternoon. As it appears now, the potential for snowfall amounts to reach 12 or 24hr warning criteria is limited so will go with winter weather advisories at this point, highlighting a period of wet moderate system snow Fri morning and then the potential for moderate to possibly heavy lake enhanced snow late Fri into Fri night. Will continue advisories over the ne counties through Sat for combination of light les and blsn as northwest wind gust at or above 30 mph. Some light les could linger for the west to northwest wind snowbelts Sat night into early Mon as h85 temps hover around -14c through much of the period. The only other fcst item of note occurs during the midweek period next week. Shortwave dropping down the W Coast Sun/Mon is fcst to shift e and ne to the Great Lakes midweek. GFS is weaker and much farther se than the 12z run yesterday. The CMC/ECMWF remain more amplified and stronger with sfc low that will lift into the Great Lakes, and suggest a low track far enough n for mixed pcpn or even just rain for a time for at least the southeast parts of the fcst area. Majority of CMC ensembles favor a warmer look, and fcst will continue to include mixed pcpn. Thus will definitely be a system to monitor for next week. After this system departs late Wed, models suggest that at a clipper system will move through the Upper Lakes region on Thu with the potential for some more light system snow. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 643 PM EST THU FEB 23 2017 There wl be some lo clds/MVFR cigs at times at the TAF sites this evng, but overall coverage wl be limited by a llvl acyc flow/dry air. As a lo pres to the sw moves toward the area later tngt, more widespread MVFR cigs wl overspread the area along with incrsg chcs for -sn. Although there is still some uncertainty on the track of the sfc lo/overall sn coverage, incrsg ne winds along with some sn/blsn wl incrs the potential for IFR/perhaps LIFR vsbys thru Fri. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 406 PM EST THU FEB 23 2017 NE to N gales to 35-40 kts are expected over much of Lake Superior Fri morning into Fri night and NW gales to 35-40 knots are expected for much of central and eastern Lake Superior Sat into Sat evening. Some heavy freezing spray is possible Fri night into Sat, but coverage will be limited to mainly the shoreline areas along north central Upper Mi. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Winter Weather Advisory from 7 AM EST /6 AM CST/ Friday to 7 AM EST /6 AM CST/ Saturday for MIZ001>005-009-084. Winter Weather Advisory from 7 AM Friday to 7 PM EST Saturday for MIZ006-007-014-085. Winter Weather Advisory from 4 AM EST /3 AM CST/ Friday to 1 AM EST /midnight CST/ Saturday for MIZ010>013. Lake Superior... Gale Warning from noon Friday to 10 PM EST Saturday for LSZ264>267. Gale Warning from 7 AM EST /6 AM CST/ Friday to 1 AM EST /midnight CST/ Saturday for LSZ162-263. Lake Michigan... Gale Warning from 7 AM to 7 PM EST Friday for LMZ248-250. && $$ UPDATE...KC SHORT TERM...Ritzman LONG TERM...Voss AVIATION...KC MARINE...Voss
Area Forecast Discussion
National Weather Service Omaha/Valley NE
935 PM CST Thu Feb 23 2017 .UPDATE... Issued at 922 PM CST Thu Feb 23 2017 Overall going forecast in good shape tonight. Strong ascent associated with CDPVA in the 700-300 mb layer coupled with weak static stability to some upright instability has led to an area of moderate to occasionally heavy precipitation from northern KS into eastern NEb/western IA. Models are consistent that this area of lift will shift north and east over the next several hours with mid-level dry intrusion working into the southern 2/3 of the FA. This will likely shut off precipitation for a time overnight. For precipitation type so far we have seen snow in northeast NEb with some moderate accumulations to this point. Within the strongly forced band we have seen some thunderstorms with a mix of hail/sleet and some snow on the northwest edge. Late tonight as the mid-level cyclone center works east across NEb we will see the deformation band sink to the southeast associated with moderately strong thermal advection with associated frontogenetic circulation. This should be an all snow band as it drops to the southeast with snow moving back into the I80 corridor around 09-10Z. The snow is then expected to continue in northeast NEb/w-central IA down to the I80 corridor and a bit south into Friday afternoon. The precipitation intensity will be much lighter late tonight and through the day on Friday as the static stability increases as mid-level lapse rates decrease, but snow ratios will also be increasing. One concern for accumulations along the I80 corridor is the increasing sun angle and generally light nature to the snow on Friday may limit to some degree the impact on roadways, but a good deal of uncertainty remains on how that affect the impacts of the storm. This concern is less over the northern CWA where much of the heavy accumulations will be overnight. Otherwise snow amounts from previous series of forecasts looks on track and no changes to those or the headlines are anticipated at this time. && .SHORT TERM...