Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/22/17


Area Forecast Discussion
National Weather Service Wakefield VA
956 PM EDT Mon Aug 21 2017 .SYNOPSIS... High pressure becomes centered off the Mid Atlantic coast through Tuesday. A cold front crosses the area late Wednesday, with strong high pressure building north of the area from Thursday into the upcoming weekend. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Update...Showers and storms from earlier this evening have all but dissipated with the loss of daytime heating and instability. Have trimmed POPs back accordingly and made minor adjustments to dewpoints that are running a degree or two warmer. Otherwise, forecast is on track for stratus and potential fog development overnight. Previous discussion (410 PM)... Latest surface analysis centers ~1023mb high pressure just offshore, resulting in light south to southeast flow over the local area. A weak wave visible on water vapor and in the RAP analysis is located over the Delmarva this afternoon. The wave coupled with increasing moisture, afternoon destabilization, and a lee/thermal trough over the northern Piedmont has helped fire off scattered showers and thunderstorms generally north and west of Richmond. Overall storm strength has been limited due to westerly flow and modest lapse rates. However, cannot rule out some gusty winds and brief heavy downpours. Showers and thunderstorms push northeast through the afternoon and into the evening hours as the wave pushes offshore. Coverage wanes tonight with the loss of daytime heating/destabilization and upper level support. Warm and humid tonight with lows mainly 70-75 F tonight. Fog/stratus possible again tonight over the Piedmont into central Virginia, but not expected to be as dense as this morning. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/... Increasing return flow on the back side of departing high pressure and ahead of an approaching cold front will result in warm and humid conditions Tuesday. Highs generally in the low to mid 90`s, cooler along the coast. Dewpoints in the upper 60`s to low 70`s will produce heat indices in the 100 to 103 degree range. While the atmosphere will be quite moist with precipitable waters around 1.75 inches, warm air aloft, weak lapse rates, and a lack of appreciable forcing will limit the convective potential Tuesday afternoon. Will retain silent PoPs. Mild Tuesday night with lows in the mid 70`s. Clouds increase across the north ahead of the approaching cold front. Better forcing arrives along the front Wednesday as a lead wave drops over the Mid-Atlantic. The cold front progged to slowly push across the area Wednesday afternoon into Wednesday night. PoP`s increase during the morning, becoming likely Wednesday afternoon with the arrival of the better dynamics. The air mass ahead of the front will become modestly unstable, with mixed- layer CAPE values progged around 1000-2000 J/kg. Deep layer flow also progged around 25-30 knots as mid level flow increases, resulting in better organization and overall storm strength. Mid level lapse rates also improve to around 6 to 6.5 C/km. SPC maintains a marginal risk for severe weather, with damaging winds and heavy rainfall the main threats. Highs generally in the mid 80`s northwest to around 90 south. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Strong Sfc cold front drops south across the area Wednesday night into Thursday morning. Modest ascent accompanies the front within the RRQ of a ~110kt jet over New England, along with pw values to around 2.0" (around +1 st dev). By Wed evening, have maintained highest (70%/Likely) POP across srn VA/NE NC, with slight to low end rain chances by Wed night NW of RIC, where drier air arrives first. PoPs across SE portions gradually diminish to 20-40% by Thursday aftn. Thunder will be maintained into Wednesday evening, with showers thereafter as stable NE flow prevails in the wake of the front. Drier air gradually filters in from the NW late Wednesday night into Thursday with partial clearing across the nrn tier counties. Thereafter, the late week period will be characterized by the gradual development of a longwave upper level trough over the eastern United States for the late week period into next weekend. Meanwhile, broad 1024+ mb surface high pressure builds south over the interior northeast from Great Lakes Thursday and Friday, eventually setting up over New England and ridging down the east coast over the weekend into early next week. Resultant E-NE flow will result in markedly cooler and drier conditions over the region, with early morning lows in the 50s inland to mid 60s along the coast. Maintained a dry forecast through the forecast period. High temperatures Thu-Mon will be at or just slightly below normal through the period, mainly in the upper 70s to low 80s. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... Showers and storms from earlier this evening have all but dissipated with the loss of daytime heating and instability. Otherwise, forecast is on track for stratus development across SE VA/NE NC and potential fog development overnight (initially inland after 22/0600Z and then closer to the coast around sunrise). Any fog/stratus that develops should dissipate/lift after 22/1300Z. A cold front pushes into the Ohio Valley on Tuesday with the region remaining dry with SCT cumulus developing in the afternoon. The front approaches the region Tuesday night and is expected to cross the area during Wednesday. Flight restrictions will be possible Wednesday... mainly in the afternoon and through Wednesday night due to showers and thunderstorms. The front should exit the coast Thursday morning with lingering showers possible across far SE VA/NE NC. Conditions are anticipated to improve Thursday afternoon into Friday as the front shifts farther southeast and high pressure builds north of the region. Breezy NE winds are also anticipated near the coast Thursday and Friday. && .MARINE... Latest surface analysis has a high pressure centered just off the coast. The high will continue to move out to sea overnight and Tuesday. A cold front approaches the waters Tuesday night and into Wednesday morning. The front crosses the area late Wednesday and moves SE of the area Thursday with high pressure returning for the remainder of the forecast period. Obs indicate generally S/SE winds of 10 to 15 knots over the waters with waves of 1 to 2 feet and seas around 2 feet. Winds increase out of the SSW Tuesday through Tuesday night as the front approaches the waters. Wind speeds may approach 15 to 20 over the Chesapeake Bay and ocean with seas building to 3 to 4 feet and potentially 5 feet north/20nm out, and waves building to 2 to 3 feet. A Small Craft Advisory may be needed for the Chesapeake Bay and northern two ocean zones Tuesday night into early Wednesday. Winds shift to the N/NE behind the front late Wednesday through Thursday around 10 to 15 knots. Strong surface cold front drops across the waters Wed afternoon and evening...pushing well SE of the area during Thu. Winds shift to the N/NE behind the front late Wed through Thu around 10 to 15 kt. Post-frontal, look for onshore (E-NE flow) for the remainder of the forecast period as high pressure builds NNW of the local area. Winds increase to 15-20 kt Thu night as a couple of waves move across the stalled front to the south across the Carolinas. Seas will remain choppy for the late week period into the weekend with the persistent onshore flow, remaining 3-4 ft northern waters...4-5ft southern waters. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...LKB NEAR TERM...BMD/LKB/SAM SHORT TERM...LKB/SAM LONG TERM...AJZ/MAM AVIATION...BMD MARINE...SAM
Area Forecast Discussion
National Weather Service Albany NY
1042 PM EDT Mon Aug 21 2017 .SYNOPSIS... Warm and humid conditions will prevail tonight as high pressure continues to move east of the Mid Atlantic Region. It will be hot and muggy tomorrow with highs 10 to 15 degrees above normal. Showers, along with the potential for strong to severe thunderstorms are expected during the afternoon and evening hours ahead of a strong cold front. Cooler and less humid air will move into the region for Wednesday, with dry and cool conditions expected for the rest of the week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... As of 1042 PM EDT...The isolated showers and thunderstorms over central NY just west of the eastern Catskills weakened and dissipated shortly after sunset with the loss of the diurnal heating. The slight chc pops for isolated showers/thunderstorms were removed south and west of Albany. Some leftover cirrus and mid level clouds drifted through the region based on the latest IR imagery. The latest 3-KM HRRR supports a dry overnight period. The rest of the night time should be warm and humid with the boundary layer winds increasing out of the south with the sfc high drifting off the Mid Atlantic Coast. The sfc winds will be decoupling in many locations with some patchy and locally dense radiative mist or fog forming in the major river valleys. Some low stratus may form and drift up the Hudson River Valley well after midnight especially based on the NAM BUFKIT profiles. We have kept the cloud cover partly cloudy to account for this. Lows tonight will be mainly in the mid to upper 60s with a few 70F readings in the mid-Hudson River Valley. Some slightly cooler readings are likely in the lower 60s over the southern Adirondacks and southern VT. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/... A strong upper level trough will be digging from south-central Canada across the Great Lakes, bringing a surface cold front through the Ohio Valley into New England. Ahead of this boundary, a surface pre-frontal trough will help kick off some showers and thunderstorms during the early afternoon hours. These showers/storms will track eastward across our area by later in the afternoon and through the evening hours. Strong south-southwesterly flow will allow for another unseasonably warm and humid day, with highs well into the 80s and dewpoints approaching 70 degrees. Some locations might even hit the 90 degree mark. It looks like quite a breezy day as well as the latest GEFS indicates that the 850 mb u-component of the wind is 2-4 standard deviations above normal. GEFS also shows PWATS 2-3 standard deviations above normal. These warm temperatures along with a moist environment and strong southerly winds should allow for at least a moderate amount of instability tomorrow afternoon/evening. The NAM12 is more bullish with CAPE in excess of 2K but also shows dewpoints in the lower 70s. The GFS still shows moderate CAPE around 1-1.5K across our western zones with even higher instability west of the forecast area. Even though there is still model disagreement on the amount of instability, there still looks like there will be plenty for storms to tap into. Additionally, with strong upper level dynamics approaching, 0-6 km bulk shear will be reaching around 40 kts, so the ingredients are coming together for some stronger storms tomorrow afternoon/evening. One mitigating factor will be that mid-level lapse rates will be fairly weak (generally 6 deg/km or less), but the combo of instability/shear should allow for some storm organization. The main threat will be gusty winds, but with PWATs reaching around two inches, will also have to watch for some locally heavy downpours and isolated flash flooding as well. The storms may linger into the first part of tomorrow night, but should be ending from west to east as the front crosses the area, as lows fall into the 60s. On Wednesday, dewpoints will be falling during the day, as much cooler and drier air moves into the area. Highs will generally be in the 70s with a partly sunny sky. There still may be a lingering shower due to the passing upper level trough, but most areas should be dry. Skies should continue to clear out by Wednesday night, as lows fall into the upper 40s to upper 50s, as high pressure builds into the area. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... The extended forecast continues to feature a mean longwave trough over the region with high pressure building in at the sfc with mainly fair and dry weather with temps slightly below normal for late August. Wed night into Thu...A broad upper level trough will be over southeastern Canada, the Great Lakes Region, and the Northeast. The latest GEFS has H500 heights 1 to 2 standard deviations below normal. Initially, some lake enhanced isolated showers tapping Lake Ontario moisture will impact the western Adirondacks Wed night. Variable cloudiness and cool temps are expected with H850 temps falling back to +6C to +10C from northwest to southeast across the forecast area. Lows will be in the mid 40s to around 50F over the mountains, and lower to mid 50s in the valleys. A short-wave associated with the upper level low and a sfc trough will focus some isolated to scattered showers especially west of the Hudson River Valley, and over the higher terrain. It will be cool and breezy with highs in the lower to mid 70s over many of the valley locations with a few upper 70s in the mid-Hudson Valley and NW CT, and 60s to around 70F over the hills and mountains. Thu night through into Sat night... A large dome of Canadian high pressure builds in from Ontario and the western Great Lakes Region Thu night into Fri. The strong subsidence associated with the broad sfc anticyclone will yield fair and dry weather to close the week and enter the weekend. The sfc high shifts eastward over s-cntrl Quebec and the Northeast by Saturday night. Slightly cooler than normal temps and comfortable humidity levels are expected. The 12Z GEFS H850 temps are 1 to 2 standard deviations below normal. Lows will generally be in the mid 40s to lower 50s. Highs Friday and Saturday will be mainly in the lower to mid 70s in the valley areas, and lower to upper 60s over the higher terrain. Sunday into Monday...The 12Z GFS and ECMWF both show some short-wave energy swinging around the H500 upper low over the Northeast and southeast Canada on Sunday. A few instability showers could pop up over the southern Greens and the southern Adirondacks. The low- level moisture profiles are not impressive. We placed a slight chance of showers in for those locations, otherwise high pressure builds back in from the Great Lakes Region Sunday night into Monday, and low and mid level heights begin to rise. Temps continue to be slightly below normal by a few degrees late in the weekend into early next week. Humidity levels continue to be comfortable with sfc dewpts in the 40s to 50s. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... High pressure continues to move east of the Mid Atlantic Region tonight. A cold front will slowly approach from the eastern Great Lakes Region tomorrow with a prefrontal trough focusing showers and thunderstorms late in the afternoon into the early evening. VFR conditions early this evening with sct-bkn cirrus around due to some dissipating convection over central NY. Some mid level clouds may also move into KPOU. A southerly flow will continue in the boundary layer tonight advecting in higher dewpoint air, and with the skies mostly clear and the sfc winds decoupling we are expecting some mist and fog to develop especially at KGFL and KPSF. We have forecasted LIFR/IFR conditions at these sites. Our confidence was not as great at KPOU and KALB, as some stratus may develop and move up the Hudson River Valley tomorrow morning. We have placed some MVFR stratus at KPOU at 1.5 KFT AGL, and kept it scattered at KALB but with vsbys at 3SM for both sites. The mist/fog or low stratus should gradually burn off between 12Z-14Z. At KPSF, the stratus may linger at the MVFR levels the longest in terms of cigs. The southerly winds will increase at the sfc and the prefrontal trough thunderstorms are possible in the afternoon. We have used a PROB30 group for the possibility of thunderstorms as early as 18Z at KGFL, 19Z at KALB/KPSF, and 20Z at KPOU. The convection may linger into the evening at some of these sites. Later TAF issuances will narrow in on the time period. Expect MVFR or brief lapses to IFR/LIFR conditions with any thunderstorms. The winds will be south at around 5 kts at KALB tonight, but will become light and variable at 4 kts or less or calm at KPOU/KPSF/KGFL. The winds will increase from the south at 5-9 kts in the late morning, and be 9-15 kts during the afternoon with some gusts in the 20-25 kts range especially at KALB/KPSF/KGFL. Outlook... Tuesday Night: High Operational Impact. Likely SHRA...TSRA. Wednesday: No Operational Impact. NO SIG WX. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: No Operational Impact. NO SIG WX. Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: No Operational Impact. NO SIG WX. && .FIRE WEATHER... Most areas will see showers or thunderstorms tomorrow afternoon and evening thanks to a cold front and strong upper level trough passing through the area. Min RH on Tuesday will only be 50 to 65 percent with south winds at 10 to 20 mph. RH values will recover to near 100 percent tonight and tomorrow night with some patchy fog possible tonight. && .HYDROLOGY... Dry weather is expected through tomorrow morning across the region. An approaching cold front will allow for showers and thunderstorms tomorrow, mainly during the afternoon and evening hours. Any thunderstorm will be capable of producing locally heavy downpours and could lead to isolated flash flooding. The locally heavy rainfall may result in minor flooding of urban, poor drainage and low lying areas. Behind this frontal system, mainly dry weather is expected for the rest of the week. Basin average rainfall on Tuesday will generally be around a half of an inch to an inch, although point totals may be higher. This rainfall will only allow for minor rises on rivers and streams. River and stream levels should quickly recede by Wednesday and then remain steady for the rest of the week. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .EQUIPMENT... The KENX radar will likely be down through at least Friday, September 1st for the bull gear replacement. We are waiting for a ROC maintenance team and parts to arrive to assist local technicians with the repairs. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...JVM/Wasula NEAR TERM...Wasula SHORT TERM...SND/Frugis/JVM LONG TERM...Wasula AVIATION...Wasula FIRE WEATHER...Frugis/JVM HYDROLOGY...Frugis/JVM EQUIPMENT...WFO ALY
Area Forecast Discussion
National Weather Service Gaylord MI
1150 PM EDT Mon Aug 21 2017 .UPDATE... Issued at 939 PM EDT Mon Aug 21 2017 Upstream cold front remains west of Michigan late this evening... extending from near the arrowhead of Minnesota thru western Iowa into Kansas. Plenty of warm/moist air streaming northward ahead of this front continues to interact with a large axis of instability to generate several areas of convection across the Western Great Lakes and the Upper Mississippi Valley. Area of convection quickly developed over the past hour or two across portions of Northern Lower Michigan...featuring some thunder and heavy rainfall. Marginal severe threat appears to be largely finished with loss of instability in agreement with latest SPC Day 1 Outlook which now puts all of Michigan in only general thunder for the remainder of the night. Latest short term models show this initial wave of convection lifting off to our NE over the next couple of hours... with a more widespread wave of precip developing later tonight just head of the approaching cold front. && .NEAR TERM...(Tonight through Tuesday) Issued at 330 PM EDT Mon Aug 21 2017 Ill-defined and stalling cold front is draped across the Straits region. This front connects with low pressure in Nebraska, which will intensify as it lifts ne along the front. Intensification will be most rapid over and downstream of northern MI, overnight into Tuesday. This coincides with falling heights aloft, and the eventual arrival of an upper trof Tuesday. Diurnal heating was interrupted this afternoon by the eclipse (temps fell by a few degrees in many locales), but has resumed. Steamiest surface parcels are found from PLN to APN (with APN 81/69f), leading to MlCape values near 1500j/kg along that axis. Earlier cu field here faded with the eclipse, but some mid-clouds are approaching which indicate some weak mid-level forcing and erosion of any capping. HRRR runs are becoming inconsistent as to whether something can pop in ne lower MI this afternoon/early evening. If it does, earlier discussions about favorable shear/instability for supercells and svr wx remain valid. We are seeing some cells cook off sw of CAD, which is not handled well by the CAMs. There is certainly a nose of better instability (MlCape just above 1k j/kg) poking into that region, but there is much less in the way of shear down that way. More widespread convective activity is still expected to break out tonight, with the arrival of stronger forcing (to counter decreasing instability). Last several runs of the HRRR show this occurring in the 8-9pm range in nw lower MI, which would probably be soon enough to support a strong/svr threat before instability wanes too much. Will maintain an evening mention of strong/svr storms in northern lower MI. Very juicy airmass (PWATs around 1.75in) will support locally heavy rainfall. This will become a bigger player overnight, as forcing and precip coverage increases. 0.50-1.0 inch amounts should be common, and locally higher amounts are anticipated. Numerous to widespread pops in order for the overnight. Showers will end from nw to se on Tuesday, as the low departs and associated cold front swings thru. By mid-afternoon, only hanging onto a slight chance of a shower for OSC/Tawas. We will be on the breezy side from about late morning onward. Decreasing cloud cover, though with enough diurnal heating and cool air aloft to support a cu field (especially away from Lakes MI/Superior). Min temps tonight quite mild, ranging thru the 60s. Max temps Tuesday mainly in the 70s, some upper 60s near Superior. && .SHORT TERM...(Tuesday night through Thursday) Issued at 330 PM EDT Mon Aug 21 2017 ...Much cooler weather for midweek... High Impact Weather Potential: Nothing. Longwave pattern becomes more amplified for the midweek period as deep fall-like trough digs into the Great Lakes and Northern CONUS. Embedded shortwave energy rotating through the trough may bring some light scattered precipitation to eastern areas Wednesday, otherwise quiet weather. Deep layer drying Tuesday night behind the front as much cooler air sweeps into northern Michigan. Early Wednesday, a well-defined shortwave pinwheels around the stacked low now over Quebec, pushing a secondary cold front and associated band of deeper moisture across northern Michigan. A few scattered/light showers could result, mainly over eastern Upper. Otherwise, even cooler temperatures will headline the midweek portion of the forecast with high temps ranging from the low-mid 60s north to the upper 60s to 70 degrees elsewhere...some 10 or so degrees below normal for the third week of August. Additional shortwave energy may pinwheel through the eastern lakes on Thursday, possibly brushing Lake Huron areas with an isolated shower. Otherwise, large Canadian high pressure will slowly slide southeast into the area resulting in lots of sunshine but still cool temperatures. .LONG TERM...(Thursday night through Monday) Issued at 330 PM EDT Mon Aug 21 2017 High pressure will be over the Great Lakes region through Saturday along with dry air, mostly clear skies, and rain free weather through Saturday night. Sunday will see increased cloudiness and rain chances throughout the day as an upper level area of low pressure and surface reflection develops over the southern Great Lakes with accompanying moisture. Rain chances will stick around Monday as well as said area of low pressure remains over the forecast area. Temperatures will only be around 70 Friday and warm a bit the remainder of the period...in the low to mid 70s. Friday morning has an opportunity to see some frost, with clear skies and light winds...some mid to upper 30s are not out of the question for our colder locales. The rest of the forecast period will see lows in the mid 40s Saturday morning and warming to the mid 50s by Monday morning. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1150 PM EDT Mon Aug 21 2017 Showers and thunderstorms will redevelop across Northern Michigan overnight ahead of an approaching cold front. Conditions will deteriorate to MVFR/IFR...especially within heavier showers and thunderstorms. Convection will continue into Tuesday morning before cold FROPA brings precip chances to a close Tuesday afternoon. SW winds under 10 kts will shifting to the W/NW on Tuesday and strengthening to 15 to 25 kts in the wake of the cold front. && .MARINE... Issued at 330 PM EDT Mon Aug 21 2017 Light sw winds will persist for much of tonight, ahead of low pressure that will intensify as it crosses northern MI late tonight. Winds will veer nw behind the low, becoming quite gusty Tuesday into Wednesday. Small craft advisories will be hoisted for many waters shortly. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LH...SMALL CRAFT ADVISORY from 6 AM Tuesday to 6 PM EDT Wednesday for LHZ345>349. LM...SMALL CRAFT ADVISORY from 6 AM Tuesday to 6 PM EDT Wednesday for LMZ323-341-342-344>346. LS...SMALL CRAFT ADVISORY from 6 AM Tuesday to 6 PM EDT Wednesday for LSZ321-322. && $$ UPDATE...MR NEAR TERM...JZ SHORT TERM...JK LONG TERM...TL AVIATION...MR MARINE...JZ
Area Forecast Discussion
National Weather Service Caribou ME
1156 PM EDT Mon Aug 21 2017 .SYNOPSIS... High pressure will build south of the area this evening. Low pressure will approach from the west on Tuesday. The low will track to our north Tuesday night into Wednesday as it brings a cold front across the area. && .NEAR TERM /THROUGH TUESDAY/... 1155 PM Update...Made minor adjustments to placement of isolated thunderstorm chances across the north next few hours based on current radar imagery and lightning data. Activity seems to be lining up along weak frontal boundary across far northern Maine. Latest HRRR shows the activity diminishing the next few hours. Otherwise, expect a very warm and muggy night, as lows not expected to fall much lower than the mid 60s across much of the region. Patchy fog still possible overnight in spots. Previous Discussion... Humid airmass rmns ovrngt with dwpts rebounding into the lwr 60s and this wl lkly lead to patchy fog acrs the north as clds dissipate. Late tonight and Tue mrng wl be quiet, other than patchy fog as brief ridging takes hold thru about 15z tomorrow. Wmfnt lifts thru tomorrow aftn with showers and thunder dvlpng acrs the nw aft about 18z. CAPES increase aft this time and 0-6km bulk shear increase to 30-40kts in the aftn bfr increasing substantially drg the evng hrs. PW values begin to rise in the aftn to nr 1.50 inches acrs srn areas, thus hv retained mention of hvy rain and gusty winds to where convection is lkly. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... For Tuesday night, a strong cold front will cross the area later in the night. This front has the potential to produce locally heavy rainfall and will maintain that threat in the forecast. PW values will approach 2 inches with a deep warm cloud layer around 13K ft. A strong LLJ will be in place and Corfidi vectors show the possibility of some back-building cells. The LLJ also heightens the threat of gusty winds mixing down with thunderstorms and will maintain mention of that in Tuesday night`s forecast. It`s still unclear how much of the action will be with a pre-frontal trough or with the front itself later in the night. Otherwise, it will be a warm and humid night ahead of the front with lows in the mid to upper 60s for much of the area. Humidity will be high with dew points also in the mid to upper 60s. Fog is likely along the coast and in high terrain. Elsewhere, marine layer moisture will be streaming northward in the form of stratus and some patchy fog. On Wednesday, clouds with the front will exit the Down East region with a few residual showers...but no thunderstorms can reasonably be expected. Fog and low clouds will linger along the coast during the morning. It will be a rather breezy day with a deep mixing layer and still warm with highs in the mid to upper 70s. The cooler air behind the front arrives gradually during the day and it will be cooler and less humid Wednesday night with lows mostly in the low to mid 50s. The cool Canadian air mass will be fully in place for Thursday with highs in the low to mid 70s and dew points in the upper 40s to lower 50s. Some cu fields will be possible north of Houlton with the NW flow. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... In the longer term starting Thursday night, a quiet and cool pattern appears likely with persistent upper level troughing and surface high pressure. The primary challenges will be identifying cumulus and stratocu fields in the a north to northwest flow...and when minor shortwaves may kick off some light afternoon showers Friday, Saturday and Sunday. In general, little precipitation is expected and will hold off on specifying chance pops for these days. && .AVIATION /04Z TUESDAY THROUGH SATURDAY/... NEAR TERM: VFR next 24 hours with potential MVFR vsbys btwn 07z and 12z for northern terminals. SHORT TERM: IFR conditions due to cigs, fog and thunderstorms will affect all terminals Tuesday night. The low clouds will linger into Wednesday morning for BHB and coastal sites, but all of the area will be VFR by Wednesday afternoon and remain so into Saturday. && .MARINE... NEAR TERM: Winds and seas will remain below SCA levels thru Tue aftn bfr beginning to climb to near 5ft at the very end of the period. SHORT TERM: There is a credible threat of SCA conditions Tuesday night into Wednesday in spite of the stable conditions and fog that will be in place. Wind-driven waves could hit up to 6 feet. After Wednesday, no significant weather is forecast through the end of the period. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Duda Short Term... Long Term... Aviation...Duda/ Marine...Duda/
Area Forecast Discussion
National Weather Service Cheyenne WY
