Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/19/19

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
324 PM AKDT Sun Aug 18 2019 .DISCUSSION... Our main forecast concern in the short term will be high water on rivers in the Interior. While the heavy rainfall ended Friday night, it will take a few days for all of the water to work its way through the system. The operational models are all in relatively good agreement out through Tuesday. Thereafter, they begin to diverge on the synoptic scale pattern. The ECMWF and the NAM both want to drop a 500 mb low south from the Brooks Range into the Interior on Wednesday, while the GFS wants to keep it over the Brooks Range. We will lean more with the NAM/ECMWF solution as it seems to be more consistent from run to run. Interior: Recent heavy rains have left many rivers across the Interior high. There is ongoing flood products out for parts of the Chena, Salcha, Tanana and Nenana Rivers. This will be described in more detail in the hydrology section below. Relatively clear skies tonight will allow for temperatures to drop into the 30s tonight with a few places dropping down into upper 20s. For Fairbanks, we expect that the temperatures will remain in the upper 30s in town; however, it is not out of the question that some of the lower elevation locations on the outskirts of Fairbanks will see a frost overnight. Shortwaves around an upper low over the eastern Brooks Range will bring chances for showers to areas along the Canadian Border during the day on Monday. The HRRR actually has the showers as far west as Fairbanks. We opted to give this a little bit of play by extending the isolated PoPs into Fairbanks. Chances for showers for Tuesday and Wednesday; however, the exact placement and amount of precipitation expected still remains a little bit fuzzy. The fine scale details with this will depend on the placement of the upper low. The ECMWF has the low diving to the ECMWF has the low diving to the south Tuesday night, bringing around a quarter of an inch of rainfall to the Interior, mainly along a line from Coldfoot to Fairbanks to Denali National Park, the Nam doesn`t bring the low as far to the south and keeps bulk heaviest precipitation east of Fairbanks, mainly over the Fortymile Country. The GFS doesn`t really move the low that far south and keeps most of the precipitation along the Canadian Border. We kept out PoPS chance over the area at the moment until we can get some better agreement with the models. North Slope and Brooks Range: We will likely see some fog and low stratus overnight tonight. An upper low will move west to be situated over the eastern Brooks Range by Tuesday afternoon. This low will bring precipitation to the eastern Arctic Coast and the eastern Brooks Range late Tuesday into early Wednesday. Along the coast this we expect that this precipitation will be in the form of rain. In the Brooks range, we expect snow for areas above 2,000 feet in elevation. This system has the potential to bring a couple of inches of snow. The models aren`t in the best of agreement on how this low will progress on Wednesday. The GFS keeps the low in place over the eastern Brooks Range longer than the ECMWF or the NAM. The GFS solution would result in higher snowfall totals over the Brooks range given the more persistent upslope flow on the north side of the range. We are leaning more to the NAM/ECMWF solution that moves the low and the associated precipitation south into the Interior much quicker. West Coast: A shortwave will dive south over the west coast on Monday this will bring rainfall to the Seward Peninsula (including Nome) during the Morning hours on Monday and to the Yukon Delta in the afternoon. After this precipitation passes through the area we aren`t expecting any precipitation for the remainder of the week. Coastal Hazard Potential Days 3 and 4...None. && .FIRE WEATHER... No big concerns for the upcoming week. A cool and mainly dry pattern will persist into Monday. Minimum RH values are expected to remain above 35 percent across the entire area for Monday. RH values will increase slightly for Tuesday. && .HYDROLOGY... Rainfall between Thursday and Saturday was over 1 inch in the area south of Circle to Tanana (excluding the Fortymile Basin which was drier), with 2 inches over most of the area south of Wonder Lake to Fairbanks to the Gerstle River, and 3 to 4 inches along the Alaska Range between the Delta Junction and Denali, with the Eielson Visitor Center come in at 4 inches. Most of this rain fell in a 24 hours period between early Fri morning and Saturday morning. Most of the water has moved out of streams and into larger rivers. The Nenana River has a flood advisory, with minor flooding occuring in the city of Nenana, and that flooding is expected to continue for several more days. The Tanana River has a flood advisory from Shaw Creek all the way to the city of Tanana with flooding in low lying areas along the Tanana River, which will last for several more days. The Little Chena and Goodpaster Rivers crested Sat below bankfull and the threat of flooding is over on both of those rivers. The Upper Chena River crested Saturday at minor flood stage, and the Chena River near Hunts Creek is expected to crest today near minor flood stage, with the Chena in Fairbanks cresting on Monday below bankfull. The Salcha River will crest today over a foot above flood stage, which is the highest water level on the Salcha River since 2014. && .AFG WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory for PKZ245. && $$ AUG 19
