Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/08/19

Area Forecast Discussion
National Weather Service Lake Charles LA
949 PM CDT Tue May 7 2019 .UPDATE... IR satellite and regional radar imagery show an area of deep convection currently ongoing over the Houston metro area. Outflow from this convection is enhancing low-level convergence along the coast and is forcing conditionally unstable parcels characterized by 2000 J/kg MLCAPE to ascend, resulting in continued development of deep convection. Abundant deep layer moisture indicated by 1.7"-2.0" PWAT and warm cloud layer depths greater than 3 km has resulted in efficient precipitation processes with totals approaching 12 inches in some locations. An analysis of Corfidi vectors across the region indicate the potential for this convective complex to progress eastward at around 15-20 knots. As a result, the greatest potential for heavy rainfall is expected to remain west of the CWA over the next 1-3 hours (for more detailed information see WPC MPD 204). However, there will be the potential for the eastern portions of this convective complex to reach western portions of Jefferson County and southwestern Hardin County between now and 1 AM. Therefore, PoPs for this timeframe have be updated to better reflect the greatest potential for rainfall across the region. Beyond the next 1-3 hours, the majority of the short term guidance has the convective complex weakening and ending by the time it reaches the far SW portions of the CWA. However, given the mesoscale nature of this system, radar and satellite trends will continue to be monitored to see if cold pool balance will persist and result in continued localized forcing for convective redevelopment. For now, the inherited forecast for the overnight period remains representative with no changes made at this time. && .PREV DISCUSSION... /issued 647 PM CDT Tue May 7 2019/ AVIATION... Storms this evening are moving to the north. Radar was indicating a few around BPT but they should dissipate over the next hour or two. Storms moving into Rapides parish will move up to Alexandria over the next 30 to 45 minutes. For aircraft the main threat will be from winds... low clouds and lightning. Low ceilings overnight and through sunrise. PREV DISCUSSION... /issued 425 PM CDT Tue May 7 2019/ DISCUSSION... Although a bit earlier than expected, scattered to numerous showers and thunderstorms have begun moving into southeast Texas this afternoon in association with a weak upper trof moving up the the central Texas coastline. A few areas of heavy precipitation have been producing very high rainfall rates as something of a preamble of things to come over the next few days. Expect this activity to continue for the next few hours before becoming more isolated as the upper support shifts off to the northeast. A weak warm front lingering over the area overnight will allow for isolated convection to continue overnight with activity increasing somewhat by mid morning Wednesday. The area will be warm sectored between this front and a cold front extending south from a surface low over the northern plains for much of the day. A few discreet cells will have the potential to develop across the area although anemic shear should help limit supercell development. A swath of already ongoing showers and thunderstorms associated with the cold front will begin to envelope the region from the west during the afternoon and evening. Forecast guidance shows considerable differences in the intensity of this activity with several short range and high res models showing a general weakening trend as the line moves into southeast Texas although confidence in the weakening is somewhat below average owing to the ECMWF`s consistency in maintaining the convection. This will have to be monitored closely through the day tomorrow. SPC continues to highlight an area roughly from Alexandria southwest to Beaumont in a slight risk for severe weather with damaging winds and large hail being the primary threats. A marginal risk extends northwest roughly from Lafayette to Cameron. The front is still expected to stall somewhere over the area Wednesday night into Thursday setting up several days of widespread heavy rainfall and thunderstorms. Several upper level features are progged to overrun the surface boundary further enhancing precipitation although the exact timing and intensity of these upper level features remains highly in question. A low end severe weather threat will persist Thursday through Saturday although the threat appears to be confined to damaging winds. In addition to the severe weather threat, a heavy rain threat also remains in play. Precipitable water values in the 1.8 to 2 inch range will allow for very efficient rain makers while the long duration of the event will set up a potential flash flood threat especially Friday and Saturday when the ground is expected to be fully saturated. Overall QPF values are a bit lower than the previous forecast, but the highest values of 6+ inches are still expected across interior parts of southeast Texas and central Louisiana while 4 to 5 inches are expected along a large swath of the I-10 corridor. The QPF values remain highly subject to change and will likely do so over the next 24 to 48 hours. Beyond Saturday, guidance remains highly divergent with the ECMWF shunting the frontal boundary and the associated moisture offshore by late Sunday morning showing dry conditions to start the week. The GFS meanwhile continues to stream copious moisture over the region within the subtropical jet. Presently have no justification to lean one way or the other so the official forecast follows a split the difference philosophy and carries low end PoPs into early next week. Jones MARINE... Moderate southeasterly winds can be expected this afternoon into tonight as the pressure gradient tightens in response to lowering pressures from West Texas to the Plains. A series of upper level disturbances will traverse the region and a weak frontal boundary will stall across the area Thursday through the weekend resulting in several days of widespread showers and thunderstorms some of which could be strong to severe. && .PRELIMINARY POINT TEMPS/POPS... AEX 69 85 72 83 / 20 60 40 70 LCH 74 84 75 83 / 30 50 20 60 LFT 72 87 75 86 / 10 40 20 50 BPT 74 82 75 83 / 40 50 40 60 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...None. TX...None. GM...Small Craft Exercise Caution through Wednesday evening for GMZ450-452-455-470-472-475. Small Craft Exercise Caution from Wednesday morning through Wednesday evening for GMZ430-432-435. && $$ PUBLIC...26
Area Forecast Discussion...Corrected
National Weather Service Phoenix AZ
