December 4, 2013
An active and cold pattern shaping up for much of the Plains and Midwest heading into next week. A storm over the Great Lakes lifting into Canada will push a cold front across the Plains and Midwest on Wednesday and Wednesday night with only light precipitation. A disturbance moving along the front will produce a swath of wintry precipitation from southern KS to TX on northeastward across the mid- and lower-MS valley and TN valley to OH valley on Thursday and Friday. Very cold across the northern and central Plains over the next 2 or 3 days with lows as much as 10 to 15 below zero (-26 to -23C) as far south as western and northern NE. Another low is expected to take show near the Mississippi Delta then lift northeastward into southeast Canada this weekend into Monday with another round of winter weather spreading northward across the eastern Plains and Midwest. Dry and cold across much of the Plains and Midwest from Tuesday through next Thursday. Another system can bring rain and snow to these areas next Friday, but the ECMWF is less bullish on the front for day 10 so kept water amounts conservative.
Very cold across Nebraska and northern Kansas on Wednesday night and Thursday night with lows of -15 to 5 which can lead to some damage to winter wheat. A front can lead to a small snow accumulation ahead of the cold push which may help insulate the crop from the extreme cold.
A blast of arctic air into the western US later this week will bring the threat for a frost and freeze into the citrus areas of California Wednesday night and Thursday night. The coldest temperatures are expected to be 28-34 with local spots possibly as low as the middle 20s.
As of early Wednesday morning, EST, Tropical Depression 33W has become less organized with the low level center now exposed on satellite imagery. The system is expected to continue to weaken over the next couple of days as wind shear remains strong over the region. As such, the system is no longer classified as a tropical cyclone. The remnant low will track to the northeast and dissipate in the next 24-48 hour as it nears the northern Mariana Islands.
As of early Wednesday morning, EST, there are no active tropical cyclones over the Indian Ocean Basin, and none are expected to form within the next 24 hours. There are, however, two disturbances that are worthy of some attention. The first area of interest is currently located just to the east of Sri Lanka and will slowly parallel the coast over the next few days. Given how close this disturbance is to the coast and the fact that moderate wind shear will persist for at least the next 48 hours, development is expected to be slow to occur. Latest satellite imagery shows scattered and disorganized showers and thunderstorms, so certainly nothing threatening in the near-term... though that could change by the weekend as shear relaxes some. In the meantime, the gathering low will trigger rain of increasing coverage and intensity during the next few days. Excessive rainfall and flooding will be possible in eastern Sri Lanka with greatest threat starting on Wednesday and continuing into Saturday.
The second area of interest is in the southern Indian Ocean, just south of Sumatra. This system is also poorly organized and in an area of moderate wind shear, so any development is expected to be slow to occur. More likely than not this disturbance will dissipate over the next few days as it heads to the west-southwest away from land.
Much better model agreement across South America as the ECMWF has fallen in line with what the GFS was showing yesterday. As a result, croplands in Argentina from Entre Rios to Cordoba on south will remain dry through Friday while scattered thunderstorms fire from Salta and Catamarca to Misiones and Corrientes. Most models now show the front crossing lifting northward across the Argentina croplands this weekend to be the main feature over the next week. Some models are showing the possible for light rainfall in southern BA with this front on Saturday, but the consensus is for heavier rainfall from northern BA and Cordoba on northward this weekend into Monday. Rainfall is forecast at 0.25-0.75 of an inch (6-19mm) with this front with local amounts over an inch (25mm) likely. Another weaker front can bring light to moderate rainfall from BA and La Pampa to Entre Rios and Santa Fe next Wednesday and Thursday.
Across Brazil, there now looks to be two main rain makers for southern Brazil. A system will bring widespread showers and storms to RGS and SC tonight into Thursday, then Parana, SP, and MGDS on Thursday and Friday. Drying out across RGS and SC Friday through Sunday with spotty storms possible over Center-South Brazil this weekend. Another front will spread showers and thunderstorms from RGS northward to SP and MGDS Sunday night through Tuesday. As a result, most of southern Brazil still looks to have 90-110% of normal rainfall over the next 10 days. Not much change for Center-West Brazil with isolated to scattered thunderstorms expected each of the next 10 days.
Drier than normal weather across southwest Australia over the next 10 days will favor winter grain harvesting.
A cold front lifting northeastward will produce rain and thunderstorms from southern QLD to eastern VIC over the next couple of days. These rains will likely cause some fieldwork delays while maintaining or boosting soil moisture levels for summer crops. Drying out across the croplands in eastern Australia on Friday and Saturday. Another front will spread light to perhaps moderate rainfall from SA and VIC to southern QLD Sunday into early next week.
A slow-moving frontal boundary will produce a swath of rain and mountain snow from Lebanon and Syria to northern Iraq and northern Iran from today into Friday. These rains will disrupt fieldwork but will bring some beneficial moisture to already sown winter wheat. These rains will largely miss the drier areas of central Turkey, where rainfall would be welcomed for winter wheat establishment.