Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/26/19

Area Forecast Discussion
National Weather Service Bismarck ND
812 PM CST Wed Dec 25 2019 .UPDATE... Issued at 812 PM CST Wed Dec 25 2019 Latest water vapor shows the 700mb low circulating up into Sargent County, with the 500mb low hanging back into LaMoure County. Per SPC Winter Mesoanalysis and radar, the combination of 925mb frontogenesis, sufficient Omega, and weak EPV interlocking together in the southern James River Valley has lead to some narrow banding of snow, from Jamestown to Streeter and into Wishek. Following the RAP/NAM, expect this to wane over the next 3 hours as the upper low continues to progress northeast taking the stronger ascent and instability with it. However, light snow is expected to continue tonight in the James River Valley. Have increased PoPs to categorical where we have the banded snow, otherwise will continue to let the winter weather advisory continue in the far southern James River Valley until midnight as saturation through the column per latest Oakes BUFKIT sounding doesn`t commence until that time. The previous forecast remains on track with that idea. The shortwave trough mentioned in the previous update across the southwest is now working into Mountrail County south into Stark County. Still expect some light snow and then light freezing drizzle into Bismarck/central ND later tonight. UPDATE Issued at 521 PM CST Wed Dec 25 2019 Latest water vapor imagery suggests a 700mb low circulation in northeastern South Dakota this evening, with a wintry mix on the northwestern side - which includes the southern James River Valley. Webcams still indicate a light freezing drizzle within the winter weather advisory area. A neighboring county in the Grand Forks WFO indicated light freezing rain, however calls were made to Stutsman County where a deputy said nothing was occurring in Medina, which was where the highest reflectivitys were located at the time. Webcams up to this point show no precipitation at Jamestown or Medina, and RAP BUFKIT soundings show neutral to downward vertical motion within the low level saturated layer. This remains the case until 04z, when saturation through the column occurs and light snow will commence as vertical motion increases as the 700mb-500mb low slides through. The RAP BUFKIT sounding for Carrington is similar to that of Jamestown, thus, will hold off on expanding the winter weather advisory further north until more evidence comes into play that freezing precipitation is/will occur. Another 700mb low/trough was located in southwest ND, and this will scoot into south central ND/Bismarck by around 09z. Soundings at this time show light freezing drizzle possible. We have a Special Weather Statement covering southwest ND due to this shortwave and light freezing drizzle being reported in Adams County - so certainly possible those environmental conditions across the southwest will be maintained as it nears Bismarck after midnight. && .SHORT TERM...(This evening through Thursday) Issued at 215 PM CST Wed Dec 25 2019 Forecast highlights in the short term period will be areas of fog now through Thursday morning, along with chances for light snow and/or light freezing drizzle later today through Thursday AM. Currently, long wave trough across the western CONUS with a ridge across the east puts a south/southwesterly flow aloft across the Dakotas. Extensive stratus deck remains across the region along with areas of fog/mist. Dense fog continues across the southern James River Basin and west into parts of Logan and McIntosh counties, but has shown signs of decreasing coverage outside of the James River counties. Embedded S/WV will lift north across central South Dakota into eastern North Dakota early this evening, then morphs into a cutoff low via the RAP/GFS depictions. As all this occurs, expect precipitation to increase in aerial coverage across the eastern third of North Dakota, including the James River Valley area, where models show several hundreths of QPF. BUFKIT analysis continues to indicate a lack of ice in the Dendritic Growth Zone (DGZ) over my southeast corner now through this evening. Surrounding counties in far southeast ND and northeastern SD already have winter weather advisory headlines for the freezing precip potential. Thus the plan is to hoist one as well for the southern James counties of LaMoure and Dickey where I expect the longer duration of freezing drizzle and higher ice accumulation potential. Will also include McIntosh county. Farther north across Stutsman county, BUFKIT indicate a shorter window for freezing drizzle at Jamestown (2-3 hours) saturating and turning over to all snow by mid evening, so will hold off on any headlines for them at this time. Will drop the dense fog advisory and mention fog within the winter weather advisory which will start with this forecast issuance. Winter weather advisory headlines will run through 06Z, as by then all current indications are the DGZ will be completey saturated over my southeast with precip type turning over to all snow. Farther west across western North Dakota, areas of light snow or light freezing drizzle will expand northward now through early this evening, then will move from west to east as steering winds transition to more west/northwesterly. Models remain in agreement and are consistent in developing lack of ice aloft here too, so will see a wintry mix of light snow/freezing drizzle chances advance east across western and central ND this evening through Thursday morning. QPF associated with this moisture push is light so not anticipating widespread impacts and thus no headlines at this time. Thursday will see clouds decreasing west into central, and all precipitation chances ending by 18Z. CAA behind this evening`s mid level low will produce daytime highs in the 20s for Thursday. .LONG TERM...