Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/21/20


Area Forecast Discussion
National Weather Service La Crosse WI
1042 PM CDT Fri Mar 20 2020 .SHORT TERM...(Tonight through Saturday) Issued at 150 PM CDT Fri Mar 20 2020 A brisk and winter-like day on this first (full) day of Spring. Tight pressure gradient on the backside of departing storm system that dropped 1/2 to 2 inches of rain and a band of 1-3 inches of snow over the last 24 hours was producing gusty northwest winds of 10-20 mph, gusting 30 mph. Temperatures as of 1 pm under mostly cloudy skies were in the middle 20s to middle 30s with wind chills mostly in the teens. Brr. High pressure will build in across the area tonight for mostly clear/partly cloudy skies. This will lead to some chilly overnight lows as readings dip into the single digits to near 20. Saturday will see increasing clouds as the high slides off and a weak mid-level trough approaches from the Northern Plains. Highs are expected to top off in the 30s. .LONG TERM...(Saturday Night through Friday) Issued at 150 PM CDT Fri Mar 20 2020 Light snow is looking likely Saturday night for areas mainly north of I-90 as lift associated with the aforementioned mid-level wave saturates the column. Accumulators look on the very light side though with generally a 1/2 inch or less expected. Light snow chances will linger north of I-94 Sunday morning...and then rain chances move in across portions of northeast IA into southern WI Sunday afternoon as another mid-level trough pushes east from the Central Plains. Otherwise, looks a mostly cloudy day with highs in the 40s. Light rain and snow chances are on tap for much of the area Sunday night as yet another trough rolls across the area. Again, this precipitation looks very light with minimal amounts expected. A ridge of high pressure builds into the area Monday for partly sunny skies and a bit milder temperatures in the mid 40s to lower 50s. On/off precipitation chances will be seen through the remainder of next week as a fairly high-zonal flow brings several weak impulses through. Still a bit too early to determine exact amounts of precipitation or any snowfall if any but looks fairly light at this time because of the progressive nature of the flow aloft. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1042 PM CDT Fri Mar 20 2020 VFR conditions expected to continue through the TAF period as high pressure currently centered over northwest MN slowly drifts eastward. Remaining stratocu has retreated south for tonight and will eventually wrap northward around the backside of the high as it drifts over the Upper Great Lakes on Saturday. That will spread increasing mid/low clouds into the area during the afternoon. Model consensus generally favors VFR through the TAF period, with a drop to MVFR more likely after 06Z Sunday as the next system moves through. The RAP remains more aggressive with bringing MVFR clouds in earlier, so will continue to monitor trends. Light and variable winds overnight will pick up a bit out of the southeast on Saturday, around 10 knots or less. && .HYDROLOGY... Issued at 150 PM CDT Fri Mar 20 2020 Rainfall of 0.5 to near 2 inches fell over the last 24 hours with the heaviest rainfall across portions of northeast IA into southern WI. Ongoing runoff of this precipitation and melting snow will produce river rises along with some minor flooding -mainly on stretches along the Kickapoo, Black, and Trempealeau Rivers. The Mississippi will be on the rise as well over the next few day with some minor flooding expected at McGregor by Tuesday. Thankfully, no additional major rainfalls are expected through this next week. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...NMB/DAS LONG TERM...DAS AVIATION...Kurz HYDROLOGY...DAS
Area Forecast Discussion
National Weather Service Goodland KS
633 PM MDT Fri Mar 20 2020 .UPDATE... Issued at 633 PM MDT Fri Mar 20 2020 Based on the current...stagnant low cloud cover over portions of NE Colorado, have opted to increase sky cover for the evening period. This is expected to trend ENE overnight so have changed wording in portions of SW Nebraska as well. Will have mostly cloudy to cloudy skies trending to partly cloudy towards morning. No other changes at this time. && .SHORT TERM...