Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/12/21


Area Forecast Discussion
National Weather Service Denver/Boulder CO
819 PM MST Thu Mar 11 2021 .UPDATE... Issued at 815 PM MST Thu Mar 11 2021 Radars are indicating some light showers scattered, mostly, over the northern half of the CWA`s plains. There are also some over the mountains and foothills, even Park County. There is some enhancement notes on the satellite pictures too. The jet maximum is right on top of the CWA. The 00Z Denver soundings had a couple 140 knot west-southwest measurements on it around 250-300 mb. I will increase pops a bit in many areas of the plains overnight. The new 00Z model runs show a bit more QPF as well from now through 12Z. && .SHORT TERM...(This evening through Friday) Issued at 328 PM MST Thu Mar 11 2021 A strong southwesterly flow aloft will be over CO tonight ahead of the developing upper trough just off the southern CA coast this afternoon. The models still develop light snow showers this evening as a 150 kt jet max ejects northeastward across the state. The models still show the best moisture, lift and instability will be west and north of Denver. No significant adjustments to the current pop grids. The best chance of accumulating snowfall will be in and near the foothills of Larimer and Boulder counties as well as the Cheyenne Ridge. The latest HRRR favors the time frame from around 00-06z. With the passing jet aloft, narrow enhanced bands of light accumulating snowfall will be possible, with amounts in the 1-3 inch range. This feature will lift northeast on Friday. On Friday, the upper low that will be impacting the region over the weekend will be over southern CA with a fairly dry southwesterly flow over the forecast area. This system will not move much through the day on Friday, where it is progged to be spinning over the southern tip of NV 00z Saturday. Weak qg ascent will be over the region in the mid and upper levels on Friday. Mid and upper level moisture will increase in the mountains by Friday afternoon, with generally scattered shower coverage expected. Across the northeast plains, spatial cross-sections show the moisture increasing across the plains in the low levels, generally below 700 mb, The flow aloft however will remain quite dry. This may result in some light showers or drizzle near the higher terrain but not much elsewhere. Pockets of freezing drizzle may be possible during the morning hours. Overall confidence in precipitation will be on the low side through the day on Friday aside from drizzle in the afternoon. .LONG TERM...(Friday night through Thursday) Issued at 328 PM MST Thu Mar 11 2021 ...SIGNIFICANT WINTER STORM STILL ON TRACK... A major late season winter storm is still on track to hit northeast and north central Colorado this weekend. Travel will become difficult if not impossible in/near the Front Range Mountains, Foothills, and I-25 Corridor, with the worst conditions expected from Saturday afternoon through Sunday. The heart of the upper level circulation which will become the powerful storm is still just off the central California coast and is rather disorganized at this hour. However, that will all change as this circulation center drifts eastward late Friday night and Saturday to the Four Corners area. That`s when this storm begins to tap into a deep plume of Gulf of Mexico moisture. Models then diverge somewhat in location, but especially in intensity most likely due to differing internal model physics. We, along with national guidance, still support a blend of the ensembles especially since this storm is still so disorganized just off the west coast. The GFS and GEFS ensemble average is right near 3" of water for Denver (on the high end), while the EC and its ensemble is averaging about 1.7" for water equivalent. Meanwhile, the GEM and its ensembles are pretty much middle of the road with closer to 2.5" of water on average. We, in coordination with national guidance, are leaning toward the blend of EC and GEM numbers for now. However, there has been a slight shift southward in the latest operational member tracks so heavier (and near historic) numbers are still indeed possible. This storm has a lot going for it... 1) Strong infusion of Gulf of Mexico moisture 2) Moderate to strong dynamics as seen in the derived QG vertical motion fields 3) Slow movement thanks to blocking ridge over the top, resulting in a long duration event, at least 36 hours of high precipitation rates 4) Strong upslope, as the latest NAEFS ensembles show record or near record easterly component. (although other ensembles are not as strong) 5) TROWAL (or trough of warm air aloft), representing the infusion and upward vertical motion in the plume of rich gulf moisture Saturday and Saturday night, and possibly into Sunday if storm slows All of these ingredient would support snowfall rates of 1-2 inches per hour in the I-25 Corridor, and up to 3" per hour or more in the foothills. Now, a couple limiting factors... 1) A dry slot may work northward and effectively shut down precipitation. Right now, given the location and stalling of the upper low we think the dry slot would mainly impact the southeast part of the forecast area. However, if the storm track ends up being farther north, then precipitation amounts over the rest of our forecast area could be cut back a little as well. 2) Temperatures. With very strong warm advection, some rain will likely work westward across the plains. Right now, we don`t see that getting any farther west than a Greeley to Limon line, as low level cold/cool air should be firmly entrenched. Thus, we`d probably end up with a formation of a barrier jet as precipitation rates increase significantly Saturday and Saturday night. We`ve kept the forecast as consistent as possible at this point, with forecasts of 2-4 feet for the foothills and up to 2 feet for the I-25 Corridor. As a result of some growing confidence and messaging for this storm, we`ve upgraded to Winter Storm Warnings for the Front Range Mountains, Foothills, and I-25 Corridor. To be clear, these are the most likely forecast amounts. Should the storm track stay farther south and closer to the GFS/GEFS solutions then we could still be looking at a near or historic snowfall event. The one nudge down we made was over the eastern plains where models continue to indicate such strong warm advection that we`ll likely see a fair amount of precipitation in the form of rain Saturday and Saturday night. We kept the eastern plains under a Winter Storm Watch, as there`s still uncertainty with regard to p-type and eventual snow accumulations. Winds will increase on the back side of this system for Sunday, resulting in areas of blowing and drifting snow. Peak gusts may reach 40-45 mph east of I-25 where more significant blowing snow impacts are likely. Near blizzard conditions will be possible especially in the windier areas which would include areas near the Wyoming border north of Greeley and perhaps the Palmer Divide to Limon. After this storm, there will be a trailing short wave with additional chances of snow. Right now there is considerable spread in exactly when that system arrives (Tuesday - Wednesday). && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 820 PM MST Thu Mar 11 2021 Weak northerly winds are in place at DIA at this time. Models did not show this very well. Going forward this evening/tonight, all the models have weak east-southeasterly winds at the big airport overnight. No drainage. Will keep the ceilings in the BKN- OVC040-060 range for the rest of this evening into overnight. Will also put some VCSH back in the TAF. Ceilings now look to get at or below OVC010 by 12Z Friday. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Storm Watch from late Friday night through late Sunday night for COZ042-044>046-048>051. Winter Storm Warning from midnight MST Friday night to 6 AM MDT Monday for COZ033>036. Winter Storm Warning from 5 AM MST Saturday to 6 AM MDT Monday for COZ038>041-043. && $$ UPDATE.......RJK SHORT TERM...Cooper LONG TERM....Barjenbruch AVIATION.....RJK
