Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/22/18

Area Forecast Discussion
National Weather Service Bismarck ND
944 PM CST Sun Jan 21 2018 .UPDATE... Issued at 940 PM CST Sun Jan 21 2018 Expanded the Dense Fog Advisory into Emmons, Logan, McIntosh and McLean counties based on GOES16 Advanced Nighttime Microphysics RGB and webcam trends through 0342 UTC. UPDATE Issued at 707 PM CST Sun Jan 21 2018 Based on current satellite trends, reports, and webcams through 01 Z, we expanded the Dense Fog Advisory westward. We will continue to monitor trends for a possible expansion further west. UPDATE Issued at 632 PM CST Sun Jan 21 2018 Current GOES-16 imagery and surface weather stations show areas of patchy to dense fog persisting this evening along the James Valley into north-central North Dakota. With the recent snowmelt, cooler temperatures, and mixing remaining weak through tomorrow morning, low level moisture continues to be sufficient enough to support areas of fog and low stratus. A Dense Fog Advisory has been issued for the northern James Valley and the Turtle Mountains through noon CST tomorrow. The 23 UTC iteration for the RAP and HRRR suggests areas of fog will expand westward into central North Dakota towards US Highway 83 tonight. For these reasons, the Dense Fog Advisories may need to expand westward later tonight. && .SHORT TERM...(This evening through Monday) Issued at 150 PM CST Sun Jan 21 2018 Low level moisture from snowmelt, lack of mixing and cooler temperatures are leading to dense fog development along the James Valley today. This fog is expected to persist and expand westward later tonight. Therefore, a Dense Fog Advisory has been issued for the northern James Valley through tomorrow morning. Tonight, it appears the low stratus/fog will overspread areas along, north and east of Lake Sakakawea and the Missouri River. Short-term models continue to indicate stratus mainly across eastern North Dakota and central North Dakota seeing decreasing mid and high level clouds tonight with good radiational cooling. Thus fog should develop on the west edge of the stratus tonight. .LONG TERM...(Monday night through Sunday) Issued at 150 PM CST Sun Jan 21 2018 The long term also appears quiet, for the most part. Models keep the Tuesday clipper further north and east, leaving most of North Dakota dry. There still appears to be a storm that will impact portions of the Northern Plains Friday into Saturday, but there is a lot of uncertainty with respect to the track of the storm and associated impacts. Temperatures over the next week should be slightly above normal, except Thursday which may be well above normal, ahead of the aforementioned storm system. Models have backed off on the precipitation potential Friday into Saturday. A model blend still brings some chance pops Friday into Saturday but the trend is certainly drier. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 940 PM CST Sun Jan 21 2018 Widespread low to very low LIFR conditions continue across the James Valley and into the Turtle Mountains this evening in areas of dense fog and stratus. Fog and low stratus will expand west towards KBIS and KMOT through the evening and overnight. Fog and stratus will likely persist through Monday morning with conditions slowly improving during the afternoon. && .BIS WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until noon CST Monday for NDZ003>005-012-013- 021>023-025-035>037-046-047-050. && $$ UPDATE...PA SHORT TERM...AJ LONG TERM...AJ AVIATION...PA
Area Forecast Discussion
National Weather Service Quad Cities IA IL
627 PM CST Sun Jan 21 2018 .UPDATE... Issued at 624 PM CST Sun Jan 21 2018 Based on webcams and obseverations, and after coordination with DMX I have extended the dense fog advisory westward to include the rest of the Highway 30 to I-80 corridor tonight. && .SYNOPSIS... Issued at 322 PM CST Sun Jan 21 2018 Strong low pressure system was centered over central Kansas this afternoon. A warm front stretched east from the low, cutting across southern Iowa. This warm front was slowly moving north today as temperatures reached near 60 degrees in the far southern CWA. This low pressure system will drive the weather in the short term. && .SHORT TERM...(This Evening through Monday) ISSUED AT 322 PM CST Sun Jan 21 2018 Convergence along and just north of the warm front is leading to patchy dense fog. This will likely continue until stronger forcing arrives in the area later this afternoon and into the evening. At this time, rain will likely improve visibilities. Due to the spotty nature of the dense fog decided to go with a SPS to cover it. Overall, the blended models appear to be biased lower in temps and northward progression of the warm front due to the NAM. Again the NAM believes that there is snow where there isn`t and that melting is not occurring today. This of course is incorrect. Trends in hourly temps have warmer temps across the CWA than any guidance today. This leads credence to the idea that the H85 WAA tonight will lead to warming temps and moistening of the BL tonight across the area. As the low approaches the area, the system begins to occlude. The triple point is forecast to move directly over the CWA. Then a clear slot is expected to rush across the eastern CWA during the day and into the afternoon tomorrow. Consensus on this evolution of the system is high. What is still of question is exact placement of these elements. I believe that the bias in the models is for a more cooler solution than what will actually occur, as a result have trended fields towards a slightly more northern, and warmer track. That latest HRRR hourly temps suggest that I am not warm enough tonight. As far as sensible weather goes, the drizzle will turn to rain showers tonight as the H5 divergence and H85 LLJ moves into our area. Withe terminus of the jet nearby and a deepening cyclone, would not rule out isolated thunder tonight. SPC has the entire area in a risk for thunderstorms. Into tomorrow, it appears that the CAMs try to produce thunderstorms on the back end of the precip shield. This would correspond to high low level shear, but a lack of 0-3km CAPE. These cells could lead to an isolated wind gust or small hail. The main threat for severe weather will be associated with the clear slot. Consistent signal in the CAMs suggests thunderstorm development tomorrow afternoon. This would coincide with the triple point across the central CWA. Low levels winds are backed in the lowest 1km of the atmosphere. This coupled with 0-3km CAPE forecast to be near 200 J/kg in the 18z NAM (320-360 J/kg in the 12Z NAM) will lead to a HSLC tornado threat from these storms. The 0-3km CAPE drops off as the system pulls north later in the afternoon. This may be premature as the models still think there is snow there. Updraft helicity in the NAMnest suggests that virtually every updraft could rotate. The question of rotation to the ground will be tied to where the 0-3km CAPE is. SPC has introduced a marginal risk for our far southeast tomorrow. This event will need to be watched for potential increased messaging as an off-season fast moving event could lead to greater impacts. If the convection and the 0-3km CAPE do not overlap near the triple point, then the threat for tornadoes would be very low. That said, this event looks like an almost textbook example for cold-core low tornadoes. This needs to be monitored, especially if thermal trends do not hold as currently forecast. .LONG TERM...(Monday Night through Sunday) ISSUED AT 322 PM CST Sun Jan 21 2018 There is good overall agreement between the synoptic models on the overall pattern and progression but some differences exist in the finer scale details. The main forecast concerns are precipitation type through 12z Tuesday and then again at the end of the week and into next weekend. 00z Tuesday to 12z Tuesday morning, a deep closed 500 mb and surface low be exiting into the southern Great Lakes. As this shortwave moves eastward, precipitation will be dictated by the race between cold air advection and drier air moving into the air. Currently, the GFS is most aggressive in drying out the atmosphere as the deformation zone rotates across eastern Iowa, northwest Illinois, and far northwest Missouri in the wake of the low. Other models continue to be saturated in the dendritic growth zone (-10C to -20C) which is key for ice production and a transition to snow or drizzle. With the uncertainty in the timing of colder air and saturation decided to go with a rain and snow mix and assume that moisture. will linter aloft until precipitation come to an end. Any freezing rain or drizzle will be dependent on the surface temperatures but models have them dropping below freezing after 06 utc on Tuesday which is about the time precipitation will come to an end from west to east by 12 utc on Tuesday. Snow amounts will be light with 1 to 2 inches possible in my far northwest Illinois counties with less than 1 inch possible in other locations. Tuesday through Wednesday, the 500 hpa pattern will be more of a northwesterly flow aloft with a shortwave passing to our north on Wednesday. The surface low will moving across northern Minnesota and Wisconsin with limited moisture thus only overcast skies are expected in our area. High temperatues will be closer to climatological normals in the upper 20s north to lower to mid 30s south. However, low temperatures will be 5 to 10 degrees above normal resulting in a slightly above average period. Thursday through Saturday, 500 mb ridging will move across the area with another surge in warmer air ahead of another storm system diving into the Desert Southwest. As the ridge moves to the east strong warm advection will take place with similar temperatures to Saturday and Sunday of the past week for Friday into Saturday. This will bring the chance of precipitation into the region Friday night into Saturday. Right now precipitation amounts are light despite the fact that the Gulf of Mexico appears to be open so this forecast may change. Precipitation type may start out as a rain snow mix before transiting to all a rain during the day on Saturday. In the wake of the this system, Canadian High pressure will build into the region with a return to near normal temperatures and dry conditions for the start of the week. && .AVIATION...