Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/24/17

Area Forecast Discussion
National Weather Service Bismarck ND
942 PM CDT Tue May 23 2017 .UPDATE... Issued at 942 PM CDT Tue May 23 2017 Did expand the Frost Advisory into the James River Valley for tonight. Upper level RAP relative humidity fields through the 01 UTC iteration suggest cirrus will be thinnest across the James River Valley with light winds in the weakening surface ridge axis. However, did cancel the advisory for Hettinger, Adams, Stark and Dunn counties where greater cirrus and increasing return flow will prevent frost formation. UPDATE Issued at 634 PM CDT Tue May 23 2017 Little change with this update other than to blend to observed trends through 23 UTC. Will continue to evaluate guidance through the evening as an expansion of the Frost Advisory into the James River Valley tonight may be needed. && .SHORT TERM...(This evening through Wednesday) Issued at 241 PM CDT Tue May 23 2017 A few highlights in the short term period: A frost advisory for portions of southwest and south central ND tonight into early Wednesday morning; Clouds and winds will continue to diminish over the James River Valley west to the Missouri Valley this afternoon/evening. The gusty winds from earlier today, near 40 MPH over south central North Dakota were related to the strong temperature/pressure differences between the cloud and rain cooled air southeast and the clearing skies/subsidence to the west. For tonight have trended the minimum temperatures down by using the lowest of all guidance for low temperatures tonight. This would have worked out well last night as well as temperatures were 5 to 7 degrees cooler across the southwest than the ensemble guidance was. Issued the frost advisory for late tonight and early tomorrow for these adjusted temperatures. For Wednesday, skies will be mostly sunny through most of the day until an advancing shortwave and associated cold front move to eastern Montana. This will bring some late afternoon clouds and a chance for showers and a few thunderstorms to the far west. However CAPE is pretty modest so expected fairly widely scattered non severe thunderstorms. Return flow from the South and warm advection should warm temperatures into the upper 60s to lower 70s. .LONG TERM...(Wednesday night through Tuesday) Issued at 241 PM CDT Tue May 23 2017 The cold front will be the focus for showers and isolated thunderstorms along a narrow band of instability Wednesday night. By Thursday the showers will be departing to the east and cooler temperatures into the 60s to around 70 seam reasonable. Not getting a lot of cold advection from this shortwave trough that initially tracks across the southern Prairie Provinces of Canada. But then the GFS dumbbells this upper low across the Northern Plains through the weekend keeping an extended period of scattered showers and cool temperatures through Memorial day weekend, especially Sunday. The ECMWF is a bit warmer and dryer through Sunday then brings a cold front through Monday. So with this disagreement between global models will keep the Superblend guidance for the weekend which gives moderate chances of showers and slightly cooler temperatures through the Memorial Day weekend. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 942 PM CDT Tue May 23 2017 VFR conditions are forecast across western and central North Dakota for the 00 UTC TAF cycle. Strong southeast winds will develop on Wednesday with gusts of 30-35kts expected for most areas. Low level wind shear is possible across western North Dakota early Wednesday morning with strong winds within a low level inversion. && .BIS WATCHES/WARNINGS/ADVISORIES... Frost Advisory from 3 AM CDT /2 AM MDT/ to 9 AM CDT /8 AM MDT/ Wednesday for NDZ019>023-025-034>037-042-045>048-050-051. && $$ UPDATE...AYD SHORT TERM...WAA LONG TERM...WAA AVIATION...AYD
Area Forecast Discussion
National Weather Service State College PA
1120 PM EDT Tue May 23 2017 .SYNOPSIS... Weak system passing to our south today producing mainly clouds. A very deep upper low will bring clouds across the region Wednesday with rain developing overnight and into Thursday. This deep low will produce cooler showery weather through Friday. As this low lifts out Friday into Saturday a weak upper-level ridge should provide several relatively nice days to start the Memorial Day weekend. Alas another low may approach the region on Memorial Day. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Showers continue to straddle the Mason Dixon line late this evening...with BKN-OVC skies covering all of central PA. HRRR has been consistent in bringing a small batch of showers northward into the West Central and Central Mountains later tonight, and will carry slight chance pops for this through the pre dawn hours. Shower area becomes more fractured after midnight and latest HRRR actually favors showers reaching the Northwest mountains...but am not convinced of this just yet. Any rain that does fall will be light...with only areas near the Mason Dixon line potentially receiving up to a tenth of an inch. Expect patchy fog across the southern half of PA as well. Overnight lows will range generally through the 50s. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... Tomorrow we should be mostly between systems. The clouds and moisture from the wave to our southeast should be pulling away overnight. And the clouds and rain from the deep 500 hPa low will be heading our way from the west-southwest. Most areas should have a pretty nice day, but once again on the cloudier side of things. Kept POPS in the chance range in southwest before 18 UTC and brought them up higher and into central PA by 00 UTC. Sometime from 2100 UTC Wed to about 0300 UTC it`s going to get wet. But highest probability of rainfall in current guidance will likely be on Thursday. New guidance might change this. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... As upper low drops into the TN Valley Wed night, surface low develops over the Ohio Valley with a warm front extending eastward across the mid atlantic states. Initial question will be timing of onset of precip over CWA. Precip will be working across W PA by early eve and will spread eastward as flow turns from the SE around to the S, overspreading all of central PA by the overnight hours. System slides through Thu into Thu night, with a widespread rainfall around 0.75 inch. On Friday, cool cyclonic flow on backside of departing cyclone will maintain risk for showers. A lower-amplitude mid level flow pattern will develop into the weekend with some ridging likely at 500mb. Uncertainty regarding location and timing of shortwave impulses rounding the ridge and effect of prior upstream convection leaves plenty of question marks for Saturday - but there is more agreement in area of max POPs over S OH/into WV and SW PA in the afternoon. NBM/ECE blend yielded the highest POPs for Sunday across Central PA associated with cold front moving south/eastward across the Great Lakes/Appalachians. A severe risk may accompany the cold front but still to early for details. The large scale pattern evolves into a broadly cyclonic regime into early next week around an upper low between the Great Lakes and Hudson Bay. This should keep the pattern unsettled with continued threat for showers/Tstorms through Tuesday. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... Most of the flying area is under a blanket of high clouds. Some MVFR has crept into MDT and this lowering ceiling trend over southern areas as the area of rain slowly overspreads the region. Expect the mainly light rain to move into about the southern half of the forecast area during the remainder of the overnight and early Wednesday with MVFR/IFR conditions developing. Northern areas will see just spotty light showers and widespread sub VFR conditions are not expected. Conditions will improve slowly Wednesday morning with most areas improving to VFR by mid day. MVFR could hang tough over the Laurels. Clouds will increase west to east as another system approaches with rain and reduced conditions overnight Wednesday into Thursday. .OUTLOOK... Thu...Rain/low cigs likely through at least midday. Fri...Showers/MVFR cigs NW. Mainly VFR SE. Sat...No sig wx expected. Sun...Reduced conditions with scattered showers. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Grumm NEAR TERM...Grumm/DeVoir SHORT TERM...Grumm LONG TERM...RXR/Steinbugl AVIATION...La Corte
Area Forecast Discussion
National Weather Service Green Bay WI
1042 PM CDT Tue May 23 2017 Updated aviation portion for 06Z TAF issuance .UPDATE... Issued at 649 PM CDT Tue May 23 2017 Area of concern this evening focusing on Calumet county. Surface frontal boundary and surface low was located over southern Wisconsin, however radar shows a convergent area north of the surface boundary extending from Dodge County to Calumet County and northern Manitowoc County. This convergent region was pivoting with the bands of rain over MTW County lifting north. However parts of the southern two thirds of Calumet County may pick up 1 to 2 inches of rain this evening if this band maintains. Will consider an urban small stream advisory for this area if this convergent band holds over the area this evening. && .SHORT TERM...Tonight and Wednesday Issued at 240 PM CDT Tue May 23 2017 The latest rap analysis and satellite/radar imagery show surface low pressure centered near the Dells, and associated warm front extending east across east-central WI. Instability has developed south of the warm front, leading to thunderstorms developing along and just north of the boundary. Some of these storms may make it into areas from Waushara to Manitowoc this afternoon, but convergence does weaken by early this evening, so think the threat of storms will end by this time. Looking elsewhere, deeper moisture is wrapping around the upper circulation across eastern WI, which should keep the chance of showers highest over eastern parts of the state for the afternoon. As additional showers move north from northern Illinois, precip trends are the main forecast concern. Tonight...Center of the upper low will drift south across Iowa and Missouri, but the upper level trough axis will extend north across Wisconsin through the night. As the low moves south, think precip chances will come to an end over north-central WI by late evening. Eastern WI will not be as lucky, as deeper moisture will rotate around the trough and across eastern WI from about mid-evening through the overnight hours. Some of these showers will likely rotate into central WI as well, but coverage should not be as high as further east. With ample cloud cover, lows will range from the low 40s north to upper 40s south. Wednesday...The upper low will continue to move to the southeast across the mid-Mississippi Valley. Meanwhile, corridor of deeper moisture will continue to impact eastern WI into at least early afternoon with occasional showers, before diminishing. Have increased precip potential in this area considerably. Otherwise, skies will remain mostly cloudy and breezy with a stiff northeast wind. Cool temps rising into the upper 50s to lower 60s. .LONG TERM...Wednesday Night Through Tuesday Issued at 240 PM CDT Tue May 23 2017 Expecting dry weather for the beginning of the period, then uncertain precipitation chances for the Memorial day weekend. Near normal temperatures are anticipated through the period. A weak ridge of high pressure at the surface and aloft should bring mainly dry conditions late Wednesday night through Thursday evening, though an isolated diurnal shower cannot be ruled out Thursday afternoon. Weak WAA will bring a small chance of showers back to the forecast area late Thursday night into Friday. Models offer widely varying solutions for the Memorial Day weekend. Saturday is looking like the driest and warmest day of the weekend, with only a weak cold front moving through the region. The GFS drops an upper low into the western Great Lakes on Sunday and Monday, and also brings a swath of a rain to the southeast part of the forecast area as low pressure lifts through the Lake Michigan region Saturday night into Sunday. Meanwhile, the ECMWF keeps the main upper low to our north, with a series of short-waves and frontal passages bringing the best precipitation chances to northern WI. Given the poor run to run consistency of the GFS, would lean toward the ECMWF for now. However, overall confidence in the precipitation chances over the holiday weekend are low. && .AVIATION...for 06Z TAF Issuance Issued at 1040 PM CDT Tue May 23 2017 An upper level low system with a surface low will track into the Ohio Valley region overnight into Wednesday. Showers with patchy IFR/mvfr conditions will linger over eastern Wisconsin tonight into Wednesday morning and then showers will taper off while conditions gradually improve later Wednesday. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE.........TDH SHORT TERM.....MPC LONG TERM......Kieckbusch AVIATION.......TDH