(tonight through Sunday) Issued at 220 PM CST Thu Feb 23 2017 ...Major winter storm still on track to affect the region through Friday... Forecast overall remains on track for a major winter storm to affect the region tonight into Friday. Some complications for the expected weather include a chance of thunderstorms this evening across southeast Nebraska and southwest Iowa, which will include a severe threat with some hail possible. Second compounding factor will be a changeover from rain to snow, where that initially sets up, and how fast it moves southeast through time. Northeasterly winds will continue to increase to 20 to 30 mph through time, with gusts 30 to 40 mph possible. One of the major changes that we have made with the upcoming package is to include a slightly faster changeover from rain to snow based pm Rap model trends. A couple of notes regarding QPF, the GFS model came in a little lower, while the SREF and NAM models perhaps a little higher, which both indicate up to 12 inches or more from northern NE through northern IA. The ECMWF as not as high, similar to the GFS. Blending all of that together, combined with input from WPC. Overall, forecast snowfall amounts have not changed significantly from the previous package. We are still forecasting 6 to 10 inches for the northern half of the forecast area, from 2 to 5 along and either side of Interstate 80, and an inch or less in southeast Nebraska. Concerning our current package of winter weather headlines, we anticipate no major changes with this package, although we may adjust the start time of the last group of headlines. We feel the the overall alignment and message of expected impacts looks good with current products in effect. We do have very strong winds forecast with this system, and will continue to mention near blizzard conditions expected with 1/2 mile visibility along with blowing snow and possibly drifting. However, just not confident we`ll see widespread 1/4 mile visibility for 3+ hours, thus have no plans to upgrade any of the area to a blizzard warning at this time. Snow accumulation rates will be winding down significantly Friday afternoon, tapering to flurries, and ending altogether before midnight. Due to recent warmth, soil temperatures are running in the mid to upper 40s. This will easily be overcome by expected rates. Impacts to travel will eventually develop. Near blizzard conditions are expected across northeast NE and northwest IA. Travel may eventually become impossible over parts of of the area. Quiet weather expected on Saturday. Another weather system brings a chance of small snow and rain south of I80 on Sunday, with the GFS a little more robust than the ECMWF. .LONG TERM...(Sunday night through Thursday) Issued at 220 PM CST Thu Feb 23 2017 Another quick moving weather system moves through the region on Tuesday. Again, the GFS is more robust with this than the ECMWF, but we will have a chance of snow and rain in the forecast. And one more system may graze our northern counties on Wednesday. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 555 PM CST Thu Feb 23 2017 Precipitation has switched over to snow at KOFK, and periods of moderate to heavy snow are expected to continue through the evening with gusty north and northeast winds. Lighter snowfall and some blowing snow is then expected late tonight and into Friday with IFR conditions continuing. Scattered TSRA are still expected at KLNK/KOMA this evening, with some possibility of a sleet and rain mixture near the end around 06Z. We then expect a dry period into the night with continued IFR conditions. The snowband is likely to move into KLNK/KOMA around 08-10Z and continue through the day on Friday with IFR conditions expected through the day. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Winter Storm Warning from 3 AM Friday to midnight CST Friday night for NEZ034-044-045. Winter Weather Advisory from 3 AM Friday to midnight CST Friday night for NEZ050>053-065>067. Winter Storm Warning until midnight CST Friday night for NEZ015- 032-033-042-043. Winter Storm Warning until midnight CST Friday night for NEZ011- 012-016>018-030-031. IA...Winter Storm Warning from 3 AM Friday to midnight CST Friday night for IAZ043-055. Winter Weather Advisory from 3 AM Friday to midnight CST Friday night for IAZ056-069-079. && $$ UPDATE...Boustead SHORT TERM...DeWald LONG TERM...DeWald AVIATION...Boustead
Area Forecast Discussion
National Weather Service Spokane WA
745 PM PST Thu Feb 23 2017 .SYNOPSIS... A cool and unsettled pattern will continue over the Inland NW right into the weekend and into early next week. The main precipitation threat will be mainly mountain based snow showers, but a stronger system on Sunday may bring minor snow accumulations to the valleys and Basin. Temperatures will be cooler than normal for this time of year with overnight lows in the teens and 20s and daytime highs only in the 30s. A gradual warm up is forecast by the middle of next week. && .DISCUSSION... Small update this evening to remove snow showers in the Camas Prairie, adjust sky cover, and lower temperatures in the Blue Mtns. There has been no snow observed on the area cams and models are in good agreement that the dendritic layer is dried out over the Camas Prairie. There is still some cloud cover wrapping into the area from the storm system well to the south however any precipitation that falls from this deck will be in the form of flurries. A better chance for a light snow showers will exist across far SE Shoshone County not really impacting any populated areas. It will be a chilly night with overnight lows in the teens and twenties. Areas of freezing fog expected to develop but confidence is not stellar if it will be as widespread as this morning with HRRR indicating only very shallow activity and far less coverage. This makes sense as nearly all ASOS sites are 4 to 9 degrees drier than this time last night. /sb && .AVIATION... 