Area Forecast Discussion
National Weather Service La Crosse WI
639 PM CDT Sun Aug 18 2019 .SHORT TERM...(This evening through Monday) Issued at 258 PM CDT Sun Aug 18 2019 A much quieter short term period today, though plenty of cloud cover was seen as a cold front was still making its way through the forecast area and occasionally producing light showers and some drizzle. Farther northwest and behind the front, high pressure was leading to mostly sunny skies. Clouds will continue to scatter out through the afternoon from northwest to southeast, with the entire area becoming mostly clear just after sunset. This sets the stage for potential fog development, especially in the river valleys. Trends in RAP model soundings have been toward a deeper light wind layer near the surface, which would be favorable for more fog. However, light northerly winds on the east side of surface high pressure will continue to bring in drier air which could hinder development. Overall, still think there will be at least some patchy fog around. Quiet weather will remain in place for Monday with zonal flow aloft and surface high pressure remaining in control just east of the forecast area. Light southerly winds will start to bring some slightly warmer and more humid air to the area, with highs generally in the upper 70s to mid 80s. .LONG TERM...(Monday night through Sunday) Issued at 258 PM CDT Sun Aug 18 2019 Monday Night through Tuesday night...High pressure shifts east Monday night and return flow begins the moisture advection through IA/MN. A rich, high dewpoint airmass is poised just south of I-80 Monday and this will rapidly invade on Tuesday. A number of ingredients are in play for Tuesday, but the orchestration of those ingredients still seems tough to discern. A well-defined shortwave trough over northern CA at 19Z today, per GOES water vapor imagery, will begin tracking for the area and arrive Tuesday morning. It seems to have enough depth to elicit height falls and a low-level moisture transport ramp-up and isentropic lift region from the west Tuesday morning. Good consensus exists Monday in the High Plains on these features, but the strength and location vary quite a bit by 12Z Tuesday. Some solutions, however, are suggesting forcing for rain chances in southeast MN and northeast IA Tuesday morning. A cold front in the northwest flow will also push in, during the afternoon or evening depending on the model chosen, providing another lift source into a developing CAPE pool in the 2000-30002k J/Kg range. Capping is in play however, and moderately strong south of I-90. This may favor areas north of I-90 more for TSRA Tuesday afternoon/evening. Convergence along the front is weak-moderate, not helping TSRA development in a capped environment. The 18.12Z NAM 4km Nest at 60hours does have some TSRA development entering sern MN Tuesday eve for what it is worth. So, continued storm chances Tuesday and Tuesday evening, but confidence is low on the outcome. The mid-level wind max of 45-50 kts is more coincident over the front, per 18.12Z NAM/GFS vs. yesterdays model guidance, suggesting a tick up on severe storm chances. Hodographs would suggest a straight-line supercell shear profile favoring hail/wind. Bottom line: too much spread in the forcing, timing, and cap to change risk message at this time. /DB Thursday through Sunday...Towards the weekend, warmer air returns as the high pressure moves off to the east. Although relatively low (<30%), precipitation chances also return with the flow becoming more out of the southwest. /MA && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 639 PM CDT Sun Aug 18 2019 There is the potential for valley fog at KLSE tonight after 10Z with VLIFR conditions possible. Currently the temperature/dew point spread is sitting at 20 degrees and KLSE stays in a light wind gradient through much of the night. Given these two factors, have held off on including VLIFR conditions in the TAF and maintained BCFG for dense fog in the area. Will continue to monitor winds and temperature/dew point spread closely this evening for a possible update. Otherwise, after the valley fog dissipates Monday morning, expect VFR conditions with high pressure in control. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...CA LONG TERM...Baumgardt/Aufforth AVIATION...Wetenkamp