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1044 PM CDT Tue May 23 2017 .UPDATE... Cleared near shore waters from Severe Thunderstorm Watch 259 as the showers and thunderstorms associated with the surface front have diminished. Also lowered PoPs to account for radar imagery which is picking up on the line of showers with isolated thunder, moving in from the north associated with the 850 mb front. Hathaway && .PREV DISCUSSION... /ISSUED 926 PM CDT Tue May 23 2017/ UPDATE... Main updates to the forecast tonight have been clearing counties from Severe Thunderstorm Watch 259. The surface cold front and associated thunderstorm activity continue to push off the Upper Texas coast tonight, taking the threat for severe weather with it. The KHGX radar is showing a secondary line of showers developing approximately 100 miles to the north in the vicinity of the 850 MB front. Despite a uniform wind direction at this level, there is sufficient speed convergence along this feature (30 knot winds flowing into 10 knot winds) to result in isolated to scattered showers. The atmosphere as destabilized significantly since this evening`s storms moved through and severe weather is not expected, but cannot rule out a rumble of thunder. Otherwise, remainder of forecast remains on track with dry conditions expected after midnight and clearing skies allowing overnight temperatures to fall to the mid 50s to mid 60s... much below normal for this time in May. Huffman PREV DISCUSSION... /ISSUED 644 PM CDT Tue May 23 2017/ AVIATION... Storms occurring ahead of the cold front will be moving across the terminals from 00Z at KUTS to about 04-05Z at KGLS. A strong thunderstorm should be east of KCLL by 00Z; however, more showers were developing to the west of the site. There is a slight possibility of a strong or severe storm with gusts in excess of 50 knots and large hail making its way through the sites between KCXO and KHOU between 00Z and 02Z. Expect the storms to be off the coast by 06Z. VFR conditions are then expected. Breezy winds are expected to then develop after 15Z Wednesday. 40 PREV DISCUSSION... /ISSUED 438 PM CDT Tue May 23 2017/ DISCUSSION... Surface analysis as of 1 PM CDT showed an approaching cold front stretching from Del Rio to Waco towards Shreveport, with a weak prefrontal wind shift entering portions of the Brazos Valley. Regional radar mosaic this afternoon shows a few cells developing along and behind the front as it continues to push towards the southeast. With RAP guidance instability increasing ahead of the approaching boundary and lift overspreading the region from a passing 90 knot upper jet, expect the severe weather threat to increase over the next few hours for Southeast Texas as scattered thunderstorms continue to develop along the front. Expect the front to clear the Brazos Valley late this afternoon, reaching the Houston metro mid-evening, and clearing the coast around midnight tonight. Steep mid-level lapse rates will result in a large hail and damaging wind threat (especially if any storms bow out) as the front progresses southward. A few showers may linger behind the front tonight before dissipating as drier air moves into the region, with clearing clouds and cold air advection behind the front resulting in cool overnight low temperatures in the mid 50s to mid 60s. Dry weather will continue through the rest of the week with high temperatures gradually warming into into the low 90s by Friday as shortwave ridging translates across the region. Northerly winds will gradually swing around to the south by Thursday as surface high pressure slides off to the east, allowing moisture to gradually return by the beginning of the weekend. A cold front looks to slide into Texas by the beginning of the weekend and stall at the beginning of next week as an upper low reaches the Great Lakes. Will have to keep an eye on the Monday/Tuesday portion of the forecast next week as disturbances overriding this stalled boundary look to result in a very wet period for the region. Huffman AVIATION... A cold front will push off the coast tonight with strengthening northerly winds and building seas in its wake (some thunderstorms developing along and ahead of the front could become strong or severe as they move off the coast this evening). Onshore winds will return early Thursday and quickly strengthen during the day. Elevated winds and seas can be expected from the end of the week on through the upcoming Memorial Day weekend. Caution flags will probably be needed, and advisories will be possible. 42 CLIMATE... Low temperatures Wednesday morning will be well-below normal for late May and observations across parts of the Brazos Valley and Piney Woods regions may approach or reach record low temperatures for May 24. A listing of record low temperatures for May 24 for the first order climate sites are provided below. LOCATION RECORD LOW YEAR City of Houston 54 1892 Houston Hobby 57 1940 College Station 55 1913 Galveston 62 1940 Huffman && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 56 82 60 90 73 / 50 10 0 0 10 Houston (IAH) 59 83 64 89 74 / 60 10 0 0 0 Galveston (GLS) 63 81 73 84 79 / 40 10 0 0 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 10 AM CDT Wednesday 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...Waters from Freeport to the Matagorda Ship Channel from 20 to 60 NM...Waters from High Island to Freeport from 20 to 60 NM. && $$ Discussion...08
Area Forecast Discussion
National Weather Service Huntsville AL
936 PM CDT Tue May 23 2017 .NEAR TERM...(Tonight) Issued at 920 PM CDT Tue May 23 2017 One batch of showers and storms has finally moved off to the east into GA. However, another round will be moving across the MS River in the next hour or so. These showers and storms are forming along a cold front that extends S/SE out of a low pressure system over the Great Lakes into the ArkLaMiss. Latest radar and surface analysis is showing a secondary low pressure system forming over NE TX along the front. This feature is forecast to lift NE into northern MS and then into central TN tonight through Wednesday morning. Last few runs of the HRRR seem to have a good handle on the movement although believe they are a bit on the slower side in the progression of showers across the area. Initial forecast had PoPs increasing well after 06z tonight but have shifted those to around midnight with 60-70 PoPs going for much of the overnight period. Forecast soundings and model guidance all indicate some limited elevated instability (200-500 J/kg) and 30-40kts of shear. Which is enough to continue thunderstorm wording for tonight. Main hazards would be heavy rainfall and wind gusts of 30-40 mph. Lows in the lower 60s still seem reasonable based on temps upstream and latest hires guidance. .SHORT TERM...