(For the 00Z TAFS through 00Z Monday Evening) ISSUED AT 531 PM CST Sun Jan 21 2018 Mainly IFR with LIFR/VLIFR at CID, DBQ and MLI through Monday, with periods of drizzle/fog followed by rounds of showers overnight and Monday through midday with some thunder possible. Conditions may improve to MVFR or possibly VFR at CID and MLI during the afternoon as the front lifts north of the area, but then expect low clouds and MVFR to IFR ceilings to rotate back into the terminals late afternoon and Monday evening. At BRL, expect mostly VFR with periods of MVFR with periods of showers and possibly a few rumbles of thunder late this evening into Monday AM. Then expect low clouds and light rain to develop back into BRL mid to late afternoon. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...Dense Fog Advisory until 6 AM CST Monday for Benton-Cedar- Clinton-Iowa-Jackson-Johnson-Jones-Linn-Muscatine-Scott. IL...Dense Fog Advisory until 6 AM CST Monday for Bureau-Carroll- Henry IL-Jo Daviess-Putnam-Rock Island-Stephenson-Whiteside. MO...NONE. && $$ UPDATE...McClure SYNOPSIS...Gibbs SHORT TERM...Gibbs LONG TERM...Cousins AVIATION...McClure
Area Forecast Discussion
National Weather Service Sioux Falls SD
912 PM CST Sun Jan 21 2018 .UPDATE... Issued at 839 PM CST Sun Jan 21 2018 Very difficult forecast this evening. Models continue to trend downward with snow totals along and north of I-90 in southeast South Dakota and in the highway 14 corridor in southwest Minnesota. Radar shows widespread light echoes throughout the forecast area, however surface observations are indicating that very little of this is actually reaching the surface, with the exception of areas near and south of the Missouri River. Forecast soundings support a very dry layer above the surface between 900 mb and 750 mb which is impeding the development of precipitation. This layer is particularly dry in the I-90 corridor, with the RAP and HRRR indicating that saturation will be difficult for much of the night. Meanwhile, convection has developed north of Kansas City into the Omaha area and is lifting to the north northeast, on a trajectory a bit further east than previous runs. High res models and the 00z NAM still peg northeast Iowa and northeast Nebraska with significant snowfall late tonight into Monday, with strong frontogenesis and instability still on track to develop in the Blizzard warning area after midnight. Further north and west where the Winter Storm warning was issued, confidence is much lower. Models continue to show a very tight gradient between the extreme snowfall areas expecting 6 inches plus of snow, versus areas with little to no snowfall. With the storm track trending further east, at this time, it likewise appears that the heaviest snow (6+ inches) has also shifted east - and will fall south and east of a line from Lake Andes to Menno to Canton to Slayton. Sioux Falls metro remains on the edge of this gradient, however model trends overwhelmingly have shifted the heavier QPF to the southeast - significantly lowering amounts. Right now the expectation is 2 to 5 inches, however it should be noted that the last several runs of the RAP and HRRR are producing well under an inch in Sioux Falls. Given the dry mid levels tonight and the strongest lift/forcing developing to the south and east, have gone ahead and downgraded the winter storm warning in the Sioux Falls area (Minnehaha, McCook, Pipestone Co) to an advisory. && .SHORT TERM...(This evening through Monday night) Issued at 323 PM CST Sun Jan 21 2018 Very unclear forecast tonight as strong deepening upper level low moves from the intermountain west into the Central Plains tonight, and into the upper Midwest on Monday. In the short term, stationary frontogenetic band of light snow across the north along highway 14 is expected to weaken by 00Z as a secondary frontogenetic band develops from Tyndall to Sioux Falls over towards Worthington MN. Along this line, could see light snow through the evening hours. However, dry northeast fetch in the near surface layer will limit the potential of this band, especially the further east you go along this band. 12Z model trends are to shift the heavy snow band south slightly. This is because the atmosphere appears to be less capped across southern Nebraska into southern Iowa allowing convection to develop further to the south than previously expected. Short term hi-res models suggest convection will develop in the 00-02Z time range along and south of I-80 lifting north through the evening hours. The trends in the evening convection will be critical in producing an accurate forecast!! After 06Z, these storms are expected to lift north into the forecast area. Expect moderate to heavy snow to first develop along the Missouri River, and developing into a significant TROWAL across far southeastern South Dakota into northwest Iowa. With the unstable nature of the atmosphere, expect snowfall rates to exceed 1"/hr rates in the band. Precipitation type for our far southeast near Storm Lake is VERY difficult with pronounced warm nose between 900-800 mb. Further aloft, saturation is a question through the overnight hours, making precipitation type a real concern through 12Z. Am not expecting more than a few hundredths of precipitation till after 12z, when dynamics significantly increase and the thermodynamic profile cools and saturates leading to snow. Snow could be quite heavy through the morning hours, and will keep blizzard warning in place as this will be the prevailing precipitation type. Winds still look to be strong as low pressure system deepens tonight into Monday. Pressure falls around 1mb/hr coupled with increasing winds at 925 hpa to 35-45 knots are expected to lead to strong winds across the forecast areas, but especially east of the James River Valley after 06Z tonight into Monday. As mentioned by the previous forecaster, there will be a very clearly defined northern edge to the TROWAL precipitation, but where exactly this occurs still remains unclear. Have lowered snow amounts on the northern edge of the band (mainly within the winter storm warning), but have still kept 12-15" in the heart of the band, where very intense snowfall can be expected. Evening crew will need to monitor convective trends closely, and adjust the forecast accordingly. .LONG TERM...(Tuesday through Sunday) Issued at 323 PM CST Sun Jan 21 2018 Have not adjusted the forecast beyond the storm. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 532 PM CST Sun Jan 21 2018 Many aviation impacts expected throughout the TAF period. Light to moderate snow will begin lifting northeast from Nebraska this evening, becoming moderate to heavy at times in far southeast SD into east central SD, northwest IA, and southwest MN. Rain may briefly mix with the snow this evening to the west of I-29. In northwest Iowa, rain will be possible this evening, gradually mixing with snow and changing entirely to snow by daybreak Monday. Snow will continue on Monday, finally tapering off from west to east by the evening. Northerly winds will increase tonight, causing further visibility reductions in snowfall. Expect conditions to rapidly deteriorate in snowfall, with IFR and LIFR conditions likely for much of the TAF period. Near zero visibility is possible at times as well, especially for the KSUX TAF site. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...Winter Storm Warning until 6 PM CST Monday for SDZ065-066-068. Blizzard Warning from midnight tonight to midnight CST Monday night for SDZ067-069>071. Winter Storm Warning until noon CST Monday for SDZ050-063-064. Winter Weather Advisory until 6 PM CST Monday for SDZ040-054>056- 060>062. Winter Weather Advisory until 6 AM CST Monday for SDZ052-053- 057>059. MN...Blizzard Warning from midnight tonight to midnight CST Monday night for MNZ081-089-090. Winter Weather Advisory until 6 PM CST Monday for MNZ071-072-097. Winter Storm Warning until midnight CST Monday night for MNZ080- 098. IA...Blizzard Warning from midnight tonight to midnight CST Monday night for IAZ001>003-012>014-020>022-031-032. NE...Blizzard Warning from midnight tonight to midnight CST Monday night for NEZ013-014. && $$ UPDATE... SHORT TERM...BT LONG TERM...BT AVIATION...