(This evening through Sunday) Issued at 141 PM MDT Fri Mar 20 2020 Satellite imagery and 500mb RAP analysis showed southwest flow across the region today, with an upper trough near the Great Lakes. Cloud cover mainly stayed west of the region; however, some low to mid clouds nosed into eastern Colorado and southwest Nebraska throughout the day. North winds decreased through the morning. At 1:30 PM MT, light and variable winds were observed with temperatures in the mid 20s to mid 30s. Surface high pressure persists over the region tonight as temperatures fall into the upper teens to low 20s. Wind chill values in the single digits are anticipated, with south/southeast winds around 10 knots. Dry weather continues into Saturday, as flow aloft becomes zonal and surface high pressure shifts eastward. High temperatures should be in the upper 40s to upper 50s. Meanwhile, a shortwave travels through the flow across the desert southwest and approaches the region. This disturbance generates rain chances for the area Saturday night. Snow could mix in overnight as temperatures fall into the upper 20s/low 30s, but little to no accumulation is forecast. Precipitation chances continue into Sunday morning, with highs in the 50s by the afternoon. Skies clear through the day as any remaining rain dissipates. A weak shortwave ridge progresses over the High Plains Sunday night, with temperatures in the upper 20s/low 30s once again. .LONG TERM...(Monday through Friday) Issued at 124 PM MDT Fri Mar 20 2020 For the extended period the models are showing a mostly zonal flow with embedded shortwaves over the southern portion of the U.S. through the middle of next week. Towards the end of the week the flow becomes more meridional as a major shortwave moved into the High Plans from the west-northwest. On the surface, the models are showing a low pressure system developing off the Front Range, over the Texas Panhandle, and moving into the Great Lakes region by Wednesday. This system looks to produce wet conditions on Monday, with a chance of rainshowers and possible isolated thunderstorms, followed by dry conditions through Wednesday afternoon. Highs should reach into the middle 60s to around 70 while the overnight lows drop into the middle 30s during this time. Wednesday afternoon the models are showing another low pressure system developing off the Front Range; however, this time over the Nebraska Panhandle. This system looks to have stronger upper-level support and produce another round of winter weather impacts for the area during the end next week. Expect chance of rainshowers on Thursday and Friday, were the highs should reach into the lower to middle 50s. Overnight hours, look for the rain to become snow as the lows drop into the upper 20s to lower 30s. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 512 PM MDT Fri Mar 20 2020 High pressure north and east of the region will provide both terminals with VFR conditions for the entire forecast period, w/ mainly scattered high clouds expected. Winds for KGLD, SE 10-15kts thru 08z Saturday, then SSW 10-15kts. By 20z Saturday, SE around 10kts. Winds for KMCK, ENE 5-10kts thru 04z Saturday, then SE around 10kts. By 18z Saturday, S 10-15kts. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...JN SHORT TERM...JBH LONG TERM...BW AVIATION...JN
Area Forecast Discussion
National Weather Service Green Bay WI
1049 PM CDT Fri Mar 20 2020 Updated aviation portion for 06Z TAF issuance .SHORT TERM...Tonight and Saturday Issued at 231 PM CDT Fri Mar 20 2020 The latest RAP analysis and satellite/radar imagery show Wisconsin positioned between high pressure over the northern Plains and a cold front moving across the eastern Great Lakes and Ohio Valley. North winds between these two features continue to generate lake effect clouds over Lake Superior which are streaming across Wisconsin. The airmass associated with the high is very dry as evident by below zero dewpoints north of Lake Superior, causing the back edge of the lake effect streamers to shift closer to the southern Lake Superior shoreline. As a result, think snow showers will be diminishing over Vilas county by the end of the afternoon, while skies gradually clear over the rest of northern WI. As this very dry airmass moves into the region, temps and cloud cover are the main forecast concerns. Tonight...Skies will become mostly clear across the region as high pressure moves into Wisconsin. Gusty north winds should subside early in the evening, leaving nearly ideal radiational cooling conditions across the snow covered northwoods. Though some cirrus may invade the region after midnight, think it probably won`t be thick enough to cause much of an impact on temps. Sided with the coldest statistical guidance for low temps, which may approach zero at the