(Wednesday Night through Thursday Night) Issued at 249 PM CDT Tue May 23 2017 The upper low pulls away Wednesday night which should end precip completely from southwest to northeast. Thursday should be a fine weather day with a surface ridge shifting east with corresponding confluent northwesterly flow at 500 mb. Highs should bounce back into the lower to middle 70s, followed by lows in the lower to middle 50s by Friday morning. We will hold off on patchy fog, but it may be something for consideration if the winds are able to drop off. .LONG TERM...(Friday through Monday Night) Issued at 249 PM CDT Tue May 23 2017 Upper level ridging and subsidence behind the departed front become established over the Tennessee Valley into the northeastern Gulf of Mexico on Thursday night into Friday morning. This continues into Friday afternoon, as the storm system over Oklahoma edges east only slightly, mainly due to the upper level ridging to its east over the Tennessee Valley. Although models hint at some energy moving through almost zonal flow over northern Tennessee and Kentucky, the atmosphere should still be too dry for even any isolated shower/storm activity. Could see high cloudiness move into the area in response to this upper level forcing, but most of it will be in Southern Middle Tennessee. Models continue to show very moist conditions returning northward quickly Friday night into Saturday, as low level winds become more southerly. However, synoptic models diverge concerning how far south a warm front extending from the storms system over Oklahoma sets up. GFS is much further north, while ECMWF is much further south by late Saturday afternoon into Saturday evening. Thus, if GFS is right, timing of precipitation potential may be later than the current forecast indicates and hold off until late Saturday night. At this point used a blend of models. This pushes scattered showers/storms into Southern Middle Tennessee and northern Alabama Friday night into Saturday. Warm temperatures aloft should keep wet-bulb heights fairly high. Models show decent bulk shear values between 40 and 50 knots Friday night into Saturday, but the lack of forcing should limit coverage to mainly near and north of the Tennessee River. However, a few storms could be strong during this period producing gusty winds around 50 mph and frequent lightning. Breezy conditions with winds of 10-15 mph with gusts up to 25 mph should return on Saturday. Higher elevations may see wind gusts a bit higher, especially Saturday night. Expect more widespread coverage of showers and thunderstorms to occur Saturday night into Sunday (as forcing associated with the surface low moving northeast into the western Great Lakes approaches and then moves into Alabama from Mississippi). Most synoptic models are not too different concerning the timing of this frontal boundary and have the actual front approaching northwestern Alabama Sunday afternoon. PWATS increase to between 1.6 and 1.8 inches and remain in this range most of this period. This may lead to flash flooding/river flooding issues during this period as well, given the slow movement eastward of the front. Plenty of surface based and elevated CAPE is forecast by models Saturday night into Sunday, especially on Sunday (2000-3500 J/KG). 0-6 km bulk shear values will be between 40 and 55 knots as well. Low level helicity is forecast to increase Saturday night to around 200 to 300 m2/s2 (especially west of I-65). This helicity quickly decreases on Sunday. Couldn`t rule out a low potential for a brief, weak tornado spinup on Saturday night before helicity decreases. However, we are more confident that we will see strong thunderstorms producing wind gusts around 50 mph, heavy rainfall, and frequent lightning Saturday night through Sunday. Wet- bulb heights remain fairly high, but lower to around 10,000 feet. GFS more quickly moves the front south of the Tennessee River, but ECMWF keeps the back edge of precipitation further north on Monday. For now, went with a blend of models. Kept 30 to 40 percent chance of showers and thunderstorms in the forecast to cover any convection along and just behind the front. Kept mostly cloudy conditions in place most of Monday as the upper low and associated moisture will be slow to exit the area. By Monday night, a few showers may linger, but this may be overdone due to blending of model differences. Either way, cooler and drier weather should return with lows in the lower 60s and highs around 80s degrees expected. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 620 PM CDT Tue May 23 2017 The storms have moved off to the east and we are left with VFR conditions through about 06Z tonight. A cold front and associated showers and thunderstorms will move across the area tonight. MVFR cigs and vis accompany the storms tonight. Showers may continue past 12Z Wednesday morning but most of the activity will be off to the east. MVFR cigs continue through the morning with winds increasing out of the NW. Gusts of 15kts are possible in the afternoon. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...Stumpf SHORT TERM...17 LONG TERM...KTW AVIATION...Stumpf For more information please visit our website at
National Weather Service Jackson KY
1105 PM EDT Tue May 23 2017 .UPDATE... Issued at 1055 PM EDT TUE MAY 23 2017 Hourly pops have been updated based on recent radar trends. Showers and even a rumble of thunder in the far southeast has occurred in the last hour as a mid level disturbance works through the area. The current round of showers should weaken and shift out of the area over the next couple of hours. However, another disturbance should bring another round of showers and perhaps a thunderstorm encroaching on the area around dawn. UPDATE Issued at 835 PM EDT TUE MAY 23 2017 Some late afternoon heating and a mid level disturbance have combined to bring some showers and thunderstorms to parts of Central KY and parts of Middle TN and the Cumberland Plateau of TN. Much of these have experienced a downward trend in intensity over the past hour or so with the exception of the convection in the Bluegrass Region of KY while showers persist across much of southeast KY. Thunder chances were added for the evening with the upstream thunder detected. Also, dewpoint depressions across much of the area are just a few degrees. With low level moisture lingering and some cooling in between the current shortwave and the next to approach late tonight and on Wednesday at least some patchy fog will be experienced possibly both on the ridges and int the valleys and this has been included. Otherwise, no substantial changes were needed at this time. && .SHORT TERM...