Area Forecast Discussion
National Weather Service Houston/Galveston TX
915 PM CST Sun Jan 21 2018 .NEAR TERM [Through Monday]... No major changes were made to the forecast this evening. Current radar imagery shows scattered showers splattered across much of the region tonight. The surface low associated with the cold front is currently situated over northeastern Oklahoma and southeastern Kansas. This has left the area with the best surface convergence, along with upper level divergence well to the north of even our northern most counties from Burleson to Houston. AMDAR soundings still reveal a strong cap in place between 800-700mb this evening, which has helped to hinder thunderstorm development. Forecast soundings continue to indicate the best moisture available through 06Z, with precipitable water values ranging between 1.0-1.3 inches. Low- level lapse rates and K-index values also decrease after 06Z. Therefore, our best chance for an isolated thunderstorm would be most likely before 06Z tonight. Short term guidance such as the HRRR and Texas Tech WRF have begun to back off on thunderstorm coverage as this line of precipitation slides east of I-45. The main front will eventually overtake the dryline/Pacific front, as it continues to push westward across east Texas this evening between 06-09Z. Nine o`clock observations have temperatures and dew points in the middle to upper 60s across much of the SE TX. Onshore winds will begin to veer overnight and eventually turn out of the northwest by sunrise increasing to between 10 to 15 MPH. Clear skies are in store behind the front with Monday morning temperatures beginning in the upper 40s to upper 50s. As drier air filters into the region, high temperatures will reach into the upper 60s to lower 70s late Monday afternoon. Hathaway && .PREV DISCUSSION /Issued 549 PM CST Sun Jan 21 2018/... .AVIATION [00Z TAF Issuance]... Radar this evening shows a smattering of showers across SE Texas that will intermittently pass over terminals. This will continue through the night as a Pacific front pushes through the area. The front should reach KCLL/UTS around 06-07Z, KIAH/KHOU around 08-10Z and then the coast around 12Z. Ceilings should drop to MVFR levels ahead of the front and there may be a brief period of IFR but confidence in IFR is low. Front should feature a line of showers but full TSRA are yet to be determined. AMDAR soundings still show an elevated mixed layer around 800-700mb which would need to erode before deep convection can form. TAFs will go with VCTS but likely just have a line of showers as HRRR and a few WRF runs indicate. TSRA may need to be put in for KCLL and KUTS but those sites may even be just far enough south from upper level forcing that the cap will still hold. Ceilings improve behind the front with NW winds which become gusty during the day. Overpeck .MARINE... Periods of fog (some dense) will continue across the bays and nearshore waters until the front pushes off the coast early Monday morning. Moderate onshore flow ahead of this front is also producing 15 to 20 knot winds and 6 foot seas in the offshore waters, and caution flags are currently in effect. Expect some shower development out ahead of the front this evening and tonight, with the front itself dragging a thin line of showers and thunderstorms through the waters Monday morning. This will be accompanied by a gradual wind shift to the northwest. Caution flags will likely be required Monday into Monday night. Winds gradually become NE to E by midweek before returning to SE by the weekend. Sea fog could become an issue again by the end of the week as deeper moisture moves back over the waters. Another much stronger front should push off the coast next weekend. 11 .FIRE WEATHER... A cold front will pass through the region overnight tonight, bringing drier and breezy conditions in its wake. RHs on Monday afternoon could fall into the mid to upper 20s with winds near 15 mph. This will create elevated fire conditions across the area for Monday. Tuesday will be just as dry but with much lighter winds. Moisture will begin filtering back over the area Wednesday. 11 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 48 68 37 67 37 / 60 0 0 0 0 Houston (IAH) 57 70 41 67 40 / 60 0 0 0 0 Galveston (GLS) 58 70 47 64 45 / 60 10 0 0 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...Dense Fog Advisory until 3 AM CST Monday for the following zones: Coastal waters from Freeport to the Matagorda Ship Channel out 20 NM...Coastal waters from High Island to Freeport out 20 NM...Galveston Bay...Matagorda Bay. SMALL CRAFT SHOULD EXERCISE CAUTION until 3 AM CST Monday for the following zones: Waters from Freeport to the Matagorda Ship Channel from 20 to 60 NM...Waters from High Island to Freeport from 20 to 60 NM. && $$ NEAR TERM...08 AVIATION...Overpeck
Area Forecast Discussion
National Weather Service Lincoln IL
900 PM CST Sun Jan 21 2018 .UPDATE... Issued at 900 PM CST Sun Jan 21 2018 A focused band of forcing for precip is advancing from Missouri into Illinois, and will continue to advance across our forecast area the rest of the night and into Monday morning. At 9 pm, the surface warm front extends across Illinois roughly along a line from Galesburg to Kankakee, with a slight northward drift over the last few hours. We expect the warm front to continue to lift northward as the surface low in eastern Kansas progresses toward NW Illinois overnight. Instability params continue to look marginal, but moderate speed shear upstream appears to be fueling some lightning strikes across Missouri. Will continue with isolated thunder the rest of the night and tomorrow morning as this initial wave of precip advances eastward. A break in the rain looks on track, due to a dry slot cutting into the southwest side of the surface low. A re-development of rain and storms still appears possible tomorrow afternoon, as a 60KT LLJ progresses across IL. Once again, marginal instability is expected, but wind shear could fuel some strong storms, or at least storms that produce damaging wind gusts. Temps tonight look on track for a steady or slowly rising scenario. Temps are generally in the upper 40s and low 50s, with little movement, and mainly upward, expected through sunrise. Wind gusts may need to be bumped up tomorrow morning, when daytime mixing drags down some of very strong low level winds. && .SHORT TERM...(This evening through Monday) ISSUED AT 250 PM CST Sun Jan 21 2018 A deep trough and upper low over the southern High Plains this afternoon will be the main issue for the forecast through tonight and Monday. A warm front stretching out into the Midwest today has brought significant moisture and very warm temperatures up into Central IL. Persistent fog along the boundary continued into the early evening hours to the well as east central and southeastern portions of the state. Moisture to the east and southeast not properly handled in most of the models early...and now models are having issue with the much warmer sfc temps that are starting to erode the southern edge of the more limited visibilities. Later tonight, precip develops along and ahead of a cold frontal feature as the low further occludes and moves into the Central Plains. Precip moves into the forecast area mainly later tonight and into tomorrow morning. Although the instability is somewhat limited in the early hours, there is still some assistance offered by a LLJ, particularly in the southern half of the state. Strong winds will be the main threat with the early storms. Gusts in the overnight hours remain high mainly for just that issue, even with only moderate tightening of the pressure won`t take much to pull some of those winds down with a shower. Some isolated thunder will remain possible through the overnight hours. As for Monday, a significant dry slot has been consistent in models for tomorrow into the early afternoon. In the past few runs, NAM/4km WRF have been developing scattered thunderstorms in the expansive dry slot. With lingering surface moisture, cooler air moving in aloft, the lapse rates increase considerably in that environment...with instability parameters less than impressive. Any thunderstorms that do develop in that environment will have a vertical assist from the proximity of the low, as well as offering some shear to help with potential for mini/low topped supercells. Threat for any severe weather will end quite quickly in the early evening as the low moves into the Great Lakes. .LONG TERM...