Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/30/21

Area Forecast Discussion
National Weather Service Columbia SC
1032 PM EDT Thu Apr 29 2021 .SYNOPSIS... A dry cold frontal passage is expected late tonight and into Friday. High pressure will build in behind the front with cooler temperatures expected on Saturday. Temperatures rise to back above normal Sunday with upper ridging building over the region. Increased moisture and a series of shortwaves for the first half of next week will lead to increased chances for rain. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... The approaching cold front currently extends from a low over southern NY southwestward through the Ohio Valley and lower Mississippi Valley. Regional radar shows scattered showers along and just ahead of the front. This front is being driven by a slightly positively tilted upper trough moving across the Great Lakes region which will push the front through our area late tonight and early Friday morning. As the front crosses the mountains later tonight, the hi-res guidance suggests the showers will dissipate as the mid level flow becomes northwesterly and the downslope flow will limit rain for our area. Cannot rule out some sprinkles but measurable rainfall looks unlikely, so will continue to carry a dry forecast. Winds will stay up through the night and there will be a 30-35 knot low level jet keeping the boundary layer mixed so radiational cooling will be very limited. Expect overnight lows to range from the lower 60s west to mid-upper 60s east. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... Cold front will push through the area early Friday but dry conditions are expected to continue, especially with downslope flow developing across the area. Expect low levels to dry out fairly quickly but temperatures to once again rise to above normal with increased solar insolation as well as the downslope winds. Elevated fire danger will be possible with winds gusting to near 20mph and RH dropping below 30 percent. Friday night, low level jet will limit radiational cooling but wind winds turning more northerly, cold advection will drop lows into the low to mid 50s. High pressure will be centered over the area Saturday with cooler temperatures and lower 500mb heights. Mostly clear and dry through the day. Saturday night should be favored for good radiational cooling although some high and mid level clouds may work their way into the CSRA before sunrise. Still expect most of the area to drop into the low 50s outside of the CSRA. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Surface high pressure will push offshore Sunday with increasing low level moisture. Meanwhile, mid-level ridging will build back in with temperatures climbing to back above normal. Bit of uncertainty as to how fast deep moisture returns Sunday but by Monday, agreement among ensembles of PWATs climbing to around 1.5 inches across the entire forecast area as deep SW flow develops with the axis of the ridge pushing east. Forcing does appear to be subtle over the area with the ridge remaining fairly strong and any surface convergence along boundaries appearing to be fairly weak. As a result, early next week will remain unsettled with better chances for rain along the western forecast area where shortwave energy may pass. May get some afternoon thunderstorms to develop as well with ensembles showing some limited instability with continued above normal temperatures thanks to a persistent SW low level flow. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... VFR. A cold front, with limited if any precipitation, will come through Friday morning. Ahead of the front expect WSW winds staying up enough overnight to preclude any fog concerns. Surface wind speeds have dropped off to about 8 to 10 kt. GFS BUFKIT indicating low level jet 30-35 kt, and is confirmed by latest AMDAR sounding at CAE. Decided to include LLWS. Winds will shift to NW behind the front Friday. EXTENDED AVIATION OUTLOOK...VFR through Sunday. CIG restrictions possible Sunday night. Chance of rain and associated restrictions Mon/Tue. && .FIRE WEATHER... There is increased fire danger Friday afternoon due to low relative humidities and gusty winds as a dry cold front crosses the area early. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$
Area Forecast Discussion
National Weather Service Phoenix AZ