cold spots over the northwoods. Winds are expected to diminish last over central and northeast Wisconsin, and without the snow cover, temps shouldnt fall nearly as far. Lows ranging from near zero in the north to the mid teens over the Fox Valley and lakeshore. Saturday...The surface high will shift east across northern Lake Michigan and northern lower Michigan. Low level winds will shift to the east as this occurs, and may bring in scattered clouds and flurries to the Lake Michigan shoreline by mid-morning. Otherwise should see a mostly sunny day with only filtered sunshine overhead. Temps will remain below normal and range from the upper 20s to middle 30s. .LONG TERM...Saturday Night Through Friday Issued at 231 PM CDT Fri Mar 20 2020 Zonal flow will dominate much of the period, with typical model struggles with the timing and strength of several fast moving systems. Temperatures will start off around normal on Sunday, then return to above normal for much of the next week. A potent short-wave trof is expected to pass through the northwest part of the forecast area late Saturday night into Sunday morning. Have increased pops considerably with this system, and would expect to see a half inch to an inch of snow over north central WI. Another system is expected to track south of the region Sunday into Sunday night, as a weakening cold front approaches our northwest counties. Expecting little impact from these systems at this time. Surface high pressure will bring dry weather to the region Monday and Monday night. A short-wave trof will pass through the region Tuesday into Tuesday night, as low pressure tracks through Illinois. Models are significantly different, with the ECMWF bringing precipitation through most of the forecast area, while the GFS keeps it to our south. Have stayed close to the model blend for these periods, with nothing higher than chance pops for a wintry mix expected at this time. A potentially more significant low pressure system is expected to move through the western Great Lakes Wednesday night. This system will have more dynamic forcing, with the LFQ of a 140-150 knot upper jet impacting the region. This system is still a long way out, but there are indications it could produce an accumulating snowfall across northern WI. Any lingering mixed rain or snow should quickly exit northeast WI Thursday morning. High pressure will build into the region for the rest of Thursday into Friday, along with a period of dry weather. && .AVIATION...for 06Z TAF Issuance Issued at 1049 PM CDT Fri Mar 20 2020 Mostly clear skies and dry weather are expected during the TAF period as high pressure tracks through the western Great Lakes region. The only clouds of note will be some high cirrus clouds at times. Winds are expected to remain relatively light through the period. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....MPC LONG TERM......Kieckbusch AVIATION.......Kurimski
Area Forecast Discussion
National Weather Service Grand Rapids MI
740 PM EDT Fri Mar 20 2020 LATEST UPDATE... Update/Aviation/Marine .SYNOPSIS... Issued at 330 PM EDT Fri Mar 20 2020 - Snow flurries early then mostly clear late tonight through Sunday morning - Chance of some snow Sunday afternoon into Monday morning - Rain expected Tuesday into Tuesday night - Model disparity for the end of the week && .UPDATE... Issued at 740 PM EDT Fri Mar 20 2020 I added a chance of snow showers this evening to the forecast and delayed the clearing of the sky till toward midnight. As it turns out, there was enough cold advection with deep enough moisture (cloud tops near 6000 ft) with the north at low to mid levels to saturate the DGZ and cause snow flurries or light snow showers this evening. Our radar continues to show an increase in reflectivity just north of Kent County. This matches the where the 22z RAP model shows the strongest cold advection in the 925 mb to 850 mb layer this evening. Reports from surface observations where as low as 3 miles at CAD. We even had a few snow flakes at the office here. So, I put a chance for snow showers in our forecast and delayed the clearing till toward midnight. The 22z RAP model shows the DGZ becoming unsaturated after 10 pm. Winds start turning more to the north northeast at low levels too, so both of those should allow for clearing to finally take place. && .DISCUSSION...