451 PM MDT Mon Aug 21 2017 .SHORT TERM...(This evening through Wednesday night) Issued at 230 PM MDT Mon Aug 21 2017 West-northwest flow aloft prevails this afternoon under the influence of a broad mid-upper level northern CONUS trough. A shortwave was pushing southeast across WY and western Dakotas. A surface front extended from northeast NE into extreme northern CO. A slightly drier and more stable air mass should preclude convective development this afternoon, except for scattered CU over the mountains. Temperatures dropped between 7 and 12 degrees during the solar eclipse. Lowered high temperatures a couple of degrees. It was breezy, especially over the plains with northerly winds gusting from 20 to 25 mph. The short range models and ensembles are in good agreement progging eastward progression of the northern CONUS trough and arrival of a mid/upper level ridge Wednesday. Generally dry conditions will prevail through the next 24 to 36 hours with precipitable water values between 0.50" and 0.75". The exception will be the southeast WY mountains Tuesday afternoon/early evening where isolated convection may erupt due to favorable orographic lift. High temperatures Tuesday will be near seasonal normals with mid 70s to mid 80s. Breezy south-southeast winds will develop across the plains Tuesday afternoon. The flow aloft becomes more west-southwest Wednesday, which will advect some monsoonal moisture north-northeast into WY and CO. Isolated convection develops by midday over the southeast WY mountains, increasing in coverage as far east as the I-25 and I-80 corridor into the evening. 700mb temperatures rise to 12-14 degrees Celsius Wednesday afternoon, yielding highs in the 80s to around 90 degrees for lower elevations. .LONG TERM...(Thursday through Monday) Issued at 230 PM MDT Mon Aug 21 2017 More like August weather for the long term as upper ridge overhead and we get impacted by shortwaves moving through the flow along the northern periphery of the ridge. What this does for us here is southeast Wyoming and Nebraska Panhandle this time of year is create gusty west to southwest winds and dry conditions possibly leading to fire weather concerns. Starting off Thursday, this looks to be the case as the ECMWF shows a shortwave over southwest Montana move northeastward through the ridge. Southwest winds across Carbon County with 15-20kts mixing down to the surface. Some differences in the EC and GFS on precip coverage. EC much more bullish on PoPs over the GFS. Will go with the EC solution right now with fairly widespread slight chance PoPs across the CWFA. Secondary low pressure system tracks across northern Montana Friday on the ECMWF with 700mb winds increasing to 20-25kts. Could be a fire weather day Friday with afternoon humidities falling into the upper teens/low 20s. We will need to keep an eye on this as the event draws closer. Montana shortwave then drops southeast over the weekend into the Dakotas. When this happens, we see a backdoor cold front moving into the area from the northeast. ECMWF 850mb winds shift to the northeast over the Panhandle Saturday, eventually shifting to the southeast as the ridge begins to build back into the west. Weather looks dry over the weekend with precip well east and south of the CWFA. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 449 PM MDT Mon Aug 21 2017 Mainly VFR tonight with the exception of down here near KCYS. Latest HRRR guidance suggesting some LIFR conditions in fog/low stratus towards sunrise Tuesday. Did start to trend the KCYS TAF down towards what the HRRR guidance is suggesting. We will continue looking at trends this evening and provide a more definitive forecast for KCYS on the 06Z TAFs. && .FIRE WEATHER... Issued at 230 PM MDT Mon Aug 21 2017 A cool front will push south of the districts this afternoon. Afternoon humidities will fall to around 15 percent across lower elevations of Carbon County, however winds will be light. Across the plains, minimum humidities will range from 25 to 40 percent with breezy northerly winds through early evening. Dry and warm conditions are forecast Tuesday with lowest humidities across lower elevations of Carbon County. It will be breezy east of the Laramie Range Tuesday afternoon with south-southeast winds gusting to around 20 mph. Moisture will increase Wednesday as monsoonal flow from the southwest returns to the districts, and persists through the end of the week. Higher humidities and better chances of showers and thunderstorms can be expected at that time. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...MAJ LONG TERM...GCC AVIATION...GCC FIRE WEATHER...MAJ
Area Forecast Discussion
National Weather Service Dodge City KS
659 PM CDT Mon Aug 21 2017 ...Updated for aviation discussion... .SHORT TERM...(This evening through Tuesday) Issued at 250 PM CDT Mon Aug 21 2017 Regional 88-D radar showed and area of showers continuing to spread northeast across the Texas panhandle into the Meade and Comanche county areas. This trend is expected to continue through the afternoon. Although the reflectivity appears rather light, there should be potential for light to brief moderate rain rates under this southwest to northeast oriented max in precipitable water (around 1.8"). Between the precipitation and cloudiness persisting over the south central Kansas counties, and the eclipse which accounted for a 2 to 3 degree temperature drop this afternoon, keeping a decent temperature trend as been difficult. However there is a dry slot on satellite expanding slowly northeast across extreme se Colorado. This subsident zone should ensure a dry rest of the daytime hours in the west, while scattered showers expand north east through south cental Kansas. Another chance for scattered showers and isolated thunderstorms will follow this evening as the 850mb front drops south into Kansas. The overall coverage will probably be limited by the loss of maximum moisture and theta-e transport by that time. However the Hi-Res ARW/NMM and HRRR continue to hold on to the potential toward late evening and beyond. Any areas of fog that develop over south central Kansas overnight likely will not last as the increasing northerly surface winds increase mixing, and the model fields generally do not favor at this time. Widespread low level cloudiness will rapidly advance across most of the area with breezy northeast winds during the morning hours, and clearing across the north in the afternoon. A dry push of boundary layer air characterized by dewpoints in the 50s and upper 40s Tuesday night will will advance into the lower plains, creating a zone of baroclinicity immediately south of our area. .LONG TERM...(Tuesday night through Monday) Issued at 250 PM CDT Mon Aug 21 2017 By midweek, the GFS displays another weak northwest flow pattern, where any little weak midlevel impulse could bring showers or storms daily, especially after peak heating. the same general idea is supported in the ECMWF fields. The model consensus maintains a somewhat seasonal temperatures spread, with highs just a few degrees below normal for late August, in the mid 80s, and lows generally in the low 60s. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 657 PM CDT Mon Aug 21 2017 A cold front will pass across the TAF sites after 09z. Thunderstorms with gusty winds are possible ahead of the front. In the wake of the front, winds will shift to the northeast at 15 kts. There will likely be low cloud development behind the front with low MVFR and possibly IFR CIGs for a few hours before daytime heating burns it off. && .PRELIMINARY POINT TEMPS/POPS... DDC 68 84 58 85 / 30 10 10 0 GCK 66 85 58 84 / 20 10 0 0 EHA 66 80 61 83 / 30 20 20 10 LBL 68 83 61 85 / 20 30 10 10 HYS 67 84 57 85 / 30 0 0 0 P28 71 87 61 85 / 30 20 10 0 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Russell LONG TERM...Russell AVIATION...Finch
Area Forecast Discussion
National Weather Service Hastings NE
814 PM CDT Mon Aug 21 2017 .MESOSCALE DISCUSSION... Issued at 814 PM CDT Mon Aug 21 2017 CU towers and tstms are trying to form from just N of LXN to Greeley. The 00Z LBF sounding shows why tstms are struggling. There is a strong cap at the base of the EML with +14C near 700 mb. It is unlikely that the modest lift from the approaching trof will be able to erase all of the CIN. The 22Z HRRRX suggests we won`t see much tonight. POPs were lowered quite a bit with an update associated with the 00Z TAFs. No additional changes planned. && .MESOSCALE DISCUSSION... Issued at 528 PM CDT Mon Aug 21 2017 We cont to monitor potential for initiation of tstms. The cool front currently extends from just N of LXN to just S of OLU (just N of I-80). The RAP/NMM/WRF-ARW/RGEM are too aggressive... already indicating tstms should have developed. So that leaves the NAM/GFS which are later suggesting initiation between 00Z-03Z just W-NW-N of the CWA. If this occurs...they should move into areas N and W of the Tri-Cities before 03Z. If initiation occurs...these storms will be in the post-frontal air mass where deep layer shear will be increasing from 25 up to 35 kts. We will be warning on 50 dBZ cores that reach 35K ft and 60 dBZ cores that reach 23K ft. && .SHORT TERM...(This evening through Tuesday) Issued at 242 PM CDT Mon Aug 21 2017 Much of the focus today has involved keeping an eye on the high cloud deck and the eclipse, but will also need to talk about the expected weather over the next 7 days. 17Z Discussion --- Current water vapor imagery and upper air analysis shows an active northern stream continues over the region although the better forcing looks to be a little north of us. A subtle mid level should move through west to east later this afternoon. While the flow is weaker across and to the south of our CWA, there is vort max to our southwest that could affect the southeast part of the CWA later today. One other thing of note on satellite is the sub-tropical tap that starts south of the Baja region and has been streaming NNE through KS and SE Neb. This is a big contributing factor to the eclipse-hampering cirrus in our area. At the surface at 10 am, low pressure was situated over west central Neb with a warm front extending ENE. Fog/Stratus deck was taking its time burning off north of the warm front, but ODX has gone from a quarter mile to 10 miles between 14 & 15Z Primary question will be the extent of any convection firing later this afternoon and into tonight. The shortwave noted above should help drag the surface front into and through the CWA, starting in the northwest CWA between 22-00Z and exiting the southeast part of the CWA by sunrise Tue. The best instability should occur a little to the north of our CWA but ML CAPE will still be in the 1000-1500 j/kg range in the northern half of the CWA. Deep layer shear not as impressive with 20 kt 0-6 km shear progged at 00Z. Will continue to monitor real time radar and CAM models for convective initiation. Earlier runs of the HRRR have shown this to occur around 4 pm in our northwest. HRRR does show some convection along the front across much of the CWA during the evening and overnight, however the bulk of this remains in our far northern CWA and into NE Neb closer to the better forcing. 1930Z Update... Storms have indeed initiated along an outflow boundary across northeast Neb and are just to the north of our CWA. Latest HRRR guidance now showing this activity will push southward through the CWA the remainder of the afternoon and overnight, exiting the southern CWA just before sunrise. Deep layer shear still lacking but enough instability that a few strong/severe storms cannot be ruled out. Tuesday should be quiet in terms of the active weather as the surface front pushes well south with high pressure dropping into northeast Neb. Will be a bit cooler with highs in the lower 80s, but even more noticeable will be the lower dewpoints which should be in the mid 50s, about 15 degrees lower than what we are seeing today. .LONG TERM...(Tuesday night through Monday) Issued at 242 PM CDT Mon Aug 21 2017 Quiet conditions continue Wed and Thu as mid level ridge builds into the Rockies before that pattern reverts to something similar to the last few days for the weekend as the next wave moves onto the PAC NW coast and dampens the ridge. Superblend producing Pops during the day Thursday but don`t see a lot of evidence for that. Tstm chances do return by Thu night into the weekend with series of wave passages. If models are correct, the ridge then builds back into the Rockies again early next week, lowering our precipitation chances. At least early next week, high temps remain in the lower 80s as the ridge axis remains far enough west of here to keep the hotter temps at bay. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday) Issued at 648 PM CDT Mon Aug 21 2017 Significant Wx: Low probability of IFR TSRA tonight. Tonight: Cold frontal passage 02Z-03Z. Predominantly VFR with multi-layered CIGs at or above 10K ft. A few CU around 4K ft will be possible thru the night with some developing into sct TSRAs. Lgt S winds will shift to the N after frontal passage. Confidence: Medium Tue: VFR SKC or becoming SKC before 17Z. N winds 8-12 kts becoming NE. Confidence: High && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ MESOSCALE...Kelley SHORT TERM...Ewald LONG TERM...Ewald AVIATION...Kelley
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
732 PM CDT Mon Aug 21 2017 .SYNOPSIS... Issued at 318 PM CDT Mon Aug 21 2017 Large MCS progressing across southeast SD into IA, northeast NE and srn MN. Weak development noted across Holt, Boyd and Keya Paha counties earlier. Elsewhere broad trough across southern Canada into the northern Plains with PV anomaly just over the Canadian border. PV axis rotating through Dakotas serving as large scale support for convergence along associated from now stalled across the middle of NE. && .UPDATE... Issued at 730 PM CDT Mon Aug 21 2017 A look at the KLBF 00z UA flight this evening indicates a strong 700mb cap which explains why no thunderstorms have formed. The focus for storm development is moving south of I-80 at this time but continues across Custer County. A new forecast is in place using a 4-way blend of the HRRR models, the RAP and GFS models for isolated storm coverage. && .SHORT TERM...(This evening through Tuesday) Issued at 318 PM CDT Mon Aug 21 2017 The aforementioned stalled frontal boundary showing increasing convergence along it with several waves of outflow moving southward as well. Mesoscale analysis continues to support strong deep moist convergence in this vcnty so would expect thunderstorms to develop along the boundary by 4 PM CDT and would expect some supercell potential with decent shear (30-40 kts)from LBF northeastward. 0-6km shear orientation would suggest some storm interactions in the LBF- BBW area, but more of a linear fashion further north. Despite a clearing of stratus across southwest NE earlier this morning low level lapse rates were not overly impressive yet. Think this will change in the next couple hours though and scattered TSRA developing, though more isolated the further southwest you go in NE. Very unstable aloft and hail parameters look good. Heavy rain also a possibility as PW values around 1.6" on the sounding this morning which is significant but no where near records. Appears as though the corridor from LBF to BBW would be favored for TSRA development with overall progression into Custer Co. which could cause issues since they`ve had so much rain lately. TSRA development should exit the area along with the front by midnight or so and would therefore expect a drier and cooler airmass in place tmrw. .LONG TERM...(Tuesday night through Monday) Issued at 318 PM CDT Mon Aug 21 2017 The main forecast challenge this forecast period will be precipitation chances towards the end of the week. High pressure builds across the western CONUS bringing a northwest flow across the central US through mid week. The ridge then flattens out towards the end of the week. A short wave trough then moves across the area Thursday into Friday bringing chances for showers and thunderstorms. At this time widespread severe weather is not expected. That being said models show a good flow of moisture into Nebraska Thursday into Friday which could lead to the potential for decent rainfall amounts to end the week. Saturday and beyond...precipitation chances look slim for the rest of the period. Temperatures will remain seasonal with highs in the 80s. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 638 PM CDT Mon Aug 21 2017 A look at the KLBF 00z UA flight this evening indicates a strong 700mb cap which explains why no thunderstorms have formed. The focus for storm development is moving south of I-80 at this time. Thus the potential for thunderstorms at KLBF appears unlikely. There is potential for storm development east of KLBF but this will also diminish in time this evening. Otherwise MVFR cigs are underway near KONL and these cigs may spread south along and east of a line from KLBF-KBBW this evening. Some models don`t capture this and one them is the SREF which maintains VFR. The forecast follows the SREF model for now. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...CDC SYNOPSIS...Stoppkotte SHORT TERM...Stoppkotte LONG TERM...Gomez AVIATION...CDC
