Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/14/18

Area Forecast Discussion
National Weather Service State College PA
1044 PM EST Tue Feb 13 2018 .SYNOPSIS... High pressure will drift east and off the New England coast tonight. An increasingly moist southerly flow will bring unsettled conditions from mid week until a cold front passes through Friday ushering drier conditions for the weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Near term forecast problem remains centered on the potential for some light icing overnight into early Wednesday morning. The favorable right entrance region of an upper jet streak and increasing warm advection/isentropic lift will bring a small chance of some very light rain/drizzle/freezing drizzle. The latest radar shows some light disorganized showers moving through WRN PA. With surface temps hanging close to freezing, we will issue an SPS to cover potential for icy pockets. If it becomes apparent precip is actually hitting the ground as it moves into the CWA, we may need a short lived advisory. From earlier... The HRRR shows a small area of very light precip streak across the area from I-80 northward after midnight. The SPC HREF keeps the area dry so the confidence in actually seeing precip is pretty low. Covered the low threat and spotty nature of any light icing in the Hazardous Weather Outlook for now. If confidence increases that some light precipitation will actually develop, we will have to issue a short lived headline for slippery travel. Min temps overnight will be in the 25-30 deg range. The wind will be mainly east to southeast at 5-10 mph. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... Better chances for rain arrive late in the day or early evening Wed with upper level diffluence increasing and mid-lvl winds into the 50s out of the West. Max temps Wednesday will be about 10F warmer than Tuesday and it will be mild enough for plain rain everywhere by then. Rainfall amounts will stay rather light and generally several hundredths to around 0.10 of an inch, as the forcing continues to look disorganized. Temps will be very mild with well above normal mins and maxes Wed night and Thursday. So, despite the cloudiness on Thursday, the temps should rise into the 50s and some 60s across the south. 70F might not be all that far south of the Mason-Dixon line. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... Temperatures will be on the rise for the second half of the week, along with the opportunity for rain. The springlike surge of mild air should send temperatures 20+ degrees above average Thursday and Thursday night. The mild weather will be erased (briefly) as a cold front sends temperatures falling on Friday before readings bottom near normals levels for mid February on Saturday. High temperatures on Saturday will be 20 to 30 degrees colder than Thursday (48-hour change). As high pressure migrates off the Eastern Seaboard, broad ascent in the warm air advection pattern will allow for clouds and periods of light rain, drizzle and fog to develop Wednesday night and Thursday. Model guidance continues to advertise the potential for enhanced rainfall Thursday night into Friday in response to strengthening southwesterly low level jet along a tightening baroclinic zone/frontal boundary pushing southeast from the Midwest/OH Valley. Ensemble PWAT values reach +3SD above normal. The anomalous moisture combined with cold ground/enhanced runoff could lead to heavy rainfall (1-2+ inches) and flooding potential. At this time, the greatest risk area is focused from southern OH into northern WV and southwest PA including the Laurel Highlands. The placement of the high QPF axis is still uncertain and the Day 3 WPC excessive rain risk area splits the difference between the southern GFS and northern ECMWF precip axis. An ECMWF/CMC/GEFS consensus brings the possibility of some wintry weather back into the picture later Saturday into Saturday night. Will need to see if this recent model trends hold and the GFS comes on-board before increasing confidence and sensible wx elements. But it is something to definitely monitor in the coming days. Sunday looks dry for now with precipitation returning into early next week. After a short break, the mild trend should resume next week with above average temperatures a good bet. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... MVFR has spread through the western TAF sites as southwesterly upper level flow couples with moist southerly flow at the surface. Expect this flow to continue as the night continues. Cigs and vsbys will continue to degrade as the night continues and through the daybreak. There is a low probability for some patchy little mixed precipitation (mainly light freezing rain or freezing drizzle) late. For now...left this out of the TAF fcsts... given how dry the low levels are and anticipated spottiness with little organized upper dynamics to generate appreciable swaths of precipitation. Outlook... Wed-Thu...Low cigs/light rain possible, mainly N Mtns (KBFD). Fri...Windy and turning much colder. AM rain, changing to periods of light snow or snow showers mainly across the Western Mtns. Cig reductions likely early, and continuing during the afternoon across the NW mtns and Laurel Highlands. Sat...No sig wx expected. Sat night and Sunday...Chance of snow and lowering Cigs/Vsbys to MVFR with areas of IFR. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...Lambert LONG TERM...Steinbugl AVIATION...Lambert/Ceru
Area Forecast Discussion
National Weather Service Duluth MN
631 PM CST Tue Feb 13 2018 .UPDATE... Issued at 628 PM CST Tue Feb 13 2018 Increased wind speeds and gusts along the north shore as Grand Marais is gusting to 40 to 45 mph. Also, HRRR suggests just offshore that these winds could be sustained through at least midnight. UPDATE Issued at 532 PM CST Tue Feb 13 2018 Updated aviation section for 00Z TAFs. && .SHORT TERM...(This evening through Wednesday) Issued at 255 PM CST Tue Feb 13 2018 Mostly sunny skies were observed this afternoon across much of the Northland. The mid-level shortwave that brought light snow this morning has moved off to the east, and mid-level zonal flow will take its place. There is some expanding cloud cover over central Minnesota where there is a lack of snow pack on the surface. This cloud cover is anticipated to consolidate with a band of low- to mid- level stratus currently located over north-central Minnesota per GOES East satellite imagery later this afternoon and evening. This cloud cover should linger over the Arrowhead region this evening before shifting off to the east, leading to clearing skies to the west, and a period of enhanced radiational cooling. Due to this, I decreased the overnight low by a few degrees. Overnight lows will range in the lower to middle teens. For Wednesday, winds will remain from the southwest, so warm air advection will continue. A thermal ridge will build into the Northland, which will warm 850 mb temperatures to around +2 to +5 degrees C, so expect the warmest day across the Northland since January 26, when Duluth reached a high of 45 degrees. It shouldn`t be quite that warm, but highs are still forecast to reach into the middle to upper 30s for much of the region. Surface low pressure is expected to develop over Alberta/Saskatchewan Canada, and advance east-southeastward to southwest Ontario Canada. This surface low will bring our next chances of precipitation. There is only a small chance for any precipitation over northern Koochiching county Wednesday afternoon, with the better chances Wednesday evening and overnight. .LONG TERM...(Wednesday night through Tuesday) Issued at 255 PM CST Tue Feb 13 2018 The extended period will feature several shortwaves moving through the region bringing opportunities for snow. Westerly flow aloft will exist to start off the period. A cold front will move south through the Northland Wednesday night and a surface low will track across eastern Lake Superior into southern Ontario by 12Z Thursday. Light snow will occur with the front Wednesday night into Thursday. Snow accumulation is expected to be light, less than an inch for most areas. A couple of inches will be possible along portions of the South Shore into Thursday evening, especially the snowbelt of Ashland and Iron Counties as winds turn northerly and temperatures cool. Highs Thursday will be much colder than Wednesday, especially over northern Minnesota. Highs will range from 10 to 15 over the Borderland to the mid to upper twenties over northwest Wisconsin. High pressure will move through the region late Thursday night into Friday then another shortwave will arrive Friday night/Saturday bringing another chance for light snow with light accumulation expected. Highs Friday will be in the teens but warm into the lower twenties to around 30 on Saturday. Yet another chance for snow will occur Sunday into Sunday night and a few inches could occur. Southern portions of the Northland are expected to warm into the lower thirties Sunday with twenties elsewhere. Quite a bit of uncertainty surrounds the Monday through Tuesday period. A western trough is expected during that time but the position of the trough and the track and strength of downstream shortwaves differ between the various models. Some accumulating snow could occur over portions of the Northland Monday/Tuesday but it`s too early to say much more than that at this time. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 532 PM CST Tue Feb 13 2018 VFR, but strong low level winds continue to make LLWS a threat. Winds gradually weaken overnight. A little concerned that the region could see advection fog Wednesday morning as warm air continues to usher into the region, but think atmosphere may be dry enough to stave off its formation and we may just see elevated RHs more than anything. && .PRELIMINARY POINT TEMPS/POPS... DLH 15 35 21 25 / 0 0 20 40 INL 13 38 11 13 / 0 20 60 40 BRD 13 37 20 24 / 0 0 20 30 HYR 15 40 22 31 / 0 0 10 20 ASX 18 40 24 28 / 0 0 20 40 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...None. && $$ UPDATE...Wolfe SHORT TERM...JTS LONG TERM...Melde AVIATION...Wolfe
