Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/08/17

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
731 PM CDT Fri Apr 7 2017 UPDATE Issued at 621 PM CDT Fri Apr 7 2017 Will allow the wind advisory to expire at 7pm. Winds continue to slowly diminish, but there are still a few sites reaching avisory criteria. UPDATE Issued at 558 PM CDT Fri Apr 7 2017 Cancelled the RFW a little early this evening. RH was only meeting criteria as winds diminished to 15 to 20 mph. No sites within the warned area were meeting criteria this evening. Gusty winds will linger across the east through the evening, but are expected to slowly diminish after sunset. && .SHORT TERM...(This Evening through Saturday) Issued at 334 PM CDT Fri Apr 7 2017 Forecast challenges continue to swirl around fire weather conditions heading into the first of the weekend. Currently, under a mostly sunny sky, temperatures are warming through the 60s and 70s and breezy to rather windy southerly winds continue. A Wind Advisory remains in effect across northeast South Dakota until 7 PM CDT for sustained winds around 30 mph and gusts up to 45 mph. Also, a Red Flag Warning continues until 8 PM CDT this evening across Fire Weather Zones 267 and 270 due to a combination of much above normal warm temperatures, very dry air and breezy south- southwesterly surface winds. Very dry conditions and above normal warmth will stick around through Saturday out ahead of a cold front`s passage. The cold front will push its way across the region late tonight through Saturday afternoon. Expect elevated fire weather conditions again Saturday afternoon along and ahead of this frontal passage. When the front shifts winds to northwesterly, there is the potential for some preliminary strong gustiness, before conditions settle down to just breezy northwest winds for a few hours. The airmass behind this frontal passage will gradually cool things down during the second half of the weekend. Relative Humidity values will recover some as well. Along with the precipitation chances later in the period, these cooler/higher moisture conditions will considerably reduce grassland fire danger indices. The airmass tonight and Saturday will remain warm and dry. Winds will continue from a south-southwesterly direction but not as strong, except up on and in the lee of the Prairie Coteau where breezy conditions are possible. The aforementioned cold frontal passage on Saturday should be a dry frontal passage, and initially could pack a bit of wind gustiness punch post-frontal, especially over north central South Dakota. Earlier in the day a few iterations of the RAP model`s 0.5km wind progs had increased to between 45 and 50 knots in a slim north/south corridor running right behind the fropa/wind-shift. The latest RAP output from 19Z appears to have backed down to more like 35 to 40 knots immediately post-frontal. This may be something to closely monitor for the rest of the evening and overnight (strength of initial post-frontal wind gusts). .LONG TERM...(Saturday Night through Friday) Issued at 334 PM CDT Fri Apr 7 2017 A pronounced low pressure system will slowly cross the region Saturday night through Monday evening. WAA showers and thunderstorms are possible Saturday night/Sunday morning, depending on the location of the LLJ. Weather conditions Sunday and Monday will be rather interesting and complicated. The GFS suggests the upper level trough will become slightly negatively tilted with clearing, destabilizing conditions possible by midday. If this occurs, then there is the potential for a few stronger storms Sunday afternoon. Otherwise, colder air will begin to move into north-central and western SD Sunday evening through Monday morning with PCPN gradually changing over to all snow. Snowfall amounts of 1-3 inches will be possible in north-central SD. Pcpn will slowly end from west to east on Monday as the storm system pushes east. Dry conditions will not last long as another storm system will cross the region Tuesday night through Wednesday with additional showers and thunderstorms expected. Of note, the GFS is the faster model solution and brings this system through before 12Z Wednesday. Thursday and Friday should be dry as upper level ridging builds into the region. && .AVIATION...(For the 00Z TAFS through 00Z Saturday Evening) Issued at 621 PM CDT Fri Apr 7 2017 VFR conditions are expected through the period. Gusty southerly winds will diminish tonight and shift to the northwest on Saturday behind a front. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Wise SHORT TERM...Dorn LONG TERM...SD AVIATION...Wise
Area Forecast Discussion
National Weather Service Cheyenne WY