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
832 PM CDT Mon Aug 21 2017 .UPDATE... 831 PM CDT Little change to going forecast this evening, though severe threat continues to appear minimal in the wake in the wake of extensive morning MCS cold pool and cloud cover across eastern IA and northern IL/IN. SPC has removed the northern 2/3 and northwest IN from the marginal risk for the remainder of the overnight hours. Evening surface analysis depicts weak surface low pressure over the Upper Mississippi Valley, along a cold front which stretches from the northern Great Lakes to the Central Plains. Strong low- level baroclinic zone was noted across Missouri and downstate IL however, in association with strong outflow boundary from MCS which decayed across the region earlier in the day. Despite warm and humid warm sector air mass ahead of the cold front, RAP mesoanalysis and 00Z soundings indicate relatively stable/capped near-surface conditions, with weak low-level lapse rates north of the outflow boundary. Remnants of strong linear MCS over IA continues to weaken as it propagates east-southeast toward the Mississippi. While the threat of severe weather diminishes, especially across northern parts of the cwa, shower and thunderstorm coverage should continue to increase across the area through late evening as forcing strengthens in association with a digging/amplifying upper trough across the Upper Midwest. The resulting increase in southwesterly low level jet, large scale height falls and the increasingly favorable upper jet position is expected to allow showers/storms to spread across the region overnight in advance of the cold front. While some potential for isolated strong wind gusts will persist across the southern tier or so of counties, locally heavy rainfall looks to be the primary concern with overnight storms. PW`s around 2 inches and southwesterly low level jet parallel to the cold frontal zone may produce some training/back-building in some spots which could produce isolated rainfall amounts in excess of 1-1.50 inches. Thunderstorm coverage should diminish from the north/northwest toward morning, with the focus quickly shifting to the east/south of the forecast area after sunrise. Ratzer && .SHORT TERM... 313 PM CDT Through Tuesday... Main concern is showers and thunderstorms this evening and overnight and associated risk for primarily heavy downpours and localized flooding. Current subsident regime behind earlier short-wave has yielded dry conditions for the time being this afternoon. Fairly quiet conditions should continue through about sunset. Thereafter, in the evening into the overnight, trend should be for increasing coverage of showers and storms tied to additional short-wave energy arriving from the Plains. Main wave is tied to well defined MCS over NW IA, with another arriving from KS/MO area. A signal on high-res and WRF guidance for a subtle disturbance and perhaps better lower-level convergence could provide an earlier evening focus for convection breaking out in mainly NW Indiana (possibly extending into parts of NE IL). Later in the evening and into the overnight as activity expands in from the west, strengthening low level jet could help sustain more robust showers and storms, with PWAT of 2-2.25" supportive of very heavy downpours and even localized flooding in stronger storms depending on residence time/training. Overall storm motions do appear to be quick enough to preclude a more significant flooding risk. Severe risk appears to be unfavorably timed diurnally, with an isolated gusty/damaging wind risk (wet microburst/precip loading) and deep layer shear possibly supportive of a hail risk (marginally severe on the high end). A cold front will sweep across the area on Tuesday, with lingering isolated-scattered storms possible in the morning (12z-15z) and focus shifting to mainly southeast of I-55 in the early-mid afternoon for any additional showers/isolated storms immediately tied to frontal passage. Clouds will clear from the northwest behind the front in dry air advection and CAA, with breezy west to northwest winds. Highs will reach the upper 70s to lower 80s. Castro && .LONG TERM... 241 PM CDT Tuesday night through Monday... Transition to drier and much cooler weather occurs mid-week and lingers through the end of the week before a gradual warm-up brings temps back to near normal for late August. Surface cold front clears the forecast area to the southeast by Tuesday evening, with breezy northwest winds bringing a cooler and less humid air mass into the region. This trend persists through the end of the week, as a long-wave upper trough deepens across the eastern CONUS, and keeps us in deep northwest flow. Surface high pressure spreads across the region during the period, though models have been fairly consistent in depicting a mid-level short wave which digs across the Upper Midwest and Great Lakes region late Wednesday night into early Thursday, with a reinforcing push of cooler air and a surface cold front passage. Guidance continues to indicate the potential for some spotty showers early Thursday as 850 mb temps drop to about +6C over the warm late-August waters of Lake Michigan. Otherwise, dry conditions are expected to persist into the weekend as the surface high strengthens across the western Lakes. 925 mb temps support daytime highs in the low-mid 70`s, with overnight lows dropping into the low-mid 50`s. A few upper 40`s are possible in our typical cool spots away from the immediate Chicago metro area and warmer lake front areas. The eastern CONUS upper trough eventually is progged to drift off to the east this weekend, with the surface high pressure ridge also moving off and allowing winds to become more southeasterly. Medium range solutions of the ECMWF and GFS both indicate a short wave trough propagating from the Northern Plains southeast into the Midwest Saturday night into Sunday, though there are differences with the evolution beyond that time. The EC develops a deep closed upper low over the area which lingers into the following Monday, while the GFS is much less amplified. In general however, a gradual moderation in low-level temps and a modest increase in low-level moisture is likely. Ratzer && .AVIATION... For the 00Z TAFs... 641 pm...Main forecast concern is thunderstorm potential through sunrise Tuesday morning. Short term guidance has been in good agreement showing thunderstorms developing early this evening over the terminals and this appears to be starting now and slightly further east then was expected with convection extending from southern Lake Michigan and then more scattered into eastern IL. This activity is expected to shift east over the next few hours with a lull expected through mid/late evening. However...the airmass is moist and unstable so its possible scattered showers or isolated thunderstorms could develop at any time. Focus then shifts to convection across IA and models differ as to how far east this activity will move overnight as it appears the strongest convection and more solid line may move south of the terminals overnight. Confidence is too low to make any significant changes with this forecast and maintained tempo thunder during the same time period from the previous forecast. Trends will need to be monitored later this evening and overnight. Once this activity moves east/southeast of the terminals by sunrise Tuesday morning only lingering/scattered showers are expected Tuesday morning. Southwesterly winds 10-15 kts this evening will slowly turn more westerly overnight and then shift northwest Tuesday morning as a cold front moves across the area. Winds may turn more northerly for a time Tuesday afternoon. Speeds in the 12-16kt range with gusts into the 20kt range are expected Tuesday. Any of the stronger storms will produce heavy rain and brief ifr/ mvfr cigs. Prevailing mvfr cigs are possible overnight and into Tuesday morning. Maintained previous forecast for mvfr cigs but confidence is low regarding how widespread and how long mvfr cigs may persist. Cigs should lift and scatter Tuesday afternoon. cms && .MARINE... 241 PM CDT Main marine forecast concerns continue to be on a period of northerly winds down the length of the lake Tuesday night into Wednesday. While not overly strong, the long fetch will likely result in small craft advisory conditions for the shores of southern Lake Michigan. In the near term, a cold front has become nearly stationary near the north shore of the Lake in the Upper Peninsula. Low pressure is expected to develop along this front over Wisconsin tonight, moving northeast over far northern Lake Michigan early Tuesday morning and trailing a cold front which will push down the lake during the day. The low is expected to deepen later in the day as it pulls away into Quebec, setting the stage for breezy northwest winds across the lake. These north-northwest winds will continue into Wednesday before weakening as high pressure spreads into the region. The high eventually late Thursday, allowing winds to diminish and waves to subside. The strongest winds, 20-25 kts, are expected late Tuesday and Tuesday night, with small craft advisory conditions expected along the southern shores of the lake from Tuesday afternoon through Wednesday. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...Beach Hazards Statement...INZ002...1 PM Tuesday to 4 PM Wednesday. LM...Small Craft Advisory...LMZ744-LMZ745...1 PM Tuesday to 4 PM Wednesday. && $$ 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 Norman OK
906 PM CDT Mon Aug 21 2017 .UPDATE... Modified PoPs earlier for activity moving into southwest/west- central Oklahoma. Continued development possible into the overnight hours southwest into north-central Oklahoma within plume of elevated moisture. Convective development late tonight into early tomorrow morning near frontal boundary still plausible, with stronger/more extensive storm development late tomorrow into tomorrow night primarily near and south of I-40. && .PREV DISCUSSION... /issued 610 PM CDT Mon Aug 21 2017/ AVIATION... VFR conditions to continue tonight with mainly mid-clouds expected to increase across the area. There is also an increasing chance for shower/thunderstorms to impact GAG/WWR overnight. Elsewhere, chances remain too low to mention overnight. A front will drop south to near or just south of I-40 Tuesday afternoon and will be focus for additional thunderstorm development. Will include a prob30 at several of the sites for late in the forecast. Still anticipate VFR conditions. 30 PREV DISCUSSION... /ISSUED 440 PM CDT Mon Aug 21 2017/ DISCUSSION... Storm chances begin to go up this evening, mainly across northwestern Oklahoma, although the RAP and especially the 18Z NAM suggest chances farther south into west central Oklahoma than earlier expected this evening. Have expanded POPs farther south, but will watch trends to see if additional adjustments will be necessary. A cold front will move into the area tomorrow morning, with additional storms expected to redevelop near the front tomorrow afternoon. But the front will also being mild-for-August weather with high temperatures generally expected to be in the 80s beginning Wednesday and through the end of the week. Some precipitation chances will persist (mainly south) with the surface front somewhere in the vicinity mid-week. As we get farther into the week, the will be some additional uncertainty with precipitation chances influenced by the track of the tropical system currently south west of the Yucatan Peninsula that models suggest may move north through the western Gulf and perhaps into the southern Plains. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 75 92 70 84 / 20 50 50 20 Hobart OK 76 95 70 86 / 30 50 50 30 Wichita Falls TX 77 98 72 88 / 10 20 50 30 Gage OK 72 89 65 85 / 30 40 20 10 Ponca City OK 76 90 65 85 / 40 40 20 10 Durant OK 75 95 73 88 / 10 20 50 40 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ 11/30
Area Forecast Discussion
National Weather Service Pueblo CO
304 PM MDT Mon Aug 21 2017 .SHORT TERM...(This evening through Tuesday) Issued at 303 PM MDT Mon Aug 21 2017 Scattered thunderstorms developing over the mountains as of 21z, with greatest coverage so far near the Continental Divide from Monarch Pass northward. Over the plains, surface cold front was slowly moving southward, with boundary just north of the Arkansas River at mid afternoon. For the rest of the afternoon and into the evening, expect isolated to scattered storms to continue to develop over the mountains, with very slow/erratic storm motions as steering currents have a very weak ely component west of I-25. On the plains, last few runs of the HRRR and NAM both suggest at least isolated activity developing along the cold front as it continues to push south, and expect most storms to end up south of the Arkansas River by mid to late evening. Main threat from any storms will be heavy rainfall, with 06z NAM hinting at higher QPF amounts over the San Juans/La Garitas this afternoon, then potentially over the srn Sangres/Raton Mesa later in the evening. Front continues to sink south overnight, and will keep some low pops for at least showers going into Tue morning over the srn mts and near the Raton Mesa, where N-NE upslope is maximized and residual convection is slow to dissipate. Cold front will be well south of the area on Tue, with cooler/moister air mass over the plains through the day. GFS and NAM both break out convection in the morning across much of the region, with convective focus shifting across the mountains in the afternoon. NAM would suggest little/no precip over the plains after 18z despite reasonably unstable (CAPE around 1000 J/KG) air mass, while GFS hints at enough wly steering flow to push mountain storms onto the plains late in the day. Will keep pops fairly high in the mountains, with a broadbrush of isolated to sct at lower elevations. Heavy rain again the main storm threat with weak shear and slow storm motions. Max temps will run several degf lower than Mon along and east of the mountains, while areas farther west see readings just slightly cooler. .LONG TERM...(Tuesday night through Monday) Issued at 303 PM MDT Mon Aug 21 2017 Relatively active weather is expected to continue, with daily chances for showers/tstms, especially over and near the higher terrain, as moisture remains over the area and occasional weather disturbance move across the state Tue night through Sat night. At this time, it looks like the southeast CO plains could see fairly widespread pcpn chances Thu night as one of those disturbances moves acrs the area. Sat night, another disturbance drops southward through eastern CO and could again bring widespread pcpn. On Sun and Mon an upper level ridge is expected to be centered over UT and will cover the western U.S. Overall, southern CO looks drier on these days but there will likely still be enough residual moisture for afternoon and evening pcpn over some of the higher terrain. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 303 PM MDT Mon Aug 21 2017 Thunderstorms will drift across the lower elevations/adjacent plains late this afternoon and into the evening. Will carry VCTS this afternoon and early this evening at all 3 terminal sites, with lowest chance at KPUB. VFR cigs along with locally heavy rainfall and erratic gusty winds up to 45 kts will be the primary storm threats. Thunderstorms will diminish this evening with winds shifting to the north at both KCOS and KPUB as a cold front moves through. Could see some isolated -shra Tue morning across the area, then more widespread convection develops over the mountains after 18z. Expect a risk of tsra at all taf sites after about 20z as storms drift away from the higher terrain. && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...PETERSEN LONG TERM...28 AVIATION...PETERSEN
