Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/13/17

Area Forecast Discussion
National Weather Service Bismarck ND
956 PM CDT Sun Mar 12 2017 .UPDATE... Issued at 954 PM CDT Sun Mar 12 2017 Have removed more areas from the winter weather advisory. The only remaining counties until 11 PM CDT are for Sioux, Emmons, McIntosh, and Dickey, so along the South Dakota border from south of Bismarck to south of Jamestown. UPDATE Issued at 815 PM CDT Sun Mar 12 2017 Have updated to remove the northern areas from the winter weather advisory as snow had diminished to flurries there. Will expect to be able to remove another layer along and north of Interstate 94 soon. Radar returns continue to weaken from the north as the storm pulls away and high pressure ridges in from the northeast. Winds were also decreasing nicely, under 20 mph. && .SHORT TERM...(This evening through Monday) Issued at 402 PM CDT Sun Mar 12 2017 Snow will end from northwest to southeast through the evening, and winds will concurrently decrease, as well. As of 20 UTC, preliminary, non-operational satellite imagery from GOES-16 reveals two primary vorticity maxima associated with the mid-level shortwave trough crossing the region. Each maxima has an area of low-level drying in its wake as well as a rather distinct circulation center per the moisture channel and visible bands. A notable decrease in snowfall intensity occurred during the midday hours from Williston toward Bismarck as synoptic-scale ascent with the shortwave trough ebbed, but since them a broader area of light snow has taken over with ASOS/AWOS visibilities generally in the 1 to 3 SM range in most areas. This is likely tied to deformation on the north side of the vorticity maxima traversing SD at this hour. Recent RAP iterations key on that deformation and simulate an area of slightly enhanced Omega in the dendritic growth zone which sinks southward across central ND through late afternoon. This area of forcing is almost entirely driven via deformation since mid-level cold air advection is ongoing, and frontogenesis worthy of more intense banded snow is now focused over eastern SD and southern MN. Therefore, while we expect a broad area of light snow to continue sinking southward and ending from northwest to southeast through the evening, additional accumulations will range from an inch or less in western ND to between 1 and 3 inches in the southern James River valley, where snow will last longest. The 16 to 19 UTC RAP and HRRR iterations are generally in line with our observation- based conceptual model and were relied on for the forecast through the early evening. In general, web camera images suggest impacts to travel are more of an inconvenience than anything else, but we have chosen to maintain the areal extent of the advisory as-is with this forecast release given widespread sub-2SM visibilities being reported at mid afternoon. We did, however, choose to end the advisory several hours sooner than earlier advertised given these trends. Thus, the winter weather advisory end time was set back to 00 UTC (7 PM CDT) for areas along and northwest of a line from Bismarck to Rugby, and at 04 UTC (11 PM CDT) along and to the southeast of a line from Fort Yates to Harvey, including Jamestown and Ellendale. In the big picture, a 1040 mb surface ridge located across central Manitoba this afternoon is forecast to sink southward tonight with its western influence nosing into north central ND. This will set the stage for significant cooling if clouds thin or clear enough in the Rugby and Rolla areas, where we leaned on the cooler edge of the guidance envelope since model-derived soundings do indeed suggest enough column drying to support efficient radiational cooling. Elsewhere, lingering cloud cover will tend to inhibit a drastic temperature fall, but given fresh snow cover temperatures will certainly fall to between zero and 5 below in most areas. As heights aloft begin to slowly rise by Monday afternoon and warmer air surges eastward across MT, light snow may break out ahead of a mid-level warm frontal zone in western ND by afternoon. The 12 UTC global models generally agree on that scenario. .LONG TERM...(Monday night through Sunday) Issued at 402 PM CDT Sun Mar 12 2017 A warm-up is in store this week as 500 mb flow across the lower 48 becomes characterized by mean ridging in the west and a deep and energetic trough in the eastern part of the country. The 12 UTC GFS and ECMWF and their ensembles are in good agreement with this scenario and suggest that the ridge will flex eastward with time and deliver several surges of mild air of Pacific origins to the northern plains from mid-week on. This pattern fits well with the hemispheric flow, which had been associated with a blocking ridge aloft north of Alaska the last 10 or so days. The slow breakdown of that feature will yield a more progressive downstream flow into the western and central parts of the nation, particularly by next weekend. Forecast 850 mb temperatures of 10+ C in both the GFS and ECMWF should readily yield highs in the 40s to lower 50s F across western and parts of south central ND beginning Wednesday. Global models do suggest that light warm-advection-induced precipitation may accompany the mild air on about Wednesday, though confidence in its occurrence is low. Moreover, guidance suggests a stronger mid-level shortwave may cross the region with a cold front about Thursday or Friday, which could yield more light precipitation and gusty winds along with a brief interruption in the warm-up. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 815 PM CDT Sun Mar 12 2017 Low pressure was pulling away from the area and toward Iowa as high pressure was ridging in from the northeast. Snow had decreased to flurries north and will be decreasing to flurries south by 04Z. Expect IFR ceilings and visibilities to improve with MVFR ceilings holding on even after the snow stops falling. Note that ASOS at KISN is malfunctioning. Electronic technicians will attempt repairs on Monday. && .BIS WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 11 PM CDT /10 PM MDT/ this evening for NDZ045-046-050-051. && $$ UPDATE...JPM SHORT TERM...CJS LONG TERM...CJS AVIATION...JPM
Area Forecast Discussion
National Weather Service Columbia SC
728 PM EDT Sun Mar 12 2017 .SYNOPSIS... An area of low pressure developing off the coast will bring the next chance of rain to the area Monday through Tuesday morning. The remainder of the week will be dry with temperatures well below normal. Possible frost and freeze concerns through Friday morning. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Visible satellite imagery this evening shows clearing skies in the northern portion of the area pushing southward. Most of the snow that fell earlier today has melted although there is some remaining near the NC border as noted on SCDOT road cameras. Roadways also continue to dry and with warm ground temperatures do not expect much water to be left to refreeze on roads overnight. Expect clouds to continue to diminish from north to south through tonight although clearing may not reach the southern portion of the FA. Overnight lows will generally be around 30 along the NC border...the lower 30s in the central Midlands and the mid 30s in the CSRA. A freeze warning is in effect from the central Midlands northward. && .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/... Monday will bring additional cold air southward into the region as on low-level wedge flow. Along the coast, an area of low pressure will be developing off the South Carolina coast in response to a deepening upper level trough moving towards the southeastern states. Models start the day off dry, then begin bringing some rainfall into the CSRA through the morning, then spreading northward through the afternoon. Temperatures above freezing through this event, so an all rain forecast at this time. The surface low will continue to deepen through the day Monday, and then will begin moving northward along the Atlantic Coast Monday night through Tuesday morning in response to the approaching upper level trough and support. Models keep rainfall in the area for much of Monday night, then towards sunrise on Tuesday, majority of the moisture will rapidly move off to the northeast away from the area. Generally have likely pops for much of the early portion of Monday night up through about Midnight, then begin tapering precip down to chance pops, finally drying conditions out by sunrise. Temperatures by Tuesday morning will be cold and in the 30s, but should be bottoming out after the rain and moisture have left the area. At this time it appears as if temperatures will remain above freezing at all locations, so no freeze warning expected at this time. Tuesday will see some warming, although minor, compared to previous few days as some downsloping and sunshine help to counter any cold advection. Readings in the 50s expected. Tuesday Night will see dry conditions, but a return to freezing temperatures. Just about the entire cwa will be at or below freezing, with some areas possibly seeing a hard freeze. Anticipate a freeze warning being needed for late Tuesday night. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Dry weather expected through Friday. The main issue through the end of the week is going to be the very cold morning temperatures. After starting off the day on Wednesday at or below freezing for many areas, highs will be in the middle 40s to lower 50s with plenty of wind through the day. Wednesday night into Thursday morning will be a critical period in regards to temperatures. Models continue to indicate a high chance of the entire cwa experiencing a hard freeze, with a prolonged period of temperatures below freezing. Readings are expected to bottom out in the lower to middle 20s. Unless things change significantly between now and then, a freeze warning will likely be needed for this period. Temperatures will begin to rebound on Friday with temperatures climbing back to around 60. A weather system is then expected to move through on Friday night or Saturday with another chance of rain. However, both overnight lows and afternoon temperatures should remain mild through the weekend with lows in the 40s and highs in the 60s. && .AVIATION /23Z SUNDAY THROUGH FRIDAY/... MVFR to IFR restrictions expected for much of the TAF period. Satellite showing clearing to the north of CAE moving south. Based on satellite observation expect CAE and CUB to go VFR during the early evening with scattered low clouds. The clearing may spread into the OGB terminal. This is somewhat supported by HRRR and Lamp. The low cloud restrictions are more likely to remain at AGS/DNL through the overnight. Despite improving conditions this evening...low clouds will spread inland from the coast after 06z as shallow onshore flow/isentropic lift develops. Guidance suggesting MVFR and possibly IFR at times through the morning. Rain may develop by afternoon as weak low pressure develops along the coast. This may lead to visibility restrictions late in the taf period. EXTENDED AVIATION OUTLOOK...Widespread MVFR or IFR conditions expected through Monday night associated with low pressure off the coast. Breezy conditions will likely occur Tuesday and Wednesday. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...Freeze Warning until 10 AM EDT Monday for SCZ015-016-020>022- 026>029-031-038. && $$
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1107 PM EDT Sun Mar 12 2017 .UPDATE... Main point is that a winter weather advisory for light snow accumulations has been issued for the southern 3 tiers of counties from 6 AM EDT to 11 PM EDT Monday, excluding St Clair County. Justification for the advisory is expectation to hit 4 inch snowfall amounts in the Detroit Metro area. There is really not much to add at the big picture for the northern stream energy/warm advection that will impact southeastern Michigan on Monday. Decaying system coasting in here locally, with sheared out shortwave, virtually no favorable jet dynamics aloft, putrid deep layer moisture, and much higher static stability than one would like in the mid tropospheric frontal zone (between a high 9-20 kft agl). However, there are overachievers and with this particular system there are a number of items that appear to line up favorably to hit the 4 inch snowfall mark over a long duration. 1. Latest HRRR, RAP and some 4km hi-res WRF solutions are hinting at a 1000-900mb convergence axis developing over and along the northern shore of Lake Erie in easterly flow, funneling directly into areas of the Detroit Metro area. In other words, lake enhancement. Guidance suggests it could be along I 96 or 696 at light snow onset through the morning commute before quickly transitioning southward south of I 94, Downriver into portions of Washtenaw, Monroe, and Lenawee counties between 14-17Z. Not comfortable to jump on any talk of high snowfall rates now, but there are a couple solutions showing in the in-house Probabilistic metrics, that suggests snowfall rates in any lake enhancement could exceed one half inch per hour. Despite cold surface lake water temperatures of about +1C, 1000-900mb theta e lapse rates are neutral to negative within the band. More importantly is the pre-existing mixed layer that exists in the 1000- 800mb layer. Models show the Lake Erie convergence axis providing enough moisture to allow for a persistence of saturation in this steep lapse rate pocket right through the afternoon. Top of this mixed layer is shown to keep a connection with -15C. Therefore, could very well see light snow fall off across much of southeastern Michigan during the afternoon expect for those areas downwind of Lake Erie. Confidence is too low to highlight a specific location or a residence time of the band at any one location. However, there is enough signal to provide support for an advisory with 4 inch snow totals. 2. Near surface layer of theta e lapse rates is suggesting a potential for late afternoon diurnal heating to contribute to lower level ascent and light snow activity. Confidence in this is low. 3. Deep isothermal layer between 6 kft and 10 kft agl is interesting. Expectations for weaker frontal forcing aloft to be generating the seeder-feeder setup with hydrometeors at generally at or above 600mb with snowflakes then falling down through this deep isothermal layer. Favorable thermodynamics for snow is also supported by supersaturation with respect to ice all day throughout much of the entire column. 4. Not convinced on some of the MOS guidance that we can make a run at surface temperatures of 30 degrees. Given mean 1000-850 mb temps of -8 to -10C over semich and aforementioned deep isothermal layer preference is to shade higher than climatology for liquid to snow ratios. To generate the snowfall amounts used 16:1. Did not want to get to go too much above that with overall lighter uvvs, however, if the lake enhancement gets going these snow ratios would probably be low. && .PREV DISCUSSION... Issued at 833 PM EDT Sun Mar 12 2017 AVIATION... Quiet aviation weather in place over southeastern Michigan for the majority of tonight as top-down saturation commences ahead of approaching low pressure system. Latest probability trends are suggesting that onset of light snow may wait until 11z. Once the light snow begins, the area is looking at a long duration-low snowfall rate grinder lasting from approximately 11Z-22Z. Probability numbers match the qualitative eye-test (straight midlevel warm advection, weak front structure aloft, virtually no jet forcing aloft) in supporting very meager snowfall rates of a less than .5 inch per hour rates during the aforementioned 11 hour period. Flake size remains a wildcard and will probably support some periods of IFR visbility restrictions. Given the setup, it is a low confidence forecast at this juncture to include in the