Area Forecast Discussion
National Weather Service Jackson MS
1002 PM CST Tue Feb 13 2018 .UPDATE... Updated for evening discussion. && .DISCUSSION... The ArkLaMiss remains under the influence of southwesterly flow aloft which continues to keep a moist airmass in place across the area. Earlier elevated convection over south central Louisiana has weakened as it moved further northeast into the CWA due to less MUCAPE to further sustain more robust updrafts. Sufficient MUCAPE will remain over the area tonight to help support a few rumbles of thunder, especially with any deeper activity over the Delta, but overall expect mainly showers along and northwest of the Natchez Trace corridor where the moisture/ThetaE ridge will reside. The other forecast concern tonight will be the potential for dense fog along the Hwy 84 corridor and I-59 north to the Golden Triangle. These areas won`t be as impacted by any precip and light to calm winds combined with warm cross over temps and cool soils will favor stratus build down fog. This fog is expected to build in during the early evening hours and persist through the mid morning. While areas of fog are likely, confidence in dense fog is lower. Nonetheless, went ahead and added a limited area in the HWO/graphics for patchy dense fog potential. /TW/ Prior discussion below: Tonight through Wednesday: Latest rap and satellite imagery showed southwest flow aloft with high heights over the region thanks to a 593 dam ridge just east of Florida. Partly cloudy skies were noted across the region at mid afternoon. On the surface a warm frontal boundary was noted off the Gulf Coast. Area radars were picking pickup some showers over the ArkLaTex area extending toward our Northeast Louisiana Parishes. Afternoon readings varied from the 40s to the lower 70s, depending on sky conditions. We will be looking at unsettled weather during the period with a warming trend, esp for Wednesday, with above normal temperatures. For tonight, as a weak disturbance approaches the region clouds will increase from the west. Showers will develop across the region overnight from west to east. The best rain coverage will be in the north. There will be just enough elevated instability per model soundings for some isolated embedded thunderstorms overnight. Pwats will increase to around 1.5 inches. Expect to see some patchy fog late tonight until mid morning Wednesday. During the night dewpoints will rise through the 50s as a more moderate airmass helps temps to slowly rise after midnight, which will temperatures to slowly rise during the night. Lows for tonight will range from the middle 40s northwest to the middle 50s south. For Wednesday the elevated instability will wane as showers continue through the day. Dewpoints will surge into the lower to middle 60s as low level instability will be limited due to rain coverage. Rain chances will gradually decrease from the south during the afternoon. It will be a spring-like day with highs in the middle 60s northwest to near 75 south. /17/ Wednesday night into early next week: An unsettled pattern looks to remain through the period in the vicinity of the Lower Mississippi Valley, but there are some indications a majority of the Arklamiss region may remain outside of the axis of the worst weather. That said, model agreement on key features through the period is not at all great and lends to more uncertainty than is typical for the mentioned time ranges. The greatest uncertainty focuses on Friday through early Sunday. During this time a shallow cold front will come in from the northwest and stall, perhaps right in the middle of the forecast area. Locations on the warm (east) side of the boundary could continue to see abnormal warmth (highs 70-80 and lows in the 55-65), continuing the taste of spring that will slowly build over our region now through Thursday. Of course on the cool side of the boundary temps will be much lower, perhaps 20 degrees cooler, with conditions tending to be more cloudy with a greater prevalence of showers and/or drizzle. As you can see, if you want to have a nice weekend you