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
730 PM EDT Mon Aug 21 2017 .UPDATE (Overnight through Tuesday)... 23Z water vapor and H4 RAP analysis shows the Florida peninsula resides between a large expanse of upper ridging from Carolinas/Georgia to the western Atlantic...and an upper trough retrograding westward across the central/western Gulf of Mexico. A swath of quite dry mid/upper level air has pivoted over the central and southern peninsula during the past 24 hours from the SE within the large-scale flow between these two features. This drier air as significantly held back the coverage of storms from the I-4 corridor southward this afternoon/evening. We were actually able to mix high enough to tap into this drier air...and evaporate quite a bit of the cumulus field. This process that began a bit before the effects of the passing eclipse shadow was actually enhanced by the loss of solar insolation. An even more dramatic decrease in cumulus coverage was evident in satellite imagery closer to where totality passed well off to our north. Have seen a few widely scattered storms the past few hours across the Nature coast where the impacts of the drier air have not been as great today. However, the swath of drier air will continue to pivot slowly north and northwest the next 24 hours, and it will be these nature coast zones (north of I-4) that see the greatest impact/suppression of storms from the dry air during Tuesday. So, for the rest of tonight, the few isolated shower that have been able to survive the hostile thermodynamic environment aloft will dissipate with sunset and loss of diurnal heating. The remainder of the overnight will see a dry forecast, with typical August overnight temperatures. Tuesday, the dry forecast continues over the landmass through the morning hours, with just a slow development of a few-sct cumulus field. As mentioned above, the driest mid- level air will have move up over the Nature Coast zones to the north of I-4, and it will be these areas that struggle to see much in the way of showers/storms during the afternoon/evening. A renewed influx of deep moisture will be slowly trying to move back into the central and southern part of the FL peninsula, with greatest influence the further south and SE one travels. Therefore, isolated storms (20% PoPs) are expected in and around the I-4 corridor the second half of Tuesday, ramping up to scattered coverage (30-40%) down toward Sebring/Punta Gorda/Fort Myers). Temperatures look quite warm for your Tuesday, with many spots...even close to the coast...reaching the middle 90s. Have a great evening everyone! && .AVIATION (22/00Z through 23/00Z)... VFR conditions will prevail for all terminals through much, if not all, of the the TAF period. Light easterly or northeast winds overnight will continue into the daylight hours of Tuesday, with some potential for winds to turn NW during the afternoon at KTPA/KPIE/KSRQ. Thunderstorm potential will still be below normal, although returning moisture will increase the chance for a passing storm at KPGD/KFMY/KRSW late in the afternoon or evening. Potential further north is still low enough to exclude form current TAFs. && .Prev Discussion... /issued 351 PM EDT Mon Aug 21 2017/ SHORT TERM (Tonight-Tuesday)... One tropical wave lifting off to the NW over northern FL, another wave in place over the eastern Bahamas, and high pressure ridging in between with a little dry slot across the central and southern zones this afternoon. This drier mid level air is limiting rain chances for this afternoon, with the greatest chances in place across the Nature Coast. These features will continue to shift to the W/NW through Tuesday with the dry slot lifting north and moisture returning from the south as the tropical wave approaches and then moves over southern FL through Tuesday. For Tuesday afternoon, the Nature Coast will have low rain chances, while the southern half of the area increases to 40-50 percent chances. Generally E/NE flow will be in place through the period, with a weak sea breeze possible near the coast Tuesday afternoon. Temperatures will be near normal for lows, generally in the 70s, and highs will be on the warm side in the lower to mid 90s. LONG TERM (Tuesday Night through Next Monday)... The start of the long range period will feature a strong upper trough centered over the Great Lakes with upper level high pressure from the western CONUS into the Gulf of Mexico. At the surface, high pressure will extend across the western Atlantic Ocean and the Gulf of Mexico with a weak tropical low across the far eastern Gulf. The forecast remains highly uncertain with respect to the tropical low/easterly wave expected to move across the southern tip of Florida or Florida Straits. This feature is currently being affected by an area of drier air and weak wind shear, which is good because it limits the potential for this feature to strengthen into a tropical cyclone. However, conditions may become slightly more favorable by Wednesday. So if this low makes it into the eastern Gulf of Mexico, it will have to be monitored closely. Given the feature is generally being poorly resolved, models vary in its position over the next 72 hours, with some solutions showing it over the Gulf and others just of the east coast of Florida. In the current forecast, we expect the low to track across south Florida, bringing greatly increased rain chances to areas along and south of I-4. The most recent guidance shows this low will remain a relevant feature through the latter half of the week as it slowly meanders either over south Florida, or just off the southwest Florida coast. It goes without saying, this will need to be watched closely for potential tropical development. At the very least, this feature will maintain high rain chances each day as deep tropical moisture mingles with the seabreezes and daytime heating. Locally heavy rainfall may also become a concern, especially south of I-4 where the greatest QPF signal is apparent. Heading into the weekend, a potent shortwave is expected to lead to a deepening of the Great Lakes trough, allowing a cold front to drop southward into the southeast U.S. The more aggressive European brings the drier post frontal air all the way into northern Florida with the more reserved GFS confining it more to Georgia and the Carolinas. In both cases, an interaction between the remnants of the tropical disturbance and the frontal boundary will likely promote heavy rainfall across portions of the southeastern U.S. including Florida. Temperatures will remain seasonal, becoming slightly cooler for the latter half of the week into the weekend as humidity increases. MARINE... Winds will increase with an easterly surge overnight as the area remains in weak high pressure between two tropical waves, one over northern Florida, and the other over the eastern Bahamas. The features will shift west through mid- week, with high pressure then returning over the waters for the end of the week. Scattered showers and storms possible as moisture returns across the area through the rest of the week. No headlines expected through the period. FIRE WEATHER... No concerns. && .Preliminary Point Temps/PoPs... TPA 78 94 78 92 / 10 20 10 30 FMY 77 95 77 92 / 10 40 40 60 GIF 75 95 76 94 / 0 30 10 40 SRQ 77 95 78 92 / 10 20 30 30 BKV 72 95 75 94 / 10 10 10 20 SPG 80 94 79 92 / 10 20 20 30 && .TBW WATCHES/WARNINGS/ADVISORIES... FL...None. Gulf waters...None. && $$ UPDATE/AVIATION...Mroczka PREVIOUS DISCUSSION...HUBBARD
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Tuesday) Issued at 257 PM CDT Mon Aug 21 2017 19Z water vapor imagery shows a low amplitude shortwave moving through the northern plains. A weak MCV from the early morning convection has become difficult to discern over northeast KS and likely has sheared out. Otherwise water vapor imagery shows a plume of mid level moisture from wester TX through northeast KS. At the surface, a prefrontal trough was noted from northwest KS into the eastern Dakotas with a cold front over western ND and into eastern WY. For tonight models still show some weak vorticity advection ahead of the northern plains shortwave and some frontogenesis overnight with the front. With the very moist airmass in place, showers and thunderstorms are expected to become widespread this evening and move through the area overnight. Models have trended slightly faster with the frontal system and some of the high resolution models show precip exiting the forecast area to the southeast by 7 am Tuesday. The clouds and shower activity have slowed down the destabilization of the boundary layer. But RAP analysis suggests MLCAPE values over 2000 J/kg beginning to develop. Deep layer shear remains a little marginal, but look to be good enough that if a discrete storm were able to persist it could go on to produce some severe hail and winds. Aside from that, the main focus remains on the heavy rain potential. With PWs still progged over 2 inches, the airmass looked primed for heavy rainfall. Although with the model trends of a faster progression to the frontal system, the risk for flash flooding looks to have diminished somewhat. While the ensemble means for QPF have also lessened, a few members continue to show the potential for isolated heavy to excessive rain. Because of this will maintain the flash flood watch as is. Showers and thunderstorms should be moving southeast of the area Tuesday morning and have POPs decreasing with virtually a dry forecast for much of the area by noon. The stronger cold air advection looks to hold off until late morning or early afternoon so Lows tonight are expected to remain muggy with readings in the upper 60s to around 70. Have trended highs cooler by a degree or two with models showing decent low level cold air advection through the afternoon. Have forecast highs in the lower and middle 80s. .LONG TERM...(Tuesday night through Monday) Issued at 257 PM CDT Mon Aug 21 2017 By Tuesday night, the mid-level trough will be shifting into the northeastern U.S. with surface high pressure sliding southward from the Northern Plains into the central U.S. The region will remain under the influence of this surface high pressure and northwesterly flow aloft through Thursday, resulting in dry conditions and temperatures cooler than the seasonal normals with highs in the low 80s. By Thursday night, models show a mid-level ridge briefly building into the central U.S. ahead of a mid-level trough diving into the Pacific Northwest. Models are in decent agreement with showing an embedded shortwave developing within this ridge Thursday night and gradually tracking across the CWA Friday and Friday night. The mid- level trough over the Pacific Northwest will get pushed back into Canada as a broad mid-level ridge builds across the western U.S. Saturday through Monday. The central U.S. will remain under northwesterly flow aloft into early next week, with models showing additional embedded waves developing within the mid-level flow. As a result, some periods of scattered showers and thunderstorms will be possible from Thursday night into Sunday, with some isolated precipitation possibly continuing into early next week. Temperatures through the weekend and into early next week will remain below the seasonal normals, with highs staying in the low 80s and low temperatures in the low 60s. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 610 PM CDT Mon Aug 21 2017 Scattered TSRA developing north and west of terminals currently. Radar trends has the cluster through KMHK by 02Z with no reduction in flight category. A little more uncertain how the band of TSRA evolves as it moves eastward towards KTOP/KFOE. Sfc analysis shows a frontal boundary in the area with ample instability, despite meager amounts of wind shear. Have therefore kept a mentioned of VCTS with scattered showers through 08Z when short term models clear the convection eastward. Next focus is the convection that develops along the front currently in Nebraska in the 06-09Z time frame. Current indications is that coverage may not be as widespread as previous guidance. Nonetheless kept the mention of TSRA with MVFR stratus developing along and just behind the boundary through 16Z. && .TOP WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Tuesday morning for KSZ011-012-022>024- 026-035>040-054>056-058-059. && $$ SHORT TERM...Wolters LONG TERM...Hennecke AVIATION...Prieto
Area Forecast Discussion
National Weather Service Wakefield VA