(Thursday night through Wednesday) Issued at 215 PM CST Wed Dec 25 2019 Models continue to show deep low pressure ejecting out of the Desert Southwest and merging with a northern stream S/WV somewhere over the central high plains. Last three runs of the ECMWF have been consistently showing the low closing off earlier and farther to the west versus the GFS, bringing the potential for heavy precipitation across South Dakota and much of central and eastern North Dakota. The GFS continues to be faster and more to the east, keeping the bulk of precipitation over eastern South Dakota and far southeast ND and across Minnesota. It should be noted the last few runs of the GFS have trended towards the more consistent ECMWF. Blend of models also reflects in this trend, now putting 30-40% snow chances over my southeast, where 2 days ago there was nothing. Will definitely be watching this one closely, and will throw a mention in the HWO. Little confidence after this weekend, but should see near normal end-of-year temperatures. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 521 PM CST Wed Dec 25 2019 LIFR to IFR cigs will continue until about 18z Thursday, then a gradual improvement to MVFR and/or low VFR from 18z Thursday to 00z Friday. Light snow is forecast for KJMS from 04z Thursday through 15Z Thursday, while KBIS has potential for light snow 04z- 08z Thursday followed by light freezing rain 08z-14z Thursday. Also, light freezing drizzle is forecast at KDIK between 08z-12z Thursday. KMOT and KXWA should remain precipitation free this taf cycle. && .BIS WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until midnight CST tonight for NDZ048- 050-051. && $$ UPDATE...KS SHORT TERM...NH LONG TERM...NH AVIATION...KS
Area Forecast Discussion
National Weather Service Cheyenne WY
841 PM MST Wed Dec 25 2019 .UPDATE... Issued at 830 PM MST Wed Dec 25 2019 Short Term update... Added some fog and additional POPs to the forecast for the snow ongoing across western Carbon and Albany Counties in Wyoming. Light snow is expected to continue overnight. Accumulations should be minor but the Sierra Madres and the remaining Advisories look on track. Fog is likely to develop along and north of the pseudo stationary front across the panhandle and eastern Wyoming overnight. This should impact some Aviation terminals and may make for some locally reduced visibility through 6 am tomorrow. Potential Winter Storm this Weekend... Looking at the latest 18 and 00z Guidance, models continue to show a well organized longwave trough developing across the Rockies through the weekend. An embedded shortwave trough will dive through the southern stream late Friday spinning up a surface low along the front range early Saturday morning. Favorable dynamic lift moisture transport and upslope trajectories should result in widespread precipitation overspreading the region through Sunday morning. Latest WPC guidance favors a mix of the ECMWF and UKmet which increase QPF across the western Nebraska panhandle and eastern Wyoming. Have upped snow totals this update in accordance with this guidance. The GFS and ensemble members continue to show a faster and more easterly ejection trending away from heavier QPF. Thus, confidence in a favored solution is low with the potential for moderate impacts. Continue to monitor the forecast as details will likely change quickly as the low track is refined and snowfall estimates are finalized. && .SHORT TERM...(Late this afternoon - Thursday) Issued at 225 PM MST Wed Dec 25 2019 Afternoon WV/IR imagery depicted a broad upper trough over the western CONUS. A quasi-stationary front extended from the Midwest across the Central Plains, then north over the far western NE/SD into eastern MT. Temperatures to the east of the front remained in the 20s (Chadron), with 30s and 40s to the west. Snow showers were increasing in coverage over portions of south central and southeast WY. Gusty winds of 25 to 35 mph and lower visibility will accompany the snow showers. Looking at webcams, snow continues to fall across much of Carbon County. Sierra Madre SNOTEL data estimated 3 to 6 inches have fallen earlier, with another 3 to 6 inches expected through this evening. The lower elevations of Carbon County can expect total accumulations of 3 to 5 inches. The Winter Weather Advisory remains in effect until 11 PM MST this evening. Snow showers will taper off Thursday, lingering into the afternoon over the Snowy/Sierra Madre mountains. High temperatures will be near seasonal normals with mainly 20s and 30s. Winds will be light. .LONG TERM...