forecast. Easterly low level winds will try to sustain a feed of lower level dry air. Easterly winds are forecasted Monday in the 10 to 20 knot range. For DTW... Onset timing of snow is projected for 10Z or 11Z starting out MVFR and transitioning to periods of IFR. Slow grinder of an event with snow accumulations of 3 to 4 inches by Monday evening. //DTW THRESHOLD PROBABILITIES... * Low for ceiling 5000 feet or less through 10Z, high after and through Monday. * High for a dry snow precipitation type. PREV DISCUSSION... Issued at 343 PM EDT Sun Mar 12 2017 DISCUSSION... Remnant circulation of Pacific Northwest cyclone is streaming down the front range of the Rockies in advance of a broad Canadian trough axis. This energy will shear into Lower Michigan late tonight into early Monday as a developing jet core forces further trough amplification across the southern United States. This will set the stage for a period of warm advection during the day Monday followed by a glancing blow of deformation Monday night as the Canadian trough phases with the deepening southern wave. Echoes over the Upper Midwest this afternoon will continue to translate east as isentropic ascent builds into the area after 06z. Fairly dry progged soundings and low surface dewpoints obs suggest at least a couple hours of virga before hydrometeors reach the ground. Latest RAP/HRRR output paints a reasonable depiction of an onset time between 10-12z. Moisture quality is quite poor per NAM12 progs of 850-700mb layer specific humidity of under 1.5 g/kg for the balance of the day. Nonetheless, the resident cold thermal profile should be able to make the most of the environment with predominant dendrite and plate production. This is particularly the case given a DGZ dipping down into the boundary layer during peak ascent early Monday. Thus, relatively paltry QPF may still result in an inch or two in most places. Some lake enhancement along the shorelines is not out of the question, but overlake instability is modeled to be poor, so a significant departure from the background moisture/forcing field is not anticipated at this time. The greatest potential for meaningful snowfall will be Metro Detroit and points south where the northern reaches of the warm conveyor may provide a burst of moderate or even locally heavy snow between 14- 18z Monday, when 2 to 3 inches will be possible. Evolution of the large scale pattern toward east coast cyclogenesis will greatly limit the potential duration as it forces the flow up the frontal slope to rapidly back, bringing an end to any respectable snowfall rates prior to 18z. The remainder of the event into Monday night will simply be a low-intensity grinder yielding a few tenths every 6 hours or so. There is at least an outside chance that intensity within the warm conveyor could approach 6 hour advisory criteria of 3 inches, most likely after the morning commute. Marginal confidence and lower impact timing tipped scales in favor of withholding from a headline. Uncertainty increases Monday night into Wednesday owing to uncertain character of phasing and evolution of the East Coast cyclone. Strong consensus among the 12z suite on a lack of impactful snow in SE Michigan during this time as the core of deformation centers over Ohio. However, the 12z ECMWF allows low intensity deformation to linger Monday night right into Wednesday, the result being continued grinding of low-intensity snowfall rates. Chc pops in place for this scenario, particularly since it appeared to be the only member of the NWP in the company of the RAP with regard to handling upper energy this afternoon. This period of the forecast will likely be the subject of multiple refinements in the coming forecast cycles. Temperatures gradually moderate toward climatological averages through this week as a more progressive pattern takes hold across the CONUS and heights rise in the wake of the departing east coast storm. MARINE... Light and variable wind will increase from the east tonight as high pressure exits into the New England states. The next low pressure system will then move into the Ohio valley during Monday and boost the easterly flow even more by Monday evening. The moderate easterly flow is expected to build waves above 4 feet Monday night and likely require a small craft advisory for the Bay and nearshore waters of southern Lake Huron. The Ohio valley low is then projected to merge with a nor`easter off the Atlantic coast Tuesday. This will turn the wind to north over Lake Huron and increase speed to near gales through Tuesday night. At this point, gust potential appears marginal for a watch headline but this will be monitored in upcoming forecast cycles. Cold northerly flow then continues through mid week but mostly below 30 knots. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory from 6 AM to 11 PM EDT Monday for MIZ068>070-075-076-082-083. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ UPDATE.......CB AVIATION.....CB DISCUSSION...JVC MARINE.......BT You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Houston/Galveston TX