Area Forecast Discussion
National Weather Service Caribou ME
915 PM EST Thu Mar 11 2021 .SYNOPSIS... A cold front will cross the area overnight and early Friday morning. An Arctic cold front will cross the area Friday night with high pressure ridging across the region on Saturday. Upper level disturbances are expected to move across the region Sunday into Monday, followed by high pressure on Tuesday. && .NEAR TERM /THROUGH FRIDAY/... 9:15 PM Update: An unseasonably mild night with 9 PM temperatures more typical of high temperatures in mid April. The 00z Caribou sounding shows the warm air mass with a freezing level of 7800 ft agl and temps in the mid 50s (F) at 925H, which is about as warm as it gets for this time of year. There is an inversion present which is preventing some stronger wind aloft from mixing down to the surface. A cold front is evident across Quebec to the west of the Saint Lawrence River that extends south into northern NY State. There has even been some lightning observed this evening along the front. The front is expected to move into western sections of the FA after midnight and sweep across the remainder of the area by Friday morning. A few showers will likely accompany the front, mainly across the western mountains and north of Baxter State Park. Made some minor adjustments to account for current and expected conditions, but overall changes were minor. Previous discussion: Tonight...SW flow aloft will continue to bring WAA into the region. Temps have climbed well into the 50s across Bangor region into western and northern areas. Far northern areas such as Caribou into the NE St. John Valley, temps were in the mid 40s. Dewpoints have been slow to rise, especially across the n and w as the SW flow not able to mix down due to the S wind at the sfc. The RAP and GEM have handled the current setup well and keep dewpoints in the low to mid 30s into the late evening timeframe. This has slowed up the melting process some. However, further s, dewpoints have climbed into the 30s and even lower 40s across the Downeast areas w/good melting underway. The sfc analysis showed still back across the eastern Great Lakes slowly pushing to the e. Warming will continue into tonight w/dewpoints climbing. This will lead to increased melting of the snowpack and ice as well as contributing to some fog. The gusty S winds tonight will offset the fog from becoming to extensive. Stayed w/patchy fog for tonight. Showers are expected to move across the region later tonight w/the pre-frontal trof. Strong jet at 850-700mbs to allow for an areas of showers and the potential for some strong wind gusts 850-700mb lapse rates are forecast to hit >/= 6.0 c/km to lead to some instability aloft and even for a few showers to contain a brief downpour as they move through. Areal coverage of the expected rainfall is to be no more and a few hundreths, w/the highest amts back to the w and across the nrn border. The model guidance can be notorious for bringing the colder air too soon given the SW flow aloft. Therefore, backed off on the cooling by at 3 hrs into Friday morning. Friday...Cold front is expected to slide across during the morning, but as mentioned above, colder air will be offset by a few hrs. A gradual cooldown w/dewpoints dropping back below 32F which will aid in slowing down the melting process. The bigger story will be the gusty W winds. Sounding data along w/momentum transfer showing gust potential to hit 40 mph or higher across the n and w starting in the mid morning hrs. There is potential for some of the higher terrain could see gusts to hit 45 mph. Attm, confidence is not high enough to issue a Wind Advisory. The later shifts can assess if a headline is needed. Will address this item in the Hazardous Weather Outlook. The continuation of the mild air will lead to possible ice breakup on the souther rivers. More on this in the Hydrology section below. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... Cold front will be swinging through the state Friday night. It will result in a sharp decline in temps and potentially a flash freeze of any area standing water on roads/sidewalks from Fridays warm temps. Lows drop back into the lower to mid-20s Downeast, and the teens across the north. Accompanying the passage will be some snow showers, mainly through the Central Highlands and St. John Valley. Shower chances diminish during the day Saturday, but winds it will be brisk as cold air infiltrates the region with a tight pressure grad overhead. Temps continue to fall into the upper single digits Sat night, to around 20 Downeast. Winds remain breezy straight into Sunday, when they may be maximized, some areas seeing gusts to 35 mph. For now, these winds seem most probable across western areas; the Bangor Region, Central Highlands, and North Woods, as low pres drifts through far eastern Maine. The GFS seems to be most on board with these winds, but momentum transfer within the NAM also supports these gusts per BUFKIT soundings. And momentum transfer will be the thing to watch given widespread low-level lapse rates around 9c/km and the broad 25-35 kt LLJ from ME to PA. With two of the three ingredients checked off for snow squalls, what are the chances of seeing these heavier snow showers or squalls move through the region on Sunday? Wind and low-level lapse rates are good as is delta Theta E for instability. Moisture is maybe the only ingredient limited. But given the amount of convergence embedded in the wave and pressure gradient, some corridors of snow squalls will be watched for development. As a result, the SNSQ parameter for NAM, GFS, and ECMWF, all display higher end values during the afternoon, tapering Sun evening. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Temps after all of the cold air advection flow will truly be felt Sun night and Monday as highs rise only into the teens across the north and lower 20s Downeast. Some moderation occurs mid week as temps climb back towards normal after the chilly start. As far as precip chances, there is a lot of uncertainty in the long range. Towards Wednesday, the det GFS runs a low up the St. Lawrence with a coastal redevelopment off Mass and into the Gulf of Maine. The GFS has the features the most well-defined, whereas the ECMWF carries a similar setup, but slower. GEM guidance doesnt phase systems well, resulting in a storm mostly out to sea. Ptype will depend on how this system evolves, but this appears to be a cooler solution to overrunning, perhaps keeping much of the precip as snow across the north and central areas depending on how developed the secondary low is. Again, confidence is fleeting with GEFS members also displaying a wide selection of solutions. The area remaining in SW flow into Thurs means temperatures may remain mild into late week with highs back into the mid 30s across the north and around 40 Downeast. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... NEAR TERM: VFR for all terminals late this evening, and then a gradual decline to MVFR overnight w/the potential for IFR later at night. Fog is a threat w/the greatest potential across KBGR and KBHB. LLWS will be a concern as well. S wind 10-15 kt w/higher gusts becoming SW later tonight. Friday...SW winds becoming W and increasing to 15-20 kt w/higher gusts. Gust potential to 35+ kt is there starting from mid morning and continuing into the afternoon. The stronger wind gusts will be across the northern TAF sites. MVFR in the morning across the northern TAF sites becoming VFR. VFR for KBGR and KBHB. SHORT TERM: Fri night...MVFR possible across the north and Downeast terminals with -SHSN possible into GNR, BGR, and BHB through midnight local. WNW 10-15kts with gusts to 35kts in the afternoon and evening. Sat...VFR. Strong gusty NW winds. Sat night-Sun night...Mainly VFR, ocnl MVFR across the north. SHSN possible causing IFR vis. NW 5-15kts and gusty. Monday and Mon night...VFR. NW 5-15kts and gusty. Tuesday...VFR. Light W winds. && .MARINE... NEAR TERM: SCA stays up into Fri as SSW winds increase to 20-25 kt tonight becoming W. Gusts to 30 kt are expected. Seas will be building to 5-8 ft by Fri. SW winds 20-25 kt w/higher gusts will shift to the W and decrease to 15-20 kt by early afternoon. Seas will drop back to 4-5 ft by later in the day. SHORT TERM: SCA winds with gale possible Fri night into Sat afternoon. SCA winds continue with gusts to 30 through Sat night. Winds briefly fall below SCA before ramping up towards Gale again Sunday afternoon into Monday. Winds then slacken to SCA through Monday night, falling below Tues afternoon. Waves of 4 to 6 feet can be expected through Sunday night, subsiding to 2 to 3 feet Mon night and Tues. && .HYDROLOGY... Ice movement is possible along the Piscataquis and Penobscot River basins into Friday night, which includes the Mattawamkeag River. Ice thickness is around 1 foot, and w/a 1-2 foot river rise anticipated, there could be some ice movement. Attm, major flooding in not anticipated. Cooler air arriving Friday night into Saturday should help to alleviate any further threat of ice breakup. && .CLIMATE... The preliminary high temperature of 57F in Houlton, Maine this afternoon broke the previous record high of 51F, set in 1977. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Gale Watch from late Friday night through Saturday afternoon for ANZ050>052. Small Craft Advisory until 1 PM EST Friday for ANZ050>052. && $$ Near Term...CB/Hewitt Short Term...Cornwell Long Term...Cornwell Aviation...CB/Hewitt/Cornwell Marine...CB/Hewitt/Cornwell Hydrology...Hewitt Climate...CB
Area Forecast Discussion
National Weather Service Gray ME
1106 PM EST Thu Mar 11 2021 .SYNOPSIS... Warm ridging over the East Coast has arrived and will continue until a cold front crosses on Friday. A series of cold fronts Friday through the weekend will gradually usher in a cooler air mass with gusty, possibly strong at times, northwest winds. The strongest front arrives Sunday. High pressure arrives during the first half of the next work week, but the active weather pattern threatens the area with precipitation during the second half of the week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 1100 PM Update...Wildly fluctuating temperatures around the region this evening based on who`s mixing and who is not. For example, our weather balloon shelter here at the office is currently 56 degrees while just a couple of miles down the road in a low spot in New Gloucester it`s 34 degrees. KHIE rose 20 degrees in less that 1 hour. This is a common theme around the region at this time. The low level jet continues to strengthen at this hour and is expected to do so into the early overnight hours. Therefore, it`s likely that many spots in the 30s and 40s right now will eventually pop in to the 50s for a short time. Cold front passes through after 06z with gusty winds likely in many areas. 9:45 PM UPDATE... Made some adjustments to temperatures, which have been tough to pin down this evening as some of the sheltered valley locations have experienced significant swings. Some adjustments to sky cover were also made to better align with satellite imagery, which shows mostly cirrus clouds with some embedded stratus. Radar shows a line of heavy showers and embedded thunderstorms across western NY which is associated with the advancing cold front. While these showers and storms will weaken before crossing through our area, gusty winds up to around 30 mph will be possible immediately behind the frontal passage. The rest of the forecast remains on track. Previously... 6:45 PM UPDATE... Made some minor adjustments to forecast temperatures based on trends in surface observations and model guidance. Satellite imagery shows some breaks in the cirrus clouds which may briefly allow temperatures to locally drop rather abruptly but relatively high surface dew points and increasing winds overnight in association with the approaching surface cold front will likely prevent them from falling below freezing in most locations. Latest near-term model guidance such as the HRRR indicates that there could be locally strong downsloping winds after midnight across the eastern slopes and therefore forecast wind gusts were increased some in this update. The rest of the forecast remains well on track. Previously... Sfc cold front approaches this evening and moves through toward daybreak. It could produce a few rain showers on the mountains, but is expected to go through dry elsewhere. Given the warm temps this afternoon in places where onshore flow has minimal effect, and increasing SW flow this evening, temps will not drop to much with lows mostly in the mid 30s to mid 40s, but even those temps will likely happen closer to daybreak with the evening being balmy. In the mtns, and the wrn NH, should see W winds pick up a bit late tonight behind the front. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Behind the front that exits the CWA early Friday, there will be some cooling, but this is he first in a series of 3 cold fronts, that work through this weekend. So temps behind are cooler , but still mostly above normal, and the stronger westerly flow will allow for good downsloping, which will allow tempos to mix out behind the front and rise into the mid 50w to around 60 in SW ME and srn NH, while limited to the the 40s in the mtns. Also, approaching weak wave from the west, which will usher in the second front, should prevent temps aloft from cooling too much. Overall, it looks like a partly sunny day, with more clouds in the morning. The second front moves through Fri night, and once again brings a better threat for showers in the mtns Sat evening. These will be more in the form of snow showers. There is a better chc that showers make it further S and E into southern NH and central ME, but chances are still mostly in the slt chc category, as wind never really shifts from downsloping. Better cooling aloft could give some of the showers a more convective and thus squally feel, but the better chc will be later in the weekend. && .LONG TERM /SATURDAY THROUGH THURSDAY/... A fairly benign weather pattern continues through the extended portion of the forecast, but not without its hiccups mainly this weekend. Generally speaking, New England will be caught between a negatively tilted trough stretched over eastern Canada and a strengthening ridge upstream over the Mississippi River/Ohio River/Great Lakes basins through the weekend into Monday... northwest flow brings in a cooler airmass but also gusty winds which have the potential to be strong. Thereafter, high pressure briefly builds over the northeast and the upper air pattern grows more active over the mid-latitudes with numerous waves of low pressure with potential to impact our region (but low confidence in timing, impacts, etc.). The main story this weekend will be wind and snow showers. A steady train of disturbances moving along the base of Canadian troughing will provide a couple cold fronts... which allows for good mixing. This combined with the tightening PGF between maritime low pressure and upstream high pressure will bring gusty to potentially strong winds and by extension snow squall chances to the region. As discussed above one of these fronts crosses Friday night, another later on Saturday evening into the overnight, and another yet on Sunday. While each front provides an uptick in winds, the Sunday fropa will be the one to keep a special eye turned to. The statistical suite favors Sunday as the windiest day of the stretch... with wind gusts in the 30-35 mph range being common over the region and some potential for wind gusts to approach 40 mph in some places. While most clouds and showers should stay over the mountains late Saturday through Sunday... the snow squall parameter and Froude number continue to suggest a favorable environment for showers to track into the lowlands on Sunday which may cause travel impacts if a proper squall or two can come together. The strongest shot of cool air comes on the heels of Sunday`s front with the h850 thermal trough of around -23C passing through New England that night. Thus Monday will be the coolest day of the forecast period with highs in the teens (north) to near 30 (southern interior/coast). Winds will relax through Monday as well with high pressure arriving by Tuesday. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/... Short Term...Mainly VFR through Fri night, could see W wind gusts of 20-25kt Friday. Long Term...The primary aviation impact will be gusty northwest winds Saturday through Monday with strongest winds up to 35kts possible on Sunday. VFR will prevail at most terminals except for MVFR ceilings and local IFR in SN for HIE. There`s an outside chance of a snow shower to track out of the mountains toward a southern or eastern TAF site on Sunday. VFR prevails thereafter with lighter winds by Tuesday. && .MARINE... Short Term...Sw winds increase this evening and will see wind gusts to 30 kts at times. Winds shift to W behind a cold front late tonight, with continues SCA gusts Fri into Fri evening, with a second front moving through Sat night and potential for gales before daybreak Saturday. Long Term...A series of cold fronts crosses the waters Saturday through Sunday with gusty offshore winds in its wake. A Gale Watch remains in effect into Saturday, and another will likely be necessary by late Sunday through Sunday night. Conditions begin to quiet down again late Monday into Tuesday as high pressure approaches from the west. && .CLIMATE... Warm temperatures are expected through Friday. Record warmth has been observed at Concord so far today and remains possible into tomorrow for the region. Here`s a look at Friday`s records at each climate location. Friday, March 12, 2021 REC HIGH FCST PROB OF BREAKING PORTLAND 63 in 1973 57 Low chance of breaking record CONCORD 69 in 2012 57 Unlikely to reach record AUGUSTA 64 in 2012 54 Unlikely to reach record && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Gale Watch from Friday evening through Saturday afternoon for ANZ150-152-154. Small Craft Advisory until 1 PM EST Friday for ANZ150>152-154. && $$ NEAR TERM...Ekster/Tubbs SHORT TERM...Cempa LONG TERM...Casey
Area Forecast Discussion
National Weather Service Louisville KY
833 PM EST Thu Mar 11 2021 ...Mesoscale Update... .Mesoscale Update... Issued at 830 PM EST Thu Mar 11 2021 A weak line of showers and thunderstorms have pushed south of the Ohio River this evening. Surface observations have generally reported wind gusts 25 to 35 mph with an outflow boundary on the leading edge of this line, but then quickly weakening behind it. Radar trends over the last few hours have shown this line generally weakening as it pushes southward, mainly due to waning instability. Not anticipating any strong/severe storms the remainder of the overnight hours. The line of moderate to heavy precipitation along the outflow boundary has also moved at a fairly modest pace southward, and as a result has limited precipitation accumulations in any one given location. Precipitation will still continue to stream in from the west and southwest, but rates and amounts should be low enough that flooding issues shouldn`t be a concern for the rest of the overnight hours. Issued at 540 PM EST Thu Mar 11 2021 Showers and thunderstorms have began drifting into portions of southern IN over the last hour ahead of a cold front. Regional radars reveal the bulk of this precipitation stretching as far east as southwestern MO. The strongest convective activity has been confined to portions of southern MO/IL where an axis of marginal instability just ahead of the front is co-located with strong deep layer shear. Over the next few hours, we will like see a narrow corridor of ~60 degree dewpoints pool up ahead of the cold front as it slowly sinks southward into southern IN and portions of northern KY. The increasing low level moisture along with steepening mid level lapse rates will result in marginal instability generally north of the Western Kentucky/Bluegrass Parkways for the next several hours. Deep layer shear will also continue to be strong