(Thursday Night - Wednesday) Issued at 354 AM MST Wed Dec 25 2019 Forecast confidence degrades quickly as we advance toward Friday & Saturday. The GFS & ECMWF remain in excellent agreement w/ a large closed low over the southwestern US at 12z Fri. In the meantime, a potent short wave will be diving rapidly south across the Northern Plains. This has been well advertised for some time now, but there has been a trend toward some differences with exactly how this may evolve. The GFS acts as a kicker for the southern low which should lead to most of the energy being focused to our east. However, the ECMWF now has these systems merging over eastern CO, w/ a sub-1000 mb low over northwest KS. This would be a favorable track for snow over the western Nebraska Panhandle. The ECM and several of the EC ensembles show appreciable snowfall for those areas, while the GFS shows things staying relatively dry. The bottom line is we are not out of the woods yet, so this remains a key thing to watch through the end of the week. Otherwise, a windy pattern will likely evolve across the southeast WY wind corridors later in the period with increasing gradients in the low levels and periods of strong H7-H8 flow. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 406 PM MST Wed Dec 25 2019 Concerns for low flight conditions this evening for many of the airports in southeast Wyoming and Nebraska panhandle. HRRR and LAMP guidance showing IFR and below conditions developing after 02Z and continuing overnight. Followed their guidance on the 00Z TAFs. Airfield most uncertain will be KCYS where we have a westerly downsloping wind. Confidence not high on low conditions...but did follow the LAMP/HRRR bringing lower conditions after 05Z. && .FIRE WEATHER... Issued at 215 PM MST Wed Dec 25 2019 Chances for snowfall, cooler temperatures and non-critical humidities will preclude fire weather concerns through the weekend. Winds will be increasing this weekend into early next week, especially southeast WY. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Winter Weather Advisory until 11 PM MST this evening for WYZ104- 109-111>113. NE...None. && $$ UPDATE...LYONS SHORT TERM...MAJ LONG TERM...CLH AVIATION...GCC FIRE WEATHER...MAJ
Area Forecast Discussion
National Weather Service Dodge City KS
528 PM CST Wed Dec 25 2019 ...Updated Aviation Discussion... .SHORT TERM...(This evening through Thursday) Issued at 343 PM CST Wed Dec 25 2019 Excellent downslope conditions in the low levels today as the ejecting shortwave trough from last night helped veer out the low level winds to a more westerly component. This spread very warm low level air across much of Kansas. Numerous obs were showing mid to upper 60s by mid-afternoon. Colder air was not all that far away, though, as mid afternoon obs were showing lower 30s as far south as Kearney, NE. GOES-16 Satellite showed low stratus nicely up there, nosing down toward the far north-central KS border as of 2030z. The forecast for tonight calls for this shallow cold airmass pushing south-southwest into western Kansas tonight -- reaching I-70 Trego- Ellis County by around 03z and continuing its ooze southwestward through the night. It will likely stall out somewhere across far southwest Kansas by early Thursday morning, and this will present a big challenge in short term temperature and sky cover forecasting. In fact, the latest 18z NAM keeps much of southwest and central Kansas shrouded in low cloud and fog through midday. We lowered temperatures for much of the area tomorrow, but we may not have lowered them enough, especially if the NAM is the better forecast. It seems to have the best handle right now compared to observations mid afternoon. Given how shallow this airmass is, especially once it reaches southwest Kansas, the low cloud and fog will likely erode on the edges, albeit slowly. Areas that remain in the low cloud through afternoon will likely remain in the 30s all day, even though our official forecast calls for highs in the mid 40s for most areas. This airmass will remain locked in through Thursday Night into early Friday, and this is where things could get potentially interesting. Moisture transport above the surface will be increasing late Thursday Night into Friday morning, with light precipitation breaking out sometime in the 06-12z time frame Friday across portions of the Texas Panhandle and/or Oklahoma. The very northern edge of this initial precip by daybreak Friday (should it develop that early) may be in a mixed form of light freezing rain and/or sleet, near the Oklahoma border in particular. More is discussed on the main body of the upcoming storm (Friday into Saturday) in the Long Term section. .LONG TERM...(Thursday night through Wednesday) Issued at 343 PM CST Wed Dec 25 2019 A significant cold-season precipitation event appears to still be on track. It has been interesting to observe the changes in numerical prediction over the past couple of days from what was once a southern-stream dominant upper low expected to come out across the Central Plains to what we have now portrayed in the models -- a rapid and rather significant amplification of the northern stream, which will carry with it substantial mid level potential vorticity and mid level cold air diving south-southeast across the Great Basin and western portion of the Rockies. The former southern stream upper low will rapidly become engulfed by the now much more dominant northern stream wave Friday into Saturday. The global model consensus now supports new mid level cyclogenesis to the northwest of our southwest Kansas region, effectively keeping southwest Kansas in the warm, moist