(This evening through next Friday) Issued at 330 PM EDT Fri Mar 20 2020 -- Quiet weather tonight through Sunday morning -- High pressure builds in tonight into Saturday which will help clear the skies out and provide dry weather. We expect the skies to become partly cloudy later this evening and clear out overnight. There is the possibility that some lake effect stratocumulus tries to hang on tonight, but the overwhelming signal in the model data is for clearing. Dry weather is forecast from now through Sunday morning. It will be a cool night tonight with lows in the teens. Highs on Saturday will push into the 30s. -- Chance of some snow Sunday afternoon into Monday morning -- The next potential for impactful weather comes Sunday afternoon lasting into Monday morning. The weather of concern is snow, especially from I-96 to the south. The models at this point have quite a bit of disparity in terms of how much precipitation we see. The ECMWF is lowest with amounts around a tenth of an inch, the GFS is a bit higher around a quarter of an inch and the NAM being the highest at potentially around a half inch in the far south. Obviously the jury is still out on this. It is a weaker wave in zonal flow with a surface feature that is nothing to write home about. Given the range of precipitation we could be looking at anything from a dusting to an inch in the ECWMF to several inches via the NAM. We will be watching this wave closely. The good thing is that the bulk of the weather will come Sunday night. Also of note is that many folks are now working from home so the Monday morning commute will not be as heavy as it normally would be. Plenty of time to watch this weaker system and zero in on snow amounts and any potential impacts. -- Rain expected Tuesday into Tuesday night -- A stronger system is expected around the Tuesday time frame of next week. The low will have some "warmer" air with it so, we are expecting mainly rain as it passes through and nothing too heavy at this point. -- Model disparity for the end of the week -- Another system out in the Thursday and Thursday night time frame will bring the chance of rain once again. The GFS is stronger with a low passing off to our north. The ECMWF is weaker with more of an inverted trough moving through. The bottom line to the pattern over the next 7 days is zonal flow with a system affecting the area every couple of days. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 740 PM EDT Fri Mar 20 2020 Slowly but surely skies will clear at all TAF sites tonight. However early this evening we do have some snow showers that we have to move out of the area first. The snow showers are very light and I do not expect anything less than VFR visibilities in most of them (an isolated 3-4SM -SHSN it not out of the question). In the time frame of 03z to 06z skies should clear from north to south. I expect clear skies from that point through all of Saturday. Winds will be lighter and turn to the northeast later tonight and continue into Saturday. && .MARINE... Issued at 740 PM EDT Fri Mar 20 2020 I have ended the coastal flood advisory and gale warning and replaced it with a small craft advisory. Looking at lake levels (for the coastal flood advisory)the most recent water level at Ludington was 581.4 feet, which is below the 581.7 foot level we use for an advisory. Holland was at 581.5 feet, which is also below the threshold for an advisory. Since winds have decreased below gale force already water levels have dropped already, it seems reasonable to replace all of that with a Small Craft Advisories. && .HYDROLOGY... Issued at 330 PM EDT Fri Mar 20 2020 No significant flooding is expected from the recent rainfall. Rainfall varied across the area from as little as a quarter of an inch towards I-94 to in some cases above an inch in parts of the Grand River basin. The highest total from our COCORAHS database shows 1.31 inches of rain near Allendale in Ottawa County. This area had repeated bursts of heavy rain in showers that moved through. So, the bottom line is we will certainly see some within bank rises in a few locations. A site or two in the Muskegon basin may even come close to bankfull. All sites will remain well below flood stage. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...Small Craft Advisory until 8 AM EDT Saturday for LMZ844>849. && $$ UPDATE...WDM SYNOPSIS...Duke DISCUSSION...Duke AVIATION...WDM HYDROLOGY...Duke MARINE...WDM