Area Forecast Discussion
National Weather Service Bismarck ND
1010 PM CDT Sun Aug 18 2019 .UPDATE... Issued at 1009 PM CDT Sun Aug 18 2019 Some clouds continue to pass over the far north late this evening. These clouds will continue to move off to the east overnight. Otherwise, quiet weather continues. UPDATE Issued at 628 PM CDT Sun Aug 18 2019 Quiet weather continues. With the exception of increasing cloud cover a little bit over the west, remainder of forecast remains in good shape. && .SHORT TERM...(This evening through Monday evening) Issued at 127 PM CDT Sun Aug 18 2019 Quiet and warmer in the short term period. Mostly clear and quiet tonight. A southerly low level flow develops as a shortwave approaches from the west. Temperatures will be warmer than last night with lows in the upper 40s to mid 50s. Mostly sunny and warmer on Monday. A midlevel shortwave and associated surface trough is expected to track into western North Dakota by the late afternoon hours. Moist southerly return flow in the prefrontal region will bring surface dew points into the low to mid 60s over south central ND, to mid 50s north central. Steep midlevel lapse rates, 1500-3000 J/kg of MLCAPE is expected along and east of the front. Thunderstorms will be possible Monday evening as the surface trough deepens under the approaching upper level wave. There`s a little more certainty in precipitation placement with global models and CAMS that go out through tomorrow evening generally showing two favored areas of convection. One along the International Border, closer the the large scale ascent, and another over southwest/south central ND within the area of greatest instability and convergence along the surface boundary. Uncertainty does remain in thunderstorm coverage. Instability has increased from previous model runs with shear about the same (around 40kts Bulk Shear) but coverage remains limited. The ECMWF seems the most robust, developing convection earlier over southwest ND late afternoon and spreading it into the southern JRV By evening. And another area of convection near and to the east of the Turtle Mountains during the evening. The GFS indicates very little qpf in the evening over western and central ND with best coverage after midnight far north central and mostly east of the forecast area. The NAM is basically dry across the entire forecast area. CAMS that develop convection over the southwest and south central Monday evening, are quick to suppress the convection as it propagates east. All in all with around 40 kts of 0-6 km bulk shear oriented orthogonal to the initiating boundary and the anticipated instability, discrete supercell thunderstorms will be possible with a large hail and damaging wind threat. A nonzero tornado threat may also be possible with guidance indicating around 15 kts of 0-1 km shear and some curvature in the lower portions of forecast hodographs over the southwest, south central. Even with two favored areas we opted for a blanket slight chance pop Monday evening at this time as we can not rule out convection anywhere along the boundary and coverage from all guidance remains isolated. With western North Dakota west of the surface trough late Monday afternoon, breezy westerly winds and temperatures around 90 are expected. On the eastern side, breezy southerly winds and highs in the 80s are forecast. NBM guidance was a tad lower than the previous forecast so we stuck with the previous forecast highs for Monday. We did blend some of the latest HRRR dewpoint guidance with Official to better indicate the expected mixing out and drying behind the front in the far west Monday afternoon. .LONG TERM...(Monday night through Sunday) Issued at 127 PM CDT Sun Aug 18 2019 Convection is expected to be exiting the eastern CWA around or shortly after midnight. There will be a period of gusty winds behind the cold front late Monday and Tuesday morning with generally subsiding winds by Tuesday afternoon as surface high pressure builds over the area. We utilized a blend of Official and CONSMOS Monday night into Tuesday for winds. Cooler with highs in the 70s on Tuesday. Chances for convection return beginning Thursday afternoon as an upper ridge breaks down into a quasi-zonal pattern and a trough approaches from the west. The envelope of model solutions widens as we head into next weekend, but expect periodic chances for convection through the weekend. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 628 PM CDT Sun Aug 18 2019 VFR conditions will prevail through the forecast period. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JJS SHORT TERM...TWH LONG TERM...TWH AVIATION...JJS
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
