Area Forecast Discussion
Issued by NWS Little Rock, AR

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000 FXUS64 KLZK 191730 AFDLZK Area Forecast Discussion National Weather Service Little Rock AR 1230 PM CDT Mon Apr 19 2021 .UPDATE... Updated to include the 18Z aviation discussion. && .AVIATION... VFR conditions are forecast for all terminals during the period. Mostly clear conditions are expected Monday afternoon, with light westerly winds. Winds will become more southwesterly overnight. Scattered cloud cover will expand over the southern parts of the state overnight. Cloud cover will increase from the NW Tuesday morning as a cold front enters the state, bringing rain showers that will expand across the northern half of the state by Tuesday afternoon. && .PREV DISCUSSION...(ISSUED 633 AM CDT Mon Apr 19 2021) UPDATE... Updated to include the 12Z aviation discussion. AVIATION... Aside from patchy BR/FG this morning, VFR conditions will prevail at all terminals this period. Winds will remain W/SW at or below 10 kts, becoming light/VRB overnight. High clouds may move over southern terminals this afternoon with cloud cover increasing for northern terminals near the end of the period. PREV DISCUSSION...(ISSUED 418 AM CDT Mon Apr 19 2021) SHORT TERM...Today Through Tuesday Night Morning mesoanalysis depicts an elongated area of low-amplitude mid/upper troughing stretching from near New England southwestward to the Baja peninsula, punctuated by modest shortwave impulses. The embedded shortwave responsible for yesterday`s rain and thunder continues pushing east across the TN Valley with a surface ridge expanding across the south- central CONUS. Do expect tranquil weather today and tonight with temps running near to slightly below average, yielding highs in the upper 60s to low 70s and lows in the 40s tonight. Meanwhile, water vapor imagery shows the next mid/upper trough queuing up across the northern Rockies. While guidance has trended a touch slower with this feature, do still expect it will cross the central Rockies overnight and move across the Plains states through the day Tuesday before pivoting northeast over MO by Tuesday evening. Attendant to this upper feature is a strong Canadian cold front, poised to sweep across the area Tuesday into Tuesday night. Ahead of the front, temps will climb to near average over roughly the southeastern half of the state. Over the northwest, increasing cloud cover ahead of and strong cold air advection in the wake of the front will limit high temps to the 40s and 50s. Moisture remains modest given the lack of substantial return flow from the Gulf, although PWAT values on the order of 0.75 to 0.8 inches will be enough to squeeze out rain showers along and ahead of the front, primarily over the northern half of AR where moisture and dynamic forcing are most in phase. That said, there could be enough moisture farther south to generate isolated to scattered showers, but confidence in more widespread coverage remains very low. Winds will pick up markedly as the front approaches with breezy westerly winds becoming north to northwesterly behind the boundary. Wind headlines are not anticipated, although gusts could approach 30 mph Tuesday afternoon and evening. Temps will quickly fall in the wake of the front, both at the surface and in the lower troposphere. Based on forecast soundings, ensemble guidance, and calibrated statistical guidance, there is a small window for mixed wintry precip over northern AR Tuesday night assuming moisture isn`t entirely scoured out by then. Should any wintry precip materialize, no accumulation or impacts are expected and precip will end before dawn on Wednesday. Of more consequence will be temperatures very late in the period as the post-frontal Canadian air mass begins to settle over the area. Initialized guidance remains on the warm side, likely a consequence of climatological influence, so skewed temps Tuesday night closely to the 25th percentile which yields near to sub- freezing temps over roughly the northwestern half of AR. Readings in the mid/upper 20s are likely over northwestern AR. Based on this trend, did expand the Freeze Watch to include Polk, Randolph, and Lawrence Counties with no changes to the remainder of the watch. Sensitive vegetation is certainly at risk given the magnitude of cold air expected and several record lows may be challenged if not broken. Strong surface ridging immediately behind the front suggests winds will drop off fairly quickly Tuesday night. Clearing skies and light winds in the presence of the anticipated cold will readily produce frost over a large area. Did include patchy frost as far south as a Camden to Pine Bluff to Stuttgart line with widespread frost expected farther north and west. While min temps over the southeastern half of the area will likely end up near to above freezing, sensitive vegetation will still be at risk from frost, so please prepare accordingly. LONG TERM...Wednesday Through Sunday A large area of Canadian high pressure will follow a cold front, and will build into Arkansas by Wednesday morning. Low temperatures will be in the upper 20s to upper 30s, with a freeze likely in much of the Ozark and Ouachita Mountains. Frost will be widespread as well. Temperatures will start slowly modifying on Thursday as the high exits to the east and return flow kicks in. Even so, readings will remain below average. A large storm system will approach from the southern Plains on Friday, with rain becoming widespread. There may be rumbles of thunder as well. Amounts from a half inch to an inch are expected, with the heaviest totals in southern sections of the state. Precipitation will begin tapering off Saturday as another cold front arrives from the north with drier air. Temperatures will get closer to seasonal as the period ends, but may still fall a little short. There should be additional warming beyond the period as ridging occurs over the middle of the country ahead of a large storm system/trough out west. && .LZK Watches/Warnings/Advisories... Freeze Watch from late Tuesday night through Wednesday morning FOR Baxter-Boone-Cleburne-Conway-Fulton-Independence-Izard- Johnson-Lawrence-Logan-Marion-Montgomery-Newton-Polk-Pope- Randolph-Scott-Searcy-Sharp-Stone-Van Buren-Yell. && $$ Aviation...SHELTON

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