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1019 PM EDT Fri Mar 20 2020 .SYNOPSIS... A strong cold front will bring rain chances to our area into Saturday. This front will become stationary along the Gulf coast as low pressures ride the front into the first half of the week. Cooler high pressure will pass to our north Sunday and Monday. Expect a warming trend in the middle of the week. && .NEAR TERM /THROUGH SATURDAY/... As of 1010 PM: A sfc cold front has pushed into Middle TN and central KY. Elevated convergence/frontogenesis band preceding the main front has reached the Appalachians. Areas of light rain are present within this band; enough instability remains per RAP analysis to allow a couple convective showers here and there, especially along leading edge of cold pool noted on KGSP radar. This cold pool will effectively introduce the front into the area over the next few hrs, though the actual front likely won`t arrive until the daytime hours Saturday. Despite the cooling effect of the decaying rain, overnight low temperatures will remain far above normal (as much as 20 above) with cloud cover lingering. On Saturday, anticipate the main cold front to back-door through the area from the north. Do anticipate a lull in precipitation and a break in the clouds from early morning into the early afternoon with light WNW winds behind the front. A seasonable amount of diurnal cu should break out, and a small precip chance will linger north of the front with modest instability. Max temperatures will once again climb above normal, capping off in the low to upper 70s outside of the mountains. && .SHORT TERM /SATURDAY NIGHT THROUGH TUESDAY/... As of 115 PM EDT Friday: Residual moisture will persist across the far ern zones to begin the period, while a strong and dry sfc wedge develops down the east coast. Expect dry conds and cooler temps most of Sun before moisture returns from the south Sun afternoon. The atmos looks to remain quite stable as the wedge front pushes into central GA...yet a couple tstms cannot be ruled out across the far srn zones late in the day Sun. Meanwhile, a couple ulvl trofs will cross the FA late Sun thru Mon which will lower mlvl lapse rates and possibly instigate a few relatively weak storms, due to lack of destabilization, over the mtns early on and then across the ern zones thru mid-day Mon. The sfc wedge is expected to break down Mon afternoon while a weak front to the south begins lifting north thru the day Tue. This front will also be weakly forced and will not have much available instability with the best chance for tstms held south of I-85 by afternoon. Below normal temps Sun with high cloud cover and sfc wedge building in...then temps return to or abv normal levels Mon/Tue. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... As of 1235 PM EDT Friday: The pattern continues to remain active as the subtrop high remains dominant with little changes in it/s overall config. This will keep more pronounced ulvl s/w trofs north and west of the FA, thus there will be little dyno support for weak frontal systems affecting the region. The most active time period will be early Wed when a cold front pushes in and lays across the FA. With limited instability overnight...wont expect stg storms...yet stronger upstream convection will likely push into the wrn FA Tue evening and diminish in intensity thru the overnight period. No hydro concerns with this system as it continues to advance east of the area by 18z. The models have come in much drier for the Wed afternoon thru Thu period with general hipres aided by flat ridging aloft. PoPs have been reduced thru this period with little chance of afternoon thunder both days outside the mtns. The models are also backing off on bringing in a cold front Thu night thru Fri while a warm front remains north of the area. Thus, the area shud remain in warm sector with the best -shra/tstm chances remaining across the higher elevations. In this environment, max and min temps will be well abv normal for this time of the year. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... At KCLT and Elsewhere: Ahead of a strong cold front now crossing the lower Ohio Valley, a moist convergence zone will shift across the terminals tonight. SHRA will occur with this feature, though the now contiguous rain shield now seen on radar from East TN to AL is expected to become more spotty as it crosses the mountains. Enough elevated instability could support a few embedded TSRA. With impacts generally low, some sites only get a VCSH mention, but KCLT/KHKY/KAVL get a TEMPO. Mainly VFR will be seen outside precip. Winds will be initially SW, veering to NW at KAVL following onset of precip, and later at KHKY/KAVL. VFR and diminishing precip expected in the early morning. The main cold front will settle south through the area Saturday aftn/evening, allowing winds to continue to veer to NE at KCLT. Low VFR cu/stratocu should break out diurnally, likely forming into an increasingly lower cig near the end of the period at KCLT. Outlook: An unsettled weather pattern will continue into next week allowing for periodic flight restrictions. Confidence Table... 