653 PM EDT Sun Aug 18 2019 .AVIATION... Line of convection has developed along the near surface trough axis upstream. These storms will affect the Detroit regional terminals and Flint in the first couple hours of the forecast. Winds will snap around to the west in the wake of the front for a few hours before relaxing back to southwest overnight. Enough moisture will remain locked into the boundary layer to support nocturnal fog and low cloud development. A cold front will slide south through the region Monday morning - flipping winds to light northerly during the morning hours. Post-frontal clouds are expected across the southern terminals but should remain VFR. For DTW...line of thunderstorms should begin to affect the western areas of the DTW airspace after 00z with the main window of affecting the terminal in the 01z-02z window. Light fog and low cloud development is expected after midnight. Lingering ceilings below 5kft are likely Monday. .DTW THRESHOLD PROBABILITIES... * Moderate for ceilings aob 5kft tonight and Monday. * High for thunderstorms 01-02Z. && .PREV DISCUSSION... Issued at 319 PM EDT Sun Aug 18 2019 DISCUSSION... The numerous showers and thunderstorms which worked through southeast Michigan this afternoon (a few severe), helped drop temperatures into the 70s, leading to a significant stabilization of the airmass (see 19z SPC mesoscale analysis). Thus, confidence is low that activity with the actual cold front will be severe, not to mention the coverage of activity is in question this far north. At least, the 17z Rap looks to be trending in the right direction (less activity). None-the-less, still a short window to destabilize (lower 80s) before sunset, and the upper level dynamics/shear (50 knots of effective shear) needs to be respected as it sweeps through around 00z. On the flip side, could be in the shadow of the organizing thunderstorm complex developing over central Indiana into Ohio where the max instability (MLcapes of 2500 J/kg) presently resides, which should help mitigate our severe chances as well. Strong upper level low (545 DAM at 500 MB) over northern Manitoba will be the main influence/director to our weather over the several day, as it swings through Ontario during the mid week period, supporting a significant cool down. An extension of trough axis will be lifting through the northern Great Lakes tonight, with 500 MB heights beginning to rebound over southern Lower Michigan on Monday. Thus, the cold front that slips through southeast Michigan tonight, will more or less wash out. With the lingering low level moisture, especially with the rainfall from this afternoon, and weak surface convergence, some fog and/or low stratus development appears possible late tonight. 500 MB heights rise to around 588 DAM on Monday, but still enough residual low level moisture/850 MB Theta-e and instability around to support low chance pops along/south of I-94. Pseudo zonal upper level flow with upper level energy/PV coming out of the Rockies and tracking through Midwest Monday night. It appears the potential thunderstorm complex will track off to the southeast during Tuesday and miss the state. This will also help cut off some of the moisture advection ahead of the cold front, which tracks through late Tuesday night or Wednesday. Thus, a dry frontal passage remains possible. Warmer temperatures, with highs in the 80s, will remain in place on Wednesday before cooler temps come back for the remainder of the week. By Thursday, 850mb temps will be back in the single digits. A slight chance of precipitation also remains in the forecast Wednesday afternoon, as a wave passes over. The rest of the forecast period going into the weekend will feature pleasant temperatures and dry weather as high pressure settles in over the region. MARINE... A low pressure system lifting through lake Superior this afternoon will pull a cold front through the region this evening. This front may produce another round of thunderstorms this evening before pushing east of the area. Southwesterly winds will veer westerly behind this front tonight and to the northwest on Monday as a secondary front drops through the region. Winds will be strongest this evening out of the southwest with gusts reaching 25 knots. Though cooler air will advect in behind the front tonight, high pressure building in will weaken the gradient and prevent stronger gusts tonight and Monday. Though mostly a dry forecast beyond tonight, additional showers and thunderstorms will continue to be possible over Lake Erie and St. Clair with the frontal boundary stalling nearby. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Small Craft Advisory until 4 AM EDT Monday for LHZ421-422. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....Mann DISCUSSION...SF/SP MARINE.......DRK You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Quad Cities IA IL
