Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/29/17

Area Forecast Discussion
National Weather Service Bismarck ND
928 PM CDT Fri Apr 28 2017 .UPDATE... Issued at 926 PM CDT Fri Apr 28 2017 Current forecast looks good. No changes needed. UPDATE Issued at 628 PM CDT Fri Apr 28 2017 High pressure extending from central Manitoba south into North Dakota will keep skies mainly clear and the weather quiet tonight. Current forecast looks good. && .SHORT TERM...(This evening through Saturday) Issued at 319 PM CDT Fri Apr 28 2017 Currently, surface high pressure extended from the Canadian Prairies into the Dakotas, with low pressure over Hudson Bay and another low over the 4-Corners area affecting the Front Range and central Plains states. A weak upper level shortwave low was noted over southern Alberta/Saskatchewan. The weak surface high will weaken and move east slowly tonight, and the surface wind flow will change from north/northeast today to southerly on Saturday. The very dry airmass over ND, represented by surface dewpoints ranging from 5F to around 20F this afternoon, along with mainly clear skies tonight will allow temperatures to drop into the 20s once again. We may again drop into the teens in some locales, but we should be in the 20s most areas. Mostly sunny and a bit warmer on Saturday with highs from the mid 50s to lower 60s. Noted the HRRR high res model indicating much lower relative humidity again for much of western and central ND. Thus attempted to match the 12z HRRR model run for afternoon relative humidities...with ranges from 15% to around 25% for much of our area. Luckily south to southwest winds should remain below 15 mph for the most part, and there should not be any fire weather issues. Went a tad higher for afternoon highs as nam and gfs based guidance was a bit higher than the blends...and seeing a bit warmer conditions today with the same airmass in place tomorrow. .LONG TERM...(Saturday night through Friday) Issued at 319 PM CDT Fri Apr 28 2017 Mild, but seasonably cool weather is still forecast for Sunday through Wednesday, with highs in the mid 50s to lower 60s. Then a warmer end of the week in store for Thursday and Friday with highs in the 60s. A chance of precipitation also remains for the early to middle part of next week. The 12z global model runs were consistent with yesterday`s runs with development of the larger 4-Corners area system mentioned in the short term portion. The models develop the low eastward into the southern Plains Sunday, lifting northeastward to Iowa by daybreak Monday and into the Great Lakes Monday night/Tuesday. This scenario would have the precipitation shield clipping eastern North Dakota with mainly rain - but any westward movement of the track could affect parts of central ND, especially the James Valley. Meanwhile another shortwave in the northwest flow aloft ejects out of southern Alberta Sunday and moves across ND Monday, bringing a chance of light rain to western and central ND from this secondary system on Monday. Another shortwave in the northwest flow aloft will also bring a chance of light rain to our area Tuesday, followed by another weak wave Wednesday. For the end of the week, a western upper level ridge builds into the Front Range and northern Plains, for a dry and warmer end to the week. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 628 PM CDT Fri Apr 28 2017 High pressure will maintain VFR conditions across the state tonight and Saturday. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...WAA SHORT TERM...JV LONG TERM...JV AVIATION...WAA
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1159 PM EDT Fri Apr 28 2017 .AVIATION... Late evening observations continue to suggest the main area of showers will remain to the north and south of the SE Michigan area with just minimal shower coverage before activity exits eastward by sunrise. There remains a short time window for MVFR ceiling confined to locations south of FNT as the remnants of the central Great Lakes trough merge with the Ohio Valley front. A rising ceiling trend will then be aided by dry air arriving on wind becoming moderate northeast from high pressure building over the northern Great Lakes. Low pressure will concurrently move from Texas along the Ohio Valley front and bring the next round of rain to our region spreading from Ohio border northward through the day. For DTW... Light showers will brush the terminal from the northern fringes of the Ohio Valley front during the morning before sunrise. Meanwhile, the central Great Lakes front will wash out and merge with the Ohio front, and may produce a short period of MVFR ceiling in the process. The main concern will be the wind turning northeast by sunrise and becoming moderate in speed through the day which will likely direct NE traffic flow operations. //DTW THRESHOLD PROBABILITIES... * Moderate confidence for ceilings 5000 ft or less through the morning and again Saturday night. && .PREV DISCUSSION... Issued at 1055 PM EDT Fri Apr 28 2017 UPDATE... An interesting set up this evening as a double barrel frontal structure is supported by a broad 130 knot level jet. The resulting complex frontal circulations resulted in surface based convection along the primary front over the Ohio Valley and a broad band of ordinary showers to the north of the trough/front over the central Great Lakes. Weaker showers on the fringes of these areas has brushed SE Michigan during the evening with an occasional pocket developing overhead and moving quickly eastward. All of this continues to battle dry air in the low levels, mainly below about 750 mb with the end result being scattered light rain showers across the area. The same general pattern will continue through the night before a diminishing trend is forced mainly by the short wave ridge building into the Midwest and Great Lakes ahead of the large system digging into Texas. The relative break in the action will last through the morning before a renewed surge of moisture develops through the rest of Saturday. PREV DISCUSSION... Issued at 320 PM EDT Fri Apr 28 2017 DISCUSSION... 12Z DTX sounding revealed an 850 mb dew pt depression of 31 C, with PW value of 0.42 inches. None-the-less, looks like there will be just enough isentropic ascent (295 K) and moisture advection working through southeast Michigan (mainly south of M-59) this evening/overnight to support some light showers based on latest satellite/radar trends and hi-res solutions of HRRR and Rap13. Negative LI`s stay south of the border, and left thunder mention out. Surface cold front sinking south and exiting jet forcing up north will also support chance/scatter pops there. Latest water vapor imagery shows highly amplified upper level pattern over North America, with longwave trough over the Rockies and excellent upper level jet energy tracking into Four Corners region. A convergence of Pacific Moisture/Pineapple connection, coupled with the Gulf of Mexico/Caribbean moisture as large Bermuda High will remain in place through the weekend, drawing flooding concerns by Monday as large and powerful 500 MB low develops over the Central Conus over the weekend. The system will be lifting northeast into the Midwest (Iowa) by Monday Morning. Moisture parameters will be record/near record for end of April/start of May this far north, as 700 mb dew pts approach 5 C toward Monday morning, nearing tropical status, with 850 mb dew pts equally impressive checking in between 13-15 C. With sufficient destabilization/convective elements, showalter index going slightly negative and deep warm cloud layer, several inches of rainfall is certainly possible for the second half of the Weekend into Monday, which will create flood concerns. Unfortunately, placement