02-08Z 08-14Z 14-20Z 20-00Z KCLT High 100% High 100% High 100% High 98% KGSP High 100% High 100% High 100% High 100% KAVL High 97% High 97% High 98% High 100% KHKY High 100% High 93% High 100% High 100% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 100% High 100% High 100% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables are available at the following link: www.weather.gov/gsp/aviation && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...12/08 SHORT TERM...SBK LONG TERM...SBK AVIATION...08
Area Forecast Discussion
National Weather Service Marquette MI
741 PM EDT Fri Mar 20 2020 .SHORT TERM...(This evening through Saturday) Issued at 336 PM EDT FRI MAR 20 2020 RAP analysis shows Upper Michigan remains between a deepening low pressure system of 993mb over S Quebec and an approaching 1041mb high pressure system over the Dakotas this afternoon. Under the tight pressure gradient, pressure rises, and CAA strong N winds have been the norm today with BLSN and LES continuing. As a shortwave passed overhead today, brief enhancement with blizzard conditions were seen, but conditions have slowly improved since. GOES imagery this morning has shown the strong winds "rip apart" developing LES bands as they moved into the inland counties. Now, GOES imagery shows a decreasing in LES coverage and lake-effect clouds as high pressure and drier air makes it into the UP (see IWD at 23/9, CMX 19/5). Have even seen pockets of sun poke through at the office this afternoon. Heading into tonight, this trend is expecting to continue as remaining LES and BLSN snow continues to diminish from west to east. models suggest heights will rise briefly before more of a zonal flow aloft takes hold. Depending on how much clearing is seen across the western interior tonight, it could get pretty chilly as a fresh snowpack and calming winds under a high pressure move in. Right now, how lows dipping slightly into the blo zero mark for some in the w interior, with single digits elsewhere and perhaps teens in the east downwind of continued lake-effect snow/clouds for most of the evening/night. Should winds cut off and clear skies take hold, expect these temps to bottom out further. Tomorrow, expect a generally calm day with partly cloudy skies and lighter winds under high pressure. In the late afternoon/evening, a shortwave trof approaches Upper Michigan from the Dakotas. Will see some increasing clouds into the afternoon, and maybe some lake- effect clouds across the south-central. Grids may be a little too fast to bring clouds in the afternoon but the difference between partly cloudy and slightly more partly cloudy is probably fine. .LONG TERM...(Saturday night through Friday) Issued at 255 PM EDT FRI MAR 20 2020 Upper air pattern consists of a 500 mb shortwave over the northern plains 00z Sun with another over the northern and central Rockies and another over the Canadian Rockies. A shortwave moves into the upper Great Lakes 12z Sun with a stronger shortwave moving in 00z Mon which then moves out late Mon. So, active weather pattern continues, but systems remain weak. In the extended, the GFS and ECMWF show a 500 mb trough in the western U.S. and a shortwave over the northern and central plains 12z Tue. This shortwave moves to the lower Great Lakes 12z Wed with a shortwave in the Canadian Prairies. This shortwave moves into the upper Great Lakes 12z Thu. Troughing moves into the Rockies 12z Fri with another shortwave in the upper Great Lakes. Temperatures will remain above normal for this forecast period. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 737 PM EDT FRI MAR 20 2020 VFR conditions are taking over the terminals this evening as lake-effect snow winds down. These benign conditions are expected to continue through the TAF period at all three terminals as high pressure builds into the region. Expect light and variable winds overnight, becoming southerly to southeasterly (but still light) tomorrow. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 336 PM EDT FRI MAR 20 2020 N gales and heavy freezing spray will continue to diminish this afternoon into tonight as the pressure gradient relaxes and high pressure takes over tonight. Winds become light for Sat, under 15 kts, as the high pres passes across the area. S to SE winds will then increase to 15-25 kts across much of Lake Superior Sun into Sun night as the high exits and a weakening low pressure trough approaches. Weaker winds are then expected again for Tuesday and Wednesday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Lakeshore Flood Warning until 8 PM EDT this evening for MIZ005- 006. Lake Superior... Heavy Freezing Spray Warning until 8 PM EDT this evening for LSZ243>245-248>251-263>267. Gale Warning until 8 PM EDT this evening for LSZ243>251-264>267. Lake Michigan... Gale Warning until 8 PM EDT this evening for LMZ221-248-250. && $$ SHORT TERM...JAW LONG TERM...07 AVIATION...lg MARINE...JAW
Area Forecast Discussion
National Weather Service San Francisco Bay Area
900 PM PDT Fri Mar 20 2020 .SYNOPSIS...Scattered showers will continue overnight and into Saturday, mainly south of Monterey Bay. Otherwise, expect dry and mild conditions for most areas through Sunday morning. Look for widespread rain to develop late Sunday into Sunday night as the next system sweeps across the region. Cool unsettled weather will continue through the next work week. && .DISCUSSION...As of 9:00 PM PDT Friday...Isolated showers developed this afternoon, mainly over the hills to the south and east of San Francisco. By this evening, shower activity had ended in most areas, except for western Monterey County. This is precisely where the 00Z NAM focuses most shower activity this evening and overnight. A weak upper low, currently centered near the Delta, is forecast to drift slowly to the west overnight. Sufficient moisture and instability are forecast to continue to the south of the low center to maintain scattered shower activity going into Saturday. But once again, most of that shower activity will be across Monterey and San Benito Counties, although the NAM and HRRR forecast at least isolated showers as far north and west as Contra Costa County and San Mateo County on Saturday afternoon. Most of the SF Bay Area, however, should experience dry and mild weather on Saturday. Precipitation should end in all areas by Saturday night as the weak upper low fills and subsidence develops ahead of the next upper low approaching from offshore. This next system is forecast to spread rain across most of the region late Sunday and Sunday night as it moves onshore along the Central Coast, although models generally agree that the North Bay will mostly miss out on rain with this system. Most precipitation is expected to end by Monday morning as the low opens up and moves quickly to the east in response to a cold upper trough dropping in from the North. But scattered showers will likely persist on Monday. Rainfall totals with the late Sunday-Sunday night system are forecast to range from less than a tenth of an inch in the North Bay to as much as an inch in the mountains of Monterey and San Benito Counties. Most urban areas will likely see a half inch or less. The models maintain a cold/showery pattern for much of the remainder of next week as a cold upper trough gradually digs south along the West Coast. This system is not expected to contain a whole lot of moisture and so rainfall amounts will be mostly light. The cold air with next week`s system will make it feel more likely winter than spring, with low snow levels, daytime highs mostly in the 50s, and lows in the upper 30s and 40s. Coldest nights are likely to occur later in the week when precipitation tapers off and skies clear. && .AVIATION...as of 05:05 PM PDT Friday...For 00Z TAFs. VFR conditions through the period, aside from possibility of late night haze or fog in the North Bay Valleys. Instability from an upper low over the area has resulted in SCT to BKN cumulus, with KMUX radar showing a few embedded showers. Vertical development appears to be capped around the 700 mb level however, so very unlikely to be any thunderstorms even over our higher terrain. Latest GFS and NAM model output indicate some increase in shower activity later this evening from around the Monterey Peninsula southward, diminishing by Saturday morning. Generally light onshore winds into this evening, turning light offshore overnight. Vicinity of KSFO...VFR through the period. Any late afternoon/evening showers look to be confined to the East Bay. West to northwest winds less than about 10 kt into the evening then light and variable overnight. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals..VFR through the period. Possible scattered showers through the late evening hours, mainly over the hills. Light winds, onshore the next couple of hours, then turning offshore. && .MARINE...as of 01:36 PM PDT Friday...Generally light south to southeast winds across the coastal waters today. An upper level low pressure system over the Sierra Nevada will move westward reaching the Bay Area tonight shifting winds out of the north to northeast. A wet system will approach the waters on Sunday splitting the flow with southerly winds over the southern waters and northerly winds over the northern waters. Generally light seas will persist before a long period northwest swell arrives tomorrow evening. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...NONE. && $$ PUBLIC FORECAST: Dykema AVIATION: Blier MARINE: AS Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea
Area Forecast Discussion
National Weather Service Pocatello ID
200 PM MDT Fri Mar 20 2020 .SHORT TERM...Tonight through Sun night. Upper level pattern staying the same through this period; a closed low over CA and northwesterly flow over the ID-MT border with short waves embedded in it will keep the threat of light precipitation over the highlands that border MT, WY, and UT--the farther east the more likely the precipitation. There is a trough moving through the northern part of the pattern that does expand the precipitation threat to the central Idaho mountains and brings a slight chance type of threat to the southeast side of the Snake River plain on Sat afternoon and evening. An incoming intense low starts changing things late Sun night by shifting the northwesterly flow to the north to more westerly, but not enough to affect weather in eastern Idaho-yet. .LONG TERM...Mon through next Fri night. Large low moving into British Columbia flushes out the CA low and brings a warm rain and high elevation snow event into the Gem State. The guidance has been accelerating the arrival of precipitation from this low, with good chances now during the day Mon. Light to moderate precipitation over the high elevations may meet Advisory criteria for late Mon night and continue into Tue. The associated cold front slides through Tue evening, and so there is a threat of thunderstorms both Mon and Tue, along with windy to very windy conditions possible with this storm. Harder to say if this aspect will reach Advisory conditions for wind. The upper level troughing stalls right over Idaho, NV, and eastern CA, continuing cold temperatures in the cloudiness and snow level should be reaching the Snake River plain during the overnight hours. Snowfall and precipitation in general is much lighter for Thu, but still not done. Thu night and Fri finally look dry and clear, but will be concerned with fog depending on how much precipitation is dropped during the preceding days. Messick && .AVIATION...A nearly stationary low pressure center over NV continues to keep our weather unsettled and provide moisture for isolated to scattered rain and snow showers. Most of this activity is yet again expected to target the southern/eastern highlands, but we can`t rule out some of this activity spilling into the Snake Plain/Teton Valley at times and affecting KBYI/KPIH/KIDA/KDIJ, and this is broadly supported by nearly all high-res model guidance and the NAM12 (yet with no strong agreement on any particular period being wettest at any given location). Beyond early afternoon TEMPO/FM groups through 19-22z, we did not have confidence to go higher than VCSH as far as showers directly hitting a terminal, but we painted VCSH everywhere through the end of the TAF period. The only potential vsby restrictions would be if a moderate snow shower directly hits a terminal, so generally expecting P6SM. At KSUN, a few localized radar returns in the region have prompted VCSH to be added for this afternoon there. Regionwide, cigs should predominantly be VFR (and satellite is even showing many breaks in the clouds this afternoon), but HRRR guidance is developing some low stratus tonight at KIDA and KDIJ with some support from NAM time-heights, so allowed some reductions there. There certainly is low-level moisture available and recent precip here and there, so this isn`t unreasonable, but confidence is low. Also allowed some low SCT clouds into KPIH, but they might remain on the southern edge of stratus development. More of the same is expected across the region Sat, with perhaps drier conditions and a bit more sun on Sun. - KSmith && .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$