525 PM MST Thu Apr 29 2021 .UPDATE...Updated 00Z Aviation Discussion. && .SYNOPSIS... A large closed low will slowly move eastward across northern Mexico, allowing a strong area of high pressure to build over the Southwest. This will bring much warmer temperatures, with highs potentially reaching 100 degrees by Saturday. Temperatures will moderate somewhat early next week, but stay well above normal as dry conditions and mostly clear skies prevail. && .DISCUSSION... Latest satellite imagery shows our departed low pressure system centered over Chihuahua, MX, with subsidence aloft over Arizona that is producing mostly clear skies. Current temperatures are in the low 90s, nearly 10 degrees warmer than at this point yesterday, with several more hours of daytime heating to go. High pressure ridging, marked by rapidly increasing atmospheric heights, thickness, and temperature, is building over the west coast in the wake of the aforementioned low. This morning`s 16Z Yuma sounding shows H5 height have increased by nearly 15 dm since 16Z yesterday. Comparison of ACARS soundings over the last 24 hrs also reveals significant increases in temperatures throughout the lower half of the atmosphere. Latest NAEFS guidance indicates the ridge will continue to strengthen, peaking over northcentral California and Nevada by tomorrow, with H5 heights of 582-590 dm spreading over our forecast area. The ridge is forecast to weaken somewhat by Saturday as a shortwave approaches the region. The WPC Cluster tool and all individual global ensembles show the ridge being replaced by troughing by Sunday and remaining in place through the first part of next week. Clear skies and a warming atmospheric column under high pressure will undoubtedly lead to above normal temperatures with afternoon highs reaching the mid-90s today. For Friday and Saturday, afternoon highs are forecast to reach the 99-103 degree range in southeastern California/western Arizona while temps reach 95-100 in south-central Arizona, including the Phoenix area. NBM Probability guidance for Phoenix reaching 100 degrees is at 20% Friday and 50% Saturday. Increasing cloud cover Saturday as the aforementioned shortwave approaches could help temper Saturdays highs a degree or two and prevent Phoenix from officially reaching the century mark. The climatological normal date for Phoenixs first 100 is right around May 2nd. A tighter pressure gradient will also produce breezy conditions with afternoon and evening gusts of 20-30 mph Saturday and Sunday. The continental trajectory of this system will likely limit any moisture transport sufficient enough for lower desert rain with showers limited to the higher terrain of northeastern Arizona on Monday. High temperatures will also dip into the low 90s by Monday but temps are favored for a quick rebound given day 5-7 ensemble agreement for ridging later next week. Guidance agreement produces confidence that high temperatures will once again warm into the upper 90s no later than next Wednesday. The NBM Probability guidance for 100 degrees in Phoenix is 65 percent for next Thursday. If we are able to avoid 100 degrees this weekend, odds favor we will see them late next week. && .AVIATION...Updated at 0020Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Light west winds are still expected to become prevailing by 1-2Z this evening and then shift back east before midnight. A 20-25 kt southeasterly gradient wind around 1 kft AGL will develop early Friday morning and result in a slight boost in surface speeds up to 10-12 kts around sunrise. Southeast gusts up to 15-20 kts will also be possible through the late morning. Winds then gradually subside through midday and slowly shift to the west to southwest by 22-23Z. Skies should remain mostly clear. Southeast California/Southwest Arizona including KIPL and KBLH: Winds will be light at both terminals through the TAF period. Directions at KBLH will favor the east to southeast during the day and west to northwest overnight, while KIPL sees a south to southeast during the day and west overnight. Periods of variability will also be possible at both terminals. Skies will remain mostly clear with occasional cirrus. && .FIRE WEATHER... Sunday through Thursday: Temperatures will begin to cool slightly Sunday, and then cool into the upper 80s/low 90s by Monday, as a weather disturbance passes by to the north. However, temperatures will quickly warm back into the upper 90s by Wednesday. Seasonably dry conditions are expected through the period with min RH values mostly in the mid single digit-low teen range. Winds will follow diurnal trends, but with somewhat elevated winds/fire danger levels on Saturday through Monday. && .CLIMATE... .Daily Record Highs... Phoenix Yuma El Centro .......... .......... ......... Fri 4/30 102 (1943) 103 (1943) 104 (1965) Sat 5/1 103 (1985) 106 (1947) 106 (1947) Sun 5/2 107 (1947) 111 (1947) 113 (1947) && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...AD AVIATION...Benedict FIRE WEATHER...AD/Rogers CLIMATE...Kuhlman