of heavy rain axis remains difficult, but good low level FGEN/isentropic ascent will be established by Sunday, as strong high (1032-1034 MB) remains parked over/near James Bay. Do think the surface warm front will not clear much past the southern Michigan border during the day on Sunday (Lake Erie influence), which should help showers persist even in southern areas, but max mid level forcing does appear to be lining up across northern sections of the CWA into northern lower Michigan Sunday Night. As of right now, it appears the robust max 6HR height fall center will already be over Central Great Lakes Monday afternoon, thus strong cold frontal/occlusion passage with good upper level support will occur early in the day. Moisture/instability axis passing east by around NOON, helping to mitigate any severe threat. Still not out of the woods Sunday night with 65 knot jet at 850 MB, but meager lapse rates within the moist airmass should be hindrance. Bottom- line, Heavy rain remains the biggest concern, and flood watch will likely be needed for the second half of the weekend. Lingering precipitation and gusty conditions will be possible Monday evening into Tuesday afternoon as low pressure travels northeast from Wisconsin into the Upper Peninsula. Cooler air that is expected to wrap around the low and push into Michigan throughout Monday afternoon will help to increase stability, minimizing the chance for thunderstorms, as conditions remain breezy. The low pressure system will continue to push northeast through Quebec late Tuesday into Wednesday, as a surface high edges eastward across the Great Lakes region. This will act to keep us dry and will keep winds light through the middle of the week, as temperatures remain moderate with daytime highs capped in the mid-50s. The next chance for rain will return Thursday into Friday as a warm front slowly pushes north into the MI/OH border. The GEM model run suggests that the warm front will protrude into Michigan, allowing rain showers to fall over our southern counties that border Ohio, however, several other long-range models hold the rain south of Michigan through the end of the week. MARINE... Gusty southwesterly winds over the morning will slowly continue to diminish this afternoon. Relatively light winds are then expected by early tonight before strong high pressure builds into Ontario and low pressure begins to organize over the plains. This will bring an increase in north/northeast winds to the marine areas and potentially allowing waves to build high enough to warrant a Small Craft Advisory for nearshore waters of Lake Huron and Saginaw Bay. Monday will then see wave heights decreasing as southerly winds take over ahead of a cold front. However, winds will once again gust up to 30 knots. As the low approaches the Great Lakes region this weekend, an increasingly unsettled, wet pattern will set up. Thunderstorms will also be possible Sunday into Monday. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Small Craft Advisory from 3 AM Saturday to 6 AM EDT Monday for LHZ421-422. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....BT UPDATE.......BT DISCUSSION...SF/AM MARINE.......SS You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Quad Cities IA IL
652 PM CDT Fri Apr 28 2017 ...00z AVIATION UPDATE... .SYNOPSIS... Issued at 313 PM CDT Fri Apr 28 2017 18Z surface data has a frontal boundary from central Kansas into northwest Indiana. Dew points were in the 20s and 30s from the Great Lakes into the northern Plains. South of the front dew points were in the 50s and 60s. && .SHORT TERM...(This Evening through Saturday) ISSUED AT 313 PM CDT Fri Apr 28 2017 Current radar trends show a period of dry weather late this afternoon across the southeast half of the area. This evening, the rain across the northwest half of the area will end but spotty light rain or drizzle will persist or move into the area from the southwest. After midnight, the question becomes how quickly will the atmosphere re-saturate under the persistent northeast flow off the lake. The current forecast has light rain moving back into the southern half of the area prior to sunrise. However, if the depth of the dry air is deeper than what the models depict, like today, then most areas south of I-80 could remain dry until sunrise Saturday. On Saturday, the first part of the main storm system moves into the area. Strong northeast flow will be seen across the area with rain overspreading the area during the morning. As lift increases in the late morning and afternoon hours, some embedded thunderstorms are expected to develop which will increase rainfall amounts across the southeast half of the area. The combination of clouds, rain, and northeast winds on Saturday will keep nearly all of the area in the 40s. The possible exception is south of a Galesburg, IL to Kahoka, MO line were temperatures may get just above 50 degrees. .LONG TERM...(Saturday Night through Friday) ISSUED AT 313 PM CDT Fri Apr 28 2017 Model trends remain fairly consistent, lending increased confidence to active weather through the weekend, featuring heavy rain, resulting river flooding and isolated short term flooding, and possibly a window of severe storms. Long term river flooding is discussed in detail below. Synoptic models still favor the southeast third of the forecast area for the heaviest rain axis, on the order of 3 to 4 inches. By Saturday night into Sunday, increasingly moist soils will make conditions prime for localized flash flooding from rain swollen creeks, streams and ditches. Heavy rainfall rates could also produce some significant street flooding. Most synoptic and convective allowing models support some potential for severe weather Sunday afternoon and evening as a surface low and warm front lift north through the area. There are still disagreements in the eventual path and timing of the low, but it is becoming increasingly clear that at least some portion of the forecast area, especially the southeast, will be at risk. Would not be surprised to see an upgrade from marginal to slight risk, at least in the south. Clouds may limit the amount of destabilization and areal coverage of severe storms, but even a modest amount of MUCAPE would support a QLCS wind/tornado threat given the strong shear and favorably aligned 0-3km shear vector. For Monday, a well-developed TROWAL will sustain lingering showers, with afternoon temps struggling to get out of the 40s. Tuesday through Friday, expect mainly quiet weather with near to slightly below normal temperatures. && .AVIATION...(For the 00Z TAFS through 00Z Saturday Evening) ISSUED AT 643 PM CDT Fri Apr 28 2017 Light rain along/n of I-80 will taper off this eve with exiting upper level wave, with some patchy drizzle lingering along with mvfr to local ifr conditions this evening. Overnight, I went with hrrr cig height trends which are verifying well and show gradual improvement to vfr all sites but BRL where kept mvfr conditions. On Saturday, anticipate next round of rain aided by isentropic ascent to overspread the terminals by mid morning through midday with conditions lowering to mvfr with pockets of ifr possible. Winds will remain northeasterly throughout the taf cycle at around 10-15 kts and turn gusty on Saturday. && .HYDROLOGY... Issued at 1141 AM CDT Fri Apr 28 2017 Updated morning forecast guidance from the North Central River Forecast Center now includes 72 hrs of QPF, through the bulk of the heavy rain event for the forecast area. Confidence is increasing on the potential for widespread heavy rain through the period. Parts of west central and northwest Illinois remain favored for the heaviest amounts, potentially 2 to 3 inches and locally higher. These amounts place the Illinois tribs and the Mississippi River south of the Quad Cities at the most risk of significant flooding. Moderate flooding is possible into next week on the Rock River, as well as the La Moine River, and the mainstem Mississippi from New Boston to Burlington. Other faster responding points in eastern Iowa will also be watched closely this weekend. There is still some uncertainty on the axis of heavy rain, and those with interests along area rivers, streams and creeks should check back for updates through the weekend. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ SYNOPSIS...08 SHORT TERM...08 LONG TERM...RP Kinney AVIATION...McClure HYDROLOGY...RP Kinney
