Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/18/18

Area Forecast Discussion
National Weather Service Bismarck ND
900 PM CDT Tue Apr 17 2018 .UPDATE... Issued at 850 PM CDT Tue Apr 17 2018 Mesoscale models continue to trend farther west with snow. 18Z NAM keeps any snow accumulation west of Bismarck and Minot. And the 18 April 00 UTC RAP and HRRR keep accumulations well west of Bismarck and Minot. Utilized a blend which still kept a couple tenths in Bismarck but kept Minot dry. Overall theme here is precipitation remains confined to the vicinity of the inverted trough, which continues to weaken overnight and Wednesday. Heaviest snow totals remain in this area, from around Crosby and Tioga, through eastern Dunn county and between Dickinson and Hebron and south into South Dakota. Generally an inch amounts in this area, maybe up to 1.5 inches. Snowfall tapers quickly as you go east or west of this line. Updated text products will be sent shortly. UPDATE Issued at 540 PM CDT Tue Apr 17 2018 Quick update to update pops/qpf. Latest 18Z medium range model guidance and latest mesoscale models continue to trim back on the eastward extend of precipitation and total qpf with this system. Utilized a blend of latest mesoscale guidance with current Superblend and medium range models. This delays higher pops and precip around Bismarck/Mandan until after midnight and knocks back snow totals to around a half inch (in Bismarck/Mandan). This may even be overdone if trends continue, but at least a good start. Still may see an are of 1-2 inches but likely in a narrower band. Updated text products will be sent shortly. && .SHORT TERM...(This evening through Wednesday) Issued at 220 PM CDT Tue Apr 17 2018 Light rain will continue moving eastward from eastern Montana into western and central North Dakota this evening. Expect light rain to change over to light snow later this evening as the forecast NAM BUFR soundings show temperatures falling below freezing throughout the entire column with a saturated snow growth zone. The forecast NAM sounding in Bismarck for 12z matches the observed 12z sounding very well, so confidence is high that the NAM will continue performing well into tonight. Light snow will likely continue through tonight and into tomorrow morning as a convergence zone with associated mid-level frontogenesis becomes nearly stationary over central North Dakota. Any leftover snow will change back over to light rain during the late morning and early afternoon tomorrow as surface temperatures warm into the 40s for most spots. Expect a trace to an inch or two of snow accumulation from most of western and central North Dakota by tomorrow afternoon. Conditions dry out tomorrow afternoon and evening as a surface high pressure system begins building in from the west. .LONG TERM...(Wednesday night through Tuesday) Issued at 220 PM CDT Tue Apr 17 2018 High pressure will dominate western and central North Dakota Wednesday night through Thursday night, making for calm weather. Some leftover clouds will keep temperatures in the 40s and lower 50s on Thursday. A split flow pattern with a large upper- level low over the four-corners region will prevail on Friday, giving southern North Dakota a slight chance of light rain for Friday and Friday night. A ridge will build over North Dakota on Saturday and Sunday, leading to sinking motion and mostly clear skies. This will allow for strong mid-April sunshine to warm western and central North Dakota into the low to mid 60s on both Saturday and Sunday. Although the latest suite of model guidance suggests colder conditions mainly in the 50s, the bias-corrected models have been about 5 to 10 degrees too cold in most spots the past couple of days, likely due to a pattern change to warmer weather. The ECM and MAV MOS guidance has been performing much better, suggesting highs very close to what has been observed. For these reasons, the high temperatures for Saturday and Sunday have been manually increased by 5 degrees or more across all of western and central North Dakota to account for model guidance likely being too cold. Chances for light rain and snow return to southern North Dakota for Monday through early Tuesday morning as a shortwave moves through from the northwest. Conditions dry back out Tuesday afternoon and evening as a ridge begins building back in from the west. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 850 PM CDT Tue Apr 17 2018 Light rain will spread into central North Dakota this evening while changing over to snow, leading to MVFR/IFR conditions for KBIS by 07z and KMOT by 10z. Once MVFR/IFR conditions arrive at any given terminal, expect those conditions to continue through the morning with improving conditions in the afternoon. MVFR conditions currently forecast to not quite reach KJMS. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...TWH SHORT TERM...TK LONG TERM...TK AVIATION...TWH