913 PM CDT Sun Mar 12 2017 .UPDATE... Cloudiness associated with the upper level system moving over and east of the forecast area will continue over Southeast Texas tonight. There may be enough breaks in the cloud cover to lead to some slightly lower overnight temperatures than earlier forecast. Tweaked the temperature forecast for the first period. 40 && .PREV DISCUSSION... /ISSUED 641 PM CDT Sun Mar 12 2017/ AVIATION.../00Z TAF/ Overall aviation weather impacts look minimal with only concern begin borderline MVFR/VFR ceilings. Visible satellite shows cloud eroding from the east as drier air moves into SE Texas. The problem will be timing if MVFR ceilings develop back over the area. There will be some return flow at 925mb so could support cloud cover overnight into Monday morning. Overall TAF continued previous trends and went more optimistic with ceilings/visibility than model guidance. HRRR seems to be preforming well to that end. Models do have another front pushing through the area tomorrow afternoon. This should help clear cloud cover and increase winds from the NNW in the afternoon. Overpeck PREV DISCUSSION... /ISSUED 315 PM CDT Sun Mar 12 2017/ DISCUSSION... Cloud cover has remained fairly persistent across Southeast Texas this evening, but drier air has been able to work its way into the extreme eastern counties and has cleared some of the low clouds in place behind the front. Temperatures have been able to warm into the lower 60s in this part of the region, with low to mid 50s being observed elsewhere. Mostly cloudy to cloudy and cool conditions will persist overnight, with most areas seeing lows in the mid 40s to mid 50s. Will have to keep an eye on the eastern counties in case cloud cover does not fill back in with nocturnal cooling as low temperatures will likely be a few degrees cooler than forecast. A reinforcing cold front will move across the region during the day on Monday, but temperatures will be able to rebound into the upper 60s to low 70s as forecast soundings show the saturated layer trapped beneath a persistent inversion becoming more shallow... indicating drier air behind Monday`s front will be able to help thin (or possibly scour) cloud cover across the region and allow for more insolation to promote warmer temperatures. Clearing skies will promote excellent conditions for radiational cooling Monday night, with low temperatures falling into the 40s Tuesday morning. Dry northwest flow aloft will keep rain chances low and temperatures near to just below seasonal normals through mid-week. Strengthening onshore flow will allow for a few showers Thursday and Friday, with temperatures warming into the mid to upper 70s by Friday. Still some uncertainty with the advertisement of a weekend cold front, with the GFS completely flipping the solution it advertised 24 hours ago and now stalling the front north of the region. The European now attempts to backdoor this front into the region on Sunday, breaking out a few showers along it as it slides into the region. Even if this weak front is able to make it into the region by the end of the weekend, warm air advection ahead of it looks to result in temperatures climbing to near 80 degrees by Saturday. Huffman MARINE... High pressure building into the area will help to decrease winds and seas tonight. A reinforcing front on Monday could briefly increase the offshore winds and raise seas once again. Onshore winds return to the area Tuesday night and Wednesday as high pressure moves off to the east, and this flow will persist for the remainder of the week with winds and/or seas reaching caution/advisory levels at times. 42 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 47 70 45 70 51 / 10 10 0 0 10 Houston (IAH) 50 72 48 72 50 / 10 10 0 0 0 Galveston (GLS) 56 69 56 67 58 / 10 10 0 0 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 1 AM CDT Monday for the following zones: Coastal waters from Freeport to the Matagorda Ship Channel out 20 NM...Coastal waters from High Island to Freeport out 20 NM. Small Craft Advisory until 1 AM CDT Monday for the following zones: Waters from Freeport to the Matagorda Ship Channel from 20 to 60 NM...Waters from High Island to Freeport from 20 to 60 NM. && $$ Discussion...40 Aviation/Marine...39
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
636 PM CDT Sun Mar 12 2017 .SYNOPSIS... Issued at 325 PM CDT Sun Mar 12 2017 H5 analysis from this morning had a longwave trough of low pressure over eastern Canada and New england with a trough extending south into the central Atlantic. West of the trough ridging extended up the west coast of the CONUS into northeastern British Columbia and northwestern Alberta. Broad northwesterly flow extended east of the ridge into the western Great Lakes. Embedded in this flow, a nice shortwave was located over northwestern Wyoming into central Montana. As of midday, this feature has tracked into the western Dakotas and the Nebraska panhandle. At the surface, low pressure was located northwest of Valentine Nebraska. A warm front extended east of the low and roughly along highway 18 in southern South Dakota while a cold front extended to the west southwest of the low into the northern Nebraska panhandle. With the upper level wave pushing into the western Dakotas, showers have developed from southwestern South Dakota into the Nebraska panhandle. Most of the precipitation has remained aloft with these showers, however, some precipitation is hitting the ground over the Pine Ridge and northwestern Sandhills per DOT cameras. Skies were mostly cloudy across western and north central Nebraska and 2 PM CDT readings ranged from 42 at O`Neill to 56 at Ogallala. && .SHORT TERM...