(Monday night through Sunday) ISSUED AT 250 PM CST Sun Jan 21 2018 Cold air moving into the region behind the low will result in potential for light snow for late Monday night...but little more than a dusting on already wet ground will limit accumulations. Forecast settles into a northwesterly flow regime with temperatures closer to seasonal normals. 12Z runs of ECMWF and GFS both pointing to a wave moving through aloft on Tues night/Wed morning, but so far the wave is moisture starved aloft and sliding over a surface high...producing zero qpf. Behind that wave, high pressure ridge slips eastward, starting another warm advection pattern through the end of the week. Highs are back to the low 50s by Friday. A developing storm system in the desert SW will push moisture and precip chances northeast into the Midwest to start the weekend. Another rainy Saturday shaping up so far...warmer but rainy. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 600 PM CST Sun Jan 21 2018 A warm front extending across the northern portion of central Illinois will gradually shift northward this evening. Pockets of dense fog will affect the area this evening, but timing of 1/4sm FG at the airports is uncertain. HRRR and other high res models show patchy dense fog possible at PIA, BMI and CMI through mid to late evening. For now, have left VLIFR vis out of the 00z TAF`s. Forecast soundings indicate that ceilings will decrease from MVFR to LIFR overnight, then generally remain low until tomorrow afternoon when MVFR conditions possibly re-develop. Thunder chances increase tomorrow afternoon, as a squall line possibly pushes across the area while a LLJ at 60+ knots develops across Illinois. Even some marginal momentum transfer during a thunderstorm could produce some wind damage. Weak instability will help to limit severe potential. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Shimon SHORT TERM...HJS LONG TERM...HJS AVIATION...Shimon
Area Forecast Discussion
National Weather Service Northern Indiana
845 PM EST Sun Jan 21 2018 .SYNOPSIS... Issued at 223 PM EST Sun Jan 21 2018 Mild and moist air will continue to lift north across the Ohio Valley and southern Great Lakes region through Monday. Areas of dense fog and drizzle with continue into this evening, with at least some improvement overnight as rain develops. The rain will cause rises on rivers with some flooding likely, particularly from northwest Indiana to southern Lower Michigan. Lows tonight should stay in the 40s with highs Monday around 50 to 55. && .UPDATE... Issued at 845 PM EST Sun Jan 21 2018 Surface warm front continues to very slowly mix northward this evening. This...coupled with lost snowpack...will favor improving visibilities through the overnight, as suggested by latest RAP13 and HRRR. Southern obs already showing some improvement with KFWA now up to 1SM. Should have no problem letting majority of counties drop out of dense fog advisory by 11pm. Exception may be across the north where hi-res guidance indicates dense fog may hold on until 07-09Z. May need an extension along/north of the toll road for a few hours but do anticipate dense fog will dissipate everywhere by sunrise as mixing steadily increases ahead of approaching wave and moderate rain spreads across the CWA. Only minor changes to going forecast this evening. Did maintain thunder mention in the west where latest forecast soundings still show a brief window of modest elevated instability. Also lowered QPF slightly based on latest guidance with a slight northward shift in best convergence/fgen, but still expecting close to an inch in the northwest with some minor river flooding concerns extending through the week as a result. && .SHORT TERM...(This Evening through Monday) Issued at 222 PM EST Sun Jan 21 2018 Extended the dense fog advisory earlier through this evening. Moist air will continue to spread north as areas of drizzle develop and increase with relatively weak wind flow. The remaining snow cover over mainly northern areas will accentuate the fog development. There should be improvement as rain develops tonight, although some fog is likely to linger throughout the night. May need to extend the northern portion of the Dense Fog Advisory through tonight and possibly into mid morning as moisture continues to spread north. Rainfall amounts should top an inch over northwest areas as edge best of lift and upper level support extends into these areas. The remaining snow cover should melt and provide additional runoff. && .LONG TERM...(Monday Night through Sunday) Issued at 222 PM EST Sun Jan 21 2018 Hydrologic issues should continue through Monday night and Tuesday as runoff continues and causes rises on streams and rivers. Otherwise, colder air will spread across the area Monday night and Tuesday. Cold air advection should offset diurnal warming during the day Tuesday causing temperatures to continue to fall during the day. A light wintry mix with falling temperatures may cause travel issues during the day Tuesday. Will mention this hazard in the Hazardous Weather Outlook. Limited arctic air behind this system will only provide a couple of cold days during the middle of the week. Temperatures will then rise much above normal by next weekend with highs near 50 Saturday. A rain/snow mix is likely by Sunday as the next system brings colder air to area. There has been some hint to the chance for heavy snow, but model support for this scenario is limited. && .AVIATION...(For the 00Z TAFS through 00Z Monday Evening) Issued at 635 PM EST Sun Jan 21 2018 1/4 SM fog will continue across the area through the evening. Some improvement in visibilities expected around 03Z as slightly warmer/drier air is advected north. HRRR and RAP13 both catching onto this trend with support in latest upstream obs. KFWA will clear out first while KSBN may hold on to fog until 05Z-06Z. LIFR ceilings will continue at both TAF sites through much of the overnight though. Improvement to IFR/MVFR not expected until morning when cold front passes and mixing increases. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...Dense Fog Advisory until 11 PM EST /10 PM CST/ this evening for INZ003>009-012>018-020-022>027-032>034. MI...Dense Fog Advisory until 11 PM EST this evening for MIZ077>081. OH...Dense Fog Advisory until 11 PM EST this evening for OHZ001-002- 004-005-015-016-024-025. LM...NONE. && $$ UPDATE...AGD SYNOPSIS...Marsili/Skipper SHORT TERM...Skipper LONG TERM...Skipper AVIATION...AGD Visit us at Follow us on Facebook...Twitter...and YouTube at:
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
907 PM CST Sun Jan 21 2018 .UPDATE... Updated for evening discussion. && .DISCUSSION... An upper low currently over eastern Kansas has a cold front extending south through Oklahoma and Texas. Along the front, a line of severe storms has broken out. This main line is projected to enter our CWA around 09Z or so. At this point, with no diurnal heating for instability fuel, the storms will begin waning. There may be some leftover punch to the storms entering our area though and some strong wind gusts may be possible in the far northwest part of the CWA. The latest hi-res guidance continues to show the line petering out east of I-55 late tomorrow morning/early afternoon. Overall, for this update, the pops were adjusted to match latest timing thinking and lows were adjusted a bit as well. With less cloud cover in eastern MS, low temps will fall into the lower 50s with low temps near 60 in the west. /10/ Prior discussion below: Tonight through Monday: Latest rap and satellite analysis shows short wave ridging over the region with an upper trough approaching the plains. Spring like conditions was noted under warm advection southerly flow with readings in the 60s and 70s. For tonight the closed upper low system will move into the plains along with a squall line ahead of an approaching cold front. Warm advection showers and breezy conditions is expected to develop ahead of the line. The line is expected to reach our northeast Louisiana parishes