201 PM EDT Tue Aug 22 2017 .SYNOPSIS... High pressure remains centered off the Mid Atlantic coast through tonight as a cold front begins to approach from the west. The front crosses the area late Wednesday afternoon through Wednesday night, with strong high pressure building north of the area from Thursday into the upcoming weekend. && .NEAR TERM /THROUGH TONIGHT/... Latest surface analysis centers ~1021mb high pressure from eastern NC to well off the coast, resulting in a light southerly flow over the local area. Some lingering low clouds still visible over southeast Virginia/northeast North Carolina, but expect those clouds to dissipate in the next hour or so. Humid conditions, with dewpoints ranging from the low 70`s northwest to upper 70`s southeast. For today, increasing return SSW flow will prevail on the back side of departing high pressure offshore and ahead of an approaching cold front. A weak thermal/lee trough by this aftn will provide a bit more of a pressure gradient than the past few days, resulting in SSW winds of 10-15 mph this aftn. Highs today should rise about 2 to 5 degrees above Monday`s values, with low-mid 90s for most locations (and only a little cooler near the coast). Humid air mass remains entrenched over the area, with dewpoints mixing down only into the low to mid 70`s. Heat indices this afternoon will approach 105 F for an hour or two, especially across southeast Virginia and northeast North Carolina. Given that it will be marginal and latest guidance and trends are consistent, did not issue a heat advisory but will mention in the HWO. While the atmosphere will be quite moist with precipitable waters around 1.75 inches, warm air aloft, weak lapse rates, and a lack of appreciable forcing will limit the convective potential this afternoon. Will retain silent PoPs for most areas, did add a 20% over a few spots across interior NE NC where RAP and hi-res guidance indicate some convergence away from the coast. Warm/humid tonight with little chance for any rain under a SW wind of 10 mph. Lows mainly in the mid to upper 70s. Clouds increase across the north ahead of the approaching cold front and lead shortwave. Have introduced a slight chance PoP for the Maryland Eastern Shore late tonight, but best chances for measurable precipitation remain north and west of the local area. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... Better forcing arrives along the front Wednesday as a lead wave drops over the Mid-Atlantic. The cold front progged to slowly push across the area Wednesday afternoon into Wednesday night. Latest models generally depict somewhat weaker forcing with the lead wave as the vort gets sheared out, and have dropped PoPs a little from previous forecast through 18Z. PoP`s increase more during the 18Z/Wed to 00Z/Thu period, with some sharpening of the upper trough looking to focus best lift over southern/SE zones. Will have high chc PoPs N/NW zones to likely over the S/SE late in the day. The air mass ahead of the front will become modestly unstable, with mixed- layer CAPE values progged around 1000-2000 J/kg. Deep layer flow also progged around 25-30 knots as mid level flow increases, resulting in better organization and overall storm strength. Mid level lapse rates also improve to around 6 to 6.5 C/km late. SPC maintains a marginal risk for severe weather for most of the CWA, with damaging winds and heavy rainfall the main threats. The NW, where PoPs are a little lower and where the lift is weaker is not included in the marginal risk at this time. Highs generally in the mid-upper 80`s north to around 90 F south. Strong Sfc cold front drops south across the area Wednesday night into Thursday morning. Modest ascent accompanies the front within the RRQ of a ~110kt jet over New England, along with PW values to around 2.0" (around +1 st dev). By Wed evening, have maintained highest (70%/Likely) POP across srn VA/NE NC, with slight to low end rain chances by Wed night NW of RIC, where drier air arrives first. PoPs across SE portions gradually diminish to high chance by daybreak Thu morning. Thunder will be maintained into Wednesday evening, with showers thereafter as stable NE flow prevails in the wake of the front. Drier air gradually filters in from the NW late Wednesday night into Thursday with partial clearing across the nrn tier counties. Lows lower 70s SE to mid-upper 60s NW. && .LONG TERM /THURSDAY THROUGH MONDAY/... The pattern will be characterized by the gradual development of a longwave upper level trough over the eastern United States for the late week period into next weekend. Meanwhile, broad 1024+ mb surface high pressure builds south over the interior northeast from Great Lakes Thursday and Friday, eventually setting up over New England and ridging down the east coast over the weekend into early next week. Resultant E-NE flow will result in markedly cooler and drier conditions over the region, with early morning lows in the 50s to lower 60s inland to mid-upper 60s along the coast. Maintained a dry forecast through the forecast period. Overall, high temperatures Thu-Mon will be below normal for late August, mainly in the upper 70s to low 80s. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... VFR and dry conditions prevail to begin the 18Z TAF period as high pressure remains centered just offshore. Scattered cu with decks around 3 to 4k feet AGL has developed across the region. South to southwest winds generally 10-15 knots. Few gusts to 20 knots inland. Not much chance for any tstms today or this evening. A cold front approaches the region late tonight, but with a continued SW flow, expect VFR conditions tonight/early wed morning with fog/low stratus unlikely. Flight restrictions will be possible with the front later on Wednesday...mainly in the afternoon and through Wednesday night due to showers and thunderstorms. The front should exit the coast Thursday morning with lingering showers possible across far SE VA/NE NC. Conditions are anticipated to improve Thursday afternoon into Friday as the front shifts farther southeast and high pressure builds north of the region. Breezy NE winds expected near the coast Thursday and Friday. && .MARINE... Early this morning, sfc high pressure was cntrd off the Mid Atlc coast. Winds were SSW 5 to 15 kt over the waters with Waves 1 to 2 ft, and Seas 2 to 3 ft. The high will slide farther out to sea during today. A cold front will approach the waters from the NW tonight, then crosses the area Wed thru Wed night. High pressure will then gradually build down into the region from the NW Thu aftn into Sat. SSW winds will increase later today into tonight, as the front approaches the waters fm the NW. Have kept wind speeds at 15 kt for the Ches Bay tonight, and 15 to 20 kt for the coastal waters, with a few gusts up to 25 kt possible over the nrn two coastal zns. Waves will build to 2 to 3 ft in the Ches Bay, and Seas will build to 3 to 5 ft over the nrn coastal zns. Thus, have issued a SCA for the nrn two zns (650-652) fm late this evening into early Wed morning. Winds shift to the N/NE behind the front fm later Wed aftn into Thu morning, mainly 10 to 15 kt. Post-frontal, look for onshore (NE flow) for the remainder of the forecast period, as high pressure builds in fm the NW. Expect wind speeds at 10 to 15 kt (could be gusts to 20 kt) acrs most of the waters, with the highest winds over the SE VA/NE NC waters. Waves will be 1 to 3 ft, and Seas will be 2 to 4 ft. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 10 PM this evening to 6 AM EDT Wednesday for ANZ650-652. && $$ SYNOPSIS...LKB NEAR TERM...LKB/SAM SHORT TERM...LKB/SAM LONG TERM...MAM AVIATION...LKB/SAM MARINE...TMG
Area Forecast Discussion
National Weather Service Albany NY
147 PM EDT Tue Aug 22 2017 .SYNOPSIS... Warm and muggy conditions are expected today with showers and thunderstorms developing ahead of a cold front, mainly this afternoon into this evening. Any thunderstorm will be capable of producing gusty winds and heavy rainfall. The threat for showers and thunderstorms will end tonight with the passage of the cold front. Much cooler and drier air will move into the region tomorrow, with dry and comfortable conditions expected for the rest of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... ...Tornado Watch 461 is in effect until 9PM for the Adirondacks, Mohawk Valley, and Warren county... As of 130 PM EDT, Strong line of convection has developed across western NY/eastern Great Lakes with some isolated cells expected ahead of it. This main line of convection will make its way eastward and into the forecast area from NW to SE beginning around 20Z, where damaging winds and heavy rain will be the primary threats. Cannot rule out an isolated tornado/spin-up along the convective line, especially in the Adirondacks and Mohawk Valley regions where there is a tornado watch. That being said, made no major changes to the forecast but freshen up the hourly temps and sent updates to NDFD and web servers. Prev Disc... As of 1041 AM EDT...skies range from clear to mostly cloudy around the area. temperatures are in the 70s to around 80F. dewpoints have risen to around 70F. Winds are generally from a southerly direction. Isolated showers and thunderstorms popped up this morning along back door warm front. These showers have dissipated. The surface cold front is still crossing Michigan, still well upstream. With 850 hpa temps rather warm (16-18 degrees C), it should be yet another warm day. Max temps look to reach the mid to upper 80s for valley areas by early afternoon and dewpoints will be very sticky in the mid to upper 60s. Previous... As the cold front and upper level trough continues to move eastward, some scattered showers/thunderstorms should develop along a pre-frontal trough by the early to mid afternoon hours for the Adirondacks, as seen in the 3km HRRR and NAM. There could be multiple bands of thunderstorms for late today, as more organized convection (perhaps a QLCS) looks to develop just ahead of the front boundary for late this afternoon into this evening and move across the entire region from west to east. There is considerable concern for some strong to severe thunderstorms today. 0-6 km bulk shear increase to 35-45 kts by late today, especially across northern/western areas. There is also a decent amount of shear within the bottom 1-2 km (as much as 30-35 kts), especially just ahead of the frontal boundary across the Hudson Valley, where the low-level flow will remain backed within the valley, resulting in locally higher helicity. This would favor the development of a localized tornado threat, especially in any supercells that develop and any notches along a QLCS. There still is question about the exact degree of instability, and the models still vary the amount of CAPE that will be present. Considering the warm/humid air mass, 1500-2500 J/kg of surface-based CAPE is reasonable. If dewpoints are a little lower than what models suggest, it could be more in the 1000-2000 J/kg range, but still more than sufficient to support severe thunderstorms. One mitigating factor will be that mid- level lapse rates will be rather weak due to the warm temps aloft, generally less than 6 deg/km. Still, the strong shear and dynamical forcing should be enough to support organized and persistent thunderstorms today. As a result, SPC has placed the western and central Adirondacks and Mohawk Valley in an Enhanced Risk for severe storms, with a slight risk across much of the remaining parts of the area. Main threat is damaging winds, but cannot rule out an isolated tornado or large hail within any discrete cells. In addition, PWATS rising in excess of two inches would result in a threat for heavy rainfall within a short period of time, which could result in localized flooding, especially for urban and poor drainage areas. Although the fast flow aloft should keep cells moving, the expected multiple rounds of convection could result in some training, which may allow for excessive rainfall in some areas. WPC has much of the area in a slight risk for excessive rainfall today, so flash flooding cannot be ruled out today. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... Thunderstorms will be continuing this evening, with the main threat for severe storms through about midnight, as storms track west to east across the area. The threat for showers and thunderstorms should end with the passage of the cold front by late tonight, with lows remaining in the 60s. Behind the front, cooler and less humid air will work into the region for the middle of the week. Mainly dry weather is expected through the rest of the short-term period, although cannot totally rule out a lingering rain shower across the Adirondacks or Mohawk Valley for later Wednesday into Thursday, as the passing upper level trough picks up some moisture off Lake Ontario and allows for a lake- enhanced shower or two. Highs on Wednesday will reach the mid 70s to low 80s, but temps on Thursday only look to reach the low to mid 70s for valley areas. Overnight lows will mainly be in the 50s, with some 40s across the higher elevations. Sky cover will generally be partly cloudy. && .LONG TERM /FRIDAY THROUGH TUESDAY/... Extended period of fair weather with slightly below normal temperatures. Canadian high pressure at the surface will build in and shift southward as it expands across the Great Lakes region and the Northeast over the weekend into early next week. An upper level trough will remain over region however heights are expected rise some as the trough weakens. Short waves are expected to rotate through the trough however guidance differs on the timing and strengthen of them; mainly expecting an increase in cloud cover as the individual short waves approach and move through. Looking at temperatures around 5 degrees below normal with highs generally in the mid 60s to upper 70s and lows in mid 40s to mid 50s. Cooler readings are expected across the higher terrain of the western Adirondacks, eastern Catskills and southern Green Mountains of Vermont. In addition to the cooler temperatures, we will have low humidity levels with dew points in the 40s and lower/mid 50s. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... Line of showers and some strong thunderstorms currently extends from the Saint Lawrence River Valley southwest to Watertown, Rochester and then to Bradford, PA. We expect this line to gradually move southeast this afternoon and evening and bring thunderstorms to all the TAF sites between 23/00Z and 23/05Z. A stray shower or storm is possible this afternoon at the TAF sites, but only a low probability Highest probability is at KGFL. Gusty south to southwest winds of 10 to 20 kts expected today. Frontal passage is expected between 06Z and 12Z Wednesday with the winds shifting to the northwest behind the front. Winds Wednesday will be mainly from the northwest at 5 to 15 kts. Outlook... Wednesday-Saturday: No Operational Impact. NO SIG WX. && .FIRE WEATHER... Ahead of an approaching frontal boundary, it will be warm and muggy today. RH values will only fall to 55 to 65 percent this afternoon. Most areas should see a wetting rainfall due to passing afternoon and evening showers and thunderstorms. Southerly winds will be 10 to 20 mph today, and will switch to the west by tonight at 5 to 15 mph. Behind the front, cooler and less humid conditions will be in place for the rest of the week. RH values look to fall to 45 to 55 percent on Wednesday afternoon with westerly winds of 10 to 20 mph. && .HYDROLOGY... An approaching cold front will allow for showers and thunderstorms today, mainly during the afternoon and evening hours. Any thunderstorm will be capable of producing locally heavy downpours and could lead to isolated flash flooding. The locally heavy rainfall may also result in minor flooding of urban, poor drainage and low lying areas. Behind this frontal system, mainly dry weather is expected for the rest of the week. Basin average rainfall on Tuesday will generally be around a half of an inch to an inch, although point totals may be higher. This rainfall will only allow for minor rises on rivers and streams. River and stream levels should quickly recede by Wednesday and then remain steady for the rest of the week. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .EQUIPMENT... The KENX radar will likely be down through at least Friday, September 1st for the bull gear replacement. We are waiting for a ROC maintenance team and parts to arrive to assist local technicians with the repairs. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...Tornado Watch until 9 PM EDT this evening for NYZ032-033- 038>040-042-082-083. MA...None. VT...None. && $$ SYNOPSIS...SND NEAR TERM...SND/JVM SHORT TERM...Frugis LONG TERM...IAA AVIATION...SND FIRE WEATHER...Frugis HYDROLOGY...Frugis EQUIPMENT...
