529 FXUS62 KMLB 052052 AFDMLB Area Forecast Discussion National Weather Service Melbourne FL 352 PM EST Sun Jan 5 2020 .DISCUSSION... ...Another Colder Night, Patchy Frost Possible Late Tonight/Early Monday Morning... Tonight-Monday...Progressive WX pattern in play as strong zonal flow prevails thru the H40-H20 lyr acrs the GOMex/Deep South. The flow will pull a strong H100-H70 anticyclone from the NW GOMex acrs the FL peninsula. This will keep the lcl airmass highly suppressed with a sharp subsidence inversion dominating the H100-H70 lyr (H85-H70 lapse rates btwn 2.0-2.5C/KM). The airmass assocd with the ridge is also quite dry with H100-H70 mean RH values blo 30pct and H85-H50 avg dewpoint depressions btwn 30-35C. Diminishing winds overnight as the ridge drifts into the FL peninsula...falling to AOB 5mph over much of central FL. Coupled with dry air/clear skies, conditions for radiational cooling will be optimal. Temps along the immediate coast and the urbanized areas will hold in the L/M40s, but outlying rural areas west of I-95 expected to drop into the M/U30s. Frost could form in the predawn hrs, especially in wind protected areas. One catch in this is that dewpoints acrs the interior are also quite low, generally L/M30s. Given this, no need to increase the frost threat beyond, "patchy". Cool/dry WX continues into Monday as the high pres ridge begins to build into the W Atlc...H100-H70 flow slowly shifting from NW to N/NE, but with a loose pgrad overhead. While dvlpg onshore flow will allow the airmass to begin to modify, the pgrad will only support winds AOB 10mph...not enough to make huge inroads. Max temps in the M/U60s, within about 5F of climo avgs. Mon night-Wednesday...A high pressure will start this period elongated across the FL peninsula and quickly moving towards the central Atlantic. At the same time, a low pressure will move NE from the Lower Mississippi Valley to the NE U.S. coast line. On Tue night, an expansive area of high pressure will build across south U.S. and retake the southeast U.S. through Wed. As the aforementioned low lifts northeast, a weak short wave trough will be pushed towards the FL peninsula late on Tue, crossing the local area on Tue night. This front will be very weak and falling apart as it transitions south. No weather is expected from this trough, rather a brief advection of cooler northerly air into east central FL on Tue night. But as the high shifts east and then northeast from Texas, the local wind flow will veer from the northeast on Wed. Dry weather for this period will be accompanied by lows in the 40 on Mon night, middle 40s to lower 50s on Tue night and mid 50s to lower 60s on Wed night. For daytime temps, these will be more smooth across the area on Tue as these range in the lower 70s but for Wed the range will increase as temps are expected to climb to the mid 60s over Lake and Volusia counties while Treasure Coast will observe mid 70s. Thursday-Sunday (previous)...A large/strong mid level ridge will build N-NW from the Greater Antilles across Florida and the adjacent Atlantic. This will prevent any more intrusions of colder air, while bringing a warming trend through next weekend. A prolonged period of onshore/SE flow will advect increasing low level moisture, that will in turn bring a coastal shower threat Thu, which will increase and spread inland with time through the weekend. Max temps averaging about a category above normal Thu will warm to well above average through the period. && .AVIATION...Thru 06/18Z. Sfc Winds: Thru 05/22Z...N/NW 8-13KTS...coastal sites ocnl sfc G18- 22KTS. Btwn 05/22Z-06/01Z...bcmg N/NW 3-5KTS. Btwn 06/12-06/15... bcmg N/NW 7-10KTS. Vsbys/WX/Cigs: VFR/SKC all sites. && .MARINE... Tonight-Monday...Latest obs from the data buoy/C-MAN network continues to trend down...seas at buoy 41009 now blo 6FT...coastal obs show winds down to 10-15KTS with ocnl G18-22KTS. Still rough through early evng, but improving conditions overnight as high pres builds over the region and allow the lcl pgrad to loosen up. Tue-Fri...East winds on Tue thanks to a weak high pressure area building over the FL peninsula, will dissipate during the day and be pushed by a weak trough approaching FL from the northwest on Tue night. Winds will veer and should remain below advisory criteria. Then late Wed into Wed night, a high pressure over the eastern U.S. will stretch south, increasing the local pressure gradient. Winds will pick up from the east and will trigger another period of hazardous winds and seas lasting through the weekend. && .FIRE WEATHER... Monday...Northerly surface and transport winds will decrease to less than 10 mph. Meanwhile, lingering cold and dry air will keep mixing heights below 3,000 feet and RHs dropping to around 25 percent from Volusia to Osceola and higher towards the coast. && .PRELIMINARY POINT TEMPS/POPS... DAB 40 65 44 69 / 0 0 0 0 MCO 40 68 45 71 / 0 0 0 0 MLB 40 66 48 71 / 0 0 0 10 VRB 42 67 48 71 / 0 0 10 10 LEE 38 68 45 71 / 0 0 0 0 SFB 39 69 44 71 / 0 0 0 0 ORL 42 69 47 70 / 0 0 0 0 FPR 42 68 50 72 / 0 0 10 10 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...Small Craft Advisory until 10 PM EST this evening for Sebastian Inlet to Jupiter Inlet 0-20 nm-Sebastian Inlet to Jupiter Inlet 20-60 nm-Volusia-Brevard County Line to Sebastian Inlet 20-60 nm. && $$ Negron/Bragaw