1104 PM CDT Sun Aug 18 2019 ...AVIATION UPDATE... .SYNOPSIS... Issued at 310 PM CDT Sun Aug 18 2019 18Z surface data had the cold front from KLSE to KOMA with a pre- frontal trof from northeast Illinois back through KOTM. Dew points were in the 70s from Ohio Valley into the southern Plains and deep South. Behind the front dew points were in the 50s and 60s. && .SHORT TERM...(This Evening through Monday) ISSUED AT 310 PM CDT Sun Aug 18 2019 Cloud cover has resulted in a slow recovery of the atmosphere today. Satellite trends show very weak diurnal cumulus clouds developing along the front in central Iowa. So the question is will any diurnal convection develop along the front late this afternoon and overnight. RAP has shown convergence in the frontal zone as it moves into the area late this afternoon and evening with unstable air aloft. However the trends with the convergence has been to slowly weaken with each new run. If convection develops late this afternoon it would be confined to the immediate frontal zone and likely isolated in nature. There may be a small area where areal coverage becomes scattered. Thus will go with isolated showers and storms developing late this afternoon and persisting through the evening as the front moves through the area. After midnight any convection that develops will slowly dissipate through sunrise. On Monday there may or may not be a few lingering showers in the far southeast and east areas around sunrise. If there are showers they will end by mid-morning. The rest of the day will be warm and humid as skies slowly clear. Heat index readings of 90 to 95 are possible south of an Ottumwa, IA to Galesburg, IL line. .LONG TERM...(Monday Night through Sunday) ISSUED AT 310 PM CDT Sun Aug 18 2019 Models are in good overall agreement through the long term period. The main forecast concerns are temperatures on Tuesday and chances of precipitation through the period. The long term period opens with northwesterly flow aloft as closed area of high pressure expands eastward across Texas and Oklahoma and into western Missouri and Arkansas. Tuesday looks to be the warmest day of the period ahead of a cold front that will move across the region Tuesday afternoon and evening. This will bring the chance of showers and thunderstorms area during peak heating. There is a marginal risk of severe thunderstorms across the area on Tuesday. The timing of the front and potential precipitation calls into question how warm we could get during the day. Current highs are in the mid to upper 80s with dewpoints in the lower to mid 70s could produce heat indices of 100 to 104 for 3 or 4 hours so there is also the potential for a heat advisory but that will depend on the timing of precipitation. After Tuesday night, a strong upper level low will dig southward out of eastern Canada and into the northeastern US. This will continue to bring pieces of shortwave energy across the area every 18 to 24 hours with daily chances of showers and thunderstorms. There will be dry periods in the forecast as ridging will follow in the wake of these shortwave troughs but timing individual features this far in advance is very difficult. Temperatures will be near normal on Wednesday but then run slightly below normal Thursday into next weekend. && .AVIATION...(For the 06Z TAFS through 06Z Monday Night) ISSUED AT 1102 PM CDT Sun Aug 18 2019 Light northeast winds may allow for some fog and MVFR cigs/vis late tonight into Monday morning, then followed by VFR conds for most of the day on Monday. North to northeast winds less than 10 knots. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ SYNOPSIS...08 SHORT TERM...08 LONG TERM...Cousins AVIATION...Haase
Area Forecast Discussion
National Weather Service Lincoln IL
844 PM CDT Sun Aug 18 2019 .SYNOPSIS... Issued at 843 PM CDT Sun Aug 18 2019 Very warm and humid conditions are on tap for the next couple days, as heat index values return to triple digits by Tuesday. Scattered thunderstorms are possible again on Monday, primarily in east central and southeast Illinois. Storm chances will increase on Tuesday, and a few may be strong to severe. && .UPDATE... Issued at 843 PM CDT Sun Aug 18 2019 Storm activity has pushed east of the forecast area this evening, with water vapor imagery showing the upper wave along the Indiana border. Have largely eliminated much of the PoP`s overnight, though some isolated showers/storms may still linger across the eastern CWA. Concern overnight will be more with fog potential, especially across the northeast CWA where the heavy rains occurred a few hours ago. Skies have already largely cleared there, though some narrow bands of stratocumulus linger from near Decatur to Danville. Latest HRRR/LAMP guidance has been hinting at this for the last few runs, though varying in the overall coverage. For now, will only mention the fog from about Decatur eastward. && .SHORT TERM...