sector for just about the entirety of the upcoming precipitation event. The good news (for the moisture lovers out there), is that given this trend, it appears southwest Kansas may remain in the warm conveyor belt of this major cyclone longer, thus a longer potential duration of moderate to heavy rain late Friday into Friday Night. The trends in the northern stream digging/slowing down may not be done yet, and if this is really the case, this entire cyclone may take on a form we have not seen yet in the models with a mid latitude cyclone center perhaps even farther south than shown. For now, the official forecast still keeps snow largely away from our forecast area, even the northwest zones, but if Canadian and ECMWF models start trending more toward the deterministic GFS with respect to backside mid-level deformation zone across southwest and west central Kansas, then more snow will need to be forecast on Saturday. As mentioned in previous discussions, please keep checking back for updates, as the writing is still not on the wall yet regarding magnitude, duration, and location of greatest snow impacts with this upcoming storm. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 513 PM CST Wed Dec 25 2019 IFR ceilings along with some areas of fog will spread across north central and much of southwest Kansas tonight behind a cold front. This cold front is currently expected to cross the Hays area between 00z and 02z Thursday and then spread south southwest during the remainder of the night. As north winds develop behind this front the ceilings will decrease into at least the 500 to 1000 ft level AGL for Hays, Dodge City and Garden City. This is based on 23z observations across Nebraska and the latest forecast NAM and RAP BUFR soundings. Areas of fog will also develop during the early morning hours and may at times around daybreak reduce visibilities to less than one mile, especially in the Hays area and locations near and north of Dodge City and Garden City. After 12z Thursday the ceilings are expected to gradually improve some but given the depth of the moist layer near the surface will hold MVFR conditions in for all locations but Liberal through at least 18z Thursday. && .PRELIMINARY POINT TEMPS/POPS... DDC 28 46 27 40 / 0 0 10 80 GCK 24 46 25 39 / 0 0 0 80 EHA 29 52 29 38 / 0 0 10 90 LBL 27 51 26 40 / 0 0 10 80 HYS 25 44 24 40 / 0 0 0 70 P28 34 48 32 44 / 0 0 20 60 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Umscheid LONG TERM...Umscheid AVIATION...Burgert
Area Forecast Discussion
National Weather Service North Platte NE
629 PM CST Wed Dec 25 2019 .SHORT TERM...(This evening through Thursday night) Issued at 310 PM CST Wed Dec 25 2019 A weak upper level disturbance across the cntl Rockies will lift northeast tonight and produce light snow across northwest Nebraska. The blended model solution continues to indicate less than an inch of snow accumulation. In fact, the HRRR and RAP show little or no snow accumulation. Weak Pacific high pressure will build into wrn and ncntl Nebraska tonight through Thursday night. The blended forecast indicates the expansive area of arctic fog across wrn and ncntl Nebraska will lift this afternoon and not reform tonight or Thursday night. However, fog has been plaguing the Dakotas for a couple of days so the forecast is persistence and includes areas of fog tonight and Thursday morning across nrn Nebraska and parts of southwest Nebraska. Skies should slowly clear late tonight and Thursday from south to north as the high pressure builds into and across wrn and ncntl Nebraska. The temperature forecast leans on the guidance blend plus bias correction for lows mostly in the 20s and highs in the 30s to lower 40s. High temperatures Thursday came in a few degrees cooler than the previous forecast. This is likely the result of the expected cloud cover. .LONG TERM...(Friday through Wednesday) Issued at 310 PM CST Wed Dec 25 2019 The models are beginning to come into better agreement with the storm system off the California Coast. Still, the battle of the models continues with the GFS, GFS ensemble and CMC ensemble tracking the storm east through swrn and ncntl Nebraska, while the ECM, NAM, CMC and SREF track the storm through wrn Nebraska. All models open up a warm sector across cntl Nebraska which will produce significant freezing rain Friday night through Saturday morning before the h700mb trof moves through Saturday afternoon. The blended model approach, which is an average of the models, produces a 24 hour total snowfall of 5 to 9 inches across all of wrn and ncntl Nebraska Friday night and Saturday. The slowest model, the ECM, continues snow across northern Nebraska Saturday night through Sunday night leading to 48 hour totals of 15 inches in that area. The GFS ensemble indicates the same but over cntl Nebraska. Given the uncertainty in the storm track (wrn vs ncntl Nebraska) and duration (possibly into Sunday), it might be best to wait one more forecast cycle before issuing a Winter Storm Watch. The wind forecast uses a blend of guidance plus bias correction. This produced 15 to 25 mph wind speeds Saturday through Monday as the storm system lifts slowly into the Great Lakes. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 628 PM CST Wed Dec 25 2019 Low clouds have backed into the LBF TAF site and will continue to monitor as the western extent has been fluctuating last hour. Otherwise expect IFR or below conditions through the night in the north with light snow showers possible. Some restrictions in VIS will be possible in areas of the north but confidence is low so have not included them at this point. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Stoppkotte