and southeast arkansas counties prior to dawn. There may be a few strong storms there before the line goes into a weakening trend prior to dawn. SPC has a marginal risk, will hold off on that risk as the window may be brief before the line weakens. It will be a mild night with lows from the lower 50s to the lower 60s. On Monday the line of storms will continue its weakening trend per hi-res models across the region through most of the morning. However late in the morning through the mid afternoon instability will pick up some over the southeast quarter of the region. So have kept the marginal risk for isolated severe storms in the southeast quarter for Monday. THere will be plenty of shear (30-40 knots in the low levels and 60s knots of deep layer shear), MUCAPE 500-1000 joules and lower 60s dewpoints. The primary risk will be for damaging winds from isolated severe storms. THe line and cold front will exit the region by mid afternoon. The rain will end from west to east by Monday night. It will be another mild day with highs from the lower 60s to the lower 70s./17/ Monday night through Saturday: A cool off will be underway at the beginning of the period as the cold front will have exited the area. Not a drastic cool down is anticipated, given source region of the airmass, but minimums dropping into the upper 20s and 30s will be the rule through a good portion of the upcoming week. Maximums in the 50s will be common with a gradual moderation by the end of the week as better ridging aloft takes control. The ridging will be short-lived as another storm system begins to take shape over the Intermountain West Friday. Though the ambient airmass will be somewhat dry early Friday, warm/moist advection will be as such for isentropic rains to moisten the lower levels through the course of the day with precipitation getting to the ground during the afternoon. Strong warm advection ahead of the approaching cold front will produce widespread rains Friday night into Saturday. Models soundings indicate deep moisture in place and rather feeble lapse rates. While isolated thunder may be possible, will not mention this far in advance as the rains will be the primary focus of the forecast./26/ && .AVIATION... 00Z TAF discussion: VFR conds were observed areawide at 00Z but cigs wl lower to MVFR from the west after 05Z. IFR Cigs wl be psbl at HBG by 09Z. SHRA/TSRA coverage wl increase from the west after 06Z along and ahead of a cold front that wl move across the region through Monday morning. Gusty south winds in excess of 20kts wl develop ahead of the cold front tonight and shift to the west Monday in the wake of the front. /22/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 56 68 38 57 / 42 89 3 2 Meridian 50 69 38 57 / 14 78 8 2 Vicksburg 58 68 37 57 / 70 85 2 2 Hattiesburg 54 71 39 60 / 20 78 6 1 Natchez 59 68 38 57 / 70 88 2 2 Greenville 55 64 36 53 / 86 68 2 1 Greenwood 56 66 37 53 / 61 89 2 2 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
920 PM CST Sun Jan 21 2018 .UPDATE... Issued at 915 PM CST Sun Jan 21 2018 Forecast largely on target and only a few cosmetic changes made as well as some refinement on onset and exit times of the rain tonight. Main instability corridor per SB and ML CAPE, such as it is, extends into far western MO and according to latest hi-res short term model guidance and this is probably where the best chance for the stronger storm potential will exist, but given the high shear environment, a short-lived strong storm is still possible over much of central MO late this evening. TES && .SHORT TERM... (Through Late Monday Afternoon) Issued at 323 PM CST Sun Jan 21 2018 A very well developed storm system will move across the central Plains and into the Midwest over the next 24 hours. The mid and upper level cut off low is currently over eastern Colorado and will be moving east tonight across the low level baroclinic zone over Kansas. This will cause the surface low currently over Kansas to deepen and begin moving northeast. The vertically stacked system will then move east-northeast into southeast Iowa and central Illinois on Monday. Warm and moist air continues to flow into the Mid Mississippi Valley ahead of the system and dew point temperatures across our forecast area are in the low to mid 50s...up 10 to 15 degrees from 24 hours ago. Thunderstorms are already forming over eastern Oklahoma ahead of the system and these storms are expected to increase in coverage and intensity this evening as the system intensifies and the dryline rushes east-northeast out of the Plains. Current thinking is that the storms will form into a broken line this evening as they move eastward and the line should affect most if not all of the forecast area. MOS PoPs are in the categorical range tonight, and I see no reason to dispute them. There may be a few showers out ahead of the line early this evening but the best chance of rain should be from 03Z and later as the storms move across central into eastern Missouri and then southern and central Illinois. Convection allowing models show areas of simulated reflectivity in excess of 50dBZ. There should be more than enough deep-layer shear 50kts+ with this wound up system to make severe thunderstorms a real possibility. However, GFS/NAM really put a damper on the instability after about 03Z, dropping MUCAPE down to 200 J/Kg or less as the line would be . moving into eastern Missouri. The RAP is more stout, keeping as much as 300-400 J/Kg even after 06Z into Illinois. Given the differences, it still looks like the SPC marginal risk is in the right spot over our central Missouri counties tonight. Thunderstorms will continue to be possible on Monday morning as boundary layer heating ahead of the cold front increases instability along and east of the Mississippi River. Again, the RAP is more robust with this instability, pushing MUCAPE above 500 J/Kg by 17Z. This may be too high as the GFS and NAM only around 200 to 350 J/Kg. Still, it bears watching and there could be a quick threat for severe storms before the convection exits the eastern portions of the forecast area early Monday afternoon. Carney .LONG TERM... (Monday Night through Next Sunday) Issued at 323 PM CST Sun Jan 21 2018 Global models are still in good agreement that the upper low that will be located near Quincy on Monday evening will move northeastward into the eastern Great Lakes by midday Tuesday. Colder air will already be moving into the area behind the front on Monday night, and the rain is still expected to changeover to snow as the low level thermal profiles fall below freezing. There may also be some light freezing rain or drizzle after midnight over central and northeast Missouri as the upper low lifts out of the area and the mid level ascent weakens. Little if any snow/ice accumulation is expected on Monday night as QPF amounts are less than a 0.10" on all of the global models. Then mainly dry weather is expected from Tuesday afternoon into Friday as subsidence sets in behind the upper low and an upper ridge builds over the central CONUS mid-late week. There will be a weak shortwave trough move across the area on Wednesday, but it will have little moisture to work with, so will keep the forecast dry for now. Temperatures will stay above normal this week, with highs near 50 on Tuesday and Wednesday. By late in the week, a surface high will move off into the southeast CONUS allowing the low level flow to turn out of the southwest and warmer air to move into the area. Temperatures will be 10-20 degrees above normal by late in the week. While the global models agree that a longwave trough will dig into the central CONUS by next weekend, there are differences in the details. The GFS is showing a is showing a more progressive trough with a slightly quicker frontal passage next Friday night into Saturday which would mean more rain followed by a cooler, drier weekend. The ECMWF is showing a slower trough with a cold front moving through on Saturday, with rain changing to snow with the cold frontal passage, and snow lingering Saturday night as the upper trough deepens. Have gone with rain Friday night and Saturday, with a changeover to snow on Saturday night. Temperatures will return close to normal by Sunday as 850mb temperatures fall