(This evening through Wednesday night) Issued at 500 PM EDT TUE MAY 23 2017 20z sfc analysis shows a broad area of low pressure over the middle of the Tennessee Valley encompassing Kentucky. This has brought showers and sprinkles to eastern Kentucky as well as plenty of clouds. The rain has also kept temperatures in check and on the cool side through much of the JKL CWA with readings currently in the low 70s northwest and southwest where the clouds were thinnest to the mid 60s in the rain further east. Dewpoints are generally in the upper 50s to lower 60s while the winds are light and variable. The models are in good agreement aloft through the short term portion of the forecast. They all depict a deep and cut off closed low digging into the Deep South through Thursday morning along with ample energy swirling around. The core will roll down the backside of this larger trough and generally target locations to the south of Kentucky on Wednesday into Wednesday night. The good model agreement lends support to a blended model solution along with the use of the high res HRRR through the near term. Sensible weather will feature scattered showers departing to the northeast this evening - with a stray thunderstorm possible. This will be followed by a lull in the activity through midnight for most locations under cloudy skies before the next surge in moisture moves in late tonight with showers and thunderstorms increasingly possible toward dawn. The thick clouds should keep most of the fog at bay tonight, but for places that saw the rain late this afternoon and into the evening - should the clouds thin enough - patchy fog will be possible and will need to be monitored. Showers and thunderstorms will then sweep over all of eastern Kentucky on Wednesday with some gusty winds and a window of heavier rain possible should they manage to be more organized - perhaps helped from a mid level wave swinging through around midday. Have highlighted this time frame in the grids for the best shot at thunder, as well. Later in the day the thunder chances fade out from west to east as the main sfc low lifts past to the east. Lighter shower will linger, though, into the night. The CONSShort and ShortBlend were used as a starting point for the grids` with only minor adjustments to temps through the period. As for PoPs, made some significant adjustments to them to better represent the spatial and timing aspects of the rain shield moving into East Kentucky from late tonight through Wednesday afternoon. .LONG TERM...(Thursday through Tuesday) Issued at 400 PM EDT TUE MAY 23 2017 An upper level low will be centered over Kentucky to start out the period Thursday morning, shifting northeast throughout the day and into Thursday night, with rising heights expected across the Commonwealth. Ridging will take hold Friday, however will be dampened as several shortwaves move through the pattern and affect the region over the next couple of days. By Saturday, another upper level low will drop south from central Canada, allowing for longwave troughing to develop across the central U.S. While timing on this system is still somewhat unresolved between the models, as is the intensity of the trough, much of the state can expect some type of height falls and destabilization to occur to round out the weekend and start the beginning of the workweek. Models actually come back into better agreement by the very end of the extended period, with the axis of the trough nearing the state Tuesday, and traversing the state into the day Wednesday. At the surface, the presence of a surface low pressure system just north of the CWA (in conjunction with the upper level low) will result in precip chances throughout the day Thursday. This precip will pull northeast of the region into Friday morning as the surface low exits in this direction. However, given our location on the backside of the cold front, latest forecast soundings aren`t supporting much in the way of instability, so chose to keep out mention of thunder Thursday. A brief area of high pressure will move into place with the building heights, keeping us mostly dry Friday. However, incoming shortwaves that will ride along this pattern will bring the return of unsettled weather and shower/thunderstorm chances by Friday night, continuing through Saturday and increasing in intensity and coverage by Saturday night into Sunday as a surface low moves NE towards the state and a cold front drags eastward. This cold front will cross eastern KY Sunday night into Monday, with another brief area of high pressure moving in behind during the day Monday. Yet another cold front will near the state Tuesday, attached to a stronger surface low to our north (in conjunction with the second upper level low referenced above). This will bring yet another round of precip (showers and thunderstorms) to the region through the day Tuesday. Temperatures should start out below normal during the day Thursday behind the departing cold front, with highs in the mid 60s. stronger S to SW flow will take place by Friday, bumping temps into the mid and upper 70s Friday afternoon, and into the upper 70s and low 80s on Saturday and Sunday afternoon. Despite a cold front moving through on Sunday night/Monday morning, temps will only be slightly (a couple degrees) cooler on Monday and Tuesday than the weekend thanks to the quick return of SW flow behind the frontal passage. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) ISSUED AT 820 PM EDT TUE MAY 23 2017 In advance of a shortwave, areas of showers and thunderstorms are moving across East KY this evening with the strongest activity headed toward the far northwest counties and could affect SYM with MVFR or IFR for a time. Additional showers could affect LOZ and SME as well. This activity should diminish 3Z to 5Z before showers increase again 10Z to 16Z. The low levels remain moist so outside of showers some MVFR fog should develop and could affect all of the TAF ties. This next round should lead to saturation at all levels again and cigs should fall to MVFR if not IFR at times as shra and some tsra move in from the southwest with the next shortwave. Winds should average less than 10KT through the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...GREIF LONG TERM...JMW AVIATION...JP