Area Forecast Discussion
National Weather Service Gaylord MI
128 PM EDT Tue Aug 22 2017 .UPDATE... Issued at 1017 AM EDT Tue Aug 22 2017 Secondary cold front/trough swinging through Northern Lower Michigan this morning with a band of mainly showers and possibly a rumble of thunder. Fairly tight gradient with fropa and have seen some gusty winds of 30-40 mph along the nearshore waters. The gustier winds will be translating across the rest of the CWA over the next few hours, highest along some of our coastal locations. I raised POPS across much of the area for the next few hours as the front moves through. Quite a bit of subsidence/dry air coming in for the afternoon hours, so clouds should scatter out with increasing sunshine for most areas. Temperatures fairly steady for the afternoon hours. The most noticeable difference for the afternoon hours will be steadily lowering dewpoints - much less humidity! && .NEAR TERM...(Today through Tonight) Issued at 342 AM EDT Tue Aug 22 2017 High impact weather potential: Thunderstorms early this morning. Pattern synopsis and forecast: Upper level troughing was working into the western Great Lakes early this morning, with an associated sfc low pressure deepening while tracking into eastern Lake Superior. The system cold front extended from this low back through eastern Wisconsin and Iowa. Showers and some isolated thunderstorms have finally developed over the last couple of hours as low level convergence and DPVA have increased within a region of 400-900 j/kg of MUCAPE. Latest RUC analysis also suggests that maybe some right entrance region dynamics from 100+kt jet are in play. Quite the warm/muggy morning with temperatures and dew points in the middle 60s to lower 70s. Upper troughing settles in over the region through the day with the sfc low lifting into Quebec, while dragging the cold front through nrn Michigan this morning into early afternoon. The forcing continues to increase through daybreak with showers and isolated storms likely to continue to increase in coverage. No severe storms with not much instability around and lapse rates not all that impressive at less than 6c/km. A secondary sfc trough axis looks to follow behind the cold front, resulting in a band of lighter rains, especially into the higher terrain of nrn lower. There is likely to be some afternoon cumulus, but the overall air mass dries through this evening. As cold advection continues through the night however, temperatures get cold enough for overlake instability, almost to 850mb. Gotta believe that lake effect clouds in NW flow will be common by daybreak Wednesday. Highs not really going anywhere through the day with middle 60s to lower 70s, slightly higher in downsloping areas of NE lower. Lows tonight in the middle 50s most areas with less humidity. && .SHORT TERM...(Wednesday through Thursday) Issued at 342 AM EDT Tue Aug 22 2017 ...Cool weather for midweek... High Impact Weather Potential: Minimal. Pattern Forecast: North American pattern features a decent short wave trough for late August moving through the Midwest and adjacent portions of Manitoba/Ontario. Overall pattern from the Midwest back into the eastern Pacific has become more amplified over the past 36 hours with short wave ridging having developed over British Columbia downstream of a compact upper low south of Alaska. Associated with the Midwest short wave trough is a 1008mb surface low over northeast Minnesota...with an eastward extending warm front across Upper Michigan and into southern Quebec...and a trailing cold front back into northwest Iowa/Nebraska. Plenty of humidity south of the warm front with dew points well into the 60s/precipitable water values in the 1.50-2.00 inch range (1.58 inches on 00z APX sounding). Cold advection into the mid level short wave trough moving through the Midwest suggests continued deepening of this feature... eventually closing off north of the Great Lakes later today. The result will be deep layer cyclonic flow across Michigan for the midweek period...followed by rising heights for the end of the week as short wave ridging crosses the prairie provinces. Impressive surface low for late August will drag cooler air across the Great Lakes...followed by high pressure building in for Thursday/Friday. Thermal troughing will ensure a much cooler pattern. Primary Forecast Concerns: Cold air getting pulled across the lakes should bring about a good deal of lake plus diurnally induced cloud cover Wednesday. Some scattered light rain showers also possible within typical northwest flow lake effect areas at least into early afternoon. Breezy day expected with gusts 20-25+mph...winds should subside by Wednesday evening. Highs Wednesday will be mostly stuck in the 60s...generally 8-12 degrees below normal. No real issues for Thursday outside of some nuisance cloud issues between thermal trough in place and short wave trough rotating across the area from the north...again probably through early afternoon with decreasing clouds north to south. Probably another afternoon with highs in the 60s...and chilly Friday morning where some of the typical cold spots will probably drop into the 30s. .LONG TERM...(Thursday night through Monday) Issued at 342 AM EDT Tue Aug 22 2017 High Impact Weather Potential: Minimal. Great Lakes looks to be stuck in split flow between ridging across northern Ontario and a southern branch weakness that develops over the Mississippi Valley this weekend. The result is fairly weak upper level flow across Michigan for the weekend. High pressure will be in place Friday...and given lack of "direction" from above will probably linger through the weekend though a couple short wave troughs may slide across Michigan. How weakness in the southern branch of the split flow evolves early next week is uncertain. Overall weather looks quiet through the weekend...with a moderating trend in temperatures. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 122 PM EDT Tue Aug 22 2017 A cold front has pushed through the area, with generally MVFR CIGS in its wake. Drier air is working into the area from the northwest and this will continue through the afternoon hours, resulting in clouds gradually scattering out. This evening will likely be fairly clear, before cold air advection over the warm lakes begins to produce lake clouds overnight. These clouds will persist through the first half of Wednesday. VFR cigs are generally expected at this time, with pockets of MVFR possible. A few light lake effect rainshowers are also possible. Northwest winds will be gusty both this afternoon and Wednesday, with a strong gradient across the Great Lakes. Gusts of 20+ kts are expected this afternoon, subsiding some tonight, with gusts of 20+ kts expected again on Wednesday. && .MARINE... Issued at 342 AM EDT Tue Aug 22 2017 A cold front will sweep across the region this morning into early afternoon, with winds shifting out of the NW and becoming quite gusty due to a tight gradient and developing overlake instability. Widespread advisory winds, with low end Gales expected in Whitefish Bay and through Presque Isle light for this afternoon and evening. Advisory speeds will be common in most nearshore waters into Wednesday before higher pressure approaches Wednesday night into Friday. Showers and isolated non severe storms ahead of the front this morning. && .APX WATCHES/WARNINGS/ADVISORIES... MI...BEACH HAZARDS STATEMENT through late tonight for MIZ016-019>021- 025-031. LH...SMALL CRAFT ADVISORY until 6 PM EDT Wednesday for LHZ345-346-349. GALE WARNING until midnight EDT tonight for LHZ347-348. LM...SMALL CRAFT ADVISORY until 6 PM EDT Wednesday for LMZ323-341-342- 344>346. LS...SMALL CRAFT ADVISORY until 6 PM EDT Wednesday for LSZ322. GALE WARNING until midnight EDT tonight for LSZ321. && $$ UPDATE...JK NEAR TERM...SMD SHORT TERM...JPB LONG TERM...JPB AVIATION...JK MARINE...SMD
Area Forecast Discussion
National Weather Service State College PA
244 PM EDT Tue Aug 22 2017 .SYNOPSIS... A strong cold front will move through the region late today and early tonight. Much cooler and drier conditions will return for the second half of the week. Temperatures will average a few degrees below normal highs starting tomorrow and lasting into early next week. && .NEAR TERM /THROUGH TONIGHT/... Radar motor was installed and it has been up for over an hour. In a nick of time. Updated forecast to show the potential for severe thunderstorms this afternoon and evening. First lead cells developed over Warren County. Stronger storms are to our west. The NCEP and GSD HRRR show at least two potential lines this afternoon and evening. With deep cores and 850 hPa winds 40 to 55kts strong and severe winds at the surface are possible. Tornado watch was for more QLCS type tornadoes. Though we have had a few initial rotating cells in KCCX and KBUF radar. More linear features to our west. Ahead of the convection a very hot humid Summer day. Farther east you live the more likely this day will end on a good note as convection will be in evening and SPC may issue watch for eastern PA later this afternoon. Behind the line POPS drop fast and drier air comes. Some areas of fog possible. But a cooler and drier AM Wednesday. && .SHORT TERM /WEDNESDAY/... Wednesday will be noticeably drier as the PW values crash to -1 sigma below normal after being well +1 to +2 sigma above normal. It will also be significantly cooler. The 850 hPa temperatures fall to near normal Wednesday and will fall below normal overnight Wednesday into Thursday. Chance of rain should be very low Wednesday. The cool air aloft will likely produce some cumulus in the mountains during the afternoon hours. It should be a nice and notably cooler day. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... An extended period of early autumn-like weather will begin Wednesday and continue right through the upcoming weekend as a -2 sigma upper trough (and similarly anomalous/cool 850 mb temps) move over the Great Lakes and NE U.S. 1026-1028 mb SFC High (+2-3 Sigma) over south-central Canada will drift slowly to the Great Lakes by this weekend Daytime high temps will be about 5-7 Deg F below normal across the Western Mtns on Wednesday, though still just slightly below normal across the SE zones prior to the arrival of the deeper/colder air for the latter part of the week. GEFS mean 850 mb temps will dip about 2-3 deg C in all locations for Thursday-Sunday, leading to max temps averaging 5-10 F below normal (with min temp departures about 10-13F below normal Friday-Sunday) as a large Canadian High Pressure area pushes SE across the Glakes Region and becomes centered over the NE states. Lows Fri/Sat/Sun mornings with high centered overhead will be dipping into the l-m 40s over the Northern Mountains (and deeper valleys of the Central Mountains) and solidly into the 50s elsewhere. Some of the perennial cold spots near and to the east of KBFD could see readings of 38 or 39F. && .AVIATION /19Z TUESDAY THROUGH SUNDAY/... Most of the eastern areas mostly sunny with some cumulus clouds about making for a bumpy ride in the boundary layer. Over western PA and OH there is a line of strong and severe storms. Strong winds and large hail are possible. Check radar before flying over western PA this afternoon and central areas this evening. The line of storms will move east this afternoon and evening. Areas of patchy fog will develop around/after midnight. Spotty MVFR and IFR. Conditions will improve rapidly Wednesday morning, as cool Canadian high pressure builds into the area. .OUTLOOK... Wed...AM low cigs BFD/JST, otherwise VFR. Thu-Sat...No sig wx expected. && .EQUIPMENT... KCCX is fixed with new motor installed. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Grumm SHORT TERM...Grumm LONG TERM...La Corte/Lambert AVIATION...Grumm/Lambert EQUIPMENT...