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Thursday) Issued at 315 PM CST Wed Dec 25 2019 A weak cold front moves through tonight, with increasing clouds and cooler (but still likely above average) temperatures following in its wake. Upper-tropospheric ridging, which has dominated the weather pattern since last weekend, is shifting eastward as it is replaced by an amplified longwave trough over the western CONUS. At the surface, a tightening inverted pressure trough extending northeastward from a Front Range low pressure cell is positioned just northwest of the forecast area. This enabled highs this afternoon in the warm sector to push the mid-60s. Meanwhile, just upstream of the surface trough, locations in central Nebraska resided under a low stratus/fog deck throughout the day. The short-term guidance suite has struggled to resolve this cloud shield all day (especially compared to the Hastings radiometer data). With daytime insolation waning and erosion of the southern flank of the shield ceasing, am expecting that the cloud shield begins advancing southward after sunset. The evolution of this saturated layer, in particular if it will be more akin to a stratus deck or fog, is quite uncertain. To cover both ends of the spectrum, did add fog to the grids for tonight in addition to increasing clouds. There is also a chance that lower visibilities will be relegated to higher elevations owing to the warm near-surface ground temperatures and winds of 5-10 kts. These clouds look to linger into Thursday and have lowered post-frontal highs slightly from the going forecast. Skies should clear with increasing subsidence aloft by late Thursday and a 1024 mb surface high pressure cell settling southeastward into Nebraska by sunset. .LONG TERM...(Thursday night through Wednesday) Issued at 315 PM CST Wed Dec 25 2019 A wet storm system affects the area late Friday through early Sunday with cooler (seasonal) temperatures arriving in its wake. The aforementioned southern stream trough over the West Coast cuts off Thursday night, with the energy phasing with a northern stream trough late Friday into Saturday and lifting northeastward. There are still some uncertainties with how these two energy sources will interact, but confidence is high that there will be a period of moderate to even heavy rainfall beginning late Friday night and persisting through Saturday. Isentropic upglide over the baroclinic zone lifting northward as a warm front on Friday will be the main driver for increasing mid-level clouds and light rainfall, though have trimmed back PoPs earlier in the day with forecast soundings showing drier lower-tropospheric air holding firm. Increasing upper level kinematic support with the maturing H300 wave/theta-e advection along with a low-static stability airmass should result in bands of rainfall throughout Saturday, with some hints of instability through the -10 to -30 C regime supporting a slight chance of thunder through the day, mainly east. Lows Friday night will likely be reached early in the evening with temperatures rising through the night owing to strong WAA. Highs on Saturday surge back into 50s to 60s ahead of the approaching cold front. Dewpoints also push into the 40s and 50s, quite high for this time of year. PWATS are still progged to reach 0.75 to 1 inches--the 99th percentile of observed values for Topeka in late December--underscoring the unusual moisture fetch attendant with this system. The GEFS storm-total QPF has backed off slightly from yesterday, but still depicts a solid band of 1-1.5 inches of rain by the time the storm ends early Sunday. Colder air streams in on the heels of a cold front Saturday night. Whether a deformation zone forms within the colder sub- freezing airmass on Sunday remains uncertain and hinges on the structure of the lower to mid-troposphere cyclone. The 12Z GFS is the more bullish of the guidance suite in keeping a light snow band lingering through the day, with other solutions devoid of QPF or displaced further north. The main CAA surge with this event will be north of the region, enabling temperatures to stabilize and even start warming by early in the week. The first half of the work week looks to remain dry, but the pattern amplifies by mid- week, increasing the threat for additional precipitation in the central U.S. later in the week. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 544 PM CST Wed Dec 25 2019 Main concern for this forecast will be low stratus moving southward out of nebraska this evening behind a cold front. Models are not handling the situation very well with the progression of the low clouds. Expect IFR to LIFR cigs will be possible at MHK by 08Z and at TOP and FOE around 11Z. Forecast soundings from the RAP suggest improvement to VFR by 15Z. Winds will shift from the southwest to west, then to the north and northwest after 12Z. LLWS will be possible at TOP and FOE around 2000 FT through 07Z. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Skow LONG TERM...Skow AVIATION...53