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
825 PM CDT Tue May 23 2017 .UPDATE... 825 PM CDT The going forecast of scattered/periods of showers tonight remains on track. There was a slight diminishing in coverage since 7 pm owing more to the passing of a shortwave than a true diurnal downtick. While some diurnal dissipation should be the case through the evening, variation in coverage is likely with continued cold mid-level air and subtle short wave impulses ahead of the main low center. The 00Z DVN and ILX soundings indicated 200-400 J/kg of MUCAPE and 25-40 kt of deep layer shear that will continue to be tapped for showers with some organization and spotty moderate to heavy rates. As an example, Pontiac Airport had 1/2SM visibility around 7 pm with a shower. The potential for funnel clouds likely has ended as surface winds are generally light and variable with little for low-level convergence, and any lightning should be few and far between. Given the rain and low T/Td spreads, fog is a possibility. There is quite a bit of existing cloud cover that would hint at low stratus being more dominant than fog, but confidence is low. Certainly at least shallow patchy fog is a good bet in some locations, and would be likely and even dense in any areas that have a thinning in cloud cover (presently not favored for most of the CWA). MTF && .SHORT TERM... 240 PM CDT Through Wednesday... Deep low pressure will continue to sink south from the corn belt to the lower Mississippi valley Thursday. The first in a series of waves ahead of the low will shift northeast through the flying area this afternoon. Expect an increase in shower coverage and intensity over the coming hours with the enhanced lift from this wave, with some moderate showers due to a narrow moisture plume precipitable water values in excess of 1 inch There is a small pocket of instability across north Central Illinois into adjacent Wisconsin where the best near term chances for embedded thunderstorms exists. With the upper low shifting farther east, cold temperatures aloft will allow some of this weak instability to shift over northeast Illinois and northwest Indiana. This combined with the vort max still warrants a low chance thunder mention. RAP forecast of non-supercell tornado threat are still low but low level cape does exist in very localized pockets near the cold frontal boundary where low level vorticity is enhanced, and with some limited clearing there is still a limited severe weather concern for gusty winds as the vort max encounters the front this afternoon. As the low sinks south tonight into Wednesday, Expect continued waves of showers as additional energy spreads northward ahead of the low, with coverage likely decreasing though possibly becoming more narrowly focused on eastern half of the area. There could be a modest rainfall axis that will setup tomorrow, with the I-55 eastward corridor still favored, but still challenging to pinpoint at this time. A low thunder chance exists across east Central IL and northwest IN as well. Elsewhere just expect occasional showers and cool cloudy conditions. KMD && .LONG TERM... 240 PM CDT Wednesday night through Tuesday... Looking ahead through the extended part of the forecast, there are not many periods without a mention of rain chances. We transition away from one upper low late this week but into another this weekend, with only weak ridging in between. However, despite the frequent chances for rainfall, it does not appear that each day will be a washout. In general the showers should be to some extent diurnally driven under a cyclonic upper level circulation, which means at least the early part of most days could be favorable for outdoor activity. The most likely period for a break in activity appears to be Thursday afternoon into the early part of Friday as the first system moves out and cooler, drier air moves in with northerly surface flow. Warmer and more humid air returns for Friday and Saturday. The biggest uncertainty for this forecast period comes late Friday and into the weekend, with the deterministic GFS and ECMWF in poor agreement with the timing of an upper wave and surface low pressure system moving through the southern Great Lakes. Presently the much faster well as the GEM...brings this system through late Friday and leaves behind just some light activity for Saturday. The GFS is about a day slower and shows widespread rainfall Saturday afternoon and evening. Both have a stationary front extending east from a larger center of low pressure across Oklahoma early Friday. They both also depict a wave forming along the front as the one that pushes through the local area. Given the proximity of the boundary and the uncertainty with the movement of the surface wave, will continue to carry increasing precip chances late Friday, especially south, and again Saturday afternoon and evening for a larger portion of the area. Models are in somewhat better agreement in depicting another break in the weather early Sunday, then a large upper low becoming parked over the Great Lakes from late in the weekend through at least midweek. This would support ongoing widespread chances of rainfall, especially during periods of afternoon heating. Lenning && .AVIATION... For the 00Z TAFs... The main concerns are precipitation trends, winds and CIG/VSBY trends. A slow moving upper level low pressure will continue to bring waves of showers at least into Wednesday morning which will be capable of reduced visibility. The more frequent or prevailing rain/shower activity should on the large scale focus over the eastern terminals, with isolated to at times scattered showers near RFD. The wind field is quite light with a light pressure gradient but as weak low pressure organizes south of area tonight, tendency should be for gradually increasing northeast winds. By mid-day Wednesday and likely through Wednesday evening, the position of stronger low pressure off to the east will support gusty north-northeast winds with gust speeds forecast of 18-20 kt and potential for up to 25 kt at eastern terminals. Regarding CIG trends, the most widespread low clouds are over Wisconsin from MKE and to the north and northwest of there. Much of the guidance, but not all, brings these low clouds southward tonight with time and then lingers it into Wednesday. Am concerned that this a bit overdone, so limited the duration of IFR in the TAFs, leaning on probabilistic ensemble guidance for trend toward improvement by the mid-late morning through the afternoon. Confidence is low- medium with CIG trends overall. If the low clouds do scatter as anticipated, some guidance hints at them spreading back southwest Wednesday evening. The lighter wind and moist regime overnight into Wednesday morning may support VSBY reductions in BR outside of shower activity. Castro && .MARINE... 309 PM CDT Low pressure dropping from Wisconsin into Indiana tonight and then moving to Ohio Wednesday evening will support northeast winds across the lake through Thursday night. Winds are lighter and more variable Friday and Saturday under the influence of a ridge of weak high pressure moving over the lake. Lenning && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