Area Forecast Discussion
National Weather Service Wilmington NC
956 PM EDT Fri Apr 28 2017 .SYNOPSIS... High pressure will extend across the area from offshore through Sunday. Expect warm temperatures and isolated sea breeze showers or storms, mainly Sunday. The next cold front will bring a chance of showers and thunderstorms late Monday into early Tuesday. High pressure will follow for the mid-week period. Low pressure system may impact the region during Thursday with a soaking rain. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... As of 1000 PM Friday...It`s been fascinating watching the low clouds along the coast on 11-3.9 micron satellite imagery this evening. Low clouds from Myrtle Beach northward appear to eroding along the south edge, but clouds in the Georgetown vicinity are holding together a little better. Not even the HRRR model is good enough to forecast the movement of such a small mesoscale phenomenon, so I`ve attempted to manually extrapolate the cloud movement northward in the forecast grids over the next 4-6 hours as they spread inland but spare the immediate Cape Fear coastline. No significant changes to forecast low temperatures. Discussion from 630 PM follows... An unbelievably humid airmass for this early in the year covers the Carolinas. Dewpoints in the mid 70s are practically unheard of in April, and even with nearshore ocean water temperatures near record warm territory these dewpoints have generated areas of sea stratus and even sea fog earlier along the GA and SC coast. Inland cumulus should die away fairly quickly this evening with the loss of daytime heating. It`s a little more uncertain how clouds will respond near the coast: very humid air streaming onshore will experience frictional/speed convergence which could maintain a very low stratocumulus deck affecting Georgetown, Myrtle Beach, and Wilmington through the evening hours. Precipitation appears unlikely overnight as the depth of our moisture is very limited and will be capped off by warm and very dry air aloft. Lows tonight will run at least 15 degrees above normal for the date with 69-74 expected, coolest inland. Climate note: Wilmington`s low temperature so far today has been 74 degrees. Assuming we don`t drop below 74 between now and midnight standard time (1 AM daylight time) this will establish a new all-time record warm low temperature for the month of April in Wilmington. Records extend back to the year 1874. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY NIGHT/... Saturday and Sunday: The synoptic pattern will be dominated by deep layered subtropical ridging with the region positioned just to the west of the 850-500 hPa anticyclone. Modified forecast soundings for both Saturday and Sunday show pronounced capping with only the far interior west of I-95 becoming uncapped for about 1-2 hours with the sea breeze. Given lower tropospheric moisture looks pretty meager outside of the boundary layer, prefer to go with a dry forecast for both days. Temperatures will remain above normal with highs ranging form the lower 90s well inland to around 80 at the beaches. Lows Sunday morning will range from the upper 60s inland to the lower 70s at the beaches. Monday: A cold front will approach from the west Monday as high pressure shifts farther offshore and a powerful storm system moves into the upper Mississippi Valley. Moisture return ahead of the front looks solid with taps noted from off the Gulf of Mexico and Atlantic. Although the upper low and the core of the strongest forcing looks to pass well to the north, there will be enough to support a broad swath of showers/tstms across the frontal zone. Pops will be increased to 70% for most zones Monday night as the front sweeps offshore. Highs will warm into the lower-mid 80s away from the beaches Monday afternoon with lows Tuesday morning ranging from the upper 50s well inland to the mid 60s at the beaches. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Surface and mid level ridge will weaken and drift east Mon, allowing a cold front to approach from the W. Low pressure and associated strong dynamics and upper level support will be well dislocated from the Carolinas as a cold front moves across the area Mon night. This suggests convection weakening as it moves into the eastern Carolinas. Current timing brings the likelihood for showers and thunderstorms later Mon and Mon night. As the front moves off the coast Tue morning, high pressure along the Gulf Coast will slide east and then offshore to our S during Wed. This should bring a dry period. Deep low pressure will move out of the mid south and Gulf coast states Wed, lifting slowly to the NE. Its associated cold front will move into the Southeast states Thu-Thu night, bringing the risk for robust thunderstorms. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... As of 00Z Saturday...Low confidence forecast with cloud heights along the coast over the next several hours as we transition from day to night. Very rich low level moisture streaming onshore has supported MVFR/IFR ceilings along the coast of the Carolinas this afternoon. While the moisture will remain overnight, the loss of daytime heating could cause an erosion of this cloud cover -- but to what degree is unknown. The last few visible satellite images show fairly solid low cloud cover extending from Charleston and Georgetown which should move northward along the coast now through 06Z. Forecasts are for IFR ceilings to perhaps improve to MVFR temporarily in the MYR/CRE area after 02Z, but confidence in low. At least scattered low clouds below 1000 feet AGL will persist all night even if ceilings do not develop. Models even suggest after 06Z enough moisture will push inland that FLO and LBT could see some scattered low clouds develop. VFR conditions should develop after daybreak. Extended outlook...Periods of IFR/MVFR conditions are possible in showers and thunderstorms late Monday into early Tuesday. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1000 PM Friday...The seabreeze has died away leaving winds mainly in the 10-13 knot range which should persist overnight. No significant changes are needed to the forecast. Discussion from 630 PM follows... South winds across the coastal waters have been strongest nearshore for the afternoon with the seabreeze. Farther offshore winds are barely 10 knots at the Frying Pan Shoals buoy and the Edisto buoy east of Charleston. Once the seabreeze dies away expect a very warm and humid onshore flow to continue overnight. Although we don`t expect true sea fog to develop, periods of low stratus clouds and hazy visibilities in the 2-4 mile range are possible. SHORT TERM /SATURDAY THROUGH MONDAY/... As of 300 PM Friday...Southerly wind regime will persist through Monday as the region remains along the western flanks of Atlantic high pressure centered well offshore. Speeds will generally remain 10-15 kt through the period, except Sunday Night into Monday where speeds increase to 15-20 kt and 20-25 kt Monday night as low-level jetting and a tightening pressure gradient settle in ahead of a cold front. Seas will slowly build over the weekend, peaking 5-7 ft by Monday night ahead of the cold front. A Small Craft Advisory could be needed as early as Monday morning. LONG TERM /TUESDAY THROUGH WEDNESDAY/... As of 300 PM Friday...In the wake of the cold frontal passage early Tuesday, offshore winds will slowly diminish. The offshore trajectories will knock seas down and should drop below Small Craft Advisory levels by Tuesday afternoon. There are no concerns for Wednesday into Thursday. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...Coastal Flood Advisory until 2 AM EDT Saturday for NCZ107. MARINE...None. && $$ SYNOPSIS...99/CHS NEAR TERM...TRA SHORT TERM...99/CHS LONG TERM...99/CHS AVIATION...TRA