below -10C. Britt && .AVIATION... (For the 00z TAFs through 00z Monday Evening) Issued at 550 PM CST Sun Jan 21 2018 Area of IFR CIGs over southeast MO and southern IL is heading north now that the sun has gone down and should impact STL metro sites for a period this evening. CIGs have already deteriorated per latest obs in the past few mins. Lower MVFR CIGs should also make a return to UIN by 03z or so. In the meantime, SHRA with a few TSRA will increase the next few hours over the region, exiting from west (COU) to east (STL Metro) from 09z to 12z Monday. While conditions should improve to VFR after the rain exits with even some cloud clearing, another round of MVFR CIGs looks likely for Monday afternoon-night with the wraparound and colder air return. S winds at most sites will occasionally gust to 15-20kts tonight, increasing on Monday and continuing into Monday night with gusts to 25-30kts at times. Another round of light pcpn is possible late Monday afternoon-night with it changing from rain to snow as the colder air deepens. Probs look low enough at this time to focus on the front-end of the TAF with weather and will address in later issuances. SPECIFICS FOR KSTL: Period of IFR conditions looks likely this evening and may continue at times overnight with heavier rain in SHRA or TSRA. VFR then looks likely for Monday morning before a return of marginal VFR conditions late in the day. TES && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Memphis TN
821 PM CST Sun Jan 21 2018 .DISCUSSION...02Z Surface analysis places a surface low over Eastern Kansas with a cold front extending south over Eastern Oklahoma and into Central Texas. A warm and moist airmass remains in place across the Mid-South with temperatures as of 8 PM CST in the 60s. Latest short term models including the HRRR and 00Z WRF indicate showers and thunderstorms should reach the Mississippi River by about 11Z. (5 AM CST) Upstream instability is still expected to be pinched off as it reaches the forecast area despite ample shear being present. Thus, would expect any organized convection to weaken substantially as it encounters a less than favorable airmass across the area. Consequently, confidence on severe weather potential overnight into Monday morning remains low at best. Will make some minor adjustments to grids to account for short term trends. Otherwise, the overall forecast is in good shape. CJC && .PREV DISCUSSION... /issued 536 PM CST Sun Jan 21 2018/ UPDATE... Updated to include the 00z aviation discussion. PREV DISCUSSION... /issued 257 PM CST Sun Jan 21 2018/ DISCUSSION... Clouds have scattered out across most of West Tennessee and North Mississippi this afternoon which have allowed temperatures to rise into the mid 60s to lower 70s across most of the CWA. Clouds will begin to fill back into the area this evening as a low pressure system tracks eastward across Missouri. A line of convection is expected to develop over the next 2-3 hours along the trailing cold front. Models continue to show the SFC low occluding before the line enters Eastern Arkansas around midnight tonight. With the SFC low occluding, the warm sector will get pinched off thus limiting instability as the line pushes into the Mid-South. As a result, expect the line to be diminishing in strength as it pushes into the CWA. Can`t rule out an isolated strong or severe storm initially occurring across Eastern Arkansas and the Missouri Bootheel, but elsewhere should just be general thunderstorms. Whatever is left of the line will push east into Middle Tennessee and Alabama around noon. Wrap around clouds from the upper level low will begin to move into Eastern Arkansas during the late afternoon hours, spreading over the areas along and north of I-40 Monday Night. Colder air will also filter into the area on the backside of the upper low thus temperatures across Northeast Arkansas and the Missouri Bootheel may drop to around 50 degrees during the late afternoon hours on Monday. Clouds from the upper low may linger across portions of West Tennessee on Tuesday otherwise sunny conditions will return. Temperatures will be near normal with highs ranging from the mid 40s to the lower 50s. Tranquil weather conditions and seasonable temperatures will continue through the end of the week as high pressure settles over the region. On Friday, another upper trof will begin digging into the Plains allowing a cold front to move into the Mid-South Friday Night into Saturday. Rain chances will begin as early as Friday across Eastern Arkansas, but the best chances for rain will occur on Saturday. Colder temperatures will filter back into the Mid-South behind the front on Sunday. KRM && .AVIATION... /00z TAFs/ Generally VFR conditions will prevail overnight with the exception being northeast AR into the MO Bootheel where MVFR ceilings have developed. A line of storms will move into the Mid-South overnight, mainly between 8-14z, but this convection is expected to weaken as it moves east through the CWA. A few showers are possible this evening and during the early morning hours ahead of this line, but operational impacts should be minimal. Expect MVFR conditions for a few hours as the line of storms move through with improving conditions throughout the day. Gusty south winds this evening and overnight will shift more southwesterly on Monday in the wake of a cold front. Johnson && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$
Area Forecast Discussion
National Weather Service Paducah KY
908 PM CST Sun Jan 21 2018 .UPDATE... Issued at 908 PM CST Sun Jan 21 2018 Still monitoring severe weather potential after midnight over our far western counties in southeast Missouri. The 00Z NAM sounding from around Van Buren, MO shows a stable layer near the surface just above 900mb at 09Z as the column becomes saturated. This effectively wastes much of the immense shear. The low-level jet will be near 70kts, so it would not be far-fetched for some of that momentum to come to ground within a precipitation core. Farther east toward the Mississippi River, the stable layer deepens and the LLJ is weaker. In addition, the mid and upper- level winds back with time as the system moves eastward, further decreasing the severe weather potential with eastward extent overnight. We will continue to monitor the convective line as it approaches the area just after midnight, but the prospects for any organized severe weather are low and appear to be limited to Carter and Ripley counties in Missouri as depicted by SPC`s final Day 1 Outlook. && .SHORT TERM...(Tonight through Monday) Issued at 302 PM CST Sun Jan 21 2018 Upper low will move from the central Plains this evening, to over western IL by Monday evening. Mostly quiet conditions can be expected through the early p.m. hours, with shower and isolated storm chances entering SEMO toward the midnight hour. Until then, from SEMO, into SW IL, just a slight chance of showers. Essentially dry weather this evening west KY, as drier air works north. Even notable clearing late today moving up from west TN. We do expect some clouds to move back in through the evening. From midnight on through Monday morning, showers and a few storms will progress east reaching southern IL and west KY by 12z. Through the morning the band of convection will continue east across SW IN and the rest of west KY. Limited TSRA chance across the west 2/3 of the CWFA. It`s basically outta here by 18z. First, ground conditions some areas are super saturated, especially west KY into parts of southern IL. It will not take much rain at all to possibly create some standing water issues. Having said that, our latest QPF forecast is not as high. The models have backed down. We think any problems would be isolated. Not too concerned with the marginal SPC risk over our west 4 counties in SEMO. Mainly elevated instability forecast. Will monitor for gusty wind potential. The low level jet is quite impressive into SEMO by 06-09z, 50 to 65+ kts at 850mb. But low level lapse rates are not impressive at all. So we may not realize the potential. Monday afternoon will be rather breezy in the dry slot, with some decrease in clouds, and mild temperatures, especially from SEMO into west KY. We used a model blend overall, incorporating GFS and NAM 1 hr data with some HRRR guidance timing the PoPs overnight. Temperatures will not go down much overnight. .LONG TERM...