Area Forecast Discussion
National Weather Service Fort Worth TX
948 PM CDT Tue Apr 17 2018 .UPDATE... The forecast is generally in good shape with just a few minor tweaks to sky and wind grids for the overnight time period. Satellite imagery at this hour revealed a decent plume of mid and upper level moisture continued to stream overhead mainly for locations near and north of I-20. A strong cold front was noted plowing through the Oklahoma and Texas panhandles at this hour. Based on pure extrapolation of this feature as well as the latest 3 km NAM, have bumped up the speed of FROPA across the area with the front now forecast to near the I-20 corridor in the 9-10 UTC Wednesday time frame and across Central Texas by around 12-13 UTC. A majority of the colder air looks to lag behind the front (though it`s likely that adiabatic compression behind the front is modifying the cooler airmass) and as a result, I`ll not make any noteworthy changes to overnight lows. In terms of the sensible weather elements, there may be the potential for a few sprinkles across the East and across Central Texas. Low level moisture seems really scarce per our evening weather balloon, but some of the clouds in the satellite imagery do have some cumuliform elements so it (sprinkles) can`t be completely ruled out. I`ve added in a silent 10 PoP across North, East and Central Texas to account for this. The other element to monitor during the overnight period into Wednesday morning will be the possibility for patchy smoke/haze---especially along the Red River. Experimental HRRR smoke products do suggest that the wind shift associated with FROPA across Oklahoma will allow the plume to become more oriented to the east and eventually southeast into the area. The degree of mixing/dispersion at this time, however, is unknown and precludes mention in the forecast at this time. If HRRR guidance becomes more aggressive/consistent with greater smoke/aerosol concentrations into North Texas, patchy smoke/haze may be inserted into the forecast. 24 && .AVIATION... /Issued 632 PM CDT Tue Apr 17 2018/ Concerns---Shift from S`ly to N`ly flow (all sites) and MVFR cigs (KACT). Visible satellite imagery shows high clouds beginning to stream over North and Central Texas. These clouds are quite or above FL250 and should pose no operational impact. S`ly flow persists this evening as a surface low develops over the Great Plains. A few low clouds could develop, but moisture should be sparse enough to preclude any MVFR cigs...but will mention FEW018 for now. Cold front will approach the Metroplex TAF sites around 18/1100Z. As front passes...winds will veer sharply out of the NW at 15-20 KT and any low clouds that may be around will clear out. High clouds should clear out by Wednesday afternoon with winds subsiding after sunset. As for the MVFR possibility at KACT...time-height cross-sections as well as forecast soundings indicate that just enough boundary layer moisture should be available for some cloud cover to develop below FL020 by 18/0900Z. MVFR should not last long however as the cold front should reach KACT by 18/1400Z...clearing out any low- level moisture and bringing a return to VFR through the end of the forecast period. Godwin && .SHORT TERM... /Issued 401 PM CDT Tue Apr 17 2018/ Temperatures this afternoon have risen into the lower 80s southeast to lower 90s northwest as strong warm air advection takes place across the Southern Plains. This warm air advection is occurring in response to lee cyclogenesis underway along the Front Range of the Central Rockies. In the upper-levels, a ridge axis is making its way through the Central CONUS, with the next trough axis located through the Great Basin as of this morning. Height falls as this trough axis propagates eastward should push a cold front through North and Central Texas late tonight and Wednesday morning. In the near-term (rest of today), the main concern will be for elevated fire conditions in the far western counties (west of a Bowie to Comanche line). Relative humidity values should bottom out in the 20-25 percent range, along with south-southwesterly winds of 15-20 MPH, and temperatures near (or even slightly above) the 90-degree mark. These conditions combined with ERC values near the 50th percentile suggest that conditions are modestly favorable for wildfire spread. Strong caution is urged if using flames outdoors. Heading into tonight, model guidance is in good agreement with the timing of the cold front. The cold front should enter our northwestern counties by 4 AM, then reach the Dallas/Fort Worth area by daybreak. Precipitation is not