(This evening through Monday) Issued at 325 PM CDT Sun Mar 12 2017 Tonight and Monday...The main forecast challenge in the short term is determining the ending time of the pcpn threat this evening, then temperatures on Monday. For tonight: The before mentioned cold front will clear the forecast area by 00z tonight with the h5 trough axis clearing the forecast area in the following 3 to 6 hours. The latest HRRR does indicate some limited post frontal lift in the east through this evening and will hold onto at least a mention of light pcpn in the east through midnight. Much colder air, in association with a back door arctic front, will back into the forecast area overnight with lows bottoming out in the lower teens in the north to lower 20s in the south. For Monday, the front will move only slightly east as a warm front, and will extend from the far southwestern corner of the forecast area into the southwestern panhandle. Highs Monday will vary widely across the forecast area with mid 20s in the far northeast, to the mid 40s in western Chase county and Deuel county. .LONG TERM...(Monday night through Sunday) Issued at 325 PM CDT Sun Mar 12 2017 Mid range...Monday night through Wednesday: In the mid range, the main forecast issue will be the threat for light freezing precipitation Tuesday night. For Monday night, an upper level jet streak will approach northern Nebraska from the western Dakotas. Mid level frontogenesis will increase from north central into south central Nebraska Monday night. Lift along this mid level front will be enhanced by the approaching jet streak, leading to an increased threat for light snow Monday night from north central into eastern portions of the forecast area. Forecast QPF`s are generally under a tenth of an inch per the NAM and GFS solutions, so any accumulations will be an inch or less. On Tuesday, the arctic cold front will push east as a warm front and will make it as far east as a Valentine to Broken Bow line. Like Monday, a large range in highs is expected across western and north central Nebraska with highs around 30 in the northeast to around 60 in the southwest. On Tuesday night, a mid level warm front will push into central Nebraska with good lift noted in the dendritic zone overnight. Looking at bufkit soundings, there is a shallow, above freezing, layer just off the surface, which would be favorable for light freezing precipitation. Normally wouldn`t mention freezing pcpn in day 3, however the NAM and GFS solutions are very similar in their solutions this morning. Also the GFS solutions from yesterday were hinting at this freezing pcpn threat as well. That being said, went ahead and introduced a mention of light freezing precipitation in the central and east Tuesday night into early Wednesday. Wednesday night through Sunday: Ridging aloft will work into the forecast area Wednesday night into Thursday. This will force the stationary fronto boundary, forcing the frontal boundary into the eastern CWA for Thursday. Highs Thursday will reach the mid 50s in the northeast to the middle 70s in the southwest. Warm temperatures Thursday will be followed by a cold front Thursday night and an increased threat for light rain in northern and northeastern portions of the forecast area Thursday evening. A temporary cool down in highs is expected Friday as highs reach the 50s. Ridging will begin to build back into the western CONUS Friday night into Saturday. This ridge will transition east onto the plains by Sunday. Highs Saturday will be in the 60s to lower 70s, followed by upper 60s to upper 70s for Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 636 PM CDT Sun Mar 12 2017 MVFR cigs are expected across Nrn Neb tonight through at least noon Monday. VFR is expected overnight and Monday elsewhere. The models show the cold air stratus across Nrn Neb shifting east of KVTN by noon Monday. This bank of low clouds may last throughout the day near KONL. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Buttler SHORT TERM...Buttler LONG TERM...Buttler AVIATION...CDC
Area Forecast Discussion
National Weather Service Memphis TN
915 PM CDT Sun Mar 12 2017 .DISCUSSION...Surface analysis this evening places an Alberta Clipper cold front over portions of Nebraska and Kansas. Meanwhile, high pressure is in place across the Mid-South with temperatures as of 8 pm CDT in the 40s at most locations. Regional WSR-88D radar trends the Middle Mississippi Valley already showing some returns from Northeast Missouri back through Southwest Missouri. Latest HRRR and 00z WRF suggests a potential for precipitation to arrive after 09Z across areas mainly west of the Mississippi River. Model soundings indicate predominantly rain as the precipitation type and perhaps some light sleet or snow initially mixed in before switching to all rain Monday morning. In addition, short term models indicate a potential for some isolated to perhaps scattered rain showers for Monday afternoon into Monday evening as 700-500 mb layer lapse rates steepen to 7-8 C/km in association with a mid-level trough. Will make some adjustments to timing of precipitation overnight, add rain chances in for Monday afternoon/evening, and