during this timeframe, so there will be a low-end threat of organized convection and isolated strong/severe storms. The good news in regard to the severe threat is that storm motions generally support storms moving nearly parallel to the front, resulting in them ingesting rain-cooled air from other nearby showers or storms. Storms that have been able to tap into a nearly `untouched` warm sector have thrived a bit more, like the one that moved across southeastern MO into southern IL this afternoon. The timing for any severe threat across southern IN and central KY will likely occur before midnight, as it appears after midnight we stabilize enough to keep any severe threat very low. The other threat to watch will be low-end flooding potential. With training showers and storms drifting in from the west and southwest, we could see some quick accumulations over a short period of time. The cold front should drop south at a fast enough rate to cut off showers/storms from persisting too long to result in widespread hydro issues, but can`t rule out some narrow stripes of +2" rain across southwestern IN and western Kentucky by tomorrow morning. Flash flood guidance values across these areas are fairly high, so think any instances of flooding will be isolated. && .Short Term...(This evening through Friday) Issued at 310 PM EST Thu Mar 11 2021 Latest sfc analysis places the cold front along the I-70 corridor, stretching from Indianapolis to St. Louis. Second round of thunderstorms are firing up just ahead of the boundary in a region where SBCAPE is around 500 J/kg. Hi-res CAMs seem to be doing alright with how current radar trends are, but the ARW-East and HRRR appear to have the best handle on current wx. While KLVX radar is mostly quiet at the time of writing this, what is developing over southern IL will be tracking this way by later this afternoon and into the evening. By 23z-00z or so, expect to see a line of heavier rain and embedded thunderstorms approach our southern IN counties. RAP Mesoanalysis and HRRR soundings continue to show a region of 500 J/kg of SBCAPE along the Ohio River early evening ahead of this second wave of precip that is currently developing to our west. While CAPE is marginal, abundant wind shear makes up for the slack and keeps the SPC Marginal Risk along the Ohio River. Model guidance suggests a region of effective bulk shear around 50 kts and 0-1km SRH near 150-200 m2/s2. Could see a few stronger storms, but per MD 154, a watch is unlikely at this point. PWATs of 1" or slightly higher have nosed into Kentucky. Expect to see these values increase to around 1.2-1.3" this afternoon. SW winds have been gusty all day, with gusts primarily in the 25-30 mph range. These gusts will continue until the front passes through, bringing NW flow in its wake. With SW winds feeding into the boundary this evening, efficient moisture convergence could support rain rates of half an inch or more per hour. Expect to see NW winds first arrive at our NW CWA (Dubois County) by 00z. The front looks to stall across Kentucky as an east-west oriented boundary overnight. With the boundary remaining parallel to the upper flow, this will support training showers and thunderstorms across the region overnight and into tomorrow. From 18-00z tomorrow, could see the front sag a bit further south, which would help push the better rain chances south of the parkways. QPF from tonight and tomorrow ranges from half an inch to just under 2 inches. Higher QPF is forecast for an area between the I-64 and WKY/Bluegrass Pkwys. Temps for tonight will remain mild once again since SW flow will dominate for most of the region. Lows will be in the upper 40s for our southern IN counties since they should begin to see NW flow and CAA overnight. Lows will be in the low 50s for central KY, and upper 50s for south-central KY. Highs for tomorrow should be around 60F. .Long Term...(Friday night through Thursday) Issued at 245 PM EST Thu Mar 11 2021 ========================================== Synoptic Overview ========================================== Very large/deep closed upper level low over the southwestern US is forecast to move eastward into the Plains before lifting northward and opening up into an open wave by mid-week. This trough axis is then forecast to shift eastward through the Ohio Valley by mid-late week. In the Ohio Valley, a stalled out frontal boundary is forecast to drop southward into the Tennessee Valley on Saturday and then retreat back northward as a warm front on Sunday. As the upper level low across the Plains opens up, surface low pressure well to our northwest will send a likely occluded front through the area in the Sunday night-Monday time frame. This feature will bring another round of showers and a few thunderstorms with locally heavy rainfall. Unsettled weather is likely to continue until mid-week when the aforementioned upper trough axis pushes through which should bring drier weather to the area by late week. ========================================== Model Discussion and Sensible Weather ========================================== Overall, the model guidance remains in pretty good agreement in the first half of the period. At the beginning of the period, a surface frontal boundary is forecast to bisect the region Friday night before dropping southward into Tennessee on Saturday. This front is then forecast to lift back northward as a warm front on Sunday. On Monday, well defined mid-latitude cyclone will continue to wind up across the Plains with a large frontal occlusion working across the region. The GFS v12 and v16 runs have trended slower and agree more with the Euro solutions here with the best chances of rainfall looking to be more on Monday now. As this feature works through a band of moderate to heavy rain showers with some embedded thunder will push thorugh the region. With decent atmospheric moisture in the region, another round of heavy rainfall is expected with this system. For this forecast, plan on going slightly drier across the region on Saturday with the front expected to be south of our region and no strong forcing within the area. While it looks to be mainly dry, can`t rule out some scattered showers here and there, though the best chances on Saturday look to be across southern KY in closer proximity to the front. Scattered showers look to be a good bet on Sunday as the warm front pushes back northward across the region. Highs Saturday should remain in the mid-upper 50s. Readings on Sunday will likely exhibit a gradient initially with highs in the upper 40s to the low 50s across southern IN and northern Kentucky with upper 50s to near 60 along the KY/TN border. Temperatures are likely to rise throughout the night on Sunday as the warm front surges northward. Complex of showers and a few thunderstorms will move eastward and into the region on Monday ahead of the frontal boundary. Good lift along the front and plenty of moisture should result in another round of moderate to occasionally heavy rainfall. A solid 1-2 inches of rain will be