(This evening through Monday) ISSUED AT 330 PM CDT Sun Aug 18 2019 A broken line of strong to severe thunderstorms was over far southeast IL into se MO and ne AR at mid afternoon. These storms formed along an outflow boundary the was pushing southeast through southeast IL and strongest storms currently south of CWA in Edwards and southern Wayne counties. Unstable CAPEs of 2500-3600 j/kg were east of I-57, highest along the Wabash river. A thunderstorm was over Champaign county from Savoy/CMI airport south and tracking eastward toward Vermilion county. Surface analysis shows the main synoptic front extended from 1001 mb low pressure over eastern Lake Superior thru central WI/IA and into central KS. Aloft a broad/weak upper level trof was over the Great Lakes, much of the Midwest and over the northern Plains/Rockies, while 594 dm 500 mb subtropical ridge was near the southeast atlantic coast and sprawled back into TX/NM. Diurnally driven scattered convection in eastern IL should diminish toward early evening as sunsets, and only carried slight chances or dry rest of tonight into mid Mon morning over CWA. Lows overnight in the upper 60s to around 70 degrees. The latest models show the frontal boundary pushing se into IL river valley around midnight tonight and into southeast IL near I-70 by 18Z/1 pm Mon. This boundary to help develop more isolated to scattered convection by midday Monday and continue into early Mon evening mainly over areas from I-72 south. Airmass gets unstable again over areas south of I-72 by Mon afternoon and could see a few more strong thunderstorms especially in southeast IL. Highs Mon of 85-90F warmest in southeast IL where heat indices reach the upper 90s to near 100 Mon afternoon. .LONG TERM...(Monday night through Sunday) ISSUED AT 311 PM CDT Sun Aug 18 2019 Isolated to scattered convection over southern CWA early Mon evening to diminish after sunset, with another lull expected into mid Tue morning. A disturbance and possible MCS to affect area by Tue afternoon and evening bringing next chance of thunderstorms. SPC has much of area in a slight risk of severe storms Tue afternoon/evening as very unstable airmass develops with CAPES rising to 3000-4000 j/kg during Tue afternoon over southern CWA. Highs in the upper 80s/lower 90s on Tue with afternoon heat indices in the upper 90s to around 105F, highest in sw CWA where heat advisory may eventually be needed Tue afternoon. The main frontal boundary to push sse into nw CWA late Tue night and thru rest of CWA during the day Wed. This will likely continue chances of showers and thunderstorms on Wed especially central and southern CWA. Highs Wed range from lower 80s by Galesburg, to the upper 80s to near 90F in southeast IL where heat indices peak around 100F in southeast IL Wed afternoon. Frontal boundary pushes south of area during Wed night and Thu while upper level trof over the Great Lakes brings in cooler and less humid air into central IL. Still have 20-30% chance of convection over areas south of I-74 Wed night into Thu as Ecmwf model is keeping qpf over southern half of CWA thru Thu afternoon, and not as far south with frontal boundary as the GEM and GFS models which are dry over our CWA overnight Wed night and Thu. Stayed close to model consensus for convection chances here but confidence of convection chances is low during Wed night and Thu. Highs Thu and Fri of 79 to 83 degrees, warmest in southeast IL. Lows Thu and Fri nights in the upper 50s and lower 60s. Generally dry conditions expected much of the time from Thu night thru next Sunday, with weak high pressure over the Great Lakes. But the subtropical ridge over the sw and southern states and upper level trof moving into the eastern Great Lakes and New England puts IL in a WNW upper level flow, and could see some disturbances tracking ESE and possibly affecting the area, though timing and placement of these are difficult to project that far out. Consensus of models has slight chance of convection over much of CWA on Fri afternoon, Sat and again Sunday afternoon. Highs in the low to mid 80s next weekend and humidity levels gradually increase. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 645 PM CDT Sun Aug 18 2019 A broken band of convection was well se of the central IL airports and will continue to pull away from central IL during this evening. Clearing wedge pushed into areas from I-55 west early this evening and will move into DEC and CMI during next hour or two, but still VFR conditions prevailing there with mainly scattered to broken mid/high clouds present early this evening. A frontal boundary over southeast parts of WI/IA and far nw MO has 4-7k ft cloud decks in central and southern IA into far northern IL with isolated showers in central IA. This front to move toward the IL river valley late tonight and be over central IL much of Monday. This should increase clouds during overnight with ceilings of 3-6k ft possible and some fog to develop especially by CMI which had half inch rain this afternoon. The HRRR and GFSlamp even brings some patchy dense fog to east central IL around CMI by sunrise, while RAP keeps dense fog patches just se of DEC and CMI late tonight. Will need to watch for fog development and possibly lower vsbys especially at CMI and maybe DEC too. Have VCSH at PIA and BMI after 15Z/Mon and VCTS along I-72 after 19Z/Mon where instability will become higher Monday afternoon. SW winds 5-10 kts early this evening stay fairly light next 24 hours, and become light and variable during tonight. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Geelhart SYNOPSIS...Geelhart SHORT TERM...07 LONG TERM...07 AVIATION...07