are hoping to be stuck on the warm side of the boundary. Over the next few days we will build confidence of frontal position this weekend. Despite the mentioned uncertainty regarding temperatures, confidence is rather high that the potential for hazardous weather from heavy rainfall and severe weather is low through the period. There certainly may be some isolated/embedded storms around Friday through the weekend, but instability and shear levels should not be enough to worry of severe weather and the synoptic/mesoscale focusing for concentrated heavy rain should not be in place. One potential concern will be the possibility of troubling fog on many nights as the atmosphere will be very moist and southerly flow could promote a hybrid advection fog advancing north from the coast. Otherwise, after this weekend the focus will turn to our west as a front aligning from north to south between the subtropical ridge to our east and a long-wave trough to our west should be producing a variety of bad weather. Model consensus suggests this front will have a tough time moving into our region from the west, although there is certainly non-zero potential this front could get into parts of the Arklamiss Delta with rain and vigorous storms before the middle of next week. We will watch the evolution of forecasts closely over the next few days but at this point we do not have enough evidence to include hazardous threats in the HWO/graphics. /BB/ && .AVIATION... 00Z TAF discussion: Aside from the chances for SHRA activity, the primary concerns will be for redevelopment of stratus overnight, and potentially dense fog in areas that have cleared out for the early morning hours. While the fog should dissipate mid/late morning, it is questionable how soon the stratus will lift late Wednesday morning and afternoon. Have kept TAFs on the pessimistic side in line with most guidance, but would not be surprised if mixing is greater and conditions improve more quickly than currently forecast resulting in MVFR restrictions at worst. /EC/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 55 73 63 80 / 71 41 12 12 Meridian 53 71 63 80 / 31 37 16 13 Vicksburg 56 74 62 79 / 84 46 10 13 Hattiesburg 57 74 62 80 / 9 22 14 13 Natchez 60 74 63 78 / 78 36 12 13 Greenville 48 67 61 76 / 72 68 15 13 Greenwood 55 69 63 78 / 50 70 21 13 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ TW/17/EC/BB
Area Forecast Discussion...UPDATED
National Weather Service Norman OK
858 PM CST Tue Feb 13 2018 .UPDATE... Lowered overnight lows in many locations tonight. Also, made minor adjustments to hourly elements tonight, mainly temperature and sky cover. && .DISCUSSION... Fog potential tonight into Wednesday morning is the main concern. Latest satellite imagery and surface observations at 845 pm CST depicted abundant low cloud cover east of an Archer City, Texas to Watonga to Medford line. Some high level cloud cover was over Oklahoma and north Texas as well. Rest of tonight, low level moisture/surface dewpoints will continue to increase across much of Oklahoma and western north Texas. The increase in moisture will allow for the expansion of the low level cloud shield westward and northwestward. This cloud cover should lower closer to the ground as well. Thus, think some patchy fog will occur across much of Oklahoma and western north Texas later tonight into Wednesday morning. Do not think the fog will get too dense (visibilities staying above 1/4 mile) due increasing low level winds which will veer from the southeast to the southwest through the night into Wednesday morning. The highest potential for dense fog may be across parts of south central and southeastern Oklahoma (southeast of a Ardmore to Ada line) where low level moisture will be deepest, deep enough to support some drizzle. Noticed the latest surface observation from Durant depicted 3 miles of surface visibility, which should continue to fall in the next several hours. Will not issue a Dense Fog Advisory at this time due to low confidence of widespread dense fog. Temperatures tonight will not fall too much more in most locations and may actually rise by sunrise in some locations. Wednesday will be much warmer across the area compared to today. Fire weather conditions will be near critical levels Wednesday afternoon across northwestern Oklahoma, but due to abundant mid/high level cloud cover which may limit vertical mixing and keep 20 ft winds below 20 mph, will not issue a Fire Weather Watch or Red Flag Warning at this time. Products will be updated shortly. MBS && .PREV DISCUSSION... /issued 553 PM CST Tue Feb 13 2018/ DISCUSSION... 