Area Forecast Discussion
National Weather Service Duluth MN
110 PM CDT Tue Aug 22 2017 .SHORT TERM...(Today through Wednesday) Issued at 321 AM CDT Tue Aug 22 2017 The remnants of a mid-level shortwave will move out later this morning, which will bring a brief respite to any precipitation chances this morning. However, as the shortwave departs to the east, northwest flow aloft will continue, along with some weak cold air advection. This will support chances of showers and perhaps a small chance of a thunderstorm late this morning and through the afternoon, mainly along the International Border and Iron Range regions. Some of this activity may reach as far south as the Twin Ports and South Shore regions as well as some of the convective- allowing models (HRRR and NAMNest) are progging this solution. 850 mb temperatures will fall to the 6 to 8 degree C range, with some decent instability possible, as MUCAPE values range from a few hundred up to around 1000 J/kg. 850 mb wind speeds will also increase, with values between 25 to 35 kts. NAM and RAP model soundings both indicate some decent boundary layer mixing expected, which will help to mix down these low-level winds. Moreover, pressure rises from the west will enhance the sfc pressure gradient. To account for this, I bumped up the winds a bit more from the previous forecast package, leaning towards the MOS guidance. Wind gusts across the Northland could increase up to 25 kts, with possibly some isolated stronger gusts. Temperatures will be on the cool side today, with highs ranging from the lower 60s over the tip of the Minnesota Arrowhead, into the upper 60s and lower 70s further inland. Chances of showers and storms will quickly decrease this evening as diurnal heating diminishes. As such, cloud cover should also diminish. This, coupled with light winds, will lead to a night of rather cool temperatures due to radiational cooling. Temperatures over northern Minnesota could drop to as low as the lower 40s in some spots. Due to the expected reduction in temperatures, introduced some patchy fog to the forecast for tonight, mainly from north-central Minnesota, southeast towards Hayward, WI. Most of the day Wednesday looks to be dry, but cool, with highs in the mid to upper 60s. A compact mid-level shortwave trough is progged to then bring another round of showers to the Northland, late in the day Wednesday. .LONG TERM...(Wednesday night through Monday) Issued at 319 AM CDT Tue Aug 22 2017 The Northland will be under northwest flow aloft through much of the extended period with high temperatures mostly below normal. There will be a few opportunities for mainly showers as several shortwaves move through the region. A shortwave will move through the region Wednesday night and combine with low-mid level FGEN to cause a chance for showers during the evening from the Walker area to the Twin Ports to Hayward and points south. As those features exit late Wednesday night, high pressure will nose into the area, bringing dry conditions Thursday and Thursday night. Mainly dry conditions will continue into Friday as the high shifts further east. Highs Thursday and Friday will range from the upper sixties to lower seventies. A couple more shortwaves will affect the region over the weekend aiding to knock down the upper ridge with a trough developing over the region. There will be a chance for showers over the weekend into early next week with highs Saturday from the upper sixties to lower seventies warming slightly by Monday. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 107 PM CDT Tue Aug 22 2017 Mainly VFR across all sites through the forecast period. There may be some MVFR cigs with rain showers this afternoon across the DLH/HIB/INL airports. There could be some early morning fog Wedensday but conditions should stay VFR through midday Wednesday. && .PRELIMINARY POINT TEMPS/POPS... DLH 70 49 66 47 / 20 20 20 20 INL 67 44 66 41 / 30 20 10 0 BRD 72 47 69 48 / 0 0 30 20 HYR 70 49 67 44 / 10 10 10 20 ASX 71 50 66 46 / 20 30 10 10 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...Small Craft Advisory until 10 PM CDT this evening for LSZ146-147. && $$ SHORT TERM...JTS LONG TERM...Melde AVIATION...Stewart
Area Forecast Discussion
National Weather Service Flagstaff AZ
949 AM MST Tue Aug 22 2017 .SYNOPSIS...Isolated showers and thunderstorms will develop along the Arizona-Utah border today. An uptick in thunderstorm activity is forecast across all of northern Arizona Wednesday and Thursday. For Friday and over the weekend...thunderstorm chances will decrease. && .UPDATE...Latest radar trends indicate isolated showers rotating north of a line from Grand Canyon Village to Tuba City to Fort Defiance. The latest HRRR progs scattered thunderstorms developing near the AZ/UT border this afternoon. As a result, updated the forecast to indicate the greatest chances of convection near the AZ/UT border. Also updated the sky cover based on current obs/trends. Otherwise, the remaining forecast elements are in good shape. && .PREV DISCUSSION /241 AM MST/...A low pressure system continued to spin just off the central California coast during the morning hours. Showers and thunderstorms across the northwest portion of Arizona will subside by noon as a drier air mass and a warm layer aloft spins around the California low and across Arizona. As a result, expecting mainly isolated shower and thunderstorm activity for most of today through Thursday. For Friday and the weekend...The low weakens as high pressure surges northward across Arizona, Nevada and Utah. The drier air mass and shorter days will make it tough for much more than isolated afternoon and evening thunderstorms across much of the area. The exception will be the White Mountains region of east central Arizona where moisture will remain more substantial and storms more numerous. Early next week...Monsoon moisture will attempt to make a comeback, pushed northward by an increase in thunderstorm activity over northwest Mexico. At this time the best chances look to be from the Mogollon Rim southward. We`ll see. && .AVIATION...For the 18Z package...Expect isolated thunderstorms after 18z with coverage mostly north along the Arizona and Utah border, decreasing after 02Z this evening. Heavier storms may produce IFR/MVFR conditions temporarily. Winds less than 10 kts outside of showers/storms. Otherwise, VFR expected to prevail. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Expect isolated to scattered thunderstorms today and Wednesday, favoring the mountainous areas of northern Arizona. Daytime temperatures will be near average with generally light winds. Thursday through Saturday...Thunderstorm chances will continue through Thursday afternoon. A drying trend is forecast Friday through Sunday. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && $$ PUBLIC...TM/McCollum AVIATION...ET FIRE WEATHER...TM For Northern Arizona weather information visit weather.gov/flagstaff
Forecast discussion for routine afternoon forecast issuance

.SYNOPSIS... Issued at 220 PM CDT Tue Aug 22 2017 Generally quiet late-summer weather into early next week. Seasonably cool the next couple days, then temperatures close to normal. The large scale pattern will complete an amplification cycle the next couple days as a rather strong upper trough becomes established from eastern Canada into the lower Great Lakes region. Jet energy working east across Canada will cause the trough to begin weakening by late in the week. By early next week, the main westerlies will recede north into Canada, leaving just a weak remnant of the trough lingering across the forecast area. Temperatures will begin the period below normal, then rebound to near normal levels by the weekend. Rainfall will be limited with precipitation events consisting of just scattered showers. As such, amounts for the period are likely to end up below normal. && .SHORT TERM...Tonight and Wednesday Issued at 220 PM CDT Tue Aug 22 2017 The latest RAP analysis and satellite/radar imagery show upper troughing settling over the western Great Lakes early this afternoon. A widespread cu field has developed across the region, though cu has the most vertical extent over far northwest WI and northeast MN where the highest capes reside. Some of this more enhanced cu and even a few showers will move into north-central WI later this afternoon. As cold air continues to funnel across the region, forecast concerns revolve around light showers early this evening, followed by lake effect showers/drizzle late tonight. Tonight...As a secondary surge of cold air arrives from the northwest tonight, high res models continue to indicate that scattered showers will persist over north-central WI through the mid evening hours. Then attention turns to precip off western Lake Superior overnight. 1000-850mb flow veers around to the NNW direction after midnight, which is a good trajectory for showers or drizzle to move into north-central WI. Increased cloud cover some late as a result, but 10-15 kts of low level flow should not be strong enough for these clouds to move into central or east-central WI. With enough wind to prevent temps from tanking, should see lows ranging from the mid 40s north to mid 50s south. Wednesday...Broken cloud cover along with patchy drizzle/showers will likely linger into the mid-morning hours over northern WI. With day time heating, however, think mixing will cause these clouds to scatter by midday. Elsewhere, should see scattered fair weather cu develop, which will lead to a partly cloudy day for most. Highs ranging from the low 60s in the far north to mid 70s at Wautoma. .LONG TERM...Wednesday Night Through Tuesday Issued at 220 PM CDT Tue Aug 22 2017 At low-levels, a cool, dry Canadian air mass will settle across the area and linger through the weekend. Some pretty chilly nights are likely unless clouds move through during the nighttime hours. The typical cool spots across the north will probably fall into the 30s Wednesday night and Thursday night, and would not be surprised if there is some patchy frost. The anticyclone and its associated air mass will linger across the area for much of the forecast period, but moderation of the air mass should allow temperatures to rebound to near seasonal levels by the weekend. While the dry anticyclone dominates at low-levels, the forecast area will be at least brushed by some middle and upper level shortwave energy at times. That will lead to some clouds and maybe some showers. But given the limited moisture, any rains are likely to be scattered and light. Tweaked mins down in the typical cool spots Wednesday night and Thursday night, but tempered the adjustments some due to uncertainty about passing clouds. Otherwise, the standard forecast initialization grids based on a broad blend of model output seemed reasonable, so no other significant changes were necessary. && .AVIATION...for 18Z TAF Issuance Issued at 1052 AM CDT Tue Aug 22 2017 Cloud bases continue to rise at midday, and should settle in the 4000-5000 ft range this afternoon. As a weak disturbance moves southeast, short range guidance indicates that a few showers could move into north-central WI this evening, though confidence is not high enough to include in the RHI taf. Otherwise, cool north- northwest flow off Lake Superior will bring some low clouds and patchy light showers or drizzle to north central WI late tonight, but conditions should remain VFR farther south and east. Gusty northwest winds will diminish after sunset. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS.......Skowronski SHORT TERM.....MPC LONG TERM......Skowronski AVIATION.......MPC
Area Forecast Discussion
National Weather Service Lincoln IL
1218 PM CDT Tue Aug 22 2017 .UPDATE... Issued at 1035 AM CDT Tue Aug 22 2017 The latest surface map indicates a cold front stretching roughly just south of the Interstate 72 corridor late this morning. The band of showers and thunderstorms that brought locally heavy rainfall to parts of central and east central Illinois early this morning has shifted into southeast Illinois late this morning. the last few runs of the RAP and HRRR models continue to suggest any redevelopment of thunderstorms along the cold front will occur just to our southeast this afternoon. Based on these trends will continue to push precip chances out of the central and east central counties early this afternoon and over southeast Illinois by late afternoon, and even there, will only hold on to low chance POPs. RAP forecast soundings indicate clouds will be slow to clear initially early this afternoon, but as drier air filters south into the region, we should see the clouds gradually lift and then dissipate by late afternoon or early this evening. The front will be southeast of our area by early this evening with drier air filtering southeast into central Illinois as much cooler air moves in for later tonight into Wednesday morning. Under a clear sky and light winds late tonight, look for early morning lows to drop into the low to mid 50s over our far northern counties, with upper 50s forecast for areas south of Interstate 70. Updated forecast should be out by 11 am. && .SHORT TERM...(Today and tonight) ISSUED AT 241 AM CDT Tue Aug 22 2017 Both 00z model suites and more recent CAMs show a speed up of the precipitation ending across the forecast area. This seems reasonable given the progression of the energy moving across western Missouri this morning. As it interacts with the digging trough and help to intensify it. Will be ending the precip from northwest to southeast. Due to training nature of some of the storms tonight, soil moisture should be high in some areas. Will have to watch for the potential for fog tonight. Will leave it out for now and let day shift analyze precip reports and wind forecasts to determine if mention is warrented. .LONG TERM...(Wednesday through Monday) ISSUED AT 241 AM CDT Tue Aug 22 2017 Cool northwest flow will persist at least through the first part of the weekend. Several waves will rotate through the trough during the period, but with limited moisture available the biggest impacts may be a brief increase in clouds and a reinforcement of the cool air in place. Temps should be 5-10 degrees below normal. There are several differences in the way the models are handling the tropical moisture associated with the remants of Harvey and its interaction with the longwave trough over the eastern U.S. For now will keep rain chances low Monday given the uncertainty. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 1215 PM CDT Tue Aug 22 2017 Cigs will lift to VFR and scatter out this afternoon as much drier air filters southeast into the forecast area. Based on current trends with the visible satellite loop, we may see a brief period of bkn cigs at 2000-3000 feet early this afternoon before the drier air starts to work on the cig bases after 20z. Most of the area will see a tempo scattered to broken group early on with a trend towards a scattered deck by mid to late afternoon. A clear sky is expected overnight into Wednesday morning with west to northwest wind of 10 to 15 kts with a few gusts approaching 20 kts at times this afternoon. The winds will be light northwest tonight with speeds of 5 kts or less. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Smith SHORT TERM...Barker LONG TERM...Barker AVIATION...Smith
...Previous Extended Marine Forecast Discussion Slightly Modified...

Fri-Sat...Meandering low pressure and lingering tropical moisture will team to keep plenty of showers and storms in the forecast. Wind direction and wind speed will be tricky as there is some potential for a surface low to form over or near the ECFL/NEFL coastal waters. Seas generally 2-3 ft, perhaps 4 ft well offshore. && .Climate...Potential warm minimum temperature records for 22-Aug-17. Melbourne...82 which would tie the record from 2007. Vero Beach..80 which would break the record of 78 set in 1944. && .PRELIMINARY POINT TEMPS/POPS... DAB 75 92 75 92 / 10 30 30 40 MCO 76 95 76 93 / 10 30 30 60 MLB 78 91 77 91 / 20 60 40 60 VRB 76 90 75 90 / 30 70 50 60 LEE 77 96 78 95 / 10 30 20 40 SFB 76 96 77 95 / 10 30 30 50 ORL 78 96 78 94 / 10 30 30 60 FPR 76 90 76 90 / 40 70 50 60 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ Sedlock/Pendergrast/Smith
Area Forecast Discussion
National Weather Service Nashville TN
131 PM CDT Tue Aug 22 2017 .DISCUSSION... A wide band of showers has developed across Middle Tennessee early this afternoon. Additional activity is occurring farther upstream, just on the other side of the Ohio River in the vicinity of a surface boundary that is approaching Middle Tennessee. Latest HRRR shows the activity persisting throughout the afternoon, and even increasing late this afternoon and into the evening as the front pushes into Middle Tennessee. Most of the cells will diminish by 06Z, with some lingering showers mainly across eastern and southern Middle Tennessee tomorrow morning before the front finally exits the mid state. There is a marginal risk of severe storms this afternoon and evening, but the potential for severe activity is quite limited. Expect cooler temperatures beginning tomorrow as post-frontal air filters into the mid state, and below normal temperatures will persist right through the end of the forecast period. The remainder of the week looks to be dry, so we won`t see any appreciable rain chance until the weekend as deeper moisture drifts up from the south in advance of a tropical system coming onshore along the western Gulf of Mexico. At this time, it appears that the tropical system will have a more direct impact on Middle Tennessee next Thursday and Friday, and already the GFS and ECMWF are coming into good agreement over placement and timing. && .AVIATION... 18Z TAF DISCUSSION. Deteriorating conditions is trend for this period as a front approaches later today into tonight...and passes overnight. Showers/storms currently developing expected to become bit more widespread late afternoon/early evening. Will include vcnty until mid afternoon...then ramp up chance toward 00z. Not much precipitation expected overnight but MVFR/IFR cigs/vsbys likely to form. && .PRELIMINARY POINT TEMPS/POPS... Nashville 72 84 62 83 61 / 70 10 0 0 0 Clarksville 67 81 58 81 58 / 50 10 0 0 0 Crossville 68 78 57 77 56 / 70 30 10 0 0 Columbia 71 83 61 83 60 / 70 20 0 0 0 Lawrenceburg 70 83 61 82 59 / 70 20 0 0 0 Waverly 69 81 60 81 59 / 50 10 0 0 0 && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......08 AVIATION........07