541 PM CDT Tue May 23 2017 .SHORT TERM... (Through Late Wednesday Afternoon) Issued at 309 PM CDT Tue May 23 2017 Showers and isolated thunderstorms are currently moving east across the area along and behind a cold front. This initial wave of showers will shift east into south central and southwest Illinois as well as southeast Missouri. This is where the RAP is showing low level moisture convergence becoming concentrated from early evening until after midnight underneath mid-level ascent ahead of a shortwave trough coming around the south side of the the upper low. The shortwave trough will move off to the southeast by early tomorrow before the main upper low sinks south into Missouri during the day tomorrow. This will bring scattered showers and thunderstorms to the area under the cold pool of the upper low during the day. Temperatures will be cooler tonight and tomorrow behind the front. Highs will be much below normal tomorrow underneath the upper low with 850mb temperatures only around +5C resulting in highs only in the mid 60s. Britt .LONG TERM... (Wednesday Night through Next Tuesday) Issued at 309 PM CDT Tue May 23 2017 The upper level flow will undergo significant transition during the period from Wednesday night through early next week. A deep trof will be centered over eastern portions of the MS Valley with an upper low in the vicinity of southeast MO at the beginning of this time frame. Cyclonic flow will be present across the region attendant with the departing cyclone and residual/lingering diurnally driven showers will be possible near and east of the MS River on Wednesday evening. Low level cyclonic flow will diminish overnight as the upper trof progresses eastward into the OH/TN Valley Region. Thursday looks to be the tranquil and pick-day of the week. The upper level trof will continue to depart through the eastern U.S. with rising heights aloft in the wake of the trof and ahead of a deepening long wave trof in the western U.S.. Weak high pressure will dominate at the surface with low-level WAA getting underway above the PBL. An active and stormy weather pattern will take hold late Thursday night through Saturday night. Continued progression of the upper air pattern and evolution of the upstream broad longwave trof will result in active west-southwest flow. A migratory short wave within this flow will move across the area late Thursday night through early Friday morning. An increasing southwesterly LLJ will result in pronounced low level WAA and moisture return, and elevated instability due to these advective processes and steep mid level lapse rates. The primary focus for showes and storms on Thursday night will be across central and northeast MO expanding to the remainder of the CWA on Friday morning. A cold front will then settle into the region late Friday becoming quasi-stationary late Friday night into early Saturday. The environment during this time frame remains quite supportive of deep convection with weak- moderate instability due to a large expanse of steep mid level lapse rates atop a warm moist low level air mass within a persistent low level WAA regime. There are some model differences with the evolution of the front Saturday into Saturday night with the new ECMWF a bit more progressive, and faster moving the cold front out of the area by daybreak Saturday. Alternatively the consistent GFS and GEFS mean is suggesting the potential for a very volatile period from Saturday afternoon into Saturday Night. In this scenario a deepening surface low would translate northeastward along the cold front which would advance southeast on Saturday night, and the warm sector will be quite favorable for organized severe weather characterized by strong instability and strong deep layer shear. Cooler weather would dominate in the wake of the front Sunday through the Memorial Day and thru the early part of next week. Several disturbances in the northwest flow aloft will bring reinforcing surges of cooler air, as well as the potential for a few showers and thunderstorms. The greatest threat of any additional precipitation should be across northeast MO into west central IL. Glass && .AVIATION... (For the 00z TAFs through 00z Wednesday Evening) Issued at 517 PM CDT Tue May 23 2017 Upper level low over IA will drop southeastward through eastern MO on Wednesday. It appears that much of the scattered shower activity, now mainly in the St Louis metro area will dissipate this evening with the loss of daytime heating, although could not rule out isolated light showers through the overnight hours. Scattered showers and a few storms should redevelop over the area Wednesday afternoon. For now will likely just include VCSH in the St Louis metro area tafs early this evening, then include VCSH in all the tafs Wednesday afternoon. Should have mainly VFR cigs through the period, but possibly dropping into the MVFR catagory early Wednesday morning with plenty of low level moisture across the area. Northwesterly surface winds will continue through the period with surface troffing across the OH and TN Valley regions and surface ridging over the Plains. SPECIFICS FOR KSTL: Upper level low over IA will drop southeastward through eastern MO on Wednesday. It appears that much of the scattered shower activity, now mainly in the St Louis metro area will dissipate this evening with the loss of daytime heating, although could not rule out isolated light showers through the overnight hours. Scattered showers and a few storms should redevelop over the area Wednesday afternoon. For now will likely just include VCSH in the STL taf early this evening, then include VCSH again Wednesday afternoon. Should have mainly VFR cigs through the period, but possibly dropping into the MVFR catagory early Wednesday morning with plenty of low level moisture across the area. Northwesterly surface winds will continue through the period with surface troffing across the OH and TN Valley regions and surface ridging over the Plains. GKS && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Marquette MI