926 PM MDT Fri Apr 7 2017 .UPDATE... Issued at 914 PM MDT Fri Apr 7 2017 We have decided to leave the high wind warning for Arlington and the Laramie in tact during the next 18hrs. Latest low level water vapor imagery is showing some shortwave energy moving northeast out of Utah with pretty good mountain wave activity in its wake. The models are also hinting at a 50-55kt of 700mb jet energy moving through southern Wyoming late tonight into tomorrow morning. Otherwise, it looks like a fairly quiet night. Latest HRRR is showing a decent shot of some convection developing in in Carbon County late tomorrow afternoon into tomorrow evening. Not much cape is associated with this convection, but there is a lot of strong winds aloft which may cause some showers and isolated thunderstorms with some strong winds. UPDATE Issued at 700 PM MDT Fri Apr 7 2017 We did lower wind speeds a bit tonight except in the wind prone area of Arlington where the high wind warning remains in effect. The models are showing the local height gradients weakening with the thicker cloud cover continuing to stream across the area. This may limit the potential to reach high wind criteria. We will leave the warning in effect for now, and see how the trends go && .SHORT TERM...(This evening through Sunday) Issued at 212 PM MDT Fri Apr 7 2017 Tonight...Southwest flow aloft strengthens as a weak cold front also passes west to east across our counties. Although 700 height differences from Craig to Casper are not all that impressive this evening, the models prog 50 knots of wind at 700 mb and with current gusts of 40 to 50 mph in the Arlington area, would not be surprised at all to see some gusts exceed 60 mph tonight, thus have upgraded the Arlington zone to a high wind warning starting at 6 pm. Quite mild overnight with nearly all low temperatures in the 40s due to decent mixing. Saturday...Strong southwest flow aloft continues and with progged low and mid level winds, felt confident enough to upgrade to a high wind warning for the Laramie Valley and Laramie. Continued mild temperatures, especially east of Interstate 25 with downslope warming despite cloud cover. Enough low and mid level moisture to aid in the production of scattered afternoon showers west of a Douglas to Laramie line. Saturday night...Next powerful negatively tilted shortwave trough aloft moves into western Wyoming with a strong cold front entering our western counties after midnight. Shower chances will continue west of a Douglas to Laramie line along the cold front and baroclinic band, otherwise dry. Not as mild as Friday night. Sunday...Powerhouse closed low aloft moves to northeast Wyoming in the afternoon with strong cold air advection across our counties. Based on the strength of the low and mid level gradients, some locations across southeast Wyoming will likely be near or exceed high wind criteria, though felt it would be most prudent to hold off on high wind watches with the expected high winds at Arlington and Laramie tonight and Saturday. Considerably cooler with strong cold advection in the wake of the cold front. Wraparound showers most common north of a Laramie to Chadron line closer to the deeper moisture associated with the closed low aloft. .LONG TERM...(Sunday night through Friday) Issued at 212 PM MDT Fri Apr 7 2017 We will keep chance PoPs for scattered snow and rain showers going across the northern zones and out west in the mountains Sunday night into Monday, then we maintain a dry period Tuesday through Thursday as GFS and ECMWF keep most shortwave energy to our north. We will bring in some small PoPs towards late next week as the upper flow goes southwesterly and we see the potential for increased shortwave activity ejecting northeast from a larger trough moving onshore in California. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 542 PM MDT Fri Apr 7 2017 VFR conditions are expected across the area tonight and tomorrow, with gusty winds continuing to be the main issue. Winds will begin to drop off over the next 1-2 hours for sites east of the Laramie Range. KRWL and KLAR will continue to have gusts around 30kts overnight. Tomorrow afternoon, gusts ranging from 25 to 35 kts are expected, across all sites. High to mid level clouds will continue to hang over southeast Wyoming and western Nebraska tonight and tomorrow. && .FIRE WEATHER... Issued at 212 PM MDT Fri Apr 7 2017 Red flag warning continues until early this evening along and east of Interstate 25 for gusty winds and low humidities. Slightly higher humidities the next several days will limit fire weather concerns. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...High Wind Warning from 6 AM to 6 PM MDT Saturday for WYZ115. High Wind Warning until 6 PM MDT Saturday for WYZ110. NE...None. && $$ UPDATE...REC SHORT TERM...RUBIN LONG TERM...JG AVIATION...KC FIRE WEATHER...RUBIN
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