to adjust any other elements as needed to account for trends. Update will be out shortly. CJC && .PREV DISCUSSION... /issued 627 PM CDT Sun Mar 12 2017/ UPDATE... Updated to include the 00z aviation discussion. PREV DISCUSSION... /issued 240 PM CDT Sun Mar 12 2017/ DISCUSSION... Clocks and Calendars doing more than an hour switcheroo today. Melting of the overnight snow has drawn warmth out the lower atmosphere...keeping temperatures well below normal...with readings mainly in the 40s. The air was dry and northeast winds were a bit gusty providing for wind chills in the 30s. For tonight through Tuesday...diving clipper system in the Midwest will bring increased clouds...warmer air relatively speaking and rain to the midsouth starting after midnight tonight. Short term model soundings place a small window where rain may be mixed with snow or sleet across northeast Arkansas and the Bootheel of Missouri just before sunrise when temperatures were hovering a degree or two above freezing. Feel only very minor accumulations are possible on elevated surfaces...with most of the solid precipitation melting as it hits the ground. So a winter weather advisory is not currently anticipated. Better chances for liquid precipitation will arrive in the 13/12z to 13/21z time frame...with most locations picking up a quarter of an inch or so. The cold front associated with the clipper will exit the Midsouth tomorrow evening...but low level cloud cover will hang around behind it through Tuesday...a typical winter scenario. This will provide for temperatures to stay just above freezing tomorrow night...and only climb into the 40s for highs. A light rain or snow shower will be possible in the east from the moisture wrapping around the intensifying East Coast storm. Clearing skies Tuesday night will likely prompt the need for freeze headlines. Wednesday through next through the period with fingers crossed that some of region will see 60F degrees. Wednesday will be cold and dry with a likely second freeze/frost headline during the overnight. Clouds will increase Thursday with rain chances ramping up during the night and through Friday. There may be a few cracks of thunder also as a swath of elevated instability slides overhead. This all being triggered by a surface low tracking from Texas to the central Gulf Coast. A few lingering showers are expected Saturday. A northwest upper flow will keep the latter half of the weekend dry as upper heights slowly build in from the west. The following Monday may be the first day depicted by the GFS and ECMWF where a strong enough south wind will raise temperatures above normal. JAB && .AVIATION... /00z TAFs/ VFR conditions will prevail through much of the overnight period with light east to northeast winds. The next shortwave trough will result in an area of light rain after 10z in northeast AR, moving across the remainder of the Mid-South through early afternoon. Ceilings are expected to be predominantly MVFR during this time, but IFR conditions may accompany this rain for a few hours, mainly during the morning hours. A few snowflakes could mix in with the rain in JBR, but it will remain operationally insignificant. Winds will veer from the southwest, then eventually from the west, after the band of rain moves east, but should generally remain under 10 kts. A few afternoon showers will be possible as well, but coverage should remain limited. Johnson && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$
Area Forecast Discussion
National Weather Service Melbourne FL
1000 PM EDT Sun Mar 12 2017 .UPDATE... ...High Rain Chances Mon and Mon Night, then Drier and much Cooler Mid-Late Week... Tonight...A northerly wind surge (weak frontal boundary) had settled into central sections but there is just a little air mass change behind it. Low level winds will quickly veer overnight as surface high pressure to our north pushes to the eastern seaboard. This will cause the weak frontal boundary to stall and gradually wash out, but the models show an inverted coastal trough forming again late tonight, with east/southeast winds over the waters and light north/northeast winds inland. This configuration usually keeps significant showers confined to the Atlantic, so 30-50 percent POPs along the coast might be too high. However, the NAM doesn`t show much of an inverted trough and generates a little more precip close to the coast. Additionally, the GFS develops some isentropic lift late and the HRRR model has been generating light rain towards sunrise in the north. With radar continuing to show some convection, and outflow boundaries, over the Atlantic late this evening, do not plan to lower POPs any. Otherwise, considerable mid-high level cloudiness will continue to stream across and scattered/broken low cloudiness should persist in the north behind the weakening boundary. Little change in min temps, around 60 to the lower 60s. && .AVIATION... Some MVFR ceilings have been occurring behind a weak frontal boundary that settled into central Florida, mainly KTIX-KMCO-KISM northward. This cloudiness may persist into late night and there is also a slight chance for showers and light rain late in that area. There will be considerable mid-high level cloudiness areawide into Mon morning then modest daytime heating should cause convection