expected with this cold front given the dry air mass that remains in place ahead of it. While precipitation is not expected, enough low-level moisture will be in place for some cloud cover to develop ahead of the front, particularly in our eastern and southeastern counties where moisture is more abundant (though still shallow). Time-height cross-sections as well as forecast soundings indicate shallow, but rich moisture settling in late tonight ahead of the frontal passage. This should allow for mostly cloudy to overcast skies generally east of a Sulphur Springs to Hillsboro to Lampasas line. As the cold front passes, winds will veer out of the northwest at 10-15 MPH. With the exception of the northwestern counties, most locations should hit their low temperature prior to to the arrival of the cold front (and even then, cold air advection behind the cold front should not be particularly robust). Because of this, most areas will see low temperatures tonight near to slightly above where they were Tuesday morning. Over the northwest, the frontal passage will result in lows being about five degrees lower than last night. Godwin && .LONG TERM... /Issued 401 PM CDT Tue Apr 17 2018/ A dry cold will sweep through the region on Wednesday. Veering surface winds will reduce the already thin moisture across our southeastern zones, which should have northwest winds by midday, and no rain chances are expected. Breezy north winds will result in a noticeably cooler day, but the sunshine should still allow temperatures to reach the 70s Wednesday afternoon. Dew points will plunge behind the boundary, and even with the cooler temperatures, afternoon relative humidity values will likely fall below 25 percent in areas west of the I-35 corridor. But if the vegetation is green enough to fight off fire initiation today, with temperatures in the 90s, near normal daytime temperatures are even less likely to cause fire weather concerns. A seasonally cool night will follow, and northeast winds should prevent Thursdays` highs from exceeding Wednesdays`. The storm system that brought rare hail to the San Francisco Bay area and is now dropping snow on the Rockies will transit the Plains well to our north. Our next rainmaker is still over the Pacific Ocean, dropping south out of the Gulf of Alaska. Though not yet sampled by the North American RAOB network, satellite data confirm that is moving equatorward. While it`s still near the 49th parallel, this motion is improving confidence in the more southerly track guidance is advertising. There is fairly good agreement with this upper low becoming separated from the polar flow. This would tend to slow its eastward progress significantly, but the progressive pattern overall should prevent it from stalling. As this system crosses the Continental Divide, spreading lift across eastern New Mexico and West Texas, a fetch of 850mb moisture will feed afternoon convective development along a sharpening dryline. It now appears that Friday`s activity may be west of the New Mexico border, reducing the chances that any of this will reach North Texas late Friday night. However, as the upper low spreads large-scale forcing for ascent downstream of the ongoing convection, a complex of storms will likely survive overnight into Saturday morning as it invades North and Central Texas. Additional rounds of rain may significantly disrupt outdoor activities throughout the day Saturday, and we will prevail extraordinarily high PoPs for a day 4 forecast. While embedded strong storms will still appear possible during the day Saturday, the widespread rainfall should limit the available instability. For much of the region, the rather dry start to the spring means that, even with multiple rounds of rainfall during the event, significant flooding concerns are unlikely. However, the likelihood of training echoes and the slower speed of the system overall means that heavy rain may continue into Saturday night in areas east of the I-35 corridor. A cold front will invade on Saturday and result in a chilly, breezy spring day on Sunday. Some postfrontal rain chances will linger east of I-35 as the upper system plods eastward. Northerly flow on the backside of the exiting low will maintain below normal daytime temperatures into the upcoming workweek. 25 && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 61 77 52 76 52 / 10 10 0 0 0 Waco 62 78 50 77 52 / 0 5 0 0 5 Paris 60 73 45 71 47 / 10 10 0 0 0 Denton 58 75 46 74 49 / 10 10 0 0 0 McKinney 60 75 46 73 49 / 10 10 0 0 0 Dallas 62 77 53 76 52 / 10 10 0 0 0 Terrell 61 76 50 74 50 / 10 10 0 0 0 Corsicana 61 76 52 75 51 / 0 10 0 0 0 Temple 61 79 52 77 52 / 0 10 5 0 5 Mineral Wells 58 77 46 77 49 / 0 10 0 0 5 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ 24/79