919 PM CDT Fri Apr 7 2017 .UPDATE... Issued at 918 PM CDT Fri Apr 7 2017 Forecast still appears on track with only high clouds moving across the area at mid evening. Latest surface analysis shows that the ridge axis has moved into Illinois, and the RAP shows it continuing to move east overnight. Latest indications are that winds will pick up even in the eastern counties toward morning which will lower the frost potential. Coldest lows will still occur over the eastern counties where the current temperatures are the coldest and the winds are the lowest compared to central MO where winds will increase through the night. Britt && .SHORT TERM... (Through Late Saturday Afternoon) Issued at 210 PM CDT Fri Apr 7 2017 Not a lot of change thru the period from the prev forecast. Sfc ridge continues to build ewd thru the region. Nwly winds will gradually diminish this afternoon and evening and become sly as the ridge axis passes. This is expected to allow temps to drop fairly quickly this evening, then become steady. Temps across the wrn half of the CWA may even rise somewhat late tonight as winds begin to pick up. This once again raises the question of frost potential for tonight. Winds will eventually pick up from the south over ern portions of the CWA and shud limit frost potential. Have used temps that occurred over central MO this morning for the forecast tonight over IL counties. The main difference is that IL has far fewer low lying areas. With expected temps in the upper 30s and dewpoints in the lower 30s, believe frost will be more difficult to develop. Conditions are borderline across far ern counties, but have held off issuing a headline attm. Otherwise, with sly winds increasing on Sat and thermal ridge pushing 10C to 12C 850mb temps into the area, expect temps to reach the 70s. Tilly .LONG TERM... (Saturday Night through Next Friday) Issued at 323 PM CDT Fri Apr 7 2017 Temperatures on Sunday look quite warm due to the lingering influence of the departing upper ridge axis, favorable southwest winds at the surface, and mixing to near H9. Mixing does not look as deep on Sunday compared to Saturday due to a stronger temperature inversion between approximately H9-H85 on Sunday. Most areas should reach the mid to upper 70s on Sunday, which is 10-15 degrees warmer than average. SHRA/TSRA chances will increase on Sunday evening ahead of a low pressure system, but the highest precipitation chances are on Monday afternoon/evening associated with the passage of the surface cold front and upper trough axis. Strong to severe thunderstorms may be possible with this system given model depictions of around 40kts of 0-6km shear. Depending on the speed of the cold front, there may be a sharp temperature gradient somewhere across the CWA on Monday afternoon. Temperatures will be cooler on Tuesday within the post-frontal air mass. Dry weather is expected on Tuesday and Wednesday, but recent model runs show much more disagreement (compared to 24hrs ago) regarding a disturbance in either southern Canada or the northern plains during this time period. This leads to lower confidence in a dry forecast for Tuesday and Wednesday, especially if Monday`s frontal boundary stalls in southern MO. An upper ridge begins to build across the west-central CONUS towards the end of the week. Model solutions depict a few weak disturbances which attempt to undercut the ridge axis as well as a separate vort max near the Great Lakes on the downstream side of the ridge. The pattern resembles an omega blocking pattern on the GFS, but the ECMWF shows a more slanted ridge axis. Precipitation chances late in the week are tied to the evolution of these features, but there is low confidence in the details because model solutions diverge after 12z Thursday. Kanofsky && .AVIATION... (For the 00z TAFs through 00z Saturday Evening) Issued at 614 PM CDT Fri Apr 7 2017 Dry and VFR conditions are expected through the period. Winds will turn out of the south after 06-12Z as high pressure moves off to the east. SPECIFICS FOR KSTL: Dry and VFR conditions are expected through the period. Winds will turn out of the south after 12Z as high pressure moves off to the east. Britt && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Pocatello ID
137 PM MDT Fri Apr 7 2017 .SHORT TERM...Tonight through Sunday. Clouds and showers continue over a good chunk of eastern Idaho this afternoon. Most of the activity is along and behind the first front/windshift which appears to be pushing into the Magic Valley as of 1pm. Expect showers to continue increasing from west to east through early evening. We`ve seen a couple of storms already and where we can maximize instability, we will likely see more isolated thunderstorms. Expect locally heavy rain or mountain snow along with small hail and gusty winds over 45mph. The overall pattern has been breezy today but not enough to trigger a Wind Advisory but that could change between now and midnight. That boundary pushes into the eastern highlands and stalls/washes out there overnight. That area will see the best chance