(Monday night through Sunday) Issued at 302 PM CST Sun Jan 21 2018 The upper low will reach the Great Lakes region by 12z Tuesday, and head on east and away from the area. Will monitor the I-64 corridor Monday night for a small rain chance. Then high pressure builds in, and keeps our weather dry from Tuesday through Thursday night. It will be a little cooler once again Tuesday and Wednesday due to the influence of surface high pressure. Then it will turn milder Thursday through Saturday ahead of the next system forecast to affect the area as it moves in from the west. That system is forecast to be an evolving mid level trof that will end up over the central U.S. by 12z Saturday. Return southerly flow will develop ahead of it from Thursday on. Rain shower chances are expected to increase late Friday into Friday night, peak Saturday, then diminish from west to east Saturday night. There is somewhat limited confidence with respect to timing. More solutions than not were showing slower solutions, and suggesting the precip could last longer into the weekend. However the 12z GFS is radically faster. The 12z ECMWF is a tad quicker than several previous runs. All of this includes taking into account ensemble mean solutions from both models. We are somewhere in the middle of these timing differences for now. There is a chance that the precip could end with a rain/snow mix. That`s way out there in time, so just something we noticed for now. && .AVIATION... Issued at 302 PM CST Sun Jan 21 2018 Difficult aviation forecast as some areas are still experiencing IFR cigs, while conditions have significantly improved into west KY as drier air works north. We do expect improving cig conditions through this evening. Not sure how far north and west the improvements will carry. Best chances of showers, and possibly thunder will be after 06z, continuing from west to east through tomorrow morning, and ending from west to east. Gusty SSW winds will persist tonight. Some gusts 20 to 30 kts possible mainly after 06z. MVFR/IFR vsbys possible with the main band of showers and embedded storms later tonight into early tomorrow morning. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ UPDATE...DRS
Area Forecast Discussion
National Weather Service Shreveport LA
954 PM CST Sun Jan 21 2018 .UPDATE... Will be quick as we continue to track a long lived Super Cell which has likely produced a tornado across several counties in Northeast Texas. Low level shear is very strong ahead of the cold front/dryline merger which was located just west of our CWA as of 10pm. New Tornado Watch will be forthcoming soon which will take in the remainder of SW AR and Deep East Texas as well as much of NW LA and will await it`s issuance before a new updated zone package is sent forth. Otherwise, did increase pops along and aheadof the approaching cold front for the remainder of the night. Thanks for the coordination SPC. 13 && .PREV DISCUSSION... /issued 614 PM CST Sun Jan 21 2018/ AVIATION... For the ArkLaTex, VFR for now with looming wx just a couple of hrs away for TYR/GGG as dryline near DFW ahead of a cold front gathers up the Gulf moisture. SHV likely just after midnight. The HRRR model is showing a line of TS progressing over the area during the evening/overnight hrs. Tornado watch for E TX until 05Z with expectation for some strong/severe storms as winds remain breezy off the Gulf S10-20KT with higher gusts. Low level climb winds are S/SW 25-45KT near speed shear criteria with broad SW flow aloft for flight levels increasing to 100KT by FL320. /24/ && .PRELIMINARY POINT TEMPS/POPS... SHV 51 62 37 60 / 100 10 0 0 MLU 57 64 38 58 / 100 30 0 0 DEQ 44 56 32 56 / 70 10 0 0 TXK 47 59 35 57 / 90 10 0 0 ELD 52 61 36 58 / 100 10 0 0 TYR 46 61 36 59 / 40 10 0 0 GGG 47 61 36 59 / 90 10 0 0 LFK 51 64 36 62 / 90 10 0 0 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...Lake Wind Advisory until midnight CST tonight for ARZ070-071. LA...Lake Wind Advisory until midnight CST tonight for LAZ001>003- 010>012. OK...None. TX...Lake Wind Advisory until midnight CST tonight for TXZ096-097- 108>112-124>126-136>138-149>153. && $$ 24/13
Area Forecast Discussion
National Weather Service Sacramento CA
205 PM PST Sun Jan 21 2018 .Synopsis... Pacific storm moves through today into Monday bringing light to moderate precipitation. A stronger system impacts the area midweek into Friday bringing moderate to heavy rain and mountain snow, and gusty wind. && .Discussion... Pacific frontal system continues to make a slow progression inland this afternoon as 5H flow nearly parallels surface boundary. Run to run of the HRRR has trended slower with front advancement. Latest showing precip spreading over the Coastal and Shasta mountains through the afternoon and across the Sacramento Valley into Western Plumas county this evening. Bulk of precip moves through overnight. Snow levels expected to slowly rise to 3500 to 4000 feet by Monday morning. Snow accumulations up to 5 inches possible in the Shasta and Coastal mountains, with local amounts up to 10 inches over highest terrain. Slightly less accumulations expected in the mountains of Western Plumas overnight, while only up to 3 inches forecast for the Northern Sierra Nevada. Showers Monday morning decrease in the afternoon as subsidence increases over Interior NorCal. Upper ridging brings drier weather Monday night into Tuesday. Some patchy morning fog may develop in southern portions of the Sacramento Valley and Northern San Joaquin Valley Tuesday morning. Temperatures trend up early next week to near or slightly above normal Tuesday. Stronger Pacific frontal system spreads inland over far NW CA Tuesday night then across all of Interior NorCal Wednesday. Breezy to windy conditions develop ahead of the front Wednesday. Models currently showing significant QPF with this storm. Snow levels attm initially look to be around 5000 to 6000 feet Wednesday morning, but lower to 2500 to 3500 feet Wednesday night into Thursday in post-frontal colder AMS. Showery weather follows Thursday. PCH && .EXTENDED DISCUSSION (Thursday THROUGH Sunday) A pacific front will be tracking to our south and east to start the extended period with the tough axis working through NorCal. This will bring showers to the area throughout Thursday. Cold air quickly builds in behind the front and we will see low snow levels, 2000 to 3000 feet. Mountain travel will likely be difficult on Thursday and this includes both I-80 and I-5. Mountain showers will continue into Friday due to onshore flow but should diminish by Friday afternoon. A warm front pushes into the PacNW late Friday into Saturday and that may bring a few isolated showers to the Shasta Mountains Friday night. Otherwise quiet weather settles in for the weekend as a ridge builds in overhead. We will see a cool start to the period with highs generally running 5-10 degrees below normal but as the ridge builds in towards the weekend we will see them return to near normal. -CJM && .AVIATION... VFR conditions expected through 02z Monday. Cigs lower to MVFR, 1500 to 3000 feet after 02z from north to south. Light showers are also expected through the overnight. Showers diminish between 12-15z with improving conditions into Monday afternoon but areas of MVFR will still be possible. 5-10 knot winds are expected throughout the period. -CJM && .STO WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 4 PM PST Monday for Mountains Southwestern Shasta County to Northern Lake County-Shasta Lake Area / Northern Shasta County-Western Plumas County/Lassen Park. && $$
Area Forecast Discussion
National Weather Service Tallahassee FL