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
859 PM CDT Fri Apr 28 2017 .UPDATE... 859 PM CDT For Evening Update: Minor adjustments to going forecast this evening, mainly to refine pops based on radar trends. Generally, only light showers over far north/northwest and far south/southeast parts of of the FA expected. Evening surface analysis depicts a stationary frontal boundary from southern IL/IN...extending southwest to low pressure over west Texas. Scattered thunderstorm clusters were occurring along the front well south of the area this evening. Farther north, 925-850 mb obs indicate an elevated frontal zone from KS into northwest IL and southern WI. Showers were occurring with a pair of low-amplitude short wave disturbances, mainly north of and southeast of the cwa, with a minimal in precip across the forecast area in a region of weak warm/moist advection and isentropic ascent though with little forcing. 3km WRF and HRRR seem to be capturing the general character of the precip fields and trends, which suggest maintaining some low-chance pops for some spotty light rain across the far north and far south parts of the area this evening. Guidance does depict a sheared mid-level wave approaching from the southwest toward morning which looks to increase precip potential across the southern tier or two of WFO LOT counties toward sunrise, but otherwise little in the way of significant rainfall is expected overnight. Most guidance is in good agreement in spreading rainfall northeast across the forecast area mid-late Saturday morning, with another low-amplitude short wave rippling along the elevated baroclinic zone across the area. Will have to watch convective development north of the surface front overnight however, which may tend to block some of the stronger moisture transport into northern IL and IN. Stout northeast winds develop by early Saturday as well, which will also work to maintain a feed of drier low level air into the region. While periods of rain on Saturday are a good bet, these factors may help initially reduce heavy rainfall threat somewhat. Ratzer && .SHORT TERM... 305 PM CDT Through Saturday... Concerns through Saturday are with moderate to potentially heavy rainfall beginning Saturday afternoon. A Flash Flood Watch has been issued from Saturday afternoon through the rest of the weekend. Light rain has struggled to become widespread across the area with this initial mid-level disturbance and start to isentropic ascent, due to weak forcing for lift and inherent low-level dry air. Spotty light showers should continue through early evening, with likely a wedge in the central CWA with little to no rain. As gradual cyclogenesis occurs across the southern Plains tonight, the synoptic boundary (initial warm front) that is located just north of I-80, will start to collapse southward with northeast winds slowly increasing. While a spotty light shower or two through the rest of tonight cannot be ruled out, a general lull in forcing is expected with focus well to the southwest of the immediate area. As the frontal zone to the south develops warm frontal characteristics on Saturday morning, it will start to slowly progress northward. The low-level northeast flow will initially be problematic for rain, but this should be overcome from south-to- north during the afternoon. Just how quickly this occurs will hinge heavily on amount of convection to the south robbing moisture transport. If slower, rain may not begin in the far north until late day or even early evening. Confidence in rainfall amounts for Saturday afternoon is somewhat low, especially the northern half of the CWA, and it could end up being lower during that period. MTF && .LONG TERM... 251 PM CDT Saturday night through Friday... The potential for copious amounts of rain still exists for Saturday night in particular, and continuing into Sunday. However, still have concerns that convection to our south will result in less moisture and rainfall than the models are currently predicting. While models may be too high on specific precipitation forecasts, still have enough confidence to go with a Flash Flood Watch for areas along and east of the I-55 corridor Saturday afternoon through Sunday night. Saturday night...The surface low organizes over southeast Missouri with its warm front remaining just south of the forecast area. Expecting moisture to pool across central and northern IL and northwest IN, mainly along and east of I-55. However, have serious concerns about how much moisture will actually pool in this area. Convection to the south may hog some of the forecasted moisture leading to less moisture/rainfall than forecast. Current forecasts feature 1.5 to around 1.8 inches of PWAT, well above normal for this time of year. Given my concerns, went with lower forecasted rainfall than many of the models would suggest. Either way, expecting widespread rainfall across the region Saturday night. Will keep a chance of embedded thunder in the forecast since the saturated soundings still feature a little elevated CAPE. Thinking the better coverage of thunderstorms will be also along and east of I-55, but will keep a chance along and south of I-88. Sunday...Rain continues as the warm front lifts north to either the I-80 to I-88 corridor. PWAT values are still forecast to remain over 1.5 inches so the threat of heavy rain will continue. Agree with SPC`s Day 3 outlook for our area. Have low confidence in severe storm coverage and strength because I am unsure how well and quickly the atmosphere will recover from Saturday night`s rainfall. In addition, cloud cover may limit CAPE values. If we get get breaks in sun and are able to recover, strong to severe storms are expected. Shear values will be 60-80 kt. CAPE values will likely be highest south of I-80 and forecast values range from 500-1000 J/kg in the GFS to 1000-2000 J/kg in the typically overly aggressive NAM. Therefore, will lean more toward the GFS` solution. If strong to severe storms form, expecting discrete storms. Severity of threats will depend on how much CAPE we have to work with, but all severe types and flooding are possible with the storms. Have low confidence in high temps Sunday as any breaks in clouds will likely lead to higher temperatures than forecast especially south of the warm front. Sunday night.... The low`s cold front moves through Sunday evening and night and expecting storms to consolidate along the front leading to additional rainfall. Monday through Friday... Cooler air arrives with the upper level trough early next week leading to highs in the 50s most of next week. Light wrap around showers are expected Monday as the upper level low rotates over the region. While we do not need more rain, rainfall amounts should be minimal. Monday also looks gusty with southwest winds gusting to around 30-35 MPH. Rain finally moves out and high pressure moves in Tuesday, and we may even see a little sunshine! The high should keep rainfall associated with the next low off to our southeast, but the GFS has the precip clipping the southeast corner of the forecast area. Have low confidence in whether the showers will reach the forecast area or not. JEE && .AVIATION... For the 00Z TAFs... Period of MVFR cigs expected this evening with potential for some lifting of cigs back to VFR later tonight as some drier low level air advects in from the northeast. First, wave of rain is expected to move into the area midday Saturday with cigs likely quickly falling back to MVFR. Steadiest moderate rain expected Saturday afternoon with some abatement in the rain looking possible toward evening and continuing into Saturday evening. Cigs expected to continue to fall to IFR Saturday evening with some drizzle or light rain possible. Northeast winds will begin to pick up late tonight, but should grow increasingly strong and gusty Saturday, with occasional gusts around 30kt by afternoon and continuing into the evening. Izzi && .MARINE... 