00Z TAFs: Fog and stratus development are expected tonight over the KGEG...KSFF and KCOE TAF sites as the cold air mass decouples overnight. Overrunning clouds from a weak system off the coast may help break the stratus between 16Z and 18Z into MVFR stratocumulus ceilings with a small chance of -SHSN during the afternoon hours. It is uncertain and low confidence forecast for a return of stratus to KPUW overnight tonight with the favorable upslope westerly winds expected to weaken and shift more southerly overnight which would favor less of a threat for IFR conditions by Friday morning. KLWS is expected to remain VFR overnight as is KMWH and KEAT. During the day Friday upslope low level flow into the Cascades will allow thickening and lowering ceilings at KEAT and may deteriorate to MVFR during the afternoon with -SHSN developing near the TAF site. /MJF && .PRELIMINARY POINT TEMPS/POPS... Spokane 18 34 19 34 24 34 / 0 10 10 10 30 60 Coeur d`Alene 17 34 16 34 22 34 / 0 10 10 10 50 60 Pullman 20 36 20 36 25 36 / 0 10 10 20 30 60 Lewiston 25 40 25 41 27 40 / 0 10 10 20 20 60 Colville 18 35 18 35 24 35 / 0 20 10 10 30 60 Sandpoint 19 33 17 34 23 33 / 0 20 10 20 50 60 Kellogg 19 33 18 33 23 33 / 0 20 10 20 50 70 Moses Lake 18 35 19 35 25 36 / 0 10 10 0 20 30 Wenatchee 20 32 19 34 24 35 / 0 20 10 0 30 40 Omak 19 32 19 32 24 33 / 0 20 10 0 40 50 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Friday) Issued at 245 PM CST Thu Feb 23 2017 The short-term period will consist of precipitation chances along with a return more seasonable February temperatures. As of Thursday afternoon a deepening surface low was situated over southwestern KS. An east to west oriented warm was located over the southern CWA. Mid level lapse rates continue to steepened in response to the upper level low progressing from northern Colorado into western Nebraska. The biggest question mark through the evening hours is whether the EML will hold across northern KS. Latest 00Z-03Z forecast soundings from the RAP and HRRR suggest a stronger EML than previous runs. Sufficient large scale forcing is expected as a upper level short wave will move across north-central KS and south-central KS. Modest isentropic lift within the 300-305K will remain across the area through 06Z. If parcels were able to break the cap, around 500 J/KG of MUcape and 40-50 knots of effective shear would be available. With this potential for supercells, SPC has upgraded portions of north-central KS to a slight risk with the primary hazard being large hail. We then transition back to typical winter conditions overnight into Friday. As the surface low pushes east of the area overnight, CAA in response to gusty northwest winds will cool temperatures throughout the day on Friday. High temperatures for Friday will occur at midnight, with afternoon temperatures ranging from the low 30s in the north to low 40s in the southern areas. The bulk of precipitation associated with upper level low in Nebraska is expected to stay north of the area. However, sufficient low level moisture may exist for light wintry precipitation, mainly along the KS/NE border, possibly as far south as I-70 throughout the day on Friday. Forecast soundings suggest a brief period near dawn across far north-central KS, where only low level saturation exists. With surface temperatures hovering near freezing, I have introduced a couple hours of light freezing drizzle. Pavement temperatures are well above freezing across the entire area, therefore expect minimal accumulation and impacts to roads. .LONG TERM...(Friday night through Thursday) Issued at 245 PM CST Thu Feb 23 2017 Lingering deformation zone on the backside of our departing system may continue to bring light snow to portions of far NE Kansas early Friday night, but little to no accrual is expected. Surface ridging will build in overnight Friday into Saturday morning resulting in a gradual decrease in winds and cloud cover. The progressive zonal flow pattern behind the departing trough will allow the 1026 mb high to slide through the region through the afternoon on Saturday and set the stage for our next system on Sunday. Medium range solutions are struggling with how this upstream wave will interact with a cutoff low NE of Hawaii, which is having a direct impact on the timing and location of the wave as it translates ESE on Sunday. The GFS solution brings out a more amplified H500 wave for Sunday, which in turn brings more precip to the area. Continued using a blend of the GFS/ECMWF for POPs through this period, with confidence in this portion of the forecast lower than average. Temperatures for the weekend will linger around climatological average for this time of year with a slight warming trend for Sunday as weak WAA takes place behind the departing ridge. An active pattern will continue into mid week as a longwave trough slides east across the CONUS. This will likely bring another round of precip (mostly in the form of rain) to the area on Tuesday into Wednesday, but as with the Sunday system, confidence in the placement of the precip is lower than average. Highs on Tuesday will likely rebound back into the 60s ahead of the approaching frontal boundary, falling back into the 40s and 50s for mid to late week. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 527 PM CST Thu Feb 23 2017 A surface cold front will push southeast across the terminals this evening and switch winds to north at 14 KTS with gusts to 22 KTS. There may be a chance for showers at MHK this evening...and possibly some isolated showers at KFOE and KTOP late this evening. Low stratus of 1000 to 1500 feet will move southeast across the TAF sites during the early morning hours of Friday. The ceilings may gradually rise above 2,000 feet during the late afternoon hours of Friday. There may also be some isolated to scattered showers Friday afternoon. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Baerg LONG TERM...Skow AVIATION...Gargan