927 PM EST Sun Jan 21 2018 .NEAR TERM [Through Tonight]... 02 UTC surface analysis shows an area of high pressure NE of the region over Middle Georgia. The next approaching frontal system was still back across the Central Plains. The beginning signs of stronger return flow off the Gulf was present over the Central and Western Gulf, while over the Eastern Gulf, the low level flow was fairly light. Satellite imagery reveals extensive cirrus moving over the region and this will likely continue through the overnight hours. The main forecast difficulty rests with the development of fog and any other low clouds. One thing in favor of lower clouds/fog is the very cool waters over Apalachee Bay (water temps are in the low 50s), and not much additional airmass modification would be necessary for stratus to develop later tonight and advect inland once the southerly flow picks up. Our local hi-res ensemble products suggest this fog/stratus should develop just after 09z and spread quickly inland across the Florida Big Bend and into South Central Georgia. There is also some support for this from the 18z GFS and the last few HRRR runs. As a result, have made some adjustments to the inherited forecast to show fog and increased cloud cover in our eastern zones. But given the uncertainty, will let future shifts monitor any need for a dense fog advisory. && .PREV DISCUSSION [637 PM EST]... .SHORT TERM [Monday Through Tuesday Night]... The cold front will move into our southeast Alabama and eastern Florida Panhandle late Monday afternoon. Deep layer (0-6 km) shear still looks favorable for severe weather at around 40-50 kts Monday evening, but instability remains the limiting factor tomorrow with SBCAPE below 400 J/kg. The highest chances for marginally severe wind gusts will be west of a line from Dothan to Panama City in the afternoon and early evening. Instability will lower further after sunset, limiting chances for severe weather as storms continue eastward overnight. Storms will exit the area Tuesday morning. Temperatures will rise into the 70s Monday ahead of the front and will peak mostly in the 60s Tuesday in its wake. Overnight temperatures will range from low 40s to the west and upper 50s to the east Monday night as the front cross the area and return to the 30s Tuesday night. .LONG TERM [Wednesday Through Sunday]... Deep layer ridging will move in behind the front and dominate the forecast through Friday. As we head into the weekend, a mid and upper level trough will move through the central CONUS once again, this time with a shortwave at the base of the trough enhancing development in the western GoMex. If things unfold the way the ECMWF and GFS have been showing the past few runs, we may be looking forward to some much needed rainfall next weekend. Highs will be in the 60s with lows in the 30s and 40s through the remainder of the work week, with temperatures warming up again by the weekend. .AVIATION [Through 00Z Tuesday]... Current VFR conditions around the region are anticipated to drop to IFR at TLH/VLD/ABY before sunrise with MVFR conditions elsewhere. With strengthening southerly winds, expect conditions to only slowly improve to MVFR everywhere by 15z-17z. TSRA will approach DHN/ECP after 22z with the other sites remaining dry through the end of the TAF period. .MARINE... Winds will increase ahead of Monday night`s front and remain elevated for the next several days, which may bring a prolonged period of cautionary conditions to our coastal waters. .FIRE WEATHER... No fire weather concerns. .HYDROLOGY... Storm total accumulations of around a half inch of rain or less are expected with Monday`s cold front, which will not cause any flooding on our currently low rivers. Another frontal system next weekend, however, appears to be more favorable for producing some much needed rainfall. .SPOTTER INFORMATION STATEMENT... Spotter activation is not requested. However, spotters are always encouraged to safely report significant weather conditions when they occur by calling the office or tweeting us @NWSTallahassee. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 48 70 53 66 38 / 0 10 50 10 0 Panama City 53 69 52 64 42 / 0 30 60 0 0 Dothan 49 72 48 62 35 / 0 30 60 0 0 Albany 48 72 53 64 37 / 0 10 40 0 0 Valdosta 45 74 56 67 38 / 0 10 60 20 0 Cross City 49 77 58 71 37 / 0 10 60 40 0 Apalachicola 53 67 54 67 41 / 0 20 50 10 0 && .TAE WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AL...None. GM...None. && $$ NEAR TERM...Godsey SHORT TERM...Nguyen LONG TERM...Nguyen AVIATION...Godsey MARINE...Nguyen FIRE WEATHER...Barry HYDROLOGY...Nguyen
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Monday) Issued at 257 PM CST Sun Jan 21 2018 A surface low continues to trek eastward towards northeast Kansas with a surface boundary bisecting the CWA from the southwest to northeast. In the warm sector, dewpoints have risen into the low 50s with high temperatures reaching the upper 50s to low 60s. Models indicate 100-300 J/kg of MUCAPE overspreading east central Kansas up towards very northeastern Kansas in the early evening. Showers and a few thunderstorms are expected to form later this afternoon with peak heating near the surface low and advance northeastward. With the RAP indicating roughly 200 m2/s2 of helicity coupled with a boundary in the area, this leaves the concern for some rotating thunderstorms to form near this boundary. If storms do form in this area, there is a chance that pre-existing vertical vorticity along this boundary may induce a weak, brief tornado. Isolated wind gusts with storms may also be a hazard. This whole scenario is highly dependent on whether or not a cap that has overspread northeast Kansas breaks this afternoon. In east central Kansas, models break this cap between 5-8 PM, leaving this time the most probable if any severe weather was to occur. Showers and any storms will come to an end by late night as the low continues to push into the area, along with a dry slot which will give a break between this activity and the coming deformation zone progged to reach northeast Kansas in the early morning. With temperatures in north central Kansas slightly above freezing as this precipitation moves into the area, rain will first be observed before temperatures continue to fall and mixed precipitation eventually transitions to snow. Snow is likely across most of the area from a line from Hiawatha to Emporia with the highest amounts upwards of three inches confined to very north central Kansas. A Winter Weather Advisory has been issued for areas where the highest snowfall is likely. Very eastern counties may see some mixed precipitation, but overall rain will be the prominent precipitation type. Precipitation will eventually change back to rain across northeast Kansas and temperatures on Monday rise into the upper 30s and low 40s. On top of the precipitation Monday, winds will be strong behind this departing low with sustained speeds in central Kansas up to 30 mph with gusts up to 40 mph. Elsewhere, gusts up to 35 mph are expected. This may cause blowing snow, especially in north central and central Kansas where the greatest snow totals are forecast. With this, expect extremely reduced visibilities and hazardous travel conditions. Gusty winds continue through the afternoon keeping this a hazard through all of Monday. .LONG TERM...(Monday night through Sunday) Issued at 257 PM CST Sun Jan 21 2018 Snow continues move out to the northeast through Monday evening and clears most of the CWA by around the midnight hour, as the upper low move into the Ohio Valley. Lows fall into the 20s as CAA continues overnight. Pattern across the Central US moderates behind the system rather quickly with the coldest air well north of the forecast area. The westerly flow that transitions over the week to more southwesterly brings a gradual warm up in temperatures, with 40s Tuesday to upper 40s Wednesday, then into the mid to upper 50s by Thursday and Friday. The next chance for rain is progged to move into the area possibly late Friday into early Saturday as the next more amplified upper trof moves out of the Rockies into the Central Plains. Highs on Saturday are currently forecast back down into the 40s, but could be higher if the system slows its eastward progress. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 547 PM CST Sun Jan 21 2018 First roughly half of this forecast should be VFR, though could see a few showers in the next few hours. Have not changed timing of main precip and lower cloud into the area, in the 10-13Z time frame. Kept conditions MVFR at this point but IFR certainly possible at times. && .TOP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 2 AM to 3 PM CST Monday for KSZ008- 009-020-021-034. && $$ SHORT TERM...Heller LONG TERM...67 AVIATION...65