to develop in the afternoon. Overall greater forcing is indicated so coverage should be higher than today and a chance for lightning storms exists again. && .MARINE... Tonight-Mon...A wedge of stronger N/NE winds worked down the coast this afternoon/evening. Winds are forecast to veer around to the east over the coastal waters overnight with the pressure gradient easing a bit. Will continue an exercise caution statement in the north overnight. On Mon, a low pressure center approaching from the Gulf of Mexico will veer winds around to southerly and they may increase late in the day to 15-20 knots. Scattered to numerous showers and isolated storms should push offshore during the afternoon and evening. && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ Forecasts...Lascody Impact Wx...Volkmer
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
723 PM CDT Sun Mar 12 2017 .SHORT TERM...(This evening through Monday) Issued at 315 CDT Sun Mar 12 2017 The short term concern remains heavy snow potential to the south and west of the metro into the evening...and how far east real accumulation will occur. Also...headline resolution remains. Snow...heavy at times is working across about the southern third of the state at this time. Expect this to continue to work east/southeast during the early evening...affecting mainly south central MN into the evening. The nam was indicating fairly decent -EPV potential across the region...into the southwest metro. SREF and deterministic models paint a rather large dendritic growth zone working over the region...with the best vertical motion directed along the Minnesota River Valley into this evening. Snowfall rates will likely range around 1 inch an hour in the heavier snow area. Still looks like a potential for up to 11 inches in a portion of south central MN before it begins to taper off. Total QPF around 0.60 inch likely into south central MN. Lesser totals are expected to the it still is working into the very dry low level airmass...with some below zero dewpoints remaining over west central Wisconsin at 20z. It should gradually saturate the rest of the afternoon. Overall...current headline configuration is looking good at this time. Will retain as is for the interim. Will most likely cancel headlines early into central MN...especially 06z-12z...when upper trough exits to the southeast and somewhat drier air works in. Some gusty wind potential into tonight and we continued to mention patchy blowing snow west central into south central MN through 12z Mon. Some wind gusts 20-25kts possible as surface low exits to the south later tonight. The snow comes to an end over the far southeast early Monday with clouds remaining...mainly to the southeast. We could see some sunshine develop to the northwest during the afternoon as high pressure builds southeast. .LONG TERM...(Monday night through Sunday) Issued at 330 PM CDT Sun Mar 12 2017 Models are fairly consistent in the overall long wave pattern through the end of the week. Only concerns are timing on the next weather system that will move into the Upper Midwest late Thursday and into Friday. The EC is much flatter on the upper ridge by the end of the week, which leads to a faster shortwave on Friday, but much stronger than the GFS/GEM. This stronger shortwave also translates into a stronger surface reflection vs. the GFS/GEM on Friday. The thermal profile suggest that a mixture of rain/snow will become snow on the back side once this shortwave moves through. Otherwise, the only other concern is temperatures, especially considering the snowfall today and how it will play on highs/lows this week. Models seem to indicate a cooler reference where the highest totals are expected. Didn`t deviate too much from this scenario, which will likely be altered this week. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 723 PM CDT Sun Mar 12 2017 Snow will continue through much of the night, though the worst of the snow (1/2sm or less vis) as moved southeast of the MPX terminals. Followed the HRRR to time snow through the area and main change was to delay the snows departures a little. MVFR cigs are expected to persist through the rest of the night, though upstream obs do not really support the widespread IFR cigs the LAMP has, so continued to be more optimistic than it. Lower confidence on CIG improvements, though we may see lower clouds/moisture get scoured out a bit faster than currently indicated. KMSP...One more band of 1/2sm at times type snow has developed over the Twin Cities and will slowly slide thru over the first hour of the taf. Once it`s gone, we should see vis 1sm or greater until the snow departs. /OUTLOOK FOR KMSP/ Tue...VFR. Wind NE 5 kts. Wed...VFR. Wind becoming S 5-10 kts. Thu...VFR. Wind S 6-12 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...Winter Weather Advisory until 1 PM CDT Monday for WIZ023>026-028. MN...Winter Storm Warning until 1 PM CDT Monday for MNZ076-077- 083>085-092-093. Winter Weather Advisory until 7 AM CDT Monday for MNZ041-047>049- 051-058-059-066. Winter Weather Advisory until 10 AM CDT Monday for MNZ060>063- 068>070. Winter Storm Warning until 7 AM CDT Monday for MNZ054>057-064- 065-067-073>075-082-091. Winter Weather Advisory until 1 PM CDT Monday for MNZ078. && $$ SHORT TERM...DWE LONG TERM...JLT AVIATION...MPG