043 FXCA62 TJSJ 041109 CCA AFDSJU Area Forecast Discussion...CORRECTED National Weather Service San Juan PR 709 AM AST Wed Mar 4 2020 .SYNOPSIS... Surface high pressure ridge over the north central Atlantic will slowly lift northeastward today through Thursday as a cold front will enter and move across the west and northwest Atlantic. This will result in a moderate easterly wind flow across the region. A mid to upper level ridge will build eastwards across the region from the western Caribbean and increase the trade wind cap inversion, while eroding low level moisture advection and therefore support stable conditions aloft during the next few days. && .SHORT TERM...Today through Friday... A drying trend is expected over the local area as a drier than normal air mass approaches from the east. An upper level ridge will support stability aloft, providing mainly fair weather conditions through the end of the forecast period. However, satellite imagery indicates there is still remaining patches of low-level moisture that will aid in development of afternoon convection over interior and western portions of PR. Increasing winds are anticipated for Thursday and Friday, associated with a surface ridge pushing southward towards the area. For Friday, models are suggesting the arrival of a broad upper-level trough that will flatten the existing ridge and will then bring an increase in moisture and instability aloft. Therefore, periods of passing showers are expected during the morning hours followed by afternoon convection across interior and western portions of the islands. .LONG TERM...Saturday through Thursday... Generally fair weather conditions will persist over the local area from at least through Saturday into early Sunday, with a cold front still forecast to bring an increase in moisture and instability across the region late Sunday through Monday. Thereafter, a gradual drying trend is again expected by late Tuesday through Thursday. There may however be occasional patches of moisture, briefly affecting the islands and local waters, early Saturday and during the afternoon hours. In the upper levels, the approach of the broad polar trough will begin to erode the ridge aloft move through the local area Sunday through Monday. By then, an area of low pressure entering the western Atlantic, and the surface high pressure northeast of the area will induce a low level surface trough across the region. This will result in better moisture convergence across the forecast areas as well as the instability aloft. A frontal boundary associated with the aforementioned low pressure will sink southwards across the region Sunday through Monday, as high pressure will again build and spread across the western Atlantic. This overall pattern may cause a significant increase in moisture and instability, followed by increasing winds during the early part of the week. Recent model guidance remain consistent in showing a fairly moist pattern during the early part of the period along with a significant increase in low level wind speeds by Monday. In addition, cold air advection suggested in the 500 millibar level would also suggest and favor good potential for increase rainfall rates with the possibility of isolated thunderstorm activity especially Sunday through Monday or early Tuesday. For the rest of the period, expect a gradual improvement in the overall weather condition based on the latest model guidance. && .AVIATION...Drier air is approaching the area. Therefore, VFR conds will prevail during the 24 hour period across all terminals. Sfc winds ENE 10-15 kt with higher gusts til 04/22Z. VCSH across TJMZ and TJBQ around 03/18Z due to afternoon convection. && .MARINE...Hazardous marine conditions will persist mainly across the Atlantic waters and Mona Passage into the early morning hours, but will gradually improve throughout the day, as a northerly swell will continue to fade. Small Craft Advisories are therefore in effect for these waters until 8 AM AST. Small craft operators should exercise caution elsewhere during the rest of today. Mariners can expect seas between 5 to 8 feet and winds between 15 to 20 knots offshore and 10 to 15 knots near shore. Please refer to the latest Coastal Waters Forecast (CWFSJU)and Marine Weather Message (MWWSJU) issued by WFO San Juan PR. && .PRELIMINARY POINT TEMPS/POPS... SJU 85 73 85 73 / 20 20 20 30 STT 85 74 84 73 / 10 10 20 20 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through this afternoon for Culebra- Mayaguez and Vicinity-North Central-Northeast-Northwest-San Juan and Vicinity-Southeast. VI...High Rip Current Risk until 6 AM AST early this morning for St.Thomas...St. John...and Adjacent Islands. AM...Small Craft Advisory until 8 AM AST this morning for Atlantic Waters of Puerto Rico and USVI from 10 NM to 19.5N-Coastal Waters OF Northwestern Puerto Rico out 10 NM-Coastal Waters of Northern Puerto Rico out 10 NM-Mona Passage Southward to 17N. && $$ SHORT TERM...FRG LONG TERM....RAM