652 PM EDT Tue May 23 2017 .SHORT TERM...(This evening through Wednesday) Issued at 322 PM EDT TUE MAY 23 2017 12Z raobs/latest wv imagery and RAP analysis show a closed upr lo sinking slowly swd thru the Upr MS River Valley under general upr troffing stretching fm Quebec into the Plains downstream of an upr rdg in wrn NAmerica. There is a good deal of cld cover stretching into the Upr Lks under the upr troffing, and there have been some sct showers mainly over the scentral where wv imagery hints there may be a weaker shrtwv lifting nwd toward the Upr Lks within the ssw flow aloft e of the upr trof axis. Main fcst concerns thru Wed focus on pops for mainly the se cwa, which wl remain under a ssw flow alf e of the slowly progressive upr trof axis. Tngt...Although the main closed h5 lo is fcst to continue to drift slowly s and into nrn Missouri by 12Z Wed, most of the guidance indicate some hier mid lvl rh/large scale forcing wl impact roughly the se half of the cwa, where the winds alf wl be out of the sw on the ern flank of upr trof stretching fm James Bay to the slowly departing closed upr lo. Since the llvl flow wl remain weakly cyc, wl retain some pops in this area. But absence of any daytime heating, exit of closed lo/sharpest forcing to the s, and concerns about impact of some dry air in the h9-85 lyr supporting more breaks in the clds to the ne and e wl restrict pops into the chc range. Even over the w where the forcing wl be weak or even negative, guidance shows a good deal of mid cld lingering, which wl limit the diurnal temp fall. Wed...As the closed lo to the s and upr trof axis drift slowly to the ese, the guidance shows mid lvl drying/larger scale subsidence pressing slowly to the ese as well. But since some large scale qvector cnvgc/deeper mstr wl linger to the e of the upr trof axis and over the se portion of the cwa thru most of the day, wl retain some chc pops there thru the day as well. With earlier arrival of larger scale drying/subsidence, expect at least some sunshine over the w. Expect temps to rise aoa 60 away fm cooling off Lk Sup in llvl ne flow. .LONG TERM...(Wednesday night through Tuesday) Issued at 246 PM EDT TUE MAY 23 2017 No high impact weather is expected through the long term. Only item to mention specifically is that there`s a slim chance of some frost over far western Upper Michigan Wed night. Otherwise, looks like chances for some light rain over at least portions of the CWA in each period with temps near or below normal. Did not make any changes to blended initialization. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 651 PM EDT TUE MAY 23 2017 Expect generally VFR cigs into this evng, when some lower MVFR cigs likely to dvlp at the TAF sites with upslope llvl nne flow and loss of daytime heating/mixing. Upstream obs over ne MN/adjoining Ontario show a good deal of loW clOUd, so lower IFR cigs may impact IWD for a time. With the arrival of drier air on Wed and daytime heating/mixing, cigs wl rebound into the VFR range. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 322 PM EDT TUE MAY 23 2017 Expect winds under 20 kts into this coming weekend as a relatively flat pres gradient dominates the Upper Lakes. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...KC LONG TERM...Titus AVIATION...07 MARINE...KC
Area Forecast Discussion
National Weather Service Sacramento CA
310 PM PDT Tue May 23 2017 .SYNOPSIS... Triple digit heat continues today in the Central Valley then cooling Wednesday into Friday with near to slightly below normal readings by the end of the week. Isolated afternoon showers or thunderstorms possible over the southern Sierra Nevada today and over the northern interior mountains Wednesday. && .Discussion (Today through Friday)... Strong upper ridging over Interior NorCal today is resulting in triple digit heat again in portions of the Central Valley. Hottest temps across the CWA this afternoon are occurring in the Northern Sacramento and Northern San Joaquin Valleys. Potential for some additional record highs to be broken today as the record for KRDD and KRBL is 101 and 99 at Modesto. Afternoon CU and some TCU have developed along the Sierra Nevada and will need to be watched, however latest HRRR not showing any showers or thunderstorms developing. Delta breeze expected to ramp up this evening becoming moderate to strong tonight into Wednesday morning. Marine layer deepens tonight as offshore upper low approaches and combined with Delta breeze will provide low level CAA into portions of the Central Valley overnight. Upper troughing over the PacNW digs towards the Great Basin tomorrow as associated weak cold front stalls over northern portions of CA. This may provide enough lift to set off a few afternoon showers or thunderstorms over the Coastal and northern interior mountains. Increased Delta breeze and synoptic cooling over the area Wednesday will result in about a 10 degree drop in max temps. Broad upper troughing continues over the forecast Thursday into Friday providing additional cooling. Highs expected in the 80s throughout the Central Valley Thu/Fri, 70s in the Delta, and 50s to around 80 for the mountains and foothills. PCH && .EXTENDED DISCUSSION (Saturday THROUGH Tuesday) A ridge will be in place for the holiday weekend and that will bring warming temperatures and quiet weather. If you have outdoor plans over the weekend you will want to be prepared for hot weather. Highs on Saturday will be in the 80`s and 90`s but we will warm into the 90`s and lower 100`s by Memorial Day. A Delta breeze will keep that region a little more comfortable throughout the weekend though. We will also see some instability build into the higher elevations and we could see a few isolated afternoon and evening t-storms in the Sierra. The ridge starts to flatten out later Monday and a short wave trough moves into the region on Tuesday. This will keep isolated t-storm chances in the forecast for the Sierra. Temperatures will also be a bit cooler on Tuesday but still above normal. -CJM && .AVIATION... VFR conditions expected at the TAF sites the next 24 hours. Local wind gusts to 20 knots possible in the Delta after 00z Wed otherwise 5-10 knot winds can be expected. Slight chance for isolated t-storms over the Sierra south of US-50 between 23-03z. -CJM && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$