251 PM CDT Headlines...Will continue the Small Craft Advisory for late tonight into Sunday afternoon. While gales are possible over the southern half of the lake Saturday evening, I think it will be a brief 5 hour window that will not need a watch at this point. However, I did have enough confidence to issue a gale watch for the northern half of the lake Sunday afternoon into Monday morning. Weak high pressure shifts southeast this evening and winds become north to northeast. Winds increase as the gradient tightens between a high building over south central Canada and low pressure taking shape over the southern plains. Guidance differs on whether the gradient will be strong enough to support low end gales over the southern end of the lake Saturday afternoon and evening. As the low shifts north to Iowa Sunday afternoon, the area of stronger winds also shifts north. Have higher confidence in gales occurring over the northern end of the lake Sunday afternoon into Monday morning, so decided to go with a gale watch. The low moves over the northern end of the lake late Monday night/early Tuesday morning along with the low`s cold front. Winds become west behind the front with at least 30 kt expected. Another Small Craft Advisory will likely be needed Monday and Tuesday. There is a chance that low end gales may occur over the southern half of the lake but confidence is medium-low given differences in model solutions. The low continues to Quebec Tuesday night followed by high pressure building over the lake Wednesday night into Thursday. JEE && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Flash Flood Watch...ILZ014-ILZ021-ILZ022-ILZ023-ILZ032-ILZ033- ILZ039...1 PM Saturday to 7 AM Monday. IN...Flash Flood Watch...INZ001-INZ002-INZ010-INZ011-INZ019...1 PM Saturday to 7 AM Monday. LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744- LMZ745...4 AM Saturday to 4 PM Sunday. && $$ 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
National Weather Service Saint Louis MO
932 PM CDT Fri Apr 28 2017 .UPDATE... Issued at 932 PM CDT Fri Apr 28 2017 Two surface frontal boundaries exist over our region this evening. The northern one extends from near Chicago southwestward to Quincy and to near Sedalia. This has not moved much over the past few hours and if CAA and pressure rise trends are any indication, is undergoing frontolysis and will dissolve soon. The second frontal boundary is southeast of our CWA and extends from just north of Evansville, IN to just south of Cape Girardeau to near Poplar Bluff. It is this front that will soon become the main front as its northern cousin dissipates. The 00z NAM as well as the various iterations of the HRRR models continue to support the instability axis across southern MO and far southern IL. While thunderstorm coverage, currently growing in southeast MO and southern IL, will continue to increase and expand northward, it is over the nearly stationary instability axis in the southern CWA where the greatest threat for excessive rain will be along with an isolated severe storm which will probably tend to favor hail as the primary severe threat. The northward expansion of the pcpn later tonight will be courtesy of the southern front (by this time...just "the front") buckling back to the northwest in response to a strong low pressure wave approaching from the southwest. It is how far this front buckles back to the northwest which will decide how this forecast evolves on Saturday, particularly in the afternoon and evening. Current model depictions generally favor the front getting thru STL metro, but not much more, but there remains an unusually large spread despite this being within a 24hr forecast. This should enable pcpn to expand into STL metro later tonight and into much of central MO with little problem, but questionable on whether it reaches UIN before 12z/Sat. Instability for thunder will also tend to lag the northward expansion of pcpn. All in all, the overall forecast remains in play, with increasing rain chances and main initial flood threat in the south--expanding northward after daybreak on Saturday. TES && .SHORT TERM... (Through Late Saturday Afternoon) Issued at 339 PM CDT Fri Apr 28 2017 Showers and thunderstorms that are ongoing over southwest and south central IL are occurring in association with a region of elevated CAPE, and lift via a south-southwesterly LLJ and migratory impulse in the southwest flow aloft. Present indications are this activity will continue to move east and exit the CWA before 00Z in association with continued eastward motion of the upper level disturbance. Thereafter there may be a rather tranquil period until late this evening. The wavy warm front currently extends from western KY through the bootheel curving southwest through AR into eastern OK. This front is expected to lift slowly northward and become better defined across the far southern CWA - southeast MO and southern IL tonight. Late this evening, another impulse currently located in KS will translate across the region providing some large scale ascent. More importantly the broad and stout southwesterly LLJ is expected to result in strong lift along the broad frontal zone, with the ascent primarily focused along the front and into the cool sector. This is expected to result in widespread thunderstorm development from 03-06Z across southern MO and southern IL. Attendant with these storms will be a threat of large hail, as well as heavy rainfall/flash flooding giving there west-east alignment and high rainfall rate and training potential. The axis of storms and the northward and growing adjoining stratiform rain region should then gradually spread northward through the overnight hours with the strongest storms shifting to the east into the OH Valley region. A stormy and volatile period is expected on Saturday with potential for both severe weather as well as heavy rain and flash flooding. There remains uncertainty in the specifics that we probably won`t be able to nail down until as we get much closer. The overall scenario has the mid/upper flow continuing to back and become more south- southwesterly as the upper low/trof shift across the southern/central Rockies into the Plains. The next result is the warm front will lift northward through central/eastern MO and southern IL during the day as a surface low tracks into eastern OK. The result will be an expanding unstable warm sector and therefore risk of surface-based storms with attendant hail and damaging wind threats. Complicating the whole scenario is an ongoing MCS will move from western MO and into central MO during the late morning and then across the remainder of the CWA during the afternoon hours. Current thinking is that while WAA generated showers and storms will