of rain and snow, with less shower activity to the northwest for a few hours. Snow levels drop to around 6000-6500ft in most areas. We will see a pocket of snow levels down to valley floors across the southeast corner, where heavier precipitation is expected. This will allow for rain or a mix to change to all snow. Wet and slushy accumulations are forecast even at those valley floor locations like Soda Springs, Grace and Montpelier. Showers will gradually increase areawide tomorrow as the main storm and stronger cold front arrives in the afternoon from the west. The GFS shows less of this front vs the other models so we discounted its forecast to some degree. Expect more thunderstorms tomorrow. These storms may end up a little stronger but still not necessarily severe. However, we proved a few days ago...all it takes is one to change that. Snow levels drop to valley floors by tomorrow evening. Behind tomorrow`s front it will be windy. The question is WHEN the winds behind the front develop. Some data shows that occurring late in the afternoon and extending all the way into Saturday night, will other data shows them holding off until Saturday night. For now, we will NOT issue a Wind Advisory. By Sunday morning, most of the precipitation (SNOW) will be confined to the central mountains and eastern highlands. There is some hint of a convergence band shift across the Snake Plain anywhere from Pocatello northward. We did include a better chance across the Plain in these areas until that becomes more clear. IF we see this band form, that will be any real chance of seeing measurable snow across the Snake Plain. We are only talking about an inch or so at most. Road temperatures may cool off enough for a few hours to create slushy conditions. The WINTER WEATHER ADVISORY will continue for the southeast highlands as we are expecting up to 8" (perhaps locally higher) at/above pass level and up to 3" for some valley locations. Slushy/slick roads are possible. We will also continue with a SPS advertising some snow for the central mountains and Upper Snake Highlands especially tomorrow night and Sunday. We could see up to 5" down to around 6500ft with locally higher amounts well above pass level. Keyes .LONG TERM...Sunday night through Friday. Main concern early on is a short wave ejecting out of the mean upper trough in the Pacific. This is set to impact the Central Mountains late Monday morning, expanding south and eastward to the rest of the forecast area by Monday afternoon/evening. It appears to be a fast-moving wave, thus precip amounts will be fairly light. Ridging will begin to set up on Tuesday leading to drier conditions, but warm air advection Wednesday may help trigger some precip, though the GFS has downscaled coverage of precip over the past couple runs. The ECMWF remains dry for Wednesday, and does so through Thursday night. Both models project a deeply amplified pattern late in the week with strong southerly flow continuing into Friday. The GFS is slightly faster in advancing precip into the area Thursday night while the ECMWF holds off until around mid-day Friday. Temps should be above normal Wednesday and Thursday as a result of the amplifying southerly flow and concomitant warm-air advection. Hinsberger && .AVIATION...Active pattern through the forecast period as synoptic lift increases as a cold front pushes through this afternoon. Winds should remain strong through this evening, especially along the front. Currently downslope flow is keeping low levels dry, and little precip is reaching the ground at KPIH, KIDA and KBYI. GFS and NAM depict heavy banded precip occurring along and behind the cold front. HRRR also suggests heavy banded precip this evening, but placement will be hard to pin down. Frontal forcing and instability will drive some convection this afternoon, but no severe activity is anticipated at the terminals today. Ceilings will likely drop to MVFR in the heaviest rain, and may drop to IFR. LIFR cannot be ruled out, especially at KSUN. Hinsberger && .HYDROLOGY...The FLOOD WARNING for the Portneuf at Pocatello continues and is still expected to rise to just above Moderate flood stage over the weekend. Based on the latest forecast and expected rain/snow, we re-issued the FLOOD WARNING for the Bear River at the Wyoming border. That should rise above flood stage sometime Sunday. Again, it all depends on the placement of heavier precipitation (which might be downstream of there) but it probably won`t take much. The FLOOD ADVISORY for southeast Bear Lake County remains in place as well. We`ll need to watch flows below Magic Dam once again as new rain and snowmelt could lead to flows peaking again around 5500cfs, which would produce more flooding between the dam and ID-75. Keyes && .PIH WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 6 PM this evening to 6 AM MDT Sunday for IDZ023-025. && $$