602 PM MST Tue May 7 2019 .UPDATE... Updated aviation discussion. && .SYNOPSIS... A series of weather disturbances will sweep through the Desert Southwest for the remainder of the week into the weekend to cause a prolonged period of cooler than normal temperatures. Isolated to scattered showers and a few thunderstorms will develop north and east of Phoenix tomorrow afternoon, with a slight chance of storms moving into the metro. After a brief warm up to around 90 degrees on Thursday, better chances for more widespread showers will arrive this weekend as the storm system deepens over the Desert Southwest. Isolated thunderstorms will be possible on Sunday afternoon over the Phoenix metro and Gila County. && .DISCUSSION... A closed mid-to-upper level low pressure system continues to push into eastern Arizona as slightly cooler air advects into the region. Isolated showers and thunderstorms are currently pushing out of Gila County as scattered to broken clouds with ceilings generally remaining above 6 kft continue to persist over the lower deserts with new convection developing over northern Yavapai County and pushing south. Hi-res models generally show these storms dissipating before pushing into Maricopa County. This is corroborated by drier air, negative differential vorticity advection, and a weak stable layer pushing into midlevels evident on water vapor imagery and aircraft soundings. Therefore, the remainder of the day should be quite pleasant across most of the region with high temperatures struggling to reach 80 degrees over the lower deserts of south Central Arizona and mid 80s over southwest Arizona and southeast California. Tonight will be very pleasant with low temperatures in the mid 50s to lower 60s over the lower deserts under light diurnal winds. Another shortwave currently pushing into northern Utah will dig south tonight into northern Arizona for tomorrow. Models are continuing to trend towards an increased coverage of storms along and north of the Rim tomorrow afternoon which seems reasonable given the midlevel forcing associated with the aforementioned vorticity center. Moisture may be somewhat limited over northern Arizona, but precipitable water values will increase to 0.7-0.8 along and south of the Rim. This should be sufficient to initiate thunderstorms with daytime heating tomorrow afternoon when temperatures should be 7-10 degrees warmer than today without significant capping evident on model soundings. Therefore, there is about a 10-20 percent chance of a thunderstorm or two slipping into north or northeast portions of the Phoenix metro tomorrow afternoon compared with less than a 5 percent chance today. However, most of the Phoenix metro, particularly further south and west, should remain dry. The driest and warmest conditions of the forecast period are expected on Thursday as southwest flow briefly redevelops as the trough axis becomes very positively tilted to our west. Therefore, temperatures will briefly warm back up to near 90 degrees for the lower deserts, albeit still a couple degrees below normal. Beyond Thursday, a cutoff low is forecast to develop off the coast of southern California and slowly push east through the weekend before becoming centered over southern Arizona or northern Sonora on Monday. Not only will this low pressure entity feature heights aloft substantially below average (and consequently consecutive days with temperatures some 10 deg F below normal), but better quality moisture profiles will materialize via both Pacific and cross continental origins. By the weekend, total column precipitable water values will approach 0.8-1.0 inches (near or above the 98th percentile for early/mid May) coincident with an unusually cool airmass and broad cold core aloft. An increasing lobe of vorticity will swing over this nearly saturated environment with ample SW-to-NE- oriented isentropic ascent to yield scattered showers on Friday night into Saturday morning. Surface-based instability also appears to increase for Sunday and Monday to 200-500 J/kg of CAPE as the cold core center moves overhead, making isolated thunderstorms a decent possibly on Sunday afternoon over the Phoenix metro and Gila County and Monday afternoon north and east of Phoenix. The timing uncertainty precludes pinpointing higher POPs for any specific time, but showers and possibly a few thunderstorms will occur at least once, if not twice between Friday night and Monday morning. && .AVIATION...Updated at 0100 UTC. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Late this afternoon, the greater Phoenix area is in the wake of departing low that brought showers to the area earlier today. A drier and more subsident northwest flow aloft is in place behind the low, resulting in thinning of the cumulus field that formed over the central deserts. There is another disturbance dropping in from the north - behind the main departing low - that has generated an area of showers north of the Phoenix area. However, this cluster of showers and/or storms will likely dissipate within the next 1-2 hours. as it moves off high terrain and into the deserts, and thus should not reach the terminals. Outflow winds moving in from the north early this evening - associated with the area of showers - is not likely; threat is not zero but too low to mention in the TAFs. Winds this evening should favor the west/southwest with a few gusts into the teens possible thru about 03z. Expect some lingering high based cumulus/mid level debris cloud overnight, with mid could thickening up after 11z. Thus, expect areas of BKN CIGs 10-12k feet during the morning hours before the mid cloud thin leaving behind some SCT cumulus decks with bases 7-9k feet. Otherwise, winds should return to the east/southeast after midnight, and at KPHX this transition may be late and not until 11-12Z. West winds return again after 19z with gusts into the teens likely for the TAF sites. Southeast California/Southwest Arizona including KIPL and KBLH: Winds to favor the west next 24 hours at KIPL with gusts to 25kt possible thru around 05z, after midnight wind taper off to around 10k. Winds to favor the south/southwest at KBLH next 24 hours. Skies generally clear through Wednesday afternoon with just some high clouds possible at times. Aviation Discussion not updated for amended TAFs. && .FIRE WEATHER... Friday through Tuesday: A series of weather disturbances will result in much cooler than normal temperatures, rising humidity values, and increased chances for light showers and thunderstorms over most districts. Although most areas will remain dry on Friday, several weather systems will congeal over southern California and Arizona during the weekend into Monday with showers and a few thunderstorms likely over both higher elevations and the lower deserts. Pockets of wetting rains will certainly be possible. Afternoon humidity levels will be quite moist by mid May standards only falling into a 20-30% range every day. Occasional breezy afternoon winds will exist with the approach of these weather systems, but winds may become light and variable over the weekend into Monday as clouds and showers settle over the area. Drier and warmer conditions should begin to filter into the region by Tuesday into the middle of next week. && .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected for the next 7 days. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Hopper/MO AVIATION...CB FIRE WEATHER...Hopper/MO