possible in this time frame. Lingering showers could continue into the day on Tuesday. Depending on how much rainfall we get from round one in the short term period will strongly influence how much hydrologic issues we could see early next week. Excessive rainfall will lead to some runoff with some flooding being possible during the period. Overall, there remains a substantial risk of quick rises on area creeks and streams early next week. Significant differences in the forecast emerge by Wednesday as the Euro, having an open wave aloft, quickly pushes a front through the region with much drier weather for the remainder of the week. Meanwhile, the GFS is much slower bringing another tightly wound up surface cyclone through the region in the late Wed/Thu time frame. Given the differences here, have generally gone with the blend of the GFS ensemble and Euro ensemble which generally smooth out the differences in the Wed/Thu time frame. The good news here is that a period of drier weather looks likely for the end of the week and into next weekend. Highs on Monday should top out in the low-mid 50s across southern Indiana and the northern half of KY. Low-mid 60s look likely across southern Kentucky. Behind the front on Tuesday, we`re not expecting much in the way of a cool down with highs remaining in the upper 50s to the lower 60s. Highs in the upper 50s are expected on Wednesday with cooler air arriving around Thursday with highs only reaching the lower-mid 50s. Overnight lows through the period will average in the 40s-low 50s. Temps by Friday morning could drop back to around freezing. ========================================== Weather/Societal Impacts ========================================== In terms of weather impacts, main impact here will be the rainfall for late Sunday through the day on Monday. The moderate to heavy rainfall may lead to quick rises on creeks, streams, rivers within the area given the expected rainfall plus the rainfall from the earlier time periods. Residents in low-lying areas or near creeks and streams should keep an eye on water levels this weekend and into next week. ========================================== Forecast Confidence ========================================== Temperatures through the period : Moderate Moderate/Heavy Rainfall late Sun into Mon : Moderate-High Risk of severe weather : Low Risk of hydrologic issues early next week : Low-Moderate Mid to late week forecast evolution : Low && .Aviation...(00Z TAF Issuance) Issued at 639 PM EST Thu Mar 11 2021 A cold front is draped across far southern Illinois and Indiana this evening. Widespread moderate to heavy showers with embedded TSRA likely during the first 6 hours of the TAF period at HNB/SDF/LEX. Waning instability after midnight will result in more of a showery overnight period with less thunder. HNB/SDF/LEX will see several hours steady showers overnight as the front stalls over the region. The front continues to very slowly sink south, bringing prevailing - SHRA to BWG by mid to late morning on Friday. Narrow corridor of MVFR ceilings currently being observed along the front, and these lower ceilings will affect HNB and SDF. As the band of stratus sinks south overnight and into Friday, the IFR conditions are likely to expand and impact BWG and LEX. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Mesoscale...DM Short Term...CJP Long Term...MJ Aviation...EBW
Area Forecast Discussion
National Weather Service Pueblo CO
600 PM MST Thu Mar 11 2021 .UPDATE... Issued at 553 PM MST Thu Mar 11 2021 Updated to cancel the Red Flag Warning for Las Animas County. && .SHORT TERM...(This evening through Friday) Issued at 359 PM MST Thu Mar 11 2021 ...Potential for some patchy Freezing Drizzle tonight El Paso county but expecting warm ground to minimize impacts... Upper low across southern CA will slowly migrate southeastward into western AZ/southern CA during the afternoon. This puts the forecast area under strong southwest flow aloft. Cold front across the plains has held in with temperatures only warming into the 50s. Southerly winds off the Raton Ridge have dried surface dew points to near critical thresholds around KTAD, but so far have stayed just shy. Latest runs of the HRRR have backed off on northern extent of the drying moving off the Raton Ridge but being within 3% of critical humidity thresholds at KTAD...will hang on to the Red Flag Warning along the Raton Ridge through the early evening as there is still time for sufficient drying to take place. Areal extent may be more limited to southern portions of Las Animas County. Overnight...cooler air makes a push back westward with another round of stratus developing across the southeast plains. Some WAA/overrunning will produce some rain showers across the eastern plains towards morning while shallow upslope/saturation across El Paso county could produce some areas of freezing drizzle or flurries towards morning. Depth of moisture in model soundings suggests ice processes won`t be present with super cooled liquid the primary result in and near the Palmer Divide. Fortunately with residual heat in the ground think this will mitigate impacts quite a bit with mainly light patchy icing on cold surface the main risk. Therefore no highlights expected. Scattered showers will be possible along the Continental Divide as well, but any precipitation will be light at this point given main forcing is still well off to the west. Friday will be a transition day across southern Colorado. Models have delayed the onset of precipitation some but with overrunning overtop the cold front Friday expect showers to break out across portions of the plains during the afternoon with emphasis across the Pikes Peak region given good south southeasterly fetch and orographic component. Will also see snow showers expand across the mountains along the Continental Divide as forcing approaches from the southwest and area comes under better upper level difluence in the afternoon. It will be windy once more across the mountains and San Luis Valley. Southeast plains will see increasing easterly flow as it feels the affects of the approaching low to the west but gusts will be around 20 kts in the afternoon as compared to 30 to 40 kts out west. Clouds will likely hang in and increase into the afternoon across the southeast mountains as upslope flow strengthens. -KT .LONG TERM...(Friday night through Thursday) Issued at 359 PM MST Thu Mar 11 2021 1) A High Impact Winter Storm starting Friday night and continuing through the Weekend, with heavy snow, strong winds and potential blizzard conditions across portions of south central and southeast Colorado. 2) Uncertainty continues on exact timing and track of the system leading to uncertainty on snow amounts. 