be possible at just about anytime, this anticipated MCS will re- energize by afternoon and pose a greater severe weather threat as it taps the instability of the expanding warm sector. A very moist air mass with PWs greater than 200% of normal will promote high rainfall rates and any locations seeing longevity of storms and training will have a heightened flash flood threat. Glass .LONG TERM... (Saturday Night through Next Friday) Issued at 339 PM CDT Fri Apr 28 2017 Saturday night, upper low to continue lifting northeast out of southern Plains into region, which will begin to lift warm front back to the north inconjunction with deepening surface low. Strong low level jet will pull in plenty of moisture, so continue to see PWs in excess of 1.5 inches, with some models indicating close to PWs around 2 inches. Will see several rounds of showers and storms Saturday night through Sunday. Model differences on location of main axis of highest qpf still a problem with NAM the furthest north. Will keep superblend solution, which is a bit further north than yesterday and a bit less than the WPC qpf. As for chances of severe weather, strong to severe storms possible, especially over east central/southeast MO and southwestern IL Saturday night. By Sunday as surface low moves due north over western MO, warm front to slide north of forecast area, while surface low drags cold front through region during the afternoon and early evening hours. So dry slot to move in behind cold front with precipitation tapering off towards Midnight Sunday. Strong to severe chances look best over southeast MO and far southern IL. Storm total qpf still looks to be between 3 and 5 inches with the highest amounts extending along the I-44 corridor in MO and I-55 corridor in IL. This could lead to a significant hydrologic event with moderate to major flooding occurring on a number of river basins. Flash flood watch to remain in effect through 06z Monday, though have added a few more counties along the northern side of the watch. Will see wrap around showers on backside of system late Sunday night through Monday. Beyond that, another brief break in the precipitation before next system moves Tuesday night through Thursday night. Extended models having differences in timing and placement with this system, so went with a blend for now. Otherwise, coolest temps will be on Monday with highs in the 50 to 60 degree range, then moderate back into the 60s for the remainder of the forecast period. Byrd && .AVIATION... (For the 00z TAFs through 00z Saturday Evening) Issued at 652 PM CDT Fri Apr 28 2017 IFR conditions are expected to prevail for the TAF sites for much of the valid period, especially as a frontal boundary digs in to the southeast and allows low CIGs to become more widespread and lower. Rain will increase from the south later tonight and, once it moves in, will be difficult to completely dislodge from the area and as a result was very difficult to find a break for the TAFs. Looks like the best opportunity for a break from the rain will be for the STL metro sites from late morning until late afternoon as the frontal boundary lifts northward and should also allow for an improvement in conditions to MVFR or perhaps VFR. Surface winds will be NE north of the front and will begin to become oriented this way this evening and will veer southerly when the front pushes north thru STL metro later on Saturday. Winds will also become gusty later tonight and Saturday as the storm system to the west winds up. TES && .LSX WATCHES/WARNINGS/ADVISORIES... MO...Flash Flood Watch through late Sunday night for Audrain MO-Boone MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO- Iron MO-Jefferson MO-Lincoln MO-Madison MO-Moniteau MO- Monroe MO-Montgomery MO-Osage MO-Pike MO-Ralls MO-Reynolds MO-Saint Charles MO-Saint Francois MO-Saint Louis City MO- Saint Louis MO-Sainte Genevieve MO-Warren MO-Washington MO. IL...Flash Flood Watch through late Sunday night for Bond IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-Jersey IL-Macoupin IL- Madison IL-Marion IL-Monroe IL-Montgomery IL-Pike IL- Randolph IL-Saint Clair IL-Washington IL. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
936 PM EDT Fri Apr 28 2017 .SYNOPSIS... High pressure will persist over Bermuda into Tuesday. A stationary front will linger over southern Pennsylvania late tonight through Saturday before lifting north Sunday. A stronger cold front will move across the region from the west Monday night. Canadian high pressure will then build over the area through the midweek. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... As of 9pm, low pressure is over the Big Bend region of Texas with a warm/stationary front extending NE across the Ohio valley and reaching the eastern West Virginia panhandle. Severe convective storms have developed on the north side of this front along the Ohio River valley and will move northeast through the night. Instability increases and bulk shear remains high through the night. This should allow strong to possibly locally severe thunderstorms to move along this front late tonight. This puts the northern third of the CWA at risk. Height rises associated with warm air advection should make the activity elevated with hail as the primary threat. SPC has expanded the marginal risk for this area and our hazardous weather outlook mentions this threat for this area as well. This will continue to be monitored through the night. 00Z HRRR continues recent trend of perhaps two rounds of convection, one late tonight and the second toward daybreak. This is climatologically the minimum in thunderstorm activity, but not unheard of. Lows primarily in the 60s, but the cities may not drop below 70. This has never happened before in DC (in April) - record high min is 69 set in 1896. The year 1896 holds the record high min for Baltimore for five consecutive nights in April. They dropped only to 70 on April 19, 1896. See climate section for more information. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... "Hot" will be the operative word for Saturday as high pressure moves off the southeast coast and pumps warm air into the Mid Atlantic. Again, see the climate section below for high temperature records - these will definitely be in jeopardy. Heat indices will be in the low/mid 90s in the I-95 corridor, nowhere near heat advisory levels but notable for April. Continued warm temperatures Saturday night/Sunday. There is not any real trigger for organized convection approaching, but this is somewhat of a summertime pattern. Hence it is not out of line to see orographically driven storms develop Sunday afternoon. The best thunderstorm chances hold off until Monday. && .LONG TERM /MONDAY THROUGH FRIDAY/... A cold front over the eastern Ohio Valley early Monday will move across the region Monday into Monday night. Showers and thunderstorms, some strong, will develop ahead of and along the cold front Monday afternoon and evening. Temperatures will be about 15 degrees above normal. Weak high pressure will build in behind the cold front Tuesday. A gusty westerly breeze will usher in drier air. Temperatures will not be as warm as Monday, but could still be 5 to 10 degrees above normal. As the high moves east, a secondary cold front will move across the region from the northwest Tuesday night. This front should be a dry front. The front could sag into the Carolinas Tuesday night before starting to move northward as a warm front on Wednesday. A low pressure system is expected to develop along the western end of the warm front over the Lower Mississippi Valley Wednesday night and early Thursday. We introduce a slight chance of showers or a rumble of thunder Wednesday night with a higher chance to likelihood of encountering showers and thunderstorm Thursday through early Friday. At the tail-end of an associated cold front with the storm system, another storm system could develop and deepen over the interior Southeast U.S. Friday and Friday night. The chance of showers and thunderstorms will linger during the period. Temperatures will also be closer to normal Friday and Friday night. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... VFR conditions prevail tonight through Sunday night. A few thunderstorms possible overnight with MRB being the main consideration though VCTS for IAD and BWI/MTN were also warranted. Ifr to lifr conditions possible Monday and Monday night from thunderstorms associated with a strong cold front moving through. Vfr conditions Tuesday and Tuesday night. Winds south- southwest 10 to 15 knots Monday, becoming southwest around 10 knots Monday night, then west- southwest 10 to 15 knots Tuesday, and west 5 to 10 knots Tuesday night. && .MARINE... Light southerly flow, below SCA values, tonight through Saturday night. Isolated thunderstorms possible on the northern part of the Bay late tonight into Saturday and on all of the waters Sunday. Small craft advisories likely Monday as south winds increase ahead of a cold front Monday night. Small craft advisories possible Monday night and Tuesday with the frontal passage. No marine hazards Tuesday night. Winds south 10 to 20 knots gusts 25 knots Monday, becoming southwest 10 knots Monday night, then west- southwest 10 to 15 knots Tuesday, and west 10 knots Tuesday night. && .TIDES/COASTAL FLOODING... Tidal anamolies are expected to decrease slightly over the next several days as wind flow decreases. However, return of southerly flow later today into the weekend will keep anamolies elevated. && .CLIMATE... Record highs/warm lows through the weekend: Washington DC... Saturday 29 April...91 (in 1974)/68 (in 1956) Sunday 30 April...92 (in 1942)/67 (in 1983) BWI Airport... Saturday 29 April...91 (in 1974)/67 (in 1956) Sunday 30 April...92 (in 1910)/63 (in 1983) Dulles Airport.. Saturday 29 April...87 (in 1996)/62 (in 1996) Sunday 30 April...86 (in 2007)/64 (in 1983) && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ Update...Jackson Previous...Woody!/KLW
Area Forecast Discussion...UPDATED
National Weather Service Little Rock AR
610 PM CDT Fri Apr 28 2017 .DISCUSSION... Updated to include the 00Z aviation discussion below... && .AVIATION... A warm front remains across the state early this Fri evening...with some MVFR CIGs ongoing at the NRN terminals. Along and south of this front...VFR conditions are ongoing. As time goes on this evening...some SHRA/TSRA will become possible along and south of this front early in the period. Then as the front lifts north...expect the chances for SHRA/TSRA to shift north as the central/SRN terminals a break. NRN terminals will see some precip chances remain through most of this TAF period. Chances for precip will return for the central/SRN terminals by late morning/early afternoon Sat. && .PREV DISCUSSION...(ISSUED 250 PM CDT Fri Apr 28 2017) SHORT TERM...Tonight Through Sunday There haven`t been any significant changes made to the going forecast. The initial onslaught of heavy rain is forecast to begin tonight as the warm front lifts into northern Arkansas, with convection along the stalled boundary continuing through the day Saturday. Eventually as the upper support well to the west of Arkansas shifts east into the southern plains tonight and Saturday the cold front with this system will get legs and move east into the state. This would be primarily tomorrow evening and into the overnight hours Saturday night. There remains some uncertainty with regard to rainfall amounts and severe weather chances. First, the warm front has been forecast to shift into northern Arkansas this afternoon and evening, with convective initiation late this evening in the northwest parts of the state before spreading across all of northern Arkansas during the nighttime hours. There is some indication that the front will remain hung up in the Ouachitas this afternoon and that convective initiation will occur in the western parts of the state before shifting north tonight. If this occurs, model soundings are supportive of very strong updrafts with the potential for large hail, damaging winds, and even a tornadic threat. Only time will tell, but the GFS as well as the convection-allowing HRRR indicate this will be a possibility. Otherwise the remainder of this event seems fairly straight forward, with the main opportunity of heavy rains and severe weather being along/ahead of the cold front as it moves through tomorrow. Regarding rainfall, totals have been trimmed back slightly, but storm total amounts in excess of 5" seem very likely across northern and northwestern Arkansas. Given the convection aspect of this event, I would not be surprised to see some rainfall totals in the +7-8" range pop up in the Ozarks, but this will be more of an exception. Given the setup, especially given the near-record PWAT values forecast with the stronger forcing along the cold front tomorrow evening, flash flooding and river flooding still seem to be a significant threat. Will continue with a Flash Flood Watch to cover this. Precip will come to an end Sunday morning as the front exits the state. Dry conditions will then round out the short term period. LONG TERM...Sunday Night Through Friday Drier air wl be overspreading the area as the aforementioned storm system departs the region. Some wrap-around moisture wl traverse the NW part of AR late Sun night and early Mon, producing some assocd cloud cover. NWLY flow aloft is expected to prevail thru the middle of the week, with dry conds expected thru Tue. Temps wl hover near or slightly below normal lvls. A new storm system wl bring the next rain chance to AR Wed thru Thu. Drier and cooler conditions wl return for late next week. && .LZK Watches/Warnings/Advisories... Lake Wind Advisory from 10 AM Saturday to 9 PM CDT Sunday FOR Arkansas-Bradley-Calhoun-Clark-Cleveland-Dallas-Desha-Drew-Grant- Hot Spring-Independence-Jackson-Jefferson-Lincoln-Lonoke-Monroe- Ouachita-Prairie-Pulaski-Saline-Sharp-White-Woodruff. Flash Flood Watch through Sunday evening FOR Arkansas-Baxter- Boone-Clark-Cleburne-Conway-Dallas-Faulkner-Fulton-Garland-Grant- Hot Spring-Independence-Izard-Jackson-Jefferson-Johnson-Logan- Lonoke-Marion-Monroe-Montgomery-Newton-Perry-Pike-Polk-Pope- Prairie-Pulaski-Saline-Scott-Searcy-Sharp-Stone-Van Buren-White- Woodruff-Yell. && $$ Aviation...62
Area Forecast Discussion
National Weather Service Spokane WA
