Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/21/18

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1200 AM EDT Wed Mar 21 2018 .AVIATION... Prevailing northeast flow will sustain dry low level conditions through the TAF period. While a thickening canopy of high cloud will lift into the region tonight, this will ensure skies remain clear across the lowest 7-8k ft through Wednesday. The exception remains near MBS, where a narrow strip of stratus continues to funnel off Saginaw Bay. This will maintain the potential for periodic MVFR conditions at this terminal. Firm northeast winds overnight turn gusty again with diurnal support Wednesday. For DTW...Winds hold from the north-northeast /010-030 direction/ tonight, gradually easing in both magnitude and gust frequency. Gradual backing of winds to north and north-northwest throughout Wednesday. Skies to remain clear across the lowest 5000 ft through Wednesday. /DTW THRESHOLD PROBABILITIES... * None. && .PREV DISCUSSION... Issued at 309 PM EDT Tue Mar 20 2018 DISCUSSION... Strong Canadian high pressure (1030+ MB) will remain anchored along/near Ontario/Quebec border over the next several days. 12Z DTX indicated a very dry airmass in place over southeast Michigan today, as 850 MB dew pt depression checked in at 32 C, with a PW value of 0.14 inches. Brisk northeast winds will continue through tonight (holding min temperatures in the low/mid 20s), shifting to the North-Northeast early tomorrow morning. Strengthening low-mid level circulation tracking through southern Ohio will send 850-700 MB Theta-E gradient over Lenawee/Monroe counties overnight. But with continued low level feed of dry air, still looking at the snow shield holding near the southern Michigan border. 12z Regional Gem would even argue for light accumulations south of I-94 as 700 MB specific humidity rises to 2.5 G/KG. Preference is more toward the slightly drier RAP solution, but low chance pops for light snow late tonight still seems warranted south of I-94, especially if that flow becomes a bit more easterly off Lake Erie. Upper level shortwave ridging to become established on Wednesday. With northerly flow off cold waters of Lake Huron, looks like good temp gradient setting up during the day, as 925 mb temps advertised to range from -8 C over northern tip of the Thumb to -2 C along the southern Michigan border, translating to highs in lower 30s to lower 40s. Dry airmass and skies becoming clear Wednesday night will lead to a favorable radiating night, sending temps into the lower 20s. Could even see mins sneak into the teens in the normally colder locations if winds fully decouple. Thursday and beyond... Confluent NW flow still forcing all meaningful precip south of the area while ensuring mostly sunny skies with dominant high pressure at the surface. The third week of spring will see temperatures creeping ever-closer to average values as ridging builds over the central CONUS for the remainder of the forecast period. MARINE... Large High pressure to the north and a low pressure system moving up the Ohio Valley will continue a prolonged period of moderate northeast wind which will continue this afternoon through Wednesday before gradually diminishing Wednesday night. Occasional gusts to 30 kts are likely through Wednesday. The long northeast fetch over open water will build high waves through the period and small craft advisories remain in effect through Wednesday for all marine areas except Lake St Clair which is through tonight. Advisories will continue into Wednesday night for outer Saginaw Bay and Lake Huron near shore. The wind will weaken and back north by Wednesday night as the low exits the mid Atlantic coast and as the Ontario high builds over the western Great Lakes. This will allow waves to gradually diminish below advisory levels all areas by Thursday and last through Friday. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Lakeshore Flood Advisory until 10 AM EDT this morning for MIZ083. Lake Huron...Small Craft Advisory until 2 AM EDT Thursday for LHZ421-441>443. Small Craft Advisory until 4 PM EDT this afternoon for LHZ422. Lake St Clair...Small Craft Advisory until 8 AM EDT this morning for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory until 8 AM EDT this morning for LEZ444. && $$ AVIATION.....BT DISCUSSION...SF/JVC MARINE.......DRC You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Wilmington NC
806 PM EDT Tue Mar 20 2018 .SYNOPSIS... Hazardous thunderstorms are possible this afternoon and tonight as a storm system approaches the region. Colder air will spill into the Carolinas Wednesday and especially Wednesday night, with frost and freeze conditions for portions of the area early Thursday and early Friday. High pressure will maintain cool daytime weather this weekend, with rain spreading in from the west Saturday night and Sunday. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... As of 710 PM Tuesday...Cooler surface air has knocked instability values for surface parcels down to zero with the exception of the I-95 corridor where SBCAPE is still near 1000 J/kg and new storms have lit up near and just northeast of Florence recently. As colder air aloft works in from the west, a few new cells could still develop from Dillon and Lumberton to Elizabethtown as the last of the elevated instability aloft over the frontal surface is expended. Rain chances are still anticipated to ramp down from south to north over the next few hours. Freezing levels are plunging with the incoming cold air aloft, and we`ve observed almost any echo over 60 dBZ is correlated with small hail at the ground. Emergency Management in Bladen County reported small hail in multiple locations from Elizabethtown to White Lake within the past 30 minutes. Discussion from 550 PM follows... Severe thunderstorms earlier this afternoon dropped hail at least one inch in diameter near Trio, SC, but have weakened. The convective cap has since broken and more widespread thunderstorms have since developed east of I-95 to the coast. One strong storm dropped a little pea sized hail here at the NWS office in Wilmington, and hail will remain a possibility for the next few hours as steep mid-level lapse rates will promote large parcel acceleration aloft. Visible satellite and radar shows the surface cold front moving southward through Hartsville, Marion, Whiteville, to just north Wilmington. The HRRR is doing an excellent job currently and is our model of choice for the next 6 hours with convective development and movement. Convection will remain largely east of I-95, shifting almost exclusively into SE North Carolina in the next couple of hours, then ending by late this evening as colder and more stable air wraps in behind developing low pressure exiting the coast. Some light showers should redevelop late tonight across the northern sections of the Pee Dee into SE North Carolina associated with a strong shortwave wrapping around deepening upper level low pressure to our north. One more change made to the forecast concerns sea fog that has developed over the past few hours and is reducing visibility at the beaches according to multiple beach cams across the Cape Fear area. High dewpoint boundary layer air chilled by its passage across the cold nearshore waters is responsible. Once the cold front moves through the fog should quickly dissipate. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... As of 340 PM Tuesday...NNW to NW flow through most of the column Wednesday night ushering in cooler and drier air. The flow will still be rather vort-laden, but most of the maxima will be sheared out and to our south. So while a few of these impulses may bring batches of mid level cloud the area will remain rain- free. Lows in the mid 30s will support some frost especially where winds grow light enough and guidance is trending colder away from the ocean and much of the area may experience a light freeze, at least according to the colder MET MOS. It bears pointing out at this time that there is a good 6 degree separation between these values and the warmer MAV numbers. Cold air advection continues Thursday and Thursday night albeit weakening especially late in the period. Thursday night may be a better candidate for a light freeze especially over northern zones and our normal chilly spots as surface-based decoupling appears more likely. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 340 PM Tuesday...this forecast period continues to show a cool down as an upper level trough will be remain along the east coast. In the large scale trough a shortwave is seen dropping southward on the west side. This will bring in a colder shot of air and a back door cold front. The 12 UTC GFS and ECMWF are not in good agreement with the GFS being much faster than the ECMWF. So uncertainty is high on timing of this front. Will favor the faster GFS and its ensemble and introduce a chance of showers late Saturday into Sunday night as the frontal boundary shifts southward. Temperatures will be below normal for the period with a frost/freeze possible Friday night. Otherwise lows in the 40s and highs in the mid to upper 50s to lower 60s. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... As of 00Z...Surface front was located just south of a KFLO- KILM line, with low center southwest of KFLO. Numerous weakening showers were along and north of this boundary, and will continue through about 03Z. The front will sag further south and make it to the vicinity of KMYR before the low moves offshore and winds shift to the W and NW. Expect MVFR ceilings overnight, with some potential for IFR. Westerly winds will become gusty Wednesday morning and continue through the day as low pressure deepens off the Mid-Atlantic coast. Extended outlook...VFR. MVFR/IFR/Rain Sunday. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 710 PM Tuesday...Quick update to remove the tornado watch headline from the forecast. Severe thunderstorm potential has really diminished in the past 60-90 minutes, and the remaining showers on radar should gradually diminishing from south to north over the next few hours. Discussion from 550 PM follows... Forecast has been updated for sea fog that has developed over the past few hours as high dewpoint air south of a cold front has been cooled by contact with the cold sea surface. This fog should be with us south of Cape Fear for another few hours before increasing northwesterly winds bring drier and colder air southward, dissipating the fog. Showers and thunderstorms developing across the area should clear the SC coastal waters by 8 PM, but may linger for another few hours across the SE North Carolina/Cape Fear waters as surface low pressure develops overhead. All convective activity should be out of the area by midnight, but light showers may redevelop later tonight, brought southward by cold winds draining offshore from northern North Carolina and Virginia where snow may actually be falling late tonight. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 340 PM Tuesday...As is usually the case in a strong cold advection regime accompanied by strong dynamics aloft conditions will be hostile over the marine environment early in the period. Advisory-worthy winds will be bringing steep, short period waves that will also satisfy the (6ft) criteria. Relaxation of wind and seas will be quite gradual on Thursday as cold advection continues but weakens as does the strength of the upper impulses moving overhead. Current 5PM ending time of the advisory appears on track enough this far out int time to preclude any changes. Northwest flow lasts into Thursday night with the abating trend ongoing. LONG TERM /FRIDAY THROUGH SUNDAY/... As of 340 PM Monday...high pressure will ridge down the coast with a surge of cooler air on Sunday. The high pressure will extend down over the local waters Friday through Saturday before a cold front approaches from the north. Northwest flow of 10 to 15 knots will continue through Friday before veering to the south and west on Saturday and Sunday. Winds will increase on Sunday with a backdoor front and seas are expected to increase to 4 to 7 feet by Sunday late. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until 6 PM EDT Thursday for AMZ250-252- 254-256. && $$ SYNOPSIS...DRH NEAR TERM...TRA SHORT TERM...MBB LONG TERM...DRH AVIATION...CRM
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
623 PM CDT Tue Mar 20 2018 .SYNOPSIS... Issued at 340 PM CDT Tue Mar 20 2018 H5 analysis from this morning had a fairly low amplitude pattern across the CONUS. However, numerous shortwaves were noted across the lower 48 and have led to active weather, particularly across the eastern half of the CONUS. Across the eastern CONUS, shortwaves were noted over the upper Ohio valley as well as across the lower Mississippi valley. Further west, a shortwave was located over northeastern Kansas with another upstream shortwave noted over Wyoming. Further north, a tandem of shortwaves were noted from eastern Montana into eastern Saskatchewan. Further west, a strong shortwave was noted from swrn Washington state south into swrn Oregon. Current WV imagery, continues to note an area of low pressure around 1000 miles west of the northern coast of California. At the surface: Weak high pressure was located over northern Nebraska. Skies were partly to mostly cloudy this afternoon as steepening mid level lapse rates have led to the development of CU and Alto CU across the forecast area with isolated showers. Temperatures as of 3 PM CDT ranged from 36 at O`Neill to 54 at North Platte. && .SHORT TERM...(This evening through Wednesday) Issued at 340 PM CDT Tue Mar 20 2018 Tonight and Wednesday: Skies will quickly clear by mid evening as we loose surface heating and the current steep lapse rates relax. Looking at the latest NAM12 and to a lesser degree, the HRRR soln overnight, yields a threat for fog across the north and northeastern forecast area overnight. This seems plausible given the degree of snow melt in the north today and light winds which are forecast overnight. Will keep the mention on the patchy side for now as the statistical guidance is void of fog attm. For Wednesday, a warm front will begin to push into swrn, then central Nebraska. Temps will warm into the 50s tomorrow with lower 60s in swrn Nebraska. Like this afternoon, mid level lapse rates increase, becoming nearly dry adiabatic, in swrn Nebraska late Wednesday afternoon. Cloud cover was increased in swrn Nebraska. For now, will leave the forecast dry, but wouldn`t be surprised if a stray shower or two develops in far swrn Nebraska Weds. afternoon. .LONG TERM...(Wednesday night through Tuesday) Issued at 340 PM CDT Tue Mar 20 2018 Mid range...Wednesday night through Friday...Ridging aloft will build into the central CONUS Wednesday night into Thursday night before shifting east of the area on Friday. Highs will reach the middle 50s to lower 70s both days. Mainly dry conditions are expected, however, there will be a small chance for showers across northern Nebraska Thursday night, as a weak disturbance lifts across the Dakotas. Weak lift in association with this feature will track along the SD/Nebr. border, thus the low pcpn chances. Long term...Friday night through Tuesday...The threat for precipitation will increase Friday night as a lead shortwave tracks east of the central Rockies. Better moisture is across central and eastern Kansas where the GFS pushes surface dew points into the lower 60s, however, sfc dew points do reach the middle 40s Friday afternoon. With steep lapse rates present, cannot rule out thunderstorms and have inserted them into the fcst for late Friday afternoon/Friday evening. Another shot of precipitation will track through the forecast area Saturday night followed by a stronger system on Sunday. This system will be associated with an arctic cold front so the mode of precipitation will change from rain Saturday night, to snow on Sunday night with cooler readings expected for Monday and Tuesday. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 623 PM CDT Tue Mar 20 2018 VFR is generally expected across western and north central Nebraska tonight and Wednesday. The ongoing shower activity will dissipate around sunset. Thereafter, weak high pressure and more stable air will build into the region. Patchy fog is possible for a few hours Wednesday morning affecting areas along and east of highway 183. Once this lifts, around 15z, VFR will become widespread. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Buttler SHORT TERM...Buttler LONG TERM...Buttler AVIATION...CDC
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
953 PM CDT Tue Mar 20 2018 .UPDATE...For 06Z Aviation discussion below && .SHORT TERM...(This evening through Wednesday) Issued at 315 PM CDT Tue Mar 20 2018 Two short wave were evident across the Northern Plains, and Upper Midwest this afternoon in the latest water vapor imagery. Forcing associated with these short waves, and ample moisture, led to occasional light snow. However, wind energy was weak, leading to weak convergence and very subtle lift. Therefore, any snow, combined with stronger solar insolation, kept snowfall amounts very light. Snowfall amounts after sunrise today were kept below one inch, and mainly in areas along the Minnesota River Valley where slightly stronger energy was noted with the short wave in Iowa. The main change overnight was to add some light freezing drizzle in western Minnesota due to weak lift and the lack of cloud ice seeding. A stronger wave was evident across northern Montana this afternoon which may allow for a more concentrated area of light freezing drizzle or light snow Wednesday morning in central Minnesota. The latest HRRR has some weak returns noted in central Minnesota after 12z Wednesday. However, even if some light precipitation develops, it shouldn`t have much of an impact due the very light duration/amounts expected. .LONG TERM...(Wednesday night through Tuesday) Issued at 325 PM CDT Tue Mar 20 2018 The main concern for the upcoming weekend storm is whether the current model trends have the right idea of moving the main storm system further to the south, and cutting off any significant precipitation over Minnesota, and western Wisconsin. Over the past 24 hours, models have trended drier and cooler for this upcoming weekend storm. Confidence has increased that most of the precipitation Friday night, and into early Saturday morning will be in the form of snow. A mixture of rain or snow is possible Friday, but with a drier east/southeast flow initially, the precipitation could be delayed. Plus, the higher March sun angle will also play a role of precipitation type Friday afternoon once precipitation starts in western Minnesota. Eventually the combination of strong isentropic lift along a strengthening thermal boundary will lead to widespread precipitation across western Minnesota by Friday afternoon, it will slowly move east/southeast, but the persistent drier easterly flow will limit the forward progression to the east. This may be one of those weather systems that have a very sharp precipitation gradient from west to east. Overall, there remains high confidence that precipitation will form and overspread Minnesota Friday afternoon/evening. There is lower confidence on how far east/northeast the precipitation develops. Therefore, west central Wisconsin could be in the zone where only a light dusting of snow occurs, vs a much heavier wet snow develops in central and east central Minnesota. This system is also fairly fast which leads to less likely of flooding problems. However, the mean flow becomes more southwest next week, and this is a very unsettled pattern for the Upper Midwest. It is also a warmer pattern which is more prone to liquid precipitation vs. frozen this time of year. Either way, a much wetter pattern is likely next week. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 954 PM CDT Tue Mar 20 2018 MVFR conditions will prevail into Wednesday at most MN sites, with IFR ceilings possible at times overnight at western sites (KAXN and KRWF). Improvement will be slow on Wednesday, with MN sites likely to experience MVFR ceilings through much of the day. Light and variable to southeast winds gradually become southerly on Wednesday, but speeds will be light overall(generally around 5 knots). KMSP... KMSP will be on the edge of MVFR ceilings, but expect the potential to increase during the overnight hours. Would expect them to stay above 1800 feet however. /OUTLOOK FOR KMSP/ THU...VFR. Wind ENE 5 kts. FRI...VFR early becoming MFVR with -RA/-SN. Wind ESE 10G15 kts. SAT...MVFR with Chc -RA/-SN. Wind ESE 10G15 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ SHORT TERM...JLT LONG TERM...JLT AVIATION...LS
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