3) Potential for a few strong thunderstorms across the southeast plains. A Pacific storm system spinning off the California Coast continues to be forecast to slowly move north and east across across the Desert Southwest through the day on Friday. While models continue to differ on timing and track with this cut off system, the initially slightly slower and further south solution of EC/EPS and Canadian models, where the cut off low is moving into the Four Corners region Saturday morning continues to the preferred solution at this time. With this preferred solution in mind, we have expanded winter storm watches across the rest of the higher terrain and upgraded the winter storm watches for Pikes Peak and Teller County, as well as northern El Paso County, to a winter storm warning at this time. Friday night-Saturday...This initial track across the Colorado/New Mexico border through the day Saturday would bring a round of moderate to heavy precipitation across south central and southeast Colorado, favoring the areas over and near the higher terrain with increasing and deep (Sfc-H7) east to southeast flow. Snow levels look to remain relatively high (5500-6500) with mixed precipitation across the I-25 corridor and rain across the far southeast plains. Increasing southerly flow and waa aloft ahead of this system will also lead to increasing instability across the eastern Plains which would support the potential for thunderstorms late Friday night and early Saturday morning, along with the potential for strong to marginally severe storms across the far southeast Plains later Saturday, as a developing surface low lifts out across the plains. Snowfall amounts through the period look to range from 4 to 8 inches across the higher terrain areas, with 1 to 4 inches possible across the valley locales and lower elevations, though relatively warm southerly flow aloft and daytime temperatures may limit accumulations across the lower elevations. Saturday night-Monday...Deformation band precipitation spreads east Saturday night, with the vertically stacked system across the southeast plains Sunday morning, before slowly lifting north and east into west central Kansas Sunday night. Moderate to heavy snow is expected to develop over and near the higher terrain Saturday night, with strong northerly winds expected to develop on the back of system, which will keep heavy snow and blowing in place across the Pikes Peak region through the day Sunday before slowly diminishing Sunday night into early Monday morning, as the system continues to move east. There is likely going to be precipitation wrapping around the backside of the low extending into across the southeast Plains, though with the uncertainty of the track of the system, there remains uncertainty on how much, what form and how far south this precipitation will extend. Again, with a relatively warm system and temperatures expected to be in the 40s to around 50 across the far southeast plains, most of this precipitation would be in form of rain at this time. Snow totals through this timeframe look to range for 6 to 12 inches across the higher terrain, greatest across the Pikes Peak and Palmer Dvd region, where expected conditions may warrant the upgrade of the the current winter storm warning to a blizzard warning, as travel may become difficult to impossible. Although current watches and warnings are in place across south central and southeast Colorado, there still remains uncertainty of the track of this cutoff low pressure system which could increase or decrease snow totals and impacts across all of south central and southeast Colorado. Please stay tuned to the latest forecasts and updates to this significant winter storm system. Monday night-Thursday...Another storm system looks to move across the region in the late Monday night through Wednesday timeframe, however latest models indicate significant differences on its strength and location as it moves across the Rockies. For now, NBM keeps slight and chance pops across the area through this period, with the best pops over and near the higher terrain. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 359 PM MST Thu Mar 11 2021 VFR conditions currently dominate all TAF sites. There is going to be an increasing cloud deck later on this evening due to some low level moisture advecting in for KCOS and KPUB as the winds become more easterly. LIFR conditions will more that likely be the case for KCOS after around 08Z due to low CIGs near the surface and low VIS in FZFG, and there is the potential for this cloud deck to become thick enough to cause some -FZDZ as well. KPUB will also see low CIGs but should remain at around 010 AGL. There is also a slight chance for -FZDZ at KPUB as well although the vertical depth of the low level moisture does not appear to be as significant as further to the north. The low clouds will begin break by around 15Z for KCOS and 17Z for KPUB, respectively, although some MVFR conditions could still be possible for a few hours after. Some -SHSN are possible over the San Juan and Sawatch Mountains, so be advised of reduce VIS if flying at lower levels in the vicinity of these areas. Winds will also continue to be a little strong and gusty at KALS out of the southwest and for KCOS and KPUB out of the south-southeast, until later this evening, therefore some light to moderate CAT could be possible at lower levels. winds will diminish throughout the night and then increase again by tomorrow morning but should not be as strong as they were today. Still there could be some light CAT for larger aircraft and moderate CAT for smaller aircraft after around 17Z for KALS, and 19Z for KCOS. && .PUB WATCHES/WARNINGS/ADVISORIES... Winter Storm Watch from late Friday night through late Sunday night for COZ059-062-072>080-083-085. Winter Storm Watch from Friday afternoon through late Sunday night for COZ058-060-061-063-066-068. Winter Storm Warning from 11 PM MST Friday to 6 AM MDT Monday for COZ081-082. Winter Storm Warning from 5 AM MST Saturday to 6 AM MDT Monday for COZ084. && $$ UPDATE...28 SHORT TERM...KT LONG TERM...MW AVIATION...STEWARD
Area Forecast Discussion
National Weather Service San Angelo TX
511 PM CST Thu Mar 11 2021 ...New AVIATION... .SHORT TERM... (This evening through Friday) Issued at 218 PM CST Thu Mar 11 2021 Today is pretty much a repeat of yesterday across West Central Texas, with mild and breezy conditions prevailing across the area. Low clouds from this morning have scattered out somewhat this afternoon, but a band of high level clouds continues to stream eastward across much of the region. Where the cloud cover is a little thinner temperatures have warmed into the upper 70s. Otherwise, temperatures are generally in the lower to mid 70s. Expect another very mild night with low clouds spreading back into the area. Lows will generally be in the 60s. Models indicate a weak shortwave in the southwest flow aloft brushing the northwestern Big Country overnight with some mid level instability noted in model soundings. However, high res model guidance including the HRRR and Texas Tech WRF do not show much if any convective development for our area. Thus, have capped PoPs at 20% for tonight. Tomorrow will again be warm and breezy under partly to mostly cloudy skies. With no apparent shortwaves or areas of lift moving overhead have kept