445 PM PDT Fri Apr 28 2017 .SYNOPSIS... Scattered showers will bring brief periods of rain and possibly graupel to north Idaho and northeast Washington this afternoon and evening. The majority of Saturday should be dry before a frontal system brings the potential for rain Saturday night and gusty winds for Sunday. The middle of next week will be warm with afternoon temperatures in the 60s to near 70 degrees. && .DISCUSSION... Tonight: Scattered rain and graupel showers will produce brief periods of precipitation this evening over the Idaho Panhandle and northeast Washington. As of 230 PM, regional radar showed showers under a 500mb cold pool (-27C to -28C) extending from Republic to Davenport to Couer d`Alene to Sandpoint. RAP analysis suggests up to 400 J/Kg of surface based CAPE over northeast Washington and far north Idaho. There may be enough instability for a few lightning strikes, but without a clearly defined shortwave kicker to enhance lift, it is doubtful that any thunderstorms will become very organized. By mid to late evening, upper level high pressure will build over the Inland Northwest. The loss of surface heating combined with warming aloft should cause most showers to dissipate by 8 PM. It will be a chilly night with most areas dropping into the 30s, under clearing skies and light winds. Saturday: The majority of the Inland Northwest will be dry on Saturday. The influx of moisture ahead of a frontal system will bring increasing chances for showers to the northern Cascades in the afternoon and evening, but the rest of our region will start the day with some sunshine followed by increasing mid and high clouds. Rain chances will likely peak after midnight Saturday. The GFS, NAM and ECMWF are in good agreement that a cold front will cross the Cascades overnight. The front will be accompanied by a good deal of mid-level westerly flow which favors precipitation over the Cascade Crest, the mountains of north Idaho and far northeast Washington. The models suggest up to a quarter of an inch in the Panhandle mountains with most of our region getting less than a tenth. At this time, the Columbia Basin and Wenatchee area look to get sprinkles at best. Sunday and Monday: Sunday will be breezy behind Saturday night`s cold front. Wenatchee to Mose Lake to Spokane and Pullman will likely experience sustained west winds of 15 to 20 mph with gusts to 30 mph for much of the day. Convective showers during the day Sunday should be the most concentrated over the mountainous terrain of the Idaho Panhandle and the Cascade Crest. Low chances for showers have been included in places like Lewiston, Pullman, Spokane, and Colville, but any showers in these lowland communities should be brief. Monday will be less windy, but chances for showers are in the forecast. The GFS, ECMWF, NAM, and Canadian models depict a fast moving shortwave trough. Again, mid-level westerlies should produce a rain shadow on Monday and limit showers to the mountainous terrain of the Panhandle, Northeast Washington, and the Cascade Crest. /GKoch Monday Night through Friday: Northwest flow aloft is expected Monday night as a weather disturbance moves across eastern WA and north ID. Have increased our chance of precipitation during the evening hours across the south central ID Panhandle. Kept a mention of showers in the overnight hrs into Tuesday as the disturbance exits. Tuesday night through Thursday will be be dry as an upper level ridge builds into the area. 850 mb temperatures warm to 15-16C late Thursday. Wednesday we will see temps 3-6 degrees above average, and Thursday 6-9 degrees above average. Current forecast for Spokane next Thursday is 71. We haven`t seen temps above 70 since last Sept 30th, when we were 75! Thursday night onward there is very low confidence in the forecast. The models all have differing solutions in how to break down the ridge. Currently don`t doubt the breakdown of the ridge as this spring`s weather patten has been progressive... However all models have differing timing, strength and placement of a trough moving into the Pac NW. Have kept mention of showers in for eastern WA and north ID with a dry area across the Columbia Basin. Expect this forecast to change as models hopefully come more in line with the breakdown of the ridge. /Nisbet && .AVIATION... 00Z TAFS: Isolated showers and thunderstorms moving to the southeast at around 15 mph are on the decline this evening with most of the activity ending before 06Z Saturday. Weak high pressure then moves in to allow the remainder of the overnight and daytime hours Saturday to remain dry with VFR conditions prevailing. /Pelatti && .PRELIMINARY POINT TEMPS/POPS... Spokane 37 57 44 58 37 55 / 20 0 60 20 10 10 Coeur d`Alene 36 57 42 56 35 54 / 30 10 80 40 10 20 Pullman 38 59 45 58 37 55 / 20 0 70 40 10 10 Lewiston 41 65 49 64 42 60 / 10 0 40 40 10 10 Colville 36 58 42 60 37 56 / 20 10 30 20 0 30 Sandpoint 34 56 40 54 34 53 / 20 10 80 80 20 30 Kellogg 35 55 40 52 35 51 / 30 10 90 90 20 30 Moses Lake 37 63 47 66 40 63 / 0 0 10 10 0 10 Wenatchee 40 60 45 62 41 60 / 0 0 10 10 0 10 Omak 37 61 45 65 40 62 / 10 0 10 10 0 10 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$
Area Forecast Discussion
National Weather Service Norman OK
1052 PM CDT Fri Apr 28 2017 .DISCUSSION... && .AVIATION... Thunderstorms will form and move across southwestern and central Oklahoma early Saturday. Some will likely produce very large hail and damaging winds. Heavy rainfall will occur in a subsequent large area of rain and thunderstorms from central Oklahoma eastward along a slowly-moving front. Gusty north and northeast winds will keep MVFR and IFR ceilings during the day Saturday. && .PREV DISCUSSION... /issued 723 PM CDT Fri Apr 28 2017/ DISCUSSION... AVIATION... Thunderstorms are expected to begin late this evening in southern and western Oklahoma and move across central Oklahoma during the early morning Saturday. Heavy rainfall will occuring along a slowly-moving front Saturday morning. Gusty north and northeast winds will bring MVFR and IFR ceilings during the day Saturday. PREV DISCUSSION... /issued 406 PM CDT Fri Apr 28 2017/ DISCUSSION... A warm layer and weak ridging aloft have helped prevent the formation of thunderstorms, and this will likely continue to inhibit storms until about 8 pm or so. Wide variations in severe weather threats will cover our forecast area this evening, as there will be large differences in vertical wind shear and CAPE, along with several weak surface boundaries. The short-range convective models show storms beginning to form around 8 pm near a weak surface boundary roughly from Hobart to Oklahoma City. These storms may become severe quickly, as they will be in an area of strong shear and moderate CAPE. Storms should gradually diminish (but still have substantial severe weather potential) through the night, remaining mainly near the original line of development. THere is also a possibility of an MCS forming from convection in northwest Oklahoma. In any case, strong to severe storms will be possible across central and southwest Oklahoma through most of the night. Heavy rain is expected with these storms, and training of cells is likely, which could cause areas of rapid flooding. We extended our previous Flood Watch west by three counties this morning, based on the synoptic situation and the output of the models at the time. There are indications from the HRRR and others that substantial rainfall may occur a short distance west and north of our new watch, but those areas generally have higher flash flood guidance. This forecast issuance does not include any new changes to the watch, but the evening shift will, of course, make any necessary adjustments if model trends or convective trends suggest a different outcome. A very sharp cold front will move through the southeast half of Oklahoma and into north Texas tomorrow. Most severe storms will remain along and ahead of this front. The entire assembly should exit our forecast area by midnight Saturday night. However, instability under the upper low will continue a chance for showers and perhaps a few thunderstorms into Sunday. The wraparound precipitation area may include some snow mixed with the rain in far northwest Oklahoma Sunday morning. Monday will be a rain-free day, then another storm system will arrive for midweek, bringing additional chances for showers and a few thunderstorms. CmS && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 55 57 44 54 / 70 80 60 20 Hobart OK 48 50 40 54 / 70 70 50 20 Wichita Falls TX 58 61 44 62 / 40 70 50 10 Gage OK 43 45 35 46 / 90 70 60 50 Ponca City OK 50 53 44 51 / 90 80 70 50 Durant OK 70 80 50 63 / 40 80 70 20 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...Flood Watch through Sunday morning for OKZ023>032-040>043- 046>048-050>052. TX...None. && $$ 25/09/09