Area Forecast Discussion
National Weather Service Memphis TN
903 PM CDT Sun Aug 18 2019 .DISCUSSION...GOES-16 Satellite trends/00Z upper air analysis depicts a weak mid-level shortwave trough located across Illinois then into West Tennessee and North Mississippi. This mid-level shortwave acting as a lifting mechanism combined with instability triggered the isolated to scattered showers and thunderstorms across the Mid-South this afternoon into this evening. KNQA WSR- 88D radar trends have shown some dissipation of showers and thunderstorms across the forecast area with the only areas remaining thus far along a line from Jonesboro, Arkansas to Ripley, Tennessee and including a small area near West Memphis. As of 8 PM CDT, temperatures across the Mid-South are predominantly in the 70s to lower 80s. Latest short term model trends including Convective Allowing Model (CAM) solutions and especially the HRRR suggest this activity should continue to weaken for the rest of the night and perhaps ending by 6Z if not sooner. Some adjustments to rain chances, temperatures, and the potential for some patchy fog overnight will be made to the forecast to account for these short term trends. Updated grids will be available shortly. CJC && .PREV DISCUSSION... /issued 620 PM CDT Sun Aug 18 2019/ UPDATE...Aviation Discussion. PREV DISCUSSION... /issued 238 PM CDT Sun Aug 18 2019/ Higher humidity across a good portion of the area this afternoon...with a few locations in the current heat advisory reaching 105F+ this hour. Winds were also higher with most observations in the 10-15 mph range. Showers had developed across the southwest Delta counties...with thunderstorms just outside of the CWA. Late this afternoon and tonight...have increased PoPs across the northern and western counties for tonight...and late this afternoon based off the current radar. CAM`s are indicating more activity this evening along this morning`s lingering outflow boundary draped across southeastern Missouri/northern Arkansas. A convective watch was issued just north of the AR/MO border a short while ago. Main threat would be strong gusty winds that could push south across the western counties this evening. Plan on adding a strong storm wording in the HWO. Current heat advisory goes through 8pm. Monday and changes really necessary this period. Temperatures will climb into the low and mid 90s with potentially a larger area of 105F+ heat indices. Have held off on extending or issuing a new heat advisory for Monday as tonight`s convection could disrupt both timing and area needed. Isolated convection can be expected both days with activity quickly waning during the overnight hours. Will have to watch for any lingering outflow boundaries that enhance storm intensity. Wednesday through Friday...models still suggesting the wettest period of the course of next week...mainly as the eastern edge of the Southern Plains ridge breaks down as heights gradual lower over the Midwest. A weak surface front will edge closer to the KY/TN and MO/AR borders sometime early Thursday with a series of passing shortwaves aloft aiding in convection coverage and intensity. Some of these storms may be strong as well...but will leave that wording out of this afternoon`s HWO. Highs will range from the upper 80s to low 90s...with Wednesday posing the best day for a heat advisory across southwest portions of the area. Next weekend...extended models show seasonal to slightly above normal temperatures with isolated diurnal convection. JAB && .AVIATION... 00Z TAF Set Showers and thunderstorms have become outflow dominant and should gradually weaken and diminish in coverage this evening. Outflow from storms will result in temporary increased wind speeds and non-uniform directions. There is some potential for some brief redevelopment over NW Tennessee/NE Arkansas as outflow boundaries interact...but will have to wait to see how that develops. Gradient flow will remain from the South over the next 24+ hours with wind speeds generally 3-7kt or less. Additional showers/storms may develop tomorrow afternoon but coverage is expected to be limited. 30 && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$