mentionable PoPs out of the forecast although can`t rule a very light isolated shower. Otherwise, look for highs back into the mid to upper 70s. && .LONG TERM... (Friday night through next Wednesday) Issued at 159 PM CST Thu Mar 11 2021 An upper level low over Southern California Friday evening will strengthen as it moves into Arizona early Saturday morning, then into the New Mexico/Colorado border Saturday afternoon, then slowing down and becoming mostly stationary across eastern Colorado and continuing to strengthen Saturday night through Sunday evening, before the low finally moves east across the Central Plains during the day Monday. Meanwhile at the surface Friday night/early Saturday morning, a north-to-south oriented dry line will exist across the NM/TX border and south into the Big Bend region. During the day Saturday, a Pacific cold-front will approach from the west, merge with the dry-line in the afternoon, and move east across West Central Texas through late Saturday night. In advance of the cold front, dew points in the warm sector will be in the upper 50s to low 60s, with temperatures rising into the mid to upper 70s, due to warm and moist south to southeasterly flow continuing. ML CAPEs look to increase to around 500-1000 J/KG by the afternoon. This instability will combine with the aforementioned moisture and lift from the nearby low to create thunderstorms along the cold front as it moves through the region late Saturday afternoon through late Saturday night, with any storms likely pushing east of our eastern counties by sunrise Sunday. Models are indicating the storm- mode to be that of a squall line, and with 0-6 km bulk shear of 60-75 KT, some storms could be strong to severe, so SPC has most of our region in a Slight Risk for severe weather, with damaging winds and large hail the main threats. Before the likely squall line moves through, there could also be some isolated showers/storms developing in the late morning/afternoon. Expect dry weather on Sunday with sunny skies and westerly surface/low level flow. The dry air coming in behind the front (dewpoints dropping into the high teens to mid 20s), combined with gusty wind speeds of around 15-30 mph with gusts of 35-40 mph, could bring elevated to near critical fire weather conditions Sunday. With the warm, downsloping, dry winds, expect highs in the low 70s. Mostly dry weather expected Monday through Thursday of next week, with generally zonal flow aloft. Expect a warming trend Monday through Tuesday, with warm south to southwest flow and warming of the 850 mb thermal ridge. Then a dry cold front looks to come through some-time late Tues or Wed, with big differences in the timing from the models. Depending on the strength of the cold front, it could drop highs into the low 50s or low 60s for a day or two. && .AVIATION... (00Z TAFS) Issued at 445 PM CST Thu Mar 11 2021 Stratus is forecast to develop at the southern 3 sites around 06Z, then spread north to the KSJT and KABI between 07Z and 09Z, resulting in MVFR ceilings. Ceilings may lower into the IFR category after 09Z, especially at the southern 3 sites. Expect the stratus to persist through the morning hours, with VFR conditions returning by mid to late afternoon Friday. Gusty southeast winds will decrease this evening, then become south at 10 to 15 knots, with higher gusts, by late morning Friday. && .PRELIMINARY POINT TEMPS/POPS... Abilene 63 79 61 78 / 10 5 10 30 San Angelo 63 80 61 78 / 5 5 5 30 Junction 63 79 60 78 / 10 5 5 20 Brownwood 62 79 60 77 / 5 5 5 20 Sweetwater 61 78 63 76 / 20 10 20 40 Ozona 59 77 60 75 / 5 5 5 30 && .SJT WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...42 LONG TERM....SJH AVIATION...Daniels
Area Forecast Discussion
National Weather Service Tulsa OK
910 PM CST Thu Mar 11 2021 ...UPDATE... .DISCUSSION... A nearly stationary cold front extends from SE OK northeastward into NW AR between XNA and FYV. The latest IR images have shown a gradual warming of cloud tops across SW MO after fairly cool cloud tops an hour ago with a fair amount of lightning being observed. A line of cumulus just north of the surface front was noted across far NE OK and far NW AR. Cloud top temperatures across far NE OK and far NW AR have stayed fairly consistent over the past several hours which is consistent with radar imagery of the overall shower activity. Spotty shower activity was noted close to the front across eastern Oklahoma and northwestern Arkansas. Showers, especially across far NE OK and far NW AR, have become a little more cellular in nature with locally small intensification of cores being observed. With that said, these showers are still relatively weak, but this strengthening trend is expected to continue through the night as the low level jet strengthens allowing for better shear and for better moisture. Also, as the night progresses, the nearly stationary front will slowly begin to move northward effectively transitioning to a warm front. Showers and storms are expected to focus around this boundary where shear and lift will be maximized. As for instability, MUCAPE and MLCAPE values are relatively weak in the 250 to 500J/kg range and 100 to 250J/kg range respectively with not much of an increase expected overnight. The overall strong to severe storm threat for tonight continues to be fairly limited at this time owing largely to surface CIN and low CAPE. The latest CAM solutions continue to not be overly excited about convection in our CWA through the night with the NAM Nest being a little more bullish with storms tonight. At the time of writing the NAM Nest had a line of storms along I-44 at 03Z but the latest observations obviously show this is not the case. The HRRR and the rest of the HREF CAM suite has been fairly consistent with shower activity (pretty similar to what is currently being observed) slowly strengthening into isolated to widely scattered thunderstorms through the night with peak strength below severe limits in most cases. With that said, there is a small chance for a storm (maybe two) to quickly intensify and briefly produce large hail up to quarter size or a brief damaging wind gust to 60mph. Northeast Oklahoma and far northwest Arkansas would be the most likely areas to experience severe weather. In terms of the forecast changes, opted to adjust PoPs a little over the next several hours based on the latest trends and guidance. Temperatures were also raised a little across NE OK where temperatures will be slow to fall thanks to cloud cover with small dew point depressions and rainfall/thunderstorms passing through the night. An update has already been sent. Snider && .PRELIMINARY POINT TEMPS/POPS... TUL 49 62 58 72 / 80 80 90 50 FSM 62 73 58 75 / 40 60 60 20 MLC 59 73 60 74 / 40 50 50 10 BVO 46 57 54 69 / 70 90 90 70 FYV 56 69 56 71 / 80 70 90 40 BYV 52 66 55 66 / 80 70 90 60 MKO 54 70 59 73 / 60 70 70 30 MIO 47 57 55 69 / 80 90 100 70 F10 52 71 61 74 / 60 70 70 30 HHW 62 74 60 75 / 10 40 20 10 && .TSA WATCHES/WARNINGS/ADVISORIES... OK...None. AR...None. && $$ SHORT TERM...21