00Z TAFs. AVIATION... MVFR stratus is widespread across central Oklahoma, but has eroded (at least temporarily) across western Oklahoma and western north Texas. The stratus should fill in again, lower, and spread northwest this evening encompassing all the TAF sites except KGAG and KWWR, although there is a chance that the stratus could briefly brush these sites as well according to the HRRR model. It appears that ceilings will be the main issue, although the HRRR and RAP do show for potential across western Oklahoma (KHBR, KCSM and perhaps KLAW) as moisture pushes back in to areas where skies will have cleared temporarily this evening. PREV DISCUSSION... /issued 320 PM CST Tue Feb 13 2018/ DISCUSSION... Stratus has been persistent across much of the area today in warm/moist southerly low level flow regime. This will continue through the night and upstream moisture will advect northward resulting in low clouds and fog across much of the area. Model soundings show deep enough low level saturation for drizzle across roughly the southeast third of the area. This will mostly be a non- measurable precipitation event, but a few locations in far south- central/southeast Oklahoma could receive a couple hundredths of an inch. Low clouds should gradually clear tomorrow as low level flow veers and strengthens. Temperatures will warm substantially as a result. This pattern will favor increasing concern for wildfire spread (see fire weather section below). The closed low off the California coast will open/deamplify and shift east at least partially phasing with northern stream wave. This consolidated trough will approach Thursday with one more warm day before it forces a cold front through. Windy conditions behind the front Thursday night into early Friday can be expected. Large scale ascent may be enough for showers to develop across mainly the eastern portion of the area Thursday night, but coverage/amounts should be limited. Positively tilted trough/shear axis Friday is expected to be oriented east-northeast to west-southwest across the area during the day Friday and could provide just enough mid level forcing for some precipitation across the south. A better chance may occur Friday night as another shortwave results in veering/strengthening southwesterly low level flow and isentropic ascent. There is some model disagreement, however. ECMWF is more amplified with a stronger low level response along with more robust moisture advection and QPF. If this trend continues, we may need to increase probabilities, but recent systems have proved to be less productive at rainfall in the short term than medium range. We`ve trended warmer for the weekend as mid-level height rises have trended more dramatic and southwesterly downsloped/adiabatically warmed plume should advect over the area again. We may need to increase temperatures even more if the trend continues. Although details in geometry and amplitude of western trough are yet to be resolved (still differences in deterministic guidance and a decent spread in the ensembles), the general pattern should support southerly low level moist advection beneath capping EML (a familiar pattern) again which could bring stratus and drizzle to the southeast Sunday night. As the trough approaches, assuming it doesn`t deamplify and weaken like has been the trend the past few weeks, warmth/moisture could contribute to enough instability for thunderstorms Monday-Tuesday. We`ve kept probabilities lower than we otherwise would in the pattern depicted in medium range guidance in case we do trend toward a less favorable scenario again. BRB FIRE WEATHER... Dormant fuels with ERC-G values near the 90th percentile and increasing southwesterly winds, warmer temperatures, and low RH values (as low as 10-15 percent) will all combine to result in near-critical to possibly critical fire weather conditions tomorrow afternoon across northwest Oklahoma. There is some uncertainty with how thick cirrus will be and how that may impact temperatures, and more importantly fine fuel heating. Nevertheless, the wind/RH combination will support rapid fire spread. In case any fires are ongoing, RH recovery Wednesday night is expected to be 50-60 percent. Winds may not be quite as strong and RH values may not be as low Thursday afternoon, although they will be sufficient for elevated fire weather conditions at least. The other concern for area fire managers will be the wind shift Thursday night. Strong northerly winds are expected behind a cold front that will progress through the area Thursday evening and overnight. BRB && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 42 71 56 78 / 0 0 0 0 Hobart OK 40 73 52 80 / 0 0 0 0 Wichita Falls TX 42 74 56 82 / 0 0 0 0 Gage OK 38 79 53 74 / 0 0 0 0 Ponca City OK 42 71 57 76 / 0 0 0 10 Durant OK 40 66 58 74 / 20 20 10 10 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ 17/26